Effects of Imiquimod Application Durations on Psoriasis-like Lesions and Cytokine Expression in Mice

Abstract

Introduction: Psoriasis is a chronic inflammatory skin disorder with a complex pathogenesis, prominently involving the IL-17/IL-23 pathway. The imiquimod (IMQ)-induced mouse model is widely utilized for preclinical psoriasis research. This study aims to elucidate the effects of different durations of IMQ exposure on the development and characteristics of psoriasis-like lesions and the underlying changes of related cytokines in mice. Methods: Balb/c mice were topically administered IMQ on their shaved dorsal skin for either six or twelve consecutive days to induce psoriasis-like lesions, with untreated mice serving as controls. Clinical symptoms were assessed, and the expression levels of IL-17A and IL-23 were quantified using RT-PCR and immunohistochemistry. Histopathological changes were evaluated through H&E staining. Results: Mice exposed to IMQ displayed significant psoriasis-like lesions, with peak severity observed on day six across both exposure groups. Long-term exposure (12 days) did not aggravate the severity of lesions but affected the dynamics of cytokine expression and histopathological features. Notably, IL-17A and IL-23 levels correlated with the progression and severity of lesions in the short-term exposure group, decreasing significantly after the cessation of IMQ application. Conclusion: Short-term IMQ exposure (six days) effectively induces psoriasis-like lesions in mice, highlighting the pivotal role of the IL-17/IL-23 axis in this model. Extended exposure to IMQ (twelve days) offers no additional benefit in terms of lesion severity, suggesting that a six-day protocol is optimal for establishing a mouse model of psoriasis for the evaluation of therapeutic interventions targeting the IL-17/IL-23 pathway.