Seaweed-derived extracts and their combinations display immunomodulatory activity in a porcine cell culture model

Antimicrobial resistance is a global concern affecting humans, animals, and the environment. Therefore, livestock production is exploring seaweed-based extracts as antibiotic alternatives due to their potential bioactive compounds and immunoregulatory properties. This study aimed to evaluate the in vitro immunomodulatory effect of three seaweed extracts: Ascophyllum nodosum (AN), Ulva lactuca (UL), Palmaria palmata (PP), and their 1:1 combinations (ANUL, ANPP, ULPP) on porcine alveolar macrophages (porcine AMs). Briefly, macrophages were seeded at 1 × 10⁶ cells/mL and treated with seaweed extracts and challenged with lipopolysaccharide (LPS). The experimental design was a 2 (0-1 µg/mL of LPS) × 5 (five doses of each seaweed extract and their combinations). Cell viability was determined using the MTT assay. The results demonstrated that the LPS challenge with certain doses of tested seaweeds decreased (p < 0.05) the secretion of tumor necrosis factor-α (TNF-α), interleukin 1-β (IL-1β), and transforming growth factor β1 (TGF-β1). Particularly, a dose-response decrease in TNF-α production was observed for ULPP (p < 0.05). PP treatment significantly (p < 0.05) suppressed IL-1β secretion at 100 and 200 µg/mL doses, while AN and ULPP (only in doses of 100 and 200 µg/mL) significantly (p < 0.05) reduced TGF-β1 secretion from LPS-challenged porcine AMs. These results highlighted that seaweed extracts, particularly from PP, and ULPP with their in vitro immunomodulatory effects, may be valuable candidates for managing inflammation and encourage further in vivo research to confirm their efficacy.