Increase In Hepatic Levels Research Articles

Dysregulation of hepatic one-carbon metabolism in classical homocystinuria: Implications of redox-sensitive DHFR repression and tetrahydrofolate depletion for pathogenesis and treatment.

Cystathionine beta-synthase-deficient homocystinuria (HCU) is a life-threatening disorder of sulfur metabolism. HCU can be treated by using betaine to lower tissue and plasma levels of homocysteine (Hcy). Here, we show that mice with severely elevated Hcy and potentially deficient in the folate species tetrahydrofolate (THF) exhibit a very limited response to betaine indicating that THF plays a critical role in treatment efficacy. Analysis of a mouse model of HCU revealed a 10-fold increase in hepatic levels of 5-methyl -THF and a 30-fold accumulation of formiminoglutamic acid, consistent with a paucity of THF. Neither of these metabolite accumulations were reversed or ameliorated by betaine treatment. Hepatic expression of the THF-generating enzyme dihydrofolate reductase (DHFR) was significantly repressed in HCU mice and expression was not increased by betaine treatment but appears to be sensitive to cellular redox status. Expression of the DHFR reaction partner thymidylate synthase was also repressed and metabolomic analysis detected widespread alteration of hepatic histidine and glutamine metabolism. Many individuals with HCU exhibit endothelial dysfunction. DHFR plays a key role in nitric oxide (NO) generation due to its role in regenerating oxidized tetrahydrobiopterin, and we observed a significant decrease in plasma NOx (NO2 + NO3) levels in HCU mice. Additional impairment of NO generation may also come from the HCU-mediated induction of the 20-hydroxyeicosatetraenoic acid generating cytochrome CYP4A. Collectively, our data shows that HCU induces dysfunctional one-carbon metabolism with the potential to both impair betaine treatment and contribute to multiple aspects of pathogenesis in this disease.

SIRT1 regulates hepatic vldlr levels

BackgroundEndoplasmic reticulum (ER) stress-mediated increases in the hepatic levels of the very low-density lipoprotein (VLDL) receptor (VLDLR) promote hepatic steatosis by increasing the delivery of triglyceride-rich lipoproteins to the liver. Here, we examined whether the NAD(+)-dependent deacetylase sirtuin 1 (SIRT1) regulates hepatic lipid accumulation by modulating VLDLR levels and the subsequent uptake of triglyceride-rich lipoproteins.MethodsRats fed with fructose in drinking water, Sirt1−/− mice, mice treated with the ER stressor tunicamycin with or without a SIRT1 activator, and human Huh-7 hepatoma cells transfected with siRNA or exposed to tunicamycin or different inhibitors were used.ResultsHepatic SIRT1 protein levels were reduced, while those of VLDLR were upregulated in the rat model of metabolic dysfunction-associated steatotic liver disease (MASLD) induced by fructose-drinking water. Moreover, Sirt1−/− mice displayed increased hepatic VLDLR levels that were not associated with ER stress, but were accompanied by an increased expression of hypoxia-inducible factor 1α (HIF-1α)-target genes. The pharmacological inhibition or gene knockdown of SIRT1 upregulated VLDLR protein levels in the human Huh-7 hepatoma cell line, with this increase abolished by the pharmacological inhibition of HIF-1α. Finally, SIRT1 activation prevented the increase in hepatic VLDLR protein levels in mice treated with the ER stressor tunicamycin.ConclusionsOverall, these findings suggest that SIRT1 attenuates fatty liver development by modulating hepatic VLDLR levels.

Metal Bioaccumulation, Cytogenetic and Clinico-Biochemical Alterations in Rattus norvegicus Exposed In Situ to a Municipal Solid Waste Landfill in Lagos, Nigeria.

This study aimed at determining in animal model the health effects of in situ exposure to landfill chemicals. We evaluated metal concentrations in tissues and cytogenetic and clinico-biochemical effects in Wistar rats (Rattus norvegicus) exposed in situ at Olusosun landfill in Lagos, Nigeria. Male rats (n = 30/point) were exposed at three different points to ambient air and underground water (via drinking) at the landfill for 4-, 8-, 12-, 16-, 20- and 24-week periods. Rats concurrently sited at a residential area, 17.3km from the landfill site served as control. There was significantly (p < 0.05) time-dependent: accumulation of lead, cadmium, chromium, copper and zinc in the liver and kidney and increase in body weight gain, in exposed rats compared to control. There was significant induction of micronuclei and cytotoxicity (reduced PCE/NCE ratios) in exposed rats. Haematological parameters (RBC, PCV, Hb and WBC) and serum biomarkers of hepato-renal damage [aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH) activities; creatinine and urea levels] revealed significant increases. There was significant increase in hepatic levels of reduced glutathione, malondialdehyde, catalase activities, and decrease in superoxide dismutase, at all periods. Chromium and copper concentrations in the liver and kidney revealed significant positive correlations with either one or more of AST, ALT, LDH and urea. Significant metal concentrations in the underground water and tissues suggest that heavy metals are responsible for the observed alterations, and this may have been via oxidative stress. These findings suggest potential health risk due to occupational and residential exposure to landfill pollutants.

Naringin prevents cyclophosphamide-induced hepatotoxicity in rats by attenuating oxidative stress, fibrosis, and inflammation

Cyclophosphamide (CYCP), a synthetic alkylating antineoplastic, disrupts both cancerous and non-cancerous cells to cause cancer regression and multi organotoxicity respectively. CYCP-induced hepatotoxicity is rare but possible. Evidence has shown that naringin has several beneficial potentials against oxidative stress, inflammation, and fibrosis. This study examined the chemoprotective potentials of naringin on exited radical scavenging, hepatic integrity, oxidative stress, fibrosis, and inflammation in CYCP-mediated hepatotoxicity. Rats were pre-treated orally by gavage for fourteen consecutive days with three doses (50, 100, and 200 mg/kg) of naringin before single CYCP (200 mg/kg, i.p.) administration. Subsequently, the rats were euthanized; blood and liver were removed, and assessed for serum and hepatic enzymes, oxidative stress, inflammation, and gene expression dynamics. Naringin concentrations required for 50% scavenging hydroxyl radical and 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulphonic acid) radical cation were 0.32 mg/mL and 0.39 mg/mL, respectively. Pretreatment with naringin significantly (p < 0.05) abolish CYCP-induced changes in the activities of serum and hepatic ALT, AST, GGT, ALP, and LDH. Pretreatment with naringin remarkably (p < 0.05) reversed CYCP-mediated increases in hepatic levels of malondialdehyde, hydroperoxide, and nitric oxide; reverse CYCP-induced decreases in the hepatic glutathione levels, activities of catalase, glutathione peroxidase, and glutathione reductase; and also attenuated CYCP-induced upregulation of expression of hepatic chemokine (C-C motif) ligand 2 (CCL2), interferon alpha1 (IFN-α1), interleukine-1β, interleukine-1 receptor, and transforming growth factor beta 1 (TGF-β1). Taken together, different doses of naringin can prevent CYCP-induced oxidants generation, hepatocytes dysfunctions, oxidative stress as well as inflammatory perturbations in rats when pre-administered for as few as 14 days.

Comparative Protective Effects of N-Acetylcysteine, N-Acetyl Methionine, and N-Acetyl Glucosamine against Paracetamol and Phenacetin Therapeutic Doses-Induced Hepatotoxicity in Rats.

Background and Aims Both paracetamol (PA) and phenacetin (PH) are analgesic and antipyretic agents. Part of phenacetin therapeutic activity is attributed to its metabolism into paracetamol. Paracetamol causes direct hepatic oxidative stress damage. The present study aimed to investigate the possible damaging effects of both PA and PH, when used in therapeutic doses, on rat liver and to compare the antioxidant and hepatoprotective effects of N-acetylcysteine (NAC), N-acetyl-methionine (NAM), and N-acetylglucosamine (NAG) against PA- or PH-induced hepatic damage. Methods 90 male Wistar albino rats (120-140 gm) were undertaken, categorized randomly into 9 groups of 10 rats each, and administered by gavage for 2 weeks with DMSO 1% (controls), PA, PA+NAC, PA+NAM, PA+NAG, PH, PH+NAC, PH+NAM, and PH+NAG. Biochemical assays of malondialdehyde (MDA), nitric oxide (NO), reduced glutathione (GSH), total thiols, and alpha-fetoprotein (AFP) in liver homogenates and serum assays of ALT, AST, 8-hydroxy guanine (8-OH-Gua), and AFP were done. Also histopathological examinations of liver tissues in various groups were done. Results PA and PH cause significant increase in hepatic levels of MDA, NO, and AFP and serum ALT, AST, and 8-OH-Gua levels, with significant decrease in hepatic GSH and total thiols. NAG and NAC significantly improve the PA- and PH-induced hepatic and blood, biochemical, and histopathological disturbances, respectively. Conclusions Both PA and PH induce oxidative stress in rat liver within their therapeutic doses. NAG and NAC in pharmacological doses can antagonize the oxidative damaging effect of both PA and PH.

T Cell Inhibition during Pregnancy Prevents Post‐partum Anxiety‐like Behavior in rats with a History of Severe Preeclampsia/HELLP Syndrome

INTRODUCTIONSevere preeclampsia and Hemolysis elevated liver enzyme low platelet (HELLP) syndrome, are potentially life threatening conditions with high maternal mortality and morbidity. During pregnancy these women have hypertension, increases in inflammatory cytokines, blood brain barrier (BBB) permeability and increased T cells. During the post‐partum period these women are reported to be at an increased risk of developing psychological disorders such as post‐traumatic stress disorder (PTSD). We have recently shown that T cell suppression to experimental HELLP rats during pregnancy attenuates inflammation, BBB permeability and hypertension. As T cells have been implicated in contributing to behavioral abnormalities, we hypothesized that T cell reduction during pregnancy to rats with HELLP could decrease the occurrence of anxiety‐like behavior in the post‐partum period.METHODSOn gestational day (GD) 12, mini‐osmotic pumps infusing sFlt‐1 and sEng were placed into rats to induce HELLP syndrome (n=28). A subset of HELLP rats (n=13) received 2 mg/kg of Orencia (Abatacept) on GD13 and all rats had their mini‐osmotic pumps removed 12–24 hrs post‐delivery to remove the source of sFlt‐1 and sEng. Rats without mini‐osmotic pumps served as normal pregnant (NP; n=14) controls. Beginning in the 4th post‐partum week rats underwent testing in marble burying, elevated plus maze (EPM) and locomotor activity. Mean arterial pressure was measured between postpartum day 46–48, tissue and plasma collection or Evan's blue (EB) infusion to assess BBB permeability.RESULTSPost‐partum HELLP rats buried significantly more marbles compared to NP (61.4 vs 38.9%; p=0.01) and HELLP+O rats (34.7%; p=0.05). HELLP rats also spent significantly more time in the closed arms of the EPM compared to NP (170.9 ± 14.1 vs 103.2 ± 16.6 sec; p=0.009) and HELLP+O rats (108.7± 20.4 sec; p=0.02). HELLP rats traveled a greater distance in the open field compared to NP (2571 ± 219.2 vs. 1777 ± 219.7 cm; p=0.02) and HELLP+O (1560 ± 166.6 cm; p=0.03). Rats with a history of HELLP syndrome had increased BBB permeability in the brainstem compared to NP rats (1.8 ± 0.5 vs 0.58 ± 0.1 (pg/g EB tissue)/μg/mL EB plasma; p=0.04), however this was reversed by treatment with Orencia (0.48 ± 0.13 (pg/g EB tissue)/μg/mL EB plasma; p=0.03). HELLP rats had significantly more circulating CD4+ T cells compared to NP rats (5.3 vs 2.18%; p=0.02). Similar results were seen in the liver where HELLP rats had significantly more hepatic CD4+ T cells compared to NP rats (2.9 vs 0.53%; p=0.03). HELLP rats had a significant increase in hepatic levels of IL‐6 (4.2 ± 0.44 vs 2.7 ± 0.49 pg/mg/mL; p=0.04) and IL‐1beta (31.9 ± 3.08 vs 21.9 ± 3.1pg/mg/mL; p=0.04) as well as increased sFlt‐1 (128.9 ± 13.4 vs 76.8 ± 13.9pg/mg/mL; p=0.02) compared to NP rats. There were no statistically significant changes between the groups in plasma levels of these proteins. Results on inflammation from rats treated with Orencia are pending. HELLP rats had significantly increased MAP compared to NP (136.8 ± 4.9 vs 115.3 ± 7.4 mmHg; p=0.02) and HELLP+O rats (117.2±4.7 mmHg; p=0.01).DISCUSSIONThese results suggest that HELLP syndrome during pregnancy contributes to an increase in anxiety‐like behavior, BBB permeability, liver inflammation, increased CD4+ T cells and hypertension in the post‐partum. The current results suggest that T cell suppression during pregnancy can also help prevent chronic hypertension and increased anxiety in the post‐partum period.Support or Funding InformationThis work was supported by the National Institutes of Health IDea grant P30GM103328 to KW.This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

EUS-guided portal injection chemotherapy for treatment of hepatic metastases: feasibility in the acute porcine model

Direct injection of chemotherapy into the portal vein for treatment of liver metastases may increase hepatic tissue levels while decreasing systemic levels and toxicities. We aimed to evaluate EUS-guided portal injection chemotherapy (EPIC) by using drug-eluting microbeads or nanoparticles and compare it with systemic injection. We conducted a comparative feasibility trial in the acute porcine model (24 anesthetized pigs). Pigs were treated with irinotecan, doxorubicin, or albumin-bound paclitaxel nanoparticles (n = 8/group). Within each group, pigs were treated with EPIC or a systemic intravenous injection of drug and saline solution into the portal vein (n = 4/treatment). Irinotecan or doxorubicin were loaded onto microbeads for EPIC treatment only. We examined drug levels in tissue (1 hour) and plasma (15 minutes). EUS-guided access and injection was successful in all animals. EPIC with irinotecan-loaded microbeads showed nearly double the hepatic concentration compared with systemic injection (6242 vs 3692 ng/g) and almost half the systemic levels. EPIC with doxorubicin-loaded microbeads showed a 5-fold increase in hepatic levels (35,450 vs 6930 ng/g) and a 30-fold decrease in cardiac levels (153 vs 4805 ng/g) compared with systemic administration (P < .05 for both). EPIC with albumin-bound paclitaxel nanoparticles increased hepatic concentrations by 60% and decreased systemic levels by 24% to 32%. EPIC holds promise as a new treatment for hepatic metastases.

Modulatory effects of curcumin, silybin-phytosome and alpha-R-lipoic acid against thioacetamide-induced liver cirrhosis in rats

Liver cirrhosis is the final consequence of a progressive fibrotic process characterized by excessive collagen deposition and destruction of the normal liver architecture. This study aimed to investigate the protective effects of curcumin, silybin-phytosome and alpha-R-lipoic acid against thioacetamide-induced cirrhosis. Male rats were allocated into five groups of which one group received saline and served as normal control. Animals from groups 2–5 were treated with thioacetamide administered intraperitoneally at a dose of 200mg/kg 3 times per week for 7weeks. Group 2 was left untreated while groups from 3 to 5 were given a daily oral dose of curcumin, silybin-phytosome or alpha-R-lipoic acid simultaneously with thioacetamide. Increases in hepatic levels of malondialdehyde (MDA) and protein carbonyls (Pr Co) associated with thioacetamide administration were partially blocked in those groups receiving supplements. Glutathione (GSH) depletion, collagen deposition, matrix metalloproteinase-2 (MMP-2) activity, transforming growth factor-β1 (TGF-β1) level as well as α-smooth muscle actin (α-SMA) and heat shock protein-47 (HSP-47) gene expressions were also decreased in response to supplements administration. Serological analysis of liver function and histopathological examination reinforced the results. In conclusion, the present study highlights the antioxidant and the antifibrotic potentials of these supplements against chronic liver diseases caused by ongoing hepatic damage.

Vα14iNKT cell deficiency prevents acetaminophen-induced acute liver failure by enhancing hepatic glutathione and altering APAP metabolism

Acetaminophen (APAP) overdose is widely regarded as a major cause of acute liver failure in the United States. Intentional or accidental overdose of APAP in man or rodent elicits direct hepatocellular injury that is accompanied by hepatic depletion of the antioxidant, glutathione (GSH). In recent years, the innate immune response has also been shown to promote the development of APAP hepatotoxicity via indirect liver damage. In the present study, we demonstrate that Jα18−/− mice, which are selectively deficient in the innate immune T cell, Vα14iNKT cells, were resistant to APAP hepatotoxicity relative to WT mice as reflected by biochemical and histological liver injury markers. In parallel, improvement in the biochemical and histological parameters of liver injury in Jα18−/− mice was associated with a significant increase in hepatic levels of GSH, which detoxified APAP metabolites to attenuate hepatic oxidative stress, liver injury and necrosis. Notably, the protective effect of hepatic GSH during Vα14iNKT cells deficiency was demonstrated by its depletion in Jα18−/− mice using dl-buthionine-[S,R]-sulfoximine which exacerbated hepatic oxidative and nitrosative stress as well as liver necrosis and caused mice mortality. Extraordinarily, APAP metabolism in Jα18−/− mice was altered in favor of hepatic GSH conjugates and decreased glucuronide conjugates. In summary, we reveal a novel finding establishing a unique association between hepatic innate immunity and GSH levels in altering APAP metabolism to suppress liver injury and necrosis during Vα14iNKT cells deficiency in Jα18−/− mice.

The Zinc Transporter Zip14 Influences c-Met Phosphorylation and Hepatocyte Proliferation During Liver Regeneration in Mice

Zinc homeostasis in cells is maintained through tight regulation of zinc influx, efflux, and distribution to intracellular organelles by zinc transporters. The Zrt-Irt-like protein (ZIP) transporters facilitate zinc influx to the cytosol. Expression of the ZIP family member Zip14 can be induced by inflammatory cytokines, which also initiate liver regeneration. Hepatocyte proliferation is required for liver regeneration. Zinc regulates cell proliferation, tissue growth, and many mitogenic signaling pathways; we investigated its role in hepatocytes. Wild-type and Zip14(-/-) mice that underwent partial hepatectomy (70% of liver removed) were used as models of liver regeneration. We also analyzed AML12 hepatocytes that overexpressed Zip14. Proliferation was assessed with proliferating cell nuclear antigen, CD1, and Ki67 markers and along with assays of zinc content was related to protein tyrosine phosphatase 1B (PTP1B) and extracellular signal-regulated kinase 1/2 signaling. Zip14 was up-regulated and hepatic zinc content increased during liver regeneration. Increased hepatic zinc inhibited activity of the phosphatase PTP1B and increased phosphorylation of c-Met, which promoted hepatocyte proliferation. AML12 cells that overexpressed Zip14 increased in zinc content and proliferation; PTP1B was inhibited and phosphorylation of c-Met increased. The increases in hepatic levels of zinc and hepatocyte proliferation that occurred following partial hepatectomy were not observed in Zip14(-/-) mice. The transporter Zip14 mediates hepatic uptake of zinc during liver regeneration and for hepatocyte proliferation. These findings indicate that zinc transporter activity regulates liver tissue growth by sequestering zinc. Reagents that regulate ZIP14 activity might be developed as therapeutics to promote liver regeneration in patients with chronic liver disease.

Characterization of the Hepatic and Splenic Immune Status and Immunoglobulin Synthesis in Aged Male Mice Lacking the Peroxisome Proliferator-Activated Receptor-Alpha (PPARα)

It is now well established that the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPARα) is expressed in different types of immune cells and plays a pivotal role in the regulation of age-related production of inflammatory cytokines. However, the role(s) of this receptor in the regulation of immune cell homoeostasis in ageing non-lymphoid and lymphoid organs has not yet been resolved. We examine this issue here by evaluating the hepatic and splenic immune status and immunoglobulin (Ig) production in male PPARα-null mice and their wild-type littermates at one and 2 years of age. In comparison with the age-matched control animals, PPARα-null mice exhibited age-related elevations in the numbers of total, as well as of phenotypically distinct subpopulations of intrahepatic immune cells (IHIC) and splenocytes. Moreover, at 2 years of age, these alterations in hepatic immune cells were accompanied by significant increases in hepatic levels of the pro-inflammatory cytokines tumour necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and interferon-gamma (IFN-γ), in combination with the development of hepatic inflammatory loci containing mixtures of leucocytes. Alterations in splenocytes of old PPARα-null mice were also accompanied by increases in cellularity of both white and red pulps of the spleen. Furthermore, these same animals exhibited pronounced increases in the numbers of splenic plasma cells and enhanced production of Ig of different isotypes, including IgG1, IgG2a and IgE. Thus, our findings indicate that upon ageing, PPARα plays a crucial role in regulating the total numbers, compositions and functions of immune cells in both lymphoid and non-lymphoid immune organs of mice.

OP07 Macrophage cell therapy causes the hepatic recruitment of host effector cells and improves structure and function in a murine model of chronic liver disease

IntroductionBone marrow (BM) cell populations have a number of roles in the development and resolution of chronic liver disease. Clinical trials of BM cell therapy have already begun. These have...

Dietary exposure to perfluorooctanoate or perfluorooctane sulfonate induces hypertrophy in centrilobular hepatocytes and alters the hepatic immune status in mice

It is well established that exposure of mice to perfluorooctanoate (PFOA) or perfluorooctane sulfonate (PFOS) induces hepatomegaly and, concurrently, immunotoxicity. However, the effects of these perfluorochemicals on the histology and immune status of the liver have not been yet investigated and we have examined these issues here. Dietary treatment of male C57BL/6 mice with 0.002% (w/w) PFOA or 0.005% (w/w) PFOS for 10 days resulted in significant reductions in serum levels of cholesterol and triglycerides, a moderate increase in the serum activity of alkaline phosphatase (ALP) and hepatomegaly, without affecting other immune organs. This hepatomegaly was associated with marked hypertrophy of the centrilobular hepatocytes, with elevated numbers of cytoplasmic acidophilic granules and occasional mitosis. Furthermore, dietary exposure to PFOA or PFOS altered the hepatic immune status: whereas exposure to PFOA enhanced the numbers of total, as well as of phenotypically distinct subpopulations of intrahepatic immune cells (IHIC), and in particular the presumptive erythrocyte progenitor cells, treatment with PFOS enhanced only the numbers of hepatic cells that appear immunophenotypically to be erythrocyte progenitors, without affecting other types of IHIC. In addition, exposure to these compounds attenuated hepatic levels of tumor necrosis factor-alpha (TNF-α), interferon-gamma (IFN-γ) and interleukin-4 (IL-4). Furthermore, the exposed animals exhibited a significant increase in hepatic levels of erythropoietin, a hormone required for erythropoiesis. Thus, in mice, PFOA- and PFOS-induced hepatomegaly is associated with significant alterations in hepatic histophysiology and immune status, as well as induction of hepatic erythropoiesis.

Fasting-Induced Hepatic Production of DHEA is Regulated by PGC-1α, ERRα and HNF4α

ABSTRACT The transcriptional coactivator PGC-1α is involved in the coordinate induction of changes in gene expression in the liver that enable a homeostatic response to alterations in metabolic state, environmental cues and nutrient availability. In exploring the specific pathways under PGC-1α regulation in the liver, we have made the surprising observation that this coactivator can induce the expression of CYP11A1 and CYP17A1, key rate limiting enzymes involved in the initial steps of steroidogenesis. Both of these enzymes function to produce C19-steroids, converting cholesterol into pregnenolone, and then to DHEA. ERRa mediates PGC-1α’s induction of CYP11A1 and binds within the first intron of the CYP11A1 gene. Both ERRa and HNF4a are required for PGC-1α-mediated induction of CYP17A1 and specific binding sites for these receptors have been identified in the regulatory regions of this gene. The potential physiological significance of these observations was highlighted in rats where fasting induced hepatic expression of PGC-1α and CYP17A1 and was associated with an increase in hepatic levels of DHEA. These data suggest that DHEA could be playing a role as an intracellular signaling molecule involved in modulating hepatic activity in response to fasting conditions.

Fasting-Induced Hepatic Production of DHEA Is Regulated by PGC-1α, ERRα, and HNF4α

The transcriptional coactivator peroxisome proliferator-activated receptor-gamma coactivator (PGC)-1alpha is involved in the coordinate induction of changes in gene expression in the liver that enable a homeostatic response to alterations in metabolic state, environmental cues, and nutrient availability. In exploring the specific pathways under PGC-1alpha regulation in the liver, we have made the surprising observation that this coactivator can induce the expression of CYP11A1 and CYP17A1, key rate-limiting enzymes involved in the initial steps of steroidogenesis. Both of these enzymes function to produce C(19)-steroids, converting cholesterol into pregnenolone, and then to dehydroepiandrosterone (DHEA). Estrogen-related receptor (ERR)-alpha mediates PGC-1alpha's induction of CYP11A1 and binds within the first intron of the CYP11A1 gene. Both ERR-alpha and hepatocyte nuclear factor-4alpha are required for PGC-1alpha-mediated induction of CYP17A1, and specific binding sites for these receptors have been identified in the regulatory regions of this gene. The potential physiological significance of these observations was highlighted in rats where fasting induced hepatic expression of PGC-1alpha and CYP17A1 and was associated with an increase in hepatic levels of DHEA. These data suggest that DHEA could be playing a role as an intracellular signaling molecule involved in modulating hepatic activity in response to fasting conditions.

Angiotensin II Regulates Liver Regeneration via Type 1 Receptor Following Partial Hepatectomy in Mice

Angiotensin II (Ang II) is an important mediator stimulating liver fibrosis after liver injury. However, it is not known whether Ang II plays a role in liver regeneration. Here, we investigate the effects of Ang II type 1 (AT(1)) receptor blocker (ARB), angiotensin-converting enzyme inhibitor (ACEI), systemic infusion of Ang II, and genetic deficiency of the AT(1a) receptor (AT1a-KO) on the hepatic regenerative response to partial hepatectomy (PH) in mice. Administration of ARB (candesartan cilexetil and losartan) or ACEI (enarapril and lisinopril) enhanced 5-bromo-2'-deoxyuridine (BrdU) incorporation into hepatocyte nuclei in remnant liver as well as the restoration of liver weight after PH. Systemic infusion of Ang II (100 ng/kg/min) suppressed the PH-induced BrdU incorporation and the restoration of liver weight. In contrast to Ang II infusion, these hepatic responses to PH were significantly greater in AT1a-KO mice than in wild-type mice. The PH-induced increases in hepatic levels of hepatocyte growth factor (HGF) mRNA and plasma HGF concentrations were greater in candesartan- and enarapril-treated mice or in AT1a-KO mice than in vehicle-treated mice or wild-type mice, respectively, whereas they were less in Ang II-infused mice than in vehicle-infused mice. In contrast to HGF, blockades of the renin-angiotensin system or Ang II infusion produced opposite effects on the PH-induce increases in hepatic transforming growth factor (TGF)-beta 1 mRNA and plasma TGF-beta 1 levels. These studies suggest that Ang II plays a role in the liver regeneration as a suppressor of hepatocyte proliferation via the AT(1) receptor-mediated control of growth factor production.

Chronic intermittent hypoxia causes hepatitis in a mouse model of diet-induced fatty liver

Obstructive sleep apnea (OSA) causes chronic intermittent hypoxia (CIH) during sleep. OSA is associated with nonalcoholic steatohepatitis (NASH) in obese individuals and may contribute to progression of nonalcoholic fatty liver disease from steatosis to NASH. The purpose of this study was to examine whether CIH induces inflammatory changes in the liver in mice with diet-induced hepatic steatosis. C57BL/6J mice (n = 8) on a high-fat, high-cholesterol diet were exposed to CIH for 6 mo and were compared with mice on the same diet exposed to intermittent air (control; n = 8). CIH caused liver injury with an increase in serum ALT (461 +/- 58 U/l vs. 103 +/- 16 U/l in the control group; P < 0.01) and AST (637 +/- 37 U/l vs. 175 +/- 13 U/l in the control group; P < 0.001), whereas alkaline phosphatase and total bilirubin levels were unchanged. Histology revealed hepatic steatosis in both groups, with mild accentuation of fat staining in the zone 3 hepatocytes in mice exposed to CIH. Animals exposed to CIH exhibited lobular inflammation and fibrosis in the liver, which were not evident in control mice. CIH caused significant increases in lipid peroxidation in serum and liver tissue; significant increases in hepatic levels of myeloperoxidase and proinflammatory cytokines IL-1beta, IL-6, and CXC chemokine MIP-2; a trend toward an increase in TNF-alpha; and an increase in alpha1(I)-collagen mRNA. We conclude that CIH induces lipid peroxidation and inflammation in the livers of mice on a high-fat, high-cholesterol diet.

Evaluation of Cissampelos pareira. Against Gastric Cancer and Enzymes Associated with Carcinogen Metabolism

The current study is an effort to identify the effect of a hydroalcohol (50% ethanol) extract of roots of Cissampelos pareira. (L.) Hirsuta (Menispermaceae) (CPE) in forestomach cancer and on carcinogen metabolizing phase I and phase II enzymes along with antioxidant enzymes. In forestomach, the activities of glutathione S.-transferase (GST), DT-diaphorase (DTD), and superoxide dismutase (SOD) increased significantly and dose-dependently. The protective effect of CPE was studied against benzo(a.)pyrene [B(a.)P]-induced gastric cancer in mice, and the tumor incidence was reduced and the mean number of tumors and the tumor multiplicity were reduced significantly and dose-dependently. The modulatory effect of CPE was also examined on carcinogen metabolizing phase I and phase II enzymes, antioxidant enzymes, glutathione content, lactate dehydrogenase, and lipid peroxidation in liver. Significant increases in the levels of acid-soluble sulfhydryl (–SH) and cytochrome P450 contents and in enzyme activities of cytochrome P450 reductase, cytochrome b5 reductase, GST, DTD, SOD, catalase, glutathione (GSH) peroxidase, and GSH reductase but decreased malondialdehyde (MDA) were observed. Butylated hydroxyanisole (BHA) showed an increase in hepatic levels of GSH content, cytochrome b5, DTD, GST, glutathione reductase (GR), and catalase, whereas MDA formation was inhibited significantly. BHA also showed increased levels of DTD, GST, and SOD significantly in forestomach. The enhanced GSH level and enzyme activities involved in xenobiotic metabolism and maintaining antioxidant status of cells are suggestive of a chemopreventive efficacy of Cissampelos pareira. against chemotoxicity, including carcinogenicity.

Hyperoxia increases hepatic arginase expression and ornithine production in mice

Hyperoxic exposure affects the levels and activities of some hepatic proteins. We tested the hypothesis that hyperoxic exposure would result in greater hepatic .NO concentrations. C3H/HeN mice were exposed to >95% O(2) for 72 or 96 h and compared to room air-breathing controls. In contrast to our working hypothesis, exposure to >95% O(2) for 96 h decreased hepatic nitrite/nitrate NO(X) concentrations (10.9 +/- 2.2 nmol/g liver versus 19.3 +/- 2.4 nmol/g liver in room air, P < 0.05). The hepatic levels of endothelial NO synthase (eNOS) and inducible NOS (iNOS) proteins were not different among the groups. The arginases, which convert L-arginine to urea and L-ornithine, may affect hepatic NOS activities by decreasing L-arginine bioavailability. Hepatic ornithine concentrations were greater in hyperoxic animals than in controls (318 +/- 18 nmol/g liver in room air, and 539 +/- 64, and 475 +/- 40 at 72 and 96 h of hyperoxia, respectively, P < 0.01). Hepatic arginase I protein levels were greater in hyperoxic animals than in controls. Hepatic carbamoyl phosphate synthetase (CPS) protein levels and activities were not different among groups. These results indicate that increases in hepatic levels of arginase I in mice exposed to hyperoxia may diminish .NO production, as reflected by lower liver levels of NO(X). The resultant greater hepatic ornithine concentrations may represent a mechanism to facilitate tissue repair, by favoring the production of polyamines and/or proline.

Antithrombin reduces ischemia/reperfusion-induced liver injury in mice by enhancing the activation of sensory neurons through protein kinase A activation

We recently demonstrated that antithrombin (AT) reduces ischemia/reperfusion (I/R)-induced liver injury in rats by increasing hepatic tissue levels of calcitonin gene-related peptide (CGRP), a neuropeptide released from the sensory nerve endings. In the present study, we examined the effect of AT on I/R-induced liver injury in wildtype mice (CGRP+/+) and congenital α CGRP-deficient mice (CGRP-/-). We further investigated whether AT affects CGRP release from dorsal root ganglion neurons (DRG) isolated from CGRP+/+. Based on results obtained in the present study, we attempted to determine whether the anti-inflammatory activity of AT in vivo is dependent mainly on sensory neuron activation. AT enhanced I/R-induced increases in hepatic tissue levels of CGRP and 6-keto-PGF1α a stable metabolite of PGI2, in CGRP+/+, while it did not enhance these increases in CGRP-/-. AT inhibited reperfusion-induced increases in serum alanine aminotransferase levels by increasing hepatic tissue blood flow and by attenuating increases in hepatic levels of tumor necrosis factor and myeloperoxidase in CGRP+/+, while it showed neither of these therapeutic effects in CGRP-/-. AT increased CGRP release from cultured DRGs only in the presence of anandamide, and the AT-induced increase in CGRP release was not observed in the presence of KT5720, an inhibitor of protein kinase A (PKA). AT markedly increased intracellular levels of cAMP in the presence of anandamide. In conclusion, these results strongly suggest that AT might reduce I/R-induced liver injury by enhancing activation of the sensory neurons through activation of PKA in sensory neurons.