Evidence for protection of nitrogenase from O(2) by colony structure in the aerobic diazotroph Gluconacetobacter diazotrophicus

Gluconacetobacter diazotrophicus is an endophytic diazotroph of sugarcane which exhibits nitrogenase activity when growing in colonies on solid media. Nitrogenase activity of G. diazotrophicus colonies can adapt to changes in atmospheric partial pressure of oxygen (pO(2)). This paper investigates whether colony structure and the position of G. diazotrophicus cells in the colonies are components of the bacterium's ability to maintain nitrogenase activity at a variety of atmospheric pO(2) values. Colonies of G. diazotrophicus were grown on solid medium at atmospheric pO(2) of 2 and 20 kPa. Imaging of live, intact colonies by confocal laser scanning microscopy and of fixed, sectioned colonies by light microscopy revealed that at 2 kPa O(2) the uppermost bacteria in the colony were very near the upper surface of the colony, while the uppermost bacteria of colonies cultured at 20 kPa O(2) were positioned deeper in the mucilaginous matrix of the colony. Disruption of colony structure by physical manipulation or due to 'slumping' associated with colony development resulted in significant declines in nitrogenase activity. These results support the hypothesis that G. diazotrophicus utilizes the path-length of colony mucilage between the atmosphere and the bacteria to achieve a flux of O(2) that maintains aerobic respiration while not inhibiting nitrogenase activity.

[The relationship between surgical staging, pathologic grading, operative type and postoperative recurrence in giant cell tumor of bone]

Sixty-eight surgical procedures of 58 patients with Giant Cell Tumor of Bone(GCT) were followed up over two years. The recurrence rate of GCT was Stage 1: 0 in 5, Stage 2: 15.4% in 39 and Stage 3: 37.5% in 24. It was significantly higher in Stage 3 than in Stage 2 (P < 0.05). The recurrence rate of GCT in Stage 2 was 30.8% in 13 intralesional curettage, and 0 in 17 wide or radical resection(P < 0.05). We conclude that the surgical staging of GCT has important value in predicting postoperative recurrence, in accurately evaluating the operative efforts and in guiding treatment, and that the operative type is a significant factor effecting on the recurrence of GCT.

Completion of base excision repair by mammalian DNA ligases

Three mammalian genes encoding DNA ligases--LIG1, LIG3, and LIG4--have been identified. Genetic, biochemical, and cell biology studies indicate that the products of each of these genes play a unique role in mammalian DNA metabolism. Interestingly, cell lines deficient in either DNA ligase I (46BR.1G1) or DNA ligase III (EM9) are sensitive to simple alkylating agents. One interpretation of these observations is that DNA ligases I and III participate in functionally distinct base excision repair (BER) subpathways. In support of this idea, extracts from both DNA ligase-deficient cell lines are defective in catalyzing BER in vitro and both DNA ligases interact with other BER proteins. DNA ligase I interacts directly with proliferating cell nuclear antigen (PCNA) and DNA polymerase beta (Pol beta), linking this enzyme with both short-patch and long-patch BER. In somatic cells, DNA ligase III alpha forms a stable complex with the DNA repair protein Xrcc1. Although Xrcc1 has no catalytic activity, it also interacts with Pol beta and poly(ADP-ribose) polymerase (PARP), linking DNA ligase III alpha with BER and single-strand break repair, respectively. Biochemical studies suggest that the majority of short-patch base excision repair events are completed by the DNA ligase III alpha/Xrcc1 complex. Although there is compelling evidence for the participation of PARP in the repair of DNA single-strand breaks, the role of PARP in BER has not been established.

Transactivation of the epidermal growth factor receptor is involved in 12-O-tetradecanoylphorbol-13-acetate-induced signal transduction

The mechanism of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion is still not well understood even though it is thought to be related to the protein kinase C/mitogen-activated protein kinase/AP-1 pathway. Recently, TPA was also found to induce epidermal growth factor receptor (EGFR) activity. Here, we investigated whether the EGFR is a necessary component for TPA-induced signal transduction associated with tumor promotion. We demonstrated that potent inhibitors of the EGFR, PD153035 and AG1478, blocked TPA-induced phosphorylation of extracellular signal-regulated kinases (ERKs), AP-1 activity, and cell transformation. Egfr gene deficiency blocked TPA-induced ERK activity and AP-1 binding activity. The blocking of the ectodomain of the EGFR by a monoclonal antibody depressed TPA-induced ERK activity and AP-1 DNA binding activity. The use of a neutralizing antibody for heparin-binding EGF, one of the ligands of EGFR, blocked TPA-induced phosphorylation of ERKs. BB-94, a potent inhibitor of matrix metalloproteinases, which are activators of ectodomain shedding of EGFR ligands, also blocked TPA-induced ERK activity, AP-1 DNA binding, and cell transformation but had no effect on EGF-induced signal transduction. Anti-EGFR, anti-heparin-binding EGF, and BB-94 each blocked TPA-induced EGFR phosphorylation, but only anti-EGFR could block EGF-induced EGFR phosphorylation. Based on these results, we conclude that the EGFR is required for mediating TPA-induced signal transduction. EGFR transactivation induced by TPA is a mechanism by which the EGFR mediates TPA-induced tumor promotion-related signal transduction.

Inhibitory mechanisms of tea polyphenols on the ultraviolet B-activated phosphatidylinositol 3-kinase-dependent pathway

In this study, we investigated the effect of tea polyphenols, (-)-epigallocatechin-3-gallate or theaflavins, on UVB-induced phosphatidylinositol 3-kinase (PI3K) activation in mouse epidermal JB6 Cl 41 cells. Pretreatment of cells with these polyphenols inhibited UVB-induced PI3K activation. Furthermore, UVB-induced activation of Akt and ribosomal p70 S6 kinase (p70 S6-K), PI3K downstream effectors, were also attenuated by the polyphenols. In addition to LY294002, a PI3K inhibitor, pretreatment with a specific mitogen-activated protein/extracellular signal-regulated protein kinases (Erks) kinase 1 inhibitor, U0126, or a specific p38 kinase inhibitor, SB202190, blocked UVB-induced activation of both Akt and p70 S6-K. Pretreatment with LY294002 restrained UVB-induced phosphorylation of Erks, suggesting that in UVB signaling, the Erk pathway is mediated by PI3K. Moreover, pretreatment with rapamycin, an inhibitor of p70 S6-K, inhibited UVB-induced activation of p70 S6-K, but UVB-induced activation of Akt did not change. Interestingly, UVB-induced p70 S6-K activation was directly blocked by the addition of (-)-epigallocatechin-3-gallate or theaflavins, whereas these polyphenols showed only a weak inhibition on UVB-induced Akt activation. Because PI3K is an important factor in carcinogenesis, the inhibitory effect of these polyphenols on activation of PI3K and its downstream effects may further explain the anti-tumor promotion action of these tea constituents.

Expression of cathepsins B, D and L in mouse corneas infected with Pseudomonas aeruginosa

C57BL/6J naïve and immunized mice were intracorneally infected with Pseudomonas aeruginosa. Semi-quantitative RT-PCR was performed to detect cathepsin gene expression and the results were further confirmed by immunoblot analysis. The enzymatic activities of cathepsins B, D and L were measured by peptidase assays. Immunohistochemical staining was carried out to localize the expression of the cathepsins. Cathepsins B, D and L were detected in the normal cornea by RT-PCR. A peptidase assay revealed activities of all three cathepsins under normal physiological conditions. In naïve mice, enzymatic activities of cathepsins B, D and L were all significantly enhanced when the corneas were infected with P. aeruginosa and the peak of the induction appeared around day 6 postinfection. Immunoblot analysis showed increased expression of cathepsins B, D and L. The infected corneal samples from immunized mice exhibited much lower induction of enzymatic activities compared to those from naïve mice. Immunohistochemistry showed that the expression of cathepsins in the normal cornea was restricted to the epithelial tissue while the induced expression of cathepsins was predominantly in the substantia propria. Our data revealed up-regulated enzymatic activities of cathepsins B, D and L in the naïve corneas infected with P. aeruginosa, which correlated well with the inflammatory response. Immunization of mice against P. aeruginosa attenuated the inducing effect on cathepsin expression caused by infection. The time sequence for induction of cathepsin proteins and enzymatic activities suggests a mechanism of host proteolytic degradation of the extracellular matrix resulting in corneal destruction after P. aeruginosa infection.

Induction of EGFR-dependent and EGFR-independent signaling pathways by ultraviolet A irradiation

Most of the signal pathways involved in ultraviolet (UV)-induced skin carcinogenesis are thought to originate at plasma membrane receptors. However, UVA-induced signal transduction to downstream ribosomal protein S6 kinases, p70(S6K) and p90(RSK), is not well understood. In this report, we show that UVA stimulation of the epidermal growth factor receptor (EGFR) may lead to activation of p70(S6K)/p90(RSK) through phosphatidyl isositol (PI)-3 kinase and extracellular receptor-activated kinases (ERKs). Evidence is provided that phosphorylation and activation of p70(S6K)/p90(RSK) induced by UVA were prevented in Egfr(-/-) cells and were also markedly inhibited by the EGFR-specific tyrosine kinase inhibitors AG1478 and PD153035. Furthermore, EGFR tyrosine kinase inhibitors and EGFR deficiency significantly suppressed activation of PI-3 kinase and ERKs in regulating activation of p90(RSK)/p70(S6K) but had no effect on activation of c-Jun NH(2)-terminal kinases (JNKs) and p38 kinase in response to UVA. Thus, our results suggest that UVA-induced EGFR signaling may be required for activation of p90(RSK)/p70(S6K), PI-3 kinase, and ERKs but not JNKs or p38 kinase.

[Nasal cavity dimensions in the infants measured with acoustic rhinometry]

OBJECTIVE

To investigate the range of normal value of minimal cross-sectional area (MCA) of the nasal cavity, distance of minimal cross-sectional area from the nostril (DCA), total nasal cavity volume(NV) and total nasopharyngeal cavity volume (NPV) of healthy infants.

METHOD

One hundred and seventy-five healthy infants and one hundred and eight infants suffered from acute upper respiratory tract infection were measured with acoustic rhinometry.

RESULT

The range of total MCA of healthy infants was 0.2-0.5 (cm)2, DCA was 1.93-2.47 cm, NV was 2.69-4.75 cm3 and NPV was 3.83-8.92 cm3. Comparing healthy infants with infants suffered from acute upper respiratory tract infection, there all were significant differences in MCA, DCA and NV.

CONCLUSION

Acoustic rhinometry suit objective assessment of the nasal airways in infants. It is demonstrated that these data can provide available information for the study of nasal physiology and pathophysiology, well as for the diagnosis and judgement of therapeutic effectiveness of nasal diseases.

Expression of membrane-type matrix metalloproteinases 4, 5, and 6 in mouse corneas infected with P. aeruginosa

PURPOSE

To investigate the expression and regulation of membrane-type matrix metalloproteinases (MT-MMPs) 4, 5, and 6 in the mouse corneas infected with Pseudomonas aeruginosa.

METHODS

C57BL/6J mice were intracorneally infected with P. aeruginosa. The expression of MT4-, MT5-, and MT6-MMP was detected at both the mRNA and protein levels by RT-PCR and immunoblot analysis. Immunohistochemical staining was performed to localize the expression of MT4- and MT5-MMP in the mouse corneas.

RESULTS

Expression of MT4- and MT5-MMP was detected in the normal (uninfected) cornea by RT-PCR and immunoblot analysis. When infected with P. aeruginosa, the corneas showed significant induction of each MT-MMP. Localization of MT4- and MT5-MMP revealed that the expression of MT5-MMP was restricted to the epithelial tissue in the normal cornea, whereas the induced expression of MT4- and MT5-MMP was predominantly in the substantia propria, which contained most of the infiltrating cells. MT6-MMP expression was not detected in the uninfected cornea but was upregulated in the infected corneas.

CONCLUSIONS

Expression of MT4-, MT5-, and MT6-MMP was induced in corneas infected with P. aeruginosa. Immunohistochemistry showed predominant immunoreactivity of MT4- and MT5-MMP in the substantia propria. Previous histologic studies have revealed different patterns of inflammatory cell infiltration with an increased number of polymorphonuclear neutrophils (PMNs) during the early stage of inflammation and increased macrophages during the late stage. These results indicate a good correlation between the overexpression of the MT-MMPs in the infected corneas and the inflammatory response-that is, leukocyte infiltration-indicating that inflammatory cells such as macrophages and PMNs may play a role in the upregulation of MT-MMPs during corneal infection, which in turn can cause the destruction of corneal tissue.

cDNA cloning and promoter analysis of rat caspase-9

Caspase-9 is the apex caspase of the mitochondrial pathway of apoptosis, which plays a critical role in apoptotic initiation and progression. However, gene regulation of caspase-9 is largely unknown. This is in part due to the lack of information on the gene promoter. Here we have cloned the full-length cDNA of rat caspase-9 and have isolated promoter regions of this gene. The rat caspase-9 cDNA of 2058 bp predicts a protein of 454 amino acids, which contains a caspase-recruitment domain ('CARD') at the N-terminus and enzymic domains at the C-terminus. The enzyme's active site, with a characteristic motif of QACGG, was also identified. Overall, rat and human caspase-9 have 71% identity. With the cDNA sequence, we subsequently isolated the proximal 5'-flanking regions of rat caspase-9 by the procedure of genomic walking. The 2270 bp genomic segment is 'TATA-less', but contains several GC boxes. Elements binding known transcription factors such as Sp-1, Pit-1, CCAAT-enhancer-binding protein (C/EBP), glucocorticoid receptor and hypoxia-inducible factor 1 (HIF-1) were also identified. When cloned into reporter gene vectors, the genomic segment showed significant promoter activity, indicating that the 5'-flanking regions isolated by genomic walking contain the gene promoter of rat caspase-9. Of significance is that the cloned promoter segments were activated by severe hypoxia, conditions inducing caspase-9 transcription. Thus, the genomic sequences reported here contain not only the basal promoter of rat caspase-9 but also regulatory elements responsive to pathophysiological stimuli including hypoxia.

Cannabinoid-receptor-independent cell signalling by N-acylethanolamines

Anandamide and other polyunsaturated N-acylethanolamines (NAEs) exert biological activity by binding to cannabinoid receptors. These receptors are linked to G(i/o) proteins and their activation leads to extracellular-signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) mitogen-activated protein kinase (MAP kinase) activation, inhibition of cAMP-dependent signalling and complex changes in the expression of various genes. Saturated and monounsaturated NAEs cannot bind to cannabinoid receptors and may thus mediate cell signalling through other targets. Here we report that both saturated/monounsaturated NAEs and anandamide (20:4(n-6) NAE) stimulate cannabinoid-receptor-independent ERK phosphorylation and activator protein-1 (AP-1)-dependent transcriptional activity in mouse epidermal JB6 cells. Using a clone of JB6 P(+) cells with an AP-1 collagen-luciferase reporter construct, we found that 16:0, 18:1(n-9), 18:1(n-7), 18:2(n-6) and 20:4(n-6) NAEs stimulated AP-1-dependent transcriptional activity up to 2-fold, with maximal stimulation at approx. 10-15 microM. Higher NAE concentrations had toxic effects mediated by alterations in mitochondrial energy metabolism. The AP-1 stimulation appeared to be mediated by ERK but not JNK or p38 signalling pathways, because all NAEs stimulated ERK1/ERK2 phosphorylation without having any effect on JNK or p38 kinases. Also, overexpression of dominant negative ERK1/ERK2 kinases completely abolished NAE-induced AP-1 activation. In contrast with 18:1(n-9) NAE and anandamide, the cannabinoid receptor agonist WIN 55,212-2 did not stimulate AP-1 activity and inhibited ERK phosphorylation. The NAE-mediated effects were not attenuated by pertussis toxin and appeared to be NAE-specific, as a close structural analogue, oleyl alcohol, failed to induce ERK phosphorylation. The data support our hypothesis that the major saturated and monounsaturated NAEs are signalling molecules acting through intracellular targets without participation of cannabinoid receptors.

Type 1 von Willebrand disease mutation Cys1149Arg causes intracellular retention and degradation of heterodimers: a possible general mechanism for dominant mutations of oligomeric proteins

Some families affected by von Willebrand disease type 1 show high penetrance with exceptionally low von Willebrand factor (VWF) levels. Previously, a mutation associated with this dominant phenotype, Cys1149Arg, was found to decrease the secretion of coexpressed normal VWF, and the mutation was proposed to cause intracellular retention of pro-VWF heterodimers. To demonstrate heterodimer formation, a model was developed in which subunits could be distinguished immunologically and by size. Recombinant VWF lacking domain A1 (dA1), A3 (dA3), or both (dA13) was secreted efficiently as a full range of multimers. Cotransfection of Cys1149Arg and dA13 resulted in the secretion of multimeric VWF containing about 250 kd (Cys1149Arg) and about 210 kd (dA13). Cell lysates contained pro-VWF forms of Cys1149Arg and dA13. Immunoprecipitation with an antidomain A1 antibody recovered both subunits in heterodimers, and subunit ratios were consistent with random dimerization. Similar results were obtained for cotransfection of Cys1149Arg and dA1. Normal VWF has a Cys1149-Cys1169 intrachain bond. When cotransfected with normal VWF, Cys1149Arg or the double mutant Cys1149Arg+Cys1169Ser caused a similar decrease in VWF secretion, suggesting that an unpaired Cys1169 does not explain the intracellular retention of Cys1149Arg. VWF Cys1149Arg was not secreted from BHK cells but was degraded intracellularly within about 4 hours, and the proteasome inhibitor lactacystin delayed its clearance more than 16 hours. Thus, dominant von Willebrand disease type 1 may be caused by heterodimerization of mutant and normal subunits in the endoplasmic reticulum followed by proteasomal degradation in the cytoplasm. A similar dominant negative mechanism could cause quantitative deficiencies of other multisubunit proteins.

MSK1 and JNKs mediate phosphorylation of STAT3 in UVA-irradiated mouse epidermal JB6 cells

Phosphorylation of Tyr(705) and Ser(727) of signal transducer and activator of transcription 3 (STAT3) are known to be required for maximal activation by diverse stimuli. Tyr(705) phosphorylation is generally accepted to be mediated by the Janus kinase family. But the mechanism for STAT3 (Ser(727)) phosphorylation is not well understood. Here, we provide evidence that UVA-induced phosphorylation of STAT3 at Ser(727) is inhibited by pretreatment of JB6 cells with PD98059 or SB202190. Phosphorylation of STAT3 (Ser(727)) is also markedly prevented by a dominant negative mutant of ERK2, c-Jun N-terminal kinase 1 (JNK1), or p38 kinase and in knockout Jnk1(-/-) or Jnk2(-/-) cells. Furthermore, STAT3 (Ser(727)) phosphorylation is suppressed by C- or N-terminal "kinase-dead" mutants of mitogen- and stress-activated protein kinase 1 (MSK1), a downstream kinase of ERKs and p38 kinase, and H89, a potential MSK1 inhibitor. In vitro experiments showed that active MSK1 and JNKs, but not ERKs or p38 kinase, phosphorylate STAT3 (Ser(727)). Additionally, the role of MAPKs in mediating UVA-stimulated DNA binding activity of STAT3 was investigated. Overall, these results suggest that UVA-induced Ser(727) phosphorylation of STAT3 may occur through MSK1 and JNKs.

Anatomic basis of vascularized ulnar nerve graft by the pedicle of the superior collateral ulnar artery

OBJECTIVE

To investigate the anatomic basis of vascularized ulnar nerve graft by the pedicle of the superior collateral ulnar artery (SCUA).

METHODS

Twenty-two fresh cadaver upper extremities injected i ntra-arterially with latex were dissected to study the extrinsic blood supply of the ulnar nerve. Other 6 fresh upper extremities were used to analyze the blood supply range of SCUA inside the ulnar nerve by microangiographic and histological methods.

RESULTS

The ulnar nerve was supplied by a branch of the lateral thoracic artery or directly by the axillary artery in the axillary section, by b ranches of SCUA in the upper arm, and by branches from the anastomosis of the collateral arteries and the posterior branch of the recurrent ulnar artery in the elbow. SCUA could supply the whole ulnar nerve from the axilla to the wrist.

CONCLUSIONS

The ulnar nerve can be used as a vascularized nerve graft by the pedicle of SCUA in treatment of brachial plexus roots avulsion by C7 transfer from healthy side.

Transforming growth factor beta (TGFbeta) mediates Schwann cell death in vitro and in vivo: examination of c-Jun activation, interactions with survival signals, and the relationship of TGFbeta-mediated death to Schwann cell differentiation

In some situations, cell death in the nervous system is controlled by an interplay between survival factors and negative survival signals that actively induce apoptosis. The present work indicates that the survival of Schwann cells is regulated by such a dual mechanism involving the negative survival signal transforming growth factor beta (TGFbeta), a family of growth factors that is present in the Schwann cells themselves. We analyze the interactions between this putative autocrine death signal and previously defined paracrine and autocrine survival signals and show that expression of a dominant negative c-Jun inhibits TGFbeta-induced apoptosis. This and other findings pinpoint activation of c-Jun as a key downstream event in TGFbeta-induced Schwann cell death. The ability of TGFbeta to kill Schwann cells, like normal Schwann cell death in vivo, is under a strong developmental regulation, and we show that the decreasing ability of TGFbeta to kill older cells is attributable to a decreasing ability of TGFbeta to phosphorylate c-Jun in more differentiated cells.

Immortalization of human WI38 cells is associated with differential activation of the c-myc origins

To study the possible relationships between origin activities and cellular processes leading to malignancy, we used an isogenic system of human embryo lung fibroblast cells WI38 and a SV40-transformed variant, WI38 VA13 2RA (WI38(SV40)). We found that the activities of all initiation sites at the c-myc locus were approximately two-fold as high in WI38(SV40) cells as in WI38 cells. Thus, higher initiation frequency of origins at certain loci is induced with cell immortalization, one of the steps in the multi-step process leading to malignancy. We measured the activities of the four c-myc promoters P0, P1, P2, and P3 with nuclear runon assay in the two cell lines in order to detect potential individual promoter changes that may be also associated with immortalization by SV40 virus. The results show that the activities of the promoters P0, P1, and P3 did not significantly change, but the activity of the major promoter P2 in WI38(SV40) cells was about 7.5- to 8.0-fold as high as that in WI38 cells. The increased activity of promoter P2, although approximately 600 bp downstream of one of the major DNA replication initiation sites, had no preferential influence on the major sites of origin activity. Since the distribution of nascent strand abundance was not significantly altered, binding of transcription factors does not seem to facilitate the assembly of pre-replication complex (pre-RC) or otherwise preferentially alter the activities of the DNA replication proteins at this major initiation site.

[Expression and distribution of Aquaporin 1 in the nasal polyps]

OBJECTIVE

To confirm the expression and distribution of Aquaporin 1 (AQP1) in the nasal polyps and to investigate the relation between AQP1 and the nasal polyp edema.

METHODS

fourteen cases of normal inferior turbinates and 26 cases of nasal polyps were used. The expression and distribution of AQP1 in nasal polyps were examined by immunohistochemical technique.

RESULTS

The level of AQP1 in the epithelial cells and serous cells from nasal polyps was higher than that in inferior turbinates, and the level of AQP1 in the epithelial cells and cilium cells from inferior turbinate was higher than that in nasal polyps.

CONCLUSION

There is close relationship between AQP1 and nasal polyp edema.

Inhibition of arsenite-induced apoptosis by aspirin

Arsenite exposure and subsequent arsenite-induced toxicity and carcinogenesis are common in many countries. Thus the study of chemopreventive compounds that inhibit arsenite-induced toxicity and carcinogenesis is very valuable. In the present work, we investigated the effect of aspirin on arsenite-induced apoptosis and signal transduction by means of luciferase activity, apoptosis analysis and Western blotting. Arsenite induced AP-1 transcriptional activity at the same concentration (20 microM) as was effective for inducing apoptosis. Arsenite-induced apoptosis and AP-1 transactivation in JB6 cells were blocked by aspirin and salicylate (SA). Both aspirin and SA inhibited arsenite-induced phosphorylation of Erks, but had no effect on phosphorylation of JNKs. SA inhibited arsenite-induced phosphorylation of p38 kinase, but aspirin did not. These results indicate that aspirin and SA inhibit arsenite-induced apoptosis through the inhibition of the Erks/AP-1 pathway.

Mechanisms of inhibition of the Ras-MAP kinase signaling pathway in 30.7b Ras 12 cells by tea polyphenols (-)-epigallocatechin-3-gallate and theaflavin-3,3'-digallate

Our previous study showed that tea polyphenols inhibited MAP kinase and AP-1 activities in mouse epidermal JB6 cells and the corresponding H-ras-transformed cell line 30.7b Ras 12. The present study investigated the mechanisms of this inhibition. The cells were incubated with (-)-epigallocatechin-3-gallate (EGCG) or theaflavin-3,3'-digallate (TFdiG) (20 mM) for different times, and the cell lysate was analyzed by immunoblotting. EGCG treatment decreased the levels of phospho-Erk1/2 and -MEK1/2 time-dependently (by 60% at 60 min). TFdiG lowered their levels by 38%-50% at 15 min. TFdiG effectively decreased total Raf-1 protein levels, most likely through lysosomal degradation. EGCG did not affect protein levels or the activity of Raf-1 significantly but decreased its association with MEK1 as determined by co-immunoprecipitation. In addition, EGCG and TFdiG (10 mM) inhibited the phosphorylation of Elk-1 by isolated phospho-Erk1/2 in vitro. This inhibition of Erk1/2 activity is Elk-1 concentration-dependent and ATP concentration-independent, which suggests that EGCG and TFdiG interfere with the binding of the protein substrate to the kinase. The presently demonstrated specific mechanisms of inhibition of MAP kinases by EGCG and TFdiG may help us to understand the effects of tea consumption on cancer, inflammatory diseases, and cardiovascular diseases.

Ultraviolet B-induced phosphorylation of histone H3 at serine 28 is mediated by MSK1

N-terminal tail phosphorylation of histone H3 plays an important role in gene expression, chromatin remodeling, and chromosome condensation. Phosphorylation of histone H3 at serine 10 was shown to be mediated by RSK2, mitogen- and stress-activated protein kinase-1 (MSK1), and mitogen-activated protein kinases depending on the specific stimulation or stress. Our previous study showed that mitogen-activated protein kinases MAP kinases are involved in ultraviolet B-induced phosphorylation of histone H3 at serine 28 (Zhong, S., Zhong, Z., Jansen, J., Goto, H., Inagaki, M., and Dong, Z., J. Biol. Chem. 276, 12932-12937). However, downstream effectors of MAP kinases remain to be identified. Here, we report that H89, a selective inhibitor of the nucleosomal response, totally inhibits ultraviolet B-induced phosphorylation of histone H3 at serine 28. H89 blocks MSK1 activity but does not inhibit ultraviolet B-induced activation of MAP kinases p70/85(S6K), p90(RSK), Akt, and protein kinase A. Furthermore, MSK1 markedly phosphorylated serine 28 of histone H3 and chromatin in vitro. Transfection experiments showed that an N-terminal mutant MSK1 or a C-terminal mutant MSK1 markedly blocked MSK1 activity. Compared with wild-type MSK1, cells transfected with N-terminal or C-terminal mutant MSK1 strongly blocked ultraviolet B-induced phosphorylation of histone H3 at serine 28 in vivo. These data illustrate that MSK1 mediates ultraviolet B-induced phosphorylation of histone H3 at serine 28.

Vascular endothelial growth factor: acting as an autocrine growth factor for human gastric adenocarcinoma cell MGC803

Vascular endothelial growth factor (VEGF) is known to be a highly specific mitogen for endothelial cells through two high-affinity tyrosine kinase receptors, VEGFR-1 and VEGFR-2, which are almost specifically expressed in endothelial cells. However, recent findings showed that VEGF receptors may also expressed by nonendothelial cells, especially by tumor cells. To further understand the functional expression of VEGF receptors by nonendothelial cells, our preliminary screening detected the expression of VEGFR-2 in 115 different paraffin-embedded cancer specimens including 35 cases of bladder tumor, 30 cases of breast cancer, 25 cases of intestinal cancer, and 25 cases of lung cancer with immunohistochemistry. The results showed that VEGFR-2 was widely expressed in different tumor tissues. By reverse transcription PCR, NCI-H23, NCI-H460, MGC803, MDA-MB-231, 293, and MCF7 cells were evaluated for the mRNA expression of both VEGF and VEGFR-2. The data indicated that all these tumor cell lines expressed detectable amounts of VEGF mRNA, but only 293, MCF7, and MGC803 cells coexpressed VEGFR-2. Immunoblot analysis also demonstrated the expression of VEGFR-2 at protein level. We further demonstrate that exogenous rhVEGF(165) could stimulate cell growth in MGC803, a tumor cell line derived from gastric adenocarcinoma, in a dose- and time-dependent manner. Furthermore, the antibodies against rhVEGF(165) and VEGFR-2 could block rhVEGF(165)-mediated proliferation of MGC803 cells. These unexpected results provided direct evidence that VEGF may act as an autocrine growth factor to induce the proliferation of gastric adenocarcinoma cells as well as tumor angiogenic cells, thus suggesting a promising tumor therapeutic application based upon the VEGF system.

Differential regulation of matrix metalloproteinase-9, tissue inhibitor of metalloproteinase-1 (TIMP-1) and TIMP-2 expression in co-cultures of prostate cancer and stromal cells

Tumor-stromal interactions have been suggested to be a critical factor in both tumor invasion and tumor metastasis. Here, we examined the role of tumor-stromal interactions using co-cultures of prostate cancer (PC) cells derived from primary and metastatic tumors with primary or immortalized stromal (fibroblast and smooth muscle) cells and their effect on matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase (TIMP) expression. Co-cultures of PC and stromal cells showed enhanced levels of pro-MMP-9 and reduced levels of TIMP-1 and TIMP-2. Whereas enhanced expression of pro-MMP-9 occurred in PC cells, the TIMPs were down-regulated in stromal cells. Induction of pro-MMP-9 and reduction of TIMP expression did not require cell-cell contact and were mediated by a soluble factor(s) present in the conditioned medium of the effector cell. Collagen I is a potent inducer of pro-MMP-9 in PC cells. Consistently, preliminary characterization of the soluble factor in the fibroblast conditioned medium revealed m.w. of approximately 100 to 250 kDa, and its effect on pro-MMP-9 expression was partly inhibited by an anti-alpha2 integrin antibody, a major collagen I receptor. Expression of pro-MMP-9 protein and mRNA was also induced in metastatic PC-3 cells grown in human fetal bone implants in SCID mice. Together, these findings demonstrate the importance of tumor-stromal interactions in the regulation of MMP and TIMP expression and their potential role in PC progression.