ALDOA maintains NLRP3 inflammasome activation by controlling AMPK activation.

ABBREVIATIONS: ALDOA: aldolase A; AMPK: AMP-activated protein kinase; ATG: autophagy related; ATG5: autophagy related 5; ATP: adenosine triphosphate; BMDMs: bone marrow-derived macrophages; CALCOCO2: calcium binding and coiled-coil domain 2; CASP1: caspase 1; CQ: chloroquine; FOXO3: forkhead box O3; IL1B: interleukin 1 beta; LPS: lipopolysaccharide; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MT: mutant; mtDNA: mitochondrial DNA; MTORC1: mechanistic target of rapamycin kinase complex 1; mtROS: mitochondrial reactive oxygen species; NLRP3: NLR family, pyrin domain containing 3; OPTN: optineurin; PBS: phosphate-buffered saline; PRKN/Parkin: parkin RBR E3 ubiquitin protein ligase; SN: supernatant; SQSTM1/p62: sequestosome 1; STK11/LKB1: serine/threonine kinase 11; TOMM20: translocase of outer mitochondrial membrane 20; ULK1: unc-51 like autophagy activating kinase 1; v-ATPase: vacuolar type H+-ATPase; WT: wild-type.

Oroxylin A maintains the colonic mucus barrier to reduce disease susceptibility by reconstituting a dietary fiber-deprived gut microbiota.

Dietary fiber intake helps to maintain gut homeostasis. Fiber deficiency causes commensals to utilize mucins as an energy source to destroy mucus layer, thus promoting susceptibility to inflammatory bowel disease. Here, we reported that oroxylin A, a natural flavonoid, ameliorated low-grade colonic inflammation caused by fiber deficiency, alleviated colitis, and further prevented colitis-associated colon cancer in mice. The anti-inflammatory effect of oroxylin A was due to its alteration of gut microbiota. We found that the levels of Eubacterium coprostanoligenes was significantly increased by oroxylin A and the colonized Eubacterium coprostanoligenes significantly protected against colitis and carcinogenesis in colon of mice. Together, our results in this study suggest that oroxylin A may reduce the susceptibility to intestinal diseases by increasing the level of Eubacterium coprostanoligenes which could provide a therapeutic alternation for the treatment of intestinal diseases.

Triggering apoptosis by oroxylin A through caspase-8 activation and p62/SQSTM1 proteolysis.

Emerging evidence suggests that oroxylin A exhibits antitumor effects by inducing cell apoptosis. However, the involved molecular mechanisms have not been elucidated. Here we report that the apoptosis induced by oroxylin A was dependent on p62-mediated activation of caspase-8 in hepatocellular carcinoma cells. Furthermore, oroxylin A also caused p62/SQSTM1 proteolysis at Asp329 by activating caspase-8. Further studies confirm that mutation in p62 (D329H and D329G) was resistant to oroxylin A-mediated p62 cleavage and apoptosis. Due to the absence of the KIR domain that interacts with Keap1, the cleaved p62 reduced the stability of Nrf2, thereby causing oxidative stress and increasing ROS levels. In vivo, p62 similarly contributed to oroxylin A-exerted antitumor effect in xenograft model inoculated SMMC-7721 tumor. In conclusion, our findings indicated that oroxylin A triggered apoptosis through caspase-8 activation and p62/SQSTM1 proteolysis.

Flavonoid VI-16 protects against DSS-induced colitis by inhibiting Txnip-dependent NLRP3 inflammasome activation in macrophages via reducing oxidative stress.

Emerging evidence suggests that NLRP3 inflammasome was associated with various kinds of immunological diseases including colitis. However, there are few drugs targeting inflammasomes in the treatment of colitis. Several flavonoids have been found to affect the inflammasome pathway, but the mechanism is still confusing. Here we report that VI-16, a synthetic flavonoid compound, exerts potent anti-inflammatory effects on macrophages in DSS-induced colitis mice, which intervened in the activation of NLRP3 inflammasome without affecting intestinal epithelial cells. However, the protection of VI-16 against DSS-induced colitis was dependent on NLRP3 expression in hematopoietic cells. Furthermore, this inhibitory effect of VI-16 was found to be at least partially achieved by decreasing the mitochondrial ROS generation without affecting autophagy. Further studies confirm that VI-16 inhibits the binding of Txnip to NLRP3 by reducing oxidative stress and ultimately inhibits NLRP3 inflammasome. This demonstrates the ability of VI-16 to inhibit the NLRP3 inflammasome activation and its potential use in the treatment of inflammatory bowel disease.