In vivo DNA replication dynamics unveil aging-dependent replication stress.

The genome duplication program is affected by multiple factors in vivo, including developmental cues, genotoxic stress, and aging. Here, we monitored DNA replication initiation dynamics in regenerating livers of young and old mice after partial hepatectomy to investigate the impact of aging. In young mice, the origin firing sites were well defined; the majority were located 10-50 kb upstream or downstream of expressed genes, and their position on the genome was conserved in human cells. Old mice displayed the same replication initiation sites, but origin firing was inefficient and accompanied by a replication stress response. Inhibitors of the ATR checkpoint kinase fully restored origin firing efficiency in the old mice but at the expense of an inflammatory response and without significantly enhancing the fraction of hepatocytes entering the cell cycle. These findings unveil aging-dependent replication stress and a crucial role of ATR in mitigating the stress-associated inflammation, a hallmark of aging.

First-in-class MKK4 inhibitors enhance liver regeneration and prevent liver failure.

Diminished hepatocyte regeneration is a key feature of acute and chronic liver diseases and after extended liver resections, resulting in the inability to maintain or restore a sufficient functional liver mass. Therapies to restore hepatocyte regeneration are lacking, making liver transplantation the only curative option for end-stage liver disease. Here, we report on the structure-based development and characterization (nuclear magnetic resonance [NMR] spectroscopy) of first-in-class small molecule inhibitors of the dual-specificity kinase MKK4 (MKK4i). MKK4i increased liver regeneration upon hepatectomy in murine and porcine models, allowed for survival of pigs in a lethal 85% hepatectomy model, and showed antisteatotic and antifibrotic effects in liver disease mouse models. A first-in-human phase I trial (European Union Drug Regulating Authorities Clinical Trials [EudraCT] 2021-000193-28) with the clinical candidate HRX215 was conducted and revealed excellent safety and pharmacokinetics. Clinical trials to probe HRX215 for prevention/treatment of liver failure after extensive oncological liver resections or after transplantation of small grafts are warranted.

Hepatocyte regeneration is driven by embryo-like DNA methylation reprogramming.

As a result of partial hepatectomy, the remaining liver tissue undergoes a process of renewed proliferation that leads to rapid regeneration of the liver. By following the early stages of this process, we observed dramatic programmed changes in the DNA methylation profile, characterized by both de novo and demethylation events, with a subsequent return to the original adult pattern as the liver matures. Strikingly, these transient alterations partially mimic the DNA methylation state of embryonic hepatoblasts (E16.5), indicating that hepatocytes actually undergo epigenetic dedifferentiation. Furthermore, Tet2/Tet3-deletion experiments demonstrated that these changes in methylation are necessary for carrying out basic embryonic functions, such as proliferation, a key step in liver regeneration. This implies that unlike tissue-specific regulatory regions that remain demethylated in the adult, early embryonic genes are programmed to first undergo demethylation, followed by remethylation as development proceeds. The identification of this built-in system may open targeting opportunities for regenerative medicine.

Sleeping Beauty mRNA-LNP enables stable rAAV transgene expression in mouse and NHP hepatocytes and improves vector potency.

Recombinant adeno-associated virus (rAAV) vector gene delivery systems have demonstrated great promise in clinical trials but continue to face durability and dose-related challenges. Unlike rAAV gene therapy, integrating gene addition approaches can provide curative expression in mitotically active cells and pediatric populations. We explored a novel in vivo delivery approach based on an engineered transposase, Sleeping Beauty (SB100X), delivered as an mRNA within a lipid nanoparticle (LNP), in combination with an rAAV-delivered transposable transgene. This combinatorial approach achieved correction of ornithine transcarbamylase deficiency in the neonatal Spfash mouse model following a single delivery to dividing hepatocytes in the newborn liver. Correction remained stable into adulthood, while a conventional rAAV approach resulted in a return to the disease state. In non-human primates, integration by transposition, mediated by this technology, improved gene expression 10-fold over conventional rAAV-mediated gene transfer while requiring 5-fold less vector. Additionally, integration site analysis confirmed a random profile while specifically targeting TA dinucleotides across the genome. Together, these findings demonstrate that transposable elements can improve rAAV-delivered therapies by lowering the vector dose requirement and associated toxicity while expanding target cell types.

Laparoscopic Caudate Resection: How to Safely Manage the Spiegel/IVC Interface.

BACKGROUND: Minimally invasive caudate lobectomy, or even paracaval caudate resection, can be associated with significant bleeding due to its abutment of inferior vena cava (IVC), portal pedicle and hepatic veins.1-3 This risk can be magnified by cirrhosis as well as response to neoadjuvant therapy (a common phenomenon after excellent response to neoadjuvant chemotherapy), leading to obliteration or even fusion of the hepato-caval space.4-7 PATIENT: A 68-year-old female with stage IVa colorectal adenocarcinoma was found to have a single liver metastasis (3.8 × 3.1 cm) in the paracaval caudate lobe. The patient received four cycles of neoadjuvant chemotherapy, leading to inflammatory fusion of the hepato-caval space. Despite this, the patient underwent a safe laparoscopic Spiegel process resection. TECHNIQUE: Prior to surgery, three-dimensional liver and port site modeling was performed to optimize the understanding of the spatial relationship between the tumor, IVC, and portal-hepatic veins. Following inflow control of portal veinous branches, the fused hepato-caval space was dissected. The adhesions were then sharply dissected to mobilize the paracaval caudate lobe off the IVC. Using scissors rather than an energy device reduced the risk of inadvertent thermal injury to the IVC. CONCLUSION: Preoperative virtual hepatectomy facilitates surgical planning, increasing the understanding of the tumor/vessel relationship and port placement. In case of a fused hepato-caval space, low central venous pressure and judicious management of short hepatic vein branches are the key for a successful dissection. Moreover, anticipation of a fused hepato-caval space and its strategic management are paramount when performing a minimally invasive caudate resection.

Loss of FAM172A gene prompts cell proliferation in liver regeneration.

The present study was designed to explore the function of FAM172A in liver regeneration and HCC. Mice were sacrificed after 70% partial hepatectomy (PH). RNA sequencing was performed on primary hepatocytes of WT and FAM172A-/- mice. We used HepG2 cells to construct cell lines with stably knockdown and overexpression of FAM172A. The expression of FAM172A in liver tissues was investigated by immunohistochemical staining, and we also used public database to perform survival analysis and prognostic model in HCC. Compared with WT mice after PH, normalized liver weight/body weight (LW/BW) ratio and the proliferating cell nuclear antigen (PCNA) protein level of FAM172A-/- mice elevated. The DEGs were mainly enriched in inflammatory response, tumor necrosis factor production, and wound healing. FAM172A knockdown enhanced the NFκB-TNFα and pERK-YAP1-Cyclin D1 axis. FAM172A peptide inhibited proliferation of primary hepatocytes. Moreover, the low expression of FAM172A in human HCC tissues implies a lower likelihood of survival and a valid diagnostic marker for HCC. Loss of FAM172A gene promotes cell proliferation by pERK-YAP1-Cyclin D1 and pNFκB-TNFα pathways during liver regeneration after PH. FAM172A may be a favorable diagnosis marker of HCC.

Impact of prior SARS-CoV-2 infection on postoperative recovery in patients with hepatocellular carcinoma resection.

BACKGROUND: The impact of prior SARS-CoV-2 infection on postoperative recovery of patients who underwent liver resection for hepatocellular carcinoma (HCC) remains uncertain given the lack of sufficient evidence. AIM: To investigate the impact of prior SARS-CoV-2 infection on postoperative recovery of patients who underwent liver resection for hepatocellular carcinoma (HCC). METHODS: Patients who were pathologically diagnosed with HCC and underwent elective partial hepatectomy in Guangdong Provincial People's Hospital between January 2022 and April 2023 were enrolled in this retrospective cohort study. The patients were divided into two groups based on their history of SARS-CoV-2 infection. Rehabilitation parameters, including postoperative liver function, incidence of complications, and hospitalization expenses, were compared between the two groups. Propensity score matching (PSM) was performed to reduce confounding bias. RESULTS: We included 172 patients (58 with and 114 without prior SARS-CoV-2 infection) who underwent liver resection for HCC. No significant differences in the rehabilitation parameters were observed between the two groups. After PSM, 58 patients were selected from each group to form the new comparative groups. Similar results were obtained within the population after PSM. CONCLUSION: Prior SARS-CoV-2 infection does not appear to affect postoperative rehabilitation, including liver function, postoperative complications, or hospitalization expenses among patients with HCC after elective partial hepatectomy.

Hepatocyte-derived tissue extracellular vesicles safeguard liver regeneration and support regenerative therapy.

Tissue-derived extracellular vesicles (EVs) are emerging as pivotal players to maintain organ homeostasis, which show promise as a next-generation candidate for medical use with extensive source. However, the detailed function and therapeutic potential of tissue EVs remain insufficiently studied. Here, through bulk and single-cell RNA sequencing analyses combined with ultrastructural tissue examinations, we first reveal that in situ liver tissue EVs (LT-EVs) contribute to the intricate liver regenerative process after partial hepatectomy (PHx), and that hepatocytes are the primary source of tissue EVs in the regenerating liver. Nanoscale and proteomic profiling further identify that the hepatocyte-specific tissue EVs (Hep-EVs) are strengthened to release with carrying proliferative messages after PHx. Moreover, targeted inhibition of Hep-EV release via AAV-shRab27a in vivo confirms that Hep-EVs are required to orchestrate liver regeneration. Mechanistically, Hep-EVs from the regenerating liver reciprocally stimulate hepatocyte proliferation by promoting cell cycle progression through Cyclin-dependent kinase 1 (Cdk1) activity. Notably, supplementing with Hep-EVs from the regenerating liver demonstrates translational potential and ameliorates insufficient liver regeneration. This study provides a functional and mechanistic framework showing that the release of regenerative Hep-EVs governs rapid liver regeneration, thereby enriching our understanding of physiological and endogenous tissue EVs in organ regeneration and therapy.

Comparison of the effects of remimazolam tosylate and propofol on immune function and hemodynamics in patients undergoing laparoscopic partial hepatectomy: a randomized controlled trial.

BACKGROUND: Laparoscopic partial hepatectomy inevitably decrease patient immune function. Propofol has been shown to have immunomodulatory effects but is associated with hemodynamic side effects. Despite studies showing a negligible impact of remimazolam tosylate on hemodynamics, it has not been reported for partial hepatectomy patients. Its influence on immune function also remains unexplored. This study sought to investigate the differences in immune function and intraoperative hemodynamics between patients who underwent laparoscopic partial hepatectomy with remimazolam tosylate and those who underwent laparoscopic partial hepatectomy with propofol. METHODS: This was a single-center, randomized controlled trial involving 70 patients, who underwent elective laparoscopic partial hepatectomy. The patients were randomly divided into two groups: the remimazolam group (group R) and the propofol group (group P). In this study, the primary outcomes assessed included the patient's immune function and hemodynamic parameters, and the secondary outcomes encompassed the patient's liver function and adverse events. RESULTS: Data from 64 patients (group R, n = 31; group P, n = 33) were analyzed. The differences in the percentages of CD3+, CD4+, CD8+, and NK cells and the CD4+/CD8+ ratio between the two groups were not statistically significant at 1 day or 3 days after surgery. Compared with those in group P, the MAP and HR at T2 and the MAP at T1 in group R were significantly increased(P < 0.05). The differences in HR and MAP at T0, T3, T4, T5, T6, and T7 and HR at T1 between the two groups were not statistically significant. There were no differences in liver function or adverse effects between the two groups, suggesting that remimazolam tosylate is a safe sedative drug(P > 0.05). CONCLUSION: The effects of remimazolam tosylate on the immune function of patients after partial hepatectomy are comparable to those of propofol. Additionally, its minimal effect on hemodynamics significantly decreases the incidence of hypotension during anesthesia induction, thereby enhancing overall perioperative safety. TRIAL REGISTRATION: The trial was registered on May 9, 2022 in the Chinese Clinical Trial Registry, registration number ChiCTR2200059715 (09/05/2022).

Effect of ultrasound-guided stellate ganglion block on inflammatory cytokines and postoperative recovery after partial hepatectomy: a randomised clinical trial.

BACKGROUND: Stellate ganglion block (SGB) has been shown to reduce perioperative complications in various surgeries. Because laparoscopic techniques and instruments have advanced during the past two decades, laparoscopic liver resection is being increasingly adopted worldwide. Lesser blood loss, fewer postoperative complications, and shorter postoperative hospital stays are the advantages of laparoscopic liver resection, as compared to conventional open surgery. There is an urgent need for an effective intervention to reduce perioperative complications and accelerate postoperative recovery. This study investigated the effect of ultrasound-guided SGB on enhanced recovery after laparoscopic partial hepatectomy. METHODS: We compared patients who received SGB with 0.5% ropivacaine (group S) with those who received SGB with 0.9% saline (group N). A total of 58 patients with partial hepatectomy were enrolled (30 S) and (28 N). Before induction of anesthesia, SGB was performed with 0.5% ropivacaine in group S and 0.9% saline in group N. MAIN OUTCOME: Comparison of serum inflammatory cytokines concentration at each time point. RESULTS: Main outcome: When comparing IL-6 and IL-10 concentrations among groups, group S showed less variation over time compared to group N. For comparison between groups, the serum IL-6 concentration in group S was lower than that in group N at 6 and 24 h after operation (P < 0.01), and there was a significant linear relationship between serum IL-6 concentration at 24 h after operation and hospitalization situation. CONCLUSIONS: Ultrasound-guided SGB can stabilize perioperative inflammatory cytokines plays a positive role in the enhanced recovery of patients after laparoscopic partial hepatectomy. The serum IL-6 level within 24 h after surgery may be used as a predictor of hospitalization. TRIAL REGISTRATION: The study was registered at the ClinicalTrials.gov (Registration date: 13/09/2021; Trial ID: NCT05042583).

Transcriptomic Characterization of Key Factors and Signaling Pathways for the Regeneration of Partially Hepatectomized Liver in Zebrafish.

Liver regeneration induced by partial hepatectomy (PHx) has attracted intensive research interests due to the great significance for liver resection and transplantation. The zebrafish (Danio rerio) is an excellent model to study liver regeneration. In the fish subjected to PHx (the tip of the ventral lobe was resected), the lost liver mass could be fully regenerated in seven days. However, the regulatory mechanisms underlying the liver regeneration remain largely unknown. In this study, gene expression profiles during the regeneration of PHx-treated liver were explored by RNA sequencing (RNA-seq). The genes responsive to the injury of PHx treatment were identified and classified into different clusters based on the expression profiles. Representative gene ontology (GO) enrichments for the early responsive genes included hormone activity, ribosome biogenesis and rRNA processing, etc., while the late responsive genes were enriched in biological processes such as glutathione metabolic process, antioxidant activity and cellular detoxification. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichments were also identified for the differentially expressed genes (DEGs) between the time-series samples and the sham controls. The proteasome was overrepresented by the up-regulated genes at all of the sampling time points. Inhibiting proteasome activity by the application of MG132 to the fish enhanced the expression of Pcna (proliferating cell nuclear antigen), an indicator of hepatocyte proliferation after PHx. Our data provide novel insights into the molecular mechanisms underlying the regeneration of PHx-treated liver.

Sulforaphane Is Protective against Warm Ischemia/Reperfusion Injury and Partial Hepatectomy in Rats.

Sulforaphane (SFN) has various beneficial effects on organ metabolism. However, whether SFN affects inflammatory mediators induced by warm hepatic ischemia/reperfusion injury (HIRI) is unclear. To investigate the hepatoprotective effects of SFN using an in vivo model of HIRI and partial hepatectomy (HIRI + PH), rats were subjected to 15 min of hepatic ischemia with blood inflow occlusion, followed by 70% hepatectomy and release of the inflow occlusion. SFN (5 mg/kg) or saline was randomly injected intraperitoneally 1 and 24 h before ischemia. Alternatively, ischemia was prolonged for 30 min to evaluate the effect on mortality. The influence of SFN on the associated signaling pathways was analyzed using the interleukin 1ß (IL-1ß)-treated primary cultured rat hepatocytes. In the HIRI + PH-treated rats, SFN reduced serum liver enzyme activities and the frequency of pathological liver injury, such as apoptosis and neutrophil infiltration. SFN suppressed tumor necrosis factor-alpha (TNF-α) mRNA expression and inhibited nuclear factor-kappa B (NF-κB) activation by HIRI + PH. Mortality was significantly reduced by SFN. In IL-1ß-treated hepatocytes, SFN suppressed the expression of inflammatory cytokines and NF-κB activation. Taken together, SFN may have hepatoprotective effects in HIRI + PH in part by inhibiting the induction of inflammatory mediators, such as TNF-α, via the suppression of NF-κB in hepatocytes.

HMGB1-Mediated Cell Death-A Crucial Element in Post-Hepatectomy Liver Failure.

Liver resection (LR) is the primary treatment for hepatic tumors, yet posthepatectomy liver failure (PHLF) remains a significant concern. While the precise etiology of PHLF remains elusive, dysregulated inflammatory processes are pivotal. Therefore, we explored the theragnostic potential of extracellular high-mobility-group-box protein 1 (HMGB1), a key damage-associated molecular pattern (DAMP) released by hepatocytes, in liver recovery post LR in patients and animal models. Plasma from 96 LR patients and liver tissues from a subset of 24 LR patients were analyzed for HMGB1 levels, and associations with PHLF and liver injury markers were assessed. In a murine LR model, the HMGB1 inhibitor glycyrrhizin, was administered to assess its impact on liver regeneration. Furthermore, plasma levels of keratin-18 (K18) and cleaved cytokeratin-18 (ccK18) were quantified to assess suitability as predictive biomarkers for PHLF. Patients experiencing PHLF exhibited elevated levels of intrahepatic and circulating HMGB1, correlating with markers of liver injury. In a murine LR model, inhibition of HMGB1 improved liver function, reduced steatosis, enhanced regeneration and decreased hepatic cell death. Elevated levels of hepatic cell death markers K18 and ccK18 were detected in patients with PHLF and correlations with levels of circulating HMGB1 was observed. Our study underscores the therapeutic and predictive potential of HMGB1 in PHLF mitigation. Elevated HMGB1, K18, and ccK18 levels correlate with patient outcomes, highlighting their predictive significance. Targeting HMGB1 enhances liver regeneration in murine LR models, emphasizing its role in potential intervention and prediction strategies for liver surgery.

Olprinone, a Selective Phosphodiesterase III Inhibitor, Has Protective Effects in a Septic Rat Model after Partial Hepatectomy and Primary Rat Hepatocyte.

Olprinone (OLP) is a selective inhibitor of phosphodiesterase III and is used clinically in patients with heart failure and those undergoing cardiac surgery; however, little is known about the effects of OLP on hepatoprotection. The purpose of this study aimed to determine whether OLP has protective effects in in vivo and in vitro rat models of endotoxin-induced liver injury after hepatectomy and to clarify the mechanisms of action of OLP. In the in vivo model, rats underwent 70% partial hepatectomy and lipopolysaccharide treatment (PH/LPS). OLP administration increased survival by 85.7% and decreased tumor necrosis factor-α, C-X-C motif chemokine ligand 1, and inducible nitric oxide synthase (iNOS) mRNA expression in the livers of rats treated with PH/LPS. OLP also suppressed nuclear translocation and/or DNA binding ability of nuclear factor kappa B (NF-κB). Pathological liver damage induced by PH/LPS was alleviated and neutrophil infiltration was reduced by OLP. Primary cultured rat hepatocytes treated with the pro-inflammatory cytokine interleukin-1ß (IL-1ß) were used as a model of in vitro liver injury. Co-treatment with OLP inhibited dose-dependently IL-1ß-stimulated iNOS induction and NF-κB activation. Our results demonstrate that OLP may partially inhibit the induction of several inflammatory mediators through the suppression of NF-κB and thus prevent liver injury induced by endotoxin after liver resection.

Transcriptome sequencing and metabolome analysis reveal the metabolic reprogramming of partial hepatectomy and extended hepatectomy.

Surgical resection remains a critical treatment option for many patients with primary and secondary hepatic neoplasms. Extended hepatectomy (eHx) may be required for some patients with large tumors, which may cause liver failure and death. Partial hepatectomy (pHx) and eHx mouse models were constructed, liver tissues were sampled at 18, 36, and 72 h posthepatectomy. Transcriptome and metabolome analyses were employed to explore the different potential mechanisms in regeneration and injury between pHx and eHx. The results showed that eHx was associated with more severe liver injury and lower survival rates than pHx. Transcriptomics data showed there were 1842, 2129, and 1277 differentially expressed genes (DEGs) in eHx and 962, 1305, and 732 DEGs in pHx at 18, 36, and 72 h posthepatectomy, respectively, compared with the those in the sham groups. Compared with pHx, the number of DEGs in the eHx group reached a maximum of 230 at 18 h after surgery and decreased sequentially to 87 and 43 at 36 and 72 h. Metabolomics analysis identified a total of 1399 metabolites, and 48 significant differentially produced metabolites (DPMs) were screened between eHx and pHx. Combined analysis of DEGs and DPMs indicated that cholesterol metabolism and insulin resistance may be two important pathways for liver regeneration and mouse survival postextended hepatectomy. Our results showed the global influence of pHx and eHx on the transcriptome and metabolome in mouse liver, and revealed cholesterol metabolism and insulin resistance pathways might be involved in regeneration post-pHx and -eHx.

Transient Kupffer cell depletion and subsequent replacement by infiltrating monocyte-derived cells does not alter the induction or progression of hepatocellular carcinoma.

Due to a combination of rapid disease progression and the lack of curative treatment options, hepatocellular carcinoma (HCC) is one of the deadliest cancers worldwide. Infiltrated, monocyte-derived, tumor-associated macrophages are known to play a role in HCC pathogenesis, but the involvement of Kupffer cells (KCs) remains elusive. Here, we used the Clec4F-diphteria toxin receptor transgenic mouse model to specifically investigate the effect of KC depletion on HCC initiation, progression and neoplastic growth following liver resection. For this purpose, several HCC mouse models with varying underlying etiologies were used and partial hepatectomy was performed. Our results show that in HCC, developed on a fibrotic or non-alcoholic steatohepatitis background, depletion of embryonic KCs at the onset of HCC induction and the subsequent replacement by monocyte-derived KCs does not affect the tumor burden, tumor microenvironment or the phenotype of isolated KCs at end-stage disease. In non-chronic liver disease-associated diethylnitrosamine-induced HCC, ablation of Clec4F+ KCs did not alter tumor progression or neoplastic growth following liver resection. Our results show that temporal ablation of resident KCs does not impact HCC pathogenesis, neither in the induction phase nor in advanced disease, and indicate that bone marrow-derived KCs are able to swiftly repopulate the available KC niche and adopt their phenotype.

Key hepatoprotective roles of mitochondria in liver regeneration.

Treatment of advanced liver disease using surgical modalities is possible due to the liver's innate ability to regenerate following resection. Several key cellular events in the regenerative process converge at the mitochondria, implicating their crucial roles in liver regeneration. Mitochondria enable the regenerating liver to meet massive metabolic demands by coordinating energy production to drive cellular proliferative processes and vital homeostatic functions. Mitochondria are also involved in terminating the regenerative process by mediating apoptosis. Studies have shown that attenuation of mitochondrial activity results in delayed liver regeneration, and liver failure following resection is associated with mitochondrial dysfunction. Emerging mitochondria therapy (i.e., mitotherapy) strategies involve isolating healthy donor mitochondria for transplantation into diseased organs to promote regeneration. This review highlights mitochondria's inherent role in liver regeneration.

Lack of endothelial autophagy does not impair liver regeneration after partial hepatectomy in mice.

Liver sinusoidal endothelial cells (LSEC) are key elements in regulating the liver response to injury and regeneration. While endothelial autophagy is essential to protect endothelial cells from injury-induced oxidative stress and fibrosis, its role in liver regeneration has not been elucidated. This study was intended to investigate the role of endothelial autophagy in liver regeneration in the context of partial hepatectomy (PHx). Analysis of autophagy levels in rat LSEC after PHx indicated a tendency to decrease activity the first 2 days after surgery. PHx performed in mice with impaired endothelial autophagy (Atg7flox/flox ;VE-Cadherin-Cre+ ) and their littermate controls showed no differences neither in liver-to-body weight ratio, histological analysis, hepatocyte proliferation nor vascular integrity during the first 7 days after PH and liver regeneration was completely achieved. Our results indicate that endothelial autophagy does not play an essential role in the coordination of the liver regeneration process after PHx.

Evidence for Adverse Effects on Liver Development and Regeneration in Zebrafish by Decabromodiphenyl Ethane.

Decabromodiphenyl ethane (DBDPE), a ubiquitous emerging pollutant, could be enriched in the liver of organisms, but its effects and mechanisms on liver development and regeneration remain largely unknown. In the present study, we first investigated the adverse effects on liver development and found decreased area and intensity of fluorescence in transgenic zebrafish larvae exposed to DBDPE; further results in wild-type zebrafish larvae revealed a possible mechanism involving disturbed MAPK/Fox O signaling pathways and cell cycle arrest as indicated by decreased transcription of growth arrest and DNA-damage-inducible beta a (gadd45ba). Subsequently, an obstructed recovery process of liver tissue after partial hepatectomy was characterized by the changing profiles of ventral lobe-to-intestine ratio in transgenic female adults upon DBDPE exposure; further results confirmed the adverse effects on liver regeneration by the alterations of the hepatic somatic index and proliferating cell nuclear antigen expression in wild-type female adults and also pointed out a potential role of a disturbed signaling pathway involving cell cycles and glycerolipid metabolism. Our results not only provided novel evidence for the hepatotoxicity and underlying mechanism of DBDPE but also were indicative of subsequent ecological and health risk assessment.

A negative reciprocal regulatory axis between cyclin D1 and HNF4α modulates cell cycle progression and metabolism in the liver.

Hepatocyte nuclear factor 4α (HNF4α) is a master regulator of liver function and a tumor suppressor in hepatocellular carcinoma (HCC). In this study, we explore the reciprocal negative regulation of HNF4α and cyclin D1, a key cell cycle protein in the liver. Transcriptomic analysis of cultured hepatocyte and HCC cells found that cyclin D1 knockdown induced the expression of a large network of HNF4α-regulated genes. Chromatin immunoprecipitation-sequencing (ChIP-seq) demonstrated that cyclin D1 inhibits the binding of HNF4α to thousands of targets in the liver, thereby diminishing the expression of associated genes that regulate diverse metabolic activities. Conversely, acute HNF4α deletion in the liver induces cyclin D1 and hepatocyte cell cycle progression; concurrent cyclin D1 ablation blocked this proliferation, suggesting that HNF4α maintains proliferative quiescence in the liver, at least, in part, via repression of cyclin D1. Acute cyclin D1 deletion in the regenerating liver markedly inhibited hepatocyte proliferation after partial hepatectomy, confirming its pivotal role in cell cycle progression in this in vivo model, and enhanced the expression of HNF4α target proteins. Hepatocyte cyclin D1 gene ablation caused markedly increased postprandial liver glycogen levels (in a HNF4α-dependent fashion), indicating that the cyclin D1-HNF4α axis regulates glucose metabolism in response to feeding. In AML12 hepatocytes, cyclin D1 depletion led to increased glucose uptake, which was negated if HNF4α was depleted simultaneously, and markedly elevated glycogen synthesis. To summarize, mutual repression by cyclin D1 and HNF4α coordinately controls the cell cycle machinery and metabolism in the liver.