Association between Polyunsaturated Fatty Acid Profile and Bronchial Inflammation in Bronchiolitis Obliterans.

Introduction: Bronchiolitis obliterans (BO) is a chronic lung disease, which occurs after an insult to the lower airways, in particular after airway infections or after stem cell transplantation, and which results in persistent inflammation. -3 and -6 polyunsaturated fatty acids (PUFA) have been shown to influence the inflammatory processes in chronic inflammatory conditions. Since BO is maintained by persistent pulmonary inflammation, a disbalanced -6/-3 fatty acid profile could support the inflammatory process in patients with BO and therefore, could become an approach to new therapeutic options.

Methods: Twenty-five patients with BO (age: 13; 7-39) and 26 healthy controls (age: 19; 7-31) participated in the study. Lung function (forced viral capacity (FVC), forced expiratory volume 1 (FEV1), residual volume (RV)), and lung clearance index (LCI) were measured. Induced sputum was analyzed for cytology and cytokine levels (IL-1, IL-6, IL-8, TNF-) using cytometric bead array (CBA). The PUFA profile was determined in the serum and induced sputum by gas chromatography.

Results: Patients presented with significantly lower FVC and FEV1 as well as higher RV and LCI measurements compared to the control group. Apart from a massive airway inflammation indicated by elevated numbers of total cells and neutrophils, the CBA analysis showed significantly increased levels of IL-1, IL-6, and IL-8. The analysis of PUFA in sputum and serum revealed a significant difference in the ratio between the -6 PUFA arachidonic acid (AA) and the -3 PUFA docosahexaenoic acid (DHA) (AA : DHA). Furthermore, the AA : DHA ratio significantly correlated with the inflammatory cytokines in induced sputum.

Conclusion: Lung function in BO is significantly impaired and associated with uncontrolled neutrophil-dominated airway inflammation. Furthermore, the imbalance in the AA/DHA ratio in favor of -6 PUFA demonstrates a pro-inflammatory microenvironment in the cell membrane, which correlates with the inflammatory cytokines in induced sputum and might be an option for an anti-inflammatory therapy in BO.