The Effect And Mechanism Of Hepericin Protecting INS-1 Cells From Glucotoxicity And Lipotoxicity

By 2025,people with impaired glucose tolerance will increase to 472 million,and 40-50% of them will develop to type 2 diabetes.It's well known that diabetes can cause a serious of severe complications and increase the risk of occurrence of various cancers.Thus,to get anti-diabetes drugs with low side effects and high therapeutic validity is always the focus in the field of drug development.Previous research in our laboratory have shown that natural compound hypericin can inhibit Ca²⁺influx in islet?cell line INS-1 cells.High calcium influx can cause cell apoptosis and islet beta cell apoptosis is one of the main reasons leading to diabetes.Thus,here we investigated whether hypericin could inhibit?cell apoptosis by down regulating the Ca²⁺influx and thereby elicit protective effects on islet?cells.This study provide foundation for further exploring the therapeutic function of hypericin to diabetes.The main results are as follows:?1?Confirmation of the inhibitory effect of hypericin on Ca²⁺influx in INS-1 cells.Through high content analysis,we found that hypericin treatment could decrease the amount of Ca²⁺influx stimulated by high concentration of K⁺in INS-1 cells significantly.It indicated that hypericin can indeed play a role in inhibiting Ca²⁺influx.?2?Exploration of the protective effect of hepericin on INS-1 cells against high glucose toxicity.On the basis of establishing cellular model of high glucose toxicity,the results showed that hypericin can improve cell viability of high glucose treated INS-1 cells,accompanied with increasing the expression of Pdx-1 at both mRNA and protein levels,reducing the expression of apoptosis related proteins,and decreasing iNOS mRNA level and NO production.?3?Investigation of the mechanism by which hypericin protects INS-1 cells from high glucose toxicity.Our previous research found that ERK pathway was involved in regulating the expression of Pdx-1.In our study,we found that high glucose can inhibit the activation of ERK pathway,as evidence by deceased phosphorylated Erk1/2.However,under hypericin treatment,the decreased level of Erk1/2phosphorylation returned to normal levels.Similarly,high glucose led to decreased expression of Pdx-1 which was reversed by hypericin as well furthermore,after using U0126 to block ERK pathway,hypericin couldn't recover the levels of both phosphorylated Erk1/2 and Pdx-1 anymore.These results suggest that hypericin protects INS-1 cells from high glucose toxicity through activating ERK signaling pathway.In addition,we also explored the influence of hypercin on INS-1 cell proliferation.However,there was no effect of hypericin on cell proliferation.?4?Exploration of the protective effect of hepericin on INS-1 cells against high fatty acid toxicity:Firstly,200?M palmitic acid treatment for 24h was demonstrated to significantly decrease the viability of INS-1 cells and induce apoptosis as well,as evidenced by induced expression of apoptotic protein and formation of apoptotic bodies indicating the model of lipotoxicity was successfully established.Based on this,we proved that hypericin can increase cell viability of INS-1 cells injured by high fatty acid and enhance Pdx-1 expression and decrease the expression of apoptosis related protein and NO production as well.All these results indicate that hypericin can protect INS-1 cells from lipotoxicity.Furthermore,we explored the mechanism of this protective effects and found that it's might be regulated by ERK,P38 and AKT pathway.In conclusion,our study demonstrated that hypericin can decrease Ca²⁺influx and protect islet?cell line INS-1 cells from glucotoxicity and lipotoxicity by suppressing cell apoptosis.Moreover,hypericin exerted protection through activating signal pathways to enhance Pdx-1 expression.