Increased IkappaB expression and diminished nuclear NF-kappaB in human mononuclear cells following hydrocortisone injection

Age-related neuroinflammation and changes in AKT-GSK-3β and WNT/ β-CATENIN signaling in rat hippocampus

Aging is a multifactorial process associated with an increased susceptibility to neurodegenerative disorders which can be related to chronic inflammation. Chronic inflammation, however, can be characterized by the persistent elevated glucocorticoid (GCs) levels, activation of the proinflammatory transcription factor NF-кB, as well as an increase in cytokines. Interestingly, both NF-кB and cytokines can be even modulated by Glycogen Synthase Kinase 3 beta (GSK-3β) activity, which is a key protein that can intermediate inflammation and metabolism, once it has a critical role in AKT signaling pathway, and can also intermediate WNT/β-CATENIN signaling pathway. The aim of this study was to verify age-related changes in inflammatory status, as well as in the AKT and WNT signaling pathways. Results showed an age-related increase in neuroinflammation as indicated by NF-кB activation, TNF-α and GCs increased levels, a decrease in AKT activation and an increase in GSK-3β activity in both 12- and 24- month old animals. Aging also seems to induce a progressive decrease in canonical WNT/β-CATENIN signaling pathway once there is a decrease in DVL-2 levels and in the transcription of Axin2 gene. Little is known about the DVL-2 regulation as well as its roles in WNT signaling pathway, but for the first time it was suggested that DVL-2 expression can be changed along aging.

Suppressive effect of insulin on the gene expression and plasma concentrations of mediators of asthmatic inflammation

BACKGROUND AND HYPOTHESIS

Following our recent demonstration that the chronic inflammatory and insulin resistant state of obesity is associated with an increase in the expression of mediators known to contribute to the pathogenesis of asthma and that weight loss after gastric bypass surgery results in the reduction of these genes, we have now hypothesized that insulin suppresses the cellular expression and plasma concentrations of these mediators.

METHODS

The expression of IL-4, LIGHT, LTBR, ADAM-33, and TSLP in MNC and plasma concentrations of LIGHT, TGF-β1, MMP-9, MCP-1, TSLP, and NOM in obese patients with T2DM were measured before, during, and after the infusion of a low dose (2 U/h) infusion of insulin for 4 hours. The patients were also infused with dextrose or saline for 4 hours on two separate visits and served as controls. Results. Following insulin infusion, the mRNA expression of IL-4, ADAM-33, LIGHT, and LTBR mRNA expression fell significantly (P < 0.05 for all). There was also a concomitant reduction in plasma NOM, LIGHT, TGF-β1, MCP-1, and MMP-9 concentrations.

CONCLUSIONS

Insulin suppresses the expression of these genes and mediators related to asthma and may, therefore, have a potential role in the treatment of asthma.

The characteristic long-term upregulation of hippocampal NF-κB complex in PTSD-like behavioral stress response is normalized by high-dose corticosterone and pyrrolidine dithiocarbamate administered immediately after exposure

Nuclear factor-κB (NF-κB) is a ubiquitously expressed transcription factor for genes involved in cell survival, differentiation, inflammation, and growth. This study examined the role of NF-κB pathway in stress-induced PTSD-like behavioral response patterns in rats. Immunohistochemical technique was used to detect the expression of the NF-κB p50 and p65 subunits, I-κBα, p38, and phospho-p38 in the hippocampal subregions at 7 days after exposure to predator scent stress. Expression of p65 nuclear translocation was quantified by western blot as the level of NF-κB activation. The effects of intraperitoneally administered corticosterone or a selective NF-κB inhibitor (pyrrolidine dithiocarbamate (PDTC)) at 1 h post exposure on behavioral tests (elevated plus-maze and acoustic startle response) were evaluated 7 days later. Hippocampal expressions of those genes were subsequently evaluated. All data were analyzed in relation to individual behavior patterns. Extreme behavioral responder animals displayed significant upregulation of p50 and p65 with concomitant downregulation of I-κBα, p38, and phospho-p38 levels in hippocampal structures compared with minimal behavioral responders and controls. Immediate post-exposure treatment with high-dose corticosterone and PDTC significantly reduced prevalence rates of extreme responders and normalized the expression of those genes. Stress-induced upregulation of NF-κB complex in the hippocampus may contribute to the imbalance between what are normally precisely orchestrated and highly coordinated physiological and behavioral processes, thus associating it with stress-related disorders.

Stress- and glucocorticoid-induced priming of neuroinflammatory responses: potential mechanisms of stress-induced vulnerability to drugs of abuse

Stress and stress-induced glucocorticoids (GCs) sensitize drug abuse behavior as well as the neuroinflammatory response to a subsequent pro-inflammatory challenge. Stress also predisposes or sensitizes individuals to develop substance abuse. There is an emerging evidence that glia and glia-derived neuroinflammatory mediators play key roles in the development of drug abuse. Drugs of abuse such as opioids, psychostimulants, and alcohol induce neuroinflammatory mediators such as pro-inflammatory cytokines (e.g. interleukin (IL)-1β), which modulate drug reward, dependence, and tolerance as well as analgesic properties. Drugs of abuse may directly activate microglial and astroglial cells via ligation of Toll-like receptors (TLRs), which mediate the innate immune response to pathogens as well as xenobiotic agents (e.g. drugs of abuse). The present review focuses on understanding the immunologic mechanism(s) whereby stress primes or sensitizes the neuroinflammatory response to drugs of abuse and explores whether stress- and GC-induced sensitization of neuroimmune processes predisposes individuals to drug abuse liability and the role of neuroinflammatory mediators in the development of drug addiction.

Glucocorticoids exacerbate lipopolysaccharide-induced signaling in the frontal cortex and hippocampus in a dose-dependent manner

Although the anti-inflammatory actions of glucocorticoids (GCs) are well established, evidence has accumulated showing that proinflammatory GC effects can occur in the brain, in a poorly understood manner. Using electrophoretic mobility shift assay, real-time PCR, and immunoblotting, we investigated the ability of varying concentrations of corticosterone (CORT, the GC of rats) to modulate lipopolysaccharide (LPS)-induced activation of NF-κB (nuclear factor κB), expression of anti- and proinflammatory factors and of the MAP (mitogen-activated protein) kinase family [ERK (extracellular signal-regulated kinase), p38, and JNK/SAPK (c-Jun N-terminal protein kinase/stress-activated protein kinase)], and AKT. In the frontal cortex, elevated CORT levels were proinflammatory, exacerbating LPS effects on NF-κB, MAP kinases, and proinflammatory gene expression. Milder proinflammatory GCs effects occurred in the hippocampus. In the absence of LPS, elevated CORT levels increased basal activation of ERK1/2, p38, SAPK/JNK, and AKT in both regions. These findings suggest that GCs do not uniformly suppress neuroinflammation and can even enhance it at multiple levels in the pathway linking LPS exposure to inflammation.

Chronic unpredictable stress exacerbates lipopolysaccharide-induced activation of nuclear factor-kappaB in the frontal cortex and hippocampus via glucocorticoid secretion

Although the anti-inflammatory actions of glucocorticoids (GCs) are well established in the periphery, these stress hormones can increase inflammation under some circumstances in the brain. The transcription factor nuclear factor-kappaB (NF-kappaB), which is inhibited by GCs, regulates numerous genes central to inflammation. In this study, the effects of stress, GCs, and NMDA receptors on lipopolysaccharide (LPS)-induced activation of NF-kappaB in the brain were investigated. One day after chronic unpredictable stress (CUS), nonstressed and CUS rats were treated with saline or LPS and killed 2 h later. CUS potentiated the increase in LPS-induced activation of NF-kappaB in frontal cortex and hippocampus but not in the hypothalamus. This stress effect was blocked by pretreatment of rats with RU-486, an antagonist of the GC receptor. MK-801 [(+)-5-methyl-10,11-dihydro-5H-dibenzo [a,d] cyclohepten-5,10-imine maleate], an NMDA receptor antagonist, also reduced the effect of LPS in all three brain regions. However, the combined antagonism of both GC and NMDA receptors produced no further reduction in NF-kappaB activation when compared with the effect of each treatment alone. Our results indicate that stress, via GC secretion, can increase LPS-induced NF-kappaB activation in the frontal cortex and hippocampus, agreeing with a growing literature demonstrating proinflammatory effects of GCs.

Growing old with nuclear factor-kappaB

The transcription factor nuclear factor-kappa B (NF-kappaB) is involved in the regulation of a broad spectrum of genes that play important roles in a myriad of physiological and pathological events ranging from the immune response to carcinogenesis. Interestingly, many processes in which NF-kappa B plays a central role have long been noted for their alteration with age. A number of research groups have reported rather dramatic changes in NF-kappaB activity as humans and animals age, with tissue-specific increases and decreases in NF-kappaB activity being reported. The extent to which changes in NF-kappaB activity drive aging and influence life span in humans and other mammals is not clear. However, given the dramatic impact that NF-kappaB can have on the function of numerous tissues and organs, understanding how NF-kappaB activity changes with age will undoubtedly enhance our understanding of the many diseases associated with growing old.

Glucocorticoid receptor activation of the I kappa B alpha promoter within chromatin

The glucocorticoid receptor (GR) is a ligand-activated transcription factor that induces expression of many genes. The GR has been useful for understanding how chromatin structure regulates steroid-induced transcription in model systems. However, the effect of glucocorticoids on chromatin structure has been examined on few endogenous mammalian promoters. We investigated the effect of glucocorticoids on the in vivo chromatin structure of the glucocorticoid-responsive I kappa B alpha gene promoter, the inhibitor of the ubiquitous transcription factor, nuclear factor kappa B (NF kappa B). Glucocorticoids inhibit NF kappa B activity in some tissues by elevating the levels of I kappa B alpha. We found that glucocorticoids activated the I kappa B alpha promoter in human T47D/A1-2 cells containing the GR. We then investigated the chromatin structure of the I kappa B alpha promoter in the absence and presence of glucocorticoids with the use of micrococcal nuclease, restriction enzyme, and deoxyribonuclease (DNaseI) analyses. In untreated cells, the promoter assembles into regularly positioned nucleosomes, and glucocorticoid treatment did not alter nucleosomal position. Restriction enzyme accessiblity studies indicated that the I kappa B alpha promoter is assembled as phased nucleosomes that adopt an "open" chromatin architecture in the absence of hormone. However, glucocorticoids may be required for transcription factor binding, because DNaseI footprinting studies suggested that regulatory factors bind to the promoter upon glucocorticoid treatment.

C-erbB-2/ HER-2 upregulates fascin, an actin-bundling protein associated with cell motility, in human breast cancer cell lines

The over-expression of c-erbB-2/ HER-2, a receptor tyrosine kinase, correlates with poor prognosis in patients with breast and ovarian cancer. In the human breast cancer cell line, MDA-MB-435, c-erbB-2 over-expression results in increased chemoinvasion and higher metastatic properties in nude mice. However, the mechanisms by which c-erbB-2 increases the malignant potential of cells remains unclear. We have determined that over-expression of c-erbB-2 in MDA-MB-435 cells, and in some additional breast cancer cell lines, is associated with graphic increases in mRNA and protein levels of the actin bundling protein fascin. Heightened fascin expression has been observed in other systems to result in greatly increased cell motility, and indeed, our work employing semi-automated time-lapse microscopy demonstrates that MDA-MB-435 cells over-expressing c-erbB-2 exhibit significantly heightened cellular dynamics and locomotion, while visualization of bundled microfilaments within fixed cells revealed enhanced formation of dendritic-like processes, microspikes and other dynamic actin based structures. To address the means by which c-erbB-2 over-expression might result in elevated fascin levels, we identified multiple perfect match TCF and NF-kappaB consensus sites in fascin's promoter and first intron, which appeared consistent with the greater endogenous transcriptional activities of TCF and NF-kappaB in c-erbB-2 over-expressing MDA-MB-435 cells. While such transcriptional modulation may occur in the context of the intact gene/chromatin, subsequent tests using reporter constructs did not support involvement of these signaling pathways. In conclusion, highly increased fascin levels were observed in MDA-MB-435 over-expressing c-erbB-2, likely contributing to these cells' altered actin dynamics, and increased cell motility and malignancy. Studies in progress aim to discern the means by which c-erbB-2 over-expression leads to transcriptional activation of the fascin gene.