Antiretroviral agents as inhibitors of both human immunodeficiency virus type 1 integrase and protease

Testosterone 5alpha-reductase inhibitor bisnaphthoquinone derivative from Impatiens balsamina

The 35% EtOH extract of aerial parts of Impatiens balsamina L. has been investigated for activity against testosterone 5alpha-reductase. Activity-guided fractionation led to the identification of the bisnaphthquione derivative named impatienol (1), 3-hydroxy-2-¿[3-hydroxy-1,4-dioxo (2-naphthyl)] ethyl¿ naphthalene-1, 4-dione, which exhibited significant testosterone 5alpha-reductase inhibitory activity. This 5alpha-reductase inhibitory compound has been previously synthesized, but this is the first report of its isolation from a natural source.

Curcumin inhibits Th1 cytokine profile in CD4+ T cells by suppressing interleukin-12 production in macrophages

1 Interleukin-12 (IL-12) plays a central role in the immune system by driving the immune response towards T helper 1 (Th1) type responses which are characterized by high IFN-gamma and low IL-4 production. In this study we investigated the effects of curcumin, a natural product of plants obtained from Curcuma longa (turmeric), on IL-12 production by mouse splenic macrophages and the subsequent ability of these cells to regulate cytokine production by CD4+ T cells. 2 Pretreatment with curcumin significantly inhibited IL-12 production by macrophages stimulated with either lipopolysaccharide (LPS) or head-killed Listeria monocytogenes (HKL). 3 Curcumin-pretreated macrophages reduced their ability to induce IFN-gamma and increased the ability to induce IL-4 in Ag-primed CD4+ T cells. Addition of recombinant IL-12 to cultures of curcumin-pretreated macrophages and CD4+ T cells restored IFN-gamma production in CD4+ T cells. 4 The in vivo administration of curcumin resulted in the inhibition of IL-12 production by macrophages stimulated in vitro with either LPS or HKL, leading to the inhibition of Th1 cytokine profile (decreased IFN-gamma and increased IL-4 production) in CD4+ T cells. 5 These findings suggest that curcumin may inhibit Th1 cytokine profile in CD4+ T cells by suppressing IL-12 production in macrophages, and points to a possible therapeutic use of curcumin in the Th1-mediated immune diseases.

Inhibitors of human immunodeficiency virus integrase

Integration of the viral DNA into a host cell chromosome is an essential step for HIV replication and maintenance of persistent infection. Two viral factors are essential for integration: the viral DNA termini (the att sites) and IN. Accruing knowledge of the IN structure, catalytic mechanisms, and interactions with other proteins can be used to design strategies to block integration. A large number of inhibitors have been identified that can be used as leads for the development of potent and selective anti-IN drugs with antiviral activity.

Diversity analysis of 14 156 molecules tested by the National Cancer Institute for anti-HIV activity using the quantitative structure-activity relational expert system MCASE

Using the MCASE program, a procedure to analyze the diversity of the large amount of available HIV-1 antiviral data was proposed. A subset of 1 819 chemicals was logically selected from the original 14 156 chemicals tested by NCI. This subset of chemicals was shown to contain most of the structural and the functional information of the original database. A full analysis of the 1 819 chemicals by the MCASE program produced a correlation between chemical structures and HIV antiviral activity. In our model, 74 fragments were identified as being responsible for all the chemical's HIV antiviral activity. These fragments may be related to different inhibiting mechanisms, some known and some probably still unknown. The expert system resulting from this analysis can be used to predict the activity of new chemicals and to design new agents that can target multiple enzymes. This was shown to be the case by using the model to predict the activity of 10 diverse chemicals whose activities were not known at the time of model development. Of these, 8 were predicted in agreement with experimental observations. As far as we can tell, this is probably the first project ever to attempt to create a quantitative model of activity for such a massive database of diverse chemicals.

Structure-activity relationships: analogues of the dicaffeoylquinic and dicaffeoyltartaric acids as potent inhibitors of human immunodeficiency virus type 1 integrase and replication

The dicaffeoylquinic acids (DCQAs) and dicaffeoyltartaric acids (DCTAs) are potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) integrase. They also inhibit HIV-1 replication at nontoxic concentrations. Since integrase is an excellent target for anti-HIV therapy, structure-activity relationships were employed to synthesize compounds with: (1) improved potency against HIV-1 integrase, (2) improved anti-HIV effect in tissue culture, and (3) increased selectivity as indicated by low cellular toxicity. Thirty-four analogues of the DCTAs and DCQAs were synthesized and tested for cell toxicity, anti-HIV activity, and inhibition of HIV-1 integrase. Seventeen of the 34 analogues had potent activity against HIV-1 integrase ranging from 0. 07 to >10 microM. Seventeen analogues that were synthesized or purchased had no inhibitory activity against integrase at concentrations of 25 microM. Of the biologically active analogues, 7 of the 17 inhibited HIV replication at nontoxic concentrations. The most potent compounds were D-chicoric acid, meso-chicoric acid, bis(3,4-dihydroxydihydrocinnamoyl)-L-tartaric acid, digalloyl-L-tartaric acid, bis(3,4-dihydroxybenzoyl)-L-tartaric acid, dicaffeoylglyceric acid, and bis(3, 4-dihydroxyphenylacetyl)-L-tartaric acid. Anti-HIV activity of the active compounds in tissue culture ranged from 35 to 0.66 microM. Structure-activity relationships demonstrated that biscatechol moieties were absolutely required for inhibition of integrase, while at least one free carboxyl group was required for anti-HIV activity. These data demonstrate that analogues of the DCTAs and the DCQAs can be synthesized which have improved activity against HIV integrase.

The inhibition of the estrogenic effects of pesticides and environmental chemicals by curcumin and isoflavonoids

Many environmental chemicals and pesticides have been found to be estrogenic and have been shown to stimulate the growth of estrogen receptor-positive (ER-positive) human breast cancer cells. Since it is difficult to avoid human exposure to environmental estrogens, a potentially important area of research is the development of dietary strategies to prevent the stimulated growth of breast tumors by environmental estrogens. In this context, the inhibitory action of curcumin and a combination of curcumin and isoflavonoids were studied in ER-positive human breast cancer cells (MCF-7 and T47D) and ER-negative MDA-MB-231 cells induced by the pesticide o,p'-DDT and the environmental pollutants 4-nonylphenol and 4-octylphenol. The median inhibitory concentration (IC50) for curcumin in T47D cells was 10 microM when measured at either a 48-hr or a 6-day incubation time. The IC50 value for curcumin was within the 8-10 microM range for inhibiting the growth of T47D cells induced by a 10- microM concentration each of 4-nonylphenol, 4-octylphenol, and o, p'-DDT. The IC50 for curcumin in MCF-7 cells induced by 10 microM of either o,p'-DDT, 4-octylphenol, or 4-nonylphenol were 9, 39, and >50 microM, respectively. A combination of curcumin and isoflavonoids was able to inhibit the induced growth of ER-positive cells up to 95%. For MDA-MB-231 cells, the IC50 for curcumin was 17 microM, which was reduced to 11 microM in the presence of 25 microM genistein. Curcumin and genistein induce drastic changes in the morphological shape of both ER-positive and ER-negative cells. Data presented here indicate that a mixture of curcumin and isoflavonoids is the most potent inhibitor against the growth of human breast tumor cells. These data suggest that combinations of natural plant compounds may have preventive and therapeutic applications against the growth of breast tumors induced by environmental estrogens.

Highly potent synthetic polyamides, bisdistamycins, and lexitropsins as inhibitors of human immunodeficiency virus type 1 integrase

Alignment of the available human immunodeficiency virus type 1 (HIV-1) viral DNA termini [U5 and U3 long terminal repeats (LTRs)] shows a high degree of conservation and the presence of a stretch of five or six consecutive adenine and thymine (AT) sequences approximately 10 nucleotides away from each LTR end. A series of AT-selective minor-groove binders, including distamycin and bisdistamycins, bisnetropsins, novel lexitropsins, and the classic monomeric DNA binders Hoechst 33258, 4'-diamino-2-phenylindole, pentamidine, berenil, spermine, and spermidine, were tested for their inhibitory activities against HIV-1 integrase (IN). Although netropsin, distamycin, and all other monomeric DNA binders showed weak activities in the range of 50-200 microM, some of the polyamides, bisdistamycins, and lexitropsins were remarkably active at nanomolar concentrations. Bisdistamycins were 200 times less potent when the conserved AAAAT stretch present in the U5 LTR was replaced with GGGGG, consistent with the preferred binding of these drugs to AT sequences. DNase I footprinting of the U5 LTR further demonstrated the selectivity of these bisdistamycins for the conserved AT sequence. The tested compounds were more potent in Mg+2 than in Mn+2 and inhibited IN50-212 deletion mutant in disintegration assays and the formation of IN/DNA complexes. The lexitropsins also were active against HIV-2 IN. Some of the synthetic polyamides exhibited significant antiviral activity. Taken together, these data suggest that selective targeting of the U5 and U3 ends of the HIV-1 LTRs can inhibit IN function. Polyamides might represent new leads for the development of antiviral agents against acquired immune deficiency syndrome.

Potent inhibitors of human immunodeficiency virus type 1 integrase: identification of a novel four-point pharmacophore and tetracyclines as novel inhibitors

A four-point pharmacophore was constructed from energy-minimized structures of chicoric acid and dicaffeoylquinic acid. The search of 206,876 structures in the National Cancer Institute 3D database yielded 179 compounds that contain this pharmacophore. Thirty-nine of these compounds were tested in an in vitro assay specific for human immunodeficiency virus type 1 integrase (IN). Each retrieved structure was fit to the pharmacophore, and the conformation that afforded the best fit was identified. Twenty of the 39 compounds tested exhibited IC50 values of < 20 microM. Among the most potent inhibitors, tetracyclines emerged as a new class of inhibitors. Although the parent tetracycline exhibited marginal potency against purified IN, all substituted tetracyclines tested showed 5-100-fold increased potency. Disintegration assays with truncated IN mutants indicated that tetracyclines inhibit the IN catalytic core domain. To investigate whether chelation of divalent metals is implicated in differential potency of tetracyclines, enzyme assays were performed in the presence of both Mn2+ or Mg2+; no significance difference in potency was observed. Rolitetracycline inhibited IN/DNA complex formation in the presence of EDTA, which suggests that inhibition was metal independent. Rolitetracycline reversed DNA binding of IN after the complex was allowed to form before the addition of drug. Selectivity of tetracyclines was also examined in an assay specific for topoisomerase I, and none of the tetracyclines tested induced topoisomerase I-mediated cleavable complex or inhibited camptothecin-induced cleavable complex. Remarkable potency against the IN in the absence of divalent metals and the core enzyme coupled with water solubility makes tetracyclines potential candidates for X-ray crystal structure determination with IN.

Curcumin analogs with altered potencies against HIV-1 integrase as probes for biochemical mechanisms of drug action

We have previously reported the inhibitory activity of curcumin against human immunodeficiency virus type one (HIV-1) integrase. In the present study, we have synthesized and tested analogs of curcumin to explore the structure-activity relationships and mechanism of action of this family of compounds in more detail. We found that two curcumin analogs, dicaffeoylmethane (6) and rosmarinic acid (9), inhibited both activities of integrase with IC50 values below 10 microM. We have previously demonstrated that lysine 136 may play a role in viral DNA binding. We demonstrated equivalent potencies of two curcumin analogs against both this integrase mutant and wild-type integrase, suggesting that the curcumin-binding site and the substrate-binding site may not overlap. Combining one curcumin analog with the recently described integrase inhibitor NSC 158393 resulted in integrase inhibition which was synergistic, reflective of drug-binding sites which may not overlap. We have also determined that these analogs can inhibit binding of the enzyme to the viral DNA but that this inhibition is independent of divalent metal ion. Furthermore, kinetic studies of these analogs suggest that they bind to the enzyme at a slow rate. These studies can provide mechanistic and structural information which may guide the future design of integrase inhibitors.

Curcumin and genistein, plant natural products, show synergistic inhibitory effects on the growth of human breast cancer MCF-7 cells induced by estrogenic pesticides

Curcumin and genistein are two natural products of plants obtained from Curcuma longa Linn (turmeric) and soybeans, respectively. Both compounds when present at micromolar concentrations are able to inhibit the growth of estrogen-positive human breast MCF-7 cells induced individually or by a mixture of the pesticides endosulfane, DDT and chlordane or 17-beta estradiol. When curcumin and genistein were added together to MCF-7 cells, a synergistic effect resulting in a total inhibition of the induction of MCF-7 cells by the highly estrogenic activity of endosulfane/chlordane/DDT mixtures was noted. These data suggest that the combination of curcumin and genistein in the diet have the potential to reduce the proliferation of estrogen-positive cells by mixtures of pesticides or 17-beta estradiol. Since it is difficult to remove pesticides completely from the environment or the diet and since both turmeric and soybeans are not toxic to humans, their inclusion in the diet in order to prevent hormone related cancers deserves consideration.

Discovery of HIV-1 integrase inhibitors by pharmacophore searching

Based upon a class of known HIV-1 integrase inhibitors, several pharmacophore models were proposed from molecular modeling studies and validated using a 3D database of 152, compounds for which integrase assay data are known. Using the most probable pharmacophore model as the query, the NCI 3D database of 206,876 compounds was searched, and 340 compounds that contain the pharmacophore query were identified. Twenty-nine of these compounds were selected and tested in the HIV-1 integrase assay. This led to the discovery of 10 novel, structurally diverse HIV-1 integrase inhibitors, four of which have an IC50 value less than 30 microM and are promising lead compounds for further HIV-1 integrase inhibitor development.

HIV-1 integrase pharmacophore: discovery of inhibitors through three-dimensional database searching

Starting from a known inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase (IN); caffeic acid phenethyl ester (CAPE), a putative three-point pharmacophore for binding of inhibitors to IN was derived. This pharmacophore was used to search the National Cancer Institute three-dimensional (3D) structural database. Out of the open, nonproprietary part of this database, comprising approximately 200000 compounds, 267 structures were found to match the pharmacophore in at least one conformation, and 60 of those were tested in an in vitro assay against HIV-1 IN. Out of these, 19 were found to inhibit both the 3'-processing and strand transfer of IN at micromolar concentrations. In order to test the validity of this pharmacophore, a small 3D database of 152 published IN inhibitors was built. A search in this database yielded a statistically significant correlation of the presence of this pharmacophore and the potency of the compounds. An automated pharmacophore identification procedure performed on this set of compounds provided additional support for the importance of this pharmacophore for binding of inhibitors to IN and hinted at a possible second pharmacophore. The role of aromatic moieties in the binding of ligands to HIV-1 IN through interactions with divalent metal cations, which are known to be necessary for activity of the enzyme, was explored in ab initio calculations.

Depsides and depsidones as inhibitors of HIV-1 integrase: discovery of novel inhibitors through 3D database searching

Seventeen lichen acids comprising despides, depsidones, and their synthetic derivatives have been examined for their inhibitory activity against HIV-1 integrase, and two pharmacophores associated with inhibition of this enzyme have been identified. A search of the NCI 3D database of approximately 200,000 structures yielded some 800 compounds which contain one or the other pharmacophore. Forty-two of these compounds were assayed for HIV-1 integrase inhibition, and of these, 27 had inhibitory IC50 values of less than 100 microM; 15 were below 50 microM. Several of these compounds were also examined for their activity against HIV-2 integrase and mammalian topoisomerase I.

Diarylsulfones, a novel class of human immunodeficiency virus type 1 integrase inhibitors

A majority of reported human immunodeficiency virus type 1 integrase (HIV-1 IN) inhibitors are polyhydroxylated aromatic compounds containing two phenyl rings separated by aliphatic or aromatic linkers. Most inhibitors possessing a catechol moiety exhibit considerable toxicity in cellular assays. In an effort to identify nonhydroxylated analogs, a series of aromatic sulfones were tested for their ability to inhibit the 3' processing and strand transfer steps that are necessary for HIV replication. Several aromatic sulfones have previously been shown to have moderate activity against HIV-1 reverse transcriptase in cellular assays; however, their inhibitory potencies against IN have not been explored. In the present study, the inhibitory effect of a series of sulfones and sulfonamides against IN was determined. Among 52 diaryl sulfones tested, 4 were determined to be highly potent (50% inhibitory concentration [IC50], 0.8 to 10 micrograms/ml), 5 had good potencies (IC50, 11 to 50 micrograms/ml), 10 showed moderate potencies (IC50, 51 to 100 micrograms/ml), and 33 were inactive (IC50, > 100 micrograms/ml) against IN. All of the active compounds exhibited similar potencies against HIV-2 IN. Sulfa drugs, used extensively in treating Pneumocystis carinii pneumonia, a leading cause of morbidity and mortality in AIDs patients, were also examined. Among 19 sulfonamides tested, sulfasalazine (IC50, 50 micrograms/ml) was the most potent. We conclude that potent inhibitors of IN can be designed based on the results presented in this study.

Coumarin-based inhibitors of HIV integrase

The structures of a large number of HIV-1 integrase inhibitors have in common two aryl units separated by a central linker. Frequently at least one of these aryl moieties must contain 1,2-dihydroxy substituents in order to exhibit high inhibitory potency. The ability of o-dihydroxy-containing species to undergo in situ oxidation to reactive quinones presents a potential limitation to the utility of such compounds. The recent report of tetrameric 4-hydroxycoumarin-derived inhibitor 5 provided a lead example of an inhibitor which does not contain the catechol moiety. Compound 5 represents a large, highly complex yet symmetrical molecule. It was the purpose of the present study to determine the critical components of 5 and if possible to simplify its structure while maintaining potency. In the present study, dissection of tetrameric 5 (IC50 = 1.5 microM) into its constituent parts showed that the minimum active pharmacophore consisted of a coumarin dimer containing an aryl substituent on the central linker methylene. However, in the simplest case in which the central linker aryl unit consisted of a phenyl ring (compound 8, IC50 = 43 microM), a significant reduction in potency resulted by removing two of the original four coumarin units. Replacement of this central phenyl ring by more extended aromatic systems having higher lipophilicity improved potency, as did the addition of 7-hydroxy substituents to the coumarin rings. Combining these latter two modifications resulted in compounds such as 3,3'-(2-naphthalenomethylene)bis[4,7-dihydroxycoumarin] (34, IC50 = 4.2 microM) which exhibited nearly the full potency of the parent tetramer 5 yet were structurally much simpler.

Chemical trapping of ternary complexes of human immunodeficiency virus type 1 integrase, divalent metal, and DNA substrates containing an abasic site. Implications for the role of lysine 136 in DNA binding

We report a novel assay for monitoring the DNA binding of human immunodeficiency virus type 1 (HIV-1) integrase and the effect of cofactors and inhibitors. The assay uses depurinated oligonucleotides that can form a Schiff base between the aldehydic abasic site and a nearby enzyme lysine epsilon-amino group which can subsequently be trapped by reduction with sodium borohydride. Chemically depurinated duplex substrates representing the U5 end of the HIV-1 DNA were initially used. We next substituted an enzymatically generated abasic site for each of 10 nucleotides normally present in a 21-mer duplex oligonucleotide representing the U5 end of the HIV-1 DNA. Using HIV-1, HIV-2, or simian immunodeficiency virus integrases, the amount of covalent enzyme-DNA complex trapped decreased as the abasic site was moved away from the conserved CA dinucleotide. The enzyme-DNA complexes formed in the presence of manganese were not reversed by subsequent addition of EDTA, indicating that the divalent metal required for integrase catalysis is tightly bound in a ternary enzyme-metal-DNA complex. Both the N- and C-terminal domains of integrase contributed to efficient DNA binding, and mutation of Lys-136 significantly reduced Schiff base formation, implicating this residue in viral DNA binding.