Muscarinic acetylcholine receptor autoantibodies in patients with Sjögren's syndrome

Interstitial cystitis and systemic autoimmune diseases

The cause of interstitial cystitis, a chronic disease that affects the bladder, is unknown. Autoantibodies, such as those against nuclear and bladder epithelium antigens, have been found in patients with interstitial cystitis, but these are likely to be secondary to the disease. No data support a direct causal role of autoimmune reactivity in the pathogenesis of interstitial cystitis. Indirect evidence, however, does support a possible autoimmune nature of interstitial cystitis, such as the strong female preponderance and the clinical association between interstitial cystitis and other known autoimmune diseases within patients and families. The strongest association occurs between interstitial cystitis and Sjögren's syndrome. Increasing evidence suggests a possible role of autoantibodies to the muscarinic M3 receptor in Sjögren's syndrome. The M3 receptor is also located on the detrusor muscle cells of the bladder and mediates cholinergic contraction of the urinary bladder and other smooth muscle tissues. Autoantibodies to the M3 receptor might be important in both the early noninflammatory and the late inflammatory features of interstitial cystitis.

Antibody testing in peripheral neuropathies

Many autoantibodies have been described in association with peripheral neuropathy, but the use of antibody testing in clinical practice remains a matter of some debate. Serum autoantibodies to gangliosides or glycoproteins are implicated in a variety of sensory and motor neuropathy syndromes. Paraneoplastic antibodies help identify patients who have a neuropathy related to an underlying malignancy. Detection of an autoantibody in the right clinical setting provides some evidence that the peripheral nerve disturbance is immune mediated and that immunomodulatory therapy may be of benefit.

Efficacy prediction of cevimeline in patients with Sjögren's syndrome

The objective of this study was to examine the clinical and immunological factors influencing the efficacy of cevimeline hydrochloride hydrate (cevimeline) for the treatment of xerostomia in patients with Sjögren's syndrome (SS). Thirty primary SS patients who were medicated with cevimeline were enrolled in this study. Whole stimulated sialometry (WSS) was compared between pre- and posttreatment points (4 weeks after oral cevimeline administration) and the increment rate of WSS was calculated. Multiple regression was employed to examine the relative contributions of the clinical and immunological factors, including age, pretreatment WSS, duration of disease, sialography, minor salivary gland biopsy, anti-Ro/SS-A antibodies, anti-La/SS-B antibodies, and antibodies to muscarinic type 3 receptors to the posttreatment WSS. Patients with normal sialography findings, negative minor salivary gland biopsy, and absence of anti-La/SS-B antibodies had significantly higher increment rates of WSS compared with those with positive findings (p=0.042, 0.002, and 0.018, respectively). Results of the multiple regression analysis showed that sialography (coefficient=-0.867, p=0.004) and minor salivary gland biopsy (coefficient=-0.869, p=0.003) had significant associations with the posttreatment WSS. Our preliminary results demonstrated the relationship between the effect of cevimeline on saliva secretion and the degree of salivary gland destruction evaluated by sialography and histopathological findings in the labial minor salivary glands. These diagnostic approaches could provide useful prognostic information on the efficacy of cevimeline in SS patients.

Overexpression of phosphorylated STAT-1alpha in the labial salivary glands of patients with Sjögren's syndrome

OBJECTIVE

To clarify the molecular mechanisms of Sjögren's syndrome (SS), we analyzed the functional role of the STAT-1 gene, one of the interferon-gamma (IFNgamma)-inducible genes, in labial salivary glands (LSGs) from SS patients.

METHODS

The expression of STAT-1 messenger RNA (mRNA) was examined by real-time polymerase chain reaction (PCR) analysis, and the phosphorylation of STAT-1 protein (Tyr(701) and Ser(727) pSTAT-1) was investigated by Western blot and immunohistochemical analyses. The expression of IFNgamma-inducible 10-kd protein (IP-10), IFN regulatory factor 1 (IRF-1), and Fas was also examined by real-time PCR and immunohistochemical analyses.

RESULTS

STAT-1alpha and STAT-1beta mRNA were highly expressed in LSGs from SS patients. The level of STAT-1alpha protein in SS LSGs was higher than that in 3 control LSGs, whereas STAT-1beta protein was not clearly detected by Western blot analysis. Moreover, Tyr(701) and Ser(727) pSTAT-1alpha proteins were specifically detected in SS LSGs. Immunohistochemical analysis showed localization of Tyr(701) pSTAT-1 in infiltrating lymphocytes and the adjacent ductal epithelium from SS patients. Ser(727) pSTAT-1 was localized only in the ductal epithelium of SS LSGs. The STAT-1-inducible genes IP-10 and IRF-1 and the Fas genes were highly expressed in SS LSGs and were colocalized with Ser(727) pSTAT-1-positive, but not Tyr(701) pSTAT-1-positive, cells.

CONCLUSION

We found evidence of the up-regulation of STAT-1alpha mRNA and protein in LSGs from SS patients, as well as the presence of pSTAT-1alpha in ductal epithelium from SS patients. Our findings suggest that STAT-1alpha, especially Ser(727) pSTAT-1, may function as a key molecule in the pathogenesis of SS.