Local overexpression of toll-like receptors at the vessel wall induces atherosclerotic lesion formation: synergism of TLR2 and TLR4

SMAD4 Expression in Monocytes as a Potential Biomarker for Atherosclerosis Risk in Patients with Obstructive Sleep Apnea

Obstructive sleep apnea (OSA) patients are at special risk of suffering atherosclerosis, leading to major cardiovascular diseases. Notably, the transforming growth factor (TGF-β) plays a crucial role in the development and progression of atherosclerosis. In this context, the central regulator of TGF-β pathway, SMAD4 (small mother against decapentaplegic homolog 4), has been previously reported to be augmented in OSA patients, which levels were even higher in patients with concomitant cardiometabolic diseases. Here, we analyzed soluble and intracellular SMAD4 levels in plasma and monocytes from OSA patients and non-apneic subjects, with or without early subclinical atherosclerosis (eSA). In addition, we used in vitro and ex vivo models to explore the mechanisms underlying SMAD4 upregulation and release. Our study confirmed elevated sSMAD4 levels in OSA patients and identified that its levels were even higher in those OSA patients with eSA. Moreover, we demonstrated that SMAD4 is overexpressed in OSA monocytes and that intermittent hypoxia contributes to SMAD4 upregulation and release in a process mediated by NLRP3. In conclusion, this study highlights the potential role of sSMAD4 as a biomarker for atherosclerosis risk in OSA patients and provides new insights into the mechanisms underlying its upregulation and release to the extracellular space.

Salvia miltiorrhiza Extract Prevents the Occurrence of Early Atherosclerosis in Apoe -/- Mice via TLR4/ NF-kB Pathway

OBJECTIVE

Salvia miltiorrhiza (SM) contains four major aqueous active ingredients, which have been isolated, purified and identified as danshensu (DSS), salvianolic acid A (Sal-A), salvianolic acid B (Sal-B) and protocatechuic aldehyde (PAL), A mixture of these four ingredients is called SABP. Although aqueous extract from Salvia miltiorrhiza has been traditionally used to treat cardiovascular diseases, the efficacy and function of the optimal ratio of SABP in preventing and treating cardiovascular diseases remain unknown. This study aims to explore the antiinflammatory mechanisms underlying the attenuation of atherosclerosis development by aqueous extract from Salvia miltiorrhiza.

METHODS

Male ApoE-/- mice (6 weeks) were randomly allocated into three groups: the model group (Model), the SABP group (SABP), and the rosuvastatin calcium group (RC). Male C57BL/6 mice (6 weeks) were used as a control group. All mice were fed with an ordinary diet. After 8 weeks of treatment, the lipid profiles in serum and the lactate dehydrogenase (LDH) and creatine kinase (CK) in heart tissue were measured using an automatic biochemical analyzer. Alterations of the thoracic aorta and the heart were assessed using Hematoxylin and eosin staining. The protein expression of Toll-like receptor 4 (TLR4), TGF beta-activated kinase 1 (TAK1), nuclear factor kappa-B (NF-κB), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in the heart tissue were determined though immunohistochemistry and western blotting analysis.

RESULTS

The serum low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and total cholesterol (TC) levels were increased, and the high-density lipoprotein cholesterol (HDL-C) level was decreased in ApoE-/- mice. SABP significantly decreased serum lipid levels and improved histopathology in the thoracic aorta. In addition. SABP treatment inhibited the expression of TLR4, TAK1, NF-κB, IL-6 and TNF-α in the heart in ApoE-/- mice. The LDH and CK in the heart did not differ significantly among different groups, and the heart did not have obvious pathological changes.

CONCLUSION

These findings indicated that SABP may exert an anti-atherosclerotic effect by lowering blood lipids and inhibiting inflammatory response via TLR4/ NF-κB signaling pathway.

A Simplified Herbal Formula Improves Cardiac Function and Reduces Inflammation in Mice Through the TLR-Mediated NF-κB Signaling Pathway

Nuanxinkang tablet (NXK), a Chinese herbal formula, can improve heart function and quality of life in patients with chronic heart failure (CHF). However, the mechanisms of action of NXK are not fully understood. In this study, we investigated the effects of NXK on inflammation in the CHF mouse model. This model was established by transverse aortic constriction (TAC) and treated with NXK for 8 weeks. Then, the cardiac function and myocardial fibrosis were evaluated. The monocytes/macrophages were evaluated by immunofluorescence. The mRNA levels of IL-1β, IL-6, TNF-α, ICAM-1, and VCAM-1 were measured by quantitative real-time polymerase chain reaction (qRT-PCR), while TLR4, MyD88, NF-κB p65, P-IκBα, TLR2, TLR7 and TLR9 protein levels were evaluated by Western blot. The results showed that NXK improved the left ventricular ejection fraction (LVEF) and left ventricular end-systolic dimension, reversed myocardial fibrosis, and inhibited pro-inflammatory (CD11b + Ly6C+) monocytes/macrophages in the TAC mouse model. NXK also reduced the mRNA and protein levels of the above markers. Taken together, NXK improved heart function and reduced inflammation through the TLR-mediated NF-κB signaling pathway, suggesting that it might be used as an innovative treatment strategy for CHF.

Inflammation/bioenergetics-associated neurodegenerative pathologies and concomitant diseases: a role of mitochondria targeted catalase and xanthophylls

Various inflammatory stimuli are able to modify or even "re-program" the mitochondrial metabolism that results in generation of reactive oxygen species. In noncommunicable chronic diseases such as atherosclerosis and other cardiovascular pathologies, type 2 diabetes and metabolic syndrome, these modifications become systemic and are characterized by chronic inflammation and, in particular, "neuroinflammation" in the central nervous system. The processes associated with chronic inflammation are frequently grouped into "vicious circles" which are able to stimulate each other constantly amplifying the pathological events. These circles are evidently observed in Alzheimer's disease, atherosclerosis, type 2 diabetes, metabolic syndrome and, possibly, other associated pathologies. Furthermore, chronic inflammation in peripheral tissues is frequently concomitant to Alzheimer's disease. This is supposedly associated with some common genetic polymorphisms, for example, Apolipoprotein-E ε4 allele carriers with Alzheimer's disease can also develop atherosclerosis. Notably, in the transgenic mice expressing the recombinant mitochondria targeted catalase, that removes hydrogen peroxide from mitochondria, demonstrates the significant pathology amelioration and health improvements. In addition, the beneficial effects of some natural products from the xanthophyll family, astaxanthin and fucoxanthin, which are able to target the reactive oxygen species at cellular or mitochondrial membranes, have been demonstrated in both animal and human studies. We propose that the normalization of mitochondrial functions could play a key role in the treatment of neurodegenerative disorders and other noncommunicable diseases associated with chronic inflammation in ageing. Furthermore, some prospective drugs based on mitochondria targeted catalase or xanthophylls could be used as an effective treatment of these pathologies, especially at early stages of their development.

Tanshinone IIA Exerts Anti-Inflammatory and Immune-Regulating Effects on Vulnerable Atherosclerotic Plaque Partially via the TLR4/MyD88/NF-κB Signal Pathway

Background: Tanshinone IIA (Tan IIA), a lipophilic constituent from Salvia miltiorrhiza Bunge, has shown a promising cardioprotective effect including anti-atherosclerosis. This study aims at exploring Tan IIA’s anti-inflammatory and immune-regulating roles in stabilizing vulnerable atherosclerotic plaque in ApoE-deficient (ApoE^−/−) mice.

Methods: Male ApoE^−/− mice (6 weeks) were fed with a high-fat diet for 13 weeks and then randomized to the model group (MOD) or Tan IIA groups [high dose: 90 mg/kg/day (HT), moderate dose: 30 mg/kg/day (MT), low dose: 10 mg/kg/day (LT)] or the atorvastatin group (5 mg/kg/day, ATO) for 13 weeks. Male C57BL/6 mice (6 weeks) were fed with ordinary rodent chow as control. The plaque stability was evaluated according to the morphology and composition of aortic atherosclerotic (AS) plaque in H&E staining and Movat staining sections by calculating the area of extracellular lipid, collagenous fiber, and foam cells to the plaque. The expression of the Toll-like receptor 4 (TLR4)/myeloid differentiation factor88 (MyD88)/nuclear factor-kappa B (NF-κB) signal pathway in aorta fractions was determined by immunohistochemistry. Serum levels of blood lipid were measured by turbidimetric inhibition immunoassay. The concentrations of tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1) were detected by cytometric bead array.

Results: Tan IIA stabilized aortic plaque with a striking reduction in the area of extracellular lipid (ATO: 13.15 ± 1.2%, HT: 12.2 ± 1.64%, MT: 13.93 ± 1.59%, MOD: 18.84 ± 1.46%, P < 0.05) or foam cells (ATO: 16.05 ± 1.26%, HT: 14.88 ± 1.79%, MT: 16.61 ± 1.47%, MOD: 22.08 ± 1.69%, P < 0.05) to the plaque, and an evident increase in content of collagenous fiber (ATO: 16.22 ± 1.91%, HT: 17.58 ± 1.33%, MT: 15.71 ± 2.26%, LT:14.92 ± 1.65%, MOD: 9.61 ± 0.7%, P < 0.05) to the plaque than that in the model group, concomitant with down-regulation of the protein expression of TLR4, MyD88, and NF-κB p65, and serum level of MCP-1 and TNF-α in a dose-dependent manner. There were no differences in serum TC, LDL, HDL, or TG levels between ApoE^–/– mice and those treated with atorvastatin.

Conclusions: These results suggest that Tan IIA could stabilize vulnerable AS plaque in ApoE^−/− mice, and this anti-inflammatory and immune-regulating effect may be achieved via the TLR4/MyD88/NF-κB signaling pathway.

Interleukin-37: The Effect of Anti-Inflammatory Response in Human Coronary Artery Endothelial Cells

Interleukin-37 (IL-37) is unique in the IL-1 family since it broadly suppresses innate immunity and elevates in humans with inflammatory and autoimmune diseases. IL-37 shows definite groups and transcripts for human IL37 gene, but it is still not completely understood the effect and mechanisms of inflammatory response in endothelial cells. It is well accepted that endothelial dysfunction caused by inflammation is a key initiating event in atherosclerotic plaque formation, which leads to the occurrence and development of the cardiovascular adverse events in clinical since the inflammatory responses of endothelial cells could induce and enhance the deposition of extensive lipid and the formation of atherosclerotic plaque in the intima. Thus, it is essential to investigate the role and potential mechanisms in endothelial inflammatory response to prevent the formation and development of many cardiovascular diseases including atherosclerosis. So far, the recent studies have revealed that IL-37 is able to inhibit inflammatory response by suppressing the TLR2-NF-κB-ICAM-1 pathway intracellularly in human coronary artery endothelial cells (HCAECs). Further, the role of IL-37 may be related to the IL-18 pathway extracellularly and involved in the adhesion and transmigration of neutrophils in HCAECs.

The potential therapeutic use of renin-angiotensin system inhibitors in the treatment of inflammatory diseases

Inflammation is a normal part of the immune response to injury or infection but its dysregulation promotes the development of inflammatory diseases, which cause considerable human suffering. Nonsteroidal anti-inflammatory agents are the most commonly prescribed agents for the treatment of inflammatory diseases, but they are accompanied by a broad range of side effects, including gastrointestinal and cardiovascular events. The renin-angiotensin system (RAS) is traditionally known for its role in blood pressure regulation. However, there is increasing evidence that RAS signaling is also involved in the inflammatory response associated with several disease states. Angiotensin II increases blood pressure by binding to angiotensin type 1 (AT₁ ) receptor, and direct renin inhibitors, angiotensin-converting enzyme (ACE) inhibitors and AT₁ receptor blockers (ARBs) are clinically used as antihypertensive agents. Recent data suggest that these drugs also have anti-inflammatory effects. Therefore, this review summarizes these recent findings for the efficacy of two of the most widely used antihypertensive drug classes, ACE inhibitors and ARBs, to reduce or treat inflammatory diseases such as atherosclerosis, arthritis, steatohepatitis, colitis, pancreatitis, and nephritis.

mTORc1 activity is necessary and sufficient for phosphorylation of eNOSS1177

Nitric oxide, produced by eNOS, plays critical roles in the regulation of vascular function and maintenance. Chronic PI3K signaling has recently been associated with vascular malformations. A well described substrate downstream of PI3K signaling is eNOS. Another critical downstream target of PI3K is the metabolic regulator, mTORc1. The relationship between mTORc1 and eNOS regulation, has not been determined. We generated cells with manipulated PI3K signaling by expressing the activating mutation, PIK3CAH1047R , or knocking down PTEN expression. We investigated eNOSS1177 phosphorylation, a major activating regulatory site, following mTORC1 inhibition. We also tested the sufficiency of mTORc1 activation to stimulate eNOSS1177 phosphorylation. Our data indicate mTORc1 activity is required for the phosphorylation of eNOSS1177 , even in the presence of robust AKT activation. Moreover, we found that expression of RHEB, which functions in the absence of AKT activation to activate mTORc1, is sufficient to phosphorylate this site. Our data indicate that mTORc1, rather than AKT, may be the critical determinant of eNOSS1177 phosphorylation. As mTORc1 is a central regulator of cellular metabolism, the finding that this regulatory complex can directly participate in the regulation of eNOS provides new insights into metabolic uncoupling and vascular disease that often accompanies diabetes, high fat diets, and aging.

Cytotoxin-associated gene antigen-positive strains of Helicobacter pylori and recurring acute coronary syndromes

BACKGROUND

Cytotoxin-associated gene antigen (CagA)-positive strains of Helicobacter pylori have previously been associated with acute coronary syndromes. However, the role of CagA-positive strains of Helicobacter pylori in recurring cardiac events after ST-segment elevation myocardial infarction (STEMI) has not yet been assessed.

METHODS

We enrolled 181 consecutive patients (155 men, mean age 64±13 years) presenting with STEMI. In all patients, serum levels of IgG anti-CagA were assessed. Levels of IgG anti-hepatitis A virus were also evaluated in all patients in order to exclude the presence of a bystander activation of the immune system. Finally, a previous history of acute coronary syndrome and the rate of major adverse cardiovascular events as a composite of cardiovascular death, recurring myocardial infarction and target lesion revascularisation within 2 years follow-up were evaluated.

RESULTS

Anti-CagA IgG seropositive patients presented more frequently with a previous history of acute coronary syndrome compared with seronegative patients (28.3% vs. 14%, P=0.019). Interestingly, no differences were observed between anti-CagA IgG seropositive and anti-CagA IgG seronegative patients concerning the prevalence of anti-hepatitis A virus IgG seropositivity (20% vs. 21.4%, P=0.48). At 2-year follow-up, 40 patients experienced major adverse cardiovascular events. The major adverse cardiovascular event rate was higher in anti-CagA IgG seropositive compared with seronegative patients (hazard ratio 2.25, 95% confidence interval 1.34-2.95, P=0.013), which was confirmed at Cox multivariate analysis (hazard ratio 2.33, 95% confidence interval 1.30-3.14, P=0.009).

CONCLUSIONS

CagA-positive strains of Helicobacter pylori seem to be involved in the pathogenesis of recurring acute coronary syndromes, and seropositivity for anti-CagA IgG predicts prognosis after STEMI, possibly due to the increased risk of recurring cardiac events.

Palmitate induces VSMC apoptosis via toll like receptor (TLR)4/ROS/p53 pathway

BACKGROUND AND AIMS

Toll-like receptor 4 (TLR4) has been implicated in vascular inflammation, as well as in the pathogenesis of atherosclerosis and diabetes. Vascular smooth muscle cell (VSMC) apoptosis has been shown to induce plaque vulnerability in atherosclerosis. Previous studies reported that palmitate induced apoptosis in VSMCs; however, the role of TLR4 in palmitate-induced apoptosis in VSMCs has not yet been defined. In this study, we investigated whether or not palmitate-induced apoptosis depended on the activation of the TLR4 pathway.

METHODS

VSMCs were treated with or without palmitate, CRISPR/Cas9z-mediated genome editing methods were used to deplete TLR4 expression, while NADPH oxidase inhibitors were used to inhibit reactive oxygen species (ROS) generation. Cell apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, ROS was measured using the 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) method, the mRNA and protein expression levels of caspase 3, caspase 9, BCL-2 and p53 were studied by real-time polymerase chain reaction (RT-PCR) and ELISA.

RESULTS

Palmitate significantly promotes VSMC apoptosis, ROS generation, and expression of caspase 3, caspase 9 and p53; while NADPH oxidase inhibitor pretreatment markedly attenuated these effects. Moreover, knockdown of TLR4 significantly blocked palmitate-induced ROS generation and VSMC apoptosis accompanied by inhibition of caspase 3, caspase 9, p53 expression and restoration of BCL-2 expression.

CONCLUSIONS

Our results suggest that palmitate-induced apoptosis depends on the activation of the TLR4/ROS/p53 signaling pathway, and that TLR4 may be a potential therapeutic target for the prevention and treatment of atherosclerosis.

TLR2/4 deficiency prevents oxygen-induced vascular degeneration and promotes revascularization by downregulating IL-17 in the retina

Vascular degeneration is a critical pathological process in many human degenerative diseases, which need efficient ways to revascularization. However, little is known about cellular and molecular mechanisms that are used during vascular degeneration and revascularization. Here, we show that Toll-like receptor 2 and 4 (TLR2/4) double deficiency suppressed hyperoxia induced retinal vessel regression in an oxygen-induced retinopathy (OIR) model. Notably, the TLR2/4−/− mice experienced more revascularization after reduced vessel regression compared with wild-type mice, accompanied with less activation of glial cells. Mechanistically, TLR2/4 activation can tip the balance between Th17 cells and regulatory T cells towards Th17 cells, a critical source of the IL-17A. Less migration and infiltration of IL-17A-expressing proinflammatory cells but elevated regulatory T cells were observed in OIR-retinae from TLR2/4−/− mice. Coincidentally, TLR2/4 deficiency suppressed IL-17A production and increased expressions of anti-inflammatory genes. Furthermore, IL-17A promoted activation of glial cells. IL-17A blockade using a neutralizing antibody alleviated retinal cell apoptosis and glial activation in C57/B6-OIR mice, demonstrating the important role of IL-17A pathway in glial function during revascularization. Thus TLR2/4-mediated IL-17A inflammatory signaling is involved in vessel degeneration and revascularization, indicating that modulation of the TLR2/4-IL-17A pathway may be a novel therapeutic strategy for degenerative diseases.

TLR4 is a critical regulator of angiotensin II-induced vascular remodeling: the roles of extracellular SOD and NADPH oxidase

Toll-like receptor 4 (TLR4) and angiotensin II (AngII) induce vascular remodeling through the production of reactive oxygen species (ROS). AngII has also been shown to increase antioxidant enzyme extracellular superoxide dismutase (ecSOD). However, the roles of TLR4 in Ang II-induced ROS production, vascular remodeling and hypertension remain unknown. Mice lacking TLR4 function showed significant inhibition of vascular remodeling in response to chronic AngII infusion, with no impact on blood pressure. The increases in ROS level and NADPH oxidase activity in response to AngII infusion were markedly blunted in TLR4-deficient mice. Similar effects were observed in wild-type (WT) mice treated with a sub-depressor dose of the AT1 receptor antagonist irbesartan, which had no effects on TLR4-deficient mice. Intriguingly, the AngII infusion-induced increases in ecSOD activity and expression were rather enhanced in TLR4-deficient mice compared with WT mice, whereas the expression of the proinflammatory chemokine MCP-1 was decreased. Importantly, AngII-induced vascular remodeling was positively correlated with NADPH oxidase activity, ROS levels and MCP-1 expression levels. Notably, chronic norepinephrine infusion, which elevates blood pressure without increasing ROS production, did not induce significant vascular remodeling in WT mice. Taken together, these findings suggest that ROS elevation is required for accelerating vascular remodeling but not for hypertensive effects in this model. We demonstrated that TLR4 plays a pivotal role in regulating AngII-induced vascular ROS levels by inhibiting the expression and activity of the antioxidant enzyme ecSOD, as well as by activating NADPH oxidase, which enhances inflammation to facilitate the progression of vascular remodeling.

TLR4 rs1927911, but not TLR2 rs5743708, is associated with atherosclerotic cerebral infarction in the Southern Han population: a case-control study

The objective of this study was to explore the association of toll-like receptor (TLR) 4 rs1927911 and TLR2 rs5743708 with atherosclerotic cerebral infarction (ACI) and their effects on blood pressure, fasting blood glucose, and blood lipids in the Han population of Hunan Province. TLR4 rs1927911 and TLR2 rs5743708 were detected by polymerase chain reaction and restriction fragment length polymorphism in 170 patients with ACI and 149 healthy controls. Our results indicated that the genotype and allele frequencies of TLR4 rs1927911 were significantly different between ACI patients and controls, whereas those of TLR2 rs5743708 were not significantly different between the 2 groups. For TLR4 rs1927911, blood pressure, fasting blood sugar, and serum lipid levels were not significantly different among different genotypes in the ACI and control groups. The rs1927911 polymorphism of the TLR4 gene may be a risk factor for ACI in the Southern Han population of Hunan Province; however, it may not be associated with blood pressure, fasting blood sugar, or blood lipids.

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.

Robinin modulates TLR/NF-κB signaling pathway in oxidized LDL induced human peripheral blood mononuclear cells

This study was designed to investigate whether robinin administration modulates toll-like receptor (TLR) and nuclear factor-kappa B (NF-κB) signaling pathway in oxidized LDL induced human peripheral blood mononuclear cells (hPBMCs). The hPBMCs were isolated from healthy human volunteers and the cells were cultured in collagen coated plates at 37°C with 5% CO2 and RPMI as culture medium and were grouped as follows: Group I - control, group II - OxLDL treated and group III - OxLDL+robinin (6μg/ml). We measured mRNA expression of TLR2 and TLR4 by reverse-transcriptase polymerase chain reaction (RT-PCR) and NF-κB transcription factor assay (ELISA), and western blotting studies were done for knowing expression of monocyte chemotactic protein-1 (MCP 1), tumor necrosis factor-alpha (TNF-α) interleukin-6 (IL-6) and vascular cell adhesion molecule 1 (VCAM-1). The result indicates that OxLDL that induces hPBMCs showed an upregulated expression of TLR2, TLR4, NF-κB, pro-inflammatory cytokines and VCAM-1. Robinin inhibited the ox-LDL induced TLR2 and TLR4 expression at mRNA level and inhibited the translocation of NF-κB p65 by modulating the TLR-NF-κB signaling pathway thereby inhibiting cytokine production and down regulated inflammatory enzymes like cyclooxygenase (COX), lipoxygenase (LOX), nitric oxide synthase (NOS) and prostaglandin E2 (PGE2), thus having protective effect against the ox-LDL induced inflammation stress in hPBMCs by inhibiting TLR4-NF-κB signaling pathway.

Blueprints of signaling interactions between pattern recognition receptors: implications for the design of vaccine adjuvants

Innate immunity activation largely depends on recognition of microorganism structures by Pattern Recognition Receptors (PRRs). PRR downstream signaling results in production of pro- and anti-inflammatory cytokines and other mediators. Moreover, PRR engagement in antigen-presenting cells initiates the activation of adaptive immunity. Recent reports suggest that for the activation of innate immune responses and initiation of adaptive immunity, synergistic effects between two or more PRRs are necessary. No systematic analysis of the interaction between the major PRR pathways were performed to date. In this study, a systematical analysis of the interactions between PRR signaling pathways was performed. PBMCs derived from 10 healthy volunteers were stimulated with either a single PRR ligand or a combination of two PRR ligands. Known ligands for the major PRR families were used: Toll-like receptors (TLRs), C-type lectin receptors (CLRs), NOD-like receptors (NLRs), and RigI-helicases. After 24 h of incubation, production of tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), IL-6, and IL-10 was measured in supernatants by enzyme-linked immunosorbent assay (ELISA). The consistency of the PRR interactions (both inhibitory and synergistic) between the various individuals was assessed. A number of PRR-dependent signaling interactions were found to be consistent, both between individuals and with regard to multiple cytokines. The combinations of TLR2 and NOD2, TLR5 and NOD2, TLR5 and TLR3, and TLR5 and TLR9 acted as synergistic combinations. Surprisingly, inhibitory interactions between TLR4 and TLR2, TLR4 and Dectin-1, and TLR2 and TLR9 as well as TLR3 and TLR2 were observed. These consistent signaling interactions between PRR combinations may represent promising targets for immunomodulation and vaccine adjuvant development.

Probucol attenuates inflammation and increases stability of vulnerable atherosclerotic plaques in rabbits

Probucol, a lipid-lowering agent with anti-oxidant properties, has been implicated in protection against atherogenesis, whereas its effect on plaques stability remains to be fully elucidated. The present study was aimed to test the hypothesis that probucol may attenuate inflammation and increase stability of vulnerable atherosclerotic plaques using a rabbit model. After abdominal aortic balloon injury, 45 rabbits were fed a 1% cholesterol diet for 24 weeks. From week 12 to week 24, the animals were treated with probucol (1% by weight in the diet), simvastatin (5 mg·kg(-1), positive control) or no drugs (control), respectively. At the end of week 22, recombinant-p53 adenovirus was injected into the abdominal aortic plaques. Two weeks later, plaque disruption was induced by injection of Chinese Russell's viper venom and histamine. The results showed that the incidence of plaque disruption in probucol or simvastatin groups was significantly lower than that in the control group (7.15% or 14.29% vs. 71.43% respectively, both P < 0.01). Probucol significantly increased the thickness of fibrous caps and decreased plaque vulnerability index. Serum concentrations of inflammatory cytokines and matrix metalloproteinases, and expression levels of Toll-like receptor (TLR)-2, TLR-4, monocyte chemoattractant protein-1, intercellular adhesion molecule 1, scavenger receptor A, CD36 and oxidized low-density lipoprotein receptor 1 within the lesions were markedly lower in both treatment groups than in the control group. We conclude that probucol increases the stability of vulnerable plaques, possibly through its lipid lowering, anti-inflammation and scavenger receptors suppression effects, suggesting probucol as a promising pharmacologic approach to stabilize vulnerable plaques.

Toll-like receptors and diabetes: a therapeutic perspective

Diabetes is a mutifactorial metabolic disorder that leads to a number of complications. Diabetes is estimated to affect 36 million people in the U.S.A., and the prevalence of diagnosed and undiagnosed diabetes is at 9.3% and continues to rise. Evidence from experimental animal models as well as humans has indicated that systemic inflammation plays a role in the pathophysiological processes of diabetes and is facilitated by innate immune responses. TLRs (Toll-like receptors) are key innate immune receptors that recognize conserved PAMPs (pathogen-associated molecular patterns), induce inflammatory responses essential for host defences and initiate an adaptive immune response. Although TLR expression is increased in a plethora of inflammatory disorders, the effects of metabolic aberrations on TLRs and their role in diabetes and its complications is still emerging. In the present paper, we provide a systematic review on how TLRs play a detrimental role in the pathogenic processes [increased blood sugar, NEFAs (non-esterified 'free' fatty acids), cytokines and ROS (reactive oxygen species)] that manifest diabetes. Furthermore, we will highlight some of the therapeutic strategies targeted at decreasing TLRs to abrogate inflammation in diabetes that may eventually result in decreased complications.

A microarray study on the effect of four hormone therapy regimens on gene transcription in whole blood from healthy postmenopausal women

BACKGROUND

Postmenopausal hormone therapy is associated with many diseases and conditions, e.g., cardiovascular diseases and asthma, but the underlying molecular mechanisms are incompletely understood. The aim of the current study was to investigate the effect of four different postmenopausal hormone therapy regimens on gene transcription.

MATERIALS AND METHODS

Twenty-four healthy postmenopausal women (six women in four groups) were randomly allocated to conventional-dose 17β-estradiol/norethisterone acetate (NETA), low-dose 17β-estradiol/NETA, tibolone, or raloxifene hydrochloride. RNA was isolated from whole blood before and after 6weeks of treatment. The changes in mRNA were assessed with a microarray chip.

RESULTS

The genes FKBP5, IL13RA1, TPST1, and TLR2 were up-regulated and among the most significantly changed genes in the groups treated with conventional-dose 17β-estradiol/NETA and tibolone. Up-regulation of TPST1 was associated with reduction of tissue factor pathway inhibitor in plasma. Nine biological pathways were associated with conventional-dose 17β-estradiol/NETA, most significantly the pathways for asthma, toll-like receptor signaling, cell adhesion molecules, and MAPK signaling. Transcriptional changes with false discovery rate below 0.10 were found in 10 genes in the conventional-dose 17β-estradiol/NETA group, 7 genes in the tibolone group, and zero genes in the women on low-dose 17β-estradiol/NETA. No genes or pathways were associated with raloxifene treatment.

CONCLUSIONS

The difference between low-dose and conventional-dose17β-estradiol/NETA indicates an effect of dose on transcriptional response. Several genes and pathways related to cell adhesion molecules and immunity related cell surface receptors were influenced by conventional-dose 17β-estradiol/NETA.

Toll Like Receptors Signaling Pathways as a Target for Therapeutic Interventions

This review summarizes the key role of Toll-Like Receptor (TLRs) molecules for igniting the immune system. Activated by a broad spectrum of pathogens, cytokines or other specific molecules, TLRs trigger innate immune responses. Published data demonstrate that the targeting and suppression of TLRs and TLR-related proteins with particular inhibitors may provide pivotal treatments for patients with cancer, asthma, sepsis, Crohn's disease and thrombosis. Many drugs that target cytokines act in the late phases of the activated pathways, after the final peptides, proteins or glycoproteins are formed in the cell environment. TLR activity occurs in the early activation of cellular pathways; consequently inhibiting them might be most beneficial in the treatment of human diseases.

Combinatorial interference of toll-like receptor 2 and 4 synergistically stabilizes atherosclerotic plaque in apolipoprotein E-knockout mice

To test the hypothesis that combinatorial interference of toll-like receptor 2 (TLR2) and TLR4 is superior to isolated interference of TLR2 or TLR4 in stabilizing atherosclerotic plaques, lentiviruses carrying small interfering RNA of TLR2 or TLR4 were constructed and proved efficacious for knocking down mRNA and protein expression of TLR2 or TLR4 significantly in vitro. One hundred and fifty apolipoprotein E(-/-) mice fed a high-fat diet were divided into the control, mock, TLR2i, TLR4i and TLR2 + 4i subgroups and a constrictive collar was placed around carotid artery of these mice to induce plaque formation. TLR2i and TLR4i viral suspension was transfected into carotid plaques, respectively, in TLR2i and TLR4i subgroups, or in combination in TLR2 + 4i subgroup. Four weeks after lentivirus transfection, mRNA and protein expression of TLR2 or TLR4 was attenuated markedly in carotid plaques, leading to reduced local inflammatory cytokine expression and plaque content of lipid and macrophages, increased plaque content of collagen and lowered plaque vulnerability index. Factorial ANOVA analysis revealed that there was a synergistic effect between TLR4i and TLR2i in stabilizing plaques. In conclusion, combinatorial interference of TLR2 and TLR4 reduces local inflammation and stabilizes plaques more effectively than interference of TLR2 or TLR4 alone.

Toll-like receptors and myocardial ischemia/reperfusion, inflammation, and injury

Cardiac ischemia/reperfusion (I/R) injury occurs in several important clinical contexts including percutaneous coronary interventions for acute myocardial ischemia, cardiac surgery in the setting of cardiopulmonary bypass, and cardiac transplantation. While the pathogenesis of I/R injury in these settings is multifactorial, it is clear that activation of the innate immune system and the resultant inflammatory response are important components of I/R injury. Toll-like receptor 4 (TLR4), originally identified as the sensor for bacterial lipopolysaccharide (LPS), has also been shown to serve as a sensor for endogenous molecules released from damaged or ischemic tissues. Accordingly, recent findings have demonstrated that TLR4 not only plays a central role as a mediator of cardiac dysfunction in sepsis, but also serves as a key mediator of myocardial injury and inflammation in the setting of I/R. Furthermore, TLR4 may play a role in the development of atherosclerotic lesions. Other studies have implicated TLR4 in the adverse remodeling that may occur after ischemic myocardial injury. This emerging body of literature, which is reviewed here, has provided new insight into the early molecular events that mediate myocardial injury and dysfunction in the setting of I/R injury.

Role of toll-like receptors in cardiovascular diseases

The discovery and characterization of the TLR (Toll-like receptor) family has led to a better understanding of the innate immune system. The strategy of innate immune recognition is based on the detection of constitutive and conserved products of micro-organisms. However, host molecules that are released during injury can also activate TLRs. Engagement of TLRs by microbial or host-derived molecules induces the expression of pro-inflammatory cytokines, which may have both beneficial and detrimental effects on the host. In addition to being expressed in immune cells, TLRs are expressed in other tissues such as those of the cardiovascular system. In the present review, the role of TLRs in septic cardiomyopathy, viral myocarditis, atherosclerosis, ischaemia/reperfusion injury and cardiac remodelling after myocardial infarction are outlined, with attention paid to genetically modified murine models. Although much has been learned about stress-induced TLR activation in the tissues of the cardiovascular system, the role of individual TLRs in initiating and integrating homoeostatic responses within the heart remains to be defined. Accumulating evidence indicates that TLRs may play an important role in the pathogenesis of atherosclerosis, viral myocarditis, dilated cardiomyopathy, cardiac allograft rejection and sepsis-induced left ventricular dysfunction. Moreover, heart failure of diverse aetiology is also now recognized to have an important immune component, with TLR signalling influencing the process of cardiac remodelling and prognosis. In the present review, we outline the biology of TLRs as well as the current experimental and clinical evidence for the role of TLRs in cardiovascular diseases.

Innate immunity and monocyte-macrophage activation in atherosclerosis

Innate inflammation is a hallmark of both experimental and human atherosclerosis. The predominant innate immune cell in the atherosclerotic plaque is the monocyte-macrophage. The behaviour of this cell type within the plaque is heterogeneous and depends on the recruitment of diverse monocyte subsets. Furthermore, the plaque microenvironment offers polarisation and activation signals which impact on phenotype. Microenvironmental signals are sensed through pattern recognition receptors, including toll-like and NOD-like receptors - the latter of which are components of the inflammasome - thus dictating macrophage behaviour and outcome in atherosclerosis. Recently cholesterol crystals and modified lipoproteins have been recognised as able to directly engage these pattern recognition receptors. The convergent role of such pathways in terms of macrophage activation is discussed in this review.

Contribution of vascular cell-derived cytokines to innate and inflammatory pathways in atherogenesis

Inflammation is a central element of atherogenesis. Innate pathways contribute to vascular inflammation. However, the initial molecular process(es) starting atherogenesis remain elusive. The various risk factors, represented by particular compounds (activators), may cause altered cellular functions in the endothelium (e.g. vascular endothelial cell activation or -dysfunction), in invading cells (e.g. inflammatory mediator production) or in local vessel wall cells (e.g. inflammatory mediators, migration), thereby triggering the innate inflammatory process. The cellular components of innate immunology include granulocytes, natural killer cells and monocytes. Among the molecular innate constituents are innate molecules, such as the toll-like receptors or innate cytokines. Interleukin-1 (IL-1) and IL-6 are among the innate cytokines. Cytokines are potent activators of a great number of cellular functions relevant to maintain or commove homeostasis of the vessel wall. Within the vessel wall, vascular smooth muscle cells (SMCs) can significantly contribute to the cytokine-dependent inflammatory network by: (i) production of cytokines, (ii) response to cytokines and (iii) cytokine-mediated interaction with invading leucocytes. The cytokines IL-1 and IL-6 are involved in SMC-leucocyte interaction. The IL-6 effects are proposed to be mediated by trans-signalling. Dysregulated cellular functions resulting from dysregulated cytokine production may be the cause of cell accumulation, subsequent low-density lipoprotein accumulation and deposition of extracellular matrix (ECM). The deposition of ECM, increased accumulation of leucocytes and altered levels of inflammatory mediators may constitute an 'innate-immunovascular-memory' resulting in an ever-growing response to anew invasion. Thus, SMC-fostered inflammation, promoted by invading innate cells, may be a potent component for development and acceleration of atherosclerosis.

Oxidation-specific epitopes are danger-associated molecular patterns recognized by pattern recognition receptors of innate immunity

Oxidation reactions are vital parts of metabolism and signal transduction. However, they also produce reactive oxygen species, which damage lipids, proteins and DNA, generating "oxidation-specific" epitopes. In this review, we discuss the hypothesis that such common oxidation-specific epitopes are a major target of innate immunity, recognized by a variety of "pattern recognition receptors" (PRRs). By analogy with microbial "pathogen-associated molecular patterns" (PAMPs), we postulate that host-derived, oxidation-specific epitopes can be considered to represent "danger (or damage)-associated molecular patterns" (DAMPs). We also argue that oxidation-specific epitopes present on apoptotic cells and their cellular debris provided the primary evolutionary pressure for the selection of such PRRs. Furthermore, because many PAMPs on microbes share molecular identity and/or mimicry with oxidation-specific epitopes, such PAMPs provide a strong secondary selecting pressure for the same set of oxidation-specific PRRs as well. Because lipid peroxidation is ubiquitous and a major component of the inflammatory state associated with atherosclerosis, the understanding that oxidation-specific epitopes are DAMPs, and thus the target of multiple arcs of innate immunity, provides novel insights into the pathogenesis of atherosclerosis. As examples, we show that both cellular and soluble PRRs, such as CD36, toll-like receptor-4, natural antibodies, and C-reactive protein recognize common oxidation-specific DAMPs, such as oxidized phospholipids and oxidized cholesteryl esters, and mediate a variety of immune responses, from expression of proinflammatory genes to excessive intracellular lipoprotein accumulation to atheroprotective humoral immunity. These insights may lead to improved understanding of inflammation and atherogenesis and suggest new approaches to diagnosis and therapy.

Toll-like receptor 4 expression during cerebral aneurysm formation. Laboratory investigation

OBJECT

The pathophysiological origin of cerebral aneurysms is closely associated with chronic inflammation in arterial walls. Recently, the authors identified nuclear factor-kappa B (NF-κB) as a key mediator of cerebral aneurysm formation and progression. Because Toll-like receptor 4 (TLR4) stimulates NF-κB activation in arterial walls in atherosclerosis, the authors hypothesize that TLR4 expresses in cerebral aneurysms and contributes to the activation of NF-κB in cerebral aneurysm walls.

METHODS

Cerebral aneurysms were induced in male Sprague-Dawley rats. Expression of TLRs in cerebral aneurysm walls was assessed using reverse transcriptase polymerase chain reaction (RT-PCR). The expression of TLR4 was examined using RT-PCR, immunohistochemical studies, and Western blotting. To assess TLR4 dependency on NF-κB activation, double immunostaining and a study using NF-κB-deficient mice were done. Finally, TLR4 expression in human cerebral aneurysm walls was assessed using immunohistochemical studies.

RESULTS

In cerebral aneurysm walls, TLR1, -4, -5, -6, -10, and -11 were expressed. Among them, TLR4 and TLR10 expression changed during cerebral aneurysm formation. Expression of TLR4 was predominantly in the endothelial cell layer of cerebral aneurysm walls, and was transitionally upregulated at the early stage of cerebral aneurysm formation. The TLR4 expression coincided well with NF-κB activation. In human cerebral aneurysms, TLR4 was also expressed in the endothelial cell layer, as it was in rats.

CONCLUSIONS

Toll-like receptor 4 was expressed in cerebral aneurysm walls both in rats and humans. This receptor may play a crucial role in cerebral aneurysm formation through NF-κB activation in endothelial cells. The results of the present study will shed new light on the pathogenesis of cerebral aneurysm formation.

Polymicrobial sepsis and endotoxemia promote microvascular thrombosis via distinct mechanisms

BACKGROUND

We reported recently that endotoxemia promotes microvascular thrombosis in cremaster venules of wild-type mice, but not in mice deficient in toll-like receptor 4 (TLR4) or von Willebrand factor (VWF).

OBJECTIVE

To determine whether the clinically relevant model of polymicrobial sepsis induced by cecal ligation/perforation (CLP) induces similar responses via the same mechanisms as endotoxemia.

METHODS

We used a light/dye-injury model of thrombosis in the cremaster microcirculation of wild-type mice and mice deficient in toll-like receptor-4 (C57BL/10ScNJ), toll-like receptor 2 (TLR2), or VWF. Mice underwent CLP or sham surgery, or an intraperitoneal injection of endotoxin (LPS) or saline. In the CLP model, we assessed the influence of fluid replacement on thrombotic responses.

RESULTS

Both CLP and LPS enhanced thrombotic occlusion in wild-type mice. In contrast to LPS, CLP enhanced thrombosis in TLR4- and VWF-deficient strains. While TLR2-deficient mice did not demonstrate enhanced thrombosis following CLP, LPS enhanced thrombosis in these mice. LPS, but not CLP, increased plasma VWF antigen relative to controls. Septic mice, particularly those undergoing CLP, developed significant hemoconcentration. Intravenous fluid replacement with isotonic saline prevented the hemoconcentration and prothrombotic responses to CLP, though fluids did not prevent the prothrombotic response to LPS.

CONCLUSIONS

Polymicrobial sepsis induced by CLP and endotoxemia promote microvascular thrombosis via distinct mechanisms; enhanced thrombosis induced by CLP requires TLR2 but not TLR4 or VWF. The salutary effects of intravenous fluid replacement on microvascular thrombosis in polymicrobial sepsis remain to be characterized.

Losartan inhibits LPS-induced inflammatory signaling through a PPARgamma-dependent mechanism in human THP-1 macrophages

Macrophages have critical roles in the pathogenesis of atherosclerosis by activating the innate immune system and producing inflammatory cytokines. Accumulating evidence indicates that angiotensin type 1 receptor (AT1R) blockers exert anti-inflammatory effects in inflammatory diseases including atherosclerosis. In this study, we investigated the effect of losartan, an AT1R blocker, on the proinflammatory gene expression induced by bacterial lipopolysaccharide (LPS) in a well-defined in vitro human THP-1 macrophage system. We found that losartan significantly attenuated the LPS-induced expression of proinflammatory genes TNF-alpha, IL-8 and COX-2. However, exogenous angiotensin II (AngII) had no effect on LPS-induced inflammatory signaling despite the expression of AT1R. In addition, losartan did not block LPS-induced IkappaB phosphorylation, which is downstream of Toll-like receptor activation. Peroxisome proliferator-activated receptor-gamma (PPARgamma) antagonists, GW9662 and T0070907, reversed the inhibitory effects of losartan on LPS-induced TNF-alpha and IL-8 expression in THP-1 macrophages. These observations suggest that losartan inhibits LPS-induced proinflammatory gene expression in macrophages by activating the PPARgamma pathway rather than by the competitive inhibition of AT1R binding to AngII.

Increased toll-like receptor (TLR) activation and TLR ligands in recently diagnosed type 2 diabetic subjects

OBJECTIVE

Individuals with type 2 diabetes have a myriad of metabolic aberrations including increased inflammation, increasing their cardiovascular risk. Toll-like receptors (TLRs) and their ligands play a key role in insulin resistance and atherosclerosis. However, there is a paucity of data examining the expression and activity of TLRs in type 2 diabetes. Thus, in the present study, we examined TLR2 and TLR4 mRNA and protein expression, their ligands, and signaling in monocytes of recently diagnosed type 2 diabetic patients.

RESEARCH DESIGN AND METHODS

TLR mRNA, protein expression, TLR ligands, and TLR signaling were measured in freshly isolated monocytes from healthy human control subjects (n = 23) and type 2 diabetic subjects (n = 23) using real-time RT-PCR, Western blot, and flow cytometric assays.

RESULTS

Type 2 diabetic subjects had significantly increased TLR2, TLR4 mRNA, and protein in monocytes compared with control subjects (P < 0.05). Increased TLR2 and TLR4 expression correlated with BMI, homeostasis model assessment-insulin resistance (HOMA-IR), glucose, A1C, N(epsilon)-(carboxymethyl) lysine (CML), and free fatty acid (FFA). Ligands of TLR2 and TLR4, namely, HSP60, HSP70, HMGB1, endotoxin, and hyaluronan levels, were elevated in type 2 diabetic subjects and positively correlated with TLR2 and TLR4. Type 2 diabetic subjects showed increased MyD88, phosphorylated IRAK-1, Trif, TICAM-1, IRF-3, and NF-kappaB p65 expression in monocytes compared with control subjects. Furthermore, TLR-MyD88-NF-kappaB signaling resulted in elevated levels of cytokines (P < 0.05), but increased interleukin (IL)-1beta, interferon (IFN)-gamma, and endotoxin were not significant when adjusted for BMI.

CONCLUSIONS

In this comprehensive study, we make the novel observation that TLR2 and TLR4 expression and their ligands, signaling, and functional activation are increased in recently diagnosed type 2 diabetes and contribute to the proinflammatory state.

Over-expression of Toll-like receptors and their ligands in small-for-size graft

AIM

Toll-like receptors (TLRs) participate in several physiological and pathological processes of transplantation, including inflammation and allograft rejection, but the expression of TLRs and their ligands remains undetermined in small-for-size graft transplantation.

METHODS

A non-arterialized partial liver transplantation model was used. The expression of TLR2 and TLR4 mRNA and protein, CD14 and Myeloid Differentiation-2 (MD-2) mRNA, as well as TLR2 and TLR4 exogenous ligands (endotoxin) and endogenous ligands [heat shock protein (HSP) 60 and 70] were assessed. The signaling pathways induced by TLR2 and TLR4 were also assessed.

RESULTS

In small-for-size liver graft, the expression of mRNA and protein of TLR2 and TLR4, CD14 and MD-2 mRNA, as well as endogenous ligands of TLR2 and TLR4 such as HSP60 and HSP70 was quickly and significantly increased after reperfusion, and reached a peak at 3 h after reperfusion. The levels of exogenous ligands (endotoxin) were increased and reached a peak at 6 h after reperfusion. The appearance of TLR2 and TLR4 mRNA was accompanied by increased HSP 60 and 70 mRNA within 24 h after reperfusion. In the small-for-size group, the peak levels of TLRs and their endogenous ligands appeared earlier than those in the full size group; the peak levels of TLRs and their endogenous and exogenous ligands were higher than those in the full size group.

CONCLUSION

TLR2 and TLR4, as well as their endogenous and exogenous ligands were activated in small-for-size liver graft transplantation.

Midkine gene transfer after myocardial infarction in rats prevents remodelling and ameliorates cardiac dysfunction

AIM

We have previously reported that therapy with midkine (MK) has a protective effect in mouse models of myocardial infarction (MI) and ischemia/reperfusion. The underlying mechanism was proved to be anti-apoptosis and prevention of left ventricular (LV) remodelling following angiogenesis. Here we investigated the effects of overexpression of MK by adenoviral gene transfer on cardiac function and remodelling in an experimental rat MI model.

METHODS AND RESULTS

MI was created in male Wistar rats. Adenoviral vectors encoding mouse MK (AdMK) or beta-galactosidase (AdLacZ; as controls) were injected in myocardium at the onset of MI. One week after injection, in vivo adenoviral gene expression was assessed by western blot and histological analysis. After echocardiographic analysis at 4 weeks and haemodynamic analysis at 6 weeks after MI, AdMK animals had better cardiac function compared with AdLacZ animals. Heart weight (HW) and relative HW of AdMK animals were not different from sham-operated animals after 6 weeks, pointing to a very potent effect in the prevention of ischemic cardiomyopathy. In histological studies at 6 weeks after MI, AdMK animals had less fibrosis in the non-infarcted myocardium and higher vascular density in the border-zone area compared with AdLacZ animals. AdMK animals had strongly upregulated levels of phosphorylated extracellular signal-regulated kinase, Akt, PI 3-kinase, and Bcl-2, whereas the level of Bax was downregulated compared with AdLacZ animals.

CONCLUSION

Overexpression of MK prevents LV remodelling and ameliorates LV dysfunction by anti-apoptotic and pro-angiogenic effects. MK gene transfer may provide a new therapeutic modality in ischemic cardiomyopathy and ischemic heart failure.

Toll-like receptor-4 and lipoprotein accumulation in macrophages

Excessive lipid accumulation in macrophages, also known as foam cell formation, is a key process during the development of atherosclerosis, leading to vascular inflammation and plaque growth. Recent studies have identified a new mechanism of macrophage lipid accumulation in which minimally oxidized low-density lipoprotein (mmLDL) and its active components, polyoxygenated cholesteryl ester hydroperoxides, are involved in endogenous activation of toll-like receptor-4 (TLR4), leading to recruitment of spleen tyrosine kinase (Syk), robust cytoskeletal rearrangements and macropinocytosis. In hyperlipidemic environments, mmLDL-induced, TLR4- and Syk-dependent macropinocytosis leads to substantial lipid accumulation in macrophages and monocytes, which may constitute an important mechanism of foam cell formation in atherosclerosis. A novel hypercholesterolemic zebrafish model of early stages of atherosclerosis was used to demonstrate that the TLR4 deficiency significantly reduces the in vivo rate of macrophage lipid accumulation in vascular lesions.

Innate immune signals in atherosclerosis

Atherosclerosis is a chronic disease characterised by lipid retention and inflammation in the arterial intima. Innate immune mechanisms are central to atherogenesis, involving activation of pattern-recognition receptors (PRRs) and induction of inflammatory processes. In a complex tissue, such as the atherosclerotic lesion, innate signals can originate from several sources and promote atherogenesis through ligation of PRRs. The receptors recognise conserved molecular patterns on pathogens and endogenous products of tissue injury and inflammation. Activation of PRRs might affect several aspects of atherosclerosis by acting on lesion resident cells. Scavenger receptors mediate antigen uptake and clearance of lipoproteins, thereby promoting foam cell formation. Signalling receptors, such as Toll-like receptors (TLRs), lead to induction of pro-inflammatory cytokines and antigen-specific immune responses. In this review we describe the innate mechanisms present in the plaque. We focus on TLRs, their cross-talk with other PRRs, and how their signalling cascades influence inflammation within the atherosclerotic lesion.

Pioglitazone inhibits Toll-like receptor expression and activity in human monocytes and db/db mice

Toll-like receptors (TLRs) are key innate immune sensors of endogenous damage signals and play an important role in inflammatory diseases like diabetes and atherosclerosis. Pioglitazone (PIO), a peroxisome proliferator-activated receptor (PPAR)-gamma agonist, has been reported to be an antiinflammatory agent. Thus, in the present study, we examined the antiinflammatory effects of PIO on TLR2 and TLR4 expression in human monocytes exposed to Pam3CSK4 (Pam; TLR2 ligand) and purified lipopolysaccharide (LPS; TLR4 ligand) using flow cytometry and real-time RT-PCR. Monocytes were isolated from healthy human volunteers and pretreated with PIO (1 microM) followed by Pam (170 ng/ml) and LPS (160 ng/ml) challenge. PIO significantly decreased Pam- and LPS-induced TLR2 (-56%) and TLR4 (-78%) expression (P < 0.05). In addition, PIO decreased TLR ligand-induced nuclear factor-kappaB activity (-63%), IL-1beta (-50%), IL-6 (-52%), monocyte chemoattractant protein-1(-83%), and TNF-alpha (-87%) compared with control. Next, PIO-treated db/db mice (n = 6/group) showed decreased TLR2 (-60%) and TLR4 (-45%) expression in peritoneal macrophages compared with vehicle control mice (P < 0.001) with associated decrease in MyD88-dependent signaling and nuclear factor-kappaB activation. Data suggest that Pam- and LPS-induced TLR2 and TLR4 expression are inhibited by PIO in human monocytes and db/db mice. Thus, we define a novel pathway by which PIO could induce antiinflammatory effects.

Human cholesteryl ester transfer protein expression enhances the mouse survival rate in an experimental systemic inflammation model: a novel role for CETP

Mice expressing human cholesteryl ester transfer protein (huCETP) are more resistant to Escherichia coli bacterial wall LPS because death rates 5 days after intraperitoneal inoculation of LPS were higher in wild-type than in huCETP+/+ mice, whereas all huCETP+/+ mice remained alive. After LPS inoculation, plasma concentrations of TNF-alpha and IL-6 increased less in huCETP+/+ than in wild-type mice. LPS in vitro elicited lower TNF-alpha production by CETP expressing than by wild-type macrophages. In addition, TNF-alpha production by RAW 264.7 murine macrophages increased on incubation with LPS but decreased in a dose-dependent manner when human CETP was added to the medium. Human CETP in vitro enhanced the LPS binding to plasma high-density lipoprotein/low-density lipoprotein. The liver uptake of intravenous infused 14C-LPS from Salmonella typhimurium was greater in huCETP+/+ than in wild-type mice. Present data indicate for the first time that CETP is an endogenous component involved in the first line of defense against an exacerbated production of proinflammatory mediators.

Synergistic induction of inflammation by bacterial products lipopolysaccharide and fMLP: an important microbial pathogenic mechanism

A wide variety of stimuli have been shown to induce inflammation, but bacteria products/components are considered the major inducers during bacterial infections. We previously demonstrated that bacterial products/components such as LPS, a glycolipid component of the bacterial outer membrane, and formylated peptides (fMLP), a bacterial-derived peptide, induced proinflammatory cytokine gene expression in human peripheral blood monocytes. We now present evidence that mixtures of bacterial products/components LPS and fMLP behave synergistically in the induction of inflammation in vitro and in vivo. Furthermore, our results indicate that the TLR4 and the IKKbeta-IkappaBalpha signaling pathways are involved in the synergistic induction of inflammatory cytokines. The mechanism of synergistic activation of NF-kappaB is depended on nuclear translocation of p65 and phosphorylation of p65 at both Ser536 and Ser276 sites. These results demonstrate an important role for bacterial products/components from lysed bacteria in the pathogenesis of infectious diseases. We believe that this synergistic induction of inflammation by bacterial products LPS and fMLP represents an important pathogenic mechanism during bacterial infection, which may suggest novel therapeutic strategies or targets to minimize host injury following bacterial infection.

Toll-like receptor modulation: a novel therapeutic strategy in cardiovascular disease?

BACKGROUND

Toll-like receptors (TLRs) have been recently recognised as primary receptors in the innate immune system. Apart from initiating a prompt immune response against invading pathogens, TLRs are also considered to be an important link between innate immunity, inflammation and a variety of clinical disorders, including cardiovascular diseases. TLR signalling manipulation with novel drugs could offer important opportunities for cardiovascular disease modification.

OBJECTIVE

To present the latest knowledge supporting the involvement of TLRs in the pathogenesis and progress of cardiovascular diseases and explore the role of TLRs as potential targets for therapeutic intervention in cardiovascular territory.

METHODS

A review of the literature documenting implication of TLR signalling in cardiovascular disorders. Current progress in TLR-targeting drug development and the potential role of such a treatment strategy in cardiovascular disorders are discussed.

CONCLUSIONS

A growing body of evidence supports a role for TLRs in cardiovascular disease initiation and progression. Altering TLR signalling with novel drugs could be a beneficial therapeutic strategy for patients with cardiovascular disorders.

Candesartan inhibits Toll-like receptor expression and activity both in vitro and in vivo

INTRODUCTION

Toll-like receptors play an important role in the innate immune system and are found to be crucial in severe diseases like sepsis, atherosclerosis, and arthritis. TLR2 and TLR4 expression is upregulated in the inflammatory diseases. Angiotensin II in addition to stimulating vasoconstriction also induces an increase in ROS and a proinflammatory phenotype via AT(1)R. Angiotensin II type-1 receptor blocker (ARB), widely used as an antihypertensive drug, has been reported to also have anti-inflammatory effects. Thus, we investigated whether an ARB exerts anti-inflammatory effects via inhibiting TLR2 and TLR4 expression.

METHODS AND RESULTS

Monocytes were isolated from healthy human volunteers and treated with the synthetic lipoprotein Pam3CSK4 or LPS in the absence or presence of candesartan. Pretreatment of human monocytes with candesartan significantly decreased Pam3CSK4 or LPS induced TLR2 and TLR4 expression of both mRNA and protein levels (P<0.05 vs. control) along with decrease in the activity of NF-kappaB and the expression of IL-1beta, IL-6, TNF-alpha, and MCP-1. Furthermore, candesartan treated mice show decreased TLR2 and TLR4 expression compared to vehicle control mice.

CONCLUSION

Pam3CSK4 and LPS induced TLR2 and TLR4 expression at mRNA and protein levels are inhibited by candesartan both in vitro and in vivo. Thus, we define a novel pathway by which candesartan could induce anti-inflammatory effects.

Innate immunity and toll-like receptor antagonists: a potential role in the treatment of cardiovascular diseases

Toll-like receptors (TLRs) are germline-encoded receptors that recognize various pathogen-associated molecular patterns (PAMPs). They are key components of the innate immunity which are activated in response to pathogens as well as non-pathogenic components of damaged tissues. TLR agonists have been developed to treat allergies, cancers, and chronic infections by upregulating the innate immune system. TLR antagonists may be used to treat a number of inflammatory conditions, such as rheumatoid arthritis and systemic lupus erythematosus. Recent research also has shown that TLRs are involved in the pathogenesis of atherosclerosis, thrombosis, myocardial remodeling, ischemic/reperfusion injury, and valvular disease. This article reviews the current experimental and clinical evidence for the role of TLRs in the cardiovascular system, and examines the mechanisms by which TLR antagonists could potentially be used in targeted therapy.

Vascular cells contribute to atherosclerosis by cytokine- and innate-immunity-related inflammatory mechanisms

Cardiovascular diseases are the human diseases with the highest death rate and atherosclerosis is one of the major underlying causes of cardiovascular diseases. Inflammatory and innate immune mechanisms, employing monocytes, innate receptors, innate cytokines, or chemokines are suggested to be involved in atherogenesis. Among the inflammatory pathways the cytokines are central players. Plasma levels of cytokines and related proteins, such as CRP, have been investigated in cardiovascular patients, tissue mRNA expression was analyzed and correlations to vascular diseases established. Consistent with these findings the generation of cytokine-deficient animals has provided direct evidence for a role of cytokines in atherosclerosis. In vitro cell culture experiments further support the suggestion that cytokines and other innate mechanisms contribute to atherogenesis. Among the initiation pathways of atherogenesis are innate mechanisms, such as toll-like-receptors (TLRs), including the endotoxin receptor TLR4. On the other hand, innate cytokines, such as IL-1 or TNF, or even autoimmune triggers may activate the cells. Cytokines potently activate multiple functions relevant to maintain or spoil homeostasis within the vessel wall. Vascular cells, not least smooth muscle cells, can actively contribute to the inflammatory cytokine-dependent network in the blood vessel wall by: (i) production of cytokines; (ii) response to these potent cell activators; and (iii) cytokine-mediated interaction with invading cells, such as monocytes, T-cells, or mast cells. Activation of these pathways results in accumulation of cells and increased LDL- and ECM-deposition which may serve as an 'immunovascular memory' resulting in an ever-growing response to subsequent invasions. Thus, vascular cells may potently contribute to the inflammatory pathways involved in development and acceleration of atherosclerosis.

Toll-like receptors, transduction-effector pathways, and disease diversity: evidence of an immunobiological paradigm explaining all human illness?

Membrane-bound Toll-like receptors (TLRs) are frontline guardians in the mammalian innate immune system. They primarily function to recognize pathogen-associated molecular patterns (PAMPs) of invading microorganisms and on activation mount rapid, nonspecific innate responses and trigger sequential delayed specific adaptive cellular responses, which are mediated by complex signal transduction pathways involving adaptor molecules, costimulatory ligands and receptors, kinases, transcription factors, and modulated gene expression. Increasing evidence of multiple functionality and diversity suggests TLRs play critical roles in noninfective medical conditions such as cardiovascular, gastrointestinal, neurologic, musculoskeletal, obstetric, renal, liver, and dermatologic diseases, allergy, autoimmunity, and tissue regeneration. The significance of TLR heterogeneity underscores the possibility for establishing a universal immunobiological model to explain all human disease. Novel immunomodulatory therapies targeting specific or multiple TLRs may in the future offer new tools to combat or eradicate pathogenesis potentially transforming the landscape of current medical treatments.

TLR2 in murine atherosclerosis

Atherosclerosis was once thought to be solely a disease of lipid accumulation in the vessel wall. It does involve lipid accumulation, but inflammation appears to be an important driving factor. Consequently, our laboratory undertook to examine the role(s) of TLRs, and especially TLR2, in murine models of atherosclerosis.