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* = Presenting author

P328 P-glycoprotein 170 (P-GP) functional activity in peripheral blood lymphocytes (PBL) of IBD patients during treatment with anti-TNFs

A. Sambuelli*1, C. Cortada2, A. Gil1, S. Negreira1, M. Bellicoso1, S. Huernos1, P. Tirado1, P. Chavero1, S. Goncalves1

1IBD Section - Hospital Bonorino Udaondo, Medicine, Buenos Aires, Argentina, 2Centro de Biologia Molecular (CDM), Flow Cytometry, Buenos Aires, Argentina

Background

Pgp, encoded by the MDR1 gene is a transmembrane, ATP-dependent, efflux pump, expressed in cells with barrier function and PBL. IBD share drugs Pgp influenced (as steroids, 6MP in leukemia cells) with other diseases. Pgp overexpression was implicated in highly active resistant RA (Tsujimura, Ann Rheum Dis 2008) induced by IL2 and TNF α, influencing steroid efflux from lymphocytes, reporting that a single infliximab (IFX) infusion overcame refractoriness with elimination of Pgp high expressing CD4+lymph, and recovery of dexametasone in PBL with Ppg marked decrease. Pgp measure in PBL could be an early marker of AntiTNFs efficacy and Pgp activity could modify the efflux of concurrent Pgp substrates drugs. AIM: to study Pgp activity in PBL of IBD pts. treated with antiTNFs.

Methods

Pgp functionality was evaluated in PBL of IBD and healthy contr (HC: n30)- IBD: n123 recruited (CD 59, UC 64)in 5 groups - Before and after 20 days of AntiTNF (IFX/ADA) in steroid refractory (Group 1) or thiopurine refractory (Group 2), - Before and after 3mo of 6MP in steroid refractory (group 3), - In Thiopurine sensitive (Group 4) and Steroid sensitive (Group 5). Response criteria: at 45 days of AntiTNFs or 3 mo. of 6-MP (CDAI: 70 points drop, Mayo Sc.3 points+30% drop) categorized in: remission (CDAI ≤150, Mayo Sc. ≥ ≤2) and partial response. Rhodamine123 (fluorescent Pgp substrate) efflux was studied by flow cytometry, expressed by the behaviour of 2 markers (according % of cells with different fluoresc. levels: M1 (high fluoresc./low Pgp pump activity), M2 (low fluoresc./Pgp high activity, used for the Results).

Results

(mean±SD): Major finding was a significant decrease of Pgp after AntiTNFs in total PBL (M2) in most of responder IBD. (Δ-difference in refractory vs remission p: 0.030018, and 0.0023 for Groups 1 and 2, and vs. partial response p: 0.014 in group 2, Mann Whitney). Basal (pre AntiTNFs) Pgp values of pts. with available post AntiTNFs measures according response (remission, partial response, refractory) were: Group 1 (n 20) 38.0 ± 17.7, 44.6 ± 8.4, 38.6 ± 21.0 and Group 2 (n 23) 35.9 ± 16.0, 34.8 ± 9.9, 23.1 ± 7.1. Post AntiTNF (same criteria): 26.2 ± 16.0, 29.0 ± 12.1, 47.0 ± 19.3 (Group 1) and 21.0 ± 11.6, 22.3 ± 11.5, 36.0 ± 11.7 (Group 2). Pts. in 6MP monotherapy (n23) did not show signif. changes. Pgp dropped after AntiTNFs in CD3 lymph. in remission vs. refractory (group 2 p<0.003, B lymph. of responders showed a trend for lower values post AntiTNFs (Group 1). Post-treatment values were lower in IBD vs HC (p<0.04).

Conclusion

We found that AntiTNFs decreased Pgp activity in PBL of IBD pts, significantly associated with treatment response. It is possible that the transport of Pgp substrates can be modified by antiTNFs. MDR1 polymorphism typing is ongoing