ABSTRACT
Inflammation following tissue damage promotes lymphocyte recruitment, tissue remodeling, and wound healing while maintaining self tolerance. Endogenous signals associated with tissue damage and cell death have been proposed to initiate and instruct immune responses following injury. In this study, we have examined the effects of elevated levels of a candidate endogenous danger signal, heat shock cognate protein 70 (hsc70), on stimulation of inflammation and autoimmunity following cell damage. We find that damage to pancreatic beta cells expressing additional cytosolic hsc70 leads to an increased incidence of diabetes in a transgenic mouse model. Steady-state levels of activated APC and T cell populations in the draining lymph node were enhanced, which further increased following streptozotocin-induced beta cell death. In addition, proinflammatory serum cytokines, and lymphocyte recruitment were increased in hsc70 transgenic mice. Islet Ag-specific T cells underwent a greater extent of proliferation in the lymph nodes of mice expressing hsc70 following beta cell damage, suggesting elevated Ag presentation following release of Ag in the presence of hsc70. These findings suggest that an elevated content of hsc70 in cells undergoing necrotic or apoptotic cell death can increase the extent of sterile inflammation and increase the susceptibility to autoimmunity.
Subject(s)
Diabetes Mellitus, Experimental/immunology , Diabetes Mellitus, Experimental/pathology , HSC70 Heat-Shock Proteins/biosynthesis , HSC70 Heat-Shock Proteins/genetics , Islets of Langerhans/immunology , Islets of Langerhans/pathology , Animals , Autoimmune Diseases/epidemiology , Autoimmune Diseases/genetics , Autoimmune Diseases/pathology , CD8-Positive T-Lymphocytes/immunology , CD8-Positive T-Lymphocytes/metabolism , CD8-Positive T-Lymphocytes/pathology , Cattle , Cell Death/genetics , Cell Death/immunology , Cell Movement/genetics , Cell Movement/immunology , Cytosol/immunology , Cytosol/metabolism , Diabetes Mellitus, Experimental/epidemiology , Diabetes Mellitus, Experimental/genetics , Disease Models, Animal , Incidence , Islets of Langerhans/metabolism , Lymphocyte Activation/immunology , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Mice, Transgenic , RatsABSTRACT
AIMS: Vascular calcification (VC) is highly correlated with increased morbidity and mortality in advanced chronic kidney disease (CKD) patients. Allosteric modulation of the calcium-sensing receptor (CaR) by calcimimetics inhibits VC in animal models of advanced CKD. Here, we investigated the expression of the CaR in the vasculature and tested the ability of calcimimetics to prevent vascular smooth muscle cell (VSMC) calcification in vitro. METHODS AND RESULTS: Immunohistochemical staining demonstrated that CaR protein is present in VSMC in normal, non-calcified human arteries. In contrast, low levels of CaR immunoreactivity were detected in atherosclerotic, calcified arteries. Immunfluorescence and immunoblotting revealed that CaR protein was also expressed by human and bovine VSMC in vitro. Acute stimulation of VSMC with increased Ca2+ stimulated extracellular signal-regulated kinase (ERK1/2) phosphorylation, suggesting that the VSMC CaR is functional. VSMC CaR expression decreased when these cells deposited a mineralized matrix or following 24 h incubation in mineralization medium with increased (i.e. 1.8 or 2.5 mM) Ca2+. Culturing VSMC in mineralization medium containing 1.8 and 2.5 mM Ca2+ or with the membrane-impermeant CaR agonist Gd3+ enhanced mineral deposition compared with that observed in 1.2 mM Ca2+. Over-expression of dominant-negative (R185Q) CaR enhanced, whereas the calcimimetic R-568 attenuated, VSMC mineral deposition. CONCLUSION: These results demonstrate that: (i) VSMCs express a functional CaR; (ii) a reduction in CaR expression is associated with increased mineralization in vivo and in vitro; (iii) calcimimetics decrease mineral deposition by VSMC. These data suggest that calcimimetics may inhibit the development of VC in CKD patients.
