Exploring the Use of Serum-Derived Small Extracellular Vesicles as Liquid Biopsy to Study the Induction of Hepatic Cytochromes P450 and Organic Anion Transporting Polypeptides

Liver-derived small extracellular vesicles (sEVs), prepared from small sets of banked serum samples using a novel two-step protocol, were deployed as liquid biopsy to study the induction of cytochromes P450 (CYP3A4, CYP3A5, and CYP2D6) and organic anion transporting polypeptides (OATP1B1 and OATP1B3) during pregnancy (nonpregnant (T0), first, second, and third (T3) trimester women; N = 3 each) and after administration of rifampicin (RIF) to healthy male subjects. Proteomic analysis revealed induction (mean fold-increase, 90% confidence interval) of sEV CYP3A4 after RIF 300 mg × 7 days (3.5, 95% CI = 2.5-4.5, N = 4, P = 0.029) and 600 mg × 14 days (3.7, 95% CI = 2.1-6.0, N = 5, P = 0.018) consistent with the mean oral midazolam area under the plasma concentration time curve (AUC) ratio in the same subjects (0.28, 95% CI = 0.22-0.34, P < 0.0001; and 0.17, 95% CI = 0.13-0.22, P < 0.0001). Compared with CYP3A4, liver sEV CYP3A5 protein (subjects genotyped CYP3A5*1/*3) was weakly induced (≤ 1.5-fold). It was also possible to measure liver sEV-catalyzed dextromethorphan (DEX) O-demethylation to dextrorphan (DXO), correlated with sEV CYP2D6 expression (r = 0.917, P = 0.0001; N = 10) and 3-hour plasma DXO-to-DEX concentration ratio (r = 0.843, P = 0.002, N = 10), and show that CYP2D6 was not induced by RIF. Nonparametric analysis of liver sEV revealed significantly higher CYP3A4 (3.2-fold, P = 0.003) and CYP2D6 (3.7-fold, P = 0.03) protein expression in T3 vs. T0 women. In contrast, expression of both OATPs in liver sEV was unaltered by RIF administration and pregnancy.

Evaluation of 17β-hydroxysteroid dehydrogenase activity using androgen receptor-mediated transactivation

17β-Hydroxysteroid dehydrogenases (17β-HSDs) catalyze the reduction of 17-ketosteroids and the oxidation of 17β-hydroxysteroids to regulate the production of androgens and estrogens. Among them, 17β-HSD type 3 (HSD17B3) is expressed almost exclusively in testicular Leydig cells and contributes to development of male sexual characteristics by converting androstenedione (A4) to testosterone (T). Mutations of HSD17B3 genes cause a 46,XY disorder of sexual development (46,XY DSD) as a result of low T production. Therefore, the evaluation of 17β-HSD3 enzymatic activity is important for understanding and diagnosing this disorder. We adapted a method that easily evaluates enzymatic activity of 17β-HSD3 by quantifying the conversion from A4 to T using androgen receptor (AR)-mediated transactivation. HEK293 cells were transduced to express human HSD17B3, and incubated medium containing A4. Depending on the incubation time with HSD17B3-expressing cells, the culture media progressively increased luciferase activities in CV-1 cells, transfected with the AR expression vector and androgen-responsive reporter. Culture medium from HSD17B1 and HSD17B5-expressing cells also increased the luciferase activities. This system is also applicable to detect the conversion of 11-ketoandrostenedione to 11-ketotestosterone by HSD17B3. Establishment of HEK293 cells expressing various missense mutations in the HSD17B3 gene associated with 46,XY DSD revealed that this system is effective to evaluate the enzymatic activities of mutant proteins.

JNK2 silencing and caspase-9 activation by hyperosmotic polymer inhibits tumor progression

c-Jun N-terminal kinase 2 (JNK2) is primarily responsible for the oncogenic transformation of the transcription factor c-Jun. Expression of the proto-oncogene c-Jun progresses the cell cycle from G1 to S phase, but when its expression becomes awry it leads to uncontrolled proliferation and angiogenesis. Delivering a JNK2 siRNA (siJNK2) in tumor tissue was anticipated to reverse the condition with subsequent onset of apoptosis which predominantly requires an efficient delivering system capable of penetrating through the compact tumor mass. In the present study, it was demonstrated that polymannitol-based vector (PMGT) with inherent hyperosmotic properties was able to penetrate through and deliver the siJNK2 in the subcutaneous tumor of xenograft mice. Hyperosmotic activity of polymannitol was shown to account for the enhanced therapeutic delivery both in vitro and in vivo because of the induction of cyclooxygenase-2 (COX-2) which stimulates caveolin-1 for caveolae-mediated endocytosis of the polyplexes. Further suppression of JNK2 and hence c-Jun expression led to the activation of caspase-9 to induce apoptosis and inhibition of tumor growth in xenograft mice model. The study exemplifies PMGT as an efficient vector for delivering therapeutic molecules in compact tumor tissue and suppression of JNK2 introduces a strategy to inhibit tumor progression.

Cyclooxygenase-2, a Potential Therapeutic Target, Is Regulated by miR-101 in Esophageal Squamous Cell Carcinoma

BACKGROUND & AIMS

Cyclooxygenase-2 (COX-2) is known to promote the carcinogenesis of esophageal squamous cell carcinoma (ESCC). There are no reports on whether microRNAs (miRNAs) regulate COX-2 expression in ESCC. This study investigated the effect of miR-101 on ESCC through modulating COX-2 expression in ESCC.

METHODS

Real-time quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to quantify miR-101 expression in ESCC clinical tissues and cell lines. The effects of miR-101 on ESCC progression were evaluated by cell counting kit-8 (CCK8), transwell migration and invasion assays, as well as by flow cytometry. The COX-2 and PEG2 levels were determined by western blot and enzyme-linked immunosorbent assays (ELISA). The luciferase reporter assay was used to verify COX-2 as a direct target of miR-101. The anti-tumor activity of miR-101 in vivo was investigated in a xenograft nude mouse model of ESCC.

RESULTS

Downregulation of miR-101 was confirmed through comparison of 30 pairs of ESCC tumor and adjacent normal tissues (P < 0.001), as well as in 11 ESCC cell lines and a human immortalized esophageal cell line (P < 0.001). Transfection of miR-101 in ESCC cell lines significantly suppressed cell proliferation, migration, and invasion (all P < 0.001). The antitumor effect of miR-101 was verified in a xenograft model. Furthermore, COX-2 was shown to be a target of miR-101.

CONCLUSIONS

Overexpression of miR-101 in ESCC inhibits proliferation and metastasis. Therefore, the miR-101/COX-2 pathway might be a therapeutic target in ESCC.

Type I Interferons Function as Autocrine and Paracrine Factors to Induce Autotaxin in Response to TLR Activation

Lysophosphatidic acid (LPA) is an important phospholipid mediator in inflammation and immunity. However, the mechanism of LPA regulation during inflammatory response is largely unknown. Autotaxin (ATX) is the key enzyme to produce extracellular LPA from lysophosphatidylcholine (LPC). In this study, we found that ATX was induced in monocytic THP-1 cells by TLR4 ligand lipopolysaccharide (LPS), TLR9 ligand CpG oligonucleotide, and TLR3 ligand poly(I:C), respectively. The ATX induction by TLR ligand was abolished by the neutralizing antibody against IFN-β or the knockdown of IFNAR1, indicating that type I IFN autocrine loop is responsible for the ATX induction upon TLR activation. Both IFN-β and IFN-α were able to induce ATX expression via the JAK-STAT and PI3K-AKT pathways but with different time-dependent manners. The ATX induction by IFN-β was dramatically enhanced by IFN-γ, which had no significant effect on ATX expression alone, suggesting a synergy effect between type I and type II IFNs in ATX induction. Extracellular LPA levels were significantly increased when THP-1 cells were treated with IFN-α/β or TLR ligands. In addition, the type I IFN-mediated ATX induction was identified in human monocyte-derived dendritic cells (moDCs) stimulated with LPS or poly(I:C), and IFN-α/β could induce ATX expression in human peripheral blood mononuclear cells (PBMCs) and monocytes isolated form blood samples. These results suggest that, in response to TLR activation, ATX is induced through a type I INF autocrine-paracrine loop to enhance LPA generation.

UV-B induction of the E3 ligase ARIADNE12 depends on CONSTITUTIVELY PHOTOMORPHOGENIC 1

The UV-B inducible ARIADNE12 (ARI12) gene of Arabidopsis thaliana is a member of the RING-between-RING (RBR) family of E3 ubiquitin ligases for which a novel ubiquitination mechanism was identified in mammalian homologs. This RING-HECT hybrid mechanism needs a conserved cysteine which is replaced by serine in ARI12 and might affect the E3 ubiquitin ligase activity. We have shown that under photomorphogenic UV-B, ARI12 is a downstream target of the classical ultraviolet B (UV-B) UV Resistance Locus 8 (UVR8) pathway. However, under high fluence rate of UV-B ARI12 was induced independently of UVR8 and the UV-A/blue light and red/far-red photoreceptors. A key component of several light signaling pathways is Constitutively Photomorphogenic 1 (COP1). Upon UV-B COP1 is trapped in the nucleus through interaction with UVR8 permitting the activation of genes that regulate the biosynthesis of UV-B protective metabolites and growth adaptations. To clarify the role of COP1 in the regulation of ARI12 mRNA expression and ARI12 protein stability, localization and interaction with COP1 was assessed with and without UV-B. We found that COP1 controls ARI12 in white light, low and high fluence rate of UV-B. Furthermore we show that ARI12 is indeed an E3 ubiquitin ligase which is mono-ubiquitinated, a prerequisite for the RING-HECT hybrid mechanism. Finally, genetic analyses with transgenes expressing a genomic pmARI12:ARI12-GFP construct confirm the epistatic interaction between COP1 and ARI12 in growth responses to high fluence rate UV-B.

UCP2-induced fatty acid synthase promotes NLRP3 inflammasome activation during sepsis

Cellular lipid metabolism has been linked to immune responses; however, the precise mechanisms by which de novo fatty acid synthesis can regulate inflammatory responses remain unclear. The NLRP3 inflammasome serves as a platform for caspase-1-dependent maturation and secretion of proinflammatory cytokines. Here, we demonstrated that the mitochondrial uncoupling protein-2 (UCP2) regulates NLRP3-mediated caspase-1 activation through the stimulation of lipid synthesis in macrophages. UCP2-deficient mice displayed improved survival in a mouse model of polymicrobial sepsis. Moreover, UCP2 expression was increased in human sepsis. Consistently, UCP2-deficient mice displayed impaired lipid synthesis and decreased production of IL-1β and IL-18 in response to LPS challenge. In macrophages, UCP2 deficiency suppressed NLRP3-mediated caspase-1 activation and NLRP3 expression associated with inhibition of lipid synthesis. In UCP2-deficient macrophages, inhibition of lipid synthesis resulted from the downregulation of fatty acid synthase (FASN), a key regulator of fatty acid synthesis. FASN inhibition by shRNA and treatment with the chemical inhibitors C75 and cerulenin suppressed NLRP3-mediated caspase-1 activation and inhibited NLRP3 and pro-IL-1β gene expression in macrophages. In conclusion, our results suggest that UCP2 regulates the NLRP3 inflammasome by inducing the lipid synthesis pathway in macrophages. These results identify UCP2 as a potential therapeutic target in inflammatory diseases such as sepsis.

Mutation of the light-induced yellow leaf 1 gene, which encodes a geranylgeranyl reductase, affects chlorophyll biosynthesis and light sensitivity in rice

Chlorophylls (Chls) are crucial for capturing light energy for photosynthesis. Although several genes responsible for Chl biosynthesis were characterized in rice (Oryza sativa), the genetic properties of the hydrogenating enzyme involved in the final step of Chl synthesis remain unknown. In this study, we characterized a rice light-induced yellow leaf 1-1 (lyl1-1) mutant that is hypersensitive to high-light and defective in the Chl synthesis. Light-shading experiment suggested that the yellowing of lyl1-1 is light-induced. Map-based cloning of LYL1 revealed that it encodes a geranylgeranyl reductase. The mutation of LYL1 led to the majority of Chl molecules are conjugated with an unsaturated geranylgeraniol side chain. LYL1 is the firstly defined gene involved in the reduction step from Chl-geranylgeranylated (Chl(GG)) and geranylgeranyl pyrophosphate (GGPP) to Chl-phytol (Chl(Phy)) and phytyl pyrophosphate (PPP) in rice. LYL1 can be induced by light and suppressed by darkness which is consistent with its potential biological functions. Additionally, the lyl1-1 mutant suffered from severe photooxidative damage and displayed a drastic reduction in the levels of α-tocopherol and photosynthetic proteins. We concluded that LYL1 also plays an important role in response to high-light in rice.

Human epidermal growth factor receptor 3 (HER3) blockade with U3-1287/AMG888 enhances the efficacy of radiation therapy in lung and head and neck carcinoma

HER3 is a member of the epidermal growth factor receptor (EGFR) family of receptor tyrosine kinases. In the present study, we investigated the capacity of the HER3 blocking antibody, U3-1287/AMG888, to modulate the in vitro and in vivo radiation response of human squamous cell carcinomas of the lung and head and neck. We screened a battery of cell lines from these tumors for HER3 expression and demonstrated that all cell lines screened exhibited expression of HER3. Importantly, U3-1287/AMG888 treatment could block both basal HER3 activity and radiation induced HER3 activation. Proliferation assays indicated that HER3 blockade could decrease the proliferation of both HNSCC cell line SCC6 and NSCLC cell line H226. Further, we demonstrated that U3-1287/AMG888 can sensitize cells to radiation in clonogenic survival assays, in addition to increasing DNA damage as detected via λ-H2AX immunofluorescence. To determine if U3-1287/AMG888 could enhance radiation sensitivity in vivo we performed tumor growth delay experiments using SCC6, SCC1483, and H226 xenografts. The results of these experiments indicated that the combination of U3-1287/AMG888 and radiation could decrease tumor growth in studies using single or fractionated doses of radiation. Analysis of HER3 expression in tumor samples indicated that radiation treatment activated HER3 in vivo and that U3-1287/AMG888 could abrogate this activation. Immunohistochemistry analysis of SCC6 tumors treated with both U3-1287/AMG888 and a single dose of radiation demonstrated that various cell survival and proliferation markers could be reduced. Collectively our findings suggest that U3-1287/AMG888 in combination with radiation has an impact on cell and tumor growth by increasing DNA damage and cell death. These findings suggest that HER3 may play an important role in response to radiation therapy and blocking its activity in combination with radiation may be of therapeutic benefit in human tumors.

Smoke carcinogens cause bone loss through the aryl hydrocarbon receptor and induction of Cyp1 enzymes

Smoking is a major risk factor for osteoporosis and fracture, but the mechanism through which smoke causes bone loss remains unclear. Here, we show that the smoke toxins benzo(a)pyrene (BaP) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) interact with the aryl hydrocarbon receptor (Ahr) to induce osteoclastic bone resorption through the activation of cytochrome P450 1a/1b (Cyp1) enzymes. BaP and TCDD enhanced osteoclast formation in bone marrow cell cultures and gavage with BaP stimulated bone resorption and osteoclastogenesis in vivo. The osteoclastogenesis triggered by BaP or RANK-L was reduced in Ahr(-/-) cells, consistent with the high bone mass noted in Ahr(-/-) male mice. The receptor activator of NF-κB ligand (RANK-L) also failed to induce the expression of Cyp1 enzymes in Ahr(-/-) cells. Furthermore, the osteoclastogenesis induced by TCDD was lower in Cyp1a1/1a2(-/-) and Cyp1a1/1a2/1b1(-/-) cultures, indicating that Ahr was upstream of the Cyp enzymes. Likewise, the pharmacological inhibition of the Cyp1 enzymes with tetramethylsilane or proadifen reduced osteoclastogenesis. Finally, deletion of the Cyp1a1, Cyp1a2, and Cyp1b1 in triple knockout mice resulted in reduced bone resorption and recapitulated the high bone mass phenotype of Ahr(-/-) mice. Overall, the data identify the Ahr and Cyp1 enzymes not only in the pathophysiology of smoke-induced osteoporosis, but also as potential targets for selective modulation by new therapeutics.

Characterization of Pseudomonas aeruginosa growth on O-acylcarnitines and identification of a short-chain acylcarnitine hydrolase

To survive in various environments, from host tissue to soil, opportunistic bacterial pathogens must be metabolically flexible and able to use a variety of nutrient sources. We are interested in Pseudomonas aeruginosa's catabolism of quaternary amine compounds that are prevalent in association with eukaryotes. Carnitine and acylcarnitines are abundant in animal tissues, particularly skeletal muscle, and are used to shuttle fatty acids in and out of the mitochondria, where they undergo β-oxidation. We previously identified the genes required for carnitine catabolism as the first four genes in the carnitine operon (caiX-cdhCAB; PA5388 to PA5385). However, the last gene in the operon, PA5384, was not required for carnitine catabolism. We were interested in determining the function of PA5384. Bioinformatic analyses along with the genomic location of PA5384 led us to hypothesize a role for PA5384 in acylcarnitine catabolism. Here, we have characterized PA5384 as an l-enantiomer-specific short-chain acylcarnitine hydrolase that is required for growth and hydrolysis of acetyl- and butyrylcarnitine to carnitine and the respective short-chain fatty acid. The liberated carnitine and its downstream catabolic product, glycine betaine, are subsequently available to function as osmoprotectants in hyperosmotic environments and induce transcription of the virulence factor phospholipase C, plcH. Furthermore, we confirmed that acylcarnitines with 2- to 16-carbon chain lengths, except for octanoylcarnitine (8 carbons), can be utilized by P. aeruginosa as sole carbon and nitrogen sources. These findings expand our knowledge of short-chain acylcarnitine catabolism and also point to remaining questions related to acylcarnitine transport and hydrolysis of medium- and long-chain acylcarnitines.

Severe liver cirrhosis markedly reduces AhR-mediated induction of cytochrome P450 in rats by decreasing the transcription of target genes

Although the induction of cytochrome P450 (CYP) has long been investigated in patients with cirrhosis, the question whether liver dysfunction impairs the response to CYP inducers still remains unresolved. Moreover, the mechanism underlying the possible effect of cirrhosis on induction has not been investigated. Since ethical constraints do not permit methodologically rigorous studies in humans, this question was addressed by investigating the effect of the prototypical inducer benzo[a]pyrene (BP) on CYP1A1 and CYP1A2 in cirrhotic rats stratified according to the severity of liver dysfunction. We simultaneously assessed mRNA level, protein expression and enzymatic activity of the CYP1A enzymes, as well as mRNA and protein expressions of the aryl hydrocarbon receptor (AhR), which mediates the BP effect. Basal mRNA and protein expressions of CYP1A1 were virtually absent in both healthy and cirrhotic rats. On the contrary, CYP1A2 mRNA, protein and enzyme activity were constitutively present in healthy rats and decreased significantly as liver function worsened. BP treatment markedly increased the concentrations of mRNA and immunodetectable protein, and the enzymatic activities of both CYP1A enzymes to similar levels in healthy and non-ascitic cirrhotic rats. Induced mRNA levels, protein expressions and enzymatic activities of both CYPs were much lower in ascitic rats and were proportionally reduced. Both constitutive and induced protein expressions of AhR were significantly lower in ascitic than in healthy rats. These results indicate that the inducibility of CYP1A enzymes is well preserved in compensated cirrhosis, whereas it is markedly reduced when liver dysfunction becomes severe. Induction appears to be impaired at the transcriptional level, due to the reduced expression of AhR, which controls the transcription of CYP1A genes.

Severe liver cirrhosis markedly reduces AhR-mediated induction of cytochrome P450 in rats by decreasing the transcription of target genes

Although the induction of cytochrome P450 (CYP) has long been investigated in patients with cirrhosis, the question whether liver dysfunction impairs the response to CYP inducers still remains unresolved. Moreover, the mechanism underlying the possible effect of cirrhosis on induction has not been investigated. Since ethical constraints do not permit methodologically rigorous studies in humans, this question was addressed by investigating the effect of the prototypical inducer benzo[a]pyrene (BP) on CYP1A1 and CYP1A2 in cirrhotic rats stratified according to the severity of liver dysfunction. We simultaneously assessed mRNA level, protein expression and enzymatic activity of the CYP1A enzymes, as well as mRNA and protein expressions of the aryl hydrocarbon receptor (AhR), which mediates the BP effect. Basal mRNA and protein expressions of CYP1A1 were virtually absent in both healthy and cirrhotic rats. On the contrary, CYP1A2 mRNA, protein and enzyme activity were constitutively present in healthy rats and decreased significantly as liver function worsened. BP treatment markedly increased the concentrations of mRNA and immunodetectable protein, and the enzymatic activities of both CYP1A enzymes to similar levels in healthy and non-ascitic cirrhotic rats. Induced mRNA levels, protein expressions and enzymatic activities of both CYPs were much lower in ascitic rats and were proportionally reduced. Both constitutive and induced protein expressions of AhR were significantly lower in ascitic than in healthy rats. These results indicate that the inducibility of CYP1A enzymes is well preserved in compensated cirrhosis, whereas it is markedly reduced when liver dysfunction becomes severe. Induction appears to be impaired at the transcriptional level, due to the reduced expression of AhR, which controls the transcription of CYP1A genes.

Overexpression of DYRK1A inhibits choline acetyltransferase induction by oleic acid in cellular models of Down syndrome

Histological brain studies of individuals with DS have revealed an aberrant formation of the cerebral cortex. Previous work from our laboratory has shown that oleic acid acts as a neurotrophic factor and induces neuronal differentiation. In order to characterize the effects of oleic acid in a cellular model of DS, immortalized cell lines derived from the cortex of trisomy Ts16 (CTb) and normal mice (CNh) were incubated in the absence or presence of oleic acid. Oleic acid increased choline acetyltransferase expression (ChAT), a marker of cholinergic differentiation in CNh cells. However, in trisomic cells (CTb line) oleic acid failed to increase ChAT expression. These results suggest that the overdose of specific genes in trisomic lines delays differentiation in the presence of oleic acid by inhibiting acetylcholine production mediated by ChAT. The dual-specificity tyrosine (Y) phosphorylation-regulated kinase 1A (DYRK1A) gene is located on human chromosome 21 and encodes a proline-directed protein kinase. It has been proposed that DYRK1A plays a prominent role in several biological functions, leading to mental retardation in DS patients. Here we explored the potential role of DYRK1A in the modulation of ChAT expression in trisomic cells and in the signaling pathways of oleic acid. Down-regulation of DYRK1A by siRNA in trisomic CTb cells rescued ChAT expression up to levels similar to those of normal cells in the presence of oleic acid. In agreement with these results, oleic acid was unable to increase ChAT expression in neuronal cultures of transgenic mice overexpressing DYRK1A. In summary, our results highlight the role played by DYRK1A in brain development through the control of ChAT expression. In addition, the overexpression of DYRK1A in DS models prevented the neurotrophic effect of oleic acid, a fact that may account for mental retardation in DS patients.

Hepatic stellate cells undermine the allostimulatory function of liver myeloid dendritic cells via STAT3-dependent induction of IDO

Hepatic stellate cells (HSCs) are critical for hepatic wound repair and tissue remodeling. They also produce cytokines and chemokines that may contribute to the maintenance of hepatic immune homeostasis and the inherent tolerogenicity of the liver. The functional relationship between HSCs and the professional migratory APCs in the liver, that is, dendritic cells (DCs), has not been evaluated. In this article, we report that murine liver DCs colocalize with HSCs in vivo under normal, steady-state conditions, and cluster with HSCs in vitro. In vitro, HSCs secrete high levels of DC chemoattractants, such as MΙP-1α and MCP-1, as well as cytokines that modulate DC activation, including TNF-α, IL-6, and IL-1β. Culture of HSCs with conventional liver myeloid (m) DCs resulted in increased IL-6 and IL-10 secretion compared with that of either cell population alone. Coculture also resulted in enhanced expression of costimulatory (CD80, CD86) and coinhibitory (B7-H1) molecules on mDCs. HSC-induced mDC maturation required cell-cell contact and could be blocked, in part, by neutralizing MΙP-1α or MCP-1. HSC-induced mDC maturation was dependent on activation of STAT3 in mDCs and, in part, on HSC-secreted IL-6. Despite upregulation of costimulatory molecules, mDCs conditioned by HSCs demonstrated impaired ability to induce allogeneic T cell proliferation, which was independent of B7-H1, but dependent upon HSC-induced STAT3 activation and subsequent upregulation of IDO. In conclusion, by promoting IDO expression, HSCs may act as potent regulators of liver mDCs and function to maintain hepatic homeostasis and tolerogenicity.

A peptidoglycan fragment triggers β-lactam resistance in Bacillus licheniformis

To resist to β-lactam antibiotics Eubacteria either constitutively synthesize a β-lactamase or a low affinity penicillin-binding protein target, or induce its synthesis in response to the presence of antibiotic outside the cell. In Bacillus licheniformis and Staphylococcus aureus, a membrane-bound penicillin receptor (BlaR/MecR) detects the presence of β-lactam and launches a cytoplasmic signal leading to the inactivation of BlaI/MecI repressor, and the synthesis of a β-lactamase or a low affinity target. We identified a dipeptide, resulting from the peptidoglycan turnover and present in bacterial cytoplasm, which is able to directly bind to the BlaI/MecI repressor and to destabilize the BlaI/MecI-DNA complex. We propose a general model, in which the acylation of BlaR/MecR receptor and the cellular stress induced by the antibiotic, are both necessary to generate a cell wall-derived coactivator responsible for the expression of an inducible β-lactam-resistance factor. The new model proposed confirms and emphasizes the role of peptidoglycan degradation fragments in bacterial cell regulation.

Pregnane X receptor and yin yang 1 contribute to the differential tissue expression and induction of CYP3A5 and CYP3A4

The hepato-intestinal induction of the detoxifying enzymes CYP3A4 and CYP3A5 by the xenosensing pregnane X receptor (PXR) constitutes a key adaptive response to oral drugs and dietary xenobiotics. In contrast to CYP3A4, CYP3A5 is additionally expressed in several, mostly steroidogenic organs, which creates potential for induction-driven disturbances of the steroid homeostasis. Using cell lines and mice transgenic for a CYP3A5 promoter we demonstrate that the CYP3A5 expression in these organs is non-inducible and independent from PXR. Instead, it is enabled by the loss of a suppressing yin yang 1 (YY1)-binding site from the CYP3A5 promoter which occurred in haplorrhine primates. This YY1 site is conserved in CYP3A4, but its inhibitory effect can be offset by PXR acting on response elements such as XREM. Taken together, the loss of YY1 binding site from promoters of the CYP3A5 gene lineage during primate evolution may have enabled the utilization of CYP3A5 both in the adaptive hepato-intestinal response to xenobiotics and as a constitutively expressed gene in other organs. Our results thus constitute a first description of uncoupling induction from constitutive expression for a major detoxifying enzyme. They also suggest an explanation for the considerable tissue expression differences between CYP3A5 and CYP3A4.

Light pulse induces ALA-S gene expression in the rat Harderian gland

The rodent Harderian glands (HGs) are large paired orbital organs with highest porphyrinogenic rates. We have previously shown that continuous light exposure abolished the day/night variations of the delta-aminolevulinate synthase (ALA-S; the rate-limiting enzyme for porphyrin biosynthesis) gene expression observed under standard light: dark cycles (LD 12:12) in the rat HGs. This study was designed to examine whether the ALA-S changes were actually associated directly with light. The response of ferrochelatase (enzyme that converts protoporphyrin IX into heme) to light was also examined. Male Wistar rats were acclimatized to light: dark cycles regimen of 12:12 for 2 weeks. At the end of the 2 weeks, a 1 h-light pulse was applied in the middle of the dark phase. Animals were sacrificed immediately after the end of the light pulse. HGs were collected and stored at -80 degrees C until processed for quantitative RT-PCR. A 1 h-light pulse applied during mid-dark caused a significant increase of ALA-S gene expression (3-fold higher than in controls), whereas it was without effect on ferrochelatase gene expression. Our results suggest that light per se may regulate ALA-S gene expression in the rat HGs, and reveal that the ALA-S gene expression, and so heme biosynthesis, is under a photodynamic control.

Expression of the constitutively activated RelA/NF-kappaB in human astrocytic tumors and the in vitro implication in the regulation of urokinase-type plasminogen activator, migration, and invasion

Although malignant gliomas are highly invasive tumors, a characteristic that contributes to the commonly observed therapeutic failures and local disease recurrences, the molecular events that regulate invasion in these tumors remain poorly understood. Because the transcription factor RelA/NF-kappaB has been shown to regulate invasion during several cellular processes, we have examined immunohistochemically expression of the constitutively activated RelA/NF-kappaB in tissues obtained from 49 astrocytic tumors [8 diffuse astrocytomas, 9 anaplastic astrocytomas (AAs) and 32 glioblastomas (GBMs)]. In addition, we examined the in vitro effects of antisense oligonucleotides and curcumin on the expression and activation of RelA/NF-kappaB, urokinase-type plasminogen activator (u-PA) expression, migration, and invasion in the T98G glioma cell line. Expression of the constitutively activated RelA/NF-kappaB was observed in 2 (25%) of 8 cases of diffuse astrocytomas, 5 (55.6%) of 9 cases of AAs, and 30 (93.8%) of 32 cases of GBMs. This expression was significantly correlated with the malignant potential in astrocytic tumors (P < 0.001). Moreover, antisense oligonucleotides and curcumin inhibited phorbol-12-myristate-13-acetate (PMA)-induced RelA/NF-kappaB expression or activation (or both), down-regulated u-PA expression, and reduced the migration and invasive potentials of T98G glioma cells. Thus, the expression of constitutively activated RelA/NF-kappaB is associated with malignancy potential in astrocytic tumors and may play a critical role in the regulation of u-PA expression and invasiveness in gliomas. RelA/NF-kappaB may therefore be an intriguing candidate for studies aimed at understanding and prevention of the invasiveness of gliomas.

MicroRNA-29b induces global DNA hypomethylation and tumor suppressor gene reexpression in acute myeloid leukemia by targeting directly DNMT3A and 3B and indirectly DNMT1

Aberrant DNA hypermethylation contributes to myeloid leukemogenesis by silencing structurally normal genes involved in hematopoiesis. MicroRNAs (miRNAs) are noncoding RNAs that regulate gene expression by targeting protein-coding mRNAs. Recently, miRNAs have been shown to play a role as both targets and effectors in gene hypermethylation and silencing in malignant cells. In the current study, we showed that enforced expression of miR-29b in acute myeloid leukemia cells resulted in marked reduction of the expression of DNA methyltransferases DNMT1, DNMT3A, and DNMT3B at both RNA and protein levels. This in turn led to decrease in global DNA methylation and reexpression of p15(INK4b) and ESR1 via promoter DNA hypomethylation. Although down-regulation of DNMT3A and DNMT3B was the result of a direct interaction of miR-29b with the 3' untranslated regions of these genes, no predicted miR-29b interaction sites were found in the DNMT1 3' untranslated regions. Further experiments revealed that miR-29b down-regulates DNMT1 indirectly by targeting Sp1, a transactivator of the DNMT1 gene. Altogether, these data provide novel functional links between miRNAs and aberrant DNA hypermethylation in acute myeloid leukemia and suggest a potentially therapeutic use of synthetic miR-29b oligonucleotides as effective hypomethylating compounds.

BMP6 attenuates oxidant injury in HK-2 cells via Smad-dependent HO-1 induction

Oxidative stress is involved in a variety of kidney diseases, and heme oxygenase 1 (HO-1) induction is a protective response to oxidative stress. Downregulation of bone morphogenetic protein 6 (BMP6) is associated with renal damage in intrauterine growth-restricted newborns. However, it is unknown whether BMP6 has a renoprotective effect or HO-1 induction property. In this study, we demonstrate that BMP6 effectively protects renal proximal tubule cells (HK-2) against hydrogen peroxide (H(2)O(2))-induced cell injury. BMP6 also increased HO-1 gene expression and activity of HO. Inhibition of de novo gene expression, the HO inhibitor ZnPPIX, HO-1 knockdown, or the carbon monoxide (CO) scavenger hemoglobin attenuated the cytoprotective effect of BMP6, whereas HO-1 constitutive expression, the HO-1 inducer hemin, or the hemin metabolites bilirubin and CO ameliorated H(2)O(2)-induced cell injury. Stimulation of HK-2 cells with BMP6 activated Smad signaling but not mitogen-activated protein kinases. In addition, BMP6-mediated induction of HO-1 expression and increase in HO activity were inhibited by Smad5 knockdown. Furthermore, deletion or mutation of the Smad-binding element in the HO-1 promoter also inhibited BMP6-induced luciferase activity. In summary, these findings suggest that induction of HO-1 through a Smad-dependent mechanism is responsible for the cytoprotective effect of BMP6 in H(2)O(2)-mediated renal cell injury.

Oxidant stress stimulates expression of the human peroxiredoxin 6 gene by a transcriptional mechanism involving an antioxidant response element

Peroxiredoxin 6 (Prdx6) is a unique antioxidant enzyme that can reduce phospholipid and other hydroperoxides. A549 cells, a human lung-derived cell line, express both Prdx6 and Nrf2, a transcription factor that binds to antioxidant-response elements (AREs) and promotes expression of antioxidant genes. Treatment of A549 cells with 500 microM H(2)O(2) increased Prdx6 mRNA levels 2.5-fold, whereas treatment with 400 microM H(2)O(2) or 200 microM tert-butylhydroquinone (t-BHQ) triggered a corresponding 2.5-fold increase in reporter gene activity in A549 cells transfected with the pSEAP2:Basic vector (BD Bioscience), containing 1524 nucleotides of the human Prdx6 promoter region. Deletion of a consensus ARE sequence present between positions 357 and 349 before the start of transcription led to a striking decrease in both basal and H(2)O(2)- or t-BHQ-induced activation in A549 cells and H(2)O(2)-induced activation in primary rat alveolar type II cells. Cotransfection with Nrf2 stimulated the Prdx6 promoter in an ARE-dependent manner, whereas it was negatively regulated by Nrf3. siRNA targeting Nrf2 down-regulated reporter gene expression, whereas siRNA targeting the Nrf2 repressor, Keap1, up-regulated it. Binding of Nrf2 to the ARE sequence in chromatin was confirmed by PCR after chromatin immunoprecipitation. These data demonstrate that the ARE within the Prdx6 promoter is a key regulator of basal transcription of the Prdx6 gene and of its inducibility under conditions of oxidative stress.

Induction of human UGT1A1 by bilirubin through AhR dependent pathway

UDP-glucuronosyltransferase1A1 (UGT1A1) plays a key role to conjugate bilirubin and preventing jaundice, but there is no report showing the induction of human UGT1A1 (UGT1A1) by bilirubin. In this report, we show findings of the induction of the reporter gene (-3475/+14) of UGT1A1 in HepG2 cells by bilirubin at 50 microM, 100 microM, with human aryl hydrocarbon receptor (hAhR). We confirmed that induction of the reporter gene by bilirubin is dependent on the position of the xenobiotic responsive element (XRE) (-3328/-3319) of UGT1A1, because the XRE deletion UGT1A1 gene did not respond to stimulation by a complex of bilirubin and hAhR. alpha-Naphthoflavone (alpha-NF) of a typical AhR antagonist at 50 microM inhibited induction by bilirubin, suggesting that bilirubin stimulates through binding with hAhR. Meanwhile, bilirubin itself did not stimulate the induction of AhR, because we detected no-elevation of the mRNA level of AhR by RT-PCR. These results indicate that the induction of UGT1A1 by bilirubin-AhR did not depend on the elevation of AhR but on ligand binding. From this result, we considered that high bilirubin in neonates must induce the elevation of UGT1A1 after birth to prevent jaundice, and bilirubin in adults also regulates the level of UGT1A1. This is the first report showing direct induction of UGT1A1 by a bilirubin through AhR pathway.

Increased wild-type p53-induced phosphatase 1 (Wip1 or PPM1D) expression correlated with downregulation of checkpoint kinase 2 in human gastric carcinoma

Phosphorylation of checkpoint kinase 2 (Chk2) at Thr68 (pChk2) induced by DNA double-strand breaks is required for inhibition of cell cycle progression in the G(2) phase. The purpose of the present paper was to investigate the expression of wild-type p53-induced phosphatase 1 (Wip1 or PPM1D), a negative regulator of Chk2, to better understand its role in human gastric cancer. In non-neoplastic gastric mucosa, most epithelial cells exhibited Wip1-positive and pChk2-negative immunoreactivity, whereas an inverse pattern of protein expression was detected at the surface of the foveolar epithelium. In tumor tissues, 74% of 53 gastric cancers had intense Wip1 immunoreactivity and close correlation with both tumor size (P = 0.0497) and Chk2 dephosphorylation (P = 0.0213). In MKN-74 gastric cancer cells, ionizing radiation (IR)-induced Wip1 upregulation was detected at protein levels, but the Chk2-mediated cell cycle regulatory mechanism was disrupted. In addition, protease inhibitor Z-Leu-Leu-Leu (ZLLL) effectively upregulated Wip1 levels in the presence or absence of IR, suggesting that Wip1 expression can be modulated post-transcriptionally. Understanding the Wip1-mediated signaling pathway in gastric cancer may provide useful information for the development of new chemo- and radiotherapies.

Involvement of nitric oxide signaling in mammalian Bax-induced terpenoid indole alkaloid production of Catharanthus roseus cells

Bax, a mammalian pro-apoptotic member of the Bcl-2 family, has been demonstrated to be a potential regulatory factor for plant secondary metabolite biosynthesis recently. To investigate the molecular mechanism of Bax-induced secondary metabolite biosynthesis, we determined the contents of nitric oxide (NO) of the transgenic Catharanthus roseus cells overexpressing a mouse Bax protein and checked the effects of NO specific scavenger 2,4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPITO) on Bax-induced terpenoid indole alkaloid (TIA) production of the cells. The data showed that overexpression of the mouse Bax in C. roseus cells triggered NO generation of the cells. Treatment of cPITO not only inhibited the Bax-triggered NO burst but also suppressed the Bax-induced TIA production. The results indicated that the mouse Bax might activate the NO signaling in C. roseus cells and induce TIA production through the NO-dependent signal pathway in the cells. Furthermore, the activities of nitric oxide synthase (NOS) were significantly increased in the transgenic Bax cells as compared to those in the control cells, showing that the mouse Bax may induce NOS of C. roseus cells. Treatment of the transgenic Bax cells with NOS inhibitor PBITU blocked both Bax-induced NO generation and TIA production, which suggested that the mouse Bax might trigger NO generation and TIA production through NOS. However, the NOS-like activities and NO generation in the transgenic Bax cells did not match kinetically and the Bax-induced NOS-like activity was much later and lower than NO production. Moreover, the Bax-induced NO generation and TIA production were only partially inhibited by PBITU. Thus, our results suggested that the Bax-induced NO production and secondary metabolite biosynthesis in C. roseus cells was not entirely dependent on NOS or NOS-like enzymes.

Role of human hepatocyte nuclear factor 4alpha in the expression of drug-metabolizing enzymes and transporters in human hepatocytes assessed by use of small interfering RNA

Hepatocyte nuclear factor 4alpha (HNF4alpha) is an important transcription factor in hepatic gene expression. Here, we have investigated the role of HNF4alpha in the expression of drug-metabolizing enzymes and transporters in human hepatocytes using an adenovirus expressing human HNF4alpha-small interfering RNA (hHNF4alpha-siRNA). The hHNF4alpha-siRNA effectively reduced the mRNA and nuclear protein levels of hHNF4alpha in a concentration-dependent manner. The hHNF4alpha-siRNA also decreased the mRNA levels of CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, UGT1A1, UGT1A9, SULT2A1, ABCB1, ABCB11, ABCC2, OATP1B1 and OCT1, as well as those of PXR and CAR. To discern the role of these nuclear receptors, we co-infected hepatocytes with hHNF4alpha-siRNA and PXR- or CAR-expressing adenovirus. The hHNF4alpha-siRNA-induced reductions of the enzyme and transporter mRNA levels were not restored except CYP2B6 mRNA levels, which were returned to the control level by overexpressing CAR. Furthermore, although hHNF4alpha-siRNA did not significantly affect the fold-induction of CYP2B6, CYP2C8, CYP2C9, or CYP3A4 mRNA levels following treatment with CYP inducers, the levels in hHNF4alpha-suppressed cells fell significantly compared to the control. These results suggest that HNF4alpha plays a dominant role in the expression of drug-metabolizing enzymes and transporters in human hepatocytes, and that HNF4alpha expression levels is a possible determinant for inter-individual variations in the expression of these enzymes and transporters.

Pharmacologic induction of heme oxygenase 1 reduces acute inflammatory arthritis in mice

OBJECTIVE

To determine the consequences of pharmacologic up-regulation of heme oxygenase 1 (HO-1), and inhibition of HO-1 by injection of an anti-HO-1 small interfering RNA (siRNA), in vivo in the acute phase of a mouse model of nonautoimmune arthritis.

METHODS

In the K/BxN mouse serum transfer model, which mimics human inflammatory arthritis without lymphocyte influence, HO-1 was up-regulated by intraperitoneal injection of cobalt protoporphyrin IX (CoPP), a potent pharmacologic inducer, and was inhibited using a specific siRNA. The clinical progress of arthritis was monitored by measurement of paw thickness. Interleukin-1beta (IL-1beta), IL-6, tumor necrosis factor alpha (TNFalpha), serum antioxidant, and nitric oxide (NO) levels, prostaglandin E(2) (PGE(2)) production, and matrix metalloproteinase 9 (MMP-9) activity were measured in serum. At the end of the experiments, joints were examined for immunohistopathologic changes.

RESULTS

Intraperitoneal injection of CoPP alleviated disease symptoms, such as joint swelling, cartilage degradation, and proliferation of inflammatory tissue in joints, in the acute phase of inflammatory arthritis. The CoPP-induced expression of HO-1 in the joints and liver was associated with marked decreases in IL-1beta, IL-6, and TNFalpha levels, PGE(2) secretion, and MMP-9 activity in serum, and with a marked increase in systemic antioxidant activity. In contrast, NO production in serum and inducible NO synthase expression in chondrocytes were not affected by HO-1 induction. Specific inhibition of HO-1 by in vivo delivery of anti-HO-1 siRNA repressed the protective effects.

CONCLUSION

Our data provide the first evidence that pharmacologically induced up-regulation of HO-1 triggers a robust protective antiinflammatory response in a model of nonautoimmune arthritis in mice. This suggests that exogenously induced HO-1 may have potential as therapy in the acute phase of inflammatory arthritis in humans.

Unique N-region Determines Low Basal Activity and Limited Inducibility of A-RAF Kinase

In mammals the RAF family of serine/threonine kinases consists of three members, A-, B-, and C-RAF. A prominent feature of RAF isoforms regards differences in basal and inducible kinase activities. To elucidate the nature of these differences, we studied the role of the nonconserved residues within the N-region (Negative-charge regulatory region). The nonconserved amino acids in positions -3 and +1 relative to the highly conserved serine 299 in A-RAF and serine 338 in C-RAF have so far not been considered as regulatory residues. Here we demonstrate the essential role of these residues in the RAF activation process. Substitution of tyrosine 296 in A-RAF to arginine led to a constitutively active kinase. In contrast, substitution of glycine 300 by serine (mimicking B- and C-RAF) acts in an inhibitory manner. Consistent with these data, the introduction of glycine in the analogous position of C-RAF (S339G mutant) led to a constitutively active C-RAF kinase. Based on the three-dimensional structure of the catalytic domain of B-RAF and using the sequences of the N-regions of A- and C-RAF, we searched by molecular modeling for the putative contact points between these two moieties. A tight interaction between the N-region residue serine 339 of C-RAF and arginine 398 of the catalytic domain was identified and proposed to inhibit the kinase activity of RAF proteins, because abrogation of this interaction contributes to RAF activation. Furthermore, tyrosine 296 in A-RAF favors a spatial orientation of the N-region segment, which enables a tighter contact to the catalytic domain, whereas a glutamine residue at this position in C-RAF abrogates this interaction. Considering this observation, we suggest that tyrosine 296, which is unique for A-RAF, is a major determinant of the low activating potency of this RAF isoform.

Regulatory Factors Involved in Species-specific Modulation of Arylhydrocarbon Receptor (AhR)-dependent Gene Expression in Humans and Mice

The arylhydrocarbon receptor (AhR) mediates toxicities of dioxins, including the most potent congener 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), by being translocated to the nucleus upon ligand-binding and inducing expression of target genes. Although the species-specific activity of the AhR is primarily attributable to species-specific AhR-ligand affinity, the precise mechanism has not been clarified. We investigated the modulation mechanisms of AhR in Hepa1c1c7 and HepG2 hepatoma cells, which were derived from high-affinity-AhR-expressing C57BL/6 mice and low-affinity-AhR-expressing humans, respectively. Although, consistent with their AhR affinities, TCDD induced a greater amount of cytochrome P450 1A1 (CYP1A1) mRNA, one of the most sensitive AhR-targets, in Hepa1c1c7 cells than in HepG2 cells immediately after exposure, both cells expressed a similar level of CYP1A1 mRNA from 4 h onward. A rapid decrease in the AhR protein after nuclear translocation in Hepa1c1c7 cells was suggested to contribute to suppression of CYP1A1 induction to the same level as in HepG2 cells. Different profiles of histone deacetylase 1 (HDAC1)-binding to the CYP1A1 promoter and histone acetylation between both cell lines and lower degradation rate of CYP1A1 mRNA in HepG2 cells were also implicated in regulating their target gene expression. These factors have been highly suggested to be involved in the species-specific modulation mechanism of AhR function.

Carboxypeptidase D: A Novel TGF-β Target Gene Dysregulated in Patients with Lupus Erythematosus

Transforming growth factor-beta (TGF-beta) is a multifunctional cytokine that mainly acts as an inhibitor of immune functions. A lack of functional TGF-beta leads to autoimmune disease in animal models and dysregulated TGF-beta signaling is implicated in human autoimmune diseases. To define target genes that play a part in the inhibitory role of TGF-beta in the immune system, we have identified genes stimulated by TGF-beta in macrophages by gene-chip analysis. One of the TGF-beta regulated genes is carboxypeptidase D (CpD), a 180-kDa type I membrane protein. We have demonstrated that CpD is regulated by TGF-beta in various cell types of both, murine and human origin and, interestingly, is significantly downregulated in CD14 positive cells isolated from patients with lupus erythematosus (LE). Moreover, we show that downregulation of CpD leads to downmodulation of TGF-beta itself, suggesting a role for CpD in a positive feedback loop, providing further evidence for a role of this enzyme in LE. To our knowledge, this is the first report that demonstrates carboxypeptidase D as a TGF-beta target gene that is implicated in the pathogenesis of LE.

Arginine vasopressin increases iNOS–NO system activity in cardiac fibroblasts through NF-κB activation and its relation with myocardial fibrosis

Previous studies have shown that arginine vasopressin (AVP) promotes myocardial fibrosis (MF), whereas nitric oxide (NO) inhibits MF. Cardiac fibroblasts (CFs) are the main target cells of MF. However, the modulatory effect of AVP on NO production in CFs and the role of this effect in MF are still unknown. In the present study, CFs obtained from Sprague-Dawley rats were stimulated with or without AVP and pyrrolidine dithiocarbamate (PDTC), a specific inhibitor of nuclear factor kappa-B (NF-kappaB). NO production and NOS activity were detected with absorption spectrometry, inducible nitric oxide synthase (iNOS) protein with Western blot analysis, iNOS mRNA with real-time PCR, CF collagen synthesis with [(3)H]proline incorporation, and NF-kappaB activation with immunofluorescence staining and Western blot analysis. The results showed that AVP increased NO production in a dose- and time-dependent manner, with maximal effects at 10(-7) mol/l after 24-h stimulation. AVP also increased NOS activity, protein and mRNA levels of iNOS in a coincident manner. Furthermore, AVP also increased CF collagen synthesis in a dose- and time-dependent manner. In addition, it was found that NF-kappaB was activated by AVP, and that PDTC could inhibit NO production, NOS activity, protein and mRNA levels of iNOS stimulated by AVP in a dose-dependent manner. The inhibitory effects of PDTC on NF-kappaB translocation were coincident with the effects of PDTC on iNOS-NO system activity. It is suggested that AVP increases NO production via the regulation of iNOS gene expression, and the upregulation of iNOS gene expression stimulated by AVP is mediated through NF-kappaB activation. NO production induced by AVP may counteract the profibrotic effects of AVP, thus the development of MF perhaps depends on the balance between profibrotic AVP and antifibrotic NO effects on MF.

Ras/Erk pathway positively regulates Jak1/STAT6 activity and IL-4 gene expression in Jurkat T cells

T helper cells can be largely divided into two functional subsets, Th1 and Th2, which are characterized by the cytokines they produce. The mechanism of Th1 versus Th2 cytokine production is thought to involve interaction of TCR-induced signal and cytokine-induced signal, mainly activating the Ras/MAPK and the Jak/STAT pathway, respectively. In order to gain insight into the signal transduction network for Th1 and Th2 differentiation, we have analyzed the functional cross-talk between the Jak/STAT and the Ras/MAPK pathway. In cytokine-producing Jurkat T cells, we have found that IL-4 induces activation of Erk and Akt, and the IL-4-induced STAT6 activity is suppressed by inhibitors of Erk and PI3K. The transfection of daRas into these cells resulted in the up-regulation of specific activity of Jak1/STAT6 with a concomitant increase in Erk and Akt activity, while siRNA-mediated knock-out of Ras resulted in the inhibition of Jak1/STAT6. Furthermore, the IL-4 mRNA expression and IL-4 promoter activity were enhanced by daRas but not by dnRas. The Ras-induced increase of both STAT6 activity and IL-4 mRNA level was effectively blocked by a Mek/Erk inhibitor, suggesting that Ras/Erk pathway positively regulates STAT6 activity and IL-4 transcription. Together, the results indicate that there is a functional cross-talk between Ras/Erk and IL-4/Jak1/STAT6, which contributes to the regulation of IL-4 transcription in T cells.

Induction of cullin 7 by DNA damage attenuates p53 function

The p53 tumor suppressor gene encodes a transcription factor, which is translationally and posttranslationally activated after DNA damage. In a proteomic screen for p53 interactors, we found that the cullin protein Cul7 efficiently associates with p53. After DNA damage, the level of Cul7 protein increased in a caffeine-sensitive, but p53-independent, manner. Down-regulation of Cul7 by conditional microRNA expression augmented p53-mediated inhibition of cell cycle progression. Ectopic expression of Cul7 inhibited activation of p53 by DNA damaging agents and sensitized cells to adriamycin. Although Cul7 recruited the F-box protein FBX29 to p53, the combined expression of Cul7/FBX29 did not promote ubiquitination and degradation of p53 in vivo. Therefore, the inhibition of p53 activity by Cul7 is presumably mediated by alternative mechanisms. The interplay between p53 and Cul7 resembles the negative feedback loop described for p53 and Mdm2. Pharmacological modulation of Cul7 function may allow the sensitization of cancer cells expressing wild-type p53 to genotoxic agents used in cancer therapy.

Signal transducer and activator of transcription 3 activation promotes invasive growth of colon carcinomas through matrix metalloproteinase induction

Signal transducer and activator of transcription 3 (STAT3) is aberrantly activated in colorectal carcinomas (CRCs). Here, we define the relationship between STAT3 function and the malignant properties of colon carcinoma cells. Elevated activation of STAT3 enhances invasive growth of the CRC cell lines. To address mechanisms through which STAT3 influences invasiveness, the protease mRNA expression pattern of CRC biopsies was analyzed and correlated with the STAT3 activity status. These studies revealed a striking coincidence of STAT3 activation and strong expression of matrix metalloproteinases MMP-1, -3, -7, and -9. Immunohistological examination of CRC tumor specimens showed a clear colocalization of MMP-1 and activated STAT3. Experimentally induced STAT3 activity in CRC cell lines enhanced both the level of MMP-1 mRNA and secreted MMP-1 enzymatic activity. A direct connection of STAT3 activity and transcription from the MMP-1 promoter was shown by reporter gene experiments. Moreover, high-affinity binding of STAT3 to STAT recognition elements in both the MMP-1 and MMP-3 promoter was demonstrated. Xenograft tumors arising from implantation of CRC cells into nude mice showed simultaneous appearance and colocalization of p-Y-STAT3 and MMP-1 expression. Our results link aberrant activity of STAT3 in CRC to malignant tumor progression through upregulated expression of MMPs.

Regulation of the microsomal prostaglandin E synthase-1 in polarized mononuclear phagocytes and its constitutive expression in neutrophils

PGs are potent mediators of pain and inflammation. PGE synthases (PGES) catalyze the isomerization of PGH(2) into PGE(2). The microsomal (m)PGES-1 isoform serves as an inducible PGES and is responsible for the production of PGE(2), which mediates acute pain in inflammation and fever. The present study was designed to investigate the regulation of expression of mPGES-1 in polarized phagocytes, which represent central, cellular orchestrators of inflammatory reactions. Here, we report that human peripheral blood monocytes did not express mPGES-1. Exposure to LPS strongly induced mPGES-1 expression. Alternatively activated M2 monocytes-macrophages exposed to IL-4, IL-13, or IL-10 did not express mPGES-1, whereas in these cells, IL-4, IL-13, and to a lesser extent, IL-10 or IFN-gamma inhibited LPS-induced, mPGES-1 expression. It is unexpected that polymorphonuclear leukocytes expressed high basal levels of mPGES-1, which was up-regulated by LPS and down-regulated by IL-4 and IL-13. Induction of mPGES-1 and its modulation by cytokines were confirmed at the protein level and correlated with PGE(2) production. Cyclooxygenase 2 expression tested in the same experimental conditions was modulated in monocytes and granulocytes similarly to mPGES-1. Thus, activated M1, unlike alternatively activated M2, mononuclear phagocytes express mPGES-1, and IL-4, IL-13, and IL-10 tune expression of this key enzyme in prostanoid metabolism. Neutrophils, the first cells to enter sites of inflammation, represent a ready-made, cellular source of mPGES-1.

Catalytic characterization and cytokine mediated regulation of cytochrome P450 4Fs in rat hepatocytes

Cytochrome P450 (CYP) 4F mediated leukotriene B(4) (LTB(4)) metabolism modulates inflammation during injury and infection. Here we show that in addition to LTB(4), the recombinant rat CYP4Fs catalyze omega-hydroxylations of lipoxin A(4), and hydroxyeicosatetraeonic acids. CYP4F gene regulation studies in primary hepatocytes reveal that pro-inflammatory cytokines interleukin (IL) -1beta, IL-6 and tumor necrosis factor (TNF) -alpha produce a general inductive response whereas IL-10, an anti-inflammatory cytokine, suppresses CYP4F expression. The molecular mechanism behind IL-6 related induction of CYP4F4 and 4F5 is partially signal transducer and activator of transcription 3 (STAT3) dependent. When hepatocytes are subjected to high concentrations of LTB(4) or prostaglandin E(2), lipid mediators of inflammation, only an increase in CYP4F5 mRNA expression is observed. Collectively, the results from isozyme activity and substrate driven CYP4F induction do not support the notion that an autoregulatory pathway could control the excessive concentrations of LTB(4) during an inflammatory challenge to hepatocytes.

FGFs, Wnts and BMPs mediate induction of VEGFR-2 (Quek-1) expression during avian somite development

Regulation of VEGFR-2 (Quek1) is an important mechanism during blood vessel formation. In the paraxial mesoderm, Quek1 expression is restricted to the lateral portion of the somite and later to sclerotomal cells surrounding the neural tube. By implanting FGF 8b/8c or SU 5402 beads into the paraxial mesoderm, we show that FGF8 in addition to BMP4 from the intermediate mesoderm (IM) is a positive regulator of VEGFR-2 (Quek1) expression in the quail embryo. The expression of Quek1 in the medial somite half is normally repressed by the notochord and Sfrps-expression in the neural tube. Over-expression of Wnt 1/3a also results in an up-regulation of Quek1 expression in the somites. We also show that up-regulation of FGF8/Wnt 1/3a leads to an increase in the number of endothelial cells, whereas inhibition of FGF and Wnt signaling by SU 5402 and Sfrp-2 results in a loss of endothelial cells. Our results demonstrate that the regulation of Quek1 expression in the somites is mediated by the cooperative actions of BMP4, FGF8 and Wnt-signaling pathways.

Expression and induction of secretory phospholipase A2 group IB in brain

Secretory phospholipases A2 (sPLA2) form a diverse family of enzymes involved in physiologic and pathologic processes. Common among all sPLA2 is the ability to cleave acyl groups of phospholipids at C2 of the glycerol backbone, thereby releasing fatty acid and a lysophospholipid. Several sPLA2 have been cloned and characterized in various tissues. Furthermore, receptors have been identified. In the nervous system sPLA2 groups IIA, IIE, IIF, V, and XII have been identified, and binding sites for sPLA2 group IB (sPLA2-IB) have been found. Here, we report sPLA2-IB in rat and human brain as well as in neurons in primary culture. The distribution of sPLA2-IB seems to be mainly neuronal, with the highest abundance occurring in the cerebral cortex and hippocampus. We also find that genes encoding sPLA2-IB are induced by kainic acid and by electroshock-induced convulsions. Based on the present results we suggest that sPLA2-IB may be a neuronal intercellular signalling modulator.

Gene expression profiles of drug-metabolizing enzymes and transporters with an overexpression of hepatocyte growth factor

BACKGROUND

It is important to elucidate the precise mechanism of drug metabolism during hepatic regeneration. Although cytochromes P450 (CYPs) are well known to be down-regulated in growth-stimulated cells, the overall gene expression profile of drug metabolizing enzymes are still not fully understood during hepatic regeneration. In this study, we investigated the gene expression profiles of such enzymes with an overexpression of hepatocyte growth factor (HGF).

METHODS

Gene expression profiles were obtained using the Affymetrix MOE430A GeneChip oligonucleotide microarray by comparing HGF transgenic mice and wild-type mice.

RESULTS

HGF produced a general decrease in mice with the expression of CYP isoforms such as Cyp1a2, Cyp2b10, Cyp2c, Cyp2d9, Cyp3a11, Cyp4a10, and Cyp7a1. Some isoforms of alcohol dehydrogenase, aldehyde dehydrogenase, and carboxylesterase also decreased. In the phase II enzymes, some isoforms of glutathione S-transferase and UDP-glucuronosyl transferase showed a reduced expression, although the sulfotransferase did not. In phase III transporters, some organic anion transporter and organic cation transporters were down-regulated. Among the nuclear receptors that are known to regulate the drug-metabolizing enzymes, small heterodimer partner and constitutive androstane receptor were down-regulated with an HGF overexpression. The protein level and enzymatic activity of Cyp2c decreased with an HGF overexpression. We furthermore investigated the inducibility of Cyp2b10 with xenobiotic inducers. Although the basal expression of Cyp2b10 was repressed, the inducibility was not abolished with the HGF overexpression.

CONCLUSIONS

HGF down-regulated not only CYPs but also some drug-metabolizing enzymes, transporters, and nuclear receptors. We thus have to take in our mind the low basal expression of drug metabolizing enzymes, when treating patients with a regenerative liver state.

Substrate-inducible versions of internal alternative NADH: ubiquinone oxidoreductase from Yarrowia lipolytica

In standard laboratory strains of the obligate aerobic yeast Yarrowia lipolytica, respiratory chain complex I (proton-translocating NADH : ubiquinone oxidoreductase) is an essential enzyme, since alternative NADH dehydrogenase activity is located exclusively at the external face of the mitochondrial inner membrane. Deletions and other loss-of-function mutations in genes for nuclear coded subunits of complex I can be obtained only when an internal version of the latter enzyme, termed NDH2i, is introduced. In contrast to recent findings with Neurospora crassa, external alternative NADH dehydrogenase activity is dispensable in complex I deletion strains of Y. lipolytica. We used regulable promoters to create strains which express internal alternative NADH dehydrogenase in a substrate-dependent manner. The ability to switch between complex I-dependent and -independent mode of growth simply by changing the carbon source is an important prerequisite for screens for both loss-of-function and inhibitor resistance mutation. The isocitrate lyase promoter (pICL1), in combination with a NDH2i allele that results in reduced expression and activity, was most promising. In the presence of complex I inhibitors, this construct allowed growth on acetate, but not on glucose minimal media. A somewhat higher background was observed with the acyl-CoA oxidase 2 (pPOX2) promoter on glucose minimal media.

Identification of an alternative oxidase induction motif in the promoter region of the aod-1 gene in Neurospora crassa

The nuclear aod-1 gene of Neurospora crassa encodes the alternative oxidase and is induced when the standard cytochrome-mediated respiratory chain of mitochondria is inhibited. To study elements of the pathway responsible for alternative oxidase induction, we generated a series of mutations in the region upstream from the aod-1 structural gene and transformed the constructs into an aod-1 mutant strain. Transformed conidia were plated on media containing antimycin A, which inhibits the cytochrome-mediated electron transport chain so that only cells expressing alternative oxidase will grow. Using this functional in vivo assay, we identified an alternative oxidase induction motif (AIM) that is required for efficient expression of aod-1. The AIM sequence consists of two CGG repeats separated by 7 bp and is similar to sequences known to be bound by members of the Zn(II)2Cys6 binuclear cluster family of transcription factors. The AIM motif appears to be conserved in other species found in the order Sordariales.

p38-MAPK induced dephosphorylation of alpha-tropomyosin is associated with depression of myocardial sarcomeric tension and ATPase activity

Our objective in work presented here was to understand the mechanisms by which activated p38alpha MAPK depresses myocardial contractility. To test the hypothesis that activation of p38 MAPK directly influences sarcomeric function, we used transgenic mouse models with hearts in which p38 MAPK was constitutively turned on by an upstream activator (MKK6bE). These hearts demonstrated a significant depression in ejection fraction after induction of the transgene. We also studied hearts of mice expressing a dominant negative p38alpha MAPK. Simultaneous determination of tension and ATPase activity of detergent-skinned fiber bundles from left ventricular papillary muscle demonstrated a significant inhibition of both maximum tension and ATPase activity in the transgenic-MKK6bE hearts. Fibers from hearts expressing dominant negative p38alpha MAPK demonstrated no significant change in tension or ATPase activity. There were no significant changes in phosphorylation level of troponin-T3 and troponin-T4, or myosin light chain 2. However, compared with controls, there was a significant depression in levels of phosphorylation of alpha-tropomyosin and troponin I in fiber bundles from transgenic-MKK6bE hearts, but not from dominant negative p38alpha MAPK hearts. Our experiments also showed that p38alpha MAPK colocalizes with alpha-actinin at the Z-disc and complexes with protein phosphatases (PP2alpha, PP2beta). These data are the first to indicate that chronic activation of p38alpha MAPK directly depresses sarcomeric function in association with decreased phosphorylation of alpha-tropomyosin.

[The role of intestine in detoxification]

In the result of liver detoxification, xenobiotics change into more water soluble and thus easier for excretion from the body. It is convenient to consider this process as occurring in two phases. In phase I, the major reactions involved are hydroxylation, catalyzed by monoxygenases. In phase II, the preliminary modified xenobiotics after conjugation with some specific metabolites are transformed into less toxic and more soluble end-products. Recently, antiporter activity of MDR1 (MultiDrug Resistence) gene products in enterocytes was recognized as important stage in detoxification of xenobiotics, and definied as phase III of this process.

Effect of diet on the development of drug metabolism by cytochrome P-450 enzymes in healthy infants

Orally administered caffeine and dextromethorphan (DM) were used as pharmacologic probes to determine the effect of infant diet on acquisition of cytochrome P-450 (CYP) enzyme activity during the first 6 mo of life. The caffeine elimination rate constant (ke) was determined from serum, and concentrations of caffeine, DM, and their respective metabolites were measured in urine by high-performance liquid chromatography (HPLC). Caffeine ke was low at 2 wk and displayed a significant positive linear correlation with age (p < 0.001); increasing faster in formula-fed than in breast-fed infants (p < 0.001). This occurred concomitantly with a significant increase in urinary 1,7-dimethylxanthine (17X) and 1-methylxanthine (1X) (p < 0.001), suggesting faster acquisition of CYP1A2 activity in formula-fed infants. The urinary molar ratio of (17X + 1X)/caffeine and age strongly predicted caffeine ke (r2 = 0.65; p < 0.001) irrespective of feeding type. CYP3A4 activity, assessed as the molar ratio of 3-hydroxymorphinan/dextrorphan showed a similar marked increase with postnatal age (p < 0.001) that was also greater in formula-fed than in breast-fed infants. Formula feeding appears to accelerate maturation of caffeine and DM metabolism by increasing the activity of CYP1A2 and CYP3A4, respectively. Dietary modification of CYP activity may modulate drug biotransformation and thus alter systemic exposure to xenobiotics from a very early age.

[Transcription TIMP3, DAPk1 and AKR1B10 genes in squamous cell lung cancer]

Lung cancer is one of the most frequent neoplasia in the Russia, the United States and Europe. This cancer is associated with functional activity changes of many genes. In the present study TIMP3, DAPK1 and AKR1B10 genes transcription analysis of squamous cell lung cancer specimens was carried out using reverse transcription-PCR. Substantial increasing of AKR1B10 transcription level is revealed in 80% tumor samples. TIMP3 and DAPK1 transcription level is considerably decreased in 76 and 72% tumor specimens, accordingly. These results may point out that all three genes are important for squamous cell lung cancer tumorogenesis while AKR1B10 is potential oncogene whereas TIMP3 and DAPK1 are potential tumor suppressor genes. We suggest that revealed substantial transcription level-changes of investigated genes may be used for oncodiagnostics.

Xenobiotic- and vitamin D-responsive induction of the steroid/bile acid-sulfotransferase Sult2A1 in young and old mice: the role of a gene enhancer in the liver chromatin

The xenobiotic-activated nuclear receptors PXR (pregnane X receptor) and CAR (constitutive androstane receptor) and the vitamin D(3)-activated nuclear receptor VDR regulate steroid and xenobiotic metabolism by inducing the phase I cytochrome P450 monooxygenases, phase II conjugating transferases, and the phase III transporters, which mediate the efflux of water-soluble lipid metabolites from cells. Metabolic stress due to the deviant expression of steroid- and xenobiotic-metabolizing enzymes is known to have severe health consequences including accelerated aging, and increased expression of these enzymes is associated with extended longevity [Gachon, F, Olela, FF, Schaad, O, Descombes, P and Schibler, U, 2006. The circadian PAR-domain basic leucine zipper transcription factors DBP, TEF, and HLF modulate basal and inducible xenobiotic detoxification. 4, 25-36.; McElwee, JJ, Schuster, E, Blanc, E, Thomas, JH and Gems, D, 2004. Shared Transcriptional Signature in Caenorhabditis elegans Dauer Larvae and Long-lived daf-2 Mutants Implicates Detoxification System in Longevity Assurance. J. Biol. Chem., 279, 44533-43.]. Information on the similarities and dissimilarities in drug metabolism between the young and old, as may be uncovered by studying aging regulation of the genes relevant to steroid and xenobiotic metabolism, is likely to have clinical significance. In this report, we examined the VDR- and PXR-mediated gene induction of the phase II sulfotransferase Sult2A1 in the livers of 4-month- and 20-month-old mice. Sult2A1 converts bile acids, steroids and a number of drugs to the corresponding sulfated metabolites, which are readily eliminated from the body due to increased water solubility. In RT-PCR assay, aging did not change the induction of Sult2A1 mRNAs by the hormonally active vitamin D(3) and the catatoxic synthetic steroid PCN (pregnenolone-16alpha-carbonitrile). Chromatin immunoprecipitation (ChIP) from liver nuclei showed that aging had no effect on the activity of an IR0 enhancer in the Sult2A1 chromatin to recruit VDR, RXR-alpha (retinoid X receptor) and PXR in mice injected with D(3) or PCN. Thus, mice in late life are as competent as those in early life in responding to the hormonal and xenobiotic signaling for Sult2A1 induction. This is the first report describing the role of aging in the functional response of an enhancer in the liver chromatin to the nuclear receptor-dependent signaling.

Distinct Effects of Annexin A7 and p53 on Arachidonate Lipoxygenation in Prostate Cancer Cells Involve 5-Lipoxygenase Transcription

Tumor suppressor function for Annexin A7 (ANXA7; 10q21) is based on cancer-prone phenotype in Anxa7(+/-) mouse and ANXA7 prognostic role in human cancers. Because ANXA7-caused liposome aggregation can be promoted by arachidonic acid (AA), we hypothesized that the phospholipid-binding tumor suppressor ANXA7 is associated with AA cascade. In a comparative study of ANXA7 versus canonical tumor suppressor p53 effects on AA lipoxygenation pathway in the p53-mutant and androgen-insensitive DU145 prostate cancer cells, both tumor suppressors altered gene expression of major 5-lipoxygenase (LOX) and 15-LOXs, including response to T helper 2 (Th2)-cytokine [interleukin-4 (IL-4)] and endogenous steroids (mimicked by dexamethasone). Wild-type and mutant ANXA7 distinctly affected expression of the dexamethasone-induced 15-LOX-2 (a prostate-specific endogenous tumor suppressor) as well as the IL-4-induced 15-LOX-1. On the other hand, wild-type p53 restored 5-LOX expression in DU145 to levels comparable to benign prostate epithelial cells. Using mass spectrometry of DNA affinity-enriched nuclear proteins, we detected different proteins that were bound to adjacent p53 and estrogen response elements in the 5-LOX promoter in DU145 cells introduced with ANXA7 versus p53. Sex hormone regulator 17-beta hydroxysteroid dehydrogenase 4 was identified under p53 introduction, which induced the 5-LOX expression. Meantime, nuclear proteins bound to the same 5-LOX promoter site under introduction of ANXA7 (that was associated with the repressed 5-LOX) were identified as zinc finger proteins ZNF433 and Aiolos, pyrin domain-containing NALP10, and the p53-regulating DNA repair enzyme APEX1. Thus, ANXA7 and p53 can distinctly regulate LOX transcription that is potentially relevant to the AA-mediated cell growth control in tumor suppression.

Acquired resistance to the anticancer drug paclitaxel is associated with induction of cytochrome P450 2C8

INTRODUCTION

We have previously shown that human colorectal cancer tissue is able to inactivate the anticancer drug paclitaxel through cytochrome P450 (CYP)2C8 and CYP3A4 metabolisms. The aim of this study was to evaluate whether changes in the expression levels of genes coding for such enzymes are related to anticancer drug resistance after long-term exposure to the drug.

METHODS

Human colorectal cancer cells (Caco-2) that are sensitive to paclitaxel were exposed to increasing concentrations of the drug from 0-250 nM during one year, in order to select paclitaxel-resistant cells. Subsequently, we compared the sensitivity to paclitaxel and the extent of expression of the CYP2C8, CYP3A4 and CYP3A5 genes in original and resistant cells.

RESULTS

Resistant cancer cells displayed a 246-fold increased lethal dose (LD)50 to paclitaxel (p < 0.004) as compared with original cancer cells. A 4.4-fold (p = 0.005) enhancement of CYP2C8 expression and a 5.6-fold (p = 0.001) increase of multidrug resistance (MDR)1 expression was observed in resistant cells exposed to paclitaxel. When paclitaxel was removed from the culture medium, CYP2C8, but not MDR1 expression, reverted to basal levels and the resistance to paclitaxel decreased 3.2-fold (p = 0.005). No major changes in the expression levels of CYP3A4 and CYP3A5 were observed.

CONCLUSIONS

Caco-2 cells are capable of increasing the expression levels of CYP2C8 as a response to long-term exposure to paclitaxel. This study provides evidence for a mechanism of acquired resistance to anticancer therapy based on the induction of anticancer-metabolizing enzymes.

Defective carbohydrate metabolism in mice homozygous for the tubby mutation

Tub is a member of a small gene family, the tubby-like proteins (TULPs), with predominant expression in neurons. Mice carrying a mutation in Tub develop retinal and cochlear degeneration as well as late-onset obesity with insulin resistance. During behavioral and metabolic testing, we found that homozygous C57BL/6J-Tub(tub) mice have a lower respiratory quotient than C57BL/6J controls before the onset of obesity, indicating that tubby homozygotes fail to activate carbohydrate metabolism and instead rely on fat metabolism for energy needs. In concordance with this, tubby mice show higher excretion of ketone bodies and accumulation of glycogen in the liver. Quantitation of liver mRNA levels shows that, during the transition from light to dark period, tubby mice fail to induce glucose-6-phosphate dehydrogenase (G6pdh), the rate-limiting enzyme in the pentose phosphate pathway that normally supplies NADPH for de novo fatty acid synthesis and glutathione reduction. Reduced G6PDH protein levels and enzymatic activity in tubby mice lead accordingly to lower levels of NADPH and reduced glutathione (GSH), respectively. mRNA levels for the lipolytic enzymes acetyl-CoA synthetase and carnitine palmitoyltransferase are increased during the dark cycle and decreased during the light period, and several citric acid cycle genes are dysregulated in tubby mice. Examination of hypothalamic gene expression showed high levels of preproorexin mRNA leading to accumulation of orexin peptide in the lateral hypothalamus. We hypothesize that abnormal hypothalamic orexin expression leads to changes in liver carbohydrate metabolism and may contribute to the moderate obesity observed in tubby mice.