Store-Operated Ca2+ Channels in Mesangial Cells Inhibit Matrix Protein Expression

Calreticulin regulates hepatic stellate cell activation through modulating TGF-beta-induced Smad signaling

Liver fibrosis is characterized by excessive deposition of extracellular matrix (ECM) as a wound healing process. Activated hepatic stellate cells (HpSCs) are the major producer of the ECM and play a central role in liver fibrogenesis. It has been widely accepted that elimination of activated HpSCs or reversion to a quiescent state can be a feasible strategy for resolving the disease, further highlighting the urgent need for novel therapeutic targets. Calreticulin (CRT) is a molecular chaperone that normally resides in the endoplasmic reticulum (ER), important in protein folding and trafficking through the secretory pathway. CRT also plays a critical role in calcium (Ca2+) homeostasis, with its Ca2+ storage capacity. In the current study, we aimed to demonstrate its function in directing HpSC activation. In a mouse liver injury model, CRT was up-regulated in HpSCs. In cellular experiments, we further showed that this activation was through modulating the canonical TGF-β signaling. As down-regulation of CRT in HpSCs elevated intracellular Ca2+ levels through a form of Ca2+ influx, named store-operated Ca2+ entry (SOCE), we examined whether moderating SOCE affected TGF-β signaling. Interestingly, blocking SOCE had little effect on TGF-β-induced gene expression. In contrast, inhibition of ER Ca2+ release using the inositol trisphosphate receptor inhibitor 2-APB increased TGF-β signaling. Treatment with 2-APB did not alter SOCE but decreased intracellular Ca2+ at the basal level. Indeed, adjusting Ca2+ concentrations by EGTA or BAPTA-AM chelation further enhanced TGF-β-induced signaling. Our results suggest a crucial role of CRT in the liver fibrogenic process through modulating Ca2+ concentrations and TGF-β signaling in HpSCs, which may provide new information and help advance the current discoveries for liver fibrosis.

Calcium signalling and transport in the kidney

The kidney plays a pivotal role in regulating calcium levels within the body. Approximately 98% of the filtered calcium is reabsorbed in the nephron, and this process is tightly controlled to maintain calcium homeostasis, which is required to facilitate optimal bone mineralization, preserve serum calcium levels within a narrow range, and support intracellular signalling mechanisms. The maintenance of these functions is attributed to a delicate balance achieved by various calcium channels, transporters, and calcium-binding proteins in renal cells. Perturbation of this balance due to deficiency or dysfunction of calcium channels and calcium-binding proteins can lead to severe complications. For example, polycystic kidney disease is linked to aberrant calcium transport and signalling. Furthermore, dysregulation of calcium levels can promote the formation of kidney stones. This Review provides an updated description of the key aspects of calcium handling in the kidney, focusing on the function of various calcium channels and the physiological stimuli that control these channels or are communicated through them. A discussion of the role of calcium as an intracellular second messenger and the pathophysiology of renal calcium dysregulation, as well as a summary of gaps in knowledge and future prospects, are also included.

Microbial imidazole propionate affects glomerular filtration rate in patients with diabetic nephropathy through association with HSP90α

Imidazole propionate (ImP) is a detrimental metabolite produced by the fermentation of histidine intermediates via the intestinal flora. Here, the untargeted metabolite analysis of plasma metabolites from patients with diabetic nephropathy (DN), in combination with the Human Metabolome Database, revealed significantly increased levels of ImP in patients with DN, with a positive correlation with patients' blood creatinine concentration and urinary albumin-to-creatinine ratio, and a negative correlation with the glomerular filtration rate. RNA-seq was applied to detect the effects of ImP on renal tissue transcriptome in mice with DN. It demonstrated that ImP exacerbated renal injury in mice with DN and promoted renal tubular epithelial-mesenchymal transition (EMT), leading to renal mesenchymal fibrosis and renal impairment. Furthermore, ImP was found to directly target HAP90α and activate the PI3K-Akt signalling pathway, which is involved in EMT, by the drug affinity response target stability method. The findings showed that ImP may provide a novel target for DN quality, as it can directly bind to and activate HSP90, thereby facilitating the development of DN while acting as a potential indicator for the clinical diagnosis of DN.

Nanomedicines for the management of diabetic nephropathy: present progress and prospects

Diabetic nephropathy (DN) is a serious microvascular consequence of diabetes mellitus (DM), posing an encumbrance to public health worldwide. Control over the onset and progress of DN depend heavily on early detection and effective treatment. DN is a major contributor to end-stage renal disease, and a complete cure is yet to be achieved with currently available options. Though some therapeutic molecules have exhibited promise in treating DN complications, their poor solubility profile, low bioavailability, poor permeation, high therapeutic dose and associated toxicity, and low patient compliance apprehend their clinical usefulness. Recent research has indicated nano-systems as potential theranostic platforms displaying futuristic promise in the diagnosis and treatment of DN. Early and accurate diagnosis, site-specific delivery and retention by virtue of ligand conjugation, and improved pharmacokinetic profile are amongst the major advantages of nano-platforms, defining their superiority. Thus, the emergence of nanoparticles has offered fresh approaches to the possible diagnostic and therapeutic strategies regarding DN. The present review corroborates an updated overview of different types of nanocarriers regarding potential approaches for the diagnosis and therapy of DN.

CircRNA_0017076 acts as a sponge for miR-185-5p in the control of epithelial-to-mesenchymal transition of tubular epithelial cells during renal interstitial fibrosis

Renal interstitial fibrosis (RIF) is a common pathological hallmark of progressive chronic kidney disease (CKD). Circular RNAs (circRNAs) are involved in certain renal diseases, but their role in RIF is largely unknown. The present study investigated the effects and potential mechanisms of circRNA_0017076 in RIF. CircRNA_0017076 expression was markedly upregulated in transforming growth factor-β1 (TGF-β1)-treated renal tubular epithelial cells (RTECs) and kidney biopsy samples from patients with RIF. Functional assays showed that circRNA_0017076 colocalized with microRNA-185-5p (miR-185-5p) and inhibited miR-185-5p function via direct binding to miR-185-5p. In vitro, the knockdown of circRNA_0017076 inhibited the calcium ion (Ca²⁺) influx-mediated epithelial-to-mesenchymal transition (EMT) of RTECs and downregulated the expression of stromal interaction molecule 1 (STIM1), which is a target protein of miR-185-5p. Silencing mmu_circ_0004488 reduced fibrotic lesions in the kidneys of unilateral ureteral obstruction (UUO) mice by targeting the miR-185-5p/Stim1 axis. For the first time, we identified circRNA_0017076 as a sponge for miR-185-5p, which regulates STIM1 gene expression and is involved in RIF. Our results support circRNA_0017076 as a potential therapeutic target for RIF disease.

Ion channels and channelopathies in glomeruli

An essential step in renal function entails the formation of an ultrafiltrate that is delivered to the renal tubules for subsequent processing. This process, known as glomerular filtration, is controlled by intrinsic regulatory systems and by paracrine, neuronal, and endocrine signals that converge onto glomerular cells. In addition, the characteristics of glomerular fluid flow, such as the glomerular filtration rate and the glomerular filtration fraction, play an important role in determining blood flow to the rest of the kidney. Consequently, disease processes that initially affect glomeruli are the most likely to lead to end-stage kidney failure. The cells that comprise the glomerular filter, especially podocytes and mesangial cells, express many different types of ion channels that regulate intrinsic aspects of cell function and cellular responses to the local environment, such as changes in glomerular capillary pressure. Dysregulation of glomerular ion channels, such as changes in TRPC6, can lead to devastating glomerular diseases, and a number of channels, including TRPC6, TRPC5, and various ionotropic receptors, are promising targets for drug development. This review discusses glomerular structure and glomerular disease processes. It also describes the types of plasma membrane ion channels that have been identified in glomerular cells, the physiological and pathophysiological contexts in which they operate, and the pathways by which they are regulated and dysregulated. The contributions of these channels to glomerular disease processes, such as focal segmental glomerulosclerosis (FSGS) and diabetic nephropathy, as well as the development of drugs that target these channels are also discussed.

Store-operated Ca2+ channel signaling: Novel mechanism for podocyte injury in kidney disease

Studies over the last decade have markedly broadened our understanding of store-operated Ca2+ channels (SOCs) and their roles in kidney diseases and podocyte dysfunction. Podocytes are terminally differentiated glomerular visceral epithelial cells which are tightly attached to the glomerular capillary basement membrane. Podocytes and their unique foot processes (pedicels) constitute the outer layer of the glomerular filtration membrane and the final barrier preventing filtration of albumin and other plasma proteins. Diabetic nephropathy and other renal diseases are associated with podocyte injury and proteinuria. Recent evidence demonstrates a pivotal role of store-operated Ca2+ entry (SOCE) in maintaining structural and functional integrity of podocytes. This article reviews the current knowledge of SOCE and its contributions to podocyte physiology. Recent studies of the contributions of SOC dysfunction to podocyte injury in both cell culture and animal models are discussed, including work in our laboratory. Several downstream signaling pathways mediating SOC function in podocytes also are examined. Understanding the pivotal roles of SOC in podocyte health and disease is essential, as SOCE-activated signaling pathways are potential treatment targets for podocyte injury-related kidney diseases.

Ion channels as a therapeutic target for renal fibrosis

Renal ion channel transport and electrolyte disturbances play an important role in the process of functional impairment and fibrosis in the kidney. It is well known that there are limited effective drugs for the treatment of renal fibrosis, and since a large number of ion channels are involved in the renal fibrosis process, understanding the mechanisms of ion channel transport and the complex network of signaling cascades between them is essential to identify potential therapeutic approaches to slow down renal fibrosis. This review summarizes the current work of ion channels in renal fibrosis. We pay close attention to the effect of cystic fibrosis transmembrane conductance regulator (CFTR), transmembrane Member 16A (TMEM16A) and other Cl− channel mediated signaling pathways and ion concentrations on fibrosis, as well as the various complex mechanisms for the action of Ca2+ handling channels including Ca2+-release-activated Ca2+ channel (CRAC), purinergic receptor, and transient receptor potential (TRP) channels. Furthermore, we also focus on the contribution of Na+ transport such as epithelial sodium channel (ENaC), Na+, K+-ATPase, Na+-H+ exchangers, and K+ channels like Ca2+-activated K+ channels, voltage-dependent K+ channel, ATP-sensitive K+ channels on renal fibrosis. Proposed potential therapeutic approaches through further dissection of these mechanisms may provide new therapeutic opportunities to reduce the burden of chronic kidney disease.

Pathophysiology of mesangial expansion in diabetic nephropathy: mesangial structure, glomerular biomechanics, and biochemical signaling and regulation

Diabetic nephropathy, a kidney complication arising from diabetes, is the leading cause of death in diabetic patients. Unabated, the growing epidemic of diabetes is increasing instances of diabetic nephropathy. Although the main causes of diabetic nephropathy have been determined, the mechanisms of their combined effects on cellular and tissue function are not fully established. One of many damages of diabetic nephropathy is the development of fibrosis within the kidneys, termed mesangial expansion. Mesangial expansion is an important structural lesion that is characterized by the aberrant proliferation of mesangial cells and excess production of matrix proteins. Mesangial expansion is involved in the progression of kidney failure in diabetic nephropathy, yet its causes and mechanism of impact on kidney function are not well defined. Here, we review the literature on the causes of mesangial expansion and its impacts on cell and tissue function. We highlight the gaps that still remain and the potential areas where bioengineering studies can bring insight to mesangial expansion in diabetic nephropathy.

Enhanced Orai1-mediated store-operated Ca2+ channel/calpain signaling contributes to high glucose-induced podocyte injury

Podocyte injury induced by hyperglycemia is the main cause of kidney dysfunction in diabetic nephropathy. However, the underlying mechanism is unclear. Store-operated Ca2+ entry (SOCE) regulates a diversity of cellular processes in a variety of cell types. Calpain, a Ca2+-dependent cysteine protease, was recently shown to be involved in podocyte injury. In the present study, we sought to determine whether increased SOCE contributed to high glucose (HG)-induced podocyte injury through activation of the calpain pathway. In cultured human podocytes, whole-cell patch clamp indicated the presence of functional store-operated Ca2+ channels, which are composed of Orai1 proteins and mediate SOCE. Western blots showed that HG treatment increased the protein abundance of Orai1 in a dose-dependent manner. Consistently, calcium imaging experiments revealed that SOCE was significantly enhanced in podocytes following HG treatment. Furthermore, HG treatment caused overt podocyte F-actin disorganization as well as a significant decrease in nephrin protein abundance, both of which are indications of podocyte injury. These podocyte injury responses were significantly blunted by both pharmacological inhibition of Orai1 using the small molecule inhibitor BTP2 or by genetic deletion of Orai1 using CRISPR-Cas9 lentivirus. Moreover, activation of SOCE by thapsigargin, an inhibitor of Ca2+ pump on the endoplasmic/sarcoplasmic reticulum membrane, significantly increased the activity of calpain, which was inhibited by BTP2. Finally, the calpain-1/calpain-2 inhibitor calpeptin significantly blunted the nephrin protein reduction induced by HG treatment. Taken together, our results suggest that enhanced signaling via an Orai1/SOCE/Calpain axis contributes to HG-induced podocyte injury.

Insulin-activated store-operated Ca2+ entry via Orai1 induces podocyte actin remodeling and causes proteinuria

Podocyte, the gatekeeper of the glomerular filtration barrier, is a primary target for growth factor and Ca²⁺ signaling whose perturbation leads to proteinuria. However, the effects of insulin action on store-operated Ca²⁺ entry (SOCE) in podocytes remain unknown. Here, we demonstrated that insulin stimulates SOCE by VAMP2-dependent Orai1 trafficking to the plasma membrane. Insulin-activated SOCE triggers actin remodeling and transepithelial albumin leakage via the Ca²⁺-calcineurin pathway in podocytes. Transgenic Orai1 overexpression in mice causes podocyte fusion and impaired glomerular filtration barrier. Conversely, podocyte-specific Orai1 deletion prevents insulin-stimulated SOCE, synaptopodin depletion, and proteinuria. Podocyte injury and albuminuria coincide with Orai1 upregulation at the hyperinsulinemic stage in diabetic (db/db) mice, which can be ameliorated by the suppression of Orai1-calcineurin signaling. Our results suggest that tightly balanced insulin action targeting podocyte Orai1 is critical for maintaining filter integrity, which provides novel perspectives on therapeutic strategies for proteinuric diseases, including diabetic nephropathy.

Perturbations of Ca²⁺ signaling in podocytes may deteriorate kidney function and eventually lead to proteinuria. Here the authors show that insulin can affect the function of the calcium regulator Ora1 in podocytes, which is critical for maintaining kidney filter integrity.

The Attenuation of Diabetic Nephropathy by Annexin A1 via Regulation of Lipid Metabolism Through the AMPK/PPARα/CPT1b Pathway

Inflammation and abnormal metabolism play important roles in the pathogenesis of diabetic nephropathy (DN). Annexin A1 (ANXA1) contributes to inflammation resolution and improves metabolism. In this study, we assess the effects of ANXA1 in diabetic mice and proximal tubular epithelial cells (PTECs) treated with high glucose plus palmitate acid (HGPA) and explore the association of ANXA1 with lipid accumulation in patients with DN. It is found that ANXA1 deletion aggravates renal injuries, including albuminuria, mesangial matrix expansion, and tubulointerstitial lesions in high-fat diet/streptozotocin-induced diabetic mice. ANXA1 deficiency promotes intrarenal lipid accumulation and drives mitochondrial alterations in kidneys. In addition, Ac2-26, an ANXA1 mimetic peptide, has a therapeutic effect against lipid toxicity in diabetic mice. In HGPA-treated human PTECs, ANXA1 silencing causes FPR2/ALX-driven deleterious effects, which suppress phosphorylated Thr¹⁷² AMPK, resulting in decreased peroxisome proliferator-activated receptor α and carnitine palmitoyltransferase 1b expression and increased HGPA-induced lipid accumulation, apoptosis, and elevated expression of proinflammatory and profibrotic genes. Last but not least, the extent of lipid accumulation correlates with renal function, and the level of tubulointerstitial ANXA1 expression correlates with ectopic lipid deposition in kidneys of patients with DN. These data demonstrate that ANXA1 regulates lipid metabolism of PTECs to ameliorate disease progression; hence, it holds great potential as a therapeutic target for DN.

Annexin A1 alleviates kidney injury by promoting the resolution of inflammation in diabetic nephropathy

Since failed resolution of inflammation is a major contributor to the progression of diabetic nephropathy, identifying endogenously generated molecules that promote the physiological resolution of inflammation may be a promising therapeutic approach for this disease. Annexin A1 (ANXA1), as an endogenous mediator, plays an important role in resolving inflammation. Whether ANXA1 could affect established diabetic nephropathy through modulating inflammatory states remains largely unknown. In the current study, we found that in patients with diabetic nephropathy, the levels of ANXA1 were upregulated in kidneys, and correlated with kidney function as well as kidney outcomes. Therefore, the role of endogenous ANXA1 in mouse models of diabetic nephropathy was further evaluated. ANXA1 deficiency exacerbated kidney injuries, exhibiting more severe albuminuria, mesangial matrix expansion, tubulointerstitial lesions, kidney inflammation and fibrosis in high fat diet/streptozotocin-induced-diabetic mice. Consistently, ANXA1 overexpression ameliorated kidney injuries in mice with diabetic nephropathy. Additionally, we found Ac2-26 (an ANXA1 mimetic peptide) had therapeutic potential for alleviating kidney injuries in db/db mice and diabetic Anxa1 knockout mice. Mechanistic studies demonstrated that intracellular ANXA1 bound to the transcription factor NF-κB p65 subunit, inhibiting its activation thereby modulating the inflammatory state. Thus, our data indicate that ANXA1 may be a promising therapeutic approach to treating and reversing diabetic nephropathy.

SHROOM3, the gene associated with chronic kidney disease, affects the podocyte structure

Chronic kidney disease is a public health burden and it remains unknown which genetic loci are associated with kidney function in the Japanese population, our genome-wide association study using the Biobank Japan dataset (excluding secondary kidney diseases, such as diabetes mellitus) clearly revealed that almost half of the top 50 single nucleotide polymorphisms associated with estimated glomerular filtration rate are located in the SHROOM3 gene, suggesting that SHROOM3 will be responsible for kidney function. Thus, to confirm this finding, supportive functional analyses were performed on Shroom3 in mice using fullerene-based siRNA delivery, which demonstrated that Shroom3 knockdown led to albuminuria and podocyte foot process effacement. The in vitro experiment shows that knockdown of Shroom3 caused defective formation of lamellipodia in podocyte, which would lead to the disruption of slit diaphragm. These results from the GWAS, in vivo and in vitro experiment were consistent with recent studies reporting that albuminuria leads to impairment of kidney function.

Store-operated calcium entry: Pivotal roles in renal physiology and pathophysiology

Research conducted over the last two decades has dramatically advanced the understanding of store-operated calcium channels (SOCC) and their impact on renal function. Kidneys contain many types of cells, including those specialized for glomerular filtration (fenestrated capillary endothelium, podocytes), water and solute transport (tubular epithelium), and regulation of glomerular filtration and renal blood flow (vascular smooth muscle cells, mesangial cells). The highly integrated function of these myriad cells effects renal control of blood pressure, extracellular fluid volume and osmolality, electrolyte balance, and acid-base homeostasis. Many of these cells are regulated by Ca²⁺ signaling. Recent evidence demonstrates that SOCCs are major Ca²⁺ entry portals in several renal cell types. SOCC is activated by depletion of Ca²⁺ stores in the sarco/endoplasmic reticulum, which communicates with plasma membrane SOCC via the Ca²⁺ sensor Stromal Interaction Molecule 1 (STIM1). Orai1 is recognized as the main pore-forming subunit of SOCC in the plasma membrane. Orai proteins alone can form highly Ca²⁺ selective SOCC channels. Also, members of the Transient Receptor Potential Canonical (TRPC) channel family are proposed to form heteromeric complexes with Orai1 subunits, forming SOCC with low Ca²⁺ selectivity. Recently, Ca²⁺ entry through SOCC, known as store-operated Ca²⁺ entry (SOCE), was identified in glomerular mesangial cells, tubular epithelium, and renovascular smooth muscle cells. The physiological and pathological relevance and the characterization of SOCC complexes in those cells are still unclear. In this review, we summarize the current knowledge of SOCC and their roles in renal glomerular, tubular and vascular cells, including studies from our laboratory, emphasizing SOCE regulation of fibrotic protein deposition. Understanding the diverse roles of SOCE in different renal cell types is essential, as SOCC and its signaling pathways are emerging targets for treatment of SOCE-related diseases.

Trimetazidine Inhibits Renal Tubular Epithelial Cells to Mesenchymal Transition in Diabetic Rats via Upregulation of Sirt1

Trimetazidine (TMZ), as a metabolic regulator, is effective in treatment of coronary atherosclerotic heart disease with rare side effects in the clinic for long years. Interestingly, studies have shown that TMZ protects against several acute kidney injuries (AKI). However, the effect of TMZ on chronic kidney diseases (CKD) remains unknown. This study aimed to investigate the role of TMZ in diabetic nephropathy (DN) and its potential mechanisms. A rat model of DN was established in male Sprague-Dawley rats by streptozotocin (STZ) intraperitoneal injection. Experimental rats were separated into three groups: control, DN and DN + TMZ treatment. Metabolic parameters, pathological features and renal function markers were evaluated after 20 weeks of diabetes induction. In vitro experiments, the effect of TMZ on high fat and high glucose (HFG) induced or TGFβ1-induced epithelial-to-mesenchymal transition (EMT) was examined in HK-2 cells. Our results showed that TMZ could maintain renal function without affecting hemodynamic and plasma metabolic levels in diabetic rats. The effect was associated with a reversion of pathological progression of DN, especially for tubulointerstitial fibrosis. EMT is an important contributor to renal fibrosis. In this study, we investigated the role of TMZ in the process of EMT in DN. Mechanistically; TMZ attenuated HFG-induced EMT by relieving oxidative stress via deacetylation forkhead box O1 (FoxO1) in a Sirt1-dependent pathway. And it suppressed TGFβ1-induced EMT by deacetylating Smd4 in a Sirt1-dependent manner. Moreover, our study found that TMZ upregulated Sirt1 expression by increasing the expression of nicotinamide phosphoribosyl transferase (Nampt), which is a rate limiting enzyme for nicotinamide adenine dinucleotide (NAD⁺) generation by salvage pathway. And the increased NAD⁺ promoted Sirt1 expression. In conclusion, TMZ can prevent renal dysfunction and pathogenesis of tubulointerstitial fibrosis in DN, partly by inhibition of EMT via FoxO1/ROS pathway and TGFβ/Smad pathway in a Nampt/NAD⁺/Sirt1 dependent manner.

Stimulation of ORAI1 expression, store-operated Ca2+ entry, and osteogenic signaling by high glucose exposure of human aortic smooth muscle cells

Diabetes and chronic kidney disease (CKD) both trigger vascular osteogenic signaling and calcification leading to early death by cardiovascular events. Osteogenic signaling involves upregulation of the transcription factors CBFA1, MSX2, and SOX9, as well as alkaline phosphatase (ALP), an enzyme fostering calcification by degrading the calcification inhibitor pyrophosphate. In CKD, osteogenic signaling is triggered by hyperphosphatemia, which upregulates the serum and glucocorticoid-inducible kinase SGK1, a strong stimulator of the Ca²⁺-channel ORAI1. The channel is activated by STIM1 and accomplishes store-operated Ca²⁺-entry (SOCE). The present study explored whether exposure of human aortic smooth muscle cells (HAoSMCs) to high extracellular glucose concentrations similarly upregulates ORAI1 and/or STIM1 expression, SOCE, and osteogenic signaling. To this end, HAoSMCs were exposed to high extracellular glucose concentrations (15 mM, 24 h) without or with additional exposure to the phosphate donor ß-glycerophosphate. Transcript levels were estimated using qRT-PCR, protein abundance using Western blotting, ALP activity using a colorimetric assay kit, calcium deposits utilizing Alizarin red staining, cytosolic Ca²⁺-concentration ([Ca²⁺]_i) by Fura-2-fluorescence, and SOCE from increase of [Ca²⁺]_i following re-addition of extracellular Ca²⁺ after store depletion with thapsigargin (1 μM). As a result, glucose enhanced the transcript levels of SGK1 and ORAI1, ORAI2, and STIM2, protein abundance of ORAI1, SOCE, the transcript levels of CBFA1, MSX2, SOX9, and ALPL, as well as calcium deposits. Moreover, glucose significantly augmented the stimulating effect of ß-glycerophosphate on transcript levels of SGK1 and ORAI1, SOCE, the transcript levels of osteogenic markers, as well as calcium deposits. ORAI1 inhibitor MRS1845 (10 μM) significantly blunted the glucose-induced upregulation of the CBFA1 and MSX2 transcript levels. In conclusion, the hyperglycemia of diabetes stimulates expression of SGK1 and ORAI1, thus, augmenting store-operated Ca²⁺-entry and osteogenic signaling in HAoSMCs.

Inhibition of interleukin-6 on matrix protein production by glomerular mesangial cells and the pathway involved

Activation of immunological pathways and disturbances of extracellular matrix (ECM) dynamics are important contributors to the pathogenesis of chronic kidney diseases. Glomerular mesangial cells (MCs) are critical for homeostasis of glomerular ECM dynamics. Interleukin-6 (IL-6) can act as a pro/anti-inflammatory agent relative to cell types and conditions. This study investigated whether IL-6 influences ECM protein production by MCs and the regulatory pathways involved. Experiments were carried out in cultured human MCs (HMCs) and in mice. We found that overexpression of IL-6 and its receptor decreased the abundance of fibronectin and collagen type IV in MCs. ELISA and immunoblot analysis demonstrated that thapsigargin [an activator of store-operated Ca²⁺ entry (SOCE)], but not the endoplasmic reticulum stress inducer tunicamycin, significantly increased IL-6 content. This thapsigargin effect was abolished by GSK-7975A, a selective inhibitor of SOCE, and by silencing Orai1 (the channel protein mediating SOCE). Furthermore, inhibition of NF-κB pharmacologically and genetically significantly reduced SOCE-induced IL-6 production. Thapsigargin also stimulated nuclear translocation of the p65 subunit of NF-κB. Moreover, MCs overexpressing IL-6 and its receptor in HMCs increased the content of the glucagon-like peptide-1 receptor (GLP-1R), and IL-6 inhibition of fibronectin was attenuated by the GLP-1R antagonist exendin 9-39. In agreement with the HMC data, specific knockdown of Orai1 in MCs using the targeted nanoparticle delivery system in mice significantly reduced glomerular GLP-1R levels. Taken together, our results suggest a novel SOCE/NF-κB/IL-6/GLP-1R signaling pathway that inhibits ECM protein production by MCs.

Inhibitor of myogenic differentiation family isoform a, a new positive regulator of fibronectin production by glomerular mesangial cells

Overproduction of extracellular matrix proteins, including fibronectin by mesangial cells (MCs), contributes to diabetic nephropathy. Inhibitor of myogenic differentiation family isoform a (I-mfa) is a multifunctional cytosolic protein functioning as a transcriptional modulator or plasma channel protein regulator. However, its renal effects are unknown. The present study was conducted to determine whether I-mfa regulated fibronectin production by glomerular MCs. In human MCs, overexpression of I-mfa significantly increased fibronectin abundance. Silencing I-mfa significantly reduced the level of fibronectin mRNA and blunted transforming growth factor-β1-stimulated production of fibronectin. We further found that high glucose increased I-mfa protein content in a time course (≥48 h) and concentration (≥25 mM)-dependent manner. Although high glucose exposure increased I-mfa at the protein level, it did not significantly alter transcripts of I-mfa in MCs. Furthermore, the abundance of I-mfa protein was significantly increased in the renal cortex of rats with diabetic nephropathy. The I-mfa protein level was also elevated in the glomerulus of mice with diabetic kidney disease. However, there was no significant difference in glomerular I-mfa mRNA levels between mice with and without diabetic nephropathy. Moreover, H2O2 significantly increased I-mfa protein abundance in a dose-dependent manner in cultured human MCs. The antioxidants polyethylene glycol-catalase, ammonium pyrrolidithiocarbamate, and N-acetylcysteine significantly blocked the high glucose-induced increase of I-mfa protein. Taken together, our results suggest that I-mfa, increased by high glucose/diabetes through the production of reactive oxygen species, stimulates fibronectin production by MCs.

Recent advances in nanotechnology-based drug delivery systems for the kidney

The application of nanotechnology in medicine has the potential to make a great impact on human health, ranging from prevention to diagnosis and treatment of disease. The kidneys are the main organ of the human urinary system, responsible for filtering the blood, and concentrating metabolic waste into urine by means of the renal glomerulus. The glomerular filtration apparatus presents a barrier against therapeutic agents based on charge and/or molecular size. Therefore, drug delivery to the kidneys faces significant difficulties resulting in treatment failure in several renal disorders. Accordingly, different strategies have recently being explored for enhancing the delivery of therapeutic agents across the filtration barrier of the glomerulus. Nanosystems with different physicochemical properties, including size, shape, surface, charge, and possessing biological features such as high cellular internalization, low cytotoxicity, controllable pharmacokinetics and biodistribution, have shown promising results for renal therapy. Different types of nanoparticles (NPs) have been used to deliver drugs to the kidney. In this review, we discuss nanotechnology-based drug delivery approaches for acute kidney injury, chronic kidney disease, renal fibrosis, renovascular hypertension and kidney cancer.

Knockdown of ANGPTL-4 inhibits inflammatory response and extracellular matrix accumulation in glomerular mesangial cells cultured under high glucose condition

Diabetic nephropathy (DN) is one of the major diabetic complications that lead to end-stage renal failure. Angiopoietin-like protein-4 (ANGPTL-4) has been reported to be dysregulated in diabetes mellitus and diabetic complications. However, the role of ANGPTL-4 in glomerular mesangial cells (MCs) during DN remains unclear. In the present study, we evaluated the role of ANGPTL-4 in MCs in response to high glucose (HG) condition and the potential mechanism. The results proved that ANGPTL-4 expression is significantly increased in HG-stimulated MCs. Knockdown of ANGPTL-4 suppressed HG-induced cell proliferation of MCs. The production of pro-inflammatory cytokines including TNF-α, IL-1β, IL-6 were decreased in ANGPTL-4 knocked down MCs. Inhibition of ANGPTL-4 markedly suppressed the expressions of extracellular matrix (ECM) proteins, collagen IV (Col IV) and fibronectin (FN), in HG-stimulated MCs. Furthermore, ANGPTL-4 knockdown inhibited the HG-induced activation of NF-κB signaling pathway in MCs. Collectively, knockdown of ANGPTL-4 suppressed HG-induced cell proliferation, inflammatory response, and ECM accumulation inhibiting NF-κB signaling pathway in MCs. These findings suggested that ANGPTL-4 might be a therapeutic target for the prevention and treatment of DN.

Glucagon-like peptide-1 receptor pathway inhibits extracellular matrix production by mesangial cells through store-operated Ca2+ channel

Glomerular mesangial cell is the major source of mesangial matrix. Our previous study demonstrated that store-operated Ca2+ channel signaling suppressed extracellular matrix protein production by mesangial cells. Recent studies demonstrated that glucagon-like peptide-1 receptor (GLP-1R) pathway had renoprotective effects. However, the underlying mechanism(s) remains unclear. The present study was aimed to determine if activation of GLP-1R decreased extracellular matrix protein production by mesangial cells through upregulation of store-operated Ca2+ function. Experiments were conducted in cultured human mesangial cells. Liraglutide and exendin 9–39 were used to activate and inhibit GLP-1R, respectively. Store-operated Ca2+ function was estimated by evaluating the SOC-mediated Ca2+ entry (SOCE). We found that liraglutide treatment reduced high glucose-stimulated production of fibronectin and collagen IV. The inhibitory effects of liraglutide were not observed in the presence of exendin 9–39. Exendin-4, another GLP-1R agonist also blunted high glucose-stimulated fibronectin and collagen IV production. Treatment of human mesangial cells with liraglutide for 24 h significantly attenuated the high glucose-induced reduction of Orai1 protein. Consistently, Ca2+ imaging experiments showed that the inhibition of high glucose on SOCE was significantly attenuated by liraglutide. However, in the presence of exendin 9–39, liraglutide failed to reverse the high glucose effect. Furthermore, liraglutide effects on fibronectin and collagen IV protein abundance were significantly attenuated by GSK-7975A, a selective blocker of store-operated Ca2+. Taken together, our findings suggest that GLP-1R signaling inhibited high glucose-induced extracellular matrix protein production in mesangial cells by restoring store-operated Ca2+ function.

Impact statement

Diabetic kidney disease continues to be a major challenge to health care system in the world. There are no known therapies currently available that can cure the disease. The present study provided compelling evidence that activation of GLP-1R inhibited extracellular matrix protein production by glomerular mesangial cells. We further showed that the beneficial effect of GLP-1R was attributed to upregulation of store-operated Ca2+ channel function. Therefore, we identified a novel mechanism contributing to the renal protective effects of GLP-1R pathway. Activation of GLP-1R pathway and/or store-operated Ca2+ channel signaling in MCs could be an option for patients with diabetic kidney disease.

Multiple-microarray analysis for identification of hub genes involved in tubulointerstial injury in diabetic nephropathy

Diabetic nephropathy (DN) is a primary cause of renal failure. However, studies providing renal gene expression profiles of diabetic tubulointerstitial injury are scarce and its molecular mechanisms still await clarification. To identify vital genes involved in the diabetic tubulointerstitial injury, three microarray data sets from gene expression omnibus (GEO) were downloaded. A total of 127 differentially expressed genes (DEGs) were identified by limma package. Gene set enrichment analysis (GSEA) plots showed that sister chromatid cohesion was the most significant enriched gene set positively correlated with the DN group while retinoid X receptor binding was the most significant enriched gene set positively correlated with the control group. Enriched Gene Ontology (GO) annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of DEGs mostly included extracellular matrix organization, extracellular space, extracellular matrix structural constituent, and Staphylococcus aureus infection. Twenty hub genes from three significant modules were ascertained by Cytoscape. Correlation analysis and subgroup analysis between hub genes and clinical features of DN showed that ALB, ANXA1, APOH, C3, CCL19, COL1A2, COL3A1, COL4A1, COL6A3, CXCL6, DCN, EGF, HRG, KNG1, LUM, SERPINA3, SPARC, SRGN, and TIMP1 may involve in diabetic tubulointerstitial injury. ConnectivityMap analysis indicated the most significant three compounds are 5182598, thapsigargin and 5224221. In conclusion, this study may provide new insights into the molecular mechanisms underlying diabetic tubulointerstitial injury as well as potential targets for diagnosis and therapeutics of DN.

The Osteogenic Niche Is a Calcium Reservoir of Bone Micrometastases and Confers Unexpected Therapeutic Vulnerability

The fate of disseminated tumor cells is largely determined by microenvironment (ME) niche. The osteogenic niche promotes cancer cell proliferation and bone metastasis progression. We investigated the underlying mechanisms using pre-clinical models and analyses of clinical data. We discovered that the osteogenic niche serves as a calcium (Ca) reservoir for cancer cells through gap junctions. Cancer cells cannot efficiently absorb Ca from ME, but depend on osteogenic cells to increase intracellular Ca concentration. The Ca signaling, together with previously identified mammalian target of rapamycin signaling, promotes bone metastasis progression. Interestingly, effective inhibition of these pathways can be achieved by danusertib, or a combination of everolimus and arsenic trioxide, which provide possibilities of eliminating bone micrometastases using clinically established drugs.

Silencing of PAQR3 suppresses extracellular matrix accumulation in high glucose-stimulated human glomerular mesangial cells via PI3K/AKT signaling pathway

Progestin and AdipoQ Receptor 3 (PAQR3), a member of the PAQR family, was involved in multiple biological processes, including tumorigenesis, cholesterol homeostasis, autophagy, obesity, insulin sensitivity and energy metabolism. However, the role of PAQR3 in diabetic nephropathy is still unclear. Therefore, in this study, we investigated the effects of PAQR3 on cell proliferation and extracellular matrix (ECM) accumulation in human glomerular mesangial cells (MCs) cultured under high glucose (HG), and explored the underlying mechanism. Our results demonstrated that HG significantly up-regulated the expression of PAQR3 in human MCs. In addition, knockdown of PAQR3 efficiently suppressed MC proliferation and ECM production in HG-stimulated MCs. Furthermore, knockdown of PAQR3 markedly reversed HG-induced PI3K/AKT activation in MCs. In summary, our present study demonstrated that knockdown of PAQR3 suppressed HG-induced the proliferation and ECM accumulation in human MCs, via inhibiting the PI3K/AKT signaling pathway. Thus, PAQR3 may be a potential therapeutic target for the treatment of diabetic nephropathy.

Effect of autophagy and stromal interaction molecule 1 on podocyte epithelial-mesenchymal transition in diabetic nephropathy

AIM

We aimed to assess the effect of autophagy and stromal interaction molecule 1 (STIM1) on podocyte epithelial-mesenchymal transition in diabetic nephropathy.

METHODS

The sera of 8-week-old db/db and C57BL/KsJ rats were used to culture MPC5 cells. The experiment was divided into 4 groups: MPC5 + siRNA-Scr + 10% C57BL/KsJ (Group A), MPC5 + siRNA-STIM1 + 10% C57BL/KsJ (Group B), MPC5 + siRNA-Scr + 10% db/db (Group C), and MPC5 + siRNA-STIM1 + 10% db/db (Group D). Podocyte autophagy was evaluated via immunofluorescence staining for LC3II and P62, and via Western blotting for P62 and LC3 (LC3II/LC3I). Western blotting was also used to assess the expression of TRPC6, Orai1, Beclin-1, Bcl-2, Caspase3, E-cadherin, fibronectin, and α-SMA protein. Furthermore, podocyte apoptosis was assessed via flow cytometry.

RESULTS

We found that, in podocytes cultured in the serum of diabetic nephrotic rats, the autophagy level decreased, whereas the apoptosis level increased, and EMT can be advanced. However, after silencing STIM1 with siRNA, a converse outcome was noted. Furthermore, in diabetic nephropathy rats, the up-regulated expression of podocyte STIM1 can activate TRPC6 and Orai1 channels, which results in Ca²⁺ entry.

CONCLUSIONS

We found that, in podocytes cultured in the serum of diabetic nephrotic rats, the autophagy level increased, whereas the apoptosis level decreased, and EMT can be inhibited by silencing STIM1 with siRNA.

Short-term high-glucose treatment decreased abundance of Orai1 protein through posttranslational mechanisms in rat mesangial cells

The short-term effect of high-glucose (HG) treatment on store-operated Ca²⁺ entry in mesangial cells (MCs) is not well-known. The aim of the present study was to determine whether and how HG treatment for a short period altered protein abundance of Orai1, the channel mediating store-operated Ca²⁺ entry in MCs. Rat and human MCs were exposed to HG (25 mM) for 2, 4, 8, and 24 h, and the abundance of Orai1 protein was significantly decreased at the time points of 8 and 16 h. Consistently, HG treatment for 8 h significantly reduced store-operated Ca²⁺ entry in rat MCs. However, HG treatment for the same time periods did not alter the levels of Orai1 transcript. Cycloheximide, a protein synthesis inhibitor, did not affect the HG-induced decrease of Orai1 protein, suggesting a posttranslational mechanism was involved. However, the HG effect on Orai1 protein was significantly attenuated by MG132 (a ubiquitin-proteasome inhibitor) and NH₄Cl (a lysosomal pathway inhibitor). Furthermore, HG treatment for 8 h stimulated ubiquitination of Orai1 protein. We further found that polyethylene glycol-catalase, an antioxidant, significantly blunted the HG-induced reduction of Orai1 protein. In support of involvement of reactive oxygen species in the HG effects, hydrogen peroxide (H₂O₂) itself significantly decreased abundance of Orai1 protein and increased the level of ubiquitinated Orai1. Taken together, these results suggest that a short-term HG treatment decreased abundance of Orai1 protein in MCs by promoting the protein degradation through the ubiquitination-proteasome and -lysosome mechanisms. This HG-stimulated posttranslational mechanism was mediated by H₂O₂.

Urotensin II-induced store-operated Ca2+ entry contributes to glomerular mesangial cell proliferation and extracellular matrix protein production under high glucose conditions

Glomerular mesangial cell (GMC) proliferation and matrix expansion are pathological hallmarks of a wide range of kidney diseases, including diabetic nephropathy. Although the circulating level of peptide hormone urotensin II (UII) and kidney tissue expression of UII and UII receptors (UTR) are increased in diabetic nephropathy, it remains unclear whether UII regulates GMC growth and extracellular matrix (ECM) accumulation. In this study, we tested the hypothesis that UII-induced Ca²⁺ signaling controls GMC proliferation and ECM production under normal and high glucose conditions. Mouse GMCs cultured under normal glucose conditions proliferated and synthesized ECM proteins in response to stimulation by mouse UII. UII-induced GMC proliferation and ECM protein synthesis were dependent on TRPC4 channel-mediated store-operated Ca²⁺ entry (SOCE) and sequential activation of Ca²⁺/calmodulin-dependent protein kinase II (CaMKII) and Ca²⁺/cAMP response element-binding protein (CREB) transcription factor. Under high glucose conditions, GMCs synthesized UII. Moreover, proliferation and ECM production in high glucose-challenged GMCs were attenuated by selective UTR antagonist, TRPC4 channel blocker, and CaMKII and CREB-binding protein/p300 inhibitors. These findings indicate that UII-induced SOCE via TRPC4 channels stimulates CaMKII/CREB-dependent GMC proliferation and ECM protein production. Our data also suggest that UII synthesis contributes to GMC proliferation and ECM accumulation under high glucose conditions.

Increased glomerular filtration rate and impaired contractile function of mesangial cells in TRPC6 knockout mice

The present study was conducted to determine if TRPC6 regulates glomerular filtration rate (GFR) and the contractile function of glomerular mesangial cells (MCs). GFR was assessed in conscious TRPC6 wild type and knockout mice, and in anesthetized rats with and without in vivo knockdown of TRPC6 in kidneys. We found that GFR was significantly greater, and serum creatinine level was significantly lower in TRPC6 deficient mice. Consistently, local knockdown of TRPC6 in kidney using TRPC6 specific shRNA construct significantly attenuated Ang II-induced GFR decline in rats. Furthermore, Ang II-stimulated contraction and Ca²⁺ entry were significantly suppressed in primary MCs isolated from TRPC6 deficient mice, and the Ca²⁺ response could be rescued by re-introducing TRPC6. Moreover, inhibition of reverse mode of Na⁺-Ca²⁺ exchange by KB-R7943 significantly reduced Ca²⁺ entry response in TRPC6-expressing, but not in TRPC6-knocked down MCs. Ca²⁺ entry response was also significantly attenuated in Na⁺ free solution. Single knockdown of TRPC6 and TRPC1 resulted in a comparable suppression on Ca²⁺ entry with double knockdown of both. These results suggest that TRPC6 may regulate GFR by modulating MC contractile function through multiple Ca²⁺ signaling pathways.

Store-operated calcium entry suppressed the TGF-β1/Smad3 signaling pathway in glomerular mesangial cells

Our previous study demonstrated that the abundance of extracellular matrix proteins was suppressed by store-operated Ca²⁺ entry (SOCE) in mesangial cells (MCs). The present study was conducted to investigate the underlying mechanism focused on the transforming growth factor-β1 (TGF-β1)/Smad3 pathway, a critical pathway for ECM expansion in diabetic kidneys. We hypothesized that SOCE suppressed ECM protein expression by inhibiting this pathway in MCs. In cultured human MCs, we observed that TGF-β1 (5 ng/ml for 15 h) significantly increased Smad3 phosphorylation, as evaluated by immunoblot. However, this response was markedly inhibited by thapsigargin (1 µM), a classical activator of store-operated Ca²⁺ channels. Consistently, both immunocytochemistry and immunoblot showed that TGF-β1 significantly increased nuclear translocation of Smad3, which was prevented by pretreatment with thapsigargin. Importantly, the thapsigargin effect was reversed by lanthanum (La³⁺; 5 µM) and GSK-7975A (10 µM), both of which are selective blockers of store-operated Ca²⁺ channels. Furthermore, knockdown of Orai1, the pore-forming subunit of the store-operated Ca²⁺ channels, significantly augmented TGF-β1-induced Smad3 phosphorylation. Overexpression of Orai1 augmented the inhibitory effect of thapsigargin on TGF-β1-induced phosphorylation of Smad3. In agreement with the data from cultured MCs, in vivo knockdown of Orai1 specific to MCs using a targeted nanoparticle small interfering RNA delivery system resulted in a marked increase in abundance of phosphorylated Smad3 and in nuclear translocation of Smad3 in the glomerulus of mice. Taken together, our results indicate that SOCE in MCs negatively regulates the TGF-β1/Smad3 signaling pathway.

Negative regulation of Smad1 pathway and collagen IV expression by store-operated Ca2+ entry in glomerular mesangial cells

Collagen IV (Col IV) is a major component of expanded glomerular extracellular matrix in diabetic nephropathy and Smad1 is a key molecule regulating Col IV expression in mesangial cells (MCs). The present study was conducted to determine if Smad1 pathway and Col IV protein abundance were regulated by store-operated Ca²⁺ entry (SOCE). In cultured human MCs, pharmacological inhibition of SOCE significantly increased the total amount of Smad1 protein. Activation of SOCE blunted high-glucose-increased Smad1 protein content. Treatment of human MCs with ANG II at 1 µM for 15 min, high glucose for 3 days, or TGF-β1 at 5 ng/ml for 30 min increased the level of phosphorylated Smad1. However, the phosphorylation of Smad1 by those stimuli was significantly attenuated by activation of SOCE. Knocking down Smad1 reduced, but expressing Smad1 increased, the amount of Col IV protein. Furthermore, activation of SOCE significantly attenuated high-glucose-induced Col IV protein production, and blockade of SOCE substantially increased the abundance of Col IV. To further verify those in vitro findings, we downregulated SOCE specifically in MCs in mice using small-interfering RNA (siRNA) against Orai1 (the channel protein mediating SOCE) delivered by the targeted nanoparticle delivery system. Immunohistochemical examinations showed that expression of both Smad1 and Col IV proteins was significantly greater in the glomeruli with positively transfected Orai1 siRNA compared with the glomeruli from the mice without Orai1 siRNA treatment. Taken together, our results indicate that SOCE negatively regulates the Smad1 signaling pathway and inhibits Col IV protein production in MCs.

Large-Conductance Calcium-Activated Potassium Channels in Glomerulus: From Cell Signal Integration to Disease

Large-conductance calcium-activated potassium (BK) channels are currently considered as vital players in a variety of renal physiological processes. In podocytes, BK channels become active in response to stimuli that increase local cytosolic Ca²⁺, possibly secondary to activation of slit diaphragm TRPC6 channels by chemical or mechanical stimuli. Insulin increases filtration barrier permeability through mobilization of BK channels. In mesangial cells, BK channels co-expressed with β1 subunits act as a major component of the counteractive response to contraction in order to regulate glomerular filtration. This review aims to highlight recent discoveries on the localization, physiological and pathological roles of BK channels in glomerulus.

Blockade of Orai1 Store-Operated Calcium Entry Protects against Renal Fibrosis

Evidence supports an important role of Ca²⁺ release-activated Ca²⁺ channel protein 1 (Orai1)-mediated Ca²⁺ entry in the development of renal fibrosis, a common pathologic feature of CKDs that lead to ESRD, but the molecular mechanisms remain unclear. We determined the role of Orai1 calcium channel in renal fibrosis induced by high-fat diet and by unilateral ureteral obstruction. Mouse kidneys with fibrosis had higher levels of Orai1 protein expression than did kidneys without fibrosis. In vivo knockdown of Orai1 with adenovirus harboring Orai1-short hairpin RNA or inhibition of Orai1 with SKF96365 dramatically prevented renal fibrosis and significantly decreased protein expression of fibronectin, α‑smooth muscle actin, and TGF‑β1 in the kidney cortex of ApoE^-/- mice on a high-fat diet and in the obstructed kidneys of mice with unilateral ureteral obstruction. Compared with kidney biopsy specimens of patients with glomerular minimal change disease, those of patients with fibrotic nephropathy had higher expression levels of Orai1. In cultured human proximal tubule epithelial cells (HK2), knockdown of Orai1 Ca²⁺ channel with adenovirus-Orai1-short hairpin RNA markedly inhibited TGF-β1-induced intracellular Ca²⁺ influx and phosphorylation of smad2/3. Knockdown or blockade of the Orai1 Ca²⁺ channel in HK2 cells also prevented epithelial-to-mesenchymal transition induced by TGF‑β1. In conclusion, blockade of the Orai1 Ca²⁺ channel prevented progression of renal fibrosis in mice, likely by suppressing smad2/3 phosphorylation and TGF-β1-induced epithelial-to-mesenchymal transition. These results render the Orai1 Ca²⁺ channel a potential therapeutic target against renal fibrosis.

Store-operated calcium entry and diabetic complications

Store-operated Ca(2+) entry (SOCE) is mediated by the store-operated Ca(2+) channel (SOC) that opens upon depletion of internal Ca(2+) stores following activation of G protein-coupled receptors or receptor tyrosine kinases. Over the past two decades, the physiological and pathological relevance of SOCE has been extensively studied. Recently, accumulating evidence suggests associations of altered SOCE with diabetic complications. This review focuses on the implication of SOCE as it pertains to various complications resulting from diabetes. We summarize recent findings by us and others on the involvement of abnormal SOCE in the development of diabetic complications, such as diabetic nephropathy and diabetic vasculopathy. The underlying mechanisms that mediate the diabetes-associated alterations of SOCE are also discussed. The SOCE pathway may be considered as a potential therapeutic target for diabetes-associated diseases.