Research On TLR3 Signal Pathway In Innate Antiviral Responses Of Ovary Granulosa Cells After Virus Infection

Background:Virus infection may disturb ovarian follicle development and estradiol production. Toll-like receptor 3 (TLR-3) is a key component of the innate immune system that recognizes viral double-stranded RNA and triggers immune reaction. Poly inosinic-polycy tidylic acid [Poly (I:C)], which is a synthetic dsRNA analog, can be produced by different viruses and recognized by TLR3. The ovary and GCs can be targeted by different virus. Virus has been detected in the human oocyte and follicle fluid. Ovulation and steroidogenesis are two major functions of the ovary. Estradiol is produced by GC aromatization of theca-derived androgens.Objectives:We tested the hypothesis that TLR3 activation triggers immune reaction and regulates E2 production in human ovary granulosa cells (GCs).Methods:In situ examinations of TLR3 expression was conducted in the human ovary by immunohistochemical staining. GCs were obtained from patients undergoing in vitro fertilization (IVF) and cultured in vitro. Immunocytochemistry was performed to examine the localization of TLR3 in human GCs. Cell viability was assessed by CCK-8 solution at 450 nm. The concentration of cytokines was measured by enzyme-linked immune sorbent assay (ELISA) kits for interleukin-6 (IL-6), interleukin-8 (IL-8), and regulated upon activation normal T cell expressed and secreted (RANTES). E2 concentration was assayed by electrochemiluminescence. The mRNA levels of TLR3 and cytochrome P450 aromatase (CYP19) were determined by real-time PCR. TLR3 and P450 aromatase protein levels were determined by Western blot.Results:Ovary tissue and GCs express TLR3 constitutively. Poly (I:C) enhanced TLR3 expression. Poly (I:C) induced IL-6, IL-8 and RANTES secretion in GCs. Poly (I:C) suppressed E2 synthesis that stimulated by FSH in GCs. Poly (I:C) inhibited P450 aromatase mRNA and protein expression.Conclusions:TLR3 is a functional protein that is constitutively expressed in human GCs. Virus infection might cause immune reaction and suppress E2 synthesis in GCs through inhibiting P450 aromatase expression. These findings suggest that TLR3 might play a role in folliculogenesis and ovulation.