Difference in pyruvic acid metabolism between neonatal and adult mouse lungs exposed to hyperoxia.

Kosuke Tanaka,Takaaki Watanabe,Fuyu Miyake,Ryuta Itakura,Fumihiko Namba,Shun Matsumura,Shingo Kobayashi,Yukio Arai,Nobuhiko Nagano,Masato Ito,Junichi Ozawa,Ch Ratnasekhar

doi:10.1371/journal.pone.0238604

Kosuke Tanaka, Takaaki Watanabe + Show 10 more

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https://doi.org/10.1371/journal.pone.0238604

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Abstract

Neonatal lungs are more tolerant to hyperoxic injury than are adult lungs. This study investigated differences in the response to hyperoxic exposure between neonatal and adult mouse lungs using metabolomics analysis with capillary electrophoresis time-of-flight mass spectrometry (CE- TOFMS). Neonatal and adult mice were exposed to 21% or 95% O2 for four days. Subsequently, lung tissue samples were collected and analyzed by CE-TOFMS. Pyruvate dehydrogenase (PDH) enzyme activity was determined using a microplate assay kit. PDH kinase (Pdk) 1, Pdk2, Pdk3, and Pdk4 mRNA expression levels were determined using quantitative reverse transcription-polymerase chain reaction. Pdk4 protein expression was quantified by Western blotting and Pdk4 protein localization was evaluated by immunohistochemistry. Levels of 3-phosphoglyceric acid, 2-phosphoglyceric acid, phosphoenolpyruvic acid, and lactic acid were significantly elevated in the lungs of hyperoxia-exposed versus normoxia-exposed adult mice, whereas no significant differences were observed with hyperoxia exposure in neonatal mice. PDH activity was reduced in the lungs of adult mice only. Pdk4 mRNA expression levels after hyperoxic exposure were significantly elevated in adult mice compared with that in neonatal mice. Conversely, gene expression levels of Pdk1, Pdk2, and Pdk3 did not differ after hyperoxic exposure in either neonatal or adult mice. Pdk4 protein levels were also significantly increased in adult mouse lungs exposed to hyperoxia and were localized mainly to the epithelium of terminal bronchiole. Specific metabolites associated with glycolysis and gluconeogenesis were altered after hyperoxia exposure in the lungs of adult mice, but not in neonates, which was likely a result of reduced PDH activity due to Pdk4 mRNA upregulation under hyperoxia.

Highlights

Exposure to high oxygen (O2) level induces lung injury in newborn rodents, which are often used as an animal model of neonatal chronic lung disease due to its pathological similarity to bronchopulmonary dysplasia that occurs in humans [1]
Pdk4 mRNA expression levels after hyperoxic exposure were significantly elevated in adult mice compared with that in neonatal mice
Pdk4 protein levels were significantly increased in adult mouse lungs exposed to hyperoxia and were localized mainly to the epithelium of terminal bronchiole

Summary

Introduction

Exposure to high oxygen (O2) level induces lung injury in newborn rodents, which are often used as an animal model of neonatal chronic lung disease due to its pathological similarity to bronchopulmonary dysplasia that occurs in humans [1]. Adult mice exposed to hyperoxia in the neonatal period exhibit persistent alveolar simplification, increased lung compliance, increased sensitivity to viral infection, and pulmonary vascular disease [2, 3]. Hyperoxia causes acute lung injury and acute respiratory distress syndrome in adult mice and humans [4]. Most neonatal rodents survive hyperoxia-induced lung injury, adults die within 1 week of exposure to high O2 concentrations [5]. PDK4 is located in the mitochondrial matrix and regulates the rate of glucose oxidation and fatty acid metabolism in mammalian cells through direct inhibition of the PDH complex. The role of pyruvate metabolism differences between newborn and adult mice in the effects of hyperoxic exposure has not been investigated

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