Deletion of protein tyrosine phosphatase SHP-1 restores SUMOylation of podocin and reverses the progression of diabetic kidney disease

Targeting the NF-κB p65-MMP28 axis: Wogonoside as a novel therapeutic agent for attenuating podocyte injury in diabetic nephropathy

BACKGROUND

Although recent progress provides mechanistic insights into diabetic nephropathy (DN), effective treatments remain scarce. DN, characterized by proteinuria and a progressive decline in renal function, primarily arises from podocyte injury, which impairs the glomerular filtration barrier. Wogonoside, a bioactive compound from the traditional Chinese herb Scutellaria baicalensis, has not been explored for its role in DN.

PURPOSE

This study aimed to investigate the therapeutic effects of wogonoside on podocyte injury in DN and its molecular mechanisms.

METHODS

The effects of wogonoside were examined using HFD/STZ-induced DN mouse models and high glucose (HG)-induced MPC-5 cells. Oxidative stress and inflammation markers were analyzed via Western blot and RT-qPCR. Wogonoside targets were identified through DARTS-MS and validated by SPR, molecular docking, alanine scanning, and CETSA. RNA-Seq analysis was employed to identify downstream targets, and the p65-MMP28 axis was explored through p65 knockdown and overexpression studies. The regulatory effect of p65 on Mmp28 was confirmed through dual-luciferase reporter assays and ChIP-qPCR.

RESULTS

Wogonoside treatment significantly reduced oxidative stress and inflammation in vivo and in vitro. Mechanistic studies identified p65 as a direct target of wogonoside, with SPR confirming a strong binding affinity (KD = 25.05 μM). Molecular docking and alanine scanning identified LYS221 as a critical binding site, which was further supported by CETSA using the p65 K221A mutant. RNA-Seq analysis revealed Mmp28 as a downstream effector of p65 involved in HG-induced podocyte injury. Functional studies demonstrated that wogonoside's protective effects on antioxidant and inflammatory pathways are mediated via the p65-MMP28 axis. Dual-luciferase reporter assays revealed that p65 regulates Mmp28 transcription, and ChIP-qPCR confirmed its direct promoter binding.

CONCLUSIONS

This study highlights wogonoside as a promising candidate for the treatment of podocyte injury in DN by targeting the NF-κB p65-MMP28 signaling axis. These findings provide novel insights into wogonoside's therapeutic potential and its molecular mechanisms, paving the way for its further development as a DN intervention.

HNF-1β alleviates podocyte injury in lupus nephritis by maintaining endoplasmic reticulum homeostasis

OBJECTIVE

The current study aims to elucidate the critical function of hepatocyte nuclear factor 1-beta (HNF1-β) in lupus nephritis (LN) by investigating its modulation of the Derlin-1/valosin-containing protein (VCP)/VCP-interacting membrane selenoprotein (VIMP) complex, endoplasmic reticulum (ER) stress and podocyte apoptosis.

METHODS

In vitro and in vivo models of LN were established using glomerular podocytes treated with LN serum and MRL/lpr mice, respectively. The expression levels of HNF1-β were analysed in kidney tissues from patients with LN and MRL/lpr mice. To assess the effects of HNF1-β inhibition, an adeno-associated virus vector carrying HNF1-β short hairpin was administered to MRL/lpr mice. In vitro, glomerular podocytes were transfected with HNF1-β small interfering RNA (siRNA) or HNF1-β overexpression plasmids to explore their regulatory effects on the Derlin-1/VCP/VIMP complex and podocyte apoptosis. Dual-luciferase reporter assays and chromatin immunoprecipitation (ChIP) assays were performed to investigate the transcriptional activation of Derlin-1 and VCP promoters by HNF1-β.

RESULTS

A significant decrease in HNF1-β levels was observed in kidney tissues from patients with LN while MRL/lpr mice exhibited an initial compensatory increase followed by a subsequent decrease in renal HNF1-β expression. Overexpression of HNF1-β transcriptionally upregulated Derlin-1 and VCP mitigating LN serum-induced ER stress and podocyte apoptosis. In contrast, HNF1-β inhibition exacerbated renal dysfunction and structural damage in MRL/lpr mice. Interestingly, HNF1-β inhibition transcriptionally repressed ERP44, leading to calcium ions (Ca²+) release-mediated disruption and inactivation of the Derlin-1/VCP/VIMP complex. This finding suggests that HNF1-β not only regulates the expression of key proteins in the Derlin-1/VCP/VIMP complex but also influences their assembly through Ca²+ release regulation.

CONCLUSION

This study provides novel insights into the regulatory mechanisms of HNF1-β in LN emphasising its impact on the Derlin-1/VCP/VIMP complex, ER stress and podocyte apoptosis. These findings have the potential to inform the development of new diagnostic tools and therapeutic strategies for LN.

Exploring potential targets for natural product therapy of DN: the role of SUMOylation

Diabetic nephropathy (DN) is a common and serious micro-vascular complication of diabetes and a leading cause of end-stage renal disease globally. This disease primarily affects middle-aged and elderly individuals, especially those with a diabetes history of over 10 years and poor long-term blood glucose control. Small ubiquitin-related modifiers (SUMOs) are a group of reversible post-translational modifications of proteins that are widely expressed in eukaryotes. SUMO proteins intervene in the progression of DN by modulating various signaling cascades, such as Nrf2-mediated oxidative stress, NF-κB, TGF-β, and MAPK pathways. Recent advancements indicate that natural products regulating SUMOylation hold promise as targets for intervening in DN. In a previous article published in 2022, we reviewed the mechanisms by which SUMOylation intervenes in renal fibrosis and presented a summary of some natural products with therapeutic potential. Therefore, this paper will focus on DN. The aim of this review is to elucidate the mechanism of action of SUMOylation in DN and related natural products with therapeutic potential, thereby summarising the targets and candidate natural products for the treatment of DN through the modulation of SUMOylation, such as ginkgolic acid, ginkgolide B, resveratrol, astragaloside IV, etc., and highlighting that natural product-mediated modulation of SUMOylation is a potential therapeutic strategy for the treatment of DN as a potential therapeutic strategy.

Upregulation of Metrnl improves diabetic kidney disease by inhibiting the TGF-β1/Smads signaling pathway: A potential therapeutic target

PURPOSE

This study comprises an investigation of the role of meteorin-like (Metrnl) in an experimental model of diabetic kidney disease (DKD).

METHODS

Twenty-four db/db mice were randomly assigned to one of the following groups: DKD, DKD + Metrnl-/-, and DKD + Metrnl+/+. Plasma Metrnl concentrations were measured using ELISA. Kidney tissues were examined via western blotting, qRT-PCR, and immunohistochemistry to determine the expression levels of inflammatory factors. Electron microscopy was employed to observe stained kidney sections.

RESULTS

Compared with the NC group, FBG, BW, and UACR were elevated in the DKD and Metrnl-/- groups, with severe renal pathological injury, decreased serum Metrnl concentration, decreased renal Metrnl expression, and increased expression levels of TNF-α, TGF-β1, TGF-R1, pSmad2, pSmad3, and α-SMA. In contrast, the Metrnl+/+ group showed decreased FBG and UACR, BUN, TC and TG, increased HDL-C and serum Metrnl concentration, increased renal Metrnl expression, and decreased expression of TNF-α, TGF-β1, TGF-R1, pSmad2, pSmad3, and α-SMA, compared to the DKD and Metrnl-/- groups. A Pearson bivariate correlation analysis revealed a negative correlation between UACR and Metrnl, and a positive correlation between UACR and TGF-β1.

CONCLUSION

Upregulation of renal Metrnl expression can improve renal injury by downregulating the expression of molecules in the TGF-β1/Smads signaling pathway in the renal tissues of type 2 diabetic mice; and by reducing the production of fibrotic molecules such as α-SMA.

Schisandrin A Attenuates Diabetic Nephropathy via EGFR/AKT/GSK3β Signaling Pathway Based on Network Pharmacology and Experimental Validation

Diabetic nephropathy (DN) is one of the common complications of diabetes and the main cause of end-stage renal disease (ESRD) in clinical practice. Schisandrin A (Sch A) has multiple pharmacological activities, including inhibiting fibrosis, reducing apoptosis and oxidative stress, and regulating immunity, but its pharmacological mechanism for the treatment of DN is still unclear. In vivo, streptozotocin (STZ) and a high-fat diet were used to induce type 2 diabetic rats, and Sch A was administered for 4 weeks. At the same time, protein-protein interaction (PPI) networks were established to analyze the overlapping genes of DN and Sch A. Subsequently, the Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) analyses were performed to determine the hub pathway. In addition, molecular docking was used to preliminarily verify the affinity of hub proteins and Sch A. Further, H&E staining, Sirius red staining, immunohistochemistry, immunofluorescence, and western blot analysis were used to detect the location and expression of related proteins in DN. This study revealed the multi-target and multi-pathway characteristics of Sch A in the treatment of DN. First, Sch A could effectively improve glucose tolerance, reduce urine microprotein and urine creatinine levels, and alleviate renal pathological damage in DN rats. Second, EGFR was the hub gene screened in overlapping genes (43) of Sch A (100) and DN (2524). Finally, it was revealed that Sch A could inhibit the protein expression levels of EGFR and PTRF and reduced the expression of apoptosis-related proteins, and this effect was related to the modulation of the AKT/GSK-3β signaling pathway. In summary, Sch A has a protective effect in DN rats, EGFR may be a potential therapeutic target, throughout modulating AKT/GSK-3β pathway.

Cuproptosis associated cytoskeletal destruction contributes to podocyte injury in chronic kidney disease

The podocyte cytoskeleton determines the stability of podocyte structure and function, and their imbalance plays a pathogenic role in podocyte diseases. However, the underlying mechanism of podocyte cytoskeleton damage is not fully understood. Here, we investigate the specific role of cuproptosis in inducing podocyte cytoskeleton injury. In in vitro and in vivo studies, exposure to high levels of copper and adriamycin (ADR) caused significant increases in copper concentration in intracellular and renal tissue. Moreover, excessive accumulation of copper induced cuproptosis, resulting in the destruction of the podocyte cytoskeleton. However, inhibition of copper accumulation to reduce cuproptosis also significantly alleviated the damage of podocyte cytoskeleton. In addition, inhibition of cuproptosis mitigated ADR-induced mitochondrial damage as well as the production of reactive oxygen species and depolarization of mitochondrial membrane potential, and restored adenosine triphosphate (ATP) synthesis. Among the transcriptome sequencing data, the difference of CXCL5 (C-X-C motif chemokine ligand 5) was the most significant. Both high copper and ADR exposure can cause upregulation of CXCL5, and CXCL5 deletion inhibits the occurrence of cuproptosis, thereby alleviating the podocyte cytoskeleton damage. This suggests that CXCL5 may act upstream of cuproptosis that mediates podocyte cytoskeleton damage. In conclusion, cuproptosis induced by excessive copper accumulation may induce podocyte cytoskeleton damage by promoting mitochondrial dysfunction, thereby causing podocyte injury. This indicates that cuproptosis plays an important role in the pathogenesis of podocyte injury and provides a basis for seeking potential targets for the treatment of chronic kidney disease.NEW & NOTEWORTHY Cuproptosis induced by excessive copper accumulation leads to podocyte cytoskeleton damage by promoting mitochondrial dysfunction, and CXCL5 acts as an upstream signal mediating the occurrence of cuproptosis.

Cytoskeleton Rearrangement in Podocytopathies: An Update

Podocyte injury can disrupt the glomerular filtration barrier (GFB), leading to podocytopathies that emphasize podocytes as the glomerulus's key organizer. The coordinated cytoskeleton is essential for supporting the elegant structure and complete functions of podocytes. Therefore, cytoskeleton rearrangement is closely related to the pathogenesis of podocytopathies. In podocytopathies, the rearrangement of the cytoskeleton refers to significant alterations in a string of slit diaphragm (SD) and focal adhesion proteins such as the signaling node nephrin, calcium influx via transient receptor potential channel 6 (TRPC6), and regulation of the Rho family, eventually leading to the disorganization of the original cytoskeletal architecture. Thus, it is imperative to focus on these proteins and signaling pathways to probe the cytoskeleton rearrangement in podocytopathies. In this review, we describe podocytopathies and the podocyte cytoskeleton, then discuss the molecular mechanisms involved in cytoskeleton rearrangement in podocytopathies and summarize the effects of currently existing drugs on regulating the podocyte cytoskeleton.