Expression of bcl-2 family of genes during resection induced liver regeneration: Comparison between hepatectomized and sham groups

Daucosterol alleviates heart failure with preserved ejection fraction through activating PPARα pathway

Heart failure with preserved ejection fraction (HFpEF) has been increasing in the population in recent years and is mainly characterized by preserved left ventricle ejection fraction (LVEF), diastolic dysfunction and systemic inflammation. Daucosterol (DAU), a glycoside of β-sitosterol, has good anti-inflammatory and antioxidative properties; however, its effects and mechanisms in HFpEF have not been investigated. To detect whether DAU could alleviate HFpEF, C57BL/6J male mice were fed with N-nitro-l-arginine methyl ester (L-NAME) in drinking water and high fat diet (HFD) and treated with DAU by gavage (i.g.) for 10 weeks. The results showed that DAU treatment significantly alleviated HFpEF in mice. Mechanistically, by controlling PPARα and preventing NF-κB phosphorylation, DAU reduced oxidative stress and the inflammatory response. In conclusion, our study provides a new clue for natural product DAU in alleviating HFpEF.

Diet high in fructose promotes liver steatosis and hepatocyte apoptosis in C57BL/6J female mice: Role of disturbed lipid homeostasis and increased oxidative stress

The effects of high (H)-fructose (FR) diet (D) (HFRD) on hepatic lipid homeostasis, oxidative stress, inflammation and hepatocyte apoptosis were investigated in 6-week old female C57BL/6J mice fed a regular chow (ContD) or HFRD (35% fructose-derived calories) for 3 weeks. HFRD-fed mice exhibited increased levels of hepatic steatosis with a significant elevation of serum levels of triglyceride, cholesterol and TNFα compared to ContD-fed mice (P<0.05). HFRD-fed mice exhibited ∼2.7- fold higher levels FAS along with significantly decreased protein levels of adiponection-R2 (∼30%), P-AMPK (∼60%), P-ACC (∼70%) and RXR-α (∼55%), suggesting decreased hepatic fat oxidation compared to controls. Interestingly, hepatic fatty acid uptake into hepatocytes and lipolysis were significantly increased in HFRD-fed mice, as shown by decreased CD36 and fatty acid transporter protein-2, and increased adipose triglyceride lipase, respectively (P<0.05). Increased hepatic levels of iNOS and GSSG/GSH suggest elevated oxidative stress with a higher number of macrophages in the adipose tissue in HFRD-fed mice (P<0.05). Significantly elevated rates of hepatocyte apoptosis (∼2.4-fold), as determined by TUNEL analysis with increased Bax/Bcl2 ratio and PARP-1 levels (∼2- and 1.5-fold, respectively), were observed in HFRD-fed mice. Thus, HFRD exposure increased hepatic steatosis accompanied by oxidative stress and inflammation, leading to hepatocyte apoptosis.

Nanoparticle labeling of bone marrow-derived rat mesenchymal stem cells: their use in differentiation and tracking

Mesenchymal stem cells (MSCs) are promising candidates for cellular therapies due to their ability to migrate to damaged tissue without inducing immune reaction. Many techniques have been developed to trace MSCs and their differentiation efficacy; however, all of these methods have limitations. Conjugated polymer based water-dispersible nanoparticles (CPN) represent a new class of probes because they offer high brightness, improved photostability, high fluorescent quantum yield, and noncytotoxicity comparing to conventional dyes and quantum dots. We aimed to use this tool for tracing MSCs' fate in vitro and in vivo. MSC marker expression, survival, and differentiation capacity were assessed upon CPN treatment. Our results showed that after CPN labeling, MSC markers did not change and significant number of cells were found to be viable as revealed by MTT. Fluorescent signals were retained for 3 weeks after they were differentiated into osteocytes, adipocytes, and chondrocytes in vitro. We also showed that the labeled MSCs migrated to the site of injury and retained their labels in an in vivo liver regeneration model. The utilization of nanoparticle could be a promising tool for the tracking of MSCs in vivo and in vitro and therefore can be a useful tool to understand differentiation and homing mechanisms of MSCs.

Protective effects of melittin on transforming growth factor-β1 injury to hepatocytes via anti-apoptotic mechanism

Melittin is a cationic, hemolytic peptide that is the main toxic component in the venom of the honey bee (Apis mellifera). Melittin has multiple effects, including anti-bacterial, anti-viral and anti-inflammatory, in various cell types. However, the anti-apoptotic mechanisms of melittin have not been fully elucidated in hepatocytes. Apoptosis contributes to liver inflammation and fibrosis. Knowledge of the apoptotic mechanisms is important to develop new and effective therapies for treatment of cirrhosis, portal hypertension, liver cancer, and other liver diseases. In the present study, we investigated the anti-apoptotic effect of melittin on transforming growth factor (TGF)-β1-induced apoptosis in hepatocytes. TGF-β1-treated hepatocytes were exposed to low doses (0.5 and 1 μg/mL) and high dose (2 μg/mL) of melittin. The low doses significantly protected these cells from DNA damage in TGF-β1-induced apoptosis compared to the high dose. Also, melittin suppressed TGF-β1-induced apoptotic activation of the Bcl-2 family and caspase family of proteins, which resulted in the inhibition of poly-ADP-ribose polymerase (PARP) cleavage. These results demonstrate that TGF-β1 induces hepatocyte apoptosis and that an optimal dose of melittin exerts anti-apoptotic effects against TGF-β1-induced injury to hepatocytes via the mitochondrial pathway. These results suggest that an optimal dose of melittin can serve to protect cells against TGF-β1-mediated injury.

Alrp, a survival factor that controls the apoptotic process of regenerating liver after partial hepatectomy in rats

Augmenter of Liver Regeneration (Alrp) enhances, through unknown mechanism/s, hepatocyte proliferation only when administered to partially hepatectomized (PH) rats. Liver resection, besides stimulating hepatocyte proliferation, induces reactive oxygen species (ROS), triggering apoptosis. To clarify the role of Alrp in the process of liver regeneration, hepatocyte proliferation, apoptosis, ROS-induced parameters and morphological findings of regenerating liver were studied from PH rats Alrp-treated for 72 h after the surgery. The same parameters, evaluated on regenerating liver from albumin-treated PH rats, were used as control. The results demonstrated that Alrp administration induces the anti-apoptotic gene expression, inhibits hepatocyte apoptosis and reduces ROS-induced cell damage. These and similar data from in vitro studies and the presence of 'Alrp homologous proteins' in viruses as well as in mammals (i) allow to hypothesize that Alrp activity/ies may not be exclusive for regenerating liver and (ii) suggest the use of Alrp in the treatment of oxidative stress-related diseases.

Effect of bee venom on transforming growth factor-beta1-treated hepatocytes

Bee venom (BV) has been used as treatment against a wide variety of ailments, including inflammatory diseases. Various studies have demonstrated anti-inflammatory and anticancer effects of BV. Transforming growth factor (TGF)-beta1 induces hepatocyte apoptosis via the mitochondrial permeability transition. However, there is no evidence or information regarding the antiapoptotic effect of BV on hepatocytes. The authors investigated the antiapoptotic effect of BV on TGF-beta1-treated hepatocytes. The results showed significant protection from DNA damage by BV treatment compared to corresponding TGF-beta1-treated hepatocytes without BV. BV suppressed TGF-beta1-induced activation of the bcl-2 family and caspase family of proteins, which resulted in inhibition of poly ADP-ribose polymerase (PARP) cleavage. Furthermore, BV is not cytotoxic in the low concentrations used in this study. Low concentrations of BV potently suppress the apoptotic response in TGF-beta1-treated hepatocytes; therefore, BV may have therapeutic potential for the treatment of liver diseases.

Prostaglandin E1 prevents liver failure after excessive hepatectomy in the rat by up-regulating Cyclin C, Cyclin D1, and Bclxl

Prostaglandin E1 (PGE1) has wide-ranging effects on cytoprotection and may play a role in preventing liver failure following excessive hepatectomy. We examined the effect of PGE1 on hepatocyte apoptosis and liver regeneration after 95% hepatectomy in a rat model. PGE1 or vehicle was intravenously administered 30 minutes before and during hepatectomy. The extent of hepatocyte injury was evaluated by serum alanine aminotransferase and aspartate aminotransferase levels. To evaluate hepatocyte apoptosis and liver regeneration, terminal deoxynucleotidyl transferase dUTP nick end labeling staining and Ki67 labeling were performed. The expression levels of Bcl-xL, Bcl-2, Bax, Cyclin C, Cyclin D1, Cyclin E, p21, transforming growth factor-beta, plasminogen activator inhibitor-1, and glyceraldehyde-2-phosphate dehydrogenase mRNA were also examined by reverse transcription-polymerase chain reaction. Survival was improved in the PGE1 group (26.6%), whereas all rats in the vehicle group died within 60 hours. PGE1 significantly suppressed the release of alanine aminotransferase and aspartate aminotransferase at 12 hours postoperatively. Pretreatment with PGE1 significantly increased the Ki67-positive cell count and decreased the terminal deoxynucleotidyl transferase dUTP nick end labeling positive cell count after hepatectomy, and also significantly increased the expression levels of Bcl-xL, Cyclin C, and Cyclin D1. Our results suggest that pretreatment with PGE1 may increase survival following hepatectomy by salvaging the remaining liver tissue, which it does by inhibiting apoptosis and stimulating hepatocyte proliferation.

Hepatocyte growth factor improves survival after partial hepatectomy in cirrhotic rats suppressing apoptosis of hepatocytes

BACKGROUND

Liver failure after hepatic resection is still a critical issue in the treatment of hepatic tumors in patients with liver cirrhosis. In the current study, the effect of hepatocyte growth factor (HGF) gene transfer, which is a multipotent growth factor, was examined in rats with liver cirrhosis that underwent 2/3 partial hepatectomy (PH).

METHODS

Rats were treated with 1 mL of 1% dimethylnitrosoamine (DMN) 3 consecutive days per week for 4 weeks and then received a 2/3 PH. Three days before the PH, human HGF gene plasmid (20 microg) encapsulated in hemagglutinating virus of Japan (HVJ)-liposome was administered through a direct injection in the portal vein. Control cirrhotic rats received empty HVJ-liposome in the same manner.

RESULTS

HGF gene transfer significantly improved survival after PH in the cirrhotic rats, and it stimulated BrdU uptake in hepatocytes. Although the HGF gene transfer did not change the liver regeneration rate after PH, it suppressed hepatocyte apoptosis and upregulated an antiapoptotic protein, Bcl-xl, but it did not affect the expression of Bax, which is a proapoptotic protein.

CONCLUSION

HGF gene transfer to cirrhotic livers improves liver failure-associated death after PH upregulating expression of an antiapoptotic protein, Bcl-xl.

Effect of the immunosuppressants on hepatocyte cells proliferation and apoptosis during liver regeneration after hepatectomy - molecular studies

The regeneration and remodeling of the transplanted liver is the result of hepatocyte proliferation and apoptosis (programmed cell death). The purpose of this study was to verify the influence of immunosuppressants on the expression levels of genes: IL-6 (regulator of hepatocyte proliferation), pro-apoptotic (Bak and Bax) and anti-apoptotic (Bcl-Xl and Bcl-2). 36 newborn suckling rats (age 5-7 days, weight 6-10 g) were divided into four groups: hepatectomy, hepatectomy plus methylprednisolone, hepatectomy plus CsA and hepatectomy plus Tac. The same experiments were performed in 24 weaning rats (age 21-23 days, weight 30-50 g). The animals were killed one day after the hepatectomy and the remnant livers were analyzed. The livers of all animals exhibited histological changes of liver regeneration. The immunosuppressants did not promote any alteration on IL-6 gene expression levels. Methylprednisolone and CsA increased the expression levels of Bak gene in newborn rats. However, methylprednisolone and Tac promoted increased expression levels of Bcl-2 in all groups. We hypothesize that these effects explain the efficacy of these drugs on the treatment of acute and chronic liver rejection as the expression of Bcl-2 in cholangiocytes is decreased as a consequence of bile duct lesions

Cloning and expression profile of FLT3 gene during progenitor cell-dependent liver regeneration

BACKGROUND AND AIM

The liver has a unique capacity to regenerate upon exposure to viral infections, toxic reactions and cancer formation. Liver regeneration is a complex phenomenon in which several factors participate during its onset. Cellular proliferation is an important component of this process and the factors that regulate this proliferation have a vital role. FLT3, a well-known hematopoietic stem cell and hepatic lineage surface marker, is involved in proliferative events of hematopoietic stem cells. However, its contribution to liver regeneration is not known. Therefore, the aim of this study was to clone and examine the role of FLT3 during liver regeneration in rats.

METHODS

Partial cDNA of rat homolog of FLT3 gene was cloned from thymus and the tissue specific expression of this gene at mRNA and protein levels was examined by RT-PCR and Western blot. After treating with 2-AAF and performing hepatectomy in rats to induce progenitor-dependent liver regeneration, the mRNA and protein expression profile of FLT3 was investigated by real-time PCR and Western blot during liver regeneration. In addition, cellular localization of FLT3 protein was determined by immunohistochemistry.

RESULTS

The results indicated that rat FLT3 cDNA has high homology with mouse and human FLT3 cDNA. It was also found that FLT3 is expressed in most of the rat tissues and during liver regeneration. In addition, its intracellular localization is altered during the late stages of liver regeneration.

CONCLUSION

The FLT3 receptor is activated at the late stages of liver regeneration and participates in the proliferation response that is observed during progenitor-dependent liver regeneration.

Expression of interleukin 6 and apoptosis-related genes in suckling and weaning rat models of hepatectomy and liver regeneration

BACKGROUND/PURPOSE

The most commonly used model to study the mechanisms of liver regeneration is the adult rat submitted to 70% to 80% hepatectomy. However, there are no studies using newborn or weaning rat models. The process of liver regeneration includes both the hypertrophy and hyperplasia of cells (processes regulated by growth factors and cytokines, mainly interleukin 6 [IL-6]) as well as apoptosis, or programmed cell death (a process regulated mainly by the Bcl-2 family of proteins). Proapoptotic proteins in this family include Bax and Bak. Conversely, Bcl-2 and Bcl-XL are antiapoptotic regulators. Therefore, to expand our understanding of liver regeneration, our study had 2 goals: first, to standardize 2 animal models of hepatectomy and liver regeneration using the newborn suckling and the weaning rat and second, to quantitate the expression levels of IL-6 and several members of the Bcl-2 gene family during the regeneration process.

METHODS

To create the experimental models, newborn suckling rats (age, 5-7 days; weight, 6-10 g) and weaning rats (age, 21-23 days; weight, 30-50 g) underwent 70% hepatectomy. The animals were subsequently sacrificed at days 1, 2, 3, 4, and 7 after hepatectomy, and the remnant liver lobes were harvested for routine histologic examination. Groups of healthy animals not operated on served as controls. For the experimental study, 6 newborn rats and 6 weaning rats underwent hepatectomy. The animals were killed 1 day after liver resection and the remnant livers were harvested to assess gene expression by quantitative reverse transcription-polymerase chain reaction. The hepatectomized groups were compared with control and sham groups.

RESULTS

During the creation of the experimental models, 70% of the suckling animals and all the weaning animals survived the hepatectomy. The decreased liver weight was completely restored to control levels by day 7 after hepatectomy. Histologically, the remnant livers of both hepatectomy groups exhibited steatosis, tumefaction of hepatocytes, and mitosis, which ceased at 7 days after the hepatectomy. The weaning rat model showed more robust gene expression responses. Specifically, expression levels of IL-6 gene were significantly increased after both surgical insult (sham group) and hepatectomy. However, this increase was significantly higher in the latter group. Furthermore, hepatectomy promoted a decrease in the expression levels of the proapoptotic genes and an increase in the expression levels of Bcl-2.

CONCLUSIONS

Our data indicate that regulation of both IL-6 and genes involved in apoptosis are strongly implicated in the mechanisms of liver regeneration and that the weaning rat model represents an attractive model system for future investigations in this area.