Research On The Role Of ?-cyclodextrin In Apoptosis Of Cardiac Sca-1 Positive Cells And Underlying Mechanisms

Acute myocardial infarction is a cardiovascular disease with a higher morbidity,and there is no effective therapy currently.Our previous research found that a cyclic oligosaccharide,?-cyclodextrin(?-CD),could protect heart from acute myocardial infarction damage,but the cellular targets and molecular mechanisms have not been clarified yet.This study found that ?-CD inhibited the apoptosis of cardiac Sca-1+ cells(CSCs)under hypoxic condition,but it has no protective effects on cardiomyocytes,endothelial cells or fibroblast cells under the same hypoxic condition in vitro,therefore,?-CD might protect heart from acute myocardial infarction injury through CSCs.CSCs are endothelial-derived cells,the correlation between the apoptosis of CSCs and cardiac function has not been reported.Because heart transplantation of' CSCs could protect damaged heart,which was related to the paracrine function of CSCs,so we speculated that ?-CD could inhibit H2O2-induced apoptosis of CSCs might through increasing the paracrine of CSCs to play a protective role for heart.In this study,we used H2O2-induced apoptosis of CSCs to simulate hypoxic condition in vivo.The results proved our speculations that the conditioned medium of the H2O2 group could relieve the apoptosis of hypoxic cardiomyocytes effectively,and the conditioned medium of ?-CD and H2O2 co-treatment group had much significantly protective effect.Therefore,we further researched the molecular mechanisms of ?-CD inhibiting hypoxia-induced apoptosis of CSCs.We found that ?-CD could inhibit H2O2-induced apoptosis of CSCs specifically but Sca-1 did not participate in the protection of ?-CD.The test result of autophagy marker showed that ?-CD mainly inhibited the apoptosis of CSCs through promoting autophagy flow.We used gene chip,Western blot and siRNA technologies to selected and verified the roles of SGSM1,which was related to membrane fusion,and transcription factor NR4A2 in autophagy flow and apoptosis of CSCs.Further study showed the relationships between these two genes that NR4A2 regulated the expression of SGSM1,and NR4A2 was also regulated by SGSM1,indicating that there was a loop between NR4A2 and SGSM1.In addition,?-CD inhibited H2O2-induced nuclear translocation of NR4A2.The nuclear translocation of NR4A2 was regulated by diverse kinases,so we tested these kinase inhibitors.The results of immunofluorescence showed that p38(MAPK)inhibitor SB203580 inhibited the nuclear export of NR4A2 induced by ?-CD,reduced the protein levels of NR4A2,SGSM1 and autophagy marker LC3,promoted the apoptosis of CSCs.Therefore,?-CD promoted autophagy flow through p38(MAPK)/NR4A2/SGSM1 signal pathway,inhibited hypoxia-induced apoptosis of CSCs and enhanced its paracrine function to play a cardioprotective role indirectly.This study reported the relationship between apoptosis of CSCs and cardiomyocytes under hypoxic condition,clarified the cellular targets and molecular mechanisms of ?-CD on heart protection,which is beneficial to provide a theoretical basis for the therapy of acute myocardial infarction...