(A–B) Body weight and total plasma cholesterol of Western diet-fed male Chop+/+;Apoe−/− and Chop−/−;Apoe−/− mice (n = 20 and 21, respectively).
(C) Pooled plasma samples were subjected to fast performance liquid chromatography gel-filtration, and the fractions were assayed for cholesterol concentration. None of the differences between the two groups of mice in A–C were statistically significant.
(D) Peritoneal macrophages from Chop+/+;Apoe−/− and Chop−/−;Apoe−/− mice were loaded with lipoprotein-derived unesterified cholesterol for the indicated times, and then whole-cell lysates were subjected to immunoblot analysis for CHOP and, as a loading control, tubulin.
(E) RNA from the intima of aortic root lesions of Chop+/+;Apoe−/− and Chop−/−;Apoe−/− mice (see ) was captured by LCM, and Chop and Cypa mRNA were quantified by RT-QPCR. Relative expression was normalized to Cypa. Results are displayed as the mean ± S.E.M. (n = 3 RT-PCR replicates). **, Chop mRNA not detected.

(A) The images show representative sections of aortic roots from each group of mice were stained with hematoxylin and eosin. Quantification was conducted on lesions from 20 Chop+/+;Apoe−/− mice and 21 Chop−/−;Apoe−/− mice. *, P = 0.03.
(B) Representative sections of hematoxylin and eosin-stained aortic root sections from Chop+/+;Apoe−/− and Chop−/−;Apoe−/− mice. (*= necrotic areas). The bar graph shows quantification of anuclear, afibrotic, and eosin-negative necrotic areas (n = 20 for both groups of mice). **, P < 0.01. (C) Quantification of necrotic area in a subgroup of 12 Chop+/+;Apoe−/− lesions and 10 Chop−/−;Apoe−/− lesions with statistically identical lesion area. *, P = 0.039.

(A) Left graph, Macrophages from Chop+/+;Apoe−/− or Chop−/−;Apoe−/− mice were loaded with lipoprotein-derived unesterified cholesterol and then assayed for apoptosis. *, P < 0.01. Middle graph, Macrophages were incubated for 18 h with vehicle control (0.2% ethanol) or 50 μM 7-ketocholesterol and then assayed for apoptosis. *, P<0.01 compared with Chop+/+;Apoe−/− macrophages. Right graph, Macrophages were incubated for 15 h with vehicle control, 50 μg/ml oxidized LDL (OxLDL), 1 mM SIN-1, or both compounds. The cells were then assayed for apoptosis. Asterisk = P<0.01 compared with Chop+/+;Apoe−/− macrophages. In the case of cholesterol loading, ~5% of apoptotic cells were PI-positive. With 7-ketocholesterol and OxLDL + SIN-1, the percentage of PI-positive cells was >50%, indicating advanced apoptosis, and both annexin-positive and PI-positive cells were decreased in the CHOP–deficient macrophages.
(B) Efferocytosis assays were conducted using various combinations of peritoneal macrophages from Chop+/+;Apoe−/− and Chop−/−;Apoe−/− mice, where the macrophages served as the source of either the apoptotic cells or the efferocytes. None of the differences shown are statistically significant.
(C) Representative micrographs show less TUNEL-positive signal (red; arrows) in nuclei (blue) of aortic root lesions from Chop−/−;Apoe−/− lesions. Bar, 10 μm. Quantification of TUNEL-positive nuclei was conducted on lesions from 20 Chop+/+;Apoe−/− mice and 21 Chop−/−;Apoe−/− mice. *, P<0.01.
(D) Representative micrographs show less activated caspase-3 (red; arrows) in aortic root lesions from Chop−/−;Apoe−/− vs. Chop−/−;Apoe−/− lesions. Bar, 10 μm. Quantification of TUNEL-positive cells was conducted on lesions from 7 Chop+/+;Apoe−/− mice and 7 Chop−/−;Apoe−/− mice. *, P<0.05.
(E) Representative sequential sections of a Chop+/+;Apoe−/− lesion stained for nuclei (Hoechst), TUNEL, and macrophages. Bar, 10 μm.

(A) Body weight, plasma total cholesterol, plasma HDL cholesterol, and FPLC plasma cholesterol profile of 12-wk Western diet-fed male Chop+/+;Ldlr−/− and Chop−/−;Ldlr−/− mice (n = 12 and 17, respectively). None of the differences between the two groups of mice in these parameters were statistically significant.
(B), Quantification of total aortic root lesion area and necrotic area of the mice described in A. *, P<0.05.
(C) Representative micrographs and quantification of TUNEL-positive signal (red) in nuclei (blue) of aortic root lesions from Chop−/−;Ldlr−/− lesions. Bar, 10 μm. *, P<0.05.
(D) Quantification of activated caspase-3 in aortic root lesions from Chop+/+;Ldlr−/− and Chop−/−;Ldlr−/ lesions. *, P<0.05.