Left ventricular dysfunction induced by nonsevere idiopathic pulmonary arterial hypertension: a pressure-volume relationship study.

RATIONALE: Severe increase in right ventricular pressure can compromise left ventricular (LV) function because of impaired interventricular interaction and aggravate the symptoms. OBJECTIVES: To elucidate how nonsevere idiopathic pulmonary arterial hypertension (IPAH) influences LV function because of impaired interventricular interaction. METHODS: Invasive pressure-volume (PV) loop analysis obtained by conductance catheterization was performed at rest and during atrial pacing in patients with mild IPAH (n = 10) compared with patients with isolated LV diastolic dysfunction (DD) (n = 10) and control subjects without heart failure symptoms (n = 9). MEASUREMENTS AND MAIN RESULTS: Patients with nonsevere IPAH (pulmonary artery pressure mean 29 ± 5 mm Hg) and patients with DD showed preserved systolic (ejection fraction 63 ± 12% and 62 ± 9%) and impaired LV diastolic function at rest (LV stiffness 0.027 ± 0.012 ml(-1) and 0.029 ± 0.014 ml(-1)). During pacing at 120 per minute patients with IPAH and DD decreased their stroke volume (-25% and -30%; P < 0.05) and failed to increase cardiac output significantly. Opposite to patients with DD and control subjects, temporary preload reduction during inferior vena cava occlusion initially induced an expansion of LV end-diastolic volume in IPAH (+7%; P < 0.05), whereas end-diastolic pressure continuously dropped. This resulted in an initial downward shift to the right of the PV loop indicating better LV filling, which was associated with a temporary improvement of cardiac output (+11%; P < 0.05) in the patients with IPAH, but not in patients with DD and control subjects. CONCLUSIONS: Mild idiopathic pulmonary arterial pressure impairs LV diastolic compliance even in the absence of the intrinsic LV disease and contributes to the reduced cardiac performance at stress.

Mitochondrion-derived reactive oxygen species lead to enhanced amyloid beta formation.

AIMS: Intracellular amyloid beta (Aß) oligomers and extracellular Aß plaques are key players in the progression of sporadic Alzheimer's disease (AD). Still, the molecular signals triggering Aß production are largely unclear. We asked whether mitochondrion-derived reactive oxygen species (ROS) are sufficient to increase Aß generation and thereby initiate a vicious cycle further impairing mitochondrial function. RESULTS: Complex I and III dysfunction was induced in a cell model using the respiratory inhibitors rotenone and antimycin, resulting in mitochondrial dysfunction and enhanced ROS levels. Both treatments lead to elevated levels of Aß. Presence of an antioxidant rescued mitochondrial function and reduced formation of Aß, demonstrating that the observed effects depended on ROS. Conversely, cells overproducing Aß showed impairment of mitochondrial function such as comprised mitochondrial respiration, strongly altered morphology, and reduced intracellular mobility of mitochondria. Again, the capability of these cells to generate Aß was partly reduced by an antioxidant, indicating that Aß formation was also ROS dependent. Moreover, mice with a genetic defect in complex I, or AD mice treated with a complex I inhibitor, showed enhanced Aß levels in vivo. INNOVATION: We show for the first time that mitochondrion-derived ROS are sufficient to trigger Aß production in vitro and in vivo. CONCLUSION: Several lines of evidence show that mitochondrion-derived ROS result in enhanced amyloidogenic amyloid precursor protein processing, and that Aß itself leads to mitochondrial dysfunction and increased ROS levels. We propose that starting from mitochondrial dysfunction a vicious cycle is triggered that contributes to the pathogenesis of sporadic AD.