miR-20b attenuates airway inflammation by regulating TXNIP and NLRP3 inflammasome in ovalbumin-induced asthmatic mice.

OBJECTIVES: Asthma is a chronic inflammatory disorder of the airway and is associated with pyroptosis. microRNAs (miRNAs) underlie pathogenic mechanism in asthma. This study is expected to evaluate the role of miR-20b in asthma-induced airway inflammation via regulating thioredoxin-interacting protein (TXNIP) and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome. METHODS: The asthmatic mouse model was established via ovalbumin (OVA) induction. Expressions of miR-20b, TXNIP, and NLRP3 in lung tissues were determined. Bronchial hyperresponsiveness was appraised, cells in bronchoalveolar lavage fluid were counted and categorized, and histopathological damage was observed. Levels of inflammatory and pyroptotic cytokines were measured. The binding relationship of miR-20b and TXNIP was testified. Co-location and interaction between TXNIP and NLRP3 were detected. Mice were infected with the lentivirus packaged with pcDNA3.1-TXNIP or pcDNA3.1-NLRP3 for joint experiments to observe the pathological changes of mice. RESULTS: miR-20b was poorly expressed, while TXNIP and NLRP3 were highly expressed in OVA-induced mice. miR-20b overexpression attenuated airway inflammation and pyroptosis, manifested by alleviation of histopathological damage, declined numbers of total cells and inflammatory cells, lowered bronchial hyperresponsiveness, decreased levels of pro-inflammatory and pyroptotic cytokines, and increased anti-inflammatory cytokines. miR-20b targeted TXNIP and inhibited TXNIP expression, and TXNIP can bind to NLRP3 and upregulated NLRP3 expression. Upregulation of TXNIP or NLRP3 could reverse the protecting role of miR-20b overexpression in OVA-induced mice. CONCLUSION: miR-20b inhibited TXNIP expression to reduce the binding of TXNIP and NLRP3, thus restricting pyroptosis and airway inflammation of asthmatic mice.

Protective Effects of Dihydromyricetin against •OH-Induced Mesenchymal Stem Cells Damage and Mechanistic Chemistry.

As a natural flavonoid in Ampelopsis grossedentata, dihydromyricetin (DHM, 2R,3R-3,5,7,3',4',5'-hexahydroxy-2,3-dihydroflavonol) was observed to increase the viability of •OH-treated mesenchymal stem cells using a MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl] assay and flow cytometry analysis. This protective effect indicates DHM may be a beneficial agent for cell transplantation therapy. Mechanistic chemistry studies indicated that compared with myricetin, DHM was less effective at ABTS⁺• (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid radical) scavenging and reducing Cu(2+), and had higher •O2(-) and DPPH• (1,1-diphenyl-2-picrylhydrazyl radical) scavenging activities. Additionally, DHM could also chelate Fe(2+) to give an absorption maximum at 589 nm. Hence, such protective effect of DHM may arise from its antioxidant activities which are thought to occur via direct radical-scavenging and Fe(2+)-chelation. Direct radical-scavenging involves an electron transfer (ET) pathway. The hydrogenation of the 2,3-double bond is hypothesized to reduce the ET process by blocking the formation of a larger π-π conjugative system. The glycosidation of the 3-OH in myricitrin is assumed to sterically hinder atom transfer in the •O2(-) and DPPH• radical-scavenging processes. In DHM, the Fe(2+)-chelating effect can actually be attributed to the 5,3',4',5'-OH and 4-C=O groups, and the 3-OH group itself can neither scavenge radicals nor chelate metal.