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Brucella abortus Infection of Placental Trophoblasts Triggers Endoplasmic Reticulum Stress-Mediated Cell Death and Fetal Loss via Type IV Secretion System-Dependent Activation of CHOP.

ABSTRACT: Subversion of endoplasmic reticulum (ER) function is a feature shared by multiple intracellular bacteria and viruses, and in many cases this disruption of cellular function activates pathways of the unfolded protein response (UPR). In the case of infection with Brucella abortus, the etiologic agent of brucellosis, the unfolded protein response in the infected placenta contributes to placentitis and abortion, leading to pathogen transmission. Here we show that B. abortus infection of pregnant mice led to death of infected placental trophoblasts in a manner that depended on the VirB type IV secretion system (T4SS) and its effector VceC. The trophoblast death program required the ER stress-induced transcription factor CHOP. While NOD1/NOD2 expression in macrophages contributed to ER stress-induced inflammation, these receptors did not play a role in trophoblast death. Both placentitis and abortion were independent of apoptosis-associated Speck-like protein containing a caspase activation and recruitment domain (ASC). These studies show that B. abortus uses its T4SS to induce cell-type-specific responses to ER stress in trophoblasts that trigger placental inflammation and abortion. Our results suggest further that in B. abortus the T4SS and its effectors are under selection as bacterial transmission factors.IMPORTANCE Brucella abortus infects the placenta of pregnant cows, where it replicates to high levels and triggers abortion of the calf. The aborted material is highly infectious and transmits infection to both cows and humans, but very little is known about how B. abortus causes abortion. By studying this infection in pregnant mice, we discovered that B. abortus kills trophoblasts, which are important cells for maintaining pregnancy. This killing required an injected bacterial protein (VceC) that triggered an endoplasmic reticulum (ER) stress response in the trophoblast. By inhibiting ER stress or infecting mice that lack CHOP, a protein induced by ER stress, we could prevent death of trophoblasts, reduce inflammation, and increase the viability of the pups. Our results suggest that B. abortus injects VceC into placental trophoblasts to promote its transmission by abortion.

SUBMITTER: Byndloss MX

PROVIDER: S-EPMC6650558 | biostudies-literature | 2019 Jul

REPOSITORIES: biostudies-literature

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Brucella abortus Infection of Placental Trophoblasts Triggers Endoplasmic Reticulum Stress-Mediated Cell Death and Fetal Loss via Type IV Secretion System-Dependent Activation of CHOP.

Byndloss Mariana X MX Tsai April Y AY Walker Gregory T GT Miller Cheryl N CN Young Briana M BM English Bevin C BC Seyffert Núbia N Kerrinnes Tobias T de Jong Maarten F MF Atluri Vidya L VL Winter Maria G MG Celli Jean J Tsolis Renée M RM

mBio 20190723 4

Subversion of endoplasmic reticulum (ER) function is a feature shared by multiple intracellular bacteria and viruses, and in many cases this disruption of cellular function activates pathways of the unfolded protein response (UPR). In the case of infection with <i>Brucella abortus</i>, the etiologic agent of brucellosis, the unfolded protein response in the infected placenta contributes to placentitis and abortion, leading to pathogen transmission. Here we show that <i>B. abortus</i> infection o ...[more]

PMID: 31337727

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Project description:Brucellosis is still a widespread zoonotic disease. Very little is known about the interaction between B. abortus and trophoblastic cells, which is essential for better understanding the pathogenesis of the Brucella-induced placentitis and abortion, a key event for transmission of the disease. The goal of this study was to evaluate the profile of gene expression by bovine trophoblastic cells during infection with B abortus. Explants of chorioallantoic membranes were inoculated with B. abortus strain 2308. Microarray analysis was performed at 4 h after infection, and expression of cytokines and chemokines by trophoblastic cells was assessed by real time RT-PCR at 6 and 12 h after inoculation. In addition, cytokine and chemokine expression was evaluated in placentomes from experimentally infected cows. Expression of pro-inflammatory genes by trophoblastic cells was suppressed at 4 h after inoculation, whereas a significant up-regulation of CXC chemokines, namely CXCL6 (GCP-2) and CXCL8 (IL-8), was observed at 12, but not at 6 h after inoculation. Placentomes of experimentally infected cows had a similar profile of chemokine expression, with upregulation of CXCL6 and CXCL8. Our data indicate that B. abortus modulates the innate immune response by trophoblastic cells, suppressing expression of pro-inflammatory mediators during the early stages of infection that is followed by a delayed and mild expression of pro-inflammatory chemokines, which is similar to the profile of chemokine expression in the placentomes of experimentally infected cows. This trophoblastic response is likely to contribute to the pathogenesis of B. abortus-induced placentitis. Keywords: trophoblast response to Brucella Total RNA used for microarray analysis was obtained from 6 placentas with 12 infected and 12 control explants from each placenta. At 4 h after inoculation, total RNA was isolated from the trophoblastic surface of the explants. Three RNA pools from two placentas each were generated prior to cDNA synthesis.

Project description:Endoplasmic reticulum (ER) is a central organelle in eukaryotic cells that regulates protein synthesis and maturation. Perturbation of ER functions leads to ER stress, which has been previously associated with a broad variety of diseases. ER stress is generally regarded as compensatory, but prolonged ER stress has been involved in apoptosis induced by several cytotoxic agents. Choline kinase α (ChoKα), the first enzyme in the Kennedy pathway, is responsible for the generation of phosphorylcholine (PCho) that ultimately renders phosphatidylcholine. ChoKα overexpression and high PCho levels have been detected in several cancer types. Inhibition of ChoKα has demonstrated antiproliferative and antitumor properties; however, the mechanisms underlying these activities remain poorly understood. Here, we demonstrate that ChoKα inhibitors (ChoKIs), MN58b and RSM932A, induce cell death in cancer cells (T47D, MCF7, MDA-MB231, SW620 and H460), through the prolonged activation of ER stress response. Evidence of ChoKIs-induced ER stress includes enhanced production of glucose-regulated protein, 78 kDa (GRP78), protein disulfide isomerase, IRE1α, CHOP, CCAAT/enhancer-binding protein beta (C/EBPβ) and TRB3. Although partial reduction of ChoKα levels by small interfering RNA was not sufficient to increase the production of ER stress proteins, silencing of ChoKα levels also show a decrease in CHOP overproduction induced by ChoKIs, which suggests that ER stress induction is due to a change in ChoKα protein folding after binding to ChoKIs. Silencing of CHOP expression leads to a reduction in C/EBPβ, ATF3 and GRP78 protein levels and abrogates apoptosis in tumor cells after treatment with ChoKIs, suggesting that CHOP maintains ER stress responses and triggers the pro-apoptotic signal. Consistent with the differential effect of ChoKIs in cancer and primary cells previously described, ChoKIs only promoted a transient and moderated ER stress response in the non-tumorogenic cells MCF10A. In conclusion, pharmacological inhibition of ChoKα induces cancer cell death through a mechanism that involves the activation of exaggerated and persistent ER stress supported by CHOP overproduction.

Dataset Information

Brucella abortus Infection of Placental Trophoblasts Triggers Endoplasmic Reticulum Stress-Mediated Cell Death and Fetal Loss via Type IV Secretion System-Dependent Activation of CHOP.

Publications

Brucella abortus Infection of Placental Trophoblasts Triggers Endoplasmic Reticulum Stress-Mediated Cell Death and Fetal Loss via Type IV Secretion System-Dependent Activation of CHOP.

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