Reactive oxygen species modulate growth of cerebral aneurysms: a study using the free radical scavenger edaravone and p47phox−/− mice

Abstract

Cerebral aneurysm (CA) is a relatively common disease and can cause a catastrophic subarachnoid hemorrhage with a high mortality and morbidity rate. Despite its clinical and social importance, the detailed mechanism of CA formation remains to be elucidated, resulting in the absence of effective medical treatment against CAs. Recent studies revealed that chronic inflammation in arterial walls by hemodynamic force is implicated in CA formation. Reactive oxygen species (ROS) are a major mediator of inflammation and actively participate in the pathogenesis of various vascular diseases. In the present study, we first assessed the expression of ROS-producing and -eliminating genes in CA walls by immunohistochemistry and RT-PCR analysis. The ROS-producing gene, p47phox, was upregulated in infiltrating macrophages and medial smooth muscle cells in arterial walls. Upregulated ROS-producing genes and suppressed ROS-eliminating genes suggested that ROS overproduction occurred in aneurysmal walls. In situ superoxide imaging by dihydroethidium, which showed ROS overproduction in aneurysmal walls, confirmed this hypothesis. Edaravone, a powerful free radical scavenger, effectively inhibited CA formation by suppressing inflammation-related gene expression in aneurysmal walls. Furthermore, CA formation was markedly inhibited by p47phox deletion in mice and was accompanied by decreased inflammation in aneurysmal walls. These data suggested the active participation of ROS and p47phox in CA formation and the therapeutic potential of an ROS-eliminating agent against CA formation.

Complementary inhibition of cerebral aneurysm formation by eNOS and nNOS

“…14,41 Furthermore, iNOS also contributes to the chronic inflammation by the production of reactive oxygen species in CA walls. 42 Combined with the results from this study, the NOS family has a close relation with CA formation. Both eNOS and nNOS are constitutively expressed in cerebral arteries and have the protective role in CA formation.…”

Antioxidant Strategies in Neurocritical Care

“…In addition, treatment with alpha-lipoic acid, a dithiol antioxidant, improves neurological outcome and decreases brain edema and free radical generation [44]. In another study of rat model of aneurysm genesis, ROS were related to aneurysm formation [43]. In this study, rats were fed a high salt diet for 3 months in addition to a lysyl-oxidase inhibitor, an enzyme involved in catalyzing the crosslinking between collagen and elastin.…”

“…In rodent models of subarachnoid hemorrhage (SAH), there is evidence of increased superoxide anion and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, both powerful oxidizing agents [43,44]. In addition, treatment with alpha-lipoic acid, a dithiol antioxidant, improves neurological outcome and decreases brain edema and free radical generation [44].…”

“…In this study, rats were fed a high salt diet for 3 months in addition to a lysyl-oxidase inhibitor, an enzyme involved in catalyzing the crosslinking between collagen and elastin. Upregulation of ROS-producing genes, suppression of ROS-eliminating genes, and many highly oxidative species, such as hemeoxygenase, NOS, MMP-2, and a 47 kDa portion of NADPH oxidase were detected within the spontaneous aneurysms that formed, using reverse transcriptase PCR analysis, Western blot, and immunohistochemistry [43]. Pre-treatment with edavarone, a free-radical scavenger, decreased size of the aneurysm and the production of the previously mentioned oxidizing agents within the aneurysm, and also within infiltrating macrophages and smooth muscle cells [43].…”

“…Upregulation of ROS-producing genes, suppression of ROS-eliminating genes, and many highly oxidative species, such as hemeoxygenase, NOS, MMP-2, and a 47 kDa portion of NADPH oxidase were detected within the spontaneous aneurysms that formed, using reverse transcriptase PCR analysis, Western blot, and immunohistochemistry [43]. Pre-treatment with edavarone, a free-radical scavenger, decreased size of the aneurysm and the production of the previously mentioned oxidizing agents within the aneurysm, and also within infiltrating macrophages and smooth muscle cells [43]. These effects were more profound when studying these phenomena in a p47 NADPH oxidase knockout mouse, suggesting that this may be one of the key oxidizing agents required for initiating the aneurysm signaling cascade.…”