Oscillatory Shear Stress Induces Mitochondrial Superoxide Production: Implication of NADPH Oxidase and c-Jun NH₂-Terminal Kinase Signaling

Abstract

Fluid shear stress is intimately linked with vascular oxidative stress and atherosclerosis. We posited that atherogenic oscillatory shear stress (OSS) induced mitochondrial superoxide (mtO 2 À ) production via NADPH oxidase and c-Jun NH 2 -terminal kinase ( JNK-1 and JNK-2) signaling. In bovine aortic endothelial cells, OSS (AE3 dyn=cm 2 ) induced JNK activation, which peaked at 1 h, accompanied by an increase in fluorescein isothiocyanate-conjugated JNK fluorescent and MitoSOX Red (specific for mtO 2 À production) intensities. Pretreatment with apocynin (NADPH oxidase inhibitor) or N-acetyl cysteine (antioxidant) significantly attenuated OSS-induced JNK activation. Apocynin further reduced OSS-mediated dihydroethidium and MitoSOX Red intensities specific for cytosolic O 2 À and mtO 2 À production, respectively. As a corollary, transfecting bovine aortic endothelial cells with JNK siRNA (siJNK) and pretreating with SP600125 ( JNK inhibitor) significantly attenuated OSS-mediated mtO 2 À production. Immunohistochemistry on explants of human coronary arteries further revealed prominent phosphorylated JNK staining in OSS-exposed regions. These findings indicate that OSS induces mtO 2 À production via NADPH oxidase and JNK activation relevant for vascular oxidative stress. Antioxid. Redox Signal. 15, 1379-1388.

Shear stress modulates RAGE-mediated inflammation in a model of diabetes-induced metabolic stress

“…OSS also increases oxidative stress through enhanced NOX expression and activity. Takabe et al (40) demonstrated that OSS increased the generation of cytoplasmic O 2 Ϫ through NADPH oxidase activation, which consequently increased mitochondrial O 2 Ϫ through a JNK-dependent mechanism in EC. Consistent with these observations, we demonstrate a role for NOX contributing to enhanced cytoplasmic and mitochondrial ROS production, leading to enhanced NF-B activity underlying the RAGE activation in our model.…”

“…Consistent with these observations, we demonstrate a role for NOX contributing to enhanced cytoplasmic and mitochondrial ROS production, leading to enhanced NF-B activity underlying the RAGE activation in our model. Although the specificity of apocynin as an inhibitor of NOX is controversial and may vary by cell type, it has been widely used in mechanistic studies of shear mediated NOX activity in endothelium both in vivo and in vitro (40).…”

“…Using DHE and flow cytometry, we did not detect differences in cytoplasmic O 2 Ϫ over the range of conditions leading to enhanced VCAM-1 expression (not shown). However, O 2 Ϫ is thought to be quickly converted to H 2 O 2 in HAEC through the action of superoxide dismutase, which leads to increased mitochondrial O 2 Ϫ production and subsequent dysfunction (10,40). We assessed cytoplasmic H 2 O 2 levels in HAEC using dichlorofluorescein and found that conditioning with HG increased ROS to a comparable level above TNF-␣, regardless of ligand stimulation (Fig.…”

“…To directly elucidate the influence of SS on endothelial RAGE expression, we exposed cultured HAEC to physiological SS characteristics representing DF and UF in vitro. OSS has been used widely to model DF characteristics in vitro (7,22,40) while steady HSS is frequently used to model UF. In HAEC exposed to OSS (0 Ϯ 5 dyn/cm 2 ), RAGE mRNA levels were not changed compared with static conditions (Fig.…”

Laminar Flow Activation of ERK5 Protein in Vascular Endothelium Leads to Atheroprotective Effect via NF-E2-related Factor 2 (Nrf2) Activation

“…2 NF-E2-related factor 2 (Nrf2) is one of the major transcription factors in laminar flowmediated cytoprotective responses in ECs (3)(4)(5). Flow activation of Nrf2 induces a group of antioxidant genes via the activation of antioxidant response element (ARE) (3,6).…”