Endothelin receptor antagonism prevents hypoxia-induced mortality and morbidity in a mouse model of sickle-cell disease.

Patients with sickle-cell disease (SCD) suffer from tissue damage and life-threatening complications caused by vasoocclusive crisis (VOC). Endothelin receptors (ETRs) are mediators of one of the most potent vasoconstrictor pathways in mammals, but the relationship between vasoconstriction and VOC is not well understood. We report here that pharmacological inhibition of ETRs prevented hypoxia-induced acute VOC and organ damage in a mouse model of SCD. An in vivo ultrasonographic study of renal hemodynamics showed a substantial increase in endothelin-mediated vascular resistance during hypoxia/reoxygenation-induced VOC. This increase was reversed by administration of the dual ETR antagonist (ETRA) bosentan, which had pleiotropic beneficial effects in vivo. It prevented renal and pulmonary microvascular congestion, systemic inflammation, dense rbc formation, and infiltration of activated neutrophils into tissues with subsequent nitrative stress. Bosentan also prevented death of sickle-cell mice exposed to a severe hypoxic challenge. These findings in mice suggest that ETRA could be a potential new therapy for SCD, as it may prevent acute VOC and limit organ damage in sickle-cell patients.

Ultrasound imaging of renal vaso-occlusive events in transgenic sickle mice exposed to hypoxic stress.

One of the major clinical manifestations of sickle cell disease (SCD) is vaso-occlusive crisis in response to hypoxic exposure, leading to acute and chronic organ damages, especially in kidneys. In a SCD transgenic murine model, ultrasound imaging allowed us to characterize the circulatory changes in renal arteries during vaso-occlusive crisis. Cardiac output, heart rate and renal blood flow velocities (BFV) were measured in 10 male transgenic and 10 male wild-type (WT) mice with a conventional echograph (Vivid 7, GE Medical), before and after hypoxic exposure (8%O(2), 18h). To assess entrapment of red cells, histologic study of the kidneys was performed in both groups. Hypoxic exposure decreased heart rates in both groups (-17%, p < 0.001). Cardiac output remained stable in WT, and decreased in transgenic (-26%, p < 0.01). Peak systolic BFV in the renal artery was not modified in both groups. End-diastolic and mean BFV remained stable in WT, but decreased in sickle transgenic (-56%, p < 0.01 and -47%, p < 0.001, respectively). Transgenic mice displayed marked congestion in peritubular capillaries and glomerular abnormalities with trapped sickle red cells, whereas WT did not present any histologic injury. Five hours after hypoxic exposure, blood flow velocities returned to basal values in both groups. Decrease in end-diastolic and mean BFV in absence of peak systolic BFV after hypoxic exposure strongly indicated that the increase in vascular resistance in kidneys related to sickling of red cells. Thus, ultrasound imaging of the renal artery in mouse is a powerful, noninvasive, easy-to-repeat method to evidence circulatory changes in murine models of vascular renal human diseases.

Epidermal growth factor receptor promotes glomerular injury and renal failure in rapidly progressive crescentic glomerulonephritis.

Rapidly progressive glomerulonephritis (RPGN) is a life-threatening clinical syndrome and a morphological manifestation of severe glomerular injury that is marked by a proliferative histological pattern ('crescents') with accumulation of T cells and macrophages and proliferation of intrinsic glomerular cells. We show de novo induction of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in intrinsic glomerular epithelial cells (podocytes) from both mice and humans with RPGN. HB-EGF induction increases phosphorylation of the epidermal growth factor receptor (EGFR, also known as ErbB1) in mice with RPGN. In HB-EGF-deficient mice, EGFR activation in glomeruli is absent and the course of RPGN is improved. Autocrine HB-EGF induces a phenotypic switch in podocytes in vitro. Conditional deletion of the Egfr gene from podocytes of mice alleviates the severity of RPGN. Likewise, pharmacological blockade of EGFR also improves the course of RPGN, even when started 4 d after the induction of experimental RPGN. This suggests that targeting the HB-EGF-EGFR pathway could also be beneficial in treatment of human RPGN.