Endothelial dysfunction and vascular inflammation in type 2 diabetes: interaction of AGE/RAGE and TNF-alpha signaling

Network Pharmacology Combined with Molecular Docking Approach to Investigate the Mechanism of ChuShiWeiLing Decoction against Perianal Eczema

BACKGROUND

ChuShiWeiLing Decoction (CSWLD) is a famous classical Chinese prescription for the treatment of eczema with desirable effect in clinical practice. It has gradually exerted good curative effects on perianal eczema (PE) in recent years, but its specific mechanism is not elucidated yet.

OBJECTIVE

This research explores the underlying pharmacological mechanism of CSWLD in addressing PE through network pharmacology combined with molecular docking strategy.

METHODS

The key chemical compounds and potential target genes of CSWLD were screened by bioinformatics. The major targets of CSWLD were discovered using network modules. Functional annotation of Gene Ontology (GO) was undertaken, as well as pathway enrichment analysis using the Kyoto Encyclopedia of Genes and Genomes (KEGG). Molecular docking of core protein-ligand interactions was modeled using AutoDock software. Pymol software was used to perform a molecular dynamics simulation for the ideal core protein-ligand that was discovered by molecular docking.

RESULTS

A total of 2,853 active compounds and 922 targets of CSWLD were collected. The target with a higher degree was identified through the PPI network, namely TNF, IL6, ALB, STAT3, EGFR, TLR4, CXCL8 and PTPRC. GO and KEGG analyses suggested that CSWLD treatment of PE mainly involves cellular activation, activation of leukocytes, and adhesion among leukocytes. The molecular docking results showed that wogonin, hederagenin and quercetin of CSWLD could bind to IL-6 and TNF, respectively.

CONCLUSION

Our results indicated that the bioactives, potential targets, and molecular mechanism of CSWLD against PE.

MiR-27b attenuates mitochondrial oxidative stress and inflammation in endothelial cells

MiR-27b is highly expressed in endothelial cells (EC) but its function in this context is poorly characterized. This study aims to investigate the effect of miR-27b on inflammatory pathways, cell cycle, apoptosis, and mitochondrial oxidative imbalances in immortalized human aortic endothelial cells (teloHAEC), human umbilical vein endothelial cells (HUVEC), and human coronary artery endothelial cells (HCAEC) exposed to TNF-α. Treatment with TNF-α downregulates the expression of miR-27b in all EC lines, promotes the activation of inflammatory pathways, induces mitochondrial alteration and reactive oxygen species accumulation, fostering the induction of intrinsic apoptosis. Moreover, miR-27b mimic counteracts the TNF-α-related cytotoxicity and inflammation, as well as cell cycle arrest and caspase-3-dependent apoptosis, restoring mitochondria redox state, function, and membrane polarization. Mechanistically, hsa-miR-27b-3p targets the 3'untranslated regions of FOXO1 mRNA to downregulate its expression, blunting the activation of the Akt/FOXO1 pathway. Here, we show that miR-27b is involved in the regulation of a broad range of functionally intertwined phenomena in EC, suggesting its key role in mitigating mithochondrial oxidative stress and inflammation, most likely through targeting of FOXO1. Overall, results reveal for the first time that miR-27b could represent a possible target for future therapies aimed at improving endothelial health.

Role of peroxisome proliferators-activated receptor-gamma in advanced glycation end product-mediated functional loss of voltage-gated potassium channel in rat coronary arteries

Background

High blood glucose impairs voltage-gated K⁺ (Kv) channel-mediated vasodilation in rat coronary artery smooth muscle cells (CSMCs) via oxidative stress. Advanced glycation end product (AGE) and receptor for AGE (RAGE) axis has been found to impair coronary dilation by reducing Kv channel activity in diabetic rat small coronary arteries (RSCAs). However, its underlying mechanism remain unclear. Here, we used isolated arteries and primary CSMCs to investigate the effect of AGE incubation on Kv channel-mediated coronary dilation and the possible involvement of peroxisome proliferators-activated receptor (PPAR) -γ pathway.

Methods

The RSCAs and primary CSMCs were isolated, cultured, and treated with bovine serum albumin (BSA), AGE-BSA, alagrebrium (ALA, AGE cross-linking breaker), pioglitazone (PIO, PPAR-γ activator) and/or GW9662 (PPAR-γ inhibitor). The groups were accordingly divided as control, BSA, AGE, AGE + ALA, AGE + PIO, or AGE + PIO + GW9662. Kv channel-mediated dilation was analyzed using wire myograph. Histology and immunohistochemistry of RSCAs were performed. Western blot was used to detect the protein expression of RAGE, major Kv channel subunits expressed in CSMCs (Kv1.2 and Kv1.5), PPAR-γ, and nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-2 (NOX-2).

Results

AGE markedly reduced Forskolin-induced Kv channel-mediated dilation of RSCAs by engaging with RAGE, and ALA or PIO significantly reversed the functional loss of Kv channel. In both RSCAs and CSMCs, AGE reduced Kv1.2/1.5 expression, increased RAGE and NOX-2 expression, and inhibited PPAR-γ expression, while ALA or PIO treatment partially reversed the inhibiting effects of AGE on Kv1.2/1.5 expression, accompanied by the downregulation of RAGE and decreased oxidative stress. Meanwhile, silencing of RAGE with siRNA remarkably alleviated the AGE-induced downregulation of Kv1.2/1.5 expression in CSMCs.

Conclusion

AGE reduces the Kv channel expression in CSMCs and further impairs the Kv channel-mediated dilation in RSCAs. The AGE/RAGE axis may enhance oxidative stress by inhibiting the downstream PPAR-γ pathway, thus playing a critical role in the dysfunction of Kv channels.

Molecular Mechanism of the Effect of Huanglian Jiedu Decoction on Type 2 Diabetes Mellitus Based on Network Pharmacology and Molecular Docking

BACKGROUND

Huanglian Jiedu Decoction (HLJDD) is a Traditional Chinese Medicine (TCM) formula comprising four herbal medicines. This decoction has long been used in China for clinically treating T2DM. However, the molecular mechanism of HLJDD treat for T2DM is still not fully known. Hence, this study was designed to reveal the synergistic mechanism of HLJDD formula in the treatment of T2DM by using network pharmacology method and molecular docking.

METHODS

Retrieving and screening of active components of different herbs in HLJDD and corresponding T2DM-related target genes across multiple databases. Subsequently, STRING and Cytoscape were applied to analysis and construct PPI network. In addition, cluster and topological analysis were employed for the analysis of PPI networks. Then, the GO and KEGG enrichment analysis were performed by using ClueGO tool. Finally, the differentially expressed analysis was used to verify whether the expression of key target genes in T2DM and non-T2DM samples was statistically significant, and the binding capacity between active components and key targets was validated by molecular docking using AutoDock.

RESULTS

There are 65 active components involved in 197 T2DM-related targets that are identified in HLJDD formula. What is more, 39 key targets (AKT1, IL-6, FOS, VEGFA, CASP3, etc.) and 3 clusters were obtained after topological and cluster analysis. Further, GO and KEGG analysis showed that HLJDD may play an important role in treating T2DM and its complications by synergistically regulating many biological processes and pathways which participated in signaling transduction, inflammatory response, apoptotic process, and vascular processes. Differentially expressed analysis showed that AKT1, IL-6, and FOS were upregulated in T2DM samples and a significant between sample differential expression. These results were validated by molecular docking, which identified 5 high-affinity active components in HLJDD, including quercetin, wogonin, baicalein, kaempferol, and oroxylin A.

CONCLUSION

Our research firstly revealed the basic pharmacological effects and relevant mechanisms of the HLJDD in the treatment of T2DM and its complications. The prediction results might facilitate the development of HLJDD or its active compounds as alternative therapy for T2DM. However, more pharmacological experiments should be performed for verification.

A Network Pharmacology-Based Strategy For Predicting Active Ingredients And Potential Targets Of LiuWei DiHuang Pill In Treating Type 2 Diabetes Mellitus

Background

Traditional Chinese medicine (TCM) formulations have proven to be advantageous in clinical treatment and prevention of disease. LiuWei DiHuang Pill (LWDH Pill) is a TCM that was employed to treat type 2 diabetes mellitus (T2DM). However, a holistic network pharmacology approach to understanding the active ingredients and the therapeutic mechanisms underlying T2DM has not been pursued.

Methods

A network pharmacology approach including drug-likeness evaluation, oral bioavailability prediction, virtual docking, and network analysis has been used to predict the active ingredients and potential targets of LWDH Pill in the treatment of type 2 diabetes.

Results

The comprehensive network pharmacology approach was successfully to identify 45 active ingredients in LWDH Pill. 45 active ingredients hit by 163 potential targets related to T2DM. Ten of the more highly predictive components (such as :quercetin, Kaempferol, Stigmasterol, beta-sitosterol, Kadsurenone, Diosgenin, hancinone C, Hederagenin, Garcinone B, Isofucosterol) are involved in anti-inflammatory, anti-oxidative stress, and the reduction of beta cell damage. LWDH Pill may play a role in the treatment of T2DM and its complications (atherosclerosis and nephropathy) through the AGE-RAGE signaling pathway, TNF signaling pathway, and NF-kappa B signaling pathway.

Conclusion

Based on a systematic network pharmacology approach, our works successfully predict the active ingredients and potential targets of LWDH Pill for application to T2DM and helps to illustrate mechanism of action on a comprehensive level. This study provides identify key genes and pathway associated with the prognosis and pathogenesis of T2DM from new insights, which also demonstrates a feasible method for the research of chemical basis and pharmacology in LWDH Pill.

Ly6C+ Inflammatory Monocyte Differentiation Partially Mediates Hyperhomocysteinemia-Induced Vascular Dysfunction in Type 2 Diabetic db/db Mice

OBJECTIVE

Hyperhomocysteinemia (HHcy) is a potent risk factor for diabetic cardiovascular diseases. We have previously reported that hyperhomocysteinemia potentiates type 1 diabetes mellitus-induced inflammatory monocyte differentiation, vascular dysfunction, and atherosclerosis. However, the effects of hyperhomocysteinemia on vascular inflammation in type 2 diabetes mellitus (T2DM) and the underlying mechanism are unknown. Approach and Results: Here, we demonstrate that hyperhomocysteinemia was induced by a high methionine diet in control mice (homocysteine 129 µmol/L), which was further worsened in T2DM db/db mice (homocysteine 180 µmol/L) with aggravated insulin intolerance. Hyperhomocysteinemia potentiated T2DM-induced mononuclear cell, monocyte, inflammatory monocyte (CD11b+Ly6C+), and M1 macrophage differentiation in periphery and aorta, which were rescued by folic acid-based homocysteine-lowering therapy. Moreover, hyperhomocysteinemia exacerbated T2DM-impaired endothelial-dependent aortic relaxation to acetylcholine. Finally, transfusion of bone marrow cells depleted for Ly6C by Ly6c shRNA transduction improved insulin intolerance and endothelial-dependent aortic relaxation in hyperhomocysteinemia+T2DM mice.

CONCLUSIONS

Hyperhomocysteinemia potentiated systemic and vessel wall inflammation and vascular dysfunction partially via inflammatory monocyte subset induction in T2DM. Inflammatory monocyte may be a novel therapeutic target for insulin resistance, inflammation, and cardiovascular complications in hyperhomocysteinemia+T2DM.

Biomarkers of Oxidative Stress in Metabolic Syndrome and Associated Diseases

Metabolic syndrome (MS) represents worldwide public health issue characterized by a set of cardiovascular risk factors including obesity, diabetes, dyslipidemia, hypertension, and impaired glucose tolerance. The link between the MS and the associated diseases is represented by oxidative stress (OS) and by the intracellular redox imbalance, both caused by the persistence of chronic inflammatory conditions that characterize MS. The increase in oxidizing species formation in MS has been accepted as a major underlying mechanism for mitochondrial dysfunction, accumulation of protein and lipid oxidation products, and impairment of the antioxidant systems. These oxidative modifications are recognized as relevant OS biomarkers potentially able to (i) clarify the role of reactive oxygen and nitrogen species in the etiology of the MS, (ii) contribute to the diagnosis/evaluation of the disease's severity, and (iii) evaluate the utility of possible therapeutic strategies based on natural antioxidants. The antioxidant therapies indeed could be able to (i) counteract systemic as well as mitochondrial-derived OS, (ii) enhance the endogenous antioxidant defenses, (iii) alleviate MS symptoms, and (iv) prevent the complications linked to MS-derived cardiovascular diseases. The focus of this review is to summarize the current knowledge about the role of OS in the development of metabolic alterations characterizing MS, with particular regard to the occurrence of OS-correlated biomarkers, as well as to the use of therapeutic strategies based on natural antioxidants.

Chronic inhibition of lipoprotein-associated phospholipase A2 does not improve coronary endothelial function: A prospective, randomized-controlled trial

AIMS

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂), a novel biomarker for vascular inflammation, is associated with coronary endothelial dysfunction (CED) and independently predicts cardiovascular events. The current study aimed to determine whether darapladib, an orally administered Lp-PLA₂ inhibitor, improved CED.

METHODS AND RESULTS

Fifty-four patients with CED were enrolled in a double-blinded randomized placebo-controlled trial, and were randomized to receive oral darapladib, 160mg daily, or placebo. Coronary angiography and invasive coronary endothelial function assessment were performed at baseline and post-6months of treatment. Primary endpoints were change in coronary artery diameter and coronary blood flow in response to acetylcholine. Additionally, Lp-PLA₂ activity was measured at baseline and on follow-up to evaluate for adherence and drug effect. Fifty-four patients were randomized to placebo (n=29) and darapladib (n=25). Mean age in darapladib group was 55.2.±11.7years vs. 54.0±10.5years (p=0.11). On follow-up, there was no significant difference in the percent response to acetylcholine of coronary artery diameter in treatment vs. placebo group (+3 (IQR -9, 15) vs. +3 (-12, 19); p=0.87) or coronary blood flow (-5 (IQR -24, 54) vs. 39 (IQR -26, 67); p=0.41). There was significant reduction in Lp-PLA₂ activity in the treatment arm vs. placebo (-76 (IQR -113, -52) vs. -7(-21, -7); p<0.001).

DISCUSSION

Lp-PLA₂ inhibition with darapladib did not improve coronary endothelial function, despite significantly reduced Lp-PLA2 activity with darapladib. This study suggests endogenous Lp-PLA₂ may not play a primary role in coronary endothelial function in humans. CLINICALTRIALS.

GOV IDENTIFIER

NCT01067339.

Inhibitory effect of gallic acid on advanced glycation end products induced up-regulation of inflammatory cytokines and matrix proteins in H9C2 (2-1) cells

Accumulating evidences have demonstrated that increased production of advanced glycation end products (AGEs) contributes to etiology of cardiac complications in diabetes. However, the underlying mechanism of AGE-induced effects is not well understood. Recent studies evince the beneficial role of phytochemicals in reducing the risk of cardiovascular morbidity and mortality in patients with cardiovascular diseases and diabetes mellitus. Hence, in the present study, the cardioprotective role of gallic acid (GA) against in vitro synthesized AGE in H9C2 (2-1) cells was elucidated. H9C2 (2-1) cells exposed to AGE (100 μg/ml) with/without GA pre-treatment (10 μM) and the release of reactive oxygen species (ROS), expression of oxidative stress markers, matrix proteins, and cytokines were analyzed. Cells exposed to AGE demonstrate a significant increase in ROS release with augmented expression (P < 0.01) of receptor for AGE (RAGE) and NOX-p47 phox (P < 0.001) proteins compared to untreated control cells. Moreover, an increased expression of matrix proteins and cytokines such as TNF-α (P < 0.01), TGF-β (P < 0.001), and iNOS (P < 0.001) was also found in AGE-treated cells, whereas, cells pre-treated with N-acetyl cysteine or RAGE neutralizing antibody notably (P < 0.01) impede the ROS release. Further, cells pre-treated with GA significantly attenuated the expression of NOX, RAGE, and other cytokines. In addition, the abnormal expressions of matrix proteins were also decreased especially in GA-treated cells. Thus, the results of the present study demonstrated the deleterious effect of AGEs that directly induce oxidative stress and matrix derangement and, on the other way, the "pleiotropic" activity of GA in reducing the risk of AGE-mediated cellular complications.

Hydrogen-rich medium suppresses the generation of reactive oxygen species, elevates the Bcl-2/Bax ratio and inhibits advanced glycation end product-induced apoptosis

The purpose of the present study was to determine whether using hydrogen-rich medium (HRM) to increase hydrogen levels in endothelial cells (ECs) protects ECs from apoptosis induced by advanced glycation end products (AGEs). The thoracic aorta was removed from 2-3-year-old Sprague-Dawley rats, and ECs were isolated and cultured. After culturing ECs in the presence of AGEs and/or with HRM for 24 h, Annexin V/7-AAD and TUNEL staining were carried out to detect apoptosis. Intracellular ROS were detected by fluorescent probe and quantified by flow cytometry. The expression of antioxidative enzymes (superoxide dismutase, glutathione peroxidase) was determined by real-time PCR analysis and enzymatic assay. The relative expression levels of Bcl-2 and Bax were analyzed by western blotting. The addition of AGEs increased the apoptosis of ECs in a concentration-dependent manner and HRM reduced the AGE (400 µg/ml)-induced apoptosis from 21.61±2.52 to 11.32±1.75%. HRM also significantly attenuated the AGE-induced intracellular ROS induction and decrease in the expression of antioxidative enzymes. In conclusion, hydrogen exhibits significant protective effects against AGE-induced EC injury possibly through reducing ROS generation, intracellular antioxidant enzyme system protection and elevation of the Bcl-2/Bax ratio.

Advanced glycation end products-induced reactive oxygen species generation is partly through NF-kappa B activation in human aortic endothelial cells

Tumor necrosis factor (TNF)-α and reactive oxygen species (ROS) are involved in the endothelial dysfunction and the progression of atherosclerosis. In the pathogenesis of diabetic micro- and macro-vascular complications, advanced glycation end products (AGEs) and their receptor signaling are thought to play pivotal roles. We have studied the interaction among AGEs, TNF-α and ROS production using human aortic endothelial cells (HAoEC), and elucidated the significance of transcription factor NF-κB in that interaction. Concentration of TNF-α as well as 8-hydroxy-2'-deoxyguanosine (8-OHdG), an indicator of ROS generation, in the culture medium was significantly elevated 24 h after treatment with glycolaldehyde-derived AGE3. Antioxidant TEMPOL almost completely inhibited AGE3-induced TNF-α secretion, whereas NF-κB inhibitor PDTC partly suppressed AGE3-induced 8-OHdG production. Since NF-κB, which induces TNF-α expression is activated by ROS and TNF-α itself, AGE3-induced ROS generation is partly through NF-κB activation and subsequent TNF-α production in these cells. Our findings suggest that sustained activation of NF-κB might be crucial for endothelial dysfunction in diabetes, and that inhibition of local NF-κB and/or TNF-α action could be one of therapeutic strategies for vascular complications.

Oxidant stress and skeletal muscle microvasculopathy in the metabolic syndrome

The evolution of the metabolic syndrome in afflicted individuals is, in part, characterized by the development of a severely pro-oxidant state within the vasculature. It has been previously demonstrated by many investigators that this increasingly pro-oxidant state can have severe negative implications for many relevant processes within the vasculature, including the coordination of dilator/constrictor tone or reactivity, the structural adaptations of the vascular wall or distal networks, as well as the integrated regulation of perfusion resistance across and throughout the vascular networks. The purpose of this review article is to present the different sources of oxidant stress within the setting of the metabolic syndrome, the available mechanism for attempts at regulation and the vascular outcomes associated with this condition. It is anticipated that this overview will help readers and investigators to more effectively design experiments and interpret their results within the extremely complicated setting of metabolic syndrome.

Association between sRAGE, esRAGE levels and vascular inflammation: analysis with (18)F-fluorodeoxyglucose positron emission tomography

BACKGROUND

The receptor for advanced glycation end-products (RAGE) and its diverse ligands play a pivotal role in the development of cardiovascular disease. Soluble forms of RAGE (sRAGE), including the splice variant endogenous secretory RAGE (esRAGE), may neutralize AGE-RAGE mediated vascular damage by acting as a decoy. (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) is a novel imaging technique for detecting vascular inflammation.

METHODS

We examined vascular inflammation measured using FDG-PET in 41 type 2 diabetes patients and 41 healthy control subjects in the right carotid artery. Vascular (18)F-FDG uptake was measured as the blood-normalized standardized uptake value (SUV), known as the target-to-background ratio (TBR). In addition, their relationship with carotid intima-media thickness (CIMT), estimated GFR (eGFR), and other cardiovascular risk factors was evaluated.

RESULTS

Both mean and maximum TBR values were significantly higher in patients with type 2 diabetes compared to healthy subjects. After adjusting for age and gender, sRAGE levels were significantly correlated with both mean and maximum TBR values, but not with CIMT values. Multiple linear regression analysis showed that maximum TBR values were independently associated with sRAGE levels in addition to HbA1c and eGFR.

CONCLUSIONS

Circulating sRAGE showed significant association with TBR values measured using FDG-PET, which reflect vascular inflammation.

Knockdown of RAGE expression inhibits colorectal cancer cell invasion and suppresses angiogenesis in vitro and in vivo

The receptor for advanced glycation end-products (RAGE) is a transmembrane receptor in cells, and the interaction of RAGE with ligands results in pro-inflammatory gene activation. Aberrant RAGE activation was reported to promote the pathogenesis of colorectal cancer. This study aimed to investigate the effects of RAGE on the regulation of cell viability, invasion, and angiogenesis, as well as the underlying molecular mechanisms regulating these interactions in colorectal cancer cells. The RAGE mRNA and protein were evaluated in five colorectal cancer cell lines and in 45 cases of colorectal cancer tissue specimens (using immuohistochemistry). RAGE expression was then knockdown using RAGE shRNA for assessing cell viability and invasion assays as well as for tube formation and CAM assays in human umbilical vein endothelial cells and chick embryos, respectively. RAGE was highly expressed in colorectal cancer tissues, and was associated with increased microvessel density. Two of the four RAGE shRNA constructs were able to significantly knockdown RAGE expression in SW480 cells. RAGE knockdown inhibited invasion capacity of SW480 cells, but did not significantly affect cell viability. Furthermore, the conditioned growth medium from stable RAGE shRNA-transfected cells suppressed tube formation of human umbilical vein endothelial cells and angiogenesis of chicken embryos. Knockdown of RAGE inhibited expression of VEGF and SP1 protein in colorectal cancer cells. In summary, these data suggest that silence of RAGE expression could effectively inhibit colorectal cancer angiogenesis in vitro and in vivo.

Chinese prescription Kangen-karyu prevents dyslipidaemia and oxidative stress in mouse model of type 2 diabetes

Objectives

We have investigated the effects of Kangen-karyu, a Chinese prescription, on the lipid metabolism and oxidative stress in a type 2 diabetes model.

Methods

Male db/db mice were divided into three groups: control (vehicle), Kangen-karyu 100 or 200 mg/kg body weight/day orally administered mice. Age-matched non-diabetic m/m mice were used as a normal group.

Key findings

The administration of Kangen-karyu reduced hyperglycaemia and hyperlipidaemia in db/db type 2 diabetic mice through a decline in the serum levels of glucose and lipids, and an improvement of lipoprotein profiles. The increased oxidative stress in db/db mice was attenuated by the administration of Kangen-karyu through inhibiting the generation of reactive oxygen species and lipid peroxidation. The enhanced hepatic triglyceride and total cholesterol levels of the db/db mice were significantly reduced by Kangen-karyu administration through down-regulation of sterol regulatory element-binding protein-1 and lipogenic enzymes in liver. Furthermore, the expressions of hepatic nuclear factor-kappa B (NF-κB) and cyclooxygenase-2 and inducible nitric oxide synthase protein levels were also augmented in db/db mice. However, Kangen-karyu reduced the expressions of these inflammatory proteins by inhibiting NF-κB activation in db/db type 2 diabetes.

Conclusions

This study suggests that Kangen-karyu may improve oxidative stress via the regulation of dyslipidaemia in type 2 diabetes.

Hypolipidaemic and antioxidative effects of oligonol, a low-molecular-weight polyphenol derived from lychee fruit, on renal damage in type 2 diabetic mice

Oligonol was orally administered at 10 or 20 mg/kg body weight per d for 8 weeks to db/db mice with type 2 diabetes, and its effects were compared with those of the vehicle in db/db and m/m (misty, non-diabetic) mice. Serum and renal biochemical factors, protein expressions related to lipid metabolism and inflammation, and advanced glycation endproducts were measured. There were significant reductions in the serum lipid concentration, reactive oxygen species (ROS) and lipid peroxidation, as well as improvements in renal function parameters. In addition, oligonol treatment significantly decreased ROS levels and lipid peroxidation in the kidney. In particular, the renal lipid contents such as TAG and total cholesterol were significantly reduced in the oligonol-administered groups through the up-regulation of PPARα and down-regulation of sterol regulatory element-binding protein-1 in db/db mice. Moreover, oligonol inhibited non-fluorescent AGE formation and their receptor expression, suggesting that it could effectively inhibit AGE development caused by oxidative stress and/or dyslipidaemia in the kidney of db/db mice. Furthermore, augmented expressions of NF-κBp65, cyclo-oxygenase-2 and inducible NO synthase were down-regulated to the levels of m/m mice in the group given oligonol at 20 mg/kg. This means that oligonol would act as a regulator in the inflammatory response of type 2 diabetes. The present results suggest that oligonol could have renoprotective effects against abnormal lipid metabolism and ROS-related AGE formation in type 2 diabetes.

Rosiglitazone via upregulation of Akt/eNOS pathways attenuates dysfunction of endothelial progenitor cells, induced by advanced glycation end products

BACKGROUND AND PURPOSE

Advanced glycation end products (AGEs) and endothelial progenitor cells (EPCs) play key roles in pathogenesis of diabetes-related vascular complications. AGEs can induce dysfunction in EPCs. The peroxisome proliferator-activated receptor-gamma (PPARgamma) agonists are widely used in the treatment of type 2 diabetes, and it remains unknown if they could attenuate EPC dysfunction induced by AGEs.

EXPERIMENTAL APPROACH

EPCs isolated from healthy adults were cultured with various concentrations of AGEs (0, 50, 100 and 200 mg L(-1)) with or without rosiglitazone (10 nM), antibody for the receptors for AGE-human serum albumin (anti-receptor for advanced glycation end products (RAGE); 50 microg mL(-1)), phosphatidylinositol-3-kinase (PI3K) inhibitor (LY294002, 5 microM), nitric oxide (NO) synthase inhibitor (L-N(G)-nitro-arginine methyl ester (L-NAME), 100 microM) or sodium nitroprusside (SNP, 25 microM). Proliferation, apoptosis, cell adhesion, migration and NO production in EPCs were assessed, and expressions of endothelial NO synthase (eNOS) and Akt were determined.

KEY RESULTS

Number, proliferation/migration capacities, eNOS and Akt phosphorylation as well as NO synthesized by EPCs were increased by rosiglitazone and reduced by AGEs. AGEs promoted while rosiglitazone reduced EPC apoptosis. The AGE-induced effects were significantly ameliorated by pre-incubation with rosiglitazone, RAGE antibody and SNP. The beneficial effects of rosiglitazone could be blocked by pretreatment with L-NAME and LY294002.

CONCLUSIONS AND IMPLICATIONS

The PPARgamma agonist rosiglitazone increased EPC function and attenuated EPC dysfunction induced by AGEs via upregulating the Akt-eNOS signal pathways of EPCs.

Rho kinase inhibition by fasudil ameliorates diabetes-induced microvascular damage

OBJECTIVE

Leukocyte adhesion in retinal microvasuculature substantially contributes to diabetic retinopathy. Involvement of the Rho/Rho kinase (ROCK) pathway in diabetic microvasculopathy and therapeutic potential of fasudil, a selective ROCK inhibitor, are investigated.

RESEARCH DESIGN AND METHODS

Localization of RhoA/ROCK and Rho activity were examined in retinal tissues of rats. Impact of intravitreal fasudil administration on retinal endothelial nitric oxide synthase (eNOS) and myosin phosphatase target protein (MYPT)-1 phosphorylation, intercellular adhesion molecule-1 (ICAM-1) expression, leukocyte adhesion, and endothelial damage in rat eyes were investigated. Adhesion of neutrophils from diabetic retinopathy patients or nondiabetic control subjects to cultured microvascular endothelial cells was quantified. The potential of fasudil for endothelial protection was investigated by measuring the number of adherent neutrophils and terminal transferase-mediated dUTP nick-end labeling-positive endothelial cells.

RESULTS

RhoA and ROCK colocalized predominantly in retinal microvessels. Significant Rho activation was observed in retinas of diabetic rats. Intravitreal fasudil significantly increased eNOS phosphorylation, whereas it reduced MYPT-1 phosphorylation, ICAM-1 expression, leukocyte adhesion, and the number of damaged endothelium in retinas of diabetic rats. Neutrophils from diabetic retinopathy patients showed significantly higher adhesion to cultured endothelium and caused endothelial apoptosis, which was significantly reduced by fasudil. Blockade of the Fas-FasL interaction prevented endothelial apoptosis. The protective effect of fasudil on endothelial apoptosis was significantly reversed by Nomega-nitro-l-arginine methyl ester, a NOS inhibitor, whereas neutrophil adhesion remained unaffected.

CONCLUSIONS

The Rho/ROCK pathway plays a critical role in diabetic retinal microvasculopathy. Fasudil protects the vascular endothelium by inhibiting neutrophil adhesion and reducing neutrophil-induced endothelial injury. ROCK inhibition may become a new strategy in the management of diabetic retinopathy, especially in its early stages.