Apolipoproteins prevent glomerular albumin permeability induced in vitro by serum from patients with focal segmental glomerulosclerosis.
Glomerular albumin permeability alterations can be induced in vitro by serum from patients with end-stage renal disease caused by primary focal segmental glomerulosclerosis (FSGS). It was hypothesized that inhibitory substances may be present in normal serum, which may prevent the permeability alterations in isolated glomeruli, and the present study sought to isolate and characterize these factors. Albumin permeability was determined from the change in glomerular volume induced by applying oncotic gradients across the basement membrane of healthy isolated rat glomeruli preincubated with FSGS serum and normal serum fractionated using standard techniques. Fractions of normal serum with inhibitory activity obtained by a multistep chromatographic procedure underwent two-dimensional electrophoresis and staining. Approximately 50 protein spots were recovered, renatured, and tested for antipermeability activity. Five of these proteins demonstrated consistent inhibitory activity, and desorption ionization and mass spectrometry proved them to be components of high-density lipoprotein: apolipoproteins (apo) E(2) and E(4), high-molecular-weight J and L, and a 28-kD fragment of A-IV. Polyclonal antibodies to apo E or apo J added to the whole normal serum restored the permeability activity of the FSGS serum in the bioassay. Commercially available apo E and apo J also demonstrated antipermeability activity when added to FSGS serum. Cyanogen bromide digestion of apo A-IV produced fragments that inhibited the permeability activity of the FSGS serum, whereas the intact protein did not. Thus, components of high-density lipoprotein are capable of preventing glomerular albumin permeability induced by serum from patients with FSGS in an in vitro system. The specificity and mechanism of the inhibition remain to be determined; the alteration of normal inhibitory activity in vivo may be a component in the pathophysiology of FSGS.
Candiano
Giovanni
G
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
Musante
Luca
L
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
Carraro
Michele
M
Istituto di Medicina Clinica, University of Trieste, Trieste, Italy.
Faccini
Luigi
L
Istituto di Medicina Clinica, University of Trieste, Trieste, Italy.
Campanacci
Luciano
L
Istituto di Medicina Clinica, University of Trieste, Trieste, Italy.
Zennaro
Cristina
C
Istituto di Medicina Clinica, University of Trieste, Trieste, Italy.
Artero
Mary
M
Istituto di Medicina Clinica, University of Trieste, Trieste, Italy.
Ginevri
Fabrizio
F
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
Perfumo
Francesco
F
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
Gusmano
Rosanna
R
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
Ghiggeri
Gian Marco
GM
Unit and Laboratory of Nephrology, Istituto G. Gaslini, Genoa, Italy.
D000418:Albumins / Q000378:metabolism*; D000595:Amino Acid Sequence; D000906:Antibodies / Q000494:pharmacology; D001053:Apolipoproteins / Q000037:antagonists & inhibitors / Q000097:blood* / Q000737:chemistry; D002648:Child; D002675:Child, Preschool; D005260:Female; D005923:Glomerulosclerosis, Focal Segmental / Q000097:blood* / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D007678:Kidney Glomerulus / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010539:Permeability
D000418:Albumins; D000906:Antibodies; D001053:Apolipoproteins; D010446:Peptide Fragments