Hypothesis: angiogenesis cytokines in high altitude cerebral oedema

The Effect of High-Altitude Hypoxia on Neuropsychiatric Functions

Liu, Bo, Minlan Yuan, Mei Yang, Hongru Zhu, and Wei Zhang. The effect of high-altitude hypoxia on neuropsychiatric functions. High Alt Med Biol. 25:26-41, 2024. Background: In recent years, there has been a growing popularity in engaging in activities at high altitudes, such as hiking and work. However, these high-altitude environments pose risks of hypoxia, which can lead to various acute or chronic cerebral diseases. These conditions include common neurological diseases such as acute mountain sickness (AMS), high-altitude cerebral edema, and altitude-related cerebrovascular diseases, as well as psychiatric disorders such as anxiety, depression, and psychosis. However, reviews of altitude-related neuropsychiatric conditions and their potential mechanisms are rare. Methods: We conducted searches on PubMed and Google Scholar, exploring existing literature encompassing preclinical and clinical studies. Our aim was to summarize the prevalent neuropsychiatric diseases induced by altitude hypoxia, the potential pathophysiological mechanisms, as well as the available pharmacological and nonpharmacological strategies for prevention and intervention. Results: The development of altitude-related cerebral diseases may arise from various pathogenic processes, including neurovascular alterations associated with hypoxia, cytotoxic responses, activation of reactive oxygen species, and dysregulation of the expression of hypoxia inducible factor-1 and nuclear factor erythroid 2-related factor 2. Furthermore, the interplay between hypoxia-induced neurological and psychiatric changes is believed to play a role in the progression of brain damage. Conclusions: While there is some evidence pointing to pathophysiological changes in hypoxia-induced brain damage, the precise mechanisms responsible for neuropsychiatric alterations remain elusive. Currently, the range of prevention and intervention strategies available is primarily focused on addressing AMS, with a preference for prevention rather than treatment.

Expression Profiles of Long Noncoding RNAs in Mice with High-Altitude Hypoxia-Induced Brain Injury Treated with Gymnadenia conopsea (L.) R. Br

BACKGROUND

The unique geographical environment at high altitudes may cause a series of diseases, such as acute altitude reaction, cerebral edema, and pulmonary edema. Gymnadenia conopsea (L.) R. Br. has been reported to have an effect on high-altitude hypoxia. However, the molecular mechanism, especially the expression of long noncoding RNAs (lncRNAs), is not yet clear.

METHODS

The expression profiles of lncRNAs in high-altitude hypoxia-induced brain injury mice treated with Gymnadenia conopsea (L.) R. Br. by using a microarray method.

RESULTS

A total of 226 differentially expressed lncRNAs, 126 significantly dysregulated mRNAs and 23 differentially expressed circRNAs were detected (>2.0-fold, p<0.05). The expression of selected lncRNAs, mRNAs and circRNAs was validated by qRT-PCR. KEGG analysis showed that the mRNAs coexpressed with lncRNAs were involved in inflammation and hypoxia pathways, including the HIF-1, PI3K-Akt, and NF-kappa B signaling pathways. The lncRNA-TF network analysis results indicated that the lncRNAs were regulated mostly by HMGA2, SRY, GATA4, SOX5, and ZBTB16.

CONCLUSION

This study is the first to report the expression profiles of lncRNAs, mRNAs and circRNAs in mice with high-altitude hypoxia-induced brain injury treated with Gymnadenia conopsea (L.) R. Br. and may improve the understanding of the molecular mechanism of Gymnadenia conopsea (L.) R. Br. in treating high altitude hypoxia-induced brain injury.

Angiogenic/lymphangiogenic factors and adaptation to extreme altitudes during an expedition to Mount Everest

AIM

To analyse the correlation between production of angiogenic [vascular endothelial growth factor A (VEGF-A) and interleukin 8 (IL-8)] and lymphangiogenic factors (VEGF-C and D) and adaptation to high altitude (>8000 m). Erythropoietin (EPO) served as a positive control.

METHODS

We analysed the percentage of oxygen saturation and the plasmatic contents of VEGF-A, C, D, IL-8 and EPO in seven mountaineers and four Sherpas during an expedition to Mount Everest. Acute mountain sickness was also evaluated using the Lake Louise score.

RESULTS

Whereas VEGF-A, IL-8, VEGF-C and EPO were transiently up-regulated at 5000 m and decreased at the highest altitudes, VEGF-D remained elevated throughout the ascent. Sherpas had increased basal levels of VEGF-A, C, IL-8 and EPO and up-regulation of all the tested factors when they passed the altitude at which they lived.

CONCLUSION

Our data suggest that expression of angiogenic and lymphangiogenic factors is up-regulated directly or indirectly by altitude-dependent hypoxia. Both factors could be involved in a mechanism of adaptation to high altitudes.

The cerebral effects of ascent to high altitudes

Cellular hypoxia is the common final pathway of brain injury that occurs not just after asphyxia, but also when cerebral perfusion is impaired directly (eg, embolic stroke) or indirectly (eg, raised intracranial pressure after head injury). We Review recent advances in the understanding of neurological clinical syndromes that occur on exposure to high altitudes, including high altitude headache (HAH), acute mountain sickness (AMS), and high altitude cerebral oedema (HACE), and the genetics, molecular mechanisms, and physiology that underpin them. We also present the vasogenic and cytotoxic bases for HACE and explore venous hypertension as a possible contributory factor. Although the factors that control susceptibility to HACE are poorly understood, the effects of exposure to altitude (and thus hypobaric hypoxia) might provide a reproducible model for the study of cerebral cellular hypoxia in healthy individuals. The effects of hypobaric hypoxia might also provide new insights into the understanding of hypoxia in the clinical setting.

High Altitude Cerebral Edema

This review focuses on the epidemiology, clinical description, pathophysiology, treatment, and prevention of high altitude cerebral edema (HACE). HACE is an uncommon and sometimes fatal complication of traveling too high, too fast to high altitudes. HACE is distinguished by disturbances of consciousness that may progress to deep coma, psychiatric changes of varying degree, confusion, and ataxia of gait. It is most often a complication of acute mountain sickness or high altitude pulmonary edema. The current leading theory of its pathophysiology is that HACE is a vasogenic edema; that is, a disruption of the blood-brain barrier, and we review possible mechanisms to explain this. Treatment and prevention of HACE are similar to those for the other altitude illnesses, but with greater emphasis on descent and steroids. We conclude the review with several case histories to illustrate key clinical features of the disorder.

[Acute mountain sickness: the clinical characteristics of a cohort of 615 patients]

OBJECTIVE

To study the acute mountain sickness (AMS) and the influence the altitude has on individuals according to time of exposure, age and place of residence. Study cohort prospective in the shelters of Cotopaxi and Chimborazo (4,800 and 5,000 m), in the Ecuatorian Andes.

SUBJECTS AND METHODS

Tourists from 8 to 51 years of age, residents of the coastal and mountain regions, exposed suddenly to the altitude. Signs and symptoms were recorded at 2, 8, 20 and 24 h of exposure and categorized according to the degree of acute mountain sickness found: AMS 1 [4 to 7 points (light), AMS 2 [8 to 11 points (moderate)] and AMS 3 [more than 12 points (severe)].

RESULTS

The study, consisted of 615 patients, was completed by 564. Neurological symptoms are prevalent (headache in the 81.7% of patients) over cardiopulmonary symptoms (cardiac frequency over 100/min in the 25.6%). At 20 h (after one night), the signs and symptoms are more intense and affect a greater number of people (p < 0.0001). Patients from 8 to 22 years of age and residents of the coast have a greater risk of developing AMS 2 (p < 0.01). Overweight, a sedentary life style and a previous incidence of altitude sickness are factors which contribute to the development of AMS 2 (p < 0.001).

CONCLUSIONS

AMS is an important neurological affection. Young people, individuals from sea-level, as well as those whose are overweight, sedentary or who have previously experienced AMS, have a higher risk of developing AMS 2 after a sudden exposure to altitudes between 4,800 and 5,000 meters. Lack of balance and coordination, and shortness of breath at rest imply AMS 3 and the presence of high altitude cerebral or pulmonary edema.

Plasma vascular endothelial growth factor in acute mountain sickness

STUDY OBJECTIVES

To investigate the hypothesis that an increase in circulating vascular endothelial growth factor (VEGF) occurs in mountaineers at high altitude, particularly in association with acute mountain sickness (AMS) and/or low hemoglobin oxygen saturation.

DESIGN

: Collection of medical histories, AMS scores, plasma samples, and arterial oxygen saturation (SaO(2)) measurements from mountaineers at 1,500 feet (sea level) and at 14,200 feet.

SETTING

Mount McKinley ("Denali"), AK.

PARTICIPANTS

Sixty-six mountaineers.

INTERVENTIONS

None.

MEASUREMENTS AND RESULTS

Plasma VEGF at 14,200 feet was not increased in any group. In fact, plasma VEGF was significantly lower in subjects who did not develop AMS (53 +/- 7.9 pg/mL; mean +/- SEM; n = 47) compared to control subjects at sea level (98.4 +/- 14.3 pg/mL; n = 7; p = 0.005). Plasma VEGF at 14, 200 feet for subjects with AMS (62 +/- 12 pg/mL; n = 15) did not differ significantly from subjects at 14,200 feet without AMS, or from control subjects at sea level. Of a small number of subjects with paired specimens at sea level and at base camp (n = 5), subjects who exhibited a decrease in plasma VEGF at 14,200 feet were those who did not develop AMS. Neither SaO(2), prior AMS, AMS symptom scores, or acetazolamide use were correlated with plasma VEGF.

CONCLUSIONS

Subjects at high altitude who do not develop AMS have lower plasma VEGF levels compared to control subjects at sea level. Plasma VEGF at high altitude is not elevated in association with AMS or hypoxia. Sustained plasma VEGF at altitude may reflect a phenotype more susceptible to AMS.