The role of toll-like receptors 2 and 4 in the pathogenesis of feline pyometra.

Pyometra is the most common uterine disease in queens. To protect itself from infection, the female reproductive tract possesses several immune mechanisms that are based on germline-encoded pattern recognition receptors (toll-like receptors [TLRs]). The aim of our study was to examine endometrial immunolocalization of TLR2/4, study the influence of lipopolysaccharide (LPS) and tumor necrosis factor (TNF) α on messenger RNA expression of both receptors in pyometric queens, and compare these patterns between estrous cycling queens and those hormonally treated with medroxyprogesterone acetate (MPA). Thirty-six queens, ranging in age from 7 months to 11 years, were allocated into seven groups (anestrus, estrus, mid-diestrus and late diestrus, short-term and long-term hormonally treated queens, and pyometric queens). At the messenger RNA level, the real-time polymerase chain reaction was applied, whereas at the TLR2/4 protein level, the expression was tested by immunohistochemistry. In queens at estrus, gene expression of TLR2 was upregulated after stimulation of endometrial explants by TNF (P < 0.001) and by TNF together with the LPS (P < 0.01). Moreover, gene expression of TLR2 was significantly upregulated after stimulation by TNF (P < 0.001) and LPS (P < 0.01) explants derived from queens that had been long-term hormonally treated with MPA. Endometrial gene expression of TLR4 was significantly upregulated after incubation of explants with TNF (P < 0.001) in queens at estrus and with LPS (P < 0.05) in queens short-term hormonally treated with MPA. Immunolocalization reported that TLR2/4 receptors are mainly localized in the surface and glandular epithelia. These data show that short-term and especially long-term administration of progesterone derivatives impairs TLRs in the endometrial epithelium, presumably enabling pathogens to break through this first natural barrier and thereby increase the risk of pyometra development.

Prostaglandin endoperoxide synthase 2 (PTGS2) and prostaglandins F2α and E2 synthases (PGFS and PGES) expression and prostaglandin F2α and E2 secretion following oestrogen and/or progesterone stimulation of the feline endometrium.

Sex steroids in synergy with prostaglandins (PG) are involved in the regulation of cyclic ovarian function. In this study, we investigated the mRNA expression of three genes involved in arachidonic acid (AA) metabolism and hence PG production in domestic cats: PG-endoperoxide synthase (PTGS2), PGF(2α) synthase (PGFS) and PGE(2) synthase (PGES). Feline endometria (n = 16) were collected at oestrus and mid and late phases of pseudopregnancy. In addition, the effects of E(2) and/or P(4) on PG secretion and gene expression on endometrial explants were studied in an in vitro culture system. Expression levels of all examined genes were up-regulated at the mid phase of pseudopregnancy. The effects of E(2) and/or P(4) treatment on both PG secretion and expression of the genes were observed after 12 h of culture. Expression of PGES was significantly up-regulated by E(2) plus P(4) at oestrus and the mid phase of pseudopregnancy and was also up-regulated by a single treatment with P(4) at late pseudopregnancy (p < 0.05). Simultaneous incubation with E(2) and P(4) up-regulated PTGS2 gene expression at oestrus and mid-luteal phase (p < 0.05). Progesterone plus E(2) significantly increased PGE(2) secretion at oestrus and the mid phase of pseudopregnancy. However, treatment with E(2) and/or P(4) affected neither PGF(2α) secretion nor PGFS expression at any phase after 12 h of culture. The overall findings indicate that genes involved in PG synthesis are up-regulated at the mid phase of pseudopregnancy. An increase in PGE(2) secretion and up-regulation of PGES and PTGS2 are the main responses of the endometrium to treatment with E(2) and P(4) at oestrus and the mid phase of pseudopregnancy in the cat. These data support the hypothesis that ovarian sex steroids via endometrial PGE(2) are involved in endocrine homoeostasis, especially at oestrus and the mid, but not the late, phase of pseudopregnancy in cats.