The peptidyl-prolyl isomerase, Pin1, facilitates NF-kappaB binding in hepatocytes and protects against hepatic ischemia/reperfusion injury

Berbamine attenuates hind limb ischemia-reperfusion injury by eliminating lipid ROS and inhibiting p65 nuclear translocation

This research aims to explore whether Berbamine (BBM) can mitigate tissue damage in mice resulting from hind limb muscle ischemia-reperfusion by scavenging lipid ROS and inhibiting p65 nuclear translocation. The hind limb ischemia-reperfusion (IR) injury model in mice was employed. Forty-eight mice (n = 12 per group) were randomly allocated into four groups: Sham group, IR group, IR + BBM (20 mg/kg) group, and IR + BBM (50 mg/kg) group. We observed that BBM pretreatment shielded against muscle damage and diminished levels of cell apoptosis compared to the control group. The mechanism likely involves reducing the movement of p65 into the nucleus and lessening the build-up of lipid ROS in muscle tissue. This action helps to decrease the release of substances that cause inflammation, ultimately reducing the inflammation in tissues that occurs as a result of hind limb IR. Our findings suggest that BBM has a protective impact on hindlimb ischemia-reperfusion injury, potentially due to its capacity to eliminate tissue lipid ROS and prevent p65 nuclear translocation.

PEP-1-PIN1 Promotes Hippocampal Neuronal Cell Survival by Inhibiting Cellular ROS and MAPK Phosphorylation

Background: The peptidyl-prolyl isomerase (PIN1) plays a vital role in cellular processes, including intracellular signaling and apoptosis. While oxidative stress is considered one of the primary mechanisms of pathogenesis in brain ischemic injury, the precise function of PIN1 in this disease remains to be elucidated. Objective: We constructed a cell-permeable PEP-1-PIN1 fusion protein and investigated PIN1's function in HT-22 hippocampal cells as well as in a brain ischemic injury gerbil model. Methods: Transduction of PEP-1-PIN1 into HT-22 cells and signaling pathways were determined by Western blot analysis. Intracellular reactive oxygen species (ROS) production and DNA damage was confirmed by DCF-DA and TUNEL staining. Cell viability was determined by MTT assay. Protective effects of PEP-1-PIN1 against ischemic injury were examined using immunohistochemistry. Results: PEP-1-PIN1, when transduced into HT-22 hippocampal cells, inhibited cell death in H2O2-treated cells and markedly reduced DNA fragmentation and ROS production. This fusion protein also reduced phosphorylation of mitogen-activated protein kinase (MAPK) and modulated expression levels of apoptosis-signaling proteins in HT-22 cells. Furthermore, PEP-1-PIN1 was distributed in gerbil hippocampus neuronal cells after passing through the blood-brain barrier (BBB) and significantly protected against neuronal cell death and also decreased activation of microglia and astrocytes in an ischemic injury gerbil model. Conclusions: These results indicate that PEP-1-PIN1 can inhibit ischemic brain injury by reducing cellular ROS levels and regulating MAPK and apoptosis-signaling pathways, suggesting that PIN1 plays a protective role in H2O2-treated HT-22 cells and ischemic injury gerbil model.

Targeting NF-κB in Hepatic Ischemia-Reperfusion Alleviation: from Signaling Networks to Therapeutic Targeting

Hepatic ischemia-reperfusion injury (HIRI) is a major complication of liver trauma, resection, and transplantation that can lead to liver dysfunction and failure. Scholars have proposed a variety of liver protection methods aimed at reducing ischemia-reperfusion damage, but there is still a lack of effective treatment methods, which urgently needs to find new effective treatment methods for patients. Many studies have reported that signaling pathway plays a key role in HIRI pathological process and liver function recovery mechanism, among which nuclear transfer factor-κB (NF-κB) signaling pathway is one of the signal transduction closely related to disease. NF-κB pathway is closely related to HIRI pathologic process, and inhibition of this pathway can delay oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction. In addition, NF-κB can also interact with PI3K/Akt, MAPK, and Nrf2 signaling pathways to participate in HIRI regulation. Based on the role of NF-κB pathway in HIRI, it may be a potential target pathway for HIRI. This review emphasizes the role of inhibiting the NF-κB signaling pathway in oxidative stress, inflammatory response, cell death, and mitochondrial dysfunction in HIRI, as well as the effects of related drugs or inhibitors targeting NF-κB on HIRI. The objective of this review is to elucidate the role and mechanism of NF-κB pathway in HIRI, emphasize the important role of NF-κB pathway in the prevention and treatment of HIRI, and provide a theoretical basis for the target NF-κB pathway as a therapy for HIRI.

Tspan15-ADAM10 signalling enhances cancer stem cell-like properties and induces chemoresistance via Notch1 activation in ICC

BACKGROUND & AIMS

Notch1 activation promotes ICC progression and is associated with chemoresistance; however, therapies directly targeting Notch1 showed severe adverse effects. Notch1 activation is mediated by ADAM10, a molecular scissor that separates the target protein from its substrates in the cell membrane. Tspan15 regulates ADAM10 function, but the role of Tspan15 in ICC progression is unclear.

METHODS

Tspan15, ADAM10, and Notch1 expression and activation in fresh surgical specimens from 80 ICC patients and ICC cells were evaluated by immunohistochemistry, RT-PCR, western blotting, and flow cytometry.

RESULTS

Tspan15 expression was increased in ICC compared with adjacent liver tissue, and high Tspan15 expression was an independent factor for poor prognosis. In ICC with high Tspan15 expression, vascular invasion, lymph node metastasis, and haematogenous recurrence were increased. Tspan15 was co-expressed with ADAM10 in ICC, and associated with the expression of stemness and EMT markers. In ICC cells, Tspan15 induced ADAM10 activation by mediating the translocation of activated m-ADAM10 from the cytoplasm to the surface of the cell membrane, which further activated Notch1 by separating the intracellular domain of Notch1 from its extracellular domain, leading to enhancement of CSC-like properties and EMT. This signalling was associated with enhanced chemoresistance against gemcitabine and cisplatin. Inhibition of Tspan15 or ADAM10 is a promising therapeutic strategy in ICC, as Tspan15 or ADAM10 knockdown or treatment with ADAM10 inhibitor reduced chemoresistance and invasiveness by suppressing Notch1-mediated CSC-like properties and EMT.

CONCLUSIONS

Tspan15-ADAM10-Notch1 signalling is associated with aggressive tumour progression and poor prognosis in ICC.

Sufentanil inhibits Pin1 to attenuate renal tubular epithelial cell ischemia-reperfusion injury by activating the PI3K/AKT/FOXO1 pathway

BACKGROUND

Renal ischemia-reperfusion injury (RIRI) has become a great concern in clinical practice with high morbidity and mortality rates. Sufentanil has protective effects on IRI-induced organ injury. Herein, the effects of sufentanil on RIRI were investigated.

METHODS

RIRI cell model was established by hypoxia/reperfusion (H/R) stimulation. The mRNA and protein expressions were assessed using qRT-PCR and western blot. TMCK-1 cell viability and apoptosis were assessed using MTT assay and flow cytometry, respectively. The mitochondrial membrane potential and ROS level were detected by JC-1 mitochondrial membrane potential fluorescent probe and DCFH-DA fluorescent probe, respectively. LDH, SOD, CAT, GSH and MDA levels were determined by the kits. The interaction between FOXO1 and Pin1 promoter was analyzed using dual luciferase reporter gene and ChIP assays.

RESULTS

Our results revealed that sufentanil treatment attenuated H/R-induced cell apoptosis, mitochondrial membrane potential (MMP) dysfunction, oxidative stress, inflammation and activated PI3K/AKT/FOXO1 associated proteins, while these effects were reversed by PI3K inhibitor, suggesting that sufentanil attenuated RIRI via activating the PI3K/AKT/FOXO1 signaling pathway. We subsequently found that FOXO1 transcriptionally activated Pin1 in TCMK-1 cells. Pin1 inhibition ameliorated H/R-induced TCMK-1 cell apoptosis, oxidative stress and inflammation. In addition, as expected, the biological effects of sufentanil on H/R-treated TMCK-1 cells were abrogated by Pin1 overexpression.

CONCLUSION

Sufentanil reduced Pin1 expression through activation of the PI3K/AKT/FOXO1 signaling to suppress cell apoptosis, oxidative stress and inflammation in renal tubular epithelial cells during RIRI development.

The regulatory role of Pin1 in neuronal death

Regulated cell death predominantly involves apoptosis, autophagy, and regulated necrosis. It is vital that we understand how key regulatory signals can control the process of cell death. Pin1 is a cis-trans isomerase that catalyzes the isomerization of phosphorylated serine or threonine-proline motifs of a protein, thereby acting as a crucial molecular switch and regulating the protein functionality and the signaling pathways involved. However, we know very little about how Pin1-associated pathways might play a role in regulated cell death. In this paper, we review the role of Pin1 in regulated cell death and related research progress and summarize Pin1-related pathways in regulated cell death. Aside from the involvement of Pin1 in the apoptosis that accompanies neurodegenerative diseases, accumulating evidence suggests that Pin1 also plays a role in regulated necrosis and autophagy, thereby exhibiting distinct effects, including both neurotoxic and neuroprotective effects. Gaining an enhanced understanding of Pin1 in neuronal death may provide us with new options for the development of therapeutic target for neurodegenerative disorders.

Inflammatory response to the ischaemia-reperfusion insult in the liver after major tissue trauma

BACKGROUND

Polytrauma is often accompanied by ischaemia-reperfusion injury to tissues and organs, and the resulting series of immune inflammatory reactions are a major cause of death in patients. The liver is one of the largest organs in the body, a characteristic that makes it the most vulnerable organ after multiple injuries. In addition, the liver is an important digestive organ that secretes a variety of inflammatory mediators involved in local as well as systemic immune inflammatory responses. Therefore, this review considers the main features of post-traumatic liver injury, focusing on the immuno-pathophysiological changes, the interactions between liver organs, and the principles of treatment deduced.

METHODS

We focus on the local as well as systemic immune response involving the liver after multiple injuries, with emphasis on the pathophysiological mechanisms.

RESULTS

An overview of the mechanisms underlying the pathophysiology of local as well as systemic immune responses involving the liver after multiple injuries, the latest research findings, and the current mainstream therapeutic approaches.

CONCLUSION

Cross-reactivity between various organs and cascade amplification effects are among the main causes of systemic immune inflammatory responses after multiple injuries. For the time being, the pathophysiological mechanisms underlying this interaction remain unclear. Future work will continue to focus on identifying potential signalling pathways as well as target genes and intervening at the right time points to prevent more severe immune inflammatory responses and promote better and faster recovery of the patient.

FAM49B, restrained by miR-22, relieved hepatic ischemia/reperfusion injury by inhibiting TRAF6/IKK signaling pathway in a Rac1-dependent manner

Hepatic ischemia/reperfusion (I/R) injury plays a pivotal pathogenic role in trauma, hepatectomy, and liver transplantation. However, the whole mechanism remains undescribed. The objective of this study is to investigate the internal mechanism by which microRNA-22 (miR-22) targets family with sequence similarity 49 member B (FAM49B), thus aggravating hepatic I/R injury. Here, we found that miR-22 was upregulated while FAM49B was reduced in hepatic I/R injury. Inhibition of miR-22 in vitro was able to intensify expression of FAM49B, thus reducing phosphorylation of inhibitors of nuclear factor kappa-B kinase (IKK) and downstream pro-inflammatory proteins. A dual luciferase reporter assay indicated that miR-22 directly targeted FAM49B. Remission of hepatic pathologic alterations, apoptosis, and release of cytokines derived from constraints of miR-22 were abolished in vivo by repressing FAM49B. Further interference of Ras-related C3 botulinum toxin substrate 1 (Rac1) reversed the function of FAM49B inhibition, thus achieving anti-inflammatory consequences.

The Suppression of Pin1-Alleviated Oxidative Stress through the p38 MAPK Pathway in Ischemia- and Reperfusion-Induced Acute Kidney Injury

Background

Pin1, as the peptidyl-prolyl isomerase, plays a vital role in cellular processes. However, whether it has a regulatory effect on renal ischemia and reperfusion (I/R) injury still remains unknown.

Methods

The hypoxia/reoxygenation (H/R) model in human kidney (HK-2) cells and the I/R model in rats were assessed to investigate the role of Pin1 on I/R-induced acute kidney injury. Male Sprague-Dawley rats were used to establish the I/R model for 15, 30, and 45 min ischemia and then 24 h reperfusion, with or without the Pin1 inhibitor, to demonstrate the role of Pin1 in acute kidney injury. HK-2 cells were cultured and experienced the H/R model to identify the molecular mechanisms involved.

Results

In this study, we found that Pin1 and oxidative stress were obviously increased after renal I/R. Inhibition of Pin1 with juglone decreased renal structural and functional injuries, as well as oxidative stress. Besides, Pin1 inhibition with the inhibitor, juglone, or the small interfering RNA showed significant reduction on oxidative stress markers caused by the H/R process in vitro. Furthermore, the results indicated that the expression of p38 MAPK was increased during H/R in vitro and Pin1 inhibition could reduce the increased expression of p38 MAPK.

Conclusion

Our results illustrated that Pin1 aggravated renal I/R injury via elevating oxidative stress through activation of the p38 MAPK pathway. These findings indicated that Pin1 might become the potential treatment for renal I/R injury.

Polysaccharides from Enteromorpha prolifera protect against carbon tetrachloride-induced acute liver injury in mice via activation of Nrf2/HO-1 signaling, and suppression of oxidative stress, inflammation and apoptosis

EPP protected against hepatic injury induced by CCl₄-derived reactive intermediates through the suppression of hepatic oxidative stress, inflammation, and apoptosis.

Pin1 Plays Essential Roles in NASH Development by Modulating Multiple Target Proteins

Pin1 is one of the three known prolyl-isomerase types and its hepatic expression level is markedly enhanced in the obese state. Pin1 plays critical roles in favoring the exacerbation of both lipid accumulation and fibrotic change accompanying inflammation. Indeed, Pin1-deficient mice are highly resistant to non-alcoholic steatohepatitis (NASH) development by either a high-fat diet or methionine-choline-deficient diet feeding. The processes of NASH development can basically be separated into lipid accumulation and subsequent fibrotic change with inflammation. In this review, we outline the molecular mechanisms by which increased Pin1 promotes both of these phases of NASH. The target proteins of Pin1 involved in lipid accumulation include insulin receptor substrate 1 (IRS-1), AMP-activated protein kinase (AMPK) and acetyl CoA carboxylase 1 (ACC1), while the p60 of the NF-kB complex and transforming growth factor β (TGF-β) pathway appear to be involved in the fibrotic process accelerated by Pin1. Interestingly, Pin1 deficiency does not cause abnormalities in liver size, appearance or function. Therefore, we consider the inhibition of increased Pin1 to be a promising approach to treating NASH and preventing hepatic fibrosis.

PIN1, a perspective on genetic biomarker for nonalcoholic fatty liver disease (NAFLD)

OBJECTIVE

A novel genetic and molecular basis of nonalcoholic fatty liver disease (NAFLD) was explored.

STUDY DESIGN

A 38-year-old male, who has no bad living and dietary habits, was diagnosed as NAFLD. The potential pathogenic role of Pin1 was evaluated by enzyme-linked immunosorbent (ELISA) assay and single nucleotide polymorphism (SNP) sequencing.

RESULTS

ELISA determined a six-time higher concentration of plasma Pin1 compared to our previous data. Nine PIN1 SNPs were sequenced and classified according to their NAFLD-pathogenic risks, suggesting that rs2233678 and rs2287839 may be the most important genotypes that result in Pin1 overexpression and NAFLD development.

CONCLUSION

In summary, this work explores a novel basis for early-onset NAFLD and highlights that elevated plasma Pin1 may predict NAFLD risk at early stage. Hypothetically, inhibiting Pin1 may benefit NAFLD prevention in the future.

Roles of Pin1 as a Key Molecule for EMT Induction by Activation of STAT3 and NF-κB in Human Gallbladder Cancer

BACKGROUND

Despite developments in multidisciplinary treatment, the prognosis for advanced gallbladder cancer (GBC) still is poor because of its rapid progression. Epithelial-mesenchymal transition (EMT) plays a central role in promoting tumor invasion and metastasis in malignancies thorough signal transducer and activator of transcription-3 (STAT3) and nuclear factor κB (NF-κB) activation. Whereas Pin1 mediates STAT3 and NF-κB activation, the involvement of Pin1 in GBC progression is unclear.

METHODS

Factors regulating Pin1-related STAT3 and NF-κB activation were evaluated using surgical specimens collected from 76 GBC patients, GBC cells, and orthotopic GBC xenograft mice.

RESULTS

In the patients with GBC, high Pin1 expression in GBC was associated with aggressive tumor invasion and increased tumor metastasis, and was an independent factor for a poor prognosis. Pin1 expression was correlated with phosphorylation of STAT3(Ser727) and NF-κB-p65(Ser276), thereby activating STAT3 and NF-κB in GBC. Pin1-mediated STAT3 and NF-κB activation induced EMT in GBC. When Pin1 knockdown was performed in GBC cells, the phosphorylation of STAT3(Ser727) and NF-κB-p65(Ser276) was inhibited, and STAT3 and NF-κB activation was suppressed. Inactivation of STAT3 and NF-κB in Pin1-depleted cells decreased snail and zeb-2 expression, thereby reducing the rate of mesenchymal-like cells, suggesting that EMT was inhibited in GBC cells. PiB, a Pin1-specific inhibitor, inhibited EMT and reduced tumor cell invasion by inactivating STAT3 and NF-κB in vitro. Moreover, PiB treatment inhibited lymph node metastasis and intrahepatic metastasis in orthotopic GBC xenograft tumor in vivo.

CONCLUSIONS

Pin1 accelerates GBC invasion and metastasis by activating STAT3 and NF-κB. Therefore, Pin1 inhibition by PiB is an excellent therapy for GBC by safely inhibiting its metastasis.

Dual Effect of Hepatic Macrophages on Liver Ischemia and Reperfusion Injury during Liver Transplantation

Ischemia-reperfusion injury (IRI) is a major complication in liver transplantation (LT) and it is closely related to the recovery of grafts' function. Researches has verified that both innate and adaptive immune system are involved in the development of IRI and Kupffer cell (KC), the resident macrophages in the liver, play a pivotal role both in triggering and sustaining the sterile inflammation. Damage-associated molecular patterns (DAMPs), released by the initial dead cell because of the ischemia insult, firstly activate the KC through pattern recognition receptors (PRRs) such as toll-like receptors. Activated KCs is the dominant players in the IRI as it can secret various pro-inflammatory cytokines to exacerbate the injury and recruit other types of immune cells from the circulation. On the other hand, KCs can also serve in a contrary way to ameliorate IRI by upregulating the anti-inflammatory factors. Moreover, new standpoint has been put forward that KCs and macrophages from the circulation may function in different way to influence the inflammation. Managements towards KCs are expected to be the effective way to improve the IRI.

Downregulation of Pin1 in human atherosclerosis and its association with vascular smooth muscle cell senescence

OBJECTIVE

Pin1 is prevalently overexpressed in human cancers and implicated to regulate cell growth and apoptosis. Thus far, however, no role for Pin1 has been described in modulating vascular smooth muscle cell (VSMC) senescence.

METHODS

Immunohistochemistry and Western blotting were used to assess Pin1 protein level in human normal and atherosclerotic tissues. β-galactosidase staining, cumulative population doubling level, telomerase activity, and relative telomere length measurement were used to confirm VSMC senescence. The expressions of Pin1 and other genes involved in this research were analyzed by quantitative reverse-transcription polymerase chain reaction and Western blotting in VSMCs. Apolipoprotein E gene-deleted mice (ApoE^-/-) fed a high-fat diet were treated with juglone or 10% ethanol, respectively, for 3 weeks. The extent of atherosclerosis was evaluated by Oil Red O, Masson trichrome staining, and immunohistology.

RESULTS

Pin1 protein level decreased in human atherosclerotic tissues and VSMCs, synchronously with increased VSMC senescence. Adenoviral-mediated Pin1 overexpression rescued cellular senescence in atherosclerotic VSMCs, with concurrent down-regulation of P53, p21, growth arrest and DNA-damage-inducible protein 45-alpha (Gadd45a), phosphorylated retinoblastoma (p-pRb), p65 and upregulation of cyclin subfamilies (cyclin B, D, and E), and cyclin-dependent kinase subfamilies (2, 4, and 6), whereas Pin1 knockdown resulted in the converse effects, indicating that VSMC senescence mediated by Pin1 is an integrated response to diverse signals. In vivo data from ApoE^-/- mice showed that treatment of juglone led to accelerated atherosclerosis development.

CONCLUSIONS

Altogether this work supports a role for Pin1 as a vital modulator of VSMC senescence, thereby providing a novel target for regulation and control of atherosclerosis.

Type I Interferon Supports Inducible Nitric Oxide Synthase in Murine Hepatoma Cells and Hepatocytes and during Experimental Acetaminophen-Induced Liver Damage

Cytokine regulation of high-output nitric oxide (NO) derived from inducible NO synthase (iNOS) is critically involved in inflammation biology and host defense. Herein, we set out to characterize the role of type I interferon (IFN) as potential regulator of hepatic iNOS in vitro and in vivo. In this regard, we identified in murine Hepa1-6 hepatoma cells a potent synergism between pro-inflammatory interleukin-β/tumor necrosis factor-α and immunoregulatory IFNβ as detected by analysis of iNOS expression and nitrite release. Upregulation of iNOS by IFNβ coincided with enhanced binding of signal transducer and activator of transcription-1 to a regulatory region at the murine iNOS promoter known to support target gene expression in response to this signaling pathway. Synergistic iNOS induction under the influence of IFNβ was confirmed in alternate murine Hepa56.1D hepatoma cells and primary hepatocytes. To assess iNOS regulation by type I IFN in vivo, murine acetaminophen (APAP)-induced sterile liver inflammation was investigated. In this model of acute liver injury, excessive necroinflammation drives iNOS expression in diverse liver cell types, among others hepatocytes. Herein, we demonstrate impaired iNOS expression in type I IFN receptor-deficient mice which associated with diminished APAP-induced liver damage. Data presented indicate a vital role of type I IFN within the inflamed liver for fine-tuning pathological processes such as overt iNOS expression.

Macrophage inflammatory protein-2 as mediator of inflammation in acute liver injury

Macrophage inflammatory protein (MIP)-2 is one of the CXC chemokines and is also known as chemokine CXC ligand (CXCL2). MIP-2 affects neutrophil recruitment and activation through the p38 mitogen-activated-protein-kinase-dependent signaling pathway, by binding to its specific receptors, CXCR1 and CXCR2. MIP-2 is produced by a variety of cell types, such as macrophages, monocytes, epithelial cells, and hepatocytes, in response to infection or injury. In liver injury, activated Kupffer cells are known as the major source of MIP-2. MIP-2-recruited and activated neutrophils can accelerate liver inflammation by releasing various inflammatory mediators. Here, we give a brief introduction to the basic molecular and cellular sources of MIP-2, and focus on its physiological and pathological functions in acute liver injury induced by concanavalin A, lipopolysaccharides, irradiation, ischemia/reperfusion, alcohol, and hypoxia, and hepatectomy-induced liver regeneration and tumor colorectal metastasis. Further understanding of the regulatory mechanisms of MIP-2 secretion and activation may be helpful to develop MIP-2-targeted therapeutic strategies to prevent liver inflammation.

Inhibition of p66Shc-mediated mitochondrial apoptosis via targeting prolyl-isomerase Pin1 attenuates intestinal ischemia/reperfusion injury in rats

Intestinal epithelial oxidative stress and apoptosis constitute key pathogenic mechanisms underlying intestinal ischemia/reperfusion (I/R) injury. We previously reported that the adaptor 66 kDa isoform of the adaptor molecule ShcA (p66Shc)-mediated pro-apoptotic pathway was activated after intestinal I/R. However, the upstream regulators of the p66Shc pathway involved in intestinal I/R remain to be fully identified. Here, we focused on the role of a prolyl-isomerase, peptidyl–prolyl cis–trans isomerase (Pin1), in the regulation of p66Shc activity during intestinal I/R. Intestinal I/R was induced in rats by superior mesenteric artery (SMA) occlusion. Juglone (Pin1 inhibitor) or vehicle was injected intraperitoneally before I/R challenge. Caco-2 cells were exposed to hypoxia/reoxygenation (H/R) in vitro to simulate an in vivo I/R model. We found that p66Shc was significantly up-regulated in the I/R intestine and that this up-regulation resulted in the accumulation of intestinal mitochondrial reactive oxygen species (ROS) and massive epithelial apoptosis. Moreover, intestinal I/R resulted in elevated protein expression and enzyme activity of Pin1 as well as increased interaction between Pin1 and p66Shc. This Pin1 activation was responsible for the translocation of p66Shc to the mitochondria during intestinal I/R, as Pin1 suppression by juglone or siRNA markedly blunted p66Shc mitochondrial translocation and the subsequent ROS generation and cellular apoptosis. Additionally, Pin1 inhibition alleviated gut damage and secondary lung injury, leading to improvement of survival after I/R. Collectively, our findings demonstrate for the first time that Pin1 inhibition protects against intestinal I/R injury, which could be partially attributed to the p66Shc-mediated mitochondrial apoptosis pathway. This may represent a novel prophylactic target for intestinal I/R injury.

Altered miR-370 expression in hepatic ischemia-reperfusion injury correlates with the level of nuclear kappa B (NF-κB) related factors

BACKGROUND & AIMS

MicroRNAs (miRNAs) are a class of small endogenous, non-coding RNAs that regulate gene expression at both the transcription and translation levels. Whether miRNAs have taken part in liver ischemia-reperfusion (IR) injury was rarely reported. The purpose of this article is to investigate the potential role of miR-370 in hepatic IR injury.

METHODS

Male C57BL/6 mice were divided into 5 groups (sham-operated group, I/R group, IPC group, antagomir-370 group and antagomir-NC), and the expression levels of miR-370 were assessed by quantitative real-time PCR. Serum enzyme analysis and histological examination of liver were used as the index of the effect of miR-370 on hepatic IR injury and following treatment of mice with antagomir-370 or antagomir-NC. The classical pathway factors of NF-κB (TAK₁, TAB₁, TAB₂, IkBα, IKKα, IKKβ, p50, p65) were studied by quantitative real-time PCR and Western blot.

RESULTS

The results showed that the IR group's miR-370 expression level was significantly upregulated as compared with the sham-operated group and IPC group. Also inhibition of miR-370 led to the low expression levels of miR-370 and low levels of serum aminotransferase and hepatic histological damage as compared with the IR group. Quantitative real-time PCR showed the levels of TAK1, TAB₁, TAB2, IkBα, IKKα, p65 was elevated when improving the miR-370 levels, at the same time, Western blot showed the levels of TAK₁, TAB₁, TAB₂, IkBα, IKKα, IKKβ, p50, p65 were all elevated.

CONCLUSION

miR-370 acting via NF-κB might play a crucial role in hepatic IR injury, and inhibition of miR-370 could alleviate the injury to the liver. And miR-370 might positively regulated the NF-κB pathway.

PIN1 Suppresses the Hepatic Differentiation of Pulp Stem Cells via Wnt3a

This study aimed to investigate the role of PIN1 on the hepatic differentiation of human dental pulp stem cells (hDPSCs) and its signaling pathway, as well as the potential therapeutic effects of hDPSC transplantation and PIN1 inhibition on CCl₄ (carbon tetrachloride)-induced liver fibrosis in mice. The in vitro results showed that hepatic differentiation was suppressed by infection with adenovirus-PIN1 and promoted by PIN1 inhibitor juglone via the downregulation of Wnt3a and β-catenin. Compared with treatment with either hDPSC transplantation or juglone alone, the combination of hDPSCs and juglone into CCl₄-injured mice significantly suppressed liver fibrosis and restored serum levels of alanine transaminase, aspartate transaminase, and ammonia. Collectively, the present study shows for the first time that PIN1 inhibition promotes hepatic differentiation of hDPSCs through the Wnt/β-catenin pathway. Furthermore, juglone in combination with hDPSC transplantation effectively treats liver fibrosis, suggesting that hDPSC transplantation with PIN1 inhibition may be a novel therapeutic candidate for the treatment of liver injury.

Pin1 facilitates NF-κB activation and promotes tumour progression in human hepatocellular carcinoma

BACKGROUND

NF-κB promotes HCC progression; however, therapies targeting NF-κB are not used due to severe adverse reactions. Pin1 is reported to induce tumour progression in vitro. However, the role of Pin1 in HCC is unclear. Moreover, little is known about the mechanism of Pin1-mediated NF-κB activation.

METHODS

Fresh surgical specimens were collected from 144 HCC patients. Pin1 and NF-κB-p65 expression was evaluated by immunohistochemistry and western blotting. NF-κB activation was assessed by EMSA.

RESULTS

Pin1 was increased in HCC compared to adjacent liver tissue. The multivariate analysis revealed that high Pin1 expression was an independent factor for poor prognosis. In HCC with high Pin1 expression, tumour size was larger and portal vein invasion was increased. Pin1 expression was correlated with phosphorylated (p-) NF-κB-p65(Thr254) and p-NF-κB-p65(Ser276), and thereby NF-κB activation. Pin1-induced NF-κB activation accelerated cell cycle progression, induced angiogenesis, and inhibited apoptosis. Pin1 knockdown in HCC cells inhibited the phosphorylation of NF-κB-p65(Ser276), and reduced NF-κB activation, which resulted in inhibiting tumour cell progression. When HCC cells were treated with the Pin1 inhibitors, p-NF-κB-p65(Ser276) expression and NF-κB activation was reduced, and cell proliferation was inhibited.

CONCLUSIONS

Pin1 is associated with aggressive tumour progression and poor prognosis in HCC by mediating NF-κB activation.

[Oxidative stress and its effect on cells functional activity of alzheimer's disease]

The paper summarizes literature data on the importance of oxidative stress as one of the pathogenetic mechanisms in Alzheimer's disease. The paper describes the main specific and nonspecific ways of reactive oxygen species generation in the course of the disease development. The effect of reactive oxygen species generated by the functional activity of cells, i.e. apoptosis and mitotic cycle, is shown. The role of the regulatory system of nodal cells is performed by phosphorylation/dephosphorylation process which is associated with intense phosphorylation of tau protein and mitosis-specific proteins. In Alzheimer's disease, the regulating function of peptidyl-prolyl isomerases in particular of Pin1 associated with maintaining a balanced state of phosphorylation/dephosphorylation processes is disturbed. Taking into consideration the multifactorial impairment of the cell cycle control, this process should be considered from the standpoint of the general state of metabolic processes, and oxidative stress has one of the key positions in aging.

Interaction of p53 with prolyl isomerases: Healthy and unhealthy relationships

BACKGROUND

The p53 protein family, comprising p53, p63 and p73, is primarily involved in preserving genome integrity and preventing tumor onset, and also affects a range of physiological processes. Signal-dependent modifications of its members and of other pathway components provide cells with a sophisticated code to transduce a variety of stress signaling into appropriate responses. TP53 mutations are highly frequent in cancer and lead to the expression of mutant p53 proteins that are endowed with oncogenic activities and sensitive to stress signaling.

SCOPE OF REVIEW

p53 family proteins have unique structural and functional plasticity, and here we discuss the relevance of prolyl-isomerization to actively shape these features.

MAJOR CONCLUSIONS

The anti-proliferative functions of the p53 family are carefully activated upon severe stress and this involves the interaction with prolyl-isomerases. In particular, stress-induced stabilization of p53, activation of its transcriptional control over arrest- and cell death-related target genes and of its mitochondrial apoptotic function, as well as certain p63 and p73 functions, all require phosphorylation of specific S/T-P motifs and their subsequent isomerization by the prolyl-isomerase Pin1. While these functions of p53 counteract tumorigenesis, under some circumstances their activation by prolyl-isomerases may have negative repercussions (e.g. tissue damage induced by anticancer therapies and ischemia-reperfusion, neurodegeneration). Moreover, elevated Pin1 levels in tumor cells may transduce deregulated phosphorylation signaling into activation of mutant p53 oncogenic functions.

GENERAL SIGNIFICANCE

The complex repertoire of biological outcomes induced by p53 finds mechanistic explanations, at least in part, in the association between prolyl-isomerases and the p53 pathway. This article is part of a Special Issue entitled Proline-directed foldases: Cell signaling catalysts and drug targets.

PIN1 inhibition suppresses osteoclast differentiation and inflammatory responses

Inflammatory responses and osteoclast differentiation play pivotal roles in the pathogenesis of osteolytic bone diseases such as periodontitis. Although overexpression or inhibition of peptidyl-prolyl cis/trans isomerase NIMA-interacting 1 (PIN1) offers a possible therapeutic strategy for chronic inflammatory diseases, the role of PIN1 in periodontal disease is unclear. The aim of the present study was to evaluate PIN1 expression in periodontitis patients as well as the effects of PIN1 inhibition by juglone or PIN1 small-interfering RNA (siRNA) and of PIN1 overexpression using a recombinant adenovirus encoding PIN1 (Ad-PIN1) on the inflammatory response and osteoclastic differentiation in lipopolysaccharide (LPS)- and nicotine-stimulated human periodontal ligament cells (PDLCs). PIN1 was up-regulated in chronically inflamed PDLCs from periodontitis patients and in LPS- and nicotine-exposed PDLCs. Inhibition of PIN1 by juglone or knockdown of PIN1 gene expression by siRNA markedly attenuated LPS- and nicotine-stimulated prostaglandin E2 (PGE2) and nitric oxide (NO) production, as well as cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, whereas PIN1 overexpression by Ad-PIN1 increased it. LPS- and nicotine-induced nuclear factor (NF)-κB activation was blocked by juglone and PIN1 siRNA but increased by Ad-PIN1. Conditioned medium prepared from LPS- and nicotine-treated PDLCs increased the number of tartrate-resistant acid phosphatase-stained osteoclasts and osteoclast-specific gene expression. These responses were blocked by PIN1 inhibition and silencing but stimulated by Ad-PIN1. Furthermore, juglone and PIN1 siRNA inhibited LPS- and nicotine-induced osteoclastogenic cytokine expression in PDLCs. This study is the first to demonstrate that PIN1 inhibition exhibits anti-inflammatory effects and blocks osteoclastic differentiation in LPS- and nicotine-treated PDLCs. PIN1 inhibition may be a therapeutic strategy for inflammatory osteolysis in periodontal disease.

Prolyl isomerases in gene transcription

BACKGROUND

Peptidyl-prolyl isomerases (PPIases) are enzymes that assist in the folding of newly-synthesized proteins and regulate the stability, localization, and activity of mature proteins. They do so by catalyzing reversible (cis-trans) rotation about the peptide bond that precedes proline, inducing conformational changes in target proteins.

SCOPE OF REVIEW

This review will discuss how PPIases regulate gene transcription by controlling the activity of (1) DNA-binding transcription regulatory proteins, (2) RNA polymerase II, and (3) chromatin and histone modifying enzymes.

MAJOR CONCLUSIONS

Members of each family of PPIase (cyclophilins, FKBPs, and parvulins) regulate gene transcription at multiple levels. In all but a few cases, the exact mechanisms remain elusive. Structure studies, development of specific inhibitors, and new methodologies for studying cis/trans isomerization in vivo represent some of the challenges in this new frontier that merges two important fields.

GENERAL SIGNIFICANCE

Prolyl isomerases have been found to play key regulatory roles in all phases of the transcription process. Moreover, PPIases control upstream signaling pathways that regulate gene-specific transcription during development, hormone response and environmental stress. Although transcription is often rate-limiting in the production of enzymes and structural proteins, post-transcriptional modifications are also critical, and PPIases play key roles here as well (see other reviews in this issue). This article is part of a Special Issue entitled Proline-directed Foldases: Cell Signaling Catalysts and Drug Targets.

TRAF1 is a key mediator for hepatic ischemia/reperfusion injury

Tumor necrosis factor receptor-associated factor 1 (TRAF1), an adapter in signal transduction, is involved in immunity and in apoptotic processes in various cell types. However, little is known about its function and the molecular mechanism of its activation during liver injury. This study tested the hypothesis that TRAF1 is a mediator of cell injury after hepatic ischemia/reperfusion injury (I/R). In a mouse hepatic I/R injury model, we found that TRAF1 expression was highly induced. TRAF1 deficiency was liver protective, whereas sustained TRAF1 overexpression aggravated liver injury in response to hepatic I/R injury. Mechanistic studies demonstrated that a deficiency of TRAF1 in cultured hepatocytes led to the inhibition of NF-κB-mediated inflammatory responses, suppression of the ASK/JNK pro-death pathway and promotion of cellular regeneration capacity. In contrast, the converse occurred in hepatocyte-specific TRAF1 transgenic mice. TRAF1 activated the ASK1/JNK pathway and promoted hepatic injury. Our study demonstrates that TRAF1 is a crucial early mediator of hepatic I/R injury and suggests that TRAF1 may be a potential gene therapy target for the treatment of liver injury.

SPA0355 attenuates ischemia/reperfusion-induced liver injury in mice

Hepatic ischemia/reperfusion (I/R) injury leads to oxidative stress and acute inflammatory responses that cause liver damage and have a considerable impact on the postoperative outcome. Much research has been performed to develop possible protective techniques. We aimed to investigate the efficacy of SPA0355, a synthetic thiourea analog, in an animal model of hepatic I/R injury. Male C57BL/6 mice underwent normothermic partial liver ischemia for 45 min followed by varying periods of reperfusion. The animals were divided into three groups: sham operated, I/R and SPA0355 pretreated. Pretreatment with SPA0355 protected against hepatic I/R injury, as indicated by the decreased levels of serum aminotransferase and reduced parenchymal necrosis and apoptosis. Liver synthetic function was also restored by SPA0355 as reflected by the prolonged prothrombin time. To gain insight into the mechanism involved in this protection, we measured the activity of nuclear factor-κB (NF-κB), which revealed that SPA0355 suppressed the nuclear translocation and DNA binding of NF-κB subunits. Concomitantly, the expression of NF-κB target genes such as IL-1β, IL-6, TNF-α and iNOS was significantly downregulated. Lastly, the liver antioxidant enzymes superoxide dismutase, catalase and glutathione were upregulated by SPA0355 treatment, which correlated with the reduction in serum malondialdehyde. Our results suggest that SPA0355 pretreatment prior to I/R injury could be an effective method to reduce liver damage.

PTPRO plays a dual role in hepatic ischemia reperfusion injury through feedback activation of NF-κB

BACKGROUND & AIMS

Nuclear factor-κB (NF-κB) activation in hepatocytes and macrophages appeared as a double-edged-sword in hepatic ischemia reperfusion (IR) injury. Protein tyrosine phosphatase receptor type O (PTPRO) was recently identified as a potential activator of c-Src, which can in turn activate the NF-κB pathway. In this study, we aimed to determine the change and function of PTPRO in hepatocytes and macrophages during IR.

METHODS

Clinical patients with benign liver condition undergoing liver surgery were recruited in our study. Wild type (WT) and ptpro(-/-) C57BL/6 mice were processed to construct hepatic IR models. Isolated mouse hepatocytes and macrophages were treated with peroxide or TNFα in vitro.

RESULTS

In human and mouse IR models, PTPRO level was decreased in the early phase but reversed in the late phase. In vitro studies demonstrated that NF-κB up-regulated PTPRO transcription. Using ptpro(-/-) mice and primary cells, we found that PTPRO deficiency resulted in reduction of NF-κB activation in both hepatocytes and macrophages and was correlated to c-Src phosphorylation; PTPRO in hepatocytes alleviated, but PTPROt in macrophages exacerbated IR injury.

CONCLUSIONS

PTPRO activates NF-κB in a positive feedback manner, and plays a dual role in hepatic IR injury.

Sterile inflammation in hepatic ischemia/reperfusion injury: present concepts and potential therapeutics

Ischemia and reperfusion (I/R) injury is an often unavoidable consequence of major liver surgery and is characterized by a sterile inflammatory response that jeopardizes the viability of the organ. The inflammatory response results from acute oxidative and nitrosative stress and consequent hepatocellular death during the early reperfusion phase, which causes the release of endogenous self-antigens known as damage-associated molecular patterns (DAMPs). DAMPs, in turn, are indirectly responsible for a second wave of reactive oxygen and nitrogen species (ROS and RNS) production by driving the chemoattraction of various leukocyte subsets that exacerbate oxidative liver damage during the later stages of reperfusion. In this review, the molecular mechanisms underlying hepatic I/R injury are outlined, with emphasis on the interplay between ROS/RNS, DAMPs, and the cell types that either produce ROS/RNS and DAMPs or respond to them. This theoretical background is subsequently used to explain why current interventions for hepatic I/R injury have not been very successful. Moreover, novel therapeutic modalities are addressed, including MitoSNO and nilotinib, and metalloporphyrins on the basis of the updated paradigm of hepatic I/R injury.

Antioxidant Stress and Anti-Inflammation of PPARα on Warm Hepatic Ischemia-Reperfusion Injury

Hepatic ischemia-reperfusion (IR) injury is a serious clinical problem. Minimizing the adverse effect of ischemia-reperfusion injury after liver surgery or trauma is an urgent need. It has been proved that besides the effect of regulating the lipid and lipoprotein metabolism, PPARα also undertakes the task of organ protection. In this paper, related literature has been summarized and we come to the conclusion that administration of PPARα agonists can strengthen the antioxidant and anti-inflammation defense system by the upregulation of the expression of antioxidant enzymes and inhibition of NF-κB activity. This may provide a potential clinical treatment for hepatic ischemia-reperfusion injury.

Lithium exacerbates hepatic ischemia/reperfusion injury by inhibiting GSK-3β/NF-κB-mediated protective signaling in mice

Lithium (an inhibitor of GSK-3β activity) has beneficial effects on ischemia/reperfusion (I/R) injury in the central nervous system, heart and kidney. However, the role of lithium in hepatic I/R injury is unknown. The aim of this study was to assess the effects of lithium on hepatic I/R injury in a mouse model of partial hepatic I/R. Previous studies showed that lithium chloride (LiCl) can phosphorylate residue Ser9, inhibit GSK-3β activity, and improve I/R injury in other organs. In the present study, mice were pretreated with either vehicle or LiCl, which had similar effects on GSK-3β activity. Surprisingly, treatment with LiCl significantly exacerbated hepatic I/R injury, which was determined by serological and histological analyses. Acute and chronic LiCl treatment caused serious damage in hepatic I/R injury, including increased apoptosis and oxidative stress. To gain insight into the mechanism involved in this damage, the activity of nuclear factor-κB (NF-κB) (GSK-3β can regulate the transcriptional complex of NF-κB) was analyzed, which revealed that LiCl treatment significantly down-regulated the activity of NF-κB. The NF-κB-mediated protective genes were then further evaluated, including anti-apoptotic genes (RAF2, cIAP 2, Bfl-1 and cFLIP) and the antioxidant gene MnSOD. The expression of these protective genes was obviously suppressed compared with the vehicle group. Taken together, these findings show that lithium exacerbates hepatic I/R injury by suppressing the expression of GSK-3β/NF-κB-mediated protective genes.

Interleukin-33 is hepatoprotective during liver ischemia/reperfusion in mice

Interleukin (IL)-33 is a recently identified member of the IL-1 family that binds to the receptor, ST2L. In the current study, we sought to determine whether IL-33 is an important regulator in the hepatic response to ischemia/reperfusion (I/R). Male C57BL/6 mice were subjected to 90 minutes of partial hepatic ischemia, followed by up to 8 hours of reperfusion. Some mice received recombinant IL-33 (IL-33) intraperitoneally (IP) before surgery or anti-ST2 antibody IP at the time of reperfusion. Primary hepatocytes and Kupffer cells were isolated and treated with IL-33 to assess the effects of IL-33 on inflammatory cytokine production. Primary hepatocytes were treated with IL-33 to assess the effects of IL-33 on mediators of cell survival in hepatocytes. IL-33 protein expression increased within 4 hours after reperfusion and remained elevated for up to 8 hours. ST2L protein expression was detected in healthy liver and was up-regulated within 1 hour and peaked at 4 hours after I/R. ST2L was primarily expressed by hepatocytes, with little to no expression by Kupffer cells. IL-33 significantly reduced hepatocellular injury and liver neutrophil accumulation at 1 and 8 hours after reperfusion. In addition, IL-33 treatment increased liver activation of nuclear factor kappa light-chain enhancer of activated B cells (NF-κB), p38 mitogen-activated protein kinase (MAPK), cyclin D1, and B-cell lymphoma 2 (Bcl-2), but reduced serum levels of CXC chemokines. In vitro experiments demonstrated that IL-33 significantly reduced hepatocyte cell death as a result of increased NF-κB activation and Bcl-2 expression in hepatocytes.

CONCLUSION

The data suggest that IL-33 is an important endogenous regulator of hepatic I/R injury. It appears that IL-33 has direct protective effects on hepatocytes, associated with the activation of NF-κB, p38 MAPK, cyclin D1, and Bcl-2 that limits liver injury and reduces the stimulus for inflammation.

All-trans retinoic acid preconditioning protects against liver ischemia/reperfusion injury by inhibiting the nuclear factor kappa B signaling pathway

BACKGROUND

Inflammatory response plays a pathogenic role in liver ischemia/reperfusion (I/R) injury. All-trans retinoic acid (ATRA) is an active metabolite of vitamin A with anti-inflammatory effects. However, there are few reports on the anti-inflammatory effects of ATRA on liver I/R injury. The purpose of this study was to investigate the effects of ATRA on liver I/R injury and related mechanisms.

METHODS

A total of 54 male Sprague-Dawley rats were randomly divided into three groups (18 rats each), namely, sham, I/R, and I/R+ATRA groups. ATRA was intraperitoneally administered at a dose of 15mg/kg/d 14d before ischemia surgery. The segmental (70%) hepatic ischemia model was used by clamping the portal vein, hepatic artery, and bile duct of the left and median for 1h. The rats were sacrificed 3, 6, and 24h after reperfusion, and blood and liver tissue samples were obtained. Liver injury was evaluated by biochemical and histopathologic examinations. Myeloperoxidase activity was spectrophotometrically measured. The expression of pro-inflammatory cytokines, such as tumor necrosis factor-α and interleukin-6 was measured by enzyme-linked immunosorbent assay and real-time polymerase chain reaction. Liver nuclear factor kappa B (NF-κB) was detected by immunohistochemistry. The expression of NF-κB p65 and inhibitor NF-κB-α (IκBα) was determined by Western blot analysis.

RESULTS

The serum alanine aminotransferase level, Suzuki scores of hepatic histology, and hepatic myeloperoxidase activity, as indices of hepatic injury, were increased after reperfusion. The increase was attenuated by preadministration with ATRA. Compared with the I/R group, ATRA treatment increased IκBα expression and suppressed NF-κB p65 expression. Subsequently, the levels of tumor necrosis factor-α and interleukin-6 after liver I/R were effectively downregulated.

CONCLUSIONS

ATRA administration can significantly attenuate I/R injury in rat liver. The protective mechanism is related to its anti-inflammatory function of inhibiting NF-κB activation.

Receptor activator of nuclear factor-κB ligand (RANKL) protects against hepatic ischemia/reperfusion injury in mice

The transcription factor nuclear factor kappaB (NF-κB) plays diverse roles in the acute injury response to hepatic ischemia/reperfusion (I/R). Activation of NF-κB in Kupffer cells promotes inflammation through cytokine expression, whereas activation in hepatocytes may be cell protective. The interaction of receptor activator of NF-κB (RANK) and its ligand (RANKL) promotes NF-κB activation; however, this ligand-receptor system has not been studied in acute liver injury. In the current study, we sought to determine if RANK and RANKL were important in the hepatic response to I/R. Mice were subjected to partial hepatic ischemia followed by reperfusion. In some experiments, mice received recombinant RANKL or neutralizing antibodies to RANKL 1 hour prior to surgery or at reperfusion to assess the role of RANK/RANKL signaling during I/R injury. RANK was constitutively expressed in the liver and was not altered by I/R. RANK was strongly expressed in hepatocytes and very weakly expressed in Kupffer cells. Serum RANKL concentrations increased after I/R and peaked 4 hours after reperfusion. Serum levels of osteoprotegerin (OPG), a decoy receptor for RANKL, steadily increased over the 8-hour period of reperfusion. Treatment with RANKL, before ischemia or at reperfusion, increased hepatocyte NF-κB activation and significantly reduced liver injury. These beneficial effects occurred without any effect on cytokine expression or liver inflammation. Treatment with anti-RANKL antibodies had no effect on liver I/R injury.

CONCLUSION

During the course of injury, endogenous OPG appears to suppress the effects of RANKL. However, exogenous administration of RANKL, given either prophylactically or postinjury, reduces liver injury in a manner associated with increased hepatocyte NF-κB activation. The data suggest that RANK/RANKL may be a viable therapeutic target in acute liver injury.

Aggravation of post-ischemic liver injury by overexpression of A20, an NF-κB suppressor

BACKGROUND & AIMS

A20 is an intracellular ubiquitin-editing enzyme that plays an important role in the negative feedback regulation of NF-κB activation in response to a diverse range of stimuli. Liver ischemia/reperfusion injury is associated with rapid activation of NF-κB signaling, but the role of NF-κB in hepatic ischemia/reperfusion injury remains controversial. The NF-κB signaling pathway mediates both protective and deleterious effects in the liver. Here, we examined whether A20 inhibited or aggravated hepatic ischemia/reperfusion injury.

METHODS

We used IκBα super-repressor as a positive control and overexpressed A20 and IκBα super-repressor in the liver of C57BL/6 mice. Mice underwent 45min of partial hepatic ischemia and were then reperfused.

RESULTS

Protein level of A20 was increased after reperfusion. Mice subjected to ischemia/reperfusion injury showed increased NF-κB activation, as evidenced by phosphorylation of IκBα and nuclear translocation of NF-κB. Prior transfection with Ad-A20 or Ad-IκBα super-repressor attenuated NF-κB activation and aggravated liver injury. Serum aminotransferases and proinflammatory cytokines, hepatocellular necrosis, and hepatic neutrophil infiltration were markedly increased compared to those of uninfected or control virus infected mice. In addition, A20 abolished the beneficial effect of ischemic preconditioning.

CONCLUSIONS

Our results suggest that inhibition of NF-κB activation by A20 aggravated partial hepatic ischemia/reperfusion injury. Understanding how the NF-κB pathway plays a role in directing a clinical outcome may lead to better prospects of more rational approaches to reduce post-ischemic liver injury.

Detrimental effect of the proteasome inhibitor, bortezomib in bacterial superantigen- and lipopolysaccharide-induced systemic inflammation

Bacterial superantigen (BSAg)-induced toxic shock syndrome (TSS) and bacterial lipopolysaccharide (LPS)-induced shock are characterized by severe systemic inflammation. As nuclear factor kappaB (NF kappaB) plays an important role in inflammation and bortezomib, a proteasome inhibitor widely used in cancer chemotherapy, is a potent inhibitor of NF kappaB activation, we evaluated the therapeutic and prophylactic use of bortezomib in these conditions using murine models. Bortezomib prophylaxis significantly reduced serum levels of many cytokines and chemokines induced by BSAg. However, at 3 hours, serum level of TNF-a, an important cytokine implicated in TSS, was significantly reduced but not abolished. At 6 hours, there was no difference in the serum TNF-a levels between bortezomib treated and untreated mice challenged with staphylococcal enterotoxin B (SEB). Paradoxically, all mice treated with bortezomib either before or after BSAg challenge succumbed to TSS. Neither bortezomib nor BSAg was lethal if given alone. Serum biochemical parameters and histopathological findings suggested acute liver failure as the possible cause of mortality. Liver tissue from SEB-challenged mice treated with bortezomib showed a significant reduction in NF kappaB activation. Because NF kappaB-dependent antiapoptotic pathways protect hepatocytes from TNF-alpha-induced cell death, inhibition of NF kappaB brought forth by bortezomib in the face of elevated TNF-alpha levels caused by BSAg or LPS is detrimental.

Pim-2 activates API-5 to inhibit the apoptosis of hepatocellular carcinoma cells through NF-kappaB pathway

Pim-2 is proved to be relevant to the tumorigenesis of hepatocellular carcinoma (HCC), but the mechanism is unclear. We studied the relationship among Pim-2, NF-kappaB and API-5. In our experiment, expression level of the three factors and phosphorylation level of API-5, as well as NF-kappaB activity, were detected in HCC tissues and the nontumorous controls. Then Pim-2 gene was transfected into nontumorous liver cells L02, and Pim-2 SiRNA was transfected into hepatoblastoma cell line HepG2. Parthenolide was added as NF-kappaB inhibitor. The same detections as above were repeated in the cells, along with the apoptosis analysis. We found the levels of Pim-2, NF-kappaB and API-5, as well as NF-kappaB activity, were significantly higher in HCC tissues. Pim-2 level was increased in L02 cells after the transfection of Pim-2 gene, but decreased in HepG2 cells after the transfection of Pim-2 SiRNA. The levels of NF-kappaB and API-5, as well as NF-kappaB activity and API-5 phosphorylation level, were in accordance with Pim-2 level, but could be reversed by Parthenolide. Cell apoptosis rates were negatively correlated with API-5 phosphorylation level. Therefore, we infer that Pim-2 could activate API-5 to inhibit the apoptosis of liver cells, and NF-kappaB is the key regulator.

Role of nuclear factor kappaB in liver health and disease

NF-kappaB (nuclear factor kappaB) is a heterodimeric transcription factor that is constitutively expressed in all cell types and has a central role as a transcriptional regulator in response to cellular stress. In the present review, we discuss the role of NF-kappaB signalling in the maintenance of liver homoeostasis as well as in the pathogenesis of a wide variety of conditions affecting the liver, including viral hepatitis, steatohepatitis, cirrhosis and hepatocellular carcinoma. Much of the current knowledge of NF-kappaB signalling in the liver relates to the canonical pathway, the IKK [IkappaB (inhibitor of kappaB) kinase] complex and the RelA subunit. We explore the weaknesses of the experimental approaches to date and suggest that further work is needed to investigate in detail the discreet functions of each of the Rel subunits in liver physiology and disease.

Thr435 phosphorylation regulates RelA (p65) NF-kappaB subunit transactivation

Phosphorylation of the RelA (p65) NF-κB (nuclear factor κB) subunit has been previously shown to modulate its ability to induce or repress transcription. In the present study we have investigated the consequences of Thr⁴³⁵ phosphorylation within the C-terminal transactivation domain of RelA. We confirm that Thr⁴³⁵ is phosphorylated in cells and is induced by TNFα (tumour necrosis factor α) treatment. Mutational analysis of this site revealed gene-specific effects on transcription, with a T435D phosphomimetic mutant significantly enhancing Cxcl2 (CXC chemokine ligand 2) mRNA levels in reconstituted Rela^−/− mouse embryonic fibroblasts. Chromatin immunoprecipitation analysis revealed that this mutation results in enhanced levels of histone acetylation associated with decreased recruitment of HDAC1 (histone deacetylase 1). Moreover, mutation of this site disrupted RelA interaction with HDAC1 in vitro. Thr⁴³⁵ phosphorylation of promoter-bound RelA was also detected at NF-κB target genes following TNFα treatment in wild-type mouse embryonic fibroblasts. Phosphorylation at this site therefore provides an additional mechanism through which the specificity of NF-κB transcriptional activity can be modulated in cells.