Lung Health in the Solomon Islands: A Mixed Methods Study.

BACKGROUND AND OBJECTIVES: Despite a population of 600,000 people from 900 islands, there is little published data on the prevalence of lung disease in the Solomon Islands. We sought to 1) estimate the prevalence of obstructive lung disease (OLD) in Gizo, Solomon Islands, 2) identify risk factors for respiratory disease in this population and 3) review current management practices for respiratory disease through an audit of local emergency department (ED) presentations. METHODS: A two-part mixed methods study was performed between March and May 2019; the first was a population-based, cross-sectional study conducted in Gizo, Solomon Islands, with a random sample undergoing questionnaires and spirometry. The second was an audit of Gizo Hospital ED records to assess presentation numbers, diagnoses and outcomes. RESULTS: A total of 104 patients were randomly selected for spirometry. The mean age was 46.9 years. Current smoking rates were high (24.0% overall, 43.3% age < 40, 16.2% age ≥ 40) as was regular (>10h/week) exposure to indoor/enclosed wood fire ovens (51.5%). The prevalence of COPD was 3.2% overall. A further 9.7% of participants demonstrated significant bronchodilator responsiveness suggestive of possible asthma. Most patients seen in ED presented with a respiratory condition or fever/viral illness, but spirometry was not available. Only four outpatients were prescribed salbutamol and two patients inhaled corticosteroid. CONCLUSION: There appears to be a high burden of obstructive lung disease in the Solomon Islands with high smoking rates, indoor smoke exposure and bronchodilator responsiveness. Respiratory symptoms are common amongst hospital ED presentations; however, inhaled asthma treatments are infrequently prescribed to outpatients.

Cigarette smoke-induced changes to alveolar macrophage phenotype and function are improved by treatment with procysteine.

Defective efferocytosis may perpetuate inflammation in smokers with or without chronic obstructive pulmonary disease (COPD). Macrophages may phenotypically polarize to classically activated M1 (proinflammatory; regulation of antigen presentation) or alternatively activated M2 (poor antigen presentation; improved efferocytosis) markers. In bronchoalveolar lavage (BAL)-derived macrophages from control subjects and smoker/ex-smoker COPD subjects, we investigated M1 markers (antigen-presenting major histocompatibility complex [MHC] Classes I and II), complement receptors (CRs), the high-affinity Fc receptor involved with immunoglobulin binding for phagocytosis (Fc-gamma receptor, FcγR1), M2 markers (dendritic cell-specific intercellular adhesion molecule-grabbing nonintegrin [DC-SIGN] and arginase), and macrophage function (efferocytosis and proinflammatory cytokine production in response to LPS). The availability of glutathione (GSH) in BAL was assessed, because GSH is essential for both M1 function and efferocytosis. We used a murine model to investigate macrophage phenotype/function further in response to cigarette smoke. In lung tissue (disaggregated) and BAL, we investigated CRs, the available GSH, arginase, and efferocytosis. We further investigated the therapeutic effects of an oral administration of a GSH precursor, cysteine l-2-oxothiazolidine-4-carboxylic acid (procysteine). Significantly decreased efferocytosis, available GSH, and M1 antigen-presenting molecules were evident in both COPD groups, with increased DC-SIGN and production of proinflammatory cytokines. Increased CR-3 was evident in the current-smoker COPD group. In smoke-exposed mice, we found decreased efferocytosis (BAL and tissue) and available GSH, and increased arginase, CR-3, and CR-4. Treatment with procysteine significantly increased GSH, efferocytosis (BAL: control group, 26.2%; smoke-exposed group, 17.66%; procysteine + smoke-exposed group, 27.8%; tissue: control group, 35.9%; smoke-exposed group, 21.6%; procysteine + smoke-exposed group, 34.5%), and decreased CR-4 in lung tissue. Macrophages in COPD are of a mixed phenotype and function. The increased efferocytosis and availability of GSH in response to procysteine indicates that this treatment may be useful as adjunct therapy for improving macrophage function in COPD and in susceptible smokers.