Erythropoietin and Wnt1 govern pathways of mTOR, Apaf-1, and XIAP in inflammatory microglia.
Inflammatory microglia modulate a host of cellular processes in the central nervous system that include neuronal survival, metabolic fluxes, foreign body exclusion, and cellular regeneration. Elucidation of the pathways that oversee microglial survival and integrity may offer new avenues for the treatment of neurodegenerative disorders. Here we demonstrate that erythropoietin (EPO), an emerging strategy for immune system modulation, prevents microglial early and late apoptotic injury during oxidant stress through Wnt1, a cysteine-rich glycosylated protein that modulates cellular development and survival. Loss of Wnt1 through blockade of Wnt1 signaling or through the gene silencing of Wnt1 eliminates the protective capacity of EPO. Furthermore, endogenous Wnt1 in microglia is vital to preserve microglial survival since loss of Wnt1 alone increases microglial injury during oxidative stress. Cellular protection by EPO and Wnt1 intersects at the level of protein kinase B (Akt1), the mammalian target of rapamycin (mTOR), and p70S6K, which are necessary to foster cytoprotection for microglia. Downstream from these pathways, EPO and Wnt1 control "anti-apoptotic" pathways of microglia through the modulation of mitochondrial membrane permeability, the release of cytochrome c, and the expression of apoptotic protease activating factor-1 (Apaf-1) and X-linked inhibitor of apoptosis protein (XIAP). These studies offer new insights for the development of innovative therapeutic strategies for neurodegenerative disorders that focus upon inflammatory microglia and novel signal transduction pathways.
Laboratory of Cellular and Molecular Signaling, University of Medicine and Dentistry, New Jersey Medical School, Newark, New Jersey 07101, USA.
Yan Chen
YC
Shang
Zhao Zhong
ZZ
Chong
Shaohui
S
Wang
Kenneth
K
Maiese
D000704:Analysis of Variance; D000818:Animals; D000906:Antibodies / Q000494:pharmacology; D053477:Apoptotic Protease-Activating Factor 1 / Q000378:metabolism*; D016923:Cell Death / Q000187:drug effects; D002461:Cell Line, Transformed; D045304:Cytochromes c / Q000378:metabolism; D053938:DNA Fragmentation / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D004921:Erythropoietin / Q000276:immunology / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects; D005947:Glucose / Q000172:deficiency; D006801:Humans; D000860:Hypoxia; D020287:In Situ Nick-End Labeling; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D051379:Mice; D008928:Mitochondria / Q000187:drug effects; D009457:Neuroglia / Q000187:drug effects* / Q000378:metabolism / Q000648:ultrastructure; D010718:Phosphatidylserines / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D013997:Time Factors; D051155:Wnt1 Protein / Q000276:immunology / Q000494:pharmacology*; D051636:X-Linked Inhibitor of Apoptosis Protein / Q000378:metabolism*
D000906:Antibodies; C506593:Apaf1 protein, mouse; D053477:Apoptotic Protease-Activating Factor 1; D010718:Phosphatidylserines; D051155:Wnt1 Protein; D051636:X-Linked Inhibitor of Apoptosis Protein; D004921:Erythropoietin; D045304:Cytochromes c; D058570:TOR Serine-Threonine Kinases; D005947:Glucose