Alveolar
hypoxia elicits increases in mitochondrial
reactive oxygen species (ROS) signaling in pulmonary arterial (PA) smooth muscle cells (PASMCs), triggering hypoxic pulmonary vasoconstriction. Mice deficient in
sirtuin (
Sirt) 3, a
nicotinamide adenine dinucleotide-dependent mitochondrial deacetylase, demonstrate enhanced
left ventricular hypertrophy after aortic banding, whereas cells from these mice reportedly exhibit augmented
hypoxia-induced ROS signaling and
hypoxia-inducible factor (HIF)-1 activation. We therefore tested whether deletion of
Sirt3 would augment
hypoxia-induced ROS signaling in PASMCs, thereby exacerbating the development of
pulmonary hypertension (PH) and
right ventricular hypertrophy. In PASMCs from
Sirt3 knockout (
Sirt3(-/-)) mice in the C57BL/6 background, we observed that acute
hypoxia (1.5% O2; 30 min)-induced changes in ROS signaling, detected using targeted redox-sensitive, ratiometric fluorescent
protein sensors (roGFP) in the mitochondrial matrix, intermembrane space, and the cytosol, were indistinguishable from
Sirt3(+/+) cells. Acute
hypoxia-induced cytosolic calcium signaling in
Sirt3(-/-) PASMCs was also indistinguishable from
Sirt3(+/+) cells. During sustained
hypoxia (1.5% O2; 16 h),
Sirt3 deletion augmented mitochondrial matrix
oxidant stress, but this did not correspond to an augmentation of intermembrane space or cytosolic
oxidant signaling.
Sirt3 deletion did not affect HIF-1α stabilization under normoxia, nor did it augment HIF-1α stabilization during sustained
hypoxia (1.5% O2; 4 h).
Sirt3(-/-) mice housed in chronic
hypoxia (10% O2; 30 d) developed PH, PA wall remodeling, and
right ventricular hypertrophy that was indistinguishable from
Sirt3(+/+) littermates. Thus,
Sirt3 deletion does not augment
hypoxia-induced ROS signaling or its consequences in the cytosol of PASMCs, or the development of PH. These findings suggest that
Sirt3 responses may be cell type specific, or restricted to certain genetic backgrounds.