Ammonium perfluorooctanoate may cause testosterone reduction by adversely affecting testis in relation to PPARα

Abstract

Perfluorooctanoate, a peroxisome proliferator-activated receptor alpha (PPARα) agonist, has the potential to lower testosterone levels as a result of testicular toxicity. To elucidate the mechanism and impact of PPARα on this reproductive toxicity, ammonium perfluorooctanoate (APFO) at doses of 0, 1.0 (low) mg/kg/day, or 5.0 (high) mg/kg/day was orally given daily to 129/sv wild-type (mPPARα), Pparα-null and PPARα-humanized (hPPARα) mice for 6 weeks. Both low- and high-dose APFO significantly reduced plasma testosterone concentrations in mPPARα and hPPARα mice, respectively. These decreases may, in part, be associated with decreased expression of mitochondrial cytochrome P450 side-chain cleavage enzyme, steroidogenic acute regulatory protein or peripheral benzodiazepine receptor as well as microsomal cytochrome P450(17α) involved in the steroidogenesis. Additionally, both doses increased abnormalities in sperm morphology and vacuolated cells in the seminiferous tubules of both mouse lines. In contrast, APFO caused only a marginal effect either on the testosterone synthesis system or sperm and testis morphology in Pparα-null mice. These results suggest that APFO may disrupt testosterone biosynthesis by lowering the delivery of cholesterol into the mitochondria and decreasing the conversion of cholesterol to pregnenolone and androstandione in the testis of mPPARα and hPPARα mice, which may, in part, be related to APFO-induced mitochondrial damage.

Fig. 1.

Effects of APFO exposures on plasma hormone levels, sperm number and quality. (A) Plasma testosterone concentrations; (B) sperm abnormalities; (C) sperm numbers. Values are expressed as means ± SD for 8–10mice per group. *Significantly different from respective control group (P<0.05).

Fig. 2.

Real-time quantitative PCR analysis of testicular mRNA encoding enzymes involved in testosterone biosynthesis and mitochondrial function from control and APFO-exposed mice. Values are expressed as means ±SD for 8–10 mice per group. *Significantly different from mPPARα control group (P<0.05); ^#Significantly different from Pparα-null control group (P<0.05); Significantly different from respective control group (P<0.05).

Fig. 3.

Western blot analysis of StAR, P450scc, and P450 17α protein expression levels in the testes of control mice and 1.0 mg/kg, 5.0 mg/kg dose APFO-exposed mice (8–10 per group). (A) Western blot analyses of StAR, P450scc, and P450_17α. (B) Each band obtained by immunoblot analysis was quantified by densitometric analysis. Histogram shows the relative densitometric ratio (mean ± SD) of StAR, P450scc, and P450_17α to GAPDH. ^†Significantly different from respective control group (P<0.05).

Fig. 4.

Light microscopic findings of testis. Bar in the photos indicates 100 μm. Testis from mPPARα and hPPARα mice exposed to 5.0 mg/kg d PFOA showed vacuoles. Arrows show seminiferous tubules with vacuoles.