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.