M3 Muscarinic Acetylcholine Receptor Antagonist Darifenacin Protects against Pulmonary Fibrosis through ERK/NF-κB/miR-21 Pathway

Idiopathic pulmonary fibrosis is an untreatable lethal lung disease, which is related to the aberrant proliferation of fibroblasts. M3 muscarinic acetylcholine receptor (M3-mAChR) activation exerts proliferative effect on various kinds of cells. However, whether M3-mAChR inhibition has a protective effect on pulmonary fibrosis remains unexplored. A rat model of pulmonary fibrosis was established by intratracheal instillation of bleomycin. Darifenacin was used to block M3-mAChR. Histological changes were observed using Masson’s Trichrome and hematoxylin and eosin (HE) staining. Hydroxyproline was measured by Hydroxyproline detection kit. Transforming growth factor β1 (TGF-β1) and tumor necrosis factor-α (TNF-α) were measured by enzyme-linked immunosorbent assay (ELISA). In vitro, pulmonary fibroblasts were isolated from lungs of neonatal rat. After treatment, the cell viability, Hydroxyproline level was measured by MTT and Hydroxyproline detection kit respectively. The expression level of extracellular signal-regulated kinase (ERK), nuclear factor kappa-B (N-NF-κB), and microRNA-21 (miR-21) was detected by western blot or quantitative real-time PCR (qRT-PCR). Darifenacin relieved the fibrotic effects provoked by bleomycin. The expression level of hydroxyproline, TGF-β1 and TNF-α level was all downregulated after darifenacin treatment. In lung fibroblasts, darifenacin decreased cell viability and hydroxyproline level induced by bleomycin. Besides, phosphorylation-ERK and nuclear N-NF-κB protein level was downregulated, as well as miR-21 level. M3-mAChR antagonist darifenacin attenuates bleomycin-induced pulmonary fibrosis in rats, which may relate to the ERK/NF-κB/miRNA-21 signaling pathway.

Serum IgA against type 3 muscarinic acetylcholine receptor is a novel marker in diagnosis of Sjoegren＇s syndrome

Background Antibodies against type 3 muscarinic acetylcholine receptor （M3R） are involved in the pathogenesis of Sj6gren＇s syndrome （SS）, but the clinical value of them in SS patients has been controversial. The aims of this study were to： （1） establish an improved enzyme-linked immunosorbent assay （ELISA） to detect IgA antibodies against M3R; （2） evaluate the value of IgA antibodies against the second extracellular loop of M3R205-220 （c2M3RP） in diagnosis of SS. Methods To increase the ELISA sensitivity, c2M3RP was coupled to bovine serum albumin （BSA） by the glutaraldehyde method and a 96-well microplate was treated by ultraviolet rays before coated. Concentrations of anti-c2M3RP, anti-SSA, and anti-SSB were measured in the sera of 240 individuals： 91 patients with primary SS and 149 controls （16 secondary SS, 27 systemic lupus erythematosus, 40 rheumatoid arthritis and 66 healthy controls）. Diagnostic properties of anti-c2M3RP were determined by receiver-operating characteristic curve analysis. Results The prevalence of serum IgA anti-c2M3RP antibodies in patients with pSS （46%, 42/91） was significantly higher than that in patients with systemic lupus erythematosus （19%, 5/27）, in rheumatoid arthritis （15%, 6/40） and in healthy controls （5%, 3/66）. However, there was no significant difference between the two $S groups （P=-0.727）. The diagnostic performance of IgA anti-M3RP antibodies was similar to anti-SSA assay, but had 22% higher sensitivity than anti-SSB. By analyzing of IgA anti-c2M3RP antibodies, combination of anti-SSA and anti-SSB resulted in increased sensitivity, whereas their specificity was not significantly changed. Conclusions The improved anti-c2M3RP ELISA is a novel, sensitive, and specific serological test for the diagnosis of SS. The combined application of anti-c2M3RP, anti-SSA and anti-SSB tests can improve the laboratory diagnosis of SS. The IgA anti-c2M3RP antibodies may serve as a novel diagnostic marker for SS.

Mechanisms mediating cholinergic antral circular smooth muscle contraction in rats

AIM:To investigate the pathway(s)mediating rat antral circular smooth muscle contractile responses to the cholinomimetic agent,bethanechol and the subtypes of muscarinic receptors mediating the cholinergic contraction. METHODS:Circular smooth muscle strips from the antrum of Sprague-Dawley rats were mounted in muscle baths in Krebs buffer.Isometric tension was recorded.Cumulative concentration-response curves were obtained for(+)-cis- dioxolane(cD),a nonspecific muscarinic agonist,at 10^(-8)- 10^(-4)mol/L,in the presence of tetrodotoxin(TTX,10^(-7)mol/L). Results were normalized to cross sectional area.A repeat concentration-response curve was obtained after incubation of the muscle for 90 min with antagonists for M1(pirenzepine), M2(methoctramine)and M3(darifenadn)muscarinic receptor subtypes.The sensitivity to PTX was tested by the ip injection of 100 mg/kg of PTX 5 d before the experiment.The antral circular smooth muscles were removed from PTX-treated and non-treated rats as strips and dispersed smooth muscle cells to identify whether PTX-linked pathway mediated the contractility to bethanechol. RESULTS:A dose-dependent contractile response observed with bethanechol,was not affected by TTx.The pretreatment of rats with pertussis toxin decreased the contraction induced by bethanechol.Lack of calcium as well as the presence of the L-type calcium channel blocker,nifedipine,also inhibited the cholinergic contraction,with a reduction in response from 2.5±0.4 g/mm^2 to 1.2±0.4 g/mm^2(P<0.05).The dose- response curves were shifted to the right by muscarinic antagonists in the following order of affinity:darifenacin (M_3)>methocramine(M_2)>pirenzepine(M_1). CONCLUSION:The muscarinic receptors-dependent contraction of rat antral circular smooth muscles was linked to the signal transduction pathway(s)involving pertussis-toxin sensitive GTP-binding proteins and to extracellular calcium via L-type voltage gated calcium channels.The presence of the residual contractile response after the treatment with nifedipine,suggests that an additional pathway could mediate the cholinergic contraction.The involvement of more than one muscarinic receptor(functionally predominant type 3 over type 2)also suggests more than one pathway mediating the cholinergic contraction in rat antrum.