TGF-beta reduced binding of high-density lipoproteins in murine macrophages and macrophage-derived foam cells

Dietary compounds have potential in controlling atherosclerosis by modulating macrophage cholesterol metabolism and inflammation via miRNA

Atherosclerosis (AS) is a typical example of a widespread fatal cardiovascular disease. Accumulation of cholesterol-laden macrophages in the artery wall forms the starting point of AS. Increased influx of oxidized low-density lipoprotein to macrophages and decreased efflux of free cholesterol out of macrophages constitute major factors promoting the development of AS. Inflammation further aggravates the development of AS along or via interaction with the cholesterol metabolism. Many microRNAs (miRNAs) are related to the regulation of macrophage in AS in aspects of cholesterol metabolism and inflammation signaling. Dietary compounds perform AS inhibitory effects via miRNAs in the cholesterol metabolism (miR-19b, miR-378, miR-10b, miR-33a, and miR-33b) and two miRNAs in the inflammation signaling (miR-155 and miR-146a). The targeted miRNAs in the cholesterol metabolism vary greatly among different food compounds; however, in inflammation signaling, most food compounds target miR-155. Many receptors are involved in macrophages via miRNAs, including ABCA1 and ABCG1 as major receptors in the cholesterol metabolism, while nuclear factor-κB (NF-κB) and Nrf2 signaling and PI3K/AKT signaling pathways are targeted during inflammation. This article reviews current literature to investigate possible AS therapy with dietary compounds via targeting miRNAs. Currently existing problems were also discussed to guide further studies.

Protective effects of curcumin against aflatoxicosis: A comprehensive review

Aflatoxicosis is a deleterious medical condition that results from aflatoxins (AFs) or ochratoxins (OTs). Contamination with these toxins exerts detrimental effects on the liver, kidneys, reproductive organs, and also on immunological and cardiovascular systems. Aflatoxicosis is closely associated with overproduction of reactive oxygen species (ROS) as key contributors to oxidative and nitrosative stress responses, and subsequent damages to lipids, proteins, RNA, and DNA. The main target organ for AF toxicity is the liver, where DNA adducts, degranulation of endoplasmic reticulum, increased hepatic lipid peroxide, GSH depletion, mitochondrial dysfunction, and reduction of enzymatic and non-enzymatic antioxidants are manifestations of aflatoxicosis. Curcuma longa L. (turmeric) is a medicinal plant widely utilized all over the world for culinary and phytomedical purposes. Considering the antioxidant characteristic of curcumin, the main active component of turmeric, this review is intended to critically summarize the available evidence supporting possible effectiveness of curcumin against aflatoxicosis. Curcumin can serve as a promising candidate for attenuation of the adverse consequences of aflatoxicosis, acting mainly through intrinsic antioxidant effects aroused from its structure, modulation of the immune system as reflected by interleukin-1β and transforming growth factor-β, and interfering with AF's biotransformation by cytochrome P450 isoenzymes CYP1A, CYP3A, CYP2A, CYP2B, and CYP2C.

Foam Cell Formation In Vivo Converts Macrophages to a Pro-Fibrotic Phenotype

Formation of foam cell macrophages, which sequester extracellular modified lipids, is a key event in atherosclerosis. How lipid loading affects macrophage phenotype is controversial, with evidence suggesting either pro- or anti-inflammatory consequences. To investigate this further, we compared the transcriptomes of foamy and non-foamy macrophages that accumulate in the subcutaneous granulomas of fed-fat ApoE null mice and normal chow fed wild-type mice in vivo. Consistent with previous studies, LXR/RXR pathway genes were significantly over-represented among the genes up-regulated in foam cell macrophages. Unexpectedly, the hepatic fibrosis pathway, associated with platelet derived growth factor and transforming growth factor-β action, was also over-represented. Several collagen polypeptides and proteoglycan core proteins as well as connective tissue growth factor and fibrosis-related FOS and JUN transcription factors were up-regulated in foam cell macrophages. Increased expression of several of these genes was confirmed at the protein level in foam cell macrophages from subcutaneous granulomas and in atherosclerotic plaques. Moreover, phosphorylation and nuclear translocation of SMAD2, which is downstream of several transforming growth factor-β family members, was also detected in foam cell macrophages. We conclude that foam cell formation in vivo leads to a pro-fibrotic macrophage phenotype, which could contribute to plaque stability, especially in early lesions that have few vascular smooth muscle cells.

'Correction:' Serum transforming growth factor beta-1 (TGF-beta-1) levels in diabetic patients are not associated with pre-existent coronary artery disease

Background

The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM). The association between TGF-β1 levels and long-term major adverse cardiovascular events (MACE) in patients with coronary artery disease (CAD) is controversial. No study specifically addressed patients with CAD and diabetes mellitus (DM).

Methods

Patients (n = 135, 30–80 years) referred for coronary angiography were submitted to clinical and laboratory evaluation, and the coronary angiograms were evaluated by two operators blinded to clinical characteristics. CAD was defined as the presence of a 70% stenosis in one major coronary artery, and DM was characterized as a fasting glycemia > 126 mg/dl or known diabetics (personal history of diabetes or previous use of anti-hyperglycemic drugs or insulin). Based on these criteria, study patients were classified into four groups: no DM and no CAD (controls, C n = 61), DM without CAD (D n = 23), CAD without DM (C-CAD n = 28), and CAD with DM (D-CAD n = 23). Baseline differences between the 4 groups were evaluated by the χ² test for trend (categorical variables) and by ANOVA (continuous variables, post-hoc Tukey). Patients were then followed-up during two years for the occurrence of MACE (cardiac death, stroke, myocardial infarction or myocardial revascularization). The association of candidate variables with the occurrence of 2-year MACE was assessed by univariate analysis.

Results

The mean age was 58.2 ± 0.9 years, and 51% were men. Patients with CAD had a higher mean age (p = 0.011) and a higher percentage were male (p = 0.040). There were no significant baseline differences between the 4 groups regarding hypertension, smoking status, blood pressure levels, lipid levels or inflammatory markers. TGF-β1 was similar between patients with or without CAD or DM (35.1 ×/÷ 1.3, 33.6 ×/÷ 1.6, 33.9 ×/÷ 1.4 and 31.8 ×/÷ 1.4 ng/ml in C, D, C-CAD and D-CAD, respectively, p = 0.547). In the 2-year follow-ip, independent predictors of 2-year MACE were age (p = 0.007), C-reactive protein (p = 0.048) and systolic blood pressure (p = 0.008), but not TGF-β1.

Conclusion

Serum TGF-β1 was not associated with CAD or MACE occurrence in patients with or without DM.

Acute hypoxia-reperfusion triggers immunocompromise in Nile tilapia

Inadequate dissolved oxygen in the aquatic environment is a well-established cause of fish morbidity and mortality. The specific effects of hypoxia on immune function in fish, however, are not well characterized. In this study, the effects of acute hypoxia followed by reoxygenation (rapid tissue reperfusion) as a source of immunocompromise in Nile tilapia Oreochromis niloticus were investigated. Using a precision apparatus developed in our laboratory for hypoxia exposures, a series of assays of increasing specificity for immune function were performed on acutely hypoxia-stressed Nile tilapia: tier I consisted of histopathology, tier II of hematology, plasma chemistry, and determining cortisol concentration, and tier III of determining the phagocytic index and analyzing the expression of the cytokines transforming growth factor-beta (TGF-beta) and interleukin-1beta (IL-1beta). Nile tilapia were exposed to 7% oxygen saturation for 96 h, then tank water was rapidly reoxygenated. Sampling intervals were 48 and 96 h during hypoxia and 12 and 84 h during reperfusion. Histopathology showed no remarkable microscopic abnormalities in lymphoid or other tissues. Lymphopenia and neutrophilia were observed in peripheral blood. Plasma total protein, partial pressure of oxygen, and oxygen saturation were decreased in response to hypoxia. Plasma lipase decreased in response to hypoxia but returned to normal during reperfusion. Phagocytic capability and the phagocytic index decreased during hypoxia and 12 h reperfusion, whereas these values were recovered by 84 h reperfusion. The TGF-beta transcription continued to increase during the exposures, the greatest production being at 12 h reperfusion, whereas IL-1beta transcription decreased in response to hypoxia and reperfusion. We conclude that acute hypoxia triggered an overall downregulation of the immune system in the test fish. This suggests a possible factor in the pathogenesis of disease outbreaks in fish in which repeated, sublethal bouts of environmentally induced hypoxia lead to increased disease susceptibility and individual mortalities rather than massive fish kills.

Transforming growth factor-beta-regulated expression of genes in macrophages implicated in the control of cholesterol homoeostasis

The regulation of macrophage cholesterol homoeostasis is of crucial importance in the pathogenesis of atherosclerosis, an underlying cause of heart attack and stroke. Several recent studies have revealed a critical role for the cytokine TGF-beta (transforming growth factor-beta), a key regulator of the immune and inflammatory responses, in atherogenesis. We discuss here the TGF-beta signalling pathway and its role in this disease along with the outcome of our recent studies on the action of the cytokine on the expression of key genes implicated in the uptake or efflux of cholesterol by macrophages and the molecular mechanisms underlying such regulation.

Antiatherogenic effects of dietary plant sterols are associated with inhibition of proinflammatory cytokine production in Apo E-KO mice

Dietary phytosterols significantly reduce atherosclerosis in apo E-deficient mice. Because atherosclerosis is a chronic inflammatory disease, we investigated whether the antiatherogenic effects of phytosterols are associated with reductions in proinflammatory cytokine production as well as the effect of this diet on global immunocompetence. Apolipoprotein (apo) E-deficient mice were fed a cholesterol-supplemented diet in the presence or absence of 2% dietary phytosterols for 14 wk and then immunized with ovalbumin. The relations between plasma lipid concentrations, atherosclerotic lesions, and cytokine production and proinflammatory stimuli or foreign antigens were characterized. Phytosterol-enriched diets were strongly associated with reduced plasma cholesterol concentrations and atherosclerosis in conjunction with higher anti-inflammatory [interleukin (IL)-10] and lower proinflammatory cytokine [IL-6, tumor necrosis factor (TNF)-alpha] production. In contrast, development of cytokine and chemokine responses to ovalbumin was as strong as or even improved in the phytosterol-treated mice relative to controls. The antiatherogenic effects of dietary phytosterols in apo E-knockout mice were associated with beneficial alterations in both lipoprotein metabolism and inflammatory pathways. Decreased capacity to mount proinflammatory cytokine and chemokine responses to inflammatory stimuli did not interfere with the global immunocompetence of such mice. Thus, the desirable suppression of proinflammatory cytokine production that was associated with inhibition of atherogenesis did not impair the capacity to mount responses to foreign antigens.

Thematic review series: The Immune System and Atherogenesis. Cytokine regulation of macrophage functions in atherogenesis

This review will focus on the role of cytokines in the behavior of macrophages, a prominent cell type of atherosclerotic lesions. Once these macrophages have immigrated into the vessel wall, they propagate the development of atherosclerosis by modifying lipoproteins, accumulating intracellular lipids, remodeling the extracellular environment, and promoting local coagulation. The numerous cytokines that have been detected in atherosclerosis, combined with the expression of large numbers of cytokine receptors on macrophages, are consistent with this axis being an important contributor to lesion development. Given the vast literature on cytokine-macrophage interactions, this review will be selective, with an emphasis on the major cytokines that have been detected in atherosclerotic lesions and their effects on properties that are relevant to lesion formation and maturation. There will be an emphasis on the role of cytokines in regulating lipid metabolism by macrophages. We will provide an overview of the major findings in cell culture and then put these in the context of in vivo studies.

Comparison of inflammatory and acute-phase responses in the brain and peripheral organs of the ME7 model of prion disease

Chronic neurodegenerative diseases such as prion disease and Alzheimer's disease (AD) are reported to be associated with microglial activation and increased brain and serum cytokines and acute-phase proteins (APPs). Unlike AD, prion disease is also associated with a peripheral component in that the presumed causative agent, PrPSc, also accumulates in the spleen and other lymphoreticular organs. It is unclear whether the reported systemic acute-phase response represents a systemic inflammatory response to prion disease or merely reflects central nervous system (CNS) inflammation. For this study, we investigated whether intracerebrally initiated prion disease (ME7 model) provokes splenic, hepatic, or brain inflammatory and acute-phase responses. We detected no significant elevation of proinflammatory cytokines or activation of macrophages in the spleens of these animals, despite clear PrPSc deposition. Similarly, at 19 weeks we detected no significant elevation of transcripts for the APPs serum amyloid A, complement C3, pentraxin 3, and alpha2-antiplasmin in the liver, despite CNS neurodegeneration and splenic PrPSc deposition at this time. However, despite the low CNS expression levels of proinflammatory cytokines, there was robust expression of these APPs in degenerating brains. These findings suggest that PrPSc is not a stimulus for splenic macrophages and that neither peripheral PrPSc deposition nor CNS neurodegeneration is sufficient to produce a systemic acute-phase response. We also propose that serum cytokine and APP measurements are not useful during preclinical disease. Possible consequences of the clear chronic elevation of APPs in the CNS are discussed.

The role of the high-density lipoprotein receptor SR-BI in the lipid metabolism of endocrine and other tissues

Because cholesterol is a precursor for the synthesis of steroid hormones, steroidogenic tissues have evolved multiple pathways to ensure adequate supplies of cholesterol. These include synthesis, storage as cholesteryl esters, and import from lipoproteins. In addition to endocytosis via members of the low-density lipoprotein receptor superfamily, steroidogenic cells acquire cholesterol from lipoproteins by selective lipid uptake. This pathway, which does not involve lysosomal degradation of the lipoprotein, is mediated by the scavenger receptor class B type I (SR-BI). SR-BI is highly expressed in steroidogenic cells, where its expression is regulated by various trophic hormones, as well as in the liver. Studies of genetically manipulated strains of mice have established that SR-BI plays a key role in regulating lipoprotein metabolism and cholesterol transport to steroidogenic tissues and to the liver for biliary secretion. In addition, analysis of SR-BI-deficient mice has shown that SR-BI expression is important for alpha-tocopherol and nitric oxide metabolism, as well as normal red blood cell maturation and female fertility. These mouse models have also revealed that SR-BI can protect against atherosclerosis. If SR-BI plays similar physiological and pathophysiological roles in humans, it may be an attractive target for therapeutic intervention in cardiovascular and reproductive diseases.

Glycated albumin increases oxidative stress, activates NF-kappa B and extracellular signal-regulated kinase (ERK), and stimulates ERK-dependent transforming growth factor-beta 1 production in macrophage RAW cells

Albumin modified by Amadori glucose adducts has been shown to modulate signal transduction and induce alterations in renal glomerular cells that contribute to the development of diabetic nephropathy. However, the participation of this nonenzymatically glycated protein in the pathobiology of atherosclerotic cardiovascular disease in diabetes has not been established. To probe this issue, we used macrophage RAW cells to assess the effects of glycated albumin on molecular events implicated in the pathogenesis of diabetes-related vascular complications. RAW cells were cultured in medium containing 5.5 mmol/L glucose and glycated or nonglycated albumin, with and without the addition of PD98059, a specific inhibitor of mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK), followed by analysis of phosphorylated ERK and the nuclear translocation of nuclear factor (NF)-kappa B and measurement of cellular content of thiobarbituric acid-reactive substances and the concentration of transforming growth factor (TGF)-beta(1) in the spent medium. We demonstrate, for the first time, that glycated albumin activates RAW cell ERK and promotes ERK-dependent increases in TGF-beta(1) production, oxidative stress, and NF-kappa B activation. Preincubation with the antioxidant alpha-lipoic acid partially prevented the glycated albumin-induced increase in NF-kappa B activation. These findings indicate that Amadori-modified glycated albumin modulates macrophage cell biology independent of high glucose concentration. The effects of glycated albumin on RAW cell molecular mediators and cytokine production may have pathophysiologic significance with respect to the accelerated atherosclerosis that occurs in diabetes.

Prognostic significance of plasma concentrations of transforming growth factor-beta in patients with coronary artery disease

BACKGROUND

Cytokines play an important role in modulating inflammatory and proliferative responses, including atherosclerosis. Transforming growth factor-beta (TGF-beta) and macrophage-colony stimulating factor (M-CSF) are one of the major antiinflammatory and proinflammatory cytokines, respectively. We have previously demonstrated that plasma concentrations of TGF-beta are decreased while those of M-CSF are increased in patients with coronary artery disease (CAD). In this study, we examined whether those alterations in plasma levels of cytokines have a prognostic significance in patients with CAD.

METHODS AND RESULTS

Sixty-eight consecutive patients with proven CAD were studied. The plasma concentrations of TGF-beta and those of M-CSF were measured by enzyme-linked immunosorbent assay (ELISA). They were divided into groups: high (> or =6 ng/ml, n = 19) and low (<6 ng/ml, n = 49) TGF-beta groups and high (>500 ng/ml, n = 52) and low (< or =500 ng/ml, n = 16) M-CSF groups. The long-term prognosis of these patients was prospectively followed up for a mean period of 979 +/- 27 days. The prognosis was analyzed by Kaplan-Meier analysis in terms of total survival, survival without myocardial infarction, survival without cardiovascular events and survival without coronary interventions. The analysis showed that the low TGF-beta group had a significantly poor prognosis in terms of survival without cardiovascular events and survival without coronary interventions as compared with the high TGF-beta group (both P < 0.05), while other prognoses were comparable between the two groups. By contrast, no significant prognostic influence was noted regarding M-CSF.

CONCLUSIONS

These results suggest that plasma concentrations of TGF-beta may have a prognostic significance in patients with CAD.

Transforming growth factor-beta(1) modulates oxidatively modified LDL-induced expression of adhesion molecules: role of LOX-1

Oxidatively modified LDL (ox-LDL) activates a lectin-like receptor, LOX-1, which results in the expression of adhesion molecules on endothelial surface. We investigated the regulation of the expression of transforming growth factor-beta(1) (TGF-beta(1)) and its receptors by ox-LDL and the functional significance of this interaction with regard to adhesion molecule expression in human coronary artery endothelial cells (HCAECs). Ox-LDL, in a time- and concentration-dependent manner, upregulated the expression of all 3 subtypes (1, 2, and 3 [including endoglin]) of TGF-beta(1) receptors and decreased active TGF-beta(1) synthesis (all P<0.05 versus control and native-LDL-treated cells). Treatment of HCAECs with a monoclonal antibody to LOX-1 attenuated ox-LDL-mediated upregulation of TGF-beta(1) receptors and decrease in TGF-beta(1) synthesis (P<0.05 versus ox-LDL alone). Ox-LDL also enhanced the expression of P-selectin and ICAM-1 as well as monocyte adhesion to HCAECs (P<0.05 versus control untreated cells). Pretreatment with recombinant TGF-beta(1) attenuated the enhanced expression of adhesion molecules and monocyte adhesion to HCAECs (P<0.05 versus ox-LDL alone). Effects of recombinant TGF-beta(1) were blocked by antibody to TGF-beta(1) receptor type 2, but not by antibody to endoglin. Thus ox-LDL, via activation of LOX-1, increases the expression of TGF-beta(1) receptors and decreases TGF-beta(1) synthesis in HCAECs. Recombinant TGF-beta(1), by binding to TGF-beta(1) type 2 receptors, modulates ox-LDL-mediated expression of adhesion molecules and monocyte adhesion to HCAECs.