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M.). cells). To focus on studying the functions of ACAT1 in macrophages, Huang (28) developed a myeloid-specific KO mouse (only in the myeloid cell lineage, which includes macrophages, microglia, and neutrophils. The myeloid-specific KO mice do not exhibit dry eye syndrome nor leukocytosis (28). When crossed with the KO (KO significantly reduced lesion macrophage content and suppressed atherosclerosis progression; mechanistic studies showed that ACAT1 deficiency in macrophages slows down the entry of these macrophages into the subendothelial layer of the arterial vessel (28). During various stages of atherosclerosis, in addition to CEs, cholesterol crystals, often referred to as cholesterol clefts, also develop and accumulate within lesions. These crystals cause damage to lysosomal membranes, trigger the formation of inflammasomes, and cause severe adverse immune responses (30, 31). Studies in macrophage cell culture showed that cholesterol crystal formations are initiated within the late endo/lysosomes (32, 33). Cell culture studies showed that without cholesterol acceptors present in the cell exterior, ACAT blockage in macrophages caused a significant increase in the cholesterol crystal content that led to detrimental consequences; however, when external cholesterol acceptors were present, ACAT blockage did not induce cholesterol crystal formation, and no detrimental consequence could be observed (34). FAZF At the level, whether ACAT blockage affects cholesterol crystal formation in atherosclerotic lesions had not been closely examined, because of one important technical limitation: in mouse models, cholesterol crystals become a prominent feature within the necrotic core in advanced atherosclerotic lesions, and it takes continuous feedings of a atherosclerosis diet for 15C20 weeks to develop advanced lesions in mouse. Both the total KO mouse and the myeloid-specific KO (KO genetic background, presumably because of exaggerated xanthomatosis, the whole-body KO mouse had a much-shortened life span and began to die 8C10 weeks after continuous high-cholesterol diet feeding. The much-shortened life span of the KO in advanced atherosclerotic lesions. Recently, Huang (28) showed that when fed continuously with a high-cholesterol diet, the KO in the KO mouse model for advanced and reported our findings. Results Silencing myeloid Acat1 reduces the development of advanced atherosclerosis in ApoE?/? mouse To assess the effect of a prolonged modified Paigen diet treatment on the overall health of the knockout was guarded from the occurrence of early death associated with the total knockout mouse. On average, 76% of in late stage atherosclerosis. To compare the atherosclerotic burden in 20-week altered Paigen dietCfed slowed the progression of advanced lesions (Fig. 2and rather than silencing globally extends the life span of altered Paigen dietCfed reduces the atherosclerotic burden in and and 0.05; **, 0.01. Previously, we showed that the mechanism by which myeloid deletion prevents early lesions likely involves the reduction of macrophage content within the ascending atherosclerotic plaques (28). Here, by performing fluorescent confocal microscopic analysis using CD68 to monitor macrophage presence, we again observed a marked reduction of macrophage content, in the intimal layer of both the ascending plaques and the descending plaques from in the in the represent atherosclerotic plaques. The data are reported as means S.E. *, 0.05. Open in a separate window Physique 4. Deleting myeloid in the and and is 10. and deletion caused a significant decrease in macrophage 10-Oxo Docetaxel content in the lesion. To provide a plausible cellular basis for this finding, we hypothesize that ACAT1 blockage may cause macrophages to produce less proinflammatory responses upon cholesterol loading. To test this possibility, 10-Oxo Docetaxel we isolated peritoneal macrophages from and and and 0.05. Open in a separate window Physique 6. Blocking ACAT1 ameliorates AcLDL induced iNOS and COX2 expressions in RAW macrophages. RAW macrophages were treated without or with K604 at 0.5 m for 18 h and then treated without or with 100 g/ml of AcLDL for 24 h. and and 0.05; **, 0.01. We next monitored cholesterol crystal contents in the lesions after the H&E staining of aortic cross-sections isolated from the in 0.05. Open in 10-Oxo Docetaxel a separate window Physique 8. TUNEL analysis of apoptosis in aortic lesions. Cell death was detected by TUNEL analysis in 0.05. Both ACAT1 and ACAT2 are expressed in advanced atherosclerotic lesions Given that ACAT1 is usually a major contributor to foam cell formation in macrophages (16), we next wanted to compare the percentage of foam.