Oxidative stress, macrophages, iron, and atherosclerosis
1997 (English)Licentiate thesis, comprehensive summary (Other academic)
Macrophages have a great capacity to take up exogenous material, such as oxidatively modified low density lipoproteins (oxLDL) and different sources of iron containing structures. OxLDL is taken up into macrophage lysosomes by receptor-mediated endocytosis, but poorly degraded, resulting in foam-cell formation. The foam cell formation and the cytotoxicity of oxLDL to several arterial wall cells might contribute to atherogenesis. The iron sequestrated by macrophages could potentially become cytotoxic, particularly following intralysosomal accumulation of low-molecular weight iron in a redox-active form, and under conditions of oxidative stress. Following autophagocytosis, endogenous ferritin/apoferritin may serve as chelators of such lysosomal iron and counteract the occurrence of iron-mediated intra-lysosomal oxidative reactions.
In the present study, we estimated the influence of oxLDL on lysosomal enzyme activity, lysosomal membrane stability, and the modulation of these cellular characteristics by high density lipoprotein (HDL) and vitamin E (vit-E). We also examined iron-stimulated ferritin synthesis, and the effects of exogenously added apoferritin on cells and lysosomal membrane stability following oxidative stress. Human monocyte-derived macrophages and J-774 cells were used in the study. The activities of the lysosomal enzymes, cathepsin-L and N-acetyl-ß-glucosarninidase (NAßGase), were biochemically assayed on cellular fractions. The lysosomal integrity was estimated by an acridine orange (AO) vital staining test as well as by immunocytochemical cathepsin-D demonstration. Cellular ferritin was assayed by ELISA, and lysosomal iron was demonstrated by autometallography and transmission electron microscopy.
We found that the total activities of NAßGase and cathepsin-L were significantly decreased, whereas their relative cytosolic activities were enhanced after oxLDL-exposure. Labilization of the lysosomal membranes was further proven by a decreased lysosomal AO-uptake and a relocation to the cytosol of cathepsin-D. as estimated by light- and electron microscopic immunocytochemistry. HDL and vit-E diminished the cytotoxicity of oxLDL by decreasing the lysosomal damage. The synthesis and accumulation of ferritin in HMDM are responses to the iron-exposure, but ferritin is not efficient enough to protect the lysosomes from oxidative stress. Endocytosed apoferritin acts as a stabilizer of the acidic vacuolar compartment of iron-loaded macrophages.
Place, publisher, year, edition, pages
Linköping: Linköpings universitet , 1997. , 40 p.
Linköping Studies in Health Sciences. Thesis, ISSN 1100-6013 ; 31
Medical and Health Sciences
IdentifiersURN: urn:nbn:se:liu:diva-28266Local ID: 13014ISBN: 91-7219-080-9OAI: oai:DiVA.org:liu-28266DiVA: diva2:249070
1997-11-21, Seminarierummet, Patologbyggnaden, Hälsouniversitetet, Linköping, 11:00 (English)
Papers, included in licentiate theses, are not registered and included in the posts from 1999 and earlier.2009-10-092009-10-092013-07-08