Stimuli through Toll-like receptor (TLR) 3 and 9 affect human chorionic gonadotropin (hCG) production in a choriocarcinoma cell line

Aim: Toll-like receptors (TLR) are expressed mostly on mucosal innate immune cells which recognize microorganism-associated structures, the so called pathogen-associated molecular patterns (PAMP). Recently, possible roles of TLR in placental tissue, especially their role in protecting the conceptus from maternal infection, have been discussed, but the physiopathological roles of TLR in placental functions have yet to be examined. Methods: The choriocarcinoma cell line BeWo was used as a model of trophoblast stem cells. First, the expression of TLR 1-9 on BeWo cells was investigated using reverse transcriptase-polymerase chain reaction. Then, the cells were treated with TLR 1-9 agonists, using the human TLR 1-9 agonist kit (Pam3CKS4, HKLM, Poly (I:C), Escherichia coli K12 lipopolysaccharide (LPS), Salmonella typhimurium flagellin, FSL1, imiquimod, ssRNA 40, and ODN 2006). The concentration of human chorionic gonadotropin (hCG) in the cell culture supernatants was examined on ELISA. Results: BeWo cells constitutively expressed TLR 1-9 mRNA in the presence or absence of forskolin. The TLR 3 agonist, Poly(I:C), and the TLR 9 agonist, CpG-DNA (ODN2006), upregulated hCG production but had minimal effects in the absence of forskolin. Stimulation with the other TLR agonists produced no remarkable increase, whether in the presence or absence of forskolin. Conclusions: TLR 3 and TLR 9 agonists upregulated hCG production in BeWo cells. The present observations suggest alternative roles of TLR signaling in the control of placental functions and blastocyst-endometrial dialogue, as well as in pathophysiology, including for infertility and ectopic pregnancy.