Study On Mechanism Of Carbon-sulfur- And Carbon-nitrogen-Bond Modified Podophyllum Derivates Induced Apoptosis By Mitochondrial Pathway In Hela Cells

As a colchicine-binding-site natural anticancer compound,podophyllotoxin has several shortages such as low anticancer activity and side effect of high toxicity.To obtain a series of activity improved and toxicity reduced podophyllotoxin derivatives,the 4 position of C ring(C-4)of podophyllotoxin efficaciously modified with carbon-sulfur-and carbon-nitrogen-bond.Comparing four couples of carbon-sulfur-and carbon-nitrogen-bond substituted compounds,the carbon-sulfur substituted compounds performed higher potent activity than the carbon-nitrogen substituted compounds.However,the molecular mechanism of difference between apoptosis induced by two kinds of modification on podophyllum derivates is still unclear.Based on four couples respectively podophyllotoxin derivatives substituted by carbon-sulfur-and carbon-nitrogen-bond as object,we explore the specific molecular mechanism of difference between their effects on anticancer activity against human cervical carcinoma HeLa cells.It turns out,S series compounds substituted by carbon-sulfur bond have higher depolymerization ability on their target microtubule,which is superior to N series compounds substituted by carbon-nitrogen bond.The increasing free tubulin caused by depolymerization in cytoplasm bond with VDAC(voltage-dependent anion-selective channel)located at mitochondrial outer membrane resulting in significantly MMP(mitochondrial membrane potential)deceasing and mitochondria depolarization after 24 hours treatment in HeLas.Meanwhile,PKA(cAMP-dependent protein kinase A),the direct effetors of second massager cAMP,is activated by S series compounds after 6 hours treatment.The first round of signal regulation in HeLas is induced by the activation of PKA: on the one hand,VDAC is phosphorylated to enhance its conbination with free tubulin leading to mitochondria depolarization;on the other hand,JNK signaling pathway is activated to promote apoptosis in MAPK(mitogen-activated protein kinases)cascade reaction.Phosphorylated JNK results in MMP decreasing further and mitochondrial dysfunction by inducing a mass of increasing ROS production.Massive ROS from mitochondria released into cytoplasm begin to switch second round of signal regulation through activating p38 MAPK-mediated apoptosis signaling and inhibiting ERK-mediated in growth and survival signaling at the same time,leading to HeLa cells apoptotic death.However,comparing with S series compounds,N series compounds just actvate the first round of signal regulation after 12-hours treatments,which is much later.As a result of their lower cellular uptake,N series compounds are impeded getting into HeLa cells to play their antitumor roles.This research study on comparing antitumor mechanism of four couples of S and N series compounds in HeLa cells.It founds out massive free tubulin depolymerized by S series compounds induce MMP decreased,while activation of PKA modulate ROS mediated two-round signal regulation.on the activation PKA on cell for ROS between guide of two round signal regulation of MAPK cascade reaction.However,N series compouds with slight microtubule depolymerizing ability induce mitochondrial apoptosis in HeLa cells by acvtivating PKA signaling after treatments delay.