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Cannabinoid (CB2) Receptor Deficiency Reduces the Susceptibility of Macrophages to Oxidized LDL/Oxysterol-Induced Apoptosis

Macrophage apoptosis is an important process in the pathophysiology of atherosclerosis. Oxidized low-density lipoproteins (OxLDL) are a major component of lesions and potently induce macrophage apoptosis. Cannabinoid receptor 2 (CB2), the predominant macrophage cannabinoid receptor, modulates several macrophage processes associated with ongoing atherosclerosis; however, the role of CB2 in macrophage apoptosis is unknown. To determine if CB2 influences a macrophage apoptotic pathway relevant to atherosclerosis, we examined the effect of CB2 deficiency on OxLDL-induced macrophage apoptosis. In situ terminal transferase-mediated dUTP nick end labeling (TUNEL) analysis of resident peritoneal macrophages detected significantly fewer apoptotic CB2-/- macrophages than CB2+/+ macrophages after incubation with OxLDL (27.9 ± 4.7% vs. 61.9 ± 8.5%, P < 0.001) or 7-ketocholesterol (7KC) (18.9 ± 10.5% vs. 54.1 ± 6.9%, P < 0.001), an oxysterol component of OxLDL. Caspase-3 activity; proteolytic conversion of procaspase-3; and cleavage of a caspase-3 substrate, PARP, were also diminished in 7KC-treated CB2-/-macrophages. Furthermore, the deactivation of the prosurvival kinase, Akt, in response to 7KC was impaired in CB2-/-macrophages. These results suggest that CB2 expression increases the susceptibility of macrophages to OxLDL-induced apoptosis, in part, by modulating the effect of oxysterols on the Akt survival pathway and that CB2 may influence atherosclerosis by modulating lesional macrophage apoptosis.

Identiferoai:union.ndltd.org:ETSU/oai:dc.etsu.edu:etsu-works-18712
Date01 December 2008
CreatorsFreeman-Anderson, Natalie, Pickle, Theresa G., Netherland, Courtney D., Bales, Alicia, Buckley, Nancy E., Thewke, Douglas P.
PublisherDigital Commons @ East Tennessee State University
Source SetsEast Tennessee State University
Detected LanguageEnglish
Typetext
Formatapplication/pdf
SourceETSU Faculty Works
Rightshttp://creativecommons.org/licenses/by/4.0/

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