Role of Rac1 GTPase in NADPH Oxidase Activation and Cognitive Impairment Following Cerebral Ischemia in the Rat

Abstract

BackgroundRecent work by our laboratory and others has implicated NADPH oxidase as having an important role in reactive oxygen species (ROS) generation and neuronal damage following cerebral ischemia, although the mechanisms controlling NADPH oxidase in the brain remain poorly understood. The purpose of the current study was to examine the regulatory and functional role of the Rho GTPase, Rac1 in NADPH oxidase activation, ROS generation and neuronal cell death/cognitive dysfunction following global cerebral ischemia in the male rat.Methodology/Principal FindingsOur studies revealed that NADPH oxidase activity and superoxide (O2 −) production in the hippocampal CA1 region increased rapidly after cerebral ischemia to reach a peak at 3 h post-reperfusion, followed by a fall in levels by 24 h post-reperfusion. Administration of a Rac GTPase inhibitor (NSC23766) 15 min before cerebral ischemia significantly attenuated NADPH oxidase activation and O2 − production at 3 h after stroke as compared to vehicle-treated controls. NSC23766 also attenuated “in situ” O2 − production in the hippocampus after ischemia/reperfusion, as determined by fluorescent oxidized hydroethidine staining. Oxidative stress damage in the hippocampal CA1 after ischemia/reperfusion was also significantly attenuated by NSC23766 treatment, as evidenced by a marked attenuation of immunostaining for the oxidative stress damage markers, 4-HNE, 8-OHdG and H2AX at 24 h in the hippocampal CA1 region following cerebral ischemia. In addition, Morris Water maze testing revealed that Rac GTPase inhibition after ischemic injury significantly improved hippocampal-dependent memory and cognitive spatial abilities at 7–9 d post reperfusion as compared to vehicle-treated animals.Conclusions/SignificanceThe results of the study suggest that Rac1 GTPase has a critical role in mediating ischemia/reperfusion injury-induced NADPH oxidase activation, ROS generation and oxidative stress in the hippocampal CA1 region of the rat, and thus contributes significantly to neuronal degeneration and cognitive dysfunction following cerebral ischemia.

TRPM2 mediates ischemic kidney injury and oxidant stress through RAC1

“…To determine the functional significance of such RAC1 activation, we treated mice with NSC23766, a potent and specific inhibitor of RAC1 activation (41,42), prior to ischemic injury. As shown in Figure 8A, the NSC23766-treated mice had better preservation of kidney function than did vehicle-treated mice.…”

Treatment with Evasin-3 Reduces Atherosclerotic Vulnerability for Ischemic Stroke, but Not Brain Injury in Mice

“…21 This endogenous halogenated derivative the aromatic amino acid L-Phenylalanine has been recently shown to protect neurons from ischemic brain injury in rats. 21 Thus, beside that fact Evasin-3 treatment did not improve the cerebral levels of specific inflammatory mediators of cerebral injury (such as proteases, TNF, IL-6, and other oxidants), 24,34 the selective reduction in neutrophilic ROS in the presence of Evasin-3 treatment might even be deleterious for the ischemic brain. 20,33 Our results are in partial contrast with previous studies indicating that the abrogation of poststroke neutrophil cerebral infiltration might be a promising therapeutic target to reduce brain injury during reperfusion.…”

Inhibiting NADPH oxidase protects against long-term memory impairment induced by neonatal sevoflurane exposure in mice

“…11 12 Indeed, previous studies have shown that superoxide production by NADPH oxidase underlies cognitive impairment after cerebral ischaemia and traumatic brain injury. [13][14][15] However, the role of NADPH oxidase in memory impairment has not been examined in animals exposed to anaesthesia in the neonatal period. Furthermore, it is not known whether targeting NADPH oxidase during anaesthesia protects the neonatal brain from long-term memory deficits.…”