Activator of Mitochondrial Aldehyde Dehydrogenase (Alda-1) Could Enhance Quality of Equine Cooled Semen by Ameliorating Loss of Mitochondrial Function Over Time

Equine sperm energy metabolism is mainly dependent on mitochondrial oxidative phosphorylation, causing abundant production of reactive oxygen species (ROS). Reacting with fatty acids, ROS result in formation of aldehydes, which diminish sperm viability and motility. Aldehyde dehydrogenases are responsible for removal of aldehydes. Aldehyde dehydrogenase(Alda-1) is the activator of mitochondrial aldehyde dehydrogenase and has been shown to alleviate the detrimental effects of aldehydes in different tissues. The present study was conducted to evaluate the influence of Alda-1 on cooled stallion semen over a 72-hour period. Motility was evaluated using computer-assisted sperm analysis. Viability, mitochondrial membrane potential, and superoxide anion production were assessed using flow cytometry-based methods by SYBR14 plus propidium iodine, JC-1, and dihydroethidium, respectively. Adenosine triphosphate (ATP) content was measured using a luciferase-based ATP bioluminescent assay. Preliminarily, 50 μM dose of Alda-1 was found to be effective on equine cooled semen based on the greater progressive motility observed after exposure to 50 μM Alda-1 as compared with control group (P < .05). Furthermore, it was revealed that Alda-1 (50 μM) ameliorated the decrease in viability, motility, velocity, mitochondrial membrane potential, and ATP production during 72-hour preservation of equine cooled semen (P < .05). In addition, proportion of sperm positive for superoxide anion was higher in Alda-1 than the control group (P < .05), which was interpreted as positive impact of Alda-1 on sperm mitochondrial respiration. In conclusion, the present study showed that Alda-1 could enhance cooling preservation of equine semen by maintaining mitochondrial function and mitigating reduction in ATP generation, motility, and viability over time.