Reducing conditions significantly attenuate the neuroprotective efficacy of competitive, but not other NMDA receptor antagonists in vitro

Inappropriate activation of NMDA receptors during a period of cerebral ischaemia is a crucial event in the pathway leading to neuronal degeneration. However, significant research has failed to deliver a clinically active NMDA receptor antagonist, and competitive NMDA antagonists are ineffective in many experimental models of ischaemia. The NMDA receptor itself has a number of modulatory sites which may affect receptor function under ischaemic conditions. Using rat organotypic hippocampal slice cultures we have investigated whether the redox modulatory site affects the neuroprotective efficacy of NMDA receptor antagonists against excitotoxicity and experimental ischaemia (OGD). NMDA toxicity was significantly enhanced in cultures pretreated with a reducing agent. The noncompetitive antagonist MK-801 and a glycine-site blocker were equally neuroprotective in both normal and reduced conditions, but there was a significant rightward shift in the dose–response curves of the competitive antagonists APV and CPP and the uncompetitive antagonist memantine. OGD produced neuronal damage predominantly in the CA1 region, which was prevented by MK-801 and memantine, but not by APV or CPP. Inclusion of an oxidizing agent during the period of OGD had no effect alone, but significantly enhanced the neuroprotective potency of the competitive antagonists. These data clearly demonstrate that chemical reduction of the redox modulatory site of the NMDA receptor decreases the ability of competitive antagonists to block NMDA receptor-mediated neuronal damage, and that the reducing conditions which occur during simulated ischaemia are sufficient to produce a similar effect. This may have important implications for the design of future neuroprotective agents

Fiber intake and total and cause-specific mortality in the European Prospective Investigation into Cancer and Nutrition cohort.

BACKGROUND: Previous studies have shown that high fiber intake is associated with lower mortality. However, little is known about the association of dietary fiber with specific causes of death other than cardiovascular disease (CVD). OBJECTIVE: The aim of this study was to assess the relation between fiber intake, mortality, and cause-specific mortality in a large European prospective study of 452,717 men and women. DESIGN: HRs and 95% CIs were estimated by using Cox proportional hazards models, stratified by age, sex, and center and adjusted for education, smoking, alcohol consumption, BMI, physical activity, total energy intake, and, in women, ever use of menopausal hormone therapy. RESULTS: During a mean follow-up of 12.7 y, a total of 23,582 deaths were recorded. Fiber intake was inversely associated with total mortality (HR(per 10-g/d increase): 0.90; 95% CI: 0.88, 0.92); with mortality from circulatory (HR(per 10-g/d increase): 0.90 and 0.88 for men and women, respectively), digestive (HR: 0.61 and 0.64), respiratory (HR: 0.77 and 0.62), and non-CVD noncancer inflammatory (HR: 0.85 and 0.80) diseases; and with smoking-related cancers (HR: 0.86 and 0.89) but not with non-smoking-related cancers (HR: 1.05 and 0.97). The associations were more evident for fiber from cereals and vegetables than from fruit. The associations were similar across BMI and physical activity categories but were stronger in smokers and participants who consumed >18 g alcohol/d. CONCLUSIONS: Higher fiber intake is associated with lower mortality, particularly from circulatory, digestive, and non-CVD noncancer inflammatory diseases. Our results support current recommendations of high dietary fiber intake for health maintenance