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S W French

Publications and source records attributed to S W French.

At least 19 recordsLinked to original sources
PubMed2003

Heat shock proteins are present in mallory bodies (cytokeratin aggresomes) in human liver biopsy specimens.

Mallory bodies (MBs) are aggresomes, composed of cytokeratin and various other proteins, which form in diseased liver because of disruption in the ubiquitin-proteasome protein degradation pathway. Heat shock proteins (hsp's) are thought to be involved in this process because it was discovered that MB formation is induced by heat shock in drug-primed mice. It has been reported that ubiquitin and a mutant form of ubiquitin (UBB(+1)) are found in aggresomes formed in the neurons in Alzheimer's disease and in the liver MBs in various liver diseases. In addition, hsp 70 has been found in aggresomes in Alzheimer's and in MBs in drug-primed mice. Therefore, we hypothesized that hsp's might be involved in MB formation in human liver diseases. Liver biopsy sections were double-stained using ubiquitin and hsp 70 or 90b antibodies. Both hsps 70 and 90b were found in MBs in all liver diseases investigated including primary billiary cirrhosis, nonalcoholic steatohepatitis, hepatitis B and C, idiopathic cirrhosis, alcoholic hepatitis, and hepatocellular carcinoma. Ubiquitin and the hsp's colocalized in all MBs in the diseased liver sections. These results indicate that hsp involvement in MB formation is similar to that seen in aggresome formation in other conformational diseases.

Animals↗
PubMed2003

The mechanism of cytokeratin aggresome formation: the role of mutant ubiquitin (UBB+1).

Aggresome formation in cells involves the failure of the ubiquitin-proteasome pathway to dispose of proteins destined for degradation by the 26S proteasome. UBB(+1) is present in Mallory bodies in alcoholic liver disease and in aggresomes formed in Alzheimer's desease. The present investigation focuses on the role that UBB(+1) plays in cytokeratin aggresome formation in Mallory bodies (MBs) in vitro. Immunoprecipitation with a monoclonal antibody to cytokeratin-8 (CK-8) was used. The immunoprecipitate was incubated for 24 h in the presence of different constituents involved in aggresome formation including ubiquitin, UBB(+1), the proteasome inhibitor PS341, an ATP generating energy source, a deubiquitinating enzyme inhibitor, a purified proteasome fraction, and an E(1-3) conjugating enzyme fraction. MB-like protein aggregates formed in the presence of ubiquitin, plus UBB(+1) or PS341. These aggregates stained positively for CK-8. UBB(+1), and a proteasome subunit Tbp7, as demonstrated on Western blots. A second approach was used to form MBs in vitro in cultured hepatocytes transfected with UBB(+1) protein using Chariot. The cells were double stained using CK-8 and ubiquitin antibodies. The two proteins colocalized in MB-like aggregates. The results support the possibility that aggresome formation is a complex multifactor process, which is favored by inhibition of the proteasome and by the presence of UBB(+1).

Adenosine Triphosphate↗
PubMed2003

Microtubules are required for cytokeratin aggresome (Mallory body) formation in hepatocytes: an in vitro study.

Mallory bodies are cytokeratin-ubiquitin aggresomes that form in hepatocytes in many different chronic liver diseases. One of the key components in aggresome formation, not yet investigated in Mallory body formation, is the role of microtubules. An in vitro tissue culture assay is required to test for microtubule involvement in Mallory body formation so that Mallory body formation can be observed in the presence or absence of microtubule-disrupting agents. In this report, a new model of in vitro Mallory body formation was developed, which uses cultured hepatocytes isolated from drug-primed mice. When hepatocytes were incubated in the presence of antimicrotubule agents, they failed to form Mallory bodies. It is concluded that intact microtubules are required for Mallory body formation.

Animals↗
PubMed2002

The Mallory body as an aggresome: in vitro studies.

Prior in vivo studies supported the concept that Mallory bodies (MBs) are aggresomes of cytokeratins 8 and 18. However, to test this hypothesis an in vitro model is needed to study the dynamics of MB formation. Such a study is difficult because MBs have never been induced in tissue culture. Therefore, MBs were first induced in vivo in drug-primed mice and then primary cultures of hepatocytes from these mice were studied. Two approaches were utilized: 1. Primary cultures were transfected with plasmids containing the sequence for cytokeratin 18 (CK 18) tagged with green fluorescent protein (GFP). 2. Immunofluorescent staining was used to localize the ubiquitin-proteasome pathway components involved in MB-aggresome complex formation in primary hepatocyte cultures. The cells were double stained with a ubiquitin antibody and one of the following antibodies: CK 8, CK 18, tubulin, mutant ubiquitin (UBB+1), transglutaminase, phosphothreonine, and the 20S and 26S proteasome subunits P25 and Tbp7, respectively. In the first approach, fluorescence was observed in keratin filaments and MBs 48 h after the cells were transfected with the CK 18 GFP plasmid. Nascent cytokeratin 18 was preferentially concentrated in MBs. Less fluorescence was observed in the normal keratin filaments. This indicated that MBs continued to form in vitro. The immunofluorescent staining of the hepatocytes showed that CK 8 and 18, ubiquitin, mutant ubiquitin (UBB+1), P25, Tbp7, phosphothreonine, tubulin, and transglutaminase were all located at the border or the interior of the MB. These results support the concept that MBs are aggresomes of CK 8 and CK18 and are a result of inhibition of the ubiquitin-proteasome pathway of protein degradation possibly caused by UBB+1.

Animals↗
PubMed2001

Mallory bodies formed in proteasome-depleted hepatocytes: an immunohistochemical study.

Mallory bodies (MBs) are aggregates of proteins, principally cytokeratin proteins found in liver cells. They are also found in a few other cell types such as type II pneumocytes and trophoblasts. Studies on the liver thus far indicate that MBs are derived from hyperphosphorylated, heavily ubiquitinated proteins which have undergone conformational change. The aggregated protein may accumulate because of the failure of the proteasome to remove the altered proteins from the cytoplasm of liver cells. To investigate this possibility, the proteasomes were assessed immunohistochemically in individual liver cells of mice fed a drug which induced MB formation. To accelerate and enhance MB formation, cytochrome P450 2EI knockout mice were used. Proteasomes in individual cells were visualized by immunofluorescence using an antibody to a subunit of the proteasome (P25). The results showed that the groups of liver cells that had formed MBs were often partially depleted of proteasomes. These findings support the possibility that MBs formed as a result of the loss of the proteasome to remove misfolded cytokeratin proteins. Thus MBs may share their pathogenesis with other types of cellular inclusions seen where proteins aggregate in the cytoplasm due to mutation, misfolding, or loss of proteasomes.

Animals↗
PubMed2001

Liver necrosis induced by thyroid hormone administration in rats fed ethanol.

Recently it was observed that the hypothyroid state induced by propylthiouracil treatment reduced the elimination rate of ethanol. This was based on the fact that hypothyroid rats could only tolerate 10 g/kg/day of ethanol infusion over 24 h. Euthyroid rats tolerate 13 to 14 g/kg/day of ethanol infusion. In the present report it was postulated that thyroid supplements would increase the daily dose of ethanol that the treated rats could tolerate. Daily thyroid supplements, given intraperitoneally or orally, did, in fact, result in an increase in the elimination rate of ethanol. Death from ethanol overdose did not occur until the amount of ethanol given reached 16 to 19 g/kg/day. In addition, thyroxine supplements blunted or completely inhibited the urinary ethanol cycle. Submassive centrilobular liver necrosis was present in 9 of 10 rats given thyroid hormone and fed ethanol. Periportal duct metaplasia and fibrosis were also observed. Thus, thyroid supplements probably enhanced central hypoxia caused by ethanol to the point where ischemic necrosis developed. The latter healed by scar formation. Thyroid treatment completely prevented ethanol-induced steatohepatitis, indicating that the fatty change is responsive to the metabolic rate.

Administration, Oral↗
PubMed2001

Oral low-carbohydrate alcohol liquid diet induces experimental steatohepatitis in the rat.

The intragastric tube feeding model of alcoholic liver disease in the rat induces significant liver histopathology, including steatohepatitis and fibrosis. The question is, if the same low-carbohydrate diet is fed ad lib, will the same pathology develop? Rats were fed a liquid diet with ethanol ad lib that was low in calories derived from carbohydrates for 2 months. The urinary ethanol levels (UALs) were monitored at hourly, daily, and weekly intervals, and the growth of the rats was charted. The liver histopathology and blood transaminase levels were determined. Rats fed ethanol grew 1 g/day, which was 2 g/day less than when they were fed the same diet intragastrically. UALs varied hourly between 150 and 500 mg%, daily between 120 and 360 mg%, and weekly between 0 and 500 mg%. Individual rat UALs showed no predictable pattern. The pair-fed controls ate all of their daily ration within 12 h, then fasted until the next day. The histopathology and blood alanine aminotransferase were similar to those seen with the intragastric tube feeding of the same diet, except that necrosis, inflammation, and fibrosis did not develop. The conclusion was that the oral feeding of a low-carbohydrate diet produces less liver injury than that produced by the same diet fed intragastrically. The UALs varied hourly, daily, and weekly in individual rats, making it difficult to synchronize UALs at the time of sacrifice.

Administration, Oral↗
PubMed2001

"Piecemeal" necrosis: renamed troxis necrosis.

Piecemeal necrosis, currently called interface hepatitis, is a feature of viral hepatitis as well as autoimmune hepatitis and steatohepatitis. The mechanism of liver cell loss and piecemeal necrosis needs to be determined. We hypothesize that piecemeal necrosis in hepatitis is due to a piecemeal removal of hepatocyte cytoplasm by lymphocytic ingestion. To test this hypothesis, 61 consecutive liver biopsies were examined by light microscopy, by immunohistochemistry and by electron microscopy, and the lymphocytic-hepatocytic interaction was morphologically assessed. In cases of hepatitis C, hepatitis B, autoimmune hepatitis, primary biliary cirrhosis, and steatohepatitis, piecemeal necrosis was found. Using cytokeratin stains, it was apparent that the lymphocyte-hepatocyte interaction and piecemeal necrosis leads first to binding of the lymphocyte to hepatocyte plasma membrane and then blebbing or indentation of the hepatocyte by the lymphocyte, followed by endocytosis of liver cell cellular components and digestion in the lymphocyte lysosomes. This process is repeated while the cytoplasm and the nucleus of the hepatocyte disappear bite by bite, and only nubbins of residual hepatocytic cytoplasm remain, either attached to intact hepatocytes or surrounded and sequestered within scar tissue and lymphocytes. We conclude that piecemeal necrosis is a gradual disappearance of hepatocytes as a result of lymphocyte-hepatocyte binding and ligand internalization of liver surface molecules by the lymphocyte. This gradual process leads to a slow reduction of hepatocyte size and eventual disappearance at the interface between the lobule and portal tracts. To term this new kind of necrosis, we propose the name troxis necrosis, after the Greek noun meaning "nibbling."

Biopsy↗
PubMed2001

Aggresome formation in liver cells in response to different toxic mechanisms: role of the ubiquitin-proteasome pathway and the frameshift mutant of ubiquitin.

Aggresomes form in cells when intracellular proteins undergo conformational changes, as in so-called conformational diseases. This phenomenon has been observed in the liver and brain and in cell culture in response to abnormal protein formation, such as mutant proteins. In the case of the brain the frameshift mutant ubiquitin (UBB+1) is involved. Mallory body formation in the liver is one example of this phenomenon in vivo. Mallory body formation is common in a variety of liver diseases of diverse pathogenesis. The study of the Mallory body forming model indicated that drug-conditioned hepatocytes form Mallory bodies when mice are given colchicine, ethanol, okadaic acid, or exposure to heat shock. These findings suggest that aggresome formation is a common pathway of liver injury due to diverse mechanisms. To further characterize the role of this common pathway, drug-primed mice were exposed to different types of liver injury, i.e., using such drugs as thioacetamide, galactosamine, tautomycin, and the proteasome inhibitor PS341. Mallory body formation was induced by treatment with all the toxins tested, giving credence to the proposal that aggresome formation in the liver is a common pathway in response to different primary mechanisms of liver injury. The frameshift mutant UBB+1 was invariably found to colocalize with ubiquitin in the Mallory body, indicating its essential involvement in the mechanism of MB formation.

Animals↗
PubMed2001

TCL1 oncogene expression in B cell subsets from lymphoid hyperplasia and distinct classes of B cell lymphoma.

Activation of the TCL1 oncogene has been implicated in T cell leukemias/lymphomas and recently was associated with AIDS diffuse large B cell lymphomas (AIDS-DLBCL). Also, in nonmalignant lymphoid tissues, antibody staining has shown that mantle zone B cells expressed abundant Tcl1 protein, whereas germinal center (GC; centrocytes and centroblasts) B cells showed markedly reduced expression. Here, we analyze isolated B cell subsets from hyperplastic tonsil to determine a more precise pattern of Tcl1 expression with development. We also examine multiple B cell lines and B lymphoma patient samples to determine whether different tumor classes retain or alter the developmental pattern of expression. We show that TCL1 expression is not affected by Epstein-Barr virus (EBV) infection and is high in naïve B cells, reduced in GC B cells, and absent in memory B cells and plasma cells. Human herpesvirus-8 infected primary effusion lymphomas (PEL) and multiple myelomas are uniformly TCL1 negative, whereas all other transformed B cell lines tested express moderate to abundant TCL1. This observation supports the hypothesis that PEL, like myeloma, usually arise from post-GC stages of B cell development. Tcl1 protein is also detected in most naïve/GC-derived B lymphoma patient samples (23 of 27 [85%] positive), whereas most post-GC-derived B lymphomas lack expression (10 of 41 [24%] positive). These data indicate that the pattern of Tcl1 expression is distinct between naïve/GC and post-GC-derived B lymphomas (P < 0.001) and that the developmental pattern of expression is largely retained. However, post-GC-derived AIDS-DLBCL express TCL1 at a frequency equivalent to naïve/GC-derived B lymphomas in immune-competent individuals (7 of 9 [78%] positive), suggesting that TCL1 down-regulation is adversely affected by severe immune system dysfunction. These findings demonstrate that TCL1 expression in B cell lymphoma usually reflects the stage of B cell development from which they derive, except in AIDS-related lymphomas.

B-Lymphocyte Subsets↗
PubMed2001

Transforming growth factor-alpha (TGF-alpha) is not needed for malignant transformation in experimental colitis.

BACKGROUND: Transforming growth factor-alpha (TGF-alpha) is a key mediator of colonic mucosal protection and/or repair mechanisms in orally induced acute dextran sodium sulphate (DSS) colitis. However, it also has been suggested that TGF-alpha may contribute to malignant transformation in the colon. The aim of the studies was to determine whether TGF-alpha is needed for malignant transformation in orally induced chronic DSS colitis using TGF-alpha deficient mice (wa-1) and Balb/c mice, a strain competent in TGF-alpha. METHODS: Chronic colitis was induced by oral administration of DSS (5%) for 7 days followed by drinking water for 10 days in wa-1 and Balb/c mice (n = 20, per group). In the two subsequent cycles (7 days DSS, 10 days water) 3% DSS-water was utilized due to a high mortality in the wa-1 group. Mucosal injury severity was assessed histologically and graded (three grades). A crypt damage score (CDS) reflecting all three grades of mucosal pathology was calculated. Mucosal dysplasia and cancerous lesions were noted. RESULTS: Seven per cent of the entire colonic mucosa was completely destroyed in wa-1 animals compared to 3% in Balb/c mice (P < 0.05). The CDS was 10.2 +/- 0.4 and 4.8 +/- 0.3 in wa-1 and Balb/c mice, respectively (P < 0.05). Fifteen incidences of mucosal dysplasia were found in the 10 surviving wa-1 animals and 31 incidences were found in 20 Balb/c animals. In both groups, one fully developed adenomatous cancerous lesion was present. CONCLUSIONS: The markedly increased severity of mucosal injury in chronic induced DSS colitis in TGF-alpha deficient wa-1 mice compared to Balb/c mice further substantiates that endogenous TGF-alpha is a pivotal mediator of protection and/or healing mechanisms in the colon. The appearance of dysplastic and cancerous lesions in TGF-alpha deficient animals suggests that TGF-alpha per se is not essential for malignant mucosal cell transformation in colitis.

Animals↗
PubMed2001

The ubiquitin-proteasome 26s pathway in liver cell protein turnover: effect of ethanol and drugs.

This article represents the proceedings of a symposium at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were Samuel W. French and R. J. Mayer. The presentations were (1) The ubiquitin-proteasome 26s pathway in liver cell protein turnover: Effect of alcohol and drugs, by Samuel W. French and F. Bardag-Gorce; (2) The role of CYP2E1 phosphorylation and degradation pathway in the induction of the enzyme, by Magnus Ingelman-Sundberg; (3) Role of proteasome in the proteolysis of oxidized proteins in experimental chronic alcoholism, by Helen Rouach; (4) Alcohol, proteolysis and liver cancer, by R. J. Mayer; (5) Effect of ethanol feeding on the ATP-ubiquitin-proteasome pathway in the liver cell, by F. Bardag-Gorce; (6) Novel mechanisms and targets for intracellular transport of CYP2E1, by E. Neve; and (7) Gankyrin, an oncoprotein commonly over expressed in hepatoma, by H. Higashitsuji.

Animals↗
PubMed2001

Models of alcoholic liver disease in rodents: a critical evaluation.

This article represents the proceedings of a workshop at the 2000 ISBRA Meeting in Yokohama, Japan. The chairs were J. Christian Bode and Hiroshi Fukui. The presentations were (1) Essentials and the course of the pathological spectrum of alcoholic liver disease in humans, by P. de la M. Hall; (2) Lieber-DeCarli liquid diet for alcohol-induced liver injury in rats, by C. S. Lieber and L. M. DeCarli; (3) Tsukamoto-French model of alcoholic liver injury, by S. W. French; (4) Animal models to study endotoxin-ethanol interactions, by K. O. Lindros and H. Järveläinen; and (5) Jejunoileal bypass operation in rats-A model for alcohol-induced liver injury? by Christiane Bode, Alexandr Parlesak, and J. Christian Bode.

Animals↗
PubMed2001

Nesidioblastosis coexisting with islet cell tumor and intraductal papillary mucinous hyperplasia.

A coexisting of intraductal papillary mucinous hyperplasia (IPMH) and islet cell tumor with nesidioblastosis of the pancreas in a 51-year-old man is reported. All of the clinical data indicated an insulinoma. A distal pancreatectomy was performed. A discrete mass measuring 1.9 x 2.0 cm was grossly identified in the tail of the pancreas. There were no other gross lesions. An islet cell tumor with nesidioblastosis was confirmed by immunostains and ultrastructural study. In addition, an IPMH was found that involved mainly branches of the pancreatic duct. The islet cell tumor and IPMH were topographically separated; however, there was a histologically intimate relationship between the nesidioblastosis and the IPMH. These findings indicate that the IPMH may have derived from autocrine and paracrine influences on the existing duct epithelial cells. To the best of our knowledge, this is the first report of nesidioblastosis coexisting with islet cell tumor and IPMH.

Adenoma, Islet Cell↗
PubMed2000

The effect of ethanol-induced cytochrome p4502E1 on the inhibition of proteasome activity by alcohol.

The present investigation was undertaken to determine the effect of CYP2E1 induction by ethanol on the inhibition of proteasomal activity in wild-type and CYP2E1 knockout C57 black mice. The proteasomal chymotrypsin-like activity decreased significantly in ethanol-fed wild-type mice liver, but was not reduced in ethanol-fed knockout mice liver. The 26S proteasomal activity was decreased more by ethanol feeding than was the 20S proteasomal fraction. Individual hepatocytes lost immunostaining of the proteasomes in the centrilobular zone in the livers of ethanol-fed wild-type mice and the knockout mouse liver. There was increased product of protein oxidation in the liver in the wild type but not in the knockout mice given ethanol. Taken together, these results suggest that CYP2E1 induction was responsible for the decrease in proteasome activity seen in the wild-type mice which head to the accumulation of oxidized proteins which were increased as the result of free radicals generated by CYP2E1 metabolism of ethanol.

Animals↗
PubMed2000

Dexamethasone enhances mallory body formation in drug-primed mouse liver.

In a clinical study in which patients with alcoholic hepatitis were treated with prednisone for 1 month, posttreatment liver biopsies showed diminished inflammation, but Mallory bodies were not diminished. This suggested that steroid treatment may reduce inflammation by inhibiting NFkappaB activation. Sparing of Mallory bodies suggests that NFkappaB activation may not be involved mechanistically in Mallory body formation. To test this idea, we induced Mallory body formation in drug-primed mice with or without dexamethasone treatment. As predicted, dexamethasone decreased NFkappaB activation; however, Mallory body formation was increased. Surprisingly, TNFalpha and iNOS, which normally increase as a result of NFkappaB activation, were upregulated by the dexamethasone treatment. It was concluded that NFkappaB activation is not involved in Mallory body formation. Despite this, induced increases in TNFalpha, iNOS, c-jun/API and c-myc expression indicate that oxidative stress is likely involved in Mallory body formation.

Animals↗
PubMed2000

Adaptation to chronic ethanol administration emphasized by fatty acid hydroxylations in rat liver and kidney microsomes.

BACKGROUND: Long-term ethanol consumption in laboratory animals is associated with histological alterations of liver cells and modifications of fatty acid metabolism. AIM OF THE STUDY: The present study was aimed at investigating the effect of 1- and 2-month chronic treatment of rats with ethanol on the metabolism of two unsaturated (oleic and linoleic) fatty acids in liver and kidney microsomes, in relation to the CYP2E1 enzyme content in both tissues. METHODS: Rats were fed ethanol (14 g/Kg/d) or dextrose through a permanently implanted gastric cannula, as described in the intragastric feeding rat model for alcoholic liver disease (ALD). CYP2E1 level was immuno-quantified in both liver and kidney microsomes by Western blot, whereas fatty acid omega- and (omega-1)-hydroxylations were measured using HPLC and radiometric analytical methods. RESULTS: One- and two-month ethanol treatment led to a 3- to 4-fold rise of the CYP2E1 protein in both liver and kidney microsomes. Oleic and linoleic acid (omega-1)-hydroxylations were increased (approximately 3-fold) in liver microsomes after one-month of ethanol administration, but surprisingly such a rise was not observed after a two-month treatment; on the other hand, no effect was observed on the omega-hydroxylations of these fatty acids. Furthermore, as previously described for lauric acid, ethanol intake did not significantly act on the kidney microsome capability to hydroxylate unsaturated fatty acids. CONCLUSIONS: CYP2E1 is strongly inducible by ethanol and therefore accounts for the tolerance for this hepatotoxicant. Our results support the development of an adaptation process in the liver hydroxylating enzyme system, which occurs between one and two months of ethanol feeding. Although it is usually not appropriate to extrapolate animal findings to humans, rat and human CYP2E1s were observed to have comparable specificities and similar mechanisms of regulation. Thus, the present study allowed the acquirement of detailed information of CYP2E1 activity in patients with severe manifestations of ALD.

Adaptation, Physiological↗