Effects of N-Acetyl Cysteine on Human Post-Thaw Sperm Quality and Mitochondrial Uncoupling Protein 2 Relative Quantity.

Reactive oxygen species (ROS) during cryopreservation causes mechanical, biochemical, and structural damage to the sperm, which leads to reduced sperm motility and fertility. N-acetyl cysteine is a cysteine-derived amino acid antioxidant that functions as a scavenger of ROS and regulates mitochondrial activity. Mitochondrial uncoupling protein 2 (UCP2) plays a leading role in this process and is one of the major regulators of human spermatozoa motility and metabolism. The purpose of the study was to examine the changes in UCP2 in frozen-thawed human sperm when exposed to N-acetyl cysteine, an effective antioxidant commonly used in human semen freezing. Semen samples were collected from 20 normozoospermia men and were divided into four experimental groups: fresh, frozen control, frozen N-Acetylcysteine (NAC, 100 μM), and frozen negative control with Genipin (25 μM). Subsequently, post-thaw sperm quality parameters, as well as UCP2 relative quantity, ROS, mitochondrial membrane potential (MMP), and malondialdehyde, were assessed. Semen treated with NAC exhibited significantly higher total and progressive motility, as well as viability, when compared to the control and genipin groups ( < 0.05). Moreover, UCP2 relative quantity was significantly lower in all frozen groups compared to the fresh group ( < 0.0001). The UCP2 relative quantity was not significantly different between NAC and control groups ( ≥ 0.05). Also, there were no significant differences in MMP, ROS, and malondialdehyde levels among the frozen groups ( ≥ 0.05). It can be concluded that UCP2 undergoes a modification during cryopreservation, and it could be an explanation of the reduction in post-thaw motility of sperm. Additionally, NAC supplementation in freezing media enhances post-thaw sperm motility and viability.