No abstract

Changes in vascular permeability occur during inflammation and the actin cytoskeleton plays a crucial role in regulating endothelial cell contacts and permeability. We demonstrated recently that the actin-binding protein cortactin regulates vascular permeability via Rap1. However, it is unknown if the actin cytoskeleton contributes to increased vascular permeability without cortactin. As we consistently observed more actin fibres in cortactin-depleted endothelial cells, we hypothesised that cortactin depletion results in increased stress fibre contractility and endothelial barrier destabilisation. Analysing the contractile machinery, we found increased ROCK1 protein levels in cortactin-depleted endothelium. Concomitantly, myosin light chain phosphorylation was increased while cofilin, mDia and ERM were unaffected. Secretion of the barrier-stabilising hormone adrenomedullin, which activates Rap1 and counteracts actomyosin contractility, was reduced in plasma from cortactin-deficient mice and in supernatants of cortactin-depleted endothelium. Importantly, adrenomedullin administration and ROCK1 inhibition reduced actomyosin contractility and rescued the effect on permeability provoked by cortactin deficiency in vitro and in vivo. Our data suggest a new role for cortactin in controlling actomyosin contractility with consequences for endothelial barrier integrity.

Our data support the relevance of NO as an antagonist to superoxide in renal tissues and suggest that the loss of this mechanism promotes the progression of kidney failure.

Low levels of chronic lead exposure can produce hypertension and endothelial dysfunction, which could be associated with oxidative stress, changes in vascular tone and an imbalance of endothelial-derived vasoconstriction and vasodilator factors. The aim was to investigate the effect of chronic lead-exposure on angiotensin II-induced vasoconstriction in isolated perfused kidney and microvessels. Male Wistar rats (230—250 g) were treated for 12 weeks with lead acetate (100 ppm, Pbgroup) or pure water (control group). We evaluated the vascular reactivity in the kidneys and renal microvessels in the presence and absence of Nω-nitro-L-arginine methyl ester (L-NAME) in both groups. The nitrite concentration in renal perfusate was measured as an index of NO released, renal abundance of 3-nitrotyrosine was measured as well as endothelial NO synthase (eNOS) expression. Oxidative stress was measured by using the oxidative fluorescence dye dihydroethidium (DHE) to evaluate in situ production of superoxide and identified by confocal microscopy. Lead-exposure significantly increased blood pressure, eNOS protein expression, oxidative stress and vascular reactivity to angiotensin II. L-NAME potentiated vascular response to angiotensin II in control group but had no effect on the Pb-group. Nitrites released from the kidney of lead-group was lower compared to the control group while 3-nitrotyrosine was higher. This data suggest that lead-induced hypertension could be caused partially by an altered NOsystem. Human & Experimental Toxicology (2007) 26: 499—507

Peripheral arterial occlusive disease (PAD) describes vascular disorders associated with ischemia and PAD affects about 8 million people in the United States. Moreover, PAD's prevalence can increase dramatically if cardiovascular disease is present. In healthy individuals reducing blood flow through the lower extremity is followed by a physiological process to limit ischemia in the distal tissue. This process is called revascularization and impairing revascularization results in PAD. Studies suggest nitric oxide (NO) maybe involved in the ischemia-dependent hindlimb revascularization process. NO is increased in the ischemic hindlimb and eliminating NO impairs the revascularization process. Moreover, restoring NO improves hindlimb revascularization. NO may be acting through its effects on vascular tone, cell migration, or extracellular matrix degradation. The present review illustrates nitric oxide's critical role in the ischemia-induced hindlimb revascularization. Thus, restoring normal NO levels in diseased arteries may represent a viable therapeutic avenue by supplementing exogenous NO or employing therapeutic strategies to either increase NO synthesis and its messengers or decrease NO catabolism.