GSH, SOD, GPX, and proinflammatory factor activity was quantified using Quantikine ELISA Immunoassay kits (R&D Systems). In brief, after macrophages underwent siRNA transfection, 1 mL of fresh cell culture medium was added to each well of a 6-well plate, and conditioned medium was collected 6 hours after elastase exposure [58 (link)]. Conditioned media were centrifuged at 3,000 × g for 15 minutes to remove cell debris. Undiluted conditioned media were used to quantify target protein levels according to the manufacturer's instructions [59 (link)]. All samples were run in triplicate.
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