Analysis of the thiol status of peripheral blood leukocytes in
rheumatoid arthritis patients
Joan H. Pedersen-Lane,* Robert B. Zurier,†and David A. Lawrence*,1
*Wadsworth Center, New York State Department of Health, Albany, New York, USA; and†Department of Medicine,
Division of Rheumatology, University of Massachusetts Medical School, Worcester, Massachusetts, USA
toid arthritis (RA) remains unknown, there is in-
creasing evidence that reactive oxygen species and
a pro-oxidant/antioxidant imbalance are an impor-
tant part of the pathogenesis of joint tissue injury.
Flow cytometry was used to evaluate the thiol sta-
tus [surface-thiols and intracellular glutathione
(iGSH)] of leukocytes from RA patients and con-
trols. Levels of surface-thiols and iGSH of leuko-
cytes from RA patients were significantly lower
than of leukocytes from controls. CD53, a glyco-
protein of the tetraspanin superfamily, which co-
precipitates with the GSH recycling enzyme ?-glu-
tamyl transpeptidase, was elevated significantly on
leukocytes from RA patients compared with leuko-
cytes from controls. Surface-thiols and GSH play
important roles in redox buffering of cells, provid-
ing protection from oxidative stress. The chronic
inflammation of RA has been associated with oxi-
dative stress, which is shown to cause a decline in
the levels of cellular antioxidant sulfhydryls (R-
SH). As antioxidant-protective levels also decline
with age, the problem is compounded in older RA
patients, who did have fewer R-SH. Chronic stress
can also have an effect on telomere lengths, deter-
mining cell senescence and longevity. Although
telomeres shorten with increasing age, our flow
cytometry studies indicate that accelerated short-
ening in telomere lengths occurs with increasing
age of RA patients, suggesting premature cellular
aging. The paradox is that lymphocytes from RA
patients are believed to resist apoptosis, and we
suggest that the elevated expression of CD53,
which results from the increased oxidative stress,
may protect against apoptosis. J. Leukoc. Biol. 81:
Although the exact etiology of rheuma-
Key Words: glutathione ? CD53 ? flow cytometry ? telomeres
Rheumatoid arthritis (RA) is a chronic, systemic, inflamma-
tory, autoimmune syndrome, which produces degradation of
articular cartilage and bone erosion. The long-term outcomes of
this progressive disease are significant morbidity, loss of func-
tional capacity, and increased mortality [1, 2]. RA affects
1–2% of the general population worldwide , and the occur-
rence in women is three times greater than in men. Although
the onset of RA can occur at any age, the incidence increases
with age. The exact etiology of RA remains unknown.
The formation and scavenging activity of free radicals in
biological systems have been linked closely to a number of
pathological conditions. In healthy individuals, reactive oxygen
species (ROS) and associated oxidative stresses are kept in
check by a combination of antioxidant activities [4, 5]. Human
cells have developed a formidable antioxidant defense against
oxidant reactions. In particular, they possess enzymatic and
nonenzymatic antioxidant molecules, including thiols [mainly
glutathione (GSH)], for defense. One key chemical barrier
against stress-induced damage is the redox equilibrium of
sulfhydryl (SH)/disulfides, by which low molecular weight thi-
ols can be oxidized reversibly to disulfides and/or protein
mixed disulfides in response to an oxidative stress [6–8].
There is increasing evidence that ROS and the resulting pro-
oxidant/antioxidant imbalance play a major role in RA, as well
as in other disease states [9–11]. It has been shown that
lymphocytes, which are highly sensitive to thiol modification,
are impaired in many of their immune functions when exposed
to oxidative stress or SH modifiers such as those found in the
cellular microenvironment .
?-Glutamyl transpeptidase (GGT) is a cell-surface enzyme
in the recycling pathway of GSH, part of the antioxidant
defense mechanism. Through GGT cleavage of ?-glutamyl from
GSH, the cysteinylglycine dipeptide is released, thus eventu-
ally increasing the supply of cysteine available to the cell .
Studies indicate that the metabolism of extracellular GSH by
GGT is also important in T cell signaling and in the activation
of transcription factors . CD53, a glycoprotein of the tet-
raspanin superfamily, has been reported to coprecipitate with
GGT activity . The functional significance of this associa-
tion is still not fully understood; the association may be im-
portant in regulating local intracellular redox potential by
playing a role in the binding or recycling of the end products
of the GGT reaction. It has been proposed that tetraspanins act
as molecular facilitators, grouping specific cell-surface pro-
1Correspondence: Biggs Laboratory, Wadsworth Center, New York State
Department of Health, Empire State Plaza, Albany, NY 12201-0509, USA.
Received August 28, 2006; revised October 14, 2006; accepted November
934 Journal of Leukocyte Biology
Volume 81, April 2007
0741-5400/07/0081-934 © Society for Leukocyte Biology
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Pedersen-Lane et al.
Cellular thiol changes associated with arthritis941