Abstract
[Introduction] In mammals, insemination triggers endometrium epithelial cells to release pro- and anti- inflammatory cytokines. We have previously indicated that Toll-like receptor 2 (TLR2) is involved in sperm attachment and inflammatory response in the bovine uterus. In addition, CD44 has been reported as a major molecule to attach epithelial cells, which can be expressed on mammalian sperm. On the other hand, the direct association and possible interaction between CD44 and TLR2, and also induction of CD44 expression via stimulation of TLR2 by their ligands have been mentioned in few studies so far. We hypothesized that sperm can bind to the uterine epithelium by means of CD44 and uterine TLR2. Next, the impacts of different numbers (1, 5, 10, 15 and 20 molecules) of peptidoglycan (PGN: TLR2 ligand) during pathophysiological condition and three different number of hyaluronan fragments (HA: TLR2 ligand; HA4, HA8, and HA16) on the possible CD44-TLR2 interaction were considered. Of note, HA is known to be an abundant endogenous molecule in the uterus. [Materials and Methods] To the aim above, we used computational methods (MD Simulation and docking) to clarify the potential affinity between these molecules. [Results] Our findings clearly showed the strong interaction between CD44 and TLR2; the binding free energy was –436.38 KJ/mol. The average number of Hydrogen bonds (H-bond), between CD44 and TLR2, varied from 8.74 to 13.78 during 100 ns simulation time. This means that the H and O atoms of CD44 and TLR2 have strong tendencies to form H-bond with their counterparts. Moreover, the affinity between CD44 and TLR2 increased significantly in the presence of PGN (up to 15 molecules) and HA4, HA8 and HA16. These in silico bindings indicate that endogenous (HA) and exogenous (PGN) related factors could change the interaction between the sperm and the uterus.
