Infection and disruption of placental multidrug resistance (MDR) transporters: Implications for fetal drug exposure.

P-glycoprotein (P-gp, encoded by the ABCB1 gene) and breast cancer resistance protein (BCRP/ABCG2) are efflux multidrug resistance (MDR) transporters localized at the syncytiotrophoblast barrier of the placenta and protect the conceptus from drug and toxin exposure throughout pregnancy. Infection is an important modulator of MDR expression and function. This review comprehensively examines the effect of infection on the MDR transporters, P-gp and BCRP in the placenta. Infection PAMPs such as bacterial lipopolysaccharide (LPS) and viral polyinosinic-polycytidylic acid (poly I:C) and single-stranded (ss)RNA, as well as infection with Zika virus (ZIKV), Plasmodium berghei ANKA (modeling malaria in pregnancy - MiP) and polymicrobial infection of intrauterine tissues (chorioamnionitis) all modulate placental P-gp and BCRP at the levels of mRNA, protein and or function; with specific responses varying according to gestational age, trophoblast type and species (human vs. mice). Furthermore, we describe the expression and localization profile of Toll-like receptor (TLR) proteins of the innate immune system at the maternal-fetal interface, aiming to better understand how infective agents modulate placental MDR. We also highlight important gaps in the field and propose future research directions. We conclude that alterations in placental MDR expression and function induced by infective agents may not only alter the intrauterine biodistribution of important MDR substrates such as drugs, toxins, hormones, cytokines, chemokines and waste metabolites, but also impact normal placentation and adversely affect pregnancy outcome and maternal/neonatal health.

A2A adenosine receptor deletion is protective in a mouse model of Tauopathy.

Consumption of caffeine, a non-selective adenosine A2A receptor (A2AR) antagonist, reduces the risk of developing Alzheimer's disease (AD) in humans and mitigates both amyloid and Tau burden in transgenic mouse models. However, the impact of selective A2AR blockade on the progressive development of AD-related lesions and associated memory impairments has not been investigated. In the present study, we removed the gene encoding A2AR from THY-Tau22 mice and analysed the subsequent effects on both pathological (Tau phosphorylation and aggregation, neuro-inflammation) and functional impairments (spatial learning and memory, hippocampal plasticity, neurotransmitter profile). We found that deleting A2ARs protect from Tau pathology-induced deficits in terms of spatial memory and hippocampal long-term depression. These effects were concomitant with a normalization of the hippocampal glutamate/gamma-amino butyric acid ratio, together with a global reduction in neuro-inflammatory markers and a decrease in Tau hyperphosphorylation. Additionally, oral therapy using a specific A2AR antagonist (MSX-3) significantly improved memory and reduced Tau hyperphosphorylation in THY-Tau22 mice. By showing that A2AR genetic or pharmacological blockade improves the pathological phenotype in a Tau transgenic mouse model, the present data highlight A2A receptors as important molecular targets to consider against AD and Tauopathies.

Adenosine A(2A) receptor blockade reverts hippocampal stress-induced deficits and restores corticosterone circadian oscillation.

Maternal separation (MS) is an early life stress model that induces permanent changes in the central nervous system, impairing hippocampal long-term potentiation (LTP) and spatial working memory. There are compelling evidences for a role of hippocampal adenosine A(2A) receptors in stress-induced modifications related to cognition, thus opening a potential window for therapeutic intervention. Here, we submitted rats to MS and evaluated the long-lasting molecular, electrophysiological and behavioral impairments in adulthood. We then assessed the therapeutic potential of KW6002, a blocker of A(2A) receptors, in stress-impaired animals. We report that the blockade of A(2A) receptors was efficient in reverting the behavior, electrophysiological and morphological impairments induced by MS. In addition, this effect is associated with restoration of the hypothalamic-pituitary-adrenal axis (HPA-axis) activity, as both the plasma corticosterone levels and hippocampal glucocorticoid receptor expression pattern returned to physiological-like status after the treatment. These results reveal the involvement of A(2A) receptors in the stress-associated impairments and directly in the stress response system by showing that the dysfunction of the HPA-axis as well as the long-lasting synaptic and behavioral effects of MS can be reverted by targeting adenosine A(2A) receptors. These findings provide a novel evidence for the use of adenosine A(2A) receptor antagonists as potential therapy against psychopathologies.

The variability of polychlorinated biphenyls levels in urban soils from five European cities.

The concentration of PCBs in topsoils from five European cities was assessed and the highest levels were found in Glasgow (Scotland), followed by Torino (Italy), Aveiro (Portugal), Ljubljana (Slovenia) and Uppsala (Sweden). All cities showed the presence of local sources in addition to diffuse contamination from global atmospheric transport. The association of general soil parameters with PCBs in Glasgow and with heavier congeners in Torino and Ljubljana indicates that retention of these compounds is occurring. The profiles obtained resemble Aroclor 1254 and 1260, which are important local sources. Nevertheless, differences in PCB profiles were observed among cities, due to the combined effects of the age of the contamination (which determines the time available for volatilisation and degradation), different sources of PCBs and differences in climate (which influence volatilisation and deposition).

Adenosine A1 and A2A receptors are co-expressed in pyramidal neurons and co-localized in glutamatergic nerve terminals of the rat hippocampus.

Adenosine is a neuromodulator that controls neurotransmitter release through inhibitory A1 and facilitatory A2A receptors. Although both adenosine receptor-mediated inhibition and facilitation of glutamate release have been observed, it is not clear whether both A1 and A2A receptors are located in the same glutamatergic nerve terminal or whether they are located on different populations of these terminals. Thus, we have tested if single pyramidal glutamatergic neurons from the hippocampus simultaneously expressed A1 and A2A receptor mRNA and if A1 and A2A receptors were co-localized in hippocampal glutamatergic nerve terminals. Single cell PCR analysis of visually identified pyramidal neurons revealed the simultaneous presence of A1 and A2A receptor mRNA in four out 16 pyramidal cells possessing glutamatergic markers but not GABAergic or astrocytic markers. Also, A1 and A2A receptor immunoreactivities were co-localized in 26 +/- 4% of nerve terminals labeled with antibodies against vesicular glutamate transporters type 1 or 2, i.e. glutamatergic nerve terminals. This indicates that glutamatergic neurons in the hippocampus co-express A1 and A2A receptors and that these two receptors are co-localized in a subset of glutamatergic nerve terminals.

Adenosine A(2A) receptor facilitation of hippocampal synaptic transmission is dependent on tonic A(1) receptor inhibition.

Adenosine tonically inhibits synaptic transmission through actions at A(1) receptors. It also facilitates synaptic transmission, but it is unclear if this facilitation results from pre- and/or postsynaptic A(2A) receptor activation or from indirect control of inhibitory GABAergic transmission. The A(2A) receptor agonist, CGS 21680 (10 nM), facilitated synaptic transmission in the CA1 area of rat hippocampal slices (by 14%), independent of whether or not GABAergic transmission was blocked by the GABA(A) and GABA(B) receptor antagonists, picrotoxin (50 microM) and CGP 55845 (1 microM), respectively. CGS 21680 (10 nM) also inhibited paired-pulse facilitation by 12%, an effect prevented by the A(2A) receptor antagonist, ZM 241385 (20 nM). These effects of CGS 21680 (10 nM) were occluded by adenosine deaminase (2 U/ml) and were made to reappear upon direct activation of A(1) receptors with N(6)-cyclopentyladenosine (CPA, 6 nM). CGS 21680 (10 nM) only facilitated (by 17%) the K(+)-evoked release of glutamate from superfused hippocampal synaptosomes in the presence of 100 nM CPA. This effect of CGS 21680 (10 nM), in contrast to the isoproterenol (30 microM) facilitation of glutamate release, was prevented by the protein kinase C inhibitors, chelerythrine (6 microM) and bisindolylmaleimide (1 microM), but not by the protein kinase A inhibitor, H-89 (1 microM). Isoproterenol (30 microM), but not CGS 21680 (10-300 nM), enhanced synaptosomal cAMP levels, indicating that the CGS 21680-induced facilitation of glutamate release involves a cAMP-independent protein kinase C activation. To discard any direct effect of CGS 21680 on adenosine A(1) receptor, we also show that in autoradiography experiments CGS 21680 only displaced the adenosine A(1) receptor antagonist, 1,3-dipropyl-8-cyclopentyladenosine ([(3)H]DPCPX, 0.5 nM) with an EC(50) of 1 microM in all brain areas studied and CGS 21680 (30 nM) failed to change the ability of CPA to displace DPCPX (1 nM) binding to CHO cells stably transfected with A(1) receptors. Our results suggest that A(2A) receptor agonists facilitate hippocampal synaptic transmission by attenuating the tonic effect of inhibitory presynaptic A(1) receptors located in glutamatergic nerve terminals. This might be a fine-tuning role for adenosine A(2A) receptors to allow frequency-dependent plasticity phenomena without compromising the A(1) receptor-mediated neuroprotective role of adenosine.

A functional role for adenosine A3 receptors: modulation of synaptic plasticity in the rat hippocampus.

Adenosine modulates hippocampal synaptic plasticity, namely long-term potentiation (LTP) and long-term depression (LTD), through activation of A1 and A2A receptors. We now report a novel role for the recently described adenosine A3 receptor in the regulation of synaptic plasticity in the CA1 area of hippocampal slices. Activation of adenosine A3 receptors by (1-[2-chloro-6-[[(3-iodophenyl)methyl]amino]-9H-purin-p-yl]-1-deoxy-N-methyl-beta-D-ribofuranuronamide (Cl-IBMECA) (100 nM) increased the magnitude of theta-burst induced LTP (from 1.2+/-0.6% in the control solution to 25.5+/-0.8% in the presence of Cl-IBMECA) and attenuated LTD (from 30.0+/-5.5% decrease in the control solution to 13.6+/-6.6% decrease in the presence of Cl-IBMECA). The selective adenosine A3 receptor antagonist, MRS 1191 (5-10 microM), prevented the effects of Cl-IBMECA. These findings indicate a functional role for adenosine A3 receptors in the modulation of synaptic plasticity.

Cross talk between A(1) and A(2A) adenosine receptors in the hippocampus and cortex of young adult and old rats.

Adenosine modulates synaptic transmission by acting on inhibitory A(1) and facilitatory A(2A) receptors, the densities of which are modified in aged animals. We investigated how A(2A) receptor activation influences A(1) receptor function and whether this interaction is modified in aged rats. In hippocampal and cortical nerve terminals from young adult (6 wk), but not old rats (24 mo), the A(2A) receptor agonist, 2-[4-(2-carboxyethyl) phenethylamino]-5'-N-ethylcarboxamidoadenosine (CGS 21680; 30 nM) decreased the binding affinity of a selective A(1) receptor agonist, cyclopentyladenosine (CPA), an effect prevented by the A(2A) antagonist, (4-(2-[7-amino-2-(2-furyl (1,2,4)-triazolo(2,3-a (1,3,5)triazin-5-yl-aminoethyl)phenol (ZM 241385, 20 nM). This effect of CGS 21680 required intact nerve terminals and was also observed in the absence of Ca(2+). This A(2A)-induced "desensitization" of A(1) receptors was prevented by the protein kinase C inhibitor, chelerythrine (6 microM), and was not detected in the presence of the protein kinase C activator, phorbol-12,13-didecanoate (250 nM), which itself caused a reduction in binding affinity for CPA. The protein kinase A inhibitor, N-(2-guanidinoethyl)-5-isoquinolinesulfonamide (10 microM), and the protein kinase A activator, 8-Br-cAMP (1 mM), had no effects on the A(2A)-induced A(1) receptor desensitization. This A(2A)-induced A(1) receptor desensitization had a functional correlation because CGS 21680 (10 nM) attenuated by 40% the inhibition caused by CPA (10 nM) on CA1 area population spike amplitude in hippocampal slices. This A(2A)/A(1) interaction may explain the attenuation by adenosine deaminase (2 U/ml), which removes tonic A(1) inhibition, of the facilitatory effect of CGS 21680 on synaptic transmission. The requirement of tonic A(1) receptor activation for CGS 21680 to induce facilitation of synaptic transmission was reinforced by the observation that the A(1) receptor antagonist, 1, 3-dipropyl-8-cyclopentylxanthine (20 nM) prevented CGS 21680 (10 nM) facilitation of population spike amplitude. The present results show the ability of A(2A) receptors to control A(1) receptor function in a manner mediated by protein kinase C, but not protein kinase A, in young adult but not in aged rats.

ZM 241385, an adenosine A(2A) receptor antagonist, inhibits hippocampal A(1) receptor responses.

4-(2-[7-amino-2-(2-furyl¿1,2,4¿-triazolo¿2,3a¿-¿1,3, 5¿triazin-5-yl-amino]ethyl)phenol (ZM 241385) has been used as an antagonist of adenosine A(2A) receptors, exhibiting high selectivity over adenosine A(1) receptors. We now report that ZM 241385 (10-50 nM) attenuated the inhibitory action of N(6)-cyclopentyladenosine (10 nM) and R(-)-N(6)-phenylisopropyladenosine (R-PIA, 20 nM), two selective adenosine A(1) receptor agonists, on hippocampal population spike amplitude. This effect is unlikely to be a direct antagonism of adenosine A(1) receptor since the K(i) of ZM 241385 to displace [3H]PIA (2 nM) binding, from hippocampal membranes ranged from 0.8 to 1.9 microM. These results question the usefulness of ZM 241385 to define adenosine A(2A) receptors actions in functional studies.

Increase in the number, G protein coupling, and efficiency of facilitatory adenosine A2A receptors in the limbic cortex, but not striatum, of aged rats.

Adenosine's effects result from a balanced activation of inhibitory A1 and facilitatory A2A receptors. Because in aged animals there is an increased number of A2A receptors, we now compared the efficiency of A2A receptors in cortical and striatal preparations of young adult (6-week-old) and aged (2-year-old) rats. In cortical, in contrast to striatal, membranes from aged rats, A2A receptors were more tightly coupled to G proteins, because 5'-guanylylimidodiphosphate (100 microM) increased by 321% the Ki of the A2A agonist CGS21680 as a displacer of binding of the A2A antagonist [3H]ZM241385 (1 nM), compared with a 112% increase in young rats. In cortical slices, CGS21680 (30-1,000 nM) was virtually devoid of effect on cyclic AMP accumulation in young rats but increased cyclic AMP accumulation with an EC50 of 153 nM in aged rats, whereas the efficiency of CGS21680 was similar in striatal slices of young and aged rats. CGS21680 (30 nM) was virtually devoid of effect on acetylcholine release from hippocampal CA1 slices of young rats but caused a 55% facilitation in aged rats. These results show that the number of A2A receptors, their coupling to G proteins, and their efficiency are enhanced in the limbic cortex of aged rats, suggesting a greater involvement of facilitation in adenosine responses.

alpha-Interferon therapy for HBV-related glomerulonephritis.

We report a case of a patient with hepatitis B virus (HBV)-related membranous glomerulonephritis (MGN) who showed improvement after interferon-alpha (IFN-alpha) therapy. A 35-year-old man with nephrotic syndrome and HBV antigens received a 24-week course of IFN-alpha. At the end of therapy there was an elevation in the level of plasma aminotransferase and an increase in proteinuria, which were followed by antigen/antibody seroconversion. This "flare-up" before seroconversion suggests an increase in disease activity in the liver and kidney, demonstrating in vivo HBV involvement in MGN.