Modulation of endothelial cell thrombomodulin by PPAR ligands--variation according to environment

The Microvascular and Macrovascular Benefits of Fibrates in Diabetes and the Metabolic Syndrome: A review

BACKGROUND

The purpose of this article is to discuss the evidence regarding potential macrovascular and microvascular benefits of fibrate therapy in general and fenofibrate specifically.

METHODS

We performed a literature review summarizing the results of studies testing fibrates on relevant.

RESULTS

Although statins are the first line therapy with an unparalleled amount of evidence for reducing the risk of cardiovascular disease (CVD) in patients with dyslipidemia and the metabolic syndrome (MetS), there are several landmark studies that have focused on the potential benefits of fibrate therapy for reducing CVD risk. Fibrates confer benefits mostly for patients with diabetes mellitus (DM), MetS, and atherogenic dyslipidemia. Recently, many studies have shown that fibrates confer benefits on the vascular system as well as the liver and kidneys. Fibrates also have demonstrable benefits in cohorts of patients with DM and renal disease.

CONCLUSIONS

Fibrates appear to provide significant microvascular and macrovascular benefits particularly in patients with DM, MetS, or renal disease.

LXR agonist T0901317 upregulates thrombomodulin expression in glomerular endothelial cells by inhibition of nuclear factor‑κB

Dysfunction of glomerular endothelial cells (GECs) induces a variety of symptoms, including proteinuria, inflammation, vascular diseases, fibrosis and thrombosis. Thrombomodulin (TM) acts as a vasoprotective molecule on the surface of the vascular endothelial cells to maintain the homeostasis of the endothelial microenvironment by suppressing cellular proliferation, adhesion and inflammatory responses. Liver X receptor (LXR), a nuclear receptor (NR) and a bile acid‑activated transcription factor, regulates metabolism and cholesterol transport, vascular tension and inflammation. Previous studies indicated that TM expression is upregulated by various NRs; however, it is unclear whether pharmacological modulation of LXR may affect TM expression and GEC function. The current study revealed that LXR activation by its agonist, T0901317, upregulates the expression and activity of TM. This effect was mediated specifically through LXR‑α, and not through LXR‑β. Additionally, T0901317 treatment inhibited nuclear factor‑κB (NF‑κB) signaling and the secretion of high glucose‑induced proinflammatory mediators, including tumor necrosis factor‑α and interleukin‑1β in GECs. Co‑immunoprecipitation experiments determined that treatment with T0901317 enhances the interaction between LXR‑α and the transcriptional coactivator, p300, in GEC extracts. The present findings suggest that NF‑κB may be a negative regulator of TM expression, and its removal may contribute to TM gene expression, particularly when in competition with the T0901317‑enhanced formation of the LXR/p300 complex. Therefore, LXR may be a novel molecular target for manipulating TM in GECs, which may advance the treatment of endothelial cell‑associated diseases.

Involvement of Angiotensin II Type 1 and 2 Receptors in Gelatinase Regulation in Human Carotid Atheroma in vitro

AIM

Matrix metalloproteinases (MMPs), angiotensin II (AII) and its receptors are implicated in atherosclerotic plaque instability, however the roles of the two receptor subtypes, ATR1 and ATR2, in MMP regulation remain uncertain. In this study, we investigated the effect of ATR1 and ATR2 blockade on the expression and activity of MMP-2, MMP-3 and MMP-9, in human carotid atheroma.

METHODS

Atheroma samples (n=36) were obtained from patients undergoing carotid endarterectomy. The effects of ATR1 (irbesartan), ATR2 (PD123319) and combined ATR1 and ATR2 blockade on the expression and activity of the MMPs and the expression of tissue inhibitors of metalloproteinases (TIMPs) were investigated in explant culture experiments. Paired atheroma samples were incubated with the intervention or media control for 4 days. Protein levels (MMP-2, MMP-3, MMP-9, TIMP-1, TIMP-2, TIMP-4, ATR1 and ATR2) were determined by ELISA. Overall gelatinase activity and specific activation were measured by chromogenic activity assays and zymography, respectively.

RESULTS

ATR1 blockade, but not ATR2 blockade significantly reduced TIMP-1, TIMP-2 and TIMP-4 expression in atheroma supernatant. Combined ATR1 and ATR2 blockade significantly reduced MMP-2, MMP-3 and MMP-9 expression. MMP-2 and MMP-9 relative activation, and overall MMP-9 catalytic capacity were significantly increased by ATR1 blockade.

CONCLUSIONS

Our findings suggest that ATR1 blockade reduces TIMP expression and increases gelatinase activity in human carotid atheroma.

Tenascin-C is increased in atherothrombotic stroke patients and has an anti-inflammatory effect in the human carotid artery

Tenascin-C (Tn-C) is an endogenous ligand of toll-like receptor-4 (TLR-4); a key signalling molecule associated with chronic inflammatory conditions. Both Tn-C and TLR-4 are increased in unstable human atheroma, but their effects on local inflammatory conditions have not been investigated. The aim of the present study was to investigate the association and functional implications of Tn-C/TLR-4 signalling in large artery atherosclerotic stroke. Plasma Tn-C was measured by ELISA and found to be higher in recent stroke patients (n = 336; median 12.77 µg/mL, inter-quartile range 10.23-15.74 µg/mL) than in controls (n = 321; median 11.31 µg/mL, inter-quartile range 8.89-13.90 µg/mL), P < 0.001. Plasma Tn-C was also independently positively associated with stroke (odds ratio for highest Tn-C quartile 2.27, 95% confidence interval 1.37-3.76). Assessment of Tn-C associated chronic cytokine secretion was performed in vitro using paired, human, macroscopically disease matched, carotid atheroma tissue biopsies obtained from five patients undergoing carotid endarterectomy. A 4-day incubation with specific Tn-C blocking antibodies (Abs) increased secretion of TLR-4-associated cytokines, interleukin (IL)-8, IL-1β, tumour necrosis factor and C-C motif chemokine (CCL)3 and expression of TLR-4 in the tissue. These results suggest with Tn-C blockade another endogenous TLR-4 ligand upregulates TLR-4 expression and subsequent cytokine secretion. Titration of the Tn-C Abs also dose dependently increased secretion of IL-6, IL-8, IL-1β, and CCL3 in mixed, healthy, primary vascular cell culture. In summary, circulating concentrations of Tn-C are higher in patients with a recent history of atherosclerotic stroke and may play an anti-inflammatory role by reducing pro-inflammatory cytokine release from atheroma.

Fenofibrate ameliorates insulin resistance, hypertension and novel oxidative stress markers in patients with metabolic syndrome

SUMMARY

OBJECTIVE

The benefits of fenofibrate, a peroxisome proliferator-activated receptor α agonist, against cardiovascular risk factors have been established. To clarify the underlying mechanisms of these benefits, we examined the effects of fenofibrate on insulin resistance, hypertension, inflammation, oxidative stress and coagulation markers in patients with metabolic syndrome.

METHODS

Eleven Japanese patients with metabolic syndrome underwent physical examinations and blood tests before and after treatment with fenofibrate 200 mg daily for 8 weeks.

RESULTS

Fenofibrate significantly decreased systolic blood pressure, pulse wave velocity, serum insulin, insulin resistance (calculated from the homeostasis model assessment), total cholesterol, triglyceride, remnant-like particles cholesterol, uric acid, D-dimer, fibrinogen, serum amyloid A/low-density lipoprotein (LDL) and apoA1/LDL levels. It also significantly increased levels of high molecular weight adiponectin, thrombomodulin and high-density lipoprotein cholesterol in these patients. Plasminogen activator inhibitor-1, C-reactive protein, fasting plasma glucose and thrombin-antithrombin complex levels did not change.

LIMITATION

Small sample size.

CONCLUSION

Short-term fenofibrate administration not only improved lipid profiles, but also ameliorated insulin resistance, hypertension and oxidative stress markers in patients with metabolic syndrome, suggesting that fenofibrate can decrease the risk of arteriosclerosis through various pathways.

Role of the angiotensin converting enzyme 1/angiotensin II/angiotensin receptor 1 axis in interstitial collagenase expression in human carotid atheroma

BACKGROUND AND AIM

Angiotensin II (AII) receptor 1 (ATR1) and angiotensin converting enzyme 1 (ACE1) blockers have been shown to reduce acute cardiovascular events in patients, improve plaque stability and modify matrix metalloproteinase (MMP) expression. However, the role of the ACE1/AII/ATR1 axis in interstitial collagenase regulation has not been fully explored. In this study, we investigated the effect of ATR1 and ACE1 blockade on the expression and activity of MMP-1, -8 and -13 in human carotid atheroma.

METHODS

Atheroma samples (n = 24) were obtained from patients undergoing carotid endarterectomy. The effects of ATR1 (irbesartan), ACE1 (quinapril), ACE2 (DX600) and MMP (GM6001) blockade on the expression of AII, the interstitial collagenases and soluble elastin fragments were investigated in explant culture supernatants. Paired atheroma samples were incubated with intervention or media control for 4 days. Protein levels (AII, MMP-1, -8, -13 and soluble elastin) were determined by ELISA.

RESULTS

ATR1, but not ACE1, blockade significantly reduced MMP-1 and -8 concentrations in atheroma supernatants. ACE2 blockade significantly increased MMP-1 and -8 concentrations in atheroma supernatants. AII concentration in atheroma supernatants significantly increased after ATR1, ACE1 and ACE2 blockade. Release of soluble elastin fragments increased after ATR1 and ACE1 blockade, but was not changed by an MMP inhibitor.

CONCLUSIONS

Our findings suggest that ATR1 blockade alters AII, MMP-1, MMP-8 expression and a marker of elastin degradation in human atheroma, but that the elastin degradation response is not MMP driven. This data contributes to the recognised ability of ATR1 blockade to modify plaque stability.

Classical swine fever virus NS5A protein localizes to endoplasmic reticulum and induces oxidative stress in vascular endothelial cells

Classical swine fever virus (CSFV) causes a severe disease of pigs that is characterized by hemorrhage, disseminated intravascular coagulation, and leucopenia. Until now, the role of the nonstructural protein 5A (NS5A) produced by CSFV in the pathogenesis of CSF is not well known. In this study, we investigated the function of CSFV NS5A by examining its role in the induction of oxidative stress and related intracellular events. Stable swine umbilical vein endothelial cell lines expressing CSFV NS5A were established and showed that CSFV NS5A is localized to endoplasmic reticulum and induces oxidative stress associated with enhanced reactive oxygen species production. The expression of NS5A protein exerts different effects on the three major antioxidants. Particularly, it exhibits a significant increase in transcriptional activities of antioxidant proteins thioredoxin and peroxiredoxin-6, but accompanied by a concomitant decrease of antioxidant protein heme oxygenase-1. Further studies showed that cyclooxygenase-2, a pro-inflammatory protein related to oxidative stress, is up-regulated while anti-inflammatory protein peroxisome proliferator-activated receptor-γ, an important mediator in vascular functional regulation, is down-regulated in CSFV NS5A expressing cells. This study suggested that CSFV NS5A plays important roles in the induction of oxidative stress and inflammatory response in vascular endothelial cells. These findings provide novel information on the function of the poorly characterized CSFV NS5A and provide an insight into the mechanism by which CSFV NS5A can alter intracellular events associated with the viral infection.

Thrombomodulin and its role in inflammation

The goal is to provide an extensive review of the physiologic role of thrombomodulin (TM) in maintaining vascular homeostasis, with a focus on its anti-inflammatory properties. Data were collected from published research. TM is a transmembrane glycoprotein expressed on the surface of all vascular endothelial cells. Expression of TM is tightly regulated to maintain homeostasis and to ensure a rapid and localized hemostatic and inflammatory response to injury. By virtue of its strategic location, its multidomain structure and complex interactions with thrombin, protein C (PC), thrombin activatable fibrinolysis inhibitor (TAFI), complement components, the Lewis Y antigen, and the cytokine HMGB1, TM exhibits a range of physiologically important anti-inflammatory, anti-coagulant, and anti-fibrinolytic properties. TM is an essential cofactor that impacts on multiple biologic processes. Alterations in expression of TM and its partner proteins may be manifest by inflammatory and thrombotic disorders. Administration of soluble forms of TM holds promise as effective therapies for inflammatory diseases, and infections and malignancies that are complicated by disseminated intravascular coagulation.

Novel therapeutic targets for preserving a healthy endothelium: strategies for reducing the risk of vascular and cardiovascular disease

The endothelium lies in a strategic anatomical position between the circulating blood and the vascular smooth-muscle cells. It is a source of vasodilators such as nitric oxide, prostacyclin, and hyperpolarizing factor as well as heparin-like substances and other molecules with antiproliferative properties. These effects of endothelial cells may explain why platelets and monocytes usually do not adhere at the blood vessel wall. However, under pathological conditions, endothelial dysfunction occurs and significantly contributes to the increase of platelet- -vessel wall interaction, vasoconstriction, pro-inflammation, and proliferation. Under these conditions, endothelium-dependent vasodilation is reduced, and endothelium-dependent constrictor responses are augmented. Upon vessel wall injury, the platelets rapidly adhere to the exposed sub-endothelial matrix, which is mediated by several cellular receptors present on platelets or endothelial cells and various adhesive proteins. Subsequent platelet activation results in the recruitment of additional platelets and the generation of platelet aggregates, so forming a stable platelet plug. Therapeutic strategies aimed at improving or preserving endothelial function therefore may be promising in terms of preventing and treating coronary artery disease. Diagnostic modalities for assessing endothelial function should allow for the early detection of vascular endothelial dysfunction before the manifestation of serious adverse vascular disorders.