Secondary amyloidosis in autoinflammatory diseases and the role of inflammation in renal damage

Abstract

The release of proinflammatory cytokines during inflammation represents an attempt to respond to injury, but it may produce detrimental effects. The inflammasome is a large, multiprotein complex that drives proinflammatory cytokine production in response to infection and tissue injury; the best-characterized inflammasome is the nod-like receptor protein-3 (NLRP3). Once activated, inflammasome leads to the active form of caspase-1, the enzyme required for the maturation of interleukin-1beta. Additional mechanisms bringing to renal inflammatory, systemic diseases and fibrotic processes were recently reported, via the activation of the inflammasome that consists of NLRP3, apoptosis associated speck-like protein and caspase-1. Several manuscripts seem to identify NLRP3 inflammasome as a possible therapeutic target in the treatment of progressive chronic kidney disease. Serum amyloid A (SAA), as acute-phase protein with also proinflammatory properties, has been shown to induce the secretion of cathepsin B and inflammasome components from human macrophages. SAA is a well recognised potent activator of the NLRP3. Here we will address our description on the involvement of the kidney in autoinflammatory diseases driven mainly by secondary, or reactive, AA amyloidosis with a particular attention on novel therapeutic approach which has to be addressed in suppressing underlying inflammatory disease and reducing the SAA concentration.

Keywords: Amyloidosis; Autoinflammatory disease; Caspase; Chronic kidney disease; Dialysis; Inflammation; Interleukin-1; Nod-like receptor protein-3; Proteinuria.

Figure 1

Model of nod-like receptor protein-3 inflammasome activation and the role of the nod-like receptor protein-3 inflammasome in the two-step activation of interleukin-1β and interleukin-18[10,12]. Activation of the NLPR3 inflammasome requires two signals. Signal 1: Activation of TLRs, IL-1Rs and TNFRs induces the transcription and translation of NF-κB to produce pro-forms of IL-1β and IL-18; Signal 2: Enzymatic cleavage by (caspase-11-driven) caspase-1 to secrete mature cytokines, IL-1β and IL-18. ROS: Reactive oxygen species; TLR: Toll-like receptor.

Figure 2

Structural features of amyloid[25].

Figure 3

Renal biopsy: Amyloid fibrils bind congo red stain, yielding the pathognomonic apple-green birefringence under cross-polarized light microscopy[9].