The anti-proliferative and anti-inflammatory response of COPD airway smooth muscle cells to hydrogen sulfide

Background - COPD is a common, highly debilitating disease of the airways, primarily caused by smoking. Chronic inflammation and structural remodelling are key pathological features of this disease caused, in part, by the aberrant function of airway smooth muscle (ASM). We have previously demonstrated that hydrogen sulfide (H₂S) can inhibit ASM cell proliferation and CXCL8 release, from cells isolated from non-smokers.

Methods - We examined the effect of H₂S upon ASM cells from COPD patients. ASM cells were isolated from non-smokers, smokers and patients with COPD (n = 9). Proliferation and cytokine release (IL-6 and CXCL8) of ASM was induced by FCS, and measured by bromodeoxyuridine incorporation and ELISA, respectively.

Results - Exposure of ASM to H2S donors inhibited FCS-induced proliferation and cytokine release, but was less effective upon COPD ASM cells compared to the non-smokers and smokers. The mRNA and protein expression of the enzymes responsible for endogenous H2S production (cystathionine-β-synthase [CBS] and 3-mercaptopyruvate sulphur transferase [MPST]) were inhibited by H₂S donors. Finally, we report that exogenous H2S inhibited FCS-stimulated phosphorylation of ERK–1/2 and p38 mitogen activated protein kinases (MAPKs), in the non-smoker and smoker ASM cells, with little effect in COPD cells.

Conclusions - H₂S production provides a novel mechanism for the repression of ASM proliferation and cytokine release. The ability of COPD ASM cells to respond to H₂S is attenuated in COPD ASM cells despite the presence of the enzymes responsible for H2S production.