Preconditioning with Physiological Levels of Ethanol Protect Kidney against Ischemia/Reperfusion Injury by Modulating Oxidative Stress

Oxidative stress due to excessive production of reactive oxygen species (ROS) and subsequent lipid peroxidation plays a critical role in renal ischemia/reperfusion (IR) injury. The purpose of current study is to demonstrate the effect of antecedent ethanol exposure on IR-induced renal injury by modulation of oxidative stress.Bilateral renal warm IR was induced in male C57BL/6 mice after ethanol or saline administration. Blood ethanol concentration, kidney function, histological damage, inflammatory infiltration, cytokine production, oxidative stress, antioxidant capacity and Aldehyde dehydrogenase (ALDH) enzymatic activity were assessed to evaluate the impact of antecedent ethanol exposure on IR-induced renal injury.After bilateral kidney ischemia, mice preconditioned with physiological levels of ethanol displayed significantly preserved renal function along with less histological tubular damage as manifested by the reduced inflammatory infiltration and cytokine production. Mechanistic studies revealed that precondition of mice with physiological levels of ethanol 3 h before IR induction enhanced antioxidant capacity characterized by significantly higher superoxidase dismutase (SOD) activities. Our studies further demonstrated that ethanol pretreatment specifically increased ALDH2 activity, which then suppressed lipid peroxidation by promoting the detoxification of Malondialdehyde (MDA) and 4-hydroxynonenal (HNE).Our results provide first line of evidence indicating that antecedent ethanol exposure can provide protection for kidneys against IR-induced injury by enhancing antioxidant capacity and preventing lipid peroxidation. Therefore, ethanol precondition and ectopic ALDH2 activation could be potential therapeutic approaches to prevent renal IR injury relevant to various clinical conditions

First measurement of atmospheric mercury species in Qomolangma Natural Nature Preserve, Tibetan Plateau, and evidence of transboundary pollutant invasion

Located in the world's "third pole" and a remote region connecting the Indian plate and the Eurasian plate, Qomolangma National Nature Preserve (QNNP) is an ideal region to study the long-range transport of atmospheric pollutants. In this study, gaseous elemental mercury (GEM), gaseous oxidized mercury (GOM) and particle-bound mercury (PBM) were continuously measured during the Indian monsoon transition period in QNNP. A slight increase in the GEM concentration was observed from the period preceding the Indian summer monsoon (1.31 +/- 0.42 ng m(-3)) to the Indian summer monsoon period (1.44 +/- 0.36 ng m(-3)), while significant decreases were observed in the GOM and PBM concentrations, with concentrations decreasing from 35.2 +/- 18.6 to 19.3 +/- 10.9 pg m(-3) (p < 0.001) for GOM and from 30.5 +/- 12.5 to 24.9 +/- 19.8 pg m(-3) (p < 0.001) for PBM. A unique daily pattern was observed in QNNP with respect to the GEM concentration, with a peak value before sunrise and a low value at noon. Relative to the (low) GEM concentrations, GOM concentrations (with a mean value of 21.4 +/- 13.4 pg m(-3), n = 1239) in this region were relatively high compared with the measured values in some other regions of China. A cluster analysis indicated that the air masses transported to QNNP changed significantly at different stages of the monsoon, and the major potential mercury (Hg) sources shifted from northern India and western Nepal to eastern Nepal and Bangladesh. As there is a large area covered in glaciers in QNNP, local glacier winds could increase the transboundary transport of pollutants and transport polluted air masses to the Tibetan Plateau. The atmospheric Hg concentration in QNNP in the Indian summer monsoon period was influenced by transboundary Hg flows. This highlights the need for a more specific identification of Hg sources impacting QNNP and underscores the importance of international cooperation regarding global Hg controls

Highly oxygenated organic molecule (HOM) formation in the isoprene oxidation by NO₃ radical

Highly oxygenated organic molecules (HOM) are found to play an important role in the formation and growth of secondary organic aerosol (SOA). SOA is an important type of aerosol with significant impact on air quality and climate. Compared with the oxidation of volatile organic compounds by ozone (O3) and hydroxyl radical (OH), HOM formation in the oxidation by nitrate radical (NO3), an important oxidant at nighttime and dawn, has received less attention. In this study, HOM formation in the reaction of isoprene with NO3 was investigated in the SAPHIR chamber (Simulation of Atmospheric PHotochemistry In a large Reaction chamber). A large number of HOM, including monomers (C5), dimers (C10), and trimers (C15), both closed-shell compounds and open-shell peroxy radicals (RO2), were identified and were classified into various series according to their formula. Their formation pathways were proposed based on the peroxy radicals observed and known mechanisms in the literature, which were further constrained by the time profiles of HOM after sequential isoprene addition to differentiate first- and second-generation products. HOM monomers containing one to three N atoms (1–3N-monomers) were formed, starting with NO3 addition to carbon double bond, forming peroxy radicals, followed by autoxidation. 1N-monomers were formed by both the direct reaction of NO3 with isoprene and of NO3 with first-generation products. 2N-monomers (e.g., C5H8N2On(n=7–13), C5H10N2On(n=8–14)) were likely the termination products of C5H9N2On•, which was formed by the addition of NO3 to C5-hydroxynitrate (C5H9NO4), a first-generation product containing one carbon double bond. 2N-monomers, which were second-generation products, dominated in monomers and accounted for ∼34 % of all HOM, indicating the important role of second-generation oxidation in HOM formation in the isoprene + NO3 reaction under our experimental conditions. H shift of alkoxy radicals to form peroxy radicals and subsequent autoxidation (“alkoxy–peroxy” pathway) was found to be an important pathway of HOM formation. HOM dimers were mostly formed by the accretion reaction of various HOM monomer RO2 and via the termination reactions of dimer RO2 formed by further reaction of closed-shell dimers with NO3 and possibly by the reaction of C5–RO2 with isoprene. HOM trimers were likely formed by the accretion reaction of dimer RO2 with monomer RO2. The concentrations of different HOM showed distinct time profiles during the reaction, which was linked to their formation pathway. HOM concentrations either showed a typical time profile of first-generation products, second-generation products, or a combination of both, indicating multiple formation pathways and/or multiple isomers. Total HOM molar yield was estimated to be 1.2 %+1.3%−0.7%, which corresponded to a SOA yield of ∼3.6 % assuming the molecular weight of C5H9NO6 as the lower limit. This yield suggests that HOM may contribute a significant fraction to SOA yield in the reaction of isoprene with NO3

Ethanol pretreatment attenuated inflammation after renal IR.

<p>Mice were pretreated with saline or 1 g/kg ethanol, and were exposed to a 30-min bilateral renal IR 3 h later. Kidney samples were collected at 24 h post reperfusion and assessed for: <b>A.</b> CD11b, CD3 mRNA expression; <b>B.</b> MPO activity; and <b>C.</b> TNF-α, IL-6, IL-8 and IL-10 mRNA expression. Results are mean values ± SEM. (<i>n</i> = 4–6). (* <i>p</i><0.05, ** <i>p</i><0.01, *** <i>p</i><0.001).</p

Plasma ethanol concentrations in mice after ethanol administration.

<p>Mice received an <i>i.p.</i> injection of 5% ethanol at a dose of 1 g/kg body weight were sacrificed at indicated time after, and plasma ethanol concentration were assayed. The CTR group did not receive any ethanol. <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0025811#s3" target="_blank">Results</a> are mean values ± SEM (<i>n</i> = 4–6). (* <i>p</i><0.05, ** <i>p</i><0.01, *** <i>p</i><0.001; in comparison with the CTR group).</p

Ethanol pretreatment preserved kidney function after renal IR.

<p><b>A.</b> Mice were pretreated with saline or ethanol at different dose. A 30 min bilateral renal ischemia was induced 3 h later. Blood samples were harvested at 24 h after reperfusion to assess the plasma creatinine and urea. Sham controls underwent the same procedure without vascular occlusion. Results are mean values ± SEM (<i>n</i> = 4–8). <b>B.</b> Mice were pretreated with ethanol (1 g/kg) and exposed to a 30 min bilateral renal ischemia after different time interval. Blood samples were harvested at 24 h after reperfusion to assess the plasma creatinine and urea. Results are mean values ± SEM (<i>n</i> = 5–6). <b>C. & D.</b> Mice were pretreated with saline or 1 g/kg ethanol, and were exposed to a 30-min bilateral renal IR 3 h later. FE_Na and Uosm were assessed at 24 h after reperfusion. (* <i>p</i><0.05, ** <i>p</i><0.01, *** <i>p</i><0.001, in comparison with saline control of that group (sham or IR) for <b>A.</b>, and with the 15 min group for <b>B.</b>).</p

Ethanol pretreatment attenuated tubular damage after renal IR.

<p>Mice were pretreated with saline or 1 g/kg ethanol, and were exposed to a 30-min bilateral renal IR 3 h later. Kidney samples were collected at 24 h post reperfusion and assessed for: <b>A.</b> H&E staining of renal outer medulla (left panel) and cortex (right panel). Sections are representative of 6–8 independent mice per experimental group (200× original magnification). <b>B.</b> Scoring of the tubular injury according to the Jablonski's criteria. (* <i>p</i><0.05, ** <i>p</i><0.01).</p

Ethanol pretreatment increased ALDH2 enzymatic activity after renal IR.

<p><b>A.</b> Mice were pretreated with 1 g/kg ethanol and kidney samples were collected for ALDH enzymatic activity assay at different time after ethanol exposure. The CTR group did not receive any ethanol. <b>B.</b> Mice were pretreated with saline or 1 g/kg ethanol, and were exposed to a 30-min bilateral renal IR 3 h later. Kidney samples were collected at different time after reperfusion. <b>C.</b> Immunoprecipitation was performed to separate the total protein from kidney tissues to the ALDH2-enriched part (ALDH2-IP), and the ALDH2-depleted part (ALDH2-DE). <b>D.</b> ALDH enzymatic assay was performed in the ALDH2 enriched or depleted proteins. Results are mean values ± SEM. (<i>n</i> = 4–5). (* <i>p</i><0.05, ** <i>p</i><0.01).</p