Suppressive role of endogenous endothelial monocyte chemoattractant protein-1 on monocyte transendothelial migration in vitro

Ocimum sanctum leaf extracts attenuate human monocytic (THP-1) cell activation

ETHNOPHARMACOLOGICAL RELEVANCE

Ocimum sanctum (OS), commonly known as Holy basil/Tulsi, has been traditionally used to treat cardiovascular diseases (CVD) and manage general cardiac health. The present study is designed to evaluate the antiinflammatory effect of O. sanctum and its phenolic compound and eugenol (EUG) in human monocytic (THP-1) cells and validate its traditional use for treating cardiovascular diseases.

MATERIALS AND METHODS

The phytochemical analysis of alcoholic and water extracts of OS-dry leaves (OSAE and OSWE) was done using LC-QTOF-MS. A phenolic compound, EUG was quantified in both OSAE and OSWE by an LC-MS technique using a mass hunter work station software quantitative analysis system. The effect of both OSAE, OSWE, pure compound EUG and positive control imatinib (IMT) was investigated in THP-1 cells by studying the following markers: lipopolysaccharide (LPS) induced tumor necrosis factor alpha (TNF-α) secretion by ELISA, gene expression of inflammatory markers (TNF-α, IL-6, MIP-1α and MCP-1) by real time PCR and translocation of nuclear factor kappa B (NF-κB) by confocol microscopy. Furthermore, the effect of the extracts, EUG and IMT, was studied on phorbol-12-myristate-13-acetate (PMA) induced monocyte to macrophage differentiation and gene expression of CD14, TLR2 and TLR4.

RESULTS

The LC-MS analysis of OSAE and OSWE revealed the presence of several bioactive compounds including eugenol. Quantitative analysis revealed that OSAE and OSWE had EUG of 12 ng/mgdwt and 19 ng/mgdwt respectively. OSAE, OSWE (1 mg dwt/mL) pure compound EUG (60 µg/mL) and positive control IMT (20 µg/mL) showed marked inhibition on LPS induced TNF-α secretion by THP-1 cells. At the selected concentration, the plant extracts, EUG and IMT inhibited gene expression of cytokines and chemokines (IL-6, TNF-α, MIP-1α, MCP-1) and translocation of NF-κB-p65 to the nuclei. In addition, they showed significant inhibition on PMA induced monocyte to macrophage differentiation and the gene expression of CD14, TLR2 and TLR4 markers.

CONCLUSION

The result of the present study validated traditional use of Ocimum sanctum for treating cardiovascular disease for the first time by testing antiinflammatory activity of Ocimum sanctum in acute inflammatory model, LPS induced THP-1 cells. The plant extracts showed significant antiinflammatory activity, however, further to be evaluated using chronic inflammatory animal models like diabetic or apolipoprotein E-deficient mice to make it evidence based medicine. The phenolic compound eugenol (60 µg/mL) showed significant antiinflammatory activity. However the amount of eugenol present in 1mg of OSAE and OSWE (12 ng/mg and 19 ng/mg dwt respectively) used for cell based assays was very low. It suggests that several other metabolites along with eugenol are responsible for the efficacy of the extracts.

Association between the monocyte chemoattractant protein-1 -2518G/A gene polymorphism and acute myocardial infarction patients among Egyptian population

The aim of the present study was to investigate the possible association between the -2518G/A polymorphism of the monocyte chemoattractant protein-1 (MCP-1) gene and acute myocardial infarction (MI) in a sample of the Egyptian population. A total of 30 Egyptian patients with coronary artery disease (CAD) manifested as acute myocardial infarction (MI) for the first time and 25 unrelated healthy control individuals were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). The proportion of G/A and G/G genotypes were significantly higher in the acute MI group than the control group (P < 0.05). The acute MI patients group showed a significant higher frequency of the G allele compared to the controls (P < 0.05). Analysis of the relationship between the G/A, G/G genotypes and A/A genotype acute MI group regarding the conventional risk factors showed statistical significant difference regarding age, total cholesterol, low-density lipoprotein and high-density lipoprotein (P < 0.05), but there was no significant relationship regarding sex, smoking, history of diabetes mellitus, hypertension, obesity, body mass index (BMI) and triglyceride, but we observed that the percentage of men was higher than the percentage of women in both G/A, G/G genotypes and A/A genotype acute MI patients. Also, among our patients, the percentage of smokers, diabetics, hypertensive, and obesity and the mean of BMI and triglyceride were higher in the G/A, G/G genotypes acute MI patients than that in A/A genotype acute MI patients. In conclusion, our study indicated that there was a significant association between the MCP-1 -2518G/A polymorphism and acute MI in the Egyptian population, but this significant association is dependent on the presence of MI risk factors.

Role of the SDF-1/CXCR4 system in myocardial infarction

Myocardial infarction (MI) is accompanied by an inflammatory response, leading to the recruitment of leukocytes and subsequent myocardial injury and healing. Chemokines are potent chemoattractant cytokines that regulate leukocyte trafficking in inflammatory processes. Recent evidence indicates that chemokines play a role not only in leukocyte trafficking but also in angiogenesis and cardioprotection. In particular, stromal cell-derived factor-1alpha (SDF-1alpha) has generated considerable interest for its role in the pathophysiology of MI. This review will focus on the role of SDF-1 and its receptor CXC chemokine receptor 4 (CXCR4; ie, the SDF-1/CXCR4 system) in the pathophysiology of MI and discuss their potential as therapeutic targets for MI.

Transmigration across activated endothelium induces transcriptional changes, inhibits apoptosis, and decreases antimicrobial protein expression in human monocytes

We investigated the hypothesis that transmigration drives monocyte transcriptional changes. Using Agilent whole human genome microarrays, we identified over 692 differentially expressed genes (2x, P<0.05) in freshly isolated human monocytes following 1.5 h of transmigration across IL-1beta-stimulated ECs compared with untreated monocytes. Genes up-regulated by monocyte transmigration belong to a number of over-represented functional groups including immune response and inhibition of apoptosis. qRT-PCR confirmed increased expression of MCP-1 and -3 and of NAIP following monocyte transmigration. Additionally, quantification of Annexin V binding revealed a reduction in apoptosis following monocyte transmigration. Comparison of gene expression in transmigrated monocytes with additional controls (monocytes that failed to transmigrate and monocytes incubated beneath stimulated ECs) revealed 89 differentially expressed genes, which were controlled by the process of diapedesis. Functional annotation of these genes showed down-regulation of antimicrobial genes (e.g., alpha-defensin down 50x, cathelicidin down 9x, and CTSG down 3x). qRT-PCR confirmed down-regulation of these genes. Immunoblots confirmed that monocyte diapedesis down-regulates alpha-defensin protein expression. However, transmigrated monocytes were functional and retained intact cytokine and chemokine release upon TLR ligand exposure. Overall, these data indicate that the process of monocyte transmigration across stimulated ECs promotes further monocyte recruitment and inhibits monocyte apoptosis. Unexpectedly, following transmigration, monocytes displayed reduced antimicrobial protein expression.

Monocyte-endothelial cell interaction in atherogenesis and thrombosis

Cellular interactions between leukocytes and the endothelium are critical events in vascular biology, such as atherosclerosis and acute coronary syndrome. When monocytes and endothelial cells are activated via direct cell-cell interaction, both types of cells express several biologically active molecules such as adhesion molecules, cytokines, coagulation and fibrinolytic factors, metalloproteinases, and vasoactive substances. All of these molecules could contribute to atherogenesis and thrombosis.

MCP-1 induces cardioprotection against ischaemia/reperfusion injury: role of reactive oxygen species

AIMS

Monocyte chemoattractant protein-1 (MCP-1: CCL2) has been demonstrated to be involved in the pathophysiology of ischaemic heart disease; however, the precise role of MCP-1 in ischaemia/reperfusion (I/R) injury is controversial. Here, we investigated the role of cardiac MCP-1 expression on left ventricular (LV) dysfunction after global I/R in Langendorff-perfused hearts isolated from transgenic mice expressing the mouse JE-MCP-1 gene under the control of the alpha-cardiac myosin heavy chain promoter (MHC/MCP-1 mice).

METHODS AND RESULTS

In vitro experiments showed that MCP-1 prevented the apoptosis of murine neonatal cardiomyocytes after hypoxia/reoxygenation. I/R significantly increased the mRNA expression of MCP-1 in the Langendorff-perfused hearts of wild-type mice. Cardiac MCP-1 overexpression in the MHC/MCP-1 mice improved LV dysfunction after I/R without affecting coronary flow; in particular, it ameliorated LV diastolic pressure after reperfusion. This improvement was independent of both sarcolemmal and mitochondrial K(ATP) channels. Cardiac MCP-1 overexpression prevented superoxide generation in the I/R hearts, and these hearts showed decreased expression of the NADPH oxidase family proteins Nox1, gp91phox, and Nox3 compared with the hearts of wild-type mice. Further, superoxide dismutase activity in the hearts of MHC/MCP-1 mice was significantly increased compared with that in the hearts of wild-type mice.

CONCLUSION

These findings suggest that cardiac MCP-1 prevented LV dysfunction after global I/R through a reactive oxygen species-dependent but K(ATP) channel-independent pathway; this provides new insight into the beneficial role of MCP-1 in the pathophysiology of ischaemic heart diseases.

Monocyte chemoattractant protein-1 and coronary artery disease

The designation of atherosclerosis as a chronic inflammatory process represents an exciting and logical paradigm shift for cardiologists. Monocyte chemoattractant protein-1 (MCP-1) plays an important role in the recruitment and activation of monocytes and thus in the development of atherosclerosis. Enhanced MCP-1 expression has been detected in macrophages, endothelial cells, and vascular smooth muscle cells in the atheromatous plaque. Activation of macrophages by MCP-1 also appears to be involved in the vulnerability of the plaque. Indeed, circulating MCP-1 levels are elevated in patients with acute myocardial infarction and in those with unstable angina, but not in patients with stable angina. Production of MCP-1 and macrophage accumulation are also observed after coronary angioplasty or grafting, indicating that MCP-1 expression may be related not only to instability of atheromatous plaques, but also to the formation of restenotic lesions. The development of therapeutic drugs for atherosclerosis targeted specially against MCP-1 may be useful in the prevention of plaque formation and future myocardial infarction.

Enhanced Coronary Calcification Determined by Electron Beam CT Is Strongly Related to Endothelial Dysfunction in Patients With Suspected Coronary Artery Disease

BACKGROUND

Coronary artery calcification determined by electron beam CT (EBCT) is strongly associated with total plaque burden but is not related to systemic vascular inflammation.

AIMS

We sought to test the hypothesis that enhanced coronary artery calcification, a marker of atherosclerosis and plaque burden, was related to endothelial dysfunction in patients with suspected coronary artery disease (CAD).

METHODS AND RESULTS

One hundred twenty-four subjects with suspected CAD were enrolled. Coronary artery calcification was detected by EBCT. A noninvasive method of brachial ultrasound was used to measure endothelium-dependent flow-mediated vasodilation (FMD) and endothelium-independent nitroglycerin-mediated vasodilation (NMD). Serum high-sensitivity C-reactive protein (hsCRP) and monocyte chemoattractant protein-1 (MCP-1) levels were also determined. Of the 124 patients, the calcium scores ranged from 0 to 4,394. All subjects were classified into three groups according to coronary calcium scores: group 1, score 0 (n = 26); group 2, scores 1 to 199 (n = 50); group 3, scores > or = 200 (n = 48). There was an inverse association between the degree of coronary artery calcification and the endothelium-dependent FMD in the three groups (6.9 +/- 0.6% vs 5.3 +/- 0.3% vs 3.7 +/- 0.3%, respectively; p < 0.001) but not the endothelium-independent NMD. Besides, no significant difference in serum levels of hsCRP and MCP-1 were found among the three groups. However, both the serum levels of hsCRP and MCP-1 were correlated significantly with endothelium-dependent FMD (r = - 0.211, p = 0.019; and r = - 0.188, p = 0.037, respectively). By multivariate analysis, enhanced coronary calcification was a strong independent predictor of endothelial dysfunction (p < 0.001).

CONCLUSION

Enhanced coronary artery calcification strongly predicted endothelial dysfunction in patients with suspected CAD. Also, serum levels of hsCRP and MCP-1 were significantly correlated with endothelial function. These findings suggested that both calcium deposition and inflammation were involved in endothelial dysfunction.

Intravenous prostaglandin E1 reduces monocyte chemoattractant protein-1 levels in peripheral arterial obstructive disease

OBJECTIVES

Blood monocytes are the precursors of the lipid-laden foam cells that are the hallmark of early atherosclerotic lesions, and monocyte chemoattractant protein-1 (MCP-1) plays important roles in their recruitment to the vessel wall. In this study, we measured serum levels of MCP-1 in patients with peripheral arterial obstructive disease (PAOD) and investigated whether intravenous prostaglandin E1 (PGE1) treatment, which produces clinical benefits in PAOD, might decrease such levels.

METHODS

Eight patients with PAOD at Fontaine stage II to IV were treated with a daily intravenous infusion of 10 microg of PGE1 for 7 consecutive days. Blood samples before and after 7-day PGE1 treatment were used for assays of MCP-1, interleukin-6 (IL-6), high-sensitivity C-reactive protein (hs-CRP), von Willebrand factor (vWF), and endothelin-1 (ET-1).

RESULTS

Serum MCP-1 levels in patients with PAOD were significantly higher than those in healthy control subjects (263.8 +/- 52.8 vs 136.5 +/- 15.0 pg/mL, P =.002). PGE1 administration for 7 days resulted in a significant decrease in the MCP-1 level, from 263.8 +/- 52.8 to 196.1 +/- 25.5 pg/mL (P =.02), whereas levels of IL-6, hs-CRP, and ET-1 and the activity of vWF were not affected.

CONCLUSIONS

Serum MCP-1 levels were elevated in patients with PAOD, indicating the involvement of activation of monocytes in the pathogenesis of this disorder. Parenteral administration of PGE1 appeared to decrease circulating MCP-1 levels, which might lead to the suppression of the development of atherosclerotic lesions in patients with PAOD.

Regulation of chemokine expression in atherosclerosis

(1) Chemokines play a central role in the pathogenesis of atherosclerosis, contributing to leukocyte recruitment, angiogenesis and also proliferation and migration of smooth muscle cells into atherosclerotic plaques. (2) Leukocytes and endothelial cells are an important source of chemokines, and many of the risk factors associated with atherosclerosis increase chemokine expression. There is now a body of evidence to suggest that interactions between cells such as leukocytes and endothelial cells amplify chemokine release, and this may contribute to sustained chemokine generation in inflammatory conditions. (3) This article summarises, briefly, what is currently known about chemokines release. A number of important pharmacological strategies used in the treatment of atherosclerosis inhibit chemokine release and the extent to which this may contribute to their therapeutic effect will be discussed. Understanding the mechanisms controlling chemokine expression is essential for the design of specific therapeutic interventions in atherosclerosis.

Inhibition of vascular endothelial growth factor activity by transfection with the soluble FLT-1 gene

Vascular endothelial growth factor (VEGF)-induced angiogenesis is involved in the etiology of some cardiovascular diseases. The soluble form of VEGF receptor, FLT-1 (sFLT-1), is a potent antagonist of VEGF. Therefore, we investigated whether transfection with the sFLT-1 gene could inhibit VEGF-induced angiogenesis. Human embryonic kidney (HEK)-293 cells were transfected with plasmids containing VEGF and sFLT-1 (pCMV-VEGF and pCMV-sFLT-1) by the calcium-phosphate co-precipitation method. VEGF- and/or sFLT-1-transfected HEK-293 cells were incubated for 24 h, and then conditioned medium was collected. The effects of conditioned medium on angiogenesis were tested by incorporation of [3H]thymidine into human umbilical vein endothelial cells (HUVECs). Expression of VEGF protein was determined by Western blotting. The conditioned medium from sFLT-1 gene-transfected HEK-293 cells significantly inhibited recombinant VEGF-induced increase in [3H]thymidine incorporation by HUVECs. VEGF gene-transfected HEK-293 cells secreted VEGF protein into conditioned medium. This conditioned medium increased [3H]thymidine incorporation by HUVECs, which was significantly inhibited by co-transfection of sFLT-1 gene with VEGF gene. These observations suggested that sFLT-1 gene transfer could inhibit VEGF-induced DNA synthesis of vascular endothelial cells.

Amlodipine inhibits expression of matrix metalloproteinase-1 and its inhibitor in human vascular endothelial cells

Matrix metalloproteinase-1 (MMP-1) may play an important role in the pathogenesis of atherosclerosis and atherosclerotic plaque rupture. We investigated the effect of the calcium channel blockers amlodipine and nifedipine on the expression of MMP-1 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in endothelial cells (ECs). MMP-1 and TIMP-1 levels in conditioned media of human vascular ECs were measured by enzyme-linked immunosorbent assay. Collagenolytic activity was determined by fluorescence-labeled collagen digestion. The addition of interleukin-1beta (IL-1beta) increased MMP-1 levels in the culture media of ECs. Amlodipine, but not nifedipine, significantly decreased MMP-1 levels in IL-1beta-stimulated ECs. TIMP-1 levels also were significantly increased by IL-1beta, and its expression was slightly decreased by amlodipine, not by nifedipine. Amlodipine significantly inhibited collagenolytic activity in the culture media of IL-1beta-stimulated ECs, whereas nifedipine showed no significant effect on the activity. Our findings revealed that amlodipine, but not nifedipine, inhibits IL-1beta-induced MMP-1 expression in human ECs.

Infection of human endothelial cells with Staphylococcus aureus induces the production of monocyte chemotactic protein-1 (MCP-1) and monocyte chemotaxis

Bacterial infection coincides with migration of leucocytes from the circulation into the bacterium-infected tissue. Recently, we have shown that endothelial cells, upon binding and ingestion of Staphylococcus aureus, exhibit proinflammatory properties including procoagulant activity and increased intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression on the cell surface, resulting in hyperadhesiveness, mainly for monocytes. The enhanced extravasation of monocytes to bacterium-infected sites is facilitated by the local production of chemotactic factors. From another study we concluded that the locally produced chemokine MCP-1 is important in the recruitment of monocytes to the peritoneal cavity in a model of bacterial peritonitis. In the present study we investigated whether cultured human endothelial cells after infection with bacteria produce and release MCP-1, which in turn stimulates monocyte chemotaxis. We observed that endothelial cells released significant amounts of MCP-1 within 48 h after ingestion of S. aureus. This was dependent on the number and the virulence of the bacteria used to infect the endothelial cells. The kinetics as well as the amount of MCP-1 released by S. aureus-infected endothelial cells differed markedly from that released by endothelial cells upon stimulation with IL-1beta. Supernatant from S. aureus-infected or IL-1beta-stimulated cells promoted monocyte chemotaxis which was almost entirely abrogated in the presence of neutralizing anti-MCP-1 antibody, indicating that most of the chemotactic activity was due to the release of MCP-1 into the supernatant. Our findings support the notion that endothelial cells can actively initiate and sustain an inflammatory response after an encounter with pathogenic microorganisms, without the intervention of macrophage-derived proinflammatory cytokines.

Angiotensin II stimulates expression of the chemokine RANTES in rat glomerular endothelial cells. Role of the angiotensin type 2 receptor

Glomerular influx of monocytes/macrophages (M/M) occurs in many immune- and non-immune-mediated renal diseases. The mechanisms targeting M/M into the glomerulus are incompletely understood, but may involve stimulated expression of chemokines. We investigated whether angiotensin II (ANG II) induces the chemokine RANTES in cultured glomerular endothelial cells of the rat and in vivo. ANG II stimulated mRNA and protein expression of RANTES in cultured glomerular endothelial cells. The ANG II-induced RANTES protein was chemotactic for human monocytes. Surprisingly, the ANG II-stimulated RANTES expression was transduced by AT2 receptors because the AT2 receptor antagonists PD 123177 and CGP-42112A, but not an AT1 receptor blocker, abolished the induced RANTES synthesis. Intraperitoneal infusion of ANG II (500 ng/h) into naive rats for 4 d significantly stimulated glomerular RANTES mRNA and protein expression compared with solvent-infused controls. Immunohistochemistry revealed induction of RANTES protein mainly in glomerular endothelial cells and small capillaries. Moreover, ANG II- infused animals exhibited an increase in glomerular ED-1- positive cells compared with controls. Oral treatment with PD 123177 (50 mg/liter drinking water) attenuated the glomerular M/M influx without normalizing the slightly elevated systolic blood pressure caused by ANG II infusion, suggesting that the effects on blood pressure and RANTES induction can be separated. We conclude that the vasoactive peptide ANG II may play an important role in glomerular chemotaxis of M/M through local induction of the chemokine RANTES. The observation that the ANG II- mediated induction of RANTES is transduced by AT2 receptors may influence the decision as to which substances might be used for the therapeutic interference with the activity of the renin-angiotensin system.

Activation of human monocytes for enhanced production of interleukin 8 during transendothelial migration in vitro

Interleukin-8 (IL-8) is a chemokine for polymorphonuclear leukocytes (PMNs) and lymphocytes, which promotes the extravasation of these inflammatory cells. In this study, we investigated IL-8 synthesis induced by the adhesive interaction between monocytes and endothelial cells during transmigration and the capacity of transmigrated monocytes to produce IL-8. Cocultured human monocytes and human umbilical vein endothelial cell (HUVEC) monolayers induced the synergistic production of IL-8, compared with cultures of either monocytes or HUVEC monolayers alone. Coculture-induced IL-8 production almost doubled after HUVECs were stimulated with IL-1 beta. The induced IL-8 mRNA expression was consistent with the protein data, indicating the de novo synthesis of IL-8 by the coculture. Monoclonal antibodies (mAbs) against IL-8 inhibited the transendothelial chemotactic activity of the supernatants for PMNs by 55%. Immunohistochemistry revealed that both adherent and transmigrated monocytes and unstimulated HUVECs expressed IL-8 protein, whereas nonadherent monocytes did little. Transmigrated monocytes spontaneously secreted a 3.8-fold greater amount of IL-8 than the initial monocytes. Coculture-induced IL-8 production was inhibited about 30% by polyclonal Abs against IL-alpha, IL-1 beta, or tumor necrosis factor alpha, while it was not affected by mAbs against intercellular adhesion molecule 1 or vascular cell adhesion molecule 1. The results suggested that adhesive interaction during the transmigration of monocytes through HUVEC monolayers activates both cell types to produce IL-8 and that transmigrated monocytes are capable of producing ample IL-8.