m6A RNA methylation drives kidney fibrosis by upregulating ß-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 ß-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 ß-catenin mRNA, increased ß-catenin protein and induced its downstream profibrotic genes, whereas either knockdown of IGF2BP3 or inhibiting ß-catenin signaling abolished its effects. Collectively, these results indicate that METTL3 promotes kidney fibrosis by stimulating the m6A modification of ß-catenin mRNA, leading to its stabilization and its downstream profibrotic genes expression. Our findings suggest that targeting METTL3/IGF2BP3/ß-catenin pathway may be a novel strategy for the treatment of fibrotic CKD.

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.

Limonin, a natural ERK2 agonist, protects against ischemic acute kidney injury.

Acute kidney injury (AKI) is a refractory clinical syndrome with limited effective treatments. Amid AKI, activation of the extracellular signal-regulated kinase (ERK) cascade plays a critical role in promoting kidney repair and regeneration. However, a mature ERK agonist in treating kidney disease remains lacking. This study identified limonin, a member of the class of compounds known as furanolactones, as a natural ERK2 activator. Employing a multidisciplinary approach, we systemically dissected how limonin mitigates AKI. Compared to vehicles, pretreatment of limonin significantly preserved kidney functions after ischemic AKI. We revealed that ERK2 is a significant protein linked to the limonin's active binding sites through structural analysis. The molecular docking study showed a high binding affinity between limonin and ERK2, which was confirmed by the cellular thermal shift assay and microscale thermophoresis. Mechanistically, we further validated that limonin promoted tubular cell proliferation and reduced cell apoptosis after AKI by activating ERK signaling pathway in vivo. In vitro and ex vivo, blockade of ERK abolished limonin's capacity of preventing tubular cell death under hypoxia stress. Our results indicated that limonin is a novel ERK2 activator with strong translational potential in preventing or mitigating AKI.

Limonin ameliorates cisplatin-induced acute liver injury by inhibiting 11ß-hydroxysteroid dehydrogenase type 1.

BACKGROUND: Acute liver injury (ALI) is a common side effect of cisplatin treatment in the clinic and can lead to liver failure if not treated promptly. Previous studies have revealed that Limonin, a critical bioactive substance in citrus fruits, can protect multiple organs from various medical conditions. However, whether Limonin could ameliorate cisplatin-induced ALI remains unclear. METHODS: In vivo and in vitro models were induced by cisplatin in the present study. Non-targeted metabolomics was employed to analyze the metabolic changes in the liver after ALI. In addition, molecular docking was utilized to predict the potential targets of Limonin. RESULTS: Limonin attenuated hepatic histopathological injury by reducing hepatocyte apoptosis, lipid peroxidation, and inflammation in cisplatin-challenged mice. Employing metabolomics, we revealed that Limonin mediated the balance of various disturbed metabolic pathways in the liver after cisplatin-induced ALI. Integrating public data mining, molecular docking studies, and in vitro experiments demonstrated that Limonin suppressed the expression and activity of its direct target, 11ß-hydroxysteroid dehydrogenase type 1 (11ß-HSD1), in the liver, thus reducing the production of corticosterone (CORT), a key metabolite promoted hepatocyte apoptosis. CONCLUSIONS: Limonin improves the liver metabolic microenvironment by inhibiting 11ß-HSD1 to protect against cisplatin-induced ALI.