Cholesterol crystals have been linked to activation of the NLRP3
inflammasome and the formation of foreign body giant cells (FBGCs). It
has been hypothesized that FBGCs have a role in advanced atherosclerotic
plaque formation. This thesis examined the feasibility of producing
stable cultures of FBGCs starting with human monocytes with the
goal to examine pterin production by these cells in comparison to
human monocyte derived macrophages (HMDMs). The study also
investigated the effect of cholesterol crystals on 7,8-dihydroneopterin
(7,8-NP) production and modulation of IL-1β levels in macrophages.
7,8-Dihydroneopterin is a potent antioxidant generated by macrophages
which also down regulates the expression of macrophage scavenger
receptor CD36. The use of alpha-tocopherol and IL-4 as FBGC fusion
mediators was explored. Using these mediators, large numbers of
FBGC were successfully cultured. The rates of fusion achieved in the
cultures were low, and the cells had poor adhesion, which prevented
pterin measurement. FBGC, which are thought to remove crystallized
cholesterol from the plaque, cleared 21% of cholesterol crystal compared
to 50% cleared by HMDM cells. Due to this result, the effect of
cholesterol crystals on pterin production in monocytes and macrophages
was explored. Cholesterol crystals cause inflammation through the
activation of the NLRP3 inflammasome, however, it was unknown
whether they could modulate 7,8-NP production. Cholesterol crystals
caused an intracellular dose-dependent loss of 7,8-NP to its oxidized form,
neopterin, in HMDM cells. Cholesterol crystals induced intracellular
synthesis of 7,8-NP in HMDMs. 7,8-NP was released into the supernatant
and oxidized to neopterin in media. Monocytes treated with cholesterol
crystals released up to 100 nM of neopterin and 120 nM of 7,8-NP in
the media after 48 hours. The combination of IFN- and cholesterol
crystals appeared to inhibit the release of 7,8-NP into the media for the
first 48 hours, after this time 7,8-NP release rapidly increased. The
addition of exogenous 200 μM 7,8-NP showed that in the presence of
monocytes, cholesterol crystals did not cause the oxidation of 7,8-NP to
neopterin, as seen in HMDMs but possibly to 7,8-dihydroxanthopterin
or xanthopterin. The presence of 7,8-NP increased IL-1β expression in
the presence of cholesterol crystals after 24 hours incubation. FBGCs
and the removal of cholesterol crystals may be a key process in the
resolution of atherosclerotic plaques. It appears that cholesterol crystals
are able to modulate inflammatory processes including activation of
the inflammasome and balance of 7,8-dihydroneopterin to the oxidized
neopterin. The infiltrating monocytes may provide antioxidant protection
against the inflammation induced by cholesterol crystals and the activity
of the infammasome.
| Identifer | oai:union.ndltd.org:canterbury.ac.nz/oai:ir.canterbury.ac.nz:10092/7532 |
| Date | January 2012 |
| Creators | Burrowes, Hannah Mahony |
| Publisher | University of Canterbury. Biological Sciences |
| Source Sets | University of Canterbury |
| Language | English |
| Detected Language | English |
| Type | Electronic thesis or dissertation, Text |
| Rights | Copyright Hannah Mahony Burrowes, http://library.canterbury.ac.nz/thesis/etheses_copyright.shtml |
| Relation | NZCU |
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