NLRP3 Inflammasome Knockout Mice Are Protected against Ischemic but Not Cisplatin-Induced Acute Kidney Injury

Abstract

We have demonstrated that caspase-1 is a mediator of both cisplatin-induced acute kidney injury (AKI) and ischemic AKI. As caspase-1 is activated in the inflammasome, we investigated the inflammasome in cisplatin-induced and ischemic AKI. Mice were injected with cisplatin or subjected to bilateral renal pedicle clamping. Immunoblot analysis of whole kidney after cisplatininduced AKI revealed: 1) an increase in apoptosis-associated Speck-like protein containing a caspase recruitment domain (ASC), the major protein that complexes with nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain containing proteins (NLRP) 1 or 3 to form the inflammasome; 2) an increase in caspase-1 activity, caspase-5, and NLRP1, components of the NLRP1 inflammasome; and 3) a trend toward increased NLRP3. To determine whether the NLRP3 inflammasome plays an injurious role in cisplatin-induced AKI, we studied NLRP knockout (NLRP3 2/2 ) mice. In cisplatin-induced AKI, the blood urea nitrogen, serum creatinine, acute tubular necrosis score, and tubular apoptosis score were not significantly decreased in NALP3 2/2 mice compared with wild-type mice. We have previously demonstrated the injurious role of caspase-1 in ischemic AKI. NLRP3, but not ASC or NLRP1, is increased in ischemic AKI. NLRP32/2 mice with ischemic AKI had significantly lower blood urea nitrogen, serum creatinine, and acute tubular necrosis and apoptosis scores than the wild-type controls. The difference in protection against cisplatin-induced AKI compared with ischemic AKI in NLRP3 2/2 mice was not explained by the differences in proinflammatory cytokines interleukin (IL)-1b, IL-6, chemokine (C-X-C motif) ligand 1, or tumor necrosis factor a. NLRP3 inflammasome is a mediator of ischemic AKI but not cisplatin-induced AKI, and further investigation of the NLRP1 inflammasome in cisplatin-induced AKI should prove interesting.

Cytokines

“…IL-1 is responsible for enhancing neutrophil influx in IRI (44). NLRP3 inflammasome knockout (2/2) mice are protected against IRI but not in cisplatin-induced AKI (45). However, caspase-12/2 mice are protected from cisplatin-induced Cytokine-based immunomodulation can potentially be used as preventative or therapeutic in AKI.…”

Of Inflammasomes and Alarmins: IL-1β and IL-1α in Kidney Disease

“…Whenever tested, mutant mice were consistently protected from renal necroinflammation. 21,75 However, postischemic tubular necrosis depends on NLRP3 [76][77][78][79] but not on ASC. 76 This finding could imply an additional, inflammasome-independent, biologic effect of ASC in postischemic AKI.…”

Inflammation in AKI

“…2,5,6 Necrotic cells release damageassociated molecular patterns, such as high-mobility group box 1, histones, heat shock proteins, fibronectin, and biglycan into the extracellular spaces, which subsequently, activate pattern recognition receptors, such as toll-like receptors (TLRs), and nucleotide-binding oligomerization domain-like receptors, such as the nucleotide-binding oligomerization domain-, LRR-, and pyrin domain-containing 3 inflammasome, expressed in epithelial and endothelial cells, dendritic cells (DCs), monocytes/ macrophages, and lymphocytes. [6][7][8][9] Activated renal parenchyma cells and DCs also secrete chemokines, including CXCL1, CXCL8, CCL2, and CCL5, that promote acute neutrophil-and monocyte/ macrophage-dependent inflammatory responses in AKI. 6 , 1 0 Timedependent changes in the expression of proinflammatory (e.g., TNF-a, IFN-g, IL-6, IL-1b, IL-23, IL-17, C3, C5a, and C5b) and anti-inflammatory (e.g., IL-4, TGF-b, IL-10, heme oxygenase 1, resolvins, and protectin D1) mediators by resident and recruited cell populations are important determinants of the injury and repair phases.…”

“…Many laboratories have shown in rodent models that interfering with the triggering of pattern recognition receptors prevents the expansion of renal tubular cell injury. 6,8,28 Other concepts that require better definition to develop clinically relevant therapeutics involve the soluble mediators of cellular injury, which may be produced locally (within the injured kidney) or systemically. Cytokines and chemokines produced locally recruit a cascade of inflammatory effector cells into injured tissue, and experimental blockade of several cytokines and chemokines can abrogate AKI.…”