Expression of cyclooxygenase isoforms in the rat spinal cord and their regulation during adjuvant-induced arthritis F. Beiche 1 , K. Brune 2 , G. Geisslinger 2 and M. Goppelt-Struebe 1 1 Medizinische Klinik IV, Universita ¨t Erlangen-Nu ¨rnberg, Loschgestr. 8, D-91054 Erlangen, Germany, Fax +49 9131 8539202, e-mail: mfm421@rzmail.uni-erlangen.de 2 Institut fu ¨r Experimentelle und Klinische Pharmakologie und Toxikologie, Universita ¨t Erlangen-Nu ¨rnberg, Universita ¨tsstr. 22, D-91054 Erlangen, Germany Received 18 May 1998; returned for revision 9 July 1998; accepted by M. J. Parnham 9 September 1998 Abstract. Objective and Design: Spinal regulation of cyclooxygenase (COX) isoforms was investigated in the animal model of peripheral inflammation induced by injection of complete Freund’s-type adjuvant (CFA) in the rat hindpaw. Subjects and Treatment: Peripheral inflammation was induced by intraplantar injection of CFA in one hind footpad of male Sprague Dawley rats (n ¼ 3 per time point). Methods: Spinal cord was removed after different times (3 h to 22 d). mRNA and protein were isolated and analyzed by comparative reverse transcriptase-polymerase chain reaction (RT-PCR) and Western blot analysis, respectively. Results: Under the acute inflammatory stimulus 6 h after CFA application, RT-PCR revealed a twofold increase in COX-2 mRNA that reached baseline again at day 3. This transient increase occurred in the lumbar spinal cord, but changes in COX-2 mRNA expression were also registered in RNA preparations from cervical sections, spinal COX-2 induction thus not being a spatially confirmed phenomenon. Western blot analysis of spinal membrane preparations reflected the transient COX-2 mRNA induction at protein levels. During the chronic phase of arthritis at day 22, COX- 2 levels were again raised significantly (1.6 fold) over baseline. Spinal levels of COX-1 were not altered at any time point of the peripheral inflammation. Conclusion: These data imply a regulatory role for COX-2 but not COX-1 in the spinal modulation under acute and chronic peripheral inflammation. Key words: Cyclooxygenase – Prostaglandin G/H synthase – Spinal cord – Inflammation – RT-PCR Introduction In the central nervous system, prostaglandins are thought to play a role in a variety of neurological functions [1] including sleep-wake regulation [2], febrile response [3] and nociceptive processing [4, 5]. Hyperalgesic effects were observed after intrathecal administration of prostaglandins [6–8] and a spinal site of action [9–1] is proposed for the analgesic actions of cyclooxygenase-inhibiting non-steroidal anti-inflammatory drugs [12]. Furthermore, release of prostaglandins in the spinal cord was observed after stimulation of afferent nerves [13], noxious thermal stimulation [14] and by increased potassium levels [15]. All these data suggest that activation of prostaglandin biosynthesis is involved in sensory transmission. Of the biosynthetic enzymes, the inducible isoform of the prosta- glandin synthases, cyclooxygenase-2 (COX-2), seems to be the major isoform expressed in the central nervous system. By immunocytochemistry, COX-2 was detected in dendrites and neuronal cell bodies localized chiefly in the cerebral cortex and allocortial structures such as hippocampus and amygdala [16–18]. In normal rat brain, COX-2 was primarily observed in neurons involved in processing and integration of nociceptive, visceral and special sensory input and in the integration of autonomic, endocrine and behavioural responses [17]. Colocalization with glutamate immunoreactivity and increased expression after seizure suggest a role in excitatory synaptic activity [16, 18]. In very recent studies COX-2 was also shown to be the primary COX isoform detectable in spinal cord preparations by immuno- cytochemistry [19, 20]. We are aiming to elucidate the role of COX isoforms in the spinal inflammatory and nociceptive processing. In a preliminary study we could demonstrate expression of COX- 1 and COX-2 mRNA in the rat spinal cord [21]. The current analysis correlates COX mRNA levels with protein expres- sion and gives a detailed analysis of COX expression in the acute phase of the adjuvant-induced peripheral inflammation as well as the chronic phase of adjuvant-induced arthritis, Inflamm. res. 47 (1998) 482–487  Birkha ¨user Verlag, Basel, 1998 1023-3830/98/120482-06 $ 1.50+0.20/0 Inflammation Research Correspondence to: M. Goppelt-Struebe 