Effects of azathioprine and its metabolites on inflammatory cytokines in human nasal polyp organ cultures

Background Oral steroids are recommended for the treatment of nasal polyps (NPs), but prolonged use is avoided because of side effects. Topical steroids can also control NPs without significant complications; however, the response to this is partially successful, and additional therapies are needed to treat glucocorticoid‐resistant NPs. Azathioprine (AZA) and its first metabolite 6‐mercaptopurine (6‐MP) are important immunosuppressants used for the therapy of various diseases. The aim of this study was to investigate the effects of AZA and 6‐MP on inflammatory cytokines in organ‐cultured NPs. Methods NP explants were cultured using an air‐liquid interface method. Cultures were maintained in the absence and presence of steroid, AZA, and 6‐MP for 72 hours. Elaboration of cytokines tumor necrosis factor alpha (TNF‐α), interleukin (IL)‐2, IL‐4, IL‐5, and IL‐13 into the supernatant was quantitated using the enzyme‐linked immunosorbent assay (ELISA). The messenger RNA (mRNA) expression levels of TNF‐α, IL‐2, IL‐4, IL‐5, and IL‐13 in cultured mucosa were measured using real‐time polymerase chain reaction. Hematoxylin and eosin staining of cultured mucosa was performed to observe inflammatory cells. Immunohistochemistry was done to evaluate the distribution pattern of inflammatory cytokines in NP explants. Results On histologic examination, less inflammatory cell infiltration was found in NPs treated by steroid, AZA, and 6‐MP than in control, but there was no statistical significance (p = 0.218). On immunohistochemistry, IL‐13 showed a steady falling tendency in submucosal glands by steroid, AZA, and 6‐MP. Expression of TNF‐α, IL‐2, IL‐4, IL‐5, and IL‐13 mRNA in the NPs treated by steroid, AZA, and 6‐MP were significantly lower than those of the control (p