Hyperbaric Oxygen Reduces Matrix Metalloproteinases in Ischemic Wounds through a Redox-Dependent Mechanism

Little is known about the impact of hyperbaric oxygen treatment (HBOT) on matrix metalloproteinase (MMP) production in pre-existing high-oxidant wounds. This study aimed to investigate whether HBOT modulates reactive oxygen species (ROS) and MMP regulation in ischemic wound tissue. Using a validated ischemic wound model, Sprague Dawley rats were divided into four groups for daily treatment: HBOT, N-acetylcysteine (NAC), HBO and NAC, and control (normoxia at sea level). High levels of inducible nitric oxide synthase (iNOS), gp91-phox, and 3-nitrotyrosine were detected in ischemic wounds, indicating high-oxidant stress. HBOT not only increased antioxidant enzyme expression, such as Cu/Zn-superoxide dismutase, catalase, and glutathione peroxidase, but also significantly decreased pro-oxidant enzyme levels, such as iNOS and gp91-phox, thereby decreasing net oxygen radical production by means of negative feedback. This effect was blocked by NAC treatment in ischemic wounds. HBO-treated ischemic wounds also manifested reduced phosphorylation of extracellular signal regulated kinases 1/2, c-Jun N-terminal kinase, and c-Jun, indicating downregulation of mitogen-activated protein kinases (MAPKs). Furthermore, HBOT decreased the expression of several MMPs while simultaneously increasing tissue inhibitor of MMP (tissue inhibitor of metalloproteinase 2). These results indicate that HBOT acts via the ROS/MAPK/MMP signaling axis to reduce tissue degeneration and improve ischemic wound healing.