Hypertension
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Obstructive sleep apnea occurs frequently in patients with drug-resistant hypertension. The factors accounting for this observation, however, are unclear. Both conditions demonstrate clinical features suggestive of extracellular fluid volume overload. ⋯ The overnight reduction in calf circumference and increase in neck circumference were also greater in drug-resistant hypertension (both P ≤ 0.02). In hypertensive subjects, rostral fluid displacement strongly relates to the severity of obstructive sleep apnea with its magnitude being greater in drug-resistant hypertension. Our findings support the concept that fluid redistribution centrally during sleep accounts for the high prevalence of obstructive sleep apnea in drug-resistant hypertension.
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The major cause of death among pulmonary hypertension patients is right heart failure, but the biology of right heart is not well understood. Previous studies showed that mechanisms of the activation of GATA4, a major regulator of cardiac hypertrophy, in response to pressure overload are different between left and right ventricles. In the left ventricle, aortic constriction triggers GATA4 activation via posttranslational modifications without influencing GATA4 expression, while pulmonary artery banding enhances GATA4 expression in the right ventricle. ⋯ The right ventricle contains a higher level of CBF/NF-Y compared to the left ventricle, and this may allow for efficient activation in response to annexin A1 degradation. Signaling via iron-catalyzed protein oxidation mediates hypoxic pulmonary hypertension-induced annexin A1 degradation, Gata4 gene transcription, and right ventricular hypertrophy. These results establish a right heart-specific signaling mechanism in response to pressure overload, which involves metal-catalyzed carbonylation and degradation of annexin A1 that liberates CBF/NF-Y to activate Gata4 gene transcription.