‘Efferocytosis of infected apoptotic cells inhibits Th17 differentiation via PGE2-EP4 signaling’

Abstract

Abstract Clearance of infected apoptotic cells (IAC) by dendritic cells (DC) triggers the production of Th17-related cytokines. Moreover, we have found that prostaglandin E2 (PGE2) is also produced during efferocytosis containing microbial products, but the effect of this prostanoid on Th17-differentiation is still unknown. The purpose of this study was to evaluate the role of PGE2, produced during recognition of IAC by DC, on Th17 differentiation. As source of IAC, Raw 264-7 cells were cultured with Escherichia coli during 2h for phagocytosis and apoptosis was induced by UV irradiation. BMDC were co-culture with IAC during 18h, and the supernatant from this co-culture was used to differentiate naïve CD4+ T cells for 4d, plus anti-CD3/anti-CD28. Phagocytosis of IAC by DC promotes the production of high levels of PGE2 (15±0.7 ng/ml), IL-6 (26±0.4 ng/ml), TGF-β (3.5±0.09 ng/ml) and IL-1β (5.4±0.1 ng/ml), when compared to phagocytosis of uninfected-AC. The treatment with COX inhibitor significantly decreased PGE2 level and promotes Th17 cell differentiation at least 4 times higher (16%) than untreated co-cultures (4%). Moreover, adding back exogenous PGE2 decreased drastically the percentage of Th17 cells (2%). Moreover, the treatment of naive T cells with antagonists of PGE2 receptor (EP1/EP2/EP4) suggests that the suppressor effect of this prostanoid on Th17 cell differentiation is mainly mediated by EP4/cAMP/PKA activation pathway. Taken all together, our results show that PGE2 is able to suppress Th17 differentiation in vitro through EP4 signaling. Further studies are needed to clarify how PGE2 can modulate the Th17 differentiation using in vivo model. Financial Support: FAPEP 14/17374-3, 12/23580-0, 11/17611-7.