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Celecoxib Inhibits Interleukin-12 and ₂ Folding and Secretion by a Novel COX2-Independent Mechanism Involving Chaperones of the Endoplasmic Reticulum

Applied Genomics Research Group, School of Pharmacy, McClay Research Center for Pharmaceutical Sciences, Queen's University Belfast, Belfast, United Kingdom (I.A., K.V.); Arakis Ltd., Saffron Walden, Essex, United Kingdom (A.B.); Department of Immunology, Queen's University of Belfast, Belfast, United Kingdom (Q.C.); and Bioinformatics Group, CIC bioGUNE, Bilbao, Spain (R.M.)

Celecoxib (CE) is a nonsteroidal anti-inflammatory drug (NSAID) that is a specific inhibitor of cyclooxygenase 2 (COX2). It is indicated for a variety of chronic inflammatory conditions, including rheumatoid arthritis. Over the last few years, adverse cardiovascular effects and increased risk for heart attacks have been associated with this drug. In addition, evidence is emerging for COX2-independent molecular targets. CE has been shown to induce apoptosis in various cancer cells lines through a COX2-independent mechanism that seems to involve inactivation of protein kinase Akt and inhibition of endoplasmic reticulum (ER) Ca²⁺ ATPase. In this study, we show that both CE and an analog devoid of COX2 inhibitory activity [1-(4-sulfamoyl phenyl)-3-trifluoromethyl-5-(4-trifluoromethylphenyl)pyrazole, CEA] inhibit the secretion of the dimeric interleukin-12 (IL-12) and ₂ forms with identical IC₅₀ values of 20 and 30 µM, respectively, whereas no such effect was seen with rofecoxib. Reverse transcription-polymerase chain reaction analysis showed that this inhibition was not due to a blockage of transcription of the - and -chain expression cassettes. Secretion of the monomer form was less strongly inhibited, suggestive for a mechanism primarily targeting dimer assembly in the ER. Analysis of intracellular fractions revealed that both CE and CEA increased the association of IL-12 with calreticulin, an endoplasmic reticulum-resident chaperone involved in the retention of misfolded cargo proteins while blocking interaction with ERp44. Our findings reveal a previously undescribed effect of celecoxib on oligomer protein folding and assembly in the endoplasmic reticulum and ensuing secretion and suggest that celecoxib-driven alteration of the secretome may be involved in some of its clinical side effects.

Received for publication November 8, 2005.

Accepted for publication February 7, 2006.

Address correspondence to: Dr. Koen Vandenbroeck, Chair in Applied Genomics, School of Pharmacy, Queen's University Belfast, 97 Lisburn Road, Belfast BT3 7BL, UK. E-mail: k.vandenbroeck{at}qub.ac.uk

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