The Protective Effect And Mechanism Of SEMA4A-NRP1 Axis On Renal Ischemia Reperfusion Injury In Mice

Ischemia reperfusion injury(IRI)was the leading cause of delay graft function(DGF)in renal transplantation and various of adverse effects can by induced by IRI,the prevention and attenuation of IRI are critical for improving long-term living of grafts.Recent studies have shown that inflammatory cells and factors were key factors for IRI development,on the other hand,immunoregulatory cells represented by regulatory T cells(Treg)are able to alleviate IRI by suppressing inflammation during IRI,so promoting the infiltration of Tregs in renal is an effective approach to reduce tissue damage and protect renal function.Neuropilin 1(NRP1)is essential for the maintenance of the immunoregulatory effect of Treg,previous study has shown that NRP1 acted as a receptor binding with semaphorin IVa(SEMA4A)promoted the stability and function of Treg by inhibiting Akt-mTOR signaling pathway,thereby increasing the infiltration of Tregs in tumor tissue.However,the effect of SEMA4A-NRP1 axis in renal IRI is not clear yet.Therefore,in our present study,SEMA4A-Fc was used as an intervention to investigate whether SEMA4A-Fc increased the infiltration of Tregs and alleviated IRI in kidney of mouse.The results suggested that:treatment by SEMA4A-Fc prior to IRI decreased the serum creatinine,blood urea nitrogen(BUN),inflammatory factors,tubular injury score and apoptosis of kidney cells.Moreover,flow cytometric showed that SEMA4A-Fc treatment decreased the infiltration the neutrophils and macrophages,and increased the Tregs infiltration in kidney.When administrating of anti-CD25 monoclonal antibody(PC61),the benefits of SEMA4A-Fc mentioned above were eliminated,this result confirmed the effect of SEMA4A-Fc was exerted by Tregs.In the further experiment based on FoxP3CreNRP1f/f mice showed that NRP1 knockout in Tregs reversed the beneficial effect of SEMA4A-Fc and reduced the infiltration of Tregs,indicated that NRP1 was the key molecular for mediating the effects of SEMA4A on Tregs infiltration and IRI alleviation.In the part of mechanism research,both in-vivo and in-vitro study suggested that the administration of SEMA4A-Fc in wild-type mice promoted PTEN recruited to NRP1 and subsequently decreased the level of pAkt(S473/T308)and pS6K1,but administration of SEMA4A-Fc in NRP1 knock-out mice did not show the same effect.The results clarified SEMA4A binding to NRP1 promotes the recruitment of PTEN and suppressed Akt-mTOR pathway,which increased the stability of Tregs.In conclusion,this study revealed the following points:SEMA4A-NRP1 axis alleviated the development of IRI in kidneys of mice,SEMA4A binding with NRP1 promoted PTEN recruitment and inhibited Akt-mTOR pathway in Tregs,this process increased the stability and function of Tregs and inhibited the inflammation in mice kidneys,which attenuate the tissue damage of kidney during the IRI.