Aurin tricarboxylic acid protects against red blood cell hemolysis in patients with paroxysmal nocturnal hemoglobinemia.
OBJECTIVE
Paroxysmal nocturnal hemoglobinemia (PNH) is a rare but serious condition characterized by complement-mediated red blood cell (RBC) hemolysis and episodic thrombotic attack. It results from decay accelerating factor (CD55), and protectin (CD59), becoming attached to RBC and other cell surfaces. Absence of these protective proteins leaves such cells vulnerable to self attack at the C3 convertase and membrane attack complex (MAC) stages of complement activation. We have previously reported that aurin tricarboxylic acid (ATA) is an orally effective agent that selectively blocks complement activation at the C3 convertase stage as well as MAC formation at the C9 insertion stage.


METHODS
We used a CH50 assay method and western blot analysis to investigate the vulnerability to complement attack of PNH RBCs compared with normal RBCs. Zymosan was used as the activator of normal serum and PNH serum. ATA was added to the sera to determine the concentration necessary to protect the RBCs from lysis by the zymosan-activated sera.


RESULTS
We found that erythrocytes from PNH patients on long term treatment with eculizumab were twice as vulnerable as normal erythrocytes to lysis induced by complement activated serum. Western blot data showed the presence of both C3 and C5 convertases on the PNH patient erythrocyte membranes. These data indicate persistent vulnerability of PNH erythrocytes to complement attack due to deficiencies in CD55 and CD59. ATA, when added to serum in vitro, protected PNH erythrocytes from complement attack, restoring their resistance to that of normal erythrocytes.


CONCLUSIONS
We conclude that ATA, by protecting PNH erythrocytes from their decay accelerating factor (CD55) and protectin (CD59) deficiencies, may be an effective oral treatment in this disorder.
Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver, British Columbia, Canada.
Moonhee
M
Lee
Leukemia/BMT Program of BC, Division of Hematology, Vancouver General Hospital, BC Cancer Agency, Vancouver, British Columbia, Canada.
Sujaatha
S
Narayanan
Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver, British Columbia, Canada.
Edith G
EG
McGeer
Kinsmen Laboratory of Neurological Research, University of British Columbia, Vancouver, British Columbia, Canada.
Patrick L
PL
McGeer
D000328:Adult; D061067:Antibodies, Monoclonal, Humanized / Q000494:pharmacology; D001312:Aurintricarboxylic Acid / Q000494:pharmacology*; D003179:Complement C3b / Q000378:metabolism; D015935:Complement C4b / Q000378:metabolism; D003182:Complement C5 / Q000037:antagonists & inhibitors / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D004912:Erythrocytes / Q000187:drug effects / Q000502:physiology; D005260:Female; D006401:Hematologic Agents / Q000494:pharmacology*; D006457:Hemoglobinuria, Paroxysmal / Q000097:blood / Q000188:drug therapy*; D006461:Hemolysis / Q000187:drug effects*; D006801:Humans; D008297:Male; D055815:Young Adult
D061067:Antibodies, Monoclonal, Humanized; D003182:Complement C5; D006401:Hematologic Agents; D001312:Aurintricarboxylic Acid; D003179:Complement C3b; D015935:Complement C4b; C481642:eculizumab