[Tea polyphenol protects against HK-2 cell injury induced by oxalate and calcium oxalate monohydrate crystals].

OBJECTIVE

To test whether the antioxidants tea polyphenol (TP) can provide protection against oxalate and calcium oxalate monohydrate (COM) crystals toxicity in HK-2 cells.

METHODS

Four groups were chosen for the study: Negative control group, positive control group (COM+oxalate), TP group (TP+COM+oxalate), VitE group (vitamin E+COM+oxalate). HK-2 cells were exposed for 4, 8, 12 and 24 h. The viability of the cells was assessed by MTT. The cellular injury was assessed by the concentration of lactate dehydrogenase (LDH), hydrogen peroxide and viability of Na+/K+ ATP enzyme. The peroxidation level was assessed by malondialdehyde (MDA) content and viability of superoxide dismutase (SOD). The morphological changes of HK-2 cells after being exposed for 4 and 12 h in each group were observed by transmission electron microscope (TEM).

RESULTS

The effects of TP and vitamin E on oxalate and COM exposed cells were tested. The HK-2 cells exposed to oxalate and COM showed a significant reduction in viability of cells, Na+/K+ ATPase and SOD. LDH release, MDA content and concentration of H2O2 were significantly increased. In TP group, the addition of TP significantly increased viability of cells, activity of Na+/K+ ATPase and SOD while LDH release, MDA content and concentration of H2O2 were significant decreased compared with the positive control group. In the Vitamn E group, compared with the positive control group, viability of cells, and activity of Na+/K+ ATPase were not significantly changed and after addition of vitamin E, SOD activity was restored, LDH release, MDA content and concentration of H2O2 were significant decreased compared with the positive control group. The morphological changes of HK-2 cells were observed by TEM in the positive control group, TP group and VitE group. In the VitE and TP groups, the amount of the cells with vacuoles formed in kytoplasms, mitochondria swelling, karyotheca dissolved and nucleolus disappearing were less than in the positive group. The morphological changes in the TP group were less than in the VitE group.

CONCLUSION

TP and vitamin E administration may prevent oxalate and COM mediated peroxidative injury and restore intracellular antioxidant enzyme activity. The protection rendered by TP was greater than that of vitamin E.