Amino Sugar-Enriched Fraction of Korean Red Ginseng Extract Induces the Priming Step of NLRP3 Inflammasome.

Intracellular protein complexes, known as inflammasomes, activate caspase-1 and induce the secretion of pro-inflammatory cytokines, namely interleukin (IL)-1ß and -18. Korean Red Ginseng extract (RGE) is a known immunomodulator and a potential candidate for the regulation of inflammasomes. The saponins, such as ginsenosides, of RGE inhibit inflammasome signaling, while non-saponin substances containing amino sugars promote the priming step, up-regulating inflammasome components (pro-IL-1ß, NLRP3, caspase-1, and Asc). In this study, the amino sugar-enriched fraction (ASEF), which increases only non-saponin components, including amino sugars, without changing the concentration of saponin substances, was used to investigate whether saponin or non-saponin components of RGE would have a greater impact on the priming step. When murine macrophages were treated with ASEF, the gene expression of inflammatory cytokines (IL-1α, TNFα, IL-6, and IL-10) increased. Additionally, ASEF induced the priming step but did not affect the inflammasome activation step, such as the secretion of IL-1ß, cleavage of caspase-1, and formation of Asc pyroptosome. Furthermore, the upregulation of gene expression of inflammasome components by ASEF was blocked by inhibitors of Toll-like receptor 4 signaling. Maltol, the main constituent of ASEF, promoted the priming step but inhibited the activation step of the inflammasome, while arginine, sugars, arginine-fructose-glucose, and fructose-arginine, the other main constituents of ASEF, had no effect on either step. Thus, certain amino sugars in RGE, excluding maltol, are believed to be the components that induce the priming step. The priming step that prepares the NLRP3 inflammasome for activation appears to be induced by amino sugars in RGE, thereby contributing to the immune-boosting effects of RGE.

Riboflavin, vitamin B2, attenuates NLRP3, NLRC4, AIM2, and non-canonical inflammasomes by the inhibition of caspase-1 activity.

Riboflavin is commonly taken as a nutritional supplement, and it converts to coenzymes during the process of energy production from carbohydrates, fats, and proteins. Although riboflavin is considered to be an anti-inflammatory vitamin because of its antioxidant properties, the effects of riboflavin on inflammasome have been not reported. Inflammasome, a cytosolic surveillance protein complex, leads to the activation of caspase-1, cytokine maturation, and pyroptosis. In the present study, riboflavin attenuated the indicators of NLRP3 inflammasome activation in macrophages, such as the maturation and secretion of interleukin (IL)-1ß, IL-18, and caspase-1; the formation of Asc pyroptosome; and the cleavage of gasdermin D. In addition, the oral and peritoneal administration of riboflavin inhibited the peritoneal production of IL-1ß and IL-18 in a mouse model. Mechanistically, riboflavin prevented mitochondrial perturbations, such as mitochondrial ROS production and mitochondrial DNA release, which trigger the NLRP3 inflammasome assembly. Riboflavin was further confirmed to disrupt the activity of caspase-1, and it also inhibited the AIM2, NLRC4, and non-canonical inflammasomes. Therefore, riboflavin has both an antioxidant effect and an anti-inflammasome property that regulates the inflammatory response.

Obovatol inhibits NLRP3, AIM2, and non-canonical inflammasome activation.

BACKGROUND: Obovatol, a biphenolic chemical originating from Magnolia obovata, has been utilized as a traditional medicine for the treatment of inflammatory diseases. Inflammasome induces maturation of inflammatory cytokines in response to intracellular danger signals, and its dysregulation induces inflammatory diseases. PURPOSE: The effect of obovatol on inflammasome activation has not been reported, although its anti-inflammatory properties have been studied. STUDY DESIGN/METHODS: Obovatol was treated to macrophages with inflammasome triggers, and secretions of interleukin (IL)-1ß, IL-18, and caspase-1 were measured as readouts of inflammasome activation. In addition, Asc pyroptosome formation, caspase-1 activity, and mitochondrial reactive oxygen species (ROS) production were analyzed in mechanical studies. Anti-inflammasome properties of obovatol were confirmed in an animal model. RESULTS: Obovatol inhibited NLRP3, AIM2, and non-canonical inflammasomes through inhibition of Asc pyroptosome formation and mitochondrial ROS generation. In addition, obovatol disrupted the priming step of inflammasome activation and inhibited transcription of inflammatory cytokines. In mice, obovatol attenuated serum IL-1ß elevation in response to monosodium urate crystals. CONCLUSION: Obovatol is suggested as an inhibitor of NLRP3, AIM2, and non-canonical inflammasomes.

Isorhamnetin and hyperoside derived from water dropwort inhibits inflammasome activation.

BACKGROUND: Water dropwort (Oenanthe javanica), an umbelliferous plant, has been reported as hypolipidemic, antiplatelet, antitumor, or immune-stimulating agents and it has been suggested to cure cardiovascular disease and cancer. PURPOSE: Present study aimed to evaluate the effect of the extracts of water dropwort (EWD) and its pharmacological molecules, hyperoside and isorhamnetin, on inflammatory response, especially inflammasome activation. STUDY DESIGN/METHODS: The anti-inflammasome properties of EWD, isorhamnetin, and hyperoside were elucidated by human and mouse macrophages. RESULTS: EWD attenuated secretion of interleukin (IL)-1ß and formation of Asc pyroptosome resulting from NLRP3, NLRC4, and AIM2 inflammasome activation without interruption of cytokine transcription. Isorhamnetin selectively inhibited NLRP3 and AIM2 inflammasome activation and down-regulated expression of pro-inflammatory cytokines. Hyperoside selectively interrupted NLRC4 and AIM2 inflammasome activation but did not alter cytokine expression. In addition, EWD, isorhamnetin, and hyperoside inhibited caspase-1. CONCLUSION: Isorhamnetin and hyperoside, a key molecule of water dropwort, have been suggested as candidates to attenuate inflammasome inhibition.

Korean red ginseng extracts inhibit NLRP3 and AIM2 inflammasome activation.

Korean red ginseng extract (RGE) is one of the most popular natural herbs modulating the immune system. Although the effects of RGE on immunity have been reported, its effects on inflammasomes, multi-protein complexes that activate caspase-1 to induce maturation of interleukin (IL)-1ß, have not been studied yet. In this study, we elucidated the effect of RGE on inflammasome activation using mouse and human macrophages. In our results, RGE inhibited IL-1ß maturation resulting from NLRP3 inflammasome activation in both in vitro and in vivo models. In addition, RGE strongly attenuated IL-1ß secretion as well as pathogen clearance via pyroptotic cell death by macrophages through inhibition of AIM2 inflammasome activation. Ginsenosides Rg1 and Rh3 were suggested as inhibitors of the inflammasome activation. Thus, we demonstrated that RGE inhibits both NLRP3 and AIM2 inflammasome activation, with predominant involvement of the AIM2 inflammasome.