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- Creators: Newbern, Jason
- Resource Type: Text
Neuroinflammation Following Experimental Diffuse Brain Injury in Pre-pubertal and Peri-pubertal Rats
Description
Traumatic brain injury is the leading cause of mortality and morbidity in children and adolescents. Adolescence is a critical time in development where the body and brain undergoes puberty, which not only includes reproductive maturation, but also adult social and cognitive development. Brain-injury-induced disruptions can cause secondary inflammation processes and as a result, pediatric TBI can lead to significant life-long and debilitating morbidities that continue long after initial injury. In this study, neuroinflammation following diffuse brain injury was explored in prepubertal and peripubertal rats using an adapted method of midline fluid percussion injury (mFPI) for juvenile rats to further understand the relationship between pediatric TBI and puberty disruption due to endocrine dysfunction. We expect the adapted mFPI model to be effective in producing diffuse, moderate brain injury in juvenile rats and hypothesize that pre-pubertal rats (PND35) will have increased neuroinflammation compared to peri-pubertal rats (PND17) and shams because of the potential neuroprotective nature of sex steroids. Male Sprague-Dawley rats (n=90) were subjected to either a diffuse midline fluid percussion injury (mFPI) or sham injury at post-natal day (PND) 17 (pre-puberty) or PND35 (peri-puberty). Animals were sacrificed at different time points defined as days post injury (DPI) including 1DPI, 7DPI and 25DPI to represent both acute and chronic time points, allowing for comparisons within groups (injury vs. sham) and across groups (PND17 vs PND35). Body weight of the rats was measured postoperatively at various time points throughout the study to follow recovery. Tissue was collected and subjected to Heamatoxylin and Eosin (H&E) stain to visualize histology and evaluate the application of diffuse mFPI to juvenile rats. In addition, tissue underwent immunohistochemical analysis using 3,3'-diaminobenzidine (DAB) to stain for ionized calcium binding proteins (Iba1) in order to assess injury-related neuroinflammation in the form of microglia activation. Diffuse brain injury using the mFPI model did not affect rat body weight or cause overt cell death, suggesting adaption of the adult mFPI model for juvenile rats is representative of moderate diffuse brain injury. In addition, diffuse TBI lead to morphological changes in microglia suggesting there is an increased inflammatory response following initial insult, which may directly contribute to improper activation of pubertal timing and progression in adolescent children affected. Since there is little literature on the full effects of puberty dysfunction following TBI in the pediatric population, there is a significant need to further assess this area in order to develop improved interventions and potential therapies for this affected population.
ContributorsNewbold, Kelsey Bevier (Author) / Newbern, Jason (Thesis director) / Rowe, Rachel (Committee member) / Ortiz, J. Bryce (Committee member) / School of Mathematical and Natural Sciences (Contributor) / Department of Psychology (Contributor) / Barrett, The Honors College (Contributor)
Created2018-05
Description
The RAS/MAPK (RAS/Mitogen Activated Protein Kinase) pathway is a highly conserved, canonical signaling cascade that is highly involved in cellular growth and proliferation as well as cell migration. As such, it plays an important role in development, specifically in development of the nervous system. Activation of ERK is indispensable for the differentiation of Embryonic Stem Cells (ESC) into neuronal precursors (Li z et al, 2006). ERK signaling has also shown to mediate Schwann cell myelination of the peripheral nervous system (PNS) as well as oligodendrocyte proliferation (Newbern et al, 2011). The class of developmental disorders that result in the dysregulation of RAS signaling are known as RASopathies. The molecular and cell-specific consequences of these various pathway mutations remain to be elucidated. While there is evidence for altered DNA transcription in RASopathies, there is little work examining the effects of the RASopathy-linked mutations on protein translation and post-translational modifications in vivo. RASopathies have phenotypic and molecular similarities to other disorders such as Fragile X Syndrome (FXS) and Tuberous Sclerosis (TSC) that show evidence of aberrant protein synthesis and affect related pathways. There are also well-defined downstream RAS pathway elements involved in translation. Additionally, aberrant corticospinal axon outgrowth has been observed in disease models of RASopathies (Xing et al, 2016). For these reasons, this present study examines a subset of proteins involved in translation and translational regulation in the context of RASopathy disease states. Results indicate that in both of the tested RASopathy model systems, there is altered mTOR expression. Additionally the loss of function model showed a decrease in rps6 activation. This data supports a role for the selective dysregulation of translational control elements in RASopathy models. This data also indicates that the primary candidate mechanism for control of altered translation in these modes is through the altered expression of mTOR.
ContributorsHilbert, Alexander Robert (Author) / Newbern, Jason (Thesis director) / Olive, M. Foster (Committee member) / Bjorklund, Reed (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2017-05
Description
Traumatic brain injury (TBI) consists of the primary mechanical forces to the head followed by secondary inflammatory cascades. This inflammatory cascade consists of neuroinflammation characterized by microglial activation as the first line of defense. Another component of secondary inflammation comprises of activation of peripheral immune cells that can infiltrate the compromised blood brain barrier and susceptible organs such as the lungs. Acute inflammatory processes in the lungs include a disruption of the epithelial barriers allowing infiltration of neutrophils, and edema build up in the alveoli. This is known as acute lung injury (ALI) and it dampens respiratory function in approximately 20-25% of TBI patients necessitating an intervention. Remote ischemic conditioning (RIC) is an intervention consisting of repeated intervals of cessation and reperfusion of blood flow to a distal limb and has treated ALI, myocardial infarction, and neurological injury. TBI was hypothesized to induce ALI through degradation of alveolar-capillary membrane and infiltration of peripheral leukocytes. Furthermore, RIC was hypothesized to protect the integrity of the alveolar-capillary membrane, reduce infiltration of peripheral immune cells, and reduce microglial activation in the brain through myokine recruitment. Male CD1 mice were subject to either midline fluid percussion or sham injury and further randomized into 4 groups: sham, sham RIC, TBI, TBI RIC. RIC was administered on proximal thigh for 4x5 minutes, with 5-minute reperfusion one hour prior to TBI. One-hour post-injury, brain, lung, BAL fluid, and blood were collected. Lung histopathology showed RIC reduced hydrostatic edema in the alveoli by protecting the alveolar capillary membrane. BAL findings revealed TBI mice had increased neutrophil counts, RIC lowered neutrophil counts. In the brain, RIC increased cortex microglial endpoints were observed with no other significant differences in microglial morphology as well as plasma myokine levels across all sham, sham RIC, TBI, and TBI RIC animals. While underlying mechanisms still have to be further studied, this current study provides evidence that RIC can be used as a therapeutic intervention to ameliorate TBI-induce ALI.
ContributorsChristie, Immaculate (Author) / Newbern, Jason (Thesis director) / Lifshitz, Jonathan (Committee member) / Saber, Maha (Committee member) / School of Life Sciences (Contributor, Contributor) / Barrett, The Honors College (Contributor)
Created2020-05