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M Hiron

Publications and source records attributed to M Hiron.

At least 19 recordsLinked to original sources
PubMed2001

Chromosomal assignments of mammalian genes with an acute inflammation-regulated expression in liver.

A set of acute inflammation-regulated genes expressed in liver has been assigned to rat, mouse, and human chromosomes by detecting species-specific PCR amplicons in rat(x)mouse or mouse(x)hamster somatic cell hybrids or radiation hybrids or by in silico matches of corresponding rat cDNAs to various libraries of previously assigned rat, mouse, or human genes or expressed-sequence tags. This allowed us to assign 24, 22, and 21 inflammation-regulated genes to rat, mouse, and human chromosomes, respectively. From these assignments as well as those previously determined for a larger set of genes with an acute inflammation-regulated transcription in liver, we further investigated whether such genes are clustered onto given chromosomes. A cluster was found on rat Chromosome (Chr) 6q with a conserved synteny on mouse Chr 12 and human Chr 14q13-q32, and another cluster previously reported on human Chr 1q has been extended with five further genes. Our data suggest that during an acute inflammation, a higher-order regulation may control some liver-expressed genes that share a given chromosome area.

Acute Disease↗
PubMed2001

Up-regulated expression of HGF in rat liver cells after experimental endotoxemia: a potential pathway for enhancement of liver regeneration.

A lipopolysaccharide (LPS)-induced inflammation prior to an hepatic resection has been shown to enhance liver regeneration in rat. The aim of the present study was to investigate the expression of hepatocyte growth factor (HGF) and its c-Met receptor under such experimental conditions. Animals were submitted to a two-third hepatectomy or a LPS challenge carried out 12 h prior to resection. Non parenchymal and parenchymal cells were isolated from livers obtained at various times post-hepatectomy. Quantitative RT-PCR for HGF and c-Met mRNAs were performed from total liver or purified cell fractions and HGF mRNA was also analyzed by in situ RT-PCR on liver sections. A LPS challenge alone induced a marked up-regulation of HGF mRNA level in whole liver and isolated hepatocytes. Furthermore, when partial hepatectomy (PH) was preceded by a LPS challenge, an increase of HGF mRNA level was seen in whole liver and contrasted with a decreased level in non parenchymal cells. These results were confirmed by in situ RT-PCR. In isolated hepatocytes from endotoxemic rats, the mRNA level for the LPS-specific membranous receptor mCD14 was markedly up-regulated and even more so when LPS was followed by PH. Moreover, a TNFalpha challenge alone induced an up-regulation of HGF mRNA in hepatocytes and a down-regulation in non parenchymal cells (NPCs). Overall, when a LPS challenge is given prior to PH the major source of hepatic HGF appears to be the hepatocyte itself rather than NPCs. An autocrine HGF/c-Met loop which promotes the proliferative potential of the hepatic parenchymal cell and participates in liver regeneration is postulated.

Animals↗
PubMed2000

Differential expression of apoptosis-associated genes post-hepatectomy in cirrhotic vs. normal rats.

Liver regeneration after partial hepatectomy or liver injury is controlled by a wide variety of growth factors that are proven activators or inhibitors of hepatocyte proliferation. Liver regeneration post-hepatectomy has been proven to be decreased and delayed in cirrhotic vs. normal liver. Apoptosis seems to play an important role in cellular proliferation and in liver regeneration. Therefore, this study has analyzed the expression of apoptosis-associated genes following 2/3 hepatectomy in cirrhotic vs. normal rats. Cirrhosis was induced by a weekly intragastric administration of CCl4 for 16 weeks followed by hepatectomy and histological examination of the resected liver. Rats were sacrificed at 6 h, 12 h, 24 h, or 72 h after liver resection. The expression of proapoptotic (Bad, Bak, Bax) and antiapoptotic (Bcl-2, Bcl-XL) genes was analyzed by quantitative RT-PCR. We have observed an early increase in antiapoptotic mRNA levels and a delayed increase in proapoptotic mRNA levels in normal liver following hepatectomy. Before resection, proapoptotic mRNA levels were significantly higher in cirrhotic vs. normal liver. After hepatectomy, apoptotic mRNA levels were decreased and delayed as compared with that observed following hepatectomy in normal liver. These results indicate that apoptosis takes place in liver during CCl4-induced cirrhosis and could participate in the impaired regenerative response observed in cirrhotic liver.

Animals↗
PubMed2000

Reduced synthesis of inflammatory cytokines by a free radical scavenger after hemorrhagic shock in rats.

OBJECTIVES: Intestinal ischemia/reperfusion during hemorrhage and resuscitation may be a major trigger for cytokine expression. To assess whether free radicals produced on tissue reperfusion may play a role in the inflammatory response after hemorrhage, we tested the effect of a free radical scavenger on the production of inflammatory cytokines in a rat model of hemorrhagic shock. DESIGN: A prospective, controlled animal study. SETTING: A university research laboratory. SUBJECTS: Male Wistar rats. INTERVENTIONS: Hemorrhage was induced in anesthetized rats. by bleeding the animal to achieve a mean arterial blood pressure of 40 mm Hg for 60 mins. Resuscitation was then induced by reinjecting shed blood followed by NaCl 0.9% to maintain arterial blood pressure within control values. Treated rats received the free radical scavenger N-2-mercaptopropionyl glycine (MPG; 20mg/kg iv bolus 30 mins before resuscitation followed by 20 mg/kg/hr). MEASUREMENTS AND MAIN RESULTS: MPG reduced the volume of saline necessary to restore blood pressure during resuscitation (untreated 85+/-6; MPG 35+/-5 mL/kg; p < .05). As compared with untreated rats, MPG markedly reduced the systemic and mesenteric plasma concentrations of tumor necrosis factor (TNF)-alpha (as measured by ELISA) and interleukin (IL)-6 (as measured by bioassay), assessed at the end of resuscitation. MPG also reduced TNF-alpha and IL-6 mRNA expression (as measured by reverse transcriptase-polymerase chain reaction) assessed in peritoneal macrophages isolated from shock rats. Finally, in vitro experiments showed that MPG also markedly reduced the mRNA expression and release of TNF-alpha and IL-6 in peritoneal macrophages isolated from normal rats and subjected to hypoxia and reoxygenation. CONCLUSION: Reactive oxygen species contribute to the production of proinflammatory cytokines during posthemorrhage resuscitation. Free radicals scavengers may be a useful treatment in the prevention of the systemic inflammatory response that occurs in shock states.

Animals↗
PubMed1999

Induction of haem oxygenase contributes to the synthesis of pro-inflammatory cytokines in re-oxygenated rat macrophages: role of cGMP.

Macrophage activation and the resulting inflammatory response may be a major component of tissue injury upon hypoxia and re-oxygenation. Activation of the haem oxygenase (HO)/carbon monoxide (CO) pathway may be an important regulator of the inflammatory response, through production of cyclic 3', 5'-monophosphate (cGMP). We have assessed whether HO contributes to the increased production of the pro-inflammatory cytokines TNF-alpha and IL-6 in re-oxygenated rat peritoneal macrophages.Hypoxia/re-oxygenation markedly increased levels of HO-1 mRNA and cGMP. The increase in cGMP was reduced by the HO-1 inhibitor tin-protoporphyrin (SnPP-9) given during re-oxygenation. Hypoxia and re-oxygenation also increased IL-6 and TNF-alpha mRNA expression, as well as IL-6 and TNF-alpha concentrations in the cell supernatant. These increases were nullified by SnPP-9 and by Methylene Blue, an inhibitor of guanylate cyclase, but were not affected by L-NNA, an inhibitor of NO synthesis. The inhibitory effect of SnPP on the synthesis of cytokines was reversed by co-administration of the stable analogue of cGMP, 8-Br-cGMP. Our results indicate that activation of haem oxygenase and of the CO/cGMP pathway is a major stimulus for the synthesis and release of pro-inflammatory cytokines in re-oxygenated macrophages. This pathway may play a central role in pathological situations in which local tissue hypoxia/re-oxygenation triggers a systemic inflammatory response, for example in patients with shock.

Animals↗
PubMed1999

Heme and acute inflammation role in vivo of heme in the hepatic expression of positive acute-phase reactants in rats.

Acute-phase protein synthesis in the liver during inflammation is regulated via cytokines and glucocorticoids. Using quantitative reverse transcription (RT)-PCR analysis and immunoassay, we explored, in the rat, the response of the acute-phase protein, alpha-2 macroglobulin (A2M), after systemic inflammation induced by lipopolysaccharide (LPS) or localized inflammation induced by turpentine oil (TO). The results indicate that synthesis of A2M is higher following TO-induced inflammation than LPS-induced inflammation and is not correlated with interleukin (IL)-6 or glucocorticoid levels. We studied the putative role of heme in this differential A2M expression following localized vs. systemic inflammation; addition of heme during LPS-induced inflammation can boost the expression of A2M, whereas blocking heme synthesis (by succinyl acetone) or enhancing its consumption in parallel biosynthetic pathways (cytochrome P450 induction by phenobarbital) decreases A2M expression. This decrease was abolished by exogenous heme supplementation. Finally, we demonstrate that heme supplementation is also able to increase the A2M response in female rats to a level similar to that in male rats providing a new insight into the puzzling sexual dimorphism observed previously during localized inflammation. We propose that heme should be considered a new regulatory element in controlling liver A2M expression during inflammation.

Acute-Phase Proteins↗
PubMed1999

Differential regenerative response and expression of growth factors following hepatectomy of variable extent in rats.

AIMS/BACKGROUND: Liver regeneration is a physiological mechanism which leads to restoration of the hepatic parenchyma following hepatectomy or toxic injury. This process is mediated by a wide variety of cytokines and growth factors. The aim of the present study was to evaluate the influence of hepatectomy extent on the levels of intrahepatic mRNAs for cell-cycle markers and growth factors in rats submitted to a 30%, two-third or 80% hepatectomy. METHODS: Cyclins, thymidine kinase and growth factors mRNA levels were quantitatively assessed by RT-PCR at different time points post-hepatectomy (2h, 6h, 12h, days 1, 2, 6). RESULTS: As compared with a two-third hepatectomy, cyclins and thymidine kinase mRNA levels were increased but with a delayed peak at day 2 in the 80% hepatectomy group and showed a progressive increase until day 6 in the 30% hepatectomy group; mRNA levels for HGF or TGFalpha were increased with a delayed peak at 12 h or day 2 in the 80% hepatectomy group, respectively and this delay was more pronounced in the 30% hepatectomy group with a peak at day 1 or day 6. CONCLUSION: A regenerative response occurs whatever the extent of hepatectomy but the course of regeneration and expression of growth factors differs according to the volume of resected liver. A better knowledge of these events could improve the clinical results of hepatic resection for primary or metastatic liver disease.

Animals↗
PubMed1999

Changes in growth factor and cytokine mRNA levels after hepatectomy in rat with CCl(4)-induced cirrhosis.

Cirrhotic liver is considered to regenerate less actively than normal liver after hepatic resection. However, the mechanisms responsible for this impaired regeneration and the cross talk of implicated factors still remain unclear. In the present study, mRNA levels for cyclins, growth factors, and cytokines were quantitatively assessed by a RT-PCR method at different times after hepatectomy in order to determine the relationships between these factors and the impaired regenerative process observed in cirrhotic liver. In our model of CCl(4)-induced cirrhosis, mRNA levels for cyclins and thymidine kinase provide evidence for the impaired and delayed hepatic regeneration. Moreover, we observed a significant decrease in interleukin (IL)-6 and tumor necrosis factor-alpha mRNA and a significant increase for IL-1beta mRNA. No significant change of hepatocyte growth factor (HGF) mRNA level was detected, contrasting with the decrease both at mRNA and protein levels in the expression of the c-Met/HGF receptor. Therefore, the impaired regeneration of the cirrhotic liver is associated not only with a lowered level of signals that normally promote liver growth but also with a strong decrease in c-Met receptor despite a normal expression of its specific ligand.

Animals↗
PubMed1998

Hepatic and extra-hepatic transcription of inter-alpha-inhibitor family genes under normal or acute inflammatory conditions in rat.

The expression and level of the mRNAs for the five genes that code for a set of plasma proteins collectively referred to as the inter-alpha-inhibitor family have been studied in rat under a normal condition or in the course of a turpentine-induced, systemic inflammation. In healthy rats, all five mRNAs [H1, H2, H3, H4, and alpha1-microglobulin/bikunin precursor (AMBP)] are expressed primarily in liver and two of them (H2 and H3) are found to a lower extent in brain. By in situ hybridization onto sections of a normal brain, the H3 mRNA has been precisely localized to the hypothalamus, amygdala, pontine area, optic tectum, and cerebellum. By reverse transcriptase-polymerase chain reaction of total RNAs obtained from a panel of organs, low amounts of one or more mRNA(s) could be detected in other locations (e.g., intestine and stomach). Furthermore, the extrahepatic expressions of several of these genes are up- or downregulated at 20 h after the start of a turpentine-induced inflammation. In liver, the contents of H3 and H4 mRNA are upregulated, whereas those of AMBP and H2 are downregulated during the acute phase. This is accounted for by changes in gene transcription, the kinetics of which is gene-specific. This behavior of H1, H2, H3, H4, and AMBP mRNAs in rat liver is in keeping with more limited analyses made at mRNA and/or protein levels in other species (human, pig) suffering from an acute inflammation. Therefore, the inflammation-associated regulation of these five genes that is conserved between species indicates that the inter-alpha-inhibitor family members are likely to be important partners of the acute phase response.

Alpha-Globulins↗
PubMed1998

The H4P heavy chain of inter-alpha-inhibitor family largely differs in the structure and synthesis of its prolin-rich region from rat to human.

The family of plasma proteins collectively referred to as Inter-alpha-Inhibitor (I alpha I) family is comprised of a set of multi-polypeptide molecules and a single-chain molecule designated I alpha IH4P. Although the 4 heavy chain precursors H1P to H4P that lead to these molecules are evolutionarily related, only H4P harbours a Pro-rich region (PRR) in its C-terminal third. A comparison of hepatic H4P cDNAs in human and rat has now unraveled an extensive variability of this PRR. Within the rat PRR, 6 repeats of a Gly-X-Pro motif participate in a collagen-like pattern that is absent in human. Within the human PRR, a domain that is absent in rat can be transcribed or deleted by alternative splicing which results in two variant forms of human H4P. In rat liver, the single mRNA is up-regulated by an acute, systemic inflammation whereas neither mRNA is up-regulated in human liver. Finally the shortest human mRNA is also transcribed in peripheral blood mononuclear cells where it is down-regulated by bacterial lipopolysaccharides. Therefore, in contrast to what is seen for the ITIH1 to -3 genes, the rat and human ITIH4 gene transcriptions and products thereof present marked differences, which suggests species-specific functions for I alpha IH4P.

Alpha-Globulins↗
PubMed1998

Induction and modulation of acute-phase response by protein malnutrition in rats: comparative effect of systemic and localized inflammation on interleukin-6 and acute-phase protein synthesis.

The acute-phase protein (APP) response is regulated by cytokines such as interleukin-6 (IL-6), interleukin-1 (IL-1) and tumor necrosis factor (TNF), but may also be influenced by malnutrition. The aims of this study were as follows: 1) to determine in rats the effect of a protein-deficient diet on IL-6 mRNA expression in intestine, liver and peripheral blood mononuclear cells (PBMC), and on alpha-1 acid glycoprotein (AGP) and alpha-2 macroglobulin (A2M) serum levels and hepatic mRNA expression; 2) to compare, in protein-deficient rats, the IL-6 and APP responses after a turpentine (TO)- or a lipopolysaccharide (LPS)-induced inflammation; and 3) to determine the effect of a protein malnutrition on IL-6 mRNA expression in rat PBMC treated ex vivo with LPS. Interleukin-6 mRNA was present in intestine and PBMC but not in the liver of malnourished rats, and was absent in any tissue or cells of controls. A2M was present in the serum from malnourished rats but not after refeeding. AGP mRNA expression was not influenced by protein malnutrition. In malnourished rats, IL-6 serum level peaked later than in controls after TO and LPS treatment. In malnourished TO-treated rats, A2M mRNA increased earlier than in controls and remained detectable later than in controls. AGP mRNA expression after TO was not influenced by protein malnutrition. In PBMC of malnourished rats, LPS-induced IL-6 mRNA expression occurred earlier and lasted longer than in controls. Our results indicate that protein malnutrition by itself induces IL-6 and A2M expression, and that it modulates the APP response to inflammation.

Acute-Phase Proteins↗
PubMed1997

Cytokine gene expression in liver following minor or major hepatectomy in rat.

Interleukin 6 (IL-6), tumour necrosis factor alpha (TNF-alpha), interleukin 1 (IL-1), and transforming growth factors alpha and beta (TGF-alpha and TGF-beta) are important mediators which play a pleiotropic role in both inflammatory and hepatic regeneration processes. It has also been proposed that a major hepatectomy impairs the liver-related host defence mechanisms. The aim of this study was to evaluate the influence of minor (30%) vs major (80%) hepatectomy on cytokines, growth factors and acute-phase proteins both at the protein and mRNA levels in rat. For that purpose, rats were submitted to either 30% or 80% hepatectomy and sacrificed at intervals up to day 14 post-hepatectomy to collect liver and blood samples. Serum levels of IL-6 and acute-phase proteins (APPs) were determined after RNA extraction, cytokine and acute-phase proteins gene expression were evaluated using a quantitative RT-PCR method. The results demonstrate that liver mRNA levels for IL-6 were early unregulated after a 80% resection only, whereas liver mRNA levels for IL-1 slowly increased following 30 or 80% hepatectomy. For TNF-alpha, no significant changes were observed between groups. Growth factor expression differed according to the extent of hepatic resection. Moreover, plasma levels of alpha2-macroglobulin (alpha2M) and alpha1 acid glycoprotein (AGP), two major APPs which respond differently to combination of cytokines, were significantly lowered after a major resection whereas levels of serum IL-6 showed no significant changes between groups. Paradoxically, in the 80% hepatectomized group, alpha2M mRNA expression was strongly increased at 4 h and 6 h post-hepatectomy as compared with the 30% hepatectomized group. Taken together, these results suggest that, although an increased level of hepatic IL-6 expression was observed following a major resection, the liver's capacity to synthesize normal levels of APPs was impaired. Moreover, these specific changes of cytokine gene expression seen in the liver following major hepatectomy might reflect a preferential activation of the IL-6-dependent APPs.

Acute-Phase Proteins↗
PubMed1997

Transforming growth factor alpha (TGF-alpha) expression correlates with DNA replication in regenerating rat liver whatever the hepatectomy extent.

Liver regeneration is a physiological mechanism that leads to restoration of the hepatic parenchyma following hepatectomy or toxic injury. As a two-third hepatectomy is the usual model to analyse this phenomenon, few studies have compared liver regeneration after minor vs major hepatectomy. We have used a quantitative RT-PCR technique to study the hepatic transcription of the TGF-alpha gene in rats submitted to 30% or 80% hepatectomy and we have correlated this transcription with the regenerative response assessed by flow cytometry and Ki-67 expression. The level of TGF-alpha expression and the regenerative response were different, according to the volume of liver removed, and were statistically correlated (r = 0.679, p = 0.002). TGF-alpha expression and phase S peaked at day 2 vs 6 in the 80% vs 30% hepatectomized rat groups, respectively. Ki-67 expression occurred at 2 h post-hepatectomy in the two groups of rats and was observed until day 14 mainly in the 80% hepatectomy group. Our results indicate that TGF-alpha expression in regenerating liver is strongly correlated with hepatocyte mitosis, that a delayed regenerative response occurs following 30% hepatectomy and that the course of regeneration differs between minor vs major hepatectomy.

Animals↗
PubMed1996

Differential expression of cytokine genes in monocytes, peritoneal macrophages and liver following endotoxin- or turpentine-induced inflammation in rat.

Pro-inflammatory cytokines are produced after systemic or local inflammation by a wide variety of cell types including monocytes, macrophages, Kupffer and endothelial cells. Previous studies have shown that IL-6 gene expression does not occur in liver from rats undergoing an acute phase response after turpentine injection or controls. These data do not rule out the possibility that delivery of a pathogen to the liver via the portal circulation could directly activate the Kupffer cells. Rats were injected either intravenously or intraperitoneally with LPS, or subcutaneously with turpentine oil. The changes in IL-1 beta, IL-6, and TNF mRNA levels in monocytes (collected from portal vein or caval cein), peritoneal macrophages and liver over a 3-hour period post-treatment were examined. The kinetics of LPS-vs turpentine-induced cytokine mRNAs in these various cell types were compared by quantitative reverse transcription and polymerase chain reaction (RT-PCR). Our data demonstrate that an intrahepatic expression of cytokines in the non parenchymal cells was induced by an LPS challenge but not by a turpentine-induced inflammation. This process could act as a paracrine mechanism in the acute-phase response and play a role in the modulation of hepatic regeneration.

Animals↗
PubMed1993

Human inter-alpha-inhibitor family in inflammation: simultaneous synthesis of positive and negative acute-phase proteins.

The inter-alpha-inhibitor (I alpha I) family encompasses four plasma proteins, namely free bikunin as well as I alpha I, pre-alpha-inhibitor (P alpha I) and inter-alpha-like inhibitor (I alpha LI). Each of the last three proteins is a distinct assembly of one bikunin chain with one or more unique heavy (H) chains designated H1, H2 and H3. The three H chains and the bikunin chain are encoded by four distinct mRNAs. These molecules and chains, as well as the corresponding mRNAs, were quantified in sera and liver biopsies from a series of patients with or without mild or severe acute infection. The decrease or increase observed for a given molecule or chain in the serum was in agreement with a similar change in the corresponding liver mRNA. In acute inflammation the H2 and bikunin chains are down-regulated and the relevant molecules (I alpha I, I alpha LI) behave as negative acute-phase proteins, whereas the H3 chain is up-regulated and the corresponding P alpha I molecule is a positive acute-phase protein. Also, P alpha I displays a higher-than-usual M(r); this is probably due to ligand binding. The H1 gene does not seem to be affected by the inflammatory condition. The quantitative changes in RNA levels seen in vivo were confirmed in vitro in the human hepatoma Hep3B cell line prior to or after induction with the acute-phase mediators interleukin-1 and/or -6. These results provide the first example in humans of positive and negative acute-phase proteins that are encoded by evolutionary related genes.

Acute-Phase Proteins↗
PubMed1993

Absence of expression of interleukin-6 (IL-6) mRNA in regenerating rat liver.

The serum level of IL-6 and expression of IL-6 mRNA in hepatocytes from regenerating liver were investigated in the rat. The IL-6 level in the serum was not significantly different from that of a control group of rats submitted to an acute experimental inflammation. IL-6 mRNA expression did not occur in the liver of hepatectomized rats as judged from Northern blotting experiments using an IL-6 riboprobe. These results suggest that if IL-6 is implicated in hepatic regeneration, this cytokine is not produced by the regenerating liver and must be delivered exogenously to the liver to modulate hepatic regeneration.

Animals↗
PubMed1992

The human hepatoma Hep3B cell line as an experimental model in the study of the long-term regulation of acute-phase proteins by cytokines.

The regulation of the synthesis by the cytokines interleukin-1 (IL-1) and IL-6 of the positive acute-phase protein alpha 1-acid glycoprotein (AGP) and of the negative acute-phase protein alpha 2-HS glycoprotein (AHSG) has been studied in a long-term culture system of the human hepatoma cell line Hep3B. The culture system contained 30 nM-sodium selenite as the only supplement. This allowed maintenance of the synthesis of the proteins under study at a near steady state for over 3 months. An increase in AGP mRNA and a decrease in AHSG mRNA were observed when cells were treated for two successive 48 h-periods with monocyte-conditioned medium. A return to basal levels was obtained after cessation of the cytokine addition. Two further additions of cytokines led to alterations in mRNA levels similar to those observed following the first cytokine treatment. The amounts of AGP and AHSG secreted were altered in accordance with the mRNA modifications. These results suggest that new cytokine receptors were being constantly synthesized during cell culture. When cytokines were present in the culture medium for 10 days, maximum alterations in AGP and AHSG synthesis were obtained following 2 and 4 days of treatment respectively, but further alterations in protein levels could not be observed afterwards. Expression of IL-6 receptor mRNA was not up-regulated by cytokines, but only by 1 microM-dexamethasone. Our results show that, in this long-term culture system, cytokines induce a response in hepatoma cells similar to that observed in vivo during human inflammatory states. This model could be used to evaluate the effects of agonists or antagonists of cytokines responsible for the hepatic acute-phase protein response.

Acute-Phase Proteins↗