Airway Inflammation and Lung Function in Sickle Cell Disease

Rationale: Asthma is a common comorbid condition in sickle cell disease (SCD). However, obstructive lung disease is prevalent in SCD, independent of a diagnosis of asthma. It is speculated that the heightened state of inflammation in SCD, involving pathways distinct from allergic asthma, may underlie the SCD-specific obstructive disease. Objective: The objective of the study was to compare airway and systemic inflammatory markers between SCD patients with pulmonary manifestations and patients with allergic asthma, and correlate the discriminating inflammatory markers with clinical measures of pulmonary disease. Materials and Methods: In a pilot translational study conducted at the Children's Hospital at Montefiore, 15 patients with SCD, and history of asthma, airway obstruction, or airway hyper-reactivity, and 15 control patients with allergic asthma 6-21 years of age were recruited. Inflammatory markers, including peripheral blood T helper cell subsets, serum and exhaled breath condensate (EBC) cytokines and chemokines of the Th-1/Th-17, Th-2, and monocytic pathways, and serum cysteinyl leukotrienes B4 (LTB4), were quantified, compared between the study groups, and correlated with atopic sensitization, pulmonary function tests, and markers of hemolysis. Results: White blood cells (P < 0.05) and monocytes (P < 0.001) were elevated in the SCD group, while atopic characteristics were higher in the control asthma group. Tumor necrosis factor-alpha (P < 0.01), interferon gamma inducible protein (IP)-10 (P < 0.05), and interleukin-4 (P < 0.01) in serum and monocyte chemotactic protein (MCP)-1 in EBC were higher in the SCD group (P ≤ 0.05). Forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1) in patients with SCD inversely correlated with serum IP-10 and LTB4 levels. Conclusions: Compared with atopic asthmatic patients, inflammatory markers involving Th-1, Th-2, and monocytic pathways were higher in the SCD group, among which Th-1 measures correlated with pulmonary function deficits.