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Steroid receptor coactivator 3 is required for clearing bacteria and repressing inflammatory response in Escherichia coli-induced septic peritonitis.

ABSTRACT: Steroid receptor coactivator 3 (SRC-3) is a multifunctional protein that plays an important role in regulation of bacterial LPS-induced inflammation. However, its involvement in host defense against bacterial infection remains unclear. In this study, we used SRC-3 knockout mice to assess the role of SRC-3 in antibacterial defense in Escherichia coli-induced septic peritonitis. After E. coli bacteria were injected i.p., SRC-3-deficient mice exhibited excessive local and systemic inflammatory responses and more severe bacterial burdens, leading to a significantly higher mortality compared with wild-type mice. Peritoneal macrophages of SRC-3-deficient mice showed a decrease in bacterial phagocytosis in culture and an increase in apoptosis, which was consistent with the defective bacterial clearance observed in SRC-3-deficient mice. Accordingly, SRC-3 null macrophages expressed much lower levels of scavenger receptor A, the antioxidant enzyme catalase, and antiapoptotic gene Bcl-2. Collectively, our data demonstrate that SRC-3 is important not only in modulating the local and systemic inflammation but also in intensifying bacterial clearance, which highlights a pivotal role of SRC-3 in the host defense system against bacterial infection.

SUBMITTER: Chen Q

PROVIDER: S-EPMC3640995 | biostudies-literature | 2010 Nov

REPOSITORIES: biostudies-literature

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Steroid receptor coactivator 3 is required for clearing bacteria and repressing inflammatory response in Escherichia coli-induced septic peritonitis.

Chen Qiang Q Chen Tenghui T Xu Yixiang Y Zhu Jingwei J Jiang Yuan Y Zhao Yang Y Xu Jianming J Yu Chundong C

Journal of immunology (Baltimore, Md. : 1950) 20100929 9

Steroid receptor coactivator 3 (SRC-3) is a multifunctional protein that plays an important role in regulation of bacterial LPS-induced inflammation. However, its involvement in host defense against bacterial infection remains unclear. In this study, we used SRC-3 knockout mice to assess the role of SRC-3 in antibacterial defense in Escherichia coli-induced septic peritonitis. After E. coli bacteria were injected i.p., SRC-3-deficient mice exhibited excessive local and systemic inflammatory resp ...[more]

PMID: 20881187

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Project description:Commensal microbes are exposed to enterohepatically circulated steroids such as bile acids and hormones in the gastrointestinal, vaginal, and urinary tracts. Since commensal microbes are exposed to these molecules exclusively in association with their host, we hypothesized that they may serve as effectors to identify and characterize genetic pathways involved in the commensal-host relationship. Host specific and some ingested steroids (phytoestrogens) are enterohepatically circulated through the lumen of the small intestine. Bile acid steroids are present at high concentrations, approximating 4 to 20 mM in the duodenum, and are released in bile from the common bile duct. Steroid hormones are secreted in bile at levels approximating 6 to 13 mg per day once conjugated to glucuronide or sulfate by the liver. Re-absorption of steroids by the terminal ileum is an incomplete process: for example, 200 to 600 mg of bile acid steroids per day in humans escape to the colon where complex microbial populations exist. We have shown that steroid hormones estradiol, progesterone, and hydrocortisone serve as strong substrates for the major RND- and MFS-type (except hydrocortisone) tripartite multidrug efflux systems, AcrAB-TolC and EmrAB-TolC respectively, even though such molecules fail to demonstrate antimicrobial properties in this bacterial background (Elkins and Mullis [2006] J. Bacteriol. 188:1191-1195). Although bile acids are subject to efflux, they are also known to directly interact with intracellular global regulators such as MarR (Prouty et al. [2004] Microbiol. 150:775-783) and Rob (Rosenberg et al., [2003] Mol. Microbiol. 48:1609-1619) consequently altering antimicrobial and bile resistance profiles. In our present study, whole-genome DNA microarrays of E. coli were used to determine what general effect steroids, both bile acid and hormones, may have on the transcriptome in relation to the human commensal environment. Keywords: Comparative Chemical Class Treatment

Project description:Estradiol and progesterone bind to their respective receptors in the hypothalamus and hippocampus to influence a variety of behavioral and physiological functions, including reproduction and cognition. Work from our lab and others has shown that the nuclear receptor coactivators, steroid receptor coactivator-1 (SRC-1) and SRC-2, are essential for efficient estrogen receptor (ER) and progestin receptor (PR) transcriptional activity in brain and for hormone-dependent behaviors. While the expression of SRC-1 in brain has been studied extensively, little is known about the expression of SRC-2 in brain. In the present studies, we found that SRC-2 was highly expressed throughout the hippocampus, amygdala and hypothalamus, including the medial preoptic area (MPOA), ventral medial nucleus (VMN), arcuate nucleus (ARC), bed nucleus of the stria terminalis, supraoptic nucleus and suprachiasmatic nucleus. In order for coactivators to function with steroid receptors, they must be expressed in the same cells. Indeed, SRC-2 and ER(alpha) were coexpressed in many cells in the MPOA, VMN and ARC, all brain regions known to be involved in female reproductive behavior and physiology. While in vitro studies indicate that SRC-2 physically associates with ER and PR, very little is known about receptor-coactivator interactions in brain. Therefore, we used pull-down assays to test the hypotheses that SRC-2 from hypothalamic and hippocampal tissue physically associate with ER and PR subtypes in a ligand-dependent manner. SRC-2 from both brain regions interacted with ER(alpha) bound to agonist, but not in the absence of ligand or in the presence of the selective ER modulator, tamoxifen. Analysis by mass spectrometry confirmed these ligand-dependent interactions between ER(alpha) and SRC-2 from brain. In dramatic contrast, SRC-2 from brain showed little to no interaction with ERbeta. Interestingly, SRC-2 from both brain regions interacted with PR-B, but not PR-A, in a ligand-dependent manner. Taken together, these findings reveal that SRC-2 is expressed in brain regions known to mediate a variety of steroid-dependent functions. Furthermore, SRC-2 is expressed in many ER(alpha) containing cells in the hypothalamus. Finally, SRC-2 from brain interacts with ER and PR in a subtype-specific manner, which may contribute to the functional differences of these steroid receptor subtypes in brain.

Dataset Information

Steroid receptor coactivator 3 is required for clearing bacteria and repressing inflammatory response in Escherichia coli-induced septic peritonitis.

Publications

Steroid receptor coactivator 3 is required for clearing bacteria and repressing inflammatory response in Escherichia coli-induced septic peritonitis.

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