5-Aminolevulinic acid regulates the immune response in LPS-stimulated RAW 264.7 macrophages.

BACKGROUND: Macrophages are crucial players in a variety of inflammatory responses to environmental cues. However, it has been widely reported that macrophages cause chronic inflammation and are involved in a variety of diseases, such as obesity, diabetes, metabolic syndrome, and cancer. In this study, we report the suppressive effect of 5-aminolevulinic acid (ALA), via the HO-1-related system, on the immune response of the LPS-stimulated mouse macrophage cell line RAW264.7.

RESULTS: RAW264.7 cells were treated with LPS with or without ALA, and proinflammatory mediator expression levels and phagocytic ability were assessed. ALA treatment resulted in the attenuation of iNOS and NO expression and the downregulation of proinflammatory cytokines (TNF-α, cyclooxygenase2, IL-1β, IL-6). In addition, ALA treatment did not affect the phagocytic ability of macrophages. To our knowledge, this study is the first to investigate the effect of ALA on macrophage function. Our findings suggest that ALA may have high potential as a novel anti-inflammatory agent.

CONCLUSIONS: In the present study, we showed that exogenous addition of ALA induces HO-1 and leads to the downregulation of NO and some proinflammatory cytokines. These findings support ALA as a promising anti-inflammatory agent.