Chronic Low Dose Morphine Does Not Alter Two In Vitro BBB Models.

The blood-brain barrier (BBB) mediates cellular and molecular passage between the central nervous system (CNS) and peripheral circulation. Compromised BBB integrity has been linked to neurocognitive deficits in multiple diseases and various infections, including those associated with HIV-1 infection. Understanding the impact of exposure to pharmaceuticals, such as those utilized for pain management by patients suffering from CNS disease, on BBB regulation and function is clinically important. In this study, we modelled two different BBB systems; a primary human co-culture and a cell line monoculture. These systems were both exposed to three daily repeat doses of morphine and examined for alterations to BBB integrity via permeability, PBMC transmigration, and chemokine gradient changes. We did not find any significant changes to either BBB system with repeat morphine dosing, suggesting that repeat morphine exposure may not play a significant role in BBB changes.

Functional impact of HIV-1 Tat on cells of the CNS and its role in HAND.

Human immunodeficiency virus type 1 (HIV-1) transactivator of transcription (Tat) is a potent mediator involved in the development of HIV-1-associated neurocognitive disorders (HAND). Tat is expressed even in the presence of antiretroviral therapy (ART) and is able to enter the central nervous system (CNS) through a variety of ways, where Tat can interact with microglia, astrocytes, brain microvascular endothelial cells, and neurons. The presence of low concentrations of extracellular Tat alone has been shown to lead to dysregulated gene expression, chronic cell activation, inflammation, neurotoxicity, and structural damage in the brain. The reported effects of Tat are dependent in part on the specific HIV-1 subtype and amino acid length of Tat used. HIV-1 subtype B Tat is the most common subtype in North American and therefore, most studies have been focused on subtype B Tat; however, studies have shown many genetic, biologic, and pathologic differences between HIV subtype B and subtype C Tat. This review will focus primarily on subtype B Tat where the full-length protein is 101 amino acids, but will also consider variants of Tat, such as Tat 72 and Tat 86, that have been reported to exhibit a number of distinctive activities with respect to mediating CNS damage and neurotoxicity.

The tracking of lipopolysaccharide through the feto-maternal compartment and the involvement of maternal TLR4 in inflammation-induced fetal brain injury.

PROBLEM: Exposure to intrauterine inflammation (IUI) has been shown to induce fetal brain injury and increase the risk of acquiring a neurobehavioral disorder. The trafficking of the inflammatory mediator, lipopolysaccharide (LPS), in the pregnant female reproductive tract in the setting of IUI and the precise mechanisms by which inflammation induces fetal brain injury are not fully understood. METHOD OF STUDY: FITC-labeled LPS was utilized to induce IUI on E15, tissues were collected, and fluorescence was visualized via the Spectrum IVIS. Embryo transfer was utilized to create divergent maternal and fetal genotypes. Wild-type (WT) embryos were transferred into TLR4-/- pseudopregnant dams (TLR4-/-mat /WTfet ). On E15, TLR4-/-mat /WTfet dams or their WT controls (WTmat /WTfet ) received an intrauterine injection of LPS or phosphate-buffered saline (PBS). Endotoxin and IL-6 levels were assessed in amniotic fluid, and cytokine expression was measured via QPCR. RESULTS: Lipopolysaccharide trafficked to the uterus, fetal membranes, placenta, and the fetus and was undetectable in other tissues. Endotoxin was present in the amniotic fluid of all animals exposed to LPS. However, the immune response was blunted in TLR4-/-mat /WTfet compared with WT controls. CONCLUSION: Intrauterine administered LPS is capable of accessing the entire feto-placental unit with or without a functional maternal TLR4. Thus, bacteria or bacterial byproducts in the uterus may negatively impact fetal development regardless of the maternal genotype or endotoxin response. Despite the blunted immune response in the TLR4-deficient dams, an inflammatory response is still ignited in the amniotic cavity and may negatively impact the fetus.

Prolonged Morphine Exposure Induces Increased Firm Adhesion in an in Vitro Model of the Blood-Brain Barrier.

The blood-brain barrier (BBB) has been defined as a critically important protective barrier that is involved in providing essential biologic, physiologic, and immunologic separation between the central nervous system (CNS) and the periphery. Insults to the BBB can cause overall barrier damage or deregulation of the careful homeostasis maintained between the periphery and the CNS. These insults can, therefore, yield numerous phenotypes including increased overall permeability, interendothelial gap formation, alterations in cytokine and chemokine secretion, and accelerated cellular passage. The current studies expose the human brain microvascular endothelial cell line, hCMEC/D3, to prolonged morphine exposure and aim to uncover the mechanisms underlying alterations in barrier function in vitro. These studies show alterations in the mRNA and protein levels of the cellular adhesion molecules (CAMs) intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and activated leukocyte cell adhesion molecule that correlate with an increased firm adhesion of the CD3⁺ subpopulation of peripheral blood mononuclear cells (PBMCs). Overall, these studies suggest that prolonged morphine exposure may result in increased cell migration into the CNS, which may accelerate pathological processes in many diseases that involve the BBB.

Co-culture model consisting of human brain microvascular endothelial and peripheral blood mononuclear cells.

BACKGROUND: Numerous systems exist to model the blood-brain barrier (BBB) with the goal of understanding the regulation of passage into the central nervous system (CNS) and the potential impact of selected insults on BBB function. These models typically focus on the intrinsic cellular properties of the BBB, yet studies of peripheral cell migration are often excluded due to technical restraints. NEW METHOD: This method allows for the study of in vitro cellular transmigration following exposure to any treatment of interest through optimization of co-culture conditions for the human brain microvascular endothelial cells (BMEC) cell line, hCMEC/D3, and primary human peripheral blood mononuclear cells (PBMCs). RESULTS: hCMEC/D3 cells form functionally confluent monolayers on collagen coated polytetrafluoroethylene (PTFE) transwell inserts, as assessed by microscopy and tracer molecule (FITC-dextran (FITC-D)) exclusion. Two components of complete hCMEC/D3 media, EBM-2 base-media and hydrocortisone (HC), were determined to be cytotoxic to PBMCs. By combining the remaining components of complete hCMEC/D3 media with complete PBMC media a resulting co-culture media was established for use in hCMEC/D3-PBMC co-culture functional assays. COMPARISON WITH EXISTING METHODS: Through this method, issues of extensive differences in culture media conditions are resolved allowing for treatments and functional assays to be conducted on the two cell populations co-cultured simultaneously. CONCLUSION: Described here is an in vitro co-culture model of the BBB, consisting of the hCMEC/D3 cell line and primary human PBMCs. The co-culture media will now allow for the study of exposure to potential insults to BBB function over prolonged time courses.

Interaction between Tat and Drugs of Abuse during HIV-1 Infection and Central Nervous System Disease.

In many individuals, drug abuse is intimately linked with HIV-1 infection. In addition to being associated with one-third of all HIV-1 infections in the United States, drug abuse also plays a role in disease progression and severity in HIV-1-infected patients, including adverse effects on the central nervous system (CNS). Specific systems within the brain are known to be damaged in HIV-1-infected individuals and this damage is similar to that observed in drug abuse. Even in the era of anti-retroviral therapy (ART), CNS pathogenesis occurs with HIV-1 infection, with a broad range of cognitive impairment observed, collectively referred to as HIV-1-associated neurocognitive disorders (HAND). A number of HIV-1 proteins (Tat, gp120, Nef, Vpr) have been implicated in the etiology of pathogenesis and disease as a result of the biologic activity of the extracellular form of each of the proteins in a number of tissues, including the CNS, even in ART-suppressed patients. In this review, we have made Tat the center of attention for a number of reasons. First, it has been shown to be synthesized and secreted by HIV-1-infected cells in the CNS, despite the most effective suppression therapies available to date. Second, Tat has been shown to alter the functions of several host factors, disrupting the molecular and biochemical balance of numerous pathways contributing to cellular toxicity, dysfunction, and death. In addition, the advantages and disadvantages of ART suppression with regard to controlling the genesis and progression of neurocognitive impairment are currently under debate in the field and are yet to be fully determined. In this review, we discuss the individual and concerted contributions of HIV-1 Tat, drug abuse, and ART with respect to damage in the CNS, and how these factors contribute to the development of HAND in HIV-1-infected patients.