Mallory-Denk-body formation in alcoholic liver disease associated with upregulation of metallothionein 1

Alcoholic liver disease (ALD) is a leading cause of liver-related death in Western countries, but its pathogenesis remains incompletely understood. Mallory-Denk bodies (MDBs) constitute a characteristic morphologic feature of ALD but their clinical and biological significance remains unknown. To change this, we systematically analyzed liver biopsies from ALD subjects and validated the key findings in a corresponding animal model. Biopsies from 37 ALD individuals that were all cut in half and used for histological analysis and RNA isolation, respectively. The sections stained with hematoxylin and eosin as well as immunohistochemically against keratins and were scored by two independent pathologists. The frozen samples were subjected to a microarray analysis. The agreement between both pathologists was evaluated and the microarray results from samples with differing in MDB (analysis 1) or inflammation scores (analysis 2) were compared. Real time PCR was used to validate the findings, while animals treated with 0.1% 3,5-diethoxycarbonyl-1,4,-dihydrocollidine (DDC) for 10 weeks were examined as an established MDB model. The cohort comprised predominantly of male, middle-aged patients with intermediate to advanced liver fibrosis. MDBs and satellitosis were the parameters with the highest agreement between both pathologists while inflammation was evaluated less uniformly. Assessment of subjects with low vs. high MDBs revealed fifty-five differentially expressed genes. Among them, metallothioneins were particularly prominent and their upregulation was confirmed in subsequent real time PCR. In contrast, the differences in several other genes were not reproducible. Among the genes previously implicated in MDB pathogenesis, chaperones HSPA5 and HSPA9 were also diminished in the high MDB group. Metallothionein 1 was elevated while Hspa9 was diminished in the experimental MDB model. Seventy-four genes were differentially expressed in subjects with high vs. low inflammation. Among them, the overexpression of collagens COL1A1 and COL1A2 as well integrin beta-like 1 gene and down-regulation of CYP1A2 was confirmed by real time PCR, whereas the change in several other genes was not reproducible. In summary, my thesis systematically evaluated histological features of ALD as well as molecular alterations associating with MDBs as well as inflammation. Given the limited size of the examined cohort, further studies are needed to confirm my findings.