Inhibitory effects of cigarette smoke extracts on neural differentiation of mouse embryonic stem cells

Establishment of a platform for measuring mitochondrial oxygen consumption rate for cardiac mitochondrial toxicity

The heart has an abundance of mitochondria since cardiac muscles require copious amounts of energy for providing continuous blood through the circulatory system, thereby implying that myocardial function is largely reliant on mitochondrial energy. Thus, cardiomyocytes are susceptible to mitochondrial dysfunction and are likely targets of mitochondrial toxic drugs. Various methods have been developed to evaluate mitochondrial toxicity by evaluating toxicological mechanisms, but an optimized and standardized assay for cardiomyocytes remains unmet. We have therefore attempted to standardize the evaluation system for determining cardiac mitochondrial toxicity, using AC16 human and H9C2 rat cardiomyocytes. Three clinically administered drugs (acetaminophen, amiodarone, and valproic acid) and two anticancer drugs (doxorubicin and tamoxifen) which are reported to have mitochondrial effects, were applied in this study. The oxygen consumption rate (OCR), which directly reflects mitochondrial function, and changes in mRNA levels of mitochondrial respiratory complex I to complex V, were analyzed. Our results reveal that exposure to all five drugs results in a concentration-dependent decrease in the basal and maximal levels of OCR in AC16 cells and H9C2 cells. In particular, marked reduction in the OCR was observed after treatment with doxorubicin. The reduction in OCR after exposure to mitochondrial toxic drugs was found to be associated with reduced mRNA expression in the mitochondrial respiratory complexes, suggesting that the cardiac mitochondrial toxicity of drugs is majorly due to dysfunction of mitochondrial respiration. Based on the results of this study, we established and standardized a protocol to measure OCR in cardiomyocytes. We expect that this standardized evaluation system for mitochondrial toxicity can be applied as basic data for establishing a screening platform to evaluate cardiac mitochondrial toxicity of drugs, during the developmental stage of new drug discovery.

Effect of cigarette smoke condensate on mouse embryo development and expression of pluripotency and apoptotic genes in vitro

The aim of the present study was to investigate the effect of cigarette smoke condensate (CSC) on in vitro development of mouse embryos. In total 3000 NMRI mice 2PN embryos were divided into six groups (n = 500). The test group was exposed to 20, 40, 80, 160 or 320 μg/ml of CSC. In the control group, CSC was not added to the culture medium during the development of 2PN embryos. The effects of 20 and 80 μg/ml of CSC on genes involved in pluripotency and apoptosis, and also, the aryl hydrocarbon receptor gene was assessed in the blastocysts. Our results showed that CSC had an adverse effect on the viability of mouse embryos at the concentrations of 80, 160 and 320 μg/ml compared with the control group (P < 0.05). In contrast, it had positive effects on the viability of mouse embryos at the concentrations of 20 and 40 μg/ml compared with the control group (P < 0.05). The 20 and 80 μg/ml concentrations of CSC increased the expression of pluripotency, apoptotic, and aryl hydrocarbon receptor genes in the blastocyst embryo stage compared with the control group (P < 0.05). It can be concluded that concentrations higher than 40 μg/ml of CSC have an adverse effect on mouse embryo development in the preimplantation stages. Also, 20 and 80 μg/ml concentrations of CSC have a significant effect on the expression of pluripotency, apoptotic, and the aryl hydrocarbon receptor genes in the blastocyst embryo stage compared with the control group.