Guben-Qushi-Huayu formula and calycosin improve epidermal barrier function in psoriasis by inhibiting small proline-rich protein 1A.

BACKGROUND

As a persistent inflammatory skin disease, psoriasis is notably challenging to treat effectively. Guben-Qushi-Huayu formula (GQH) has proven effective in enhancing epidermal barrier function and quality of life in psoriasis patients. However, its underlying mechanisms and active compounds remain elusive.

PURPOSE: To elucidate the therapeutic target of GQH in epidermal barrier restoration and identify its active compound(s).

METHODS

GQH efficacy was evaluated in imiquimod-induced psoriatic mice. RNA sequencing (RNA-seq) analysis revealed underlying mechanisms, validated by RT-PCR, immunohistochemistry, western blotting, ELISA, and Gene Expression Omnibus database analyses. The role of small proline-rich protein 1A (SPRR1A) was confirmed via siRNA knockdown and overexpression in human keratinocyte (HaCaT) cells. UPLC-MS/MS was used to identify active compounds in GQH-containing serum (GCS). GCS and calycosin on cell viability and migration were assessed in SPRR1A-knockdown HaCaT cells. GCS-SPRR1A binding was evaluated using drug affinity responsive target stability assay, whereas calycosin-SPRR1A binding was evaluated by surface plasmon resonance.

RESULTS

GQH significantly ameliorated psoriatic lesions by reducing inflammation, suppressing keratinocyte hyperproliferation, and restoring epidermal barrier function. RNA-seq analysis revealed GQH's potent regulatory effect on cornified envelope (CE)-related genes, and identified SPRR1A as a key target. Functional validation via SPRR1A knockdown/overexpression in HaCaT cells demonstrated its critical role in modulating keratinocyte migration, proliferation, and inflammatory factor secretion. Significantly, GCS inhibited these pathological processes in HaCaT cells through SPRR1A-dependent mechanisms. UPLC-MS/MS identified eight bioactive compounds in GCS, including calycosin, which directly suppressed keratinocyte proliferation and migration. A high affinity was observed between calycosin and SPRR1A (KD = 4.13×10-6 M).

CONCLUSION

SPRR1A represents a previously unrecognized druggable target in psoriasis pathogenesis, which can be effectively modulated by both the herbal formula GQH and its purified component calycosin.