Regulatory Effect Of Platycodon Grandifloras Polysaccharides On Mitophagy Of DF-1 Cells Induced By Cr(?)

Chromium is one of the ten richest elements in the earth's crust and a common source of pollutants.Chromium exists in the natural environment in a valence of-2 to+6.Among the valence states,trivalent chromium(Cr(III))and hexavalent chromium(Cr(VI))are the most common valence states.Cr(VI)is the most toxic and most easily absorbed.Recent studies have shown that Cr(VI)exposure can cause mitochondrial depolarization and induce mitophagy.Platycodon grandiflorum polysaccharide is a biologically active ingredient extracted from Chinese medicinal herbs,and has various pharmacological effects.In order to fully understand the protective effect of Platycodon grandiflorum total polysaccharides(PGPS_t)on Cr(VI)-damaged Df-1 cells,the protective effects of mitophagy and mitochondrial damage on PGPS_t were explored.In the experiment,DF-1 cells were used to establish a model of Cr(VI)poisoning,and the total polysaccharides(PGPS_t)of Platycodon grandiflorum and Cr(VI)were incubated alone or together for 6 h.CCK8 method was used to determine cell viability to verify the damage level of DF-1 cells induced by Cr(VI)and the protective effect of PGPS_t;ROS and MMP were detected by fluorescence microscopy,ELIAS,and flow cytometry to verify that PGPS_t caused DF-1 Protective effect of cell mitochondrial damage;detection of changes in autophagy marker proteins(LC3 and P62)and mitophagy proteins(PINK1,Parkin,and TOMM20)related to the PINK1/Parkin pathway by Western Blot,ELISA,and laser confocal methods To further examine the effects of Cr(VI)and PGPS_t on mitochondrial damage and mitophagy in DF-1 cells.The test results show that Cr(VI)can cause the decline of DF-1 cell survival rate,and the addition of PGPS_t can restore the decrease of cell survival rate caused by Cr(VI).When 3-MA or CsA is added to inhibit autophagy or mitophagy,it can also improve the damage of DF-1 cells caused by Cr(VI).PGPS_t has similar efficacy with two autophagy inhibitors and improves the survival rate of DF-1 cells.When PGPS_t was added,it could alleviate the accumulation of ROS caused by Cr(VI)and inhibit the decline of MMP.Cr(VI)can significantly increase the levels of autophagy protein(LC3),PINK1/Parkin signaling pathway protein(PINK1,Parkin),and inhibit the expression of mitochondrial outer membrane protein(TOMM20)and autophagy key protein P62 protein levels.The addition of PGPS_t significantly alleviated the expression of the aforementioned protein levels caused by Cr(VI).In summary,the results show that Cr(VI)can increase ROS in DF-1 cells,decrease MMP and cause mitochondrial damage and induce excessive mitophagy in cells,which is related to the PINK1/Parkin signaling pathway;and platycodon polysaccharide(PGPS_t)can relieve Cr(VI)-induced mitochondrial damage and mitophagy provide a theoretical basis for the selection of protective agents for heavy metal poisoning caused by Cr(VI).