Selective enhancement of cytochrome p-450 activity in rat hepatocytes by in vitro heat shock

High-throughput toxicity testing of chemicals and mixtures in organotypic multi-cellular cultures of primary human hepatic cells

High-throughput screening (HTS) of liver toxicants can bridge the gap in understanding adverse effects of chemicals on humans. Toxicity testing of mixtures is time consuming and expensive, since the number of possible combinations increases exponentially with the number of chemicals. The combination of organotypic culture models (OCMs) and HTS assays can lead to the rapidly evaluation of chemical toxicity in a cost and time-effective manner while prioritizing chemicals that warrant additional investigation. We describe the design, assembly and toxicant response of multi-cellular hepatic organotypic culture models comprised of primary human or rat cells assembled in 96-well plates (denoted as μOCMs). These models were assembled using automated procedures that did not affect hepatocyte function or viability, rendering them ideal for large-scale toxicity evaluations. Rat μOCMs were assembled to obtain insights into deviations from human toxicity. Four test chemicals (acetaminophen, ethanol, isoniazid, and perfluorooctanoic acid) were added to the μOCMs individually or in mixtures. HTS assays were utilized to measure cell death, apoptosis, glutathione depletion, mitochondrial membrane damage, and cytochrome P450 2E1 activity. The μOCMs exhibited increased toxicant sensitivity compared to hepatocyte sandwich cultures. Synergistic and non-synergistic interactions were observed when the toxicants were added as mixtures. Specifically, chemical interactions in the μOCMs were manifested by changes in apoptosis and decreased glutathione. The μOCMs accurately predicted hepatotoxicity for individual and mixtures of toxicants, demonstrating their potential for large-scale toxicity evaluations in the future.

Regulation of cytochrome P4501A by protein kinase C: the role of heat shock protein70

Carbofuran is a pesticide, which is used throughout the world as a nematicide and an acaricide. This pesticide integrates into living organisms through aquatic ecosystem. In earlier report, we had demonstrated that cytochrome P4501A was induced in cultured catfish hepatocytes in response to carbofuran, which might be responsible for the detoxification of this pesticide. As the underlying signaling mechanism associated with induction and regulation of cytochrome P4501A has not yet been well defined, we therefore in the present study have investigated to identify the regulatory network of cytochrome P4501A in catfish liver or cultured hepatocytes by targeting several key signaling molecules such as phosphatidyl inositol (PI) or protein kinase C (PKC), which are critical molecules for many important pathways. PKC and heat shock protein70 (HSP70) have been shown to be induced in response to carbofuran in catfish hepatocytes. Results also indicate that induction of CYP1A is modulated by HSP70 and PKC in fish hepatocytes. Thus our data shed light on the regulation of EROD activity, which has been used as a bio-monitoring tool for measuring aquatic pollution.

3D hepatic cultures simultaneously maintain primary hepatocyte and liver sinusoidal endothelial cell phenotypes

Developing in vitro engineered hepatic tissues that exhibit stable phenotype is a major challenge in the field of hepatic tissue engineering. However, the rapid dedifferentiation of hepatic parenchymal (hepatocytes) and non-parenchymal (liver sinusoidal endothelial, LSEC) cell types when removed from their natural environment in vivo remains a major obstacle. The primary goal of this study was to demonstrate that hepatic cells cultured in layered architectures could preserve or potentially enhance liver-specific behavior of both cell types. Primary rat hepatocytes and rat LSECs (rLSECs) were cultured in a layered three-dimensional (3D) configuration. The cell layers were separated by a chitosan-hyaluronic acid polyelectrolyte multilayer (PEM), which served to mimic the Space of Disse. Hepatocytes and rLSECs exhibited several key phenotypic characteristics over a twelve day culture period. Immunostaining for the sinusoidal endothelial 1 antibody (SE-1) demonstrated that rLSECs cultured in the 3D hepatic model maintained this unique feature over twelve days. In contrast, rLSECs cultured in monolayers lost their phenotype within three days. The unique stratified structure of the 3D culture resulted in enhanced heterotypic cell-cell interactions, which led to improvements in hepatocyte functions. Albumin production increased three to six fold in the rLSEC-PEM-Hepatocyte cultures. Only rLSEC-PEM-Hepatocyte cultures exhibited increasing CYP1A1/2 and CYP3A activity. Well-defined bile canaliculi were observed only in the rLSEC-PEM-Hepatocyte cultures. Together, these data suggest that rLSEC-PEM-Hepatocyte cultures are highly suitable models to monitor the transformation of toxins in the liver and their transport out of this organ. In summary, these results indicate that the layered rLSEC-PEM-hepatocyte model, which recapitulates key features of hepatic sinusoids, is a potentially powerful medium for obtaining comprehensive knowledge on liver metabolism, detoxification and signaling pathways in vitro.

Protective effects of vitamin E against 3,3',4,4',5-pentachlorobiphenyl (PCB126) induced toxicity in zebrafish embryos

3,3',4,4',5-Pentachlorinated biphenyls 126 (PCB126) is a global environmental contaminant that can induce cellular oxidative stress. We investigated whether vitamin E can protect against toxicity from PCB126 during zebrafish (Danio rerio) development. Zebrafish embryos were exposed to 100nM PCB126 and compared with a second group that was co-exposed with 100muM vitamin E until 5 days post fertilization. PCB126 induced pericardial sac edema, yolk sac edema, and growth retardation in zebrafish embyos. In contrast, vitamin E co-exposure group did not show any gross changes. Real-time PCR results showed that vitamin E co-exposure group were restored to control group for the expression levels of heat shock protein 70 Cognate, aryl hydrocarbon receptor type-2, cytochrome P450 1A, and superoxide dismutase-1. These data give insights into the use of vitamin E to reduce PCB126-mediated toxicity and into the use of zebrafish embryos for exploring mechanisms underlying the oxidative potential of AHR agonists.

Beneficial effects of Kampo medicine Inchin-ko-to on liver function and regeneration after hepatectomy in rats

AIM

Inchin-ko-to (ICKT), Kampo medicine, is known to inhibit hepatocyte apoptosis as well as promote the secretion and excretion of bile. The aim of this study is to clarify the effects of ICKT on liver function and hepatic regeneration after massive hepatectomy in rats.

METHODS

Male Wistar rats received 2 g/kg ICKT from 3 days preoperatively and underwent 90% hepatectomy. Liver sections were stained using immunohistochemistry (hemeoxygenase-1 [HO-1], alpha-smooth muscle actin [SMA], and proliferating cell nuclear antigen [PCNA]).

RESULTS

The survival period was significantly prolonged, and the remnant liver/body weight ratio was significantly increased postoperatively in the ICKT group. The values of transaminase, total bile acid, and total bilirubin were significantly improved in the ICKT group. In the ICKT group, PCNA and HO-1 were strongly expressed early postoperatively, but the expression of alpha-SMA was weak.

CONCLUSION

The preoperative administration of ICKT has been suggested to provide beneficial effects in promoting hepatic regeneration and preventing postoperative hepatic failure. The reduced activation of stellate cells may be involved in their mechanisms.

Signaling mechanisms in alcoholic liver injury: Role of transcription factors, kinases and heat shock proteins

Alcoholic liver injury comprises of interactions of various intracellular signaling events in the liver. Innate immune responses in the resident Kupffer cells of the liver, oxidative stress-induced activation of hepatocytes, fibrotic events in liver stellate cells and activation of liver sinusoidal endothelial cells all contribute to alcoholic liver injury. The signaling mechanisms associated with alcoholic liver injury vary based on the cell type involved and the extent of alcohol consumption. In this review we will elucidate the oxidative stress and signaling pathways affected by alcohol in hepatocytes and Kupffer cells in the liver by alcohol. The toll-like receptors and their down-stream signaling events that play an important role in alcohol-induced inflammation will be discussed. Alcohol-induced alterations of various intracellular transcription factors such as NFκB, PPARs and AP-1, as well as MAPK kinases in hepatocytes and macrophages leading to induction of target genes that contribute to liver injury will be reviewed. Finally, we will discuss the significance of heat shock proteins as chaperones and their functional regulation in the liver that could provide new mechanistic insights into the contributions of stress-induced signaling mechanisms in alcoholic liver injury.

A dual-functional fibrous scaffold enhances P450 activity of cultured primary rat hepatocytes

We have designed a novel dual-functional electrospun fibrous scaffold comprising two fiber mesh layers that were modified differently to induce two separate biological responses from hepatocytes. The first fiber layer was galactosylated on the surface to mediate hepatocyte attachment, while the second layer was loaded with 3-methylcholanthrene (3-Mc) to enhance cytochrome P450 activity of hepatocytes. Primary rat hepatocytes cultured on the galactosylated fibrous scaffolds loaded with different concentrations of 3-Mc were compared for their cell attachment efficiency, albumin secretion activity and cytochrome P450-dependent 7-ethoxycoumarin O-deethylase activity. This hybrid fibrous scaffold mediated hepatocyte attachment with slightly lower efficiency (76+/-2.3%) than a single-layer galactosylated fibrous scaffold (84+/-3.5%). More importantly, the cytochrome P450 activity of the hepatocytes cultured on the hybrid scaffold correlated well with the 3-Mc loading level. The results also showed that transfer of 3-Mc to hepatocytes through direct cell-fiber contact was the dominant transport route, with the induced cytochrome P450 activity being 1.9- to 4.8-fold higher than that of transfer of 3-Mc to hepatocytes via dissolution from fibers to medium. This study demonstrates the feasibility of creating multi-functional fibrous scaffolds that serve both as an adhesive substrate and as a delivery vehicle for bioactive molecules.