Gene expression profile of lipopolysaccharide-induced apoptosis of nucleus pulposus cells reversed by syringic acid

Abstract

Apoptosis of nucleus pulposus (NP) cells has an important role in the process of intervertebral disc degeneration (IDD ), and the search for novel compounds to prevent apoptosis from occurring is urgently required. In the present study, syringic acid (SyrA) was found to exhibit no cytotoxicity on NP cells, and was able to reverse the cytotoxicity, as well as the abnormal expression of Bcl-2 and caspase-3, that were induced by lipopolysaccharide (LPS). The transcriptomes of each group were then analyzed using RNA- Seq. A total of 65 differentially expressed genes (DE Gs) were identified in LPS-stimulated groups (LPS group vs. control group), 819 DEGs were identified in the SyrA-reversed groups (SyrA plus LPS group vs. LPS group), and a further 25 DE Gs were identified in the SyrA plus LPS group compared with the control group. Reverse transcription-quantitative PCR validation indicated that the alterations in expression of uroplakin 3B-like 1 (UPK3BL1), voltage-dependent calcium channel subunit α-2/δ-1 (CACNA 2D1) and polo-like kinase 4 (PLK4) were consistent with the corresponding results of RNA- Seq, and that these genes were involved in both LPS-stimulation and SyrA- reversion processes. Kyoto Encyclopedia of Genes and Genomes analyses indicated that the DE Gs in SyrA- reversed groups were involved in, amongst other pathways, 'Autophagy-other' and 'Apoptosis-multiple species'. In conclusion, the addition of SyrA to the NP cells co-incubated with LPS appeared to help prevent the abnormal expression of mRNA s and apoptosis that had been identified in NP cells incubated with LPS alone. The potential mechanism underlying the reversion of SyrA might be attributed to the regulation of CACNA 2D1 and PLK4.