Mechanism of temporal gradients in shear-induced ERK1/2 activation and proliferation in endothelial cells

Abstract

The aim of the current study was to investigate the intracellular signaling cascade that leads to temporal gradients in shear (TGS)-induced endothelial cell proliferation, with a focus on the involvement of extracellular signal-regulated kinases 1 and 2 (ERK1/2). With the use of well-defined pulsatile, impulse, step, and ramp laminar flow profiles, we found that TGS (impulse flow and pulsatile flow) induced an enhanced and sustained (>30 min) phosphorylation of ERK1/2 relative to step flow (which contains a step increase in shear followed by steady shear), whereas steady shear (ramp flow) alone downregulated activated ERK1/2. Nitric oxide (NO) was found to mediate both the stimulatory effect of TGS and the inhibitory effect of steady shear on endothelial ERK1/2 phosphorylation. Reactive oxygen species (ROS) were also demonstrated to be associated with TGS-induced ERK1/2 phosphorylation. Both G(q/11) and G(i3) were necessary for the activation of ERK1/2 by TGS. Finally, the TGS-induced endothelial proliferative response was abolished by ERK1/2 inhibition. Our study demonstrated the essential role of G proteins, NO, and ROS in TGS-dependent ERK1/2 activation and proliferative response in vascular endothelial cells.

Molecular Biology of Atherosclerosis

“…After several hours of laminar flow, however, NO is favored through multiple mechanisms (see FIGURES 11 AND 12) (451). Indeed, enhanced production of NO is one of the hallmarks of the atheroprotective state (105).…”

Effect of Frequency of Uniform and Disturbed Pulsatility Flow on Tissue Factor Expression of Human Umbilical Vein Endothelial Cells

“…It is also now evident that sites of atherosclerosis correlate with areas of disturbed fluid dynamics and links the observations that temporal or spatial gradients in these hemodynamic forces are more potent stimuli for ECs than the actual magnitude of the force [21]. ECs exposed to unidirectional flow, especially high laminar shear, have been reported to express atheroprotective genes [2].…”

“…In addition, an acute decrease from 100 cpm to 60 cpm also resulted in an immediate increase in IP 3 [19]. Bao et al [21] demonstrated that EC exposed to different shear segments of either step flow, ramp flow, impulse flow or pulsatile shear had variable activation of signaling pathway. Likewise, we showed that bovine aortic ECs exposed to pulsatile flow frequencies of 0.5 and 1.0 Hz, but not 1.5 Hz, exhibited elongated morphologies and oriented with the direction of flow [22].…”

Mitochondrial Ca 2+ transport in the endothelium: regulation by ions, redox signalling and mechanical forces

“…The Asp240 (red space fill) and Glu243 (orange space fill) residues which bind Mn 2þ cooperatively are indicated within the DXXE motif. The outer and inner coiled-coil bundles (CC1, brown ribbons (residues [180][181][182][183][184][185][186][187][188][189][190][191][192][193] alignment of ID1/2 domains when EF1/2 are in the Ca 2þ -loaded and -depleted states show only minor structural differences ( figure 1b,c) Although a high-resolution structure of the pore-forming and coiled-coil regions of human MCU is currently unavailable, a nuclear magnetic resonance (NMR) spectroscopy-and transmission electron microscopy-driven pentameric model of Caenorhabditis elegans MCU with a deleted N-terminal domain has been constructed [62]. This structure shows that the second TM domain is positioned to line the pore of the channel with a short DXXE motif contributed by each subunit lining the entrance to the pore (figure 1d).…”

“…induced an increase upon the onset of flow, but, after the first couple of hours, the increase in ROS was compensated by upregulation of antioxidant defences, such as haem oxygenase-1 (HO-1) and NADPH quinone oxidoreductase 1 (NQO1), under the control of nuclear factor erythroid 2-related factor 2 (Nrf2) [153,[182][183][184][185][186]. NADPH oxidases (NOXs), xanthine oxidase, mitochondria and uncoupled eNOS are the main sources of cytosolic ROS in ECs [187].…”