METTL3 contributes to renal ischemia-reperfusion injury by regulating Foxd1 methylation

METTL3 inhibits BMSC apoptosis and facilitates osteonecrosis repair via an m6A-IGF2BP2-dependent mechanism

Hypoxia-induced apoptosis of bone marrow mesenchymal stem cells (BMSCs) limits the efficacy of their transplantation for steroid-induced osteonecrosis of the femoral head (SONFH). As apoptosis and RNA methylation are closely related, exploring the role and mechanism of RNA methylation in hypoxic apoptosis of BMSCs is expected to identify new targets for transplantation of BMSCs for SONFH and enhance transplantation efficacy. We performed methylated RNA immunoprecipitation sequencing (MeRIP-seq) combined with RNA-seq on a hypoxia-induced apoptosis BMSC model and found that the RNA methyltransferase-like 3 (METTL3) is involved in hypoxia-induced BMSC apoptosis. The expression of METTL3 was downregulated in BMSCs after hypoxia and in BMSCs implanted in osteonecrosis areas. Knockdown of METLL3 under normoxic conditions promoted apoptosis of BMSCs. In contrast, overexpression of METTL3 promoted the survival of BMSCs under hypoxic conditions, and overexpression of METTL3 promoted the survival of BMSCs in the osteonecrosis area and the repair of the osteonecrosis area. Regarding the mechanism, the m6A levels of the mRNAs of anti-apoptotic genes Bcl-2, Mcl-1, and BIRC5 were significantly increased upon the overexpression of METTL3 under hypoxic conditions, which promoted the binding of Bcl-2, Mcl-1, and BIRC5 mRNAs to IGF2BP2, enhanced the mRNA stability, and increased the protein expression of the three anti-apoptotic genes. In conclusion, overexpression of METTL3 promoted m6A modification of mRNAs of Bcl-2, Mcl-1, and BIRC5, promoted the binding of IGF2BP2 to the above-mentioned mRNAs, enhanced mRNA stability, inhibited hypoxia-induced BMSC apoptosis, and promoted repair of SONFH, thereby providing novel targets for transplantation of BMSCs for SONFH.

Targeted Restoration of GPX3 Attenuates Renal Ischemia/Reperfusion Injury by Balancing Selenoprotein Expression and Inhibiting ROS-mediated Mitochondrial Apoptosis

BACKGROUND

Renal ischemia/reperfusion (IR) injury is the leading cause of acute kidney injury in both autologous and transplanted kidneys. Low-level glutathione peroxidase 3 (GPX3) is associated with renal IR injury. The exact mechanism of targeted GPX3 restoration in renal IR injury has yet to be determined.

METHODS

The distribution of GPX3 in different tissues and organs of the body was investigated. The level of GPX3 in renal IR injury was assessed. To confirm the action of GPX3 and its mechanisms, IR models were used to introduce adeno-associated virus 9 containing GPX3, as well as hypoxia/reoxygenation-exposed normal rat kidney cells that consistently overexpressed GPX3. Reverse molecular docking was used to confirm whether GPX3 was a target of ebselen.

RESULTS

GPX3 is abundant in the kidneys and decreases in expression during renal IR injury. GPX3 overexpression reduced renal IR injury and protected tubular epithelial cells from apoptosis. Proteomics analysis revealed a strong link between GPX3 and mitochondrial signaling, cellular redox state, and different expression patterns of selenoproteins. GPX3 inhibited reactive oxygen species-induced mitochondrial apoptosis and balanced the disordered expression of selenoproteins. GPX3 was identified as a stable selenoprotein that interacts with ebselen. Ebselen enhanced the level of GPX3 and reduced IR-induced mitochondrial damage and renal dysfunction.

CONCLUSIONS

Targeted restoration of GPX3 attenuates renal IR injury by balancing selenoprotein expression and inhibiting reactive oxygen species-mediated mitochondrial apoptosis, indicating that GPX3 could be a potential therapeutic target for renal IR injury.

Targeting the m6A RNA methyltransferase METTL3 attenuates the development of kidney fibrosis

Kidney fibrosis is a major mechanism underlying chronic kidney disease (CKD). N6-methyladenosine (m6A) RNA methylation is associated with organ fibrosis. We investigated m6A profile alterations and the inhibitory effect of RNA methylation in kidney fibrosis in vitro (TGF-β-treated HK-2 cells) and in vivo (unilateral ureteral obstruction [UUO] mouse model). METTL3-mediated signaling was inhibited using siRNA in vitro or the METTL3-specific inhibitor STM2457 in vivo and in vitro. In HK-2 cells, METTL3 protein levels increased in a dose- and time-dependent manner along with an increase in the cellular m6A levels. In the UUO model, METTL3 expression and m6A levels were significantly increased. Transcriptomic and m6A profiling demonstrated that epithelial-to-mesenchymal transition- and inflammation-related pathways were significantly associated with RNA m6A methylation. Genetic and pharmacologic inhibition of METTL3 in HK-2 cells decreased TGF-β-induced fibrotic marker expression. STM2457-induced inhibition of METTL3 attenuated the degree of kidney fibrosis in vivo. Furthermore, METTL3 protein expression was significantly increased in the tissues of CKD patients with diabetic or IgA nephropathy. Therefore, targeting alterations in RNA methylation could be a potential therapeutic strategy for treating kidney fibrosis.

NAT10 promotes renal ischemia-reperfusion injury via activating NCOA4-mediated ferroptosis

Ischemia-reperfusion injury (IRI) is a significant contributor to acute kidney injury (AKI) and is associated with substantial morbidity and mortality rates. In this study, we aimed to investigate the role of NAT10 and its ac4C RNA modification in IRI-induced renal injury. Our findings revealed that both the expression level of NAT10 and the RNA ac4C level in the kidneys were elevated in the IRI group compared to the sham group. Functionally, we observed that inhibition of NAT10 activity with Remodelin or the specific knockout of NAT10 in the kidney led to a significant attenuation of IRI-induced renal injury. Furthermore, in vitro experiments demonstrated that NAT10 inhibition and specific knockout of NAT10 in the kidney markedly suppressed global ac4C RNA modification, providing protection against hypoxia/reoxygenation-induced tubular epithelial cell injury and ferroptosis. Mechanistically, our study uncovered that NAT10 promoted ac4C RNA modification of NCOA4 mRNA, thereby enhancing its stability and contributing to IRI-induced ferroptosis in tubular epithelial cells (TECs). These findings underscore the potential of NAT10 and ac4C RNA modification as promising therapeutic targets for the treatment of AKI. Overall, our study sheds light on the critical involvement of NAT10 and ac4C RNA modification in the pathogenesis of IRI-induced renal injury, offering valuable insights for the development of novel AKI treatment strategies.

The role of N-methyladenosine modification in acute and chronic kidney diseases

N6-methyladenosine (m6A) modification is a kind of RNA modification in which methylation occurs at the sixth N position in adenosine in RNA, which can occur in various RNAs such as mRNAs, lncRNAs and miRNAs. This is one of the most prominent and frequent posttranscriptional modifications within organisms and has been shown to function dynamically and reversibly in a variety of ways, including splicing, export, attenuation and translation initiation efficiency to regulate RNA expression. There are three main enzymes associated with m6A modification: writers, readers and erasers. Increasing evidence has shown that m6A modification is associated with the onset and development of kidney disease. In this article, we address the important physiological and pathological roles of m6A modification in kidney diseases (uremia, ischemia-reperfusion kidney injury, drug-induced kidney injury, and diabetic nephropathy) and its molecular mechanisms to provide reference for the diagnosis and clinical management of kidney diseases.

Key m6A regulators mediated methylation modification pattern and immune infiltration characterization in hepatic ischemia-reperfusion injury

BACKGROUND

N6-methyladenosine (m6A) mRNA modification plays a critical role in various human biological processes. However, there has been no study reported to elucidate its role in hepatic ischemia-reperfusion injury (IRI). This study was aimed to explore the expression pattern together with the potential functions of m6A regulators in hepatic IRI.

METHODS

The gene expression data (GSE23649) of m6A regulators in human liver tissue samples before cold perfusion and within 2 h after portal vein perfusion from Gene Expression Omnibus database was analyzed. The candidate m6A regulators were screened using random forest (RF) model to predict the risk of hepatic IRI. The evaluation of infiltrating abundance of 23 immune cells was performed using single sample gene set enrichment analysis. Besides, quantitative real time polymerase chain reaction (qRT-PCR) assay was carried out to validate the expression of key m6A regulators in mouse hepatic IRI model.

RESULTS

The expressions of WTAP, CBLL1, RBM15, and YTHDC1 were found to be increased in liver tissues 2 h after portal vein perfusion; in contrast, the expressions of LRPPRC, FTO, METTL3, and ALKBH5 were decreased. Based on RF model, we identified eight m6A methylation regulators for the prediction of the risk of hepatic IRI. Besides, a nomogram was built to predict the probability of hepatic IRI. In addition, the levels of WTAP, ALKBH5, CBLL1, FTO, RBM15B, LRPPRC and YTHDC1 were correlated with the immune infiltration of activated CD4 T cell, activated dendritic cell (DC), immature DC, mast cell, neutrophil, plasmacytoid DC, T helper (Th) cell (type 1, 2, and 17), gamma delta T cell, T follicular helper (Tfh) cell, myeloid-derived suppressor cell (MDSC), macrophage, natural killer cell, and regulatory Th cell. Among mouse hepatic IRI model, the mRNA level of CBLL1 and YTHDC1 was increased with statistical significance; however, the mRNA level of FTO and METTL3 was decreased among post-reperfusion liver samples compared with those in pre-reperfusion samples with statistical significance.

CONCLUSIONS

The m6A regulators exerted a pivotal impact on hepatic IRI. The m6A patterns that found in this study might provide novel targets and strategies for the alleviation/treatment of hepatic IRI in the future.

N6-methyladenosine methylation in kidney injury

Multiple mechanisms are involved in kidney damage, among which the role of epigenetic modifications in the occurrence and development of kidney diseases is constantly being revealed. However, N6-methyladenosine (M6A), a well-known post-transcriptional modification, has been regarded as the most prevalent epigenetic modifications in higher eukaryotic, which is involved in various biological processes of cells such as maintaining the stability of mRNA. The role of M6A modification in the mechanism of kidney damage has attracted widespread attention. In this review, we mainly summarize the role of M6A modification in the progression of kidney diseases from the following aspects: the regulatory pattern of N6-methyladenosine, the critical roles of N6-methyladenosine in chronic kidney disease, acute kidney injury and renal cell carcinoma, and then reveal its potential significance in the diagnosis and treatment of various kidney diseases. A better understanding of this field will be helpful for future research and clinical treatment of kidney diseases.

The role of N6-methyladenosine (m6A) in kidney diseases

Chemical modifications are a specific and efficient way to regulate the function of biological macromolecules. Among them, RNA molecules exhibit a variety of modifications that play important regulatory roles in various biological processes. More than 170 modifications have been identified in RNA molecules, among which the most common internal modifications include N6-methyladenine (m6A), n1-methyladenosine (m1A), 5-methylcytosine (m5C), and 7-methylguanine nucleotide (m7G). The most widely affected RNA modification is m6A, whose writers, readers, and erasers all have regulatory effects on RNA localization, splicing, translation, and degradation. These functions, in turn, affect RNA functionality and disease development. RNA modifications, especially m6A, play a unique role in renal cell carcinoma disease. In this manuscript, we will focus on the biological roles of m6A in renal diseases such as acute kidney injury, chronic kidney disease, lupus nephritis, diabetic kidney disease, and renal cancer.

Remimazolam relieved the injury of hypoxia/reperfusion treated human embryo liver cell line through the targeting METTL3 mediated m6A modification of P53

Background

This study was performed to explore the role of Re in liver IRI progression. Hypoxia and reperfusion (H/R) treated human embryo liver cell line (L-02) was used to establish a liver IRI model.

Materials and methods

Cell behaviors were detected using CCK-8, flow cytometry and TUNEL staining assays. The m6A content was detected using m6A dot blot assay. RT-qPCR and western blot assays were used to assessed the relative mRNA and protein levels. MeRIP assay was conducted to determine the m6A levels of P53. The relationship between METTL3 and P53 was demonstrated using RIP and dual-luciferase reporter assays.

Results

The results showed that Re treatment significantly decreased the cell apoptosis and promoted the cell viability in the H/R treated L-02 cells. Besides, H/R treatment increased the METTL3 and m6A levels in the L-02 cells, and Re treatment decreased them. Additionally, METTL3 overexpression reversed the role of Re in the H/R treated L-02 cells. Mechanistically, METTL3 overexpression enhanced the m6A levels and mRNA stability and expressions of P53. The combination of METTL3 and P53 was further confirmed.

Conclusion

In conclusion, this study demonstrated that Re treatment relieved the H/R induced injury in the L-02 cells through decreasing the METTL3 levels. METTL3 enhanced the mRNA stability and expressions of P53 through m6A modification. Re-METTL3-P53 axis might a new direction for the treatment of liver IRI in the future.

HNRNPC promotes collagen fiber alignment and immune evasion in breast cancer via activation of the VIRMA-mediated TFAP2A/DDR1 axis

BACKGROUND

Cancers aggressively reorganize collagen in their microenvironment, leading to the evasion of tumor cells from immune surveillance. However, the biological significance and molecular mechanism of collagen alignment in breast cancer (BC) have not been well established.

METHODS

In this study, BC-related RNA-Seq data were obtained from the TCGA database to analyze the correlation between DDR1 and immune cells. Mouse BC cells EO771 were selected for in vitro validation, and dual-luciferase experiments were conducted to examine the effect of TFAP2A on DDR1 promoter transcription activity. ChIP experiments were performed to assess TFAP2A enrichment on the DDR1 promoter, while Me-RIP experiments were conducted to detect TFAP2A mRNA m6A modification levels, and PAR-CLIP experiments were conducted to determine VIRMA's binding to TFAP2A mRNA and RIP experiments to investigate HNRNPC's recognition of m6A modification on TFAP2A mRNA. Additionally, an in vivo mouse BC transplant model and the micro-physiological system was constructed for validation, and Masson staining was used to assess collagen fiber arrangement. Immunohistochemistry was conducted to identify the number of CD8-positive cells in mouse BC tumors and Collagen IV content in ECM, while CD8 + T cell migration experiments were performed to measure CD8 + T cell migration.

RESULTS

Bioinformatics analysis showed that DDR1 was highly expressed in BC and negatively correlated with the proportion of anti-tumor immune cell infiltration. In vitro cell experiments indicated that VIRMA, HNRNPC, TFAP2A, and DDR1 were highly expressed in BC cells. In addition, HNRNPC promoted TFAP2A expression and, therefore, DDR1 transcription by recognizing the m6A modification of TFAP2A mRNA by VIRMA. In vivo animal experiments further confirmed that VIRMA and HNRNPC enhanced the TFAP2A/DDR1 axis, promoting collagen fiber alignment, reducing anti-tumor immune cell infiltration, and promoting immune escape in BC.

CONCLUSION

This study demonstrated that HNRNPC promoted DDR1 transcription by recognizing VIRMA-unveiled m6A modification of TFAP2A mRNA, which enhanced collagen fiber alignment and ultimately resulted in the reduction of anti-tumor immune cell infiltration and promotion of immune escape in BC.

Asiaticoside ameliorates renal ischemia/reperfusion injury by promoting CD4+CD25+FOXP3+ treg cell differentiation

Ischemia/reperfusion injury (I/R) is the major cause of acute kidney injury, which becomes a global health problem. The effects of asiaticoside, as an anti-inflammatory drug, on renal ischemia-reperfusion injury have not been well defined. After the CD4+ cells were treated with asiaticoside, the CD4+CD25+FOXP3+ Treg cell differentiation was detected by flow cytometry. The viability and release of inflammatory factors of CD4+CD25+FOXP3+ Treg cell were detected by CCK-8 and ELISA. Renal I/R injury mice model was established, and the mice were pre-treated with asiaticoside or CD25 antibody or infused with Treg cells. The histological changes of renal tissue were evaluated by Hematoxylin-eosin, PAS, and Masson staining. The renal function markers were evaluated by colorimetry, the release of inflammatory factors was determined by ELISA. The Th17 and Treg cells in the blood and spleen were quantified by flow cytometry. The expressions of FOXP3 and RoR-γt in renal tissues were determined by western blotting. Asiaticoside promoted CD4+CD25+FOXP3+ Treg cell differentiation, increased the cell viability and down-regulated TNF-α, IL-1β, and IL-6, while up-regulated IL-10 of CD4+CD25+FOXP3+ Treg cells. Moreover, asiaticoside ameliorated the histological damage, decreased the Th17 cells and increased Treg cells, and down-regulated the TNF-α, IL-1β, IL-6, blood urea nitrogen, serum creatinine, and RoR-γt, while up-regulated IL-10 and FOXP3 of renal I/R injury mice. Effect of asiaticoside on renal I/R injury mice was reversed by CD25 antibody whose role was further reversed by Treg cell infusing. In conclusion, asiaticoside ameliorated renal I/R injury due to promoting CD4+CD25+FOXP3+ Treg cell differentiation.

BMSC-Derived Exosomes Carrying lncRNA-ZFAS1 Alleviate Pulmonary Ischemia/Reperfusion Injury by UPF1-Mediated mRNA Decay of FOXD1

Bone marrow-derived mesenchymal stem cells (BMSCs) exert protective effects against pulmonary ischemia/reperfusion (I/R) injury; however, the potential mechanism involved in their protective ability remains unclear. Thus, this study aimed to explore the function and underlying mechanism of BMSC-derived exosomal lncRNA-ZFAS1 in pulmonary I/R injury. Pulmonary I/R injury models were established in mice and hypoxia/reoxygenation (H/R)-exposed primary mouse lung microvascular endothelial cells (LMECs). Exosomes were extracted from BMSCs. Target molecule expression was assessed by qRT-PCR and Western blotting. Pathological changes in the lungs, pulmonary edema, apoptosis, pro-inflammatory cytokine levels, SOD, MPO activities, and MDA level were measured. The proliferation, apoptosis, and migration of LMECs were detected by CCK-8, EdU staining, flow cytometry, and scratch assay. Dual-luciferase reporter assay, RNA pull-down, RIP, and ChIP assays were performed to validate the molecular interaction. In the mouse model of pulmonary I/R injury, BMSC-Exos treatment relieved lung pathological injury, reduced lung W/D weight ratio, and restrained apoptosis and inflammation, whereas exosomal ZFAS1 silencing abolished these beneficial effects. In addition, the proliferation, migration inhibition, apoptosis, and inflammation in H/R-exposed LMECs were repressed by BMSC-derived exosomal ZFAS1. Mechanistically, ZFAS1 contributed to FOXD1 mRNA decay via interaction with UPF1, thereby leading to Gal-3 inactivation. Furthermore, FOXD1 depletion strengthened the weakened protective effect of ZFAS1-silenced BMSC-Exos on pulmonary I/R injury. ZFAS1 delivered by BMSC-Exos results in FOXD1 mRNA decay and subsequent Gal-3 inactivation via direct interaction with UPF1, thereby attenuating pulmonary I/R injury.

MetBil as a novel molecular regulator in ischemia-induced cardiac fibrosis via METTL3-mediated m6A modification

Cardiac fibrosis is a common pathological manifestation in multiple cardiovascular diseases and often results in myocardial stiffness and cardiac dysfunctions. LncRNA (long noncoding RNA) participates in a number of pathophysiological processes. However, its role in cardiac fibrosis remains unclear. The purpose of this study was to investigate the role and molecular mechanism of MetBil in regulating cardiac fibrosis. Our data showed that METTL3 binding lncRNA (MetBil) was significantly increased both in fibrotic tissue following myocardial infarction (MI) in mice and in cardiac fibroblasts (CFs) exposed to TGF-β1 (20 ng/mL) or 20% FBS. Overexpression of MetBil augmented collagen deposition, CF proliferation and activation while silencing MetBil exhibited the opposite effects. Importantly, heterozygous knockout of MetBil alleviated cardiac fibrosis and improved cardiac function after MI. RNA pull-down and RNA-binding protein immunoprecipitation assay showed that METTL3 is a direct downstream target of MetBil; consistently, MetBil and METTL3 were co-localized in both the nucleus and cytoplasm of CFs. Interestingly, MetBil regulated METTL3 expression at protein level, but not mRNA level, in ubiquitin-proteasome pathway. Enforced expression of METTL3 canceled the antifibrotic effects of silencing MetBil reflected by increased collagen production, CF proliferation and activation. Most notably, the m6A-modified fibrosis-regulated genes mediated by METTL3 are profoundly involved in the regulation of MetBil in the cardiac fibrosis following MI. Our study reveals that MetBil as a novel regulator of fibrosis promotes cardiac fibrosis via interacting with METTL3 and regulating the expression of the methylated fibrosis-associated genes, providing a new intervening target for fibrosis-associated cardiac diseases.

Inhibition of ALKBH5 attenuates I/R-induced renal injury in male mice by promoting Ccl28 m6A modification and increasing Treg recruitment

Ischemia reperfusion injury (IRI) is a common cause of acute kidney injury (AKI). The role of N^6-methyladenosine (m6A) modification in AKI remains unclear. Here, we characterize the role of AlkB homolog 5 (ALKBH5) and m6A modification in an I/R-induced renal injury model in male mice. Alkbh5-knockout mice exhibit milder pathological damage and better renal function than wild-type mice post-IRI, whereas Alkbh5-knockin mice show contrary results. Also conditional knockout of Alkbh5 in the tubular epithelial cells alleviates I/R-induced AKI and fibrosis. CCL28 is identified as a target of ALKBH5. Furthermore, Ccl28 mRNA stability increases with Alkbh5 deficiency, mediating by the binding of insulin-like growth factor 2 binding protein 2. Treg recruitment is upregulated and inflammatory cells are inhibited by the increased CCL28 level in IRI-Alkbh5^fl/flKsp^Cre mice. The ALKBH5 inhibitor IOX1 exhibits protective effects against I/R-induced AKI. In summary, inhibition of ALKBH5 promotes the m6A modifications of Ccl28 mRNA, enhancing its stability, and regulating the Treg/inflammatory cell axis. ALKBH5 and this axis is a potential AKI treatment target.

N6-methyladenine RNA Methylation Epigenetic Modification and Kidney Diseases

RNA methylation modification is a rapidly developing field in epigenetics. N6-methyladensine (m⁶A) is the most common internal modification in eukaryotic mRNA. m⁶A group regulates RNA splicing, stability, translocation, and translation. Enzymes catalyzing this process were termed as writers, erasers, and readers. Recent studies have focused on exploring the role of RNA methylation in human diseases. RNA methylation modifications, particularly m⁶A, play important roles in the pathogenesis of kidney diseases. In this review, we provide a brief description of m⁶A and summarize the impact of m⁶A on acute and chronic kidney disease (CKD) and possible future study directions for this research.

N(6)-methyladenosine modification: A vital role of programmed cell death in myocardial ischemia/reperfusion injury

N(6)-methyladenosine (m⁶A) modification is closely associated with myocardial ischemia/reperfusion injury (MIRI). As the most common modification among RNA modifications, the reversible m⁶A modification is processed by methylase ("writers") and demethylase ("erasers"). The biological effects of RNA modified by m⁶A are regulated under the corresponding RNA binding proteins (RBPs) ("readers"). m⁶A modification regulates the whole process of RNA, including transcription, processing, splicing, nuclear export, stability, degradation, and translation. Programmed cell death (PCD) is a regulated mechanism that maintains the internal environment's stability. PCD plays an essential role in MIRI, including apoptosis, autophagy, pyroptosis, ferroptosis, and necroptosis. However, the relationship between PCD modified with m⁶A and MIRI is still not clear. This review summarizes the regulators of m⁶A modification and their bioeffects on PCD in MIRI.

Alteration of N6-methyladenosine epitranscriptome profiles in bilateral ureteral obstruction-induced obstructive nephropathy in juvenile rats

BACKGROUND

Urinary tract obstruction is a common cause of renal failure in children and infants, and the pathophysiological mechanisms of obstructive nephropathy are largely unclear. It has been reported that m6A modulation is involved in renal injury. However, whether m6A RNA modulation is associated with obstructive nephropathy has not yet been reported. The aim of this study was to investigate the m6A epitranscriptome profiles in the kidneys of bilateral ureteral obstruction (BUO) in young rats.

METHODS

The total level of m6A in the kidneys was measured by liquid chromatography-tandem mass spectrometry. The mRNAs of related genes were detected by real-time PCR. Methylated RNA immunoprecipitation sequencing was performed to map the epitranscriptome-wide m6A profile.

RESULTS

Global m6A levels were increased after BUO, and the mRNA expression levels of m6A methyltransferases and demethylases were significantly decreased in BUO group rat kidneys; the expression levels of EGFR and Brcal were significantly upregulated, while the mRNA expression levels of Notch1 were downregulated (P < 0.05). A total of 154 genes associated with 163 m6A peaks were identified.

CONCLUSION

The m6A epitranscriptome was significantly altered in BUO rat kidneys, which is potentially implicated in the pathophysiological processes of obstructive nephropathy.

IMPACT

The m6A RNA modification was associated with the process of renal injury in ureteral obstructive nephropathy by participating in multiple dimensions. The dysregulation of m6A methyltransferases and demethylases may be related to the pathophysiological changes of BUO-induced obstructive nephropathy. The m6A RNA modulation of the genes EGFR, Brca1, and Notch1 that were related to the regulation of aquaporin2 might be the potential mechanism for the polyuresis after ureteral obstruction.

Inhibition of Circ-Snrk ameliorates apoptosis and inflammation in acute kidney injury by regulating the MAPK pathway

Background

Circular RNA (circRNA) is involved in the process of acute kidney injury (AKI), but only a few circRNAs have been reported. In the study, we investigated a new circRNA and its association with AKI.

Methods

An AKI model was established in Sprague-Dawley rats, followed by serum creatinine and urea nitrogen tests measured by a biochemical analyzer. The pathological changes and apoptosis in the renal tissue were detected by Hematoxylin and Eosin, and TUNEL staining. Then, circRNA expression in AKI was determined by quantitative real-time-PCR (qRT-PCR). NRK-52E cells were induced with hypoxia/reoxygenation (H/R) as in vitro models and the circ-Snrk level was tested by qRT-PCR. The effects of circ-Snrk in H/R-induced NRK-52E cells were assessed by flow cytometry, western blot, and enzyme-linked immunosorbent assay. Finally, RNA sequencing and western blot analysis were used to validate the mRNA profile and pathways involved in circ-Snrk knockdown in H/R-induced NRK-52E.

Results

A reliable AKI rat model and H/R cell model were established. qRT-PCR demonstrated that circ-Snrk level was upregulated in AKI left kidney tissue and NRK-52E cells with H/R treatment. Circ-Snrk knockdown inhibited apoptosis of NRK-52E cells and secretion of inflammatory factors (IL-6 and TNF-α). RNA sequencing showed that the mRNA profile changed after inhibition of circ-Snrk and differential expression of mRNA mainly enriched various signaling pathways, including MAPK signaling pathway. Furthermore, western blot indicated that circ-Snrk knockdown could inhibit the activation of p-JNK and p-38 transcription factors.

Conclusions

Circ-Snrk is involved in AKI development and associated with the MAPK signaling pathway in AKI.

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-β-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.

Mechanism of METTL3-Mediated m6A Modification in Cardiomyocyte Pyroptosis and Myocardial Ischemia–Reperfusion Injury

OBJECTIVE

Myocardial ischemia/reperfusion (MI/R) injury is a complicated pathophysiological process associated with cardiomyocyte pyroptosis. Methyltransferase-like protein 3 (METTL3) catalyzes the formation of N⁶-methyl-adenosine (m⁶A) and participates in various biological processes. This study probed into the mechanism of METTL3 in cardiomyocyte pyroptosis in MI/R injury.

METHODS

A rat model of MI/R was established. Rat cardiomyocytes were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) treatment for the establishment of a cell model in vitro. METTL3 expression in myocardial tissues of MI/R rats and OGD/R-treated cardiomyocytes was determined using RT-qPCR and Western blot. The pathological changes of rat myocardial tissues were observed using hematoxylin and eosin staining. The positive expression of NLRP3 in myocardial tissues or cardiomyocytes was observed through immunohistochemistry or immunofluorescence. The activity of caspase-1 was measured using the colorimetric method. The expressions of GSDMD and cleaved caspase-1, as well as the levels of IL-1β and IL-18 in rat myocardial tissues or cardiomyocytes were determined. m⁶A modification level was quantified. The binding relationship between pri-miR-143-3p and DGCR8 and the enrichment of m⁶A on pri-miR-143-3p were detected. The binding relationship between miR-143-3p and protein kinase C epsilon (PRKCE) was verified.

RESULTS

METTL3 expression was elevated in MI/R rats and OGD/R cardiomyocytes. METTL3 silencing alleviated myocardial injury, reduced the number of NLRP3-positive cardiomyocytes, suppressed caspase-1 activity, decreased the protein levels of GSDMD-N and cleaved caspase-1, and decreased IL-1β and IL-18 levels. METTL3 increased the total m⁶A level in MI/R rats and injured cardiomyocytes, promoted DGCR8 binding to pri-miR-143-3p, and enhanced miR-143-3p expression. miR-143-3p suppressed PRKCE transcription, and miR-143-3p overexpression reversed the inhibitory effect of METTL3 silencing on cardiomyocyte pyroptosis.

CONCLUSION

METTL3 promoted DGCR8 binding to pri-miR-143-3p through m⁶A modification, thus enhancing miR-143-3p expression to inhibit PRKCE transcription and further aggravating cardiomyocyte pyroptosis and MI/R injury.

Methyltransferase-like 3 (METTL3) attenuates cardiomyocyte apoptosis with myocardial ischemia-reperfusion (I/R) injury through miR-25-3p and miR-873-5p

Methyltransferase-like 3 (METTL3) mediated N⁶ -methyladenosine (m6A) promotes microRNAs (miRNAs) maturation by processing the primary miRNAs, and METTL3 involves in regulating the development of various diseases, including myocardial ischemia-reperfusion (I/R) injury. However, up until now, the association between METTL3 regulated miRNAs and I/R injury is not fully investigated, which makes investigations on this academic issue necessary. In this study, we showed that METTL3 was downregulated in mice I/R myocardial tissues and hypoxic/re-oxygenated (H/R) cardiomyocytes, and upregulation of METTL3 attenuated I/R and H/R-induced cell apoptosis. In addition, we screened out that two miRNAs, including miR-25-3p and miR-873-5p, were positively regulated by METTL3 in cardiomyocytes in a DGCR8-dependent manner. In addition, both miR-25-3p and miR-873-5p were significantly downregulated by I/R and H/R treatments in mice tissues and cardiomyocytes, and overexpression of the above two miRNAs were effective to improve cell viability in cardiomyocytes under H/R stress. Next, we evidenced that METTL3 suppressed H/R-induced cell death via upregulating miR-25-3p and miR-873-5p. Finally, the potential downstream mechanisms were investigated, and we expectedly found that METTL3 activated the PI3K/Akt pathway in H/R-treated cardiomyocytes through modulating miR-25-3p and miR-873-5p, and the PI3K/Akt pathway inhibitor (LY294002) abrogated the protective effects of METTL3 overexpression in cardiomyocytes with H/R treatment. Collectively, we concluded that METTL3 upregulated miR-25-3p and miR-873-5p to activate the PI3K/Akt pathway, resulting in the suppression of I/R injury.

Alteration of N6-Methyladenosine RNA Profiles in Cisplatin-Induced Acute Kidney Injury in Mice

Aim: To identify the alterations of N6-methyladenosine (m⁶A) RNA profiles in cisplatin-induced acute kidney injury (Cis-AKI) in mice.

Materials and Methods: The total level of m⁶A and the expression of methyltransferases and demethylases in the kidneys were measured. The profiles of methylated RNAs were determined by the microarray method. Bioinformatics analysis was performed to predict the functions.

Results: Global m⁶A levels were increased after cisplatin treatment, accompanied by the alterations of Mettl3, Mettl14, Wtap, Fto, and Alkbh5. A total of 618 mRNAs and 98 lncRNAs were significantly differentially methylated in response to cisplatin treatment. Bioinformatics analysis indicated that the methylated mRNAs predominantly acted on the metabolic process.

Conclusion: M⁶A epitranscriptome might be significantly altered in Cis-AKI, which is potentially implicated in the development of nephrotoxicity.