Expression of kappa-opioid receptor mRNA in human peripheral blood lymphocytes and the relationship between its expression and the inflammatory changes in rheumatoid arthritis
N. Gunji et al., Expression of kappa-opioid receptor mRNA in human peripheral blood lymphocytes and the relationship between its expression and the inflammatory changes in rheumatoid arthritis, RHEUM INTL, 19(3), 2000, pp. 95-100
The expression of the kappa-opioid receptor on human peripheral blood cells
(in rheumatoid arthritis cases and normal volunteers) was examined using r
everse transcriptase polymerase chain reaction (RT-PCR), and the relationsh
ip between its expression and the inflammatory activity or chronic pain in
patients with rheumatoid arthritis (RA) was determined. RT-PCR was performe
d on the peripheral blood cells obtained from 37 patients with RA and 13 he
althy volunteers. kappa-Opioid receptor mRNA expression was exhibited on th
e blood cells of 37% of RA patients (14/ 37) and 54% of healthy volunteers
(7/13), and the levels of expression were lower in the RA patients than in
the healthy volunteers. Regarding the relationship between the expression o
f kappa-opioid receptor mRNA and the symptoms in RA patients, it was noted
that the expression of the receptor mRNA was significantly decreased in RA
patients in whom erythrocyte sedimentation rate (ESR), Lansbury index, and
visual analogue pain scores were high. The kappa-opioid receptor mRNA was e
xpressed on four cell types, namely, T and B cells, macrophages, and natura
l killer (NK) cells in RA patients; however, it was expressed only on the T
and B cells and macrophages (and not on NK cells) in the healthy volunteer
s. Our findings suggest that the levels of expression of kappa-opioid recep
tor mRNA were decreased in RA patients in comparison with those in healthy
volunteers; and that they were significantly related to the inflammatory ac
tivity or chronic pain in the RA patients. The higher the mRNA expression l
evel, the less severe the inflammatory changes of RA. The kappa-opioid rece
ptor may thus play a role in the modulation of nociception and anti-inflamm
atory changes in chronic inflammatory disorders.