Nephrology Dialysis Transplantation, Vol 12, Issue 7 1330-1335, Copyright © 1997 by Oxford University Press
S Greiber, M Kreusel, H Pavenstadt, P Schollmeyer and C Wanner
BACKGROUND: Lipoprotein(a) (Lp(a)) is considered to accelerate glomerular
injury in various forms of renal disease. Several tissue culture studies
suggested that biological effects of Lp(a) are inhibitable by oxygen
radical scavengers. Since reactive oxygen metabolites (ROM) are important
mediators of renal disease, we studied the effects of native and oxidized
Lp(a) on generation of the ROM superoxide anion in isolated glomeruli and
compared them with the effects of native (nLDL) and oxidized LDL
cholesterol (oxLDL). METHODS: The effect of native and oxidized Lp(a) and
LDL on ROM production in isolated rat glomeruli was investigated with a
lucigenin chemiluminescence assay. RESULTS: Native Lp(a) caused a moderate,
dose dependent stimulation of glomerular ROM production: Maximum ROM
production to 159 +/- 9% of control glomeruli was induced by nLp(a) 20
micrograms/ml. Lp(a)-induced chemiluminescence was completely inhibited by
the cell permeable oxygen radical scavenger Tiron (10 Mm). Oxidized Lp(a)
(20 micrograms/ml) caused a more pronounced stimulation of ROM production
to 204 +/- 12% of control values. Interestingly, only oxLDL, but not nLDL
had a significant effect on glomerular ROM production (ox LDL 50
micrograms/ml: 192 +/- 19% of control). Lp(a) stimulated ROM production was
completely inhibited by the protein kinase C inhibitor bis- indolyl
malemide (BIM): BIM 10(-6) M inhibited 52 +/- 3%, BIM 10(- 5) M inhibited
94 +/- 5% of Lp(a)-induced ROM production. ROM production was also
inhibited, when intracellular CAMP levels were elevated by forskolin.
CONCLUSION: Lp(a) and oxLp(a) induce the activation of ROM in glomeruli by
a pathway that is sensitive to inhibition of protein kinase C and elevation
of intracellular CAMP levels.
ORIGINAL ARTICLES
Lipoprotein(a) induces glomerular superoxide anion production
Department of Medicine, University Hospital of Freiburg, Germany.
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