Ramona E. von Leden, PhD - US grants

? DESCRIPTION (provided by applicant): Over 250,000 people in the US are currently living with disabilities related to spinal cord injury (SCI). The number of SCI's among the aging population has been steadily increasing since the 1980's, and is associated with high rates of co-morbidities. Oxidative stress and reactive oxygen species (ROS) are increased in aging tissue and have been causally implicated in tissue damage and chronic inflammation in the central nervous system (CNS). These stressors influence the activity of glial cells, contributing to the delayed recovery to SCI seen in the aging population. No work to date has examined age-related alterations in glial cell response to SCI. The NADPH oxidase (NOX) family of enzymes is suggested to play a modulatory role in microglial/macrophage activation, inflammation and tissue damage through the production of ROS, and is chronically up-regulated after SCI. NOX, microglia and astrocytes all show altered profiles with increased inflammatory morphology and basal activation states in both human and rodent aged populations. Thus, we hypothesize that age-related upregulation in NOX activity and expression leads to increased proinflammatory glial cell activation states, resulting in exaggerated glial responses and diminished recovery to spinal cord injury. To test this hypothesis, we propose three specific aims. In aim 1, we will characterize basal glial cell activation states and NOX expression and activity in the aging rodent spinal cord. In this aim, we will use double labeled immunohistochemistry and biochemical techniques to characterize NOX and glial cell activation state in 3 and 12 month aged rats. In aim 2, we will demonstrate the effects of aging on NOX expression and activity, glial cell activation, lesion size and functional recovery after spinal cod injury. In this aim, we will assess NOX and glial cell activation after a moderate contusion SCI in 3 and 12 month aged rats using immunohistochemistry, biochemistry, RT-qPCR and functional assessment. In aim 3, we will evaluate the effect of inhibition of NOX activity and expression on basal glial activation and response to injury. In this aim, we will assess the modulatory effects o NOX on microglia and astrocyte activation in aged rats using a NOX2 specific inhibitor. This effect will be investigated using immunohistochemistry, biochemistry, subcellular fractionation and functional assessment. The data generated in these aims will help to guide researchers and clinicians in more effective diagnosis and may provide important insight into potential future therapeutic targets for SCI in the aging population.

Traumatic brain injury (TBI) is the leading cause of disability in children in the U.S., with the highest risk reported in infants and young children (0-4 years old). There is a high prevalence of previous TBI among cocaine users and an association between early age at time of TBI and cocaine use in adolescence. Thus, early age at time of TBI is an important risk factor for development of addiction. Here I will propose to study the relationship between injury to the rodent brain at postnatal day 21 (pnd21), an age that approximates the toddler-aged child, neuroinflammation, and addiction to cocaine at adolescence. Cocaine and other common drugs of abuse share a mechanistic link between increasing dopaminergic transmission in the mesolimbic and mesocortical pathways and addictive behavior. Dopaminergic neurons originate in the ventral tegmental area (VTA) of the midbrain, and project to the ventral striatum, including the nucleus accumbens (NAc), and the prefrontal cortex (PFC). TBI at pnd21 reduces dopaminergic signaling in the striatum and VTA at adulthood. Such a decreased dopaminergic state may increase the likelihood for sensitivity to addiction as a mechanism to restore dopamine. What remains unclear is whether disruption to this signaling is evident during the adolescent period, where there is an established high risk of substance abuse, and the extent to which immune responses, expressed within in the acutely injured brain, alter long-term addictive behaviors. The young brain shows a profound inflammatory response to TBI; we have found that interleukin-1 related signaling is upregulated in cortical and subcortical structures within the first week after injury at pnd21. I will determine if this upregulation likewise occurs in the reward pathways, a possibility that is reinforced by studies of TBI to the adolescent brain where there is an upregulation of IL-1 cytokines and factors in the cortex and NAc. I hypothesize that traumatic injury to the developing brain produces a robust early inflammatory response in the reward pathway that enhances addictive liability to cocaine at adolescence. To test this hypothesis, Aim 1 will determine if TBI at pnd21 leads to disruption of the reward pathway and enhanced addictive liability of cocaine during subsequent brain development, utilizing a self-administration model of cocaine addiction at adolescence and adulthood, and stereology to assess dopaminergic signaling in the reward pathways. Aim 2 will evaluate inflammatory signaling in the reward pathway in the acutely injured brain, and determine if IL-1 signaling contributes to addictive liability to cocaine at adolescence. Biochemical techniques will be used to profile inflammation in the reward pathway after early age TBI. Brain-injured animals will be acutely treated with an IL-1R antagonist or vehicle to assess impact of IL-1 on addictive liability at adolescence. The data generated in these aims will broaden our understanding of age-dependent vulnerability to TBI, including mechanistic insights into long-term maladaptive behaviors including drug addiction. Such findings will contribute to a platform for optimizing recovery in the brain injured child.