Traditional and contemporary herbal medicines in management of cancer: A scoping review.

BACKGROUND: Cancer is one of the leading causes of death worldwide and is primarily managed by chemotherapy, radiation and surgery. Traditional medicine is widely used worldwide due to availability, affordability, wide applicability and accessibility. While potential for traditional medicines in management of cancer is well-documented, there is limited literature that collates traditional knowledge and contemporary herbal medicine practice. To collate available evidence on herbal medicines used in the management of all cancers from traditional world-wide sources, and the management of lung and colorectal cancers in contemporary practice. Medicinal plants with anti-cancer properties were identified following JBI methodology for scoping reviews through searches of the following sources: Trove, Archive.Org, and Henriette's herbal medicine page (traditional texts), book list available from World Naturopathic Federation white paper (contemporary naturopathic texts), and in PubMed, MEDLINE, SCOPUS, ScienceDirect, AMED and JSTOR (case studies). Of the 1973 citations retrieved, 38 traditional texts, 3 contemporary naturopathic texts and 10 case studies were included in the review. The traditional texts (n = 110) noted the highest number of different anti-cancer herbal species, followed by case reports (n = 52) and contemporary texts (n = 13). This review identified various herbal medicines used to treat cancer traditionally which is distinct to those found in contemporary use. Moreover, this review identified the use of herbs from other native medical systems around the world in the contemporary naturopathic practice and individual case management. The evidence presented in the review could be utilized in pre-clinical settings to research traditional preparations of herbs.

Characterization of RFLP probe sequences for gene discovery and SSR development in Sorghum bicolor (L.) Moench.

In this study, we collected and analyzed DNA sequence data for 789 previously mapped RFLP probes from Sorghum bicolor (L.) Moench. DNA sequences, comprising 894 non-redundant contigs and end sequences, were searched against three GenBank databases, nucleotide (nt), protein (nr) and EST (dbEST), using BLAST algorithms. Matching ESTs were also searched against nt and nr. Translated DNA sequences were then searched against the conserved domain database (CDD) to determine if functional domains/motifs were congruent with the proteins identified in previous searches. More than half (500/894 or 56%) of the query sequences had significant matches in at least one of the GenBank searches. Overall, proteins identified for 148 sequences (17%) were consistent among all searches, of which 66 sequences (7%) contained congruent coding domains. The RFLP probe sequences were also evaluated for the presence of simple sequence repeats (SSRs) and 60 SSRs were developed and assayed in an array of sorghum germplasm comprising inbreds, landraces and wild relatives. Overall, these SSR loci had lower levels of polymorphism ( D = 0.46, averaged over 51 polymorphic loci) compared with sorghum SSRs that were isolated by library hybridization screens ( D = 0.69, averaged over 38 polymorphic loci). This result was probably due to the relatively small proportion of di-nucleotide repeat-containing markers (42% of the total SSR loci) obtained from the DNA sequence data. These di-nucleotide markers also contained shorter repeat motifs than those isolated from genomic libraries. Based on BLAST results, 24 SSRs (40%) were located within, or near, previously annotated or hypothetical genes. We determined the location of 19 of these SSRs relative to putative coding regions. In general, SSRs located in coding regions were less polymorphic ( D = 0.07, averaged over three loci) than those from gene flanking regions, UTRs and introns ( D = 0.49, averaged over 16 loci). The sequence information and SSR loci generated through this study will be valuable for application to sorghum genetics and improvement, including gene discovery, marker-assisted selection, diversity and pedigree analyses, comparative mapping and evolutionary genetic studies.

Role of taurine in regulation of intracellular calcium level and neuroprotective function in cultured neurons.

Glutamate-induced excitotoxicity has been implicated as an important mechanism underlying a variety of brain injuries and neurodegenerative diseases. Previously we have shown that taurine has protective effects against glutamate-induced neuronal injury in cultured neurons. Here we propose that the primary underlying mechanism of the neuroprotective function of taurine is due to its action in preventing or reducing glutamate-induced elevation of intracellular free calcium, [Ca(2+)](i). This hypothesis is supported by the following findings. First, taurine transport inhibitors, e.g., guanidinoethyl sulfonate and beta-alanine, have no effect on taurine's neuroprotective function, suggesting that taurine protects against glutamate-induced neuronal damage through its action on the extracellular membranes. Second, glutamate-induced elevation of [Ca(2+)](i) is reduced to the basal level upon addition of taurine. Third, pretreatment of cultured neurons with taurine prevents or greatly suppresses the elevation of [Ca(2+)](i) induced by glutamate. Furthermore, taurine was found to inhibit the influx but not the efflux of (45)Ca(2+) in cultured neurons. Taurine has little effect on the binding of [(3)H]glutamate to the agonist binding site and of [(3)H]MDL 105,519 to the glycine binding site of the N-methyl-D-aspartic acid receptors, suggesting that taurine inhibits (45)Ca(2+) influx through other mechanisms, including its inhibitory effect on the reverse mode of the Na(+)/Ca(2+) exchangers (Wu et al. [2000] In: Taurine 4: taurine and excitable tissues. New York: Kluwer Academic/Plenum Publishers. p 35-44) rather than serving as an antagonist to the N-methyl-D-aspartic acid receptors.

Oxygen-induced seizures and inhibition of human glutamate decarboxylase and porcine cysteine sulfinic acid decarboxylase by oxygen and nitric oxide.

The recombinant forms of the two human isozymes of glutamate decarboxylase, GAD65 and GAD67, are potently and reversibly inhibited by molecular oxygen (Ki = 0.46 and 0.29 mM, respectively). Inhibition of the vesicle-associated glutamate decarboxylase (GAD65) by molecular oxygen is likely to result in incomplete filling of synaptic vesicles with gamma-aminobutyric acid (GABA) and may be a contributing factor in the genesis of oxygen-induced seizures. Under anaerobic conditions, nitric oxide inhibits both GAD65 and GAD67 with comparable potency to molecular oxygen (Ki = 0.5 mM). Two forms of porcine cysteine sulfinic acid decarboxylase (CSADI and CSADII) are also sensitive to inhibition by molecular oxygen (Ki = 0.30 and 0.22 mM, respectively) and nitric oxide (Ki = 0.3 and 0.2 mM, respectively). Similar inhibition of glutamate decarboxylase and cysteine sulfinic acid decarboxylase by two different radical-containing compounds (O2 and NO) is consistent with the notion that these reactions proceed via radical mechanisms.

Direct synthesis of previously inaccessible bridgehead azabicyclics by intramolecular cyclization of alpha-sulfonamido and alpha-sulfonimido radicals.

Syntheses of the first bridgehead sultams and the only known bridgehead disulfonimide are described. Both approaches capitalize on the electrophilicity of alpha-sulfonyl radicals and their propensity to undergo intramolecular ring closure. Where double bonds are concerned, 5-exo and 6-exo pathways operate preferentially as long as structural strain is not excessive. When the reaction center is a carbon-carbon triple bond, the first cyclization gives rise to vinyl radicals that hold sufficient reactivity to capture solvent benzene. In the case of 45, this sequential reaction leads importantly to the introduction of a styrene functionality sufficiently activated to allow a second ring closure to be kinetically feasible. The solid-state structural features of 12 and 17 have been elucidated by X-ray crystallographic methods. Despite key differences from the norm in the alignment of the nitrogen lone pair relative to the adjacent sulfonyl groups, these compounds exhibit good hydrolytic stability. For 13, generation of the alpha-sulfonamide carbanion is possible and regiospecific oxidation with chromyl acetate has been achieved.

Neurotoxic effect of acamprosate, n-acetyl-homotaurine, in cultured neurons.

Acamprosate (AC), N-acetyl-homotaurine, has recently been introduced for treating alcohol craving and reducing relapses in weaned alcoholics. AC may exert its action through the taurine system rather than the glutamatergic or GABAergic system. This conclusion is based on the observations that AC strongly inhibits the binding of taurine to taurine receptors while it has little effect on the binding of glutamate to glutamate receptors or muscimol to GABA(A) receptors. In addition, AC was found to be neurotoxic, at least in neuronal cultures, triggering neuronal damage at 1 mM. The underlying mechanism of AC-induced neuronal injury appears to be due to its action in increasing the intracellular calcium level, [Ca2+](i). Both AC-induced neurotoxicity and elevation of [Ca2+](i) can be prevented by taurine suggesting that AC may exert its effect through its antagonistic interaction with taurine receptors.

S-methyl-N,N-diethylthiocarbamate sulfoxide elicits neuroprotective effect against N-methyl-D-aspartate receptor-mediated neurotoxicity.

Glutamatergic neurotransmission, particularly of the NMDA receptor type, has been implicated in the excitotoxic response to several external and internal stimuli. In the present investigation, we report that S-methyl-N,N-diethylthiocarbamate sulfoxide (DETC-MeSO) selectively and specifically blocks the NMDA receptor subtype of the glutamate receptors, and attenuates glutamate-induced neurotoxicity in rat-cultured primary neurons. Other major ionotropic glutamate receptor subtypes, alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid and kainate, were insensitive to DETC-MeSO both in vitro and in vivo. Disulfiram, the parent compound of DETC-MeSO, also inhibits glutamate receptors partially in vivo; however, it fails to inhibit glutamate receptors in mice pretreated with N-butyl imidazole, a cytochrome P450 enzyme inhibitor, implicating the need for bioactivation of disulfiram to be an effective antagonist. We showed that glutamate-induced increase in (45)Ca2+ was attenuated in rat-cultured primary neurons following pretreatment with DETC-MeSO. The Ca2+ influx into primary neurons, studied by confocal microscopy of the fluorescent Ca2+ dye fura-2, demonstrated a complete attenuation of NMDA-induced Ca2+ influx. Similarly, DETC-MeSO attenuated NMDA-induced (45)Ca2+ uptake. Glutamate-induced (45)Ca2+ uptake and Ca2+ influx, however, were partially blocked by DETC-MeSO, and this is consistent with both in vitro and in vivo studies in which DETC-MeSO partially blocked mouse brain glutamate receptors. In addition, DETC-MeSO pretreatment effectively prevented seizures in mice induced either by NMDA, ammonium acetate, or ethanol-induced kindling seizures, all of which are believed to be mediated by NMDA receptors. These data demonstrate that DETC-MeSO produces the neuroprotective effect through antagonism of NMDA receptors in vivo.

Interaction of the herbicide glyphosate with its target enzyme 5-enolpyruvylshikimate 3-phosphate synthase in atomic detail.

Biosynthesis of aromatic amino acids in plants, many bacteria, and microbes relies on the enzyme 5-enolpyruvylshikimate 3-phosphate (EPSP) synthase, a prime target for drugs and herbicides. We have identified the interaction of EPSP synthase with one of its two substrates (shikimate 3-phosphate) and with the widely used herbicide glyphosate by x-ray crystallography. The two-domain enzyme closes on ligand binding, thereby forming the active site in the interdomain cleft. Glyphosate appears to occupy the binding site of the second substrate of EPSP synthase (phosphoenol pyruvate), mimicking an intermediate state of the ternary enzyme.substrates complex. The elucidation of the active site of EPSP synthase and especially of the binding pattern of glyphosate provides a valuable roadmap for engineering new herbicides and herbicide-resistant crops, as well as new antibiotic and antiparasitic drugs.

Polyhydroxylated C(60), fullerenols, as glutamate receptor antagonists and neuroprotective agents.

Derivatives of C(60) have been shown to be effective free radical scavengers. Hence, many of the biological functions of fullerene are believed to be due to their antioxidant properties. Here we present evidence to show that fullerenols, that are caged fullerene oxides, exert their neuroprotective functions by blocking glutamate receptors and lowering the intracellular calcium, [Ca(2+)](i). In neuronal cultures, fullerenols reduce glutamate-induced neurotoxicity by about 80% at 50microM. No significant effect was observed on H(2)O(2)/Fe(2+)-induced neurotoxicity under the same conditions. Fullerenols were found to inhibit glutamate receptor binding in a dose-dependent manner inhibiting 50% of glutamate binding at 50 microM. Furthermore, AMPA receptors were found to be more sensitive to fullerenols than NMDA and KA receptors. On the other hand, GABA(A) receptors and taurine receptors were not significantly affected by fullerenols at the same concentrations used, suggesting that fullerenols inhibit primarily the glutamate receptors. In addition, fullerenols were also found to lower glutamate (Glu) receptor-induced elevation of [Ca(2+)](i), suggesting that the underlying mechanism of neuronal protective function of fullerenols is likely due to its ability to block the glutamate receptors and to reduce the level of [Ca(2+)](i).

Association of L-glutamic acid decarboxylase to the 70-kDa heat shock protein as a potential anchoring mechanism to synaptic vesicles.

Recently we have reported that the membrane-associated form of the gamma-aminobutyric acid-synthesizing enzyme, l-glutamate decarboxylase (MGAD), is regulated by the vesicular proton gradient (Hsu, C. C., Thomas, C., Chen, W., Davis, K. M., Foos, T., Chen, J. L., Wu, E., Floor, E., Schloss, J. V., and Wu, J. Y. (1999) J. Biol. Chem. 274, 24366-24371). In this report, several lines of evidence are presented to indicate that l-glutamate decarboxylase (GAD) can become membrane-associated to synaptic vesicles first through complex formation with the heat shock protein 70 family, specifically heat shock cognate 70 (HSC70), followed by interaction with cysteine string protein (CSP), an integral protein of the synaptic vesicle. The first line of evidence comes from purification of MGAD in which HSC70, as identified from amino acid sequencing, co-purified with GAD. Second, in reconstitution studies, HSC70 was found to form complex with GAD(65) as shown by gel mobility shift in non-denaturing gradient gel electrophoresis. Third, in immunoprecipitation studies, again, HSC70 was co-immunoprecipitated with GAD by a GAD(65)-specific monoclonal antibody. Fourth, HSC70 and CSP were co-purified with GAD by specific anti-GAD immunoaffinity columns. Furthermore, studies here suggest that both GAD(65) and GAD(67) are associated with synaptic vesicles along with HSC70 and CSP. Based on these findings, a model is proposed to link anchorage of MGAD to synaptic vesicles in relation to its role in gamma-aminobutyric acid neurotransmission.

A novel method for expression and large-scale production of human brain l-glutamate decarboxylase.

l-Glutamate decarboxylase (GAD; EC 4.1.1.15) is the rate-limiting enzyme involved in the synthesis of gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian brain. Imbalance in the conversion of glutamate to GABA has been implicated in a host of human diseases. Studies on the structure, function, and therapeutic use of GAD have been precluded by insufficient quantities of purified active enzyme. Here we report a novel methodology for the expression and large-scale production of enzymatically active, pure, recombinant human GAD65 and GAD67. This method circumvents the sequestering of expressed protein into insoluble inclusion bodies and reduces production of truncated proteins. The availability of sufficient quantities of purified HGAD65 and HGAD67 has allowed for the production of specific polyclonal antibodies that discriminate between the two isoforms. This methodology, in addition to providing key human brain enzymes, may be generally applicable to other systems.

Role of synaptic vesicle proton gradient and protein phosphorylation on ATP-mediated activation of membrane-associated brain glutamate decarboxylase.

Previously, we have shown that the soluble form of brain glutamic acid decarboxylase (GAD) is inhibited by ATP through protein phosphorylation and is activated by calcineurin-mediated protein dephosphorylation (Bao, J., Cheung, W. Y., and Wu, J. Y. (1995) J. Biol. Chem. 270, 6464-6467). Here we report that the membrane-associated form of GAD (MGAD) is greatly activated by ATP, whereas adenosine 5'-[beta,gamma-imido]triphosphate (AMP-PNP), a non-hydrolyzable ATP analog, has no effect on MGAD activity. ATP activation of MGAD is abolished by conditions that disrupt the proton gradient of synaptic vesicles, e.g. the presence of vesicular proton pump inhibitor, bafilomycin A1, the protonophore carbonyl cyanide m-chorophenylhydrazone or the ionophore gramicidin, indicating that the synaptic vesicle proton gradient is essential in ATP activation of MGAD. Furthermore, direct incorporation of (32)P from [gamma-(32)P]ATP into MGAD has been demonstrated. In addition, MGAD (presumably GAD65, since it is recognized by specific monoclonal antibody, GAD6, as well as specific anti-GAD65) has been reported to be associated with synaptic vesicles. Based on these results, a model linking gamma-aminobutyric acid (GABA) synthesis by MGAD to GABA packaging into synaptic vesicles by proton gradient-mediated GABA transport is presented. Activation of MGAD by phosphorylation appears to be mediated by a vesicular protein kinase that is controlled by the vesicular proton gradient.

The sulfonimidamide as a novel transition state analog for aspartic acid and metallo proteases.

We have developed a novel strategy for the preparation of tetrahedral transition state analogs for aspartic acid and metallo-proteases based upon the sulfonimidamide functional group. Our best alpha-des-amino dipeptide analog binds at least 100-fold tighter than the corresponding ground state structure (i.e., amide). A previously unpublished five-membered cyclic sulfonimidamide was also synthesized.

Inhibitors of branched-chain amino acid biosynthesis as potential antituberculosis agents.

Leucine auxotrophs of Mycobacterium bovis (BCG) were found to have a reduced ability to survive in spleens and lungs of mice. This indicated that inhibitors of branched-chain amino acid biosynthesis could possibly be used as antituberculosis agents. Herbicides that inhibit plant branched-chain amino acid biosynthetic enzymes were tested for inhibition of Mycobacterium tuberculosis growth in vitro. Sulphometuron methyl (SM) and metsulphuron methyl, inhibitors of acetolactate synthase (ALS), had a modest effect on growth of M. tuberculosis strain ATCC 35801 (inhibitory concentrations <20 microM). Two inhibitors of ketol acid reductoisomerase (KARI) were ineffective against growth of strain ATCC 35801 in vitro. On the other hand, ALS and KARI inhibitors were more effective against growth of clinical drug-resistant isolates than against strain ATCC 35801. Mouse model studies of tuberculosis infection showed that high doses of SM significantly prevented growth of M. tuberculosis strain ATCC 35801 in the lungs but did not affect the level of infection in the spleen. The results suggest that inhibitors of branched-chain amino acid biosynthesis may be useful as new antituberculosis agents.

Biosynthesis of 2-aceto-2-hydroxy acids: acetolactate synthases and acetohydroxyacid synthases.

Two groups of enzymes are classified as acetolactate synthase (EC 4. 1.3.18). This review deals chiefly with the FAD-dependent, biosynthetic enzymes which readily catalyze the formation of acetohydroxybutyrate from pyruvate and 2-oxobutyrate, as well as of acetolactate from two molecules of pyruvate (the ALS/AHAS group). These enzymes are generally susceptible to inhibition by one or more of the branched-chain amino acids which are ultimate products of the acetohydroxyacids, as well as by several classes of herbicides (sulfonylureas, imidazolinones and others). Some ALS/AHASs also catalyze the (non-physiological) oxidative decarboxylation of pyruvate, leading to peracetic acid; the possible relationship of this process to oxygen toxicity is considered. The bacterial ALS/AHAS which have been well characterized consist of catalytic subunits (around 60 kDa) and smaller regulatory subunits in an alpha2beta2 structure. In the case of Escherichia coli isozyme III, assembly and dissociation of the holoenzyme has been studied. The quaternary structure of the eukaryotic enzymes is less clear and in plants and yeast only catalytic polypeptides (homologous to those of bacteria) have been clearly identified. The presence of regulatory polypeptides in these organisms cannot be ruled out, however, and genes which encode putative ALS/AHAS regulatory subunits have been identified in some cases. A consensus sequence can be constructed from the 21 sequences which have been shown experimentally to represent ALS/AHAS catalytic polypeptides. Many other sequences fit this consensus, but some genes identified as putative 'acetolactate synthase genes' are almost certainly not ALS/AHAS. The solution of the crystal structures of several thiamin diphosphate (ThDP)-dependent enzymes which are homologous to ALS/AHAS, together with the availability of many amino acid sequences for the latter enzymes, has made it possible for two laboratories to propose similar, reasonable models for a dimer of catalytic subunits of an ALS/AHAS. A number of characteristics of these enzymes can now be better understood on the basis of such models: the nature of the herbicide binding site, the structural role of FAD and the binding of ThDP-Mg2+. The models are also guides for experimental testing of ideas concerning structure-function relationships in these enzymes, e.g. the nature of the substrate recognition site. Among the important remaining questions is how the enzyme suppresses alternative reactions of the intrinsically reactive hydroxyethylThDP enamine formed by the decarboxylation of the first substrate molecule and specifically promotes its condensation with 2-oxobutyrate or pyruvate.

Regulation of taurine biosynthesis and its physiological significance in the brain.

Cysteine sulfinic acid decarboxylase (CSAD), the rate-limiting enzyme in taurine biosynthesis, was found to be activated under conditions that favor protein phosphorylation and inactivated under conditions favoring protein dephosphorylation. Direct incorporation of 32P into purified CSAD has been demonstrated with [gamma 32P]ATP and PKC, but not PKA. In addition, the 32P labeling of CSAD was inhibited by PKC inhibitors suggesting that PKC is responsible for phosphorylation of CSAD in the brain. Okadaic acid had no effect on CSAD activity at 10 microM suggesting that protein phosphatase-2C (PrP-2C) might be involved in the dephosphorylation of CSAD. Furthermore, it was found that either glutamate- or high K(+)-induced depolarization increased CSAD activity as well as 32P-incorporation into CSAD in neuronal cultures, supporting the notion that the CSAD activity is endogenously regulated by protein phosphorylation in the brain. A model to link neuronal excitation, phosphorylation of CSAD and increase in taurine biosynthesis is proposed.

Glutathione carbamoylation with S-methyl N,N-diethylthiolcarbamate sulfoxide and sulfone. Mitochondrial low Km aldehyde dehydrogenase inhibition and implications for its alcohol-deterrent action.

S-Methyl N,N-diethylthiolcarbamate sulfoxide (DETC-MeSO) and sulfone (DETC-MeSO2) both inhibit rat liver low Km aldehyde dehydrogenase (ALDH2) in vitro and in vivo (Nagendra et al., Biochem Pharmacol 47: 1465-1467, 1994). DETC-MeSO has been shown to be a metabolite of disulfiram, but DETC-MeSO2 has not. Studies were carried out to further investigate the inhibition of ALDH2 by DETC-MeSO and DETC-MeSO2. In an in vitro system containing hydrogen peroxide and horseradish peroxidase, the rate of DETC-MeSO oxidation corresponded to the rate of DETC-MeSO2 formation. Carbamoylation of GSH by both DETC-MeSO and DETC-MeSO2 was observed in a rat liver S9 fraction. Carbamoylation of GSH was not observed in the presence of N-methylmaleimide. In in vitro studies, DETC-MeSO and DETC-MeSO2 were equipotent ALDH2 inhibitors when solubilized mitochondria were used, but DETC-MeSO was approximately four times more potent than DETC-MeSO2 in intact mitochondria. In studies with rats, the dose (i.p. or oral) required to inhibit 50% ALDH2 (ED50) was 3.5 mg/kg for DETC-MeSO and approximately 35 mg/kg for DETC-MeSO2, approximately a 10-fold difference. Furthermore, maximum ALDH2 inhibition occurred 1 hr after DET(-MeSO administration, whereas maximal ALDH2 inhibition occurred 8 hr after DETC-MeSO2 dosing. DETC-MeSO is, therefore, not only a more potent ALDH2 inhibitor than DETC-MeSO2 in vivo, but also in vitro when intact mitochondria are utilized. The in vitro results thus support the in vivo findings. Since oxidation of DETC-MeSO can occur both enzymatically and non-enzymatically, it is possible that DETC-MeSO2 is formed in vivo. DETC-MeSO2, however, is not as effective as DETC-MeSO in inhibiting ALDH2, probably because it has difficulty penetrating the mitochondrial membrane. Thus, even if DETC-MeSO2 is formed in vivo from DETC-MeSO, it is the metabolite DETC-MeSO that is most likely responsible for the inhibition of ALDH2 after disulfiram administration.

New targets for the treatment of vascular diseases and diabetes.

This symposium was organized by Dan Flynn (Monsanto Life Sciences, USA) and Timothy M Willson (Glaxo Wellcome, USA). PPARs (peroxisome proliferator-activated receptors), are nuclear hormone receptors that govern glucose and lipid homeostasis. There are several subtypes of receptors that share activation by unsaturated fatty acids and work in combination with retinoic acid receptors (RXR), which were a topic covered in an earlier symposium. Two classes of chemistry were discussed at the symposium: (i) thiazolidinediones, that interact directly with PPARs and alter lipid metabolism; and, (ii) benzothiepines or benzothiazepines, that inhibit the ileal bile acid transporter (IBAT) and reduce cholesterol levels by increasing bile acid excretion.