Salivary antimicrobial peptides (LL-37 and alpha-defensins HNP1-3), antimicrobial and IgA responses to prolonged exercise

There are many factors in mucosal secretions that contribute to innate immunity and the 'first line of defence' at mucosal surfaces. Few studies, however, have investigated the effects of exercise on many of these 'defence' factors. The aim of the present study was to determine the acute effects of prolonged exercise on salivary levels of selected antimicrobial peptides (AMP) that have not yet been studied in response to exercise (HNP1-3 and LL-37) in addition to immunoglobulin A (IgA). A secondary objective was to assess the effects of exercise on saliva antibacterial capacity. Twelve active men exercised on a cycle ergometer for 2.5 h at approximately 60% of maximal oxygen uptake. Unstimulated whole saliva samples were obtained before and after exercise. There was a significant decrease (P < 0.05) in salivary IgA:osmolality ratio, following exercise, but IgA concentration and secretion rate were unaltered. Salivary HNP1-3 and LL-37 concentrations (P < 0.01 and P < 0.05, respectively), concentration:osmolality ratios (P < 0.01) and secretion rates (P < 0.01) all increased following exercise. Salivary antibacterial capacity (against E. coli) did not change. The increased concentration of AMPs in saliva may confer some benefit to the 'first line of defence' and could result from synergistic compensation within the mucosal immune system and/or airway inflammation and epithelial damage. Further study is required to determine the significance of such changes on the overall 'defence' capacity of saliva and how this influences the overall risk for infection.

Aspects of the in vitro bioactivity and antimicrobial properties of Ag+- and Zn2+-exchanged 11 Å tobermorites

11 Å tobermorite, Ca5Si6O16(OH)2 · 4H2O, is a layer lattice ion exchange mineral whose potential as a carrier for Ag+ and Zn2+ ions in antimicrobial, bioactive formulations has not yet been explored. In view of this, the in vitro bioactivity of Ag+- and Zn2+-exchanged 11 Å tobermorites and their bactericidal action against S. aureus and P.aeruginosa are reported. The in vitro bioactivity of the synthetic unsubstituted tobermorite phase was confirmed by the formation of bone-like hydroxycarbonate apatite (HCA) on its surface within 48 h of contact with simulated body fluid. The substitution of labile Ag+ ions into the tobermorite lattice delayed the onset of HCA-formation to 72 h; whereas, the Zn2+-substituted phase failed to elicit an HCA-layer within 14 days. Both Ag+- and Zn2+-exchanged tobermorite phases were found to exhibit marked antimicrobial action against S. aureus and P.aeruginosa, two common pathogens in biomaterial-centred infections.

Ag+- and Zn2+-exchange kinetics and antimicrobial properties of 11 angstrom tobermorites

Ag+- and Zn2+-exchanged zeolites zeolites and clays have been used as coatings and in composites to confer broad-spectrum antimicrobial properties on a range of technical and biomedical materials. 11 angstrom tobermorite is a bioactive layer lattice ion exchanger whose potential as a carrier for Ag+ and Zn2+ ions in antimicrobial formulations has not yet been explored. In view of this, batch Ag+- and Zn2+-exchange kinetics of two structurally distinct synthetic 11 angstrom tobermorites and their subsequent bactericidal action against Staphylococcus aureus and Pseudomonas aeruginosa are reported. During the exchange reactions, Ag+ ions were found to replace labile interlayer cations; whereas, Zn2+ ions also displaced structural Ca2+ ions from the tobermorite lattice. In spite of these different mechanisms, a simple pseudo-second-order model provided a suitable description of both exchange processes (R-2 >= 0.996). The Ag+- and Zn2+-exchanged tobermorite phases exhibited marked bacteriostatic effects against both bacteria, and accordingly, their potential for use as antimicrobial materials for in situ bone tissue regeneration is discussed. (C) 2008 Elsevier Ltd. All rights reserved.

Vibrational spectroscopy and DFT calculations of di-amino acid cyclic peptides. Part I: cyclo(Gly-Gly), cyclo(L-Ala-L-Ala) and cyclo(L-Ala-Gly) in the solid state and in aqueous solution

Investigations of the vibrational spectra of cyclo(Gly-Gly), cyclo(L-Ala-L-Ala) and cyclo(t-Ala-Gly) are reported. Raman scattering and Fourier transform infrared (FTIR) spectra of solid-state and aqueous protonated samples, as well as their corresponding N-deuterated isotopomers, have been examined. In addition, density functional theory (DFT) (B3-LYP/cc-pVDZ) calculations of molecular structures and their associated vibrational modes were carried out. In each case, the calculated structures of lowest energy for the isolated gas-phase molecules have boat conformations. Assignments have been made for the observed Raman and FTIR vibrational bands of the cyclic di-amino acid peptides (CDAPs) examined. Raman polarization studies of aqueous phase samples are consistent with C-2 and C-1 symmetries for the six-membered rings of cyclo(L-Ala-L-Ala) and cydo(L-Ala-Gly), respectively. There is a good correlation between experimental and calculated vibrational bands for the three CDAPs. These data are in keeping with boat conformations for cydo(L-Ala-L-Ala) and cyclo(L-Ala-Gly) molecules, predicted by the ab initio calculations, in both the solid and aqueous solution states. However, Raman spectroscopic results might infer that cyclo(L-AlaGly) deviates only slightly from planarity in the solid state. The potential energy distributions of the amide I and II modes of a cis-peptide linkage are shown to be significantly different from those of the trans-peptides. For example, deuterium shifts have shown that the cis-amide I vibrations found in cyclo(Gly-Gly), cyclo(L-Ala-L-Ala), and cyclo(L-Ala-Gly) have larger N-H contributions compared to their trans-amide counterparts. Compared to trans-amide II vibrations, cis-amide II vibrations show a considerable decrease in N-H character.

Vibrational spectroscopic studies of the structure of di-amino acid peptides. Part II: cyclo(L-Asp-L-Asp) in the solid state and in aqueous solution

Solid-state protonated and N,O-deuterated Fourier transform infrared (IR) and Raman scattering spectra together with the protonated and deuterated Raman spectra in aqueous solution of the cyclic di-amino acid peptide cyclo(L-Asp-L-Asp) are reported. Vibrational band assignments have been made on the basis of comparisons with previously cited literature values for diketopiperazine (DKP) derivatives and normal coordinate analyses for both the protonated and deuterated species based upon DFT calculations at the B3-LYP/cc-pVDZ level of the isolated molecule in the gas phase. The calculated minimum energy structure for cyclo(L-Asp-L-Asp), assuming C-2 symmetry, predicts a boat conformation for the DKP ring with both the two L-aspartyl side chains being folded slightly above the ring. The C=O stretching vibrations have been assigned for the side-chain carboxylic acid group (e.g. at 1693 and 1670 cm(-1) in the Raman spectrum) and the cis amide I bands (e.g. at 1660 cm(-1) in the Raman spectrum). The presence of two bands for the carboxylic acid C=O stretching modes in the solid-state Raman spectrum can be accounted for by factor group splitting of the two nonequivalent molecules in a crystallographic unit cell. The cis amide II band is observed at 1489 cm(-1) in the solid-state Raman spectrum, which is in agreement with results for cyclic di-amino acid peptide molecules examined previously in the solid state, where the DKP ring adopts a boat conformation. Additionally, it also appears that as the molecular mass of the substituent on the C-alpha atom is increased, the amide II band wavenumber decreases to below 1500 cm(-1); this may be a consequence of increased strain on the DKP ring. The cis amide II Raman band is characterized by its relatively small deuterium shift (29 cm(-1)), which indicates that this band has a smaller N-H bending contribution than the trans amide II vibrational band observed for linear peptides.

IR/Raman spectroscopy and DFT calculations of cyclic di-amino acid peptides. Part III: comparison of solid state and solution structures of cyclo(L-Ser-L-Ser)

B3-LYP/cc-pVDZ calculations of the gas-phase structure and vibrational spectra of the isolated molecule cyclo(L-Ser-L-Ser), a cyclic di-amino acid peptide (CDAP), were carried out by assuming C-2 symmetry. It is predicted that the minimum-energy structure is a boat conformation for the diketopiperazine (DKP) ring with both L-Beryl side chains being folded slightly above the ring. An additional structure of higher energy (15.16 kJ mol(-1)) has been calculated for a DKP ring with a planar geometry, although in this case two fundamental vibrations have been calculated with imaginary wavenumbers. The reported X-ray crystallographic structure of cyclo(L-Ser-L-Ser), shows that the DKP ring displays a near-planar conformation, with both the two L-Beryl side chains being folded above the ring. It is hypothesized that the crystal packing forces constrain the DKP ring in a planar conformation and it is probable that the lower energy boat conformation may prevail in the aqueous environment. Raman scattering and Fourier-transform infrared (FT-IR) spectra of solid state and aqueous solution samples of cyclo(L-Ser-L-Ser) are reported and discussed. Vibrational band assignments have been made on the basis of comparisons with the calculated vibrational spectra and band wavenumber shifts upon deuteration of labile protons. The experimental Raman and IR results for solid-state samples show characteristic amide I vibrations which are split (Raman:1661 and 1687 cm(-1), IR:1666 and 1680 cm(-1)), possibly due to interactions between molecules in a crystallographic unit cell. The cis amide I band is differentiated by its deuterium shift of ~ 30 cm(-1), which is larger than that previously reported for trans amide I deuterium shifts. A cis amide II mode has been assigned to a Raman band located at 1520 cm(-1). The occurrence of this cis amide II mode at a wavenumber above 1500 cm(-1) concurs with results of previously examined CDAP molecules with low molecular weight substituents on the C-alpha atoms, and is also indicative of a relatively unstrained DKP ring.

Effects of exercise intensity on salivary antimicrobial proteins and markers of stress in active men

In the present study, we assessed the effects of exercise intensity on salivary immunoglobulin A (s-IgA) and salivary lysozyme (s-Lys) and examined how these responses were associated with salivary markers of adrenal activation. Using a randomized design, 10 healthy active men participated in three experimental cycling trials: 50% maximal oxygen uptake (VO2max), 75%VO2max, and an incremental test to exhaustion. The durations of the trials were the same as for a preliminary incremental test to exhaustion (22.3 min, sx = 0.8). Timed, unstimulated saliva samples were collected before exercise, immediately after exercise, and 1 h after exercise. In the incremental exhaustion trial, the secretion rates of both s-IgA and s-Lys were increased. An increase in s-Lys secretion rate was also observed at 75%VO2max. No significant changes in saliva flow rate were observed in any trial. Cycling at 75%VOmax and to exhaustion increased the secretion of alpha-amylase and chromogranin A immediately after exercise; higher cortisol values at 75%VO2max and in the incremental exhaustion trial compared with 50%VO2max were observed 1 h immediately after exercise only. These findings suggest that short-duration, high-intensity exercise increases the secretion rate of s-IgA and s-Lys despite no change in the saliva flow rate. These effects appear to be associated with changes in sympathetic activity and not the hypothalamic - pituitary - adrenal axis.