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 Posidonia oceanica (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 P. oceanica’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 Nos2 expression, reduced levels of COX-2 and TNFα proteins, and a decrease in Nfkb1 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.