Association of increased risk of asthma with elevated arginase & interleukin-13 levels in serum & rs2781666 G/T genotype of arginase I

Background & objectives: High expression of arginase gene and its elevated level in serum and bronchial lavage reported in animal models indicated an association with the pathogenesis of asthma. This study was undertaken to assess the serum arginase activity in symptomatic asthma patients and healthy controls and to correlate it with cytokine levels [interleukin (IL)-4 and IL-13] and arginase I (ARG1) gene polymorphism. Methods: Asthma was confirmed by lung function test according to the GINA guidelines in patients attending Allergy and Pulmonology Clinic, Bhagwan Mahavir Hospital and Research Centre, Hyderabad, India, a tertiary care centre, during 2013-2015. Serum arginase was analyzed using a biochemical assay, total IgE and cytokine levels by enzyme-linked immunosorbent assay and genotyping of ARG1 for single-nucleotide polymorphisms (SNPs) rs2781666 and rs60389358 using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method. Results: There was a significant two-fold elevation in the arginase activity in asthmatics as compared to healthy controls which correlated with disease severity. Non-atopic asthmatics showed elevated activity of arginase compared to atopics, indicating its possible role in intrinsic asthma. Levels of serum IL-13 and IL-4 were significantly high in asthma group which correlated with disease severity that was assessed by spirometry. A positive correlation was observed between arginase activity and IL-13 concentration. Genetic analysis of ARG1 SNPs revealed that rs2781666 G/T genotype, T allele and C-T haplotype (rs60389358 and rs2781666) were associated with susceptibility to asthma. Interpretation & conclusions: This study indicated that high arginase activity and IL-13 concentration in the serum and ARG1 rs2781666 G/T genotype might increase the risk of asthma in susceptible population. Further studies need to be done with a large sample to confirm these findings.