Protective Effects of Syringic Acid Against Oxidative Damage, Apoptosis, Autophagy, Inflammation, Testicular Histopathologic Disorders, and Impaired Sperm Quality in the Testicular Tissue of Rats Induced by Mercuric Chloride.

Mercury (Hg) is one of the most toxic heavy metals that damage testicular tissue. Mercury chloride (HgCl 2 ) is one of the most toxic forms of mercury that can easily cross biological membranes. Syringic acid (SA) is a natural flavonoid found in many vegetables and fruits. In this study, the effects of SA against HgCl 2 -induced testicular damage in rats were determined by biochemical, histopathological, and spermatological analyses. For this study, a total of 35 Spraque Dawley rats were used. Rats were divided into five groups as control, HgCl 2 , SA 50, HgCl 2  + SA 25, and HgCl 2  + SA 50. HgCl 2 was administered intraperitoneal (IP) at a dose of 1.23 mg/kg/bw, while SA was administered by oral gavage at doses of 25 and 50 mg/kg/bw. The rats were then sacrificed, and testicular tissues were removed. HgCl 2 caused an increase in MDA level and a decrease in SOD, CAT, and GPx activity and GSH level in the testicular tissue of rats. HgCl 2 is involved in the increase of eIF2-α, PERK, ATF-4, ATF-6, CHOP, NF-κB, TNF-α, IL-1β, Apaf-1, Bax, and Caspase-3 mRNA expression. HgCl 2 caused a decrease in sperm motility, an increase in the rate of abnormal sperm and sperm DNA fragmentation in rats. However, SA oral administration dose-dependently inhibited endoplasmic reticulum stress, oxidative stress, inflammation, and apoptosis and preserved epididymal sperm quality and testicular histoarchitectures. In conclusion, SA had protective effects against HgCl 2 -induced testicular oxidative damage, inflammation, endoplasmic reticulum stress, and apoptosis.