Resibufogenin corrects hypertension in a rat model of human preeclampsia

The study of the pathogenesis of preeclampsia has been hampered by a relative dearth of animal models. We developed a rat model of preeclampsia in which the excretion of a circulating inhibitor of Na/K ATPase, marinobufagenin (MBG), is elevated. These animals develop hypertension, proteinuria, and intrauterine growth restriction. The administration of a congener of MBG, resibufogenin (RBG), reduces blood pressure to normal in these animals, as is the case when given to pregnant animals rendered hypertensive by the administration of MBG. Studies of Na/K ATPase inhibition by MBG and RBG reveal that these agents are equally effective as inhibitors of the enzyme.     

Interaction of NaCl and behavioral stress on endogenous sodium pump ligands in rats

Our study investigated the hypothesis that the combination of a high NaCl diet and social isolation stress would increase systolic blood pressure (SBP) and endogenous sodium pump ligands (SPL), ouabainlike compound (OLC), and marinobufagenin (MBG). Excretion of MBG and OLC, SBP, and organ weights were studied in four groups (n = 8) of male Fisher 344 x Norwegian brown rats: controls, socially isolated (Iso), 4% NaCl diet (Salt), and the combination of Salt and Iso (Iso+Salt). In Salt, MBG excretion increased by 78% (P < 0.01), whereas SBP and OLC remained unchanged. In Iso, SBP and MBG did not change, but OLC peaked on day 1. In the Iso+Salt, SBP increased by 9 mmHg, MBG excretion increased (42.0 +/- 7.6 vs. 10.0 +/- 1.5 pmol/24 h, P < 0.01), whereas OLC peaked at day 1 (25.0 +/- 2.5 vs. 10.0 +/- 2.0 pmol/24 h, P < 0.01) and remained elevated. Heart and kidney weights were increased in Salt and Iso+Salt. Aortic weights were increased in Iso and Iso+Salt. Thus a high NaCl intake stimulates MBG excretion, whereas isolation stress stimulates OLC. The combination of Salt and Iso is accompanied by marked stimulation of both SPL.     

Endogenous sodium pump inhibitors and age-associated increases in salt sensitivity of blood pressure in normotensives

Factors that mediate increases in salt sensitivity of blood pressure with age remain to be clarified. The present study investigated 1) the effects of high-NaCl intake on two Na pump inhibitors, endogenous ouabain (EO) and marinobufagenin (MBG), in middle-aged and older normotensive Caucasian women; and 2) whether individual differences in EO and MBG are linked to variations in sodium excretion or salt sensitivity. A change from 6 days of a lower (0.7 mmol.kg(-1).day(-1))- to 6 days of a higher (4 mmol.kg(-1).day(-1))-NaCl diet elicited a sustained increase in MBG excretion that directly correlated with an increase in the fractional Na excretion and was inversely related to age and to an age-dependent increase in salt sensitivity. In contrast, EO excretion increased only transiently in response to NaCl loading and did not vary with age or correlate with fractional Na excretion or salt sensitivity. A positive correlation of both plasma and urine levels of EO and MBG during salt loading may indicate a casual link between two Na pump inhibitors in response to NaCl loading, as observed in animal models. A linear mixed-effects model demonstrated that age, dietary NaCl, renal MBG excretion, and body mass index were each independently associated with systolic blood pressure. Thus, a sustained increase in MBG in response to acutely elevated dietary NaCl is inversely linked to salt sensitivity in normotensive middle-aged and older women, and a relative failure of MBG elaboration by these older persons may be involved in the increased salt sensitivity with advancing age.     

Exercise prevents leptin-induced increase in blood pressure in Sprague–Dawley rats

Although leptin has been shown to increase blood pressure (BP), it is however unclear if this increase can be prevented by exercise. This study therefore investigated the effect of leptin treatment with concurrent exercise on blood pressure (BP), sodium output, and endothelin-1 (ET-1) levels in normotensive rats. Male Sprague–Dawley rats weighing 250–270 g were divided into four groups consisting of a control group (n?=?6), leptin-treated (n?=?8), non-leptin-treated exercise group (n?=?8), and a leptin-treated exercise group (n?=?8). Leptin was given subcutaneously daily for 14 days (60 μg/kg/day). Animals were exercised on a treadmill for 30 min at a speed of 0.5 m/s and at 5° incline four times per week. Measurement of systolic blood pressure (SBP) and collection of urine samples for estimation of sodium and creatinine was done once a week. Serum samples were collected at the end of the experiment for determination of sodium, creatinine and ET-1. At day 14, mean SBP and serum ET-1 level in the leptin-treated group was significantly higher than that in the control group whereas mean SBP and serum ET-1 level was significantly lower in the leptin-treated exercise group than those in leptin-treated and control groups. Creatinine clearance, urinary sodium excretion, and urine output were not different between the four groups. Regular treadmill exercise prevents leptin-induced increases in SBP in rats, which might in part result from increased urinary sodium excretion and preventing the leptin-induced increases in serum ET-1 concentration.     

Marinobufagenin,resibufogenin and preeclampsia

The bufodienolides are cardiac glycosides which have the ability to inhibit the enzyme, Na⁺/K⁺ ATPase (sodium potassium adenosine triphosphatase). They are cardiac inotropes, cause vasoconstriction (and, potentially, hypertension) and are natriuretic. Evidence has accrued over time which supports the view that they are mechanistically involved in volume expansion-mediated hypertension. In this communication, the authors summarize data which support the view that the bufodienolides and, in particular, marinobufagenin (MBG) are involved in the pathogenesis of preeclampsia. In a rat model of the syndrome, MBG causes hypertension, proteinuria, intrauterine growth restriction and increased weight gain. All of these phenotypic characteristics are prevented by an antagonist to MBG, resibufogenin (RBG). The “preeclamptic” animals also develop a vascular leak syndrome, resulting in hemoconcentration. Abnormalities in the MAPK (mitogen-activated protein kinase) system play a role in the mechanism by which MBG produces the abnormalities in the pregnant rat. Studies to discover the relevance of these findings to human preeclampsia are currently underway in several laboratories and clinics.     

Marinobufagenin is an upstream modulator of Gadd45a stress signaling in preeclampsia

Preeclampsia (PE) is a hypertensive disorder of pregnancy, in which marinobufagenin (MBG), a circulating cardiotonic steroid, is increased. The Gadd45a stress sensor protein is an upstream modulator of the pathophysiological changes observed in PE. However, the effects of MBG on Gadd45a stress signaling remain unknown. We examined the expression of Gadd45a, the sFlt-1 receptor, and p38, as well as caspase 3 and 8 activities in placental samples from four groups of rats. These were: normal pregnant (NP, n = 8); pregnant rats which received weekly injections of desoxycorticosterone acetate and 0.9% saline as their drinking water (PDS, n = 9); normal pregnant rats injected with MBG (NPM, n = 8); and PDS rats injected with resibufogenin (RBG), an in vivo antagonist of MBG (PDSR, n = 8). Utilizing human cytotrophoblast (CTB) cells, we examined the effect of MBG on these stress signaling proteins in vitro. Placental Gadd45a expression, caspase 3 and 8 activities, sFlt-1 concentrations, and sFlt-1 receptor expression were significantly higher in PDS and NPM compared to NP and PDSR rats. Gadd45a protein was significantly upregulated in the CTB cells when MBG was present in concentrations ≥1 nM. Treatment with MBG (≥ 1 nM) also significantly arrested cell cycle progression and activated the expression of the Gadd45a-mediated stress signaling proteins. Inhibition of Gadd45a through RNAi-mediation attenuated MBG-induced CTB cell stress signaling. In conclusion, MBG is involved in the alteration in Gadd45a stress signaling both in vivo and in vitro and RBG prevents these changes when administered in vivo.     

Antioxidant treatment normalizes nitric oxide production, renal sodium handling and blood pressure in experimental hyperleptinemia

Recent studies suggest that adipose tissue hormone, leptin, is involved in the pathogenesis of arterial hypertension. However, the mechanism of hypertensive effect of leptin is incompletely understood. We investigated whether antioxidant treatment could prevent leptin-induced hypertension. Hyperleptinemia was induced in male Wistar rats by administration of exogenous leptin (0.25 mg/kg twice daily s.c. for 7 days) and separate groups were simultaneously treated with superoxide scavenger, tempol, or NAD(P)H oxidase inhibitor, apocynin (2 mM in the drinking water). After 7 days, systolic blood pressure was 20.6% higher in leptin-treated than in control animals. Both tempol and apocynin prevented leptin-induced increase in blood pressure. Plasma concentration and urinary excretion of 8-isoprostanes increased in leptin-treated rats by 66.9% and 67.7%, respectively. The level of lipid peroxidation products, malonyldialdehyde + 4-hydroxyalkenals (MDA+4-HNE), was 60.3% higher in the renal cortex and 48.1% higher in the renal medulla of leptin-treated animals. Aconitase activity decreased in these regions of the kidney following leptin administration by 44.8% and 45.1%, respectively. Leptin increased nitrotyrosine concentration in plasma and renal tissue. Urinary excretion of nitric oxide metabolites (NO(x)) was 57.4% lower and cyclic GMP excretion was 32.0% lower in leptin-treated than in control group. Leptin decreased absolute and fractional sodium excretion by 44.5% and 44.7%, respectively. Co-treatment with either tempol or apocynin normalized 8-isoprostanes, MDA+4-HNE, aconitase activity, nitrotyrosine, as well as urinary excretion of NO(x), cGMP and sodium in rats receiving leptin. These results indicate that oxidative stress-induced NO deficiency is involved in the pathogenesis of leptin-induced hypertension.     

Long-term AT1 receptor blockade improves metabolic function and provides renoprotection in Fischer-344 rats

Fischer-344 (F344) rats exhibit proteinuria and insulin resistance in the absence of hypertension as they age. We determined the effects of long-term (1 yr) treatment with the angiotensin (ANG) II type 1 (AT(1)) receptor blocker L-158,809 on plasma and urinary ANG peptide levels, systolic blood pressure (SBP), and indexes of glucose metabolism in 15-mo-old male F344 rats. Young rats at 3 mo of age (n = 8) were compared with two separate groups of older rats: one control group (n = 7) and one group treated with L-158,809 (n = 6) orally (20 mg/l) for 1 yr. SBP was not different between control and treated rats but was higher in young rats. Serum leptin, insulin, and glucose levels were comparable between treated and young rats, whereas controls had higher glucose and leptin with a similar trend for insulin. Plasma ANG I and ANG II were higher in treated than untreated young or older rats, as evidence of effective AT(1) receptor blockade. Urinary ANG II and ANG-(1-7) were higher in controls compared with young animals, and treated rats failed to show age-related increases. Protein excretion was markedly lower in treated and young rats compared with control rats (young: 8 +/- 2 mg/day vs. control: 129 +/- 51 mg/day vs. treated: 9 +/- 3 mg/day, P < 0.05). Long-term AT(1) receptor blockade improves metabolic parameters and provides renoprotection. Differential regulation of systemic and intrarenal (urinary) ANG systems occurs during blockade, and suppression of the intrarenal system may contribute to reduced proteinuria. Thus, insulin resistance, renal injury, and activation of the intrarenal ANG system during early aging in normotensive animals can be averted by renin-ANG system blockade.     

Renal effects of long-term leptin infusion and preventive role of losartan treatment in rats

BACKGROUND: Leptin has direct and indirect effects on renal pathophysiological characteristics. In the present study, the effects of long-term leptin infusion on the renal hemodynamics, renal excretory functions, and the expression of transforming growth factor-beta (TGF-beta), plasma endothelin-1 (ET-1) levels, and preventive effects of the angiotensin II type 1 receptor antagonist, losartan, on these renal changes were evaluated. METHODS: The study was performed by using forty Wistar albino rats. On day 0, osmotic mini-pumps filled with leptin or placebo were intraperitoneally placed under sterile conditions. The rats in Group L (Leptin group, n=15) and Group LL (Leptin-losartan group, n=15) were given recombinant murine leptin at a rate of 250 ng per hour for 28 days. Control rats (Group C, n=10) were administered placebo at the same infusion rate. The rats in Group LL were also administered losartan (10 mg kg(-1) d(-1)) perorally for 28 days. On day 28, the rats were placed in metabolic cages, and the food and water intakes were determined, and the urine was collected for 24 h. At the end of the study, systolic blood pressure (SBP), diastolic blood pressure (DBP) were determined directly from the left femoral artery, and renal blood flow (RBF) was recorded indirectly using a laser Doppler flow module. RESULTS: Leptin infusion did not produce any changes in systemic arterial blood pressures and urinary flow rate. The rates of creatinine (Cr), sodium (Na), and protein excretions of the animals infused leptin were significantly increased. The urinary Cr and Na excretions were decreased, while the urinary protein excretion was normalized with the losartan treatment. The rats infused leptin had also higher circulating ET-1 levels. ET-1 levels were also reversed to the normal values with the losartan treatment. Renal TGF-beta1 expression was determined immunohistochemically, and it was more prominent in the renal tubules from the rats treated with leptin. The losartan treatment had no effect on renal TGF-beta1 expression. CONCLUSIONS: Our results indicate that pathophysiological increases in plasma leptin concentrations cause enhanced renal Na, Cr and protein excretions, and high circulating ET-1 levels. Na and Cr excretions were decreased, while proteinuria and plasma ET-1 levels were normalized by losartan treatment, suggesting that renin-angiotensin system activation may have a role in leptin induced renal changes. TGF-beta1 may have an important role in leptin induced nephropathy.     

Role of nitric oxide and endothelium-derived hyperpolarizing factor (EDHF) in the regulation of blood pressure by leptin in lean and obese rats

We investigated the role of nitric oxide (NO) and endothelium-derived hyperpolarizing factor (EDHF) in hemodynamic action of leptin. The effect of leptin (1 mg/kg i.p.) on systolic blood pressure (SBP) was examined in lean rats and in rats made obese by feeding highly palatable diet for either 1 or 3 months. Separate groups received NO synthase inhibitor, L-NAME, or EDHF inhibitors, the mixture of apamin+charybdotoxin or sulfaphenazole, before leptin administration. Leptin increased NO production, as evidenced by increase in plasma and urinary NO metabolites and cyclic GMP. This effect was impaired in both obese groups. In lean rats either leptin or EDHF inhibitors had no effect on blood pressure. L-NAME increased blood pressure in lean animals and this effect was prevented by leptin. However, when leptin was administered to animals pretreated with both L-NAME and EDHF inhibitors, blood pressure increased even more than after L-NAME alone. In the 1-month obese group leptin had no effect on SBP, however, pressor effect of leptin was observed in animals pretreated with EDHF inhibitors. In the 3-month obese group leptin alone increased SBP, and EDHF inhibitors did not augment its pressor effect. The results suggest that leptin may stimulate EDHF when NO becomes deficient, e.g. after NOS blockade or in short-term obesity. Although the effect of leptin on NO production is impaired in the 1-month obese group, BP does not increase, probably because EDHF compensates for NO deficiency. In contrast, leptin increases BP in 3-month obesity because its effect on EDHF is also attenuated.     

Renal Hemodynamic and Morphological Changes after 7 and 28 Days of Leptin Treatment: The Participation of Angiotensin II via the AT1 Receptor

The role of hyperleptinemia in cardiovascular diseases is well known; however, in the renal tissue, the exact site of leptin’s action has not been established. This study was conducted to assess the effect of leptin treatment for 7 and 28 days on renal function and morphology and the participation of angiotensin II (Ang II), through its AT₁ receptor. Rats were divided into four groups: sham, losartan (10 mg/kg/day, s.c.), leptin (0.5 mg/kg/day for the 7 days group and 0.25 mg/kg/day for the 28 days group) and leptin plus losartan. Plasma leptin, Ang II and endothelin 1 (ET-1) levels were measured using an enzymatic immuno assay. The systolic blood pressure (SBP) was evaluated using the tail-cuff method. The renal plasma flow (RPF) and the glomerular filtration rate (GFR) were determined by p-aminohippuric acid and inulin clearance, respectively. Urinary Na⁺ and K⁺ levels were also analyzed. Renal morphological analyses, desmin and ED-1 immunostaining were performed. Proteinuria was analyzed by silver staining. mRNA expression of renin-angiotensin system (RAS) components, TNF-α and collagen type III was analyzed by quantitative PCR. Our results showed that leptin treatment increased Ang II plasma levels and progressively increased the SBP, achieving a pre-hypertension state. Rats treated with leptin 7 days showed a normal RPF and GFR, but increased filtration fraction (FF) and natriuresis. However, rats treated with leptin for 28 showed a decrease in the RPF, an increase in the FF and no changes in the GFR or tubular function. Leptin treatment-induced renal injury was demonstrated by: glomerular hypertrophy, increased desmin staining, macrophage infiltration in the renal tissue, TNF-α and collagen type III mRNA expression and proteinuria. In conclusion, our study demonstrated the progressive renal morphological changes in experimental hyperleptinemia and the interaction between leptin and the RAS on these effects.     

Centrally acting leptin induces a resuscitating effect in haemorrhagic shock in rats

Centrally acting leptin induces the activation of the sympathetic nervous system with a pressor effect in normotensive rats. The purpose of the study was to examine central leptin-evoked action in critical haemorrhagic hypotension. In anaesthetized male Wistar rats subjected for irreversible haemorrhagic shock with mean arterial pressure (MAP) 20-25 mmHg haemodynamic parameters and plasma concentrations of adrenaline and noradrenaline were measured. Leptin given intracerebroventricularly (20 μg) evoked long-lasting rises in MAP and heart rate (HR), with a subsequent increase in renal, mesenteric and hindquarters blood flows and a 100% survival at 2 h. MAP and peripheral blood flow changes were inhibited by a pre-treatment with α(1)- and α(2)-adrenoceptor antagonists prazosin (0.5 mg/kg) and yohimbine (1 mg/kg), while β-adrenoceptor antagonist propranolol (1 mg/kg) blocked leptin-induced HR changes, without influence on MAP, peripheral blood flows and survival. Twenty min after leptin treatment, there were higher plasma concentrations of noradrenaline, but not adrenaline, in comparison with the saline-treated control group. In conclusion, centrally acting leptin induces a long-lasting pressor effect with an improvement in the survival rate in haemorrhage-shocked rats. The effect may be associated with the activation of the sympathetic nervous system.     

Sexual Dimorphism in Urinary Angiotensinogen Excretion During Chronic Angiotensin II−Salt Hypertension

BackgroundThe intrarenal renin−angiotensin system contributes to hypertension by regulating sodium and water reabsorption throughout the nephron. Sex differences in the intrarenal components of the renin−angiotensin system have been involved in the greater incidence of high blood pressure and progression to kidney damage in males than females.ObjectiveThis study investigated whether there is a sex difference in the intrarenal gene expression and urinary excretion of angiotensinogen (AGT) during angiotensin II (Ang II)−dependent hypertension and high-salt (HS) diet.MethodsMale and female Sprague-Dawley rats were divided into 5 groups for each sex: Normal-salt control, HS diet (8% NaCl), Ang II−infused (80 ng/min), Ang II−infused plus HS diet, and Ang II−infused plus HS diet and treatment with the Ang II receptor blocker, candesartan (25 mg/L in the drinking water). Rats were evaluated for systolic blood pressure (SBP), kidney AGT mRNA expression, urinary AGT excretion, and proteinuria at different time points during a 14-day protocol.ResultsBoth male and female rats exhibited similar increases in urinary AGT, with increases in SBP during chronic Ang II infusion. HS diet greatly exacerbated the urinary AGT excretion in Ang II−infused rats; males had a 9-fold increase over Ang II alone and females had a 2.5-fold increase. Male rats displayed salt-sensitive SBP increases during Ang II infusion and HS diet, and female rats did not. In the kidney cortex, males displayed greater AGT gene expression than females during all treatments. During Ang II infusion, both sexes exhibited increases in AGT gene message compared with same-sex controls. In addition, HS diet combined with Ang II infusion exacerbated the proteinuria in both sexes. Concomitant Ang II receptor blocker treatment during Ang II infusion and HS diet decreased SBP and urinary AGT similarly in both sexes; however, the decrease in proteinuria was greater in the females.ConclusionDuring Ang II−dependent hypertension and HS diet, higher intrarenal renin-angiotensin system activation in males, as reflected by higher AGT gene expression and urinary excretion, indicates a mechanism for greater progression of high blood pressure and might explain the sex disparity in development of salt-sensitive hypertension.     

Oxidative stress, nitric oxide production, and renal sodium handling in leptin-induced hypertension

Chronic hyperleptinemia induces arterial hypertension in experimental animals and may contribute to the development of hypertension in obese humans; however, the mechanism of hypertensive effect of leptin is not completely elucidated. We investigated the effect of leptin on whole-body oxidative stress, nitric oxide production, and renal sodium handling. The study was performed on male Wistar rats divided into 3 groups: 1) control, fed standard chow ad libitum, 2) leptin-treated group, receiving leptin injections (0.25 mg/kg twice daily s.c. for 7 days), 3) pair-fed group, in which food intake was adjusted to the leptin group. Leptin caused 30.5% increase in systolic blood pressure. Plasma concentration and urinary excretion of 8-isoprostanes in animals receiving leptin was 46.4% and 49.2% higher, respectively. The level of lipid peroxidation products, malonyldialdehyde + 4-hydroxyalkenals, increased by 52.5% in the renal cortex and by 48.4% in the renal medulla following leptin treatment, whereas aconitase activity decreased in these regions of the kidney by 45.3% and 39.2%, respectively. Urinary excretion of nitric oxide metabolites (NOx) was 55.0% lower, and fractional excretion of NOx was 55.8% lower in the leptin-treated group. Urinary excretion of cGMP decreased in leptin-treated rats by 26.3%. Following leptin treatment, absolute and fractional sodium excretion decreased by 35.0% and 41.2%, respectively. These results indicate that hyperleptinemia induces systemic and intrarenal oxidative stress, decreases the amount of bioactive NO possibly due to its degradation by reactive oxygen species, and causes renal sodium retention by stimulating tubular sodium reabsorption. NO deficiency and abnormal renal Na+ handling may contribute to leptin-induced hypertension.     

Role of extracellular signal-regulated kinases (ERK) in leptin-induced hypertension

We investigated if extracellular signal-regulated kinases (ERK) and oxidative stress are involved in the pathogenesis of arterial hypertension induced by chronic leptin administration in the rat. Leptin was administered at a dose of 0.25 mg/kg twice daily s.c. for 4 or 8 days. Blood pressure (BP) was higher in leptin-treated than in control animals from the third day of the experiment. The superoxide dismutase (SOD) mimetic, tempol, normalized BP in leptin-treated rats on days 6, 7 and 8, whereas the ERK inhibitor, PD98059, exerted a hypotensive effect on days 3 through 6. Leptin increased ERK phosphorylation level in renal and aortic tissues more markedly after 4 than after 8 days of treatment. In addition, leptin reduced urinary Na(+) excretion and increased renal Na(+),K(+)-ATPase activity, and these effects were abolished on days 4 and 8 by PD98059 and tempol, respectively. The levels of NO metabolites and cGMP were reduced in animals receiving leptin for 8 days. Markers of oxidative stress (H(2)O(2) and lipid peroxidation products) were elevated to a greater extent after 4 than after 8 days of leptin treatment. In contrast, nitrotyrosine, a marker of protein nitration by peroxynitrite, was higher in animals receiving leptin for 8 days. NADPH oxidase inhibitor, apocynin, prevented leptin's effect on BP, ERK, Na(+),K(+)-ATPase/Na(+) excretion and NO formation at all time points. SOD activity was reduced, whereas glutathione peroxidase (GPx) activity was increased in the group treated with leptin for 8 days. These data indicate that: (1) ERK, activated by oxidative stress, is involved only in the early phase of leptin-induced BP elevation, (2) the later phase of leptin-induced hypertension is characterized by excessive NO inactivation by superoxide, (3) the time-dependent shift from ERK to O(2)(-)-NO dependent mechanism may be associated with reduced SOD/GPx ratio, which favors formation of O(2)(-) instead of H(2)O(2).     

Role of PI3K and PKB/Akt in acute natriuretic and NO-mimetic effects of leptin

Apart from controlling energy balance, leptin, a peptide hormone secreted by white adipose tissue, is also involved in the regulation of cardiovascular function. Previous studies have documented that leptin stimulates natriuresis and nitric oxide (NO) production, but the mechanism of these effects is incompletely elucidated. We examined whether phosphoinositide 3-kinase (PI3K) and its downstream effector, protein kinase B/Akt are involved in acute natriuretic and NO-mimetic effects of leptin in anaesthetized rats. Leptin (1 mg/kg i.v.) induced a marked increase in natriuresis and this effect was abolished by pretreatment with either wortmannin (15 μg/kg) or LY294002 (0.6 mg/kg), two structurally different PI3K inhibitors. Moreover, leptin increased plasma concentration and urinary excretion of NO metabolites, nitrites + nitrates (NO_x), and of NO second messenger, cyclic GMP. In addition, leptin increased NO_x and cGMP in aortic tissue. The stimulatory effect of leptin on NO_x and cGMP was prevented by PKB/Akt inhibitor, triciribine, but not by either wortmannin or LY294002. Triciribine had no effect on leptin-induced natriuresis. Leptin stimulated Akt phosphorylation at Ser⁴⁷³ in aortic tissue but not in the kidney. These results suggest that leptin-induced natriuresis is mediated by PI3K but not Akt, whereas NO-mimetic effect of leptin results from PI3K-independent stimulation of Akt.     

Renal antioxidant enzymes and glutathione redox status in leptin-induced hypertension

Previously, we have demonstrated that leptin increases blood pressure (BP) in the rats through two oxidative stress-dependent mechanisms: stimulation of extracellular signal-regulated kinases (ERK) by H(2)O(2) and scavenging of nitric oxide (NO) by superoxide (O(2-.)). Herein, we examined if renal glutathione system and antioxidant enzymes determine the mechanism of prohypertensive effect of leptin. Leptin administered at 0.5 mg/kg/day for 4 or 8 days increased BP and renal Na(+),K(+)-ATPase activity and reduced fractional sodium excretion; these effects were prevented by NADPH oxidase inhibitor, apocynin. Superoxide scavenger, tempol, abolished the effect of leptin on BP and renal Na(+) pump in rats receiving leptin for 8 days, whereas ERK inhibitor, PD98059, was effective in animals treated with leptin for 4 days. Leptin administered for 4 days decreased glutathione (GSH) and increased glutathione disulfide (GSSG) in the kidney. In animals receiving leptin for 8 days GSH returned to normal level, which was accompanied by up-regulation of gamma-glutamylcysteine synthetase (gamma-GCS), a rate-limiting enzyme of the GSH biosynthetic pathway. In addition, superoxide dismutase (SOD) activity was decreased, whereas glutathione peroxidase (GPx) was increased in rats receiving leptin for 8 days. Cotreatment with gamma-GCS inhibitor, buthionine sulfoximine (BSO), accelerated, whereas GSH precursor, N-acetylcysteine (NAC), attenuated leptin-induced changes in gamma-GCS, SOD, and GPx. In addition, coadministration of BSO changed the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent in animals receiving leptin for 4 days, whereas NAC had the opposite effect in rats treated with leptin for 8 days. These results suggest that initial change in GSH redox status induces decrease in SOD/GPx ratio, which results in greater amount of (O)2-.)) versus H(2)O(2) in later phase of leptin treatment, thus shifting the mechanism of BP elevation from H(2)O(2)-ERK to (O(2-.))-NO dependent.     

低分子肝素对子痫前期大鼠炎症反应、肝功能及胎盘组织Bcl-2、Bax蛋白表达的影响

目的:研究低分子肝素对子痫前期大鼠炎症反应、肝功能及胎盘组织Bcl-2、Bax蛋白表达的影响.方法:将90只孕期大鼠以随机数表法分成正常孕组、子痫前期组、治疗组,每组30只.其中子痫前期组和治疗组大鼠于妊娠第13 d开始皮下注射左旋硝基精氨酸甲酯,建立子痫前期大鼠模型,注射剂量为200mg/(kg·d),正常孕组予以等...     

Long-term intake of egg white hydrolysate attenuates the development of hypertension in spontaneously hypertensive rats

This paper evaluates the effect of the long-term intake of a hydrolysate of egg white with pepsin (HEW), with a potent angiotensin converting enzyme inhibitory activity, on the development of hypertension of spontaneously hypertensive rats (SHR). After being weaned, male 3-week-old SHR were randomly divided into five groups that were given until the 20th week of life the following drinking fluids: (1) tap water, (2) non-treated egg white 1 g/kg/day, (3) captopril 100 mg/kg/day, (4) HEW 0.5 g/kg/day, and (5) HEW 1 g/kg/day. From the 20th to 25th week of life, animals from all groups were given tap water. Systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured weekly in the rats, from the 6th to 25th week of life, by the tail cuff method. Development of hypertension was attenuated in the groups treated with captopril and HEW (P<0.001 vs. the group that drunk tap water). At the 20th week of life, the arterial blood pressure values of the different groups of rats were: tap water (SBP = 219.5 +/- 5.7, DBP = 167 +/- 3.7), non-treated egg white (SBP = 206.4 +/- 1.43, DBP = 166.4 +/- 4.9), captopril (SBP = 131.7 +/- 2.74, DBP = 91.5 +/- 1.62), HEW 0.5 g/kg/day (SBP = 182.9 +/- 4.64, DBP = 127.5 +/- 2.1) and HEW 1 g/kg/day (SBP = 177.7 +/- 4.72, DBP = 120.1 +/- 2.4). SBP and DBP increased in the treated SHR when the corresponding antihypertensive treatment was removed. In spite of this, SBP remained lower in the SHR that had received captopril and HEW than in the SHR of the control groups (P<0.05). The present results suggest that HEW could be used as a functional food with antihypertensive activity.