Effects of ANG II type 1 and 2 receptors on oxidative stress, renal NADPH oxidase, and SOD expression

Abstract

Oxidative stress accompanies angiotensin (ANG) II infusion, but the role of ANG type 1 vs. type 2 receptors (AT 1-R and AT2-R, respectively) is unknown. We infused ANG II subcutaneously in rats for 1 wk. Excretion of 8-isoprostaglandin F 2␣ (8-Iso) and malonyldialdehyde (MDA) were related to renal cortical mRNA abundance for subunits of NADPH oxidase and superoxide dismutases (SODs) using real-time PCR. Subsets of ANG II-infused rats were given the AT 1-R antagonist candesartan cilexetil (Cand) or the AT 2-R antagonist PD-123,319 (PD). Compared to vehicle (Veh), ANG II increased 8-Iso excretion by 41% (Veh, 5.4 Ϯ 0.8 vs. ANG II, 7.6 Ϯ 0.5 pg/24 h; P Ͻ 0.05). This was prevented by Cand (5.6 Ϯ 0.5 pg/24 h; P Ͻ 0.05) and increased by PD (15.8 Ϯ 2.0 pg/24 h; P Ͻ 0.005). There were similar changes in MDA excretion. Compared to Veh, ANG II significantly (P Ͻ 0.005) increased the renal cortical mRNA expression of p22 phox (twofold), Nox-1 (2.6-fold), and Mn-SOD (1.5-fold) and decreased expression of Nox-4 (2.1-fold) and extracellular (EC)-SOD (2.1-fold). Cand prevented all of these changes except for the increase in Mn-SOD. PD accentuated changes in p22 phox and Nox-1 and increased p67 phox . We conclude that ANG II infusion stimulates oxidative stress via AT 1-R, which increases the renal cortical mRNA expression of p22 phox and Nox-1 and reduces abundance of Nox-4 and EC-SOD. This is offset by strong protective effects of AT 2-R, which are accompanied by decreased expression of p22 phox , Nox-1, and p67 phox . O 2 Ϫ ⅐ interacts with esterified or free arachidonate to yield a family of isoprostanes that includes 8-isoprostane prostaglandin F 2␣ (8-Iso). The steady-state excretion of 8-Iso reflects oxidative stress (38). There is evidence of enhanced oxidative stress during prolonged infusion of ANG II (36) and in models of ANG IIdependent hypertension (2,8,22,24,48). However, the roles of AT 1 -R vs. AT 2 -R in the generation of oxidative stress and the expression of NADPH oxidase and SOD in kidneys has not been established.The first aim of this study was to determine the effects of AT 1 -and AT 2 -R blockade on the excretion of 8-Iso during a "slow-pressor" dose of ANG II. Because isoprostanes also can be generated by metabolism of arachidonate via cyclooxygenase (19,33), additional studies assessed the excretion of an arachidonate-independent marker of lipid peroxidation, malonyldialdehyde (MDA). The second aim was to investigate the effects of these perturbations on the renal expression of the mRNAs for the components of NADPH oxidase and SOD isoforms.

Salt Intake, Oxidative Stress, and Renal Expression of NADPH Oxidase and Superoxide Dismutase

“…Previously, we found that the normal kidney expressed the mRNA and protein for all of the subunits for phagocyte NAD(P)H oxidase and the mRNA for Nox-1 and Nox-4 (14) and for EC-, IC-, and Mn-SOD (19). Prolonged infusion of Ang II activates NAD(P)H oxidase in blood vessels (1,2,10,12), where it increases expression of the p22 phox , Nox-1, and Nox-4 components in VSMC from conduit vessels (33-35) and p67 phox in vascular adventitial cells (36).…”

“…RNA isolation and RT were performed using oligonucleotide and methods described previously (14,19). Briefly, total RNA was isolated from the kidney cortex with guanidinium isothiocyanate (Qiagen, Valencia, CA) and treated with DNase.…”

“…When the primers and the probes did not fulfill the requirements, they were redesigned. After the indicated validations, the comparative ⌬C T method was used for relative quantification and statistical analysis (ABI Prism 7700 Sequence Detection System User's Manual) (19). 2␣ .…”

The effect of short-term canola oil ingestion on oxidative stress in the vasculature of stroke-prone spontaneously hypertensive rats

“…The primers were all obtained from previous published sequences and were ordered through Geneworks (Australia): NOX2 [37], p22 phox [35], CuZn-SOD, MnSOD and Ec-SOD [36]. …”

Nox enzymes, ROS, and chronic disease: An example of antagonistic pleiotropy

“…In kidney, Nox-dependent ROS is produced in response to agonists that bind to D1-like receptors [103], to Angiotensin II [104,105] and to H + fluxes [106]. Although physiological roles are not well understood, Nox enzymes have been suggested to function in normal renal physiology in secretion of erythropoietin [100], in renal regulation of blood pressure [103], regulation of mesangial cell protein synthesis [107] and in innate immunity [23].…”