Mechanisms underlying interleukin-22-induced expression of heparin-binding epidermal growth factor-like growth factor in HaCaT cells

Objective To investigate the mechanisms underlying interleukin-22（IL-22）-induced expression of heparin-binding epidermal growth factor-like growth factor（HB-EGF）in HaCaT cells. Methods Some HaCaT cells were divided into several inverention groups treated with IL-22 at concentrations of 12.5, 25, 50, 100 μg/L, respectively and a control group treated with phosphate buffer saline（PBS）. After 24-hour culture, total proteins were extracted from the HaCaT cells, and Western blot was performed to measure the expression of phosphorylated extracellular signal-regulated kinase 1/2（P-ERK1/2）in the mitogen-activated protein kinase（MAPK）-ERK1/2 pathway, as well as phosphorylated-JAK2（P-JAK2）and phosphorylated-signal transducer and activator of transcription 3（P-STAT3）in the JAK2/STAT3 pathway. In a blocking experiment, some HaCaT cells were divided into 4 groups to be treated with PBS, IL-22, PD98059（an inhibitor of MAPK-ERK1/2）combined with IL-22（PD98059 group）, AG490（an inhibitor of JAK2/STAT3）combined with IL-22（AG490 group）, respectively. After 24-hour treatment, total proteins and mRNAs were extracted from the HaCaT cells followed by Western blot and real-time quantitative reverse transcription-PCR for the measurement of protein and mRNA expressions of HB-EGF respectively. Statistical analysis was carried out with the software SPSS 16.0 by one-way analysis of variance（ANOVA）for intergroup comparisons and by Bonferroni's test for multiple comparisons. Results After treatment with IL-22 at the above 4 concentrations, the expressions of P-ERK1/2, P-JAK2 and P-STAT3 in HaCaT cells were all increased compared with the control group（all P< 0.05）. The protein and mRNA expression levels（expressed as the HB-EGF/β-actin ratio and 2-△△Ct respectively）of HB-EGF were both significantly decreased in the PD98059 group and AG490 group than in the IL-22 group（protein: 0.183 ± 0.020 and 0.199 ± 0.011 vs. 0.924 ± 0.032, F= 37.700, 36.400, respectively, both P< 0.05; mRNA: 1.034 ± 0.072 and 0.989 ± 0.038 vs. 1.844 ± 0.135, F= 11.271, 13.429, respectively, both P< 0.05）. Conclusions IL-22 can activate the MAPK-ERK1/2 and JAK2/STAT3 signaling pathways in HaCaT cells, which may contribute to IL-22-induced expression of HB-EGF in HaCaT cells. Key words: Interleukin-22; Fibroblast growth factor 1; Keratinocytes; Mitogen-activated protein kinases; Janus kinase 2; STAT3 transcription factor; Psoriasis; HaCaT cells