scholarly journals Impairment by interleukin 1β and tumour necrosis factor α of the glucagon-induced increase in phosphoenolpyruvate carboxykinase gene expression and gluconeogenesis in cultured rat hepatocytes

1996 ◽  
Vol 320 (1) ◽  
pp. 161-166 ◽  
Author(s):  
Bruno CHRIST ◽  
Annegret NATH
Keyword(s):  
Gene Expression ◽  
Phosphoenolpyruvate Carboxykinase ◽  
Rat Hepatocytes ◽  
Mrna Levels ◽  
Tumour Necrosis Factor Α ◽  
Maximal Increase ◽  
Cultured Rat Hepatocytes ◽  
Factor Α ◽  
Glucose Formation ◽  
Necrosis Factor

The influence of the inflammatory mediators interleukin 1β (IL1β) and tumour necrosis factor α (TNFα) on the glucagon-induced expression of phosphoenolpyruvate carboxykinase (PCK) and on glucose formation via gluconeogenesis was investigated in cultured rat hepatocytes. Gene expression was monitored by determination of mRNA levels and of enzyme activity. Glucose formation was estimated with newly synthesized radioactive glucose derived from a radiolabelled lactate precursor. Glucagon (0.1 or 1 nM) induced PCK mRNA transiently to a maximum 2 h after its application. In the presence of recombinant human (rh) IL1β or rhTNFα the increase in PCK mRNA levels was totally inhibited at 0.1 nM glucagon, whereas at 1 nM glucagon the maximal increase was inhibited by only 25%. Glucagon (0.1 or 1 nM) induced PCK activity to a maximum after 4 h (4-fold and 6-fold over prestimulatory activity respectively). In the presence of rhIL1β or rhTNFα the maximal increase was inhibited by approx. 50%. Addition of rhIL1β or rhTNFα 2 h after glucagon, at the maximal glucagon-induced PCK mRNA levels, accelerated the decay of PCK mRNA. Glucagon (0.1 or 1 nM) increased glucose formation from lactate by 1.3-fold and 1.7-fold respectively over unstimulated rates. In the presence of rhIL1β or rhTNFα this increase in glucose formation was inhibited by 60–90%. At 0.1 nM, glucagon doubled the intracellular cAMP concentration. This increase was prevented by rhIL1β or rhTNFα. At 1 nM, glucagon increased cAMP concentrations by 10-fold. In the presence of rhIL1β or rhTNFα this increase was inhibited by 70%. From the results it is suggested that rhIL1β and rhTNFα prevented glucagon-stimulated PCK gene expression and gluconeogenesis at least in part by inhibition of the glucagon-stimulated increase in cAMP concentrations.

Apoptosis in cultured rat hepatocytes: The effects of tumour necrosis factor α and interferon γ

1991 ◽  
Vol 165 (3) ◽  
pp. 247-253 ◽  
Author(s):  
Tadashi Shinagawa ◽  
Kentaro Yoshioka ◽  
Shinichi Kakumu ◽  
Takaji Wakita ◽  
Tetsuya Ishikawa ◽  
...  
Keyword(s):  
Tumour Necrosis Factor ◽  
Tumour Necrosis ◽  
Rat Hepatocytes ◽  
Interferon Γ ◽  
Tumour Necrosis Factor Α ◽  
Cultured Rat Hepatocytes ◽  
Factor Α ◽  
Necrosis Factor

Cardiac Muscle Protein Gene Expression in the Endotoxin-Treated Rat

1994 ◽  
Vol 87 (5) ◽  
pp. 539-546 ◽  
Author(s):  
D. C. Macallan ◽  
G. E. Griffin
Keyword(s):  
Cardiac Muscle ◽  
Myosin Heavy Chain ◽  
Tumour Necrosis Factor ◽  
Heavy Chain ◽  
Tumour Necrosis ◽  
Muscle Protein ◽  
Mrna Levels ◽  
Tumour Necrosis Factor Α ◽  
Factor Α ◽  
Necrosis Factor

1. Sepsis is associated with marked changes in cardiac muscle protein synthesis. Such changes may be the result of altered transcription of specific myofibrillar protein mRNAs. 2. In order to investigate myofibrillar protein gene expression, a rat model of sepsis was used. Adult rats were given a single sub-lethal dose of lipopolysaccharide by the intraperitoneal route. At various times thereafter, rats were killed and ventricular muscle was removed. RNA was extracted and transferred to nylon membranes. Changes in expression of mRNA for α- and β-myosin heavy chain, α-actin, cardiac troponin C and carbonic anhydrase III were detected by Northern hybridization. 3. After treatment with lipopolysaccharide, mRNA for β-myosin heavy chain increased to 260% of control values at 24 h and reached a maximum of 310% at 48 h. α-Myosin heavy chain mRNA levels fell to 72% of control values at 24 h. mRNA levels for α-actin, cardiac troponin C and carbonic anhydrase III remained unchanged. 4. In order to investigate the role of tumour necrosis factor-α in this process, some rats were pretreated with monoclonal antibody against tumour necrosis factor-α before receiving lipopolysaccharide. Such animals showed an absence of tumour necrosis factor-α bioactivity in plasma, but changes in myocardial protein mRNA levels were no different from those seen in animals receiving lipopolysaccharide alone. 5. The reduction in protein synthesis in cardiac muscle in sepsis does not appear to be the result of reduced expression of genes for structural or soluble muscle protein. Rather there is a paradoxical increase in β-myosin heavy chain expression, which may represent a protective mechanism. Tumour necrosis factor-α does not appear to be involved in the mediation of these changes.

Modulation of cytokeratin and actin gene expression and fibrillar organization in cultured rat hepatocytes

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1238-1248 ◽  
Author(s):  
Normand Marceau ◽  
Andrée Grenier ◽  
Micheline Noel ◽  
Donald Mailhot ◽  
Anne Loranger
Keyword(s):  
Gene Expression ◽  
Dimethyl Sulfoxide ◽  
Intermediate Filaments ◽  
Mrna Level ◽  
Rat Hepatocytes ◽  
Culture Conditions ◽  
Actin Gene ◽  
Mrna Levels ◽  
Cultured Rat Hepatocytes ◽  
Hepatocyte Spheroids

Intermediate filaments of rat hepatocytes are composed of cytokeratins 8 and 18 (CK8 and CK18, respectively). Recent work from our laboratory has indicated a close relationship between the synthesis of these cytokeratins, their organization into intermediate filaments, and the promotion of growth and differentiation of cultured rat hepatocytes by insulin, epidermal growth factor, and dexamethasone. In the present study, we examined the mRNA expression, level of protein synthesis, and fibrillar distribution of cytokeratins 8 and 18 and actin in hepatocytes, isolated from normal and dexamethasone-injected rats and cultured as monolayers or spheroids in the presence of insulin, or from normal rat hepatocytes, cultured as monolayers in the presence of dexamethasone, insulin, and dimethyl sulfoxide. The CK8 mRNA level was lower in hepatocytes isolated from noninjected rats and cultured as either monolayers or spheroids, than in those from dexamethasone-injected rats. However, the CK18 mRNA level varied in a manner that was different from that of CK8 mRNA, showing that the modes of expression of the two genes were independent. The various changes in hepatocyte culture conditions led to variations in albumin mRNA levels that largely followed those observed in CK8 mRNA levels. In the case of actin, the amount of mRNAs varied from relatively high levels in hepatocyte monolayers to extremely low levels in hepatocyte spheroids, even though in both cases the cells were isolated from dexamethasone-injected rats. These changes in mRNA levels did not necessarily correlate with changes in the synthesis of cytokeratins 8 and 18, and actin. Changes in culture conditions induced a major reorganization in the distribution of cytokeratin intermediate filaments and actin filament between the region near the surface membrane and the cytoplasm. The most divergent patterns in cytokeratin intermediate filaments and actin filament distributions were observed between hepatocytes cultured as spheroidal aggregates and as monolayers in the presence of dimethyl sulfoxide. The former condition resulted in patterns of cytokeratin and actin gene expression and fibrillar organization that best matched those in situ. In the latter condition, inappropriate patterns were obtained, in spite of the fact that dimethyl sulfoxide treated hepatocytes are known to exhibit survival and functional activities equivalent to that of hepatocyte spheroids. These results demonstrate for the first time that the survival and functional activity (i.e., albumin production) of rat hepatocytes in vitro is not necessarily correlated with a particular pattern of cytokeratin and actin gene expression and fibrillar arrangement.Key words: gene expression, cytokeratins, intermediate filaments, cytoskeleton, hepatocytes.

scholarly journals Opposing effects of tumour necrosis factor α and hyperosmolarity on Na+/myo-inositol co-transporter mRNA levels and myo-inositol accumulation by 3T3-L1 adipocytes

1998 ◽  
Vol 336 (2) ◽  
pp. 317-325 ◽  
Author(s):  
Mark A. YOREK ◽  
Joyce A. DUNLAP ◽  
William L. LOWE
Keyword(s):  
Signal Transduction ◽  
Tumour Necrosis ◽  
Actinomycin D ◽  
Signal Transduction Pathways ◽  
Mrna Levels ◽  
Tumour Necrosis Factor Α ◽  
Tnf Α ◽  
Factor Α ◽  
Opposing Effects ◽  
Necrosis Factor

Tumour necrosis factor α (TNF-α) regulates the transport of myo-inositol in 3T3-L1 adipocytes. Treating 3T3-L1 adipocytes with TNF-α decreases Na+/myo-inositol co-transporter (SMIT) mRNA levels and myo-inositol accumulation in a concentration-and time-dependent manner. TNF-α decreases the V′max for high-affinity myo-inositol transport with little change in the K′m. Studies with actinomycin D suggest that RNA synthesis is required for the TNF-α-induced effect on SMIT mRNA levels. In contrast with the effect of TNF-α, hyperosmolarity increases SMIT mRNA levels and myo-inositol accumulation in 3T3-L1 adipocytes. Hyperosmolarity increases SMIT gene expression as evidenced by the inhibition of hyperosmotic induction of SMIT mRNA levels by actinomycin D, and of myo-inositol accumulation by actinomycin D and cycloheximide. TNF-α and osmotic stress have previously been shown to activate similar signal transduction pathways in mammalian cells. In 3T3-L1 adipocytes, both TNF-α and hyperosmolarity increase mitogen-activated protein kinase kinase pathway activity; however, with the possible exception of c-Jun N-terminal kinase, this pathway does not seem to regulate SMIT mRNA levels or myo-inositol accumulation. TNF-α activates nuclear factor κB (NF-κB) in 3T3-L1 adipocytes but, unlike the effect of TNF-α on cultured endothelial cells, NF-κB does not seem to contribute to the regulation by TNF-α of SMIT gene expression in 3T3-L1 adipocytes. Therefore other signal transduction pathways must be considered in the regulation by TNF-α of SMIT mRNA levels and activity. Thus TNF-α and hyperosmolarity have opposing effects on SMIT mRNA levels and activity in 3T3-L1 adipocytes. Because myo-inositol in the form of phosphoinositides is an important component of membranes and signal transduction pathways, the regulation of myo-inositol metabolism by TNF-α might represent another mechanism by which TNF-α regulates adipocyte function.

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