PDE-4 Inhibitor Rolipram Prevents Hypoxia Induced Pulmonary Hypertension in Transgenic Sickle Cell Sad Mice.

Pulmonary hypertension (PH) is one of the major causes of morbidity and mortality for young-adult patients with sickle cell disease (SCD). Little is known about the role of vaso-active agents, pro-inflammatory and pro-fibrotic mediators in the genesis of PH in SCD.

We developed a model for studying PH in transgenic sickle cell SAD mice. Wild-type (WT) and SAD mice aged between 4 and 6 months were divided in groups of 7 animals each. One group from each strain served as control under normoxia, while a second group from each strain was exposed to 7 days hypoxia (8% oxygen). The following parameters were evaluated in normoxic and hypoxic groups: lung histopathology, complete blood count, reticulocytes, bronchoalveolar lavage (BAL) total leokocyte and neutrophil count, BAL levels of IL-6, IL-10, IL-1β and TNF-α. The expression of nine genes was examined by quantitative RT-PCR. These included endothelin-1 (ET-1), endothelin-1 receptor (ET-1R), cycloxygenase-2 (COX2), NF-kBp65, transforming-growth-factor-1β (TGF-1β), metalloproteinase-2 and 9 (MMP-2, MMP-9), IL-10 and IL-1β.

Two of the seven SAD mice exposed to hypoxia died at day fourth. The remaining five mice were sacrified at day seven and showed: a) increased pulmonary arterial wall thickness and α-actin staining, suggesting a vascular remodeling; b) lung injury compatible with PH in SCD; c) increased BAL total leukocyte and neutrophil count; d) increased BAL IL1β, IL10, IL6 and TNF-α; e) increased peripheral neutrophil and reticulocyte counts, hematocrit and hemoglobin levels. In lungs of hypoxic SAD mice, ET-1, ET-1R, TGF-1β, MMP-2, MMP-9, IL-1β and IL-10 gene expression were induced, with no significant changes in NF-Kbp65 gene expression. These data were consistent with a model of PH in SCD.

We then assessed the effect of the PDE-4 inhibitor ROLIPRAM on the PH in seven hypoxic SAD mice. ROLIPRAM was administrated at the dosage of 30 mg/Kg/day by gavage. No deaths were observed in this group. ROLIPRAM a) protected SAD mice from hypoxia induced lung injury; b) decreased BAL total leukocyte and neutrophil count; c) decreased BAL IL-1β, IL-6 and IL-10 levels; d) reduced peripheral neutrophil count; d) normalized and/or modulated the expression of the hypoxia-induced genes. These data suggest that the PDE-4 inhibitor ROLIPRAM has anti-inflammatory properties and could have beneficial effects on the hypoxia-induced airway-remodeling and possibly PH in sickle cell disease.