Spermicidal activity of bacterial lipopolysaccharide is only partly due to lipid A.
We have previously shown that co-incubation of Chlamydia trachomatis lipopolysaccharide (LPS) leads to premature sperm death by an apoptosis-like mechanism. It was always assumed that lipid A is the toxic component of LPS. Here we investigate the possible involvement of 3-deoxy-D-manno-octulosonic acid (Kdo), which is an additional component of the LPS in C. trachomatis. Highly motile preparations of sperm from normozoospermic patients were incubated for 6 hours with commercial sources of lipid A and Kdo. Conventional lipid A inhibitors, polymyxin B (PMB) and anti-CD14 monoclonal antibody (mAb) were used to test the ability of both lipid A and Kdo to induce an apoptotic-like response in mature sperm. Flow cytometry was used to determine apoptosis by the expression of annexin V. Caspase activity was also measured by fluorometry and by the use of a pan-caspase inhibitor and caspase-3 inhibitor. Both lipid A and Kdo at 50 micro g/mL caused significant mortality of sperm. However, although PMB and anti-CD14 mAb were inhibitory to the activity of lipid A on sperm, no such effect was seen against Kdo. In the presence of either lipid A or Kdo, sperm death was caused by an apoptotic-like effect that was caspase mediated. We conclude that Kdo shares its spermicidal properties with lipid A and seems to kill sperm in a similar manner. These results provide an explanation for higher than expected levels of spermicidal activity of LPS that are not caused by lipid A.
Hakimi
Hamid
H
Division of Genomic Medicine, The Medical School, The University of Sheffield, Sheffield, UK.
Geary
Ian
I
Pacey
Allan
A
Eley
Adrian
A
D000911:Antibodies, Monoclonal / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D020169:Caspases / Q000378:metabolism; D006801:Humans; D008050:Lipid A / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D018950:Lipopolysaccharide Receptors / Q000276:immunology; D008070:Lipopolysaccharides / Q000494:pharmacology*; D008297:Male; D011112:Polymyxin B / Q000494:pharmacology; D013089:Spermatocidal Agents / Q000494:pharmacology*; D013094:Spermatozoa / Q000187:drug effects*; D013400:Sugar Acids / Q000494:pharmacology*
D000911:Antibodies, Monoclonal; D008050:Lipid A; D018950:Lipopolysaccharide Receptors; D008070:Lipopolysaccharides; D013089:Spermatocidal Agents; D013400:Sugar Acids; D020169:Caspases; D011112:Polymyxin B; C120356:3-deoxy-manno-oct-2-ulopyranosonic acid