br Acknowledgments br Introduction Non steroidal anti inflam

Acknowledgments
Introduction Non-steroidal anti-inflammatory drugs (NSAIDs) are a common treatment for a number of disease states involving an inflammatory reaction. This group of drugs mediate their anti-inflammatory effects mainly by inhibition of cyclooxygenase (COX), an enzyme of prime importance for the synthesis of different prostaglandins [1], [2]. A number of studies have demonstrated that neutrophils, important phagocytes of our innate immune system, have the capacity to synthesize and release prostaglandins via the COX pathway [3], [4], suggesting that the function of activated neutrophils might be affected by NSAIDs. Accordingly, piroxicam, which belongs to the oxicam family of NSAIDs and is a non-selective COX-inhibitor, has been reported to affect neutrophil functions such as the production and release of superoxide anions generated by the activated NADPH-oxidase [5], [6], [7]. Neutrophilic granulocytes have the ability to migrate in response to gradients of chemoattractants, soluble our serving as “danger signals”. In a number of inflammatory disorders the tissue damage is associated with the chemoattractant-guided accumulation of neutrophils and their subsequent release of reactive oxygen species and proteolytic enzymes. The list of structurally well-characterized leukocyte chemoattractants has steadily grown and the broad application of molecular biology techniques has led to identification of chemoattractant receptors. These receptors specifically recognize different chemoattractants, exhibit some sequence homologies and share structural features. They all belong to a pertussis toxin sensitive subfamily within the G protein-coupled receptor (GPCR) superfamily. The formyl peptide receptor (FPR) was the first neutrophil GPCR to be cloned and sequenced [8]. Soon after the FPR sequence was published, an orphan neutrophil FPR-like receptor, formyl peptide receptor like1 (FPRL1), was identified [8], [9]. The FPR is a high affinity pattern recognition receptor with the ability to track bacteria releasing formylated peptides [10], [11], supporting the idea that FPR may have a direct function in innate defence against bacterial infection. Following the discovery of FPRL1-specific ligands it has become obvious that this receptor possesses large functional similarities with the FPR [10], [12]. Binding of ligands to FPR and FPRL1 thus induces a variety of leukocyte activities such as chemotactic movement, chemoattractant induced mobilization of granules, and superoxide anion production as a result of an activation of the NADPH-oxidase. The downstream signalling of FPR has been extensively studied as a model system and it was until recently, assumed that FPRL1 uses identical routes. However, lately differences in these receptors signalling pathways have been suggested [13], [14].
Materials and methods
Results
Discussion The non-steroidal family of anti-inflammatory drugs (NSAIDs), is a heterogenous group of chemical compounds that mainly mediate their effects by reducing prostaglandin synthesis. This is achieved through an inhibition of the key enzyme cyclooxygenase (COX) [1]. Although COX inhibition is the common mechanism for all NSAIDs some of them have been reported to have anti-inflammatory effects through mechanisms distinct from COX inhibition [5], [6], [7]. We show that the NSAID piroxicam, reduces the release of superoxide anions from neutrophils stimulated with specific agonists of the formyl peptide receptor (FPR) and that this inhibition is due to blocking of ligand binding. We also show that piroxicam, in order to inhibit the cellular response triggered by an agonist that binds not only FPR but also the closely related formyl peptide receptor 1 (FPRL1), has to be combined with an antagonist for FPRL1. FPR and FPRL1 possess a high degree of amino acid identity, but despite this, they bind different agonists and the second messenger triggering part of the receptors are somewhat different [19], [23], [24]. The formyl peptide receptor (FPR) is a high affinity pattern recognition receptor with abilities to bind bacterial derived/released formylated peptides [25]. Such peptides are recognized also by FPRL1 but binding occurs with a low affinity, but in addition this receptor recognizes a number of non-formylated peptides/proteins that also activate the receptor [24], [26].