Atherosclerosis propagates when innate immune cells, myeloid-derived macrophages, undergo unregulated uptake of cholesterol-rich modified low-density lipoproteins (LDL). Excess storage and retention of this cholesterol leads to development of lipid-laden macrophage foam cells, that accumulate within the intima of arteries as developing plaque. Formation of atherosclerotic lesions reduces blood flow and can further lead to more serious complications such as myocardial infarction, stroke, and cardiovascular disease. AMP-activated protein kinase (AMPK), a master regulator of cellular energetics, has been shown to participate in many anti-atherogenic pathways within myeloid cells such as (but not limited to) the inhibition of cholesterol synthesis and stimulation of reverse cholesterol transport. However, a recent report described a pro-atherogenic role for myeloid AMPK, showing it is expression required for myeloid cell recruitment and longevity within the atherosclerotic microenvironment. Despite this, multiple reports all corroborate describing a protective role for systemic pharmacological AMPK activation. We sought to determine the consequence of modified LDL variants in myeloid AMPK signaling and to further clarify the role of myeloid AMPK signaling within atherosclerosis. In cultured macrophages primed with modified LDL variants underwent AMPK activation, which was also associated with increased markers of autophagy. In an in vivo model of intermediate atherosclerosis, we observed that neither myeloid AMPK expression nor systemic AMPK-activating therapy influenced lesion myeloid content, necrosis, or autophagic markers. Furthermore, despite a suggestive trend, both myeloid AMPK and AMPK-therapy did not significantly influence lesion size in male or female mice. Interestingly, we found that in animals lacking AMPK signaling to only one substrate, HMGCR (the rate limiting enzyme in cholesterol synthesis), knock-in mice developed accelerated atherosclerosis when compared to their wild-type littermate. Furthermore, we determined that AMPK signaling to HMGCR in the hematopoietic compartment alone is enough to protect against atherogenesis. Taken together, these studies show the benefit of interrogating specific AMPK-regulated pathways in the context of atherosclerosis, and sheds light on the benefit of utilization of single point mutation knock-in models opposed to global or cell type-specific knockout models for investigations into AMPK within atherosclerosis.
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/41211 |
| Date | 13 October 2020 |
| Creators | LeBlond, Nicholas |
| Contributors | Fullerton, Morgan |
| Publisher | Université d'Ottawa / University of Ottawa |
| Source Sets | Université d’Ottawa |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf |
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