Microglial activation decreases retention of the protease inhibitor saquinavir: implications for HIV treatment

Background Active HIV infection within the central nervous system (CNS) is confined primarily to microglia. The glial cell compartment acts as a viral reservoir behind the blood-brain barrier. It provides an additional roadblock to effective pharmacological treatment via expression of multiple drug efflux transporters, including P-glycoprotein. HIV/AIDS patients frequently suffer bacterial and viral co-infections, leading to deregulation of glial cell function and release of pro-inflammatory mediators including cytokines, chemokines, and nitric oxide. Methods To better define the role of inflammation in decreased HIV drug accumulation into CNS targets, accumulation of the antiretroviral saquinavir was examined in purified cultures of rodent microglia exposed to the prototypical inflammatory mediator lipopolysaccharide (LPS). Results [3H]-Saquinavir accumulation by microglia was rapid, and was increased up to two-fold in the presence of the specific P-glycoprotein inhibitor, PSC833. After six or 24 hours of exposure to 10 ng/ml LPS, saquinavir accumulation was decreased by up to 45%. LPS did not directly inhibit saquinavir transport, and did not affect P-glycoprotein protein expression. LPS exposure did not alter RNA and/or protein expression of other transporters including multidrug resistance-associated protein 1 and several solute carrier uptake transporters. Conclusions The decrease in saquinavir accumulation in microglia following treatment with LPS is likely multi-factorial, since drug accumulation was attenuated by inhibitors of NF-κβ and the MEK1/2 pathway in the microglia cell line HAPI, and in primary microglia cultures from toll-like receptor 4 deficient mice. These data provide new pharmacological insights into why microglia act as a difficult-to-treat viral sanctuary site

2006. HIV-1 viral envelope glycoprotein gp120 triggers an inflammatory response in cultured rat astrocytes and regulates the functional expression of P-glycoprotein. Mol

ABSTRACT In this work, we examined the ability of gp120, a human immunodeficiency virus-1 (HIV-1) viral envelope glycoprotein, to trigger the innate immune response in astrocytes, an HIV-1 brain cellular target, and we investigated the functional expression of the ATP-binding cassette membrane transporter P-glycoprotein (P-gp) in primary cultures of rat astrocytes treated with gp120 or cytokines [tumor necrosis factor-␣ (TNF-␣), interleukin-1␤ (IL-1␤), and IL-6]. Standard 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium and D-mannitol uptake assays confirmed that HIV-1 96ZM651 gp120 treatment did not alter cell viability or membrane permeability. Semiquantitative reversetranscriptase polymerase chain reaction analysis and enzymelinked immunosorbent assay demonstrated increased TNF-␣, IL-1␤, and IL-6 mRNA and protein expression in cultures treated with HIV-1 96ZM651 gp120, suggesting in vitro activation of immune responses. Cytokine secretion was detected when CXCR4 but not CCR5 was inhibited with a specific antibody, implying that cytokine secretion is primarily mediated via CCR5 in astrocytes triggered with HIV-1 96ZM651 gp120. P-gp protein expression was increased in astrocyte cultures exposed to TNF-␣ (2.9-fold) or IL-1␤ (1.6-fold) but was decreased profoundly in the presence of IL-6 (8.9-fold), suggesting that IL-6 is primarily involved in modulating P-gp expression. In parallel, after HIV-1 96ZM651 gp120 treatment, immunoblotting analysis showed a significant decrease in P-gp expression (4.7-fold). Furthermore, the accumulation of two P-gp substrates, digoxin and saquinavir (an HIV-1 protease inhibitor), was enhanced (1.5-to 1.8-fold) in HIV-1 96ZM651 gp120-treated astrocyte monolayers but was not altered by P-gp inhibitors [e.g., valspodar (PSC833) and elacridar (GF120918)], suggesting a loss of transport activity. Taken together, these data imply that HIV-1 96ZM651 gp120 or cytokine treatment modulate P-gp functional expression in astrocytes, which may lead to complex drug-transporter interactions during HIV-1 encephalitis-associated immune responses

Nrf2 signaling increases expression of ATP-binding cassette subfamily C mRNA transcripts at the blood–brain barrier following hypoxia-reoxygenation stress

Background: Strategies to maintain BBB integrity in diseases with a hypoxia/reoxygenation (H/R) component involve preventing glutathione (GSH) loss from endothelial cells. GSH efflux transporters include multidrug resistance proteins (Mrps). Therefore, characterization of Mrp regulation at the BBB during H/R is required to advance these transporters as therapeutic targets. Our goal was to investigate, in vivo, regulation of Abcc1, Abcc2, and Abcc4 mRNA expression (i.e., genes encoding Mrp isoforms that transport GSH) by nuclear factor E2-related factor (Nrf2) using a well-established H/R model. Methods: Female Sprague-Dawley rats (200-250 g) were subjected to normoxia (Nx, 21% O-2, 60 min), hypoxia (Hx, 6% O-2, 60 min) or H/R (6% O-2, 60 min followed by 21% O-2, 10 min, 30 min, or 1 h) or were treated with the Nrf2 activator sulforaphane (25 mg/kg, i.p.) for 3 h. Abcc mRNA expression in brain microvessels was determined using quantitative real-time PCR. Nrf2 signaling activation was examined using an electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) respectively. Data were expressed as mean +/- SD and analyzed via ANOVA followed by the post hoc Bonferroni t test. Results: We observed increased microvascular expression of Abcc1, Abcc2, and Abcc4 mRNA following H/R treatment with reoxygenation times of 10 min, 30 min, and 1 h and in animals treated with sulforaphane. Using a biotinylated Nrf2 probe, we observed an upward band shift in brain microvessels isolated from H/R animals or animals administered sulforaphane. ChIP studies showed increased Nrf2 binding to antioxidant response elements on Abcc1, Abcc2, and Abcc4 promoters following H/R or sulforaphane treatment, suggesting a role for Nrf2 signaling in Abcc gene regulation. Conclusions: Our data show increased Abcc1, Abcc2, and Abcc4 mRNA expression at the BBB in response to H/R stress and that Abcc gene expression is regulated by Nrf2 signaling. Since these Mrp isoforms transport GSH, these results may point to endogenous transporters that can be targeted for BBB protection during H/R stress. Experiments are ongoing to examine functional implications of Nrf2-mediated increases in Abcc transcript expression. Such studies will determine utility of targeting Mrp isoforms for BBB protection in diseases with an H/R component.National Institute of Neurological Disease and Stroke (NINDS), National Institutes of Health (NIH) [R01-NS084941]Open Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Sex-specific differences in organic anion transporting polypeptide 1a4 (Oatp1a4) functional expression at the blood–brain barrier in Sprague–Dawley rats

Background: Targeting endogenous blood-brain barrier (BBB) transporters such as organic anion transporting polypeptide 1a4 (Oatp1a4) can facilitate drug delivery for treatment of neurological diseases. Advancement of Oatp targeting for optimization of CNS drug delivery requires characterization of sex-specific differences in BBB expression and/or activity of this transporter. Methods: In this study, we investigated sex differences in Oatp1a4 functional expression at the BBB in adult and prepubertal (i.e., 6-week-old) Sprague-Dawley rats. We also performed castration or ovariectomy surgeries to assess the role of gonadal hormones on Oatp1a4 protein expression and transport activity at the BBB. Slco1a4 (i.e., the gene encoding Oatp1a4) mRNA expression and Oatp1a4 protein expression in brain microvessels was determined using quantitative real-time PCR and western blot analysis, respectively. Oatp transport function at the BBB was determined via in situ brain perfusion using [H-3] taurocholate and [H-3] atorvastatin as probe substrates. Data were expressed as mean +/- SD and analyzed via one-way ANOVA followed by the post hoc Bonferroni t-test. Results: Our results showed increased brain microvascular Slco1a4 mRNA and Oatp1a4 protein expression as well as increased brain uptake of [H-3] taurocholate and [H-3] atorvastatin in female rats as compared to males. Oatp1a4 expression at the BBB was enhanced in castrated male animals but was not affected by ovariectomy in female animals. In prepubertal rats, no sex-specific differences in brain microvascular Oatp1a4 expression were observed. Brain accumulation of [H-3] taurocholate in male rats was increased following castration as compared to controls. In contrast, there was no difference in [H-3] taurocholate brain uptake between ovariectomized and control female rats. Conclusions: These novel data confirm sex-specific differences in BBB Oatp1a4 functional expression, findings that have profound implications for treatment of CNS diseases. Studies are ongoing to fully characterize molecular pathways that regulate sex differences in Oatp1a4 expression and activity.National Institutes of Health [R01-NS084941]; Arizona Biomedical Research Commission [ADHS16-162406]Open Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Sex-specific differences in organic anion transporting polypeptide 1a4 (Oatp1a4) functional expression at the blood–brain barrier in Sprague–Dawley rats

Background: Targeting endogenous blood-brain barrier (BBB) transporters such as organic anion transporting polypeptide 1a4 (Oatp1a4) can facilitate drug delivery for treatment of neurological diseases. Advancement of Oatp targeting for optimization of CNS drug delivery requires characterization of sex-specific differences in BBB expression and/or activity of this transporter. Methods: In this study, we investigated sex differences in Oatp1a4 functional expression at the BBB in adult and prepubertal (i.e., 6-week-old) Sprague-Dawley rats. We also performed castration or ovariectomy surgeries to assess the role of gonadal hormones on Oatp1a4 protein expression and transport activity at the BBB. Slco1a4 (i.e., the gene encoding Oatp1a4) mRNA expression and Oatp1a4 protein expression in brain microvessels was determined using quantitative real-time PCR and western blot analysis, respectively. Oatp transport function at the BBB was determined via in situ brain perfusion using [H-3] taurocholate and [H-3] atorvastatin as probe substrates. Data were expressed as mean +/- SD and analyzed via one-way ANOVA followed by the post hoc Bonferroni t-test. Results: Our results showed increased brain microvascular Slco1a4 mRNA and Oatp1a4 protein expression as well as increased brain uptake of [H-3] taurocholate and [H-3] atorvastatin in female rats as compared to males. Oatp1a4 expression at the BBB was enhanced in castrated male animals but was not affected by ovariectomy in female animals. In prepubertal rats, no sex-specific differences in brain microvascular Oatp1a4 expression were observed. Brain accumulation of [H-3] taurocholate in male rats was increased following castration as compared to controls. In contrast, there was no difference in [H-3] taurocholate brain uptake between ovariectomized and control female rats. Conclusions: These novel data confirm sex-specific differences in BBB Oatp1a4 functional expression, findings that have profound implications for treatment of CNS diseases. Studies are ongoing to fully characterize molecular pathways that regulate sex differences in Oatp1a4 expression and activity.National Institutes of Health [R01-NS084941]; Arizona Biomedical Research Commission [ADHS16-162406]Open Access Journal.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Modulation of Opioid Transport at the Blood-Brain Barrier by Altered ATP-Binding Cassette (ABC) Transporter Expression and Activity

Opioids are highly effective analgesics that have a serious potential for adverse drug reactions and for development of addiction and tolerance. Since the use of opioids has escalated in recent years, it is increasingly important to understand biological mechanisms that can increase the probability of opioid-associated adverse events occurring in patient populations. This is emphasized by the current opioid epidemic in the United States where opioid analgesics are frequently abused and misused. It has been established that the effectiveness of opioids is maximized when these drugs readily access opioid receptors in the central nervous system (CNS). Indeed, opioid delivery to the brain is significantly influenced by the blood-brain barrier (BBB). In particular, ATP-binding cassette (ABC) transporters that are endogenously expressed at the BBB are critical determinants of CNS opioid penetration. In this review, we will discuss current knowledge on the transport of opioid analgesic drugs by ABC transporters at the BBB. We will also examine how expression and trafficking of ABC transporters can be modified by pain and/or opioid pharmacotherapy, a novel mechanism that can promote opioid-associated adverse drug events and development of addiction and tolerance

Transporter-Mediated Delivery of Small Molecule Drugs to the Brain: A Critical Mechanism That Can Advance Therapeutic Development for Ischemic Stroke

Ischemic stroke is the 5th leading cause of death in the United States. Despite significant improvements in reperfusion therapies, stroke patients still suffer from debilitating neurocognitive deficits. This indicates an essential need to develop novel stroke treatment paradigms. Endogenous uptake transporters expressed at the blood-brain barrier (BBB) provide an excellent opportunity to advance stroke therapy via optimization of small molecule neuroprotective drug delivery to the brain. Examples of such uptake transporters include organic anion transporting polypeptides (OATPs in humans; Oatps in rodents) and organic cation transporters (OCTs in humans; Octs in rodents). Of particular note, small molecule drugs that have neuroprotective properties are known substrates for these transporters and include 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (i.e., statins) for OATPs/Oatps and 1-amino-3,5-dimethyladamantane (i.e., memantine) for OCTs/Octs. Here, we review current knowledge on specific BBB transporters that can be targeted for improvement of ischemic stroke treatment and provide state-of-the-art perspectives on the rationale for considering BBB transport properties during discovery/development of stroke therapeutics.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Blood–Brain Barrier Transporters: Opportunities for Therapeutic Development in Ischemic Stroke

Globally, stroke is a leading cause of death and long-term disability. Over the past decades, several efforts have attempted to discover new drugs or repurpose existing therapeutics to promote post-stroke neurological recovery. Preclinical stroke studies have reported successes in identifying novel neuroprotective agents; however, none of these compounds have advanced beyond a phase III clinical trial. One reason for these failures is the lack of consideration of blood–brain barrier (BBB) transport mechanisms that can enable these drugs to achieve efficacious concentrations in ischemic brain tissue. Despite the knowledge that drugs with neuroprotective properties (i.e., statins, memantine, metformin) are substrates for endogenous BBB transporters, preclinical stroke research has not extensively studied the role of transporters in central nervous system (CNS) drug delivery. Here, we review current knowledge on specific BBB uptake transporters (i.e., organic anion transporting polypeptides (OATPs in humans; Oatps in rodents); organic cation transporters (OCTs in humans; Octs in rodents) that can be targeted for improved neuroprotective drug delivery. Additionally, we provide state-of-the-art perspectives on how transporter pharmacology can be integrated into preclinical stroke research. Specifically, we discuss the utility of in vivo stroke models to transporter studies and considerations (i.e., species selection, co-morbid conditions) that will optimize the translational success of stroke pharmacotherapeutic experiments