Immune and inflammatory responses have an important function in the pathophysiology of pulmonary hypertension (PH). However, little is known about the immune landscape in peripheral circulation in patients with high-altitude pulmonary hypertension (HAPH). We apply single-cell transcriptomics to characterize the monocytes that are significantly enriched in the peripheral blood mononuclear cells (PBMC) of HAPH patients. We discover an increase in C1 (non-classical) and C2 (intermediate) monocytes in PBMCs and a decrease in hypoxia-inducible transcription factor-1α (HIF-1α) in all monocyte subsets associated with HAPH. In addition, we demonstrate that similar immune adaptations may exist in HAPH and PH. Overall, we characterize an immune cell atlas of the peripheral blood in HAPH patients. Our data provide evidence that specific monocyte subsets and HIF-1α downregulation might be implicated in the pathogenesis of HAPH.

Pathological mechanisms of pulmonary arterial hypertension (PAH) remain largely unexplored. Effective treatment of PAH remains a challenge. The aim of this study was to discover the underlying mechanism of PAH through functional metabolomics and to help develop new strategies for prevention and treatment of PAH.Metabolomic profiling of plasma in patients with idiopathic PAH was evaluated through high-performance liquid chromatography mass spectrometry, with spermine identified to be the most significant and validated in another independent cohort. The roles of spermine and spermine synthase were examined in pulmonary arterial smooth muscle cells (PASMCs) and rodent models of pulmonary hypertension.Using targeted metabolomics, plasma spermine levels were found to be higher in patients with idiopathic PAH compared to healthy controls. Spermine administration promoted proliferation and migration of PASMCs and exacerbated vascular remodelling in rodent models of pulmonary hypertension. The spermine-mediated deteriorative effect can be attributed to a corresponding upregulation of its synthase in the pathological process. Inhibition of spermine synthasein vitrosuppressed platelet-derived growth factor-BB-mediated proliferation of PASMCs, andin vivoattenuated monocrotaline-mediated pulmonary hypertension in rats.Plasma spermine promotes pulmonary vascular remodelling. Inhibiting spermine synthesis could be a therapeutic strategy for PAH.

Uric acid metabolism is implicated in the pathogenesis of pulmonary arterial hypertension, wherein the key metabolite hypoxanthine exhibits elevated levels, thereby promoting pulmonary vascular remodeling through facilitation of cell proliferation and migration as well as regulation of adenosine triphosphate binding cassette transport signaling pathway. Consequently, therapeutic interventions targeting hypoxanthine synthesis may hold promise for the management of pulmonary arterial hypertension.

Pulmonary hypertension (PH) is a life-threatening cardio-pulmonary disorder. Whether natural killer (NK) cells could act as participants in PH and the mechanism by which NK cells moderate pulmonary vascular remodeling has not been fully elucidated. Single-cell RNA sequencing data from lungs of human pulmonary arterial hypertension (PAH) patients and monocrotaline (MCT)-induced PH rat model were retrieved from GEO database or UCSC Cell Browser. Tcf7 conditional knockout mice and TCF7 overexpression following adeno-associated virus 6 (AAV6) intratracheal delivery in rats were generated. The NK92 cell line and primary human pulmonary artery smooth muscle cells (hPASMCs) were used for in vitro experiments. Stressed NK cells were much higher in lungs from human PAH and MCT-induced PH compared to corresponding controls. Of note, TCF7 topped the list differentiating high-stressed from low-stressed human NK cells. TCF7-expressing NK cells displayed higher stress profile than TCF7-deficient cells. Tcf7-deficient NK cells exhibited lower Hsp90aa1 and Hsp90ab1 at transcriptional level and Hsp90 at protein level than Tcf7-expressing cells 24 h post-hypoxia. Mechanistically, TCF7-overexpressing NK cells secrete more SPP1 compared to control NK cells, thus promoting the proliferation and migration of hPASMCs 48 h post-hypoxia. TCF7 overexpression in rats aggravated PH features, while Tcf7 deficiency in mice alleviated pulmonary remodeling possibly due to the manipulation of HSP90 level in NK cells and SPP1 in the microenvironment. TCF7 contributes to the immunopathology of PH possibly through upregulation of stressed NK cells. Under stress conditions, NK cells promote the proliferation and migration of hPASMC through paracrine effects, thereby further promoting vascular remodeling.