Interaction of endothelial cells and triglyceride-rich lipoproteins with apolipoprotein E (Arg-->Cys) from a patient with lipoprotein glomerulopathy.
We saw a patient with proteinuria and characteristics of lipoprotein glomerulopathy (LPG). Histologic analysis of renal biopsy showed a thrombus-like substance in the markedly dilated glomerular capillaries, which stained positive with oil red O. Increased concentration of plasma apolipoprotein E (apoE) was also noted. Those findings are consistent with the diagnostic criteria of LPG, as reported by Oikawa et al. In isoelectric focusing gel electrophoresis of apoE, a band (apoE3') between apoE3 and E2 was observed. The patient's DNA sequence exhibited a C to G substitution in exon 3 of the apoE gene at the position of the 25th amino acid, resulting in an amino acid substitution of the arginine residue for cysteine residue. To clarify the pathophysiologic role of this mutation, we investigated the binding and the uptake of apoE3' triglyceride-rich lipoproteins to human umbilical vein endothelial cells (HUVEC). The binding of apoE3'-triglyceride-rich lipoproteins to the cell-surface of HUVEC increased up to 30% to 50%, compared with apoE3-triglyceride-rich lipoproteins. But the uptake of apoE3'-triglyceride-rich lipoproteins into the cells was not different between them. These findings are consistent with the idea that an increase in binding of triglyceride-rich lipoproteins possessing apoE (Arg(25)-->Cys) to endothelial cells may promote deposition of lipid in the glomerular capillaries.