HSP-70-Mediated Hyperbaric Oxygen Reduces Brain and Pulmonary Edema and Cognitive Deficits in Rats in a Simulated High-Altitude Exposure.

High-mountain sickness is characterized by brain and pulmonary edema and cognitive deficits. The definition can be fulfilled by a rat model of high-altitude exposure (HAE) used in the present study. This study aimed to investigate the protective effect of hyperbaric oxygen therapy (HBO2T) and to determine the underlying mechanisms. Rats were subjected to an HAE (9.7% O2 at 0.47 absolute atmosphere of 6,000 m for 3 days). Immediately after termination of HAE, rats were treated with HBO2T (100% O2 at 2.0 absolute atmosphere for 1 hour per day for 5 consecutive days) or non-HBO2T (21% O2 at 1.0 absolute atmosphere for 1 hour per day for 5 consecutive days). As compared to non-HAE+non-HBO2T controls, the HAE+non-HBO2T rats exhibited brain edema and resulted in cognitive deficits, reduced food and water consumption, body weight loss, increased cerebral inflammation and oxidative stress, and pulmonary edema. HBO2T increased expression of both hippocampus and lung heat shock protein (HSP-70) and also reversed the HAE-induced brain and pulmonary edema, cognitive deficits, reduced food and water consumption, body weight loss, and brain inflammation and oxidative stress. Decreasing the overexpression of HSP-70 in both hippocampus and lung tissues with HSP-70 antibodies significantly attenuated the beneficial effects exerted by HBO2T in HAE rats. Our data provide in vivo evidence that HBO2T works on a remodeling of brain/lung to exert a protective effect against simulated high-mountain sickness via enhancing HSP-70 expression in HAE rats.

Differentiated demographic histories and local adaptations between Sherpas and Tibetans.

BACKGROUND: The genetic relationships reported by recent studies between Sherpas and Tibetans are controversial. To gain insights into the population history and the genetic basis of high-altitude adaptation of the two groups, we analyzed genome-wide data in 111 Sherpas (Tibet and Nepal) and 177 Tibetans (Tibet and Qinghai), together with available data from present-day human populations. RESULTS: Sherpas and Tibetans show considerable genetic differences and can be distinguished as two distinct groups, even though the divergence between them (~3200-11,300 years ago) is much later than that between Han Chinese and either of the two groups (~6200-16,000 years ago). Sub-population structures exist in both Sherpas and Tibetans, corresponding to geographical or linguistic groups. Differentiation of genetic variants between Sherpas and Tibetans associated with adaptation to either high-altitude or ultraviolet radiation were identified and validated by genotyping additional Sherpa and Tibetan samples. CONCLUSIONS: Our analyses indicate that both Sherpas and Tibetans are admixed populations, but the findings do not support the previous hypothesis that Tibetans derive their ancestry from Sherpas and Han Chinese. Compared to Tibetans, Sherpas show higher levels of South Asian ancestry, while Tibetans show higher levels of East Asian and Central Asian/Siberian ancestry. We propose a new model to elucidate the differentiated demographic histories and local adaptations of Sherpas and Tibetans.

Rhodiola crenulata extract counteracts the effect of hypobaric hypoxia in rat heart via redirection of the nitric oxide and arginase 1 pathway.

BACKGROUND: Rhodiola crenulata is traditionally used as a folk medicine in Tibet for preventing high-altitude illnesses, including sudden cardiac death (SCD). The cardio-protective effects of Rhodiola crenulata root extract (RCE) against hypoxia in vivo have been recently confirmed. However, the way in which RCE produces these effects remains unclear. The present study is designed to confirm the protective effects of RCE on the heart in acute hypobaric hypoxia exposure and examine the mechanisms by which this occurs. METHODS: Sprague-Dawley (SD) rats were pretreated with or without RCE and then exposed to a simulated altitude of 8000 m in a hypobaric hypoxia chamber for 9 h. The expression of cardiac arginase 1 (Arg-1) and endothelial nitric oxide synthase (eNOS) and the activity of associated signaling pathways was examined. RESULTS: Hypoxia reduced cardiac eNOS phosphorylation and increased Arg-1 expression, but both responses were reversed by RCE pre-treatment. In addition, RCE decreased the hypoxia-induced oxidative stress markers of reactive oxygen species (ROS) production, malondialdehyde (MDA) level, and protein carbonyl content. Furthermore, RCE protected cardiomyocytes from hypoxia-induced cardiac apoptosis and restored the phosphorylation level of AKT and p38 MAPK as well as the superoxide dismutase 2 (SOD2) content in hypoxic animals. CONCLUSION: The findings provide evidence that the effects of Rhodiola crenulata against altitude illness are partially mediated by modulation of eNOS and Arg-1 pathways in the heart.

[MORPHOLOGICAL DIFFERENCES BETWEEN THE EFFECTS OF VARIOUS MODES OF PRECONDITIONING AIMED AT CORRECTING THE DAMAGE TO THE HIPPOCAMPAL NEURONS BY SEVERE HYPOBARIC HYPOXIA].

In 5 groups of rats (6 animals in each), the changes of neurons in hippocampal fields CA1 and CA4 were studied 7 days after severe hypobaric hypoxia (180 mm Hg, for 3 h) preceded by various numbers (1, 3 and 6) of sessions of preconditioning (PC) by mild hypobaric hypoxia (360 mm Hg, for 2 h, 24 h prior to severe hypoxia). It was found that a single session of PC did not prevent the damage to the structure of neurons and their death after exposure to severe hypoxia. Meanwhile, 6, and especially 3 sessions of PC induced protective mechanisms of neuronal damage prevention. In rats after 6 sessions of PC, unlike those exposed to 3 sessions, mild chromatolysis of hippocampal neurons was demonstrated. This could result from prolonged hypermetabolic activity of neurons and indicate their functional overloading.

EGLN1 involvement in high-altitude adaptation revealed through genetic analysis of extreme constitution types defined in Ayurveda.

It is being realized that identification of subgroups within normal controls corresponding to contrasting disease susceptibility is likely to lead to more effective predictive marker discovery. We have previously used the Ayurvedic concept of Prakriti, which relates to phenotypic differences in normal individuals, including response to external environment as well as susceptibility to diseases, to explore molecular differences between three contrasting Prakriti types: Vata, Pitta, and Kapha. EGLN1 was one among 251 differentially expressed genes between the Prakriti types. In the present study, we report a link between high-altitude adaptation and common variations rs479200 (C/T) and rs480902 (T/C) in the EGLN1 gene. Furthermore, the TT genotype of rs479200, which was more frequent in Kapha types and correlated with higher expression of EGLN1, was associated with patients suffering from high-altitude pulmonary edema, whereas it was present at a significantly lower frequency in Pitta and nearly absent in natives of high altitude. Analysis of Human Genome Diversity Panel-Centre d'Etude du Polymorphisme Humain (HGDP-CEPH) and Indian Genome Variation Consortium panels showed that disparate genetic lineages at high altitudes share the same ancestral allele (T) of rs480902 that is overrepresented in Pitta and positively correlated with altitude globally (P < 0.001), including in India. Thus, EGLN1 polymorphisms are associated with high-altitude adaptation, and a genotype rare in highlanders but overrepresented in a subgroup of normal lowlanders discernable by Ayurveda may confer increased risk for high-altitude pulmonary edema.