Effects of highly active antiretroviral therapy on platelet activating factor metabolism in naive HIV-infected patients: ii) study of the abacavir/lamivudine/efavirenz HAART regimen

Human Immunodeficiency Virus (HIV)-infected patients are at increased risk for cardiovascular diseases partly due to chronic inflammation. Some antiretroviral drugs and Highly Active Anti-Retroviral Therapy (HAART) regimens seem to be related and amplify this increased risk, especially the ones containing abacavir. Platelet-Activating-Factor (PAF) is a potent inflammatory mediator that is implicated in both cardiovascular diseases and HIV-related manifestations. Our objective is to study the in vivo effect of the abacavir/lamivudine/efavirenz first-line HAART regimen on PAF metabolism in HIV-infected patients. The specific activities of PAF basic biosynthetic enzymes in leukocytes and platelets, PAF-cholinephosphotransferase (PAF-CPT) and lyso-PAF-acetyltransferase (Lyso-PAF-AT), but also those of PAF-basic catabolic enzymes, PAF acetylhydrolase (PAF-AH) in leukocytes and platelets and Lipoprotein-associated-Phospholipase-A2 (LpPLA2) in plasma, were measured in blood samples of 10 asymptomatic naïve male HIV-infected patients just before and after 1, 3 and 6 months of treatment. CD4 cell counts, viral load and several biochemical markers were also measured in the same blood samples of these patients. The repeated ANOVA measures and the Pearson r criterion were used for studying statistical differences and correlations - partial correlations respectively. Even though viral load was decreased and CD4 cell counts were beneficially increased after treatment with the abacavir/lamivudine/efavirenz regimen, the main enzyme of the remodelling PAF-synthesis that is implicated in pro-atherogenic inflammatory procedures, Lyso-PAF-AT activity, was increased at 3 months of treatment in both leukocytes and platelets, while the main enzyme of PAF-degradation, PAF-AH, was increased as a response only in leukocytes at the 3rd month. Although the abacavir/lamivudine/efavirenz HAART regimen exhibits very efficient antiretroviral activities, on the other hand it induces an in vivo transient increase in the inflammation-related remodeling PAF-biosynthetic pathway. This finding supports the hypothesis of inflammation-mediated increased cardiovascular risk in HIV-infected patients during the first months of abacavir-containing HAART.

The implication of platelet activating factor in cancer growth and metastasis: potent beneficial role of PAF-inhibitors and antioxidants

Cancer is one of the leading causes of death in Europe and United States. New blood vessel formation penetrating into solid tumors seems to be required for their growth and metastasis. Several protein growth factors can induce endothelial cell proliferation and angiogenesis, through signal transduction cascades that result in the production of several inflammatory mediators and lipid second messengers such as prostaglandins and Platelet Activating Factor (PAF). PAF is a potent mediator of inflammation that is implicated in several inflammatory pathological conditions such as atherosclerosis, cardiovascular and renal diseases, allergy, AIDS, cancer etc. It exerts its biological activities through G-protein-coupled receptors. The presence of PAF in the microenvironment of tumors may be due to its synthesis from circulating and / or cancer cells. Moreover, cancer cells and activated endothelial cells expose PAF-receptor on their membrane surface. PAF binding on its receptor induces several pathways that result in the onset and development of tumor induced angiogenesis and metastasis. PAF-receptor antagonists have exhibited promising results in vitro and in vivo as anti-angiogenic molecules in several cancer cells and tumors. A dietary profile reach in antioxidants and PAF-inhibitors (such as the Mediterranean Diet) may provide beneficial preventive and protective effects against development, growth and metastatic manifestations of cancer cells, through either their inhibition of PAF activity and / or its biosynthesis. The clarification of factors that may down regulate pathologically increased PAF-levels in a tumor microenvironment may also contribute to the planning of a potent nontoxic preventive and therapeutic approach against cancer.