Rapid Release of Interleukin-1β from Human Platelets Is Independent of NLRP3 and Caspase

Abstract

Objective Platelets are critical in mediating both rapid responses to injury and the development and progression of coronary disease. Several studies have shown that, after prolonged exposure to agonists, they produce and release inflammatory mediators including interleukin-1β (IL-1β), via the classical pathway (NLRP3 inflammasome and caspase-1 cleavage to release active IL-1β) as described for leukocytes. This study aimed to determine whether there is rapid release of IL-1β in response to soluble platelet agonists and whether such rapid release is NLRP3- and caspase-1-dependent. Methods and Results Using flow cytometry to detect platelet activation (and release of α and dense granule contents) and the combination of Western blotting, enzyme-linked-immunosorbent assay, and immunogold labeling transmission electron and immunofluorescence microscopy, we identified that resting human platelets contain mature IL-1β. Platelets release IL-1β within minutes in response to adenosine diphosphate (ADP), collagen, and thrombin receptor agonists, but not in response to conventional NLRP3 inflammasome agonists—lipopolysaccharide and adenosine triphosphate. The rapid release of IL-1β in response to ADP and thrombin receptor agonists was independent of caspases (including caspase-1) and NLRP3. Immature and mature IL-1β were identified as low-abundance proteins on transmission electron microscopy of human platelets, and were localized to the platelet cytosol, open canalicular system, and the periphery of α granules. Conclusion Unlike monocytes and neutrophils, human platelets are capable of rapid agonist- and time-dependent release of IL-1β by a mechanism which is independent of caspase-1 and NLRP3.

Inflammasome-Independent Mechanism of NLRP3 is Critical for Platelet GPIb-IX Function and Thrombosis

“…15 Although platelets may rapidly release trace amount of IL-1β, this action does not depend on the NLRP3 inflammasome. 13 Second, the plasma IL-1β concentration may not depend heavily on the NLRP3 inflammasome in platelets, as there was only a minimal increase in the plasma IL-1β concentration (15.23 AE 1.61 pg/mL) in Nlrp3 A350V/þ CrePF4 mice. Third, as much as 10 ng/mL exogenous IL-1β 12,40 is needed to rescue the defects in platelet functions caused by NLRP3 deficiency, which is nearly 1,000 times greater than that produced by the physiological concentrations circulating platelets.…”

“…For example, rapid IL-1β release from platelets during activation does not depend on NLRP3 inflammasome. 13 The rapid formation of thrombi does not seem to provide enough time for a significant amount of IL-1β to be produced by platelets, as this process appears to take hours according to previous studies. 14,15 This evidence indicates that the function of NLRP3 in platelets may be independent of intrinsic IL-1β production and may facilitate rapid platelet activation.…”

Thrombosis and Haemostasis 2022 Editors' Choice Papers

“…New insights revealed that human resting platelets contain an active form of IL-1β that is released in an NLRP3-and caspase-1-independent manner. 76 MicroRNAs (miRNAs) are key regulators in gene expression and contribute greatly to cardiovascular homeostasis and pathology. 77 A systematic review of 16 studies identified 44 and 1 miRNAs associated with platelet function and maturity, respectively.…”

Colchicine as a Modulator of Platelet Function: A Systematic Review

“…119 120 We recently showed that platelets also contain pre-formed IL-1β and release IL-1β rapidly in response to activation. 121 While leukocytes are the main contributor of IL-1β to the systemic inflammatory response and the amount of cytokine produced/released by a platelet is much lower than that manufactured by monocytes, macrophages and neutrophils, this does not negate the potential contribution of platelet-derived cytokines or other factors to the inflammatory process. There is a platelet concentration-dependent augmentation of inflammatory cytokine (IL-1β) production by monocytes, macrophages, and neutrophils, and, in the absence of platelets, the ability of the monocyte population to produce IL-1β is drastically diminished.…”