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

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 cisplatin-induced 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(-/-)) 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(-/-) 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. NLRP3(-/-) 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(-/-) mice was not explained by the differences in proinflammatory cytokines interleukin (IL)-1 beta, IL-6, chemokine (C-X-C motif) ligand 1, or tumor necrosis factor alpha. 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.