The subunit composition of human extracellular superoxide dismutase (EC-SOD) regulate enzymatic activity

<p>Abstract</p> <p>Background</p> <p>Human extracellular superoxide dismutase (EC-SOD) is a tetrameric metalloenzyme responsible for the removal of superoxide anions from the extracellular space. We have previously shown that the EC-SOD subunit exists in two distinct folding variants based on differences in the disulfide bridge pattern (Petersen SV, Oury TD, Valnickova Z, Thøgersen IB, Højrup P, Crapo JD, Enghild JJ. Proc Natl Acad Sci USA. 2003;100(24):13875–80). One variant is enzymatically active (aEC-SOD) while the other is inactive (iEC-SOD). The EC-SOD subunits are associated into covalently linked dimers through an inter-subunit disulfide bridge creating the theoretical possibility of 3 dimers (<it>aa</it>, <it>ai </it>or <it>ii</it>) with different antioxidant potentials. We have analyzed the quaternary structure of the endogenous EC-SOD disulfide-linked dimer to investigate if these dimers in fact exist.</p> <p>Results</p> <p>The analyses of EC-SOD purified from human tissue show that all three dimer combinations exist including two homo-dimers (<it>aa </it>and <it>ii</it>) and a hetero-dimer (<it>ai</it>). Because EC-SOD is a tetramer the dimers may combine to generate 5 different mature EC-SOD molecules where the specific activity of each molecule is determined by the ratio of aEC-SOD and iEC-SOD subunits.</p> <p>Conclusion</p> <p>This finding shows that the aEC-SOD and iEC-SOD subunits combine in all 3 possible ways supporting the presence of tetrameric enzymes with variable enzymatic activity. This variation in enzymatic potency may regulate the antioxidant level in the extracellular space and represent a novel way of modulating enzymatic activity.</p

Developmental expression of the receptor for advanced glycation end-products (RAGE) and its response to hyperoxia in the neonatal rat lung

BACKGROUND: The receptor for advanced glycation end products (mRAGE) is associated with pathology in most tissues, while its soluble form (sRAGE) acts as a decoy receptor. The adult lung is unique in that it expresses high amounts of RAGE under normal conditions while other tissues express low amounts normally and up-regulate RAGE during pathologic processes. We sought to determine the regulation of the soluble and membrane isoforms of RAGE in the developing lung, and its expression under hyperoxic conditions in the neonatal lung. RESULTS: Fetal (E19), term, 4 day, 8 day and adult rat lung protein and mRNA were analyzed, as well as lungs from neonatal (0–24 hrs) 2 day and 8 day hyperoxic (95% O(2)) exposed animals. mRAGE transcripts in the adult rat lung were 23% greater than in neonatal (0–24 hrs) lungs. On the protein level, rat adult mRAGE expression was 2.2-fold higher relative to neonatal mRAGE expression, and adult sRAGE protein expression was 2-fold higher compared to neonatal sRAGE. Fetal, term, 4 day and 8 day old rats had a steady increase in both membrane and sRAGE protein expression evaluated by Western Blot and immunohistochemistry. Newborn rats exposed to chronic hyperoxia showed significantly decreased total RAGE expression compared to room air controls. CONCLUSION: Taken together, these data show that rat pulmonary RAGE expression increases with age beginning from birth, and interestingly, this increase is counteracted under hyperoxic conditions. These results support the emerging concept that RAGE plays a novel and homeostatic role in lung physiology

Carcass characteristics and beef quality of young grass-fed Angus x Salers bovines

To characterize carcass and meat attributes, such as beef eating quality in specific farming conditions, 31 young grass-fed crossbred Angus x Salers cattle in two farming systems (a mono-cattle system versus a mixed system with beef cattle and sheep) were used in this study. Three muscle cuts (striploin—m. longissimus dorsi et thoracis; bolar blade—m. triceps brachii caput longum; internal flank plate—m. obliquus internus abdominis) were used for consumer eating quality testing and striploin was used for panelist eating quality assessment, and objective measurements [Warner–Bratzler shear force (WBSF) and fatty acid (FA) and antioxidant contents]. Results indicated that the farming system had no impact on carcass characteristics or meat quality, but it tended to affect FA content, which is likely explained by between-system differences in animal maturity (assessed by ossification score). Animal gender had significant effects on three eating quality traits evaluated by untrained consumers, with higher flavor liking, overall liking, and overall meat eating quality (MQ4) scores in females than in males. Additionally, FA contents were correlated with sensory quality traits to varying extents: consumer-scored tenderness, flavor, and overall liking were mainly positively correlated with ω-3 and ω-6 polyunsaturated fatty acid (PUFA) contents, and panelist-evaluated tenderness and abnormal flavor were more positively correlated with total lipids, saturated fatty acid (SFA), and monounsaturated fatty acid (MUFA) contents. Overall, this study showed that specific grass-fed crossbred Angus x Salers cattle can produce lean meat rich in ω-3 PUFAs with a low ω-6/ω-3 ratio and with “better than average” beef eating quality

Primary and secondary agonists can use P2X1 receptors as a major pathway to increase intracellular Ca2+ in the human platelet

See also Nurden AT. Does ATP act through P2X1 receptors to regulate platelet activation and thrombus formation? This issue, pp 907–9

The Role of the Receptor for Advanced Glycation End-Products in a Murine Model of Silicosis

Background: The role of the receptor for advanced glycation end-products (RAGE) has been shown to differ in two different mouse models of asbestos and bleomycin induced pulmonary fibrosis. RAGE knockout (KO) mice get worse fibrosis when challenged with asbestos, whereas in the bleomycin model they are largely protected against fibrosis. In the current study the role of RAGE in a mouse model of silica induced pulmonary fibrosis was investigated. Methodology/Principal Findings: Wild type (WT) and RAGE KO mice received a single intratracheal (i.t.) instillation of silica in saline or saline alone as vehicle control. Fourteen days after treatment mice were subjected to a lung mechanistic study and the lungs were lavaged and inflammatory cells, protein and TGF-β levels in lavage fluid determined. Lungs were subsequently either fixed for histology or excised for biochemical assessment of fibrosis and determination of RAGE proteinand mRNA levels. There was no difference in the inflammatory response or degree of fibrosis (hydroxyproline levels) in the lungs between WT and RAGE KO mice after silica injury. However, histologically the fibrotic lesions in the RAGE KO mice had a more diffuse alveolar septal fibrosis compared to the nodular fibrosis in WT mice. Furthermore, RAGE KO mice had a significantly higher histologic score, a measure of affected areas of the lung, compared to WT silica treated mice. A lung mechanistic study revealed a significant decrease in lung function after silica compared to control, but no difference between WT and RAGE KO. While a dose response study showed similar degrees of fibrosis after silica treatment in the two strains, the RAGE KO mice had some differences in the inflammatory response compared to WT mice. Conclusions/Significance: Aside from the difference in the fibrotic pattern, these studies showed no indicators of RAGE having an effect on the severity of pulmonary fibrosis following silica injury. © 2010 Ramsgaard et al

Iron bioavailability in two commercial cultivars of wheat: a comparison between wholegrain and white flour and the effects of nicotianamine and 2'-deoxymugineic acid on iron uptake into Caco-2 cells

Iron bioavailability in unleavened white and wholegrain bread made from two commercial wheat varieties was assessed by measuring ferritin production in Caco-2 cells. The breads were subjected to simulated gastrointestinal digestion and the digests applied to the Caco-2 cells. Although Riband grain contained a lower iron concentration than Rialto, iron bioavailability was higher. No iron was taken up by the cells from white bread made from Rialto flour or from wholegrain bread from either variety, but Riband white bread produced a small ferritin response. The results probably relate to differences in phytate content of the breads, although iron in soluble monoferric phytate was demonstrated to be bioavailable in the cell model. Nicotianamine, an iron chelator in plants involved in iron transport, was a more potent enhancer of iron uptake into Caco-2 cells than ascorbic acid or 2'-deoxymugineic acid, another metal chelator present in plants

HMGB1 promotes ductular reaction and tumorigenesis in autophagy-deficient livers

Autophagy is important for liver homeostasis, and the deficiency leads to injury, inflammation, ductular reaction (DR), fibrosis, and tumorigenesis. It is not clear how these events are mechanistically linked to autophagy deficiency. Here, we reveal the role of high-mobility group box 1 (HMGB1) in two of these processes. First, HMGB1 was required for DR, which represents the expansion of hepatic progenitor cells (HPCs) implicated in liver repair and regeneration. DR caused by hepatotoxic diets (3,5-diethoxycarbonyl-1,4-dihydrocollidine [DDC] or choline-deficient, ethionine-supplemented [CDE]) also depended on HMGB1, indicating that HMGB1 may be generally required for DR in various injury scenarios. Second, HMGB1 promoted tumor progression in autophagy-deficient livers. Receptor for advanced glycation end product (RAGE), a receptor for HMGB1, was required in the same two processes and could mediate the proliferative effects of HMBG1 in isolated HPCs. HMGB1 was released from autophagy-deficient hepatocytes independently of cellular injury but depended on NRF2 and the inflammasome, which was activated by NRF2. Pharmacological or genetic activation of NRF2 alone, without disabling autophagy or causing injury, was sufficient to cause inflammasome-dependent HMGB1 release. In conclusion, HMGB1 release is a critical mechanism in hepatic pathogenesis under autophagy-deficient conditions and leads to HPC expansion as well as tumor progression