Three subjects were African Americans included in our original genome-wide DNA methylation study, and we incorporated four new matched samples from Caucasian subjects

anifestation of ROS and a biological system’s ability to readily detoxify the reactive intermediates, leading to sperm dysfunctions. activity is also an early indicator of apoptosis. The caspases are a family of proteins within the cell as inactive pro-forms which can be cleaved to form active enzymes following the induction of apoptosis. In the present study, a possible link between HBs exposure and caspases-3, -8 and -9 activations in sperm cells was investigated. The results showed that there were a markedly increase of caspases-3, -8 and -9 positive cells in the exposed cells when compared with the unexposed cells, indicating that HBs exposure was able to induce caspases-3, -8 and -9 activation in sperm cells. The effects of HBs exposure on caspases-3, -8 and -9 activations in sperm cells also exhibited dose dependence. DNA fragmentation is commonly considered as the key feature of apoptosis in many cell types. In the present study, we detected apoptosis in sperm cells after 3 h of exposure to 25 mg/ml of HBs, the average rate of TUNEL positive cells was significantly elevated as compared to the control. In addition, the effects of HBs exposure on oxidative DNA damage in sperm cells also showed dose dependence. Oxidative stress, loss of MMP and apoptosis caused sperm dysfunctions Since the mitochondria of the sperm midpiece generate energy to support motility, the state of sperm MMP is a useful indicator of functional impairments on the reproductive system. It was well documented that a high correlation between poor sperm mitochondrial functions and diminished motility and reduced fertility. In our previous study, it was detected that HBs caused sperm MMP loss to reduce sperm motility, leading to the death of sperm cells and a lower fertilization rate and a lower fertilizing index. The present study showed that HBs exposure was not only able to induce ROS generation and lipid peroxidation but also cause apoptosis in sperm cells, which were intimately associated with the findings in the previous study. It has been confirmed that the increased ROS generation can cause mitochondrial injury with a marked decrease in MMP. Damaged mitochondria may release some pro-apoptotic molecules including MK886 biological activity cytochrome c and apoptosis-inducing factor, which caused caspase-dependant and caspase-independent apoptosis, respectively. The loss of MMP could lead to lack of energy required for sperm motility, and lipid peroxidation of the sperm membrane could result in the 11277518” loss of membrane integrity, and the pathway of sperm cell death might be switched from caspasedependent to caspase-independent apoptosis. All these events HBs exposure induced apoptosis in sperm cell It is well known that apoptosis plays a critical role in many physiological and pathological processes. An altered apoptosis process has been found to be closely associated with male infertility and with sperm quality such as motility, viability and sperm defects. In the present study, the relationship between HBs exposure and sperm apoptosis was investigate by using annexin-V staining for detection of membrane PS externalization, TUNEL for the measurement of DNA fragmentation and fluorochromelabeled caspase ” inhibitors for detection of caspases activation. In the present study, after 3 h of exposure to 25 mg/ml of HBs, the average rate of annexin V positive and PI negative cells was significantly different as compared to the control. In addition, the effects of HBs exposure on PS externalization