Study Of The Effect Of Neuropeptide Cortistatin On Transplantation

Transplantation tolerance is the ultimate goal in organ transplantation. CD25⁺CD4⁺ regulatory T(Treg) cells have emerged as key players in the development of tolerance to autoantigens as well as to foreign antigens. Enhancement of CD25⁺CD4⁺ Treg cell activity may protect individuals from graft rejection and autoimmune diseases.Forkhead family transcription factor Foxp3 is recognized as one of the specific Treg cell marker,predominantly expressed in CD25⁺CD4⁺ Treg cells and play a critical role for their development and function.Immunosuppressive drugs,such as FK506 and cyclosporin A(CsA), inhibit the alloreactive T cells very efficiently.However,the treatment with FK506 and CsA may be accompanied by several side effects,including interfering with the generation of Treg cell.Thus,the establishment of additional strategies for immunosuppression of allograft rejection to minimize complications is desirable.Cortistatin(CST),a cyclic neuropeptide,could bind to all of SSTRs,MrgX2 and GHSR.Various human immune cells produce CST and its levels correlate with cell differentiation and activation state.CST might be a major endogenous regulatory factor in the immune system.CST could decrease the frequency and reduces the severity of autoimmune diseases such as collagen-induced arthritis and inflammatory bowel disease.Similar cellular and molecular mechanisms are responsible for the pathogenesis of transplant rejection and autoimmunit.However,little research has been done on the effect of CST on the immunologic response to allografts in vivo.We therefore studied the effects of CST on the alloimmune response to fully allogeneic skin grafts in a mice model.We also compared the effects of CST and SMS 201-995(SMS,Octreotide, one of metabolically stable analogues of somatostatin) administration in a skin transplantation model of miceAim:In the present study,we examined whether CST affects the alloimmune response in a mice model of skin transplantation and the effects of CST on T-lymphocytes in vivo and in vitro.Methods:BALB/c(H-2K^d) recipients were given intraperitoneal injection of CST or somatostatin analogue SMS 201-995 on the day of transplantation of skin from C57BL/6(B6)(H-2K^b) donors and on seven consecutive days.The dosage in injection may vary from 0.02 to 2mg/kg.Survival of the allografts was recorded.The effect of the CST or SMS 201-995 treatment on cell proliferation and cytokine production was assessed by mixed leukocyte culture and enzyme-linked immunosorbent assays.RT-PCR study of Foxp3 expression and flow cytometry study of CD4 and CD25 marker of T lymphocytes were conducted to determine whether CD25⁺CD4⁺ Foxp3^high regulatory T cells were generated in vivo.Results:BALB/c recipients given CST(0.2mg/kg or 2mg/kg) prolonged graft survival(median survival time,13 days and 14 days,respectively).Recipients given SMS 201-995 had not significantly effect on allograft survival(median survival time,7 days,8days,8days,respectively).Both CST and SMS 201-995 could inhibit alloproliferative response,increase IL-10 concentration and decrease IFN-gamma concentration in MLC.CST was more potent to inhibit alloproliferative and to increase IL-10 concentration compared with SMS 201-995 in MLC.We found more than two-fold increase of CD25⁺CD4⁺ T cells in the CD4⁺T cells and the expression of Foxp3 were up-regulated in CST treatment groups,compared with controls and SMS 201-995 treatment groups.Conclusion:In our study,CST induced significantly prolongation survival time of allogeneic skin grafts and generated CD25⁺CD4⁺ Foxp3^high regulatory T cells, which may become a new modality in controlling allograft rejection.