HYPOXIC SIGNALS IN THE ISCHEMIC MYOCARDIUM: ROLE OF GALECTIN-1 AND GALECTIN-3

Myocardial infarction is the most serious manifestation of coronary artery disease and the cause of significant levels of mortality and morbidity worldwide. Galectin-1 (GAL-1) and Galectin-3 (GAL-3) are beta galactoside binding lectins with diverse functions. Hypoxia inducible factor-1 alpha (HIF-1α) is a transcription factor mediating early and late responses to myocardial ischemia. We aim to study the direct effects of ischemia on GAL-1, GAL-3 and HIF-1α in the heart. Male C57B6/J and GAL-3 knockout mice were used for our two disease models. In the Myocardial infarction (MI) model, the left anterior descending artery of the heart is permanently ligated to create ischemia in the anterior myocardium. In the Ischemia reperfusion model (IR), the artery is temporarily ligated for a specific period of time and then reperfusion is established. Heart samples were processed for immunohistochemical and immunofluorescent labeling, western blotting, Enzyme linked immunosorbent assay and quantitative real time PCR. Inflammatory, Apoptotic and Oxidative stress markers were also studied. We show for the first time that GAL-1, GAL-3 and HIF-1α levels in the left ventricle are raised in early ischemic period in conjunction with a predominant antiapoptotic activity in the heart. Our identification of the pattern of expression of GAL-1, GAL-3 and HIF-1α in the heart during the first 24 hours following acute MI has helped in understanding early molecular changes in this event and may provide methods to overcome serious complications. Our work further showed that GAL-3 acted as a regulator of proinflammatory and antiapoptotic mechanisms in the myocardium after myocardial infarction that will shape the future course of the disease. GAL-3 was also shown to interfere with vii redox pathways controlling cell survival and death and plays a protective role in the pathogenesis of ischemia reperfusion injury in the heart. Our work has contributed in understanding the local microenvironment in which GAL-3 works in the heart after ischemia/infarction or ischemia-reperfusion and has opened a new window in understanding the exact role of GAL-3 in the heart

Galectin-1 in early acute myocardial infarction

Myocardial infarction (MI) is the most serious manifestation of coronary artery disease and the cause of significant mortality and morbidity worldwide. Galectin-1(GAL-1), a divalent 14.5-kDa protein, is present both inside and outside cells, and has both intracellular and extracellular functions. Hypoxia inducible factor-1 alpha (HIF-1α) is a transcription factor mediating early and late responses to myocardial ischemia. Identification of the pattern of expression of GAL-1 and HIF-1α in the heart during the first 24 hours following acute MI will help in understanding early molecular changes in this event and may provide methods to overcome serious complications. Mouse model of MI was used and heart samples were processed for immunohistochemical and immunofluorescent labeling and Enzyme linked immunosorbent assay to identify GAL-1 and HIF 1α levels in the heart during the first 24 hours following MI. There was significant increase in left ventricular GAL-1 at 20 (p = 0.001) and 30 minutes (p = 0.004) following MI. There was also a significant increase in plasma GAL-1 at 4 hours (p = 0.012) and 24 hours (p = 0.001) following MI. A significant increase in left ventricular HIF-1 α was seen at 20 minutes (p = 0.047) following MI. In conclusion, we show for the first time that GAL-1 level in the left ventricle is increased in early ischemic period. We also report for the first time that HIF-1 α is significantly increased at 20 minutes following MI. In addition we report for the first time that mouse plasma GAL-1 level is significantly raised as early as 4 hours following MI

Molecular switch model for cardiomyocyte proliferation

This review deals with the human adult cardiomyocyte proliferation as a potential source for heart repair after injury. The mechanism to regain the proliferative capacity of adult cardiomyocytes is a challenge. However, recent studies are promising in showing that the \u27locked\u27 cell cycle of adult cardiomyocytes could be released through modulation of cell cycle checkpoints. In support of this are the signaling pathways of Notch, Hippo, Wnt, Akt and Jak/Stat that facilitate or inhibit the transition at cell cycle checkpoints. Cyclins and cyclin dependant kinases (CDKs) facilitate this transition which in turn is regulated by inhibitory action of pocket protein e.g. p21, p27 and p57. Transcription factors e.g. E2F, GATA4, TBx20 up regulate Cyclin A, A2, D, E, and CDK4 as promoters of cell cycle and Meis-1 and HIF-1 alpha down regulate cyclin D and E to inhibit the cell cycle. Paracrine factors like Neuregulin-1, IGF-1 and Oncostatin M and Extracellular Matrix proteins like Agrin have been involved in cardiomyocyte proliferation and dedifferentiation processes. A molecular switch model is proposed that transforms the post mitotic cell into an actively dividing cell. This model shows how the cell cycle is regulated through on- and off switch mechanisms through interaction of transcription factors and signaling pathways with proteins of the cell cycle checkpoints. Signals triggered by injury may activate the right combination of the various pathways that can \u27switch on\u27 the proliferation signals leading to myocardial regeneration

Is biological repair of heart on the horizon?

The stem cells keep us young by endogenously repairing us upon need. They do so bysmartly one step forward towards differentiation while another step backward to nurturethe undifferentiated stem cells. They are building blocks for every organ witha differential rate of repair of worn out tissues. Since stem cells can be cultured with a normal karyo type, they could be the ideal source for heart repair after myocardial infarction. As opposed to lower vertebrates and neonatal mice, cardiac regeneration in adult mammalian heart seems to be difficult to assess with a solid evidence of cytokinesis. It becomes more difficult to quantify the level of regeneration after myocardial infarction injury against a background of a large invasion of proliferating inflammatory cells. The question to beraised is how the renewal of a piece of myocardium follows the time line of picking upcell types in series: cardiomyocytes, endothelial cells, smooth muscle cells, fibroblast, pacemaker cells, conducting and Purkinje cells to bring the orchestration of rhythmically contracting and relaxing heart. This review focuses on where we are onthe status of heart repair and cardiac regeneration

Galectin-1: A biomarker of surgical stress in murine model of cardiac surgery

Galectin-1 (GAL-1) belongs to the family of β-galactoside-binding lectins. It regulates cell-cell and cell-matrix interactions, the immune response, apoptosis, cell cycle, RNA splicing and neoplastic transformation. We investigate the effect of heart manipulation secondary to cardiac surgery on the level of GAL-1 in murine heart and plasma. Male C57B6/J mice were used for adopted model of cardiac surgery. Heart samples were processed for immunohistochemical and immunofluorescent labeling, Enzyme linked immunosorbent assay and quantitative RT-PCR to identify GAL-1 levels in the heart and plasma during the first 24 hours following cardiac surgery. There is significant increase of GAL-1 in the LV at 30 minutes (

Loss of dystrophin staining in cardiomyocytes: A novel method for detection early myocardial infarction

Myocardial infarction (MI) is the most frequent diagnosis made in majority of sudden death cases subjected to clinical and medicolegal autopsies. When sudden death occurs at a very early stage of MI, traditional macroscopic examination, or histological stains cannot easily detect the myocardial changes. For this reason we propose a new method for detecting MI at an early stage. Murine model of MI was used to induce MI through permanent ligation of left anterior descending branch of left coronary artery. Five groups of C57B6/J mice were used for inducing MI, which includes 20 minutes, 30 minutes, one hour, four hours and 24 hours post MI groups. One naïve group and sham-operated groups were used as controls. There is loss of dystrophin membranous staining in cardiac myocytes occurs as early as 20 minutes post myocardial infarction. This can be used as a novel method to diagnose early myocardial infarction in post mortem cases where diagnosis is unclear. In conclusion, evaluation of immunohistochemical expression of dystrophin represents a highly sensitive method for detecting early myocardial infarction due to the loss of staining in the infarcted areas. Dystrophin immunostaining can also be used to assess myocardial architecture

Myocardial ischemia reperfusion injury: Apoptotic, inflammatory and oxidative stress role of galectin-3

Background/aims: Myocardial reperfusion has the potential to salvage the ischemic myocardium after a period of coronary occlusion. Reperfusion, however, can cause a wide spectrum of deleterious effects. Galectin-3 (GAL-3), a beta galactoside binding lectin, is closely associated with myocardial infarction (MI), myocardial fibrosis and heart failure. In our study, we investigated its role in ischemia-reperfusion injuries (IR) as this phenomenon is extremely relevant to the early intervention after acute MI.Methods: C57B6/J wild type (WT) mice and GAL-3 knockout (KO) mice were used for murine model of IR injury in the heart where a period of 30 minutes ischemia was followed by 24 hours of reperfusion. Heart samples were processed for immunohistochemical and immunofluorescent labeling, morphometric analysis, western blot and enzyme-linked immunosorbent assay to identify the apoptotic, inflammatory and oxidative stress role of GAL-3.Results: Our results show that there was a significant increase in GAL-3 levels in the heart which shows GAL-3 is playing a role in the ischemia reperfusion injury. Troponin I was also significantly higher in GAL-3-KO group than wild type. Our study shows that GAL-3 is associated with an increase in the antioxidant activity in the IR injured myocardium. Antioxidant enzymes superoxide dismutase, glutathione and catalase were found to be significantly raised in the GAL-3 wild type IR as compared to the GAL-3 KO IR group. A significant increase in apoptotic activity is seen in GAL-3 KO IR group as compared with GAL-3 wild IR group.Conclusion: Our study shows that GAL-3 can affect the redox pathways, controlling cell survival and death, and plays a protective role on the myocardium following IR injury

\u27Refractory epilepsy\u27: What lies beneath?

A 30-year-old woman presented to the emergency room with recurrent seizures for 5 days. She had been diagnosed with epilepsy 2 years previously but stopped treatment due to the side effects of her medications. She was now experiencing episodes every 15-30 min. While undergoing a brain MRI to investigate for structural central nervous system pathology, she experienced another episode, preceded by prodromal symptoms. Polymorphic ventricular tachycardia was noted during the event. Further investigation revealed a normal QT interval, normal electrolyte panel, normal coronaries and severe left ventricular systolic dysfunction. Cardiac MRI revealed non-ischaemic cardiomyopathy. The patient was managed with heart failure and antiarrhythmic medications and an implantable cardioverter defibrillator. She remained symptom free at 6-month follow-up. This case highlights the importance of differentiating between cardiogenic syncope and epilepsy and reiterates the importance of re-evaluating a diagnosis of epilepsy when presentation is atypical or symptoms are refractory

Acute myocardial infarction and myocardial ischemia-reperfusion injury: A comparison

Myocardial infarction (MI) denotes the death of cardiac myocytes due to extended ischemia. Myocardial reperfusion is the restoration of coronary blood flow after a period of coronary occlusion. Reperfusion has the potential to salvage ischemic myocardium but paradoxically can cause injury, a phenomenon called as \u27reperfusion injury\u27 (IR). Standard histologic, immunohistochemical and Elisa techniques were used to study the histopathologic, oxidative, apoptotic and inflammatory changes in MI and IR. The IL-6 levels in the LV of the MI group were significantly raised as compared to the IR group (P=0.0008). Plasma IL-6 was also significantly increased in the MI group as compared to the IR group (P=0.031). MI model was also associated with increase in the neutrophil polymorphs number in the infarction related myocardium as compared to the re-perfused myocardium. A significant increase in troponin I level in the MI group as compared to the IR group is also seen (P=0.0001). Our IR model showed enhanced pro-apoptotic mediators like cleaved caspase-3 (P=0.005) and cytochrome c in the myocardium as compared to the MI model. In conclusion, myocardial damage in MI is mainly due to ischemic necrosis and inflammatory mechanisms while apoptosis is the main mechanism of cell death in IR in addition to limited ischemic necrosis

Teaching shock pathophysiology by flipped classroom

Objective: To assess usefulness of flipped style of teaching conducted as small-group format in Cardiovascular and Respiration module for Year-I undergraduate medical students at Aga Khan University.Methods: The study was planned and conducted over a period of eight months from March to October 2017 including the time taken for planning, mock run, execution followed by analysis and dissemination. It was carried out at the Aga Khan University Medical College, Karachi. Pre and post test scores of students after flipped class room sessions was compared. Moreover, perception of students was assessed on Likert scale (0-4) by a pretested validated questionnaire.Results: The mean pre-test scores of the students was 4.86 ± 0.91 which improved to 6.09 ± 0.81 (p = 0.021) after attending the flipped class session. Students approved that the frame work helped to promote their learning motivation and engagement with improvement in understanding of the course materials and enhancement of learning during Face to Face activity.Conclusions: The flipped classroom approach showed promise in teaching and learning of \u27Pathophysiology of Shock\u27 by clinical scenarios in small group discussions. Implementation of flipped class room activity on a wider scale however needs careful selection of course objectives and logistics