autophagy checkpoint inhibitors mediated proteolysis . Lastly, the induction of autophagy was confirmed by ultrastructural TEM analysis, showing in depth cytoplasmic vacuolization with numerous doublemembraned autophagosomes and single membraned autolysosome like vesicles containing cellular material . These data clearly demonstrate that apoptosis coincideswith autophagy in OHDA treated SH SYY cells. OHDA induced autophagy is dependent upon AMPK mTOR signaling To evaluate molecularmechanisms of OHDA mediated autophagy, we analyzed the activation status in the major members of autophagyregulating AMPK mTOR signaling pathway. The treatment with OHDA led to an increase in phosphorylation of AMPK and its direct downstream target Raptor . The activation of AMPK Raptor was related to the reduced phosphorylation in the significant autophagy repressor mTOR and its substrate SK .
The RNA interference mediated knockdown of AMPK expression prevented OHDAmediated activation of Raptor and subsequentmTOR pSK inhibition, LC conversion, p degradation and intracellular checkpoint inhibitors acidification . These data indicate that AMPK dependent mTOR inhibition is involved in oxidopamine stimulated autophagy in SH SYY cells. AMPK dependent autophagy is involved in OHDA neurotoxicity To ascertain the role of autophagy in OHDA toxicity towards SH SYY cells, we tested if the latter could possibly be modulated by inhibition or induction of autophagy. Pharmacological inhibitors of autophagy, which block either class III phosphoinositide kinasedependent formation of autophagosomes or formation acidification of autolysosomes , all markedly diminished OHDA induced cell damage .
Accordingly, autophagy knockdown with LC shRNA, confirmed by flow cytometric analysis of acridine orange red fluorescence and LC immunoblot , also considerably improved the viability of OHDA treated SH SYY cells . The protective effects Ganetespib of autophagy knockdown in oxidopamine treated neuroblastoma cells were related to the reduction in phosphatidylserine externalization , caspase activation and oxidative tension . Similar final results were obtained in AMPK shRNA transfected SH SYY cells exposed to OHDA, which displayed reduced cell death , phosphatidylserine externalization , caspase activation and oxidative tension in response to OHDA. It should be noted that, in accordance using the prior findings , AMPK deficient cells displayed reduced proliferation rate, but the difference was not significant after h.
In contrast to AMPK knockdown, a effectively recognized mTOR inhibitor and autophagy inducer rapamycin considerably increased OHDA induced death of SH SYY cells , indicating a role for mTOR inhibition in cytotoxic autophagy NSCLC triggered by the neurotoxin. Consequently, it appears that the AMPK mTOR dependent induction of autophagy is involved in apoptotic demise of SH SYY cells upon oxidopamine treatment. AMPK dependent p activation mediates OHDA neurotoxicity independently of autophagy Considering Ganetespib the critical role of mitogen activated protein kinase loved ones member p in OHDA induced neurotoxicity , as well as in autophagy induction by several agents , we next investigated if p MAPK is involved in oxidopamine stimulated cytotoxic autophagy in SH SYY cells.
The treatment with OHDA markedly stimulated the phosphorylation of p in both manage and LC? SH SYY cells, but not in AMPK deficient cells , regardless of the equivalent efficiency of LC and AMPK knockdown . SB, checkpoint inhibitor the pharmacological p inhibitor that blocks its activity, but not phosphorylation , considerably reduced oxidopamine induced neuroblastoma cell killing . Therapy with SB had no effect on AMPK activity and LC conversion in OHDA exposed cells . Consequently, it seems that AMPK mediated activation of p MAPK contributes to the OHDA neurotoxicity in an autophagyindependent manner. Oxidative tension is responsible for AMPK mediated cytotoxic autophagy and p activation Oxidative tension has been implicated in OHDA induced p activation and subsequent neurotoxicity , as well as in AMPK phosphorylation in dopamine treated neurons .
Accordingly, the antioxidantN acetyl cysteine,which efficiently reduced ROS production , partly rescued neuroblastoma cells from OHDA induced cytotoxicity . In addition, Ganetespib NAC prevented oxidopaminestimulated activation of AMPK and p MAP kinase . Lastly, oxidative tension was involved in autophagy induction, as NAC reduced OHDA stimulated LC conversion and Ganetespib intracellular acidification . These data indicate that oxidative tension is involved in oxidopamine mediated AMPK activation and subsequent induction of cytotoxic autophagy and p activation Discussion The present study demonstrates that neurotoxin OHDA induces autophagy in SH SYY neuroblastoma cells via the oxidative tension dependent activation of intracellular energy sensor AMPK and subsequent inhibition in the major autophagy repressor mTOR . Furthermore, we show that both AMPK dependent autophagy, as well as AMPK mediated autophagy unrelated pMAPK activation contribute to in vitro neurotoxicity of OHDA . We assesse
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