The phosphoinositide 3-kinase/Akt-signal pathway mediates proliferation and secretory function of hepatic sinusoidal endothelial cells in rats after partial hepatectomy

Comparative Analysis of Regulatory Role of Notch Signaling Pathway in 8 Types Liver Cell During Liver Regeneration

Notch signaling is closely related to cell proliferation, cell apoptosis, cell fate decisions, DNA damage repair, and so on. However, the exactly regulatory mechanism of Notch signaling pathway in liver regeneration (LR) remains unclear. To reveal the role of Notch signaling pathway in rat liver regeneration, Ingenuity Pathway Analysis (IPA) software and related pathway database were firstly used to construct the Notch signaling pathway in this study. Next, eight type cells with high purity were obtained by Percoll density centrifugation and immunomagnetic beads sorting. Then, the expression profiles of Notch signaling pathway-related genes in eight type cells were checked by using Rat Genome 230 2.0 Array, and the results showed that the expression of 42 genes were significantly regulated. H-cluster results showed that the hepatic stellate cells are attributed to one cluster; hepatocyte cell, oval cell, sinusoidal endothelial cell, and Kupffer cell are clustered together; and biliary epithelial cell, pit cell, and dendritic cell are one cluster. IPA software and Expression analysis systematic explorer analysis indicated that Notch signaling pathway-related genes were involved in cell proliferation, apoptosis, cell cycle, DNA damage repair, etc. In conclusion, Notch signaling pathway might regulate various physiological activities of LR through multiple pathways.

Mechanical strain promotes osteogenic differentiation of bone mesenchymal stem cells from ovariectomized rats via the phosphoinositide 3‑kinase/Akt signaling pathway

Osteoporosis has become an overwhelming public health problem worldwide. As an elementary physiological factor to regulate bone formation and regeneration, mechanical strain may be used as a non‑invasive intervention in osteoporosis prevention and treatment. However, little is known regarding the underlying mechanism. The aim of the current study was to investigate the effect of continuous mechanical strain (CMS) on osteogenic differentiation of bone mesenchymal stem cells (BMSCs) from ovariectomized rats (OVX BMSCs). In addition, involvement of the phosphatidylinositol 3‑kinase (PI3K)/Akt signaling pathway in biomechanical signal transduction and its function were evaluated. The results demonstrated that OVX BMSCs subjected to CMS exhibited higher alkaline phosphatase (ALP) activity and deeper staining at 24 and 48 h. In addition, CMS upregulated the mRNA expression levels of ALP, collagen type I, runt related transcription factor 2 (Runx2), as well as the protein expression level of Runx2 in a time‑dependent manner. The PI3K/Akt signaling pathway was rapidly activated by CMS, with its phosphorylation level reaching its maximum in a short duration and a large quantity of phosphorylated‑Akt remaining in the nucleus. Pre‑treatment with a selective blocker significantly blocked the strain‑induced activation of PI3K/Akt and reduced the commitment of OVX BMSCs into osteoblasts, demonstrating a dominated regulative effect of PI3K/Akt signaling in strain‑induced osteogenesis. These results indicated that CMS induced the early differentiation of OVX BMSCs towards an osteogenic phenotype by activating the PI3K/Akt signaling pathway.

New Insights into PI3K Inhibitor Design using X-ray Structures of PI3Kα Complexed with a Potent Lead Compound

Phosphatidylinositol 3-kinase α is an attractive target to potentially treat a range of cancers. Herein, we described the evolution of a reported PI3K inhibitor into a moderate PI3Kα inhibitor with a low molecular weight. We used X-ray crystallography to describe the accurate binding mode of the compound YXY-4F. A comparison of the p110α–YXY-4F and apo p110α complexes showed that YXY-4F induced additional space by promoting a flexible conformational change in residues Ser773 and Ser774 in the PI3Kα ATP catalytic site. Specifically, residue 773(S) in PI3Kα is quite different from that of PI3Kβ (D), γ (A), and δ (D), which might guide further optimization of substituents around the NH group and phenyl group to improve the selectivity and potency of PI3Kα.

Akt-mediated foxo1 inhibition is required for liver regeneration

Understanding the hepatic regenerative process has clinical interest as the effectiveness of many treatments for chronic liver diseases is conditioned by efficient liver regeneration. Experimental evidence points to the need for a temporal coordination between cytokines, growth factors, and metabolic signaling pathways to enable successful liver regeneration. One intracellular mediator that acts as a signal integration node for these processes is the serine-threonine kinase Akt/protein kinase B (Akt). To investigate the contribution of Akt during hepatic regeneration, we performed partial hepatectomy in mice lacking Akt1, Akt2, or both isoforms. We found that absence of Akt1 or Akt2 does not influence liver regeneration after partial hepatectomy. However, hepatic-specific Akt1 and Akt2 null mice show impaired liver regeneration and increased mortality. The major abnormal cellular events observed in total Akt-deficient livers were a marked reduction in cell proliferation, cell hypertrophy, glycogenesis, and lipid droplet formation. Most importantly, liver-specific deletion of FoxO1, a transcription factor regulated by Akt, rescued the hepatic regenerative capability in Akt1-deficient and Akt2-deficient mice and normalized the cellular events associated with liver regeneration.

CONCLUSION

The Akt-FoxO1 signaling pathway plays an essential role during liver regeneration.

The variation of AkT/TSC1-TSC1/mTOR signal pathway in hepatocytes after partial hepatectomy in rats

OBJECTIVE

The aim of this study was to investigate the role and regulatory mechanisms of Akt/TSC1-TSC2/mTOR signal pathway on the hepatocyte growth and proliferation after partial hepatectomy in rats.

METHODS

We used the animal model of 70% hepatectomy, separated and cultivated hepatocytes. According to the different time points after partial hepatectomy, it could be grouped into 0 h, 2 h, 6 h, 24 h and 72 h. According to the different kinds of specific inhibitor in the nutritive medium after the separation of hepatocytes, it could be grouped into Triciribine (TR), Rapamycin (RA) and Control (CO). We investigated (3)H-Leucine incorporation into protein, the cross section areas of hepatocytes, and detected cell cycle through FCM. The expressions of phosphorylated protein TSC2 and mTOR were observed.

RESULTS

(1) The content of phosphorylated protein TSC2 in group CO began to increase at 2 h and got to the peak at 6 h but declined at 24 h. The content of phosphorylated protein TSC2 in group RA had the same variation with that of phosphorylated protein TSC2 in group CO. (2) At the time point of 0 h, 2 h, 6 h and 24 h after operation, the incorporation efficiency of (3)H-Leucine in groups RA and TR was different from that in group CO in statistics (P<0.01). (3) It could be seen that the cross section areas of hepatocytes in groups RA and TR were different from that in group CO in statistics at 2 h and 6 h after operation (P<0.05). (4) Comparing with the other two inhibitor groups (TR and RA), the number of cells during the period of G0/G1 in group CO became fewer, while the number of cells during the period of S and G2/M grew obviously (referring to Fig. 8). After operation, each time point was different from the inhibitor groups obviously (P<0.05 or P<0.01). The peak declined greatly at 24 h and 72 h after operation.

CONCLUSIONS

These data strongly suggest the effects of Akt/TSC1-TSC2/mTOR signal pathway on hepatocyte growth, protein synthesis and cell cycle, and prove its contribution to liver regeneration.

Laser-induced thermotherapy (LITT) elevates mRNA expression of connective tissue growth factor (CTGF) associated with reduced tumor growth of liver metastases compared to hepatic resection

BACKGROUND AND OBJECTIVES

Proliferation and synthesis of hepatocellular tissue after tissue damage are promoted by specific growth factors such as hepatic tissue growth factor (HGF) and connective growth factor (CTGF). Laser-induced thermotherapy (LITT) for the treatment of liver metastases is deemed to be a parenchyma-saving procedure compared to hepatic resection. The aim of this study was to compare the impact of LITT and hepatic resection on intrahepatic residual tumor tissue and expression levels of mRNA HGF/CTGF within liver and tumor tissue.

STUDY DESIGN/MATERIALS AND METHODS

Two independent adenocarcinomas (CC531) were implanted into 75 WAG rats, one in the right (untreated tumor) and one in the left liver lobe (treated tumor). The left lobe tumor was treated either by LITT or partial hepatectomy. The control tumor was submitted to in-situ hybridization of HGF and CTGF 24-96 hours and 14 days after intervention.

RESULTS

Volumes of the untreated tumors prior to intervention were 38+/-8 mm(3) in group I (laser), 39 +/- 7 mm(3) in group II (resection), and 42 +/- 12 mm(3) in group III (control) and did not differ significantly (P > 0.05). Fourteen days after the intervention the mean tumor+/-SEM volume of untreated tumor in group I (laser) [223 +/- 36] was smaller than in group II (resection) [1233.28 +/- 181.52; P < 0.001], and in group III (control) [978.92 +/- 87.57; P < 0.003]. Forty-eight hours after the intervention intrahepatic mRNA expression level of HGF in group II (resection) was almost twofold higher than in group I (laser) [7.2 +/- 1.0 c/mf vs. 3.9 +/- 0.4 c/mf; P<0.01]. Fourteen days after the intervention intrahepatic mRNA expression level of CTGF in group I (laser) was higher than in group II (resection) [13.89 +/- 0.77 c/mf vs. 9.09 +/- 0.78 c/mf; P < 0.003].

CONCLUSIONS

LITT leads to a decrease of residual tumor growth in comparison to hepatic resection. Accelerated tumor growth after hepatic resection is associated with higher mRNA level of HGF and reduced tumor growth after LITT with higher mRNA level of CTGF. The increased CTGF-mediated regulation of ECM may cause reduced residual tumor growth after LITT.

Role of ischaemic preconditioning in liver regeneration following major liver resection and transplantation

Liver ischaemic preconditioning (IPC) is known to protect the liver from the detrimental effects of ischaemic-reperfusion injury (IRI), which contributes significantly to the morbidity and mortality following major liver surgery. Recent studies have focused on the role of IPC in liver regeneration, the precise mechanism of which are not completely understood. This review discusses the current understanding of the mechanism of liver regeneration and the role of IPC in this setting. Relevant articles were reviewed from the published literature using the Medline database. The search was performed using the keywords “liver”, “ischaemic reperfusion”, “ischaemic preconditioning”, “regeneration”, “hepatectomy” and “transplantation”. The underlying mechanism of liver regeneration is a complex process involving the interaction of cytokines, growth factors and the metabolic demand of the liver. IPC, through various mediators, promotes liver regeneration by up-regulating growth-promoting factors and suppresses growth-inhibiting factors as well as damaging stresses. The increased understanding of the cellular mechanisms involved in IPC will enable the development of alternative treatment modalities aimed at promoting liver regeneration following major liver resection and transplantation.