Graduation Date

Spring 5-7-2022

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Programs

Medical Sciences Interdepartmental Area

First Advisor

Yulong Li

MeSH Headings

ischemia-reperfusion injury

Abstract

Ischemia-reperfusion (IR) is a pathological condition characterized by an initial restriction of blood supply to an organ followed by subsequent restoration of reperfusion associated with exacerbation of tissue damage. For pre-hospital emergency situations and surgical procedures, tourniquet or femoral artery ligation are widely used to stop extremity hemorrhage or create a bloodless operating field. To fully evaluate the underlying mechanisms in IR pathophysiology and potential therapeutic options, we compared tourniquet- and femoral artery ligation-induced IR injuries in the hindlimb of mice. We found that tourniquet/IR-induced acute hindlimb injuries are more severe than those induced by femoral artery ligation/IR, including alteration of skeletal muscle function and morphology, motor nerve endings, proinflammatory cytokines, and edema. Tourniquet-induced IR also results in significant IR injuries to the nerves, leading to neurological deficits. In this study, we investigated the therapeutic effects of an anti-neuroinflammatory drug, masitinib (Mas), on the mechanoreception of sensory neurons in a mouse model of tourniquet/IR. The results showed that treatment with Mas significantly ameliorated paw numbness and allodynia by decreasing reactive oxygen species (ROS) and pro-inflammatory cytokines. Other than inflammation, depletion of adenosine triphosphate (ATP), ROS production, and other substances will also lead to tourniquet/IR. Hyperbaric oxygen (HBO) therapy is a method to increase the oxygen supply in cells to ameliorate IR in the skeletal muscle. In this study, we investigated the effects of HBO pretreatment in tourniquet/IR. These data suggest that one hour of HBO pretreatment with 100% oxygen at 2.5 atmospheres absolute (ATA) increases the antioxidant response to lower ROS accumulation but does not increase ATP levels in IR muscles and improve tourniquet/IR-injured muscle morphology and contractile function. Tourniquet/IR can also induce permanent injuries (neurological deficits and limb paralysis). We found that nicotinic acetylcholine receptor (nAChR) at the neuromuscular junction (NMJ) was fragmented, and the amplitude of endplate potential (EPP), and sciatic nerve-stimulated gastrocnemius muscle contraction did not restore to the normal level after 6-wk tourniquet/IR. Rapsyn (a cytoplasmic nAChR-associated protein) is located on the skeletal muscle membrane and can thus help form and stabilize nAChR clusters by crosslinking with nAChRs and tethering them to the cytoskeleton. In this study, we investigated the role of Rapsyn in gastrocnemius muscle function after 6-wk of tourniquet/IR. We found up-regulation of Rapsyn in the gastrocnemius muscle significantly improved the NMJ and skeletal muscle function after 6-wk of tourniquet/IR.

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