Nicotinamide modulates mitochondrial membrane potential and cysteine protease activity during cerebral vascular endothelial cell injury.
Microvascular endothelial cell (EC) apoptosis or programmed cell death (PCD) during free radical injury may be involved in the development of cerebral ischemic and degenerative diseases. Yet, the cellular mechanisms that mediate cerebral EC injury require further definition. We therefore used the agent nicotinamide as an investigative tool in EC cultures to examine the role of free radical nitric oxide (NO)-induced PCD. EC injury was evaluated by the trypan blue dye exclusion method, DNA fragmentation, membrane phosphatidylserine (PS) exposure, cysteine protease activity, mitochondrial membrane potential, and mitogen-activated protein kinase phosphorylation. We demonstrate that cerebrovascular PCD consists of two distinct pathways that involve the degradation of genomic DNA and the exposure of membrane PS residues. Each of these pathways is reversible in nature and is controlled independently by caspase 8, caspase 1, and caspase 3. As a cytoprotectant, nicotinamide is novel in the vascular system and functions at two levels. Nicotinamide not only maintains the mitochondrial membrane potential and the prevention of cytochrome c release, but also prevents the induction of caspase-8-, caspase-1- and caspase-3-like activities linked to the DNA repair enzyme poly(ADP-ribose) polymerase through mechanisms that are independent from the MAP kinase systems of p38 and JNK. The work begins to identify therapeutic strategies for the protection of the cerebral vasculature during both acute and chronic degenerative disorders.
Chong
Zhao Zhong
ZZ
Division of Cellular and Molecular Cerebral Ischemia, Center for Molecular Medicine and Genetics, Wayne State University School of Medicine, Detroit, Mich 48201, USA.
Lin
Shi-Hua
SH
Maiese
Kenneth
K
D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001921:Brain / Q000098:blood supply*; D020170:Caspase 1 / Q000378:metabolism; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases / Q000378:metabolism; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D003546:Cysteine Endopeptidases / Q000378:metabolism*; D003574:Cytochrome c Group / Q000378:metabolism; D053938:DNA Fragmentation; D004730:Endothelium, Vascular / Q000473:pathology*; D005609:Free Radicals; D020287:In Situ Nick-End Labeling; D007425:Intracellular Membranes / Q000187:drug effects* / Q000502:physiology; D008564:Membrane Potentials / Q000187:drug effects; D008928:Mitochondria / Q000648:ultrastructure*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009536:Niacinamide / Q000494:pharmacology*; D009569:Nitric Oxide / Q000494:pharmacology; D010718:Phosphatidylserines / Q000378:metabolism; D010766:Phosphorylation; D051381:Rats; D017207:Rats, Sprague-Dawley
D003574:Cytochrome c Group; D005609:Free Radicals; D010718:Phosphatidylserines; D009536:Niacinamide; D009569:Nitric Oxide; D020928:Mitogen-Activated Protein Kinases; C505410:Casp3 protein, rat; C505528:Casp8 protein, rat; C506435:Casp9 protein, rat; D053148:Caspase 3; D053181:Caspase 8; D053453:Caspase 9; D020169:Caspases; D003546:Cysteine Endopeptidases; D020170:Caspase 1