Protective effects of phosphodiesterase‐4 (PDE‐4) inhibition in the early phase of pulmonary arterial hypertension in transgenic sickle cell mice

Abstract

Pulmonary arterial hypertension (PAH) is one of the leading causes of morbidity and mortality in adult patients with sickle cell disease (SCD). Here, we developed a model to study the early stage of PAH in SCD. We exposed wild-type and transgenic sickle cell SAD (Hbb(s)/Hbb(s)) mice to hypoxia (8% O(2)) for 7 days. Prolonged hypoxia in SAD mice only induced 1) increased neutrophil count in both bronchoalveolar lavage (BAL) and peripheral circulation; 2) increased BAL IL1beta, IL10, IL6, and TNF-alpha; and 3) up-regulation of the genes endothelin-1, cyclo-oxygenase-2, angiotensin-converting-enzyme, and IL-1beta, suggesting that amplified inflammatory response and activation of the endothelin-1 system may contribute to the early phase of PAH in SCD. Since phosphodiesterases (PDEs) are involved in pulmonary vascular tone regulation, we evaluated gene expression of phosphodiesterase-4 (PDE-4) isoforms and of PDE-1, -2, -3, -7, -8, which are the main cyclic-adenosine-monophosphate hydrolyzing enzymes. In SAD mouse lungs, prolonged hypoxia significantly increased PDE-4 and -1 gene expressions. The PDE-4 inhibitor, rolipram, prevented the hypoxia-induced PDE-4 and -1 gene up-regulation and interfered with the development of PAH, most likely through modulation of both vascular tone and inflammatory factors. This finding supports a possible therapeutic use of PDEs inhibitors in the earlier phases of PAH in SCD.

Abnormal modulation of cell protective systems in response to ischemic/reperfusion injury is important in the development of mouse sickle cell hepatopathy

“…In the late phase of hypoxia, we observed increased hematocrit, hemoglobin levels and reticulocyte count in both mouse strains, which were changes compatible with the effect of hypoxia on erythropoiesis. 27 As we previously reported, prolonged hypoxia also induced a slight worsening of hemolysis in SAD mice, as indicated by the increase in bilirubin and plasma iron levels observed at 168 h of hypoxia only in SAD mice (Table 2). 27 We then evaluated the effects of I/R injury on NF-κB mRNA levels (Nfkb) in laser-captured hepatocytes from both mouse strains.…”

“…26,27 In brief, WT (n=6) and SAD (n=6) mice were evaluated in ambient air and then after hypoxia (8% O2) maintained for 4 h (WT and SAD, n=6), 48 h (WT and SAD, n=6) or 168 h (WT and SAD, n=8), followed by 2 h of reoxygenation. No major problems in mouse behavior or significant changes in mouse weight occurred during the I/R protocol.…”

“…Blood sampling and vehicle administration had been previously shown not to affect the blood parameters measured in this study. 26,27 Treatment was started 48 h before hypoxia and maintained during the 168 h of hypoxia. Mice did not show major side effects related to rolipram treatment.…”

Using biological networks to search for interacting loci in genome-wide association studies

“…These two SNPs belong to two phosphodiesterase-4, and experimental evidence argues in favour of protective effects of these enzymes with hypertension. 26 More precisely, phosphodiesterase-4 are enzymes that break a phosphodiester bond, and these enzymes have been identified as new potential therapeutics. 35 The fourth SNP pair involves rs2830075 and rs2163786 in susceptibility to RA.…”

“…Genes PDE4B and PDE8B are connected to hypertension as members of phosphodiesterase-4, which have been recently reported to have protective effects in the early stage of pulmonary arterial hypertension in mice. 26 …”