title: Zinc promotes the death of hypoxic astrocytes by upregulating hypoxia-induced hypoxia-inducible factor-1alpha expression via poly(ADP-ribose) polymerase-1.
abstract: OBJECTIVE
  Pathological release of excess zinc ions has been implicated in ischemic brain cell death. However, the underlying mechanisms remain to be elucidated. In stroke, ischemia-induced zinc release and hypoxia-inducible factor-1 (HIF-1) accumulation concurrently occur in the ischemic tissue. The present study tests the hypothesis that the presence of high intracellular zinc concentration is a major cause of modifications to PARP-1 and HIF-1α during hypoxia, which significantly contributes to cell death during ischemia.
  
  
  METHODS
  Primary cortical astrocytes and C8-D1A cells were exposed to different concentrations of zinc chloride. Cell death rate and protein expression of HIF-1 and Poly(ADP-ribose) polymerase (PARP)-1 were examined after 3-h hypoxic treatment.
  
  
  RESULTS
  Although 3-h hypoxia or 100 μM of zinc alone did not induce noticeable cytotoxicity, their combination led to a dramatic increase in astrocytic cell death in a zinc-concentration-dependent manner. Exposure of astrocytes to hypoxia for 3 h remarkably increased the levels of intracellular zinc and HIF-1α protein, which was further augmented by added exogenous zinc. Notably, HIF-1α knockdown blocked zinc-induced astrocyte death. Moreover, knockdown of PARP-1, another important protein in the response of hypoxia, attenuated the overexpression of HIF-1α and reduced the cell death rate.
  
  
  CONCLUSIONS
  Our studies show that zinc promotes hypoxic cell death through overexpression of the hypoxia response factor HIF-1α via the cell fate determine factor PARP-1 modification, which provides a novel mechanism for zinc-mediated ischemic brain injury.
authors.affiliation: Department of Pharmaceutical Sciences, University of New Mexico Health Sciences Center, Albuquerque, NM 87131, USA.
authors.forename: Rong
authors.initials: R
authors.lastname: Pan
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Wen-Lan
authors.initials: WL
authors.lastname: Liu
authors.forename: Ke-Jian
authors.initials: KJ
authors.lastname: Liu
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001253:Astrocytes / Q000187:drug effects*; D015153:Blotting, Western; D016923:Cell Death / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects*; D002460:Cell Line; D003627:Data Interpretation, Statistical; D005456:Fluorescent Dyes; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000096:biosynthesis* / Q000235:genetics; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism*; D011083:Polycyclic Compounds; D034741:RNA, Small Interfering / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D015854:Up-Regulation; D015032:Zinc / Q000494:pharmacology*
chemical_list: C451182:FluoZin-3; D005456:Fluorescent Dyes; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D011083:Polycyclic Compounds; D034741:RNA, Small Interfering; C499322:Parp1 protein, rat; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; D015032:Zinc