Tohoku J. Exp. Med., 2016 February, 238(2)

Lipopolysaccharide Compromises Human Sperm Function by Reducing Intracellular cAMP

ZHONGYUAN LI,¹ DAHU ZHANG,¹ YUANQIAO HE,^2,3 ZHIYONG DING,¹ FEI MAO,¹ TAO LUO³ and XIAOPING ZHANG¹

¹Department of Urology, Xiangyang Hospital, Hubei University of Medicine, Xiangyang, Hubei, P.R. China
²Department of Laboratory Animal Science, Nanchang University, Nanchang, Jiangxi, P.R. China
³Institute of Life Science, Nanchang University, Nanchang, Jiangxi, P.R. China

A worldwide decline in the quality of human semen is currently occurring. In mammals, sperm are produced from diploid stem-cell spermatogonia by spermatogenesis in testes and become mature in epididymis. Nevertheless, these biological processes can be affected by Gram-negative bacterial infection mediated by lipopolysaccharide (LPS), the major endotoxin of Gram-negative bacteria. It is well known that LPS can disturb spermatogenesis and affect sperm maturation and quality in vivo. However, the effect of LPS on the ejaculated mature sperm in vitro remains unclear. Thus, this study aimed to assess the in vitro toxicity of LPS on human sperm function and to elucidate the underlying mechanism. Human sperm were incubated with LPS (0.1-100 μg/ml) for 1-12 h in vitro and, subsequently, sperm viability, motility and capacitation, and the acrosome reaction were examined. LPS dose-dependently inhibited total and progressive motility and the ability to move through a viscous medium of the sperm but did not affect sperm viability, capacitation, and the acrosome reaction. To explore the underlying mechanism of LPS's actions, we examined the effects of LPS on the intracellular concentrations of cyclic adenosine monophosphate (cAMP) and calcium ([Ca²⁺]_i) and protein-tyrosine phosphorylation of human sperm, which are key regulators of human sperm function. LPS decreased intracellular cAMP dose-dependently but had no effect on [Ca²⁺]_i and protein-tyrosine phosphorylation of human sperm. These findings suggest that LPS inhibits human sperm motility by decreasing intracellular cAMP.

keywords —— [Ca²⁺]_i; cyclic adenosine monophosphate; lipopolysaccharide; protein-tyrosine phosphorylation; sperm motility

© 2016 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2016, 238, 105-112

Correspondence: Xiaoping Zhang, Department of Urology, Xiangyang Hospital, Hubei University of Medicine, No.15, Jiefan Road, Xiangyang, Hubei 441000, P.R. China.

e-mail: xiangyangurology@163.com