Effect of Tumor Necrosis Factor-α on the Intracellular Ca2+ Homeostasis in Human Sperm

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Abstract

Problem

Inflammation and genital infections promote the increase in leukocytes, pro-inflammatory cytokines, and oxygen reactive species, impairing sperm functions such as motility, capacitation, and acrosome reaction. All these functions are primarily regulated by cytoplasmic concentration of Ca2+ ([Ca2+]cyto). This study evaluated the effect of tumor necrosis factor (TNF)-α on the [Ca2+]cyto and its regulation in human sperm.

Method of study

Sperm loaded with fura-2 were incubated with or without TNF-α (0–500 pg/mL) from 0 to 120 min. After incubation, the basal [Ca2+]cyto and membrane permeability to Ca2+ were evaluated by spectrofluorometry, before and after Ca2+ addition to the extracellular medium.

Results

Without TNF-α, the addition of Ca2+ promotes an transitory increase in [Ca2+]cyto in the spermatozoa, that returns in a few minutes to a basal level, indicating calcium regulation activation. TNF-α decreases the Ca2+ permeation and increases the basal level of [Ca2+]cyto after a Ca2+ pulse (P < 0.04); affecting calcium regulation in a way that is time and concentration dependent. TNF-α effect was partially prevented by the addition of an antioxidant (butylated hydroxytoluene) (P< 0.03).

Conclusion

Tumor necrosis factor-α decreases membrane permeability to Ca2+ and affects Ca2+ regulation in sperm cells in vitro, probably via lipid peroxidation, which may explain the decrease in sperm fertilizing capacity during inflammatory and infectious processes.

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