IAP antagonists Birinapant and AT-406 efficiently synergise with either TRAIL, BRAF, or BCL-2 inhibitors to sensitise BRAFV600E colorectal tumour cells to apoptosis.

BACKGROUND: High expression levels of Inhibitors of Apoptosis Proteins (IAPs) have been correlated with poor cancer prognosis and block the cell death pathway by interfering with caspase activation. SMAC-mimetics are small-molecule inhibitors of IAPs that mimic the endogenous SMAC and promote the induction of cell death by neutralizing IAPs. METHODS: In this study, anti-tumour activity of new SMAC-mimetics Birinapant and AT-406 is evaluated against colorectal adenocarcinoma cells and IAP cross-talk with either oncogenic BRAF or BCL-2, or with the TRAIL are further exploited towards rational combined protocols. RESULTS: It is shown that pre-treatment of SMAC-mimetics followed by their combined treatment with BRAF inhibitors can decrease cell viability, migration and can very efficiently sensitize colorectal tumour cells to apoptosis. Moreover, co-treatment of TRAIL with SMAC-mimetics can efficiently sensitize resistant tumour cells to apoptosis synergistically, as shown by median effect analysis. Finally, Birinapant and AT-406 can synergise with BCL-2 inhibitor ABT-199 to reduce viability of adenocarcinoma cells with high BCL-2 expression. CONCLUSIONS: Proposed synergistic rational anticancer combined protocols of IAP antagonists Birinapant and AT-406 in 2D and 3D cultures can be later further exploited in vivo, from precision tumour biology to precision medical oncology.

Phenylephrine postconditioning increases myocardial injury: are alpha-1 sympathomimetic agonist cardioprotective?

OBJECTIVE: We studied effects of phenylephrine (PHE) on postischemic functional recovery and myocardial injury in an ischemia-reperfusion (I-R) experimental model. MATERIALS AND METHODS: Rat hearts were Langendorff-perfused and subjected to 30 min zero-flow ischemia (I) and 60 min reperfusion (R). During R PHE was added at doses of 1 µM (n = 10) and 50 µM (n = 12). Hearts (n = 14) subjected to 30 and 60 min of I-R served as controls. Contractile function was assessed by left ventricular developed pressure (LVDP) and the rate of increase and decrease of LVDP; apoptosis by fluorescent imaging targeting activated caspase-3, while myocardial injury by lactate dehydrogenase (LDH) released during R. Activation of kinases was measured at 5, 15, and 60 min of R using western blotting. RESULTS: PHE did not improve postischemic contractile function. PHE increased LDH release (IU/g); 102 ± 10.4 (Mean ± standard error of mean) control versus 148 ± 14.8 PHE (1), and 145.3 ± 11 PHE (50) hearts, (P < 0.05). PHE markedly increased apoptosis. Molecular analysis showed no effect of PHE on the activation of proapoptotic c-Jun N-terminal kinase signaling; a differential pattern of p38 mitogen activated protein kinase (MAPK) activation was found depending on the PHE dose used. With 1 µM PHE, p-p38/total-p38 MAPK levels at R were markedly increased, indicating its detrimental effect. With PHE 50 µM, no further changes in p38 MAPK were seen. Activation of Akt kinase was decreased implying involvement of different mechanisms in this response. CONCLUSIONS: PHE administration during reperfusion does not improve postischemic recovery due to exacerbation of myocardial necrosis and apoptosis. This finding may be of clinical and therapeutic relevance.

Thyroid hormone can favorably remodel the diabetic myocardium after acute myocardial infarction.

It has been previously shown that regulators of physiological growth such as thyroid hormone (TH) can favorably remodel the post ischaemic myocardium. Here, we further explored whether this effect can be preserved in the presence of co-morbidities such as diabetes which accelerates cardiac remodeling and increases mortality after myocardial infarction. Acute myocardial infarction (AMI) was induced by left coronary ligation in rats with type I diabetes (DM) induced by streptozotocin administration (STZ; 35 mg/kg; i.p.) while sham-operated animals served as controls (SHAM). AMI resulted in distinct changes in cardiac function and geometry; EF% was significantly decreased in DM-AMI [37.9 ± 2.0 vs. 74.5 ± 2.1 in DM-SHAM]. Systolic and diastolic chamber dimensions were increased without concomitant increase in wall thickness and thus, wall tension index [WTI, the ratio of (Left Ventricular Internal Diameter at diastole)/2*(Posterior Wall thickness)], an index of wall stress, was found to be significantly increased in DM-AMI; 2.27 ± 0.08 versus 1.70 ± 0.05. 2D-Strain echocardiographic analysis showed reduced systolic radial strain in all segments, indicating increased loss of cardiac myocytes in the infarct related area and less compensatory hypertrophy in the viable segments. This response was accompanied by a marked decrease in the expression of TRα1 and TRß1 receptors in the diabetic myocardium without changes in circulating T3 and T4. Accordingly, the expression of TH target genes related to cardiac contractility was altered; ß-MHC and PKCα were significantly increased. TH (L-T4 and L-T3) administration prevented these changes and resulted in increased EF%, normal wall stress and increased systolic radial strain in all myocardial segments. Acute myocardial infarction in diabetic rats results in TH receptor down-regulation with important physiological consequences. TH treatment prevents this response and improves cardiac hemodynamics.

Morphine administration at reperfusion fails to improve postischaemic cardiac function but limits myocardial injury probably via heat-shock protein 27 phosphorylation.

BACKGROUND AND OBJECTIVES: We explored the effects of morphine administration during reperfusion period after an index ischaemia as well as potential molecular mechanisms underlying this response. This is of important clinical value, as morphine is used routinely in cardiovascular anaesthesia and in the emergency management of cardiac infarction. METHODS: Male Wistar rat hearts, mounted on constant flow isolated Langendorff preparation, were subjected to stabilization, 30 min of zero-flow global ischaemia and 45 min of reperfusion (CONT; n = 10). Morphine (10(-6) mol l(-1)) was administered only at reperfusion (MORPH; n = 10). Postischaemic recoveries of left ventricular developed pressure were expressed as percentage of the initial value. At the end of the experimental protocol, lactate dehydrogenase release in the perfusate was measured and the left ventricle was isolated and used for determination of oxidized actin, mitogen-activated protein kinase activation and heat-shock protein 27 phosphorylation. RESULTS: Left ventricular developed pressure percentage did not differ between groups, whereas lactate dehydrogenase release was significantly reduced in MORPH compared with CONT hearts. Left ventricular developed pressure percentage was negatively correlated with lactate dehydrogenase release in CONT hearts (r = -0.8, P = 0.006), whereas in MORPH hearts no correlation was found (r = -0.2, P = 0.57). Phosphorylated p38 mitogen-activated protein kinase, c-jun N-terminal protein kinases, extracellular signal-regulated kinases and Akt at 45 min of reperfusion were similar between groups. However, a 1.5-fold increase in phospho-heat-shock protein 27 was found in MORPH hearts compared with CONT hearts (P < 0.05). Additionally, the ratio of oxidized actin to total actin was found to be 1.9-fold more in MORPH compared with CONT hearts (P < 0.05). CONCLUSION: Morphine administration at reperfusion does not affect cardiac function but limits the extent of myocardial injury, possibly through increased heat-shock protein 27 phosphorylation.