To verify this possibility, the concentration dependence of inflammasome activation in WT and KI cells (in the presence and absence of ATP) Epigenetics inhibitor was determined. It was found that while inflammasome activation increased in both the cell types with increasing LPS concentrations, WT cells required massive amounts of LPS (>1000 ng/mL) to activate the inflammasome in the absence of ATP, whereas KI cells required only minute amounts of LPS. It thus appears that KI cells do not require co-stimulation by ATP because the small amounts of TLR ligand that enter in the absence of ATP are sufficient to activate the altered inflammasome.

Overall, these data Selleck LDE225 are consistent with the concept previously suggested from studies of CAPS patients that NLRP3 mutations lead to changes in the conformation of the protein that, in turn, result in a reduced activation threshold and thus an inflammasome capable of responding to reduced amounts of TLR ligand or other activating factors 9, 19. However, NLRP3 may not be able to directly bind to such a wide variety of ligands including PAMP and DAMP, rather an endogenous activator induced by all these upstream stimuli may serve as the direct ligand for NLRP3 (Fig. 1). This concept has also been proposed independently by other researchers 20, 21. NLRP3 KI mice bearing an R258W

mutation raised under pathogen-free facility exhibit spontaneous clinical symptoms similar to those of the counterpart Muckle–Wells syndrome patients. These symptoms consist of poor linear growth, reduced reproductive capacity, impaired hair development and, in many animals, severe dermatitis affecting the Phosphoribosylglycinamide formyltransferase ears, top of

the head and tail base area occurring at 6–12 wk of age that is associated with a deterioration of health. The skin lesions were clinically more severe than the urticaria-like skin disease seen in human CAPS and characterized by neutrophilic infiltration of the dermis and epidermis. Spleen and draining lymph nodes were enlarged in the KI mice and showed poorly developed follicles along with a diffuse infiltrate, again containing many neutrophils. However, these KI mice were free of lung, kidney or gut inflammation and the level of circulating inflammatory cytokines was normal 9. The clinical features of mice bearing A350V and L351P mutations were qualitatively similar to those described for R258W mice, but were far more severe. These A350V/L351P KI mice had lifespan measured in days rather than weeks, and had more widespread skin inflammation and inflammatory infiltration (mainly neutrophilic) of many organs, including the joints, sinus, bone marrow and tongue. In addition, there was evidence of “necrotic degeneration” in the gut and kidney.