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Original Research: SLEEP MEDICINE |

Tumor Necrosis Factor-α Expression in Uvular Tissues Differs Between Snorers and Apneic Patients FREE TO VIEW

Lionel Loubaki, MSc; Eric Jacques, MSc; Abdelhabib Semlali, PhD; Sabrina Biardel; Jamila Chakir, PhD; Frédéric Sériès, MD
Author and Funding Information

* From the Centre de Recherche de l'Hôpital Laval, Institut Universitaire de Cardiologie et de Pneumologie, Québec, QC, Canada.

Correspondence to: Jamila Chakir, PhD, Centre de Recherche, Hôpital Laval, 2725 Chemin Sainte-Foy, Québec, QC, Canada G1V 4G5; e-mail: jamila.chakir@med.ulaval.ca


The authors have reported to the ACCP that no significant conflicts of interest exist with any companies/organizations whose products or services may be discussed in this article.

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/misc/reprints.shtml).


Chest. 2008;134(5):911-918. doi:10.1378/chest.08-0886
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Background:  Inflammatory changes such as subepithelial edema and excessive inflammatory cell infiltration have been observed in uvular tissues of obstructive sleep apnea (OSA) subjects. The levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin-6 are elevated in the serum of apneic patients and have been proposed as mediators of muscle weakness. TNF-α has been shown to affect diaphragm contractility in mice and rabbit in vivo.

Objectives:  To assess total and compartmental TNF-α expression in uvular tissues of apneic and nonapneic patients.

Methods:  Uvular tissues were collected from 14 snorers without sleep disorders breathing, 14 subjects with OSA (OSA 1 group) whose body mass index (BMI) was similar to that of snorers, and 12 additional obese OSA subjects (OSA 2 group) who underwent an uvulopalatopharyngoplasty. Sections were examined using immunohistochemistry and Western blot analysis. TNF-α expression was evaluated in the musculus uvulae (MU), epithelial layer, and perimuscular tissues from proximal uvular sections.

Results:  TNF-α was more highly expressed in whole uvular protein extracts of apneic groups than in snorers ([mean ± SEM] snorers, 100.5 ± 3.0%; OSA 1 group, 127.1 ± 6.9%; OSA 2 group, 140.7 ± 11.0%; p = 0.01). In the muscular area, TNF-α levels were higher in the more obese OSA subjects than in the other two groups (snorers, 100.3 ± 3%; OSA 1 group, 107.4 ± 0.7%; OSA 2 group, 124.1 ± 4.2%; p = 0.007). In the muscular area, TNF-α was correlated with BMI, but no relationship was found with the apnea-hypopnea index.

Conclusions:  We conclude that MU is the major TNF-α source in uvular tissue and that TNF-α is more highly expressed in the heaviest OSA patients compared to less obese OSA patients and nonapneic snorers.

Figures in this Article

Obstructive sleep apnea (OSA) is characterized by repeated episodes of upper airway (UA) obstruction during sleep. OSA leads to periodic desaturation and fragmentation of sleep, and is associated with cardiovascular complications.15 Epidemiologic studies4,6 have estimated that OSA affects approximately 24% of men and 9% of women between the ages of 30 and 60 years. Age,7 sex,8 and weight5 are the three major factors influencing prevalence of the disease.

Among the different factors that are involved in the pathophysiology of OSA, such as reflexively mediated UA muscle activity,9 the UA respiratory muscle activation pattern,10 and the efficiency of UA contraction,11 the role of the deleterious effects of local and systemic inflammation has also been examined. A histopathologic analysis of uvular tissues obtained from patients undergoing uvulopalatopharyngoplasty (UPPP) for the treatment of OSA revealed a marked increase in subepithelial edema and a reduction in the surface area of connective tissue papillae that provide anchorage for the epithelium.12 We previously observed a more important CD4+ T-cell infiltration in the subepithelial area and also highlighted a disorganized elastin fiber network in the uvular tissue in these patients.13 These inflammatory features may originate in part from tissue damage consecutive to UA fluttering.14 In addition to these local inflammation features, many studies15,16 have indicated that the levels of proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 are elevated in the serum of patients with OSA.

TNF-α is a pleiotropic proinflammatory cytokine that exerts multiple physiologic effects, including a role in sleep regulation and muscle contractility.17,18 Thus, TNF-α has been shown to reduce non-rapid eye movement sleep17 and to reduce UA muscle contractility in animal models such as dogs or hamster.1921 Kataoka et al22 also reported a decrease in TNF-α plasma level following the surgical cure of OSA. Moreover, the serum TNF-α level is reduced following 1 month of nasal continuous positive airway pressure therapy,15 suggesting that sleep-disordered breathing may have a causal role in local and systemic TNF-α production. Despite the importance of the expression pattern of inflammatory markers in the pathophysiology of OSA, to our knowledge, no study has focused on the particular expression of this cytokine on UA muscular and perimuscular tissues. Considering the proinflammatory properties of TNF-α and its ability to alter muscle contraction, the aim of the present study was to compare TNF-α expression in uvular tissues between snorers and OSA patients.

Subjects

Forty consecutive subjects who underwent UPPP for the treatment of OSA or nonapneic snoring were included in the study over a 4-year period. None of the subjects had been previously treated for OSA or snoring at the time of surgery. No subject was receiving therapy with neuroleptics, antidepressants, thyroid hormone, or any medication that affects breathing during sleep. No subjects with diabetes mellitus were included. Reported alcohol consumption went from absent (3 nonapneic subjects, 7 apneic subjects) to moderate (two or fewer glasses of an alcoholic beverage per day) among the other subjects. No subject was known to have asthma or allergic rhinitis, and none were using topical steroids. All subjects underwent a conventional polysomnographic recording before undergoing UPPP. When patients were scheduled for UPPP, one of the investigator (F.S.) looked at the eligibility criteria (ie, the absence of exclusion criteria), and subjects were then contacted for participation. Of note, no eligible patient refused to participate. The 40 subjects were distributed into three groups. The first group consisted of nonapneic snorers, the second one consisted of patients with OSA whose body mass index (BMI) was similar to those of nonapneic snorers (OSA 1 group), and the third group was made up of subjects with OSA who could not be matched with nonapneic snorers on the basis of their BMI (OSA 2 group). We did not use any BMI cutoff point to attribute each subject to a specific group. The first step in the assignment of subjects to the different groups was to collect their phenotypes in terms of apnea-hypopnea index (AHI). After OSA patients and nonapneic snorers, subjects from these two groups were matched for BMI without using any given cutoff value. This strategy was used to define the nonapneic snorers and the subjects in OSA 1 group. Subjects whose BMI could not be matched with that of nonapneic subjects thereafter were assigned to the OSA 2 group. The assignment of subjects in each group was performed at the end of the study according to polysomnography results and anthropometric characteristics. The ethical review board of our institution (Hôpital Laval; Québec, QC, Canada) approved the protocol, and a written informed consent form was obtained from each subject.

Sleep Studies

The sleep studies were conducted using conventional polysomnographic techniques.23 Airflow was quantified with the nasal pressure signal obtained from nasal prongs (nasal CO2 sample line; Datex-Ohmeda; Madison, WI) connected to a pressure transducer (Validyne Engineering; Northbridge, CA) ± 100 cm H2O.24 Apnea was defined as an interruption of airflow for > 10 s. Hypopnea was defined as a 50% reduction in the airflow or a clear reduction in signal amplitude for > 10 s that was associated with a drop of at least 4% in blood oxygen saturation and/or arousal or awakening.

Tissue Processing

Uvular tissue samples were resected during a conventional UPPP procedure as previously described.25 After surgery, the resected tissue was immediately divided into two sections. The proximal section was divided transversely. One half was frozen in optimal cutting temperature compound (Ted Pella; Redding, CA) for immunochemistry and Western blot analysis, while the other half was carefully dissected into muscular and perimuscular areas and then was frozen in liquid nitrogen for Western blot analysis. The remaining specimens were kept frozen at − 80°C for further use. All experimental analyses were performed with the investigators blinded to the sleep apnea status of the subjects.

Immunohistochemistry

Sections (6 μm each) were cut from frozen tissues and fixed with an acetone (60%)/methanol (40%) solution for 10 min at − 20°C. Immunochemistry staining was performed as we previously reported.26 Briefly, sections were washed three times for 5 min with Tris-buffered solution. Endogenous peroxidase was blocked for 30 min with a peroxidase block solution (Dako; Ontario, CA). Sections were treated with the protein block solution (Dako) to avoid an unspecific signal. Sections were then stained with a rabbit antihuman TNF-α antibody solution (dilution, 1:75) [Abcam; Cambridge, MA] or with an isotopic antibody as a negative control for 1 h. Sections were washed and incubated with a biotinylated secondary antibody (Dako). A preformed avidin-biotin-horseradish peroxidase complex (Dako) was then added. To detect bounded antibodies, sections were incubated with an aminoethylcarbazole substrate until staining was visible by microscope. Washing with water stopped the reaction. Mayer hematoxylin was used for counterstaining. Slides were mounted with a reagent (crystal/Mount reagent; Biomeda; Foster City, CA).

Western Blot Analysis

Western blot analysis was performed as we previously reported.27 Briefly, uvular samples were crushed and then lysed in lysis buffer containing 25 mmol/L Tris-Cl (pH 7.5), 150 mmol/L NaCl, 1 mmol/L ethylenediaminetetraacetic acid, 10% glycerol, 1% Triton, 0.1% sodium dodecyl sulfate (SDS), and 0.05% sodium deoxycholate. Proteinase inhibitor phenylmethylsulfonyl fluoride (1 mmol/L) was added to the homogenized samples. After 1 h of incubation at 4°C, the samples were centrifuged at ≥ 12,000g for 3 min. Supernatants were collected and stored at − 80°C. Protein concentration was determined using the Bradford assay.

Equal amounts of total protein (20 μg) in reducing sample buffer (61.5 mmol/L Tris, 2% SDS, 10% glycerol, and 5% β-mercaptoethanol) were boiled for 5 min and migrated using 4.5% stacking gel followed by 10% or 12% acrylamide SDS-polyacrylamide gel electrophoresis for 120 min at 75 V. Proteins were then transferred to polyvinylidene difluoride membranes using a Tris-glycine refrigerated transfer buffer (25 mmol/L Tris, 192 mmol/L glycine, and 20% methanol) for 60 min at 100 V. Blots were incubated overnight with anti-TNF-α antibody solution (1:1000) [Biomeda]. Membranes were washed with Tris-buffered solution-Tween and incubated for 60 min with an antimouse peroxidase-conjugated antibody (1:5,000) [Amersham Pharmacia Biotech; Piscataway, NJ]. Detection was carried out (ECL detection system; Millipore; Billerica, MA) according to the instructions of the manufacturer. Luminescence was visualized by autoradiography.

Quantification and Analysis

Image analysis was used to quantify the staining. All slides were labeled by using a randomly assigned numeric code to achieve blinding as to group designation. Four consecutive visual fields of stained slides of the proximal muscular and epithelial areas were randomly analyzed at × 20 magnification, using a slider camera (SPOT RT; Diagnostic Instruments; Sterling Heights, MI). Analysis of the muscular and epithelial staining was performed by manual tag using a commercial software package (Image-Pro Plus; Media Cybernetics; Silver Spring, MD), which allowed us to retrieve all nonmuscular or epithelial space during the quantification process. Sections with a muscle or epithelial layer area of < 0.5 mm2 were excluded from staining quantification. Data were expressed as the percentage of staining per square millimeter of the entire surface measured.

Western blot analysis was performed on six randomly chosen patients from each group. Two sets of Western blot analyses were performed, with each set using three different patients from each group. These two Western blot experiments provided the same results using densitometric analysis software (GeneSnap; Syngene; Frederick, MD). Data were expressed as the percentage of TNF expression.

Statistical Analysis

Data were expressed as the mean ± SEM. The cross-nested design was used to analyze three experimental factors, one associated with the comparison among groups (factor fixed); one linked to the subjects (nested random factor in the group); and one associated with the comparison among results from the different tissues (factor fixed). A mixed-model analysis was performed with interaction terms between the fixed factors. To proceed with the analysis, we used a model with an unstructured covariance among measurements. Values were log transformed to stabilize variances, and the arcsinus of the square root transformation was used for data expressed as a percentage. The reported p values are based on these transformations. The variance assumptions were verified using the Brown and Forsythe variation of the Levene test statistic. The univariate normality assumptions were verified with the Shapiro-Wilks test. The results were considered to be significant with p values ≤ 0.05. All analyses were conducted using a statistical software package (SAS, version 9.1.3; SAS Institute; Cary, NC).

Subject Characteristics

Anthropometric and polysomnographic data of participating subjects are summarized in Table 1. There was a similar number of smokers in each group (three smokers among 14 nonapneic snorers; three smokers among 14 subjects in the OSA 1 group; and three smokers among 12 subjects in the OSA 2 group). The other subjects were nonsmokers or had stopped smoking for > 1 year. According to the selection criteria, patients in OSA 2 group had a significantly higher BMI than subjects in the two other groups (p < 10−8). Patients in the OSA 1 and OSA 2 groups differed in neck circumference, which was also significantly higher than for snorers (p < 10−7). Associated comorbidities were not frequently seen in the studied population (Table 1). No significant difference was found in AHI or in the magnitude of the nocturnal fall in arterial oxygen saturation (Sao2) between the two OSA groups (Table 1).

Table Graphic Jump Location
Table 1 Anthropometric and Polysomnographic Data of Nonapneic Snorers and Patients With OSA*

*Values are given as the mean ± SD, unless otherwise indicated. NS = not significant; GERD = gastroesophageal reflux disease; %TST < 90% Sao2 = percentage of total sleep time spent with Sao2 < 90%; ASA = acetylsalicylic acid.

†No significant difference among groups.

‡Significantly different from the other two groups.

§All groups are significantly different from each other.

Immunohistochemistry

The immunohistochemical analysis of frozen sections of uvula revealed a strong TNF staining in the different uvula compartments such as blood vessels, muscular tissue, and epithelial layer (Fig 1). The three groups did not differ in their respective values of muscle and epithelial section area (Table 2). TNF-α staining in the musculus uvulae (MU) area was significantly higher than that in the epithelial area (61.8 ± 5.2 vs 35.7 ± 5.4 staining per square millimeter; p = 0.0006) in all subjects independent of the group they belonged to.

Figure Jump LinkFigure 1 Immunohistochemical staining (original × 20) of TNF-α expression in uvula sections. TNF-α in the MU (right) and in the epithelial layer (left) in an OSA subject. Positive structures are brown, corresponding to the common staining. M = muscle; E = epithelial layerGrahic Jump Location
Table Graphic Jump Location
Table 2 Area Sections Measured for Quantification Analysis*

*Values are given as the mean ± SD, unless otherwise indicated. Values for each group are not significantly different from each other.

TNF-α Expression in Uvular Tissue Protein Extract

TNF-α expression measured in the whole proximal uvula significantly differed between snorers and subjects in the two apneic groups, but no difference was found between the OSA 1 and OSA 2 groups (Fig 2). In order to determine which compartment was the most important source of TNF-α, muscular and perimuscular area protein extracts were prepared. In the muscular area, TNF-α was more highly expressed in subjects in the OSA 2 group than in those in the OSA 1 and snorers groups (snorers, 100.3 ± 3%; OSA 1 group, 107.4 ± 0.7%; OSA 2 group, 124.1 ± 4.2%; p = 0.007) [Fig 3]. A strong correlation was found between the muscular area TNF expression and both BMI (r = 0.87; p = 0.02) and Epworth sleepiness score (r = 0.82; p = 0.007), while no significant correlation was found with neck circumference, apnea index, AHI, oxygen desaturation index, and the percentage of total sleep time spent with an Sao2 < 90%. The same pattern of correlation was found when only considering apneic patients in the OSA 1 and OSA 2 groups. In the perimuscular area, no significant difference was found between groups (data not shown).

Figure Jump LinkFigure 2 TNF-α expression in whole proximal uvula tissue. Top, A: a representative blot of TNF-α expression in the whole proximal uvula for snorers, and subjects in the OSA 1 and OSA 2 groups. Bottom, B: a densitometric analysis of all experiments. For a given parameter, data assigned with different letters are significantly different from those of the other groupsGrahic Jump Location
Figure Jump LinkFigure 3 TNF-α expression in muscular area of the uvula. Top, A: a representative blot of TNF-α expression in samples from the muscular area of the uvula obtained from snorers, and subjects in the OSA 1 and OSA 2 groups. Bottom, B: a densitometric analysis of all experiments. For a given parameter, data assigned with different letters are significantly different from those of the other groupsGrahic Jump Location

The contribution of the muscular and perimuscular compartments to TNF-α expression in the uvular tissue was compared in each group. TNF-α expression was significantly lower in the muscular area than in the perimuscular area in the snorers group (Fig 4). The opposite pattern was observed in the OSA 2 group, but no difference was found in the OSA 1 group (Fig 4).

Figure Jump LinkFigure 4 Individual values of TNF-α expression in the muscular and perimuscular areas in each group. The results of densitometric analysis of TNF-α expression determined by Western blot analysis performed for the MU and perimuscular areas in snorers, and subjects in the OSA 1 and OSA 2 groupsGrahic Jump Location

We found that TNF-α is more highly expressed in the MU of obese patients and in the perimuscular area of nonapneic snorers. This suggests that in snoring patients with or without sleep apnea, obesity plays a more important role than sleep apnea status in the expression of inflammatory markers in uvula muscular tissue. However, the compartmental expression of TNF-α may also be influenced by sleep apnea status.

For a decade, systemic and UA inflammation has been linked to OSA, and it has been hypothesized that this inflammatory process may contribute to UA mechanical tissue injury. Systemic inflammation in patients with OSA is characterized by increased plasma levels of TNF-α, IL-6, C-reactive protein, IL-1β, reactive oxygen species, and adhesion molecules.28,29 Several studies30,31 have focused on systemic inflammation in OSA subjects, but local airway tissue inflammation is also present and likely contributes to UA mechanical and neuromuscular dysfunction. In this study, we found that TNF-α was expressed in muscular and nonmuscular uvula compartments mainly in the MU, the epithelial layer, and the glands. MU and epithelial layer TNF-α staining did not reveal a significant difference among the three groups, but in each group the MU was more highly stained than the epithelial layer, suggesting that the MU is the main TNF-α source in the uvula. We did not determine the circulating TNF-α level and therefore cannot make a link between tissular and circulating TNF-α levels. Interestingly, a previous study by Kataoka et al22 demonstrated that in OSA patients, UA surgery leads to a significant decrease in circulating TNF-α levels. This suggests that the UA represent a potential source of inflammatory mediators that are prone to be released into the circulation and contribute to a systemic inflammatory state. Further studies will have to investigate to what extent circulating levels of TNF-α mirror the inflammatory profile of UA tissue. Of interest, some drugs such as indomethacin have been shown to modulate circulating TNF-α levels, but their effect on levels of TNF-α in tissue remains unknown. Considering the effects of medications that were described previously and the fact that we were able to identify differences in the levels of TNF-α in tissue among the different groups, we do not believe that our results were influenced by medication intake in any way.

One aim of our study was to identify the main histologic structure responsible for TNF-α expression in the uvula. To investigate this, we evaluated TNF-α expression in the whole uvula as well as in muscular and perimuscular areas by Western blot analysis. In the whole uvula, we found that TNF-α was more highly expressed among apneic patients (OSA 1 group and OSA 2 group) compared to snorers without significant difference between OSA 1 and OSA 2 subjects. We also found that TNF-α was highly expressed in the muscular areas of OSA 2 subjects compared to both OSA 1 subjects and snorers, while no differences were found in the perimuscular area among the three groups. These data emphasize the importance of compartmental TNF-α expression in the uvula, with the MU being the main source of TNF-α in the uvula. Changes in UA histologic features associated with obesity and/or recurrent UA closure at night could account for these findings. Muscle is able to produce TNF-α in response to different stimuli such as eccentric muscle contraction. Histologic damage compatible with such a contraction pattern has been reported in UA muscles in animal models of OSA31,32 and also in humans.33 On the other hand, adipose tissue is also able to produce TNF-α,34 and several studies35,36 have reported an increased muscle and fat content in the uvular tissue of OSA patients. As OSA 2 and OSA 1 subjects differ on the basis of their BMI, the difference between OSA 2 subjects and both OSA 1 subjects and snorers may be explained by the increased TNF-α production by the UA muscle tissue, by adipose tissue infiltration that is generally interdigitated in muscle bundles, and/or by increased TNF-α production by the seromucous glands, which are in close proximity with the muscle bundles in more obese OSA patients.3739 Taken together, these conditions could account for the increased TNF-α expression in OSA patients compared to snorers and at the same time highlight the fact that obesity is a determining factor for the TNF expression of the MU but not for TNF-α expression in the uvula overall. The pathophysiologic conditions detailed previously in this study could account for the switch from higher perimuscular TNF-α expression in the snorers group to higher muscular expression in the OSA 2 group.

No measurements were obtained from subjects in a nonsnoring group. We acknowledge that results from such a group would be helpful in evaluating the effect of snoring per se on UA tissue inflammatory features. Since it would be inconceivable to perform a UPPP in the absence of snoring, one possibility would have been to perform a postmortem UA resection. However, just as a polysomnographic study had to be performed in all of our subjects, the positive value of including a nonsnoring group would strictly depend on our ability to firmly exclude any possible diagnosis of sleep-disordered breathing in these subjects. Given the low diagnostic value of clinical prediction rules,40 we believe that including data from subjects whose nocturnal respiratory status was not quantitatively assessed would be associated with a nonacceptable bias. Another possibility would be to collect other UA tissues such as tonsillar tissue from patients undergoing tonsillectomies. However, the effect of recurrent infection on tissue inflammatory features could significantly interfere with measurements such as those conducted in the present study independent of any potential effect of age and BMI.41 Therefore, when it is ethically unacceptable to collect UA tissue samples (other than limited tongue biopsy specimens) in a well-selected and well-identified population, free of any surgical indication, the absence of data coming from nonsnoring subjects in our study should be considered as inevitable.

Several studies have revealed an association between excess weight and increased levels of circulating inflammatory markers such as IL-6 and TNF-α.42 In a dog model of sleep apnea,19,20 the systemic administration of TNF-α reduced diaphragm force production, thus supported the role of TNF-α in muscle dysfunction. A similar alteration in muscle contractile properties can be replicated in vitro by exposing isolated muscle preparations to recombinant TNF-α in other animal models such as hamster or rat.1921 Vgontzas and coworkers43 have shown that inhibiting TNF-α binding to its receptor with etanercept, which is a dimeric fusion protein that specifically binds to TNF-α and blocks its interaction with cell surface TNF-α receptors, is associated with a significant reduction in the frequency of sleep-induced disordered breathing in obese patients with OSA. In this context, the improvement in sleep-related disordered breathing following weight loss may be attributed to the decrease in UA loading but also to the improvement in the dilating force developed by UA muscle contraction due to the reduction of local TNF-α infiltration in a reciprocal relationship. Thus, further studies are required to evaluate the importance of this local inflammation and the mechanisms by which it may contribute to the pathophysiology of OSA.

AHI

apnea-hypopnea index

BMI

body mass index

IL

interleukin

MU

musculus uvulae

OSA

obstructive sleep apnea

Sao2

arterial oxygen saturation

SDS

sodium dodecyl sulfate

TNF

tumor necrosis factor

UA

upper airway

UPPP

uvulopalatopharyngoplasty

The authors thank Doris Cantin, of the “Banque de tissus de l'Hôpital Laval,” for technical assistance, and Serge Simard for statistical analysis. We also thank the patients for their acceptance to participate in the study, and Dr. Sylvain Saint-Pierre for his collaboration during surgical procedures.

Remmers JE, deGroot WJ, Sauerland EK, et al. Pathogenesis of upper airway occlusion during sleep. J Appl Physiol. 1978;44:931-938. [PubMed]
 
Onal E, Lopata M, O'Connor T. Pathogenesis of apneas in hypersomnia-sleep apnea syndrome. Am Rev Respir Dis. 1982;125:167-174. [PubMed]
 
Kales A, Soldatos CR, Kales JD. Sleep disorders: insomnia, sleepwalking, night terrors, nightmares, and enuresis. Ann Intern Med. 1987;106:582-592. [PubMed]
 
Bixler EO, Vgontzas AN, Ten Have T, et al. Effects of age on sleep apnea in men: I. Prevalence and severity. Am J Respir Crit Care Med. 1998;157:144-148. [PubMed]
 
Weitzman ED, Pollak C, Borowiecki B, et al. The hypersomnia sleep-apnea syndrome: site and mechanism of upper airway obstruction. Trans Am Neurol Assoc. 1977;102:150-153. [PubMed]
 
Young T, Palta M, Dempsey J, et al. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med. 1993;328:1230-1235. [PubMed] [CrossRef]
 
Redline S, Tishler PV, Hans MG, et al. Racial differences in sleep-disordered breathing in African-Americans and Caucasians. Am J Respir Crit Care Med. 1997;155:186-192. [PubMed]
 
Guilleminault C, Van den Hoed J, Mitler M.Guilleminault C, Dement WC. Clinical overview of the sleep apnea syndrome. Sleep apnea syndromes. 1978; New York, NY Alan R. Liss:1-12
 
Tobin MJ. Sleep-disordered breathing, control of breathing, respiratory muscles, and pulmonary function testing in AJRCCM 2001. Am J Respir Crit Care Med. 2002;165:584-597. [PubMed]
 
Wiegand L, Zwillich CW, Wiegand D, et al. Changes in upper airway muscle activation and ventilation during phasic REM sleep in normal men. J Appl Physiol. 1991;71:488-497. [PubMed]
 
Carrera M, Barbe F, Sauleda J, et al. Patients with obstructive sleep apnea exhibit genioglossus dysfunction that is normalized after treatment with continuous positive airway pressure. Am J Respir Crit Care Med. 1999;159:1960-1966. [PubMed]
 
Paulsen FP, Steven P, Tsokos M, et al. Upper airway epithelial structural changes in obstructive sleep-disordered breathing. Am J Respir Crit Care Med. 2002;166:501-509. [PubMed]
 
Series F, Chakir J, Boivin D. Influence of weight and sleep apnea status on immunologic and structural features of the uvula. Am J Respir Crit Care Med. 2004;170:1114-1119. [PubMed]
 
Rubinstein I. Nasal inflammation in patients with obstructive sleep apnea. Laryngoscope. 1995;105:175-177. [PubMed]
 
Minoguchi K, Tazaki T, Yokoe T, et al. Elevated production of tumor necrosis factor-α by monocytes in patients with obstructive sleep apnea syndrome. Chest. 2004;126:1473-1479. [PubMed]
 
Vgontzas AN, Papanicolaou DA, Bixler EO, et al. Elevation of plasma cytokines in disorders of excessive daytime sleepiness: role of sleep disturbance and obesity. J Clin Endocrinol Metab. 1997;82:1313-1316. [PubMed]
 
Takahashi S, Kapas L, Seyer JM, et al. Inhibition of tumor necrosis factor attenuates physiological sleep in rabbits. Neuroreport. 1996;7:642-646. [PubMed]
 
Reid MB, Lannergren J, Westerblad H. Respiratory and limb muscle weakness induced by tumor necrosis factor-α: involvement of muscle myofilaments. Am J Respir Crit Care Med. 2002;166:479-484. [PubMed]
 
Wilcox PG, Wakai Y, Walley KR, et al. Tumor necrosis factor α decreasesin vivodiaphragm contractility in dogs. Am J Respir Crit Care Med. 1994;150:1368-1373. [PubMed]
 
Wilcox P, Milliken C, Bressler B. High-dose tumor necrosis factor α produces an impairment of hamster diaphragm contractility: attenuation with a prostaglandin inhibitor. Am J Respir Crit Care Med. 1996;153:1611-1615. [PubMed]
 
Li X, Moody MR, Engel D, et al. Cardiac-specific overexpression of tumor necrosis factor-α causes oxidative stress and contractile dysfunction in mouse diaphragm. Circulation. 2000;102:1690-1696. [PubMed]
 
Kataoka T, Enomoto F, Kim R, et al. The effect of surgical treatment of obstructive sleep apnea syndrome on the plasma TNF-α levels. Tohoku J Exp Med. 2004;204:267-272. [PubMed]
 
American Sleep Disorders Association. EEG arousals: scoring rules and examples; a preliminary report from the Sleep Disorders Atlas Task Force of the American Sleep Disorders Association. Sleep. 1992;15:173-184. [PubMed]
 
Series F, Marc I. Nasal pressure recording in the diagnosis of sleep apnoea hypopnoea syndrome. Thorax. 1999;54:506-510. [PubMed]
 
Series FJ, Simoneau SA, St. Pierre S, et al. Characteristics of the genioglossus and musculus uvulae in sleep apnea hypopnea syndrome and in snorers. Am J Respir Crit Care Med. 1996;153:1870-1874. [PubMed]
 
Chakir J, Laviolette M, Boutet M, et al. Lower airways remodeling in nonasthmatic subjects with allergic rhinitis. Lab Invest. 1996;75:735-744. [PubMed]
 
Semlali A, Jacques E, Plante S, et al. TGF-β suppresses EGF-induced MAPK signalling and proliferation in asthmatic epithelial cells. Am J Respir Cell Mol Biol. 2008;38:202-208. [PubMed]
 
Hatipoglu U, Rubinstein I. Inflammation and obstructive sleep apnea syndrome pathogenesis: a working hypothesis. Respiration. 2003;70:665-671. [PubMed]
 
Lavie L. Obstructive sleep apnoea syndrome: an oxidative stress disorder. Sleep Med Rev. 2003;7:35-51. [PubMed]
 
Sekosan M, Zakkar M, Wenig BL, et al. Inflammation in the uvula mucosa of patients with obstructive sleep apnea. Laryngoscope. 1996;106:1018-1020. [PubMed]
 
Boyd JH, Petrof BJ, Hamid Q, et al. Upper airway muscle inflammation and denervation changes in obstructive sleep apnea. Am J Respir Crit Care Med. 2004;170:541-546. [PubMed]
 
Petrof BJ, Pack AI, Kelly AM, et al. Pharyngeal myopathy of loaded upper airway in dogs with sleep apnea. J Appl Physiol. 1994;76:1746-1752. [PubMed]
 
Petrof BJ, Hendricks JC, Pack AI. Does upper airway muscle injury trigger a vicious cycle in obstructive sleep apnea? A hypothesis. Sleep. 1996;19:465-471. [PubMed]
 
Ryden M, Arner P. Tumour necrosis factor-α in human adipose tissue: from signalling mechanisms to clinical implications. J Intern Med. 2007;262:431-438. [PubMed]
 
Stauffer JL, Buick MK, Bixler EO, et al. Morphology of the uvula in obstructive sleep apnea. Am Rev Respir Dis. 1989;140:724-728. [PubMed]
 
Zohar Y, Buler N, Shvilli Y, et al. Reconstruction of the soft palate by uvulopalatal flap. Laryngoscope. 1998;108:47-50. [PubMed]
 
Berger G, Gilbey P, Hammel I, et al. Histopathology of the uvula and the soft palate in patients with mild, moderate, and severe obstructive sleep apnea. Laryngoscope. 2002;112:357-363. [PubMed]
 
Ettema SL, Kuehn DP. A quantitative histologic study of the normal human adult soft palate. J Speech Hear Res. 1994;37:303-313. [PubMed]
 
Kuehn DP, Templeton PJ, Maynard JA. Muscle spindles in the velopharyngeal musculature of humans. J Speech Hear Res. 1990;33:488-493. [PubMed]
 
Herer B, Roche N, Carton M, et al. Value of clinical, functional, and oximetric data for the prediction of obstructive sleep apnea in obese patients. Chest. 1999;116:1537-1544. [PubMed]
 
Tauman R, Gulliver TE, Krishna J, et al. Persistence of obstructive sleep apnea syndrome in children after adenotonsillectomy. J Pediatr. 2006;149:803-808. [PubMed]
 
Laimer M, Ebenbichler CF, Kaser S, et al. Markers of chronic inflammation and obesity: a prospective study on the reversibility of this association in middle-aged women undergoing weight loss by surgical intervention. Int J Obes Relat Metab Disord. 2002;26:659-662. [PubMed]
 
Vgontzas AN, Zoumakis E, Lin HM, et al. Marked decrease in sleepiness in patients with sleep apnea by etanercept, a tumor necrosis factor-α antagonist. J Clin Endocrinol Metab. 2004;89:4409-4413. [PubMed]
 

Figures

Figure Jump LinkFigure 1 Immunohistochemical staining (original × 20) of TNF-α expression in uvula sections. TNF-α in the MU (right) and in the epithelial layer (left) in an OSA subject. Positive structures are brown, corresponding to the common staining. M = muscle; E = epithelial layerGrahic Jump Location
Figure Jump LinkFigure 2 TNF-α expression in whole proximal uvula tissue. Top, A: a representative blot of TNF-α expression in the whole proximal uvula for snorers, and subjects in the OSA 1 and OSA 2 groups. Bottom, B: a densitometric analysis of all experiments. For a given parameter, data assigned with different letters are significantly different from those of the other groupsGrahic Jump Location
Figure Jump LinkFigure 3 TNF-α expression in muscular area of the uvula. Top, A: a representative blot of TNF-α expression in samples from the muscular area of the uvula obtained from snorers, and subjects in the OSA 1 and OSA 2 groups. Bottom, B: a densitometric analysis of all experiments. For a given parameter, data assigned with different letters are significantly different from those of the other groupsGrahic Jump Location
Figure Jump LinkFigure 4 Individual values of TNF-α expression in the muscular and perimuscular areas in each group. The results of densitometric analysis of TNF-α expression determined by Western blot analysis performed for the MU and perimuscular areas in snorers, and subjects in the OSA 1 and OSA 2 groupsGrahic Jump Location

Tables

Table Graphic Jump Location
Table 1 Anthropometric and Polysomnographic Data of Nonapneic Snorers and Patients With OSA*

*Values are given as the mean ± SD, unless otherwise indicated. NS = not significant; GERD = gastroesophageal reflux disease; %TST < 90% Sao2 = percentage of total sleep time spent with Sao2 < 90%; ASA = acetylsalicylic acid.

†No significant difference among groups.

‡Significantly different from the other two groups.

§All groups are significantly different from each other.

Table Graphic Jump Location
Table 2 Area Sections Measured for Quantification Analysis*

*Values are given as the mean ± SD, unless otherwise indicated. Values for each group are not significantly different from each other.

References

Remmers JE, deGroot WJ, Sauerland EK, et al. Pathogenesis of upper airway occlusion during sleep. J Appl Physiol. 1978;44:931-938. [PubMed]
 
Onal E, Lopata M, O'Connor T. Pathogenesis of apneas in hypersomnia-sleep apnea syndrome. Am Rev Respir Dis. 1982;125:167-174. [PubMed]
 
Kales A, Soldatos CR, Kales JD. Sleep disorders: insomnia, sleepwalking, night terrors, nightmares, and enuresis. Ann Intern Med. 1987;106:582-592. [PubMed]
 
Bixler EO, Vgontzas AN, Ten Have T, et al. Effects of age on sleep apnea in men: I. Prevalence and severity. Am J Respir Crit Care Med. 1998;157:144-148. [PubMed]
 
Weitzman ED, Pollak C, Borowiecki B, et al. The hypersomnia sleep-apnea syndrome: site and mechanism of upper airway obstruction. Trans Am Neurol Assoc. 1977;102:150-153. [PubMed]
 
Young T, Palta M, Dempsey J, et al. The occurrence of sleep-disordered breathing among middle-aged adults. N Engl J Med. 1993;328:1230-1235. [PubMed] [CrossRef]
 
Redline S, Tishler PV, Hans MG, et al. Racial differences in sleep-disordered breathing in African-Americans and Caucasians. Am J Respir Crit Care Med. 1997;155:186-192. [PubMed]
 
Guilleminault C, Van den Hoed J, Mitler M.Guilleminault C, Dement WC. Clinical overview of the sleep apnea syndrome. Sleep apnea syndromes. 1978; New York, NY Alan R. Liss:1-12
 
Tobin MJ. Sleep-disordered breathing, control of breathing, respiratory muscles, and pulmonary function testing in AJRCCM 2001. Am J Respir Crit Care Med. 2002;165:584-597. [PubMed]
 
Wiegand L, Zwillich CW, Wiegand D, et al. Changes in upper airway muscle activation and ventilation during phasic REM sleep in normal men. J Appl Physiol. 1991;71:488-497. [PubMed]
 
Carrera M, Barbe F, Sauleda J, et al. Patients with obstructive sleep apnea exhibit genioglossus dysfunction that is normalized after treatment with continuous positive airway pressure. Am J Respir Crit Care Med. 1999;159:1960-1966. [PubMed]
 
Paulsen FP, Steven P, Tsokos M, et al. Upper airway epithelial structural changes in obstructive sleep-disordered breathing. Am J Respir Crit Care Med. 2002;166:501-509. [PubMed]
 
Series F, Chakir J, Boivin D. Influence of weight and sleep apnea status on immunologic and structural features of the uvula. Am J Respir Crit Care Med. 2004;170:1114-1119. [PubMed]
 
Rubinstein I. Nasal inflammation in patients with obstructive sleep apnea. Laryngoscope. 1995;105:175-177. [PubMed]
 
Minoguchi K, Tazaki T, Yokoe T, et al. Elevated production of tumor necrosis factor-α by monocytes in patients with obstructive sleep apnea syndrome. Chest. 2004;126:1473-1479. [PubMed]
 
Vgontzas AN, Papanicolaou DA, Bixler EO, et al. Elevation of plasma cytokines in disorders of excessive daytime sleepiness: role of sleep disturbance and obesity. J Clin Endocrinol Metab. 1997;82:1313-1316. [PubMed]
 
Takahashi S, Kapas L, Seyer JM, et al. Inhibition of tumor necrosis factor attenuates physiological sleep in rabbits. Neuroreport. 1996;7:642-646. [PubMed]
 
Reid MB, Lannergren J, Westerblad H. Respiratory and limb muscle weakness induced by tumor necrosis factor-α: involvement of muscle myofilaments. Am J Respir Crit Care Med. 2002;166:479-484. [PubMed]
 
Wilcox PG, Wakai Y, Walley KR, et al. Tumor necrosis factor α decreasesin vivodiaphragm contractility in dogs. Am J Respir Crit Care Med. 1994;150:1368-1373. [PubMed]
 
Wilcox P, Milliken C, Bressler B. High-dose tumor necrosis factor α produces an impairment of hamster diaphragm contractility: attenuation with a prostaglandin inhibitor. Am J Respir Crit Care Med. 1996;153:1611-1615. [PubMed]
 
Li X, Moody MR, Engel D, et al. Cardiac-specific overexpression of tumor necrosis factor-α causes oxidative stress and contractile dysfunction in mouse diaphragm. Circulation. 2000;102:1690-1696. [PubMed]
 
Kataoka T, Enomoto F, Kim R, et al. The effect of surgical treatment of obstructive sleep apnea syndrome on the plasma TNF-α levels. Tohoku J Exp Med. 2004;204:267-272. [PubMed]
 
American Sleep Disorders Association. EEG arousals: scoring rules and examples; a preliminary report from the Sleep Disorders Atlas Task Force of the American Sleep Disorders Association. Sleep. 1992;15:173-184. [PubMed]
 
Series F, Marc I. Nasal pressure recording in the diagnosis of sleep apnoea hypopnoea syndrome. Thorax. 1999;54:506-510. [PubMed]
 
Series FJ, Simoneau SA, St. Pierre S, et al. Characteristics of the genioglossus and musculus uvulae in sleep apnea hypopnea syndrome and in snorers. Am J Respir Crit Care Med. 1996;153:1870-1874. [PubMed]
 
Chakir J, Laviolette M, Boutet M, et al. Lower airways remodeling in nonasthmatic subjects with allergic rhinitis. Lab Invest. 1996;75:735-744. [PubMed]
 
Semlali A, Jacques E, Plante S, et al. TGF-β suppresses EGF-induced MAPK signalling and proliferation in asthmatic epithelial cells. Am J Respir Cell Mol Biol. 2008;38:202-208. [PubMed]
 
Hatipoglu U, Rubinstein I. Inflammation and obstructive sleep apnea syndrome pathogenesis: a working hypothesis. Respiration. 2003;70:665-671. [PubMed]
 
Lavie L. Obstructive sleep apnoea syndrome: an oxidative stress disorder. Sleep Med Rev. 2003;7:35-51. [PubMed]
 
Sekosan M, Zakkar M, Wenig BL, et al. Inflammation in the uvula mucosa of patients with obstructive sleep apnea. Laryngoscope. 1996;106:1018-1020. [PubMed]
 
Boyd JH, Petrof BJ, Hamid Q, et al. Upper airway muscle inflammation and denervation changes in obstructive sleep apnea. Am J Respir Crit Care Med. 2004;170:541-546. [PubMed]
 
Petrof BJ, Pack AI, Kelly AM, et al. Pharyngeal myopathy of loaded upper airway in dogs with sleep apnea. J Appl Physiol. 1994;76:1746-1752. [PubMed]
 
Petrof BJ, Hendricks JC, Pack AI. Does upper airway muscle injury trigger a vicious cycle in obstructive sleep apnea? A hypothesis. Sleep. 1996;19:465-471. [PubMed]
 
Ryden M, Arner P. Tumour necrosis factor-α in human adipose tissue: from signalling mechanisms to clinical implications. J Intern Med. 2007;262:431-438. [PubMed]
 
Stauffer JL, Buick MK, Bixler EO, et al. Morphology of the uvula in obstructive sleep apnea. Am Rev Respir Dis. 1989;140:724-728. [PubMed]
 
Zohar Y, Buler N, Shvilli Y, et al. Reconstruction of the soft palate by uvulopalatal flap. Laryngoscope. 1998;108:47-50. [PubMed]
 
Berger G, Gilbey P, Hammel I, et al. Histopathology of the uvula and the soft palate in patients with mild, moderate, and severe obstructive sleep apnea. Laryngoscope. 2002;112:357-363. [PubMed]
 
Ettema SL, Kuehn DP. A quantitative histologic study of the normal human adult soft palate. J Speech Hear Res. 1994;37:303-313. [PubMed]
 
Kuehn DP, Templeton PJ, Maynard JA. Muscle spindles in the velopharyngeal musculature of humans. J Speech Hear Res. 1990;33:488-493. [PubMed]
 
Herer B, Roche N, Carton M, et al. Value of clinical, functional, and oximetric data for the prediction of obstructive sleep apnea in obese patients. Chest. 1999;116:1537-1544. [PubMed]
 
Tauman R, Gulliver TE, Krishna J, et al. Persistence of obstructive sleep apnea syndrome in children after adenotonsillectomy. J Pediatr. 2006;149:803-808. [PubMed]
 
Laimer M, Ebenbichler CF, Kaser S, et al. Markers of chronic inflammation and obesity: a prospective study on the reversibility of this association in middle-aged women undergoing weight loss by surgical intervention. Int J Obes Relat Metab Disord. 2002;26:659-662. [PubMed]
 
Vgontzas AN, Zoumakis E, Lin HM, et al. Marked decrease in sleepiness in patients with sleep apnea by etanercept, a tumor necrosis factor-α antagonist. J Clin Endocrinol Metab. 2004;89:4409-4413. [PubMed]
 
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