Browsing by Author "Schreihofer, Derek A."
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Item Androgen Modulation of CNS During Chronic Intermittent Hypoxia(2018-05) Snyder, Brina D.; Cunningham, Rebecca L.; Barber, Robert C.; Cunningham, J. Thomas; Schreihofer, Derek A.; Planz, John V.The underlying causes of age-related neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease, are unknown. It is likely conditions which contribute to an abundance of oxidative stress throughout life renders an individual more susceptible to late-life neurodegenerative processes. Sex differences are observed in the onset and prevalence of these diseases, suggesting estrogens and androgens influence these processes. This study investigates the early role of androgens under a known oxidative stressor, sleep apnea, which frequently goes untreated in the clinical population but is but is associated with an increased risk of late-life neurodegeneration. The hypoxic events of sleep apnea can be modeled in rats by the use of chronic intermittent hypoxia (CIH). Male rats are more susceptible to hypertensive effects of CIH, a key characteristic of sleep apnea. After one week of CIH treatment, they also exhibit oxidative stress and inflammation in circulation and in brain nuclei associated with early stages of Parkinson's disease or Alzheimer's disease. This led to the hypothesis that oxidative stress and inflammation would be associated with behavior deficits and these effects are mediated by androgens. Results show that oxidative stress and inflammatory dysregulation can be prevented by testosterone, but are highly exacerbated by testosterone's non-aromatizable metabolite, dihydrotestosterone (DHT). Administration of DHT also resulted in significant memory impairments under CIH. In the central nervous system, DHT significantly altered oxidative stress and pro-inflammatory signals, which may underlie its detrimental actions in an oxidative stress environment. There was also evidence of hypothalamic-pituitary-adrenal axis dysregulation, which can influence testosterone and circadian rhythms. These findings have broad implications for clinical populations with conditions which chronically increase oxidative stress and inflammation, while at the same time alter endocrine function. Conditions, such as untreated sleep apnea, may pose a latent risk for neurodegeneration and should be addressed early to prevent later detrimental effects.Item Assessment of Sex Differences Following Repeated Mild Head Injuries(2022-05) Duggal, Aakaash; Schreihofer, Derek A.; Sumien, Nathalie; Luedtke, Robert R.There is limited information about sex differences in mRHI, despite some studies suggesting females participating in contact sports experience more head injuries than males. This study will test the hypothesis that mRHI will lead to more severe neurological deficits in female mice than in male mice. C57BL/6 female mice were assigned to sham and mRHI groups (n=30/group). Lightly anesthetized mice received 25 mild head injuries, once a day (M-F) over 5 weeks using a weight drop model that included a free fall with rotational injury. Acutely, mRHI female mice performed worse than sham injured mice on the balance beam (F (1,28) =4.309, P=0.0472) whereas there was no difference in males. 5 weeks and 15 weeks after injury mice underwent a 3-week series of behavioral tests. Both male and female mice in the mRHI groups performed significantly (T-test P< 0.01) worse on the Rotarod than uninjured controls. Only males in MWM showed significant impairment on memory for 5-week and significant impairment on spatial learning and memory for 15-week (Probe T-test P< 0.05). Only 15-week male mice showed deficits in elevated plus maze (EPM) (T-test P< 0.05). Acutely, female mice showed balance deficits that were not apparent in males. Fifteen weeks after mRHI, males no longer displayed deficits in the rotarod, but female mice continued to have a decrease in performance compared to controls (T-test, P<0.05). Unlike the males, female mice did not display any significant deficits in the MWM and EPM.Item Brainstem mechanisms that impair autonomic regulation of blood pressure with obesity(2018-12) Chaudhary, Parul; Schreihofer, Ann M.; Mifflin, Steve W.; Cunningham, J. Thomas; Schreihofer, Derek A.Metabolic syndrome (MetS) is emerging as a global health threat due to its strong association with increased risk for cardiovascular disease and diabetes. Currently, 20-25% of the world's population exhibits some traits of MetS, namely obesity, dyslipidemia, hyperinsulinemia, hypertension, and hyperglycemia. In addition, MetS also promotes the development of impaired short-term regulation of mean arterial pressure (AP) by baroreflexes, which normally act to stabilize AP. The resulting increased AP variability, which is an independent risk factor for poor outcomes, is overlooked as a trait of MetS and goes without evaluation or treatment. People who have controlled hypertension without minimizing elevated AP variability are still at significant risk for detrimental cardiovascular events such as stroke and cognitive decline. Therefore, understanding mechanisms impairing baroreflexes with MetS will help determine appropriate therapeutic management to restore baroreflexes and promote stability of AP. Furthermore, because sex differences in the development of impaired baroreflexes with obesity have been reported, an understanding of how females are protected would provide valuable insights for underlying causes for early onset of impaired baroreflexes in obese males and eventual development of impaired baroreflexes in obese females. In this project, I utilized a rodent model of MetS, obese Zucker rats (OZR), to examine contributions of hypertension and hyperglycemia in the development of impaired baroreflexes in male OZR, and whether hypertensive female OZR have delayed onset of impaired baroreflexes because they have the ability to maintain glycemic control. Male and female OZR have excess weight gain from an early age because the mutation of a leptin receptor renders them insensitive to leptin's actions to regulate appetite and metabolism, promoting excess intake of standard chow and storage of ingested calories. Like obese humans, OZR develop dyslipidemia, hypertension, and insulin resistance that eventually progresses to type 2 diabetes, making them a suitable model for the consequences of MetS. Young adult male OZR (12-15 weeks) develop sympathetically driven hypertension with pronounced attenuation of baroreflex control of heart rate (HR) and sympathetic nerve activity (SNA) compared to juvenile OZR and lean Zucker rats (LZR). In male OZR, the development of impaired baroreflexes coincides with blunted activation of the NTS, the brain stem region that receives baroreceptor afferent inputs to promote baroreflex-mediated changes in HR and SNA, and this deficit likely yields diminished baroreflexes observed in young adult male OZR. In the first project I examined whether improvement of impaired glycemic control in young adult male OZR restores baroreflex-mediated bradycardia and activation of the NTS. Both type 1 and type 2 diabetic rats have impaired vagally-mediated activation of the NTS, in agreement with the reported loss of glucose's ability to enhance glutamatergic neurotransmission within the NTS of hyperglycemic, diabetic rodents. Male OZR develop insulin resistance at an early age, characterized by elevated insulin and triglycerides with impaired glucose tolerance but normal fasting hyperglycemia. We examined glucose homeostasis using chronic measures of blood glucose by telemetry in undisturbed rats because of previous reports of exaggerated stress responses. We observed that although young adult (12-14 weeks old) male OZR have normal fasting blood glucose, they are chronically hyperglycemic with access to food. Treatment of OZR with metformin or pioglitazone restored fed blood glucose levels with access to food and enhanced baroreflex-mediated bradycardia and activation of the NTS, as suggested by phenylehphrine-induced c-Fos expression. In contrast, treatment of LZR did not alter glucose or affect baroreflex-mediated bradycardia and activation of the NTS. Neither treatment reduced elevated AP and insulin in OZR, suggesting the lowering of blood glucose was effective for restoring baroreflexes in young adult male OZR, even in the face of hypertension. In the second project I examined whether the delayed onset of impaired baroreflexes in hypertensive female OZR could be due to their ability to maintain a normal blood glucose and baroreflex-mediated activation of the NTS. Premenopausal obese women protected from diabetes, suggesting they would be protected from deficits produced by hyperglycemia. I observed that intact baroreflex-mediated bradycardia in young adult female OZR extended to preserved sympathetic baroreflexes and baroreflex-mediated activation of the NTS in 12-15-week-old female OZR. Furthermore, although these OZR were hypertensive and hyperinsulinemic, fed glucose levels and glucose tolerance are comparable to LZR. In contrast, by 6 months of age, baroreflex-mediated bradycardia was blunted in female OZR. However, fed glucose was only mildly elevated and baroreflex-mediated activation of the NTS was comparable in OZR and LZR. These data suggest the ability to maintain glucose homeostasis in young adult female OZR coincides with a preservation of baroreflex-mediated bradycardia and activation of the NTS. However, the later development of impaired baroreflex-mediated bradycardia in female OZR occurs through mechanisms distinct from those observed in male OZR. The third project examined whether preventing hypertension in male OZR protected against the development of impaired baroreflexes and activation of the NTS. Treatment with losartan or hydralazine normalized baseline AP in male OZR without affecting hyperinsulinemia, dyslipidemia, or hyperglycemia. Furthermore, these treatments enhanced baroreflex-mediated bradycardia and activation of the NTS in male OZR. However, even when AP was normalized in male OZR, baroreflex-mediated bradycardia was still smaller in treated OZR compared to like-treated LZR, suggesting other mechanisms also contribute to the blunted baroreflexes. Together these studies suggest that the development of hyperglycemia and hypertension in male OZR contribute to impaired baroreflex-mediated bradycardia and activation of the NTS in male OZR. However, the ability of female OZR to maintain glucose homeostasis preserves baroreflexes despite the presence of hypertension and hyperinsulinemia. Furthermore, when female OZR later develop impaired baroreflex-mediated bradycardia, this deficit occurs by mechanisms that differ from male OZR, highlighting the need to examine both sexes for the development of cardiovascular and metabolic disorders.Item Chronic testosterone deprivation sensitizes the middle-aged rat brain to damaging effects of testosterone(2020-05) Smith, Charity; Schreihofer, Derek A.; Cunningham, Rebecca L.; Singh, Meharvan; Yang, Shaohua; Jones, Harlan P.Levels of the testosterone (T) fall in aging men. Recently, the number of men obtaining testosterone replacement therapy (TRT) has increased dramatically. However, other consequences of aging, such as increased oxidative stress, may result in detrimental effects when combined with TRT, including an increased stroke risk. Whether such a delay would alter the effects of TRT on stroke is not known. We hypothesized that a delay TRT following castration in middle-aged male rats would result in increased oxidative stress and a reduction in the neuroprotective effects of testosterone following stroke. We evaluated the effects of testosterone treatment after short (2 week) and long-term testosterone deprivation (10 weeks) in middle-aged male rats on cerebral ischemia, oxidative stress and cognitive function. Our data suggest testosterone treatment after long-term hypogonadism can exacerbate functional recovery after focal cerebral ischemia, however in the absence of injury improves cognition. Both effects are regulated by oxidative stress.Item Computational Pharmacology Towards RGS12 Inhibitors(2021-05) Dadeboe, Ian R.; Siderovski, David; Sumien, Nathalie; Schreihofer, Derek A.Background/Introduction: "Regulator of G protein Signaling" proteins, also referred to as RGS proteins, inhibit signal transduction by accelerating the hydrolysis of guanosine triphophate (GTP) to guanosine diphosphate (GDP) on the G-alpha subunit of G protein-coupled receptors (GPCRs). Sequence variations of RGS12, which is a member of the RGS protein superfamily, have been observed in some genetic profiles of people with attention-deficit hyperactivity disorder (ADHD), bipolar disorder, and schizophrenia. Hence the purpose of this study was to perform an in silico exploration of the structure/function correlation of small molecule inhibitors of the RGS12 RGS-box domain predicted to inhibit RGS12. Using these small molecule inhibitors in the mouse or rat brain would provide information on whether inhibition of RGS12 can lead to brain changes and/or behavioral changes similar to the human mental health disorders of ADHD, bipolar disorder, or schizophrenia. Method: In silico visualization and exploration of predicted small molecule inhibitors of the RGS box of RGS proteins were evaluated using the Schrodinger software suite (version 2020-3). Ninety-six predicted inhibitors underwent ligand preparation (e.g., tautomer resolution) and Glide docking within structural models of RGS4, RGS12 and RGS14. The resulting ligand and receptor interactions were quantified using Schrodinger Maestro (2020-3). In parallel, all 96 compounds were sent to BellBrook Labs for in vitro testing of GAP inhibitory activity. Results: Three compounds Z##6112, Z##0043, and Z##6197 with shared chemical features, i.e., thioether linkages, and linked sulfur and nitrogen heteroatoms, were observed to inhibit RGS12's GAP activity at least three standard deviations away from the average assay signal. Two unique features of the Z##6197 compound, a carboxylic acid group and a halogenated, ether-coupled phenolic ring, were found to inhibit in silico Glide docking or be docked in varied poses with differing chemical-bond engagements within the RGS-box receptor grids, respectively. Conclusions: Discrepancies between the in silico Glide docking and in vitro biochemical results bring into question the validity of the Glide algorithm to correctly predict the geometry and chemical-bonding character of RGS-box / small molecule inhibitor engagement. Further testing of the three identified compounds in other in vitro assays and in establishing three-dimensional structural models of their RGS-box engagement will assist in resolving these discrepancies and reveal both shared and unique determinants of RGS12 inhibition necessary for future in vivo and clinical applications.Item Connexin 43 Contributes to Estrogen Protection against Oxidative Stress in Cortical Astrocytes(2019-05) Kubelka, Nicholas K.; Singh, Meharvan; Uht, Rosalie M.; Schreihofer, Derek A.; Yang, Shaohua; Planz, John V.Age-related brain disorders are associated with the decline in the ability of brain cells to cope with homeostatic challenge. Although all major brain cell types have the capacity to respond to homeostatic challenges, astrocytes are particularly well-equipped to counteract these challenges. Here, we focused on Connexin 43 (Cx43) as a protein that is not only highly expressed in astrocytes, but whose expression is critical to inter-cellular communication that in turn, can influence cell viability. Most studies to date have focused on the expression (i.e., abundance) of Cx43. However, a critical limitation of these studies is that they did not thoroughly examine functionality of the Cx43 channels. In particular, there is a paucity of data describing the differential contributions of Cx43-containing hemichannels versus Cx43-containing gap junctions to cellular functions. We hypothesized the astrocyte Cx43 hemichannel as a yet unreported target of androgens and estrogens based on three notions. First, our laboratory has determined that astrocytes are a relevant and important target of such gonadal steroid hormones as estrogens (e.g., 17[beta]-estradiol (abbreviated herein as estradiol or E2)) and androgens (such as DHT), through which these hormones promote healthy brain cell function. Second, oxidative stress is associated with an increase in Cx43 opening. Finally, the Cx43 gene promoter contains functional estrogen response element (ERE) half sites, and estradiol, as well as other estrogenic compounds, decrease Cx43 channel opening in peripheral (non-CNS) tissue. Based on these notions, we hypothesized that gonadal androgens and estrogens will inhibit Cx43 hemichannel opening in cortical astrocytes as well. My data revealed that while E2, dihydrotestosterone (DHT), and the estrogenic metabolite of DHT (3[beta]diol) all protect primary cortical astrocytes from the mixed metabolic/oxidative insult, iodoacetic acid (IAA), only DHT decreased astrocyte Cx43 mRNA expression. Consistent with their cytoprotective effects, however, all three steroids decrease astrocyte Cx43 hemichannel opening, and antagonized the increased opening of Cx43 hemichannels induced by IAA. In an effort to pursue the mechanism by which these steroids reduced Cx43 hemichannel opening, we evaluated the phosphorylation of Cx43 at two key residues, Ser 368 and Tyr 265. Phosphorylation at these residues is associated with channel closing, and as such, we predicted that the three hormones would increase the phosphorylation of Cx43 at one or both of these residues. Whereas Tyr265 phosphorylation was unaffected any of the three hormones, DHT significantly reduced the phosphorylation of Cx43 at Ser368. These observations may indicate that while all three steroids contribute to astrocyte protection through a mechanism that involves blocking astrocyte Cx43 hemichannel opening, DHT may induce molecular changes in the astrocytes that are distinct from those induced by estradiol or 3[beta]diol. The knowledge gained through the experiments conducted not only enhance our understanding of how Cx43 hemichannels and Cx43 gap junctions influence astrocyte function and viability but also define Cx43 hemichannels as relevant targets of gonadal steroid hormone induced regulation of cell viability. Such knowledge may facilitate the development of more precise therapeutics (i.e., selectively targeting Cx43 hemichannels without activity at Cx43 gap junctions in the same cells or tissue), the benefit of which would be to better treat age-associated neurodegenerative disorders as well as disorders of peripheral tissueItem Creation of a biotechnology discovery platform for fighting the transmission of vector-borne infectious diseases(2017-08) Wang, Huanyu; Schetz, John A.; Schreihofer, Derek A.; Gonzales, Eric B.; Allen, Michael S.Vector-borne diseases have become a global pandemic threatening 40% of the world's population with infectious diseases like malaria and Lyme disease becoming ever more of a concern. The best treatment of vector-borne diseases is to prevent their transmission through the usage of personal protective measures (PPMs). However, mosquitoes and ticks are becoming resistant to common PPMs, including DEET, and this demands development of next generation deterrents with new mechanisms of action. The octopamine receptor (OctR) is an attractive target for next generation deterrent development because it is invertebrate specific and plays an important role in fine motor control. In this study, Anopheles gambiae OctRs and Ixodes scapularis OctRs were cloned into HEK293 cells followed by characterization of these receptors with agonist/antagonist pharmacological profiles. Further Structure-Activity Relationships (SAR) of octopamine-like compounds and novel series compounds to the receptor were assessed. SAR assessments would be helpful to design new OctRs ligands that are highly selective for the OctRs over mammalian off-targets. By associating in vitro biting assay results with agonist profiles of the OctRs, a new biotechnology platform is being tested. Using these methodologies we plan to address the growing concern of vector-borne diseases by discovering mechanistically new PPMs. As part of this initiative, the biotechnology platform we developed will provide a rapid way to identify potential next generation deterrents by exploring the structure-activity relationship of novel compounds on octopamine receptors from disease-transmitting arthropod species.Item Neural Cytoskeleton Modulation after Transient Ischemic Attack and Region-Specific Brain Metabolism Insights(2022-08) Wang, Linshu; Yang, Shaohua; Sumien, Nathalie; Schreihofer, Derek A.; Liu, RanTransient ischemic attack (TIA) is a symptomatic diagnosis disease characterized as reversible ischemic stroke-like neurological deficit. One-third of the TIA patients have recurrent episodes, and TIA presents as a high vascular risk factor for severe stroke, mild cognitive impairment, and dementia. However, the neuropathophysiology of TIA has been less studied. Here, we established recurrent TIA model in rats with no neurological deficits and no/minimal apoptosis cells detected. Our study demonstrated that recurrent TIA induces neuronal cytoskeleton modification, astrogliosis and microgliosis in the TIAaffected cortical and basal ganglia regions, as well as in the white matter in terms of corpus callosum in the acute and subacute stage. Our data indicate recurrent TIA-induced neuronal cytoskeletal modification and neuroinflammation, may be potentially involved in the vascular contribution to cognitive impairment and dementia. Even though neurological deficits are transient in TIA patients, the brain presents morphologic and metabolic change in response to transient ischemic insult. This can be reflected on the remodeling of cytoskeleton, which plays a critical role in the mitochondria shape and motility maintenance. In addition, the interaction between cytoskeletal components and mitochondria is highly involved in the oxidative phosphorylation and mitochondrial respiration regulation. To investigate the brain metabolic signatures in the normal and pathological conditions, our study optimized a method that enables metabolic function assessment of anatomically defined brain structures by the Seahorse XFe96 analyzer in rodents. Our data demonstrated that the rodent brain has region-specific glucose metabolic profile, the cerebellum displays a more quiescent phenotype than cerebral cortex, basal ganglia, and hippocampus. Additionally, the rodent brain has relatively low mitochondrial oxidative phosphorylation efficiency with high proton leaklinked respiration. Through our proof-of-principle study, we expect to acquire critical insights that will enable future research in pursuit of spatial mapping of the brain glucose metabolism in physiological and pathological conditions (e.g., TIA condition), and further explore the mechanisms and significance of mitochondrial uncoupling of the brain.Item Neurobehavioral and biochemical consequences of chronic, low-dose methamphetamine exposure in male and female mice(2022-08) Davis, Delaney L.; Sumien, Nathalie; Huang, Ren-Qi; Gatch, Michael B.; Phillips, Nicole R.; Schreihofer, Derek A.; Ma, RongAlthough prescription psychostimulants are effective in reducing attention deficit hyperactivity disorder (ADHD) symptomology, misuse of these drugs can pose serious risks such as potential abuse, dependence, and/or neurotoxicity. Of particular concern is that young adults have the highest prevalence of prescription stimulant misuse, with almost 10% of college students admitting to using amphetamine (e.g. Adderall) or methylphenidate (e.g. Ritalin) products. Despite these drugs being widely used for therapeutic and recreational use, the long-term effects of prescription stimulants have not been systematically evaluated in controlled clinical trials. Therefore, it is critical to conduct this research because young adults may be a vulnerable, at-risk population to the potential adverse consequences of long-term amphetamine use. This dissertation research evaluates the biochemical and behavioral consequences of chronic exposure of the prototypical psychostimulant, methamphetamine (METH), in a rodent model. It is hypothesized that repeated doses of METH, within the therapeutic dosing range used in a clinical setting, will induce neurotoxicity through the interplay of biological mechanisms of oxidative stress, glutamate excitotoxicity, neuroinflammation and epigenetic alterations and increase susceptibility to addiction that will be exacerbated by aging processes. Overall, the body of results showed short-term alterations in brain biochemistry and behavioral function, that do not necessarily persist past 5 months after METH treatment. In conclusion, this dissertation highlights the importance of long-term studies in addressing prescription stimulant misuse in an adult population to better understand the safety of these widely used and prescribed psychostimulants.Item Presence of Androgen Receptor Variant in Neuronal Lipid Rafts(Society for Neuroscience, 2017-08-29) Garza-Contreras, Jo; Duong, Phong; Snyder, Brina D.; Schreihofer, Derek A.; Cunningham, Rebecca L.Fast, nongenomic androgen actions have been described in various cell types, including neurons. However, the receptor mediating this cell membrane-initiated rapid signaling remains unknown. This study found a putative androgen receptor splice variant in a dopaminergic N27 cell line and in several brain regions (substantia nigra pars compacta, entorhinal cortex, and hippocampus) from gonadally intact and gonadectomized (young and middle-aged) male rats. This putative splice variant protein has a molecular weight of 45 kDa and lacks an N-terminal domain, indicating it is homologous to the human AR45 splice variant. Interestingly, AR45 was highly expressed in all brain regions examined. In dopaminergic neurons, AR45 is localized to plasma membrane lipid rafts, a microdomain involved in cellular signaling. Further, AR45 protein interacts with membrane-associated G proteins Galphaq and Galphao. Neither age nor hormone levels altered AR45 expression in dopaminergic neurons. These results provide the first evidence of AR45 protein expression in the brain, specifically plasma membrane lipid rafts. AR45 presence in lipid rafts indicates that it may function as a membrane androgen receptor to mediate fast, nongenomic androgen actions.Item Sigma-1 Receptors and and their Effects on Mice with rmTBI(2023-05) Kuo, Aaron, J.; Schreihofer, Derek A.; Sumien, Nathalie; Ortega, SterlingRepetitive mild traumatic brain (rmTBI) injury is common in contact sports, yet there are no specific treatments to mitigate the potential long-term detrimental effects of such injuries. Retrospective studies have observed athletes in contact sports such as American football, boxing, rugby, soccer, and martial arts have higher rates of Chronic Traumatic Encephalopathy (CTE), mood and behavior disturbance, motor and dementia-related diseases, and other neuropathological diseases. We propose that activation of S1R can mitigate detrimental behavioral and biochemical consequences of repetitive mild head injury in a mouse model. Sigma-1 receptors (S1R) are intracellular chaperone proteins that are involved in numerous cell processes. Among their diverse actions, activation of the S1R has been observed to reduce neurodegeneration in experimental models of stroke, Alzheimer's disease, Parkinson's disease and others. This wide range of effectiveness suggests that targeting S1R could also be beneficial for other neurological injuries including traumatic brain injury. In this short-term study of rmTBI in male mice, we observed only minor behavioral deficits 5 weeks after the last of 7 closed head injuries that may be mitigated by treatment with the prototypical S1R agonist PRE-084. However, PRE-084 itself had basal effects on cognition, making firm conclusions premature. Continued observation of these mice will help to determine whether there are additional long-term effects of the injury modelItem The Long-Term Neurodegenerative Effects of Repetitive Mild Traumatic Brain Injury and Treatment With Sigma-1 Receptor Agonist PRE-084(2021-05) Abad-Jacobi, Christopher; Schreihofer, Derek A.; Sumien, Nathalie; Schreihofer, Ann M.An estimated 1.6 – 3.8 million sports-related traumatic brain injuries (TBI) occur every year in the U.S. Recent retrospective studies suggest that repetitive mild TBI (rmTBI) is associated with the earlier onset of neurodegenerative diseases. Mild TBI can be hard to detect, and there are currently no widely accepted biomarkers that could aid in the diagnosis of mTBI. Further, there is currently no standard pharmacological treatment for TBI. Our previous work demonstrated neurological deficits 1 week following 20-25 rmTBI in young male mice. We hypothesized that some of these deficits would persist up to 5-15 weeks following injury and that treatment with an agonist of the Sigma-1 receptor (PRE-084) could reduce these deficits, as has been demonstrated in other neurodegenerative models. Eight-week-old male C57BK6 mice were divided into sham injury + Vehicle, rmTBI + Vehicle, and rmTBI+PRE084 groups (n=10/gp). Mice were lightly anesthetized with isoflurane and administered either PRE084 (1mg/kg sc or ip) or vehicle immediately prior to experiencing closed head-injury with rotational acceleration via a 65g weight drop 5 days a week for 5 weeks. Five (group 1) and fifteen weeks (group 2) after the final injury mice were assessed for neurological deficits. Injured mice in test 1 demonstrated significant (P<0.05) deficits in motor and vestibular-motor. Wake times were significantly increased (P<0.05) for Hit mice in both tests one and two. However, cognitive performance in T-maze active avoidance, anxiety-related behavior in the elevated plus maze, and Water Maze on group 1 were not affected. Water maze data on group 2 yielded significant results (P<0.05) indicating both groups of Hit mice performed worse on percent time in annulus 40 centimeters, and on path length in trials one and three. Treatment with PRE-084 did not ameliorate any of these deficits. On group 2, Hit + PRE-084 mice performed significantly worse than their counterparts on the rotarod test. The data suggest that there are some chronic deficits for at least 5 weeks after rmTBI, and that sigma-1 activation does not reverse negative effects of rmTBI. Ongoing studies are examining the persistence of these deficits in mice 15 weeks after the final injury, which are relevant to rmTBI related deficits in military personnel that persist up to a year. Water maze data is beginning to persistent deficits due to rmTBI in the long-term.Item The role of aging and length of hypogonadism on the neuroprotective effects of dietary genistein following focal cerebral ischemia(2021-05) Oppong-Gyebi, Anthony; Schreihofer, Derek A.; Singh, Meharvan; Sumien, Nathalie; Yang, Shaohua; Shi, XiangrongThe risk of ischemic stroke increases with increasing age. Women beyond menopause have an exponential increase in stroke risk with worse post-stroke prognosis and mortalities compared to men of similar ages. One of the key reasons for this discrepancy is the sudden and drastic drop in the levels of the circulating principal female sex hormones estrogen and progesterone after menopause. Both sex hormones have been shown in several studies to provide neuroprotection against ischemic insults in stroke models and other disease models including Alzheimer's Disease and Parkinson's Disease. However, from clinical studies, neither estrogen nor progesterone alone or in combination has met clinical needs for the prevention of chronic cardiovascular diseases. These clinical failures were mainly evidenced by the absence of benefits in the human population or an increased predisposition to adverse side effects. Reports from studies including the Women's Health Initiative and Nurse's Health Study showed that the timing of initiation and age of recipients significantly influence the outcome of estrogen therapy. In this dissertation project, we investigated the plant-based estrogenic compound genistein as a possible alternative to estrogen therapy. It was hypothesized that the neuroprotective benefits of genistein will be less sensitive to the length of hypogonadism and age under experimental ischemic conditions. We used a rodent model of transient middle cerebral artery occlusion under varied lengths of estrogen deprivation and age to test the neuroprotection of dietary genistein. Findings from this dissertation show that early initiation of dietary genistein after hypogonadism improves aspects of cognition, an effect that is diminished following the long absence of circulating estrogen. Furthermore, pre-treatment with dietary genistein improves age-associated locomotor deficits after long-term hypogonadism after stroke. This dissertation, therefore, provides new considerations on the time-dependent sensitivity of the brain to genistein's effect as a potential therapeutic option to improve aspects of cognition and reduce the severity of stroke in the target population with low circulating estrogens.