3'-Sialyllactose protects against LPS-induced endothelial dysfunction by inhibiting superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis

AIM

Endothelial hyperpermeability is an early stage of endothelial dysfunction associated with the progression and development of atherosclerosis. 3'-Sialyllactose (3'-SL) is the most abundant compound in human milk oligosaccharides, and it has the potential to regulate endothelial dysfunction. This study investigated the beneficial effects of 3'-SL on lipopolysaccharide (LPS)-induced endothelial dysfunction in vitro and in vivo.

MAIN METHODS

We established LPS-induced endothelial dysfunction models in both cultured bovine aortic endothelial cells (BAECs) and mouse models to determine the effects of 3'-SL. Western blotting, qRT-PCR analysis, immunofluorescence staining, and en face staining were employed to clarify underlying mechanisms. Superoxide production was measured by 2',7'-dichlorofluorescin diacetate, and dihydroethidium staining.

KEY FINDINGS

LPS significantly decreased cell viability, whereas 3'-SL treatment mitigated these effects via inhibiting ERK1/2 activation. Mechanistically, 3'-SL ameliorated LPS-induced ROS accumulation leading to ERK1/2 activation-mediated STAT1 phosphorylation and subsequent inhibition of downstream transcriptional target genes, including VCAM-1, TNF-α, IL-1β, and MCP-1. Interestingly, LPS-induced ERK1/2/STAT1 activation leads to the HMGB1 release from the nucleus into the extracellular space, where it binds to RAGE, while 3'-SL suppressed EC hyperpermeability by suppressing the HMGB1/RAGE axis. This interaction also led to VE-cadherin endothelial junction disassembly and endothelial cell monolayer disruption through ERK1/2/STAT1 modulation. In mouse endothelium, en face staining revealed that 3'-SL abolished LPS-stimulated ROS production and VCAM-1 overexpression.

SIGNIFICANCE

Our findings suggest that 3'-SL inhibits LPS-induced endothelial hyperpermeability by suppressing superoxide-mediated ERK1/2/STAT1 activation and HMGB1/RAGE axis. Therefore, 3'-SL may be a potential therapeutic agent for preventing the progression of atherosclerosis.

Involvement of multiple scavenger receptors in advanced glycation end product-induced vessel tube formation in endothelial cells

Toxic advanced glycation end products (toxic AGEs) derived from glycolaldehyde (AGE3) have been implicated in the development of diabetic vascular complications such as retinopathy characterised by excessive angiogenesis. Different receptor types, such as receptor for AGEs (RAGE), Toll like receptor-4 and scavenger receptors, are expressed in endothelial cells and contribute to AGE-elicited alteration of cell function. In the present study, we examined the involvement of AGE-related receptors on AGE-induced angiogenesis in endothelial cells. The effects of pharmacological inhibitors or receptor neutralizing antibodies on AGE3-induced tube formation were investigated using the in vitro Matrigel tube formation assay in b.End5 cells (mouse endothelial cells). AGE3-induced signalling pathways and receptor expression changes were analysed by Western blot analysis and flow cytometry, respectively. Both FPS-ZM1, a RAGE inhibitor, and fucoidan, a ligand for scavenger receptors, suppressed AGE3-induced tube formation. Cocktails of neutralizing antibodies against the scavenger receptors CD36, CD163 and LOX-1 prevented AGE3-induced tube formation. AGE3 activated mTOR signalling, resulting in facilitation of tube formation. Activation of the AGE-RAGE pathway also led to the upregulation of scavenger receptors. Taken together, our findings suggest that the scavenger receptors CD36, CD163 and LOX-1 in conjunction with the RAGE receptor work together to mediate toxic AGE-induced facilitation of angiogenesis.

Network Pharmacology and Molecular Docking Study on the Potential Mechanism of Yi-Qi-Huo-Xue-Tong-Luo Formula in Treating Diabetic Peripheral Neuropathy

OBJECTIVE

To investigate the potential mechanism of action of Yi-Qi-Huo-Xue-Tong-Luo formula (YQHXTLF) in the treatment of diabetic peripheral neuropathy (DPN).

METHODS

Network pharmacology and molecular docking techniques were used in this study. Firstly, the active ingredients and the corresponding targets of YQHXTLF were retrieved using the Traditional Chinese Medicine Systems Pharmacology (TCMSP) platform; subsequently, the targets related to DPN were retrieved using GeneCards, Online Mendelian Inheritance in Man (OMIM), Pharmgkb, Therapeutic Target Database (TTD) and Drugbank databases; the common targets of YQHXTLF and DPN were obtained by Venn diagram; afterwards, the "YQHXTLF Pharmacodynamic Component-DPN Target" regulatory network was visualized using Cytoscape 3.6.1 software, and Gene Ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed on the potential targets using R 3.6.3 software. Finally, molecular docking of the main chemical components in the PPI network with the core targets was verified by Autodock Vina software.

RESULTS

A total of 86 active ingredients and 229 targets in YQHXTLF were screened, and 81 active ingredients and 110 targets were identified to be closely related to diabetic peripheral neuropathy disease. PPI network mapping identified TP53, MAPK1, JUN, and STAT3 as possible core targets. KEGG pathway analysis showed that these targets are mostly involved in AGE-RAGE signaling pathway in diabetic complications, TNF signaling pathway, and MAPK signaling pathway. The molecular docking results showed that the main chemical components of YQHXTLF have a stable binding activity to the core pivotal targets.

CONCLUSION

YQHXTLF may act on TP53, MAPK1, JUN, and STAT3 to regulate inflammatory response, apoptosis, or proliferation as a molecular mechanism for the treatment of diabetic peripheral neuropathy, reflecting its multitarget and multipathway action, and providing new ideas to further uncover its pharmacological basis and mechanism of action.

Study on the Mechanism of Prunella Vulgaris L on Diabetes Mellitus Complicated with Hypertension Based on Network Pharmacology and Molecular Docking Analyses

The role of traditional Chinese medicine Prunella vulagaris L in the treatment of tumors and inflammation has been widely confirmed. We found that some signaling pathways of Prunella vulgaris L action can also regulate diabetes and hypertension, so we decided to study the active ingredients, potential targets and signaling pathway of Prunrlla vulgaris L, and explore the "multi-target, multi-pathway" molecular mechanism of Prunella vulgaris L on diabetes mellitus complicated with hypertension(DH). Methods. Based on TCMSP(Traditional Chinese Medicine Systems Pharmacology Database and Analysis Platform) and CNKI(China National Knowledge Infrastructure), the components and action targets related to Prunella vulgaris L were screened. The OMIM(Online Mendelian Inheritance in Man) and GeneCards (The human gene database) were used to search for targets related to DH. The "gene - drug - disease" relationship map was drawn by Cytoscape_v3.7.2 plug-in. The target was amplified by the STRING platform, and the "protein - protein" interaction relationship (PPI) network of the interacting target was obtained by the STRING online analysis platform and the Cytoscape_v3.7.2 plug-in. Finally, GO enrichment analysis and KEGG pathway enrichment analysis were conducted on David and Metascape platform to study the co-acting targets. Results. 11 active components, 41 key targets and 16 significant signaling pathways were identified from Prunella vulgaris L. The main active components of Prunella vulgaris L against DH were quercetin and kaumferol, etc, and potential action targets were IL-6 and INS, etc and signaling pathways were AGE-RAGE signaling pathway, TNF signaling pathway, MAPK signaling pathway, PI3K-AKT signaling pathway, etc. It involves in biological processes such as cell proliferation, apoptosis and inflammatory response. Conclusions. The main molecular mechanism of Prunella vulgaris L against DH is that sterols and flavonoids play an active role by affecting TNF signaling pathway, AGE-RAGE signaling pathway, MAPK pathway, PI3K-Akt pathway related targets such as IL-6 and INS.

RAGE-NF-κB-PPARγ Signaling is Involved in AGEs-Induced Upregulation of Amyloid-β Influx Transport in an In Vitro BBB Model

The receptor for advanced glycation end products (RAGE) at the blood-brain barrier (BBB) is critical for regulation of amyloid-β (Aβ) homeostasis in the diabetic brain. In this study, we used an in vitro BBB model consisting of mouse brain capillary endothelial cells (MBCECs) to investigate whether advanced glycation end products (AGEs) increase Aβ influx transport across the BBB and the underlying mechanisms. We found that AGEs induced Aβ influx transport across the BBB in concentration- and time-dependent manner, accompanied by increased RAGE expression and nuclear factor-kappa B p65 (NF-κB p65), and decreased nuclear peroxisome proliferator-activated receptor γ (PPARγ). Blockade of RAGE with its antibody and inhibition of NF-κB signaling with PDTC as well as activation of PPARγ with rosiglitazone significantly decreased Aβ transport across the BBB from the periphery to the brain. These treatments also pronouncedly suppressed AGEs-induced increases in RAGE expression and nuclear NF-κB p65 and reversed the decrease in nuclear PPARγ. These results suggest that RAGE-NF-κB-PPARγ signaling is involved in regulation of AGEs-induced influx transport of Aβ across the BBB and targeting the signaling pathway could serve as a novel strategy to modify such Aβ transport.

Effect of crocetin on vascular smooth muscle cells migration induced by advanced glycosylation end products

Crocetin is a major active constituent of Gardenia jasminoides J. Ellis, and can aid in the prevention of cardiovascular disease. The effect and possible mechanism of crocetin on the migration of vascular smooth muscle cells (VSMCs) induced by advanced glycosylation end products (AGEs) were investigated. VSMCs were pre-incubated with or without crocetin and exposed to AGEs subsequently. The invasion of the cells was investigated using a 24-well Cell Invasion Chamber. The anti-proliferative activity of crocetin was evaluated by MTT assay and VSMCs cell-cycle distribution was examined by flow cytometry. Cytokine TNF-α and IL-6 secreted by VSMCs and the amount of matrix metalloproteinase MMP-2 and MMP-9 in the culture supernatant were detected by ELISA. The expression level of RAGE (AGEs receptor), in cells was analyzed by western blot. The results demonstrated that AGEs increased about two-fold migration of VSMCs compared with control (OD=0.778±0.191 vs OD=0.413±0.214, P<0.01), and the proliferation increased by about 20% (OD=0.335±0.043 vs OD=0.281±0.037, P<0.01). Pre-treatment with crocetin (1.0μM) or RAGE antibody (10μg/ml) could inhibit the AGEs triggered migration of VSMCs obviously. Furthermore, both crocetin and RAGE antibody inhibited the increase of RAGE protein in VSMCs stimulated by AGEs. The levels of TNF-α and IL-6 decreased in the crocetin (1.0μM) pre-treated group compared to the AGEs (without pre-treated) group (37.60±3.08pg/ml vs 46.59±1.92pg/ml, 32.11±4.69pg/ml vs 49.99±8.84pg/ml, respectively). Crocetin (1.0μM) also reduced the value of MMP-2 and MMP-9 compared with the AGEs group (2.81±0.35ng/ml vs 6.40±0.85ng/ml, 2.69±0.25ng/ml vs 4.32±0.57ng/ml, respectively). In summary, crocetin inhibits the migration of VSMCs induced by AGEs through RAGE-dependent signaling pathway. And it is meaningful to diabetic vascular complications.

RAGE-Aptamer Blocks the Development and Progression of Experimental Diabetic Nephropathy

The interaction of advanced glycation end products (AGEs) and their receptor (RAGE) plays a central role in diabetic nephropathy. We screened DNA aptamers directed against RAGE (RAGE-aptamers) in vitro and examined the effects on the development and progression of diabetic nephropathy in streptozotocin-induced diabetic rats. RAGE-aptamer bound to RAGE with a K_d of 5.68 nmol/L and resultantly blocked the binding of AGEs to RAGE. When diabetic rats received continuous intraperitoneal injection of RAGE-aptamer from week 7 to 11 of diabetes, the increases in renal NADPH oxidase activity, oxidative stress generation, AGE, RAGE, inflammatory and fibrotic gene and protein levels, macrophage and extracellular matrix accumulation, and albuminuria were significantly suppressed, which were associated with improvement of podocyte damage. Two-week infusion of RAGE-aptamer just after the induction of diabetes also inhibited the AGE-RAGE-oxidative stress system and MCP-1 levels in the kidneys of 8-week-old diabetic rats and simultaneously ameliorated podocyte injury and albuminuria. Moreover, RAGE-aptamer significantly suppressed the AGE-induced oxidative stress generation and inflammatory and fibrotic reactions in human cultured mesangial cells. The findings suggest that continuous infusion of RAGE-aptamer could attenuate the development and progression of experimental diabetic nephropathy by blocking the AGE-RAGE axis.

Sulforaphane reduces advanced glycation end products (AGEs)-induced inflammation in endothelial cells and rat aorta

BACKGROUND AND AIMS

Advanced glycation end products (AGEs)-receptor RAGE interaction evokes oxidative stress and inflammatory reactions, thereby being involved in endothelial cell (EC) damage in diabetes. Sulforaphane is generated from glucoraphanin, a naturally occurring isothiocyanate found in widely consumed cruciferous vegetables, by myrosinase. Sulforaphane has been reported to protect against oxidative stress-mediated cell and tissue injury. However, effects of sulforaphane on AGEs-induced vascular damage remain unclear.

METHODS AND RESULTS

In this study, we investigated whether and how sulforaphane could inhibit inflammation in AGEs-exposed human umbilical vein ECs (HUVECs) and AGEs-injected rat aorta. Sulforaphane treatment for 4 or 24 h dose-dependently inhibited the AGEs-induced increase in RAGE, monocyte chemoattractant protein-1 (MCP-1), intercellular adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecular-1 (VCAM-1) gene expression in HUVECs. AGEs significantly stimulated MCP-1 production by, and THP-1 cell adhesion to, HUVECs, both of which were prevented by 1.6 μM sulforaphane. Sulforaphane significantly suppressed oxidative stress generation and NADPH oxidase activation evoked by AGEs in HUVECs. Furthermore, aortic RAGE, ICAM-1 and VCAM-1 expression in AGEs-injected rats were increased, which were suppressed by simultaneous infusion of sulforaphane.

CONCLUSION

The present study demonstrated for the first time that sulforaphane could inhibit inflammation in AGEs-exposed HUVECs and AGEs-infused rat aorta partly by suppressing RAGE expression through its anti-oxidative properties. Inhibition of the AGEs-RAGE axis by sulforaphane might be a novel therapeutic target for vascular injury in diabetes.

Metformin Inhibits Advanced Glycation End Products-Induced Inflammatory Response in Murine Macrophages Partly through AMPK Activation and RAGE/NFκB Pathway Suppression

Advanced glycation end products (AGEs) are major inflammatory mediators in diabetes, affecting atherosclerosis progression via macrophages. Metformin slows diabetic atherosclerosis progression through mechanisms that remain to be fully elucidated. The present study of murine bone marrow derived macrophages showed that (1) AGEs enhanced proinflammatory cytokines (interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α)) mRNA expression, RAGE expression, and NFκB activation; (2) metformin pretreatment inhibited AGEs effects and AGEs-induced cluster designation 86 (CD86) (M1 marker) expression, while promoting CD206 (M2 marker) surface expression and anti-inflammatory cytokine (IL-10) mRNA expression; and (3) the AMPK inhibitor, Compound C, attenuated metformin effects. In conclusion, metformin inhibits AGEs-induced inflammatory response in murine macrophages partly through AMPK activation and RAGE/NFκB pathway suppression.

Empagliflozin, an Inhibitor of Sodium-Glucose Cotransporter 2 Exerts Anti-Inflammatory and Antifibrotic Effects on Experimental Diabetic Nephropathy Partly by Suppressing AGEs-Receptor Axis

Advanced glycation end products (AGEs) and receptor RAGE play a role in diabetic nephropathy. We have previously shown that increased glucose uptake into proximal tubular cells via sodium-glucose cotransporter 2 (SGLT2) stimulates oxidative stress generation and RAGE expression, thereby exacerbating the AGE-induced apoptosis in this cell type. However, the protective role of SGLT2 inhibition against the AGE-RAGE-induced renal damage in diabetic animals remains unclear. In this study, we investigated the effects of empagliflozin, SGLT2 inhibitor on AGE-RAGE axis, inflammatory and fibrotic reactions, and tubular injury in the kidney of streptozotocin-induced diabetic rats.Administration of empagliflozin for 4 weeks significantly improved hyperglycemia and HbA1c, and decreased expression levels of AGEs, RAGE, 8-hydroxydeoxyguanosine (8-OHdG), and F4/80, markers of oxidative stress and macrophages, respectively, in the diabetic kidney. Although empagliflozin did not reduce albuminuria, it significantly decreased urinary excretion levels of 8-OHdG and L-fatty acid binding protein, a marker of tubular injury. Moreover, inflammatory and fibrotic gene expression such as monocyte chemoattractant protein-1, intercellular adhesion molecule-1, plasminogen activator inhibitor-1, transforming growth factor-β, and connective tissue growth factor was enhanced in the diabetic kidney, all of which were prevented by empagliflozin. The present study suggests that empagliflozin could inhibit oxidative, inflammatory and fibrotic reactions in the kidney of diabetic rats partly via suppression of the AGE-RAGE axis. Blockade of the increased glucose uptake into renal proximal tubular cells by empagliflozin might be a novel therapeutic target for tubulointerstitial damage in diabetic nephropathy.

Glycated serum albumin stimulates expression of endothelial cell specific molecule-1 in human umbilical vein endothelial cells: Implication in diabetes mediated endothelial dysfunction

Pro-inflammatory conditions induced by products of protein glycation in diabetes substantially enhance the risk of endothelial dysfunction and related vascular complications. Endothelial cell specific molecule-1 (ESM-1) or endocan has been demonstrated as a potential biomarker in cancer and sepsis. Its role in diabetes-induced pathologies remains unknown. The expression of ESM-1 gene is under cytokine regulation, indicating its role in endothelium-dependent pathological disorders. In this study, we investigated the effect of advanced glycated human serum albumin (AGE-HSA) on the production of ESM-1. We show that AGE-HSA exerts a modulating role on the expression of ESM-1 in human umbilical vein endothelial cells. It up-regulates expression of ESM-1 protein in a dose-dependent manner which correlates with its messenger RNA (mRNA) transcription. RAGE and galectin-3, both AGE receptors, show antagonistic action on its expression. While gene silencing of RAGE has down-regulatory effect, that of galectin-3 has up-regulatory effect on AGE-induced expression of ESM-1. Inhibition of MAPKKK and JNK pathways did not alter the expression. In contrast, phosphatidylinositol 3 kinase (PI3K) inhibition significantly up-regulated ESM-1 expression. In conclusion, these results suggest that AGE-induced activation of human umbilical vein endothelial cells promotes formation of endocan which is an endothelial dysfunction marker and may be related to vascular disease in diabetes.

Hyperglycemia-induced reactive oxygen species increase expression of the receptor for advanced glycation end products (RAGE) and RAGE ligands

OBJECTIVE

RAGE interacts with the endogenous ligands S100 calgranulins and high mobility group box 1 (HMGB1) to induce inflammation. Since hyperglycemia-induced reactive oxygen species (ROS) activate many pathways of diabetic tissue damage, the effect of these ROS on RAGE and RAGE ligand expression was evaluated.

RESEARCH DESIGN AND METHODS

Expression of RAGE, S100A8, S100A12, and HMGB1 was evaluated in human aortic endothelial cells (HAECs) incubated in normal glucose, high glucose, and high glucose after overexpression of either uncoupling protein 1 (UCP1), superoxide dismutase 2 (SOD2), or glyoxalase 1 (GLO1). Expression was also evaluated in normal glucose after knockdown of GLO1. Expression was next evaluated in high glucose after knockdown of nuclear factor (NF)-kappaB p65 (RAGE) and after knockdown of activated protein-1 (AP-1) (S100A8, S100A12, and HMGB1), and chromatin immunoprecipitation (ChIP) was performed +/- GLO1 overexpression for NFkappaB p65 (RAGE promoter) and AP-1 (S100A8, S100A12, and HMGB1 promoters). Finally, endothelial cells from nondiabetic mice, STZ diabetic mice, and STZ diabetic mice treated with the superoxide dismutase mimetic Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP) were evaluated.

RESULTS

High glucose increased RAGE, S100A8, S100A12, and HMGB1 expression, which was normalized by overexpression of UCP1, SOD2, or GLO1. GLO1 knockdown mimicked the effect of high glucose, and in high glucose, overexpression of GLO1 normalized increased binding of NFkappaB p65 and AP-1. Diabetes increased RAGE, S100A8, and HMGB1 expression, and MnTBAP treatment normalized this.

CONCLUSIONS

These results show that hyperglycemia-induced ROS production increases expression of RAGE and RAGE ligands. This effect is mediated by ROS-induced methylglyoxal, the major substrate of glyoxalase 1.

S100A8 and S100A9 activate MAP kinase and NF-κB signaling pathways and trigger translocation of RAGE in human prostate cancer cells

S100 proteins, a multigenic family of calcium-binding proteins, have been linked to human pathologies in recent years. Deregulated expression of S100 proteins, including S100A8 and S100A9, was reported in association with neoplastic disorders. In a previous study, we identified enhanced expression of S100A8 and S100A9 in human prostate cancer. To investigate potential functional implications of S100A8 and S100A9 in prostate cancer, we examined the influence of over-expressed and of purified recombinant S100A8 and S100A9 proteins in different prostate epithelial cell lines. S100A8 and S100A9 were secreted by prostate cancer cells, a finding which prompted us to analyze a possible function as extracellular ligands. S100A8/A9 induced the activation of NF-kappaB and an increased phosphorylation of p38 and p44/42 MAP kinases. In addition, extracellular S100A8/A9 stimulated migration of benign prostatic cells in vitro. Furthermore, in immunofluorescence experiments, we found a strong speckled co-localization of intracellular S100A8/A9 with RAGE after stimulating cells with recombinant S100A8/A9 protein or by increasing cytosolic Ca2+ levels. In summary, our findings show that S100A8 and S100A9 are linked to the activation of important features of prostate cancer cells.