Overexpression of carbamoyl-phosphate synthase 1 significantly improves ureagenesis of human liver HepaRG cells only when cultured under shaking conditions

Publication date: Available online 22 February 2019Source: MitochondrionAuthor(s): Aziza A.A. Adam, Vincent A. van der Mark, Jos P.N. Ruiter, Ronald J.A. Wanders, Ronald P.J. Oude Elferink, Robert A.F.M. Chamuleau, Ruurdtje HoekstraAbstractHyperammonemia is an important contributing factor to hepatic encephalopathy in end-stage liver failure patients. Therefore reducing hyperammonemia is a requisite of bioartificial liver support (BAL).Ammonia elimination by human liver HepaRG cells occurs predominantly through reversible fixation into amino acids, whereas the irreversible conversion into urea is limited. Compared to human liver, the expression and activity of the three urea cycle (UC) enzymes carbamoyl-phosphate synthase1 (CPS1), ornithine transcarbamoylase (OTC) and arginase1, are low. To improve HepaRG cells as BAL biocomponent, its rate limiting factor of the UC was determined under two culture conditions: static and dynamic medium flow (DMF) achieved by shaking. HepaRG cells increasingly converted escalating arginine doses into urea, indicating that arginase activity is not limiting ureagenesis. Neither was OTC activity, as a stable HepaRG line overexpressing OTC exhibited a 90- and 15.7-fold upregulation of OTC transcript and activity levels, without improvement in ureagenesis. However, a stable HepaRG line overexpressing CPS1showed increased mitochondrial stress and reduced hepatic differentiation without promotion of the CPS1 transcript level or ureagenesis under stat...
Source: Mitochondrion - Category: Biochemistry Source Type: research