Effects of cigarette smoke condensate and nicotine on human gingival fibroblast-mediated collagen degradation

BACKGROUND

Members of the matrix metalloproteinase (MMP) family have been shown to be involved in periodontal disease. Risk factors for periodontal disease include tobacco smoking. Cigarette smoke condensate (CSC) is comprised of thousands of chemicals. Nicotine is one of the active components in tobacco. This study compares the effects of CSC and nicotine at the level in CSC on the collagen-degrading ability of human gingival fibroblasts (HGFs) and the expression of selected MMPs and tissue inhibitors of metalloproteinases (TIMPs).

METHODS

HGFs were seeded in six-well collagen-coated plates, exposed to 100 μg/mL (2.4 μg/mL nicotine) of CSC or 2.4 μg/mL nicotine for 3 days, and then collagen degradation was analyzed. After 3 days exposure to CSC or nicotine, the conditioned media from HGFs was collected and the membrane proteins were extracted for gelatin zymography and Western blot analyses. The mRNA levels of MMP-2, MMP-14, and TIMP-2 were measured by reverse transcription-polymerase chain reaction.

RESULTS

The CSC increased collagen degradation, and increased the levels of TIMP-2, MMP-14, and the active MMP-2 in the membrane extracts, and their mRNA levels. CSC also increased the level of active MMP-2 in the conditioned media. Nicotine at the level in CSC (2.4 μg/mL) had little influence on collagen degradation, as well as on the protein and mRNA levels of MMP-2, MMP-14, and TIMP-2.

CONCLUSIONS

CSC may increase HGF-mediated collagen degradation by affecting membrane-associated MMPs and TIMPs.

Matrix metalloproteinase-2 and -9 are induced differently by metal nanoparticles in human monocytes: The role of oxidative stress and protein tyrosine kinase activation

Recently, many studies have shown that nanoparticles can translocate from the lungs to the circulatory system. As a particulate foreign body, nanoparticles could induce host responses such as reactive oxygen species (ROS) generation, inflammatory cytokine and matrix metalloproteinase (MMP) release which play a major role in tissue destruction and remodeling. However, the direct effects of nanoparticles on leukocytes, especially monocytes, are still unclear. The objective of the present study was to compare the ability of Nano-Co and Nano-TiO(2) to cause alteration of transcription and activity of MMPs and to explore possible mechanisms. We hypothesized that non-toxic doses of some transition metal nanoparticles stimulate an imbalance of MMP/TIMP that cause MMP production that may contribute to their health effects. To test this hypothesis, U937 cells were treated with Nano-Co and Nano-TiO(2) and cytotoxic effects and ROS generation were measured. The alteration of MMP-2 and MMP-9 expression and activity of MMP-2 and MMP-9 after exposure to these metal nanoparticles were subsequently determined. To investigate the potential signaling pathways involved in the Nano-Co-induced MMP activation, the ROS scavengers or inhibitors, AP-1 inhibitor, and protein tyrosine kinase (PTK) inhibitors were also used to pre-treat U937 cells. Our results demonstrated that exposure of U937 cells to Nano-Co, but not to Nano-TiO(2), at a dose that does not cause cytotoxicity, resulted in ROS generation and up-regulation of MMP-2 and MMP-9 mRNA expression(..) Our results also showed dose- and time-related increases in pro-MMP-2 and pro-MMP-9 gelatinolytic activities in conditioned media after exposure of U937 cells to Nano-Co, but not to Nano-TiO(2). Nano-Co-induced pro-MMP-2 and pro-MMP-9 activity increases were inhibited by pre-treatment with ROS scavengers or inhibitors. We also demonstrated dose- and time-related decreases in tissue inhibitors of metalloproteinases 2 (TIMP-2) in U937 cells after exposure to Nano-Co, but not to Nano-TiO(2). However, neither Nano-Co nor Nano-TiO(2) exposure led to any transcriptional change of TIMP-1. The decrease of TIMP-2 after exposure to Nano-Co was also inhibited by pre-treatment with ROS scavengers or inhibitors. Our results also showed that pre-treatment of U937 cells with AP-1 inhibitor, curcumin, or the PTK specific inhibitor, herbimycin A or genistein, prior to exposure to Nano-Co, significantly abolished Nano-Co-induced pro-MMP-2 and-9 activity. Our results suggest that Nano-Co causes an imbalance between the expression and activity of MMPs and their inhibitors which is mediated by the AP-1 and tyrosine kinase pathways due to oxidative stress.

Imatinib inhibits colorectal cancer cell growth and suppresses stromal-induced growth stimulation, MT1-MMP expression and pro-MMP2 activation

Tumor progress depends on the proliferation of cancer cells, their interactions with stroma and the proteolytic action of enzymes. Colon cancer is c-kit positive and responsive to the specific tyrosine kinase inhibitor imatinib. We investigated the effect of imatinib on the proliferation of a panel of epithelial colon cancer cell lines in presence and absence of the antimetabolite 5-FU, and the effect of conditioned media (CM) derived from colon stromal fibroblasts with and without previous exposure to imatinib. The effects of imatinib on gene expression of MMPs and TIMPs were also studied. Imatinib effectively inhibited the proliferation of all cell lines, showing IC(50) from 0.3 to 3 microM. Its combination with 5-FU significantly enhances the growth inhibition of the highly tumourigenic HT-29 cells. CM derived from stromal fibroblasts induced the proliferation of the HT-29 cells; this stimulatory effect was abolished upon treatment with CM obtained after exposure of fibroblasts to imatinib. Gene expression of MT1-, MT2-MMP and MMP-7 was also inhibited depending on the cell line, whereas that of TIMP-2 was not affected. CM stimulated MT1-MMP protein expression by HT-29; this stimulatory effect was suppressed in the presence of imatinib. Activation of pro-MMP2 to MMP2 in culture medium of HT-29 treated with CM was increased and this activity was inhibited in presence of imatinib. The obtained data showed that imatinib is a powerful inhibitor of human colon cancer cell growth and effectively suppresses the stromal-induced stimulation of cancer cell growth and activation of proMMP2. Further studies are warranted to evaluate the in vivo effects.

Local and systemic pathophysiological alterations induced by a serine proteinase from the venom of the snake Bothrops jararacussu

The local and systemic pathophysiological alterations induced by BjussuSP-I, a thrombin-like serine proteinase from the venom of the snake Bothrops jararacussu, were assessed in mice. BjussuSP-I induced a mild edema but no local myonecrosis or hemorrhage. It did not induce any microvascular alteration in the cremaster muscle. Intramuscular injection of BjussuSP-I promoted an increase in the expression of proMMP-9, but it did not induce the activation of proMMP-2 or proMMP-9 synthesized in muscle tissue injected with a myotoxic phospholipase A(2) homolog. BjussuSP-I induced defibrin(ogen)ation upon intravenous and intramuscular injections, with reduction in plasma fibrinogen concentration and increments in the levels of fibrin degradation products and D-dimer. When compared with animals having normal coagulation, mice defibrin(ogen)ated by BjussuSP-I developed a slightly larger hemorrhagic lesion in the skin when injected with metalloproteinase BaP1. Intravenous injection of sublethal doses of BjussuSP-I promoted a series of behavioral and motor changes similar to those previously described for 'gyroxin', i.e. opisthotonus and a circular body movement along the longitudinal axis.

Effects of lipopolysaccharide on gene expression of antimicrobial peptides (penaeidins and crustin), serine proteinase and prophenoloxidase in haemocytes of the Pacific white shrimp, Litopenaeus vannamei

For shrimp immune defences, prophenoloxidase (proPO) activating system and antimicrobial peptides in circulating haemocytes play important roles. In the present study, the effects of lipopolysaccharide (LPS) injection on gene expression of penaeidins, crustin, serine proteinase and proPO in haemocytes were determined using real-time reverse transcription-polymerase chain reaction (PCR) in the Pacific white shrimp Litopenaeus vannamei. After injection of LPS, mRNA levels of antimicrobial peptides, penaeidin 2 (PEN2), penaeidin 3 (PEN3), penaeidin 4 (PEN4) and crustin decreased in a dose-dependent manner, while mRNA levels of serine proteinase and proPO did not change significantly. In a time-course experiment, injection of LPS caused significant depression in mRNA levels of PEN2, PEN3, PEN4 and crustin at 4h post-injection, and the depressed mRNA levels returned to initial levels by 72h post-injection. On the other hand, mRNA levels of serine proteinase and proPO did not show a significant change after injection. These results suggest that the antimicrobial peptide system responds to LPS injection at a gene expression level while the proPO system does not respond at a gene expression level.

Hydrogen peroxide-mediated downregulation of matrix metalloprotease-2 in indomethacin-induced acute gastric ulceration is blocked by melatonin and other antioxidants

Gastric mucosal damage is directly associated with extracellular matrix degradation in which matrix metalloproteinases (MMPs) play a crucial role. Remodeling of connective tissues and loss of tissue integrity due to the action of MMPs are reported in several inflammatory diseases, including gastric ulcer. Indomethacin-induced gastric ulceration involves the generation of reactive oxygen species (ROS) and a reduction in MMP-2 transcription and translation. Our aim was to identify the mechanism for suppression of MMP-2 activity by ROS during acute ulceration and further to examine the possible actions of antioxidants, especially melatonin, during healing. Melatonin (N-acetyl-5-methoxytryptamine) blocked hydroxyl radical and nitrite anion generation, protein oxidation, mucosal cell disruption, and MMP-2 downregulation. In addition, suppression of MMP-2 activity by H2O2 in a dose- and time-dependent manner in vitro is blocked by melatonin, omeprazole, and curcumin. We observed that melatonin and other antioxidants (e.g., curcumin and omeprazole) offered gastroprotection in vivo by upregulation of suppressed MMP-2 expression and activity at the level of secretion and synthesis. Moreover, antioxidants reversed the suppression of MMP-2 expression by upregulation of MT1-MMP and downregulation of TIMP-2. Hence, we hypothesize that antioxidants exerted protection against H2O2-mediated inactivation and downregulation of MMP-2 expression during onset of indomethacin-induced ulceration.

Novel role of TGF-beta in differential astrocyte-TIMP-1 regulation: implications for HIV-1-dementia and neuroinflammation

Astrocyte production of tissue inhibitor of metalloproteinase (TIMP)-1 is important in central nervous system (CNS) homeostasis and inflammatory diseases such as HIV-1-associated dementia (HAD). TIMPs and matrix metalloproteinases (MMPs) regulate the remodeling of the extracellular matrix. An imbalance between TIMPs and MMPs is associated with many pathologic conditions. Our recently published studies uniquely demonstrate that HAD patients have reduced levels of TIMP-1 in the brain. Astrocyte-TIMP-1 expression is differentially regulated in acute and chronic inflammatory conditions. In this and the adjoining report (Gardner et al., 2006), we investigate the mechanisms that may be involved in differential TIMP-1 regulation. One mechanism for TIMP-1 downregulation is the production of anti-inflammatory molecules, which can activate signaling pathways during chronic inflammation. We investigated the contribution of transforming growth factor (TGF)-signaling in astrocyte-MMP/TIMP-1-astrocyte regulation. TGF-beta1 and beta2 levels were upregulated in HAD brain tissues. Co-stimulation of astrocytes with IL-1beta and TGF-beta mimicked the TIMP-1 downregulation observed with IL-1beta chronic activation. Measurement of astrocyte-MMP protein levels showed that TGF-beta combined with IL-1beta increased MMP-2 and decreased proMMP-1 expression compared to IL-1beta alone. We propose that one of the mechanisms involved in TIMP-1 downregulation may be through TGF-signaling in chronic immune activation. These studies show a novel extracellular regulatory loop in astrocyte-TIMP-1 regulation.

Inhibition of matrix degrading enzymes and invasion in human glioblastoma (U87MG) cells by isoflavones

Glioblastoma multiforme is a primary brain tumor associated with extensive invasion into surrounding brain tissue. Matrix metalloproteinases (MMPs) and urokinase plasminogen activation (uPA) system are shown to be involved in tumor invasion as they help in degradation of extracellular matrix (ECM) proteins and thus assist in the movement of cells. MMP-2 and 9 were shown to be upregulated in gliomas, suggesting their involvement in invasion. Genistein and biochanin A are isoflavones commonly known as phytoestrogens and have some anticancer properties. We hypothesize that these two isoflavones can induce a lowering of tumor invasion by decreasing the activity of matrix degrading enzymes. In this study we investigated the effects of genistein and biochanin A on invasive activity of U87MG cells using the Calbiochem in vitro invasion assay system. Our results suggest that genistein and biochanin A induced a decrease in invasive activity of U87MG cells in a dose-related manner. Genistein also induced a decrease in EGF-stimulated invasion thereby implicating an involvement of EGF-mediated signaling in invasion. Our results also show that treatment of U87MG cells with the two isoflavones induced decreases in the enzymatic activity of MMP-9 and the protein levels of MT1-MMP and uPAR.

High yield synthesis and characterization of phosphorylated recombinant human procathepsin D expressed in mammalian cells

We used a vaccinia virus expression system for the production of recombinant human cathepsin D (CD), a lysosomal protease implicated in various patho-physiological processes including cancer, neurodegeneration, and development. The recombinant protein was successfully expressed in various human and non-human cells. It was correctly synthesized as a glycosylated 53 kDa precursor (proCDrec) that reacted with a polyclonal antibody against residues 7-21 of the propeptide sequence. In contrast to the control, in cells infected with the recombinant virus proCDrec was largely secreted into the culture medium, although it contained high-mannose oligosaccharides with uncovered mannose-6-phosphate residues. Intracellular proCDrec was processed into the 48 kDa intermediate single-chain and the 31 plus 13 kDa double-chain forms, however, the processing was slower than in normal cells. A method based on Pepstatin A-affinity chromatography allowed to isolate the recombinant protein from the medium of infected cells. Based on its latency in activity assay at acid pH and on its reactivity with antibodies specific for the N-terminus, the purified protein was judged to be in the inactive precursor form. During incubation at acid pH the purified proCDrec underwent autocatalytic processing and acquired pepstatin A-sensitive enzyme activity, as expected for correctly folded proCD. Antiserum raised in rabbits against proCDrec specifically reacted with human, but not with mouse proCD under non-denaturing conditions. We conclude that our vaccinia virus-directed proCDrec displays structural and functional features resembling those of native human proCD. This system can therefore be exploited for the synthesis of large quantities of human proCD, allowing further studies on the structure and function of this interesting protein.

Inhibition of gelatinase B (matrix metalloproteinase-9) by dihydrolipoic acid

Alpha-lipoic acid (LA) is a disulphide-containing fatty acid that is absorbed from the diet and transported to tissues. Once it has been taken up by mammalian cells, LA is reduced to dihydrolipoic acid (DHLA), a vicinal dithiol, and rapidly effluxed into the extracellular milieu. We hypothesized that DHLA may be an effective inhibitor of human gelatinase B (GelB). Purified human GelB was incubated with 0 to 200 µmol/L DHLA, and residual enzyme activity was measured by HPLC using a fluorogenic substrate (matrix metalloproteinase substrate III). DHLA inhibited GelB in a dose-dependent fashion with an IC50of 20 µmol/L. Oxidation of DHLA resulted in a loss of DHLA's capacity to inhibit GelB. The DHLA-mediated inhibition of GelB was independent of the zinc concentration in the reaction buffer. DHLA had no inhibitory effect on gelatinase A. Zymographs of activated neutrophil lysates demonstrated that higher concentrations of DHLA also prevent the activation of GelB proenzyme. Bronchoalveolar lavage fluid from mice fed a diet enriched with LA showed significantly increased GelB inhibitory capacity (p = 0.0002 vs. regular diet). We conclude that DHLA can modulate neutrophil-derived GelB activity through direct inhibition of enzyme activity and by preventing the activation of GelB proenzyme.Key words: matrix metalloproteinases, pulmonary fibrosis, thiols, neutrophils, inflammation.

Matrilysin (MMP-7) promotes invasion of ovarian cancer cells by activation of progelatinase

Although matrilysin (MMP-7) is overexpressed in various malignancies, few studies have evaluated its role in epithelial ovarian cancer (EOC) invasion and metastasis. We report that the secretion of MMP-7 in EOC is stimulated significantly by vascular endothelial growth factor (VEGF) and interlukin-8 (IL-8). We also examined the in vivo expression of MMP-7 in EOC and its effects on the in vitro invasion and progelatinase activation. We report that MMP-7 is overexpressed in ovarian cancer cell lines and EOC surgical specimens. DOV13 cells incubated with active rhMMP-7 significantly increased cellular invasion and proMMP-2 activation. RhMMP-7 also showed the ability to activate proMMP-2 and proMMP-9 in immortalized ovarian epithelial cell (IOSE-29) conditioned medium. In addition, rhMMP-7 was able to activate progelatinase in a concentration-dependent manner in vitro. TIMP-2 or the generic MMP inhibitor-GM6001 inhibited both the activation of proMMP-2 and the increased invasion of DOV13 cells promoted by rhMMP-7. By incubation of MMP2-TIMP-2 complex with equal molar rhMMP-7, MMP-2 was dissociated from the complex and activated in a time-dependent manner, suggesting that TIMP-2 helps to keep the latency of MMP-2. TIMP-2 also showed inhibitory effects on the MMP-7 induced increase of gelatinolytic activity in DOV13 and IOSE-29 conditioned media. A strong co-localization of MMP-7 and MMP-2 was observed in DOV13 cells and ovarian carcinoma permanent tissue sections. These results indicate MMP-7 is overexpressed in malignant ovarian epithelium and suggest MMP-7 may facilitate tumor cell invasion in vivo partly through the induction of progelatinase activation.

A Comparison of Six Statins on the Development of Intimal Hyperplasia in a Human Vein Culture Model

OBJECTIVE

Intimal hyperplasia (IH) threatens the patency of up to 35% of saphenous vein (SV) bypass grafts. In addition to reducing cholesterol levels, statins may modulate smooth muscle cell proliferation and migration. Statins inhibit matrix metalloproteinase (MMP) activity. We therefore investigated the effect of six statins on neointimal formation and MMP activity in human SV organ culture.

STUDY DESIGN

Human SV specimens were cultured for 14 days in the presence of six different statins and subsequently processed for measurement of neointimal thickness and MMP activity. The drug concentrations chosen corresponded to the manufacturers' Cmax.

RESULTS

The six statins all significantly reduced IH development (P = 0.004) in association with reduced expression of proMMP-2 and 9 (P = 0.03) and reduced activity of activated MMP-2 and 9 (P = 0.03).

CONCLUSION

This study suggests that the potential benefit of statins in reducing IH is a class effect and not confined to specific statins. The reduction of IH produced by statins may in part be due to their inhibition of MMPs.

Effector-induced Syk-mediated phosphorylation in human erythrocytes

Band 3 (AE1), the most prominent polypeptide of the human erythrocyte membrane, becomes heavily tyrosine phosphorylated following treatment of intact cells with protein tyrosine phosphatase inhibitors such as diamide, pervanadate, vanadate, or N-ethylmaleimide (NEM). The mechanism underlying this tyrosine phosphorylation is thought to involve the sequential action of two protein tyrosine kinases, Syk (p72syk) and Lyn (p53/56lyn). While Lyn catalysed phosphorylation appears to be strictly dependent on prior phosphorylation of Tyr8 and 21 of band 3 by Syk, little is known about the mechanism of induction of Syk phosphorylation. Data presented here show that both the fraction of Syk that associates with the membrane and the extent of phosphorylation of band 3 differ in response to the above inhibitors. While diamide and NEM stimulate syk translocation to the membrane during their induction of band 3 tyrosine phosphorylation, pervanadate and vanadate induce no change in kinase distribution. Moreover, diamide and NEM-induced Syk recruitment to the membrane are phosphotyrosine independent and involve their preferential association with Triton X-100-insoluble membrane skeletons. Together these data reveal a complex process controlling the association and catalytic activity of protein tyrosine kinases syk and lyn with the human erythrocyte membrane.

Modulation of tamoxifen sensitivity by antisenseBcl-2 and trastuzumab in breast carcinoma cells

BACKGROUND

Because the overexpression of HER-2 and Bcl-2 is associated with resistance to tamoxifen (TAM), the authors examined the effect of antisense (AS) Bcl-2 on sensitivity to TAM compared with the effect of trastuzumab on sensitivity to TAM in breast carcinoma cell lines.

METHODS

Drug sensitivity was assessed in vitro using a [3-4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay with the breast carcinoma cell lines ZR-75-1, MDA-MB-453, and BT-474. AS Bcl-2 18-mer phosphorothioate oligonucleotide was applied. Apoptotic cell death was assessed with the terminal deoxynucleotidyl transferase-mediated biotinylated UTP nick-end labeling method, and gene expression was evaluated with Western blot analysis.

RESULTS

The expression of Bcl-2 was identified in ZR-75-1 and BT-474 cells and, to a lesser extent, in MDA-MB-453 cells. Overexpression of HER-2 was identified in BT-474 cells, and moderate expression was identified in MDA-MB-453 and ZR-75-1 cells. Combination treatment with trastuzumab or AS Bcl-2 enhanced TAM sensitivity in ZR-75-1 cells, which showed 50% inhibitory concentration (IC50) values of 0.9 microM (7.2-fold increase) and 0.5 microM (13.0-fold), respectively. Combination treatment with trastuzumab or AS Bcl-2 slightly enhanced TAM sensitivity of BT-474 cells, with IC50 values of 3.0 microM (1.3-fold) and 1.5 microM (2.6-fold), respectively. The sensitivity of MDA-MB-453 cells to TAM was not enhanced by combination with trastuzumab or AS Bcl-2. Modulation of TAM sensitivity by AS Bcl-2 was superior to modulation by trastuzumab in HER-2-expressing and Bcl-2-expressing breast carcinoma cells. Enhanced sensitivity in combination with AS Bcl-2 was associated with down-regulation of Bcl-2 and pAkt, which was correlated with the induction of Bax and caspase-3, leading to apoptosis.

CONCLUSIONS

AS Bcl-2 appeared to be superior to trastuzumab with respect to regulating the signal-transduction pathways involved in breast carcinoma cells.

In malignant myeloid cells expression of Daxx downregulates expression of p53 and of the inhibitors of apoptosis proteins

The role of Daxx, in particular its ability to promote or hinder proliferation, still remains controversial. In order to elucidate the functional relevance of Daxx in malignant myelocytes, the erythroleukemia cell line HEL was stably transfected with a Daxx-expressing vector or with the respective Daxx-negative control vector. Assessing the molecular consequences of ectopic Daxx-expression, we present evidence that Daxx downregulates p53. Moreover, we demonstrate that Daxx overexpressing myelocytes downregulate the proapoptotic Bcl-2 family member Bax, while expression of antiapoptotic Bcl-2 is not influenced. Furthermore, expression of Daxx diminishes expression levels of the initiator-procaspase-8 and -10, and the executioner procaspase-7, whereas the procaspase-3, -6 and -9 remain unaltered. The altered protein levels of the caspases in Daxx overexpressing myelocytes are accompanied by a decrease of expression levels of the inhibitor of apoptosis proteins (IAPs) cIAP-1, -2 and survivin. Despite the described impact of Daxx expression on major molecules of the apoptotic cascade, expression of Daxx in neoplastic myelocytes does not impact on the rate of proliferation. Upon a proapoptotic stimulus such as serum withdrawal Daxx is unable to maintain its influence on expression levels of p53, Bax, IAPs and the procaspase-8, -10 and -7.

Apoptotic effects of LPS on fibroblasts are indirectly mediated through TNFR1

During periods of periodontal attachment loss, one of the most significant cellular changes is a decrease in the number of fibroblasts. We previously demonstrated that LPS induces apoptosis of fibroblastic cells in vivo, largely through TNF-alpha. We conducted in vivo experiments by subcutaneous inoculation of LPS in wild-type, TNFR1-/-R2-/-, TNFR1-/-, and TNFR2-/- mice to identify which TNF receptors are involved and the specific caspase pathway activated. LPS stimulated apoptosis through TNFR1 but not TNFR2, which was accompanied by the induced expression of 12 apoptotic genes. Fluorometric studies demonstrated that LPS in vivo significantly increased caspase-8 and caspase-3 activity, which was also dependent on TNF receptor signaling. By the use of specific caspase inhibitors, caspases-3 and -8 were shown to play an important role in LPS-induced apoptosis in vivo. Thus, LPS acts through TNFR1 to modulate the expression of apoptotic genes and activate caspases-3 and -8.

Limited processing of pro-matrix metalloprotease-2 (gelatinase A) overexpressed by transfection in PC-3 human prostate tumor cells: association with restricted cell surface localization of membrane-type matrix metalloproteinase-1

The expression and activation of matrix metalloproteinases (MMPs) by tumor cells is correlated with progression to invasive and metastatic status. The purpose of this study was to examine the role of increased MMP-2 (gelatinase A) expression in prostate cancer progression utilizing human prostate PC-3 cancer cells that overexpress MMP-2 using gene transfection. PC-3 cells were transfected with pCR-3 vector only and pCR-3 MMP-2 plasmids employing the LipofectAMINE method, and stable transfectants were selected with G418. The expression of MMP-2, tissue inhibitor of metalloproteinase-2 (TIMP-2), and membrane-type MMP 1 (MT1-MMP) in PC-3 parental and transfected cells under serum-free conditions was determined by zymography, immunoblotting, immunofluorescent microscopy, Northern blotting, and/or reverse transcriptase-polymerase chain reaction (RT-PCR). MMP-2 transfected cells produced primarily the proenzyme form of MMP-2; the parental and vector control transfected PC-3 cells did not express any MMP-2 that was detectable by the methods we employed. Treatment of PC-3 MMP-2 transfected cells with Concanavalin A (Con A), in contrast to HT-1080 cells, processed only a small amount of the secreted 72-kd proenzyme to a 62-kd intermediate and a cell-associated 59-kd active form. The low level of secreted pro-MMP-2 processing induced by Con A was inhibited by serine protease inhibitors and was unaffected by cyclic adenosine monophosphate (cAMP). Immunoblotting showed that these cells produced abundant TIMP-2 and lower amounts of MT1-MMP in comparison with Con A-responding HT-1080 cells. HT-1080 cells respond to Con A by translocating MT1-MMP from intracellular localization sites to the plasma membrane, an effect not observed in PC-3 cells. The molecular basis for the low level of processing of pro-MMP-2 by PC-3 cells may be due to an overabundance of TIMP-2 and/or a low level of cell surface active MT1-MMP.

Platelet‐activating factor (PAF) induces activation of matrix metalloproteinase 2 activity and vascular endothelial cell invasion and migration

Tumor-induced angiogenic responses lead to complex phenotypic changes in vascular endothelial cells, which must coordinate the expression of both proteases and protease inhibitors prior to the proliferation and invasion of surrounding stroma. Matrix metalloproteinase 2 (MMP2), which degrades Type IV collagen, is produced as proMMP2. proMMP2 is activated in part through its interactions with membrane Type 1 MMP (MT1-MMP) and tissue inhibitor of matrix metalloproteinase 2 (TIMP2). In this study, we demonstrate that platelet-activating factor (PAF) is a potent inducer of human umbilical vein endothelial cell (HUVEC) migration and invasion, which is attenuated by PAF receptor antagonists, and that PAF receptor antagonists inhibit the migration and invasion of HUVEC mediated by medium conditioned by a prostatic carcinoma cell line. We confirm that PAF receptor antagonists inhibit proliferation of HUVEC grown in rich growth medium. We show that PAF increases mRNA levels for MT1-MMP and TIMP2, followed by increased temporal conversion of latent proMMP2 to MMP2. Finally, we demonstrate that the ratio of MT1-MMP to TIMP2 in membrane preparations from PAF-stimulated HUVEC is 1.6:1, approximating the hypothesized ideal ratio of 2:1 necessary for the conversion of proMMP2 to MMP2. Our data support the involvement of PAF in vascular endothelial cell migration and invasion.

Calcium-induced activation and truncation of promatrix metalloproteinase-9 linked to the core protein of chondroitin sulfate proteoglycans

In the leukemic macrophage cell-line THP-1, a fraction of the secreted matrix metalloproteinase 9 (MMP-9) is linked to the core protein of chondroitin sulfate proteoglycans (CSPG). Unlike the monomeric and homodimeric forms of MMP-9, the addition of exogenous CaCl2 to the proMMP-9/CSPG complex resulted in an active gelatinase due to the induction of an autocatalytic removal of the N-terminal prodomain. In addition, the MMP-9 was released from the CSPG through a process that appeared to be a stepwise truncation of both the CSPG core protein and a part of the C-terminal domain of the gelatinase. The calcium-induced activation and truncation of the MMP-9/CSPG complex was independent of the concentration of the complex, inhibited by the MMP inhibitors EDTA, 1,10-phenanthroline and TIMP-1, but not by general inhibitors of serine, thiol and acid proteinases. This indicated that the activation and truncation process was not due to a bimolecular reaction, but more likely an intramolecular reaction. The negatively charged chondroitin sulfate chains in the proteoglycan were not involved in this process. Other metal-containing compounds like amino-phenylmercuric acetate (APMA), NaCl, ZnCl2 and MgCl2 were not able to induce activation and truncation of the proMMP-9 in this heterodimer. On the contrary, APMA inhibited the calcium-induced process, whereas high concentrations of either MgCl2 or NaCl had no effect. Our results indicate that the interaction between the MMP-9 and the core protein of the CSPG was the causal factor in the calcium-induced activation and truncation of the gelatinase, and that this process was not due to a general electrostatic effect.

Inhibition of Drynariae Rhizoma extracts on bone resorption mediated by processing of cathepsin K in cultured mouse osteoclasts

In the traditional Korean medicine, Drynariae Rhizoma (DR) [Drynaria fortunei (kunze) J. Sm] has been reported as a good enhancer for bone healing. In this experiment, we investigate the effects of DR on bone resorption using the bone cells culture. Different concentrations of crude extract of DR were added to mouse bone cells culture. The mitochondria activity of the bone cells after exposure was determined by colorimetric MTT assay. It was demonstrated that DR has potential effects on the bone cells culture without any cytotoxicity. The most effective concentration of DR on bone cells was 100 micro g/ml. On the other hand, cathepsin K (Cat K) is the major cysteine protease expressed in osteoclasts and is thought to play a key role in matrix degradation during bone resorption. In this study, Mouse long bone cells including osteoclasts and osteoblast were treated with the PI3-kinase inhibitor, wortmannin (WT), and a specific inhibitor of protein kinase C (PKC), calphostin C. Although WT prevented the osteoclast-mediated intracellular processing of Cat K, calphostin C did not. Similarly, treatment of osteoclasts-containing long bone cells with Drynariae Rhizoma (DR) extracts prevented the intracellular maturation of Cat K, suggesting that DR may disrupt the intracellular trafficking of pro Cat K. This is similar to that of WT. Since secreted proenzymes have the potential to reenter the cell via mannose-6-phosphate (M6P) receptor, to prevent this possibility, we tested WT and DR in the absence or presence of M6P. Inhibition of Cat K processing by WT or DR was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of WT and DR. DR dose-dependently inhibited in vitro bone resorption with a potency similar to that observed for inhibition of Cat K processing.

Procaspase-3 and its active large subunit localized in both cytoplasm and nucleus are activated following application of apoptotic stimulus in Ramos-Burkitt lymphoma B cells

Ramos-Burkitt lymphoma (Ramos-BL) B cell line is a neoplastic model of normal B cell selection by apoptosis at the germinal center site during maturation of the humoral immune response and can be triggered into apoptosis by cross-linking their surface antigen receptor with antibodies directed against immunoglobulin (Ig)M (anti-IgM) or by treating with the calcium ionophore ionomycin. We have recently demonstrated that anti-IgM and ionomycin trigger significant activation of caspase-3, -7 and -8 and for cleavage of the resident nuclear proteins poly(ADP-ribose) polymerase (PARP) and lamin B1 in Ramos-BL B cells, suggesting that these caspases may be localized to the nucleus as well as to the cytoplasm of Ramos-BL B cells. In order to examine this hypothesis further, we fractionated Ramos-BL B cells into their cytosolic and nuclear components and examined for expression of the endogenous proform and active large subunit of caspase-3; procaspase-3 and its active p17 large subunit were identified in both the cytosolic and nuclear fractions of Ramos-BL B cells. Immunofluorescence staining together with ordinary and confocal microscopy confirmed the observations that procaspase-3 immunoreactivity was clearly identified in the cytoplasm and nucleus while Fas ligand staining was localized to the cell surface and PARP immunoactivity to the nucleus, which were used as controls; procaspase-3 exhibited granular nuclear immunoreactivity whereas PARP displayed diffuse nuclear immunoreactivity; both of which was more intense in the internucleolar regions. Taken together, we now present evidence that procaspases and their active large subunits are found in both the cytoplasm and the nucleus and that procaspases localized not only in the cytoplasm but also in the nucleus are activated following application of apoptotic stimulus in Ramos-BL B cells.

Protein inhibitors form complexes with procathepsin L and augment cleavage of the propeptide

The proregion fits tightly into the active site in the tertiary structure of procathepsin L and prevents its activity. We show that complexes between enzyme precursor and its endogenous protein inhibitors-the cystatins-can be formed without prior proteolytic removal of the propeptide. Complexes between cystatins and procathepsin L are formed at acidic pH and their formation is facilitated by acidic oligosaccharides. Binding of the inhibitor to the proenzyme is reversible and the slow dissociation of complex around neutral pH may serve as a pool for the sustained release of the enzyme. Formation of the complex between cystatin and procathepsin L increases the susceptibility of the proregion to proteolytic cleavage. This process may constitute an alternative mechanism of formation of the complex between enzyme and inhibitor without prior activation of the proenzyme.

Essential role for Ca2+ in regulation of IL-1beta secretion by P2X7 nucleotide receptor in monocytes, macrophages, and HEK-293 cells

Interleukin (IL)-1beta is a proinflammatory cytokine that elicits the majority of its biological activity extracellularly, but the lack of a secretory signal sequence prevents its export via classic secretory pathways. Efficient externalization of IL-1beta in macrophages and monocytes can occur via stimulation of P2X7 nucleotide receptors with extracellular ATP. However, the exact mechanisms by which the activation of these nonselective cation channels facilitates secretion of IL-1beta remain unclear. Here we demonstrate a pivotal role for a sustained increase in cytosolic Ca2+ to potentiate secretion of IL-1beta via the P2X7 receptors. Using HEK-293 cells engineered to coexpress P2X7 receptors with mature IL-1beta (mIL-1beta), we show that activation of P2X7 receptors results in a rapid secretion of mIL-1beta by a process(es) that is dependent on influx of extracellular Ca2+ and a sustained rise in cytosolic Ca2+. Moreover, reduction in extracellular Ca2+ attenuates approximately 90% of P2X7 receptor-mediated IL-1beta secretion but has no effect on enzymatic processing of precursor IL-1beta (proIL-1beta) to mIL-1beta by caspase-1. Similar experiments with THP-1 human monocytes and Bac1.2F5 murine macrophages confirm the unique role of Ca2+ in P2X7 receptor-mediated secretion of IL-1beta. In addition, we report that cell surface expression of P2X7 receptors in the absence of external stimulation also results in enhanced release of IL-1beta and that this can be repressed by inhibitors of P2X7 receptors. We clarify an essential role for Ca2+ in ATP-induced IL-1beta secretion and indicate an additional role of P2X7 receptors as enhancers of the secretory apparatus by which IL-1beta is released.

Modulation of angiogenesis and progelatinase a by thrombin receptor mimetics and antagonists

The angiogenic action of thrombin has been shown to be mediated by activation of the thrombin receptor. In this report we studied the effects of SFLLR, an agonist of the activated thrombin receptor and thrombin receptor peptide and non peptide antagonists on angiogenesis in the chick chorioallantoic membrane (CAM) system. As antagonists were used the tripeptide FPR and non-peptide 1,4-disubstituted piperazine derivatives. The pentapeptide SFLLR, like thrombin, caused a marked stimulation of angiogenesis in the CAM. FPR and the piperazine derivatives caused suppression of angiogenesis and in combination with thrombin antagonized its angiogenic effect. Thrombin and SFLLR activated progelatinase A (MMP-2) in the culture medium of human umbilical cord endothelial cells (HUVECs). MMP-2 is involved in the early steps of angiogenesis leading to local dissolution of basement membrane collagen and migration of the activated endothelial cells. FPR and the piperazine derivatives inhibited the activation of this enzyme. They also antagonised the effects of both thrombin and SFLLR on MMP-2 activation. These results suggest that non-thrombogenic agonists or antagonists of the activated thrombin receptor can be used as modulators of angiogenesis.

Differential effects of quercetin and resveratrol on Band 3 tyrosine phosphorylation signalling of red blood cells

The protective effects of eating fruits and vegetables in the prevention of several degenerative pathologies have been attributed at least in part to the antioxidant and anti-inflammatory properties of polyphenols. In this study, we investigated the effects of two polyphenols, quercetin and resveratrol, on red blood cell Band 3 tyrosine phosphorylation signalling activated by peroxynitrite. Peroxynitrite is a physiological oxidant scavenged largely by the erythrocyte and formed by the reaction between nitrogen monoxide and superoxide anion. Quercetin and its structurally analogous (+)-catechin inhibited the peroxynitrite-dependent upregulation of Band 3 tyrosine phosphorylation. Quercetin was found to downregulate the activity of syk, which is upstream in the Band 3 tyrosine phosphorylation cascade, and partially prevented peroxynitrite-mediated phosphotyrosine phosphatase inhibition. Resveratrol and hydroxytyrosol, unexpectedly, amplified peroxynitrite-dependent upregulation of Band 3 tyrosine phosphorylation through the activation of lyn, a kinase of the src family. The present results clearly indicate that polyphenols may activate cell transduction pathways in different and sometimes opposite ways.

The influence of nitric oxide synthesis modulation on the pancreatic acinar cells in caerulein-induced acute pancreatitis. An ultrastructural and morphometric study

The goal of our study was to evaluate the influence of NO synthesis modulation on the ultrastructural changes in the pancreatic acinar cells in connection with morphometric assessment of the volume and numerical densities of mitochondria (Vvm, Nvm) and zymogen granules (Vvz, Nvz) in caerulein-induced acute pancreatitis (AP). During AP induction rats were treated with L-arginine--substrate for NO synthesis, N(G)-nitro-L-arginine (L-NNA)--NO synthase inhibitor, gliceryl trinitrate (NTG)--NO donor, L-arginine+L-NNA or saline. This study demonstrated that administration of L-NNA leads to the formation of numerous, large autophagosomes and mitochondria oedema in pancreatic acinar cells. Treatment with L-arginine or NTG during AP induction resulted in a diminution of the ultrastructural changes with a concomitant increase of Vvz. Vvm and Nvm were significantly lower in the L-arginine treated group compared to the untreated AP. The results indicate that: L-NNA enhances damage to acinar cells which may be indicative of a protective role for endogenous NO in oedematous AP. The application of L-arginine or NTG decreases the damage to acinar cells evaluated ultrastructurally, suggesting the morphological changes accompanying the onset of AP in rats after the administration of either substrate for endogenous NO synthesis or exogenous NO donor follow a favourable course.

In vitro hypoxia and excitotoxicity in human brain induce calcineurin-Bcl-2 interactions

Although pathogenesis of neuronal ischemia is incompletely understood, evidence indicates apoptotic neuronal death after ischemia. Bcl-2, an anti-apoptotic and neuroprotective protein, interacts with calcineurin in non-neuronal tissues. Activation of calcineurin, which is abundant in the brain, may play a role in apoptosis. Using co-immunoprecipitation experiments in biopsy-derived, fresh human cortical and hippocampal slices, we examined possible interactions between calcineurin and Bcl-2. Calcineuin-Bcl-2 interactions increased after exposure in vitro to excitotoxic agents and conditions of hypoxia/aglycia. This interaction may shuttle calcineurin to substrates such as the inositol-1,4,5-tris-phosphate receptor because under these experimental conditions interactions between calcineurin and inositol-1,4,5-tris-phosphate receptor also increased. A specific calcineurin inhibitor, FK-520, attenuated insult-induced increases in calcineurin-Bcl-2 interactions and augmented caspase-3 like activity. These data suggest that Bcl-2 modulates neuroprotective effects of calcineurin and that calcineurin inhibitors increase ischemic neuronal damage.

A new approach to treat tissue destruction in periodontitis with chemically modified dextran polymers

Periodontitis are diseases of the supportive tissues of the teeth provoked by bacteria and characterized by gingival inflammation and bone destruction. We have developed a new strategy to repair tissues by administrating agents (RGTA) that mimic heparan sulfates by protecting selectively some of the growth factors naturally present within the injured tissue and interfering with inflammation. After periodontitis induction in hamsters, the animals were left untreated or received weekly i.m. injections of RGTA1507 at a dose of 100 microg/kg, 400 microg/kg, 1.5 mg/kg, or 15 mg/kg for 4 wk. RGTA treatment significantly reduced gingival tissue inflammation, thickened the pocket epithelium by increasing cell proliferation, and enhanced collagen accumulation in the gingiva. A marked reduction in bone loss was observed, resulting from depression of osteoclasia and robust stimulation of bone formation at the dose of 1.5 mg/kg. RGTA treatment for 8 wk at this dose reversed macroscopic bone loss, sharply contrasting with the extensive bone destruction in the untreated animals. RGTA treatment decreased gelatinase A (MMP-2) and B (MMP-9) pro-forms in gingival tissues. Our data indicate that a 4 wk treatment dose-dependently attenuated gingival and bone manifestations of the disease, whereas a longer treatment restored alveolar bone close to controls. By modulating and coordinating host responses, RGTA has unique therapeutic properties and is a promising candidate for the treatment of human periodontitis.

5-Fluorouracil efficiently enhanced apoptosis induced by adenovirus-mediated transfer of caspase-8 in DLD-1 colon cancer cells

BACKGROUND

In order to develop a safe and effective gene therapy for cancer, more powerful therapeutic genes must be selected and a gene transduction methodology needs to be devised that minimizes the total dose of vector required. We investigated the combination effect of 5-fluorouracil (5-FU), a first-choice drug for the treatment of colorectal cancer and adenovirus-mediated transfer of caspase-8 in DLD-1 colon cancer cells.

METHODS

The degree of cell death was assessed by determining the percentage of cells which had died, and the degree of DNA fragmentation. The protein expression levels and degree of activation of caspase-8 were analyzed by Western blot analysis. The degree of transgene expression was assessed using adenoviral vectors expressing lacZ and GFP.

RESULTS

Combination treatment led to a significant induction of apoptosis, whereas treatment with either approach alone resulted in only minimal cytotoxicity. Caspase-8 was only activated in cells that received the combined treatment. Exposure to 5-FU increased the quantity of transgene expression per cell, 48 h post-infection. A potentiating effect of adenoviral treatment was also seen when 5-FU treatment was substituted by the overexpression of cyclin-dependent kinase inhibitors, p21(WAF1/CIP1) and p27(KIP1), suggesting that the cytostatic effect of 5-FU augmented apoptosis induced by caspase-8 gene transduction by inhibiting the dilution of gene products associated with cell division.

CONCLUSIONS

This combination strategy may be very useful in the treatment of 5-FU-resistant colorectal cancers and may also be more generally helpful in minimizing the dose of therapeutic vectors used in cancer gene therapy.

Bax cleavage implicates caspase-dependent H2O2-induced apoptosis of hepatocytes

Oxidative stress plays an important role in the development of ischemia/reperfusion (I/R)-induced apoptosis of hepatocytes. We aimed to examine the involvement of caspases and calpains in H2O2-induced hepatic cell apoptosis. TUNEL-positive apoptotic cells appeared in parallel with poly(ADP-ribose) polymerase (PARP) cleavage and procaspase-3 proteolysis by H2O2 treatment in a dose-dependent manner (250-1,000 micro M). Bcl-xL and intact Bax expression levels decreased when H2O2 was >250 micro M. The cleaved form of Bax appeared prior to caspase-3 activation, increasing in a dose-dependent manner. A pan-caspase inhibitor, Z-VAD-fmk, completely blocked H2O2-induced procaspase-3 proteolysis and PARP cleavage without changing Bax cleavage, but partially attenuated H2O2-induced apoptosis. Calpeptin, a calpain inhibitor, did not inhibit caspase-3 activation, Bax cleavage or apoptosis. Our results indicate that Bax cleavage is upstream signal of caspase-dependent apoptosis in hepatocytes exposed to H2O2, but not independent upon calpain. Molecular targeting of Bax cleavage may allow the development of strategies to prevent hepatic I/R injury.

Heat shock protects HCT116 and H460 cells from TRAIL-induced apoptosis

Heat shock proteins have been shown to protect cells from a variety of stressful conditions, including hyperthermia, oxidative and DNA damage, serum withdrawal, and a variety of chemicals. HSP27, HSP70, and HSP90 have been shown to downregulate different aspects of apoptosome assembly. TRAIL is a member of the TNF family of ligands and is a promising anti-cancer agent. It has been shown to be nontoxic to most normal cell types, while it is a potent killer of many different cancer cells. TRAIL engages both the receptor-mediated (extrinsic) and the mitochondria-initiated (intrinsic) cascades. We tested whether heat shock affects TRAIL-induced apoptosis in different cancer cells. TRAIL treatment does not induce HSP27, HSP70, or HSP90 levels. Nonetheless, when treated with TRAIL for 3 h after release from heat shock, the human colon cancer cell line HCT116 is protected from apoptosis whereas the human colon cancer cell line SW480 is not. This pattern is consistent with the previously observed behavior of HCT116 as Type II cells that depend on mitochondrial signaling and SW480 as Type I, whose TRAIL-induced death is not sensitive to inhibition of caspase 9. Moreover, the failure of heat shock to protect SW480 cells is not due to a lack of HSP70 or HSP90 upregulation. HSP70 and HSP90 are induced 3 h after release from heat shock, whereas HSP27 is induced much later. Thus, the observed protective effect against TRAIL is probably due to the anti-apoptotic effects of HSP70 and HSP90. These results further illustrate interactions between TRAIL receptor signaling and the intrinsic cell death pathway and have practical implications for the potential use of TRAIL and hyperthermia in cancer therapy.

N-terminal domain of the dual-targeted pea glutathione reductase signal peptide controls organellar targeting efficiency

Import of nuclear-encoded proteins into mitochondria and chloroplasts is generally organelle specific and its specificity depends on the N-terminal signal peptide. Yet, a group of proteins known as dual-targeted proteins have a targeting peptide capable of leading the mature protein to both organelles. We have investigated the domain structure of the dual-targeted pea glutathione reductase (GR) signal peptide by using N-terminal truncations. A mutant of the GR precursor (pGR) starting with the second methionine residue of the targeting peptide, pGRdelta2-4, directed import into both organelles, negating the possibility that dual import was controlled by the nature of the N terminus. The deletion of the 30 N-terminal residues (pGRdelta2-30) inhibited import efficiency into chloroplasts substantially and almost completely into mitochondria, whereas the removal of only 16 N-terminal amino acid residues (pGRdelta2-16) resulted in the strongly stimulated mitochondrial import without significantly affecting chloroplast import. Furthermore, N-terminal truncations of the signal peptide (pGRdelta2-16 and pGRdelta2-30) greatly stimulated the mitochondrial processing activity measured with the isolated processing peptidase. These results suggest a domain structure for the dual-targeting peptide of pGR and the existence of domains controlling organellar import efficiency therein.

Abundant expression of Dec1/stra13/sharp2 in colon carcinoma: its antagonizing role in serum deprivation-induced apoptosis and selective inhibition of procaspase activation

The basic helix-loop-helix (bHLH) proteins are intimately associated with developmental events such as cell differentiation and lineage commitment. The HLH domain in the bHLH motif is responsible for dimerization, whereas the basic region mediates DNA binding. Based on sequence alignment and domain analysis, differentially expressed in chondrocytes/stimulated with retinoic acid/split and hairy-related proteins (DEC/STRA/SHARPs) represent a new class of bHLH proteins. The present study describes the functional characterization of DEC1. Subtractive experiments and blotting analyses demonstrated that DEC1 was highly expressed in colon carcinomas, but not in the adjacent normal tissues. Several cell cycle blockers markedly induced DEC1 expression. Stable transfectants with a tetracycline-inducible construct demonstrated that DEC1 caused proliferation inhibition, antagonized serum deprivation-induced apoptosis and selectively inhibited the activation of procaspases. These activities were highly correlated with the abundance of tetracycline-induced DEC1. Stable transfectants expressing a mutant DEC1 (lacking the DNA-binding domain) exhibited neither proliferation inhibition nor apoptotic antagonism, which suggests that DNA binding is required for these actions. Enzymic assays and immunoblotting analyses demonstrated that induction of DEC1 by tetracycline significantly decreased the activation of procaspases 3, 7 and 9 but not procaspase 8. The selective suppression on the activation of procaspases 3, 7 and 9 over procaspase 8 suggests that DEC1-mediated anti-apoptosis is achieved by blocking apoptotic pathways initiated via the mitochondria. The results functionally distinguish DEC1 from other bHLH proteins and directly link this factor to oncogenesis.

Involvement of redox events in caspase activation in zinc-depleted airway epithelial cells

Airway epithelial cells (AEC) contain both pro- and anti-apoptotic factors but little is known about mechanisms regulating apoptosis of these cells. In this study we have examined the localization of pro-caspase-3 and Zn(2+), a cellular regulator of pro-caspase-3, in primary sheep and human AEC. Zn(2+) was concentrated in both cytoplasmic vesicles and ciliary basal bodies, in the vicinity of both pro-caspase-3 and the antioxidant Cu/Zn superoxide dismutase (Cu/Zn SOD). Depletion of intracellular Zn(2+) in sheep AEC, using the membrane permeant Zn(2+) chelator TPEN, increased lipid peroxidation in the apical cell membranes (as assessed by immunofluorescence with anti-hydroxynonenal) as well as increasing activated pro-caspase-3 and apoptosis. There were smaller increases in caspase-2 and -6 but not other caspases. Activation of caspase-3 in TPEN-treated AEC was inhibited strongly by N-acetylcysteine and partially by vitamin C and vitamin E. These findings suggest that cytoplasmic pro-caspase-3 is positioned near the lumenal surface of AEC where it is under the influence of Zn(2+) and other anti-oxidants.

Release of cytochrome c and activation of pro-caspase-9 following lysosomal photodamage involves Bid cleavage

Photodynamic therapy (PDT) protocols employing lysosomal sensitizers induce apoptosis via a mechanism that causes cytochrome c release prior to loss of mitochondrial membrane potential (DeltaPsi(m)). The current study was designed to determine how lysosomal photodamage initiates mitochondrial-mediated apoptosis in murine hepatoma 1c1c7 cells. Fluorescence microscopy demonstrated that the photosensitizer N-aspartyl chlorin e6 (NPe6) localized to the lysosomes. Irradiation of cultures preloaded with NPe6 induced the rapid destruction of lysosomes, and subsequent cleavage/activation of Bid, pro-caspases-9 and -3. Pro-caspase-8 was not activated. Release of cytochrome c occurred at about the time of Bid cleavage and preceded the loss of DeltaPsi(m). Extracts of purified lysosomes catalyzed the in vitro cleavage of cytosolic Bid, but not pro-caspase-3 activation. Pharmacological inhibition of cathepsin B, L and D activities did not suppress Bid cleavage or pro-caspases-9 and -3 activation. These studies demonstrate that photodamaged lysosomes trigger the mitochondrial apoptotic pathway by releasing proteases that activate Bid.

Molecular characterization of a senescence-associated gene encoding cysteine proteinase and its gene expression during leaf senescence in sweet potato

The structure and expression of a senescence-associated gene (SPG31) encoding a cysteine proteinase precursor of sweet potato have been characterized. The coding region of the gene consists of two exons encoding an enzyme precursor of 341 amino acids with conserved catalytic amino acids of papain. Examination of the expression patterns of the SPG31 gene in sweet potato by Northern blot analyses reveals that the transcripts of SPG31 are specifically induced in the senescing leaves but not in other organs. The differential accumulation of the mature SPG31 protein in the senescing leaves was further identified by two-dimensional electrophoresis of leaf proteins and N-terminal sequencing. This result suggests the important role played by SPG31 in proteolysis and nitrogen remobilization during the leaf senescence process. Furthermore, treatment of mature green leaves with ethylene for 3 d resulted in a high-level induction of SPG31 transcripts. Ethylene-regulated expression of SPG31 is consistent with the presence of a number of putative ethylene-responsive elements in the 899-bp SPG31 promoter region.

Role of sulfated O-linked glycoproteins in zymogen granule formation

Packaging of proteins into regulated secretory granules is mediated by the mildly acidic pH of the trans Golgi network and immature secretory granules. This need for an acidic pH indicates that ionic interactions are important. The mouse pancreatic acinar cell contains four major sulfated glycoproteins,including the zymogen granule structural component Muclin. I tested the hypothesis that sulfation and the O-linked glycosylation to which the sulfates are attached are required for normal formation of zymogen granules in the exocrine pancreas. Post-translational processing was perturbed with two chemicals: sodium chlorate was used to inhibit sulfation and benzyl-N-acetyl-α-galactosaminide was used to inhibit O-linked oligosaccharide elongation. Both chemicals resulted in the accumulation in the Golgi region of the cell of large vacuoles that appear to be immature secretory granules, and the effect was much more extensive with benzyl-N-acetyl-α-galactosaminide than chlorate. Both chemical treatments inhibited basal secretion at prolonged chase times, and again benzyl-N-acetyl-α-galactosaminide had a greater effect than chlorate. In addition, benzyl-N-acetyl-α-galactosaminide, but not chlorate, totally inhibited stimulated secretion of newly synthesized proteins. These data provide evidence for a role of sulfated O-linked glycoproteins in protein condensation and maturation of zymogen granules. Under maximal inhibition of O-linked oligosaccharide biosynthesis, anterograde post-Golgi traffic in the regulated pathway is almost totally shut down, demonstrating the importance of these post-translational modifications in progression of secretory proteins through the regulated pathway and normal granule formation in the pancreatic acinar cell.

Angiotensin II inhibits renin gene transcription via the protein kinase C pathway

Angiotensin II (ANGII) inhibits renin gene expression in vivo, a mechanism considered to be a physiologically important negative feedback of the renin-angiotensin-system. How this particular effect of ANGII is achieved at the cellular level is unknown. Our study therefore aimed to determine whether ANGII exerts a direct effect on renin gene expression and, if so, to characterise the molecular mechanisms involved. In the mouse renal juxtaglomerular cell line As4.1, ANGII decreased steady-state renin mRNA levels and prorenin secretion time and concentration (EC(50) 100 nmol/l) dependently. The effects of ANGII were blunted by the protein kinase C (PKC) inhibitor bisindolylmaleimide I and mimicked by the PKC activator phorbol 12-myristate-13-acetate (PMA) (EC(50) 10 nmol/l). ANGII also inhibited renin promoter activity PKC-dependently. The inhibitory sequences triggered by ANGII appear to reside within the first 2.9 kb in the 5'-flanking region of the mouse ren1c gene but are not related to the two canonical activator protein-1 (AP-1) binding sites at positions -16 to -22 and -141 to -147. In summary, our data suggest that ANGII acts directly on renal juxtaglomerular cells to inhibit renin gene transcription through the PKC pathway. Since the PKC pathway can be activated by a variety of hormones it represents a powerful and probably rather important downstream pathway in the control of renin gene expression.

Association between alphavbeta6 integrin expression, elevated p42/44 kDa MAPK, and plasminogen-dependent matrix degradation in ovarian cancer

Altered expression of alphav integrins plays a critical role in tumor growth, invasion, and metastasis. In this study, we show that normal human epithelial ovarian cell line, HOSE, and ovarian cancer cell lines, OVCA 429, OVCA 433, and OVHS-1, expressed alphav integrin and associated beta1, beta3, and beta5 subunits, but only ovarian cancer cell lines OVCA 429 and OVCA 433 expressed alphavbeta6 integrin. The expression of alphavbeta6 in OVCA 429 and OVCA 433 was far higher than alphavbeta3 and alphavbeta5 integrin and correlated with high p42/p44 mitogen activated protein kinase (MAPK) activity and high secretion of high molecular weight urokinase plasminogen activator (HMW-uPA), pro-metalloproteinase 2 and 9 (pro-MMP-9 and pro-MMP-2). In contrast to HOSE and OVHS 1, OVCA 433 and OVCA 429 exhibited approximately 2-fold more plasminogen-dependent [3H]-collagen type IV degradation. Plasminogen-dependent [3H]-collagen IV degradation was inhibited by inhibitor of uPA (amiloride) and MMP (phenanthroline) and by antibodies against uPA or MMP-9 or alphavbeta6 integrin, indicating the involvement of alphavbeta6 integrin, uPA and MMP-9 in the process. The alphavbeta6 correlated increase in HMW-uPA and pro-MMP secretion could be inhibited by tyrosine kinase inhibitor genistein or the MEK 1 inhibitor U0126, consistent with a role of active p42/44 MAPK in the elevation of uPA, MMP-9, and MMP-2 secretion. Under similar conditions, genistein and U0126 inhibited plasminogen-dependent [3H]-collagen type IV degradation. These data suggest that sustained elevation of p42/44 MAPK activity may be required for the co-expression of alphavbeta6 integrin, which in turn may regulate the malignant potential of ovarian cancer cells via proteolytic mechanisms.

Serum-dependent effects of IGF-I and insulin on proliferation and invasion of human first trimester trophoblast cell models

Extravillous cytotrophoblasts are specialised epithelial cells of the placenta that proliferate or invade the maternal decidua. Little is known about the mechanisms that regulate these processes. Here the effects of several insulin and insulin-like growth factor-I (IGF-I) doses, either singly or in synergy with serum, on human chorionic gonadotropin-beta (hCG-beta) secretion (RIA), proliferation (cell counting, cyclin B(1) levels) and invasion [Matrigel invasion assay, secretion of matrix metalloproteinases (MMP) 2 and 9] were investigated. The choriocarcinoma cell lines BeWo, JAR and JEG-3 served as models for first trimester human trophoblasts. Both growth factors altered hCG-beta secretion and proliferation dependent on the cell line. Insulin stimulated proliferation in JAR cells and, to a lesser extent, in JEG-3 cells, and when cultured in serum-free medium, BeWo was not affected. Invasion was not affected although proMMP-2 levels in culture medium were altered under some conditions. A strong synergistic effect with serum was noted. In the presence of serum both growth factors reduced proliferation and invasion in a similar fashion. Since the cell models differ by their degree of differentiation, the data demonstrate that the effects of insulin and IGF-I strongly depend on serum and the degree of differentiation. It can be speculated that IGF-I can take on tasks of insulin in the regulation of trophoblast functions under conditions of insulinopenia.

Inhibition of the MAPK and PI3K pathways enhances UDCA-induced apoptosis in primary rodent hepatocytes

The mechanisms by which bile acids induce apoptosis in hepatocytes and the signaling pathways involved in the control of cell death are not understood fully. Here, we examined the impact of mitogen-activated protein kinase (MAPK) and phosphatidyl inositol 3-kinase (PI3K) signaling on the survival of primary hepatocytes exposed to bile acids. Treatment of hepatocytes with deoxycholic acid (DCA), chenodeoxycholic acid (CDCA) or ursodeoxycholic acid (UDCA) caused sustained MAPK activation that was dependent on activation of the epidermal growth factor receptor (EGFR). Activation of MAPK was partially blocked by inhibitors of PI3K. Inhibition of DCA-, CDCA-, and UDCA-stimulated MAPK activation resulted in approximately 20%, approximately 35%, and approximately 55% apoptosis, respectively. The potentiation of DCA- and CDCA-induced apoptosis by MEK1/2 inhibitors correlated with cleavage of procaspase 3, which was blocked by inhibitors of caspase 8 (ile-Glu-Thr-Asp-p-nitroanilide [IETD]) and caspase 3 (DEVD). In contrast, the potentiation of UDCA-induced apoptosis weakly correlated with procaspase 3 cleavage, yet this effect was also blocked by IETD and DEVD. Incubation of hepatocytes with the serine protease inhibitor AEBSF reduced the death response of cells treated with UDCA and MEK1/2 inhibitor to that observed for DCA and MEK1/2 inhibitor. The apoptotic response was FAS receptor- and neutral sphingomyelinase-dependent and independent of FAS ligand expression, and neither chelation of intracellular and extracellular Ca(2+) nor down-regulation of PKC expression altered the apoptotic effects of bile acids. In conclusion, bile acid apoptosis is dependent on the production of ceramide and is counteracted by activation of the MAPK and PI3K pathways.

Linear mixed irreversible inhibition of the autocatalytic activation of zymogens. Kinetic analysis checked by simulated progress curves

Autocatalytic zymogen activation is a phenomenon of great importance for understanding some fundamental physiological processes involved in the enzyme regulation of gastrointestinal-tract enzymes, blood coagulation, fibrinolysis and the complement system. Examples of such processes are the activation of prekallikrein, trypsinogen and pepsinogen, all of which are controlled by natural proteinase inhibitors. This work studies the kinetics of a general autocatalytic zymogen activation process overlapped by two two-step irreversible inhibitions, i.e. a linear mixed irreversible inhibition. The kinetic equations for the whole course of the reaction are derived for this mechanism. In addition, we determine the corresponding kinetics for a number of particular cases of the general model analyzed, i.e. for reversible and irreversible non-competitive, competitive and uncompetitive inhibition systems which are considered particular cases of the general mechanism studied. The kinetic behavior of the system is related to a parameter, a dimensionless quantity, which shows whether the inhibition or the activation route prevails, in a similar way to that which we have previously carried out for other mechanisms. Finally, based on the kinetic equations obtained, a procedure for discriminating between the different mechanisms considered is suggested. The results of this contribution can be directly applied to most physiological autocatalytic zymogen activations in the presence of an inhibitor, allowing their complete kinetic characterization and suggesting procedures for varying the relative weight of the catalytic and inhibition routes or for changing the predominant route.

Apoptotic pathway activation from mitochondria and death receptors without caspase-3 cleavage in failing human myocardium: fragile balance of myocyte survival?

OBJECTIVES

Activation of the caspase cascade through the mitochondrial and/or death receptor pathway was investigated in the failing human myocardium, in which the mode and extent of the cascade activation are unknown.

BACKGROUND

In terminal heart failure, a loss of cardiomyocytes by overload-induced apoptosis is an attractive mechanism, explaining the progressive character of the disease. However, its relevance is unclear, because the specificity of probes for apoptotic deoxyribonucleic acid damage is under debate.

METHODS

Left ventricular specimens from 36 explanted failing and 21 nonfailing donor hearts were used for messenger ribonucleic acid detection by semiquantitative reverse-transcription polymerase chain reaction. From these groups, immunoblot analysis was performed in samples from nine failing and six nonfailing donor hearts.

RESULTS

In terminally failing hearts, there was a significant accumulation of cytochrome c in the cytosol, which was associated with activation of caspase-9 and downregulation of its inhibitor, caspase-9S. Similarly, the death receptor-induced pathway revealed activation of caspase-8, combined with downregulation of its inhibitors, flice-like inhibitory protein-L (FLIP(L)) and FLIP(S). The unspecific caspase inhibitors, XIAP, hIAP-1 and hIAP-2, were also downregulated. However, the terminal effector caspase-3 was not activated, and its substrate gelsolin, acting in its uncleaved form as a feedback inhibitor of caspase-3, was not cleaved.

CONCLUSIONS

In the terminally failing human myocardium, the caspase cascade is partially activated in the presence of a consistent phenotype shift toward enhanced susceptibility to apoptosis. Although the system is still under a fragile control, the partial initiation of the apoptotic program may be of functional relevance also for the surviving cardiomyocytes.

Curcumin induces apoptosis in human melanoma cells through a Fas receptor/caspase-8 pathway independent of p53

In this study, we investigated the molecular pathways targeted by curcumin during apoptosis of human melanoma cell lines. We found that curcumin caused cell death in eight melanoma cell lines, four with wild-type and four with mutant p53. We demonstrate that curcumin-induced apoptosis is both dose- and time-dependent. We found that curcumin did not induce p53, suggesting that curcumin activates other apoptosis pathways. Our data show that curcumin activates caspases-3 and -8 but not caspase-9, supporting the rationale that apoptosis occurs via a membrane-mediated mechanism. Both a caspase-8 and broad-based caspase inhibitor, but not a caspase-9 specific inhibitor, suppressed curcumin-induced cell death. To further support our hypothesis that curcumin induces activation of a death receptor pathway, we show that curcumin induces Fas receptor aggregation in a FasL-independent manner and that low-temperature incubation, previously shown to inhibit receptor aggregation, prevented curcumin-induced cell death. Moreover, we demonstrate that expression of dominant negative FADD significantly inhibited curcumin-induced cell death. In addition, our results indicate that curcumin also blocks the NF-kappaB cell survival pathway and suppresses the apoptotic inhibitor, XIAP. Since melanoma cells with mutant p53 are strongly resistant to conventional chemotherapy, curcumin may overcome the chemoresistance of these cells and provide potential new avenues for treatment.

Dimeric procaspase-3 unfolds via a four-state equilibrium process

We have examined the folding and assembly of a catalytically inactive mutant of procaspase-3, a homodimeric protein that belongs to the caspase family of proteases. The caspase family, and especially caspase-3, is integral to apoptosis. The equilibrium unfolding data demonstrate a plateau between 3 and 5 M urea, consistent with an apparent three-state unfolding process. However, the midpoint of the second transition as well as the amplitude of the plateau are dependent on the protein concentration. Overall, the data are well described by a four-state equilibrium model in which the native dimer undergoes an isomeration to a dimeric intermediate, and the dimeric intermediate dissociates to a monomeric intermediate, which then unfolds. By fitting the four-state model to the experimental data, we have determined the free energy change for the first step of unfolding to be 8.3 +/- 1.3 kcal/mol. The free energy change for the dissociation of the dimeric folding intermediate to two monomeric intermediates is 10.5 +/- 1 kcal/mol. The third step in the unfolding mechanism represents the complete unfolding of the monomeric intermediate, with a free energy change of 7.0 +/- 0.5 kcal/mol. These results show two important points. First, dimerization of procaspase-3 occurs as a result of the association of two monomeric folding intermediates, demonstrating that procaspase-3 dimerization is a folding event. Second, the stability of the dimer contributes significantly to the conformational free energy of the protein (18.8 of 25.8 kcal/mol).

Piceatannol is an effective inhibitor of IgE-mediated secretion from human basophils but is neither selective for this receptor nor acts on syk kinase at concentrations where mediator release inhibition occurs

BACKGROUND

Syk kinase is probably an early necessary tyrosine kinase involved in IgE-mediated secretion from human basophils. Causal testing of the role of syk kinase in the secretion requires a selective pharmacological agent. Piceatannol has previously been used to demonstrate the causal role of syk in secretion but its selectively has recently come into question.

OBJECTIVE

To determine whether piceatannol inhibits IgE-mediated signalling events in a manner consistent with its putative inhibitory effects on syk kinase and at concentrations relevant to its inhibition of mediator release.

METHODS

Human basophils were examined for the effects of piceatannol on mediator release or various signalling steps.

RESULTS

We show that while piceatannol has an IC50 for inhibition of IgE-mediated histamine release of 3-5 microm, these same concentrations inhibit secretion of phorbol 12-myristate 13-acetate (PMA)-induced histamine release (as previously shown) and leukotriene C (LTC)4 release induced by fMLP. Concentrations of piceatannol up to 100 microm also did not inhibit IgE-mediated phosphorylation of shc, a immediate downstream target of syk kinase. Similar concentrations also did not inhibit IgE-mediated cytosolic calcium elevations, another downstream signal thought to be dependent on syk kinase. In contrast, piceatannol did modify the cytosolic calcium response that follows stimulation with formyl methionyl-leucyl-phenylalanine (fMLP).

CONCLUSION

Taken together with published studies using other cell types, we conclude that piceatannol does not inhibit secretion from human basophils by inhibiting the activity of syk kinase.

Expression and regulation of MMP-20 in human tongue carcinoma cells

Human matrix metalloproteinase-20 (MMP-20, enamelysin) fragments the enamel-specific protein amelogenin and has been shown to be synthesized exclusively by odontoblasts and ameloblasts and in certain odontogenic tumors. Here we demonstrate, for the first time, the expression of MMP-20 mRNA and protein in two carcinoma cell lines originating from the tongue. Treatment of the SCC-25 and HSC-3 cells with phorbol 12-myristate 13-acetate (10 nmol/L) up-regulated MMP-20 mRNA and protein expression by up to 1.6-fold, but transforming growth factor beta (10 ng/mL) had no effect. The latent proform of recombinant (r) human MMP-20 was converted by tumor-related trypsin-2. Activated rMMP-20 did not degrade type I or type II collagen, but efficiently hydrolyzed fibronectin, type IV collagen, laminin-1 and -5, tenascin-C, and beta-casein. This implies that MMP-20 not only participates in dental matrix remodeling but is also present in tongue carcinoma cells.

Activation of progelatinase A by mammalian legumain, a recently discovered cysteine proteinase

The activation of progelatinase A to gelatinase A requires cleavage of an asparaginyl bond to form the N-terminus of the mature enzyme. We have asked whether the activation can be mediated by legumain, the recently discovered lysosomal cysteine proteinase that is specific for hydrolysis of asparaginyl bonds. Addition of purified legumain to the concentrated conditioned medium from HT1080 cell culture that contained both progelatinases A and B caused the conversion of the 72 kDa progelatinase A to the 62 kDa form. The progelatinase B in the medium was unaffected. Incubation of recombinant progelatinase A with legumain resulted in an almost instantaneous activation as judged by the fluorometric assay with a specific gelatinase A substrate, Mca-Pro-Leu-Gly-Leu-Dpa-Ala-Arg-NH2. Legumain also activated progelatinase A when it was in complex with TIMP-2. Zymographic analysis and N-terminal sequencing revealed that legumain cleaved the 72 kDa progelatinase A at the bonds between Asn109-Tyr110 or Asn111-Phe112 to produce the 62 kDa mature enzyme, and that further cleavage at Asn430 also occurred to generate a 36 kDa active form. More 62 kDa gelatinase A was detected in cultures of C13 cells that over-expressed legumain than in those of the control HEK293 cells. We conclude that legumain is clearly capable of processing progelatinase A to the active enzyme in vitro and in cultured cells.

Requirement of tyrosine-phosphorylated Vav for morphological differentiation of all-trans-retinoic acid-treated HL-60 cells

Our previous data demonstrated that cellular and nuclear tyrosine-phosphorylated Vav associate with phosphoinositide 3-kinase during all-trans-retinoic acid-dependent granulocytic differentiation of HL-60 cells. In this study, aimed to analyze the mechanism by which Vav is recruited and activated, we report that the Src homology 2 domain of Vav interacts with tyrosine-phosphorylated proteins in a differentiation-dependent manner. Two adaptor proteins, Cbl and SLP-76, were identified, showing a discrete distribution inside the cells, with Cbl absent from the nuclei and SLP-76 particularly abundant in the nuclear compartment. Of note, Vav interacts with the tyrosine kinase Syk, which is also present in the nuclear compartment and may phosphorylate Vav in vitro when cells differentiate. Inhibition of Syk activity by piceatannol prevents both in vitro and in vivo Vav tyrosine phosphorylation, its association with the regulatory subunit of phosphoinositide 3-kinase, and the nuclear modifications typically observed during granulocytic differentiation of this cell line. These findings suggest that tyrosine-phosphorylated Vav and its association with phosphoinositide 3-kinase play a crucial role in all-trans-retinoic acid-induced reorganization of the nucleoskeleton, which is responsible for the changes in nuclear morphology observed during granulocytic differentiation of HL-60 cells.

Mutations of the C-terminal end of cathepsin K affect proenzyme secretion and intracellular maturation

Transfection of the human cathepsin K cDNA into CHO cells results in the expression of mature catalytically active 27-kDa protein and in cells secreting the 39-kDa proenzyme form. Monensin, which neutralizes the pH of acidic organelles, was found to inhibit intracellular processing of the proenzyme and to stimulate its secretion into the culture medium. Brefeldin A caused alterations in immunofluorescence staining consistent with interference of lysosomal targeting and inhibited both intracellular processing and secretion of cathepsin K. Inhibition of glycosylation by tunicamycin also abolished cathepsin K maturation. Furthermore, the processing of the proenzyme to the mature form was abolished by a single mutation of the terminal Met(329) to Ala. The triple mutation of Ser(325), Pro(327), and Met(329) (all to Ala) inhibited both maturation and secretion, using either transient or stable expression systems. The results indicate that intracellular maturation and secretion of cathepsin K can be affected differentially by various treatments and by mutations of the C-terminal end of the protein. These results are consistent with the involvement of both the secreted proenzyme and the intracellularly processed enzyme in cathepsin K-mediated processes.