Linoleic acid increases monocyte chemotaxis and adhesion to human aortic endothelial cells through protein kinase C- and cyclooxygenase-2-dependent mechanisms

The effects of polyunsaturated n-6 linoleic acid on monocyte-endothelial interactions were investigated with particular emphasis on the expression of platelet/endothelial cell adhesion molecule (PECAM)-1 and the role of protein kinase C (PKC) and cyclooxygenase-2 (COX-2). As a diet rich in polyunsaturated fatty acids may favour atherosclerosis in hyperglycaemia, this study was performed in both normal and high-glucose media using human aortic endothelial cells (HAEC). The HAEC were preincubated with normal (5 mM) or high (25 mM) d-glucose for 3 days before addition of fatty acids (0.2 mM) for 3 days. Linoleic acid enhanced PECAM-1 expression independently of tumor necrosis factor (TNF)-a and significantly increased TNF-a-induced monocyte adhesion to HAEC in comparison to the monounsaturated n-9 oleic acid. Chronic glucose treatment (25 mM, 6 days) did not modify the TNF-a-induced or fatty acid-induced changes in monocyte binding. The increase in monocyte binding was accompanied by a significant increase in E-selectin and vascular cell adhesion molecule (VCAM)-1 expression and could be abrogated by an interleukin (IL)-8 neutralising antibody and by the PKC and COX inhibitors. Inhibition of PKC-d reduced VCAM-1 expression regardless of experimental condition and was accompanied by a significant decrease in monocyte binding. Conditioned medium from linoleic acid-treated HAEC grown in normal glucose conditions significantly increased THP-1 chemotaxis. These results suggest that linoleic acid-induced changes in monocyte chemotaxis and subsequent binding are not solely mediated by changes in adhesion molecule expression but may be due to secreted factors such as IL-8, monocyte chemoattractant protein-1 or prostaglandins (PGs) such as PGE2, as IL-8 neutralisation and COX-2 inhibition reduced monocyte binding without changes in adhesion molecule expression.

Glucose lowers the threshold for human aortic vascular smooth muscle cell migration: inhibition by protein phosphatase-2A

AIMS/HYPOTHESIS: Atherosclerosis, which occurs prematurely in individuals with diabetes, incorporates vascular smooth muscle cell (VSMC) chemotaxis. Glucose, through protein kinase C-beta(II) signalling, increases chemotaxis to low concentrations of platelet-derived growth factor (PDGF)-BB. In VSMC, a biphasic response in PDGF-beta receptor (PDGF-betaR) level occurs as PDGF-BB concentrations increase. The purpose of this study was to determine whether increased concentrations of PDGF-BB and raised glucose level had a modulatory effect on the mitogen-activated protein kinase/extracellular-regulated protein kinase pathway, control of PDGF-betaR level and chemotaxis.

METHODS: Cultured aortic VSMC, exposed to normal glucose (NG) (5 mmol/l) or high glucose (HG) (25 mmol/l) in the presence of PDGF-BB, were assessed for migration (chemotaxis chamber) or else extracted and immunoblotted.

RESULTS: At concentrations of PDGF-BB <540 pmol/l, HG caused an increase in the level of PDGF-betaR in VSMC (immunoblotting) versus NG, an effect that was abrogated by inhibition of aldose reductase or protein kinase C-beta(II). At higher concentrations of PDGF-BB (>540 pmol/l) in HG, receptor level was reduced but in the presence of aldose reductase or protein kinase C-beta(II) inhibitors the receptor levels increased. It is known that phosphatases may be activated at high concentrations of growth factors. At high concentrations of PDGF-BB, the protein phosphatase (PP)2A inhibitor, endothall, caused an increase in PDGF-betaR levels and a loss of biphasicity in receptor levels in HG. At higher concentrations of PDGF-BB in HG, the chemoattractant effect of PDGF-BB was lost (chemotaxis chamber). Under these conditions inhibition of PP2A was associated with a restoration of chemotaxis to high concentrations of PDGF-BB.

CONCLUSION/INTERPRETATION: The biphasic response in PDGF-betaR level and in chemotaxis to PDGF-BB in HG is due to PP2A activation.

Improved detection of acute myocardial infarction in patients with chest pain and significant left main stem coronary stenosis.

Background: Non-invasive diagnosis of acute myocardial infarction (AMI) associated with significant left main stem (LMS) stenosis remains challenging.

Methods: Consecutive patients presenting with acute ischaemic-type chest pain from 2000 to 2010 were analysed. Entry criteria: 12-lead ECG and Body Surface Potential Map (BSPM) at presentation, cardiac troponin T (cTnT) =12?h and coronary angiography during admission. cTnT =0.03?µg/l defined AMI. ECG abnormalities assessed: STEMI by Minnesota criteria; ST elevation (STE) aVR =0.5?mm; ST depression (STD) =0.5?mm in =2 contiguous leads (CL); T-wave inversion (TWI) =1?mm in =2 CL. BSPM STE was =2?mm in anterior, =1?mm in lateral, inferior, right ventricular or high right anterior and =0.5?mm in posterior territories. Significant LMS stenosis was =70%.

Results: Enrolled were 2810 patients (aged 60?±?12 years; 71% male). Of these, 116 (4.1%) had significant LMS stenosis with AMI occurring in 92 (79%). STEMI by Minnesota criteria occurred in 13 (11%) (sensitivity 12%, specificity 92%), STE in lead aVR in 23 (20%) (sensitivity 23%, specificity 92%), TWI in 38 (33%) (sensitivity 34%, specificity 71%) and STD in 51 (44%) (sensitivity 49%, specificity 75%). BSPM STE occurred in 85 (73%): sensitivity 88%, specificity 83%, positive predictive value 95% and negative predictive value 65%. Of those with AMI, 74% had STE in either the high right anterior or right ventricular territories not identified by the 12-lead ECG. C-Statistic for AMI diagnosis using BSPM STE was 0.800 (P?<?0.001).

Conclusion: In patients with significant LMS stenosis presenting with chest pain, BSPM STE has improved sensitivity (88%), with specificity 83%, over 12-lead ECG in the diagnosis of AMI.

Abdominal aortic aneurysm is associated with a variant in low-density lipoprotein receptor-related protein 1

Abdominal aortic aneurysm (AAA) is a common cause of morbidity and mortality and has a significant heritability. We carried out a genome-wide association discovery study of 1866 patients with AAA and 5435 controls and replication of promising signals (lead SNP with a p value < 1 × 10 -5) in 2871 additional cases and 32,687 controls and performed further follow-up in 1491 AAA and 11,060 controls. In the discovery study, nine loci demonstrated association with AAA (p < 1 × 10 -5). In the replication sample, the lead SNP at one of these loci, rs1466535, located within intron 1 of low-density-lipoprotein receptor-related protein 1 (LRP1) demonstrated significant association (p = 0.0042). We confirmed the association of rs1466535 and AAA in our follow-up study (p = 0.035). In a combined analysis (6228 AAA and 49182 controls), rs1466535 had a consistent effect size and direction in all sample sets (combined p = 4.52 × 10 -10, odds ratio 1.15 [1.10-1.21]). No associations were seen for either rs1466535 or the 12q13.3 locus in independent association studies of coronary artery disease, blood pressure, diabetes, or hyperlipidaemia, suggesting that this locus is specific to AAA. Gene-expression studies demonstrated a trend toward increased LRP1 expression for the rs1466535 CC genotype in arterial tissues; there was a significant (p = 0.029) 1.19-fold (1.04-1.36) increase in LRP1 expression in CC homozygotes compared to TT homozygotes in aortic adventitia. Functional studies demonstrated that rs1466535 might alter a SREBP-1 binding site and influence enhancer activity at the locus. In conclusion, this study has identified a biologically plausible genetic variant associated specifically with AAA, and we suggest that this variant has a possible functional role in LRP1 expression.