Growing old with nuclear factor-kappaB

Renin-angiotensin system inhibitors positively impact on multiple aging regulatory pathways: Could they be used to protect against human aging?

The renin-angiotensin system (RAS)-a classical blood pressure regulator-largely contributes to healthy organ development and function. Besides, RAS activation promotes age-related changes and age-associated diseases, which are attenuated/abolished by RAS-blockade in several mammalian species. RAS-blockers also increase rodent lifespan. In previous work, we discussed how RAS-blockade downregulates mTOR and growth hormone/IGF-1 signaling, and stimulates AMPK activity (together with klotho, sirtuin, and vitamin D-receptor upregulation), and proposed that at least some of RAS-blockade's aging benefits are mediated through regulation of these intermediaries and their signaling to mitochondria. Here, we included RAS-blockade's impact on other aging regulatory pathways, that is, TGF-ß, NF-kB, PI3K, MAPK, PKC, Notch, and Wnt, all of which affect mitochondria. No direct evidence is available on RAS/RAS-blockade-aging regulatory pathway-mitochondria interactions. However, existing results allow to conjecture that RAS-blockers neutralize mitochondrial dysfunction by acting on the discussed pathways. The reviewed evidence led us to propose that the foundation is laid for conducting clinical trials aimed at testing whether angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARB)-even at subclinical doses-offer the possibility to live longer and in better health. As ACEi and ARB are low cost and well-tolerated anti-hypertension therapies in use for over 35 years, investigating their administration to attenuate/prevent aging effects seems simple to implement.

Role of NF-κB in Ageing and Age-Related Diseases: Lessons from Genetically Modified Mouse Models

Ageing is a complex process, induced by multifaceted interaction of genetic, epigenetic, and environmental factors. It is manifested by a decline in the physiological functions of organisms and associated to the development of age-related chronic diseases and cancer development. It is considered that ageing follows a strictly-regulated program, in which some signaling pathways critically contribute to the establishment and maintenance of the aged state. Chronic inflammation is a major mechanism that promotes the biological ageing process and comorbidity, with the transcription factor NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) as a crucial mediator of inflammatory responses. This, together with the finding that the activation or inhibition of NF-κB can induce or reverse respectively the main features of aged organisms, has brought it under consideration as a key transcription factor that acts as a driver of ageing. In this review, we focused on the data obtained entirely through the generation of knockout and transgenic mouse models of either protein involved in the NF-κB signaling pathway that have provided relevant information about the intricate processes or molecular mechanisms that control ageing. We have reviewed the relationship of NF-κB and premature ageing; the development of cancer associated with ageing and the implication of NF-κB activation in the development of age-related diseases, some of which greatly increase the risk of developing cancer.

Clinical validation of nuclear factor kappa B expression in invasive breast cancer

Breast cancer is the most commonly diagnosed cancer in Polish women. The expression of transcription nuclear factor kappa B, a key inducer of inflammatory response promoting carcinogenesis and cancer progression in breast cancer, is not well-established. We assessed the nuclear factor kappa B expression in a total of 119 invasive breast carcinomas and 25 healthy control samples and correlated this expression pattern with several clinical and pathologic parameters including histologic type and grade, tumor size, lymph node status, estrogen receptor status, and progesterone receptor status. The data used for the analysis were derived from medical records. An immunohistochemical analysis of nuclear factor kappa B, estrogen receptor, and progesterone receptor was carried out and evaluation of stainings was performed. The expression of nuclear factor kappa B was significantly higher than that in the corresponding healthy control samples. No statistical difference was demonstrated in nuclear factor kappa B expression in relation to age, menopausal status, lymph node status, tumor size and location, grade and histologic type of tumor, and hormonal status (estrogen receptor and progesterone receptor). Nuclear factor kappa B is significantly overexpressed in invasive breast cancer tissues. Although nuclear factor kappa B status does not correlate with clinicopathological findings, it might provide important additional information on prognosis and become a promising object for targeted therapy.

The role of astrocytes in amyloid production and Alzheimer's disease

Alzheimer's disease (AD) is marked by the presence of extracellular amyloid beta (Aβ) plaques, intracellular neurofibrillary tangles (NFTs) and gliosis, activated glial cells, in the brain. It is thought that Aβ plaques trigger NFT formation, neuronal cell death, neuroinflammation and gliosis and, ultimately, cognitive impairment. There are increased numbers of reactive astrocytes in AD, which surround amyloid plaques and secrete proinflammatory factors and can phagocytize and break down Aβ. It was thought that neuronal cells were the major source of Aβ. However, mounting evidence suggests that astrocytes may play an additional role in AD by secreting significant quantities of Aβ and contributing to overall amyloid burden in the brain. Astrocytes are the most numerous cell type in the brain, and therefore even minor quantities of amyloid secretion from individual astrocytes could prove to be substantial when taken across the whole brain. Reactive astrocytes have increased levels of the three necessary components for Aβ production: amyloid precursor protein, β-secretase (BACE1) and γ-secretase. The identification of environmental factors, such as neuroinflammation, that promote astrocytic Aβ production, could redefine how we think about developing therapeutics for AD.

Saponins from Panax japonicus attenuate age-related neuroinflammation via regulation of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways

Neuroinflammation is recognized as an important pathogenic factor for aging and related cognitive disorders. Mitogen-activated protein kinase and nuclear factor kappa B signaling pathways may mediate neuroinflammation. Saponins from Panax japonicus are the most abundant and bioactive members in rhizomes of Panax japonicus, and show anti-inflammatory activity. However, it is not known whether saponin from Panax japonicus has an anti-inflammatory effect in the aging brain, and likewise its underlying mechanisms. Sprague-Dawley rats were divided into control groups (3-, 9-, 15-, and 24-month-old groups) and saponins from Panax japonicus-treated groups. Saponins from Panax japonicus-treated groups were orally administrated saponins from Panax japonicus at three doses of 10, 30, and 60 mg/kg once daily for 6 months until the rats were 24 months old. Immunohistochemical staining and western blot assay results demonstrated that many microglia were activated in 24-month-old rats compared with 3- and 9-month-old rats. Expression of interleukin-1β, tumor necrosis factor-α, cyclooxygenase-2, and inducible nitric oxide synthase increased. Each dose of saponins from Panax japonicus visibly suppressed microglial activation in the aging rat brain, and inhibited expression levels of the above factors. Each dose of saponins from Panax japonicus markedly diminished levels of nuclear factor kappa B, IκBα, extracellular signal-regulated kinase, c-Jun N-terminal kinase, and p38. These results confirm that saponins from Panax japonicus can mitigate neuroinflammation in the aging rat brain by inhibition of the mitogen-activated protein kinase and nuclear factor kappa B signaling pathways.

Transcriptome analysis of human ageing in male skin shows mid-life period of variability and central role of NF-κB

Age is well-known to be a significant factor in both disease pathology and response to treatment, yet the molecular changes that occur with age in humans remain ill-defined. Here, using transcriptome profiling of healthy human male skin, we demonstrate that there is a period of significantly elevated, transcriptome-wide expression changes occurring predominantly in middle age. Both pre and post this period, the transcriptome appears to undergo much smaller, linear changes with increasing age. Functional analysis of the transient changes in middle age suggest a period of heightened metabolic activity and cellular damage associated with NF-kappa-B and TNF signaling pathways. Through meta-analysis we also show the presence of global, tissue independent linear transcriptome changes with age which appear to be regulated by NF-kappa-B. These results suggest that aging in human skin is associated with a critical mid-life period with widespread transcriptome changes, both preceded and proceeded by a relatively steady rate of linear change in the transcriptome. The data provides insight into molecular changes associated with normal aging and will help to better understand the increasingly important pathological changes associated with aging.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.

NF-κB inhibition delays DNA damage-induced senescence and aging in mice

The accumulation of cellular damage, including DNA damage, is thought to contribute to aging-related degenerative changes, but how damage drives aging is unknown. XFE progeroid syndrome is a disease of accelerated aging caused by a defect in DNA repair. NF-κB, a transcription factor activated by cellular damage and stress, has increased activity with aging and aging-related chronic diseases. To determine whether NF-κB drives aging in response to the accumulation of spontaneous, endogenous DNA damage, we measured the activation of NF-κB in WT and progeroid model mice. As both WT and progeroid mice aged, NF-κB was activated stochastically in a variety of cell types. Genetic depletion of one allele of the p65 subunit of NF-κB or treatment with a pharmacological inhibitor of the NF-κB-activating kinase, IKK, delayed the age-related symptoms and pathologies of progeroid mice. Additionally, inhibition of NF-κB reduced oxidative DNA damage and stress and delayed cellular senescence. These results indicate that the mechanism by which DNA damage drives aging is due in part to NF-κB activation. IKK/NF-κB inhibitors are sufficient to attenuate this damage and could provide clinical benefit for degenerative changes associated with accelerated aging disorders and normal aging.

Systems genetics of the nuclear factor-κB signal transduction network. I. Detection of several quantitative trait loci potentially relevant to aging

A theory of aging holds that senescence is caused by a dysregulated nuclear factor kappa B (NF-κB) signal transduction network (STN). We adopted a systems genetics approach in our study of the NF-κB STN. Ingenuity Pathways Analysis (IPA) was used to identify gene/gene product interactions between NF-κB and the genes in our transcriptional profiling array. Principal components factor analysis (PCFA) was performed on a sub-network of 19 genes, including two initiators of the toll-like receptor (TLR) pathway, myeloid differentiation primary response gene (88) (MyD88) and TIR (Toll/interleukin-1 receptor)-domain-containing adapter-inducing interferon-β (TRIF). TLR pathways are either MyD88-dependent or TRIF-dependent. Therefore, we also performed PCFA on a subset excluding the MyD88 transcript, and on another subset excluding two TRIF transcripts. Using linkage analysis we found that each set gave rise to at least one factor with a logarithm of the odds (LOD) score greater than 3, two on chromosome 15 at 15q12 and 15q22.2, and another two on chromosome 17 at 17p13.3 and 17q25.3. We also found several suggestive signals (2<LOD score<3) at 1q32.1, 1q41, 2q34, 3q23, and 7p15.3. We are currently examining potential associations with single nucleotide polymorphisms within the 1-LOD intervals of our linkage signals.

NF-κB in Aging and Disease

Stochastic damage to cellular macromolecules and organelles is thought to be a driving force behind aging and associated degenerative changes. However, stress response pathways activated by this damage may also contribute to aging. The IKK/NF-κB signaling pathway has been proposed to be one of the key mediators of aging. It is activated by genotoxic, oxidative, and inflammatory stresses and regulates expression of cytokines, growth factors, and genes that regulate apoptosis, cell cycle progression, cell senescence, and inflammation. Transcriptional activity of NF-κB is increased in a variety of tissues with aging and is associated with numerous age-related degenerative diseases including Alzheimer's, diabetes and osteoporosis. In mouse models, inhibition of NF-κB leads to delayed onset of age-related symptoms and pathologies. In addition, NF-κB activation is linked with many of the known lifespan regulators including insulin/IGF-1, FOXO, SIRT, mTOR, and DNA damage. Thus NF-κB represents a possible therapeutic target for extending mammalian healthspan.

Characteristics of lymphocyte nuclear factor-κB signal transduction kinase expression in aging process and regulatory effect of epimedium flavonoids

OBJECTIVE

To study the characteristics of lymphocyte nuclear factor kappa B (NF-κB) signal transduction kinase-related molecular mRNA differential expressions at various month age segments in aging process and the intervening effect of Epimedium flavonoids (EF) on it.

METHODS

Sixty SD rats were divided into six groups, according to animals' age, i.e., the 3 days (d) group, the 4 months (m) group, the 10 m group, the 18 m group, the 27 m group, and the 27 m+EF group. RNA was extracted from separated splenic lymphocytes. Adopting NF-κB signal path functional genome oligonucleotide gene-chip (128 related genes), the integral characteristics and differences of NF-κB signal transduction kinase-related mRNA expressions were determined, and the intervening effect of EF was examined.

RESULTS

The mean level of the NF-κB signal transduction kinase-related mRNA expressions in rats' splenic lymphocytes lowered with aging; the highest expression was presented at 3 d after birth, and then, it lowered gradually, with the lowest level at 18 m or 27 m. After EF intervention, the expression level was raised to the 10-18 m level in the aged rats.

CONCLUSION

The changing rules of lymphocyte NF-κB-signal-transduction-kinase-related mRNA expressions in various stages of aging are helpful for selecting the well time for preventing and intervening aging, and will also give a hint to the molecular index for assessment of senility retarding researches.

Human serum-derived hydroxy long-chain fatty acids exhibit anti-inflammatory and anti-proliferative activity

Background

Circulating levels of novel long-chain hydroxy fatty acids (called GTAs) were recently discovered in the serum of healthy subjects which were shown to be reduced in subjects with colorectal cancer (CRC), independent of tumor burden or disease stage. The levels of GTAs were subsequently observed to exhibit an inverse association with age in the general population. The current work investigates the biological activity of these fatty acids by evaluating the effects of enriched human serum extracts on cell growth and inflammation.

Methods

GTAs were extracted from commercially available bulk human serum and then chromatographically separated into enriched (GTA-positive) and depleted (GTA-negative) fractions. SW620, MCF7 and LPS stimulated RAW264.7 cells were treated with various concentrations of the GTA-positive and GTA-negative extracts, and the effects on cell growth and inflammation determined.

Results

Enriched fractions resulted in poly-ADP ribose polymerase (PARP) cleavage, suppression of NFκB, induction of IκBα, and reduction in NOS2 mRNA transcript levels. In RAW264.7 mouse macrophage cells, incubation with enriched fractions prior to treatment with LPS blocked the induction of several pro-inflammatory markers including nitric oxide, TNFα, IL-1β, NOS2 and COX2.

Conclusions

Our results show that human serum extracts enriched with endogenous long-chain hydroxy fatty acids possess anti-inflammatory and anti-proliferative activity. These findings support a hypothesis that the reduction of these metabolites with age may result in a compromised ability to defend against uncontrolled cell growth and inflammation, and could therefore represent a significant risk for the development of CRC.

NF-kappaB signaling in the aging process

INTRODUCTION

The aging process represents a progressive decline in cellular and organism function. Explaining the aging process has given rise to a cornucopia for different theories in which the basic difference has been the question whether aging is genetically regulated or an entropic degeneration process.

DISCUSSION

Different screening techniques have revealed that mammalian aging is associated with the activation of NF-kappaB transcription factor system. The NF-kappaB system is an ancient host defense system concerned with immune responses and different external and internal dangers, such as oxidative and genotoxic stress. NF-kappaB signaling is not only the master regulator of inflammatory responses but can also regulate several homeostatic responses such as apoptosis, autophagy, and tissue atrophy. We will describe how chronic activation of NF-kappaB signaling has the capacity to induce the senescent phenotype associated with aging. Interestingly, several longevity genes such as SIRT1, SIRT6, and FoxOs can clearly suppress NF-kappaB signaling and in this way delay the aging process and extend lifespan.

CONCLUSION

It seems that the aging process is an entropic degeneration process driven by NF-kappaB signaling. This process can be regulated by a variety of longevity genes along with a plethora of other factors such as genetic polymorphism, immune and dietary aspects, and environmental insults.

Activation of innate immunity system during aging: NF-kB signaling is the molecular culprit of inflamm-aging

Innate and adaptive immunity are the major defence mechanisms of higher organisms against inherent and environmental threats. Innate immunity is present already in unicellular organisms but evolution has added novel adaptive immune mechanisms to the defence armament. Interestingly, during aging, adaptive immunity significantly declines, a phenomenon called immunosenescence, whereas innate immunity seems to be activated which induces a characteristic pro-inflammatory profile. This process is called inflamm-aging. The recognition and signaling mechanisms involved in innate immunity have been conserved during evolution. The master regulator of the innate immunity is the NF-kB system, an ancient signaling pathway found in both insects and vertebrates. The NF-kB system is in the nodal point linking together the pathogenic assault signals and cellular danger signals and then organizing the cellular resistance. Recent studies have revealed that SIRT1 (Sir2 homolog) and FoxO (DAF-16), the key regulators of aging in budding yeast and Caenorhabditis elegans models, regulate the efficiency of NF-kB signaling and the level of inflammatory responses. We will review the role of innate immunity signaling in the aging process and examine the function of NF-kB system in the organization of defence mechanisms and in addition, its interactions with the protein products of several gerontogenes. Our conclusion is that NF-kB signaling seems to be the culprit of inflamm-aging, since this signaling system integrates the intracellular regulation of immune responses in both aging and age-related diseases.

Signaling mechanisms involved in the response to genotoxic stress and regulating lifespan

Ageing is defined by the loss of functional reserve over time, leading to a decreased capacity to maintain homeostasis under stress and increased risk of morbidity and mortality. Ageing is extremely heterogeneous between individuals and even between tissues within an organism, making it challenging to identify the molecular basis of ageing. Much of our current understanding of ageing comes from genetic studies in model organisms seeking genes that either accelerate or decelerate the ageing process. These studies revealed not only causes of ageing, but also signaling mechanisms that both promote and protect against ageing. In all cases, the signaling pathways that influence lifespan are familiar mechanisms that regulate cellular metabolism, growth, proliferation, differentiation and survival. This review highlights the significant overlap in signaling mechanisms implicated in both the cellular response to genotoxic stress and regulation of organism lifespan.

Differential regulation of BACE1 promoter activity by nuclear factor-κB in neurons and glia upon exposure to β-amyloid peptides

The brains of Alzheimer's disease (AD) patients display cerebrovascular and parenchymal deposits of beta-amyloid (A beta) peptides, which are derived by proteolytic processing by the beta-site APP-cleaving enzyme 1 (BACE1) of the amyloid precursor protein (APP). The rat BACE1 promoter has a nuclear factor-kappaB (NF-kappaB) binding site. Deletion studies with a BACE1 promoter/luciferase reporter suggest that the NF-kappaB binding DNA consensus sequence plays a suppressor role, when occupied by NF-kappaB, in the regulation of neuronal brain BACE1 expression. Here we characterize a signal transduction pathway that may be responsible for the increases in A beta associated with AD. We propose that the transcription factor NF-kappaB acts as a repressor in neurons but as an activator of BACE1 transcription in activated astrocytes present in the CNS under chronic stress, a feature present in the AD brain. The activated astrocytic stimulation of BACE1 may in part account for increased BACE1 transcription and subsequent processing of Ab eta in a cell-specific manner in the aged and AD brain. As measured by reporter gene promoter constructs and endogenous BACE1 protein expression, a functional NF-kappaB site was stimulatory in activated astrocytes and A beta-exposed neuronal cells and repressive in neuronal and nonactivated astrocytic cells. Given the evidence for increased levels of activated astrocytes in the aged brain, the age- and AD-associated increases in NF-kappaB in brain may be significant contributors to increases in A beta, acting as a positive feedback loop of chronic inflammation, astrocyte activation, increased p65/p50 activation of BACE1 transcription, and further inflammation.

Tissue specific and non-specific changes in gene expression by aging and by early stage CR

Aging alters the expression of a variety of genes. Calorie restriction (CR), which extends life span in laboratory rodents, also changes gene expression. This study investigated changes in gene expression across three different tissues from the same mouse to examine how aging and early stage CR influence gene expression in different tissues of an organism. Expression profiling of heart, liver, and hypothalamus tissues was done in young (4-6 months) ad libitum fed (AL), young CR (2.5-4.5 months of CR), and old (26-28 months) AL male C57BL/6 mice. Aging significantly altered the expressions of 309, 1819, and 1085 genes in heart, liver, and hypothalamus tissues, respectively. In nine genes, aging altered expression across all three tissues although the regulation directions did not agree across all three tissues for some genes. Early stage CR in young mice significantly changed the expressions of 192, 839, and 100 genes in heart, liver, and hypothalamus tissues, respectively, and seven genes altered expression across all three tissues; three were up regulated and four were down regulated. The results of Gene Ontology (GO) Biological Process analysis indicated up regulation of antigen processing/presentation genes by aging and down regulation of stress response genes by early stage CR in all three tissues. The comparison of the results of aging and short term CR studies showed there were 389 genes, 18 GO biological processes, and 20 GO molecular functions in common.

The ubiquitin-proteasome system at the crossroads of stress-response and ageing pathways: a handle for skin care?

The regulation of gene expression at the transcriptional level has been considered for long as the main mechanism of cellular adaptive responses. Since the turn of the century, however, it is becoming clear that higher organisms developed a complex, sensitive and maybe equally important network of regulatory pathways, relying largely on protein interactions, post-translational modifications and proteolysis. Here we review the involvement of the ubiquitin-proteasome pathway of protein degradation at different levels of cellular life in relation with ageing, and with a special focus on skin. It comes out that the ubiquitin system plays a major role in signal transduction associated with stress and ageing, in skin in particular through the control of retinoid and NF-kappaB pathways. The understanding of specific proteolytic targeting by E3 ubiquitin-ligases paves the way for a new generation of active molecules that may control particular steps of normal and pathological ageing.

Activation of nuclear factor-kappaB (NFkappaB) identifies a high-risk subset of hormone-dependent breast cancers

Activation of nuclear factor-kappaB (NFkappaB) has been linked to the development of hormone-independent, estrogen receptor (ER)-negative human breast cancers. To explore the possibility that activated NFkappaB marks a subset of clinically more aggressive ER-positive breast cancers, NFkappaB DNA-binding was measured in ER-positive breast cancer cell lines and primary breast cancer extracts by electrophoretic mobility shift assay and ELISA-based quantification of specific NFkappaB p50 and p65 DNA-binding subunits. Oxidant (menadione 100 microMx30 min) activation of NFkappaB was prevented by pretreatment with various NFkappaB inhibitors, including the specific IkappaB kinase (IKK) inhibitor, parthenolide (PA), which was found to sensitize MCF-7/HER2 and BT474 but not MCF-7 cells to the antiestrogen tamoxifen. Early stage primary breast cancers selected a priori for lower ER content (21-87 fmol/mg; n=59) and known clinical outcome showed two- to four-fold increased p50 and p65 NFkappaB DNA-binding over a second set of primary breast cancers with higher ER content (>100 fmol/mg; n=22). Breast cancers destined to relapse (13/59) showed significantly higher NFkappaB p50 (but not p65) DNA-binding over those not destined to relapse (46/59; p=0.04). NFkappaB p50 DNA-binding correlated positively with several prognostic biomarkers; however, only NFkappaB p50 DNA-binding (p=0.04), Activator Protein-1 DNA-binding (AP-1; p<or=0.01) and urokinase-type plasminogen activator expression (uPA; p=0.0014) showed significant associations with metastatic relapse and disease-free patient survival. These clinical findings indicate that high-risk ER-positive breast cancers may be prognostically identified by increased NFkappaB p50 DNA-binding, and support preclinical models suggesting that therapeutic inhibition of NFkappaB activation may improve the endocrine responsiveness of high-risk ER-positive breast cancers.

Functional genetic screen for genes involved in senescence: role of Tid1, a homologue of the Drosophila tumor suppressor l(2)tid, in senescence and cell survival

We performed a genetic suppressor element screen to identify genes whose inhibition bypasses cellular senescence. A normalized library of fragmented cDNAs was used to select for elements that promote immortalization of rat embryo fibroblasts. Fragments isolated by the screen include those with homology to genes that function in intracellular signaling, cellular adhesion and contact, protein degradation, and apoptosis. They include mouse Tid1, a homologue of the Drosophila tumor suppressor gene l(2)tid, recently implicated in modulation of apoptosis as well as gamma interferon and NF-kappaB signaling. We show that GSE-Tid1 enhances immortalization by human papillomavirus E7 and simian virus 40 T antigen and cooperates with activated ras for transformation. Expression of Tid1 is upregulated upon cellular senescence in rat and mouse embryo fibroblasts and premature senescence of REF52 cells triggered by activated ras. In accordance with this, spontaneous immortalization of rat embryo fibroblasts is suppressed upon ectopic expression of Tid1. Modulation of endogenous Tid1 activity by GSE-Tid1 or Tid1-specific RNA interference alleviates the suppression of tumor necrosis factor alpha-induced NF-kappaB activity by Tid1. We also show that NF-kappaB sequence-specific binding is strongly downregulated upon senescence in rat embryo fibroblasts. We therefore propose that Tid1 contributes to senescence by acting as a repressor of NF-kappaB signaling.

Inhibition of transcription factor activity by nuclear compartment-associated Bcl-2

Using a reporter gene assay in PC12, HEK293, HeLa, and NIH-3T3 cells, we show that the anti-apoptotic protein Bcl-2 significantly inhibits transcriptional activation of various transcription factors, including NF kappa B, AP1, CRE, and NFAT. A Bcl-2 mutant lacking its BH4 domain (Delta BH4) also inhibited transcription, whereas a Bcl-2 mutant lacking its transmembrane domain (Delta TM) was ineffective. Furthermore, Bcl-2 chimeric proteins containing transmembrane domains from the mitochondrial protein monoamine oxidase B (MaoB) or the endoplasmic reticulum protein cytochrome b(5) showed no effect on transcription factor activity. Subcellular localization studies showed that under conditions of transient transfection, the active Bcl-2 forms (wild type and Delta BH4) were predominantly found in the nuclear fraction, whereas the non-active forms (Delta TM, MaoB, and cytochrome b(5)) were in the non-nuclear fraction. Additionally, stably expressed Bcl-2 loses its ability to inhibit transcriptional activation and localizes predominantly to the non-nuclear fraction. Expression of FKBP38 (a chaperone that shuttles Bcl-2 to the mitochondria) removes co-expressed Bcl-2 from the nuclear fraction and reverses its effect on transcription factor activity. Finally, using an inducible gene expression system, we show that nuclear compartment-associated Bcl-2 prevents entry of NF kappa B subunits to the nucleus without affecting NF kappa B release from its cytosolic inhibitory sub-unit I kappa B alpha. These results suggest that (a) Bcl-2 suppresses transcriptional activity of multiple transcription factors; (b) Bcl-2 does not interfere with NF kappa B activation but prevents entrance of its active subunits to the nucleus; (c) membrane anchoring is required for this function of Bcl-2; and (d) association of Bcl-2 with the nuclear compartment is also necessary. We speculate that nuclear compartment-associated Bcl-2 may affect nuclear trafficking of multiple factors necessary for transcriptional activity.

Involvement of Rel/NF-kappa B transcription factors in senescence

Senescence is now established as a genetically controlled phenomenon that alters different cell functions, including proliferation, apoptosis, resistance to stress, and energetic metabolism. Underlying changes in gene expression are governed by some transcription factors, whose expression or activity must change with senescence as well. Transcription factors of the Rel/NF-kappa B family are good candidates to participate in the establishment of senescence. Arguments range from correlation between cell functions controlled by these factors and cell functions altered during senescence, to phenotypes resulting from in vitro manipulations of Rel/NF-kappa B activity.

In vivo ozone exposure induces antioxidant/stress-related responses in murine lung and skin

Lung and skin are the organs directly exposed to environmental pollution. Ozone (O(3)) is a toxic, oxidant air pollutant, and exposure has been shown to induce antioxidant depletion as well as oxidation of lipids and proteins within the outermost skin layer (stratum corneum) and the lung respiratory tract lining fluids (RTLFs). To further define skin and lung responses to O(3) exposure, SKH-1 hairless mice were exposed to either 0.8 ppm of O(3) (a level occasionally reached in very polluted areas) or ambient air 6 h/day for 6 consecutive days. O(3) exposure resulted in the depletion of alpha-tocopherol in lung and plasma and induction in both skin and lung of heme oxygenase 1, cyclooxygenase 2, and proliferating cell nuclear antigen. O(3)-exposed animals showed a similar extent of upregulation of COX-2 and PCNA in lung and skin, whereas HO-1 was more responsive in skin than in lung (7-fold induction vs. 2-fold induction). In addition to these measures of response to oxidative stress, O(3) exposure led to the activation of nuclear factor kappaB measured as IkappaBalpha phosphorylation in both tissues. We conclude that in this model, O(3) at high pollutant levels is able to affect both lung and skin biology, inducing depletion of alpha-tocopherol and inducing stress-related responses in both skin epidermis and respiratory tract epithelium.