Repeated PM2.5 exposure inhibits BEAS-2B cell P53 expression through ROS-Akt-DNMT3B pathway-mediated promoter hypermethylation.

Long-term exposure to fine particulate matter (PM2.5) has been reported to be closely associated with the increased lung cancer risk in populations, but the mechanisms underlying PM-associated carcinogenesis are not yet clear. Previous studies have indicated that aberrant epigenetic alterations, such as genome-wide DNA hypomethylation and gene-specific DNA hypermethylation contribute to lung carcinogenesis. And silence or mutation of P53 tumor suppressor gene is the most prevalent oncogenic driver in lung cancer development. To explore the effects of PM2.5 on global and P53 promoter methylation changes and the mechanisms involved, we exposed human bronchial epithelial cells (BEAS-2B) to low concentrations of PM2.5 for 10 days. Our results indicated that PM2.5-induced global DNA hypomethylation was accompanied by reduced DNMT1 expression. PM2.5 also induced hypermethylation of P53 promoter and inhibited its expression by increasing DNMT3B protein level. Furthermore, ROS-induced activation of Akt was involved in PM2.5-induced increase in DNMT3B. In conclusion, our results strongly suggest that repeated exposure to PM2.5 induces epigenetic silencing of P53 through ROS-Akt-DNMT3B pathway-mediated promoter hypermethylation, which not only provides a possible explanation for PM-induced lung cancer, but also may help to identify specific interventions to prevent PM-induced lung carcinogenesis.

Toxicological evaluation of z24, a novel indolin-2-ketone compound, in cultured human liver cells using toxicogenomic techniques.

The current study was designed to investigate the toxicity of 3Z-3-[((1)H-pyrrol-2-yl)-methylidene]-1-(1-piperidinylmethyl)-1, 3-2H-indol-2-one (Z24), a novel synthetic indolin-2-ketone small molecule compound, using toxicogenomic techniques (complementary DNA [cDNA] microarray). Bioinformatic analysis suggested that the main functions of genes with altered expression were consistent with liver cell regeneration, apoptosis, metabolism of energy and fat, and the death receptor (DR)-mediated apoptosis-signaling pathway. Death receptor 4, Bcl-2, Bcl-xl, caspase 3, and cytochrome C, which are involved in the DR-mediated apoptosis-signaling pathway, were altered after Z24 treatment as determined by Western blotting analysis. When hepatocarcinoma cell line (HepG2 cells) treated with Z24 at 0.248 mmol/L for 24 hours, DNA fragmentation reached a maximum, and examination of cell morphology showed typical signs of apoptosis. These results indicate that Z24 can initiate apoptosis in hepatocytes, which in turn causes hepatotoxicity. A possible toxicological mechanism is that apoptosis was induced in hepatocytes by initiating the DR-mediated signal transduction pathway. Apoptosis of hepatocytes might lead to impairment of energy and lipid metabolism and provoke hepatocyte necrosis or inflammation, resulting in hepatotoxicity.

Study of a novel indolin-2-ketone compound Z24 induced hepatotoxicity by NMR-spectroscopy-based metabonomics of rat urine, blood plasma, and liver extracts.

Antiangiogenic compound has been believed to be an ideal drug in the current cancer biological therapy, but the angiogenesis inhibitors suffer setback for unknown toxicity now. A novel synthetic indolin-s-ketone small molecular compound, 3Z-3-[((1)H-pyrrol-2-yl)-methylidene]-1-(1-piperidinylmethyl)-1,3-2H-indol-2-one (Z24) can inhibit angiogenesis in new blood vessels. The hepatotoxicity effects of Z24 oral administration (dosed at 60, 130 and 200 mg/kg) have been investigated in female Wistar rats by using metabonomic analysis of (1)H NMR spectra of urine, plasma and liver extracts, as well as by clinical chemistry analysis, liver histopathology and electron micrographs examination. The (1)H NMR spectra of the biofluids were analyzed visually and via pattern recognition by using principal component analysis. The metabonomic trajectory analysis on the time-related hepatotoxicity of Z24 was carried out based on the (1)H NMR spectra of urine samples, which were collected daily predose and postdose over an 8-day period. Urinary excretion of citrate, lactate, 2-oxo-glutarate and succinate increased following Z24 dosing. Increased plasma levels of lactate, TMAO and lipid were observed, with concomitant decrease in the level of glucose and phosphatidylcholine. Metabolic profiling on aqueous soluble extracts of liver tissues with the high dose level of Z24 showed an increase in lactate and glutamine, together with a decrease in glucose, glycogen and choline. On the other hand, studies on lipid soluble extracts of liver tissues with the high dose level of Z24 showed increased level in lipid triglycerides and decreased level in unsaturated fatty acids and phosphatidylcholine. Moreover, the most notable effect of Z24 on the metabolism was the reduction in the urinary levels of creatinine and TMAO and the increase in acetate, citrate, succinate and 2-oxo-glutamate with time dependence. The results indicate that in rats Z24 inhibits mitochondrial function through altering the energy and lipid metabolism, which results in the accumulation of free fatty acids and lactate because of the lack of aerobic respiration. These data show that the metabonomic approach represents a promising new technology for the toxicological mechanism study.

Inhibition by agmatine on morphine-induced conditioned place preference in rats.

Our previous studies demonstrated the ability of exogenous agmatine to inhibit tolerance to and physical dependence on morphine in mice, rats and monkeys. The present study further evaluated the effect of agmatine on the psychological dependence induced by morphine in conditioned place preference assay. Agmatine (0.75-20 mg/kg, s.c.) co-administered with morphine during the conditioning sessions completely abolished the acquisition of morphine-induced conditioned place preference in rats, which was associated with activation of imidazoline receptors. Agmatine (0.75-10 mg/kg, s.c.) administered on the test day inhibited the expression of the place preference. After 30 days of extinction of conditioned place preference, agmatine 2.5 and 40 mg/kg inhibited the priming effect of morphine 0.5 mg/kg on the place preference. Furthermore, agmatine inhibited the increased expression of FosB in the nucleus accumbens caused by chronic morphine. All these results suggest that agmatine could inhibit morphine-induced psychological dependence and relapses by affecting the expression of transcription factor FosB.