Effect of L-cysteine on colonic motility and the underlying mechanism / 生理学报

The purpose of the present study is to investigate the effect of L-cysteine on colonic motility and the underlying mechanism. Immunohistochemical staining and Western blot were used to detect the localization of the HS-generating enzymes cystathionine-β-synthase (CBS) and cystathionine-γ-lyase (CSE). Organ bath system was used to observe the muscle contractile activities. Whole-cell patch-clamp technique was applied to record ionic channels currents in colonic smooth muscle cells. The results showed that both CBS and CSE were localized in mucosa, longitudinal and circular muscle and enteric neurons. L-cysteine had a dual effect on colonic contraction, and the excitatory effect was blocked by pretreatment with CBS inhibitor aminooxyacetate acid (AOAA) and CSE inhibitor propargylglycine (PAG); L-cysteine concentration-dependently inhibited L-type calcium channel current (I) without changing the characteristic of L-type calcium channel (P < 0.01); In contrast, the exogenous HS donor NaHS increased I at concentration of 100 μmol/L, but inhibited I and modified the channel characteristics at concentration of 300 μmol/L (P < 0.05); Furthermore, L-cysteine had no effect on large conductance calcium channel current (I), but NaHS significantly inhibited I (P < 0.05). These results suggest that L-cysteine has a potential dual effect on colonic smooth muscle and the inhibitory effect might be directly mediated by L-type calcium channel while the excitatory effect might be mediated by endogenous HS.

IL-6 inhibits colonic longitudinal muscle contraction by inactivating L-type calcium channel in rats with pancreatitis / 生理学报

The aim of this study was to investigate the effect of interleukin 6 (IL-6) on the contraction of colon longitudinal muscle strips in rats with acute pancreatitis (AP) and its underlying mechanism. Rat AP model was established by combined injection (i. p.) of ceruletide and lipopolysaccharide. The effect of IL-6 on spontaneous contraction of longitudinal smooth muscle strips of rat colon was observed by biological function experiment system. The level of serum IL-6 was detected by ELISA, the expression and distribution of IL-6 in colon were observed by histochemical staining, and the effect of IL-6 on L-type calcium channel in colon smooth muscle cells was observed by whole cell patch clamp technique. The results showed that, compared with the control group, AP group exhibited reduced contractile amplitude and longer contraction cycle of colon smooth muscle strips. IL-6 prolonged the contraction cycle of colon smooth muscle strips, but did not affect their spontaneous contraction amplitude. Serum IL-6 concentration in AP group was significantly higher than that in control group (P > 0.05). IL-6 was diffusely distributed in the colon of the control group, but the expression of IL-6 was significantly up-regulated in the colon gland, mucosa and submucosa of the AP group. IL-6 significantly decreased the peak current density of L-type calcium channel in rat colon smooth muscle cells. These results suggest that the colon motility of AP rats is weakened, and the mechanism may be that up-regulated IL-6 inactivates L-type voltage-dependent calcium channels, and then inhibits the contraction of colon longitudinal smooth muscle.

Actions of endogenous hydrogen sulfide on colonic hypermotility in a rat model of chronic stress / 生理学报

The present study was designed to investigate the potential role of endogenous hydrogen sulfide (H2S) in chronic stress-induced colonic hypermotility. Male Wistar rats were submitted daily to 1 h of water avoidance stress (WAS) or sham WAS (SWAS) for 10 consecutive days. The total number of fecal pellets was counted at the end of each 1 h of WAS or SWAS session. Organ bath recordings were used to test the colonic motility. H₂S production of colon was determined, and immunohistochemistry and Western blot were performed on rat colonic samples to detect the distribution and expression of H₂S-producing enzymes. The results showed that i) repeated WAS increased the number of fecal pellets per hour and the area under the curve (AUC) of the spontaneous contractions of colonic strips (P < 0.05), ii) repeated WAS decreased the endogenous production of H₂S and the expression of H₂S-producing enzymes in the colon devoid of mucosa and submucosa (P < 0.001), iii) cystathionine-γ-lyase (CSE) was strongly expressed in the cytosols of the circular and longitudinal smooth muscle cells and the nucleus of the myenteric plexus neurons, iv) cystathionine-β-synthase (CBS) was primarily localized in the cytosols of myenteric plexus neurons and weakly localized in the epithelial cells and v) inhibitors of H₂S-producing enzymes increased the contractile activity of colonic strips in the SWAS rats (P < 0.001). In conclusion, the results suggest that the colonic hypermotility induced by repeated WAS may be associated with the decreased production of endogenous H2S.