Efficacy and action mechanisms of a Chinese herbal formula on experimental models of atopic dermatitis

Atopic dermatitis (AD) is a skin inflammatory disease characterized by erythema, eruption, lichenification and pruritus. Shi Zhen Formula (SZF), an empirical Chinese herbal preparation, has clinical efficacy in relieving the symptoms of AD patients. However, the underlying molecular mechanisms of SZF remained unclear. We aimed to investigate the anti-AD effects of SZF and elucidate its underlying molecular mechanisms using in vitro and in vivo models of AD. High-performance liquid chromatography analysis was performed for quality control of SZF extract. The anti-inflammatory effect of SZF was investigated through evaluating the levels of nitric oxide (NO), chemokines and pro-inflammatory cytokines in the lipopolysaccharide (LPS) stimulated RAW264.7 cells. AD-like skin lesions in female BALB/c mice were induced by 2,4-dinitrochlorobenzene (DNCB). SZF (3.15, 6.30 and 9.45 g/kg) and dexamethasone (5 mg/kg) were administered by gavage daily for 15 consecutive days. The body weight, skin thickness, skin dermatitis severity and scratching behaviors were recorded throughout the study. Histological analysis, reverse transcription-quantitative polymerase chain reaction (RT-PCR), western blot (WB) and ELISA analysis were used to illuminate the molecular targets associated with the anti-AD effects of SZF. SZF markedly decreased the epidermal thickening and infiltration of mast cells in the ears and dorsal skin of the 2,4-dinitrochlorobenzene (DNCB)-treated mice. SZF not only suppressed the levels of immunoglobulin E (IgE), histamine, thymic stromal lymphopoietin (TSLP) and IL-4 in the serum but also suppressed the over-production of IL-4 and IL-6 and gene expressions of IL-4, IL-13, IL-31 and TSLP in the dorsal skin. Moreover, SZF improved epidermal barrier by increasing the protein expressions of filaggrin, involucrin and loricrin and inhibited the activation of NF-κB p65 pathway in the dorsal skin of the DNCB-treated mice. SZF alleviates DNCB induced AD-like skin lesions in mice through regulating Th1/Th2 balance, improving epidermal barrier and inhibiting skin inflammation. Our research findings provide scientific footing on the use of this Chinese herbal formula for the treatment of AD.