Macrophages are active participants in many important biological processes, including antimicrobial activity, tumour surveillance, apoptotic cell clearance, homeostasis and wound healing. The activity of all cells is under the direct influence of their genetic makeup and macrophages are no exception. Natural resistance-associated macrophage protein 1 (Nramp1, also known as SLC11A1) is a macrophage-restricted gene that confers resistance to intracellular pathogens in mice. Mitogen activated protein kinase activated protein kinase 2 (MAPKAPK-2 or MK2), a substrate of p38 MAPK, is known to influence the activation of macrophages in response to stressors, including the Toll-like receptor (TLR)-4 ligand LPS. Like NRAMP1, MK2 has also been shown to influence the efficiency of the antibacterial response. The present study evaluates the role of NRAMP1 and MK2 in TLR-mediated cytokine induction and their role in cutaneous wound healing. Mice lacking NRAMP1 are severely impaired in their rate of cutaneous wound healing. Nramp1 gene ablation has been associated with lower levels of SLPI, a protein previously demonstrated to influence the rate of wound healing in a non-redundant fashion. Macrophages derived from Nramp1-null mice are less efficient in activating p38 MAPK signaling, which results in lower levels of MK2 phosphorylation. The reduced level of p38 MAPK and MK2 activation in Nramp1-null macrophages also correlates with decreased cytokine induction in response to TLR7 ligand stimulation of these cells. Using p38 MAPK inhibitor and MK2-deficient macrophages, we demonstrate that TLR7- and TLR9-mediated cytokine induction is directly under the control of this signaling pathway. Furthermore, cytokine induction is regulated by MK2 at the post-transcriptional level. Macrophage-induced cytokines play an important role in cutaneous wound healing. Since MK2-deficient macrophages are severely impaired in their ability to induce cytokines following activation, we next evaluated the role of MK2 in cutaneous wound healing. Our results demonstrate that the rate of wound healing is significantly delayed in the absence of MK2. The level of cytokine expression in the wounds is impaired and macrophages are major players in cutaneous wound healing. Our data also show that intradermal transfer of macrophages with intact MK2 significantly improved wound healing kinetics. Overall, the studies presented in this dissertation demonstrate the importance of NRAMP1 and MK2 in the modulation of macrophage gene expression, and their important role in the control of cutaneous wound healing.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:QMM.111902 |
| Date | January 2007 |
| Creators | Thuraisingam, Thusanth. |
| Publisher | McGill University |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Format | application/pdf |
| Coverage | Doctor of Philosophy (Department of Human Genetics.) |
| Rights | All items in eScholarship@McGill are protected by copyright with all rights reserved unless otherwise indicated. |
| Relation | alephsysno: 002698766, proquestno: AAINR51008, Theses scanned by UMI/ProQuest. |
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