Blood, 1 March 2003, Vol. 101, No. 5, pp. 2071-2071
CORRESPONDENCE
To the editor:
Acidic and neutral sialidase in the erythrocytes of patients
with type 2 diabetes: an answer to comments by Richard et al
In a recent letter to the editor by Richard et al,1
the letter authors made some comments about our work published early this year.2 In our study we observed a sharp decrease of
neutral sialidase activity on the surface of erythrocytes of diabetic patients, which accounts at the same time for the significant increase
(40%) of sialic acid content. At the end of our discussion, we
hypothesized that the higher negative charge at the erythrocyte surface
due to this increase results in a premature sequestration of diabetic
red cells by macrophages, in accordance with the data reported by
Mazzanti et al3 and Jain et al.4 Our
hypothesis has been criticized by Richard and coworkers because it
conflicts with the notion that a reduction of total sialic acid content is responsible for phagocytosis of senescent red cells.
Our thoughts on this matter are as follows: (1) The hypothesis reported
by Richard et al has been extensively debated over the
years,5 and contrary to what the authors hint, it is not the only one known nor the most accepted, nonetheless it was not in our
intentions to discredit it. (2) We believe in the importance of sialic
acid in the process of recognition of senescent red cells, but as part
of a more complex process, where other molecules are involved, as
suggested in other hypotheses.6 Indeed, according to Beppu
et al7 and Kannan et al,8 the molecular
consequences of the oxidative damage occurring in senescent
erythrocytes are likely responsible for their clearance. We think that
the reduction of sialic acid content in specific domains of the
surface, and not its overall decrease, may trigger the macrophage
recognition.9,10 (3) The theory reported by Richard et al
is eventually unsuitable to explain our experimental results. In fact,
if the overall sialic acid decrease was responsible for senescent
erythrocytes recognition, we should have observed an increase in life
span of erythrocytes in diabetes mellitus, yet we observed the opposite phenomenon.
In conclusion we would like to emphasize once again that it was not in
our intentions to invalidate the role of sialic acid decrease in
erythrocyte removal, even though we do believe in a different
hypothesis on erythrocytes senescence, at least in diabetic patients.
Bruno Venerando, Amelia Fiorilli, Gianluigi Croci, Cristina Tringali, Giancarlo Goi, Laura Mazzanti, Giovanna Curatola, Giovanni Segalini, Luca Massaccesi, Adriana Lombardo, and Guido Tettamanti
Correspondence: Bruno Venerando, Department of
Medical Chemistry and Biotechnology, The Medical School, University of
Milan, Via Fratelli Cervi, 93, 20090-Segrate (Milan)
Italy; e-mail:
bruno.venerando{at}unimi.it
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Acidic and neutral sialidase in the erythrocytes of patients with Type 2 diabetes: influence on erythrocyte lifespan [letter].
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Acidic and neutral sialidase in the erythrocyte membrane of type 2 diabetic patients.
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Ando K, Kikugawa K, Beppu M.
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