N6-methyladenosine-modified circIRF2, identified by YTHDF2, suppresses liver fibrosis via facilitating FOXO3 nuclear translocation.

Circular RNA (circRNA) has been implicated in liver fibrosis and modulated by multiple elusive molecular mechanisms, while the effects of N6-methyladenosine (m6A) modification on circRNA are still elusive. Herein, we identify circIRF2 from our circRNA sequencing data, which decreased in liver fibrogenesis stage and restored in resolution stage, indicating that dysregulated circIRF2 may be closely associated with liver fibrosis. Gain/loss-of-function analysis was performed to evaluate the effects of circIRF2 on liver fibrosis at both the fibrogenesis and resolution in vivo. Ectopic expression of circIRF2 attenuated liver fibrogenesis and HSCs activation at the fibrogenesis stage, whereas downregulation of circIRF2 impaired mouse liver injury repair and inflammation resolution. Mechanistically, YTHDF2 recognized m6A-modified circIRF2 and diminished circIRF2 stability, partly accounting for the decreased circIRF2 in liver fibrosis. Microarray was applied to investigate miRNAs regulated by circIRF2, our data elucidate cytoplasmic circIRF2 may directly harbor miR-29b-1-5p and competitively relieve its inhibitory effect on FOXO3, inducing FOXO3 nuclear translocation and accumulation. Clinically, circIRF2 downregulation was prevalent in liver fibrosis patients compared with healthy individuals. In summary, our findings offer a novel insight into m6A modification-mediated regulation of circRNA and suggest that circIRF2 may be an exploitable prognostic marker and/or therapeutic target for liver fibrosis.

RIPK3 inhibitor-AZD5423 alleviates acute kidney injury by inhibiting necroptosis and inflammation.

Acute kidney injury (AKI) is a clinical syndrome that is defined as a sudden decline in renal function and characterized by inflammation and programmed cell death of renal tubular epithelial cells. Necroptosis is a form of regulated cell death that requires activation of receptor interacting protein kinase 3 (RIPK3) and its phosphorylation of the substrate MLKL. RIPK3 plays an important role in acute kidney injury, and hence developing its inhibitors is considered as one of the promising strategies aimed at prevention and treatment of AKI. Recently, we discovered AZD5423 as a novel potent RIPK3 inhibitor using a computer-aided hybrid virtual screening strategy according to three-dimensional structure of RIPK3. Our findings revealed that AZD5423 strongly inhibits activation of RIPK3, and MLKL phosphorylation upon cisplatin-, hypoxia/reoxygenation (H/R)- and TNF-α stimuli as compared with GSK872, which is a previously identified RIPK3 inhibitor. Importantly, AZD5423 exerts effective protection against cisplatin- and ischemia/reperfusion (I/R)-induced AKI mouse model. The results of cellular thermal shift assay and experiments in RIPK3 knockout cells indicated that AZD5423 could directly target RIPK3 to inhibit RIPK3 kinase activity. Mechanistically, the docking of AZD5423 and RIPK3 suggested that the kinase domain of RIPK3 for Lys50, Arg313, Lys29, Arg37 might form hydrogen bonds with AZD5423. Site-directed mutagenesis further revealed that AZD5423 reduces injury response via interacting with the key RIPK3 amino acid residues of Lys50 and Arg313. In conclusion, our study has demonstrated that AZD5423 may serve as a potent inhibitor of RIPK3 kinase and a promising clinical candidate for AKI treatment.

miR-301a-3p promotes hepatic stellate cells activation and liver fibrogenesis via regulating PTEN/PDGFR-ß.

Hepatic fibrosis is an essential pathology of multiple chronicliverdiseases. The aim of this study was to investigate the role of miR-301a-3p in hepatic fibrosis. We found that miR-301a-3p was upregulated in hepatic fibrosis patients and in culture-activated human hepatic stellate cells (HSCs). Interestingly, miR-301a-3p expression was increased in hepatic fibrosis progression mice while decreased in hepatic fibrosis recovery mice, indicating that miR-301a-3p may participate in the hepatic fibrosis pathology. Functionally, the effects of miR-301a-3p both on hepatic fibrosis progression and regression were assessed in vivo. Inhibiting miR-301a-3p amelioratedmouse liver fibrogenesis and collagen deposition and suppressed HSC activation and fibrogenic factor expression. Whereas, in hepatic fibrosis regression, upregulating miR-301a-3p impaired mouse hepatic fibrosis recovery by inducing HSC activation and triggering inflammation. Consistently, gain-of-function and loss-of-function analysis of miR-301a-3p were performed to evaluate its effects on human HSCs LX-2 cell. We found that suppressing miR-301a-3p inhibited LX-2 cell activation and proliferation, and induced LX-2 cell apoptosis, accompaniedby decreased fibrotic mediators expression. Collectively, these findings suggest miR-301a-3p drives liver fibrogenesis and HSC activation in hepatic fibrosis. Mechanistically, we demonstrated miR-301a-3p binds directly to phosphatase and tensin homolog (PTEN) by luciferase reporter analysis, pull-down, and RIP assay. Indicating that miR-301a-3p plays a critical rolein promotingliverfibrogenesis viamodulating the PTEN/platelet derived growth factor ß (PDGFR-ß) pathway. In conclusion, our findings demonstrate that miR-301a-3p expression is closely correlated with hepatic fibrosis pathology, and that enhancing miR-301a-3p maintains the HSC profibrogenic phenotype, triggers inflammatoryresponses, promotes fibrogenic factor production, and further exacerbates liver fibrogenesis. These findings suggest that miR-301a-3p may serve as a promising diagnostic and prognosis biomarker for hepatic fibrosis treatment.

Inhibition of METTL3 attenuates renal injury and inflammation by alleviating TAB3 m6A modifications via IGF2BP2-dependent mechanisms.

The role of N6-methyladenosine (m6A) modifications in renal diseases is largely unknown. Here, we characterized the role of N6-adenosine-methyltransferase-like 3 (METTL3), whose expression is elevated in renal tubules in different acute kidney injury (AKI) models as well as in human biopsies and cultured tubular epithelial cells (TECs). METTL3 silencing alleviated renal inflammation and programmed cell death in TECs in response to stimulation by tumor necrosis factor-α (TNF-α), cisplatin, and lipopolysaccharide (LPS), whereas METTL3 overexpression had the opposite effects. Conditional knockout of METTL3 from mouse kidneys attenuated cisplatin- and ischemic/reperfusion (I/R)-induced renal dysfunction, injury, and inflammation. Moreover, TAB3 [TGF-ß-activated kinase 1 (MAP3K7) binding protein 3] was identified as a target of METTL3 by m6A methylated RNA immunoprecipitation sequencing and RNA sequencing. The stability of TAB3 was increased through binding of IGF2BP2 (insulin-like growth factor 2 binding protein 2) to its m6A-modified stop codon regions. The proinflammatory effects of TAB3 were then explored both in vitro and in vivo. Adeno-associated virus 9 (AAV9)-mediated METTL3 silencing attenuated renal injury and inflammation in cisplatin- and LPS-induced AKI mouse models. We further identified Cpd-564 as a METTL3 inhibitor that had better protective effects against cisplatin- and ischemia/reperfusion-induced renal injury and inflammation than S-adenosyl-l-homocysteine, a previously identified METTL3 inhibitor. Collectively, METTL3 promoted m6A modifications of TAB3 and enhanced its stability via IGF2BP2-dependent mechanisms. Both genetic and pharmacological inhibition of METTL3 attenuated renal injury and inflammation, suggesting that the METTL3/TAB3 axis is a potential target for treatment of AKI.