Abstract
Hyperbaric oxygen (HBO) treatment promotes early recovery from muscle injury. Reactive oxygen species (ROS) upregulation is a key mechanism of HBO, which produces high O2 content in tissues through increased dissolution of oxygen at high pressure. Nitric oxide (NO), a type of ROS, generally stabilizes hypoxia-inducible factor (HIF) 1α and stimulates secretion of vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) from endothelial cells and macrophages, which then induces angiogenesis. The purpose of the present study was to investigate whether HBO could promote angiogenesis via induction of NO and induce muscle regeneration in contused rat skeletal muscles. The HBO protocol consisted of 2.5 atmospheres absolute (ATA) 100% oxygen for 120 minutes, once a day for 5 consecutive days. We also evaluated the effects of a ROS inhibitor (NAC) or NOS-specific inhibitor (L-NAME) on HBO. HBO significantly increased NO3−, VEGF, and bFGF levels and stabilized HIF1α within 1 day. HBO promoted blood vessel formation at 3–7 days and muscle healing at 5–7 days after contusion. Administration of both NAC and L-NAME before HBO suppressed angiogenesis and muscle regeneration even after HBO. HBO thus promoted angiogenesis and muscle regeneration mainly through generation of NO in the early phase after muscle contusion injury.
Highlights
Hyperbaric oxygen (HBO) treatment promotes early recovery from muscle injury
We quantified the amounts of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), hepatocyte growth factor (HGF), and angiopoietin 2 protein in contused muscles at 3 hours, 6 hours, 1 day, and 3 days after injury by enzyme-linked immunoassay (ELISA) (Fig. 1)
VEGF levels were significantly increased in the HBO group at 3 hours after injury (NT group: 311.2 ± 58.2 pg/ml, HBO group: 827.5 ± 83.8 pg/ml, F(3, 20) = 21.21, p < 0.001.) (Fig. 2A). bFGF levels significantly increased in the HBO group at 6 hours after injury(NT group: 1314.6 ± 144.3 pg/ml, HBO group: 1939.8 ± 138.0 pg/ml, F(3,20) = 4.471, p = 0.03) (Fig. 2B)
Summary
Hyperbaric oxygen (HBO) treatment promotes early recovery from muscle injury. Reactive oxygen species (ROS) upregulation is a key mechanism of HBO, which produces high O2 content in tissues through increased dissolution of oxygen at high pressure. HBO promoted blood vessel formation at 3–7 days and muscle healing at 5–7 days after contusion Administration of both NAC and L-NAME before HBO suppressed angiogenesis and muscle regeneration even after HBO. HBO promoted angiogenesis and muscle regeneration mainly through generation of NO in the early phase after muscle contusion injury. Among the factors associated angiogenesis, upregulation of VEGF9–11, basic fibroblast growth factor (bFGF)[6,11], hepatocyte growth factor (HGF)[6], and angiopoietin 211 activates migration and proliferation of endothelial cells, and promotes angiogenesis[12,13] it has been reported that stabilization of hypoxia-inducible factor (HIF) 1α stimulates vascular endothelial growth factor (VEGF) secretion[11,12,14] and is an important factor for VEGF-mediated angiogenesis. These changes stimulate collagen synthesis[23], proliferation of cells such as satellite cells[24,25,26], and angiogenesis[9,27]
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