Effect of tumor necrosis factor-α on the intracellular Ca(2+) homeostasis in human sperm.

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 Ca(2+) ([Ca(2+) ]cyto ). This study evaluated the effect of tumor necrosis factor (TNF)-α on the [Ca(2+) ]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 [Ca(2+) ]cyto and membrane permeability to Ca(2+) were evaluated by spectrofluorometry, before and after Ca(2+) addition to the extracellular medium. RESULTS: Without TNF-α, the addition of Ca(2+) promotes an transitory increase in [Ca(2+) ]cyto in the spermatozoa, that returns in a few minutes to a basal level, indicating calcium regulation activation. TNF-α decreases the Ca(2+) permeation and increases the basal level of [Ca(2+) ]cyto after a Ca(2+) 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 Ca(2+) and affects Ca(2+) regulation in sperm cells in vitro, probably via lipid peroxidation, which may explain the decrease in sperm fertilizing capacity during inflammatory and infectious processes.

Resistance of rumen bacteria murein to bovine gastric lysozyme.

BACKGROUND: Lysozymes, enzymes mostly associated with defence against bacterial infections, are mureinolytic. Ruminants have evolved a gastric c type lysozyme as a digestive enzyme, and profit from digestion of foregut bacteria, after most dietary components, including protein, have been fermented in the rumen. In this work we characterized the biological activities of bovine gastric secretions against membranes, purified murein and bacteria. RESULTS: Bovine gastric extract (BGE) was active against both G+ and G- bacteria, but the effect against Gram- bacteria was not due to the lysozyme, since purified BGL had only activity against Gram+ bacteria. We were unable to find small pore forming peptides in the BGE, and found that the inhibition of Gram negative bacteria by BGE was due to an artefact caused by acetate. We report for first time the activity of bovine gastric lysozyme (BG lysozyme) against pure bacterial cultures, and the specific resistance of some rumen Gram positive strains to BGL. CONCLUSIONS: Some Gram+ rumen bacteria showed resistance to abomasum lysozyme. We discuss the implications of this finding in the light of possible practical applications of such a stable antimicrobial peptide.