Document Type
Dissertation
Date of Award
2024
Degree Name
Doctor of Philosophy (PhD)
Department
Basic Biomedical Science
First Advisor
Yifan Li
Abstract
Originally discovered in the brain, brain-derived neurotrophic factor (BDNF) has been shown to be expressed and released from skeletal muscle as a myokine. However, the function of myokine BDNF is not fully understood. Of interest to this study is the function of the BDNF precursor proBDNF in skeletal muscle. We first show that skeletal muscle expresses unique BDNF splice variants compared to the brain, and at the protein level, skeletal muscle expresses significantly more proBDNF than mature BDNF under basal conditions. Consistent with this, expression of major protein convertases in skeletal muscle were significantly lower. The role of myokine proBDNF was determined using two murine models of skeletal muscle injury: skeletal muscle ischemia reperfusion (IR) injury and sciatic denervation. Skeletal muscle IR injury is prevalent in trauma, peripheral vascular diseases, and surgical procedures while denervation injuries occur in spinal injury, nerve damage, and peripheral neuropathies. Remarkably, proBDNF was significantly increased in both models. This was accompanied by increased proinflammatory cytokines and immune cell infiltration. Thus, it was hypothesized that proBDNF may be necessary for facilitating the inflammatory response. Mice with skeletal muscle-specific knockout of BDNF showed that in the absence of proBDNF proinflammatory cytokine production and macrophage infiltration following skeletal muscle injury were significantly reduced. To confirm the role of proBDNF receptor, p75NTR, small molecule LM11A-31 was used to modulate p75NTR signaling. In injured muscle, LM11A-31 treatment also significantly reduced the proinflammatory response and macrophage infiltration compared to vehicle treated animals, confirming the role of p75NTR. Further, proBDNF was significantly upregulated in serum following skeletal muscle injury, which was confirmed to be specifically from the injured skeletal muscle, which establishes proBDNF as myokine capable of endocrine function. The function of the released proBDNF was tested using splenic monocyte populations. P75NTR was significantly upregulated in monocytes and showed functional significance in monocyte activation as LM11A-31 blunted the lipopolysaccharide induced cytokine release. Overall, this study makes substantial progress to myokine and skeletal muscle research by establishing proBDNF as a myokine predominantly expressed by skeletal muscle, released into circulation, and having a significant role in skeletal muscle injury.
Subject Categories
Molecular Biology | Pharmacology
Keywords
brian derived neurotrophic factor, ischemia reperfusion, LM11A-31, myokine, proBDNF, skeletal muscle injury
Number of Pages
150
Publisher
University of South Dakota
Recommended Citation
Aby, Katherine, "MYOKINE PROBDNF-P75NTR SIGNALING IN SKELETAL MUSCLE INJURY AND STERILE INFLAMMATION" (2024). Dissertations and Theses. 222.
https://red.library.usd.edu/diss-thesis/222