Lung-restricted ALK5 inhibition avoids systemic toxicities associated with TGFß pathway inhibition.

Systemic therapies targeting transforming growth factor beta (TGFß) or TGFßR1 kinase (ALK5) have been plagued by toxicities including cardiac valvulopathy and bone physeal dysplasia in animals, posing a significant challenge for clinical development in pulmonary indications. The current work aims to demonstrate that systemic ALK5-associated toxicities can be mitigated through localized lung delivery. Lung-selective (THRX-144644) and systemically bioavailable (galunisertib) ALK5 inhibitors were compared to determine whether lung selectivity is sufficient to maintain local tissue concentrations while mitigating systemic exposure and consequent pathway-related findings. Both molecules demonstrated potent ALK5 activity in rat precision cut lung slices (PCLS; p-SMAD3 half-maximal inhibitory concentration [IC50], 141 nM and 1070 nM for THRX-144644 and galunisertib, respectively). In 14-day repeat-dose studies in rats, dose-related cardiac valvulopathy was recapitulated with oral galunisertib at doses ≥150 mg/kg/day. In contrast, inhaled nebulized THRX-144644 did not cause similar systemic findings up to the maximally tolerated doses in rats or dogs (10 and 1.5 mg/kg/day, respectively). THRX-144644 lung-to-plasma ratios ranged from 100- to 1200-fold in rats and dogs across dose levels. THRX-144644 lung trough (24 h) concentrations in rats and dogs ranged from 3- to 17-fold above the PCLS IC50 across tolerated doses. At a dose level exceeding tolerability (60 mg/kg/day; 76-fold above PCLS IC50) minimal heart and bone changes were observed when systemic drug concentrations reached pharmacologic levels. In conclusion, the current preclinical work demonstrates that localized pulmonary delivery of an ALK5 inhibitor leads to favorable TGFß pathway pharmacodynamic inhibition in lung while minimizing key systemic toxicities.

Atypical presentation and pathogenesis of a macaque lymphocryptoviral-associated B-cell lymphoma in a cynomolgus monkey.

We report the unique pathogenesis and presentation of a rapidly progressive B-cell lymphoma in a 3-year-old female cynomolgus monkey on day 50 of a 13-week toxicity study. Clinical pathology evaluation revealed a marked leukocytosis with bicytopenia. A serum protein electrophoresis was consistent with monoclonal gammopathy. The architecture of the lymph node, spleen, and thymus were variably effaced by neoplastic cells, which also infiltrated other tissues. Immunohistochemistry of the affected tissues confirmed a predominant population of CD20+, CD79a+, CD3-, CD68-, and CD34-neoplastic cells. The full data best support a diagnosis of Stage V lymphoma. Nextgen sequencing and negative prestudy serology results suggested a recent infection by macaque lymphocryptovirus (mLCV) with a unique transcriptional profile comparable with a rarely observed direct LCV infection model. This infection model might be associated with a temporary lack of an LCV antigen-specific cytotoxic T-cell adaptive immune response. Consistent with the established mechanisms of LCV-related lymphoproliferation, MYC and BCL2L11 gene expression were increased and decreased, respectively. While there was no overt immunosuppression, immunophenotyping revealed the index animal had a relatively low NK cell count, which further decreased by >50% on day 24 of the study. In addition to the temporary lack of adaptive immunity, the low NK cell counts were suggestive of an impaired innate immunity to control the virally-transformed cells and the subsequent unchecked lymphoproliferation. To our knowledge, this is the first report of a Stage V lymphoma with a unique pathogenesis in an otherwise immunocompetent cynomolgus monkey.

Identification of a functional antioxidant response element within the eighth intron of the human ABCC3 gene.

The ATP-binding cassette (ABC) family of transporters, including ABCC3, is a large family of efflux pumps that plays a pivotal role in the elimination of xenobiotics from the body. ABCC3 has been reported to be induced during hepatic stress conditions and through the progression of some forms of cancer. Several lines of evidence have implicated the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2) in this induction. However, although rodent models have been investigated, a functional antioxidant response element (ARE) in the human ABCC3 gene has not been identified. The purpose of this study was to identify and characterize the ARE(s) responsible for mediating the Nrf2-dependent induction of the human ABCC3 gene. A high-throughput chromatin immunoprecipitation-sequencing analysis performed in A549 cells revealed a specific interaction between Nrf2 and the eighth intron of the human ABCC3 gene rather than the more prototypical flanking region of the gene. Subsequent in silico analysis of the intron identified two putative ARE elements that contained the core consensus ARE sequence commonly found in several Nrf2-responsive genes. Functional characterization of these two AREs using luciferase-reporter constructs with ARE mutant constructs revealed that one of these putative AREs is functionally active. Finally, DNA pull-down assays confirmed specific binding of these intronic AREs by Nrf2 in vitro. Our findings identify a functional Nrf2 response element within the eighth intron of the ABCC3 gene, which may provide mechanistic insight into the induction of ABCC3 during antioxidant response stimuli.

Nrf2 regulates ferroportin 1-mediated iron efflux and counteracts lipopolysaccharide-induced ferroportin 1 mRNA suppression in macrophages.

Iron is an essential element of hemoglobin, and efficient iron recycling from senescent erythrocytes by splenic macrophages is required for erythrocyte hemoglobin synthesis during erythropoiesis. Ferroportin 1 (Fpn1) is the sole iron exporter in mammals, and it also regulates iron reutilization. In this study, we demonstrated genetically that a redox-sensitive transcription factor, Nrf2, regulates Fpn1 mRNA expression in macrophages. Nrf2 activation by several electrophilic compounds commonly resulted in the upregulation of Fpn1 mRNA in bone marrow-derived and peritoneal macrophages obtained from wild-type mice but not from Nrf2 knockout mice. Further, Nrf2 activation enhanced iron release from the J774.1 murine macrophage cell line. Previous studies showed that inflammatory stimuli, such as LPS, downregulates macrophage Fpn1 by transcriptional and hepcidin-mediated post-translational mechanisms leading to iron sequestration by macrophages. We showed that two Nrf2 activators, diethyl maleate and sulforaphane (SFN; a natural Nrf2 activator found in broccoli), restored the LPS-induced suppression of Fpn1 mRNA in human and mouse macrophages, respectively. Furthermore, SFN counteracted the LPS-induced increase of Hepcidin mRNA by an Nrf2-independent mechanism in mouse peritoneal macrophages. These results demonstrate that Nrf2 regulates iron efflux from macrophages through Fpn1 gene transcription and suggest that Nrf2 may control iron metabolism during inflammation.

Nrf2-deficiency creates a responsive microenvironment for metastasis to the lung.

The Nrf2 transcription factor is crucial for regulating the cellular defense against various carcinogens. However, relationship between host Nrf2 and cancer metastasis remains unexplored. To address this issue, we examined susceptibility of Nrf2-deficient mice to pulmonary cancer metastasis following implantation of the mouse Lewis lung carcinoma (3LL) cell line. Nrf2-deficient mice reproducibly exhibited a higher number of pulmonary metastatic nodules than wild-type mice did. The lung and bone marrow (BM) of cancer-bearing Nrf2-deficient mice contained increased numbers of inflammatory cells, including myeloid-derived suppressor cells (MDSCs), a potent population of immunosuppressive cells. MDSCs can attenuate CD8(+) T-cell immunity through modification of the T-cell receptor complex exploiting reactive oxygen species (ROS). MDSCs of Nrf2-deficient mice retained elevated levels of ROS relative to wild-type mice. BM transplantation experiments revealed functional disturbance in the hematopoietic and immune systems of Nrf2-deficient mice. Wild-type recipient mice with Nrf2-deficient BM cells showed increased levels of lung metastasis after cancer cell inoculation. These mice exhibited high-level accumulation of ROS in MDSCs, which showed very good coincidence to the decrease of splenic CD8(+) T-cells. In contrast, Keap1-knockdown mutant mice harboring high-level Nrf2 expression displayed increased resistance against the cancer cell metastasis to the lung, accompanied by a decrease in ROS in the MDSCs fraction. Our results thus reveal a novel function for Nrf2 in the prevention of cancer metastasis, presumably by its ability to preserve the redox balance in the hematopoietic and immune systems.

Genetic analysis of cytoprotective functions supported by graded expression of Keap1.

Keap1 regulates Nrf2 activity in response to xenobiotic and oxidative stresses. Nrf2 is an essential regulator of cytoprotective genes. Keap1-null mice are lethal by weaning age due to malnutrition caused by severe hyperkeratosis of the upper digestive tract. Analysis of Keap1::Nrf2 double mutant mice revealed that currently recognizable phenotypes of Keap1-null mice are all attributable to constitutive activation of Nrf2. We previously reported that hepatocyte-specific Keap1 knockout (Keap1(flox/-)::Albumin-Cre) mice are viable and more resistant to acute toxicity of acetaminophen (APAP). In the current study, we found that the floxed Keap1 allele is hypomorphic and that Keap1 expression was decreased in all examined tissues of Keap1(flox/-) mice. Taking advantage of the hypomorphic phenotype of Keap1(flox/-) mice, we examined the effects of graded reduction of Keap1 expression in adult mice. When challenged with APAP, Keap1(flox/-) mice were more protected from mortality than wild-type and even Keap1(flox/-)::Albumin-Cre mice. In contrast, a decrease in Keap1 levels to less than 50% resulted in increased mortality in a study of 2-year-old mice. These results support our contention that the benefits of Nrf2 activation in acute toxicity are hormetic and that constitutive Nrf2 activation beyond a certain threshold is rather disadvantageous to long-term survival.

Nrf2 counteracts cholestatic liver injury via stimulation of hepatic defense systems.

The transcription factor Nrf2 is a key regulator for hepatic induction of detoxifying enzymes, antioxidative stress genes and Mrp efflux transporters. We aimed to investigate whether Nrf2 activation counteracts liver injury associated with cholestasis. The role of Nrf2 activation in counteracting cholestatic liver injury was studied using a bile duct-ligation (BDL) model of Keap1 gene-knockdown (Keap1-kd) mice that represent the sustained activation of Nrf2 in the liver. Upon Nrf2 activation, Keap1-kd mice showed large increases in Mrp efflux transporters, detoxifying enzymes and antioxidative stress genes in the livers. After BDL, the number of hepatic parenchymal necrosis and the reactive oxygen species content were significantly smaller in the livers of the Keap1-kd mice than in those of the WT mice. Moreover, the increase in serum bilirubin levels was attenuated in the Keap1-kd mice. In conclusion, the results suggest a hepatoprotective role of sustained Nrf2 activation against liver injury associated with cholestasis.

Hepatocyte-specific deletion of heme oxygenase-1 disrupts redox homeostasis in basal and oxidative environments.

Heme oxygenase-1 (HO-1) is the rate-limiting enzyme of heme catabolism and has been assumed to be important in cellular response against oxidative stress through modification of the pro-oxidant heme into less toxic catabolites that behave as antioxidants. However, the precise mechanisms involved and the physiological significance of such activity remain to be clarified. To elucidate roles HO-1 plays in vivo, hepatocyte-specific conditional knockout (CKO) mice of HO-1 gene were generated by site-specific recombination using albumin-promoter-driven Cre-loxP system. In livers of HO-1 CKO mice HO-1 protein level decreased to approximately 30% of control mouse livers. The HO-1 CKO mice are viable, exhibit normal growth curves over six months, and show no histological and serological abnormalities. We found that several cytoprotective genes, such as NAD(P)H dehydrogenase quinone 1 and glutathione S-transferase P1, showed markedly elevated expression, suggesting the increase of oxidative stress in HO-1 CKO mice even under quiescent conditions. In vivo electron paramagnetic resonance studies demonstrated that signal decay times of nitroxyl radicals were significantly longer in livers of HO-1 CKO mice than that of control mice, indicating that radical scavenging activity was significantly compromised in the mutant liver. HO-1 CKO mice were susceptible to carbon tetrachloride hepatotoxicity. These results provide the first in vivo evidence that HO-1 acts to protect cells against the oxidative stress in both basal conditions and upon chemical insult.

Nrf2- and PPAR alpha-mediated regulation of hepatic Mrp transporters after exposure to perfluorooctanoic acid and perfluorodecanoic acid.

Perfluorooctanoic acid and perfluorodecanoic acid (PFDA) are commonly used as emulsifiers and surfactants in fluoropolymer manufacturing and are known peroxisome proliferator-activated receptor alpha (PPAR alpha) agonists. PPAR alpha activation induces beta- and omega-oxidation enzymes such as Cyp4a14 and acyl-CoA oxidase, which are a likely cause of subsequent oxidative stress and peroxisome proliferation. Conversely, NF-E2-related factor-2 (Nrf2) is a transcription factor that protects against oxidative stress and inflammation by regulating several detoxification and xenobiotic transporter genes. Because PFDA markedly induces hepatic metabolism and oxidative stress, we hypothesized that PFDA exposure would increase expression of hepatic efflux multidrug resistance-associated protein (Mrp) transporters. A single PFDA dose (80 mg/kg) administered to mice increased hepatic Mrp3 (fourfold) and Mrp4 (31-fold) mRNA expression. Upregulation of Mrp3 and Mrp4 correlated with elevated serum-conjugated bilirubin and bile acids, respectively. To determine the mechanism of Mrp3 and Mrp4 induction, PFDA was administered to Nrf2-null mice, PPAR alpha-null mice, and mice pretreated with gadolinium chloride, a Kupffer cell-depleting chemical capable of inhibiting the inflammatory cytokine response. In both PPAR alpha- and Nrf2-null mice, maximal induction of Mrp3 and Mrp4 mRNA after PFDA administration was attenuated. Gadolinium chloride pretreatment reduced serum and hepatic tumor necrosis factor-alpha levels after PFDA treatment, as well as Mrp4 mRNA expression by 30%, suggesting that Kupffer cell-derived mediators may contribute to Mrp induction. Thus, after PFDA administration, the liver mounts a compensatory hepatoprotective response via PPAR alpha and Nrf2, markedly increasing Mrp3 and Mrp4 expression, with corresponding increases in serum of known Mrp3 and Mrp4 substrates.

Ursodeoxycholic acid stimulates Nrf2-mediated hepatocellular transport, detoxification, and antioxidative stress systems in mice.

The protective action of ursodeoxycholic acid (UDCA) in cholestatic liver diseases may be mediated by choleresis, detoxification, and cytoprotection against oxidative stress. Nrf2, one transcription factor, serves as a cellular stress sensor and is a key regulator for hepatic induction of detoxifying enzymes, antioxidative stress genes, and numerous Mrp family members. We aimed to investigate whether UDCA induces hepatic Mrp expression along with that of detoxifying enzymes and antioxidative stress genes via the Nrf2 transcriptional pathway. The protein level, subcellular localization, and mRNA level of Mrp family members were assessed in livers of Keap1 gene-knockdown (Keap1-kd) mice and those of UDCA-fed wild-type (WT) and Nrf2 gene-null (Nrf2-null) mice. Nuclear levels of Nrf2 in livers of Keap1-kd mice markedly increased, resulting in constitutive activation of Nrf2. Keap1-kd mice have high-level expression of hepatic Mrp2, Mrp3, and Mrp4 relative to WT mice. UDCA potently increased nuclear Nrf2 expression level in livers of WT mice, and the treatment showed maximal hepatic induction of Mrp2, Mrp3, and Mrp4 in association with enhanced membranous localizations in an Nrf2-dependent manner. UDCA similarly increased nuclear Nrf2 expression level in rat hepatocytes. Chromatin immunoprecipitation assays using mouse hepatocytes revealed the binding of Nrf2 to antioxidant response elements in the promoter regions of Mrp2, Mrp3, and Mrp4. These findings demonstrate an important role of Nrf2 in the induction of Mrp family members in livers and suggest that a therapeutic mechanism of UDCA action is, via Nrf2 activation, a stimulation of detoxification and antioxidative stress systems, along with Mrp-mediated efflux transport.

The Nrf2 activator oltipraz also activates the constitutive androstane receptor.

Oltipraz (OPZ) is a well known inducer of NAD(P)H:quinone oxidoreductase (NQO1) along with other enzymes that comprise the nuclear factor E2-related factor 2 (Nrf2) battery of detoxification genes. However, OPZ treatment also induces expression of CYP2B, a gene regulated by the constitutive androstane receptor (CAR). Therefore, this study was designed to determine whether OPZ induces gene expression in the mouse liver through activation of CAR in addition to Nrf2. OPZ increased the mRNA expression of both Cyp2b10 and Nqo1 in C57BL/6 mouse livers. As expected, in livers from Nrf2-/- mice, OPZ induction of Nqo1 was reduced, indicating Nqo1 induction is dependent on Nrf2 activation, whereas Cyp2b10 induction was unchanged. The robust induction of Cyp2b10 by OPZ in wild-type mice was completely absent in CAR-/- mice, revealing a CAR-dependent induction by OPZ. OPZ also induced transcription of the human CYP2B6 promoter-reporter containing the phenobarbital (PB) responsive element in mouse liver using an in vivo transcription assay. Additionally, OPZ induced in vivo nuclear accumulation of CAR at 3 h but, as with PB, was unable to reverse androstanol repression of mouse CAR constitutive activity in transiently transfected HepG2 cells. In summary, OPZ induces expression of Cyp2b10 and Nqo1 via the activation of CAR and Nrf2, respectively.

Ischemia-reperfusion of rat livers decreases liver and increases kidney multidrug resistance associated protein 2 (Mrp2).

Hepatic ischemia-reperfusion (IR) injury during liver transplantation can lead to cholestasis and remote organ dysfunction. Multidrug resistance-associated proteins (Mrps) are efflux transporters known to transport a diverse set of substrates, such as amphipathic chemicals, organic anions, and endogenous molecules. The purpose of this study was to determine the effect of hepatic IR injury on the expression of Mrps in rat liver and kidney. Male Sprague-Dawley rats were subjected to 60 min of partial hepatic ischemia. At various times after reperfusion (0, 3, 6, 24, and 48 h), the ischemic lobes were harvested as well as kidneys. RNA and protein expression of Mrps in livers and kidneys were determined by the branched DNA method, Western blot analysis, and tissue immunofluorescence. Mrp2 mRNA and protein expression in livers decreased after IR. Conversely, Mrp2 mRNA and protein expression in kidneys increased after IR. Mrp3 mRNA expression, and Mrp4 mRNA and protein expression in kidneys transiently increased after IR. The intensity of immunofluorescent staining of Mrp2 corresponded to changes in Mrp2 expression in livers and kidneys after IR as detected by Western blot analysis and was localized to the apical membrane domain in both tissues. These results demonstrate that after hepatic IR, downregulation of hepatic Mrp2 and upregulation of renal Mrp2 occur. These decreases in hepatic Mrp2 may contribute to cholestasis, yet increases in kidney may protect from oxidative stress and/or inflammation after hepatic IR.

Induction of Mrp3 and Mrp4 transporters during acetaminophen hepatotoxicity is dependent on Nrf2.

The transcription factor NFE2-related factor 2 (Nrf2) mediates detoxification and antioxidant gene transcription following electrophile exposure and oxidative stress. Mice deficient in Nrf2 (Nrf2-null) are highly susceptible to acetaminophen (APAP) hepatotoxicity and exhibit lower basal and inducible expression of cytoprotective genes, including NADPH quinone oxidoreductase 1 (Nqo1) and glutamate cysteine ligase (catalytic subunit, or Gclc). Administration of toxic APAP doses to C57BL/6J mice generates electrophilic stress and subsequently increases levels of hepatic Nqo1, Gclc and the efflux multidrug resistance-associated protein transporters 1-4 (Mrp1-4). It was hypothesized that induction of hepatic Mrp1-4 expression following APAP is Nrf2 dependent. Plasma and livers from wild-type (WT) and Nrf2-null mice were collected 4, 24 and 48 h after APAP. As expected, hepatotoxicity was greater in Nrf2-null compared to WT mice. Gene and protein expression of Mrp1-4 and the Nrf2 targets, Nqo1 and Gclc, was measured. Induction of Nqo1 and Gclc mRNA and protein after APAP was dependent on Nrf2 expression. Similarly, APAP treatment increased hepatic Mrp3 and Mrp4 mRNA and protein in WT, but not Nrf2-null mice. Mrp1 was induced in both genotypes after APAP, suggesting that elevated expression of this transporter was independent of Nrf2. Mrp2 was not induced in either genotype at the mRNA or protein levels. These results show that Nrf2 mediates induction of Mrp3 and Mrp4 after APAP but does not affect Mrp1 or Mrp2. Thus coordinated regulation of detoxification enzymes and transporters by Nrf2 during APAP hepatotoxicity is a mechanism by which hepatocytes may limit intracellular accumulation of potentially toxic chemicals.

Oxidative and electrophilic stress induces multidrug resistance-associated protein transporters via the nuclear factor-E2-related factor-2 transcriptional pathway.

UNLABELLED: Multidrug resistance-associated proteins (Mrps) are adenosine triphosphate-dependent transporters that efflux chemicals out of cells. In the liver, Mrp2 transports bilirubin-glucuronide, glutathione (GSH), and drug conjugates into bile, whereas Mrp3 and Mrp4 efflux these entities into blood. The purpose of this study was to determine whether oxidative conditions (that is, the disruption of hepatic GSH synthesis) or the administration of nuclear factor-E2-related factor-2 (Nrf2) activators (oltipraz and butylated hydroxyanisole) can induce hepatic Mrp transporters and whether that induction is through the Nrf2 transcriptional pathway. Livers from hepatocyte-specific glutamate-cysteine ligase catalytic subunit-null mice had increased nuclear Nrf2 levels, marked gene and protein induction of the Nrf2 target gene NAD(P)H:quinone oxidoreductase 1, as well as Mrp2, Mrp3, and Mrp4 expression. The treatment of wild-type and Nrf2-null mice with oltipraz and butylated hydroxyanisole demonstrated that the induction of Mrp2, Mrp3, and Mrp4 is Nrf2-dependent. In Hepa1c1c7 cells treated with the Nrf2 activator tert-butyl hydroquinone, chromatin immunoprecipitation with Nrf2 antibodies revealed the binding of Nrf2 to antioxidant response elements in the promoter regions of mouse Mrp2 [-185 base pairs (bp)], Mrp3 (-9919 bp), and Mrp4 (-3767 bp). CONCLUSION: The activation of the Nrf2 regulatory pathway stimulates the coordinated induction of hepatic Mrps.

Nrf2 and p53 cooperatively protect against BBN-induced urinary bladder carcinogenesis.

Nuclear factor-erythroid 2 (NF-E2)-related factor 2 (Nrf2), a transcription factor that regulates inducible expression of detoxifying enzymes, is critical in preventing N-nitrosobutyl(4-hydroxybutyl)amine (BBN)-induced urinary bladder carcinogenesis. To explore whether Nrf2 and the tumor suppressor p53 cooperatively act in tumor prevention, we investigated the susceptibility of Nrf2-/-::p53+/- mice to BBN-induced urinary bladder carcinogenesis. The incidence of BBN-induced urinary bladder carcinoma was 63.0% in Nrf2-/- mice (P = 0.115), 75.8% in p53+/- mice (P < 0.01) and 89.6% in Nrf2-/-::p53+/- mice (P < 0.01) compared with 37.9% in wild-type. Higher incidence of carcinoma was observed in Nrf2-/-::p53+/- mice when compared with either Nrf2-/- (P < 0.01) or p53+/- mice (P = 0.382). Similarly, muscular invasive carcinoma incidence was higher in Nrf2-/-::p53+/- mice (62.0%) than either wild-type (6.9%, P < 0.01), p53+/- (38.0%, P = 0.110) or Nrf2-/- mice (3.7%, P < 0.01). Furthermore, urinary concentrations of N-nitrosobutyl(3-carboxypropyl)amine, a proximate carcinogen of BBN, were only increased when Nrf2 but not p53 was disrupted. These results demonstrate that tumor susceptibility is synergistically exacerbated in Nrf2-/-::p53+/- mice due to poor detoxification and accelerated proliferation in comparison with either single mutant alone. BBN administration increased p53-mediated expression of p21, Mdm2 and Bax, and the inducible expression of p21 was significantly enhanced in Nrf2-/- mice. Conversely, modest increases in NAD(P)H dehydrogenase, quinone 1 (NQO1) and uridine diphosphate (UDP) glucuronosyltransferase 1A6 (UGT1A6) expression were observed in p53+/- compared with those of wild-type mice after BBN exposure. These results thus reveal potential interactions between p53 and Nrf2 and their gene batteries, and indicate that both factors cooperatively contribute to tumor prevention.

Induction of drug-metabolizing enzymes by garlic and allyl sulfide compounds via activation of constitutive androstane receptor and nuclear factor E2-related factor 2.

Garlic oil (GO) contains several linear sulfur compounds, including diallyl sulfide (DAS), diallyl disulfide (DADS), and diallyl trisulfide (DATS), that induce drug-metabolizing enzymes such as CYP2B and NAD(P)H quinone oxidoreductase 1 (NQO1). CYP2B and NQO1 are primarily regulated by constitutive androstane receptor (CAR) and nuclear factor E2-related factor 2 (Nrf2) transcription factors, respectively. The purpose of this study was to determine whether GO and its specific constituents induce these two enzymes via CAR and Nrf2 activation. Female Wistar-Kyoto (WKY) rats express little CAR protein and exhibit less induction of CYP2B1/2 than males. GO, DAS, and DADS, but not DATS, induced CYP2B1/2 mRNA levels to a greater extent in WKY males than in females, suggesting CAR activation. Conversely, DAS induced NQO1 levels equally in WKY males and females, indicating CAR-independent induction in rats. DAS, but not GO, DADS, or DATS, induced CYP2B10 mRNA levels 530-fold in wild-type (WT) mice, whereas this induction was attenuated in CAR(-/-) mice. DAS induced NQO1 in WT and CAR(-/-) mice equally, suggesting CAR-independent induction in mice. DAS induced NQO1 5-fold in WT mice, whereas induction was completely absent in Nrf2(-/-) mice, indicating DAS also activates Nrf2. DAS induction of CYP2B10 mRNA was independent of Nrf2 presence or absence. In in vivo transcription assays, DAS activated the human CYP2B6 promoter, and the antioxidant response element of the human NQO1 promoter, respectively. These studies indicate that GO constituents, particularly DAS, activate CAR and Nrf2 to induce drug-metabolizing enzymes.

Nrf2 Neh5 domain is differentially utilized in the transactivation of cytoprotective genes.

The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) contains two transcription activation domains, Neh4 (Nrf2 ECH homology 4) and Neh5, which co-ordinately regulate transactivation of cytoprotective genes. In the present study we aimed to clarify the role of the Neh5 domain in Nrf2-mediated gene regulation. Deletion of the complete Neh5 domain reduces expression of endogenous Nrf2 target genes, such as HO-1 (haem oxygenase 1), NQO1 [NAD(P)H:quinone oxidoreductase 1] and GCLM (glutamate cysteine ligase modulatory subunit), in human kidney epithelial cells. Furthermore, the deletion of Neh5 markedly repressed CBP [CREB (cAMP-response-element-binding protein)-binding protein] and BRG1 (Brahma-related gene 1) from associating with Nrf2, diminishing their co-operative enhancement of HO-1 promoter activity. Mutational analysis of the Neh5 domain revealed a motif that shares significant homology with beta-actin and ARP1 (actin-related protein 1). Mutagenesis of this motif selectively decreased HO-1, but not NQO1 and GCLM, expression. Taken together, these results indicate that the Neh5 domain has the ability to regulate Nrf2 target gene transcription, yet the role of the Neh5 domain in transcription varies from gene to gene.

Hepatic ischemia-reperfusion induces renal heme oxygenase-1 via NF-E2-related factor 2 in rats and mice.

Hepatic ischemia-reperfusion (IR) results in Kupffer cell activation and subsequent tumor necrosis factor (TNF) alpha release, leading to localized hepatic injury and remote organ dysfunction. Heme oxygenase (HO)-1 is an enzyme that is induced by various stimuli, including proinflammatory cytokines, and exerts antioxidative and anti-inflammatory functions. Up-regulation of HO-1 is known to protect against hepatic IR injury, but the effects of hepatic IR on the kidney are poorly understood. Thus, the purpose of this study was to determine whether hepatic IR and resultant Kupffer cell activation alters renal HO-1 expression. Male Sprague-Dawley rats and wild-type and NF-E2-related factor 2 (Nrf2)-null mice were subjected to 60 min of partial hepatic ischemia, and at various times thereafter, blood, liver, and kidneys were collected. After reperfusion, 1) creatinine clearance decreased; 2) HO-1 mRNA and protein expression in liver and kidney markedly increased; 3) renal NAD(P)H: quinone oxidoreductase 1 mRNA expression was induced; 4) serum TNFalpha levels increased; 5) Nrf2 translocation into the nucleus of renal tissue increased; and 6) renal and urinary 15-deoxy-Delta(12,14)-prostaglandin J2 (15-d-PGJ2) levels increased. Kupffer cell depletion by pretreating with gadolinium chloride 1) attenuated increased mRNA expression of HO-1 in kidney; 2) attenuated the increase in TNFalpha; 3) inhibited the increase in Nrf2 nuclear translocation; and 4) tended to attenuate renal 15-d-PGJ2 levels. Whereas renal HO-1 mRNA expression increased in wild-type mice, it was attenuated in Nrf2-null mice. These results suggest that renal HO-1 is induced via Nrf2 to protect the kidney from remote organ injury after hepatic IR.

Regulation of transporter expression in mouse liver, kidney, and intestine during extrahepatic cholestasis.

It is hypothesized that during cholestasis, the liver, kidney, and intestine alter gene expression to prevent BA accumulation; enhance urinary excretion of BA; and decrease BA absorption, respectively. To test this hypothesis, mice were subjected to either sham or bile-duct ligation (BDL) surgery and liver, kidney, duodenum, ileum, and serum samples were collected at 1, 3, 7, and 14 days after surgery. Serum total BA concentrations were 1-5 mumol/l in sham-operated mice and were elevated at 1, 3, 7, and 14 days after BDL, respectively. BDL decreased liver Ntcp, Oatp1a1, 1a5, and 1b2 mRNA expression and increased Bsep, Oatp1a4, and Mrp1-5 mRNA levels. In kidney, BDL decreased Oatp1a1 and increased Mrp1-5 mRNA levels. In intestine, BDL increased Mrp3 and Ibat mRNA levels in ileum. BDL increased Mrp1, 3, 4, and 5 protein expression in mouse liver. These data indicate that the compensatory regulation of transporters in liver, kidney, and intestine is unable to fully compensate for the loss of hepatic BA excretion because serum BA concentration remained elevated after 14 days of BDL. Additionally, hepatic and renal Oatp and Mrp genes are regulated similarly during extrahepatic cholestasis, and may suggest that transporter expression is regulated not to remove bile constituents from the body, but instead to remove bile constituents from tissues.