OBJECTIVES: The aim of this study is to determine the effect of cannabinoid receptor (CB) 2 inhibitor on desmoglein 3 (DSG3) expression in HaCaT cells co-cultured with pemphigus serum. METHODS: Immunohistochemical staining was used to compare CB expression in pemphigus patients and normal individuals. Enzyme-linked immunosorbent assay (ELISA) was employed to quantify the concentration of CB2 in the serum of pemphigus patients and normal individuals. A correlation analysis was performed to examine the relationship between the serum CB2 and DSG of pemphigus patients. The CCK-8 assay was used to evaluate the inhibitory effect of AM630 on HaCaT cells, and the half-maximal inhibitory concentration (IC₅₀) value was utilized to determine the experimental concentration. Serum from normal individuals (negative control group) and pemphigus patients (pemphigus group) was co-cultured with HaCaT cells at a 1∶1 ratio. HaCaT cells cultured in complete medium were used as the control group. HaCaT cells in the pemphigus group treated with AM630 were employed as the AM630 group. Real-time polymerase chain reaction (PCR) and Western blot were conducted to assess the expression levels of CB2, DSG3, and β-catenin. Cell dissociation experiments were conducted to evaluate the effect of AM630 on the adhesion of HaCaT cells. RESULTS: Immunohistochemistry revealed significant differences in CB2 expression between pemphigus and normal mucosa (P<0.000 1), but no difference was found in CB1 expression. ELISA analysis revealed a statistically significant difference in the expression levels of CB2 in the serum between normal individuals and pemphigus patients (P<0.001). The expression of CB2 in the serum of pemphigus patients exhibited a significant positive correlation with that of DSG3 (r=0.831, P=0.003). The CCK-8 assay indicated that the IC₅₀ of AM630 on HaCaT cells was 0.55 μmol/L. Real-time PCR and Western blot showed that the expression levels of CB2 and DSG3 increased in the pemphigus group, while the expression level of β-catenin decreased compared with that in the AM630 groups (P<0.05). CONCLUSIONS CB2 is highly expressed in oral mucosal pemphigus. AM630 inhibits overexpression of CB2 and DSG3 and underexpression of β-catenin levels, which can provide new therapeutic targets for pemphigus.
Humans ; Pemphigus/pathology* ; Receptor, Cannabinoid, CB2/metabolism* ; Desmoglein 3/metabolism* ; Acantholysis/metabolism* ; Mouth Mucosa/pathology* ; HaCaT Cells ; Coculture Techniques ; beta Catenin/metabolism*

BACKGROUNDThe presence of autoantibodies against multiple epidermal proteins is an important feature in paraneoplastic pemphigus (PNP). Circulating anti-desmoglein 3 autoantibody, the major pathogenic autoantibody in pemphigus vulgaris (PV), has been proved pathogenic in PNP. Because of many clinical differences between PNP and PV, we speculate about the involvement of other autoantibodies in the pathogenesis of PNP. Envoplakin (EPL) and periplakin (PPL) are recognized by most PNP sera. Their linker subdomains are highly homologous and necessary for the association of intermediate filaments.

METHODSWe characterized the autoantibodies against the linker subdomains of EPL and PPL in PNP patients' sera and their associated tumors by enzyme-linked immunosorbent assay (ELISA) and immunofluorence. We also applied the purified autoantibodies against EPL and PPL from PNP sera to cultured human epidermal keratinocytes (HEK), to evaluate the changes of cell-cell adhesion.

RESULTSAutoantibodies against EPL and PPL were detected in most PNP patients by ELISA, and the decrease of these autoantibodies after removal of the tumors was roughly comparable to the improvement of clinical symptoms. Cultured tumor cells from PNP patients secreted these autoantibodies. Specific immunoglobulin receptors for EPL and PPL were found on B lymphocytes in tumors from PNP. Furthermore, purified anti-EPL and anti-PPL autoantibodies from PNP sera were capable of dissociating cultured human epidermal keratinocytes.

CONCLUSIONAutoantibodies against EPL and PPL may also be pathogenic in PNP.

Adolescent ; Adult ; Autoantibodies ; immunology ; pharmacology ; Cell Adhesion ; drug effects ; Cells, Cultured ; Desmoglein 3 ; immunology ; Enzyme-Linked Immunosorbent Assay ; Epidermis ; cytology ; Female ; Humans ; Keratinocytes ; cytology ; drug effects ; Male ; Membrane Proteins ; immunology ; Middle Aged ; Paraneoplastic Syndromes ; immunology ; metabolism ; Pemphigus ; immunology ; metabolism ; Plakins ; immunology ; Protein Precursors ; immunology ; Young Adult

During a search for keratinocyte differentiation-related genes, we obtained a cDNA fragment from the 5'-untranslated region of a previously identified splicing variant of desmoglein 3 (Dg3). This transcript encodes a protein of 282 amino acids, which corresponds to the N-terminal truncated intracellular domain of Dg3 (Delta NDg3). Northern blot analysis detected a 4.6-kb transcript matching the predicted size of Delta NDg3 mRNA, and Western blot analysis with an antibody raised against the Dg3 C-terminus (H-145) detected a 31-kDa protein. Increased Delta NDg3 expression was observed in differentiating keratinocytes by RT-PCR and Western blot analysis, suggesting that Delta NDg3 is indeed a differentiation-related gene product. In immunohistochemical studies of normal and pathologic tissues, H-145 antibody detected the protein in the cytoplasm of suprabasal layer cells, whereas an antibody directed against the N-terminal region of Dg3 (AF1720) reacted with a membrane protein in the basal layer. In addition, Delta NDg3 transcript and protein were upregulated in psoriatic epidermis, and protein expression appeared to increase in epidermal tumors including Bowen's disease and squamous cell carcinoma. Moreover, overexpression of Delta NDg3 led to increased migration and weakening of cell adhesion. These results suggest that Delta NDg3 have a role in keratinocyte differentiation, and that may be related with tumorigenesis of epithelial origin.
Cell Adhesion ; *Cell Differentiation ; Cell Movement ; Cells, Cultured ; Desmoglein 3/*genetics/*metabolism ; Epidermis/cytology ; Gene Expression ; Humans ; Keratinocytes/*cytology ; Skin Diseases/genetics/metabolism ; gamma Catenin/metabolism