Nitric Oxide Synthase-3 Overexpression Causes Apoptosis and Impairs Neuronal Mitochondrial Function: Relevance to Alzheimer's-Type Neurodegeneration

Abstract

SUMMARY:Dementia in Alzheimer's disease (AD) is correlated with cell loss that is mediated by apoptosis, mitochondrial (Mt) dysfunction, and possibly necrosis. Previous studies demonstrated increased expression of the nitric oxide synthase 3 (NOS3) gene in degenerating neurons of AD brains. For investigating the role of NOS3 overexpression as a mediator of neuronal loss, human PNET2 central nervous system-derived neuronal cells were infected with recombinant adenovirus vectors that expressed either human NOS3 or green fluorescent protein cDNA under the control of a CMV promoter. NOS3 overexpression resulted in apoptosis accompanied by increased levels of p53, p21/Waf1, Bax, and CD95. In addition, NOS3 overexpression impaired neuronal Mt function as demonstrated by the reduced levels of 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide and nicotinamide adenine dinucleotide (reduced form)-tetrazolium reductase activities and MitoTracker Red fluorescence. These adverse effects of NOS3 were associated with increased cellular levels of reactive oxygen species and impaired membrane integrity and were not produced in cells that were transfected with a cDNA encoding catalytically inactive NOS3. Importantly, modest elevations in NOS3 expression, achieved by infection with low multiplicities of adenovirus-NOS3 infection, did not cause apoptosis but rendered the cells more sensitive to oxidative injury by H 2 O 2 or diethyldithiocarbamate. In contrast, treatment with NO donors did not enhance neuronal sensitivity to oxidative injury. These results suggest that NOS3-induced neuronal death is mediated by Mt dysfunction, oxidative injury, and impaired membrane integrity, rather than by NO production, and that neuroprotection from these adverse effects of NOS3 may be achieved by modulating intracellular levels of oxidative stress. (Lab Invest 2003, 83:287-298).

Amyloid β-induced Changes in Nitric Oxide Production and Mitochondrial Activity Lead to Apoptosis

“…Hereby, NO itself causes a selective reversible inhibition of cytochrome c oxidase (31), whereas RNS inactivate multiple respiratory chain complexes and ATP synthase (32). In accordance, both oxidative and nitrosative stress seem to represent early events in the pathogenesis of AD (33)(34)(35)(36).…”

Driving Cellular Plasticity and Survival Through the Signal Transduction Pathways of Metabotropic Glutamate Receptors

“…NO produces apoptotic death in hippocampal and dopaminergic neurons , Sharma, SK and Ebadi, M, 2003, Witting, A et al, 2000. Injury during NO exposure can result not only from a loss of balance between itself and the superoxide ion (Blandini, F et al, 2004), but also NO can become synergistic with hydrogen peroxide to render neurons more sensitive to oxidative injury (de la Monte, SM et al, 2003, Wang, JY et al, 2003. Hydrogen peroxide also results in neuronal injury through impaired mitochondrial function and increased levels of pro-apoptotic gene products, such as CD95/Fas (de la Monte, SM et al, 2000, Pugazhenthi, S et al, 2003, Vaudry, D et al, 2002.…”

Expression of Constitutive Endothelial, Neuronal and Inducible Nitric Oxide Synthase in the Testis and Epididymis of Horse

“…It is postulated that over-activation of eNOS mediates the cell death program through the generation of NO, and may play a role in the cell-selection process that occurs in the seminiferous tubules. Spermatogenesis in the tubules is essentially a result of ongoing cell proliferation, cell selection, and cell death [7,19].…”