Abstract-Preeclampsia (PE), a syndrome affecting 5% of pregnancies, characterized by hypertension and proteinuria, is a leading cause of maternal and fetal morbidity and mortality. The condition is often accompanied by the presence of a circulating maternal autoantibody, the angiotensin II type I receptor agonistic autoantibody (AT 1 -AA). However, the prevalence of AT 1 -AA in PE remains unknown, and the correlation of AT 1 -AA titers with the severity of the disease remains undetermined. We used a sensitive and high-throughput luciferase bioassay to detect AT 1 -AA levels in the serum of 30 normal, 37 preeclamptic (10 mild and 27 severe), and 23 gestational hypertensive individuals. Here we report that AT 1 -AA is highly prevalent in PE (Ϸ95%). Next, by comparing the levels of AT 1 -AA among women with mild and severe PE, we found that the titer of AT 1 -AA is proportional to the severity of the disease. Intriguingly, among severe preeclamptic patients, we discovered that the titer of AT 1 -AA is significantly correlated with the clinical features of PE: systolic blood pressure (rϭ0.56), proteinuria (rϭ0.70), and soluble fms-like tyrosine kinase-1 level (rϭ0.71), respectively. Notably, only AT 1 -AA, and not soluble fms-like tyrosine kinase-1, levels are elevated in gestational hypertensive patients. These data serve as compelling clinical evidence that AT 1 -AA is highly prevalent in PE, and its titer is strongly correlated to the severity of the disease. (Hypertension. 2010;55:386-393.)Key Words: preeclampsia Ⅲ gestational hypertension Ⅲ angiotensin receptor autoantibodies Ⅲ sFlt-1 Ⅲ proteinuria P reeclampsia (PE) is a serious hypertensive disorder of pregnancy that affects Ϸ5% of pregnancies and remains a leading cause of maternal and neonatal mortality and morbidity in the United States and the world. 1-3 The disease is multifactorial and includes such clinical features as high blood pressure, proteinuria, inflammation, endothelial dysfunction, vasoconstriction, and placental abnormalities. 4 -7 The clinical symptoms in the advanced stages of preeclampsia include cerebral hemorrhage, renal failure, hemolysis, elevated liver enzymes, and low platelets syndrome. In serious cases, termination of pregnancy is the only available option to prevent further deterioration of the fetus and mother. Despite being a leading cause of maternal death and a major contributor to maternal and perinatal morbidity, the triggering factors and underlying mechanisms responsible for the pathogenesis of PE remain elusive.Numerous studies have shown that women with PE possess angiotensin (Ang) II type 1 (AT 1 ) receptor agonistic autoantibodies (AAs) that bind to and activate the AT 1 Ang receptor in multiple cellular systems and provoke biological responses that are relevant to the pathophysiology of PE. 8 -13 For example, AT 1 -AAs increase the contraction rate of rat cardiomyocytes, elevate levels of the antiangiogenic factor soluble fms-like tyrosine kinase 1 (sFlt-1) leading to decreased angiogenesis in endothelial cells, in...

Angiotensin II AT 2 receptors have been implicated to play a role in the regulation of renal/cardiovascular functions under pathological conditions. The present study is designed to investigate the function of the AT 2 receptors on renal sodium excretion and AT2 receptor expression in the cortical membranes of streptozotocin (STZ)-induced diabetic rats. The STZ treatment led to a significant weight loss, hyperglycemia, and decrease in plasma insulin levels compared with control rats. STZinduced diabetic rats had significantly elevated basal urine flow, urinary sodium excretion rate (U NaV), urinary fractional sodium excretion, and urinary cGMP compared with control rats. Infusion of PD-123319, an AT 2 receptor antagonist, caused a significant decrease in UNaV (mol/ min) in STZ-induced diabetic rats (1 Ϯ 0.09 vs. 0.45 Ϯ 0.1) but not in control rats (0.35 Ϯ 0.05 vs. 0.4 Ϯ 0.07). The decrease in U NaV was associated with a significant decrease in urinary cGMP levels (pmol/min) in STZ-induced diabetic rats (21 Ϯ 2 vs. 10 Ϯ 0.8) but not in control rats (11.75 Ϯ 3 vs. 12.6 Ϯ 2). The infusion of PD-123319 did not alter glomerular filtration rate (STZ: 0.3 Ϯ 0.02 vs. 0.25 Ϯ 0.03; control: 1.4 Ϯ 0.05 vs. 1.5 Ϯ 0.09 ml/min) or mean arterial pressure (STZ: 82 Ϯ 3 vs. 79 Ϯ 3.5; control: 90 Ϯ 4 vs. 89 Ϯ 4 mmHg), suggesting a tubular effect of the drug. Western blot analysis using an AT 2 receptor antibody revealed a significantly enhanced expression of the AT 2 receptor protein (ϳ45 kDa) in brush-border (ϳ50-fold) and basolateral membranes (ϳ80-fold) of STZ-induced diabetic compared with control rats. In conclusion, our data suggest that the tubular AT 2 receptors in diabetic rats are profoundly enhanced and possibly via a cGMP pathway promote sodium excretion in this model of diabetes. kidney; hypertension OF THE ANGIOTENSIN II receptors, AT 1 receptors are predominantly expressed in adult tissues and perform most of the known ANG II-elicited functions such as vasoconstriction, hypertrophy, and sodium/fluid retention (26). AT 2 receptor expression in adult tissues is relatively low; however, AT 2 receptors are implicated in the cellular and physiological functions that are opposite to the functions mediated by the AT 1 receptors (10,18,19). The activation of AT 2 receptors has been shown to promote cell differentiation and apoptosis (18,26). The AT 2 receptors are also implicated in blood pressure regulation via vasodilatation and possibly affecting fluid/sodium homeostasis (6,12,15).There is evidence that the expression and function of the AT 2 receptors become relevant under pathophysiological conditions (16, 18), such as diabetes. Diabetic patients and animal models exhibit altered sodium/fluid metabolism associated with changes in the renin-angiotensin system (RAS) (1, 27). Because evidence suggests that some of the diabetic animal models may not have altered production of ANG II (8, 12, 21), the altered expression and function of the ANG II receptors may be the site of regulation that affects sodium metabolism in diabe...

Preeclampsia (PE) is a life-threatening hypertensive disorder of pregnancy associated with decreased circulating aldosterone levels. However, the molecular mechanisms underlying aldosterone reduction in PE remain unidentified. Here we demonstrate that reduced circulating aldosterone levels in the preeclamptic women are associated with the presence of angiotensin II type 1 receptor agonistic autoantibody (AT1-AA) and elevated soluble Fms-like tyrosine kinase-1 (sFlt-1), two prominent pathogenic factors in PE. Using an adoptive transfer animal model of PE, we provide in vivo evidence that the injection of IgG from women with PE, but not IgG from normotensive individuals, resulted in hypertension, proteinuria and a reduction in aldosterone production from 1377±272 pg/ml to 544±92 pg/ml (P<0.05) in pregnant mice. These features were prevented by co-injection with an epitope peptide that blocks antibody-mediated AT1 receptor (AT1R) activation. In contrast, injection of IgG from preeclamptic women into non-pregnant mice induced aldosterone levels from 213±24 pg/ml to 615±48 pg/ml (P<0.05). These results indicate that maternal circulating autoantibody in preeclamptic women is a detrimental factor causing decreased aldosterone production via AT1R activation in a pregnancy-dependent manner. Next, we found that circulating sFlt-1 was only induced in autoantibody-injected pregnant mice but not non-pregnant mice. As such, we further observed vascular impairment in adrenal glands of pregnant mice. Finally, we demonstrated that infusion of VEGF121 attenuated autoantibody-induced adrenal gland vascular impairment resulting in a recovery in circulating aldosterone (from 544±92 to 1110±269 pg/ml, P<0.05). Overall, we revealed that AT1-AA-induced sFlt-1 elevation is a novel pathogenic mechanism underlying decreased aldosterone production in PE.

Abstract-Earlier, we reported that there was an increase in angiotensin II type 2 (AT 2 ) receptor expression in the renal proximal tubule, and selective activation of the AT 2 receptor by AT 2 agonist inhibits Na,K-ATPase activity in the proximal tubules and increases urinary Na excretion in obese Zucker rats. We hypothesized that the AT 2 receptor has a protective role against blood pressure increase in obese Zucker rats. To test this hypothesis, we treated obese Zucker rats with the AT 2 receptor antagonist PD123319 (PD; 30 g/kg per minute) using osmotic pumps. Age-matched lean rats and vehicle-treated obese Zucker rats served as controls. On day 15 of the treatment with PD, arterial blood pressure was measured by cannulation of the left carotid artery under anesthesia. Control obese rats exhibited higher mean arterial pressure (122.0Ϯ3.4 mm Hg) compared with lean control rats (97.0Ϯ4.8 mm Hg). The PD treatment of obese rats raised mean arterial pressure further by 13 mm Hg. The plasma renin activity was significantly increased in the PD-treated obese compared with control-obese or lean rats. Western blot analysis revealed that the PD treatment in obese rats caused an Ϸ3-fold increase in the renin expression in the kidney cortex but had no effect on the expression of the cortical angiotensin II type 1 and AT 2 receptors. The present study suggests that the renal AT 2 receptors provide a protective role against blood pressure increase in obese Zucker rats, and this protective effect, in part, could be because of the ability of the AT 2 receptors to keep the kidney renin expression low in obese rats.

Increased renal sodium retention is considered a major risk factor contributing to hypertension associated with chronic hyperinsulinemia and obesity. However, the molecular mechanism involved is not understood. The present study investigates the effect of insulin treatment on AT1 receptor expression and ANG II-induced stimulation of Na/H exchanger (NHE) and Na-K-ATPase (NKA) in opossum kidney (OK) cells, a proximal tubule cell line. The presence of the AT1 receptors in OK cells was confirmed by the specific binding of 125I-sar-ANG II and by detecting approximately 43-kDa protein on Western blot analysis with AT1 receptor antibody and blocking peptide as well as by expression of AT1 receptor mRNA as determined by RT-PCR. Insulin treatment (100 nM for 24 h) caused an increase in 125I-sar-ANG II binding, AT1 receptor protein content, and mRNA levels. The whole cell lysate and membrane showed similar insulin-induced increase in the AT1 receptor protein expression, which was blocked by genistein (100 nM), a tyrosine kinase inhibitor, and cycloheximide (1.5 microg/ml), a protein synthesis inhibitor. Determination of ethyl isopropyl amiloride-sensitive 22Na+ uptake, a measure of the NHE activity, revealed that ANG II (1-100 pM)-induced stimulation of NHE in insulin-treated cells was significantly greater than in the control cells. Similarly, ANG II (1-100 pM)-induced stimulation of ouabain-sensitive 86Rb+ uptake, a measure of NKA activity in insulin-treated cells, was significantly greater than in the control cells. ANG II stimulation of both the transporters was blocked by AT1 receptor antagonist losartan, suggesting the involvement of AT1 receptors. Thus chronic insulin treatment causes upregulation of AT1 receptors, which evoked ANG II-induced stimulation of NHE and NKA. We propose that insulin-induced increase in the renal AT1 receptor function serves as a mechanism responsible for the increased renal sodium reabsorption and thus may contribute to development of hypertension in conditions associated with hyperinsulinemia.