Biology subjects

Mactutus, C. F.

Publications and source records attributed to Mactutus, C. F..

6 recordsLinked to original sources

bioRxiv2021

SYNAPTIC DYSFUNCTION UNDERLIES ALTERATIONS IN THE INITIATION OF GOAL-DIRECTED BEHAVIORS: IMPLICATIONS FOR HIV-1 ASSOCIATED APATHY

Individuals living with human immunodeficiency virus type 1 (HIV-1) exhibit an increased prevalence of neuropsychiatric comorbities (e.g., apathy) relative to their seronegative counterparts. Given the profound functional consequences associated with apathy, conceptualizing the multidimensional neuropsychiatric syndrome, and associated neural mechanisms, following chronic HIV-1 viral protein exposure remains a critical need. HIV-1 associated apathy was examined by quantifying goal-directed behaviors, indexed using voluntary wheel running, during the diurnal and nocturnal cycle. Apathetic behaviors in the HIV-1 Tg rat were characterized by a profound decrease in the number of running bouts during both the diurnal and nocturnal cycle, supporting a prominent deficit in the self-initiation of spontaneous behaviors. Additionally, HIV-1 Tg animals exhibited a decreased reinforcing efficacy of voluntary wheel running during the nocturnal cycle. Following the completion of voluntary wheel running, synaptic dysfunction in medium spiny neurons (MSNs) of the nucleus accumbens (NAc) was examined as a potential neural mechanism underlying HIV-1 associated apathy. HIV-1 Tg animals displayed prominent synaptic dysfunction in MSNs of the NAc, characterized by decreased synaptic connectivity and a population shift towards an immature dendritic spine phenotype relative to control animals. Synaptic dysfunction accounted for 42.0% to 68.5% of the variance in the number of running bouts affording a key neural mechanism underlying the self-initiation of spontaneous behaviors. The establishment of a fundamental neural mechanism underlying apathy affords a key target for the development of novel therapeutics and cure strategies for affective alterations associated with HIV-1.

neuroscience↗

bioRxiv2021

Neurodevelopmental processes in the prefrontal cortex derailed by chronic HIV-1 viral protein exposure

Due to the widespread access to, and implementation of, combination antiretroviral therapy, individuals perinatally infected with human immunodeficiency virus type 1 (HIV-1) are living into adolescence and adulthood. Perinatally infected adolescents living with HIV-1 (pALHIV) are plagued by progressive, chronic neurocognitive impairments; the pathophysiological mechanisms underlying these deficits, however, remains understudied. A longitudinal experimental design from postnatal day (PD) 30 to PD 180 was utilized to establish the development of pyramidal neurons, and associated dendritic spines, from layers II-III of the medial prefrontal cortex (mPFC). Three putative neuroinflammatory markers (i.e., IL-1{beta}, IL-6, and TNF-) were evaluated early in development (i.e., PD 30) as a potential mechanism underlying synaptic dysfunction in the mPFC. Constitutive expression of HIV-1 viral proteins induced prominent neurodevelopmental alterations, independent of biological sex, in pyramidal neurons from layers II-III of the mPFC. Specifically, HIV-1 transgenic rats exhibited prominent deficits in dendritic and synaptic pruning, a developmental decrease in synaptic connectivity, and an age-related decline in synaptic efficacy. Examination of dendritic spine morphology revealed an age-related population shift towards a more immature dendritic spine phenotype in HIV-1 transgenic animals. There was no compelling evidence for neuroinflammation in the mPFC during early development. Understanding the neural mechanisms underlying chronic neurocognitive impairments in pALHIV may afford a key target for innovative therapeutics and cure strategies; an urgent need given the growing population of pALHIV.

neuroscience↗

bioRxiv2021

Chronic SSRI treatment reverses HIV-1 protein-mediated synaptodendritic damage

HIV-1 infection affects approximately 37 million individuals and approximately 50% of seropositive individuals will develop symptoms of clinical depression and apathy. Dysfunctions of both serotonergic and dopaminergic neurotransmission have been implicated in the pathogenesis of motivational alterations. The present study evaluated the efficacy of a SSRI (escitalopram) in the HIV-1 transgenic (Tg) rat. Behavioral, neurochemical, and neuroanatomical outcomes with respect to HIV-1 and sex were evaluated to determine the efficacy of chronic escitalopram treatment. Escitalopram treatment restored function in each of the behavioral tasks that were sensitive to HIV-1 induced impairments. Further, escitalopram treatment restored HIV-1-mediated synaptodendritic damage in the nucleus accumbens; treatment with escitalopram significantly increased dendritic proliferation in HIV-1 Tg rats. However, restoration did not consistently occur with the neurochemical analysis in the HIV-1 rat. Taken together, these results suggest a role for SSRI therapies in repairing long-term HIV-1 protein-mediated neuronal damage and restoring function.

neuroscience↗

bioRxiv2021

HIV-1-induced apathy: Mitigation by the gut metabolite, S-equol

The persistence of motivational alterations, including apathy, in older HIV-1 seropositive individuals, despite treatment with combination antiretroviral therapy, necessitates the development of innovative adjunctive therapeutics. S-Equol (SE), a selective estrogen receptor {beta} agonist, has been implicated as a neuroprotective and/or neurorestorative therapeutic for HIV-1 associated neurocognitive disorders (HAND); its therapeutic utility for apathy, however, has yet to be systematically evaluated. Thus, beginning at approximately seven to nine months of age, HIV-1 transgenic (Tg) and control animals were treated with either a daily oral dose of SE (0.2 mg) or vehicle and assessed in a series of tasks to evaluate goal-directed behavior. First, at the genotypic level, apathetic behavior in older HIV-1 Tg rats treated with vehicle was characterized by a diminished reinforcing efficacy of, and sensitivity to, sucrose and enhanced drug seeking for cocaine relative to control animals treated with vehicle. Second, treatment with SE ameliorated alterations in goal-directed behaviors and reduced drug seeking behavior in HIV-1 Tg rats. Following a history of cocaine self-administration, HIV-1 Tg animals treated with vehicle exhibited prominent decreases in dendritic branching and a shift towards longer dendritic spines with decreased head diameter; synaptic dysfunction that was partially restored by SE treatment. Taken together, SE restored motivated behavior in the HIV-1 Tg rat, expanding the potential clinical utility of SE to include both neurocognitive and affective alterations.

neuroscience↗

bioRxiv2020

Valid statistical approaches for clustered data: A Monte Carlo simulation study

The translation of preclinical studies to human applications is associated with a high failure rate, which may be exacerbated by limited training in experimental design and statistical analysis. Nested experimental designs, which occur when data have a multilevel structure (e.g., in vitro: cells within a culture dish; in vivo: rats within a litter), often violate the independent observation assumption underlying many traditional statistical techniques. Although previous studies have empirically evaluated the analytic challenges associated with multilevel data, existing work has not focused on key parameters and design components typically observed in preclinical research. To address this knowledge gap, a Monte Carlo simulation study was conducted to systematically assess the effects of inappropriately modeling multilevel data via a fixed effects ANOVA in studies with sparse observations, no between group comparison within a single cluster, and interactive effects. Simulation results revealed a dramatic increase in the probability of type 1 error and relative bias of the standard error as the number of level-1 (e.g., cells; rats) units per cell increased in the fixed effects ANOVA; these effects were largely attenuated when the nesting was appropriately accounted for via a random effects ANOVA. Thus, failure to account for a nested experimental design may lead to reproducibility challenges and inaccurate conclusions. Appropriately accounting for multilevel data, however, may enhance statistical reliability, thereby leading to improvements in translatability. Valid analytic strategies are provided for a variety of design scenarios.

scientific communication and education↗

bioRxiv2020

HIV-1 and microglia: EcoHIV and HIV-1 transgenic rats

The persistence of HIV-1 viral reservoirs in the brain, despite treatment with combination antiretroviral therapy (cART), remains a critical roadblock for the development of a novel cure strategy for HIV-1. To enhance our understanding of viral reservoirs, two complementary studies were conducted to 1) evaluate the HIV-1 mRNA neuroanatomical distribution pattern and major cell type expressing HIV-1 mRNA in the HIV-1 transgenic (Tg) rat (i.e., under conditions of latent infection), and 2) to validate our findings by developing and critically testing a novel biological system to model active HIV-1 infection in the rat. First, a restricted, region-specific HIV-1 mRNA distribution pattern was observed in the HIV-1 Tg rat. Microglia were the predominant cell type expressing HIV-1 mRNA in the HIV-1 Tg rat. Second, we developed and critically tested a novel biological system to model key aspects of HIV-1 by infusing F344/N control rats with chimeric HIV (EcoHIV). In vitro, primary cultured microglia were treated with EcoHIV revealing prominent expression within 24 hours of infection. In vivo, EcoHIV expression was observed seven days after stereotaxic injections. Following EcoHIV infection, microglia were the major cell type expressing HIV-1 mRNA, results which are consistent with observations in the HIV-1 Tg rat. Within eight weeks of infection, EcoHIV rats exhibited neurocognitive impairments, synaptic dysfunction, which may result from activation of the NogoA-NgR3/PirB-RhoA signaling pathway, and neuroinflammation. Collectively, these studies enhance our understanding of HIV-1 viral reservoirs in the brain and offer a novel biological system to model HIV-associated neurocognitive disorders and associated comorbidities (i.e., drug abuse) in rats.

neuroscience↗