Background &a... more Background & Aims: Aminosalicylates are widely used in the treatment of ulcerative colitis (UC). Balsalazide is a novel mesalamine prodrug, activated by colonic bacteria. The aim of this study was to compare the efficacy and safety of balsalazide with that of a pH-dependent formulation of mesalamine in active UC. Methods: A randomized, double-blind study was performed comparing balsalazide, 6.75 g
Insufficient donor organs for orthotopic liver transplantation worldwide have urgently increased ... more Insufficient donor organs for orthotopic liver transplantation worldwide have urgently increased the requirement for new therapies for acute and chronic liver disease. Whilst none are yet clinically proven there are at least two different approaches for which there is extensive experimental data, some human anecdotal evidence and some data emerging from Phase 1 clinical trials. Both approaches involve bio-engineering. In vivo tissue engineering involves isolated liver cell transplantation into the liver and/or other ectopic sites and in vitro tissue engineering, using an extracorporeal hepatic support system or bioartificial liver. Some questions are common to both these approaches, such as the best cell source and the therapeutic mass required, and are discussed. Others are specific to each approach. For cell transplantation in vivo the initial engraftment and repopulation will make a critical difference to the outcome, and development of markers for transplanted cells has enabled significant advances in understanding, and therefore manipulating, the process. Moreover, the role of immunosuppression is also important and novel approaches to natural immunosuppression are discussed. For use in a bioartificial liver, the ability for hepatocytes to perform ex vivo at in vivo levels is critical. Three dimensional culture improves cell performance over monolayer cultures. Alginate encapsulated cells offer a suitable 3-D environment for a bioartificial liver since they are both easily manipulatable and cryopreservable. The use of cells derived from stem cells or foetal rather than adult liver cells is also emerging as a potential human cell source which may overcome problems associated with xenogeneic cells.
Acute liver failure has high mortality due to donor organ shortages. A bioartificial liver could ... more Acute liver failure has high mortality due to donor organ shortages. A bioartificial liver could "bridge the gap" to transplant or spontaneous recovery. Alginate encapsulation of HepG2 cells enables cell spheroid formation, thus providing sufficient functional biomass. Cryopreservation (CryoP) of these spheroids would allow an off-the-shelf capability for unpredictable emergency use. Cell death during CryoP often results from intracellular ice formation, after supercooling. An ice nucleating agent (INA), crystalline cholesterol, was trialled to reduce supercooling and subsequent cryoinjury. Spheroids were cooled in a controlled rate freezer in 12% dimethylsulfoxide/Celsior +/- INA, and sample temperatures were recorded throughout. Viability was assessed using fluorescent staining with image analysis, cell number by nuclei count, function using assays to detect liver-specific protein synthesis and secretion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction, and broad-spectrum cytochrome P450 activity. Spheroids cryopreserved without INA displayed latent cryoinjury in the first 6 h after thawing. INA reduced supercooling during CryoP and also latent cryoinjury. Cell numbers, viability, and function as measured over 72 h post-thaw were all improved when INA was present during CryoP.
A bioartificial liver comprising alginate-encapsulated liver cell spheroids (ELS) could bridge th... more A bioartificial liver comprising alginate-encapsulated liver cell spheroids (ELS) could bridge the gap to transplant or spontaneous recovery in acute liver failure, but will be required for emergency use, necessitating cryopreservation. A cryopreservation protocol has been developed, but beyond this, the feasibility of cold-chain storage is considered here. Cryopreservation will be increasingly required for timely delivery of tissue and bioengineered products, and significant, but often, over-looked factors that impact on cost and ease of clinical application are the storage temperature and useful preservation time. Storage in the vapor phase of liquid nitrogen (∼-170°C) is the gold standard, but for safety and economic purposes, storing ELS in electric freezers at -80°C may be preferable. ELS were cryopreserved using an optimized protocol and stored at either -80°C or at -170°C for up to 1 year. ELS were removed from storage after 1, 2, 3, 6, 9, or 12 months, and recovery was assessed 24 h postwarming. Cell recovery was assessed using viability (fluorescent staining with image analysis), cell number (nuclei count), and functional (hepatospecific protein enzyme-linked immunosorbent assay) assays. Viability, the viable cell number, and function of ELS stored at -170°C were maintained at similar values throughout the year. In contrast, ELS stored at -80°C exhibited decreased viability, viable cell numbers, and function by as early as 1 month. Progressive deterioration was subsequently observed. After 12 months of storage at -80°C, viable cell recovery of ELS was ∼15% that of ELS stored at -170°C. While convenience and cost might support the use of -80°C for storage of multicellular bioengineered products such as ELS, results indicate rapid deterioration in functional recoveries after only a few weeks. This study demonstrates that storage temperature is an important consideration in regenerative medicine and caution should be applied by limiting storage at -80°C to only a few weeks.
The International Journal of Biochemistry & Cell Biology, 2007
A possible cell source for a bio-artificial liver is the human hepatblastoma-derived cell line He... more A possible cell source for a bio-artificial liver is the human hepatblastoma-derived cell line HepG2 as it confers many hepatocyte functions, however, the urea cycle is not maintained resulting in the lack of ammonia detoxification via this cycle. We investigated urea cycle activity in HepG2 cells at both a molecular and biochemical level to determine the causes for the lack of urea cycle expression, and subsequently addressed reinstatement of the cycle by gene transfer. Metabolic labelling studies showed that urea production from 15N-ammonium chloride was not detectable in HepG2 conditioned medium, nor could 14C-labelled urea cycle intermediates be detected. Gene expression data from HepG2 cells revealed that although expression of three urea cycle genes Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase was evident, Ornithine Transcarbamylase and Arginase I expression were completely absent. These results were confirmed by Western blot for arginase I, where no protein was detected. Radiolabelled enzyme assays showed that Ornithine Transcarbamylase functional activity was missing but that Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase were functionally expressed at levels comparable to cultured primary human hepatocytes. To restore the urea cycle, HepG2 cells were transfected with full length Ornithine Transcarbamylase and Arginase I cDNA constructs under a CMV promoter. Co-transfected HepG2 cells displayed complete urea cycle activity, producing both labelled urea and urea cycle intermediates. This strategy could provide a cell source capable of urea synthesis, and hence ammonia detoxificatory function, which would be useful in a bio-artificial liver.
Massive hepatic necrosis (MHN) is a condition that offers an opportunity to study the remarkable ... more Massive hepatic necrosis (MHN) is a condition that offers an opportunity to study the remarkable ability of the liver to become repopulated with hepatocytes. A maximal regenerative stimulus is expected in cases of MHN (Roskams et al. APMIS Suppl 1991;23:32-39). Sequential chronological observations, after a severe degree of liver cell loss, permit study of the human equivalent of the situation in animal models in which circulating and bone marrow-derived stem and liver progenitor cells are recruited to the hepatopoietic process. To date, the bone marrow and circulating precursors have not been identified morphologically in human material. We present data that suggest that the circulating liver progenitor could have a lymphoblastoid morphological appearance. Similar cells are seen among the cellular infiltrate of MHN. We have found that combinations of markers, such as CD117/CD133 positive CD45/tryptase negative are useful to isolate these cells using cell-sorting technology. This may facilitate their expansion in vitro and the development of their use for therapeutic purposes. In MHN, the residual portal tracts and ductular reaction with the associated lymphoid infiltrate (some of which are probably liver cell progenitors derived from the circulation) constitute the fundamental regenerative community unit in which hepatopoiesis takes place. Defining the hepatopoietic process is hindered by the lack of morphological transitional forms in the period between the progenitors within the circulation and when they assume recognizable hepatocytic form as "metaplastic" hepatocytes associated with the ductular reaction. By achieving a better comprehension of these processes of liver cell restoration, we will be better placed to accelerate liver recovery in MHN, for example by the administration of granulocyte colony stimulating factor (GCSF). Thus, more patients will be able to restore their own livers and avoid liver transplantation.
The main non-parenchymal cells of the liver, Kupffer cells, sinusoidal endothelial cells and stel... more The main non-parenchymal cells of the liver, Kupffer cells, sinusoidal endothelial cells and stellate cells, participate in liver growth with respect to both their own proliferation, and effects on hepatocyte proliferation. In the well-characterised paradigm of 70% partial hepatectomy, they undergo DNA synthesis and cell division 20-24h later than the hepatocyte population. They exert both positive and negative influences on hepatocyte proliferation, including provision of an extracellular matrix-bound reservoir of hepatocyte growth factor that is activated after damage; priming of hepatocytes for DNA synthesis through rapid generation of TNF-alpha and IL-6; and generation of factors at later time points that curb hepatocyte DNA synthesis (IL-1, TGF-beta) and initiate reconstruction and reformation of matrix proteins.
Thyroxine and tri-iodothyronine are essential for normal organ growth, development and function. ... more Thyroxine and tri-iodothyronine are essential for normal organ growth, development and function. These hormones regulate the basal metabolic rate of all cells, including hepatocytes, and thereby modulate hepatic function; the liver in turn metabolizes the thyroid hormones and regulates their systemic endocrine effects. Thyroid dysfunction may perturb liver function, liver disease modulates thyroid hormone metabolism, and a variety of systemic diseases affect both organs. We highlight the intricate relations between the thyroid gland and the liver in health and disease.
Proliferation of isolated hepatocytes in long-term splenic implants was assessed by flash labelli... more Proliferation of isolated hepatocytes in long-term splenic implants was assessed by flash labelling with a 1 pulse of tritiated thymidine (3H TdR). Cell kinetics showed that the basal labelling index was 0.9% which was greater than normal non-regenerating liver. Twenty four hours following partial hepatectomy the labelling index was 2.0%, a significant rise. These results suggest that hepatocytes transplanted to the spleen constitute a suitable model for screening putative hepatotrophic factors, and are of relevance in establishing clinically useful models of hepatocyte transplantation.
The purpose of this study was to correlate the hyperintensity in the globus pallidus seen on T1-w... more The purpose of this study was to correlate the hyperintensity in the globus pallidus seen on T1-weighted magnetic resonance imaging (MRI) of the brain in chronic liver disease with changes in metabolite ratios measured from both proton and phosphorus-31 magnetic resonance spectroscopy (MRS) localised to the basal ganglia. T1-weighted spin echo (T1WSE) images were obtained in 21 patients with biopsy-proven cirrhosis (nine Child's grade A, eight Child's grade B and four Child's grade C). Four subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, four showed evidence of subclinical hepatic encephalopathy and 13 had overt hepatic encephalopathy. Signal intensities of the globus pallidus and adjacent brain parenchyma were measured and contrast calculated, which correlated with the severity of the underlying liver disease, when graded according to the Pugh's score (p < 0.05). Proton MRS of the basal ganglia was performed in 12 patients and 14 healthy volunteers. Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr ratios were observed in the patient population. Phosphorus-31 MRS of the basal ganglia was performed in the remaining nine patients and in 15 healthy volunteers. Peak area ratios of phosphomonoesters (PME), inorganic phosphate, phosphodiesters (PDE) and phosphocreatine relative to beta ATP (ATP) were then measured. Mean values of PME/ATP and PDE/ATP were significantly lower in the patient population. No correlation was found between the T1WSE MRI contrast measurements of the globus pallidus and the abnormalities in the metabolite ratios measured from either proton or phosphorus-31 MR spectra. Our results suggest that pallidal hyperintensity seen on T1WSE MR imaging of patients with chronic liver disease is not related to the functional abnormalities of the brain observed in hepatic encephalopathy.
Oxidative damage plays a major part in the pathogenesis of liver disease. Uncoupling proteins (UC... more Oxidative damage plays a major part in the pathogenesis of liver disease. Uncoupling proteins (UCPs) may be able to limit the generation of reactive oxygen species (ROS) and be cytoprotective. We investigated the effect of up-regulation of UCP2 in a hepatoblastoma cell line exposed to menadione or hypoxia/re-oxygenation. Lipid and protein oxidation was increased in HepG2 cells exposed to ROS but this increase was significantly lower in cells over-expressing UCP2 under identical conditions. LDH release increased 2.5-fold in response to hypoxia/re-oxygenation in control HepG2 cells with no significant increase in UCP2 transfected cells. Hypoxia/re-oxygenation resulted in a reduction in liver-specific protein secretion that was attenuated in transfected cells and UCP2 over-expression also resulted in a 66% reduction in apoptosis compared with non-transfected controls. These data suggest that UCP2 can limit oxidative damage in HepG2 cells in response to oxidative stress resulting in improved cell function and resistance to apoptosis.
Background &a... more Background & Aims: Aminosalicylates are widely used in the treatment of ulcerative colitis (UC). Balsalazide is a novel mesalamine prodrug, activated by colonic bacteria. The aim of this study was to compare the efficacy and safety of balsalazide with that of a pH-dependent formulation of mesalamine in active UC. Methods: A randomized, double-blind study was performed comparing balsalazide, 6.75 g
Insufficient donor organs for orthotopic liver transplantation worldwide have urgently increased ... more Insufficient donor organs for orthotopic liver transplantation worldwide have urgently increased the requirement for new therapies for acute and chronic liver disease. Whilst none are yet clinically proven there are at least two different approaches for which there is extensive experimental data, some human anecdotal evidence and some data emerging from Phase 1 clinical trials. Both approaches involve bio-engineering. In vivo tissue engineering involves isolated liver cell transplantation into the liver and/or other ectopic sites and in vitro tissue engineering, using an extracorporeal hepatic support system or bioartificial liver. Some questions are common to both these approaches, such as the best cell source and the therapeutic mass required, and are discussed. Others are specific to each approach. For cell transplantation in vivo the initial engraftment and repopulation will make a critical difference to the outcome, and development of markers for transplanted cells has enabled significant advances in understanding, and therefore manipulating, the process. Moreover, the role of immunosuppression is also important and novel approaches to natural immunosuppression are discussed. For use in a bioartificial liver, the ability for hepatocytes to perform ex vivo at in vivo levels is critical. Three dimensional culture improves cell performance over monolayer cultures. Alginate encapsulated cells offer a suitable 3-D environment for a bioartificial liver since they are both easily manipulatable and cryopreservable. The use of cells derived from stem cells or foetal rather than adult liver cells is also emerging as a potential human cell source which may overcome problems associated with xenogeneic cells.
Acute liver failure has high mortality due to donor organ shortages. A bioartificial liver could ... more Acute liver failure has high mortality due to donor organ shortages. A bioartificial liver could "bridge the gap" to transplant or spontaneous recovery. Alginate encapsulation of HepG2 cells enables cell spheroid formation, thus providing sufficient functional biomass. Cryopreservation (CryoP) of these spheroids would allow an off-the-shelf capability for unpredictable emergency use. Cell death during CryoP often results from intracellular ice formation, after supercooling. An ice nucleating agent (INA), crystalline cholesterol, was trialled to reduce supercooling and subsequent cryoinjury. Spheroids were cooled in a controlled rate freezer in 12% dimethylsulfoxide/Celsior +/- INA, and sample temperatures were recorded throughout. Viability was assessed using fluorescent staining with image analysis, cell number by nuclei count, function using assays to detect liver-specific protein synthesis and secretion, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) reduction, and broad-spectrum cytochrome P450 activity. Spheroids cryopreserved without INA displayed latent cryoinjury in the first 6 h after thawing. INA reduced supercooling during CryoP and also latent cryoinjury. Cell numbers, viability, and function as measured over 72 h post-thaw were all improved when INA was present during CryoP.
A bioartificial liver comprising alginate-encapsulated liver cell spheroids (ELS) could bridge th... more A bioartificial liver comprising alginate-encapsulated liver cell spheroids (ELS) could bridge the gap to transplant or spontaneous recovery in acute liver failure, but will be required for emergency use, necessitating cryopreservation. A cryopreservation protocol has been developed, but beyond this, the feasibility of cold-chain storage is considered here. Cryopreservation will be increasingly required for timely delivery of tissue and bioengineered products, and significant, but often, over-looked factors that impact on cost and ease of clinical application are the storage temperature and useful preservation time. Storage in the vapor phase of liquid nitrogen (∼-170°C) is the gold standard, but for safety and economic purposes, storing ELS in electric freezers at -80°C may be preferable. ELS were cryopreserved using an optimized protocol and stored at either -80°C or at -170°C for up to 1 year. ELS were removed from storage after 1, 2, 3, 6, 9, or 12 months, and recovery was assessed 24 h postwarming. Cell recovery was assessed using viability (fluorescent staining with image analysis), cell number (nuclei count), and functional (hepatospecific protein enzyme-linked immunosorbent assay) assays. Viability, the viable cell number, and function of ELS stored at -170°C were maintained at similar values throughout the year. In contrast, ELS stored at -80°C exhibited decreased viability, viable cell numbers, and function by as early as 1 month. Progressive deterioration was subsequently observed. After 12 months of storage at -80°C, viable cell recovery of ELS was ∼15% that of ELS stored at -170°C. While convenience and cost might support the use of -80°C for storage of multicellular bioengineered products such as ELS, results indicate rapid deterioration in functional recoveries after only a few weeks. This study demonstrates that storage temperature is an important consideration in regenerative medicine and caution should be applied by limiting storage at -80°C to only a few weeks.
The International Journal of Biochemistry & Cell Biology, 2007
A possible cell source for a bio-artificial liver is the human hepatblastoma-derived cell line He... more A possible cell source for a bio-artificial liver is the human hepatblastoma-derived cell line HepG2 as it confers many hepatocyte functions, however, the urea cycle is not maintained resulting in the lack of ammonia detoxification via this cycle. We investigated urea cycle activity in HepG2 cells at both a molecular and biochemical level to determine the causes for the lack of urea cycle expression, and subsequently addressed reinstatement of the cycle by gene transfer. Metabolic labelling studies showed that urea production from 15N-ammonium chloride was not detectable in HepG2 conditioned medium, nor could 14C-labelled urea cycle intermediates be detected. Gene expression data from HepG2 cells revealed that although expression of three urea cycle genes Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase was evident, Ornithine Transcarbamylase and Arginase I expression were completely absent. These results were confirmed by Western blot for arginase I, where no protein was detected. Radiolabelled enzyme assays showed that Ornithine Transcarbamylase functional activity was missing but that Carbamoyl Phosphate Synthase I, Arginosuccinate Synthetase and Arginosuccinate Lyase were functionally expressed at levels comparable to cultured primary human hepatocytes. To restore the urea cycle, HepG2 cells were transfected with full length Ornithine Transcarbamylase and Arginase I cDNA constructs under a CMV promoter. Co-transfected HepG2 cells displayed complete urea cycle activity, producing both labelled urea and urea cycle intermediates. This strategy could provide a cell source capable of urea synthesis, and hence ammonia detoxificatory function, which would be useful in a bio-artificial liver.
Massive hepatic necrosis (MHN) is a condition that offers an opportunity to study the remarkable ... more Massive hepatic necrosis (MHN) is a condition that offers an opportunity to study the remarkable ability of the liver to become repopulated with hepatocytes. A maximal regenerative stimulus is expected in cases of MHN (Roskams et al. APMIS Suppl 1991;23:32-39). Sequential chronological observations, after a severe degree of liver cell loss, permit study of the human equivalent of the situation in animal models in which circulating and bone marrow-derived stem and liver progenitor cells are recruited to the hepatopoietic process. To date, the bone marrow and circulating precursors have not been identified morphologically in human material. We present data that suggest that the circulating liver progenitor could have a lymphoblastoid morphological appearance. Similar cells are seen among the cellular infiltrate of MHN. We have found that combinations of markers, such as CD117/CD133 positive CD45/tryptase negative are useful to isolate these cells using cell-sorting technology. This may facilitate their expansion in vitro and the development of their use for therapeutic purposes. In MHN, the residual portal tracts and ductular reaction with the associated lymphoid infiltrate (some of which are probably liver cell progenitors derived from the circulation) constitute the fundamental regenerative community unit in which hepatopoiesis takes place. Defining the hepatopoietic process is hindered by the lack of morphological transitional forms in the period between the progenitors within the circulation and when they assume recognizable hepatocytic form as "metaplastic" hepatocytes associated with the ductular reaction. By achieving a better comprehension of these processes of liver cell restoration, we will be better placed to accelerate liver recovery in MHN, for example by the administration of granulocyte colony stimulating factor (GCSF). Thus, more patients will be able to restore their own livers and avoid liver transplantation.
The main non-parenchymal cells of the liver, Kupffer cells, sinusoidal endothelial cells and stel... more The main non-parenchymal cells of the liver, Kupffer cells, sinusoidal endothelial cells and stellate cells, participate in liver growth with respect to both their own proliferation, and effects on hepatocyte proliferation. In the well-characterised paradigm of 70% partial hepatectomy, they undergo DNA synthesis and cell division 20-24h later than the hepatocyte population. They exert both positive and negative influences on hepatocyte proliferation, including provision of an extracellular matrix-bound reservoir of hepatocyte growth factor that is activated after damage; priming of hepatocytes for DNA synthesis through rapid generation of TNF-alpha and IL-6; and generation of factors at later time points that curb hepatocyte DNA synthesis (IL-1, TGF-beta) and initiate reconstruction and reformation of matrix proteins.
Thyroxine and tri-iodothyronine are essential for normal organ growth, development and function. ... more Thyroxine and tri-iodothyronine are essential for normal organ growth, development and function. These hormones regulate the basal metabolic rate of all cells, including hepatocytes, and thereby modulate hepatic function; the liver in turn metabolizes the thyroid hormones and regulates their systemic endocrine effects. Thyroid dysfunction may perturb liver function, liver disease modulates thyroid hormone metabolism, and a variety of systemic diseases affect both organs. We highlight the intricate relations between the thyroid gland and the liver in health and disease.
Proliferation of isolated hepatocytes in long-term splenic implants was assessed by flash labelli... more Proliferation of isolated hepatocytes in long-term splenic implants was assessed by flash labelling with a 1 pulse of tritiated thymidine (3H TdR). Cell kinetics showed that the basal labelling index was 0.9% which was greater than normal non-regenerating liver. Twenty four hours following partial hepatectomy the labelling index was 2.0%, a significant rise. These results suggest that hepatocytes transplanted to the spleen constitute a suitable model for screening putative hepatotrophic factors, and are of relevance in establishing clinically useful models of hepatocyte transplantation.
The purpose of this study was to correlate the hyperintensity in the globus pallidus seen on T1-w... more The purpose of this study was to correlate the hyperintensity in the globus pallidus seen on T1-weighted magnetic resonance imaging (MRI) of the brain in chronic liver disease with changes in metabolite ratios measured from both proton and phosphorus-31 magnetic resonance spectroscopy (MRS) localised to the basal ganglia. T1-weighted spin echo (T1WSE) images were obtained in 21 patients with biopsy-proven cirrhosis (nine Child's grade A, eight Child's grade B and four Child's grade C). Four subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, four showed evidence of subclinical hepatic encephalopathy and 13 had overt hepatic encephalopathy. Signal intensities of the globus pallidus and adjacent brain parenchyma were measured and contrast calculated, which correlated with the severity of the underlying liver disease, when graded according to the Pugh's score (p < 0.05). Proton MRS of the basal ganglia was performed in 12 patients and 14 healthy volunteers. Peak area ratios of choline (Cho), glutamine and glutamate (Glx) and N-acetylaspartate relative to creatine (Cr) were measured. Significant reductions in mean Cho/Cr and elevations in mean Glx/Cr ratios were observed in the patient population. Phosphorus-31 MRS of the basal ganglia was performed in the remaining nine patients and in 15 healthy volunteers. Peak area ratios of phosphomonoesters (PME), inorganic phosphate, phosphodiesters (PDE) and phosphocreatine relative to beta ATP (ATP) were then measured. Mean values of PME/ATP and PDE/ATP were significantly lower in the patient population. No correlation was found between the T1WSE MRI contrast measurements of the globus pallidus and the abnormalities in the metabolite ratios measured from either proton or phosphorus-31 MR spectra. Our results suggest that pallidal hyperintensity seen on T1WSE MR imaging of patients with chronic liver disease is not related to the functional abnormalities of the brain observed in hepatic encephalopathy.
Oxidative damage plays a major part in the pathogenesis of liver disease. Uncoupling proteins (UC... more Oxidative damage plays a major part in the pathogenesis of liver disease. Uncoupling proteins (UCPs) may be able to limit the generation of reactive oxygen species (ROS) and be cytoprotective. We investigated the effect of up-regulation of UCP2 in a hepatoblastoma cell line exposed to menadione or hypoxia/re-oxygenation. Lipid and protein oxidation was increased in HepG2 cells exposed to ROS but this increase was significantly lower in cells over-expressing UCP2 under identical conditions. LDH release increased 2.5-fold in response to hypoxia/re-oxygenation in control HepG2 cells with no significant increase in UCP2 transfected cells. Hypoxia/re-oxygenation resulted in a reduction in liver-specific protein secretion that was attenuated in transfected cells and UCP2 over-expression also resulted in a 66% reduction in apoptosis compared with non-transfected controls. These data suggest that UCP2 can limit oxidative damage in HepG2 cells in response to oxidative stress resulting in improved cell function and resistance to apoptosis.
Uploads
Papers by Humphrey Hodgson