A Novel AKT Activator, SC79, Prevents Acute Hepatic Failure Induced by Fas-Mediated Apoptosis of Hepatocytes

RND1 inhibits epithelial-mesenchymal transition and temozolomide resistance of glioblastoma via AKT/GSK3-β pathway

GBM is one of the most malignant tumor in central nervous system. The resistance to temozolomide (TMZ) is inevitable in GBM and the characterization of TMZ resistance seriously hinders clinical treatment. It is worthwhile exploring the underlying mechanism of aggressive invasion and TMZ resistance in GBM treatment. Bioinformatic analysis was used to analyze the association between RND1 and a series of EMT-related genes. Colony formation assay and cell viability assay were used to assess the growth of U87 and U251 cells. The cell invasion status was evaluated based on transwell and wound-healing assays. Western blot was used to detect the protein expression in GBM cells. Treatment targeted RND1 combined with TMZ therapy was conducted in nude mice to evaluate the potential application of RND1 as a clinical target for GBM. The overexpression of RND1 suppressed the progression and migration of U87 and U251 cells. RND1 knockdown facilitated the growth and invasion of GBM cells. RND1 regulated the EMT of GBM cells via inhibiting the phosphorylation of AKT and GSK3-β. The promoted effects of RND1 on TMZ sensitivity was identified both in vitro and in vivo. This research demonstrated that the overexpression of RND1 suppressed the migration and EMT status by downregulating AKT/GSK3-β pathway in GBM. RND1 enhanced the TMZ sensitivity of GBM cells both in vitro and in vivo. Our findings may contribute to the targeted therapy for GBM and the understanding of mechanisms of TMZ resistance in GBM.

Molecular profiling of sponge deflation reveals an ancient relaxant-inflammatory response

A hallmark of animals is the coordination of whole-body movement. Neurons and muscles are central to this, yet coordinated movements also exist in sponges that lack these cell types. Sponges are sessile animals with a complex canal system for filter-feeding. They undergo whole-body movements resembling "contractions" that lead to canal closure and water expulsion. Here, we combine live 3D optical coherence microscopy, pharmacology, and functional proteomics to elucidate the sequence and detail of shape changes, the tissues and molecular physiology involved, and the control of these movements. Morphometric analysis and targeted perturbation suggest that the movement is driven by the relaxation of actomyosin stress fibers in epithelial canal cells, which leads to whole-body deflation via collapse of the incurrent and expansion of the excurrent canal system. Thermal proteome profiling and quantitative phosphoproteomics confirm the control of cellular relaxation by an Akt/NO/PKG/PKA pathway. Agitation-induced deflation leads to differential phosphorylation of proteins forming epithelial cell junctions, implying their mechanosensitive role. Unexpectedly, untargeted metabolomics detect a concomitant decrease in antioxidant molecules during deflation, reflecting an increase in reactive oxygen species. Together with the secretion of proteinases, cytokines, and granulin, this indicates an inflammation-like state of the deflating sponge reminiscent of vascular endothelial cells experiencing oscillatory shear stress. These results suggest the conservation of an ancient relaxant-inflammatory response of perturbed fluid-carrying systems in animals and offer a possible mechanism for whole-body coordination through diffusible paracrine signals and mechanotransduction.

Isolation, culture, and delivery considerations for the use of mesenchymal stem cells in potential therapies for acute liver failure

Acute liver failure (ALF) is a high-mortality syndrome for which liver transplantation is considered the only effective treatment option. A shortage of donor organs, high costs and surgical complications associated with immune rejection constrain the therapeutic effects of liver transplantation. Recently, mesenchymal stem cell (MSC) therapy was recognized as an alternative strategy for liver transplantation. Bone marrow mesenchymal stem cells (BMSCs) have been used in clinical trials of several liver diseases due to their ease of acquisition, strong proliferation ability, multipotent differentiation, homing to the lesion site, low immunogenicity and anti-inflammatory and antifibrotic effects. In this review, we comprehensively summarized the harvest and culture expansion strategies for BMSCs, the development of animal models of ALF of different aetiologies, the critical mechanisms of BMSC therapy for ALF and the challenge of clinical application.

Benzo[b]fluoranthene induces male reproductive toxicity and apoptosis via Akt-Mdm2-p53 signaling axis in mouse Leydig cells: Integrating computational toxicology and experimental approaches

This study aims to explore the male reproductive toxicity of Benzo[b]fluoranthene (BbF) and related mechanisms. The results of computational toxicology analysis indicated male reproductive toxicity of BbF was related to apoptosis of Leydig cells and that Akt/p53 pathway might play a key role. In experiments, BbF induced testosterone decline, decreased concentration and motility of sperm and aggravated testicular pathological injury in mice. Besides, BbF led to apoptosis in Leydig cells, and decreased expressions of p-Akt and Bcl2, while improving the expressions of p53, Bax and Cleaved Caspase-3 in vivo and in vitro. Further, compared with BbF group, Akt activator SC79 significantly reduced cell apoptosis rate, improved cell viability, promoted the expressions of p-Akt and p-Mdm2, and reversed the above molecular expressions. Similarly, p53 inhibitor Pifithrin-α also significantly enhanced the cell vitality, alleviated the apoptosis of TM3 cells induced by BbF, and decreased the expressions of Bax and Cleaved Caspase-3, with the up-regulation of Bcl2. To sum up, by inhibiting Akt-Mdm2 signaling, BbF activated the p53-mediated mitochondrial apoptosis pathway, further inducing the apoptosis of Leydig cells, therefore resulting in testosterone decline and male reproductive damage. Besides, this study provided a valid mode integrating computational toxicology and experimental approaches in toxicity testing.

Molecular profiling of sponge deflation reveals an ancient relaxant-inflammatory response

A hallmark of animals is the coordination of whole-body movement. Neurons and muscles are central to this, yet coordinated movements also exist in sponges that lack these cell types. Sponges are sessile animals with a complex canal system for filter-feeding. They undergo whole-body movements resembling "contractions" that lead to canal closure and water expulsion. Here, we combine 3D optical coherence microscopy, pharmacology, and functional proteomics to elucidate anatomy, molecular physiology, and control of these movements. We find them driven by the relaxation of actomyosin stress fibers in epithelial canal cells, which leads to whole-body deflation via collapse of the incurrent and expansion of the excurrent system, controlled by an Akt/NO/PKG/A pathway. A concomitant increase in reactive oxygen species and secretion of proteinases and cytokines indicate an inflammation-like state reminiscent of vascular endothelial cells experiencing oscillatory shear stress. This suggests an ancient relaxant-inflammatory response of perturbed fluid-carrying systems in animals.

Activation of the JNKs/ATM-p53 axis is indispensable for the cytoprotection of dermal fibroblasts exposed to UVB radiation

Although UVB radiation is mainly absorbed by the epidermis, ~5-10% of its photons reach and affect the upper part of the dermis. Physiologically relevant UVB doses, able to provoke erythema, induce apoptosis in human dermal fibroblasts in vitro, as well as in the dermis of SKH-1 mice. Given the sparse and even contradictory existing information on the effect of UVB radiation on dermal fibroblasts' viability, aim of this work was to unravel the crucial signaling pathways regulating the survival of UVB-treated human dermal fibroblasts. We found that UVB radiation immediately stimulates the phosphorylation of MAPK family members, as well as Akt, and is genotoxic leading to the delayed ATM-p53 axis activation. Akt phosphorylation after UVB radiation is EGFR-mediated and EGFR inhibition leads to a further decrease of viability, while the Akt activator SC79 rescues fibroblasts to an extent by a mechanism involving Nrf2 activation. The known Nrf2 activator sulforaphane also exerts a partial protective effect, although by acting in a distinct mechanism from SC79. On the other hand, inhibition of JNKs or of the ATM-p53 axis leads to a complete loss of viability after UVB irradiation. Interestingly, JNKs activation is necessary for p53 phosphorylation, while the ATM-p53 pathway is required for the long-term activation of JNKs and Akt, reassuring the protection from UVB. Although UVB radiation results in intense and prolonged increase of intracellular ROS levels, classical anti-oxidants, such as Trolox, are unable to affect Akt, JNKs, or p53 phosphorylation and to reverse the loss of fibroblasts' viability. Collectively, here we provide evidence that the main viability-regulating UVB-triggered biochemical pathways act synergistically towards the protection of human dermal fibroblasts, with EGFR/Akt and Nrf2 serving as auxiliary anti-apoptotic machineries, while JNKs/ATM-p53 activation and interplay being overriding and indispensable for the perpetuation of cellular defense and the maintenance of cell viability.

The New PI3K/mTOR Inhibitor GNE-477 Inhibits the Malignant Behavior of Human Glioblastoma Cells

The most common primary central nervous system tumor in adults is glioblastoma multiforme (GBM). The high invasiveness of GBM cells is an important factor leading to inevitable tumor recurrence and a poor prognosis of patients. GNE-477, a novel PI3K/mTOR inhibitor, has been reported to exert antiproliferative effects on other cancer cells. However, researchers have not clearly determined whether GNE-477 produces antitumor effects on GBM. In the present study, GNE-477 significantly inhibited the proliferation, migration and invasion of U87 and U251 cells. In addition, GNE-477 also induced apoptosis of GBM cells, arresting the cell cycle in G0/G1 phase. More importantly, GNE-477 also reduced the levels of AKT and mTOR phosphorylation in the AKT/mTOR signaling pathway in a concentration-dependent manner. An increase in AKT activity induced by SC79 rescued the GNE-477-mediated inhibition of GBM cell proliferation and apoptosis. The antitumor effects of GNE-477 and the regulatory effects on related molecules were further confirmed in vivo using a nude mouse intracranial xenograft model. In conclusion, our study indicated that GNE-477 exerted significant antitumor effects on GBM cells in vitro and in vivo by downregulating the AKT/mTOR pathway.

REV-ERBα Agonist GSK4112 attenuates Fas-induced Acute Hepatic Damage in Mice

Fas-induced apoptosis is a central mechanism of hepatocyte damage during acute and chronic hepatic disorders. Increasing evidence suggests that circadian clock plays critical roles in the regulation of cell fates. In the present study, the potential significance of REV-ERBα, a core ingredient of circadian clock, in Fas-induced acute liver injury has been investigated. The anti-Fas antibody Jo2 was injected intraperitoneally in mice to induce acute liver injury and the REV-ERBα agonist GSK4112 was administered. The results indicated that treatment of GSK4112 decreased the level of plasma ALT and AST, attenuated the liver histological changes, and promoted the survival rate in Jo2-insulted mice. Treatment with GSK4112 also downregulated the activities of caspase-3 and caspase-8, suppressed hepatocyte apoptosis. In addition, treatment with GSK4112 decreased the level of Fas and enhanced the phosphorylation of Akt. In conclusion, treatment with GSK4112 alleviated Fas-induced apoptotic liver damage in mice, suggesting that REV-ERBα agonist might have potential value in pharmacological intervention of Fas-associated liver injury.

ACTL6A knockdown inhibits cell migration by suppressing the AKT signaling pathway and enhances the sensitivity of glioma cells to temozolomide

Molecular-targeted therapy has had a significant impact on glioma. Notably, actin-like 6A (ACTL6A) has been indicated to be essential for embryonic development and tumor progression. However, the role of ACTL6A in glioma remains unclear. The present study aimed to investigate the effects of ACTL6A on glioma cell migration and sensitivity to temozolomide (TMZ). The expression levels of ACTL6A were analyzed in patients with glioma, and survival curves were created using data from The Cancer Genome Atlas. U251 and T98G cells were transfected with short hairpin (sh)RNA for use in loss-of-function experiments to investigate the biological function and molecular mechanisms of ACTL6A. Furthermore, an MTT assay was used to assess the effect of ACTL6A on the sensitivity of glioma cells to TMZ. The results demonstrated that ACTL6A was expressed at higher levels in glioma tissues compared with normal brain tissues. Furthermore, high expression of ACTL6A was associated with a poor prognosis. The knockdown of ACTL6A significantly inhibited the migration phenotype in glioma cells and significantly decreased the levels of phosphorylated AKT in glioma cells. The AKT signaling activator SC79 partly attenuated the inhibitory effects of ACTL6A shRNA on glioma cell migration. Additionally, the knockdown of ACTL6A enhanced the sensitivity of glioma cells to TMZ. In conclusion, these results suggest that ACTL6A knockdown inhibited the migration of human glioma cells, at least in part through inactivation of the AKT signaling pathway, and increased the sensitivity of glioma cells to TMZ. Therefore, ACTL6A may be a potential therapeutic target for glioma.

Apigenin 7-O-glucoside promotes cell apoptosis through the PTEN/PI3K/AKT pathway and inhibits cell migration in cervical cancer HeLa cells

Epidemiologic evidence promote the inclusion of flavones in diet due to their inhibitory effects on certain types of cancers, particularly in women. Among the naturally occurring plant flavonoids, Apigenin 7-O-glucoside (AGL) is endowed with anti-inflammatory, anti-oxidant, and anti-cancer activities. However, its mechanism of action on cervical cancer, the fourth largest cancer in women, has not yet been clarified. In the current study, we have determined the effect of AGL on human cervical cancer cells and studied its molecular mechanism against cervical cancer. The results showed that AGL inhibited the proliferation of HeLa cells (IC₅₀ was 47.26 μM at 48 h) by inducing apoptosis. Furthermore, AGL treatment caused G0/G1 phase arrest, reduced mitochondrial membrane potential (MMP), and upgraded intracellular ROS production. AGL could promote the release of cytochrome c by regulating Bcl-2 family proteins, and then activated caspase 9/3 to promote cell apoptosis. Moreover, AGL treatment promoted the expression of p16 INK4A, while inhibited the expression of Cyclin A/D/E and CDK2/6. At the same time in HeLa cells treated with AGL, the PTEN/PI3K/AKT pathway was inhibited in a concentration-dependent manner, and cell migration was also impeded correspondingly through the matrix metalloproteinase 2 and 9. Our study may provide a new research direction for harnessing the novel natural compounds in cervical cancer treatment.

Contribution of glutaredoxin-1 to Fas s-glutathionylation and inflammation in ethanol-induced liver injury

AIMS

The reversible protein S-glutathionylation (PSSG) modification of Fas augments apoptosis, which can be reversed by the cytosolic deglutathionylation enzyme glutaredoxin-1 (Grx1), but its roles in alcoholic liver injury remain unknown. Therefore, the objective of this study was to investigate the impact of genetic ablation of Grx1 on Fas S-glutathionylation (Fas-SSG) in regulating ethanol-induced injury.

MATERIALS AND METHODS

We evaluated the Grx1 activity and oxidative damage, hepatic injury related indicators, Fas-SSG, we also assess the nuclear factor-κB (NF-κB) signaling, its downstream signal, and Akt signaling cascades, Furthermore, the number of Kupffer cells and related proinflammatory cytokines between WT and Grx1- groups after alcohol exposure.

KEY FINDINGS

Ethanol-fed mice had increased Grx1 activity and oxidative damage in the liver. Grx1-deficient mice had more serious liver damage when exposed to ethanol compared to that of wild-type mice, accompanied by increased alanine aminotransferase and aspartate aminotransferase levels, Fas-SSG, cleaved caspase-3 and hepatocyte apoptosis. Grx1 ablation resulted in the suppression of ethanol-induced NF-κB signaling, its downstream signal, and Akt signaling cascades, which are required for protection against Fas-mediated apoptosis. Accordingly, blocking NK-κB prevented Fas-induced apoptosis in WT mice but not Grx1-/- mice. Furthermore, the number of Kupffer cells and related proinflammatory cytokines, including Akt, were lower in Grx1-/- livers than those of the controls.

SIGNIFICANCE

Grx1 is essential for adaptation to alcohol exposure-induced oxidative injury by modulating Fas-SSG and Fas-induced apoptosis.

Targeting the Inositol Pyrophosphate Biosynthetic Enzymes in Metabolic Diseases

In mammals, a family of three inositol hexakisphosphate kinases (IP6Ks) synthesizes the inositol pyrophosphate 5-IP7 from IP6. Genetic deletion of Ip6k1 protects mice from high fat diet induced obesity, insulin resistance and fatty liver. IP6K1 generated 5-IP7 promotes insulin secretion from pancreatic β-cells, whereas it reduces insulin signaling in metabolic tissues by inhibiting the protein kinase Akt. Thus, IP6K1 promotes high fat diet induced hyperinsulinemia and insulin resistance in mice while its deletion has the opposite effects. IP6K1 also promotes fat accumulation in the adipose tissue by inhibiting the protein kinase AMPK mediated energy expenditure. Genetic deletion of Ip6k3 protects mice from age induced fat accumulation and insulin resistance. Accordingly, the pan IP6K inhibitor TNP [N2-(m-trifluorobenzyl), N6-(p-nitrobenzyl)purine] ameliorates obesity, insulin resistance and fatty liver in diet induced obese mice by improving Akt and AMPK mediated insulin sensitivity and energy expenditure. TNP also protects mice from bone loss, myocardial infarction and ischemia reperfusion injury. Thus, the IP6K pathway is a potential target in obesity and other metabolic diseases. Here, we summarize the studies that established IP6Ks as a potential target in metabolic diseases. Further studies will reveal whether inhibition of this pathway has similar pleiotropic benefits on metabolic health of humans.

Ataxia telangiectasia mutated pathway disruption affects hepatic DNA and tissue damage in nonalcoholic fatty liver disease

To overcome the rising burdens of nonalcoholic fatty liver disease, mechanistic linkages in mitochondrial dysfunction, inflammation and hepatic injury are critical. As ataxia telangiectasia mutated (ATM) gene oversees DNA integrity and mitochondrial homeostasis, we analyzed mRNAs and total proteins or phosphoproteins related to ATM gene by arrays in subjects with healthy liver, fatty liver or nonalcoholic steatohepatitis. Functional genomics approaches were used to query DNA damage or cell growth events. The effects of fatty acid-induced toxicity in mitochondrial health, DNA integrity and cell proliferation were validated in HuH-7 cells, including by inhibiting ATM kinase activity or knckdown of its mRNA. In fatty livers, DNA damage and ATM pathway activation was observed. During induced steatosis in HuH-7 cells, lowering of ATM activity produced mitochondrial dysregulation, DNA damage and cell growth inhibition. In livers undergoing steatohepatitis, ATM was depleted with increased hepatic DNA damage and growth-arrest due to cell cycle checkpoint activations. Moreover, molecular signatures of oncogenesis were associated with upstream mechanistic networks directing cell metabolism, inflammation or growth that were either activated (in fatty liver) or inactivated (in steatohepatitis). To compensate for hepatic growth arrest, preoncogenic oval cell populations expressing connexin-43 and/or albumin emerged. These oval cells avoided DNA damage and proliferated actively. We concluded that ATM is a major contributor to the onset and progression of nonalcoholic fatty liver disease. Therefore, specific markers for ATM pathway dysregulation will allow prospective segregation of cohorts for disease susceptibility and progression from steatosis to steatohepatitis. This will offer superior design and evaluation parameters for clinical trials. Restoration of ATM activity with targeted therapies should be appropriate for nonalcoholic fatty liver disease.

Ginsenoside Rg3 Reduces Epithelial-Mesenchymal Transition Induced by Transforming Growth Factor-β1 by Inactivation of AKT in HMrSV5 Peritoneal Mesothelial Cells

Background

Ginsenosides, including ginsenoside Rg3, are components of Panax ginseng C.A. Meyer (Araliaceae) used in traditional Chinese medicine. Long-term peritoneal dialysis induces peritoneal fibrosis that impairs ultrafiltration and is associated with epithelial-mesenchymal transition (EMT) of peritoneal cells. This study aimed to investigate the effects of ginsenoside Rg3 on EMT induced by transforming growth factor-β1 (TGF-β1) in HMrSV5 human peritoneal mesothelial cells.

Material/Methods

The cell counting kit-8 (CCK-8) assay measured HMrSV5 cell viability. The expression of EMT markers, E-cadherin, vimentin, and α-smooth muscle actin (α-SMA) were measured by quantitative reverse transcription polymerase chain reaction (qRT-PCR). The wound-healing assay determined cell migration. The S-phase of the cell cycle was assessed by 5-ethynyl-2′-deoxyuridine (EdU) labeling, and expression of phosphorylated AKT was measured by Western blot. The effect of ginsenoside Rg3 and the AKT activator SC79 on the TGF-β1-induced EMT of HMrSV5 cells were evaluated.

Results

Low concentration of ginsenoside Rg3 did not effect cell viability of HMrSV5 cells. TGF-β1 treatment decreased the expression of E-cadherin, and increased the expression of vimentin and α-SMA and promoted cell migration of HMrSV5 cells. However, co-treatment of ginsenoside Rg3 and TGF-β1 significantly reduced TGF-β1-induced EMT in HMrSV5 cells. TGF-β1 increased the phosphorylation of AKT and increased the expression of Smurf2. Ginsenoside Rg3 reduced TGF-β1-induced activation of AKT and Smurf2. SC79 reversed the effects of ginsenoside Rg3 on TGF-β1-induced EMT in HMrSV5 cells.

Conclusions

Ginsenoside Rg3 inhibited EMT induced by TGF-β1 in HMrSV5 human peritoneal mesothelial cells by inhibiting the activation of AKT.

Repression of Death Receptor-Mediated Apoptosis of Hepatocytes by Hepatitis B Virus e Antigen

Hepatitis B virus (HBV) e antigen (HBeAg) is associated with viral persistence and pathogenesis. Resistance of HBV-infected hepatocytes to apoptosis is seen as one of the primary promotors for HBV chronicity and malignancy. Fas receptor/ligand (Fas/FasL) and the tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) system plays a key role in hepatic death during HBV infection. We found that HBeAg mediates resistance of hepatocytes to FasL or TRAIL-induced apoptosis. Introduction of HBeAg into human hepatocytes rendered resistance to FasL or TRAIL cytotoxicity in a p53-dependent manner. HBeAg further inhibited the expression of p53, total Fas, membrane-bound Fas, TNF receptor superfamily member 10a, and TNF receptor superfamily member 10b at both mRNA and protein levels. In contrast, HBeAg enhanced the expression of soluble forms of Fas through facilitation of Fas alternative mRNA splicing. In a mouse model, expression of HBeAg in mice injected with recombinant adenovirus-associated virus 8 inhibited agonistic anti-Fas antibody-induced hepatic apoptosis. Xenograft tumorigenicity assay also found that HBeAg-induced carcinogenesis was resistant to the proapoptotic effect of TRAIL and chemotherapeutic drugs. These results indicate that HBeAg may prevent hepatocytes from FasL and TRAIL-induced apoptosis by regulating the expression of the proapoptotic and antiapoptotic forms of death receptors, which may contribute to the survival and persistence of infected hepatocytes during HBV infection.

PI3K/AKT inhibitors aggravate death receptor-mediated hepatocyte apoptosis and liver injury

The PI3K/AKT signaling pathway is one of the most frequently activated signaling networks in human cancers and has become a valuable target in anticancer therapy. However, accumulating reports suggest that adverse effects such as severe liver injury and inflammation may accompany treatment with pan-PI3K and pan-AKT inhibitors. Our prior work has demonstrated that activation of the PI3K/AKT pathway has a protective role in Fas- or TNFα-induced hepatocytic cell death and liver injury. We postulated that PI3K or AKT inhibitors may exacerbate liver damage via the death factor-mediated hepatocyte apoptosis. In this study we found that several drugs targeting PI3K/AKT either clinically used or in clinical trials sensitized hepatocytes to agonistic anti-Fas antibody- or TNFα-induced apoptosis and significantly shortened the survival of mice in in vivo liver damage models. The PI3K or AKT inhibitors promoted Fas aggregation, inhibited the expression of cellular FLICE-inhibitory protein S and L (FLIP_L/S), and enhanced procaspase-8 activation. Conversely, cotreatment with the AKT specific activator SC79 reversed these effects. Taken together, these findings suggest that PI3K or AKT inhibitors may render hepatocytes hypersensitive to Fas- or TNFα-induced apoptosis and liver injury.

Paeonol Ameliorates Glucose and Lipid Metabolism in Experimental Diabetes by Activating Akt

Our previous study proved that paeonol (Pae) could lower blood glucose levels of diabetic mice. There are also a few reports of its potential use for diabetes treatment. However, the role of Pae in regulating glucose and lipid metabolism in diabetes remains largely unknown. Considering the critical role of serine/threonine kinase B (Akt) in glucose and lipid metabolism, we explored whether Pae could improve glucose and lipid metabolism disorders via Akt. Here, we found that Pae attenuated fasting blood glucose, glycosylated serum protein, serum cholesterol and triglyceride (TG), hepatic glycogen, cholesterol and TG in diabetic mice. Moreover, Pae enhanced glucokinase (GCK) and low-density lipoprotein receptor (LDLR) protein expressions, and increased the phosphorylation of Akt. In insulin-resistant HepG2 cells, Pae increased glucose uptake and decreased lipid accumulation. What’s more, Pae elevated LDLR and GCK expressions as well as Akt phosphorylation, which was consistent with the in vivo results. Knockdown and inhibition experiments of Akt revealed that Pae regulated LDLR and GCK expressions through activation of Akt. Finally, molecular docking assay indicated the steady hydrogen bond was formed between Pae and Akt2. Experiments above suggested that Pae ameliorated glucose and lipid metabolism disorders and the underlying mechanism was closely related to the activation of Akt.

AKT activator SC79 protects hepatocytes from TNF-α-mediated apoptosis and alleviates d-Gal/LPS-induced liver injury

Tumor necrosis factor-α (TNF-α) is a highly pleiotropic cytokine executing biological functions as diverse as cell proliferation, metabolic activation, inflammatory responses, and cell death. TNF-α can induce multiple mechanisms to initiate apoptosis in hepatocytes leading to the subsequent liver injury. Since the phosphoinositide-3-kinase/protein kinase B (PI3K/Akt) pathway is known to have a protective role in death factor-mediated apoptosis, it is our hypothesis that activation of Akt may represent a therapeutic strategy to alleviate TNF-α-induced hepatocyte apoptosis and liver injury. We report here that the Akt activator SC79 protects hepatocytes from TNF-α-induced apoptosis and protects mice from d-galactosamine (d-Gal)/lipopolysaccharide (LPS)-induced TNF-α-mediated liver injury and damage. SC79 not only enhances the nuclear factor-κB (NF-κB) prosurvival signaling in response to TNF-α stimulation, but also increases the expression of cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein L and S (FLIP_L/S), which consequently inhibits the activation of procaspase-8. Furthermore, pretreatment of the PI3K/Akt inhibitor LY294002 reverses all the SC79-induced hepatoprotective effects. These results strongly indicate that SC79 protects against TNF-α-induced hepatocyte apoptosis and suggests that SC79 is likely a promising therapeutic agent for ameliorating the development of liver injury. NEW & NOTEWORTHY SC79 protects hepatocytes from TNF-α-mediated apoptosis and mice from Gal/LPS-induced liver injury and damage. Cytoprotective effects of SC79 against TNF-α act through both AKT-mediated activation of NF-κB and upregulation of FLIP_L/S.

Hepatitis B Spliced Protein (HBSP) Suppresses Fas-Mediated Hepatocyte Apoptosis via Activation of PI3K/Akt Signaling

Hepatitis B spliced protein (HBSP) is known to associate with viral persistence and pathogenesis; however, its biological and clinical significance remains poorly defined. Acquired resistance to Fas-mediated apoptosis is thought to be one of the major promotors for hepatitis B virus (HBV) chronicity and malignancy. The purpose of this study was to investigate whether HBSP could protect hepatocytes against Fas-initiated apoptosis. We showed here that HBSP mediated resistance of hepatoma cells or primary human hepatocytes (PHH) to agonistic anti-Fas antibody (CH11)- or FasL-induced apoptosis. Under Fas signaling stimulation, expression of HBSP inhibited Fas aggregation and prevented recruitment of the adaptor molecule Fas-associated death domain (FADD) and procaspase-8 (or FADD-like interleukin-1β-converting enzyme [FLICE]) into the death-inducing signaling complex (DISC) while increasing recruitment of cellular FLICE-inhibitory protein L (FLIP_L) into the DISC. Those effects may be mediated through activation of the phosphoinositide 3-kinase (PI3K)/Akt pathway as evidenced by increased cellular phosphatidylinositol (3,4,5)-trisphosphate (PIP3) content and PI3K activity and enhanced phosphorylation of mTORC2 and PDPK1 as well as Akt itself. Confirmedly, inhibition of PI3K by LY294002 reversed the effect of HBSP on Fas aggregation, FLIP_L expression, and cellular apoptosis. These results indicate that HBSP functions to prevent hepatocytes from Fas-induced apoptosis by enhancing PI3K/Akt activity, which may contribute to the survival and persistence of infected hepatocytes during chronic infection.IMPORTANCE Our study revealed a previously unappreciated role of HBSP in Fas-mediated apoptosis. The antiapoptotic activity of HBSP is important for understanding hepatitis B virus pathogenesis. In particular, HBV variants associated with hepatoma carcinoma may downregulate apoptosis of hepatocytes through enhanced HBSP expression. Our study also found that Akt is centrally involved in Fas-induced hepatocyte apoptosis and revealed that interventions directed at inhibiting the activation or functional activity of Akt may be of therapeutic value in this process.

Hepatitis B Virus Surface Antigen Enhances the Sensitivity of Hepatocytes to Fas-Mediated Apoptosis via Suppression of AKT Phosphorylation

The Fas receptor/ligand system plays a prominent role in hepatic apoptosis and hepatocyte death. Although hepatitis B virus (HBV) surface Ag (HBsAg) is the most abundant HBV protein in the liver and peripheral blood of patients with chronic HBV infection, its role in Fas-mediated hepatocyte apoptosis has not been disclosed. In this study, we report that HBsAg sensitizes HepG2 cells to agonistic anti-Fas Ab CH11-induced apoptosis through increasing the formation of SDS-stable Fas aggregation and procaspase-8 cleavage but decreasing both the expression of cellular FLIP_L/S and the recruitment of FLIP_L/S at the death-inducing signaling complex (DISC). Notably, HBsAg increased endoplasmic reticulum stress and consequently reduced AKT phosphorylation by deactivation of phosphoinositide-dependent kinase-1 (PDPK1) and mechanistic target of rapamycin complex 2 (mTORC2), leading to enhancement of Fas-mediated apoptosis. In a mouse model, expression of HBsAg in mice injected with recombinant adenovirus-associated virus 8 aggravated Jo2-induced acute liver failure, which could be effectively attenuated by the AKT activator SC79. Based on these results, it is concluded that HBsAg predisposes hepatocytes to Fas-mediated apoptosis and mice to acute liver failure via suppression of AKT prosurviving activity, suggesting that interventions directed at enhancing the activation or functional activity of AKT may be of therapeutic value in Fas-mediated progressive liver cell injury and liver diseases.