Inflammation is an initial response of the body to a harmful stimuli and it is achieved by the increased movement of leukocytes (especially granulocytes) from blood into injured tissues. It is required for healing wounds and infections. Despite their indispensable role in microbial killing, the inflammation reactions may also cause diseases to a host such as hay fever, atherosclerosis, and rheumatoid arthritis. The enzymes and oxidizing species released during the inflammatory process can cause damages to the host tissues which lead to inflammatory syndromes. The role of myeloperoxidase (MPO) in the inflammatory reactions is well documented. It contributes in killing the pathogens but it is also implicated in several inflammatory syndromes such as Parkinson's disease, Alzheimer’s disease and atherosclerosis. Thus, this enzyme has attracted more attention of the scientists and it has become a target for drug designing. In the last decade, several reversible and irreversible MPO inhibitors were identified as very high potent inhibitors such as fluoroalkylindole, aromatic hydroxamic acid, thioxanthine and benzoic acid hydrazide derivatives. In this review, we tried to illustrate the MPO inhibitors and highlight their structure activity relationship (SAR). In this paper we also discussed the mechanism of the inhibitory effect of the most potent compounds.

Objectives: Major depressive disorder (MDD) is accompanied with an imbalance in the immune system and cardiovascular impairments, such as atherosclerosis. Several mechanisms have been pointed out to underlie this rather unexpected association, and among them the activity of myeloperoxidase (MPO). The aim of our study was to find compounds that inhibit both MPO and serotonin transporter (SERT) for treating MDD associated with cardiovascular diseases. Methods: SERT inhibition was assessed with measuring of [3H]-serotonin uptake using HEK-293 MSR cells. MPO inhibition was determined by taurine chloramine test on 3-(aminoalkyl)-5-fluoroindole derivatives and on clinically relevant antidepressants. All kinetic measurements were performed using a temperature-controlled stopped-flow apparatus (model SX-18 MV). Promising lead compounds were docked onto SERT 3D structure modelled using the LeuT structure complexed to tryptophan (PDB code 3F3A). Their toxicological profile was also assessed. Key findings: 3-(aminoalkyl)-5-fluoroindole derivative with 5 carbons on the side chain and paroxetine showed the best activity on both MPO and SERT at the nanomolar range. Paroxetine was found to be the first irreversible MPO inhibitor at nanomolar concentrations. Conclusions: Our results put forward the first hybrid molecule (compound 25) and drug (paroxetine) that can be especially used in MDD associated with inflammatory syndrome.