Anti-inflammatory and/or immunomodulatory activities of Uncaria tomentosa (cat's claw) extracts: A systematic review and meta-analysis of in vivo studies.

Background: Uncaria tomentosa (Willd. ex Schult.) DC. (Rubiaceae) is traditionally used by Amazonian indigenous groups to treat inflammatory diseases. To date, there are no systematic reviews and meta-analyses on the use of U. tomentosa for inflammation control in animals supporting the traditional knowledge about this species. This study was conducted to evaluate the effect of U. tomentosa extracts in modulating inflammatory mediators and to determine which types of inflammatory diseases can be treated by this species. Methods: We conducted a systematic review and meta-analysis of preclinical studies published before 26 July 2023, identified in PubMed, Embase, and Scopus. Four independent reviewers extracted the data and assessed the risks of bias. The effects of U. tomentosa on inflammatory diseases and the inflammatory mediators involved were extracted from the studies. Standardized mean differences (SMD) and 95% confidence intervals (95%CI) of the outcomes were estimated. The meta-analyses were conducted using RevMan 5.4 (Cochrane Collaboration). This protocol was registered in PROSPERO (CRD42023450869). Results: Twenty-four of 523 studies were included. U. tomentosa extracts decreased the cytokines interleukin (IL)-6 (SMD: -0.72, 95%CI: -1.15, -0.29, p = 0.001) and transcription factor nuclear factor kappa-B (NF-κB) (SMD: -1.19, 95%CI: -1.89, -0.48, p = 0.001). However, the extracts did not significantly alter IL-1 (SMD: -0.16, 95%CI: -0.87, +0.56, p = 0.67), IL-10 (SMD: -0.05, 95%CI:-0.35, 0.45, p = 0.80), or tumor necrosis factor-alpha (TNF-α) levels (SMD: 0.18, 95%CI: -0.25, 0.62, p = 0.41). Conclusion: Many extracts of stem bark, roots, and leaves of U. tomentosa, mostly aqueous and hydroethanolic, exhibited anti-inflammatory and/or immunomodulatory activities and low toxicity. The extracts decreased NF-κB and IL-6. These findings suggest that this species has the potential to treat inflammatory diseases in which these markers are increased, according to the ethnopharmacological use. These activities are not related to a specific class of compounds.Systematic Review Registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=450869, Identifier CRD42023450869.

Isoflurane increases the activity of the vascular matrix metalloproteinase-2 in non-pregnant rats and increases the nitric oxide metabolites in pregnancy.

Surgeries that require general anesthesia occur in 1.5-2% of gestations. Isoflurane is frequently used because of its lower possibility of affecting fetal growth. Therefore, we examined the isoflurane anesthesia-induced effects on maternal hemodynamic and vascular changes. We hypothesized that isoflurane would enhance endothelium-dependent vasodilation as a consequence of increased nitric oxide and decreased metalloproteinases (MMPs). Female rats (n=28) were randomized into 4 groups (7 rats/group): conscious (non-anesthetized) non-pregnant group, non-pregnant anesthetized group, conscious pregnant group, and pregnant anesthetized group. Anesthesia was performed on the 20th pregnancy day, and hemodynamic parameters were monitored. Nitric oxide metabolites, gelatinolytic activity of MMP-2 and MMP-9, and the vascular function were assessed. Isoflurane caused no significant hemodynamic changes in pregnant compared with non-pregnant anesthetized group. Impaired acetylcholine-induced relaxations were observed only in conscious non-pregnant group (by approximately 62%) versus 81% for other groups. Phenylephrine-induced contractions were greater in endothelium-removed aorta segments of both pregnant groups (with or without isoflurane) compared with non-pregnant groups. Higher nitric oxide metabolites were observed in anesthetized pregnant in comparison with the other groups. Reductions in the 75 kDa activity and concomitant increases in 64 kDa MMP-2 isoforms were observed in aortas of pregnant anesthetized (or not) groups compared with conscious non-pregnant group. Isoflurane anesthesia shows stable effects on hemodynamic parameters and normal MMP-2 activation in pregnancy. Furthermore, there were increases in nitric oxide bioavailability, suggesting that isoflurane provides protective actions to the endothelium in pregnancy.

Sodium Nitrite Attenuates Reduced Activity of Vascular Matrix Metalloproteinase-2 and Vascular Hyper-Reactivity and Increased Systolic Blood Pressure Induced by the Placental Ischemia Model of Preeclampsia in Anesthetized Rats.

Preeclampsia is a maternal hypertension disorder associated with vascular dysfunction and fetal and placental growth restrictions. Placental ischemia is suggested as the primary trigger of preeclampsia-associated impairments of both endothelium-derived nitric oxide (NO) and the vascular activity of extracellular matrix metalloproteinase-2 (MMP-2). Reduced uteroplacental perfusion pressure (RUPP) is a placental ischemia model of preeclampsia. Reduction of sodium nitrite to NO may occur during ischemic conditions. However, sodium nitrite effects in the RUPP model of preeclampsia have not yet been investigated. Pregnant rats were divided into four groups: normotensive pregnant rats (Norm-Preg), pregnant rats treated with sodium nitrite (Preg + Nitrite), preeclamptic rats (RUPP), and preeclamptic rats treated with sodium nitrite (RUPP + Nitrite). Maternal blood pressure and fetal and placental parameters were recorded. Vascular function, circulating NO metabolites, and the gelatinolytic activity of vascular MMP-2 were also examined. Sodium nitrite attenuates increased blood pressure, prevents fetal and placental weight loss, counteracts vascular hyper-reactivity, and partially restores NO metabolites and MMP-2 activity. In conclusion, sodium nitrite reduction to NO may occur during RUPP-induced placental ischemia, thereby attenuating increased blood pressure, fetal and placental growth restriction, and vascular hyper-reactivity associated with preeclampsia and possibly restoring NO and MMP-2 activity, which underlie the blood pressure-lowering effects.

Pregnancy hypertension-associated endothelial dysfunction is attenuated by isoflurane anesthesia: Evidence of protective effect related to increases in nitric oxide.

AIMS: Pregnancy hypertension-induced endothelial dysfunction associated with impairment of nitric oxide (NO) bioavailability and hemodynamic derangements is a challenging for urgent procedures requiring maternal anesthesia. The volatile anesthetic isoflurane has demonstrated NO-associated protective effects. However, this isoflurane-induced effect is still unclear in pregnancy hypertension. Therefore, the present study examined the potential protective effects of isoflurane anesthesia on endothelial dysfunction and hemodynamic changes induced by hypertensive pregnancy associated with fetal and placental growth restrictions. MATERIALS AND METHODS: Animals were distributed into four groups: normotensive pregnant rats (Preg), anesthetized pregnant rats (Preg+Iso), hypertensive pregnant rats (HTN-Preg), and anesthetized hypertensive pregnant rats (HTN-Preg+Iso). Systolic and diastolic pressures, mean arterial pressure (MAP), heart rate, fetal and placental weights, vascular contraction, endothelium-derived NO-dependent vasodilation, and NO levels were assessed. The vascular endothelial growth factor (VEGF) levels and endothelial NO synthase (eNOS) Serine (1177) phosphorylation (p-eNOS) expression were also examined. KEY FINDINGS: Isoflurane produced more expressive hypotensive effects in the HTN-Preg+Iso versus Preg+Iso group, with respective reductions in MAP by 50 ± 13 versus 25 ± 4 mmHg (P < 0.05). Also, HTN-Preg+Iso compared to the HTN-Preg group showed (respectively) preventions against the weight loss of the fetuses (4.0 ± 0.6 versus 2.8 ± 0.6 g, P < 0.05) and placentas (0.37 ± 0.06 versus 0.30 ± 0.06 mg, P < 0.05), hyper-reactive vasocontraction response (1.8 ± 0.4 versus 2.8 ± 0.6 g, P < 0.05), impaired endothelium-derived NO-dependent vasodilation (84 ± 8 versus 50 ± 17 %, P < 0.05), reduced VEGF levels (147 ± 46 versus 25 ± 13 pg/mL, P < 0.05), and decreased p-eNOS expression (0.24 ± 0.07 versus 0.09 ± 0.05 arbitrary units, P < 0.05). SIGNIFICANCE: Isoflurane anesthesia protects maternal endothelial function in pregnancy hypertension, and possibly endothelium-derived NO is involved.

MMP-2 and its implications on cardiac function and structure: Interplay with inflammation in hypertension.

Hypertension is one of the leading risk factors for the development of heart failure. Despite being a multifactorial disease, in recent years, preclinical and clinical studies suggest strong evidence of the pivotal role of inflammatory cells and cytokines in the remodeling process and cardiac dysfunction. During the heart remodeling, activation of extracellular matrix metalloproteinases (MMPs) occurs, with MMP-2 being one of the main proteases secreted by cardiomyocytes, fibroblasts, endothelial and inflammatory cells in cardiac tissue. In this review, we will address the process of cardiac remodeling and injury induced by the increase in MMP-2 and the main signaling pathways involving cytokines and inflammatory cells in the process of transcriptional, secretion and activation of MMP-2. In addition, an interaction and coordinated action between MMP-2 and inflammation are explored and significant in maintaining the cardiac cycle. These observations suggest that new therapeutic opportunities targeting MMP-2 could be used to reduce inflammatory biomarkers and reduce cardiac damage in hypertension.

Pravastatin Prevents Increases in Activity of Metalloproteinase-2 and Oxidative Stress, and Enhances Endothelium-Derived Nitric Oxide-Dependent Vasodilation in Gestational Hypertension.

Pre-eclampsia (PE) is a hypertensive disorder of pregnancy and has been associated with placental growth restriction. The pre-eclamptic placenta releases free radicals to maternal circulation, thus increasing oxidative stress. An impaired redox state leads to reduction in circulating nitric oxide (NO) levels and activation of extracellular matrix metalloproteinases (MMPs). However, activation of MMPs induced by oxidative stress is still unclear in PE. Antioxidant effects have been demonstrated with the use of pravastatin. Therefore, we hypothesized that pravastatin protects against oxidative stress-induced activation of MMPs in a rat model of PE. The animals were divided into four groups: normotensive pregnant rats (Norm-Preg); pregnant rats treated with pravastatin (Norm-Preg + Prava); hypertensive pregnant rats (HTN-Preg); and hypertensive pregnant rats treated with pravastatin (HTN-Preg + Prava). The deoxycorticosterone acetate (DOCA) and sodium chloride (DOCA-salt) model was used to induce hypertension in pregnancy. Blood pressure, and fetal and placental parameters were recorded. The gelatinolytic activity of MMPs, NO metabolites and lipid peroxide levels were also determined. Endothelium function was also examined. Pravastatin attenuated maternal hypertension, prevented placental weight loss, increased NO metabolites, inhibited increases in lipid peroxide levels, and reduced the activity of MMP-2, and these effects were observed along with enhanced endothelium-derived NO-dependent vasodilation. The present results provide evidence that pravastatin protects against activation of MMP-2 induced by oxidative stress in pre-eclamptic rats. These findings may also involve improvement in endothelial function related to NO and antihypertensive effects of pravastatin, thus suggesting pravastatin as a therapeutic intervention for PE.

Sevoflurane and isoflurane anesthesia induce redox imbalance, but only sevoflurane impairs vascular contraction.

Volatile anesthetics may cause vascular dysfunction; however, underlying effects are unclear. The aim of the present study was to investigate whether sevoflurane and isoflurane affect vascular function, nitric oxide (NO) bioavailability, and biomarkers of oxidative stress and inflammation. Wistar rats were divided into three experimental groups: Not anesthetized (control group) or submitted to anesthesia with isoflurane (Iso group) or sevoflurane (Sevo group). Hemodynamic parameters were monitored during anesthesia, and blood gas values and biochemical determinants were analyzed. Isometric contractions were recorded in aortic rings. Vasoconstriction induced by potassium chloride (KCl) and phenylephrine (Phe) were measured. No differences in hemodynamic parameters and blood gasses variables were observed. Impaired KCl and Phe-induced contractions were observed in endothelium-intact aorta of Sevo compared to Iso and Control groups. Redox imbalance was found in Sevo and Iso groups. Reduced NO bioavailability and increased activity of matrix metalloproteinase 2 (MMP-2) were observed in Sevo, but not in the Iso group. While reduced IL-10 and IL-1ß were observed in Sevo, increases in IL-1ß in the Iso group were found. Sevoflurane, but not isoflurane, anesthesia impairs vasocontraction, and reduced NO and cytokines and increased MMP-2 activity may be involved in vascular dysfunction after sevoflurane anesthesia.

Resveratrol Supplants Captopril's Protective Effect on Cardiac Remodeling in a Hypertension Model Elicited by Renal Artery Stenosis.

Background: Renovascular hypertension elicits cardiac damage and remodeling. Two-kidney, one-clip (2K1C) is an experimental model used to study hypertension pathophysiology. In this model, the renin-angiotensin-system (RAS) is overactive due to renal artery stenosis, leading to cardiac remodeling. Redox mechanisms underlying RAS activation mediate hypertension-induced cardiovascular damage. Preclinical studies and clinical trials demonstrated resveratrol's protective effects in cardiovascular diseases, mainly attributed to its antioxidant properties. We hypothesized resveratrol alone or in combination with an angiotensin-converting enzyme (ACE) inhibitor would be beneficial against cardiac damage caused by renovascular hypertension. Objective: We investigated the benefits of resveratrol against cardiac remodeling in 2K1C rats compared with captopril. Methods: Male Wistar rats underwent unilateral renal stenosis - 2K1C Goldblatt model of hypertension. Systolic Blood Pressure (SBP) was measured before and 6 weeks after surgery. Hypertensive 2K1C rats presented SBP≥160 mmHg. From the 6th week after the surgery, the animals received oral resveratrol (20 mg/kg), captopril (12 mg/kg), or their combination for 3 times per week for 3 weeks. Whole heart hypertrophy was evaluated. Histological assays assessed left ventricle hypertrophy and fibrosis. Results: Renovascular hypertension caused cardiac hypertrophy, accompanied by increased myocyte diameter and collagen deposition. Resveratrol reduced 2K1C rats' SBP and whole heart hypertrophy, independently of captopril. Resveratrol caused a higher reduction in ventricular hypertrophy than captopril. Collagen deposition was greater reduced by 2K1C treated only with resveratrol than with captopril alone or combined with resveratrol. Conclusion: Independent of captopril, resveratrol prompts cardioprotective effects on cardiomyocyte remodeling and fibrosis resulting from renovascular hypertension in 2K1C rats.

Cellular and Molecular Response of Macrophages THP-1 during Co-Culture with Inactive Trichophyton rubrum Conidia.

Trichophyton rubrum is causing an increasing number of invasive infections, especially in immunocompromised and diabetic patients. The fungal invasive infectious process is complex and has not yet been fully elucidated. Therefore, this study aimed to understand the cellular and molecular mechanisms during the interaction of macrophages and T. rubrum. For this purpose, we used a co-culture of previously germinated and heat-inactivated T. rubrum conidia placed in contact with human macrophages cell line THP-1 for 24 h. This interaction led to a higher level of release of interleukins IL-6, IL-2, nuclear factor kappa beta (NF-κB) and an increase in reactive oxygen species (ROS) production, demonstrating the cellular defense by macrophages against dead fungal elements. Cell viability assays showed that 70% of macrophages remained viable during co-culture. Human microRNA expression is involved in fungal infection and may modulate the immune response. Thus, the macrophage expression profile of microRNAs during co-culture revealed the modulation of 83 microRNAs, with repression of 33 microRNAs and induction of 50 microRNAs. These data were analyzed using bioinformatics analysis programs and the modulation of the expression of some microRNAs was validated by qRT-PCR. In silico analysis showed that the target genes of these microRNAs are related to the inflammatory response, oxidative stress, apoptosis, drug resistance, and cell proliferation.

Reductions of Circulating Nitric Oxide are Followed by Hypertension during Pregnancy and Increased Activity of Matrix Metalloproteinases-2 and -9 in Rats.

Hypertensive pregnancy has been associated with reduced nitric oxide (NO), bioavailability, and increased activity of matrix metalloproteinases (MMPs). However, it is unclear if MMPs activation is regulated by NO during pregnancy. To this end, we examined activity of MMP-2 and MMP-9 in plasma, placenta, uterus and aorta, NO bioavailability, oxidative stress, systolic blood pressure (SBP), and fetal-placental development at the early, middle, and late pregnancy stages in normotensive and Nω-Nitro-L-arginine methyl-ester (L-NAME)-induced hypertensive pregnancy in rats. Reduced MMP-2 activity in uterus, placenta, and aorta and reduced MMP-9 activity in plasma and placenta with concomitant increased NO levels were found in normotensive pregnant rats. By contrast, increased MMP-2 activity in uterus, placenta, and aorta, and increased MMP-9 activity in plasma and placenta with concomitant reduced NO levels were observed in hypertensive pregnant rats. Also, elevated oxidative stress was displayed by hypertensive pregnant rats at the middle and late stages. These findings in the L-NAME-treated pregnant rats were also followed by increases in SBP and associated with fetal growth restrictions at the middle and late pregnancy stages. We concluded that NO bioavailability may regulate MMPs activation during normal and hypertensive pregnancy.

Antioxidant and antihypertensive responses to oral nitrite involves activation of the Nrf2 pathway.

Impaired redox balance contributes to the cardiovascular alterations of hypertension and activation of nuclear factor erythroid 2-related factor 2 (Nrf2) pathway may counteract these alterations. While nitrite recycles back to NO and exerts antioxidant and antihypertensive effects, the mechanisms involved in these responses are not fully understood. We hypothesized that nitrite treatment of two-kidney, one-clip (2K1C) hypertensive rats activates the Nrf2 pathway, promotes the transcription of antioxidant genes, and improves the vascular redox imbalance and dysfunction in this model. Two doses of oral nitrite were studied: 15 mg/kg and the sub-antihypertensive dose of 1 mg/kg. Nitrite 15 mg/kg (but not 1 mg/kg) decreased blood pressure and increased circulating plasma nitrite and nitrate. Both doses blunted hypertension-induced increases in mesenteric artery reactive oxygen species concentrations assessed by DHE technique and restored the impaired mesenteric artery responses to acetylcholine. While 2K1C hypertension decreased nuclear Nrf2 accumulation, both doses of nitrite increased nuclear Nrf2 accumulation and mRNA expression of Nrf2-regulated genes including superoxide dismutase-1 (SOD1), catalase (CAT), glutathione peroxidase (GPX), thioredoxin-1(TRDX-1) and -2 (TRDX-2). To further confirm nitrite-mediated antioxidant effects, we measured vascular SOD and GPX activity and we found that nitrite at 1 or 15 mg/kg increased the activity of both enzymes (P < 0.05). These results suggest that activation of the Nrf2 pathway promotes antioxidant effects of nitrite, which may improve the vascular dysfunction in hypertension, even when nitrite is given at a sub-antihypertensive dose. These findings may have many clinical implications, particularly in the therapy of hypertension and other cardiovascular diseases.

Nitrite treatment downregulates vascular MMP-2 activity and inhibits vascular remodeling in hypertension independently of its antihypertensive effects.

Hypertension is associated with cardiovascular remodeling. Given that impaired redox state activates matrix metalloproteinase (MMP)- 2 and promotes vascular remodeling, we hypothesized that nitrite treatment at a non-antihypertensive dose exerts antioxidant effects and attenuates both MMP-2 activation and vascular remodeling of hypertension. We examined the effects of oral sodium nitrite at antihypertensive (15 mg/kg) or non-antihypertensive (1 mg/kg) daily dose in hypertensive rats (two kidney, one clip; 2K1C model). Sham-operated and 2K1C hypertensive rats received vehicle or nitrite by gavage for four weeks. Systolic blood pressure decreased only in hypertensive rats treated with nitrite 15 mg/Kg/day. Both low and high nitrite doses decreased 2K1C-induced vascular remodeling assessed by measuring aortic cross-sectional area, media/lumen ratio, and number of vascular smooth muscle cells/aortic length. Both low and high nitrite doses decreased 2K1C-induced vascular oxidative stress assessed in situ with the fluorescent dye DHE and with the lucigenin chemiluminescence assay. Vascular MMP-2 expression and activity were assessed by gel zymography, Western blot, and in situ zymography increased with hypertension. While MMP-2 levels did not change in response to both doses of nitrite, both doses completely prevented hypertension-induced increases in vascular MMP activity. Moreover, incubation of aortas from hypertensive rats with nitrite at 1-20 µmol/L reduced gelatinolytic activity by 20-30%. This effect was fully inhibited by the xanthine oxidase (XOR) inhibitor febuxostat, suggesting XOR-mediated generation of nitric oxide (NO) from nitrite as a mechanism explaining the responses to nitrite. In vitro incubation of aortic extracts with nitrite 20 µmol/L did not affect MMP-2 activity. These results show that nitrite reverses the vascular structural alterations of hypertension, independently of anti-hypertensive effects. This response is mediated, at least in part, by XOR and is attributable to antioxidant effects of nitrite blunting vascular MMP-2 activation. Our findings suggest nitrite therapy to reverse structural alterations of hypertension.

Hypertension, augmented activity of matrix metalloproteinases-2 and -9 and angiogenic imbalance in hypertensive pregnancy are attenuated by doxycycline.

Preeclampsia is manifested as maternal hypertension and fetal growth restriction. Matrix metalloproteinases (MMPs) are involved in hypertension and doxycycline reduces blood pressure by inhibition of MMPs. Moreover, excessive levels of MMPs and reduced nitric oxide (NO) bioavailability have been related to preeclampsia. We investigated the involvement of MMPs in hypertension in pregnancy induced by Nω-Nitro-L-arginine methyl ester (L-NAME) in rats. To this end, zimography was performed to evaluate the activity of MMPs -2 and -9 in placenta, uterus and thoracic aorta, and systolic blood pressure, feto-placental development and metabolites of NO were evaluated. Also, plasma antioxidant capacity, plasma levels of soluble fms-like tyrosine kinase-1 (sFlt-1) and placental growth factor (PLGF) were examined. Doxycycline prevented hypertensive pregnancy and significant reductions in number of pups induced by L-NAME. Low NO bioavailability was found in hypertensive pregnant rats treated (or not) with doxycycline. Increased activity of placental MMP-2 and MMP-9 and uterine MMP-2 were attenuated by doxycycline. MMP-2 activity of thoracic aorta showed no change after hypertension. Increases in PLGF with concomitant decreases in sFlt-1 levels were found with doxycycline treatment. Also, plasma antioxidant capacity was improved with doxycycline. Also, elevations of plasma antioxidant capacity were observed in hypertensive rats treated with doxycycline. Therefore, we suggest that L-NAME reduced NO and this triggered the increases in MMP-2 and -9 activities during hypertensive pregnancy. Importantly, increases in MMPs activation and angiogenic imbalance were attenuated by doxycycline and these effects were associated with decreases in systolic blood pressure.

Matrix metalloproteinase-2-induced epidermal growth factor receptor transactivation impairs redox balance in vascular smooth muscle cells and facilitates vascular contraction.

Increased reactive oxygen species (ROS) formation may enhance matrix metalloproteinase (MMP)-2 activity and promote cardiovascular dysfunction. We show for the first time that MMP-2 is upstream of increased ROS formation and activates signaling mechanisms impairing redox balance. Incubation of vascular smooth muscle cells (VSMC) with recombinant MMP-2 increased ROS formation assessed with dihydroethidium (DHE) by flow cytometry. This effect was blocked by the antioxidant apocynin or by polyethylene glycol-catalase (PEG-catalase), and by MMP inhibitors (doxycycline or GM6001). Next, we showed in HEK293 cells that MMP-2 transactivates heparin-binding epidermal growth factor (HB-EGF) leading to EGF receptor (EGFR) activation and increased ROS concentrations. This effect was prevented by the EGFR kinase inhibitor Ag1478, and by phospholipase C (PLC) or protein kinase C (PKC) inhibitors (A778 or chelerythrine, respectively), confirming the involvement of EGFR pathway in MMP-2-induce responses. Next, we showed that intraluminal exposure of aortas to MMP-2 increased vascular MMP-2 levels detected by immunofluorescence and gelatinolytic activity (by in situ zimography) in association with increased ROS formation. This effect was inhibited by MMP inhibitors (phenanthroline or doxycycline) and by apocynin or PEG-catalase. MMP-2 also increased aortic contractility to phenylephrine and this effect was prevented by MMP inhibitor GM6001 and by apocynin or PEG-catalase, showing again that increased ROS formation mediates functional effects of MMP-2. These results show that MMP-2 activates the EGFR and triggers downstream signaling pathways increasing ROS formation and promoting vasoconstriction. These findings may have various implications for cardiovascular diseases.

Nitrite exerts antioxidant effects, inhibits the mTOR pathway and reverses hypertension-induced cardiac hypertrophy.

Cardiac hypertrophy is a common consequence of chronic hypertension and leads to heart failure and premature death. The anion nitrite is now considered as a bioactive molecule able to exert beneficial cardiovascular effects. Previous results showed that nitrite attenuates hypertension-induced increases in reactive oxygen species (ROS) production in the vasculature. Whether antioxidant effects induced by nitrite block critical signaling pathways involved in cardiac hypertrophy induced by hypertension has not been determined yet. The Akt/mTOR signaling pathway is responsible to activate protein synthesis during cardiac remodeling and is activated by increased ROS production, which is commonly found in hypertension. Here, we investigated the effects of nitrite treatment on cardiac remodeling and activation of this hypertrophic signaling pathway in 2 kidney-1 clip (2K1C) hypertension. Sham and 2K1C rats were treated with oral nitrite at 1 or 15 mg/kg for four weeks. Nitrite treatment (15 mg/kg) reduced systolic blood pressure and decreased ROS production in the heart tissue from hypertensive rats. This nitrite dose also blunted hypertension-induced activation of mTOR pathway and cardiac hypertrophy. While the lower nitrite dose (1 mg/kg) did not affect blood pressure, it exerted antioxidant effects and tended to attenuate mTOR pathway activation and cardiac hypertrophy induced by hypertension. Our findings provide strong evidence that nitrite treatment decreases cardiac remodeling induced by hypertension as a result of its antioxidant effects and downregulation of mTOR signaling pathway. This study may help to establish nitrite as an effective therapy in hypertension-induced cardiac hypertrophic remodeling.

Direct renin inhibition is not enough to prevent reactive oxygen species generation and vascular dysfunction in renovascular hypertension.

Renin-angiotensin system activation promotes oxidative stress and endothelial dysfunction. However, no previous study has examined the effects of the renin inhibitor aliskiren, either alone or combined with angiotensin II type 1 antagonists on alterations induced by two-kidney, one-clip (2K1C) hypertension. We compared the vascular effects of aliskiren (50mg/kg/day), losartan (10mg/kg/day), or both by gavage for 4 weeks in 2K1C and control rats. Treatment with losartan, aliskiren, or both exerted similar antihypertensive effects. Aliskiren lowered plasma Ang I concentrations in sham rats and in hypertensive rats treated with aliskiren or with both drugs. Aliskiren alone or combined with losartan decreased plasma angiotensin II concentrations measured by high performance liquid chromatography, whereas losartan alone had no effects. In contrast, losartan alone or combined with aliskiren abolished hypertension-induced increases in aortic angiotensin II concentrations, whereas aliskiren alone exerted no such effects. While hypertension enhanced aortic oxidative stress assessed by dihydroethidium fluorescence and by lucigenin chemiluminescence, losartan alone or combined with aliskiren, but not aliskiren alone, abolished this alteration. Hypertension impaired aortic relaxation induced by acetylcholine, and losartan alone or combined with aliskiren, but not aliskiren alone, reversed this alteration. Losartan alone or combined with aliskiren, but not aliskiren alone, increased plasma nitrite concentrations in 2K1C rats. These findings show that antihypertensive effects of aliskiren do not prevent hypertension-induced vascular oxidative stress and endothelial dysfunction. These findings contrast those found with losartan and suggest that renin inhibition is not enough to prevent hypertension-induced impaired redox biology and vascular dysfunction.

Atorvastatin and sildenafil decrease vascular TGF-ß levels and MMP-2 activity and ameliorate arterial remodeling in a model of renovascular hypertension.

Imbalanced matrix metalloproteinase (MMP)-2 activity and transforming growth factor expression (TGF-ß) are involved in vascular remodeling of hypertension. Atorvastatin and sildenafil exert antioxidant and pleiotropic effects that may result in cardiovascular protection. We hypothesized that atorvastatin and sildenafil alone or in association exert antiproliferative effects by down-regulating MMP-2 and TGF-ß, thus reducing the vascular hypertrophy induced by two kidney, one clip (2K1C) hypertension. Sham and 2K1C rats were treated with oral atorvastatin 50 mg/kg, sildenafil 45 mg/kg, or both, daily for 8 weeks. Blood pressure was monitored weekly. Morphologic changes in the aortas were studied. TGF-ß levels were determined by immunofluorescence. MMP-2 activity and expression were determined by in situ zymography, gel zymography, Western blotting, and immunofluorescence. The effects of both drugs on proliferative responses of aortic smooth muscle cells to PDGF and on on MMP-2 activity in vitro were determined. Atorvastatin, sildenafil, or both drugs exerted antiproliferative effects in vitro. All treatments attenuated 2K1C-induced hypertension and prevented the increases in the aortic cross-sectional area and media/lumen ratio in 2K1C rats. Aortas from 2K1C rats showed higher collagen deposition, TGF-ß levels and MMP-2 activity and expression when compared with Sham-operated animals. Treatment with atorvastatin and/or sildenafil was associated with attenuation of 2K1C hypertension-induced increases in these pro-fibrotic factors. However, these drugs had no in vitro effects on hr-MMP-2 activity. Atorvastatin and sildenafil was associated with decreased vascular TGF-ß levels and MMP-2 activity in renovascular hypertensive rats, thus ameliorating the vascular remodeling. These novel pleiotropic effects of both drugs may translate into protective effects in patients.

The Nuclear Factor kappaB Inhibitor Pyrrolidine Dithiocarbamate Prevents Cardiac Remodelling and Matrix Metalloproteinase-2 Up-Regulation in Renovascular Hypertension.

Imbalanced matrix metalloproteinase (MMP) activity is involved in hypertensive cardiac hypertrophy. Pharmacological inhibition of nuclear factor kappaB (NF-кB) with pyrrolidine dithiocarbamate (PDTC) can prevent MMP up-regulation. We suggested that treatment with PDTC could prevent 2-kidney, 1-clip (2K1C) hypertension-induced left ventricular remodelling. Sham-operated controls or 2K1C rats with hypertension received either vehicle or PDTC (100 mg/kg/day) by gavage for 8 weeks. Systolic blood pressure was monitored every week. Histological assessment of left ventricles was carried out with haematoxylin/eosin sections, and fibrosis was quantified in picrosirius red-stained sections. Oxidative stress was evaluated in heart samples with the dihydroethidium probe. Cardiac MMP activity was determined by in situ zymography, and cardiac MMP-2 was assessed by immunofluorescence. 2K1C surgery significantly increased systolic blood pressure in the 2K1C vehicle. PDTC exerted antihypertensive effects after 2 weeks of treatment. Histology revealed increased left ventricular and septum wall thickness associated with augmented myocyte diameter in hypertensive rats, which were reversed by treatment with PDTC. Hypertensive rats developed pronounced cardiac fibrosis with increased interstitial collagen area, increased cardiac reactive oxygen species levels, gelatinase activity and MMP-2 expression. PDTC treatment decreased these alterations. These findings show that PDTC modulates myocardial MMP-2 expression and ameliorates cardiac remodelling in renovascular hypertension. These results suggest that interfering with MMP expression at transcriptional level may be an interesting strategy in the therapy of organ damage associated with hypertension.

Acute restraint stress induces endothelial dysfunction: role of vasoconstrictor prostanoids and oxidative stress.

We hypothesized that acute stress would induce endothelial dysfunction. Male Wistar rats were restrained for 2 h within wire mesh. Functional and biochemical analyses were conducted 24 h after the 2-h period of restraint. Stressed rats showed decreased exploration on the open arms of an elevated-plus maze (EPM) and increased plasma corticosterone concentration. Acute restraint stress did not alter systolic blood pressure, whereas it increased the in vitro contractile response to phenylephrine and serotonin in endothelium-intact rat aortas. NG-nitro-l-arginine methyl ester (l-NAME; nitric oxide synthase, NOS, inhibitor) did not alter the contraction induced by phenylephrine in aortic rings from stressed rats. Tiron, indomethacin and SQ29548 reversed the increase in the contractile response to phenylephrine induced by restraint stress. Increased systemic and vascular oxidative stress was evident in stressed rats. Restraint stress decreased plasma and vascular nitrate/nitrite (NOx) concentration and increased aortic expression of inducible (i) NOS, but not endothelial (e) NOS. Reduced expression of cyclooxygenase (COX)-1, but not COX-2, was observed in aortas from stressed rats. Restraint stress increased thromboxane (TX)B(2) (stable TXA(2) metabolite) concentration but did not affect prostaglandin (PG)F2α concentration in the aorta. Restraint reduced superoxide dismutase (SOD) activity, whereas concentrations of hydrogen peroxide (H(2)O(2)) and reduced glutathione (GSH) were not affected. The major new finding of our study is that restraint stress increases vascular contraction by an endothelium-dependent mechanism that involves increased oxidative stress and the generation of COX-derived vasoconstrictor prostanoids. Such stress-induced endothelial dysfunction could predispose to the development of cardiovascular diseases.

Interference of doxycycline pretreatment in a model of abdominal aortic aneurysms.

BACKGROUND: Abdominal aortic aneurysm (AAA) is characterized by chronic inflammation and degradation of the extracellular matrix, mediated by matrix metalloproteinases (MMPs). Doxycycline has been reported to control the progression of AAA by regulation of MMP. We hypothesized that doxycycline pretreatment in a rat model of AAA would cause reduction in gelatinolytic activity of MMP-2 and -9 and the inflammatory response in the wall of an aneurysm, consequently decreasing the formation and development of AAAs. METHODS: Male Wistar rats were divided into the following four groups: aneurysm (A); control (C); aneurysm+doxycycline (A+D) and control+doxycycline (C+D), with 24 animals per group subdivided into n=6 animals at different time points [1, 3, 7, and 15 days postsurgery (dps)]. The (A) and (A+D) groups simultaneously received the injury and extrinsic stenosis of the aortic wall. The (C) and (C+D) groups received sham operation. The treated animals received doxycycline via gavage (30 mg/kg/day) from 48 h before surgery until the end of experiment. At 1, 3, 7, and 15 dps, the animals were euthanized, and the aortas were collected for morphological analyses, immunohistochemistry, and zymography. RESULTS: The animals from the (A) group developed AAAs. However, the animals treated with doxycycline showed a 85% decrease in AAA development, which was associated with a large reduction in gelatinolytic activity of MMP-2 and -9, and decreased inflammatory response (P<.05). CONCLUSIONS: These results suggest that pretreatment with doxycycline before surgery inhibited the activity of MMP-2 and -9, as well as the inflammatory response, and may play an important role in the prevention of the development of AAAs.