Neuroprotection by 7-nitroindazole against iron-induced hippocampal neurotoxicity

Abstract

(1) Iron plays an important role in maintaining normal brain function. In some neurodegenerative disorders including Parkinson's and Alzheimer's disease, iron levels rise in the brain. It is known that higher iron levels induce neuronal hyperactivity and oxidative stress. A body of evidence indicates a relationship between neuronal death and nitric oxide (NO). The aim of present study was to evaluate the effects of NO produced by neuronal nitric oxide synthase (nNOS) on iron-induced neuronal death. (2) Animals were classified into four groups: control, iron, iron+7-nitroindazole, and iron+vehicle. Rats in iron, iron+7-nitroindazole, and iron+vehicle groups received intracerebroventricular (i.c.v.) FeCl3 injection (200 mM, in 2.5 microl). Rats belonging to control groups received the same amount of saline into the cerebral ventricles. All animals were kept alive for 10 days following the operation. Animals in iron+7-nitroindazole group received intraperitoneal 7-nitroindazole (30 mg/kg/day) injections once a day during this period, while the rats belonging to vehicle group received daily intraperitoneal injection of peanut oil. After 10 days, rats were perfused intracardially under deep urethane anesthesia. Removed brains were processed using the standard histological techniques. (3) The total number of neurons in hippocampus of all rats was estimated with the unbiased stereological techniques. Results of present study show that 7-nitroindazole decreased mean neuron loss from 43% to 11%. Treatment of peanut oil alone did not affect iron-induced hippocampal cell loss with respect to iron group values. (4) Findings of our study suggest that 7-nitroindazole may have neuroprotective effects against iron-induced hippocampal neurotoxicity by inhibiting nNOS.

Fig. 1

Representative photomicrographs from the same level of hippocampal sections. (a) Control. (b) Iron (200 mM) decreased hippocampal pyramidal cell number. (c) Peanut oil did not affect hippocampal neuron loss. (d) 7-nitroindazole treatment (30 mg/kg) reversed iron-induced neurotoxicity. Scale bar: 2 μm

Fig. 2

The effects of iron, iron+7-nitroindazole, and iron+vehicle on left and right hippocampal pyramidal cell number. Error bars represent ± SEM. * P < 0.001 compared to control and ^# P < 0.001 compared to iron group. 7-NI, 7-nitroindazole; V, vehicle