Synergistic Protective Effects of Haematococcus pluvialis-Derived Astaxanthin and Walnut Shell Polyphenols Against...

Airborne particulate matter (PM) triggers oxidative stress and inflammation in pulmonary tissues, contributing to chronic respiratory diseases. This study evaluated the antioxidant and anti-inflammatory effects of a combined extract of Haematococcus pluvialis (H. pluvialis) and walnut shell (HW extract) and its protective efficacy against PM_2.5-induced pulmonary inflammation. Extracts mixed at different ratios (10:0-0:10, w/w) were tested using 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, cell-based assays, HPLC quantification, molecular docking, and a PM_2.5-induced pulmonary inflammation mouse model. The optimized 6:4 mixture showed the strongest antioxidant activity (RC₅₀ = 0.61 ± 0.14 μg/mL) and significantly reduced nitric oxide (NO) and cyclooxygenase-2 (COX-2) expression without cytotoxicity. HPLC confirmed the presence of astaxanthin (1.714 μg/mg) and quercetin (0.722 μg/mg). Docking simulations indicated strong COX-2 binding affinities (-9.501 and -8.753 kcal/mol) through hydrogen bonding and hydrophobic interactions. In vivo, HW extract reduced leukocyte infiltration, serum IL-6 levels, and pulmonary expression of COX-2, interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α) while improving alveolar structure. These results suggest that HW extract exerts synergistic antioxidant and anti-inflammatory actions via dual-site COX-2 modulation, providing a promising natural therapeutic approach for mitigating PM_2.5-induced respiratory inflammation.