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.
Objective To explore the effect of pyropheophorbide-a methyl ester-mediated photodynamic therapy (MPPa-PDT) on the apoptosis in human osteosarcoma cell line MG63 and the underlying mechanism. Methods Human osteosarcoma MG63 cells in logarithmic growth phase were divided into 4 groups: blank control group (control group), the MPPa treatment group (MPPa group), the light irradiation group (LED group), and MPPa-PDT treatment group (MPPa-PDT group). MPPa-PDT group and MPPa group were incubated with MPPa (0.75 μmol/ L) for 20 hours in dark condition; control group and LED group were incubated with equal volume of fresh medium for 20 hours in the same condition. After washing with PBS and replacement with fresh culture medium, LED group and MPPa-PDT group cells were exposed to light (4.8 J/cm2) for 120 seconds. After light exposure, all groups were cultured in dark condition again. Then cellular morphology changes were observed by an inverted phase contrast microscopy, endoplasmic reticulum morphology changes were observed by transmission electron microscopy, cellular apoptosis was detected by Hoechst33258 nuclear staining, cell apoptotic rate and the levels of Ca in cells were analyzed by flow cytometry, the expression of p-PERK, C/EBP homologous protein (CHOP), cleaved-Caspase-12 were assayed by Western blot. Results In MPPa-PDT group, the retracted and round cells were observed; Hoechst33258 nuclear staining showed nuclear condensation, fragmentation, and other typical apoptotic morphological changes; the cell apoptotic rate (48.76%±3.54%) was significantly higher than that of control group (5.04%±0.41%), MPPa group (5.33%±0.38%), and LED group (6.48%±0.46%) (P < 0.05); the levels of Ca2+ in cells (485.29±58.77) was also significantly higher than that of control group (97.24±4.77), MPPa group (97.95±6.30), and LED group (101.17±5.26) (P < 0.05); swelling endoplasmic reticulum was observed under transmission electron microscope; the expressions of p-PERK, CHOP, and cleaved-Caspase-12 gradually increased at 1, 3, and 6 hours after treatment respectively, which were significantly higher than those of the other groups (P < 0.05). There was no typical apoptotic morphological changes and endoplasmic reticulum morphological changes in control group, MPPa group, and LED group, and there was no significant difference in the above indexes among 3 groups (P > 0.05). Conclusion MPPa-PDT can significantly induce apoptosis in MG63 cells. The endoplasmic reticulum stress pathway is involved in the MPPa-PDT induced apoptosis.