302. Characterisation of lipopolysaccharide (LPS) receptor expression and the inflammatory response of the rat testis
W. Winnall A , J. Muir A , P. Hutchinson A and M. Hedger ACentre for Reproduction and Development, Monash Institute of Medical Research, Clayton, VIC, Australia
Reproduction, Fertility and Development 17(9) 128-128 https://doi.org/10.1071/SRB05Abs302
Submitted: 26 July 2005 Accepted: 26 July 2005 Published: 5 September 2005
Abstract
Inflammation in the testis is disastrous for the developing spermatogenic cells, leading to temporary and sometimes permanent sterility. The majority of testicular macrophages display a unique protective phenotype whereby production of some key inflammatory mediators, specifically interleukin-1β (IL-1β), tumour necrosis factor-α (TNFα) and NO, in response to stimulation with LPS is relatively poor. Leydig cells and Sertoli cells also respond to high doses of LPS, producing the inflammatory cytokines, particularly IL-1α and IL-6. Although these data suggest that the LPS receptor (toll-like receptor 4, TLR4) and its associated binding proteins, CD14 and MD2, are expressed on several testicular cell types, expression of these proteins in the testis has not been described previously.
Using real-time PCR and Western blotting, we established that TLR4, CD14 and MD2 are all expressed by testicular macrophages, Leydig cells, Sertoli cells, spermatocytes and round spermatids. Unexpectedly, the spermatogenic cells displayed the highest level of TLR4 surface expression as determined by flow cytometry. There was no response of the spermatogenic cells to LPS stimulation in vitro, at least in terms of mRNA expression for the inflammatory cytokines, IL-1α, IL-1β, TNFα, IL-6, activin A and the chemoattractants, CXCL-1 and CXCL-2. Although production of several cytokines was relatively diminished, testicular macrophages responded to LPS with a significant increase in mRNA expression for all of these inflammatory regulators. These data indicate that the protective phenotype of the testicular macrophages is not due to insensitivity to LPS or absence of the receptor, but may involve downstream regulation of specific inflammatory responses. The data also suggest that spermatogenic cells are capable of responding to TLR4 ligands, although not by producing inflammatory mediators. The actual function of the LPS receptor on the spermatogenic cells remains to be discovered.
