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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-α, and macrophage inflammatory protein [MIP]-1α, and -1β) in COPD MDMs. NTHI challenge led to statistically significant reductions in CD16 (FcγRIII), 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.

Rationale: COPD patients have a high risk of community-acquired pneumonia (CAP). We studied Streptococcus pneumoniae (SP) and non-typeable Haemophilus influenzae (NTHI) effects on COPD macrophage responses and how budesonide (BUD) and fluticasone propionate (FP) alter host-pathogen interactions. Methods: Blood monocytes from 10 controls, 20 healthy smokers and moderate-severe COPD [19 current smokers (CS), 21 ex-smokers (ES)] were cultured with GM-CSF to generate monocyte-derived macrophages (MDM). MDM were pre-treated with 10nM BUD, FP or vehicle for 24h and exposed to live SP or NTHI. After 24h cell surface bacterial recognition receptor expression was analyzed by flow cytometry and supernatant cytokines by bead array. Data at p≤0.05 (2-sided paired t-test) are shown. Results: SP and NTHI reduced receptor expression on MDM from COPD (mainly in ES) and healthy smokers but not controls. SP and NTHI reduced SRA-1 in CS & ES and MARCO in ES. SP also reduced CD1d, TLR2 and TLR4 in CS & ES and CD93 in ES. NTHI also reduced CD11b in CS & ES and CD35 and CD206 in ES. BUD prevented reductions by SP on SRA-1 and by NTHI on CD206, both in ES. FP prevented SP reductions of TLR2 in CS & ES and TLR4 in ES but had no effect on reductions by NTHI. BUD and FP inhibited NTHI- and SP-induced cytokines. Conclusions: Reduction of bacterial recognition receptors on macrophages may be part of the enhanced risk of CAP in COPD. BUD prevented receptor reductions induced in ex-smokers by both SP and NTHI while FP affected only SP-induced reductions. These differential effects may contribute to the difference in pneumonia risk between inhaled BUD and FP treatments in COPD. Support: AstraZeneca.