Autophagy Links Inflammasomes to Atherosclerotic Progression

We investigated the role of autophagy in atherosclerosis. During plaque formation in mice, autophagic markers colocalized predominantly with macrophages (m phi). Atherosclerotic aortas had elevated levels of p62, suggesting that dysfunctional autophagy is characteristic of plaques. To determine whether autophagy directly influences atherogenesis, we characterized Beclin-1 heterozygous-null and m phi-specific ATG5-null (ATG5-m phi KO) mice, commonly used models of autophagy haploinsufficiency and deficiency, respectively. Haploinsufficent Beclin-1 mice had no atherosclerotic phenotype, but ATG5-m phi KO mice had increased plaques, suggesting an essential role for basal levels of autophagy in atheroprotection. Defective autophagy is associated with proatherogenic inflammasome activation. Classic inflammasome markers were robustly induced in ATG5-null m phi, especially when coincubated with cholesterol crystals. Moreover, cholesterol crystals appear to be increased in ATG5-m phi KO plaques, suggesting a potentially vicious cycle of crystal formation and inflammasome activation in autophagy-deficient plaques. These results show that autophagy becomes dysfunctional in atherosclerosis and its deficiency promotes atherosclerosis in part through inflammasome hyperactivation.