Autophagy: A target for therapeutic interventions in myocardial pathophysiology

Background: Autophagy is a major degradative and highly conserved process in eukaryotic cells that is activated by stress signals. This self-cannibalisation is activated as a response to changing environmental conditions, cellular remodelling during development and differentiation, and maintenance of homeostasis. Objective: To review autophagy regarding its process, molecular mechanisms and regulation in mammalian cells, and its role in myocardial pathophysiology. Results/conclusion: Autophagy is a multistep process regulated by diverse, intracellular and/or extracellular signalling complexes and pathways. In the heart, normally, autophagy occurs at low basal levels, where it represents a homeostatic mechanism for the maintenance of cardiac function and morphology. However, in the diseased heart the functional role of the enhanced autophagy is unclear and studies have yielded conflicting results. Recently, it was shown that during myocardial ischemia autophagy promotes survival by maintaining energy homeostasis. Also, rapamycin was demonstrated to prevent cardiac hypertrophy. In heart failure, upregulation of autophagy acts as an adaptive response that protects cells from hemodynamic stress. In addition, sirolimus-eluting stents have been shown to lower re-stenosis rates in patients with coronary artery disease after angioplasty. Thus, this mechanism can become a major target for therapeutic intervention in heart pathophysiology. © 2008 Informa UK Ltd

PTH-related protein and Type 1 PTH receptor mRNA expression in ventricular myocardial hypertrophy

Background: The parathyroid hormone (PTH)-related protein (PTHrP) and Type 1 PTH receptor (PTH-1.R) bioregulation system exerts positive inotropic and chronotropic actions on myocardium in vivo, and it is implicated in cell-cell interactions, which can lead to myocardial hypertrophy. Objective: We analyzed the expression of PTHrP and PTH-1.R (mRNA and protein) in adult male Wistar rat ventricular myocardium after the induction of myocardial hypertrophy using aortic constricted and hyperthyroid models. Materials & methods: Expression of PTHrP and PTH-1.R mRNA was studied by semiquantitative reverse transcriptase polymerase chain reaction, while the nature of the polymerase chain reaction products was confirmed by direct DNA sequence. The expression of PTHrP and PTH-1.R in rat ventricular myocardium was confirmed using western blot and immunocytochemistry analysis. Results: The data showed that aortic banding-induced ventricular hypertrophy was associated with an increase in PTHrP mRNA expression, while hyperthyroid-induced ventricular hypertrophy was associated with PTH-1.R (mRNA and protein) overexpression in rat myocardium. Conclusion: Transcriptional changes of the PTHrP/PTH-1.R bioregulation system are differentially regulated in aortic constricting-induced and hyperthyroid-induced rat ventricular hypertrophy. © 2005 Future Drugs Ltd

Systemic cytokine response following exercise-induced muscle damage in humans

Background: Muscle adaptation which occurs following eccentric exercise-induced muscle damage has been associated with an acute inflammatory response. The purpose of this study was to investigate serum interleukin-6 (IL-6), osteoprotegerin and receptor activator of nuclear factor kB ligand (OPG/RANKL) concentrations following muscle damage. We measured changes for several days following muscle damage. Methods: Ten healthy young males performed an eccentric exercise protocol using their quadriceps. Blood samples were withdrawn before and at 6 h, 2 days, 5 days and 16 days post-exercise. Functional and clinical measurements were performed before, and on days 1, 2, 5, 8, 12 and 16 post-exercise. Results: The exercise protocol resulted in muscle damage, indicated by changes in biochemical markers. An increase in IL-6 and OPG, and a decrease in RANKL concentrations were seen at 6 h and on day 2 post-exercise; the OPG:RANKL ratio was increased at 6 h post-exercise (p<0.05). Conclusions: Changes in IL-6 and OPG/RANKL system may represent systemic responses in muscle inflammation and repair processes. However, further studies are needed to elucidate a potential systemic and/or local role of the OPG/RANKL system in skeletal muscle repair. © 2009 by Walter de Gruyter

Molecular detection of tyrosinase transcripts in peripheral blood from patients with malignant melanoma: Correlation of PCR sensitivity threshold with clinical and pathologic disease characteristics

Background: Positive molecular detection of tyrosinase transcripts (TYR mRNA) in RNA extracts of peripheral blood (PB) samples from patients with malignant melanoma provides evidence of disease dissemination. Methods: Total RNA extracted from PB was quantified and subjected to RT-PCR under ultra-sensitive and reduced-sensitivity PCR conditions using SSRT-II. Positive TYR mRNA detection in 78 melanoma patients and 40 healthy volunteers was correlated with clinical stage, Breslow's evaluation of tumor thickness, Clark's assessment of tumor invasion, the location of the primary tumor site, and tumor histology. The assay sensitivity was evaluated by spiking PB with the melanoma cell line SK-MEL-28. Results: Using ultra-sensitive PCR conditions, eight out of 40 RNA (20%) samples from healthy volunteers and 50 out of 78 RNA (64.1%) samples from melanoma patients tested positive. Using reduced-sensitivity PCR conditions, we found only two positives in 40 RNA samples from healthy subjects and 20 positives in 78 RNA samples (25.6%) from melanoma patients. Only positive PCR samples for the reduced-sensitivity PCR assay correlated significantly with stage IV (metastatic) disease (p=0.0395). There was no significant correlation between positive TYR mRNA samples for either PCR condition (ultra-sensitive and reduced-sensitivity) with Breslow's classification of tumor thickness, Clark's assessment of tumor invasion, location of the primary tumor site, and type of tumor histology. Conclusions: We conclude that reduced-sensitivity rather than ultra-sensitive PCR conditions correlate with clinical stage in melanoma patients. © 2006 by Walter de Gruyter

Molecular diagnosis of the viral component in cardiomyopathies: Pathopgysiological, clinical and therapeutic implications

Background: Myocarditis is defined as the inflammation of myocardium associated with cardiac dysfunction. Despite this clear-cut definition, diagnosis and etiologic treatment continue to create considerable debate. Viral infections are frequent causes of myocarditis and there is evidence that persistent viral infection is associated with poor prognosis in different subtypes of cardiomyopathy. Objective: To review methods for diagnosis of viral myocarditis and present the use of polymerase chain reaction (PCR)-based protocols for evaluating viral infection in myocarditis/cardiomyopathies. Methods: A review of published literature. Results/conclusion: There is increasing evidence that PCR-based protocols can provide reliable molecular evidence for the presence of viral infection in myocardium. Thus application of molecular techniques will allow collection and analysis of more information on the epidemiology of viral cardiomyopathies, patient risk stratification and appropriate medical treatment. © 2008 Informa UK Ltd

Experimental hyperthyroidism increases expression of parathyroid hormone-related peptide and type-1 parathyroid hormone receptor in rat ventricular myocardium of the Langendorff ischaemia-reperfusion model

Parathyroid hormone-related peptide (PTHrP) is released under ischaemic conditions and it improves contractile function of stunned myocardium. The actions of PTHrP are mediated primarily by the type 1 parathyroid hormone receptor (PTH.1R), while PTHrP and PTH.1R expression levels are increased in ventricular hypertrophy associated with experimental hyperthyroidism. Since chronic administration of thyroxine (T4) improves postischaemic recovery in isolated heart models subjected to ischaemia-reperfusion stress, we tested the hypothesis that experimentally induced hyperthyroidism is associated with elevated expression of PTHrP and PTH.1R in rat myocardium. Hyperthyroid and control male Wistar rats were subjected to ischaemia-reperfusion stress using the Langendorff technique, and the PTHrP and PTH.1R expression was assessed by relative quantitative reverse transcriptase-polymerase chain reaction, Western blot analysis and immunohistochemistry. In the Langendorff model, the recovery of left ventricular developed pressure at the end of the stablization period and 45 min into the reperfusion period was used to assess the cardioprotective actions of T4 administration. Our data show that hyperthyroid animals had increased tolerance to the ischaemia-reperfusion stress and that this was associated with an increase of PTHrP and PTH.1R expression levels compared with those of control animals. In the control animals, the expression of PTHrP was increased 45 min into the reperfusion phase, while the PTH.1R expression pattern was significantly and gradually decreased throughout the ischaemia and reperfusion phases. In the hyperthyroid animals, the PTHrP and PTH.1R expression pattern was significantly higher throughout the ischaemia and reperfusion phases compared with that of control hearts. Our data suggest that increasing levels of PTHrP and PTH.1R expression can mediate, at least in part, the T 4 administration-induced cardioprotection in rat ventricular myocardium. © 2007 The Authors

Serum levels of the osteoprotegerin, receptor activator of nuclear factor κ-B ligand, metalloproteinase-1 (MMP-1) and tissue inhibitors of MMP-1 levels are increased in men 6 months after acute myocardial infarction

Background: Osteoprotegerin (OPG) and receptor activator of nuclear factor κ-B ligand (RANKL) are critical regulators of bone remodeling and RANKL/RANK signaling could also play an important role in the remodeling process of several tissues, such as myocardium. Therefore, we investigated whether the serum concentrations of OPG and RANKL correlate with the serum levels of metalloproteinase-1 (MMP-1), MMP-9 and tissue inhibitors of MMP-1 (TIMP-1), which are known regulators of myocardial healing in acute myocardial infarction (AMI) patients. Methods: We analyzed blood samples from 51 consecutively hospitalized men with AMI, 12 men with established ischemic heart failure (New York Heart Association category II, NYHA-II) and 12 healthy men age-matched to the NYHA-II patients. Serum levels of MMP-1, MMP-9, TIMP-1, OPG and RANKL were quantified using commercially available ELISA kits. AMI patients were sampled 4 days and 6 months after MI. Results: Our data revealed increased serum levels of OPG, RANKL, MMP-1 and TIMP-1 levels and significant correlations between increased RANKL levels and MMP-1 and TIMP-1 serum levels 6 months after MI. In addition, the ratio OPG/RANKL was very low 6 months after MI, suggesting that the nuclear factor κ-B signaling is possibly more active 6 months post-MI than it is on day 4 post-MI. Conclusions: Our data suggest that OPG, RANKL, MMP-1 and TIMP-1 serum levels can be potential mediators of myocardial healing after MI. However, further large studies are needed to confirm the utility of OPG and RANKL as markers of healing after ST elevation in MI. © 2008 by Walter de Gruyter