NF-kappa B inhibits glucocorticoid and cAMP-mediated expression of the phosphoenolpyruvate carboxykinase gene

Recurrent Hypoglycemia in a 67-Year-Old Woman with CD5- Positive Diffuse Large B-Cell Lymphoma

Hypoglycemia is a rare complication of diffuse large B-cell lymphoma. We are presenting a case of 67-year-old woman presented to her primary care physician with fatigue and hyperhidrosis. Laboratory evaluation revealed a glucose level of 1.9 mmol/L. Computed tomographic scan of the abdomen and subsequent positron emission tomographic scan revealed extensive lymphadenopathy. The patient was then diagnosed with CD5-positive-diffuse large B-cell lymphoma and developed recurrent hypoglycemia despite continuous infusion of glucose. Following immunochemotherapy, hypoglycemia was resolved. Several explanations have been postulated but the exact pathophysiology is not well understood. Further investigation is warranted to more clearly define the pathophysiology of persistent hypoglycemia in patients with diffuse large B-cell lymphoma.

Etiology of lactic acidosis in malaria

Lactic acidosis and hyperlactatemia are common metabolic disturbances in patients with severe malaria. Lactic acidosis causes physiological adverse effects, which can aggravate the outcome of malaria. Despite its clear association with mortality in malaria patients, the etiology of lactic acidosis is not completely understood. In this review, the possible contributors to lactic acidosis and hyperlactatemia in patients with malaria are discussed. Both increased lactate production and impaired lactate clearance may play a role in the pathogenesis of lactic acidosis. The increased lactate production is caused by several factors, including the metabolism of intraerythrocytic Plasmodium parasites, aerobic glycolysis by activated immune cells, and an increase in anaerobic glycolysis in hypoxic cells and tissues as a consequence of parasite sequestration and anemia. Impaired hepatic and renal lactate clearance, caused by underlying liver and kidney disease, might further aggravate hyperlactatemia. Multiple factors thus participate in the etiology of lactic acidosis in malaria, and further investigations are required to fully understand their relative contributions and the consequences of this major metabolic disturbance.

Checks and balances: The glucocorticoid receptor and NFĸB in good times and bad

Mutual regulation and balance between the endocrine and immune systems facilitate an organism's stress response and are impaired following chronic stress or prolonged immune activation. Concurrent alterations in stress physiology and immunity are increasingly recognized as contributing factors to several stress-linked neuropsychiatric disorders including depression, anxiety, and post-traumatic stress disorder. Accumulating evidence suggests that impaired balance and crosstalk between the glucocorticoid receptor (GR) and nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) - effectors of the stress and immune axes, respectively - may play a key role in mediating the harmful effects of chronic stress on mood and behavior. Here, we first review the molecular mechanisms of GR and NFκB interactions in health, then describe potential shifts in the GR-NFκB dynamics in chronic stress conditions within the context of brain circuitry relevant to neuropsychiatric diseases. Furthermore, we discuss developmental influences and sex differences in the regulation of these two transcription factors.

Tyrosine kinase inhibitors of Ripk2 attenuate bacterial cell wall-mediated lipolysis, inflammation and dysglycemia

Inflammation underpins aspects of insulin resistance and dysglycemia. Microbiota-derived cell wall components such as muropeptides or endotoxin can trigger changes in host immunity and metabolism. Specific peptidoglycan motifs promote metabolic tissue inflammation, lipolysis and insulin resistance via Nucleotide-binding oligomerization domain-containing protein 1 (Nod1). Receptor-interacting serine/threonine-protein kinase 2 (Ripk2) mediates Nod1-induced immunity, but the role of Ripk2 in metabolism is ill-defined. We hypothesized that Ripk2 was required for Nod1-mediated inflammation, lipolysis and dysglycemia. This is relevant because certain tyrosine kinase inhibitors (TKIs) inhibit Ripk2 and there is clinical evidence of TKIs lowering inflammation and blood glucose. Here, we showed that only a subset of TKIs known to inhibit Ripk2 attenuated Nod1 ligand-mediated adipocyte lipolysis. TKIs that inhibit Ripk2 decreased cytokine responses induced by Nod1-activating peptidoglycan, but not endotoxin in both metabolic and immune cells. Pre-treatment of adipocytes or macrophages with the TKI gefitinib inhibited Nod1-induced Cxcl1 and Il-6 secretion. Furthermore, treatment of mice with gefitinib prevented Nod1-induced glucose intolerance in vivo. Ripk2 was required for these effects on inflammation and metabolism, since Nod1-mediated cytokine and blood glucose changes were absent in Ripk2^−/− mice. Our data show that specific TKIs used in cancer also inhibit Nod1-Ripk2 immunometabolism responses indicative of metabolic disease.

A Review of the Benefits of Satureja Species on Metabolic Syndrome and Their Possible Mechanisms of Action

Metabolic syndrome, also known as insulin resistance disorder, is the simultaneous manifestation of multiple metabolic disorders in an individual. The present-day complementary and alternative therapies suggest several medicinal herbs that may have the potential to improve one or multiple complications of metabolic syndrome. All of them have their own limitations in efficacy and unwanted effects. Therefore, we reviewed species of Satureja as widespread medicinal herbs and potentially good remedies for metabolic syndrome. We reviewed literature found in PubMed and the ISI Web of Knowledge with the key word Satureja in the title. The influence of any species of Satureja on any disease or syndrome, enzymatic, metabolic, or physiological pathways, in human, animals, or in vitro conditions related to any characteristics of metabolic syndrome were considered. The main outcomes of treatment with Satureja species were categorized, and the possible mechanisms of action are discussed in this article.

Adiponectin signaling in the liver

High glucose production contributes to fed and fasted hyperglycemia in Type 1 Diabetes (T1D) and Type 2 Diabetes (T2D). The breakdown of the adiponectin signaling pathway in T1D and the reduction of circulating adiponectin in T2D contribute to this abnormal increase in glucose production. Sufficient amounts of insulin could compensate for the loss of adiponectin signaling in T1D and T2D and reduce hyperglycemia. However, the combination of low adiponectin signaling and high insulin resembles an insulin resistance state associated with cardiovascular disease, fatty liver disease and decreased life expectancy. The future development of "adiponectin sensitizers", medications that correct the deficiency in adiponectin signaling, could restore the metabolic balance in T1D and T2D and reduce the need for insulin. This article reviews the adiponectin signaling pathway in the liver through T-cadherin, AdipoR1, AdipoR2, AMPK, ceramidase activity, APPL1 and the recently discovered Suppressor Of Glucose from Autophagy (SOGA).

Growth and Development Symposium: Impacts of inflammation on cattle growth and carcass merit

Inflammation caused by bovine respiratory disease (BRD) continues to be one of the greatest challenges facing beef cattle producers and feedlot managers. Inflammation decreases DMI, ADG, and G:F in feedlot calves, decreasing growth rate and increasing days on feed, which results in economic losses during the feeding period. During the past decade, marketing of feedlot animals has changed from selling cattle on a live basis to a grid-based marketing system. When cattle are marketed on a live basis, the economic effects of BRD stop at increased health cost and decreased feedlot performance, carcass weight, and death loss. However, when cattle are marketed in a grid-based system, inflammation has the potential to also affect carcass cutability and quality. The effects of inflammation on feedlot cattle in regards to performance are well understood; however, specific effects on cattle growth and ultimately carcass merit are not as well described. Recent studies in feedlot cattle have indicated that the incidence of BRD decreases both HCW and marbling; however, mechanisms are not understood. Research in other species has demonstrated that during the acute phase response, pro-inflammatory cytokines promote skeletal muscle catabolism to supply AA and energy substrates for immune tissues. Further, during this early immune response, the liver changes its metabolic priorities to the production of acute phase proteins for use in host defense. Together these dramatic shifts in systemic metabolism may explain the detrimental effects on performance and carcass traits commonly associated with BRD in feedlot calves. Moreover, recent studies relative to human health have revealed complex multilevel interactions between the metabolic and immune systems, and highlighted inflammation as being a significant contributor to major metabolic diseases. The objective of this paper is to review data to help explain the economical and physiological effects of inflammation on cattle growth and carcass merit.

Insulin inhibits hepatocyte iNOS expression induced by cytokines by an Akt-dependent mechanism

Hepatocyte inducible nitric oxide synthese (iNOS) expression is a tightly controlled pathway that mediates hepatic inflammation and hepatocyte injury in a variety of disease states. We have shown that cyclic adenosine monophosphate (cAMP) regulates cytokine-induced hepatocyte iNOS expression through mechanisms that involve protein kinase B/Akt. We hypothesized that insulin, which activates Akt signaling in hepatocytes, as well as signaling through p38 and MAPK p42/p44, would regulate iNOS expression during inflammation. In primary rat hepatocytes, insulin inhibited cytokine-stimulated nitrite accumulation and iNOS expression in a dose-dependent manner. Inhibition of MAPK p42/p44 with PD98059 had no effect on iNOS activation, whereas SB203580 to block p38 reversed insulin's inhibitory effect. However, insulin did not increase p38 activation and inhibition of p38 signaling with a dominant negative p38 plasmid had no effect on cytokine- or insulin-mediated effects on iNOS. We found that SB203580 blocked insulin-induced Akt activation. Inhibition of Akt signaling with LY294002 or a dominant negative Akt plasmid increased cytokine-stimulated nitrite production and iNOS protein expression and blocked the inhibitory effects of insulin. NF-κB induces iNOS expression and can be regulated by Akt, but insulin had no effect on cytokine-mediated IκBα levels or NF-κB p65 translocation. Our data demonstrate that insulin inhibits cytokine-stimulated hepatocyte iNOS expression and does so through effects on Akt-mediated signaling.

Glyceroneogenesis is inhibited through HIV protease inhibitor-induced inflammation in human subcutaneous but not visceral adipose tissue

Glyceroneogenesis, a metabolic pathway that participates during lipolysis in the recycling of free fatty acids to triglycerides into adipocytes, contributes to the lipid-buffering function of adipose tissue. We investigated whether glyceroneogenesis could be affected by human immunodeficiency virus (HIV) protease inhibitors (PIs) responsible or not for dyslipidemia in HIV-infected patients. We treated explants obtained from subcutaneous adipose tissue (SAT) and visceral adipose tissue (VAT) depots from lean individuals. We observed that the dyslipidemic PIs nelfinavir, lopinavir and ritonavir, but not the lipid-neutral PI atazanavir, increased lipolysis and decreased glyceroneogenesis, leading to an increased release of fatty acids from SAT but not from VAT. At the same time, dyslipidemic PIs decreased the amount of perilipin and increased interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) secretion in SAT but not in VAT. Parthenolide, an inhibitor of the NFκB pathway, counteracted PI-induced increased inflammation and decreased glyceroneogenesis. IL-6 (100 ng) inhibited the activity of phosphoenolpyruvate carboxykinase, the key enzyme of glyceroneogenesis, in SAT but not in VAT. Our data show that dyslipidemic but not lipid-neutral PIs decreased glyceroneogenesis as a consequence of PI-induced increased inflammation in SAT that could have an affect on adipocytes and/or macrophages. These results add a new link between fat inflammation and increased fatty acids release and suggest a greater sensitivity of SAT than VAT to PI-induced inflammation.

The nuclear isoform of the LIM domain protein Trip6 integrates activating and repressing signals at the promoter-bound glucocorticoid receptor

Trip6 belongs to a family of cytosolic LIM domain proteins involved in cell adhesion and migration. Recent findings show that these proteins also regulate transcription. We have previously reported that nTrip6, a nuclear isoform of Trip6, acts as a co-activator for AP-1 and NF-kappaB transcription factors. Here we report that nTrip6 is an essential regulator of glucocorticoid receptor (GR) transcriptional activity. nTrip6 is recruited to GR-bound promoters through an interaction with GR, and increases GR-mediated transcription. nTrip6 is also essential for the transrepression of GR by NF-kappaB and AP-1. The interaction of nTrip6 with NF-kappaB and AP-1 at a GR-bound promoter is required for the repression. Thus, nTrip6 serves as the molecular mediator of the crosstalk between nuclear receptors and other transcription factors in that it assembles these factors at promoters. Our results reveal an essential role for LIM domain proteins in the integration of positive and negative signals at target promoters.

In vivo phosphoenolpyruvate carboxykinase promoter mapping identifies disrupted hormonal synergism as a target of inflammation during sepsis in mice

In mammals, proper maintenance of blood glucose levels within narrow limits is one of the most critical prerequisites for healthy energy homeostasis and body function. Consequently, hyper- and hypoglycemia represent hallmarks of severe metabolic pathologies, including type II diabetes and acute sepsis, respectively. Although the liver plays a crucial role in the control of systemic glucose homeostasis, the molecular mechanisms of aberrant hepatic glucose regulation under metabolic stress conditions remain largely unknown. Here we report the development of a liver-specific adenoviral in vivo system for monitoring promoter activity of the key gluconeogenic enzyme gene phosphoenolpyruvate carboxykinase (PEPCK) in mice. By employing in vivo promoter deletion technology, the glucocorticoid response unit (GRU) and the cyclic adenosine monophosphate (cAMP)-responsive element (CRE) were identified as critical cis-regulatory targets of proinflammatory signaling under septic conditions. In particular, both elements were found to be required for inhibition of PEPCK transcription during sepsis, thereby mediating endotoxic hypoglycemia. Indeed, expression of nuclear receptor cofactor peroxisome proliferator-activator receptor coactivator 1alpha (PGC-1alpha), the molecular mediator of GRU/CRE synergism on the PEPCK promoter, was found to be specifically repressed in septic liver, and restoration of PGC-1alpha in cytokine-exposed hepatocytes blunted the inhibitory effect of proinflammatory signaling on PEPCK gene expression.

CONCLUSION

The dysregulation of hormonal synergism through the repression of PGC-1alpha as identified by in vivo promoter monitoring may provide a molecular rationale for hypoglycemia during sepsis, thereby highlighting the importance of hepatic glucose homeostasis for metabolic dysfunction in these patients.

Lipopolysaccharide inhibition of glucose production through the Toll-like receptor-4, myeloid differentiation factor 88, and nuclear factor kappa b pathway

Acute exposure to lipopolysaccharide (LPS) can cause hypoglycemia and insulin resistance; the underlying mechanisms, however, are unclear. We set out to determine whether insulin resistance is linked to hypoglycemia through Toll-like receptor-4 (TLR4), myeloid differentiation factor 88 (MyD88), and nuclear factor kappaB (NFkappaB), a cell signaling pathway that mediates LPS induction of the proinflammatory cytokine tumor necrosis factor alpha (TNFalpha). LPS induction of hypoglycemia was blocked in TLR4(-/-) and MyD88(-/-) mice but not in TNFalpha(-/-) mice. Both glucose production and glucose utilization were decreased during hypoglycemia. Hypoglycemia was associated with the activation of NFkappaB in the liver. LPS inhibition of glucose production was blocked in hepatocytes isolated from TLR4(-/-) and MyD88(-/-) mice and hepatoma cells expressing an inhibitor of NFkappaB (IkappaB) mutant that interferes with NFkappaB activation. Thus, LPS-induced hypoglycemia was mediated by the inhibition of glucose production from the liver through the TLR4, MyD88, and NFkappaB pathway, independent of LPS-induced TNFalpha. LPS suppression of glucose production was not blocked by pharmacologic inhibition of the insulin signaling intermediate phosphatidylinositol 3-kinase in hepatoma cells. Insulin injection caused a similar reduction of circulating glucose in TLR4(-/-) and TLR4(+/+) mice. These two results suggest that LPS and insulin inhibit glucose production by separate pathways. Recovery from LPS-induced hypoglycemia was linked to glucose intolerance and hyperinsulinemia in TLR4(+/+) mice, but not in TLR4(-/-) mice.

CONCLUSION

Insulin resistance is linked to the inhibition of glucose production by the TLR4, MyD88, and NFkappaB pathway.

Plasma glucose lowering effect of the wild Satureja khuzestanica Jamzad essential oil in diabetic rats: role of decreased gluconeogenesis

This study was to evaluate the effect of the wild SKEO on activities and genes expression of hepatic Glycogen Phosphorylase (GP) and phosphoenolpyruvate carboxykinase (PEPCK) in normal and diabetic rats. The wild SKEO was orally administered at different doses (50 and 100 mg/kg/day) to normal as well as diabetic rats for 21 days. The levels of mRNA were determined using the quantitative real-time RT-PCR technique. The plasma glucose concentrations of diabetic rats receiving SKEO (100 mg kg(-1)) compared with diabetic control were significantly decreased. Hepatic GP activity and its mRNA levels of diabetic rats treated with SKEO moderately increased. The activity of hepatic PEPCK and its mRNA levels were significantly decreased in normal rats treated with SKEO (100 mg kg(-1)). The enhancement of PEPCK activity and its mRNA levels of diabetic treated rats with SEKO (100 mg kg(-1)) was significantly decreased compared with diabetic control. In conclusion, an excessive inhibition of PEPCK in liver of diabetic rats treated with the wild SKEO may contribute to the plasma glucose lowering action of SKEO that seems to be in relation with antioxidant properties of SKEO.

Identification of genes, including the gene encoding p27Kip1, regulated by serine 276 phosphorylation of the p65 subunit of NF-kappaB

Phosphorylation of the p65 subunit of NF-kappaB is required for its transcriptional activity. Recent reports show that phosphorylation of p65 at serine 276 regulates only a subset of genes, such as those encoding IL-6, IL-8, Gro-beta, and ICAM-1. In order to identify additional genes regulated by serine 276 phosphorylation, HepG2 hepatoma cells were infected with adenoviruses encoding either wild-type p65 or the S276A mutant of p65, followed by DNA microarray analysis. The results show that mutation of serine 276 affected the expression of several genes that encode proteins involved in cell cycle regulation, signal transduction, transcription, and metabolism. Notably, expression of S276A increased the mRNA and protein level of p27, a cell cycle inhibitory protein, which led to an increased association of p27 with cdk2, and inhibition of cdk2 activity. Furthermore, while wild-type NF-kappaB is known to increase cell proliferation in a number of different cancer cell lines, our data shows that S276A inhibited cell proliferation. Evidence is mounting that NF-kappaB plays a pivotal role in oncogenesis. Therapeutic agents that regulate the phosphorylation of serine 276 and p27 gene expression, therefore, may be useful as anti-cancer agents in the future.

Inhibition of phorbol ester-dependent peroxiredoxin I gene activation by lipopolysaccharide via phosphorylation of RelA/p65 at serine 276 in monocytes

Peroxiredoxin I (Prx I) is an antioxidant enzyme with thioredoxin-dependent peroxidase activity which is involved in various cellular processes such as regulation of cell proliferation. Here, it is shown that the proinflammatory mediator lipopolysaccharide (LPS) inhibits the induction of Prx I expression and promoter activity by the phorbol ester 12-O-tetradecanoylphorbol- 13-acetate (TPA) in RAW264.7 monocytes, but not that of cyclooxygenase-2. LPS-dependent repression of Prx I induction by TPA was mediated via a newly identified kappaB site in the Prx I promoter, but the "classical" NF-kappaB cascade was not involved in this regulatory pathway, because IkappaB did not affect LPS-mediated Prx I repression. By contrast, phosphorylation of p65 at serine 276, which enhances the transcriptional activity of NF-kappaB, was up-regulated by TPA and was reduced by simultaneous exposure to LPS. Functional studies with Gal4-p65 constructs revealed that serine 276 is crucial to confer LPS-dependent repression of TPA-mediated induction of p65 transactivation. Finally, repression of TPA-dependent Prx I induction by LPS was mediated via Bruton's tyrosine kinase as indicated by studies with the pharmacological inhibitor LFM-A13. In summary, LPS-dependent inhibition of Prx I gene activation by TPA in monocytes is regulated via a pathway that involves phosphorylation of the NF-kappaB subunit p65 at serine 276.

Interleukin-1beta impairment of transforming growth factor beta1 signaling by down-regulation of transforming growth factor beta receptor type II and up-regulation of Smad7 in human articular chondrocytes

OBJECTIVE

Extracellular matrix deposition is tightly controlled by a network of regulatory cytokines. Among them, interleukin-1beta (IL-1beta) and transforming growth factor beta1 (TGFbeta1) have been shown to play antagonistic roles in tissue homeostasis. The purpose of this study was to determine the influence of IL-1beta on TGFbeta receptor type II (TGFbetaRII) regulation and TGFbeta1 responsiveness in human articular chondrocytes.

METHODS

TGFbeta1-induced gene expression was analyzed through plasminogen activator inhibitor 1 and p3TP-Lux induction. Receptor-activated Smad (R-Smad) phosphorylation, TGFbeta receptors, and Smad expression were determined by Western blotting and real-time reverse transcription-polymerase chain reaction techniques. Signaling pathways were investigated using specific inhibitors, messenger RNA (mRNA) silencing, and expression vectors.

RESULTS

IL-1beta down-regulated TGFbetaRII expression at both the protein and mRNA levels and led to inhibition of the TGFbeta1-induced gene expression and Smad2/3 phosphorylation. Moreover, IL-1beta strongly stimulated the expression of inhibitory Smad7. TGFbetaRII overexpression abolished the loss of TGFbeta1 responsiveness induced by IL-1beta. The decrease in TGFbetaRII required de novo protein synthesis and involved both the NF-kappaB and JNK pathways.

CONCLUSION

We demonstrate that IL-1beta impairs TGFbeta1 signaling through down-regulation of TGFbetaRII, which is mediated by the p65/NF-kappaB and activator protein 1/JNK pathways, and secondarily through the up-regulation of Smad7. These findings show that there is cross-talk in the signaling of 2 regulatory cytokines involved in inflammation.

Nuclear corepressor is required for inhibition of phosphoenolpyruvate carboxykinase expression by tumor necrosis factor-alpha

Inhibition of phosphoenolpyruvate carboxykinase (PEPCK) by TNF-alpha contributes to the pathogenesis of hypoglycemia in endotoxin shock. In this study, the molecular mechanism underlying the inhibition was investigated in hepatoma cells (rat H4IIE and human HepG2). PEPCK expression was induced by cAMP, and the induction was reduced by TNF-alpha at protein and mRNA levels in H4IIE cells. The inhibition was observed in the PEPCK gene promoter in a PEPCK-luciferase reporter. Activation of nuclear factor kappaB (NF-kappaB) pathway was required for the transcriptional inhibition of PEPCK gene. Degradation of NF-kappaB inhibitor (IkappaB) and p65 nuclear translocation were involved in the inhibition. An interaction of histone deacetylase 3 (HDAC3) and silencing mediator for retinoic acid receptor and thyroid hormone receptor (SMRT) with the PEPCK gene promoter was induced by TNF-alpha and observed in a chromatin immunoprecipitation assay. The TNF-induced inhibition was blocked by HDAC inhibitor or HDAC3 knockdown. The blocking effect was also observed in knockdown of corepressor SMRT. Point mutation suggests that cAMP response element (CRE) is required for TNF-induced inhibition of the PEPCK gene promoter. Phosphorylation of cAMP response element-binding protein at Ser133 and expression of peroxisome proliferator-activated receptor-gamma coactivator 1alpha were not changed by TNF-alpha in H4IIE cells. The transcriptional activity of CRE-binding protein was inhibited by TNF-alpha in a CRE-luciferase reporter. The data suggests that the nuclear corepressor proteins of HDAC3 and SMRT mediate TNF inhibition of PEPCK transcription. The inhibition mechanism is related to activation of NF-kappaB and inhibition of CRE-binding protein activity by the corepressor. These data suggest a novel activity of nuclear corepressor in the regulation of PEPCK expression by TNF-alpha.

Amelioration of glucose tolerance by hepatic inhibition of nuclear factor kappaB in db/db mice

AIMS/HYPOTHESIS

Recent studies have identified the involvement of inhibitor IkappaB kinase (IKK) in the pathogenesis of insulin resistance. To investigate the mechanism involved, we examined the role of nuclear factor kappaB (NF-kappaB), the distal target of IKK, in hepatic glucose metabolism.

METHODS

To inhibit NF-kappaB activity, db/db mice were infected with adenovirus expressing the IkappaBalpha super-repressor.

RESULTS

The IkappaBalpha super-repressor adenovirus infection caused a moderate reduction of NF-kappaB activity in liver. The treatment was associated with improved glucose tolerance, reduction in the serum insulin level, and increased hepatic triacylglycerol and glycogen contents, but had no effect on insulin-stimulated phosphorylation of Akt. On the other hand, quantification of mRNA in the liver revealed marked reduction of expression of gluconeogenic genes, such as those encoding phosphoenolpyruvate carboxykinase (PEPCK) and glucose-6-phosphatase, concurrent with reduced expression of gene encoding peroxisome proliferator-activated receptor gamma coactivator-1alpha (PPARGC1A, also known as PGC-1alpha). Furthermore, the production of super-repressor IkappaBalpha suppressed the increase in blood glucose level after pyruvate injection.

CONCLUSIONS/INTERPRETATION

Our results indicate that moderate inhibition of NF-kappaB improved glucose tolerance through decreased gluconeogenesis associated with reduced PGC-1alpha gene expression in db/db mice, and suggest that inhibition of NF-kappaB activity in liver is a potentially suitable strategy for the normalisation of blood glucose concentration in type 2 diabetes.

Oxidative stress induces phosphoenolpyruvate carboxykinase expression in H4IIE cells

Oxidative stress is closely associated with diabetes and is a major cause of insulin resistance. Impairment of hepatic insulin action is thought to be responsible for perturbations in hepatic glucose metabolism. In this study, we found that oxidative stress is involved in the dysregulation of gene expression of phosphoenolpyruvate carboxykinase (PEPCK), a key gluconeogenic enzyme, by a mechanism independent of insulin. Elevation of oxidative stress by injection of ferric nitrilotriacetate in rats increased the expression of hepatic PEPCK mRNA. To examine the direct action of oxidative stress on PEPCK expression, we treated H4IIE hepatoma cells with buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis. BSO increased intracellular oxidative stress and the expression of PEPCK mRNA. Inhibition of p38 mitogen-activated protein kinase (p38 MAP kinase), which mediates responses to oxidative stress, suppressed the induction of PEPCK mRNA by BSO. These results suggest that oxidative stress dysregulates hepatic PEPCK expression by an insulin-independent mechanism.

Correlation between FOXO1a (FKHR) and FOXO3a (FKHRL1) binding and the inhibition of basal glucose-6-phosphatase catalytic subunit gene transcription by insulin

Insulin inhibits transcription of the genes encoding the glucose-6-phosphatase catalytic subunit (G6Pase), phosphoenolpyruvate carboxykinase, and IGF binding protein-1 through insulin response sequences (IRSs) that share the same core sequence, T(G/A)TTTT(G/T). The transcription factors FOXO1a and FOXO3a have been shown to bind these elements, but there are conflicting reports as to whether this binding correlates with the action of insulin on gene transcription. Some researchers concluded, from overexpression experiments using FOXO1a, that binding correlated with the insulin response, whereas others concluded, mainly from gel retardation competition experiments using FOXO3a, that it did not. We show here that, although these factors can differentially activate gene transcription in a context-dependent manner, these conflicting data are not explained by a difference in FOXO1a and FOXO3a binding specificity. Instead, we find that gel retardation competition and binding experiments give different results; the latter reveal a correlation between FOXO1a/3a binding and the inhibition of basal G6Pase gene transcription by insulin. In addition, these data show that the binding of FOXO1a/3a to two adjacent IRSs in the G6Pase promoter is cooperative and that promoter context alters the specific IRS base requirements for FOXO1a-stimulated fusion gene expression. Surprisingly, an analysis of insulin action mediated through the G6Pase and IGF binding protein-1 IRSs in the context of a heterologous thymidine kinase promoter reveals that signaling through the latter does not support the accepted model for insulin-stimulated FOXO nuclear exclusion.

Paraquat-induced gene expression in rat kidney

Paraquat, one of the most widely used herbicides, is highly toxic to humans and animals. There is much information regarding its toxic effects on the lungs, but less is known about its toxicity in other organs. Paraquat is thought to play pivotal roles in the pathophysiology of acute renal failure and the progression of chronic kidney disease. We investigated the effects of paraquat on gene expression in the kidneys of rats treated with paraquat using a DNA array system, and the gene up-regulation observed was confirmed by quantitative real-time RT-PCR. Rats were sacrificed at 3, 24 h after the first injection (20 mg/kg), and at 3 h after the second injection. Expression of six genes had increased significantly by 3 h after the first injection: metallothionein-1 (MT-1), phosphoenolpyruvate carboxykinase, Na/K-transporting ATPase beta1 subunit, glutamate oxaloacetic transaminase, glutathione-S-transferase, and heme oxygenase-1 (HO-1). The transcription levels of MT-1 and HO-1 showed the biggest increases, but the increases did not continue until 24 h after injection, and the second injection had less effect than the first. Up-regulation of MT-1 and HO-1 mRNA levels was confirmed at the protein level. We observed a paraquat-induced increase of these proteins at 3 h post-injection, whereas this level did not continue until 24 h, as observed in RNA levels. The MT-1 protein in kidneys had been consumed. In addition, the protein level due to the second injection did not increase to the same level as that due to the first injection. These results suggest that protection against paraquat injury is mediated by induction of expression of some genes, and suppression on the induction of MT-1 and HO-1 may explain the injury observed due to paraquat intake. This is the first report of inducible pathways of defense against paraquat-induced oxidative stress in the kidney.

Control of CREB-binding Protein Signaling by Nuclear Fibroblast Growth Factor Receptor-1

In integrative nuclear fibroblast growth factor receptor-1 (FGFR1) signaling a newly synthesized FGFR1 translocates to the nucleus to stimulate cell differentiation and associated gene activities. The present study shows that FGFR1 accumulates and interacts with the transcriptional co-activator CREB-binding protein (CBP) in nuclear speckle domains in the developing brain and in neural progenitor-like cells in vitro, which accompanies differentiation and postmitotic growth. Cell differentiation and gene activation by nuclear FGFR1 do not require tyrosine kinase activity. Instead, FGFR1 stimulates transcription in cooperation with CBP by increasing recruitment of RNA polymerase II and histone acetylation at the active gene promoter. FGFR1 is a multifactorial protein whose N terminus interacts with CBP and C terminus with ribosomal S6 kinase 1 (RSK1). Nuclear FGFR1 augments CBP-mediated transcription by 1) releasing the CBP C-terminal domain from RSK1 inhibition and 2) activating the CBP N-terminal domain. The interaction of FGFR1 with CBP and RSK1 allows activation of gene transcription and may play a role in cell differentiation.

Kupffer cell cytokines interleukin-1beta and interleukin-10 combine to inhibit phosphoenolpyruvate carboxykinase and gluconeogenesis in cultured hepatocytes

BACKGROUND AND AIMS

Recent evidence suggests that inflammatory cytokines may mediate reduced hepatic glucose production and reduced blood glucose concentrations in sepsis. Therefore the aim of this study is to provide direct evidence of a cytokine-mediated interaction between Kupffer cells and hepatocytes by characterising the effects of lipopolysaccharide-stimulated Kupffer cells on hepatocyte gluconeogenesis, and the activity of key regulatory enzymes of this pathway.

METHODS AND RESULTS

Primary isolates of hepatocytes co-cultured with lipopolysaccharide-stimulated Kupffer cells in Transwell inserts showed a 48% inhibition of gluconeogenesis (P < 0.001). RNase protection assay and ELISA of Kupffer cells and the culture media following exposure to lipopolysaccharide showed increased levels of interleukin-1 alpha and beta, tumour necrosis factor alpha and IL-10. The addition of IL-1beta and IL-10 to hepatocyte cultures inhibited gluconeogenesis by 52% (P < 0.001), whereas each cytokine alone was ineffective. To determine whether altered production or activity of phosphoenolpyruvate carboxykinase or pyruvate kinase was responsible for the reduced glucose synthesis, their mRNA, protein levels and enzyme activities were measured. Primary hepatocytes co-cultured with lipopolysaccharide-stimulated Kupffer cells or cultured with a combination of IL-1beta and IL-10 displayed reduced levels of phosphoenolpyruvate carboxykinase mRNA, protein and enzyme activity. In contrast the mRNA, protein levels and enzyme activity of pyruvate kinase were not altered; suggesting that gluconeogenesis was suppressed by downregulation of phosphoenolpyruvate carboxykinase.

CONCLUSIONS

Therefore, hypoglycaemia, which is often observed in sepsis, may be mediated by Kupffer cell-derived IL-1beta and IL-10. In addition this study suggests these cytokines inhibit phosphoenolpyruvate carboxykinase production and thereby hepatic gluconeogenesis.

Possible pathomechanisms of sudden infant death syndrome: key role of chronic hypoxia, infection/inflammation states, cytokine irregularities, and metabolic trauma in genetically predisposed infants

Chronic hypoxia, viral infections/bacterial toxins, inflammation states, biochemical disorders, and genetic abnormalities are the most likely trigger of sudden infant death syndrome (SIDS). Autopsy studies have shown increased pulmonary density of macrophages and markedly more eosinophils in the lungs accompanied by increased T and B lymphocytes. The elevated levels of immunoglobulins, about 20% more muscle in the pulmonary arteries, increased airway smooth muscle cells, and increased fetal hemoglobin and erythropoietin are evidence of chronic hypoxia before death. Other abnormal findings included mucosal immune stimulation of the tracheal wall, duodenal mucosa, and palatine tonsils, and circulating interferon. Low normal or higher blood levels of cortisol often with petechiae on intrathoracic organs, depleted maternal IgG antibodies to endotoxin core (EndoCAb) and early IgM EndoCAb triggered, partial deletions of the C4 gene, and frequent IL-10-592*A polymorphism in SIDS victims as well as possible hypoxia-induced decreased production of antiinflammatory, antiimmune, and antifibrotic cytokine IL-10, may be responsible for the excessive reactions to otherwise harmless infections. In SIDS infants, during chronic hypoxia and times of infection/inflammation, several proinflammatory cytokines are released in large quantities, sometimes also representing a potential source of tissue damage if their production is not sufficiently well controlled, eg, by pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP). These proinflammatory cytokines down-regulate gene expression of major cytochrome P-450 and/or other enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity, thus affecting metabolism of several endogenous lipophilic substances, such as steroids, lipid-soluble vitamins, prostaglandins, leukotrienes, thromboxanes, and exogenous substances. In SIDS victims, chronic hypoxia, TNF-alpha and other inflammatory cytokines, and arachidonic acid (AA) as well as n-3 polyunsaturated fatty acids (FA), stimulated and/or augmented superoxide generation by polymorphonuclear leukocytes, which contributed to tissue damage. Chronic hypoxia, increased amounts of nonheme iron in the liver and adrenals of these infants, enhanced activity of CYP2C9 regarded as the functional source of reactive oxygen species (ROS) in some endothelial cells, and nicotine accumulation in tissues also intensified production of ROS. These increased quantities of proinflammatory cytokines, ROS, AA, and nitric oxide (NO) also resulted in suppression of many CYP450 and other enzymes, eg, phosphoenolpyruvate carboxykinase (PEPCK), an enzyme important in the metabolism of FA during gluconeogenesis and glyceroneogenesis. PEPCK deficit found in SIDS infants (caused also by vitamin A deficiency) and eventually enhanced by PACAP lipolysis of adipocyte triglycerides resulted in an increased FA level in blood because of their impaired reesterification to triacylglycerol in adipocytes. In turn, the overproduction and release of FA into the blood of SIDS victims could lead to the metabolic syndrome and an early phase of type 2 diabetes. This is probably the reason for the secondary overexpression of the hepatic CYP2C8/9 content and activity reported in SIDS infants, which intensified AA metabolism. Pulmonary edema and petechial hemorrhages often present in SIDS victims may be the result of the vascular leak syndrome caused by IL-2 and IFN-alpha. Chronic hypoxia with the release of proinflammatory mediators IL-1alpha, IL-1beta and IL-6, and overloading of the cardiovascular and respiratory systems due to the narrowing airways and small pulmonary arteries of these children could also contribute to the development of these abnormalities. Moreover, chronic hypoxia of SIDS infants induced also production of hypoxia-inducible factor 1alpha (HIF-1alpha), which stimulated synthesis and release of different growth factors by vascular endothelial cells and intensified subclinical inflammatory reactions in the central nervous system, perhaps potentiated also by PACAP and VIP gene mutations. These processes could lead to the development of brainstem gliosis and disorders in the release of neuromediators important for physiologic sleep regulation. All these changes as well as eventual PACAP abnormalities could result in disturbed homeostatic control of the cardiovascular and respiratory responses of SIDS victims, which, combined with the nicotine effects and metabolic trauma, finally lead to death in these often genetically predisposed children.

Tumour necrosis factor alpha decreases glucose-6-phosphatase gene expression by activation of nuclear factor kappaB

The key insulin-regulated gluconeogenic enzyme G6Pase (glucose-6-phosphatase) has an important function in the control of hepatic glucose production. Here we examined the inhibition of G6Pase gene transcription by TNF (tumour necrosis factor) in H4IIE hepatoma cells. TNF decreased dexamethasone/dibtuyryl cAMP-induced G6Pase mRNA levels. TNFalpha, but not insulin, led to rapid activation of NFkappaB (nuclear factor kappaB). The adenoviral overexpression of a dominant negative mutant of IkappaBalpha (inhibitor of NFkappaB alpha) prevented the suppression of G6Pase expression by TNFalpha, but did not affect that by insulin. The regulation of G6Pase by TNF was not mediated by activation of the phosphoinositide 3-kinase/protein kinase B pathway, extracellular-signal-regulated protein kinase or p38 mitogen-activated protein kinase. Reporter gene assays demonstrated a concentration-dependent down-regulation of G6Pase promoter activity by the transient overexpression of NFkappaB. Although two binding sites for NFkappaB were identified within the G6Pase promoter, neither of these sites, nor the insulin response unit or binding sites for Sp proteins, was necessary for the regulation of G6Pase promoter activity by TNFalpha. In conclusion, the data indicate that the activation of NFkappaB is sufficient to suppress G6Pase gene expression, and is required for the regulation by TNFalpha, but not by insulin. We propose that NFkappaB does not act by binding directly to the G6Pase promoter.

Suppression of PTEN expression by NF-kappa B prevents apoptosis

NF-kappa B is a heterodimeric transcription activator consisting of the DNA binding subunit p50 and the transactivation subunit p65/RelA. NF-kappa B prevents cell death caused by tumor necrosis factor (TNF) and other genotoxic insults by directly inducing antiapoptotic target genes. We report here that the tumor suppressor PTEN, which functions as a negative regulator of phosphatidylinositol (PI)-3 kinase/Akt-mediated cell survival pathway, is down regulated by p65 but not by p50. Moreover, a subset of human lung or thyroid cancer cells expressing high levels of endogenous p65 showed decreased expression of PTEN that could be rescued by specific inhibition of the NF-kappa B pathway with I kappa B overexpression as well as with small interfering RNA directed against p65. Importantly, TNF, a potent inducer of NF-kappa B activity, suppressed PTEN gene expression in IKK beta(+/+) cells but not in IKK beta(-/-) cells, which are deficient in the NF-kappa B activation pathway. These findings indicated that NF-kappa B activation was necessary and sufficient for inhibition of PTEN expression. The promoter, RNA, and protein levels of PTEN are down-regulated by NF-kappa B. The mechanism underlying suppression of PTEN expression by NF-kappa B was independent of p65 DNA binding or transcription function and involved sequestration of limiting pools of transcriptional coactivators CBP/p300 by p65. Restoration of PTEN expression inhibited NF-kappa B transcriptional activity and augmented TNF-induced apoptosis, indicating a negative regulatory loop involving PTEN and NF-kappa B. PTEN is, thus, a novel target whose suppression is critical for antiapoptosis by NF-kappa B.

Novel concepts in insulin regulation of hepatic gluconeogenesis

The regulation of hepatic gluconeogenesis is an important process in the adjustment of the blood glucose level, and pathological changes in the glucose production of the liver are a central characteristic in type 2 diabetes. The pharmacological intervention in signaling events that regulate the expression of the key gluconeogenic enzymes phosphoenolpyruvate carboxykinase (PEPCK) and the catalytic subunit glucose-6-phosphatase (G-6-Pase) is regarded as a potential strategy for the treatment of metabolic aberrations associated with this disease. However, such intervention requires a detailed understanding of the molecular mechanisms involved in the regulation of this process. Glucagon and glucocorticoids are known to increase hepatic gluconeogenesis by inducing the expression of PEPCK and G-6-Pase. The coactivator protein PGC-1 has been identified as an important mediator of this regulation. In contrast, insulin is known to suppress both PEPCK and G-6-Pase gene expression by the activation of PI 3-kinase. However, PI 3-kinase-independent pathways can also lead to the inhibition of gluconeogenic enzymes. This review focuses on signaling mechanisms and nuclear events that transduce the regulation of gluconeogenic enzymes.

Identification of signal transduction pathways that modulate dibutyryl cyclic adenosine monophosphate activation of stanniocalcin gene expression in neuroblastoma cells

Stanniocalcin (STC) is a new mammalian polypeptide hormone and appears to be a regulator of neuronal function. We have already shown that the induction of STC mRNA and protein expression by cAMP is integral to neuroblastoma cell differentiation, particularly neurite outgrowth. In this study, we examined the cAMP pathway in greater detail. Some common neuritogenic agents, euxanthone (PW1) and trans-retinoic acid (RA), were studied for possible interactions with the dibutyryl cAMP (dbcAMP)-mediated response. Our results showed that STC mRNA induction by dbcAMP was mediated by protein kinase A-cAMP response element binding protein (CREB) pathway, accompanied with phosphorylation of CREB and a reduction of p50, p65, and phosphorylated inhibitor kappaBalpha levels. Using a synthetic peptide nuclear factor-kappaB SN50, stimulation of dbcAMP-mediated STC expression was observed; indicating the nuclear translocation of nuclear factor kappaB might possibly repress STC expression. dbcAMP-induced STC mRNA expression was enhanced by PW1. In contrast, RA had highly suppressive effects. Cotreatment of cell with PW1 and cAMP provoked an increase in phosphorylated CREB (pCREB). Conversely, cotreatment with RA suppressed pCREB. The results highlighted the importance of phosphorylation of CREB in mediating STC gene expression. Taking a step further to dissect the possible regulatory pathways involved, with the aid of phorbol 12-myristate 13-acetate or ionomycin, additive effects on STC gene expression were observed. The induction was aided by further elevation of pCREB, which was completely abolished by Gö 6976, a Ca2+-dependent protein kinase C (PKC) alpha and PKCbeta1 inhibitor. Our results indicated that cross-talk with PKC and/or Ca2+ signaling pathways might sensitize cAMP-mediated effects, on CREB phosphorylation and STC gene expression.

Troglitazone antagonizes tumor necrosis factor-alpha-induced reprogramming of adipocyte gene expression by inhibiting the transcriptional regulatory functions of NF-kappaB

Troglitazone (TGZ), a member of the thiazolidinedione class of anti-diabetic compounds and a peroxisome proliferator activator receptor-gamma (PPAR-gamma) agonist, restores systemic insulin sensitivity and improves the full insulin resistance syndrome in vivo. The mechanisms underlying its in vivo function are not understood. Here we investigated the potential functional interaction between PPAR-gamma and NF-kappaB in adipocytes. We show that TGZ selectively blocked tumor necrosis factor-alpha-induced and NF-kappaB-dependent repression of multiple adipocyte-specific genes and induction of growth phase and other genes. This occurs without interfering with NF-kappaB expression, activation, nuclear translocation, or DNA binding and without suppressing NF-kappaB-dependent survival signals. Notably, the expressions of some tumor necrosis factor-alpha-induced genes in adipocytes were unaffected by PPAR-gamma activation. In reporter gene assays in HeLa cells, ectopic expression of PPAR-gamma abolished induction of a NF-kappaB-responsive reporter gene by the p65 subunit (RelA) of NF-kappaB, and the inhibition was further enhanced in the presence of TGZ. Conversely, overexpression of p65 inhibited induction of a PPAR-gamma-responsive reporter gene by activated PPAR-gamma in a dose-dependent manner. The inhibitory effect was independent of the presence of NF-kappaB-binding sites in the promoter region. Other NF-kappaB family members, p50 and c-Rel as well as the S276A mutant of p65, blocked PPAR-gamma-mediated gene transcription less effectively. Thus, p65 antagonizes the transcriptional regulatory activity of PPAR-gamma in adipocytes, and PPAR-gamma activation can at least partially override the inhibitory effects of p65 on the expression of key adipocyte genes. Our data suggest that inhibition of NF-kappaB activity is a mechanism by which PPAR-gamma agonists improve insulin sensitivity in vivo and that adipocyte NF-kappaB is a potential therapeutic target for obesity-linked type 2 diabetes.

Insulin inhibits hepatocellular glucose production by utilizing liver-enriched transcriptional inhibitory protein to disrupt the association of CREB-binding protein and RNA polymerase II with the phosphoenolpyruvate carboxykinase gene promoter

Hormones regulate glucose homeostasis, in part, by controlling the expression of gluconeogenic enzymes, such as phosphoenolpyruvate carboxykinase (PEPCK). Insulin and glucocorticoids reciprocally regulate PEPCK expression primarily at the level of gene transcription. We demonstrate here that glucocorticoids promote, whereas insulin disrupts, the association of CREB-binding protein (CBP) and RNA polymerase II with the hepatic PEPCK gene promoter in vivo. We also show that accessory factors, such as CCAAT/enhancer-binding protein beta (C/EBP beta), can recruit CBP to drive transcription. Insulin increases protein levels of liver-enriched transcriptional inhibitory protein (LIP), an inhibitory form of C/EBP beta, in a phosphatidylinositol 3-kinase-dependent manner. LIP concomitantly replaces liver-enriched transcriptional activator protein on the PEPCK gene promoter, which can abrogate the recruitment of CBP and polymerase II, culminating in the repression of PEPCK expression and the attenuation of hepatocellular glucose production.

Myotrophin/V-1, a protein up-regulated in the failing human heart and in postnatal cerebellum, converts NFkappa B p50-p65 heterodimers to p50-p50 and p65-p65 homodimers

Myotrophin/V-1 is a cytosolic protein found at elevated levels in failing human hearts and in postnatal cerebellum. We have previously shown that it disrupts nuclear factor of kappaB (NFkappaB)-DNA complexes in vitro. In this study, we demonstrated that in HeLa cells native myotrophin/V-1 is predominantly present in the cytoplasm and translocates to the nucleus during sustained NFkappaB activation. Three-dimensional alignment studies indicate that myotrophin/V-1 resembles a truncated IkappaBalpha without the signal response domain (SRD) and PEST domains. Co-immunoprecipitation studies reveal that myotrophin/V-1 interacts with NFkappaB proteins in vitro; however, it remains physically associated only with p65 and c-Rel proteins in vivo during NFkappaB activation. In vitro studies indicate that myotrophin/V-1 can promote the formation of p50-p50 homodimers from monomeric p50 proteins and can convert the preformed p50-p65 heterodimers into p50-p50 and p65-p65 homodimers. Furthermore, adenovirus-mediated overexpression of myotrophin/V-1 resulted in elevated levels of both p50-p50 and p65-p65 homodimers exceeding the levels of p50-p65 heterodimers compared with Adbetagal-infected cells, where the levels of p50-p65 heterodimers exceeded the levels of p50-p50 and p65-p65 homodimers. Thus, overexpression of myotrophin/V-1 during NFkappaB activation resulted in a qualitative shift by quantitatively reducing the level of transactivating heterodimers while elevating the levels of repressive p50-p50 homodimers. Correspondingly, overexpression of myotrophin/V-1 resulted in significantly reduced kappaB-luciferase reporter activity. Because myotrophin/V-1 is found at elevated levels during NFkappaB activation in postnatal cerebellum and in failing human hearts, this study cumulatively suggests that myotrophin/V-1 is a regulatory protein for modulating the levels of activated NFkappaB dimers during this period.

Antidiabetic effect of a nitrosamine-free dephostatin analogue, methoxime-3,4-dephostatin, in db/db mice

Et-3,4-dephostatin, a protein-tyrosine phosphatase (PTPase) inhibitor, potentiates insulin-dependent signal transduction and shows an antidiabetic effect in mice. However, it contains a nitrosamine moiety that is often mutagenic and carcinogenic. Therefore, we previously designed and synthesized methoxime-3,4-dephostatin as a nitrosamine-free analogue of dephostatin. In the present paper, we studied in situ and in vivo antidiabetic effects of this PTPase inhibitor. Methoxime-3,4-dephostatin induced 2-deoxyglucose transport by mouse 3T3-L1 adipocytes and rat L6 myocytes without insulin. It also inhibited glucagon-induced glucose release from primary culture rat hepatocytes. When hepatocytes were prepared from starved rats, methoxime-3,4-dephostatin did not inhibit the release of glucose, indicating that the chemical may act on glycogenolysis. Oral administration of methoxime-3,4-dephostatin for 3-7 days inhibited the increase in the blood glucose level in type-2 diabetes model db/db mice. It also decreased food and water intakes of mice, but showed no liver or blood toxicity.

Nuclear factor kappa B signaling in catabolic disorders

The nuclear factor kappa B family of inducible transcription factors regulates the expression of many genes. Nuclear factor kappa B has been implicated in autoimmune and inflammatory diseases, infection, cell survival, and cell transformation with subsequent promotion of cancer. In this review, we summarize features of nuclear factor kappa B regulation in several catabolic disorders, and describe its role in normal cellular function as well as provide an important link to the role of scaffold proteins, cellular receptors, and other cell signaling pathway kinases that converge on the nuclear factor kappa B signaling cascade. Subsequently, we focus on the role of nuclear factor kappa B in cell survival and oxidative stress. Finally, potential therapeutic strategies are discussed that may modify nuclear factor kappa B activity including endogenous antioxidant systems and the Fas/FasL system. However, challenges still remain in developing new therapeutic strategies that not only include identifying novel agents, but also by improving clinical endpoint definitions and by defining biological efficacy.

New ideas about aldosterone signaling in epithelia

The systemic actions of aldosterone are well documented; however, in comparison, our understanding of the cellular and molecular mechanisms by which aldosterone orchestrates these actions is rudimentary. Aldosterone exerts most of its physiological actions by modifying gene expression. It is now apparent that aldosterone represses almost as many genes as it induces. Several aldosterone-sensitive genes, including serum and glucocorticoid-inducible kinase (sgk) and small, monomeric Kirsten Ras GTP-binding protein (Ki-ras) have recently been identified. The molecular mechanisms and elements bestowing corticosteroid sensitivity on these and many other genes are becoming clear. Induction of Ki-Ras and Sgk is necessary and sufficient for some portion of aldosterone action in epithelia. These two signaling factors are components of a converging pathway with phosphatidylinositol 3-kinase positioned between them that enables both stabilizing the epithelial Na(+) channel (ENaC) in the open state as well as increasing the number of ENaC in the apical membrane. This aldosterone-induced signaling pathway contains many potential sites for feedback regulation and cross talk from other cascades and potentially impinges directly on the activity of transport proteins and/or cellular differentiation to modify electrolyte transport.

Selective tonic inhibition of G-6-Pase catalytic subunit, but not G-6-P transporter, gene expression by insulin in vivo

The regulation of glucose-6-phosphatase (G-6-Pase) catalytic subunit and glucose 6-phosphate (G-6-P) transporter gene expression by insulin in conscious dogs in vivo and in tissue culture cells in situ were compared. In pancreatic-clamped, euglycemic conscious dogs, a 5-h period of hypoinsulinemia led to a marked increase in hepatic G-6-Pase catalytic subunit mRNA; however, G-6-P transporter mRNA was unchanged. In contrast, a 5-h period of hyperinsulinemia resulted in a suppression of both G-6-Pase catalytic subunit and G-6-P transporter gene expression. Similarly, insulin suppressed G-6-Pase catalytic subunit and G-6-P transporter gene expression in H4IIE hepatoma cells. However, the magnitude of the insulin effect was much greater on G-6-Pase catalytic subunit gene expression and was manifested more rapidly. Furthermore, cAMP stimulated G-6-Pase catalytic subunit expression in H4IIE cells and in primary hepatocytes but had no effect on G-6-P transporter expression. These results suggest that the relative control strengths of the G-6-Pase catalytic subunit and G-6-P transporter in the G-6-Pase reaction are likely to vary depending on the in vivo environment.

Sterol regulatory element-binding protein-1c mimics the negative effect of insulin on phosphoenolpyruvate carboxykinase (GTP) gene transcription

We have assessed the potential role of sterol regulatory element-binding protein-1c (SREBP-1c) on the transcription of the gene for the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) (EC ) (PEPCK-C). SREBP-1c introduced into primary hepatocytes with an adenovirus vector caused a total loss of PEPCK-C mRNA and a marked induction of fatty acid synthase mRNA that directly coincided with the appearance of SREBP-1c in the hepatocytes. It also blocked the induction of PEPCK-C mRNA by cAMP and dexamethasone in these cells. In contrast, a dominant negative form of SREBP-1c (dnSREBP-1c) stimulated the accumulation of PEPCK-C mRNA in these cells. SREBP-1c completely blocked the induction of PEPCK-C gene transcription by the catalytic subunit of protein kinase A (PKA), and increasing concentrations of dnSREBP-1c reversed the negative effect of insulin on transcription from the PEPCK-C gene promoter in WT-IR cells. The more than 10-fold induction of PKA-stimulated PEPCK-C gene transcription caused by the co-activator CBP, was also blocked by SREBP-1c. In addition, dnSREBP-1c reversed the strong negative effect of E1A and NF1 on PKA-stimulated transcription from the PEPCK-C gene promoter. An analysis of the possible site of action of SREBP-1c using stepwise truncations of the PEPCK-C gene promoter indicated that the negative effect of SREBP-1c on transcription is exerted at a site between -355 and -277. We conclude that SREBP-1c is an intermediate in the action of insulin on PEPCK-C gene transcription in the liver and acts by blocking the stimulatory effect cAMP that is mediated via an interaction with cAMP-binding protein.

Gene- and activation-specific mechanisms for insulin inhibition of basal and glucocorticoid-induced insulin-like growth factor binding protein-1 and phosphoenolpyruvate carboxykinase transcription. Roles of forkhead and insulin response sequences

The insulin response sequence (IRS) of the phosphoenolpyruvate carboxykinase (PEPCK) promoter, located within the glucocorticoid response unit, was first characterized by its ability to mediate insulin inhibition when inserted into a thymidine kinase promoter. The IRSs of the PEPCK and insulin-like growth factor binding protein-1 (IGFBP-1) promoters have been proposed to contribute to regulation by glucocorticoids and insulin. Forkhead (FKHR) recognizes IRS sequences, is phosphorylated in response to insulin, and mediates insulin inhibition of basal IGFBP-1 transcription in an IRS-dependent manner. Here, we investigate the contributions of FKHR and IRSs to insulin inhibition of basal and glucocorticoid-induced transcription of PEPCK and IGFBP-1. Expression of T/S/S, in which three putative protein kinase B (PKB) sites in FKHR are mutated, reduced insulin inhibition of basal expression of IGFBP-1 but not PEPCK. Mutation of the IGFBP-1 IRSs abolished insulin inhibition in the presence of T/S/S. Mutation of the PEPCK IRS had no effect on insulin inhibition in the presence of T/S/S, indicating that insulin inhibits PEPCK transcription independently of the IRS or of the putative PKB phosphorylation sites in FKHR. Mutations in the IRS or FKHR had no effect on insulin inhibition of glucocorticoid-induced transcription of either the PEPCK or IGFBP-1 gene. Thus, insulin uses gene- and activation-specific mechanisms to regulate the basal and glucocorticoid-induced activity of these genes.