Mechanism of black phosphorus regulating oxidative stress-inflammation cascade in retarding intervertebral disc degeneration / 中国组织工程研究

ABSTRACT

BACKGROUND:Oxidative stress plays a critical role in intervertebral disc degeneration.As a reducing material with good biocompatibility,black phosphorus quantum dots have the potential to resist oxidative stress and retard intervertebral disc degeneration.OBJECTIVE:To evaluate the effect of black phosphorus quantum dots on scavenging reactive oxygen species in the microenvironment of an intervertebral disc through in vivo and in vitro experiments,and further explore the role of black phosphorus quantum dots in Nrf2/ARE pathway and intervertebral disc inflammation.METHODS:Black phosphorus quantum dots were prepared by a liquid exfoliation technique.(1)In vitro experiment:The nucleus pulposus cells of SD rats were isolated and extracted,and the passages 2-4 nucleus pulposus cells were cocultured with different solutions,including F12-DMEM medium(blank group),black phosphorus quantum dot solution,hydrogen peroxide solution,hydrogen peroxide+black phosphorus quantum dot solution,hydrogen peroxide+black phosphorus quantum dot+Nrf2 specific inhibitor ML385 solution.Cell live/dead staining and intracellular reactive oxygen species,mitochondrial membrane potential and western blot assay were performed respectively.(2)In vivo experiment:Thirty SD rats were randomly divided into sham operation,puncture and puncture + black phosphorus groups,with 10 rats in each group.A Co7-10 intervertebral disc degeneration model was established using intervertebral disc puncture in the puncture group and the puncture+black phosphorus group.Black phosphorus quantum dot solution was injected in the intervertebral disc after a puncture in the puncture+black phosphorus group.The intervertebral disc tissue imaging and histological staining were evaluated at 4 and 8 weeks after surgery.RESULTS AND CONCLUSION:(1)In vitro experiment:Live/dead staining revealed that the black phosphorus quantum dots had good biocompatibility,were non-toxic to cells,and had a protective effect on nucleus pulposus cells under oxidative stress.Intracellular reactive oxygen species and JC-1 fluorescent probes showed that black phosphorus quantum dots could regulate the reduction of mitochondrial membrane potential caused by oxidative stress in nucleus pulposus cells and protected cells from hydrogen peroxidation-induced intracellular oxidative stress.Western blot analysis showed that compared with the blank group,the protein expressions of Nrf2,heme oxygenase 1,quinone oxidoreductase and type Ⅱ collagen were decreased in the hydrogen peroxide group(P<0.05),while the protein expressions of tumor necrosis factor α,interleukin 1β,matrix metalloproteinase 13 and p65 were increased(P<0.05).The addition of black phosphorus quantum dots could reverse the inhibitory effect of hydrogen peroxide on the Nrf2 pathway and reduce the inflammatory response caused by oxidative stress,but NrF2-specific inhibitors could cancel this effect.(2)In vivo experiment:X-ray and MRI demonstrated that at 4 and 8 weeks after surgery,the intervertebral disc height and water content of nucleus pulposus in the puncture group were lower than those in the sham operation group(P<0.05),and the intervertebral disc height and water content of nucleus pulposus in the puncture+black phosphorus group were higher than those in the puncture group(P<0.05).Histological staining exhibited that the degree of intervertebral disc degeneration in the puncture+black phosphorus group was less than that in the puncture group,and the expression of heme oxygenase 1 protein was higher than that in the puncture+black phosphorus group.(3)Our results have indicated that black phosphorus quantum dots can exert an antioxidant effect and delay intervertebral disc degeneration by regulating Nrf2/ARE pathway.