Vitamin D3 up-regulated protein 1 controls the priming phase of liver regeneration

Increased serum extracellular vesicle miR-144-3p and miR-486a-3p in a mouse model of adipose tissue regeneration promote hepatocyte proliferation by targeting Txnip

Adipose-derived stem cells are expected to be applied to regenerative medicine for various incurable diseases including liver cirrhosis. Although microRNAs contained in extracellular vesicles (EV-miRNAs) have been implicated in their regenerative effects, the precise mechanism has not been fully elucidated. Tamoxifen-inducible adipocyte-specific insulin receptor knockout (iFIRKO) mice are known to exhibit acute adipose tissue regeneration with increased numbers of adipose stem and progenitor cells (ASPCs). Because adipose tissue is the major source of circulating EV-miRNAs, we investigated alterations in serum EV-miRNAs in iFIRKO mice. A comprehensive analysis using miRNA sequencing on serum EVs revealed that most EV-miRNAs were decreased due to the loss of mature adipocytes, but there were 19 EV-miRNAs that were increased in the serum of iFIRKO mice. Among them, miR-144-3p and miR-486a-3p were found to be increased in the liver as well as serum EVs. While the expression levels of pri-miR-144-3p and pri-miR-486a-3p were not increased in the liver, they were elevated in the adipose tissue, suggesting that these miRNAs may be delivered from ASPCs increased in the adipose tissue to the liver via EVs. Increased hepatocyte proliferation was observed in the liver of iFIRKO mice, and we found that both miR-144-3p and miR-486a-3p have a function to promote hepatocyte proliferation by suppressing Txnip expression as a target gene. miR-144-3p and miR-486a-3p can be candidate therapeutic tools for conditions requiring hepatocyte proliferation, such as liver cirrhosis, and our current study suggests that examining EV-miRNAs secreted in vivo may lead to the discovery of miRNAs involved in regenerative medicine that have not been identified by in vitro analysis.

TXNIP/VDUP1 attenuates steatohepatitis via autophagy and fatty acid oxidation

Impaired macroautophagy/autophagy has been implicated in experimental and human nonalcoholic steatohepatitis (NASH). However, the mechanism underlying autophagy dysregulation in NASH is largely unknown. Here, we investigated the role and mechanism of TXNIP/VDUP1 (thioredoxin interacting protein), a key mediator of cellular stress responses, in the pathogenesis of NASH. Hepatic TXNIP expression was upregulated in nonalcoholic fatty liver disease (NAFLD) patients and in methionine choline-deficient (MCD) diet-fed mice, as well as in palmitic acid (PA)-treated hepatocytes. Upregulation of hepatic TXNIP was positively correlated with impaired autophagy, as evidenced by a decreased number of MAP1LC3B/LC3B (microtubule-associated protein 1 light chain 3 beta) puncta and increased SQSTM1/p62 (sequestosome 1) expression. Deletion of the Txnip gene enhanced hepatic steatosis, inflammation, and fibrosis, accompanied by impaired autophagy and fatty acid oxidation (FAO) in MCD diet-fed mice. Mechanistically, TXNIP directly interacted with and positively regulated p-PRKAA, leading to inactivation of MTOR (mechanistic target of rapamycin kinase) complex 1 (MTORC1) and nuclear translocation of TFEB (transcription factor EB), which in turn promoted autophagy. Inhibition of MTORC1 by rapamycin induced autophagy and increased the expression levels of FAO-related genes and concomitantly attenuated lipid accumulation in PA-treated txnip-knockout (KO) hepatocytes, which was further abolished by silencing of Atg7. Rapamycin treatment also attenuated MCD diet-induced steatosis, inflammation, and fibrosis with increased TFEB nuclear translocation and restored FAO in txnip-KO mice. Our findings suggest that elevated TXNIP ameliorates steatohepatitis by interacting with PRKAA and thereby inducing autophagy and FAO. Targeting TXNIP may be a potential therapeutic approach for NASH.Abbreviations: ACOX1: acyl-Coenzyme A oxidase 1, palmitoyl; ACSL1: acyl-CoA synthetase long-chain family member 1; ACTA2/α-SMA: actin, alpha 2, smooth muscle, aorta; ACTB: actin beta; ADGRE1/F4/80: adhesion G protein-coupled receptor E1; AMPK: AMP-activated protein kinase; ATG: autophagy-related; BafA1: bafilomycin A1; COL1A1/Col1α1: collagen, type I, alpha 1; CPT1A: carnitine palmitoyltransferase 1a, liver; CQ: chloroquine; DGAT1: diacylglycerol O-acyltransferase 1; DGAT2: diacylglycerol O-acyltransferase 2; ECI2/Peci: enoyl-Coenzyme A isomerase 2; EHHADH: enoyl-Coenzyme A, hydratase/3-hydroxyacyl Coenzyme A dehydrogenase; FAO: fatty acid oxidation; FASN: fatty acid synthase; FFA: free fatty acids; GFP: green fluorescent protein; GK/GYK: glycerol kinase; GOT1/AST: glutamic-oxaloacetic transaminase 1, soluble; GPAM: glycerol-3-phosphate acyltransferase, mitochondrial; GPT/ALT: glutamic pyruvic transaminase, soluble; H&E: hematoxylin and eosin; IL1B/IL-1β: interleukin 1 beta; IL6: interleukin 6; IOD: integral optical density; KO: knockout; Leu: leupeptin; LPIN1: lipin 1; MAP1LC3B/LC3B: microtubule-associated protein 1 light chain 3 beta; MCD: methionine choline-deficient; MMP9: matrix metallopeptidase 9; mRNA: messenger RNA; MTORC1: mechanistic target of rapamycin kinase complex 1; NAFLD: nonalcoholic fatty liver diseases; NASH: nonalcoholic steatohepatitis; PA: palmitic acid; PPARA/PPARα: peroxisome proliferator activated receptor alpha; PPARG/PPARγ: peroxisome proliferator activated receptor gamma; qRT-PCR: quantitative real-time PCR; RPS6KB1/p70S6K1: ribosomal protein S6 kinase, polypeptide 1; RPTOR: regulatory associated protein of MTOR complex 1; SCD1: stearoyl-Coenzyme A desaturase 1; SEM: standard error of the mean; siRNA: small interfering RNA; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB; TG: triglyceride; TGFB/TGF-β: transforming growth factor, beta; TIMP1: tissue inhibitor of metalloproteinase 1; TNF/TNF-α: tumor necrosis factor; TXNIP/VDUP1: thioredoxin interacting protein; WT: wild-type.

Mechanism and significance of apoptosis of the immortalized human oral mucosal epithelial cells established by Lentivirus-mediated hTERT

During the transition from human oral mucosal epithelial cells (HOMEC) to oral squamous cell carcinoma cells (Cal27), the cells must have undergone a precancerous state. To explore the malignant rule of HOMEC, plv-HOMEC was used as a model cell for the precancerous state to investigate plv-HOMEC's apoptosis by comparing human oral mucosal epithelial cells established by Lentivirus-mediated hTERT (plv-HOMEC) with HOMEC and human Cal27. The lentiviral particles overexpressing hTERT were packaged and transfected into primary HOMEC to obtain plv-HOMEC. Expression levels of NF-κB were detected in the cytoplasm and nucleus of Cal27, plv-HOMEC and HOMEC. The level of intracellular reactive oxygen species was measured to verify the endoplasmic reticulum pathway, cytochrome C expression was detected to verify the mitochondrial pathway, and FasL gene expression was detected to verify the death receptor apoptosis pathway. The total expression of NF-κB in plv-HOMEC increased, mainly due to the greater nuclear import of NF-κB, but it was still much lower than Cal27. The endoplasmic reticulum apoptosis pathway of plv-HOMEC was not significantly affected, and there were no significant differences between them and the HOMEC cells; the mitochondrial apoptosis pathway of plv-HOMEC was inhibited, and the expression of Cyt C was very close to that of Cal27, indicating that the characteristics of plv-HOMEC are so familiar with cancer cells; the death receptor apoptosis pathway of plv-HOMEC was also inhibited, and in this apoptotic pathway, plv-HOMEC were more similar to cancer cells than to HOMEC cells. The present data suggest that NF-κB nucleation may increase in the early stage of healthy cells' carcinogenesis, followed by inhibition of the mitochondrial pathway and the death receptor apoptotic pathway.

Enhancement or inhibition of PLCγ2 expression in rat hepatocytes by recombinant adenoviral vectors that contain full-length gene or siRNA

We investigated the effects of recombinant adenovirus vectors that overexpress or silence PLCγ2 on the expression of this gene during hepatocyte proliferation. Hepatocytes were isolated, identified by immunofluorescent cytochemical staining and infected by previously constructed Ad-PLCγ2 and Ad-PLCγ2 siRNA1, siRNA2 and siRNA3. Green fluorescent protein (GFP) expression was observed by fluorescence microscopy. Infection percentage was calculated by flow cytometry. mRNA and protein levels of PLCγ2 were detected by quantitative reverse transcription-PCR (qRT-PCR) and western blotting, respectively. The viability of the infected hepatocytes was measured by 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. We found that nearly 97% of cells were positive for the hepatocyte marker, CK18. After infection of Ad-PLCγ2 and Ad-PLCγ2 siRNA, more than 99% of hepatocytes expressed GFP significantly, and mRNA and protein expression of PLCγ2 was up-regulated significantly in Ad-PLCγ2 infected hepatocytes, but down-regulated in Ad-PLCγ2 siRNA2 infected cells. The cell proliferation rate decreased in PLCγ2-overexpressing cells, while the rate increased in PLCγ2-silencing cells. We verified that recombinant Ad-PLCγ2 and Ad-PLCγ2 siRNA2 were constructed successfully. These two recombinant vectors promoted or decreased the expression of PLCγ2 in rat hepatocytes and affected the cell proliferation rate, which provides a useful tool for further investigation of the role of PLCγ2 in hepatocyte apoptosis.

Liver regeneration after partial hepatectomy

Liver regeneration after partial hepatectomy is an extremely complicated pathophysiologic process, which involves the up-regulation of many proliferation associated proteins and genes. The molecular mechanisms responsible for initiating, maintaining, and terminating this process are still under active investigation and remain one of the research focuses in the field of regenerative medicine. Studies of the mechanism of liver regeneration can provide a theoretical foundation for regeneration promotion and hepatic failure prevention, which is extremely important in clinical practice. This review aims to elucidate the molecular mechanism responsible for the initiation, proliferation and termination of liver regeneration.