Cardiac resistance to adriamycin in transgenic mice expressing a rat alpha-cardiac myosin heavy chain/human multiple drug resistance 1 fusion gene.

Cardiac toxicity is a major factor that limits the use of anthracyclines in cancer chemotherapy. Heart failure frequently develops in patients treated with doxorubicin (Adriamycin), when they receive a cumulative dose greater than 500 mg/m2. To make a mouse model for gene therapy designed to prevent this toxic effect, we have produced transgenic mice overexpressing the human cDNA for the multiple drug resistance (h-mdr1) gene driven by 2.12 kb of the 5' flanking region of the rat alpha-cardiac myosin (aCM) heavy chain gene. Two lines of transgenic mice expressed the transgene at a high level in heart muscle. Transgenic and control animals were treated with Adriamycin intravenously at either a single dose of 10 mg/kg or a cumulative dose of 30 mg/kg in three injections. Subsequent light and electron microscopic examination of heart tissue demonstrated degenerative changes in control mice that were absent in transgenic animals at both doses. These results show that expression of the alphaCM/h-mdr1 transgene in heart confers protection from the toxic effect of Adriamycin and suggest that such constructs, if employed effectively in cardiac gene therapy protocols, could allow a more aggressive use of anthracyclines in the treatment of cancer.

Experimental arterial thrombosis in genetically or diet induced hyperlipidemia in rats--role of vitamin K-dependent clotting factors and prevention by low-intensity oral anticoagulation.

To investigate the relationship among lipids, coagulation and thrombosis in the absence of atherosclerosis, spontaneous or dietary-induced hyperlipidemic (FHL) rats were studied. FHL showed higher levels of coagulation factors VII, IX, X, VIII and XII and a shortening of the occlusion time (OT) of an artificial arterial prosthesis as compared with normolipidemic (FNL) animals. Damage of abdominal aorta of FHL was followed by increased fibrin deposition in the vascular intima as compared to FNL. After 5 months of cholesterol-rich diet FNL showed increased cholesterol, triglycerides and factor II, VII, IX, X, XII levels. A significant shortening of the OT and increased fibrin deposition was also observed. Two-month diet withdrawal restored the initial condition. Warfarin treatment, at a dose decreasing vitamin K-dependent factor to levels found in FNL, prolonged the OT and reduced fibrin deposition, without modifying F XII or changing lipid profile. An increase in the activated form of F VII was observed. In contrast, no difference was found in F VII clearance. High lipid levels favour the process of thrombus formation by increasing the activation of vitamin K-dependent coagulation factors. Low-dose warfarin treatment reverts the prothrombotic effect of hyperlipidemia.

Antithrombotic activity of dermatan sulphates, heparins and their combination in an animal model of arterial thrombosis.

Dermatan sulphates have been shown to inhibit thrombus formation and thrombus growth in different experimental model of venous thrombosis. At variance with heparins, they show a remarkably low haemorrhagic potential. On the other hand, very few data are available on the effect of dermatan sulphates on arterial thrombus formation. We evaluated the effects of a low molecular weight (LMW)-dermatan sulphate, a high molecular weight (HMW)-dermatan sulphate and sulodexide (a mixture of fast-moving heparin fraction and dermatan sulphate) in comparison with LMW- and HMW-heparin, in a model of arterial thrombosis in rats. The insertion of an artificial prosthesis into the abdominal aorta of the animals induced the formation of an occluding thrombus within 2-5 days. The time in which 50% of the loops became occluded (OT50) was also calculated and used to compare the efficacy of the different drug treatments. This was 2.84 days for control animals and 4.25 and 5.80 days for HMW- and LMW-dermatan sulphate, respectively. Neither drug changed the "template" bleeding time, even at higher doses. In contrast, HMW-heparin at doses (8 mg/kg, sc, twice a day) inducing an antithrombotic activity comparable to that of dermatan sulphates, dramatically prolonged the bleeding time. LMW-heparin at the same doses was ineffective. Sulodexide (10 mg/Kg, sc, twice a day) prolonged the occlusion time to the same extent as HMW-heparin (OT50 5.10 vs. 4.14 days), with less an effect on the bleeding time (144 +/- 6 s vs. > 300 s, respectively). Histological examination confirms that the prolongation of occlusion time induced by the drugs is really related to thrombus formation inhibition at the site of arterial wall injury. Acetyl salicylic acid (ASA) (100 mg/kg/day in drinking water as lysine acetylsalicylate) did not modify the effect of Desmin 370 and Sulodexide on both occlusion and bleeding time. However, while it did not increase the antithrombotic activity of HMW-heparin, it significantly prolonged its haemorrhagic effect. In conclusion, dermatan sulphates are effective inhibitors of arterial thrombosis in rats, without inducing bleeding complications.