Increased circulating rather than spinal cytokines accompany chronic pain behaviors in experimental bone cancer and arthritis

Pourtau L, Heeringa AN, Rovere C, Aubert A, Nahon JL, Miraux S, Konsman JP. Incr

Line Pourtau1, Amarins Nieske Heeringa1, Carole Ro

1 CNRS, PsychoNeuroImmunologie, Nutrition et Génét

2014

153-160

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Aim: Peripheral cytokines contribute to arthritis and bone cancer pain through sensory nerve actions. However, increased spinal cytokine and glial filament expression, coined neuroinflammation, has also been proposed to play a part in chronic pain. Therefore, spinal cord, dorsal root ganglia and circulating cytokines were compared in murine arthritis and bone cancer models in relationship to behavioral signs of pain. Methods: Exploratory behaviors were studied after intra-articular complete Freund's adjuvant or bone intramedullary sarcoma cell injection. Nervous tissue and blood cytokine expression were determined by real-time polymerase chain reaction (PCR) and multiplex immunoassays, respectively. Results: PCR analysis did not reveal any hallmark of spinal neuroinflammation in spontaneously-behaving mice with cartilage or bone lesions. However, imposed paw stimulation during joint inflammation increased spinal interleukin-1β (IL-1β) expression. Spontaneous paw guarding during rearing was displayed by animals with joint inflammation and bone destruction and was accompanied by increased circulating IL-6 and monocyte chemoattractant protein-1, respectively. In addition, dorsal root ganglia were found to constitutively express receptors for this chemotactic cytokine. Conclusion: Our findings indicate that spinal neuroinflammation is not a necessary condition for chronic pain and suggest that circulating cytokine action in dorsal root ganglia may contribute to experimental joint inflammation and bone cancer pain.