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

Dietary limonin ameliorates heart failure with preserved ejection fraction by targeting ferroptosis via modulation of the Nrf2/SLC7A11/GPX4 axis: an integrated transcriptomics and metabolomics analysis

Heart failure with preserved ejection fraction (HFpEF) is a complex syndrome characterized by hypertension, metabolic disorders, and impaired diastolic function, with limited therapeutic options. Recent studies have highlighted the role of ferroptosis in the pathogenesis of HFpEF, and the inhibition of ferroptosis occurrence can significantly improve cardiac function. Limonin, a bioactive ingredient derived from citrus fruits, has been confirmed to exert potential anti-inflammatory and antioxidant effects in some cardiovascular diseases. This study aims to investigate the therapeutic effects of limonin on HFpEF and the underlying mechanisms of inhibiting ferroptosis. HFpEF mice were established by a combination of Nω-nitro-L-arginine methyl ester and a high-fat diet for 6 weeks. Subsequently, the HFpEF mice were treated with empagliflozin or limonin via oral gavage for an additional 6 weeks. Limonin curbed body weight gain and improved metabolic disorders and hypertension. Limonin also ameliorated concentric cardiac hypertrophy and diastolic dysfunction. Transcriptomics and metabolomics analyses revealed that limonin regulated ferroptosis-related pathways and lipid peroxidation. In vivo, limonin improved mitochondrial morphology, reduced cardiac Fe2+ levels and ferroptosis markers such as ROS, 4-HNE and MDA, and increased GSH levels, thereby enhancing antioxidant capacity. Mechanistically, limonin regulated the P53/SLC7A11/GPX4 signaling pathway, promoted the nuclear translocation of Nrf2 (its upstream signaling molecule), and subsequently activated its downstream antioxidant elements, ultimately inhibiting ferroptosis. Furthermore, limonin decreased the expressions of ACSL4, COX2, and ALOXs, which reduced the accumulation of lipid peroxides. These results demonstrate that limonin ameliorates HFpEF by targeting ferroptosis via modulation of the Nrf2/SLC7A11/GPX4 axis, providing a novel strategy for HFpEF treatment.

Insights into the effects of apelin-13 on renal function and NHE3 activity following ischemia/reperfusion-induced acute kidney injury

Introduction

Acute kidney injury (AKI) is a clinical syndrome characterized by rapid decline in renal function with varying severity. In this context, tubular function is impaired in ischemia-induced AKI. Although there are no effective therapies for AKI, many compounds have been reported to reduce kidney injury, such as apelin-13. Considering the relevance of proximal tubular cells in maintaining fluid and electrolyte homeostasis, the effects of apelin-13 on tubular injury or sodium proximal transport remain unclear. Thus, the present study aims to evaluate the effects of exogenous administration of apelin-13 in the renal ischemia/reperfusion (I/R) model, with particular focus on renal function, injury markers, and tubular proliferation.

Methods

Male C57BL/6 mice were initially treated with a vehicle or high dose of apelin-13 (200 μg/kg/day) and subjected to kidney bilateral ischemia procedure for 30 min or a sham surgery. The mice were euthanized by exsanguination 2 d after the ischemic procedure. Then, the renal function was assessed through the plasma urea level and creatinine clearance. Tubular injury was evaluated by hematoxylin and eosin staining. Kidney injury molecule 1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL), megalin, Ki67, and phospho ERK 1/2 (Thr202/Tyr204) were evaluated through immunohistochemical or immunoblotting experiments. Moreover, the murine proximal tubular cells (TKPTS) were treated with apelin-13 (100 nM) to evaluate the activity of the Na+/H+ exchanger isoform 3 (NHE3) via intracellular pH measurements.

Results

Initial administration of apelin-13 did not improve tubular injury, creatinine clearance, or plasma urea level after renal I/R. Moreover, KIM-1 and NGAL markers were markedly increased after renal I/R and were not reduced in the apelin-13 + I/R group. Furthermore, megalin downregulation by renal I/R was not prevented by apelin-13. Interestingly, apelin-13 worsened the renal responses to tubular proliferation after renal I/R as Ki67 and phosphorylation of ERK/1/2 (Thr202/Tyr204) were sharply reduced in the apelin-13 + I/R group. In vitro experiments also demonstrated that apelin-13 inhibited NHE3 activity in murine proximal tubular cells.

Conclusion

The overall findings suggest that apelin-13 suppresses tubular proliferation and potentially impairs the adaptive response to renal I/R injury, thereby highlighting its relevance in ischemia-induced AKI.

Autophagy Dysfunction: The Kernel of Hair Loss?

Autophagy is recognized as a crucial regulatory process, instrumental in the removal of senescent, dysfunctional, and damaged cells. Within the autophagic process, lysosomal digestion plays a critical role in the elimination of impaired organelles, thus preserving fundamental cellular metabolic functions and various biological processes. Mitophagy, a targeted autophagic process that specifically focuses on mitochondria, is essential for sustaining cellular health and energy balance. Therefore, a deep comprehension of the operational mechanisms and implications of autophagy and mitophagy is vital for disease prevention and treatment. In this context, we examine the role of autophagy and mitophagy during hair follicle cycles, closely scrutinizing their potential association with hair loss. We also conduct a thorough review of the regulatory mechanisms behind autophagy and mitophagy, highlighting their interaction with hair follicle stem cells and dermal papilla cells. In conclusion, we investigate the potential of manipulating autophagy and mitophagy pathways to develop innovative therapeutic strategies for hair loss.

Insights into the Mechanism of Action of the Degraded Limonoid Prieurianin

Limonoids are extremely diversified in plants, with many categories of products bearing an intact, rearranged or fragmented oxygenated scaffold. A specific subgroup of fragmented or degraded limonoids derives from the tetranortriterpenoid prieurianin, initially isolated from the tree Trichilia prieuriana but also found in other plants of the Meliaceae family, including the more abundant species Aphanamixis polystachya. Prieurianin-type limonoids include about seventy compounds, among which are dregeanin and rohitukin. Prieurianin and analogs exhibit insecticidal, antimicrobial, antiadipogenic and/or antiparasitic properties but their mechanism of action remains ill-defined at present. Previous studies have shown that prieurianin, initially known as endosidin 1, stabilizes the actin cytoskeleton in plant and mammalian cells via the modulation of the architecture and dynamic of the actin network, most likely via interference with actin-binding proteins. A new mechanistic hypothesis is advanced here based on the recent discovery of the targeting of the chaperone protein Hsp47 by the fragmented limonoid fraxinellone. Molecular modeling suggested that prieurianin and, to a lesser extent dregeanin, can form very stable complexes with Hsp47 at the protein-collagen interface. Hsp-binding may account for the insecticidal action of the product. The present review draws up a new mechanistic portrait of prieurianin and provides an overview of the pharmacological properties of this atypical limonoid and its chemical family.

Limonin ameliorates cisplatin-induced acute liver injury by inhibiting 11β-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, 11β-hydroxysteroid dehydrogenase type 1 (11β-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 11β-HSD1 to protect against cisplatin-induced ALI.

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.