Abstract-Studies were performed to test the hypothesis that reactive oxygen species (ROS) and mitogen-activated protein kinase (MAPK) contribute to the pathogenesis of aldosterone/salt-induced renal injury. Rats were given 1% NaCl to drink and were treated with one of the following combinations for 6 weeks: vehicle (0.5% ethanol, SC, nϭ6); aldosterone (0.75 g/H, SC, nϭ8); aldosterone plus a selective mineralocorticoid receptor antagonist; eplerenone (0.125% in chow, nϭ8); aldosterone plus an antioxidant; and tempol (3 mmol/L in drinking solution, nϭ8). The activities of MAPKs, including extracellular signal-regulated kinases (ERK)1/2, c-Jun-NH 2 -terminal kinases (JNK), p38MAPK, and big-MAPK-1 (BMK1) in renal cortical tissues were measured by Western blot analysis. Aldosteroneinfused rats showed higher systolic blood pressure (165Ϯ5 mm Hg) and urinary excretion of protein (106Ϯ24 mg/d) than vehicle-infused rats (118Ϯ3 mm Hg and 10Ϯ3 mg/d). Renal cortical mRNA expression of p22phox, Nox-4, and gp91phox, measured by real-time polymerase chain reaction, was increased in aldosterone-infused rats by 2.3, 4.3, and 3.0-fold, respectively. Thiobarbituric acid-reactive substances (TBARS) content in renal cortex was also higher in aldosterone (0.23Ϯ0.02) than vehicle-infused rats (0.09Ϯ0.01 nmol/mg protein). ERK1/2, JNK, and BMK1 activities were significantly elevated in aldosterone-infused rats by 3.3, 2.3, and 3.0-fold, respectively, whereas p38MAPK activity was not changed. Concurrent administration of eplerenone or tempol to aldosterone-infused rats prevented the development of hypertension (127Ϯ2 and 125Ϯ5 mm Hg), and the elevations of urinary excretion of protein (10Ϯ2 and 9Ϯ2 mg/day) or TBARS contents (0.08Ϯ0.01 and 0.11Ϯ0.01 nmol/mg protein). Furthermore, eplerenone and tempol treatments normalized the activities of ERK1/2, JNK, and BMK1. These data suggest that ROS and MAPK play a role in the progression of renal injury induced by chronic elevations in aldosterone.

In this study, we investigated whether orally administered nitrite is changed to NO and whether nitrite attenuates hypertension in a dose-dependent manner. We utilized a stable isotope of [15N]nitrite (15NO2-) as a source of nitrite to distinguish between endogenous nitrite and that exogenously administered and measured hemoglobin (Hb)-NO as an index of circulating NO in whole blood using electron paramagnetic resonance (EPR) spectroscopy. When 1 mg/kg Na15NO2 was orally administered to rats, an apparent EPR signal derived from Hb15NO (A(Z) = 23.4 gauss) appeared in the blood. The peak blood HbNO concentration occurred at the first measurement after intake (5 min) for treatment with 1 and 3 mg/kg (HbNO: 4.93 +/- 0.52 and 10.58 +/- 0.40 microM, respectively) and at 15 min with 10 mg/kg (HbNO: 38.27 +/- 9.23 microM). In addition, coadministration of nitrite (100 mg/l drinking water) with N(omega)-nitro-L-arginine methyl ester (L-NAME; 1 g/l) for 3 wk significantly attenuated the L-NAME-induced hypertension (149 +/- 10 mmHg) compared with L-NAME alone (170 +/- 13 mmHg). Furthermore, this phenomenon was associated with an increase in circulating HbNO. Our findings clearly indicate that orally ingested nitrite can be an alternative to L-arginine as a source of NO in vivo and may explain, at least in part, the mechanism of the nitrite/nitrate-rich Dietary Approaches to Stop Hypertension diet-induced hypotensive effects.

Abstract. It was shown recently that renal injury in Dahl salt-sensitive (DS) hypertensive rats is accompanied by mitogen-activated protein kinase (MAPK) activation. The present study was conducted to elucidate the contribution of reactive oxygen species to MAPK activities and renal injury in DS rats. DS rats were maintained on high salt (H; 8.0% NaCl; n ϭ 7) or low salt (L; 0.3% NaCl; n ϭ 6) diets; H ϩ a superoxide dismutase mimetic, tempol (3 mmol/L in drinking water; n ϭ 8); or H ϩ hydralazine (0.5 mmol/L in drinking water; n ϭ 8) for 4 wk. Mean BP (MBP) in DS/H and DS/L rats was 185 Ϯ 7 and 113 Ϯ 3 mmHg, respectively. DS/H rats showed a higher ratio of urinary protein excretion and creatinine (U protein V/ U cr V; 20.3 Ϯ 1.1) and a higher cortical collagen content (22 Ϯ 1 g/mg) than in DS/L rats (2.4 Ϯ 0.1 and 13 Ϯ 1 g/mg, respectively). The expression of p22-phox and Nox-1, essential components of NAD(P)H oxidase, in renal cortical tissue was approximately threefold higher in DS/H rats than in DS/L rats. Increased activities of renal cortical MAPK, including extracellular signal-regulated kinases (ERK) 1/ERK2 and c-Jun NH 2 -terminal kinases (JNK) were also observed in DS/H rats by 7.0 Ϯ 0.7-and 4.3 Ϯ 0.2-fold, respectively. Tempol treatment significantly decreased MBP (128 Ϯ 3 mmHg), U protein V/ U cr V (4.8 Ϯ 0.4), and cortical collagen content (14 Ϯ 1 g/mg) and normalized ERK1/ERK2 and JNK activities in DS/H rats. Histologically, tempol markedly ameliorated progressive sclerotic and proliferative glomerular changes in DS/H rats. Hydralazine-treated DS/H rats showed similar MBP (127 Ϯ 5 mmHg) to tempol-treated DS/H rats. Hydralazine also decreased U protein V/U cr V (16.2 Ϯ 1.5) and cortical collagen content (19 Ϯ 1 g/mg) in DS/H rats. However, these values were significantly higher than those of tempol-treated rats. Furthermore, although hydralazine significantly reduced JNK activity (Ϫ56 Ϯ 3%), ERK1/ERK2 activities were unaffected. These data suggest that reactive oxygen species, generated by NAD(P)H oxidase, contribute to the progression of renal injury through ERK1/ERK2 activation in DS/H hypertensive rats.Increasing evidence supports the role of reactive oxygen species (ROS) in the pathophysiology of hypertension and organ damage. Clinical studies have shown that vitamins and other antioxidants have BP-lowering effects in hypertensive patients (1, 2). Furthermore, exaggerated vascular superoxide anion (O 2 -) production has been observed in different animal models of hypertension, including spontaneously hypertensive rats (SHR) (3), stroke-prone SHR (4), deoxycorticosterone acetate (DOCA)-salt hypertensive rats (3), and angiotensin II (Ang II)-induced hypertensive rats (5). The Dahl salt-sensitive (DS) rat is a genetic model of salt-sensitive hypertension and develops renal damage, characterized by glomerular injury (6). Previous studies showed that the nephrosclerosis was associated with elevated renal cortical contents of malondialdehyde, an index of lipid peroxidation in DS hypertensive rats (7...

We report the demonstrated irradiation effect of laser-accelerated protons on human cancer cells. In vitro (living) A549 cells are irradiated with quasimonoenergetic proton bunches of 0.8–2.4 MeV with a single bunch duration of 15 ns. Irradiation with the proton dose of 20 Gy results in a distinct formation of γ-H2AX foci as an indicator of DNA double-strand breaks generated in the cancer cells. This is a pioneering result that points to future investigations of the radiobiological effects of laser-driven ion beams. Unique high-current and short-bunch features make laser-driven proton bunches an excitation source for time-resolved determination of radical yields.