Bacterial lipopolysaccharide (LPS) impairs sperm mitochondrial membrane potential and induces sperm apoptosis in infertile men

Context Lipopolysaccharide (LPS), a major component of Gram-negative bacteria membrane, is widely implicated in the pathogenesis of male reproductive system infections. Aims This study aims to elucidate the LPS effect on sperm motility, mitochondrial membrane potential (ΔΨm) and apoptosis in human sperms. Methods Our experimental study was conducted on 34 sperm samples from male partners of infertile couples divided into fertile group (n = 8) and infertile group (n = 26). For each sample, two sperm suspensions were prepared, namely, a control suspension (non-treated with LPS) and an LPS-treated suspension (200 ng/mL). The two suspensions were incubated for 18 h at room temperature. Sperm motility was evaluated by microscopic observation, whereas sperm mitochondrial membrane potential and apoptosis were assessed using flow cytometry after JC-10 and 7-AAD staining. Key results In fertile group, no significant differences in sperm motility, sperm ΔΨm and apoptotic sperm rates were detected after incubation with LPS. However, in infertile group, the LPS reduced sperm motility significantly and induced significant decrease in the rates of sperm with high ΔΨm. Furthermore, a significant decrease in viable sperm rates was detected concomitantly with a significant increase of apoptotic sperm rates. Conclusions This study showed that LPS may impair sperm mitochondrial membrane potential and lead to the activation of some pathways responsible for sperm apoptosis in infertile men. Implications This study has contributed to better understanding of the mechanisms underlying sperm disorders induced by bacterial endotoxins, in particular LPS, especially in infertile men.