Letter to the Editor
Leukocytosis, Vascular Disease, and Adenine
Nucleotide Metabolism
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to CD39, the NTPDase which converts ATP into ADP and also ADP
into adenosine monophosphate (AMP).9 We also saw that leukocytosis results in modified platelet aggregation responses to both ATP
and ADP; platelet aggregation in blood induced by ATP is more
rapid in leukocytosis while aggregation induced by ADP is followed
by rapid disaggregation. A systematic analysis of the role of blood
cells and plasma enzymes in adenine nucleotide metabolism by
high-performance liquid chromatography (HPLC) was then performed.10 This confirmed that leukocytes are the principle means
through which ATP and ADP added to blood are broken down to
ADP and AMP respectively. Thus leukocytes provide a means of
metabolising adenine nucleotides that is additional to that provided
by vascular endothelial cells and thus provide a clearance mechanism
that is active within the blood itself as well as at the blood periphery.
In view of the current discussion on leukocytosis we show in
Figure 1 the results of new experiments in which we added ATP or
ADP to normal blood, blood to which autologous leukocytes had
been added to increase the count from 4.4 to 26⫻103/␮L and blood
from a patient with hyperleukocytosis with a white cell count of
126⫻103/␮L. Nucleotides and products were determined by HPLC.
It can be seen that in the presence of normal numbers of leukocytes
ATP was converted to ADP which peaked at about 15 minutes and
was then subsequently broken down to AMP; ADP was converted
directly to AMP. With added leukocytes the rate of ATP metabolism
is markedly enhanced (t1/2 from ⬇15 minutes to ⬇4 minutes) with
ADP produced more quickly, but present for a shorter duration
before conversion to AMP; the rate of ADP conversion to AMP was
also markedly enhanced. In hyperleukocytosis both ATP and ADP
To the Editor:
We read with interest the paper by Barry S. Coller on leukocytosis
and its relationship with vascular disease morbidity and mortality1
and the subsequent correspondence.2,3 We are intrigued to learn that
relative leukocytopenia may be associated with increased morbidity
and mortality in patients with acute myocardial infarction1,4 and in
those undergoing percutaneous coronary intervention.5 We note the
discussion on whether leukocyte count is merely a marker of general
disturbances in inflammation and general poor health, or whether
leukocytes might contribute directly to thrombosis and
atherosclerosis.
Although several mechanisms through which leukocytes may
contribute to thrombosis and atherosclerosis were discussed,1–3
nothing has been said about the role of leukocytes in adenine
nucleotide metabolism. Adenosine diphosphate (ADP) is, of course,
a major contributor to the thrombotic mechanism as evidenced by the
successful use of ADP antagonists which reduce ADP-induced
platelet activation and aggregation and thereby act as anti-thrombotic
agents.6
It was recognized that leukocytes are active in the metabolism of
adenine nucleotides many years ago7 but recent papers from our own
group have re-emphasized their importance.8 –10 In summary, first we
found that adenosine triphosphate (ATP) added to blood induces
platelet aggregation via a mechanism involving leukocytes and ADP
formation.8 We then found that leukocytes (all neutrophils, all
monocytes and a subset of lymphocytes) test positive for an antibody
Figure 1. Metabolism of ATP (a, c and e)
and ADP (b, d and f) in blood (anticoagulated with hirudin) from normal volunteers (a, b; WCC⫽4.4⫻103/␮L), blood to
which autologous leukocytes had been
added (c, d; WCC⫽26⫻103/␮L) and
blood from a patient with hyperleukocytosis (e, f; WCC⫽126⫻103/␮L). Measurement of ATP, ADP and AMP was by
HPLC.10 Results are mean⫾SEM, n⫽3
(a– d) or a single determination (e, f). ATP
(100 ␮mol/L) or ADP (100 ␮mol/L, except
for f where 30 ␮mol/L ADP was used)
was added to blood samples which were
incubated at 37°C for up to 30 minutes.
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Letter to the Editor
Downloaded from http://atvb.ahajournals.org/ by guest on June 18, 2017
were metabolized very quickly with rapid conversion to AMP which
was subsequently removed.
It seems to us that differences in adenine nucleotide metabolism as
determined by leukocyte count may well have relevance to thrombosis and also to hemostasis. On the one hand, leukocytes in blood
provide a mechanism for platelet activation via ATP, as well as ADP.
Further, because high leukocyte counts provide a means of converting ATP to ADP more rapidly, earlier platelet activation can occur.
In this regard, leukocytes can be thought of as being prothrombotic.
On the other hand, leukocytes also provide an effective means of
removing ADP thus limiting platelet responses to this important
nucleotide, possibly an important anti-hemostatic role.
We believe the extent to which the increased morbidity and
mortality associated with leukocytosis may be a consequence of
altered adenine nucleotide metabolism needs to be investigated
further. Erythrocytes are a huge source of ATP which can be released
physiologically in response to hypoxia11 and via cell damage.
Activated platelets also release ATP as well as ADP. There is also
the possibility that the increased morbidity and mortality associated
with leukocytopenia in acute myocardial infarction and in percutaneous coronary intervention may be a consequence of ineffective
ADP removal. In which case there would be further justification for
the use of ADP antagonists in these conditions.
Stan Heptinstall
Jacqueline R. Glenn
Andrew Johnson
Bethan Myers
Ann E. White
Lian Zhao
Departments of Cardiovascular Medicine and Haematology
Queens Medical Centre, Nottingham
University of Nottingham and University Hospital NHS Trust
Nottingham, United Kingdom
e23
1. Coller BS. Leukocytosis and ischemic vascular disease morbidity and
mortality: is it time to intervene? Arterioscler Thromb Vasc Biol. 2005;
25:658 – 670.
2. Kaski JC, Avanzas P, Arroyo-Espliguero R. Neutrophil count and
complex lesions in patients with coronary artery disease. Arterioscler
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3. Coller BS. Neutrophil count and complex lesions in patients with
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4. Grzybowski M, Welch RD, Parsons L, Ndumele CE, Chen E, Zalenski R,
Barron HV. The association between white blood cell count and acute
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1049 –1060.
5. Gurm HS, Bhatt DL, Gupta R, Ellis SG, Topol EJ, Lauer MS. Preprocedural white blood cell count and death after percutaneous coronary
intervention. Am Heart J. 2003;146:692– 698.
6. Hacke W. From CURE to MATCH: ADP receptor antagonists as the
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9. Glenn JR, White AE, Johnson A, Fox SC, Behan MWH, Dolan G,
Heptinstall S. Leukocyte count and leukocyte ecto-nucleotidase are major
determinants of the effects of adenosine triphosphate and adenosine
diphosphate on platelet aggregation in human blood. Platelets. 2005;16:
159 –170.
10. Heptinstall S, Johnson A, Glenn JR, White AE. Adenine nucleotide
metabolism in human blood - important roles for leukocytes and erythrocytes. J Thromb Haemost. 2005;3:2331–2339.
11. Wang L, Olivecrona G, Götberg M, Olsson ML, Winzell MS, Erlinge D.
ADP acting on P2Y13 receptors is a negative feedback pathway for ATP
release from human red blood cells. Circ Res. 2005;96:189 –196.
Downloaded from http://atvb.ahajournals.org/ by guest on June 18, 2017
Leukocytosis, Vascular Disease, and Adenine Nucleotide Metabolism
Stan Heptinstall, Jacqueline R. Glenn, Andrew Johnson, Bethan Myers, Ann E. White and Lian
Zhao
Arterioscler Thromb Vasc Biol. 2006;26:e22-e23
doi: 10.1161/01.ATV.0000197801.28944.41
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