Response of a calcium sulfate bone graft substitute in a confined cancellous defect

Calcium sulfate, plaster of Paris, has a long clinical history for use as a bone graft substitute in various skeletal sites. The current authors examined the in vivo response of calcium sulfate pellets alone or in combination with autogenous bone graft in a bilateral critical-size distal femoral cancellous defect in an adult sheep model. New thick bone formation was seen in defects filled with calcium sulfate pellets alone. Increased immunostaining for bone morphogenetic protein-2, bone morphogenetic protein-7, transforming growth factor-beta, and platelet derived growth factor was seen in defects filled with calcium sulfate pellets alone and in combination with autograft. The local acidity during calcium sulfate resorption is proposed as a possible in vivo mechanism for this type of material.

Alteration of cadmium-induced mutational spectrum by catalase depletion in Chinese hamster ovary-K1 cells

Previously, we have demonstrated that cadmium acetate significantly induces hprt mutation frequency in Chinese hamster ovary (CHO)-K1 and that 3-amino-1,2,4-triazole (3AT), a catalase inhibitor, potentiates the mutagenicity of cadmium [Chem. Res. Toxicol. 9 (1996) 1360-1367]. In this study, we investigate the role of intracellular peroxide in the molecular nature of mutations induced by cadmium. Using 2',7'-dichlorofluorescin diacetate and fluorescence spectrophotometry, we have shown that cadmium dose-dependently increased the amounts of intracellular peroxide and the levels were significantly enhanced by 3AT. Furthermore, we have characterized and compared the hprt mutation spectra in 6-thioguanine-resistant mutants derived from CHO-K1 cells exposed to 4 microM of cadmium acetate for 4h in the absence and presence of 3AT. The mutation frequency induced by cadmium and cadmium plus 3AT was 11- and 16-fold higher than that observed in untreated populations (2.2 x 10(-6)), respectively. A total of 40 and 51 independent hprt mutants were isolated from cadmium and cadmium plus 3AT treatments for mRNA-polymerase chain reaction (PCR), genomic DNA-PCR and DNA sequencing analyses. 3AT co-administration significantly enhanced the frequency of deletions induced by cadmium. Cadmium induced more transversions than transitions. In contrast, 3AT co-administration increased the frequency of GC-->AT transitions and decreased the frequencies of TA-->AT and TA-->GC transversions. Together, the results suggest that intracellular catalase is important to prevent the formation of oxidative DNA damage as well as deletions and GC-->AT transitions upon cadmium exposure.

Opposite roles of ERK and p38 mitogen-activated protein kinases in cadmium-induced genotoxicity and mitotic arrest

The roles of extracellular signal-regulated kinase (ERK) and p38 mitogen-activation protein kinase (MAPK) in guarding genome stability and regulating cell cycle progression were explored in CL3 human lung adenocarcinoma cells treated with cadmium (Cd), a human carcinogen. Exposing asynchronous cells to CdCl(2) for 2 h (45% viability) caused irreversible mitotic arrest. Exposing early-G(2) cells to Cd markedly delayed mitotic exit and subsequently induced sub-G(1) populations; however, this did not alter the levels of Cdc2 and cyclin B1. These results suggest that Cd elicits mitotic arrest without affecting the progression of G(2) to mitosis. Using counterflow centrifugal elutriation and flow cytometry analysis, CL3 cells synchronized at G(1)-, S-, and G(2)/M-phases were collected and treated with CdCl(2). G(2)/M was the most sensitive cell cycle phase to Cd for the induction of ERK and p38 MAPK activities, cytotoxicity, apoptosis, micronucleus, and intracellular peroxide; despite that similar Cd accumulation was observed in G(1)-, S-, and G(2)/M-cells. Co-treatment early-G(2) cells with Cd and SB202190, an inhibitor of p38 MAPK, significantly decreased the induction of micronucleus, mitotic arrest, and apoptosis. Conversely, PD98059, an inhibitor of the ERK upstream activators MKK1/2, enhanced micronucleus and apoptosis in Cd-treated early-G(2) cells. Together, the results suggest that intracellular peroxide may participate in the activation of ERK and p38 MAPK by Cd; also, the activated-p38 MAPK may contribute to mitotic arrest and genome instability, whereas the activated-ERK may help to maintain genome integrity and survival.

Genetic markers of survival and liver recurrence after resection of liver metastases from colorectal cancer

A significant number of patients with liver metastases from colorectal cancer (CRC) achieve 5-year survival after liver resection. Increased expression of genetic markers in the primary tumor are known to predict outcome after colonic resection, but the predictive value of such markers after resection of hepatic metastases is unknown. The objective of this study was to evaluate whether DNA content and multiple genetic markers, separately or expressed together, can predict patient outcome (liver recurrence and survival) after resection of hepatic metastases. We studied the paraffin-embedded liver tissue of 71 consecutive patients who had undergone a potentially curative resection of hepatic metastases from CRC. Using DNA flow cytometry and immunohistochemical staining techniques we determined the DNA content and the level of co-expression of seven tumor-associated proteins: proliferating cellular nuclear antigen (PCNA), epidermal growth factor receptor (EGFr), p53, c-erbB-2, H-ras, c-myc, and nm23. Three endpoints (liver recurrence, cancer specific, overall survival) were correlated with these tumor markers. The 5-year overall survival of the group was 31.2%. There was no correlation detected between the DNA aneuploidy and overall or cancer-specific survival. Similarly, expression of the individual tumor-associated proteins did not predict survival. Patients whose tumors co-expressed multiple markers had survivals similar to those whose tumors expressed fewer markers. However, a significant difference in hepatic recurrence was found between the p53-positive and p53-negative patients (p = 0.007), with marker-negative tumors having decreased recurrence. In conclusion, this study demonstrates that the DNA content and genetic markers c-myc, c-erbB-2, EGFr, H-ras, p53, PCNA, and nm23 do not predict survival after potentially curative resection of hepatic metastases from CRC. However, the immunoreactivity of p53 may be an important marker of local recurrence in the liver, which may be useful if re-resection of metastatic liver tumors is considered a viable management option in this disease.

Effect of nifedipine in metastatic colon cancer with DNA mismatch repair gene defect

Cancer cells that have DNA mismatch repair deficiency are resistant to many cytotoxic drugs. Calcium channel blockers may inhibit the pathways that cause such resistance. We report a patient with hereditary non-polyposis coli and metastatic colon cancer who had a complete response after treatment with a high dose of nifedipine, a calcium channel blocker. Our findings suggest that drugs that interfere with signal transduction could have a clinical role and deserve further study in selected patients.

Comparison of roles of three mitogen-activated protein kinases induced by chromium(VI) and cadmium in non-small-cell lung carcinoma cells

Chromium(VI) [Cr(VI)] and cadmium (Cd) compounds are ubiquitous environmental carcinogens that have been associated with lung tumors and can induce apoptosis in various cell types. Three major mitogen-activation protein kinases (MAPKs), extracellular signal-regulated kinase (ERK), c-JUN N-terminal kinase (JNK) and p38, have been shown to regulate apoptosis. In this study we explore the abilities of Cr(VI) and Cd to activate JNK, p38 and ERK, including their roles in metal-mediated growth inhibition and apoptosis in a human non-small-cell lung carcinoma cell line, CL3. Exposure to K2Cr2O7 markedly activated JNK and p38 and moderately activated ERK in a dose- and time-dependent manner. The activated p38 decreased markedly and rapidly and the activated JNK decreased gradually when Cr(VI) was removed from media. At low cytotoxic doses, CdCl2 decreased ERK activity with concurrently transient activation of JNK, whereas at high cytotoxic doses it persistently activated all three MAPKs. The strength and duration of JNK and p38 activated by Cd were higher and longer than Cr(VI) did when compared at similar cytotoxic doses. In comparable experiment conditions Cd is a much stronger apoptotic inducer than Cr(VI) in CL3 cells. Cross-talk of MAPKs was observed in cells exposed to Cr(VI) but not Cd. Both metals could increase JNK activity through MKK7 but not MKK4. The Cd-activated JNK is involved in apoptosis, but the Cr-activated JNK is not. PD98059, an inhibitor of the ERK upstream activators MKK1/2, greatly enhanced the cytotoxicity and apoptosis of cells treated with low Cd doses. SB202190, an inhibitor of p38, decreased the cytotoxicity and apoptosis induced by high Cd doses. Conversely, neither SB202190 nor PD98059 altered Cr(VI)-induced cytotoxicity. The results suggest that JNK and p38 signals cooperatively participate in apoptosis induced by Cd and that the decreased ERK signal by low Cd doses contributes to growth inhibition or apoptosis. Oppositely, activation of ERK, JNK and p38 by Cr(VI) does not affect cytotoxicity.

Tandem ligation of unprotected peptides through thiaprolyl and cysteinyl bonds in water

Tandem ligation for the synthesis and modification of proteins entails forming two or more regiospecific amide bonds of multiple free peptide segments without a protecting-group scheme. We here describe a semi-orthogonal strategy for ligating three unprotected peptide segments, two of which contain N-terminal (NT) cysteine, to form in tandem two amide bonds, an Xaa-SPro (thiaproline), and then an Xaa-Cys. This strategy exploits the strong preference of an NT-cysteinyl peptide under acidic conditions to undergo selectively an SPro-imine ligation rather than a Cys-thioester ligation. Operationally, it was performed in the N --> C direction, first by an imine ligation at pH < 3 to afford an Xaa-thiazolidine ester bond between a peptide containing a carboxyl terminal (CT)-glycoaldehyde ester and a second peptide containing both an NT-Cys and a CT-thioester. The newly created O-ester-linked segment with a CT-thioester was then ligated to another NT-cysteinyl peptide through thioester ligation at pH > 7 to form an Xaa-Cys bond. Concurrently, this basic condition also catalyzed the O,N-acyl migration of an Xaa-thiazolidine ester to the Xaa-SPro bond at the first ligation site to complete the tandem three-segment ligation. Both ligation reactions were performed in aqueous buffered solvents. The effectiveness of this three-segment ligation strategy was tested in six peptides ranging from 19 to 70 amino acids, including thiaproline --> proline analogues of somatostatins and two CC-chemokines. The thiaproline replacements in these peptides and proteins did not result in altered biological activity. By eliminating the protecting-group scheme and coupling reagents, tandem ligation of multiple free peptide segments in aqueous solutions enhances the scope of protein synthesis and may provide a useful approach for combinatorial segment synthesis.

Benzo[g,h,i]perylene synergistically transactivates benzo[a]pyrene-induced CYP1A1 gene expression by aryl hydrocarbon receptor pathway

Although benzo[g,h,i]perylene (BghiP) has been found to promote the carcinogenesis of benzo[a]pyrene (BaP) in animal models, not much is known about this cocarcinogenic mechanism. In this study, human hepatoma HepG2 cells cotreated with BaP and BghiP were used as a model to investigate the cocarcinogenic mechanism of BghiP in BaP-induced carcinogenesis. DNA adduct formation is thought to initiate carcinogenesis, so the effect of BghiP on BaP-DNA adduct formation was evaluated using a (32)P-postlabeling assay. The BaP-DNA adduct levels increased following the addition of BghiP, in a dose-dependent manner. However, no adducts were formed with BghiP alone. Our previous report showed that cytochrome P450 1A1 (CYP1A1) is responsible for the metabolic activation of BaP and the formation of B[a]P adduct in HepG2 cells. Western blot and Northern blot analyses were used to evaluate whether BaP-induced CYP1A1 protein and mRNA levels increased following the addition of BghiP. Our data showed that BghiP enhanced BaP-induced CYP1A1 protein and its mRNA levels. To understand whether BghiP enhances BaP-induced CYP1A1 gene expression through the aryl hydrocarbon receptor (AhR) signaling pathway, a gel retardation assay was performed to elucidate the synergistic mechanism of BghiP in BaP-induced CYP1A1 gene expression. The results showed that BghiP causes an increase in the nuclear accumulation of AhR in cells and/or activation of AhR to a DNA-binding form. There was a concordant increase in the transcription activation of CYP1A1 gene and the induction of AhR signal pathway. Our findings demonstrated that BghiP enhances BaP-induced CYP1A1 transcription by AhR activation and suggested that the induction mechanism of CYP1A1 contributes to the cocarcinogenic potential of BghiP in BaP-induced carcinogenesis.

Oxidative stress before and after operation in patients with chronic cholecystitis containing gallstone

To study the relationship of oxidative, antioxidative constituents and antioxidases in blood with chronic cholecystitis containing gallstone, levels of lipoperoxides (LPO), nitric oxide (NO), vitamin C(VC), vitamin E (VE) and beta-carotene (beta-CAR) in plasma as well as level of LPO, activities of superoxide dismulase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in erythrocytes were investigated by spectrophotometric assay in 107 patients with this condition (PCg) and 100 healthy volunteers (HVs). Compared with HVs group, the average value of LPO and NO in plasma and that of LPO in erythrocytes of PCg group were significantly increased (P < 0.0001), while that of VC, VE and beta-CAR in plasma and the average activities of SOD, CAT and GSH-Px in erythrocytes were significantly decreased (P < 0.0001). Linear regression and correlation analysis for 107 preoperative PCg showed that the value of LPO and NO in plasma and that of LPO in erythrocytes of PCg gradually increased (P < 0.0001), representing a significant linear positive correlation. The value of VC, VE and beta-CAR in plasma and that of SOD, CAT and GSH-Px in erythrocytes of PCg gradually decreased (P < 0.0001), representing a significant linear negative correlation. Stepwise regression and correlation analysis for 107 preoperative PCg suggested that the closest correlation was observed between the course of disease and the value of NO and VC in plasma and that of SOD, GSH-Px and LPO in erythrocytes, r = 0.7306, F = 32.1408, P < 0.0001. Compared with the preoperative PCg group, the average value of LPO and NO in plasma and that of LPO in erythrocytes of the postoperative PCg group were significantly decreased (P < 0.0001). Furthermore, the average value of VC in plasma and that of SOD, CAT and GSH-Px in erythrocytes of the postoperative PCg group were significantly increased (P < 0.0001), whereas no significant difference was found between their average value of VE and beta-CAR in plasma. These findings suggested that oxidative stress was an aggravating pathological condition in PCg group. Therefore, we recommend that in treating PCg, antioxidants such as VC, VE, beta-CAR should be given in order to alleviate their potential oxidative damages.

Urokinase-type plasminogen activator and its receptor in colorectal cancer: independent prognostic factors of metastasis and cancer-specific survival and potential therapeutic targets

Urokinase-type plasminogen activator (uPA) and its receptor (uPAR), plasminogen (Plg), and plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) have been observed in many cancers and may contribute to progression and metastasis. In our study, we examined the expression of the 5 proteins by immunohistochemistry in 59 consecutive primary colorectal cancers (CRC) and correlated the protein expression with patient outcome. In addition, we determined the effect of down-regulation of uPAR on the invasive/metastatic capability of CRC cells, by measuring antisense-uPAR transfected HCT116 and control cell lines, in terms of uPAR expression, uPA-binding activity, invasiveness through Matrigel in vitro and metastasis after cecal orthotopic implantation in nude mice in vivo. We found that higher expression of uPA or uPAR in primary tumor tissues was positively correlated with distant metastasis of CRC (Mann-Whitney, p < 0.02) and negatively correlated with both patient overall survival (OS) and cancer-specific survival (CSS; Cox model, p < 0.04). The prognostic value of uPA and uPAR for both OS and CSS was independent of other variables (multivariate Cox model, p < 0. 007). Antisense-uPAR transfected HCT116 cells, which expressed significantly lower levels of total cellular and cell surface uPAR proteins and uPA-binding activity compared with either wild-type or cells transfected with vector alone (Bonferroni, p < 0.05/3), consistently showed decreased invasiveness through Matrigel (Bonferroni, p < 0.05/3) and decreased metastasis formation in nude mice (Fisher, p < 0.05). Our data suggest that uPAR and uPA are independent prognostic factors in CRC; anti-uPAR treatment, which affects both uPAR and uPA levels, may have potential for new treatment of the disease.

Brain expression of presenilins in sporadic and early-onset, familial Alzheimer's disease

BACKGROUND

Mutations in the presenilin proteins cause early-onset, familial Alzheimer's disease (FAD).

MATERIALS AND METHODS

We characterized the cellular localization and endoproteolysis of presenilin 2 (PS2) and presenilin 1 (PS1) in brains from 25 individuals with presenilin-mutations causing FAD, as well as neurologically normal individuals and individuals with sporadic Alzheimer's disease (AD).

RESULTS

Amino-terminal antibodies to both presenilins predominantly decorated large neurons. Regional differences between the broad distributions of the two presenilins were greatest in the cerebellum, where most Purkinje cells showed high levels of only PS2 immunoreactivity. PS2 endoproteolysis in brain yielded multiple amino-terminal fragments similar in size to the PS1 amino-terminal fragments detected in brain. In addition, two different PS2 amino-terminal antibodies also detected a prominent 42 kDa band that may represent a novel PS2 form in human brain. Similar to PS1 findings, neither amino-terminal nor antiloop PS2 antibodies revealed substantial full-length PS2 in brain. Immunocytochemical examination of brains from individuals with the N141I PS2 mutation or eight different PS1 mutations, spanning the molecule from the second transmembrane domain to the large cytoplasmic loop domain, revealed immunodecoration of no senile plaques and only neurofibrillary tangles in the M139I PS1 mutation stained with PS1 antibodies.

CONCLUSIONS

Overall presenilin expression and the relative abundance of full-length and amino-terminal fragments in presenilin FAD cases were similar to control cases and sporadic AD cases. Thus, accumulation of full-length protein or other gross mismetabolism of neither PS2 nor PS1 is a consequence of the FAD mutations examined.

Urokinase-type plasminogen activator and its receptor in colorectal cancer: independent prognostic factors of metastasis and cancer-specific survival and potential therapeutic targets

Urokinase-type plasminogen activator (uPA) and its receptor (uPAR), plasminogen (Plg), and plasminogen activator inhibitors-1 and -2 (PAI-1 and PAI-2) have been observed in many cancers and may contribute to progression and metastasis. In our study, we examined the expression of the 5 proteins by immunohistochemistry in 59 consecutive primary colorectal cancers (CRC) and correlated the protein expression with patient outcome. In addition, we determined the effect of down-regulation of uPAR on the invasive/metastatic capability of CRC cells, by measuring antisense-uPAR transfected HCT116 and control cell lines, in terms of uPAR expression, uPA-binding activity, invasiveness through Matrigel in vitro and metastasis after cecal orthotopic implantation in nude mice in vivo. We found that higher expression of uPA or uPAR in primary tumor tissues was positively correlated with distant metastasis of CRC (Mann-Whitney, p < 0.02) and negatively correlated with both patient overall survival (OS) and cancer-specific survival (CSS; Cox model, p < 0.04). The prognostic value of uPA and uPAR for both OS and CSS was independent of other variables (multivariate Cox model, p < 0. 007). Antisense-uPAR transfected HCT116 cells, which expressed significantly lower levels of total cellular and cell surface uPAR proteins and uPA-binding activity compared with either wild-type or cells transfected with vector alone (Bonferroni, p < 0.05/3), consistently showed decreased invasiveness through Matrigel (Bonferroni, p < 0.05/3) and decreased metastasis formation in nude mice (Fisher, p < 0.05). Our data suggest that uPAR and uPA are independent prognostic factors in CRC; anti-uPAR treatment, which affects both uPAR and uPA levels, may have potential for new treatment of the disease.

Activation of JNK, p38 and ERK mitogen-activated protein kinases by chromium(VI) is mediated through oxidative stress but does not affect cytotoxicity

In this study we have explored the involvement of oxidative stress in Cr(VI)-induced JNK, p38 and ERK signaling pathways and their effects on Cr(VI) cytotoxicity in human non-small cell lung carcinoma CL3 cells. Exposure to K(2)Cr(2)O(7) markedly activated JNK and p38 and moderately activated ERK in a dose- (10-80 microM) and time-dependent (1-12 h) manner. The activated p38 decreased markedly and rapidly and the activated JNK decreased gradually when Cr(VI) was removed from the medium. Post-incubation of Cr(VI)-treated cells with H(2)O(2) increased the activities of JNK and p38, but not ERK. Co-administering Cr(VI) with 3-amino-1,2, 4-triazole (3AT), a catalase inhibitor, enhanced p38 activation, but did not influence JNK and ERK activation by Cr(VI). Conversely, co-administering Cr(VI) with mannitol, a hydroxyl radical scavenger and a Cr(V) chelator, reduced p38 activation and increased JNK and ERK activation by Cr(VI). These results indicate that p38 activation by Cr(VI) is positively correlated with oxidative stress, while JNK activity can be enhanced by either a quencher (mannitol) or activator (H(2)O(2)) of redox reactions in Cr(VI)-exposed CL3 cells. However, both 3AT and mannitol reduced the cytotoxicity of Cr(VI), but H(2)O(2) did not. The JNK activated by Cr(VI) was decreased (approximately 50%) by expression of a kinase-defective form of MKK7 (MKK7A) but not that of MKK4 (MKK4KR), suggesting that activation of JNK by Cr(VI) is mediated through MKK7. SB202190, a specific inhibitor of p38, markedly decreased JNK but did not change ERK activation by Cr(VI). PD98059, a specific inhibitor of ERK kinases MKK1/2, blocked ERK and p38 but did not alter JNK activation by Cr(VI). Neither the specific kinase inhibitors nor expression of MKK7A altered Cr(VI)-induced cytotoxicity. Together, these results suggest that activation of the JNK, p38 and ERK pathways by Cr(VI) is mediated through diverse redox mechanisms, yet their activation does not correlate with Cr(VI) cytotoxicity.

Roles of JNK, p38 and ERK mitogen-activated protein kinases in the growth inhibition and apoptosis induced by cadmium

Cadmium (Cd), a human carcinogen, can induce apoptosis in various cell types. Three major mitogen-activated protein kinases (MAPKs), c-JUN N-terminal kinase (JNK), p38 and extracellular signal-regulated kinase (ERK), have been shown to regulate apoptosis. In this study we explore the ability of Cd to activate JNK, p38 and ERK, including their effects on Cd-mediated growth inhibition and apoptosis in a human non-small cell lung carcinoma cell line, CL3. The kinase activity of JNK was induced dose-dependently by 30-160 microM CdCl(2). High cytotoxic doses of Cd (130-160 microM) markedly activated p38, but low Cd doses did not. Conversely, the activities of ERK1 and ERK2 were decreased by low cytotoxic doses of Cd (</=80 microM) and moderately activated by high Cd doses. Low cytotoxic doses of Cd transiently activated JNK and simultaneously reduced ERK activity, whereas high cytotoxic doses of Cd persistently activated JNK and p38. PD98059, an inhibitor of ERK upstream activators MAPK kinase (MKK) 1 and MKK2, greatly enhanced cytotoxicity and apoptosis in cells treated with low Cd doses. In contrast, SB202190, an inhibitor of p38, decreased the cytotoxicity and apoptosis induced by high Cd doses. Transient expression of a dominant negative form of JNK1, but not that of JNK2, significantly increased the viability and prevented apoptosis of Cd-treated cells. However, expression of wild-type JNK1 did not affect viability and apoptosis of Cd-treated cells. Transfection of wild-type JNK2 or p38 enhanced apoptosis of cells exposed to low Cd doses but did not affect those exposed to high Cd doses. The JNK activity stimulated by low Cd doses was partially suppressed by expression of a dominant negative form of MKK7, but not a dominant negative form of MKK4, indicating that MKK7 is involved in JNK activation by Cd. Together, the results of this study suggest that JNK and p38 cooperatively participate in apoptosis induced by Cd and that the decreased ERK signal induced by low Cd doses contributes to growth inhibition or apoptosis.

Design of salt-insensitive glycine-rich antimicrobial peptides with cyclic tricystine structures

Cyclic peptide backbone and cystine constraints were used to develop a broadly active salt-insensitive antimicrobial peptide [Gly(6)]ccTP 1a with eight Gly residues in an 18-residue sequence. The importance of rigidity and amphipathicity imparted by the cyclic and cystine constraints was examined in two peptide series based on tachyplesin, a known beta-stranded antimicrobial peptide. The first series, which retained the charge and hydrophobic amino acids of tachyplesin, but contained zero to four covalent constraints, included a cyclic tricystine tachyplesin (ccTP 1). Corresponding [Gly(6)] analogues were prepared in a parallel series with all six bulky hydrophobic amino acids in their sequences replaced with Gly. Circular dichroism measurements showed that ccTP 1 and [Gly(6)]ccTP 1a exhibited well-ordered beta-sheet structures, while the less constrained [Gly(6)] analogues were disordered. Except for linear peptides assayed under high-salt conditions, peptides with increased or decreased conformational constraints retained broad activity spectra with small variations in potency of 2-10-fold compared to that of tachyplesin. In contrast, Gly replacement analogues resulted in large variations in activity spectra and significant decreases in potency that roughly correlated with the decreases in conformational constraints. Except against Escherichia coli, the Gly-rich analogues with two or fewer covalent constraints were largely inactive under high-salt conditions. Remarkably, the most constrained [Gly(6)]ccTP 1a retained a broad activity spectrum against all 10 test microbes in both low- and high-salt assays. Collectively, our results show that [Gly(6)]ccTP 1acould serve as a template for further analogue study to improve potency and specificity through single or multiple replacements of hydrophobic or unnatural amino acids.

Membranolytic selectivity of cystine-stabilized cyclic protegrins

To correlate conformational rigidity with membranolytic selectivity of antimicrobial activity and cytotoxicity, we prepared six cyclic analogs of protegrin-1 (PG-1), an 18-residue cationic peptide with a broad-spectrum antimicrobial activity. These cyclic protegrins bear end-to-end peptide bonds together with varying numbers (zero to three) of cross-strand disulfide constraints. The most constrained analog is a cyclic tricystine protegrin (ccPG 3) containing three evenly spaced, parallel disulfide bonds. Antimicrobial assays against 10 organisms in low- and high-salt conditions showed that these cyclic protegrins were broadly active with different antimicrobial profiles against Gram-positive and Gram-negative bacteria, fungi and one tested virus, HIV-1. Compared to PG-1, the cyclic tricystine ccPG 3 displayed approximately a 10-fold decrease in hemolytic activity against human cells and 6- to 30-fold improvement of membranolytic selectivity against six of the 10 tested organisms. In contrast, [DeltaSS]cPG 8, a cyclic protegrin with no disulfide bond, and [DeltaCys6,15]cPG 5, a cyclic mimic of PG-1 with one disulfide bond, exhibited activity spectra, potency, and cytotoxicity similar to PG-1. Circular dichroism showed that cyclic protegrins containing with one to three cystine bonds displayed some degree of beta-strand structures in water/trifluoroethanol or phosphate-buffered solutions. Collectively, our results indicate that cyclic structures are useful in the design of antimicrobial peptides and that an increase in the conformational rigidity of protegrins may confer membranolytic selectivity that dissociates antimicrobial activity from hemolytic activity.

Evidence for post-transcriptional down-regulation of the apoptosis-related gene bcl-2 in human colorectal cancer

This retrospective study was undertaken to investigate the expression of bcl-2 protein and messenger RNA in colorectal cancer (CRC). Immunohistochemical analysis using a monoclonal mouse antibody to the bcl-2 protein and in situ hybridization using a digoxigenin-labelled bcl-2 cRNA probe were carried out on formalin-fixed and paraffin-embedded specimens from 53 colorectal adenocarcinomas, 27 liver secondaries, and 60 adenomas with various degrees of dysplasia. Normal human tonsil sections were used as positive controls. Expression of bcl-2 protein and of messenger RNA was evaluated semiquantitatively. The expression of bcl-2 protein was gradually and significantly lost during the progression from moderately dysplastic adenoma to primary CRC (moderate/severe dysplasia: Mann-Whitney U-test, p=0.0001; severe dysplasia/primary CRC: p=0.027), whereas the cellular expression of bcl-2 mRNA was gradually increased during the dysplasia/adenoma-carcinoma neoplastic sequence. These observations suggest that in a proportion of colorectal cancer cases, the bcl-2 proto-oncogene expression may be down-regulated at a post-transcriptional level.

[Studies on kinetics of somatic embryo suspension culture in Picea meyeri Rehd. et Wils]

Embryogenic calli were produced from mature zygotic embryos of Picea meyeri Rehd. et Wils. which were cultured on modified LP medium containing 30 g/L sucrose, 2 mg/L 2,4-D and 1 mg/L 6-BA. The growth rate of embryogenic calli could be improved by way of suspension culture in medium MS containing 20 g/L sucrose, 1 mg/L 2,4-D and 1 mg/L KT. The optimum values of initial cell density and shake rate of flask in suspension culture were 3.0% (fresh weight) and 150 r/min respectively. Several parameters which might be correlated with growth were determined over a 10 day period. Maximum growth in terms of fresh weight, dry weight and number of ESM occurred during 6-10 day. pH and conductivity attained the lowest point during 6-8 day. A lot of somatic embryos were obtained following transfer of the suspension cultures to medium MS containing 5 mg/L ABA. Mature somatic embryos grew into plantlets with well developed cotyledons after being cultured on 1/2 MS medium supplemented with 0.5% activated charcoal but without hormone.

Marked increase in membranolytic selectivity of novel cyclic tachyplesins constrained with an antiparallel two-beta strand cystine knot framework

We have developed a highly constrained 18-residue cyclic peptide template based on the antimicrobial peptide tachyplesin-1 that features an end-to-end peptide backbone and a cystine knot-like motif with three evenly spaced disulfide bonds to cross-brace the antiparallel beta-strands and to approximate an amphiphatic "beta-tile"-like structure. Six beta-tile analogs were prepared to correlate different topological patterns with membranolytic specificity. Their conformations and antimicrobial and hemolytic activities were compared with tachyplesin-1 and the recently discovered Rhesus monkey theta defensin (RTD) which contains similar beta-tile structural elements. The beta-tile peptides and RTD retained broad spectrum antimicrobial activities. In general, they were less active than tachyplesin-1 in 10 tested organisms but their activity increased under high-salt (100 mM NaCl) rather than in low-salt conditions. The beta-tile peptides are highly nontoxic to human erythrocytes with EC(25) ranging from 600 to 4000 microM. Collectively, our results show that the design of a highly rigid peptide template is useful for further analog study to dissociate antimicrobial activity from cytotoxicity which would be helpful in discovering clinical applications for peptide antibiotics.

Effects of mannitol or catalase on the generation of reactive oxygen species leading to DNA damage by Chromium(VI) reduction with ascorbate

Interaction of Cr(VI) and ascorbate in vitro generates Cr(V), Cr(IV), Cr(III), carbon-based alkyl radicals, COO(*)(-), (*)OH, and ascorbate radicals and induces DNA interstrand cross-links at guanines. To determine which specific Cr species and free radicals cause DNA damage, we investigated the effects of mannitol and catalase on the formation of reactive intermediates, Cr-DNA associations, DNA polymerase-stop sites, and 8-hydroxydeoxyguanosine (8-OHdG) adducts induced by Cr(VI)/ascorbate in a Hepes buffer. EPR spectra showed that mannitol trapped reactive Cr(V), forming a stable Cr(V)-diol complex, and inhibited the radicals induced by Cr(VI)/ascorbate, whereas catalase or heat-denatured catalase enhanced the levels of Cr(V) without altering the radical signals. Mannitol markedly inhibited the retarded gel electrophoretic mobility of supercoiled plasmids and the formation of DNA polymerase-stop sites induced by Cr(VI)/ascorbate, but catalase did not. On the other hand, mannitol reduced only 32% of the Cr-DNA adducts induced by Cr(VI)/ascorbate, suggesting that Cr monoadducts (possibly DNA-Cr-mannitol adducts) are the major lesions generated in the Cr(VI)/ascorbate/mannitol/DNA solution. Native catalase but not heat-denatured catalase protected approximately 25% of the Cr-DNA adducts induced by Cr(VI)/ascorbate, suggesting that hydrogen peroxide may be involved. Mannitol could not completely inhibit the formation of 8-OHdG adducts induced by Cr(VI)/ascorbate, indicating that this DNA damage may be generated before the action of mannitol to trap Cr(V) and reactive oxygen species. Alternatively, Cr-peroxide intermediates may also lead to 8-OHdG formation to account for the incomplete prevention by mannitol. Catalase or heat-denatured catalase partially protected the formation of 8-OHdG adducts induced by Cr(VI)/ascorbate, suggesting an effect of proteins. Together, the results from this study suggest that the primary species generated during the reduction of Cr(VI) by ascorbate are hydroxyl radicals and Cr(V) species, responsible for the formation of 8-OHdG and DNA cross-links, respectively.

An unusual structural motif of antimicrobial peptides containing end-to-end macrocycle and cystine-knot disulfides

Four macrocyclic cystine-knot peptides of 29-31 residues, kalata, circulin A and B (CirA and CirB), and cyclopsychotride, have been isolated from coffee plants but have undetermined physiological functions. These macrocycles and 10 of their analogs prepared by chemical synthesis were tested against nine strains of microbes. Kalata and CirA were specific for the Gram-positive Staphylococcus aureus with a minimum inhibition concentration of approximately 0.2 microM. They were relatively ineffective against Gram-negative bacteria such as Escherichia coli and Pseudomonas aeruginosa. However, CirB and cyclopsychotride were active against both Gram-positive and Gram-negative bacteria. In particular, CirB showed potent activity against E. coli with a minimum inhibitory concentration of 0.41 microM. All four cyclic peptides were moderately active against two strains of fungi, Candida kefyr and Candida tropicalis, but were inactive against Candida albicans. These macrocycles are cytotoxic and lysed human red blood cell with a lethal dose 50% of 400 microM. Modifying the Arg residue in kalata with a keto aldehyde significantly reduced its activity against S. aureus whereas blocking the arg in CirA produced no significant effect. The two-disulfide variants and their scrambled disulfide isomers exhibited antimicrobial profiles and potency similar to their native peptides. However, in high-salt assays (100 mM NaCl), few of these macrocyclic peptides, natives or analogs, retained antimicrobial activity. These results show that the macrocyclic peptides possess specific and potent antimicrobial activity that is salt-dependent and that their initial interactions with the microbial surfaces may be electrostatic, an effect commonly found in defensin antimicrobial peptides. Furthermore, their end-to-end cyclic structure with a cystine-knot motif represents a molecular structure of antimicrobials and may provide a useful template for the design of novel peptide antibiotics.

Singlet oxygen is the major species participating in the induction of DNA strand breakage and 8-hydroxydeoxyguanosine adduct by lead acetate

To investigate DNA damage induced by Pb2+ and its prevention by scavengers, we determined DNA strand breakage and the formation of 8-hydroxydeoxyguanosine (8-OHdG) in DNA using plasmid relaxation assay and HPLC with electrochemical detection, respectively. Lead acetate induced DNA strand breakage in 10 mM of Hepes buffer, pH 6.8, in a time- and dose-dependent manner. Compared with lead, zinc acetate did not significantly induce DNA breakage. The singlet oxygen scavengers NaN3 and 2,2,6,6-tetramethyl-4-piperidone (TEMP) inhibited lead-induced DNA breakage more efficiently than the hydroxyl radical scavengers mannitol and DMPO. Deuterium oxide (D2O), a singlet oxygen enhancer, potentiated lead-induced DNA breakage. At low ratios to Pb2+, NADPH, glutathione, and 2-mercaptoethanol enhanced lead-induced DNA breakage, whereas high ratios of these agents protected it. Catalase and superoxide dismutase (SOD) did not protect DNA breaks induced by Pb2+. Lead-induced DNA breakage was markedly enhanced by H2O2, and this induction was inhibited by NaN3, TEMP, EDTA, catalase, BSA, and glutathione. In contrast, mannitol and SOD potentiated Pb2+/H2O2-induced DNA breaks. The results indicate that singlet oxygen, lead, and H2O2 are all involved in the reaction system, whereas hydroxyl radical and superoxide did not. Lead could cause a small amount of 8-OHdG formation in calf thymus DNA and dose-dependently induced the formation of this adduct in the presence of H2O2. Singlet oxygen scavengers were more effective than hydroxyl radical scavengers in protection from lead/H2O2-induced 8-OHdG adducts. Taken together, these results suggest that lead may induce DNA damage through a Fenton-like reaction and that singlet oxygen is the principal species involved.

Blockade of tumor cell transforming growth factor-betas enhances cell cycle progression and sensitizes human breast carcinoma cells to cytotoxic chemotherapy

We have examined the effect of neutralizing TGF-beta antibodies on cisplatin-mediated cytotoxicity against MDA-231 human breast tumor cell spheroids. These tridimensional in vitro systems have been shown to recapitulate the drug sensitivity pattern of tumor cells in vivo. MDA-231 tumor cell spheroids exhibit higher protein levels of the cyclin-dependent kinase (Cdk) inhibitors p21 and p27 and >10-fold lower Cdk2 activity compared to adherent cell monolayers, as well as pRb hypophosphorylation, a predominant G1 population, and a cisplatin 1-h IC50 of approximately 100 microM. Treatment of MDA-231 cells in monolayer with cisplatin for 1 h, subsequently grown as spheroids, increased steady-state TGF-beta1 mRNA levels, secretion of active TGF-beta, cellular Cdk2 activity, pRb phosphorylation, and p21 protein levels, while downregulating p27. Accumulation of cells in G2M and progression into S were noted 48 h after treatment with 100 microM cisplatin. We tested whether drug-induced upregulation of TGF-beta1 and p21, perhaps by preventing cell cycle progression, were protective mechanisms against drug-mediated toxicity by using neutralizing anti-TGF-beta antibodies. Anti-TGF-beta antibodies diminished the induction of p21, enhanced the activation of Cdk2, and facilitated progression into S and G2M following cisplatin treatment. This resulted in a >twofold enhancement of drug-induced DNA fragmentation and a shift in the cisplatin 1-h IC50 from 100 to <10 microM. These data suggest that tumor cell TGF-beta1 may protect from DNA damage and that postchemotherapy administration of TGF-beta inhibitors may facilitate progression beyond G1/S, potentially increasing the efficacy of cytotoxic chemotherapy.

Effect of 3-aminotriazole on anchorage independence and mutagenicity in cadmium- and lead-treated diploid human fibroblasts

Cadmium and lead have been shown to induce cellular transformations and gene mutations in cultured rodent cells, as well as tumours in live animals. However, the mechanisms by which these metals cause cellular transformations and mutations in human cells have not been explored. In this study, we investigated the abilities of cadmium and lead to induce anchorage-independent transformations and hprt gene mutations in diploid human fibroblasts. Human fibroblasts were exposed to either cadmium acetate (0-60 microM) or lead acetate (0-2 mM) for 24 h. After removal of the metals, the cells were kept in exponential growth for 7 and 9 days before mutation and anchorage-independence assays were taken, respectively. Both cadmium and lead significantly induced anchorage-independent colonies in dose-dependent manners; the frequencies of anchorage-independent colonies induced by these metals were similar to those induced by N-methyl-N'-nitro-N-nitrosoguanidine at approximately equal cytotoxic dose ranges (30-10% survival). 3-Aminotriazole at non-cytotoxic dosages decreased catalase activity by >80%, and markedly enhanced cadmium-induced cytotoxicity and anchorage-independent colonies. Cadmium uptake by human fibroblasts was not affected by 3-aminotriazole co-administered with 10 microM of cadmium; whereas cadmium uptake and accumulation were enhanced 1.5-fold by 3-aminotriazole co-administered with 1-2.5 microM of cadmium. Lead-induced anchorage-independence or cytotoxicity was not affected by 3-aminotriazole co-treatment; however, 3-aminotriazole did significantly enhance lead uptake and accumulation in human fibroblasts. Neither cadmium- nor lead-induced 6-thioguanine-resistant mutation frequency in human fibroblasts. Co-administering these metals with 3-aminotriazole did not enhance mutations in human fibroblasts. These results suggest that cadmium and lead may both act as tumour promoters in diploid human fibroblasts, and that reactive oxygen species is more important in cadmium- than lead-induced cytotoxicity and anchorage-independence.

Overexpression of nm23 protein assessed by color video image analysis in metastatic colorectal cancer: correlation with reduced patient survival

The function and prognostic significance of the nm23 gene is controversial in colorectal cancer (CRC). The aim of this study was to determine if nm23 protein expression correlated with the subsequent development of liver metastasis. Paraffin-embedded sections of 30 metastasizing CRC primaries and their subsequently resected liver secondaries were compared with those of 28 nonmetastasizing CRCs, 20 adenomas, and 20 cases of normal colonic mucosa. Expression of nm23 protein, assayed by immunohistochemistry, was measured using a standard semiquantitative scaling system and compared with a microcomputerbased color video image analysis (VIA). There was good correlation between color VIA and semiquantitative evaluation of nm23 immunoreactivity, confirming the validity of quantitative analysis (Pearson's r = 0.88; p < 0.001). Metastasizing CRC primaries and secondaries overexpressed nm23 protein when compared with the other clinical groups, particularly nonmetastasizing CRC (Student's t-test, p < 0.001). Furthermore, more nm23 immunoreactivity was associated with a higher risk of death from CRC (log-rank test, p = 0.002). These results suggest that overexpression of nm23 is highly associated with liver metastases from CRC and reduced survival.