Differential \u3cem\u3eFmo3\u3c/em\u3e gene expression in various liver injury models involving hepatic oxidative stress in mice

Flavin-containing monooxygenase-3 (FMO3) catalyzes metabolic reactions similar to cytochrome P450 monooxygenase, however, most metabolites of FMO3 are considered non-toxic. Recent findings in our laboratory demonstrated Fmo3 gene induction following toxic acetaminophen (APAP) treatment in mice. The goal of this study was to evaluate Fmo3 gene expression in other diverse mouse models of hepatic oxidative stress and injury. Fmo3 gene regulation by Nrf2 was also investigated using Nrf2 knockout (Nrf2 KO) mice. In our studies, male C57BL/6J mice were treated with toxic doses of hepatotoxicants or underwent bile duct ligation (BDL, 10 days). Hepatotoxicants included APAP (400 mg/kg, 24–72 h), alpha-naphthyl isothiocyanate (ANIT; 50 mg/kg, 2–48 h), carbon tetrachloride (CCl4; 10 or 30 μL/kg, 24 and 48 h) and allyl alcohol (AlOH; 30 or 60 mg/kg, 6 and 24 h). Because oxidative stress activates nuclear factor (erythroid-derived 2)-like 2 (Nrf2), additional studies investigated Fmo3 gene regulation by Nrf2 using Nrf2 knockout (Nrf2 KO) mice. At appropriate time-points, blood and liver samples were collected for assessment of plasma alanine aminotransferase (ALT) activity, plasma and hepatic bile acid levels, as well as liver Fmo3 mRNA and protein expression. Fmo3 mRNA expression increased significantly by 43-fold at 12 h after ANIT treatment, and this increase translates to a 4-fold change in protein levels. BDL also increased Fmo3 mRNA expression by 1899-fold, but with no change in protein levels. Treatment of mice with CCl4 decreased liver Fmo3 gene expression, while no change in expression was detected with AlOH treatment. Nrf2 KO mice are more susceptible to APAP (400 mg/kg, 72 h) treatment compared to their wild-type (WT) counterparts, which is evidenced by greater plasma ALT activity. The Fmo3 mRNA and protein expression increased in Nrf2 KO mice after APAP treatment. Collectively, not all hepatotoxicants that produce oxidative stress alter Fmo3 gene expression. Along with APAP, toxic ANIT treatment in mice markedly increased Fmo3 gene expression. While BDL increased the Fmo3 mRNA expression, the protein level did not change. The discrepancy with Fmo3 induction in cholestatic models, ANIT and BDL, is not entirely clear. Results from Nrf2 KO mice with APAP suggest that the transcriptional regulation of Fmo3 during liver injury may not involve Nrf2

Characterization of Flavin-containing Monooxygenase-3 (FMO3) as a Novel Genetic Determinant of Acetaminophen (APAP) Induced Hepatotoxicity

Mice pretreated with a mild toxic dose of acetaminophen (APAP) acquire resistance to a second, higher APAP dose. This phenomenon is termed APAP autoprotection and the exact mechanism by which such resistance develops is not clearly known. Given the prevalence of APAP-hepatotoxicity and the human health impact of this potentially hepatotoxic agent, a further understanding of the mechanism(s) involved in such protection are of considerable significance and could lead to new modalities of treatment of acute drug-induced liver injury. The work presented in this thesis investigates FMO3 gene expression during APAP-induced liver injury as well as the functional significance of FMO3 over-expression during APAP-induced liver injury. Furthermore, FMO3 gene regulation during oxidative stress conditions is also examined. Acetaminophen treatment resulted in up-regulation of liver Fmo3 protein in male mice. Female mice express higher liver Fmo3 than males and are highly resistant to APAP hepatotoxicity. Inhibition of Fmo3, by methimazole, renders female mice susceptible to APAP-induced liver injury. These findings are suggestive of a protective function for Fmo3. In addition to APAP, ANIT and BDL also increase Fmo3 gene expression in mice. Because these hepatotoxicants also induce oxidative stress, we also investigated the potential role of the oxidative stress sensor and transcription factor, NRF2, in FMO3 gene regulation. Both in vivo and in vitro results show that transcriptional regulation of FMO3 might not involve the NRF2-KEAP1 regulatory pathway. Human liver can adapt to APAP-induced hepatotoxicity similar to our APAP autoprotection mouse model. The last part of this dissertation examined FMO3 gene induction in a human hepatoma cell line, HepaRG. APAP induced FMO3 gene expression in HepaRG cells, and over-expression of FMO3 protects cells against APAP-induced cytotoxicity. The unexpected observation of a faster differentiation phenotype in HepaRG cells over-expressing FMO3 suggests that FMO3 may play an important role in cellular differentiation. Collectively, data presented in this thesis provide evidence for Fmo3 as a novel genetic determinant of APAP-induced liver injury. Furthermore, this thesis describes a novel protective function for FMO3. Findings from HepaRG cells suggest that FMO3 over-expression in response to APAP may be a driving force for differentiation in regenerating hepatocytes

From hepatoprotection models to new therapeutic modalities for treating liver diseases: a personal perspective [version 2; referees: 2 approved]

A variety of rodent models of hepatoprotection have been developed in which tolerance to acetaminophen-induced hepatotoxicity occurs. Autoprotection/heteroprotection is a phenomenon where prior exposure to a mildly toxic dose of toxicant confers protection against a subsequently administered higher dose of the same toxicant (as in the case of autoprotection) or to a different toxicant (referred to as heteroprotection). Multiple mechanisms regulate this adaptive response, including hepatocellular proliferation, proteostasis, enhanced expression of cytoprotective genes, and altered tissue immune response. In this review, we will discuss recent findings that highlight the complexity of these adaptive mechanisms and we also outline the usefulness of these findings to devise therapeutic and/or diagnostic tools for acetaminophen-induced liver damage in patients

Bioactive polymeric scaffolds for tissue engineering

A variety of engineered scaffolds have been created for tissue engineering using polymers, ceramics and their composites. Biomimicry has been adopted for majority of the three-dimensional (3D) scaffold design both in terms of physicochemical properties, as well as bioactivity for superior tissue regeneration. Scaffolds fabricated via salt leaching, particle sintering, hydrogels and lithography have been successful in promoting cell growth in vitro and tissue regeneration in vivo. Scaffold systems derived from decellularization of whole organs or tissues has been popular due to their assured biocompatibility and bioactivity. Traditional scaffold fabrication techniques often failed to create intricate structures with greater resolution, not reproducible and involved multiple steps. The 3D printing technology overcome several limitations of the traditional techniques and made it easier to adopt several thermoplastics and hydrogels to create micro-nanostructured scaffolds and devices for tissue engineering and drug delivery. This review highlights scaffold fabrication methodologies with a focus on optimizing scaffold performance through the matrix pores, bioactivity and degradation rate to enable tissue regeneration. Review highlights few examples of bioactive scaffold mediated nerve, muscle, tendon/ligament and bone regeneration. Regardless of the efforts required for optimization, a shift in 3D scaffold uses from the laboratory into everyday life is expected in the near future as some of the methods discussed in this review become more streamlined

Role of nuclear factor-erythroid 2-related factor 2 (Nrf2) in the transcriptional regulation of brain ABC transporters during acute acetaminophen (APAP) intoxication in mice

Changes in expression of liver ABC transporters have been described during acute APAP intoxication. However, the effect of APAP on brain ABC transporters is poorly understood. The aim of this study was to evaluate the effect of APAP on brain ABC transporters expression and the role of the oxidative stress sensor Nrf2. Male C57BL/6J mice were administered APAP (400 mg/kg) for analysis of brain mRNA and protein expression of Mrp1-6, Bcrp and P-gp. The results show induction of P-gp, Mrp2 and Mrp4 proteins, with no changes in Bcrp, Mrp1 or Mrp5-6. The protein values were accompanied by corresponding changes in mRNA levels. Additionally, brain Nrf2 nuclear translocation and expression of two Nrf2 target genes, NAD(P)H:quinone oxidoreductase 1 (Nqo1) and Hemoxygenase 1 (Ho-1), was evaluated at 6, 12 and 24 h after APAP treatment. Nrf2 nuclear content increased by 58% at 12 h after APAP along with significant increments in mRNA and protein expression of Nqo1 and Ho-1. Furthermore, APAP treated Nrf2 knockout mice did not increase mRNA or protein expression of Mrp2 and Mrp4 as observed in wildtypes. In contrast, P-gp induction by APAP was observed in both genotypes. In conclusion, acute APAP intoxication induces protein expression of brain P-gp, Mrp2 and Mrp4. This study also suggests that brain changes in Mrp2 and Mrp4 expression may be due to in situ Nrf2 activation by APAP, while P-gp induction is independent of Nrf2 function. The functional consequences of these changes in brain ABC transporters by APAP deserve further attention.Fil: Ghanem, Carolina Inés. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Rudraiah, Swetha. University Of Connecticut; Estados UnidosFil: Bataille, Amy M.. University Of Connecticut; Estados UnidosFil: Vigo, María B.. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Farmacológicas (i); Argentina. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica; ArgentinaFil: Goedken, Michael J.. Rutgers University. Office of Translational Science; Estados UnidosFil: Manautou, José E.. University Of Connecticut; Estados Unido

Spiral Layer-by-Layer Micro-Nanostructured Scaffolds for Bone Tissue Engineering

This Article reports the fabrication and characterization of composite micro-nanostructured spiral scaffolds functionalized with nanofibers and hydroxyapatite (HA) for bone regeneration. The spiral poly­(lactic acid-<i>co</i>-glycolic acid) (PLGA) porous microstructure was coated with sparsely spaced PLGA nanofibers and HA to enhance surface area and bioactivity. Polyelectrolyte-based HA coating in a layer-by-layer (LBL) fashion allowed 10–70 μM Ca²⁺/mm² incorporation. These scaffolds provided a controlled release of Ca²⁺ ions up to 60 days with varied release kinetics accounting up to 10–50 μg. Spiral scaffolds supported superior adhesion, proliferation, and osteogenic differentiation of rat bone marrow stromal cells (MSCs) as compared to controls microstructures. Spiral micro-nanostructures supported homogeneous tissue ingrowth and resulted in bone-island formation in the center of the scaffold as early as 3 weeks in a rabbit ulnar bone defect model. In contrast, control cylindrical scaffolds showed tissue ingrowth only at the surface because of limitations in scaffold transport features