Secondary Exposure to IMQ or Irritants Enhances Psoriasiform Recurrence Through Inflammatory Memory

Area of Science:

• Dermatology
• Immunology
• Pathophysiology

Background:

• Psoriasis relapse often involves heightened inflammation compared to initial onset.
• Mechanisms driving psoriasis recurrence are not fully understood.
• Investigating inflammatory memory in skin could reveal relapse drivers.

Purpose of the Study:

• To determine if secondary skin exposure to imiquimod (IMQ) or other irritants exacerbates psoriasiform inflammation via inflammatory memory.
• To establish a model for studying psoriasis relapse mechanisms.

Main Methods:

• BALB/c mice were induced with psoriasiform dermatitis using IMQ, followed by a recovery period.
• Secondary challenges involved IMQ, TPA, or SDS.
• Evaluations included clinical scoring, histopathology, immunohistochemistry, ELISA, Western blotting, and RT-qPCR.

Main Results:

• Secondary stimulation led to significantly more severe skin inflammation than initial exposure.
• Increased clinical severity, epidermal thickness, and inflammatory cell infiltration were observed.
• Elevated IL-17A and TNF-α levels and cross-stimulus inflammatory memory were noted.

Conclusions:

• Repeated cutaneous exposure to IMQ or irritants aggravates psoriasiform inflammation through inflammatory memory.
• This exacerbation suggests cross-stimulus inflammatory memory in the skin.
• The findings provide a model for studying disease relapse and therapeutic interventions.