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Hypoxia induced pulmonary hypertension (HPH) represents a complex pathology that involves active vascular remodeling, loss of vascular tone, enhanced pulmonary inflammation, and increased deposition of extracellular matrix proteins. Megakaryocytic leukemia 1 (MKL1) is a transcriptional regulator known to influence cellular response to stress signals in the vasculature. We report here that in response to chronic hypobaric hypoxia, MKL1 expression was up-regulated in the lungs in rats. Short hairpin RNA (shRNA) mediated depletion of MKL1 significantly ameliorated the elevation of pulmonary arterial pressure in vivo with a marked alleviation of vascular remodeling. MKL1 silencing also restored the expression of NO, a key vasoactive molecule necessary for the maintenance of vascular tone. In addition, hypoxia induced pulmonary inflammation was dampened in the absence of MKL1 as evidenced by normalized levels of pro-inflammatory cytokines and chemokines as well as reduced infiltration of pro-inflammatory immune cells in the lungs. Of note, MKL1 knockdown attenuated fibrogenesis in the lungs as indicated by picrosirius red staining. Finally, we demonstrate that MKL1 mediated transcriptional activation of type I collagen genes in smooth muscle cells under hypoxic conditions. In conclusion, we data highlight a previously unidentified role for MKL1 in the pathogenesis of HPH and as such lay down groundwork for future investigation and drug development. [ABSTRACT FROM AUTHOR]

Hypobaric hypoxia is the primary cause of high altitude polycythemia (HAPC). Mitochondria are critical organelles that consume high levels of oxygen and generate ATP. We hypothesize that the mitochondrion may be at the center of HAPC, and mitochondrial DNA (mtDNA) SNPs may be involved in its development. First, we conducted a case-control study to investigate the association of mtDNA variants with HAPC in Han Chinese migrating to the Qinghai-Tibetan Plateau. Pearson’s chi-square tests revealed that mtDNA 8414T (MU) frequency (19.5%) in the HAPC group was significantly higher than that of the control (13.0%, P = 0.04, OR = 1.615, 95%CI: 1.020–2.555). The multivariate logistic regression analysis, after adjustment for environmental factors, revealed that mtDNA 10609T (WT) was significantly associated with an increased risk of HAPC (P<0.01, OR = 2.558, 95%CI: 1.250–5.236). Second, to verify the association, in vitro experiments of transmitochondrial cybrids was performed and revealed that the mtDNA 10609 variant promoted hypoxia-induced increase of intracellular ROS, but the mtDNA 8414 variant did not. Our findings provide evidence that, in Han Chinese, mtDNA 10609T promotes hypoxia-induced increase of intracellular ROS and is a HAPC risk factor. [ABSTRACT FROM AUTHOR]

High-altitude pulmonary edema (HAPE) is a severe disease caused by high-altitude hypoxia. Since some individuals are more susceptible to high altitude than others, the incidence is variable and cannot be predicted. Furthermore, multiple genes can contribute to the occurrence of HAPE, making it even more difficult to predict. The genes associated with HAPE include those in the renin-angiotensin-aldosterone system pathway, the nitric oxide pathway and the hypoxia-inducible factor pathway. Other genes associated with HAPE include tyrosine hydroxylase (TH), vascular endothelial growth factor (VEGF), pulmonary surfactant proteins and β2-adrenergic receptor. The association of the polymorphisms of these genes with HAPE susceptibility has previously been investigated. Among the genes evaluated, polymorphisms of NOS3, ACE, CYP11B2, Hsp70 and endothelin-1 and pulmonary surfactant proteins A1 and A2 were shown to be associated with HAPE incidence, while associations between TH, VEGF and HAPE remain to be fully elucidated. Novel technological approaches, including genome-wide association studies and next-generation sequencing, are currently being used to identify new HAPE susceptibility genes. The goal of this review article is to summarize the current literature and to define the outstanding areas of research that need to be explored to advance our ability to predict when HAPE will occur. Copyright © 2012 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background.—: The role of genetics in determining an individual''s susceptibility to high altitude pulmonary edema (HAPE) is unclear. However a number of genetic polymorphisms have recently been found to be overrepresented in patients with HAPE. Changes at the mitochondrial level may play an important role in the human body''s adaptation to hypoxia. Polymorphisms of mitochondrial DNA (mtDNA) have been shown to be responsible for differences in organelle function. Therefore, the frequency of mtDNA 3397A/G and 3552T/A polymorphisms were studied to determine their potential role in HAPE. Objectives.—: To further study the role of mtDNA 3397A/G and 3552T/A variations of reduced nicotinamide adenosine dinucleotide dehydrogenase 1 in HAPE susceptibility. Methods.—: The single-nucleotide polymorphisms of mtDNA 3397 and 3552 in patients with HAPE (n = 132) and their matched control subjects (n = 233) were studied using polymerase chain reaction sequencing. Results.—: The frequency of mtDNA 3397G in the HAPE group (2.3%) was significantly higher than that of the control group (0%; P = .021; odds ratio, 2.806; 95% confidence interval, 2.443 to 3.223). The frequency of mtDNA 3552A in the HAPE group (6.8%) also was significantly higher than in the control group (1.7%; P = .012; odds ratio, 4.198; 95% confidence interval, 1.264 to 13.880). Conclusions.—: In this study, we present the first evidence of differences in mtDNA polymorphism frequencies between HAPE victims and healthy Han Chinese. Genotypes of mtDNA 3397G and 3552A were correlated with HAPE susceptibility. This result could contribute to defining the role of the mitochondrial genome in the pathogenesis of HAPE. [Copyright &y& Elsevier]

The article discusses hypoxic pathophysiology and high-altitude medicine as of December 2012, with a focus on physiological adaptations in mitochondria and their potential role in high-altitude illness susceptibility. Topics include cerebral cortex mitochondria and the respiratory control rate (RCR), mitochondrial membrane potential (MMP), and genetic adaptations to hypobaric hypoxia exposure. Additional information is presented on the oxidative phosphorylation ratio (OPR) and Tibetans' mitochondrial DNA (mtDNA) sequences.