Novel lipid mediator aspirin-triggered lipoxin A₄induces heme oxygenase-1 in endothelial cells

Abstract

-Lipoxins (LX) and aspirintriggered LX (ATL) are eicosanoids generated during inflammation via transcellular biosynthetic routes that elicit distinct anti-inflammatory and proresolution bioactions, including inhibition of leukocytemediated injury, stimulation of macrophage clearance of apoptotic neutrophils, repression of proinflammatory cytokine production, and inhibition of cell proliferation and migration. Recently, it was reported that aspirin induces heme oxygenase-1 (HO-1) expression on endothelial cells (EC) in a COX-independent manner, what confers protection against prooxidant insults. However, the underlying mechanisms remain unclear. In this study, we investigated whether an aspirin-triggered lipoxin A4 stable analog, 15-epi-16-(para-fluoro)-phenoxy-lipoxin A4 (ATL-1) was able to induce endothelial HO-1. Western blot analysis showed that ATL-1 increased HO-1 protein expression associated with increased mRNA levels on EC in a timeand concentration-dependent fashion. This phenomenon appears to be mediated by the activation of the G protein-coupled LXA4 receptor because pertussis toxin and Boc-2, a receptor antagonist, significantly inhibited ATL-1-induced HO-1 expression. We demonstrate that treatment of EC with ATL-1 inhibited VCAM and E-selectin expression induced by TNF-␣ or IL-1␤. This inhibitory effect of the analog is modulated by HO-1 because it was blocked by SnPPIX, a competitive inhibitor that blocks HO-1 activity. Our results establish that ATL-1 induces HO-1 in human EC, revealing an undescribed mechanism for the anti-inflammatory activity of these lipid mediators. signaling transduction; resolution of inflammation LIPOXINS (LX) are endogenous lipid mediators that dampen the host response and orchestrate resolution of inflammation. In humans, three main biosynthetic pathways are described for LX formation, each involves transcellular biosynthetic use of intermediates between distinct cell types that are in close proximity during inflammatory responses (43). Monocytes, eosinophils, and airway-epithelial cells can convert arachidonate into 15S-hydroxyeicosatetraenoic acid (15S-HETE) by a 15-lipoxygenase (LO) catalyzed reaction. 15S-HETE is rapidly taken up by neutrophils and converted to lipoxin A 4 by a 5-LO-catalyzed reaction (43). The second pathway for lipoxin biosynthesis was determined for interactions that occur predominantly within the vasculature between 5-LO, present in myeloid cells, and 12-LO, which is present in platelets. The 5-LO product leukotriene A 4 is converted in a transcellular manner by platelet 12-LO to lipoxins (43). More recently, a third major pathway for lipoxin generation was discovered that involves aspirin and the action of cyclooxygenase (COX)-2 and 5-LO (11). Endothelial and epithelial cells express COX-2 in response to diverse stimuli such as cytokines, hypoxia, and bacterial infections. Aspirin acetylates COX-2 and switches its catalytic activity for conversion of arachidonic acid to 15R-HETE in lieu of prostanoid biosynthesis. 15R-HETE is released from endot...

Nuclear Factor-κB-Independent Anti-Inflammatory Action of Salicylate in Human Endothelial Cells: Induction of Heme Oxygenase-1 by the c-Jun N-Terminal Kinase/Activator Protein-1 Pathway

“…This finding is in line with many studies that link HO-1 to anti-inflammatory features (Wagener et al, 2003) and is strengthened by observations made in the case of HO-1 deficiency (Yachie et al, 1999). Two recently published studies (Grosser et al, 2003;Nascimento-Silva et al, 2005) showing the ability of aspirin to induce HO-1 in ECV304 also support our data.…”

Resolvin D1 reduces deterioration of tight junction proteins by upregulating HO-1 in LPS-induced mice

“…33 In addition, ATL-1 induces HO-1 in human endothelial cells, revealing an undescribed mechanism for the antiinflammatory activity of these lipid mediators. 34 Another study has discovered that protectin D1 regulates HO-1 in a renal model. 35 HO-1, which is a rate-limiting enzyme that metabolizes heme accumulates in tissues because of blood red cell turnover, is correlated with the production of ROS.…”

Pharmacological and Clinical Aspects of Heme Oxygenase

“…It is believed that this mechanism is mediated by the activation of the G protein-coupled lipoxin A 4 receptor (Nascimento-Silva et al, 2005). It has been suggested that aspirin-triggered lipoxin induces HO-1 in human endothelial cells and that this increase in HO-1 protein is responsible for the antiinflammatory activity of these lipid mediators Nascimento-Silva et al, 2005).…”