Calcium Restores the Macrophage Response to Nontypeable Haemophilus influenzae in Chronic Obstructive Pulmonary Disease.

Alveolar macrophages in chronic obstructive pulmonary disease (COPD) have demonstrated impaired bacterial phagocytosis and disordered cytokine secretion, which are calcium-dependent processes. We determined how calcium moderates the macrophage response to nontypeable Haemophilus influenzae (NTHI). We hypothesized that augmenting extracellular calcium during bacterial challenge would restore bacterial phagocytosis and cytokine secretion in monocyte-derived macrophages (MDMs) from subjects with COPD. We further determined whether restoration of pattern recognition and scavenger receptors correlated with the calcium-induced improvements in macrophage function. Monocytes were purified from whole blood from healthy control subjects (n = 20) and patients with moderate to severe COPD (n = 35), and cultured in suspension with granulocyte macrophage colony-stimulating factor to generate MDMs. The MDMs were incubated with fluorescently labeled NTHI with and without calcium lactate and calcium channel inhibitors. Phagocytosis efficiency was evaluated by flow cytometry. Supernatants were assayed for cytokines using bead array technology. Cell surface receptor expression was assayed by multicolor flow cytometry. Extracellular calcium significantly improved phagocytosis and cytokine secretion (IL-8, TNF-alpha, and macrophage inflammatory protein [MIP]-1 alpha, and -1 beta) in COPD MDMs. NTHI challenge led to statistically significant reductions in CD16 (Fc gamma RIII), and extracellular calcium up-regulated both CD16 and macrophage receptor with collagenous structure (MARCO). Specific calcium channel inhibitors abrogated calcium-mediated MARCO up-regulation and cytokine secretion. Extracellular calcium improved phagocytosis, restored innate cytokine secretion, and increased cell surface expression of bacterial recognition receptors, CD16 and MARCO. These observations support the therapeutic use of calcium to improve macrophage function in COPD to decrease exacerbations and chronic bacterial infection.