The KCa3.1 blocker TRAM34 reverses renal damage in a mouse model of established diabetic nephropathy

A new perspective on proteinuria and drug therapy for diabetic kidney disease

Diabetic kidney disease (DKD) is one of the leading causes of end-stage renal disease worldwide and significantly increases the risk of premature death due to cardiovascular diseases. Elevated urinary albumin levels are an important clinical feature of DKD. Effective control of albuminuria not only delays glomerular filtration rate decline but also markedly reduces cardiovascular disease risk and all-cause mortality. New drugs for treating DKD proteinuria, including sodium-glucose cotransporter two inhibitors, mineralocorticoid receptor antagonists, and endothelin receptor antagonists, have shown significant efficacy. Auxiliary treatment with proprietary Chinese medicine has also yielded promising results; however, it also faces a broader scope for development. The mechanisms by which these drugs treat albuminuria in patients with DKD should be described more thoroughly. The positive effects of combination therapy with two or more drugs in reducing albuminuria and protecting the kidneys warrant further investigation. Therefore, this review explores the pathophysiological mechanism of albuminuria in patients with DKD, the value of clinical diagnosis and prognosis, new progress and mechanisms of treatment, and multidrug therapy in patients who have type 2 diabetic kidney disease, providing a new perspective on the clinical diagnosis and treatment of DKD.

The key mediator of diabetic kidney disease: Potassium channel dysfunction

Diabetic kidney disease is a leading cause of end-stage renal disease, making it a global public health concern. The molecular mechanisms underlying diabetic kidney disease have not been elucidated due to its complex pathogenesis. Thus, exploring these mechanisms from new perspectives is the current focus of research concerning diabetic kidney disease. Ion channels are important proteins that maintain the physiological functions of cells and organs. Among ion channels, potassium channels stand out, because they are the most common and important channels on eukaryotic cell surfaces and function as the basis for cell excitability. Certain potassium channel abnormalities have been found to be closely related to diabetic kidney disease progression and genetic susceptibility, such as KATP, KCa, Kir, and KV. In this review, we summarized the roles of different types of potassium channels in the occurrence and development of diabetic kidney disease to discuss whether the development of DKD is due to potassium channel dysfunction and present new ideas for the treatment of DKD.

Effect of fullerenol C60 on lung and renal tissue in lower extremity ischemia‑reperfusion injury in sevoflurane‑treated rats

The aim of the present study was to examine the effect of fullerenol C60 on lung and kidney tissue in sevoflurane‑treated rats with lower extremity ischemia‑reperfusion (IR) injury. A total of 30 Wistar albino rats weighing 225‑275 g were used and were equally divided into five groups (n=6/group): i) Sham; ii) IR; iii) IR‑fullerenol C60 (IR‑FUL); iv) IR‑sevoflurane; and v) IR‑fullerenol C60‑sevoflurane (IR‑FUL‑SEVO). Fullerenol C60 was administered intraperitoneally prior to lower extremity IR induction and sevoflurane was administered during the IR injury. Subsequently, lung and kidney histopathological examinations, and serum biochemical analyses were performed. Lung tissue showed markedly increased congestion and neutrophil infiltration in the IR group compared with in the sham group, and notable decreases in congestion and neutrophil infiltration were observed in the treatment groups compared with in the IR group. In the histopathological evaluation of the kidney samples, vacuolization, loss of brush border in tubular epithelial cells, tubular epithelial loss and varying degrees of tubular damage were observed in all groups that underwent IR. There was a significant increase in the mean renal tubule injury score in all IR groups compared with that in the sham group. In addition, the mean kidney injury score was significantly lower in the IR‑FUL and IR‑FUL‑SEVO groups than that in the IR group. It was observed that the expression levels of tumor necrosis factor‑α, interleukin 1β and intercellular adhesion molecule 1 in the lung and kidney tissues were increased following IR, and were decreased in the groups treated with fullerenol C60 and sevoflurane. Notably, it was determined that the reduction in cytokine expression was greatest in the IR‑FUL group. When the oxidant status parameters in the lungs and kidneys were examined, thiobarbituric acid reactive substances levels, and catalase and glutathione S‑transferase enzyme activities were significantly different in the groups receiving sevoflurane or fullerenol C60 treatment compared with those in the IR group. The present study demonstrated the protective effects of fullerenol C60 on the lung and kidney tissues of rats under sevoflurane anesthesia after establishment of lower extremity IR. The results of the present study showed that fullerenol C60 can reduce oxidative and histopathological damage in the lungs and kidneys following IR of the lower extremities.

Optimizing diabetic kidney disease animal models: Insights from a meta-analytic approach

Diabetic kidney disease (DKD) is a prevalent complication of diabetes, often leading to end-stage renal disease. Animal models have been widely used to study the pathogenesis of DKD and evaluate potential therapies. However, current animal models often fail to fully capture the pathological characteristics of renal injury observed in clinical patients with DKD. Additionally, modeling DKD is often a time-consuming, costly, and labor-intensive process. The current review aims to summarize modeling strategies in the establishment of DKD animal models by utilizing meta-analysis related methods and to aid in the optimization of these models for future research. A total of 1215 articles were retrieved with the keywords of "diabetic kidney disease" and "animal experiment" in the past 10 years. Following screening, 84 articles were selected for inclusion in the meta-analysis. Review manager 5.4.1 was employed to analyze the changes in blood glucose, glycosylated hemoglobin, total cholesterol, triglyceride, serum creatinine, blood urea nitrogen, and urinary albumin excretion rate in each model. Renal lesions shown in different models that were not suitable to be included in the meta-analysis were also extensively discussed. The above analysis suggested that combining various stimuli or introducing additional renal injuries to current models would be a promising avenue to overcome existing challenges and limitations. In conclusion, our review article provides an in-depth analysis of the limitations in current DKD animal models and proposes strategies for improving the accuracy and reliability of these models that will inspire future research efforts in the DKD research field.

Role of Calcium-Activated Potassium Channels in Proliferation, Migration and Invasion of Human Chronic Myeloid Leukemia K562 Cells

Calcium-activated potassium channels (KCa) are important participants in calcium signaling pathways due to their ability to be activated by an increase in intracellular free calcium concentration. KCa channels are involved in the regulation of cellular processes in both normal and pathophysiological conditions, including oncotransformation. Previously, using patch-clamp, we registered the KCa currents in the plasma membrane of human chronic myeloid leukemia K562 cells, whose activity was controlled by local Ca²⁺ entry via mechanosensitive calcium-permeable channels. Here, we performed the molecular and functional identification of KCa channels and have uncovered their role in the proliferation, migration and invasion of K562 cells. Using a combined approach, we identified the functional activity of SK2, SK3 and IK channels in the plasma membrane of the cells. Selective SK and IK channel inhibitors, apamin and TRAM-34, respectively, reduced the proliferative, migratory and invasive capabilities of human myeloid leukemia cells. At the same time, the viability of K562 cells was not affected by KCa channel inhibitors. Ca²⁺ imaging showed that both SK and IK channel inhibitors affect Ca²⁺ entry and this could underlie the observed suppression of pathophysiological reactions of K562 cells. Our data imply that SK/IK channel inhibitors could be used to slow down the proliferation and spreading of chronic myeloid leukemia K562 cells that express functionally active KCa channels in the plasma membrane.

Role of ion channels in the mechanism of proteinuria (Review)

Proteinuria is a common clinical manifestation of kidney diseases, such as glomerulonephritis, nephrotic syndrome, immunoglobulin A nephropathy and diabetic nephropathy. Therefore, proteinuria is considered to be a risk factor for renal dysfunction. Furthermore, proteinuria is also significantly associated with the progression of kidney diseases and increased mortality. Its occurrence is closely associated with damage to the structure of the glomerular filtration membrane. An impaired glomerular filtration membrane can affect the selective filtration function of the kidneys; therefore, several macromolecular substances, such as proteins, may pass through the filtration membrane and promote the manifestation of proteinuria. It has been reported that ion channels play a significant role in the mechanisms underlying proteinuria. Ion channel mutations or other dysfunctions have been implicated in several diseases, therefore ion channels could be used as major therapeutic targets. The mechanisms underlying the action of ion channels and ion transporters in proteinuria have been overlooked in the literature, despite their importance in identifying novel targets for treating proteinuria and delaying the progression of kidney diseases. The current review article focused on the four key ion channel groups, namely Na⁺, Ca²⁺, Cl^- and K⁺ ion channels and the associated ion transporters.

Identification of the molecular mechanism and candidate markers for diabetic nephropathy

Background

Diabetic nephropathy (DN) is one of the most common complications in diabetic patients. New strategies are needed to delay the occurrence and development of this pathology.

Methods

Differentially expressed genes (DEGs) in glomeruli and renal tubules were identified using the GSE30122 dataset, and a co-expression network was constructed to identify the hub genes of modules. The biological function and signaling pathway of the module genes were also analyzed. In addition, the expression of 24 immune cells and the area under the receiver operating characteristic (ROC) curve (AUC) values of the hub genes were also calculated.

Results

A total of 1,778 DEGs were isolated from glomeruli and 1,996 DEGs were isolated from renal tubules. Nine modules and their hub genes were identified using the co-expression network. Enrichment analysis showed that the module genes were mainly enriched in immune inflammation and oxidative stress. The expressions of B cells, activated dendritic cell, and T cells in the glomeruli and renal tubules of DN patients were higher than those in the controls, and the correlation between these immune cells was the strongest. Collagen type I alpha 2 chain (COL1A2), the hub gene of the brown module, had the highest AUC values and may have a better clinical diagnostic ability.

Conclusions

In conclusion, the module genes and related biological functions and signaling pathways found in this study can deepen our understanding of the molecular mechanism of DN progression. COL1A2 may be a potential biomarker for DN.

Efficacy of epalrestat combined with alprostadil for diabetic nephropathy and its impacts on renal fibrosis and related factors of inflammation and oxidative stress

OBJECTIVE

To explore the efficacy of epalrestat (Ep) combined with alprostadil (Alp) in the treatment of diabetic nephropathy (DN) and its impacts on renal fibrosis (RF) and inflammation and oxidative stress (OS)-related factors.

METHODS

In this retrospective study, 120 patients with DN treated in the Cangzhou Central Hospital from January 2020 to January 2021 were selected as the research subjects. Among them, 80 cases treated with Ep combined with Alp were assigned to group A, and the rest 40 patients treated with Alp only were assigned to group B. The two groups were compared with respect to the following items: serum OS indexes (malondialdehyde, MDA; superoxide dismutase, SOD; total antioxidant capacity, TAOC), inflammatory factors (tumor necrosis factor-α, TNF-α; interleukin-2, IL-2), RF index transforming growth factor-β1 (TGF-β1), urinary protein indexes (urinary albumin excretion, UAE; serum albumin, ALB), blood glucose (fasting blood glucose, FBG), fasting C-peptide, postprandial 2hC peptide levels, overall response rate (ORR) and incidence of adverse reactions.

RESULTS

Compared with group B, the levels of MDA, TNF-α, IL-2 and TGF-β1 were lower, while SOD and TAOC were higher in group A. In addition, ALB was higher, while UAE and FBG were lower in group A as compared with group B. Moreover, group A had a higher ORR and fewer adverse reactions as compared with group B.

CONCLUSION

The combined therapy of Ep and Alp is more effective in the treatment of DN. This combination can effectively reduce RF and better alleviate inflammation and OS.

KCa3.1 in diabetic kidney disease

PURPOSE OF REVIEW

Diabetic kidney disease (DKD) is a significant health concern. Innovative strategies to prevent or limit the progression of DKD are urgently needed due to the limitation of existing treatments. KCa3.1, a potassium channel, is involved in a range of biological processes from cell survival to cell death. This review summarizes the current knowledge on the pathophysiological functions of the KCa3.1 channel, specifically its involvement in maintaining mitochondrial function. More specifically, the therapeutic potential of targeting KCa3.1 in DKD is systematically discussed in the review.

RECENT FINDINGS

Mitochondrial dysfunction contributes to the development and progression of DKD. Accumulating evidence indicates that KCa3.1 dysregulation plays a crucial role in mitochondrial dysfunction, in addition to driving cellular activation, proliferation and inflammation. Recent studies demonstrate that KCa3.1 deficiency improves diabetes-induced mitochondrial dysfunction in DKD, which is attributed to modulation of mitochondrial quality control through mitigating the altered mitochondrial dynamics and restoring abnormal BNIP3-mediated mitophagy.

SUMMARY

Based on its role in fibrosis, inflammation and mitochondrial dysfunction, pharmacological inhibition of KCa3.1 may offer a promising alternative for the treatment of DKD. Due to its safety profile in humans, the repurposing of senicapoc has the potential to expedite an urgently needed new drug in DKD.

Animal models of diabetes-associated vascular diseases: an update on available models and experimental analysis

Diabetes is a chronic metabolic disorder associated with the accelerated development of macrovascular (atherosclerosis and coronary artery disease) and microvascular complications (nephropathy, retinopathy and neuropathy), which remain the principal cause of mortality and morbidity in this population. Current understanding of cellular and molecular pathways of diabetes-driven vascular complications, as well as therapeutic interventions has arisen from studying disease pathogenesis in animal models. Diabetes-associated vascular complications are multi-faceted, involving the interaction between various cellular and molecular pathways. Thus, the choice of an appropriate animal model to study vascular pathogenesis is important in our quest to identify innovative and mechanism-based targeted therapies to reduce the burden of diabetic complications. Herein, we provide up-to-date information on available mouse models of both Type 1 and Type 2 diabetic vascular complications as well as experimental analysis and research outputs.

Crocin Improves Endothelial Mitochondrial Dysfunction via GPx1/ROS/KCa3.1 Signal Axis in Diabetes

Mitochondrial dysfunction contributes to excessive reactive oxygen species (ROS) generation, which is a dramatic cause to promote endothelial dysfunction in diabetes. It was previously demonstrated that crocin protected the endothelium based on its diverse medicinal properties, but its effect on the mitochondrion and the potential mechanism are not fully understood. In this study, mitochondrial function was analyzed during the process of excessive ROS generation in high glucose (HG)-cultured human umbilical vein endothelial cells (HUVECs). The role played by KCa3.1 was further investigated by the inhibition and/or gene silence of KCa3.1 in this process. In addition, nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase 2 (NOX2), superoxide dismutase 1 (SOD1), and glutathione peroxidase 1 (GPx1) were also detected in this study. Our data showed that crocin improved mitochondrial dysfunction and maintained normal mitochondrial morphology by enhancing the mitochondrial membrane potential (MMP), mitochondrial mass, and mitochondrial fusion. Furthermore, KCa3.1 was confirmed to be located in the mitochondrion, and the blockade and/or silencing of KCa3.1 improved mitochondrial dysfunction and reduced excessive ROS generation but did not affect NOX2 and/or the SOD1 system. Intriguingly, it was confirmed that KCa3.1 expression was elevated by ROS overproduction in the endothelium under HG and/or diabetes conditions, while crocin significantly suppressed this elevation by promoting GPx1 and subsequently eliminating ROS generation. In addition, crocin enhanced CD31, thrombomodulin (TM), and p-/t-endothelial nitric oxide synthase (eNOS) expressions as well as NO generation and decreased vascular tone. Hence, crocin improved mitochondrial dysfunction through inhibiting ROS-induced KCa3.1 overexpression in the endothelium, which in turn reduced more ROS generation and final endothelial dysfunction in diabetes.

Targeted knockdown of Kv1.3 channels in T lymphocytes corrects the disease manifestations associated with systemic lupus erythematosus

Lupus nephritis (LN) is an autoimmune disease with substantial morbidity/mortality and limited efficacy of available therapies. Memory T (Tm) lymphocytes infiltrate LN kidneys, contributing to organ damage. Analysis of LN, diabetic nephropathy, and healthy donor kidney biopsies revealed high infiltration of active CD8⁺ Tm cells expressing high voltage-dependent Kv1.3 potassium channels-key T cell function regulators-in LN. Nanoparticles that selectively down-regulate Kv1.3 in Tm cells (Kv1.3-NPs) reduced CD40L and interferon-γ (IFNγ) in Tm cells from LN patients in vitro. Kv1.3-NPs were tested in humanized LN mice obtained by engrafting peripheral blood mononuclear cells (PBMCs) from LN patients into immune-deficient mice. LN mice exhibited features of the disease: increased IFNγ and CD3⁺CD8⁺ T cell renal infiltration, and reduced survival versus healthy donor PBMC engrafted mice. Kv1.3-NP treatment of patient PBMCs before engraftment decreased CD40L/IFNγ and prolonged survival of LN mice. These data show the potential benefits of targeting Kv1.3 in LN.

Ca2+ signalling in fibroblasts and the therapeutic potential of KCa3.1 channel blockers in fibrotic diseases

The role of Ca²⁺ signalling in fibroblasts is of great interest in fibrosis-related diseases. Intracellular free Ca²⁺ ([Ca²⁺ ]_i ) is a ubiquitous secondary messenger, regulating a number of cellular functions such as secretion, metabolism, differentiation, proliferation and contraction. The intermediate conductance Ca²⁺ -activated K⁺ channel K_Ca 3.1 is pivotal in Ca²⁺ signalling and plays a central role in fibroblast processes including cell activation, migration and proliferation through the regulation of cell membrane potential. Evidence from a number of approaches demonstrates that K_Ca 3.1 plays an important role in the development of many fibrotic diseases, including idiopathic pulmonary, renal tubulointerstitial fibrosis and cardiovascular disease. The K_Ca 3.1 selective blocker senicapoc was well tolerated in clinical trials for sickle cell disease, raising the possibility of rapid translation to the clinic for people suffering from pathological fibrosis. This review after analysing all the data, concludes that targeting K_Ca 3.1 should be a high priority for human fibrotic disease.