Pravastatin up-regulates transforming growth factor-β1 in THP-1 human macrophages: effect on scavenger receptor class A expression

Genetic association of lipids and lipid-lowering drug target genes with breast cancer

BACKGROUND

Although several preclinical and epidemiological studies have shown that blood lipids and lipid-lowering drugs can reduce the risk of breast cancer, this finding remains controversial. This study aimed to explore the causal relationship between dyslipidemia,lipid-lowering drugs, and breast cancer. We also aimed to evaluate the potential impact of lipid-lowering drug targets on breast cancer.

METHOD

Data of 431 lipid- and lipid-related phenotypes were obtained from genome-wide association study (GWAS), and mendelian randomization (MR) analyses were performed using two independent breast cancer datasets as endpoints. Genetic variants associated with genes encoding lipid-lowering drug targets were extracted from the Global Lipid Genetics Consortium. Expression quantitative trait loci data in relevant tissues were used to further validate lipid-lowering drug targets that reached significance and combined with bioinformatics approaches for molecular expression and prognostic exploration. Further mediation analyses were performed to explore potential mediators.

RESULT

In two independent datasets, phosphatidylcholine (18:1_0:0 levels) was associated with breast cancer risk (discovery: odds ratio (OR) = 1.255 [95% confidence interval (CI) 1.120-1.406]; p = 8.936 × 10-5, replication: OR = 1.016 [95% CI, 1.003-1.030]; p = 0.017), HMG- CoA reductase (HMGCR) inhibition was genetically modeled and associated with a reduced risk of breast cancer (discovery: OR = 0.833 [95% CI 0.752-0.923], p = 5.12 × 10-4; replication: OR = 0.975 [95% CI 0.960-0.990], p = 1.65 × 10-3). There was a significant MR correlation between HMGCR expression in whole blood and breast cancer (OR = 1.11 [95% 1.01-1.22] p = 0.04). Bioinformatics analysis revealed that HMGCR expression higher in breast cancer tissues than in normal tissues, along with poor overall survival and relapse-free survival, and was associated with multiple immune cell infiltration. Finally, the mediation analysis showed that HMGCR inhibitors affected breast cancer through different immune cell phenotypes and C-reactive protein levels.

CONCLUSION

In this study, we found for the first time that phosphatidylcholine (18:1_0:0) levels are associated with breast cancer risk. We found that HMGCR inhibitors are associated with a reduced risk of breast cancer, and part of their action may be through pathways other than lipid-lowering, including modulation of immune function and reduction of inflammation represented by C-reactive protein levels.

Statin-induced microRNAome alterations modulating inflammation pathways of peripheral blood mononuclear cells in patients with hypercholesterolemia

Statins inhibit cholesterol biogenesis and modulate atheroma inflammation to reduce cardiovascular risks. Promoted by immune and non-immune cells, serum C-reactive protein (CRP) might be a biomarker suboptimal to assess inflammation status. Although it has been reported that statins modulated inflammation via microRNAs (miRNAs), evidence remains lacking on comprehensive profiling of statin-induced miRNAome alterations in immune cells. We recruited 19 hypercholesterolemic patients receiving 2 mg/day pitavastatin and 15 ones receiving 10 mg/day atorvastatin treatment for 12 weeks, and performed microarray-based profiling of 1733 human mature miRNAs in peripheral blood mononuclear cells (PBMCs) before and after statin treatment. Differentially expressed miRNAs were determined if their fold changes were >1.50 or <0.67, after validated using quantitative polymerase chain reaction (qPCR). The miRSystem and miTALOS platforms were utilized for pathway analysis. Of the 34 patients aged 63.7 ± 6.2 years, 27 were male and 19 were with coronary artery disease. We discovered that statins induced differential expressions of miR-483-5p, miR-4667-5p, miR-1244, and miR-3609, with qPCR-validated fold changes of 1.74 (95% confidence interval, 1.33-2.15), 1.61 (1.25-1.98), 1.61 (1.01-2.21), and 1.68 (1.19-2.17), respectively. The fold changes of the four miRNAs were not correlated with changes of low-density-lipoprotein cholesterol or CRP, after sex, age, and statin type were adjusted. We also revealed that RhoA and transforming growth factor-β signaling pathways might be regulated by the four miRNAs. Given our findings, miRNAs might be involved in statin-induced inflammation modulation in PBMCs, providing likelihood to assess and reduce inflammation in patients with atherosclerotic cardiovascular diseases.

Effect of Statin Supplementation on Pulmonary Function and Inflammatory Markers in Patients of Chronic Obstructive Pulmonary Disease

Background:

COPD being a systemic inflammatory disease is accompanied by alteration of various inflammatory cytokines which affect the metabolic equilibrium of body. Some therapeutic options, mainly statins via their wide range of pharmacologic actions alter the level of proinflammatory cytokines hence, helpful in attenuating various extra-pulmonary consequences of COPD. We did a randomised case-control study to study the effect of statin supplementation on pulmonary function and inflammatory markers in patients of COPD.

Methods:

We included 40 stable COPD subjects & randomized them in two groups, Intervention & Non-intervention. Intervention group received 40 mg atorvastatin once daily for 3 months in addition to the conventional treatment of COPD similar to the prior one. We studied levels of IL-6 & CRP and correlated them with disease severity before and after the aforementioned intervention.

Results:

We observed that CRP levels decreased in both the groups after a follow up of 3 months, but neither of them was statistically significant (p=0.57 & 0.63 respectively) nor the mean of their difference (p=0.969). IL-6 levels showed a persistent decline in intervention group but, was not significant (p=0.91). In this study, we noticed statistically significant improvement in FEV1 (p=0.008) in the intervention group which was in contrast to non-intervention group. Similarly, the exercise capacity also statistically increased in the intervention group (p=0.002). There was also evident negative correlation between exercise capacity and IL-6 as well CRP levels. FEV1 also showed statistically significant negative correlation with IL-6 levels (p=0.023).

Conclusion:

We can improve the disease outcome and alter its natural progression by altering the levels of inflammatory markers with the aid of some additional pharmacological interventions i.e., in this study was atorvastatin.

Role of TGFβ signaling in the pathogenesis of Alzheimer's disease

Aging is the main risk factor for Alzheimer’s disease (AD); being associated with conspicuous changes on microglia activation. Aged microglia exhibit an increased expression of cytokines, exacerbated reactivity to various stimuli, oxidative stress, and reduced phagocytosis of β-amyloid (Aβ). Whereas normal inflammation is protective, it becomes dysregulated in the presence of a persistent stimulus, or in the context of an inflammatory environment, as observed in aging. Thus, neuroinflammation can be a self-perpetuating deleterious response, becoming a source of additional injury to host cells in neurodegenerative diseases. In aged individuals, although transforming growth factor β (TGFβ) is upregulated, its canonical Smad3 signaling is greatly reduced and neuroinflammation persists. This age-related Smad3 impairment reduces protective activation while facilitating cytotoxic activation of microglia through several cellular mechanisms, potentiating microglia-mediated neurodegeneration. Here, we critically discuss the role of TGFβ-Smad signaling on the cytotoxic activation of microglia and its relevance in the pathogenesis of AD. Other protective functions, such as phagocytosis, although observed in aged animals, are not further induced by inflammatory stimuli and TGFβ1. Analysis in silico revealed that increased expression of receptor scavenger receptor (SR)-A, involved in Aβ uptake and cell activation, by microglia exposed to TGFβ, through a Smad3-dependent mechanism could be mediated by transcriptional co-factors Smad2/3 over the MSR1 gene. We discuss that changes of TGFβ-mediated regulation could at least partially mediate age-associated microglia changes, and, together with other changes on inflammatory response, could result in the reduction of protective activation and the potentiation of cytotoxicity of microglia, resulting in the promotion of neurodegenerative diseases.

Cytokines, macrophage lipid metabolism and foam cells: implications for cardiovascular disease therapy

Cardiovascular disease is the biggest killer globally and the principal contributing factor to the pathology is atherosclerosis; a chronic, inflammatory disorder characterized by lipid and cholesterol accumulation and the development of fibrotic plaques within the walls of large and medium arteries. Macrophages are fundamental to the immune response directed to the site of inflammation and their normal, protective function is harnessed, detrimentally, in atherosclerosis. Macrophages contribute to plaque development by internalizing native and modified lipoproteins to convert them into cholesterol-rich foam cells. Foam cells not only help to bridge the innate and adaptive immune response to atherosclerosis but also accumulate to create fatty streaks, which help shape the architecture of advanced plaques. Foam cell formation involves the disruption of normal macrophage cholesterol metabolism, which is governed by a homeostatic mechanism that controls the uptake, intracellular metabolism, and efflux of cholesterol. It has emerged over the last 20 years that an array of cytokines, including interferon-γ, transforming growth factor-β1, interleukin-1β, and interleukin-10, are able to manipulate these processes. Foam cell targeting, anti-inflammatory therapies, such as agonists of nuclear receptors and statins, are known to regulate the actions of pro- and anti-atherogenic cytokines indirectly of their primary pharmacological function. A clear understanding of macrophage foam cell biology will hopefully enable novel foam cell targeting therapies to be developed for use in the clinical intervention of atherosclerosis.

IL-32 is a host protective cytokine against Mycobacterium tuberculosis in differentiated THP-1 human macrophages

Macrophages provide a first line of defense against Mycobacterium tuberculosis. However, in instances where macrophage activation for killing is suboptimal, M. tuberculosis is capable of surviving intracellularly. IL-32 is a recently described cytokine induced by M. tuberculosis in a variety of cell types including human monocytes and macrophages. In this study, we investigated the biological significance of IL-32 in an in vitro model of M. tuberculosis infection in differentiated THP-1 human macrophages in which IL-32 expression was silenced using stable expression of short hairpin RNA (shRNA). Inhibition of endogenous IL-32 production in THP-1 cells that express one of three distinct shRNA-IL-32 constructs significantly decreased M. tuberculosis induction of TNF-alpha by approximately 60%, IL-1beta by 30-60%, and IL-8 by 40-50% and concomitantly increased the number of cell-associated M. tuberculosis bacteria compared with THP-1 cells stably expressing a scrambled shRNA. In THP-1 cells infected with M. tuberculosis and stimulated with rIL-32, a greater level of apoptosis was observed compared with that with M. tuberculosis infection alone. Obversely, there was significant abrogation of apoptosis induced by M. tuberculosis and a concomitant decrease in caspase-3 activation in cells depleted of endogenous IL-32. rIL-32gamma significantly reduced the number of viable intracellular M. tuberculosis bacteria, which was modestly but significantly abrogated with a caspase-3 inhibitor. We conclude that IL-32 plays a host defense role against M. tuberculosis in differentiated THP-1 human macrophages.

Transcriptional and translational regulation of TGF-beta production in response to apoptotic cells

Interaction between apoptotic cells and phagocytes through phosphatidylserine recognition structures results in the production of TGF-beta, which has been shown to play pivotal roles in the anti-inflammatory and anti-immunogenic responses to apoptotic cell clearance. Using 3T3-TbetaRII and RAWTbetaRII cells in which a truncated dominant-negative TGF-beta receptor II was stably transfected to avoid autofeedback induction of TGF-beta, we investigate the mechanisms by which TGF-beta was produced through PSRS engagement. We show, in the present study, that TGF-beta was regulated at both transcriptional and translational steps. P38 MAPK, ERK, and JNK were involved in TGF-beta transcription, whereas translation required activation of Rho GTPase, PI3K, Akt, and mammalian target of rapamycin with subsequent phosphorylation of translation initiation factor eukaryotic initiation factor 4E. Strikingly, these induction pathways for TGF-beta production were different from those initiated in the same cells responding to LPS or PMA.

15-Lipoxygenase-2 expression in human macrophages induces chemokine secretion and T cell migration

BACKGROUND

We determined previously that hypoxia results in increased 15-lipoxygenase type 2 (15-LOX-2) expression and CXCL8 secretion in macrophages. This study sought to determine whether 15-LOX-2 expression links directly with the secretion of inflammatory molecules in macrophages and also investigated its subsequent effects on T cell migration.

METHODS

Adenovirus-mediated gene delivery caused overexpression of 15-LOX-2 in human macrophages. We used cytometric bead array to measure chemokine secretion, and assessed T cell migration by counting cells in chemotaxis chambers. Expression of chemokine receptors was determined by FACS analysis. Using siRNA, we reduced 15-LOX-2 expression in human macrophages. We used scrambled siRNA as control.

RESULTS

Macrophages that overexpress 15-LOX-2 showed increased secretion of chemokine CXCL10 after 24h incubation. In addition, preconditioned medium from 15-LOX-2-overexpressing cells increased T cell migration and surface expression of CXCR3, the CXCL10 receptor. Knockdown of 15-LOX-2 expression decreased CXCL10 secretion from hypoxic macrophages and also reduced T cell migration.

CONCLUSION

In macrophages, overexpression of 15-LOX-2 results in increased secretion of CXCL10 and CCL2. Products released in response to increased 15-LOX-2 activation lead to increased expression of CD69, the T cell activation marker as well as increased T cell migration. Therefore, increased expression of 15-LOX-2 induced by hypoxia may participate in T cell recruitment in diseases such as atherosclerosis.

Statins and foam cell formation: Impact on LDL oxidation and uptake of oxidized lipoproteins via scavenger receptors

The uptake of oxidized lipoproteins via scavenger receptors and the ensuing formation of foam cells are key events during atherogenesis. Foam cell formation can be reduced by treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins). The efficacy of statins is evidently due not only to their cholesterol-lowering properties, but also to lipid-independent pleiotropic effects. This review focuses on lipid-independent pleiotropic effects of statins that influence foam cell formation during atherogenesis, with special emphasis on oxidative pathways and scavenger receptor expression.

Lovastatin enhances clearance of apoptotic cells (efferocytosis) with implications for chronic obstructive pulmonary disease

Statins are potent, cholesterol-lowering agents with newly appreciated, broad anti-inflammatory properties, largely based upon their ability to block the prenylation of Rho GTPases, including RhoA. Because phagocytosis of apoptotic cells (efferocytosis) is a pivotal regulator of inflammation, which is inhibited by RhoA, we sought to determine whether statins enhanced efferocytosis. The effect of lovastatin on efferocytosis was investigated in primary human macrophages, in the murine lung, and in human alveolar macrophages taken from patients with chronic obstructive pulmonary disease. In this study, we show that lovastatin increased efferocytosis in vitro in an 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase-dependent manner. Lovastatin acted by inhibiting both geranylgeranylation and farnesylation, and not by altering expression of key uptake receptors or by increasing binding of apoptotic cells to phagocytes. Lovastatin appeared to exert its positive effect on efferocytosis by inhibiting RhoA, because it 1) decreased membrane localization of RhoA, to a greater extent than Rac-1, and 2) prevented impaired efferocytosis by lysophosphatidic acid, a potent inducer of RhoA. Finally, lovastatin increased efferocytosis in the naive murine lung and ex vivo in chronic obstructive pulmonary disease alveolar macrophages in an HMG-CoA reductase-dependent manner. These findings indicate that statins enhance efferocytosis in vitro and in vivo, and suggest that they may play an important therapeutic role in diseases where efferocytosis is impaired and inflammation is dysregulated.

Pravastatin Inhibits Expression of Lectin-Like Oxidized Low-Density Lipoprotein Receptor-1 (LOX-1) in Watanabe Heritable Hyperlipidemic Rabbits

BACKGROUND

LOX-1, a receptor for oxidized low-density lipoprotein (OxLDL), seems to play a critical role in foam cell formation of macrophages (Mphis) and smooth muscle cells (SMC). Inhibition of LOX-1 expression reduces foam cell formation and might influence lipid core formation in atherosclerotic lesions. Because statins are able to downregulate LOX-1 expression in vitro, we examined if pravastatin can be used to reduce LOX-1 expression and lipid core formation in lesions of Watanabe heritable hyperlipidemic (WHHL) rabbits.

METHODS AND RESULTS

Pravastatin downregulated LOX-1 expression in cultured human Mphis and in cultured human aortic SMCs. Homozygous WHHL rabbits were treated with 50 mg kg(-1) d(-1) pravastatin for 32 weeks. Immunohistochemical studies revealed that LOX-1 was expressed in intimal Mphis and SMCs of atherosclerotic lesions. The pravastatin-treated rabbits showed, compared with untreated rabbits, a significantly reduced LOX-1 protein and mRNA expression in the aortic arch. Lipid labeling of this aorta region also demonstrated a strong reduction of the ratio of lipid core area/total lesion area in pravastatin-treated rabbits.

CONCLUSIONS

The in vivo inhibition of LOX-1 expression by pravastatin demonstrated here represents a new pleiotropic effect of pravastatin. This in vivo inhibition of LOX-1 might be one mechanism for the lipid core reducing effect of pravastatin in atherogenesis.

Effects of pravastatin on the in vitro phagocytic function and hydrogen peroxide production by monocytes of healthy individuals

Macrophages play a part in pathogenesis of atherosclerosis, oxidizing LDL-cholesterol and transforming themselves in foam cells and producing free radicals of oxygen that may also oxidize LDL-cholesterol. HMG-CoA reductase inhibitors are very efficient in long-term control of atherogenesis acting by different mechanisms not fully established. Thus, we investigated the in vitro influence of pravastatin on phagocytosis and hydrogen peroxide production by monocytes of healthy individuals. Phagocytosis of Saccharomyces erevisiae by peripheral blood monocytes of 20 healthy individuals was assessed in the absence or presence of pravastatin. Hydrogen peroxide production was assessed based on the horseradish peroxidase-dependent oxidation of phenol red method. Pravastatin had no influence on phagocytosis through scavenger receptors, while it decreased by 20% the mean+/-SD phagocytic index of monocytes through complement receptors, from 141+/-77 to 113+/-56 (p=0.017), due to a decrease in the number of particles ingested by monocytes, from 2.1+/-0.5 to 1.7+/-0.3 (p=0.003). This statin also decreased the baseline production of hydrogen peroxide, by 7.7%, from 0.098+/-0.013 to 0.091+/-0.013 (OD by 2x10(5) monocytes per hour) (p=0.025). Pravastatin was able to decrease the phagocytosis through complement receptors and caused a decrease in the production of hydrogen peroxide by monocytes. It is possible this statin may directly inhibit the development of atherosclerotic plaque and its instability dependent on phagocytosis and the presence of reactive species of oxygen.

Statins inhibit synthesis of an oxysterol ligand for the liver x receptor in human macrophages with consequences for cholesterol flux

OBJECTIVE

Cholesterol efflux from macrophages in the artery wall, a key cardioprotective mechanism, is largely coordinated by the nuclear oxysterol-activated liver X receptor, LXRalpha. We investigated the effect of statins on LXR target gene expression and cholesterol efflux from human macrophages.

METHODS AND RESULTS

In human macrophages (THP-1 cell line and primary cells), the archetypal statin, compactin, greatly reduced mRNA levels of 2 LXR target genes, ABCA1 and ABCG1 mRNA, as well as decreased cholesterol efflux. Commonly prescribed statins also downregulated LXR target gene expression in THP-1 cells. We provide several lines of evidence indicating that statins decrease expression of LXR target genes by inhibiting the synthesis of an oxysterol ligand for LXR, 24(S),25-epoxycholesterol. When THP-1 cells were cholesterol-loaded via incubation with acetylated low-density lipoprotein, synthesis of 24(S),25-epoxycholesterol was greatly reduced and the downregulatory effect of compactin on ABCA1 mRNA levels and cholesterol efflux was lost.

CONCLUSIONS

Our results suggest that statins may downregulate cholesterol efflux from nonloaded human macrophages by inhibiting synthesis of an oxysterol ligand for LXR. Further work is needed to determine how relevant our observations are to arterial foam cells in vivo.

Atorvastatin reduces CD68, FABP4, and HBP expression in oxLDL-treated human macrophages

With the aim of identifying new target genes that could contribute to limit foam cell formation, we analyzed changes in the pattern of gene expression in human THP-1 macrophages treated with atorvastatin and oxidized-LDL (oxLDL). To this end, we used a human cDNA array containing 588 cardiovascular-related cDNAs. Exposure to oxLDL resulted in differential expression of 26 genes, while coincubation with atorvastatin modified the expression of 29 genes, compared to treatment with oxLDL alone. Changes in the expression of candidate genes, potentially connected to the atherosclerotic process, were confirmed by quantitative RT-PCR and Western blot. We show that atorvastatin prevents the increase in the expression of scavenger receptor CD68 and that of fatty acid binding protein 4 caused by oxLDL. In addition, atorvastatin reduces the expression of HDL-binding protein, apolipoprotein E, and matrix metalloproteinase 9. These findings are relevant to understand the direct antiatherogenic effects of statins on macrophages.