Proliferation of epidermal growth factor-stimulated hepatocytes in a hormonally defined serum-free medium

Slc7a11 stimulates glutathione synthesis to preserve fatty acid metabolism in primary hepatocytes

Primary hepatocytes are widely used as a tool for studying metabolic function and regulation in the liver. However, the metabolic properties of primary hepatocytes are gradually lost after isolation. Here, we illustrated that fatty acid metabolism is the major compromised metabolic process in isolated primary hepatocytes, along with drastically decreased GSH and ROS content, while lipid peroxidation is increased. Gain- and loss-of-function studies revealed that Slc7a11 expression is critical in maintaining fatty acid metabolism and facilitating hormone-induced fatty acid metabolic events, which is synergistic with dexamethasone treatment. Intriguingly, Slc7a11 expression and dexamethasone treatment cooperatively upregulated AKT and AMPK signaling and mitochondrial complex expression in primary hepatocytes. Furthermore, direct treatment with reduced GSH or inhibition of ferroptosis is sufficient to drive protective effects on fatty acid metabolism in primary hepatocytes. Our results demonstrate that Slc7a11 expression in isolated primary hepatocytes induces GSH production, which protects against ferroptosis, to increase fatty acid metabolic gene expression, AKT and AMPK signaling and mitochondrial function in synergy with dexamethasone treatment, thereby efficiently preserving primary hepatocyte metabolic signatures, thus providing a promising approach to better reserve primary hepatocyte metabolic activities after isolation to potentially improve the understanding of liver biological functions from studies using primary hepatocytes.

Primary hepatocytes and their cultures for the testing of drug-induced liver injury

Drug-induced liver injury is a major reason for discontinuation of drug development and withdrawal of drugs from the market. Intensive efforts in the last decades have focused on the establishment and finetuning of liver-based in vitro models for reliable prediction of hepatotoxicity triggered by drug candidates. Of those, primary hepatocytes and their cultures still are considered the gold standard, as they provide an acceptable reflection of the hepatic in vivo situation. Nevertheless, these in vitro systems cope with gradual deterioration of the differentiated morphological and functional phenotype. The present paper gives an overview of traditional and more recently introduced strategies to counteract this dedifferentiation process in an attempt to set up culture models that can be used for long-term testing purposes. The relevance and applicability of such optimized cultures of primary hepatocytes for the testing of drug-induced cholestatic liver injury is demonstrated.

Use of real-time cellular analysis and Plackett-Burman design to develop the serum-free media for PC-3 prostate cancer cells

In this study, we developed a rapid strategy to screen a serum-free medium for culturing the anchorage-dependent PC-3 prostate cancer cells, which was going to be prepared in large scale to generate GM-CSF/TNFα-surface-modified whole cell prostate cancer vaccine. Automated real-time cellular analysis as a rapid and non-invasive technology was used to monitor the growth of PC-3 cells in 16-well plates. At the same time, Plackett-Burman design was employed to identify the most influential formulation by integrating relevant information statistically. The effects of the 16 selected factors were evaluated during exponential cell growth and three medium constituents (EGF, FGF and linoleic acid) were identified to have significant effects on the cell growth. Subsequently, the response surface methodology with central composite design was applied to determine the interactions among the three factors so that these factors were optimized to improve cell growth. Finally, the prediction of the best combination was made under the maximal response to optimize cell growth by Design-Expert software 7.0. A total of 20 experiments were conducted to construct a quadratic model and a second-order polynomial equation. With the optimized combination validated by the stability test of serial passaging PC-3 cells, the serum-free medium had similar cell density and cell viability to the original serum medium. In summary, this high-throughput scheme minimized the screening time and may thus provide a new platform to efficiently develop the serum-free media for adherent cells.

Evaluation of the major royal jelly proteins as an alternative to fetal bovine serum in culturing human cell lines

Royal jelly (RJ) is a well-known bioactive substance. It contains large amounts of major royal jelly proteins (MRJPs), which express growth-factor-like activity in several animal and human cell lines. However, the question on whether MRJPs possess growth-factor-like activity on all types of cell cultures remains. In order to determine whether MRJPs can be used as an alternative to fetal bovine serum (FBS) in different types of human cell culture, the proliferation of the complex serum with different ratios of MRJPs/FBS (M/F) was evaluated on five cell lines: 293T, HFL-I, 231, HCT116, and Changliver using MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay. The proliferation activity of the combination of the complex M/F serum with cytokines on the test cell lines was also measured. The results demonstrated that the complex serum with M/F 6/4 possessed the highest proliferation activity similar to or in excess of FBS. However, no activity of complex medium with M/F 6/4 was observed in 231 cells, indicating a selectivity of MRJPs on cell types. Compared with the complex medium with M/F 6/4, the complex medium with M/F 6/4 together with two cytokines, epidermal growth factor (EGF) and insulin-transferrin-selenium (ITS), promoted proliferations of Changliver, 293T, HCT116, and HFL-I by 18.73%‒56.19% (P<0.01). Our findings demonstrate that MRJPs could partially replace FBS in culturing many human cell lines.

Inhibition of NF-kappaB activation by the histone deacetylase inhibitor 4-Me2N-BAVAH induces an early G1 cell cycle arrest in primary hepatocytes

OBJECTIVE

Benzoylaminoalkanohydroxamic acids, including 5-(4-dimethylaminobenzoyl)aminovaleric acid hydroxamide (4-Me(2)N-BAVAH), are structural analogues of Trichostatin A, a naturally occurring histone deacetylase inhibitor (HDACi). 4-Me(2)N-BAVAH has been shown to induce histone hyperacetylation and to inhibit proliferation in Friend erythroleukaemia cells in vitro. However, the molecular mechanisms have remained unidentified.

MATERIALS AND METHODS

In this study, we evaluated the effects of 4-Me(2)N-BAVAH on proliferation in non-malignant cells, namely epidermal growth factor-stimulated primary rat hepatocytes.

RESULTS AND CONCLUSION

We have found that 4-Me(2)N-BAVAH inhibits HDAC activity at non-cytotoxic concentrations and prevents cells from responding to the mitogenic stimuli of epidermal growth factor. This results in an early G(1) cell cycle arrest that is independent of p21 activity, but instead can be attributed to inhibition of cyclin D1 transcription through a mechanism involving inhibition of nuclear factor-kappaB activation. In addition, 4-Me(2)N-BAVAH delays the onset of spontaneous apoptosis in primary rat hepatocyte cultures as evidenced by down-regulation of the pro-apoptotic proteins Bid and Bax, and inhibition of caspase-3 activation.

Modulation of CYP1A1 and CYP2B1 expression upon cell cycle progression in cultures of primary rat hepatocytes

Primary cultures of epidermal growth factor (EGF)-stimulated hepatocytes are a valuable tool to study the regulation of hepatocyte proliferation. As progression through the cell cycle is generally associated with a reduction in liver-specific functions, we studied the effects of a proliferative response triggered by EGF on the albumin secretion and urea production, and on cytochrome P450 (CYP) 1A1 and CYP2B1 expression and their corresponding 7-ethoxyresorufin-O-deethylase (EROD) and 7-pentoxyresorufin-O-dealkylase (PROD) activities. It was found that cell cycle entry is associated with decreased albumin secretion and urea production. Furthermore, western blot analysis revealed that in hepatocytes cultured under proliferative conditions, the protein expression of CYP1A1 and CYP2B1 was substantially decreased, as well as the CYP2B-mediated PROD activity. In contrast, EROD activity was not altered. In addition, the expression levels of the liver enriched transcription factors (LETFs) hepatic nuclear factor (HNF) 3beta and HNF4alpha were downregulated under proliferative conditions, whereas the expression of HNF1alpha remained constant. In conclusion, we show that in cultured primary hepatocytes, cell cycle progression significantly modulates albumin secretion, urea production and CYP-mediated biotransformation, probably involving transcriptional regulation by hepatic nuclear factors. Therefore, in order to maintain primary hepatocytes functional in culture, cell cycle inhibition must be achieved.