RESUMEN
Hepatocyte to biliary transdifferentiation has been documented in various models of bile duct injury. In this process, mature hepatocytes transform into mature biliary epithelial cells by acquiring biliary phenotypic markers. Several signaling pathways including PI3 kinase, Notch, Hes1, Sox9, and Hippo are shown to be involved in the process. However, whether Oct4 is involved in hepatocyte to biliary transdifferentiation is unknown. We investigated the role of Oct4 in hepatocyte to biliary transdifferentiation utilizing an in vitro organoid culture system as a model of transdifferentiation. Oct4 was inhibited using adenovirus containing Oct4 shRNA. Hepatocyte-specific HNF-4α and biliary-specific HNF-1ß and CK19 expression were assessed to gauge the extent of transdifferentiation. Oct4 was induced during hepatocyte to biliary transdifferentiation. Oct4 inhibition significantly downregulated the appearance of biliary cells from hepatocytes. This was accompanied by a significant downregulation of signaling pathways including Notch, Sox9, and Hippo. Our findings suggest that Oct4 is crucial for hepatocyte to biliary transdifferentiation and maturation and that it acts upstream of Notch, Sox9, and Hippo signaling in this model. This finding identifies new signaling through Oct4 in plasticity between hepatocytes and biliary epithelial cells, which can be potentially utilized to identify new strategies in chronic biliary diseases.
Asunto(s)
Transdiferenciación Celular , Hepatocitos/metabolismo , Factor 3 de Transcripción de Unión a Octámeros/metabolismo , Animales , Conductos Biliares/citología , Células Cultivadas , Factores Nucleares del Hepatocito/genética , Factores Nucleares del Hepatocito/metabolismo , Hepatocitos/citología , Masculino , Factor 3 de Transcripción de Unión a Octámeros/genética , Organoides/citología , Organoides/metabolismo , Ratas , Ratas Endogámicas F344 , Receptores Notch/genética , Receptores Notch/metabolismo , Factor de Transcripción SOX9/genética , Factor de Transcripción SOX9/metabolismo , Transducción de SeñalRESUMEN
Previous studies from our laboratory have found glypican 3 (GPC3) as a negative regulator of growth. CD81 was found to be a binding partner for GPC3, and its expression and co-localization with GPC3 increased at the end of hepatocyte proliferation. However, the mechanisms through which these two molecules might regulate liver regeneration are not known. We tested the hypothesis that GPC3 down-regulates the hedgehog (HH) signaling pathway by competing with patched-1 for HH binding. We found decreased GPC3-Indian HH binding at peak proliferation in mice followed by increase in glioblastoma 1 protein (effector of HH signaling). We performed a yeast two-hybrid assay and identified hematopoietically expressed homeobox (Hhex, a known transcriptional repressor) as a binding partner for CD81. We tested the hypothesis that Hhex binding to CD81 keeps it outside the nucleus. However, when GPC3 binds to CD81, CD81-Hhex binding decreases, resulting in nuclear translocation of Hhex and transcriptional repression. In support of this, we found decreased GPC3-CD81 binding at hepatocyte proliferation peak, increased CD81-Hhex binding, and decreased nuclear Hhex. GPC3 transgenic mice were used as an additional tool to test our hypothesis. Overall, our data suggest that GPC3 down-regulates cell proliferation by binding to HH and down-regulating the HH signaling pathway and binding with CD81, thus making it unavailable to bind to Hhex and causing its nuclear translocation.
Asunto(s)
Proliferación Celular , Glipicanos/metabolismo , Proteínas Hedgehog/metabolismo , Hepatocitos/metabolismo , Proteínas de Homeodominio/metabolismo , Regeneración Hepática/fisiología , Tetraspanina 28/metabolismo , Factores de Transcripción/metabolismo , Animales , Biomarcadores/metabolismo , Western Blotting , Regulación hacia Abajo , Hepatocitos/fisiología , Inmunohistoquímica , Masculino , Ratones , Ratones TransgénicosRESUMEN
UNLABELLED: Reprogramming factors have been used to induce pluripotent stem cells as an alternative to somatic cell nuclear transfer technology in studies targeting disease models and regenerative medicine. The neuronal repressor RE-1 silencing transcription factor (REST) maintains self-renewal and pluripotency in mouse embryonic stem cells by maintaining the expression of Oct3/4, Nanog, and cMyc. We report that primary hepatocytes express REST and most of the reprogramming factors in culture. Their expression is up-regulated by hepatocyte growth factor (HGF) and epidermal growth factor (EGF). REST inhibition results in down-regulation of reprogramming factor expression, increased apoptosis, decreased proliferation, and cell death. The reprogramming factors are also up-regulated after 70% partial hepatectomy in vivo. CONCLUSION: These findings show that genes inducing the iPS phenotype, even though expressed at lower levels than embryonic stem cells, nonetheless are associated with control of apoptosis and cell proliferation in hepatocytes in culture and may play a role in such processes during liver regeneration.
Asunto(s)
Apoptosis/genética , Hepatocitos/citología , Regeneración Hepática/genética , Proteínas del Tejido Nervioso/genética , Proteínas Represoras/genética , Análisis de Varianza , Animales , Western Blotting , Proliferación Celular , Supervivencia Celular/genética , Células Cultivadas , Proteínas Co-Represoras , ADN Complementario/biosíntesis , Modelos Animales de Enfermedad , Hepatocitos/metabolismo , Técnicas In Vitro , Células Madre Pluripotentes Inducidas/metabolismo , Masculino , Ratones , Proteínas del Tejido Nervioso/metabolismo , Fenotipo , ARN/análisis , Ratas Endogámicas F344 , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Valores de Referencia , Proteínas Represoras/metabolismoRESUMEN
UNLABELLED: TCBOPOP (1,4-bis [2-(3,5-dichaloropyridyloxy)] benzene) an agonist of the constitutive androstane receptor (CAR), produces rapid hepatocyte hyperplasia and hepatomegaly in the absence of hepatic injury. In this study we demonstrate that integrin-linked kinase (ILK), which is involved in transmission of the extracellular matrix (ECM) signaling by way of integrin receptors, plays an important role in regulating TCPOBOP-induced proliferation of hepatocytes and hepatomegaly. Hepatocyte-specific ILK knockout mice (ILK/liver-/- mice) and wildtype mice (WT) were given a single dose of TCPOBOP (3 mg/kg) by oral gavage. Mice were sacrificed at days 1, 2, 5, and 7 after TCPOBOP administration. WT mice showed maximum proliferation on days 1 and 2, which came back to baseline levels by days 5 and 7 after TCPOBOP administration. The ILK/liver-/- mice, on the other hand, showed a prolonged and a sustained proliferative response as evident by an increased number of proliferative cell nuclear antigen assay (PCNA)-positive cells even at days 5 and 7 after TCPOBOP administration. At day 7 the WT mice showed close to a 2.5-fold increase in liver weight, whereas the ILK/liver-/- mice showed a 3.7-fold increase in liver weight. The prolonged proliferative response in the ILK/liver-/- mice seems to be due to sustained induction of CAR leading to sustained induction of c-Myc, which is known to be a key mediator of TCPOPOP-CAR induced direct liver hyperplasia. CONCLUSION: The data indicate that ECM-mediated signaling by way of ILK is essential for adjustment of final liver size and proper termination of TCPOBOP-induced proliferation of hepatocytes.
Asunto(s)
Hepatocitos/metabolismo , Hepatocitos/patología , Hepatomegalia/inducido químicamente , Hepatomegalia/patología , Proteínas Serina-Treonina Quinasas/metabolismo , Piridinas/efectos adversos , Animales , Peso Corporal/fisiología , Ciclo Celular/fisiología , Proliferación Celular , Modelos Animales de Enfermedad , Matriz Extracelular/fisiología , Hepatomegalia/metabolismo , Ratones , Ratones Noqueados , Tamaño de los Órganos/fisiología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , Transducción de Señal/fisiologíaRESUMEN
UNLABELLED: Glypican 3 (GPC3) is a family of glycosylphosphatidylinositol-anchored, cell-surface heparan sulfate proteoglycans. Loss-of-function mutations of GPC3 cause Simpson-Golabi-Behmel syndrome characterized by overgrowth of multiple organs, including liver. Our previous study showed that in GPC3 transgenic (TG) mice, hepatocyte-targeted overexpression of GPC3 suppresses hepatocyte proliferation and liver regeneration after partial hepatectomy and alters gene expression profiles and potential cell cycle-related proteins. This study investigates the role of GPC3 in hepatocyte proliferation and hepatomegaly induced by the xenobiotic mitogens phenobarbital (PB) and TCPOBOP (1, 4-bis [2-(3, 5-dichloropyridyloxy)] benzene). Wildtype (WT) and GPC3 TG mice were given 0.1% PB in drinking water for 10 days or a single dose of TCPOBOP (3 mg/kg) by oral gavage. At day 5 the WT mice showed a 2.2- and 3.0-fold increase in liver weight, whereas the GPC3 TG mice showed a 1.3- and 1.6-fold increase in liver weight after PB and TCPOBOP administration, respectively. There was a significant suppression of proliferative response in the GPC3 TG mice, as assessed by percent of Ki67-positive hepatocyte nuclei. Moreover, gene array analysis showed a panel of changes in the gene expression profile of TG mice, both before and after administration of the xenobiotic mitogens. Expression of cell cycle-related genes in the TG mice was also decreased compared to the WT mice. CONCLUSION: Our results indicate that in GPC3 TG mice, hepatocyte-targeted overexpression of GPC3 plays an important role for regulation of liver size and termination of hepatocyte proliferation induced by the xenobiotic mitogens PB and TCPOBOP, comparable to the effects seen in the GPC3 TG mice during liver regeneration after partial hepatectomy.
Asunto(s)
Proliferación Celular/efectos de los fármacos , Glipicanos/genética , Hepatocitos/efectos de los fármacos , Hepatocitos/fisiología , Hepatomegalia/genética , Fenobarbital/farmacología , Piridinas/farmacología , Animales , Regulación de la Expresión Génica , Genes cdc , Hepatomegalia/inducido químicamente , Ratones , Ratones TransgénicosRESUMEN
We have previously reported that among the other death proteins, hepatic secretory phospholipase A2 (sPLA2) is a leading mediator of progression of liver injury initiated by CCl4 in rats. The aim of our present study was to test the hypothesis that increased hepatic sPLA2 released after acetaminophen (APAP) challenge mediates progression of liver injury in wild type (WT) and COX-2 knockout (KO) mice. COX-2 WT and KO mice were administered a normally non lethal dose (400 mg/kg) of acetaminophen. The COX-2 KO mice suffered 60% mortality compared to 100% survival of the WT mice, suggesting higher susceptibility of COX-2 KO mice to sPLA2-mediated progression of acetaminophen hepatotoxicity. Liver injury was significantly higher at later time points in the KO mice compared to the WT mice indicating that the abatement of progression of injury requires the presence of COX-2. This difference in hepatotoxicity was not due to increased bioactivation of acetaminophen as indicated by unchanged cyp2E1 protein and covalently bound ¹4C-APAP in the livers of KO mice. Hepatic sPLA2 activity and plasma TNF-α were significantly higher after APAP administration in the KO mice. This was accompanied by a corresponding fall in hepatic PGE2 and lower compensatory liver regeneration and repair (³H-thymidine incorporation) in the KO mice. These results suggest that hindered compensatory tissue repair and poor resolution of inflammation for want of beneficial prostaglandins render the liver very vulnerable to sPLA2-mediated progression of liver injury. These findings are consistent with the destructive role of sPLA2 in the progression and expansion of tissue injury as a result of continued hydrolytic breakdown of plasma membrane phospholipids of perinecrotic hepatocytes unless mitigated by sufficient co-induction of COX-2.
Asunto(s)
Acetaminofén/toxicidad , Analgésicos no Narcóticos/toxicidad , Enfermedad Hepática Inducida por Sustancias y Drogas/etiología , Ciclooxigenasa 2/genética , Fosfolipasas A2 Secretoras/metabolismo , Animales , Enfermedad Hepática Inducida por Sustancias y Drogas/enzimología , Enfermedad Hepática Inducida por Sustancias y Drogas/fisiopatología , Dinoprostona/metabolismo , Progresión de la Enfermedad , Regeneración Hepática/fisiología , Masculino , Ratones , Ratones Noqueados , Sobrevida , Factores de Tiempo , Factor de Necrosis Tumoral alfa/sangreRESUMEN
Particularly interesting new cysteine-histidine-rich protein (PINCH) protein is part of the ternary complex known as the IPP (integrin linked kinase (ILK)-PINCH-Parvin-α) complex. PINCH itself binds to ILK and to another protein known as Rsu-1 (Ras suppressor 1). We generated PINCH 1 and PINCH 2 Double knockout mice (referred as PINCH DKO mice). PINCH2 elimination was systemic whereas PINCH1 elimination was targeted to hepatocytes. The genetically modified mice were born normal. The mice were sacrificed at different ages after birth. Soon after birth, they developed abnormal hepatic histology characterized by disorderly hepatic plates, increased proliferation of hepatocytes and biliary cells and increased deposition of extracellular matrix. After a sustained and prolonged proliferation of all epithelial components, proliferation subsided and final liver weight by the end of 30 weeks in livers with PINCH DKO deficient hepatocytes was 40% larger than the control mice. The livers of the PINCH DKO mice were also very stiff due to increased ECM deposition throughout the liver, with no observed nodularity. Mice developed liver cancer by one year. These mice regenerated normally when subjected to 70% partial hepatectomy and did not show any termination defect. Ras suppressor 1 (Rsu-1) protein, the binding partner of PINCH is frequently deleted in human liver cancers. Rsu-1 expression is dramatically decreased in PINCH DKO mouse livers. Increased expression of Rsu-1 suppressed cell proliferation and migration in HCC cell lines. These changes were brought about not by affecting activation of Ras (as its name suggests) but by suppression of Ras downstream signaling via RhoGTPase proteins. In conclusion, our studies suggest that removal of PINCH results in enlargement of liver and tumorigenesis. Decreased levels of Rsu-1, a partner for PINCH and a protein often deleted in human liver cancer, may play an important role in the development of the observed phenotype.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales/metabolismo , Carcinogénesis/metabolismo , Carcinogénesis/patología , Proteínas con Dominio LIM/metabolismo , Hígado/metabolismo , Hígado/patología , Proteínas de la Membrana/metabolismo , Factores de Transcripción/metabolismo , Proteínas Adaptadoras Transductoras de Señales/deficiencia , Animales , Apoptosis , Peso Corporal , Carcinoma Hepatocelular/metabolismo , Carcinoma Hepatocelular/patología , Proliferación Celular , Regulación hacia Abajo , Matriz Extracelular/metabolismo , Hepatocitos/metabolismo , Hepatocitos/patología , Humanos , Cinética , Proteínas con Dominio LIM/deficiencia , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patología , Regeneración Hepática , Proteínas de la Membrana/deficiencia , Ratones , Ratones Noqueados , Modelos Biológicos , Tamaño de los Órganos , Ratas , Transducción de Señal , Regulación hacia ArribaRESUMEN
Our previous study [Bhave, V. S., Donthamsetty, S., Latendresse, J. R., Muskhelishvili, L., and Mehendale, H. M. 2008-this issue. Secretory phospholipase A(2) mediates progression of acute liver injury in the absence of sufficient COX-2. Toxicol Appl Pharmacol] showed that in the absence of sufficient induction and co-presence of cyclooxygenase-2 (COX-2), secretory phospholipase A(2) (sPLA(2)) appearing in the intercellular spaces for cleanup of post-necrotic debris seems to contribute to the progression of toxicant-initiated liver injury, possibly by hydrolysis of membrane phospholipids of hepatocytes in the perinecrotic areas. To further test our hypothesis on the protective role of COX-2, male Fisher-344 rats were administered a selective COX-2 inhibitor, NS-398, and then challenged with a moderately toxic dose of CCl(4). This led to a 5-fold increase in the susceptibility of the COX-2 inhibited rats to CCl(4) hepatotoxicity and mortality. The CCl(4) bioactivating enzyme CYP2E1 protein, CYP2E1 enzyme activity, and the (14)CCl(4)-derived radiolabel covalently bound to the liver proteins were unaffected by the COX-2 inhibitor suggesting that the increased hepatotoxic sensitivity of the COX-2 inhibited rats was not due to higher bioactivation of CCl(4). Further investigation showed that this increased mortality was due to higher plasma and hepatic sPLA(2) activities, inhibited PGE(2) production, and progression of liver injury as compared to the non-intervened rats(.) In conclusion, inhibition of COX-2 mitigates the tissue protective mechanisms associated with COX-2 induction, which promotes sPLA(2)-mediated progression of liver injury in an acute liver toxicity model. Because increased sPLA(2) activity in the intercellular space is associated with increased progression of injury, and induced COX-2 is associated with hepatoprotection, ratios of hepatic COX-2 and sPLA(2) activities may turn out to be a useful tool in predicting the extent of hepatotoxicities.
Asunto(s)
Inhibidores de la Ciclooxigenasa 2/toxicidad , Ciclooxigenasa 2/metabolismo , Hígado/efectos de los fármacos , Fosfolipasas A2 Secretoras/metabolismo , Enfermedad Aguda , Alanina Transaminasa/sangre , Animales , Western Blotting , Radioisótopos de Carbono , Tetracloruro de Carbono/administración & dosificación , Tetracloruro de Carbono/toxicidad , Intoxicación por Tetracloruro de Carbono/mortalidad , Aceite de Maíz/administración & dosificación , Inhibidores de la Ciclooxigenasa 2/administración & dosificación , Citocromo P-450 CYP2E1/metabolismo , Dinoprostona/metabolismo , Progresión de la Enfermedad , Sinergismo Farmacológico , Hígado/lesiones , Hígado/metabolismo , Masculino , Microsomas Hepáticos/efectos de los fármacos , Microsomas Hepáticos/metabolismo , Nitrobencenos/administración & dosificación , Nitrobencenos/toxicidad , Nitrofenoles/metabolismo , Ratas , Ratas Endogámicas F344 , Sulfonamidas/administración & dosificación , Sulfonamidas/toxicidad , Tasa de SupervivenciaRESUMEN
The objective was to investigate if the hepatotoxic sensitivity in nonalcoholic steatohepatitic mice to acetaminophen (APAP) is due to downregulation of nuclear receptor PPARalpha via lower cell division and tissue repair. Male Swiss Webster mice fed methionine and choline deficient diet for 31 days exhibited NASH. On the 32nd day, a marginally toxic dose of APAP (360 mg/kg, ip) yielded 70% mortality in steatohepatitic mice, while all non steatohepatitic mice receiving the same dose survived. (14)C-APAP covalent binding, CYP2E1 protein, and enzyme activity did not differ from the controls, obviating increased APAP bioactivation as the cause of amplified APAP hepatotoxicity. Liver injury progressed only in steatohepatitic livers between 6 and 24 h. Cell division and tissue repair assessed by (3)H-thymidine incorporation and PCNA were inhibited only in the steatohepatitic mice given APAP suggesting that higher sensitivity of NASH liver to APAP-induced hepatotoxicity was due to lower tissue repair. The hypothesis that impeded liver tissue repair in steatohepatitic mice was due to downregulation of PPARalpha was tested. PPARalpha was downregulated in NASH. To investigate whether downregulation of PPARalpha in NASH is the critical mechanism of compromised liver tissue repair, PPARalpha was induced in steatohepatitic mice with clofibrate (250 mg/kg for 3 days, ip) before injecting APAP. All clofibrate pretreated steatohepatitic mice receiving APAP exhibited lower liver injury, which did not progress and the mice survived. The protection was not due to lower bioactivation of APAP but due to higher liver tissue repair. These findings suggest that inadequate PPARalpha expression in steatohepatitic mice sensitizes them to APAP hepatotoxicity.
Asunto(s)
Acetaminofén/toxicidad , Clofibrato/farmacología , Hígado Graso/metabolismo , Hígado/efectos de los fármacos , PPAR alfa/biosíntesis , Adenosina Trifosfato/análisis , Alanina Transaminasa/sangre , Animales , Citocromo P-450 CYP2E1/metabolismo , Citoprotección , Replicación del ADN , Masculino , Ratones , Estrés Oxidativo , Antígeno Nuclear de Célula en Proliferación/análisisRESUMEN
Previous studies have shown that injury initiated by toxicants progresses even after most of the toxicant is eliminated from the body. One mechanism of progression of injury is the extracellular appearance of hydrolytic enzymes following leakage or upon cell lyses. Under normal conditions, after exposure to low to moderate doses of toxicants, secretory phospholipase A(2) (sPLA(2)) and other hydrolytic enzymes are known to appear in the extracellular spaces in order to cleanup the post-necrotic debris in tissues. We tested the hypothesis that sPLA(2) contributes to progression of toxicant-initiated liver injury because of hydrolysis of membrane phospholipids of hepatocytes in the perinecrotic areas in the absence of sufficient cyclooxygenase-2 (COX-2). Male Sprague-Dawley rats were administered either a moderately hepatotoxic dose (MD, 2 ml CCl(4)/kg, ip) or a highly hepatotoxic dose (HD, 3 ml CCl(4)/kg, ip) of CCl(4). After MD, liver sPLA(2) and COX-2 were co-localized in the necrotic and perinecrotic areas and their activities in plasma and liver increased before decreasing in tandem with liver injury (ALT and histopathology) leading to 100% survival. In contrast, after the HD, high extracellular and hepatic sPLA(2) activities were accompanied by minimal COX-2 activity and localization in the liver throughout the time course. This led to progression of liver injury and 70% mortality. These data suggested a destructive role of sPLA(2) in the absence of sufficient COX-2. Time- and dose-dependent destruction of hepatocytes by sPLA(2) in isolated hepatocyte incubations confirmed the destructive ability of sPLA(2) when present extracellularly, suggesting its ability to spread injury in vivo. These findings suggest that sPLA(2), secreted for cleanup of necrotic debris upon initiation of hepatic necrosis, requires the co-presence of sufficiently induced COX-2 activity to prevent the run-away destructive action of sPLA(2) in the absence of the tissue protective mechanisms afforded by COX-2 induction.
Asunto(s)
Ciclooxigenasa 2/metabolismo , Hepatocitos/efectos de los fármacos , Hígado/efectos de los fármacos , Fosfolipasas A2 Secretoras/metabolismo , Enfermedad Aguda , Alanina Transaminasa/metabolismo , Animales , Tetracloruro de Carbono/administración & dosificación , Tetracloruro de Carbono/toxicidad , Intoxicación por Tetracloruro de Carbono/mortalidad , Supervivencia Celular/efectos de los fármacos , Ciclooxigenasa 1/metabolismo , Dinoprostona/metabolismo , Progresión de la Enfermedad , Relación Dosis-Respuesta a Droga , Hepatocitos/metabolismo , Hepatocitos/patología , Inmunohistoquímica , Inyecciones Intraperitoneales , L-Lactato Deshidrogenasa/metabolismo , Hígado/lesiones , Hígado/metabolismo , Masculino , Modelos Biológicos , Ratas , Ratas Sprague-Dawley , Tasa de Supervivencia , Factores de TiempoRESUMEN
UNLABELLED: This study tested whether hepatic steatosis sensitizes liver to toxicant-induced injury and investigated the potential mechanisms of hepatotoxic sensitivity. Male Sprague-Dawley rats were fed a methionine- and choline-deficient diet for 31 days to induce steatosis. On the 32nd day, administration of a nonlethal dose of CCl4 (2 mL/kg, intraperitoneally) yielded 70% mortality in steatotic rats 12-72 hours after CCl4 administration, whereas all nonsteatotic rats survived. Neither CYP2E1 levels nor covalent binding of [14C] CCl4-derived radio-label differed between the groups, suggesting that increased bioactivation is not the mechanism for this amplified toxicity. Cell division and tissue repair, assessed by [3H]thymidine incorporation and proliferative cell nuclear antigen assay, were inhibited in the steatotic livers after CCl4 administration and led to progressive expansion of liver injury culminating in mortality. The hypothesis that fatty hepatocytes undergo cell cycle arrest due to (1) an inability to replenish ATP due to overexpressed uncoupling protein-2 (UCP-2) or (2) induction of growth inhibitor p21 leading to G1/S phase arrest was tested. Steatotic livers showed 10-fold lower ATP levels due to upregulated UCP-2 throughout the time course after CCl4 administration, leading to sustained inhibition of cell division. Western blot analysis revealed an up-regulation of p21 due to overexpression of TGF beta1 and p53 and down-regulation of transcription factor Foxm 1b in steatotic livers leading to lower phosphorylated retinoblastoma protein. Thus, fatty hepatocytes fail to undergo compensatory cell division, rendering the liver susceptible to progression of liver injury. CONCLUSION: Impaired tissue repair sensitizes the steatotic livers to hepatotoxicity.
Asunto(s)
Tetracloruro de Carbono/toxicidad , Tolerancia a Medicamentos/fisiología , Hígado Graso/fisiopatología , Hígado/efectos de los fármacos , Adenosina Trifosfato/metabolismo , Animales , Ciclo Celular/efectos de los fármacos , Ciclo Celular/fisiología , División Celular , Inhibidor p21 de las Quinasas Dependientes de la Ciclina/metabolismo , Citocromo P-450 CYP2E1/metabolismo , ADN/metabolismo , Hígado Graso/complicaciones , Hígado Graso/metabolismo , Glucógeno/metabolismo , Hepatocitos/fisiología , Canales Iónicos/metabolismo , Peroxidación de Lípido/efectos de los fármacos , Hígado/metabolismo , Hígado/patología , Masculino , Proteínas Mitocondriales/metabolismo , Antígeno Nuclear de Célula en Proliferación/metabolismo , Ratas , Ratas Sprague-Dawley , Proteína Desacopladora 2RESUMEN
Acute liver failure induced by hepatotoxic drugs results from rapid progression of injury. Substantial research has shown that timely liver regeneration can prevent progression of injury leading to a favorable prognosis. However, the mechanism by which compensatory regeneration prevents progression of injury is not known. We have recently reported that calpain released from necrotic hepatocytes mediates progression of liver injury even after the hepatotoxic drug is cleared from the body. By examining expression of calpastatin (CAST), an endogenous inhibitor of calpain in three liver cell division models known to be resistant to hepatotoxicity, we tested the hypothesis that increased CAST in the dividing hepatocytes affords resistance against progression of injury. Liver regeneration that follows CCl(4)-induced liver injury, 70% partial hepatectomy, and postnatal liver development were used. In all three models, CAST was upregulated in the dividing/newly divided hepatocytes and declined to normal levels with the cessation of cell proliferation. To test whether CAST overexpression confers resistance against hepatotoxicity, CAST was overexpressed in the livers of normal SW mice using adenovirus before challenging them with acetaminophen (APAP) overdose. These mice exhibited markedly attenuated progression of liver injury and 57% survival. Whereas APAP-bioactivating enzymes and covalent binding of the APAP-derived reactive metabolites remained unaffected, degradation of calpain specific target substrates such as fodrin was significantly reduced in these mice. In conclusion, CAST overexpression could be used as a therapeutic strategy to prevent progression of liver injury where liver regeneration is severely hampered.