Eluate derived by extracorporal antibody-based immunoadsorption elevates the cytosolic Ca2+ concentration in podocytes via B-2 kinin receptors
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vor 22 Jahren
Background/Aim: Patients with idiopathic focal segmental
glomerulosclerosis (FSGS) often develop a recurrence of the disease
after kidney transplantation. In a number of FSGS patients,
plasmapheresis and immunoadsorption procedures have been shown to
transiently reduce proteinuria and are thought to do this by
eliminating a circulating factor. Direct cellular effects of
eluates from immunoadsorption procedures on podocytes, the primary
target of injury in FSGS, have not yet been reported. Methods:
Eluates were derived from antibody-based immunoadsorption of a
patient suffering from primary FSGS, a patient with systemic lupus
erythematosus, and a healthy volunteer. The cytosolic free Ca2+
concentration ({[}Ca2+](i)) of differentiated podocytes was
measured by single-cell fura-2 microfluorescence measurements. Free
and total immunoreactive kinin levels were measured by
radioimmunoassay. Results: FSGS eluates increased the {[}Ca2+](i)
levels concentration dependently (EC50 0.14 mg/ml; n = 3-19). 1
mg/ml eluate increased the {[}Ca2+](i) values reversibly from 82
+/- 12 to 1,462 +/- 370 nmol/l, and then they returned back to 100
16 nmol/l (n = 19). The eluate-induced increase of {[}Ca2+](i)
consisted of an initial Ca2+ peak followed by a Ca2+ plateau which
depended on the extracellular Ca2+ concentration. The
eluate-induced increase of {[}Ca2+](i) was inhibited by the
specific B-2 kinin receptor antagonist Hoe 140 in a
concentration-dependent manner (IC50 2.47 nmol/l). In addition,
prior repetitive application of bradykinin desensitized the effect
of eluate on {[}Ca2+](i). A colonic epithelial cell line not
reacting to bradykinin did not respond to eluate either (n = 6).
Similar to FSGS eluates, the eluate preparations of both the
systemic lupus patient and the healthy volunteer led to a biphasic,
concentration-dependent {[}Ca2+](i) increase in poclocytes which
again was inhibited by Hoe 140. Free kinins were detected in all
eluate preparations. Conclusion: The procedure of antibody-based
immunoadsorption leads to kinin in the eluate which elevates the
{[}Ca2+](i) level of podocytes via B-2 kinin receptors. Copyright
(C) 2002 S. Karger AG, Basel.
glomerulosclerosis (FSGS) often develop a recurrence of the disease
after kidney transplantation. In a number of FSGS patients,
plasmapheresis and immunoadsorption procedures have been shown to
transiently reduce proteinuria and are thought to do this by
eliminating a circulating factor. Direct cellular effects of
eluates from immunoadsorption procedures on podocytes, the primary
target of injury in FSGS, have not yet been reported. Methods:
Eluates were derived from antibody-based immunoadsorption of a
patient suffering from primary FSGS, a patient with systemic lupus
erythematosus, and a healthy volunteer. The cytosolic free Ca2+
concentration ({[}Ca2+](i)) of differentiated podocytes was
measured by single-cell fura-2 microfluorescence measurements. Free
and total immunoreactive kinin levels were measured by
radioimmunoassay. Results: FSGS eluates increased the {[}Ca2+](i)
levels concentration dependently (EC50 0.14 mg/ml; n = 3-19). 1
mg/ml eluate increased the {[}Ca2+](i) values reversibly from 82
+/- 12 to 1,462 +/- 370 nmol/l, and then they returned back to 100
16 nmol/l (n = 19). The eluate-induced increase of {[}Ca2+](i)
consisted of an initial Ca2+ peak followed by a Ca2+ plateau which
depended on the extracellular Ca2+ concentration. The
eluate-induced increase of {[}Ca2+](i) was inhibited by the
specific B-2 kinin receptor antagonist Hoe 140 in a
concentration-dependent manner (IC50 2.47 nmol/l). In addition,
prior repetitive application of bradykinin desensitized the effect
of eluate on {[}Ca2+](i). A colonic epithelial cell line not
reacting to bradykinin did not respond to eluate either (n = 6).
Similar to FSGS eluates, the eluate preparations of both the
systemic lupus patient and the healthy volunteer led to a biphasic,
concentration-dependent {[}Ca2+](i) increase in poclocytes which
again was inhibited by Hoe 140. Free kinins were detected in all
eluate preparations. Conclusion: The procedure of antibody-based
immunoadsorption leads to kinin in the eluate which elevates the
{[}Ca2+](i) level of podocytes via B-2 kinin receptors. Copyright
(C) 2002 S. Karger AG, Basel.
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