Function and Regulation of the Vascular Cell Adhesion Molecule-l in TNF-Stimulated Endothelial Cells

The accumulation of circulating monocytes in the vessel wall is an important aspect of the pathogenesis of atherosclerosis and allied problems such as restenosis after percutaneous transluminal angioplasty (PTA). Three distinct steps can be distinguished in the stimulated accumulation of these cells. First there is an increased rolling, followed by firm adhesion, and finally migration of the monocytes in the direction of a chemotactic gradient. These different steps are regulated by specific endothelial cell adhesion molecules. In general rolling is mediated by the selectins, while immunoglobulin supergene family member vascular cell adhesion molecule (VCAM)-l specifically mediates rolling and fiml adhesion of monocytes. VCAM-I may thus enhance the local accumulation of monocytes even in the absence of seledin expression. In experimental models of atherosclerosis VCAM-I expression is an early feature of the atheromatous lesion, which suggests that VCAM-l plays a role in the initiation and progression of the atherosclerotic plaque. The expression of VCAM-l on endothelial cells is induced by the cytokine tumor necrosis factor a (TNF) and presumably regulated at the transcriptional level in part through the activation of the transcription factor nuclear factor (NF) KB. TNF stimulates intracellular signalling in endothelial cells through the production of lipid second messengers and mitogen activated protein kinase cascades. It has been hypothesized that reactive oxygen species (ROS), such as hydrogen peroxide, function as intracellular second messengers in the signal transduction of TNF. This putative role for ROS may comprise a novel mechanism of intracellular signalling next to protein phosphorylation. the cyclic nucleotide system, and signalling through the inositol phosphates and intracellular calcium. In the present thesis we have investigated the possible role of ROS as second messengers in the TNF stimulated expression of VCAM-l by endothelial cells

P38 mitogen activated protein kinase regulates endothelial VCAM-1 expression at the post-transcriptional level

The cytokine tumor necrosis factor (TNF) alpha was found to stimulate the p38 mitogen activated protein (MAP) kinase signalling cascade in human umbilical vein endothelial cells. TNFalpha increased the activity of the p38 substrate MAP kinase-activated-protein (MAPKAP) kinase 2 and the subsequent phosphorylation of the small heat shock protein Hsp27 about two to three fold. This stimulation was blocked almost completely by the specific p38 MAP kinase inhibitor SB203580. This inhibitor also suppressed the TNFalpha-induced surface expression of the endothelial adhesion molecule vascular cell adhesion molecule (VCAM)-1. In contrast, inhibition of p38 MAP kinase had no effect on the stimulated surface expression of the intercellular cell adhesion molecule (ICAM)-1. VCAM-1 mRNA accumulation induced by TNFalpha was not affected by SB203580, suggesting that the p38 MAP kinase signalling cascade regulates the endothelial expression of VCAM-1 at the post-transcriptional level

Late Lumen Loss After Coronary Angioplasty Is Associated With the Activation Status of Circulating Phagocytes Before Treatment

Background The purpose of this pilot study was to identify biological risk factors for restenosis after percutaneous transluminal coronary angioplasty (PTCA) to predict the long-term outcome of PTCA before treatment. Methods and Results To investigate whether blood granulocytes and monocytes could determine luminal renarrowing after PTCA, several characteristics of these phagocytes were assessed before angioplasty in 32 patients who underwent PTCA of one coronary artery and who had repeat angiograms at 6-month follow-up. The plasma levels of interleukin (IL)-1ß, tumor necrosis factor-, IL-6, fibrinogen, C-reactive protein, and lipoprotein(a) before angioplasty were assessed as well. We found that the expression of the membrane antigens CD64, CD66, and CD67 by granulocytes was inversely associated with the luminal renarrowing normalized for vessel size (relative loss) at 6 months after PTCA, while the production of IL-1ß by stimulated monocytes was positively associated with the relative loss. Next, these univariate predictors were corrected for the established clinical risk factors of dilation of the left anterior descending coronary artery and current smoking, which were statistically significant classic predictors in our patient group. Only the expression of CD67 did not predict late lumen loss independent of these established clinical risk factors. Multiple linear regression analysis showed that luminal renarrowing could be predicted reliably (R2=.65; P<.0001) in this patient group on the basis of the vessel dilated and only two biological risk factors that reflect the activation status of blood phagocytes, ie, the expression of CD66 by granulocytes and the production of IL-1ß by stimulated monocytes. Conclusions The results of the present study indicate that activated blood granulocytes prevent luminal renarrowing after PTCA, while activated blood monocytes promote late lumen loss. To validate this new finding, further study in an independent patient group is required

Targeting Cattle-Borne Zoonoses and Cattle Pathogens Using a Novel Trypanosomatid-Based Delivery System

Trypanosomatid parasites are notorious for the human diseases they cause throughout Africa and South America. However, non-pathogenic trypanosomatids are also found worldwide, infecting a wide range of hosts. One example is Trypanosoma (Megatrypanum) theileri, a ubiquitous protozoan commensal of bovids, which is distributed globally. Exploiting knowledge of pathogenic trypanosomatids, we have developed Trypanosoma theileri as a novel vehicle to deliver vaccine antigens and other proteins to cattle. Conditions for the growth and transfection of T. theileri have been optimised and expressed heterologous proteins targeted for secretion or specific localisation at the cell interior or surface using trafficking signals from Trypanosoma brucei. In cattle, the engineered vehicle could establish in the context of a pre-existing natural T. theileri population, was maintained long-term and generated specific immune responses to an expressed Babesia antigen at protective levels. Building on several decades of basic research into trypanosomatid pathogens, Trypanosoma theileri offers significant potential to target multiple infections, including major cattle-borne zoonoses such as Escherichia coli, Salmonella spp., Brucella abortus and Mycobacterium spp. It also has the potential to deliver therapeutics to cattle, including the lytic factor that protects humans from cattle trypanosomiasis. This could alleviate poverty by protecting indigenous African cattle from African trypanosomiasis