Bax and caspases are inhibited by endogenous nitric oxide in dorsal root ganglion neurons in vitro.
Axotomised dorsal root ganglia (DRG) neurons show an increased expression of neuronal nitric oxide synthase (nNOS) compared with neurons from the intact ganglia. Increased nNOS expression resulted in synthesis of nitric oxide (NO) and the subsequent activation of cGMP in satellite glia cells surrounding the DRG neuron soma. In dissociated DRG we have demonstrated that the increase in nNOS expression is regulated by nerve growth factor and that the subsequent inhibition of NO production or cGMP synthesis precipitates apoptosis of neurons expressing nNOS and some non-nNOS neurons. Hence, NO or the NO-cGMP cascade appears to have a neuroprotective action in trophic factor-deprived DRG neurons. In the present study, using immunocytochemistry, we have investigated some of the factors associated with apoptosis that are activated when nNOS activity is blocked with NOS inhibitor in DRG neurons in vitro. Marked elevation of bax was observed within a few hours of NOS inhibition in nNOS containing neurons, whereas pretreatment of cultures with l-arginine completely abolished this effect in almost all nNOS neurons and 8-bromo-cGMP in some neurons. The apoptosis precipitated by NOS inhibition was also partially prevented by a number of caspase inhibitors; of those a caspase-9 blocker was the most effective. These observations further support the neuroprotective role of NO/NO-cGMP in stressed DRG neurons in an autocrine fashion that involves the suppression of bax, caspase-3 and -9 activation.
Thippeswamy
T
T
Department of Veterinary Preclinical Science, University of Liverpool, Liverpool, L69 7ZJ, UK. tswamy@liv.ac.uk
McKay
J S
JS
Morris
R
R
D000818:Animals; D000831:Animals, Newborn; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology*; D001120:Arginine / Q000494:pharmacology; D019898:Autocrine Communication / Q000187:drug effects / Q000502:physiology; D061945:Caspase Inhibitors; D020169:Caspases / Q000378:metabolism*; D002478:Cells, Cultured; D006152:Cyclic GMP / Q000031:analogs & derivatives* / Q000378:metabolism* / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D005727:Ganglia, Spinal / Q000187:drug effects / Q000201:enzymology* / Q000503:physiopathology; D007150:Immunohistochemistry; D008297:Male; D009410:Nerve Degeneration / Q000201:enzymology / Q000503:physiopathology; D009475:Neurons, Afferent / Q000187:drug effects / Q000201:enzymology*; D009569:Nitric Oxide / Q000378:metabolism*; D019001:Nitric Oxide Synthase / Q000037:antagonists & inhibitors / Q000378:metabolism; D010523:Peripheral Nervous System Diseases / Q000201:enzymology / Q000503:physiopathology; D011518:Proto-Oncogene Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000037:antagonists & inhibitors / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013312:Stress, Physiological / Q000201:enzymology / Q000503:physiopathology; D051028:bcl-2-Associated X Protein
C494828:Bax protein, rat; D061945:Caspase Inhibitors; D004791:Enzyme Inhibitors; D011518:Proto-Oncogene Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; C016276:8-bromocyclic GMP; D009569:Nitric Oxide; D001120:Arginine; D019001:Nitric Oxide Synthase; D020169:Caspases; D006152:Cyclic GMP