Determination of temporal expression patterns for multiple genes in the rat carotid artery injury model.

Vascular injury induces extensive alteration to the extracellular matrix (ECM). These changes contribute to lesion formation and promote cell migration and proliferation. To elucidate ECM response to arterial injury, we used real-time polymerase chain reaction monitoring to quantitate the expression levels of 81 genes involved in the synthesis and breakdown of ECM as well as receptors and signaling proteins that communicate and respond to ECM molecules. The temporal regulation of gene expression in the carotid was measured at 1, 3, 5, 7, 9, 14, and 28 days postinjury. Among the 68 genes that showed detectable expression by our method, 47 (69%) were significantly induced or repressed over time, confirming the extensive ECM gene response in this model. More ECM-related genes (31) were regulated at day 1 than at any other time point, and the number of regulated genes decreased over time. However, 14 of the genes were still induced or repressed at day 28, indicating that return to preinjury expression patterns did not occur and no new steady state was achieved over 28 days. In spite of the large number of changes in gene expression, only a small number of expression patterns was observed, suggesting that ECM-related genes could potentially be coregulated.

Modulation of doxorubicin efficacy in P388 leukemia following co-administration of verapamil in mini-osmotic pumps.

Co-administration of doxorubicin and verapamil in Alzet mini-osmotic pumps increased the survival of B6D2F1 mice bearing the multidrug-resistant P388/ADR leukemia. A range of doxorubicin and verapamil combinations was studied to define dose-dependent efficacy and toxicity. High doses of doxorubicin (10 mg/kg/day) and verapamil (150 mg/kg/day) could be administered alone without any effect on survival. However, combining high doses of these two agents resulted in host toxicity. Doxorubicin doses of 1 to 10 mg/kg/day in combination with verapamil at 25-100 mg/kg/day were found to improve survival compared with either agent alone. Combination therapy also improved the survival of mice bearing the drug-sensitive P388/0 leukemia when compared to anthracycline treatment alone. The efficacy of the mini-osmotic pump delivery protocol was compared with other regimens delivering the same total cumulative dose of doxorubicin via repeated i.p. injections.

Suppression by mycophenolate mofetil of the neointimal thickening caused by vascular injury in a rat arterial stenosis model.

Injury of the rat carotid artery by gentle perfusion of air causes vascular thickening, similar to that seen in the clinic setting in humans after percutaneous angioplasty or bypass surgery to repair injured or diseased blood vessels. In the animal model as well as in patients, this stenosis appears to be the result of smooth muscle cell migration and proliferation. Various cell types in the lesion area may contribute by producing inflammatory cytokines, adhesion molecules and growth factors. In the present study, mycophenolate mofetil (MMF), an inosine monophosphate dehydrogenase inhibitor with antiproliferative and immunosuppressive properties, was tested for its ability to inhibit this process. With a daily oral dose of 30 mg MMF/kg started 6 days before injury to one carotid artery by air perfusion, MMF reduced cross-sectional areas of total vessel wall (intima-media) thickness by 17% to 25% and of neointimal thickness by 48% to 60% at 14 days after injury in four tests (P < .001 when MMF- and vehicle-treated groups were compared for these thickened areas, n = 29 or 30). In addition, intima/media ratios ranged from 0.26 +/- 0.03 to 0.46 +/- 0.04 for MMF-treated vs. 0.55 +/- 0.05 to 0.93 +/- 0.08 for vehicle-treated animals in the four different tests (P < .001). Starting MMF treatment at either 14 or 0 days before arterial injury made no difference in the degree of reduction, suggesting that any biological process that might be altered by MMF is not one that requires much time to become established. Intima/media ratios were 0.31 +/- 0.04 or 0.34 +/- 0.04 for MMF-treated vs. 0.55 +/- 0.05 or 0.65 +/- 0.07 for vehicle-treated animals (P < .001 for day 14 or 0, respectively, n = 30). Thus, MMF reduced the vascular thickening after carotid artery injury in rats, suggesting that this class of compound may be able to control the pathological processes that lead to restenosis.

CVT-313, a specific and potent inhibitor of CDK2 that prevents neointimal proliferation.

The activity of cyclin-dependent kinase 2 (CDK2) is essential for progression of cells from G1 to the S phase of the mammalian cell cycle. CVT-313 is a potent CDK2 inhibitor, which was identified from a purine analog library with an IC50 of 0.5 microM in vitro. Inhibition was competitive with respect to ATP (Ki = 95 nM), and selective CVT-313 had no effect on other, nonrelated ATP-dependent serine/threonine kinases. When added to CDK1 or CDK4, a 8.5- and 430-fold higher concentration of CVT-313 was required for half-maximal inhibition of the enzyme activity. In cells exposed to CVT-313, hyperphosphorylation of the retinoblastoma gene product was inhibited, and progression through the cell cycle was arrested at the G1/S boundary. The growth of mouse, rat, and human cells in culture was also inhibited by CVT-313 with the IC50 for growth arrest ranging from 1.25 to 20 microM. To evaluate the effects of CVT-313 in vivo, we tested this agent in a rat carotid artery model of restenosis. A brief intraluminal exposure of CVT-313 to a denuded rat carotid artery resulted in more than 80% inhibition of neointima formation. These observations suggest that CVT-313 is a promising candidate for evaluation in other disease models related to aberrant cell proliferation.