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Oxidative protein modification alters proteostasis under acute hypobaric hypoxia in skeletal muscles: a comprehensive in vivo study.

ABSTRACT: While numerous maladies are associated with hypobaric hypoxia, muscle protein loss is an important under studied topic. Hence, the present study was designed to investigate the mechanism of muscle protein loss at HH. SD rats were divided into normoxic rats, while remaining rats were exposed to simulated hypoxia equivalent to 282-torr pressure (equal to an altitude of 7620 m, 8% oxygen), at 25 °C for 6, 12, and 24 h. Post-exposure rats were sacrificed and analysis was performed. Ergo, muscle loss-related changes were observed at 12 and 24 h post-HH exposure. An increased reactive oxygen species production and decreased thiol content was observed in HH-exposed rats. This disturbance caused substantial protein oxidative modification in the form of protein carbonyl content and advanced oxidation protein products. The analysis showed increase levels of bityrosine, oxidized tryptophan, lysine conjugate, lysine conjugate with MDA, protein hydroperoxide, and protein-MDA product. These changes were also in agreement with increase in lipid hydroperoxides and MDA content. HSP-70 and HSP-60 were upregulated significantly, and this finding is corroborated with increase in ER stress biomarker, GRP-78. Overloading of cells with misfolded proteins further activated degradative machinery. Consequently, pro-apoptotic signaling cascade, caspase-3, and C/EBP homologous protein were also activated in 24-h HH exposure. Release of tryptophan and tyrosine was also increased with 24-h HH exposure, indicated protein degradation. Elevation in resting intracellular calcium ion, [Ca²⁺]i, was also observed at 12- and 24-h HH exposure. The present study provides a detailed mechanistic representation of muscle protein loss during HH exposure.

SUBMITTER: Agrawal A

PROVIDER: S-EPMC5425375 | biostudies-literature | 2017 May

REPOSITORIES: biostudies-literature

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Oxidative protein modification alters proteostasis under acute hypobaric hypoxia in skeletal muscles: a comprehensive in vivo study.

Agrawal Akanksha A Rathor Richa R Suryakumar Geetha G

Cell stress & chaperones 20170419 3

While numerous maladies are associated with hypobaric hypoxia, muscle protein loss is an important under studied topic. Hence, the present study was designed to investigate the mechanism of muscle protein loss at HH. SD rats were divided into normoxic rats, while remaining rats were exposed to simulated hypoxia equivalent to 282-torr pressure (equal to an altitude of 7620 m, 8% oxygen), at 25 °C for 6, 12, and 24 h. Post-exposure rats were sacrificed and analysis was performed. Ergo, muscle loss ...[more]

PMID: 28425050

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Project description:Cerium oxide nanoparticles (nanoceria) are effective at quenching reactive oxygen species (ROS) in cell culture and animal models. Although nanoceria reportedly deposit in lungs, their efficacy in conferring lung protection during oxidative stress remains unexplored. Thus, the study evaluated the protective efficacy of nanoceria in rat lung tissue during hypobaric hypoxia.A total of 48 animals were randomly divided into four equal groups (control [C], nanoceria treated [T], hypoxia [H], and nanoceria treated plus hypoxia [T+H]). Animals were injected intraperitoneally with either a dose of 0.5 ?g/kg body weight/week of nanoceria (T and T+H groups) or vehicle (C and H groups) for 5 weeks. After the final dose, H and T+H animals were challenged with hypobaric hypoxia, while C and T animals were maintained at normoxia. Lungs were isolated and homogenate was obtained for analysis of ROS, lipid peroxidation, glutathione, protein carbonylation, and 4-hydroxynonenal-adduct formation. Plasma was used for estimating major inflammatory cytokines using enzyme-linked immunosorbent assay. Intact lung tissues were fixed and both transmission electron microscopy and histopathological examinations were carried out separately for detecting internalization of nanoparticles as well as altered lung morphology.Spherical nanoceria of 7-10 nm diameter were synthesized using a microemulsion method, and the lung protective efficacy of the nanoceria evaluated during hypobaric hypoxia. With repeated intraperitoneal injections of low micromole concentration, we successfully localized the nanoceria in rodent lung without any inflammatory response. The lung-deposited nanoceria limited ROS formation, lipid peroxidation, and glutathione oxidation, and prevented oxidative protein modifications like nitration and carbonyl formation during hypobaric hypoxia. We also observed reduced lung inflammation in the nanoceria-injected lungs, supporting the anti-inflammatory properties of nanoceria.Cumulatively, these results suggest nanoceria deposit in lungs, confer protection by quenching noxious free radicals during hypobaric hypoxia, and do not evoke any inflammatory response.

Project description:BackgroundMice lacking vitamin D receptor (VDR) exhibit a glycogen storage disorder, disrupting carbohydrate utilization in muscle. Here, we asked if the defective carbohydrate metabolism alters the fat utilization by the skeletal muscles of vdr-/- mice.MethodsTo check the effect of high-fat-containing diets on muscle mass and metabolism of vdr-/- mice, we subjected them to two different milk fat-based diets (milk fat diet with 60% of energy from milk fat and milk-based diet [MBD] with 37% of energy from milk fat) and lard-based high-fat diet (HFD) containing 60% of energy from lard fat. Skeletal muscles and pancreas from these mice were analysed using RNA sequencing, quantitative reverse transcription polymerase chain reaction and western blot to understand the changes in signalling and metabolic pathways. Microscopic analyses of cryosections stained with haematoxylin and eosin, BODIPY, succinate dehydrogenase and periodic acid-Schiff reagent were performed to understand changes in morphology and metabolism of muscle fibres and pancreatic islets.ResultsTranscriptomic analyses showed that the skeletal muscles of vdr-/- mice exhibit upregulation of the fatty acid oxidation pathways, suggesting a shift towards increased lipid utilization even in a carbohydrate-enriched regular chow diet (chow). Two different milk fat-enriched diets restored body weight (12.01 ± 0.33 g in chow vs. 17.99 ± 0.62 g in MBD) and muscle weights (38.58 ± 3.84 mg in chow vs. 110.72 ± 1.96 mg in MBD for gastrocnemius [GAS]) of vdr-/- mice. Muscle ATP levels (0.56 ± 0.18 μmol in chow vs. 1.48 ± 0.08 μmol in MBD) and protein synthesis (0.25 ± 0.04 A.U. in chow vs. 2.02 ± 0.06 A.U. in MBD) were upregulated by MBD. However, despite increasing muscle energy levels, HFD failed to restore the muscle mass and cross-sectional area to that of wild-type (WT) mice (104.95 ± 2.6 mg for WT mice on chow vs. 77.26 ± 1.7 mg for vdr-/- mice on HFD for GAS). Moreover, HFD disrupted glucose homeostasis in vdr-/- mice, while MBD restored it. We further analysed insulin response and pancreatic insulin levels of these mice to show that HFD led to reduced insulin levels in pancreatic beta cells of vdr-/- mice (mean intensity of 1.5 × 10-8 for WT mice on chow vs. 4.3 × 10-9 for vdr-/- mice on HFD). At the same time, MBD restored glucose-stimulated pancreatic insulin response (mean intensity of 9.2 × 10-9 ).ConclusionsSkeletal muscles of vdr-/- mice are predisposed to utilize fatty acids as their primary energy source to circumvent their defective carbohydrate utilization. Thus, HFDs could restore energy levels in the skeletal muscles of vdr-/- mice. This study reveals that when mice are subjected to a lard-based HFD, VDR signalling is essential for maintaining insulin levels in pancreatic islets. Our data show a critical role of VDR in muscle metabolic flexibility and pancreatic insulin response.

Dataset Information

Oxidative protein modification alters proteostasis under acute hypobaric hypoxia in skeletal muscles: a comprehensive in vivo study.

Publications

Oxidative protein modification alters proteostasis under acute hypobaric hypoxia in skeletal muscles: a comprehensive in vivo study.

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