Objective To investigate the effect of heme oxygenase 1 (HO-1) on the apoptosis of human degenerated nucleus pulposus (NP) cells induced by tumor necrosis factor α (TNF-α), and explore its possible molecular mechanism. Methods The intervertebral disc tissues were derived from patients with lumbar intervertebral disc herniation. Then, the NP cells were cultured in vitro and the third generation of NP cells were used for subsequent experiments. Cell counting kit 8 (CCK-8) method was used to observe the proliferative effect of TNF-α on the NP cells in vitro at the concentration of 10, 20, 50, 100, and 200 ng/mL. The most apropriate concentration was selected according to the result of CCK-8. The NP cells were cultured with basal medium (control group), TNF-α (TNF-α group), TNF-α and CoPP 10 μmol/L (CoPP group), and TNF-α and ZnPP 15 μmol/L (ZnPP group), respectively. After cultured, the cell poptosis was detected by Hoechst staining and flow cytometry; the expression of cleaved Caspase-3, epithelial membrane protein 1 (EMP-1), HO-1, and p-P65 proteins were detected by Western blot. In order to further explore the potential molecular mechanisms of HO-1 for cell apoptosis, the NP cells were cultured with TNF-α (TNF-α stimulated group), TNF-α and pyrrolidine dithiocarbamate (PDTC) 5 μmol/L (TNF-α+PDTC stimulated group), respectively. Then the cell apoptosis rate was measured by flow cytometry at 24 hours after cultured. Results The optimal concentration of TNF-α was 100 ng/mL. Hoechst staining showed that a few apoptotic cells could be observed in control group and CoPP group; the apoptosis-like nucleis were observed in TNF-α group and ZnPP group, which was the most significant in ZnPP group. Flow cytometry showed that the cell apoptosis rates of TNF-α group, CoPP group, and ZnPP group were significantly increased when compared with the control group (P<0.05). Compared with TNF-α group, the cell apoptosis rate in CoPP group decreased (P<0.05), while in ZnPP group it increased (P<0.05). Western blot showed that the expression of HO-1 protein in TNF-α group was decreased, and the expressions of cleaved Caspase-3, EMP-1, and p-P65 proteins were increased when compared with the control group (P<0.05). Compared with TNF-α group, the expression of HO-1 protein in CoPP group increased, and the expressions of cleaved Caspase-3, EMP-1, and p-P65 proteins were reduced (P<0.05); the expression of HO-1 protein in ZnPP group decreased (P<0.05), the expressions of cleaved Caspase-3 and EMP-1 proteins increased (P<0.05), and the expression of p-P65 protein was not significantly changed (P>0.05). Compared with TNF-α stimulated group, the cell apoptosis rate in TNF-α+PDTC stimulated group was significantly reduced (t=3.076, P=0.031). Conclusion HO-1 can inhibit the apoptosis of degerated NP cells induced by TNF-α, and its mechanism effect is by inhibiting the nuclear factor кB signaling pathway.
ObjectiveTo investigate the influence of endoplasmic reticulum stress (ERS) on smoking-induced nucleus pulposus cells apoptosis and inflammatory response.MethodsBetween October 2016 and October 2018, 25 patients with cervical disc herniation receiving discectomy were collected and divided into smoking group (14 cases) and non-smoking group (11 cases). The baseline data of age, gender, herniated segment, and Pfirrmann grading showed no significant difference between the two groups (P>0.05). The obtained nucelus pulposus tissues were harvested to observe the cell apoptosis via detecting the apoptosis-related proteins (Caspase-3 and PRAP) by TUNEL staining and Western blot test. The nucleus pulposus cells were isolated and cultured with enzyme digestion, of which the third generation cells were used in follow-up experiments. Then, the expressions of inflammatory factors [interleukin 1β (IL-1β) and tumor necrosis factor α (TNF-α)] were detected by ELISA; the nuclear translocation of P65 was monitored by cell immunofluorescence staining. Furthermore, ERS-related proteins (GRP78 and CHOP) were detected by Western blot; and endoplasmic reticulum ultrastructure was observed under transmission electron microscope. To verify the regulatory effect of ERS, cells were pretreated by ERS specific inhibitor (4-PBA), then cell apoptosis and inflammatory response were tested.ResultsThe nucleus pulposus tissue observation showed that the cell apoptotic rate and the expressions of apoptosis-related proteins (Caspase-3 and PARP) were obviously higher in smoking group than in non-smoking group (P<0.05). The nucleus pulposus cells observation indicated that the expressions of the inflammatory factors (IL-1β and TNF-α) and the ERS-related proteins (GRP78 and CHOP) were also higher in smoking group than in non-smoking group (P<0.05). The results of cell immunofluorescence staining further confirmed that smoking stimulated nuclear translocation of P65 in nucleus pulposus cells. The ERS injury was much more serious in smoking group than in non-smoking group. Furthermore, after 4-PBA inhibiting ERS, the expressions of GRP78, CHOP, IL-1β, TNF-α, and P65 were significantly decreased (P<0.05), and flow cytometry results showed that cell apoptotic rate in smoking group was decreased, showing significant difference compared with the non-smoking group (P<0.05).ConclusionSomking can stimulate cell apoptosis and inflammatory response in nucleus pulposus cells via ESR pathway. Suppressing ESR may be a novel target to suspend smoking-induced intervertebral disc degeneration.