Influence of duration of focal cerebral ischemia and neuronal nitric oxide synthase on translocation of apoptosis-inducing factor to the nucleus

Abstract

Translocation of apoptosis-inducing factor (AIF) from the mitochondria to the nucleus can play a major role in neuronal death elicited by oxidant stress. The time course of nuclear translocation of AIF after experimental stroke may vary with the severity of injury and may be accelerated by oxidant stress associated with reperfusion and nitric oxide (NO) production. Western immunoblots of AIF on nuclear fractions of ischemic hemisphere of male mice showed no significant increase with 1 hour of middle cerebral artery occlusion and no reperfusion, whereas increases were detectable after 6 and 24 hours of permanent ischemia. However, as little as 20 minutes of reperfusion after 1 hour of middle cerebral artery occlusion resulted in an increase in nuclear AIF coincident with an increase in poly(ADP-ribose) polymer (PAR) formation. Further nuclear AIF accumulation was seen at 6 and 24 hours of reperfusion. In contrast, 20 minutes of reperfusion after 2 hours of occlusion did not increase nuclear AIF. In this case, nuclear AIF became detectable at 6 and 24 hours of reperfusion. With brief occlusion of 30 minute duration, nuclear AIF remained undetectable at both 20 minutes and 6 hours and became evident only after 24 hours of reperfusion. Inhibition of neuronal NO synthase attenuated formation of PAR and nuclear AIF accumulation. Gene deletion of neuronal NO synthase also attenuated nuclear AIF accumulation. Therefore, reperfusion accelerates AIF translocation to the nucleus when focal ischemia is of moderate duration (1 hour), but is markedly delayed after brief ischemia (30 minutes). Nuclear translocation of AIF eventually occurs with prolonged focal ischemia with or without reperfusion. Neuronally-derived NO is a major factor contributing to nuclear AIF accumulation after stroke.

Regulation of poly(ADP-ribose) polymerase 1 activity by the phosphorylation state of the nuclear NAD biosynthetic enzyme NMN adenylyl transferase 1

“…The observation that the overexpression of NMNAT-1 enhanced the relocation of AIF from the mitochondria in response to oxidant treatment further corroborates this notion. It has been demonstrated that AIF translocation is directly triggered by PAR in a dose-dependent manner (39,40). Importantly, NMNAT-1 overexpression does not alter the steady-state level of NAD ϩ (48,49).…”

“…Overactivation of the enzyme may almost completely deplete cellular NAD ϩ stores (36,37). Poly(ADP-ribosyl)ation also triggers cell death by releasing apoptosis-inducing factor (AIF) from the mitochondria (38)(39)(40). Such a broad range of functions requires mechanisms controlling the catalytic activity of PARP-1 to assure the balanced activation of individual pathways.…”

Antioxidant effect of salvianolic acid B on hippocampal CA1 neurons in mice with cerebral ischemia and reperfusion injury

“…(23)(24)(25)(26)(27) It has been shown that Bcl-2 can take its anti-apoptotic effect by inhibiting mitochondrial PTP opening and cytochrome c release and Bax can take its pro-apoptotic effect by inducing mitochondrial PTP opening. (28)(29)(30) These findings suggest that both caspase and Bcl-2 family regulate apoptosis by controlling mitochondrial permeability. Therefore, the apoptosis regulatory function of Bcl-2 protein family is mitochondria dependent.…”

Ischemic preconditioning attenuates mitochondrial localization of PTEN induced by ischemia-reperfusion

“…Cytosolic, mitochondrial, and nuclear protein fractions were extracted as previously described (25). Heart tissue was homogenized and then centrifuged at 2,000 g at 4°C.…”