Cell stress increases ATP release in NLRP3 inflammasome-mediated autoinflammatory diseases, resulting in cytokine imbalance

Significance Single amino acid mutations in NLRP3 in patients with cryopyrin-associated periodic syndromes (CAPS) lead to oversecretion of IL-1β, resulting in severe inflammatory manifestations. How this occurs is unclear. We show here that cellular stress in blood monocytes contributes to CAPS pathophysiology, allowing copious release of ATP in response to minute concentrations of inflammatory stimuli. As a consequence, the released ATP enhances NLRP3-mediated secretion of IL-1β and IL-18 by activating P2X purinoceptor 7. Later, CAPS cells undergo oxidative stress, which impairs secretion of the anti-inflammatory IL-1 receptor antagonist, worsening the clinical picture. Antioxidants rescue the reduced production of the antagonist. Blocking extracellular ATP and improving stress tolerance may represent novel therapeutic strategies in autoinflammatory diseases. Cell stress is implicated in triggering bouts of systemic inflammation in patients with autoinflammatory disorders. Blood monocytes from patients affected by NLRP3-mediated cryopyrin-associated periodic syndromes (CAPS) release greater amounts of IL-1β than monocytes from unaffected subjects. Here we show that stress lowers the threshold of activation; blood monocytes from CAPS patients maintain the high levels of secreted IL-1β (fivefold) and IL-18 (10-fold) when stimulated with 1,000-fold less LPS than that required for full IL-1β secretion in control subjects. Unexpectedly, IL-1α secretion is increased 10-fold, indicating that inflammatory episodes in CAPS may not be entirely a result of IL-1β but may also involve IL-1α. In CAPS monocytes, LPS induces the externalization of copious amounts of ATP (10-fold), which drive IL-1β, IL-18, and IL-1α release via activation of the P2X purinoceptor 7. This enhanced ATP release appears to be the link between cell stress and increased cytokine secretion in CAPS. In the later phase after LPS stimulation, CAPS monocytes undergo oxidative stress, which impairs production of the anti-inflammatory IL-1 receptor antagonist (IL-1Ra). Remarkably, IL-1Ra secretion is fully restored by treatment with antioxidants. In two patients with the same NLRP3 mutation, but different disease severity, monocytes from the mildly affected patient exhibited more efficient redox response, lower ATP secretion, and more balanced cytokine production. Thus, the robustness of the individual antioxidant response increases the tolerance to stress and reduces the negative effect of the disease. Pharmacologic block of P2X purinoceptor 7 and improved stress tolerance may represent novel treatment strategies in stress-associated inflammatory diseases.