Genetic background effects of keratin 8 and 18 in a DDC-induced hepatotoxicity and Mallory-Denk body formation mouse model

Abstract

Keratin 8 (K8) and keratin 18 (K18) form the major hepatocyte cytoskeleton. We investigated the impact of genetic loss of either K8 or K18 on liver homeostasis under toxic stress with the hypothesis that K8 and K18 exert different functions. krt8À/À and krt18 À/À mice crossed into the same 129-ola genetic background were treated by acute and chronic administration of 3,5-diethoxy-carbonyl-1,4-dihydrocollidine (DDC). In acutely DDC-intoxicated mice, macrovesicular steatosis was more pronounced in krt8 À/À and krt18 À/À compared with wild-type (wt) animals. Mallory-Denk bodies (MDBs) appeared in krt18 À/À mice already at an early stage of intoxication in contrast to krt8 À/À mice that did not display MDB formation when fed with DDC. Keratin-deficient mice displayed significantly lower numbers of apoptotic hepatocytes than wt animals. krt8 À/À , krt18 À/À and control mice displayed comparable cell proliferation rates. Chronically DDC-intoxicated krt18 À/À and wt mice showed a similarly increased degree of steatohepatitis with hepatocyte ballooning and MDB formation. In krt8 À/À mice, steatosis was less, ballooning, and MDBs were absent. krt18 À/À mice developed MDBs whereas krt8 À/À mice on the same genetic background did not, highlighting the significance of different structural properties of keratins. They are independent of the genetic background as an intrinsic factor. By contrast, toxicity effects may depend on the genetic background. krt8À/À and krt18 À/À mice on the same genetic background show similar sensitivity to DDC intoxication and almost resemble wt animals regarding survival, degree of porphyria, liver-to-body weight ratio, serum bilirubin and liver enzyme levels. This stands in contrast to previous work where krt8 À/À and krt18 À/À mice on different genetic backgrounds were investigated.

Mallory-Denk bodies: Correlation with steatosis, severity, zonal distribution, and identification with ubiquitin

“…Nevertheless, in the pediatric patients with NASH frequently deficiencies MDBs, which indicates that aging-related cumulative oxidative damages or genetic factors may take part a contributing effect (14,15). In addition, Haybaeck et al (16) demonstrated that the structural features of Keratin 8 and Keratin 18 are genetic agents that are independent of the influence of genetic background as toxicity effects rely on the genetic background in a DDC-stimulated hepatotoxicity and MDB occurrence mouse form. At present, the in situ proximity ligation assay (isPLA) is an increasingly utilized technology for the in situ determination of protein interactive relations, post-translational modifications, and spatial connections of antigens in cells and tissues, in general.…”

940 Loss of Keratin 19 Predisposes to the Development of Cholestatic Liver Disease

“…This does not seem to be due to differences in porphyrin accumulation given that similar levels were found in both groups. The latter observation is not surprising since K8-loss also did not result in porphyrin retention [167]. A reduced bile flow might be responsible for the increased stone formation, given that DDC feeding leads to reduced bile flow in both K8-and K18-KO mice compared to DDC-fed WTs [126].…”

“…Collectively, the combination of the above clinical findings suggests that loss of K19 leads to a more severe DDC-induced cholestatic liver injury. In contrast, loss of either K8 or K18 had no effect on the DDC-induced cholestasis since comparable levels of serum ALP and total bilirubin were measured both 1 week and 12 weeks after DDC feeding [167]. On the other hand, the peak of DDC-induced biliary injury occurs 4 weeks after the start of feeding, and this time point might therefore be more useful to evaluate the role of K8/K18 in DDC-induced biliary injury.…”

“…On the other hand, previous studies showed that K8-KO, K8-and K18-mutant mice are more sensitive to Fas-mediated apoptosis [29,40,183]. However, importance of keratins in apoptosis may be condition-and tissuedependent, given that K8 deficiency renders colonocyte resistant to apoptosis in a microflora-dependent manner [184], and decreased hepatic apoptosis was observed in K8-and K18-KO mice after DDC feeding [167]. Similarly, K18 R90C mutation predisposes to Fas-, but not to hyperglycosylation-induced injury [183,185].…”

“…For example, in K7-KO mice, no apparent biliary alterations were reported, however, it remains unclear, how detailed analysis of biliary system was performed in these animals [166]. Much more data are available on K8-and K18-KO animals that displayed unaltered serum ALP and total bilirubin levels as well as normal relative bile duct area [126,167]. Of note, the lack of apparent biliary phenotype in K8-KOs is rather surprising, since they have obvious changes in other tissues.…”