Effect of L-carnitine on the synthesis of nitric oxide in RAW 264·7 murine macrophage cell line.

L-Carnitine (β-hydroxy-γ-trimethyl aminobutyric acid) plays a critical role in inflammatory diseases by modulating inflammatory cell functions. Inducible nitric oxide synthase (iNOS), a proinflammatory enzyme responsible for the generation of nitric oxide (NO), has been implicated in the pathogenesis of inflammatory diseases. Mechanism of action of L-carnitine on inflammation via iNOS and nuclear factor κB (NF-κB) is unclear. In this study, we aimed to investigate the effect of L-carnitine on nitric oxide synthesis in lipopolysaccharide (LPS)-stimulated RAW 264·7 macrophage cells. For this purpose, cells were pretreated with various concentrations of L-carnitine and subsequently incubated with LPS (1 µg·ml(-1) ). NO levels, iNOS protein expression, and NF-κB activity were determined using colorimetric detection, Western blotting and transfection assays. Our results showed that treatment with L-carnitine suppressed nitric oxide production, iNOS protein expression and NF-κB activity. We demonstrated that inhibitory effect of L-carnitine on iNOS protein expression is at transcriptional level. This study may contribute to understanding the anti-inflammatory effect of L-carnitine.