Nuclear factor erythroid 2-related factor 2 (Nrf2) is a key regulator that activates many
antioxidant enzymes. Oxidative stress, which accumulates in diseased lungs associated with
pulmonary hypertension (PH), is thought to be responsible for the progression of cardiopulmonary changes. To test whether Nrf2 activation would exert therapeutic efficacy against cardiopulmonary changes in a
hypoxia-induced PH model, wild-type (WT) and Nrf2-deficient mice as well as Kelch-like ECH associating
protein 1 (Keap1) (negative regulator of Nrf2) knockdown mutant mice were exposed to hypobaric
hypoxia for 3 weeks. This chronic
hypoxia exacerbated right ventricular systolic pressure,
right ventricular hypertrophy (RVH), and pulmonary
vascular remodeling in the WT mice. These pathological changes were associated with aberrant accumulation of
Tenascin-C, a disease-indicative extracellular
glycoprotein. Simultaneous administration of
oltipraz, a potent Nrf2 activator, significantly attenuated RVH and pulmonary
vascular remodeling and concomitantly ameliorated
Tenascin-C accumulation in the hypoxic mice.
Hypoxia-exposed Nrf2-deficient mice developed more pronounced RVH than WT mice, whereas
hypoxia-exposed Keap1-knockdown mice showed less RVH and pulmonary
vascular remodeling than WT mice, underscoring the beneficial potency of Nrf2 activity against PH. We also demonstrated that expression of the Nrf2-regulated
antioxidant enzymes was decreased in a patient with
chronic obstructive pulmonary disease associated with PH. The decreased
antioxidant enzymes may underlie the pathogenesis of cardiopulmonary changes in the patient with
chronic obstructive pulmonary disease and PH. The pharmacologically or genetically induced Nrf2 activity clearly decreased RVH and pulmonary
vascular remodeling in the hypoxic PH model. The efficacy of
oltipraz highlights a promising therapeutic potency of Nrf2 activators for the prevention of PH in patients with hypoxemic
lung disease.