TP53-induced glycolysis and apoptosis regulator alleviates hypoxia/ischemia-induced microglial pyroptosis and ischemic brain damage

Our previous studies have demonstrated that TP53-induced glycolysis and apoptosis regulator(TIGAR)can protect neurons after cerebral ischemia/reperfusion.However,the role of TIGAR in neonatal hypoxic-ischemic brain damage(HIBD)remains unknown.In the present study,7-day-old Sprague-Dawley rat models of HIBD were established by permanent occlusion of the left common carotid artery followed by 2-hour hypoxia.At 6 days before induction of HIBD,a lentiviral vector containing short hairpin RNA of either TIGAR or gasdermin D(LV-sh_TIGAR or LV-sh_GSDMD)was injected into the left lateral ventricle and striatum.Highly aggressively proliferating immortalized(HAPI)microglial cell models of in vitro HIBD were established by 2-hour oxygen/glucose deprivation followed by 24-hour reoxygenation.Three days before in vitro HIBD induction,HAPI microglial cells were transfected with LV-sh_TIGAR or LV-sh_GSDMD.Our results showed that TIGAR expression was increased in the neonatal rat cortex after HIBD and in HAPI microglial cells after oxygen/glucose deprivation/reoxygenation.Lentivirusmediated TIGAR knockdown in rats markedly worsened pyroptosis and brain damage after hypoxia/ischemia in vivo and in vitro.Application of exogenous nicotinamide adenine dinucleotide phosphate(NADPH)increased the NADPH level and the glutathione/oxidized glutathione ratio and decreased reactive oxygen species levels in HAPI microglial cells after oxygen/glucose deprivation/reoxygenation.Additionally,exogenous NADPH blocked the effects of TIGAR knockdown in neonatal HIBD in vivo and in vitro.These findings show that TIGAR can inhibit microglial pyroptosis and play a protective role in neonatal HIBD.The study was approved by the Animal Ethics Committee of Soochow University of China(approval No.2017LW003)in 2017.

Saponins from Paris forrestii(Takht.) H. Li displays potent activity against acute myeloid leukemia by suppressing RNF6/AKT/mTOR signaling pathway

Acute myeloid leukemia(AML) is a heterogeneous disease characterized by the accu.mulation of immature myeloid progenitor cells in the bone marrow,compromising of normal hematopoi.esis and ultimately resulting in bone marrow failure.Chemotherapy is the mainstay treatment for all AML patients,however,drug resistance and clinical relapse limits its efficacy.The 5-year survival rate of AML patients is only 26.6%.Survival rates are even lower among patients ages 65 to 74 years(5.3%) and 75 years or older(1.6%).Therefore,exploring novel therapeutic agents is urgent for improving the outcome of patients with AML.Saponins are amphipathic glycosides found in traditional Chinese medicines.In the present study,we isolated a panel of saponins from Paris forrestii(Takht.) H.Li,a unique plant found in Tibet and Yunnan provinces,China.By examining their activities in suppressing acute myeloid leukemia cell proliferation,total saponins from Paris forrestii(TSPf) displayed more potent activity than individual ones.TSPf induced more than 40% AML cell apoptosis within 24 h and decreased the viability of all leukemia cell lines.TSPf-induced apoptosis was confirmed by both Annexin V staining and caspase-3 activation.TSPf downregulated pro-survival proteins Mcl-1,Bcl-xL and Bcl-2,but upreg.ulated the expression of tumor suppressor proteins p53,p27,Bax and Beclin 1.The AKT/mTOR signaling pathway is frequently over activated in various AML cells,and TSPf was found to suppress the activa.tion of both AKT and mTOR,but had no effects on their total protein expression.This was further con.firmed by the inactivation of 4 EBP-1 and p70 S6 K,two typical downstream signal molecules in the AKT/mTOR pathway.More specifically,TSPf-inactivated AKT/mTOR signaling was found to be associated with downregulated RNF6,a recently identified oncogene in AML.RNF6 activated AKT/mTOR,and consistently,knockdown of RNF6 led to inactivation of the AKT/mTOR pathway.Furthermore,TSPf suppressed the growth of AML xenografts in nude mice models.Oral administration of 100 mg · kg^(-1) body weight almost fully suppressed tumor growth within 14 d,without gross toxicity.This study thus demonstrated that TSPf displays potent anti-AML activity by suppressing the RNF6/AKT/mTOR pathway.Given its low toxicity,TSPf could be developed for the treatment of AML.