Three Generation of β-Blockers for Atrial Fibrillation Treatment

The efficiency of blood flowing from the heart depends on its electrical properties. Myocardial electrical activity is associated with the generation of cardiac action potentials in isolated myocardial cells and their coordinated propagation, which are mediated by gap junctions. Atrial fibrillation (AF) is a common cardiac arrhythmia, which causes an aggressive disturbance in cardiac electromechanical function. Moreover, AF increases the risk of stroke and mortality and is a major cause of death. The mechanisms underlying AF involve electrophysiological changes in ion channel expression and function. β-blockers may be useful in patients with chronic AF or in preventing postoperative AF in subjects undergoing coronary artery bypass grafting (CABG) or other types of surgery. The reduction in heart rate induced by β1-adrenergic receptor antagonists may be associated with the beneficial effect of this drug class. Second generation beta blockers may be considered superior to the first generation due to their selectivity to the β1 receptor as well as avoiding pulmonary or metabolic adverse effects. Third generation beta blockers may be considered a great option for their vasodilation and antioxidant properties. There is also a new β-blocker, named landilol that also results on reduced risk of post operative AF without adverse effects and its use has been increasing on clinical trials.

Inducible nitric oxide synthase (iNOS) mediates ethanol-induced redox imbalance and upregulation of inflammatory cytokines in the kidney

Overexpression of the inducible isoform of the enzyme nitric oxide synthase (iNOS) has been associated to pathological processes in the kidney. Ethanol consumption induces the renal expression of iNOS; however, the contribution of this enzyme to the deleterious effects of ethanol in the kidney remains elusive. We examined whether iNOS plays a role in the renal dysfunction and oxidative stress induced by ethanol consumption. With this purpose, male C57BL/6 wild-type (WT) or iNOS-deficient (iNOS^-/-) mice were treated with ethanol (20% v/v) for 10 weeks. Treatment with ethanol increased the expression of Nox4 as well as the concentration of thiobarbituric acid reactive substances and the levels of tumor necrosis factor α in the renal cortex of WT but not iNOS^-/- mice. Augmented serum levels of creatinine and increased systolic blood pressure were found in WT and iNOS^-/- mice treated with ethanol. WT mice treated with ethanol showed increased production of reactive oxygen species and myeloperoxidase activity, but these responses were attenuated in iNOS^-/- mice. We concluded that iNOS played a role in ethanol-induced oxidative stress and pro-inflammatory cytokine production in the kidney. These are mechanisms that may contribute to the renal toxicity induced by ethanol.

Epigenetic Regulation of the N-Terminal Truncated Isoform of Matrix Metalloproteinase-2 (NTT-MMP-2) and Its Presence in Renal and Cardiac Diseases

Several clinical and experimental studies have documented a compelling and critical role for the full-length matrix metalloproteinase-2 (FL-MMP-2) in ischemic renal injury, progressive renal fibrosis, and diabetic nephropathy. A novel N-terminal truncated isoform of MMP-2 (NTT-MMP-2) was recently discovered, which is induced by hypoxia and oxidative stress by the activation of a latent promoter located in the first intron of the MMP2 gene. This NTT-MMP-2 isoform is enzymatically active but remains intracellular in or near the mitochondria. In this perspective article, we first present the findings about the discovery of the NTT-MMP-2 isoform, and its functional and structural differences as compared with the FL-MMP-2 isoform. Based on publicly available epigenomics data from the Encyclopedia of DNA Elements (ENCODE) project, we provide insights into the epigenetic regulation of the latent promoter located in the first intron of the MMP2 gene, which support the activation of the NTT-MMP-2 isoform. We then focus on its functional assessment by covering the alterations found in the kidney of transgenic mice expressing the NTT-MMP-2 isoform. Next, we highlight recent findings regarding the presence of the NTT-MMP-2 isoform in renal dysfunction, in kidney and cardiac diseases, including damage observed in aging, acute ischemia-reperfusion injury (IRI), chronic kidney disease, diabetic nephropathy, and human renal transplants with delayed graft function. Finally, we briefly discuss how our insights may guide further experimental and clinical studies that are needed to elucidate the underlying mechanisms and the role of the NTT-MMP-2 isoform in renal dysfunction, which may help to establish it as a potential therapeutic target in kidney diseases.

The role of IL-10 in immune responses against Pseudomonas aeruginosa during acute lung infection

Pseudomonas aeruginosa is considered an opportunistic pathogen of great clinical importance. The clearance of this bacterium occurs through recognition of the pathogen by innate immune system receptors, leading to a lung inflammatory response. However, this response must be controlled via immunoregulatory pathways. In this study, we evaluate the role of endogenous murine IL-10 after acute infection with the virulent strain P. aeruginosa PA14. To assess the role of IL-10, intratracheal infection with the PA14 strain was performed in C57BL/6 or IL-10 KO mice. The PA14 strain was recovered in both types of animals, although IL-10 KO mice presented a higher number of viable bacteria in the lung when compared to the C57BL/6 group. Histopathological and stereological analyses showed that IL-10 KO mice had higher tissue damage and inflammatory infiltrate when compared to control animals. The activity of MMP-9 but not MMP-2, as well as IL-6 and TNF-α expression, were augmented in the lungs of infected animals and was much more evident in IL-10 KO animals when compared to the other analyzed groups. This work indicates that endogenous IL-10 control P. aeruginosa infection, the expression of pro-inflammatory genes, MMP-9 activity and histopathological processes of the infectious process in question.

Three Generations of β-blockers: History, Class Differences and Clinical Applicability

BACKGROUND

Beta-adrenergic receptors are expressed in cardiomyocytes and activated by either noradrenaline released from sympathetic synapses or circulating catecholamines. Their corresponding receptors have three subtypes, namely, β1, β2 and β3, which are members of the G protein-coupled receptors (GPCRs) family. Activation of β1-adrenergic receptors causes various physiological reactions including cardiac contraction and renin secretion from juxtaglomerular cells of the kidney. Antagonists of β-adrenergic receptors, known as β-blockers, have been used effectively for over four decades and have beneficial effects in the treatment of cardiovascular diseases. There are three generations of β-blockers according to their pharmacological properties. Firstgeneration β-blockers are non-selective, blocking both β1- and β2-receptors; second-generation β- blockers are more cardioselective in that they are more selective for β1-receptors; and thirdgeneration β-blockers are highly selective drugs for β1-receptors. The latter also display vasodilator actions by blocking α1-adrenoreceptors and activating β3-adrenergic receptors. In addition, thirdgeneration β-blockers exhibit angiogenic, antioxidant, anti-proliferative, anti-hypertrophic and antiapoptotic activities among other effects that are still under investigation.

CONCLUSION

The objective of this review is to describe the evolution observed during the development of the three distinctive generations, thereby highlighting the advantages of third-generation β- blockers over the other two drug classes.

Quercetin decreases the activity of matrix metalloproteinase-2 and ameliorates vascular remodeling in renovascular hypertension

BACKGROUND AND AIMS

Increased activity of matrix metalloproteinase (MMP)-2 is observed in aortas of different models of hypertension, and its activation is directly mediated by oxidative stress. As quercetin is an important flavonoid with significant antioxidant effects, the hypothesis here is that quercetin will reduce increased MMP-2 activity by decreasing oxidative stress in aortas of hypertensive rats and then ameliorate hypertension-induced vascular remodeling.

METHODS

Male two-kidney one-clip (2K1C) hypertensive Wistar rats and controls were treated with quercetin (10 mg/kg/day) or its vehicle for three weeks by gavage. Rats were then analyzed at five weeks of hypertension. Systolic blood pressure (SBP) was determined by tail-cuff plethysmography. Aortas were used to determine MMP activity by in situ zymography and reactive oxygen species (ROS) levels by dihydroethidium. Western blot was performed to detect focal adhesion kinase (FAK) and phosphorylated-FAK levels.

RESULTS

SBP was increased in 2K1C rats and only a borderline reduction in SBP was observed after treating 2K1C rats with quercetin. Cross-sectional area and the number of vascular smooth muscle cells were significantly increased in aortas of hypertensive rats, and quercetin reduced them. Quercetin reduced ROS levels in aortas of 2K1C rats and the increased activity of gelatinases in situ. However, quercetin did not affect the levels of tissue inhibitor of MMP (TIMP)-2 and did not interfere with FAK and p-FAK levels in aortas of hypertensive rats. Furthermore, different concentrations of quercetin did not directly reduce the activity of human recombinant MMP-2 in vitro.

CONCLUSIONS

Quercetin reduces hypertension-induced vascular remodeling, oxidative stress and MMP-2 activity in aortas.

An intracellular matrix metalloproteinase-2 isoform induces tubular regulated necrosis: implications for acute kidney injury

Acute kidney injury (AKI) causes severe morbidity, mortality, and chronic kidney disease (CKD). Mortality is particularly marked in the elderly and with preexisting CKD. Oxidative stress is a common theme in models of AKI induced by ischemia-reperfusion (I-R) injury. We recently characterized an intracellular isoform of matrix metalloproteinase-2 (MMP-2) induced by oxidative stress-mediated activation of an alternate promoter in the first intron of the MMP-2 gene. This generates an NH₂-terminal truncated MMP-2 (NTT-MMP-2) isoform that is intracellular and associated with mitochondria. The NTT-MMP-2 isoform is expressed in kidneys of 14-mo-old mice and in a mouse model of coronary atherosclerosis and heart failure with CKD. We recently determined that NTT-MMP-2 is induced in human renal transplants with delayed graft function and correlated with tubular cell necrosis. To determine mechanism(s) of action, we generated proximal tubule cell-specific NTT-MMP-2 transgenic mice. Although morphologically normal at the light microscopic level at 4 mo, ultrastructural studies revealed foci of tubular epithelial cell necrosis, the mitochondrial permeability transition, and mitophagy. To determine whether NTT-MMP-2 expression enhances sensitivity to I-R injury, we performed unilateral I-R to induce mild tubular injury in wild-type mice. In contrast, expression of the NTT-MMP-2 isoform resulted in a dramatic increase in tubular cell necrosis, inflammation, and fibrosis. NTT-MMP-2 mice had enhanced expression of innate immunity genes and release of danger-associated molecular pattern molecules. We conclude that NTT-MMP-2 "primes" the kidney to enhanced susceptibility to I-R injury via induction of mitochondrial dysfunction. NTT-MMP-2 may be a novel AKI treatment target.

Data on the effects of losartan on protein expression, vascular reactivity and antioxidant capacity in the aorta of ethanol-treated rats

We describe the effects of losartan, a selective AT₁ receptor antagonist on the alterations induced by treatment with ethanol in the rat aorta. The data shown here are related to the article entitled “Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress” (P. Passaglia, C.S. Ceron, A.S. Mecawi, J. Antunes-Rodrigues, E.B. Coelho, C.R. Tirapelli, 2015) [1]. Here we include new data on the protective effect of losartan against ethanol-induced oxidative stress. Male Wistar rats treated for 2 weeks with ethanol (20%, vol./vol.) exhibited increased aortic production of reactive oxygen species (ROS) and losartan (10 mg/kg/day; p.o. gavage) prevented this response. Ethanol did not alter the expression of eNOS in the rat aorta. Losartan prevented ethanol-induced increase in the aortic expression of nNOS. Neither ethanol nor losartan affected superoxide dismutase (SOD) or catalase (CAT) activities in the rat aorta. Treatment with ethanol increased the contraction induced by phenylephrine in both endothelium-intact and endothelium-denuded aortas and these responses were prevented by losartan. Conversely, neither ethanol nor losartan affected the endothelium-dependent relaxation induced by acetylcholine.

Gastric S-nitrosothiol formation drives the antihypertensive effects of oral sodium nitrite and nitrate in a rat model of renovascular hypertension

Many effects of nitrite and nitrate are attributed to increased circulating concentrations of nitrite, ultimately converted into nitric oxide (NO(•)) in the circulation or in tissues by mechanisms associated with nitrite reductase activity. However, nitrite generates NO(•) , nitrous anhydride, and other nitrosating species at low pH, and these reactions promote S-nitrosothiol formation when nitrites are in the stomach. We hypothesized that the antihypertensive effects of orally administered nitrite or nitrate involve the formation of S-nitrosothiols, and that those effects depend on gastric pH. The chronic effects of oral nitrite or nitrate were studied in two-kidney, one-clip (2K1C) hypertensive rats treated with omeprazole (or vehicle). Oral nitrite lowered blood pressure and increased plasma S-nitrosothiol concentrations independently of circulating nitrite levels. Increasing gastric pH with omeprazole did not affect the increases in plasma nitrite and nitrate levels found after treatment with nitrite. However, treatment with omeprazole severely attenuated the increases in plasma S-nitrosothiol concentrations and completely blunted the antihypertensive effects of nitrite. Confirming these findings, very similar results were found with oral nitrate. To further confirm the role of gastric S-nitrosothiol formation, we studied the effects of oral nitrite in hypertensive rats treated with the glutathione synthase inhibitor buthionine sulfoximine (BSO) to induce partial thiol depletion. BSO treatment attenuated the increases in S-nitrosothiol concentrations and antihypertensive effects of oral nitrite. These data show that gastric S-nitrosothiol formation drives the antihypertensive effects of oral nitrite or nitrate and has major implications, particularly to patients taking proton pump inhibitors.

Atorvastatin and sildenafil decrease vascular TGF-β 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-β) 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-β, 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-β 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-β 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-β 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.

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Atorvastatin and sildenafil exert antioxidant and other pleotropic effects.

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Imbalanced MMP-2 activity and TGF-β expression promote vascular remodeling in hypertension.

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Atorvastatin and sildenafil exerted antiproliferative effects in vitro.

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Both drugs prevented hypertension-induced increases pro-fibrotic factors.

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These additional pleiotropic effects 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.

Angiotensin type 1 receptor mediates chronic ethanol consumption-induced hypertension and vascular oxidative stress

OBJECTIVES

We hypothesized that chronic ethanol intake enhances vascular oxidative stress and induces hypertension through renin-angiotensin system (RAS) activation.

METHODS AND RESULTS

Male Wistar rats were treated with ethanol (20% v/v). The increase in blood pressure induced by ethanol was prevented by losartan (10mg/kg/day; p.o. gavage), a selective AT1 receptor antagonist. Chronic ethanol intake increased plasma renin activity (PRA), angiotensin converting enzyme (ACE) activity, plasma angiotensin I (ANG I) and angiotensin II (ANG II) levels and serum aldosterone levels. No differences on plasma osmolality and sodium or potassium levels were detected after treatment with ethanol. Ethanol consumption did not alter ACE activity, as well as the levels of ANG I and ANG II in the rat aorta or mesenteric arterial bed (MAB). Ethanol induced systemic and vascular oxidative stress (aorta and MAB) and these effects were prevented by losartan. The decrease on plasma and vascular nitrate/nitrite (NOx) levels induced by ethanol was prevented by losartan. Ethanol intake did not alter protein expression of ACE, AT1 or AT2 receptors in both aorta and MAB. Aortas from ethanol-treated rats displayed decreased ERK1/2 phosphorylation and increased protein expression of SAPK/JNK. These responses were prevented by losartan. MAB from ethanol-treated rats displayed reduced phosphorylation of p38MAPK and ERK1/2 and losartan did not prevent these responses.

CONCLUSIONS

Our study provides novel evidence that chronic ethanol intake increases blood pressure, induces vascular oxidative stress and decreases nitric oxide (NO) bioavailability through AT1-dependent mechanisms.

β1-Adrenergic blockers exert antioxidant effects, reduce matrix metalloproteinase activity, and improve renovascular hypertension-induced cardiac hypertrophy

Hypertension induces left-ventricular hypertrophy (LVH) by mechanisms involving oxidative stress and unbalanced cardiac matrix metalloproteinase (MMP) activity. We hypothesized that β1-adrenergic receptor blockers with antioxidant properties (nebivolol) could reverse hypertension-induced LVH more effectively than conventional β1-blockers (metoprolol) when used at doses that exert similar antihypertensive effects. Two-kidney one-clip (2K1C) hypertension was induced in male Wistar rats. Six weeks after surgery, hypertensive and sham rats were treated with nebivolol (10 mg kg(-1)day(-1)) or metoprolol (20 mg kg(-1)day(-1)) for 4 weeks. Systolic blood pressure was monitored weekly by tail-cuff plethysmography. LV structural changes and fibrosis were studied in hematoxylin/eosin- and picrosirius-stained sections, respectively. Cardiac MMP levels and activity were determined by in situ zymography, gel zymography, and immunofluorescence. Dihydroethidium and lucigenin-derived chemiluminescence assays were used to assess cardiac reactive oxygen species (ROS) production. Nitrotyrosine levels were determined in LV samples by immunohistochemistry and green fluorescence and were evaluated using the ImageJ software. Cardiac protein kinase B/Akt (AKT) phosphorylation state was assessed by Western blot. Both β-blockers exerted similar antihypertensive effects and attenuated hypertension-induced cardiac remodeling. Both drugs reduced myocyte hypertrophy and collagen deposition in 2K1C rats. These effects were associated with lower cardiac ROS and nitrotyrosine levels and attenuation of hypertension-induced increases in cardiac MMP-2 levels and in situ gelatinolytic activity after treatment with both β-blockers. Whereas hypertension increased AKT phosphorylation, no effects were found with β-blockers. In conclusion, we found evidence that two β1-blockers with different properties attenuate hypertension-induced LV hypertrophy and cardiac collagen deposition in association with significant cardiac antioxidant effects and MMP-2 downregulation, thus suggesting a critical role for β1-adrenergic receptors in mediating those effects. Nebivolol is not superior to metoprolol, at least with respect to their capacity to reverse hypertension-induced LVH.

Nebivolol attenuates prooxidant and profibrotic mechanisms involving TGF-β and MMPs, and decreases vascular remodeling in renovascular hypertension

Nebivolol and metoprolol are β1-adrenergic receptor blockers with different properties. We hypothesized that nebivolol, but not metoprolol, could attenuate prooxidant and profibrotic mechanisms of hypertension and therefore protect against the vascular remodeling associated with hypertension. Hypertension was induced in male Wistar rats by clipping the left renal artery. Six weeks after surgery, hypertensive and sham rats were treated with nebivolol (10 mg kg(-1) day(-1)) or metoprolol (20 mg kg(-1) day(-1)) for 4 weeks. Systolic blood pressure was monitored weekly. Morphologic changes in the aortic wall were studied in hematoxylin/eosin and picrosirius red sections. Aortic NAD(P)H activity and superoxide production were evaluated by luminescence and dihydroethidium, respectively, and TBARS levels were measured in plasma. Aortic nitrotyrosine staining was evaluated to assess peroxynitrite formation. TGF-β levels and p-ERK 1/2 expression were determined by immunofluorescence and Western blotting, respectively. Matrix metalloproteinase (MMP) activity and expression were determined by in situ zymography, gel zymography, Western blotting, and immunofluorescence, and TIMP-1 was assessed by immunohistochemistry. Both β1-receptor antagonists exerted very similar antihypertensive effects. However, while metoprolol had no significant effects, nebivolol significantly attenuated vascular remodeling and collagen deposition associated with hypertension. Moreover, nebivolol, but not metoprolol, attenuated hypertension-induced increases in aortic NAD(P)H oxidase activity, superoxide production, TBARS concentrations, nitrotyrosine levels, TGF-β upregulation, and MMP-2 and -9 expression/activity. No effects on p-ERK 1/2 and TIMP-1 expression were found. These results show for the first time that nebivolol, but not metoprolol, attenuates prooxidant and profibrotic mechanisms involving TGF-β and MMP-2 and MMP-9, which promote vascular remodeling in hypertension.

Atorvastatin and sildenafil lower blood pressure and improve endothelial dysfunction, but only atorvastatin increases vascular stores of nitric oxide in hypertension

Nitric oxide (NO)-derived metabolites including the anion nitrite can recycle back to NO and thus complement NO formation independent of NO synthases. While nitrite is as a major vascular storage pool and source of NO, little is known about drugs that increase tissue nitrite concentrations. This study examined the effects of atorvastatin or sildenafil, or the combination, on vascular nitrite concentrations and on endothelial dysfunction in the 2 kidney-1 clip (2K1C) hypertension model. Sham-operated or 2K1C hypertensive rats were treated with vehicle, atorvastatin (50 mg/Kg), sildenafil (45 mg/Kg), or both for 8 weeks. Systolic blood pressure (SBP) was monitored weekly. Nitrite concentrations were assessed in the aortas and in plasma samples by ozone-based reductive chemiluminescence assay. Aortic rings were isolated to assess endothelium-dependent and independent relaxation. Aortic NADPH activity and ROS production were evaluated by luminescence and dihydroethidium, respectively, and plasma TBARS levels were measured. Aortic nitrotyrosine staining was evaluated to assess peroxynitrite formation. Atorvastatin and sildenafil, alone or combined, significantly lowered SBP by approximately 40 mmHg. Atorvastatin significantly increased vascular nitrite levels by 70% in hypertensive rats, whereas sildenafil had no effects. Both drugs significantly improved the vascular function, and decreased vascular NADPH activity, ROS, and nitrotyrosine levels. Lower plasma TBARS concentrations were found with both treatments. The combination of drugs showed no improved responses compared to each drug alone. These findings show evidence that atorvastatin, but not sildenafil, increases vascular NO stores, although both drugs exert antioxidant effects, improve endothelial function, and lower blood pressure in 2K1C hypertension.

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Nitrite recycles back to NO and complements NO formation independent of NO synthases.

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Little is known about drugs that increase tissue nitrite concentrations.

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Atorvastatin or sildenafil lowered blood pressure in renovascular hypertension.

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Both drugs exerted antioxidant effects and improved endothelial dysfunction.

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Only atorvastatin increased vascular nitrite levels by 70% in hypertensive rats.

Matrix metalloproteinase inhibition attenuates right ventricular dysfunction and improves responses to dobutamine during acute pulmonary thromboembolism

Activated matrix metalloproteinases (MMPs) cause cardiomyocyte injury during acute pulmonary thromboembolism (APT). However, the functional consequences of this alteration are not known. We examined whether doxycycline (a MMP inhibitor) improves right ventricle function and the cardiac responses to dobutamine during APT. APT was induced with autologous blood clots (350 mg/kg) in anaesthetized male lambs pre-treated with doxycycline (Doxy, 10 mg/kg/day, intravenously) or saline. Non-embolized control lambs received doxycycline pre-treatment or saline. The responses to intravenous dobutamine (Dob, 1, 5, 10 μg/kg/min.) or saline infusions at 30 and 120 min. after APT induction were evaluated by echocardiography. APT increased mean pulmonary artery pressure and pulmonary vascular resistance index by ∼185%. Doxycycline partially prevented APT-induced pulmonary hypertension (P < 0.05). RV diameter increased in the APT group (from 10.7 ± 0.8 to 18.3 ± 1.6 mm, P < 0.05), but not in the Doxy+APT group (from 13.3 ± 0.9 to 14.4 ± 1.0 mm, P > 0.05). RV dysfunction on stress echocardiography was observed in embolized lambs (APT+Dob group) but not in embolized animals pre-treated with doxycycline (Doxy+APT+Dob). APT increased MMP-9 activity, oxidative stress and gelatinolytic activity in the RV. Although doxycycline had no effects on RV MMP-9 activity, it prevented the increases in RV oxidative stress and gelatinolytic activity (P < 0.05). APT increased serum cardiac troponin I concentrations (P < 0.05), doxycycline partially prevented this alteration (P < 0.05). We found evidence to support that doxycycline prevents RV dysfunction and improves the cardiac responses to dobutamine during APT.

Antioxidant effect of doxycycline decreases MMP activity and blood pressure in SHR

Increased matrix metalloproteinase (MMP) levels are involved in vascular remodeling of hypertension. In this study, we hypothesized that doxycycline (a MMP inhibitor) could exert antioxidant effects, reverse establish vascular remodeling, and lower blood pressure in spontaneously hypertensive rats (SHR). SHR and Wistar-Kyoto rats received either doxycycline at 30 mg/kg/day by gavage or vehicle. Systolic blood pressure (SBP) was assessed weekly by tail cuff. After 5 weeks of treatment, morphologic changes in the aortic wall were studied in hematoxylin/eosin sections. MMP activity and expression were determined by in situ zymography using DQ gelatin and immunofluorescence for MMP-2. Dihydroethidium was used to evaluate aortic reactive oxygen species (ROS) production by fluorescence microscopy. Doxycycline reduced SBP by 25 mmHg. However, the antihypertensive effects were not associated with significant reversal of hypertension-induced vascular hypertrophy. SHR showed increased aortic MMP-2 levels which co-localized with higher aortic MMP activity and ROS levels, and all those biochemical alterations associated with hypertension were blunted by treatment with doxycycline. These results show that MMP inhibition with doxycycline in SHR with established hypertension resulted in antioxidant effects, lower gelatinolytic activity, and antihypertensive effects which were not associated with reversal of hypertension-induced vascular remodeling.

Abstract 301: Nebivolol Attenuates Prooxidant and Profibrotic Mechanisms and Decreases Vascular Remodeling in Renovascular Hypertension

Nebivolol and metoprolol are β1-adrenergic receptor blockers with different properties. We hypothesized that nebivolol, but not metoprolol, could attenuate prooxidant and profibrotic mechanisms of hypertension vascular remodeling. Hypertension was induced in male Wistar rats by clipping the left renal artery. Six weeks after surgery, hypertensive and sham rats were treated with nebivolol (Nebi 10 mg/kg/day), metoprolol (Meto 20 mg/kg/day) or vehicle for four weeks. Systolic blood pressure was monitored weekly. Morphologic changes in the aortic wall were studied in picrosirius red sections. Aortic NAD(P)H activity was evaluated by luminescence. Nitrotyrosine staining was evaluated to assess peroxynitrite formation by immunohistochemistry. TGF-β and matrix metalloproteinase-9 (MMP-9) levels were determined by immunofluorescence, and p-ERK 1/2 expression by western blotting. Both β1-receptor antagonists exerted very similar antihypertensive effects (156 ± 8 mmHg and 151 ± 9 mmHg, respectively, versus 206 ± 7 mmHg in hypertensive controls; both P<0.05). However, while metoprolol had no significant effects, nebivolol significantly (all P<0.05) attenuated vascular collagen surface (237944 ± 59567, 69784 ± 17686, 183215 ± 30338 μm2, respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), attenuated hypertension-induced increases in aortic NAD(P)H oxidase activity (253887 ± 13712, 143765 ± 15642, and 232465 ± 14352 AU, respectively in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), in nitrotyrosine levels (166.3 ± 2.9, 145.3 ± 1.5, 172.1 ± 7.3 AU, respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), in TGF-β upregulation (7.2 ± 0.12, 6.5 ± 0.03, 7.0 ± 0.3 AU, respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups) and in MMP-9 levels (18.27 ± 0.8, 12.73 ± 0.4, 15.76 ± 1.4 AU, respectively in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups). No effects on p-ERK 1/2 expression were found with both drugs (P>0.05) (1.0 ± 0.16, 0.92 ± 0.15, 0.87 ± 0.37 AU, respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups). These results show for the first time that nebivolol, but not metoprolol, attenuates prooxidant and profibrotic mechanisms involving TGF-β and MMP-9, which promote vascular remodeling in hypertension.

Abstract 645: Atorvastatin and Sildenafil Reduce Oxidative Stress, MMP-2 And MMP-9 Levels, TGF-beta Expression and Prevent Vascular Remodeling in 2K1C-hypertension

Hypertension-induced vascular remodeling is associated with oxidative stress, and matrix metalloproteinase (MMP) and TGF (transforming growth factor)-beta up-regulation. Atorvastatin (ATORVA) and sildenafil (SILD) exert pleiotropic effects that may result in cardiovascular protection. We evaluated the effects of ATORVA and SILD alone or in association on oxidative stress, MMPs and TGF-beta up-regulation, and vascular hypertrophy induced by 2 kidney-1 clip (2K1C) hypertension. Sham and 2K1C rats were orally treated with vehicle, ATORVA (50 mg/kg), SILD (45 mg/kg) or both for 8 weeks. ATORVA, SILD, or both drugs exerted antihypertensive effects (systolic blood pressure: 148±7, 156±5, and 138±4 mmHg, respectively, vs. 207±4 mmHg in 2K1C untreated rats; P<0.05). All treatments prevented the increases in the aortic cross-sectional area and media/lumen ratio in 2K1C rats (P<0.05). Hypertension increased NADPH oxidase activity when compared with control groups and the treatments reduced oxidative stress. Aortas from 2K1C rats showed higher MMP-2 levels when compared with sham (0.399±0.06 vs. 0.173±0.05 A.U.) and all treatments attenuated 2K1C hypertension-induced increases in MMP-2 levels (ATORVA: 0.191±0.04; SILD: 0.136±0.05; ATORVA+SILD: 0.173±0.03; P<0.05). However, these drugs had no in vitro effects on human recombinant MMP-2 activity (P>0.05). Moreover, 2K1C rats showed higher MMP-9 (12.64±0.86 vs. 8.70±0.92) and TGF-beta expression (14.25±0.97 vs. 9.07±1.67) compared with sham groups. All treatments prevented 2K1C hypertension-induced increases in these pro-fibrotic factors. Treatment with ATORVA or SILD, or both, exerted antihypertensive effects and prevented 2K1C hypertension-induced vascular remodeling through antioxidant and anti-fibrotic mechanisms. Our results suggest that ATORVA and SILD may prevent the vascular alterations of hypertension.

Abstract 393: Chronic Nebivolol Treatment Attenuates MMP Activity and Oxidative Stress and Improves Renovascular Hypertension-induced Cardiac Hypertrophy

Nebivolol (Nebi) is the most selective cardiac β1-adrenergic receptor blocker and exerts antioxidant effects. Reactive oxygen species (ROS) enhance cardiac matrix metalloproteinase activity (MMPs) and contribute to hypertension-induced left ventricular hypertrophy (LVH). However, it is uncertain whether Nebi decreases MMP-2 levels and cardiac remodeling associated with hypertension as a result of its antioxidant properties. Hypertension was induced by clipping the left renal artery (2K1C). Six weeks after surgery, hypertensive and sham rats were treated with Nebi, Metoprolol (Meto) or Vehicle (by gavage) for four weeks. Systolic blood pressure (SBP) was monitored weekly by tail-cuff plethysmography. LV structural changes were studied in hematoxylin/eosin sections. MMP levels and activity were determined by immunofluorescence and in situ zymography. ROS and nitrotyrosine levels were evaluated by dihydroethidium and immunohistochemistry, respectively. Similar reduction in SBP was found with both treatments (202±5 mmHg in 2K1C+Vehicle versus 161±19 and 162±18 mmHg in 2K1C Nebi or Meto groups, respectively; P<0.05). Both treatments reduced LV remodeling and ROS formation (P<0.05). Both drugs decreased nitrotyrosine levels (3.9±0.2, 2.3±0.3, and 2.4±0.3 arbitrary units, respectively in 2K1C+vehicle, 2K1C+Meto, and 2K1C+Nebi groups, respectively; P<0.05). Increased MMP-2 levels (16.0±2.0 versus 7.0±0.9 arbitrary units; P<0.05) and activity (8.0±0.4 versus 6.0±0.1 arbitrary units; P<0.05) were observed in the 2K1C+vehicle group when compared to the sham group. These alterations were normalized by both treatments (similar levels to those found in the sham group). No significant changes were observed in the sham groups. These findings suggest that different β-blockers exert important antioxidant effects that may underlie the lower LV MMP activity and cardiac remodeling in 2K1C hypertension.

Temporal changes in cardiac matrix metalloproteinase activity, oxidative stress, and TGF-β in renovascular hypertension-induced cardiac hypertrophy

Cardiovascular remodeling found in later phases of two-kidney, one-clip (2K1C) hypertension may involve key mechanisms particularly including MMP-2, oxidative stress, transforming growth factor-β (TGF-β), and inactivation of the endogenous MMP inhibitor, the tissue inhibitor of MMP (TIMP)-4. We examined whether temporal cardiac remodeling resulting from 2K1C hypertension occurs concomitantly with alterations in cardiac collagen, MMP activity, MMP-2, TIMP-4, TGF-β, and reactive oxygen species (ROS) levels during the development of 2K1C hypertension. Sham-operated and 2K1C hypertensive rats were studied after 15, 30, and 75 days of hypertension. Systolic blood pressure was monitored weekly. Left ventricle (LV) morphometry and fibrosis were evaluated in hematoxylin/eosin and picrosirius red-stained sections, respectively. Cardiac MMP-2 levels/activity was determined by gelatin zymography, immunofluorescence, and in situ zymography. TIMP-4 levels were determined by western blotting. Cardiac TGF-β levels were evaluated by immunofluorescence and ROS levels were evaluated with a dihydroethidium probe. 2K1C hypertension induced LV hypertrophy associated with augmented gelatinolytic activity at an early phase of hypertension and further increased after 75 days of hypertension. These alterations were associated with increased cardiac MMP-2, TGF-β, and ROS in hypertensive rats. Higher TIMP-4 levels were found in hypertensive rats only after 75 days after surgery. Our findings show that increased MMP-2 activity is associated with concomitant development of LV hypertrophy and increased TGF-β and ROS levels.

Abstract 189: Omeprazole Decreases Chronic Antihypertensive Effects of Sodium Nitrite

Introduction: Recent studies showed that sodium nitrite decreases blood pressure (BP) in two kidney, one clip (2K1C) hypertension, probably as a result of nitrite being converted into nitric oxide in the acid environment of the stomach. This study aimed at examining whether increasing gastric pH with omeprazol reduces the chronic antihypertensive effects of nitrite.

Methods: 2K1C hypertensive and sham operated control rats were treated with omeprazole (10mg/Kg; i.p.) or vehicle and sodium nitrite (15mg/Kg; gavage) or saline for two weeks. Systolic BP (SBP) was measured by tail pletismografy weekly. Circulating nitrite levels were measured by chemiluminesce and gastric pH was measured with an electrode. The results were analyzed by two-way ANOVA. The results are show as mean ± standard deviation.

Results: 2K1C rats were hypertensive two weeks after surgery (SBP=180±17 mmHg). After 4 weeks of treatment, nitrite exerted antihypertensive effects in rats treated with vehicle (SBP=161±23 mmHg versus 200±29 mmHg, respectively, in the 2K1C+nitrite and in the 2K1C+saline groups; P<0.05). However, nitrite exerted no antihypertensive effects in 2K1C rats treated with omeprazole (SBP=200±34 mmHg; P>0.05 versus 2K1C+saline group). We found no significant differences among the sham operated groups. Similar increases in plasma nitrite concentrations were found when animals treated with nitrite and omeprazol were compared with those treated with nitrite and vehicle (8.5±4.1 versus 5.2±3.6 μM, respectively; P>0.05). Omeprazole increased gastric pH in all animals treated with this drug (P<0.05).

Conclusion Treatment with omeprazole blunts the chronic antihypertensive effects of sodium nitrite in 2K1C rats. However, this effect is probably not associated with significant differences in plasma nitrite concentrations.

Abstract 322: Imbalance Between MMP-2 and TIMP-4 Associated With Oxidative Stress Contributes to Temporal Renovascular Hypertension-Induced Cardiac Hypertrophy

Imbalanced matrix metalloproteinase (MMP) activity is associated with left ventricular hypertrophy (LVH). Increased reactive oxygen species (ROS) formation enhances MMP activity and decrease tissue inhibitor of MMP (TIMP) activity. We examined the temporal relationship between ROS, MMP-2, and TIMP-4 levels in the heart during the progression of LVH in two-kidney, one-clip (2K1C) hypertension. Sham or 2K1C hypertensive rats were studied after 15, 30, and 75 days of hypertension, and the results are expressed as % of values found in corresponding sham animals at each time point. Systolic blood pressure increased with time in 2K1C rats: 167±3, 201±1, and 203±2 mmHg after 15, 30, and 75 days of hypertension (all P<0.05). Hypertension induced LVH in a time-dependent manner (P<0.05). Collagen deposition increased by 250±23%, 213±20% and 235±16% in 2K1C rats, respectively, after 15, 30, and 75 days of hypertension; all P<0.05 vs. respective sham). Cardiac MMP-2 levels increased from 13±1 (sham) to 19±2, 17±1, and 20±2 arbitrary units (AU) after 15, 30, and 75 days of hypertension, respectively (all P<0.05 vs. sham). Cardiac TIMP-4 levels increased by 325±68% (P<0.05) only after 75 days of hypertension. Cardiac gelatinolytic activity increased by 129±4%, 150±6%, and 152±6% after 15, 30, and 75 of hypertension, respectively (all P<0.05 vs. sham). Cardiac ROS levels increased by 137±5%, 154±15%, and 130 ±10% after 15, 30, and 75 days of hypertension, respectively (all P<0.05 vs. sham). These results indicate that LVH in is an early process associated with imbalanced MMP-2 and TIMP-4 levels in renovascular hypertension, thus resulting in increased gelatinolytic activity and fibrosis, which may be due to oxidative stress.

Abstract 265: Chronic Treatment with Nebivolol Attenuates the Vascular Changes in the 2-Kidney, 1-Clip Model of Renovascular Hypertension

Nebivolol (Nebi) is a β-1 receptor antagonist with vasodilator and antioxidant properties. Matrix metalloproteinases (MMPs) are enzymes involved in cardiovascular remodeling, and MMP upregulation has been associated with increased reactive oxygen species (ROS). Because vascular remodeling is associated with increased ROS and MMPs, it is possible that Nebi reverses the increased MMP levels and vascular remodeling associated with 2K-1C hypertension through its antioxidant activity. Hypertension was induced in male Wistar rats by clipping the left renal artery. Six weeks after surgery, hypertensive and sham rats were treated with Nebi (10 mg/kg/day), metoprolol (Meto; 20 mg/kg/day) or vehicle for four weeks. Systolic blood pressure (SBP) was monitored weekly by tail-cuff plethysmography. Structural changes of the aortic wall were studied in hematoxylin/eosin sections. MMPs levels and activity were determined by zymography and in situ zymography. NADPH oxidase activity and ROS production were evaluated by luminescence and dihydroethidium. Similar reductions in SBP were found with both Meto or Nebi treatments (156 ± 8 mmHg and 151 ± 9 mmHg, respectively, versus 206 ± 7 mmHg in hypertensive controls; both P<0.05). However, only Nebi (all P<0.05) reversed aortic hypertrophy (aortic cross sectional area x 10 4 = 89±5, 68±3, and 80±8 μm 2 , respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), the increases in aortic MMP-2 levels (0.18±0.04, 0.07±0.02, and 0.12±0.06 arbitrary units; AU, respectively in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), in aortic MMP activity (21071±700, 16217±818, and 18848±1396, respectively in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups), in aortic NADPH oxidase activity (253887±13712, 143765±15642, and 232465±14352 AU, respectively in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups) and in aortic ROS levels (8057±800, 4400±480, and 6230±1190 AU, respectively, in the 2K1C, 2K1C+Nebi, and 2K1C+Meto groups). No significant differences were found in the Sham groups. Our results suggest that lower vascular NADPH oxidase may explain, at least in part, the attenuation of oxidative stress and vascular remodeling associated with Nebi.

Pyrrolidine dithiocarbamate down-regulates vascular matrix metalloproteinases and ameliorates vascular dysfunction and remodelling in renovascular hypertension

BACKGROUND AND PURPOSE

Mounting evidence implicates matrix metalloproteinase (MMP) in the vascular dysfunction and remodelling associated with hypertension. We tested the hypothesis that treatment with pyrrolidine dithiocarbamate (PDTC), which interferes with NF-κB-induced MMPs gene transcription, could exert antihypertensive effects, prevent MMP-2 and MMP-9 up-regulation, and protect against the functional alterations and vascular remodelling of two-kidney, one clip (2K1C) hypertension.

EXPERIMENTAL APPROACH

Sham-operated or hypertensive rats were treated with vehicle or PDTC (100 mg·Kg(-1) ·day(-1)) by gavage for 8 weeks. Systolic blood pressure (SBP) was monitored weekly. Aortic rings were isolated to assess endothelium-dependent relaxations. Quantitative morphometry of structural alterations of the aortic wall was carried out in haematoxylin/eosin sections. Formation of vascular reactive oxygen species (ROS), and inducible (i) NOS and phosphorylated-p65 NF-κB subunit expression were measured in the aortas. MMP-2 and MMP-9 aortic levels and gelatinolytic activity were determined by gelatin and in situ zymography and by immunofluorescence.

KEY RESULTS

Treatment with PDTC attenuated the increases in SBP and prevented the endothelial dysfunction associated with 2K1C hypertension. Moreover, PDTC reversed the vascular aortic remodelling, the increases in aortic ROS levels and in iNOS and phosphorylated-p65 NF-κB expression found in 2K1C rats. These effects were associated with attenuation of 2K1C up-regulation of aortic MMP-2 and MMP-9 levels and gelatinolytic activity.

CONCLUSION AND IMPLICATIONS

These findings suggest that PDTC down-regulates vascular MMPs and ameliorates vascular dysfunction and remodelling in renovascular hypertension, thus providing evidence supporting the suggestion that PDTC is probably a good candidate to be used to treat hypertension.

Time course involvement of matrix metalloproteinases in the vascular alterations of renovascular hypertension

Increased vascular matrix metalloproteinases (MMPs) levels play a role in late phases of hypertensive vascular remodeling. However, no previous study has examined the time course of MMPs in the various phases of two-kidney, one-clip hypertension (2K1C). We examined structural vascular changes, collagen and elastin content, vascular oxidative stress, and MMPs levels/activities during the development of 2K1C hypertension. Plasma angiotensin converting enzyme (ACE) activity was measured to assess renin-angiotensin system activation. Sham or 2K1C hypertensive rats were studied after 2, 4, 6, and 10weeks of hypertension. Systolic blood pressure (SBP) was monitored weekly. Morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin, orcein and picrosirius red sections. Aortic NADPH activity and superoxide production was evaluated. Aortic gelatinolytic activity was determined by in situ zymography, and MMP-2, MMP-14, and tissue inhibitor of MMPs (TIMP)-2 levels were determined by gelatin zymography, immunofluorescence and immunohistochemistry. 2K1C hypertension was associated with increased ACE activity, which decreased to normal after 10 weeks. We found increased aortic collagen and elastin content in the early phase of hypertension, which were associated with vascular hypertrophy, increased vascular MMP-2 and MMP-14 (but not TIMP-2) levels, and increased gelatinolytic activity, possibly as a result of increased vascular NADPH oxidase activity and oxidative stress. These results indicate that vascular remodeling of renovascular hypertension is an early process associated with early increases in MMPs activities, enhanced matrix deposition and oxidative stress. Using antioxidants or MMPs inhibitors in the early phase of hypertension may prevent the vascular alterations of hypertension.

Consistent alterations of circulating matrix metalloproteinases levels in untreated hypertensives and in spontaneously hypertensive rats: a relevant pharmacological target

Inconsistent matrix metalloproteinases (MMPs) levels have been reported in hypertension, with higher, similar and lower MMPs levels reported in hypertensives compared with normotensives. Differences between studies may reflect lack of control of drug effects, accompanying diseases and pre-analytical issues. We compared MMP-2, MMP-8 and MMP-9 levels in 38 untreated hypertensive patients (with no other diseases) with those found in 33 normotensive controls. We also studied endogenous MMPs inhibitors (TIMP-1, TIMP-2 and alpha-2-macroglobulin-A2M). Additionally, we assessed MMPs and A2M levels in spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats. We hypothesized that similar MMPs/endogenous inhibitors' profiles would be found in this animal model of hypertension and in clinical hypertension. MMPs, TIMPs and A2M were measured in plasma samples with commercially available ELISA and gelatin zymography. We found unaltered MMP-2, MMP-8, TIMP-1, TIMP-2 and A2M levels in hypertension. However, hypertensives had higher MMP-9 levels and MMP-9/A2M ratios than normotensives. Moreover, while we found similar MMP-2 and A2M levels in SHR and WKY rats, we found higher MMP-9 levels and MMP-9/A2M ratios in SHR versus WKY rats. These findings show consistent abnormal net plasma MMP-9 (but not MMP-2) activity in clinical and experimental hypertension. These parallel alterations in clinical hypertension and in SHR suggest an important role for MMPs in hypertension. While MMPs may be a relevant pharmacological target, antihypertensive drugs that down-regulate MMPs may offer advantages in the management of this disease.

Doxycycline dose-dependently inhibits MMP-2-mediated vascular changes in 2K1C hypertension

Hypertension induces vascular alterations that are associated with up-regulation of matrix metalloproteinases (MMPs). While these alterations may be blunted by doxycycline, a non-selective MMPs inhibitor, no previous study has examined the effects of different doses of doxycycline on these alterations. This is important because doxycycline has been used at sub-antimicrobial doses, and the use of lower doses may prevent the emergence of antibiotic-resistant microorganisms. We studied the effects of doxycycline at 3, 10 and 30 mg/kg per day on the vascular alterations found in the rat two kidney-one clip (2K1C) hypertension (n = 20 rats/group). Systolic blood pressure (SBP) was monitored during 4 weeks of treatment. We assessed endothelium-dependent and independent relaxations. Quantitative morphometry of structural changes in the aortic wall was studied, and aortic MMP-2 levels/proteolytic activity were determined by gelatin and in situ zymography, respectively. All treatments attenuated the increases in SBP in hypertensive rats (195.4 ± 3.9 versus 177.2 ± 6.2, 176.3 ± 4.5, and 173 ± 5.1 mmHg in 2K1C hypertensive rats treated with vehicle, or doxycycline at 3, 10, 30 mg/kg per day, respectively (all p < 0.01). However, only the highest dose prevented 2K1C-induced reduction in endothelium-dependent vasorelaxation (p < 0.05), vascular hypertrophy and increases in MMP-2 levels (all p < 0.05). In conclusion, our results suggest that relatively lower doses of doxycycline do not attenuate the vascular alterations found in the 2K1C hypertension model, and only the highest dose of doxycycline affects MMPs and vascular structure. Our results support the idea that the effects of doxycycline on MMP-2 and vascular structure are pressure independent.

Comparative study on antioxidant effects and vascular matrix metalloproteinase-2 downregulation by dihydropyridines in renovascular hypertension

The vascular remodeling associated with hypertension involves oxidative stress and enhanced matrix metalloproteinases (MMPs) expression/activity, especially MMP-2. While previous work showed that lercanidipine, a third-generation dihydropyridine calcium channel blocker (CCB), attenuated the oxidative stress and increased MMP-2 expression/activity in two-kidney, one-clip (2K1C) hypertension, no previous study has examined whether first- or second-generation dihydropyridines produce similar effects. We compared the effects of nifedipine, nimodipine, and amlodipine on 2K1C hypertension-induced changes in systolic blood pressure (SBP), vascular remodeling, oxidative stress, and MMPs levels/activity. Sham-operated and 2K1C rats were treated with water, nifedipine 10 mg/kg/day, nimodipine 15 mg/kg/day, or amlodipine 10 mg/kg/day by gavage, starting 3 weeks after hypertension was induced. SBP was monitored weekly. After 6 weeks of treatment, quantitative morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin-stained sections. Aortic and systemic reactive oxygen species levels were measured by using dihydroethidine and thiobarbituric acid-reactive substances (TBARs), respectively. Aortic MMP-2 levels and activity were determined by gelatin zymography, in situ zymography, and immunofluorescence. Nifedipine, nimodipine, or amlodipine attenuated the increases in SBP in hypertensive rats by approximately 17% (P < 0.05) and prevented vascular hypertrophy (P < 0.05). These CCBs blunted 2K1C-induced increases in vascular oxidative stress and plasma TBARs concentrations (P < 0.05). All dihydropyridines attenuated the increases in aortic MMP-2 levels and activity associated with 2K1C hypertension. These findings suggest lack of superiority of one particular dihydropyridine, at least with respect to antioxidant effects, MMPs downregulation, and inhibition of vascular remodeling in hypertension.

Spironolactone and hydrochlorothiazide exert antioxidant effects and reduce vascular matrix metalloproteinase-2 activity and expression in a model of renovascular hypertension

BACKGROUND AND PURPOSE

Increased oxidative stress and up-regulation of matrix metalloproteinases (MMPs) may cause structural and functional vascular changes in renovascular hypertension. We examined whether treatment with spironolactone (SPRL), hydrochlorothiazide (HCTZ) or both drugs together modified hypertension-induced changes in arterial blood pressure, aortic remodelling, vascular reactivity, oxidative stress and MMP levels and activity, in a model of renovascular hypertension.

EXPERIMENTAL APPROACH

We used the two-kidney,one-clip (2K1C) model of hypertension in Wistar rats. Sham-operated or hypertensive rats were treated with vehicle, SPRL (25 mg.kg(-1).day(-1)), HCTZ (20 mg.kg(-1).day(-1)) or a combination for 8 weeks. Systolic blood pressure was monitored weekly. Aortic rings were isolated to assess endothelium-dependent and -independent relaxations. Morphometry of the vascular wall was carried out in sections of aorta. Aortic NADPH oxidase activity and superoxide production were evaluated. Formation of reactive oxygen species was measured in plasma as thiobarbituric acid-reactive substances. Aortic MMP-2 levels and activity were determined by gelatin and in situ zymography, fluorimetry and immunohistochemistry.

KEY RESULTS

Treatment with SPRL, HCTZ or the combination attenuated 2K1C-induced hypertension, and reversed the endothelial dysfunction in 2K1C rats. Both drugs or the combination reversed vascular aortic remodelling induced by hypertension, attenuated hypertension-induced increases in oxidative stress and reduced MMP-2 levels and activity.

CONCLUSIONS AND IMPLICATIONS

SPRL or HCTZ, alone or combined, exerted antioxidant effects, and decreased renovascular hypertension-induced MMP-2 up-regulation, thus improving the vascular dysfunction and remodelling found in this model of hypertension.

Antioxidant treatment reduces matrix metalloproteinase-2-induced vascular changes in renovascular hypertension

Mounting evidence indicates that structural and functional vascular changes associated with two-kidney, one-clip (2K-1C) hypertension result, at least in part, from altered activity of matrix metalloproteinases (MMPs). Because MMPs are upregulated by increased formation of reactive oxygen species (ROS), we hypothesized that antioxidant approaches could attenuate the increases in MMP-2 expression/activity and the vascular dysfunction and remodeling associated with 2K-1C hypertension. Sham-operated or 2K-1C hypertensive rats were treated with tempol 18 mg/kg/day or apocyanin 25 mg/kg/day (or vehicle). Systolic blood pressure was monitored weekly. After 8 weeks of treatment, aortic rings were isolated to assess endothelium-dependent and -independent relaxation. Quantitative morphometry of structural changes in the aortic wall was studied in hematoxylin/eosin sections. Aortic and systemic ROS levels were measured using dihydroethidine and thiobarbituric acid-reactive substances, respectively. Aortic MMP-2 levels and activity were determined by gelatin and in situ zymography, fluorimetry, and immunohistochemistry. Tempol and apocyanin attenuated 2K-1C hypertension (181+/-20.8 and 192+/-17.6 mm Hg, respectively, versus 213+/-18 mm Hg in hypertensive controls; both p<0.05) and prevented the reduction in endothelium-dependent vasorelaxation found in 2K-1C rats. Tempol, but not apocyanin (p>0.05), prevented the vascular remodeling found in 2K-1C rats (all p<0.01). Tempol was more effective than apocyanin in attenuating hypertension-induced increases in oxidative stress (both p<0.05), MMP-2 levels, and MMP-2 activity in hypertensive rats (all p<0.05). Our results suggest that antioxidant approaches decrease MMP-2 upregulation and attenuate the vascular dysfunction and remodeling during 2K-1C hypertension.