l-Carnitine ameliorates the oxidative stress response to angiotensin II by modulating NADPH oxidase through a reduction in protein kinase c activity and NF-κB translocation to the nucleus.

l-Carnitine (LC) exerts beneficial effects in arterial hypertension due, in part, to its antioxidant capacity. We investigated the signalling pathways involved in the effect of LC on angiotensin II (Ang II)-induced NADPH oxidase activation in NRK-52E cells. Ang II increased the generation of superoxide anion from NADPH oxidase, as well as the amount of hydrogen peroxide and nitrotyrosine. Co-incubation with LC managed to prevent these alterations and also reverted the changes in NADPH oxidase expression triggered by Ang II. Cell signalling studies evidenced that LC did not modify Ang II-induced phosphorylation of Akt, p38 MAPK or ERK1/2. On the other hand, a significant decrease in PKC activity, and inhibition of nuclear factor kappa B (NF-kB) translocation, were attributable to LC incubation. In conclusion, LC counteracts the pro-oxidative response to Ang II by modulating NADPH oxidase enzyme via reducing the activity of PKC and the translocation of NF-kB to the nucleus.

Leptin Induces Oxidative Stress Through Activation of NADPH Oxidase in Renal Tubular Cells: Antioxidant Effect of L-Carnitine.

Leptin is a protein involved in the regulation of food intake and in the immune and inflammatory responses, among other functions. Evidences demonstrate that obesity is directly associated with high levels of leptin, suggesting that leptin may directly link obesity with the elevated cardiovascular and renal risk associated with increased body weight. Adverse effects of leptin include oxidative stress mediated by activation of NADPH oxidase. The aim of this study was to evaluate the effect of L-carnitine (LC) in rat renal epithelial cells (NRK-52E) exposed to leptin in order to generate a state of oxidative stress characteristic of obesity. Leptin increased superoxide anion (O2 (•) -) generation from NADPH oxidase (via PI3 K/Akt pathway), NOX2 expression and nitrotyrosine levels. On the other hand, NOX4 expression and hydrogen peroxide (H2 O2 ) levels diminished after leptin treatment. Furthermore, the expression of antioxidant enzymes, catalase, and superoxide dismutase, was altered by leptin, and an increase in the mRNA expression of pro-inflammatory factors was also found in leptin-treated cells. LC restored all changes induced by leptin to those levels found in untreated cells. In conclusion, stimulation of NRK-52E cells with leptin induced a state of oxidative stress and inflammation that could be reversed by preincubation with LC. Interestingly, LC induced an upregulation of NOX4 and restored the release of its product, hydrogen peroxide, which suggests a protective role of NOX4 against leptin-induced renal damage. J. Cell. Biochem. 117: 2281-2288, 2016. © 2016 Wiley Periodicals, Inc.

Inflammatory and fibrotic processes are involved in the cardiotoxic effect of sunitinib: Protective role of L-carnitine.

Sunitinib (Su) is currently approved for treatment of several malignances. However, along with the benefits of disease stabilization, cardiovascular toxicities have also been increasingly recognized. The aim of this study was to analyze which mechanisms are involved in the cardiotoxicity caused by Su, as well as to explore the potential cardioprotective effects of l-carnitine (LC). To this end, four groups of Wistar rats were used: (1) control; (2) rats treated with 400mg LC/kg/day; (3) rats treated with 25mg Su/kg/day; and (4) rats treated with LC+Su simultaneously. In addition, cultured rat cardiomyocytes were treated with an inhibitor of nuclear factor kappa B (NF-κB), in order to examine the role of this transcription factor in this process. An elevation in the myocardial expression of pro-inflammatory cytokines, together with an increase in the mRNA expression of NF-κB, was observed in Su-treated rats. These results were accompanied by an increase in the expression of pro-fibrotic factors, nitrotyrosine and NOX 2 subunit of NADPH oxidase; and by a decrease in that of collagen degradation factor. Higher blood pressure and heart rate levels were also found in Su-treated rats. All these alterations were inhibited by co-administration of LC. Furthermore, cardiotoxic effects of Su were blocked by NF-κB inhibition. Our results suggest that: (i) inflammatory and fibrotic processes are involved in the cardiac toxicity observed following treatment with Su; (ii) these processes might be mediated by the transcription factor NF-κB; (iii) LC exerts a protective effect against arterial hypertension, cardiac inflammation and fibrosis, which are all observed after Su treatment.

L-carnitine attenuates the development of kidney fibrosis in hypertensive rats by upregulating PPAR-γ.

BACKGROUND: The development of renal fibrosis is a consequence of arterial hypertension. L-carnitine plays an essential role in the ß-oxidation of fatty acids, and we have previously demonstrated hypotensive, antioxidant, and anti-inflammatory effects of L-carnitine in arterial hypertension. This work aims to analyze the effect of L-carnitine on renal fibrosis and to explore the participation of peroxisome-proliferator activated receptor (PPAR)-γ in this effect. METHODS: Four groups or rats were used: control, treated with L-carnitine, treated with L-NAME, and treated with L-carnitine + L-NAME. Cultured rat kidney cells were also used to examine the role of PPAR-γ in L-carnitine effect. RESULTS: An increase in the expression of collagen, transforming growth factor beta 1 (TGF-ß1), connective tissue growth factor (CTGF), Nox2, and Nox4 was found in the kidney of L-NAME-treated rats. Hypertensive rats presented with an expansion of renal fibrotic areas, which was also accompanied by overexpression of proinflammatory cytokines, interleukin (IL)-1ß, and IL-6. A reduction in the expression of PPAR-γ and in that of anti-inflammatory IL-10 was found in the kidney of these rats. Simultaneous treatment with L-carnitine attenuated the renal fibrosis (which correlated with a reduction of plasma TGF-ß1 levels) and the pro-oxidative and proinflammatory status reported in L-NAME groups, with a concomitant increase in the expression of PPAR-γ. Furthermore, the antifibrotic effect of L-carnitine could be blocked by PPAR-γ inhibition. CONCLUSIONS: This study confirms the efficacy of L-carnitine against hypertension-associated renal fibrosis from in vivo and in vitro studies and suggests that the L-carnitine effect occurs in a PPAR-γ-dependent manner.

L-Carnitine protects against arterial hypertension-related cardiac fibrosis through modulation of PPAR-γ expression.

Cardiac fibrosis is a pathogenic factor in a variety of cardiovascular diseases and is characterized by an abnormal accumulation of extracellular matrix protein that leads to cardiac dysfunction. l-Carnitine (LC) plays an essential role in the ß-oxidation of long-chain fatty acids in lipid metabolism. We have previously demonstrated the beneficial effects of LC in hypertensive rats. The aim of this study was to analyze the effect of LC on arterial hypertension-associated cardiac fibrosis and to explore the mechanisms of LC action. To this end, four groups of rats were used: Wistar (control), rats treated with 400mg/kg/day of LC, rats treated with 25mg/kg/day of l-NAME (to induce hypertension), and rats treated with LC+l-NAME simultaneously. We found an elevation in the myocardial expression of profibrotic factors (TGF-ß1 and CTGF), types I and III of collagen, and NADPH oxidase subunits (NOX2 and NOX4), in hypertensive rats when compared with normotensive ones. In addition, an increase in myocardial fibrosis was also found in the l-NAME group. These results were accompanied by a down-regulation of PPAR-γ in the heart of hypertensive animals. When hypertensive rats were treated with LC, all these alterations were reversed. Moreover, a significant negative correlation was observed between myocardial interstitial fibrosis and mRNA expression of PPAR-γ. In conclusion, the reduction of cardiac fibrosis and the down-regulation of NOX2, NOX4, TGF-ß1 and CTGF induced by LC might be, at least in part, mediated by an upregulation of PPAR-γ, which leads to a reduction on hypertension-related cardiac fibrosis.

Systemic antioxidant properties of L-carnitine in two different models of arterial hypertension

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In spite of a wide range of drugs being available in the market, treatment of arterial hypertension still remains a challenge, and new therapeutic strategies could be developed in order to improve the rate of success in controlling this disease. Since oxidative stress has gained importance in the last few years as one of the mechanisms involved in the origin and development of hypertension, and considering that L-carnitine (LC) is a useful compound in different pathologies characterized by increased oxidative status, the aim of the present study was to investigate the systemic antioxidant effect of LC and its correlation to blood pressure in two experimental models of hypertension: (1) spontaneously hypertensive rats (SHR) and (2) rats with hypertension induced by Nù-nitro-L-argininemethyl ester (L-NAME). Treatment with captopril was also performed in SHR in order to compare the antioxidant and antihypertensive effects of LC and captopril. The antioxidant defense capacity, in terms of antioxidant enzyme activity, glutathione system availability and plasma total antioxidant capacity, was measured in both animal models with or without an oral, chronic treatment with LC. All the antioxidant parameters studied were diminished in SHR and in L-NAME-treated animals, an alteration that was in general reversed after treatments with LC and captopril. In addition, LC produced a significant but not complete reduction of systolic and diastolic blood pressure levels in these two models of hypertension, whereas captopril was able to normalize blood pressure. Both LC and captopril prevented the reduction in nitric oxide (NO) levels observed in hypertensive animals. This suggests a decrease in the systemic oxidative stress and a higher availability of NO induced by LC in a similar way to captopril’s effects, which could be relevant in the management of arterial hypertension eventually (AU)

Captopril reduces cardiac inflammatory markers in spontaneously hypertensive rats by inactivation of NF-kB.

BACKGROUND: Captopril is an angiotensin-converting enzyme (ACE) inhibitor widely used in the treatment of arterial hypertension and cardiovascular diseases. Our objective was to study whether captopril is able to attenuate the cardiac inflammatory process associated with arterial hypertension. METHODS: Left ventricle mRNA expression and plasma levels of pro-inflammatory (interleukin-1beta (IL-1beta) and IL-6) and anti-inflammatory (IL-10) cytokines, were measured in spontaneously hypertensive rats (SHR) and their control normotensive, Wistar-Kyoto (WKY) rats, with or without a 12-week treatment with captopril (80 mg/Kg/day; n = six animals per group). To understand the mechanisms involved in the effect of captopril, mRNA expression of ACE, angiotensin II type I receptor (AT1R) and p22phox (a subunit of NADPH oxidase), as well as NF-kappaB activation and expression, were measured in the left ventricle of these animals. RESULTS: In SHR, the observed increases in blood pressures, heart rate, left ventricle relative weight, plasma levels and cardiac mRNA expression of IL-1beta and IL-6, as well as the reductions in the plasma levels and in the cardiac mRNA expression of IL-10, were reversed after the treatment with captopril. Moreover, the mRNA expressions of ACE, AT1R and p22phox, which were enhanced in the left ventricle of SHR, were reduced to normal values after captopril treatment. Finally, SHR presented an elevated cardiac mRNA expression and activation of the transcription nuclear factor, NF-kappaB, accompanied by a reduced expression of its inhibitor, IkappaB; captopril administration corrected the observed changes in all these parameters. CONCLUSION: These findings show that captopril decreases the inflammation process in the left ventricle of hypertensive rats and suggest that NF-kappaB-driven inflammatory reactivity might be responsible for this effect through an inactivation of NF-kappaB-dependent pro-inflammatory factors.

Systemic antioxidant properties of L-carnitine in two different models of arterial hypertension.

In spite of a wide range of drugs being available in the market, treatment of arterial hypertension still remains a challenge, and new therapeutic strategies could be developed in order to improve the rate of success in controlling this disease. Since oxidative stress has gained importance in the last few years as one of the mechanisms involved in the origin and development of hypertension, and considering that L-carnitine (LC) is a useful compound in different pathologies characterized by increased oxidative status, the aim of the present study was to investigate the systemic antioxidant effect of LC and its correlation to blood pressure in two experimental models of hypertension: (1) spontaneously hypertensive rats (SHR) and (2) rats with hypertension induced by N(omega)-nitro-L-arginine methyl ester (L-NAME). Treatment with captopril was also performed in SHR in order to compare the antioxidant and antihypertensive effects of LC and captopril. The antioxidant defense capacity, in terms of antioxidant enzyme activity, glutathione system availability and plasma total antioxidant capacity, was measured in both animal models with or without an oral, chronic treatment with LC. All the antioxidant parameters studied were diminished in SHR and in L-NAME-treated animals, an alteration that was in general reversed after treatments with LC and captopril. In addition, LC produced a significant but not complete reduction of systolic and diastolic blood pressure levels in these two models of hypertension, whereas captopril was able to normalize blood pressure. Both LC and captopril prevented the reduction in nitric oxide (NO) levels observed in hypertensive animals. This suggests a decrease in the systemic oxidative stress and a higher availability of NO induced by LC in a similar way to captopril's effects, which could be relevant in the management of arterial hypertension eventually.

The therapeutic prospects of using L-carnitine to manage hypertension-related organ damage.

Subclinical organ damage is a very important aspect when assessing total cardiovascular risk in hypertensive subjects. Therapeutic strategies in those patients should consider treatment of hypertension-related cardiovascular and renal damage in addition to achieving the recommended blood pressure targets. l-carnitine (LC) is a naturally occurring compound that is administered exogenously for treatment of patients that are deficient in carnitine. The currently available data do not support a preferential role of LC as an antihypertensive agent compared to other available drugs. However, its ability to simultaneously modulate several targets and/or pathways provides antioxidant and anti-inflammatory properties. These additional properties might justify the therapeutic use of LC as a protective agent against cardiovascular and renal remodelling in arterial hypertension.

Comparative effects of captopril and l-carnitine on blood pressure and antioxidant enzyme gene expression in the heart of spontaneously hypertensive rats.

It has been shown that oxidative stress is involved in the pathogenesis of arterial hypertension. The aim of this work was to study and compare the molecular mechanisms of the antioxidant properties of l-carnitine and captopril in spontaneously hypertensive rats (SHR). Antioxidant enzyme activity/regulation (glutathione peroxidase, glutathione reductase and superoxide dismutase) was measured in the erythrocytes and hearts of SHR. The molecular expression of endothelial nitric oxide synthase (eNOS), NADPH oxidase, angiotensin converting enzyme (ACE), angiotensin II type I receptor (AT(1) receptor) and NF-kappaB/IkappaB system was also measured in the hearts of these animals. Both l-carnitine and captopril augmented the antioxidant defense capacity in SHRs. This effect was mediated by an upregulation of antioxidant enzymes, an increase in the plasma total antioxidant capacity and a reduction of lipid peroxidation and superoxide anion production in the heart. The administration of both compounds to hypertensive animals also produced an upregulation of eNOS and a normalization of ACE, angiotensin AT(1) receptor, and the NF-kappaB/IkappaB system expression. In addition, captopril reduced the arterial blood pressure and the relative heart weights back to control values, whereas l-carnitine caused only a partial reduction of blood pressure values and did not alter the cardiac hypertrophy found in SHRs. In conclusion, we have found that l-carnitine and captopril have a similar antioxidant effect in the hearts of hypertensive rats. The molecular regulation of antioxidant enzymes through an inhibition of the renin-angiotensin system and a modulation of the NF-kappaB/IkappaB system seems to be responsible for this antioxidant effect.

The role of inflammatory markers in the cardioprotective effect of L-carnitine in L-NAME-induced hypertension.

BACKGROUND: The mechanism(s) underlying the effects of L-carnitine (beta-hydroxy-gamma-N-trimethylammonium-butyrate; LC) in cardiovascular diseases are not well clarified. Previous studies have demonstrated that oxidative stress and inflammation contribute to arterial hypertension, and antioxidant and/or anti-inflammatory therapies have been proposed. We hypothesized that LC might attenuate the hypertensive status through an inhibition of inflammation process. METHODS: Heart mRNA expression and plasma levels of inflammatory markers, interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-alpha), were measured in rats that were made hypertensive with N(omega)-nitro-L-arginine methyl ester (L-NAME) and subjected to a simultaneous administration of LC. To clarify the role of the renin-angiotensin system (RAS) in this effect of LC, the activity and expression of angiotensin I-converting enzyme (ACE) as well as the expression of angiotensin II type I receptor (AT1R) in the heart were also determined. RESULTS: LC produced a significant, but not complete, reduction of blood pressure in L-NAME-treated rats. Plasma levels and heart expression of IL-1 beta, IL-6, and TNF-alpha showed an increase in the L-NAME group, which was reversed by LC treatment. The plasma ACE activity was not modified between normotensive and hypertensive rats although LC treatment produced a reduction of these values in the latter. Finally, protein and mRNA expression of ACE and AT1R was enhanced in the heart of L-NAME-treated animals, and LC reversed these values. CONCLUSIONS: The chronic administration of LC reduces blood pressure and attenuates the inflammatory process associated with arterial hypertension. LC might produce a partial inactivation in the RAS resulting in a reduction in the production and effects of angiotensin II.

L-carnitine attenuates oxidative stress in hypertensive rats.

The present study aimed to investigate whether l-carnitine (LC) protects the vascular endothelium and tissues against oxidative damage in hypertension. Antioxidant enzyme activities, glutathione and lipid peroxidation were measured in the liver and heart of spontaneously hypertensive rats (SHR) and Wistar-Kyoto (WKY) rats. Nitrite and nitrate levels and total antioxidant status (TAS) were evaluated in plasma, and the expression of endothelial nitric oxide synthase (eNOS) and p22phox subunit of NAD(P)H oxidase was determined in aorta. Glutathione peroxidase activity was lower in SHR than in WKY rats, and LC increased this activity in SHR up to values close to those observed in normotensive animals. Glutathione reductase and catalase activities, which were higher in SHR, tended to increase after LC treatment. No differences were found in the activity of superoxide dismutase among any animal group. The ratio between reduced and oxidized glutathione and the levels of lipid peroxidation were respectively decreased and increased in hypertensive rats, and both parameters were normalized after the treatment. Similarly, LC was able to reverse the reduced plasma nitrite and nitrate levels and TAS observed in SHR. We found no alterations in the expression of aortic eNOS among any group; however, p22phox mRNA levels showed an increase in SHR that was reversed by LC. In conclusion, chronic administration of LC leads to an increase in hepatic and cardiac antioxidant defense and a reduction in the systemic oxidative process in SHR. Therefore, LC might increase NO availability in SHR aorta by a reduction in superoxide anion production.