Bacteria induce expression of apoptosis in human spermatozoa

Abstract

An increased number of sperm undergoing apoptosis has been observed during inflammatory processes in the male genital tract, which might be associated with elevated reactive oxygen species (ROS) levels. However, another factor to stimulate apoptosis could be the direct contact with bacteria or its products, even in the absence of ROS. The aim of this study was to investigate whether bacteria can directly initiate apoptosis in human spermatozoa. Human spermatozoa selected by density gradient centrifugation were incubated with polymorphonuclear granulocytes (PMN) isolated from blood and/or E. faecalis, E. coli or S. aureus. As ROS inductor in PMN, phorbol-12-myristate-13-acetate was used. After incubating the cells for 60 min at 37 degrees C, ROS were determined by chemiluminescence and phosphatidyl serine (PS) externalization was analyzed by flow cytometry with Annexin V-FITC and propidium iodide (PI). The increase in the percentage of spermatozoa Annexin V-FITC-positive/ PI-negative (early event of late apoptosis) was significant after the incubation with PMN plus PMA, PMN plus E. coli and E. coli alone. The percentage of spermatozoa Annexin V-FITC-positive/ PI-positive (apoptosis/necrosis) increased significantly in sperm incubated with E. coli and S. aureus (20.3% +/- 3 and 13.6% +/- 3.2 compared to sperm alone, 6% +/- 0.5). Sperm incubated with PMN-PMA activated showed only a relative increase in apoptosis/necrosis (8.4% +/- 1). Our results show that bacteria directly increase the PS externalisation in ejaculated human sperm. This way of inducing apoptosis does not require external ROS and may result from anyone of the molecular mechanisms that account for changes in motility, vitality and DNA integrity, that are characteristics of spermatozoa in male genital tract infection.

The Impact of Bacterial Infections on Human Spermatozoa

“…For example E. coli strains are known for their ability to immobilize and damage the morphology of spermatozoa by direct contact, mediated by attachment organelles such as pili or type-1 fimbriae (projections) and mannose receptor-dependent interactions (68). Also, the sperm surface is rich in glycoproteins and is therefore susceptible to the nitration of bacteria such as E. coli, C. trachomatis, U. urealyticum, Staphylococcus haemolyticus and Bacteroides ureolyticus with spermatozoa leading to the loss of sperm motility and normal morphology (1).…”

“…and C. albicans. They can induce the expression of apoptosis in the male genital tract during inflammatory processes (68).…”

“…Villegas et al (68) concluded that the direct exposure of spermatozoa to E. coli is enough to decrease sperm quality. They noticed that the early apoptosis incident (phosphatidyl serine [PS] externalization) was significantly increased in spermatozoa after incubation with E. coli alone.…”

Lipid Peroxidation in Human Spermatozoa from Men with Genitourinary Infections

“…However, even in the absence of ROS, a direct role of bacteria inducing apoptosis in human sperm has been demonstrated [Villegas et al 2005]. Using an in vitro model, reported that bacteria trigger oxygen radical release and LPO.…”

Testicular innate immune defense against bacteria

“…Page 10 of 24 A c c e p t e d M a n u s c r i p t 10 stress and apoptosis of spermatozoa was also observed following incubation with E. coli (Villegas et al, 2005;Fraczek et al, 2007). In rat in vivo models the retrograde inoculation of E. coli into the vas deferens promoted clinically recognizable acute orchitis characterized by severe degeneration of germinal epithelial cells, tubular atrophy, moderate inflammation and mild interstitial fibrosis with subsequent testicular damage (Demir et al, 2007).…”