Mechanisms underlying modulation of podocyte TRPC6 channels by suPAR: Role of NADPH oxidases and Src family tyrosine kinases

The soluble urokinase receptor (suPAR) has been implicated in the pathogenesis of chronic kidney diseases (CKD) and may function as a circulating “permeability factor” driving primary focal and segmental glomerulosclerosis (FSGS). Here we examined the mechanisms whereby suPAR causes mobilization and increased activation of Ca²⁺-permeable TRPC6 channels, which are also implicated in FSGS. Treatment of immortalized mouse podocytes with recombinant suPAR for 24?h caused a marked increase in cytosolic reactive oxygen species (ROS) that required signaling through integrins. This effect was associated with increased assembly of active cell surface NADPH oxidase 2 (Nox2) complexes and was blocked by the Nox2 inhibitor apoycynin. Treatment with suPAR also evoked a functionally measurable increase in TRPC6 channels that was blocked by concurrent treatment with the ROS-quencher TEMPOL as well as by inhibition of Rac1, an essential component of active Nox2 complexes. Elevated ROS evoked by exposing cells to suPAR or H₂O₂ caused a marked increase in the abundance of tyrosine-phosphorylated proteins including Src, and suPAR-evoked Src activation was blocked by TEMPOL. Moreover, mobilization and increased activation of TRPC6 by suPAR or H₂O₂ was blocked by concurrent exposure to PP2, an inhibitor of Src family tyrosine kinases. These data suggest that suPAR induces oxidative stress in podocytes that in turn drives signaling through Src family kinases to upregulate TRPC6 channels. The combination of oxidative stress and altered Ca²⁺ signaling may contribute to loss of podocytes and progression of various forms of CKD.     

代谢、血液碱化和纯氧影响呼吸调控的人体实验研究III： 血液碱化后纯氧运动试验*

目的: 在急性血液碱化前、后空气吸入下完成症状限制性最大极限心肺运动试验(CPET)的基础上,本文探讨在血液碱化后吸入纯氧对呼吸调控的影响。方法: 正常志愿者5名在碱化血液后呼吸纯氧CPET,在静息、热身、运动及恢复期,连续测定肺通换气指标及每分钟动脉取样的血气指标,对CPET期间的呼吸气体交换和血气指标的动态变化进行分析,同时与急性碱化血液前、后空气CPET数据比较。结果: 碱化血液后吸入纯氧运动呼吸反应与急性碱化血液前、后空气CPET呼吸反应基本一致。CPET期间,各运动状态下的每分通气量均与对照组相似(P>0.05);仅静息每分通气量较血液碱化空气CPET略高(P<0.05),而其它状态和恢复2min时均相近(P>0.05)。潮气量仅峰值运动时较对照和血液碱化空气CPET略低(P<0.05);而运动过程和恢复2min时的潮气量均相近(P>0.05)。呼吸频率在各个时间与血液碱化前后CPET均无差异(P>0.05)。在碱化血液后吸入纯氧运动各个时期的PaO₂和SaO₂较碱化血液前后空气CPET时明显提高(P<0.001,P<0.05)。血红蛋白浓度虽然较急性血液碱化前后均低,但仅较血液碱化前显著降低(P<0.05),比血液碱化后差异不显著(P>0.05) ; 开始时的PaCO₂较碱化血液前后空气CPET时降低(P<0.05),无氧阈时相近(P>0.05),但到峰值及恢复2 min时明显增高(P<0.05);pH仅较对照增高(P<0.05),但与碱化血液空气试验时无差异;乳酸水平较对照略高,但仅在热身和恢复期有差异(P<0.05)。纯氧提高了两人无氧阈和三人峰值运动的功率和时间。结论: 虽然血液碱化给予纯氧, CPET呼吸反应与碱化血液前、后空气CPET呼吸反应模式相似,表明运动中呼吸反应主要取决于代谢变化,而非动脉血气平均值高低。     

Enantioselective hydrolysis of racemic methyl jasmonate using microorganisms and isolated enzymes

A variety of microorganisms were used to hydrolyze racemic methyl jasmonate [I] with varying degrees of enantioselectivity. The fungi tested included species from the genera Aspergillus, Penicillium, and Talaromyces. All fungi tested showed a preference for the [1S,2S(Z)]-(+)-isomer. The yeasts Saccharomyces cerevisiae and Candida albicans showed no activity. A number of bacterial genera were also tested. No activity could be shown for members of the genera Bacillus, Pseudomonas, Escherichia, Nocardia, and Thermoactinomyces. Hydrolytic activity was found in the genera Streptomyces and Mycobacterium. S. henetus showed the same enantioselectivity as the fungi, while M. phlei hydrolyzed the [1R,2R(Z)]-(−)-isomer preferentially. A number of isolated enzymes were also screened for activity. Varying degrees of hydrolytic activity and enantioselectivity were found.     

Effect of CO2, CO2 and Diamox on photosynthesis and photorespiration in Chlamydomonas reinhardtii (green alga) and Anacystis nidulans (Cyanobacterium, blue-green alga)

Photorespiration by Chlamydomonas reinhardtii and Anacystis nidulans was measured as the oxygen inhibition of CO₂ uptake and the CO₂ compensation points. Net photosynthesis was oxygen dependent in Chlamydomonas grown in 5% CO₂, but CO₂ insensitive in cultures bubbled with air. Anacystis, even when cultured in 5% CO₂, exhibited an CO₂ insensitive net photosynthesis. The CO₂ compensation point of Chlamydomonas grown in cultures bubbled with air and Anacystis grown in 5% CO₂ enriched air, were reached shortly after the measurement was begun and the values were very low, less than 10 μl CO₂ 1^?1; while Chlamydomonas grown in 5% CO₂ enriched air for 4 days showed a high, but temporary CO₂ compensation point (60 μl CO₂ 1^?1). After a two hour adaptation in low CO₂, a stable, low CO₂ compensation point was reached. It seems that photorespiration can only be detected by the methods used in this study when the algae are cultured in high CO₂, but a mechanism exists which blocks photorespiration when the green algae are adapted to low CO₂ concentrations. When Chlamydomonas was treated with Diamox, an inhibitor of carbonic anhydrase, after cultivation in low CO₂ (air), the cells behaved as if they had been grown in high CO₂. They showed an oxygen sensitive net photosynthesis and a high CO₂ compensation point. This indicates that carbonic anhydrase plays an important role in the regulation of a measurable photorespiration in Chlamydomonas. The results are discussed in relation to previous observations of photorespiration measured by enzyme assay, metabolic products and gas exchange properties.     

Yarrowia lipolytica lipase production enhanced by increased air pressure

Aims: To study the cellular growth and morphology of Yarrowia lipolytica W29 and its lipase and protease production under increased air pressures. Methods and Results: Batch cultures of the yeast were conducted in a pressurized bioreactor at 4 and 8 bar of air pressure and the cellular behaviour was compared with cultures at atmospheric pressure. No inhibition of cellular growth was observed by the increase of pressure. Moreover, the improvement of the oxygen transfer rate (OTR) from the gas to the culture medium by pressurization enhanced the extracellular lipase activity from 96·6 U l^?1 at 1 bar to 533·5 U l^?1 at 8 bar. The extracellular protease activity was reduced by the air pressure increase, thereby eliciting further lipase productivity. Cell morphology was slightly affected by pressure, particularly at 8 bar, where cells kept the predominant oval form but decreased in size. Conclusions: OTR improvement by total air pressure rise up to 8 bar in a bioreactor can be applied to the enhancement of lipase production by Y. lipolytica. Significance and Impact of the Study: Hyperbaric bioreactors can be successfully applied for yeast cells cultivation, particularly in high‐density cultures used for enzymes production, preventing oxygen limitation and consequently increasing overall productivity.     

ROS-Mediated ABA Signaling

In plants, reactive oxygen species (ROS) are short-lived molecules produced through various cellular mechanisms in response to biotic and abiotic stimuli. ROS function as second messengers for hormone signaling, development, oxygen deprivation, programmed cell death, and plant–pathogen interactions. Recent research on ROS-mediated responses has produced stimulating findings such as the specific sources of ROS production, molecular elements that work in ROS-mediated signaling and homeostasis, and a ROS-regulated gene network (Neill et al., Curr Opin Plant Biol 5:388–395, 2002a; Apel and Hirt, Annu Rev Plant Biol 55:373–399, 2004; Mittler et al., Trends Plant Sci 9:490–498, 2004; Mori and Schroeder, Plant Physiol 135:702–708, 2004; Kwak et al., Plant Physiol 141:323–329, 2006; Torres et al., Plant Physiol 141:373–378, 2006; Miller et al., Physiol Plant 133:481–489, 2008). In this review, we highlight new discoveries in ROS-mediated abscisic acid (ABA) signaling. Drs. Daeshik Cho and June M. Kwak are the corresponding authors for this paper.     

Efficacy of β-mannanase supplementation to corn–soya bean meal-based diets on growth performance,nutrient digestibility,blood urea nitrogen,faecal coliform and lactic acid bacteria and faecal noxious gas emission in growing pigs

A study was conducted to determine the efficacy of β-mannanase supplementation to a diet based on corn and soya bean meal (SBM) on growth performance, nutrient digestibility, blood urea nitrogen (BUN), faecal coliforms and lactic acid bacteria, and noxious gas emission in growing pigs. A total of 140 pigs [(Landrace × Yorkshire) × Duroc; average body weight 25 ± 3 kg] were randomly allotted to a 2 × 2 factorial arrangement with dietary treatments consisting of hulled or dehulled SBM without or with supplementation of 400 U β-mannanase/kg. During the 6 weeks of experimental feeding, β-mannanase supplementation had no effect on body weight gain, feed intake and gain:feed (G:F) ratio. Compared with dehulled SBM, feeding hulled SBM caused an increased feed intake of pigs in the entire trial (p = 0.05). The G:F ratio was improved in pigs receiving dehulled SBM (p < 0.05). Dietary treatments did not influence the total tract digestibility of dry matter, nitrogen and gross energy. Enzyme supplementation reduced (p < 0.05) the population of faecal coliforms and tended to reduce the NH₃ concentration after 24 h of fermentation in a closed box containing faecal slurry. Feeding hulled SBM tended to reduce NH₃ emission on days 3 and 5 of fermentation. In conclusion, mannanase supplementation had no influence on growth performance and nutrient digestibility but showed a positive effect on reducing coliform population and tended to reduce NH₃ emission. Dehulled SBM increased G:F ratio and hulled SBM tended to reduce NH₃ emission.     

Detoxification enzymes of freshwater crayfish Procambarus clarkii fed a diet enriched in selenium: Preliminary results

This study aimed at investigating the extent of accumulation of selenium in the hepatopancreas of the crayfish Procambarus clarkii and its effects on the enzymatic activities of catalase, glutathione peroxidase, and glutathione reductase. Crayfish were fed for 15 days either a diet enriched in Se, ED (1.21 mg kg^-1) or a standard diet, SD (0.30 mg kg^-1). Results showed that Se accumulation is higher in the sample subject to ED rather than to SD. A sexual difference was found for the response of the analyzed enzymes in the ED sample only. Catalase activity and glutathione peroxidase activity decreased in females and males, respectively, whereas glutathione reductase activity showed significant reductions in both sexes. These preliminary data might provide information about prooxidant effects of Se on P. clarkii when fed a Se enriched diet.     

Kinin-mediated inflammation in neurodegenerative disorders

The mediatory role of kinins in both acute and chronic inflammation within nervous tissues has been widely described. Bradykinin, the major representative of these bioactive peptides, is one of a few mediators of inflammation that directly stimulates afferent nerves due to the broad expression of specific kinin receptors in cell types in these tissues. Moreover, kinins may be delivered to a site of injury not only after their production at the endothelium surface but also following their local production through the enzymatic degradation of kininogens at the surface of nerve cells. A strong correlation between inflammatory processes and neurodegeneration has been established. The activation of nerve cells, particularly microglia, in response to injury, trauma or infection initiates a number of reactions in the neuronal neighborhood that can lead to cell death after the prolonged action of inflammatory substances. In recent years, there has been a growing interest in the effects of kinins on neuronal destruction. In these studies, the overexpression of proteins involved in kinin generation or of kinin receptors has been observed in several neurologic disorders including neurodegenerative diseases such Alzheimer's disease and multiple sclerosis as well as disorders associated with a deficiency in cell communication such as epilepsy. This review is focused on recent findings that provide reliable evidence of the mediatory role of kinins in the inflammatory responses associated with different neurological disorders. A deeper understanding of the role of kinins in neurodegenerative diseases is likely to promote the future development of new therapeutic strategies for the control of these disorders. An example of this could be the prospective use of kinin receptor antagonists.