Preventive effects of the deleted form of hepatocyte growth factor against various liver injuries

Promising protein biomarkers in the early diagnosis of Alzheimer's disease

Alzheimer's disease (AD) is an insidious, multifactorial disease that involves the devastation of neurons leading to cognitive impairments. Alzheimer's have compounded pathologies of diverse nature, including proteins as one important factor along with mutated genes and enzymes. Although various review articles have proposed biomarkers, still, the statistical importance of proteins is missing. Proteins associated with AD include amyloid precursor protein, glial fibrillary acidic protein, calmodulin-like skin protein, hepatocyte growth factor, matrix Metalloproteinase-2. These proteins play a crucial role in the AD hypothesis which includes the tau hypothesis, amyloid-beta (Aβ) hypothesis, cholinergic neuron damage, etc. The present review highlights the role of major proteins and their physiological functions in the early diagnosis of AD. Altered protein expression results in cognitive impairment, synaptic dysfunction, neuronal degradation, and memory loss. On the medicinal ground, efforts of making anti-amyloid, anti-tau, anti-inflammatory treatments are on the peak, having these proteins as putative targets. Few proteins, e.g., Amyloid precursor protein results in the formation of non-soluble sticky Aβ₄₀ and Aβ₄₂ monomers that, over time, aggregate into plaques in the cortical and limbic brain areas and neurogranin is believed to regulate calcium-mediated signaling pathways and thus modulating synaptic plasticity are few putative and potential forthcoming targets for developing effective anti-AD therapies. These proteins may help to diagnose the disease early, bode well for the successful discovery and development of therapeutic and preventative regimens for this devasting public health problem.

Recombinant human hepatocyte growth factor (HGF), but not rat HGF, elicits glomerular injury and albuminuria in normal rats via an immune complex-dependent mechanism

1. Hepatocyte growth factor (HGF) has the therapeutic potential to improve renal fibrosis and proteinuria in rodents with chronic kidney disease. In contrast, long-term administration of human HGF to normal rats reportedly elicits proteinuria. Thus, the role of HGF during proteinuria remains contentious. The aim of the present study was to demonstrate that human HGF is antigenic to rodents and that immune complex formation causes proteinuria. 2. We administered either human or rat HGF to normal rats for 28 days. Albuminuria was evaluated by sodium dodecyl sulphate-polyacrylamide gel electrophoresis. The renal phenotypes of the two HGF treatments were examined using histological techniques. 3. Administration of human HGF (1 mg/kg per day, i.v.) to rats led to severe albuminuria and glomerular hypertrophy in association with increased blood levels of anti-human HGF IgG and IgG deposition in mesangial areas. Furthermore, an immune complex between human HGF and anti-human HGF IgG stimulated the production of proteinuric cytokines (including transforming growth factor-β) in rat cultured mesangial cells. In contrast, treatment of healthy rats with rat HGF for 4 weeks caused neither mesangial IgG deposition nor elevated anti-HGF IgG in the blood. Overall, rat HGF did not provoke albuminuria. 4. We conclude that human HGF produces pseudotoxic effects in normal rat kidneys via an immune complex-mediated pathway, whereas syngenic HGF is safe due to less deposition of glomerular IgG. Our results affirm the safety of the repeated use of syngenic HGF for the treatment of chronic organ diseases, such as renal fibrosis and liver cirrhosis.

HGF-Met Pathway in Regeneration and Drug Discovery

Hepatocyte growth factor (HGF) is composed of an α-chain and a β-chain, and these chains contain four kringle domains and a serine protease-like structure, respectively. Activation of the HGF–Met pathway evokes dynamic biological responses that support morphogenesis (e.g., epithelial tubulogenesis), regeneration, and the survival of cells and tissues. Characterizations of conditional Met knockout mice have indicated that the HGF–Met pathway plays important roles in regeneration, protection, and homeostasis in various cells and tissues, which includes hepatocytes, renal tubular cells, and neurons. Preclinical studies designed to address the therapeutic significance of HGF have been performed on injury/disease models, including acute tissue injury, chronic fibrosis, and cardiovascular and neurodegenerative diseases. The promotion of cell growth, survival, migration, and morphogenesis that is associated with extracellular matrix proteolysis are the biological activities that underlie the therapeutic actions of HGF. Recombinant HGF protein and the expression vectors for HGF are biological drug candidates for the treatment of patients with diseases and injuries that are associated with impaired tissue function. The intravenous/systemic administration of recombinant HGF protein has been well tolerated in phase I/II clinical trials. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing.

High-level expression and characterization of bioactive human truncated variant of hepatocyte growth factor in Escherichia coli

Hepatocyte growth factor (HGF) is an effective anti-fibrotic factor because of its bioactivity in inhibiting fibrosis-related proteins in the development of hepatic fibrosis. However, high-level production of bioactive mature form HGF is difficult because of its complex structure. Here, we report a non-fusion protein expression system to obtain truncated variant of N-terminal hairpin and first kringle domains of HGF (tvNK1) in Escherichia coli to determine its anti-fibrotic effects on hepatic stellate cells (HSCs). Under the selected conditions of cultivation and isopropyl-β-D-1-thiogalactopyranoside induction, the expression level of tvNK1 accounted for approximately 65 % of the total cellular protein and 50 % of fusion protein in the supernatant of whole cell lysates. The recombinant protein could be purified in one step with Ni(2+)-affinity chromatograph. Finally, about 65 mg recombinant tvNK1 was obtained from 1 l fermentation culture with no <95 % purity. In vitro, the final purified tvNK1 was shown to inhibit the proliferation of HSCs and decrease the mRNA and protein expression levels of fibrosis-related COL1A1 and α-smooth muscle actin genes.

Therapeutic effect of collagenase Ⅱ against rat liver cirrhosis

AIM: To explore the therapeutic effect of an adenovirus-HBV chimeric vector expressing collagenase Ⅱ against cirrhosis in a rat model.

METHODS: Rat liver cirrhosis was induced with 0.03% thioacetamide in drinking water for 16 wk. Ad-CH-tMMP8 and Ad-C-MMP8 were constructed using an adenovirus shuttle plasmid and a HBV chimeric vector expressing truncated and full-length collagenase Ⅱ gene. Ad-CH-RFP2 expressing red fluorescent protein was used as a negative control. Liver cirrhosis rats were injected with the three plasmids through the tail vein.

RESULTS: Compared with the model group and negative control group, fibrosis was dramatically attenuated four weeks after the infection. HE staining and picric acid-Sirius red staining showed that hepatocyte steatosis, necrosis and inflammation were significantly milder in the treatment group, along with hepatocyte proliferation, recovery of hepatic lobule structure, and diminished content of HYP (28.97 µg/g ± 2.36 µg/g vs 17.04 µg/g ± 0.61 µg/g, 17.62 µg/g ± 1.30 µg/g, P < 0.05), whereas the fibrosis in Ad-CH-RFP2-treated rats persisted.

CONCLUSION: Adenovirus-HBV chimeric vector expressing collagenase Ⅱ effectively reduces the degree of liver fibrosis in rats.

Protein engineered variants of hepatocyte growth factor/scatter factor promote proliferation of primary human hepatocytes and in rodent liver

BACKGROUND & AIMS

Hepatocyte growth factor/scatter factor (HGF/SF) stimulates hepatocyte DNA synthesis and protects against apoptosis; in vivo it promotes liver regeneration and reduces fibrosis. However, its therapeutic value is limited by its complex domain structure, high cost of production, instability, and poor tissue penetration due to sequestration by heparin sulfate proteoglycans (HSPGs).

METHODS

Using protein engineering techniques, we created a full-length form of HGF/SF (called HP21) and a form of the small, naturally occurring HGF/SF fragment, NK1 (called 1K1), which have reduced affinity for HSPG. We characterized the stability and proliferative and anti-apoptotic effects of these variants in primary human hepatocytes and in rodents.

RESULTS

Analytical ultracentrifugation showed that 1K1 and NK1 were more stable than the native, full-length protein. All 4 forms of HGF/SF induced similar levels of DNA synthesis in human hepatocytes; 1K1 and NK1 required heparin, an HSPG analogue, for full agonistic activity. All the proteins reduced levels of Fas ligand-mediated apoptosis, reducing the activity of caspase-3/7 and cleavage of poly(adenosine diphosphate-ribose) polymerase. 1K1 was more active than NK1 in rodents; in healthy mice, 1K1 significantly increased hepatocyte DNA synthesis, and in mice receiving carbon tetrachloride, it reduced fibrosis. In rats, after 70% partial hepatectomy, daily administration of 1K1 for 5 days significantly increased liver mass and the bromodeoxyuridine labeling index compared with mice given NK1.

CONCLUSIONS

1K1, an engineered form of the small, naturally occurring HGF/SF fragment NK1, has reduced affinity for HSPG and exerts proliferative and antiapoptotic effects in cultured hepatocytes. In rodents, 1K1 has antifibrotic effects and promotes liver regeneration. The protein has better stability and is easier to produce than HGF/SF and might be developed as a therapeutic for acute and chronic liver disease.

Improvement of sepsis by hepatocyte growth factor, an anti-inflammatory regulator: emerging insights and therapeutic potential

Sepsis-induced multiple organ failure (MOF) is the most frequent lethal disease in intensive care units. Thus, it is important to elucidate the self-defensive mechanisms of sepsis-induced MOF. Hepatocyte growth factor (HGF) is now recognized as an organotrophic factor, which is essential for organogenesis during embryonic growth and regeneration in adulthood. HGF production is enhanced in response to infectious challenges, but the increase in endogenous HGF levels is transient and insufficient, with a time lag between tissue injuries and HGF upregulation, during progression of septic MOF. Thus, administration of active-formed HGF might be a new candidate for therapeutic development of MOF. HGF has an ability to target endotoxin-challenged macrophages and inhibits the upregulation of inflammatory cytokines through nuclear factor-κB-inactivated mechanisms. HGF also targets the endothelium and epithelium of various organs to suppress local inflammation, coagulation, and apoptotic death. This paper summarizes the novel mechanisms of HGF for attenuating sepsis-related pathological conditions with a focus on sepsis-induced MOF.

Translational research to identify clinical applications of hepatocyte growth factor

Hepatocyte growth factor (HGF), originally purified from the plasma of patients with fulminant hepatic failure, has been shown to carry out various physiological functions. HGF not only stimulates liver regeneration, but also acts as an antiapoptotic factor in in vivo experimental models. Therefore, HGF is a promising therapeutic agent for the treatment of fatal liver diseases, including fulminant hepatic failure. After performing a number of preclinical tests, our group began an investigator-initiated registered phase I/II clinical trial of patients with fulminant hepatic failure to examine the safety and clinical efficacy of recombinant human HGF. In this article, we will discuss the basic research results as well as the translational research that underpins current attempts to use HGF in various clinical settings.

Advances in antifibrotic therapy

Sustained progress in defining the molecular pathophysiology of hepatic fibrosis has led to a comprehensive framework for developing antifibrotic therapies. Indeed, the single greatest limitation in bringing new drugs to the clinical setting is a lack of clarity regarding clinical trial and treatment end points, not a lack of promising agents. A range of treatments, including those developed for other indications, as well as those specifically developed for hepatic fibrosis, are nearing or in clinical trials. Most are focused on attacking features of either hepatic injury and/or activated stellate cells and myofibroblasts, which are the primary sources of extracellular matrix (scar) proteins. Thus, features of injury and stellate cell activation provide a useful template for classifying these emerging agents and point to a new class of therapies for patients with fibrosing liver disease.

Translational research on HGF: A phase I/II study of recombinant human HGF for the treatment of fulminant hepatic failure

Hepatocyte growth factor (HGF) is a potential therapeutic agent for fatal liver diseases, including fulminant hepatic failure (FHF). After performing a number of preclinical tests with recombinant human HGF (rh-HGF), we started a phase I/II study in September 2005 of patients with FHF or late-onset hepatic failure (LOHF), to examine the safety and clinical efficacy of rh-HGF. We first administered rh-HGF (0.6 mg/m(2)/day) for 13 days to a 67-year-old Japanese man with FHF. All data from this patient were reviewed by the independent data monitoring committee, and the safety of rh-HGF was recognized. Finally, a clinical trial of rh-HGF was approved to be continued. As of August 2007, we have administered rh-HGF to four patients with FHF or LOHF. All patients showed a moderate decrease in systolic blood pressure during rh-HGF administration, while the urinary excretion of albumin did not increase in all cases. In the first and third patients, hepatic failure gradually progressed, and they died 66 and 29 days, respectively, after encephalopathy occurred. The second and fourth patients are presently still alive. In conclusion, we started a clinical trial that examined the effects of rh-HGF in patients with FHF or LOHF, and in the four patients with FHF or LOHF enrolled in this study, repeated doses of rh-HGF did not produce any severe side effects.

Hepatic fibrosis -- overview

The study of hepatic fibrosis, or scarring in response to chronic liver injury, has witnessed tremendous progress in the past two decades. Clarification of the cellular sources of scar, and emergence of hepatic stellate cells not only as a fibrogenic cell type, but also as a critical immunomodulatory and homeostatic regulator are among the most salient advances. Activation of hepatic stellate cells remains a central event in fibrosis, complemented by evidence of additional sources of matrix-producing cells including bone marrow, portal fibroblasts, and epithelial-mesenchymal transition from both hepatocytes and cholangiocytes. A growing range of cytokines and their receptors and inflammatory cell subsets have further expanded our knowledge about this dynamic process. Collectively, these findings have laid the foundation for continued elucidation of underlying mechanisms, and more importantly for the implementation of rationally based approaches to limit fibrosis, accelerate repair and enhance liver regeneration in patients with chronic liver disease.

Prolonged engraftment of human hepatocytes in mice transgenic for the deleted form of human hepatocyte growth factor

AIM

Small animal models chimeric for human hepatocytes have provided valuable insights into the biology of hepatotropic viral infection and provided a platform for the study of therapeutic agents. Existing models of human hepatocyte transplantation are limited by phenotypic fragility and impaired immunity. We hypothesized that mice transgenic for human hepatocyte growth factor (HGF), a potent human hepatocyte mitogen, would engraft human hepatocytes in the absence of immunodeficiency.

METHODS

A plasmid construct containing the 2.3 kb coding region of the 723 amino acid isoform of HGF cDNA under the transcriptional control of the mouse albumin promoter/enhancer was used to generate transgenic mice. Cryopreserved human hepatocytes were transplanted into nine transgenic and six non-transgenic mice. Engraftment of human hepatocytes was followed for a period of 12 weeks by immunoblotting for human albumin in mouse serum samples.

RESULTS

In six out of the nine transgenic mice, abundance of human albumin, following an initial decline, increased andpeaked at > 70 days post transplantation, demonstrating sustained engraftment of transplanted human hepatocytes. In all the non-transgenic mice, post-transplant human albumin levels declined sequentially without evidence of sustained engraftment. Immunostaining of mouse liver sections indicated the presence of human hepatocytes adjacent to clusters of non-staining murine hepatocytes.

CONCLUSION

These results demonstrate that sustained engraftment of human hepatocytes in mice is facilitated by expression of the human dHGF transgene. Human hepatocyte engraftment in this model has been achieved on an immunocompetent strain background and merits further study as a candidate for the study of hepatotropic viral infections.

Hepatocyte growth factor: a regenerative drug for acute hepatitis and liver cirrhosis

Liver cirrhosis is a major cause of morbidity worldwide and is characterized by the loss of hepatocytes with interstitial fibrosis. In this review, we discuss the potential uses of hepatocyte growth factor for treating hepatic diseases, focusing on the molecular mechanisms whereby hepatocyte growth factor reverses liver cirrhosis. Hepatic myofibroblasts play a central role in the development of liver cirrhosis, while myofibroblasts acquire c-Met. Using a rat model of liver cirrhosis, we recently delineated the direct effect of hepatocyte growth factor toward myofibroblasts: the induction of apoptotic cell death associated with matrix degradation, the inhibition of overproliferation and the suppression of transforming growth factor-beta1 production in myofibroblasts. Hepatocyte growth factor elicits mitogenic, anti-apoptotic and anti-inflammatory functions in hepatocytes, therefore contributing to reversing liver dysfunction. Considering the insufficient production of hepatocyte growth factor is responsible for the manifestation of chronic hepatitis, supplementation with or reinduction of hepatocyte growth factor represents a new strategy for attenuating intractable liver diseases.

Antinecrotic and antiapoptotic effects of hepatocyte growth factor on cholestatic hepatitis in a mouse model of bile-obstructive diseases

Cholestasis, an impairment of bile outflux, frequently occurs in liver diseases. In this process, an overaccumulation of bile acids causes hepatocyte necrosis and apoptosis, leading to advanced hepatitis. Hepatocyte growth factor (HGF) is mitogenic toward hepatocytes, but it is still unclear whether HGF has physiological and therapeutic functions during the progression of cholestasis. Using anti-HGF IgG or recombinant HGF in mice that had undergone bile duct ligation (BDL), we investigated the involvement of HGF in cholestasis-induced hepatitis. After the BDL surgery, HGF and c-Met mRNA levels transiently increased in livers during the progression of cholestatic hepatitis. When c-Met tyrosine phosphorylation was blocked in the livers of BDL-treated mice by anti-HGF IgG, hepatic dysfunction became evident, associated with the acceleration of hepatocyte necrosis and apoptosis. Inversely, administration of recombinant HGF into the mice led to the prevention of cholestasis-induced inflammation: HGF suppressed the hepatic expression of intracellular adhesion molecule-1 and neutrophil infiltration in BDL-treated mice. As a result, parenchymal necrosis was suppressed in the HGF-injected BDL mice. In addition, HGF supplement therapy reduced the number of apoptotic hepatocytes in cholestatic mice, associated with the early induction of Bcl-xL. The administration of HGF enhanced hepatic repair, via accelerating G1/S progression in hepatocytes. Our study showed that 1) upregulation of HGF production is required for protective mechanisms against cholestatic hepatitis and 2) enhancement of the intrinsic defense system by adding HGF may be a reasonable strategy to attenuate hepatic inflammation, necrosis, and apoptosis under bile-congestive conditions.

Hepatocyte growth factor accelerates the proliferation of hepatic oval cells and possibly promotes the differentiation in a 2-acetylaminofluorene/partial hepatectomy model in rats

BACKGROUND

Hepatocyte growth factor (HGF) is the primary agent promoting the proliferation of mature hepatocytes. The purpose of the present paper was to clarify the effects of HGF on the proliferation and differentiation of hepatic oval cells using a 2-acetylaminofluorene/partial hepatectomy (2-AAF/PH) model in rats.

METHODS

Recombinant human HGF (0.2 mg/day) was administered to 2-AAF/PH rats for 7 days using osmotic pumps intraperitoneally implanted in conjunction with hepatectomy (day zero).

RESULTS

Periportal basophilic areas consisting of oval cells were significantly enlarged by treatment with HGF on day 8. In control animals, expression of alpha-fetoprotein (AFP) in the liver was gradually upregulated, leading a marked increase on day 12. In HGF-treated rats, AFP expression was stimulated at an earlier date and decreased to an undetectable level on day 12. Conversely, expression of albumin transcripts, which was stimulated by HGF-treatment at a later date, continued to increase even after HGF administration ceased, leading to an extremely high level on day 12. Moreover, treatment with HGF also stimulated the expression of hepatocyte nuclear factor-1alpha and -4alpha at an early date.

CONCLUSIONS

These results indicate that, besides the proliferation of hepatic oval cells, HGF possibly promotes the differentiation to hepatocytes in vivo, suggesting that recombinant human HGF accelerates the regeneration of severely damaged livers, a situation in which the proliferation of mature hepatocytes is impaired.

Reduction of monocrotaline-induced hepatic injury by deleted variant of hepatocyte growth factor (dHGF) in rats

BACKGROUND

Monocrotaline is a hepatotoxic agent which exerts predominant toxicity to central veins and centrilobular sinusoids. In this study, we investigated the effects of deleted variant of hepatocyte growth factor (dHGF) on monocrotaline-induced hepatic injury in rats.

METHODS

100 mg/kg monocrotaline was gavaged to male rats twice with a 4-days' interval. Treatment of dHGF was started 4 days before the initial administration of monocrotaline and 500 microg/kg was intravenously injected twice daily for 11 days.

RESULTS

Monocrotaline induced severe damage of central veins and destruction of central zone of hepatic lobules concurrent with derangement of blood levels of total protein, albumin, alanine-aminotransferase, total bilirubin, direct bilirubin, and hepaplastin time. dHGF reduced the structural and blood-chemical abnormalities induced by monocrotaline.

CONCLUSIONS

These results suggest that dHGF prevented and repaired the monocrotaline-induced hepatic injury, and could have therapeutic potency in hepatic failure with sever centrilobular destruction.

Hepatocyte growth factor: renotropic role and potential therapeutics for renal diseases

Hepatocyte growth factor (HGF), a ligand for the c-Met receptor tyrosine kinase, has mitogenic, motogenic, anti-apoptotic, and morphogenic (for example, induction of branching tubulogenesis) activities for renal tubular cells, while it has angiogenic and angioprotective actions for endothelial cells. Stromal cells such as mesangial cells, endothelial cells, and macrophages are sources of renal HGF; thus, HGF mediates epithelial-stromal and endothelial-mesangial interactions in the kidney. In response to acute renal injury, the expression of HGF increases in the injured kidney and in distant intact organs such as the lung and spleen. Locally and systemically increased HGF supports renal regeneration, possibly not only by enhancing cell growth but also by promoting morphogenesis of renal tissue. During progression of chronic renal failure/renal fibrosis, the expression of HGF decreases in a manner reciprocal to the increase in expression of transforming growth factor-beta (TGF-beta), a key player in tissue fibrosis. A decrease in endogenous HGF, as well as increase in TGF-beta, augments susceptibility to the onset of chronic renal failure/renal fibrosis. On the other hand, supplements of exogenous HGF have preventive and therapeutic effects in cases of acute and chronic renal failure/renal fibrosis in laboratory animals. HGF prevents epithelial cell death and enhances regeneration and remodeling of renal tissue with injury or fibrosis. A renotropic system underlies the vital potential of the kidney to regenerate, while an impaired renotropic system may confer susceptibility to the onset of renal diseases. Thus, HGF supplementation may be one therapeutic strategy to treat subjects with renal diseases, as it enhances the intrinsic ability of the kidney to regenerate.

Continuous intravenous infusion of deleted form of hepatocyte growth factor attenuates hepatic ischemia-reperfusion injury in rats

BACKGROUND/AIMS

Although beneficial roles of hepatocyte growth factor (HGF) and its variants on several hepatic disorders have been reported, their effects on hepatic ischemia-reperfusion (IR) injury remain undetermined. We investigated the action of a deleted form of HGF (dHGF) on hepatic IR injury in rats.

METHODS

dHGF or phosphate-buffered saline was continuously infused intravenously for 20 h prior to a 20-min occlusion of hepatic vessels. Samples were taken before and after IR, for measurement of serum dHGF and released enzymes, liver gamma-glutamylcysteinyl glycine (GSH) level, as well as histological and immunohistochemical examinations.

RESULTS

After reperfusion, histological injury, as well as increase in the serum activities of aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and creatine kinase-BB were significantly attenuated in the dHGF-treated rats. dHGF maintained a high GSH level and suppressed oxidative stress and intercellular adhesion molecule-1 (ICAM-1) expression on sinusoidal endothelial cells (SECs), on which c-Met was not detected. IR caused activation of c-Met expression, which was milder in the dHGF-treated group, in hepatocytes at the pericentral region.

CONCLUSIONS

dHGF attenuated liver injury after IR. It also maintained a higher GSH level, depressed oxidative stress and inhibited ICAM-1 expression on c-Met negative SECs, suggesting a paracrine effect of dHGF.

Differential expression of hepatocyte growth factor in liver, kidney, lung, and spleen following burn in rats

Hepatocyte growth factor (HGF) plays a role as an organotropic factor for regeneration of injured organs. HGF is synthesized as an inactive single-chain precursor which is then converted to a biologically active heterodimeric form by proteolytic processing. Burn is the insult that results in hypovolemia which causes systemic organ injury. In this study, we investigated the induction and activation of HGF in various rat organs following burn trauma. Tissue HGF content determined as the total amount of the single-chain and heterodimeric form increased significantly in liver, lung, spleen, and kidney 12 h after burn. Molecular analysis revealed that HGF in these four organs of control rats was the single-chain precursor. In the burned rats, HGF was the single-chain form in the liver and lung, whereas heterodimeric HGF was detected in the spleen and kidney. Tissue protein content, an index of tissue injury, decreased significantly in the spleen and kidney, indicating that tissue damage was severe in these two organs. These results suggest that burn induces the production of HGF in various organs, and that the induced HGF is activated according to the severity of tissue damage caused by burn.

Liver fibrogenesis and the role of hepatic stellate cells: new insights and prospects for therapy

Hepatic fibrosis is a wound-healing response to chronic liver injury, which if persistent leads to cirrhosis and liver failure. Exciting progress has been made in understanding the mechanisms of hepatic fibrosis. Major advances include: (i) characterization of the components of extracellular matrix (ECM) in normal and fibrotic liver; (ii) identification of hepatic stellate cells as the primary source of ECM in liver fibrosis; (iii) elucidation of key cytokines, their cellular sources, modes of regulation, and signalling pathways involved in liver fibrogenesis; (iv) characterization of key matrix proteases and their inhibitors; (v) identification of apoptotic mediators in stellate cells and exploration of their roles during the resolution of liver injury. These advances have helped delineate a more comprehensive picture of liver fibrosis in which the central event is the activation of stellate cells, a transformation from quiescent vitamin A-rich cells to proliferative, fibrogenic and contractile myofibroblasts. The progress in understanding fibrogenic mechanisms brings the development of effective therapies closer to reality. In the future, targeting of stellate cells and fibrogenic mediators will be a mainstay of antifibrotic therapy. Points of therapeutic intervention may include: (i) removing the injurious stimuli; (ii) suppressing hepatic inflammation; (iii) down-regulating stellate cell activation; and (iv) promoting matrix degradation. The future prospects for effective antifibrotic treatment are more promising than ever for the millions of patients with chronic liver disease worldwide.

Effects of deletion-type human hepatocyte growth factor on murine septic model

BACKGROUND

Sepsis is known to be the main cause of multiple organ failure. The liver especially is vulnerable to the stress of infection. In this study, the effects of deletion-type human hepatocyte growth factor (dHGF) on a murine septic model were studied.

MATERIALS AND METHODS

Sepsis was induced in male adult Sprague-Dawley rats by cecal ligation and puncture method (CLP). Controls were given a sham operation. Intravenous injection of 1000 micrograms/kg dHGF or the same volume of vehicle was given every 12 h for 3 days before and/or after the CLP from a central vein catheter inserted 1 week prior to the operation. The daily percentage of survival after CLP was followed up for 1 week, and blood samples and liver specimens were collected from the surviving animals 72 h after CLP or sham operation.

RESULTS

The survival rate, the degree of liver damage and liver protein synthesis, and coagulation function were all favorable in the dHGF-treated animals compared to the untreated animals. Immunohistochemical staining showed that dHGF prevented the disappearance of thrombomodulin (TM) in liver sinusoid endothelium.

CONCLUSIONS

dHGF appears to prevent liver injury caused by disturbance of microcirculation through preservation of TM expression and the antithrombotic function in the endothelium of sinusoids. dHGF also facilitates repair of damaged hepatic tissue by stimulating regeneration of the cells and by preserving hepatic functions such as protein synthesis. dHGF exerts protective effects on even quiescent hepatocytes, but is most effective on injured but competent hepatocytes.

Acute liver failure

Severe hepatitis A infection is an infrequent but well-recognized cause of acute liver failure that can now be effectively prevented with vaccination against hepatitis A virus. Bromfenac and troglitazone hepatotoxicity as well as various herbal remedies are some of the newly identified causes of acute liver failure. The recently identified transfusion-transmitted virus has been implicated in some cases of idiopathic acute liver failure whereas hepatitis G virus does not appear to be a causative agent. Recognizing, monitoring, and treating patients with life-threatening cerebral edema remain critically important but difficult aspects of the clinical care of acute liver failure. Hypothermia and N-acetylcysteine are promising experimental approaches to cerebral edema but emergency liver transplantation is the only proven means of improving patient survival. Although recent changes in organ allocation may reduce waiting time to transplantation, more reliable and validated markers of liver regeneration and prognosis are needed to triage patients. The potential application and limitations of novel technologies including bioartificial liver devices and auxiliary liver transplantation continue to evolve from pioneering work in animal models and human subjects.

A mutant of deleted variant of hepatocyte growth factor (dHGF) with alanine substitution in the N-terminal basic region has higher activity in vivo

In a previous study, we generated a mutant of dHGF (deleted variant of hepatocyte growth factor), termed #2, with higher specific activity than dHGF in assays of mitogenic activity on rat hepatocytes and America opossum kidney epithelial cells (OK). In the present study, we examine in vivo hepatotropic and renotropic activities of #2 and its distribution to target tissues, liver and kidney. Administration of #2 to normal rats significantly increased serum levels of total protein, albumin, free-cholesterol, and HDL-cholesterol and liver weight in a dose-dependent manner. Analysis of these parameters suggests that #2 is more potent than dHGF as a hepatotropic factor in vivo. In addition, #2 reduced mortality of mercuric chloride-administered mice and the effect was stronger than that of dHGF. When injected to mice, a larger amount of #2 than dHGF was rapidly distributed to the liver. Sixty minutes after injection, the concentrations of #2 in plasma, liver, and kidney were higher than those of dHGF. These distribution properties and the higher mitogenic activity in vitro may explain why #2 exerts more potent in vivo biological activity than dHGF.

Effective administration route for the deleted form of hepatocyte growth factor To exert its pharmacological effects

The pharmacokinetics and the pharmacological effects of the deleted form of hepatocyte growth factor (dHGF) after intravenous (iv), subcutaneous (sc), or intramuscular (im) administration (0.25 and 2. 5 mg/kg) were studied in rats. After single iv administration (2.5 mg/kg), dHGF in serum rapidly decreased (alpha- and beta-phase half-life: 3.2 and 26.5 min, respectively). Two to four hours after single sc or im administration (2.5 mg/kg), the serum level of dHGF reached a maximum and then gradually declined (half-life: 2.7 h). The serum levels were not changed by repetitive iv administration, but were dramatically decreased by repetitive sc or im administration. Liver weight and serum levels of total protein, albumin, and HDL-cholesterol were significantly increased by iv administration of dHGF (twice daily for 4 days at 0.25 mg/kg). Sc or im administration of dHGF did not increase these parameters at the same dose, but did significantly at 2.5 mg/kg. These observations suggest that iv administration is the most effective in exerting the pharmacological effects of dHGF among three administration routes. dHGF after iv administration was distributed mainly and rapidly into liver (53.6% of the injected dHGF within 5 min) and was sustained at a higher level in the liver than in plasma. In infusion (0.5 mg/kg/3 h), dHGF level in plasma and liver reached a steady-state 15 and 60 min after starting the infusion, respectively. The steady-state level of dHGF was 7- to 9-fold higher in liver than in plasma, and the higher level in liver was sustained beyond the steady-state.