Phosphatidic acid (PA) is an important second messenger produced by the activation of numerous cell surface receptors. Recent data have suggested that PA regulates multiple cellular processes. This review addresses primarily the role of PA in the regulation of the Erk1/2 cascade pathway. A model for the regulation of Erk1/2 phosphorylation by cell surface receptors is presented. According to this model, agonists stimulate the binding of GTP to Ras and the activation of phospholipase D to generate phosphatidic acid. PA promotes the binding of cRaf-1 kinase to the membrane, where it interacts with Ras.GTP and other regulatory components of the pathway. Ras^Raf complexes remain bound to the surface of endosomes, where sca¡olding complexes involving Ras, cRaf-1, MEK and Erk are formed. Complete activation and coupling of the cascade requires endocytosis, a process that is also modulated by PA. ß 2002 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

Abstract-Activation of reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase by angiotensin II is integral to the formation of oxidative stress in the vasculature and the kidney. 3-Hydroxy-3-methylglutaryl-coenzyme A reductase inhibition is associated with reductions of oxidative stress in the vasculature and kidney and associated decreases in albuminuria. Effects of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibition on oxidative stress in the kidney and filtration barrier integrity are poorly understood. To investigate, we used transgenic TG(mRen2)27 (Ren2) rats, which harbor the mouse renin transgene and renin-angiotensin system activation, and an immortalized murine podocyte cell line. We treated young, male Ren2 and Sprague-Dawley rats with rosuvastatin (20 mg/kg IP) or placebo for 21 days. Compared with controls, we observed increases in systolic blood pressure, albuminuria, renal NADPH oxidase activity, and 3-nitrotryosine staining, with reductions in the rosuvastatin-treated Ren2. Structural changes on light and transmission electron microscopy, consistent with periarteriolar fibrosis and podocyte foot-process effacement, were attenuated with statin treatment. Nephrin expression was diminished in the Ren2 kidney and trended to normalize with statin treatment. Angiotensin II-dependent increases in podocyte NADPH oxidase activity and subunit expression (NOX2, NOX4, Rac, and p22 phox ) and reactive oxygen species generation were decreased after in vitro statin treatment. These data support a role for increased NADPH oxidase activity and subunit expression with resultant reactive oxygen species formation in the kidney and podocyte. Furthermore, statin attenuation of NADPH oxidase activation and reactive oxygen species formation in the kidney/podocyte seems to play roles in the abrogation of oxidative stress-induced filtration barrier injury and consequent albuminuria. Key Words: angiotensin II Ⅲ albuminuria Ⅲ glomerular filtration barrier Ⅲ transgenic Ren2 rat Ⅲ rosuvastatin R enin-angiotensin system (RAS) activation and subsequently elevated angiotensin II (Ang II) exert the pressor, proliferative, profibrotic, and proinflammatory actions. 1-3 Activation of tissue reduced nicotinamide-adenine dinucleotide phosphate (NADPH) oxidase seems to contribute to deleterious actions, such as oxidative stress and endothelial dysfunction manifesting as hypertension, albuminuria, and progressive glomerular dysfunction, that may ultimately lead to chronic kidney disease. 1,4 There is accumulating evidence that tissue-based RAS further modulates cell growth, metabolism, and tissue remodeling. 5,6 Evidence for a local RAS in the glomerulus raises the prospect of NADPH oxidase-induced podocyte and filtration barrier injury. 7,8 Furthermore, in vitro protein exposure, mechanical stretch, and glomerular hypertension enhance tissue Ang II production, which may potentiate the impact of elevated blood pressure on glomerular injury manifesting as albuminuria. 9,10 Previous work related to the pathogenesis...

Endothelial cell injury and dysfunction are the major triggers of pathophysiological processes leading to cardiovascular disease. Endothelial dysfunction (ED) has been implicated in atherosclerosis, hypertension, coronary artery disease, vascular complications of diabetes, chronic renal failure, insulin resistance and hypercholesterolemia. Although now recognized as a class of physiological second messengers, reactive oxygen species (ROS) are important mediators in cellular injury, specifically, as a factor in endothelial cell damage. Uncontrolled ROS production and/or decreased antioxidant activity results in a deleterious state referred to as 'oxidative stress'. A candidate factor in causing ROS production in endothelial cells is tumor necrosis factor alpha (TNF-α), a pleiotropic inflammatory cytokine. TNF-α has been shown to both be secreted by endothelial cells and to induce intracellular ROS formation. These observations provide a potential mechanism by which TNF-α may activate and injure endothelial cells resulting in ED. In this review, we focus on the relationship between intracellular ROS formation and ED in endothelial cells or blood vessels exposed to TNF-α to provide insight into the role of this important cytokine in cardiovascular disease.

Dellsperger KC. Oxidative stress contributes to pulmonary hypertension in the transgenic (mRen2)27 rat. Am J Physiol Heart Circ Physiol 294: H2659-H2668, 2008. First published April 18, 2008 doi:10.1152/ajpheart.00953.2007.-The transgenic (mRen2)27 (Ren2) rat overexpresses mouse renin in extrarenal tissues, causing increased local synthesis of ANG II, oxidative stress, and hypertension. However, little is known about the role of oxidative stress induced by the tissue renin-angiotensin system (RAS) as a contributing factor in pulmonary hypertension (PH). Using male Ren2 rats, we test the hypothesis that lung tissue RAS overexpression and resultant oxidative stress contribute to PH and pulmonary vascular remodeling. Mean arterial pressure (MAP), right ventricular systolic pressure (RVSP), and wall thickness of small pulmonary arteries (PA), as well as intrapulmonary NADPH oxidase activity and subunit protein expression and reactive oxygen species (ROS), were compared in age-matched Ren2 and Sprague-Dawley (SD) rats pretreated with the SOD/catalase mimetic tempol for 21 days. In placebo-treated Ren2 rats, MAP and RVSP, as well as intrapulmonary NADPH oxidase activity and subunits (Nox2, p22 phox , and Rac-1) and ROS, were elevated compared with placebo-treated SD rats (P Ͻ 0.05). Tempol decreased RVSP (P Ͻ 0.05), but not MAP, in Ren2 rats. Tempol also reduced intrapulmonary NADPH oxidase activity, Nox2, p22 phox , and Rac-1 protein expression, and ROS in Ren2 rats (P Ͻ 0.05). Compared with SD rats, the cross-sectional surface area of small PA was 38% greater (P Ͻ 0.001) and luminal surface area was 54% less (P Ͻ 0.001) in Ren2 rats. Wall surface area was reduced and luminal area was increased in tempol-treated SD and Ren2 rats compared with untreated controls (P Ͻ 0.05). Collectively, the results of this investigation support a seminal role for enhanced tissue RAS/oxidative stress as factors in development of PH and pulmonary vascular remodeling. renin; angiotensin II; NADPH oxidase CARDIOVASCULAR GENERATION of reactive oxygen species (ROS), such as superoxide and H 2 O 2 , has been implicated in the pathogenesis of hypertension, cardiac hypertrophy, pulmonary hypertension (PH), and heart failure (7). Molecular complexes known to generate superoxide within vascular endothelial and smooth muscle cells (SMC) include the NADPH oxidases (18), xanthine oxidase (32), the mitochondrial transport chain, and uncoupled nitric oxide synthase (NOS) (10,19). NADPH oxidase is a major source of ROS in the vasculature and is activated by hormones, growth factors, cytokines, and shear stress (16). An important stimulus for NADPH oxidase-generated ROS is ANG II. In fact, many of the deleterious effects of ANG II on vascular structure and function are mediated by ROS generation (16,73). ANG II causes rapid induction of NADPH oxidase-dependent superoxide synthesis via PKC (15) and more prolonged stimulation via transactivation of growth factors (62, 69). ANG II also causes redox-sensitive xanthine oxidase activation and endothelial N...