Abstract
Lifestyle, cigarette smoking and environmental pollution have a negative impact on male fertility. Therefore, the aim of this study was to evaluate the in-vitro effects of benzo-α-pyrene (BaP) and aryl hydrocarbon receptor (AHR) agonists on motility and bio-functional sperm parameters. We further assessed whether resveratrol (RES), an AHR antagonist and antioxidant molecule, had any protective effect. To accomplish this, 30 normozoospermic, healthy, non-smoker men not exposed to BaP were enrolled. Spermatozoa of 15 men were incubated with increasing concentrations of BaP to evaluate its effect and to establish its dose response. Then, spermatozoa of the 15 other men were incubated with BaP (15 µM/mL), chosen according to the dose-response and/or RES to evaluate its antagonistic effects. The effects of both substances were evaluated after 3 h of incubation on total and progressive sperm motility and on the following bio-functional sperm parameters evaluated by flow cytometry: Degree of chromatin compactness, viability, phosphatidylserine externalization (PS), late apoptosis, mitochondrial membrane potential (MMP), DNA fragmentation, degree of lipoperoxidation (LP), and concentrations of mitochondrial superoxide anion. Benzo-α-pyrene decreased total and progressive sperm motility, impaired chromatin compactness, and increased sperm lipoperoxidation and mitochondrial superoxide anion levels. All these effects were statistically significant at the lowest concentration tested (15 µM/mL) and they were confirmed at the concentration of 45 µM/mL. In turn, RES was able to counteract the detrimental effects of BaP on sperm motility, abnormal chromatin compactness, lipid peroxidation, and mitochondrial superoxide. This study showed that BaP alters sperm motility and bio-functional sperm parameters and that RES exerts a protective effect on BaP-induced sperm damage.
Highlights
Benzo-α-pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) originating from the incomplete combustion of fossil fuels, tobacco smoke, diesel exhaust, and broiled foods [1]
The effects of BaP on the latter became significant at the concentration of 15 μM/mL (p < 0.05 vs. BaP 0) and it was significantly more pronounced at the concentration of 45 μM/mL (Figure 1, panel A)
BaP is an environmental compound that exerts its toxic effects by binding to the aryl hydrocarbon receptor (AHR)
Summary
Benzo-α-pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) originating from the incomplete combustion of fossil fuels, tobacco smoke, diesel exhaust, and broiled foods [1]. BaP has been classified as carcinogenic yet it must be metabolically activated to cause its deleterious effects [2]. The main route of BaP metabolism involves hydrolase, phase 1 enzyme, which metabolizes BaP into the precancerous compound benzo[a]pyrene-r-7,t-8-dihydrodiol-t9,10-epoxide (BPDE) that binds covalently to DNA [3,4,5,6,7]. Activated BaP increases reactive oxygen species (ROS) production and oxidative stress, resulting in increased lipid peroxidation, caspase, and endonuclease activation [8,9]. It is well known that increased ROS production is a cause of male infertility [10]
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