The neuropeptide VIP modulates the pro-inflammatory maternal response inducing tolerance to trophoblast cells: implications in patients with Recurrent Spontaneous Abortions

R. RAMHORST; L. FRACCAROLI; E. GRASSO; C. PÉREZ LEIRÓS

Rio de Janeiro

Simposio; 2nd symposium on Reproductive Immunology-4th Brazilian Symposium on HLA and Disease; 2009

The appropriate generation of a pro-inflammatory response is thought to be a prerequisite for successful implantation. However, elevated leukocyte infiltration and inappropriate activation may be an underlying cause of pregnancy complications and failures, attributed to an exacerbated inflammatory/Th1 response ultimately responsible for tissue damage and embryo resorption. VIP (vasoactive intestinal peptide) has anti-inflammatory effects and promotes tolerogenic responses while favours embryonic development. Results presented herein provide experimental evidence that VIP might contribute to embryo survival in the trophoblast-maternal microenvironment through two relevant strategies. As an embryotrophic factor inducing trophoblast cell proliferation and pro-implantatory markers and as a tolerogenic factor controlling the initial pro-inflammatory response, increasing maternal Tregs and suppressing effector Th1 cells and the pro-inflammatory microenvironment (chemokine, cytokines and NO), promoting an overall balance that favours tolerance to fetal antigens. These conclusions are based on several observations: we have demonstrated that first trimester trophoblast cell line (Swan-71 cells) constitutively express both VIP and their receptors, VPAC1 and VPAC2, which were functional since the neuropeptide was able to induce trophoblast cell proliferation and to increase the expression of LIF and its receptor, both markers of a pro-implantatory milieu. Regarding VIP tolerogenic effects on maternal response at the local level, we analyzed VIP effects in co cultures of trophoblast cell line and maternal PBMCs as a model representative of embryonic-maternal dialogue. VIP modulated maternal response after the interaction with trophoblast cells, reflected as an increased frequency of Tregs CD4+CD25+Foxp3+ associated with an increase in TFG expression. In addition, VIP could also modulate the balance of pro/anti inflammatory mediators, evidenced as a reduction in IL-6, MCP-1 and nitrites production and as an increase in IL-10 production. On the other hand, maternal T cells activated in response to paternal alloantigens may be at the centre of a local regulatory mechanism during and after the process of implantation. Data presented here show that conditioned media from trophoblast cells suppressed alloactivated maternal T cells and reduced T-bet expression. The effect seems to be partly mediated by endogenous VIP as it was specifically blunted by its antagonist peptide. Since a potential exacerbated pro/inflammatory/Th1 response could implicate into immunological abortion failures, we investigated whether VIP could control the initial pro-inflammatory response in patients with recurrent spontaneous abortions (RSA). These patients presented an exacerbated inflammatory/Th1 response and lower frequency of Treg cells compared to fertile women in basal conditions. However, VIP could modulate the initial inflammatory response in favour of a tolerogenic response; observed by an increase of Treg cells CD4+CD25+Foxp3+ and suppressor cytokines and a decrease in Th1 response, based on T-bet expression and pro-inflammatory mediators. The control of the initial inflammatory response at the feto-maternal interface is a hallmark of a successful implantation and given the action of VIP in the development of regulatory T cells and the efficacy of these cells to control inflammatory processes, this peptide arises as a promising candidate for an effective treatment for early pregnancy losses as recurrent spontaneous abortions or repetitive implantation failures after in vitro fertilization procedures.