Effect of different high altitudes on vascular endothelial function in healthy people

Phospholipase D regulates ferroptosis signal transduction in mouse spleen hypoxia response

High-altitude hypoxia exposure can lead to phospholipase D-mediated lipid metabolism disorder in spleen tissues and induce ferroptosis. Nonetheless, the key genes underlying hypoxia-induced splenic phospholipase D and the ferroptosis pathway remain unclear. This study aimed to establish a hypoxia animal model. Combined transcriptomic and proteomic analyses showed that 95 predicted target genes (proteins) were significantly differentially expressed under hypoxic conditions. Key genes in phospholipase D and ferroptosis pathways under hypoxic exposure were identified by combining Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis techniques. Gene set enrichment analysis (GSEA) showed that the differential gene sets of the phospholipase D and ferroptosis signaling pathways were upregulated in the high-altitude hypoxia group. The genes in the phospholipase D signalling pathway were verified, and the expression levels of KIT and DGKG were upregulated in spleen tissues under hypoxic exposure. Subsequently, the mRNA and protein expression levels of genes from the exogenous pathway such as TFRC, SLC40A1, SLC7A11, TRP53, and FTH1 and those from the endogenous pathway such as GPX4, HMOX1, and ALOX15 differentials in the ferroptosis signalling pathway were verified, and the results indicated significant differential expression. In summary, exposure to high-altitude hypoxia mediated phospholipid metabolism disturbance through the phospholipase D signalling pathway and further induced ferroptosis, leading to splenic injury.

Histological and cytochemical analysis of the brain under conditions of hypobaric hypoxia-induced oxygen deficiency in albino rats

High altitude sickness is a life-threatening disease that occurs among acclimatized individuals working or living at a high altitude accompanied by hypobaric hypoxia exposure. The prolonged influence of hypobaric hypoxia on the brain may trigger neuronal damage and cell death due to an oxygen deficiency. The purpose of the current study was to investigate the histomorphological changes in the hippocampus, cerebral cortex, cerebellar cortex, and striatum of the rat's brain following chronic hypobaric hypoxia. Fourteen albino rats were used for this investigation. The animals were exposed to chronic hypobaric hypoxia in the special decompression chamber at an altitude of 7000 m for 7 days. The histological analysis was conducted via toluidine staining and silver impregnation. DNA damage and cell apoptosis were assessed via Feulgen staining. The histochemical assessment revealed increased dark neurons in the hippocampus with cell swelling. Silver impregnation showed increased argyrophilic neurons in the cerebellar cortex, striatum, CA1 subfield of the hippocampus, and cerebral cortex. The cytochemical analysis determined the increased apoptotic cells with hyperchromatic condensation and pyknosis in the hippocampus subfields and cerebral cortex. In addition, it has been observed that hypoxia has resulted in small hemorrhages and perivascular edema within the cerebellar and cerebral cortex. The results indicate brain injury observed in the various parts of the brain towards hypobaric hypoxia, however, the hippocampus showed greater vulnerability against hypoxic exposure in comparison to the striatum, cerebellum, and cerebral cortex. These changes support our insights regarding brain intolerance under conditions of hypoxia-induced oxygen deficiency and its histomorphological manifestations.

Temporal changes in biomarkers in individuals with and without acute mountain sickness following rapid ascent

BACKGROUND

Field studies have reported conflicting results regarding changes in biomarkers at high altitude. This study measured temporal changes in biomarkers and compared the differences between individuals with and without acute mountain sickness (AMS).

MATERIALS AND METHODS

This study included 34 nonacclimatized healthy participants. Ten-milliliters of blood were collected at four time points: 3 days before ascent (T0), on two successive nights at 3150 m (T1 and T2), and 2 days after descent (T3). Participants were transported by bus from 555 m to 3150 m within 3 hours. AMS was diagnosed using the self-reported Lake Louise Scoring (LLS) questionnaire.

RESULTS

Compared with T0, significant increases in E-selectin and decreases in vascular endothelial growth factor (VEGF) levels were observed at high altitude. Significantly increased C-reactive protein (CRP), monocyte chemoattractant protein-1 (MCP-1), and S100 calcium-binding protein B (S100B) levels were observed at T2, and significantly decreased vascular cell adhesion molecule-1 (VCAM-1) levels were observed at T3. Eighteen (53%) participants developed AMS. Changes in E-selectin, CRP, MCP-1, and S100B levels were independent of AMS. Relative to individuals without AMS, those with AMS had significantly higher atrial natriuretic peptide (ANP) and VCAM-1 levels and lower plasminogen activator inhibitor-1 (PAI-1) levels at T1 and higher brain natriuretic peptide and lower VEGF and PAI-1 levels at T3. LLSs were positively correlated with ANP and VCAM-1 levels and negatively correlated with PAI-1 levels measured at T1.

CONCLUSIONS

After acute ascent, individuals with and without AMS exhibited different trends in biomarkers associated with endothelial cell activation and natriuretic peptides.

Adaptation and altitude sickness: A 40-year bibliometric analysis and collaborative networks

Introduction

We analyze the scientific production and collaboration networks of studies based on adaptation and altitude diseases in the period 1980-2020.

Methods

The publications were extracted from journals indexed in Scopus. The bibliometric analysis was used to analyze the scientific production, including the number of annual publications, the documents, and the characteristics of the publications. With the VOSviewer software, the analysis of collaborative networks, productivity of the countries, as well as the analysis of the co-occurrence of keywords were visualized.

Results

15,240 documents were registered, of which 3,985 documents were analyzed. A significant trend was observed in the number of publications (R ²: 0.9847; P: < 0.001), with annual growth of 4.6%. The largest number of publications were original articles (77.8%), these published more frequently in the journal "Altitude Medicine and Biology". The largest number of countries were from Europe and Asia; however, the largest collaboration network was with the United States. Of the countries with high altitudes, China and Peru ranked first in scientific productivity. The research priorities were on the adaptation mechanism (37.1%), mainly anoxia and respiratory function. Acute mountain sickness (18.4%) and pulmonary edema (14.7%) were the most reported diseases. Of the top 10 institutions, "University of Colorado" and "Universidad Peruana Cayetano Heredia" contributed more than 100 publications.

Conclusions

Scientific production on adaptation and altitude illnesses continues to grow. The United States and United Kingdom present collaborative networks with high-altitude countries. The research is aimed at studying the mechanisms of adaptation to altitude and acute mountain sickness.

Circulating Microparticles Are Differentially Increased in Lowlanders and Highlanders with High Altitude Induced Pulmonary Hypertension during the Cold Season

The role of microparticles (MPs) and cold in high altitude pulmonary hypertension (HAPH) remains unexplored. We investigated the impact of long-term cold exposure on the pulmonary circulation in lowlanders and high-altitude natives and the role of MPs. Pulmonary hemodynamics were evaluated using Doppler echocardiography at the end of the colder and warmer seasons. We further examined the miRNA content of MPs isolated from the study participants and studied their effects on human pulmonary artery smooth muscle (hPASMCs) and endothelial cells (hPAECs). Long-term exposure to cold environment was associated with an enhanced pulmonary artery pressure in highlanders. Plasma levels of CD62E-positive and CD68-positive MPs increased in response to cold in lowlanders and HAPH highlanders. The miRNA-210 expression contained in MPs differentially changed in response to cold in lowlanders and highlanders. MPs isolated from lowlanders and highlanders increased proliferation and reduced apoptosis of hPASMCs. Further, MPs isolated from warm-exposed HAPH highlanders and cold-exposed highlanders exerted the most pronounced effects on VEGF expression in hPAECs. We demonstrated that prolonged exposure to cold is associated with elevated pulmonary artery pressures, which are most pronounced in high-altitude residents. Further, the numbers of circulating MPs are differentially increased in lowlanders and HAPH highlanders during the colder season.

Network Pharmacology and In Vivo Analysis of Dahuang-Huangqi Decoction Effectiveness in Alleviating Renal Interstitial Fibrosis

Dahuang and Huangqi are the most frequently prescribed treatment methods for chronic kidney disease in China. Our study aimed to clarify the pharmacological mechanism of action of Dahuang-Huangqi decoction (DHHQD) in renal interstitial fibrosis (RIF). The intersection of genes targeted by DHHQD active ingredients and RIF target genes was searched using network pharmacology to build a chemical ingredient and disease target network. For in vivo analysis, Sprague–Dawley rats with unilateral urethral obstruction (UUO) were administered DHHQD, and their kidney function-related indicators and pathological indices were determined. The expression of core targets was quantified using real-time polymerase chain reaction and western blotting. A total of 139 common targets for DHHQD and RIF in chronic kidney disease were detected. Compared with the untreated UUO rats, the DHHQD-treated rats showed reductions in the following: blood urea nitrogen and serum creatinine levels, kidney tubular atrophy and necrosis, interstitial fibrosis, hyperplasia and abnormal deposition of extracellular matrix, and microstructural changes in the mesangial matrix and glomerular basement membrane. DHHQD treatment significantly regulated the levels of renal core proteins, such as eNOS, IL-6, EGFR, and VEGF and reduced the mRNA and protein expression of the core targets involved in inflammation pathways, such as PI3K/AKT and TLR4/NF-κB. DHHQD treatment ameliorated the severity of RIF by potentially regulating the AKT/PI3K and TLR4/NF-κB signaling pathways. Our study findings provide insights into the mechanisms associated with DHHQD action and essential data for future research.

GLOBAL REACH 2018: intra-arterial vitamin C improves endothelial-dependent vasodilatory function in humans at high altitude

High altitude-induced hypoxaemia is often associated with peripheral vascular dysfunction. However, the basic mechanism(s) underlying high-altitude vascular impairments remains unclear. This study tested the hypothesis that oxidative stress contributes to the impairments in endothelial function during early acclimatization to high altitude. Ten young healthy lowlanders were tested at sea level (344 m) and following 4-6 days at high altitude (4300 m). Vascular endothelial function was determined using the isolated perfused forearm technique with forearm blood flow (FBF) measured by strain-gauge venous occlusion plethysmography. FBF was quantified in response to acetylcholine (ACh), sodium nitroprusside (SNP) and a co-infusion of ACh with the antioxidant vitamin C (ACh+VitC). The total FBF response to ACh (area under the curve) was ∼30% lower at high altitude than at sea level (P = 0.048). There was no difference in the response to SNP at high altitude (P = 0.860). At sea level, the co-infusion of ACh+VitC had no influence on the FBF dose response (P = 0.268); however, at high altitude ACh+VitC resulted in an average increase in the FBF dose response by ∼20% (P = 0.019). At high altitude, the decreased FBF response to ACh, and the increase in FBF in response to ACh+VitC, were associated with the magnitude of arterial hypoxaemia (R² = 0.60, P = 0.008 and R² = 0.63, P = 0.006, respectively). Collectively, these data support the hypothesis that impairments in vascular endothelial function at high altitude are in part attributable to oxidative stress, a consequence of the magnitude of hypoxaemia. These data extend our basic understanding of vascular (mal)adaptation to high-altitude sojourns, with important implications for understanding the aetiology of high altitude-related vascular dysfunction. KEY POINTS: Vascular dysfunction has been demonstrated in lowlanders at high altitude (>4000 m). However, the extent of impairment and the delineation of contributing mechanisms have remained unclear. Using the gold-standard isolated perfused forearm model, we determined the extent of vasodilatory dysfunction and oxidative stress as a contributing mechanism in healthy lowlanders before and 4-6 days after rapid ascent to 4300 m. The total forearm blood flow response to acetylcholine at high altitude was decreased by ∼30%. Co-infusion of acetylcholine with the antioxidant vitamin C partially restored the total forearm blood flow by ∼20%. The magnitude of forearm blood flow reduction, as well as the impact of oxidative stress, was positively associated with the individual severity of hypoxaemia. These data extend our basic understanding of vascular (mal)adaptation to high-altitude sojourns, with important implications for understanding the aetiology of high altitude-related changes in endothelial-mediated vasodilatory function.