Fatty Acid Amide Hydrolase Deficiency Enhances Intraplaque Neutrophil Recruitment in Atherosclerotic Mice

Abstract

Objective-Endocannabinoid levels are elevated in human and mouse atherosclerosis, but their causal role is not well understood. Therefore, we studied the involvement of fatty acid amide hydrolase (FAAH) deficiency, the major enzyme responsible for endocannabinoid anandamide degradation, in atherosclerotic plaque vulnerability. Methods and Results-We assessed atherosclerosis in apolipoprotein E-deficient (ApoE -/-) and ApoE -/-FAAH -/-mice. Before and after 5, 10, and 15 weeks on high-cholesterol diet, we analyzed weight, serum cholesterol, and endocannabinoid levels, and atherosclerotic lesions in thoracoabdominal aortas and aortic sinuses. Serum levels of FAAH substrates anandamide, palmitoylethanolamide (PEA), and oleoylethanolamide (OEA) were 1.4-to 2-fold higher in case of FAAH deficiency. ApoE -/-FAAH -/-mice had smaller plaques with significantly lower content of smooth muscle cells, increased matrix metalloproteinase-9 expression, and neutrophil content. Circulating and bone marrow neutrophil counts were comparable between both genotypes, whereas CXC ligand1 levels were locally elevated in aortas of FAAH-deficient mice. We observed enhanced recruitment of neutrophils, but not monocytes, to large arteries of ApoE -/-mice treated with FAAH inhibitor URB597. Spleens of ApoE

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“…The indirect and sustained activation of CB1 needs to be carefully addressed in the context of the cardiovascular system, since genetic deletion of FAAH in a doxorubicin-induced cardiomyopathy model promotes myocardial injury (600). Moreover, chronic pharmacological FAAH inhibition enhances intraplaque neutrophil recruitment in atherosclerotic mice (467).…”

Endogenous cannabinoid receptor CB1 activation promotes vascular smooth-muscle cell proliferation and neointima formation

“…These mice have strongly increased anandamide levels, in particular in brain and liver, confi rming the key role of FAAH in anandamide degradation ( 11,18 ). We recently demonstrated that FAAH defi ciency in atherosclerosis-prone mice leads to the development of an unstable atherosclerotic plaque phenotype due to enhanced neutrophil recruitment ( 19 ).…”

“…Our latest published fi ndings demonstrate that FAAH defi ciency leads to a striking increase of neutrophil recruitment into atherosclerotic plaques ( 19 ). This was related to enhanced expression of pro-infl ammatory Th1 cytokines (TNF-␣ , IFN-␥ ) and increased local expression of neutrophil chemoattractant CXCL1 in mice lacking FAAH.…”

“…Ϫ / Ϫ mice in a C57BL/6J background ( 11 ) were backcrossed with apoE Ϫ / Ϫ mice to generate apoE Ϫ / Ϫ FAAH Ϫ / Ϫ mice as described ( 19 ). We used 10 week-old male apoE Ϫ / Ϫ and apoE Ϫ / Ϫ FAAH Ϫ / Ϫ mice that we fed with a high-cholesterol diet (1.25% cholesterol) for 8 weeks before and up to 4 weeks after balloon injury until euthanasia.…”

“…In fact, anandamide is a partial agonist at CB 1 and CB 2 receptors (CB 1 K i value = 61 to 543 nM, CB 2 K i value = 279 to 1,940 nM), with higher effi cacy at CB 1 than CB 2 receptors. Other FAAH substrates that are also systemically elevated in FAAH-defi cient mice, i.e., PEA and OEA ( 19 ), do not bind to CB 1 and CB 2 receptors, but are thought to activate PPAR-␣ ( 13,14 ). The increase of anandamide in response to arterial injury was paralleled by reduced levels of the other major endocannabinoid, 2-AG, which is mainly metabolized by FAAH-independent pathways.…”