ggti-298 and Acute-Disease

The ICAM-1-mediated brain endothelial cell (EC)-signaling pathway induced by adherent lymphocytes is a central element in facilitating lymphocyte migration through the tight endothelial barrier of the brain. Rho proteins, which must undergo posttranslational prenylation to be functionally active, have been shown to be an essential component of this signaling cascade. In this study, we have evaluated the effect of inhibiting protein prenylation in brain ECs on their ability to support T lymphocyte migration. ECs treated in vitro with protein prenylation inhibitors resulted in a significant reduction in transendothelial T lymphocyte migration. To determine the therapeutic potential of this approach, an animal model of multiple sclerosis, experimental autoimmune encephalomyelitis, was induced in Biozzi ABH mice. Animals treated before disease onset with protein prenylation inhibitors exhibited a dramatic and significant reduction in both leukocyte infiltration into the CNS and clinical presentation of disease compared with untreated animals. These studies demonstrate, for the first time, the potential for pharmacologically targeting CNS EC signaling responses, and particularly endothelial Rho proteins, as a means of attenuating leukocyte recruitment to the CNS.

Topics: Acute Disease; Animals; Benzamides; Brain; Cell Line; Cell Membrane; Cell Movement; Dimethylallyltranstransferase; Disease Models, Animal; Drug Combinations; Encephalomyelitis, Autoimmune, Experimental; Endothelium, Vascular; Enzyme Inhibitors; Guinea Pigs; Leukocytes; Methionine; Mice; Mice, Inbred Strains; Multiple Sclerosis; Myelin Basic Protein; Protein Prenylation; Rats; Rats, Inbred Lew; rho GTP-Binding Proteins; T-Lymphocytes

Lovastatin is an inhibitor of the enzyme 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the major regulatory enzyme of the mevalonate pathway. We have previously reported that lovastatin induces a significant apoptotic response in human acute myeloid leukemia (AML) cells. To identify the critical biochemical mechanism(s) essential for lovastatin-induced apoptosis, add-back experiments were conducted to determine which downstream product(s) of the mevalonate pathway could suppress this apoptotic response. Apoptosis induced by lovastatin was abrogated by mevalonate (MVA) and geranylgeranyl pyrophosphate (GGPP), and was partially inhibited by farnesyl pyrophosphate (FPP). Other products of the mevalonate pathway including cholesterol, squalene, lanosterol, desmosterol, dolichol, dolichol phosphate, ubiquinone, and isopentenyladenine did not affect lovastatin-induced apoptosis in AML cells. Our results suggest that inhibiting geranylgeranylation of target proteins is the predominant mechanism of lovastatin-induced apoptosis in AML cells. In support of this hypothesis, the geranylgeranyl transferase inhibitor (GGTI-298) mimicked the effect of lovastatin, whereas the farnesyl transferase inhibitor (FTI-277) was much less effective at triggering apoptosis in AML cells. Inhibition of geranylgeranylation was monitored and associated with the apoptotic response induced by lovastatin and GGTI-298 in the AML cells. We conclude that blockage of the mevalonate pathway, particularly inhibition of protein geranylgeranylation holds a critical role in the mechanism of lovastatin-induced apoptosis in AML cells.

Topics: Acute Disease; Apoptosis; Benzamides; Deoxyuracil Nucleotides; Fluorescein-5-isothiocyanate; Humans; Hydroxymethylglutaryl CoA Reductases; Hydroxymethylglutaryl-CoA Reductase Inhibitors; Leukemia, Myeloid; Lovastatin; Methionine; Mevalonic Acid; Polyisoprenyl Phosphates; Protein Prenylation; Sesquiterpenes; Tumor Cells, Cultured