Antiatherogenic effects of S-nitroso-N-acetylcysteine in hypercholesterolemic LDL receptor knockout mice

N-Acetylcysteine and Atherosclerosis: Promises and Challenges

Atherosclerosis remains a leading cause of cardiovascular diseases. Although the mechanism for atherosclerosis is complex and has not been fully understood, inflammation and oxidative stress play a critical role in the development and progression of atherosclerosis. N-acetylcysteine (NAC) has been used as a mucolytic agent and an antidote for acetaminophen overdose with a well-established safety profile. NAC has antioxidant and anti-inflammatory effects through multiple mechanisms, including an increase in the intracellular glutathione level and an attenuation of the nuclear factor kappa-B mediated production of inflammatory cytokines like tumor necrosis factor-alpha and interleukins. Numerous animal studies have demonstrated that NAC significantly decreases the development and progression of atherosclerosis. However, the data on the outcomes of clinical studies in patients with atherosclerosis have been limited and inconsistent. The purpose of this review is to summarize the data on the effect of NAC on atherosclerosis from both pre-clinical and clinical studies and discuss the potential mechanisms of action of NAC on atherosclerosis, as well as challenges in the field.

N-acetylcysteine ameliorates erectile dysfunction in rats with hyperlipidemia by inhibiting oxidative stress and corpus cavernosum smooth muscle cells phenotypic modulation

Hyperlipidemia is a major risk factor for erectile dysfunction (ED). Oxidative stress and phenotypic modulation of corpus cavernosum smooth muscle cells (CCSMCs) are the key pathological factors of ED. N-acetylcysteine (NAC) can inhibit oxidative stress; however, whether NAC can alleviate pathological variations in the corpus cavernosum and promote erectile function recovery in hyperlipidemic rats remains unclear. A hyperlipidemia model was established using 27 eight-week-old male Sprague-Dawley (SD) rats fed a high-fat and high-cholesterol diet (hyperlipidemic rats, HR). In addition, 9 male SD rats were fed a normal diet to serve as controls (NC). HR rats were divided into three groups: HR, HR+normal saline (NS), and HR+NAC (n = 9 for each group; NS or NAC intraperitoneal injections were administered daily for 16 weeks). Subsequently, the lipid profiles, erectile function, oxidative stress, phenotypic modulation markers of CCSMCs, and tissue histology were analyzed. The experimental results revealed that erectile function was significantly impaired in the HR and HR + NS groups, but enhanced in the HR + NAC group. Abnormal lipid levels, over-activated oxidative stress, and multi-organ lesions observed in the HR and HR + NS groups were improved in the HR + NAC group. Moreover, the HR group showed significant phenotypic modulation of CCSMCs, which was also inhibited by NAC treatment. This report focuses on the therapeutic effect of NAC in restoring erectile function using a hyperlipidemic rat model by preventing CCSMC phenotypic modulation and attenuating oxidative stress.

Ethereal Extract of Pepper: Preventing Atherosclerosis and Left Ventricle Remodeling in LDL Receptor Knockout Mice

Cardiovascular diseases are the leading cause of mortality and morbidity worldwide. In this study we compared the effects of oral treatment with red pepper ethereal extracts or simvastatin on dyslipidemia, left ventricle remodeling, and atherosclerotic lesions of low-density lipoprotein (LDL) receptor knockout mice (LDLr^-/-) fed a hyperlipidic diet. Forty 3-month-old male mice were distributed into four groups: control (C; animals fed a standard diet), HL (ani-mals fed a hyperlipidic diet), and HL+P or HL+S (animals fed a hyperlipidic diet plus red pepper ethereal extracts or simvastatin, respectively). After 60 days, treatment with both red pepper ethereal extracts and simvastatin prevented dyslipidemia, atherosclerotic lesion progression, and left ventricle hypertrophy. Our results suggest a cardioprotective effect of red pepper ethereal extracts in LDLr^-/- mice, which is comparable to the well-known effects of simvastatin.

Phenotypic Modulation of Macrophages and Vascular Smooth Muscle Cells in Atherosclerosis-Nitro-Redox Interconnections

Monocytes/macrophages and vascular smooth muscle cells (vSMCs) are the main cell types implicated in atherosclerosis development, and unlike other mature cell types, both retain a remarkable plasticity. In mature vessels, differentiated vSMCs control the vascular tone and the blood pressure. In response to vascular injury and modifications of the local environment (inflammation, oxidative stress), vSMCs switch from a contractile to a secretory phenotype and also display macrophagic markers expression and a macrophagic behaviour. Endothelial dysfunction promotes adhesion to the endothelium of monocytes, which infiltrate the sub-endothelium and differentiate into macrophages. The latter become polarised into M1 (pro-inflammatory), M2 (anti-inflammatory) or Mox macrophages (oxidative stress phenotype). Both monocyte-derived macrophages and macrophage-like vSMCs are able to internalise and accumulate oxLDL, leading to formation of “foam cells” within atherosclerotic plaques. Variations in the levels of nitric oxide (NO) can affect several of the molecular pathways implicated in the described phenomena. Elucidation of the underlying mechanisms could help to identify novel specific therapeutic targets, but to date much remains to be explored. The present article is an overview of the different factors and signalling pathways implicated in plaque formation and of the effects of NO on the molecular steps of the phenotypic switch of macrophages and vSMCs.

Grape juice attenuates left ventricular hypertrophy in dyslipidemic mice

OBJECTIVE

We evaluated the effects of grape juice (Vitis labrusca L.) on dyslipidemia, resistance to insulin, and left ventricular hypertrophy (LVH) in mice homozygous for the absence of the LDL receptor gene (LDLr -/-) under a hyperlipidemic diet.

METHODOLOGY

We divided 30 male mice (3 months old) into three groups (n = 10); the HL group was fed a high-fat diet, the HLU group received a high-fat diet and 2 g/kg/day of grape juice, and the HLS group was fed a high-fat diet and simvastatin (20 mg/kg/day). We assessed the blood pressure profile of the mice. We also determined the levels of C-reactive protein (CRP) and lipid profile, glycemic and insulinemic profiles, and calculated the HOMA-IR. Cardiomyocyte hypertrophy, interstitial collagen deposit, and the expression of CD40 ligand (CD40L) and metalloproteinases 2 and 9 were assessed immunohistologically.

RESULTS

After 60 days, the mice treated with grape juice showed similar results as those of the group treated with simvastatin. The use of grape fruit attenuated dyslipidemia and insulin resistance and significantly increased the levels of high cholesterol density lipoproteins (HDLc). The antioxidant potential of phenolic compounds associated with the increase in HDLc levels in the mice of the HLU group prevented the development of LVH and arterial hypertension since it inhibited the inflammatory response induced by the CD40 pathway and its ligand CD40L. Consequently, there was a lower expression of MMP-2 and MMP-9 and lower serum levels of CRP.

CONCLUSION

Grape juice has a hypolipidemic and cardiac protective potential, presenting a similar effect as that of simvastatin through a direct antioxidant action of phenolic compounds, or indirectly, via antioxidant action and anti-inflammatory activity of the HDLc. These results suggest that grape juice is a functional food possessing a high potential to prevent cardiovascular diseases.

Effect of Camellia sinensis teas on left ventricular hypertrophy and insulin resistance in dyslipidemic mice

The control of dyslipidemia using plants is an important subject of studies since it has numerous benefits in cardiovascular protection. The objective of this study was to evaluate the effect of three Camellia sinensis L. teas (green, red, and white) on left ventricular hypertrophy and insulin resistance in low-density lipoprotein receptor knockout (LDLr-/-) mice fed a high-fat diet. The LDLr-/- mice were divided into four experimental groups: Group C: standard feed; Group CT: standard feed and three teas, Group HL: high-fat feed; HLT Group: high-fat feed and three teas. The three types of tea (green, red, and white) originated from different processing of the Camellia sinensis L. plant, and were administered associated once a day at a dose of 25 mg/kg by gavage for 60 days. The teas partially prevented hyperlipidemia, the decrease of the serum levels of high-density lipoproteins (HDL), insulin resistance, and increased C-reactive protein (CRP) levels, and completely prevented left ventricular hypertrophy in LDLr -/- mice of the HLT group. In conclusion, the three Camellia sinensis L. teas used to control genetic dyslipidemia associated with a high-fat diet can be used as an auxiliary treatment associated with the control of lipid intake, thus promoting cardiac protection against hyperlipidemia.

Long-term decomposition of aqueous S-nitrosoglutathione and S-nitroso-N-acetylcysteine: Influence of concentration, temperature, pH and light

Primary S-nitrosothiols (RSNOs) have received significant attention for their ability to modulate NO signaling in many physiological and pathophysiological processes. Such actions and their potential pharmaceutical uses demand a better knowledge of their stability in aqueous solutions. Herein, we investigated the effects of concentration, temperature, pH, room light and metal ions on the long-term kinetic behavior of two representative primary RSNOs, S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylcysteine (SNAC). The thermal decomposition of GSNO and SNAC were shown to be affected by the auto-catalytic action of the thiyl radicals. At 25 °C in the dark and protected from the catalytic action of metal ions, GSNO and SNAC solutions 1 mM showed half-lives of 49 and 76 days, and apparent activation energies of 84 ± 14 and 90 ± 6 kJ mol^-1, respectively. Both GSNO and SNAC exhibited increased stability in the pH range 5-7. At high pH the decomposition pathway of GSNO involves the formation of an intermediate (GS-NO₂^2-), which decomposes generating GSH and nitrite. GSNO solutions displayed lower sensitivity to the catalytic action of metal ions than SNAC and the exposure to room light led to a 5-fold increase in the initial rates of decomposition of both RSNOs. In all comparisons, SNAC solutions showed higher stability than GSNO solutions. These findings provide strategic information about the stability of GSNO and SNAC and may open new perspectives for their use as experimental or therapeutic NO donors.

Intestinal absorption of S-nitrosothiols: Permeability and transport mechanisms

S-Nitrosothiols, a class of NO donors, demonstrate potential benefits for cardiovascular diseases. Drugs for such chronic diseases require long term administration preferentially through the oral route. However, the absorption of S-nitrosothiols by the intestine, which is the first limiting barrier for their vascular bioavailability, is rarely evaluated. Using an in vitro model of intestinal barrier, based on human cells, the present work aimed at elucidating the mechanisms of intestinal transport (passive or active, paracellular or transcellular pathway) and at predicting the absorption site of three S-nitrosothiols: S-nitrosoglutathione (GSNO), S-nitroso-N-acetyl-l-cysteine (NACNO) and S-nitroso-N-acetyl-d-penicillamine (SNAP). These S-nitrosothiols include different skeletons carrying the nitroso group, which confer different physico-chemical characteristics and biological activities (antioxidant and anti-inflammatory). According to the values of apparent permeability coefficient, the three S-nitrosothiols belong to the medium class of permeability. The evaluation of the bidirectional apparent permeability demonstrated a passive diffusion of the three S-nitrosothiols. GSNO and NACNO preferentially cross the intestinal barrier though the transcellular pathway, while SNAP followed both the trans- and paracellular pathways. Finally, the permeability of NACNO was favoured at pH 6.4, which is close to the pH of the jejunal part of the intestine. Through this study, we determined the absorption mechanisms of S-nitrosothiols and postulated that they can be administrated through the oral route.

Soy milk versus simvastatin for preventing atherosclerosis and left ventricle remodeling in LDL receptor knockout mice

Functional food intake has been highlighted as a strategy for the prevention of cardiovascular diseases by reducing risk factors. In this study, we compared the effects of oral treatment with soy milk and simvastatin on dyslipidemia, left ventricle remodeling and atherosclerotic lesion of LDL receptor knockout mice (LDLr-/-) fed a hyperlipidic diet. Forty 3-month old male LDLr-/- mice were distributed into four groups: control group (C), in which animals received standard diet; HL group, in which animals were fed a hyperlipidic diet; HL+SM or HL+S groups, in which animals were submitted to a hyperlipidic diet plus soy milk or simvastatin, respectively. After 60 days, both soy milk and simvastatin treatment prevented dyslipidemia, atherosclerotic lesion progression and left ventricle hypertrophy in LDLr-/- mice. These beneficial effects of soy milk and simvastatin were associated with reduced oxidative stress and inflammatory state in the heart and aorta caused by the hyperlipidic diet. Treatment with soy milk was more effective in preventing HDLc reduction and triacylglycerol and VLDLc increase. On the other hand, simvastatin was more effective in preventing an increase in total cholesterol, LDLc and superoxide production in aorta, as well as CD40L both in aorta and left ventricle of LDLr-/-. In conclusion, our results suggest a cardioprotective effect of soy milk in LDLr-/- mice comparable to the well-known effects of simvastatin.

Disruption of steroidogenesis after dimethoate exposure and efficacy of N-acetylcysteine in rats: an old drug with new approaches

Organophosphates (OPs) like dimethoate (DMT), are pesticides used worldwide, which can affect both animals and human. Whereas their toxicity is due to acetylcholinesterase inhibition, their secondary toxic effects have been related to free oxygen radical biosynthesis. The present study was designed to investigate the reprotoxic effects of DMT and the protective role of N-acetylcysteine (NAC) in male rat. DMT (20 mg/ kg/body weight) was administered daily to rats via gavage in corn oil and NAC (2 g/l) was added to drinking water for 30 days. Rats were sacrificed on the 30th day, 2 h after the last administration. Markers of testis injury (steroidogenesis impairment) and oxidative stress (lipid peroxidation, reduced glutathione, and antioxidant status) were assessed. In DMT-exposed rats, the serum level of testosterone was decreased. Further, a significant increase in lipid peroxidation level and a significant decrease in the activities of antioxidant enzymes were observed in the testis of rats during DMT intoxication. Real-time PCR (RT-PCR) analysis demonstrated a decrease in messenger RNA (mRNA) levels for testicular steroidogenic acute regulatory StAR protein, cytochrome P450scc, 3β-hydroxysteroid dehydrogenase (3β-HSD), and 17β hydroxysteroid dehydrogenase (17β-HSD) in the testis after DMT exposure. No significant changes in the oxidative stress status and selected reproductive variables were observed on CTN group, whereas NAC restored the oxidative stress and the steroidogenesis on NAC group. Dimethoate induces reprotoxicity and oxidative stress. N-acetylcysteine showed therapeutic recovery effects against dimethoate toxicity.

A minireview on N-acetylcysteine: An old drug with new approaches

N-acetylcysteine (NAC), a cysteine pro-drug and glutathione precursor has been used in therapeutic practices for several decades, as a mucolytic agent and for the treatment of numerous disorders including paracetamol intoxication. There is a growing interest concerning the beneficial effects of NAC against the early stages of toxicity-induced by pesticides. Nevertheless, the mechanisms underlying the therapeutic and clinical applications of NAC are not fully understood. In this review we aimed to focus on the protective effects of NAC against oxidative stress caused by pesticide in many organs. The possible mechanisms of action may be associated to its antioxidant properties. The anti-oxidative activity of NAC has been attributed to the fast reaction with free radicals as well as the restitution of reduced glutathione (GSH).

Propolis and swimming in the prevention of atherogenesis and left ventricular hypertrophy in hypercholesterolemic mice

AIMS

The present study verified the effect of propolis alone and its association with swimming in dyslipidemia, left ventricular hypertrophy and atherogenesis of hypercholesterolemic mice.

METHODS AND RESULTS

The experiments were performed in LDLr-/- mice, fed with high fat diet for 75 days, and were divided into four experimental groups (n=10): HL, sedentary, subjected to aquatic stress (5 min per day, 5 times per week); NAT submitted to a swimming protocol (1 hour per day, 5 times per week) from the 16th day of the experiment; PRO, sedentary, submitted to aquatic stress and which received oral propolis extract (70 uL/animal/day) from the 16th day of the experiment; HL+NAT+PRO, submitted to swimming and which received propolis as described above. After 75 days, blood was collected for analysis of serum lipids. The ratio between the ventricular weight (mg) and the animal weight (g) was calculated. Histological sections of the heart and aorta were processed immunohistochemically with anti-CD40L antibodies to evaluate the inflammatory process; stained with hematoxylin/eosin and picrosirius red to assess morphological and morphometric alterations. The HL animals showed severe dyslipidemia, atherogenesis and left ventricular hypertrophy, associated with a decrease in serum HDLc levels and subsequent development of cardiovascular inflammatory process, characterized by increased expression of CD40L in the left ventricle and aorta. Swimming and propolis alone and\or associated prevented the LVH, atherogenesis and arterial and ventricular inflammation, decreasing the CD40L expression and increasing the HDLc plasmatic levels.

CONCLUSION

Propolis alone or associated with a regular physical activity is beneficial in cardiovascular protection through anti-inflammatory action.

Impact of N-acetylcysteine and sesame oil on lipid metabolism and hypothalamic-pituitary-adrenal axis homeostasis in middle-aged hypercholesterolemic mice

Hyperlipidemia and stress are important factors affecting cardiovascular health in middle-aged individuals. We investigated the effects of N-acetylcysteine (NAC) and sesame oil on the lipidemic status, liver architecture and the hypothalamic-pituitary-adrenal (HPA) axis of middle-aged mice fed a cholesterol-enriched diet. We randomized 36 middle-aged C57bl/6 mice into 6 groups: a control group, a cholesterol/cholic acid diet group, a cholesterol/cholic acid diet group with NAC supplementation, a cholesterol/cholic acid diet enriched with 10% sesame oil and two groups receiving a control diet enriched with NAC or sesame oil. NAC administration prevented the onset of the disturbed lipid profile, exhibiting decreased lipid peroxidation and alkaline phosphatase (ALP) levels, restored nitric oxide bioavailability and reduced hepatic damage, compared to non-supplemented groups. High-cholesterol feeding resulted in increased hypothalamic glucocorticoid receptors (GR) levels, while NAC supplementation prevented this effect. NAC supplementation presented significant antioxidant capacity by means of preventing serum lipid status alterations, hepatic damage, and HPA axis disturbance due to high-cholesterol feeding in middle-aged mice. These findings suggest a beneficial preventive action of plant-derived antioxidants, such as NAC, on lipid metabolism and on the HPA axis.

N-Acetylcysteine Ameliorates Experimental Autoimmune Myocarditis in Rats via Nitric Oxide

BACKGROUND

Oxidative stress may play an important role in the development of myocarditis. We investigated the effects of N-acetylcysteine (NAC), a potent antioxidant, on experimental autoimmune myocarditis (EAM) in rats.

METHODS AND RESULTS

A rat model of porcine myosin-induced EAM was used. After the immunization with myosin, NAC (20 mg/kg/d) or saline was injected intraperitoneally on days 1 to 21. Additional myosin-immunized rats treated with NAC were orally given 25 mg/kg/d of N(G)-nitro-l-arginine methylester (l-NAME), an inhibitor of nitric oxide (NO) synthase, and N(G)-nitro-d-arginine methylester (d-NAME), an inactive enantiomer. The NAC treatment improved cardiac pathology associated with reduced superoxide production. In the EAM rats treated with NAC associated with oral l-NAME, but not with oral d-NAME, the severity of myocarditis was not reduced. Expression of intercellular adhesion molecule 1 was reduced by NAC treatment. Myocardial c-kit(+) cells were demonstrated only in the NAC-treated group. Hemodynamic study showed that the increased left ventricular mass produced by myocardial inflammation tended to be reduced by NAC treatment.

CONCLUSION

Treatment with NAC ameliorated myocardial injury via NO system in a rat model of myocarditis.

Cardioprotective effects of a proanthocyanidin-rich fraction from Croton celtidifolius Baill: focus on atherosclerosis

Proanthocyanidins are the most abundant polyphenols in human diets. Epidemiological studies have pointed to proanthocyanidins as promising molecules that could prevent the development of several coronary syndromes by inhibiting the atherogenic process. The present study was designed to investigate the antiatherogenic effects of a proanthocyanidin-rich fraction (PRF) obtained from Croton celtidifolius Baill (Euphorbiaceae) barks. In isolated human LDL, PRF caused a concentration-dependent inhibition of Cu2+-induced oxidative modifications, evidenced by the increasing of the lag phase of lipid peroxidation and decreasing in the oxidation rate (Vmax), moreover, the protein moieties from LDL were protected against Cu2+-induced oxidation. In human umbilical vein endothelial cells (HUVECs), PRF reduced the ROS production stimulated by oxidized LDL. Herein, we demonstrate that oral treatment with PRF improved endothelium-dependent vasorelaxation in hypercholesterolemic LDL receptor knockout mice (LDLr-/-), however, the fraction did not modify plasma lipids and atherosclerotic lesion size in this experimental model. Finally, our results showed for the first time that PRF prevent isolated LDL oxidation, decrease oxidative stress in endothelial cells and improve endothelial function in mice.

Effect of hyperlipidemia on femoral biomechanics and morphology in low-density lipoprotein receptor gene knockout mice

The objective of this study was to evaluate the effect of hyperlipidemia on the biomechanical and morphological properties of the femur of low-density lipoprotein receptor gene knockout mice (LDLr-/-) mice. Ten wild-type mice (C57BL6) and 10 LDLr-/- mice generated on a C57BL6 background were used. Male 3-month-old animals were divided into four groups (n = 5): group W (wild type) and group L (LDLr-/-) receiving low-fat commercial ration, and group WH (wild type) and group LH (LDLr-/-) receiving a high-fat diet. After 60 days, blood samples were collected for laboratory analysis of calcium, triglycerides, and cholesterol. The femur was excised for mechanical testing and morphometric analysis. LDLr-/- mice receiving the high-fat diet presented more marked alterations in the mechanical and morphological properties of femoral cortical and trabecular bone. Changes in the plasma levels of calcium, triglycerides, cholesterol, and fractions were also more pronounced in this group. The present results demonstrate that hyperlipidemia causes alterations in the structure and mechanical properties of the femur of LDLr-/- mice. These effects were more pronounced when associated with a high-fat diet.

A nanoparticle delivery vehicle for S-nitroso-N-acetyl cysteine: sustained vascular response

Interest in the development of nitric oxide (NO) based therapeutics has grown exponentially due to its well elucidated and established biological functions. In line with this surge, S-nitroso thiol (RSNO) therapeutics are also receiving more attention in recent years both as potential stable sources of NO as well as for their ability to serve as S-nitrosating agents; S-nitrosation of protein thiols is implicated in many physiological processes. We describe two hydrogel based RSNO containing nanoparticle platforms. In one platform the SNO groups are covalently attached to the particles (SNO-np) and the other contains S-nitroso-N-acetyl cysteine encapsulated within the particles (NAC-SNO-np). Both platforms function as vehicles for sustained activity as trans-S-nitrosating agents. NAC-SNO-np exhibited higher efficiency for generating GSNO from GSH and maintained higher levels of GSNO concentration for longer time (24 h) as compared to SNO-np as well as a previously characterized nitric oxide releasing platform, NO-np (nitric oxide releasing nanoparticles). In vivo, intravenous infusion of the NAC-SNO-np and NO-np resulted in sustained decreases in mean arterial pressure, though NAC-SNO-np induced longer vasodilatory effects as compared to the NO-np. Serum chemistries following infusion demonstrated no toxicity in both treatment groups. Together, these data suggest that the NAC-SNO-np represents a novel means to both study the biologic effects of nitrosothiols and effectively capitalize on its therapeutic potential.

Nitric oxide enhances the anti-inflammatory and anti-atherogenic activity of atorvastatin in a mouse model of accelerated atherosclerosis

AIMS

The aim of the present study was to assess whether the addition of a nitric oxide (NO)-donating moiety to atorvastatin enhances anti-inflammatory and anti-atherogenic effects in an animal model of endothelial dysfunction, systemic peroxidation and inflammation, and accelerated atherosclerosis.

METHODS AND RESULTS

Low-density lipoprotein receptor (LDLR)(-/-) mice kept on a high-fat diet (HFD) for 16 weeks underwent photochemical injury to the femoral artery with the local production of oxygen radicals. HFD markedly enhanced cholesterol, inflammatory biomarkers in plasma and in the femoral arterial wall, and atherosclerotic lesions in the aortic arch; inflammation and atherosclerosis were further increased by photochemically generated oxygen radicals. Treatment with the NO-donating atorvastatin NCX 6560 (11.7 mg/kg) was significantly more effective than atorvastatin (10 mg/kg) in reducing the following parameters: lipid-rich lesions in the aortic arch (surface covered: atorvastatin = 24 ± 5%; NCX 6560 = 14.7 ± 3.9%; P< 0.05); the production of radical oxygen species in the aorta (dichlorofluorescein fluorescence intensity per milligram of protein: atorvastatin = 2419 ± 136.7; NCX 6560 = 1766 ± 161.2; P< 0.05); femoral artery intima/media thickness (atorvastatin = 1.2 ± 0.11; NCX 6560 = 0.3 ± 0.14; P< 0.05); circulating interleukin-6 (atorvastatin = 34.3 ± 6.8 pg/mL; NCX 6560 = 17.7 ± 14.4 pg/mL; P< 0.05); and matrix metalloproteinase 2 in the arterial wall (atorvastatin = 55.2 ± 1.9 ng/µg of proteins; NCX 6560 = 45.8 ± 2.6 ng/µg of proteins; P < 0.05).

CONCLUSION

In conditions of severe endothelial dysfunction, systemic peroxidation and inflammation, and accelerated atherosclerosis, atorvastatin, even at high doses, displays suboptimal anti-atherogenic and anti-inflammatory effects, while the addition of a NO-donating property confers enhanced anti-atherogenic and anti-inflammatory effects.

[Anti-inflammatory effect of high-density lipoprotein on the cardiovascular system of hyperlipidemic mice]

INTRODUCTION

LDLr-/- mice are spontaneously hyperlipidemic and resistant to the development of neointimal lesions.

OBJECTIVES

This study aimed to determine the factor that prevents the inflammatory process and neointimal lesions and insulin resistance in LDLr-/- mice.

METHODS

Three groups of 3-month-old male mice were used: wild-type mice (WT group); LDLr-/- mice fed a standard diet (S group); and LDLr-/- mice fed a high-fat diet (HF group). After 15 days, blood was collected for analysis of plasma lipids, glucose and insulin. The HOMA index was calculated to determine insulin resistance. The heart and aorta were removed for histological study. Histological sections of the heart were processed immunohistochemically with anti-CD40L antibodies to evaluate the inflammatory process. Histological sections of the aorta were stained with hematoxylin/eosin and picrosirius red to assess morphological and morphometric alterations.

RESULTS

The S mice were resistant to the inflammatory process, as shown by low immunoreactivity to CD40L, with high plasma HDL levels, and did not develop insulin resistance, even with moderate hyperlipidemia compared to WT. The HF mice showed severe hyperlipidemia, increased cardiac immunoreactivity to CD40L, pronounced morphological changes in the aortic wall and insulin resistance, associated with a decrease in plasma HDL levels, compared to S. This severe hyperlipidemia in the HF mice can be considered the major metabolic factor inducing oxidative stress in the cardiovascular system, increasing the lipid peroxidation of HDL and hence its removal by the liver, with consequent lowering of plasma HDL levels.

CONCLUSION

High HDL plasma levels are a protective factor against the development of cardiovascular inflammation and insulin resistance in LDLr-/- mice, preventing the development of neointimal lesions.

Comparative antilipidemic effect of N-acetylcysteine and sesame oil administration in diet-induced hypercholesterolemic mice

Background

There is an increasing number of novel antilipidemic therapies under consideration. The putative hypolipidemic effect of N-acetylcysteine (NAC) and sesame oil was studied in a mouse model of dietary-induced hypercholesterolemia.

Methods

Male C57bl/6 mice were assigned to the following groups: (NC) control group, (HC) group receiving test diet supplemented with 2% cholesterol and 0.5% cholic acid for 8 weeks, (HCN) group receiving the test diet with NAC supplementation (230 mg/kg p.o.) and (HCS) group fed the test diet enriched with 10% sesame oil. Total serum cholesterol, LDL-cholesterol, HDL-cholesterol and triglycerides were assayed at the beginning and at the end of the experiment. Total peroxides and nitric oxide (NO) levels were measured in the serum at the end of the experiment. Hepatic and aortic lesions were evaluated by haematoxylin-eosin staining.

Results

Higher serum levels of total and LDL-cholesterol were recorded in all groups fed the high cholesterol diet. The HCN group presented reduced lipid levels compared to HC and HCS groups. No differences were observed between HCS and HC groups. Peroxide content in serum was markedly increased in mice consuming high cholesterol diet. NAC and sesame oil administration led to a significant decrease of serum lipid peroxidation in the levels of control group, whereas only NAC restored NO bioavailability. In terms of liver histology, the lesions observed in HCN group were less severe than those seen in the other high cholesterol groups.

Conclusion

Co-administration of NAC, but not sesame oil, restored the disturbed lipid profile and improved hepatic steatosis in the studied diet-induced hypercholesterolemic mice. Both agents appear to ameliorate serum antioxidant defense.

Baroreflex sensitivity and oxidative stress in the LDL receptor knockout mice

This study aims at observing the effect of low-density lipoprotein (LDL) receptor deficiency in cholesterol blood levels, baroreflex sensitivity (BRS), nitric oxide (NO) bioavailability, and oxidative stress. The lack of LDL receptors in mice significantly increased the cholesterol blood levels (179+/-35 vs. 109+/-13mg/dL) in the knockout (KO) mice compared to control. There was no difference in basal mean arterial pressure and heart rate between the groups. However, in KO mice the BRS was significantly attenuated and the antioxidant enzyme activities, measured in erythrocytes and heart, were significantly decreased. On the other hand, the oxidative damage measured by chemiluminescence and carbonyls was increased, while total plasma nitrate levels were lower in KO mice, indicating a decrease in NO availability. In conclusion, these results indicate that the lack of LDL receptor increased cholesterol blood levels, induced oxidative stress and decreased BRS.

S-nitroso-N-acetylcysteine (SNAC) prevents myocardial alterations in hypercholesterolemic LDL receptor knockout mice by antiinflammatory action

We investigated the ability of S-nitroso-N-acetylcyseine (SNAC) to prevent structural and functional myocardial alterations in hypercholesterolemic mice. C57BL6 wild-type (WT) and LDL-R-/- male mice (S) were fed a standard diet for 15 days. LDL-R-/- mice (S) showed an 11% increase in blood pressure, 62% decrease in left atrial contractility, and lower CD40L and eNOS expression relative to WT. LDL-R-/- mice fed an atherogenic diet for 15 days (Chol) showed significant increased left ventricular mass compared to S, which was characterized by: (1) 1.25-fold increase in the LV weight/body weight ratio and cardiomyocyte diameter; (2) enhanced expression of the NOS isoforms, CD40L, and collagen amount; and (3) no alteration in the atrial contractile performance. Administration of SNAC to Chol mice (Chol + SNAC) (0.51 micromol/kg/day for 15 day, IP) prevented increased left ventricular mass, collagen deposit, NOS isoforms, and CD40L overexpression, but it had no effect on the increased blood pressure or atrial basal hypocontractility. Deletion of the LDL receptor gene in mice resulted in hypertension and a marked left atrial contractile deficit, which may be related to eNOS underexpression. Our data show that SNAC treatment has an antiinflammatory action that might contribute to prevention of structural and functional myocardial alterations in atherosclerotic mice independently of changes in blood pressure.

Recent developments in nitric oxide donor drugs

During the 1980s, the free radical, nitric oxide (NO), was discovered to be a crucial signalling molecule, with wide-ranging functions in the cardiovascular, nervous and immune systems. Aside from providing a credible explanation for the actions of organic nitrates and sodium nitroprusside that have long been used in the treatment of angina and hypertensive crises respectively, the discovery generated great hopes for new NO-based treatments for a wide variety of ailments. Decades later, however, we are still awaiting novel licensed agents in this arena, despite an enormous research effort to this end. This review explores some of the most promising recent advances in NO donor drug development and addresses the challenges associated with NO as a therapeutic agent.

Oral administration of S-nitroso-N-acetylcysteine prevents the onset of non alcoholic fatty liver disease in rats

AIM: To evaluate the potential of S-nitroso-N-acetylcysteine (SNAC) in inhibition of lipid peroxidation and the effect of oral SNAC administration in the prevention of nonalcoholic fatty liver disease (NAFLD) in an animal model.

METHODS: NAFLD was induced in Wistar male rats by choline-deficient diet for 4 wk. SNAC-treated animals (n=6) (1.4 mg/kg/day of SNAC, orally) were compared to 2 control groups: one (n=6) received PBS solution and the other (n=6) received NAC solution (7 mg/kg/d). Histological variables were semiquantitated with respect to macro and microvacuolar fat changes, its zonal distribution, foci of necrosis, portal and perivenular fibrosis, and inflammatory infiltrate with zonal distribution. LOOHs from samples of liver homogenates were quantified by HPLC. Nitrate levels in plasma of portal vein were assessed by chemiluminescence. Aqueous low-density lipoprotein (LDL) suspensions (200 µg protein/mL) were incubated with CuCl₂ (300 µmol/L) in the absence and presence of SNAC (300 µmol/L) for 15 h at 37 °C. Extent of LDL oxidation was assessed by fluorimetry. Linoleic acid (LA) (18.8 µmol/L) oxidation was induced by soybean lipoxygenase (SLO) (0.056 µmol/L) at 37 °C in the presence and absence of N-acetylcysteine (NAC) and SNAC (56 and 560 µmol/L) and monitored at 234 nm.

RESULTS: Animals in the control group developed moderate macro and microvesicular fatty changes in periportal area. SNAC-treated animals displayed only discrete histological alterations with absence of fatty changes and did not develop liver steatosis. The absence of NAFLD in the SNAC-treated group was positively correlated with a decrease in the concentration of LOOH in liver homogenate, compared to the control group (0.7±0.2 nmol/mg vs 3.2±0.4 nmol/mg protein, respectively, P<0.05), while serum levels of aminotransferases were unaltered. The ability of SNAC in preventing lipid peroxidation was confirmed in in vitro experiments using LA and LDL as model substrates.

CONCLUSION: Oral administration of SNAC prevents the onset of NAFLD in Wistar rats fed with choline-deficient diet. This effect is correlated with the ability of SNAC to block the propagation of lipid peroxidation in vitro and in vitro.