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BACKGROUND AND PURPOSEBradykinin, through its B2 receptor, is involved in inflammatory processes related to arthropathies. In carrageenan and lipopolysaccharide (LPS)-induced arthritis in rat, the anti-inflammatory activity of MEN16132, a potent and selective kinin B2 receptor antagonist, was compared with that of steroidal and nonsteroidal anti-inflammatory drugs. The interaction between MEN16132 and dexamethasone was also investigated. EXPERIMENTAL APPROACHDrugs, alone or in combination, were injected into the knee joint 30 min before intra-articular administration of carrageenan or LPS, in pentobarbital anaesthetized rats. Effects on incapacitation, oedema, neutrophil recruitment and kallikrein system activation, in the knee joint, were assessed. KEY RESULTSMEN16132 and dexamethasone (10-300 mg per knee) dose-dependently reduced carrageenan-induced joint pain, oedema and neutrophil infiltration, reaching a maximal inhibition of about 50%. Dexketoprofen exerted a similar analgesic activity, whereas it did not affect the other inflammatory responses. MEN16132 showed a partial inhibition of LPS-induced joint pain, whereas dexamethasone produced a full analgesic effect. Combination of MEN16132 and dexamethasone showed a strong synergistic interaction in inhibiting both carrageenan and LPS-induced knee joint inflammation. Dexamethasone did not prevent the contact activation of prekallikrein by carrageenan and the subsequent release of kallikreins and bradykinin in the synovium. CONCLUSIONS AND IMPLICATIONSSteroids and kinin B2 receptor antagonists appear to relieve arthritic symptoms induced by carrageenan or LPS and act synergistically to inhibit joint inflammation. This could have interesting therapeutic implications, possibly opening the way for combination therapies in the control of inflammatory arthropathies. AbbreviationsCI, combination index; COX, cyclooxygenase; IL, interleukin; LPS, lipopolysaccharide; MPO, myeloperoxidase; NSAID, non-steroidal anti-inflammatory drug; PBS, phosphate buffered saline; PBS-T, PBS 0.1% Tween 20; TNF, tumour necrosis factor BJP British Journal of Pharmacology

Since its introduction a decade ago, the Caco-2 in vitro model for testing intestinal permeability has found wide application, in particular for screening new molecules in the pharmaceutical industry. An important issue for the validation of the model is to verify integrity and proper functionality of the Caco-2 cells monolayer, to ensure reproducibility and consistency of results. Several of these methods are based on measuring the apparent permeability coefficients (Papp) of well-characterized reference compounds, having known absorption characteristics, and comparing the observed values to those expected. Most of them use fluorescent or radioactive chemicals to test different parameters. The main limitation of such approaches is that each parameter to be tested is associated with a single specific method, so that multiple procedures are needed to adequately characterize the cell monolayer. This work describes the use of a unique LC-MS/MS method to simultaneously determine the Papp of a set of reference substances having well-characterized absorption behavior, i.e., phenylalanine, atenolol, and propranolol. The method is routinely used in our laboratory to check on model reproducibility and proved useful in verifying the consistency of the results derived from the experiments.