The tuberin/mTOR pathway promotes apoptosis of tubular epithelial cells in diabetes

Eupatilin attenuates doxorubicin-induced cardiotoxicity by activating the PI3K-AKT signaling pathway in mice

Eupatilin is a pharmacologically active flavonoid with a variety of biological activities, such as anticancer, anti-inflammatory, antioxidant, neuroprotective, anti-allergic and cardioprotective effects. However, whether eupatilin has protective effects on doxorubicin-induced cardiotoxicity remains unknown. Thus, this study aimed to investigate the role of eupatilin in doxorubicin-induced cardiotoxicity. Mice were exposed to a single dose of doxorubicin (15 mg/kg) to generate doxorubicin-induced cardiotoxicity or normal saline as a control. To explore the protective effects, mice were intraperitoneally injected with eupatilin daily for 7 days. Then, we examined the changes in cardiac function, inflammation, apoptosis, and oxidative stress to evaluate the effects of eupatilin on doxorubicin-induced cardiotoxicity. Additionally, RNA-seq analysis was introduced to explore the potential molecular mechanisms. Eupatilin ameliorated doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and cardiomyocyte apoptosis and ameliorated doxorubicin-induced cardiac dysfunction. Mechanistically, eupatilin activated the PI3K-AKT signaling pathway, as evidenced by RNA-seq analysis and Western blot analysis. This study provides the first evidence that eupatilin ameliorates doxorubicin-induced cardiotoxicity by attenuating inflammation, oxidative stress, and apoptosis. Pharmacotherapy with eupatilin provides a novel therapeutic regimen for doxorubicin-induced cardiotoxicity.

Angiotensin 1-7 exerts antioxidant effects, suppresses Mammalian Target of Rapamycin (mTOR) signaling, and inhibits apoptosis in renal proximal tubular cells

Oxidative stress is one of the crucial pathogenic factors involved in the progression of renal injury. Angiotensin (ANG) 1-7, a bioactive heptapeptide of the renin-angiotensin-aldosterone system is known to exert antioxidant and nephroprotective effects. However, the cellular mechanism involved in the beneficial effect of ANG 1-7 is not clear. Here, we assessed ANG 1-7's effect on H2O2-mediated oxidative damage in the human proximal tubular (HK2) cells and the underlying mechanisms. HK2 cells were incubated with H2O2 (500 µM, 4 h) pre-treated with and without ANG 1-7 (100 nM, 24 h), and reactive oxygen species (ROS) generation, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, apoptosis and mammalian target of rapamycin (mTOR) signaling were determined H2O2 induced an increase in oxidative and ER stress together with loss of mitochondrial membrane potential, decreased ATP levels, and induced apoptosis in HK2 cells. Moreover, H2O2 treatment resulted in the activation of mTOR complexes (mTORC1 and mTORC2) in these cells. ANG 1-7 significantly attenuated H2O2-induced ROS generation, ER stress and apoptosis, and also improved mitochondrial function. Additionally, pre-treatment of ANG 1-7 inhibited the H2O2-mediated mTOR activation. These effects of ANG 1-7 were blocked by co-treatment with the Mas receptor (MasR) inhibitor, A779. Furthermore, transfection of HK2 cells with Mas receptor siRNA also abolished the inhibitory effect of ANG 1-7 on mTOR activities. In conclusion, ANG 1-7 via MasR mitigates oxidative stress, suppresses mTOR signaling, and protects HK2 cells from ER stress, mitochondrial dysfunction, and apoptosis, suggesting ANG 1-7-MasR renoprotective effects.

Hyperglycemia and Hyperlipidemia with Kidney or Liver Transplantation: A Review

Although solid organ transplantation in persons with diabetes mellitus is often associated with hyperglycemia, the risk of hyperlipidemia in all organ transplant recipients is often underestimated. The diagnosis of diabetes often predates transplantation; however, in a moderate percentage of allograft recipients, perioperative hyperglycemia occurs triggered by antirejection regimens. Post-transplant prescription of glucocorticoids, calcineurin inhibitors and mTOR inhibitors are associated with increased lipid concentrations. The existence of diabetes mellitus prior to or following a liver transplant is associated with shorter times of useful allograft function. A cycle involving Smad, TGF beta, m-TOR and toll-like receptors has been identified in the contribution of rejection and aging of allografts. Glucocorticoids (prednisone) and calcineurin inhibitors (cyclosporine and tacrolimus) induce hyperglycemia associated with insulin resistance. Azathioprine, mycophenolate and prednisone are associated with lipogenesis. mTOR inhibitors (rapamycin) are used to decrease doses of atherogenic agents used for immunosuppression. Post-transplant medication management must balance immune suppression and glucose and lipid control. Concerns regarding rejection often override those relative to systemic and organ vascular aging and survival. This review focuses attention on the underlying mechanism of relationships between glycemia/lipidemia control, transplant rejection and graft aging.

Relationship Between Vitamin D Levels and β Cell Function and Insulin Resistance

Background This study aimed to determine the relationship between vitamin D levels and β cell function and insulin resistance in patients with diabetes, glucose tolerance disorder, or impaired fasting glucose. Methodology A total of 75 outpatients (55 females and 20 males) between the ages of 30 and 65 years were included in the study. There were 25 healthy individuals, 25 individuals with prediabetes, and 25 individuals with diabetes. The Homeostasis Model Assessment (HOMA) score was used to evaluate insulin resistance. Results The mean levels of vitamin 25(OH)D among the groups included in the study were 35 ± 16.9 nmol/L in the control group, 44.5 ± 34.5 nmol/L in the prediabetes group, and 35.7 ± 13.1 nmol/L in the diabetes group. There were no significant differences. The mean level of vitamin 1.25(OH)₂D₃ was 15.95 ± 8 pg/mL in the control group, 18.4 ± 7.5 pg/mL in the prediabetes group, and 21.5 ± 7.9 pg/mL in the diabetes group. While the levels of vitamin 25(OH)D were similar between the groups, the levels of vitamin 1,25(OH)₂D₃  were significantly higher in the diabetes group. Considering all individuals, no significant difference was found between the vitamin 25(OH)D and glucose levels at minutes 0, 30, 60, 90, and 120. While there was a significant positive relationship between the 1,25(OH)₂D₃ vitamin and glucose levels at minutes 0, 30, 60, and 90, there was no significant relationship between the levels at minute 120. When the 1,25(OH)₂D₃ vitamin and HOMA insulin resistance and HOMA β scores were compared, a significant positive relationship was found between the 1,25(OH)₂D₃ vitamin and HOMA β levels. Conclusions In our study, there was no significant difference between the groups (control, prediabetes, and diabetes) in 25(OH)D levels. Similarly, there was no significant relationship between the 25(OH)D levels and insulin sensitivity and resistance between the groups. The positive relationship identified between the 1,25(OH)₂D₃ vitamin levels and the glucose concentration at minutes 0, 30, 60, and 90 and the higher 1,25(OH)₂D₃ vitamin levels in the diabetes group compared to the control group in our study can be interpreted as the effort of the organism to prevent glucose-induced β-cell apoptosis.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

The Role of the Epidermal Growth Factor Receptor in Diabetic Kidney Disease

The epidermal growth factor receptor (EGFR) is expressed in numerous cell types in the adult mammalian kidney and is activated by a family of EGF-like ligands. EGFR activation has been implicated in a variety of physiologic and pathophysiologic functions. There is increasing evidence that aberrant EGFR activation is a mediator of progressive kidney injury in diabetic kidney disease. This review will highlight recent studies indicating its potential role and mechanisms of injury of both glomerular and tubular cells in development and progression of diabetic kidney disease.

TP63 Is Significantly Upregulated in Diabetic Kidney

The role of tumor protein 63 (TP63) in regulating insulin receptor substrate 1 (IRS-1) and other downstream signal proteins in diabetes has not been characterized. RNAs extracted from kidneys of diabetic mice (db/db) were sequenced to identify genes that are involved in kidney complications. RNA sequence analysis showed more than 4- to 6-fold increases in TP63 expression in the diabetic mice’s kidneys, compared to wild-type mice at age 10 and 12 months old. In addition, the kidneys from diabetic mice showed significant increases in TP63 mRNA and protein expression compared to WT mice. Mouse proximal tubular cells exposed to high glucose (HG) for 48 h showed significant decreases in IRS-1 expression and increases in TP63, compared to cells grown in normal glucose (NG). When TP63 was downregulated by siRNA, significant increases in IRS-1 and activation of AMP-activated protein kinase (AMPK (p-AMPK-Th¹⁷²)) occurred under NG and HG conditions. Moreover, activation of AMPK by pretreating the cells with AICAR resulted in significant downregulation of TP63 and increased IRS-1 expression. Ad-cDNA-mediated over-expression of tuberin resulted in significantly decreased TP63 levels and upregulation of IRS-1 expression. Furthermore, TP63 knockdown resulted in increased glucose uptake, whereas IRS-1 knockdown resulted in a decrease in the glucose uptake. Altogether, animal and cell culture data showed a potential role of TP63 as a new candidate gene involved in regulating IRS-1 that may be used as a new therapeutic target to prevent kidney complications in diabetes.

PCR Array Technology in Biopsy Samples Identifies Up-Regulated mTOR Pathway Genes as Potential Rejection Biomarkers After Kidney Transplantation

Background: Antibody-mediated rejection (AMR) is the major cause of kidney transplant rejection. The donor-specific human leukocyte antigen (HLA) antibody (DSA) response to a renal allograft is not fully understood yet. mTOR complex has been described in the accommodation or rejection of transplants and integrates responses from a wide variety of signals. The aim of this study was to analyze the expression of the mTOR pathway genes in a large cohort of kidney transplant patients to determine its possible influence on the transplant outcome. Methods: A total of 269 kidney transplant patients monitored for DSA were studied. The patients were divided into two groups, one with recipients that had transplant rejection (+DSA/+AMR) and a second group of recipients without rejection (+DSA/-AMR and -DSA/-AMR, controls). Total RNA was extracted from kidney biopsies and reverse transcribed to cDNA. Human mTOR-PCR array technology was used to determine the expression of 84 mTOR pathway genes. STRING and REVIGO software were used to simulate gene to gene interaction and to assign a molecular function. Results: The studied groups showed a different expression of the mTOR pathway related genes. Recipients that had transplant rejection showed an over-expressed transcript (≥5-fold) of AKT1S1, DDIT4, EIF4E, HRAS, IGF1, INS, IRS1, PIK3CD, PIK3CG, PRKAG3, PRKCB (>12-fold), PRKCG, RPS6KA2, TELO2, ULK1, and VEGFC, compared with patients that did not have rejection. AKT1S1 transcripts were more expressed in +DSA/-AMR biopsies compared with +DSA/+AMR. The main molecular functions of up-regulated gene products were phosphotransferase activity, insulin-like grown factor receptor and ribonucleoside phosphate binding. The group of patients with transplant rejection also showed an under-expressed transcript (≥5-fold) of VEGFA (>15-fold), RPS6, and RHOA compared with the group without rejection. The molecular function of down-regulated gene products such as protein kinase activity and carbohydrate derivative binding proteins was also analyzed. Conclusions: We have found a higher number of over-expressed mTOR pathway genes than under-expressed ones in biopsies from rejected kidney transplants (+DSA/+AMR) with respect to controls. In addition to this, the molecular function of both types of transcripts (over/under expressed) is different. Therefore, further studies are needed to determine if variations in gene expression profiles can act as predictors of graft loss, and a better understanding of the mechanisms of action of the involved proteins would be necessary.

SGLT2 Inhibitors: Emerging Roles in the Protection Against Cardiovascular and Kidney Disease Among Diabetic Patients

PURPOSE OF REVIEW

Type 2 diabetes mellitus (T2DM) is a prevalent disease with the severe clinical implications including myocardial infarction, stroke, and kidney disease. Therapies focusing on glycemic control in T2DM such as biguanides, sulfonylureas, thiazolidinediones, and insulin-based regimens have largely failed to substantially improve cardiovascular and kidney outcomes. We review the recent findings on sodium-glucose co-transporter type 2 (SGLT2) inhibitors which have shown to have beneficial cardiovascular and kidney-related effects.

RECENT FINDINGS

SGLT2 inhibitors are a new class of diabetic medications that reduce the absorption of glucose in the kidney, decrease proteinuria, control blood pressure, and are associated with weight loss. SGLT2 inhibitors provide complementary therapy independent of insulin secretion or action with proved glucose-lowering effects. Recent placebo-controlled clinical trials have demonstrated that these medications can decrease cardiovascular death, progression of kidney disease, and all-cause mortality in diabetic and non-diabetic patients. Interestingly, SGT2 inhibitors such as dapagliflozin have also proven to decrease heart failure admissions and cardiovascular endpoints in non-diabetic patients, suggesting pleiotropic effects. The exact mechanisms responsible for reductions in atherosclerotic heart disease, need for kidney replacement therapy, and progressive kidney disease remain unknown. While regulation of glomerular hyperfiltration, albuminuria, and natriuresis may be part of the explanation, it is possible that complex cellular effects including energy balance optimization, downregulation of oxidative stress, and modulation of pro-inflammatory signaling pathways are associated with favorable outcomes observed in large clinical studies.

CONCLUSION

SGLT2 inhibitors are novel antidiabetic medications with immense utility in the management of patients with T2DM. Furthermore, SGLT2 inhibitors have demonstrated to reduce the progression to advanced forms of kidney disease and its associated complications. These medications should be front and center in the management of patients with diabetic kidney disease with and without chronic kidney disease as they confer protection against cardiovascular/renal death and improve all-cause mortality. Future studies should evaluate the benefits and implications of early initiation of SGLT2 inhibitors, as well as the long-term effects of this therapy.

Perspectives on the role of PTEN in diabetic nephropathy: an update

Phosphatase and tensin homolog (PTEN) is a potent tumor suppressor gene that antagonizes the proto-oncogenic phosphatidylinositol 3 kinase (PI3K)/protein kinase B (Akt) signaling pathway and governs basic cellular metabolic processes. Recently, its role in cell growth, metabolism, architecture, and motility as an intramolecular and regulatory mediator has gained widespread research interest as it applies to non-tumorous diseases, such as insulin resistance (IR) and diabetic nephropathy (DN). DN is characterized by renal tubulointerstitial fibrosis (TIF) and epithelial-mesenchymal transition (EMT), and PTEN plays a significant role in the regulation of both. Epigenetics and microRNAs (miRNAs) are novel players in post-transcriptional regulation and research evidence demonstrates that they reduce the expression of PTEN by acting as key regulators of autophagy and TIF through activation of the Akt/mammalian target of rapamycin (mTOR) signaling pathway. These regulatory processes might play an important role in solving the complexities of DN pathogenesis and IR, as well as the therapeutic management of DN with the help of PTEN K27-linked polyubiquitination. Currently, there are no comprehensive reviews citing the role PTEN plays in the development of DN and its regulation via miRNA and epigenetic modifications. The present review explores these facets of PTEN in the pathogenesis of IR and DN.

The tubular hypothesis of nephron filtration and diabetic kidney disease

Kidney size and glomerular filtration rate (GFR) often increase with the onset of diabetes, and elevated GFR is a risk factor for the development of diabetic kidney disease. Hyperfiltration mainly occurs in response to signals passed from the tubule to the glomerulus: high levels of glucose in the glomerular filtrate drive increased reabsorption of glucose and sodium by the sodium-glucose cotransporters SGLT2 and SGLT1 in the proximal tubule. Passive reabsorption of chloride and water also increases. The overall capacity for proximal reabsorption is augmented by growth of the proximal tubule, which (alongside sodium-glucose cotransport) further limits urinary glucose loss. Hyperreabsorption of sodium and chloride induces tubuloglomerular feedback from the macula densa to increase GFR. In addition, sodium-glucose cotransport by SGLT1 on macula densa cells triggers the production of nitric oxide, which also contributes to glomerular hyperfiltration. Although hyperfiltration restores sodium and chloride excretion it imposes added physical stress on the filtration barrier and increases the oxygen demand to drive reabsorption. Tubular growth is associated with the development of a senescence-like molecular signature that sets the stage for inflammation and fibrosis. SGLT2 inhibitors attenuate the proximal reabsorption of sodium and glucose, normalize tubuloglomerular feedback signals and mitigate hyperfiltration. This tubule-centred model of diabetic kidney physiology predicts the salutary effect of SGLT2 inhibitors on hard renal outcomes, as shown in large-scale clinical trials.

Podocyte Lysosome Dysfunction in Chronic Glomerular Diseases

Podocytes are visceral epithelial cells covering the outer surface of glomerular capillaries in the kidney. Blood is filtered through the slit diaphragm of podocytes to form urine. The functional and structural integrity of podocytes is essential for the normal function of the kidney. As a membrane-bound organelle, lysosomes are responsible for the degradation of molecules via hydrolytic enzymes. In addition to its degradative properties, recent studies have revealed that lysosomes may serve as a platform mediating cellular signaling in different types of cells. In the last decade, increasing evidence has revealed that the normal function of the lysosome is important for the maintenance of podocyte homeostasis. Podocytes have no ability to proliferate under most pathological conditions; therefore, lysosome-dependent autophagic flux is critical for podocyte survival. In addition, new insights into the pathogenic role of lysosome and associated signaling in podocyte injury and chronic kidney disease have recently emerged. Targeting lysosomal functions or signaling pathways are considered potential therapeutic strategies for some chronic glomerular diseases. This review briefly summarizes current evidence demonstrating the regulation of lysosomal function and signaling mechanisms as well as the canonical and noncanonical roles of podocyte lysosome dysfunction in the development of chronic glomerular diseases and associated therapeutic strategies.

Blockade of the mTOR signaling pathway with rapamycin ameliorates aristolochic acid nephropathy

Chronic aristolochic acid nephropathy (CAAN) is characterized by widespread apoptosis and interstitial fibrosis, which severely impairs kidney function. mTOR is crucial for cell proliferation and protein synthesis. In the present study, the therapeutic effects of blockade of mTOR activity by rapamycin on aristolochic acid nephropathy were investigated. In vitro experiments to determine cell apoptosis and cell cycle alterations caused by aristolochic acid (AA)-induced injury were conducted on three groups of cells: Untreated control, AAI (treated with aristolochic acid I), and AAI + rapamycin (RMS). In vivo experiments were conducted in a CAAN mouse model. One group of mice was treated with AAI (the CAAN group), while another group was treated with AAI and rapamycin (the treatment group). Kidney function and pathological changes in these mice were assessed by serum creatinine and urea nitrogen analysis. Hematoxylin and eosin staining of renal tissue was performed to evaluate the treatment effects of rapamycin. Western blotting and immunohistochemical staining were used to explore the mechanisms by which rapamycin inhibited cell proliferation, apoptosis and tissue fibrosis. In the in vitro experiments, rapamycin prevented AAI-induced cell apoptosis and G₂/M checkpoint cell cycle arrest. In the in vivo experiments, the treatment group exhibited lower serum creatinine and urea nitrogen, less extensive tubular atrophy and increased amount of glomerulus. Additionally, western blotting and immunohistochemical staining showed that the treatment group exhibited decreased expression levels of fibrosis-, proliferation- and apoptosis-related proteins compared with the CAAN group. The findings suggest that rapamycin can ameliorate kidney injury induced by AAI via blockade of mTOR, and thus could be a therapeutic strategy for patients with CAAN.

Exercise intervention attenuates neuropathic pain in diabetes via mechanisms of mammalian target of rapamycin (mTOR)

This study was to examine the role of exercise intervention in modulating neuropathic pain induced by diabetes. Diabetes was induced by streptozotocin (STZ, i.p.) in rats and mechanical hyperalgesia was observed three weeks after STZ. Mechanical withdrawal thresholds were increased after four to five weeks of exercise in STZ rats. We also examined the role of signal of mammalian target of rapamycin (mTOR) in regulating neuropathic pain. Inhibition of neuropathic pain by exercise in STZ rats was accompanied with decreases of p-mTOR, p-S6K1, and p-4E-BP1 in sensory nerves. Blocking mTOR also elevated mechanical withdrawal thresholds in STZ rats. Furthermore, pro-inflammatory IL-6 was greater in sensory nerves of STZ rats. Inhibition of IL-6 decreased mTOR and increased mechanical withdrawal thresholds in STZ rats. Overall, our data suggest the role played by exercise in improving neuropathic pain after STZ and that IL-6-mTOR signal is a part of mechanisms engaged in the effects of exercise.

SPAG5-AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway

Objectives

Podocyte injury is a prediction marker of diabetic nephropathy (DN), and AKT/mTOR pathway–mediated inhibition of autophagy is widely reported to contribute to podocyte damage. Recent study stated that sperm‐associated antigen 5 (SPAG5) activated AKT/mTOR signalling in bladder urothelial carcinoma, indicating SPAG5 might regulate autophagy and play a role in podocyte damage.

Materials and methods

Apoptosis and autophagy of human podocytes (HPCs) were detected by flow cytometry and immunofluorescence (IF). Gene level was assessed by Western blot and RT‐qPCR. Molecular interactions were determined by pulldown, RNA immunoprecipitation (RIP), co‐immunoprecipitation (co‐IP), chromatin immunoprecipitation (ChIP) and luciferase reporter assays.

Results

SPAG5 mRNA and protein levels were upregulated under high glucose treatment in HPCs. Silencing SPAG5 reversed the increase of apoptosis and decrease of autophagy in high glucose–treated HPCs. Later, we found a long non‐coding RNA (lncRNA) SPAG5 antisense RNA1 (SPAG5‐AS1) as a neighbour gene to SPAG5. Mechanistically, YY1 transcriptionally upregulated SPAG5‐AS1 and SPAG5 in high glucose–treated podocytes. SPAG5‐AS1 acted as a competitive endogenous RNA (ceRNA) to regulate miR‐769‐5p/YY1 axis and induce SPAG5. SPAG5‐AS1 interacted with ubiquitin‐specific peptidase 14 (USP14) and leads to de‐ubiquitination and stabilization of SPAG5 protein.

Conclusions

This study revealed that SPAG5‐AS1 inhibited autophagy and aggravated apoptosis of podocytes via SPAG5/AKT/mTOR pathway, indicating SPAG5‐AS1/SPAG5 as a potential target for the alleviation of podocyte injury and offering new thoughts for the treatments of DN.

YY1: A novel therapeutic target for diabetic nephropathy orchestrated renal fibrosis

BACKGROUND

Renal fibrosis promotes the development of diabetic nephropathy (DN). A growing number of studies have reported that Yin Yang 1 (YY1), which is involved in cellular proliferation and differentiation, plays a crucial role in the pathogenesis of many diseases, such as pulmonary fibrosis, hepatic steatosis and cancer.

METHODS

We detected the expression of YY1 under various glucose concentration and time gradient conditions. Rapamycin was used to verify the mTORC1/p70S6K/YY1 signaling pathway in HK-2 cells. We used db/db mice to examine the connection between renal fibrosis and YY1. A luciferase assay and chromatin immunoprecipitation (ChIP) assay were used to identify whether YY1 directly regulated α-SMA by binding to the α-SMA promoter. RNA silencing and overexpression were performed by using a YY1 expression/knockdown plasmid to investigate the function of YY1 in renal fibrosis of DN.

RESULTS

YY1 expression and subsequent nuclear translocation were upregulated in a glucose- and time-dependent manner via the mTORC1/p70S6K signaling pathway in HK-2 cells. YY1 expression and nuclear translocation was significantly upregulated in db/db mice. Furthermore, YY1 upregulated α-SMA expression and activity in high-glucose-cultured HK-2 cells. Overexpression of YY1 promoted renal fibrosis in db/m mice mainly by upregulating α-SMA expression and inducing epithelial-mesenchymal transition (EMT) in vitro and in vivo. Finally, downregulation of YY1 reversed renal fibrosis by improving EMT in vivo and in vitro.

CONCLUSIONS

These results reveal that upregulation of YY1 plays a critical role in HG-induced deregulation of EMT-associated protein expression, which finally results in renal fibrosis of DN. Therefore, decreasing YY1 expression might represent a new therapeutic target for diabetic nephropathy-induced renal fibrosis.

CSF-1 in Osteocytes Inhibits Nox4-mediated Oxidative Stress and Promotes Normal Bone Homeostasis

CSF-1 is a key factor in regulating bone remodeling; osteocytes express CSF-1 and its receptor. Viable osteocytes are essential for bone remodeling through cell-cell contact and secretion of factors that regulate osteoblasts and osteoclasts. Increased oxidative stress contributes to osteocyte death and correlates with bone loss during aging. The NADPH oxidase Nox4 is a major source of ROS in bone. CSF-1 decreases Nox4, suggesting that CSF-1 protects against oxidative stress. Here, we show that osteocyte apoptosis previously reported in our global CSF-1KO mice is associated with increased Nox4, as well as 4-HNE expression in osteocytes. Osteocytes isolated from CSF-1KO mice were less viable and showed increased intracellular ROS, elevated NADPH oxidase activity/Nox4 protein, activation of mTOR/S6K, and downstream apoptosis signals compared with WT osteocytes. Nox4 expression was also increased in CSF-1KO osteocytes and colocalized with MitoTracker Red in mitochondria. Notably, CSF-1 inhibited Nox4 expression and apoptosis cascade signals. In additional studies, shNox4 decreased these signals in CSF-1KO osteocytes, whereas overexpression of Nox4 in WT osteocytes activated the apoptosis pathway. To determine the role of CSF-1 in osteocytes, DMP1Cre-CSF-1cKO (CSF-1cKO) mice that lack CSF-1 in osteocytes/late osteoblasts were developed. Osteocyte defects in CSF-1cKO mice overlapped with those in CSF-1KO mice, including increased apoptosis, Nox4, and 4-HNE-expressing osteocytes. CSF-1cKO mice showed unbalanced cancellous bone remodeling with decreased bone formation and resorption. Continued exposure to high Nox4/ROS levels may further compromise bone formation and predispose to bone loss and skeletal fragility. Taken together, our findings suggest a novel link between CSF-1, Nox4-derived ROS, and osteocyte survival/function that is crucial for osteocyte-mediated bone remodeling. Results reveal new mechanisms by which CSF-1/oxidative stress regulate osteocyte homeostasis, which may lead to therapeutic strategies to improve skeletal health in aging. © 2018 American Society for Bone and Mineral Research.

Proximal Tubule Autophagy Differs in Type 1 and 2 Diabetes

BACKGROUND

Evidence of a protective role of autophagy in kidney diseases has sparked interest in autophagy as a potential therapeutic strategy. However, understanding how the autophagic process is altered in each disorder is critically important in working toward therapeutic applications.

METHODS

Using cultured kidney proximal tubule epithelial cells (PTECs) and diabetic mouse models, we investigated how autophagic activity differs in type 1 versus type 2 diabetic nephropathy. We explored nutrient signals regulating starvation-induced autophagy in PTECs and used autophagy-monitoring mice and PTEC-specific autophagy-deficient knockout mice to examine differences in autophagy status and autophagy's role in PTECs in streptozotocin (STZ)-treated type 1 and db/db type 2 diabetic nephropathy. We also examined the effects of rapamycin (an inhibitor of mammalian target of rapamycin [mTOR]) on vulnerability to ischemia-reperfusion injury.

RESULTS

Administering insulin or amino acids, but not glucose, suppressed autophagy by activating mTOR signaling. In db/db mice, autophagy induction was suppressed even under starvation; in STZ-treated mice, autophagy was enhanced even under fed conditions but stagnated under starvation due to lysosomal stress. Using knockout mice with diabetes, we found that, in STZ-treated mice, activated autophagy counteracts mitochondrial damage and fibrosis in the kidneys, whereas in db/db mice, autophagic suppression jeopardizes kidney even in the autophagy-competent state. Rapamycin-induced pharmacologic autophagy produced opposite effects on ischemia-reperfusion injury in STZ-treated and db/db mice.

CONCLUSIONS

Autophagic activity in PTECs is mainly regulated by insulin. Consequently, autophagic activity differs in types 1 and 2 diabetic nephropathy, which should be considered when developing strategies to treat diabetic nephropathy by modulating autophagy.

High Glucose-Induced Apoptosis in Human Kidney Cells Was Alleviated by miR-15b-5p Mimics

MicroRNAs were involved in a wide range of biological processes of diabetic nephropathy (DN). It is reported that miR-15b-5p was downregulated in the patients with DN. However, the mechanisms underlying the regulatory effects of miR-15b-5p on patients with diabetes remain unclear. Thus, this study aimed to investigate the role of miR-15b-5p during high glucose (HG)-induced apoptosis in human kidney cells. Quantitative real-time (qRT)-PCR was used to detect the level of miR-15b-5p. CCK-8 assay, EdU staining assays and flow cytometry were used to detect cell proliferation, apoptosis respectively in vitro. In addition, Western blotting was used to determine active caspase-3, cleaved poly(ADP-ribose) polymerase (PARP), phosphorylated (p)-AKT, p-mammalian target of rapamycin (mTOR), p-S6, p-c-Jun N terminal kinase (JNK), p-p38 and p-extracellular signal-regulated kinase (ERK) proteins levels. The expression of miR-15b-5p in patients with DN were dramatically decreased compared with health persons. Similarly, HG down-regulated the expression of miR-15b-5p in HK-2 cells. In contrast, miR-15b-5p mimics alleviated HG-induced apoptosis in HK-2 cells via decreasing the expressions of active caspase 3 and cleaved PARP. EdU detection further confirmed that miR-15b-5p mimics attenuated the anti-proliferation effect of HG in HK-2 cells. Furthermore, HG-induced Akt/mTOR pathway downregulation and JNK upregulation were markedly reversed by miR-15b-5p mimics in cells. The data suggested that miR-15b-5p mimics protects HK-2 cells from HG-induced apoptosis. The anti-apoptotic effects of miR-15b-5p may due to the activation of the Akt/mTOR pathway as well as inactivation of JNK. Taken together, miR-15b-5p might be a potential therapeutic target for the treatment of patients with DN.

Cell Apoptosis and Autophagy in Renal Fibrosis

Renal fibrosis is the final common pathway of all chronic kidney diseases progressing to end-stage renal diseases. Autophagy, a highly conserved lysosomal degradation pathway, plays important roles in maintaining cellular homeostasis in all major types of kidney cells including renal tubular cells as well as podocytes, mesangial cells and endothelial cells in glomeruli. Autophagy dysfunction is implicated in the pathogenesis of various renal pathologies. Here, we analyze the pathological role and regulation of autophagy in renal fibrosis and related kidney diseases in both glomeruli and tubulointerstitial compartments. Further research is expected to gain significant mechanistic insights and discover pathway-specific and kidney-selective therapies targeting autophagy to prevent renal fibrosis and related kidney diseases.

Effect of Puerarin Regulated mTOR Signaling Pathway in Experimental Liver Injury

It is known that excessive hepatocellular apoptosis is a typical characteristic of hepatic disease, and is regulated by the mammalian target of rapamycin (mTOR) signaling pathway. As the main active component of Kudzu (Pueraria lobata) roots, which is frequently used to treat hepatic diseases, Puerarin (Pue) has been reported to alleviate and protect against hepatic injury. However, it is unclear whether Pue can inhibit mTOR signaling to prevent excessive apoptosis in the treatment of hepatic diseases. In the present study, Pue effectively ameliorated pathological injury of the liver, decreased serum enzyme (ALT, AST, γ-GT, AKP, DBIL, and TBIL) levels, regulated the balance between pro-inflammatory (TNF-α, IL-1β, IL-4, IL-6, and TGF-β1) and anti-inflammatory cytokines (IL-10), restored the cell cycle and inhibited hepatocellular apoptosis and caspase-3 expression in rats with liver injury induced by 2-AAF/PH. Pue inhibited p-mTOR, p-AKT and Raptor activity, and increased Rictor expression in the liver tissues of rats with experimental liver injury. These results indicated that Pue effectively regulated the activation of mTOR signaling pathway in the therapeutic and prophylactic process of Pue on experimental liver injury.

Preclinical evidence of the enhanced effectiveness of combined rapamycin and AICAR in reducing kidney cancer

Loss of Von Hippel-Lindau in renal carcinoma cells results in upregulation of the activity of hypoxia-inducible factor (HIF-α), a major transcription factor involved in kidney cancer. Rapamycin as mammalian target of rapamycin inhibitor and 5-aminoimidazole-4-carboxamide-riboside (AICAR) as AMPK activator are used separately to treat cancer patients. In the current study, the possible additive effect of drug combinations in reducing kidney tumorigenesis was investigated. Treatment with drug combinations significantly decreased cell proliferation, increased cell apoptosis, and abolished Akt phosphorylation and HIF-2α expression in renal cell carcinoma cells, including primary cells isolated from kidney cancer patients. Significant decreases in cell migration and invasion were detected using drug combinations. Drug combinations effectively abolished binding of HIF-2α to the Akt promoter and effected formation of the DNA-protein complex in nuclear extracts from 786-O cells, as demonstrated using electromobility shift assay and examination of Akt promoter activity. Importantly, we tested the effect of each drug and the combined drugs on kidney tumor size in the nude mouse model. Our data show that treatment with rapamycin, AICAR, and rapamycin+AICAR decreased tumor size by 38%, 36%, and 80%, respectively, suggesting that drug combinations have an additive effect in reducing tumor size compared with use of each drug alone. Drug combinations effectively decreased cell proliferation, increased apoptotic cells, and significantly decreased p-Akt, HIF-2α, and vascular endothelial growth factor expression in tumor kidney tissues from mice. These results show for the first time that drug combinations are more effective than single drugs in reducing kidney tumor progression. This study provides important evidence that may lead to the initiation of pre-clinical trials in patients with kidney cancer.

The mTOR promotes oxidative stress-induced apoptosis of mesangial cells in diabetic nephropathy

Glomerular mesangial cell (MC) apoptosis is one of the important mechanisms of glomerulosclerosis, which induces an increased severity of albuminuria and promotes the development of diabetic nephropathy (DN). However, the mechanism by which high glucose (HG) induces MCs apoptosis is not fully understood. In the present study, we investigated the effects of mTOR signalling on apoptosis in cultured MCs exposed to HG and in type I diabetes, and tried to clarify the specific mechanisms underlying these effects. In vitro, exposure of MCs to HG stimulated ROS production, decreased the antioxidant enzyme superoxide dismutase (SOD) activity and glutathione (GSH) level, increased nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, upregulated P53 expression and Bax/Bcl-2 ratio and enhanced cleavage of caspase 3, resulting in an increase in programmed cell death. Pretreatment of the cells with rapamycin ameliorated oxidative stress, reduced the number of apoptotic cells induced by HG and caused the downstream effects of mTOR activation. In vivo, compared with control rats, diabetic rats had more apoptotic cells in glomeruli. Induction of diabetes increased the level of MDA and NADPH oxidase activity, decreased the SOD activity and GSH level, elevated the Bax/Bcl ratio and P53 expression and activated caspase 3. mTOR inhibitor rapamycin treatment prevented these changes further alleviated albuminuria and improved renal function. Taken together, our data suggest that mTOR plays a key role in mediating ROS-induced MC apoptosis in diabetic nephropathy, and these effects have been associated with the promotion of ROS production by upregulating the antioxidant enzyme and downregulating the NADPH oxidase activity.

A new drug combination significantly reduces kidney tumor progression in kidney mouse model

Tuberous sclerosis complex (TSC) disease is associated with tumors in many organs, particularly angiomyolipoma (AML) in the kidneys. Loss or inactivation of TSC1/2 results in high levels of HIF-α activity and VEGF expression. mTOR inhibitor (rapamycin) and the AMPK activator 5-aminoimidazole-4-carboxamide (AICA)-riboside (AICAR) are currently used separately to treat cancer patients. Here, we investigated the effect of a novel combination of rapamycin and AICAR on tumor progression. Our data show that treatment of AML human cells with drug combinations resulted in 5-7-fold increase in cell apoptosis compared to each drug alone. In addition, drug combinations resulted in 4-5-fold decrease in cell proliferation compared to each drug alone. We found that drug combinations abolished Akt and HIF activity in AML cells. The drug combinations resulted in decrease in cell invasion and cell immigration by 70% and 84%, respectively in AML cells. The combined drugs also significantly decreased the VEGF expression compare to each drug alone in AML cells. Drug combinations effectively abolished binding of HIF-2α to the putative Akt site in the nuclear extracts isolated from AML cells. Treatment TSC mice with drug combinations resulted in 75% decrease in tumor number and 88% decrease in tumor volume compared to control TSC mice. This is first evidence that drug combinations are effective in reducing size and number of kidney tumors without any toxic effect on kidney. These data will provide evidence for initiating a new clinical trial for treatment of TSC patients.

Kidney atrophy vs hypertrophy in diabetes: which cells are involved?

One of the first structural changes in diabetic nephropathy (DN) is the renal enlargement. These changes resulted in renal hypertrophy in both glomerular and tubular cells. Shrink in the kidney size, which described as kidney atrophy resulted from the loss of nephrons or abnormal nephron function and lead to loss of the kidney function. On the other hand, increase in kidney size, which described as hypertrophy resulted from increase in proximal tubular epithelial and glomerular cells size. However overtime, tubular atrophy and tubulointerstitial fibrosis occurs as subsequent changes in tubular cell hypertrophy, which is associated with the infiltration of fibroblast cells into the tubulointerstitial space. The rate of deterioration of kidney function shows a strong correlation with the degree of tubulointerstitial fibrosis. A consequence of long-standing diabetes/hyperglycemia may lead to major changes in renal structure that occur but not specific only to nephropathy. Identifying type of cells that involves in renal atrophy and hypertrophy may help to find a therapeutic target to treat diabetic nephropathy. In summary, the early changes in diabetic kidney are mainly includes the increase in tubular basement membrane thickening which lead to renal hypertrophy. On the other hand, only renal tubule is subjected to apoptosis, which is one of the characteristic morphologic changes in diabetic kidney to form tubular atrophy at the late stage of diabetes.

Galectin-1 is a new fibrosis protein in type 1 and type 2 diabetes

Chronic exposure of tubular renal cells to high glucose contributes to tubulointerstitial changes in diabetic nephropathy. In the present study, we identified a new fibrosis gene called galectin-1 (Gal-1), which is highly expressed in tubular cells of kidneys of type 1 and type 2 diabetic mouse models. Gal-1 protein and mRNA expression showed significant increase in kidney cortex of heterozygous Akita^+/- and db/db mice compared with wild-type mice. Mouse proximal tubular cells exposed to high glucose showed significant increase in phosphorylation of Akt and Gal-1. We cloned Gal-1 promoter and identified the transcription factor AP4 as binding to the Gal-1 promoter to up-regulate its function. Transfection of cells with plasmid carrying mutations in the binding sites of AP4 to Gal-1 promoter resulted in decreased protein function of Gal-1. In addition, inhibition of Gal-1 by OTX-008 showed significant decrease in p-Akt/AP4 and protein-promoter activity of Gal-1 and fibronectin. Moreover, down-regulation of AP4 by small interfering RNA resulted in a significant decrease in protein expression and promoter activity of Gal-1. We found that kidney of Gal-1^-/- mice express very low levels of fibronectin protein. In summary, Gal-1 is highly expressed in kidneys of type 1 and 2 diabetic mice, and AP4 is a major transcription factor that activates Gal-1 under hyperglycemia. Inhibition of Gal-1 by OTX-008 blocks activation of Akt and prevents accumulation of Gal-1, suggesting a novel role of Gal-1 inhibitor as a possible therapeutic target to treat renal fibrosis in diabetes.-Al-Obaidi, N., Mohan, S., Liang, S., Zhao, Z., Nayak, B. K., Li, B., Sriramarao, P., Habib, S. L. Galectin-1 is a new fibrosis protein in type 1 and type 2 diabetes.

Oxyresveratrol prevents lipopolysaccharide/d-galactosamine-induced acute liver injury in mice

Oxyresveratrol (Oxy) is a natural polyhydroxystilbene abundant in mulberry that has anti-inflammation and anti-oxidant activities. We evaluated the protective effect of Oxy in the context of the lipopolysaccharide and d-galactosamine (LPS/d-GalN) induced acute liver injury. Oxy restricted the development of histopathological changes, markedly reduced the activity of alanine transaminase (ALT) and aspartate transaminase (AST), which are indicators of impaired liver function. Oxy significantly regulated the contents of oxidative stress related enzymes and products, and inhibited expressions of inflammatory mediators and cytokines. Oxy treatment diminished the Toll-like receptor 4/nuclear factor-kappa B (TLR4/NF-κB) signaling pathway in liver, activated the Kelch-like ECH-associated protein 1(Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway, and increased expressions of heme oxygenase 1 (HO-1) and quinine oxidoreductase 1(NQO1). Pretreatment with Oxy decreased LPS/d-GalN stimulated hepatocyte apoptosis by efficaciously raising the B-cell lymphoma 2 (Bcl-2)/Bcl-2 associated X (Bax) ratio, inhibiting the expression and activation of caspases, and activating the phosphoinoside-3-kinase (PI3K)-Akt pathway. Our results demonstrate the hepatoprotective efficacy of Oxy. The protection is mainly due to the prevention of TLR4/NF-κB pathway activation, induced activation of Keap1-Nrf2 signaling pathway, and decreased hepatocyte apoptosis. Oxy warrants further study as a potential therapeutic agent candidate for the management of acute liver injury.

Autophagy in diabetic kidney disease: regulation, pathological role and therapeutic potential

Diabetic kidney disease, a leading cause of end-stage renal disease, has become a serious public health problem worldwide and lacks effective therapies. Autophagy is a highly conserved lysosomal degradation pathway that removes protein aggregates and damaged organelles to maintain cellular homeostasis. As important stress-responsive machinery, autophagy is involved in the pathogenesis of various diseases. Emerging evidence has suggested that dysregulated autophagy may contribute to both glomerular and tubulointerstitial pathologies in kidneys under diabetic conditions. This review summarizes the recent findings regarding the role of autophagy in the pathogenesis of diabetic kidney disease and highlights the regulation of autophagy by the nutrient-sensing pathways and intracellular stress signaling in this disease. The advances in our understanding of autophagy in diabetic kidney disease will facilitate the discovery of a new therapeutic target for the prevention and treatment of this life-threatening diabetes complication.

Modulations of Keap1-Nrf2 signaling axis by TIIA ameliorated the oxidative stress-induced myocardial apoptosis

Mounting evidence has strongly implicated oxidative stress in the development of cardiac dysfunction, and myocardial apoptosis contributes to the pathogenesis of heart failure. Quantitative cardiac proteomics data revealed that pressure load by TAC resulted in a significant decline in mitochondrial metabolic activity, where TIIA (Tanshinone IIA sulfonate) treatment reversed it in vivo, which might be mediated by Nrf2. In NRVMs, TIIA treatment ameliorated H₂O₂-induced caspase-3/9 activations through the suppression of p38 and mTOR signaling pathways, where caspase-mediated cleavage of YY1 and PARP resulted in the defects in mitochondrial biogenesis and DNA repair, and this event finally led to cardiomyocyte apoptosis. Mass spectrometry analysis showed that TIIA hydrophobically interacted with Keap1 (the cytoplasmic repressor of Nrf2) and induced its degradation in vitro. Site-directed mutagenesis of Keap1 identified V122/V123/I125 to be the critical residues for the TIIA-induced de-dimerization and degradation of Keap1. Besides, TIIA treatment also epigenetically up-regulated Nrf2 gene transcription, where it hypomethylated the first 5 CpGs of Nrf2 promoter. Furthermore, cardiac-specific Nrf2 knockout mice exhibited the significantly dampened anti-apoptotic effects of TIIA.

Berberine activates Nrf2 nuclear translocation and inhibits apoptosis induced by high glucose in renal tubular epithelial cells through a phosphatidylinositol 3-kinase/Akt-dependent mechanism

Apoptosis of tubular epithelial cells is a major feature of diabetic kidney disease, and hyperglycemia triggers the generation of free radicals and oxidant stress in tubular cells. Berberine (BBR) is identified as a potential anti-diabetic herbal medicine due to its beneficial effects on insulin sensitivity, glucose metabolism and glycolysis. In this study, the underlying mechanisms involved in the protective effects of BBR on high glucose-induced apoptosis were explored using cultured renal tubular epithelial cells (NRK-52E cells) and human kidney proximal tubular cell line (HK-2 cells). We identified the pivotal role of phosphatidylinositol 3-kinase (PI3K)/Akt in BBR cellular defense mechanisms and revealed the novel effect of BBR on nuclear factor (erythroid-derived 2)-related factor-2 (Nrf2) and heme oxygenase (HO)-1 in NRK-52E and HK-2 cells. BBR attenuated reactive oxygen species production, antioxidant defense (GSH and SOD) and oxidant-sensitive proteins (Nrf2 and HO-1), which also were blocked by LY294002 (an inhibitor of PI3K) in HG-treated NRK-52E and HK-2 cells. Furthermore, BBR improved mitochondrial function by increasing mitochondrial membrane potential. BBR-induced anti-apoptotic function was demonstrated by decreasing apoptotic proteins (cytochrome c, Bax, caspase3 and caspase9). All these findings suggest that BBR exerts the anti-apoptosis effects through activation of PI3K/Akt signal pathways and leads to activation of Nrf2 and induction of Nrf2 target genes, and consequently protecting the renal tubular epithelial cells from HG-induced apoptosis.

Oxidative Stress, Apoptosis, and Mitochondrial Function in Diabetic Nephropathy

Diabetic nephropathy (DN) is the second most frequent and prevalent complication of diabetes mellitus (DM). The increase in the production of oxidative stress (OS) is induced by the persistent hyperglycemic state capable of producing oxidative damage to the macromolecules (lipids, carbohydrates, proteins, and nucleic acids). OS favors the production of oxidative damage to the histones of the double-chain DNA and affects expression of the DNA repairer enzyme which leads to cell death from apoptosis. The chronic hyperglycemic state unchains an increase in advanced glycation end-products (AGE) that interact through the cellular receptors to favor activation of the transcription factor NF-κB and the protein kinase C (PKC) system, leading to the appearance of inflammation, growth, and augmentation of synthesis of the extracellular matrix (ECM) in DN. The reactive oxygen species (ROS) play an important role in the pathogenesis of diabetic complications because the production of ROS increases during the persistent hyperglycemia. The primary source of the excessive production of ROS is the mitochondria with the capacity to exceed production of endogenous antioxidants. Due to the fact that the mechanisms involved in the development of DN have not been fully clarified, there are different approaches to specific therapeutic targets or adjuvant management alternatives in the control of glycemia in DN.

Evaluation of mTOR signaling pathway proteins in rat gastric mucosa exposed to sulfite and ghrelin

BACKGROUND/AIMS

Mammalian target of rapamycin (mTOR) signaling serves as a central regulator of cell growth, proliferation, and survival. In this study, we planned to evaluate the expressions of mTOR signaling constituents (p-p70S6K, p-mTOR, and p-Tuberin) in rat gastric mucosa and to compare the results in sulfite- and sulfite+ghrelin-exposed groups.

MATERIALS AND METHODS

Rats were divided into three groups: the control group (C), the sodium metabisulfite (Na2S2O5) (S) group, and sulfite+ghrelin (SG) group. Sodium metabisulfite at 100 mg/kg/day was administered via gavage, and ghrelin at 20 μg/kg/day was administered intraperitoneally for 35 days. We have used immunohistochemistry for mTOR signaling pathway components.

RESULTS

There were no significant differences for p-p70S6K and p-mTOR expression among the C, S, and SG groups. Tuberin expression was significantly increased in the S group compared to the C group. Furthermore, tuberin expression was found to be significantly decreased in the SG group.

CONCLUSION

This study is the first one in the literature that shows the expression of mTOR signaling proteins in gastric mucosa of rats exposed to sulfite and ghrelin. Furthermore, it demonstrates that ghrelin treatment reduces p-Tuberin expression induced by ingested sulfite.

The cellular selection between apoptosis and autophagy: roles of vitamin D, glucose and immune response in diabetic nephropathy

BACKGROUND AND AIMS

Apoptosis, autophagy and cell cycle arrest are cellular responses to injury which are supposed to play fundamental roles in initiation and progression of diabetic nephropathy (DN). The aims of the present study is to shed light on the potential effects of vitamin D analog 22-oxacalcitriol (OCT) on different cell responses during DN, and the possible interplay between both glucose, immune system and vitamin D in determining the cell fate.

METHOD

All rats were randomly allocated into one of three groups: control, vehicle-treated DN group and OCT-treated DN group. Eight weeks after induction of diabetes, the rats were killed. Fasting blood glucose levels, serum 25 (OH) D, renal functions, cytokines and gene expression of autophagy, apoptotic and cell cycle arrest markers were assessed. In addition, the histological assessment of renal architecture was done.

RESULTS

OCT treatment remarkably improved the renal functions and albuminuria. The reductions in mesangial cell hypertrophy, extracellular matrix as well as cell loss were significantly associated with upregulation of pro-autophagy gene expressions and downregulation of both pro-apoptotic and G1-cell cycle arrest genes expression. The reno-protective effects of OCT treatment were associated with significant attenuation of the fasting blood glucose, serum IL-6, renal TLR-4 and IFN-g gene expression.

CONCLUSION

Modulator effects of OCT on glucose and immune system play important roles in renal cell fate decision and chronic kidney disease progression.

Erzhi Pill® Repairs Experimental Liver Injury via TSC/mTOR Signaling Pathway Inhibiting Excessive Apoptosis

The present study aimed to investigate the mechanism of hepatoprotective effect of Erzhi Pill (EZP) on the liver injury via observing TSC/mTOR signaling pathway activation. The experimental liver injury was induced by 2-acetylaminofluorene (2-AAF) treatment combined with partial hepatectomy (PH). EZP treated 2-AAF/PH-induced liver injury by the therapeutic and prophylactic administration. After the administration of EZP, the activities of aspartic transaminase (AST), alanine aminotransferase (ALT), alkaline phosphatase (AKP), and gamma-glutamyl transpeptidase (γ-GT) were decreased, followed by the decreased levels of hepatocyte apoptosis and caspase-3 expression. However, the secretion of albumin, liver weight, and index of liver weight were elevated. Microscopic examination showed that EZP restored pathological liver injury. Meanwhile, Rheb and mammalian target of rapamycin (mTOR) activation were suppressed, and tuberous sclerosis complex (TSC) expression was elevated in liver tissues induced by 2-AAF/PHx and accompanied with lower-expression of Bax, Notch1, p70S6K, and 4E-EIF and upregulated levels of Bcl-2 and Cyclin D. Hepatoprotective effect of EZP was possibly realized via inhibiting TSC/mTOR signaling pathway to suppress excessive apoptosis of hepatocyte.

T cells and autoimmune kidney disease

Glomerulonephritis is traditionally considered to result from the invasion of the kidney by autoantibodies and immune complexes from the circulation or following their formation in situ, and by cells of the innate and the adaptive immune system. The inflammatory response leads to the proliferation and dysfunction of cells of the glomerulus, and invasion of the interstitial space with immune cells, resulting in tubular cell malfunction and fibrosis. T cells are critical drivers of autoimmunity and related organ damage, by supporting B-cell differentiation and antibody production or by directly promoting inflammation and cytotoxicity against kidney resident cells. T cells might become activated by autoantigens in the periphery and become polarized to secrete inflammatory cytokines before entering the kidney where they have the opportunity to expand owing to the presence of costimulatory molecules and activating cytokines. Alternatively, naive T cells could enter the kidney where they become activated after encountering autoantigen and expand locally. As not all individuals with a peripheral autoimmune response to kidney antigens develop glomerulonephritis, the contribution of local kidney factors expressed or produced by kidney cells is probably of crucial importance. Improved understanding of the biochemistry and molecular biology of T cells in patients with glomerulonephritis offers unique opportunities for the recognition of treatment targets for autoimmune kidney disease.

Nickel-smelting fumes increased the expression of HIF-1α through PI3K/ERK pathway in NIH/3T3 cells

OBJECTIVE

The purpose of this study was to investigate the effects of Nickel (Ni) -smelting fumes on oncogenic proteins in vivo and in vitro.

METHODS

Ni fallout beside a Ni smelting furnace in a factory was sampled to study its toxic effect. The effects of Ni-smelting fumes on the regulation of PI3K and ERK signaling pathways and the important downstream hypoxia inducible factor, HIF-1α, were studied both in NIH/3T3 cells and in the lung tissue of rats. NIH/3T3 cell transformation induced by Ni-smelting fumes was also observed.

RESULTS

Ni-smelting fumes activated PI3K, p-AKT, p70S6K1, and ERK proteins and increased HIF-1α expression in a time- and dose-dependent manner. However, activation was suppressed when NIH/3T3 cells were pretreated with PI3K/AKT or ERK inhibitors. Ni-smelting fumes caused malignant transformation of NIH/3T3 cells.

CONCLUSIONS

Ni-smelting fumes increased the expression of HIF-1α through the PI3K/ERK pathway in NIH/3T3 cells and induced malignant transformation in these cells indicating that Ni-smelting fumes may be a potential carcinogen in mammalian cells.

Role of mTOR Inhibitors in Kidney Disease

The first compound that inhibited the mammalian target of rapamycin (mTOR), sirolimus (rapamycin) was discovered in the 1970s as a soil bacterium metabolite collected on Easter Island (Rapa Nui). Because sirolimus showed antiproliferative activity, researchers investigated its molecular target and identified the TOR1 and TOR2. The mTOR consists of mTOR complex 1 (mTORC1) and mTORC2. Rapalogues including sirolimus, everolimus, and temsirolimus exert their effect mainly on mTORC1, whereas their inhibitory effect on mTORC2 is mild. To obtain compounds with more potent antiproliferative effects, ATP-competitive inhibitors of mTOR targeting both mTORC1 and mTORC2 have been developed and tested in clinical trials as anticancer drugs. Currently, mTOR inhibitors are used as anticancer drugs against several solid tumors, and immunosuppressive agents for transplantation of various organs. This review discusses the role of mTOR inhibitors in renal disease with a particular focus on renal cancer, diabetic nephropathy, and kidney transplantation.

Hsp90β is involved in the development of high salt-diet-induced nephropathy via interaction with various signalling proteins

A high-salt diet often leads to a local intrarenal increase in renal hypoxia and oxidative stress, which are responsible for an excess production of pathogenic substances. Here, Wistar Kyoto/spontaneous hypertensive (WKY/SHR) rats fed a high-salt diet developed severe proteinuria, resulting from pronounced renal inflammation, fibrosis and tubular epithelial cell apoptosis. All these were mainly non-pressure-related effects. Hsp90β, TGF-β, HIF-1α, TNF-α, IL-6 and MCP-1 were shown to be highly expressed in response to salt loading. Next, we found that Hsp90β might play the key role in non-pressure-related effects of salt loading through a series of cellular signalling events, including the NF-κB, p38 activation and Bcl-2 inactivation. Hsp90β was previously proven to regulate the upstream mediators in multiple cellular signalling cascades through stabilizing and maintaining their activities. In our study, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG) or Hsp90β knockdown dramatically alleviated the high-salt-diet-induced proteinuria and renal damage without altering blood pressure significantly, when it reversed activations of NF-κB, mTOR and p38 signalling cascades. Meanwhile, Co-IP results demonstrated that Hsp90β could interact with and stabilize TAK1, AMPKα, IKKα/β, HIF-1α and Raptor, whereas Hsp90β inhibition disrupted this process. In addition, Hsp90β inhibition-mediated renal improvements also accompanied the reduction of renal oxidative stress. In conclusion, salt loading indeed exhibited non-pressure-related impacts on proteinuria and renal dysfunction in WKY/SHR rats. Hsp90β inhibition caused the destabilization of upstream mediators in various pathogenic signalling events, thereby effectively ameliorating this nephropathy owing to renal hypoxia and oxidative stress.

1, 25(OH)2D3 protects β cell against high glucose-induced apoptosis through mTOR suppressing

Diabetes mellitus is a leading cause of death and disability worldwide, which presents a serious public health crisis in China nowadays. It has been well recognized that excessive β-cell apoptosis is the key pathogenesis of diabetes, of which the mammalian target of rapamycin (mTOR) serves as the critical signaling pathway. Emerging evidence indicates that vitamin D deficiency acts as a potential risk factor for diabetes. The present study aims to test the hypothesis that 1 alpha, 25-dihydroxyvitamin D(3) [1, 25(OH)2D3] can inhibit β-cell apoptosis via the suppression of mTOR signaling pathway. β-cells (INS-1) were cultured in the context of normal glucose or high glucose media with or without 1, 25(OH)2D3 treatment. β-cell apoptosis was evaluated by inverted fluorescence microscope, flow cytometry and electron microscope, respectively. Quantitative RT-PCR and Western blotting were performed to assess the possible perturbations in mTOR signaling pathway. High glucose significantly increased β-cell apoptosis. Of importance, RT-PCR and Western blotting demonstrated that high glucose inhibited DNA-damage-inducible transcript 4 (DDIT4) and TSC1/TSC2, up-regulated Rheb/mTOR/p70S6K and enhanced expression of the apoptosis regulating proteins, such as phospho-Bcl-2, cytochrome C and cleaved caspase. Interestingly, 1, 25(OH)2D3 treatment reversed high glucose induced pathological changes in mTOR signaling pathway, restored expression of DDIT4 and TSC1/TSC2, blocked aberrant up-regulation of Rheb/mTOR/p70S6K and the apoptosis regulating proteins, and effectively inhibited β-cell apoptosis. Therefore, 1, 25(OH)2D3 treatment can effectively protects β cell against high glucose-induced apoptosis mainly via the suppression of mTOR signaling pathway, which may be considered as a potential therapy for patients with diabetes.

Microarray profile of human kidney from diabetes, renal cell carcinoma and renal cell carcinoma with diabetes

Recent study from our laboratory showed that patients with diabetes are at a higher risk of developing kidney cancer. In the current study, we have screened whole human DNA genome from healthy control, patients with diabetes or renal cell carcinoma (RCC) or RCC+diabetes. We found that 883 genes gain/163 genes loss of copy number in RCC+diabetes group, 669 genes gain/307 genes loss in RCC group and 458 genes gain/38 genes loss of copy number in diabetes group, after removing gain/loss genes obtained from healthy control group. Data analyzed for functional annotation enrichment pathways showed that control group had the highest number (280) of enriched pathways, 191 in diabetes+RCC group, 148 in RCC group, and 81 in diabetes group. The overlap GO pathways between RCC+diabetes and RCC groups showed that nine were enriched, between RCC+diabetes and diabetes groups was four and between diabetes and RCC groups was eight GO pathways. Overall, we observed majority of DNA alterations in patients from RCC+diabetes group. Interestingly, insulin receptor (INSR) is highly expressed and had gains in copy number in RCC+diabetes and diabetes groups. The changes in INSR copy number may use as a biomarker for predicting RCC development in diabetic patients.

Hyperactivation of Akt/mTOR and deficiency in tuberin increased the oxidative DNA damage in kidney cancer patients with diabetes

Recent study from our laboratory showed that patients with diabetes are at a higher risk of developing kidney cancer. In the current study, we have explored one of the mechanisms by which diabetes accelerates tumorigenesis in the kidney. Kidney cancer tissue from patients with diabetes showed a higher activity of Akt and decreased in total protein of tuberin compared to kidney cancer patient without diabetes or diabetes alone. In addition, a significant increase in phospho-Akt/tuberin expression was associated with an increase in Ki67 expression and activation of mTOR in kidney tumor with or without diabetes compared to diabetes alone. In addition, decrease in tuberin expression resulted in a significant decrease in protein expression of OGG1 and increased in oxidative DNA damage, 8-oxodG in kidney tissues from patients with cancer or cancer+diabetes. Importantly, these data showed that the majority of the staining of Akt/tuberin/p70S6K phosphorylation was more prominently in the tubular cells. In addition, accumulation of oxidative DNA damage is localized only in the nucleus of tubular cells within the cortex region. These data suggest that Akt/tuberin/mTOR pathway plays an important role in the regulation DNA damage and repair pathways that may predispose diabetic kidneys to pathogenesis of renal cell carcinoma.

Cytotoxicity, genotoxicity and alteration of cellular antioxidant enzymes in silver nanoparticles exposed CHO cells

The broad applications of silver nanoparticles (Ag NPs) increase human exposure, thus potential risk associated with their toxicity; therefore, the toxicity of Ag NPs, synthesized by chemical route was studied using Chinese Hamster Ovary (CHO) cells.

PKCδ promotes high glucose induced renal tubular oxidative damage via regulating activation and translocation of p66Shc

Diabetic kidney disease (DKD) is a leading cause of end-stage renal disease (ESRD). Renal tubular injury by overproduction of ROS in mitochondria plays a critical role in the pathogenesis of DKD. Evidences have shown that p66Shc was involved in renal tubular injury via mitochondrial-dependent ROS production pathway, but little is known about the upstream signaling of p66Shc that leads to tubular oxidative damage under high glucose conditions. In this study, an increased PKCδ and p66Shc activation and ROS production in renal tissues of patients with diabetic nephropathy were seen and further analysis revealed a positive correlation between the tubulointerstitial damage and p-PKCδ, p-p66Shc, and ROS production. In vitro, we investigated the phosphorylation and activation of p66Shc and PKCδ during treatment of HK-2 cells with high glucose (HG). Results showed that the activation of p66Shc and PKCδ was increased in a dose- and time-dependent manner, and this effect was suppressed by Rottlerin, a pharmacologic inhibitor of PKCδ. Moreover, PKCδ siRNA partially blocked HG-induced p66Shc phosphorylation, translocation, and ROS production in HK-2 cells. Taken together, these data suggest that activation of PKCδ promotes tubular cell injury through regulating p66Shc phosphorylation and mitochondrial translocation in HG ambient.

Naringenin accords hepatoprotection from streptozotocin induced diabetes in vivo by modulating mitochondrial dysfunction and apoptotic signaling cascade

Diabetic complications cause noticeable liver damage, which finally progresses to diabetic hepatopathy. Nutritive antioxidants not only reduce the liver damage, but also prevent it by modulating the release of various proteins involved in apoptotic signaling cascades. This study explores the molecular mechanisms underlying diabetes-induced liver damage and its modulation by naringenin. Antioxidant status, liver & kidney biomarker enzymes, reactive oxygen species (ROS) generation, mitochondrial membrane potential, expression of apoptotic proteins like Bax (bcl-2 associated X), Bcl-2 (b-cell Lymhoma-2), Caspase-3, Caspase-9, AIF (Apoptosis inducing factor) and Endo-G (Endonuclease-G) were studied in streptozotocin induced diabetic rats. Significant hyperglycemia, disturbed antioxidant status, altered carbohydrate metabolizing enzymes, increased ROS and lipid peroxidation; decreased mitochondrial membrane potential and enhanced release of AIF and Endo-G were observed. Hyperglycemia also affected apoptosis and its related genes at both transcriptional and translational level (Caspase-3 & 9, Bax and Bcl-2) in the liver of diabetic rats. Naringenin, a flavonone, exerted anti-hyperglycemic effect and was able to prevent oxidative stress and resultant apoptotic events caused due to diabetes-induced hepatotoxicity. Thus, our study shows, a protective effect of naringenin against diabetes induced liver damage and redox imbalance, which could further be exploited for the management of diabetic hepatopathy.