TitleMechanisms mediating macrophage activation during acetaminophen-induced hepatotoxicity
NameDragomir, Ana-Cristina (author), Laskin, Debra L (chair), Laskin, Jeffrey D (internal member), GOW, ANDREW (internal member), GERECKE, DEONALD (internal member), HALL, LEROY B (outside member), Rutgers University, Graduate School - New Brunswick,
DescriptionClassically and alternatively activated macrophages and inflammatory mediators they release play a key role in the pathogenesis of acetaminophen (APAP)-induced hepatotoxicity. In the present studies, we investigated the role of the DNA-binding protein, high mobility group box-1 (HMGB1), and the β-galactoside binding lectin, galectin-3 (Gal-3), in regulating the phenotype of activated macrophages in the liver following APAP intoxication. Culture medium collected from hepatocytes treated for 24 h with 5 mM APAP (CM-AA) stimulated macrophage production of reactive oxygen species and upregulated expression of the antioxidant enzymes catalase and heme oxygenase-1 (HO-1). CM-AA also upregulated expression of the proinflammatory chemokines MIP-1α (CCL3) and MIP-2 (CXCL2), and the eicosanoid biosynthetic enzymes, COX-2 and 12/15-LOX, effects dependent on the p44/42 MAP kinase. Treatment of hepatocytes with ethyl pyruvate (EP) prior to APAP blunted the effects of CM-AA on macrophage ROS production, expression of antioxidant proteins, and COX-2, suggesting that part of the activity in CM-AA was HMGB1. Further studies demonstrated that APAP-induced hepatotoxicity was associated with upregulation of Gal-3 mRNA and protein expression. Loss of Gal-3 resulted in reduced hepatotoxicity in response to APAP. This correlated with decreases in APAP-induced expression of the inflammatory proteins lipocalin 2 (24p3), inducible nitric oxide synthase (iNOS), interleukin-12 (IL-12), tumor necrosis factor- (TNF-), macrophage inflammatory protein-3 (MIP-3α), CD98, the macrophage Gal-3 receptor, and TNF-α receptor 1 (TNFR1). In contrast, APAP-induced expression of the alternative activation markers Ym1 and Fizz-1, as well as tissue repair, was increased in Gal-3-/- mice. These results suggest that Gal-3 contributes to inflammatory mediator production and hepatotoxicity after APAP. We next investigated the role of Gal-3 in regulating macrophage proinflammatory phenotype. Following APAP intoxication, increased numbers of proinflammatory CD11b+/Ly6Chi macrophages accumulated in necrotic regions of the liver. These cells were distinct from resident Kupffer cells and expressed Gal-3. Loss of Gal-3 resulted in reduced accumulation of CD11b+/Ly6Chi macrophages in response to APAP and increased accumulation of anti-inflammatory CD11b+/Ly6Clo macrophages. These results suggest that Gal-3 promotes a proinflammatory, classically activated macrophage phenotype in the liver during APAP-induced hepatotoxicity. Taken together, these studies indicate that multiple mechanisms contribute to proinflammatory macrophage activation following APAP intoxication.
NoteIncludes bibliographical references
Noteby Ana-Cristina Dragomir
CollectionGraduate School - New Brunswick Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.