DNA damage in lead-exposed hepatocytes: coexistence of apoptosis and necrosis?

Abstract

The aim of the present study was to investigate the coexistence of oxidative DNA damage and apoptosis- and necrosis-related DNA damage, and to correlate with ultrastructural changes in hepatocyte nuclei in the lead-nitrate–exposed liver. Adult male Wistar rats were exposed to 0, 0.5, and 1% lead nitrate for 60 days, and the livers were sampled the next day. Ultrastructurally, hepatocyte nuclei showed no apoptosis-related morphological changes, but showed necrotic changes. Competitive enzyme-linked immunosorbent assay showed no change in 8-oxo-dG activity (P > 0.05), but immunohistochemistry showed its localization in hepatocytes, Kupffer cells, endothelium, and bile ductule epithelium. TUNEL-labeled DNA breaks presenting 3′-OH ends increased in hepatocytes in all functional zones of the portal acini and bile ductule epithelium (zones I>III>II). In situ oligo ligation revealed the existence of DNA breaks bearing duplex 3′ overhangs and 5′ P-blunt ends in hepatocytes of all functional zones and bile ductule epithelium. In conclusion, both apoptosis- and necrosis-related DNA damage coexist without significant oxidative DNA damage. Hepatocytes display changes related to necrosis, but not those related to apoptosis.

Keywords::

• Heavy metals
• oxidative stress
• DNA damage
• duplex 3′ overhangs
• 5′ P-blunt ends
• hepatocytes

Acknowledgments

The authors thank the Electron Microscopy Unit for availing the facilities. The technical assistance of Ms. Susan Veghese, Ms. Jeena Prashanth, Ms. Amal Wagdi, Dr. Saju S. Jacob, and Mr. Srinivas Sridhara is gratefully acknowledged.

Declaration of interest

This work was supported by Kuwait University (grant no.: YS05/09).