Changes in Hsp60 level of the failing heart following acute myocardial infarction and the effect of long-term treatment with trandolapril.

Changes in heat shock protein (Hsp) 60 of the viable left ventricular muscle (viable LV) after myocardial infarction in rats and the effect of the angiotensin I-converting enzyme inhibitor (ACEI) trandolapril were examined. Myocardial infarction was induced in rats by ligation of the left coronary artery. The coronary artery-ligated (CAL) and sham-operated (Sham) rats were orally treated with 3 mg/kg/d trandolapril from the 2nd to 8th week after surgery. Hemodynamic parameters and tissue weights of the left and right ventricles of the animals at the 8th week after CAL (8w-CAL rats) showed signs indicating chronic heart failure. An increase in Hsp60 content, a decrease in mitochondrial oxygen consumption rate (OCR), and an increase in the mitochondrial thiobarbiturate-reacting substance (TRS) of the viable LV were detected. Eight weeks after CAL. Long-term treatment of the CAL rats with trandolapril improved the hemodynamic parameters, attenuated the CAL-induced increase in Hsp60 content, the decrease in mitochondrial OCR, and the increase in the mitochondrial TRS content of the viable LV at the 8th week after myocardial infarction. The increase in Hsp60 content was closely related to the decrease in the mitochondrial OCR and to a rise in the LVEDP of the CAL animal at the 8th week after myocardial infarction. These results suggest that a series of pathophysiological alterations, including a reduction in mitochondrial function, appearance of reactive oxygen stress, and production of Hsp60 is involved in the development of cardiac failure and that trandolapril is beneficial for preventing these alterations.

Induction of heat shock protein 72 in the failing heart is attenuated after an exposure to heat shock.

Induction of heat shock protein (Hsp) 72 in the right ventricular muscle of the rat with heart failure following acute myocardial infarction (AMI) was examined. AMI was induced by the left coronary artery ligation (CAL). The animals at the 8th, but not 2nd, week after CAL revealed a decrease in cardiac output index (COI), suggesting that heart failure had developed by 8 weeks after CAL. Increases in the right ventricular developed pressure and the ratios of right ventricle/body weight and lung/body weight at the 2nd and 8th weeks showed the development of the right ventricular hypertrophy. After measurement of hemodynamic parameters, the hearts isolated from animals at the 2nd and 8th weeks after CAL (2w- and 8w-CAL hearts, respectively) were perfused and subjected to heat shock (at 42 degrees C, for 15 min) followed by 6-h perfusion. At the end of perfusion, Hsp72 content in the left ventricle without infarct area (viable LV) and the right ventricle (RV) was determined by the Western immunoblotting method. The production of myocardial Hsp72 in the viable LV and RV of the 2w-CAL heart increased after an exposure to heat shock. In contrast, induction of Hsp72 in the viable LV and RV of the 8w-CAL heart was blunted. The results suggest that the development of heart failure following AMI may result in a decrease in the ability for Hsp72 induction not only in the viable LV but also in the RV, leading to contractile dysfunction of the heart.

[Induction of heat shock protein 70 in failing heart].

Heat shock protein (Hsp) 70s including Hsp72 and Hsp73 are suggested to play an important role in the cardioprotection against stress-induced functional damage. Myocardial tolerance against ischemia/reperfusion injury is increased when myocardial Hsp72 is accumulated after an exposure of normal animals to heat shock. Post-ischemic contractile recovery is improved in the perfused heart of Hsp72-overexpressed mice. However, the role of Hsp72 and Hsp73 in the failing heart following acute myocardial infarction remains unclear. The present study was undertaken to determine whether Hsp72 and Hsp73 production may contribute to the protection of cardiac function in rats with chronic heart failure (CHF) following coronary artery ligation (CAL). The rats with CAL revealed the signs of CHF at the 8th week after the operation. The hearts isolated from rats with CHF were perfused and then subjected to heat shock (at 42 degrees C) for 15 min followed by 6-h perfusion (HS group). The cardiac function of the HS group was markedly decreased and the heat shock-induced increase in myocardial Hsp72 and Hsp73 was attenuated after 6-h perfusion. In the CAL rat treated with the ACE inhibitor trandolapril from the 2nd to the 8th week, induction of Hsp70s was preserved and heat stress-induced reduction in cardiac function was attenuated. The results suggest that a reduction in the production of Hsp70s may play a significant role in the decrease in contractile function during the development of heart failure.

Tyrosine kinase inhibitor as a therapeutic drug for chronic myelogenous leukemia and gastrointestinal stromal tumor.

The Philadelphia chromosome found in leukemia cells of chronic myelogenous leukemia (CML) patients is produced by translocation between chromosomes 9 and 22, resulting in expression of a chimera protein of Bcr and Abl kinase in the cytoplasm. Bcr-Abl kinase attracted oncology researchers as a molecular target for CML therapy, and a variety of small Abl kinase inhibitors were synthesized. STI571 (imatinib mesylate) was produced by modification of 2-phenylaminopyrimidine, a core structure of protein kinase C inhibitor, to improve selectivity, stability, solubility, and bioavailability. STI571 competitively binds to the ATP binding site of Bcr-Abl kinase and inhibits Abl tyrosine kinase activity. STI571 showed significant efficacy in the clinical study with CML patients at all stages: chronic phase, accelerated phase, and blast crisis. More than 90% of the patients showed good hematologic response to STI571. STI571 is also a potent inhibitor of a receptor-type c-Kit tyrosine kinase. Therefore, STI571 was examined for therapeutic efficacy against malignant Gastro-Intestinal Stromal Tumors (GIST), which are mainly caused by aberrant expression of a mutated c-Kit that is constitutively active without binding of a ligand, stem cell factor (SCF). More than a half of the metastatic GIST patients enrolled in the clinical study responded to STI571. Thus, STI571 is now used as a therapeutic drug for both CML and GIST in more than 80 countries worldwide. Certain point mutations in the ATP binding site were found to be a cause of resistance to STI571 in both Bcr-Abl and c-Kit kinases. Therefore, it would be better to make a precise therapeutic strategy with STI571 based on the gene analysis data. It is also expected that it will be possible to design an inhibitor to overcome such resistance by using the structural information on the mutants.

Hsp70 attenuates hypoxia/reoxygenation-induced activation of poly(ADP-ribose) synthetase in the nucleus of adult rat cardiomyocytes.

Effects of heat shock protein 70 (Hsp70) translocated to nuclear fraction on hypoxia/reoxygenation injury was examined by using adult cardiomyocytes isolated from rats. Cardiomyocytes were exposed to heat shock at 42 degrees C for 15 min (HS group), and then incubated at 37 degrees C for 6-24 h. Hsp70 production increased and the protein translocated from cytosol to nucleus. The maximum level of Hsp70 in the nuclear fraction was observed 12 h after HS. When cardiomyocytes without exposure to HS (nHS group) were subjected to 120 min hypoxia/15 min reoxygenation (Hypo/Reoxy), post-hypoxic cell viability was approximately 25% of the pre-hypoxic value. A rise in poly(ADP-ribose) synthetase (PARS) activity in the nuclear fraction was observed in nHS group, associated with an increase in polyADP-ribosylated protein. In contrast, post-hypoxic cell viability of HS group was approximately 60% of the pre-hypoxic value. Hypo/reoxy-induced rise in PARS activity and increase in polyADP-ribosylated protein were attenuated in HS group. To confirm the relationship between an increase in cell viability after Hypo/Reoxy and attenuation of PARS activation, cardiomyocytes without exposure to HS were subjected to Hypo/Reoxy in the presence of 1 mM 3-aminobenzamide, an inhibitor of PARS. Treatment of cells with 3-aminobenzamide attenuated Hypo/ Reoxy-induced decrease in cell viability. These results suggest that Hsp70 translocated into nucleus after HS may attenuate PARS activation during Hypo/Reoxy, leading to the cytoprotection of cardiomyocytes against Hypo/Reoxy injury.

[Preclinical and clinical profile of imatinib mesilate, a potent protein-tyrosine kinase inhibitor for CML therapy].

Imatinib mesilate (Glivec) is a protein-tyrosine kinase inhibitor that potently inhibits the Bcr-Abl tyrosine kinase as well as the receptors for platelet-derived growth factor (PDGF) and stem cell factor (SCF), c-Kit, at in vitro and cellular kinase assay levels. Since Bcr-Abl tyrosine kinase plays a key role in chronic myelogenous leukemia (CML) patients, treatment with imatinib mesilate that potently inhibits Bcr-Abl tyrosine kinase could be a promising therapeutic approach to CML. Imatinib mesilate was shown to inhibit proliferation of bcr-abl-positive cell lines and suppress the formation of bcr-abl-positive colonies in cells derived from bone marrow of CML patients. This compound induced apoptosis in a variety of bcr-abl-positive cells. Moreover, in vivo data indicated that imatinib mesilate suppress growth and formation of bcr-abl-positive tumors in mice. As the profile expected from the preclinical studies, imatinib mesilate showed impressive hematological and cytogenic responses in the clinical trials, including interferon-alpha-resistant or intolerant patients.

Myocardial heat shock protein changes in the failing heart following coronary artery ligation.

BACKGROUND: Production of several heat shock proteins (Hsp) is enhanced after exposure to stress. There is little information concerning changes in myocardial Hsp under pathophysiological conditions. The aim of this study was to determine alterations in Hsp content in the viable left ventricular myocardium during the development of heart failure following coronary artery ligation (CAL). METHODS: Myocardial infarction was produced by CAL of Wistar rats. One and eight weeks after the operation, haemodynamic parameters of rats with CAL were determined and then expression of Hsp27, Hsp60 and Hsp72 was measured by western blotting. RESULTS: Animals showed a decrease in cardiac output and an increase in left ventricular end-diastolic pressure, symptoms of chronic heart failure (CHF), 8 weeks after CAL. Myocardial Hsp27 and Hsp72 at 1 week after CAL significantly increased, whereas expression of both proteins at 8 weeks was similar to that in rats which underwent a sham operation (without coronary artery ligation). In contrast, Hsp60 at 8 weeks, but not at 1 week, significantly increased in the sham rats. CONCLUSIONS: Diverse changes in myocardial Hsp occurred during the development of CHF.