Immunohistochemical characteristics of porcine intrahepatic nerves under physiological conditions and after bisphenol A administration

BACKGROUND

The neurochemistry of hepatic nerve fibres was investigated in large animal models after dietary exposure to the endocrine disrupting compound known as bisphenol A (BPA).

MATERIALS AND METHODS

Antibodies against neuronal peptides were used to study changes in hepatic nerve fibres after exposure to BPA at varying concentrations using standard immunofluorescence techniques. The neuropeptides investigated were substance P (SP), galanin (GAL), pituitary adenylate cyclase activating polypeptide (PACAP), calcitonin gene regulated peptide (CGRP) and cocaine and amphetamine regulated transcript (CART). Immunoreactive nerve fibres were counted in multiple sections of the liver and among multiple animals at varying exposure levels. The data was pooled and presented as mean ± standard error of the mean.

RESULTS

It was found that all of the nerve fibres investigated showed upregulation of these neural markers after BPA exposure, even at exposure levels currently considered to be safe. These results show very dramatic increases in nerve fibres containing the above-mentioned neuropeptides and the altered neurochemical levels may be causing a range of pathophysiological states if the trend of over-expression is extrapolated to developing humans.

CONCLUSIONS

This may have serious implications for children and young adults who are exposed to this very common plastic polymer, if the same trends are occurring in humans.

Overview of the role of vitamins and minerals on the kynurenine pathway in health and disease

The kynurenine pathway (KP) of L-tryptophan metabolism produces several neuroactive metabolites with an amino acid structure. These metabolites may play an important role in the pathophysiology of irritable bowel syndrome, Alzheimer's disease, Parkinson's disease, Huntington's disease, schizophrenia, AIDS-dementia complex, depression, epilepsy and the aging process. Modulation of the KP through inhibition or stimulation of enzyme synthesis and activity can be an alternative approach to traditional therapy. Furthermore, it may be responsible for the altered functioning of the enteric nervous system and the central nervous system. There is evidence that the KP is sensitive to changes in the concentration of many vitamins and minerals that play a crucial role as coenzymes and cofactors in the de novo synthesis of nicotinamide adenine dinucleotide coenzyme. A reduction in the availability of the active form of vitamin B6 (pyridoxal 5'-phosphate, PLP) is known to affect tryptophan hydroxylase, kynurenine aminotransferase and kynureninase (KYNU). Vitamin B2 deficiencies result in a reduction in the activity of the flavin adenine dinucleotide dependent enzyme, kynurenine 3-monooxygenase. Minerals are also responsible for the proper functioning of enzymes engaged in L-tryptophan metabolism. Mn(2+), Zn(2+), Co(2+) and Cu(2+) influence KYNU activity, and Mg(2+) regulates quinolinate phosphoribosyl transferase. Fe(2+) is responsible for the proper functioning of both indoleamine 2,3-dioxygenase and 3-hydroxy-anthranilic acid dioxygenase. Changes in the concentration of KP metabolites and in enzymatic activity have been found in many pathological states. Therefore, it is justifiable to regulate the concentration of certain kynurenines or enzymes in the KP which may provide a potential therapeutic target for the treatment of various health impairments. This review demonstrates the role of vitamin and mineral activity on the KP, which may have an effect on the proper functioning of the human organism. Surplus administration of vitamins did not elicit any beneficial effects on L-tryptophan metabolism. Whether a mineral surplus influences L-tryptophan metabolism is still not established. It seems that cofactor deficiencies influence the KP far more than surpluses.

NCD activation of tubulin polymerization

Tubulin dimer (tT) was purified from turkey erythrocytes. The motor domain of Drosophila non-claret disjunctional protein, NCD(335-700), was expressed in E. coli and purified. At 37 degrees C in the presence of GTP, the rate of polymerization of tT to microtubule (tMt) is accelerated over threefold by the presence of NCD(335-700). At 10 degrees C, the rate of tT polymerization is increased from zero, within experimental error, in the absence of NCD(335-700) to rates near those observed at 37 degrees C when NCD(335-700) is present. The NCD(335-700) concentration dependence of the rate indicated the reactive species was NCD(335-700)(n).tT, with n approximately 2. At 10 degrees C in the absence of GTP, polymerization does not occur, but tT activates NCD(335-700) MgATPase activity 10-fold. For the same conditions, using mians-NCD(335-700), which is modified with 2-(4'-maleimidylanilino) naphthalene-6-sulfonic acid, the apparent K(D) for binding to tT is 2.3 x 10(-5) M in the presence of MgADP. Replacing ADP with AMPPNP or ATP has a negligible effect on K(D). Mians-NCD(335-700) binding to tMt is 10-fold stronger than to tT. The above data indicate NCD(335-700) binds at a functional site on tT. The stoichiometry is consistent with the formation of NCD(335-700)(2).tT which in vitro accelerates self-assembly initiation and/or polymerization by binding a second tT in a position favorable for tubulin-tubulin interaction. The data suggest that in vivo functional NCD binding to microtubule involves one motor domain binding to alpha- and beta-subunits at the interface of two different tubulin dimers in a protofilament.

The 0.78 A structure of a serine protease: Bacillus lentus subtilisin

Ultrahigh-resolution X-ray diffraction data from cryo-cooled, B. lentus subtilisin crystals has been collected to a resolution of 0.78 A. The refined model coordinates have a rms deviation of 0.22 A relative to the same structure determined at room temperature and 2.0 A resolution. Several regions of main-chain and side-chain disorder have been identified for 21 out of 269 residues in one polypeptide chain. Hydrogen atoms appear as significant peaks in the Fo - Fc difference electron density map, and carbon, nitrogen, and oxygen atoms can be differentiated. The estimated standard deviation (ESD) for all main-chain non-hydrogen bond lengths is 0.009 A and 0.5 degrees for bond angles based on an unrestrained full-matrix least-squares refinement. Hydrogen bonds are resolved in the serine protease catalytic triad (Ser-His-Asp). Electron density is observed for an unusual, short hydrogen bond between aspartic acid and histidine in the catalytic triad. The hydrogen atom, identified by NMR in numerous serine proteases, appears to be shared by the heteroatoms in the bond. This represents the first reported correlation between detailed chemical features identified by NMR and those in a cryo-cooled crystallographic structure determination at ultrahigh resolution. The short hydrogen bond, designated "catalytic hydrogen bond", occurs as part of an elaborate hydrogen bond network, involving Asp of the catalytic triad. While unusual, these features appear to have conserved analogues in other serine protease families although specific details differ from family to family.