Anti-Inflammatory and Immunomodulatory Effects of Aqueous Extracts from Green Leaves and Rhizomes of Posidonia oceanica (L.) Delile on LPS-Stimulated RAW 264.7 Macrophages

The marine angiosperm <i>Posidonia oceanica</i> (Linnaeus) Delile, 1813 is a rich source of phytotherapeutic compounds whose potential applications for human health remain largely uninvestigated. Here, we determined the differential impact of aqueous extracts from <i>P. oceanica</i>'s green leaves (GLE) and rhizomes (RE) on the inflammation-related mRNA expressions and protein levels, nitric oxide (NO) release, and endocytic activity in LPS-stimulated RAW 264.7 macrophages. We also examined the influence of the extracts in modulating the activation of components of intracellular signaling pathways. Co-treatments of LPS-stimulated RAW 264.7 cells in the presence of either GLE or RE resulted in a reduction in NO production, associated with a down-regulation of <i>Nos2</i> expression, reduced levels of COX-2 and TNFα proteins, and a decrease in <i>Nfkb1</i> expression and NF-κB activation. No effect was exerted on the release of IL-6. Moreover, co-exposures to LPS and the extracts led to an elevation in pJNK and pAKT levels alongside a reduction in pERK. In contrast to GLE, RE specifically lowered IL-1β production, induced a more robust increase in IL-10, positively influenced the endocytic function of RAW 264.7 cells, and drastically up-regulated the phosphorylation of p38. The data obtained indicate that GLE and RE exhibit considerable promise as prospective anti-inflammatory and immunomodulatory agents.