Caffeine Increases Apolipoprotein A-1 and Paraoxonase-1 but not Paraoxonase-3 Protein Levels in Human-Derived Liver (HepG2) Cells.

BACKGROUND: Apolipoprotein A-1, paraoxonase-1 and paraoxonase-3 are antioxidant and anti-atherosclerotic structural high-density lipoprotein proteins that are mainly synthesized by the liver. No study has ever been performed to specifically examine the effects of caffeine on paraoxonase enzymes and on liver apolipoprotein A-1 protein levels. AIMS: To investigate the dose-dependent effects of caffeine on liver apolipoprotein A-1, paraoxonase-1 and paraoxonase-3 protein levels. STUDY DESIGN: In vitro experimental study. METHODS: HepG2 cells were incubated with 0 (control), 10, 50 and 200 µM of caffeine for 24 hours. Cell viability was evaluated by 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay. Apolipoprotein A-1, paraoxonase-1 and paraoxonase-3 protein levels were measured by western blotting. RESULTS: We observed a significant increase on apolipoprotein A-1 and paraoxonase-1 protein levels in the cells incubated with 50 µM of caffeine and a significant increase on paraoxonase-1 protein level in the cells incubated with 200 µM of caffeine. CONCLUSION: Our study showed that caffeine does not change paraoxonase-3 protein level, but the higher doses used in our study do cause an increase in both apolipoprotein A-1 and paraoxonase-1 protein levels in liver cells.

Asymmetric dimethylarginine in experimental breast cancer; action of Vitamin C and E.

OBJECTIVE: To investigate the arginase-nitric oxide synthase paradox through asymmetric dimethylarginine, symmetric dimethylarginine and nitric oxide levels, and to see the effect of antioxidant vitamins on this mechanism of cancer action. METHODS: The animal-based study was conducted at Trakya University, Turkey, in 2008, and comprised mice that were divided into five equal groups. Group 1 had healthy controls, while in the other four groups breast cancer was induced. Group 2 received saline solution, group 3 received 200 mg/kg/day vitamin C (tumour +vit C), group 4 received 300 mg/kg/day vitamin E (tumour +vitE) and group 5 received both 200 mg/kg/day vitamin C and 300 mg/kg/day vitamin E (tumour +vit C+vit E) for 15 days intra-peritoneally.Arginine, asymmetric dimethylarginine, symmetric dimethylarginine and nitric oxide levels were determined in each group. RESULTS: The 50 mice in the study were divided into five groups of 10(20%) each. Plasma arginine levels were significantly decreased, asymmetric dimethylarginine and symmetric dimethylarginine levels were increased, while plasma nitric oxide level was significantly decreased in group 2. There was no statistically significant difference in treatment groups for all parameters (p>0.05 each). CONCLUSIONS: Understanding of the mechanism may help to develop new anti-cancer agents.

Effect of rosuvastatin on arginase enzyme activity and polyamine production in experimental breast cancer.

BACKGROUND: Breast cancer is the most common malignant tumour of women around the world. As a key enzyme of the urea cycle, arginase leads to the formation of urea and ornithine from L-arginine. In the patients with several different cancers, arginase has been found to be higher and reported to be a useful biological marker. AIMS: The aim of this study was to investigate the effect of rosuvastatin on serum and cancer tissue arginase enzyme activity, and ornithine and polyamine (putrescine, spermidine, spermine) levels. STUDY DESIGN: Animal experiment. METHODS: In this study, 50 male Balb/c mice were used. Erchlich acid tumour cells were injected into the subcutaneous part of their left foot. The mice were divided into five groups: healthy control group, healthy treatment, tumour control, treatment 1 and treatment 2. Then, 1 mg/kg and 20 mg/kg doses of rosuvastatin were given intraperitoneally. Serum and tissue arginase enzyme activities and tissue ornithine levels were determined spectrophotometrically. HPLC measurement of polyamines were applied. RESULTS: Increased serum arginase activity and polyamine levels were significantly decreased with rosuvastatin treatment. In the tumour tissue, arginase activity and ornithine levels were significantly decreased in treatment groups compared to the tumour group. Tissue polyamine levels also decreased with rosuvastatin treatment. CONCLUSION: We suggest that rosuvastatin may have some protective effects on breast cancer development as it inhibits arginase enzyme activity and ornithine levels, precursors of polyamines, and also polyamine levels. This protective effect may be through the induction of nitric oxide (NO) production via nitric oxide synthase (NOS). As a promising anticancer agent, the net effects of rosuvastatin in this mechanism should be supported with more advanced studies and new parameters.

The effect of melatonin on protein oxidation and nitric oxide in the brain tissue of hypoxic neonatal rats.

Melatonin is a potent antioxidant agent that can scavenge oxy- and nitroradicals generated under hypoxic conditions in the brain. In this study, we investigated the effect of melatonin on protein oxidation and nitric oxide (NO) during hypoxia. Seven-day-old Sprague-Dawley newborn rats were divided into three groups. Hypoxic (n=9) and melatonin (n=11) groups were subjected to 2h of hypoxic exposure (a humidity mixture of gases consisting of 92% nitrogen and 8% oxygen). Melatonin (at a dose of 10mg/kg) was administrated 30 min before the onset hypoxia and then at 24th and 48th hours after the end of the hypoxic exposure. Control (n=10) and hypoxic groups received the isotonic sodium chloride according to the same schedule. The brain tissue concentration of advanced oxidation protein products (AOPP) and protein thiol (P-SH) was used as an index of protein oxidation. In our study, although AOPP and NO increased significantly, the levels of P-SH decreased in the hypoxic group. The level of AOPP was declined by melatonin treatment. However, perturbed thiol status could not be recovered by melatonin treatment. There was no relationship between the levels of NO and protein oxidation markers. These results indicate that exogenous melatonin could prevent AOPP, but that it is inadequate in recovering perturbed thiol status. Therefore, melatonin alone was observed to be an incomplete treatment to prevent protein oxidation in hypoxia-induced brain damage.