Interaction of Digibind with endogenous cardiotonic steroids from preeclamptic placentae.
BACKGROUND
Preeclampsia is a major cause of maternal and fetal mortality, and its pathogenesis is not fully understood. Endogenous digitalis-like cardiotonic steroids (CTS) have been implicated in the pathophysiology of preeclampsia; this is illustrated by clinical observations that Digibind, a therapeutic digoxin antibody fragment which binds CTS, lowers blood pressure and reverses Na/K-ATPase inhibition in patients with preeclampsia. Recently we reported that plasma levels of marinobufagenin (MBG), a bufadienolide vasoconstrictor CTS, are increased four-fold in patients with severe preeclampsia.


METHODS
In the present study, we compared levels of MBG in normal and preeclamptic placentae, as well as the interactions of Digibind and antibodies against MBG and ouabain with material purified from preeclamptic placentae using high-performance liquid chromatography (HPLC).


RESULTS
Levels of endogenous MBG, but not that of endogenous ouabain, exhibited a four-fold elevation in preeclamptic placentae vs. normal placentae (13.6 +/- 2.5 and 48.6 +/- 7.0 nmoles/g tissue; P < 0.01). The elution time of endogenous placental MBG-like immunoreactive material from reverse-phase HPLC column was identical to that of authentic MBG. A competitive immunoassay based on Digibind exhibited reactivity to HPLC fractions having retention times similar to that seen with MBG and other bufadienolides, but not to ouabain-like immunoreactive material.


CONCLUSIONS
Our results suggest that elevated levels of endogenous bufadienolide CTS represent a potential target for immunoneutralization in patients with preeclampsia.
Fedorova
Olga V
OV
Laboratory of Cardiovascular Science, National Institute on Aging, Intramural Research Program, NIH, Baltimore, Maryland 21224, USA.
Tapilskaya
Natalia I
NI
Bzhelyansky
Anton M
AM
Frolova
Elena V
EV
Nikitina
Elena R
ER
Reznik
Vitaly A
VA
Kashkin
Vladimir A
VA
Bagrov
Alexei Y
AY
D000328:Adult; D001667:Binding, Competitive; D002018:Bufanolides / Q000276:immunology / Q000378:metabolism; D002301:Cardiac Glycosides / Q000276:immunology* / Q000378:metabolism*; D016022:Case-Control Studies; D003429:Cross Reactions; D004077:Digoxin / Q000276:immunology*; D005260:Female; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000378:metabolism* / Q000627:therapeutic use; D066298:In Vitro Techniques; D007700:Kinetics; D010042:Ouabain / Q000276:immunology / Q000378:metabolism; D010920:Placenta / Q000276:immunology / Q000378:metabolism*; D011225:Pre-Eclampsia / Q000209:etiology / Q000378:metabolism* / Q000628:therapy; D011247:Pregnancy
D002018:Bufanolides; D002301:Cardiac Glycosides; D007140:Immunoglobulin Fab Fragments; C050199:digoxin antibodies Fab fragments; C093896:marinobufagenin; D010042:Ouabain; D004077:Digoxin