The morphological and immunocytochemical evaluation of primary rat hepatocytes undergoing spontaneous cell death: modulation by the nitric oxide donor S-nitroso-N-acetylpenicillamine

Nitric oxide (NO) is one of the smallest molecules synthesised in the human body. It is produced by three distinct nitric oxide synthase isoenzymes (NOS) and plays a number of physiological functions in many organs and tissues. Among its numerous properties is the ability to influence programmed cell death. NO can either inhibit or induce apoptosis depending on the context of its production. In the liver, NO is produced in greater amounts especially during inflammation. The effect of NO in liver physiology and pathophysiology can be both beneficial and detrimental. Therefore, the aim of our study was to examine NO effect on cell viability and cell death in primary rat hepatocyte culture. By using NO donor, S-nitroso-N-acetylpenicillamine (SNAP), the potential of exogenously delivered NO to influence spontaneous cell death in culture was examined. The morphological approach was used in order to discriminate between apoptotic and necrotic cell death. The nitrite level, urea production and alanine aminotransferase leakage were determined in the culture medium. The immunocytochemical detection of three apoptotic markers: cleaved caspase-3, cleaved caspase-9 and lamin A, was performed. Immunocytochemical analysis of hepatocyte apoptosis revealed different labelling pattern for each method, while the detection of cleaved caspase-3 best correlated with defined phenotypical criteria. Our data showed that under present conditions NO improved the viability of primary rat hepatocytes compared to untreated cells. This was manifested by the increase of viable hepatocytes in contrast to the decrease of necrotic and apoptotic hepatocytes as assessed by the morphological examination of cell culture. The NO effect was dose-dependent in the range of SNAP concentration between 200-800 microM.