Intense immunostaining of heat shock protein 70 within renal interstitium associates with long-term renal survival in an ANCA-associated vasculitis cohort

摘要

In anti-neutrophilic cytoplasmic antibody (ANCA)-associated vasculitis (AAV) genetic predisposition, ANCA autoantibodies, neutrophil extracellular traps (NETs), complement activation, and toll-like receptor signaling are implicated in AAV pathogenesis. Heat shock proteins (HSPs), a highly conserved group of small-sized molecular chaperones, take part in protein folding during cellular stress. Although HSPs were initially observed intracellularly, it has been shown that they can be secreted in the extracellular space and modulate the immune response in various autoimmune diseases including AAV. The scope of the present study is to investigate the role of heat shock protein 60 (HSP60) and 70 (HSP70) in the long renal effects in an ANCA vasculitis cohort. In this cohort of ANCA-associated vasculitis, 29 patients were followed up over 20 years. At diagnosis, immunohistochemistry was performed for HSP60 and HSP70 within the various nephron compartments. Higher renal HSP60 expression was associated with increased interstitial inflammatory infiltrates at diagnosis, while HSP70 expression was associated with a greater extent of interstitial fibrosis at diagnosis. Notably, intense tissue expression of HSP70 at the time of biopsy was associated with a worsened kidney survival. Renal HSP70 expression was associated with poor renal outcomes during long-term follow-up. This finding may indicate a role of HSPs in renal disease progression in ANCA vasculitis. Further validating studies are needed to verify a causative association between HSP70 expression and renal outcomes in ANCA-associated vasculitis. Keywords: ANCA-vasculitis, Heat shock protein, Pauci-immune glomerulonephritis, Interstitial inflammation, Interstitial fibrosisIntroductionHeat shock proteins (HSPs), a highly conserved group of cellular chaperones, are involved in transmembrane protein transport and protein folding under cellular stress conditions (Jindal et al. 1989). They are classified into different families according to their molecular weight. While HSP60 is located in the cytosol and the mitochondria, HSP70 shows a wider distribution including localization within the nucleus, the mitochondria, and the cytoplasm (O’Neill et al. 2014). Although HSPs were initially detected within the cytoplasm and their function has been thought to be restricted within the cell itself, it has been shown that they can be additionally secreted into the extracellular space, where they have an active role in immune response modulation. For example, HSP72 release within exosomes leads to upregulate CD83 expression and stimulates IL-12 release by naive dendritic cells (Bausero et al. 2005). HSP60 interacts as a ligand with toll-like receptors TLR2 and TLR4 (Vabulas et al. 2002). Furthermore, HSP60 as well as HSP70 (and anti-HSP70 antibodies) circulate in plasma of normal subjects (Pockley et al. 1998). HSP60 as well as HSP70 seem to exert both inhibitory and stimulatory effects on an immune response (Venkataseshan and Marquet 1996). Patients with borderline hypertension, peripheral vascular disease, patients with end-stage renal disease, as well as patients with cardiovascular disease present increased levels of circulating HSP60, HSP70, and anti-HSP70 antibodies respectively and are associated with disease progression (Pockley et al. 2000; Prohaszka et al. 2001; Wright et al. 2000;?O’Neill et al. 2014). Decrease of anti-HSP70 antibodies is associated with lower complications of diabetic microangiopathy (Gruden et al. 2009). HSPs have been implicated in the pathogenesis of several vasculitis syndromes. In Kawasaki disease, an increase in plasma HSP70/HSP60 has been described in the subacute phase of the disease (Lu et al. 1998). Extracellular HSP60 seems to play a regulatory role in the subacute phase of the disease (Yin Ji et al. 2007). Anti-HSP70 antibodies are involved in the pathogenesis of Cogan syndrome, a rare form of vasculitis (Bonaguri et al. 2014). In Beh?et disease patients, HSP60 binds with HSP65 and seems to induce a Th1 cell response (Imamura et al. 2005).ANCA-associated vasculitis (AAV) belongs to primary small vessel vasculitis syndromes including granulomatosis with polyangiitis (GPA), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA), which are associated with elevated serum anti-neutrophil cytoplasm antibodies (ANCA) (Jennette 2013). Although the understanding of the underlying mechanisms leading to kidney injury in these patients is limited, ANCA antibodies are directly involved in the pathophysiology of AAV. The activated ANCA-expressing neutrophils adhere to endothelial cells inducing the release of pro-inflammatory cytokines and the production of reactive oxygen species. ANCA antibodies induce crescent formation in animal models of ANCA-associated vasculitis and cause glomerulonephritis and lung hemorrhage in neonates through transplacental transfer (Rowaiye et al. 2015). In a subset of microscopic polyangiiti