IND43945067 - The Journal of Trace Elements in Experimental...

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Dietary Boron: An Overview of the Evidence for Its Role in Immune Function Curtiss D. Hunt* Agricultural Research Service, US Dept. of Agriculture, Grand Forks Human Nutrition Research Center, Grand Forks, North Dakota This review summarizes the evidence for boron essentiality across the biological spectrum with special focus on biochemical pathways and biomolecules relevant to immune function. Boron is an essential trace element for at least some organisms in each of the phylogenetic kingdoms Eubacteria, Stramenopila (brown algae and dia- toms), Viridiplantae (green algae and familiar green plants), Fungi, and Animalia. Discovery of several of the currently recognized boron-containing biomolecules was achieved because the bound boron formed four coordinate covalent bonds with the ligand, creating a thermodynamically stable complex that is almost undissociable in water. Boron is a constitutive element in three antibiotics and a quorum-sensing signal in bacteria. It enhances Fc receptor expression and interleukin-6 production in cultured mammalian macrophages. Boron binds tightly to the diadenosine polyphosphates and inhibits the in vitro activities of various serine protease and oxidoreductase enzymes. Physiological amounts of dietary boron decrease skinfold thickness after antigen in- jection in gilts and elevated circulating natural killer cells after adjuvant injection in rats. It is predicted that several boron biomolecules waiting discovery are signaling molecules that interact with the cell surface and are probably composed of two mirror or near-mirror halves stabilized by a single boron atom to form a large circular bio- molecule. J. Trace Elem. Exp. Med. 16:291 ÿ 306, 2003. Published 2003 Wiley-Liss, Inc.   Key words: boron; immune function; boron essentiality; natural killer cells; boroesters BORON CHEMISTRY Chemical Characteristics The biomolecules known to contain boron are either directly involved in im- mune defense mechanisms or affect components of the immune system of a particular organism. The unusual nature of boron chemistry is summarized here to serve as a guide to the discovery of other boron biomolecules involved in immune function. Although many synthetic boron compounds are made in the laboratory, boron does not occur free nor bind directly to any element other than oxygen in geological systems except for trivial exceptions [1]. Only those organic compounds that contain B-O or B-N bonds (the organoboron compounds) are in important in biological systems during normal physiological conditions. Exper- *Correspondence to: Curtiss D. Hunt, Agricultural Research Service, US Dept. of Agriculture, Grand Forks Human Nutrition Research Center, Grand Forks, ND 58202 ÿ 9034. Received 17 March 2003; Accepted 16 July 2003 Published 2003 Wiley-Liss, Inc.   This article is a US Government work and, as such, is in the public domain in the United States of America.
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IND43945067 - The Journal of Trace Elements in Experimental...

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