Current insights into the regulation of programmed cell death by NF-kappaB

The I{kappa}B kinase {beta}/nuclear factor {kappa}B signaling pathway protects the heart from hemodynamic stress mediated by the regulation of manganese superoxide dismutase expression

Cardiomyocyte death plays an important role in the pathogenesis of heart failure. The nuclear factor (NF)-kappaB signaling pathway regulates cell death, however, the effect of NF-kappaB pathway on cell death can vary in different cells or stimuli. The purpose of the present study was to clarify the in vivo role of the NF-kappaB pathway in response to pressure overload. First, we subjected C57Bl6/J mice to pressure overload by means of transverse aortic constriction (TAC) and examined the activity of the NF-kappaB pathway in response to pressure overload. IkappaB kinase (IKK) and NF-kappaB were activated after TAC. Then, we investigated the role of the activation using cardiac-specific IKKbeta-deficient mice (CKO). CKO displayed normal global cardiac structure and function compared with control littermates. We subjected CKO and control mice to pressure overload. One week after TAC, CKO showed cardiac dilation, dysfunction, and lung congestion, which are characteristics of heart failure. The number of apoptotic cells in the hearts of CKO mice increased significantly after TAC. The levels of manganese superoxide dismutase mRNA and protein expression in CKO after TAC were significantly attenuated compared with control mice. The levels of oxidative stress and c-Jun N-terminal kinase (JNK) activation in CKO after TAC were significantly greater than those in control mice. Isoproterenol-induced cell death of isolated adult CKO cardiomyocytes was inhibited by treatment with either a manganese superoxide dismutase mimetic or a JNK inhibitor. Thus, the IKKbeta/NF-kappaB signaling pathway plays a protective role in cardiomyocytes because of the attenuation of oxidative stress and JNK activation in a setting of acute pressure overload.

Peptidyl-prolyl isomerase Pin1 markedly enhances the oncogenic activity of the rel proteins in the nuclear factor-kappaB family

The peptidyl-prolyl isomerase Pin1 is frequently up-regulated in human cancers in which Rel/nuclear factor-kappaB (NF-kappaB) is constitutively activated, but its role in these cancers remains to be determined, and evidence is still lacking to show that Pin1 contributes to cell transformation by Rel/NF-kappaB. Rel/NF-kappaB transcriptional and oncogenic activities are modulated by several posttranslational modifications and coregulatory proteins, and previous studies showed that cytokine treatment induces binding of Pin1 to the RelA subunit of NF-kappaB, thereby enhancing RelA nuclear localization and stability. Here we show that Pin1 associates with the Rel subunits of NF-kappaB that are implicated in leukemia/lymphomagenesis and modulates their transcriptional and oncogenic activities. Pin1 markedly enhanced transformation of primary lymphocytes by the human c-Rel protein and also increased cell transformation by the potent viral Rel/NF-kappaB oncoprotein v-Rel, in contrast to a Pin1 mutant in the WW domain involved in interaction with NF-kappaB. Pin1 promoted nuclear accumulation of Rel proteins in the absence of activating stimuli. Importantly, inhibition of Pin1 function with the pharmacologic inhibitor juglone or with Pin1-specific shRNA led to cytoplasmic relocalization of endogenous c-Rel in human lymphoma-derived cell lines, markedly interfered with lymphoma cell proliferation, and suppressed endogenous Rel/NF-kappaB-dependent gene expression. Together, these results show that Pin1 is an important regulator of Rel/NF-kappaB transforming activity and suggest that Pin1 may be a potential therapeutic target in Rel/NF-kappaB-dependent leukemia/lymphomas.

PUMA is directly activated by NF-kappaB and contributes to TNF-alpha-induced apoptosis

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine that has an important role in immunity and inflammation by inducing cellular responses such as apoptosis. The transcription factor nuclear factor-kappaB (NF-kappaB) can paradoxically suppress and promote apoptosis in response to TNF-alpha. In this study, we found that p53 upregulated modulator of apoptosis (PUMA), a p53 downstream target and a BH3-only Bcl-2 family member, is directly regulated by NF-kappaB in response to TNF-alpha. TNF-alpha treatment led to increases in PUMA mRNA and protein levels in human colon cancer cells. The induction of PUMA was p53 independent, and mediated by the p65 component of NF-kappaB through a kappaB site in the PUMA promoter. The apoptotic effect of PUMA induction by TNF-alpha was unmasked by depleting the antiapoptotic protein Bcl-X(L). In mice, PUMA was also induced by TNF-alpha in an NF-kappaB-dependent manner. TNF-alpha-induced apoptosis in a variety of tissues and cell types, including small intestinal epithelial cells, hepatocytes, and thymocytes, was markedly reduced in PUMA-deficient mice. Collectively, these results demonstrated that PUMA is a direct target of NF-kappaB and mediates TNF-alpha-induced apoptosis in vitro and in vivo.

Cyclic AMP enhances resolution of allergic pleurisy by promoting inflammatory cell apoptosis via inhibition of PI3K/Akt and NF-kappaB

Selective and timely induction of apoptosis is an effective means of resolving inflammation. The effects and putative mechanisms by which cyclic AMP (cAMP) modulates leukocyte apoptosis in vivo are still unclear. The present study aims at identifying intracellular pathways underlying the ability of cAMP elevating agents to resolve eosinophilic inflammation in a model of allergic pleurisy in mice. Ovalbumin (OVA) challenge of immunized mice induced eosinophil recruitment that peaked at 24h and persisted till 48h. Treatment with the PDE4 inhibitor rolipram, cAMP mimetic db-cAMP or adenylate cyclase activator forskolin, at 24h after antigen-challenge resulted in profound resolution of eosinophilic inflammation, without a decrease of mononuclear cell numbers. There was a concomitant increase in number of apoptotic cells in the pleural cavity. The effects of rolipram and db-cAMP were inhibited by the PKA inhibitor H89. Inhibition of PI3K/Akt or NF-kappaB induced resolution of inflammation that was associated with increased apoptosis. OVA-challenge resulted in a time-dependent activation of Akt and NF-kappaB, which was blocked by treatment with rolipram or PI3K/Akt pathway inhibitors. Thus, cAMP elevating agents resolve established eosinophilic inflammation by inducing leukocyte apoptosis. Mechanistically, the actions of cAMP are dependent on PKA and target a PI3K/Akt-dependent NF-kappaB survival pathway.

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.

Butanol fraction containing berberine or related compound from nexrutine inhibits NFkappaB signaling and induces apoptosis in prostate cancer cells

BACKGROUND

Epidemiological and laboratory studies support the hypothesis that several plant components influence prostate carcinogenesis and holds promise for disease prevention. Previously we reported that Nexrutine (bark extract from Phellodendron amurense) inhibits proliferation of prostate cancer cells and prostate tumor development in the transgenic adenocarcinoma of mouse prostate (TRAMP) model through modulation of Akt signaling pathway. In the present investigation we conducted studies to further define the mechanism of action of Nexrutine and to identify the active component associated with its biological activity.

METHODS

Androgen-responsive, androgen-independent human prostate cancer cell lines and tissues from TRAMP mice fed Nexrutine(R) were used in these studies. Activity guided fractionation identified butanol fraction recapitulating the activities of Nexrutine assessed by proliferation assays, apoptotic assays (DAPI and TUNEL staining), transient transfections, gel shift assays and Western blotting. In addition ultra-performance liquid chromatography (UPLC) of butanol fraction was used to identify active component of Nexrutine.

RESULTS

Butanol fraction recapitulated the activities of Nexrutine in (i) inhibiting proliferation; (ii) inducing apoptosis; and (iii) modulating transcriptional activity of NFkappaB in prostate cancer cells. Our data also indicates that both Nexrutine and butanol fraction modulates NFkappaB transcriptional activity by inhibiting IkappaBalpha phosphorylation. Expression of p65 and phosphorylated IkappaBalpha are high in tumors from TRAMP mice. In contrast dietary administration of Nexrutine reduced expression of p65 and phosphorylated IkappaBalpha in prostate from TRAMP mice. In addition using UPLC, we have identified berberine or closely related compound in the butanol fraction.

CONCLUSION

The results suggest that berberine or closely related component of butanol fraction may be responsible for the observed biological activities and induce apoptosis in prostate cancer cells by targeting critical cell survival signaling pathways both in vitro and in vivo.

Repression of NF-kappaB and activation of AP-1 enhance apoptosis in prostate cancer cells

TNFalpha and TRAIL, 2 members of the tumor necrosis factor family, share many common signaling pathways to induce apoptosis. Although many cancer cells are sensitive to these proapoptotic agents, some develop resistance. Recently, we have demonstrated that upregulation of c-Fos/AP-1 is necessary, but insufficient for cancer cells to undergo TRAIL-induced apoptosis. Here we present a prostate cancer model with differential sensitivity to TNFalpha and TRAIL. We show that inhibition of NF-kappaB or activation of AP-1 can only partially sensitize resistant prostate cancer cells to proapoptotic effects of TNFalpha or TRAIL. Inhibition of NF-kappaB by silencing TRAF2, by silencing RIP or by ectopic expression of IkappaB partially sensitized resistant prostate cancer. Similarly, activation of c-Fos/AP-1 only partially sensitized resistant cancer cells to proapoptotic effects of TNFalpha or TRAIL. However, concomitant repression of NF-kappaB and activation of c-Fos/AP-1 significantly enhanced the proapoptotic effects of TNFalpha and TRAIL in resistant prostate cancer cells. Therefore, multiple molecular pathways may need to be modified, to overcome cancers that are resistant to proapoptotic therapies.

Synthesis and nuclear factor-kappaB inhibitory activities of 6- or 7-methylchroman-2-carboxylic acid N-(substituted) phenylamides

A series of 6- or 7-methylchroman-2-carboxylic acid N-(substituted) phenylamides (2a-s, 3a-s) were synthesized. Their abilities to inhibit nuclear factor-kappaB (NF-kappaB) activity were evaluated in lipopolysaccharide (LPS)-stimulated macrophage RAW 264.7 cells. Compounds with substituents such as -H, -CH(3), and -CF(3) on the phenyl ring were poor inhibitors of NF-kappaB. The most active NF-kappaB inhibitors contained 4-Cl (3s) and 4-OMe (3g) in the 7-methylchroman-2-carboxamide derivatives and 2-OH (2b) and 4-Cl (2s) in the 6-methylchroman-2-carboxamide derivatives (IC(50): 20.2-24.0 microM). These were slightly more potent than a reference compound, KL-1156 (1) (IC(50): 43.9 microM).

Loss of IKKbeta activity increases p53 stability and p21 expression leading to cell cycle arrest and apoptosis

Elevated levels of NF-kappaB are frequently detected in many inflammatory diseases and cancers. Blocking the IKK-NF-kappaB pathway has been seen as a promising approach for new therapies. By employing the dominant-negative mutant of IKKbeta, our data revealed that loss of IKKbeta activity reduces not only the proliferation and invasion of lung adenocarcinoma A549 cells in vitro but also the tumour formation, metastasis and angiogenesis in mouse xenograft model. Treatment of IKKbeta inhibitors (CYL-19s and CYL-26z) leads to the arrest of cell cycle progression at G1 and G2/M, followed by apoptosis. IKKbeta inhibitors can increase the protein stability, nuclear accumulation and promoter-binding activity of p53, leading to the p21 gene transcription. Furthermore, knockdown of IKKbeta by siRNA increased the stability and expression of p53 and p21 promoter activity. In addition, IKKbeta inhibitor-induced p53 and p21 expressions were augmented in the presence of IKKbeta siRNA. Correlation between p53 acetylation and its protein stabilization was also seen after treatment with IKKbeta inhibitors. These results suggest that loss of IKKbeta activation is important for the enhancement of p53 stability, leading to p21 expression and cell cycle arrest and apoptosis of tumour cells.

Shift from apoptotic to necrotic cell death during human papillomavirus-induced transformation of keratinocytes

Oncogenic transformation is a complex, multistep process, which goes through several stages before complete malignant transformation occurs. To identify early processes in carcinogenesis, we used an in vitro model, based on the initiating event in cervical cancer, papillomavirus transformation of keratinocytes. We compared gene expression in primary keratinocytes (K) and papillomavirus-transformed keratinocytes from early (E) and late (L) passages and from benzo[a]pyrene-treated L cells (BP). The transformed cells exhibit similar transcriptional changes to clinical cervical carcinoma. The number of transcripts expressed progressively decreased during the evolution from K to BP cells. Bioinformatic analysis, validated by detailed biochemical analysis, revealed substantial contraction of both pro- and antiapoptotic networks during transformation. Nonetheless, L and BP cells were not resistant to apoptotic stimuli. At doses of cisplatin that led to 30-60% apoptosis of K and E cells, transformed L and BP cells underwent 80% necrotic cell death, which became the default response to genotoxic stress. Moreover, appreciable necrotic fractions were observed in the cervical carcinoma cell line, HeLa, in response to comparable doses of cisplatin. The shrinkage of biochemical networks, including the apoptotic network, may allow a cancer cell to economize on energy usage to facilitate enhanced proliferation but leaves it vulnerable to stress. This study supports the hypothesis that the process of cancer transformation may be accompanied by a shift from apoptosis to necrosis.

Nuclear-cytosolic transport of COMMD1 regulates NF-kappaB and HIF-1 activity

Copper metabolism MURR1 domain1 (COMMD1) is a novel inhibitor of the transcription factors NF-kappaB and HIF-1, which play important roles in inflammation and tumor growth, respectively. In this study, we identified two highly conserved nuclear export signals (NESs) in COMMD1 and revealed that these NESs were essential and sufficient to induce maximal nuclear export of COMMD1. Inhibition of CRM1-mediated nuclear export by Leptomycin B resulted in nuclear accumulation of COMMD1. In addition, low oxygen concentrations induced the active export of COMMD1 from the nucleus in a CRM1-dependent manner. Disruption of the NESs in COMMD1 increased the repression of COMMD1 in transcriptional activity of NF-kappaB and HIF-1. In conclusion, these data indicate that COMMD1 undergoes constitutive nucleocytoplasmic transport as a novel mechanism to regulate NF-kappaB and HIF-1 signaling.

Is NF-kappaB a good target for cancer therapy? Hopes and pitfalls

Nuclear factor kappaB (NF-kappaB) transcription factors have a key role in many physiological processes such as innate and adaptive immune responses, cell proliferation, cell death, and inflammation. It has become clear that aberrant regulation of NF-kappaB and the signalling pathways that control its activity are involved in cancer development and progression, as well as in resistance to chemotherapy and radiotherapy. This article discusses recent evidence from cancer genetics and cancer genome studies that support the involvement of NF-kappaB in human cancer, particularly in multiple myeloma. The therapeutic potential and benefit of targeting NF-kappaB in cancer, and the possible complications and pitfalls of such an approach, are explored.

Cleaved caspase-3 and nuclear factor-kappaB p65 are prognostic factors in metastatic serous ovarian carcinoma

Tumor progression and treatment failure in ovarian carcinoma are frequently associated with metastasis to effusions. The present study analyzed the expression and clinical role of nuclear factor-kappaB p65, nuclear factor-kappaB inhibitor alpha, and parameters of apoptosis in serous carcinoma. Cleaved caspase-3 and caspase-8 levels and deoxyuridine triphosphate incorporation were measured in 65 effusions using flow cytometry. Effusions (n = 209) and corresponding primary carcinomas and solid metastases (n = 114) were immunohistochemically analyzed for nuclear factor-kappaB p65 and nuclear factor-kappaB inhibitor alpha expression. Effusions (n = 75) were further analyzed for nuclear factor-kappaB phospho-p65 (Ser536) levels using immunoblotting. Results were analyzed for association with anatomic site, clinicopathologic parameters, and survival. Caspase cleavage and deoxyuridine triphosphate incorporation were limited to less than 10% of cells in most effusions. Nuclear factor-kappaB p65 expression was frequently detected at all anatomic sites, with less frequent cytoplasmic nuclear factor-kappaB p65 and nuclear factor-kappaB inhibitor alpha expressions. Immunoblotting showed nuclear factor-kappaB p65 phosphorylation in 72 (96%) of 75 effusions. Higher than median cleaved caspase-3 levels correlated with improved overall and progression-free survival in univariate analysis of all patients (P = .024 and P = .046, respectively) and of those with postchemotherapy effusions (P = .042 and P = .036, respectively). Cleaved caspase-3 expression was an independent predictor of longer progression-free survival for patients with postchemotherapy effusions (P = .029). Nuclear factor-kappaB p65 expression correlated with poor progression-free survival for all patients (P = .048) and for those with postchemotherapy effusions (P = .025). Ovarian carcinoma cells in effusions undergo little apoptosis, but high levels of cleaved caspase-3 are associated with improved survival. Nuclear factor-kappaB p65 is frequently expressed in advanced-stage serous ovarian carcinoma, and its nuclear localization is associated with poor progression-free survival.

Deregulation of Tpl2 and NF-kappaB signaling and induction of macrophage apoptosis by the anti-depressant drug lithium

Lithium is an anti-depressant drug that also possesses immunomodulatory functions. The anti-inflammatory effect of lithium is thought to involve activation of the transcription factor CREB, although the underlying mechanism is incompletely understood. We show here that in macrophages lithium stimulates Tpl2, a MAP kinase kinase kinase (MAP3K) known to mediate activation of extracellular signal regulated kinase (ERK) and the downstream target CREB. Lithium activates Tpl2 by inducing degradation of p105, an NF-kappaB precursor protein that functions as a physiological inhibitor of Tpl2. This novel function of lithium does not involve inhibition of a well-characterized lithium target, GSK3beta, since other known GSK3beta inhibitors do not induce p105 degradation or Tpl2 activation. Lithium also promotes the activation of Tpl2 and ERK by the TLR4 ligand LPS. On the other hand, prolonged incubation of macrophages with lithium results in dramatic loss of p105 and inhibition of LPS-stimulated NF-kappaB activation. Consequently, lithium both attenuates LPS-mediated pro-inflammatory gene induction and induces apoptosis in macrophages. These results provide novel insight into the anti-inflammatory function of lithium.

The life of a cell: apoptosis regulation by the PI3K/PKB pathway

The activation of PI3K (phosphoinositide 3-kinase) family members is a universal event in response to virtually all cytokines, growth factors and hormones. As a result of formation of PtdIns with an added phosphate at the 3 position of the inositol ring, activation of the protein kinases PDK1 (phosphoinositide-dependent kinase 1) and PKB (protein kinase B)/Akt occurs. The PI3K/PKB pathway impinges upon a remarkable array of intracellular events that influence either directly or indirectly whether or not a cell will undergo apoptosis. In this review, the many ways in which PI3K/PKB can control these processes are summarized. Not all of the events described will necessarily play a role in any one cell type, but a subset of these events is probably essential for the survival of every cell.

Nuclear factor-kappaB binds to the Epstein-Barr Virus LMP1 promoter and upregulates its expression

The latent membrane protein 1 (LMP1) oncogene carried by Epstein-Barr virus (EBV) is essential for transformation and maintenance of EBV-immortalized B cells in vitro, and it is expressed in most EBV-associated tumor types. The activation of the NF-kappaB pathway by LMP1 plays a critical role in the upregulation of antiapoptotic proteins. The EBV-encoded EBNA2 transactivator is required for LMP1 activation in latency III, while LMP1 itself appears to be critical for its activation in the latency II gene expression program. In both cases, additional viral and cellular transcription factors are required in mediating transcription activation of the LMP1 promoter. Using DNA affinity purification and chromatin immunoprecipitation assay, we showed here that members of the NF-kappaB transcription factor family bound to the LMP1 promoter in vitro and in vivo. Electrophoretic mobility shift assay analyses indicated the binding of the p50-p50 homodimer and the p65-p50 heterodimer to an NF-kappaB site in the LMP1 promoter. Transient transfections and reporter assays showed that the LMP1 promoter is activated by exogenous expression of NF-kappaB factors in both B cells and epithelial cells. Exogenous expression of NF-kappaB factors in the EBNA2-deficient P3HR1 cell line induced LMP1 protein expression. Overall, our data are consistent with the presence of a positive regulatory circuit between NF-kappaB activation and LMP1 expression.

Regulatory effect of compatibility of Astragalus membranaceus and Rhizoma curcumae on COX-2 expression in gastric cancer MKN-45 cells

AIM: To investigate the effect of Astragalus membranaceus and Rhizoma curcumae′s compatibility on MKN-45 cells and the regulatory action of the compatibility on expression of cyclooxygenase 2 (COX-2), peroxisome proliferators activated receptorγ (PPARγ) and nuclear factor κB (NF-κB).

METHODS: The compatibility of Astragalus membranaceus and Rhizoma curcumae was used on MKN-45 cells and there were five groups including Celecoxib group, Rosiglitazone group, Astragalus membranaceus group, Rhizoma curcumae group and control group. The inhibition ratio in each group was determined using MTT method, and the expressions of COX-2 mRNA, PPARγ mRNA, NF-κB mRNA and COX-2 protein were measured using RT-PCR and Western blot methods.

RESULTS: Both the Chinese drugs and Western medicines had suppression on NF-κB mRNA and COX-2 mRNA. All medicines except Rhizoma curcumae promoted the expression of PPARγ mRNA. The most obvious suppressive effect on COX-2 mRNA expression was detected in celecoxib group and compatibility group. And suppressive effect was significantly stronger in compatibility group than either in Astragalus membranaceus group or Rhizoma curcumae group. Both Rosiglitazone group and compatibility group had the best suppressive effect on NF-κB mRNA and the best promoting effect on PPARγ mRNA.

CONCLUSION: Astragalus membranaceus and Rhizoma curcumae′s compatibility has better effect with marked suppressive effect. The compatibility group showed stronger suppressive effect on COX-2 expression than Astragalus membranaceus and Rhizoma curcumae used alone, closing to Celecoxib. Its suppressive effect on COX-2 may be produced through the signal pathway of PPARγ/NF-κB.

Epstein-Barr virus renders the infected natural killer cell line, NKL resistant to doxorubicin-induced apoptosis

We established two Epstein–Barr virus (EBV)-infected NKL sublines, which acquired stress resistant phenotype against DNA damage and starvation compared with EBV-negative NKL. EBV-rendered doxorubicin resistance at least partially through NF-κB activation and the resultant sustenance of antiapoptotic proteins including Bcl-X_L and FLIP_L/S.

Overexpression of the zinc uptake transporter hZIP1 inhibits nuclear factor-kappaB and reduces the malignant potential of prostate cancer cells in vitro and in vivo

PURPOSE

Intracellular zinc levels and expression of the zinc uptake transporter, hZIP1, are markedly down-regulated in prostate adenocarcinomatous tissue compared with normal prostate tissue. Our previous studies have shown that zinc inhibits nuclear factor-kappaB (NF-kappaB) activity and reduces the malignant potential of prostate cancer cells in vitro. In this study, we investigate the functional effect of hZIP1 overexpression on NF-kappaB activity and tumorigenic potential in human prostate cancer cells in vitro and in vivo.

EXPERIMENTAL DESIGN

NF-kappaB activity in PC-3 prostate cancer cells was examined by Western blotting and luciferase assay. ELISA was used to examine the expression of tumorigenic cytokines. Terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, adhesion, and invasiveness assays were used to assess the malignant potential of tumor cells. The effect of hZIP1 overexpression on prostate tumor progression in vivo was assessed using a xenograft model.

RESULTS

Overexpression of the hZIP1 transporter in PC-3 cells results in significant inhibition of NF-kappaB activity in the presence of physiologic levels of zinc. NF-kappaB inhibition coincides with a reduction in expression of several NF-kappaB controlled prometastatic and antiapoptotic factors as well as sensitization of the cells to etoposide and tumor necrosis factor-mediated apoptosis-inducing ligand-mediated cell death. Moreover, overexpression of the hZIP1 transporter induces regression of prostate tumor growth in a xenograft model.

CONCLUSIONS

Our results show that hZIP1 overexpression has a functional effect on the malignant potential of prostate cancer cells via inhibition of NF-kappaB-dependent pathways and support the concept that hZIP1 may function as a tumor suppressor gene in prostate cancer.

NF-kappaB1 and c-Rel cooperate to promote the survival of TLR4-activated B cells by neutralizing Bim via distinct mechanisms

The nuclear factor-kappaB (NF-kappaB) pathway is crucial for the survival of B cells stimulated through Toll-like receptors (TLRs). Here, we show that the heightened death of TLR4-activated nfkb1(-/-) B cells is the result of a failure of the Tpl(2)/MEK/ERK pathway to phosphorylate the proapo-ptotic BH3-only protein Bim and target it for degradation. ERK inactivation of Bim after TLR4 stimulation is accompanied by an increase in A1/Bim and Bcl-x(L)/Bim complexes that we propose represents a c-Rel-dependent mechanism for neutralizing Bim. Together these findings establish that optimal survival of TLR4-activated B cells depends on the NF-kappaB pathway neutralizing Bim through a combination of Bcl-2 prosurvival protein induction and Tpl2/ERK-dependent Bim phosphorylation and degradation.

Proteasome inhibitors enhance TRAIL-induced apoptosis through the intronic regulation of DR5: involvement of NF-kappa B and reactive oxygen species-mediated p53 activation

Manipulation of TRAIL receptor 2 (DR5) pathway is a promising therapeutic strategy to overcome TRAIL-resistant lung cancer cells. Preclinical studies have shown that proteasome inhibitors enhance TRAIL-induced apoptosis in lung cancer cells, but the underlying mechanism has not been fully elucidated. In this study, we demonstrated the enhancement of TRAIL-mediated apoptosis in human alveolar epithelial cells by proteasome inhibitors that up-regulate DR5 expression. This effect was blocked by DR5-neutralizing Ab. Using reporter assay, we demonstrated that the p53 and NF-kappaB elements on the DR5 first intron region were involved in proteasome inhibitor-induced DR5 expression. Both p53 small interfering RNA and NF-kappaB inhibitor suppressed DR5 expression, strengthening the significance of p53 and NF-kappaB in DR5 transcription. The protein stability, Ser(392) phosphorylation and Lys(373)/Lys(382) acetylation of p53 were enhanced by MG132. In addition to p53, IkappaBalpha degradation and NF-kappaB translocation was also observed. Moreover, the binding of p53 and p65 to the first intron of DR5 was demonstrated by DNA affinity protein-binding and chromatin immunoprecipitation assays. Intracellular reactive oxygen species (ROS) generation after MG132 treatment contributed to p53, but not p65 nuclear translocation and DNA-binding activity. ROS scavenger dramatically inhibited the apoptosis induced by proteasome inhibitors plus TRAIL. The p53-null H1299 cells were resistant to proteasome inhibitor-induced DR5 up-regulation and enhancement of TRAIL-induced apoptosis. These findings reveal that proteasome inhibitor-mediated NF-kappaB and ROS-dependent p53 activation are contributed to intronic regulation of DR5 transcription, and resulted in the subsequent enhancement of TRAIL-induced apoptosis in human lung cancer cells.

Platelet-activating factor stimulates ovine foetal pulmonary vascular smooth muscle cell proliferation: role of nuclear factor-kappa B and cyclin-dependent kinases

OBJECTIVE

Platelet-activating factor (PAF) is implicated in pathogenesis of persistent pulmonary hypertension of the neonate (PPHN); PAF is a mitogen for lung fibroblasts. PAF's role in pulmonary vascular smooth muscle cell (PVSMC) proliferation and in hypoxia-induced pulmonary vein (PV) remodelling has not been established and mechanisms for PAF's cell-proliferative effects are not well understood. We investigated involvement of PAF and PAF receptors in PVSMC proliferation.

MATERIALS AND METHODS

Cells from pulmonary arteries (SMC-PA) and veins (SMC-PV) were serum starved for 72 h in 5% CO2 in air (normoxia). They were cultured for 24 h more in normoxia or 2% O(2) (hypoxia) in 0.1% or 10% foetal bovine serum with 5 microCi/well of [(3)H]-thymidine, with and without 10 nm PAF. Nuclear factor-kappa B (NF-kappaB), CDK2 and CDK4 protein expression, and their roles in cell proliferation control were studied.

RESULTS

PAF and hypoxia increased SMC-PA and SMC-PV proliferation. WEB2170 inhibited PAF-induced cell proliferation while lyso-PAF had no effect. SMC-PV proliferated more than SMC-PA and PAF plus hypoxia augmented NF-kappaB protein expression. NF-kappaB inhibitory peptide attenuated PAF-induced cell proliferation by 50% and PAF increased CDK2 and CDK4 protein expression. The data show that hypoxia and PAF up-regulate PVSMC proliferation via PAF receptor-specific pathway involving NF-kappaB, CDK2 and CDK4 activations.

CONCLUSION

They suggest that in vivo, in foetal lung low-oxygen environment, where PAF level is high, proliferation of PVSMC will occur readily to modulate PV development and that failure of down-regulation of PAF effects postnatally may result in PPHN.

Dysregulation of apoptotic signaling in cancer: molecular mechanisms and therapeutic opportunities

Apoptosis is a tightly regulated cell suicide program that plays an essential role in the maintenance of tissue homeostasis by eliminating unnecessary or harmful cells. Defects in this native defense mechanism promote malignant transformation and frequently confer chemoresistance to transformed cells. Indeed, the evasion of apoptosis has been recognized as a hallmark of cancer. Given that multiple mechanisms function at many levels to orchestrate the regulation of apoptosis, a multitude of opportunities for apoptotic dysregulation are present within the intricate signaling network of cell. Several of the molecular mechanisms by which cancer cells are protected from apoptosis have been elucidated. These advances have facilitated the development of novel apoptosis-inducing agents that have demonstrated single-agent activity against various types of cancers cells and/or sensitized resistant cancer cells to conventional cytotoxic therapies. Herein, we will highlight several of the central modes of apoptotic dysregulation found in cancer. We will also discuss several therapeutic strategies that aim to reestablish the apoptotic response, and thereby eradicate cancer cells, including those that demonstrate resistance to traditional therapies.

Thioredoxin-like 6 protects retinal cell line from photooxidative damage by upregulating NF-kappaB activity

Apoptosis is the common pathway to photoreceptor cell death in many eye diseases including age-related macular degeneration which affects more than 8 million individuals in the United States alone. RdCVF, a truncated mouse thioredoxin is specifically expressed by rod photoreceptor cells and prevents the apoptosis of cone cells. However the protective mechanism of RdCVF and the implications of its human homologue, thioredoxin-like 6 (TXNL6), on the apoptosis of retinal cells remain unknown. In this study, we examined the function of TXNL6 and investigated its mechanism of protection using a cone photoreceptor cell line, 661W. We found that the photooxidative stress-induced degradation of NF-kappaB proteins is rescued by overexpression of TXNL6, which enabled the NF-kappaB transactivation activity. Furthermore, the overexpression of TXNL6 rescued the photooxidative stress-induced apoptosis of 661W cells. Interestingly, this protective effect was significantly blocked by NF-kappaB specific inhibitors demonstrating that TXNL6 exerts its protective effect against apoptosis via NF-kappaB. Taken together, our study shows that the TXNL6 probably protects retinal cells from photooxidative damage-induced apoptosis via upregulation of NF-kappaB activity. The identification of TXNL6 and the demonstration of its protective mechanism offer new insights into treatment possibilities for photoreceptor cell degradation.

Death receptor-4 (DR4) expression is regulated by transcription factor NF-kappaB in response to etoposide treatment

Tumour necrosis factor related apoptosis inducing ligand (TRAIL) binds to death receptor 4 (DR4) activating the apoptotic signalling pathway. DNA damaging agents (genotoxins) such as etoposide increase DR4 expression and when combined with TRAIL induce a synergistic apoptotic response. The mechanism for up-regulation of DR4 expression following genotoxin treatment is not well understood. Herein, we determined that transcription factor NF-kappaB plays a role in genotoxin induced DR4 expression. Increased expression of DR4 following etoposide treatment is blocked by inhibition of the NF-kappaB pathway. Moreover, expression of the p65 subunit of NF-kappaB is sufficient to increase DR4 protein levels. Indeed, knockdown of p65 by RNA interference blocked etoposide up-regulation of DR4. We further identified a functional NF-kappaB binding site located in the DR4 promoter. Mutation of this site abrogates the induction of luciferase activity after p65 over-expression. Furthermore, electromobility shift assays and chromatin immunoprecipitaton suggest that NF-kappaB binds to this site upon etoposide treatment. MEK kinase 1 (MEKK1) is a serine threonine kinase that is activated following etoposide treatment and activates NF-kappaB. Expression of the kinase inactive MEKK1 (MEKK1-KM) abrogates the up-regulation of DR4 after etoposide treatment. Taken together, NF-kappaB plays a role in up-regulation of DR4 following etoposide treatment.

Induction of nuclear factor-kappaB and its downstream genes by TNF-alpha and IL-1beta has a pro-apoptotic role in pancreatic beta cells

AIMS/HYPOTHESIS

IL-1beta and TNF-alpha contribute to pancreatic beta cell death in type 1 diabetes. Both cytokines activate the transcription factor nuclear factor-kappaB (NF-kappaB), but recent observations suggest that NF-kappaB blockade prevents IL-1beta + IFN-gamma- but not TNF-alpha + IFN-gamma-induced beta cell apoptosis. The aim of the present study was to compare the effects of IL-1beta and TNF-alpha on cell death and the pattern of NF-kappaB activation and global gene expression in beta cells.

METHODS

Cell viability was measured after exposure to IL-1beta or to TNF-alpha alone or in combination with IFN-gamma, and blockade of NF-kappaB activation or protein synthesis. INS-1E cells exposed to IL-1beta or TNF-alpha in time course experiments were used for IkappaB kinase (IKK) activation assay, detection of p65 NF-kappaB by immunocytochemistry, real-time RT-PCR and microarray analysis.

RESULTS

Blocking NF-kappaB activation protected beta cells against IL-1beta + IFNgamma- or TNFalpha + IFNgamma-induced apoptosis. Blocking de novo protein synthesis did not increase TNF-alpha- or IL-1beta-induced beta cell death, in line with the observations that cytokines induced the expression of the anti-apoptotic genes A20, Iap-2 and Xiap to a similar extent. Microarray analysis of INS-1E cells treated with IL-1beta or TNF-alpha showed similar patterns of gene expression. IL-1beta, however, induced a higher rate of expression of NF-kappaB target genes putatively involved in beta cell dysfunction and death and a stronger activation of the IKK complex, leading to an earlier translocation of NF-kappaB to the nucleus.

CONCLUSIONS/INTERPRETATION

NF-kappaB activation in beta cells has a pro-apoptotic role following exposure not only to IL-1beta but also to TNF-alpha. The more marked beta cell death induced by IL-1beta is explained at least in part by higher intensity NF-kappaB activation, leading to increased transcription of key target genes.

Legionella pneumophila EnhC is required for efficient replication in tumour necrosis factor alpha-stimulated macrophages

Legionella pneumophila enhC(-) mutants were originally identified as being defective for uptake into host cells. In this work, we found that the absence of EnhC resulted in defective intracellular growth when dissemination of intracellular bacteria to neighbouring cells was expected to occur. No such defect was observed during growth within the amoeba Dictyostelium discoideum. Culture supernatants containing the secreted products of infected macrophages added to host cells restricted the growth of the DeltaenhC strain, while tumour necrosis factor alpha (TNF-alpha), at concentrations similar to those found in macrophage culture supernatants, could reproduce the growth restriction exerted by culture supernatants on L. pneumophilaDeltaenhC. The absence of EnhC also caused defective trafficking of the Legionella-containing vacuole in TNF-alpha-treated macrophages. EnhC was shown to be an envelope-associated protein largely localized to the periplasm, with its expression induced in post-exponential phase, as is true for many virulence-associated proteins. Furthermore, the absence of EnhC appeared to affect survival under stress conditions, as the DeltaenhC mutant was more susceptible to H(2)O(2) treatment than the wild-type strain. EnhC therefore is a unique virulence factor that is required for growth specifically when macrophages have heightened potential to restrict microbial replication.

Induction of a pro-apoptotic ATM-NF-kappaB pathway and its repression by ATR in response to replication stress

The transcription factor NF-kappaB has critical functions in biologic responses to genotoxic stimuli. Activation of NF-kappaB in response to DNA double strand break (DSB) inducers can be mediated by ATM (ataxia telangiectasia mutated)-dependent phosphorylation of NEMO (NF-kappaB essential modulator). Here, we show that the replication stress inducers hydroxyurea (HU) and aphidicolin also activate this ATM-dependent signalling pathway. We further show that ATR (ATM- and Rad3-related) interacts with NEMO but surprisingly does not cause NEMO phosphorylation. Consequently, ATR represses NF-kappaB activation induced by replication stress. Reduction or increase of ATR expression by RNA interference or overexpression increased or reduced ATM-NEMO association and NF-kappaB activation induced by HU. Apoptosis gene expression and chromatin immunoprecipitation analyses indicated that HU and the DSB inducer etoposide caused complex patterns of NF-kappaB-dependent pro- and antiapoptotic gene expression with the overall outcome for the former being pro-apoptotic, whereas the latter antiapoptotic. Thus, replication stress and DSB inducers activate NF-kappaB through a conserved pathway with opposite biologic outcomes, and ATR antagonizes ATM function at least in part by competing for NEMO association.

The nuclear factor-kappaB and p53 pathways function independently in primary cells and transformed fibroblasts responding to genotoxic damage

With nuclear factor-kappaB (NF-kappaB) and p53 functions generally having disparate outcomes for cell survival and cell division, understanding how these pathways are coordinated following a common activation signal such as DNA damage has important implications for cancer therapy. Conflicting reports concerning NF-kappaB and p53 interplay in different cell line models prompted a reexamination of this issue using mouse primary thymocytes and embryonic fibroblasts, plus fibroblasts transformed by E1A12S. Here, we report that following the treatment of these cells with a range of stress stimuli, p53 and NF-kappaB were found to regulate cell cycling and survival independently.

Ellagic acid induces apoptosis through inhibition of nuclear factor κB in pancreatic cancer cells

AIM: To determine the effect of ellagic acid on apop-tosis and proliferation in pancreatic cancer cells and to determine the mechanism of the pro-survival effects of ellagic acid.

METHODS: The effect of ellagic acid on apoptosis was assessed by measuring Phosphatidylserine externalization, caspase activity, mitochondrial membrane potential and DNA fragmentation; and proliferation by measuring DNA thymidine incorporation. Mitochondrial membrane potential was measured in permeabilized cells, and in isolated mitochondria. Nuclear factor κB (NF-κB) activity was measured by electromobility shift assay (EMSA).

RESULTS: We show that ellagic acid, a polyphenolic compound in fruits and berries, at concentrations 10 to 50 mmol/L stimulates apoptosis in human pancreatic adenocarcinoma cells. Further, ellagic acid decreases proliferation by up to 20-fold at 50 mmol/L. Ellagic acid stimulates the mitochondrial pathway of apoptosis associated with mitochondrial depolarization, cytochrome C release, and the downstream caspase activation. Ellagic acid does not directly affect mitochondria. Ellagic acid dose-dependently decreased NF-κB binding activity. Furthermore, inhibition of NF-κB activity using IkB wild type plasmid prevented the effect of ellagic acid on apoptosis.

CONCLUSION: Our data indicate that ellagic acid stimulates apoptosis through inhibition of the prosu-rvival transcription factor NF-κB.

Renal cell apoptosis induced by nephrotoxic drugs: cellular and molecular mechanisms and potential approaches to modulation

Apoptosis plays a central role not only in the physiological processes of kidney growth and remodeling, but also in various human renal diseases and drug-induced nephrotoxicity. We present in a synthetic fashion the main molecular and cellular pathways leading to drug-induced apoptosis in kidney and the mechanisms regulating it. We illustrate them using three main nephrotoxic drugs (cisplatin, gentamicin, and cyclosporine A). We discuss the main regulators and effectors that have emerged as key targets for the design of therapeutic strategies. Novel approaches using gene therapy, antisense strategies, recombinant proteins, or compounds obtained from both classical organic and combinatorial chemistry are examined. Finally, key issues that need to be addressed for the success of apoptosis-based therapies are underlined.

Selection and characterization of anti-NF-kappaB p65 RNA aptamers

NF-kappaB transcription factors include a group of five mammalian proteins that form hetero- or homodimers and regulate hundreds of target genes involved in acute inflammation, HIV-1 transcription activation, and resistance to cancer therapy. We previously used in vitro selection to develop a small RNA aptamer (anti-p50) that binds the DNA-binding domain of NF-kappaB p50(2) with low nanomolar affinity but does not bind NF-kappaB p65(2). Here, we report the in vitro selection of anti-NF-kappaB p65 RNA aptamers using parallel in vitro selections with either a fully randomized RNA library or a degenerate RNA library based on the primary sequence of the 31-nucleotide anti-p50 RNA aptamer. We report the characterization of these aptamers with respect to NF-kappaB target specificity, affinity, minimal sequence requirements, secondary structure, and competition with DNA kappaB sites. These results expand opportunities for artificial inhibition of NF-kappaB transcription factor dimers containing p65 subunits.

BAY 11-7082 induces cell death through NF-kappaB-independent mechanisms in the Ewing's sarcoma family of tumours

The role of NF-kappaB in the Ewing's sarcoma family of tumours (ESFT) and their response to fenretinide has been investigated. Basal levels of phosphorylated NF-kappaB were low in all ESFT cells. BAY 11-7082 decreased cell viability, which was accompanied by caspase-3 cleavage. This was independent of the increase in reactive oxygen species, p38(MAPK) phosphorylation and expression of NF-kappaB target proteins. NF-kappaB knockdown did not induce death under normal growth conditions, but did reduce TNFalpha-dependent cell survival. Fenretinide-induced apoptosis was independent of NF-kappaB. BAY 11-7082-induced cell death through an NF-kappaB-independent mechanism and enhanced cell death when combined with fenretinide.

Proteasome inhibitors induce apoptosis of prostate cancer cells by inducing nuclear translocation of IkappaBalpha

Proteasome inhibitors are known to suppress the proteasome-mediated degradation of IkappaBalpha in stimulated cells. This results in the cytoplasmic retention of NFkappaB and its reduced nuclear transcriptional activity. In this study, we show that in the metastatic prostate cancer cells, the proteasome inhibitors exhibit a novel, previously unrecognized effect: they increase the cellular levels of IkappaBalpha, which then translocates to the nucleus, associates with the nuclear p65 NFkappaB, thus inhibiting the constitutive NFkappaB DNA binding activity and inducing apoptosis. The proteasome inhibition-induced nuclear translocation of IkappaBalpha is dependent on de novo protein synthesis, occurs also in other cell types, and does not require IkappaBalpha phosphorylation on Ser-32. Since NFkappaB activity is constitutively increased in many human cancers as well as in inflammatory disorders, the proteasome inhibition-induced nuclear translocation of IkappaBalpha could thus provide a new therapeutic strategy aimed at the specific inhibition of NFkappaB activity by the nuclear IkappaBalpha.

Gonadotropin-regulated testicular helicase (DDX25), an essential regulator of spermatogenesis, prevents testicular germ cell apoptosis

Gonadotropin-regulated testicular helicase (GRTH)/DDX25 is an essential post-transcriptional regulator of spermatogenesis. In GRTH null mice severe apoptosis was observed in spermatocytes entering the metaphase of meiosis. Pro- and anti-apoptotic factors were found to be under GRTH regulation in comparative studies of spermatocytes from wild type and GRTH(-/-) knock-out (KO) mice. KO mice displayed decreased levels of Bcl-2 and Bcl-xL (anti-apoptotic factors), an increase in Bid, Bak, and Bad (pro-apoptotic), reduced phospho-Bad, and release of cytochrome c. Also, an increase on Smac, a competitor of inhibitor apoptotic proteins that release caspases, was observed. These changes caused an increase in cleavage of caspases 9 and 3, activation of caspase 3 and increases in cleavage products of PARP. The half-life of caspase 3 transcripts was markedly increased in KO, indicating that GRTH had a negative role on its mRNA stability. IkappaBalpha, which sequesters NF-kappaB from its transcriptional activation of pro-apoptotic genes, was highly elevated in KO, and its phospho-form, which promotes its dissociation, was reduced. The increase of HDAC1 and abolition of p300 expression in KO indicated a nuclear action of GRTH on the NF-kappaB-mediated transcription of anti-apoptotic genes. It also regulates the associated death domain pathway and caspase 8-mediated events. GRTH-mediated apoptotic regulation was further indicated by its selective binding to pro- and anti-apoptotic mRNAs. These studies have demonstrated that GRTH, as a component of mRNP particles, acts as a negative regulator of the tumor necrosis factor receptor 1 and caspase pathways and promotes NF-kappaB function to control apoptosis in spermatocytes of adult mice.

Induction of apoptosis in Epstein-Barr virus-infected B-lymphocytes by the NF-kappaB inhibitor DHMEQ

Epstein-Barr virus (EBV) causes EBV-associated lymphoproliferative diseases in patients with profound immune suppression. Most of these diseases are life-threatening and the prognosis of AIDS-associated lymphomas is extremely unfavorable. Polyclonal expansion of virus infected B-cell predisposes them to transformation. We investigated the possibility of nuclear factor kappa B (NF-kappaB) inhibition by dehydroxymethylepoxyquinomicin (DHMEQ) for the treatment and prevention of EBV-associated lymphoproliferative diseases. We examined the effect of DHMEQ on apoptosis induction in four EBV-transformed lymphoblastoid cell lines as well as peripheral blood mononuclear cells infected with EBV under immunosuppressed condition. DHMEQ inhibits NF-kappaB activation in EBV-transformed lymphoblastoid cell lines and induces apoptosis by activation of mitochondrial and membranous pathways. Using an in vivo NOD/SCIDgammac mouse model, we showed that DHMEQ has a potent inhibitory effect on the growth of lymphoblastoid cells. In addition, DHMEQ selectively purges EBV-infected cells expressing latent membrane protein (LMP) 1 from peripheral blood mononuclear cells and inhibits the outgrowth of lymphoblastoid cells. These results suggest that NF-kappaB is a molecular target for the treatment and prevention of EBV-associated lymphoproliferative diseases. As a potent NF-kappaB inhibitor, DHMEQ is a potential compound for applying this strategy in clinical medicine.

Nuclear factor kappa B and hepatitis viruses

BACKGROUND

Hepatitis can be caused by a number of viruses, which have similar clinical manifestations and render infected individuals at high risk of death from cirrhosis and liver cancer. Current therapies for hepatitis have limited effects and unsatisfactory patient outcomes. Nuclear factor kappa B (NF-kappaB) is critical for immune and inflammatory responses. During its lifetime the cell demands specific and highly regulated control of NF-kappaB activity.

OBJECTIVE

To develop novel strategies to overcome various hepatitides and related liver cancer with NF-kappaB as the key point.

METHODS

All aspects of NF-kappaB control with regard to hepatitis are covered.

RESULTS/CONCLUSION

NF-kappaB plays an important role in the process of hepatitis and is hypothesized to be an anti-cancer factor in the subsequent inflammation-associated hepatocarcinogenesis.

Differential roles of Yersinia outer protein P-mediated inhibition of nuclear factor-kappa B in the induction of cell death in dendritic cells and macrophages

Yersinia outer protein P (YopP) induces cell death in macrophages and dendritic cells (DC). In DC this YopP-dependent cell death coincides with the inhibition of nuclear factor-kappa B (NF-kappaB) activation. However, as shown by measurement of propidium iodide uptake via disrupted cellular membranes, the preincubation of DC with several NF-kappaB inhibitors prior to infection with Yersinia did not restore the death-inducing capacity of a YopP-deficient Yersinia mutant. These results suggest that in contrast to macrophages, in DC the YopP-dependent inhibition of NF-kappaB activation is not causative for the induction of cell death. Instead, in DC, the inhibition of mitogen-activated protein kinases (MAPKs), in particular, p38 and c-Jun N-terminal kinase, prior to infection with a YopP-deficient Yersinia mutant substituted the death-inducing capacity of the Yersinia wild-type strain, indicating that the YopP-dependent inhibition of MAPKs mediates Yersinia-induced DC death. The differences between DC and macrophages in the mechanisms of cell death induction by YopP presented herein might be crucial for the function of these antigen-presenting cells.

Role of insulin metabolism disturbances in the development of Alzheimer disease: mini review

Alzheimer disease (AD) is the most common form of dementia. Different pathogenic processes have been studied that underlie characteristic changes of AD, including A beta protein aggregation, tau phosphorylation, neurovascular dysfunction, and inflammatory processes. Insulin exerts pleiotropic effects in neurons, such as the regulation of neural proliferation, apoptosis, and synaptic transmission. In this setting, any disturbance in the metabolism of insulin in the central nervous system (CNS) may put unfavorable effects on CNS function. It seems that disturbances in insulin metabolism, especially insulin resistance, play a role in most pathogenic processes that promote the development of AD. In this article, the relationships of disturbances in the metabolism of insulin in CNS with A beta peptides aggregation, tau protein phosphorylation, inflammatory markers, neuron apoptosis, neurovascular dysfunction, and neurotransmitter modulation are discussed, and future research directions are provided.

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.

Mechanisms by which S-albuterol induces human bronchial smooth muscle cell proliferation

BACKGROUND

Racemic albuterol is a 50:50 mixture of the R-isomer, levalbuterol, and the S-isomer, S-albuterol. S-Albuterol increases airway hyperresponsiveness to spasmogens, exacerbates asthmatic conditions and stimulates cell growth, whereas levalbuterol attenuates cell growth in culture. The mechanisms of S-albuterol-induced cell proliferation are not well understood. We studied the role of albuterol isomers and intracellular cell cycle regulators on proliferation of human bronchial smooth muscle cells.

METHODS

Serum-starved cells (72 h) were fed test agents for 24 h and cell proliferation was measured. The expression of nuclear factor-kappaB inhibitory protein IkappaBalpha, nuclear factor-kappaB, cyclin-dependent kinases 2 and 4, interleukin (IL)-6, and retinoblastoma and platelet-activating factor (PAF) receptor protein were measured by Western blotting.

RESULTS

S-Albuterol, PAF and platelet-derived growth factor stimulated cell proliferation, but levalbuterol and the racemic mixture inhibited cell proliferation compared with the effect of 5% fetal bovine serum alone. The proliferative effect of platelet-derived growth factor on S-albuterol was not additive, suggesting that the 2 mediators act by different mechanisms. S-Albuterol induced greater expression of all the measured proteins than either levalbuterol, the racemic mixture or 5% fetal bovine serum. S-Albuterol stimulated IL-6 secretion and abolished the ability of levalbuterol to inhibit IL-6 secretion.

CONCLUSION

Our data show that S-albuterol stimulates cell proliferation by activating expression and phosphorylation of several intracellular mitogenic proteins and may exacerbate asthma by stimulating the release of IL-6. Induction of PAF receptor protein expression by S-albuterol strongly suggests that S-albuterol may exert its adverse effects by binding to a G protein-coupled receptor such as the PAF receptor.

Toll-like receptors' two-edged sword: when immunity meets apoptosis

Toll-like receptors (TLR) have emerged as key players in the detection of pathogens and the induction of anti-microbial immune response. TLR recognize pathogen-associated molecular patterns, and trigger anti-microbial innate immune responses ranging from the secretion of pro-inflammatory mediators to the increase of natural killer cell cytotoxicity. Besides activating the innate immune response, TLR engagement also shapes the adaptive immune response. Indeed, the broad diversity of signaling pathways initiated by TLR is progressively unraveled. Recent reports suggested that among the anti-microbial defenses they initiate, members of the TLR family can induce apoptosis. This review focuses on this newly described function of TLR, and emphasizes the similarities and differences between the different apoptosis-signaling pathways described downstream of TLR. The functional relevance of TLR-triggered apoptosis is also discussed, as therapeutic applications are likely to ensue in the near future.

Maternal diabetes modulates renal morphogenesis in offspring

Maternal diabetes leads to an adverse in utero environment, but whether maternal diabetes impairs nephrogenesis is unknown. Diabetes was induced with streptozotocin in pregnant Hoxb7-green fluorescence protein mice at embryonic day 13, and the offspring were examined at several time points after birth. Compared with offspring of nondiabetic controls, offspring of diabetic mice had lower body weight, body size, kidney weight, and nephron number. The observed renal dysmorphogenesis may be the result of increased apoptosis, because immunohistochemical analysis revealed significantly more apoptotic podocytes as well as increased active caspase-3 immunostaining in the renal tubules compared with control mice. Regarding potential mediators of these differences, offspring of diabetic mice had increased expression of intrarenal angiotensinogen and renin mRNA, upregulation of NF-kappaB isoforms p50 and p65, and activation of the NF-kappaB pathway. In conclusion, maternal diabetes impairs nephrogenesis, possibly via enhanced intrarenal activation of the renin-angiotensin system and NF-kappaB signaling.

Repression of B-cell linker (BLNK) and B-cell adaptor for phosphoinositide 3-kinase (BCAP) is important for lymphocyte transformation by rel proteins

Persistent Rel/nuclear factor-kappaB (NF-kappaB) activity is a hallmark of many human cancers, and the Rel proteins are implicated in leukemia/lymphomagenesis but the mechanism is not fully understood. Microarray analysis to identify transformation-impacting genes regulated by NF-kappaB's oncogenic v-Rel and c-Rel proteins uncovered that Rel protein expression leads to transcriptional repression of key B-cell receptor (BCR) components and signaling molecules like B-cell linker (BLNK), the B-cell adaptor for phosphoinositide 3-kinase (BCAP) and immunoglobulin lambda light chain (Ig lambda), and is accompanied by a block in BCR-mediated activation of extracellular signal-regulated kinase, Akt, and c-Jun-NH(2)-kinase in response to anti-IgM. The BLNK and BCAP proteins were also down-regulated in lymphoid cells expressing a transformation-competent chimeric RelA/v-Rel protein, suggesting a correlation with the capacity of Rel proteins to transform lymphocytes. DNA-binding studies identified functional NF-kappaB-binding sites, and chromatin immunoprecipitation (ChIP) data showed binding of Rel to the endogenous blnk and bcap promoters in vivo. Importantly, restoration of either BLNK or BCAP expression strongly inhibited transformation of primary chicken lymphocytes by the potent NF-kappaB oncoprotein v-Rel. These findings are interesting because blnk and other BCR components and signaling molecules are down-regulated in primary mediastinal large B-cell lymphomas and Hodgkin's lymphomas, which depend on c-Rel for survival, and are consistent with the tumor suppressor function of BLNK. Overall, our results indicate that down-regulation of BLNK and BCAP is an important contributing factor to the malignant transformation of lymphocytes by Rel and suggest that gene repression may be as important as transcriptional activation for Rel's transforming activity.