The anti-inflammatory sesquiterpene lactone helenalin inhibits the transcription factor NF-kappaB by directly targeting p65

Induction of human leukemia HL-60 cell differentiation via a PKC/ERK pathway by helenalin, a pseudoguainolide sesquiterpene lactone

Helenalin, a cell-permeable pseudoguainolide sesquiterpene lactone, is a potent anti-inflammatory agent that inhibits nuclear factor-kappa B (NF-kappa B) DNA binding activity. In this report, we investigated the effect of helenalin on cellular differentiation in the human promyelocytic leukemia HL-60 cell culture system. Helenalin by itself markedly induced HL-60 cell differentiation in a concentration-dependent manner. Cytofluorometric analysis and cell morphologic studies indicated that helenalin induced cell differentiation predominantly into granulocytes. Protein kinase C (PKC) and extracellular signal-regulated kinase (ERK) inhibitors significantly inhibited HL-60 cell differentiation induced by helenalin, while p38 mitogen-activated protein kinase (MAPK) inhibitors did not. Moreover, helenalin enhanced PKC activity and protein level of PKC beta I and PKC beta II isoforms, and also increased the level of pERK in a concentration-dependent manner. In addition, the enhanced levels of cell differentiation closely correlated with the decreased levels of NF-kappa B binding activity by helenalin. These results indicate that PKC, ERK, and NF-kappa B may be involved in HL-60 cell differentiation induced by helenalin.

Activation of Nuclear Factor-κB Contributes to Induction of Death Receptors and Apoptosis by the Synthetic Retinoid CD437 in DU145 Human Prostate Cancer Cells

Activation of the transcription factor, nuclear factor-kappaB (NF-kappaB), results in up-regulation of not only antiapoptotic genes but also proapoptotic genes, including death receptor 4 (DR4) and death receptor 5 (DR5). Therefore, NF-kappaB activation either suppresses or promotes apoptosis depending on the type of stimulus or cell context. We showed previously that the synthetic retinoid, 6-[3-(1-adamantyl)-4-hydroxyphenyl]-2-naphthalene carboxylic acid (CD437), effectively induces apoptosis particularly in androgen-independent prostate carcinoma cells. This effect was associated with the ability of CD437 to induce the expression of DR4 and DR5. In the present study, we examined the hypothesis that NF-kappaB activation plays a role in CD437-induced death receptor expression and apoptosis. Treatment of DU145 cells with CD437 resulted in a rapid decrease (> or = 3 hours) of IkappaBalpha, which was accompanied by increased translocation of the NF-kappaB subunit p65 from the cytoplasm to the nucleus and increased NF-kappaB DNA-binding activity (> or = 4 hours). The NF-kappaB inhibitor, helenalin, inhibited CD437-induced IkappaBalpha reduction and p65 nuclear translocation. Accordingly, it also abrogated CD437-induced up-regulation of DR4, activation of caspase-8 and caspase-3, and increased DNA fragmentation. Overexpression of an IkappaBalpha dominant-negative mutant blocked not only CD437-induced p65 nuclear translocation but also DR4 up-regulation, caspase activation, and DNA fragmentation. CD437 was unable to decrease IkappaBalpha protein levels and up-regulate DR4 expression in CD437-resistant DU145 cells. Moreover, knockdown of Fas-associated death domain, caspase-8, and DR4, respectively, suppressed CD437-induced apoptosis. Collectively, these results indicate that CD437 activates NF-kappaB via decreasing IkappaBalpha protein and thereby induces DR4 expression and subsequent apoptosis in DU145 cells.

Apoptosis Induction by a Novel Retinoid-Related Molecule Requires Nuclear Factor-κB Activation

Nuclear factor-kappaB (NF-kappaB) activation has been shown to be both antiapoptotic and proapoptotic depending on the stimulus and the specific cell type involved. NF-kappaB activation has also been shown to be essential for apoptosis induction by a number of agents. The novel retinoid-related molecule 4-[3-Cl-(1-adamantyl)-4-hydroxyphenyl]-3-chlorocinnamic acid (3-Cl-AHPC) activates NF-kappaB with subsequent apoptosis in a number of cell types. We have found that NF-kappaB activation is essential for 3-Cl-AHPC-mediated apoptosis. 3-Cl-AHPC activates NF-kappaB through IKKalpha kinase activation and the subsequent degradation of IkappaB alpha. IKKalpha kinase activation is associated with IKKalpha-enhanced binding to HSP90. The HSP90 inhibitor geldanamycin enhances the degradation of IKKalpha and blocks 3-Cl-AHPC activation of NF-kappaB and 3-Cl-AHPC-mediated apoptosis. In addition, inhibition of IkappaB alpha degradation using a dominant-negative IkappaB alpha inhibits 3-Cl-AHPC-mediated apoptosis. NF-kappaB p65 activation is essential for 3-Cl-AHPC apoptosis induction as evidenced by the fact that inhibition of p65 activation utilizing the inhibitor helenalin or loss of p65 expression block 3-Cl-AHPC-mediated apoptosis. NF-kappaB has been shown to be antiapoptotic through its enhanced expression of a number of antiapoptotic proteins including X-linked inhibitor of apoptosis protein (XIAP), c-IAP1, and Bcl-X(L). Whereas exposure to 3-Cl-AHPC results in NF-kappaB activation, it inhibits the expression of XIAP, c-IAP1, and Bcl-X(L) and enhances the expression of proapoptotic molecules, including the death receptors DR4 and DR5 as well as Fas and Rip1. Thus, 3-Cl-AHPC, which is under preclinical development, has pleotrophic effects on malignant cells resulting in their apoptosis.

Ethacrynic acid inhibits multiple steps in the NF-kappaB signaling pathway

Ethacrynic acid has been used as a safe and effective diuretic for more than 30 years. In this study, we tested the hypothesis that ethacrynic acid is also an anti-inflammatory agent that inhibits signaling by the proinflammatory transcription factor NF-kappaB. We showed that ethacrynic acid inhibited luciferase expression in lipopolysaccharide-stimulated macrophage-like RAW 264.7 cells transfected with an NF-kappaB-dependent luciferase reporter vector and also inhibited NF-kappaB DNA binding in lipopolysaccharide-stimulated RAW 264.7 cells (electrophoretic mobility shift assay). Ethacrynic acid inhibited degradation of IkappaBalpha and IkappaBbeta in lipopolysaccharide-stimulated RAW 264.7 cells. Ethacrynic acid impaired DNA binding of wild-type p65 subunits of NF-kappaB in cells. However, DNA binding of a Cys--> Ser p65 mutant was not inhibited by ethacrynic acid, suggesting that ethacrynic acid inhibits DNA binding by alkylating p65 at Cys. In a cell-free system, binding of p50 homodimers to an NF-kappaB consensus sequence was inhibited by ethacrynic acid at concentrations from 10 to 100 microM, indicating that ethacrynic acid probably also covalently modifies the p50 subunit. These data indicate that ethacrynic acid inhibits activation of the NF-kappaB pathway at multiple points and suggest that this well-studied drug warrants further investigation as a potential therapeutic for various conditions that are associated with excessive inflammation.

Novel Mechanism of Inhibition of Nuclear Factor-κB DNA-Binding Activity by Diterpenoids Isolated from Isodon rubescens

The development of specific inhibitors that can block nuclear factor-kappaB (NF-kappaB) activation is an approach for the treatment of cancer, autoimmune, and inflammatory diseases. Several diterpenoids, oridonin, ponicidin, xindongnin A, and xindongnin B were isolated from the herb Isodon rubescens. These compounds were found to be potent inhibitors of NF-kappaB transcription activity and the expression of its downstream targets, cyclooxygenase-2 and inducible nitric-oxide synthase. The mechanisms of action of the diterpenoids against NF-kappaB are similar, but significant differences were also identified. All of the diterpenoids directly interfere with the DNA-binding activity of NF-kappaB to its response DNA sequence. Oridonin and ponicidin have an additional impact on the translocation of NF-kappaB from the cytoplasm to nuclei without affecting IkappaB-alpha phosphorylation and degradation. The effect of these compounds on the interaction of NF-kappaB with consensus DNA sequences is unique. Different inhibitory effects were observed when NF-kappaB bound to various DNA sequences. Both p65/p65 and p50/p50 homodimers, as well as p65/p50 heterodimer association with their responsive DNA, were inhibited. Kinetic studies on NF-kappaB-DNA interaction indicate that the diterpenoids decrease the B(max app) but have no effect on K(d app). This suggests that this class of compounds interacts with both p65 and p50 subunits at a site other than the DNA binding site and subsequently modulates the binding affinity of the transcription factor toward DNA with different NF-kappaB binding sequences. The diterpenoid structure could therefore serve as a scaffold for the development of more potent and selective NF-kappaB inhibitors that target regulated gene transcription.

NF-κB Activation Plays a Role in Superoxide-Mediated Cerebral Endothelial Dysfunction After Hypoxia/Reoxygenation

Background and Purpose— Cerebral vascular injury occurs in response to hypoxia/reoxygenation (H/R). However, the cellular signaling pathways that regulate this event remain unclear. The present study was designed to determine whether reactive oxygen species (ROS) mediate endothelial dysfunction after H/R in cerebral resistance arteries and, if so, the relative contribution of ROS, NADPH oxidase, and a nuclear factor-κB (NF-κB) pathway.

Methods— Arterial diameter and intraluminal pressure were simultaneously measured on rat posterior cerebral arteries (PCA). Superoxide was measured by 5-μmol/L lucigenin-enhanced chemiluminescence.

Results— Hypoxia/reoxygenation selectively inhibited cerebral vasodilation to the endothelium-dependent agonist acetylcholine (Ach) (0.01 to 10 μmol/L) by ≈50%. Impaired vasodilation after H/R was reversed by 2,2,6,6-tetramethylpiperidine- N -oxyl (Tempo) (100 μmol/L), a cell-permeable superoxide dismutase mimetic, and partially by ebselen (10 μmol/L), a peroxynitrite scavenger. H/R-impaired vasodilation to Ach was also preserved by apocynin (1 mmol/L), a specific inhibitor for NADPH oxidase. Correspondingly, H/R significantly increased lucigenin-detectable superoxide, which was reduced by either Tempo or apocynin, but not by allopurinol (10 μmol/L), an inhibitor of xanthine oxidase. Finally, the NF-κB inhibitors helenalin (10 μmol/L) and MG-132 (1 μmol/L) independently antagonized H/R-impaired Ach-induced vasodilation without affecting dilator response to sodium nitroprusside, an endothelium-independent vasodilator.

Conclusions— These results indicate that superoxide mediates cerebral endothelial dysfunction after hypoxia/reoxygenation largely via activation of NADPH oxidase and possibly activation of NF-κB pathway.

NF-κB Activation Is Not Required forChlamydia trachomatisInhibition of Host Epithelial Cell Apoptosis

Chlamydia trachomatis, an obligate intracellular bacterial species, is known to inhibit host cell apoptosis. However, the chlamydial antiapoptotic mechanism is still not clear. Because NF-kappaB activation is antiapoptotic, we tested the potential role of NF-kappaB activation in chlamydial antiapoptotic activity in the current study. First, no obvious NF-kappaB activation was detected in the chlamydia-infected cells when these cells were resistant to apoptosis induced via either the intrinsic or extrinsic apoptosis pathways. Second, inhibition of NF-kappaB activation with pharmacologic reagents failed to block the chlamydial antiapoptotic activity. Finally, NF-kappaB p65 gene deletion did not prevent chlamydia from inhibiting host cell apoptosis. These observations together have demonstrated that NF-kappaB activation is not required for the chlamydial antiapoptotic activity.

Analgesic activity of di-caffeoylquinic acids from roots of Lychnophora ericoides (Arnica da serra)

The Brazilian medicinal plant Lychnophora ericoides Mart. (Asteraceae) has been used in traditional medicine to treat wounds, pain and inflammation. As part of our continuing investigation of this commercial phytomedicine, we focused on the polar fractions of the plant, since it is employed as alcoholic and hydroalcoholic preparations. The analgesic bioguided fractionation of the root polar extract yielded 3,5-di-O-[E]-caffeoylquinic acid, 4,5-di-O-[E]-caffeoylquinic acid and 3,4,5-tri-O-[E]-caffeoylquinic acid. The n-butanol fraction and the di-caffeoylquinic acids showed significant analgesic activity in the acetic acid-induced mouse writhing test at low but not at high doses. These findings support, at least in part, the validity of the use of Lychnophora ericoides roots in traditional medicine.

Quantitative structure-activity relationship of sesquiterpene lactones as inhibitors of the transcription factor NF-kappaB

Sesquiterpene lactones (SLs) are the active compounds of a variety of traditionally used medicinal plants from the Asteraceae family. They are known to possess a considerable antiinflammatory activity in different inflammation models. They inhibit the transcription factor NF-kappaB probably by alkylating cysteine38 in the DNA binding domain of the p65 subunit. Here we investigate a set of 103 different sesquiterpene lactones representing 6 structural groups (44 germacranolides, 16 heliangolides, 22 guaianolides, 9 pseudoguaianolides, 2 hypocretenolides, 10 eudesmanolides) for their NF-kappaB inhibiting properties and the resulting IC(100)-values were submitted to a QSAR study. Properties important for the inhibition potency are discussed for the whole data set and for subsets of the different structural classes.

The nuclear factor κB inhibitor parthenolide restores ICI 182,780 (Faslodex; fulvestrant)–induced apoptosis in antiestrogen-resistant breast cancer cells

The molecular mechanisms underlying the acquisition of resistance to the antiestrogen Faslodex are poorly understood, although enhanced expression and activity of nuclear factor κB (NFκB) have been implicated as a critical element of this phenotype. The purpose of this study was to elucidate the mechanism by which NFκB up-regulation contributes to Faslodex resistance and to determine whether pharmacologic inhibition of NFκB by the small molecule parthenolide could restore Faslodex-mediated suppression of cell growth. Basal expression of multiple NFκB-related molecules in MCF7-derived LCC1 (antiestrogen-sensitive) and LCC9 (antiestrogen-resistant) breast cancer cells was determined, and cells were treated with Faslodex or parthenolide. The effect of these drugs either singly or in combination was assessed by cell proliferation, estrogen receptor (ER)–dependent transcriptional activation, cell cycle analysis, and apoptosis assays. Expression of the p65 NFκB subunit and the upstream NFκB regulator IκB kinase γ/NFκB essential modulator were increased in the resistant MCF7/LCC9 cells (P = 0.001 and 0.04, respectively). Whereas MCF7/LCC9 cells were unresponsive to Faslodex alone, parthenolide effectively inhibited MCF7/LCC9 cell proliferation and the combination of Faslodex and parthenolide resulted in a 4-fold synergistic reduction in cell growth (P = 0.03). This corresponded to a restoration of Faslodex-induced apoptosis (P = 0.001), with no observable changes in ER-dependent transcription or cell cycle phase distribution. Because parthenolide has shown safety in Phase I clinical trials, these findings have direct clinical relevance and provide support for the design of clinical studies combining antiestrogens and parthenolide in ER-positive breast cancer.

Ethyl Pyruvate Inhibits Nuclear Factor-κB-Dependent Signaling by Directly Targeting p65

Ethyl pyruvate has been shown to have anti-inflammatory properties in numerous cell culture and animal studies. In this series of experiments, we tested the hypothesis that ethyl pyruvate inhibits signaling by the pro-inflammatory transcription factor, NF-kappaB. Ethyl pyruvate inhibited luciferase expression in lipopolysaccharide-stimulated murine macrophage-like RAW 264.7 cells transfected with an NF-kappaB-dependent luciferase reporter vector. Ethyl pyruvate also decreased NF-kappaB DNA-binding activity in lipopolysaccharide-stimulated RAW 264.7 cells and decreased lipopolysaccharide-induced expression of an NF-kappaB-dependent gene, inducible nitric oxide synthase. Ethyl pyruvate had no effect on the degradation of IkappaBalpha or IkappaBbeta in lipopolysaccharide-stimulated RAW 264.7 cells, suggesting that ethyl pyruvate acts distally to this step in the activation of NF-kappaB. In a cell-free system, binding of p50 homodimers to an NF-kappaB consensus oligonucleotide sequence was unaffected by ethyl pyruvate over a wide range of concentrations, indicating that ethyl pyruvate probably does not modify or interact with the p50 subunit of NF-kappaB. In contrast, ethyl pyruvate inhibited DNA binding by ectopically overexpressed wild-type p65 homodimers. However, ethyl pyruvate failed to inhibit the DNA-binding activity of homodimers of an overexpressed mutant form of a p65 with substitution of serine for cysteine 38. Taken together, these results suggest that ethyl pyruvate inhibits DNA-binding by covalently modifying p65 at Cys(38). We conclude that some of the beneficial anti-inflammatory effects of ethyl pyruvate may be due to modification of p65, thereby inhibiting signaling via the NF-kappaB pathway.

Involvement of p42/p44 MAPK, p38 MAPK, JNK, and NF-kappaB in IL-1beta-induced VCAM-1 expression in human tracheal smooth muscle cells

Interleukin-1beta (IL-1beta) has been shown to induce the expression of adhesion molecules on airway epithelial and smooth cells and contributes to inflammatory responses. Here, the roles of mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB) pathways for IL-1beta-induced vascular cell adhesion molecule (VCAM)-1 expression were investigated in human tracheal smooth muscle cells (HTSMC). IL-1beta induced expression of VCAM-1 protein and mRNA in a time-dependent manner, which was significantly inhibited by inhibitors of MEK1/2 (U0126 and PD-98059), p38 (SB-202190), and c-Jun NH(2)-terminal kinase (JNK; SP-600125). Consistently, IL-1beta-stimulated phosphorylation of p42/p44 MAPK, p38, and JNK was attenuated by pretreatment with U0126, SB-202190, or SP-600125, respectively. IL-1beta-induced VCAM-1 expression was significantly blocked by the specific NF-kappaB inhibitors helenalin and pyrrolidine dithiocarbamate. As expected, IL-1beta-stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha were blocked by helenalin but not by U0126, SB-202190, or SP-600125. Moreover, the resultant enhancement of VCAM-1 expression increased the adhesion of polymorphonuclear cells to a monolayer of HTSMC, which was blocked by pretreatment with helenalin, U0126, SB-202190, or SP-600125 before IL-1beta exposure or by anti-VCAM-1 antibody. Together, these results suggest that in HTSMC, activation of p42/p44 MAPK, p38, JNK, and NF-kappaB pathways is essential for IL-1beta-induced VCAM-1 gene expression. These results provide new insight into the mechanisms of IL-1beta action that cytokines may promote inflammatory responses in airway disease.

Overexpression of NtERF5, a new member of the tobacco ethylene response transcription factor family enhances resistance to tobacco mosaic virus

A new member of the tobacco (Nicotiana tabacum) AP2/ERF (ethylene response factor) transcription factor family, designated NtERF5, has been isolated by yeast one-hybrid screening. In vitro, recombinant NtERF5 protein weakly binds GCC box cis-elements, which mediate pathogen-regulated transcription of several PR (pathogenesis related) genes. NtERF5 transcription is transiently activated by wounding, by infection with the bacterial pathogen Pseudomonas syringae, as well as by inoculation with Tobacco mosaic virus (TMV). In contrast, NtERF5 transcription is not enhanced after application of salicylic acid, jasmonic acid, or ethylene. Constitutive overexpression of NtERF5 (ERF5-Oex) under control of the 35S promoter results in no visible alterations in plant growth or enhanced resistance to Pseudomonas infection. Furthermore, no constitutive expression of PR genes has been observed. In contrast, ERF5-Oex plants show enhanced resistance to TMV with reference to reduced size of local hypersensitive-response lesions and impaired systemic spread of the virus. Since, in TMV-infected ERF5-Oex plants, the viral RNA accumulates only up to 10 to 30% of the wild-type level, we suggest that NtERF5-regulated gene expression is controlling resistance to viral propagation. Previous research has demonstrated that overexpression of ERF genes enhances resistance to bacterial and fungal pathogens. Here, we provide further evidence that resistance to viral infection can be engineered by overexpression of ERF transcription factors.

Intracellular signalings underlying bradykinin-induced matrix metalloproteinase-9 expression in rat brain astrocyte-1

Bradykinin (BK), an inflammatory mediator, has been shown to increase the expression of proteins such as matrix metalloproteinases (MMPs) on brain cells and contributes to the pathophysiology of inflammatory responses. However, the mechanisms regulating MMP-9 expression by BK in rat brain astrocytes-1 (RBA-1) remain unclear. Here we report that the mitogen-activated protein kinase (MAPK) and NF-kappaB pathways participate in the induction of MMP-9 expression induced by BK in RBA cells. Zymographic, Western blotting, and RT-PCR analyses showed that BK increased expression of MMP-9 mRNA and protein in a time- and concentration-dependent manner. BK-induced MMP-9 mRNA and protein expression was inhibited by MEK1/2 inhibitor PD98059, PI3-K inhibitor LY294002, and NF-kappaB inhibitor helenalin. In accordance with these findings, BK-induced phosphorylation of p42/p44 MAPK and Akt and activation of NF-kappaB was attenuated by prior treatment with PD98059, LY294002, and helenalin, respectively. The effects of BK on MMP-9 expression and p42/p44 MAPK and Akt phosphorylation were inhibited by B(2) receptor antagonist Hoe 140, indicating the involvement of B(2) receptors revealed by [(3)H]-BK binding assay. Furthermore, BK-stimulated translocation of NF-kappaB into the nucleus was revealed by Western blotting and immnofluorescence staining and blocked by Hoe140, PD98059, LY294002, and helenalin. Taken together, these results suggest that in RBA cells, activation of p42/p44 MAPK and Akt cascades mediated through NF-kappaB pathway are essential for BK-induced MMP-9 gene expression. This study may provide insights into the regulation of MMP-9 production in CNS, which may occur in vivo in pathological situations such as CNS inflammation and brain astrocytoma.

Role of cysteine residues of p65/NF-κB on the inhibition by the sesquiterpene lactone parthenolide and N-ethyl maleimide, and on its transactivating potential

Sesquiterpene lactones (SLs) are potent anti-inflammatory substances. It was previously shown that the anti-inflammatory effect could be partly explained by the inhibition of the transcription factor NF-kappaB. Whether they inhibit the DNA binding of NF-kappaB, the activation of the IkappaB-kinase, or both is still a matter of debate. The data supporting these hypotheses were obtained using different cell systems. In this contribution we analyzed the mechanism of the sesquiterpene lactone-mediated inhibition using different cell systems, and showed that in all the cell lines analyzed, SLs inhibited both NF-kappaB binding and the IkappaB-kinase, but that the former played a more preponderant role in the inhibition. These results again confirm the importance of cysteine 38 in the inhibition and regulation of NF-kappaB's function. Moreover, we compared the selectivity of the SL parthenolide with that of N-ethyl maleimide (NEM). We showed that NEM directly alkylated p65 as well as p50 of NF-kappaB, whereas SLs possess a selectivity towards p65. Finally, we studied the transactivating properties of various p65 mutants, to analyze the effect of exchanged cysteine residues in the DNA binding domain of NF-kappaB/p65 on its function and demonstrated that the transactivating potential of the mutants did not correlate with their DNA binding strenght.

Nuclear factor-(kappa)B modulates the p53 response in neurons exposed to DNA damage

Previous studies have shown that DNA damage-evoked death of primary cortical neurons occurs in a p53 and cyclin-dependent kinase-dependent (CDK) manner. The manner by which these signals modulate death is unclear. Nuclear factor-kappaB (NF-kappaB) is a group of transcription factors that potentially interact with these pathways. Presently, we show that NF-kappaB is activated shortly after induction of DNA damage in a manner independent of the classic IkappaB kinase (IKK) activation pathway, CDKs, ATM, and p53. Acute inhibition of NF-kappaB via expression of a stable IkappaB mutant, downregulation of the p65 NF-kappaB subunit by RNA interference (RNAi), or pharmacological NF-kappaB inhibitors significantly protected against DNA damage-induced neuronal death. NF-kappaB inhibition also reduced p53 transcripts and p53 activity as measured by the p53-inducible messages, Puma and Noxa, implicating the p53 tumor suppressor in the mechanism of NF-kappaB-mediated neuronal death. Importantly, p53 expression still induces death in the presence of NF-kappaB inhibition, indicating that p53 acts downstream of NF-kappaB. Interestingly, neurons cultured from p65 or p50 NF-kappaB-deficient mice were not resistant to death and did not show diminished p53 activity, suggesting compensatory processes attributable to germline deficiencies, which allow p53 activation still to occur. In contrast to acute NF-kappaB inhibition, prolonged NF-kappaB inhibition caused neuronal death in the absence of DNA damage. These results uniquely define a signaling paradigm by which NF-kappaB serves both an acute p53-dependent pro-apoptotic function in the presence of DNA damage and an anti-apoptotic function in untreated normal neurons.

Kaurene Diterpene Induces Apoptosis in Human Leukemia Cells Partly through a Caspase-8-Dependent Pathway

Defects in apoptosis signaling pathways contribute to tumorigenesis and drug resistance, and these defects are often a cause of failure of chemotherapy. Thus, a major goal in chemotherapy is to find cytotoxic agents that restore the ability of tumor cells to undergo apoptosis. We previously found that an Ent-kaurene diterpene, Ent-11alpha-hydroxy-16-kauren-15-one (KD), induced apoptosis in human promyelocytic leukemia HL-60 cells. Here, we found that caspase-8, an apoptotic factor, is involved in KD-induced apoptosis. Although treatment of HL-60 cells with KD resulted in the activation of caspase-8 and -9, a caspase-8-specific inhibitor but not a caspase-9-specific inhibitor attenuated KD-induced apoptosis. Expression of a catalytically inactive caspase-8 partly attenuated KD-induced apoptosis. Treatment with KD led to a time-dependent cleavage of Bid, a substrate of caspase-8, as well as to the proteolytic processing of procaspase-8, indicating that KD treatment induces apoptosis through a caspase-8-dependent pathway. Moreover, overexpression of the drug resistance factor Bcl-2, which is frequently overexpressed in many tumors, failed to confer resistance to KD-induced cytotoxicity. Thus, KD may be a promising experimental cytotoxic agent that possibly points to new strategies to overcome a drug resistance.

The tobacco bZIP transcription factor BZI-1 binds the GH3 promoter in vivo and modulates auxin-induced transcription

Summary In order to establish the biological function of the tobacco basic leucine zipper (bZIP) transcription factor BZI-1 in hormone signalling, we have analysed transgenic plants which were altered with respect to the protein level or the activation potential of BZI-1. Overexpression of a dominant-negative derivative of BZI-1, lacking the N-terminal activation domain, resulted in plants displaying reduced internode size, enhanced lateral shoot formation and small, curly leaves. The response to auxin monitored with reference to root organogenesis, epinastic leaf curvature and transcription of the auxin-induced GH3 gene was reduced. In vitro, BZI-1 specifically binds to ACGT elements (ACEs) present in the GH3 promoter. In vivo, binding to the GH3 promoter was confirmed by chromatin immunoprecipitation (ChIP). Overexpression of BZI-1 in transgenic plants did not lead to a significant activation of the GH3 target gene. In contrast, plants expressing a VP16 (Herpes simplex virion protein 16)-BZI-1 fusion protein showed enhanced auxin-induced GH3 transcription. However, VP16-BZI-1 is insufficient to trigger GH3 expression independently of the auxin stimulus. Whereas auxin responsiveness has been shown to be mediated by ARF (auxin response factor) transcription factors, we discuss a function of BZI-1 assisting in fine-tuning of auxin-induced transcription.

Involvement of p42/p44 MAPK, JNK, and NF-?B in IL-1?-induced ICAM-1 expression in human pulmonary epithelial cells

Interleukin-1beta (IL-1beta) has been shown to induce the expression of intercellular adhesion molecule-1 (ICAM-1) on airway epithelial cells and contributes to inflammatory responses. However, the mechanisms regulating ICAM-1 expression by IL-1beta in human A549 cells was not completely understood. Here, the roles of mitogen-activated protein kinases (MAPKs) and NF-kappaB pathways for IL-1beta-induced ICAM-1 expression were investigated in A549 cells. IL-1beta induced expression of ICAM-1 protein and mRNA in a time- and concentration-dependent manner. The IL-1beta induction of ICAM-1 mRNA and protein were partially inhibited by U0126 and PD98059 (specific inhibitors of MEK1/2) and SP600125 [a specific inhibitor of c-Jun-N-terminal kinase (JNK)]. U0126 was more potent than other inhibitors to attenuate IL-1beta-induced ICAM-1 expression. Consistently, IL-1beta stimulated phosphorylation of p42/p44 MAPK and JNK which was attenuated by pretreatment with U0126 or SP600125, respectively. Moreover, transfection with dominant negative mutants of MEK1/2 (MEK K97R) or ERK2 (ERK2 K52R) also attenuated IL-1beta-induced ICAM-1 expression. The combination of PD98059 and SP600125 displayed an additive effect on IL-1beta-induced ICAM-1 gene expression. IL-1beta-induced ICAM-1 expression was almost completely blocked by a specific NF-kappaB inhibitor helenalin. Consistently, IL-1beta stimulated translocation of NF-kappaB into the nucleus and degradation of IkappaB-alpha which was blocked by helenalin, U0126, or SP600125. Taken together, these results suggest that activation of p42/p44 MAPK and JNK cascades, at least in part, mediated through NF-kappaB pathway is essential for IL-1beta-induced ICAM-1 gene expression in A549 cells. These results provide new insight into the mechanisms of IL-1beta action that cytokines may promote inflammatory responses in the airway disease.

Potent induction of apoptosis by germacranolide sesquiterpene lactones on human myeloid leukemia cells

This paper studies the cytotoxic effect induced by four known natural sesquiterpene lactones (tatridin A, tamirin, reynosin, ineupatorolide A) and one synthetic derivative (tatridin A diacetate) on the myeloid leukemia cell lines HL-60 and U937. Tatridin A diacetate and ineupatorolide A were found to be the most cytotoxic compounds with growth inhibition caused by induction of apoptosis as determined by flow cytometry and microscopy of nuclear changes. The results reported here support the conclusion that apoptosis was accompanied by both the activation of caspase-3 and the fragmentation of poly(ADP-ribose) polymerase-1 and was also associated with an early release of cytochrome c from the mitochondria.

Regulation of elastin gene transcription by interleukin-1 beta-induced C/EBP beta isoforms

We previously showed that interleukin (IL)-1beta decreases elastin gene transcription through activation of the NF-kappaB subunit p65 in neonatal rat lung fibroblasts. The present study was undertaken to further explore the molecular mechanisms responsible for the inhibitory effect of IL-1beta on elastin gene transcription. We found that cycloheximide blocked IL-1beta-induced downregulation of elastin mRNA but did not inhibit IL-1beta-induced translocation of p65 into the nucleus. IL-1beta treatment increased CCAAT/enhancer-binding protein (C/EBP)beta mRNA and protein levels including liver-enriched activating protein (LAP) and liver-enriched inhibitory protein (LIP), which was cycloheximide sensitive. C/EBPbeta isoforms bound a GCAAT-containing sequence in the proximal elastin promoter as determined by electrophoretic gel shift studies and confirmed by using specific anti-C/EBPbeta antibodies and by competition studies with oligonucleotides. Transient transfection of LIP expression vectors strongly decreased the transcriptional activity of the cotransfected elastin promoter and decreased levels of endogenous elastin mRNA. We demonstrated that IL-1beta-induced downregulation of elastin mRNA is dependent on NF-kappaB activation and C/EBPbeta expression. These results indicate that IL-1beta treatment activates NF-kappaB, which subsequently induces LIP expression and inhibition of elastin gene transcription.

Influence of helenanolide-type sesquiterpene lactones on gene transcription profiles in Jurkat T cells and human peripheral blood cells: anti-inflammatory and cytotoxic effects

Sesquiterpene lactones (SLs) are known to have potent anti-inflammatory and cytotoxic properties. So far, the anti-inflammatory effects have mainly been attributed to their inhibition of DNA-binding of the transcription factor NF-kappa B (p65), which is a pivotal regulator of the cellular immune response. Since NF-kappa B is involved in the transcriptional control of several pro-inflammatory and regulatory genes, we investigated the effects of one bifunctional NF-kappa B (p65) inhibiting and two monofunctional NF-kappa B (p65) inactive helenanolide-type SLs on PMA and LPS-induced mRNA expression in CD4(+) Jurkat T and human peripheral blood mononuclear cells (PBMCs) with reverse transcription real-time PCR (RT-rt-PCR). The monofunctional SLs 11 alpha,13-dihydrohelenalin acetate (DHAc) and chamissonolide significantly reduced mitogen-induced cytokine and iNOS mRNA levels in PBMCs and Jurkat T cells at low micromolar concentrations. DHAc also showed significant effects on the gene expression of the house-keeping genes GAP-DH and beta-actin, as well as on NF-ATc, p65, I-kappa B alpha, bcl-2, and cyclin D1. The bifunctional NF-kappa B inhibitor helenalin not only effectively inhibited pro-inflammatory gene expression, but also strongly down-regulated all investigated mRNA levels in a time-dependent manner. Flow cytometry and caspase-8 and -3 assays revealed that helenalin strongly and DHAc moderately induced apoptosis in Jurkat T cells, whereas chamissonolide caused cytoprotective effects. In PBMCs, DHAc and chamissonolide did not inhibit NF-kappa B (p65) DNA-binding at concentrations effective on the transcriptome. Thus, it can be concluded that the biological effects of SLs are not only due to NF-kappa B inhibition, but must be coupled to other mechanisms.

Suppression of RelA/p65 transactivation activity by a lignoid manassantin isolated from Saururus chinensis

In our search for NF-kappaB inhibitors from natural resources, we have previously identified two structurally related dilignans, manassantin A and B as specific inhibitors of NF-kappaB activation from Saururus chinensis. However, their molecular mechanism of action remains unclear. We here demonstrate that manassantins A and B are potent inhibitors of NF-kappaB activation by the suppression of transciptional activity of RelA/p65 subunit of NF-kappaB. These compounds significantly inhibited the induced expression of NF-kappaB reporter gene by LPS or TNF-alpha in a dose-dependent manner. However, these compounds did not prevent the DNA-binding activity of NF-kappaB assessed by electrophoretic mobility shift assay as well as the induced-degradation of IkappaB-alpha protein by LPS or TNF-alpha. Further analysis revealed that manassantins A and B dose-dependently suppressed not only the induced NF-kappaB activation by overexpression of RelA/p65, but also transactivation activity of RelA/p65. Furthermore, treatment of cells with these compounds prevented the TNF-alpha-induced expression of anti-apoptotic NF-kappaB target genes Bfl-1/A1, a prosurvival Bcl-2 homologue, and resulted in sensitizing HT-1080 cells to TNF-alpha-induced cell death. Similarly, these compounds also suppressed the LPS-induced inducible nitric oxide synthase expression and nitric oxide production. Taken together, manassantins A and B could be valuable candidate for the intervention of NF-kappaB-dependent pathological condition such as inflammation and cancer.

Anti-inflammatory activity and effect on gastric acid secretion of dehydroleucodine isolated from Artemisia douglasiana

The effect of Dehydroleucodine (DhL) on gastric acid secretion in rats was investigated at a dose of 40 mg/kg, while its anti-inflammatory effect was investigated in two experimental models: arthritis induced by Freund's adjuvant carrageenan- and cotton pellet-induced granuloma. DhL did not inhibit gastric acid secretion, suggesting that its anti-ulcerogenic effect can be attributed to its action on the mucosa defense factors. On the other hand, DhL inhibited both chronic and acute adjuvant carrageenan-induced inflammation phases, being most effective in the chronic phase. In the granuloma test, DhL also inhibited inflammation. It is suggested that the anti-inflammatory activity of DhL may be attributed to interference with multiple targets on the level of transcription factors, such as NF-kappaB, and cytokines.

Regulation of microglial inflammatory response by histone deacetylase inhibitors

The activation of microglial cells is involved in the pathogenesis of a variety of neurodegenerative diseases, stroke and traumatic brain injuries. Recent studies suggest that protein acetylation can affect the extent of inflammatory responses. Our aim was to elucidate whether histone deacetylase inhibitors, inducers of protein hyperacetylation, regulate the inflammatory response in neural models of inflammation in vitro and whether neurone-glia interactions affect this regulation. Interestingly, we observed that histone deacetylase inhibitors, such as trichostatin A (TSA) and suberoylanilide hydroxamic acid, strongly potentiated the lipopolysaccharide (LPS)-induced inflammatory response in murine N9 and rat primary microglial cells as well in neural co-cultures and hippocampal slice cultures. TSA clearly potentiated the LPS-induced expression of interleukin (IL)-6 and inducible nitric oxide synthase mRNAs, as well as the secretion of cytokines IL-6, tumour necrosis factor-alpha and macrophage inflammatory protein (MIP)-2, and nitric oxide (NO). Co-culture and slice culture experiments showed that the presence of astrocytes and neurones did not stimulate or prevent the pro-inflammatory potentiation induced by histone deacetylase inhibitor in microglial cells. The potentiation of cytokine and NO responses was blocked by the nuclear factor kappa B (NF-kappa B) inhibitors caffeic acid phenethyl ester and helenalin, demonstrating that the NF-kappa B signalling pathway is involved. The DNA-binding activity of the NF-kappa B complex was strongly increased by LPS treatment but not enhanced by TSA. This suggests that potentiation of the inflammatory response is not dependent on the level of cytoplasmic NF-kappa B activation or DNA-binding activity but that site of action may be at the level of transcriptional regulation. Our results suggest that environmental stresses, ageing, diet and diseases that regulate protein acetylation status may also affect the inflammatory response.

Identification of cis-regulatory regions necessary for robust Nos2 promoter activity in glial cells: indirect role for NF-kappaB

Previous reports suggest the nitric-oxide synthase 2 (Nos2) promoter contains negative and positive cis-regulatory regions. This study identified such regions using rat C6 glial cells. Activity of the serially deleted rat Nos2 promoter fused to a luciferase reporter gene was found to vary with construct size independent of stimuli, decreasing markedly from 160 to 130 bp then increasing significantly from 110 to 94 bp. In contrast, time to peak activity was stimulus-dependent but size-independent; 4-8 h for a cytokine mixture or lipopolysaccharide + interferon-gamma, and 8-16 h for lipopolysaccharide + phorbol 12-myristate 13-acetate. Peak activity with heterologous promoters also varied; 4 h for 3.7 kb of the human Nos2A promoter, and 36 h for 1.8 kb of the murine promoter. Electrophoretic mobility shift assays and in vivo DNA footprinting data confirmed nuclear protein binding to promoter regions suspected of containing important regulatory sites based on reporter gene data. A binding site for NF-kappaB was not required for Nos2 promoter activity. These findings provide significant new information on the relative importance of different regions of the rat Nos2 promoter for transcriptional activation and nitric oxide production by glial cells and support the existence of cell- and species-specific mechanisms for transcriptional regulation of Nos2 activation.

Cytotoxic sesquiterpene lactones from the root of Saussurea lappa

Bioassay-directed fractionation of Saussurea lappa led to the isolation of a novel lappadilactone (1) and seven sesquiterpene lactones (2-8) as cytotoxic principles against selected human cancer cell lines. Lappadilactone (1), dehydrocostuslactone (2), and costunolide (5) exhibited the most potent cytotoxicity with CD50 values in the range 1.6-3.5 microg/mL in dose- and time-dependent manners. The cytotoxicities were not specific and showed similar activities against HepG2, OVCAR-3 and HeLa cell lines. The structure-activity relationship showed that the alpha-methylene-gamma-lactone moiety is necessary for cytotoxicity, and activity is reduced with the presence of a hydroxyl group. In addition, seven noncytotoxic compounds (9-15) were also isolated, including two novel sesquiterpenes, a guaianolide-type with a C17 skeleton, lappalone (13), and 1beta,6alpha-dihydroxycostic acid ethyl ester (14). The structures of the new compounds were elucidated from spectroscopic and/or X-ray data interpretations. Some representative compounds were also tested for antibacterial activity; however, only marginal activities were observed. Therefore, compounds 1-8 are potential cytotoxic agents but without significant antibacterial effect.

Artemisinin inhibits inducible nitric oxide synthase and nuclear factor NF-kB activation

Artemisinin is a natural product used as an alternative drug in the treatment of severe and multidrug-resistant malaria. In the present work we show that artemisinin shares with other sesquiterpene lactones the ability to inhibit the activation of the nuclear factor NF-kB: by this mechanism, artemisinin, as well as parthenolide, inhibits nitric oxide synthesis in cytokine-stimulated human astrocytoma T67 cells. These results suggest that artemisinin, in addition to its antiparasitic properties, could also exert a therapeutic effect on neurological complications of malaria.

Effect of sesquiterpene lactones on the expression of the activation marker CD69 and of IL-2 in T-lymphocytes in whole blood

We used flow cytometry to investigate the inhibitory effect of sesquiterpene lactones (SLs) on T-cell activation measured by the expression of its early marker CD69, and on interleukin (IL)-2, a mediator of activation, in whole blood. SLs are biologically active compounds found especially in plants from the Asteraceae family. Overnight treatment of blood with these substances led to the inhibition of CD69 and IL-2 expression. Interestingly, bifunctional SLs showed a weaker activity than monofunctional substances, which is in contradiction with the data obtained so far, using other biological test systems. Additionally, SLs did not completely inhibit CD69 or IL-2 expression. We also determined their toxicity and observed only a low effect. Up to now, studies on cytotoxicity have only been performed using cultured cell lines. From these results it may be supposed that these natural compounds preferentially show toxic effects towards transformed cell lines. Altogether, the results demonstrated that SLs effectively inhibit the activation of the T-lymphocyte response in whole blood and proved the utility of a whole blood system in studying their biological effects.

Modulation of human beta-defensin-2 transcription in pulmonary epithelial cells by lipopolysaccharide-stimulated mononuclear phagocytes via proinflammatory cytokine production

Human beta-defensin (hBD)-2, a cationic antimicrobial peptide primarily induced in epithelial cells in response to inflammatory stimuli, plays an important role in host defense. To elucidate the expression mechanism of hBD-2 in the lung, we investigated the modulation of hBD-2 transcription in pulmonary epithelial cells by mononuclear phagocytes stimulated with LPS. Coculture of A549 pulmonary epithelial cells with Mono-Mac-6 monocytic cells in the presence of Escherichia coli LPS markedly up-regulated hBD-2 promoter activity, whereas A549 alone did not respond to LPS to activate the hBD-2 promoter. Furthermore, IL-1beta and TNF-alpha in the culture supernatants from LPS-stimulated monocytic cells activated the hBD-2 promoter in A549 cells. Of note, IL-1beta was more potent than TNF-alpha in this effect. In addition, a mutation of the NF-kappaB site at -200 (pkappaB1 site) completely abolished this IL-1beta- and TNF-alpha-induced hBD-2 promoter activation, whereas NF-kappaB inhibitors (MG-132 and helenalin) strongly suppressed it. Moreover, electrophoretic mobility shift assay suggested that NF-kappaB, consisting of p65-p50 heterodimer, could bind to the pkappaB1 site in cytokine-stimulated A549 cells. Interestingly, flow cytometric analysis revealed that A549 cells expressed CD14 but lacked Toll-like receptor 4, which may account for the hyporesponsiveness of A549 cells to LPS. Taken together, these results suggest that hBD-2 expression in pulmonary epithelial cells is modulated by NF-kappaB via the actions of IL-1beta and TNF-alpha produced by LPS-stimulated mononuclear phagocytes.

Effects of sesquiterpenes and amino acid-sesquiterpene conjugates from the roots of Saussurea lappa on inducible nitric oxide synthase and heat shock protein in lipopolysaccharide-activated macrophages

The methanolic extract of the roots of Saussurea lappa CLARKE, a Chinese medicinal herb Saussureae Radix, was found to inhibit nitric oxide (NO) production in lipopolysaccharide (LPS)-activated mouse peritoneal macrophages. Among the constituents from the methanolic extract, two sesquiterpene lactones (costunolide and dehydrocostus lactone) and two amino acid-sesquiterpene conjugates (saussureamines A and B) potently inhibited LPS-induced NO production (IC(50)=1.2-2.8 microM). Saussureamines A and B in addition to costunolide and dehydrocostus lactone did not inhibit iNOS enzyme activity, but they inhibited both induction of inducible NO synthase and activation of nuclear factor-kappaB in accordance with induction of heat shock protein 72.

The effect of sesquiterpene lactones on the release of human neutrophil elastase

Sesquiterpene lactones (SLs) are natural products responsible for the anti-inflammatory activity of a variety of medicinal plants, mainly from the Asteraceae family. Here, we investigated whether they also influence the process of exocytosis of pro-inflammatory enzymes, such as the human neutrophil elastase (HNE). Altogether, eight structurally different SLs from the eudesmanolide, guaianolide, pseudoguaianolide, and germacranolide type were studied. Neutrophils were isolated from fresh human blood. After pre-incubation with different concentrations of the respective SL and cytochalasin B, the exocytosis of elastase was initiated either by platelet activating factor or N-formyl-methionyl-leucyl-phenylalanine. Inhibition of HNE release was measured by p-nitroaniline formation. The SLs exhibited an inhibitory effect on elastase release from neutrophils challenged either by platelet activating factor or N-formyl-methionyl-leucyl-phenylalanine. Concentration-response curves were recorded and the IC(50) values ranged from 2 to 30 microM. Studies on isolated HNE showed that a selective direct inhibition on HNE can be excluded. Interestingly, the inhibitory activity did not correlate with the number of alpha,beta-unsaturated carbonyl functions. The structure-activity relationship and the molecular mechanism are discussed.

Discovery of quinazolines as a novel structural class of potent inhibitors of NF-kappa B activation

We disclose here a new structural class of low-molecular-weight inhibitors of NF-kappa B activation that were designed and synthesized by starting from quinazoline derivative 6a. Structure-activity relationship (SAR) studies based on 6a elucidated the structural requirements essential for the inhibitory activity toward NF-kappa B transcriptional activation, and led to the identification of the 6-amino-4-phenethylaminoquinazoline skeleton as the basic framework. In this series of compounds, 11q, containing the 4-phenoxyphenethyl moiety at the C(4)-position, showed strong inhibitory effects on both NF-kappa B transcriptional activation and TNF-alpha production. Furthermore, 11q exhibited an anti-inflammatory effect on carrageenin-induced paw edema in rats.

Melanoma cell migration to type IV collagen requires activation of NF-kappaB

Chemotaxis is the consequence of environmental factors engaging their receptors to initiate signaling cascades. However, the biochemical mechanisms controlling this phenomenon are not clear. We employed an in vitro modified Boyden 48-well chemotaxis migration system to characterize the role of signal transducers in type IV collagen (CIV) induced A2058 human melanoma cell migration. Using specific pharmacological inhibitors and a series of dominant-negative and constitutively active signaling proteins, we show that Ras and Rac GTPases, PI-3K, and PKC participate in cell migration mediated by beta1 integrins. Collagen also induces a time- dependent degradation of IkappaB-alpha and an increase in nuclear translocation of NF-kappaB which is dependent on PKC pathway. More importantly, collagen-stimulated melanoma cell migration directly correlated with an increase in NF-kappaB transactivation. Furthermore, CIV induced an increase in beta1 integrin mRNA levels. Specific NF-kappaB inhibitors Helenalin and SN-50 inhibited melanoma cell migration to collagen, indicating a novel requirement for NF-kappaB transactivation in cell chemotaxis mediated by beta1 integrin signals. These results describe signal transduction events that are initiated by type IV collagen through beta1 integrins and demonstrate an important role for NF-kappaB in regulating melanoma chemotaxis.

Nuclear factor-kappaB as a therapeutic target in critical care medicine

Nuclear factor-kappaB is a transcriptional factor required for the gene expression of many inflammatory mediators. Nuclear factor-kappaB activation requires removal and degradation of its inhibitor kappaB, an event that occurs after phosphorylation of inhibitor kappaB by a complex of inhibitor kappaB kinases. These events allow nuclear factor-kappaB to translocate into the nucleus, where it binds to kappaB elements and initiates transcription. Inappropriate and prolonged activation of nuclear factor-kappaB has been linked to several diseases associated with inflammatory events, including septic shock, acute respiratory distress syndrome, ischemia, and reperfusion injury. Thus, the key role of nuclear factor-kappaB in regulating inflammation makes this factor a therapeutic target for reducing tissue and organ damage. Regulation and control of nuclear factor-kappaB can be achieved by gene modification strategies or by pharmacologic inhibition of the key components of the cascade that leads to nuclear factor-kappaB activation. The purpose of our review is to describe these novel therapeutic approaches and their potential efficacy.

Characterization of the molecular events following impairment of NF-kappaB-driven transcription in neurons

Nuclear factor-kappaB (NF-kappaB) is a transcription factor with a pivotal role in neuronal homeostasis. Indeed, NF-kappaB trans-activates several antiapoptotic genes in neurons and inhibition of NF-kappaB transcriptional activity triggers neuronal apoptosis. However, the exact mechanisms by which neurons undergo apoptosis in conditions of NF-kappaB inhibition are poorly understood. To further clarify how NF-kappaB operates in neurons, and to gather information on the molecular events occurring during NF-kappaB inhibition-dependent neuronal apoptosis, this study evaluated the effects of recently identified NF-kappaB inhibitors such as parthenolide, SN50, BAY 11-7082 and helenalin on primary cultures of rat cortical neurons. Data show that NF-kappaB was constitutively activated in neurons, and demonstrate for the first time that drug-dependent NF-kappaB inhibition induced rapid mitochondrial release of cytochrome c, caspase-9 and -3 activation, poly(ADP-ribose) polymerase-1 cleavage, membrane blebbing and nuclear fragmentation, without evidence of procaspase-8 and Bid processing. Interestingly, a burst of Akt activation occurred in neurons exposed to NF-kappaB inhibitors. These events were preceded by selective reduction of mRNAs of NF-kappaB-dependent, antiapoptotic Bcl-2 family members such as Bcl-x(L), Bcl-2 and, in particular, A1/Bfl-1. The present study reports a novel, detailed temporal analysis of the molecular events following impairment of NF-kappaB-driven transcription in neurons and demonstrates that inhibition of constitutive neuronal NF-kappaB activity triggers selective activation of the intrinsic apoptotic program.

Rocaglamide derivatives are potent inhibitors of NF-kappa B activation in T-cells

Crude extracts from different Aglaia species are used as anti-inflammatory remedies in the traditional medicine of several countries from Southeast Asia. Because NF-kappaB transcription factors represent key regulators of genes involved in immune and inflammatory responses, we supposed that the anti-inflammatory effects of Aglaia extracts are mediated by the inhibition of NF-kappaB activity. Purified compounds of Aglaia species, namely 1H-cyclopenta[b]benzofuran lignans of the rocaglamide type as well as one aglain congener were tested for their ability to inhibit NF-kappaB activity. We show that a group of rocaglamides represent highly potent and specific inhibitors of tumor necrosis factor-alpha (TNFalpha) and phorbol 12-myristate 13-acetate (PMA)-induced NF-kappaB-dependent reporter gene activity in Jurkat T cells with IC(50) values in the nanomolar range. Some derivatives are less effective, and others are completely inactive. Rocaglamides are able to suppress the PMA-induced expression of NF-kappaB target genes and sensitize leukemic T cells to apoptosis induced by TNFalpha, cisplatin, and gamma-irradiation. The suppression of NF-kappaB activation correlated with the inhibition of induced IkappaB(alpha) degradation and IkappaB(alpha) kinase activation. The level of interference was determined and found to be localized upstream of the IkappaB kinase complex but downstream of the TNF receptor-associated protein 2. Our data suggest that rocaglamide derivatives could serve as lead structures in the development of anti-inflammatory and tumoricidal drugs.

Sesquiterpene lactones as inhibitors of human neutrophil elastase

Human neutrophil elastase (HNE) is a serine protease that has been implicated in the abnormal turnover of connective tissue proteins and has been described as an important pathogenic factor in several inflammatory diseases such as rheumatoid arthritis or cystic fibrosis. Here we investigated 17 sesquiterpene lactones (SLs) for their ability to inhibit human neutrophil elastase in an in vitro assay. Podachaenin was the most active compound with an IC(50) value of 7 microM. SLs do not covalently bind to the amino acids of the catalytic triad, thus differing from other elastase inhibitors with a lactone moiety. In contrast to most other biological activities of SLs HNE inhibition is not mediated by alpha,beta-unsaturated carbonyl functions. Ligand binding calculations using the X-ray structure of HNE and the program FlexX revealed structural elements which are a prerequisite for their inhibitory activity.

Guaianolides from Viguiera gardneri inhibit the transcription factor NF-kappaB

Five guaianolides and a germacrolide were isolated from the leaf rinse extract of Viguiera gardneri (Asteraceae), together with known compounds. All compounds were detected in glandular trichomes collected from the leaves and were analyzed by HPLC. Structure elucidation was based on the analysis of spectroscopic data. Low energy conformations were obtained by quantum mechanical calculations. Three closely related guaianolides which were isolated as the main compounds were studied for their anti-inflammatory activity using the transcription factor NF-kappaB as molecular target. NF-kappaB DNA binding was inhibited at sesquiterpene lactones concentrations of 10 or 50 microM.

Kaurane diterpene, kamebakaurin, inhibits NF-kappa B by directly targeting the DNA-binding activity of p50 and blocks the expression of antiapoptotic NF-kappa B target genes

Kaurane diterpenes have been identified from numerous medicinal plants, which have been used for treatment of inflammation and cancer, however, their molecular mechanism of action remains unclear. We have previously shown that kamebakaurin and other three kaurane diterpenes selectively inhibit activation of transcription factor NF-kappaB, a central mediator of apoptosis and immune responses. We here demonstrate that kamebakaurin is a potent inhibitor of NF-kappaB activation by directly targeting DNA-binding activity of p50. Kamebakaurin prevented the activation of NF-kappaB by different stimuli in various cell types. Kamebakaurin did not prevent either stimuli-induced degradation of IkappaB-alpha or nuclear translocation of NF-kappaB, however, it significantly interfered DNA binding activity of activated NF-kappaB in cell and in vitro and preferentially prevented p50-mediated DNA-binding activity of NF-kappaB rather than that of RelA as measured using in vitro translated p50 and RelA proteins. Moreover, a p50 mutant with a Cys-62 --> Ser mutation was not inhibited with kamebakaurin, indicating that the effect of kamebakaurin was probably due to its interaction with cysteine 62 in p50. The covalent modification of p50 by kamebakaurin was further demonstrated by mass spectrometry analysis that showed an increase in the molecular mass of kamebakaurin-treated p50, and this modification was not reverted by addition of dithiothreitol. These results suggested that kamebakaurin exhibited its inhibitory activity by a direct covalent modification of cysteine 62 in the p50. Also, treatment of cells with kamebakaurin prevented the tumor necrosis factor-alpha (TNF-alpha)-induced expression of antiapoptotic NF-kappaB target genes encoding c-IAP1 (hiap-2) and c-IAP2 (hiap-1), members of the inhibitor of apoptosis family, and Bfl-1/A1, a prosurvival Bcl-2 homologue, and augmented the TNF-alpha-induced caspase 8 activity, thereby resulting in sensitizing MCF-7 cells to TNF-alpha-induced apoptosis. Taken together, kamebakaurin is a valuable candidate for the intervention of NF-kappaB-dependent pathological conditions such as inflammation and cancer.

Dimethylfumarate inhibits TNF-induced nuclear entry of NF-kappa B/p65 in human endothelial cells

Fumaric acid esters, mainly dimethylfumarate (DMF), have been successfully used to treat psoriasis. Based on previous observations that DMF inhibited expression of several TNF-induced genes in endothelial cells, we wished to explore the molecular basis of DMF function in greater detail. In first experiments we analyzed DMF effects on tissue factor expression in human endothelial cells in culture, because tissue factor is expressed by two independent sets of transcription factors, by NF-kappa B via TNF and by early gene response-1 transcription factor via vascular endothelial growth factor (VEGF). We show that DMF inhibits TNF-induced tissue factor mRNA and protein expression as well as TNF-induced DNA binding of NF-kappa B proteins, but not VEGF-induced tissue factor protein, mRNA expression, or VEGF-induced early gene response-1 transcription factor/DNA binding. To determine where DMF interferes with the TNF/NF-kappa B signaling cascade, we next analyzed DMF effects on I kappa B and on the subcellular distribution of NF-kappa B. DMF does not inhibit TNF-induced I kappa B alpha phosphorylation and I kappa B degradation; thus, NF-kappa B is properly released from I kappa B complexes even in the presence of DMF. Importantly, DMF inhibits the TNF-induced nuclear entry of NF-kappa B proteins, and this effect appears selective for NF-kappa B after the release from I kappa B, because the constitutive shuttling of inactive NF-kappa B/I kappa B complexes into and out from the nucleus is not blocked by DMF. Moreover, DMF does not block NF-kappa B/DNA binding. In conclusion, DMF appears to selectively prevent the nuclear entry of activated NF-kappa B, and this may be the basis of its beneficial effect in psoriasis.

Parthenolide, an inhibitor of the nuclear factor-kappaB pathway, ameliorates cardiovascular derangement and outcome in endotoxic shock in rodents

Parthenolide is a sesquiterpene lactone used in folk medicine for its anti-inflammatory activity. Recent in vitro studies have shown that this compound inhibits the nuclear factor (NF)-kappaB pathway. This study examines the effect of parthenolide in endotoxic shock in rodents. Endotoxic shock was induced by administration of Escherichia coli endotoxin in rats. Three groups of rats received parthenolide (0.25, 0.5, or 1 mg/kg) 15 min before endotoxin; another group received parthenolide (1 mg/kg) 3 h after endotoxin. In vehicle-treated rats, administration of endotoxin caused severe hypotension, which was associated with a marked hyporeactivity to norepinephrine in ex vivo thoracic aortas. Immunohistochemistry showed positive staining for nitrotyrosine, poly(ADP-ribose) synthetase (PARS) and apoptosis, whereas Northern blot analysis showed increased mRNA expression of inducible nitric-oxide synthase (iNOS) in thoracic aortas. Elevated levels of plasma nitrate/nitrite were also found. Elevated lung levels of myeloperoxidase activity were indicative of infiltration of neutrophils. These inflammatory events were preceded by cytosolic degradation of inhibitor kappaBalpha (IkappaBalpha) and activation of nuclear NF-kappaB in the lung. In vivo pretreatment and post-treatment with parthenolide improved the hemodynamic profile and reduced plasma nitrate/nitrite and lung neutrophil infiltration in a dose-dependent fashion. Vascular hyporeactivity of ex vivo aortas was ameliorated. Treatment with parthenolide also abolished nitrotyrosine formation, PARS expression, and apoptosis and reduced iNOS mRNA content in thoracic aortas. DNA binding of NF-kappaB was inhibited by parthenolide in the lung, whereas degradation of IkappaBalpha was unchanged. In a separate set of experiments, pretreatment or post-treatment with parthenolide significantly improved survival in mice challenged with endotoxin. We conclude that parthenolide exerts beneficial effects during endotoxic shock through inhibition of NF-kappaB.

Cyclopentenone causes cell cycle arrest and represses cyclin D1 promoter activity in MCF-7 breast cancer cells

Evidence indicates that overexpression of cyclin D1 is an important event in malignant transformation of breast cancer cells. Therefore, cyclin D1 is a potential target for mechanistically-based chemoprevention/treatment of breast cancer. Treatment of serum-stimulated quiescent MCF-7 breast cancer cells with cyclopentenone (2-cyclopenten-1-one) blocked progression through G1 and into S phase. Growth arrest of the cyclopentenone-treated cells in G1 was associated with changes in the levels of several proteins that control the cell cycle, including a dramatic decrease in cyclin D1 protein expression. Cyclopentenone also decreased the abundance of cyclin D1 mRNA and nuclear transcripts, indicating that it regulated cyclin D1 expression at the transcriptional level. Cyclopentenone selectively inhibited the activity of the cyclin D1 and cyclin A promoters but not the activity of several other control promoters. Deletion analysis indicated that the cyclopentenone response element was located in the cyclin D1 core promoter. Additional functional studies showed that a sequence within the core promoter (CycY, located downstream from the initiator element) played an important role in activation of the cyclin D1 promoter in MCF-7 cells. Electrophoretic mobility shift assays demonstrated specific binding of the transcription factor BTEB to the CycY site. The cyclopentenone response element did not correspond to the CycY site but rather mapped to the initiator element itself. The overall results suggest that cyclopentenone interferes with the transcription initiation complex that assembles over the cyclin D1 initiator element, leading to selective inhibition of cyclin D1 gene transcription.

Reactions of purines-containing butenolides with L-cysteine or N-acetyl-L-cysteine as model biological nucleophiles: a potent mechanism-based inhibitor of ribonucleotide reductase caused apoptosis in breast carcinoma MCF7 cells

Thiols are the most reactive nucleophilic reagents among the biological models investigated. The reactivity of butenolides 1a-c, 2-4, and 6-8 toward L-cysteine, a model biological nucleophile, was studied spectrophotometrically. The rates of the reactions were measured and correlated with antitumour activity of these molecules. N-Acetylcysteine addition product 5, resulting from the treatment of butenolide 4 with glutathione precursor, N-acetyl-L-cysteine, was isolated. Unlike purine-containing gamma-(Z)-ethylidene-2,3-dimethoxybutenolides 1a-c, 4, 6, and 7, adduct 5 and butenolides 10-12 did not exhibit inhibitory activity against murine leukemias (L1210 and P388), breast carcinoma (MCF7), and human T-lymphoblasts (Molt4/C8 and CEM/0) cell lines. As such, the biological activity of purine-containing butenolides can be attributed to their adenine moiety as a recognition site as well as their reactivity towards the cysteine residues of functional proteins forming covalent bond via reverse Michael type addition. Adenine-containing phosphonothioanhydride derivative 8 was also synthesised. Its reaction with N-acetyl-L-cysteine produced N,S-diacetylcysteine and thiophosphonate 9. Compound 9 did not exhibit anticancer activity; yet its precursor 8 displayed the most pronounced inhibition on all the examined malignant tumour cell lines. In the presence of L-cysteine, cytotoxicity of 4 and 8 was decreased, whereas glutathione addition more influenced on the cytotoxicity of 8. It was found that adenine-containing phosphonothioanhydride 8 functions as a significant irreversible inactivator of the Escherichia coli ribonucleoside diphosphate reductase. After treatment of MCF7 cells with compound 8, fluorescence microscopy demonstrated the presence of nucleus shrinkage or segmentation. This apoptotic morphology, however, was not pronounced in the presence of glutathione or dithiotheritol.

Cysteine 38 in p65/NF-kappaB plays a crucial role in DNA binding inhibition by sesquiterpene lactones

Sesquiterpene lactones (SLs) have potent anti-inflammatory properties. We have shown previously that they exert this effect in part by inhibiting activation of the transcription factor NF-kappaB, a central regulator of the immune response. We have proposed a molecular mechanism for this inhibition based on computer molecular modeling data. In this model, SLs directly alkylate the p65 subunit of NF-kappaB, thereby inhibiting DNA binding. Nevertheless, an experimental evidence for the proposed mechanism was lacking. Moreover, based on experiments using the SL parthenolide, an alternative mode of action has been proposed by other authors in which SLs inhibit IkappaB-alpha degradation. Here we report the construction of p65/NF-kappaB point mutants that lack the cysteine residues alkylated by SLs in our model. In contrast to wild type p65, DNA-binding of the Cys(38) --> Ser and Cys(38,120) --> Ser mutants is no longer inhibited by SLs. In addition, we provide evidence that parthenolide uses a similar mechanism to other SLs in inhibiting NF-kappaB. Contrary to previous reports, we show that parthenolide, like other SLs, inhibits NF-kappaB most probably by alkylating p65 at Cys(38). Although a slight inhibition of IkappaB degradation was detected for all SLs, the amount of remaining IkappaB was too low to explain the observed NF-kappaB inhibition.

Inhibitory effects of helenalin and related compounds on 5-lipoxygenase and leukotriene C(4) synthase in human blood cells

The sesquiterpene lactone helenalin, which can be isolated from several plant species of the Asteraceae family, is a potent anti-inflammatory and antineoplastic agent. In agreement, alcohol extracts of these plants are used for local external treatment of inflammatory conditions. Since leukotrienes are important mediators in inflammatory processes, the inhibitory effects of helenalin and some derivatives on leukotriene (LT) biosynthesis were studied. Treatment of human platelets with helenalin provoked irreversible inhibition of LTC(4) synthase in a concentration- and time-dependent manner with an IC(50) of 12 microM after a 60 min preincubation. 11alpha,13-Dihydrohelenalin acetate was less potent. Interestingly, individual donors could be divided into two distinct groups with respect to the efficacy of helenalin to suppress platelet LTC(4) synthase. In human granulocytes, helenalin inhibited both the 5-lipoxygenase (IC(50) 9 microM after 60 min preincubation) and LTC(4) synthase in a concentration- and time-dependent fashion. In contrast, the drug was without effect on LTA(4) hydrolase. The GSH-containing adducts (2beta-(S-glutathionyl)-2,3-dihydrohelenalin and 2beta-(S-glutathionyl)-2,3,11alpha,13-tetra hydrohelenalin acetate) did not significantly inhibit LTC(4) synthase. The present results indicate a mechanism for the anti-inflammatory effect of helenalin and related compounds.