Background: The post-myocardial infarction (MI) scar interrupts electrical impulse propagation and delays regional contraction, which contributes to ventricular dysfunction. We investigated the potential of an injectable conductive biomaterial to restore scar tissue conductivity and re-establish synchronous ventricular contraction.Methods: A conductive biomaterial was generated by conjugating conductive polypyrrole (PPY) onto chitosan (CHI) backbones. Trypan blue staining of neonatal rat cardiomyocytes (CMs) cultured on biomaterials was used to evaluate the biocompatibility of the conductive biomaterials. Ca2+ imaging was used to visualize beating CMs. A cryoablation injury rat model was used to investigate the ability of PPY:CHI to improve cardiac electrical propagation in the injured heart in vivo. Electromyography was used to evaluate conductivity of scar tissue ex vivo.Results: Cell survival and morphology were similar between cells cultured on biomaterials-coated and uncoated-control dishes. PPY:CHI established synchronous contraction of two distinct clusters of spontaneously-beating CMs. Intramyocardial PPY:CHI injection into the cryoablation-induced injured region improved electrical impulse propagation across the scarred tissue and decreased the QRS interval, whereas saline- or CHI-injected hearts continued to have delayed propagation patterns and significantly reduced conduction velocity compared to healthy controls. Ex vivo evaluation found that scar tissue from PPY:CHI-treated rat hearts had higher signal amplitude compared to those from saline- or CHI-treated rat heart tissue.Conclusions: The PPY:CHI biomaterial is electrically conductive, biocompatible and injectable. It improved synchronous contraction between physically separated beating CM clusters in vitro. Intra-myocardial injection of PPY:CHI following cardiac injury improved electrical impulse propagation of scar tissue in vivo.

Cysteinyl leukotrienes (CysLTs) are potent inflammatory mediators that predominantly exert their effects by binding to cysteinyl leukotriene receptors of the G protein-coupled receptor family. CysLT receptor 2 (CysLT 2 R), expressed in endothelial cells of some vascular beds, has been implicated in a variety of cardiovascular functions. Endothelium-specific overexpression of human CysLT 2 R in transgenic mice (hEC-CysLT 2 R) greatly increases myocardial infarction damage. Investigation of this receptor, however, has been hindered by the lack of selective pharmacological antagonists. Here, we describe the characterization of 3-(((3-carboxycyclohexyl)amino)carbonyl)-4-(3-(4-(4-phenoxybutoxy)phenyl)-propoxy)benzoic acid (BayCysLT 2 ) and explore the selective effects of this compound in attenuating myocardial ischemia/reperfusion damage and vascular leakage. Using a recently developed ␤-galactosidase-␤-arrestin complementation assay for CysLT 2 R activity (Mol Pharmacol 79: 270-278, 2011), we determined BayCysLT 2 to be ϳ20-fold more potent than the nonselective dual CysLT receptor 1 (CysLT 1 R)/ CysLT 2 R antagonist 4-(((1R,2E,4E,6Z,9Z)-1-((1S)-4-carboxy-1-hydroxybutyl)-2,4,6,9-pentadecatetraen-1-yl)thio)benzoic acid (Bayu9773) (IC 50 274 nM versus 4.6 M, respectively). Intracellular calcium mobilization in response to cysteinyl leukotriene administration showed that BayCysLT 2 was Ͼ500-fold more selective for CysLT 2 R compared with CysLT 1 R. Intraperitoneal injection of BayCysLT 2 in mice significantly attenuated leukotriene D 4 -induced Evans blue dye leakage in the murine ear vasculature. BayCysLT 2 administration either before or after ischemia/reperfusion attenuated the aforementioned increased myocardial infarction damage in hECCysLT 2 R mice. Finally, decreased neutrophil infiltration and leukocyte adhesion molecule mRNA expression were observed in mice treated with antagonist compared with untreated controls. In conclusion, we present the characterization of a potent and selective antagonist for CysLT 2 R that is useful for discerning biological activities of this receptor.

Leukotrienes have been implicated in the pathogenesis of degenerative diabetic retinopathy, with research focusing primarily on leukotriene B(4), with little attention devoted to the cysteinyl leukotrienes (cysLTs), which act through cysLT receptors (CysLT(1)R and CysLT(2)R). We demonstrate here the presence of CysLT(2)R in pericytes and endothelial cells of superficial retinal vasculature using an indirect assay by assessment of β-galactosidase expression in CysLT(2)R-knockout (KO) mice. Retinal damage was induced in KO and wild-type (WT) mice using an established oxygen-induced retinopathy (OIR) model. CysLT(2)R expression following OIR was intensely up-regulated compared to sham-treated controls. Staining with Griffonia simplicifolia lectin revealed enhanced tissue damage (as assessed by vasoobliteration/vasoproliferation) in KO mice compared to WT controls, yet the opposite was true with respect to retinal edema. However, vascular endothelial growth factor receptor 1 (VEGFR1) transcripts were increased by OIR similarly with respect to genotype. Intravitreal application of exogenous cysLTs elicited greater vasculature leakage (assessed ex vivo) in eyes from WT mice compared to KO mice. While mRNA encoding enzymes for various components of the leukotriene cascade were detected in sham- and OIR-treated retinas, only prostaglandins and hydroxyeicosatetraenoic acids, but not leukotrienes, were detected in A23187-treated retina preparations. Together, these results implicate the CysLT(2)R in the progression of ischemic retinopathy.

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We established that folate-porphysomes are suitable for non-invasive imaging of macrophages and used it to investigate active macrophage behavior in the infarcted heart.

Leukotrienes are potent proinflammatory lipid mediators synthesized from arachidonic acid via the actions of 5-lipoxygenase and 5-lipoxygenase-activating protein.Cysteinyl leukotrienes (cysLTs) are a subfamily of leukotriene molecules, thus termed because of a common cysteine moiety in their respective structures. The cysLTs, leukotriene C 4 , D 4 , and E 4 (LTC 4 , D 4 , and E 4 , respectively), exert their effects by binding to sequenced G-protein-coupled receptors: cysteinyl leukotriene receptor 1 (CysLT 1 R), cysteinyl leukotriene receptor 2 (CysLT 2 R), and a novel CysLT E receptor (GPR99).3 CysLT 1 R binds LTD 4 preferentially to LTC 4 , whereas CysLT 2 R binds LTD 4 and LTC 4 with equal affinity. Both receptors bind LTE 4 , the most stable and abundant cysLT, with weak affinity. 4 In contrast, GPR99 displays preferential binding affinity for LTE 4 , with weak affinity for LTC 4 and LTD 4 . Objective-Transgenic overexpression of the human cysteinyl leukotriene receptor 2 (CysLT 2 R) in murine endothelium exacerbates vascular permeability and ischemia/reperfusion injury. Here, we explore the underlying mechanisms of CysLT 2 R activation-mediated inflammation and delineate the relative contributions of endogenous murine CysLT 2 R and the transgene-derived receptor. Approach and Results-We created a novel mouse with only endothelial-expressed CysLT 2 R (endothelium-targeted overexpression mice [EC]/CysLT 2 R-knockout mice [KO]) by crossing EC with KO to dissect the role of endothelial CysLT 2 R in tissue injury. Surprisingly, we discovered that damage in EC/KO mice was not elevated (24% versus 47% EC) after ischemia/reperfusion. We examined vascular permeability and leukocyte recruitment/rolling responses in the cremaster vasculature after cysteinyl leukotriene (cysLT) stimulation. Mice possessing transgenic endothelial CysLT 2 R overexpression, whether EC or EC/KO, when stimulated with cysLTs, exhibited vascular hyperpermeability, declining leukocyte flux, and a transient increase in slow-rolling leukocyte fraction. and coronary endothelial cells. 9 CysLT 2 R research had been previously hampered by a lack of selective pharmacological agents, 10 the majority of work instead using the nonselective cysLT antagonist/partial agonist 11 or genetic models of CysLT 2 R expression modulation. 11,12 However, recent studies have characterized 2 novel CysLT 2 R-selective antagonists: HAMI3379 13 and BayCysLT 2 , [14][15][16] which are proving to be useful as tools in eicosanoid research.There is evidence linking cysLTs to cardiovascular disease and inflammation. Expression of components of the leukotriene synthesis pathway is found in human atherosclerotic lesions.17 Furthermore, genetic polymorphisms in 5-lipoxygenase pathway genes have been correlated to increased myocardial infarction and stroke risk in some populations 18 but not all. 19,20 CysLT 2 R can mediate vascular permeability, 12,21 susceptibility to gastrointestinal tract inflammation, 22 and increased vulnerability to ischemic injury in the heart 11 a...