Assessing the Effectiveness of Selected Biomarkers in the Acute and Cumulative Physiological Stress Response in Professional Rugby Union through Non-invasive Assessment

Rugby union is a sport involving high force and frequency impacts making the likelihood of injury a significant risk. The aim of this study was to measure and report the individual and group acute and cumulative physiological stress response during 3 professional rugby games through non-invasive sampling. 24 professional rugby players volunteered for the study. Urine and saliva samples were collected pre and post 3 matches. Myoglobin, salivary immunoglobulin A, cortisol, neopterin and total neopterin (neopterin+7,8-dihydroneopterin) were analysed by high performance liquid chromatography or enzyme linked immunosorbent assay. Significant increases in cortisol, myoglobin, neopterin and total neopterin when urine volume was corrected with specific gravity were observed (p<0.05). Significant decreases in salivary immunoglobulin A concentration were observed for games 1 and 2 while secretion rate decreased after games 2 and 3. Significant decreases were seen with the percent of 7,8-dihydroneopterin being converted to neopterin following games 2 and 3. The intensity of 3 professional rugby games was sufficient to elicit significant changes in the physiological markers selected for our study. Furthermore, results suggest the selected markers not only provide a means for analysing the stress encountered during a single game of rugby but also highlight the unique pattern of response for each individual player.

Ribose-cysteine increases glutathione-based antioxidant status and reduces LDL in human lipoprotein(a) mice

OBJECTIVE

D-ribose-L-cysteine (ribose-cysteine) is a cysteine analogue designed to increase the synthesis of glutathione (GSH). GSH is a cofactor for glutathione peroxidase (GPx), the redox enzyme that catalyses the reduction of lipid peroxides. A low GPx activity and increased oxidised lipids are associated with the development of cardiovascular disease (CVD). Here we aimed to investigate the effect of ribose-cysteine supplementation on GSH, GPx, lipid oxidation products and plasma lipids in vivo.

METHODS

Human lipoprotein(a) [Lp(a)] transgenic mice were treated with 4 mg/day ribose-cysteine (0.16 g/kg body weight) for 8 weeks. Livers and blood were harvested from treated and untreated controls (n = 9 per group) and GSH concentrations, GPx activity, thiobarbituric acid reactive substances (TBARS), 8-isoprostanes and plasma lipid concentrations were measured.

RESULTS

Ribose-cysteine increased GSH concentrations in the liver and plasma (P < 0.05). GPx activity was increased in both liver (1.7 fold, P < 0.01) and erythrocytes (3.5 fold, P < 0.05). TBARS concentrations in the liver, plasma and aortae were significantly reduced with ribose-cysteine (P < 0.01, P < 0.0005 and P < 0.01, respectively) as were the concentrations of 8-isoprostanes in the liver and aortae (P < 0.0005, P < 0.01, respectively). Ribose-cysteine treated mice showed significant decreases in LDL, Lp(a) and apoB concentrations (P < 0.05, P < 0.01 and P < 0.05, respectively), an effect which was associated with upregulation of the LDL receptor (LDLR).

CONCLUSIONS

As ribose-cysteine lowers LDL, Lp(a) and oxidised lipid concentrations, it might be an ideal intervention to increase protection against the development of atherosclerosis.

Changes in acute biochemical markers of inflammatory and structural stress in rugby union

Rugby union is a sport governed by the impacts of high force and high frequency. Analysis of physiological markers following a game can provide an understanding of the physiological response of an individual and the time course changes in response to recovery. Urine and saliva were collected from 11 elite amateur rugby players 24 h before, immediately after, and at 17, 25, 38, 62 and 86 h post-game. Myoglobin, salivary immunoglobulin A and cortisol were analysed by ELISA, whereas neopterin and total neopterin were analysed by high-performance liquid chromatography. There was a significant post-game increase of all four markers. The increases were cortisol 4-fold, myoglobin 2.85-fold, neopterin 1.75-fold and total neopterin 2.3-fold when corrected with specific gravity. All significant changes occurred post-game only, with markers returning to and remaining at baseline within 17 h. The intensity of the game caused significant changes in key physiological markers of stress. They provide an understanding of the stress experienced during a single game of rugby and the time course changes associated with player recovery. Neopterin provides a new marker of detecting an acute inflammatory response in physical exercise, while specific gravity should be considered for urine volume correction post-exercise.

Measurement of changes in urinary neopterin and total neopterin in body builders using SCX HPLC

Body building is a sport where ultrastructual damage to muscle fibres aids the development of dense muscle layers. Using a new strong cation exchange (SCX) based chromatography technique to measure neopterin and 7,8-dihydroneopterin, we investigated whether this muscle damage caused increased levels of inflammation. Urine samples were collected over eight consecutive mornings from 10 natural competitive body builders. Samples were analysed using SCX high performance liquid chromatography (HPLC) with urine volume corrected for creatinine and specific gravity (SG). The majority of subjects showed large changes in both neopterin and total neopterin (7,8-dihydroneopterin+neopterin) levels, though the mean data for the group showed no significant change over the week. There was no evidence of the high intensity resistance training causing an accumulation of inflammation as the values for all the body builders returned to close to the starting values after 2 days rest. The SCX analysis had an intra-specific viability of 3.04% and the inter-specific viability was 5.42%. Urine volume correction with SG was found to give the same values as using creatinine. Creatinine and specific gravity are both reliable methods for correcting for urine volume while SCX HPLC provides a new means of measuring urinary neopterin and total neopterin.

Spectral CT of carotid atherosclerotic plaque: comparison with histology

OBJECTIVE

To distinguish components of vulnerable atherosclerotic plaque by imaging their energy response using spectral CT and comparing images with histology.

METHODS

After spectroscopic calibration using phantoms of plaque surrogates, excised human carotid atherosclerotic plaques were imaged using MARS CT using a photon-processing detector with a silicon sensor layer and microfocus X-ray tube (50 kVp, 0.5 mA) at 38-μm voxel size. The plaques were imaged, sectioned and re-imaged using four threshold energies: 10, 16, 22 and 28 keV; then sequentially stained with modified Von Kossa, Perl's Prussian blue and Oil-Red O, and photographed. Relative Hounsfield units across the energies were entered into a linear algebraic material decomposition model to identify the unknown plaque components.

RESULTS

Lipid, calcium, iron and water-like components of plaque have distinguishable energy responses to X-ray, visible on spectral CT images. CT images of the plaque surface correlated very well with histological photographs. Calcium deposits (>1,000 μm) in plaque are larger than iron deposits (<100 μm), but could not be distinguished from each other within the same voxel using the energy range available.

CONCLUSIONS

Spectral CT displays energy information in image form at high spatial resolution, enhancing the intrinsic contrast of lipid, calcium and iron within atheroma.

KEY POINTS

Spectral computed tomography offers new insights into tissue characterisation. Components of vulnerable atherosclerotic plaque are spectrally distinct with intrinsic contrast. Spectral CT of excised atherosclerotic plaques can display iron, calcium and lipid. Calcium deposits are larger than iron deposits in atheroma. Spectral CT may help in the non-invasive detection of vulnerable plaques.

Intracellular glutathione protects human monocyte-derived macrophages from hypochlorite damage

AIMS

Macrophages must function in an inflammatory environment of high oxidative stress due to the production of various oxidants. Hypochlorous acid (HOCl) is a potent cytotoxic agent generated by neutrophils and macrophages within inflammatory sites. This study determines whether glutathione is the key factors governing macrophage resistance to HOCl.

MAIN METHODS

Human monocyte derived macrophages (HMDM) were differentiated from human monocytes prepared from human blood. The HMDM cells were exposed to micromolar concentrations of HOCl and the timing of the cell viability loss was measured. Cellular oxidative damage was measured by loss of glutathione, cellular ATP, tyrosine oxidation, and inactivation of glyceraldehyde 3-phosphate dehydrogenase (GAPDH).

KEY FINDINGS

HOCl causes a rapid loss in HMDM cell viability above threshold concentrations. The cell death occurred within 10 min of treatment with the morphological characteristics of necrosis. The HOCl caused the extensive cellular protein oxidation with the loss of tyrosine residue and inactivation of GAPDH, which was accompanied with the loss of cellular ATP. This cellular damage was only observed after the loss of intracellular GSH from the cell. Removal of intracellular GSH with diethyl maleate (DEM) increased the cells' sensitivity to HOCl damage while protecting the intracellular GSH pool with the antioxidant 7,8-dihydroneopterin prevented the HOCl mediated viability loss. Variations in the HOCl LD(50) for inducing cell death were strongly correlated with initial intracellular GSH levels.

SIGNIFICANCE

In HMDM cells scavenging of HOCl by intracellular glutathione is sufficient to protect against oxidative loss of key metabolic functions within the cells.

HOCl causes necrotic cell death in human monocyte derived macrophages through calcium dependent calpain activation

The abundance of dead macrophages in close proximity to HOCl-modified proteins in advanced atherosclerotic plaques implicates HOCl in the killing of macrophages and the formation of the necrotic core region. The mechanism of HOCl mediated death of macrophages was unknown, so using human monocyte derived macrophages (HMDM) we here have shown that HOCl causes a rapid necrotic cell death characterized by loss of MTT reduction, cellular ATP and cell lysis without caspase-3 activation in HMDM cells. The HOCl causes a rise in cytosolic calcium level via the plasma membrane L- and T-type calcium channels and endoplasmic reticulum RyR channel. Blocking of the calcium channels or the addition of calpain inhibitors prevents the HOCl mediated loss of mitochondrial potential, lysosome failure and HMDM cell death. Blocking MPT-pore formation with cyclosporin A also prevents the loss of mitochondrial membrane potential, lysosomal destabilization and HMDM cell death. Blocking the calcium mitochondrial uniporter with ruthenium red also blocks the loss of mitochondrial potential but only at high concentrations. HOCl appears to cause HMDM cell death through destabilization of cytosolic calcium control resulting in the failure of both the mitochondria and lysosomes.

Oxidant production, oxLDL uptake, and CD36 levels in human monocyte–derived macrophages are downregulated by the macrophage-generated antioxidant 7,8-dihydroneopterin

The severity of atheroma burden in patients strongly correlates to increasing levels of plasma neopterin, the oxidation product of 7,8-dihydroneopterin. Interferon-γ stimulation of macrophages causes the synthesis of 7,8-dihydroneopterin, a potent antioxidant that inhibits oxidative damage to cells, and the cytotoxicity of oxidized low-density lipoprotein (oxLDL) to monocyte-like U937 cells but not THP-1 cells. With human monocyte-derived macrophages (HMDMs), oxLDL triggered a large oxidative stress, causing the rapid loss of cellular glutathione, glyceradehyde-3-phosphate dehydrogenase (GAPDH) inhibition, and eventual loss of viability without caspase-3 activation. Inhibition of oxLDL cytotoxicity to HMDMs occurred at 7,8-dihydroneopterin concentrations >100 μM. The oxLDL-mediated glutathione loss and GAPDH inactivation was inhibited by 7,8-dihydroneopterin. 7,8-Dihydroneopterin rapidly entered the HMDMs, suggesting that much of the protective effect was scavenging of intracellular oxidants generated in response to oxLDL. OxLDL uptake by HMDMs was reduced by 30% by 7,8-dihydroneopterin. Immunoblot analysis suggests that this decrease in oxLDL uptake was due to a significant downregulation in the levels of CD36. These results imply that 7,8-dihydroneopterin protects human macrophages both by scavenging oxidants generated in response to oxLDL and by decreasing CD36-mediated uptake of oxLDL.

Effects of rested harvesting on muscle metabolite concentrations and K-values in Chinook salmon (Oncorhynchus tshawytscha) fillets during storage at 15 degrees C

Improvement of harvesting procedures in aquaculture may also improve the quality and storage properties of the fish. The use of an anesthetic allows fish to be harvested with reduced stress and exhaustion, which affect fillet properties. We report here on the effects of rested harvesting on the postharvest metabolic profiles and K-values in Chinook salmon (Oncorhynchus tshawytscha) fillets stored near to the fish's acclimation temperature at 15 degrees C for 36 h. Fresh rested fillets were obtained by anesthesia with AQUI-S. They had high cut surface pHs (7.63) and high concentrations of adenosine triphosphate (ATP) and creatine phosphate (3.75 and 8.73 micromol g(-1) respectively), which depleted over 12 h. In contrast, fresh exhausted fillets had low cut surface pHs (6.66) and ATP and creatine phosphate were depleted. Adenosine diphosphate (ADP) and beta-nicotinamide adenine dinucleotide (NAD(+)) concentrations also remained significantly higher during the first 12 h of storage in rested fillets. In fresh rested fillets inosine monophosphate (IMP) concentrations reached maximum after 12 h storage (4.78 micromol g(-1)), whereas maximum IMP concentrations occurred immediately postharvest in the exhausted fillets (6.42 micromol g(-1)). After 36 h storage, K-values in exhausted fillets reached 52.11% compared to 19.27% in rested fillets. Rested harvesting of Chinook salmon improved the fillets' metabolic potential postharvest, extending metabolite depletion times, changing IMP concentrations and reducing K-values.

Serum Protein-Bound 3,4-Dihydroxyphenylalanine and Related Products of Protein Oxidation and Chronic Hemodialysis

INTRODUCTION

Protein-bound dihydroxyphenylalanine (PB-DOPA) and its oxidation products are formed by free radical and oxidative attack on proteins. Hemodialysis and uremic toxins can activate leukocytes leading to overproduction of reactive oxygen species such as hydrogen peroxide and hypochlorous acid (HOCl) that increases protein oxidation.

METHODS

We have used a sensitive fluorometric method to measure PB-DOPA and its oxidation products in proteins after gamma-irradiation and incubation with HOCl and in serum from hemodialysis patients and healthy controls. These PB-DOPA concentrations were compared with those measured by HPLC (PB-DOPAHPLC).

RESULTS

Fluorescent PB-DOPA increased linearly with increasing amounts of human serum and with increasing amounts of gamma-irradiated bovine serum albumin. Concentrations of fluorescent PB-DOPA paralleled PB-DOPAHPLC levels but were approximately 60-70 times higher. Incubation of BSA and human serum albumin (HSA) with HOCl (39.4 mM) significantly (P < 0.0001) increased fluorescent PB-DOPA by 5 fold and 10 fold respectively and PB-DOPAHPLC by 6-fold for both proteins Fluorescent PB-DOPA concentration increased significantly (P < 0.0001) by 16-fold in human serum incubated with HOCl (39.4 mM). Mean serum fluorescent PB-DOPA was significantly (P < 0.0001) higher in 19 hemodialysis patients (57.7 +/- 16.1 microM) compared with 21 healthy controls (33.5 +/- 3.7 microM). Mean PB-DOPAHPLC was 4.45 +/- 1.63 microM in the healthy controls and 12 hemodialysis patients had values within the range of values in these controls while five patients had values that were outside eight SDs of the mean for healthy subjects. Serum fluorescent PB-DOPA was not correlated significantly with PB-DOPAHPLC in these subjects.

CONCLUSIONS

The results of this study suggest that fluorophores of the type, which are derived from DOPA can be reproducibly measured in delipidated serum protein and that HOCl can increase levels of these fluorophores-generating proteins and may potentially contribute to the high levels in serum from hemodialysis patients. This high level of fluorescent PB-DOPA compounds is only partially due to authentic PB-DOPA and might also be derived from other related protein oxidation products including those from DOPA oxidation.

Lipid oxidation predominates over protein hydroperoxide formation in human monocyte-derived macrophages exposed to aqueous peroxyl radicals

In U937 and mouse myeloma cells, protein hydroperoxides are the predominant hydroperoxide formed during exposure to AAPH or gamma irradiation. In lipid-rich human monocyte-derived macrophages (HMDMs), we have found the opposite situation. Hydroperoxide measurements by the FOX assay showed the majority of hydroperoxides formed during AAPH incubation were lipid hydroperoxides. Lipid hydroperoxide formation began after a four hour lag period and was closely correlated with loss of cell viability. The macrophage pterin 7,8-dihydroneopterin has previously been shown to be a potent scavenger of peroxyl radicals, preventing oxidative damage in U937 cells, protein and lipoprotein. However, when given to HMDM cells, 7,8-dihydroneopterin failed to inhibit the AAPH-mediated cellular damage. The lack of interaction between 7,8-dihydroneopterin and AAPH peroxyl radicals suggests that they localize to separate cellular sites in HMDM cells. Our data shows that lipid peroxidation is the predominant reaction occurring in HMDMs, possibly due to the high lipid content of the cells.

Macrophage antioxidant protection within atherosclerotic plaques

Macrophage cells within inflammatory lesions are exposed to a wide range of degrading and cytotoxic molecules including reactive oxygen species. Unlike neutrophils, macrophages do not normally die in this environment but continue to generate oxidants, phagocytose cellular remains, and release a range of cyto-active agents which modulate the immune response. It is this potential of the macrophage cell to survive in an oxidative environment that allows the growth and complexity of advanced atherosclerotic plaques. This review will examine the oxidants encountered by macrophages within an atherosclerotic plaque and describe some of the potential antioxidant mechanisms which enable macrophages to function within inflammatory lesions. Ascorbate, a-tocopherol, and glutathione appear to be central to the protection of macrophages yet additional antioxidant mechanisms appear to be involved. Gamma-Interferon causes macrophages to generate 7,8-dihydroneopterin, neopterin and 3-hydroxyanthranilic acid both of which have antioxidant properties. Manganese superoxide dismutase is also upregulated in macrophages. The evidence that these antioxidants provide further protection, so allowing the macrophage cells to survive within sites of chronic inflammation such as atherosclerotic plaques, will be described.

Redistribution of metal ions to control low density lipoprotein oxidation in Ham's F10 medium

The study of cell-mediated low density lipoprotein (LDL) oxidation has traditionally been undertaken using Ham's F10 media due to its high metal content and low levels of antioxidants. Although there has been no acknowledged change to this media in recent years by the suppliers, Ham's F10 medium has been found to be extremely inconsistent in its promotion of LDL oxidation in the absence of cells. This variability contrasts with the relatively consistent rates of THP-1 cell-mediated LDL oxidation. This study has now shown that the variability in cell-free LDL oxidation is medium-dependent and not an artefact of experimental protocol. It presents evidence that suggests the variable rates of cell-free LDL oxidation are caused by iron auto-oxidation during storage of the Ham's F10 medium. The medium can be standardized by removal of all transition metals, by treatment with Chelex, before the addition of known amounts of iron or copper. This treatment generates a cell culture medium that only allows very slow LDL oxidation in the absence of cells.

Potential to inhibit growth of atherosclerotic plaque development through modulation of macrophage neopterin/7,8-dihydroneopterin synthesis

The rise in plasma neopterin observed with increasing severity of vascular disease is a strong indicator of the inflammatory nature of atherosclerosis. Plasma neopterin originates as the oxidation product of 7,8-dihydroneopterin secreted by gamma-interferon stimulated macrophages within atherosclerotic plaques. Neopterin is increasingly being used as a marker of inflammation during clinical management of patients with a range of disorders including atherosclerosis. Yet the role of 7,8-dihydroneopterin/neopterin synthesis during the inflammatory process and plaque formation remains poorly understood and controversial. This is partially due to the unresolved role oxidants play in atherosclerosis and the opposing roles of 7,8-dihydroneopterin/neopterin. Neopterin can act as pro-oxidant, enhancing oxidant damage and triggering apoptosis in a number of different cell types. Neopterin appears to have some cellular signalling properties as well as being able to chelate and enhance the reactivity of transition metal ions during Fenton reactions. In contrast, 7,8-dihydroneopterin is also a radical scavenger, reacting with and neutralizing a range of reactive oxygen species including hypochlorite, nitric oxide and peroxyl radicals, thus protecting lipoproteins and various cell types including macrophages. This has led to the suggestion that 7,8-dihydroneopterin is synthesized to protect macrophages from the oxidants released during inflammation. The oxidant/antioxidant activity observed in vitro appears to be determined both by the relative concentration of these compounds and the specific chemistry of the in vitro system under study. How these activities might influence or modulate the development of atherosclerotic plaque in vivo will be explored in this review.

Aqueous peroxyl radical exposure to THP-1 cells causes glutathione loss followed by protein oxidation and cell death without increased caspase-3 activity

Protein oxidation within cells exposed to oxidative free radicals has been reported to occur in an uninhibited manner with both hydroxyl and peroxyl radicals. In contrast, THP-1 cells exposed to peroxyl radicals (ROO(*)) generated by thermo decomposition of the azo compound AAPH showed a distinct lag phase of at least 6 h, during which time no protein oxidation or cell death was observed. Glutathione appears to be the source of the lag phase as cellular levels were observed to rapidly decrease during this period. Removal of glutathione with buthionine sulfoxamine eliminated the lag phase. At the end of the lag phase there was a rapid loss of cellular MTT reducing activity and the appearance of large numbers of propidium iodide/annexin-V staining necrotic cells with only 10% of the cells appearing apoptotic (annexin-V staining only). Cytochrome c was released into the cytoplasm after 12 h of incubation but no increase in caspase-3 activity was found at any time points. We propose that the rapid loss of glutathione caused by the AAPH peroxyl radicals resulted in the loss of caspase activity and the initiation of protein oxidation. The lack of caspase-3 activity appears to have caused the cells to undergo necrosis in response to protein oxidation and other cellular damage.

OxLDL induced cell death is inhibited by the macrophage synthesised pterin, 7,8-dihydroneopterin, in U937 cells but not THP-1 cells

The atherosclerotic plaque is an inflammatory site where macrophage cells are exposed to cytotoxic oxidised low density lipoprotein (oxLDL). Interferon-gamma released from T-cells results in macrophage synthesis of 7,8-dihydroneopterin which has antioxidant and cytoprotective activity. Using the human derived monocyte-like U937 and THP-1 cell lines, we examined whether 7,8-dihydroneopterin could inhibit the cytotoxic effect of oxLDL. In U937 cells, oxLDL caused a dramatic loss of cellular glutathione and caspase independent cell death associated with phosphatidylserine exposure on the plasma membrane. 7,8-Dihydroneopterin completely blocked the cytotoxic effect of oxLDL. In contrast, oxLDL initiated THP-1 cell apoptosis with reduction in cellular thiols, caspase-3 activation and plasma membrane phosphatidylserine exposure. 7,8-Dihydroneopterin was unable to alter these processes or restore the THP-1 cellular thiol content. 7,8-Dihydroneopterin did provide some protection to both THP-1 cells and U937 cells from AAPH derived peroxyl radicals. The preincubation of oxLDL with 7,8-dihydroneopterin did not reduce cytotoxicity, suggesting that 7,8-dihydroneopterin may be acting in U937 cells by scavenging intracellular oxidants generated by the oxLDL. The data show that muM levels of 7,8-dihydroneopterin may prevent oxLDL mediated cellular death within atherosclerotic plaques.

Oxidized LDL triggers phosphatidylserine exposure in human monocyte cell lines by both caspase-dependent and -independent mechanisms

Monocytic cell lines have been extensively used to characterize and model various features of the atherogenic process. We found striking differences in the apoptotic pathways of U937 cells and THP-1 cells exposed to copper-oxidized LDL. While phosphatidylserine exposure occurred in both lines, caspase activation was only apparent in the THP-1 cells. OxLDL caused caspase activity to decrease below that seen in untreated U937 cells, and this corresponded with a loss in intracellular thiols. In conclusion, exposure of U937 cells to oxLDL did not trigger a conventional apoptosis response, but still resulted in phosphatidylserine externalization.