Inhibition of Wnt Signaling Pathways Impairs Chlamydia trachomatis Infection in Endometrial Epithelial Cells

Abstract

Chlamydia trachomatis infections represent the predominant cause of bacterial sexually transmitted infections. As an obligate intracellular bacterium, C. trachomatis is dependent on the host cell for survival, propagation, and transmission. Thus, factors that affect the host cell, including nutrition, cell cycle, and environmental signals, have the potential to impact chlamydial development. Previous studies have demonstrated that activation of Wnt/β-catenin signaling benefits C. trachomatis infections in fallopian tube epithelia. In cervical epithelial cells chlamydiae sequester β-catenin within the inclusion. These data indicate that chlamydiae interact with the Wnt signaling pathway in both the upper and lower female genital tract (FGT). However, hormonal activation of canonical and non-canonical Wnt signaling pathways is an essential component of cyclic remodeling in another prominent area of the FGT, the endometrium. Given this information, we hypothesized that Wnt signaling would impact chlamydial infection in endometrial epithelial cells. To investigate this hypothesis, we analyzed the effect of Wnt inhibition on chlamydial inclusion development and elementary body (EB) production in two endometrial cell lines, Ishikawa (IK) and Hec-1B, in nonpolarized cell culture and in a polarized endometrial epithelial (IK)/stromal (SHT-290) cell co-culture model. Inhibition of Wnt by the small molecule inhibitor (IWP2) significantly decreased inclusion size in IK and IK/SHT-290 cultures (p < 0.005) and chlamydial infectivity (p ≤ 0.01) in both IK and Hec-1B cells. Confocal and electron microscopy analysis of chlamydial inclusions revealed that Wnt inhibition caused chlamydiae to become aberrant in morphology. EB formation was also impaired in IK, Hec-1B and IK/SHT-290 cultures regardless of whether Wnt inhibition occurred throughout, in the middle (24 hpi) or late (36 hpi) during the development cycle. Overall, these data lead us to conclude that Wnt signaling in the endometrium is a key host pathway for the proper development of C. trachomatis.

Bacterial Manipulation of Wnt Signaling: A Host-Pathogen Tug-of-Wnt

“…It is unclear if disruption of these junctions amplifies β-catenin nuclear localization and target gene expression, but infected epithelium does demonstrate increased Wnt pathway activity evidenced by phosphorylation-dependent inactivation of GSK3β and redistribution of APC which indicates inactivation of the β-catenin destruction complex (25). Additionally, inhibition of Wnt signaling through either RNA silencing of β-catenin or a small molecule inhibitor reduces infectivity of the chlamydiae and impairs chlamydiae intracellular development (25, 26). Thus, signaling is beneficial to chlamydiae and may be synergistically activated through inhibition of the β-catenin destruction complex and disruption of adherens junctions.…”

Nutrition and Bipartite Metabolism of Intracellular Pathogens

“…Compared to other intracellular pathogens, Chlamydia accesses host amino acids and cholesterol through the lysosome, presumably via its close association with lysosomes and the golgi apparatus throughout development [37,79]. Chlamydia likely access transferrinbound iron in a similar fashion [37].…”

“…C. trachomatis manipulate various host nutritional and inflammatory pathways to override host depletion of tryptophan and to obtain host nutrients such as cholesterol, iron, and glucose [79,[83][84][85]. The host SLC35D2, a UDP-glucose transporter, to the C. trachomatis inclusion [86].…”

A renewed tool kit to explore Chlamydia pathogenesis: from molecular genetics to new infection models

“…Notably, the localization of these Wnt effectors also changed in neighboring uninfected cells but was rescued upon the addition of Wnt inhibitors, suggesting that infection can alter tissue-level Wnt signaling programs 42 . More recently, pharmacological inhibition of Wnt signaling in endometrial epithelial cells resulted in smaller and aberrant inclusions and significantly reduced the production of EBs 64 .…”