Granulocyte/macrophage colony-stimulating factor plays an essential role in oxidized low density lipoprotein-induced macrophage proliferation

Association between hyperlipidemia and prostatic enlargement: A case-control study

OBJECTIVE

A high-fat diet is associated with the development of benign prostatic enlargement (BPE), but whether hyperlipidemia is associated with BPE remains unclear. This study aimed to evaluate whether hyperlipidemia is a risk factor for the development of BPE.

MATERIAL AND METHODS

This study included 265 BPE patients with lower urinary tract symptoms (LUTS) and 248 age-matched healthy individuals without LUTS. The patient and control groups included in the study were compared in terms of fasting serum glucose, serum lipid values, prostate specific antigen (PSA), and prostate size measured by abdominal ultrasonography.

RESULTS

The prostate sizes of the patient and healthy control group were 59.4 ± 12.6 and 41.8 ± 11.1 ml, respectively (p = 0.007). It was observed that the mean PSA value of the patient group (2.33 ± 1.69) was statistically higher than that of the control group (1.21 ± 1.05) (p = 0.002). Total cholesterol and LDL-cholesterol were significantly higher and HDL-cholesterol was significantly lower among the patients compared to the controls. Prostate size had a negative correlation with HDL-cholesterol and a positive correlation with LDL-cholesterol and total cholesterol. Additionally, LDL-cholesterol and total cholesterol were independent risk factors for prostate enlargement.

CONCLUSION

This study indicates that increased levels of LDL-cholesterol and total cholesterol are significantly associated with the enlargement of the prostate. Hyperlipidemia may be one of the risk factors in the processes of prostatic growth and progression.

Atherogenic LOX-1 signaling is controlled by SPPL2-mediated intramembrane proteolysis

The intramembrane proteases SPPL2a/b control pro-atherogenic signaling of membrane-bound proteolytic fragments derived from the oxLDL receptor LOX-1. In mice deficient for these proteases, plaque development and fibrosis is enhanced. This highlights SPPL2a/b as crucial players of a novel athero-protective mechanism, which is conserved in humans.

The lectin-like oxidized LDL receptor 1 (LOX-1) is a key player in the development of atherosclerosis. LOX-1 promotes endothelial activation and dysfunction by mediating uptake of oxidized LDL and inducing pro-atherogenic signaling. However, little is known about modulators of LOX-1–mediated responses. Here, we show that the function of LOX-1 is controlled proteolytically. Ectodomain shedding by the metalloprotease ADAM10 and lysosomal degradation generate membrane-bound N-terminal fragments (NTFs), which we identified as novel substrates of the intramembrane proteases signal peptide peptidase–like 2a and b (SPPL2a/b). SPPL2a/b control cellular LOX-1 NTF levels which, following self-association via their transmembrane domain, can activate MAP kinases in a ligand-independent manner. This leads to an up-regulation of several pro-atherogenic and pro-fibrotic targets including ICAM-1 and the connective tissue growth factor CTGF. Consequently, SPPL2a/b-deficient mice, which accumulate LOX-1 NTFs, develop larger and more advanced atherosclerotic plaques than controls. This identifies intramembrane proteolysis by SPPL2a/b as a novel atheroprotective mechanism via negative regulation of LOX-1 signaling.

Time course of cardiac inflammation during nitric oxide synthase inhibition in SHR: impact of prior transient ACE inhibition

We have previously demonstrated that angiotensin-converting enzyme (ACE) inhibition with enalapril produces persistent effects that protect against future nitric oxide synthase (NOS) inhibitor (L-arginine methyl ester, L-NAME)-induced cardiac dysfunction and outer wall collagen deposition in spontaneously hypertensive rats (SHR). In the present study, we dissect the cytokine/chemokine release profile during NOS inhibition, its correlation to pathological cardiac remodeling and the impact of transient ACE inhibition on these effects. Adult male SHR were treated with enalapril (E+L) or tap water (C+L) for 2 weeks followed by a 2-week washout period. Rats were then subjected to 0, 3, 7 or 10 days of L-NAME treatment. The temporal response to NOS inhibition was evaluated by measuring arterial pressure, cardiac remodeling and cytokine/chemokine levels. L-NAME equivalently increased blood pressure and myocardial and vascular injury in C+L and E+L rats. However, pulse pressure (PP) was only transiently altered in C+L rats. The levels of several inflammatory mediators were increased during L-NAME treatment. However, interleukin-6 (IL-6) and IL-10 and monocyte chemoattractant protein-1 were uniquely increased in C+L hearts; whereas IL-4 and fractalkine were only elevated in E+L hearts. By days 7 and 10 of L-NAME treatment, there was a significant increase in the cardiac density of macrophages and proliferating cells, respectively only in C+L rats. Although myocardial injury was similar in both treatment groups, PP was not changed and there was a distinct cardiac chemokine/cytokine signature in rats previously treated with enalapril that may be related to the lack of proliferative response and macrophage infiltration in these hearts.

PI3K p110γ deletion attenuates murine atherosclerosis by reducing macrophage proliferation but not polarization or apoptosis in lesions

Atherosclerosis is an inflammatory disease regulated by infiltrating monocytes and T cells, among other cell types. Macrophage recruitment to atherosclerotic lesions is controlled by monocyte infiltration into plaques. Once in the lesion, macrophage proliferation in situ, apoptosis, and differentiation to an inflammatory (M1) or anti-inflammatory phenotype (M2) are involved in progression to advanced atherosclerotic lesions. We studied the role of phosphoinositol-3-kinase (PI3K) p110γ in the regulation of in situ apoptosis, macrophage proliferation and polarization towards M1 or M2 phenotypes in atherosclerotic lesions. We analyzed atherosclerosis development in LDLR^−/−p110γ^+/− and LDLR^−/−p110γ^−/− mice, and performed expression and functional assays in tissues and primary cells from these and from p110γ^+/− and p110γ^−/− mice. Lack of p110γ in LDLR^−/− mice reduces the atherosclerosis burden. Atherosclerotic lesions in fat-fed LDLR^−/−p110γ^−/− mice were smaller than in LDLR^−/−p110γ^+/− controls, which coincided with decreased macrophage proliferation in LDLR^−/−p110γ^−/− mouse lesions. This proliferation defect was also observed in p110γ^−/− bone marrow-derived macrophages (BMM) stimulated with macrophage colony-stimulating factor (M-CSF), and was associated with higher intracellular cyclic adenosine monophosphate (cAMP) levels. In contrast, T cell proliferation was unaffected in LDLR^−/−p110γ^−/− mice. Moreover, p110γ deficiency did not affect macrophage polarization towards the M1 or M2 phenotypes or apoptosis in atherosclerotic plaques, or polarization in cultured BMM. Our results suggest that higher cAMP levels and the ensuing inhibition of macrophage proliferation contribute to atheroprotection in LDLR^−/− mice lacking p110γ. Nonetheless, p110γ deletion does not appear to be involved in apoptosis, in macrophage polarization or in T cell proliferation.

Macrophage proliferation and apoptosis in atherosclerosis

PURPOSE OF REVIEW

Atherosclerosis is driven by cardiovascular risk factors that cause the recruitment of circulating immune cells beneath the vascular endothelium. Infiltrated monocytes differentiate into different macrophage subtypes with protective or pathogenic activities in vascular lesions. We discuss current knowledge about the molecular mechanisms that regulate lesional macrophage proliferation and apoptosis, two processes that occur during atherosclerosis development and regulate the number and function of macrophages within the atherosclerotic plaque.

RECENT FINDINGS

Lesional macrophages in early phases of atherosclerosis limit disease progression by phagocytizing modified lipoproteins, cellular debris and dead cells that accumulate in the plaque. However, macrophages in advanced lesions contribute to a maladaptive, nonresolving inflammatory response that can lead to life-threatening acute thrombotic diseases (myocardial infarction or stroke). Macrophage-specific manipulation of genes involved in cell proliferation and apoptosis modulates lesional macrophage accumulation and atherosclerosis burden in mouse models, and studies are beginning to elucidate the underlying mechanisms.

SUMMARY

Despite recent advances in our understanding of macrophage proliferation and apoptosis in atherosclerotic plaques, it remains unclear whether manipulating these processes will be beneficial or harmful. Advances in these areas may translate into more efficient therapies for the prevention and treatment of atherothrombosis.

Oxidatively modified low density lipoprotein (LDL) inhibits TLR2 and TLR4 cytokine responses in human monocytes but not in macrophages

Inflammation characterized by the expression and release of cytokines and chemokines is implicated in the development and progression of atherosclerosis. Oxidatively modified low density lipoproteins, central to the formation of atherosclerotic plaques, have been reported to signal through Toll-like receptors (TLRs), TLR4 and TLR2, in concert with scavenger receptors to regulate the inflammatory microenvironment in atherosclerosis. This study evaluates the role of low density lipoproteins (LDL) and oxidatively modified LDL (oxmLDL) in the expression and release of proinflammatory mediators IκBζ, IL-6, IL-1β, TNFα, and IL-8 in human monocytes and macrophages. Although standard LDL preparations induced IκBζ along with IL-6 and IL-8 production, this inflammatory effect was eliminated when LDL was isolated under endotoxin-restricted conditions. However, when added with TLR4 and TLR2 ligands, this low endotoxin preparation of oxmLDL suppressed the expression and release of IL-1β, IL-6, and TNFα but surprisingly spared IL-8 production. The suppressive effect of oxmLDL was specific to monocytes as it did not inhibit LPS-induced proinflammatory cytokines in human macrophages. Thus, TLR ligand contamination of LDL/oxmLDL preparations can complicate interpretations of inflammatory responses to these modified lipoproteins. In contrast to providing a proinflammatory function, oxmLDL suppresses the expression and release of selected proinflammatory mediators.

PI3Ks-drug targets in inflammation and cancer

Phosphoinositide 3-kinases (PI3Ks) control cell growth, proliferation, cell survival, metabolic activity, vesicular trafficking, degranulation, and migration. Through these processes, PI3Ks modulate vital physiology. When over-activated in disease, PI3K promotes tumor growth, angiogenesis, metastasis or excessive immune cell activation in inflammation, allergy and autoimmunity. This chapter will introduce molecular activation and signaling of PI3Ks, and connections to target of rapamycin (TOR) and PI3K-related protein kinases (PIKKs). The focus will be on class I PI3Ks, and extend into current developments to exploit mechanistic knowledge for therapy.

Periadventitial delivery of anti-EGF receptor antibody inhibits neointimal macrophage accumulation after angioplasty in a hypercholesterolaemic rabbit

Monocyte recruitment and their differentiation into macrophages are both early events in native and accelerated atherosclerosis that follows angioplasty. We have investigated the putative functional role of the epidermal growth factor receptor (EGFR) present on rabbit monocytes/macrophages. The impact of periadventitial delivery of an EGFR-specific, blocking monoclonal antibody (ICR62, which inhibits EGF-binding to its receptor) was investigated in a rabbit model of accelerated atherosclerosis induced by a combination of carotid injury and 4 weeks of a 2% cholesterol-diet. Two weeks after the initiation of the diet, a balloon-catheter angioplasty of the left common carotid artery was performed and a collar placed around the injured carotid artery immediately, for the delivery of ICR62 antibody, isotype-matched antibody or saline control. Monocyte/macrophage accumulation, cell proliferation and neointimal thickening were determined 2 weeks after the delivery of the antibodies. The function of the EGFR on rabbit monocytes was also investigated in vitro, using chemotaxis assays. Treatment with ICR62 was associated with a significant reduction in macrophage accumulation and neointimal thickening and a 76% reduction in neointimal area of the vessel wall compared with controls. In vitro ICR62 inhibited macrophage and smooth muscle cell migration towards EGFR ligands including EGF and HB-EGF. These findings suggest that EGFR ligation may be important in the development of early atherosclerotic lesions following balloon-catheter angioplasty, and periadventitial delivery may provide a feasible approach for administration of the inhibitors of EGFR-binding such as ICR62.

Simvastatin Reduces Chlamydophila pneumoniae –Mediated Histone Modifications and Gene Expression in Cultured Human Endothelial Cells

Inflammatory activation of the endothelium by Chlamydophila pneumoniae infection has been implicated in the development of chronic vascular lesions and coronary heart disease by seroepidemiological and animal studies. We tested the hypothesis that C pneumoniae induced inflammatory gene expression is regulated by Rho-GTPase–related histone modifications. C pneumoniae infection induced the liberation of proinflammatory interleukin-6, interleukin-8, granulocyte colony-stimulating factor, macrophage inflammatory protein-1β, granulocyte/macrophage colony-stimulating factor, and interferon-γ by human endothelial cells. Cytokine secretion was reduced by simvastatin and the specific Rac1 inhibitor NSC23766 but was synergistically enhanced by inhibitors of histone deacetylases trichostatin A and suberoylanilide hydroxamic acid. Infection of endothelial cells with viable C pneumoniae , but not exposure to heat-inactivated C pneumoniae or infection with C trachomatis , induced acetylation of histone H4 and phosphorylation and acetylation of histone H3. Pretreatment of C pneumoniae –infected cells with simvastatin or NSC23766 reduced global histone modifications as well as specific modifications at the il8 gene promoter, as shown by chromatin immunoprecipitation. Reduced recruitment of nuclear factor κB p65/RelA as well as of RNA polymerase II was observed in statin-treated cells. Taken together, Rac1-mediated histone modifications seem to play an important role in C pneumoniae –induced cytokine production by human endothelial cells.

Targeting phosphoinositide 3-kinase: moving towards therapy

Phosphoinositide 3-kinases (PI3K) orchestrate cell responses including mitogenic signaling, cell survival and growth, metabolic control, vesicular trafficking, degranulation, cytoskeletal rearrangement and migration. Deregulation of the PI3K pathway occurs by activating mutations in growth factor receptors or the PIK3CA locus coding for PI3Kalpha, by loss of function of the lipid phosphatase and tensin homolog deleted in chromosome ten (PTEN/MMAC/TEP1), by the up-regulation of protein kinase B (PKB/Akt), or the impairment of the tuberous sclerosis complex (TSC1/2). All these events are linked to growth and proliferation, and have thus prompted a significant interest in the pharmaceutical targeting of the PI3K pathway in cancer. Genetic targeting of PI3Kgamma (p110gamma) and PI3Kdelta (p110delta) in mice has underlined a central role of these PI3K isoforms in inflammation and allergy, as they modulate chemotaxis of leukocytes and degranulation in mast cells. Proof-of-concept molecules selective for PI3Kgamma have already successfully alleviated disease progress in murine models of rheumatoid arthritis and lupus erythematosus. As targeting PI3K moves forward to therapy of chronic, non-fatal disease, safety concerns for PI3K inhibitors increase. Many of the present inhibitor series interfere with target of rapamycin (TOR), DNA-dependent protein kinase (DNA-PK(cs)) and activity of the ataxia telangiectasia mutated gene product (ATM). Here we review the current disease-relevant knowledge for isoform-specific PI3K function in the above mentioned diseases, and review the progress of >400 recent patents covering pharmaceutical targeting of PI3K. Currently, several drugs targeting the PI3K pathway have entered clinical trials (phase I) for solid tumors and suppression of tissue damage after myocardial infarction (phases I,II).

Deletion of the phosphoinositide 3-kinase p110gamma gene attenuates murine atherosclerosis

Inflammatory cell activation by chemokines requires intracellular signaling through phosphoinositide 3-kinase (PI3-kinase) and the PI3-kinase-dependent protein serine/threonine kinase Akt. Atherosclerosis is a chronic inflammatory process driven by oxidatively modified (atherogenic) lipoproteins, chemokines, and other agonists that activate PI3-kinase. Here we show that macrophage PI3-kinase/Akt is activated by oxidized low-density lipoprotein, inflammatory chemokines, and angiotensin II. This activation is markedly reduced or absent in macrophages lacking p110gamma, the catalytic subunit of class Ib PI3-kinase. We further demonstrate activation of macrophage/foam cell PI3-kinase/Akt in atherosclerotic plaques from apolipoprotein E (apoE)-null mice, which manifest an aggressive form of atherosclerosis, whereas activation of PI3-kinase/Akt was undetectable in lesions from apoE-null mice lacking p110gamma despite the presence of class Ia PI3-kinase. Moreover, plaques were significantly smaller in apoE-/-p110gamma-/- mice than in apoE-/-p110gamma+/+ or apoE-/-p110gamma+/-mice at all ages studied. In marked contrast to the embryonic lethality seen in mice lacking class Ia PI3-kinase, germ-line deletion of p110gamma results in mice that exhibit normal viability, longevity, and fertility, with relatively well tolerated defects in innate immune and inflammatory responses that may play a role in diseases such as atherosclerosis and multiple sclerosis. Our results not only shed mechanistic light on inflammatory signaling during atherogenesis, but further identify p110gamma as a possible target for pharmacological intervention in the primary and secondary prevention of human atherosclerotic cardiovascular disease.

Granulocyte colony-stimulating factor and granulocyte macrophage colony-stimulating factor exacerbate atherosclerosis in apolipoprotein E-deficient mice

BACKGROUND

Recent studies have suggested a potential contribution of bone marrow-derived progenitor cells to vascular repair. Preliminary clinical studies have explored the possibility that mobilization of progenitor cells with granulocyte macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) can affect vascular repair. However, it is not known whether the short-term administration of G-CSF or GM-CSF exerts beneficial effects on atherosclerosis.

METHODS AND RESULTS

Apolipoprotein E-deficient mice were treated with either GM-CSF or G-CSF at a dose of 10 microg x kg(-1) x d(-1) s.c. administered daily for 5 days per week on alternating weeks for a total of 20 doses over an 8-week treatment period. We found that in animals maintained on a high-fat diet, both G-CSF and GM-CSF actually demonstrated an increase in atherosclerotic lesion extent. The increase in atherosclerotic extent was not associated with an increase in either inflammatory cells or expression of proinflammatory genes. Interestingly, adventitial vascularity significantly increased, suggesting a mechanistic role for vasa vasorum neovascularization.

CONCLUSIONS

These findings demonstrate that in this animal model of atherosclerosis, not only did administration of G-CSF or GM-CSF fail to demonstrate any beneficial therapeutic effect, but both resulted in a worsening of atherosclerosis.

Lethal and severe coronary arteritis in DBA/2 mice induced by fungal pathogen, CAWS, Candida albicans water-soluble fraction

CAWS is a microbial pathogen-associated molecular patterns (PAMPs) produced by Candida albicans. CAWS is a mannoprotein-beta-glucan complex and secreted into the culture supernatant. CAWS has various biological effects, causing acute shock and disrupting vascular permeability. Intraperitoneal administration of CAWS induces coronary arteritis in various strains of inbred mice. The CAWS-induced coronary arteritis is strain-dependent and most severe in DBA/2 mice with a significant number of these animals expiring with cardiomegaly during the observation period. In vivo and in vitro, splenocytes of DBA/2 mice produced various cytokines, such as IL-6, TNF-alpha, and IFN-gamma in response to CAWS. GM-CSF was also produced in response to CAWS. The production of cytokines was significantly enhanced in the presence of recombinant GM-CSF. In contrast, anti-GM-CSF significantly reduced the production of TNF-alpha and IFN-gamma. Augmented production of cytokines in response to CAWS would be a key to the severity of coronary arteritis.

Hyperinsulinemia and dyslipidemia in non-diabetic benign prostatic hyperplasia

BACKGROUND

BPH is a multifactorial disease. Several studies have elucidated the role of hormones and growth factors in its etiology. Insulin is a growth-stimulating hormone. Previous studies have reported the association between hyperinsulinemia, dyslipidemia and BPH in patients with metabolic disorders like diabetes. We evaluated insulin and lipid profile parameters in non-diabetic BPH cases and correlated it with prostate size.

METHODS

50 symptomatic BPH cases and 38 controls were included in this study. Fasting serum insulin concentrations were measured by radioimmunoassay. Insulin resistance was assessed by HOMA. Fasting glucose, total cholesterol and triglycerides were quantified by enzymatic methods. HDL-cholesterol was quantified by phosphotungstate magnesium chloride method. LDL-cholesterol was calculated by Friedwald's formula.

RESULTS

Fasting serum insulin, HOMA, total cholesterol, and LDL-cholesterol were significantly higher and HDL-cholesterol was significantly lower in cases as compared to controls. Insulin was significantly associated with prostate size, cholesterol, triglycerides, VLDL-cholesterol and LDL-cholesterol in BPH cases. Stepwise regression analysis showed insulin as an independent risk factor in the development of BPH.

CONCLUSIONS

Hyperinsulinemia associated with insulin resistance is an independent risk factor in the development of BPH.

EGF mediates monocyte chemotaxis and macrophage proliferation and EGF receptor is expressed in atherosclerotic plaques

The recruitment of peripheral monocytes to the sub-endothelial space, their development into macrophages and subsequent proliferation are critical events during atherosclerosis. Receptors for epidermal growth factor (EGF) have been identified on cells of the myeloid lineage, but a role for them in atherogenesis has yet to be described. We have identified functional EGF receptors (EGFR, ErbB1/HER-1) on peripheral blood monocytes and monocyte-derived macrophages. Uniquely, these receptors were found to mediate both chemotaxis in monocytes and macrophages and proliferation in macrophages. EGFR mRNA was detected in atherosclerotic plaques, but not in morphologically normal aortae and EGFR receptor staining co-localised with macrophage staining in these plaques. The identification of receptors for EGF on peripheral blood monocytes, macrophages and atherosclerotic lesions, together with their transduction of two functionally important cellular events, heightens the potential importance of members of the EGF super-family in atherogenesis and other chronic inflammatory processes.

GM-CSF activates RhoA, integrin and MMP expression in human monocytic cells

Monocyte migration is one of the key events occurring in the early stage of atherosclerosis. This process includes monocytic adhesion to and penetration through the arterial intima. In such an environment, many factors stimulate the monocytes to enhance integrin activation and extracellular matrix degradation. To investigate the coordinative operation of these two events in relation to monocyte migration, we paid particular attention to the effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) on monocytes in terms of RhoA activation and matrix metalloproteinase (MMP) expression. RhoA and integrin clustering were activated by GM-CSF, monocyte chemoattractant protein-1 (MCP-1) and platelet-derived growth factor-BB (PDGF-BB) in human monocytic cell lines. Furthermore, enhancement of migration was observed with stimulation by MCP-1 and PDGF-BB. Granulocyte-macrophage colony-stimulating factor did not enhance the migration, even though it activated RhoA and integrin. However, GM-CSF is known to stimulate monocytes to express MCP-1, suggesting the presence of an indirect mechanism for GM-CSF-mediated migratory activity. In contrast, only GM-CSF enhanced the expression of MMP-1 and MMP-9. These results provide evidence that GM-CSF has multiple functions enhancing monocytic migration via RhoA and integrin activation, and via MMP expression.

A model for PKC involvement in the pathogenesis of inborn errors of metabolism

A model for the possible involvement of Protein Kinase C (PKC) in the pathogenesis of inborn errors of metabolism has been proposed. According to this model, perturbation of PKC activity by the accumulation of naturally occurring compounds serves as a unifying functional link between genotype and phenotype. Recent reports regarding an increasing number of modulating metabolites, specific PKC-subtypes activities, their effect on transcription factors and gene expression in various diseases and additional PKC-substrates expand the model. A re-examination of the proposed model in view of these reports and, vice versa, a review of these reports in the context of the proposed model reveal some common phenotypic outcomes in inborn errors of fatty acid-, cholesterol- and homocystine-metabolism as well as lysosomal and peroxisomal diseases.