Down-regulation of focal adhesion kinase by short hairpin RNA increased apoptosis of rat hepatic stellate cells

Role of AGAP2 in the profibrogenic effects induced by TGFβ in LX-2 hepatic stellate cells

Liver damage induces hepatic stellate cells (HSC) activation, characterised by a fibrogenic, proliferative and migratory phenotype. Activated HSC are mainly regulated by transforming growth factor β 1 (TGFβ1), which increases the production of extracellular matrix proteins (e.g. collagen-I) promoting the progression of hepatic fibrosis. AGAP2 (ArfGAP with GTPase domain, ankyrin repeat and PH domain 2) is a GTPase/GTP-activating protein involved in the actin remodelling system and receptor recycling. In the present work the role of AGAP2 in human HSC in response to TGFβ1 was investigated. LX-2 HSC were transfected with AGAP2 siRNA and treated with TGFβ1. AGAP2 knockdown prevented to some extent the proliferative and migratory TGFβ1-induced capacities of LX-2 cells. An array focused on human fibrosis revealed that AGAP2 knockdown partially prevented TGFβ1-mediated gene expression of the fibrogenic genes ACTA2, COL1A2, EDN1, INHBE, LOX, PDGFB, TGFΒ12, while favored the expression of CXCR4, IL1A, MMP1, MMP3 and MMP9 genes. Furthermore, TGFβ1 induced AGAP2 promoter activation and its protein expression in LX-2. Moreover, AGAP2 protein levels were significantly increased in liver samples from rats with thioacetamide-induced fibrosis. In addition, AGAP2 silencing affected TGFβ1-receptor 2 (TGFR2) trafficking in U2OS cells, blocking its effective recycling to the membrane. AGAP2 silencing in LX-2 cells prevented the TGFβ1-induced increase of collagen-I protein levels, while its overexpression enhanced collagen-I protein expression in the presence or absence of the cytokine. AGAP2 overexpression also increased focal adhesion kinase (FAK) phosphorylated levels in LX-2 cells. FAK and MEK1 inhibitors prevented the increase of collagen-I expression caused by TGFβ1 in LX-2 overexpressing AGAP2. In summary, the present work shows for the first time, that AGAP2 is a potential new target involved in TGFβ1 signalling, contributing to the progression of hepatic fibrosis.

Effects and mechanism of adenovirus-mediated phosphatase and tension homologue deleted on chromosome ten gene on collagen deposition in rat liver fibrosis

AIM

To evaluate the effects of phosphatase and tension homologue deleted on chromosome ten (PTEN) gene on collagen metabolism in hepatic fibrosis and the underlying mechanisms.

METHODS

Rat primary hepatic stellate cells (HSCs) and human LX-2 cells were transfected with adenovirus containing cDNA constructs encoding wild-type PTEN (Ad-PTEN), PTEN mutant G129E gene (Ad-G129E), and RNA interference constructs targeting the PTEN sequence PTEN short hairpin RNA to up-regulate and down-regulate the expression of PTEN. HSCs were assayed using fluorescent microscopy, real-time polymerase chain reaction, and western blotting. Moreover, a CCl₄-induced rat hepatic fibrosis model was established to investigate the in vivo effects. Hematoxylin and eosin, and Masson’s trichrome were used to assess the histological changes. The expression of collagen I and III was assessed using immunohistochemistry and western blot analysis.

RESULTS

Elevated expression of PTEN gene reduced serum levels of alanine transaminase and aspartate transaminase, decreased collagen deposition in the liver, and reduced hepatocyte necrosis. In contrast, knockdown of PTEN expression had an opposite effect, such as increased collagen deposition in the liver, and was molecularly characterized by the increased expression of matrix metalloproteinase (MMP)-13 (P < 0.01) and MMP-2 (P < 0.01), as well as decreased expression of the tissue inhibitor of metalloproteinase (TIMP)-1 (P < 0.01) and TIMP-2 (P < 0.01).

CONCLUSION

These data indicated that gene therapy using recombinant adenovirus encoding PTEN might be a novel way of treating hepatic fibrosis.

Focal adhesion kinase maintains, but not increases the adhesion of dental pulp cells

Focal adhesion kinase (FAK) functions as a key enzyme in the integrin-mediated adhesion-signalling pathway. Here, we aimed to investigate the effects of FAK on adhesion of human dental pulp (HDP) cells. We transfected lentiviral vectors to silence or overexpress FAK in HDP cells ex vivo. Early cell adhesion, cell survival and focal contacts (FCs)-related proteins (FAK and paxillin) were examined. By using immunofluorescence, the formation of FCs and cytoskeleton was detected, respectively. We found that both adhesion and survival of HDP cells were suppressed by FAK inhibition. However, FAK overexpression slightly inhibited cell adhesion and exhibited no change in cell survival compared with the control. A thick rim of cytoskeleton accumulated and smaller dot-shaped FCs appeared in FAK knockdown cells. Phosphorylation of paxillin (p-paxillin) was inhibited in FAK knockdown cells, verifying that the adhesion was inhibited. Less cytoskeleton and elongated FCs were observed in FAK-overexpressed cells. However, p-paxillin had no significant difference compared with the control. In conclusion, the data suggest that FAK maintains cell adhesion, survival and cytoskeleton formation, but excessive FAK has no positive effects on these aspects.

Regulatory Effects and Mechanism of Adenovirus-Mediated PTEN Gene on Hepatic Stellate Cells

BACKGROUND

Tension homology deleted on chromosome ten (PTEN) is important in liver fibrosis.

AIMS

The purpose of this study was to evaluate the PTEN gene effects and mechanism of action on hepatic stellate cells (HSCs).

METHODS

The rat primary HSCs and human LX-2 cells were transfected by an adenovirus containing cDNA constructs encoding the wild-type PTEN (Ad-PTEN), the PTEN mutant G129E gene (Ad-G129E) and RNA interference targeting the PTEN sequence PTEN short hairpin RNA (PTEN shRNA), to up-regulate and down-regulate PTEN expression, respectively. The HSCs were assayed with a fluorescent microscope, real time PCR, Western blot, MTT, flow cytometry and Terminal-deoxynucleoitidyl transferase mediated nick end labeling. In addition, the CCl4 induced rat hepatic fibrosis model was also established to check the in vivo effects of the recombinant adenovirus with various levels of PTEN expression.

RESULTS

The data have shown that the over-expressed PTEN gene led to reduced HSCs activation and viability, caspase-3 activity and cell cycle arrest in the G0/G1 and G2/M phases, as well as negative regulation of the PI3K/Akt and FAK/ERK signaling pathways in vitro. The over-expressed PTEN gene improved liver function, inhibited proliferation and promoted apoptosis of HSCs both in vitro and in vivo.

CONCLUSIONS

These data have shown that gene therapy using the recombinant adenovirus encoding wild-type PTEN inhibits proliferation and induces apoptosis of HSCs, which is a potential treatment option for hepatic fibrosis.

Effects of Ganfukang on expression of connective tissue growth factor and focal adhesion kinase/protein kinase B signal pathway in hepatic fibrosis rats

OBJECTIVE

To investigate the effect of Ganfukang (GFK) on connective tissue growth factor (CTGF) and focal adhesion kinase (FAK)/protein kinase B (PKB or Akt) signal pathway in a hepatic fibrosis rat model and to explore the underlying therapeutic molecular mechanisms of GFK.

METHODS

Fifty SD rats were randomly divided into five groups as follows: the control group, the model group (repeated subcutaneous injection of CCl4), and the three GFK treatment groups (31.25, 312.5, and 3125 mg/kg, intragastric administration). Reverse transcriptase-polymerase chain reaction (RT-PCR), Western blotting, and immunohistochemistry were used to examine the expression of CTGF, integrin α5, integrin β1, FAK/Akt signal pathway, cyclinD1, and collagen in the different-treated rats.

RESULTS

GFK attenuated the up-regulation of CTGF, integrin α5, and integrin β1 in hepatic fibrosis rats and suppressed both the phosphorylation of FAK and the phosphorylation of Akt simultaneously (P<0.01). At the same time, the expression of cyclinD1, collagen I, and collagen III was decreased by GFK significantly (P<0.01).

CONCLUSIONS

CTGF and FAK/Akt signal pathway were activated in the CCl4-induced hepatic fibrosis rats, which contribute to increased expression of cyclinD1 and collagen genes. The mechanisms of the anti-fibrosis activity of GFK may be due to its effects against CTGF and FAk/Akt signal pathway.

The Salvia miltiorrhiza monomer IH764-3 induces apoptosis of hepatic stellate cells in vivo in a bile duct ligation-induced model of liver fibrosis

During the process of liver fibrosis, hepatic stellate cells (HSCs) play a critical role in the excessive production of extracellular matrix (ECM). Previous studies have indicated that the monomer IH764-3, one of the major bioactive components of Salvia miltiorrhiza, is able to inhibit HSC proliferation and induce the apoptosis of activated HSCs in vitro. In the current study, we used a rat model of liver fibrosis induced by bile duct ligation (BDL) to investigate the effect of the monomer IH764-3 on the induction of apoptosis in HSCs in vivo. The rat model of liver fibrosis was established by BDL. Immunohistochemical staining of α-smooth muscle actin (α-SMA) was performed to detect HSC activation and proliferation and HSC apoptosis was detected by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and α-SMA immunohistochemical double staining. In addition, the protein expression levels of focal adhesion kinase (FAK), p-FAK (Tyr397), extracellular signal-regulated kinase (ERK) and p-ERK and the mRNA expression levels of FAK and ERK were measured by western blotting and reverse transcription-polymerase chain reaction (RT-PCR), respectively. The monomer IH764-3 was associated with a significant decrease in intrahepatic fibrogenesis and collagen deposition and attenuated the liver fibrosis induced by BDL. Immunohistochemical staining revealed that the expression of α-SMA in the IH764-3 group was significantly decreased compared with that in the model group (12.92±2.45 vs. 22.65±2.16%, P<0.01). TUNEL and α-SMA immunohistochemical double staining also confirmed that IH764-3 increased the apoptotic rate of the activated HSCs (34.8±4.5 vs. 4.72±0.37%, P<0.01). Moreover, the results revealed that IH764-3 downregulated the expression levels of FAK, p-FAK (Tyr397), ERK and p-ERK in the liver tissue of rats with liver fibrosis. The monomer IH764-3 ameliorates experimental liver fibrosis by inhibiting HSC proliferation and inducing HSC apoptosis, warranting its use as a potential therapeutic agent in the treatment of liver fibrosis.