Differential regulation of myocardial NF kappa B following acute or chronic TNF-alpha exposure

The dichotomic role of single cytokines: Fine-tuning immune responses

Cytokines are known for their pleiotropic effects. They can be classified by their function as pro-inflammatory, such as tumor necrosis factor (TNF), interleukin (IL) 1 and IL-12, or anti-inflammatory, like IL-10, IL-35 and transforming growth factor β (TGF-β). Though this type of classification is an important simplification for the understanding of the general cytokine's role, it can be misleading. Here, we discuss recent studies that show a dichotomic role of the so-called pro and anti-inflammatory cytokines, highlighting that their function can be dependent on the microenvironment and their concentrations. Furthermore, we discuss how the back-and-forth interplay between cytokines and immunometabolism can influence the dichotomic role of inflammatory responses as an important target to complement cytokine-based therapies.

PARP Traps Rescue the Pro-Inflammatory Response of Human Macrophages in the In Vitro Model of LPS-Induced Tolerance

Secondary infections cause sepsis that lead to patient disability or death. Contact of macrophages with bacterial components (such as lipopolysaccharide—LPS) activates the intracellular signaling pathway downstream of Toll-like receptors (TLR), which initiate an immune proinflammatory response. However, the expression of nuclear factor-kappa B (NF-κB)-dependent proinflammatory cytokines significantly decreases after single high or multiple LPS stimulations. Knowing that poly(ADP-ribose) polymerase-1 (PARP1) serves as a cofactor of NF-κB, we aimed to verify a hypothesis of the possible contribution of PARP1 to the development of LPS-induced tolerance in human macrophages. Using TNF-α mRNA expression as a readout, we demonstrate that PARP1 interaction with the TNF-α promoter, controls macrophage immunoparalysis. We confirm that PARP1 is extruded from the gene promoter, whereas cell pretreatment with Olaparib maintains macrophage responsiveness to another LPS treatment. Furthermore, cell pretreatment with proteasome inhibitor MG132 completely abrogates the effect of Olaparib, suggesting that PARP1 acts with NF-κB in the same regulatory pathway, which controls pro-inflammatory cytokine transcription. Mechanistically, PARP1 trapping allows for the re-rebinding of p65 to the TNF-α promoter in LPS-stimulated cells. In conclusion, PARP traps prevent PARP1 extrusion from the TNF-α promoter upon macrophage stimulation, thereby maintaining chromatin responsiveness of TLR activation, allowing for the re-binding of p65 and TNF-α transcription.

Astaxanthin suppresses lipopolysaccharide‑induced myocardial injury by regulating MAPK and PI3K/AKT/mTOR/GSK3β signaling

Cardiac dysfunction is a significant manifestation of sepsis and it is associated with the prognosis of the disease. Astaxanthin (ATX) has been discovered to serve a variety of pharmacological effects, including anti‑inflammatory, antioxidant and antiapoptotic properties. The present study aimed to investigate the role and mechanisms of ATX in sepsis‑induced myocardial injury. Male C57BL/6 mice were divided into three groups (15 mice per group): Control group, lipopolysaccharide (LPS) group and LPS + ATX group. The cardiac dysfunction model was induced through an intraperitoneal injection of LPS (10 mg/kg) and ATX (40 mg/kg) was administered to the LPS + ATX group by intraperitoneal injection 30 min following the administration of LPS. All animals were sacrificed after 24 h. Inflammatory cytokine levels in the serum were detected using ELISAs, and cardiac B‑type natriuretic peptide (BNP) levels were analyzed using western blot analysis and reverse transcription‑quantitative PCR. Furthermore, the extent of myocardial injury was evaluated using pathological analysis, and cardiomyocyte apoptosis was analyzed using a TUNEL assay, in addition to determining the expression levels of Bcl‑2 and Bax. The expression levels of proteins involved in the mitogen activated protein kinase (MAPK) and PI3K/AKT signaling pathways were also analyzed using western blot analysis. ATX significantly suppressed the LPS‑induced increased production of TNF‑α and IL‑6 and suppressed the protein expression levels of BNP, Bax and Bcl‑2 to normal levels. ATX also prevented the histopathological changes to the myocardial tissue and reduced the extent of necrosis. Furthermore, the treatment with ATX suppressed the LPS‑activated MAPK and PI3K/AKT signaling. ATX additionally exerted a protective effect on cardiac dysfunction caused by sepsis by inhibiting MAPK and PI3K/AKT signaling.

JNK and NF-κB signaling pathways are involved in cytokine changes in patients with congenital heart disease prior to and after transcatheter closure

Congenital heart disease (CHD) is a problem in the structure of the heart that is present at birth. Due to advances in interventional cardiology, CHD may currently be without surgery. The present study aimed to explore the molecular mechanism underlying CHD. A total of 200 cases of CHD treated by transcatheter closure as well as 200 controls were retrospectively assessed. Serum cytokines prior to and after treatment were assessed by reverse-transcription quantitative polymerase chain reaction analysis. Furthermore, the levels of proteins associated with c-Jun N-terminal kinase (JNK) and nuclear factor (NF)-κB were assessed by western blot analysis and immunohistochemistry. Furthermore, an animal model of CHD in young pigs was successfully constructed and treated with inhibitors of JNK and/or NF-κB to investigate the roles of these pathways in CHD. The results revealed that tumor necrosis factor-α, interleukin (IL)-6 and IL-8 were significantly elevated in the experimental group following transcatheter closure treatment, compared with those in the healthy control group, and the serum levels of the anti-inflammatory cytokine IL-10 were significantly reduced. Phosphorylated c-Jun and p65 levels in the experimental group were notably higher in the experimental group compared with the control group, but were restored to normal levels following transcatheter closure treatment. Similar results were also obtained in the pig model. The results of the present study suggested that the CHD-associated changes in cytokines, as well as their recovery following transcatheter closure treatment were associated with the JNK and NF-κB signaling pathways. The present study may provide further understanding of the underlying molecular mechanisms in CHD and propose a potential novel target for the treatment of CHD.

TNF Tolerance in Monocytes and Macrophages: Characteristics and Molecular Mechanisms

Tumor necrosis factor (TNF) tolerance in monocytes and macrophages means that preexposure to TNF reduces the sensitivity in these cells to a subsequent restimulation with this cytokine. Differential effects arise following preincubation with both low and high doses of TNF resulting in absolute as well as induction tolerance affecting specific immunologically relevant gene sets. In this review article, we summarize the relevance of TNF tolerance in vivo and the molecular mechanisms underlying these forms of tolerance including the role of transcription factors and signaling systems. In addition, the characteristics of cross-tolerance between TNF and lipopolysaccharide (LPS) as well as pathophysiological aspects of TNF tolerance are discussed. We conclude that TNF tolerance may represent a protective mechanism involved in the termination of inflammation and preventing excessive or prolonged inflammation. Otherwise, tolerance may also be a trigger of immune paralysis thus contributing to severe inflammatory diseases such as sepsis. An improved understanding of TNF tolerance will presumably facilitate the implementation of diagnostic or therapeutic approaches to more precisely assess and treat inflammation-related diseases.

Differential hypoxic tolerance is mediated by activation of heat shock response and nitric oxide pathway

The fall in ambient oxygen pressure in high-altitude milieu elicits a wide range of physiological responses in the myocardium, which may differ from individual to individual. This condition, known as hypobaric hypoxia, invokes the cardioprotective heat shock response. The present study focuses on the role played by this ubiquitous response in mediating a differential tolerance to acute hypoxic stress. Sprague Dawley rats were exposed to simulated hypoxia equivalent to 223 mmHg pressure, screened on the basis of time taken for onset of a characteristic hyperventilatory response, and categorized as susceptible (<10 min), normal (10-25 min), or tolerant (>25 min). The tolerant animals displayed a significant upregulation of heat shock protein (Hsp)70/HSPA, evident through immunohistochemical staining of the cardiac tissue. The increased expression of transcription factor heat shock factor-1 led to the downstream activation of other chaperones, including Hsp90/HSPC, Hsp60/HSPD1, and Hsp27/HSPB1. The higher induction of HSPs in tolerant animals contributed to higher nitric oxide synthesis mediated by both endothelial nitric oxide synthase and inducible nitric oxide synthase activation. Conversely, susceptible animals showed significantly higher expression of the proinflammatory markers tumor necrosis factor alpha and nuclear factor kappa-light-chain enhancer of activated B cells in the myocardium. Evaluation of circulatory stress markers identified increased levels of reactive oxygen species, corticosterone and endothelin-1 in the susceptible animals highlighting their vulnerability to hypoxic stress. The heat shock response, through the action of chaperones and enhanced NO generation thus contributes substantially to the ability to sustain survival under acute sub lethal hypoxia.

Side effects of TNF-α blockers in patients with psoriatic arthritis: evidences from literature studies

Psoriatic arthritis is an inflammatory rheumatic disorder, which occurs in patients with skin and/or nail psoriasis. In psoriatic arthritis, the importance of biologic mediators modulating inflammatory reaction, such as tumor necrosis factor, and the knowledge on their role in the pathogenesis of psoriatic arthritis influence the therapeutic choices. In the last years, the introduction of biologic drugs has greatly changed the treatment of psoriasis and psoriatic arthritis. In fact, tumor necrosis factor-α blockers demonstrated an effective action in the treatment of both skin and joint manifestations of psoriatic arthritis, but they have some adverse effects. The aim of this review is to revisit the literature data on adverse effects of tumor necrosis factor-α blockers in patients with psoriatic arthritis.

Estradiol modulates tumor necrosis factor-induced endothelial inflammation: role of tumor necrosis factor receptor 2

The sex hormone estradiol (E(2)) appears to mediate both anti-atherogenic and pro-inflammatory effects in premenopausal women, suggesting a complex immunomodulatory role. Tumor necrosis factor (TNF) is a key pro-inflammatory cytokine involved in the pathogenesis of atherosclerosis and other inflammatory diseases. Alterations at the TNF receptors (TNFRs) and their downstream signaling/transcriptional pathways can affect inflammatory responses. Given this background, we hypothesized that chronic E(2) exposure would alter endothelial inflammatory response involving modulation at the levels of TNFRs and signaling pathways. HUVECs were used as the model system. Pre-treatment with E(2) did not significantly alter TNF-induced upregulation of pro-inflammatory molecules ICAM-1 (3-6 times) and VCAM-1 (5-7 times). However, pharmacological inhibition of transcriptional pathways suggested a partial shift from NF-ĸB (from 97 to 64%) towards the JNK/AP-1 pathway in ICAM-1 upregulation on E(2) treatment. In contrast, VCAM-1 expression remained NF-ĸB dependent in both control (∼96%) and E(2) treated (∼85%) cells. The pro-inflammatory TNF effects were mediated by TNFR1. Interestingly, E(2) pre-treatment increased TNFR2 levels in these cells. Concomitant TNFR2 activation (but not TNFR1 activation alone) led to the shift towards JNK/AP-1-mediated ICAM-1 upregulation in E(2)-treated cells, suggesting the effects of chronic E(2) to be dependent on TNFR2 signaling.

Identification of a NF-κB cardioprotective gene program: NF-κB regulation of Hsp70.1 contributes to cardioprotection after permanent coronary occlusion

The transcription factor Nuclear Factor Kappa B (NF-κB) has been shown to be cardioprotective after permanent coronary occlusion (PO) and late ischemic preconditioning (IPC), and yet it is cell injurious after ischemia/reperfusion (I/R) in the heart. There is limited information regarding NF-κB-dependent cardioprotection, and the NF-κB-dependent genes that contribute to the cardioprotection after PO are completely unknown. The objective of the study was to identify NF-κB-dependent genes that contribute to cardioprotection after PO. Microarray analysis was used to delineate genes that potentially contribute to the NF-κB-dependent cardioprotection by determining the overlap between the set of PO regulated genes and genes regulated by NF-κB, using mice with genetic abrogation of NF-κB activation in the heart. This analysis identified 16 genes as candidates for NF-κB-dependent effects after PO. This set of genes overlaps with, but is significantly different from the set of genes we previously identified as regulated by NF-κB after IPC. The genes encoding heat shock protein 70.3 (hspa1a) and heat shock protein 70.1 (hspa1b) were the most significantly regulated genes after PO and were up-regulated by NF-κB. Results using knockout mice show that Hsp70.1 contributes to NF-κB-dependent cardioprotection after PO and likely underlies, at least in part, the NF-κΒ-dependent cardioprotective effect. Our previous results show that Hsp70.1 is injurious after I/R injury. This demonstrates that, like NF-κB itself, Hsp70.1 has antithetical effects on myocardial survival and suggests that this may underlie the similar antithetical effects of NF-κB after different ischemic stimuli. The significance of the research is that understanding the gene network regulated by NF-κB after ischemic insult may lead to identification of therapeutic targets more appropriate for clinical development.

FGF-16 is a target for adrenergic stimulation through NF-kappaB activation in postnatal cardiac cells and adult mouse heart

AIMS

The fibroblast growth factor (FGF) family plays an important role in cardiac growth and development. However, only FGF-16 RNA levels are reported to increase during the perinatal period and to be expressed preferentially in the myocardium, suggesting control at the transcriptional level and a role for FGF-16 in the postnatal heart. Beyond the identification of two TATA-like elements (TATA1 and TATA2) in the mouse FGF-16 promoter region and the preferential cardiac activity of TATA2, there is no report of Fgf-16 gene regulation. Assessment of promoter sequences, however, reveals putative nuclear factor-kappaB (NF-kappaB) elements, suggesting that Fgf-16 is regulated via NF-kappaB activation and thereby implicated in a number of cardiac events. Thus, the Fgf-16 gene was investigated as a target for NF-kappaB activation in cardiac cells.

METHODS AND RESULTS

Assessments of Fgf-16 promoter activity were made using truncated and transfected hybrid genes with NF-kappaB inhibitors and/or beta-adrenergic stimulation via isoproterenol (IsP) treatment (a known NF-kappaB activator) in culture, and on endogenous mouse and human Fgf-16 genes in situ. The mouse Fgf-16 promoter region was stimulated in response to IsP treatment, but this response was lost with NF-kappaB inhibitor pretreatment. Deletion analysis revealed IsP responsiveness linked to sequences between TATA2 and TATA1 and, more specifically, a NF-kappaB element upstream and adjacent to TATA1 that associates with NF-kappaB p50/p65 subunits in chromatin. Finally, TATA1 and the proximal NF-kappaB element are conserved in the human genome and responsive to IsP.

CONCLUSION

The mouse and human Fgf-16 gene is a target for NF-kappaB activation in the postnatal heart.

TNFα is required to confer protection in an in vivo model of classical ischaemic preconditioning

Although Tumor Necrosis Factor alpha (TNFalpha) is used as a preconditioning mimetic in vitro, its role in ischaemic preconditioning (IPC) has not been clearly defined. Here, we propose to use an in vivo model (that takes into account the activation of leukocytes which may affect levels of TNFalpha) to demonstrate that i) TNFalpha acts as a trigger in IPC and ii) the dose-dependent nature of this cardioprotective effect of TNFalpha. Male Wistar rats were subjected to 30 min of left coronary artery occlusion (index ischaemia), followed by 24 h reperfusion. In the presence or absence of a soluble TNFalpha receptor (sTNFalpha-R), preconditioning was induced by 3 cycles of ischaemia (3 min)/reperfusion (5 min) (IPC) or various doses (0.05-4 microg/kg) of exogenous TNFalpha. Following 24 h reperfusion, infarct size (IS, expressed as % of the area at risk (AAR)) was assessed. Tissue levels of TNFalpha from the AAR, following IPC and TNFalpha stimulus were determined using Western Blot. IPC caused decrease in IS (4.5+/-1.3% vs 30.8+/-4.3% in ischaemic rats; P<0.001) and increase of TNFalpha levels following the IPC stimulus. The protective effect of IPC was abrogated in the presence of the sTNFalpha-R. In addition, exogenous TNFalpha dose-dependently reduced IS with maximal protection at a dose of 0.1 microg/kg (IS=12.6%, P<0.01 vs ischaemic). In conclusion our data provide strong evidence for a role of TNFalpha during the trigger phase of IPC. In addition, exogenous TNFalpha mimics IPC by providing a dose-dependent cardioprotective effect against ischaemia-reperfusion injury in vivo.

Inhibition of NF-κB improves left ventricular remodeling and cardiac dysfunction after myocardial infarction

Several studies have demonstrated that NF-κB is substantially involved in the progression of cardiac remodeling; however, it remains uncertain whether the continuous inhibition of NF-κB is effective for the prevention of myocardial remodeling. Myocardial infarction (MI) was produced by ligation of the left anterior coronary artery of rats. IMD-0354 (10 mg/kg per day), a novel phosphorylation inhibitor of IκB that acts via inhibition of IKK-β, was injected intraperitoneally starting 24 h after induction of MI for 28 days. After 28 days, the IMD-0354-treated group showed significantly improved survival rate compared with that of the vehicle-treated group ( P < 0.05). Although infarct size was similar in both groups, improved left ventricular (LV) remodeling and diastolic dysfunction, as indicated by smaller LV cavity (LV end-diastolic area: vehicle, 74.13 ± 3.57 mm2; IMD-0354, 55.00 ± 3.73 mm2; P < 0.05), smaller peak velocity of early-to-late filling wave (E/A) ratio (vehicle, 3.87 ± 0.26; IMD-0354, 2.61 ± 0.24; P < 0.05), and lower plasma brain natriuretic peptide level (vehicle, 167.63 ± 14.87 pg/ml; IMD-0354, 110.75 ± 6.41 pg/ml; P < 0.05), were observed in the IMD-0354-treated group. Moreover, fibrosis, accumulation of macrophages, and expression of several factors (transforming growth factor-β1, monocyte chemoattractant protein-1, matrix metalloproteinase-9 and -2) in the noninfarcted myocardium was remarkably inhibited by IMD-0354. In conclusion, inhibition of NF-κB activation may reduce the proinflammatory reactions and modulate the extracellular matrix and provide an effective approach to prevent adverse cardiac remodeling after MI.

Blockade of NF-kappaB improves cardiac function and survival after myocardial infarction

NF-kappaB is a key transcription factor that regulates inflammatory processes. In the present study, we tested the hypothesis that blockade of NF-kappaB ameliorates cardiac remodeling and failure after myocardial infarction (MI). Knockout mice with targeted disruption of the p50 subunit of NF-kappaB (KO) were used to block the activation of NF-kappaB. MI was induced by ligation of the left coronary artery in male KO and age-matched wild-type (WT) mice. NF-kappaB was activated in noninfarct as well as infarct myocardium in WT+MI mice, while the activity was completely abolished in KO mice. Blockade of NF-kappaB significantly reduced early ventricular rupture after MI and improved survival by ameliorating congestive heart failure. Echocardiographic and pressure measurements revealed that left ventricular fractional shortening and maximum rate of rise of left ventricular pressure were significantly increased and end-diastolic pressure was significantly decreased in KO+MI mice compared with WT+MI mice. Histological analysis demonstrated significant suppression of myocyte hypertrophy as well as interstitial fibrosis in the noninfarct myocardium of KO+MI mice. Blockade of NF-kappaB did not ameliorate expression of proinflammatory cytokines in infarct or noninfarct myocardium. In contrast, phosphorylation of c-Jun NH2-terminal kinase was almost completely abolished in KO+MI mice. The present study demonstrates that targeted disruption of the p50 subunit of NF-kappaB reduces ventricular rupture as well as improves cardiac function and survival after MI. Blockade of NF-kappaB might be a new therapeutic strategy to attenuate cardiac remodeling and failure after MI.

Cardiac-specific blockade of NF-κB in cardiac pathophysiology: differences between acute and chronic stimuli in vivo

The role of NF-κB in cardiac physiology and pathophysiology has been difficult to delineate due to the inability to specifically block NF-κB signaling in the heart. Cardiac-specific transgenic models have recently been developed that repress NF-κB activation by preventing phosphorylation at specific serine residues of the inhibitory κB (IκB) protein isoform IκBα. However, these models are unable to completely block NF-κB because of a second signaling pathway that regulates NF-κB function via Tyr42 phosphorylation of IκBα. We report the development of transgenic (3M) mouse lines that express the mutant IκBα(S32A,S36A,Y42F)in a cardiac-specific manner. NF-κB activation in cardiomyopathic TNF-1.6 mice is completely blocked by the 3M transgene but only partially blocked (70–80%) by the previously described double-mutant 2M [IκBα(S32A,S36A)] transgene, which demonstrates the action of two proximal pathways for NF-κB activation in TNF-α-induced cardiomyopathy. In contrast, after acute stimuli including administration of TNF-α and ischemia-reperfusion (I/R), NF-κB activation is blocked in both 2M and 3M transgenic mice. This result suggests that phosphorylation of the regulatory Ser32 and Ser36 predominantly mediates NF-κB activation in these situations. We show that infarct size after I/R is reduced by 70% in 3M transgenic mice, which conclusively demonstrates that NF-κB is involved in I/R injury. In summary, we have engineered novel transgenic mice that allow us to distinguish two major proximal pathways for NF-κB activation. Our results demonstrate that the serine and tyrosine phosphorylation pathways are differentially activated during different pathophysiological processes (cardiomyopathy and I/R injury) and that NF-κB contributes to infarct development after I/R.

Tumor necrosis factor-alpha-induced caspase activation mediates endotoxin-related cardiac dysfunction

OBJECTIVE

Sepsis-induced cardiac dysfunction is a serious clinical syndrome characterized by hypotension, decreased systemic vascular resistance, and elevated cardiac index. Although cytokines such as tumor necrosis factor (TNF)-alpha have been shown to play a significant role early in this response, the downstream effects of TNF-alpha signaling on cardiac function, specifically its relationship to apoptosis, have not been fully elucidated.

DESIGN

Previous studies from our laboratory have identified endotoxin-induced apoptosis in cardiac cells in vitro. To further determine the role of lipopolysaccharide-induced apoptosis in vivo, mice were injected intraperitoneally with lipopolysaccharide (4 mg/kg), and cardiac apoptosis was detected and inhibited using a broad-spectrum caspase inhibitor.

SETTING

University research laboratory.

SUBJECTS

Adult male wild-type (B6:129PF1/J) and TNF receptor 1/receptor 2 (TNFR-1/2) knockout mice (B6;129S-Tnfrsf1aTnfrsf1b).

INTERVENTIONS

We sought to determine the dependence of cardiac apoptosis on TNF-alpha signaling and determine the physiologic role of caspase activation on lipopolysaccharide-induced cardiac dysfunction.

MEASUREMENTS AND MAIN RESULTS

Cardiac apoptosis was determined at baseline and at 2, 4, 8, and 24 hrs by detection of capase-3 and -8 activity, cytoplasmic levels of Bax/Bcl-2, cleaved caspase-3 immunohistochemistry, and terminal deoxynucleotidyl transferase UTP nick-end labeling (TUNEL) staining of histologic sections in wild-type and TNFR-1/2 knockout mice. To determine the role of caspase activation in lipopolysaccharide-induced cardiac dysfunction, a broad-spectrum caspase inhibitor Z-Val-Ala-Asp (ome)-FMK (sad) was given, and cardiac function was determined in isolated beating hearts (Langendorff preparation). Our experiments determined that caspase-3-dependent apoptosis was active in cardiac tissue by 2 hrs and that this activation was completely mediated by TNFR-1/2. The Bax/Bcl-2 ratios supported the finding and time course of apoptosis, whereas TUNEL staining of cardiac tissue sections identified sporadic apoptotic ventricular cells. The administration of zVAD significantly inhibited myocardial caspase-3 activity and preserved cardiac physiologic function (Langendorff preparation).

CONCLUSIONS

Endotoxin induces a TNF-alpha-dependent apoptotic cascade in the myocardium, which contributes to the development of cardiac dysfunction.

In vivo cytokine secretion and NF-kappaB activation around titanium and copper implants

The early biological response at titanium (Ti), copper (Cu)-coated Ti and sham sites was evaluated in an in vivo rat model. Material surface chemical and topographical properties were characterized using Auger electron spectroscopy, energy dispersive X-ray spectroscopy and interferometry, respectively. The number of leukocytes, cell types and cell viability (release of lactate dehydrogenase) were determined in the implant-interface exudate. The contents of activated nuclear transcription factor NF-kappaB, interleukin-6 (IL-6) and interleukin-10 (IL-10) were determined by enzyme linked immunosorbent assay. An increase in the number of leukocytes, in particular, polymorphonuclear leukocytes, was observed between 12 and 48 h around Cu. A marked decrease of exudate cell viability was found around Cu after 48 h. The total amounts of activated NF-kappaB after 12 h was highest in Ti exudates whereas after 48 h the highest amount of NF-kappaB was detected around Cu. The levels of cytokine IL-6 were consistently high around Cu at both time periods. No differences in IL-10 contents were detected, irrespective of material/sham and time. The results show that materials with different toxicity grades (titanium with low and copper with high toxicity) exhibit early differences in the activation of NF-kappaB, extracellular expression and secretion of mediators, causing major differences in inflammatory cell accumulation and death in vivo.

Macrophage inhibitor, semapimod, reduces tumor necrosis factor-alpha in myocardium in a rat model of ischemic heart failure

Pharmaceutical agents aimed at reducing tumor necrosis factor-alpha (TNF-alpha) levels appeared to be attractive possibilities in the medical management of heart failure, as heart failure was shown to be associated with high TNF-alpha levels. However, therapies specifically targeting TNF-alpha failed to show any survival benefit. We examined whether a broad inhibition of inflammatory cytokine production secondary to macrophage inhibition would be more effective at improving cardiac function in the setting of heart failure. To this end, we studied Semapimod (formerly known as CNI-1493), a synthetic guanylhydrazone that inhibits macrophage activation and the production of several inflammatory cytokines. Left anterior descending coronary ligation surgery was performed on each animal to induce a myocardial infarction. After confirming heart failure by echocardiography, the animals were randomly assigned to one of four groups: (1) rats with myocardial infarct receiving high-dose Semapimod, 10 mg/kg/d (MI-H, N = 13); (2) rats with myocardial infarct receiving low-dose Semapimod, 3 mg/kg/d (MI-L, N = 9); (3) rats with myocardial infarct receiving vehicle treatment, 2.5% mannitol in water (MI-0, N = 9); and (4) control rats with sham operation and vehicle treatment (Sham, N = 10). Both Semapimod and vehicle treatments were administered by daily tail vein injections over a course of five days. Echoes were repeated at 2, 5, and 9 weeks following treatment. At 9 weeks, hemodynamic data were collected and the animals were euthanized. Trichrome staining was done to assess infarct, and immunohistochemistry was performed to assess TNF-alpha levels. Prior to drug administration, serum was taken from 5 random rats. No detectable level of TNF-alpha was seen (lower limit of detection for the assay used = 12.5 pg/mL). Also prior to any treatment, echocardiography confirmed significant cardiac impairment of rats undergoing LAD ligation as compared with sham. Over the course of the 9 weeks, there were 4 deaths, all in the MI-H group. There was no difference between Semapimod-treated animals and vehicle-treated MI animals in any echocardiographic or hemodynamic parameter. TNF-alpha staining in the noninfarcted region was evident only in the MI groups, not the sham group. When blindly compared on a semiquantitative scale (ie, 0 = no visible staining to 3 = marked staining), a significant difference in staining was observed between MI-0 versus MI-H (1.19 +/- 0.32 versus 0.33 +/- 0.14; P = 0.03) and between MI-0 and MI-L (1.19 +/- 0.32 versus 0.39 +/- 0.22; P = 0.05). In this setting, despite the fact that Semapimod treatment decreased tissue TNF-alpha levels, it did not improve cardiac function, and at high doses it was associated with higher mortality. These results in a rodent model confirm the results of clinical trials with etanercept and infliximab (ie, that decreasing TNF levels in plasma or tissues does not improve cardiac function and may actually increase mortality).

Tumor necrosis factor alpha and phorbol 12‐myristate‐13‐acetate down‐regulate human 11β‐hydroxysteroid dehydrogenase type 2 through p50/p50 NF‐κB homodimers and Egr‐1

The 11beta-hydroxysteroid dehydrogenase type 2 (11beta-HSD2) regulates access of 11beta-hydroxyglucocorticoids to the mineralocorticoid receptor by reducing the hydroxyl group of these steroids at position 11. Previous cell culture studies revealed that tumor necrosis factor-alpha (TNF-alpha) down-regulates 11beta-HSD2 activity. Here, we demonstrate that transgenic mice overexpressing TNF-alpha have decreased mRNA abundance and activity of 11beta-HSD2 in kidney tissue, indicating that this effect may occur also in vivo. The analysis of the transcriptional regulation of 11beta-HSD2 by TNF-alpha and phorbol 12-myristate-13-acetate (PMA) with in vivo genomic footprinting in human colon SW620 cells revealed stimulus-dependent protein-DNA interactions in three promoter regions, kappaB1, Sp1/Egr-1I, and Sp1/Egr-1II. Chromatin immunoprecipitation and electrophoretic mobility shift assays demonstrated the relevance of NF-kappaB binding to kappaB1 and of Egr-1 binding to Sp1/Egr-1 sites for the PMA and TNF-alpha effect. We observed a temporal switch of binding to kappaB1 site from active p65/p50 heterodimers to inactive p50/p50 homodimers. TNF-alpha or PMA treatment for 24 h resulted in accumulation of p50 and decrease of p65 nuclear proteins. Overexpression of p50 inhibited HSD11B2 promoter activity and overexpression of Egr-1 inhibited transactivation of the HSD11B2 promoter by p65/p50. In conclusion, TNF-alpha and PMA down-regulate expression and activity of 11beta-HSD2 most likely by a coordinate binding of p50/p50 and Egr-1 to the HSD11B2 promoter.

Stabilization of p53 is a novel mechanism for proapoptotic function of NF-kappaB

Both pro- and antiapoptotic activities of NF-kappaB transcription factor have been observed; however, less is known about the mechanism by which NF-kappaB induces apoptosis. To elucidate how NF-kappaB regulates proapoptotic signaling, we performed functional analyses using wild-type, ikk1(-/-), ikk2(-/-), rela(-/-) murine fibroblasts, MDAPanc-28/Puro, MDAPanc-28/IkappaBalphaM, and HCT116/p53(+/+) and HCT116/p53(-/-) cells with investigational anticancer agent doxycycline as a superoxide inducer for generating apoptotic stimulus. In this report, we show that doxycycline increased superoxide generation and subsequently activated NF-kappaB, which in turn up-regulated p53 expression and increased the stability and DNA binding activity of p53. Consequently, NF-kappaB-dependent p53 activity induced the expression of p53-regulated genes PUMA and p21(waf1) as well as apoptosis. Importantly, lack of RelA, IKK, and p53 as well as expression of a dominant negative IkappaBalpha (IkappaBalphaM) inhibited NF-kappaB-dependent p53 activation and apoptosis. The doxycycline-induced NF-kappaB activation was not inhibited in HCT116/p53(-/-) cells. Our results demonstrate that NF-kappaB plays an essential role in activation of wild-type p53 tumor suppressor to initiate proapoptotic signaling in response to overgeneration of superoxide. Thus, these findings reveal a mechanism of NF-kappaB-regulated proapoptotic signaling.

Macrophage migration inhibitory factor is a cardiac-derived myocardial depressant factor

Macrophage migration inhibitory factor (MIF) is a pluripotent proinflammatory cytokine that is ubiquitously expressed in organs, including the heart. However, no specific role for MIF in modulating cardiac performance has yet been described. Therefore, we examined cardiac MIF expression in mice after LPS challenge (4 mg/kg) and tested the hypothesis that MIF is a mediator of LPS-induced cardiac dysfunction. Western blots of whole heart lysates, as well as immunohistochemistry, documented constitutive MIF protein expression in the heart. Cardiac MIF protein levels significantly decreased after LPS challenge, reaching a nadir at 12 h, and then returned to baseline by 24 h. This pattern was consistent with MIF release from cytoplasmic stores after endotoxin challenge. After release of protein, MIF mRNA levels increased 24-48 h postchallenge. To determine the functional consequences of MIF release, we treated LPS-challenged mice with anti-MIF neutralizing antibodies or isotype control antibodies. Anti-MIF-treated animals had significantly improved cardiac function, as evidenced by a significant improvement in left ventricular (LV) fractional shortening percentage at 8, 12, 24, and 48 h after endotoxin challenge. In support of these findings, perfusion of isolated beating mouse hearts (Langendorff preparation) with recombinant MIF (20 ng/ml) led to a significant decrease in both systolic and diastolic performance [LV pressure (LVP), positive and negative first derivative of LVP with respect to time, and rate of LVP rise at developed pressure of 40 mmHg]. This study demonstrates that MIF mediates LPS-induced cardiac dysfunction and suggests that MIF should be considered a pharmacological target for the treatment of cardiac dysfunction in sepsis and potentially other cardiac diseases.

Interleukins in atherosclerosis: molecular pathways and therapeutic potential

Interleukins are considered to be key players in the chronic vascular inflammatory response that is typical of atherosclerosis. Thus, the expression of proinflammatory interleukins and their receptors has been demonstrated in atheromatous tissue, and the serum levels of several of these cytokines have been found to be positively correlated with (coronary) arterial disease and its sequelae. In vitro studies have confirmed the involvement of various interleukins in pro-atherogenic processes, such as the up-regulation of adhesion molecules on endothelial cells, the activation of macrophages, and smooth muscle cell proliferation. Furthermore, studies in mice deficient or transgenic for specific interleukins have demonstrated that, whereas some interleukins are indeed intrinsically pro-atherogenic, others may have anti-atherogenic qualities. As the roles of individual interleukins in atherosclerosis are being uncovered, novel anti-atherogenic therapies, aimed at the modulation of interleukin function, are being explored. Several approaches have produced promising results in this respect, including the transfer of anti-inflammatory interleukins and the administration of decoys and antibodies directed against proinflammatory interleukins. The chronic nature of the disease and the generally pleiotropic effects of interleukins, however, will demand high specificity of action and/or effective targeting to prevent the emergence of adverse side effects with such treatments. This may prove to be the real challenge for the development of interleukin-based anti-atherosclerotic therapies, once the mediators and their targets have been delineated.

Peripheral mechanisms involved with catabolism

PURPOSE OF REVIEW

This review summarizes recent developments concerning the mechanisms of skeletal muscle and adipose tissue breakdown, which are a hallmark of cachexia during many diseases. Current knowledge on the hypermetabolism which often contributes to cachexia is also considered.

RECENT FINDINGS

Recent studies have identified interactions between Ca2+, proinflammatory cytokines (in particular tumor necrosis factor-alpha) and the activation of transcription factors (e.g. nuclear factor-kappaB) in the stimulation of major proteolytic pathways in cachexia. Progress has also been made in explaining the inhibiting effects of several drugs on protein breakdown. Advances in our understanding of the mechanisms of adipose tissue catabolism in cachexia include demonstrations that (1) tumor necrosis factor-alpha, in addition to its direct lipolytic effect, promotes adipose tissue breakdown by inhibiting adipocyte differentiation and increasing adipocyte apoptosis, (2) interleukin-6 has a lipolytic effect, and (3) chemokines are expressed by adipocytes and interact with tumor necrosis factor-alpha to cause lipolysis. Concerning the hypermetabolism in cachexia, new evidence supports previous theories that uncoupling protein-2 and 3 are primarily involved in the generation of reactive oxygen species and in the control of fatty acid flux across the mitochondrial membrane, respectively. Furthermore, the cytokine-induced transcriptional coactivator-1 for the peroxysome proliferator-activated receptor-gamma was recently identified as a contributor to hypermetabolism.

SUMMARY

These new insights into major catabolic pathways during cachexia provide a focus for future studies in this area and may help to develop promising therapeutic approaches.

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.

Cardiac inflammation and innate immunity in septic shock: is there a role for toll-like receptors?

Our current understanding of the pathogenesis of sepsis suggests that bacteria as well as bacterial-derived products activate an uncontrolled network of host-derived mediators such as proinflammatory cytokines (ie, tumor necrosis factor [TNF] and interleukin [IL]-1beta), which can ultimately lead to cardiovascular collapse and death. Despite the potentially important role that TNF and IL-1beta may play in producing cardiac dysfunction in human septic shock, little is known with regard to the basic biochemical mechanism(s) by which bacterial pathogens induce their expression in the heart. A major advance in understanding the early events that are downstream from bacterial-mediated signaling has been the identification of Toll-like receptors (TLRs). TLR-mediated signaling is known to activate the transcription factor nuclear factor-kappaB and to upregulate TNF expression. It has recently been shown that the heart expresses TLRs, raising the possibility that these receptors may be responsible for mediating the deleterious effects of bacterial pathogens on cardiac function. In this review, we will discuss the emerging role for TLRs in the pathogenesis of the cardiovascular collapse that occurs during sepsis.

Myocardial inflammatory activation in children with congenital heart disease

OBJECTIVE

In several cardiac-related diseases, there is a strong association between systemic endotoxemia, myocardial cytokine production, and cardiac failure. Because pre- and postoperative endotoxemia recently was reported in children with congenital heart disease, we sought direct evidence of myocardial inflammatory activation in a cohort of children undergoing congenital heart surgery on cardiopulmonary bypass. Inflammatory activation was prospectively defined as the presence of nuclear factor-kappaB nuclear translocation in myocardial tissue samples.

DESIGN

Prospective observational study.

SETTING

Tertiary care pediatric intensive care unit.

PATIENTS

Fifteen children with congenital heart disease undergoing operative repair on cardiopulmonary bypass.

INTERVENTIONS

All patients underwent operative repair of congenital heart disease on cardiopulmonary bypass and had plasma samples obtained for endotoxin and tumor necrosis factor-alpha, both pre- and postoperatively. Myocardial tissue samples were obtained intraoperatively, both before and during cardiopulmonary bypass.

MEASUREMENTS AND MAIN RESULTS

Elevated plasma endotoxin concentrations were documented in all 15 patients during the study period. In 12 patients, plasma endotoxin was elevated before cardiopulmonary bypass. The median preoperative tumor necrosis factor-alpha concentration was 16.4 pg/mL, which is higher than concentrations reported in adults with New York Heart Association class III congestive heart failure. Examination of myocardial tissue samples revealed nuclear factor-kappaB nuclear translocation (predominantly p50/p65 heterodimers) in nine of 15 patients (60%). Four of these nine patients had nuclear factor-kappaB nuclear translocation before initiation of cardiopulmonary bypass, with p50/p50 homodimers present in two of the four.

CONCLUSIONS

These data provide the first evidence of nuclear factor-kappaB activation in children with congenital heart disease and the first evidence of myocardial nuclear factor-kappaB translocation in human hearts before explant for transplantation. Furthermore, these data suggest that, similar to adults with advanced congestive heart failure, the myocardial inflammatory cascade may contribute to the pathophysiology of congenital heart disease in infants and children.

Tumor necrosis factor-alpha in cardiovascular biology and the potential role for anti-tumor necrosis factor-alpha therapy in heart disease

The functional role of tumor necrosis factor (TNF)-alpha in the heart has been extensively studied over the last 15 years. Collectively, these studies have demonstrated that TNF-alpha has both diverse and potentially conflicting roles in cardiac function and pathology. These include beneficial effects, such as cardioprotection against ischemia, myocarditis, and pressure overload, as well as potentially adverse effects, such as the development of atherosclerosis, reperfusion injury, hypertrophy, and heart failure. TNF-alpha antagonist therapy recently has been demonstrated to be clinically applicable in inflammatory conditions, and clinical trials are currently in progress in the use of these agents in cardiovascular diseases. The scope for clinical applications of anti-TNF-alpha therapy in cardiovascular diseases is potentially extensive. Hence, this review has been undertaken to evaluate the cardiovascular effects of this pleiotropic cytokine and to evaluate the potential of targeting this cytokine in cardiovascular therapeutics. An overview of the TNF-alpha peptide and its associated signaling are described. This is followed by a discussion of the known roles of TNF-alpha in cardiac physiology and in a diverse array of cardiac pathologies. Reference to experimental and clinical studies using anti-TNF-alpha therapies are described where applicable. The postulated role of TNF-alpha signaling concerning innate cardiac cellular processes that may have direct adaptive effects in the heart will be reviewed with respect to future research directions. Finally, the author postulates that attenuation of TNF-alpha biosynthesis in selected individuals will need to be tested if true benefits of this therapeutic approach are to be realized in the management of cardiovascular diseases.