Inhibition of HIV-2 protease by HIV-1 protease inhibitors in clinical use

Over the past 10 years, protease inhibitors have been a key component in antiretroviral therapies for HIV/AIDS. While the vast majority of HIV/AIDS cases in the world are due to HIV-1, HIV-2 infection must also be addressed. HIV-2 is endemic to Western Africa, and has also appeared in European countries such as Portugal, Spain, and Estonia. Current protease inhibitors have not been optimized for treatment of HIV-2 infection; therefore, it is important to assess the effectiveness of currently FDA-approved protease inhibitors against the HIV-2 protease, which shares only 50% sequence identity with the HIV-1 protease. Kinetic inhibition assays were performed to measure the inhibition constants (K(i)) of the HIV-1 protease inhibitors indinavir, nelfinavir, saquinavir, ritonavir, amprenavir, lopinavir, atazanavir, tipranavir, and darunavir against the HIV-2 protease. Lopinavir, saquinavir, tipranavir, and darunavir exhibit the highest potency with K(i) values of 0.7, 0.6, 0.45, and 0.17 nm, respectively. These K(i) values are 84, 2, 24, and 17 times weaker than the corresponding values against the HIV-1 protease. In general, inhibitors show K(i) ratios ranging between 2 and 80 for the HIV-2 and HIV-1 proteases. The relative drop in potency is proportional to the affinity of the inhibitor against the HIV-1 protease and is related to specific structural characteristics of the inhibitors. In particular, the potency drop is high when the maximum cap size of the inhibitors consists of very few atoms. Caps are groups located at the periphery of the molecule that are added to core structures to increase the specificity of the inhibitor to its target. The caps positioned on the HIV-1 protease inhibitors affect selectivity through interactions with distinct regions of the binding pocket. The flexibility and adaptability imparted by the higher number of rotatable bonds in large caps enables an inhibitor to accommodate changes in binding pocket geometry between HIV-1 and HIV-2 protease.     

Inhibition of HIV-1 infectivity with curdlan sulfate in vitro

Polymethoxylated flavones and C-glycosyl derivatives isolated from medicinal plants besides other flavonoid compounds were studied for their influence on lipid peroxidation induced by FeSO4+ cysteine in rat liver microsomes. A number of hydroxyflavones (e.g. luteolin); C-glycosyl-flavones (e.g. orientin); methoxyflavones (e.g. gardenin D) and flavonols (e.g. datiscetin), as well as the flavanol leucocyanidol and the biflavone amentoflavone behaved as inhibitors of non-enzymic lipid peroxidation. Structure-activity relationships were established and it was observed that the structural features for active polyhydroxylated compounds were different from those of polymethoxylated flavones, antiperoxidative flavonoids possessing a high lipophilicity.     

去甲斑蝥素体外抗HIV-1作用研究

为从天然产物中获得与现有药物作用机制不同、结构新颖的有效抗HIV-1化合物, 在细胞培养系统 及体外无细胞复制酶系统中进行抗HIV-1药物筛选。结果发现, 去甲斑蝥素 (NCTD) 在传代和原代淋巴细胞培养系统内抑制HIV-1实验室传代病毒株的p24抗原, 在人外周血单核细胞培养系统内对临床分离的AZT敏感病毒株和耐药病毒株也有抑制作用, 半数抑制浓度为1.8～20.2 μmol·L⁻¹, 在MT-4细胞培养系统内与AZT合用的联合指数<0.3, 具有明显的协同抗HIV-1作用, 但在体外NCTD对HIV-1逆转录酶、整合酶和蛋白酶均无抑制作用。由于NCTD结构简单, 不同于现有结构类型的抗HIV-1药物, 如经修饰改造并优化, 可望获得高效低毒的新型抗HIV-1化合物。     

七叶树皂苷和熊果酸类化合物对HIV—1蛋白酶活性抑制作用的初步研究*

目的:探讨七叶树皂苷和熊果酸及其衍生物对HIV-1蛋白酶活性的抑制作用,探讨构效关系。方法:采用体外实验法,将待测化合物、HIV-1蛋白酶基质与HIV-1蛋白酶在37℃共温育,根据HIV-1蛋白酶对其基质的水解强度计算待测化合物对HIV-1蛋白酶活性的抑制作用。结果:七叶树总皂苷、七叶树皂苷-Ia和七叶树皂苷-Ib混合物、异七叶树皂苷-Ia和异七叶树皂苷-Ib混合物、七叶树皂苷-Ia、全乙酰化七叶树皂苷-Ia、七叶树皂苷-Ib、熊果酸和乙酰熊果酸在100μmol.L-1浓度对HIV-1蛋白酶活性的抑制率分别为86%,89.9%,50.8%,100%,74.6%,89.3%,100%和100%。七叶树皂苷-Ia、全乙酰化七叶树皂苷-Ia、七叶树皂苷-Ib、熊果酸和乙酰熊果酸对HIV-1蛋白酶活性抑制作用的IC50分别为35,35,50,8和13μmol.L-1。阳性对照药乙酰胃酶抑素在本实验条件下的IC50为0.30μmo.lL-1。在100μmol.L-1浓度,七叶树皂苷-IVc,-IVd,-IVe,-IVf,异七叶树皂苷-Ia,-Ib,-IIa,-IIb,原七叶树皂苷元,21β-O-巴豆酰基原七叶树皂苷元,21β-O-当归酰基原七叶树皂苷元,2α-羟基熊果酸和委陵菜酸对HIV-1蛋白酶活性的抑制率<50%。结论:七叶树总皂苷、七叶树皂苷-Ia和七叶树皂苷-Ib混合物、异七叶树皂苷-Ia和异七叶树皂苷-Ib混合物、七叶树皂苷-Ia、全乙酰化七叶树皂苷-Ia、七叶树皂苷-Ib、熊果酸和乙酰熊果酸对HIV-1蛋白酶活性有抑制作用,最强者为七叶树皂苷-Ia、熊果酸和乙酰熊果酸。     

Nanoparticle Based Galectin-1 Gene Silencing, Implications in Methamphetamine Regulation of HIV-1 Infection in Monocyte Derived Macrophages

Galectin-1, an adhesion molecule, is expressed in macrophages and implicated in human immunodeficiency virus (HIV-1) viral adsorption. In this study, we investigated the effects of methamphetamine on galectin-1 production in human monocyte derived macrophages (MDM) and the role of galectin-1 in methamphetamine potentiation of HIV-1 infection. Herein we show that levels of galectin-1 gene and protein expression are significantly increased by methamphetamine. Furthermore, concomitant incubation of MDM with galectin-1 and methamphetamine facilitates HIV-1 infection compared to galectin-1 alone or methamphetamine alone. We utilized a nanotechnology approach that uses gold nanorod (GNR)-galectin-1 siRNA complexes (nanoplexes) to inhibit gene expression for galectin-1. Nanoplexes significantly silenced gene expression for galectin-1 and reversed the effects of methamphetamine on galectin-1 gene expression. Moreover, the effects of methamphetamine on HIV-1 infection were attenuated in the presence of the nanoplex in MDM.     

Inhibition of replication of primary HIV-1 isolates in huPBL-NOD/Scid mice by antibodies from HIV-1 infected patients

Although a limited number of HIV-infected patients have broadly neutralizing antibodies, it has not been examined whether these antibodies can protect against infection with primary virus in vivo. Here we screened the plasma of 23 HIV-1-infected patients for broadly neutralizing antibodies. Purified antibodies from subjects with broad and more narrow responses were administered to huPBL-NOD/Scid mice that were subsequently challenged with primary viruses of clade A, B and CRF01_AE. Although we observed a lack of correlation between the data from the in vitro neutralization assay and the results from the passive immunization experiments, we report for the first time that antibodies from HIV-infected persons can inhibit replication of primary virus isolates in an animal model.     

Voltage-gated Potassium Channel Modulation of Neurotoxic Activity in Human Immunodeficiency Virus Type-1(HIV-1)-Infected Macrophages

Macrophages play an important role in brain immune and inflammatory responses. They are also critical cells in mediating the pathology of neurodegenerative disorders such as HIV-associated dementia. This is largely through their capacity to secrete a variety of bioactive molecules such as cytokines, leading to neuronal dysfunction and/or death. Accumulating evidence indicates that voltage-gated potassium (Kv) channels play a pivotal role in the modulation of macrophage proliferation, activation, and secretion. Blockade of Kv channels by specific antagonists decreases macrophage cytokine production and ameliorates macrophage-associated neuronal injury. These results suggest that Kv channels might become a potential target for the development of new therapeutic strategies for chronic inflammatory diseases.     

Nanoformulated Antiretroviral Drug Combinations Extend Drug Release and Antiretroviral Responses in HIV-1-Infected Macrophages: Implications for NeuroAIDS Therapeutics

We posit that improvements in pharmacokinetics and biodistributions of antiretroviral therapies (ART) for human immunodeficiency virus type one-infected people can be achieved through nanoformulationed drug delivery systems. To this end, we manufactured nanoparticles of atazanavir, efavirenz, and ritonavir (termed nanoART) and treated human monocyte-derived macrophages (MDM) in combination therapies to assess antiretroviral responses. This resulted in improved drug uptake, release, and antiretroviral efficacy over monotherapy. MDM rapidly, within minutes, ingested nanoART combinations, at equal or similar rates, as individual formulations. Combination nanoART ingested by MDM facilitated individual drug release from 15 to >20 days. These findings are noteworthy as a nanoART cell-mediated drug delivery provides a means to deliver therapeutics to viral sanctuaries, such as the central nervous system during progressive human immunodeficiency virus type one infection. The work brings us yet another step closer to realizing the utility of nanoART for virus-infected people.     

HIV-1 Viral Protein R Activates NLRP3 Inflammasome in Microglia: implications for HIV-1 Associated Neuroinflammation

Human Immunodeficiency virus (HIV) enters the brain soon after seroconversion and induces chronic neuroinflammation by infecting and activating brain macrophages. Inflammasomes are cytosolic protein complexes that mediate caspase-1 activation and ensuing cleavage and release of IL-1β and ?18 by macrophages. Our group recently showed that HIV-1 infection of human microglia induced inflammasome activation in NLRP3-dependent manner. The HIV-1 viral protein R (Vpr) is an accessory protein that is released from HIV-infected cells, although its effects on neuroinflammation are undefined. Infection of human microglia with Vpr-deficient HIV-1 resulted in reduced caspase-1 activation and IL-1β production, compared to cells infected with a Vpr-encoding HIV-1 virus. Vpr was detected at low nanomolar concentrations in cerebrospinal fluid from HIV-infected patients and in supernatants from HIV-infected primary human microglia. Exposure of human macrophages to Vpr caused caspase-1 cleavage and IL-1β release with reduced cell viability, which was dependent on NLRP3 expression. Increased NLRP3, caspase-1, and IL-1β expression was evident in HIV-1 Vpr transgenic mice compared to wild-type littermates, following systemic immune stimulation. Treatment with the caspase-1 inhibitor, VX-765, suppressed NLRP3 expression with reduced IL-1β expression and associated neuroinflammation. Neurobehavioral deficits showed improvement in Vpr transgenic animals treated with VX-765. Thus, Vpr-induced NLRP3 inflammasome activation, which contributed to neuroinflammation and was abrogated by caspase-1 inhibition. This study provides a new therapeutic perspective for HIV-associated neuropsychiatric disease.     

Preincubation With Everolimus and Sirolimus Reduces Organic Anion-Transporting Polypeptide (OATP)1B1- and 1B3-Mediated Transport Independently of mTOR Kinase Inhibition: Implication in Assessing OATP1B1- and OATP1B3-Mediated Drug-Drug Interactions

Organic anion transporting polypeptides (OATP)1B1 and OATP1B3 mediate hepatic uptake of many drugs including lipid-lowering statins. Current studies determined the OATP1B1/1B3-mediated drug-drug interaction (DDI) potential of mammalian target of rapamycin (mTOR) inhibitors, everolimus and sirolimus, using R-value and physiologically based pharmacokinetic models. Preincubation with everolimus and sirolimus significantly decreased OATP1B1/1B3-mediated transport even after washing and decreased inhibition constant values up to 8.3- and 2.9-fold for OATP1B1 and both 2.7-fold for OATP1B3, respectively. R-values of everolimus, but not sirolimus, were greater than the FDA-recommended cutoff value of 1.1. Physiologically based pharmacokinetic models predict that everolimus and sirolimus have low OATP1B1/1B3-mediated DDI potential against pravastatin. OATP1B1/1B3-mediated transport was not affected by preincubation with INK-128 (10 μM, 1 h), which does however abolish mTOR kinase activity. The preincubation effects of everolimus and sirolimus on OATP1B1/1B3-mediated transport were similar in cells before preincubation with vehicle control or INK-128, suggesting that inhibition of mTOR activity is not a prerequisite for the preincubation effects observed for everolimus and sirolimus. Nine potential phosphorylation sites of OATP1B1 were identified by phosphoproteomics; none of these are the predicted mTOR phosphorylation sites. We report the everolimus/sirolimus-preincubation-induced inhibitory effects on OATP1B1/1B3 and relatively low OATP1B1/1B3-mediated DDI potential of everolimus and sirolimus.     

Macrophages but not Astrocytes Harbor HIV DNA in the Brains of HIV-1-Infected Aviremic Individuals on Suppressive Antiretroviral Therapy

Journal of Neuroimmune Pharmacology - The question of whether the human brain is an anatomical site of persistent HIV-1 infection during suppressive antiretroviral therapy (ART) is critical, but...     

Inhibition of the CYP3A4-mediated metabolism and P-glycoprotein-mediated transport of the HIV-1 protease inhibitor saquinavir by grapefruit juice components

AIMS: Cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp) are both expressed in the intestinal mucosa and present a barrier to oral drug delivery. CYP3A4 and P-gp share both overlapping tissue distribution and substrate specificity. Grapefruit juice interactions with CYP3A4 substrates are well documented and occur as a consequence of down regulation of intestinal CYP3A4. The aim of the present study was to screen grapefruit juice components against the CYP3A4-mediated metabolism and P-gp mediated transport of the HIV-1 protease inhibitor saquinavir. METHODS: Five grapefruit juice components: quercetin, naringin, naringenin, 6', 7'-dihydroxybergamottin and bergamottin were screened as potential inhibitors of the metabolism of saquinavir by human liver microsomes. The known CYP3A4 inhibitor ketoconazole was also screened for inhibitory potential. These compounds were also screened as modulators of P-gp activity by assessing the directional transport of saquinavir across Caco-2 cell monolayers which express P-gp. The effect of verapamil, a known modulator of P-gp function, was also determined in these cell lines. RESULTS: On preincubation, 6', 7'-dihydroxybergamottin and bergamottin inhibited the metabolism of saquinavir, with IC50 values of 0.33+/-0.23 muM and 0.74+/-0.13 muM, respectively (n=3). Ketoconazole achieved an IC50 of 0. 55+/-0.12 muM (n=4). The other compounds studied failed to reach IC50 at concentrations of up to 100 muM. The transport of saquinavir in the basolateral-->apical (BL-->AP) direction exceeded that in the apical -->basolateral direction (AP-->BL), with apparent permeability coefficients of 199.2+/-15.8x10-7 cm s-1 and 8.00+/-1. 13x10-7 cm s-1, respectively (n=3) which is indicative of a polarized efflux mechanism. The ratio of BL-->AP/AP-->BL for saquinavir was 25, but in the presence of verapamil and ketoconazole this ratio was reduced to 3.6 and 4.0, respectively (n=3), indicating extensive inhibition of P-gp mediated saquinavir efflux. Of the grapefruit juice components studied only naringin and 6', 7'-dihydroxybergamottin had any appreciable effect, reducing the ratio to 7.6 and 7.1, respectively (n=3); but this was due solely to increased AP-->BL transport. CONCLUSIONS: Grapefruit juice components inhibit CYP3A4-mediated saquinavir metabolism and also modulate, to a limited extent, P-gp mediated saquinavir transport in Caco-2 cell monolayers. The in vivo effects of grapefruit juice coadministration are most likely the result of effects on CYP3A4 (inhibition and down regulation) and only to a minor extent on modulation of P-gp function.