Establishment of an ex vivo model of monocytes-derived macrophages differentiated from peripheral blood mononuclear cells (PBMCs) from HIV-1 transgenic rats

Involvement of TRPM7 in Alcohol-Induced Damage of the Blood-Brain Barrier in the Presence of HIV Viral Proteins

Ethanol (EtOH) exerts its effects through various protein targets, including transient receptor potential melastatin 7 (TRPM7) channels, which play an essential role in cellular homeostasis. We demonstrated that TRPM7 is expressed in rat brain microvascular endothelial cells (rBMVECs), the major cellular component of the blood-brain barrier (BBB). Heavy alcohol drinking is often associated with HIV infection, however mechanisms underlying alcohol-induced BBB damage and HIV proteins, are not fully understood. We utilized the HIV-1 transgenic (HIV-1Tg) rat to mimic HIV-1 patients on combination anti-retroviral therapy (cART) and demonstrated TRPM7 expression in rBMVECs wass lower in adolescent HIV-1Tg rats compared to control animals, however control and HIV-1Tg rats expressed similar levels at 9 weeks, indicating persistent presence of HIV-1 proteins delayed TRPM7 expression. Binge exposure to EtOH (binge EtOH) decreased TRPM7 expression in control rBMVECs in a concentration-dependent manner, and abolished TRPM7 expression in HIV-1Tg rats. In human BMVECs (hBMVECs), TRPM7 expression was downregulated after treatment with EtOH, HIV-1 proteins, and in combination. Next, we constructed in vitro BBB models using BMVECs and found TRPM7 antagonists enhanced EtOH-mediated BBB integrity changes. Our study demonstrated alcohol decreased TRPM7 expression, whereby TRPM7 could be involved in the mechanisms underlying BBB alcohol-induced damage in HIV-1 patients on cART.

The HIV-1 Transgenic Rat: Relevance for HIV Noninfectious Comorbidity Research

HIV noninfectious comorbidities (NICMs) are a current healthcare challenge. The situation is further complicated as there are very few effective models that can be used for NICM research. Previous research has supported the use of the HIV-1 transgenic rat (HIV-1TGR) as a model for the study of HIV/AIDS. However, additional studies are needed to confirm whether this model has features that would support NICM research. A demonstration of the utility of the HIV-1TGR model would be to show that the HIV-1TGR has cellular receptors able to bind HIV proteins, as this would be relevant for the study of cell-specific tissue pathology. In fact, an increased frequency of HIV receptors on a specific cell type may increase tissue vulnerability since binding to HIV proteins would eventually result in cell dysfunction and death. Evidence suggests that observations of selective cellular vulnerability in this model are consistent with some specific tissue vulnerabilities seen in NICMs. We identified CXCR4-expressing cells in the brain, while specific markers for neuronal degeneration demonstrated that the same neural types were dying. We also confirm the presence of gp120 and Tat by immunocytochemistry in the spleen, as previously reported. However, we observed very rare positive cells in the brain. This underscores the point that gp120, which has been reported as detected in the sera and CSF, is a likely source to which these CXCR4-positive cells are exposed. This alternative appears more probable than the local production of gp120. Further studies may indicate some level of local production, but that will not eliminate the role of receptor-mediated pathology. The binding of gp120 to the CXCR4 receptor on neurons and other neural cell types in the HIV-1TGR can thus explain the phenomena of selective cell death. Selective cellular vulnerability may be a contributing factor to the development of NICMs. Our data indicate that the HIV-1TGR can be an effective model for the studies of HIV NICMs because of the difference in the regional expression of CXCR4 in rat tissues, thus leading to specific organ pathology. This also suggests that the model can be used in the development of therapeutic options.

HIV-1 proteins dysregulate motivational processes and dopamine circuitry

Motivational alterations, such as apathy, in HIV-1+ individuals are associated with decreased performance on tasks involving frontal-subcortical circuitry. We used the HIV-1 transgenic (Tg) rat to assess effect of long-term HIV-1 protein exposure on motivated behavior using sucrose (1–30%, w/v) and cocaine (0.01–1.0 mg/kg/infusion) maintained responding with fixed-ratio (FR) and progressive-ratio (PR) schedules of reinforcement. For sucrose-reinforced responding, HIV-1 Tg rats displayed no change in EC₅₀ relative to controls, suggesting no change in sucrose reinforcement but had a downward shifted concentration-response curves, suggesting a decrease in response vigor. Cocaine-maintained responding was attenuated in HIV-1 Tg rats (FR1 0.33 mg/kg/infusion and PR 1.0 mg/kg/infusion). Dose-response tests (PR) revealed that HIV-1 Tg animals responded significantly less than F344 control rats and failed to earn significantly more infusions of cocaine as the unit dose increased. When choosing between cocaine and sucrose, control rats initially chose sucrose but with time shifted to a cocaine preference. In contrast, HIV-1 disrupted choice behaviors. DAT function was altered in the striatum of HIV-1 Tg rats; however, prior cocaine self-administration produced a unique effect on dopamine homeostasis in the HIV-1 Tg striatum. These findings of altered goal directed behaviors may determine neurobiological mechanisms of apathy in HIV-1+ patients.

Modulation Effect of HIV-1 Viral Proteins and Nicotine on Expression of the Immune-Related Genes in Brain of the HIV-1 Transgenic Rats

The human immunodeficiency virus-1 transgenic (HIV-1Tg) rat is a non-infectious rodent model for HIV-1 infection which develops altered immune-responses similar to those in persons infected with HIV-1. HIV-1Tg and F344 rats respond significantly different to morphine, ethanol, nicotine and other psychostimulants, although the molecular mechanisms underlying these differences remain largely undetermined. Here, we compared expression of 52 immune-related genes in the prefrontal cortex (PFC), nucleus accumbens (NAc), and ventral tegmental area (VTA) of HIV-1Tg and F344 rats treated with either nicotine (0.4 mg/kg nicotine, base, s.c.) or saline for 27 days, to identify differentially expressed genes in the presence of HIV-1 with and without nicotine treatment. Using quantitative RT-PCR array, we measured RNA expression levels. Results showed that RNA expression of CASP3, CCL5, CX3CL1, CX3CR1, IL1α, LRF4, LFR7, TGFβ1 and TLR4 in NAc, CCL2, CCL5, TGFβ1 and TLR4 in PFC, and CASP3, CX3CR1, IFNα1, IL1β and IL6 in VTA was significantly modulated in HIV-1Tg rats compared with F344 rats. IL1α showed a 58 % (P = 0.000072) decrease and IRF6 showed a 93.7 % increase (P = 0.000227) in the NAc of HIV-1Tg compared with F344 rats; results remained significant after correction for multiple testing. We also found that several genes were significantly modulated by nicotine in HIV-1Tg rats while only a small number of immune-related genes were altered by nicotine in F344 rats. These findings imply that HIV-1 viral proteins greatly impact immune function and alter responsiveness to nicotine in certain immune-related genes.

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.

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

The HIV-1 transgenic (TG) rat has been shown to be a useful model of nervous system disease that occurs in human HIV-1 infection. Studies were, therefore, performed to examine characteristics of the immune response in the periphery and brain of the animals and expression of factors in the nervous system that might be associated with neurotoxicity. Activated splenocytes from wild-type (WT) and TG rats were stimulated with either CD3/CD28 or with lipopolysaccharide (LPS) and examined for proliferative responses and for proinflammatory cytokine (IFN-γ, TNF-α and IL-1β) secretion. Brain tissue lysates from the rats were also examined for proinflammatory cytokine levels and tissue sections were stained by immunofluorescence for class II MHC+, ED1+ or Iba1+ (for macrophages and microglial cells), and for GFAP+ (for astrocytes) cells and for co-labeling of these cells for TNF-α. Co-labeling was also performed to identify cells expressing HIV-1 gp160, tat, nef and vif. Finally, on Western blots brain tissue lysates were examined for phosphorylation of Erk1/2, p38, JNK-SAPK and Erk5. TG rat splenocyte proliferative responses were higher than for WT with CD3/CD28-stimulation but lower than WT with LPS stimulation. CD3/CD28-stimulated TG rat splenocytes also secreted higher levels of IFN-γ, TNF-α and IL-1β whereas LPS-stimulated TG rat splenocytes secreted higher levels of only TNF-α than cultures from WT rats. Levels of all three cytokines were higher in brain lysates from TG rats than for WT rats. On immunofluorescence staining of corresponding sections of brain, TG rats contained increased numbers of class II MHC+ and ED1+ cells, and there was also increased co-labeling or these cells as well as astrocytes for TNF-α. Iba1+ cells showed positive staining for all of the HIV proteins whereas astrocytes showed significant positive staining for only nef and vif. Phosphorylation of Erk1/2, p38 and JNK/SAPK was detected for both TG and WT rat tissues with higher levels of phosphorylation forms of these proteins detected in the TG rat brain. Phosphorylation of Erk5, a marker that is associated with specifically neuronal repair, was detected only in TG rat brain. These studies suggest that activated nervous system mononuclear phagocytes and astrocytes expressing HIV-1 gene products in specific patterns are associated with neurodegeneration in the HIV-1 TG rat.

Behavioral and molecular evidence for a feedback interaction between morphine and HIV-1 viral proteins

Morphine use and addiction is common among HIV infected individuals. There is an abundance of research supporting the effects of morphine and other mu opioid receptor (MOR) ligands, on the function of HIV-1 viral proteins and progression of HIV-1 viral infection to AIDS. On the other hand, there is much less research that investigates the possible effects of the persistent presence of HIV-1 viral proteins on the expression of the MOR and the analgesic and rewarding effects of MOR ligands such as morphine. While researchers have made a great deal of progress in the past several years, the overall investigation of the interaction between opiates such as morphine and HIV-1 viral proteins is largely unilateral. It has become widely accepted that drugs of abuse interact with HIV-1 viral proteins, but the mechanisms by which this takes place are only recently being discovered. Molecular and behavioral research suggests a feedback interaction between morphine and HIV-1 viral proteins. This interaction is mediated largely by the MOR as well as interplay between MOR ligands and cytokines, chemokines and their receptors. Some of the mechanisms underlying the feedback interaction between morphine and HIV-1 viral proteins has been demonstrated using cell culture and the recently engineered HIV-1 transgenic (HIV-1Tg) rat models.

Regional gene expression of LOX-1, VCAM-1, and ICAM-1 in aorta of HIV-1 transgenic rats

Background

Increased prevalence of atherosclerotic cardiovascular disease in HIV-infected patients has been observed. The cause of this accelerated atherosclerosis is a matter of controversy. As clinical studies are complicated by a multiplicity of risk-factors and a low incidence of hard endpoints, studies in animal models could be attractive alternatives.

Methodology/Principal Findings

We evaluated gene expression of lectin-like oxidized-low-density-lipoprotein receptor-1 (LOX-1), vascular cell adhesion molecule-1 (VCAM-1), and intercellular adhesion molecule-1 (ICAM-1) in HIV-1 transgenic (HIV-1Tg) rats; these genes are all thought to play important roles in early atherogenesis. Furthermore, the plasma level of sICAM-1 was measured. We found that gene expressions of LOX-1 and VCAM-1 were higher in the aortic arch of HIV-1Tg rats compared to controls. Also, the level of sICAM-1 was elevated in the HIV-1Tg rats compared to controls, but the ICAM-1 gene expression profile did not show any differences between the groups.

Conclusions/Significance

HIV-1Tg rats have gene expression patterns indicating endothelial dysfunction and accelerated atherosclerosis in aorta, suggesting that HIV-infection per se may cause atherosclerosis. This transgenic rat model may be a very promising model for further studies of the pathophysiology behind HIV-associated cardiovascular disease.

Neurotoxic profiles of HIV, psychostimulant drugs of abuse, and their concerted effect on the brain: current status of dopamine system vulnerability in NeuroAIDS

There are roughly 30-40 million HIV-infected individuals in the world as of December 2007, and drug abuse directly contributes to one-third of all HIV infections in the United States. Antiretroviral therapy has increased the lifespan of HIV-seropositives, but CNS function often remains diminished, effectively decreasing quality of life. A modest proportion may develop HIV-associated dementia, the severity and progression of which is increased with drug abuse. HIV and drugs of abuse in the CNS target subcortical brain structures and DA systems in particular. This toxicity is mediated by a number of neurotoxic mechanisms, including but not limited to, aberrant immune response and oxidative stress. Therefore, novel therapeutic strategies must be developed that can address a wide variety of disparate neurotoxic mechanisms and apoptotic cascades. This paper reviews the research pertaining to the where, what, and how of HIV and cocaine/methamphetamine toxicity in the CNS. Specifically, where these toxins most affect the brain, what aspects of the virus are neurotoxic, and how these toxins mediate neurotoxicity.

Spatial learning and memory in HIV-1 transgenic rats

HIV-1 infection of the central nervous system impairs neural, cognitive, and behavioral functioning in patients despite antiretroviral therapy. However, studying mechanisms underlying HIV-1-related neurological and cognitive dysfunction has been limited without an adequate animal model. A novel, noninfectious HIV-1 transgenic (HIV-1Tg) rat model was recently created that expresses an HIV-1 provirus with a deletion of functional gag and pol genes. This HIV-1Tg rat reportedly develops clinical manifestations of human HIV disease and thus appears to mimic the persistent infection that results from the presence of HIV viral proteins in the host. We evaluated the HIV-1Tg rat model using the Morris water maze, a popular paradigm for testing learning and memory deficits in rodents. Because of congenital cataracts in HIV-1Tg rats, however, the traditional use of visual navigational cues in this paradigm were precluded. We first designed a modified Morris water maze and demonstrated that neurologically intact rats can effectively learn the water maze in the absence of visual cues and in the presence of non-visual navigation cues. We then tested HIV-1Tg rats in this modified Morris water maze. These HIV-1Tg rats showed a deficit in learning how to swim to the location of the hidden platform but did not show a deficit in their memory of the general location of the hidden platform. These results suggest that the noninfectious HIV-1Tg rat can be a valid model for the behavioral studies of HIV-related neurological dysfunction.

Battle of animal models

This is a brief summary of the animal models session held during the 12th Annual Meeting of the Society on NeuroImmune Pharmacology, Santa Fe, NM, USA. This session provided important information for participants on availability and utility of animal models for the studies of HIV-1 central nervous system infection and drug abuse. It highlighted animal model relevance to human disease/condition, its utility for the studies of pathogenesis, potential importance for the development of therapeutics, and demonstrated limitations/pitfalls.

A vitamin A deficient diet enhances proinflammatory cytokine, Mu opioid receptor, and HIV-1 expression in the HIV-1 transgenic rat

The HIV-1 (HIV) transgenic (Tg) rat develops several immune abnormalities in association with clinical impairments that are similar to what are seen with HIV infection in humans. In HIV infection, retinoids and opioids can have separate and potentially combined effects on the clinical course of HIV disease. In these studies, the effects of a vitamin A deficient diet on T cell proinflammatory cytokine and mu opioid receptor (MOR) expression were examined in the Tg and in wild-type (WT) rats. The effects of the diet on HIV gene expression were also analyzed in the Tg rats. Phytohemagglutinin-stimulated T cells from WT rats on the vitamin A diet and from Tg rats on either diet were more likely to either produce increased percentages of T cells expressing intracytoplasmic IFN-gamma, secrete higher levels of TNF-alpha, and express higher levels of MOR mRNA and surface MOR. Mitogen stimulation also increased Tg rat HIV env, tat, and nef mRNA expression with even higher env and nef mRNA produced in association with the vitamin A deficient diet. All together, these data suggest that a vitamin A deficient diet can result in cellular effects that increase T cell proinflammatory responses and HIV expression, which may alter the course of disease in the HIV Tg rat model.

Resveratrol suppresses tumor necrosis factor-alpha-induced fractalkine expression in endothelial cells

Up-regulation of fractalkine is involved in vascular and tissue damage in inflammatory conditions. Resveratrol has been shown to have anti-inflammatory, antioxidant, and antitumor activities. Its regulatory effects on expression of fractalkine in vascular endothelial cells and fractalkine receptor CX3CR1 in monocytes have not been studied. We evaluated the effects of resveratrol on fractalkine expression in human umbilical vein endothelial cells and CX3CR1 expression in THP-1 cells in response to treatment with tumor necrosis factor (TNF)-alpha. TNF-alpha significantly induced fractalkine mRNA and protein expression in endothelial cells. Resveratrol strongly suppressed TNF-alpha-induced fractalkine expression in endothelial cells through suppression of nuclear factor-kappaB and Sp1 activities. Resveratrol decreased the number of TNF-alpha-induced fractalkine-positive endothelial cells and CX3CR1-positive cells determined by flow cytometric analysis. Resveratrol suppressed TNF-alpha-stimulated monocytes adhesion to human umbilical vein endothelial cells. Immunohistochemical analysis revealed that resveratrol suppressed TNF-alpha-induced arterial endothelial fractalkine expression in heart, kidney, and intestine and decreased ED-1-positive cell infiltration in intestinal villi. Resveratrol may provide a new pharmacological approach for suppressing fractalkine/CX3CR1-mediated injury in inflammatory conditions.