title: Inhibition of calpain-regulated p35/cdk5 plays a central role in sildenafil-induced protection against chemical hypoxia produced by malonate.
abstract: Phosphodiesterase 5 (PDE5) inhibitors have recently been reported to exert beneficial effects against ischemia-reperfusion injury in several organs but their neuroprotective effects in brain stroke models are scarce. The present study was undertaken to assess the effects of sildenafil against cell death caused by intrastriatal injection of malonate, an inhibitor of succinate dehydrogenase; which produces both energy depletion and lesions similar to those seen in cerebral ischemia. Our data demonstrate that sildenafil (1.5mg/kg by mouth (p.o.)), given 30min before malonate (1.5μmol/2μL), significantly decreased the lesion volume caused by this toxin. This protective effect can be probably related to the inhibition of excitotoxic pathways. Thus, malonate induced the activation of the calcium-dependent protease, calpain and the cyclin-dependent kinase 5, cdk5; which resulted in the hyperphosphorylation of tau and the cleavage of the protective transcription factor, myocyte enhancer factor 2, MEF2. All these effects were also significantly reduced by sildenafil pre-treatment, suggesting that sildenafil protects against malonate-induced cell death through the regulation of the calpain/p25/cdk5 signaling pathway. Similar findings were obtained using inhibitors of calpain or cdk5, further supporting our contention. Sildenafil also increased MEF2 phosphorylation and Bcl-2/Bax and Bcl-xL/Bax ratios, effects that might as well contribute to prevent cell death. Finally, sildenafil neuroprotection was extended not only to rat hippocampal slices subjected to oxygen and glucose deprivation when added at the time of reoxygenation, but also, in vivo when administered after malonate injection. Thus, the therapeutic window for sildenafil against malonate-induced hypoxia was set at 3h.
authors: Department of Pharmacology, School of Pharmacy, University of Navarra, Spain.
authors: Lucía
authors: L
authors: Barros-Miñones
authors: Dolores
authors: D
authors: Martín-de-Saavedra
authors: Sergio
authors: S
authors: Perez-Alvarez
authors: Lourdes
authors: L
authors: Orejana
authors: Verónica
authors: V
authors: Suquía
authors: Beatriz
authors: B
authors: Goñi-Allo
authors: Isabel
authors: I
authors: Hervias
authors: Manuela G
authors: MG
authors: López
authors: Joaquin
authors: J
authors: Jordan
authors: Norberto
authors: N
authors: Aguirre
authors: Elena
authors: E
authors: Puerta
mesh_terms: D000818:Animals; D002154:Calpain / Q000378:metabolism*; D051360:Cyclin-Dependent Kinase 5 / Q000378:metabolism*; D002534:Hypoxia, Brain / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control; D008297:Male; D008314:Malonates / Q000633:toxicity*; D018696:Neuroprotective Agents / Q000494:pharmacology*; D058986:Phosphodiesterase 5 Inhibitors / Q000494:pharmacology*; D010766:Phosphorylation / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology*; D011687:Purines / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects; D000068677:Sildenafil Citrate; D013450:Sulfones / Q000494:pharmacology*; D051028:bcl-2-Associated X Protein / Q000378:metabolism; D051020:bcl-X Protein / Q000378:metabolism; D016875:tau Proteins / Q000378:metabolism
chemical_list: C494828:Bax protein, rat; C494813:Bcl2l1 protein, rat; D008314:Malonates; C489131:Mapt protein, rat; D018696:Neuroprotective Agents; D058986:Phosphodiesterase 5 Inhibitors; D010879:Piperazines; D011687:Purines; D013450:Sulfones; D051028:bcl-2-Associated X Protein; D051020:bcl-X Protein; D016875:tau Proteins; C030290:malonic acid; D000068677:Sildenafil Citrate; D051360:Cyclin-Dependent Kinase 5; C495907:Cdk5 protein, rat; D002154:Calpain