Nasal instillation of povidone‐iodine ameliorates ongoing mucosal inflammation in a pre‐sensitized murine model of Der p1‐induced allergic rhinitis

Abstract Background Interleukin (IL)‐33, when cleaved into smaller fragments by proteases, becomes hyperactive, contributing to allergic inflammation. Povidone‐iodine (PVP‐I) is an iodine‐based compound that exhibits antimicrobial properties and inhibits proteases. This study aimed to investigate whether PVP‐I treatment inhibits IL‐33 cleavage, improves allergic rhinitis (AR) symptoms, and suppresses allergic inflammation in a mouse model. Methods In vitro experiments using full‐length recombinant human IL‐33 and allergens, including house dust mites or Dermatophagoides pteronyssinus 1, were conducted using western blotting. Fifty BALB/c mice were divided into five groups: control (CON), AR with phosphate‐buffered saline treatment (AR), PVP‐I treatment (AR + PVP), trans ‐epoxysuccinyl‐L‐leucylamido(4‐guanidino)butane (E64) treatment (AR + E64), and dexamethasone treatment (AR + Dexa). Nasal symptom scores, including rubbing and sneezing, were measured. The cytokine levels in the nasal lavage fluid (NLF) and the concentration of immunoglobulins in the blood serum were assessed. Nasal mucosa from each group was used for reverse transcriptase‐polymerase chain reaction (RT‐PCR) and histological analyses were conducted. Results PVP‐I treatment reduced nasal symptoms, suppressed allergic inflammation, and decreased the levels of IL‐33, IL‐5, and IL‐13 in the NLF and total immunoglobulin E (IgE) and specific IgE in the serum. Histopathological analysis revealed a reduction in the number of eosinophils and goblet cells in the nasal mucosa of the AR + PVP group when compared to the AR group. RT‐PCR and immunofluorescence staining confirmed the downregulation of genes and proteins associated with allergic inflammation. Conclusions These findings suggest that nasal irrigation with PVP‐I may be a promising therapeutic option for managing AR by inhibiting IL‐33 activation and suppressing allergic inflammation.