Impact of dihydrolipoic acid on mouse embryonic stem cells and related regulatory mechanisms.

α-Lipoic acid (LA) is a thiol with antioxidant properties that protects against oxidative stress-induced apoptosis. LA is absorbed from the diet, taken up by cells and tissues, and subsequently reduced to dihydrolipoic acid (DHLA). Recently, DHLA has been used as the hydrophilic nanomaterial preparations, and therefore, determination of its bio-safety profile is essential. In this article, we show that DHLA (50-100 µM) induces apoptotic processes in mouse embryonic stem cells (ESC-B5), but exerts no injury effects at treatment dosages below 50 µM. Higher concentrations of DHLA (50-100 µM) directly increased the reactive oxygen species (ROS) content in ESC-B5 cells, along with a significant increase in cytoplasmic free calcium and nitric oxide (NO) levels, loss of mitochondrial membrane potential (MMP), activation of caspases-9 and -3, and cell death. Pretreatment with NO scavengers suppressed the apoptotic biochemical changes induced by 100 µM DHLA and promoted the gene expression levels of p53 and p21 involved in apoptotic signaling. Our results collectively indicate that DHLA at concentrations of 50-100 µM triggers apoptosis of ESC-B5 cells, which involves both ROS and NO. Importantly, at doses of less than 50 µM (0-25 µM), DHLA does not exert hazardous effects on ESC-B5 cell properties, including viability, development and differentiation. These results provide important information in terms of dosage safety and biocompatibility of DHLA to facilitate its further use as a precursor for biomaterial preparation.

Dihydrolipoic acid induces cytotoxicity in mouse blastocysts through apoptosis processes.

α-Lipoic acid (LA) is a thiol with antioxidant properties that protects against oxidative stress-induced apoptosis. LA is absorbed from the diet, taken up by cells and tissues, and subsequently reduced to dihydrolipoic acid (DHLA). In view of the recent application of DHLA as a hydrophilic nanomaterial preparation, determination of its biosafety profile is essential. In the current study, we examined the cytotoxic effects of DHLA on mouse embryos at the blastocyst stage, subsequent embryonic attachment and outgrowth in vitro, in vivo implantation by embryo transfer, and early embryonic development in an animal model. Blastocysts treated with 50 µM DHLA exhibited significantly increased apoptosis and a corresponding decrease in total cell number. Notably, the implantation success rates of blastocysts pretreated with DHLA were lower than that of their control counterparts. Moreover, in vitro treatment with 50 µM DHLA was associated with increased resorption of post-implantation embryos and decreased fetal weight. Data obtained using an in vivo mouse model further disclosed that consumption of drinking water containing 100 µM DHLA led to decreased early embryo development, specifically, inhibition of development to the blastocyst stage. However, it appears that concentrations of DHLA lower than 50 µM do not exert a hazardous effect on embryonic development. Our results collectively indicate that in vitro and in vivo exposure to concentrations of DHLA higher than 50 µM DHLA induces apoptosis and retards early pre- and post-implantation development, and support the potential of DHLA to induce embryonic cytotoxicity.