Adipose c-Jun NH2-terminal kinase promotes angiotensin II-induced and deoxycorticosterone acetate salt-induced hypertension and vascular dysfunction by inhibition of adiponectin production and activation of SGK1 in mice

BACKGROUND

Adipose c-Jun NH2-terminal kinase 1/2 (JNK1/2) is a central mediator involved in the development of obesity and its complications. However, the roles of adipose JNK1/2 in hypertension remain elusive. Here we explored the role of adipose JNK1/2 in hypertension.

METHODS AND RESULTS

The roles of adipose JNK1/2 in hypertension were investigated by evaluating the impact of adipose JNK1/2 inactivation in both angiotensin II (Ang II)-induced and deoxycorticosterone acetate (DOCA) salt-induced hypertensive mice. Specific inactivation of JNK1/2 in adipocytes significantly alleviates Ang II-induced and DOCA salt-induced hypertension and target organ damage in mice. Interestingly, such beneficial effects are also observed in hypertensive mice after oral administration of JNK1/2 inhibitor SP600125. Mechanistically, adipose JNK1/2 acts on adipocytes to reduce the production of adiponectin (APN), then leads to promote serum and glucocorticoid-regulated kinase 1 (SGK1) phosphorylation and increases epithelial Na + channel α-subunit (ENaCα) expression in both renal cells and adipocytes, respectively, finally exacerbates Na + retention. In addition, chronic treatment of recombinant mouse APN significantly augments the beneficial effects of adipose JNK1/2 inactivation in DOCA salt-induced hypertension. By contrast, the blood pressure-lowering effects of adipose JNK1/2 inactivation are abrogated by adenovirus-mediated SGK1 overexpression in Ang II -treated adipose JNK1/2 inactivation mice.

CONCLUSION

Adipose JNK1/2 promotes hypertension and targets organ impairment via fine-tuning the multiorgan crosstalk among adipose tissue, kidney, and blood vessels.

CD4+ T-Cell Legumain Deficiency Attenuates Hypertensive Damage via Preservation of TRAF6

BACKGROUND

T cells are central to the immune responses contributing to hypertension. LGMN (legumain) is highly expressed in T cells; however, its role in the pathogenesis of hypertension remains unclear.

METHODS

Peripheral blood samples were collected from patients with hypertension, and cluster of differentiation (CD)4+ T cells were sorted for gene expression and Western blotting analysis. TLGMNKO (T cell-specific LGMN-knockout) mice (Lgmnf/f/CD4Cre), regulatory T cell (Treg)-specific LGMN-knockout mice (Lgmnf/f/Foxp3YFP Cre), and RR-11a (LGMN inhibitor)-treated C57BL/6 mice were infused with Ang II (angiotensin II) or deoxycorticosterone acetate/salt to establish hypertensive animal models. Flow cytometry, 4-dimensional label-free proteomics, coimmunoprecipitation, Treg suppression, and in vivo Treg depletion or adoptive transfer were used to delineate the functional importance of T-cell LGMN in hypertension development.

RESULTS

LGMN mRNA expression was increased in CD4+ T cells isolated from hypertensive patients and mice, was positively correlated with both systolic and diastolic blood pressure, and was negatively correlated with serum IL (interleukin)-10 levels. TLGMNKO mice exhibited reduced Ang II-induced or deoxycorticosterone acetate/salt-induced hypertension and target organ damage relative to wild-type (WT) mice. Genetic and pharmacological inhibition of LGMN blocked Ang II-induced or deoxycorticosterone acetate/salt-induced immunoinhibitory Treg reduction in the kidneys and blood. Anti-CD25 antibody depletion of Tregs abolished the protective effects against Ang II-induced hypertension in TLGMNKO mice, and LGMN deletion in Tregs prevented Ang II-induced hypertension in mice. Mechanistically, endogenous LGMN impaired Treg differentiation and function by directly interacting with and facilitating the degradation of TRAF6 (tumor necrosis factor receptor-associated factor 6) via chaperone-mediated autophagy, thereby inhibiting NF-κB (nuclear factor kappa B) activation. Adoptive transfer of LGMN-deficient Tregs reversed Ang II-induced hypertension, whereas depletion of TRAF6 in LGMN-deficient Tregs blocked the protective effects.

CONCLUSIONS

LGMN deficiency in T cells prevents hypertension and its complications by promoting Treg differentiation and function. Specifically targeting LGMN in Tregs may be an innovative approach for hypertension treatment.

Bioactive Peptides from Ruditapes philippinarum Attenuate Hypertension and Cardiorenal Damage in Deoxycorticosterone Acetate-Salt Hypertensive Rats

Hypertension is a common disease that affects human health and can lead to damage to the heart, kidneys, and other important organs. In this study, we investigated the regulatory effects of bioactive peptides derived from Ruditapes philippinarum (RPP) on hypertension and organ protection in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We found that RPPs exhibited significant blood pressure-lowering properties. Furthermore, the results showed that RPPs positively influenced vascular remodeling and effectively maintained a balanced water-sodium equilibrium. Meanwhile, RPPs demonstrated anti-inflammatory potential by reducing the serum levels of inflammatory cytokines (TNF-α, IL-2, and IL-6). Moreover, we observed the strong antioxidant activity of RPPs, which played a critical role in reducing oxidative stress and alleviating hypertension-induced damage to the aorta, heart, and kidneys. Additionally, our study explored the regulatory effects of RPPs on the gut microbiota, suggesting a possible correlation between their antihypertensive effects and the modulation of gut microbiota. Our previous studies have demonstrated that RPPs can significantly reduce blood pressure in SHR rats. This suggests that RPPs can significantly improve both essential hypertension and DOAC-salt-induced secondary hypertension and can ameliorate cardiorenal damage caused by hypertension. These findings further support the possibility of RPPs as an active ingredient in functional anti-hypertensive foods.

JMJD3 ablation in myeloid cells confers renoprotection in mice with DOCA/salt-induced hypertension

Hypertension-induced renal injury is characterized by robust inflammation and tubulointerstitial fibrosis. Jumonji domain containing-3 (JMJD3) is closely linked with inflammatory response and fibrogenesis. Here we examined the effect of myeloid JMJD3 ablation on kidney inflammation and fibrosis in deoxycorticosterone acetate (DOCA)/salt hypertension. Our results showed that JMJD3 is notably induced in the kidneys with hypertensive injury. DOCA/salt stress causes an elevation in blood pressure that was no difference between myeloid specific JMJD3-deficient mice and wild-type control mice. Compared with wild-type control mice, myeloid JMJD3 ablation ameliorated kidney function and injury of mice in response to DOCA/salt challenge. Myeloid JMJD3 ablation attenuated collagen deposition, extracellular matrix proteins expression, and fibroblasts activation in injured kidneys following DOCA/salt treatment. Furthermore, myeloid JMJD3 ablation blunts inflammatory response in injured kidneys after DOCA/salt stress. Finally, myeloid JMJD3 ablation precluded myeloid myofibroblasts activation and protected against macrophages to myofibroblasts transition in injured kidneys. These beneficial effects were accompanied by reduced expression of interferon regulator factor 4. In summary, JMJD3 ablation in myeloid cells reduces kidney inflammation and fibrosis in DOCA salt-induced hypertension. Inhibition of myeloid JMJD3 may be a novel potential therapeutic target for hypertensive nephropathy. Myeloid JMJD3 deficiency reduces inflammatory response, myeloid fibroblasts activation, macrophages to myofibroblasts transition, and delays kidney fibrosis progression.

Interferon regulatory factor 4 deletion protects against kidney inflammation and fibrosis in deoxycorticosterone acetate/salt hypertension

BACKGROUND

Inflammation and renal interstitial fibrosis are the main pathological features of hypertensive nephropathy. Interferon regulatory factor 4 (IRF-4) has an important role in the pathogenesis of inflammatory and fibrotic diseases. However, its role in hypertension-induced renal inflammation and fibrosis remains unexplored.

METHOD AND RESULTS

We showed that deoxycorticosterone acetate (DOCA)-salt resulted in an elevation of blood pressure and that there was no difference between wild-type and IRF-4 knockout mice. IRF-4 -/- mice presented less severe renal dysfunction, albuminuria, and fibrotic response after DOCA-salt stress compared with wild-type mice. Loss of IRF-4 inhibited extracellular matrix protein deposition and suppressed fibroblasts activation in the kidneys of mice subjected to DOCA-salt treatment. IRF-4 disruption impaired bone marrow-derived fibroblasts activation and macrophages to myofibroblasts transition in the kidneys in response to DOCA-salt treatment. IRF-4 deletion impeded the infiltration of inflammatory cells and decreased the production of proinflammatory molecules in injured kidneys. IRF-4 deficiency activated phosphatase and tensin homolog and weakened phosphoinositide-3 kinase/AKT signaling pathway in vivo or in vitro . In cultured monocytes, TGFβ1 also induced expression of fibronectin and α-smooth muscle actin and stimulated the transition of macrophages to myofibroblasts, which was blocked in the absence of IRF-4. Finally, macrophages depletion blunted macrophages to myofibroblasts transition, inhibited myofibroblasts accumulation, and ameliorated kidney injury and fibrosis.

CONCLUSION

Collectively, IRF-4 plays a critical role in the pathogenesis of kidney inflammation and fibrosis in DOCA-salt hypertension.

Endothelium-specific sepiapterin reductase deficiency in DOCA-salt hypertension

The endothelial nitric oxide synthase (eNOS) requires tetrahydrobiopterin (H(4)B) as a cofactor and, in its absence, produces superoxide (O(2)(·-)) rather than nitric oxide (NO(·)), a condition referred to as eNOS uncoupling. DOCA-salt-induced hypertension is associated with H(4)B oxidation and uncoupling of eNOS. The present study investigated whether administration of sepiapterin or H(4)B recouples eNOS in DOCA-salt hypertension. Bioavailable NO(·) detected by electron spin resonance was markedly reduced in aortas of DOCA-salt hypertensive mice. Preincubation with sepiapterin (10 μmol/l for 30 min) failed to improve NO(·) bioavailability in hypertensive aortas while it augmented NO(·) production from control vessels, implicating a hypertension-associated deficiency in sepiapterin reductase (SPR), the rate-limiting enzyme for sepiapterin conversion to H(4)B. Indeed, a decreased SPR expression was observed in aortic endothelial cells, but not in endothelium-denuded aortic remains, implicating an endothelium-specific SPR deficiency. Administration of hypertensive aortas with H(4)B (10 μmol/l, 30 min) partially restored vascular NO(·) production. Combined administration of H(4)B and the NADPH oxidase inhibitor apocynin (100 μmol/l, 30 min) fully restored NO(·) bioavailability while reducing O(2)(·-) production. In angiotensin II-induced hypertension, however, aortic endothelial SPR expression was not affected. In summary, administration of sepiapterin is not effective in recoupling eNOS in DOCA-salt hypertension, due to an endothelium-specific loss in SPR, whereas coadministration of H(4)B and apocynin is highly efficient in recoupling eNOS. This is consistent with our previous observations that in angiotensin II hypertension, endothelial deficiency in dihydrofolate reductase is alternatively responsible for uncoupling of eNOS. Taken together, these data indicate that strategies specifically targeting at different H(4)B metabolic enzymes might be necessary in restoring eNOS function in different types of hypertension.

Effects of soy protein isolate feeding on severe kidney damage in DOCA salt-treated obese Zucker rats

This study assessed the effects of soy protein isolate (SPI) on severe kidney damage in deoxycorticosterone acetate (DOCA) salt-treated obese Zucker rats. These rats underwent heminephrectomy and were fed either casein or SPI diet for 12 weeks. From weeks 8 to 10 of the experiment, kidney damage was induced by biweekly injection of 25 mg/kg DOCA and administration of 0.5% NaCl (w/v) ad libitum. Urinary protein and N-acetyl-β-d-glucosaminidase excretions of SPI rats were much lower than those of casein rats at weeks 1 (p < 0.01) and 2 (p < 0.05) after DOCA treatment. Abnormal mineral excretions induced by DOCA treatment in casein rats were hardly detected in SPI rats. Severe atrophy of tubular epithelium and some flattened/detached renal tubules were also observed in casein rats, but not in SPI rats. These results indicate that consecutive treatment of SPI protects against renal dysfunction, particularly tubulointerstitial nephritis, in DOCA salt-treated obese Zucker rats.

Epicatechin lowers blood pressure, restores endothelial function, and decreases oxidative stress and endothelin-1 and NADPH oxidase activity in DOCA-salt hypertension

Flavanol-rich diets have been reported to exert beneficial effects in preventing cardiovascular diseases, such as hypertension. We studied the effects of chronic treatment with epicatechin on blood pressure, endothelial function, and oxidative status in deoxycorticosterone acetate (DOCA)-salt-induced hypertension. Rats were treated for 5 weeks with (-)-epicatechin at 2 or 10 mg kg(-1)day(-1). The high dose of epicatechin prevented both the increase in systolic blood pressure and the proteinuria induced by DOCA-salt. Plasma endothelin-1 and malondialdehyde levels and urinary iso-prostaglandin F(2α) excretion were increased in animals of the DOCA-salt group and reduced by the epicatechin 10 mg kg(-1) treatment. Aortic superoxide levels were enhanced in the DOCA-salt group and abolished by both doses of epicatechin. However, only epicatechin at 10 mg kg(-1) reduced the rise in aortic nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity and p47(phox) and p22(phox) gene overexpression found in DOCA-salt animals. Epicatechin increased the transcription of nuclear factor-E2-related factor-2 (Nrf2) and Nrf2 target genes in aortas from control rats. Epicatechin also improved the impaired endothelium-dependent relaxation response to acetylcholine and increased the phosphorylation of both Akt and eNOS in aortic rings. In conclusion, epicatechin prevents hypertension, proteinuria, and vascular dysfunction. Epicatechin also induced a reduction in ET-1 release, systemic and vascular oxidative stress, and inhibition of NADPH oxidase activity.

CXCR4 antagonism attenuates the cardiorenal consequences of mineralocorticoid excess

BACKGROUND

Extensive evidence implicates aldosterone excess in the development and progression of cardiovascular disease states including hypertension, metabolic syndrome, cardiac hypertrophy, heart failure, and cardiorenal fibrosis. Recent studies show that activation of inflammatory cascade may play a specific role in the sequelae of mineralocorticoid activation, although the linking mechanism remains unclear. We tested the possibility that secondary stimulation of the stromal-derived factor 1/CXC chemokine receptor 4 (SDF-1/CXCR4) pathway plays a contributory role.

METHODS AND RESULTS

We investigated the effect of the highly selective CXCR4 antagonist AMD3465 (6 mg/kg per day for 6 weeks through minipump) in dexoycorticosterone acetate (DOCA)-treated, uninephrectomized mice. CXCR4 antagonism significantly attenuated the induction of cardiac fibrosis, renal fibrosis, hypertension, and left ventricular hypertrophy by DOCA. Mineralocorticoid excess also stimulated the accumulation of T-lymphocytes in the heart and kidney and this was significantly blunted by CXCR4 inhibition.

CONCLUSIONS

Taken together, these data strongly implicate the SDF-1/CXCR4 axis in the pathogenesis of mineralocorticoid excess induced hypertension, inflammation, and cardiorenal fibrosis. This insight provides a new potential therapeutic approach for the treatment of specific aspects of mineralocorticoid mediated cardiovascular disease.

Vasorelaxant and antihypertensive effect of Cocos nucifera Linn. endocarp on isolated rat thoracic aorta and DOCA salt-induced hypertensive rats

ETHNOPHARMACOLOGICAL RELEVANCE

The fruits of Cocos nucifera Linn. (Arecaceae) have long been used in traditional medicine for the treatment of cardio-metabolic disorders.

AIM OF THE STUDY

To evaluate the ethanolic extract of Cocos nucifera Linn. endocarp (CNE) for its vasorelaxant activity on isolated rat aortic rings and antihypertensive effects in deoxycorticosterone acetate (DOCA) salt-induced hypertensive rats.

MATERIALS AND METHODS

Cocos nucifera Linn. endocarp was extracted with ethanol and characterized by HPLC. CNE was examined for its in vitro vascular relaxant effects in isolated norepinephrine, phenylephrine or potassium chloride pre-contracted aortic rings (both intact endothelium and denuded). In vivo anti-hypertensive studies were conducted in DOCA salt-induced uninephrectomized male Wistar rats.

RESULTS

Removal of endothelium or pretreatment of aortic rings (intact endothelium) with l-NNA (10μM) or ODQ (10 μM) followed by addition of contractile agonists prior to CNE significantly blocked the CNE-induced relaxation. Indomethacin (10μM) and atropine (1 μM) partially blocked the relaxation, whereas glibenclamide (10 μM) did not alter it. CNE significantly reduced the mean systolic blood pressure in DOCA salt-induced hypertensive rats (from 185.3 ± 4.7 mmHg to 145.6±6.1 mmHg). The activities observed were supported by the polyphenols, viz. chlorogenic acid, vanillic acid and ferulic acid identified in the extract.

CONCLUSIONS

These findings reveal that the vasorelaxant and antihypertensive effects of CNE, through nitric oxide production in a concentration and endothelium-dependent manner, is due to direct activation of nitric oxide/guanylate cyclase pathway, stimulation of muscarinic receptors and/or via cyclooxygenase pathway.

GTP cyclohydrolase I/BH4 pathway protects EPCs via suppressing oxidative stress and thrombospondin-1 in salt-sensitive hypertension

Endothelial progenitor cells (EPCs) are both reduced and dysfunctional in hypertension that correlates inversely with its mortality, but the mechanisms are poorly understood. Endothelial nitric oxide synthase (eNOS) critically regulates EPC mobilization and function but is uncoupled in salt-sensitive hypertension because of the reduced cofactor tetrahydrobiopterin (BH4). We tested the hypothesis that GTP cyclohydrolase I (GTPCH I), the rate-limiting enzyme of BH4 de novo synthesis, protects EPCs and its function in deoxycorticosterone acetate (DOCA)-salt mice. EPCs were isolated from peripheral blood and bone marrow of wild-type (WT), WT DOCA-salt, endothelial-specific GTPCH transgenic (Tg-GCH), GTPCH transgenic DOCA-salt, and BH4-deficient hph-1 mice. In WT DOCA-salt and hph-1 mice, EPCs were significantly decreased with impaired angiogenesis and adhesion, which were restored in Tg-GCH DOCA-salt mice. Superoxide (O₂⁻) and nitric oxide (NO) levels in EPCs were elevated and reduced, respectively, in WT DOCA-salt and hph-1 mice; both were rescued in Tg-GCH DOCA-salt mice. eNOS(-/-)/GCH(+/-) hybrid mice demonstrated that GTPCH preserved the circulating EPC number, reduced intracellular O₂⁻ in EPCs, and ameliorated EPC dysfunction independent of eNOS in DOCA-salt hypertension. Secreted thrombospondin-1 (TSP-1; a potent angiogenesis inhibitor) from EPCs was elevated in WT DOCA-salt and hph-1 but not DOCA-salt Tg-GCH mice. In vitro treatment with BH4, polyethylene glycol-superoxide dismutase (PEG-SOD), or Nomega-nitro-L-arginine (L-NNA) significantly augmented NO and reduced TSP-1 and O₂⁻ levels from EPCs of WT DOCA-salt mice. These results demonstrated, for the first time, that the GTPCH/BH4 pathway critically regulates EPC number and function in DOCA-salt hypertensive mice, at least in part, via suppressing TSP-1 expression and oxidative stress.

A Rat Model of Preeclampsia

Preeclampsia/eclampsia is a disorder of human pregnancy that continues to exact significant maternal morbidity and mortality and fetal wastage. Therapy of these disorders has not changed in over 50 years and there are no proven preventive measures. We describe a model of the development of a syndrome in the pregnant rat that resembles preeclampsia, which results from the imposition of excessive volume expansion early in gestation. We administered desoxycorticosterone acetate (DOCA) to pregnant animals whose drinking water had been replaced with saline. We compared the results obtained in these animals with those resulting from the study of control, virgin animals, virgin animals receiving DOCA and saline, and normal pregnant (NP) animals. The virgin animals given DOCA and saline did not become hypertensive. The experimental paradigm in the DOCA plus saline pregnant (PDS) animals provides many of the phenotypic characteristics of the human disorder including the development of hypertension, proteinuria, and intrauterine growth restriction. In addition, the mean blood nitrite/nitrate concentration was reduced in the PDS rats compared with their NP counterparts. We propose that this model may prove to be useful in the study of the human condition.

Sepsisähnliches Krankheitsbild bei Immunsuppression nach früherem Mallorcaurlaub

In immunosuppressed patients, a high rate of complications due to opportunistic infection is known. We report the case of a 36 year old patient with ulcerative colitis and a septic complication with ongoing pancytopenia. Due to colonic perforation, colectomy had to be performed. Despite this intervention, the septic constellation persisted. The pancytopenia in peripheral blood counts also persisted with the necessity of repetitive transfusions. A bone marrow biopsy showed an infiltration with Leishmania bodies in macrophages. Tissue culture allowed for typing of the parasites as belonging to the L. donovani/infantum complex, DNA sequencing confirmed infection with L. infantum. This infection must have been contracted during a vacation on Mallorca about 1.5 years earlier. Administration of liposomal amphotericin B cured the patient. Surprisingly, histological examination of the resected colon reveiled the presence of an immunoblastic B-cell lymphoma. In this case, immunosuppression was a prerequisite for the manifestation of leishmaniosis.

The effect of hypertension on serum nitric oxide and vascular endothelial growth factor concentrations. A study in DOCA-Salt hypertensive ovariectomized rats

CardioVascular Disease (CVD) accounts for considerable mortality and morbidity in developed countries. Most of the common forms of CVD, such as hypertension, are caused by functional and structural changes in endothelial function. This study was designed to study the effect of hypertension on serum Nitric Oxide (NO) and Vascular Endothelial Growth Factor (VEGF) concentrations in DOCA-Salt hypertensive ovariectomized rats. Thirty female rats were ovariectomized. Blood samples were taken and the animals were divided into hypertensive and control groups. Hypertension was induced by DOCA-Salt method. DOCA was injected 30 mg/kg of body weight subcutaneously, twice a week with NaCl 1% instead of tap water for drinking throughout the experiment. The control group received normal saline injection with usual drinking water. Results showed that serum NO concentration in DOCA-Salt hypertensive rats was lower than the control group (18.35 +/- 5.31, 45.01 +/- 12.54 micromol/l, respectively) (p < 0.05). Also, the mean serum VEGF concentration was raised after induced hypertension (120.55 +/- 8.11 vs. 88.58 +/- 2.24 pg/ml) (p < 0.05). In conclusion, reduced serum NO and increased serum VEGF concentrations in hypertensive animals support the concept of endothelial dysfunction in hypertensive subjects.

SGK1-dependent cardiac CTGF formation and fibrosis following DOCA treatment

The mineralocorticoids aldosterone and deoxycorticosterone acetate (DOCA) stimulate renal tubular salt reabsorption, increase salt appetite, induce extracellular volume expansion, and elevate blood pressure. Cardiac effects of mineralocorticoids include stimulation of matrix protein deposition leading to cardiac fibrosis, which is at least partially due to the direct action of the hormones on cardiac cells. The signaling mechanisms mediating mineralocorticoid-induced cardiac fibrosis have so far remained elusive. Mineralocorticoids have been shown to upregulate the serum- and glucocorticoid-inducible kinase 1 (SGK1), which participates in the effects of mineralocorticoids on renal tubular Na+ reabsorption and salt appetite. To explore the involvement of SGK1 in the pathogenesis of mineralocorticoid-induced cardiac fibrosis, SGK1 knockout mice (sgk1-/-) and wild-type littermates (sgk1+/+) were implanted a 21-day-release 50-mg DOCA pellet and supplied with 1% NaCl in drinking water for 18 days. This DOCA/high-salt treatment increased blood pressure in both genotypes but led to significant cardiac fibrosis only in sgk1+/+ but not in sgk1-/- mice. According to real-time polymerase chain reaction and Western blotting, DOCA/high-salt treatment enhanced transcript levels and protein expression of cardiac connective tissue growth factor (CTGF) only in sgk1+/+ but not in sgk1-/- mice. Furthermore, DOCA (10 microM) upregulated CTGF expression and enhanced CTGF promoter activity in lung fibroblasts isolated from sgk1+/+ but not from sgk1-/- mice, an effect involving spironolactone-sensitive mineralocorticoid receptors and activation of nuclear factor-kappaB (NFkappaB). Our results suggest that SGK1 plays a decisive role in mineralocorticoid-induced CTGF expression and cardiac fibrosis.

NAD(P)H oxidase/nitric oxide interactions in peroxisome proliferator activated receptor (PPAR)alpha-mediated cardiovascular effects

Activation of peroxisome proliferator activated receptor (PPAR)alpha and its protective role in cardiovascular function has been reported but the exact mechanism(s) involved is not clear. As we have shown that PPARalpha ligands increased nitric oxide (NO) production and cardiovascular function is controlled by a balance between NO and free radicals, we hypothesize that PPARalpha activation tilts the balance between NO and free radicals and that this mechanism defines the protective effects of PPARalpha ligands on cardiovascular system. Systolic blood pressure (SBP) was greater in PPARalpha knockout (KO) mice compared with its wild type (WT) litter mates (130+/-10 mmHg versus 107+/-4 mmHg). L-NAME (100mg/L p.o.), the inhibitor of NO production abolished the difference between PPARalpha KO and WT mice. In kidney homogenates, tissue lipid hydroperoxide generation was greater in KO mice (11.8+/-1.4 pM/mg versus 8.3+/-0.6 pM/mg protein). This was accompanied by a higher total NOS activity (46+/-6%, p<0.05) and a approximately 3 fold greater Ca2+-dependent NOS activity in kidney homogenates of untreated PPARalpha WT compared with the KO mice. Clofibrate, a PPARalpha ligand, increased NOS activity in WT but not KO mice. Bezafibrate (30 mg/kg) reduced SBP in conscious rats (19+/-4%, p<0.05), increased urinary NO excretion (4.06+/-0.53-7.07+/-1.59 microM/24 h; p<0.05) and reduced plasma 8-isoprostane level (45.8+/-15 microM versus 31.4+/-8 microM), and NADP(H) oxidase activity (16+/-5%). Implantation of DOCA pellet (20mg s.c.) in uninephrectomized mice placed on 1% NaCl drinking water increased SBP by a margin that was markedly greater in KO mice (193+/-13 mmHg versus 130+/-12 mmHg). In the rat, DOCA increased SBP and NAD(P)H oxidase activity and both effects were diminished by clofibrate. In addition, clofibrate reduced ET-1 production in DOCA/salt hypertensive rats. Thus, apart from inhibition of ET-1 production, PPARalpha activation exerts protective actions in hypertension via a mechanism that involves NO production and/or inhibition of NAD(P)H oxidase activity.

Plasma concentrations of anxiolytic neuroactive steroids in men with panic disorder

Plasma concentrations of neuroactive steroids in men with panic disorder (PD) were measured to evaluate their relations to psychopathology both before and during treatment. Participants comprised 13 men with PD and 10 normal controls. Patients were evaluated while drug-free as well as after 1 and 2 months of paroxetine therapy. Psychopathology was assessed by the State-Trait Anxiety Inventory (STAI), the Panic-Associated Symptom Scale, and the Fear Questionnaire total score. Plasma concentrations of steroids were measured by radioimmunoassay. The plasma concentrations of progesterone and dehydroepiandrosterone were greater in drug-free patients than in controls, whereas those of allopregnanolone and tetrahydrodeoxycorticosterone did not differ between the two groups. Paroxetine treatment for 2 months significantly increased the plasma concentration of allopregnanolone but did not affect those of the other steroids. At 2 months of therapy, allopregnanolone concentrations in patients were significantly greater than those in controls. The plasma concentrations of progesterone and tetrahydrodeoxycorticosterone correlated with the STAI state score in patients before treatment. Our data suggest that neuroactive steroids may play a role in PD in men.

Effects of deoxycorticosterone on renal vascular reactivity and flow-pressure curve in spontaneously hypertensive rats

The role of mineralocorticoids as sodium retaining hormones has been recently enlarged to include their function as modulators of cardiovascular function and injury. This study evaluated the contribution of possible functional changes in resistance vessels to the additional BP increase produced by the chronic administration of DOCA to SHR. The flow-pressure curve and renal responses to vasoconstrictors (phenylephrine [Phe] and angiotensin II [AII]) and vasodilators (acetylcholine [ACh] and nitroprusside [NP]) were characterized in isolated kidneys from Wistar Kyoto (WKY) and SHR treated or untreated with DOCA for nine weeks. DOCA increased BP in SHR but did not modify BP in WKY rats. Kidneys from SHR showed enhanced reactivity to Phe and AII that was not increased by DOCA. DOCA reduced sensitivity to AII in SHR. Responsiveness to ACh was increased in SHR and was not attenuated by DOCA in WKY or SHR. Vasodilator response to NP was not significantly affected by DOCA in WKY or SHR. The flow-pressure curve was markedly up-shifted in SHR when compared with kidneys from WKY rats. DOCA administration did not modify the flow-pressure curve in WKY but produced attenuation at low flow levels in SHR. Our results demonstrate that DOCA increases BP in SHR but does not increase the flow-pressure curve or renal vascular reactivity to vasoconstrictors, and does not reduce responsiveness to endothelium-dependent and independent vasodilators in SHR or WKY rats. Therefore, our data suggest that the BP increase produced by DOCA in SHR is not related to abnormalities in vascular function in resistance vessels.

How Could Aortic Arginase Activity Enhancement Be Involved in DOCA‐Salt Hypertension?

This study was to examine whether the increase in aortic arginase activity observed in DOCA-salt hypertensive rats is involved in the mechanism of physiological hypertension by participating to vessel hypertrophy and/or to the impairment of endothelium-dependent relaxation to acethylcholine. We measured polyamine content and relaxation-response to acethylcholine in aortic rings isolated from control and DOCA-salt treated Sprague-Dawley rats after in vitro modification of arginase activity. Polyamine content was significantly increased in aorta from DOCA-salt hypertensive rats compared with controls. In the normotensive rats, the addition of L-valine (an inhibitor of arginase) decreased the relaxation response to acethylcholine whereas the addition of arginase increased the relaxation dependent response. On the contrary, in DOCA-salt hypertensive rats, the addition of L-valine or of arginase did not change the endothelium dependent relaxation. The results obtained suggest that the increase in aortic arginase activity in DOCA-salt hypertension could contribute to vascular hypertrophy but not to the impairment of endothelium-dependent relaxation.

Strain differences in the development of hypertension and glomerular lesions induced by deoxycorticosterone acetate salt in mice

BACKGROUND

The genetic background may exert important modifying effects on the course and severity of experimental kidney diseases in mice. We investigated its influence on the development of hypertension and renal injury following treatment with deoxycorticosterone acetate (DOCA) salt in several mouse strains.

METHODS

Four mouse strains were used for comparison: 129/Sv, C57BL/6 and F1 and F2 intercrosses of 129/Sv x C57BL/6. Male mice were uninephrectomized and DOCA hypertension was induced for 6 weeks. DOCA animals and controls received 1% NaCl for drinking. Renal damage was evaluated following measurements of blood pressure, urine albumin and renal matrix expansion.

RESULTS

DOCA-induced blood pressure increase, glomerulosclerosis, interstitial fibrosis and albuminuria were markedly higher in 129/Sv than in C57BL/6 mice. F1 and F2 intercrosses displayed intermediate blood pressure, glomerular and interstitial fibrosis comparable to C57BL/6 but albuminuria as high as 129/Sv mice.

CONCLUSIONS

129/Sv mice are more susceptible to the development of DOCA-induced high blood pressure and renal damage than C57BL/6 mice. Intercrosses of both strains show a complex and non-uniform segregation of the susceptibility to DOCA-salt hypertension and nephrosclerosis.

Does the Sabra hypertension-prone rat represent a model of salt or mineralocorticoid sensitivity?

OBJECTIVES

Since the Sabra experimental model of hypertension was developed, it has been known as a model of salt-susceptible hypertension. Because the hypertensive response of the Sabra hypertension-prone strain (SBH/y) is classically elicited by salt loading with a combination of deoxycorticosterone acetate (DOCA) and salt, doubt has now been cast on whether the hypertensive response is due to sensitivity to salt or to mineralocorticoids. The present study was designed to resolve this question.

MATERIALS AND METHODS

We studied the blood pressure response of SBH/y to various modes of salt loading. Animals were salt-loaded by administration of: 1% NaCl in drinking water and subcutaneous implantation of a 25 mg DOCA pellet (DOCA-salt); DOCA alone; 1% NaCl in drinking water alone; or 8% NaCl in chow alone. Blood pressure was determined by the tail-cuff method in awake and undisturbed animals.

RESULTS

Within 4 weeks, the DOCA-salt treatment elicited the full hypertensive response previously reported in the SBH/y strain. Salt loading with 8% NaCl in chow reproduced the full hypertensive response observed with DOCA-salt, except that it occurred only after 7 weeks of treatment. Salt loading with DOCA alone raised blood pressure moderately and to a maximal level within 3 weeks; the magnitude of the blood pressure response was, however, significantly smaller than that observed with DOCA-salt or 8% NaCl in chow. Administration of 1% NaCl in water alone elicited no hypertensive response.

CONCLUSIONS

The hypertensive response to salt loading in the Sabra experimental model of hypertension is an expression primarily of salt sensitivity, as it can be fully reproduced with salt alone, but not with DOCA alone. The use of the DOCA-salt mode of salt loading in this model, as opposed to salt loading with 8% salt in chow, is a useful way of accelerating the development of salt-sensitive hypertension in SBH/y, which shortens, and therefore facilitates, phenotyping.

Enhanced depressor effect of centrally administered high-calcium solution in salt-loaded experimental hypertension

The depressor effect by oral calcium supplementation is known to be more pronounced in salt-dependent than in renin-dependent hypertension. This study was conducted to investigate the role of central calcium on two different pathophysiologic subtypes of experimental hypertension; (a) salt-dependent, deoxycorticosterone acetate-salt hypertensive rats (DOCA), and (b) renin-dependent, 2-kidney, 1 clip (2-K, 1C) hypertensive rats. In DOCA (n = 10), high-calcium solution (Ca+2, 65.2 mM, 10 microl) given centrally (i.c.v.) elicited a marked decrease in mean blood pressure (MBP; 170 +/- 4 to 138 +/- 5 mm Hg, p < 0.01) with a decrease in heart rate (HR; 390 +/- 18 to 344 +/- 17 beats/min, p < 0.05) lasting for 40 min. In 2-K, 1C (n = 10), high-Ca2+ i.c.v. showed a lesser decrease in MBP (178 +/- 4 to 171 +/- 5 mm Hg) and HR (419 +/- 10 to 395 +/- 12 beats/min) with shorter duration (for 20 min) than in DOCA. This significant depressor and bradycardic response to Ca2+ i.c.v. observed in DOCA was dose dependent at Ca2+ concentrations between 65.2 and 130.4 mM. In DOCA, high Ca2+ i.c.v. reduced the plasma noradrenaline (Nad) concentration significantly (479 +/- 81 to 319 +/- 62 pg/ml, p < 0.05). These results suggest that central Ca2+ plays a more important role in regulating sympathetic nerve activity and BP in salt-dependent than in renin-dependent experimental hypertension.

Increased renal expression of cytokines and growth factors induced by DOCA-NaCl treatment in Heymann nephritis

DOCA-NaCl treatment causes hypertension, accelerates development of proteinuria, and leads to glomerulosclerosis in rats with autoimmune Heymann nephritis. To study the mechanisms of kidney injury induced by renal haemodynamic load in chronic nephritis, we studied by immunohistochemistry the local expression of various cytokines, growth factors and adhesion molecules in the kidneys of Heymann nephritic rats with or without DOCA-NaCl-induced hypertension. The DOCA-NaCl-nephritis group developed hypertension and marked renal enlargement as compared with the nephritis group, the DOCA-NaCl group, and the controls. Albuminuria appeared earlier and was heavier in the DOCA-NaCl-nephritis group compared with the nephritic rats without DOCA-NaCl. Expression of IL-6, TNF-alpha, GM-CSF, b-FGF, NGF, TGF-beta, and ICAM-1 was enhanced in the kidneys of the DOCA-NaCl-nephritis group as compared with other groups, localized mainly in the glomerular mesangium (IL-6, GM-CSF, TGF-beta), glomerular and peritubular endothelium (ICAM-1), and collecting ducts (TNF-alpha, b-FGF, NGF, TGF-beta), possibly associated with the observed tubulointerstitial mononuclear cellular infiltration. Thus in autoimmune Heymann nephritis, DOCA-NaCl treatment causes hypertension and increased renal mass together with upregulation of local cytokine and growth factor production, which may further aggravate hypertension and accelerate progression of renal damage.

Effects of desoxycorticosterone pivalate administration on blood pressure in dogs with primary hypoadrenocorticism

A study was designed to evaluate the effects of desoxycorticosterone pivalate (DOCP) on blood pressure in 8 dogs with primary hypoadrenocorticism, and to attempt to identify other factors that might suggest overdosage of the drug. In 4 dogs, primary hypoadrenocorticism had been diagnosed immediately before entry of the dog into the study, and the dogs had not received any mineralocorticoid supplementation. In the other 4 dogs, primary hypoadrenocorticism had been diagnosed 1 to 6 years previously, and dogs were being treated with DOCP at the time of entry into the study. In all 8 dogs, DOCP (2.2 mg/kg of body weight, IM) was administered on days 0, 30, 60, and 90 of the study; each dog was examined on days 0, 30, 60, 75, 90, and 105. At the time of each visit, a medical history was obtained, a complete physical examination and serum biochemical analyses were performed, and body weight and blood pressure were measured. Doppler-shift ultrasonic sphygmomanometry was used to indirectly record systemic systolic and diastolic pressures. None of the dogs developed hypernatremia or hypokalemia or any clinical signs suggestive of hypoadrenocorticism during the study. However, in 6 dogs (3 that had not been previously treated with mineralocorticoids and 3 that had been), there was a significant increase in body weight over the course of the study. Compared with baseline (day 0) arterial blood pressure, neither systolic nor diastolic blood pressure was significantly increased during the study, and all systolic and diastolic blood pressure measurements were within reference ranges at all evaluation times.(ABSTRACT TRUNCATED AT 250 WORDS)

[In vitro study of the role of endothelium on the vasorelaxant effect of magnesium on the aorta from DOCA-salt hypertensive rats]

Vasorelaxant effects of magnesium (Mg) have been described in man and in animal with arterial hypertension. Some studies have shown relationships between extracellular Mg (magnesium e.c.) and endothelial function. So, our study is designed to determine whether elevated extracellular Mg leads to an endothelium-dependent vasorelaxant effect on contractile tension developed by noradrenaline in isolated aorta from DOCA-salt hypertensive rats. Elevated extracellular Mg (4.8 mM) in the bath significantly depressed the dose-response curve to noradrenaline in aorta with endothelium. Following disruption of endothelium, the vasorelaxant effect of elevated extracellular Mg on contractile response to noradrenaline was greatly inhibited. Furthermore, in presence of L. NG nitroarginine (L-NAME) (10(-4) M), inhibitor of endothelial nitric oxide (NO) biosynthesis, the vasorelaxant effect of extracellular Mg on contractility to noradrenaline was partially inhibited. The addition of sodium nitroprussiate (5 10(-9) M), known to spontaneously release NO, caused the reappearance of Mg vasorelaxation which had disappeared in aorta without endothelium. In conclusion, vascular endothelium seems to play an important role in the Mg-induced depressed contractile response to noradrenaline in isolated aorta from DOCA-salt hypertensive rat. Endothelial NO seems to be implicated in the endothelium-dependent action of extracellular Mg.

Alterations in circulating levels and cardiovascular tissue content of neuropeptide Y-like immunoreactivity during the development of deoxycorticosterone acetate-salt hypertension in the rat

OBJECTIVE

To investigate the modification of plasma and tissue neuropeptide Y-like immunoreactivity (NPY-li) concentrations, in relation to blood pressure and plasma catecholamine levels, during the development of deoxycorticosterone acetate (DOCA)-salt hypertension.

METHODS

Mean arterial pressure (MAP), heart rate, tissue and plasma NPY-li levels, and aortic norepinephrine and epinephrine plasma levels were measured in conscious DOCA-salt hypertensive rats treated for 1, 2 and 3 weeks, and in their respective normotensive controls.

RESULTS

Both norepinephrine and NPY-li plasma levels increased significantly in parallel with blood pressure during DOCA-salt treatment, so that MAP was significantly correlated with plasma norepinephrine and NPY-li levels in hypertensive rats. Plasma NPY-li levels were also correlated with norepinephrine levels only in hypertensive rats, but were correlated with epinephrine levels only in normotensive animals. Tissue NPY-li content was lower in the mesenteric artery and heart ventricles after 1-3 weeks of DOCA-salt treatment, but the content in the adrenal gland was not significantly different from that in normotensive rats.

CONCLUSIONS

In DOCA-salt hypertensive rats, increased plasma NPY-li levels originate primarily from the sympathetic nerves, since those levels were correlated exclusively with circulating norepinephrine levels and they were associated with a reduction in NPY-li content of the heart and mesenteric artery. It is thus possible that the enhanced release of NPY-li from sympathetic nerves could contribute to the rise in blood pressure and to the maintenance of hypertension in this experimental model.

Insulin resistance in spontaneously hypertensive rats but not in deoxycorticosterone-salt or renal vascular hypertension

OBJECTIVE

To investigate whether the reported association between insulin resistance and hypertension in spontaneously hypertensive rats (SHR) is a primary defect or a secondary phenomenon in hypertension.

DESIGN

Comparisons of glucose metabolism between three groups of hypertensive rats: deoxycorticosterone (DOCA)-salt hypertensive rats; two-kidney, one clip renovascular hypertensive (RVH) rats; SHR; and their respective control groups. There was also an additional group of weight-matched SHR and respective Wistar-Kyoto (WKY) controls.

METHODS

A trace amount of 3H-deoxyglucose (3H-DOG) was administered in vivo to evaluate its plasma half-life and tissue uptake. In vitro adipose tissue segments were incubated with 14C-glucose and increasing doses of insulin.

RESULTS

Compared with age-matched WKY rats, SHR had significantly higher insulin levels, longer plasma half-life and lower 3H-DOG uptake by heart and striated muscle. Plasma glucose levels and incorporation of 14C-glucose into CO2, triglycerides and glycogen by adipose tissue in response to increasing insulin concentrations was similar for both groups of SHR and WKY rats. No differences were found between hypertensive rats and controls in either the DOCA or RVH groups.

CONCLUSION

Evidence of insulin resistance in spontaneous, but not secondary, rat hypertension indicates that the resistance is a primary rather than a secondary event in hypertension.

Hypotensive action of taurine in DOCA-salt rats--involvement of sympathoadrenal inhibition and endogenous opiate

We studied the roles of the sympathoadrenal system and endogenous opiate in the antihypertensive effects of supplementation of dietary taurine, a sulfur amino acid, in deoxycorticosterone acetate (DOCA)-salt rats. Supplementation of 1% taurine in drinking water for 2 weeks was found to prevent the increase in systolic blood pressure of DOCA-salt rats (116 +/- 2 vs 138 +/- 2 mmHg, p less than 0.01), but failed to effect the systolic blood pressure of vehicle-treated control rats (115 +/- 2 vs 112 +/- 3 mmHg), taurine supplementation restored to normal increased plasma norepinephrine (326 +/- 32 vs 531 +/- 67 pg/ml, p less than 0.01) and epinephrine (204 +/- 19 vs 304 +/- 43 pg/ml, p less than 0.05) concentrations in DOCA-salt rats, but had no effect on norepinephrine (346 +/- 23 vs 338 +/- 33 pg/ml) or epinephrine (198 +/- 17 vs 224 +/- 26 pg/ml) concentrations in control rats. Accordingly, the increased epinephrine content in the adrenals of DOCA-salt rats was normalized with the supplementation of taurine, associated with a markedly increased adrenal taurine content. In conscious rats, moreover, intraperitoneal injection of naloxone (2 mg/kg), a specific opiate antagonist, increased systolic blood pressure only in taurine-supplemented DOCA-salt rats. Evidence presented suggests, therefore, that both the suppression of the increased sympathoadrenal activity and the activation of endogenous opiate might contribute to the antihypertensive effect of taurine in DOCA-salt rats.

Altered phospholipase C activity in renal medulla of DOCA-salt hypertensive rats

We investigated the alterations of phospholipase C activity in the kidney and arterial wall of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Neither DOCA nor salt administration alone affected phospholipase C activity in the kidney and arterial wall. In contrast, when the rats were given both DOCA and salt and developed high blood pressure, the phospholipase C activity became greater in the outer and inner medulla (papilla) while the enzyme activity was reduced significantly in the renal cortex and arterial wall. Such an increase in phospholipase C activity was not observed in the kidney of a genetic rat for spontaneous hypertension. Moreover, the phospholipase A2 activity was also stimulated in the renal medulla of DOCA-salt hypertensive rats. Thus, these data indicate that DOCA-salt hypertension is associated with an increase in phospholipase C activity in the renal medulla, which seems primary to the development of DOCA-salt hypertension.

The characteristics of alpha-adrenoceptors mediating the renal nerve induced antinatriuresis and antidiuresis in hypertensive rats

Selective alpha-adrenoceptor and calcium antagonists have been used to determine both the alpha 1-adrenoceptor subtype and the extracellular calcium requirement for renal nerve-mediated antinatriuresis and antidiuresis in deoxycorticosterone acetate (DOCA)-salt and two-kidney, one clip (2K1C) Goldblatt hypertensive rats. Stimulation of the renal nerves at low frequencies reduced urine flow and absolute and fractional sodium excretions by 40-60% in pentobarbitone anaesthetized control, sham-operated, DOCA-salt and 2K1C Goldblatt hypertensive rats. Administration of prazosin, but not idazoxan, inhibited the renal nerve-induced excretory responses in both models of hypertension, a result compatible with the involvement of alpha 1-adrenoceptors. By contrast, the calcium antagonist inhibited the renal nerve-dependent antinatriuresis and antidiuresis in DOCA-salt but not 2K1C Goldblatt hypertensive rats. These results showed that the renal nerves mediated their action via alpha 1-adrenoceptors, but that the postreceptor responses were dependent on extracellular calcium in DOCA-salt but not 2K1C Goldblatt rats.

Neutral metalloendopeptidase inhibition: a novel means of circulatory modulation

Inhibition of the enzyme neutral metalloendopeptidase (NEP) potentiates responses to atrial natriuretic factor (ANF) and elicits reductions in blood pressure in deoxycorticosterone acetate sodium (DOCA Na) hypertensive rats. The present study evaluated the role of ANF and bradykinin in the antihypertensive response to NEP inhibition through the use of antibodies and antagonists, respectively. In addition, the pharmacokinetic mechanism by which NEP inhibition interferes with ANF metabolism was explored. The antihypertensive response to the NEP inhibitors SCH 34826 and 42495 was abruptly reversed by an intravenous injection of a polyclonal antiserum to ANF. In contrast, the antihypertensive response to SCH 34826 was unaffected by injection of the bradykinin antagonist [thi5,8-D-phe7] bradykinin, indicating that ANF, but not bradykinin, affects this response. The NEP inhibitor SCH 39370 significantly delayed the disappearance of trichloroacetic acid (TCA)-precipitable radioactivity and the appearance of TCA-soluble radioactivity in plasma following an intravenous bolus dose of 125I-ANF(99-126). The effects were enhanced in the presence of the C-receptor ligand des[gln18,ser19,gly20,leu21,gly22]r ANF(4-23)-NH2. These data suggest that the two clearance mechanisms interact to govern plasma levels of ANF.

Effects of indapamide on the mechanical properties of the arterial wall in deoxycorticosterone acetate-salt hypertensive rats

An experimental model of "in situ" isolated carotid artery has been used to evaluate the static mechanical properties of the arterial wall in 12-week-old Wistar and deoxycorticosterone acetate (DOCA)-salt hypertensive rats. The rats were made hypertensive by left kidney removal, DOCA (50 mg) tablet implantation for 2 weeks, and saline diet (NaCl 9% solution as beverage). Normotensive control rats (n = 24) and DOCA-salt hypertensive rats (n = 24) received indapamide, 10 mg/kg, or placebo by gavage 12 hours and 1 hour before measurements were obtained. The rats were anesthetized (pentobarbital 50 mg/kg), intubated and ventilated, and a midsternal thoracotomy was performed. A first catheter was introduced into the ascending aorta through the right carotid artery. A perivascular ultrasonic flow probe was placed around the ascending aorta and allowing simultaneous recording of the phasic ascending aortic pressure and flow. Systolic and diastolic pressure, cardiac output and heart rate were directly measured. Peripheral resistance and systemic arterial compliance were calculated from hemodynamic records. After hemodynamic measurements, a segment of the left carotid artery was then isolated in vivo and its volume-pressure relationship was recorded before and 30 minutes after total abolition of the vascular muscle tone by local incubation with a potassium cyanide solution (KCN) (100 mg/liter) for pressures ranging from 50 to 175 mm Hg. The carotid compliance (CC) (microliter/mm Hg) was calculated, for every pressure step, as the slope of the volume-pressure curves. Indapamide significantly reduced the arterial pressure in hypertensive rats, and this was related to a marked decrease in total peripheral resistance. Heart rate was not modified by indapamide.(ABSTRACT TRUNCATED AT 250 WORDS)

Cardiac hypertrophy developing during DOCA-salt treatment is dissociated from systemic and regional hemodynamics

Systemic and regional hemodynamics were studied in DOCA-treated Sabra hypertensive (SBH) and normotensive (SBN) rats. In SBH rats, mean arterial pressure (MAP) and total peripheral resistance index (TPRI) increased significantly. In SBN rats, MAP remained stable and TPRI decreased. Cardiac output and heart rate were unchanged. Opposed changes in TPRI were mediated mainly by changes in vascular resistance of the skin, skeletal muscles and splanchnic organs. Both strains developed significant biventricular hypertrophy. We conclude that SBH and SBN rats' susceptibility or resistance to DOCA-salt hypertension are associated with opposed changes in TPRI. The development of biventricular hypertrophy is apparently dissociated from systemic hemodynamic changes.

Paraventricular nucleus lesions attenuate the development of hypertension in DOCA/salt-treated rats

To determine whether paraventricular nucleus (PVN) can play a role in the hypertension in DOCA/salt-treated rats, DOCA/salt hypertension was produced in PVN lesions and sham-operated rats. In lesioned rats, the development of hypertension was significantly attenuated (day 7: 132 +/- 3 v 157 +/- 5 mm Hg, P less than 0.01; day 14: 132 +/- 3 v 157 +/- 5 mm Hg, P less than 0.01; day 21: 189 +/- 2 v 224 +2- 6 mm Hg, P less than 0.01). Lesions lowered systolic blood pressure in even control rats. Mean blood pressure (mBP) from awake free moving rats was also significantly lower in lesioned DOCA/salt-treated rats than those of sham-operated DOCA/salt-treated rats (155 +/- 14 mm Hg v 193 +/- 13, P less than 0.01), while mBP was not different between lesioned and sham-operated control rats. The reduction of mBP by hexamethonium injections was significantly larger in sham-operated DOCA/salt-treated rats than those of lesioned DOCA/salt rats. (-53 +/- 3% v -45 +/- 2, P less than 0.05). Plasma norepinephrine and epinephrine were significantly elevated in DOCA/salt-treated rats, however, PVN lesions inhibited significantly those elevations. 1-Deaminopenicillamine, 4-valine, 8-D-arginine Vasopressin (dPVDAVP) injections did not affect BP and heart rate in all rats. Body weight, water intake, urine volume, urine Na, K, and vasopressin excretion, and urine osmorality were not altered by lesions. These findings suggest that PVN contributes to development of hypertension in DOCA/salt-treated rats with sympathetic nervous activations.

Central action of sodium chloride on whole body pressor responsiveness in the DOCA-treated rat

This study investigated the effect of chronic intracerebroventricular (IVT) infusion of a hypertonic NaCl (400 mmol/l) artificial cerebrospinal fluid (aCSF) on blood pressure and whole body pressor responsiveness, in control rats (CH) and in rats implanted with deoxycorticosterone acetate (DOCA; DH). An isotonic aCSF was infused into another group of control (Cl) and DOCA (Dl) rats. Indirect systolic blood pressure (SBP) was measured using a tail-cuff technique once a week prior to and during the infusion period. Following 2 weeks of infusion, SBP increased significantly only in the DH and CH groups. In urethane-anaesthetized rats, the pressor response to intravenous infusions of norepinephrine and angiotensin II (Ang II) increased significantly in DH rats. When compared with Cl and Dl rats, those from the CH group also exhibited an enhanced response to norepinephrine and Ang II. However, this increase was not as great as in the DH animal. These results show that whole body pressor responses to norepinephrine and Ang II, increase in rats receiving chronic IVT infusion of hypertonic NaCl. These responses coincide with moderate but significant increases in SBP. These data indicate that sodium chloride acts at a central site to increase norepinephrine and Ang II pressor responsiveness in mineralocorticoid hypertension.

Changes in platelet function due to hypertension: comparison of experimental hypertension with spontaneous hypertension in rats

In washed platelets both from DOCA-salt and renal hypertensive rats, there was a marked decrease in thrombin-induced aggregation and secretion responses compared with those of respective controls. Concomitantly, the platelets showed attenuated malondialdehyde (MDA) formation and reduced serotonin contents, suggesting the presence of degranulated platelets in the circulation due to hypertension. In platelets from stroke-prone spontaneously hypertensive rats (SHRSP) at early hypertensive stages, thrombin-induced aggregation and secretion responses were similarly reduced. However, the platelet hypofunctions did not accompany reduced MDA formation and serotonin contents. Properties of platelets obtained from SHRSP at late hypertensive stages resembled those of platelets from experimentally hypertensive rats. These results suggest that the mechanisms of platelet hypofunction differ between experimental hypertension and spontaneous hypertension in their early stages. The hypo-aggregability observed in experimental hypertension appears to be secondary to the hypertension, whereas that seen in spontaneous hypertension seems to be a primary defect and not secondary to hypertension at early stages of hypertension.

Attenuated cardiovascular and sympathetic nerve responses to aortic nerve stimulation in DOCA-salt hypertensive rats

In order to verify, whether baroreflex sensitivity is changed centrally in DOCA-salt hypertension, the left aortic depressor nerve (ADN) was electrically stimulated in DOCA-salt hypertensive rats. After 3 weeks, tail-cuff systolic pressure was significantly higher in DOCA-salt treated rats than in untreated rats (169 +/- 4 versus 130 +/- 4 mmHg, respectively; P less than 0.001). After cutting both ADN and the carotid sinus nerves, the central cut end of the left ADN was electrically stimulated and frequency dependent depressor, bradycardic and sympatho-inhibitory responses were elicited in both control and DOCA-salt hypertensive rats. However, these responses were significantly smaller in DOCA-salt hypertensive rats than in normotensive controls. Bradycardic and sympatho-inhibitory responses to i.v. injection of norepinephrine were also blunted in DOCA-salt hypertensive rats. These findings suggest that baroreflexes were centrally attenuated in DOCA-salt hypertensive rats and possibly contribute to overall baroreflex attenuation.

[Recurrent iatrogenic benign intracranial hypertension in a case of congenital adrenogenital syndrome with loss of salts]

Pseudotumor cerebri is a condition that produces symptoms and signs of brain tumor; the increased intracranial pressure is caused by diffuse cerebral edema. The authors describe a case of 12 years boy, with adrenal hyperplasia, treated by DOCA, presenting recurrent episodes of hyponatremia, headache, nausea and papilledema, cured definitively after correction of natremia and after institution 9-alpha-fluorohydrocortisone therapy.

Evidence for a digitalis-like substance in the hypothalamopituitary axis in rats: implications in the central cardiovascular regulation associated with an excess intake of sodium

The origin and the physiological role of an endogenous digitalis-like substance were investigated by measuring both the digoxin-like substance by a digoxin radioimmunoassay (RIA) and the inhibitory activity on the ouabain sensitive Na+,K+-ATPase in rats. The digitalis-like substance was in high concentration in the pituitary, and in decreasing concentration in the hypothalamus, adrenal and the other organs as measured by RIA using an antibody raised from a goat. However, the adrenal showed the highest content of digitalis-like substance as measured by the antibody raised from a rabbit. The plasma level markedly decreased during a 2-week sodium-loading, and the adrenal content decreased markedly on hypophysectomy as measured with the rabbit-antibody. Therefore, the substance measured with the rabbit-antibody must be one of ACTH-dependent adrenal steroids. The inhibitory activity on the Na+,K+-ATPase was high in the pituitary gland, and was decreased in order of the adrenal, hypothalamus and other organs. The 2-week sodium-loading increased both the content in the pituitary gland and the output in the urine, and decreased the hypothalamic content. Immunohistochemical staining of the hypothalamus with the antibody revealed that the immunoreactivity is restricted to the neurons of the paraventricular nucleus, supraoptic nucleus, magnocellular accessory nuclei and extended their fibers reaching to the inner layer of the median eminence. To determine the role of the substance in the brain, the crude extract dissolved in artificial cerebrospinal fluid was injected into the lateral ventricle; vasopressor responses, tachycardia and hyperactivity of the splanchnic nerve lasting for more than 30 min were recorded, which resembled the responses to ouabain injected similarly.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of steroids on the development of soft-tissue calcifications at the margin of the distal tuberosity of the fingers]

Long-term corticosteroid therapy leads to an increase in soft tissue calcification at the margin of the distal tuberosity of the fingers, which normally occurs infrequently. This steroid-induced calcification is most often seen in chronic respiratory disturbances.

KCl inhibits hypothalamic activity to attenuate hypertension in DOCA-salt rats

Potassium supplementation attenuated the development of hypertension in DOCA-salt rats but did not affect blood pressure in control rats. However, it caused a decrease in body weight in both groups of rats. Sympathetic nerve and pressor responses either to electrical stimulation of the hypothalamus or to intracisternal injections of hypertonic NaCl were enhanced in DOCA-salt rats but were normalized by KCl supplementation. Since the pressor responses to injected norepinephrine or tyramine remained unaltered by KCl treatment, a peripheral inhibition of cardiovascular reactivity was considered unlikely. Pretreatment with methyclothiazide also attenuated the elevation in blood pressure but did not affect the responsiveness to hypothalamic stimulation; hence increased natriuresis or diuresis alone could not account for the effects induced by KCl. These findings are consistent with the conclusion that KCl supplementation attenuates the development of DOCA-salt hypertension in rats by acting on the central nervous system to reduce sympathetic output.

Catecholamine synapses and contents in the paraventricular hypothalamic nucleus and nucleus tractus solitarius of DOCA-salt hypertensive rats

Central catecholamine (CA) neurons in the nucleus tractus solitarius (NTS) and paraventricular hypothalamic nucleus (PVN) were studied in Wistar rats that had been unilaterally nephrectomized. The experimental animals were then treated with deoxycorticosterone acetate (DOCA) and salt water. The control animals were treated with the vehicle and tap water. Blood pressure of animals 4 weeks after DOCA/salt treatment was significantly elevated when compared to control rats. Morphologically, CA terminals showed no noticeable changes in the DOCA/salt hypertensive rats. Furthermore, the density of CA terminals either in the NTS or in the PVN of the DOCA/salt hypertensive rats was not statistically different from that of normotensive controls, suggesting that salt does not cause lesions or destruction of CA terminals. However, an extensive electron-microscopic morphometric analysis indicated that there was an enhancement of CA synaptogenesis (expressed by increased synaptic frequency among all CA boutons labeled with 5-hydroxydopamine) in the PVN, but not in the NTS of DOCA/salt hypertensive rats. In addition, the high-performance liquid chromatography revealed decreased CA contents in the PVN, but not in the NTS, of DOCA/salt hypertensive animals. Since synapses are primary sites for neurotransmitter release, the above results collectively suggest that more CA synapses formed in the PVN may reflect a net CA release from CA terminals resulting in the decreased CA content in the axonal terminals. Such an increased CA release and enhanced CA synaptogenesis may consequently enhance CA function in the PVN of hypertensive rats 4 weeks after DOCA/salt treatment, and relate to the development and/or maintenance of hypertension in the DOCA/salt rats.

Erythrocyte membrane abnormalities in hypertension: a comparison between two animal models

Calcium-membrane interactions have been studied in two animal models of hypertension using the erythrocyte membrane as a model system. The Okamoto-Aoki strain of spontaneously hypertensive rats (SHR) was the first examined, and the activities of the Ca++/Mg++-ATPases in the membrane of SHR erythrocytes were found to be consistently higher than those of the normotensive controls (WKY), while other membrane enzymes such as Na+/K+-ATPase and acetylcholinesterase were not detectably altered. Erythrocyte membranes of the SHR also have a higher passive permeability to calcium as well as other functional and compositional differences when compared to those of the WKY. These findings suggest that the membrane alterations in the SHR may be related to an increased passive permeability to calcium, and a possibly compensatory increase in Ca++/Mg++-ATPase activity in these animals. The second animal model examined was the deoxycorticosterone/salt-induced hypertension (DOCA) in uninephrectomized rats. In DOCA rats with comparable degree of blood pressure elevation, none of the erythrocyte membrane abnormalities observed in the SHR were present, suggesting that the latter alterations are probably genetically determined and not a consequence of elevated arterial pressure.

Prevention of DOCA-salt hypertension with the calcium blocker nitrendipine

Mononephrectomized female rats on a high sodium intake developed hypertension, hypokalemia, enlarged hearts and kidneys and slight adrenal involution under deoxycorticosterone treatment. Simultaneous administration of nitrendipine (5 mg/kg twice daily) completely prevented hypertension and reduced but did not abolish cardiac enlargement. There was no effect of the calcium slow-channel inhibitor on kidney enlargement, adrenal atrophy or hypokalemia. The ability of the steroid to produce cardiomegaly in the absence of an elevated blood pressure to account for it, tends to confirm the suggestion of other investigators that the steroid may have that effect by a mechanism not involving blood pressure elevation.

Central mechanisms in DOC-salt hypertensive rats

These experiments were intended to elucidate the role of central mechanisms in the maintenance of high blood pressure produced by deoxycorticosterone (DOC) and salt in rats. We investigated the central effect of angiotensin (AII) on systemic arterial blood pressure and plasma arginine vasopressin (AVP) in DOC-salt and control rats. There was a pronounced augmentation of the pressor responsiveness to centrally injected AII in DOC-salt hypertensive rats; but there was no difference in AII induced AVP release in DOC-salt hypertensive rats compared to sham controls. The increase in vascular resistance of the perfused hindquarters induced by stimulation of the lumbar sympathetic chains did not change in DOC-salt hypertensive rats although the increases induced by norepinephrine (NE) were potentiated at the higher doses. Pressor responsiveness of the DOC-salt hypertensive rats to i.v. administration of AII, AVP and NE was shown to be augmented by factors of 3.6, 2.5 and 1.8 respectively in DOC-salt rats. Reflex bradycardia to these pressor responses was attenuated indicating impairment of baroreflex function. The potentiation of pressor responses to centrally injected AII in DOC-salt hypertensive rats was greater than could be explained by augmented pressor responsiveness to iv NE and AVP. Neither baroreflex dysfunction, facilitated release of NE at sympathetic terminals, nor augmented release of AVP into the circulation could explain the potentiation. Therefore, our data suggested that selective central amplification of sympathetic vasomotor responses to centrally injected AII stimuli may play a role in the hypertension after 3 weeks of DOC-salt treatment in rats.

Renin as a risk factor for atherogenesis. Part 2. Effects of hypercholesterolemia and hyporeninemia in the rabbit

Four groups of New Zealand rabbits were used to study the effect of suppressed plasma renin activity (PRA) on atherogenesis. Control groups were fed normal rabbit chow (Group I) or normal chow supplemented with 0.25% cholesterol--0.75% corn oil (Group III). Group II animals were fed normal chow and received periodic injections of 11-desoxycorticosterone (DOC)pivalate and 0.5% saline to drink, while Group IV animals were treated similarly except that they were also fed the atherogenic diet. Blood pressure and blood chemistry measurements were performed monthly over a 7-month period. The blood pressure was unaffected by either the diet or the DOC-saline treatment, however, the PRA was greatly reduced in the animals receiving DOC-saline (Groups II and IV). Similarly, plasma aldosterone was significantly (P less than 0.05) reduced in the DOC-saline-treated animals. No atheromata were observed in the animals consuming the regular diet, regardless of DOC-saline treatment. All of the animals fed the atherogenic diet showed extensive aortic atheromata. However, there was no difference in the lesion index between the animals with normal PRA levels (Group III) and those with suppressed PRA levels (Group IV). Likewise, microscopic evaluation of the aorta, coronary arteries, and renal arteries failed to show a consistent difference in the vascular involvement between animals of Groups III and IV. We therefore conclude that the suppression of PRA does not have a protective effect on atherogenesis in the cholesterol-fed normotensive rabbit.

Sympathetic nerve function and vascular reactivity in Doca-salt hypertensive rats

The present study was conducted to measure norepinephrine release during sympathetic nerve stimulation and to evaluate vascular reactivity in the isolated perfused mesenteric vasculature of normotensive and Doca-salt hypertensive rats. Significantly greater vasoconstrictor responses to periarterial nerve stimulation, norepinephrine, and vasopressin, but not to barium chloride, were observed in the mesenteric vasculature of the hypertensive rats in comparison with the control normotensive group. Norepinephrine release, measured as total tritium overflow, during periarterial nerve stimulation at 4 Hz for 2 min, was identical in both normotensive and hypertensive animals. Phentolamine (5.3 micro M) significantly increased tritium overflow, but to the same extent in the normotensive and the hypertensive mesenteric vasculature, suggesting that the negative feedback presynaptic alpha-adrenoceptor mechanism, which has been proposed to modulate transmitter release, was unaltered in this form of hypertension. These results indicate that hyperresponsiveness of the mesenteric vasculature to periarterial nerve stimulation in the hypertensive rats is due to increased sensitivity of the vascular alpha-adrenoceptor and not facilitation of the transmitter release. The increased vascular reactivity to norepinephrine and vasopressin may be involved in the maintenance of Doca-salt hypertension.