KCa3.1 mediates dysfunction of tubular autophagy in diabetic kidneys via PI3k/Akt/mTOR signaling pathways

Systems Biology of Human Microbiome for the Prediction of Personal Glycaemic Response

The human gut microbiota is increasingly recognized as a pivotal factor in diabetes management, playing a significant role in the body's response to treatment. However, it is important to understand that long-term usage of medicines like metformin and other diabetic treatments can result in problems, gastrointestinal discomfort, and dysbiosis of the gut flora. Advanced sequencing technologies have improved our understanding of the gut microbiome's role in diabetes, uncovering complex interactions between microbial composition and metabolic health. We explore how the gut microbiota affects glucose metabolism and insulin sensitivity by examining a variety of -omics data, including genomics, transcriptomics, epigenomics, proteomics, metabolomics, and metagenomics. Machine learning algorithms and genome-scale modeling are now being applied to find microbiological biomarkers associated with diabetes risk, predicted disease progression, and guide customized therapy. This study holds promise for specialized diabetic therapy. Despite significant advances, some concerns remain unanswered, including understanding the complex relationship between diabetes etiology and gut microbiota, as well as developing user-friendly technological innovations. This mini-review explores the relationship between multiomics, precision medicine, and machine learning to improve our understanding of the gut microbiome's function in diabetes. In the era of precision medicine, the ultimate goal is to improve patient outcomes through personalized treatments.

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.

High-Glucose-Induced Injury to Proximal Tubules of the Renal System Is Alleviated by Netrin-1 Suppression of Akt/mTOR

The kidneys have a high level of Netrin-1 expression, which protects against some acute and chronic kidney disorders. However, it is yet unknown how Netrin-1 affects renal proximal tubule cells in diabetic nephropathy (DN) under pathological circumstances. Research has shown that autophagy protects the kidneys in animal models of renal disease. In this study, we looked at the probable autophagy regulation mechanism of Netrin-1 and its function in the pathogenesis of DN. We proved that in HK-2 cell, high blood sugar levels caused Netrin-1 to be downregulated, which then triggered the Akt/mTOR signaling pathway and enhanced cell death and actin cytoskeleton disruption. By adding Netrin-1 or an autophagy activator in vitro, these pathogenic alterations were reverted. Our results indicate that Netrin-1 stimulates autophagy by blocking the Akt/mTOR signaling pathway, which underlies high-glucose-induced malfunction of the renal proximal tubules. After HK-2 cells were incubated with Netrin-1 recombination protein and rapamycin under HG conditions for 24 h, the apoptosis was significantly reduced, as shown by the higher levels of Bcl-2, as well as lower levels of Bax and cleaved caspase-3 (P = 0.012, Cohen's d = 0.489, Glass's delta = 0.23, Hedges' g = 0.641). This study reveals that targeting Netrin-1-related signaling has therapeutic potential for DN and advances our knowledge of the processes operating in renal proximal tubules in DN.

The Interplay of Autophagy and Oxidative Stress in the Kidney: What Do We Know?

BACKGROUND

Autophagy, as an indispensable metabolism, plays pivotal roles in maintaining intracellular homeostasis. Nutritional stress, amino acid deficiency, oxidative stress, and hypoxia can trigger its initiation. Oxidative stress in the kidney activates essential signal molecules, like mammalian target of rapamycin (mTOR), adenosine monophosphate-activated protein kinase (AMPK), and silent mating-type information regulation 2 homolog-1 (SIRT1), to stimulate autophagy, ultimately leading to degradation of intracellular oxidative substances and damaged organelles. Growing evidence suggests that autophagy protects the kidney from oxidative stress during acute ischemic kidney injury, chronic kidney disease, and even aging.

SUMMARY

This review emphasizes the cross talk between reactive oxygen species (ROS) signaling pathways and autophagy during renal homeostasis and chronic kidney disease according to the current latest research and provides therapeutic targets during kidney disorders by adjusting autophagy and suppressing oxidative stress.

KEY MESSAGES

ROS arise through an imbalance of oxidation and antioxidant defense mechanisms, leading to impaired cellular and organ function. Targeting the overproduction of ROS and reactive nitrogen species, reducing the antioxidant enzyme activity and the recovery of the prooxidative-antioxidative balance provide novel therapeutic regimens to contribute to recovery in acute and chronic renal failure. Although, in recent years, great progress has been made in understanding the molecular mechanisms of oxidative stress and autophagy in acute and chronic renal failure, the focus on clinical therapies is still in its infancy. The growing number of studies on the interactive mechanisms of oxidative stress-mediated autophagy will be of great importance for the future treatment and prevention of kidney diseases.

Amifostine attenuates bleomycin-induced pulmonary fibrosis in mice through inhibition of the PI3K/Akt/mTOR signaling pathway

Amifostine is a normal cell protection agent, not only used in the adjuvant therapy of lung cancer, ovarian cancer, breast cancer, nasopharyngeal cancer, bone tumor, digestive tract tumor, blood system tumor and other cancers in order to reduce the toxicity of chemotherapy drugs, and recent studies have reported that the drug can also reduce lung tissue damage in patients with pulmonary fibrosis, but its mechanism of action is not yet fully understood. In this study, we explored the potential therapeutic effects and molecular mechanisms of AMI on bleomycin (BLM)-induced pulmonary fibrosis in mice. A mouse model of pulmonary fibrosis was established using BLM. We then assessed histopathological changes, inflammatory factors, oxidative indicators, apoptosis, epithelial-mesenchymal transition, extracellular matrix changes, and levels of phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR) signaling pathway-related proteins in the BLM-treated mice to determine the effect of AMI treatment on these factors. BLM-treated mice had substantial lung inflammation and abnormal extracellular matrix deposition. Overall, treatment with AMI significantly improved BLM-induced lung injury and pulmonary fibrosis. More specifically, AMI alleviated BLM-induced oxidative stress, inflammation, alveolar cell apoptosis, epithelial-mesenchymal transition, and extracellular matrix deposition by regulating the PI3K/Akt/mTOR signaling pathway. This finding that AMI can alleviate pulmonary fibrosis in a mouse model by inhibiting activation of the PI3K/Akt/mTOR signaling pathway lays a foundation for potential future clinical application of this agent in patients with pulmonary fibrosis.

High-intensity interval training induces renal injury and fibrosis in type 2 diabetic mice

AIMS

Previous studies showed that high-intensity interval training (HIIT) improved fasting blood glucose and insulin resistance in type 2 diabetes mellitus (T2DM) mice. However, the effect of HIIT on the kidneys of mice with T2DM has not been examined. This study aimed to investigate the impact of HIIT on the kidneys of T2DM mice.

MATERIALS AND METHODS

T2DM mice were induced with a high-fat diet (HFD) and one-time 100 mg/kg streptozotocin intraperitoneal injection, and then T2DM mice were treated with 8 weeks of HIIT. Renal function and glycogen deposition were observed by serum creatinine levels and PAS staining, respectively. Sirius red staining, hematoxylin-eosin staining, and Oil red O staining were used to detect fibrosis and lipid deposition. Western blotting was performed to detect the protein levels.

KEY FINDINGS

HIIT significantly ameliorated the body composition, fasting blood glucose, and serum insulin of the T2DM mice. HIIT also improved glucose tolerance, insulin tolerance, and renal lipid deposition of T2DM mice. However, we found that HIIT increased serum creatinine and glycogen accumulation in the kidneys of T2DM mice. Western blot analysis showed that the PI3K/AKT/mTOR signaling pathway was activated after HIIT. The expression of fibrosis-related proteins (TGF-β1, CTGF, collagen-III, α-SMA) increased, while the expression of klotho (sklotho) and MMP13 decreased in the kidneys of HIIT mice.

SIGNIFICANCE

This study concluded that HIIT induced renal injury and fibrosis, although it also improved glucose homeostasis in T2DM mice. The current study reminds us that patients with T2DM should be cautious when participating in HIIT.

Pancreatic KCa3.1 channels in health and disease

Ion channels play an important role for regulation of the exocrine and the endocrine pancreas. This review focuses on the Ca²⁺-regulated K⁺ channel K_Ca3.1, encoded by the KCNN4 gene, which is present in both parts of the pancreas. In the islets of Langerhans, K_Ca3.1 channels are involved in the regulation of membrane potential oscillations characterizing nutrient-stimulated islet activity. Channel upregulation is induced by gluco- or lipotoxic conditions and might contribute to micro-inflammation and impaired insulin release in type 2 diabetes mellitus as well as to diabetes-associated renal and vascular complications. In the exocrine pancreas K_Ca3.1 channels are expressed in acinar and ductal cells. They are thought to play a role for anion secretion during digestion but their physiological role has not been fully elucidated yet. Pancreatic carcinoma, especially pancreatic ductal adenocarcinoma (PDAC), is associated with drastic overexpression of K_Ca3.1. For pharmacological targeting of K_Ca3.1 channels, we are discussing the possible benefits K_Ca3.1 channel inhibitors might provide in the context of diabetes mellitus and pancreatic cancer, respectively. We are also giving a perspective for the use of a fluorescently labeled derivative of the K_Ca3.1 blocker senicapoc as a tool to monitor channel distribution in pancreatic tissue. In summary, modulating K_Ca3.1 channel activity is a useful strategy for exo-and endocrine pancreatic disease but further studies are needed to evaluate its clinical suitability.

Role of renal tubular programed cell death in diabetic kidney disease

The pathogenic mechanism of diabetic kidney disease (DKD) is involved in various functions; however, its inadequate characterisation limits the availability of effective treatments. Tubular damage is closely correlated with renal function and is thought to be the main contributor to the injury observed in early DKD. Programed cell death (PCD) occurs during the biological development of the living body. Accumulating evidence has clarified the fundamental role of abnormalities in tubular PCD during DKD pathogenesis. Among PCD types, classical apoptosis, autophagic cell death, and pyroptosis are the most studied and will be the focus of this review. Our review aims to elucidate the current knowledge of the mechanism of DKD and the potential therapeutic potential of drugs targeting tubular PCD pathways in DKD.

KCa3.1 Promotes Proinflammatory Exosome Secretion by Activating AKT/Rab27a in Atrial Myocytes during Rapid Pacing

Purpose

The aim of this study was to investigate the role of the medium-conductance calcium-activated potassium channel (KCNN4, KCa3.1) in the secretion of proinflammatory exosomes by atrial myocytes.

Methods

Eighteen beagles were randomly divided into the sham group (n = 6), pacing group (n = 6), and pacing+TRAM-34 group (n = 6). Electrophysiological data, such as the effective refractory period, atrial fibrillation (AF) induction, and AF duration, were collected by programmed stimulation. Atrial tissues were subjected to hematoxylin and eosin, Masson's trichrome, and immunofluorescence staining. The expression of KCa3.1 and Rab27a was assessed by immunohistochemistry and western blotting. The downstream signaling pathways involved in KCa3.1 were examined by rapid pacing or overexpressing KCNN4 in HL-1 cells.

Results

Atrial rapid pacing significantly induced electrical remodeling, inflammation, fibrosis, and exosome secretion in the canine atrium, while TRAM-34 (KCa3.1 blocker) inhibited these changes. Compared with those in control HL-1 cells, the levels of exosome markers and inflammatory factors were increased in pacing HL-1 cells. Furthermore, the levels of CD68 and iNOS in macrophages incubated with exosomes derived from HL-1 cells were higher in the pacing-exo group than in the control group. More importantly, KCa3.1 regulated exosome secretion through the AKT/Rab27a signaling pathway. Similarly, inhibiting the downstream signaling pathway of KCa3.1 significantly inhibited exosome secretion.

Conclusions

KCa3.1 promotes proinflammatory exosome secretion through the AKT/Rab27a signaling pathway. Inhibiting the KCa3.1/AKT/Rab27a signaling pathway reduces myocardial tissue structural remodeling in AF.

The Interaction of Food Allergy and Diabetes: Food Allergy Effects on Diabetic Mice by Intestinal Barrier Destruction and Glucagon-like Peptide 1 Reduction in Jejunum

The increase in food allergies and diabetes leads to the assumption that they are related. This study aimed to (1) verify the interaction between food allergy and diabetes and (2) explore the potential mechanisms by which food allergy promotes diabetes. Female BALB/c mice were grouped into a control group (CK), an ovalbumin-sensitized group (OVA), a diabetes group (STZ), and a diabetic allergic group (STZ + OVA) (Mice were modeled diabetes with STZ first, then were given OVA to model food allergies), and an allergic diabetic group (OVA + STZ) (Mice were modeled food allergies with OVA first, then were given STZ to model diabetes). The results showed that OVA + STZ mice exhibited a more serious Th2 humoral response, and they were more susceptible to diabetes. Furthermore, when the OVA + STZ mice were in the sensitized state, the intestinal barrier function was severely impaired, and mast cell activation was promoted. Moreover, we found that the effect of food allergy on diabetes is related to the inhibition of GLP-1 secretion and the up-regulation of the PI3K/Akt/mTOR/NF-κB P65 signaling pathway in the jejunum. Overall, our results suggest that food allergies have interactions with diabetes, which sheds new light on the importance of food allergies in diabetes.

Autophagy in renal fibrosis: Protection or promotion?

Autophagy is a process that degrades endogenous cellular protein aggregates and damaged organelles via the lysosomal pathway to maintain cellular homeostasis and energy production. Baseline autophagy in the kidney, which serves as a quality control system, is essential for cellular metabolism and organelle homeostasis. Renal fibrosis is the ultimate pathological manifestation of progressive chronic kidney disease. In several experimental models of renal fibrosis, different time points, stimulus intensities, factors, and molecular mechanisms mediating the upregulation or downregulation of autophagy may have different effects on renal fibrosis. Autophagy occurring in a single lesion may also exert several distinct biological effects on renal fibrosis. Thus, whether autophagy prevents or facilitates renal fibrosis remains a complex and challenging question. This review explores the different effects of the dual regulatory function of autophagy on renal fibrosis in different renal fibrosis models, providing ideas for future work in related basic and clinical research.

Histomorphometric and Histopathological Alterations of Rat Testis Following Exposure to Hydrogen ‎Peroxide: Protective Role of Resveratrol Supplement

Resveratrol (RS) is widely used in medical fields as an antioxidant. Current research investigated ‎the protective role of RS supplement on histomorphometric and histopathological alterations in ‎testes were caused by hydrogen peroxide (H2O2) of rats as an animal model. Thirty-two adult ‎rats were utilized in this study, divided randomly into 4 equal groups as follows. The group C ‎was given tap water only and served as control, the 2nd group (G1) was given 0.5% of H2O2 of ‎tap water, the 3rd group (G2) was given tap water containing 0.5% of H2O2 and intubated RS ‎supplement at 87 mg/kg BW, and 4th group intubated RS supplement 87 mg/kg BW. after 56 ‎days of treatment, rats were euthanized, dissected then, specimens of testes tissue were collected ‎for histomorphometric and histopathological evaluation. Our results showed that administration ‎of H2O2 caused a significant histomorphometric with histopathological changes in the form of a ‎thickness of fibrous tunica albuginea, disarrangement of germ cells, necrosis of spermatogonia, ‎edema, and loss of sperms as compared to other groups. Meanwhile, these histological alterations ‎were partially attenuated in the G2 group that intubated resveratrol. Thus, the current study ‎concluded that resveratrol may have therapeutic value in the treatment of induced testicular injury ‎by H2O2 due to its antioxidant activity and attenuation of harmful effects of oxidative ‎stress through a mechanism that should be elucidated in future studies.

Profiling the lncRNA-miRNA-mRNA interaction network in the submandibular gland of diabetic mice

BACKGROUND

Hyposalivation is one of the common symptoms of diabetes. Although long non-coding RNAs (lncRNAs) have recently been reported to play important roles in the pathogenesis of diabetes, the role of lncRNAs in diabetes-induced hyposalivation remains unknown.

METHODS

The present study aimed to explore the function of lncRNA-microRNA-mRNA regulatory network in the submandibular gland (SMGs) under the context of diabetes. LncRNA expression profile of the SMGs was analyzed using microarray technology. Differentially expressed lncRNAs were confirmed using real-time quantitative PCR. Bioinformatics analyses were performed, and Coding-non-coding gene co-expression (CNC) and competing endogenous RNA (ceRNA) networks were constructed to explore the potential mechanisms of diabetes-induced hyposalivation.

RESULTS

A total of 1273 differentially expressed lncRNAs (536 up-regulated and 737 downregulated) were identified in the SMGs tissues of db/db mice. CNC and ceRNA network analyses were performed based on five differentially expressed lncRNAs validated by real-time quantitative PCR. Gene Ontology analysis of target genes of CNC network revealed that "calcium ion binding" was a highly enriched molecular function. Kyoto Encyclopedia of Genes and Genomes pathway analysis of target genes of ceRNA network revealed that the "mammalian target of rapamycin signaling pathway" was significantly enriched.

CONCLUSIONS

On the whole, the findings of the present study may provide insight into the possible mechanism of diabetes-induced hyposalivation.

Fucoidans from Cucumaria frondosa ameliorate renal interstitial fibrosis via inhibition of the PI3K/Akt/NF-κB signaling pathway

The effects of Cucumaria frondosa polysaccharides (CFPs) on renal interstitial fibrosis by regulating the phosphatidylinositol-3-hydroxykinase/protein kinase-B/nuclear factor-κB (PI3K/AKT/NF-κB) signaling pathway were investigated in vivo and in vitro in this research. The common unilateral urethral obstruction (UUO) model was used to examine the renoprotective effect and its mechanism in vivo. Compared to the UUO group, CFP administration could ameliorate renal function, inhibit inflammation and fibrosis, and reduce the deposition of the extracellular matrix and epithelial-mesenchymal transition. Mechanistic results indicated that CFPs could inhibit the expression of the total protein of PI3K and the conversion of the AKT and NF-κB p65 phosphorylated proteins, thereby inhibiting the transduction of the PI3K/AKT/NF-κB pathway. In addition, CFP treatment could improve inflammation and fibrosis in HK-2 cells induced by TGF-β1, and its in vitro mechanism was also verified to inhibit the PI3K/Akt/NF-κB signaling pathway. Overall, these results showed that CFP could alleviate renal interstitial fibrosis related to the PI3K/AKT/NF-κB signaling pathway.

A single domain i-body (AD-114) attenuates renal fibrosis through blockade of CXCR4

The G protein–coupled CXC chemokine receptor 4 (CXCR4) is a candidate therapeutic target for tissue fibrosis. A fully human single-domain antibody-like scaffold i-body AD-114-PA600 (AD-114) with specific high binding affinity to CXCR4 has been developed. To define its renoprotective role, AD-114 was administrated in a mouse model of renal fibrosis induced by folic acid (FA). Increased extracellular matrix (ECM) accumulation, macrophage infiltration, inflammatory response, TGF-β1 expression, and fibroblast activation were observed in kidneys of mice with FA-induced nephropathy. These markers were normalized or partially reversed by AD-114 treatment. In vitro studies demonstrated AD-114 blocked TGF-β1–induced upregulated expression of ECM, matrix metalloproteinase-2, and downstream p38 mitogen-activated protein kinase (p38 MAPK) and PI3K/AKT/mTOR signaling pathways in a renal proximal tubular cell line. Additionally, these renoprotective effects were validated in a second model of unilateral ureteral obstruction using a second generation of AD-114 (Fc-fused AD-114, also named AD-214). Collectively, these results suggest a renoprotective role of AD-114 as it inhibited the chemotactic function of CXCR4 as well as blocked CXCR4 downstream p38 MAPK and PI3K/AKT/mTOR signaling, which establish a therapeutic strategy for AD-114 targeting CXCR4 to limit renal fibrosis.

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.

Sitagliptin's renoprotective effect in a diabetic nephropathy model in rats: The potential role of PI3K/AKT pathway

Management of diabetic nephropathy (DN) is far from satisfactory. There is a rising role of the involvement of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (AKT) pathway in the pathogenesis of DN. This study aimed at investigating the renoprotective effects of PI3K/AKT pathway via sitagliptin in a rat model of DN. Thirty-two male Wistar rats were divided into four groups (eight rats each): (I) control, (II) sitagliptin, (III) DN, and (IV) DN + sitagliptin. Fasting blood glucose (FBG), kidney index, and kidney function tests in both blood and urine were measured. The levels of superoxide dismutase (SOD), tumor necrosis factor-alpha (TNF-α), and transforming growth factor-beta (TGF-β) and gene expressions of PI3K, pPI3K, AKT, and pAKT in renal tissue were detected. Renal histopathological and immunohistochemical studies were evaluated. DN + sitagliptin group showed significant decrease in FBG and kidney index, improvement in kidney function tests, and a decrease in levels of TNF-α and TGF-β in renal tissues compared with DN group. This was associated with significant increase in SOD and gene expressions of PI3K and AKT and their phosphorylated active forms in renal tissue in DN + sitagliptin group compared with DN group. Moreover, DN + sitagliptin group showed apparent decrease in amount of collagen fibers and expression of alpha-smooth muscle actin (α-SMA) compared with DN group. This work shows that sitagliptin improved renal functions and histopathological changes, impeded inflammation, and oxidative stress and upregulated PI3K/AKT pathway which highlights its renoprotective effects in a rat model of DN.

Mitochondria in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is the leading cause of end stage renal disease (ESRD) in the USA. The pathogenesis of DKD is multifactorial and involves activation of multiple signaling pathways with merging outcomes including thickening of the basement membrane, podocyte loss, mesangial expansion, tubular atrophy, and interstitial inflammation and fibrosis. The glomerulo-tubular balance and tubule-glomerular feedback support an increased glomerular filtration and tubular reabsorption, with the latter relying heavily on ATP and increasing the energy demand. There is evidence that alterations in mitochondrial bioenergetics in kidney cells lead to these pathologic changes and contribute to the progression of DKD towards ESRD. This review will focus on the dialogue between alterations in bioenergetics in glomerular and tubular cells and its role in the development of DKD. Alterations in energy substrate selection, electron transport chain, ATP generation, oxidative stress, redox status, protein posttranslational modifications, mitochondrial dynamics, and quality control will be discussed. Understanding the role of bioenergetics in the progression of diabetic DKD may provide novel therapeutic approaches to delay its progression to ESRD.

Dendrobium mixture attenuates renal damage in rats with diabetic nephropathy by inhibiting the PI3K/Akt/mTOR pathway

Dendrobium mixture (DMix) is a Traditional Chinese Medicine widely used for preventing and treating diabetic nephropathy (DN). Autophagy contributes to DN development and progression. The present study aimed to investigate the mechanism underlying the protective effects of DMix on the kidneys of rats with DN and to determine whether this involves autophagy. Herein, a high‑sugar and high‑fat diet, combined with the intra‑abdominal injection of low‑dose streptozocin, was used to induce DN in 40 Sprague‑Dawley male rats. In total, 10 additional rats were used as controls. The rats with DN were then randomly divided into three groups and treated with DMix, gliquidone or saline via gastric administration for 8 weeks. Body weight, kidney weight, kidney index, fasting blood glucose (FBG), blood lipid, hemoglobin A1c (HbA1c), insulin, blood urea nitrogen and serum creatinine levels, as well as the 24‑h urinary albumin excretion rate (UAER) were measured. H&E, Periodic Acid‑Schiff and Masson staining were used to examine the renal pathology. The mRNA and protein expression levels of LC3 and Beclin‑1 in renal tissues were measured using reverse transcription‑quantitative PCR and immunohistochemistry, respectively. Western blotting was conducted to measure the protein expression levels of PI3K, phosphorylated (p)‑PI3K, Akt, p‑Akt, mTOR, p‑mTOR, LC3 and Beclin‑1 in renal tissues. It was found that DMix significantly reduced the FBG, blood lipids, HbA1c and insulin levels, kidney weight, kidney index and UAER in rats with DN, as well as improved renal function. Rats with DN showed notable glomerular hypertrophy, an increase in mesangial matrix content and renal interstitial fibrosis. Moreover, DMix notably reduced kidney damage. The results demonstrated that DMix inhibited the phosphorylation of PI3K, Akt and mTOR in the kidney tissues of rats with DN, and increased the protein and mRNA expression levels of LC3 and Beclin‑1. Therefore, it was suggested that DMix has protective effects on the kidney of rats with DN, which may be associated with the inhibition of the PI3K/Akt/mTOR signaling pathway and activation of renal autophagy by this traditional medicine.

Cardamonin exerts a protective effect against autophagy and apoptosis in the testicles of diabetic male rats through the expression of Nrf2 via p62-mediated Keap-1 degradation

Cardamonin (CARD) is a chalconoid with anti-inflammatory and antioxidant properties, and it is present in several plants. We sought to explore whether CARD exerts any positive effects against hyperglycemia-induced testicular dysfunction caused by type 2 diabetes and aimed to identify its possible intracellular pathways. Adult male rats were subdivided into six groups: control, CARD, diabetic (DM), DM + glibenclamide (GLIB), DM + CARD and DM + GLIB + CARD. Type 2 DM induced a significant increase in blood glucose and insulin resistance, along with diminished serum insulin, testosterone and gonadotropins levels, which were associated with the impairment of key testicular androgenic enzymes and cellular redox balance. Administration of CARD at a dose of 80 mg/kg for 4 weeks effectively normalized all of these alterations, and the improvement was confirmed by epididymal sperm analysis. After treatment with CARD, the pathological changes in spermatogenic tubules were markedly improved. Significantly, CARD upregulated testicular glucose transporter-8 (GLUT-8) expression and had inhibitory effects on elevated autophagy markers and caspase-3 immunoreactive cells. Furthermore, our results revealed that CARD was able to attenuate damage via activation of Nrf2 through the p62-dependent degradation of testicular anti-Kelch-like ECH-associated protein-1 (Keap-1). In conclusion, this study suggests that CARD provides protection against diabetic stress-mediated testicular damage. The use of CARD with conventional anti-diabetic therapy was associated with improved efficacy compared with conventional therapy alone.

Update on the Mechanisms of Tubular Cell Injury in Diabetic Kidney Disease

Increasing evidence supports a role of proximal tubular (PT) injury in the progression of diabetic kidney disease (DKD), in patients with or without proteinuria. Research on the mechanisms of the PT injury in DKD could help us to identify potential new biomarkers and drug targets for DKD. A high glucose transport state and mismatched local hypoxia in the PT of diabetes patients may be the initiating factors causing PT injury. Other mechanism such as mitochondrial dysfunction, reactive oxygen species (ROS) overproduction, ER stress, and deficiency of autophagy interact with each other leading to more PT injury by forming a vicious circle. PT injury eventually leads to the development of tubulointerstitial inflammation and fibrosis in DKD. Many downstream signaling pathways have been demonstrated to mediate these diseased processes. This review focuses mostly on the novel mechanisms of proximal renal tubular injury in DKD and we believe such review could help us to better understand the pathogenesis of DKD and identify potential new therapies for this disease.

Silencing of LncRNA PVT1 inhibits the proliferation, migration and fibrosis of high glucose-induced mouse mesangial cells via targeting microRNA-93-5p

Objective: The present study aimed to investigate the regulatory role of long non-coding RNA plasmacytoma variant translocation 1 (PVT1) on high glucose (HG)-induced mouse mesangial cells (MMCs).

Methods: PVT1 expression in diabetic nephropathy (DN) mice and HG-induced MMCs was detected by qRT-PCR. EdU and Colony formation, Annexin V-PI staining, Muse cell cycle, Scratch, and Transwell assays were performed to detect the cell proliferation, apoptosis, cell cycle, migration, and invasion, respectively. The contents of fibrosis factors in cell-culture supernatants were detected by enzyme-linked immunosorbent assay (ELISA). Western blot was performed to detect the expression of factors involved in apoptosis, cell cycle, migration and invasion, fibrosis, and PI3K/Akt/mTOR pathway. The targeting relation between miR-93-5p and PVT1 was predicted by StarBase3.0 (an online software for analyzing the targeting relationship) and identified by Dual-luciferase reporter (DLR) assay.

Results: PVT1 was overexpressed in DN kidney tissues and HG-induced MMCs. HG-induced MMCs exhibited significantly increased EdU-positive cells, cell colonies, S and G₂/M phase cells, migration and invasion ability, and contents of fibrosis factors, as well as significantly decreased apoptosis rate compared with NG-induced MMCs. HG significantly up-regulated Bcl-2, CyclinD1, CDK4, N-cadherin, vimentin, Col. IV, FN, TGF-β1 and PAI-1, and down-regulated Bax, cleaved caspase-3, cleaved PARP, and E-cadherin in MMCs. Silencing of PVT1 eliminated the effects of HG in MMCs and blocked PI3K/Akt/mTOR pathway. MiR-93-5p was a target of PVT1, which eliminated the effects of PVT1 on HG-induced MMCs.

Conclusions: PVT1 silencing inhibited the proliferation, migration, invasion and fibrosis, promoted the apoptosis, and blocked PI3K/Akt/mTOR pathway in HG-induced MMCs via up-regulating miR-93-5p.

Opening of Intermediate Conductance Ca2+-Activated K+ Channels in C2C12 Skeletal Muscle Cells Increases the Myotube Diameter via the Akt/Mammalian Target of Rapamycin Pathway

The activation of potassium channels and the ensuing hyperpolarization in skeletal myoblasts are essential for myogenic differentiation. However, the effects of K+ channel opening in myoblasts on skeletal muscle mass are unclear. Our previous study revealed that pharmacological activation of intermediate conductance Ca2+-activated K+ channels (IKCa channels) increases myotube formation. In this study, we investigated the effects of 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), a Ca2+-activated K+ channel opener, on the mass of skeletal muscle. Application of DCEBIO to C2C12 cells during myogenesis increased the diameter of C2C12 myotubes in a concentration-dependent manner. This DCEBIO-induced hypertrophy was abolished by gene silencing of IKCa channels. However, it was resistant to 1 µM but sensitive to 10 µM TRAM-34, a specific IKCa channel blocker. Furthermore, DCEBIO reduced the mitochondrial membrane potential by opening IKCa channels. Therefore, DCEBIO should increase myotube mass by opening of IKCa channels distributed in mitochondria. Pharmacological studies revealed that mitochondrial reactive oxygen species (mitoROS), Akt, and mammalian target of rapamycin (mTOR) are involved in DCEBIO-induced myotube hypertrophy. An additional study demonstrated that DCEBIO-induced muscle hypertrophic effects are only observed when applied in the early stage of myogenic differentiation. In an in vitro myotube inflammatory atrophy experiment, DCEBIO attenuated the reduction of myotube diameter induced by endotoxin. Thus, we concluded that DCEBIO increases muscle mass by activating the IKCa channel/mitoROS/Akt/mTOR pathway. Our study suggests the potential of DCEBIO in the treatment of muscle wasting diseases. SIGNIFICANCE STATEMENT: Our study shows that 5,6-dichloro-1-ethyl-1,3-dihydro-2H-benzimidazol-2-one (DCEBIO), a small molecule opener of Ca2+-activated K+ channel, increased muscle diameter via the mitochondrial reactive oxygen species/Akt/mammalian target of rapamycin pathway. And DCEBIO overwhelms C2C12 myotube atrophy induced by endotoxin challenge. Our report should inform novel role of K+ channel in muscle development and novel usage of K+ channel opener such as for the treatment of muscle wasting diseases.

KCa3.1 Mediates Dysregulation of Mitochondrial Quality Control in Diabetic Kidney Disease

Mitochondrial dysfunction is implicated in the pathogenesis of diabetic kidney disease. Mitochondrial quality control is primarily mediated by mitochondrial turnover and repair through mitochondrial fission/fusion and mitophagy. We have previously shown that blockade of the calcium-activated potassium channel KCa3.1 ameliorates diabetic renal fibrosis. However, the mechanistic link between KCa3.1 and mitochondrial quality control in diabetic kidney disease is not yet known. Transforming growth factor β1 (TGF-β1) plays a central role in diabetic kidney disease. Recent studies indicate an emerging role of TGF-β1 in the regulation of mitochondrial function. However, the molecular mechanism mediating mitochondrial quality control in response to TGF-β1 remains limited. In this study, mitochondrial function was assessed in TGF-β1-exposed renal proximal tubular epithelial cells (HK2 cells) transfected with scrambled siRNA or KCa3.1 siRNA. In vivo, diabetes was induced in KCa3.1+/+ and KCa3.1−/− mice by low-dose streptozotocin (STZ) injection. Mitochondrial fission/fusion-related proteins and mitophagy markers, as well as BCL2 interacting protein 3 (BNIP3) (a mitophagy regulator) were examined in HK2 cells and diabetic mice kidneys. The in vitro results showed that TGF-β1 significantly inhibited mitochondrial ATP production rate and increased mitochondrial ROS (mtROS) production when compared to control, which was normalized by KCa3.1 gene silencing. Increased fission and suppressed fusion were found in both TGF-β1-treated HK2 cells and diabetic mice, which were reversed by KCa3.1 deficiency. Furthermore, our results showed that mitophagy was inhibited in both in vitro and in vivo models of diabetic kidney disease. KCa3.1 deficiency restored abnormal mitophagy by inhibiting BNIP3 expression in TGF-β1-induced HK2 cells as well as in the diabetic mice. Collectively, these results indicate that KCa3.1 mediates the dysregulation of mitochondrial quality control in diabetic kidney disease.

Momordica charantia silver nanoparticles modulate S/JAK/STAT and P13K/Akt/PTEN signalling pathways in the kidney of streptozotocin-induced diabetic rats

Objectives

Diabetes nephropathy (DN) is one of the complications of diabetes mellitus (DM) marked by gradual progressive loss of renal function. SOCS/JAK/STAT and PI3K/Akt/PTEN signalling pathways are among the chain of interactions implicated in the onset, progression and pathology of DN. Momordica charantia (bitter melon) is often used in folk medicine as therapy for DM due to its hypoglycemic properties. This study was designed to evaluate M. charantia silver nanoparticles' therapeutic effect on DN-induced by streptozotocin (STZ) in Wistar rats.

Methods

The M. charantia nanoparticles used was synthesized using the filtrate from the plant methanolic extract added to 1 mM concentration of aqueous silver nitrate. DM was induced in Wistar rats by intraperitoneal injection of STZ (65 mg/kg). The animals' treatment groups were divided into; Diabetic control (65 mg/kg STZ), Control, and groups treated with silver nitrate (10 mg/kg), M. charantia nanoparticles (50 mg/kg), metformin (100 mg/kg), and plant extract (100 mg/kg). Treatment was terminated after 11 days. RT-PCR determined renal mRNA expression of Akt, PI3k, PTEN, TGF-β, JAK2, STAT3, STAT5, SOCS3, SOCS4 and glucokinase (GCK). Consequently, characterized compounds from M. charantia identified from literatures were docked with PI3K, JAK2 and TGF-β and STAT3 to retrieve potential hits.

Results

Oral administration of M. charantia nanoparticles (50 mg/kg) to STZ-induced diabetic untreated rats significantly ((p < 0.05) down-regulated the mRNA expression of Akt, PI3k, TGF-β, JAK2, STAT3 and upregulated the mRNA expression of PTEN, SOCS3 and SOCS4, thus establishing the role of M. charantia nanoparticles in alleviating DN in diabetic rats. Additionally, there was a significant up-regulation of glucose metabolizing gene (glucokinase) upon administering M. charantia nanoparticles. Molecular docking results showed 12 compounds from bitter melon with docking score ranging from -6.114 kcal/mol to -8.221 kcal/mol that are likely to exert anti-diabetic properties.

Conclusion

Observation drawn from this study suggests that M. charantia nanoparticles ameliorate DN through regulation of SOCS/JAK/STAT and PI3K/Akt/PTEN signalling pathways.

Celastrol slows the progression of early diabetic nephropathy in rats via the PI3K/AKT pathway

Background

Diabetic nephropathy serves as one of the most regular microvascular complications of diabetes mellitus and is the main factor that causes end-stage renal disease and incident mortality. As the beneficial effect and minute adverse influence of Celastrol on the renal system requires further elucidation, the renoprotective function of Celastrol in early diabetic nephropathy was investigated.

Methods

In high-fat and high-glucose diet/streptozotocin-induced diabetic rats which is the early diabetic nephropathy model, ALT, AST, 24 h urinary protein, blood urea nitrogen, and serum creatinine content were observed. Periodic acid-Schiff staining, enzyme-linked immunosorbent assay, immunohistochemical analysis, reverse transcription-polymerase chain reaction, and western blot analysis were used to explore the renoprotective effect of Celastrol to diabetic nephropathy rats and the underlying mechanism.

Results

High dose of Celastrol (1.5 mg/kg/d) not only improved the kidney function of diabetic nephropathy (DN) rats, and decreased the blood glucose and 24 h urinary albumin, but also increased the expression of LC3II and nephrin, and downregulated the expression of PI3K, p-AKT, and the mRNA level of NF-κB and mTOR.

Conclusion

Celastrol functions as a potential therapeutic substance, acting via the PI3K/AKT pathway to attenuate renal injury, inhibit glomerular basement membrane thickening, and achieve podocyte homeostasis in diabetic nephropathy.

Curcumin anti-diabetic effect mainly correlates with its anti-apoptotic actions and PI3K/Akt signal pathway regulation in the liver

This study aimed to investigate the therapeutic effect of curcumin on type 2 diabetes and its underlying mechanisms. A type 2 diabetes mellitus rat model was established by providing high-fat diet and low doses of streptozotocin. Type 2 diabetes mellitus rats were treated with low dose and high dose of curcumin for 8 weeks. The results showed that high-dose curcumin significantly reduced fasting blood glucose, total cholesterol, triglyceride, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, alanine aminotransferase, and aspartate transaminase, liver coefficient, and malondialdehyde levels, and BCL2-Associated X expression in the type 2 diabetes mellitus rats. High-dose curcumin increased the levels of liver superoxide dismutase, catalase, and glutathione; as well as the expression of liver B-cell lymphoma-2, phosphatidylinositol 3-kinase, phosphorylated phosphatidylinositol 3-kinase, protein kinase B, and phosphorylated protein kinase B in type 2 diabetes mellitus rats. Furthermore, it ameliorated the histological structure of the liver and pancreas in diabetes mellitus model rats. However, low-dose curcumin had no significant effect on diabetes mellitus model rats. The results suggest that adequate doses of curcumin controls type 2 diabetes mellitus development as well as the mechanism involved in its anti-apoptotic actions and phosphatidylinositol 3-hydroxy kinase/protein kinase B signal pathway regulation in the liver.

Autophagy Induced by ROS Aggravates Testis Oxidative Damage in Diabetes via Breaking the Feedforward Loop Linking p62 and Nrf2

Testicular dysfunction due to hyperglycemia is the main cause of infertility in diabetic men. Over the years, in order to solve this growing problem, a lot of research has been done and a variety of treatments have been created, but so far, there is no safe, effective, and practical method to prevent male infertility caused by diabetes. In this review, we emphasize the male infertility mechanism caused by diabetes from the effects of oxidative stress and autophagy on the function of testes via the PI3K/Akt/mTOR signaling pathway, and we highlight that oxidative stress-induced autophagy breaks the feedforward loop linking Nrf2 and p62 and promotes oxidative damage in diabetic testes.

Ibrutinib suppresses intracellular mycobacterium tuberculosis growth by inducing macrophage autophagy

Tuberculosis (TB) is a major cause of morbidity and mortality worldwide. The host-directed therapy is a promising strategy for TB treatment that synergize with anti-TB treatment drugs. In this study, we found that the anti-chronic lymphocytic leukemia drug, ibrutinib, inhibited the growth of intracellular Mtb in human macrophages. Mechanisms studies showed that ibrutinib treatment significantly decreased p62 and increased LC3b proteins in Mtb infected macrophages. In addition, ibrutinib increased LC3b colocalization with intracellular Mtb and auto-lysosome fusion. Furthermore, inhibition of autophagy by using siRNA targeting ATG7 abolished the effect of ibrutinib-mediated suppression of intracellular Mtb. Next, we found that ibrutinib induced autophagy was through inhibition of BTK/Akt/mTOR pathway. Finally, we confirmed that ibrutinib treatment significantly reduced Mtb load in mediastinal node and spleen of Mtb infected mice. In conclusion, our data suggest that ibrutinib is a potential host-directed therapy candidate against TB.

Renoprotective effects of Gushen Jiedu capsule on diabetic nephropathy in rats

Gushen Jiedu capsule (GSJD) is a formula that has been widely used in traditional Chinese medicine for the prevention and treatment of diabetic nephropathy (DN). However, the mechanism underlying the protective effects of GSJD on DN is still unclear. This study was performed to clarify the therapeutic effects of GSJD on DN and its underlying mechanisms. High-fat diet- and streptozotocin-induced DN rats were treated with or without GSJD suspension by gavage for 8 weeks, and biochemical changes in blood and urine were analysed. Kidneys were isolated for histological, TUNEL and Western blot analysis. Compared to the DN group, the GSJD-treated groups exhibited decreased urinary albumin, ameliorated renal dysfunction, including serum creatinine and blood urea nitrogen, and attenuated total cholesterol, triglyceride and total protein levels. However, there were no significant effects of GSJD on body weight, fasting blood glucose or albuminuria. Histology showed that GSJD could retard the progression of DN and decrease the apoptosis rate from 52% to less than 20%. Western blot analysis showed that GSJD could regulate the mitochondrial apoptotic pathway by downregulating the expression of Bax and upregulating the expression of BCL-2 in the kidneys of DN rats. Moreover, the Akt pathway, an upstream signalling pathway of the BCL-2 family, was also ameliorated by GSJD. Further, the podocyte foot process markers podocin and nephrin were upregulated by GSJD in DN rats. This study demonstrated that GSJD might play a renoprotective role by inhibiting apoptosis and regulating the mitochondrial apoptotic and Akt pathways during pathological changes in DN.

Diabetic Nephropathy Assessment: Microtubule-Associated Protein 1 Light-Chain 3B a New Promising Biomarker

Autophagy is a highly conserved pathway. Impairment of autophagy is implicated in the pathogenesis of diabetic nephropathy. The current study applied a bioinformatics analysis to retrieve promising autophagy biomarker relevant diabetic nephropathy. Urinary expression of Microtubule-associated protein 1 light-chain 3B (LC3B) RNA was assessed. Urine samples of 86 type II diabetic kidney disease Egyptian patients (albuminuria group) were provided to quantify urinary expression of LC3B. A group of 30 healthy volunteers were also enrolled in addition to non-albuminuria group including 44 patients. Our study revealed a cut-off value for urinary LC3B expression level that was calculated by receiver-operating characteristic curve as 0.866. Sensitivity and specificity of LC3B were 83.7 and 78.4% respectively. The positivity rate of urinary LC3B expression level was significantly lower in diabetic nephropathy patients than control group. LC3B has great clinical value as promising biomarker in diabetic nephropathy assessment.

Nephroprotective effect of losartan in IgA model rat

Objective

This study was performed to investigate the possible nephroprotective effects of losartan in a rat model of experimental IgA nephropathy (IgAN).

Methods

Thirty male Sprague–Dawley rats were randomly divided into three groups. The rats in the model group were treated with bovine serum albumin (oral gavage), lipopolysaccharide (tail vein injection), and carbon tetrachloride (subcutaneous injection); rats in the losartan group received treatments similar to those of the model group, and were orally gavaged with losartan; and rats in the control group received phosphate-buffered saline alone (both orally and intravenously).

Results

Losartan treatment lowered the 24-hour urinary protein, serum blood urea nitrogen, and serum creatinine levels. Proliferating mesangial cells with a variable increase in the mesangial matrix were detected in the model group, whereas injury in the losartan group was significantly attenuated. Immunohistochemistry revealed that the expression levels of transforming growth factor (TGF)-β1 and α-smooth muscle actin were significantly elevated in the model group but reduced in the losartan group. The expression levels of TGF-β1 and monocyte chemoattractant protein-1 were minimal in the control group, significantly increased in the model group, and reduced in the losartan group.

Conclusion

Losartan has a protective effect against tubulointerstitial injury in IgAN.

WNT1-inducible signaling protein-1 mediates TGF-β1-induced renal fibrosis in tubular epithelial cells and unilateral ureteral obstruction mouse models via autophagy

Renal fibrosis is a common pathway for the progression of all chronic kidney diseases to end-stage kidney disease. Studies show that WNT1-inducible signaling pathway protein-1 (WISP-1) is involved in the fibrosis of various organs. The aim of the study was to explore the functional role and potential mechanism of WISP-1 in renal fibrosis. We observed that overexpression of WISP-1 in rat tubular epithelial cells (TECs) enhanced transforming growth factor-β1 (TGF-β1)-induced production of fibrotic markers, including collagen I (Col I), fibronectin (FN) and TGF-β1, while inhibition of WISP-1 suppressed such production. In vivo, the messenger RNA and protein levels of Col I, FN, and α-smooth muscle actin were significantly inhibited after anti-WISP-1 antibody treatment for 7 days in unilateral ureteral obstruction mouse models. Moreover, blockade of WISP-1 by anti-WISP-1 antibody significantly reduced autophagy-related markers, including anti-microtubule-associated protein-1 light chain 3 (LC3) and beclin 1, while increasing sequestosome 1. In addition, overexpression of WISP-1 in TECs increased autophagy as evidenced by greater numbers of GFP-LC3 puncta and increased expression of LC3 and beclin 1 in response to TGF-β1. In contrast, knockdown of WISP-1 by small interfering RNA decreased the number of GFP-LC3 puncta and the expression of LC3 and beclin 1 in TGF-β1-treated TECs. Collectively, these data suggest that WISP-1, as a profibrotic protein, may mediate renal fibrosis by inducing autophagy in both obstructive nephropathy and TGF-β1-treated TECs. WISP-1 may serve as an effective therapeutic target for the treatment of renal fibrosis.

The inhibition of SGK1 suppresses epithelial-mesenchymal transition and promotes renal tubular epithelial cell autophagy in diabetic nephropathy

Diabetic nephropathy (DN) is a common complication of diabetes that is the dominant cause of end-stage renal disease. However, the pathological mechanism of DN is yet to be elucidated. Serum and glucocorticoid induced kinase (SGK) 1, a ubiquitously expressed kinase, was employed in the current study to assess its effect on DN in vivo and in vitro. Male BALB/C mice and a human tubular epithelial cell line (HK-2) were utilized for experimentation. Male BALB/C mice and a human tubular epithelial cell line (HK-2) were utilized for experimentation. Pathological changes were measured via HE and staining and immunohistochemistry was performed to measure the expression of SGK 1. An SGK1 inhibitor, GSK650394, was applied to analyze the role of SGK1 in HK-2 cell epithelial-mesenchymal transition (EMT). Associated protein expressions were assessed via western blotting. In addition, migration was measured using a scratch wound healing assay. 3-methyladenine (3-MA), an autophagy inhibitor, was used to determine the variation of autophagy following SGK1 inhibition. The expression of autophagy proteins were analyzed. Furthermore, the expression of PI3K, AKT, mTOR and their levels of phosphorylation were measured. The results revealed that the ultrastructure of renal tissue suffered damage and that the expression of SGK1 was markedly increased. After SGK1 inhibition, HK-2 cell EMT was suppressed and cell migration was attenuated. Furthermore, the autophagy of HK-2 cells was promoted, an increased expression of Beclin-1 and LC3 II was detected, and a decreased expression of p62 was observed. Additionally, the phosphorylation of PI3K, AKT and mTOR were markedly upregulated. The results indicated that blocking autophagy signaling via 3-MA muted SGK1-protected against HG-evoked cell injury. Our study demonstrated that SGK1 inhibition promoted autophagy and suppressed renal tubular epithelial cell EMT in DN, indicating that SGK1 may serve as a potential therapeutic target of DN.

Inhibition of Interleukin 10 Transcription through the SMAD2/3 Signaling Pathway by Ca2+-Activated K+ Channel KCa3.1 Activation in Human T-Cell Lymphoma HuT-78 Cells

The hyperpolarization induced by intermediate-conductance Ca2+-activated K+ channel (KCa3.1) activation increases the driving force for Ca2+ influx, which generally promotes cell proliferation, migration, and cytokine production in immunocompetent cells. Interleukin-10 (IL-10) from tumor-infiltrating lymphocytes and macrophages, lymphoma, and carcinoma cells facilitates escape from cancer immune surveillance; however, the role of KCa3.1 in IL-10 production remains unclear. The objective of the present study was to elucidate the involvement of KCa3.1 in IL-10 expression and production using the human T-cell lymphoma HuT-78 cells. In HuT-78 cells, IL-10 gene expression and production were reduced by treatment with the KCa3.1 activator, as 6-hour Western blotting showed that the protein expression ratio of phosphorylated Smad2 (P-Smad2)/Smad2, but not P-Smad3/Smad3, was decreased by the treatment with KCa3.1 activator in HuT-78 cells. Concomitant with this, the nuclear translocation of P-Smad2 was inhibited by KCa3.1 activator. Furthermore, the KCa3.1 activator-induced transcriptional repression of IL-10 disappeared with pretreatment with the calmodulin kinase II (CaMKII) inhibitor KN-62 for 1 hour, and KCa3.1 activator-induced decreases in the nuclear translocation of P-Smad2 were also prevented by pretreatment with KN-62. Taken together, the KCa3.1 activator-induced transcriptional repression of IL-10 is due to the inhibition of the nuclear translocation of P-Smad2 in HuT-78 cells, resulting in the prevention of P-Smad2/3 complex formation in nuclei, and the activation of CaMKII induced by KCa3.1 activators suppresses the constitutive activation of P-Smad2/3 in HuT-78 cells. Therefore, KCa3.1 activators have potential as a therapeutic option to suppress the tumor-promoting activities of IL-10.

Ion channels and transporters in diabetic kidney disease

Type 1 and 2 diabetes mellitus are major medical epidemics affecting millions of patients worldwide. Diabetes mellitus is the leading cause of diabetic kidney disease (DKD), which is the most common cause of end-stage renal disease (ESRD). DKD is associated with significant changes in renal hemodynamics and electrolyte transport. Alterations in renal ion transport triggered by pathophysiological conditions in diabetes can exacerbate hypertension, accelerate renal injury, and are integral to the development of DKD. Renal ion transporters and electrolyte homeostasis play a fundamental role in functional changes and injury to the kidney during DKD. With the large number of ion transporters involved in DKD, understanding the roles of individual transporters as well as the complex cascades through which they interact is essential in the development of effective treatments for patients suffering from this disease. This chapter aims to gather current knowledge of the major renal ion transporters with altered expression and activity under diabetic conditions, and provide a comprehensive overview of their interactions and collective functions in DKD.

Aloe-Emodin Ameliorates Renal Fibrosis Via Inhibiting PI3K/Akt/mTOR Signaling Pathway In Vivo and In Vitro

Fibrosis is the major pathological feature of chronic kidney disease (CKD). Aloe-emodin (AE), one of the main active compounds in Rhubarb, is widely used for renal protection. However, mechanisms implied in the modulation of kidney fibrosis after AE treatment for CKD remain elusive. Here, we explored the protective effects of AE for renal fibrosis and the involved mechanisms in vivo and in vitro. The renal fibrosis mice model was established by unilateral ureteral obstruction (UUO). We found that AE administration significantly ameliorated UUO-induced impairment of kidney, evidenced by improved histopathological abnormalities, body weight, and abnormal renal function in mice model. Immunohistochemical staining showed that TGF-β1 and Fibronectin expressions were significantly decreased in UUO mice compared with sham group. Meanwhile, we found that AE suppressed the activation of the PI3K/Akt/mTOR pathway induced by TGF-β1 in vivo. AE improved cell survival and decreased the level of fibrosis-related proteins under TGF-β1-induced fibrosis in HK-2 cells as well as in vitro. Furthermore, both wortmannin, an inhibitor of PI3K, and short-hairpin RNAs of PI3K knockdown abrogated TGF-β1-induced phosphorylation of Akt and mTOR, and decreased the suppression of fibrosis. These findings indicated that AE alleviated fibrosis by inhibiting PI3K/Akt/mTOR pathway in vivo and in vitro, which may provide a potential therapeutic option for CKD.

Ca2+-Activated K+ Channel KCa3.1 as a Therapeutic Target for Immune Disorders

In lymphoid and myeloid cells, membrane hyperpolarization by the opening of K⁺ channels increases the activity of Ca²⁺ release-activated Ca²⁺ (CRAC) channels and transient receptor potential (TRP) Ca²⁺ channels. The intermediate-conductance Ca²⁺-activated K⁺ channel K_Ca3.1 plays an important role in cell proliferation, differentiation, migration, and cytokine production in innate and adaptive immune systems. K_Ca3.1 is therefore an attractive therapeutic target for allergic, inflammatory, and autoimmune disorders. In the past several years, studies have provided new insights into 1) K_Ca3.1 pharmacology and its auxiliary regulators; 2) post-transcriptional and proteasomal regulation of K_Ca3.1; 3) K_Ca3.1 as a regulator of immune cell migration, cytokine production, and phenotypic polarization; 4) the role of K_Ca3.1 in the phosphorylation and nuclear translocation of Smad2/3; and 5) K_Ca3.1 as a therapeutic target for cancer immunotherapy. In this review, we have assembled a comprehensive overview of current research on the physiological and pathophysiological significance of K_Ca3.1 in the immune system.

Histone Deacetylases Enhance Ca2+-Activated K⁺ Channel KCa3.1 Expression in Murine Inflammatory CD4⁺ T Cells

The up-regulated expression of the Ca²⁺-activated K⁺ channel K_Ca3.1 in inflammatory CD4⁺ T cells has been implicated in the pathogenesis of inflammatory bowel disease (IBD) through the enhanced production of inflammatory cytokines, such as interferon-γ (IFN-γ). However, the underlying mechanisms have not yet been elucidated. The objective of the present study is to clarify the involvement of histone deacetylases (HDACs) in the up-regulation of K_Ca3.1 in the CD4⁺ T cells of IBD model mice. The expression levels of K_Ca3.1 and its regulators, such as function-modifying molecules and transcription factors, were quantitated using a real-time polymerase chain reaction (PCR) assay, Western blotting, and depolarization responses, which were induced by the selective K_Ca3.1 blocker TRAM-34 (1 μM) and were measured using a voltage-sensitive fluorescent dye imaging system. The treatment with 1 μM vorinostat, a pan-HDAC inhibitor, for 24 h repressed the transcriptional expression of K_Ca3.1 in the splenic CD4⁺ T cells of IBD model mice. Accordingly, TRAM-34-induced depolarization responses were significantly reduced. HDAC2 and HDAC3 were significantly up-regulated in the CD4⁺ T cells of IBD model mice. The down-regulated expression of K_Ca3.1 was observed following treatments with the selective inhibitors of HDAC2 and HDAC3. The K_Ca3.1 K⁺ channel regulates inflammatory cytokine production in CD4⁺ T cells, mediating epigenetic modifications by HDAC2 and HDAC3.

Is autophagy associated with diabetes mellitus and its complications? A review

Diabetes mellitus (DM) is an endocrine disorder. In coming decades it will be one of the leading causes of death globally. The key factors in the pathogenesis of diabetes are cellular injuries and disorders of energy metabolism leading to severe diabetic complications. Recent studies have confirmed that autophagy plays a pivotal role in diabetes and its complications. It has been observed that autophagy regulates the normal function of pancreatic β cells and insulin-target tissues, such as skeletal muscle, liver, and adipose tissue. This review will summarize the regulation of autophagy in diabetes and its complications, and explore how this process would emerge as a potential therapeutic target for diabetes treatment.

Aquaporin 5 is degraded by autophagy in diabetic submandibular gland

Autophagy is a catabolic process which is involved in the development of many diseases including diabetes mellitus and its complications. Hyposalivation is a common complication of diabetes mellitus, whereas its mechanism remains unclear. Here, we observed that the stimulated salivary flow rate of SMG was significantly decreased in db/db mice, a diabetic mice model. The expressions of aquaporin 5 (AQP5), a water channel protein, were decreased, whereas the mRNA level of AQP5 was increased in SMGs of both diabetic patients and mice. Under transmission electron microcope, more autophagosomes were detected in diabetic SMGs. Expressions of autophagy related proteins LC3II, Beclin-1 and ATG5 were increased, meanwhile autophagy substrate p62 was decreased in SMGs of diabetic patients and mice, indicating that autophagy was activated in diabetic SMG. Double immunofluorescence staining showed that the colocalization of AQP5 and LC3 was increased in SMGs of diabetic mice. In cultured SMG-C6 cells, high glucose (HG), but not high osmotic pressure, reduced AQP5 protein expression and induced autophagy. Moreover, inhibition of autophagy by 3-methyladenin, an autophagy inhibitor, or by autophagy-related gene 5 siRNA, decreased HG-induced AQP5 reduction in SMG-C6 cells. Additionally, the expression of p-p85, p-Akt and p-mTOR were decreased in HG-treated SMG-C6 cells. Pretreatment with 740Y-P, a PI3K agonist, significantly suppressed HG-induced autophagy and AQP5 degradation. Taken together, these results indicate that autophagy plays a crucial role in AQP5 degradation in diabetic SMG via PI3K/Akt/mTOR signaling pathway, which contributes to the dysfunction of diabetic SMG. Our study provides a novel mechanism of diabetic hyposalivation.

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

Despite optimal control of hyperglycaemia, hypertension, and dyslipidaemia, the number of patients with diabetic nephropathy (DN) continues to grow. Strategies to target various signaling pathways to prevent DN have been intensively investigated in animal models and many have been proved to be promising. However, targeting these pathways once kidney disease is established, remain unsatisfactory. The clinical scenario is that patients with diabetes mellitus often present with established kidney damage and need effective treatments to repair and reverse the kidney damage. In this studies, eNOS-/- mice were administered with streptozotocin to induce diabetes. At 24 weeks, at which time we have previously demonstrated albuminuria and pathological changes of diabetic nephropathy, mice were randomised to receive TRAM34 subcutaneously, a highly selective inhibitor of potassium channel KCa3.1 or DMSO (vehicle) for a further 14 weeks. Albuminuria was assessed, inflammatory markers (CD68, F4/80) and extracellular matrix deposition (type I collagen and fibronectin) in the kidneys were examined. The results clearly demonstrate that TRAM34 reduced albuminuria, decreased inflammatory markers and reversed extracellular matrix deposition in kidneys via inhibition of the TGF-β1 signaling pathway. These results indicate that KCa3.1 blockade effectively reverses established diabetic nephropathy in this rodent model and provides a basis for progressing to human studies.