Hydroxycitric acid reverses tamoxifen resistance through inhibition of ATP citrate lyase.

Lipid metabolic reprogramming is involved in mediating tamoxifen (TAM) response in breast cancer cells. Published microarray data indicated that ATP citrate lyase (ACLY) is overexpressed in TAM-resistant BC cells. Hydroxycitric acid (HCA) is a powerful competitive inhibitor of the enzyme ACLY, which links carbohydrates and lipids metabolism. However, whether inhibition of ACLY could modulate TAM response in TAM-resistant BC cells remained unexplored. Thus the current study aimed to explore the effect of ACLY inhibition on TAM-resistant BC cells. The cytotoxicity of TAM and/or HCA on LCC2 and its TAM-sensitive counterpart MCF7 cells was evaluated. Also, the effect of TAM and/or HCA treatments on ACLY protein levels were investigated by western blotting. In addition, the effects of TAM and/or HCA on caspase-3, Bax, and Bcl2 levels were evaluated by ELISA.; besides, and flow cytometric analysis was performed for the detection of apoptosis. Moreover, cholesterol and triglyceride contents of LCC2 and MCF7 were quantified colorimetrically. Our results demonstrated that TAM/HCA co-treatment synergistically diminished LCC2 and MCF7 cell viability, with the effect being more significant on LCC2. Mechanistically, TAM/HCA co-treatment decreases the expression level of ACLY in LCC2 by 74 %, while in MCF7 by only 59 %. Moreover, apoptosis marker caspase-3 and Bax were increased, while the anti-apoptotic Bcl2 was decreased. Furthermore, the cholesterol and TG contents were increased in LCC2 than in MCF7. Our data revealed that ACLY plays a key role in TAM resistance and ACLY inhibition by HCA-mediated sensitization of BC-resistant cells to TAM.

Hydroxycitric acid potentiates the cytotoxic effect of tamoxifen in MCF-7 breast cancer cells through inhibition of ATP citrate lyase.

Hydroxycitric acid (HCA), a dietary-derived weight loss supplement, competitively inhibits ATP citrate lyase (ACLY). Tamoxifen (TAM) is the most frequently used therapy for estrogen receptor (ER)-positive breast cancer patients, but its application was restricted due to efficacy related issues. Lipid metabolic reprogramming plays a key role in cancer progression and response to treatment. This study will test the hypothesis that targeting lipid metabolic enzymes could enhance TAM effect against breast cancer cells. MCF-7 ER-positive breast cancer cell line was used, and the cytotoxic effect of TAM treatment, alone and in combination with HCA was evaluated. Flowcytometric analysis of apoptosis following TAM and/or HCA treatment was additionally performed. Besides, the effects of TAM and/or HCA on ACLY, acetyl CoA carboxylase alpha (ACC-α) and fatty acid synthase (FAS) expression were investigated. Likewise, expression of ER-α protein through TAM and/or HCA treatment was examined. Cell contents of cholesterol and triglyceride were quantified. Treatment with TAM or HCA significantly reduced cell viability in a concentration-dependent manner whereas co-treatment synergistically reduced cell viability, promoted apoptosis, and decreased the expression of ACLY, ACC-α, and FAS. Intracellular triglyceride and cholesterol were accumulated in response to treatment with TAM and/or HCA. Moreover, either solitary TAM or TAM/ HCA co-treatment increased ER-α protein levels non significantly. Our results revealed that TAM effects on breast cancer are mediated, in part, through the regulation of key genes involved in lipid metabolism. Accordingly, inhibition of ACLY by HCA might be beneficial to enhance the therapeutic index of TAM against breast cancer.

Quercetin protects against acetaminophen-induced hepatorenal toxicity by reducing reactive oxygen and nitrogen species.

High or toxic doses of acetaminophen (APAP), a mild analgesic and antipyretic drug, can cause life-threatening hepatic and renal dysfunction. This study is designed to investigate the potential protective role of quercetin to attenuate the hepatorenal toxicity induced by a high single oral dose (3g/kg) of APAP in rats. Three main groups of Sprague-Dawley rats were used: quercetin, APAP and quercetin plus APAP-receiving animals. Corresponding control animals were also used. Interestingly, oral supplementation of quercetin (15mg/kg/day) prior to APAP intoxication dramatically reduced APAP-induced hepatorenal toxicity as evidenced by measuring serum lipid profile, total protein, urea, creatinine, ALT, AST, ALP, G-GT and liver tissue content of TC and TG. Quercetin treatment markedly prevented the generation of TBARS and PCC with substantial improvement in terms of GSH and activities of antioxidant enzymes in both liver and kidney homogenates. The relationship between quercetin and NO levels which is still a matter of debate, was also investigated. NO levels in serum, liver and kidney tissues were significantly inhibited in quercetin pre-treated animals. Furthermore, quercetin administration significantly inhibited the reduction of liver and kidney contents of ATP parcels associated with this hepatorenal toxicity. These results suggest that the protective role of quercetin in the prevention of APAP-induced hepatorenal toxicity in rats was associated with the decrease of oxidative and nitrosative stress in hepatic and renal tissues as well as its capacity to improve the mitochondrial energy production. However, clinical studies are warranted to investigate such an effect in human subjects.

Erythrocyte nitric oxide synthase as a surrogate marker for mercury-induced vascular damage: the modulatory effects of naringin.

In this study, endothelial nitric oxide synthase activity and nitric oxide (NO) production by human erythrocytes in the presence and absence of mercuric chloride (HgCl2 ), L-arginine (L-ARG), N ω- nitro-L-arginine methyl ester (L-NAME), and naringin (NAR) were investigated. In addition, the levels of reduced glutathione (GSH) and related enzymes were estimated in erythrocytes hemolysate. The protein carbonyl content (PCC) and thiobarbituric acid-reactive substances (TBARS) levels were also determined. The results of this study revealed that the treatment of erythrocytes with either HgCl2 or L-NAME induced a significant decrease in NOS activity and nitrite levels compared with control cells. Furthermore, mercury exposure significantly increased the levels of PCC and TBARS but reduced the GSH level. The activities of glucose-6-phosphate dehydrogenase, glutathione reductase, glutathione peroxidase, and glutathione-S-transferase (GST) were inhibited. The exposure of erythrocytes to HgCl2 in combination with L-ARG, NAR, or both ameliorated the investigated parameters compared with erythrocytes incubated with HgCl2 alone. These results indicate that mercury exposure decreased both erythrocyte NOS activity and nitrite production, and that these parameters might be indicative of mercury exposure. The data also suggest that concomitant treatment with NAR can restore NO bioavailability through either its metal-chelating properties or its antioxidant activity.

Protective effect of dietary flavonoid quercetin against lipemic-oxidative hepatic injury in hypercholesterolemic rats.

CONTEXT: Quercetin, a dietary-derived flavonoid, is ubiquitous in fruits and vegetables and plays important roles in human health by virtue of its antioxidant activity. OBJECTIVE: This study was conducted to investigate the possible modulatory effect of quercetin against hepatic lipemic-oxidative injury in rats fed with a high cholesterol diet (HCD), and to highlight the underlying mechanisms of such effect. MATERIALS AND METHODS: Different groups of male Sprague-Dawley rats were used; one group was treated by gavage with HCD cocktail (1 mL/100 g) whereas another group was orally administered HCD-enriched with quercetin (15 mg/kg). Corresponding control animals were also used. RESULTS: Quercetin administration significantly decreased liver triglycerides (24%), liver total cholesterol (TC) (22%), serum TC (20%), serum low-density lipoprotein cholesterol (31%), and duplicated serum high-density lipoprotein cholesterol (HDL-C). This study also revealed that quercetin administration significantly reduced the activity of serum alanine aminotransferase (41%), aspartate aminotransferase (51%), and γ-glutamyl transpeptidase (G-GT) (35%). Significant inhibition of thiobarbituric acid-reacting substances (40%), together with a valuable enhancement of reduced glutathione (GSH) content (53%) in the liver homogenates, was observed. In addition, quercetin-treated hypercholesterolemic animals exhibited a reasonable improvement of hepatic antioxidant enzymes. Moreover, serum and liver content of nitric oxide (NO) were markedly decreased in this model (26 and 25%, respectively), and were almost normalized following quercetin administration. DISCUSSION AND CONCLUSION: These data revealed that quercetin has the ability to ameliorate HCD-induced lipemic-oxidative injury in rat liver possibly through its antioxidant potential and/or increased NO bioavailability.

Lycopene attenuates oxidative stress and heart lysosomal damage in isoproterenol induced cardiotoxicity in rats: A biochemical study.

The present study was designed to investigate the cardioprotective potential of lycopene (LYC) on isoproterenol (ISO)-induced oxidative stress and heart lysosomal damage in rats. Male Sprague Dawley rats were pretreated with LYC (4mg/kg, p.o.) once daily for 21 days. After the treatment period, ISO (85mg/kg) was injected subcutaneously, once daily, to rats for 2 days. Hemodynamic parameters, cardiac marker enzymes, antioxidant, and oxidative stress parameters in serum and heart tissues were measured. ISO treated rats showed significant changes in heart rates, heart weights and serum lipid profiles. The activity of aspartate aminotranferase (AST), lactate dehydrogenase (LDH), creatine kinase-MB (CK-MB) and cardiac troponin T (cTnT) were increased significantly (p<0.01) in the serum of ISO rats. The levels of lipid peroxides (thiobarbituric acid reactive substances, TBARS), protein carbonyl content (PCC) and neutrophil infiltration marker; myeloperoxidase (MPO) were significantly (p<0.01) increased. In addition, the activities of lysosomal enzymes (beta-glucuronidase, beta-N-acetylglucosaminidase, and cathepsin-d) in the serum and heart of ISO rats were increased significantly. Furthermore, a marked decrease in the levels of serum and cardiac reduced glutathione (GSH), vitamin C and cardiac enzymatic antioxidants; superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) were observed. In vitro study confirmed the strong antioxidant effect of LYC on total antioxidant activity. In conclusion, the present study demonstrated that LYC supplementation to ISO rats significantly ameliorated lysosomal membrane damage as well as the alterations in cardiac enzymes, lipid profile and oxidative stress markers. These findings revealed the cardioprotective effects of LYC against ISO-induced oxidative stress and cardiotoxicity in rats. These observed effects are mediated via antioxidant power and free radical scavenging activity of LYC.

Renal oxidative stress and nitric oxide production in streptozotocin-induced diabetic nephropathy in rats: the possible modulatory effects of garlic (Allium sativum L.).

The purpose of the present study was to investigate the effects of garlic (Allium sativum L.) on the diabetic nephropathy and oxidative stress induced by STZ (streptozotocin) in rats. Diabetes was induced in Male Sprague-Dawley rats by administering a single intraperitoneal injection of STZ (60 mg/kg of body weight). Administration of garlic, prepared as FGH (fresh garlic homogenate) significantly attenuated STZ-induced diabetic nephropathy as evaluated by assessment of serum glucose, insulin, total TAG (triacylglycerol), TC (total cholesterol) and Ccr (creatinine clearance) in control and STZ-induced diabetic rats. Urinary excretions of albumin and NAG (N-acetyl-beta-D-glucosaminidase) were also reduced following the treatment with FGH. In addition, significant inhibition of TBARSs (thiobarbituric acid-reacting substances) with a marked improvement of GSH content in the kidney homogenates was also observed. Moreover, renal tissue content and urinary excretion of nitrites were markedly decreased in this model, and virtually enhanced to the same levels as in the non-diabetic kidney following FGH supplementation. These data revealed that FGH has the ability to ameliorate STZ-induced diabetic nephropathy possibly through participation in the inhibition of oxidative damage to kidney and/or increased kidney nitric oxide bioavailability.

Nitrite-mediated inactivation of human plasma paraoxonase-1: possible beneficial effect of aromatic amino acids.

Paraoxonase-1 (PON-1) is a high-density-lipoprotein-bound enzyme, and its major function is to prevent oxidation of low-density lipoprotein. Atherogenesis could be related to decreased activity of this enzyme. Nitrites (NO2-), either present as a contaminant and/or the main metabolic end product of nitric oxide (NO) degradation, may trigger nitrative damage to PON-1 enzyme. Minimal information is available concerning the effect of nitrite on the enzyme activity and the mechanism which it exerts its effect. The aim of this study was to analyze whether nitrites could play a role in modifying human PON-1 activity. Our results revealed that PON-1 activity was inhibited by nitrite in dose- and time-dependent manner. Site-specific nitration focused on phenolic residues, particularly tyrosine residues of the enzyme, may result in modification of its biological functions. Nitration of phenolic residues occurs via peroxynitrite (ONOO(-)) formation, which requires peroxides and nitrite. Thus, we tested the presence of peroxides, which are found in all plasma samples regardless of nitrite concentration. The inhibition of PON-1 activity by nitrite was significantly reduced by tryptophan, reduced glutathione (GSH), and catalase additions. Therefore, we concluded that nitrites may have a role in the inactivation of PON-1, probably through nitration of enzyme phenyl residues, and additions of individual aromatic amino acids, with highlighting on tryptophan, could be of important value in minimizing the nitrite-induced inhibition of PON-1 enzyme.

Ginkgo biloba leaf extract (EGb 761) diminishes adriamycin-induced hyperlipidaemic nephrotoxicity in rats: association with nitric oxide production.

The aim of this experimental study was to investigate the effect of a standardized preparation of Ginkgo biloba extract (EGb 761) on the hyperlipidaemic nephrotoxicity and oxidative stress induced by a single intravenous injection (5 mg/kg) of adriamycin. EGb 761 was received daily thereafter by a gavage at the dose of 100 mg/kg for 35 consecutive days. EGb 761 administration significantly attenuated adriamycin-induced renal dysfunction, as assessed by measuring serum lipid profile, serum total protein, serum urea and Ccr (creatinine clearance). Furthermore, urinary excretions of protein and NAG (N-acetyl-beta-D-glucosaminidase; a marker of renal tubular injury) were significantly inhibited following EGb 761 administration. EGb 761 supplementation significantly prevented the generation of TBARS (thiobarbituric acid-reacting substances) with a marked improvement in terms of GSH content and activity of antioxidant enzymes in the kidney homogenate. Moreover, EGb 761 treatment significantly reduced both renal-tissue and urine total NO (nitric oxide) levels. The results suggest that the protective potential of EGb 761 in the prevention of adriamycin-induced hyperlipidaemic nephrotoxicity in rats was associated with the decrease in the oxidative stress and the total NO levels of renal tissues. Likewise, the present study demonstrates the ability of EGb 761 to reduce the hyperlipidaemia and proteinuria associated with this nephropathy, which might be beneficial to enhance the therapeutic index of adriamycin.