Children's Hospital Oakland Research Institute

About: Children's Hospital Oakland Research Institute is a based out in . It is known for research contribution in the topics: Population & Human leukocyte antigen. The organization has 1568 authors who have published 2480 publications receiving 203418 citations.

Increased adherence of sickled and phosphatidylserine-enriched human erythrocytes to cultured human peripheral blood monocytes.

Abstract: The precise mechanism by which sickle erythrocytes (RBC) are removed from the circulation is controversial, although it is possible that enhanced recognition of these cells by circulating mononuclear phagocytes could contribute to this process. We investigated this possibility by interacting sickle cells with cultured human peripheral blood monocytes. Our results show that both irreversibly sickled cells (ISC) and deoxygenated reversibly sickled cells (RSC) had a higher avidity for adherence to monocytes than did oxygenated sickle and normal RBC. ISC were the most adherent cell type. Adherence of RSC to monocytes was found to be reversible; reoxygenation of deoxygenated RSC resulted in a significant decrease in RSC--monocyte adherence. Concomitant with alterations in sickle RBC adherence were alterations in the organization and bilayer distribution of membrane phospholipids in these cells. Specifically, enhanced adherence was associated with increased exposure of RBC membrane outer leaflet phosphatidylserine (PS) and phosphatidylethanolamine, whereas lack of adherence was associated with normal patterns of membrane phospholipid distribution. To investigate the possibility of whether the exposure of PS in the outer membrane leaflet of these cells might be responsible for their recognition by monocytes, the membranes of normal RBC were enriched with the fluorescent PS analogue 1-acyl-2[(N-4-nitro-benzo-2-oxa-1,3-diazole)aminocaproyl]-phosphatidy lse rine (NBD-PS) via transfer of the exogenous lipid from a population of donor phospholipid vesicles (liposomes). RBC enriched with NBD-PS exhibited enhanced adherence to monocytes, whereas adherence of RBC enriched with similar amounts of NBD-phosphatidylcholine (NBD-PC) was not increased. Furthermore, preincubation of monocytes with PS liposomes resulted in a approximately 60% inhibition of ISC adherence to monocytes, whereas no inhibition occurred when monocytes were preincubated with PC liposomes. These findings strongly suggest that erythrocyte surface PS may be a ligand recognized by receptors on human peripheral blood monocytes and that abnormal exposure of PS in the outer leaflet of the RBC membrane, as found in sickle RBC, might serve to trigger their recognition by circulating monocytes. Our results further suggest that abnormalities in the organization of erythrocyte membrane phospholipids may have significant pathophysiologic implications, possibly including shortened cell survival.

Acrolein, a Toxicant in Cigarette Smoke, Causes Oxidative Damage and Mitochondrial Dysfunction in RPE Cells: Protection by (R)-α-Lipoic Acid

Abstract: Smoking is a primary risk factor associated with the prevalence and the incidence of neovascular macular degeneration and geographic atrophy.1,2 This link between smoking and age-associated macular degeneration (AMD) has recently been strengthened by three large epidemiologic studies, including the AREDS (Age-Related Eye Disease Study).3–5 Smoking is a cause of severe oxidative stress, due to the high concentrations of aldehydes and NOx in cigarette smoke, which markedly deplete ascorbic acid levels and protein sulfhydryl concentrations and cause oxidation of lipids and proteins.6–8 Six toxicants present in cigarette smoke are of particular concern as health risks: acrolein, acetaldehyde, acrylonitrile, benzene, 1,3-butadiene, and formaldehyde.9 Acrolein has a high hazard index and causes oxidative stress by reacting with sulfhydryl groups.10 It is more toxic (~10–1000 times) than formaldehyde, acetaldehyde, and 4-hydroxynonenal11 and can reach 80 µM in the respiratory tract fluid in smokers.12 Although the pathogenesis of AMD includes different clinical signs, the degeneration of RPE cells is often observed at early stages of the disease. Initial AMD pathogenesis includes abnormal RPE morphology and pigmentation, accumulation of lipofuscin in RPE cells, and accumulation of drusen between RPE and the underlying Bruch’s membrane. Electron microscopic and morphometric studies reveal qualitative and quantitative alterations of mitochondria in human RPE from AMD and from age- and sex-matched control subjects.13 The strong epidemiologic evidence linking smoking to AMD raises several questions that should be addressed: (1) What are the cellular and molecular mechanisms that underlie this link? (2) Do cigarette smoke components such as acrolein cause injury, especially mitochondrial dysfunction, to RPE cells, as in other cellular and tissue models? (3) Does lipoic acid, a potent inducer of phase-2 antioxidant and sulfhydryl protective enzymes, 14,15 protect RPE cells from smoke/acrolein-caused injury and mitochondrial dysfunction? (4) Are there different responses to acrolein toxicity in a human RPE cell line and primary human fetal RPE cells? In the present study, the ARPE19 cell line, was treated with acrolein, a major toxicant in tobacco smoke, and the effects on cellular toxicity and mitochondrial function were examined. Acrolein-induced toxicity was also studied using primary cultures of hfRPE, which are similar to native hfRPE.16 Both preparations were used to study the protective effects against acrolein-induced toxicity of α-lipoic acid (LA), which is a mitochondria-targeted antioxidant17 and mitochondrial nutrient.18 We hypothesize that smoking may cause oxidative mitochondrial damage in RPE cells and that the mitochondrial dysfunction may be a major cause in promoting the onset and progress of age-related macular degeneration.