Genistein Decreases the Nitric Oxide Induced Acrosome Reaction by Inhibiting Tyrosine Phosphorylation in Murrah Buffalo Spermatozoa

Spermine-NONOate, a nitric oxide donor, contributes to various physiological functions, including the acrosome reaction (AR) at physiological levels. It triggers AR by enhancing tyrosine phosphorylation in proteins ranging from 20 to 105 kDa. Genistein, an isoflavonoid known to inhibit protein tyrosine kinase, significantly (P<0.05) reduces the AR percentage compared to Spermine-NONOate. Furthermore, LPC alone markedly increases the AR percentage (P<0.05) relative to the control (51.36±1.03% vs. 19.09±1.38%). Spermine-NONOate treatment elevates phosphorylation in proteins p20, p30, p38, p80, and p105, but this phosphorylation is significantly decreased (P<0.05) when genistein is present. Notably, p20 and p30 show higher phosphorylation in the Spermine-NONOate group but are absent in both the genistein-only and Spermine-NONOate+genistein groups, with p30 specifically undetectable after genistein treatment. In contrast, proteins p80 and p105 experience substantial tyrosine phosphorylation in the Spermine-NONOate group, which diminishes significantly (P<0.05) with genistein. This decrease in tyrosine phosphorylation during AR in the presence of genistein suggests its inhibitory effect on nitric oxide-induced AR, indicating that nitric oxide facilitates AR in buffalo spermatozoa through protein tyrosine kinase-dependent phosphorylation.