Oxidation-dependent effects of alpha-1 antitrypsin on wound healing and inflammation

Wound healing requires a delicate balance between cellular and molecular factors, all affected by reactive oxygen species (ROS). While ROS decontaminate, they also might lead to impaired wound healing, as evident in radiation-exposed skin and in venous insufficiency. Human alpha-1 antitrypsin (hAAT) is a circulating antiprotease that is anti-inflammatory and tissue-protective. Accordingly, tissue repair is enhanced in hAAT-rich conditions. hAAT undergoes oxidative modification in high-ROS environments, which alters its functional properties. While its antiprotease function is lost, the consequences of oxidation on its anti-inflammatory and tissue-protective properties are still under investigation. To explore this, excisional skin wound closure rates were first examined on irradiated skin and then tested using an iron-loading venous insufficiency model. The former was tested on hAAT transgenic mice, the latter on wild-type mice using topical clinical-grade hAAT. In-vitro, hAAT was oxidized using H₂O₂ (0.5, 5 and 25 mM), then tested for elastase inhibition and added to an in-vitro A549 epithelial cell gap closure assay and a RAW 264.7 macrophage cell response assay. ROS levels, inflammatory responses and NRF2/ARE activation were determined. Results demonstrated wound closure was impaired in wild-type mice by both radiation and iron. In contrast, hAAT-transgenic mice exhibited accelerated wound closure in both normal and irradiated skin, and topical hAAT improved wound healing in the venous insufficiency model. hAAT^OX lacked elastase inhibition across the three oxidation levels, yet highly oxidized hAAT (hAAT^{OX 25mM}) impaired epithelial gap closure and weakly oxidized hAAT (hAAT^{OX 0.5mM}) enhanced gap closure. All forms of hAAT^OX elevated ROS in macrophages, as well as the expression of iNOS and catalase, IL-1β, TNFα and CXCL-1. Unexpectedly, the NRF2/ARE pathway was activated by hAAT^{OX 25mM} and suppressed by hAAT^{OX 0.5mM}, and hAAT^{OX 0.5 mM} induced IL-1 receptor antagonist expression. In conclusion, oxidation levels of hAAT modify its effects on inflammation and tissue repair. While protease inhibition is lost, anti-inflammatory and repair attributes are maintained under low oxidative conditions, suggesting a molecular profile that is physiologically attuned to local signals. Considering its safety record, the study proposes that hAAT therapy is poised for trials in the context of defective tissue repair under oxidative conditions.