Objective

2

To explore the possible action mechanism of

Qingshi Anti

-

itch Ointment

（青石止痒软膏， QAO） in the treatment of psoriasis.

Methods

2

Forty mice were randomly divided into four groups， blank group， model group， calcipotriol group and QAO group， with 10 mice in each group. Except for the blank group， psoriasis was induced by applying imiquimod cream to the dorsal skin. After modeling for 6 hours daily， the calcipotriol group and QAO group were treated with 0.5 g of calcipotriol ointment or 0.5 g of QAO， respectively， applied to the treated dorsal skin. The blank group and the model group received no treatment. The skin lesions were observed， and the psoriasis area and severity index （PASI） score was assessed every other day. After 7 days， Hematoxylin and Eosin （HE） staining was performed on dorsal skin tissue to observe pathological changes. The levels of interleukin 1β （IL-1β） and interleukin 18 （IL-18） were determined by enzym-linked immunosorbent assay （ELISA）. The protein levels of Caspase-1，Pro-Caspase-1， gasdermin D （GSDMD） and gasdermin-D-N （GSDMD-N） were detected by Western Blot （WB）. The protein levels of GSDMD were observed by immunohistochemistry.

Results

2

Compared with the blank group， the model group mice showed redness， erythema， and white scales on their skin， with histological observations indicating epidermal thickening， elongated spines， and infiltration of inflammatory cells. The PASI scores of the skin tissue on days 1， 3， 5， and 7 were elevated； the IOD and AOD values of GSDMD protein increased； the protein levels of Caspase-1， Pro-Caspase-1，GSDMD， GSDMD-N， and IL-1β and IL-18 were significantly elevated （

P

＜0.05 or

P

＜0.01）. Compared with the model group， the QAO group and calcipotriol group showed lighter skin lesions； the PASI scores on day 5 and day 7 in the QAO group， and on day 3， 5， and 7 in the calcipotriol group， were reduced； the IOD and AOD values of GSDMD protein， and the protein level of Caspase-1， GSDMD， and GSDMD-N， as well as level of IL-18 and IL-1β decreased in both groups； in the calcipotriol group， Pro-Caspase-1 protein level also decreased （

P

＜0.05 or

P

＜0.01）. Compared with the calcipotriol group， the QAO group showed slightly redder skin， more obvious thickening of the stratum corneum， and less capillary dilation； the PASI scores on day 3 and day 7 increased， while the score on day 5 was reduced； the protein level of Pro-Caspase-1， GSDMD， GSDMD-N， and the level of IL-18 and IL-1β were increased in the QAO group （

P

＜0.05）.

Conclusion

2

QAO can effectively relieve psoriasis dermatitis in mice. Its potential mechanism may be related to the regulation of the Caspase-1/GSDMD protein pathway， down-regulation of IL-18 and IL-1β levels， and alleviation of pyroptosis.