Insulin-like growth factor 2 mRNA-binding protein 3 promotes kidney injury by regulating β-catenin signaling

IGF2BP3/NCBP1 complex inhibits renal tubular senescence through regulation of CDK6 mRNA stability

Renal aging and the subsequent rise in kidney-related diseases are attributed to senescence in renal tubular epithelial cells (RTECs). Our study revealed that the abnormal expression of insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3), a reader of RNA N6-methyladenosine, is critically involved in cisplatin-induced renal tubular senescence. In cisplatin-induced senescence of RTECs, the promoter activity and transcription of IGF2BP3 is markedly suppressed. It was due to the down regulation of MYC proto-oncogene (MYC), which regulates IGF2BP3 transcription by binding to the putative site at 1852-1863 of the IGF2BP3 promoter. Overexpression of IGF2BP3 ameliorated cisplatin-induced renal tubular senescence in vitro. Mechanistic studies revealed that IGF2BP3 inhibits cellular senescence in RTECs by enhancing cyclin-dependent kinase 6 (CDK6) mRNA stability and increasing its expression. The inhibition effect of IGF2BP3 on tubular senescence is partially reversed by the knockdown of CDK6. Further, IGF2BP3 recruits nuclear cap binding protein subunit 1 (NCBP1) and inhibits CDK6 mRNA decay, by recognizing m6A modification. Specifically, IGF2BP3 recognizes m6A motif "GGACU" at nucleotides 110-114 in the 5' untranslated region (UTR) field of CDK6 mRNA. The involvement of IGF2BP3/CDK6 in alleviating tubular senescence was confirmed in a cisplatin-induced acute kidney injury (AKI)-to-chronic kidney disease (CKD) model. Clinical data also suggests an age-related decrease in IGF2BP3 and CDK6 levels in renal tissue or serum samples from patients. These findings suggest that IGF2BP3/CDK6 may be a promising target in cisplatin-induced tubular senescence and renal failure.

Phylloquinone improves endothelial function, inhibits cellular senescence, and vascular inflammation

Phylloquinon (PK) and menaquinones (MK) are both naturally occurring compounds belonging to vitamin K group. Present study aimed to comprehensively analyze the influence of PK in several models of vascular dysfunction to determine whether PK has vasoprotective properties, similar to those previously described for MK. Effects of PK and MK on endothelial dysfunction were studied in ApoE/LDLR-/- mice in vivo, in the isolated aorta incubated with TNF, and in vascular cells as regard inflammation and cell senescence (including replicative and stress-induced models of senescence). Moreover, the vascular conversion of exogenous vitamins to endogenous MK-4 was analyzed. PK, as well as MK, given for 8 weeks in diet (10 mg/kg) resulted in comparable improvement in endothelial function in the ApoE/LDLR-/- mice. Similarly, PK and MK prevented TNF-induced impairment of endothelium-dependent vasorelaxation in the isolated aorta. In in vitro studies in endothelial and vascular smooth muscle cells, we identified that both PK and MK displayed anti-senescence effects via decreasing DNA damage while in endothelial cells anti-inflammatory activity was ascribed to the modulation of NFκB activation. The activity of PK and MK was comparable in terms of their effect on senescence and inflammation. Presence of endogenous synthesis of MK-4 from PK in aorta and endothelial and smooth muscle cells suggests a possible involvement of MK in vascular effects of PK. In conclusion, PK and MK display comparable vasoprotective effects, which may be ascribed, at least in part, to the inhibition of cell senescence and inflammation. The vasoprotective effect of PK in the vessel wall can be related to the direct effects of PK, as well as to the action of MK formed from PK in the vascular wall.

Nkd1 functions downstream of Axin2 to attenuate Wnt signaling

Wnt signaling is a crucial developmental pathway involved in early development as well as stem-cell maintenance in adults and its misregulation leads to numerous diseases. Thus, understanding the regulation of this pathway becomes vitally important. Axin2 and Nkd1 are widely utilized negative feedback regulators in Wnt signaling where Axin2 functions to destabilize cytoplasmic β-catenin, and Nkd1 functions to inhibit the nuclear localization of β-catenin. Here, we set out to further understand how Axin2 and Nkd1 regulate Wnt signaling by creating axin2gh1/gh1, nkd1gh2/gh2 single mutants and axin2gh1/gh1;nkd1gh2/gh2 double mutant zebrafish using sgRNA/Cas9. All three Wnt regulator mutants were viable and had impaired heart looping, neuromast migration defects, and behavior abnormalities in common, but there were no signs of synergy in the axin2gh1/gh1;nkd1gh2/gh2 double mutants. Further, Wnt target gene expression by qRT-PCR and RNA-seq, and protein expression by mass spectrometry demonstrated that the double axin2gh1/gh1;nkd1gh2/gh2 mutant resembled the nkd1gh2/gh2 phenotype demonstrating that Nkd1 functions downstream of Axin2. In support of this, the data further demonstrates that Axin2 uniquely alters the properties of β-catenin-dependent transcription having novel readouts of Wnt activity compared with nkd1gh2/gh2 or the axin2gh1/gh1;nkd1gh2/gh2 double mutant. We also investigated the sensitivity of the Wnt regulator mutants to exacerbated Wnt signaling, where the single mutants displayed characteristic heightened Wnt sensitivity, resulting in an eyeless phenotype. Surprisingly, this phenotype was rescued in the double mutant, where we speculate that cross-talk between Wnt/β-catenin and Wnt/Planar Cell Polarity pathways could lead to altered Wnt signaling in some scenarios. Collectively, the data emphasizes both the commonality and the complexity in the feedback regulation of Wnt signaling.

m6A RNA methylation drives kidney fibrosis by upregulating β-catenin signaling

N6-methyladenosine (m6A) methylation plays a crucial role in various biological processes and the pathogenesis of human diseases. However, its role and mechanism in kidney fibrosis remain elusive. In this study, we show that the overall level of m6A methylated RNA was upregulated and the m6A methyltransferase METTL3 was induced in kidney tubular epithelial cells in mouse models and human kidney biopsies of chronic kidney disease (CKD). Proximal tubule-specific knockout of METTL3 in mice protected kidneys against developing fibrotic lesions after injury. Conversely, overexpression of METTL3 aggravated kidney fibrosis in vivo. Through bioinformatics analysis and experimental validation, we identified β-catenin mRNA as a major target of METTL3-mediated m6A modification, which could be recognized by a specific m6A reader, the insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3). METTL3 stabilized β-catenin mRNA, increased β-catenin protein and induced its downstream profibrotic genes, whereas either knockdown of IGF2BP3 or inhibiting β-catenin signaling abolished its effects. Collectively, these results indicate that METTL3 promotes kidney fibrosis by stimulating the m6A modification of β-catenin mRNA, leading to its stabilization and its downstream profibrotic genes expression. Our findings suggest that targeting METTL3/IGF2BP3/β-catenin pathway may be a novel strategy for the treatment of fibrotic CKD.

Insights into the role of the N6-methyladenosine reader IGF2BP3 in the progression of oral squamous cell carcinoma and its connection to cell-cycle control

The genome of oral squamous cell carcinoma (OSCC) has been extensively characterized via bulk sequencing, revealing a multitude of genetic changes. The gene IGF2BP3, which encodes for the insulin-like growth factor 2 mRNA-binding protein 3, has been observed to be highly expressed in several types of cancer. This finding suggests that IGF2BP3 may play a significant role in the initiation and advancement of cancer. Nevertheless, the mechanisms by which IGF2BP3 contribute to OSCC are yet to be fully understood. In this study, we have observed that IGF2BP3 exhibits overexpression in OSCC. Based on our findings from bulk sequencing analysis, we have concluded that IGF2BP3 could potentially serve as a biomarker for predicting poor prognosis in OSCC. Moreover, it has been demonstrated that IGF2BP3 exhibits a significant association with the initiation and advancement of tumors both in vivo and in vitro. The evaluation of IGF2BP3 expression levels in relation to the cell cycle stage was conducted using single-cell RNA sequencing data. Tumor cells characterized by elevated IGF2BP3 expression demonstrated a higher percentage of cells in the G2/M transition phase. This study presents new findings indicating that the molecular target IGF2BP3 can serve as a prognostic indicator for tumors and has an impact on the development and progression of OSCC by influencing the regulation of the cell cycle.

IGF2BP3 promotes glutamine metabolism of endometriosis by interacting with UCA1 to enhances the mRNA stability of GLS1

BACKGROUND

Insulin like growth factor II mRNA binding protein 3 (IGF2BP3) has been implicated in numerous inflammatory and cancerous conditions. However, its precise molecular mechanisms in endometriosis (EMs) remains unclear. The aim of this study is to examine the influence of IGF2BP3 on the occurrence and progression of EMs and to elucidate its underlying molecular mechanism.

METHODS

Efects of IGF2BP3 on endometriosis were confrmed in vitro and in vivo. Based on bioinformatics analysis, RNA immunoprecipitation (RIP), RNA pull-down assays and Fluorescent in situ hybridization (FISH) were used to show the association between IGF2BP3 and UCA1. Single-cell spatial transcriptomics analysis shows the expression distribution of glutaminase 1 (GLS1) mRNA in EMs. Study the effect on glutamine metabolism after ectopic endometriotic stromal cells (eESCs) were transfected with Sh-IGF2BP3 and Sh-UCA1 lentivirus.

RESULTS

Immunohistochemical staining have revealed that IGF2BP3 was upregulated in ectopic endometriotic lesions (EC) compared to normal endometrial tissues (EN). The proliferation and migration ability of eESCs were greatly reduced by downregulating IGF2BP3. Additionally, IGF2BP3 has been observed to interact with urothelial carcinoma associated 1 (UCA1), leading to increased stability of GLS1 mRNA and subsequently enhancing glutamine metabolism. Results also demonstrated that IGF2BP3 directly interacts with the 3' UTR region of GLS1 mRNA, influencing its expression and stability. Furthermore, UCA1 was able to bind with c-MYC protein, stabilizing c-MYC mRNA and consequently enhancing GLS1 expression through transcriptional promotion.

CONCLUSION

These discoveries underscored the critical involvement of IGF2BP3 in the elevation and stability of GLS1 mRNA in the context of glutamine metabolism by interacting with UCA1 in EMs. The implications of our study extended to the identification of possible therapeutic targets for individuals with EMs.

Myeloid-derived Wnts play an indispensible role in macrophage and fibroblast activation and kidney fibrosis

Wnt/β-catenin signaling plays a pivotal role in the pathogenesis of chronic kidney diseases (CKD), which is associated with macrophage activation and polarization. However, the relative contribution of macrophage-derived Wnts in the evolution of CKD is poorly understood. Here we demonstrate a critical role of Wnts secreted by macrophages in regulating renal inflammation and fibrosis after various injuries. In mouse model of kidney fibrosis induced by unilateral ureteral obstruction (UUO), macrophages were activated and polarized to M1 and M2 subtypes, which coincided with the activation of Wnt/β-catenin signaling. In vitro, multiple Wnts were induced in primary cultured bone marrow-derived macrophages (BMDMs) after polarization. Conversely, Wnt proteins also stimulated the activation and polarization of BMDMs to M1 and M2 subtype. Blockade of Wnt secretion from macrophages in mice with myeloid-specific ablation of Wntless (Wls), a cargo receptor that is obligatory for Wnt trafficking and secretion, blunted macrophage infiltration and activation and inhibited the expression of inflammatory cytokines. Inhibition of Wnt secretion by macrophages also abolished β-catenin activation in tubular epithelium, repressed myofibroblast activation and reduced kidney fibrosis after either obstructive or ischemic injury. Furthermore, conditioned medium from Wls-deficient BMDMs exhibited less potency to stimulate fibroblast proliferation and activation, compared to the controls. These results underscore an indispensable role of macrophage-derived Wnts in promoting renal inflammation, fibroblasts activation and kidney fibrosis.

Differential expression and clinical significance of IGF2BP3 in peritoneal dialysate of patients with varying duration of peritoneal dialysis

This study aims to investigate the differential expression of insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) in the peritoneal dialysate among patients with different durations of peritoneal dialysis and its association with the angiogenic marker vascular* endothelial growth factor (VEGF), the fibronectin (FN), and various clinical indicators. A cohort of 122 peritoneal dialysis patients was categorized into short-term (≤1 year, n = 33), mid-term (>1 and ≤5 years, n = 55), and long-term (>5 years, n = 34) groups based on dialysis duration. We utilized enzyme-linked immunosorbent assay (ELISA) and western blot assays to quantify the levels of IGF2BP3, VEGF, and FN in the dialysate. Our findings showed a progressive increase in IGF2BP3 levels with the duration of PD, with the long-term group exhibiting significantly higher levels than both the short-term and mid-term groups (p < 0.001). A positive correlation between IGF2BP3 and VEGF (r = 0.386, p = 0.013), as well as between IGF2BP3 and FN (r = 0.340, p = 0.030), was observed. IGF2BP3 levels also correlated positively with serum creatinine, calcium, and phosphorus levels. In vitro analysis further confirmed that IGF2BP3 expression is enhanced in human peritoneal mesothelial cells under high-glucose conditions (p < 0.05). The study highlights the potential of IGF2BP3 in PD effluent as a biomarker for monitoring PF progression, with its expression significantly correlated with the duration of PD (Pearson r = 0.897, p < 0.001). In conclusion, our results underscore a correlation between elevated IGF2BP3 levels and PD duration, suggesting the clinical significance of IGF2BP3 as a biomarker for PF progression.

IGF2BP3-stabilized CAMK1 regulates the mitochondrial dynamics of renal tubule to alleviate diabetic nephropathy

BACKGROUND

CAMK1 has been shown to be involved in human disease progression via regulating mitochondrial dynamics. However, whether CAMK1 mediates mitochondrial dynamics to regulate diabetic nephropathy (DN) process remains unclear.

METHODS

Mice were injected with streptozotocin (STZ) to mimic diabetic mice models in vivo, and mice with proximal tubule-specific knockout of CAMK1 (CAMK1-KO) were generated. HK-2 cells were treated with high-glucose (HG) to mimic DN cell model in vitro. Histopathological analysis was performed to confirm kidney injury in mice. ROS production and apoptosis were assessed by DHE staining and TUNEL staining. Mitochondria morphology was observed and analyzed by electron microscopy. Mitochondrial membrane potential was detected by JC-1 staining, and cell proliferation was measured by EdU assay. The mRNA and protein expression were examined by qRT-PCR, western blot and immunostaining. RNA interaction was confirmed by RIP assay and dual-luciferase reporter assay. The mRNA stability was tested by actinomycin D treatment, and m6A level was examined by MeRIP assay.

RESULTS

CAMK1 was reduced in DN patients and STZ-induced diabetic mice. Conditional deletion of CAMK1 aggravated kidney injury and promoted mitochondrial fission in diabetic mice. CAMK1 overexpression inhibited mitochondrial fission to alleviate HG-induced HK-2 cell apoptosis. IGF2BP3 promoted the stability of CAMK1 mRNA by m6A modification. IGF2BP3 inhibited mitochondrial fission to repress cell apoptosis in vitro and kidney injury in vivo by increasing CAMK1 expression.

CONCLUSION

IGF2BP3-mediated CAMK1 mRNA stability alleviated DN progression by inhibiting mitochondria fission.

Limonin mitigates cisplatin-induced acute kidney injury through metabolic reprogramming

BACKGROUND

Acute kidney injury (AKI) is a known complication of cisplatin administration; currently, there are no effective ways to prevent it. Therefore, it largely limited the use of cisplatin in chemotherapy in the clinic. In this study, we reported that Limonin, a triterpenoid compound extracted from citrus, alleviated cisplatin-induced AKI through metabolic reprogramming in the diseased kidneys.

METHODS

Cisplatin was employed to induce AKI in mice. Three groups were set up: Sham, cisplatin + vehicle, and cisplatin + Limonin. Using UHPLC-TOF/MS, we conducted metabolomics to profile the kidneys' endogenous metabolites and metabolic pathways. A network pharmacological method was performed to identify the targets of Limonin on AKI. The human proximal tubular epithelial cell line (HK-2) was applied for in vitro studies.

RESULTS

Limonin preserved serum creatinine and blood urea nitrogen levels after cisplatin-induced AKI. Employing metabolomics, we identified 33 endogenous differentially expressed metabolites and 7 significantly disturbed metabolic pathways in the diseased kidneys within three groups. After AKI, Limonin significantly reduced linoleic acid and its downstream product, arachidonic acid, thus exerting a protective effect on the kidney. The network pharmacological method identified CYP3A4 as a key target of Limonin in treating AKI, while CYP3A4 also serve as a mediator of arachidonic acid metabolism. In vitro, Limonin markedly reduced the level of arachidonic acid and HK-2 cell apoptosis triggered by cisplatin, mainly related to the targeted inhibition of CYP3A4-mediated arachidonic acid metabolism.

CONCLUSION

Limonin ameliorates cisplatin-induced AKI by inhibiting CYP3A4 activity to regulate arachidonic acid metabolism, ultimately preserving kidney function.

Animal Models of Kidney Disease: Challenges and Perspectives

Kidney disease is highly prevalent and affects approximately 850 million people worldwide. It is also associated with high morbidity and mortality, and current therapies are incurable and often ineffective. Animal models are indispensable for understanding the pathophysiology of various kidney diseases and for preclinically testing novel remedies. In the last two decades, rodents continue to be the most used models for imitating human kidney diseases, largely because of the increasing availability of many unique genetically modified mice. Despite many limitations and pitfalls, animal models play an essential and irreplaceable role in gaining novel insights into the mechanisms, pathologies, and therapeutic targets of kidney disease. In this review, we highlight commonly used animal models of kidney diseases by focusing on experimental AKI, CKD, and diabetic kidney disease. We briefly summarize the pathological characteristics, advantages, and drawbacks of some widely used models. Emerging animal models such as mini pig, salamander, zebrafish, and drosophila, as well as human-derived kidney organoids and kidney-on-a-chip are also discussed. Undoubtedly, careful selection and utilization of appropriate animal models is of vital importance in deciphering the mechanisms underlying nephropathies and evaluating the efficacy of new treatment options. Such studies will provide a solid foundation for future diagnosis, prevention, and treatment of human kidney diseases.

Genetic and pharmacological inhibition of METTL3 alleviates renal fibrosis by reducing EVL m6A modification through an IGF2BP2-dependent mechanism

BACKGROUND

N6 -methyladenosine (m6A) is of great importance in renal physiology and disease progression, but its function and mechanism in renal fibrosis remain to be comprehensively and extensively explored. Hence, this study will explore the function and potential mechanism of critical regulator-mediated m6A modification during renal fibrosis and thereby explore promising anti-renal fibrosis agents.

METHODS

Renal tissues from humans and mice as well as HK-2 cells were used as research subjects. The profiles of m6A modification and regulators in renal fibrosis were analysed at the protein and RNA levels using Western blotting, quantitative real-time polymerase chain reaction and other methods. Methylation RNA immunoprecipitation sequencing and RNA sequencing coupled with methyltransferase-like 3 (METTL3) conditional knockout were used to explore the function of METTL3 and potential targets. Gene silencing and overexpression combined with RNA immunoprecipitation were performed to investigate the underlying mechanism by which METTL3 regulates the Ena/VASP-like (EVL) m6A modification that promotes renal fibrosis. Molecular docking and virtual screening with in vitro and in vivo experiments were applied to screen promising traditional Chinese medicine (TCM) monomers and explore their mechanism of regulating the METTL3/EVL m6A axis and anti-renal fibrosis.

RESULTS

METTL3 and m6A modifications were hyperactivated in both the tubular region of fibrotic kidneys and HK-2 cells. Upregulated METTL3 enhanced the m6A modification of EVL mRNA to improve its stability and expression in an insulin-like growth factor 2 mRNA-binding protein 2 (IGF2BP2)-dependent manner. Highly expressed EVL binding to Smad7 abrogated the Smad7-induced suppression of transforming growth factor-β (TGF-β1)/Smad3 signal transduction, which conversely facilitated renal fibrosis progression. Molecular docking and virtual screening based on the structure of METTL3 identified a TCM monomer named isoforsythiaside, which inhibited METTL3 activity together with the METTL3/EVL m6A axis to exert anti-renal fibrosis effects.

CONCLUSIONS

Collectively, the overactivated METTL3/EVL m6A axis is a potential target for renal fibrosis therapy, and the pharmacological inhibition of METTL3 activity by isoforsythiaside suggests that it is a promising anti-renal fibrosis agent.