1. Novel mineralocorticoid receptor mechanisms regulate cardiac tissue inflammation in male mice
- Author
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Gregory S Y Ong, James Morgan, Jennifer K. Dowling, Peter J. Fuller, Ashley Mansell, Morag J. Young, Gregory H Tesch, and Tim J Cole
- Subjects
Lipopolysaccharides ,Male ,0301 basic medicine ,MAPK/ERK pathway ,medicine.medical_specialty ,Cardiac fibrosis ,Endocrinology, Diabetes and Metabolism ,Blotting, Western ,Receptors, Cytoplasmic and Nuclear ,030209 endocrinology & metabolism ,Inflammation ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Endocrinology ,Mineralocorticoid receptor ,Western blot ,Fibrosis ,Matrix Metalloproteinase 12 ,Internal medicine ,medicine ,Animals ,Macrophage ,medicine.diagnostic_test ,Chemistry ,Macrophages ,Myocardium ,medicine.disease ,Cell biology ,Receptors, Mineralocorticoid ,030104 developmental biology ,Nuclear receptor ,medicine.symptom - Abstract
MR activation in macrophages is critical for the development of cardiac inflammation and fibrosis. We previously showed that MR activation modifies macrophage pro-inflammatory signalling, changing the cardiac tissue response to injury via both direct gene transcription and JNK/AP-1 second messenger pathways. In contrast, MR-mediated renal electrolyte homeostasis is critically determined by DNA-binding-dependent processes. Hence, ascertaining the relative contribution of MR actions via DNA binding or alternative pathways on macrophage behaviour and cardiac inflammation may provide therapeutic opportunities which separate the cardioprotective effects of MR antagonists from their undesirable renal potassium-conserving effects. We developed new macrophage cell lines either lacking MR or harbouring a mutant MR incapable of DNA binding. Western blot analysis demonstrated that MR DNA binding is required for lipopolysaccharide (LPS), but not phorbol 12-myristate-13-acetate (PMA), induction of the MAPK/pJNK pathway in macrophages. Quantitative RTPCR for pro-inflammatory and pro-fibrotic targets revealed subsets of LPS- and PMA-induced genes that were either enhanced or repressed by the MR via actions that do not always require direct MR-DNA binding. Analysis of the MR target gene and profibrotic factor MMP12 identified promoter elements that are regulated by combined MR/MAPK/JNK signalling. Evaluation of cardiac tissue responses to an 8-day DOC/salt challenge in mice selectively lacking MR DNA-binding in macrophages demonstrated levels of inflammatory markers equivalent to WT, indicating non-DNA binding-dependent MR signalling in macrophages is sufficient for DOC/salt-induced tissue inflammation. Our data demonstrate that the MR regulates a macrophage pro-inflammatory phenotype and cardiac tissue inflammation, partially via pathways that do not require DNA binding.
- Published
- 2020