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theses

Toxic doses of the analgesic acetaminophen (APAP) cause hepatic necrosis, a response mediated, in part, by inflammatory macrophages. Herein we characterized macrophages responding to APAP. Infiltrating myeloid cells were identified as CD11b+, Ly6G+ (granulocytic) or Ly6C+ (monocytic) subsets. Ly6Chi macrophages are pro-inflammatory, while Ly6Clo are anti-inflammatory. The origin of liver macrophages and mechanisms mediating their recruitment were analyzed utilizing GFP+ bone marrow chimeric mice and CX3CR1+/GFP reporter mice. Following APAP administration, we observed increased numbers of GFP+CD11b+ cells in livers of chimeric mice at all post treatment times. Conversely, CX3CR1+CD11b+ cells were observed mainly at later times. GFP+ bone marrow-derived Ly6Chi cells consisted of mature and immature cells as measured by F4/80 expression. Increased numbers of mature anti-inflammatory Ly6Clo bone marrow-derived macrophages were observed after APAP, which was correlated with a decrease in immature anti-inflammatory Ly6Clo macrophages at the later times. Analysis of coexpression of F4/80 and CX3CR1+ showed that mature macrophages were selectively recruited at later times after APAP. This suggests that CX3CR1+ recruitment involves anti-inflammatory cell recruitment, as well as multiple M2--like macrophage subpopulations. To further assess the phenotypes of GFP+ bone marrow-derived and CX3CR1+ macrophages, cells were examined for expression of pro- and anti-inflammatory markers. Confocal microscopy confirmed the accumulation of bone marrow-derived pro-inflammatory GFP+ macrophages in the liver which expressed the inflammatory enzyme, COX-2. This correlated with Ly6Chi macrophage subpopulations in GFP+ bone marrow chimeric mice. Reduced COX-2 expression was observed on CX3CR1+ macrophages, indicating that COX-2+ cell accumulation is independent of CX3CR1. Bone marrow-derived anti-inflammatory macrophages expressing the anti-oxidative enzyme HO-1 and mannose receptor were present in the liver at similar times as Ly6Clo macrophages. Interestingly, CX3CR1+ macrophages were found to only express HO-1, but not MR suggesting that the Ly6Clo subpopulation recruited to the liver in CX3CR1+/GFP reporter mice after APAP represents a unique subpopulation of anti-inflammatory macrophages. Overall, these studies demonstrate that bone marrow provides distinct pro- and anti-inflammatory macrophage subpopulations that employ chemokine receptors, such as CX3CR1 to aid in their trafficking to the liver. Furthermore, CX3CR1 associated recruitment includes both pro- and anti-inflammatory macrophages.

ETD_7029

M.S.

Includes bibliographical references

by Chi-En Sun

doi:10.7282/T3HQ420B

ETD graduate

The author owns the copyright to this work.