Therapeutic Effect of Agmatine on Neurological Disease: Focus on Ion Channels and Receptors

The central nervous system (CNS) is the most injury-prone part of the mammalian body. Any acute or chronic, central or peripheral neurological disorder is related to abnormal biochemical and electrical signals in the brain cells. As a result, ion channels and receptors that are abundant in the nervous system and control the electrical and biochemical environment of the CNS play a vital role in neurological disease. The N-methyl-d-aspartate receptor, 2-amino-3-(5-methyl-3-oxo-1,2-oxazol-4-yl) propanoic acid receptor, kainate receptor, acetylcholine receptor, serotonin receptor, α2-adrenoreceptor, and acid-sensing ion channels are among the major channels and receptors known to be key components of pathophysiological events in the CNS. The primary amine agmatine, a neuromodulator synthesized in the brain by decarboxylation of l-arginine, can regulate ion channel cascades and receptors that are related to the major CNS disorders. In our previous studies, we established that agmatine was related to the regulation of cell differentiation, nitric oxide synthesis, and murine brain endothelial cell migration, relief of chronic pain, cerebral edema, and apoptotic cell death in experimental CNS disorders. In this review, we will focus on the pathophysiological aspects of the neurological disorders regulated by these ion channels and receptors, and their interaction with agmatine in CNS injury.

     

Involvement of surface polysaccharides in the organic acid resistance of Shiga Toxin-producing Escherichia coli O157:H7

In general, wild Escherichia coli strains can grow effectively under moderately acidic organic acid-rich conditions. We found that the Shiga Toxin-producing E. coli (STEC) O157:H7 NGY9 grows more quickly than a K-12 strain in Luria-Bertani (LB)-2-morpholinoethanesulphonic acid (MES) broth supplemented with acetic acid (pH 5.4). Hypothesizing that the resistance of STEC O157:H7 to acetic acid is as a result of a mechanism(s) other than those known, we screened for STEC mutants sensitive to acetic acid. NGY9 was subjected to mini-Tn5 mutagenesis and, from 50,000 colonies, five mutants that showed a clear acetic acid-sensitive phenotype were isolated. The insertion of mini-Tn5 in three mutants occurred at the fcl, wecA (rfe) and wecB (rffE) genes and caused loss of surface O-polysaccharide, loss of both O-polysaccharide and enterobacterial common antigen (ECA) and loss of ECA respectively. The other two mutants showed inactivation of the waaG (rfaG) gene but at different positions that caused a deep rough mutant with loss of the outer core oligosaccharide of lipopolysaccharide (LPS) as well as phenotypic loss of O-polysaccharide and ECA. With the introduction of plasmids carrying the fcl, wecA, wecB and waaG genes, respectively, all mutants were complemented in their production of O-polysaccharide and ECA, and normal growth was restored in organic acid-rich culture conditions. We also found that the growth of Salmonella LPS mutants Ra, Rb1, Rc, Rd1, Rd2 and Re was suppressed in the presence of acetic acid compared with that of the parents. These results suggest that the full expression of LPS (including O-polysaccharide) and ECA is indispensable to the resistance against acetic acid and other short chain fatty acids in STEC O157:H7 and Salmonella. To the best of our knowledge, this is a newly identified physiological role for O-polysaccharide and ECA as well as an acid resistance mechanism.     

Triphala and its active constituent chebulinic Acid are natural inhibitors of vascular endothelial growth factor-a mediated angiogenesis

Triphala churna (THL) is a combination of three fruits that has been used for many years in India for the treatment of various diseases. There are now reports which indicate that THL can inhibit growth of malignant tumors in animals. However, the mechanisms by which THL mediates its anti-tumor actions are still being explored. Because vascular endothelial growth factor-A (VEGF) induced angiogenesis plays a critical role in the pathogenesis of cancer, we therefore investigated whether tumor inhibitory effects of THL or its active constituents are through suppression of VEGF actions. We herein report that THL and chebulinic (CI) present in THL can significantly and specifically inhibit VEGF induced angiogenesis by suppressing VEGF receptor-2 (VEGFR-2) phosphorylation. These results are of clinical significance as these inexpensive and non-toxic natural products can be used for the prevention and treatment of diseases where VEGF induced angiogenesis has an important role.     

Pharmacokinetics of chronically administered all-trans-retinoyl-beta-glucuronide in mice

After the subcutaneous injection of retinoyl beta-glucuronide (RAG), both RAG and retinoic acid (RA), formed by the hydrolysis of RAG in vivo, achieved peak plasma concentrations within 1-2 h. Thereafter, RA was rapidly cleared from the plasma whereas RAG was eliminated much more slowly. No significant changes were noted in the peak (2 h) plasma levels of RAG for treatment periods up to 56 days (one injection of RAG/day), in the clearance rate of RAG from plasma, or in plasma retinol concentrations. Similarly, no consistent decrease in plasma levels of the RA hydrolysis product was observed. Mice undergoing these long-term chronic treatments with RAG did not show any clinical manifestations of retinoid toxicity. Taken together, our findings that chronic dosing with RAG produces sustained levels of both the parent compound and the RA hydrolysis product, combined with the apparent low toxicity of RAG, suggest that RAG could be a safe and useful alternative to some retinoids which are presently being utilized in the clinic.     

Effects of retinoid beta-glucuronides and N-retinoyl amines on the differentiation of HL-60 cells in vitro

Retinoyl beta-glucuronide and retinyl beta-glucuronide, which are naturally occurring water-soluble metabolites of vitamin A, induce the granulocytic differentiation of HL-60 cells in vitro, as evidenced by an increased reduction of nitroblue tetrazolium. The relative effectiveness of various retinoids in differentiation is retinoic acid greater than retinoyl beta-glucuronide greater than retinyl beta-glucuronide. Under the selected assay conditions, retinol, hydroxyphenyl-retinamide, retinamide, and N-retinoyl-phenylalanine are essentially inactive in differentiation. At concentrations of retinoids from 10(-9) to 10(-5) M, cell viability was best with the retinoid beta-glucuronides and retinamide, less with retinoic acid and retinol, and poorest with the N-retinoyl aromatic amines. Cellular growth was depressed only slightly by retinyl beta-glucuronide and retinamide, but to a greater degree by the other derivatives. Retinoyl beta-glucuronide was hydrolyzed in part to retinoic acid, whereas retinyl beta-glucuronide was cleaved to retinol, if at all, at a very slow rate. Under the selected assay conditions, retinoic acid and the retinoid beta-glucuronides primarily induce the differentiation of HL-60 cells, whereas the N-retinoyl aromatic amines show cytotoxicity.     

Coumarins in artemisia caruifolia

Isolation of daphnethin 7-methyl ether, daphnetin dimethyl ether, daphnetin methylene ether, daphnetin 7-methyl-8(3,3-dimethylallyl) ether and 3,4-dimethoxy-2-hydroxycinnamic acid from Artemisia caruifolia is reported.