Transpulmonary amino acid metabolism in the sugen hypoxia model of pulmonary hypertension

Abstract

In pulmonary artery hypertension (PAH), emerging evidence suggests that metabolic abnormalities may be contributing to cellular dysfunction in PAH. Metabolic abnormalities such as glycolytic shift have been observed intracellularly in several cell types in PAH, including microvacular endothelial cells (MVECs). Concurrently, metabolomics of human PAH samples has also revealed a variety of metabolic abnormalities; however the relationship between the intracellular metabolic abnormalities and the serum metabolome in PAH remains under investigation. In this study, we utilize the sugen/hypoxia (SuHx) rodent model of PAH to examine the RV, LV and MVEC intracellular metabolome (using targeted metabolomics) in normoxic and SuHx rats. We additionally validate key findings from our metabolomics experiments with data obtained from cell culture of normoxic and SuHx MVECs, as well as metabolomics of human serum samples from two different PAH patient cohorts. Taken together, our data, spanning rat serum, human serum and primary isolated rat MVECs reveal that: (1) key classes of amino acids (specifically, branched chain amino acids—BCAA) are lower in the pre‐capillary (i.e., RV) serum of SuHx rats (and humans); (2) intracellular amino acid levels (in particular BCAAs) are increased in SuHx‐MVECs; (3) there may be secretion rather than utilization of amino acids across the pulmonary microvasculature in PAH and (4) an oxidized glutathione gradient is present across the pulmonary vasculature, suggesting a novel fate for increased glutamine uptake (i.e., as a source of glutathione). in MVECs in PAH. In summary, these data reveal new insight into the shifts in amino acid metabolism occurring across the pulmonary circulation in PAH.

Use of Raman spectroscopy to study rat lung tissues for distinguishing asphyxia from sudden cardiac death

“…It was reported that the amount of these aromatic amino acids in the lung tissue was changed during asphyxia. 48 Moreover, phenylalanine and tyrosine are precursors to dopamine, a precursor to epinephrine and norepinephrine. Also, tryptophan is a precursor to 5-hydroxytryptamine (5-HT).…”

Spatial and temporal resolution of metabolic dysregulation in the Sugen hypoxia model of pulmonary hypertension

“…Notably, previous work by our group has shown that an oxidized glutathione transpulmonary shunt exists in the SuHx animal. 17 Because glycine contributes to glutathione synthesis (via glutamine), this observation raises the possibility that lung glycine depletion may occur, at least in part, in the course of glutathione synthesis and transpulmonary glutathione release.…”

“…Furthermore, animal models can be studied longitudinally over compressed time courses, in contrast to long follow‐up periods required to capture meaningful endpoints in clinical cohorts. Importantly, prior studies indicate shared metabolic dysregulation between experimental PH in rodents and human PAH 12,16–18 . However, no previous studies have comprehensively examined metabolic evolution over time as PH develops in the SuHx model, and only one prior study, performed in a murine PH model, assessed tissue metabolism in bulk heart and lung tissues 19 …”

“…Importantly, prior studies indicate shared metabolic dysregulation between experimental PH in rodents and human PAH. 12,[16][17][18] However, no previous studies have comprehensively examined metabolic evolution over time as PH develops in the SuHx model, and only one prior study, performed in a murine PH model, assessed tissue metabolism in bulk heart and lung tissues. 19 In the current study, we leverage targeted tissue metabolomics to examine tissue-specific relationships between evolving metabolism and pulmonary hypertensive features over time in the SuHx model.…”

“…Importantly, prior studies indicate shared metabolic dysregulation between experimental PH in rodents and human PAH. 12 , 16 , 17 , 18 However, no previous studies have comprehensively examined metabolic evolution over time as PH develops in the SuHx model, and only one prior study, performed in a murine PH model, assessed tissue metabolism in bulk heart and lung tissues. 19 …”