Die Bedeutung der Hämoxygenase-1/ Kohlenmonoxid- und NO-Synthase/Stickoxid-Signalsystem für das Wachstum von primär kultivierten adulten Rattenhepatozyten

Abstract

Carbon monoxide (CO) and nitric oxide (NO) play important roles in liver regeneration in vivo. The aim of this study was to investigate whether CO and NO are positively involved in the proliferation of cultured hepatocytes. Adult rat hepatocytes were used as the in vitro system, the cells proliferated serum-free over a period of 10 days under the influence of conditioned media. Growth of hepatocytes was determined by the amount of DNA, the amount of mRNA was quantified by RT-PCR and NO synthase (NOS) activity was measured by GC-MS. After addition of lithium chloride hepatocyte growth, induction of iNOS mRNA and NOS activity were greatly enhanced. Addition of specific iNOS inhibitors, such as L-NIL and 1400 W, did not decrease hepatocyte proliferation, although NOS activity was inhibited over 90% in the cell cultures. We conclude that NO is not required for the in vitro DNA synthesis of hepatocytes. The results, collected in this study, show that CO is a mitogenic substance for hepatocytes in vitro and that the inducible haem oxygenase-1 (HO-1) plays an important role in the growth-signaling pathway. Free NO and NO synthase did not influence the growth of hepatocytes in vitro, but the NO donor CAS 1609 stimulated growth through the induction of HO-1 and thus production of CO. This conclusion is supported by the observed mitogenic effect of the CO-releasing substance CORM 2. Our data support the findings from Schuett et al. (2007); they observed an increased hepatocyte growth in vivo after partial hepatectomy by overexpression of HO-1.