Effects of methylenedianiline on tight junction permeability of biliary epithelial cells in vivo and in vitro

Open hepatic artery flow with portal vein clamping protects against bile duct injury compared to pringles maneuver

BACKGROUND

Conventional hepatic artery and portal vein clamping strategies can prevent blood loss and ischemia-reperfusion liver injury, and such preventative measures are the key to successful liver surgery. However, ischemic-induced damage to cholangiocytes is rarely considered. Here, we aimed to investigate the effect of different hepatic inflow interruption methods on bile duct injury.

METHODS

Forty rats were randomly grouped as sham, Pringle maneuver (PM) and hepatic arterial blood flow open (HAFO) groups. We evaluated liver histology and function in liver sections, and biliary histology, cholangiocyte apoptosis and proliferation, cytokine production, and bile composition. RNA sequencing is performed to explore possible molecular mechanisms. The Blood-biliary barrier permeability and tight junctions were analyzed by HRP injection, immunofluorescence staining and analysis of ZO-1 expression by immunoblotting.

RESULTS

HAFO significantly attenuated ischemia-induced liver injury and decreased ALT, ALP, TBIL, and DBIL levels in serum. The histopathological observations showed that bile duct injury in the PM group was more serious than that in the HAFO group. The numbers of apoptotic biliary epithelial cells in HAFO-treated rat bile ducta were lower than those in the PM group. RNA-seq showed that tight junctions may be related to the mechanism underlying the protective effect of HAFO, as shown by the reduced HRP levels and increased ZO-1 and claudin-1/3 expression in the HAFO group compared to the PM group.

CONCLUSION

Compared with PM, HAFO alleviated the ischemic injury to the biliary system, which was characterized by decreased biliary epithelial cell apoptosis, reduced inflammatory responses and decreased blood-biliary-barrier permeability.

Industrial, Biocide, and Cosmetic Chemical Inducers of Cholestasis

A frequent side effect of many drugs includes the occurrence of cholestatic liver toxicity. Over the past couple of decades, drug-induced cholestasis has gained considerable attention, resulting in a plethora of data regarding its prevalence and mechanistic basis. Likewise, several food additives and dietary supplements have been reported to cause cholestatic liver insults in the past few years. The induction of cholestatic hepatotoxicity by other types of chemicals, in particular synthetic compounds, such as industrial chemicals, biocides, and cosmetic ingredients, has been much less documented. Such information can be found in occasional clinical case reports of accidental intake or suicide attempts as well as in basic and translational study reports on mechanisms or testing of new therapeutics in cholestatic animal models. This paper focuses on such nonpharmaceutical and nondietary synthetic chemical inducers of cholestatic liver injury, in particular alpha-naphthylisocyanate, 3,5-diethoxycarbonyl-1,4-dihydrocollidine, methylenedianiline, paraquat, tartrazine, triclosan, 2-octynoic acid, and 2-nonynoic acid. Most of these cholestatic compounds act by similar mechanisms. This could open perspectives for the prediction of cholestatic potential of chemicals.

Regeneration of liver after extreme hepatocyte loss occurs mainly via biliary transdifferentiation in zebrafish

BACKGROUND & AIMS

The liver has high regenerative capacity, but it is not clear whether most biliary cells (particularly larger cholangiocytes) transdifferentiate into hepatocytes in regenerating liver. We investigated how this process might contribute to liver regeneration in zebrafish.

METHODS

Zebrafish transgenic lines were generated using the standard I-SceI meganuclease transgenesis technique. Hepatocytes of the Tg(lfabp:mCherry-NTR)(cq2) animals were ablated by the administration of metronidazole. We investigated transdifferentiation of biliary cells to hepatocytes and expression of markers using whole mount antibody staining, fluorescent in situ hybridization, and Cre/loxP-based genetic lineage tracing analyses. The role of biliary cells in hepatocyte regeneration was explored using zebrafish larvae with defects in biliary cell development.

RESULTS

After extreme loss of hepatocytes, nearly all the biliary cells steadily lost their tubular morphology, proliferated, and expressed hepatocyte-specific markers. Cre/loxP-based inducible lineage tracing showed that new hepatocytes mainly arose from transdifferentiation of biliary cells; this process required Notch signaling and, in turn, activation of Sox9b in cholangiocytes. Activation of early endoderm and hepatoblast markers in most of the cholangiocytes indicated that biliary transdifferentiation includes a step of dedifferentiation into a bipotential intermediate. Defects in development of biliary cells impaired hepatocyte regeneration.

CONCLUSIONS

Using our zebrafish liver regeneration model, we found that biliary cells can transdifferentiate into hepatocytes and are the major contributors to hepatocyte regeneration after extreme hepatocyte loss.

4,4'-Methylenedianiline-induced hepatitis in an industrial worker: case report and review of the literature

4,4'-Methylenedianiline (MDA) is a chemical used in manufacturing and insulation processes and is a well-known hepatotoxin. We report the case of a 42-year-old construction-site worker who was accidentally exposed to large amounts of MDA and developed acute liver damage. The clinical course is described, with particular emphasis on the timely identification of the underlying cause and prompt management that led to an uneventful recovery. We review the relevant literature and discuss the safety measures necessary to minimize similar occupational hazards in industrial workers.

Analysis of Gene Expression in 4,4'-Methylenedianiline-induced Acute Hepatotoxicity

4,4′-Methylenedianiline (MDA) is an aromatic amine that is widely used in the industrial synthetic process. Genotoxic MDA forms DNA adducts in the liver and is known to induce liver damage in human and rats. To elucidate the molecular mechanisms associated with MDA-induced hepatotoxicity, we have identified genes differentially expressed by microarray approach. BALB/c male mice were treated once daily with MDA (20 mg/kg) up to 7 days via intraperitoneal injection (i.p.) and hepatic damages were revealed by histopathological observation and elevation of serum marker enzymes such as AST, ALT, ALP, cholesterol, DBIL, and TBIL. Microarray analysis showed that 952 genes were differentially expressed in the liver of MDA-treated mice and their biological functions and canonical pathways were further analyzed using Ingenuity Pathways Analysis (IPA). Toxicological functional analysis showed that genes related to hepatotoxicity such hyperplasia/hyperproliferation (Timpl), necrosis/cell death (Cd14, Mt1f, Timpl, and Pmaipl), hemorrhaging (Mt1f), cholestasis (Akr1c3, Hpx, and Slc10a2), and inflammation (Cd14 and Hpx) were differentially expressed in MDA-treated group. This gene expression profiling should be useful for elucidating the genetic events associated with aromatic amine-induced hepatotoxicity and for discovering the potential biomarkers for hepatotoxicity.