Dietary boron: An overview of the evidence for its role in immune function

Abstract

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 diatoms), 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 injection 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 biomolecule. J. Trace Elem. Exp. Med. 16:291À306,

Association of Boron, Copper, Germanium, Magnesium, Selenium and Zinc with Incidence of Rheumatoid Arthritis

“…Boron (B) is either directly related to immune defense mechanisms or indirectly affects components of the immune system [7]. Dietary boron affects the function of many metabolic enzymes, metabolism of steroid hormones, metabolism and utilization of several micronutrients, including calcium, magnesium, vitamin D [8], copper, nitrogen, triglycerides, glucose, and estrogen.…”

Expanding Roles for Organoboron Compounds – Versatile and Valuable Molecules for Synthetic, Biological and Medicinal Chemistry

“…[37] Although boron-containing natural products are rare, several bioactive compounds containing boron have been identified, including the antibiotic boromycin and several bacterial quorumsensing molecules, suggesting a role for boron in cell signalling and the immune function. [38,39] The potential role of boric acid as a cancer chemopreventing agent has been suggested by epidemiological and laboratory studies and it was recently documented in more detail for prostate cancer. [40] Several synthetic boron-containing molecules were recently shown to exhibit important biological properties prompting their investigation as potential therapeutics.…”

Use of Phenylboronic Acids to Investigate Boron Function in Plants. Possible Role of Boron in Transvacuolar Cytoplasmic Strands and Cell-to-Wall Adhesion

“…Borate can cross-link molecules because it contains two pair of hydroxyl moieties that can form reversible diester bonds with molecules containing cisdiols in a favorable conformation. The importance of borate serving as a cross-linking molecule is highlighted by the discovery of several borate-dependent molecules, including rhamnogalacturonan II (RG-II) in plant cell walls (Ishii and Matsunaga, 1996;Kobayashi et al, 1996;O'Neill et al, 1996;Kaneko et al, 1997;Matoh, 1997), boron-polyhydric alcohol complexes identified from phloem extracts (Hu et al, 1997), a bacterial signaling molecule and its sensor protein (Chen et al, 2002), as well as several antibiotics (Hunt, 2003).Boronates (i.e. boronic acids) are a structurally similar but diverse class of molecules that can form reversible ester bonds with cis-diols in a manner functionally identical to borates (Bergold and Scouten, 1983;Springsteen and Wang, 2002).…”