52 Similar results were obtained independently by another group using LPS injection model.53 To elucidate the mechanism by which TLR4 signaling induced preterm delivery, Wang and Hirsch, using the same mice model, examined the prostaglandin pathway in the injected uterus. They showed that ligation of TLR4

with LPS down-regulates the expression of 15-hydroxyprostaglandin dehydrogenase, a prostaglandin-catabolizing enzyme, in fetal and maternal tissue. The authors hypothesized that TLR4 mediates bacterially induced preterm labor via down-regulation of prostaglandin degradation.52 LPS administration is also shown to change the cytokine profile by increasing maternal serum concentration of TNF-α Akt inhibitor and IL6, as well as placental expression of TNF-α, IL6

and IL1-α.54 Besides the cytokine profile, LPS treatment markedly changed the profile of immune cells; up-regulated the percentages of blood CD45(+)CD86(+), CD3(+)CD69(+), CD49b(+)CD69(+) cells, and placenta CD45(+)CD86(+), CD45(+)CD49b(+), CD49b(+)CD69(+) cells.55 These observations may imply that systemic and local inflammatory responses followed by LPS administration cause preterm labor. Gram-positive bacterial components have been associated with preterm labor as well. For example, in rodents, LTA was shown to induce preterm delivery following cervical ripening and placental abruption.56 These effects PCI-32765 mw on pregnancy seems to be TLR mediated as shown by a Epothilone B (EPO906, Patupilone) recent study where either PDG or LTA, both TLR2 ligands, induced preterm delivery in mice when injected intra uterus.57 In terms of the mechanism, contrary to the effects of TLR4 ligation, TLR2 ligation

does not seem to induce inflammatory responses. The expression of TNF-α and IL1-β was examined in uterine tissues, but no up-regulation was found in PDG-treated mice.57 We also recently established a novel mouse model, injected PDG intraperitoneally on gestational day 6 and observed uterine cytokine production, NK cells activation and apoptosis on day 12. In this model, no change in cytokine production or NK cell activation was found in PDG-treated uterus,48 in contrast to the findings in LPS-treated mice where cytokine up-regulation and NK cell activation were observed.58 On the other hand, a significant increase in apoptotic trophoblasts were observed in PDG-treated mice,48 which is consistent with the in vitro studies showing that PDG treatment to trophoblasts induced TLR2-mediated apoptosis.39 These results suggested that the mechanism underlying preterm labor triggered by PDG is not the result of an inflammatory reaction but apoptosis of the trophoblast. TLR3 response and preterm labor:  Administration of poly(I:C) which is a synthetic dsRNA mimicking viral RNA during late pregnancy also has detrimental effects on pregnancy as shown by a study using intrauterine injection model. When administrated on gestational day 15.