Abstract-This study aimed to examine whether an elevated activity of heme oxygenase (HO)-1 in the tissue attenuates endothelial cell-leukocyte interactions microvessels in vivo. When rats were pretreated with an intraperitoneal injection of hemin, an HO-1 inducer, mesenteric tissues, including their microvessels, displayed a marked induction of HO-1 concurrent with an increase in plasma concentrations of bilirubin-IX␣, the product of HO-catalyzed degradation of protoheme IX. In these rats, oxidative stress such as superfusion with H 2 O 2 and ischemia-reperfusion of the tissues neither induced rolling nor exhibited adherent responses of leukocytes in venules. In contrast, the oxidative stresses evoked marked rolling and adhesion of leukocytes in the control rats without HO-1 induction. The HO-1 induction also downregulated leukocyte adhesion elicited by other pro-oxidant stimuli such as N -nitro-L-arginine methyl ester. The decreases in the oxidant-elicited leukocyte adhesive responses under HO-1-inducing conditions were restored by perfusion with zinc protoporphyrin-IX, an HO inhibitor, but not with copper protoporphyrin-IX, which did not inhibit the enzyme. Furthermore, the effects of zinc protoporphyrin-IX were repressed by superfusion with bilirubin or biliverdin at the micromolar level, but not by the same concentration of carbon monoxide, another product of HO. These results indicate that induction of the HO-1 activity serves as a potential stratagem to prevent oxidant-induced microvascular leukocyte adhesion through the action of bilirubin, a product of HO reaction. (Circ Res. 1999;85:663-671.)

Whereas pneumonia is the most common cause of death and disability worldwide, most cases of pneumonia spontaneously resolve. Mechanisms that promote pneumonia resolution remain to be determined. Resolvin E1 (RvE1) is an endogenous mediator that displays proresolving actions in sterile inflammation. In this study, we developed a new model of aspiration pneumonia to evaluate the effect of RvE1 on acute lung injury caused by acid aspiration and subsequent bacterial challenge. Mice received hydrochloric acid into the left lung followed by the enteric pathogen Escherichia coli. I.v. administration of RvE1 (∼0.005 mg/kg) prior to acid injury selectively decreased lung neutrophil accumulation by 55% and enhanced clearance of E. coli. RvE1 significantly decreased lung tissue levels of several proinflammatory chemokines and cytokines, including IL-1β, IL-6, HMGB-1, MIP-1α, MIP-1β, keratinocyte-derived chemokine, and MCP-1, in a manner independent of the anti-inflammatory mediators IL-10 and lipoxin A4. In addition, animals treated with RvE1 had a marked improvement in survival. These findings in experimental aspiration pneumonia have uncovered protective roles for RvE1 in pathogen-mediated inflammation that are both anti-inflammatory for neutrophils and protective for host defense, suggesting that RvE1 represents the first candidate for a novel therapeutic strategy for acute lung injury and pneumonia that harnesses natural resolution mechanisms.

We previously demonstrated that Siglec-15, a member of the Siglec family of glycan-recognition proteins, is expressed on a subset of macrophages and preferentially recognizes the sialyl-Tn (sTn) antigen, a tumor-associated glycan structure. In this study, we report on the biological significance of the Siglec-15-mediated interaction between monocytes/macrophages and cancer cells. Siglec-15 is expressed on tumor-associated macrophages (TAMs) in various human tumor tissues. We further demonstrated that its expression is substantially elevated in macrophage colony-stimulating factor-induced M2-like macrophages, which produced more transforming growth factor-β (TGF-β) in response to sTn-positive cells than to negative cells. We designed a co-culture model of THP-1 (human monocytic leukemia) cells and H157 (human lung carcinoma) cells mimicking the interaction between monocytes/macrophages and cancer cells that recapitulated the enhanced TGF-β production in Siglec-15 expressing THP-1 cells by the cellular interaction with sTn expressing H157 cells. The enhanced TGF-β production required a direct interaction between the two cell lines through sialic acids. Siglec-15 associates with adaptor protein DNAX activation protein of 12 kDa (DAP12) at the binding determinant Lys(274) in the transmembrane domain and transduces a signal to spleen tyrosine kinase (Syk). The enhanced TGF-β secretion was significantly attenuated by Syk inhibitor treatment of THP-1 cells or by substitution of the Siglec-15 Lys(274) to Ala, which disrupts the molecular interaction between Siglec15 and DAP12. These findings indicate that Siglec-15 recognizes the tumoral sTn antigen and transduces a signal for enhanced TGF-β secretion in TAMs and further suggest that Siglec-15 on macrophages may contribute to tumor progression by the TGF-β-mediated modulation of intratumoral microenvironments.

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Objective-Acrolein, a known toxin in tobacco smoke, might be involved in atherogenesis. This study examined the effect of acrolein on expression of cyclooxygenase-2(COX-2) and prostaglandin (PG) production in endothelial cells. Methods and Results-Cyclooxygenase (COX)-2 induction by acrolein and signal pathways were measured using Western blots, Northern blots, immunoflouresence, ELISA, gene silencing, and promoter assay. Colocalization of COX2 and acrolein-adduct was determined by immunohistochemistry. Here we report that the levels of COX-2 mRNA and protein are increased in human umbilical vein endothelial cells (HUVECs) after acrolein exposure. COX-2 was found to colocalize with acrolein-lysine adducts in human atherosclerotic lesions. Inhibition of p38 MAPK activity abolished the induction of COX-2 protein and PGE 2 accumulation by acrolein, while suppression of extracellular signal-regulated kinase (ERK) and JNK activity had no effect on the induction of COX-2 expression in experiments using inhibitors and siRNA. Furthermore, rottlerin, an inhibitor of protein kinase C␦ (PKC␦), abrogated the upregulation of COX-2 at both protein and mRNA levels. Conclusion-These results provide that acrolein may play a role in progression of atherosclerosis and new information on the signaling pathways involved in COX-2 upregulation in response to acrolein and provide evidence that PKC␦ and p38 MAPK are required for transcriptional activation of COX-2. Key Words: acrolein Ⅲ COX-2 Ⅲ p38 MAPK Ⅲ atherosclerosis Ⅲ endothelial cells A ctivation of endothelial cells by proinflammatory stimuli has been established as an important link between risk factors and the pathologic mechanisms underlying atherosclerosis. 1 Thus, control of the inflammatory status of endothelial cells, which is achieved by a balance of pro-and antiinflammatory signals, is crucial to limiting the disease. Tobacco smoking induces inflammatory reactions 2 and promotes atherosclerosis 3 ; however, the mechanism that links cigarette smoking to an increased incidence of atherosclerosis is poorly understood.Acrolein (CH 2 ϭCH-CHO), a major product of organic combustion, including tobacco smoking, is the most reactive ␣, ␤-unsaturated aldehyde found widely in the environmol/ Lent. Acrolein is highly reactive and is hazardous to human health. 4 Acrolein is produced by a wide variety of both natural and synthetic processes, including the incomplete combustion of organic materials. Acrolein also has been found to be formed from threonine by neutrophil myeloperoxidase at sites of inflammation 5 and has been identified as both a product and initiator of lipid peroxidation. 6 Recent studies have shown that acrolein levels are increased in many diseases such as atherosclerosis, Alzheimer disease, and diabetes, and is possibly related to pathogenesis in these conditions. 7-9 We and others have reported that acrolein elevates intracellular reactive oxygen species (ROS) levels, which leads to cell dysfunction. 8,10 ROS-mediated cell damage is an important etiologic factor ...

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This study aimed to examine whether livers overexpressing heme oxygenase (HO)-1 could alter the vascular resistance through the vasorelaxing action of carbon monoxide (CO). The relationship among HO-1 expression, CO generation, and the vascular resistance was assessed in perfused rat livers pretreated with hemin, an inducer of HO-1. At 18 h after the hemin treatment, livers displayed marked increases in HO-1 expression in hepatocytes and venous CO flux and a reduction of the basal resistance. The reduction of the resistance in hemin-treated livers was canceled by administration of oxyhemoglobin, a reagent trapping both CO and nitric oxide (NO), but not by methemoglobin, which captures NO but not CO. Liposome-encapsulated oxyhemoglobin, which cannot access the space of Disse, did not cause vasoconstriction. Furthermore, these livers became less sensitive to endothelin-1, a vasoconstrictive peptide, than the untreated controls through mechanisms involving CO. On the other hand, at 12 or 24 h after the treatment when the HO-1 induction was not accompanied by CO overproduction, neither a decrease in the basal resistance nor vascular hyporeactivity to endothelin-1 was observed. These results suggest that CO overproduced in the extrasinusoidal compartment is a determinant of the HO-1-mediated vasorelaxation in the liver.

This study examined the role of bilirubin in heme oxygenase (HO)-1-mediated amelioration of mast cell (MC)-elicited inflammatory responses. Pretreatment of rats with an intraperitoneal injection of hemin, an inducer of HO-1, evolved a marked induction of the enzyme in MCs. Intravital videomicroscopy revealed that hemin pretreatment attenuated compound 48/80-elicited degranulation of MCs and resultant leukocyte adhesion in venules. Superfusion with biliverdin or bilirubin, but not with carbon monoxide (CO), another product of the HO reaction, mimicked suppressive actions of the HO-1 induction on both the cell degranulation and leukocyte adhesion elicited by the stimulus, suggesting a requirement of the enzyme reaction to generate bilirubin in the inhibitory mechanisms. Such MC-desensitizing actions of bilirubin were observed in primary-cultured MCs and reproduced irrespective of the choice of stimuli, such as compound 48/80, calcium ionophore, and anti-IgE serum. Furthermore, MC-stabilizing effects of HO-1 were reproduced by the gene transfection of the enzyme into mastocytoma cell line RBL2H3. These results suggest that bilirubin generated through HO-1 serves as an anti-inflammatory substance that desensitizes MCs and ameliorates leukocyte recruitment.