6E). Accordingly, the expression of the death factor Nur77 was significantly lower in Nlrp3−/− DCs (Fig. 6F). In support of these data, we observed significant increases in expression
of the pro-survival genes Xiap and Birc3 in Nlrp3−/− cells compared with WT DCs (Fig. 6F). Taken together, these data indicate that the NLRP3 inflammasome plays an important role in the DDR after oxidative and genotoxic stress, and that the p53 pathway is involved in NLRP3-mediated pyroptosis. Oxidative stress is now emerging as a common feature of immune responses to a variety of different insults. ROS generation was proposed as crucial step for activation of the NLRP3 inflammasome . The majority of NLRP3 activators, including MSU, provoke a significant but transient Ku-0059436 ic50 increase
in ROS, pivotal for caspase-1-mediated release of IL-1β. Monocytes from patients with cryopyrinopathies associated with NLRP3 mutations display an altered redox state, which results in sustained IL-1β secretion, suggesting that redox signaling is important for NLRP3 activation Luminespib molecular weight . Transient or permanent imbalance between the excess formation of ROS and limited antioxidant defenses can damage DNA, leading to activation of the DDR pathway. We found that disruption of NLRP3 inflammasome mediated signaling markedly reduced double-strand breaks and DNA oxidation (measured as γ-H2AX and 8-oxoG, respectively) by ROS-inducing stimuli (MSU and rotenone). Similar to Nlrp3−/− DCs, H2AX phosphorylation was significantly decreased in casp-1−/− DCs when compared with WT DCs at later time points. These results highlight that the NLRP3 inflammasome, and not NLRP3 alone, seems to be directly involved in promoting the DDR. However, a role for an alternative inflammasome complex in driving cellular responses to DNA damage cannot be excluded. Several observations indicate that the diverse DDR activation in WT compared to Nlrp3−/− cells can be explained by differential compensatory mechanisms elicited by oxidative stress, rather than early
events responsible for induction of DNA damage. Both ROS production and DNA damage are similar at early time points in WT and Nlrp3−/− or casp-1−/− cells, whereas the repair elements Ogg1 and NBS1 are significantly more induced at later Isotretinoin time in cells that lack NLRP3 signaling. However, the exact link between NLRP3 activation and oxidative repair remains unclear. It was proposed that increased ROS levels cause the detachment of thioredoxin-interacting protein from thioredoxin, a critical intracellular antioxidant, and its binding to NLRP3 during high glucose mediated caspase-1 activation in murine pancreatic B cells . However, this remains controversial since caspase-1 activation and IL-1β secretion are similar in WT and Txnip−/− macrophages in response to islet amyloid polypeptide, MSU, or ATP .