Comprehensive analysis of the regenerating mouse liver: an in vivo fluorescence microscopic and immunohistological study

Liver-specific Repin1 deficiency impairs transient hepatic steatosis in liver regeneration

Transient hepatic steatosis upon liver resection supposes functional relationships between lipid metabolism and liver regeneration. Repin1 has been suggested as candidate gene for obesity and dyslipidemia by regulating key genes of lipid metabolism and lipid storage. Herein, we characterized the regenerative potential of mice with a hepatic deletion of Repin1 (LRep1−/−) after partial hepatectomy (PH) in order to determine the functional significance of Repin1 in liver regeneration. Lipid dynamics and the regenerative response were analyzed at various time points after PH. Hepatic Repin1 deficiency causes a significantly decreased transient hepatic lipid accumulation. Defects in lipid uptake, as analyzed by decreased expression of the fatty acid transporter Cd36 and Fatp5, may contribute to attenuated and shifted lipid accumulation, accompanied by altered extent and chronological sequence of liver cell proliferation in LRep1−/− mice. In vitro steatosis experiments with primary hepatocytes also revealed attenuated lipid accumulation and occurrence of smaller lipid droplets in Repin1-deficient cells, while no direct effect on proliferation in HepG2 cells was observed. Based on these results, we propose that hepatocellular Repin1 might be of functional significance for early accumulation of lipids in hepatocytes after PH, facilitating efficient progression of liver regeneration.

Delayed liver regeneration in C3H/HeJ mice: possible involvement of haemodynamic and structural changes in the hepatic microcirculation

NEW FINDINGS

What is the central question of this study? The liver regenerative process is complex and involves a sequence of signalling events, but the possible involvement of structural and haemodynamic changes in vivo during this process has never been explored. What is the main finding and its importance? Normal sinusoidal blood flow and velocity are crucial for a normal regenerative response, and delays in these haemodynamic events resulted in impaired liver regeneration in lipopolysaccharide-insensitive, C3H/HeJ mice. Toll-like receptor 4 signalling is required for restoration of normal liver architecture during the liver regenerative process. Liver regeneration is delayed in mice with a defective Toll-like receptor 4 (TLR4; C3H/HeJ mice) but is normal in TLR4 knockouts (TLR4^-/- ). Here, we investigated the possible involvement of structural and haemodynamic changes in vivo in the underlying mechanism. In lipopolysaccharide-sensitive (C3H/HeN and C57BL/6) and lipopolysaccharide-insensitive (C3H/HeJ and TLR4^-/- ) mice, a 70% partial hepatectomy (PH) was performed under inhalational anaesthesia. At days 3 and 7 after PH, the hepatic microcirculation was interrogated using intravital microscopy. Delayed liver regeneration was confirmed in C3H/HeJ, but not in C3H/HeN, C57BL/6 (WT) or TLR4^-/- mice by liver weight-to-body-weight ratio, the percentage of proliferating cell nuclear antigen (PCNA)-positive cells and mitotic index data. At day 3 after PH, sinusoidal red blood cell velocity increased by 100% in C3H/HeN mice, but by only 40% in C3H/HeJ mice. Estimated sinusoidal blood flow was significantly higher at day 7 after PH in C3H/HeN than in C3H/HeJ mice. The hepatic cord width was significantly larger in C3H/HeN than in C3H/HeJ mice at day 3 and it was significantly larger in TLR4^-/- than in C57BL/6 WT mice at day 7 after PH. Hepatocyte nucleus density and functional sinusoidal density was significantly reduced at days 3 and 7 after PH in all mouse strains compared with their zero-time controls. Functional sinusoidal density was significantly lower in C3H/HeJ compared with C3H/HeN mice at day 7 after PH. The present study indicates that altered sinusoidal blood flow and velocity in C3H/HeJ mice may contribute to the observed delay in the regenerative response in these mice. In addition, restoration of normal liver architecture may be delayed in TLR4^-/- mice.

Review article: the role of the microcirculation in liver cirrhosis

BACKGROUND

Intrahepatic microvascular derangements and microcirculatory dysfunction are key in the development of liver cirrhosis and its associated complications. While much has been documented relating to cirrhosis and the dysfunction of the microcirculation in the liver parenchyma, far less is known about the state of the extrahepatic microcirculation and the role this may have in the pathogenesis of multiple organ failure in end stage liver cirrhosis.

AIM

To provide an update on the role of the microcirculation in the pathophysiology of cirrhosis and its associated complications and briefly discuss some of the imaging techniques which may be used to directly investigate the microcirculation.

METHODS

A Medline literature search was conducted using the following search terms: 'cirrhosis', 'microcirculation', 'circulation', 'systemic', 'inflammation', 'peripheral', 'hepatorenal' and 'hepatopulmonary'.

RESULTS

Significant heterogeneous microvascular alterations exist in patients with cirrhosis. Data suggest that the systemic inflammation, associated with advanced cirrhosis, induces microcirculatory dysregulation and contributes to haemodynamic derangement. The resultant vasoconstriction and hypoperfusion in the systemic extrahepatic microvasculature, is likely to be instrumental in the pathophysiology of organ failure in decompensated cirrhosis, however the mechanistic action of vasoactive agents used to correct the circulatory disturbance of advanced cirrhosis is poorly understood.

CONCLUSIONS

Further research into the role of the microcirculation in patients with liver cirrhosis, will improve physicians understanding of the pathophysiology of cirrhosis, and may provide a platform for real time evaluation of an individual's microcirculatory response to vasoactive mediators, thus guiding their therapy.

Microcirculatory disturbances and cellular changes during progression of hepatic steatosis to liver tumors

Non-alcoholic fatty liver disease is closely associated with metabolic syndrome and comprises a pathological spectrum of liver disease ranging from steatosis to steatohepatitis and can progress to fibrosis/cirrhosis and hepatocellular carcinoma. In 2013, a mouse model was described that mimics non-alcoholic fatty liver disease progression from steatohepatitis to tumors in a short time span and with high incidence. As microcirculatory disturbances play a crucial role in liver disease, the suitability of the steatosis-inflammation-tumor model for microcirculatory studies was assessed. Herein, we present a comprehensive view on morphological, microvascular, cellular, and functional aspects of non-alcoholic fatty liver disease progression in the steatosis-inflammation-tumor model using intravital microscopy, biochemical, and histological techniques. Mice develop steatohepatitis, mild fibrosis, and liver tumors at ages of 6, 12, and 20 weeks, respectively. Non-alcoholic fatty liver disease progression was accompanied by several general aspects of disease severity like increasing liver/body weight index, non-alcoholic fatty liver disease activity score, and hepatocellular apoptosis. Intravital microscopic analysis revealed significant changes in hepatic microcirculation with increasing structural alterations, elevated leukocyte adherence, and impaired nutritive perfusion. Non-alcoholic fatty liver disease was further characterized by a lower sinusoidal density with a striking rise at 20 weeks. The characteristic microcirculatory changes make the model a convenient tool for analysis of microcirculation during progression from steatosis to liver tumor. Impact statement Significant alterations of microcirculation contribute to progression of NAFLD, a chronic liver disease with increasing medical and socio-economic impact. Characterization of microcirculation in a NAFLD model reflecting all relevant stages of disease progression was still missing. Thus, we evaluated microcirculatory and cellular changes in a steatosis-inflammation-tumor model using in vivo microscopy. Analyses revealed increasing structural alterations, elevated leukocyte-endothelial interaction, and impaired nutritive perfusion. Thus, this model is suitable for further studies investigating therapeutic approaches targeting these progressive microcirculatory disturbances.

Autofluorescence Spectroscopy for Monitoring Metabolism in Animal Cells and Tissues

Excitation of biological substrates with light at a suitable wavelength can give rise to a light emission in the ultraviolet (UV)-visible, near-infrared (IR) spectral range, called autofluorescence (AF). This is a widespread phenomenon, ascribable to the general presence of biomolecules acting as endogenous fluorophores (EFs) in the organisms of the whole life kingdom. In cytochemistry and histochemistry, AF is often an unwanted signal enhancing the background and affecting in particular the detection of low signals or rare positive labeling spots of exogenous markers. Conversely, AF is increasingly considered as a powerful diagnostic tool because of its role as an intrinsic biomarker directly dependent on the nature, amount, and microenvironment of the EFs, in a strict relationship with metabolic processes and structural organization of cells and tissues. As a consequence, AF carries multiple information that can be decrypted by a proper analysis of the overall emission signal, allowing the characterization and monitoring of cell metabolism in situ, in real time and in the absence of perturbation from exogenous markers. In the animal kingdom, AF studies at the cellular level take advantage of the essential presence of NAD(P)H and flavins, primarily acting as coenzymes at multiple steps of common metabolic pathways for energy production, reductive biosynthesis and antioxidant defense. Additional EFs such as vitamin A, porphyrins, lipofuscins, proteins, and neuromediators can be detected in different kinds of cells and bulk tissues, and can be exploited as photophysical biomarkers of specific normal or altered morphofunctional properties, from the retinoid storage in the liver to aging processes, metabolic disorders or cell transformation processes. The AF phenomenon involves all living system, and literature reports numerous investigations and diagnostic applications of AF, taking advantage of continuously developing self-assembled or commercial instrumentation and measuring procedures, making almost impossible to provide their comprehensive description. Therefore a brief summary of the history of AF observations and of the development of measuring systems is provided, along with a description of the most common EFs and their metabolic significance. From our direct experience, examples of AF imaging and microspectrofluorometric procedures performed under a single excitation in the near-UV range for cell and tissue metabolism studies are then reported.

A novel method for in vivo visualization of the microcirculation of the mandibular periosteum in rats

OBJECTIVE

The periosteum plays an important role in bone physiology, but observation of its microcirculation is greatly limited by methodological constraints at certain anatomical locations. This study was conducted to develop a microsurgical procedure which provides access to the mandibular periosteum in rats.

METHODS

Comparisons of the microcirculatory characteristics with those of the tibial periosteum were performed to confirm the functional integrity of the microvasculature. The mandibular periosteum was reached between the facial muscles and the anterior surface of the superficial masseter muscle at the external surface of the mandibular corpus; the tibial periosteum was prepared by dissecting the covering muscles at the anteromedial surface. Intravital fluorescence microscopy was used to assess the leukocyte-endothelial interactions and the RBCV in the tibial and mandibular periosteum. Both structures were also visualized through OPS and fluorescence CLSM.

RESULTS

The microcirculatory variables in the mandibular periosteum proved similar to those in the tibia, indicating that no microcirculatory failure resulted from the exposure technique.

CONCLUSION

This novel surgical approach provides simple access to the mandibular periosteum of the rat, offering an excellent opportunity for investigations of microcirculatory manifestations of dentoalveolar and maxillofacial diseases.

Anti-apoptotic therapeutic approaches in liver diseases: do they really make sense?

A variety of data suggesting apoptotic cell death as a key feature of liver injury stimulated researchers to investigate the therapeutic potential of anti-apoptotic strategies in experimental models. However, the overestimated role of apoptotic cell death in liver injury has tempered the clinical translation of the protection afforded by anti-apoptotic regimes in experimental models. Thus, the hope for apoptosis modulation as potential treatment strategy for injured liver in humans could not be confirmed. Herein, we evaluated the degree of apoptosis in different hepatic stress models which are relevant for the human pathophysiology. Using morphological criteria of apoptosis, caspase-3 activation as well as TUNEL assay in combination with a positive control of apoptosis in liver injury, we quantified apoptotic cell death discriminating between parenchymal and non-parenchymal cells and confirmed these results by cleaved caspase-3 and PARP-1 protein expression. Discussing our findings and relating them to the existing literature on the potential role of apoptotic cell death, we strongly recommend reconsidering anti-apoptotic strategies to ameliorate liver injury efficiently.

Breast cancer metastasis progression as revealed by intravital videomicroscopy

Metastasis is the spread of cells from a primary tumor to a distant site, where they arrest and grow to form a secondary tumor. Conventional metastasis models have focused primarily on analysis of end point tumor formation following inoculation with tumor cells. This approach can be used to measure the metastatic potential of cell lines, the morphology of metastases and their vasculature and the overall effectiveness of treatment strategies. However, it cannot, reveal the dynamics of metastatic progression, tumor cell interactions with host tissues or the characteristics of blood flow within the tumor microvasculature. Intravital videomicroscopy has been developed to visualize and quantify the movement of tumor cells and their interactions with host tissues as they travel through metastatic pathways within the body and arrest at secondary sites. Intravital videomicroscopy can also be used to quantify the morphology and functional capacity of tumor microvasculature, as well as the timing and dynamic effects of drugs targeted to disrupt tumor vasculaturization. With the development of new fluorescent probes and reporter genes, intravital videomicroscopy has the potential to provide evidence of the timing and location of metabolic processes within the metastatic cascade that may serve as specific targets for the treatment of breast cancer.

Simvastatin protects hepatocytes from apoptosis by suppressing the TNF-α/caspase-3 signaling pathway in mice with burn injury

OBJECTIVE

To investigate the liver cellular apoptosis in response to burn injury and find out if statin treatment can ameliorate this process. The hypothesis is that statin may modulate apoptosis-related gene expression and thereby reduce hepatocytic apoptosis after burn injury.

METHODS

Mice were subjected to 30% full-thickness burn injury and then treated either with or without simvastatin. The livers were harvested for histological assessment and determinations of gene expression. To investigate the mechanism involved, tumor necrosis factor (TNF)-α and caspase-3 knockout (KO) mice were also used to evaluate the effects of burn injury and simvastatin treatment on burn-induced liver injury. The effects of simvastatin on TNF-α and caspase-3 expressions were also evaluated in cultured mouse hepatocytes.

RESULTS

Burn injury induced significant liver damage, which was indicated by striking levels of apoptosis. Simvastatin reduced the apoptotic index in the livers of mice with burn injury and this effect could be abrogated by TNF-α or caspase-3 inhibitors. Simvastatin also decreased burn-induced TNF-α and caspase-3 expression in the liver. TNF-α and caspase-3 KO mice demonstrated lower levels of apoptotic hepatocytes in response to burn, and simvastatin did not further decrease hepatocyte apoptosis in either strain of KO mice. An in vitro study demonstrated that simvastatin suppresses TNF-α and caspase-3 expression in primary cultures of mouse hepatocytes.

CONCLUSIONS

Simvastatin reduces mouse hepatocyte apoptosis by suppressing expression of the TNF-α/caspase-3 pathway.

Proliferation and differentiation of osteoblasts from the mandible of osteoporotic rats

The objective of this study was to identify the differences between osteoblasts derived from normal adult rat mandibles and osteoporotic adult rats. An osteoporotic animal model was established by performing a bilateral ovariectomy (ovx group). The proliferation and differentiation abilities of osteoblasts were determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-2H-tetrazolium bromide), alkaline phosphatase (ALP) and osteocalcin release (OC) assays. Transmission electron microscopy (TEM) was performed to assess differences in the ultrastructure. Proliferating cell nuclear antigen (PCNA) and uncoupling protein 2 (UCP2) protein concentrations were analyzed by Western blot. In addition, UCP2 protein in osteoblasts was assessed by immunohistochemistry staining. ATP and reactive oxygen species (ROS) concentrations were analyzed separately with ATP and ROS quantification kits. At four and 12 weeks after the operation, osteoblasts of the ovx group showed earlier attachment, fewer dead cells and faster growth compared with cells in the sham group. TEM showed that osteoblasts of the ovx group had fewer folds, lysosomes, peroxisomes and less rough endoplasmic reticulum. The results of the MTT, ALP activity and OC assays were all higher in osteoblasts from the ovx group at four or 12 weeks postsurgery than osteoblasts from the sham group. PCNA protein concentrations in the ovx group increased significantly compared with those of the sham group at four or 12 weeks after the operation, but UCP2 concentrations decreased over the same time period. UCP2 immunohistochemical staining of osteoblasts showed that the protein was concentrated in the cytoplasm and that the osteoblasts from the sham group had higher expression than those from the ovx group. The ATP and ROS concentrations of the ovx groups were significantly higher than the sham groups at four or 12 weeks postsurgery. Therefore, we concluded that there are differences in cell ultrastructure, proliferation, differentiation, ATP and ROS concentrations, and PCNA and UCP2 protein expression levels in osteoblasts from the mandibles of rats of the ovx group compared with those from the sham group.

Sinusoidal microcirculatory changes after small-for-size liver transplantation in rats

Small-for-size graft injury is characterized by portal venous hypertension and loss of intracellular homeostasis early after transplant. The long-term alteration of sinusoidal microcirculatory hemodynamic state remains unknown. A syngeneic rat orthotopic liver transplantation model was developed using small-for-size grafts (35% of recipient liver weight) or whole grafts (100% of recipient liver weight). Graft survival, portal pressure, liver function, hepatocellular apoptosis as well as morphological changes (by light microscopy and electron microscopy) were assessed. Sinusoidal microcirculatory hemodynamics was examined by intravital fluorescence microscopy. Although portal hypertension lasted only for 1 h after performance of small-for-size liver transplantation, a sustained microcirculatory disturbance was accompanied by dramatic reduction of sinusoidal perfusion rate, elevation of sinusoidal diameter as well as increase in the number of apoptotic hepatocytes during the first 7 days. These resulted in lower survival rate (50% vs. 100%, P = 0.012), higher level of liver function, and more severe morphological changes, which could induce small-for-size syndrome. In conclusion, persistent microcirculatory hemodynamic derangement during the first 7 days after reperfusion as well as transient portal hypertension is significant manifestation after small-for-size liver transplantation. Long-term microcirculation disturbance displayed as decrease of sinusoidal reperfusion area and increase of spread in functional liver mass seems to be the key factor for graft injuries.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

Regeneração do fígado de ratos após oclusão parcial da drenagem venosa hepática

INTRODUÇÃO: A regeneração hepática é um mecanismo para superar a perda de tecido funcional do fígado. Este processo é estudado através de diferentes métodos. OBJETIVO: Avaliar o efeito da oclusão parcial da drenagem venosa hepática sobre a regeneração do fígado remanescente de ratos submetidos à hepatectomia parcial. MÉTODO: Foram colhidas biópsias de fígado em 30 ratos Wistar machos, e a seguir realizada hepatectomia a dois terços. Os animais foram divididos em três grupos: um grupo controle e dois grupos de estudo, submetidos a diferentes graus de estenose da veia hepática direita. Após 96 horas do estímulo para regeneração hepática, todos submeteram-se à outra biópsia hepática. Analisaram-se os fragmentos por imunoistoquímica para os marcadores Ki-67 e fator de von Willebrand. Para a leitura das amostras utilizou-se o sistema SAMBA 4000. A deposição de colágeno foi avaliada pela coloração tricrômico de Masson. RESULTADOS: A proliferação celular dos animais submetidos à hepatectomia parcial e estenose moderada ou severa da veia hepática direita persistiu mais elevada quando comparada ao grupo controle. O Índice de Marcação para o Ki-67 foi significativamente mais elevado após a hepatectomia nos grupos submetidos à oclusão parcial da veia hepática, tanto moderada quanto severa. A expressão de fator de von Willebrand estava diminuída após a hepatectomia parcial nos três grupos. Houve pouco depósito de colágeno no tecido hepático nos animais dos dois grupos com estenose da veia hepática direita. CONCLUSÃO: A oclusão parcial da drenagem venosa hepática em ratos submetidos à hepatectomia parcial prolonga o tempo de proliferação de células hepáticas quando comparado aos animais com veias de calibre normal. Como consequência, também houve atraso na restauração da matriz extracelular e na formação de novos vasos sinusoidais.

Novel tool to suppress cell proliferation in vivo demonstrates that myocardial and coronary vascular growth represent distinct developmental programs

Cell proliferation, differentiation, and vascular growth are coordinated processes that are essential for embryonic development, tissue repair, and disease pathogenesis. Of interest, whether these critical processes are dependent upon each other has not been thoroughly explored. We have generated mice that conditionally express the cell cycle inhibitor p27(Kip1), following Cre-mediated recombination, as a tool to separate tissue proliferation from other cellular processes. Using the embryonic heart as a model, we show that myocardial proliferation and coronary development are genetically separable processes. Forced expression of p27, in both a wild-type and in a genetically sensitized background, resulted in ventricular hypoplasia without having any substantial effects on coronary development. We further demonstrate that Hedgehog signaling, which is essential for coronary vascular growth, does not control myocardial proliferation. Together, these studies strongly suggest that myocardial cell proliferation and coronary development are genetically separable programs exemplifying one of the many potential uses of this genetic tool.

Immunohistochemical analysis of hepatic ganglioside distribution following a partial hepatectomy and exposure to different hyperbaric oxygen treatments

Ganglioside GM3(Neu5Ac) expression is highly increased in liver 54h following 15% partial hepatectomy in pre-operatively oxygenated rats. GM3(Neu5Gc), GM2, GalNAc-GM1b and gangliosides of the neolacto-series are less affected. GM3(Neu5Ac) is a potent inhibitor of epidermal growth factor signaling. Since GM3(Neu5Ac) growth inhibitory effect depends on its cellular localization, the aim of this study was to detect ganglioside cellular localization during liver regeneration. The experiment was performed using the same rat model which previously showed increased ganglioside expression and more efficient liver regeneration. Frozen sections of liver were analyzed using confocal microscopy after labeling for binding of five ganglioside-specific antibodies, with or without hepatocyte membrane permeabilization. Ganglioside precursors, ceramide (Cer), monohexaosylceramide and lactosylceramide (LacCer) were determined by high-performance thin-layer chromatography. Apoptosis was assessed by fluorescein-dUTP end-labeling of fragmented DNA. Liver of pre-operative oxygenated rats showed high perinuclear labeling of GM3(Neu5Ac) which was absent in post-operative oxygenated and control animals. In the same group, Cer content was lower, monohexaosylceramide and LacCer were absent, and content of apoptotic cells was significantly the lowest, compared to other groups examined (F=20.36, p=0.0001). These findings indicate that ganglioside GM3(Neu5Ac) may be involved in mediation of beneficial effects of pre-operatively oxygenation during the liver regeneration.

Loss of NF-kappaB activation in Kupffer cell-depleted mice impairs liver regeneration after partial hepatectomy

Kupffer cells (KCs) are located in the liver sinusoids adjacent to hepatocytes and are capable of producing important growth-regulating mediators that exert both stimulatory and inhibitory influences on hepatocyte proliferation by paracrine mechanisms. To elucidate the overall effect of KC depletion on liver regeneration, mice were selectively and long-standing depleted of KCs by liposome-encapsulated dichloromethylene diphosphonate. Using in vivo fluorescence microscopy, immunohistochemistry, Western blot analysis, and NF-kappaB transcription factor DNA binding activity and cytokine assays, we analyzed livers of KC-depleted and KC-competent mice at days 3, 5, and 8 after partial (i.e., 68%) hepatectomy (PH). Selective KC elimination delayed cell proliferation, as indicated by significantly reduced PCNA and cyclin B1 protein expression in liver tissue at day 3 after PH. This was associated with a lower liver weight at day 8 upon PH. Resection-associated activation of NF-kappaB with translocation into parenchymal and nonparenchymal cell nuclei was diminished in livers of KC-depleted mice, primarily at day 3 after PH. KC-depleted mice further lacked the resection-induced rise in TNF-alpha and IL-6 serum concentrations. These findings imply that KCs play a stimulatory role in liver regeneration, mainly by activating NF-kappaB with influence on the cell cycle and by enhancing expression of the proliferative cytokines TNF-alpha and IL-6.

Antileukoproteinase protects against hepatic inflammation, but not apoptosis in the response of D-galactosamine-sensitized mice to lipopolysaccharide

BACKGROUND AND PURPOSE

There is major evidence for the strong bi-directional interrelation of parenchymal cell apoptosis and leukocyte accumulation and inflammation in acute liver injury. Therefore, the aim of this in vivo study was to investigate the anti-apoptotic and anti-inflammatory potential of antileukoproteinase (ALP) in a murine model of acute liver failure.

EXPERIMENTAL APPROACH

C57BL/6J mice were given galactosamine (D-GalN) and E. coli lipopolysaccharide (LPS) followed by administration of saline or ALP. Besides survival rate, hepatic tissue damage and inflammatory response were analyzed by intravital fluorescence microscopy 6 hours after treatment. In addition, immunohistochemical analysis of NFkappaB-p65 and hepatocellular apoptosis, plasma levels of AST/ALT, TNF-alpha and IL-10 were determined.

KEY RESULTS

Administration of D-GalN/LPS provoked hepatic damage, including marked leukocyte recruitment and microvascular perfusion failure, as well as hepatocellular apoptosis and enzyme release. NFkappaB-p65 became increasingly detectable in hepatocellular nuclei, accompanied by a rise of TNF-alpha and IL-10 plasma levels. ALP markedly reduced intrahepatic leukocyte accumulation, nuclear translocation of NFkappaB and plasma levels of TNF-alpha and IL-10. Moreover, liver enzyme levels indicated the absence of necrotic parenchymal cell death. In contrast, ALP failed to block both apoptosis and caspase-3 levels and the mortality rate of ALP-treated animals was comparable to that of saline-treated mice.

CONCLUSIONS AND IMPLICATIONS

ALP could effectively prevent D-GalN/LPS-associated intrahepatic inflammatory responses by inhibition of NFkappaB activity, but not apoptosis-driven mortality. Thus, a protease-inactivating approach such as application of ALP seems to be inadequate in damaged liver where apoptosis represents the predominant mode of cell death.