Platelet-derived growth factor BB-dimer suppresses the expression of macrophage colony-stimulating factor in human vascular smooth muscle cells

Role of macrophage colony-stimulating factor in the development of neointimal thickening following arterial injury

Evidence suggests that macrophage colony-stimulating factor (M-CSF) participates critically in atherosclerosis; little is known about the role of M-CSF in the development of neointimal hyperplasia following mechanical vascular injury. We examined the expression of M-CSF and its receptor, c-fms, in rodent and rabbit models of arterial injury. Injured rat carotid arteries expressed 3- to 10-fold higher levels of M-CSF and c-fms mRNA and protein following balloon injury as compared to uninjured arteries. In the rabbit, M-CSF protein expression was greatest in neointimal smooth muscle cells (SMCs) postinjury, with some expression in medial SMCs. M-CSF-positive SMCs exhibited markers of proliferation. At 30days postinjury, neointimal SMCs in the adjacent healed area near the border between injured and uninjured zone lost both proliferative activity and overexpression of M-CSF. The presence of induced M-CSF and c-fms expression correlated with the initiation of SMCs proliferation. M-CSF stimulated incorporation of [(3)H] thymidine in human aortic smooth muscle cells in a concentration-dependent manner. Serum-free conditioned medium from aortic SMCs also promoted DNA synthesis, and this effect was blocked by M-CSF specific antibody. To test further the role of M-CSF in vivo, we induced arterial injury by placing a periadventitial collar around the carotid arteries in compound mutant mice lacking apolipoprotein apoE (apoE(-/-)) and M-CSF. Loss of M-CSF abolished the neointimal hyperplastic response to arterial injury in apoE(-/-) mice. Local delivery of M-CSF to the injured artery restored neointimal proliferation, suggesting a critical role of M-CSF for the development of neointimal thickening following arterial injury.

Ferulic acid is nephrodamaging while gallic acid is renal protective in long term treatment of chronic kidney disease

BACKGROUNDS & AIMS

The long term therapeutic effect of ferulic acid (FA) and gallic acid (GA) in treatment of chronic kidney disease (CKD) has been lacking.

METHODS

Doxorubicin (DR, Adriamycin)-induced CKD rat model was established for this study.

RESULTS

DR significantly reduced levels of serum albumin, GOT, GPT, RBC, TNF-α, and urinary creatinine and elevated serum cholesterol, TG, BUN, creatinine, uric acid, WBC, platelet count, and IL-6. In DRCKD rats, FA and GA significantly increased kidney weight and glomerular volume. FA reduced glomerular filtration rate but GA did not. FA enhanced more collagen deposition than GA in renal cortex and glomeruli. Both FA and GA showed crucial hyperlipidemic activity. The inhibitory effects of FA and GA on MMP-2 were very comparable. GA suppressed MMP-2 more effectively than FA in DRCKD rats. Both FA and GA induced SOD elevation and MDA elimination. In DRCKD rats, Western blot analysis indicated that FA further up-regulated CD34, α-SMA, tissue pDGFR, p-PDGFR, and TGF-β; and down-regulated p-PI3K, and p-Akt. Since both PDGF-BB and TGF-β are considered to induce kidney prefibrosis stage, GA was proved to be more beneficial in this regard.

CONCLUSIONS

GA tends to protect the CKD while FA is not recommended for the long term CKD therapy.

mRNA differential display identification of vascular smooth muscle early response genes regulated by PDGF

The modulation of vascular smooth muscle cells (VSMCs) from the quiescent phenotype to the proliferative and migratory phenotype is a critical event in the pathogenesis of atherosclerosis. To-date several growth factors, including platelet-derived growth factor, PDGF, have been shown to induce VSMC proliferation and migration. To further understand the mechanism of PDGF-induced VSMC activation, quiescent human coronary artery SMC were treated with PDGF, and the genes that displayed transcriptional changes within 3 and 8 h were identified using differential display RT-PCR, real-time PCR, nucleotide sequencing and bioinformatics. Eleven genes that were highly upregulated or down-regulated at 3 and/or 8 h by PDGF, designated growth-factor regulated VSMC genes (GRSG1-11), were analyzed. GRSG5 and GRSG9-1 were identified as cortactin and cytochrome c oxidase subunit II, respectively. The remaining nine GRSGs were novel. GRSG3, 4, 5 and 9-2 showed wide tissue distribution whereas GRSG10-1, 10-2, and 11 were tissue specific. Cortactin was localized by immunohistochemical staining to the neointima and fibrous cap of human coronary artery atherosclerotic plaques. Domain analysis of open reading frames suggest that the novel GRSGs may participate in signaling, metabolic, translational or migrational processes during PDGF-induced VSMC activation.

Inflammatory mechanisms: the molecular basis of inflammation and disease

Inflammation participates importantly in host defenses against infectious agents and injury, but it also contributes to the pathophysiology of many chronic diseases. Interactions of cells in the innate immune system, adaptive immune system, and inflammatory mediators orchestrate aspects of the acute and chronic inflammation that underlie diseases of many organs. A coordinated series of common effector mechanisms of inflammation contribute to tissue injury, oxidative stress, remodeling of the extracellular matrix, angiogenesis, and fibrosis in diverse target tissues. Atherosclerosis provides an example of a chronic disease that involves inflammatory mechanisms. Recruitment of blood leukocytes characterizes the initiation of this disease. Its progression involves many inflammatory mediators, modulated by cells of both innate and adaptive immunity. The complications of established atheroma, including plaque disruption and thrombosis, also intimately involve inflammation. Mastery of the inflammatory response should aid the development of novel strategies to predict disease susceptibility, target and monitor therapies, and ultimately develop new approaches to the prevention and treatment of chronic diseases associated with aging, such as atherosclerosis.

PDGF up-regulates CSF-1 gene transcription in ameloblast-like cells

Macrophage colony-stimulating factor (CSF-1) is a key regulatory cytokine for amelogenesis, and ameloblasts synthesize CSF-1. We hypothesized that PDGF stimulates DNA synthesis and regulates CSF-1 in these cells. We determined the effect of PDGF on CSF-1 expression using MEOE-3M ameloblasts as a model. By RT-PCR, MEOE-3M expressed PDGFRs and PDGF A- and B-chain mRNAs. PDGF-BB increased DNA synthesis and up-regulated CSF-1 mRNA and protein in MEOE-3M. Cells transfected with CSF-1 promoter deletion constructs were analyzed. A PDGF-responsive region between -1.7 and -0.795 kb, containing a consensus Pea3 binding motif, was identified. Electrophoretic mobility shift assay (EMSA) showed that PDGF-BB stimulated protein binding to this motif that was inhibited in the presence of anti-Pea3 antibody. Analysis of these data provides the first evidence that PDGF-BB is a mitogen for MEOE-3M and increases CSF-1 protein levels, predominantly by transcription. Elucidation of the cellular pathways that control CSF-1 expression may provide novel strategies for the regulation of enamel matrix formation.

Emodin Induces Growth Arrest and Death of Human Vascular Smooth Muscle Cells Through Reactive Oxygen Species and p53

Percutaneous coronary intervention is the main therapy for revascularization of occluded coronary arteries. However, a progressive artery restenosis caused by abnormal proliferation and migration of vascular smooth muscle cells (VSMC) hinders the effective treatment. In this study, we examined the effect of emodin, a natural anthraquinoid compound, on cultured VSMC. Lower doses of emodin suppressed cell proliferation and induced unscheduled DNA synthesis. Higher doses of emodin increased lumpy chromatin condensation and lysosomes in VSMC, suggesting the occurrence of apoptosis and autophagy. Emodin increased production of reactive oxygen species (ROS), which was abolished by an NADPH oxidase inhibitor diphenylene iodonium (DPI). DPI could also decrease the number of apoptosis induced by emodin, suggesting the involvement of ROS in emodin-induced apoptosis. Emodin upregulated the protein levels of p53 in a dose-dependent manner. Laser confocal microscope showed most of emodin scattering in the cytoplasms and a little within the nuclei. These findings collectively indicated that emodin induces both growth arrest and death of human VSMCs in 2 independent manners, implying it as a promising therapy for preventing restenosis.

Secretion of macrophage migration inhibitory factor differs from interleukin-6 in hydrogen peroxide- and LPS-stimulated human fibroblasts

To investigate the mechanism for secretion of macrophage migration inhibitory factor (MIF) in cultured human fibroblasts, we compared it with the secretion of interleukin-6 (IL-6) after stimulation with lipopolysaccharides (LPS) and H2O2. MIF content of the medium of 2.0 x 10(6) cells/20 ml after 20 h culture of nonstimulated fibroblasts was 0.30 +/- 0.06 ng/ml, whereas LPS-stimulation (10 microg/ml) only led to a 1.5-fold increase as compared with the nonstimulated cells. In contrast, a significant increase of IL-6 was induced by LPS-stimulation (6048 +/- 488 pg/ml in LPS-stimulated cells vs. 58 +/- 36 pg/ml in control cells). On the other hand, higher concentrations of H2O2 (0.6-1.2 mM) caused an increase of MIF secretion into the culture medium irrespective of LPS-stimulation; with 1.2 mM H2O2-stimulation for 20 h, it was increased to 40-fold as compared with the nonstimulated cells. However, lower concentrations (0.1-0.4 mM) did not cause this. Interestingly, H2O2-stimulation not only failed to increase IL-6 production from fibroblasts, but also repressed induction of IL-6 by LPS-stimulation in a dose-dependent manner. Genistein, a tyrosine kinase inhibitor, and H-7, a protein kinase C inhibitor, also inhibited IL-6 secretion but not MIF secretion in both LPS- and H2O2-stimulated fibroblasts. From analysis of trypan blue exclusion, formazan formation, morphological changes, and intracellular MIF content by Western blotting, we found that MIF secretion by H2O2 seemed to be mainly due to cell death and subsequent leakage of intracellular MIF. Taken together, these results suggest that MIF secretion differs from IL-6 via LPS-mediated signaling pathways.

Serum macrophage colony-stimulating factor (M-CSF) level is elevated in patients with old cerebral infarction related to vascular damage

We measured the serum levels of macrophage colony-stimulating factor (M-CSF) in 37 patients with an old cerebral infarction who had been surmised to have a damaged vessel wall and who had been in a stable condition for over three months after stroke onset, and those of 41 healthy control subjects. The M-CSF levels in the patients were significantly higher (P < 0.01) than those of the controls at 1320.4 +/- 410.6 unit/ml and 853.9 +/- 180.3 unit/ml, respectively. The plasma levels of von Willebrand factor (vWF) antigen (P < 0.01) and thrombomodulin (TM) (P < 0.05), as well as those of thrombin-antithrombin III (TAT) complex (P < 0.05), prothrombin fragment 1+2 (F1+2) (P < 0.02), D-dimer products of crosslinked fibrin degradation products (D-dimer) (P < 0.01), and plasmin-antiplasmin (PAP) complex (P < 0.05) in the patients were also significantly higher than those in the controls. Significant positive correlations (P < 0.01) were found between these parameters and the M-CSF level, but there was no significant correlation between the M-CSF level and the white blood cell count, serum lipids, or blood pressure. Based on these results, we suggest that an increased M-CSF level indicates vascular damage or a thrombotic state in patients with an old cerebral infarction.

Effects of CSF-1 on cholesterol accumulation and efflux by macrophages

To assess whether human monocyte-specific colony-stimulating factor (CSF-1) might influence atherogenesis, CSF-1-induced macrophage responses that might contribute to enhanced clearance of low-density lipoprotein (LDL) or modified LDL were investigated. Careful account was made of cell preservation and increases in cell volume and protein (representing increased cell surface area, and thus endocytically active membrane) during culture with CSF-1. This permitted distinction between selective and nonspecific effects of CSF-1, the latter paralleling increases in cellular mass and volume. CSF-1 enhanced mouse peritoneal macrophage survival in vitro during exposure to lipoprotein-deficient serum with or without native LDL or acetylated LDL (Ac-LDL), as judged by maintenance of cellular DNA and cell numbers. In the presence of copper-oxidized LDL (Ox-LDL), such effects were very slight. In all conditions, CSF-1 increased cellular protein content. CSF-1 increased the uptake of both Ac-LDL and Ox-LDL calculated per culture, but this was entirely explicable by the increased cell protein, indicating that there was no selective enhancement of scavenger receptor or other routes for uptake of the modified LDLs. Similarly, CSF-1 also increased the accumulation of cholesterol and its esters nonspecifically. CSF-1 did have a marked and specific effect on the composition of cholesterol esters, decreasing the proportion of polyunsaturated esters relative to monounsaturated and saturated esters. Finally, cholesterol efflux induced by apolipoprotein A1 from Ac-LDL-loaded macrophages was not influenced by CSF-1. Thus, the enhanced macrophage catabolism of modified LDLs by CSF-1 is part of a nonspecific action on the cells but could contribute to a reduction in circulating cholesterol, observed in some situations of CSF-1 presentation in humans.

Differentiated properties and proliferation of arterial smooth muscle cells in culture

The smooth muscle cell is the sole cell type normally found in the media of mammalian arteries. In the adult, it is a terminally differentiated cell that expresses cytoskeletal marker proteins like smooth muscle alpha-actin and smooth muscle myosin heavy chains, and contracts in response to chemical and mechanical stimuli. However, it is able to revert to a proliferative and secretory active state equivalent to that seen during vasculogenesis in the fetus, and this is a prerequisite for the involvement of the smooth muscle cell in the formation of atherosclerotic and restenotic lesions. A similar transition from a contractile to a synthetic phenotype occurs when smooth muscle cells are established in culture. Accordingly, an in vitro system has been used extensively to study the regulation of differentiated properties and proliferation of these cells. During the first few days after seeding, the cells are reorganized structurally with a loss of myofilaments and formation of a widespread endoplasmic reticulum and a prominent Golgi complex. In parallel, they lose their contractility and instead become competent to divide in response to a large variety of mitogens, including platelet-derived growth factor (PDGF) and basic fibroblast growth factor (bFGF). After entering the cell cycle, they start to produce these and other mitogens on their own, and continue to replicate in the absence of exogenous stimuli for a restricted number of generations. Furthermore, they start to secrete extracellular matrix components such as collagen, elastin, and proteoglycans. The mechanisms that control this change in morphology and function of the smooth muscle cells are still poorly understood. Adhesive proteins such as fibronectin and laminin apparently have an important role in determining the basic phenotypic state of the cells and exert their effects via integrin receptors. The proliferative and secretory activities of the cells are influenced by a multitude of growth factors, cytokines, and other molecules. Although much work remains before an integrated view of this regulatory machinery can be achieved, there is no doubt that the cell culture technique has contributed substantially to our knowledge of smooth muscle differentiation and growth. At the same time, it has been crucial in exploring the role of these cells in vascular disease and developing new therapeutic strategies to cope with major causes of human death and disability.

Independent regulation of cholesterol incorporation into free apolipoprotein-mediated cellular lipid efflux in rat vascular smooth muscle cells

Cholesterol was poorly available to free apolipoprotein (apo)A-I-mediated cellular lipid efflux from cholesterol-loaded rat vascular smooth muscle cells generating cholesterol-poorer pre-beta-HDL particles than those generated from macrophages by the same reaction (Li, Q., Komaba, A., and Yokoyama, S. (1993) Biochemistry 32, 4597-4603). The factors known to induce transformation of the smooth muscle cells into a macrophage-like stage were used in order to modulate this reaction, such as human platelet-derived growth factor, macrophage colony-stimulating factor, and phorbol 12-myristate-13-acetate (PMA). When the cells were stimulated by PMA following the pretreatment with platelet-derived growth factor plus macrophage colony-stimulating factor, cholesterol efflux mediated by free apoA-I increased 3-fold without changing phospholipid efflux, resulting in generation of pre-beta-HDL particles more rich in cholesterol. This treatment had only a little or no effect on apparent cellular cholesterol efflux to HDL or lipid microemulsion, respectively. Overall cellular free cholesterol pool size was unaffected by the treatment, and probing by extracellular cholesterol oxidase did not detect gross change in the cellular surface cholesterol. This specific enrichment of cholesterol in the apoA-I-mediated cellular lipid efflux was reversed by protein kinase C inhibitors. Measurement of intracellular cholesterol esterification suggested that PMA induced translocation of intracellular cholesterol to a specific pool for apoA-I-mediated efflux, and a protein kinase C inhibitor reversed this effect.

Effects of platelet-derived growth factor on the synthesis of lipoprotein lipase in human monocyte-derived macrophages

Lipoprotein lipase (LPL), which is secreted by the two predominant cell types in atherosclerotic plaque, macrophages and smooth muscle cells, may be involved in atherosclerosis by generating atherogenic remnant lipoproteins. We investigated the effects of platelet-derived growth factor (PDGF)-BB on the synthesis of LPL by human monocyte-derived macrophages. These cells were cultured in the presence of PDGF-BB for 8 days, after which the enzyme activity, mass, and mRNA levels of LPL were determined. The effect of PDGF-BB was time-dependent and dose-dependent at concentrations of 1 to 10 ng/mL. At 10 ng/mL PDGF-BB enhanced twofold to 2.3-fold the secretion of LPL, and a pulse-labeling study with [35S]methionine revealed that 10 ng/mL PDGF-BB significantly increased the synthesis of LPL. Northern blotting analysis showed that the LPL mRNA level increased dose dependently in macrophages treated with PDGF-BB, and 10 ng/mL PDGF-BB enhanced twofold the expression of LPL mRNA. The protein kinase C inhibitor staurosporine suppressed the effect of PDGF-BB on LPL activity. These results indicate that PDGF-BB stimulated transcription of the LPL gene in human monocyte-derived macrophages through protein kinase C activation and resulted in an increased synthesis of LPL. Therefore, we hypothesize that the augmented synthesis of LPL by PDGF-BB modulates atherosclerosis by influencing lipoprotein metabolism in the vascular wall.

Induction of LDL receptor-related protein during the differentiation of monocyte-macrophages. Possible involvement in the atherosclerotic process

The low-density lipoprotein receptor-related protein (LRP) is a multifunctional receptor that binds to apolipoprotein E-rich lipoproteins, lipoprotein lipase, alpha 2-macroglobulin, lactoferrin, and tissue plasminogen activator. We studied the mRNA expression of LRP in human monocyte-derived macrophages and THP-1 cells. mRNA expression of LRP was induced during cell differentiation from human monocytes to macrophages or after incubation with phorbol ester (tetradecanoylphorbol acetate 100 ng/mL) in THP-1 cells, and the addition of 30 ng/mL macrophage colony-stimulating factor further enhanced LRP expression. These results indicated that the expression of LRP depended on the stage of differentiation and maturation of monocytic cells. mRNA expression of LRP was also enhanced in human monocyte-derived macrophages in the presence of acetylated low-density lipoprotein and in aorta of rabbits fed a high-cholesterol diet. We hypothesize that the LRP induced in monocyte-derived macrophages is involved in the initial process of atherosclerosis by interacting with its multiple ligands.