α7nAChR ameliorating intestinal inflammation and intestinal barrier damage in rats with cerebral infarction by inhibiting MyD88-dependent Zonulin release

Objective: To observe the effect of the α7-type nicotinic acetylcholine receptor(α7nAChR) agonist PNU282987 on intestinal inflammation and intestinal barrier damage in rats with cerebral infarction. Methods: A total of 36 male SD rats were randomly divided into three groups: sham group, middle cerebral artery occlusion(MCAO) group, and PNU282987 group. MCAO group and PNU282987 group were prepared by Longa modified sature-embolus method, and PNU282987 group was intraperitoneally injected with 1 mg/kg PNU282987 for 7consecutive days. Hematoxylin-eosin(HE) staining was used to observe the pathological changes in intestinal mucosa. Enzyme-linked immunosorbent assay(ELISA) was performed to detect the levels of tumor necrosis factor(TNF)-α and interleukin(IL)-6 in colon tissue, and the diamine oxidase(DAO), D-lactate(DLA), endotoxin(ET)levels in serum. The expression of toll-like receptor 2(TLR2) protein in colon tissues was detected by immunohistochemistry. Western blotting was used to detect the expression of the key tight junction proteins in colon tissue, including occlusal proteins(Occludin), closed protein-1(Claudin-1), Zonulin, zona occludens(ZO-1), TLR2,myeloid differentiation factor 88(MyD88), nuclear factor-κB(NF-κB) and phosphorylated NF-κB(p-NF-κB) proteins. Results: Compared with the sham group, the MCAO group showed intestinal epithelial desquamation, disordered arrangement of intestinal villi, and inflammatory infiltration in the submucosal layer of the intestine. The levels of DAO, DLA, ET in serum, and TNF-α and IL-6 contents in colon tissue were significantly increased,while the expression of Occludin, Claudin-1, and ZO-1 proteins in colon tissue was significantly decreased, and the expression of Zonulin, TLR2, MyD88, and p-NF-κB proteins was significantly increased(all P<0.05). Compared with the MCAO group, the PNU282987 group showed reduced intestinal epithelial damage, significantly decreased levels of serum DAO, DLA, ET, and TNF-α and IL-6 contents in colon tissue, significantly increased expression of Occludin, Claudin-1, and ZO-1 proteins in colon tissue, and significantly decreased expression of Zonulin, TLR2, MyD88, and p-NF-κB proteins(all P<0.05). Conclusion: PNU282987 can significantly improve intestinal inflammation and intestinal barrier damage in rats with cerebral infarction, and its mechanism may be related to inhibition of TLR2/MyD88/NF-κB signaling pathway.