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Ronald J Sokol

Publications and source records attributed to Ronald J Sokol.

At least 37 records · Page 2Linked to original sources
PubMed2005

Armed CD4+ Th1 effector cells and activated macrophages participate in bile duct injury in murine biliary atresia.

Biliary atresia (BA) is an inflammatory cholangiopathy of infancy. A proposed mechanism regarding the pathogenesis of BA is that of a virus-induced, immune-mediated injury to bile ducts. The rotavirus (RRV)-induced murine model of BA was utilized to determine the hepatic inflammatory response related to ductal obstruction and if the immune response recapitulated human BA. One week after infection, there was a significant increase in liver CD4(+) T cells producing IFN-gamma and in macrophages producing TNF-alpha. The intrahepatic pattern of inflammation evolved rapidly from an initial predominant CD4(+) Th1 cellular response to a subsequent influx of activated macrophages producing TNF-alpha and iNOS. This immune response persisted despite viral clearance and was representative of the hepatic immune profile present in human BA. Utilization of the murine model of BA yielded mechanistic data that can provide much needed insight into the role played by different arms of the immune system related to the pathogenesis of human BA.

Animals↗
PubMed2005

Portopulmonary hypertension in pediatric patients.

OBJECTIVES: To investigate the clinical presentation, manifestations, and response to therapy of portopulmonary hypertension (PPHTN) in pediatric patients. STUDY DESIGN: This study was a retrospective chart review describing the evaluation and course of 7 patients with PPHTN. RESULTS: Causes of portal hypertension (HTN) included biliary atresia (3 cases), cavernous transformation of the portal vein (2 cases), and primary sclerosing cholangitis and cryptogenic cirrhosis (1 case each). The median interval from the diagnosis of portal HTN to PPHTN was 12.1 years. Four patients presented with a new heart murmur, 4 presented with syncope, and 3 presented with dyspnea. Although electrocardiograms (ECGs) and chest x-rays were normal in 3 and 2 patients, respectively, echocardiograms diagnosed pulmonary HTN in all 7 patients. Five patients had cardiac catheterizations; the average mean pulmonary artery pressure was 65 +/- 20 mm Hg. Response to therapy was variable, and 4 patients died. Postmortem lung tissue examination revealed plexiform lesions and pulmonary arteriopathy. CONCLUSIONS: Because symptoms are subtle and may be overlooked, pediatric patients with portal HTN who develop a new heart murmur, dyspnea, syncope, or who are being evaluated for liver transplantation require evaluation for PPHTN. ECG and chest x-ray are insensitive screens for PPHTN. An echocardiogram and cardiology evaluation is essential for the diagnosis.

Adolescent↗
PubMed2005

Biliary atresia: clinical profiles, risk factors, and outcomes of 755 patients listed for liver transplantation.

OBJECTIVES: To test the hypothesis that risk analysis from the time of listing for liver transplantation (LT) focuses attention on areas where outcomes can be improved. STUDY DESIGN: Competing outcomes and multivariate models were used to determine significant risk factors for pretransplantation and posttransplantation mortality and graft failure in patients with biliary atresia (BA) listed for LT and enrolled in the Studies of Pediatric Liver Transplantation (SPLIT) registry. RESULTS: Of 755 patients, most were infants (age < 1 year). Significant waiting list mortality risk factors included infancy and pediatric end-stage liver disease (PELD) score > or = 20, whose components were also continuous risk factors. Survival posttransplantation (n=567) was 88% at 3 years. Most deaths were from infection (37%). Posttransplantation mortality risk factors included infant recipients, height/weight < -2 standard deviations (SD), use of cyclosporine versus tacrolimus and retransplantation. Graft failure risks included height/weight < -2 SD, cadaveric partial donors, donor age < or = 5 months, use of cyclosporine versus tacrolimus, and rejection. CONCLUSIONS: Referral for LT should be anticipatory for infants with BA with failed portoenterostomies. Failing nutrition should prompt aggressive support. Post-LT risk factors are mainly nonsurgical, including nutrition, the relative risk of infection over rejection, and the choice of immunosuppression.

Biliary Atresia↗
PubMed2005

Connective tissue growth factor expression is increased in biliary epithelial cells in biliary atresia.

BACKGROUND/PURPOSE: Connective tissue growth factor (CTGF) has been implicated in the pathogenesis of hepatic fibrosis and is elevated in the serum of children with biliary atresia (BA). The objective of this study was to evaluate hepatic CTGF messenger RNA (mRNA) expression and its relationship to hepatic histology in children with BA. METHODS: Connective tissue growth factor mRNA expression was evaluated by in situ hybridization in 26 liver biopsies from 11 patients with BA, 11 with other diseases, and 4 autopsy controls. Serial sections were immunostained with cell-specific markers to characterize the cells expressing CTGF. Biopsies were scored for CTGF expression (0-4) and inflammation and fibrosis (1-4). RESULTS: High levels of CTGF expression were observed in 9 of 11 BA with localization to biliary epithelial cells and vascular endothelial cells. Connective tissue growth factor mRNA expression was correlated with fibrosis in BA and all livers. In the 11 patients with other liver diseases, 7 had CTGF expression limited to hepatic stellate cells and vascular endothelial cells. None of the 4 livers in children without liver disease had significant levels of CTGF. CONCLUSIONS: In BA livers, novel biliary epithelia CTGF mRNA expression is high and correlates with severity of fibrosis. These data support a role for biliary epithelial cell signaling in fibrogenesis.

Adolescent↗
PubMed2005

Increased susceptibility of fat-laden Zucker-rat hepatocytes to bile acid-induced oncotic necrosis: an in vitro model of steatocholestasis.

UNLABELLED: Metabolic liver disorders cause chronic liver disease and liver failure in childhood. Many of these disorders share the histologic features of steatosis and cholestasis, or steatocholestasis. In this study we sought to (1) develop an in vitro model of steatocholestasis, (2) determine the mechanisms of cell death in this model, and (3) determine the role of mitochondrial disturbances in this model. METHODS: Hepatocytes were isolated from 8-week-old obese (fa/fa) and lean Zucker rats. Cell suspensions were treated with glycochenodeoxycholic acid (GCDC), after which reactive oxygen species (ROS) generation, oncotic necrosis, apoptosis, and ATP content were assessed. Isolated liver mitochondria were exposed to GCDC and analyzed for ROS generation, mitochondrial membrane-permeability transition (MPT), and cytochrome c release. Oncotic necrosis was significantly increased and apoptosis reduced in fa/fa hepatocytes exposed to GCDC compared with that in lean hepatocytes. Necrosis occurred by way of an ROS- and MPT-dependent pathway. Basal and dynamic ATP content did not differ between fa/fa and lean hepatocytes. GCDC stimulated ROS generation, MPT, and cytochrome c release to a similar extent in purified mitochondria from both fa/fa and lean rats. These findings suggest that fat-laden hepatocytes favor a necrotic rather than an apoptotic cell death when exposed to low concentrations of bile acids. The protective effects of antioxidants and MPT blockers suggest novel therapeutic strategies for the treatment of steatocholestatic metabolic liver diseases.

Adenosine Triphosphate↗
PubMed2005

Human hepatic mitochondria generate reactive oxygen species and undergo the permeability transition in response to hydrophobic bile acids.

OBJECTIVES: Hydrophobic bile acids accumulate in the liver during cholestasis and are believed to cause hepatocellular necrosis and apoptosis in part through induction of the mitochondrial permeability transition (MPT) and the mitochondrial generation of oxidative stress. The purpose of this study was to determine if human hepatic mitochondria respond to bile acids in this manner. METHODS: The MPT was measured spectrophotometrically and morphologically in normal human liver mitochondria exposed to glycochenodeoxycholic acid (GCDC) with and without cyclosporin A, an inhibitor of the MPT, antioxidants, and tauroursodeoxycholic acid (TUDC). Hydroperoxide generation was measured by dichlorofluorescein fluorescence. Cytochrome c and apoptosis-inducing factor were assessed by immunoblotting. RESULTS: GCDC induced the MPT in a dose-dependent manner, which was inhibited by cyclosporin A, alpha-tocopherol, beta-carotene, idebenone, and TUDC. GCDC stimulated reactive oxygen species generation and release of cytochrome c and apoptosis-inducing factor, which were significantly inhibited by the antioxidants, cyclosporin A, and TUDC. CONCLUSIONS: Mitochondrial pathways of cell death are stimulated in human hepatic mitochondria exposed to GCDC consistent with the role of mitochondrial dysfunction in the pathogenesis of cholestatic liver injury. These results parallel those reported in rodents, supporting the extrapolation of mechanistic studies of bile acid toxicity from rodent to humans.

Antioxidants↗
PubMed2004

Enrichment of rat hepatic organelles by vitamin E administered subcutaneously.

Novel modes of administering antioxidants to improve delivery to targeted tissues or cells may be advantageous in preventing oxidant-induced pathologies. Vitamin E (alpha-tocopherol) has been shown to be protective in several models of liver injury. The objectives of this study were: (1) to determine if subcutaneously (s.q.) administered emulsified vitamin E enriched liver and hepatic subcellular fractions with the antioxidant and (2) to carry out a time-dependent analysis of serum and tissue vitamin E in rats receiving daily s.q. vitamin E. In the first experiment rats injected daily s.q. with emulsified vitamin E for 9 d increased serum, total liver, liver mitochondria, and liver microsomes by 8-, 16-, 30-, and 29-fold, respectively, compared with placebo injections. Similar enrichment was observed after intramuscular injections. In the second experiment, daily doses of s.q. vitamin E increased liver concentrations 40-fold by 9 d, which decreased to 22-fold by 18 d, whereas serum adjusted vitamin E levels maximized with a 24-fold increase by day 3 and plateaued thereafter. In conclusion, s.q. administration of emulsified vitamin E to rats resulted in substantially elevated serum and liver concentrations of alpha-tocopherol compared with levels achievable by dietary supplementation. The s.q. route of administration is a potentially effective parenteral mode of delivery of vitamin E for conditions in which hepatic oxidative stress is present.

Animals↗
PubMed2004

Biliary atresia is associated with CD4+ Th1 cell-mediated portal tract inflammation.

A proposed mechanism in the pathogenesis of biliary atresia involves an initial virus-induced, progressive T cell-mediated inflammatory obliteration of bile ducts. The aim of this study was to characterize the inflammatory environment present within the liver of infants with biliary atresia to gain insight into the role of a primary immune-mediated process versus a nonspecific secondary response to biliary obstruction. Frozen liver tissue obtained from patients with biliary atresia, neonatal giant cell hepatitis, total parenteral nutrition (TPN)-related cholestasis, choledochal cysts, and normal control subjects was used for fluorescent immunohistochemistry studies of cellular infiltrates, cytokine mRNA expression, and in situ hybridization for localization of cytokine-producing cells. Immunohistochemistry revealed increases in CD8(+) and CD4(+) T cells and Kupffer cells (CD68(+)) in the portal tracts of biliary atresia. Reverse transcription-PCR analysis of biliary atresia tissue showed a Th1-type cytokine profile with expression of IL-2, interferon-gamma, tumor necrosis factor-alpha, and IL-12. This profile was not seen in normal, neonatal hepatitis or choledochal cyst livers but was present in TPN-related cholestasis. In situ hybridization revealed that the Th1 cytokine-producing cells were located in the portal tracts in biliary atresia and in the parenchyma of TPN-related cholestasis. A distinctive portal tract inflammatory environment is present in biliary atresia, involving CD4(+) Th1 cell-mediated immunity. The absence of similar inflammation in other pediatric cholestatic conditions suggests that the portal tract inflammation in biliary atresia is not a secondary response to cholestasis but rather indicates a specific immune response involved in the pathogenesis of biliary atresia.

Bile Ducts, Extrahepatic↗
PubMed2004

Beta-carotene prevents bile acid-induced cytotoxicity in the rat hepatocyte: Evidence for an antioxidant and anti-apoptotic role of beta-carotene in vitro.

Hydrophobic bile acids are implicated in the pathogenesis of cholestatic liver disorders through mechanisms involving oxidative stress and mitochondrial dysfunction. Antioxidants ameliorate bile acid-induced cytotoxicity in rat hepatocyte suspensions. The purpose of the current study was to evaluate the potential protective role of beta-carotene (betaC), a putative fat-soluble antioxidant that is reduced in patients with cholestasis, against bile acid-induced hepatotoxicity. In freshly isolated rat hepatocyte suspensions that were exposed to the toxic hydrophobic bile acid glycochenodeoxycholic acid (100 or 500 microM), betaC (100 microM) decreased generation of reactive oxygen species by >50%, similar to the inhibition afforded by alpha-tocopherol. Commensurate with this antioxidant effect, 100 microM betaC also protected hepatocytes against both glycochenodeoxycholic acid-induced cellular necrosis and apoptosis, which was associated with reduction in caspase 3 activation, inhibition of mitochondrial cytochrome c release in rat hepatocytes, and prevention of the mitochondrial permeability transition in both liver mitochondria and rat hepatocytes. A lower concentration of betaC (50 microM) produced similar antioxidant and anti-apoptotic protection but with less inhibition against cell necrosis, suggesting that the higher concentration of betaC may have conferred additional cytoprotection not directly related to its antioxidant function. These results demonstrate that the antioxidant effects of betaC may provide hepatoprotection against cholestatic liver injury by preventing bile acid-induced oxidative stress and mitochondrial perturbations.

Animals↗
PubMed2004

Coordinate expression of regulatory genes differentiates embryonic and perinatal forms of biliary atresia.

The molecular basis for the embryonic and perinatal clinical forms of biliary atresia is largely undefined. In this study, we aimed to: 1) determine if the clinical forms can be differentiated at the transcriptional level, and 2) search for molecular mechanisms underlying phenotypic differences. To this end, we generated biotinylated cRNA probes from livers of age-matched infants with the embryonic (n = 5) and perinatal (n = 6) forms of biliary atresia at the time of diagnosis and hybridized them against the Affymetrix human HG-U133 A and B microarrays containing 44,760 gene products. Data filtering and two-way cluster analysis of the gene expression platform identified 230 genes with an expression profile that is highly distinctive of the clinical phenotypes. Functionally, the profile did not reveal a higher-order function for a specific cell type; instead, it uncovered a coordinated expression of regulatory genes. These regulatory genes were predominantly represented in the embryonic form (45% of genes), with a unique pattern of expression of genes involved in chromatin integrity/function (Smarca-1, Rybp, and Hdac3) and the uniform overexpression of five imprinted genes (Igf2, Peg3, Peg10, Meg3, and IPW), implying a failure to downregulate embryonic gene programs. In conclusion, embryonic and perinatal forms of biliary atresia are distinguished by gene expression profiling. The coordinate expression of regulators of chromatin structure/function and of imprinted genes provides evidence for a transcriptional basis for the pathogenesis of the embryonic form of biliary atresia. Further studies exploring these biological processes are required to determine the significance of these findings.

Biliary Atresia↗
PubMed2004

Interferon treatment for chronic hepatitis B: enhanced response in children 5 years old or younger.

OBJECTIVE: To test the hypothesis that there is an improved response to interferon in children with chronic hepatitis B (HBV) who are < or =5 years of age. STUDY DESIGN: Retrospective chart review of 22 consecutive children with chronic HBV (ages 17 months to 17 years; median, 83.9 months; 14 male, 8 female) treated with interferon-alpha2b. RESULTS: Ten patients (48%) responded to treatment [HBeAg (-), Anti-HBe (+), HBV DNA (-), HBsAg (+) and normal alanine aminotransferase/aspartate aminotransferase (ALT/AST) at 6 months after treatment], and 5 seroconverted HBsAg [above plus HBsAg negative and anti-HBs (+)]. Seven of 9 patients (78%) < or =5 years of age responded (5 cleared HBsAg). Three of 13 patients (23%) >5 years of age responded. Patient age at treatment was significantly lower in responders (63 +/- 70 months) versus nonresponders (104 +/- 55 months, P =.005). AST, ALT, and HBV DNA at the start of treatment were not different between responders and nonresponders or between patients < or =5 and >5 years old. CONCLUSIONS: Interferon treatment may be more effective in younger children with chronic hepatitis B.

Adolescent↗
PubMed2004

Clinical features of children with screening-identified evidence of celiac disease.

OBJECTIVE: At-risk groups commonly undergo screening for autoantibodies associated with celiac disease (CD). However, the clinical significance of a positive test remains uncertain. The objective of this study was to evaluate growth and clinical features of children who test positive for an autoantibody associated with CD. METHODS: A case-control study of Denver area healthy infants and young children with and without CD autoantibodies was conducted. A cohort of HLA-characterized children were followed prospectively since birth for the development of immunoglobulin A antitissue transglutaminase autoantibodies (TG). Clinical evaluation, questionnaire, blood draw, and small bowel biopsy were performed. Growth and nutrition and frequency of positive responses were measured. RESULTS: Compared with 100 age- and gender-matched TG-negative controls, 18 TG-positive children, 5.5 +/- 0.5 years of age, had a greater number of symptoms and lower z scores for weight-for-height and for body mass index. Responses that were independently associated with TG-positive status were irritability/lethargy, abdominal distention/gas, and difficulty with weight gain. CONCLUSIONS: Screening-identified TG-positive children demonstrate mild alterations in growth and nutrition and report more symptoms than control subjects. Additional study is needed on the benefit and risk of identifying CD in at-risk groups.

Autoantibodies↗
PubMed2003

Urinary F2-isoprostanes in young healthy children at risk for type 1 diabetes mellitus.

Oxidative stress has been linked to many diseases, but little information exists on biomarkers of oxidative stress in healthy children. The purpose of this study was to describe factors that correlate with urinary F2-isoprostanes, an indicator of oxidative stress, and to establish normal concentrations of F2-isoprostanes in children at risk to develop type 1 diabetes mellitus. Creatinine-adjusted urinary F2-isoprostanes were assessed in 342 Denver children under the age of 7 years, from whom we had collected data during 769 clinic visits from August 1997 through January 2001 (mean 2.3 visits per child). Children were identified by newborn screening for HLA-markers, of varying degrees of prediction, for the development of type 1 diabetes. Plasma antioxidants and carotenoids, age at clinic visit, vitamin supplement use, exposure to environmental tobacco smoke, gender, and race were evaluated as correlates to the degree of oxidative stress, using mixed models for longitudinal data. F2-isoprostane levels were highest in infancy and decreased nonlinearly until 7 years. Female gender, HLA-DR3/4 genotype, higher plasma gamma-tocopherol:total lipids ratio, and lower alpha-carotene:total lipids ratio correlated with higher F2-isoprostane levels. Normal values in this healthy population can be used as the basis for future studies of disease mechanisms involving oxidative stress.

Biomarkers↗
PubMed2003

Biliary diversion for progressive familial intrahepatic cholestasis: improved liver morphology and bile acid profile.

BACKGROUND AND AIMS: Progressive familial intrahepatic cholestasis (PFIC) is characterized by pruritus, intrahepatic cholestasis, low serum gamma-glutamyltransferase levels, and characteristic "Byler bile" on electron microscopy. Many patients require liver transplantation, but partial external biliary diversion (PEBD) has shown therapeutic promise. However, the effect of PEBD on liver morphology and bile composition has not been evaluated. METHODS: We reviewed liver biopsy specimens from 3 children with low gamma-glutamyltransferase PFIC before and after PEBD. Follow-up liver biopsies were performed 9-60 months after PEBD. Light and electron microscopic features were scored blindly. Biliary bile acid composition was analyzed by gas chromatography-mass spectrometry before and after PEBD in 1 patient and after PEBD in 2 patients. RESULTS: Following PEBD, all patients improved clinically. Preoperative biopsy specimens showed characteristic features of PFIC, including portal fibrosis, chronic inflammation, cholestasis, giant cell transformation, and central venous mural sclerosis. Ultrastructural findings included coarse, granular canalicular Byler bile, effaced canalicular microvilli, and proliferative pericanalicular microfilaments. Following diversion, histology showed almost complete resolution of cholestasis, portal fibrosis, and inflammation with resolution of ultrastructural abnormalities. Biliary bile acids before PEBD consisted predominantly of cholic acid. After PEBD, the proportion of chenodeoxycholic acid increased significantly in 1 patient and was above the PFIC range in a second patient. CONCLUSIONS: The resolution of hepatic morphologic abnormalities following PEBD supports PEBD as an effective therapy for PFIC. The improved biliary bile acid composition suggests enhanced bile acid secretion after PEBD, perhaps by induction of alternative canalicular transport proteins.

Bile Acids and Salts↗
PubMed2003

Gastrointestinal manifestations of mitochondrial disease.

Although non-specific gastrointestinal and hepatic symptoms are commonly found in most mitochondrial disorders, they are among the cardinal manifestations of several primary mitochondrial diseases, such as: mitochondrial neurogastrointestinal encephalomyopathy; mitochondrial DNA depletion syndrome; Alpers syndrome; and Pearson syndrome. Management of these heterogeneous disorders includes the empiric supplementation with various "mitochondrial cocktails," supportive therapies, and avoidance of drugs and conditions known to have a detrimental effect on the respiratory chain. There is a great need for improved methods of treatment and controlled clinical trials of existing therapies. Liver transplantation is successful in acquired cases; however neuromuscular involvement in primary mitochondrial disorders should be a contraindication for liver transplantation.

DNA, Mitochondrial↗
PubMed2003

A prospective study of the incidence of childhood celiac disease.

OBJECTIVES: To estimate the frequency of celiac disease (CD) in children in the general population of Denver, Colorado. STUDY DESIGN: From 22,346 newborns characterized as expressing 0, 1, or 2 HLA-DR3(DQB1*0201) alleles, 987 were selected for a prospective stratified cohort study. Participants were followed for as long as 7 years with serial testing for serum IgA anti-transglutaminase antibodies and for evidence of CD (intestinal mucosal changes or persistent seropositivity). RESULTS: Of 40 children with at least one positive serologic test, 19 had evidence of CD (10 by biopsy, 9 by persistent seropositivity). Those expressing 0, 1, or 2 HLA-DR3 alleles had, respectively, 0.3% (95% CI, 0.0-2.7), 3.4% (3.0-11.7), and 3.2% (1.0-11.0) risk for evidence of CD by age 5 years. The adjusted risk estimate for evidence of CD by age 5 years for the Denver general population was 0.9% (0.4-2.0), or 1 in 104 (1:49-221). After adjusting for number of HLA-DR3 alleles expressed, risk was higher in females: RR=3.34 (1.00-10.9, P=.048). Evidence of CD was not observed before age 2.6 years. CONCLUSIONS: Celiac disease may affect 0.9% of Denver children by 5 years of age. Children positive for the HLA-DR3 allele and females appear to be at increased risk.

Celiac Disease↗