Low levels of hepatic glutathione S-transferase and increased formation of aflatoxin B1 (AFB1)-DNA adducts correlate with hepatocyte proliferation and increased hepatocarcinogenesis in both newborn ...mice and partially hepatectomized adult mice, as compared to normal, adult C57BL/6J mice. Newborn mice, which are highly susceptible to the hepatocarcinogenic effects of AFB1, have active proliferation of hepatocytes until 3 weeks of age, when hepatocyte proliferation abruptly ceases. At about this time, the mice become highly resistant to AFB1. In adult mice, AFB1 carcinogenicity is increased after stimulation of liver proliferation by partial hepatectomy. To become carcinogenic, AFB1 is activated in the liver by the P450 enzyme system to electrophilic intermediates, some of which form DNA adducts believed to be responsible for mutations leading to cancer. The most carcinogenic intermediate, AFB(1)-8,9-epoxide, is detoxified by glutathione S-transferase-mediated conjugation to glutathione. Glutathione levels, glutathione S-transferase levels, and AFB1-DNA adduct formation were measured at 4, 10, 30, 120, 245 and 365 days of age in C57BL/6J mice. There was a 5-fold increase in hepatic glutathione S-transferase levels and 13-fold decrease in hepatic AFB1-DNA adduct formation over these ages. Induction of hepatocyte proliferation following partial hepatectomy of 120-day-old mice lowered hepatic glutathione S-transferase levels and increased the extent of hepatic AFB1-DNA formation to levels similar to those measured in 4-day-old mice. These results indicate that increased susceptibility to AFB1 hepatocarcinogenesis in newborn mice, and in adult mice following partial hepatectomy, is due to decreased GST and increased adduct formation in proliferating liver.
Orthotopic liver transplant represent the state of the art treatment for terminal liver pathologies such as cirrhosis in adults and hemochromatosis in neonates. A limited supply of transplantable ...organs in relationship to the demand means that many patients will succumb to disease before an organ becomes available. One promising alternative to liver transplant is therapy based on the transplant of liver progenitor cells. These cells may be derived from the patient, expanded in vitro, and transplanted back to the diseased liver. Inborn metabolic disorders represent the most attractive target for liver progenitor cell therapy, as many of these disorders may be corrected by repopulation of only a portion of the liver by healthy cells. Another potential application for liver progenitor cell therapy is the seeding of bio-artificial liver matrix. These ex vivo bioreactors may someday be used to bridge critically ill patients to other treatments. Conferring a selective growth advantage to the progenitor cell population remains an obstacle to therapy development. Understanding the molecular signaling mechanisms and micro-environmental cues that govern liver progenitor cell phenotype may someday lead to strategies for providing this selective growth advantage. The discovery of a population of cells within the bone marrow possessing the ability to differentiate into hepatocytes may provide an easily accessible source of cells for liver therapies.
Modern medicine has conquered an enormous spectrum of health concerns, from the neonatal to the geriatric, the chronically ill to the acutely injured. Among the unmet challenges remaining in modern ...medicine are inborn disorders of metabolism within the liver. Such inherited metabolic disorders (IMDs) often leave an otherwise healthy individual with a crippling imbalance. As the principal regulator of the body's many metabolic pathways, malencoded hepatic enzymes can drastically disrupt homeostasis throughout the entire body. Severe phenotypes are usually detected within the first few days of life, and treatments range from palliative lifestyle modifications to aggressive surgical procedures. While orthotopic liver transplantation is the single last resort “cure” for these conditions, research during the past few years has brought new therapeutic technologies ever closer to the clinic. Stem cells, therapeutic viral vectors, or a combination thereof, are projected to be the next, best, and final cure for IMDs, which is well-reflected by this generation's research initiatives.
This review illustrates promising regenerative medicine technologies that are being developed for the treatment of gastrointestinal diseases. The main strategies under validation to bioengineer or ...regenerate liver, pancreas, or parts of the digestive tract are twofold: engineering of progenitor cells and seeding of cells on supporting scaffold material. In the first case, stem cells are initially expanded under standard tissue culture conditions. Thereafter, these cells may either be delivered directly to the tissue or organ of interest, or they may be loaded onto a synthetic or natural three-dimensional scaffold that is capable of enhancing cell viability and function. The new construct harbouring the cells usually undergoes a maturation phase within a bioreactor. Within the bioreactor, cells are conditioned to adopt a phenotype similar to that displayed in the native organ. The specific nature of the scaffold within the bioreactor is critical for the development of this high-function phenotype. Efforts to bioengineer or regenerate gastrointestinal tract, liver and pancreas have yielded promising results and have demonstrated the immense potential of regenerative medicine. However, a myriad of technical hurdles must be overcome before transplantable, engineered organs become a reality.
To date the molecular signals regulating activation, proliferation, and differentiation of hepatic oval cells are not fully understood. The Wnt family is essential in hepatic embryogenesis and ...implicated in hepatic carcinogenesis. This study elucidates novel findings implicating Wnt1 in directing oval cell differentiation during the rat 2-acetylaminofluorene (2AAF) and 2/3 partial hepatectomy (PHx) liver regeneration model. Proteins of Wnt family members were predominantly localized in pericentral hepatocytes during liver injury, oval cell activation, and hepatocyte regeneration. In addition, Wnt message increased coinciding with the rise in oval cell number, whereas protein levels peaked immediately after the height of oval cell proliferation. Immunohistochemical analysis demonstrated nuclear translocation of beta-catenin within oval cells throughout the 2AAF/PHx protocol. Furthermore, RNA interference was used in vivo to confirm the physiological requirement of Wnt1 during the oval cell induction. Ultimately, inhibition of Wnt1 resulted in failure of oval cells to differentiate into hepatocytes and alternatively induced atypical ductular hyperplasia. Taken together, these data indicate that in vivo exposure to Wnt1 shRNA inhibited rat oval cell liver regeneration. In the absence of Wnt1 signaling, oval cells failed to differentiate into hepatocytes and underwent atypical ductular hyperplasia, exhibiting epithelial metaplasia and mucin production. Furthermore, changes in Wnt1 levels are required for the efficient regeneration of the liver by oval cells during massive hepatic injury.
Recent studies have demonstrated that reactive oxygen species (ROS) may be a plausible approach for treating cancer. However, the potential drawback is while many treatments halt carcinoma growth, ...they also have detrimental effects on normal tissue. Hence, creating a selective therapy would be advantageous. Our study utilized peroxide generating particles, sodium percarbonate (SPO), calcium peroxide (CPO), and magnesium peroxide (MPO), as an ROS delivery system, for targeting and killing hepatomas (HepG2), while having little to no effect on the normal healthy hepatic cells (hepatocytes). The relation between hydrogen peroxide and cell death was investigated in detail. All three peroxide delivery systems were able to reduce cell viability of the HepG2, while sustaining viability of the hepatocytes. All three systems also significantly reduced cell growth and colony formation of the HepG2 cells, whereas no significant change in the hepatocytes regarding morphological and growth patterns were observed. It was found that CPO was most effective at halting proliferative hepatomas. This data suggest that exploiting the intracellular hydrogen peroxide stress of hepatomas, may be a novel approach for targeting liver carcinomas in a selective manner. Also that peroxide is a beneficial tool for causing apoptosis of hepatomas.
Fibrosis is an underlying cause of cirrhosis and hepatic failure resulting in end stage liver disease with limited pharmacological therapeutic options. The beneficial effects of relaxin peptide ...treatment have been demonstrated previously in clinically relevant animal models of liver disease. However, the low stability of the recombinant relaxin peptide
in vivo
requires continuous intravenous delivery for chronic therapeutic application. We have recently identified a first series of small molecule allosteric biased agonists of the human relaxin receptor RXFP1 which showed efficacy similar to relaxin in several functional assays
in vitro
. Here we investigated the therapeutic effects of small molecule RXFP1 agonist on activated hepatic stellate cells, the main source of excessive collagen production in liver fibrosis. We have demonstrated that RXFP1 expression is increased in fibrotic mouse liver, specifically in activated hepatic stellate cells. The lead compound, ML290, was selected based on its effects on the expression of the genes involved in fibrosis in primary human stellate cells. RNA-Seq analysis of TGFβ1-activated LX-2 hepatic stellate cells showed that about 500 genes were misregulated by ML290. Gene Ontology analysis demonstrated that ML290 treatment primarily affects extracellular matrix remodeling and cytokine signaling, with expression profiles indicating an antifibrotic effect of ML290. ML290 treatment of human liver organoids with lipopolysaccharide-induced fibrotic phenotype resulted in dramatic reduction of type I collagen. The pharmacokinetics of ML290 in mice after multiple injections demonstrated its high stability
in vivo
, as evidenced by the sustained concentrations of compound in the liver. The ML290 treatment of mice expressing human RXFP1 gene with carbon tetrachloride-induced liver fibrosis resulted in significantly reduced collagen content, alpha-smooth muscle actin expression and cell proliferation around portal ducts, and the decrease of pro-fibrotic genes’ expression. In summary, ML290, the small molecule agonist of relaxin receptor, has anti-fibrotic effects in liver fibrosis. Funding source: NIH/NIDDK
Low levels of hepatic glutathione S-transferase and increased formation of aflatoxin B
1 (AFB
1)–DNA adducts correlate with hepatocyte proliferation and increased hepatocarcinogenesis in both newborn ...mice and partially hepatectomized adult mice, as compared to normal, adult C57BL/6J mice. Newborn mice, which are highly susceptible to the hepatocarcinogenic effects of AFB
1, have active proliferation of hepatocytes until 3 weeks of age, when hepatocyte proliferation abruptly ceases. At about this time, the mice become highly resistant to AFB
1. In adult mice, AFB
1 carcinogenicity is increased after stimulation of liver proliferation by partial hepatectomy. To become carcinogenic, AFB
1 is activated in the liver by the P450 enzyme system to electrophilic intermediates, some of which form DNA adducts believed to be responsible for mutations leading to cancer. The most carcinogenic intermediate, AFB
1-8,9-epoxide, is detoxified by glutathione S-transferase-mediated conjugation to glutathione. Glutathione levels, glutathione S-transferase levels, and AFB
1–DNA adduct formation were measured at 4, 10, 30, 120, 245 and 365 days of age in C57BL/6J mice. There was a 5-fold increase in hepatic glutathione S-transferase levels and 13-fold decrease in hepatic AFB
1–DNA adduct formation over these ages. Induction of hepatocyte proliferation following partial hepatectomy of 120-day-old mice lowered hepatic glutathione S-transferase levels and increased the extent of hepatic AFB
1–DNA formation to levels similar to those measured in 4-day-old mice. These results indicate that increased susceptibility to AFB
1 hepatocarcinogenesis in newborn mice, and in adult mice following partial hepatectomy, is due to decreased GST and increased adduct formation in proliferating liver.
PDF
