<em>Posidonia oceanica</em> (<em>L.</em>) <em>Delile</em> as a Marine Anti-Inflammatory Modulator of Keratinocyte Psoriatic Inflammation

Skin inflammation is characterized by oxidative stress, excessive keratinocyte activa-tion, and the overproduction of pro-inflammatory cytokines. In a previous study, we demonstrated that the hydroalcoholic extract from Posidonia oceanica leaves (POE) mit-igates psoriasis-like skin inflammation in a mouse model. In the present study, we in-vestigated the cellular mechanisms underlying these effects in human HaCaT keratinocytes. Non-cytotoxic lipopolysaccharide (LPS) stimulation reproduced key in-flammatory features, including impaired cell proliferation, increased production of ROS and NO, and the upregulation of IL-1β, IL-6, TNF-α and CXCL8/IL-8. Co-treatment with POE significantly attenuated these alterations by restoring cell pro-liferation, suppressing oxidative stress, particularly NOS2/NO, and normalizing both cytokine expression and release. POE alone did not affect cell viability or inflammatory markers, confirming its favorable safety profile. However, POE alone induced a mild pro-apoptotic response, which may contribute to overcoming the apoptosis re-sistance typically observed in psoriatic keratinocytes. These in vitro findings are con-sistent with our previous in vivo results and demonstrate that POE exerts antioxidant and anti-inflammatory activities. Overall, these results support the POE as a promising marine-derived candidate for complementary strategies in the management of psoria-sis-associated inflammatory skin disorders.