Myoglobin promotes nitrite-dependent mitochondrial S-nitrosation to mediate cytoprotection after hypoxia/reoxygenation

It is well established that myoglobin supports mitochondrial respiration through the storage and transport of oxygen as well as through the scavenging of nitric oxide. However, during ischemia/reperfusion (I/R), myoglobin and mitochondria both propagate myocardial injury through the production of oxidants. Nitrite, an endogenous signaling molecule and dietary constituent, mediates potent cardioprotection after I/R and this effect relies on its interaction with both myoglobin and mitochondria. While independent mechanistic studies have demonstrated that nitrite-mediated cardioprotection requires the presence of myoglobin and the post-translational S-nitrosation of critical cysteine residues on mitochondrial complex I, it is unclear whether myoglobin directly catalyzes the S-nitrosation of complex I or whether mitochondrial-dependent nitrite reductase activity contributes to S-nitrosation. Herein, using purified myoglobin and isolated mitochondria, we characterize and directly compare the nitrite reductase activities of mitochondria and myoglobin and assess their contribution to mitochondrial S-nitrosation. We demonstrate that myoglobin is a significantly more efficient nitrite reductase than isolated mitochondria. Further, deoxygenated myoglobin catalyzes the nitrite-dependent S-nitrosation of mitochondrial proteins. This reaction is enhanced in the presence of oxidized (Fe³⁺) myoglobin and not significantly affected by inhibitors of mitochondrial respiration. Using a Chinese Hamster Ovary cell model stably transfected with human myoglobin, we show that both myoglobin and mitochondrial complex I expression are required for nitrite-dependent attenuation of cell death after anoxia/reoxygenation. These data expand the understanding of myoglobin's role both as a nitrite reductase to a mediator of S-nitrosation and as a regulator of mitochondrial function, and have implications for nitrite-mediated cardioprotection after I/R.

Nitrate and nitrite-based therapy to attenuate cardiovascular remodelling in arterial hypertension

Hypertension is a highly prevalent disease marked by vascular and cardiac maladaptive remodelling induced mainly by renin-angiotensin system activation followed by oxidative stress. Here, we briefly describe these damages and review the current evidence supporting a potential role for nitrate and nitrite as antihypertensive molecules that act via nitric oxide (NO) formation-dependent and NO formation-independent mechanisms and how nitrate/nitrite inhibits cardiovascular remodelling in hypertension. The renin-angiotensin system activation and oxidative stress converge to activate proteases involved in cardiovascular remodelling in hypertension. Besides these proteases, several investigations have demonstrated that reduced endogenous NO bioavailability is a central pathological event in hypertension. In this regard, nitrate/nitrite, long considered inert products of NO, is now known as physiological molecules able to reduce blood pressure in hypertensive patients and in different experimental models of hypertension. These effects are associated with the formation of NO and other NO-related molecules, which could induce S-nitrosylation of target proteins. However, it remains unclear whether S-nitrosylation is an essential mechanism for the anti-remodelling effects of nitrate/nitrite in hypertension. Moreover, nitrate/nitrite produces antioxidant effects associated with the inhibition of signalling pathways involved in cardiovascular remodelling. Together, these findings may help to establish nitrate and nitrite as effective therapies in hypertension-induced cardiovascular remodelling.

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.

Abstract P423: Chronic Doxycycline Administration Inhibits Angiotensin Converting Enzyme Activity and Exerts Antioxidants Effects in Renovascular Hypertensive Rats

Doxycycline (Dox), an established matrix metalloproteinase (MMP) inhibitor, and angiotensin-converting enzyme inhibitors (ACEi) present beneficial cardiovascular effects which could be consequence of their antioxidants properties. Furthermore, some evidences have shown other biochemical similarities between Dox and ACEi suggesting that Dox could also inhibit ACE and ACEi directly interact with MMPs and inhibit these proteases. Supporting this idea, Dox is able to chelate divalent metals, such as calcium and zinc, which are essential for the ACE activity. In this regard, we hypothesized that Dox inhibits ACE activity in hypertensive rats which leads to a reduction in ROS production and decrease hypertension. Sham-operated or 2K1C hypertensive rats were treated with Dox (30 mg/Kg/day) or water for 4 weeks. Systolic blood pressure (SBP) was monitored weekly. Dox treatment reduced SBP in 2K1C rats from 200±12 mmHg to 158±8 mmHg (P<0.05). In addition, Dox treatment attenuated reactive oxygen species (ROS) levels in hypertensive animals measured by lucigenin chemiluminescense (in RLU/mg of aorta: from 711±1.0 to 377±93; P<0.05). ACE activity in aorta was increased in untreated 2K1C rats (22±0.8 nmols/min/g) when compared with the Sham group (12±1.0 nmols/min/g; P<0.05) and Dox treatment was able to reduce ACE activity in 2K1C rats (15±2.0 nmols/min/g; P<0.05). To evaluate whether Dox inhibits ACE activity in vitro , aortic tissues from 2K1C rats were incubated with Dox or Captopril (a known ACEi ). Dox in vitro did not affect ACE activity while captopril inhibited 80% of its activity. To verify whether Dox could inhibit ACE activity in vivo , an acute assay was performed with different doses of angiotensin I (in μg/Kg: 0.03, 0.3 and 3), after the single administration of Dox or saline (i.p.). Angiotensin I infusion increased mean arterial pressure dose-dependently and Dox pretreatment did not attenuated these increases significantly (P>0.05) as Captopril.Taken together, these results show that chronic treatment with Dox inhibits ACE activity in aorta of 2K1C rats, which contribute to ROS reduction and SBP attenuation. However, the mechanism by which Dox inhibits ACE activity needs further investigation.

Tempol improves xanthine oxidoreductase-mediated vascular responses to nitrite in experimental renovascular hypertension

Upregulation of xanthine oxidoreductase (XOR) increases vascular reactive oxygen species (ROS) levels and contributes to nitroso-redox imbalance. However, XOR can generate nitric oxide (NO) from nitrite, and increased superoxide could inactivate NO formed from nitrite. This study tested the hypothesis that XOR contributes to the cardiovascular effects of nitrite in renovascular hypertension, and that treatment with the antioxidant tempol (4-hydroxy-2,2,6,6-tetramethylpiperidine-N-oxyl) improves XOR-mediated effects of nitrite. Blood pressure was assessed weekly in two-kidney one-clip (2K1C) and control rats. After six weeks of hypertension, the relaxing responses to nitrite were assessed in aortic rings in the presence of the XOR inhibitor oxypurinol (or vehicle), either in the absence or in the presence of tempol. Moreover, in vivo hypotensive responses to nitrite were also examined in the presence of oxypurinol (or vehicle) and tempol (or vehicle). Aortic XOR activity and expression were evaluated by fluorescence and Western blot, respectively. Vascular ROS production was assessed by the dihydroethidium assay. 2K1C hypertensive rats showed increased aortic XOR activity and vascular ROS production compared with control rats. Oxypurinol shifted the nitrite concentration–response curve to the right in aortic rings from 2K1C rats (but not in controls). Oxypurinol also attenuated the hypotensive responses to nitrite in 2K1C rats (but not in controls). These functional findings agree with increased aortic and plasma XOR activity found in 2K1C rats. Tempol treatment enhanced oxypurinol-induced shift of the nitrite concentration–response curve to the right. However, antioxidant treatment did not affect XOR-mediated hypotensive effects of nitrite. Our results show that XOR is important to the cardiovascular responses to nitrite in 2K1C hypertension, and XOR inhibitors commonly used by patients may cancel this effect. This finding suggests that nitrite treatment may not be effective in patients being treated with XOR inhibitors. Moreover, while tempol may improve the vascular responses to nitrite, antihypertensive responses are not affected.

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Upregulation of xanthine oxidoreductase (XOR) is usually found in hypertension.

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While XOR produces superoxide, it can also produce NO from nitrite.

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This study shows that XOR mediates vasorelaxing effects of nitrite in renovascular hypertension.

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XOR inhibition prevents against the antihypertensive effects of nitrite.

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Antioxidant treatment improves XOR-mediated vasorelaxing effects of nitrite.

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.

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.

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.

Antihypertensive effects of inducible nitric oxide synthase inhibition in experimental pre-eclampsia

Upregulation of inducible nitric oxide synthase (iNOS) has been reported in both experimental and clinical hypertension. However, although pro-inflammatory cytokines that up-regulate iNOS contribute to pre-eclampsia, no previous study has tested the hypothesis that a selective iNOS inhibitor (1400 W) could exert antihypertensive effects associated with decreased iNOS expression and nitrosative stress in pre-eclampsia. This study examined the effects of 1400 W in the reduced uteroplacental perfusion pressure (RUPP) placental ischaemia animal model and in normal pregnant rats. Sham-operated and RUPP rats were treated with daily vehicle or 1 mg/kg/day N-[3-(Aminomethyl) benzyl] acetamidine (1400 W) subcutaneously for 5 days. Plasma 8-isoprostane levels, aortic reactive oxygen species (ROS) levels and nicotinamide adenine dinucleotide phosphate (NADPH)-dependent ROS production were evaluated by ELISA, dihydroethidium fluorescence microscopy and lucigenin chemiluminescence respectively. Inducible nitric oxide synthase expression was assessed by western blotting analysis and aortic nitrotyrosine was evaluated by immunohistochemistry. Mean arterial blood pressure increased by ∼30 mmHg in RUPP rats, and 1400 W attenuated this increase by ∼50% (P < 0.05). While RUPP increased plasma 8-isoprostane levels, aortic ROS levels, and NADPH-dependent ROS production (P < 0.05), treatment with 1400 W blunted these alterations (P < 0.05). Moreover, while RUPP increased iNOS expression and aortic nitrotyrosine levels (P < 0.05), treatment with 1400 W blunted these alterations (P < 0.05). These results clearly implicate iNOS in the hypertension associated with RUPP. Our findings may suggest that iNOS inhibitors could be clinically useful in the therapy of pre-eclampsia, especially in particular groups of patients genetically more prone to express higher levels of iNOS. This issue deserves further confirmation.

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 316: Effects of Inhibiting of Inducible Nitric Oxide Synthase in the Pathophysiology of Experimental Preeclampsia

The pathophysiology of preeclampsia (PE) is not entirely known. However, increased oxidative stress possibly leading to impaired nitric oxide activity has been implicated in the critical condition. Increased oxidative stress with increased levels of highly reactive species including superoxide may generate peroxynitrite. We examined the role of inducible nitric oxide synthase (iNOS) and oxidative stress in the reduced uterine perfusion pressure (RUPP) preeclampsia experimental model.

METHODS: RUPP was induced in wistar rats. Pregnant rats in the RUPP group had their aortic artery clipped at day 14 of gestation. After a midline incision, a silver clip (0.203 mm) was placed around the aorta above the iliac bifurcation; silver clips (0.100 mm) were also placed on branches of both the right and left ovarian arteries that supply the uterus. Sham-operated (pregnant control rats) and RUPP rats were treated with oral vehicle or 1 mg/kg/day 1400W (iNOS inhibitor) for 5 days. Mean arterial pressure (MAP) and plasma levels of thiobarbituric acid-reactive species (TBARS) and total radical-trapping antioxidant potential (TRAP) were measured determined. Aortic iNOS expression (Western blotting) and reactive oxygen species (ROS; assessed by fluorescence microscopy with dihydroethidium-DHE) were measured. We found increased mean arterial pressure in RUPP compared with pregnant control rats (MAP= 128±1 vs. 100±1.8 mmHg, respectively; P<0.05) and 1400W exerted antihypertensive effects (MAP= 114±2 vs.128±1 mmHg in RUPP treated and untreated rats, respectively; P<0.05). Higher reactive oxygen species (ROS) concentrations were found in RUPP compared with pregnant control rats (7.1±0.5 vs. 5.1±0.5 arbitrary units (A.U.), respectively; P<0.05) and 1400W decreased ROS production to 5.8±0.02 A.U. in RUPP treated rats, P<0.05. In addition, 1400W attenuated iNOS expression in RUPP rats (0.29±0.02 vs. 0.55±0.8 A.U. in RUPP treated and untreated rats, respectively; P<0.01) and had no effects on plasma TBARS and TRAP levels. Our results suggest that 1400w exerts antihypertensive effects in the RUPP model and suppresses ROS formation. Supported by FAPESP,Cnpq.

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 529: Atorvastatin and Sildenafil Reduce Vascular Remodeling and Oxidative Stress in 2K1C-hypertension

Atorvastatin (ATORVA) and sildenafil (SILD) exert beneficial effects on cardiovascular diseases through their pleiotropic effects. Hypertension-induced vascular hypertrophy is associated with oxidative stress and matrix metalloproteinase (MMP) up-regulation. We evaluated the effects of ATORVA and SILD on vascular changes induced by MMPs and on oxidative stress and MMP activity in 2 kidney-1 clip (2K1C) hypertension. Sham and 2K1C rats were 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±6, 156±2, and 138±4 mmHg, respectively, vs. 200±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). Aortas from 2K1C rats showed higher MMP-2 levels when compared with sham and all treatments attenuated 2K1C hypertension-induced increases in MMP-2 levels (both P<0.05). Increased gelatinolytic activity (20.6±0.9 vs. 13.9±1.2 A.U.; arbitrary units) co-localized with upregulated aortic MMP-2 expression (8.1±0.3 vs. 5.4±0.4 A.U.) in 2K1C vs. control rats. ATORVA, SILD, or both drugs lowered gelatinolytic activity to 14.6±0.5, 14.6±1.0 and 14.5±0.8 A.U. and lowered the aortic MMP-2 expression to 5.8±0.3, 5.9±0.5 and 5.5±0.5 A.U., respectively. However, these drugs had no in vitro effects on human recombinant MMP-2 activity (P>0.05). Hypertension induced oxidative stress assessed with dihydroethidium probe (7.9±1.2 vs. 16.5±1.5 A.U. in sham vs 2K1C), which was attenuated by ATORVA, SILD or both (9.9±0.3, 10.4±1.5 and 9.6±0.6 A.U., respectively). Plasma malondialdehyde levels paralleled dihydroethidium results. Treatment with ATORVA or SILD, or both, exert antihypertensive effects and prevents 2K1C hypertension-induced vascular remodeling and oxidative stress. These effects were associated with lower MMP-2 levels possibly resulting of antioxidants effects. Our results suggest that ATORVA and SILD may prevent the vascular alterations of hypertension.Supported by FAPESP, Cnpq.

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.

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.