Curcumin has protective and antioxidant properties on bull spermatozoa subjected to induced oxidative stress

Over the past decades, there has been an emphasis on assessment of the use of natural compounds in the prevention or repair of oxidative injury to spermatozoa. Curcumin (CUR) is a natural phenol with powerful antioxidant properties. The aim of the present study was to examine if CUR could reverse reactive oxygen species (ROS)-mediated alterations to the motility, viability and intracellular antioxidant profile of bull spermatozoa subjected to a prooxidant (i.e., ferrous ascorbate – FeAA). Spermatozoa were washed from recently collected semen samples, suspended in 2.9% sodium citrate and subjected to CUR treatment (5, 10, 25 and 50 μmol/L) in the presence or absence of FeAA (150 μmol/L FeSO4 and 750 μmol/L ascorbic acid) during a 6 h in vitro culture. Spermatozoa motility characteristics were assessed using the SpermVision computer-aided spermatozoa analysis (CASA) system. Cell viability was examined with the metabolic activity (MTT) assay, ROS generation was quantified using luminometry and the nitroblue-tetrazolium (NBT) test was used to quantify the intracellular superoxide formation. Cell lysates were prepared at the end of the culture to assess the intracellular activity of superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) as well as the concentrations of glutathione (GSH) and malondialdehyde (MDA). Treatment with FeAA led to a reduced spermatozoa motility (P < 0.001), viability (P < 0.001) and decreased the antioxidant characteristics of the samples (P < 0.001) but increased the ROS generation (P < 0.001), superoxide production (P < 0.001) and lipid peroxidation (P < 0.001). The CUR treatment led to a preservation of spermatozoa motion (P < 0.001), mitochondrial activity (P < 0.001) and antioxidant characteristics (P < 0.05 with SOD and GSH; P < 0.01 with CAT and GPx), revealing the concentration range of 25–50 μmol/L CUR to be the most effective for sustaining spermatozoa viability. Data from the present study suggest that CUR exhibits significant protective and ROS-scavenging characteristics which may prevent oxidative insults to spermatozoa and thus preserve the functional activity of male gametes.