Function of β-Adrenergic Receptors on Mononuclear Cells in Female Patients with Fibromyalgia

KENJI MAEKAWA, CHERYL TWE, ANA LOTAIF, FRANCESCO CHIAPPELLI, and GLENN T. CLARK

ABSTRACT.

Objective. To investigate the ß-adrenergic receptors (ßAR) in patients with chronic fibromyalgia syndrome (FM). These receptors are present on circulating mononuclear cells, and activation of G-protein coupled receptors like ßAR leads to an increase in the intracellular level of cyclic aminosine monophosphate (cAMP). Therefore, cAMP levels can be used to indirectly assess the functional status of the receptor.

Methods. Eight female patients with FM and 9 matched healthy female controls participated in this study. Blood samples were drawn from subjects' anterocubital vein in the morning. Mononuclear cells were isolated from the whole blood according to Boyüm's method. Basal and stimulated intracellular cAMP levels were determined by enzyme immunoassay. Aliquots of 10⁶ cells were incubated with or without stimulation of ß-agonist isoproterenol for 5 min. Two different concentrations of isoproterenol (10^-3 M and 10^-5 M) were utilized.

Results. The basal cAMP levels in patients with FM (3.02 ± 0.44 pmol/10⁶ cells) were slightly more elevated (but not statistically different; p = 0.124, Mann-Whitney U test) than that of the control group (2.26 ± 0.39 pmol/10⁶ cells). Proterenol 10^-3 M stimulation significantly increased intracellular cAMP from the basal levels in both groups (FM group, p = 0.008; control group, p = 0.011). However, isoproterenol 10^-5 M did not increase mean intracellular cAMP levels in the FM group (p = 0.74), while a significant increase was observed in the control group (p = 0.012).

Conclusion. These preliminary results suggest that diminished ßAR function is associated with the chronic FM state. (J Rheumatol 2003;30:364-8)

Key Indexing Terms:

FIBROMYALGIA
ß-ADRENERGIC RECEPTOR
cAMP

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From the Division of Oral Biology and Medicine, UCLA School of Dentistry, Los Angeles, California, USA; and Department of Oral and Maxillofacial Rehabilitation, Okayama University Graduate School of Medicine and Dentistry, Okayama, Japan.

Supported by Grant-in-Aid 12671883, awarded to Dr. K. Maekawa by the Ministry of Education, Science and Culture of Japan.

K. Maekawa, DDS, PhD, Visiting Scholar, UCLA School of Dentistry and Assistant Professor, Okayama University Graduate School of Medicine and Dentistry; C. Twe, Research Assistant, Division of Oral Biology and Medicine, UCLA; A. Lotaif, DDS, Post-Graduate Student, Division of Oral Biology and Medicine, UCLA; F. Chiappelli, PhD, Associate Professor, Division of Oral Biology and Medicine UCLA; G.T. Clark, DDS, MS, Professor, Division of Oral Biology and Medicine, UCLA.

Address reprint requests to Dr. G.T. Clark, Division of Oral Biology and Medicine, University of California, Los Angeles, 10833 Le Conte Avenue, PO Box 957063, Los Angeles, CA 90095-7063, USA. E-mail: glennc@dent.ucla.edu

Submitted March 27, 2002; revision accepted July 15, 2002.

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