Т. М. Kuchmerovska¹, G. V. Donchenko¹, T. M. Tychonenko¹, M. M. Guzyk¹,
R. V. Stavniichuk¹, L. V. Yanitska², S. P. Stepanenko¹, А. P. Klimenko¹

¹Palladin Institute of Biochemistry, National Academy of Sciences of Ukraine, Kyiv;
²Bogomolets National Medical University, Kyiv, Ukraine;
e-mail: kuch@biochem.kiev.ua

The study was undertaken to investigate the modulating effect of nicotinamide (NAm) in different concentrations and under different glucose concentrations on the viability and oxidative stress induced by streptozotocin (STZ, 5 mmol/l) and hydrogen peroxide (H₂O₂, 100 µmol/l) on isolated rat pancreatic cells of the Langerhans islets in vitro. Cell viability did not depend on the concentration of glucose in the range of 5-20 mmol/l, and in subsequent studies we used glucose in concentration of 10 mmol/l to protect cells against its hypo- and hyperglycemic action. Cytoprotective effect of NAm in concentrations from 5 to 20 mmol/l on cells survival was the same. It was found that the destructive action of STZ and H₂O₂ during 24 hours on isolated cells of the pancreas resulted in the significant cell death. It was revealed that NAm in concentration of 5 mmol/l not only had cytoprotective effects against STZ and H₂O₂ but also partially reduced the level of oxidative stress in the investigated cells induced by these compounds. High concentration of NAm, 35 mmol/l, causes cytotoxic effect on the viability of pancreatic islet cells and increase of oxidative stress induced by STZ and H₂O₂.
Most likely these effects could be associated with direct modulatory action of NAm on important effector mechanisms involved in cell death, including PARP-dependent processes, or/and indirectly, through metabolic and antioxidant effects of the compound.