Oxidative-stress response in vascular endothelial cells exposed to
acellular hemoglobin solutions.
Motterlini, Roberto, Roberta Foresti, Kim Vandegriff, Marcos
Intaglietta, and Robert M. Winslow.
Department of Bioengineering and Department of Medicine, University
of California San Diego, La Jolla, CA 92093
APStracts 2:0087H, 1995.
We investigated the effect of different hemoglobins on the activation
of endothelial heme oxygenase (HO), an inducible $QUOTstress$QUOT
protein which is responsible for heme catabolism, and we determined
whether the propensity of hemoglobins to autoxidize correlates with
endothelial heme uptake and cell injury. Porcine aortic endothelial
cells were incubated for six hours in the presence of 60 [mu]M
unmodified hemoglobin (HbA0), hemoglobin cross-linked between the
[alpha] chains with bis-(3,5-dibromosalicyl) fumarate
([alpha][alpha]Hb) or cyanomet-[alpha][alpha]-hemoglobin
(CNmet[alpha][alpha]Hb). Endothelial HO activity augmented 4.1-fold
in the presence of [alpha][alpha]Hb, 2.7-fold with HbA0 and 1.8-fold
with CNmet[alpha][alpha]Hb over the control value. Deferoxamine, but
not catalase or dimethylthiourea, partially attenuated the HO
induction produced by [alpha][alpha]Hb. The rates of methemoglobin
formation exhibited a linear relationship over the time of incubation
(r=0.94) and the apparent rate constant was 1.8-fold higher for
[alpha][alpha]Hb (0.023 h-1) than HbA0 (0.013 h-1). Endothelial heme
content and LDH release, an index of cell injury, were also higher in
[alpha][alpha]Hb compared to HbA0 and CNmet[alpha][alpha]Hb groups
(p<0.05). Deferoxamine, but not catalase, markedly reduced the
release of LDH induced by [alpha][alpha]Hb, whereas dimethylthiourea
provided only a partial cytoprotection. These studies suggest that:
1) the higher rate of oxidation of [alpha][alpha]Hb contributes to
the augmented endothelial HO activity; 2) both heme release and iron
-mediated oxygen radical formation are major contributors to
endothelial oxidative stress and cytotoxicity generated by the cross
-linked hemoglobin.
Received 19 December 1994; accepted in final form 6 March 1995.
APS Manuscript Number H1100-4.
Article publication pending Am. J. Physiol. (Heart Circ. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 21 March 1995.