Tumor necrosis factor-related apoptosis-inducing ligand in vascular inflammation and atherosclerosis: a protector or culprit?

Circulating cytokines and vascular dementia: A bi-directional Mendelian randomization study

Inflammatory responses are associated with the development of vascular dementia (VaD). Circulating cytokines modulate the inflammatory response and are important for the immune system. To further elucidate the role of the immune system in VaD, we used Mendelian randomization (MR) to comprehensively and bi-directionally assess the role of circulating cytokines in VaD. Using state-of-the-art genome-wide association studies, we primarily assessed whether different genetic levels of 41 circulating cytokines affect the risk of developing VaD and, in turn, whether the genetic risk of VaD affects these circulating cytokines. We used inverse variance weighting (IVW) and several other MR methods to assess the bidirectional causality between circulating cytokines and VaD, and performed sensitivity analyses. Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was inversely associated with VaD risk [odds ratio (OR): 0.74, 95 % confidence interval (CI): 0.60-0.92, P = 0.007, 0.007]. VaD was associated with seven circulating cytokines: macrophage inflammatory protein 1b (MIP-1 beta) [OR: 1.05, 95 % CI: 1.01-1.08, P = 0.009], Interleukin-12p70 (IL-12) [OR: 1.04, 95 % CI: 1.00-1.08, P = 0.047], Interleukin-17 (IL-17) [OR: 1.04, 95 % CI: 1.00-1.07, P = 0.038], Interleukin-7 (IL-7) [OR: 1.07, 95 % CI: 1.02-1.12, P = 0.009], Interferon gamma (IFN-γ) [OR: 1.03, 95 % CI: 1.00-1.07, P = 0.046], Granulocyte-colony stimulating factor (GCSF) [OR: 1.06, 95 % CI: 1.02-1.09, P = 0.001], Fibroblast growth factor (FGF) [P = 0.001], and Fibroblast growth factor (FGF) [P = 0.001]. Fibroblast growth factor basic (FGF-Basic) [OR: 1.04, 95 % CI: 1.01-1.08, P = 0.02] were positively correlated. Circulating cytokines are associated with VaD, and further studies are needed to determine whether they are effective targets for intervention to prevent or treat VaD.

Relation Between Plasma Proteomics Analysis and Major Adverse Cardiovascular Events in Patients With Stable Coronary Artery Disease

Objective

Despite the advances in the control of traditional risk factors, coronary artery disease (CAD) remains the greatest cause of morbidity and mortality. Our aim was to establish the relation between plasma proteomics analysis and the risk of cardiovascular events in patients with stable CAD.

Materials and Methods

Patients with stable CAD and documented coronary atherosclerosis were screened for inclusion. Using proximity extension assays, 177 plasma proteins were simultaneously measured. The endpoint consisted of the first major adverse cardiovascular event (MACE) and was the composite of cardiovascular death, acute coronary syndrome, stroke, transient ischemic attack, or acute limb ischemia at 18 months follow-up. Cox proportional-hazards regression with adjustment for multiple comparisons was used to identify biomarkers for the outcomes of interest.

Results

The cohort consisted of 229 patients. Six mediators were associated with MACE (p < 0.001). For these markers, the risk of MACE was calculated: tumor necrosis factor receptor superfamily member 13B (HR = 1.65; 95% CI: 1.30–2.10), C-C motif chemokine-3 (HR = 1.57; 95% CI: 1.23–1.98), decorin (HR = 1.65; 95% CI: 1.26–2.16), fibroblast growth factor-23 (HR = 1.56; 95% CI: 1.23–1.99), tumor necrosis factor-related apoptosis-inducing ligand-receptor 2 (TRAIL-R2) (HR = 1.61; 95% CI: 1.23–2.11), and tumor necrosis factor receptor superfamily member 10A (HR = 1.69; 95% CI: 1.25–2.29). Except for TRAIL-R2, the other proteins were associated with MACE independent of age, sex, diabetes mellitus, or estimated glomerular filtration rate.

Conclusions

In patients with stable CAD, five novel biomarkers were identified as independent risk factors for adverse outcomes. Novel biomarkers could represent pharmacological targets for the prevention of adverse cardiovascular events.

Blocking the death checkpoint protein TRAIL improves cardiac function after myocardial infarction in monkeys, pigs, and rats

Myocardial infarction (MI) is a leading cause of death worldwide for which there is no cure. Although cardiac cell death is a well-recognized pathological mechanism of MI, therapeutic blockade of cell death to treat MI is not straightforward. Death receptor 5 (DR5) and its ligand TRAIL [tumor necrosis factor (TNF)-related apoptosis-inducing ligand] are up-regulated in MI, but their roles in pathological remodeling are unknown. Here, we report that blocking TRAIL with a soluble DR5 immunoglobulin fusion protein diminished MI by preventing cardiac cell death and inflammation in rats, pigs, and monkeys. Mechanistically, TRAIL induced the death of cardiomyocytes and recruited and activated leukocytes, directly and indirectly causing cardiac injury. Transcriptome profiling revealed increased expression of inflammatory cytokines in infarcted heart tissue, which was markedly reduced by TRAIL blockade. Together, our findings indicate that TRAIL mediates MI directly by targeting cardiomyocytes and indirectly by affecting myeloid cells, supporting TRAIL blockade as a potential therapeutic strategy for treating MI.

Tianma Gouteng Decoction Exerts Cardiovascular Protection by Upregulating OPG and TRAIL in Spontaneously Hypertensive Rats

Tianma Gouteng Decoction (TGD) is widely used in traditional Chinese medicine for the treatment of hypertension and its related complications, but its mechanisms remain incompletely defined. We now aim to assess the protective effect of TGD against cardiovascular damage and to investigate its characteristics and underlying mechanisms. Blood pressure was determined in TGD-treated spontaneously hypertensive rats (SHR) by noninvasive measurements. Echocardiography was performed to assess cardiac function and structure and sirius red staining to evaluate cardiac fibrosis, and the degree of vascular remodeling was evaluated. Additionally, vasoconstriction and relaxation factor expression changes were examined by means of ELISA. Protein expression changes were verified by western blot. Compared with untreated SHR, TGD-treated SHR exhibited cardiovascular traits more akin to those of the normotensive Wistar Kyoto (WKY) rats. That is, they had lower diastolic blood pressure, systolic blood pressure and mean BP, and increased expression of vasodilation factor. We also found that TGD reduces ventricular and vascular remodeling and improves cardiac function in SHR. Finally, we tested the antiapoptosis effect TGD exerts in SHR, ostensibly by upregulating the expression of OPG, TRAIL, and death receptor 5 (DR5) and downregulating caspases 8, 7, and 3. TRAIL may also exert antiapoptotic and prosurvival effects by upregulating AKT expression. Therefore, TGD may reverse cardiovascular remodeling in SHR by upregulating the expression of OPG and TRAIL, upregulating AKT, and inhibiting apoptosis, at least in part. For the first time, we have shown that OPG and TRAIL play complimentary cardioprotective roles in SHR.

Licorice flavonoid oil supplementation promotes a reduction of visceral fat in exercised rats

BACKGROUND

The beneficial effect of exercise combined with licorice flavonoid oil supplementation on visceral fat was investigated.

METHODS

Male Sprague-Dawley rats were divided into 4 groups: control, exercise (Ex), control with licorice flavonoid oil supplementation (LFO), and exercise with licorice flavonoid oil supplementation (ExLFO) groups. The rats in the Ex and ExLFO groups ran on a treadmill (20-degree incline at 20 m/min for 30 min/day) 5 times a week for 7 weeks, and those in the LFO and ExLFO groups were orally administered with licorice flavonoid oil daily using a feeding needle.

RESULTS

Exercise or licorice flavonoid oil supplementation resulted in the reduction of the visceral fat mass and adipocyte size, respectively. In addition, exercise combined with licorice flavonoid oil supplementation more effectively decreased both measures. Exercise alone increased the β-hydroxyacyl-CoA dehydrogenase (β-HAD) and citrate synthase (CS) activities in the soleus and plantaris muscles, and licorice flavonoid oil supplementation alone increased the hepatic carnitine palmitoyl transferase-2 (CPT-2) activity. Furthermore, the combination of exercise and licorice flavonoid oil supplementation enhanced the both muscular β-HAD and CS activities, and hepatic CPT-2 activity.

CONCLUSIONS

These results suggest that exercise combined with licorice flavonoid oil supplementation may be effective to decrease visceral adipose tissue via enhancing skeletomuscular and hepatic fatty acids oxidative capacity.

Pro-inflammatory Cytokines in Acute Coronary Syndromes

BACKGROUND

Over the last decades, the role of inflammation and immune system activation in the initiation and progression of coronary artery disease (CAD) has been established.

OBJECTIVES

The study aimed to present the interplay between cytokines and their actions preceding and shortly after ACS.

METHODS

We searched in a systemic manner the most relevant articles to the topic of inflammation, cytokines, vulnerable plaque and myocardial infarction in MEDLINE, COCHRANE and EMBASE databases.

RESULTS

Different classes of cytokines (intereleukin [IL]-1 family, Tumor necrosis factor-alpha (TNF-α) family, chemokines, adipokines, interferons) are implicated in the entire process leading to destabilization of the atherosclerotic plaque, and consequently, to the incidence of myocardial infarction. Especially IL-1 and TNF-α family are involved in inflammatory cell accumulation, vulnerable plaque formation, platelet aggregation, cardiomyocyte apoptosis and adverse remodeling following the myocardial infarction. Several cytokines such as IL-6, adiponectin, interferon-γ, appear with significant prognostic value in ACS patients. Thus, research interest focuses on the modulation of inflammation in ACS to improve clinical outcomes.

CONCLUSION

Understanding the unique characteristics that accompany each cytokine-cytokine receptor interaction could illuminate the signaling pathways involved in plaque destabilization and indicate future treatment strategies to improve cardiovascular prognosis in ACS patients.

Anti-Inflammatory and Antioxidant Effects of Acetyl-L-Carnitine on Atherosclerotic Rats

Background

The purpose of the present study was to evaluate the regulatory effects of acetyl-L-carnitine (ALCAR) on atherosclerosis in Wister rats and to explore its anti-atherosclerotic mechanism.

Material/Methods

We randomly divided 32 Wister rats into 4 groups: a normal diet group (control group, n=8), a normal diet+ALCAR group (ALCAR group, n=8), an atherosclerosis group (AS group, n=8), and an atherosclerosis+ALCAR group (AS+ALCAR group, n=8). The serum lipid distribution, oxidative stress, inflammatory factors and adiponectin (APN) in the blood, and heart and aortic tissues were determined using the standard assay kits, xanthine oxidase method, and ELISA, respectively. HE staining was performed to observe aortic pathology structure change, and the level of angiotensin II (AngII) in the aorta was assessed using radioimmunoassay. In addition, real-time quantitative PCR and Western blot analysis were applied to detect the expression of iNOS, IL-1β, TNF-α, and CRP in the aortic and heart tissues.

Results

Compared with the AS group, the levels of serum TC, TG, LDL, and VLDL in rats decreased significantly, while HDL level significantly increased in the AS+ALCAR group. ALCAR administration enhanced the SOD and GSH-Px activities and decreased MDA activity. APN level was significantly elevated in the AS group, but ALCAR had no significant effect on APN. Further, ALCAR reduced the expressions of inflammation factors TNF-α, IL-1β, iNOS, and CRP, and the concentration of AngII in serum, aortic, and heart tissues.

Conclusions

ALCAR can inhibit the expressions of inflammatory factors and antioxidation to suppress the development of atherosclerosis by adjusting blood lipid in the myocardium of AS rats.

Predictive value of targeted proteomics for coronary plaque morphology in patients with suspected coronary artery disease

Background

Risk stratification is crucial to improve tailored therapy in patients with suspected coronary artery disease (CAD). This study investigated the ability of targeted proteomics to predict presence of high-risk plaque or absence of coronary atherosclerosis in patients with suspected CAD, defined by coronary computed tomography angiography (CCTA).

Methods

Patients with suspected CAD (n = 203) underwent CCTA. Plasma levels of 358 proteins were used to generate machine learning models for the presence of CCTA-defined high-risk plaques or complete absence of coronary atherosclerosis. Performance was tested against a clinical model containing generally available clinical characteristics and conventional biomarkers.

Findings

A total of 196 patients with analyzable protein levels (n = 332) was included for analysis. A subset of 35 proteins was identified predicting the presence of high-risk plaques. The developed machine learning model had fair diagnostic performance with an area under the curve (AUC) of 0·79 ± 0·01, outperforming prediction with generally available clinical characteristics (AUC = 0·65 ± 0·04, p < 0·05). Conversely, a different subset of 34 proteins was predictive for the absence of CAD (AUC = 0·85 ± 0·05), again outperforming prediction with generally available characteristics (AUC = 0·70 ± 0·04, p < 0·05).

Interpretation

Using machine learning models, trained on targeted proteomics, we defined two complementary protein signatures: one for identification of patients with high-risk plaques and one for identification of patients with absence of CAD. Both biomarker subsets were superior to generally available clinical characteristics and conventional biomarkers in predicting presence of high-risk plaque or absence of coronary atherosclerosis. These promising findings warrant external validation of the value of targeted proteomics to identify cardiovascular risk in outcome studies.

Fund

This study was supported by an unrestricted research grant from HeartFlow Inc. and partly supported by a European Research Area Network on Cardiovascular Diseases (ERA-CVD) grant (ERA CVD JTC2017, OPERATION). Funders had no influence on trial design, data evaluation, and interpretation.

Cross talk between TGF beta and TNF alfa in regression of myointimal hyperplasia

BACKGROUND

The phenomena involved in regression of arterial myointimal hyperplasia have not been analyzed in detail.

MATERIALS AND METHODS

In 24 Lewis rats, a 1-cm-long venous graft, obtained from syngenic Lewis rats, was implanted in the infrarenal aorta. After 4 wk, the grafts were removed and analyzed using scanning electron microscopy and histochemistry. The grafts showed evidence of myointimal hyperplasia; 16 of these explanted grafts were reimplanted in the vein circulation of syngenic Lewis rats. These grafts were harvested 2 wk (8 animals) and 8 wk (8 animals) later, showing complete regression of myointimal hyperplasia.

RESULTS

Regression of experimental myointimal hyperplasia was correlated with the simultaneous and complementary action of Transforming Growth Factor beta and Tumor Necrosis Factor alfa. Inflammatory cytokines (IL1, IL2, and IL6) inhibit Tumor Necrosis Factor alfa-induced apoptosis.

CONCLUSIONS

Regression of myointimal hyperplasia is an active process, which implies the action of several inhibitory factors. The analysis of these phenomena can lead to new therapeutic approaches to prevent myointimal hyperplasia progression.

Serum TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) levels of patients with bipolar disorder in manic episode, in remission and healthy controls

TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) are members of TNF superfamily, which has various roles in immunologic and inflammatory reactions in the organism. Pathophysiology in bipolar disorder is still under investigation and altered serum levels of cytokines are often encountered. Aim of this study is to detect serum TWEAK and TRAIL levels of patients with bipolar disorder and healthy controls. For this purpose, 55 patients with bipolar disorder -27 manic episode (ME), 28 remission (RE) and 29 healthy controls (HC) were included. TWEAK levels of ME and RE groups were significantly lower than HC. TWEAK levels of bipolar patients (BP) were also lower than HC. TRAIL levels of ME, RE, HC groups and BP, HC groups were statistically similar. In our knowledge, this is the first study concerning about TWEAK and TRAIL levels in bipolar disorder and our results pointed that TWEAK-related immune response might be impaired in bipolar disorder, but our study fails to eradicate the confounders such as medication, smoking and body mass index. Studies having larger samples and limited confounders are needed to be able to evaluate these changes better and detect possible alterations about TRAIL and other TNF superfamily members.

Traditional Chinese Medicine Protects against Cytokine Production as the Potential Immunosuppressive Agents in Atherosclerosis

Atherosclerosis is a chronic inflammatory disease caused by dyslipidemia and mediated by both innate and adaptive immune responses. Inflammation is a critical factor at all stages of atherosclerosis progression. Proinflammatory cytokines accelerate atherosclerosis progression, while anti-inflammatory cytokines ameliorate the disease. Accordingly, strategies to inhibit immune activation and impede immune responses towards anti-inflammatory activity are an alternative therapeutic strategy to conventional chemotherapy on cardiocerebrovascular outcomes. Since a number of Chinese medicinal plants have been used traditionally to prevent and treat atherosclerosis, it is reasonable to assume that the plants used for such disease may suppress the immune responses and the resultant inflammation. This review focuses on plants that have immunomodulatory effects on the production of inflammatory cytokine burst and are used in Chinese traditional medicine for the prevention and therapy of atherosclerosis.

Low Circulating TRAIL Levels Are Associated with Increase of Resistin and Lipocalin-2/ngal Adipokines in Postmenopausal Women

Objective

Tumor necrosis factor- (TNF-) related apoptosis-inducing ligand (TRAIL) is attracting attention for its role in the physiopathology of metabolic disease/diabetes. Evidence suggests that it might protect against metabolic abnormalities driven by obesity-induced dysregulated secretion of adipokines, but this role of TRAIL has not yet been fully established. On this basis, we aimed to investigate the potential association between TRAIL and adipokine levels in a cohort of subjects in which age/gender/hormonal interferences were excluded.

Methods

Serum levels of TRAIL and a panel of adipokines were measured in postmenopausal women (n = 147) stratified according to waist circumference measures as normal, overweight, or obese. The panel of adipokines included interleukin- (IL-) 6, IL-8, IL-1β, adipsin, lipocalin-2/neutrophil gelatinase-associated lipocalin (ngal), TNF-alpha, monocyte chemoattractant protein-1, plasminogen activator inhibitor-1, hepatocyte growth factor, resistin, leptin, adiponectin, and nerve growth factor.

Results

Low serum TRAIL concentration (deciles I–IV) was significantly and inversely correlated with resistin and lipocalin 2/ngal levels (r = −0.502 and p < 0.001 and r = −0.360 and p < 0.01, resp.). Both associations retained their statistical significance after adjustment for confounding factors, such as waist circumference and age.

Conclusions

Our data indicate a link between low circulating levels of TRAIL and markers of obesity-induced diseases (resistin and lipocalin-2/ngal), highlighting a new potential axis of TRAIL functions.

Inflammation and myointimal hyperplasia. Correlation with hemodynamic forces

OBJECTIVES

The aim of our study was to correlate flow dynamics and the release of inflammatory cytokines Interleukin 1, 2, 6, TNF (Tumour Necrosis Factor) alfa, both in vitro and in vivo.

MATERIALS AND METHODS

Endothelial cells were exposed to laminar flow (6dyne/cm²) in an in vitro circulatory system and the release of Interleukin 1, 2, 6 and TNF alfa was quantified by ELISA. Interleukin 1, 2, 6 and TNF alfa release was also assessed in vein grafts implanted in the arterial circulation of Lewis rats. Arterial vein grafts were explanted at different time intervals from 3days to 12weeks after surgery. Vein grafts implanted in the arterial circulation for 4weeks, were re implanted in the venous circulation of syngenic Lewis rats, and the release of Interleukin 1, 2, 6 and TNF alfa, was assessed in an organ culture. Six vein grafts (4 occluded, 2 patent) implanted in humans as femorodistal bypass were examined for the presence of myointimal hyperplasia and perigraft inflammatory cells.

RESULTS

In vitro, endothelial cells exposed to laminar flow released an increased amount of Interleukin 1, 2, 6 and TNF alfa in comparison to endothelial cells not exposed to flow. In experimental vein grafts implanted in the arterial circulation there was an increased release of inflammatory cytokines associated to inflammatory changes in the adventitia. Once the vein grafts were re implanted in the venous circulation, the release of these cytokines diminished, while the inflammatory changes in the adventitia regressed.

CONCLUSIONS

Increased shear stress induces release of cytokines and inflammatory changes in the adventitia. These inflammatory changes can contribute to plaque progression and to un stable plaque. These findings support the use of anti-inflammatory therapy in patients prone to develop atherosclerosis and in those who had arterial reconstructive surgery.

Stage-dependent effects of exogenous TRAIL on atherogenesis: role of ER stress-mediated sensitization of macrophage apoptosis

Deletion of the gene of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in apolipoprotein E-deficient (ApoE-/-) mice increased atherosclerosis. However, the effect of TRAIL at a supra-physiological level on early atherogenesis is unknown. ApoE-/- mice were divided into Early (high-fat diet with concomitant TRAIL treatment for 4 weeks) and Late (high-fat diet for 16 weeks with TRAIL being given during the last 4 weeks) groups. It was found that TRAIL stimulated atherogenesis in the Early group but not in the Late group. TRAIL did not change the intra-plaque macrophage content in Early group, but decreased it in the Late group. In cultured macrophages, induction of endoplasmic reticulum (ER) stress increased death receptor 5 (DR5) expression and TRAIL-induced apoptosis, which were mediated by the transcription factor CCAAT/enhancer-binding protein homologous protein (CHOP). The expression levels of CHOP, 78 kDa glucose-regulated protein (GRP78) and DR5 were all elevated in the Late group. TRAIL treatment in vivo also increased intra-plaque apoptotic only in Late lesions. Moreover, the chemical chaperone 4-phenylbutyrate blocked the development of ER stress and upregulation of DR5 in Late lesions in vivo. In conclusion, TRAIL at a supra-physiological level has a stimulatory effect on early atherogenesis, but not in the advanced lesions. The differential effects of TRAIL may be related to differences in ER stress, DR5 expression, and the sensitivity of macrophage apoptosis in response to TRAIL in early versus advanced lesions. The results presented here raise the possibility that treatment with exogenous TRAIL as a therapeutic agent may be detrimental in patients with increased risk of atherosclerosis.

Local application of paeonol prevents early restenosis: a study with a rabbit vein graft model

BACKGROUND

Neointimal hyperplasia, which is caused by dysfunction of vascular smooth muscle cells and vascular endothelial cells (VECs), is a foundation for later development of vein grafted occlusion. This study investigates whether neointimal hyperplasia could be prevented by the application of paeonol, a phenolic compound having functions of anti-inflammatory, anti-oxidant, and anti-proliferative.

METHODS

Autologous jugular veins, which engrafted to carotid arteries in rabbits, were enveloped with paeonol or left untreated. After 0, 2, and 3 wk, vein grafts were respectively harvested. Proliferating cell nuclear antigen, vascular cell adhesion molecule l (VCAM-1), and intercellular cell adhesion molecule 1 were assessed with immunohistochemistry and Western blot. VECs apoptosis was also detected with terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling assay.

RESULTS

Paeonol treatment reduced early neointimal hyperplasia by 42%-46% (P < 0.001) and early medial hyperplasia by 18%-22% (P < 0.001) compared with the controls. Immunohistochemical and Western blot results show a significant downregulation of proliferating cell nuclear antigen (P < 0.001) and VCAM-1 (P < 0.001) in paeonol treatment group in the second and third weeks. Terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick end labeling analysis discovered that VECs apoptosis was also reduced by the paeonol treatment in the second and third weeks (P < 0.001).

CONCLUSIONS

Paeonol could prevent vein graft early restenosis by suppressing intimal and medial hyperplasia via inhibition of vascular smooth muscle cells proliferation, VCAM-1 expression, and anti-apoptosis of VECs in grafted veins.

TRAIL (TNF-related apoptosis-inducing ligand) inhibits human adipocyte differentiation via caspase-mediated downregulation of adipogenic transcription factors

Tumor necrosis factor-α (TNFα) and other ligands of the TNF superfamily are potent regulators of adipose tissue metabolism and play a crucial role in the obesity-induced inflammation of adipose tissue. Adipose tissue expression levels of TRAIL (TNF-related apoptosis-inducing ligand) and its receptor were shown to be upregulated by overfeeding and decreased by fasting in mice. In the present study we aimed to elucidate the impact of TRAIL on adipogenesis. To this end, human Simpson-Golabi-Behmel syndrome (SGBS) preadipocytes as well as stromal-vascular cells isolated from human white adipose tissue were used as model systems. Human recombinant TRAIL inhibited adipogenic differentiation in a dose-dependent manner. It activated the cleavage of caspase-8 and -3, which in turn resulted in a downregulation of the key adipogenic transcription factors C/EBPα, C/EBPδ, and PPARγ. The effect was completely blocked by pharmacological or genetic inhibition of caspases. Taken together we discovered a so far unrecognized function of TRAIL in the regulation of adipogenesis. Targeting the TRAIL/TRAIL receptor system might provide a novel strategy to interfere with adipose tissue homeostasis.

Redox signaling and oxidative stress: Cross talk with TNF-related apoptosis inducing ligand activity

Redox regulation plays a key role in several physiopathological contexts and free radicals, from nitric oxide and superoxide anion up to other forms of reactive oxygen species (ROS), have been demonstrated to be involved in different biological and regulatory processes. The data reported in the current literature describe a link between ROS, inflammation and programmed cell death that is attracting interest as new pathways to be explored and targeted for therapeutic purposes. In this light, there is also growing attention to the involvement of this link in the activity of the TNF-related apoptosis inducing ligand (TRAIL). TRAIL is a member of the TNF ligands super family able to mediate multiple intracellular signals, with the potential to lead to a range of biological effects in different cell types. In particular, the hallmark of TRAIL is the ability to induce selective apoptosis in transformed cells leaving normal cells almost unaffected and this feature has already opened the door to several clinical studies for cancer treatment. Moreover, TRAIL plays a role in several physiological and pathological processes of both innate and adaptive immune systems and of the cardiovascular context, with a strong clinical potential. Nonetheless, several issues still need to be clarified about the signaling mediated by TRAIL to gain deeper insight into its therapeutic potential. In this light, the aim of this review is to summarize the main preclinical evidences about the interplay between TRAIL and redox signaling, with particular emphasis to the implications in vascular physiopathology and cancer.

17β-Estradiol inhibits TNF-α-induced proliferation and migration of vascular smooth muscle cells via suppression of TRAIL

Atherosclerosis is an inflammatory disease and involves migration of vascular smooth muscle cells (VSMCs). Estrogen inhibits VSMCs migration, while the underlying mechanism remains to be revealed. Recent years, there is emerging evidence showing that TNF-related apoptosis-inducing ligand (TRAIL) increases proliferation and migration of VSMCs. In this study, we investigated the regulatory effect of estrogen on TRAIL expression in VSMCs. TNF-α greatly enhanced TRAIL protein expression and stimulated VSMCs proliferation and migration. This effect was partially inhibited by the addition of TRAIL neutralizing antibody, suggesting that TRAIL is important in TNF-α-induced migration. 17β-estradiol (E2) inhibited TRAIL expression under TNF-α stimulation in a time- and concentration-dependent manner. This effect was was mimicked by ERα agonist 4',4″,4‴-(4-propyl-[1H]-pyrazole-1,3,5-triyl) trisphenol (PPT), but not ERβ agonist 2,3-bis-(4-hydroxyphenyl)-propionitrile (DPN), indicating that ERα is involved in this action. TNF-α led to nuclear factor kappa B (NF-κB) p65 phosphorylation and the inhibitor pyrrolidine dithiocarbama (PDTC) inhibited TRAIL expression, suggesting that NF-κB signaling is crucial for TARIL production. E2 suppressed p65 phosphorylation in VSMCs and the overexpression of p65 subunit reversed the inhibitory effect of E2 on TRAIL expression and cell proliferation and migration. Taken together, our results indicate that E2 inhibits VSMCs proliferation and migration by downregulation of TRAIL expression via suppression of NF-κB pathway.

Clinical perspectives of TRAIL: insights into central nervous system disorders

The TNF-related apoptosis inducing ligand TRAIL is a member of the TNF superfamily that has been firstly studied and evaluated for its anti-cancer activity, and the insights into its biology have already led to the identification of several TRAIL-based anticancer strategies with strong clinical therapeutic potentials. Nonetheless, the TRAIL system is far more complex and it can lead to a wider range of biological effects other than the ability of inducing apoptosis in cancer cells. By virtue of the different receptors and the different signalling pathways involved, TRAIL plays indeed a role in the regulation of different processes of the innate and adaptive immune system and this feature makes it an intriguing molecule under consideration in the development/progression/treatment of several immunological disorders. In this context, central nervous system represents a peculiar anatomic site where, despite its "status" of immune-privileged site, both innate and adaptive inflammatory responses occur and are involved in several pathological conditions. A number of studies have evaluated the role of TRAIL and of TRAIL-related pathways as pro-inflammatory or protective stimuli, depending on the specific pathological condition, confirming a twofold nature of this molecule. In this light, the aim of this review is to summarize the main preclinical evidences of the potential/involvement of TRAIL molecule and TRAIL pathways for the treatment of central nervous system disorders and the key suggestions coming from their assessment in preclinical models as proof of concept for future clinical studies.

Roles and Clinical Applications of OPG and TRAIL as Biomarkers in Cardiovascular Disease

Cardiovascular diseases (CVD) remain the major cause of death and premature disability in Western societies. Assessing the risk of CVD is an important aspect in clinical decision-making. Among the growing number of molecules that are studied for their potential utility as CVD biomarkers, a lot of attention has been focused on osteoprotegerin (OPG) and its ligands, which are receptor activator of nuclear factor κB ligand (RANKL) and TNF-related apoptosis-inducing ligand. Based on the existing literature and on our experience in this field, here we review what the possible roles of OPG and TRAIL in CVD are and their potential utility as CVD biomarkers.

Soluble TRAIL Concentration in Serum Is Elevated in People with Hypercholesterolemia

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a multi-functional cytokine, which is involved in the pathophysiological processes of cardiovascular and metabolic diseases. Previously, we demonstrated that TRAIL stimulated lipid uptake and foam cell formation in macrophages in vitro. Several clinical studies have suggested that the serum concentration of TRAIL may be increased in humans with elevated blood cholesterol; however, the current data appear to be inconclusive in this regard. In the present study, we examined the relationships between the serum TRAIL concentration and cholesterol levels in 352 generally healthy subjects undergoing the routine annual health check. We showed that there were significant correlations between TRAIL concentration and levels of total and low-density lipoprotein cholesterols. The level of TRAIL was significantly elevated in subjects with hypercholesterolemia, although this relationship might be also associated with changes of other metabolic factors. Moreover, we showed that the level of blood cholesterol was significantly higher in subjects in the upper quartile of serum TRAIL. In conclusion, our data demonstrate that the serum TRAIL concentration is elevated in people with hypercholesterolemia.

TNF-related apoptosis inducing ligand in ocular cancers and ocular diabetic complications

TNF-related apoptosis inducing ligand (TRAIL) is an intensively studied cytokine, in particular for its anticancer activity. The discovery that conjunctival sac fluid contains extremely high levels of soluble TRAIL as compared to other body fluids suggested important implications in the context of the immunological surveillance of the eye, in particular of the anterior surface. In this review, we discuss the potential physiopathologic and therapeutic role of the TRAIL/TRAIL receptor system in a variety of ocular cancers. Moreover, since an increasing amount of data has indicated the important biological activities of the TRAIL/TRAIL receptor systems also in a completely different pathologic context such as diabetes mellitus, in the second part of this review we summarize the currently available data on the involvement of TRAIL in the ocular complications of diabetes mellitus as modulator of the inflammatory and angiogenic response in the eye.