Inhibition of MRP4 prevents and reverses pulmonary hypertension in mice
Yannis Hara, … , Marc Humbert, Jean-Sébastien Hulot
Yannis Hara, … , Marc Humbert, Jean-Sébastien Hulot
Published June 13, 2011
Citation Information: J Clin Invest. 2011;121(7):2888-2897. https://doi.org/10.1172/JCI45023.
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Research Article Pulmonology

Inhibition of MRP4 prevents and reverses pulmonary hypertension in mice

Abstract

Multidrug resistance–associated protein 4 (MRP4, also known as Abcc4) regulates intracellular levels of cAMP and cGMP in arterial SMCs. Here, we report our studies of the role of MRP4 in the development and progression of pulmonary arterial hypertension (PAH), a severe vascular disease characterized by chronically elevated pulmonary artery pressure and accompanied by remodeling of the small pulmonary arteries as a prelude to right heart failure and premature death. MRP4 expression was increased in pulmonary arteries from patients with idiopathic PAH as well as in WT mice exposed to hypoxic conditions. Consistent with a pathogenic role for MRP4 in PAH, WT mice exposed to hypoxia for 3 weeks showed reversal of hypoxic pulmonary hypertension (PH) following oral administration of the MRP4 inhibitor MK571, and Mrp4–/– mice were protected from hypoxic PH. Inhibition of MRP4 in vitro was accompanied by increased intracellular cAMP and cGMP levels and PKA and PKG activities, implicating cyclic nucleotide-related signaling pathways in the mechanism underlying the protective effects of MRP4 inhibition. Our data suggest that MRP4 could represent a potential target for therapeutic intervention in PAH.

Authors

Yannis Hara, Yassine Sassi, Christelle Guibert, Natacha Gambaryan, Peter Dorfmüller, Saadia Eddahibi, Anne-Marie Lompré, Marc Humbert, Jean-Sébastien Hulot

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Figure 4

Reversal of hypoxia-induced PH after MRP4 inhibition.

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Reversal of hypoxia-induced PH after MRP4 inhibition. (A) Schematic repr...
(A) Schematic representation of PH-reversal experimental study design. (B) RVSP (mmHg) measured after 3 and 5 weeks (w) of normoxia and hypoxia conditions and in mice that were exposed for 5 weeks to hypoxia and treated with saline or 5 mg/kg/d or 25 mg/kg/d of MK571 (6 mice at least per group) during the last 2 weeks (***P < 0.001; **P < 0.01). (C) RV hypertrophy reflected by the Fulton index for the same groups (at least 6 mice per group). (D–I) Representative H&E-stained sections of small pulmonary arteries from the different groups: control normoxia versus hypoxia at 3 weeks (D and F), control normoxia at 5 weeks (E) versus hypoxia at 5 weeks after 2 weeks of saline (G), MK571 5 mg/kg/d (H), and 25 mg/kg/d (I) treatments. (J) Percentage of medial thickness of small arteries in relation to cross-sectional diameter. (K) Western blot analysis of total lung extracts from mice. Proteins were incubated with anti-MRP4 and anti–pVASP-Ser157 to assess PKA activity and anti–pVASP-Ser239 to assess PKG activity. Anti-VASP was used for normalization and anti-GAPDH as a loading control. Immunoblots are representative of 4 individual lungs for each groups (*P < 0.05). Scale bars: 20 μm.