| Objective: The main objective of this study was to clarify the effect of PPARγ on the phenotypic transformation of vascular smooth muscle after cerebral ischemia-reperfusion and to investigate the mechanism by which PPARγ regulates the phenotypic transformation of vascular smooth muscle cells after cerebral ischemia-reperfusion.Methods: Male SD rats were randomly divided into normal and ischemia reperfusion(IR)groups for 12 h,24h,48 h and 72 h.The IR group was constructed by middle cerebral artery occlusion(MCAO)method,with 8 rats in the normal and 48 h groups and 5 rats in each of the remaining groups.Expression of PPARγ,ERK1/2,α-SMA and MYH10 in vascular tissue near the ring of Willis was determined by Western blotting,and neurological dysfunction and its extent were assessed by the Zea-Longa scale.Changes in arterial diameter and wall thickness were observed by HE staining in the normal and 48 h groups,and phenotypic transformation of vascular smooth muscle in the rat brain was determined by immunofluorescence staining technique.selected for ischemia-reperfusion for 48 h,pioglitazone intervention was given and divided into normal group,sham-operated group,MACO model 48 h group and MACO model 48 h pioglitazone intervention group,7 rats in48 h and intervention group,and 6 rats in each of the remaining groups.Each group was further investigate the regulatory mechanism of PPARγ on the phenotypic transformation of vascular smooth muscle after cerebral ischemia-reperfusion.The neurological dysfunction and its extent were also assessed by Zea-Longa scale,TTC(Triphenyltetrazolium chloride)staining was used to determine the presence and extent of cerebral infarct foci in the rats,and the expression of PPARγ,ERK1/2,α-SMA and MYH10 in vascular tissue near Willis ring was determined by Western blotting,the phenotypic transformation of vascular smooth muscle in the brain of MACO model 48 h group and MACO model 48 h pioglitazone intervention group rats was determined using immunofluorescence staining technique.Results:1.Zea-Longa score results: Except for rats in the normal and sham-operated groups with a score of 0,the score was between 2.60±0.45 in the ischemia-reperfusion 48 h group and between 1.80±0.45 in the pioglitazone intervention group,and their scores were reduced and statistically significant(P<0.05).2.HE staining results: In the normal group,the structure of cerebrovascular smooth muscle cells was normal,the nuclei were regular in shape and size,and the vessel diameter and wall thickness were not significantly changed.In the ischemia-reperfused 48 h group,the cerebrovascular smooth muscle cells of rats were obviously swollen,the nuclei were narrowed and coagulated,the vessel diameter was narrowed,the vessel wall was thickened,and the surrounding tissues were edematous.3.TTC staining results: Except for the normal group and the sham-operated group without infarct foci,the cerebral infarct volume ratio was the largest in the ischemia-reperfusion48 h group,and the infarct volume ratio was relatively reduced in the pioglitazone intervention group,and the difference was statistically significant(P<0.05).4.Immunofluorescence staining results: The expression of α-SMA was more and MYH10 was less in the vascular tissue of cerebral vessels of rats in the normal group,and the expression of α-SMA was less and MYH10 was more in the vascular tissue of cerebral arteries of rats in the 48 h group;after the intervention with pioglitazone,the expression ofα-SMA increased and the expression of MYH10 decreased in the vascular tissue of cerebral arteries of rats in the 48 h group.5.Western blotting results: The expression of PPARγ,ERK1/2,α-SMA and MYH10 in vascular tissues near the ring of Willis was dynamically altered after ischemia-reperfusion in rat brain.Compared with the normal group,the expression levels of PPARγ and ERK1/2appeared to be elevated after ischemia-reperfusion,peaked at 48 h after ischemia-reperfusion,and then began to fall back,α-SMA expression was significant in the normal group and decreased significantly after ischemia-reperfusion,While MYH10 was least expressed in the normal group,its expression increased after ischemia-reperfusion,which was statistically significant in all groups compared with the normal group(P<0.05);After the intervention with pioglitazone,the expression of PPARγ in the vascular tissue near the ring of Willis was significantly higher,the expression of ERK1/2 was decreased,the expression of α-SMA was also significantly higher and the expression of MYH10 was decreased in the 48 h group compared with the 48 h group without pioglitazone intervention,and the differences were statistically significant(P<0.05).Conclusion: After activation of PPARγ using PPARγ agonists,the ERK1/2 pathway was inhibited,the expression of α-SMA,a contractile phenotypic marker of vascular smooth muscle,was increased,the expression of MYH10,a synthetic phenotypic marker,was reduced,and ischemia-reperfusion injury was attenuated in rats,probably by inhibiting the ERK1/2 signaling pathway after activation of PPARγ and suppressing the phenotypic transformation of vascular smooth muscle.thereby exerting a neurovascular protective effect is related. |
