Erectile dysfunction: an early marker for hypertension? A longitudinal study in spontaneously hypertensive rats

Erectile dysfunction (ED) is another manifestation of vascular disease. We evaluated the natural history of ED in the spontaneously hypertensive rat (SHR) and the respective participation of associated pathophysiological modifications, i.e., endothelial dysfunction and tissue remodeling. SHR and their normotensive counterparts [Wistar-Kyoto rats (WKY)] of 6, 12, and 24 wk of age (n = 12) were used to evaluate erectile function, erectile and aortic tissue reactivity, and remodeling. Erectile responses in SHR are reduced at all ages (P < 0.001). In both aortic and erectile tissues of SHR and WKY, relaxations to ACh are altered progressively with age, although more markedly in SHR. They are decreased at 12 wk of age in erectile tissue of SHR compared with WKY (maximal relaxation: -19.2 +/- 2.8% vs. -28.3 +/- 3.9%, P < 0.001) but only at 24 wk of age in aortas (-47.9 +/- 6.4% vs. -90.5 +/- 2.9%, P < 0.001). Relaxations to sodium nitroprusside are unaltered in aortic rings of both strains but enhanced in erectile tissue of SHR at 12 wk of age. Major modifications in the distribution of collagen I, III, and V in SHR occur in both types of tissue and are detectable sooner in erectile tissue compared with aortic tissue. The onset of ED is detectable before the onset of hypertension in the SHR. Structural and functional alterations, while similar, occur earlier in erectile compared with vascular tissue. If confirmed in humans, ED could be an early warning sign for hypertension, and common therapeutic strategies targeting both ED and hypertension could be investigated.     

Ebselen ameliorates renal ischemia–reperfusion injury via enhancing autophagy in rats

Renal ischemia–reperfusion (I/R) injury is one of the most common causes of chronic kidney disease (CKD). It brings unfavorable outcomes to the patients and leads to a considerable socioeconomic burden. The study of renal I/R injury is still one of the hot topics in the medical field. Ebselen is an organic selenide that attenuates I/R injury in various organs. However, its effect and related mechanism underlying renal I/R injury remains unclear. In this study, we established a rat model of renal I/R injury to study the preventive effect of ebselen on renal I/R injury and further explore the potential mechanism of its action. We found that ebselen pretreatment reduced renal dysfunction and tissue damage caused by renal I/R. In addition, ebselen enhanced autophagy and inhibited oxidative stress. Additionally, ebselen pretreatment activated the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway. The protective effect of ebselen was suppressed by autophagy inhibitor wortmannin. In conclusion, ebselen could ameliorate renal I/R injury, probably by enhancing autophagy, activating the Nrf2 signaling pathway, and reducing oxidative stress.

     

Gardiovascular responses to prostaglandin f2α in spontaneously hypertensive rats

To test the hypothesis that abnormal prostaglandin reactivity may be a characteristic of essential hypertension, cardiovascular responses to prostaglandin F_2α (PGF_2α) were measured in young spontaneously hypertensive (SHR) and Wistar normotensive rats (NR). PGF_2α(1 sec injection; 50 l/100 g.; .05, .5, 5, 50 g salt/kg) was injected retrograde into the femoral artery. Maximum changes were measured with respect to: 1) four different diameter categories of cremaster muscle arterioles, 2) mean arterial pressure (MAP), 3) pulse pressure (PP) and 4) heart rate. PGF_2α at 5 and 50 g/kg significantly increased NR and SHR blood pressure. SHR MAP increased significantly more than NR MAP with the 50 g dose (P <. 001). PGF_2α increased NR PP at the 50 g/kg dose and increased SHR PP at the .5, 5 and 50 g/kg dose. SHR PP response was significantly greater than that of the NR with the .5, 5 and 50 g/kg dose (P < .05, .01, .001 respectively). The mean SHR arteriolar constriction was greater than that of NR with the 50 g dose. The only change in heart rate was a 3% decrease from control in both NR and SHR during the pressor response to 50 g/kg. These results show an increased cardiovascular reactivity to PGF_2α in SHR and may further suggest prostaglandin involvement in hypertensive disease.     

Enhanced vasoconstriction to α_1 adrenoceptor autoantibody in spontaneously hypertensive rats

Autoimmune activities have been implicated in the pathogenesis of hypertension.High levels of autoantibodies against the second extracellular loop of α1-adrenoceptor(α1-AR autoantibody,α1-AA) are found in patients with hypertension,and α1-AA could exert a α1-AR agonist-like vasoconstrictive effect.However,whether the vasoconstrictive effect of α1-AA is enhanced in hypertension is unknown.Using aortic rings of spontaneously hypertensive rats(SHR) and normotensive Wistar-Kyoto(WKY) rats,we observed the vasoconstrictive responses to α1-AA with phenylephrine(α1-AR agonist) as a positive control drug.Aortic nitrotyrosine levels were also measured by ELISA and immunohistochemistry.The results showed that the aortic constrictive responses to α1-AA and phenylephrine(both 1 nmol L-1-10 μmol L-1) were greater in SHR than in WKY rats.Endothelial denudation or L-NAME(a non-selective NOS inhibitor)(100 μmol L-1) increased α1-AA- or phenylephrine-induced vasoconstrictions both in SHR and WKY.However,selective iNOS inhibitor 1400W(10 μmol L-1) enhanced the α1-AA-induced aortic constriction in WKY,but not in SHR.The aortic nitrotyrosine level was significantly higher in SHR than WKY,as shown by both ELISA and immunohistochemistry.These results indicate that the vasoconstrictive response to α1-AA is enhanced in SHR,and this altered responsiveness is due to endothelial dysfunction and decreased NO bioavailability.The study suggests an important role of α1-AR autoimmunity in the pathogenesis and management of hypertension especially in those harboring high α1-AA levels.     

PPARα agonist fenofibrate protects the kidney from hypertensive injury in spontaneously hypertensive rats via inhibition of oxidative stress and MAPK activity

Oxidative stress has been shown to play an important role in the development of hypertensive renal injury. Peroxisome proliferator-activated receptors α (PPARα) has antioxidant effect. In this study, we demonstrated that fenofibrate significantly reduced proteinuria, inflammatory cell recruitment and extracellular matrix (ECM) proteins deposition in the kidney of SHRs without apparent effect on blood pressure. To investigate the mechanisms involved, we found that fenofibrate treatment markedly reduced oxidative stress accompanied by reduced activity of renal NAD(P)H oxidase, increased activity of Cu/Zn SOD, and decreased phosphorylation of p38MAPK and JNK in the kidney of SHRs.Taken together, fenofibrate treatment can protect against hypertensive renal injury without affecting blood pressure by inhibiting inflammation and fibrosis via suppression of oxidative stress and MAPK activity.     

Hippocampal levels of dynorphin A (1–8) in neonatal and 16-week-old spontaneously hypertensive rats: Comparisons with DOCA-salt hypertension

In this study the possible role of hippocampal dynorphin in the development of hypertension in spontaneously hypertensive rats (SHR) was investigated by determining dynorphin A (1–8) (DN A (1–8)) levels in hippocampus in 16 week old SRH, Wistar Kyoto (WKY) controls and SHR treated with antihypertensive drugs as well as DOCA-salt hypertensive Sprague Dawley (SD) rats, using radioimmunoassay (RIA). We found that DN A (1–8) was decreased significantly in both dorsal (–68%) and ventral (–58%) hippocampus in SHR compared with WKY rats. Treatment with hydralazine and guanethidine (25 mg/kg/24 hr of each drug in drinking water) for 8 weeks to prevent the development of hypertension in young SHR had no effect on this low hippocampal dynorphin level. We failed to find significant changes in hippocampal DN A (1–8) level in DOCA-salt hypertensive rats. The low level of hippocampal dynorphin existed before the development of hypertension in 6 day neonatal SHR (–73%). Hippocampal Met-enkephalin was unchanged in all experimental groups except for a slight decrease in neonatal SHR. The results establish a genetic difference in the hippocampal dynorphin system of SHR compared with WKY, the significance of which, for the development of hypertension, remains to be investigated.     

Which comes first: renal inflammation or oxidative stress in spontaneously hypertensive rats?

The present study was undertaken to identify whether inflammation or oxidative stress is the primary abnormality in the kidney in spontaneously hypertensive rats (SHR). Renal inflammation and oxidative stress were evaluated in 2- and 3-week-old prehypertensive SHR and age-matched genetically normotensive control Wistar-Kyoto (WKY) rats. Blood pressure was similar in WKY and SHR rats at 2 and 3 weeks, of age. Renal inflammation (macrophage and nuclear factor-kappaB) was elevated in SHR at 3 weeks, but not at 2 weeks, of age compared with age-matched WKY rats. Renal oxidative stress (nitrotyrosine, 8-hydroxy-2'-deoxyguanosine and p47phox) was also clearly elevated in 3-week-old SHR compared with age-matched WKY rats. Additionally, NADPH oxidase subunit p47phox was found elevated in 2-week-old SHR compared to age-matched WKY rats. Moreover, antioxidant (N-acetyl-L-cysteine and Tempol) treatment reduced renal inflammation in prehypertensive SHR. We therefore conclude that the oxidative stress appears before inflammation as a primary abnormality in the kidney in prehypertensive SHR.     

Which comes first: Renal inflammation or oxidative stress in spontaneously hypertensive rats?

The present study was undertaken to identify whether inflammation or oxidative stress is the primary abnormality in the kidney in spontaneously hypertensive rats (SHR). Renal inflammation and oxidative stress were evaluated in 2- and 3-week-old prehypertensive SHR and age-matched genetically normotensive control Wistar-Kyoto (WKY) rats. Blood pressure was similar in WKY and SHR rats at 2 and 3 weeks, of age. Renal inflammation (macrophage and nuclear factor-κB) was elevated in SHR at 3 weeks, but not at 2 weeks, of age compared with age-matched WKY rats. Renal oxidative stress (nitrotyrosine, 8-hydroxy-2′-deoxyguanosine and p47phox) was also clearly elevated in 3-week-old SHR compared with age-matched WKY rats. Additionally, NADPH oxidase subunit p47phox was found elevated in 2-week-old SHR compared to age-matched WKY rats. Moreover, antioxidant (N-acetyl-l-cysteine and Tempol) treatment reduced renal inflammation in prehypertensive SHR. We therefore conclude that the oxidative stress appears before inflammation as a primary abnormality in the kidney in prehypertensive SHR.     

Activation of PPAR-γ ameliorates pulmonary arterial hypertension via inducing heme oxygenase-1 and p21: An in vivo study in rats

Aims

Our previous study has indicated that activation of PPAR-γ inhibits the proliferation of rat pulmonary artery smooth muscle cells (PASMCs) in vitro through inducing the expression of heme oxygenase-1 (HO-1), which in turn up-regulates the p21^WAF1 expression. In the present study, we intended to determine whether similar mechanisms have been involved in activation of PPAR-γ inhibition of development of rat PAH model.

Material and methods

Rat pulmonary arterial hypertension (PAH) model was established by subcutaneous injection of monocrotaline (MCT). Rosiglitazone was administered to activate PPAR-γ. Zinc protoporphyria IX (ZnPP-IX), was used to confirm the role of HO-1 in mediating PPAR-γ function. Parameters including the right ventricle systolic pressure (RVSP), the right ventricular hypertrophy (RVH) and the percentage of medial wall thickness were used to evaluate the development of PAH. Immunoblotting was used to determine the expression of HO-1 and p21^WAF1.

Key findings

Rosiglitazone significantly decreased the RVSP and inhibited the RVH in MCT-induced rat PAH model, and partially inhibited the pulmonary vascular remodeling. These effects were coupled with the sequential increase of HO-1 and p21^WAF1 expressions by rosiglitazone.

Significance

Activation of PPAR-γ benefits PAH by inhibiting proliferation of PASMCs and reducing pulmonary vascular remodeling. The present study suggests that enhancing PPAR-γ activity might have potential value in clinical treatment of PAH.     

Renal corticosterone 6β-hydroxylase in the spontaneously hypertensive rat

Excess 6β-OH-corticosterone production by family 3A cytochromes P-450 may play a role in genesis of hypertension in the spontaneously hypertensive rat (SHR), by producing a renal defect in Na⁺ excretion. Renal cytochromes P-450 may be a causal factor in this genetic model. Since family 3A P-450 is present in rat kidney (collecting duct), the renal family 3A catalytic (6β-OHase) and immunoreactive activities were compared in SHR and normotensive control (Wistar-Kyoto; WKY) rats. Corticosterone 6β-hydroxulation is markedly higher in SHR than in WKY renal microsomal preparations. Western blot analysis with antibodies to rat and rabbit liver family 3A isoforms demonstrated related proteins. Densitometry revealed greater relative intensity of staining in SHR compared to WKY with both antibodies. Both antibodies inhibited corticosterone 6β-hydroxylation by SHR renal microsomes. Increased renal 6β-OH-corticosterone production by increased renal family 3A cytochromes P-450 may play a role in the blood pressure elevation in SHR.     

Functional and structural characterization of anti-β1-adrenoceptor autoantibodies of spontaneously hypertensive rats

Eighteen month old spontaneously hypertensive rats (SHR-rats) showed myocardial dysfunction and autoantibodies directed against the ₁-adrenoceptor similarly as known in human dilated cardiomyopathy or Chagas' disease. The agonist-like antibodies were able to activate the ₁-adrenoceptor mediated signal transduction cascade in cultured rat cardiomyocytes and induced a long-lasting stimulatory effect resulting in a harmful adrenergic overdrive. The antibodies recognized an epitope of the second extracellular loop of the ₁-adrenoceptor identical to that epitope identified in Chagas' disease. In conclusion, our assumption is supported that old SHR-rat are an useful animal model for investigating the role of anti-₁-adrenoceptor antibodies in the induction of human cardiomyopathy.     

Effect of diabetes on aortic nitric oxide synthesis in spontaneously hypertensive rats; does captopril modulate this effect?

Nitric oxide (NO) is a potent regulator in the cardiovascular system; it is generated by the nitric oxide synthase (NOS) family of proteins. NO produced in endothelial cells plays a crucial role in vascular functions. The aim of this study was to clarify the effect of diabetes on aortic NO synthesis in a model of genetic hypertension and determine whether captopril modulates this effect. Diabetes was induced in ten weeks old spontaneously hypertensive rats (SHR) by streptozotocin injection. The rats were allocated into 3 groups: control group 1, non-diabetic SHR; group 2, diabetic SHR; group 3, diabetic SHR group receiving captopril at 80 mg/kg in drinking water for 4 weeks. Mean blood pressure (MBP) was measured once a week by tail-cuff method. Aortic NO metabolities (nitrite/nitrate) and endothelial NOS (NOS-3) were assayed by Griess reaction and by immunoblotting and immunohistochemistry, respectively. There was a significant decrease in nitrite/nitrate (NOx) in aortas of diabetic SHR compared with controls. The decrease of aortic NOx in diabetic SHR was accompanied by a decrease in NOS-3 expression. Captopril treatment reduced MBP without affecting either NOx level or NOS-3 expression in aortas of diabetic SHR. We conclude that STZ-induced diabetes decreased NO in aortas of SHR that may reflect endothelial cell dysfunction; captopril administration decreased MBP without affecting NO level in aortas of diabetic SHR which suggest that the blood pressure-lowering effects of captopril were independent of NO.     

Influence of long-term supplementation with α-linolenic acid on myocardial lipid peroxidation and antioxidative capacity in spontaneously hypertensive rats

The ischaemic vulnerability of the heart of spontaneously hypertensive rats (SHR) is enhanced after feeding an α-linolenic acid (LNA) enriched diet. Because oxygen radical-induced reactions (e.g. lipid peroxidation) are involved in the ischaemic damage, an increased susceptibility of the SHR heart to such damaging reactions might be the reason. As a sign of the enhanced susceptibility to lipid peroxidation of LNA-fed SHR, we found (measured as TBARS) higher plasma and heart lipid peroxide levels (3.84 ± 0.50 μmol/l vs 2.98 ± 0.78 μmol/l and 507 ± 127 nmol/g prot. vs 215 ± 80 nmol/g prot., respectively) after feeding LNA. Using Fe²⁺/Vit. C to induce lipid peroxidation in myocardial tissue homogenates, we demonstrated the enhanced susceptibility to lipid peroxidation of the LNA-fed SHR heart (68 ± 12 nmol/min × g prot. vs 40 ± 8 nmol/min × g prot.) also in vitro. The myocardial enrichment of n-3 polyunsaturated fatty acids (PUFA) resulting in a higher peroxidation index (Pl 227 vs. 170) and the loss in myocardial activities of the antioxidative enzymes (SOD: 76 ± 24 U × 10³/g prot. vs 235 ± 150 U × 10³/g prot.; GSH-Px: 32 ± 5 U/g prot. vs 110 ± 30 U/g prot.) by feeding LNA could be the cause of the increase in myocardial susceptibility to lipid peroxidation of PUFA supplemented SHR.     

Antihypertensive and cardioprotective effects of different monotherapies and combination therapies in young spontaneously hypertensive rats – A pilot study

Spontaneously hypertensive rats (SHR) are an established animal model for antihypertensive treatment. The aim of this pilot study was a systematic search for two lines of antihypertensive treatment – a monotherapy and a combination of two drugs – to be applied in a future study on old SHR. Originally, representatives of three drug classes recommended for antihypertensive therapy in humans should be applied, namely captopril (CAP) as an antagonist of the renin-angiotensin-aldosterone system, nifedipine (NIF) as calcium channel blocker and propranolol (PROP) as β-adrenergic blocker. As we observed that PROP had been poorly ingested, all groups with PROP therapy were excluded from the study. CAP (60 mg kg^?1 d^-1), NIF (10 mg kg^?1 d^-1) or both were administered orally to seven-week-old SHR over 3 weeks. A further group of SHR received no treatment (SHR/CTRL). Age-matched normotensive Wistar-Kyoto rats served as normotensive controls. We examined the effect of the antihypertensive therapies on systolic blood pressure, heart weight and on histological and biochemical markers of cardiac hypertrophy and fibrosis.CAP proved to be the most effective treatment reducing blood pressure and relative heart weight significantly compared to SHR/CTRL without reaching normotensive values. Beginning cardiac fibrosis observed in SHR/CTRL was completely abrogated with CAP treatment. Similar effects were achieved with a combination of CAP and NIF. CAP as monotherapy and CAP + NIF as combination therapy were chosen for the forthcoming study on old SHR.     

γ-Linolenic acid ameliorates DHEA induced pro-inflammatory response in polycystic ovary syndrome via PPAR-γ signaling in rats

The inflammatory responses associated with polycystic ovary syndrome (PCOS) may play a significant role in the severity of the disease. Emerging evidence report states that the polyunsaturated fatty acids are capable of ameliorating the PCOS condition. The therapeutic effects of γ-linolenic acid (GLA), an omega-6 fatty acid, in various inflammatory diseases have been reported. Yet, its role in PCOS associated inflammatory response remains unexplored. The aim of the study was to decipher the effects of GLA in PCOS and its role in the PPAR-γ pathway. In our study, female Wistar rats were stimulated with daily subcutaneous injections of DHEA (60 mg/kg per day) for 28 days to induce PCOS. Daily doses of GLA(10, 20, and 50 mg/kg) and Pioglitazone (P)(30 mg/kg) were administered orally for 14 days after PCOS induction. The levels of DHEA, leptin, PPAR-γ were measured by ELISA. The gene expression levels of leptin, TNF-α, IL-33, PPAR-γ, C/EBP-β, SREBP-1were determined by Real Time-PCR. We observed that the GLA significantly attenuated the DHEA and leptin levels. GLA treatment also upregulated PPAR-γ expression, when compared to the DHEA group. Further, GLA treatment showed a significant reduction in DHEA induced TNF-α, IL-33, C/EBP-β, and SREBP-1 levels in Wistar rat polycystic ovary tissue samples. The present findings could indicate that GLA is able to reduce the inflammatory response due to DHEA stimulation and thereafter potentially attenuate PCOS via the PPAR-γ pathway.     

Dietary β-carotene regulates interleukin-1β-induced expression of apolipoprotein E in astrocytes isolated from stroke-prone spontaneously hypertensive rats

Stroke-prone spontaneously hypertensive rats (SHRSP) have an abnormality in cholesterol synthesis, but the pathological relevance of this to stroke and related neuronal disorders is not yet clear. The induction of astrocyte-derived cholesterol transportation to neurons by apolipoprotein E (apoE) promotes neuronal repair after brain injuries such as stroke. Such repair is reduced by interleukin-1 beta (IL-1β) and stroke conditions. Furthermore, fibroblast growth factor 1 (FGF1) regulates the production of apoE–cholesterol-rich high density lipoproteins (HDL) and induces gliosis of astrocytes. On the other hand, high levels of plasma carotenoids reduce the risk of ischemic stroke. Thus, we investigated the expression of apoE in primary astrocytes that had been treated with IL-1β or β-carotene. In addition, we compared the expression levels of Apoe genes in astrocytes from SHRSP/Izm and normal control rats, Wistar–Kyoto rats (WKY/Izm) following hypoxia/reoxygenation (H/R). The expression levels of genes and proteins were investigated by RT-PCR, Western blotting (WB), and immunofluorescence analysis. IL-1β decreased the expression levels of the Apoe gene. Conversely, β-carotene significantly enhanced the expression levels of genes related to cholesterol regulation, including Abca1, Abcg1, Hmgcr as well as Apoe. During H/R, the gene expression levels of Apoe were decreased in the SHRSP/Izm rats in comparison with the WKY/Izm rats. These results suggest that IL-1β decreases Apoe expression levels, whereas β-carotene strongly elevates Apoe levels and inhibits FGF1-mediated gliosis of astrocytes. Furthermore, under hypoxic stress, astrocytes isolated from SHRSP/Izm rats displayed altered regulation of Apoe compared with those from WKY/Izm rats.     

Tamarix gallica ameliorates thioacetamide–induced hepatic oxidative stress and hyperproliferative response in Wistar rats

Tamarix gallica, a hepatic stimulant and tonic, was examined for its ability to inhibit thioacetamide (TAA)-induced hepatic oxidative stress, toxicity and early tumor promotion response in male Wistar rats. TAA (6.6 mmol/kg body wt. i.p) enhanced lipid peroxidation, hydrogen peroxide content, glutathione S-transferase and xanthine oxidase with reduction in the activities of hepatic antioxidant enzymes viz., glutathione peroxidase, superoxide dismutase and caused depletion in the level of hepatic glutathione content. A marked increase in liver damage markers was also observed. TAA treatment also enhanced tumor promotion markers, ornithine decarboxylase (ODC) activity and [³H] thymidine incorporation into hepatic DNA. Pretreatment of rats orally with Tamarix gallica extract (25 and 50 mg/kg body weight) prevented TAA-promoted oxidative stress and toxicity. Prophylaxis with Tamarix gallica significantly reduced the susceptibility of the hepatic microsomal membrane for iron-ascorbate induced lipid peroxidation, H₂O₂ content, glutathione S-transferase and xanthine oxidase activities. There was also reversal of the elevated levels of liver marker parameters and tumor promotion markers. Our data suggests that Tamarix gallica is a potent chemopreventive agent and may suppress TAA-mediated hepatic oxidative stress, toxicity, and tumor promotion response in rats.     

Plasma norepinephrine and dopamine-β-hydroxylase in genetic hypertensive rats

The relationship between blood pressure, plasma norepinephrine (NE), dopamine-β-hydroxylase (DBH) activity and age was investigated in spontaneously hypertensive rat (SHR), a stroke-prone substrain of the SHR and control Wistar-Kyoto rat (WKR). Blood pressure of both SHR strains increased with age and was significantly higher than that of the WKR at all ages tested (3 15 weeks). The blood pressure of stroke-prone SHR was significantly higher than that of the regular SHR after 6 weeks of age. Plasma DBH activity decreased with age in each strain, although the SHR, and especially the stroke-prone SHR, had significantly higher DBH than the controls at an early age. Plasma NE in the WKR did not change with age. Increased plasma NE was observed only in the young SHRs. The highest values were found in the 6 week old stroke-prone SHR. These data suggest that plasma DBH activity is not correlated directly with plasma NE or blood pressure, but that increased sympathetic nerve activity may occur during the development of hypertension in the SHR and the stroke-prone SHR.