The crucial role of l-arginine in macrophage activation: What you need to know about it.

Nowadays, it is well recognized that amino acids are powerful molecules responsible for regulatory control over fundamental cellular processes. However, our understanding of the signaling cascades involved in amino acid sensing in organisms, as well as signal initiation, is largely limited. This is also the case of semi-essential amino acid l-arginine, which has multiple metabolic fates, and it is considered as one of the most versatile amino acids. Recently, some new and important facts have been published considering the role of l-arginine in the regulation of inflammatory processes in several human and mouse models, mediated also via the regulation of macrophage activation. Therefore, this mini review focuses on the actual summarization of information about (i) l-arginine bioavailability in organism, (ii) l-arginine-dependent regulation of nitric oxide synthase expression and nitric oxide production, and importantly (iii) its role in the activation of intracellular signaling pathways and G-protein-coupled receptors in macrophages.