Cysteinyl Leukotriene D4 Induced Vascular Smooth Muscle Cell Proliferation: A Possible Role in Myointimal Hyperplasia

Abstract

SummaryCysteinyl leukotrienes (i.e. LTC4, LTD4), produced by activated leukocytes or by transcellular metabolism may act at different levels on vascular smooth muscle cells (VSMC) during inflammatory processes or atherosclerosis. We studied the effect of LTC4, LTD4, and LTE4 on the in vitro proliferation of rat VSMC, measured by [3H]-thymidine incorporation and cell count. LTD4 had a stronger stimulatory effect on [3H]-thymidine incorporation than LTC4, whereas LTE4 was inactive. The effect of LTD4 on [3H]-thymidine incorporation was dose-dependent, with the maximal activity at 10−6 M. The stimulatory activity of LTD4 was inhibited in a dose-dependent manner by MK-571, a specific LTD4 receptor antagonist. In addition, MK-571 (1 mg/kg/day) given for at least 1 day after injury in a model of balloon catheter injury of rat carotid artery, provided effective inhibition of myointimal VSMC proliferation, with a 58% reduction of 5-bromo-2’-deoxyuridine (BrdU) uptake in the neointima and 69% reduction of neointimal thickening. Our data support the importance of inflammatory mechanisms in the pathogenesis of atherosclerosis and suggest a possible role for cysteinyl leukotrienes, specifically LTD4, in the control of VSMC proliferation.

CysLT1 leukotriene receptor antagonists inhibit the effects of nucleotides acting at P2Y receptors

“…This was demonstrated in dimethyl sulfoxide-differentiated U937 (dU937) cells, an immortalized cell line known to constitutively express a high density of CysLT 1 receptors upon differentiation to monocytes/macrophages [10,11], CysLT 1 receptors respond to LTD 4 with a strong increase in cytosolic Ca 2+ concentration ([Ca 2+ ] i ) partially sensitive to PTX, and with the activation of the Ras-MAPK cascade totally dependent upon G i/o [12]. These signaling effects were totally inhibited by various specific CysLT 1 -receptor antagonists, and no CysLT 2 receptor mRNA was detected [13,14], thus indicating that in monocytemacrophage like U937 cells LTD 4 -induced responses can be totally ascribed to a CysLT 1 receptor. The promonocytic leukemia cell U937 was selected because closely related to the inflammatory cells responsible of many CysLT biological actions, and because monocyte/ macrophages activation leads to the release of a wide spectrum of cytokines and chemokines that have key roles in all inflammatory diseases.…”

“…Conversely, the hP2Y 1,2,4,6,11,12,13,14 receptors represent a large family of GPCRs responding to either adenine or uracil nucleotides, or to sugar-nucleotides. Montelukast and pranlukast were found to inhibit nucleotide-induced calcium mobilization in a human monocyte-macrophage like cell line, DMSO-differentiated U937 (dU937).…”

“…Cysteinyl leukotrienes (CysLTs), LTC 4 , LTD 4 and LTE 4 , potent inflammatory mediators derived from arachidonic acid [1], are known to be very potent bronchoconstrictors and to play an important role in asthma and allergic rhinitis [2,3]. They have been also implicated in a number of inflammatory conditions including cardiovascular diseases, coronary artery disease, atherosclerosis and stroke [4][5][6] or in cardiovascular complications of inflammatory processes [7].…”

“…They have been also implicated in a number of inflammatory conditions including cardiovascular diseases, coronary artery disease, atherosclerosis and stroke [4][5][6] or in cardiovascular complications of inflammatory processes [7].…”

“…In particular, when the CysLT 1 receptor is expressed in recombinant systems it shows a preferential coupling to G q/11 , whereas when constitutively expressed it has been reported to activate both pertussis toxin (PTX)-sensitive and -insensitive G-proteins [8,9]. This was demonstrated in dimethyl sulfoxide-differentiated U937 (dU937) cells, an immortalized cell line known to constitutively express a high density of CysLT 1 receptors upon differentiation to monocytes/macrophages [10,11], CysLT 1 receptors respond to LTD 4 with a strong increase in cytosolic Ca 2+ concentration ([Ca 2+ ] i ) partially sensitive to PTX, and with the activation of the Ras-MAPK cascade totally dependent upon G i/o [12]. These signaling effects were totally inhibited by various specific CysLT 1 -receptor antagonists, and no CysLT 2 receptor mRNA was detected [13,14], thus indicating that in monocytemacrophage like U937 cells LTD 4 -induced responses can be totally ascribed to a CysLT 1 receptor.…”