Blocking cysteinyl leukotriene signalling ameliorates myocardial hypoxia in chronic ischemic heart disease

Background: The involvement of cysteinyl leukotrienes (cys-LTs) and their receptors (CysLTs receptor) in the pathologic response to chronic cardiac ischemia and during bouts of ischemia remains an unresolved question. Objective: We investigated the expression of cys-LT pathway components in normal and ischemic myocardium and the potential benefits of interrupting cys-LT signalling during bouts of ischemia. Methods and Results: Heart biopsies were collected from C57BL/6J control mice and Apoe-/- mice fed a hypercholesterolemic diet for 1 year and subjected to an hypoxic stimulus for 30 minutes. Contribution of leukotriene signalling to cardiac ischemia induced by hypoxia was evaluated by administration of montelukast, a selective CysLT1 receptor antagonist. We also used a unique collection of human heart biopsies obtained from normal and chronic ischemic areas of the myocardium of 14 patients with chronic coronary artery disease. Here we report that in myocardium of Apoe-/- mice, leukotriene C4 synthase (LTC4S) and CysLT1 are upregulated compared to C57BL/6J. Acute hypoxia further induced LTC4S expression and enzyme activity along with increased CysLT1 expression. Similar mRNA expression patterns of LTC4S and CysLT1 were observed in non-ischemic versus chronic ischemic human myocardium. Treatment of Apoe-/- mice with montelukast, during acute hypoxic stress, ameliorated myocardial hypoxic load to levels equal to those observed under normoxia. Conclusions: The data show an increased leukotriene signalling in chronic ischemic myocardium. In an experimental Apoe-/- model of ischemic cardiomyopathy, inhibition of leukotriene signalling ameliorates hypoxic damage to the myocardium suggesting a possible beneficial effect of antileukotriene drugs on the ischemic heart. Figure 1: LTC4S and CysLT1 are upregulated in cardiac tissue of Apoe-/- mice In the -/-Apoe-/- heart levels of LTC4S and CysLT1 are significantly upregulated as compared to control C57BL/6J mice (Panel A). Acute hypoxic stress in Apoe-/- mice increases the cardiac expression of LTC4S (p<0.05) and CysLT1 (p=0.06) compared to normoxic conditions (Panel B). Each experiment was run in duplicate and changes in mRNA levels were expressed as \u394\u394Ct values. Values are mean \ub1 SD. *, p<0.05; **, p<0.01. References. [1] Gabrielsen A, Lawler PR, Yongzhong W, et al., Gene expression signals involved in ischemic injury, extracellular matrix composition and fibrosis defined by global mRNA profiling of the human left ventricular myocardium. J Mol Cell Cardiol. 42, 870-83, 2007. [2] Steffens S, Montecucco F, Mach F., The inflammatory response as a target to reduce myocardial ischaemia and reperfusion injury. Thromb Haemost,102, 240-7, 2009

12- and 15-lipoxygenases in human carotid atherosclerotic lesions : associations with cerebrovascular symptoms

Lipoxygenase (ALOX) enzymes are implicated in both pro- and anti-atherogenic processes. The aim of this study was to investigate mRNA expression of 12- and 15-lipoxygenases (ALOX12, ALOX12B, ALOX15, ALOX15B) and the atypical ALOXE3 in human carotid atherosclerotic lesions, in relation to cerebrovascular symptoms and risk factors.The Biobank of Karolinska Endarterectomies (BiKE) collection of human carotid plaque tissue and associated clinical data was utilized (n= 132). Lesion mRNA levels were analyzed by TaqMan qPCR (n= 132) and microarray hybridization (n= 77).Of the investigated mRNAs, only ALOX15B (15-LOX-2; epidermis-type 15-LOX) was readily detected in all plaque samples by qPCR, and thus suitable for quantitative statistical evaluation. ALOX12, ALOX12B, ALOX15 and ALOXE3 were detected with lower frequency and at lower levels, or virtually undetected. Microarray analysis confirmed ALOX15B as the most abundant 12- or 15-lipoxygenase mRNA in carotid lesions. Comparing plaques with or without attributable cerebrovascular symptoms (amaurosis fugax, transient ischemic attack, or stroke), ALOX15B mRNA levels were higher in symptomatic than asymptomatic plaques (1.31 [1.11-1.56], n= 102; and 0.79 [0.55-1.15], n= 30, respectively; p= 0.008; mean [95% CI], arbitrary units). Multiple regression analysis confirmed symptomatic/asymptomatic status as a significant determinant of ALOX15B mRNA levels, independently of potentially confounding factors. Immunohistochemical analyses showed abundant ALOX15B expression in macrophage-rich areas of carotid lesions, and lipidomic analyses demonstrated the presence of typical ALOX15B products in plaque tissue.In summary, we observed associations between high ALOX15B expression in carotid lesions and a history of cerebrovascular symptoms. These findings suggest a link between ALOX15B and atherothrombotic events that merits further investigation