H3K27 demethylase KDM6B aggravates ischemic brain injury through demethylation of IRF4 and Notch2-dependent SOX9 activation

Diverse functions of SOX9 in liver development and homeostasis and hepatobiliary diseases

The liver is the central organ for digestion and detoxification and has unique metabolic and regenerative capacities. The hepatobiliary system originates from the foregut endoderm, in which cells undergo multiple events of cell proliferation, migration, and differentiation to form the liver parenchyma and ductal system under the hierarchical regulation of transcription factors. Studies on liver development and diseases have revealed that SRY-related high-mobility group box 9 (SOX9) plays an important role in liver embryogenesis and the progression of hepatobiliary diseases. SOX9 is not only a master regulator of cell fate determination and tissue morphogenesis, but also regulates various biological features of cancer, including cancer stemness, invasion, and drug resistance, making SOX9 a potential biomarker for tumor prognosis and progression. This review systematically summarizes the latest findings of SOX9 in hepatobiliary development, homeostasis, and disease. We also highlight the value of SOX9 as a novel biomarker and potential target for the clinical treatment of major liver diseases.

TGR5 overexpression mediated by the inhibition of transcription factor SOX9 protects against hypoxia-/reoxygenation-induced injury in hippocampal neurons by activating Nrf2/HO-1 signaling

Background

Cerebral ischemia/reperfusion (CI/R) injury is a destructive cerebrovascular disease associated with long-term disability and high mortality rates. TGR5 has been discovered in multiple human and animal tissues and to modulate a variety of physiological processes. The current study sought to reveal the function of TGR5 in CI/R injury and uncover the latent regulatory mechanism.

Methods

A hypoxia/reoxygenation (H/R) model was established in mouse hippocampal HT22 cells. The TGR5 expression in the H/R-treated HT22 cells was tested by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blots. After TGR5 was overexpressed, Cell Counting Kit-8 assays were used to estimate cell viability, and lactate dehydrogenase (LDH) release was assessed by a LDH assay kit. Cell apoptosis was measured by terminal deoxynucleotidyl transferase biotin-dUTP nick end labeling assays. Cytochrome c release was detected by immunofluorescence assays and western blots were used to analyze the protein levels of apoptosis-related factors. The oxidative stress levels were assessed by corresponding kits. Next, SOX9 expression in the H/R-treated HT22 cells was tested by RT-qPCR and western blots. The interaction between the TGR5 promoter and SOX9 was verified by luciferase reporter and chromatin immunoprecipitation assays. Subsequently, after the H/R-treated HT22 cells had been co-transfected with TGR5 overexpression and SOX9 overexpression plasmids, TGR5 expression was tested by RT-qPCR and western blots, and the above-mentioned functional experiments were repeated. Finally, the expression of Nrf2/HO-1 signaling-related proteins was examined by western blots.

Results

TGR5 expression was significantly decreased in the H/R-exposed HT22 cells. The elevation of TGR5 enhanced the viability, hindered the apoptosis, and alleviated the oxidative stress of the HT22 cells under H/R conditions. Additionally, SOX9 had a strong affinity with TGR5 promoter, and TGR5 was transcriptionally inhibited by SOX9. Further, SOX9 overexpression restored the protective role of TGR5 upregulation in H/R-induced HT22 cell injury. Additionally, TGR5 overexpression mediated by SOX9 inhibition activated Nrf2/HO-1 signaling.

Conclusions

TGR5 was transcriptionally inhibited by SOX9, and the overexpression of TGR5 played a protective role in CI/R injury.

Histone demethylase JMJD3 downregulation protects against aberrant force-induced osteoarthritis through epigenetic control of NR4A1

Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.

Sox9 Promotes Cardiomyocyte Apoptosis After Acute Myocardial Infarction by Promoting miR-223-3p and Inhibiting MEF2C

Acute myocardial infarction (AMI) is a severe and even fatal cardiovascular disease. The effect of transcription factors on AMI is intensively explored. Our experiment attempts to probe the role of Sox9 in cardiomyocyte apoptosis after AMI. AMI cell model was established in AC16 cells by hypoxia treatment. Cell viability and apoptosis were assessed. Then, the levels of BAX, Bcl-2, Sox9, miR-223-3p, and MEF2C were detected. The binding relation between Sox9 and miR-223-3p and between miR-223-3p and MEF2C was verified. The expression of miR-223-3p was upregulated using the miR-223-3p mimic, and collaborative experiments were conducted as si-Sox9 or si-MEF2C was transfected into cells to inhibit the expression of Sox9 or MEF2C. Sox9 was highly expressed in cardiomyocyte apoptosis after hypoxia, while Sox9 silencing protected hypoxia-treated cardiomyocytes from apoptosis by enhancing cell viability, quenching apoptosis, and reducing activity of caspase-3 and caspase-9. Essentially, Sox9 bound to the miR-223-3p promoter region to upregulate its expression. miR-223-3p targeted MEF2C transcription. miR-223-3p overexpression and MEF2C silencing could counteract the suppressive role of Sox9 silencing in hypoxia-treated cardiomyocyte apoptosis. Sox9 exacerbated hypoxia-induced cardiomyocyte apoptosis by promoting miR-223-3p expression and inhibiting MEF2C transcription.

IRF4 suppresses osteogenic differentiation of BM-MSCs by transcriptionally activating miR-636/DOCK9 axis

OBJECTIVES

Osteoblasts are derived from Bone Marrow-derived Mesenchymal Stem Cells (BM-MSCs), which play an indispensable role in bone formation. In this study, the authors aim to investigate the role of IRF4 in the osteogenic differentiation of BM-MSCs and its potential molecular mechanism.

METHODS

The authors used lentivirus infection to overexpress IRF4 in BM-MSCs. The expression of IRF4 and osteogenesis-related genes were detected by qRT-PCR and western blot analysis. The osteogenic differentiation of BM-MSCs was evaluated by Alkaline Phosphatase (ALP) activity, Alizarin red staining, and Alkaline Phosphatase (ALP) staining. Chromatin Immunoprecipitation (ChIP), Dual-Luciferase reporter assay and RNA Immunoprecipitation Assay were applied to confirm the regulatory mechanism between IRF4, miR-636 and DOCK9.

RESULTS

The authors found IRF4 was down-regulated during the osteogenic differentiation of BM-MSCs, and IRF4 overexpression could decrease the osteogenic differentiation of BM-MSCs by specifically promoting the reduction of Alkaline Phosphatase (ALP) activity and down-regulating osteogenic indicators, including OCN, OPN, Runx2 and CollA1. Mechanistically, IRF4 activated microRNA-636 (miR-636) expression via binding to its promoter region, and Dedicator of Cytokinesis 9 (DOCK9) was identified as the target of miR-636 in BM-MSCs. Moreover, the damage in the capacity of osteogenic differentiation of BM-MSCs induced by IRF4 overexpression could be rescued by miR-636 inhibition.

CONCLUSIONS

In summary, this paper proposed that IRF4/miR-636/DOCK9 may be considered as targets for the treatment of osteoporosis (OP).