Differentiation of fibroblasts into a-smooth muscle actin (SMA)-expressing myofibroblasts represents a critical step in the pathogenesis of fibrotic disorders, and is generally regarded as irreversible. Prostaglandin E 2 (PGE 2 ) has been shown to prevent multiple aspects of fibroblast activation, including the differentiation of fibroblasts to myofibroblasts. Here, we investigated its ability to reverse this differentiated phenotype. Fetal and adult lung fibroblasts were induced to differentiate into myofibroblasts by 24-hour culture with transforming growth factor (TGF)-b1 or endothelin-1. Cells were then treated without or with PGE 2 for various intervals and assessed for a-SMA expression. In the absence of PGE 2 treatment, a-SMA expression induced by TGF-b1 was persistent and stable for up to 8 days. By contrast, PGE 2 treatment effected a dose-dependent decrease in a-SMA and collagen I expression that was observed 2 days after PGE 2 addition, peaked at 3 days, and persisted through 8 days in culture. This effect was not explained by an increase in myofibroblast apoptosis, and indeed, reintroduction of TGF-b1 2 days after addition of PGE 2 prompted dedifferentiated fibroblasts to re-express a-SMA, indicating redifferentiation to myofibroblasts. This effect of PGE 2 was associated with inhibition of focal adhesion kinase signaling, and a focal adhesion kinase inhibitor was also capable of reversing myofibroblast phenotype. These data unambiguously demonstrate reversal of established myofibroblast differentiation. Because many patients have established or even advanced fibrosis by the time they seek medical attention, this capacity of PGE 2 has the potential to be harnessed for therapy of late-stage fibrotic disorders.Keywords: E prostanoid receptor; transforming growth factor-b1; endothelin-1; a-smooth muscle actin; focal adhesion kinase Pathologic scarring or fibrosis results in impaired organ function in diseases such as cirrhosis, diabetes, end-stage renal disease, scleroderma, and pulmonary fibrosis (1, 2). The accumulation of myofibroblasts within pathologic lesions is a pivotal feature of many fibrotic disorders (1, 2). Fibroblasts possess the potential to differentiate into myofibroblasts, which are distinguished from fibroblasts by their expression of contractile proteins, such as a-smooth muscle actin (a-SMA), and their exuberant production of extracellular matrix proteins, such as collagen I. This expression of a-SMA and increased extracellular matrix production endow myofibroblasts with the ability to participate in wound contraction (3). Because the differentiation of fibroblasts to myofibroblasts is generally considered irreversible (4), resolution of normal wound repair is thought to require apoptosis of myofibroblasts (5). By contrast, pathologic fibrosis occurs when myofibroblasts fail to apoptose and instead accumulate and persist within tissues, contributing to progressive scarring. Indeed, idiopathic pulmonary fibrosis (IPF)-the most common and fatal type of lung fibrosis-is characterized b...

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Myofibroblasts, the major effector cells in pathologic fibrosis, derive from the differentiation of fibroblasts driven by mediators such as transforming growth factor-b1 (TGF-b1) and biomechanical signals. Although the myofibroblast has traditionally been considered a terminally differentiated cell, the lipid mediator prostaglandin E 2 (PGE 2 ) has been shown to not only prevent but also reverse myofibroblast differentiation, as characterized by the ability of PGE 2 to diminish expression of collagen I and a-smooth muscle actin in established myofibroblasts. Here, we use microarrays to examine the extent of transcriptomic changes that occur during TGF-b1-induced differentiation and PGE 2 -induced dedifferentiation of myofibroblasts. Normal primary human adult lung fibroblasts were cultured for 24 hours with or without TGF-b1 and treated for 48 hours with PGE 2 . Gene expression levels were assessed from total RNA on the Affymetrix U219 microarray. TGF-b1 up-regulated 588 genes and downregulated 689 genes compared with control cells. PGE 2 reversed the expression of 363 (62%) of the TGF-b1-up-regulated genes and 345 (50%) of the TGF-b1-down-regulated genes. Genes up-regulated by TGF-b1 and reversed by PGE 2 were enriched in annotations for Cell Adhesion, Contractile Fiber, and Actin Binding, whereas genes down-regulated by TGF-b1 but subsequently reversed by PGE 2 were enriched in annotations for Glycoprotein, Polysaccharide Binding, and Regulation of Cell Migration. Surprisingly, the genes whose expression was affected by PGE 2 differed between TGF-b1-induced myofibroblasts and undifferentiated fibroblasts. These data demonstrate the capacity of PGE 2 to effect marked global alterations in the transcriptomic program of differentiated myofibroblasts and emphasize the considerable plasticity of these cells.

Leukotrienes (LTs) C4, D4, and E4, collectively termed cysteinyl LTs (cysLTs), are lipid mediators formed by the 5-lipoxygenase (5-LO) pathway of arachidonic acid metabolism. Originally recognized for their potent bronchoconstrictor actions, they were subsequently determined also to promote inflammation, microvascular permeability, and mucus secretion. These actions that are so central to asthma pathophysiology are mediated to a significant extent by ligation of the cysLT receptor 1 (CysLT1). Antagonism of CysLT1 and inhibition of 5-LO have both been shown to have clinical use in the management of asthma, but substantial interindividual heterogeneity is observed in the response to these agents. In this article, we review the biologic actions of LTs, their biosynthetic pathways and cognate receptors, the pharmacology of available anti-LT agents, and the clinical evidence for the use of anti-LT agents as monotherapy and combination therapy in asthma. We also consider heterogeneity of response, the possible roles of cysLT receptors other than CysLT1, the role of another class of LT, LTB4, and the potential role of LTs in lung diseases other than asthma.

Morphological features of coronary arteries and incidental lesions are reported from hearts in five species of sharks, the shortfin mako shark, Isurus oxyrhinchus Rafinesque, thresher shark Alopias vulpinus (Bonaterre), blue shark, Prionace glauca L., the smooth dogfish, Mustelus canis (Mitchill), and spiny dogfish, Squalus acanthias L. Sharks were collected from the northwestern Atlantic between June and August from 1996 to 2010. They were necropsied dockside and the hearts were preserved in buffered formalin. Routine sections including ventricle/conus arteriosus and the atrio-ventricular junctions were embedded in paraffin, stained with common histological and immunohistochemical methods and examined by brightfield microscopy. Myointimal hyperplasia, medial myo-myxomatous hyperplasia and bifurcation pads were observed commonly, and medial muscle reorientation and epicardial myeloid tissues were rare. All the above features differed in severity, prevalence and distribution depending on anatomical site and shark species/size. Morphometric analysis indicated that myomyxomatous hyperplasia is associated with luminal narrowing of blood vessels. As suggested previously, the described morphological features are most likely physiological responses to blood flow characteristics. Vascular and cardiac lesions were uncommon and included, granulomatous proliferative epicarditis with fibroepitheliomas, myxomatous epicardial expansions, medial arterial vacuolation, myocardial fibrosis, acute ventricular emboli and parasitic granulomas. The lesions of embolism, proliferative and granulomatous epicarditis and myocardial fibrosis were in all sharks associated with capture events including retained fishing hooks. The significance and aetiopathogenesis of medial vacuolation and epicardial myxomatous expansions remains unclear.