Periostracum Cicadae exhibits immunosuppressive effects on dendritic cells and contact hypersensitivity responses

Ethnopharmacological relevance

Periostracum Cicadae (PC), the molted exoskeleton of the cicada Cryptotympana pustulata Fabricius, is frequently employed in Chinese herbal medicine. Based on traditional therapies and pharmacological studies, PC appears to have immunomodulatory activity. However, the specific impact of PC on immunomodulation, particularly its effect on dendritic cells (DCs), remains unknown. DCs act professionally as antigen-presenting cells that trigger adaptive immune responses, making them critical for immunomodulation.

Materials and methods

The DCs derived from mouse bone marrow were used to examine the suppressive effect of PC extract on DC activation and maturation. The in vivo suppressive effect was evaluated using a mouse model of contact hypersensitivity (CHS) responses. The determination of the substances in the sample was performed by Liquid chromatography-mass spectrometry/mass spectrometry.

Results

The ethyl acetate extract of PC (PCEA) significantly decreased the expressions of proinflammatory cytokines (IL-12, interleukin [IL]-6, as well as tumor necrosis factor [TNF]-α) and surface markers CD80 and CD86 in lipopolysaccharide-stimulated DCs. In the 2,4-dinitro-1-fluorobenzene-induced CHS mouse model, PCEA treatment dramatically attenuated the severity of symptoms. This was evidenced by the alleviation of ear swelling and a reduction in the count of infiltrating CD3⁺ T cells in the tested ears. In addition, N-acetyldopamine dimer and trimer were identified as major components.

Conclusion

This study is the first to show that components derived from PCEA inhibit the activation and maturation of DCs as well as CHS responses, indicating they have the potential for treating delayed-type hypersensitivity or DC-related immune disorders.