Cholesteryl Hemiazelate Induces Lysosome Dysfunction and Exocytosis in Macrophages

Abstract

OBJECTIVEA key event in atherogenesis is the formation of lipid-loaded macrophages, lipidotic cells, which exhibit irreversible accumulation of undigested modified low-density lipoproteins in lysosomes. This event culminates with the loss of cell homeostasis, inflammation and cell death. In this study we propose to identify the chemical etiological factors and understanding the molecular and cellular mechanisms responsible for the impairment of lysosome function in macrophages.APPROACH AND RESULTSUsing shotgun lipidomics we have discovered that a family of oxidized lipids (cholesteryl hemiesters, ChE), end products of oxidation of polyunsaturated cholesteryl esters, occurs at higher concentrations in the plasma of two cohorts of cardiovascular disease patients than in the plasma of a control cohort. Macrophages exposed to the most prevalent ChE, cholesteryl hemiazelate (ChA) exhibit lysosome enlargement, peripheral lysosomal positioning, lysosome dysfunction and lipidosis which are irreversible. The transcriptomic profile of macrophages exposed to ChA indicates that the lysosome pathway is deeply affected and is well correlated with lysosome phenotypic and functional changes. Interestingly, the dysfunctional peripheral lysosomes are more prone to fuse with the plasma membrane, secreting their undigested luminal content into the extracellular milieu with potential consequences to the pathology.CONCLUSIONWe identify ChA not only as one of the molecules involved in the etiology of irreversible lysosome dysfunction culminating with lipidosis but also as a promoter of exocytosis of the dysfunctional lysosomes. The latter event is a new mechanism that may be important in the pathogenesis of atherosclerosis.

Cx43 promotes exocytosis of damaged lysosomes through actin remodelling

“…Interestingly, an interactome study of injured lysosomes, revealed an interaction between Gal9, another galectin known to be recruited to damaged lysosomes, and VAMP7 68 , a SNARE protein involved in the membrane fusion of lysosomes with the plasma membrane. Nevertheless, how fusion machinery associated with secretory lysosomes, such as VAMP7 and CD63/LAMP3 [69][70][71][72] , is speci cally recruited to damaged lysosomes is still unclear. Interestingly, a very recent report showed increased cellular secretion in response to αsynuclein-induced lysosomal damage through a mechanism that relies on the autophagic secretory pathway, with a direct contribution of Gal3, Trim16 (tripartite motif containing 16) and ATG16L1 (autophagy related 16 like1) 21 .…”

“…Lysosome positioning within cells was measured as previously described 70 . Brie y, cell membrane and nuclear contours were extracted manually using ImageJ selection tools.…”

Lysosome (Dys)function in Atherosclerosis—A Big Weight on the Shoulders of a Small Organelle

“…These modifications significantly affect the physicochemical and biological properties of the lipoproteins (Aviram, 1993;Hoff and Hoppe, 1995). One of the major chemical modifications of LDL is oxidation, involving free radical mediated lipid peroxidation, which was already demonstrated to occur in vivo (Gibson et al, 2018;Domingues et al, 2021). The presence of different subsets of lipases and oxygenases in the arterial wall may result in the occurrence of numerous forms of modified LDL in vivo.…”

“…The pro-atherogenic potential of oxLDL has been solidly established (Goldstein et al, 1979;Steinberg et al, 1989;Jerome and Lewis, 1990;Aviram, 1993), although the role of each particular bioactive molecule remains largely unexplored. While most research has focused on the atherogenicity of oxidized phospholipids and oxysterols, our recent studies suggest that the end products of CE oxidation, cholesteryl hemiesters, may be responsible for some of the proatherogenic properties ascribed to oxLDL (Estronca et al, 2012;Domingues et al, 2017Domingues et al, , 2021.…”