Warm ischemia-induced alterations in oxidative and inflammatory proteins in hepatic Kupffer cells in rats

Global proteome profiling of human livers upon ischemia/reperfusion treatment

Hepatic ischemia/reperfusion (I/R) injury represents a major risk factor for liver transplantation and is related to graft dysfunction and acute/chronic rejection. However, a significant part of these processes remain poorly characterized. To reveal differences in the proteome during liver I/R injury, we collected human liver biopsy samples during hepatectomy before and after the Pringle maneuver and conducted a TMT-based proteomic analysis through quantitative high-throughput mass spectrometry. We used a fold-change threshold of 1.3 and a t-test p-value < 0.05 as the criteria to identify 5,257 total quantifiable proteins. The levels of 142 proteins were increased, while the levels of 103 proteins were decreased in response to hepatic I/R treatment. Bioinformatic analysis further revealed that these differentially expressed proteins are mainly involved in multiple biological functions and enzyme-regulated metabolic pathways. Most proteins whose expression was changed are related to the defense, immune and inflammatory responses as well as lipid and steroid metabolic processes. Based on this finding, we developed a panel for targeted proteomic analysis and used the parallel reaction monitoring (PRM) method, qPCR and western blotting experiments to validate alterations in the expression of some of the identified proteins. The upregulated proteins were found to be involved in immunity and inflammatory responses, and downregulated proteins were enriched in metabolic pathways. This study therefore may provide a research direction for the design of new therapeutic strategies for hepatic ischemia/reperfusion injury.

Hic-5 deficiency attenuates hepatic ischemia reperfusion injury through TLR4/NF-κB signaling pathways

AIM

To explore the role and mechanism of Hydrogen peroxide-inducible clone-5 (Hic-5) in hepatic ischemia reperfusion injury.

METHODS

Hic-5 KO and WT mice were used to establish the liver ischemia reperfusion model (HI/R). Primary hepatocytes were isolated to establish hypoxic reoxygenation model (H/R). AST and ALT were measured by automatic biochemical analyzer. Liver tissue sections were stained with HE and Tunnel. RNA and proteins were extracted from liver tissues, and expressions of Il-6, Il-10, CCL-2, CXCL-10, P65, Caspase-3, TLR4 and FADD were detected at gene and protein levels. Liver cell apoptosis was detected by flow cytometry and immunofluorescence. Primary hepatocytes were stimulated by LPS to establish a model of hepatocyte apoptosis, and cell inflammation and apoptosis-related proteins were detected.

RESULTS

After HI/R, ALT and AST in serum were up-regulated, some hepatocyte apoptosis were observed in pathological sections. Hic-5 expression was increased in WT mice after HI/R, and liver damage were severer than KO mice. The expression of IL-6, CCL-2 and CXCL-10 in the liver of KO mice was low, and the expression of IL-10 was high. Further studies showed that KO mice showed lower expression of P65, Caspase3 and TLR4. In H/R model, hepatocytes also showed the same trend. Finally, after LPS stimulation, the results showed that the inflammation and apoptosis induced by LPS were significantly reduced in Hic-5 knocked hepatocytes.

CONCLUSION

Hic-5 was found to promote inflammation through NF-kb signaling pathway and apoptosis through TLR4-FADD signaling pathway in mice with HI/R, thus aggravating liver injury in mice.

Peroxiredoxins in inflammatory liver diseases and ischemic/reperfusion injury in liver transplantation

Peroxiredoxins (Prxs) belong to the superfamily of thiol-dependent peroxidases, and remove reactive oxygen species (ROS) and other oxidative stress products. The expression and activity of Prxs can be substantially affected by stimuli from the microenvironment, and in turn regulate cytokine secretion in the context of inflammation in both peroxidase-dependent and -independent pathways. Prxs translocate to mitochondria and are hyperoxidized during acute liver damage, and attenuate intracellular ROS accumulation through their peroxidase activity. In particularly, Prx1 modulates the microenvironment in liver injuries by reducing adhesion molecule expression in vascular endothelial cells and inhibiting the inflammatory response and adhesion of macrophages. Prxs have potent prosurvival effects against ROS in ischemic/reperfusion (I/R) injury, but Prxs released from necrotic cells increase secretion of inflammatory cytokines by macrophages through TLR2 and 4 activation, which promotes cell death. Prxs can be used as biomarkers to evaluate I/R injury and predict graft survival in liver transplantation. Prxs are modulated in various types of chronic hepatitis and hepatosteatosis, and mediate disease progression. Alcohol administration increases oxidization and inactivation of Prxs in mice because of oxidative stress. In conclusion, Prxs are essential mediators and biomarkers in inflammatory liver diseases and I/R injury.

Hepatocellular protein profiles after hepatic ischemia/reperfusion injury with or without octreotide preconditioning in a rabbit model

Hepatic ischemic/reperfusion injury (HIRI) is a major complication of liver resection and transplantation. Octreotide, a somatostatin analogue, has been used to treat hepatic fibrosis and portal hypertension; however, its function against HIRI remains unclear. To elucidate the effect of octreotide in HIRI, we investigated the hepatocellular protein profiles in response to octreotide preconditioning in a rabbit model by using proteomic analysis. Twenty-four rabbits were divided into 3 groups: the sham operative group (control), the ischemia/reperfusion group (IR), and the ischemia/reperfusion + octreotide group (IR+Oct). They were subjected to 30 minutes of normothermic ischemia followed by 120 minutes of reperfusion by using Pringle's maneuver method. Proteomic studies were then performed to compare the protein profiles of their left liver lobe. A total of 16 differential proteins were successfully identified. These findings suggest that octreotide might exert an effect against HIRI through up-regulating the expression of the anti-injury substances, such as heat-shock proteins 70 and 27 (confirmed by using Western blot analysis); significantly raising the phosphatidylethanolamine-binding protein that alleviates IR-related apoptosis; and down-regulating mitochondrial metabolic enzymes such as NADH2 dehydrogenase and triosephosphate isomerase.

Daintain/AIF-1 accelerates the activation of insulin-like growth factor-1 receptor signaling pathway in HepG2 cells

Daintain/allograft inflammatory factor-1 (AIF-1), as a novel inflammatory factor, has been reported to accelerate the proliferation and migration of breast cancer cells. However, the effect of daintain/AIF-1 on hepatocarcinogenesis remains unclear. In order to explore the effect of daintain/AIF-1 on the progression of hepatocellular carcinoma (HCC), enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR) were performed to examine the secretion and gene expression of (IGF)-1, IGF-2 and IGFBP-3. The expression of IGF-1R and its downstream targets was evaluated by western blotting. In addition, the proliferation and cell-cycle progression of HepG2 cells was assessed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenylterazolium bromide (MTT) and flow cytometric analysis. The results showed that HepG2 cells subjected to daintain/AIF-1 treatment revealed an obvious increase in the secretion of IGF-1 and IGF-2, and a reduction in the secretion of IGFBP-3. Moreover, daintain/AIF-1 accelerated the activation of IGF-1-induced IGF-1R and its downstream AKT signaling pathway, and subsequently promoted the activation of cyclin D1 pathway, thus accelerating the progression of the cell cycle and eventually promoting the proliferation of HepG2 cells. In conclusion, daintain/AIF-1 promoted the proliferation of HepG2 cells by accelerating the activation of IGF-1R and its downstream signaling pathway, which confirms that daintain/AIF-1 plays a crucial role in the development of HCC.

Isobaric labeling-based relative quantification in shotgun proteomics

Mass spectrometry plays a key role in relative quantitative comparisons of proteins in order to understand their functional role in biological systems upon perturbation. In this review, we review studies that examine different aspects of isobaric labeling-based relative quantification for shotgun proteomic analysis. In particular, we focus on different types of isobaric reagents and their reaction chemistry (e.g., amine-, carbonyl-, and sulfhydryl-reactive). Various factors, such as ratio compression, reporter ion dynamic range, and others, cause an underestimation of changes in relative abundance of proteins across samples, undermining the ability of the isobaric labeling approach to be truly quantitative. These factors that affect quantification and the suggested combinations of experimental design and optimal data acquisition methods to increase the precision and accuracy of the measurements will be discussed. Finally, the extended application of isobaric labeling-based approach in hyperplexing strategy, targeted quantification, and phosphopeptide analysis are also examined.

Proteome analysis of hepatic non-parenchymal cells of immune liver fibrosis rats

Elucidation of the mechanisms of liver fibrogenesis is important to treat liver fibrosis. In this study, we established rat models of liver fibrosis with stages from 0-1, 2, and 3-4 to 4 at 2, 4, 6, and 8 weeks, respectively, by injection of pig serum. Liver fibrogenesis was detected by Masson's trichrome staining. Rat non-parenchymal cells (NPCs) were enriched 4-fold by Percoll density gradient centrifugation. Protein extracts from NPCs were prepared at 4 and 8 weeks, separated by two-dimensional electrophoresis, and then stained with Coomassie Blue G-250. At 4 weeks, we identified 18 non-redundant differentially expressed proteins of which protein disulfide-isomerase associated protein 3 (PDIA3) and NDUV showed consistent expression at protein and mRNA levels from 4 to 8 weeks. PDIA3 was found to be down-regulated by Western blotting in the rat model and immunohistochemically in human liver. Our results revealed important aspects of the pathogenesis/progression of liver fibrosis and demonstrated important changes in protein expression levels of NPCs at various stages of liver fibrosis.

Pattern recognition and biomarker validation using quantitative1H-NMR-based metabolomics

The collection of global metabolic data and their interpretation (both spectral and biochemical) using modern spectroscopic techniques and appropriate statistical approaches, are known as 'metabolic profiling', 'metabonomics' or 'metabolomics'. This review addresses 1H-nuclear magnetic resonance (NMR)-based metabolomic principles and their application in biomedical science, with special emphasis on their potential in translational research in transplantation, oncology, and drug toxicity or discovery. Various steps in metabolomics analysis are described in order to illustrate the types of biological samples, their respective handling and preparation for 1H-NMR analysis; provide a rationale for using pattern-recognition techniques (spectral database concept) versus quantitative 1H-NMR-based metabolomics (metabolite database concept); and identify necessary technological and logistical future developments that will allow 1H-NMR-based metabolomics to become an established tool in biomedical research and patient care.

Rat Kupffer cells: Isolation, identification and LPS-stimulated TNF-α expression and secretion

AIM: To isolate, culture and identify rat Kupffer cells, and to investigate the effect of LPS on TNF-α expression and secretion in rat Kupffer cells.

METHODS: Rat liver Kupffer cells (KCs) were isolated and purified by means of in situ perfusion, density gradient centrifugation and early medium change. Isolated cells were identified by ink phagocytosis and ED2 staining test. The expression and secretion of TNF-α was detected by RT-PCR and enzyme-linked immunosorbent assay (ELISA).

RESULTS: Rat liver KCs were successfully isolated, purified, and confirmed by ink phagocytosis and ED2 staining test. Compared with non-stimulated KCs, LPS-stimulated cells had a significantly higher level of TNF-α mRNA expression (1.10 ± 0.02 vs 0.09 ± 0.01, P < 0.001). TNF-α protein levels in cell supernatants were also significantly increased in LPS-stimulated cells than in non-stimulated cells (487.10 pg/mL± 5.56 pg/mL vs 39.41 pg/mL ± 15.30 pg/mL, P < 0.001).

CONCLUSION: Rat KCs have been successfully isolated and purified by means of in situ perfusion and density gradient centrifugation, and LPS can stimulate the expression and secretion of TNF-α.

Alterations in the redox state and liver damage: hints from the EASL Basic School of Hepatology

The importance of a correct balance between oxidative and reductive events has been shown to have a paramount effect on cell function for quite a long time. However, in spite of this body of rapidly growing evidence, the implication of the alteration of the redox state in human disease has been so far much less appreciated. Liver diseases make no exception. Although not fully comprehensive, this article reports what discussed during an EASL Basic School held in 2012 in Trieste, Italy, where the effect of the alteration of the redox state was addressed in different experimental and human models. This translational approach resulted in further stressing the concept that this topic should be expanded in the future not only to better understand how oxidative stress may be linked to a liver damage but also, perhaps more important, how this may be the target for better, more focused treatments. In parallel, understanding how alteration of the redox balance may be associated with liver damage may help define sensitive and ideally early biomarkers of the disorder.

Proteomics reveals acute pro-inflammatory and protective responses in rat Kupffer cells and hepatocytes after chemical initiation of liver cancer and after LPS and IL-6

Inflammation is a key event in the development of liver cancer. We studied early inflammatory responses of Kupffer cells (KCs) and hepatocyte (HC) after cancer initiation. The chemical carcinogen N-nitrosomorpholine (NNM) was used in a rat model. We applied a comprehensive analytical strategy including metabolic labeling, 2-D PAGE, LC-MS/MS-based spot identification and shotgun proteomics and thus determined the rates of synthesis of individual proteins, compared whole tissue with isolated constituent cells and performed in vivo to in vitro comparisons of NNM effects. NNM increased synthesis of overall and 138 individual proteins identified in HC and/or KC, indicating reprogramming of metabolism favoring protection, repair and replacement of cell constituents in HC and KC. Secretome analysis by 2-D PAGE and shotgun proteomics of HC revealed the induction of acute phase proteins, in case of KC of proteases, cytokines and chemokines, indicating inflammatory effects. All responses were induced rapidly, independently of signals from other cells, and closely mimicked the pro-inflammatory and protective effects of inflammation modulators LPS in KC and IL-6 in HC. In conclusion, the carcinogen NNM exerts pro-inflammatory effects in the liver, partially by direct activation of KC. The acute inflammation and its protective component will enhance formation, survival and proliferation of initiated cells and may therefore act synergistically with the genotoxic action of the carcinogen.

The role of molecular chaperonins in warm ischemia and reperfusion injury in the steatotic liver: a proteomic study

BACKGROUND

The molecular basis of the increased susceptibility of steatotic livers to warm ischemia/reperfusion (I/R) injury during transplantation remains undefined. Animal model for warm I/R injury was induced in obese Zucker rats. Lean Zucker rats provided controls. Two dimensional differential gel electrophoresis was performed with liver protein extracts. Protein features with significant abundance ratios (p < 0.01) between the two cohorts were selected and analyzed with HPLC/MS. Proteins were identified by Uniprot database. Interactive protein networks were generated using Ingenuity Pathway Analysis and GRANITE software.

RESULTS

The relative abundance of 105 proteins was observed in warm I/R injury. Functional grouping revealed four categories of importance: molecular chaperones/endoplasmic reticulum (ER) stress, oxidative stress, metabolism, and cell structure. Hypoxia up-regulated 1, calcium binding protein 1, calreticulin, heat shock protein (HSP) 60, HSP-90, and protein disulfide isomerase 3 were chaperonins significantly (p < 0.01) down-regulated and only one chaperonin, HSP-1 was significantly upregulated in steatotic liver following I/R.

CONCLUSION

Down-regulation of the chaperones identified in this analysis may contribute to the increased ER stress and, consequently, apoptosis and necrosis. This study provides an initial platform for future investigation of the role of chaperones and therapeutic targets for increasing the viability of steatotic liver allografts.

L-arginine in the ischemic phase protects against liver ischemia-reperfusion injury

PURPOSE: To investigate the effects of intravenous L-arginine (LG) infusion on liver morphology, function and proinflammatory response of cytokines during the early phase of ischemia-reperfusion injury (IRI). METHODS: Thirty rabbits were subjected to 60 minutes of hepatic ischemia and 120 minutes of reperfusion. An intravenous injection of saline or L-arginine was administered five minutes before the ischemia and five minutes before initiating the reperfusion and at the 55th and 115th minutes after the ischemia. Samples were collected for histological analysis of the liver and measurements of the serum AST, ALT and LDH and the cytokines IL-6 and TNF-alpha. RESULTS: It was observed a significant reduction of sinusoidal congestion, cytoplasmic vacuolization, infiltration of polymorphonuclear leukocyte, nuclear pyknosis, necrosis and steatosis in liver tissue, as well as AST, ALT and LDH after injection of LG in the ischemia (p <0.001). Lower levels of IL-6 and TNF-alpha were associated with LG infusion during ischemia. Higher levels these proteins were observed in animals receiving LG during reperfusion. CONCLUSION: L-arginine protects the liver against ischemia/reperfusion injury, mainly when is administered during the ischemic phase.

Protective effect of heme oxygenase-1 induction against hepatic injury in alcoholic steatotic liver exposed to cold ischemia/reperfusion

AIMS

The purpose of this study was to investigate the cytoprotective role of heme oxygenase-1 (HO-1) induction in hepatic injury in alcoholic steatotic liver exposed to cold ischemia/reperfusion (I/R).

MAIN METHODS

Animals were fed an ethanol liquid diet or isocaloric control diet for 5 weeks. Isolated perfused rat livers were preserved in Histidine-Tryptophan-Ketoglutarate at 4 °C. After 24 h of storage, livers were subjected to 120 min of reperfusion with Krebs-Henseleit bicarbonate buffer at 37 °C. Animals were pretreated with cobalt protoporphyrin (CoPP, 5 mg/kg, i.p.) or zinc protoporphyrin (ZnPP, 25 mg/kg, i.p.), HO-1 inducer and antagonist, respectively.

KEY FINDINGS

In the model of ischemia/isolated perfusion, endogenous HO-1 was downregulated in the livers fed with ethanol diet (ED I/R). In ED I/R group, portal pressure and lactate dehydrogenase release were significantly increased, while bile output and hyaluronic acid clearance decreased compared to rats fed on control diet (CD I/R). Furthermore, hepatic glutathione content decreased and lipid peroxidation increased in the ED I/R group compared to the CD I/R group. These alterations were attenuated by upregulation of HO-1 with CoPP pretreatment.

SIGNIFICANCE

Our results suggest that chronic ethanol consumption aggravates hepatic injury during cold I/R and it is likely due to downregulation of endogenous HO-1. Prior induction of HO-1 expression may provide a new strategy to protect livers against hepatic I/R injury or to increase the donor transplant pool through modulation of marginal alcoholic steatotic livers.

Peptide labeling with isobaric tags yields higher identification rates using iTRAQ 4-plex compared to TMT 6-plex and iTRAQ 8-plex on LTQ Orbitrap

Peptide labeling with isobaric tags has become a popular technique in quantitative shotgun proteomics. Using two different samples viz. a protein mixture and HeLa extracts, we show that three commercially available isobaric tags differ with regard to peptide identification rates: The number of identified proteins and peptides was largest with iTRAQ 4-plex, followed by TMT 6-plex, and smallest with iTRAQ 8-plex. In all experiments, we employed a previously described method where two scans were acquired for each precursor on an LTQ Orbitrap: A CID scan under standard settings for identification, and a HCD scan for quantification. The observed differences in identification rates were similar when data was searched with either Mascot or Sequest. We consider these findings to be the result of a combination of several factors, most notably prominent ions in CID spectra as a consequence of loss of fragments of the label tag from precursor ions. These fragment ions cannot be explained by current search engines and were observed to have a negative impact on peptide scores.

Differential proteomic analysis of STAT6 knockout mice reveals new regulatory function in liver lipid homeostasis

Increased inflammatory signaling is a key feature of metabolic disorders. In this context, the role of increased pro-inflammatory signals has been extensively studied. By contrast, no efforts have been dedicated to study the contrasting scenario: the attenuation of anti-inflammatory signals and their role in metabolic homeostasis. IL-4 and IL-13 are anti-inflammatory cytokines signaling through the Signal Transducer and Activator of Transcription 6 (STAT6). Our study was aimed at evaluating the lack of STAT6 signaling on liver homeostasis. To this end we analyzed the liver proteome of wild type and STAT6 knock-out mice using 2D nanoscale LC-MS/MS with iTRAQ labeling technique. The coordinated changes in proteins identified by this quantitative proteome analysis indicated disturbed lipid homeostasis and a state of hepatocellular stress. Most significantly, the expression of the liver fatty acid binding protein (FABP1) was increased in the knock-out mice. In line with the elevated FABP1 expression we found latent liver lipid accumulation in the STAT6-deficient mice which was further aggravated when mice were challenged by a high fat diet. In conclusion, our study revealed a so far uncharacterized role for STAT6 in regulating liver lipid homeostasis and demonstrates the importance of anti-inflammatory signaling in the defense against the development of liver steatosis.

Isolation of rat Kupffer cells by ex vivo perfusion and their primary culture

AIM: To explore a convenient and effective method for isolation and primary culture of rat Kupffer cells (KCs) in vitro.

METHODS: Ex vivo rat liver tissue was perfused with collagenase IV and diced into small pieces. The diced tissue was digested for 30 min at 37℃and centrifuged to remove hepatocytes. KCs were then separated by means of Percoll density gradient centrifugation and selective adherence. Phagocytosis assay and immunocytochemistry for ED2 were used to identify cells isolated.

RESULTS: The average cell yield per gram of liver before plastic adherence was (2.1 ± 0.3) × 10⁶, and (1.5 ± 0.1) × 10⁶following plastic adherence. The viability of KCs isolated was higher than 92% as determined by trypan blue exclusion. The purity of KCs, identified by immunocytochemistry for ED2, was higher than 90%. Cultured KCs were functionally intact and exhibited irregular shape.

CONCLUSION: The method for isolation and culture of Kupffer cells by ex vivo perfusion is convenient, efficient and stable. Cultured Kupffer cells retain naive biological characteristics and can be used in future studies.

Proteomic analysis of hepatic ischemia/reperfusion injury and ischemic preconditioning in mice revealed the protective role of ATP5beta

Hepatic ischemia/reperfusion (I/R) injury is an inevitable consequence during liver surgery. Ischemic preconditioning (IPC) has been shown to protect the livers from I/R injury, partially mediated by preservation of hepatic ATP contents. However, the precise molecular mechanisms of these events remain poorly elucidated. In this study, liver proteomes of the mice subjected to I/R injury pretreated with or without IPC were analyzed using 2-DE combined with MALDI-TOF/TOF mass analysis. Twenty proteins showing more than 1.5-fold difference were identified in the livers upon I/R injury. Among these proteins, four proteins were further regulated by IPC when compared with nonpretreated controls. One of these proteins, ATP synthase beta subunit (ATP5beta) catalyzes the rate-limiting step of ATP formation. The expression level of ATP5beta, which was further validated by Western blot analysis, was significantly decreased upon I/R injury while turned over by IPC pretreatment. Change pattern of hepatic ATP corresponded with that of ATP5beta expression, indicating that increasing hepatic ATP5beta expression might be a reason for ATP-preserving effect of IPC. In summary, this study provided new clues for understanding the mechanisms of IPC against I/R injury. The protective role of ATP5beta might give evidences for developing new therapeutic approaches against hepatic I/R injury.

Importance of cell-procurement methods in transforming personalized cancer treatment from concept to reality

The much-anticipated promise of personalized cancer care is to deliver therapies best suited for a patient based on the knowledge of that individual's genetics and tumor characteristics. This transformative approach will require many changes in the scientific and medical community, one of the most fundamental being the direct study of human tissue biospecimens. Biospecimens will be integral to the elucidation of biomarkers that will help identify and serve as potential diagnostic, prognostic and therapeutic targets in cancer. Despite the vast repositories of fixed-tissue biospecimens that are in existence, a number of flaws exist that hinder their reliable use as instruments from which to enable personalized cancer research and clinical care. A new view of biospecimen worth in the future will mandate that the molecules within its cells are reflective of their in vivo state, and not altered by external variables introduced during the excision and processing of the biospecimen. Research on biospecimen collection is a legitimate field of study that will be necessary for personalized cancer care to become a reality.

Advances in the relationship between Kupffer cells and liver ischemia reperfusion injury

Kupffer cells, residing within the lumen of liver sinusoids, constitute 80%-90% of tissue macrophages present in the body. Upon activation Kupffer cells release various products, including cytokines, prostanoides, nitric oxide and reactive oxygen species. These factors regulate the phenotype of Kupffer cells themselves, and the phenotypes of neighboring cells, such as hepatocytes, stellate cells, endothelial cells and other immune cells that traffic through the liver. Therefore, Kupffer cells are intimately involved in the liver's response to warm or cold ischemia reperfusion injury (IRI). This review summarizes the role of Kupffer cells in the pathogenesis of liver IRI to explore the reasonable therapeutic target.

Alterations in the proteome of pulmonary alveolar type II cells in the rat after hepatic ischemia-reperfusion

OBJECTIVE

Hepatic ischemia-reperfusion can be associated with acute lung injury. Alveolar epithelial type II cells (ATII) play an important role in maintaining lung homeostasis in acute lung injury.

DESIGN

To study potentially new mechanisms of hepatic ischemia-reperfusion-induced lung injury, we examined how liver ischemia-reperfusion altered the proteome of ATII.

SETTING

Laboratory investigation.

SUBJECTS

Spontaneously breathing male Zucker rats.

INTERVENTIONS

Rats were anesthetized with isoflurane. The vascular supply to the left and medial lobe of the liver was clamped for 75 mins and then reperfused. Sham-operated rats were used as controls. After 8 hrs, rats were killed.

MEASUREMENTS AND MAIN RESULTS

Bronchoalveolar lavage and differential cell counts were performed, and tumor necrosis factor-alpha and cytokine-induced neutrophil chemotactic factor-1 in plasma were determined by enzyme-linked immunosorbent assay. ATII were isolated, lysed, tryptically digested, and labeled using isobaric tags (iTRAQ). The samples were fractionated by cation exchange chromatography, separated by high-performance liquid-chromatography, and identified using electrospray tandem mass spectrometry. Spectra were interrogated and quantified using ProteinProspector. Quantitative proteomics provided quantitative data for 94 and 97 proteins in the two groups. Significant changes in ATII protein content included 30% to 40% increases in adenosine triphosphate synthases, adenosine triphosphate/adenosine diphosphate translocase, and catalase (all p < .001). Following liver ischemia-reperfusion, there was also a significant increase in the percentage of neutrophils in bronchoalveolar lavage (48% +/- 26%) compared with sham-operated controls (5% +/- 3%) (p < .01), and plasma tumor necrosis factor-alpha levels were also significantly increased.

CONCLUSIONS

The proteins identified by quantitative proteomics indicated significant changes in moderators of cell metabolism and host defense in ATII. These findings provide new insights into possible mechanisms responsible for hepatic ischemia-reperfusion-related acute lung injury and suggest that ATII cells in the lung sense and respond to hepatic injury.

Tandem mass spectrometry in physiology

Tandem mass spectrometry coupled to liquid chromatography (LC-MS/MS) allows identification of proteins in a complex mixture without need for protein purification ("shotgun" proteomics). Recent progress in LC-MS/MS-based quantification, phosphoproteomic analysis, and targeted LC-MS/MS using multiple reaction monitoring (MRM) has made LC-MS/MS a powerful tool for the study of cell physiology.

Modification of the hepatic mitochondrial proteome in response to ischemic preconditioning following ischemia-reperfusion injury of the rat liver

BACKGROUND/AIM

Ischemic preconditioning (IPC) may reduce hepatic ischemia-reperfusion (IR) injury, but efficacy of IPC on mitochondrial proteome is not demonstrated. We investigated how IPC modifies the mitochondrial proteome after IR injury.

METHODS

Rats were subjected to 25 min of portal triad crossclamping (IR group, n = 8). In the IPC group (n = 8), 10 min of temporal portal triad clamping was performed before 25 min of portal clamping. Samples were obtained after 24 h. The mitochondrial inner-membrane potential was measured by the uptake of a lipophilic cationic carbocyanine probe and mitochondrial proteome was also investigated using 2-dimensional differential in-gel electrophoresis and liquid chromatography-tandem mass spectrometry.

RESULTS

Mitochondrial inner-membrane potential and glutathione were lower and serum transaminase was higher in the IPC group than in the IR group. The mitochondrial precursor of aldehyde dehydrogenase 2 and alpha-methylacyl-CoA-racemase were upregulated in the IPC group in comparison to the IR group. In contrast, protein disulfide-isomerase A3 precursor, 60S acid ribosomal protein P0, carbonic anhydrase 3 and superoxide dismutase were significantly more downregulated in the IPC group than in the IR group.

CONCLUSIONS

A hepatoprotective effect by IPC was not shown; however, IPC caused significant up- or downregulation of several mitochondrial proteins.

2-APB protects against liver ischemia-reperfusion injury by reducing cellular and mitochondrial calcium uptake

Ischemia-reperfusion (I/R) injury is a commonly encountered clinical problem in liver surgery and transplantation. The pathogenesis of I/R injury is multifactorial, but mitochondrial Ca(2+) overload plays a central role. We have previously defined a novel pathway for mitochondrial Ca(2+) handling and now further characterize this pathway and investigate a novel Ca(2+)-channel inhibitor, 2-aminoethoxydiphenyl borate (2-APB), for preventing hepatic I/R injury. The effect of 2-APB on cellular and mitochondrial Ca(2+) uptake was evaluated in vitro by using (45)Ca(2+). Subsequently, 2-APB (2 mg/kg) or vehicle was injected into the portal vein of anesthetized rats either before or following 1 h of inflow occlusion to 70% of the liver. After 3 h of reperfusion, liver injury was assessed enzymatically and histologically. Hep G2 cells transfected with green fluorescent protein-tagged cytochrome c were used to evaluate mitochondrial permeability. 2-APB dose-dependently blocked Ca(2+) uptake in isolated liver mitochondria and reduced cellular Ca(2+) accumulation in Hep G2 cells. In vivo I/R increased liver enzymes 10-fold, and 2-APB prevented this when administered pre- or postischemia. 2-APB significantly reduced cellular damage determined by hematoxylin and eosin and terminal deoxynucleotidyl transferase dUTP-mediated nick-end labeling staining of liver tissue. In vitro I/R caused a dissociation between cytochrome c and mitochondria in Hep G2 cells that was prevented by administration of 2-APB. These data further establish the role of cellular Ca(2+) uptake and subsequent mitochondrial Ca(2+) overload in I/R injury and identify 2-APB as a novel pharmacological inhibitor of liver I/R injury even when administered following a prolonged ischemic insult.

A Proteomics Method Revealing Disease-Related Proteins in Livers of Hepatitis-Infected Mouse Model

In this post-genome era, a sensitive quantitative method is required for differential profiling analyses of clinical proteomes to understand the disease progress. Here, we adopt the FD-LC-MS/MS method, consisting of fluorogenic derivatization (FD), separation by liquid chromatography (LC), and identification by LC-tandem mass spectrometry (MS/MS), to reveal disease-related proteins in livers of hepatocarcinogenesis in transgenic (Tg) and non-transgenic (NTg) mice at three developmental stages. After 6 months, the expression of apoptosis-related proteins is suppressed. After 12 months, proteins related to respiration, the electron-transfer system, and anti-oxidation are significantly up-regulated. After 16 months, proteins related to defense, beta-oxidation, and apoptosis are significantly suppressed. This fluctuating expression of proteins could explain the progression of hepatocarcinogenesis. The method would be useful for clinical proteomics analysis because of its high resolution, sensitivity, and reproducibility.

Impact of low and high tidal volumes on the rat alveolar epithelial type II cell proteome

RATIONALE

Mechanical ventilation with high tidal volumes leads to increased permeability, generation of inflammatory mediators, and damage to alveolar epithelial cells (ATII).

OBJECTIVES

To identify changes in the ATII proteome after two different ventilation strategies in rats.

METHODS

Rats (n = 6) were ventilated for 5 hours with high- and low tidal volumes (VTs) (high VT: 20 ml/kg; low VT: 6 ml/kg). Pooled nonventilated rats served as control animals. ATII cells were isolated and lysed, and proteins were tryptically cleaved into peptides. Cellular protein content was evaluated by peptide labeling of the ventilated groups with (18)O. Samples were fractionated by cation exchange chromatography and identified using electrospray tandem mass spectrometry. Proteins identified by 15 or more peptides were statistically compared using t tests corrected for the false discovery rate.

MEASUREMENTS AND MAIN RESULTS

High Vt resulted in a significant increase in airspace neutrophils without an increase in extravascular lung water. Compared with low-VT samples, high-VT samples showed a 32% decrease in the inositol 1,4,5-trisphosphate 3 receptor (p < 0.01), a 34% decrease in Na(+), K(+)-ATPase (p < 0.01), and a significantly decreased content in ATP synthase chains. Even low-VT samples displayed significant changes, including a 66% decrease in heat shock protein 90-beta (p < 0.01) and a 67% increase in mitochondrial pyruvate carboxylase (p < 0.01). Significant differences were found in membrane, acute phase, structural, and mitochondrial proteins.

CONCLUSIONS

After short-term exposure to high-VT ventilation, significant reductions in membrane receptors, ion channel proteins, enzymes of the mitochondrial energy system, and structural proteins in ATII cells were present. The data supports the two-hit concept that an unfavorable ventilatory strategy may make the lung more vulnerable to an additional insult.

Warm hepatic ischemia-reperfusion promotes growth of colorectal carcinoma micrometastases in mouse liver via matrix metalloproteinase-9 induction

Surgical resection remains the best treatment for colorectal metastases isolated to the liver; however, 5-year survival rates following liver resection are only 40% to 50%, with liver recurrence being a significant reason for treatment failure. The ischemia-reperfusion (I/R) injury incurred during liver surgery can lead to cellular dysfunction and elevations in proinflammatory cytokines and matrix metalloproteinases (MMP). In rodents, I/R injury to the liver has been shown to accelerate the outgrowth of implanted tumors. The mechanism for increased tumor growth in the setting of liver I/R injury is unknown. To investigate the effect of I/R on tumor growth, an experimental model was used whereby small hepatic metastases form after 28 days. Mice subjected to 30 min of 70% liver ischemia at the time of tumor inoculation had significantly larger tumor number and volume, and had elevated MMP9 serum and liver tissue MMP9 as evidenced by zymography and quantitative real-time PCR. Mice treated with doxycycline, a broad-spectrum MMP inhibitor, had reduced MMP9 levels and significantly smaller tumor number and volume in the liver. MMP9-null mice were used to determine if the effects of doxycycline were due to the absence of stromal-derived MMP9. The MMP9-null mice, with or without doxycycline treatment, had reduced tumor number and volume that was equivalent to wild-type mice treated with doxycycline. These findings indicate that hepatic I/R-induced elevations in MMP9 contribute to the growth of metastatic colorectal carcinoma in the liver and that postresection MMP9 inhibition may be clinically beneficial in preventing recurrence following hepatic surgery.

A multiplexed proteomics approach to differentiate neurite outgrowth patterns

We report here a method for proteomics pattern discovery by utilizing a self-organizing map approach to analyze data obtained from a novel multiplex iTRAQ proteomics method. Through the application of this technique, we were able to delineate the early molecular events preceding dorsal root ganglia neurite outgrowth induced by either nerve growth factor (NGF) or an immunophilin ligand, JNJ460. Following pattern analysis we discovered that each neurotrophic agent promoted mostly distinct increases in protein expression with few overlapping patterns. In the NGF-treated group, proteins possessing "biosynthesis function" (p < 0.002) and "ribosome localization" (p < 0.0003) were increased, while proteins promoting "organogenesis" (p < 0.004) and related "signal transduction" (p < 0.008) functions were notably increased in the JNJ460-treated group. This study suggests that the properties of neurite outgrowth triggered by NGF and JNJ460 can be distinguished at the proteome level. Multiplexed proteomics analysis, along with pattern discovery bioinformatics tools, has the capability to differentiate subtle neuroproteomics patterns.