[Preliminary Studies on the Role of Mast Cells in the Phenotype and Immune Activation of Type 2 Inflammatory Cytokine Release of Atopic Dermatitis].

Objective: To investigate the role of mast cells in atopic dermatitis (AD) phenotype and the immune activation of type 2 inflammatory cytokine release. Methods: Nine AD skin samples were obtained from the Department of Dermatology, the Second Affiliated Hospital of Xi'an Jiaotong University, and nine healthy skin control samples were obtained from the surgical excision of excess normal skin by orthopedic surgery, the Second Affiliated Hospital of Xi'an Jiaotong University, which were subjected to toluidine blue staining and fluorescence staining to clarify the mast cell degranulation activation status of the AD skin lesions. We investigated whether MC903 could directly activate mast cells in vivo through the toe swelling and exudation assay in wild-type mice; we constructed the MC903-AD model using wild-type and KitW-sh/W-sh mast cell-deficient mice in order to investigate whether mast cells affected the phenotype, histopathology, and the level of type 2 inflammatory factors in AD mice; we extracted mouse peritoneal mast cells and the ability of MC903 to activate mast cells to release inflammatory mediators in vitro was explored by calcium imaging, tryptase and β-aminohexokinase release assays, and MCP-1 and CXCL-2 release assays. Results: The number of degranulated mast cells in an activated state was increased in skin lesions of AD patients compared to healthy controls, with (5.40±1.14) and (2.20±0.84), respectively (P<0.001). KitW-sh/W-sh mast cell-deficient AD mice had an attenuated phenotype with ADI scores of (5.50±1.05), compared to wild-type AD mice with (10.00±0.89) (P<0.001). The release of type 2 inflammatory factors in wild-type AD mice was higher than those in KitW-sh/W-sh mast cell-deficient AD mice, with IL-4 levels of (29.50±1.87) and (15.33±1.86) pg/mg (P<0.001), IL-13 levels were (6.32±0.25) and (3.93±0.22) pg/mg (P<0.001), IL-31 levels were (9.73±0.38) and (6.89±0.27) pg/mg (P<0.001), and TSLP levels were (206.00±4.43) and (99.00±4.86) pg/mg (P<0.001), respectively. MC903 could cause mast cell activation in wild-type mice, leading to increased swelling and exudation in the toes of mice, and MC903 could activate mast cells in vitro, leading to increased degranulation and release of inflammatory factors such as MCP-1 and CXCL-2. Conclusions: The number of activated mast cells was increased in skin lesions of AD patients than in healthy controls. KitW-sh/W-sh mast cell-deficient AD mice showed significantly reduced phenotype, histopathology, and type 2 inflammatory factor levels compared with wild-type AD mice. MC903 activates mast cells in vivo and in vitro. Mast cells play a key role in AD phenotype and immune activation.