Disruption of this process is associated with developmental abnormalities, malignancy, and, most recently, atherogenesis

Disruption of this process is associated with developmental abnormalities, malignancy, and, most recently, atherogenesis. cells, whereas control IgM antibodies did not. Confocal microscopy shown cell-surface manifestation of the oxidation-specific epitopes on apoptotic cells. Furthermore, each of these antibodies inhibited the phagocytosis of apoptotic cells by elicited peritoneal macrophages, as did OxLDL. In addition, an adduct of POVPC with BSA also efficiently prevented phagocytosis. Glycerol phenylbutyrate These data demonstrate that apoptotic cells communicate oxidation-specific epitopesincluding oxidized phospholipidson their cell surface, and that these serve as ligands for acknowledgement and phagocytosis by elicited macrophages. The importance of apoptosis in the normal development of multicellular organisms and in the maintenance of cellular homeostasis is widely appreciated. Disruption of this process is associated with developmental abnormalities, malignancy, and, most recently, atherogenesis. Compared with the explosive increase in our knowledge of the molecular events responsible for the rules of apoptosis, relatively little is known about the processes responsible for clearance of apoptotic cells. Apoptosis, or programmed cell death, is definitely a morphologically and functionally unique process of cell death by which undesirable cells are erased from the body in a manner that for the most part is not associated with an inflammatory response (1C3). A critical stage for the acknowledgement of apoptotic cells appears to involve the acquisition of cell-surface changes that result in engulfment by professional and semiprofessional phagocytes. On the one hand, the exact nature of the relevant changes on the surface of apoptotic cells responsible for this acknowledgement is definitely incompletely understood (4). Loss of membrane phospholipid asymmetry and consequent enhanced exposure of phosphatidylserine (PS) on the surface of apoptotic cells is generally thought to be responsible for phagocytosis by some macrophage populations (5, 6). In addition, changes in glycoprotein manifestation (7), loss of manifestation of glycosylphosphatidylinositol-linked protein antigens such as CD16 (8), and generation of a thrombospondin/CD36 binding site are all under study (9). On the other hand, the mechanisms by which professional phagocytes recognize apoptotic cells will also be Glycerol phenylbutyrate incompletely understood. These mechanisms are likely to be complex and may differ with differing cell types and subpopulations (4). It is noteworthy that in some ways the cellular plasma membrane is similar to the surface of a low-density lipoprotein (LDL) particle in that both are composed primarily of phospholipids comprising unsaturated fatty acids and protein. Oxidation of LDL prospects Glycerol phenylbutyrate to its enhanced uptake by numerous macrophage scavenger receptors. As demonstrated previously (10, 11) and in the friend manuscript (12), the binding of oxidized LDL (OxLDL) to macrophages is definitely inhibited either from the delipidated apoprotein B or by lipids extracted Rabbit Polyclonal to RNF144B from OxLDL and reconstituted into microemulsions (12). Similarly, oxidation of the lipid or lipid-protein matrix of a plasma membrane is definitely analogous to the oxidation of the LDL particle and might also be expected to lead to Glycerol phenylbutyrate acknowledgement by macrophage receptors. In fact, several lines of evidence raise the probability that cells undergoing apoptosis may present oxidatively revised moieties on their surface that are structurally analogous to moieties on the surface of the OxLDL particle. First, cells induced to undergo apoptosis by myriad stimuli generate reactive oxygen varieties that may induce membrane peroxidation (2, 13). Second, many of the macrophage receptors known to identify OxLDL, e.g., scavenger receptor A (SR-A), CD36, CD68, SR-B1 (CLA-I), and LOX-I, also have been reported to bind apoptotic cells or PS liposomes (14C18). Third, as demonstrated by Steinberg and colleagues (11C14), intact OxLDL, as well as lipid microemulsions prepared from OxLDL, can compete in part for binding of apoptotic cells to macrophages. These data suggest the hypothesis that both OxLDL and apoptotic cells have common ligands on their surfaces, consisting of oxidatively revised moieties that are identified by common macrophage receptors. However, the exact nature of the ligands on apoptotic cells or on OxLDL responsible for such cross-competition has not been demonstrated. In the present manuscript, we used murine monoclonal autoantibodies cloned from apoE-deficient mice that recognize specific oxidized phospholipids (OxPL)present either as free lipid or as OxPL-protein adductsto demonstrate the presence of these oxidized moieties on the surface of apoptotic cells but not normal cells. These antibodies inhibited the phagocytosis of apoptotic cells by macrophages, as did a specific oxidized phospholipid-protein adduct. In addition, we also demonstrate that additional autoantibodies directed against another oxidation-specific epitope, a malondialdehyde (MDA)-lysine adduct, also bind to apoptotic Glycerol phenylbutyrate cells and inhibit their phagocytosis by macrophages. These data demonstrate that OxPL and additional oxidation-specific epitopes on the surface of apoptotic cells are ligands that mediate acknowledgement and phagocytosis of apoptotic cells by.