Interaction between inducible nitric oxide synthase and poly(ADP-ribose) polymerase in focal ischemic brain injury.
OBJECTIVE
Overactivation of the DNA repair enzyme poly(ADP-ribose) polymerase (PARP) contributes to ischemic brain injury. Because PARP upregulates proinflammatory genes, we investigated whether inducible nitric oxide synthase (iNOS), a gene involved in the deleterious effects of postischemic inflammation, participates in the mechanisms by which PARP activation contributes to cerebral ischemic injury.


METHODS
The middle cerebral artery (MCA) was occluded in mice for 20 minutes using an intravascular filament, and injury volume was measured 72 hours later in Nissl-stained brain sections. mRNA expression was assessed in the postischemic brain by the quantitative "real-time" polymerase chain reaction.


RESULTS
The PARP inhibitor PJ34 reduced infarct volume and attenuated postischemic iNOS mRNA upregulation by 72%. To determine whether iNOS contributes to the toxicity of PARP, the iNOS inhibitor aminoguanidine was co-administered with PARP inhibitors. Unexpectedly, co-administration of PARP and iNOS inhibitors, or treatment of iNOS-null mice with PARP inhibitors, abrogated the protective effect afforded by iNOS or PARP inhibition alone. The loss of neuroprotection was associated with upregulation of the inflammatory genes iNOS, intercellular adhesion molecule-1, and gp91(phox).


CONCLUSIONS
The results suggest that iNOS expression contributes to the deleterious effects exerted by PARP activation in cerebral ischemia. However, iNOS activity is required for the protective effect of PARP inhibition and, conversely, PARP activity must be present for iNOS inhibition to be effective. The findings unveil a previously unrecognized deleterious interaction between iNOS and PARP that is relevant to the development of combination therapies for ischemic stroke.
Park
Eun-Mi
EM
Department of Pharmacology, College of Medicine, Ewha Women's University, Seoul, Republic of Korea.
Cho
Sunghee
S
Frys
Kelly
K
Racchumi
Gianfranco
G
Zhou
Ping
P
Anrather
Josef
J
Iadecola
Costantino
C
D000818:Animals; D002545:Brain Ischemia / Q000201:enzymology* / Q000503:physiopathology; D004195:Disease Models, Animal; D006146:Guanidines / Q000494:pharmacology; D020244:Infarction, Middle Cerebral Artery; D018799:Intercellular Adhesion Molecule-1 / Q000235:genetics; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases / Q000235:genetics; D018696:Neuroprotective Agents / Q000494:pharmacology; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism; D052247:Nitric Oxide Synthase Type II; D010616:Phenanthrenes / Q000494:pharmacology; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics* / Q000378:metabolism; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D015854:Up-Regulation
D006146:Guanidines; D008562:Membrane Glycoproteins; C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D018696:Neuroprotective Agents; D010616:Phenanthrenes; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D012333:RNA, Messenger; D018799:Intercellular Adhesion Molecule-1; D019001:Nitric Oxide Synthase; D052247:Nitric Oxide Synthase Type II; C496317:Nos2 protein, mouse; C488842:Cybb protein, mouse; D000074662:NADPH Oxidase 2; D019255:NADPH Oxidases; D011065:Poly(ADP-ribose) Polymerases; C004479:pimagedine