AP-1 proteins mediate hyperglycemia-induced activation of the human TGF-beta1 promoter in mesangial cells

The effect of selenium on the intestinal health of juvenile grass carp based on the ERS-autophagy pathway

Selenium (Se), a trace element, is vital for the maintenance of cellular redox balance, thyroid hormone metabolism, inflammation, and immunity. Aeromonas hydrophila (A. hydrophila) is a common Gram-negative conditional pathogenic bacterium in fish culture, posing a serious threat to intensive aquaculture. Our study investigated the influence of dietary Se on the intestinal immune function of grass carp (Ctenopharyngodon idella) and the related regulatory mechanisms. The 2160 healthy juvenile grass carp (9.76 ± 0.005 g) were randomly assigned to 6 test groups of 6 replicates each, and fed graded selenomethionine (0.05, 0.20, 0.40, 0.61, 0.77, 0.98 mg Se/kg diet) for 70 days and then injected with A. hydrophila for a 6-day attack test. The results indicated that appropriate Se levels (0.40 mg/kg diet) alleviated intestinal damage caused by A. hydrophila and increased intestinal immune substances C3 and C4 levels as well as the activity of acid phosphatase (ACP) and lysozyme (LZ) (P > 0.05). Appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) decreased intestinal pro-inflammatory cytokines (IFN-γ2, IL-6, IL-12p35, IL-17 A F and IL-17D) mRNA levels (P > 0.05) and increased intestinal anti-inflammatory factors (TGF-β1, IL-4/13A, IL-4/13B, IL-10 and IL-22) mRNA levels (P > 0.05) in juvenile grass carp. Further studies revealed that Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal endoplasmic reticulum stress (ERS)-related signaling pathway. Furthermore, we found that appropriate levels of Se (0.40 mg/kg-0.61 mg/kg diet) inhibited intestinal autophagy in juvenile grass carp, which may be related to ULK1, Beclin 1, ATG5, ATG12, LC3, and P62. In conclusion, appropriate levels of Se can alleviate intestinal inflammation and inhibit ERS and autophagy in juvenile grass carp. A quadratic regression analysis of intestinal ACP and LZ also indicated that the Se requirements of juvenile grass carp were 0.59 and 0.51 mg/kg, respectively.

Resveratrol protects mesangial cells under high glucose by regulating the miR-1231/IGF1/ERK pathway

Diabetic nephropathy (DN) is one of the complications of diabetes mellitus and the main cause of end-stage renal disease (ESRD), which is a serious threat to human health. In DN, mesangial cells (MCs) are a critical target cell that perform a variety of key functions, and abnormal proliferation of MCs is a common and prominent pathological change in DN. In recent years, the investigation of Chinese medicine interventions for DN has increased significantly in recent years due to the many potential adverse effects and controversies associated with the treatment of DN with Western medicines. In this study, we evaluated the protective effect of resveratrol (RES), an active ingredient known as a natural antioxidant, on HMCs under high glucose and explored its possible mechanism of action. We found that RES inhibited the proliferation of human mesangial cell (HMC) under high glucose and blocked cell cycle progression. In the high glucose environment, RES upregulated miR-1231, reduced IGF1 expression, inhibited the activity of the extracellular signal-regulated kinase (ERK) signaling pathway and reduced levels of the inflammatory factors TNF-α and IL-6. In addition, we found that miR-1231 mimics were synergistically inhibited with RES, whereas miR-1231 inhibitor attenuated the protective effect of RES on HMCs. Thus, our results suggest that the protective effect of RES on HMCs under high glucose is achieved, at least in part, through modulation of the miR-1231/IGF1/ERK pathway. The discovery of this potential mechanism may provide a new molecular therapeutic target for the prevention and treatment of DN, and may also bring new ideas for the clinical research in DN.

Transforming Growth Factorβ1 Overexpression Is Associated with Insulin Resistance and Rapidly Progressive Kidney Fibrosis under Diabetic Conditions

Diabetes mellitus is a global health problem. Diabetic nephropathy is a common complication of diabetes mellitus and the leading cause of end-stage renal disease. The clinical course, response to therapy, and prognosis of nephropathy are worse in diabetic than in non-diabetic patients. The role of transforming growth factorβ1 in kidney fibrosis is undebatable. This study assessed whether the overexpression of transforming growth factorβ1 is associated with insulin resistance and the rapid progression of transforming growth factorβ1-mediated nephropathy under diabetic conditions. Diabetes mellitus was induced with streptozotocin in wild-type mice and transgenic mice with the kidney-specific overexpression of human transforming growth factorβ1. Mice treated with saline were the controls. Glucose tolerance and kidney fibrosis were evaluated. The blood glucose levels, the values of the homeostasis model assessment for insulin resistance, and the area of kidney fibrosis were significantly increased, and the renal function was significantly impaired in the diabetic transforming growth factorβ1 transgenic mice compared to the non-diabetic transgenic mice, diabetic wild-type mice, and non-diabetic mice. Transforming growth factorβ1 impaired the regulatory effect of insulin on glucose in the hepatocyte and skeletal muscle cell lines. This study shows that transforming growth factorβ1 overexpression is associated with insulin resistance and rapidly progressive kidney fibrosis under diabetic conditions in mice.

Dipeptidyl Peptidase-4 Stabilizes Integrin α4β1 Complex to Promote Thyroid Cancer Cell Metastasis by Activating Transforming Growth Factor-Beta Signaling Pathway

Background: Metastatic disease is a major cause of thyroid cancer-related death. However, the mechanisms responsible for thyroid cancer metastasis are unclear. Dipeptidyl peptidase-4 (DPP4) is a multifunctional cell surface glycoprotein that has been reported to be a negative prognostic factor in thyroid cancer. We explored the molecular mechanism of the role of DPP4 in thyroid cancer cell metastasis. Methods: The effects of DPP4 on thyroid cancer cell migration/invasion in vitro were assessed by transwell assays. A lung metastatic mouse model was also established to determine the effect of DPP4 on tumor metastasis in vivo. DPP4 inhibitor sitagliptin was used to test its effect on thyroid cancer cell metastasis. The mechanism of which DPP4 promotes thyroid cancer cell metastasis was explored by a series of molecular and biochemical experiments. Results: We observed that DPP4 was significantly upregulated in papillary thyroid cancers compared with control subjects, and its expression was positively associated with lymph node metastasis and BRAF^V600E mutation. Functional studies showed that DPP4 knockdown significantly inhibited metastatic potential of thyroid cancer cells, and vice versa. However, DPP4 inhibitor sitagliptin did not affect the metastatic ability of thyroid cancer cells, indicating that the promoting effect of DPP4 on tumor metastasis was independent of its enzymatic activity. Mechanistically, DPP4 interacted with the α4 and β1 integrin subunits, and stabilized the formation of integrin α4β1 complex. DPP4-mediated integrin signal activation promoted the nuclear localization of c-Jun through the FAK/AKT pathway, thereby inducing the transcription of transforming growth factor-beta 1 (TGFB1 coding for protein TGF-β1). TGF-β1 then facilitated tumor metastasis by inducing the epithelial-mesenchymal transition. Conclusions: DPP4 promotes thyroid cancer cell metastasis through the integrins/FAK/AKT/c-Jun/TGF-β1 signaling axis. These findings may have implications for an alternative therapeutic strategy for thyroid cancer.

The multiple biotoxicity integrated study in grass carp (Ctenopharyngodon idella) caused by Ochratoxin A: Oxidative damage, apoptosis and immunosuppression

Ochratoxin A (OTA) is a common hazardous food contaminant that seriously endangers human and animal health. However, limited study is focused on aquatic animal. This research investigated the multiple biotoxicity of OTA on spleen (SP) and head kidney (HK) in grass carp and its related mechanism. Our data showed that, dietary supplemented with OTA above 1209 μg/kg caused histopathological damages by decreasing the number of lymphocytes and necrotizing renal parenchymal cells. Meanwhile, OTA caused oxidative damage and reduced the isoforms mRNAs transcripts of antioxidant enzymes (e.g., GPX1, GPX4, GSTO) partly due to suppressing NF-E2-related factor 2 (Nrf2). OTA triggered apoptosis through mitochondria and death receptor pathway potentially by p38 mitogen-activated protein kinase (p38MAPK) activation. Besides, OTA exacerbated inflammation by down-regulation of anti-inflammatory factor (e.g., IL-10, IL-4) and up-regulations of pro-inflammatory factors (e.g., TNF-α, IL-6), which could be ascribed to signaling meditation of Janus kinase / signal transducer and activator of transcription (JAK/STAT). Additionally, the safe upper limits of OTA were estimated to be 677.6 and 695.08 μg/kg based on the immune-related indexes (C3 contents in the SP and LZ activities in the HK, respectively). Our study has provided a wide insight for toxicological assessment of feed pollutant in aquatic animals.

GLUT3 Promotes Epithelial–Mesenchymal Transition via TGF-β/JNK/ATF2 Signaling Pathway in Colorectal Cancer Cells

Glucose transporter (GLUT) 3, a member of the GLUTs family, is involved in cellular glucose utilization and the first step in glycolysis. GLUT3 is highly expressed in colorectal cancer (CRC) and it leads to poor prognosis to CRC patient outcome. However, the molecular mechanisms of GLUT3 on the epithelial–mesenchymal transition (EMT) process in metastatic CRC is not yet clear. Here, we identified that activation of the c-Jun N-terminal kinase (JNK)/activating transcription factor-2 (ATF2) signaling pathway by transforming growth factor-β (TGF-β) promotes GLUT3-induced EMT in CRC cells. The regulation of GLUT3 expression was significantly associated with EMT-related markers such as E-cadherin, α- smooth muscle actin (α-SMA), plasminogen activator inhibitor-1 (PAI-1), vimentin and zinc finger E-box binding homeobox 1 (ZEB1). We also found that GLUT3 accelerated the invasive ability of CRC cells. Mechanistically, TGF-β induced the expression of GLUT3 through the phosphorylation of JNK/ATF2, one of the SMAD-independent pathways. TGF-β induced the expression of GLUT3 by increasing the phosphorylation of JNK, the nuclear translocation of the ATF2 transcription factor, and the binding of ATF2 to the promoter region of GLUT3, which increased EMT in CRC cells. Collectively, our results provide a new comprehensive mechanism that GLUT3 promotes EMT process through the TGF-β/JNK/ATF2 signaling pathway, which could be a potential target for the treatment of metastatic CRC.

Age-associated callus senescent cells produce TGF-β1 that inhibits fracture healing in aged mice

Cellular senescence plays an important role in human diseases, including osteoporosis and osteoarthritis. Senescent cells (SCs) produce the senescence-associated secretory phenotype to affect the function of neighboring cells and SCs themselves. Delayed fracture healing is common in the elderly and is accompanied by reduced mesenchymal progenitor cells (MPCs). However, the contribution of cellular senescence to fracture healing in the aged has not to our knowledge been studied. Here, we used C57BL/6J 4-month-old young and 20-month-old aged mice and demonstrated a rapid increase in SCs in the fracture callus of aged mice. The senolytic drugs dasatinib plus quercetin enhanced fracture healing in aged mice. Aged callus SCs inhibited the growth and proliferation of callus-derived MPCs (CaMPCs) and expressed high levels of TGF-β1. TGF-β–neutralizing Ab prevented the inhibitory effects of aged callus SCs on CaMPCs and promoted fracture healing in aged mice, which was associated with increased CaMPCs and proliferating cells. Thus, fracture triggered a significant cellular senescence in the callus cells of aged mice, which inhibited MPCs by expressing TGF-β1. Short-term administration of dasatinib plus quercetin depleted callus SCs and accelerated fracture healing in aged mice. Senolytic drugs represent a promising therapy, while TGF-β1 signaling is a molecular mechanism for fractures in the elderly via SCs.

Inhibitory Effect of Resveratrol on LPS-induced Glomerular Mesangial Cells Proliferation and TGF-β1 Expression via Sphingosine Kinase 1 Pathway

OBJECTIVE

To elucidate the renoprotective effect of resveratrol (RSV) on sphingosine kinase 1 (SphK1) signaling pathway and expression of its downstream molecules including activator protein 1 (AP-1) and transformation growth factor-β1 (TGF-β1) in lipopolysaccharide (LPS)-induced glomerular mesangial cells (GMCs).

METHODS

The rat GMCs line (HBZY-1) were cultured and randomly divided into 5 groups, including control, LPS (100 ng/mL), and 5, 10, 20 µmol/L RSV-treated groups. In addition, SphK1 inhibitor (SK-II) was used as positive control. GMCs were pretreated with RSV for 2 h and treated with LPS for another 24 h. GMCs proliferation was determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) assay. The proteins expression of SphK1, p-c-Jun and TGF-β1 in GMCs were detected by Western blot, and DNA-binding activity of AP-1 was performed by electrophoretic mobility shift assay (EMSA). The binding activity between RSV and SphK1 protein was detected by AutoDock Vina and visualized by Discovery Studio 2016.

RESULTS

LPS could obviously stimulate GMCs proliferation, elevate SphK1, p-c-Jun and TGF-β1 expression levels and increase the DNA-binding activity of AP-1 (P<0.05 or P<0.01), whereas these effects were significantly blocked by RSV pretreatment. It was also suggested that the effect of RSV was similar to SK-II (P>0.05). Moreover, RSV exhibited good binding affinity towards SphK1, with docking scores of -8.1 kcal/moL and formed hydrogen bonds with ASP-178 and LEU-268 in SphK1.

CONCLUSION

RSV inhibited LPS-induced GMCs proliferation and TGF-β1 expression, which may be independent of its hypoglycemic effect on preventing the development of mesangial cell fibrosis and closely related to the direct inhibition of SphK1 pathway.

Inhibition of CtBP-Regulated Proinflammatory Gene Transcription Attenuates Psoriatic Skin Inflammation

Psoriasis is a chronic immune-mediated disease characterized by excessive proliferation of epidermal keratinocytes and increased immune cell infiltration to the skin. Although it is well-known that psoriasis pathogenesis is driven by aberrant production of proinflammatory cytokines, the mechanisms underlying the imbalance between proinflammatory and anti-inflammatory cytokine expression are incompletely understood. In this study, we report that the transcriptional coregulators CtBP1 and 2 can transactivate a common set of proinflammatory genes both in the skin of imiquimod-induced mouse psoriasis model and in human keratinocytes and macrophages stimulated by imiquimod. We find that mice overexpressing CtBP1 in epidermal keratinocytes display severe skin inflammation phenotypes with increased expression of T helper type 1 and T helper type 17 cytokines. We also find that the expression of CtBPs and CtBP-target genes is elevated both in human psoriatic lesions and in the mouse imiquimod psoriasis model. Moreover, we were able to show that topical treatment with a peptidic inhibitor of CtBP effectively suppresses the CtBP-regulated proinflammatory gene expression and thus attenuates psoriatic inflammation in the imiquimod mouse model. Together, our findings suggest to our knowledge previously unreported strategies for therapeutic modulation of the immune response in inflammatory skin diseases.

Review of early circulating biomolecules associated with diabetes nephropathy - Ideal candidates for early biomarker array test for DN

BACKGROUND

Diabetic nephropathy (DN) is one of the catastrophic complications of type 2 diabetes mellitus (T2DM). 45% of DN patients progressed to End Stage Renal Disease (ESRD) which robs casualties of the quality of live. The challenge in early diagnosis of DN is it is asymptomatic in the early phase. Current gold standard test for screening and diagnosis of DN are nonspecific and are not sensitive in detecting DN early enough and subsequently monitor renal function during management and intervention plans. Recent studies reported various biomolecules which are associated with the onset of DN in T2DM using cutting-edge technologies. These biomolecules could be potential early biomarkers for DN. This review selectively identified potential early serum biomolecules which are potential candidates for developing an Early Biomarker Array Test for DN.

METHODS

An advanced literature search was conducted on 4 online databases. Search terms used were "Diabetes Mellitus, Type 2", "Diabetic nephropathy", "pathogenesis" and "early biomarker. Filters were applied to capture articles published from 2010 to 2020, written in English, human or animal models and focused on serum biomolecules associated with DN.

RESULTS

Five serum biomolecules have been evidently described as contributing pivotal roles in the pathophysiology of DN. MiR-377, miR-99b, CYP2E1, TGF-β1 and periostin are potential candidates for designing an early biomarker array for screening and diagnosis of early stages of DN. The five shortlisted biomolecules originates from endogenous biochemical processes which are specific to the progressive pathophysiology of DN.

CONCLUSION

miR-377, miR-99b, CYP2E1, TGF-β1 and periostin are potential candidate biomolecules for diagnosing DN at the early phases and can be developed into a panel of endogenous biomarkers for early detection of DN in patients with T2DM. The outcomes of this study will be a stepping stone towards planning and developing an early biomarker array test for diabetic nephropathy. The proposed panel of early biomarkers for DN has potential of stratifying the stages of DN because each biomolecule appears at distinct stages in the pathophysiology of DN.

Activated Alpha 2-Macroglobulin Is a Novel Mediator of Mesangial Cell Profibrotic Signaling in Diabetic Kidney Disease

Diabetic kidney disease (DKD) is caused by the overproduction of extracellular matrix proteins (ECM) by glomerular mesangial cells (MCs). We previously showed that high glucose (HG) induces cell surface translocation of GRP78 (csGRP78), mediating PI3K/Akt activation and downstream ECM production. Activated alpha 2-macroglobulin (α2M*) is a ligand known to initiate this signaling cascade. Importantly, increased α2M was observed in diabetic patients’ serum, saliva, and glomeruli. Primary MCs were used to assess HG responses. The role of α2M* was assessed using siRNA, a neutralizing antibody and inhibitory peptide. Kidneys from type 1 diabetic Akita and CD1 mice and human DKD patients were stained for α2M/α2M*. α2M transcript and protein were significantly increased with HG in vitro and in vivo in diabetic kidneys. A similar increase in α2M* was seen in media and kidneys, where it localized to the mesangium. No appreciable α2M* was seen in normal kidneys. Knockdown or neutralization of α2M/α2M* inhibited HG-induced profibrotic signaling (Akt activation) and matrix/cytokine upregulation (collagen IV, fibronectin, CTGF, and TGFβ1). In patients with established DKD, urinary α2M* and TGFβ1 levels were correlated. These data reveal an important role for α2M* in the pathogenesis of DKD and support further investigation as a potential novel therapeutic target.

High-risk factors related to the occurrence and development of abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a common and potentially dangerous vascular disease with many risk factors related to its occurrence and development. This review collects the results from recent studies of different comorbidities including hypertension, diabetes, and hyperlipidemia and summarizes their connections with AAA development and its underlying mechanisms. We believe that hypertension, diabetes, and hyperlipidemia can affect AAA occurrence and development, but more studies are needed to further explore the mechanisms.

Hydroxysafflor Yellow A Inhibits TNF-α-Induced Inflammation of Human Fetal Lung Fibroblasts via NF-κB Signaling Pathway

Objective

Hydroxysafflor yellow A (HSYA), an effective ingredient of the Chinese herb Carthamus tinctorius L, attenuated bleomycin-induced pulmonary fibrosis in mice. This study is to investigate the effect of HSYA on the proliferation and inflammatory level of human fetal lung fibroblasts (MRC-5 cells) induced by tumor necrosis factor-α (TNF-α) and explore the underlying mechanisms.

Methods

MRC-5 cells were treated with different concentrations of TNF-α, HSYA, or/and etanercept (ENCP, TNF-α receptor (TNFR1) antagonist, 500 ng/mL) before cell proliferation was detected. The laser confocal microscope was used to observe the role of HSYA in binding of TNF-α and its receptor. Co-immunoprecipitation was used to detect the binding of TNFR1 and TAK1-TAB2 complex. Real-time quantitative RT-PCR and western blot were used to detect the expressions of inflammation-related cytokines and proteins related with the NF-κB pathway. Luciferase reporter gene assay and chromatin coprecipitation method were used to detect the interaction between AP-1 and TGF-β1 promoter.

Results

TNF-α (5 ng/mL) was used to induce inflammation and proliferation in MRC-5 cells. HSYA can partially suppress the stimulation of TNF-α on proliferation and inflammatory response of MRC-5 cells. HSYA could compete with TNF-α to bind with TNFR1 and hamper the binding of TNFR1 to TAK1-TAB2 complex. In addition, HSYA could also inhibit the activation of the NF-κB signal pathway and suppress the binding of TGF-β1 promoter with AP-1.

Conclusion

Evidence in this study suggested that HSYA affects TNF-α-induced proliferation and inflammatory response of MRC-5 cells through the NF-κB/AP-1 signaling pathway, which may provide theoretical basis for HSYA treatment in pulmonary fibrosis.

Sirtuin 6 deficiency transcriptionally up-regulates TGF-β signaling and induces fibrosis in mice

Caloric restriction has been associated with increased life span and reduced aging-related disorders and reduces fibrosis in several diseases. Fibrosis is characterized by deposition of excess fibrous material in tissues and organs and is caused by aging, chronic stress, injury, or disease. Myofibroblasts are fibroblast-like cells that secrete high levels of extracellular matrix proteins, resulting in fibrosis. Histological studies have identified many-fold increases of myofibroblasts in aged organs where myofibroblasts are constantly generated from resident tissue fibroblasts and other cell types. However, it remains unclear how aging increases the generation of myofibroblasts. Here, using mouse models and biochemical assays, we show that sirtuin 6 (SIRT6) deficiency plays a major role in aging-associated transformation of fibroblasts to myofibroblasts, resulting in tissue fibrosis. Our findings suggest that SIRT6-deficient fibroblasts transform spontaneously to myofibroblasts through hyperactivation of transforming growth factor β (TGF-β) signaling in a cell-autonomous manner. Importantly, we noted that SIRT6 haploinsufficiency is sufficient for enhancing myofibroblast generation, leading to multiorgan fibrosis and cardiac dysfunction in mice during aging. Mechanistically, SIRT6 bound to and repressed the expression of key TGF-β signaling genes by deacetylating SMAD family member 3 (SMAD3) and Lys-9 and Lys-56 in histone 3. SIRT6 binding to the promoters of genes in the TGF-β signaling pathway decreased significantly with age and was accompanied by increased binding of SMAD3 to these promoters. Our findings reveal that SIRT6 may be a potential candidate for modulating TGF-β signaling to reduce multiorgan fibrosis during aging and fibrosis-associated diseases.

Yin Yang 1 protein ameliorates diabetic nephropathy pathology through transcriptional repression of TGFβ1

Transforming growth factor–β1 (TGFβ1) has been identified as a major pathogenic factor underlying the development of diabetic nephropathy (DN). However, the current strategy of antagonizing TGFβ1 has failed to demonstrate favorable outcomes in clinical trials. To identify a different therapeutic approach, we designed a mass spectrometry–based DNA-protein interaction screen to find transcriptional repressors that bind to the TGFB1 promoter and identified Yin Yang 1 (YY1) as a potent repressor of TGFB1. YY1 bound directly to TGFB1 promoter regions and repressed TGFB1 transcription in human renal mesangial cells. In mouse models, YY1 was elevated in mesangial cells during early diabetic renal lesions and decreased in later stages, and knockdown of renal YY1 aggravated, whereas overexpression of YY1 attenuated glomerulosclerosis. In addition, although their duration of diabetic course was comparable, patients with higher YY1 expression developed diabetic nephropathy more slowly compared to those who presented with lower YY1 expression. We found that a small molecule, eudesmin, suppressed TGFβ1 and other profibrotic factors by increasing YY1 expression in human renal mesangial cells and attenuated diabetic renal lesions in DN mouse models by increasing YY1 expression. These results suggest that YY1 is a potent transcriptional repressor of TGFB1 during the development of DN in diabetic mice and that small molecules targeting YY1 may serve as promising therapies for treating DN.

Phytic acid disrupted intestinal immune status and suppressed growth performance in on-growing grass carp (Ctenopharyngodon idella)

Phytic acid (PA) is one of the most common anti-nutritional factors in plant-derived protein feeds, and it poses considerable threats to aquaculture production. However, little is known about the effects of PA on fish intestinal health. This study aimed to investigate the impacts of PA on intestinal immune function in on-growing grass carp. To achieve this goal, a growth trial was conducted for 60 days by feeding 540 fish (120.56 ± 0.51 g) with six semi-purified diets containing graded levels of PA (0, 0.8, 1.6, 2.4, 3.2 and 4.0%). Then fish were challenged with Aeromonas hydrophila for 6 days. The results indicated that, compared with the control group (0% PA), PA did the following: (1) suppressed fish growth performance (percentage weight gain and feed efficiency) and reduced their ability to resist enteritis; (2) decreased fish intestinal antimicrobial ability by reducing intestinal lysozyme (LZ) activities, the contents of complement 3 (C3), C4 and immunoglobulin M (IgM), and downregulating the mRNA levels of hepcidin, liver-expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, and β-defensin-1; and (3) aggravated fish intestinal inflammation responses by upregulating the mRNA levels of pro-inflammatory cytokines including tumour necrosis factor α (TNF-α), interleukin 1β (IL-1β) (except in the DI), interferon γ2 (IFN-γ2), IL-8, IL-12p40, IL-15 (except in the DI) and IL-17D, which is partly related to the nuclear factor kappa B (NF-κB) signalling pathway, whereas downregulating the mRNA levels of anti-inflammatory cytokines including transforming growth factor β1 (TGF-β1), IL-4/13A, IL-4/13B, IL-10 and IL-11, which is partially associated with the target of rapamycin (TOR) signalling pathway. The possible reasons for some distinctive gene expression patterns in fish three intestinal segments were discussed. Finally, based on the percent weight gain, enteritis morbidity, IgM content and LZ activity in the PI, the maximum tolerance levels of PA for on-growing grass carp were estimated to be 2.17, 1.68, 1.47 and 1.18% of the diet, respectively.

Unraveling the Role of Inflammation in the Pathogenesis of Diabetic Kidney Disease

Diabetic kidney disease (DKD) remains the leading cause of end-stage renal disease (ESRD) and is therefore a major burden on the healthcare system. Patients with DKD are highly susceptible to developing cardiovascular disease, which contributes to increased morbidity and mortality rates. While progress has been made to inhibit the acceleration of DKD, current standards of care reduce but do not eliminate the risk of DKD. There is growing appreciation for the role of inflammation in modulating the process of DKD. The focus of this review is on providing an overview of the current status of knowledge regarding the pathologic roles of inflammation in the development of DKD. Finally, we summarize recent therapeutic advances to prevent DKD, with a focus on the anti-inflammatory effects of newly developed agents.

Identification of potential therapeutic target genes in mouse mesangial cells associated with diabetic nephropathy using bioinformatics analysis

The aim of the present study was to identify genes under the effect of transforming growth factor-β (TGF-β1), high glucose (HG) and glucosamine (GlcN) in MES-13 mesangial cells and elucidate the molecular mechanisms of diabetic nephropathy (DN). The gene expression datasets GSE2557 and GSE2558 were downloaded from the Gene Expression Omnibus database. Differentially expressed genes (DEGs) were independently screened using the GEO2R online tool. Gene Ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses were performed using the Database for Annotation, Visualization, and Integrated Discovery. The protein-protein interaction (PPI) network was constructed using the Search Tool for the Retrieval of Interacting Genes and Cytoscape software. The hub genes were identified by the NetworkAnalyzer plugin. Overlapping genes were subjected to molecular docking analysis using SystemsDock. A total of 202 upregulated and 158 downregulated DEGs from the HG-treated groups, 138 upregulated and 103 downregulated DEGs from the GlcN-treated groups, and 81 upregulated and 44 downregulated DEGs from the TGF-β1-treated groups were identified. The majority of the DEGs were independently enriched in 'nucleosome assembly', 'chromatin silencing' and 'xenobiotic glucuronidation'. In addition, KEGG pathways were significantly enriched in 'systemic lupus erythematosus', 'protein processing in endoplasmic reticulum' and 'aldarate metabolism pathway', and 'TNF signaling pathway' intersected in the TGF-β1-treated and HG-treated groups. In total, eight hub genes, Jun, prostaglandin-endoperoxide synthase 2 (Ptgs2), fibronectin 1 (Fn1), cyclin-dependent kinase (Cdk)2, Fos, heat shock protein family A (Hsp70) member 5 (Hspa5), Hsp90b1 and homo sapiens hypoxia upregulated 1 (Hyou1), and three overlapping genes, Ras homolog gene family, member B (RHOB), complement factor H (CFH) and Krüppel-like factor 15 (KLF15), were selected. Valsartan with RHOB, and fosinopril with CFH and KLF15 had preferential binding activity. In conclusion, Jun, Ptgs2, Fn1, Cdk2, Fos, Hspa5, Hsp90b1, Hyou1, RHOB, CFH and KLF15 may be potential therapeutic targets for mesangial cells associated with DN, which may provide insight into DN treatment strategies.

Interleukin 6 Function in the Skin and Isolated Keratinocytes Is Modulated by Hyperglycemia

Diabetes currently affects over twenty-five million Americans. Annual health care cost of diabetes exceeds $254 billion and is associated with a distinct set of diabetic complications that include delayed wound healing and diabetic ulcers. Interleukin 6 (IL-6) plays an important role in wound healing and is known to be elevated in the serum of both type I and type II diabetes patients. This study assesses the expression and function of IL-6 in the hyperglycemic epidermis and keratinocyte culture. Streptozotocin-treated mice were wounded six weeks after induction of hyperglycemia. Wound closure, protein, and mRNA expression were assessed up to 13 days of postwounding. Wound closure was delayed 4-5 days in hyperglycemic animals. Hyperglycemic wounds displayed greater IL-6 and IL-6Rα protein expression at 1, 7, and 10 days of postwounding compared to euglycemic control. However, IL-6Rα mRNA expression was reduced at all time points beyond day 1, while IL-6 mRNA expression did not significantly differ at any time point. SOCS3 mRNA expression was higher in the hyperglycemic skin at every time point. Imaging of fluorescent immunohistology also revealed significantly lower expression of SOCS3, but higher nuclear pSTAT3 in the epidermis of the hyperglycemic skin. Primary mouse keratinocytes cultured in high glucose for 7 days displayed 2-fold higher IL-6Rα mRNA and higher rmIL-6-induced nuclear pSTAT3, but lower SOCS3 basal levels compared to normal glucose-cultured cells. Thus, it appears that delayed diabetic skin wound healing is associated with increased induction and expression of IL-6 and its receptor, but its function in epidermal keratinocytes may be impaired.

Deoxynivalenol decreased intestinal immune function related to NF-κB and TOR signalling in juvenile grass carp (Ctenopharyngodon idella)

Deoxynivalenol (DON) is one of the most common mycotoxins in animal feed worldwide and causes significant threats to the animal production. The intestine is an important mucosal immune organ in teleost, and it is also the first target for feed-borne toxicants in animal. However, studies concerning the effect of DON on fish intestine are scarce. This study explored the effects of DON on intestinal immune function in juvenile grass carp (Ctenopharyngodon idella). A total of 1440 juvenile grass carp (12.17 ± 0.01 g) were fed six diets containing graded levels of DON (27, 318, 636, 922, 1243 and 1515 μg/kg diet) for 60 days. After the growth trial, fish were challenged with Aeromonas hydrophila. The results were analysed by the Duncan's multiple-range test (P < 0.05), indicating that compared with the control group (27 μg/kg diet), dietary DON levels up to 318 μg/kg diet: (1) decreased lysozyme (LZ) and acid phosphatase (ACP) activities, as well as complement 3 (C3), C4 and immunoglobulin M (IgM) content in the proximal intestine (PI), middle intestine (MI) and distal intestine (DI) of juvenile grass carp (P < 0.05); (2) down-regulated the mRNA levels of anti-microbial substance: liver expressed antimicrobial peptide (LEAP) -2A, LEAP-2B, hepcidin, β-defensin-1 and mucin2 in the PI, MI and DI of juvenile grass carp (P < 0.05); (3) up-regulated the mRNA levels of pro-inflammatory cytokines [interleukin 1β (IL-1β), tumour necrosis factor α (TNF-α), interferon γ2 (INF-γ2), IL-6 (only in PI), IL-8, IL-12p35, IL-12p40, IL-15 and IL-17D] in the PI, MI and DI of juvenile grass carp (P < 0.05), which might be partly related to nuclear factor kappa B (NF-κB) signalling [IκB kinase β (IKKβ) and IKKγ/inhibitor of κBα (IκBα)/NF-κB (p65 and c-Rel)]; and (4) down-regulated the mRNA levels of anti-inflammatory cytokines [IL-10, IL-11, IL-4/13A (not IL-4/13B), transforming growth factor β1 (TGF-β1) (not TGF-β2)] in the PI, MI and DI of juvenile grass carp (P < 0.05), which might be partly related to target of rapamycin (TOR) signalling [TOR/ribosomal protein S6 kinases 1 (S6K1) and eIF4E-binding proteins (4E-BP)]. All data indicated that DON could impair the intestinal immune function, and its potential regulation mechanisms were partly associated with NF-κB and TOR signalling pathways. Finally, based on the enteritis morbidity, and the LZ and ACP activities as well as IgM content in the PI, the reasonable dose of DON for grass carp were estimated to be 251.66, 305.83, 252.34 and 309.94 μg/kg diet, respectively.

Butyrate produced by gut commensal bacteria activates TGF-beta1 expression through the transcription factor SP1 in human intestinal epithelial cells

The intestinal microbiota contributes to the global wellbeing of their host by their fundamental role in the induction and maintenance of a healthy immune system. Commensal bacteria shape the mucosal immune system by influencing the proportion and the activation state of anti-inflammatory regulatory T cells (Treg) by metabolites that are still only partially unravelled. Microbiota members such as Clostridiales provide a transforming growth factor β (TGFβ)-rich environment that promotes the accumulation of Treg cells in the gut. The intestinal epithelial cells (IECs) take a central part in this process, as they are a major source of TGFβ1 upon bacterial colonisation. In this study, we investigated which gut commensal bacteria were able to regulate the TGFB1 human promoter in IECs using supernatants from cultured bacteria. We reported that Firmicutes and Fusobacteria supernatants were the most potent TGFB1 modulators in HT-29 cells. Furthermore, we demonstrated that butyrate was the main metabolite in bacterial supernatants accounting for TGFβ1 increase. This butyrate-driven effect was independent of the G-protein coupled receptors GPR41, GPR43 and GPR109a, the transporter MCT1 as well as the transcription factors NF-κB and AP-1 present on TGFB1 promoter. Interestingly, HDAC inhibitors were inducing a similar TGFB1 increase suggesting that butyrate acted through its HDAC inhibitor properties. Finally, our results showed that SP1 was the main transcription factor mediating the HDAC inhibitor effect of butyrate on TGFB1 expression. This is, to our knowledge, the first characterisation of the mechanisms underlying TGFB1 regulation in IEC by commensal bacteria derived butyrate.

The improved growth performance and enhanced immune function by DL-methionyl-DL-methionine are associated with NF-κB and TOR signalling in intestine of juvenile grass carp (Ctenopharyngodon idella)

The present study investigated the effects of dietary DL-methionyl-DL-methionine (Met-Met) on growth performance, intestinal immune function and the underlying signalling molecules in juvenile grass carp (Ctenopharyngodon idella). Fish were fed one DL-methionine (DL-Met) group (2.50 g/kg diet) and six graded levels of Met-Met groups (0, 0.79, 1.44, 1.84, 2.22 and 2.85 g/kg diet) for 10 weeks, and then challenged with Aeromonas hydrophila for 14 days. Results indicated that the optimal Met-Met supplementation: (1) increased fish growth performance, intestinal lysozyme (LZ) and acid phosphatase (ACP) activities, complement (C3 and C4) and immunoglobulin M (IgM) contents, up-regulated hepcidin, liver expressed antimicrobial peptide 2A (LEAP-2A), LEAP-2B, β-defensin-1 and Mucin2 mRNA levels; (2) down-regulated tumour necrosis factor α (TNF-α), interferon γ2 (IFN-γ2), interleukin 1β (IL-1β), IL-8 [only in the distal intestine (DI)], IL-12p35, IL-12p40 and IL-15 (not IL-17D) mRNA levels partially related to the down-regulation of IκB kinase β (IKKβ) and IKKγ (rather than IKKα), nuclear factor kappa B (NF-κB) p65 and c-Rel (rather than NF-κB p52) mRNA levels and the up-regulation of inhibitor of κBα (IκBα) mRNA levels; (3) up-regulated IL-4/13A, IL-4/13B, IL-6, IL-10, IL-11 and transforming growth factor (TGF)-β1 (not TGF-β2) mRNA levels partially associated with the target of rapamycin (TOR) signalling pathway [TOR/ribosomal protein S6 kinases 1 (S6K1), eIF4E-binding proteins (4E-BP)] in three intestinal segments of juvenile grass carp. These results suggest that Met-Met supplementation improves growth and intestinal immune function in fish. Furthermore, according to a positive effect, the optimal Met-Met supplementation was superior to the optimal DL-Met supplementation at improving the growth performance and enhancing the intestinal immune function in fish. Finally, based on percent weight gain (PWG), protection against enteritis morbidity and immune index (LZ activity), the optimal Met-Met supplementation for juvenile grass carp was estimated as 1.61, 1.64 and 1.68 g/kg diet, respectively, as the basal diet contains 8.03 g/kg total sulfur amino acids (TSAA) (4.26 g methionine/kg and 3.77 g cysteine/kg).

SP600125 suppresses Keap1 expression and results in NRF2-mediated prevention of diabetic nephropathy

c-Jun N-terminal kinase (JNK) contributes to the pathogenesis of diabetic nephropathy (DN). The JNK inhibitor SP600125 was reported to ameliorate DN. However, the mechanism remained unclear. We previously reported that SP600125 activated nuclear factor erythroid 2-related factor 2 (NRF2), a governor of the cellular antioxidant defense system, in the aortas of the diabetic mice. Given the critical role of NRF2 in preventing DN, the present study aimed to test whether or not NRF2 is required for SP600125's protection against DN. To test the role of NRF2 in SP600125's effect, streptozotocin-induced C57BL/6 wild-type (WT) and Nrf2-knockout (KO) diabetic mice were treated in the presence or absence of SP600125, for 24 weeks. To explore the mechanism by which SP600125 activates NRF2, mouse mesangial cells (MMCs) were treated with high glucose (HG), in the presence or absence of either SP600125 or JNK siRNA. SP600125 significantly attenuated the diabetes-induced renal oxidative stress, inflammation, fibrosis, pathological change and dysfunction in the WT, but not the Nrf2 KO mice. SP600125 inactivated JNK, inhibited kelch-like ECH-associated protein 1 expression, preserved NRF2 protein and facilitated its nuclear translocation in the kidneys of the WT mice, the effects of which were similarly produced by either SP600125 or JNK siRNA in HG-treated MMCs. Further, both SP600125 and JNK siRNA alleviated HG-induced mesangial oxidative stress and expression of inflammatory and fibrotic genes. The present study demonstrates that NRF2 is required for SP600125's protection against DN. SP600125 activates NRF2 possibly via inhibition of JNK-induced Keap1 expression.

Inhibition of the Effect of High Glucose on the Expression of Smad in Human Peritoneal Mesothelial Cells

Objective

As high glucose (HG) concentration in peritoneal dialysis (PD) solution is thought to contribute to peritoneal fibrosis, and angiotensin II receptor blockers (ARBs) may have a key role in preventing fibrosis as they may inhibit the TGF- ß1–Smad pathway, the aims of this in vitro study were to investigate 1) if HG affects the expression of Smad in human peritoneal mesothelial cells (HPMCs) and 2) if ARB (losartan) can inhibit this effect.

Methods

HPMCs, obtained from non-renal patients undergoing elective abdominal surgery, were stimulated by HG solutions with different concentrations (1.5%, 2.5%, 4.25%) of dextrose and mannitol, and by solutions containing combination with dextrose and losartan. The supernatant was assayed for TGF- ß1 by ELISA and cells were collected for the analysis of Smad family by RT-PCR and Western Blot.

Results

1) HG up-regulated the expression of Smad2 on both gene and protein levels, especially in 2.5% and 4.25% dextrose groups (P&0.05), and also stimulated the expression of Smad4 in 4.25% dextrose group. However, the expression of Smad3 was not affected. 2) High osmolality as such (using mannitol) did not affect the TGF-ß1-Smad signaling pathway. 3) Losartan inhibited the expression of Smad2 on the gene level but not on the protein level. 4) HG up-regulated the level of TGF- ß1 with increasing dextrose concentration, while losartan partially inhibited this effect of HG on releasing of TGF-ß1.

Conclusion

A high glucose solution up-regulated the expression of Smad2 and Smad4, suggesting that the TGF- ß1-Smad pathway could be involved in the fibrosis of the peritoneum during PD. As losartan inhibited the expression of Smad2 on the gene level and reduced the concentration of TGF- ß1 in our study, the results of this in vitro study suggest that the use of angiotensin II receptor blockers might represent a possible way to prevent and treat peritoneal fibrosis in PD patients. However, further studies in vivo are needed to confirm this hypothesis.

RhoA/Rho-kinase triggers epithelial-mesenchymal transition in mesothelial cells and contributes to the pathogenesis of dialysis-related peritoneal fibrosis

Peritoneal fibrosis (PF) with associated peritoneal dysfunction is almost invariably observed in long-term peritoneal dialysis (PD) patients. Advanced glycation end products (AGEs) are pro-oxidant compounds produced in excess during the metabolism of glucose and are present in high levels in standard PD solutions. The GTPase RhoA has been implicated in PF, but its specific role remains poorly understood. Here, we studied the effects of RhoA/Rho-kinase signaling in AGEs-induced epithelial-mesenchymal transition (EMT) in human peritoneal mesothelial cells (HPMCs), and evaluated morphological and molecular changes in a rat model of PD-related PF. Activation of RhoA/Rho-kinase and activating protein-1 (AP-1) was assessed in HPMCs using pull-down and electrophoretic mobility shift assays, respectively, while expression of transforming growth factor-β, fibronectin, α-smooth muscle actin, vimentin, N-cadherin, and E-cadherin expression was assessed using immunohistochemistry and western blot. AGEs exposure activated Rho/Rho-kinase in HPMCs and upregulated EMT-related genes via AP-1. These changes were prevented by the Rho-kinase inhibitors fasudil and Y-27632, and by the AP-1 inhibitor curcumin. Importantly, fasudil normalized histopathological and molecular alterations and preserved peritoneal function in rats. These data support the therapeutic potential of Rho-kinase inhibitors in PD-related PF.

Targeting TGF-β Signaling for Therapeutic Gain

Transforming growth factor βs (TGF-βs) are closely related ligands that have pleiotropic activity on most cell types of the body. They act through common heterotetrameric TGF-β type II and type I transmembrane dual specificity kinase receptor complexes, and the outcome of signaling is context-dependent. In normal tissue, they serve a role in maintaining homeostasis. In many diseased states, particularly fibrosis and cancer, TGF-β ligands are overexpressed and the outcome of signaling is diverted toward disease progression. There has therefore been a concerted effort to develop drugs that block TGF-β signaling for therapeutic benefit. This review will cover the basics of TGF-β signaling and its biological activities relevant to oncology, present a summary of pharmacological TGF-β blockade strategies, and give an update on preclinical and clinical trials for TGF-β blockade in a variety of solid tumor types.

Diabetes-Induced Reactive Oxygen Species: Mechanism of Their Generation and Role in Renal Injury

Diabetes induces the onset and progression of renal injury through causing hemodynamic dysregulation along with abnormal morphological and functional nephron changes. The most important event that precedes renal injury is an increase in permeability of plasma proteins such as albumin through a damaged glomerular filtration barrier resulting in excessive urinary albumin excretion (UAE). Moreover, once enhanced UAE begins, it may advance renal injury from progression of abnormal renal hemodynamics, increased glomerular basement membrane (GBM) thickness, mesangial expansion, extracellular matrix accumulation, and glomerulosclerosis to eventual end-stage renal damage. Interestingly, all these pathological changes are predominantly driven by diabetes-induced reactive oxygen species (ROS) and abnormal downstream signaling molecules. In diabetic kidney, NADPH oxidase (enzymatic) and mitochondrial electron transport chain (nonenzymatic) are the prominent sources of ROS, which are believed to cause the onset of albuminuria followed by progression to renal damage through podocyte depletion. Chronic hyperglycemia and consequent ROS production can trigger abnormal signaling pathways involving diverse signaling mediators such as transcription factors, inflammatory cytokines, chemokines, and vasoactive substances. Persistently, increased expression and activation of these signaling molecules contribute to the irreversible functional and structural changes in the kidney resulting in critically decreased glomerular filtration rate leading to eventual renal failure.

Connexin43 regulates high glucose-induced expression of fibronectin, ICAM-1 and TGF-β1 via Nrf2/ARE pathway in glomerular mesangial cells

Nrf2/ARE signaling pathway is a crucial cellular defense system to cope with oxidative stress, which is adaptively activated, in diabetic condition that is not efficient enough to resist the oxidative stress provoked by hyperglycemia. We have previously demonstrated that Connexin43 (Cx43) attenuates renal fibrosis through c-Src. However, the underlying mechanisms need to be further clarified. It has been reported that Cx43 possesses the ability of anti-oxidative. The current study aimed to determine if Cx43 exerts protective effects on renal fibrosis in diabetes via activation of Nrf2/ARE pathway and explore the underlying molecular mechanisms. The following findings were observed: (1) Cx43 expression decreased and c-Src activity increased in kidneys of diabetic animals; (2) Over-expressed Cx43 in high glucose treated GMCs inhibited protein levels of FN, ICAM-1 and TGF-β1; (3) Nrf2/ARE signaling adaptively responded to high glucose treatment in GMCs; (4) Cx43 reduced ROS generation by boost Nrf2/ARE signaling under high glucose condition; (5) Inhibition of c-Src activity promoted nucleus accumulation of Nrf2; (6) Over-expressed Cx43 inhibited c-Src activity and the interaction between c-Src and Nrf2 in GMCs cultured in high glucose. Thus we propose that Cx43 might enhance the activation of Nrf2/ARE pathway by means of inhibiting c-Src activity to hinder the nuclear export of Nrf2, and then reduce expression of FN, ICAM-1 and TGF-β1, ultimately attenuating renal fibrosis in diabetes.

Role of areca nut induced JNK/ATF2/Jun axis in the activation of TGF-β pathway in precancerous Oral Submucous Fibrosis

Oral submucous fibrosis (OSF) is potentially premalignant with progressive and irreversible extracellular matrix deposition accompanied by epithelial atrophy and like other fibrotic disorders, is primarily a TGF-β driven disease. OSF is caused by prolonged chewing of areca nut. Our previous studies reported a pivotal role for TGF-β activation and its effects contributing to OSF. However, the mechanism for activation of TGF-β signaling in OSF is still unknown. In this study we demonstrate activation of TGF-β signaling with sub-cytotoxic dose of areca nut in epithelial cells and discovered a key role for pJNK in this process. In good correlation; pJNK was detected in OSF tissues but not in normal tissues. Moreover, activation of JNK was found to be dependent on muscarinic acid receptor induced Ca²⁺/CAMKII as well as ROS. JNK dependent phosphorylation of ATF2/c-Jun transcription factors resulted in TGF-β transcription and its signaling. pATF2/p-c-Jun were enriched on TGF-β promoter and co-localized in nuclei of epithelial cells upon areca nut treatment. In corroboration, OSF tissue sections also had nuclear pATF2 and p-c-Jun. Our results provide comprehensive mechanistic details of TGF-β signaling induced by etiological agent areca nut in the manifestation of fibrosis which can lead to new therapeutic modalities for OSF.

Impairment of hepatic nuclear factor-4α binding to the Stim1 promoter contributes to high glucose-induced upregulation of STIM1 expression in glomerular mesangial cells

The present study was carried out to investigate if hepatic nuclear factor (HNF)4α contributed to the high glucose-induced increase in stromal interacting molecule (STIM)1 protein abundance in glomerular mesangial cells (MCs). Western blot and immunofluorescence experiments showed HNF4α expression in MCs. Knockdown of HNF4α using a small interfering RNA approach significantly increased mRNA expression levels of both STIM1 and Orai1 and protein expression levels of STIM1 in cultured human MCs. Consistently, overexpression of HNF4α reduced expressed STIM1 protein expression in human embryonic kidney-293 cells. Furthermore, high glucose treatment did not significantly change the abundance of HNF4α protein in MCs but significantly attenuated HNF4α binding activity to the Stim1 promoter. Moreover, knockdown of HNF4α significantly augmented store-operated Ca(2+) entry, which is known to be gated by STIM1 and has recently been found to be antifibrotic in MCs. In agreement with those results, knockdown of HNF4α significantly attenuated the fibrotic response of high glucose. These results suggest that HNF4α negatively regulates STIM1 transcription in MCs. High glucose increases STIM1 expression levels by impairing HNF4α binding activity to the Stim1 promoter, which subsequently releases Stim1 transcription from HNF4α repression. Since the STIM1-gated store-operated Ca(2+) entry pathway in MCs has an antifibrotic effect, inhibition of HNF4α in MCs might be a potential therapeutic option for diabetic kidney disease.

Effect of triptolide on expression of thrombospondin-1 and transforming growth factor-β1 in renal tubular cells

The objective of our study is to investigate the effect of triptolide on expression of thrombospondin-1 and transforming growth factor β1 in renal tubular cells. Human renal tubular epithelial cells were stimulated by different concentrations of triptolide (0.1, 1, and 10 μg/L) in the presence of angiotensin-II (10(-7)mol/L). Real Time PCR was used to detect the mRNA expression of thrombospondin-1 and transforming growth factor β1. Western blot analysis was used to detect the protein expression. ELISA was used to detect the level of total and active transforming growth factor β1. The mRNA expression of thrombospondin-1 (3.66 ± 0.48 vs. 1.33 ± 0.26, p < 0.05) and transforming growth factor β1 (3.58 ± 0.59 vs. 1.26 ± 0.28, p < 0.05) were up-regulated obviously when stimulated by angiotensin-II. And the protein expression of thrombospondin-1 (0.5126 ± 0.0936 vs. 0.1025 ± 0.0761, p < 0.01) and transforming growth factor β1 (0.5948 ± 0.0736 vs. 0.1318 ± 0.0614, p < 0.01) were also up-regulated simultaneously when stimulated by angiotensin-II. The expression of thrombospondin-1 and transforming growth factor β1 induced by angiotensin-II were down-regulated markedly with 1 μg/L and 10 μg/L of triptolide in mRNA and protein levels (p < 0.05, p <  0.01). And triptolide (1 and 10 μg/L) could reduce the expression of total and active transforming growth factor β1 (p < 0.05, p < 0.01). In conclusion, triptolide can inhibit the expression of thrombospondin-1 and transforming growth factor β1 in mRNA and protein levels and down-regulate the levels of total and active transforming growth factor β1.

Pin1 induction in the fibrotic liver and its roles in TGF-β1 expression and Smad2/3 phosphorylation

BACKGROUND & AIMS

Therapeutic management of liver fibrosis remains an unsolved clinical problem. Hepatic accumulation of extracellular matrix, mainly collagen, is mediated by the production of transforming growth factor-β1 (TGF-β1) in stellate cells. Pin1, a peptidyl-prolyl isomerase, plays an important pathophysiological role in several diseases, including neurodegeneration and cancer. Herein, we determined whether Pin1 regulates liver fibrogenesis and examined its mechanism of action by focusing on TGF-β1 signalling and hepatic stellate cell (HSC) activation.

METHODS

Pin1 expression was assessed by immunohistochemistry, Western blot or real-time-polymerase chain reaction (RT-PCR) analyses of human and mouse fibrotic liver samples. The role of Pin1 during HSC activation was estimated using Pin1-null mouse embryonic fibroblast (MEF) cells and Pin1-overexpressing LX-2 human hepatic stellate cells.

RESULTS

Pin1 expression was elevated in human and mouse fibrotic liver tissues, and Pin1 inhibition improved dimethylnitrosamine (DMN)-induced liver fibrosis in mice. Pin1 inhibition reduced the mRNA or protein expression of TGF-β1 and α-smooth muscle actin (α-SMA) by DMN treatment. Pin1 knockdown suppressed TGFβ1 gene expression in both LX-2 and MEF cells. Pin1-mediated TGFβ1 gene transcription was controlled by extracellular signal-regulated kinase (ERK)- and phosphoinositide 3-kinase/Akt-mediated activator protein-1 (AP-1) activation. Moreover, TGFβ1-stimulated Smad2/3 phosphorylation and plasminogen activator inhibitor-1 expression were inhibited by Pin1 knockdown.

CONCLUSIONS

Pin1 induction during liver fibrosis is involved in hepatic stellate cell activation, TGFβ1 expression, and TGFβ1-mediated fibrogenesis signalling.

Computational identification of potential transcriptional regulators of TGF-ß1 in human atherosclerotic arteries

TGF-ß is protective in atherosclerosis but deleterious in metastatic cancers. Our aim was to determine whether TGF-ß transcriptional regulation is tissue-specific in early atherosclerosis. The computational methods included 5 steps: (i) from microarray data of human atherosclerotic carotid tissue, to identify the 10 best co-expressed genes with TGFB1 (TGFB1 gene cluster), (ii) to choose the 11 proximal promoters, (iii) to predict the TFBS shared by the promoters, (iv) to identify the common TFs co-expressed with the TGFB1 gene cluster, and (v) to compare the common TFs in the early lesions to those identified in advanced atherosclerotic lesions and in various cancers. Our results show that EGR1, SP1 and KLF6 could be responsible for TGFB1 basal expression, KLF6 appearing specific to atherosclerotic lesions. Among the TFs co-expressed with the gene cluster, transcriptional activators (SLC2A4RG, MAZ) and repressors (ZBTB7A, PATZ1, ZNF263) could be involved in the fine-tuning of TGFB1 expression in atherosclerosis.

High glucose and diabetes enhanced store-operated Ca(2+) entry and increased expression of its signaling proteins in mesangial cells

The present study was conducted to determine whether and how store-operated Ca(2+) entry (SOCE) in glomerular mesangial cells (MCs) was altered by high glucose (HG) and diabetes. Human MCs were treated with either normal glucose or HG for different time periods. Cyclopiazonic acid-induced SOCE was significantly greater in the MCs with 7-day HG treatment and the response was completely abolished by GSK-7975A, a selective inhibitor of store-operated Ca(2+) channels. Similarly, the inositol 1,4,5-trisphosphate-induced store-operated Ca(2+) currents were significantly enhanced in the MCs treated with HG for 7 days, and the enhanced response was abolished by both GSK-7975A and La(3+). In contrast, receptor-operated Ca(2+) entry in MCs was significantly reduced by HG treatment. Western blotting showed that HG increased the expression levels of STIM1 and Orai1 in cultured MCs. A significant HG effect occurred at a concentration as low as 10 mM, but required a minimum of 7 days. The HG effect in cultured MCs was recapitulated in renal glomeruli/cortex of both type I and II diabetic rats. Furthermore, quantitative real-time RT-PCR revealed that a 6-day HG treatment significantly increased the mRNA expression level of STIM1. However, the expressions of STIM2 and Orai1 transcripts were not affected by HG. Taken together, these results suggest that HG/diabetes enhanced SOCE in MCs by increasing STIM1/Orai1 protein expressions. HG upregulates STIM1 by promoting its transcription but increases Orai1 protein through a posttranscriptional mechanism.

Combined Effects of PPAR γ Agonists and Epidermal Growth Factor Receptor Inhibitors in Human Proximal Tubule Cells

We aimed to determine whether epidermal growth factor receptor (EGFR) inhibition, in addition to a peroxisome proliferator-activated receptor gamma (PPARγ) agonist, prevents high-glucose-induced proximal tubular fibrosis, inflammation, and sodium and water retention in human proximal tubule cells exposed to normal glucose; high glucose; high glucose with the PPARγ agonist pioglitazone or with the P-EGFR inhibitor, gefitinib; or high glucose with both pioglitazone and gefitinib. We have shown that high glucose increases AP-1 and NFκB binding activity, downstream phosphorylation of EGFR and Erk1/2, and fibronectin and collagen IV expression. Pioglitazone reversed these effects but upregulated NHE3 and AQP1 expression. Gefitinib inhibited high glucose induced fibronectin and collagen IV, and EGFR and Erk1/2 phosphorylation and reversed pioglitazone-induced increases in NHE3 and AQP1 expression. Our data suggests that combination of an EGFR inhibitor and a PPARγ agonist mitigates high-glucose-induced fibrosis and inflammation and reverses the upregulation of transporters and channels involved in sodium and water retention in human proximal tubule cells. Hence EGFR blockade may hold promise, not only in limiting tubulointerstitial pathology in diabetic nephropathy, but also in limiting the sodium and water retention observed in patients with diabetes and exacerbated by PPARγ agonists.

Activation of TGF-β1 promoter by hepatitis C virus-induced AP-1 and Sp1: role of TGF-β1 in hepatic stellate cell activation and invasion

Our previous studies have shown the induction and maturation of transforming growth factor-beta 1 (TGF-β1) in HCV-infected human hepatoma cells. In this study, we have investigated the molecular mechanism of TGF-β1 gene expression in response to HCV infection. We demonstrate that HCV-induced transcription factors AP-1, Sp1, NF-κB and STAT-3 are involved in TGF-β1 gene expression. Using chromatin immunoprecipitation (ChIP) assay, we further show that AP-1 and Sp1 interact with TGF-b1 promoter in vivo in HCV-infected cells. In addition, we demonstrate that HCV-induced TGF-β1 gene expression is mediated by the activation of cellular kinases such as p38 MAPK, Src, JNK, and MEK1/2. Next, we determined the role of secreted bioactive TGF-β1 in human hepatic stellate cells (HSCs) activation and invasion. Using siRNA approach, we show that HCV-induced bioactive TGF-β1 is critical for the induction of alpha smooth muscle actin (α-SMA) and type 1 collagen, the markers of HSCs activation and proliferation. We further demonstrate the potential role of HCV-induced bioactive TGF-β1 in HSCs invasion/cell migration using a transwell Boyden chamber. Our results also suggest the role of HCV-induced TGF-β1 in HCV replication and release. Collectively, these observations provide insight into the mechanism of TGF-β1 promoter activation, as well as HSCs activation and invasion, which likely manifests in liver fibrosis associated with HCV infection.

Antioxidants in kidney diseases: the impact of bardoxolone methyl

Drugs targeting the renin-angiotensin-aldosterone system (RAAS) are the mainstay of therapy to retard the progression of proteinuric chronic kidney disease (CKD) such as diabetic nephropathy. However, diabetic nephropathy is still the first cause of end-stage renal disease. New drugs targeted to the pathogenesis and mechanisms of progression of these diseases beyond RAAS inhibition are needed. There is solid experimental evidence of a key role of oxidative stress and its interrelation with inflammation on renal damage. However, randomized and well-powered trials on these agents in CKD are scarce. We now review the biological bases of oxidative stress and its role in kidney diseases, with focus on diabetic nephropathy, as well as the role of the Keap1-Nrf2 pathway and recent clinical trials targeting this pathway with bardoxolone methyl.

Spleen tyrosine kinase mediates high glucose-induced transforming growth factor-β1 up-regulation in proximal tubular epithelial cells

The role of spleen tyrosine kinase (Syk) in high glucose-induced intracellular signal transduction has yet to be elucidated. We investigated whether Syk is implicated in high glucose-induced transforming growth factor-β1 (TGF-β1) up-regulation in cultured human proximal tubular epithelial cells (HK-2 cell). High glucose increased TGF-β1 gene expression through Syk, extracellular signal-regulated kinase (ERK), AP-1 and NF-κB. High glucose-induced AP-1 DNA binding activity was decreased by Syk inhibitors and U0126 (an ERK inhibitor). Syk inhibitors suppressed high glucose-induced ERK activation, whereas U0126 had no effect on Syk activation. High glucose-induced NF-κB DNA binding activity was also decreased by Syk inhibitors. High glucose increased nuclear translocation of p65 without serine phosphorylation of IκBα and without degradation of IκBα, but with an increase in tyrosine phosphorylation of IκBα that may account for the activation of NF-κB. Both Syk inhibitors and Syk-siRNA attenuated high glucose-induced IκBα tyrosine phosphorylation and p65 nuclear translocation. Depletion of p21-activated kinase 2 (Pak2) by transfection of Pak2-siRNA abolished high glucose-induced Syk activation. In summary, high glucose-induced TGF-β1 gene transcription occurred through Pak2, Syk and subsequent ERK/AP-1 and NF-κB pathways. This suggests that Syk might be implicated in the diabetic kidney disease.

Prostaglandin F2α facilitates collagen synthesis in cardiac fibroblasts via an F-prostanoid receptor/protein kinase C/Rho kinase pathway independent of transforming growth factor β1

Accumulation of collagen I and III in the myocardium is a prominent feature of interstitial fibrosis. Prostaglandin F(2α) (PGF(2α)) facilitates fibrosis by increasing collagen synthesis. However, the underlying mechanisms mediating the effect of PGF(2α) on collagen expression in cardiac fibroblasts are not yet fully elucidated. We measured the mRNA and protein levels of collagen I and III by quantitative real-time PCR and ELISA, respectively. Activation of signaling pathways was determined by western blot analysis. In primary rat cardiac fibroblasts, treatment with PGF(2α) stimulated both the mRNA and protein levels of collagen I and III, and pretreatment with the F-prostanoid (FP) receptor antagonist AL-8810, protein kinase C inhibitor LY-333531, and Rho kinase inhibitor Y-27632 significantly inhibited PGF(2α)-induced collagen I and III expression. FP receptor, protein kinase C, and Rho kinase were activated with PGF(2α) treatment. PGF(2α) may be an important regulator in the synthesis of collagen I and III via an FP receptor/protein kinase C/Rho kinase cascade in cardiac fibroblasts, which might be a new therapeutic target for myocardial fibrosis.

Ethyl pyruvate ameliorates albuminuria and glomerular injury in the animal model of diabetic nephropathy

Pyruvate is an endogenous antioxidant and anti-inflammatory substance. The present study was implemented to investigate the protective effect of ethyl pyruvate (EP) against the development and progression of diabetic nephropathy in an in vivo and in vitro model. Diabetic rats were prepared by injecting streptozotocin (65 mg/kg). Those that developed diabetes after 72 h were treated with EP (40 mg/kg) intraperitoneally. Diabetic rats without pyruvate treatment and nondiabetic rats were used for control. As an in vitro experiment, rat mesangial cells cultured primarily from Sprague-Dawley rats were treated in high-glucose (HG; 50 mM) or normal-glucose (NG; 5 mM) conditions and with or without pyruvate. Pyruvate-treated diabetic rats exhibited decreased albuminuria and attenuated NADPH-dependent reactive oxygen species generation. Immunohistochemistry showed reduced laminin, type IV collagen, and fibronectin deposition in the glomeruli compared with nontreated diabetic rats. Parallel changes were shown in tissue mRNA and protein expression levels of monocyte chemoattractant protein-1, transforming growth factor-β1, laminin, fibronectin, and type IV collagen in the kidney. Concordantly, protective effects were also exhibited in the mesangial cell culture system. These findings suggest that pyruvate protects against kidney injury via NADPH oxidase inhibition. The present study established that activation of NADPH oxidase plays a crucial role in diabetes-induced oxidative stress, glomerular hypertrophy, and ECM molecule expression. Pyruvate exhibited a renoprotective effect in the progression of experimental diabetic nephropathy. Future research is warranted to investigate the protective mechanism of pyruvate more specifically in relation to NADPH oxidase in diabetic nephropathy.

High glucose-induced RhoA activation requires caveolae and PKCβ1-mediated ROS generation

Glomerular matrix accumulation is a hallmark of diabetic nephropathy. We previously showed that RhoA activation by high glucose in mesangial cells (MC) leads to matrix upregulation (Peng F, Wu D, Gao B, Ingram AJ, Zhang B, Chorneyko K, McKenzie R, Krepinsky JC. Diabetes 57: 1683-1692, 2008). Here, we study the mechanism whereby RhoA is activated. In primary rat MC, RhoA activation required glucose entry and metabolism. Broad PKC inhibitors (PMA, bisindolylmaleimide, Gö6976), as well as specific PKCβ blockade with an inhibitor and small interfering RNA (siRNA), prevented RhoA activation by glucose. PKCβ inhibition also abrogated reactive oxygen species (ROS) generation by glucose. The ROS scavenger N-acetylcysteine (NAC) or NADPH oxidase inhibitors apocynin and DPI prevented glucose-induced RhoA activation. RhoA and some PKC isoforms localize to caveolae. Chemical disruption of these microdomains prevented RhoA and PKCβ1 activation by glucose. In caveolin-1 knockout cells, glucose did not induce RhoA and PKCβ1 activation; these responses were rescued by caveolin-1 reexpression. Furthermore, glucose-induced ROS generation was significantly attenuated by chemical disruption of caveolae and in knockout cells. Downstream of RhoA signaling, activator protein-1 (AP-1) activation was also inhibited by disrupting caveolae, was absent in caveolin-1 knockout MC and rescued by caveolin-1 reexpression. Finally, transforming growth factor (TGF)-β1 upregulation, mediated by AP-1, was prevented by RhoA signaling inhibition and by disruption or absence of caveolae. In conclusion, RhoA activation by glucose is dependent on PKCβ1-induced ROS generation, most likely through NADPH oxidase. The activation of PKCβ1 and its downstream effects, including upregulation of TGF-β1, requires caveolae. These microdomains are thus important mediators of the profibrogenic process associated with diabetic nephropathy.