Toll-like receptor 3 and RIG-I-like receptor activation induces innate antiviral responses in mouse ovarian granulosa cells

Abstract

Viral infections of the ovary can cause pathological conditions. However, innate antiviral responses in the ovary are poorly understood. In this study, we demonstrate that Toll-like receptor 3 (TLR3), retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated gene 5 (MDA5) are constitutively expressed in the mouse ovary and predominantly located in granulosa cells. Polyinosinic-polycytidylic acid [poly(I:C)], a common agonist of TLR3, MDA5 and RIG-I, induced innate antiviral responses in ovarian granulosa cells. Poly(I:C) up-regulated pro-inflammatory cytokines, including TNF-α and IL-6, and type I interferons (IFN-α/β). Moreover, poly(I:C) induced the expression of antiviral proteins, including 2'-5'-oligoadenylate synthetase, Mx GTPase 1 and IFN-stimulating gene 15, in granulosa cells. In contrast, P450 aromatase expression was inhibited by poly(I:C). The poly(I:C)-induced antiviral responses in TLR3 knockout (TLR3(-/-)) ovarian granulosa cells were reduced, and completely abolished by blocking of MDA5/RIG-I signaling. Further, the poly(I:C)-induced cytokine expression in TLR3(-/-) cells was reduced by knockdown of MDA5 or RIG-I. Data suggest that TLR3, MDA5 and RIG-I cooperate in mediating innate antiviral responses in granulosa cells, which may contribute to the defense of the ovary against viral infections.