RESUMO
Ischemia-reperfusion injury (IRI) consequent to major liver surgery is a still unmet clinical problem. The activation of endogenous systems of hepatoprotection can prevent the damaging effects of ischemia-reperfusion (IR) as shown by the phenomenon known as 'ischemic preconditioning'. The identification of endogenous signal mediators of hepatoprotection is of main interest since they could be targeted in future therapeutic interventions. Qiu et al. recently reported in Clin. Sci. (Lond.) (2020) 134(17), 2279-2294, the discovery of a novel protective molecule against hepatic IR damage: dual-specificity phosphatase 12 (DUSP12). IR significantly decreased DUSP12 expression in liver whereas DUSP12 overexpression in hepatocytes protected IRI and DUSP12 deletion in DUSP12 KO mice exacerbated IRI. The protective effects of DUSP12 depended on apoptosis signal-regulating kinase 1 (ASK1) and acted through the inhibition of the ASK1-dependent kinases c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinase (MAPK). These results enlighten DUSP12 as a novel intermediate negative regulator of the pro-inflammatory and pro-apoptotic ASK1/JNK-p38 MAPK pathway activated during hepatic IR and identify DUSP12 as potential therapeutic target for IRI.
Assuntos
Fosfatases de Especificidade Dupla/metabolismo , Fígado/patologia , MAP Quinase Quinase Quinase 5/antagonistas & inibidores , Traumatismo por Reperfusão/prevenção & controle , Transdução de Sinais , Animais , Células Endoteliais/metabolismo , Células Endoteliais/patologia , MAP Quinase Quinase Quinase 5/metabolismo , CamundongosRESUMO
The mechanisms responsible for the evolution of steatosis towards NASH (non-alcoholic steatohepatitis) and fibrosis are not completely defined. In the present study we evaluated the role of CD4(+) T-helper (Th) cells in this process. We analysed the infiltration of different subsets of CD4(+) Th cells in C57BL/6 mice fed on a MCD (methionine choline-deficient) diet, which is a model reproducing all phases of human NASH progression. There was an increase in Th17 cells at the beginning of NASH development and at the NASH-fibrosis transition, whereas levels of Th22 cells peaked between the first and the second expansion of Th17 cells. An increase in the production of IL (interleukin)-6, TNFα (tumour necrosis factor α), TGFß (transforming growth factor ß) and CCL20 (CC chemokine ligand 20) accompanied the changes in Th17/Th22 cells. Livers of IL-17(-/-) mice were protected from NASH development and characterized by an extensive infiltration of Th22 cells. In vitro, IL-17 exacerbated the JNK (c-Jun N-terminal kinase)-dependent mouse hepatocyte lipotoxicity induced by palmitate. IL-22 prevented lipotoxicity through PI3K (phosphoinositide 3-kinase)-mediated inhibition of JNK, but did not play a protective role in the presence of IL-17, which up-regulated the PI3K/Akt inhibitor PTEN (phosphatase and tensin homologue deleted on chromosome 10). Consistently, livers of IL-17(-/-) mice fed on the MCD diet displayed decreased activation of JNK, reduced expression of PTEN and increased phosphorylation of Akt compared with livers of wild-type mice. Hepatic infiltration of Th17 cells is critical for NASH initiation and development of fibrosis in mice, and reflects an infiltration of Th22 cells. Th22 cells are protective in NASH, but only in the absence of IL-17. These data strongly support the potentiality of clinical applications of IL-17 inhibitors that can prevent NASH by both abolishing the lipotoxic action of IL-17 and allowing IL-22-mediated protection.
Assuntos
Hepatopatia Gordurosa não Alcoólica/imunologia , Linfócitos T Auxiliares-Indutores/fisiologia , Linfócitos T Reguladores/fisiologia , Animais , Modelos Animais de Doenças , Interleucina-17/deficiência , Interleucinas/metabolismo , Fígado/imunologia , Masculino , Camundongos Endogâmicos C57BL , Interleucina 22RESUMO
BACKGROUND & AIMS: Ischemia-reperfusion (IR) of liver results in hepatocytes (HP) and sinusoidal endothelial cells (LSEC) irreversible damage. Ischemic preconditioning protects IR damage upon adenosine A2a receptor (A2aR) stimulation. Understanding the phenotypic changes that underlie hepatocellular damage and protection is critical to optimize strategies against IR. METHODS: The proteome of HP and LSEC, isolated from sham or IR exposed mice, receiving or not the A2aR agonist CGS21680 (0.5mg/kg b.w.), was analyzed by 2-D DIGE/MALDI-TOF. RESULTS: We identified 64 proteins involved in cytoprotection, regeneration, energy metabolism and response to oxidative stress; among them, 34 were associated with IR injury and A2aR protection. The main pathways, downregulated by IR and upregulated by CGS21680 in HP and LSEC, were related to carbohydrate, protein and lipid supply and metabolism. In LSEC, IR reduced stress response enzymes that were instead upregulated by CGS21680 treatment. Functional validation experiments confirmed the metabolic involvement and showed that inhibition of pyruvate kinase, 3-chetoacylCoA thiolase, and arginase reduced the protection by CGS21680 of in vitro hypoxia-reoxygenation injury, whereas their metabolic products induced liver cell protection. Moreover, LSEC, but not HP, were sensitive to H2O2-induced oxidative damage and CGS21680 protected against this effect. CONCLUSIONS: IR and A2aR stimulation produces pathological and protected liver cell phenotypes, respectively characterized by down- and upregulation of proteins involved in the response to O2 and nutrients deprivation during ischemia, oxidative stress, and reactivation of aerobic energy synthesis at reperfusion. This provides novel insights into IR hepatocellular damage and protection, and suggests additional therapeutic options.
Assuntos
Hepatócitos/metabolismo , Hepatócitos/patologia , Fígado/lesões , Receptor A2A de Adenosina/metabolismo , Traumatismo por Reperfusão/etiologia , Adenosina/análogos & derivados , Adenosina/farmacologia , Agonistas do Receptor A2 de Adenosina/farmacologia , Animais , Antioxidantes/farmacologia , Citoproteção/efeitos dos fármacos , Células Endoteliais/efeitos dos fármacos , Células Endoteliais/metabolismo , Células Endoteliais/patologia , Hepatócitos/efeitos dos fármacos , Metabolismo dos Lipídeos/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Fenetilaminas/farmacologia , Proteoma/metabolismo , Traumatismo por Reperfusão/metabolismo , Traumatismo por Reperfusão/prevenção & controleRESUMO
Pharmacological treatments for advanced hepatocellular carcinoma (HCC) have a partial efficacy. Augmented Na+ content and water retention are observed in human cancers and offer unexplored targets for anticancer therapies. Na+ levels are evaluated upon treatments with the antibiotic cation ionophore Monensin by fluorimetry, ICP-MS, 23Na-MRI, NMR relaxometry, confocal or time-lapse analysis related to energy production, water fluxes and cell death, employing both murine and human HCC cell lines, primary murine hepatocytes, or HCC allografts in NSG mice. Na+ levels of HCC cells and tissue are 8-10 times higher than that of healthy hepatocytes and livers. Monensin further increases Na+ levels in HCC cells and in HCC allografts but not in primary hepatocytes and in normal hepatic and extrahepatic tissue. The Na+ increase is associated with energy depletion, mitochondrial Na+ load and inhibition of O2 consumption. The Na+ increase causes an enhancement of the intracellular water lifetime and death of HCC cells, and a regression and necrosis of allograft tumors, without affecting the proliferating activity of either HCCs or healthy tissues. These observations indicate that HCC cells are, unlike healthy cells, energetically incapable of compensating and surviving a pharmacologically induced Na+ load, highlighting Na+ homeostasis as druggable target for HCC therapy.
Assuntos
Carcinoma Hepatocelular , Neoplasias Hepáticas , Camundongos , Humanos , Animais , Carcinoma Hepatocelular/patologia , Neoplasias Hepáticas/patologia , Sódio/metabolismo , Monensin/uso terapêutico , Linhagem Celular , ÁguaRESUMO
NEFA (non-esterified 'free' fatty acid)-mediated lipotoxicity plays a critical role in the pathogenesis of NASH (non-alcoholic steatohepatitis). In the light of the growing need for new therapeutic options for NASH, we investigated the action of A2aR (adenosine A(2a) receptor) stimulation against lipotoxicity. The effects of the A(2a)R agonist CGS21680 [2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxyamidoadenosine] were evaluated 'in vitro' in liver cells exposed to SA (stearic acid) and 'in vivo' in rats with NASH induced by 8 weeks of feeding with an MCD diet (methionine/choline-deficient diet). In cultured hepatocytes, SA promoted apoptosis by inducing MKK4 (mitogen-activated protein kinase kinase 4)/SEK1 (stress-activated protein kinase/extracellular-signal-regulated kinase kinase-1) and JNK-1/2 (c-Jun N-terminal kinase-1/2) activation. CGS21680 addition prevented JNK-1/2 activation and reduced apoptosis without interfering with lipid accumulation. CGS21680 action required PI3K (phosphoinositide 3-kinase)/Akt-mediated block of MKK4/SEK1. Consistently, PI3K inhibition with wortmannin abolished the cytoprotective action of CGS21680 and reverted MKK4 inhibition. SA lipotoxicity was also prevented by transfecting HTC cells with a specific MKK4/SEK1 siRNA (small interfering RNA). In rats receiving the MCD diet, the development of NASH was associated with MKK4/SEK1 and JNK-1/2 activation. CGS21680 (0.5 mg/kg of body weight, intraperitoneal) administration to MCD-fed rats prevented JNK-1/2 activation by acting on MKK4/SEK1. CGS21680 also effectively reduced NASH-associated ALT (alanine aminotransferase) release, hepatocyte apoptosis, liver inflammation and fibrosis without affecting hepatic steatosis. Taken together, these results demonstrate that, by inhibiting JNK-1/2, A(2a)R stimulation reduces lipotoxicity and ameliorates NASH, giving a rationale to investigate A(2a)R agonists as possible new therapeutic agents in preventing fatty liver progression to NASH.
Assuntos
Agonistas do Receptor A2 de Adenosina/uso terapêutico , Adenosina/análogos & derivados , Fígado Gorduroso/prevenção & controle , Fenetilaminas/uso terapêutico , Adenosina/farmacologia , Adenosina/uso terapêutico , Agonistas do Receptor A2 de Adenosina/farmacologia , Animais , Apoptose/efeitos dos fármacos , Biomarcadores/metabolismo , Células Cultivadas , Esquema de Medicação , Fígado Gorduroso/metabolismo , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Injeções Intraperitoneais , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Fígado/patologia , Masculino , Hepatopatia Gordurosa não Alcoólica , Fenetilaminas/farmacologia , Ratos , Ratos Wistar , Reação em Cadeia da Polimerase em Tempo Real , Receptores A2 de Adenosina/metabolismo , Ácidos Esteáricos/toxicidadeRESUMO
Postconditioning is a procedure based on the induction of intracellular protective reactions immediately after the onset of reperfusion. Because of the growing need to prevent ischemia/reperfusion (I/R) injury during liver surgery and transplantation, we investigated the possibility of pharmacologically inducing hepatic postconditioning. The effects of the adenosine A2A receptor agonist 2p-(2-carboxyethyl)-phenyl-amino-5'-N-ethylcarboxyamido-adenosine (CGS21680; 5 µmol/L) and the phosphatase and tensin homologue deleted from chromosome 10 (PTEN) inhibitor dipotassium bisperoxo-(5-hydroxypyridine-2-carboxyl)-oxovanadate [bpV(HOpic); 250 nmol/L] were investigated in primary rat hepatocytes during reoxygenation after 24 hours of cold storage and in an in vivo model of rat liver warm I/R. The addition of CGS21680 at reoxygenation significantly reduced hepatocyte death through the activation of the phosphoinositide 3-kinase (PI3K)-protein kinase B (PKB)/Akt signal pathway and through the reduction of the intracellular level of PTEN. PTEN lowering was associated with the increased generation of reactive oxygen species after A2A receptor-mediated stimulation of ß-nicotinamide adenine dinucleotide phosphate oxidase (NOX). The inhibition of PI3K or NOX with wortmannin or diphenyleneiodonium chloride, respectively, and the addition of the antioxidant N,N'-diphenyl-p-phenylenediamine reversed the effects of CGS21680. The PTEN inhibitor bpV(HOpic) mimicked the protection provided by CGS21680 against reoxygenation damage. An in vivo rat treatment with CGS21680 or bpV(HOpic) during reperfusion after 1 hour of partial hepatic ischemia also promoted PKB/Akt activation and ameliorated alanine aminotransferase release and histological lesions induced by 2 hours of reperfusion. We conclude that adenosine A2A receptor agonists and PTEN inhibitors are possibly useful agents for the pharmacological induction of postconditioning in the liver.
Assuntos
Agonistas do Receptor A2 de Adenosina/farmacologia , Adenosina/análogos & derivados , Fígado/irrigação sanguínea , Fenetilaminas/farmacologia , Traumatismo por Reperfusão/prevenção & controle , Adenosina/farmacologia , Animais , Masculino , Estresse Oxidativo , PTEN Fosfo-Hidrolase/análise , PTEN Fosfo-Hidrolase/antagonistas & inibidores , Ratos , Ratos WistarRESUMO
Hepatic ischemia/reperfusion injury (IRI) is aggravated by steatosis and is a main risk factor in fatty liver transplantation. Adenosine receptors (ARs) are emerging as therapeutic targets in liver diseases. By using cellular and in vivo systems of hepatic steatosis and IRI, here we evaluated the effects of pharmacological A2AR and A1R activation. The A2AR agonist CGS21680 protected the primary steatotic murine hepatocyte from IR damage and the activation of ASK1 and JNK. Such an effect was attributed to a phosphatidylinositol-3-kinase (PI3K)/Akt-dependent inhibition of ASK1. By contrast, the A1R agonist CCPA enhanced IR damage, intracellular steatosis and oxidative species (OS) production, thereby further increasing the lipid/OS-dependent ASK1-JNK stimulation. The CGS2680 and CCPA effects were nullified by a genetic ASK1 downregulation in steatotic hepatoma C1C7 cells. In steatotic mice livers, CGS21680 protected against hepatic IRI and ASK1/JNK activation whereas CCPA aggravated hepatic steatosis and IRI, and enhanced ASK1 and JNK stimulation. These results evidence a novel mechanism of CGS21680-mediated hepatoprotection, i.e., the PI3K/AKT-dependent inhibition of ASK1, and they show that CGS21680 and CCPA reduces and enhances the IRI of fatty liver, respectively, by preventing or increasing the activation of the cytotoxic ASK1/JNK axis. They also indicate the selective employment of A2AR agonists as an effective therapeutic strategy to prevent IRI in human fatty liver surgery.
Assuntos
Progressão da Doença , Fígado Gorduroso/complicações , MAP Quinase Quinase Quinase 5/metabolismo , Substâncias Protetoras/metabolismo , Receptor A1 de Adenosina/metabolismo , Receptor A2A de Adenosina/metabolismo , Traumatismo por Reperfusão/complicações , Agonistas do Receptor A1 de Adenosina/farmacologia , Agonistas do Receptor A2 de Adenosina/farmacologia , Animais , Morte Celular/efeitos dos fármacos , Citoproteção/efeitos dos fármacos , Ativação Enzimática/efeitos dos fármacos , Inativação Gênica , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Hepatócitos/patologia , Proteínas Quinases JNK Ativadas por Mitógeno/metabolismo , Lipídeos/análise , Masculino , Camundongos Endogâmicos BALB C , OxirreduçãoRESUMO
BACKGROUND/AIMS: The efficacy of ischemic preconditioning (IPC) in preventing reperfusion injury in human liver transplants is still questioned. Phosphoinositide-3-kinase (PI3K) is essential for IPC development in rodent livers. This work investigates whether PI3K-dependent signals might account for the inconsistent responses to IPC of transplanted human livers. METHODS: Forty livers from deceased donors were randomized to receive or not IPC before recovery. PI3K activation was evaluated in biopsies obtained immediately before IPC and 2 h after reperfusion by measuring the phosphorylation of the PI3K downstream kinase PKB/Akt and the levels of the PI3K antagonist phosphatase tensin-homologue deleted from chromosome 10 (PTEN). RESULTS: IPC increased PKB/Akt phosphorylation (p = 0.01) and decreased PTEN levels (p = 0.03) in grafts, but did not significantly ameliorate post-transplant reperfusion injury. By calculating T(2h)/T(0) PKB/Akt phosphorylation ratios, 10/19 (53%) of the preconditioned grafts had ratios above the control threshold (IPC-responsive), while the remaining nine grafts showed ratios comparable to controls (IPC-non-responsive). T(2h)/T(0) PTEN ratios were also decreased (p < or = 0.03) only in IPC-responsive grafts. The patients receiving IPC-responsive organs had ameliorated (p < or = 0.05) post-transplant aminotransferase and bilirubin levels, while prothrombin activity was unchanged. CONCLUSIONS: Impaired PI3K signaling might account for the variability in the responses to IPC of human grafts from deceased donors.
Assuntos
Precondicionamento Isquêmico , Transplante de Fígado/fisiologia , Fosfatidilinositol 3-Quinases/metabolismo , Traumatismo por Reperfusão/prevenção & controle , Adulto , Idoso , Idoso de 80 Anos ou mais , Biópsia , Feminino , Humanos , Fígado/enzimologia , Fígado/patologia , Masculino , Pessoa de Meia-Idade , PTEN Fosfo-Hidrolase/metabolismo , PTEN Fosfo-Hidrolase/fisiologia , Fosforilação , Proteínas Proto-Oncogênicas c-akt/metabolismo , Transdução de Sinais/fisiologia , Tolerância ao Transplante/fisiologiaRESUMO
UNLABELLED: The cellular mechanisms by which ischemic preconditioning increases liver tolerance to ischemia/reperfusion injury are still poorly understood. This study investigated the role of the hypoxia-inducible factor-1 (HIF-1) in the protection associated with the late phase of liver preconditioning. Late preconditioning was induced in primary cultured rat hepatocytes by a transient (10 minute) hypoxic stress or by 15 minutes incubation with the adenosine A(2A) receptors agonist CGS21680 24 hours before exposure to 90 minutes of hypoxia in a serum-free medium. Late preconditioning induced the nuclear translocation of HIF-1 and the expression of carbonic anhydrase IX (CAIX), a HIF-1-regulated transmembrane enzyme that catalyzes bicarbonate production. Such effects were associated with prevention of hepatocyte killing by hypoxia and the amelioration of intracellular acidosis and Na+ accumulation. The inhibition of PKC-mediated and PI3-kinase-mediated signals with, respectively, chelerythrine and wortmannin abolished HIF-1 activation and blocked both CAIX expression and the protective action of late preconditioning. CAIX expression was also prevented by interfering with the transcriptional activity of HIF-1 using a dominant negative HIF-1beta subunit. The inhibition of CAIX with acetazolamide or the block of bicarbonate influx with disodium-4-acetamido-4'-isothiocyanato-stilben-2,2'-disulfonate also reverted the protective effects of late preconditioning on intracellular acidosis and Na+ accumulation. CONCLUSION: The stimulation of adenosine A(2A) receptors induced late preconditioning in liver cells through the activation of HIF-1. HIF-1-induced expression of CAIX increases hepatocyte tolerance to ischemia by maintaining intracellular Na+ homeostasis. These observations along with the importance of HIF-1 in regulating cell survival indicates HIF-1 activation as a possible key event in liver protection by late preconditioning.
Assuntos
Adenosina/metabolismo , Hepatócitos/fisiologia , Fator 1 Induzível por Hipóxia/metabolismo , Precondicionamento Isquêmico , Fígado/irrigação sanguínea , Receptor A2A de Adenosina/metabolismo , Receptores Purinérgicos P1/metabolismo , Adenosina/análogos & derivados , Adenosina/farmacologia , Agonistas do Receptor A2 de Adenosina , Animais , Transporte Biológico , Anidrase Carbônica IV/metabolismo , Hipóxia Celular/fisiologia , Núcleo Celular/metabolismo , Células Cultivadas , Meios de Cultura Livres de Soro , Citoproteção , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Masculino , Fenetilaminas/farmacologia , Agonistas do Receptor Purinérgico P1 , Ratos , Ratos Wistar , Fatores de TempoRESUMO
Adenosine released by cells in injurious or hypoxic environments has tissue-protecting and anti-inflammatory effects, which are also a result of modulation of macrophage functions, such as vascular endothelial growth factor (VEGF) production. As VEGF is a well-known target of hypoxia-inducible factor 1 (HIF-1), we hypothesized that adenosine may activate HIF-1 directly. Our studies using subtype-specific adenosine receptor agonists and antagonists showed that by activating the A(2A) receptor, adenosine treatment induced HIF-1 DNA-binding activity, nuclear accumulation, and transactivation capacity in J774A.1 mouse macrophages. Increased HIF-1 levels were also found in adenosine-treated mouse peritoneal macrophages. The HIF-1 activation induced by the A(2A) receptor-specific agonist CGS21680 required the PI-3K and protein kinase C pathways but was not mediated by changes in iron levels. Investigation of the molecular basis of HIF-1 activation revealed the involvement of transcriptional and to a larger extent, translational mechanisms. HIF-1 induction triggered the expression of HIF-1 target genes involved in cell survival (aldolase, phosphoglycerate kinase) and VEGF but did not induce inflammation-related genes regulated by HIF-1, such as TNF-alpha or CXCR4. Our results show that the formation of adenosine and induction of HIF-1, two events which occur in response to hypoxia, are linked directly and suggest that HIF-1 activation through A(2A) receptors may contribute to the anti-inflammatory and tissue-protecting activity of adenosine.
Assuntos
Fator 1 Induzível por Hipóxia/metabolismo , Macrófagos Peritoneais/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Proteína Quinase C/metabolismo , Receptor A2A de Adenosina/metabolismo , Animais , Linhagem Celular , Feminino , Camundongos , Camundongos Endogâmicos , Organismos Livres de Patógenos EspecíficosRESUMO
Steatosis intensifies hepatic ischemia/reperfusion (I/R) injury increasing hepatocyte damage and hepatic inflammation. This study evaluates if this process is associated to a differential response of steatotic hepatocytes (HP) and Kupffer cells (KC) to I/R injury and investigates the molecular mechanisms involved. Control or steatotic (treated with 50 µmol palmitic acid, PA) mouse HP or KC were exposed to hypoxia/reoxygenation (H/R). C57BL/6 mice fed 9 week with control or High Fat diet underwent to partial hepatic IR. PA increased H/R damage of HP and further activated the ASK1-JNK axis stimulated by ER stress during H/R. PA also induced the production of oxidant species (OS), and OS prevention nullified the capacity of PA to increase H/R damage and ASK1/JNK stimulation. ASK1 inhibition prevented JNK activation and entirely protected HP damage. In KC, PA directly activated ER stress, ASK1 and p38 MAPK and increased H/R damage. However, in contrast to HP, ASK1 inhibition further increased H/R damage by preventing p38 MAPK activation. In mice liver, steatosis induced the expression of activated ASK1 in only KC, whereas I/R exposure of steatotic liver activated ASK1 expression also in HP. "In vivo", ASK1 inhibition prevented ASK1, JNK and p38 MAPK activation and protected I/R damage and expression of inflammatory markers. CONCLUSIONS: Lipids-induced ASK1 stimulation differentially affects HP and KC by promoting cytotoxic or protective signals. ASK1 increases H/R damage of HP by stimulating JNK and protects KC activating p38MAPK. These data support the potentiality of the therapeutic employment of ASK1 inhibitors that can antagonize the damaging effects of I/R upon fatty liver surgery by the contextual reduction of HP death and of KC-mediated reactions.
Assuntos
Fígado Gorduroso/genética , Hepatócitos/enzimologia , Células de Kupffer/enzimologia , Fígado/enzimologia , MAP Quinase Quinase Quinase 5/genética , Traumatismo por Reperfusão/genética , Animais , Dieta Hiperlipídica/efeitos adversos , Estresse do Retículo Endoplasmático/genética , Fígado Gorduroso/enzimologia , Fígado Gorduroso/etiologia , Fígado Gorduroso/patologia , Regulação da Expressão Gênica , Hepatócitos/efeitos dos fármacos , Hepatócitos/patologia , Células de Kupffer/efeitos dos fármacos , Células de Kupffer/patologia , Fígado/patologia , Fígado/cirurgia , MAP Quinase Quinase 4/genética , MAP Quinase Quinase 4/metabolismo , MAP Quinase Quinase Quinase 5/metabolismo , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Estresse Oxidativo , Ácido Palmítico/farmacologia , Cultura Primária de Células , Traumatismo por Reperfusão/enzimologia , Traumatismo por Reperfusão/patologia , Transdução de Sinais , Proteínas Quinases p38 Ativadas por Mitógeno/genética , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
Lipotoxicity and immunoinflammation are associated with the evolution of steatosis toward nonalcoholic steatohepatitis (NASH). This study reports the ability of adenosine A2a receptor (A2aR) activation to inhibit NASH development by modulating the responses of CD4+ T-helper (Th) cells to avoid an immuno-mediated potentiation of lipotoxicity. The effect of the A2aR agonist CGS21680 on immunoinflammatory signals, CD4+Th cell infiltration and immunolipotoxicity was analyzed in steatotic C57BL/6 mice fed with a methionine-choline-deficient (MCD) diet and in mouse hepatocytes exposed to palmitic acid (PA). CGS21680 inhibited NASH development in steatotic mice and decreased cytokines and chemokines involved in Th cell recruitment or polarization (namely CXCL10, CCL2, tumor necrosis factor alfa [TNFα], tumor growth factor [TGFß], and IL-12). CGS21680 also reduced the expansion of Th17, Th22, and Th1 cells and increased the immunosuppressive activity of T regulatory cells. In PA-treated mice hepatocytes, CGS21680 inhibited the production of CXCL10, TNFα, TGFß, IL-12, and CCL2; CGS21680 also prevented JNK-dependent lipotoxicity and its intensification by IL-17 or IL-17 plus IL-22 through Akt/PI3-kinase stimulation and inhibition of the negative regulator of PI3-kinase, (phosphatase and tensin homologue deleted from chromosome 10 (PTEN), which is upregulated by IL-17. In MCD livers, CGS21680 reduced JNK activation and PTEN expression and increased Akt phosphorylation. In conclusion, A2aR stimulation inhibited NASH development by reducing Th17 cell expansion and inhibiting the exacerbation of the IL-17-induced JNK-dependent lipotoxicity. These data promote the implementation of further studies to evaluate the potential clinical application of A2aR agonists that, by being able to function as both cytoprotective and immunomodulatory agents, could efficiently antagonize the multi-faced pathogenesis of NASH.
Assuntos
Lipídeos/toxicidade , Hepatopatia Gordurosa não Alcoólica/tratamento farmacológico , Hepatopatia Gordurosa não Alcoólica/imunologia , Receptor A2A de Adenosina/metabolismo , Transdução de Sinais/efeitos dos fármacos , Adenosina/análogos & derivados , Adenosina/farmacologia , Adenosina/uso terapêutico , Animais , Progressão da Doença , Ativação Enzimática/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Hepatócitos/metabolismo , Inflamação/imunologia , Inflamação/patologia , Masculino , Camundongos Endogâmicos C57BL , Hepatopatia Gordurosa não Alcoólica/enzimologia , Hepatopatia Gordurosa não Alcoólica/patologia , Fenetilaminas/farmacologia , Fenetilaminas/uso terapêutico , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , Linfócitos T Auxiliares-Indutores/efeitos dos fármacos , Linfócitos T Auxiliares-Indutores/imunologia , Linfócitos T Reguladores/efeitos dos fármacos , Linfócitos T Reguladores/imunologiaRESUMO
We investigated the signal mediators and the cellular events involved in the nitric oxide (NO)-induced hepatocyte resistance to oxygen deprivation in isolated hepatocytes treated with the NO donor (Z)-1-(N-methyl-N-[6-(N-methylammoniohexyl)amino])diazen-1-ium-1,2-diolate (NOC-9). NOC-9 greatly induced PI3K activation, as tested by phosphorylation of PKB/Akt. This effect was prevented by either 1H-(1,2,4)-oxadiazolo-(4,3)-quinoxalin-1-one, an inhibitor of the soluble guanylate cyclase (sGC), or KT5823, an inhibitor of cGMP-dependent kinase (cGK), as well as by farnesyl protein transferase inhibitor, which blocks the function of Ras GTPase. Bafilomycin A, an inhibitor of the lysosome-type vacuolar H+-ATPase, cytochalasin D, which disrupts the cytoskeleton-dependent organelle traffic, and wortmannin, which inhibits the PI3K-dependent traffic of lysosomes, all abolished the NOC-9-induced hepatocyte protection. The treatment with NOC-9 was associated with the PI3K-dependent peripheral translocation and fusion with the plasma membrane of lysosomes and the appearance at the cell surface of the vacuolar H+-ATPase. Inhibition of sGC, cGK, and Ras, as well as the inhibition of PI3K by wortmannin, prevented the exocytosis of lysosomes and concomitantly abolished the protective effect of NOC-9 on hypoxia-induced pHi and [Na+]i alterations and cell death. These data indicate that NO increases hepatocyte resistance to hypoxic injury by activating a pathway involving Ras, sGC, and cGK that determines PI3K-dependent exocytosis of lysosomes.
Assuntos
Exocitose/efeitos dos fármacos , Hepatócitos/efeitos dos fármacos , Precondicionamento Isquêmico , Lisossomos/efeitos dos fármacos , Óxido Nítrico/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Animais , Hipóxia Celular/efeitos dos fármacos , Proteínas Quinases Dependentes de GMP Cíclico/efeitos dos fármacos , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Inibidores Enzimáticos/farmacologia , Exocitose/fisiologia , Guanilato Ciclase , Lisossomos/metabolismo , Masculino , Fosfatidilinositol 3-Quinases/efeitos dos fármacos , Ratos , Ratos Wistar , Receptores Citoplasmáticos e Nucleares/efeitos dos fármacos , Receptores Citoplasmáticos e Nucleares/metabolismo , Guanilil Ciclase Solúvel , Triazenos/farmacologia , Proteínas Ativadoras de ras GTPase/efeitos dos fármacos , Proteínas Ativadoras de ras GTPase/metabolismoRESUMO
Liver hypoxia still represents an important cause of liver injury during shock and liver transplantation. We have investigated the protective effects of beta-alanine against hypoxic injury using isolated perfused rat livers and isolated rat hepatocyte suspensions. Perfusion with hypoxic Krebs-Henseleit buffer increased liver weight and caused a progressive release of lactate dehydrogenase (LDH) in the effluent perfusate. The addition of 5 mmol/l beta-alanine to the perfusion buffer completely prevented both weight increase and LDH leakage. These findings were confirmed by histological examinations showing that beta-alanine blocked the staining by trypan blue of either liver parenchymal and sinusoidal cells. Studies performed in isolated hepatocytes revealed that beta-alanine exerted its protective effects by interfering with Na+ accumulation induced by hypoxia. The addition of gamma-amino-butyric acid, which interfered with beta-alanine uptake by the hepatocytes or of Na+/H+ ionophore monensin, reverted beta-alanine protection in either hepatocyte suspensions or isolated perfused livers. We also observed that liver receiving beta-alanine were also protected against LDH leakage and weight increase caused by the perfusion with an hyposmotic (205 mosm) hypoxic buffer obtained by decreasing NaCl content from 118 to 60 mmol/l. This latter effect was not reverted by blocking K+ efflux from hepatocyte with BaCl(2) (1mmol/l). Altogether these results indicated that beta-alanine protected against hypoxic liver injury by preventing Na+ overload and by increasing liver resistance to osmotic stress consequent to the impairment of ion homeostasis during hypoxia.
Assuntos
Citoproteção , Fígado/efeitos dos fármacos , beta-Alanina/farmacologia , Animais , Hipóxia Celular , Sobrevivência Celular , Células Cultivadas , Relação Dose-Resposta a Droga , Soluções Hipotônicas , Fígado/patologia , Perfusão , Ratos , Azul TripanoRESUMO
Ischemic preconditioning (IP) of the liver by a brief interruption of the blood flow protects the damage induced by a subsequent ischemia/reperfusion (I/R) preventing parenchymal and nonparenchymal liver cell damage. The discovery of IP has shown the existence of intrinsic systems of cytoprotection whose activation can stave off the progression of irreversible tissue damage. Deciphering the molecular mediators that underlie the cytoprotective effects of preconditioning can pave the way to important therapeutic possibilities. Pharmacological activation of critical mediators of IP would be expected to emulate or even to intensify its salubrious effects. In vitro and in vivo studies have demonstrated the role of the adenosine A2a receptor (A2aR) as a trigger of liver IP. This review will provide insight into the phenotypic changes that underline the resistance to death of liver cells preconditioned by pharmacological activation of A2aR and their implications to develop innovative strategies against liver IR damage.
Assuntos
Citoproteção/efeitos dos fármacos , Fígado/efeitos dos fármacos , Receptor A2A de Adenosina/uso terapêutico , Traumatismo por Reperfusão/tratamento farmacológico , Hepatócitos/efeitos dos fármacos , Humanos , Precondicionamento Isquêmico , Fígado/irrigação sanguínea , Fígado/lesões , Traumatismo por Reperfusão/fisiopatologia , Transdução de Sinais/efeitos dos fármacosRESUMO
Nitric oxide (NO) improves liver resistance to hypoxia/reperfusion injury acting as a mediator of hepatic preconditioning. However, the mechanisms involved are still poorly understood. In this study, we have investigated the mechanisms by which short-term exposure to the NO donor (Z)-1-(N-methyl-N-[6-(N-methylammoniohexyl)amino])-diazen-1-ium-1,2-diolate (NOC-9) increases hepatocyte tolerance to hypoxic injury. Isolated rat hepatocytes preincubated 15 min with NOC-9 (0.250 mM) became resistant to the killing caused by hypoxia. NOC-9 cytoprotection did not involve the activation of protein kinase C, but was instead blocked by inhibiting soluble guanylate cyclase with 1H-(1,2,4)-oxadiazolo-(4,3) quinoxalin-1-one (ODQ) (50 microM) or cGMP-dependent kinase (cGK) with KT 5823 (5 microM). Conversely, cGMP analogue, 8Br-cGMP (50 microM) mimicked the effect of NOC-9. Western blot analysis revealed that hepatocyte treatment with NOC-9 or 8Br-cGMP significantly increased dual phosphorylation of p38 MAPK. The activation of p38 MAPK was abolished by inhibiting guanylate cyclase or cGK. Pretreatment with NO significantly reduced intracellular Na(+) accumulation in hypoxic hepatocytes. This effect was reverted by KT 5823 as well as by the p38 MAPK inhibitor SB203580. SB203580 also reverted NOC-9 protection against hypoxic injury. Altogether, these results demonstrated that NO can induce hepatic preconditioning by activating p38 MAPK through a guanylate cyclase/cGK-mediated pathway.
Assuntos
Hepatócitos/metabolismo , Precondicionamento Isquêmico , Óxido Nítrico/metabolismo , Transdução de Sinais , Animais , Western Blotting , Carbazóis/farmacologia , Proteínas Quinases Dependentes de GMP Cíclico/metabolismo , Relação Dose-Resposta a Droga , Inibidores Enzimáticos/farmacologia , Radicais Livres , Guanilato Ciclase/metabolismo , Hipóxia , Imidazóis/farmacologia , Indóis/farmacologia , Fígado/lesões , Fígado/patologia , Proteínas Quinases Ativadas por Mitógeno/metabolismo , Modelos Biológicos , Fosforilação , Proteína Quinase C/metabolismo , Piridinas/farmacologia , Ratos , Sódio/metabolismo , Fatores de Tempo , Proteínas Quinases p38 Ativadas por MitógenoRESUMO
Ischemia/reperfusion (I/R) injury still represents an important cause of morbidity following hepatic surgery and limits the use of marginal livers in hepatic transplantation. Transient blood flow interruption followed by reperfusion protects tissues against damage induced by subsequent I/R. This process known as ischemic preconditioning (IP) depends upon intrinsic cytoprotective systems whose activation can inhibit the progression of irreversible tissue damage. Compared to other organs, liver IP has additional features as it reduces inflammation and promotes hepatic regeneration. Our present understanding of the molecular mechanisms involved in liver IP is still largely incomplete. Experimental studies have shown that the protective effects of liver IP are triggered by the release of adenosine and nitric oxide and the subsequent activation of signal networks involving protein kinases such as phosphatidylinositol 3-kinase, protein kinase C δ/ε and p38 MAP kinase, and transcription factors such as signal transducer and activator of transcription 3, nuclear factor-κB and hypoxia-inducible factor 1. This article offers an overview of the molecular events underlying the preconditioning effects in the liver and points to the possibility of developing pharmacological approaches aimed at activating the intrinsic protective systems in patients undergoing liver surgery.
Assuntos
Precondicionamento Isquêmico , Fígado/irrigação sanguínea , Fígado/patologia , Traumatismo por Reperfusão/patologia , Adenosina/metabolismo , Trifosfato de Adenosina/metabolismo , Humanos , Fator 1 Induzível por Hipóxia/metabolismo , Óxido Nítrico/metabolismo , Fatores de Transcrição STAT/metabolismo , Transdução de Sinais/fisiologiaRESUMO
BACKGROUND/AIMS: Chronic hepatitis C (CHC) is often associated with auto-immune reactions. In the light of the role of alcohol in promoting CHC progression, we have investigated the possible presence of auto-reactivity against the ethanol-inducible cytochrome P4502E1 (CYP2E1) in CHC patients with and without alcohol consumption. METHODS: The IgG reactivity against recombinant human CYP2E1 was evaluated by solid-phase immunoassays in 102 CHC patients with different alcohol consumption and 59 HCV-free controls. RESULTS: Auto-antibodies against CYP2E1 were significantly (p<0.0001) increased in CHC patients as compared to controls. Anti-CYP2E1 IgG above the 97th percentile in the controls were evident in 41 (40%) CHC patients. Competition experiments revealed that CYP2E1 recognition was not due to the cross-reactivity with CYP2D6. The detection of anti-CYP2E1 IgG was unrelated to alcohol consumption and no difference in gender, age, aminotransferase levels and virus genotype was evident among the patients with or without anti-CYP2E1 auto-antibodies. However, anti-CYP2E1 auto-reactivity was significantly (p=0.025) associated with the severity of periportal/periseptal interface hepatitis. Moreover, confocal microscopy demonstrated that anti-CYP2E1 IgG associated with CHC recognized CYP2E1 exposed on the outer side of hepatocyte plasma membranes. CONCLUSIONS: HCV infection favours the breaking of self-tolerance against CYP2E1 that might contribute to hepatocyte injury.
Assuntos
Autoanticorpos/sangue , Citocromo P-450 CYP2E1/imunologia , Hepatite C Crônica/imunologia , Adulto , Idoso , Consumo de Bebidas Alcoólicas , Animais , Membrana Celular/metabolismo , Citocromo P-450 CYP2E1/metabolismo , Feminino , Hepatite C Crônica/metabolismo , Hepatite C Crônica/fisiopatologia , Hepatócitos/metabolismo , Humanos , Imunoglobulina G/imunologia , Masculino , Microscopia Confocal , Pessoa de Meia-Idade , Ratos , Ratos Sprague-Dawley , Índice de Gravidade de Doença , Distribuição TecidualRESUMO
BACKGROUND/AIMS: Glycine hepatoprotection is well known. However, the mechanisms involved are still poorly characterized. METHODS: Glycine protection was investigated in isolated rat hepatocytes pretreated with 2 mmol/L glycine 15 min before incubation under hypoxic conditions. RESULTS: Glycine significantly reduced Na+ overload and hepatocyte death caused by hypoxia. Glycine protection required the activation of a signal pathway involving Src, Pyk2 and p38 MAP kinases. Glycine treatment also induced a 11% increase of hepatocyte volume and transient ATP release. The prevention of cell swelling by hepatocyte incubation in a hypertonic medium as well as the degradation of extracellular ATP with apyrase or the block P2 purinergic receptors with suramin reverted glycine-induced cytoprotection and inhibited Src, Pyk2 and p38 MAPK activation. Glycine down-modulated Na+/H+ exchanger (NHE) activity, without affecting the development of intracellular acidosis during hypoxia. Such an effect was reverted by inhibiting p38 MAPK that also abolished glycine protection against Na+ overload caused by hypoxia. CONCLUSIONS: Glycine-induced ATP release in response to a moderate hepatocyte swelling led to the autocrine stimulation of P2 receptors and to the activation of Src, Pyk2 and p38 MAPK that increased hepatocyte resistance to hypoxia by preventing Na+ influx through NHE.
Assuntos
Hipóxia Celular/fisiologia , Citoproteção , Glicina/farmacologia , Hepatócitos/efeitos dos fármacos , Hepatócitos/enzimologia , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismo , Trifosfato de Adenosina/metabolismo , Animais , Comunicação Autócrina , Ativação Enzimática , Quinase 2 de Adesão Focal/metabolismo , Hepatócitos/metabolismo , Homeostase/efeitos dos fármacos , Masculino , Ratos , Ratos Wistar , Receptores Purinérgicos P2/metabolismo , Transdução de Sinais , Sódio/metabolismo , Trocadores de Sódio-Hidrogênio/metabolismo , Água/metabolismo , Quinases da Família src/metabolismoRESUMO
BACKGROUND/AIMS: ATP stimulation of purinergic P2 receptors (P2YR and P2XR) regulates several hepatic functions. Here we report the involvement of ATP-mediated signals in enhancing hepatocyte tolerance to lethal stress. METHODS: The protection given by purinergic agonists was investigated in rat hepatocytes exposed to hypoxia. RESULTS: ATP released after hypotonic stress (200 mOsm/L) as well as P2YR agonists prevented hepatocyte killing by hypoxia with efficiency ranking UTP > ATPgammaS > ADPbetaS, whereas the P2XR agonist, methylene-adenosine-5'-triphosphate, was ineffective. Adenosine-5'-O-3-thiotriphosphate (ATPgammaS; 100 micromol/L) also prevented Na+ -overload in hypoxic cells by inhibiting the Na+/H+ exchanger, without interfering with hypoxic acidosis. ATPgammaS activated Src and promoted a Src-dependent stimulation of both ERK1/2 and p38MAPK. Blocking p38MAPK with SB203580 reverted the protection given by ATPgammaS on both cell viability and Na+ accumulation, whereas ERK1/2 inhibition with PD98058 was ineffective. An increased phosphorylation of ERK1/2 was also evident in untreated hypoxic hepatocytes. PD98058 ameliorated Na+ accumulation and cell death caused by hypoxia. Hepatocyte pre-treatment with ATPgammaS reverted ERK1/2 activation in hypoxic cells. SB203580 blocked the effects of ATPgammaS on both ERK1/2 and Na+/H+ exchanger. CONCLUSIONS: The activation of p38MAPK by P2Y2R increases hepatocyte resistance to hypoxia by down-modulating ERK1/2-mediated signals that promote Na+ influx through the Na+/H+ exchanger.