Effect of sodium butyrate on primary cultures of adult rat hepatocytes

Microphysiological systems meet hiPSC technology - New tools for disease modeling of liver infections in basic research and drug development

Complex cell culture models such as microphysiological models (MPS) mimicking human liver functionality in vitro are in the spotlight as alternative to conventional cell culture and animal models. Promising techniques like microfluidic cell culture or micropatterning by 3D bioprinting are gaining increasing importance for the development of MPS to address the needs for more predictivity and cost efficiency. In this context, human induced pluripotent stem cells (hiPSCs) offer new perspectives for the development of advanced liver-on-chip systems by recreating an in vivo like microenvironment that supports the reliable differentiation of hiPSCs to hepatocyte-like cells (HLC). In this review we will summarize current protocols of HLC generation and highlight recently established MPS suitable to resemble physiological hepatocyte function in vitro. In addition, we are discussing potential applications of liver MPS for disease modeling related to systemic or direct liver infections and the use of MPS in testing of new drug candidates.

Propionibacterium acnes overabundance and natural killer group 2 member D system activation in corpus-dominant lymphocytic gastritis

Corpus‐dominant lymphocytic gastritis (LyG) is characterized by CD8⁺ T‐cell infiltration of the stomach epithelium by a so far uncharacterized mechanism. Although Helicobacter pylori is typically undetectable in LyG, patients respond to H. pylori antibiotic eradication therapy, suggesting a non‐H. pylori microbial trigger for the disease. Comparative microbiota analysis of specimens from LyG, H. pylori gastritis and healthy controls precluded involvement of H. pylori in LyG but identified Propionibacterium acnes as a possible disease trigger. In addition, the natural killer group 2 member D (NKG2D) system and the proinflammatory cytokine interleukin (IL)‐15 are significantly upregulated in the gastric mucosa of LyG patients, and gastric epithelial cells respond to microbe‐derived stimuli, including live P. acnes and the microbial products short‐chain fatty acids, with induction of NKG2D ligands. In contrast, H. pylori infection does not activate or even repress NKG2D ligands. Together, our findings identify P. acnes as a possible causative agent for LyG, which is dependent on the NKG2D system and IL‐15 activation. © 2016 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Models and methods for in vitro testing of hepatic gap junctional communication

Inherent to their pivotal roles in controlling all aspects of the liver cell life cycle, hepatocellular gap junctions are frequently disrupted upon impairment of the homeostatic balance, as occurs during liver toxicity. Hepatic gap junctions, which are mainly built up by connexin32, are specifically targeted by tumor promoters and epigenetic carcinogens. This renders inhibition of gap junction functionality a suitable indicator for the in vitro detection of nongenotoxic hepatocarcinogenicity. The establishment of a reliable liver gap junction inhibition assay for routine in vitro testing purposes requires a cellular system in which gap junctions are expressed at an in vivo-like level as well as an appropriate technique to probe gap junction activity. Both these models and methods are discussed in the current paper, thereby focusing on connexin32-based gap junctions.

Involvement of cell junctions in hepatocyte culture functionality

In liver, like in other multicellular systems, the establishment of cellular contacts is a prerequisite for normal functioning. In particular, well-defined cell junctions between hepatocytes, including adherens junctions, desmosomes, tight junctions, and gap junctions, are known to play key roles in the performance of liver-specific functionality. In a first part of this review article, we summarize the current knowledge concerning cell junctions and their roles in hepatic (patho)physiology. In a second part, we discuss their relevance in liver-based in vitro modeling, thereby highlighting the use of primary hepatocyte cultures as suitable in vitro models for preclinical pharmaco-toxicological testing. We further describe the actual strategies to regain and maintain cell junctions in these in vitro systems over the long-term.

Development of dexamethasone-inducible tyrosine aminotransferase activity in WB-F344 rat liver epithelial stemlike cells cultured in the presence of sodium butyrate

Sodium butyrate acts as a differentiation-promoting agent for a wide variety of cell types, including some tumor cell lines. In this study, we examined the effects of sodium butyrate (SB) on the functional differentiation of cultured WB-F344 rat liver epithelial stemlike cells. Treatment of WB-F344 cells with 3.75 mM SB resulted in an inhibition of cellular proliferation, alterations to normal cellular morphology (increased cell size and decreased nuclear/cytoplasmic ratio), and significant increases in cellular protein synthesis. The SB-mediated changes in cell morphology, proliferative status, and protein catabolism were accompanied by development of dexamethasone-inducible tyrosine aminotransferase (TAT) enzyme activity. Culture of WB-F344 cells in growth medium containing SB and dexamethasone (DEX; 1 x 10(-6) M) resulted in greater than sevenfold increase in the basal TAT activity compared with control cultures. An additional sixfold increase in TAT activity was observed when cells cultured in medium containing SB and DEX were exposed to 1 x 10(-7) M DEX during the last 24 hours of culture. The DEX-inducible TAT activity developed by SB-treated WB-F344 cells responded to the modulating effects of insulin and L-tyrosine in a manner that closely resembled that reported for cultured hepatocytes and hepatoma cell lines. These studies show that treatment of WB-F344 rat liver epithelial stemlike cells with the differentiation-promoting agent SB in vitro leads to expression of the differentiation-specific hepatocyte enzyme TAT.

HLA expression in hepatocellular carcinoma cell lines

The present study undertook to investigate the biological significance of human leucocyte antigen expression in hepatocellular carcinoma and to elucidate the role of potential modulating agents on human leucocyte antigen expression. These studies used several hepatic tumour-derived cell lines as in vitro model systems. The cell lines included PLC/PRF/5 (Alexander cell line), Hep3B, HepG2, TONG PHC, HA22T/VGH, HA59T/VGH and Mahlavu. The cell lines K562 and Raji were used as negative and positive controls, respectively. K562, a B lymphoid-derived cell line, was shown to express negligible amounts of human leucocyte antigens, while Raji, an erythromyeloid-derived cell line, expressed both class I and class II human leucocyte antigens as well as their respective invariant chains, beta 2-microglobulin and Ii. Using an ELISA, experiments performed on these cell lines confirmed the natural expression of class I and class II antigens by the HA22T/VGH and HA59T/VGH cell lines, whereas PLC/PRF/5 displayed class II surface antigens only. The effects of modulating agents such as interferon-gamma sodium butyrate and clofazimine on human leucocyte antigen expression were investigated using the HA22T/VGH, HA59T/VGH and TONG PHC cell lines. These agents increased class II and class II human leucocyte antigen expression on HA22T/VGH and TONG PHC cells, but had no effect on the HA59T/VGH cell line. The results suggest a potential use for these agents as modulators of human leucocyte antigen expression by human heptocellular cell lines.

Effects of butyrate homologues on metallothionein induction in rat primary hepatocyte cultures

Sodium butyrate (NaB), a 4-carbon fatty acid, has been reported to activate the metallothionein (MT) gene in certain carcinoma cell lines. Because the effects of NaB are dependent on the cell type investigated, this study was conducted to determine if NaB and its homologues induce MT in rat primary hepatocyte cultures. Hepatocytes were grown on monolayer for 12 h and subsequently treated with formate, acetate, propionate (NaP), NaB, and valeric acid for 10 to 58 h. To examine their interaction with known MT inducers, cadmium (Cd), zinc (Zn), or dexamethasone (Dex) were added to some cultures. MT protein in the cells was quantitated by the Cd-hemoglobin assay; MT-1 mRNA was analyzed by Northern blot hybridizations with oligonucleotide probes, and quantitated by slot-blot analysis. Among the 1 to 5 carbon carboxylic acids, only NaP (3 carbon) and NaB (4 carbon) induced MT. NaP and NaB alone produced a moderate increase in MT two- to fourfold over control), but when combined with Cd or Dex, an additive increase was observed. However, when combined with Zn, a synergistic increase was detected. NaB and Zn synergistically increased MT protein, but produced only an additive increase in MT mRNA, suggesting the involvement of some posttranscriptional event(s) in the NaB-Zn induction of MT. In conclusion, NaP and NaB induced MT in normal cultured rat hepatocytes, producing an additive increase in MT protein with Cd and Dex, and a synergistic increase in MT protein with Zn.

Regulation of surface expression of high-affinity receptors for epidermal growth factor (EGF) in hepatocytes by hormones, differentiating agents, and phorbol ester

Freshly isolated adult rat hepatocytes exhibit a nonhomogeneous population of epidermal growth factor (EGF) receptors with about 10,000 high-affinity binding sites (Kd 20 pM) and about 200,000 low-affinity sites (Kd 600 pM) per cell. With culturing as primary monolayers under conditions where the cells show a marked increase in the sensitivity to the growth-stimulatory effect of EGF, a gradual reduction in the number of EGF receptors and an almost complete loss of high-affinity EGF receptors is seen. Insulin, which promotes growth of hepatocytes in concert with EGF, enhances the down-regulation of these high-affinity receptors. The differentiating (and growth-inhibitory) agent n-butyrate counteracts this down-regulation and preserves the high-affinity receptors. This effect of butyrate is synergistic with the glucocorticoid agent dexamethasone. Another differentiating agent, dimethylsulfoxide (DMSO), also counteracts the down-regulation of high-affinity EGF receptors. Moreover, the tumor promoter, tetradecanoylphorbol acetate (TPA), down-regulates the EGF receptor. This effect is particularly evident when studying the high-affinity receptors up-regulated by prior treatment with butyrate plus dexamethasone. Taken together these results provide strong support for the notion that an inverse relationship exists between expression of high-affinity EGF binding and responsiveness to growth activation by EGF.

Regulation of rat hepatic cytochrome P450IIE1 in primary monolayer hepatocyte culture

1. Rat hepatic cytochrome P450IIE1 is an ethanol-inducible enzyme which catalyses ethanol oxidation and activation of the procarcinogen, N-nitrosodimethylamine (NDMA) to its carcinogenic metabolite. 2. Initial studies in adult rat indicated that the regulation of cytochrome P450IIE1 is complex, therefore we strove to identify a central regulatory mechanism, using primary monolayer hepatocyte culture. These studies examined the effect of a range of agents (i.e. inducers, hormones, sodium butyrate and 5-aminolaevulinic acid) on amounts of cytochrome P450IIE1 protein and mRNA expression in rat hepatocytes maintained in serum-free medium on both Vitrogen and Matrigel, a laminin-rich basement membrane. 3. At time 0, immunoreactive cytochrome P450IIE1 protein was easily detectable in control cultures, yet decreased rapidly with time in culture to nearly undetectable levels at 120 h. Addition of inducers (notably, pyrazole) to the culture medium increased cytochrome P450IIE1 above that of untreated cultures at similar time points, yet did not elevate cytochrome P450IIE1 or NDMA demethylation above their levels at time 0. 4. Cytochrome P450IIE1 hybridizable mRNA also rapidly declined in culture. The decline in mRNA was not significantly altered in cultures exposed to pyrazole or any other agent. Thus, post-transcriptional factors appear to play an important role in the regulation of hepatic cytochrome P450IIE1, with protein stabilization being the most probable mechanism.

Differential stabilization of cytochrome P-450 isoenzymes in primary cultures of adult rat liver parenchymal cells

Cytochrome P-450 dependent hydroxylation of testosterone was measured in 7-day-old cultures of primary rat liver parenchymal cells. Determinations were carried out in monocultures of parenchymal cells and co-cultures of parenchymal cells with rat liver nonparenchymal epithelial cells, or mouse embryo fibroblasts. In the monoculture system, testosterone metabolism was drastically reduced and hardly measurable after 7 days in culture. In the co-culture systems, individual P-450 isoenzymes were stabilized on different levels. P-450s p and presumably c were well preserved, P-450 a was reduced but clearly measurable, P-450 h was totally lost whereas P-450s b and e were not measurable after 7 days (the activities of these isoenzymes however were already low in freshly isolated parenchymal cells). The results were independent of the cell line used for co-cultivation and of the method of parenchymal cell isolation, that is whether collagenase or EDTA was used as the agent for dissociating the cells from the liver. The results showed that the co-cultivation of liver parenchymal cells with other nonparenchymal cells significantly improved the differentiated status of the former. In this cell culture system however, not every parameter was equally well stabilized.