Pharmacological perturbation of peroxisome-proliferator-activated receptor gamma alters motility and mitochondrial function of bovine sperm.

Background: Sperm transit through the female reproductive relies upon maintenance of sperm motility. Peroxisome-proliferator-activated receptor gamma (PPARγ) is a ligand-activated nuclear transcription factor with roles in glucose metabolism and reproductive processes including placental function. PPARγ roles in the mammalian postejaculatory sperm function are incompletely defined.

Objectives: Determine expression, localization, and functions of PPARγ in postejaculatory bovine sperm.

Materials And Methods: Frozen-thawed bovine sperm from three to four different bulls were pooled and subjected to immunofluorescence and western blot for detection and localization of PPARγ. Functions in sperm energetics were explored through the addition of pharmacological inhibition (GW; GW9662) and activation (Ros; Rosiglitazone) in the culture medium at 0 and 24 h under non-capacitating conditions. Samples were analyzed for sperm kinematics (CASA) and mitochondrial membrane potential (MMP; JC-1 fluorophore).

Results: PPARγ was detected in bovine sperm and co-localized to the acrosome with re-localization to the equatorial region in acrosome-compromised sperm. The addition of Ros 50 µM for 24 h maintained superior total and progressive motility of sperm compared to vehicle control (VC-DMSO 0.01%). The PPARγ antagonist GW 1 µM was detrimental to both total and progressive motility. A challenge experiment (Ros + GW) partially rescued total and progressive motility phenotypes observed with GW incubation. GW-treated samples had a lower number of sperm with high MMP at 24 h compared to Ros or VC. The negative GW MMP phenotype was reversed with the addition of Ros + GW. Likewise, GW-treated samples had more sperm with low MMP compared to VC and Ros, and this phenotype was partially restored with Ros + GW.

Conclusion: PPARγ is expressed in post-ejaculatory bovine sperm with regulatory roles in sperm motility and MMP. These findings implicate PPARγ as a novel regulator of postejaculatory mammalian sperm energetics through non-canonical signaling mechanisms.