Methylglyoxal induces platelet hyperaggregation and reduces thrombus stability by activating PKC and inhibiting PI3K/Akt pathway

Synergistic effects of nab-PTX and anti-PD-1 antibody combination against lung cancer by regulating the Pi3K/AKT pathway through the Serpinc1 gene

Lung cancer is a type of cancer with higher morbidity and mortality. In spite of the impressive response rates of nab-paclitaxel (nab-PTX) or programmed cell death-1 (PD-1) and its ligand inhibitors, the effective treatment remains limited. Currently, alternative strategies aim at drug combination of nab-PTX and PD-1/PD-L1 inhibitors. Even as the clinical impact of the combined agents continues to increase, basic research studies are still limited and the mechanisms underlying this synergy are not well studied. In this study, we evaluated the antitumor efficacy and the molecular mechanisms of action of nab-PTX in combination with anti-PD-1 antibody, using Lewis lung carcinoma (LLC) cell and subcutaneously transplanted tumor models. The combination of nab-PTX and anti-PD-1 antibody displayed stronger antitumor effects, manifested at tumor volume, proliferation and apoptosis through Ki67 and TUNEL staining. In-vivo experiments showed significant increases in CD4+ T cells, CD8+ T cells, IFN-γ, TNF-α, IL-2, PF, and Gzms-B, exerting antitumor effects with reductions in MDSCs and IL-10 after the treatments. Furthermore, transcriptomic analysis indicated 20 overlapped differentially expressed genes, and Serpin peptidase inhibitor clade C Member 1 (Serpinc1) was downregulated during treatment in vivo, whose expression level was markedly related to metastasis and overall survival of lung cancer patients. Functional enrichment analysis of the target gene revealed primary GO terms related to tumor, which warrants further investigation. We also found that Serpinc1 overexpression promoted cell proliferation, migration, and invasion and inhibited cell apoptosis of LLC cells in vitro, possibly regulating the associated factors via the Pi3K/AKT pathway. In summary, our results reveal the synergistic antitumor responses of nab-PTX combined with anti-PD-1 antibody, in which Serpinc1 may play an important role, providing a target gene for combination treatment strategy.

Antiplatelet and Antithrombotic Effects of Isaridin E Isolated from the Marine-Derived Fungus via Downregulating the PI3K/Akt Signaling Pathway

Isaridin E, a cyclodepsipeptide isolated from the marine-derived fungus Amphichorda felina (syn. Beauveria felina) SYSU-MS7908, has been demonstrated to possess anti-inflammatory and insecticidal activities. Here, we first found that isaridin E concentration-dependently inhibited ADP-induced platelet aggregation, activation, and secretion in vitro, but did not affect collagen- or thrombin-induced platelet aggregation. Furthermore, isaridin E dose-dependently reduced thrombosis formation in an FeCl3-induced mouse carotid model without increasing the bleeding time. Mechanistically, isaridin E significantly decreased the ADP-mediated phosphorylation of PI3K and Akt. In conclusion, these results suggest that isaridin E exerts potent antithrombotic effects in vivo without increasing the risk of bleeding, which may be due to its important role in inhibiting ADP-induced platelet activation, secretion and aggregation via the PI3K/Akt pathways.

Identification of the Antithrombotic Mechanism of Leonurine in Adrenalin Hydrochloride-Induced Thrombosis in Zebrafish via Regulating Oxidative Stress and Coagulation Cascade

Thrombosis is a general pathological phenomenon during severe disturbances to homeostasis, which plays an essential role in cardiovascular and cerebrovascular diseases. Leonurine (LEO), isolated from Leonurus japonicus Houtt, showes a crucial role in anticoagulation and vasodilatation. However, the properties and therapeutic mechanisms of this effect have not yet been systematically elucidated. Therefore, the antithrombotic effect of LEO was investigated in this study. Hematoxylin-Eosin staining was used to detect the thrombosis of zebrafish tail. Fluorescence probe was used to detect the reactive oxygen species. The biochemical indexes related to oxidative stress (lactate dehydrogenase, malondialdehyde, superoxide dismutase and glutathione) and vasodilator factor (endothelin-1 and nitric oxide) were analyzed by specific commercial assay kits. Besides, we detected the expression of related genes (fga, fgb, fgg, pkcα, pkcβ, vwf, f2) and proteins (PI3K, phospho-PI3K, Akt, phospho-Akt, ERK, phospho-ERK FIB) related to the anticoagulation and fibrinolytic system by quantitative reverse transcription and western blot. Beyond that, metabolomic analyses were carried out to identify the expressions of metabolites associated with the anti-thrombosis mechanism of LEO. Our in vivo experimental results showed that LEO could improve the oxidative stress injury, abnormal platelet aggregation and coagulation dysfunction induced by adrenalin hydrochloride. Moreover, LEO restored the modulation of amino acids and inositol metabolites which are reported to alleviate the thrombus formation. Collectively, LEO attenuates adrenalin hydrochloride-induced thrombosis partly via modulating oxidative stress, coagulation cascade and platelet activation and amino acid and inositol metabolites.

Methylglyoxal augments uridine diphosphate-induced contraction via activation of p38 mitogen-activated protein kinase in rat carotid artery

The methylglyoxal elicits diverse adverse effects on the body. Uridine diphosphate, an extracellular nucleotide, plays an important role as a signaling molecule controlling vascular tone. This study aimed to evaluate the relationship between methylglyoxal and uridine diphosphate-induced carotid arterial contraction in rats. Additionally, we examined whether p38 mitogen-activated protein kinase (MAPK) would involve such responses. Organ baths were conducted to determine vascular reactivity in isolated carotid arterial rings, and western blotting was used for protein analysis. Treatment with methylglyoxal to carotid arterial rings showed concentration-dependent augmentation to uridine diphosphate-induced contraction in the absence and presence of NG-nitro-L-arginine, which is a nitric oxide synthase inhibitor, whereas, methylglyoxal did not affect serotonin- or isotonic high K+-induced contraction in the presence of a nitric oxide synthase inhibitor. Under nitric oxide synthase inhibition, SB203580, which is a selective p38 MAPK inhibitor, suppressed uridine diphosphate-induced contraction in both the control and methylglyoxal-treated groups, and the difference in uridine diphosphate-induced contraction was abolished by SB203580 treatment. The levels of phosphorylated p38 MAPK were increased by methylglyoxal in carotid arteries, not only under the basal condition but also under uridine diphosphate stimulation. The suppression of uridine diphosphate-induced contraction by a highly selective cell-permeable protein kinase C inhibitor bisindolylmaleimide I was observed in the methylglyoxal-treated group but not in the controls. Moreover, methylglyoxal-induced augmentation of uridine diphosphate-induced contraction was prevented by N-acetyl-L-cysteine. These results suggest that methylglyoxal could enhance uridine diphosphate-induced contraction in rat carotid arteries and may be caused by activation of p38 MAPK and protein kinase C and increased oxidative stress.

Myeloid cell-derived coagulation tissue factor is associated with renal tubular damage in mice fed an adenine diet

Patients with chronic kidney disease (CKD) commonly exhibit hypercoagulability. Increased levels of uremic toxins cause thrombogenicity by increasing tissue factor (TF) expression and activating the extrinsic coagulation cascade. TF is induced in monocytes and macrophages under pathological conditions, such as inflammatory diseases. However, the role of monocyte myeloid cell TF in CKD progression remains unclear. We aimed to clarify this issue, and the present study found that patients with CKD had elevated levels of D-dimer, a marker of fibrin degradation, which was associated with decreased estimated glomerular filtration rate and increased serum levels of uremic toxins, such as indoxyl sulfate. In vitro studies showed that several uremic toxins increased cellular TF levels in monocytic THP-1 cells. Mice with TF specifically deleted in myeloid cells were fed an adenine diet to cause uremic kidney injury. Myeloid TF deletion reduced tubular injury and pro-inflammatory gene expression in the kidneys of adenine-induced CKD but did not improve renal function as measured by plasma creatinine or blood urea nitrogen. Collectively, our findings suggest a novel concept of pathogenesis of coagulation-mediated kidney injury, in which elevated TF levels in monocytes under uremic conditions is partly involved in the development of CKD.

Early AGEing and metabolic diseases: is perinatal exposure to glycotoxins programming for adult-life metabolic syndrome?

Perinatal early nutritional disorders are critical for the developmental origins of health and disease. Glycotoxins, or advanced glycation end-products, and their precursors such as the methylglyoxal, which are formed endogenously and commonly found in processed foods and infant formulas, may be associated with acute and long-term metabolic disorders. Besides general aspects of glycotoxins, such as their endogenous production, exogenous sources, and their role in the development of metabolic syndrome, we discuss in this review the sources of perinatal exposure to glycotoxins and their involvement in metabolic programming mechanisms. The role of perinatal glycotoxin exposure in the onset of insulin resistance, central nervous system development, cardiovascular diseases, and early aging also are discussed, as are possible interventions that may prevent or reduce such effects.

A new insulin-sensitive enhancer from Silene viscidula, WPTS, treats type 2 diabetes by ameliorating insulin resistance, reducing dyslipidemia, and promoting proliferation of islet β cells

Wacao pentacyclic triterpenoid saponins (WPTS) is a newly discovered insulin sensitivity enhancer. It is a powerful hypoglycemic compound derived from Silene viscidula, which has a hypoglycemic effect similar to that of insulin. It can rapidly reduce blood glucose levels, normalizing them within 3 days of administration. However, its mechanism of action is completely different from that of insulin. Thus, we aimed to determine the pharmacological effects and mechanism of activity of WPTS on type 2 diabetes to elucidate the main reasons for its rapid effects. The results showed that WPTS could effectively improve insulin resistance in KKAy diabetic mice. Comparative transcriptomics showed that WPTS could upregulate the expression of insulin resistance-related genes such as glucose transporter type 4 (Glut4), insulin receptor substrate 1 (Irs1), Akt, and phosphoinositide 3-kinase (PI3K), and downregulate the expression of lipid metabolism-related genes such as monoacylglycerol O-acyltransferase 1 (Moat1), lipase C (Lipc), and sphingomyelin phosphodiesterase 4 (Smpd4). The results indicated that the differentially expressed genes could regulate lipid metabolism via the PI3K/AKT metabolic pathway, and it is noteworthy that WPTS was found to upregulate Glut4 expression, decrease blood glucose levels, and attenuate insulin resistance via the PI3K/AKT pathway. Q-PCR and western blotting further validated the transcriptomics findings at the mRNA and protein levels, respectively. We believe that WPTS can achieve a rapid hypoglycemic effect by improving the lipid metabolism and insulin resistance of the diabetic KKAy mice. WPTS could be a very promising candidate drug for the treatment of diabetes and deserves further research.

The predictive value of stress hyperglycemia on thrombus burden in nondiabetic patients with ST-segment elevation myocardial infarction

: It is established that hyperglycemia directly effects the platelet functions and fibrin structure. In this study, we aimed to investigate the predictive value of hyperglycemia on thrombus burden in nondiabetic patients with ST-segment elevation myocardial infarction (STEMI) who underwent to primer percutaneous coronary intervention (PPCI). We enrolled 619 nondiabetic patients with STEMI who received PPCI. Patients were divided two groups according to thrombus burden. Stress hyperglycemia was determined as blood glucose concentration more than 180 mg/dl and angiographic coronary thrombus burden was scored based on thrombolysis in myocardial infarction thrombus grades. Patients with thrombus grades 4 were defined as large thrombus burden (LTB), patients with thrombus burden less than thrombus grades 4 were defined as small thrombus burden. A total of 68 (11.0%) STEMI patients had stress hyperglycemia, while 223 (36.0%) patients had LTB. Sex, the prevalence of hypertension, smoking, and dyslipidemia were not different between the thrombus burden groups (P > 0.05 for all parameters). Compared with the patients with small thrombus burden, the patients with LTB were had significantly higher admission blood glucose concentrations (135 ± 39.1 mg/dl vs. 145.9 ± 43.1, P = 0.002, respectively). The multivariate logistic regression analysis demonstrated that stress hyperglycemia is an independent predictor of LTB (odds ratio: 3.025, confidence interval 1.200-7.622, P = 0.019). Admission hyperglycemia is associated with the LTB which cause adverse cardiac outcomes. Hyperglycemia may play a role on thrombus development.

Edoxaban improves atrial fibrillation and thromboembolism through regulation of the Wnt-β-induced PI3K/ATK-activated protein C system

Thromboembolism is a commonly observed condition in geriatrics that is caused by vascular endothelial injury, platelet activation, physiological coagulation processes, reduction of anticoagulant activity, decreased fibrinolytic activity and abnormal flow in the heart chamber, artery or vein. The protein C anticoagulant system serves a crucial role in anticoagulant therapy for the treatment of thromboembolism. Previous findings have suggested that edoxaban is an efficient oral anticoagulant in the acute treatment of venous thromboembolism. In the present study, the efficacy of edoxaban on thromboembolism induced by atrial fibrillation was investigated in a mouse model. Inflammatory factors interleukin (IL)-1, −4, −8 and tumor necrosis factor (TNF)-α were analyzed in the sera of mice with fibrillation induced by thromboembolism. Expression and activity of thymic stromal lymphopoietin (TSLP) and activated protein C resistance were investigated in platelets and vascular endothelial cells (VECs). TSLP-induced platelet viability, Wnt-β phosphorylation and integrin expression were analyzed in platelets. Furthermore, Wnt-β expression and the phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling pathway in VECs were analyzed. Results demonstrated that the expression levels of IL-1, −4, −8 and TNF-α were significantly downregulated in the sera of mice with fibrillation and thromboembolism following treatment with edoxaban (P<0.01). Furthermore, the expression levels of prostacyclin (PGI2), prostaglandin (PG)E2, PGD2 and PGF2α were significantly increased in the sera of experimental mice that received edoxaban therapy (P<0.01). Results also indicated that edoxaban significantly stimulated the protein expression of TSLP and activated Wnt-β phosphorylation and integrin expression in platelets (P<0.01). In addition, edoxaban therapy significantly upregulated the expression levels of PI3K and AKT, and subsequently increased the activity of protein C and S in VECs (P<0.01). Notably, edoxaban treatment improved atrial fibrillation and thromboembolism, as determined by pathological analysis. In conclusion, these results suggested that edoxaban elicited beneficial effects for mice with atrial fibrillation induced by thromboembolism through the regulation of the Wnt-β-induced PI3K/ATK-activated protein C system.

Shotgun proteomics data on the impact of hyperglycaemia on platelet protein acetylation by aspirin

This data article associated with the manuscript "A high glucose levels is associated with decreased aspirin-mediated acetylation of platelet cyclooxygenase (COX)-1 at serine 529: a pilot study" (Finamore et al., 2018) refers to the shotgun proteomics approach carried out on platelet protein extracts from diabetic patients and healthy controls. Platelet proteins were in vitro incubated with 500 µM aspirin for 30 min at 37 °C to enhance the acetylation process. After protein digestion with trypsin, DDA data were acquired on a Thermo QExactive plus using 3 technical replicate injections per sample. Here, we were able to elucidate the preferential sites of aspirin-induced acetylation on a significant fraction of the platelet proteome and to quantify the impact of diabetes on the effect of aspirin on several platelet proteins. Data are available via ProteomeXchange with identifier PXD011582.

Methylglyoxal induces retinopathy-type lesions in the absence of hyperglycemia: studies in a rat model

The aim of this study was to evaluate whether damage to the neurovascular unit in diabetes depends on reactive metabolites such as methylglyoxal (MG), and to assess its impact on retinal gene expression. Male Wistar rats were supplied with MG (50 mM) by drinking water and compared with age-matched streptozotocin-diabetic animals and untreated controls. Retinal damage was evaluated for the accumulation of MG-derived advanced glycation end products, changes in hexosamine and PKC pathway activation, microglial activation, vascular alterations (pericyte loss and vasoregression), neuroretinal function assessed by electroretinogram, and neurodegeneration. Retinal gene regulation was studied by microarray analysis, and transcription factor involvement was identified by upstream regulator analysis. Systemic application of MG by drinking water increased retinal MG to levels comparable with diabetic animals. Elevated retinal MG resulted in MG-derived hydroimidazolone modifications in the ganglion cell layer, inner nuclear layer, and outer nuclear layer, a moderate activation of the hexosamine pathway, a pan-retinal activation of microglia, loss of pericytes, increased formation of acellular capillaries, decreased function of bipolar cells, and increased expression of the crystallin gene family. MG mimics important aspects of diabetic retinopathy and plays a pathogenic role in microglial activation, vascular damage, and neuroretinal dysfunction. In response to MG, the retina induces expression of neuroprotective crystallins.-Schlotterer, A., Kolibabka, M., Lin, J., Acunman, K., Dietrich, N., Sticht, C., Fleming, T., Nawroth, P., Hammes, H.-P. Methylglyoxal induces retinopathy-type lesions in the absence of hyperglycemia: studies in a rat model.

Electronic cigarette: A recent update of its toxic effects on humans

Electronic cigarettes (e-cigarettes), battery-powered and liquid-vaporizing devices, were invented to replace the conventional cigarette (c-cigarette) smoking for the sake of reducing the adverse effects on multiple organ systems that c-cigarettes have induced. Although some of the identified harmful components in e-cigarettes were alleged to be measured in lower quantity than those in c-cigarettes, researchers unveiled that the toxic effects of e-cigarettes should not be understated. This review is sought for an attempt to throw light on several typical types of e-cigarette components (tobacco-specific nitrosamines, carbonyl compounds, and volatile organic compounds) by revealing their possible impacts on human bodies through different action mechanisms characterized by alteration of specific biomarkers on cellular and molecular levels. In addition, this review is intended to draw the limelight that like c-cigarettes, e-cigarettes could also be accompanied with toxic effects on whole human body, which are especially apparent on respiratory system. From head to foot, from physical aspect to chemical aspect, from genotype to phenotype, potential alterations will take place upon the intake of the liquid aerosol.

N-acetylcysteine attenuates systemic platelet activation and cerebral vessel thrombosis in diabetes

Objective

We previously demonstrated that diabetes exacerbates stroke-induced brain injury, and that this correlates with brain methylglyoxal (MG)-to-glutathione (GSH) status. Cerebral injury was reversed by N-acetylcysteine (NAC). Here we tested if the pro-thrombotic phenotype seen in the systemic circulation and brain during diabetes was associated with increased MG-glycation of proteins, and if NAC could reverse this.

Methods

The streptozotocin (STZ)-induced mouse model of type 1 diabetes was used. Thrombus formation in venules and arterioles (pial circulation) was determined by intravital videomicroscopy using the light-dye method. Circulating blood platelet-leukocyte aggregates (PLAs) were analyzed by flow cytometry 1 wk before other measurements. GSH and MG levels in platelets were measured by HPLC. MG-modified proteins, glutathione peroxidase-1 (GPx-1), and superoxide dismutase-1 (SOD1) levels were detected in platelets by western blot at 20 weeks. Proteins involved in coagulation were quantified by ELISA. NAC (2 mM) was given in drinking water for 3 weeks before the terminal experiment.

Results

Thrombus development was accelerated by diabetes in a time-dependent manner. % PLAs were significantly elevated by diabetes. Plasma activated plasminogen activator inhibitor type 1 levels were progressively increased with diabetes duration, with tail bleeding time reduced by 20 wks diabetes. Diabetes lowered platelet GSH levels, GPx-1 and SOD-1 expression. This was associated with higher MG levels, and increased MG-adduct formation in platelets. NAC treatment partly or completely reversed the effects of diabetes.

Conclusion

Collectively, these results show that the diabetic blood and brain become progressively more susceptible to platelet activation and thrombosis. NAC, given after the establishment of diabetes, may offer protection against the risk for stroke by altering both systemic and vascular prothrombotic responses via enhancing platelet GSH, and GSH-dependent MG elimination, as well as correcting levels of antioxidants such as SOD1 and GPx-1.

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Diabetes elevates dicarbonyl stress leading to enhanced thrombosis in the brain.

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Glutathione levels decrease leading to impaired elimination of methylglyoxal in platelets during diabetes.

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Platelet proteins are glycated and platelets form aggregates with leukocytes in diabetes.

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Diabetes increases circulating levels of plasminogen activator inhibitor-1.

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NAC, via GSH synthesis, reverses the platelet activation, protein glycation and pro-coagulation responses & protects against thrombosis in the diabetic brain.

Increased Dicarbonyl Stress as a Novel Mechanism of Multi-Organ Failure in Critical Illness

Molecular pathological pathways leading to multi-organ failure in critical illness are progressively being unravelled. However, attempts to modulate these pathways have not yet improved the clinical outcome. Therefore, new targetable mechanisms should be investigated. We hypothesize that increased dicarbonyl stress is such a mechanism. Dicarbonyl stress is the accumulation of dicarbonyl metabolites (i.e., methylglyoxal, glyoxal, and 3-deoxyglucosone) that damages intracellular proteins, modifies extracellular matrix proteins, and alters plasma proteins. Increased dicarbonyl stress has been shown to impair the renal, cardiovascular, and central nervous system function, and possibly also the hepatic and respiratory function. In addition to hyperglycaemia, hypoxia and inflammation can cause increased dicarbonyl stress, and these conditions are prevalent in critical illness. Hypoxia and inflammation have been shown to drive the rapid intracellular accumulation of reactive dicarbonyls, i.e., through reduced glyoxalase-1 activity, which is the key enzyme in the dicarbonyl detoxification enzyme system. In critical illness, hypoxia and inflammation, with or without hyperglycaemia, could thus increase dicarbonyl stress in a way that might contribute to multi-organ failure. Thus, we hypothesize that increased dicarbonyl stress in critical illness, such as sepsis and major trauma, contributes to the development of multi-organ failure. This mechanism has the potential for new therapeutic intervention in critical care.

CXCL12 regulates platelet activation via the regulator of G-protein signaling 16

The regulators of G protein signaling (RGS) protein superfamily negatively controls G protein-coupled receptor signal transduction pathways. One of the members of this family, RGS16, is highly expressed in megakaryocytes and platelets. Studies of its function in platelet and megakaryocyte biology have been limited, in part, due to lack of pharmacological inhibitors. For example, RGS16 overexpression inhibited CXC chemokine receptor 4 (CXCR4)-mediated megakaryocyte migration. More recent studies showed that the chemokine stromal cell-derived factor (SDF1α or CXCL12) regulates platelet function via CXCR4. Based on these considerations, the present study investigated the capacity of RGS16 to regulate CXCL12-dependent platelet function, using the RGS16 knockout mouse model (Rgs16(-/-)). RGS16-deficient platelets had increased protease activated receptor 4 and collagen-induced aggregation, as well as increased CXCL12-dependent agonist-induced aggregation, dense and alpha granule secretion, integrin αIIbβ3 activation and phosphatidylserine exposure compared to those from WT littermates. CXCL12 alone did not stimulate aggregation or secretion in either RGS16-deficient or WT platelets. Furthermore, platelets from Rgs16(-/-) mice displayed enhanced phosphorylation of ERK and Akt following CXCL12 stimulation relative to controls. Finally, we also found that PKCδ is involved in regulating CXCL12-dependent activation of ERK and Akt, in the Rgs16-deficient platelets. Collectively, our findings provide the first evidence that RGS16 plays an important role in platelet function by modulating CXCL12-dependent platelet activation.

Anti-thrombotic effects of α-linolenic acid isolated from Zanthoxylum bungeanum Maxim seeds

Background

The current study was to evaluate the anti-thrombotic effect of alpha-linolenic acid (ALA) which was isolated and purified from Jiaomu in vivo.

Methods

The seeds were crushed and subsequently subjected to saponification, acid hydrolysis, gradient freezing, urea inclusion and complexation of silver nitrate to obtain the unsaturated fatty acids. The chemical characteristics of isolated ALA were validated by ¹HNMR, ¹³CNMR and mass spectrometry, and then the anti-thrombotic effect of ALA and its mixture with linoleic acid (1:1) were evaluated in the following experiments.

Results

The alpha-linolenic acid was isolated and purified from Jiaomu through our newly established methods. ALA and its mixture with linoleic acid can prolong the hemorrhage and coagulation time as well as enhanced the survival rate of mice subjected to collagen-adrenaline induced thrombosis. In addition, the thrombosis on A-V bypass and platelet aggregation of rats will be reduced after treated with ALA or its mixture, and the expression level of Akt and PI3K protein decreased 26% and 31%, respectively.

Conclusions

We designed and optimized a very simple and high-yield procedure to isolate ALA and linoleic acid mixture from seeds of Zanthoxylum bungeanum Maxim and demonstrated that such mixture can obtain a good anti-thrombotic effect through the modulation of PI3K/Akt signaling.

Activated platelets from diabetic rats cause endothelial dysfunction by decreasing Akt/endothelial NO synthase signaling pathway

Diabetes is associated with endothelial dysfunction and platelet activation, both of which may contribute to increased cardiovascular risk. The purpose of this study was to characterize circulating platelets in diabetes and clarify their effects on endothelial function. Male Wistar rats were injected with streptozotocin (STZ) to induce diabetes. Each experiment was performed by incubating carotid arterial rings with platelets (1.65×10⁷ cells/mL; 30 min) isolated from STZ or control rats. Thereafter, the vascular function was characterized in isolated carotid arterial rings in organ bath chambers, and each expression and activation of enzymes involved in nitric oxide and oxidative stress levels were analyzed. Endothelium-dependent relaxation induced by acetylcholine was significantly attenuated in carotid arteries treated with platelets isolated from STZ rats. Similarly, treatment with platelets isolated from STZ rats significantly reduced ACh-induced Akt/endothelial NO synthase signaling/NO production and enhanced TXB₂ (metabolite of TXA₂), while CD61 (platelet marker) and CD62P (activated platelet marker) were increased in carotid arteries treated with platelets isolated from STZ rats. Furthermore, the platelets isolated from STZ rats decreased total eNOS protein and eNOS dimerization, and increased oxidative stress. These data provide direct evidence that circulating platelets isolated from diabetic rats cause dysfunction of the endothelium by decreasing NO production (via Akt/endothelial NO synthase signaling pathway) and increasing TXA₂. Moreover, activated platelets disrupt the carotid artery by increasing oxidative stress.

Regulation of methylglyoxal-elicited leukocyte recruitment by endothelial SGK1/GSK3 signaling

Excessive levels of the glycolysis metabolite methylglyoxal (MG) elicit enhanced expression of adhesion molecules which foster leukocyte-endothelial cell interactions. The signaling mechanisms involved remain elusive. To address this, we investigated the signal transduction of leukocyte- and endothelial-expressed phosphoinositide 3-kinase (PI3K) effector kinases glycogen synthase kinase 3 (GSK3) and serum- and glucocorticoid-inducible kinase 1 (SGK1) in the regulation of MG-elicited leukocyte recruitment. Using intravital microscopy of mouse cremasteric microvasculature, we demonstrate that GSK3 inhibitors lithium and SB216763 mitigate MG-elicited leukocyte recruitment and microvascular hyperpermeability. In SVEC4-10EE2 endothelial cells, but not in neutrophils, MG transiently activates GSK3 by reducing inhibitory phospho-GSK3α/β (Ser21/9) which parallels decrease of phospho-Akt at early time points (<30min). At later time points (≥1h), MG induces GSK3 deactivation which is dissipated by siRNA silencing of SGK. MG treatment potentiates endothelial SGK1 mRNA, total SGK1, phospho-SGK1 and phospho-NDRG1. The SGK1 inhibitor GSK650394 attenuates MG-elicited leukocyte recruitment. Pharmacological inhibition or silencing endothelial GSK3 or SGK attenuates MG-triggered nuclear factor (NF)-κB activity. Furthermore, silencing SGK blunts MG-triggered redox-sensitive phosphorylation of endothelial transcription factor CREB. Inhibition of SGK1 or GSK3 mitigates the expression of endothelial adhesion molecules P- and E-selectins and ICAM-1. Moreover, SGK1-dependent CREB activation participates in MG-elicited ICAM-1 upregulation. We conclude that temporal activation of endothelial SGK1 and GSK3 is decisive in MG-elicited upregulation of transcription factors, adhesion molecule expression, and leukocyte-vascular endothelium interactions. This novel signaling pathway may link excessive MG levels in vivo to inflammation, thus, unraveling potential therapeutic targets.