Redox regulation and NO/cGMP plus K+ channel activation contributes to cardiorenal protection induced by Cuphea carthagenensis (Jacq.) J.F. Macbr. in ovariectomized hypertensive rats

BACKGROUND

One of the medicinal plants widely used by the population in the treatment of hypertension, atherosclerosis and circulatory disorders is Cuphea carthagenensis (Jacq.) J.F. Macbr. (Lythraceae), popularly known as 'sete sangrias', being found in Brazil, Hawaii and in South Pacific Islands. Despite the widespread use of this species by the population, its long-term antihypertensive and cardioprotective activities have not yet been scientifically evaluated.

PURPOSE

To evaluate the possible cardioprotective effects of an ethanol-soluble fraction obtained from C. carthagenensis (ESCC) using ovariectomized hypertensive rats to simulate a broad part of the female population over 50 years of age affected by hypertension. In addition, the molecular mechanism that may be responsible for its cardiorenal protective effects was also explored.

METHODS

Female Wistar rats were submitted to surgical procedures of bilateral ovariectomy and induction of renovascular hypertension (two-kidneys, one-clip model). The sham-operated group was used as negative control. ESCC was obtained and a detailed phytochemical investigation about its main secondary metabolites was performed. ESCC was orally administered at doses of 30, 100 and 300  mg/kg, daily, for 28 days, 5 weeks after surgery. Enalapril (15  mg/kg) was used as standard antihypertensive drug. Renal function was evaluated on days 1, 7, 14, 21 and 28. At the end of the experimental period, systolic, diastolic, mean arterial pressure and heart rate were recorded. The activity of the tissue enzymatic antioxidant system, thiobarbituric acid reactive substances, nitrotyrosine, nitrite, aldosterone and vasopressin levels, in addition to the activity of the angiotensin-converting enzyme were also evaluated. Additionally, vascular reactivity to acetylcholine, sodium nitroprusside, and phenylephrine, and the role of nitric oxide, prostaglandins, and K⁺ channels in the vasodilator response of ESCC on the mesenteric vascular bed were also investigated.

RESULTS

ESCC-treatment induced an important cardiorenal protective response, preserving renal function and preventing elevation of blood pressure and heart rate in ovariectomized hypertensive rats. In addition, prolonged treatment with ESCC recovered mesenteric vascular reactivity at all doses used. This effect was associated with an important modulation of the antioxidant defense system with a possible increase in NO bioavailability. Additionally, NO/cGMP activation and K⁺ channel opening-dependent vasodilator effect was observed on the mesenteric vascular bed, indicating a potential mechanism for the cardiovascular effects of ESCC.

CONCLUSION

A 28-days ESCC treatment reduces the progression of the cardiorenal disease in ovariectomized hypertensive rats. These effects seem to be involved with an attenuation of oxidative and nitrosative stress, affecting endothelial nitric oxide production and K⁺ channel opening in smooth muscle cells.

90-Day Oral Toxicity Assessment of Tropaeolum majus L. in Rodents and Lagomorphs

Tropaeolum majus L., popularly known as nasturtium, is a species widely used in the form of infusions and salads. In the last years, the antihypertensive, diuretic, and calcium and potassium sparing activities of T. majus preparations were shown. Moreover, no preclinical 90-day oral toxicity studies were conducted. Thus, this study evaluated the toxicity of the hydroethanolic extract obtained from T. majus (HETM) leaves in female and male mice, rats, and rabbits. Swiss mice and Wistar rats were treated with HETM (75, 375, and 750 mg/kg). The doses of rabbits (30, 150, and 300 mg/kg) were calculated by allometric extrapolation. The control groups received vehicle. The animals were orally treated, daily, for 90 days. At the end, the animals were anesthetized, and body weight gain, relative weight of liver, kidney, and spleen, and histopathological changes were evaluated. Serum hematological and biochemical parameters were also analyzed. No alterations were found in body and organ weights or in histopathological and biochemical evaluation. Hematological analyses revealed small changes in lymphocytes and neutrophil counts in rats after administration of 750 mg/kg of HETM. These results showed that 90-day use of T. majus is safe in rodents and lagomorphs.

Involvement of bradykinin B2 and muscarinic receptors in the prolonged diuretic and antihypertensive properties of Echinodorus grandiflorus (Cham. & Schltdl.) Micheli

BACKGROUND

Although Echinodorus grandiflorus (Cham. & Schltr.) Michel are used in Brazilian folk medicine as a diuretic drug, to date, no study has evaluated the mechanisms involved in this activity after prolonged administration in rats.

AIM OF THE STUDY

Evaluate the possible mechanisms involved in the prolonged diuretic activity of ethanol soluble fraction obtained from Echinodorus grandiflorus (ES-EG) and to assess its relationship with hypotensive and antihypertensive activity using normotensive rats and those with renovascular hypertension (2K1C).

METHODS

The diuretic effects of ES-EG (30-300 mg/kg; p.o.) were compared with hydrochlorothiazide in a repeated-dose treatment for 7 days. The urinary volume and sodium, potassium, chloride, bicarbonate contents, conductivity, pH and density were estimated in sample collected in 24 h for 7 days. Plasma sodium, potassium, total protein, urea, creatinine, aldosterone, vasopressin, nitrite, acetylcholinesterase concentration and angiotensin converting enzyme (ACE) activity were measured in samples collected at the end of the experimental period (seventh day). Using pharmacological antagonists or inhibitors, the involvement of bradykinin, prostaglandin, acetylcholine and nitric oxide (NO) in ES-EG-induced diuresis was determined. In addition, activities of erythrocytary carbonic anhydrase and renal Na+/K+/ATPase were evaluated in vitro.

RESULTS

ES-EG increased diuresis similarly to hydrochlorothiazide and also presented HCO3-sparing effects and increased serum nitrite levels. Moreover, the intraduodenal administration of ES-EG induces significant hypotensive and antihypertensive effects in 2K1C rats. Previous treatment with HOE-140, indometacin and atropine fully avoided the diuretic effect of ES-EG, and including L-NAME pre-administration, it prevented the hypotensive and hypertensive activity induced by ES-EG. In addition, the association between HOE-140 and atropine or indometacin and L-NAME fully inhibited the hypotensive and antihypertensive effects of ES-EG. The 7-day treatment with ES-EG resulted in increased plasma nitrite levels. All other parameters were not affected by treatment with ES-EG.

CONCLUSIONS

Our results suggest that the mechanisms through which Echinodorus grandiflorus extracts induce prolonged diuresis and reduce blood pressure in normotensive and 2K1C rats are mainly related to activation of muscarinic and bradykinin receptors with direct effects on prostaglandins and nitric oxide pathways.

Fetopathies associated with exposure to angiotensin converting enzyme inhibitor from Tropaeolum majus L

The prevalence of the use of herbal medicines is on the rise across the world, especially amongst pregnant women. A fact that draws attention is that many species commonly used by pregnant women, including the Tropaeolum majus L. (Tropaeolaceae), also present inhibitory activity on the angiotensin-converting enzyme (ACE). Herein, we have investigated the effects of T. majus extract (HETM) on fetal development, evaluating its relationship with possible ACE inhibitory activity. Pregnant Wistar rats were treated with different HETM doses (3, 30 and 300 mg/kg/day) from gestational days 8-20. Rats were sacrificed on the day 20 of pregnancy and the following parameters were evaluated: clinical symptoms of maternal toxicity; maternal body weight; feed and water intake; maternal liver, kidney, and ovary weights, maternal ACE activity and aldosterone levels, live fetuses mean; dead fetuses percentage, fetus weight, and fetal malformation. All pregnant rats treated with high HETM doses showed significant reduction in plasma ACE activity accompanied by a decrease in serum aldosterone levels. Moreover, significant changes in fetal development were observed, including growth retardation and renal damage after 20 days of gestation. Thus, data presented demonstrate the significant effects of the use of HETM on fetal development during pregnancy.

Ethnopharmacological investigation of the diuretic and hemodynamic properties of native species of the Brazilian biodiversity

ETHNOPHARMACOLOGICAL RELEVANCE

Although Echinodorus grandiflorus, Cuphea carthagenensis, and Phyllanthus tenellus infusions are used in Brazilian folk medicine due to their possible diuretic effect, none of these species was critically investigated as a diuretic drug. So, the aim of this study was to evaluate the possible acute diuretic activity of ethanol soluble fractions (ES) obtained from these species and assess the relationship between renal cortical blood flow and their antioxidant and hypotensive activity using normotensive Wistar rats.

MATERIAL AND METHODS

The preparation obtained from E. grandiflorus (ES-EG), C. carthagenensis (ES-CC), and P. tenellus (ES-PT) infusions was orally administered in a single dose to rats. Urine excretion rate, pH, density, conductivity and Na(+), K(+), Cl(-) and HCO3(-) contents were measured in the urine of saline-loaded animals. Concentration of electrolytes, total protein, urea, creatinine, and angiotensin converting enzyme (ACE) activity were evaluated in collected serum. The involvement of the renal cortical blood flow and antioxidative activity in the hypotensive and diuretic effects was also determined.

RESULTS

Water and Na(+), Cl(-) and Na(+) excretion rates were significantly increased by ES-EG, while urinary bicarbonate excretion was reduced. Moreover, ES obtained from E. grandiflorus was able to significantly increase renal blood flow and reduce mean arterial pressure and oxidative stress in "in vitro" and "in vivo" models. All other parameters evaluated were not affected by any treatment.

CONCLUSION

The results presented here shown that the ES-EG obtained from E. grandiflorus leaves shown a significant diuretic and hypotensive activity and suggest that these effects could be related with an important renal and systemic vasodilator effect. In addition, it was shown for the first time that the pharmacological effects of ES obtained from P. tenellus and C. carthagenensis do not support its popular use as a diuretic agent.

Cardiovascular protective effects of Casearia sylvestris Swartz in Swiss and C57BL/6 LDLr-null mice undergoing high fat diet

ETHNOPHARMACOLOGICAL RELEVANCE

Although Casearia sylvestris Swartz is used in Brazilian folk medicine to treat obesity, no study has been conducted to evaluate the effects of this species in an experimental model of dyslipidemia and atherosclerosis. So, the aim of this study was to evaluate possible hypolipemiant and antiatherogenic activity of the methanolic extract obtained from Casearia sylvestris (MECS) using Swiss and C57BL/6 LDLr-null mice undergoing high fat diet (HFD).

MATERIAL AND METHODS

Dyslipidemia and atherogenesis were induced by the administration of commercial HFD for 4 weeks. The MECS was administered orally at doses of 250 and 500mg/kg, once a day, for two weeks, starting from the 2nd week of HFD. The gain in body weight and systolic blood pressure (SBP) were measured weekly over the four week study. At the end of the experiments the levels of triglyceride (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and very low-density lipoprotein cholesterol (VLDL-C) were measured by colorimetric method. Aldosterone, vasopressin and angiotensin converting enzyme (ACE) activity were also evaluated in collected serum. The renal function, atherogenic index serum (AIS) and in vitro antiplatelet activity were investigated. Additionally, histopathological analyzes were performed to determine the intima-media thickness (IMT) and intima media ratio (IMR) in aorta samples.

RESULTS

The HFD induced dyslipidemia and major structural changes in the aortic wall, including raising of the systolic blood pressure in LDLr-null mice. In addition, we observed an increase in lipid peroxidation accompanied by a reduction of serum nitrite. The treatment with MECS was able to prevent the increase of SBP, TC, LDL-C, VLDL-C and triglycerides levels and increase HDL-C in Swiss and LDLr-null mice. These effects were accompanied by a significant reduction in oxidative stress. Moreover, AIS, IMT and IMR were significantly reduced in MECS-treated mice, and the extract was able to reduce platelet aggregation in vitro.

CONCLUSION

This study demonstrated that MECS reduces the serum lipids and oxidative stress when orally administered to Swiss and LDLr-null mice. In addition, it was able to prevent arterial thickening induced by HFD and to inhibit platelet aggregation in vitro.