Selective Vulnerability of Hippocampi for Nitric Oxide Synthases in Alzheimer's Disease Pathology and Cognitive Abilities.

Alzheimer's disease (AD) neuropathological changes (ADNC) are characterized by amyloid plaques and neurofibrillary tangles. The role of nitric oxide synthase (NOS) in disease progression remains unclear. This study investigates the expression of neural, inducible, and endothelial NOS (nNOS, iNOS, eNOS) and 3-nitrotyrosine (3-NT) in the hippocampal subregions of individuals with ADNC and their association with cognitive abilities. Immunohistochemistry was performed on hippocampal samples from 10 individuals with ADNC and 10 age- and sex-matched controls to detect NOS enzymes, and 3-NT expression in CA1, CA2, CA3, and CA4. Logistic ordinal regressions evaluated associations of NOS and 3-NT expression with AD pathology, while linear regressions assessed relationships with cognitive abilities. Overexpression of nNOS was observed in all hippocampal subregions in ADNC participants. iNOS expression was elevated in CA1 and CA3, while eNOS showed increased levels only in CA3. 3-NT was significantly higher in CA3 of ADNC participants. nNOS expression in all hippocampal regions correlated with AD pathology and cognitive impairment. iNOS in CA3 was associated with AD pathology and cognitive scores. No associations were found for eNOS, and 3-NT in CA3 correlated with cognitive impairment. Associations of nNOS and iNOS with neuropathology and cognition suggest a role for NOS in AD pathophysiology.