CD73 (ecto-5′-nucleotidase) hepatocyte levels differ across mouse strains and contribute to mallory-denk body formation

Abstract

The formation of hepatocyte Mallory-Denk bodies (MDBs), which are aggregates of keratins 8 and 18 (K8/K18), ubiquitin, and the ubiquitin-binding protein p62, has a genetic predisposition component in humans and mice. We tested the hypothesis that metabolomic profiling of the MDB-susceptible C57BL and the MDB-resistant C3H mouse strains can illuminate MDB-associated pathways. Using both targeted and unbiased metabolomic analyses we demonstrated significant differences in intermediates of purine metabolism. Further analysis revealed that C3H and C57BL livers differ significantly in the mRNA level, protein expression, and enzymatic activity of the adenosine-generating enzyme ecto-5′-nucleotidase (CD73), which was significantly lower in C57BL livers. CD73 mRNA levels were also dramatically decreased in human liver biopsies from hepatitis C and non-alcoholic fatty liver disease patients. Feeding mice with a diet containing the MDB-inducing agent 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) significantly decreased CD73 protein and activity in C57BL livers and resulted in loss of plasma membrane CD73 expression and activity in isolated mouse hepatocytes. To further examine the role of CD73 in MDB formation in vivo, we fed wild-type and CD73−/− mice a DDC-containing diet. Liver enlargement, p62 induction, and disappearance of the K8/K18 cytoskeleton were attenuated in CD73−/− compared to wild-type livers. MDB formation, as assessed by biochemical and immunofluorescence detection of keratin and ubiquitin complexes, was also absent in CD73−/− mice. CONCLUSION: Purine metabolism and CD73 expression are linked to susceptibility to MDB formation in livers of different mouse strains. The expression of the adenosine-generating enzyme CD73 contributes to experimental MDB induction and is highly regulated in MDB-associated liver injury in mice and in chronic human liver disease.

An Elf2-like transcription factor acts as repressor of the mouse ecto-5′-nucleotidase gene expression in hepatic myofibroblasts

“…Lastly, our data showing down-regulation of mouse Nt5e gene expression in fibrotic liver and activated myofibroblasts are in agreement with previous reports describing an overall decrease in Nt5e gene expression is observed in experimental mouse models of chronic liver injury such as chronically feeding with cholestasis inducer 3,5-diethoxycarbonyl-1,4-dihydrocollidine compound or long-term exposure to oxidative stress inducer cerium trichloride [48,49]. Additionally, human liver NT5E mRNA expression is decreased in biopsies from patients with established fibrosis secondary to hepatitis C infection or non-alcoholic fatty liver disease [48].…”

“…Additionally, human liver NT5E mRNA expression is decreased in biopsies from patients with established fibrosis secondary to hepatitis C infection or non-alcoholic fatty liver disease [48]. In contrast, upregulation of mouse Nt5e gene expression has been reported in experimental models acute liver injury such as ethanol-induced steatosis and thioacetamide-induced acute liver failure [50,51].…”

Diethyldithiocarbamate, an anti‐abuse drug, alleviates steatohepatitis and fibrosis in rodents through modulating lipid metabolism and oxidative stress

“…We found that MCD diet induced an increase in K8 mRNA, and DDC treatment blocked the increase. It has been demonstrated that CD73 contributes to experimental MDB induction and is highly regulated in MDB‐associated liver injury in mice (Snider et al ., ). In this study, mice on MCD diet for 8 weeks induced the expression of CD73, while DDC treatment inhibited the expression of CD73.…”

High-fat diet triggers Mallory-Denk body formation through misfolding and crosslinking of excess keratin 8

“…As a potential mechanism driving the conformational change of K8, murine MDB formation is associated with impaired chaperone function and decreased levels of Hsp72, the prototypical stress‐inducible heat shock protein . Studies in different mouse strains also manifested a significant genetic predisposition to MDB formation and several modifier genes have been identified …”

“…MDBs represent a characteristic feature distinguishing simple steatosis from NASH; however, this feature is present only in a subset of patients . Given the known genetic component in both NASH development and MDB formation, we tested the hypothesis that a diet rich in saturated fatty acid, i.e., an established murine model of diet‐induced obesity and a major alimentary factor responsible for NASH development, triggers MDB appearance and liver injury in susceptible individuals. Indeed, a high‐fat (HF) diet promoted/induced MDB formation and development of hepatic injury/inflammation in both the DDC‐fed animals as well as the K8 overexpressing mice .…”