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Hypoxia is one of the factors severely affect renal function, and, in severe cases, it can lead to renal fibrosis. Although much progress has been made in identifying the molecular mediators of fibrosis, the mechanisms that govern renal fibrosis remain unclear, and there have been no effective therapeutic anti-fibrotic strategies to date. Mammals exposed to low oxygen in the plateau environment for a long time are prone to high-altitude disease, while yaks have been living in the plateau for generations do not develop kidney fibrosis caused by low oxygen. It has been suggested that metabolic reprogramming occurs in renal fibrosis and that pyruvate dehydrogenase kinase 1 (PDK1) plays a crucial role in metabolic reprogramming as an important node between glycolysis and the tricarboxylic acid cycle. The aim of this study was to investigate the effects of hypoxia on the renal tissues and renal interstitial fibroblasts of yaks. We found that, at the tissue level, HIF-1α, PDK1, TGF-β1, Smad2, Smad3, and α-SMA were mainly distributed and expressed in tubular epithelial cells but were barely present in the renal mesenchymal fibroblasts of healthy cattle and yak kidneys. Anoptical density analysis showed that in healthy cattle kidneys, TGF-β1, Smad2, and Smad3 expression was significantly higher than in yak kidneys (p < 0.05), and HIF-1α and PDK1 expression was significantly lower than in yak kidneys (p < 0.05). The results at the protein and gene levels showed the same trend. At the cellular level, prolonged hypoxia significantly elevated PDK1 expression in the renal mesangial fibroblasts of cattle and yak kidneys compared with normoxia (p < 0.05) and was proportional to the degree of cellular fibrosis. However, PDK1 expression remained stable in yaks compared with renal interstitial fibroblast-like cells in cattle during the same hypoxic time period. At the same time, prolonged hypoxia also promoted changes in cellular phenotype, promoting the proliferation, activation, glucose consumption, lactate production, and anti-apoptosis in the both of cattle and yaks renal interstitial fibroblasts The differences in kidney structure and expression of PDK1 and HIF-1α in kidney tissue and renal interstitial fibroblasts induced by different oxygen concentrations suggest that there may be a regulatory relationship between yak kidney adaptation and hypoxic environment at high altitude. This provides strong support for the elucidation of the regulatory relationship between PDK1 and HIF-1α, as well as a new direction for the treatment or delay of hypoxic renal fibrosis; additionally, these findings provide a basis for further analysis of the molecular mechanism of hypoxia adaptation-related factors and the adaptation of yaks to plateau hypoxia.

The aim of this study was to investigate the effects of hypoxia-induced phenotype, glucose metabolism, ROS levels, and the PDK1-mediated regulation of TGF-β/Smad signaling in yellow cattles, yaks, and those overexpressing PDK1 PASMCs using growth curves, flow cytometry, scratch experiments, glucose and lactic acid assays, RT-qPCR, and Western blotting. The results showed that hypoxia significantly promoted proliferation, migration, antiapoptosis, ROS levels, glucose consumption, and lactate production in yellow cattle PASMCs (p < 0.05), and the cells were dedifferentiated from the contractile phenotype; conversely, hypoxia had no significant effect on yak PASMCs (p > 0.05). PDK1 overexpression significantly promoted proliferation, antiapoptosis, glucose consumption, and lactate production in yak PASMCs under normoxia and hypoxia (p < 0.05), decreased their migration levels under hypoxia (p < 0.05), and dedifferentiated the contractile phenotype of the cells. Overexpression of PDK1 in yak PASMCs is detrimental to their adaptation to hypoxic environments. Yak PASMCs adapted to the effects of hypoxia on lung tissue by downregulating the expression of genes related to the PDK1 and TGF-β/Smad signaling pathways. Taken together, the regulation of PDK1-mediated TGF-β/Smad signaling may be involved in the process of yaks’ adaptation to the hypoxic environment of the plateau, reflecting the good adaptive ability of yaks. The present study provides basic information to further elucidate the mechanism of PDK1-mediated TGF-β/Smad signaling induced by hypoxia in the lungs of yaks, as well as target genes for the treatment of plateau diseases in humans and animals.

The aim of this study was to investigate the molecular mechanisms by which hypoxia affects the biological behavior of yak PASMCs, the changes in the histological structure of yak and cattle lungs, and the relationships and regulatory roles that exist regarding the differences in the distribution and expression of PDK1 and its hypoxia-associated factors screened for their role in the adaptation of yak lungs to the plateau hypoxic environment. The results showed that, at the level of transcriptome sequencing, the molecular regulatory mechanisms of the HIF-1 signaling pathway, glucose metabolism pathway, and related factors (HK2/PGK1/ENO1/ENO3/ALDOC/ALDOA) may be closely related to the adaptation of yaks to the hypoxic environment of the plateau; at the tissue level, the presence of filled alveoli and semi-filled alveoli, thicker alveolar septa and basement membranes, a large number of erythrocytes, capillary distribution, and collagen fibers accounted for all levels of fine bronchioles in the lungs of yaks as compared to cattle. A higher percentage of goblet cells was found in the fine bronchioles of yaks, and PDK1, HIF-1α, and VEGF were predominantly distributed and expressed in the monolayers of ciliated columnar epithelium in the branches of the terminal fine bronchioles of yak and cattle lungs, with a small amount of it distributed in the alveolar septa; at the molecular level, the differences in PDK1 mRNA relative expression in the lungs of adult yaks and cattle were not significant (p > 0.05), the differences in HIF-1α and VEGF mRNA relative expression were significant (p < 0.05), and the expression of PDK1 and HIF-1α proteins in adult yaks was stronger than that in adult cattle. PDK1 and HIF-1α proteins were more strongly expressed in adult yaks than in adult cattle, and the difference was highly significant (p < 0.01); the relative expression of VEGF proteins was not significantly different between adult yaks and cattle (p > 0.05). The possible regulatory relationship between the above results and the adaptation of yak lungs to the plateau hypoxic environment paves the way for the regulatory mechanisms of PDK1, HIF-1α, and VEGF, and provides basic information for studying the mechanism of hypoxic adaptation of yaks in the plateau. At the same time, it provides a reference for human hypoxia adaptation and a target for the prevention and treatment of plateau diseases in humans and plateau animals.

Background Yaks are animals that have lived in plateau environments for generations. Yaks can adapt to the hypoxic plateau environment and also pass this adaptability on to the next generation. The lungs are the most important respiratory organs for mammals to adapt to their environment. Pulmonary artery smooth muscle cells play an important role in vascular remodeling under hypoxia, but the genetic mechanism underpinning the yak’s ability to adapt to challenging plateau conditions is still unknown. Methods A tandem mass tag (TMT) proteomics study together with an RNA-seq transcriptome analysis were carried out on pulmonary artery smooth muscle cells (PASMCs) that had been grown for 72 hours in both normoxic (20% O2) and hypoxic (1% O2) environments. RNA and TP (total protein) were collected from the hypoxic and normoxic groups for RNA-seq transcriptome sequencing and TMT marker protein quantification, and RT-qPCR validation was performed. Results A total of 17,711 genes and 6,859 proteins were identified. Further, 5,969 differentially expressed genes (DEGs) and 531 differentially expressed proteins (DEPs) were identified in the comparison group, including 2,924 and 186 upregulated genes and proteins and 3,045 and 345 down-regulated genes and proteins, respectively. The transcriptomic and proteomic analyses revealed that 109 DEGs and DEPs were highly positively correlated, with 77 genes showing the same expression trend. Nine overlapping genes were identified in the HIF-1 signaling pathway, glycolysis / gluconeogenesis, central carbon metabolism in cancer, PPAR signaling pathway, AMPK signaling pathway, and cholesterol metabolism (PGAM1, PGK1, TPI1, HMOX1, IGF1R, OLR1, SCD, FABP4 and LDLR), suggesting that these differentially expressed genes and protein functional classifications are related to the hypoxia-adaptive pathways. Overall, our study offers abundant data for further analysis of the molecular mechanisms in yak PASMCs and their adaptability to different oxygen concentrations.

The brain is an important part of the mammalian nervous system, is highly sensitive to hypoxia, and plays an important role in the adaptation of the body to hypoxic environments. This study was conducted to analyse the distribution and expression of hypoxia-related factors (hypoxia-inducible factor 1α, HIF-1α; erythropoietin, EPO; vascular endothelial growth factor, VEGF; vascular cell adhesion molecule, VCAM) in the cerebellum, cerebrum, medulla oblongata, and corpora quadrigemina in yaks of different ages (4d, 6-months-old and adult). Paraffin sections were obtained from the cerebellum, cerebrum, medulla oblongata, and corpora quadrigemina of healthy yak for 4-day-old, 6-months-old and adult yaks. Histological characteristics were assessed by haematoxylin staining. Immunohistochemical staining was performed to detect the distribution and expression of HIF-1α, EPO, VEGF and VCAM proteins. Immunohistochemical results showed that HIF-1α, EPO, VEGF, and VCAM were expressed in the pyramidal cell layer of the yak cerebrum, and distributed in the cerebellum granulose cell layer, Purkinje cell layer and medulla layer, and were mainly positive in Purkinje cells and medulla. It is expressed in the cell bodies of the medulla oblongata and the quadrimatous neurons. The expression level in the medulla oblongata was higher, indicating may play a crucial role in functional cohesion. The expression of HIF-1α in 4 d cerebellar tissues was higher than that in other age groups, and the expression of HIF-1α in the medulla oblongata increased with age. In addition, the expression levels of EPO and VEGF in the 6-month-old group were slightly higher than those in the other age groups. It is speculated that EPO and VEGF have obvious protective effects on brain tissue in the 6-month-old age group; VCAM showed no significant differences in the cerebrum, cerebellum, medulla oblongata, or corpora quadrigemina of the yaks. This study provides basic data for further exploration of the adaptive mechanism of plateau yak brain tissue. [ABSTRACT FROM AUTHOR]