Effects of tumor necrosis factor-alpha/extracellular signal-regulated kinase pathway on migration ability of HaCaT cells and full-thickness skin defects in mice / 中华烧伤杂志

ABSTRACT

Objective: To investigate the effects of tumor necrosis factor-alpha (TNF-α)/extracellular signal-regulated kinase (ERK) pathway on the migration ability of HaCaT cells and full-thickness skin defects in mice. Methods: The experimental research method was adopted. According to the random number table (the same below), HaCaT cells were divided into the normal oxygen group and the hypoxia group cultured under hypoxia (with oxygen volume fraction of 1%, the same below) condition. After 24 hours of culture, the significantly differentially expressed genes between the 2 groups were screened using the microarray confidence analysis software SAM4.01. The significance of the number of each gene in the signaling pathway was analyzed through the Kyoto encyclopedia of genes and genomes to screen the significantly differentially signaling pathways (n=3). HaCaT cells were cultured for 0 (immediately), 3, 6, 12, and 24 h under hypoxia condition. The secretion level of TNF-α was detected by enzyme-linked immunosorbent assay (ELISA), and the number of samples was 5. HaCaT cells were divided into normal oxygen group, hypoxia alone group, and hypoxia+inhibitor group cultured with FR180204 (an ERK inhibitor) and under hypoxia condition. The cells were cultured for 3, 6, 12, and 24 h. The migration ability of the cells was detected by scratch test (n=12). The expressions of phosphorylated nuclear factor kappa B (p-NF-κB), phosphorylated p38 (p-p38), phosphorylated ERK1/2 (p-ERK1/2), N-cadherin, and E-cadherin in HaCaT cells were detected by Western blotting under hypoxic condition for 0, 3, 6, 12, and 24 h (n=3). Sixty-four BALB/c male mice aged 6 to 8 weeks were used to make a full-thickness skin defect wound model on the dorsum of the mice. The mice were divided into the blank control group and the inhibitor group treated with FR180204, with 32 mice in each group being treated accordingly. On post injury day (PID) 0, 3, 6, 9, 12, and 15, the wound conditions of mice were observed and the healing rate was calculated (n=8). On PID 1, 3, 6, and 15, hematoxylin-eosin staining was used to observe neovascularization, inflammatory cell infiltration, and epidermal regeneration on wound, Masson staining was used to observe collagen deposition on wound, the expressions of p-NF-κB, p-p38, p-ERK12, N-cadherin, and E-cadherin in wound tissue were detected by Western blotting (n=6), the number of Ki67 positive cells and the absorbance value of vascular endothelial growth factor (VEGF) were detected by immunohistochemistry (n=5), the protein expressions of interleukin 6 (IL-6), IL-10, IL-1β, and CCL20 in wound tissue were detected by ELISA (n=6). Data were statistically analyzed with one-way analysis of variance, analysis of variance for repeated measurement, factorial design analysis of variance, Tukey test, least significant difference test, and independent sample t test. Results: After 24 hours of culture, compared with normal oxygen group, 7 667 genes were up-regulated and 7 174 genes were down-regulated in cells in hypoxic group. Among the above differentially expressed genes, the TNF-α signaling pathway had significant change (P<0.05) with large number of genes. Under hypoxia condition, the expression of TNF-α at 24 h of cell culture was (11.1±2.1) pg/mL, which was significantly higher than (1.9±0.3) pg/mL at 0 h (P<0.05). Compared with normal oxygen group, the migration ability of cells in hypoxia alone group was significantly enhanced at 6, 12, and 24 h of cell culture (with t values of 2.27, 4.65, and 4.67, respectively, P<0.05). Compared with hypoxia alone group, the migration ability of cells in hypoxia+inhibitor group was significantly decreased at 3, 6, 12, and 24 h of cell culture (with t values of 2.43, 3.06, 4.62, and 8.14, respectively, P<0.05). Under hypoxia condition, the expressions of p-NF-κB, p-ERK1/2, and N-cadherin were increased significantly at 12 and 24 h of cell culture compared with 0 h of culture (P<0.05), the expression of p-p38 was significantly increased at 3, 6, 12, and 24 h of cell culture (P<0.05), the expression of E-cadherin was significantly decreased at 6, 12, and 24 h of cell culture (P<0.05), the expression of p-ERK1/2, p-NF-κB, and E-cadherin was time-dependent. Compared with blank control group, on PID 3, 6, 9, 12, and 15, the wound healing rate of mice in inhibitor group was significantly decreased (P<0.05); there were more inflammatory cell infiltration around the wound edge of mice in inhibitor group on PID 3, 6, and 15, especially on PID 15, a large number of tissue necrosis and discontinuous new epidermal layer were observed on the wound surface, and collagen synthesis and new blood vessels were reduced; the expression of p-NF-κB in the wound of mice in inhibitor group was significantly decreased on PID 3 and 6 (with t values of 3.26 and 4.26, respectively, P<0.05) but significantly increased on PID 15 (t=3.25, P<0.05), the expressions of p-p38 and N-cadherin were significantly decreased on PID 1, 3, and 6 (with t values of 4.89, 2.98, 3.98, 9.51, 11.69, and 4.10, respectively, P<0.05), the expression of p-ERK1/2 was significantly decreased on PID 1, 3, 6, and 15 (with t values of 26.69, 3.63, 5.12, and 5.14, respectively, P<0.05), the expression of E-cadherin was significantly decreased on PID 1 (t=20.67, P<0.05) but significantly increased on PID 6 (t=2.90, P<0.05); the number of Ki67 positive cells and absorbance value of VEGF of wound in inhibitor group were significantly decreased on PID 3, 6, and 15 (with t values of 4.20, 7.35, 3.34, 4.14, 3.20, and 3.73, respectively, P<0.05); the expression of IL-10 in the wound tissue of the inhibitor group was significantly decreased on PID 6 (t=2.92, P<0.05), the expression of IL-6 was significantly increased on PID 6 (t=2.73, P<0.05), the expression of IL-1β was significantly increased on PID 15 (t=3.46, P<0.05), and CCL20 expression levels were significantly decreased on PID 1 and 6 (with t values of 3.96 and 2.63, respectively, P<0.05) but significantly increased on PID 15 (t=3.68, P<0.05). Conclusions: The TNF-α/ERK pathway can promote the migration of HaCaT cells, and regulate the healing of full-thickness skin defect wounds in mice by affecting the expression of inflammatory cytokines and chemokines.