Antitumor activity of L-2,4 diaminobuturic acid against mouse fibrosarcoma cells in vitro and in vivo

Combining the Anticancer and Immunomodulatory Effects of Astragalus and Shiitake as an Integrated Therapeutic Approach

Astragalus root (Huang Qi) and Shiitake mushrooms (Lentinus edodes) are both considered medicinal foods and are frequently used in traditional Chinese medicine due to their anticancer and immunomodulating properties. Here, the scientific literatures describing evidence for the anticancer and immunogenic properties of Shiitake and Astragalus were reviewed. Based on our experimental data, the potential to develop medicinal food with combined bioactivities was assessed using Shiitake mushrooms grown over Astragalus beds in a proprietary manufacturing process, as a novel cancer prevention approach. Notably, our data suggest that this new manufacturing process can result in transfer and increased bioavailability of Astragalus polysaccharides with therapeutic potential into edible Shiitake. Further research efforts are required to validate the therapeutic potential of this new Hengshan Astragalus Shiitake medicinal food.

Two distinct electrophysiological mechanisms underlie extensive depolarization elicited by 2,4 diaminobutyric acid in leech Retzius neurons

Recent studies suggest that 2,4-DABA, a neurotoxic excitatory amino acid present in virtually all environments, but predominantly in aquatic ecosystems may be a risk factor for development of neurodegenerative diseases in animals and humans. Despite its neurotoxicity and potential environmental importance, mechanisms underlying the excitatory and putative excitotoxic action of 2,4-DABA in neurons are still unexplored. We previously reported on extensive two-stage membrane depolarization and functional disturbances in leech Retzius neurons induced by 2,4-DABA. Current study presents the first detailed look into the electrophysiological processes leading to this depolarization. Intracellular recordings were performed on Retzius neurons of the leech Haemopis sanguisuga using glass microelectrodes and input membrane resistance (IMR) was measured by injecting hyperpolarizing current pulses through these electrodes. Results show that the excitatory effect 2,4-DABA elicits on neurons' membrane potential is dependent on sodium ions. Depolarizing effect of 5·10^-3 mol/L 2,4-DABA in sodium-free solution was significantly diminished by 91% reducing it to 3.26 ± 0.62 mV and its two-stage nature was abrogated. In addition to being sodium-dependent, the depolarization of membrane potential induced by this amino acid is coupled with an increase of membrane permeability, as 2,4-DABA decreases IMR by 8.27 ± 1.47 MΩ (67.60%). Since present results highlight the role of sodium ions, we investigated the role of two putative sodium-dependent mechanisms in 2,4-DABA-induced excitatory effect - activation of ionotropic glutamate receptors and the electrogenic transporter for neutral amino acids. Excitatory effect of 5·10^-3 mol/L 2,4-DABA was partially blocked by 10^-5 mol/L 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) a non-NMDA receptor antagonist as the first stage of membrane depolarization was significantly reduced by 2.59 ± 0.98 mV (40%), whilst second stage remained unaltered. Moreover, involvement of the sodium-dependent transport system for neutral amino acids was investigated by equimolar co-application of 5·10^-3 mol/L 2,4-DABA and L-alanine, a competitive inhibitor of this transporter. Although L-alanine exhibited no effect on the first stage of membrane depolarization elicited by 2,4-DABA, it substantially reduced the second stage (the overall membrane depolarization) from 39.63 ± 2.22 mV to 16.28 ± 2.58 mV, by 58.92%. We therefore propose that the electrophysiological effect of 2,4-DABA on Retzius neurons is mediated by two distinct mechanisms, i.e. by activation of ionotropic glutamate receptor that initiates the first stage of membrane depolarization followed by the stimulation of an electrogenic sodium-dependent neutral amino acid transporter, leading to additional influx of positive charge into the cell and the second stage of depolarization.

Catalytic Radical Process for Enantioselective Amination of C(sp3 )-H Bonds

A new catalytic radical system involving CoII -based metalloradical catalysis is effective in activating sulfamoyl azides for enantioselective radical 1,6-amination of C(sp3 )-H bonds, affording six-membered chiral heterocyclic sulfamides in high yields with excellent enantioselectivities. The CoII -catalyzed C-H amination features an unusual degree of functional-group tolerance and chemoselectivity. The unique reactivity and stereoselectivity is attributed to the underlying stepwise radical pathway. The resulting optically active cyclic sulfamides can be readily converted into synthetically useful chiral 1,3-diamine derivatives without loss in enantiopurity.

Extensive depolarization and lack of recovery of leech Retzius neurons caused by 2,4 diaminobutyric acid

In this paper we present, for the first time, a detailed account of electrophysiological effects of 2,4-diaminobutyric acid (2,4-DABA). 2,4-DABA is a neurotoxic non-protein amino acid produced by Cyanobacteria with a possible link to neurodegenerative disorders in animals and humans. Intracellular recordings were performed on Retzius nerve cells of the leech Haemopis sanguisuga using glass microelectrodes filled with 3 mol/L KCl. Our results show that 2,4-DABA is an excitatory amino acid, causing membrane depolarization in a concentration-dependent manner. The most prominent depolarizations of 39.63±2.22 mV and 47.05±4.33 mV, induced by 5×10^-3 and 10^-2 mol/L 2,4-DABA respectively, are several times larger than maximal depolarizations induced by either Glutamate, Aspartate, β-N-methylamino-alanine (BMAA) or β-N-oxalylamino-alanine (BOAA) on our model. These 2,4-DABA induced depolarizations evolve through two distinct stages, which is a novel phenomenon in electrical cell activity upon application of an excitatory amino acid, at least on our model. Involvement of two separate mechanisms, suggested by the two stage phenomenon, is discussed in the paper. We also provide evidence that 2,4-DABA induces irreversible functional disturbances in neurons in a concentration-dependent manner, since only half of the cells recovered normal electrical activity after application of 5×10^-3 mol/L 2,4-DABA, and none recovered after application of 10^-2 mol/L 2,4-DABA. Effects of both L-2,4-DABA and DL-2,4-DABA were tested and are not significantly different.

Memory of Chirality Concept in Asymmetric Intermolecular Michael Addition of α-Amino Ester Enolates to Enones and Nitroalkenes

A highly stereoselective asymmetric intermolecular conjugate addition of α-amino ester derivatives to cyclic enones via the memory of chirality (MOC) concept in high yields with excellent diastereo- and enantioselectivity (dr >99:1, up to 99% ee) is reported. The applicability and the generality of the strategy was demonstrated by its further exploration to acyclic α,β-unsaturated ketone and aromatic nitroalkenes, resulting in the formation of δ-keto-α-amino ester derivative and γ-nitro-α-amino ester derivatives, respectively, with excellent ee and dr.

Synthesis of L-2,4-diamino[4-11C]butyric acid and its use in some in vitro and in vivo tumour models

L-2,4-Diamino[4-11C]butyric acid (DAB) was synthesized by an enzyme catalysed carrier added (0.1 micromol KCN) reaction of hydrogen [11C]cyanide with O-acetyl-L-serine followed by reduction. L-[11C]DAB was obtained with a radiochemical purity higher than 96% and with a decay corrected radiochemical yield of 30-40% within a 32 min reaction time. The enantiomeric excess was 98%. The uptake of L-[11C]DAB was investigated in multicellular aggregates of six different cell lines and animal tumour models. L-[11C]DAB is potentially useful for the assessment of pharmacokinetics of L-DAB in vivo for part of its evaluation as an antitumoural agent, although its use for diagnostic purposes seems limited.

Treatment of malignant glioma by a new therapeutic principle

L-2, 4 diaminobutyric acid (DAB) is a non-physiological, cationic amino acid transported into cells by System A with potent antitumour activity in vitro against human glioma cells. This activity was the result of the pronounced concentrated uptake of DAB in glioma cells to the extent that a cellular lysis could occur due to osmotic reasons. We describe the treatment of 3 patients with inoperable malignant glioma by direct and continuous administration of DAB in tumour tissue employing a microdialysis technique. One to three microdialysis probes were implanted in the tumour tissue through small dural incisions in 3 patients with inoperable malignant glioma. Micropumps charged with 3 ml a day of a Tris-buffered 0.125 M DAB solution made isotonic at pH 7.55 were adapted to the input channel of the probe and a sampling tube to the output for continuous flowing into tumour tissue. The patients were treated in this way for a total of 14-21 days without side effects assignable to DAB. Massive tumour necrosis occurred as judged by comparison of computed tomography performed before and after DAB treatment. The yield of the dialysis procedure with regard to DAB was estimated to be 40-50%. The dialysate concentration of arginine (a cationic amino acid considered to be transported mainly by system A) was high and increased nearly 4-fold from day 3 to day 6 of treatment. DAB administered in this way into malignant brain tumour tissue was well tolerated and showed promising antitumour activity in the 3 patients with inoperable malignant glioma.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of the inhibitory effects of diverse amino acids and amino acid analogs on 12-O-tetradecanoylphorbol-13-acetate-induced ornithine decarboxylase activity in isolated epidermal cells

At a concentration of 1.25 mM, 14 amino acids were capable of inhibiting the induction of ornithine decarboxylase (L-ornithine carboxy-lyase, EC 4.1.1.17) activity by the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in isolated epidermal cells. The greatest percentages of inhibition of TPA-induced epidermal ornithine decarboxylase activity were as follows: cysteine, 98%; tryptophan, 74%; methionine, 64%; phenylalanine, 51%; glycine, 44%; asparagine, 43%; glutamic acid, 42%; leucine, 40%; and arginine, 39%. These amino acid treatments did not alter the time- and concentration-response curves for induction of ornithine decarboxylase activity by TPA. Moreover, there was no difference between the rates at which [3H]arginine, [3H]leucine, [3H]phenylalanine, [3H]methionine, [3H]tryptophan and [14C]cysteine were taken up by freshly isolated epidermal cells or incorporated into epidermal proteins. Arginine, phenylalanine and methionine inhibited the induction of ornithine decarboxylase activity by the tumor promoter to degrees comparable to those elicited by their analogs canavanine and homoarginine, beta-2-thienyl-DL-alanine, and ethionine, respectively. These amino acids and amino acid analogs did not alter the overall rate of protein synthesis. In contrast, both the amino acids and their analogs increased the rates of proteolysis in isolated epidermal cells, an effect which correlated well with the abilities of these different compounds to inhibit TPA-induced ornithine decarboxylase activity. Moreover, both methionine and phenylalanine decreased the half-life and increased the rate of heat denaturation of the TPA-induced enzyme, a result identical to that obtained after treatment with the analogs ethionine and beta-2-thienyl-DL-alanine, respectively. Taken together, these results suggest that millimolar concentrations of exogenous amino acids might induce the synthesis of abnormal proteins and nonfunctional enzymes. Therefore, it is speculated that the uptake of unbalanced amounts of amino acids into the epidermal target cells might alter the stability and the ultrastructure of the TPA-stimulated enzyme just as the amino acid analogs do.

Naloxone as an adjuvant in chemotherapy of an experimental tumor

The antitumor effect of DAB (L-2,4 diaminobuturic acid) has been demonstrated in a previous study. Severe side-effects (especially weight loss and severe neurological symptoms) accompanying DAB treatment have raised the theory that DAB, through a direct effect on the hypothalamus, might cause a diabetes insipidus-like condition, which in turn would activate endogenous opiate systems. This study has verified this state of dehydration and hemoconcentration in a group of 41 mice treated daily with 0.5 ml 0,1 M DAB solution IP. A rise in the serum albumin concentration to 28.8 g/l (SD 2.04) was demonstrated, as against 23.7 g/l (SD 2.3) in a control series. Furthermore, to prevent the neurological side-effects, an adjuvant treatment with an opiate antagonist (Nalone; naloxone) was tried in a group of 19 tumor-bearing mice receiving DAB. This group was compared with a group of 19 tumor-bearing mice receiving DAB only. The mortality rate was significantly reduced in the group receiving Nalone together with DAB (2 dead out of 19) compared with the other group (9 dead out of 19). The tumor weight reduction was about the same in the two groups, 40.5% and 46%, respectively. Combined treatment with DAB and Nalone seems to indicate a possible way of reducing the severe side-effects hitherto accompanying DAB alone, making this unique amino acid a potentially useful antitumor agent.