To investigate molecular mechanisms controlling islet vascularization and revascularization after transplantation, we examined pancreatic expression of three families of angiogenic factors and their receptors in differentiating endocrine cells and adult islets. Using intravital lectin labeling, we demonstrated that development of islet microvasculature and establishment of islet blood flow occur concomitantly with islet morphogenesis. Our genetic data indicate that vascular endothelial growth factor (VEGF)-A is a major regulator of islet vascularization and revascularization of transplanted islets. In spite of normal pancreatic insulin content and ␤-cell mass, mice with ␤-cell-reduced VEGF-A expression had impaired glucose-stimulated insulin secretion. By vascular or diffusion delivery of ␤-cell secretagogues to islets, we showed that reduced insulin output is not a result of ␤-cell dysfunction but rather caused by vascular alterations in islets. Taken together, our data indicate that the microvasculature plays an integral role in islet function. Factors modulating VEGF-A expression may influence islet vascularity and, consequently, the amount of insulin delivered into the systemic circulation. Diabetes

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To test whether the antiapoptotic protein Bcl-2 prevents apoptosis and injury of cardiomyocytes after ischemia-reperfusion (I/R), we generated a line of transgenic mice that carried a human Bcl-2 transgene under the control of a mouse alpha-myosin heavy chain promoter. High levels of human Bcl-2 transcripts and 26-kDa Bcl-2 protein were expressed in the hearts of transgenic mice. Functional recovery of the transgenic hearts significantly improved when they were perfused as Langendorff preparations. This protection was accompanied by a threefold decrease in lactate dehydrogenase (LDH) released from the transgenic hearts. The transgenic mice were subjected to 50 min of ligation of the left descending anterior coronary artery followed by reperfusion. The infarct sizes, expressed as a percentage of the area at risk, were significantly smaller in the transgenic mice than in the nontransgenic mice (36.6 +/- 5 vs 69.9 +/- 7.3%, respectively). In hearts subjected to 30 min of coronary artery occlusion followed by 3 h of reperfusion, Bcl-2 transgenic hearts had significantly fewer terminal deoxynucleodidyl-transferase nick-end labeling-positive or in situ oligo ligation-positive myocytes and a less prominent DNA fragmentation pattern. Our results demonstrate that overexpression of Bcl-2 renders the heart more resistant to apoptosis and I/R injury.

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The present experiments were designed to evaluate the effects of pifithrin-α (PFT-α), which is a p53 inhibitor, on doxorubicin (DOX)-induced apoptosis and cardiac injury. Administration of DOX (22.5 mg/kg ip) in mice upregulated the mRNA levels of Bax and MDM2, whereas PFT-α attenuated those levels when administered at a total dose of 4.4 mg/kg at 30 min before and 3 h after DOX challenge. DOX treatment led to an upregulation of p53 protein levels, which was preceded by elevated levels of phosphorylated p53 at Ser15. PFT-α had no effect on the level of p53 or its phosphorylated form. The protein levels of Bax and MDM2 were elevated by DOX and attenuated by PFT-α. DOX gave rise to increased apoptosis-positive nuclei in cardiac cells, elevated serum creatine phosphokinase, ultrastructural alterations, and cardiac dysfunction. PFT-α offered protection against all of the aforementioned changes. Finally, PFT-α did not interfere with the antitumor potency of DOX. This study demonstrates that PFT-α effectively inhibits DOX-induced cardiomyocyte apoptosis, which suggests that PFT-α has the potential to protect cancer patients against DOX-induced cardiac injury.

The present study was designed to explore the protective effects of melatonin and its analogs, 6-hydroxymelatonin and 8-methoxy-2-propionamidotetralin, on the survival of doxorubicin-treated mice and on doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Whereas 60% of the mice treated with doxorubicin (25 mg/kg ip) died in 5 days, almost all the doxorubicin-treated mice survived when melatonin or 6-hydroxymelatonin (10 mg/l) was administered in their drinking water. Perfusion of mouse hearts with 5 μM doxorubicin for 60 min led to a 50% suppression of heart rate × left ventricular developed pressure and a 50% reduction of coronary flow. Exposure of hearts to 1 μM melatonin or 6-hydroxymelatonin reversed doxorubicin-induced cardiac dysfunction. 8-Methoxy-2-propionamidotetralin had no protective effects on animal survival and on in vitro cardiac function. Infusion of melatonin or 6-hydroxymelatonin (2.5 μg/h) significantly attenuated doxorubicin-induced cardiac dysfunction, ultrastructural alterations, and apoptosis in mouse hearts. Neither melatonin nor 6-hydroxymelatonin compromised the antitumor activity of doxorubicin in cultured PC-3 cells. These results suggest that melatonin protect against doxorubicin-induced cardiotoxicity without interfering with its antitumor effect.

Heme oxygenase (HO)-1 converts heme to bilirubin, carbon monoxide, and iron. Our prior work has suggested a cardioprotective role for HO-1 in heart failure. To test whether HO-1 (heat shock protein 32) prevents cardiomyocyte apoptosis and cardiac dysfunction after ischemia-reperfusion (I/R), we generated transgenic mice overexpressing HO-1 in the heart under the control of the alpha-myosin heavy chain promoter. HO-1 transcript and protein increased markedly in the heart only. In an isolated heart preparation, we observed an enhanced functional recovery during reperfusion after ischemia in the transgenic hearts compared with nontransgenic controls. I/R injury was also performed in intact animals by coronary ligation and reperfusion to assess the protective role of HO-1 overexpression on heart apoptosis. HO-1 overexpression reduced cardiac apoptosis, as evidenced by fewer terminal deoxynucleodidyl transferase-mediated dUTP nick-end labeling-positive or in situ oligo ligation-positive myocytes, compared with nontransgenic mice. Our results indicate that cardioselective overexpression of HO-1 exerts a cardioprotective effect after myocardial I/R in mice, and this effect is probably mediated via an antiapoptotic action of HO-1.