Immune activation, viral gene product expression and neurotoxicity in the HIV-1 transgenic rat

Increased Sensitivity to Cocaine Self-Administration in HIV-1 Transgenic Rats is Associated with Changes in Striatal Dopamine Transporter Binding

Cocaine abuse in HIV patients accelerates the progression and severity of neuropathology, motor impairment and cognitive dysfunction compared to non-drug using HIV patients. Cocaine and HIV interact with the dopamine transporter (DAT); however, the effect of their interaction on DAT binding remains understudied. The present study compared the dose-response functions for intravenous self-administration of cocaine and heroin between male HIV-1 transgenic (HIV-1 Tg) and Fischer 344 rats. The cocaine and heroin dose-response functions exhibit an inverted U-shape for both HIV-1 Tg and F344 rats. For cocaine, the number of infusions for each dose on the ascending limb was greater for HIV-1 Tg versus F344 rats. No significant changes in the heroin dose-response function were observed in HIV-1 Tg animals. Following the conclusion of self-administration experiments, DAT binding was assessed in striatal membranes. Saturation binding of the cocaine analog [(125)I] 3β-(4-iodophenyl)tropan-2β-carboxylic acid methyl ester ([(125)I]RTI-55) in rat striatal membranes resulted in binding curves that were best fit to a two-site binding model, allowing for calculation of dissociation constant (Kd) and binding density (Bmax) values that correspond to high- and low-affinity DAT binding sites. Control HIV-1 Tg rats exhibited a significantly greater affinity (i.e., decrease in Kd value) in the low-affinity DAT binding site compared to control F344 rats. Furthermore, cocaine self-administration in HIV-1 Tg rats increased low-affinity Kd (i.e., decreased affinity) compared to levels observed in control F344 rats. Cocaine also increased low-affinity Bmax in HIV-1 Tg rats as compared to controls, indicating an increase in the number of low-affinity DAT binding sites. F344 rats did not exhibit any change in high- or low-affinity Kd or Bmax values following cocaine or heroin self-administration. The increase in DAT affinity in cocaine HIV-1 Tg rats is consistent with the leftward shift of the ascending limb of the cocaine dose-response curve observed in HIV-1 Tg vs. F344 rats, and has major implications for the function of cocaine binding to DAT in HIV patients. The absence of HIV-related changes in heroin intake are likely due to less dopaminergic involvement in the mediation of heroin reward, further emphasizing the preferential influence of HIV on dopamine-related behaviors.

Meloxicam blocks neuroinflammation, but not depressive-like behaviors, in HIV-1 transgenic female rats

Adolescents living with human immunodeficiency virus (HIV) comprise approximately 12% of the HIV-positive population worldwide. HIV-positive adolescents experience a higher rate of clinical depression, a greater risk of sexual and drug abuse behaviors, and a decreased adherence to highly active antiretroviral therapies (HAART). Using adolescent HIV-1 transgenic rats (HIV-1 tg) that display related immune response alterations and pathologies, this study tested the hypothesis that developmental expression of HIV-1-related proteins induces a depressive-like phenotype that parallels a decrease in hippocampal cell proliferation and an increase in pro-inflammatory cytokine expression in the hippocampus. Consistent with this hypothesis, adolescent HIV-1 tg rats demonstrated a depressive-like behavioral phenotype, had decreased levels of cell proliferation, and exhibited elevated expression of monocyte chemotactic protein-1 (Mcp-1) in the hippocampus relative to controls. Subsequently, we tested the ability of meloxicam, a selective COX-2 inhibitor, to attenuate behavioral deficits via inflammatory mechanisms. Daily meloxicam treatments did not alter the behavioral profile despite effectively reducing hippocampal inflammatory gene expression. Together, these data support a biological basis for the co-morbid manifestation of depression in HIV-positive patients as early as in adolescence and suggest that modifications in behavior manifest independent of inflammatory activity in the hippocampus.

HIV-1 transgenic female rat: synaptodendritic alterations of medium spiny neurons in the nucleus accumbens

HIV-1 associated neurocognitive deficits are increasing in prevalence, although the neuronal basis for these deficits is unclear. HIV-1 Tg rats constitutively express 7 of 9 HIV-associated proteins, and may be useful for studying the neuropathological substrates of HIV-1 associated neurocognitive disorders (HAND). In this study, adult female HIV-1 Tg rats and F344 control rats had similar growth rates, estrous cyclicity and startle reflex inhibition to a visual prepulse stimulus. Medium spiny neurons (MSNs) in the nucleus accumbens (NAcc) were ballistically-labeled utilizing the indocarbocyanine dye DiI. The branching complexity of MSNs in the NAcc was significantly decreased in HIV-1 Tg rats, relative to controls; moreover, the shorter length and decreased volume of dendritic spines, but unchanged head diameter, in HIV-1 Tg rats suggested a reduction of longer spines and an increase in shorter, less projected spines, indicating a population shift to a more immature spine phenotype. Collectively, these results from HIV-1 Tg female rats indicated significant synaptodendritic alterations of MSNs in the NAcc occur as a consequence of chronic, low-level, exposure to HIV-1 associated proteins.

Gene expression changes consistent with neuroAIDS and impaired working memory in HIV-1 transgenic rats

BACKGROUND

A thorough investigation of the neurobiology of HIV-induced neuronal dysfunction and its evolving phenotype in the setting of viral suppression has been limited by the lack of validated small animal models to probe the effects of concomitant low level expression of multiple HIV-1 products in disease-relevant cells in the CNS.

RESULTS

We report the results of gene expression profiling of the hippocampus of HIV-1 Tg rats, a rodent model of HIV infection in which multiple HIV-1 proteins are expressed under the control of the viral LTR promoter in disease-relevant cells including microglia and astrocytes. The Gene Set Enrichment Analysis (GSEA) algorithm was used for pathway analysis. Gene expression changes observed are consistent with astrogliosis and microgliosis and include evidence of inflammation and cell proliferation. Among the genes with increased expression in HIV-1 Tg rats was the interferon stimulated gene 15 (ISG-15), which was previously shown to be increased in the cerebrospinal fluid (CSF) of HIV patients and to correlate with neuropsychological impairment and neuropathology, and prostaglandin D2 (PGD2) synthase (Ptgds), which has been associated with immune activation and the induction of astrogliosis and microgliosis. GSEA-based pathway analysis highlighted a broad dysregulation of genes involved in neuronal trophism and neurodegenerative disorders. Among the latter are genesets associated with Huntington's disease, Parkinson's disease, mitochondrial, peroxisome function, and synaptic trophism and plasticity, such as IGF, ErbB and netrin signaling and the PI3K signal transduction pathway, a mediator of neural plasticity and of a vast array of trophic signals. Additionally, gene expression analyses also show altered lipid metabolism and peroxisomes dysfunction. Supporting the functional significance of these gene expression alterations, HIV-1 Tg rats showed working memory impairments in spontaneous alternation behavior in the T-Maze, a paradigm sensitive to prefrontal cortex and hippocampal function.

CONCLUSIONS

Altogether, differentially regulated genes and pathway analysis identify specific pathways that can be targeted therapeutically to increase trophic support, e.g. IGF, ErbB and netrin signaling, and reduce neuroinflammation, e.g. PGD2 synthesis, which may be beneficial in the treatment of chronic forms of HIV-associated neurocognitive disorders in the setting of viral suppression.

Progesterone protects normative anxiety-like responding among ovariectomized female mice that conditionally express the HIV-1 regulatory protein, Tat, in the CNS

Increased anxiety is co-morbid with human immunodeficiency virus (HIV) infection. Actions of the neurotoxic HIV-1 regulatory protein, Tat, may contribute to affective dysfunction. We hypothesized that Tat expression would increase anxiety-like behavior of female GT-tg bigenic mice that express HIV-1 Tat protein in the brain in a doxycycline-dependent manner. Furthermore, given reports that HIV-induced anxiety may occur at lower rates among women, and that the neurotoxic effects of Tat are ameliorated by sex steroids in vitro, we hypothesized that 17β-estradiol and/or progesterone would ameliorate Tat-induced anxiety-like effects. Among naturally-cycling proestrous and diestrous mice, Tat-induction via 7days of doxycycline treatment significantly increased anxiety-like responding in an open field, elevated plus maze and a marble-burying task, compared to treatment with saline. Proestrous mice demonstrated less anxiety-like behavior than diestrous mice in the open field and elevated plus maze, but these effects did not significantly interact with Tat-induction. Among ovariectomized mice, doxycycline-induced Tat protein significantly increased anxiety-like behavior in an elevated plus maze and a marble burying task compared to saline-treated mice, but not an open field (where anxiety-like responding was already maximal). Co-administration of progesterone (4mg/kg), but not 17β-estradiol (0.09mg/kg), with doxycycline significantly ameliorated anxiety-like responding in the elevated plus maze and marble burying tasks. When administered together, 17β-estradiol partially antagonized the protective effects of progesterone on Tat-induced anxiety-like behavior. These findings support evidence of steroid-protection over HIV-1 proteins, and extend them by demonstrating the protective capacity of progesterone on Tat-induced anxiety-like behavior of ovariectomized female mice.

Modeling deficits in attention, inhibition, and flexibility in HAND

Nearly half of all HIV-1-positive individuals on combination antiretroviral therapy (cART) are afflicted with HIV-1-associated neurocognitive disorders (HAND). The most prevalent cognitive deficits observed in the cART era are those of attention and executive function. Presently, we sought to model deficits in attention and core components of executive function (inhibition, flexibility, and set-shifting) observed in HAND using the HIV-1 transgenic (Tg) rat, which expresses 7 of the 9 HIV-1 genes. Ovariectomized female Fischer HIV-1 Tg and non-transgenic control rats (ns = 39-43) were tested in a series of operant tasks: signal detection, discrimination learning, reversal learning, and extradimensional set-shifting. The HIV-1 Tg animals attained the criterion of three sessions at 70% accuracy at a significantly slower rate than the control animals on all tasks with the exception of the extradimensional set-shifting task. Of the animals that met the criteria, there was no significant difference in percent accuracy in any task. However, the HIV-1 Tg rats showed a lower overall response rate in signal detection and discrimination learning. A discriminant function analysis classified the animals by genotype with 90.4% accuracy based on select measures of their performance. The functional consequences of chronic low-level expression of the HIV-1 proteins on attention, as well as inhibition and flexibility as core components of executive function, are apparent under conditions which resemble the brain proinflammatory immune responses and suppression of infection in HIV-1+ individuals under cART. Deficits in attention and core components of executive function may reflect an underlying impairment in temporal processing in HAND.

Major and minor group rhinoviruses elicit differential signaling and cytokine responses as a function of receptor-mediated signal transduction

Major- and minor-group human rhinoviruses (HRV) enter their host by binding to the cell surface molecules ICAM-1 and LDL-R, respectively, which are present on both macrophages and epithelial cells. Although epithelial cells are the primary site of productive HRV infection, previous studies have implicated macrophages in establishing the cytokine dysregulation that occurs during rhinovirus-induced asthma exacerbations. Analysis of the transcriptome of primary human macrophages exposed to major- and minor-group HRV demonstrated differential gene expression. Alterations in gene expression were traced to differential mitochondrial activity and signaling pathway activation between two rhinovirus serotypes, HRV16 (major-group) and HRV1A (minor-group), upon initial HRV binding. Variances in phosphorylation of kinases (p38, JNK, ERK5) and transcription factors (ATF-2, CREB, CEBP-alpha) were observed between the major- and minor-group HRV treatments. Differential activation of signaling pathways led to changes in the production of the asthma-relevant cytokines CCL20, CCL2, and IL-10. This is the first report of genetically similar viruses eliciting dissimilar cytokine release, transcription factor phosphorylation, and MAPK activation from macrophages, suggesting that receptor use is a mechanism for establishing the inflammatory microenvironment in the human airway upon exposure to rhinovirus.

NeuroHIV and use of addictive substances

In the past three decades, substance abuse has been identified as a key comorbidity of human immunodeficiency virus-1 (HIV-1) infection. Many studies have found that the use and abuse of addictive substances hastens the progression of HIV-1 infection and HIV-associated neurocognitive disorders. Advances in highly active antiretroviral therapy (HAART) in the mid-1990s have been successful in limiting the HIV-1 viral load and maintaining a relatively healthy immune response, allowing the life expectancy of patients infected with HIV to approach that of the general population. However, even with HAART, HIV-1 viral proteins are still expressed and eradication of the virus, particularly in the brain, the key reservoir organ, does not occur. In the post-HAART era, the clinical challenge in the treatment of HIV infection is inflammation of the central nervous system (CNS) and its subsequent neurological disorders. To date, various explicit and implicit connections have been identified between the neuronal circuitry involved in immune responses and brain regions affected by and implicated in substance abuse. This chapter discusses past and current medical uses of prototypical substances of abuse, including morphine, alcohol, cocaine, methamphetamine, marijuana, and nicotine, and the evidence that systemic infections, particularly HIV-1 infection, cause neurological dysfunction as a result of inflammation in the CNS, which can increase the risk of substance abuse.

Intersection of Smoking, Human immunodeficiency virus/acquired immunodeficiency syndrome and Cancer: Proceedings of the 8(th) Annual Texas Conference on Health Disparities

The Texas Center for Health Disparities, a National Institute on Minority Health and Health Disparities Center of Excellence, presents an annual conference to discuss prevention, awareness education and ongoing research about health disparities both in Texas and among the national population. The 2013 Texas Conference on Health Disparities brought together experts, in research, patient care and community outreach, on the "Intersection of Smoking, Human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) and Cancer". Smoking, HIV/AIDS and cancer are three individual areas of public health concern, each with its own set of disparities and risk factors based on race, ethnicity, gender, geography and socio-economic status. Disparities among patient populations, in which these issues are found to be comorbid, provide valuable information on goals for patient care. The conference consisted of three sessions addressing "Comorbidities and Treatment", "Public Health Perspectives", and "Best Practices". This article summarizes the basic science, clinical correlates and public health data presented by the speakers.

Time and time again: temporal processing demands implicate perceptual and gating deficits in the HIV-1 transgenic rat

HIV-1-associated neurocognitive disorders (HAND) afflict up to 50 % of HIV-1+ individuals, despite the effectiveness of combination antiretroviral therapy (CART) in reducing the prevalence of more severe neurocognitive impairment. Alterations in brainstem auditory evoked potentials (BAEP), a measure of temporal processing, are one of the earliest neurological abnormalities of HIV-1-positive individuals. Prepulse inhibition (PPI) of the auditory startle response (ASR), a measure of sensorimotor gating, was studied in HIV-1 transgenic (Tg) rats, which express 7 of the 9 HIV-1 genes. Ovariectomized female Fischer HIV-1 Tg and control rats (ns = 41-42) were tested for PPI at three test periods, with at least 2 months separating each test period, using auditory and visual prepulses, an auditory startle stimulus, and interstimulus intervals (ISI) ranging from 0 to 4000 msec. Auditory and visual prepulse trial blocks were presented in counterbalanced order. For both auditory and visual prepulses, HIV-1 Tg animals exhibited a flatter ISI function, which did not sharpen with age, as it did in controls. Over time, auditory prepulses precipitated a temporal shift in peak inhibition in HIV-1 Tg animals relative to controls, whereas with visual prepulses, both groups displayed peak inhibition at the 40 msec ISI. A lack of perceptual sharpening with age and a relative insensitivity to the temporal dimension of sensorimotor gating are evident in the HIV-1 Tg rat prior to clinical signs of wasting. Deficits in sensorimotor gating may not only provide an early subtle diagnostic marker of HAND, but may also afford a key target for development of potential therapeutics.

Transcriptome sequencing of gene expression in the brain of the HIV-1 transgenic rat

The noninfectious HIV-1 transgenic (HIV-1Tg) rat was developed as a model of AIDs-related pathology and immune dysfunction by manipulation of a noninfectious HIV-1^gag-pol virus with a deleted 3-kb SphI-MscI fragment containing the 3′ -region of gag and the 5′ region of pol into F344 rats. Our previous studies revealed significant behavioral differences between HIV-1Tg and F344 control rats in their performance in the Morris water maze and responses to psychostimulants. However, the molecular mechanisms underlying these behavioral differences remain largely unknown. The primary goal of this study was to identify differentially expressed genes and enriched pathways affected by the gag-pol-deleted HIV-1 genome. Using RNA deep sequencing, we sequenced RNA transcripts in the prefrontal cortex, hippocampus, and striatum of HIV-1Tg and F344 rats. A total of 72 RNA samples were analyzed (i.e., 12 animals per group × 2 strains × 3 brain regions). Following deep-sequencing analysis of 50-bp paired-end reads of RNA-Seq, we used Bowtie/Tophat/Cufflinks suites to align these reads into transcripts based on the Rn4 rat reference genome and to measure the relative abundance of each transcript. Statistical analyses on each brain region in the two strains revealed that immune response- and neurotransmission-related pathways were altered in the HIV-1Tg rats, with brain region differences. Other neuronal survival-related pathways, including those encoding myelin proteins, growth factors, and translation regulators, were altered in the HIV-1Tg rats in a brain region-dependent manner. This study is the first deep-sequencing analysis of RNA transcripts associated the HIV-1Tg rat. Considering the functions of the pathways and brain regions examined in this study, our findings of abnormal gene expression patterns in HIV-1Tg rats suggest mechanisms underlying the deficits in learning and memory and vulnerability to drug addiction and other psychiatric disorders observed in HIV-positive patients.

Inflammation and oxidative stress induced by cigarette smoke in Lewis rat brains

Exposure to cigarette smoke has been associated with an increased risk of neurological diseases such as stroke, Alzheimer's disease and multiple sclerosis. In these studies, serum and brain sections from Lewis rats or those exposed to cigarette smoke and control rats were examined for evidence of increased inflammation and oxidative stress. Immunocytochemical staining of brain sections from CS-exposed rats showed increased expression of class II MHC and, in ELISA, levels of IFN-gamma and TNF-α were higher than for non-exposed rats. In polymerase chain reaction assays there was increased interferon-gamma, TNF-α, IL-1α, IL-1β, IL-23, IL-6, IL-23, IL-17, IL-10, TGF-β, T-bet and FoxP3 gene expression with CS exposure. There was also markedly elevated MIP-1α/CCL3, less prominent MCP-1/CCL2 and no elevation of SDF-1α gene expression. Analysis of samples from CS-exposed and control rats for anti-oxidant expression showed no significant difference in serum levels of glutathione and, in brain, similar levels of superoxide dismutase and decreased thioredoxin gene expression. In contrast, there was increased brain gene expression for the pro-oxidants iNOS and the NADPH components NOX4, dual oxidase 1 and p22(phox). Nrf2 expression, which is typically triggered as a secondary response to oxidative stress, was also increased in brains from CS-exposed rats with nuclear translocation of this protein from cytoplasm demonstrated in astrocytes in association with increased expression of the aryl hydrocarbon receptor gene, an Nrf2 target. These studies, therefore, demonstrate that CS exposure in these animals can trigger multiple immune and oxidative responses that may have important roles in the pathogenesis of CNS inflammatory neurological diseases.