ABSTRACT
Kidney disease represents a major medical and economic burden for which improved treatments are urgently needed. Emerging data have implicated Th17 cells and IL-17 signaling in the underlying pathogenesis of autoantibody-induced glomerulonephritis (AGN). However, the downstream transduction pathways mediated by IL-17 in autoimmunity are not well defined. In this article, we show that CCAAT/enhancer-binding protein (C/EBP) δ is elevated in kidney biopsies from multiple manifestations of human AGN. C/EBPδ is similarly upregulated in a mouse model of anti-glomerular basement membrane protein-mediated kidney disease, and Cebpd-/- mice were fully refractory to disease. Although C/EBPδ is expressed in a variety of cell types, C/EBPδ was required only in the radioresistant compartment to drive GN pathology. C/EBPδ induced expression of several IL-17-induced kidney injury markers and cytokines implicated in disease, including Il6 and Lcn2. Because mouse AGN models do not progress to fibrosis, we employed a nephrotoxic injury model using aristolochic acid I to assess the contribution of the IL-17-C/EBPδ pathway to renal fibrotic events. Surprisingly, deficiency of either C/EBPδ or the IL-17 receptor caused kidney fibrosis to be enhanced. Thus, C/EBPδ and IL-17 play divergent and apparently stage-specific roles in the pathogenesis of kidney disease.
Subject(s)
CCAAT-Enhancer-Binding Protein-delta , Glomerulonephritis , Animals , Humans , Mice , Aristolochic Acids/toxicity , Autoantibodies/immunology , CCAAT-Enhancer-Binding Protein-delta/genetics , Disease Models, Animal , Glomerulonephritis/immunology , Glomerulonephritis/pathology , Interleukin-17/immunology , Interleukin-17/metabolism , Kidney/immunology , Kidney/pathology , Lipocalin-2/genetics , Lipocalin-2/metabolism , Lipocalin-2/immunology , Mice, Inbred C57BL , Mice, Knockout , Signal Transduction , Th17 Cells/immunologyABSTRACT
Cachexia occurs in patients with advanced cancers. Despite the adverse clinical impact of cancer-induced muscle wasting, pathways causing cachexia are controversial, and clinically reliable therapies are not available. A trigger of muscle protein loss is the Jak/Stat pathway, and indeed, we found that conditioned medium from C26 colon carcinoma (C26) or Lewis lung carcinoma cells activates Stat3 (p-Stat3) in C2C12 myotubes. We identified two proteolytic pathways that are activated in muscle by p-Stat3; one is activation of caspase-3, and the other is p-Stat3 to myostatin, MAFbx/Atrogin-1, and MuRF-1 via CAAT/enhancer-binding protein δ (C/EBPδ). Using sequential deletions of the caspase-3 promoter and CHIP assays, we determined that Stat3 activation increases caspase-3 expression in C2C12 cells. Caspase-3 expression and proteolytic activity were stimulated by p-Stat3 in muscles of tumor-bearing mice. In mice with cachexia caused by Lewis lung carcinoma or C26 tumors, knock-out of p-Stat3 in muscle or with a small chemical inhibitor of p-Stat3 suppressed muscle mass losses, improved protein synthesis and degradation in muscle, and increased body weight and grip strength. Activation of p-Stat3 stimulates a pathway from C/EBPδ to myostatin and expression of MAFbx/Atrogin-1 and increases the ubiquitin-proteasome system. Indeed, C/EBPδ KO decreases the expression of MAFbx/Atrogin-1 and myostatin, while increasing muscle mass and grip strength. In conclusion, cancer stimulates p-Stat3 in muscle, activating protein loss by stimulating caspase-3, myostatin, and the ubiquitin-proteasome system. These results could lead to novel strategies for preventing cancer-induced muscle wasting.
Subject(s)
Cachexia/metabolism , Carcinoma, Lewis Lung/metabolism , Caspase 3/metabolism , Colonic Neoplasms/metabolism , Muscle, Skeletal/metabolism , Proteasome Endopeptidase Complex/metabolism , STAT3 Transcription Factor/metabolism , Ubiquitin/metabolism , Animals , CCAAT-Enhancer-Binding Protein-delta/genetics , CCAAT-Enhancer-Binding Protein-delta/metabolism , Cachexia/genetics , Cachexia/pathology , Carcinoma, Lewis Lung/genetics , Carcinoma, Lewis Lung/pathology , Caspase 3/genetics , Cell Line, Tumor , Colonic Neoplasms/genetics , Colonic Neoplasms/pathology , Mice , Mice, Knockout , Muscle Proteins/genetics , Muscle Proteins/metabolism , Muscle, Skeletal/pathology , Myostatin/genetics , Myostatin/metabolism , Proteasome Endopeptidase Complex/genetics , Proteolysis , SKP Cullin F-Box Protein Ligases/genetics , SKP Cullin F-Box Protein Ligases/metabolism , STAT3 Transcription Factor/genetics , Tripartite Motif Proteins , Ubiquitin/genetics , Ubiquitin-Protein Ligases/genetics , Ubiquitin-Protein Ligases/metabolismABSTRACT
PURPOSE: Extracellular Hsp70 has anti-inflammatory potential, demonstrated in different models of inflammatory diseases. We investigated probable mechanisms used by Hsp70 to down-regulate pro-inflammatory cytokines. MATERIALS AND METHODS: We analysed cytokine mRNA levels in bone marrow-derived murine dendritic cells treated with Hsp70, lipopolysaccharide (LPS) and peptidoglycan (PGN) or OVA (an irrelevant protein control), hypothesising that this was mediated by C/EBPß and C/EBPδ transcription factors. We also tested the involvement of TLR2, IL-10, ERK and STAT3, using genetically deficient mice and pharmacological inhibitors. RESULTS: C/EBPß and C/EBPδ levels were inhibited in bone marrow derived dendritic cells (BMDCs) treated with Hsp70, and that correlated with inhibition of TNF-α, IFN-γ and MCP-1. Such inhibition was not observed in TLR2 or IL-10 knockout mice, and was also abrogated upon pretreatment of cells with ERK and JAK2/STAT3 inhibitors. CONCLUSIONS: C/EBPß and C/EBPδ transcription factors are inhibited by Hsp70 treatment, and their inhibition occurs via the TLR2-ERK-STAT3-IL-10 pathway in BMDCs, mediating the anti-inflammatory effects of Hsp70.