TNF regulates transcription of NLRP3 inflammasome components and inflammatory molecules in cryopyrinopathies

The NLRP3 inflammasome is a protein complex responsible for caspase-1-dependent maturation of the proinflammatory cytokines IL-1 beta and IL-18. Gain-of-function missense mutations in NLRP3 cause the disease spectrum known as the cryopyrin-associated periodic syndromes (CAPS). In this study, we generated Nlrp3-knockin mice on various KO backgrounds including Il1b/Il18-, caspase-1-, caspase-11-(Casp1/11-), and Tnf-deficient strains. The Nlrp3(L351P) Il1b(-/-) Il18(-/-) mutant mice survived and grew normally until adulthood and, at 6 months of age, exhibited marked splenomegaly and leukophilia. Injection of these mice with low-dose LPS resulted in elevated serum TNF levels compared with Nlrp3(L351P) Casp1/11(-/-) mice and Il1b(-/-) Il18(-/-) littermates. Treatment of Nlrp3(A350V) mice with the TNF inhibitor etanercept resulted in all pups surviving to adulthood, with normal body and spleen/body weight ratios. Nlrp3(A350V) Tnf(-/-) mice showed a similar phenotypic rescue, with marked reductions in serum IL-1 beta and IL-18, reduced myeloid inflammatory infiltrate in the skin and spleen, and substantial decreases in splenic mRNA expression of both inflammasome components (Nlrp3, Pycard, pro-Casp1) and pro-cytokines (Il1b, Il18). Likewise, we observed a reduction in the expression of both pro-Casp1 and pro-Il1b in cultured Nlrp3(A350V) Tnf(-/-) BM-derived DCs. Our data show that TNF is an important transcriptional regulator of NLRP3 inflammasome components in murine inflammasomopathies. Moreover, these results may have therapeutic implications for CAPS patients with partial responses to IL-1-targeted therapies.