Nitric oxide and superoxide anion differentially activate poly(ADP-ribose) polymerase-1 and Bax to induce nuclear translocation of apoptosis-inducing factor and mitochondrial release of cytochrome c after spinal cord injury.
We reported previously that complete spinal cord transection (SCT) results in depression of mitochondrial respiratory chain enzyme activity that triggers apoptosis via sequential activations of apoptosis-inducing factor (AIF)- and caspase-dependent cascades in the injured spinal cord. This study tested the hypothesis that nitric oxide (NO) and superoxide anion (O(2)(.-)) serve as the interposing signals between SCT and impaired mitochondrial respiratory functions. Adult Sprague-Dawley rats manifested a significant increase in NO or O(2)(.-) level in the injured spinal cord during the first 3 days after SCT. The augmented O(2)(.-) production, along with concomitant reduction in mitochondrial respiratory chain enzyme activity or ATP level, nuclear translocation of AIF, cytosolic release of cytochrome c, and DNA fragmentation were reversed by osmotic minipump infusion of a NO trapping agent, carboxy-PTIO, or a superoxide dismutase mimetic, tempol, into the epicenter of the transected spinal cord. Intriguingly, carboxy-PTIO significantly suppressed upregulation of poly(ADP-ribose) polymerase-1 (PARP-1) in the nucleus, attenuated nuclear translocation of AIF, inhibited mitochondrial translocation of Bax and antagonized mitochondrial release of cytochrome c; whereas tempol only inhibited the later two cellular events after SCT. We conclude that overproduction of NO and O(2)(.-) in the injured spinal cord promulgates mitochondrial dysfunction and triggers AIF- and caspase-dependent apoptotic signaling cascades via differential upregulation of nuclear PARP-1 and mitochondrial translocation of Bax.
Wu
Kay L H
KL
Department of Medical Education and Research, Kaohsiung Veterans General Hospital, Kaohsiung, Taiwan, Republic of China.
Hsu
Chin
C
Chan
Julie Y H
JY
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000255:Adenosine Triphosphate / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D051033:Apoptosis Inducing Factor / Q000378:metabolism*; D015153:Blotting, Western; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D045304:Cytochromes c / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D007550:Isothiuronium / Q000031:analogs & derivatives / Q000494:pharmacology; D008297:Male; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D052247:Nitric Oxide Synthase Type II / Q000037:antagonists & inhibitors; D010616:Phenanthrenes / Q000494:pharmacology; D000071137:Poly (ADP-Ribose) Polymerase-1; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism*; D013119:Spinal Cord Injuries / Q000378:metabolism*; D013481:Superoxides / Q000378:metabolism*; D013904:Thoracic Vertebrae; D051028:bcl-2-Associated X Protein / Q000378:metabolism*
D051033:Apoptosis Inducing Factor; C434926:N-(oxo-5,6-dihydrophenanthridin-2-yl)-N,N-dimethylacetamide hydrochloride; D010616:Phenanthrenes; D000067856:Poly(ADP-ribose) Polymerase Inhibitors; D051028:bcl-2-Associated X Protein; D013481:Superoxides; D007550:Isothiuronium; D009569:Nitric Oxide; D000255:Adenosine Triphosphate; D045304:Cytochromes c; D052247:Nitric Oxide Synthase Type II; C499322:Parp1 protein, rat; D000071137:Poly (ADP-Ribose) Polymerase-1; D011065:Poly(ADP-ribose) Polymerases; C027744:S-methylisothiopseudouronium