Cadmium promotes senescence of annulus fibrosus cells via activation of PI3K/Akt signaling pathway / 中国组织工程研究

ABSTRACT

BACKGROUND:Cadmium is a common environmental pollutant,which can damage multiple organs and tissues,such as the kidney and bone,but its effect on annulus fibrosus cells in the intervertebral disc has been less reported. OBJECTIVE:To investigate the effect of cadmium chloride on the senescence of annulus fibrosus cells and the role of PI3K/Akt signaling pathway. METHODS:Annulus fibrosus cells from Sprague-Dawley rat intervertebral discs were harvested and passage 3 cells were intervened with different concentrations of cadmium chloride(0,1,5,10,20 μmol/L).Cell viability and proliferation were detected by cell counting kit-8 assay.Transcriptome sequencing and Kyoto Encyclopedia of Genes and Genomes functional enrichment analysis were performed on annulus fibrosus cells with or without cadmium chloride addition.Passage 3 annulus fibrosus cells were divided into control group,cadmium chloride group and LY294002 group.Cell proliferation rate was detected by EdU method,positive cell rate was detected by senescence-associated β-galactosidase staining,and expressions of senescence-associated proteins(p16,p21 and p53)and p-Akt at protein and mRNA levels were measured by western blot,RT-PCR and immunofluorescence. RESULTS AND CONCLUSION:5 μmol/L cadmium chloride could inhibit the proliferation of annulus fibrosus cells.Results from the Kyoto Encyclopedia of Genes and Genomes functional enrichment analysis showed that the main signal transduction pathways included PI3K/Akt,cell cycle and p53 signaling pathways,which were related to cell senescence and proliferation.PI3K/Akt signaling pathways with significant differential expression were selected for validation.Compared with the control group,the EdU-positive rate was significantly decreased in the cadmium chloride group(P<0.05),while the β-galactosidase-positive rate,the expression of senescence-associated proteins(p16,p21 and p53)and p-Akt significantly increased(P<0.05).Compared with the cadmium chloride group,the EdU-positive rate and p-Akt expression were significantly decreased in the LY294002 group(P<0.05),while the β-galactosidase-positive rate and the expression of senescence-associated proteins(p16,p21 and p53)significantly increased(P<0.05).To conclude,cadmium chloride can regulate the senescence of annulus fibrosus cells by activating the PI3K/Akt signaling pathway,thereby inducing the occurrence and progression of intervertebral disc degeneration.