Role for Chemokines in the Vasculopathy Associated with Sickle Cell Dsease and Pulmonary Hypertension

Sickle cell disease (SCD) is a hemolytic disorder characterized by transient vaso-occlusive crisis (VOC). Moreover, there is a high prevalence of SCD-associated pulmonary arterial hypertension (PAH), indicated by a tricuspid regurgitant jet velocity (TRV) ≥ 2.5 m/sec, leading to increased risk for early mortality. Monocytes have been proposed as pivotal cells in vascular inflammation in animal models of SCD. Preliminary studies in our group have shown a potential role for monocyte chemokines in the vasculopathy of SCD. The objective of this study is to investigate the role of two chemokines: regulated upon activation, normal T cell expressed and secreted (RANTES) and macrophage inflammatory protein-1β (MIP-1β) in SCD and SCD-associated PAH. Plasma samples were collected from patients with SCD at steady state and from healthy African-American control subjects. Plasma levels of RANTES and MIP-1β were measured using an enzyme immunoassay system. Patients with SCD exhibited significantly higher levels of both MIP-1β (median 465.3 vs. 398.5 pg/ml, p<0.0001) and RANTES (median 47774 vs. 17445pg/ml, p<0.0004) than healthy controls. Further characterization of SCD patients with or without PAH demonstrated that whereas MIP-1β exhibited no correlation with PAH, RANTES demonstrated an inverse correlation with PAH (r= −0.25, p<0.03) with significance achieved in patients that exhibited severe PAH (TRV> 2.9, p<0.05). These findings suggest that

1. both chemokines, RANTES and MIP-1β, are associated with the vasculopathy of SCD, and

2. whereas MIP-1β does not appear to be associated with SCD-associated PAH, RANTES levels are inversely correlated to the severity of PAH. RANTES merits further investigation as a potential marker in PAH, and for a possible role in its progression.