Signaling pathways in the induction of c-met receptor expression by its ligand scatter factor/hepatocyte growth factor in human glioblastoma

Scatter factor/hepatocyte growth factor (SF/HGF) and its tyrosine kinase receptor c-met are developmentally expressed, neuroprotective, and tumorigenic within the CNS. In the present study SF/HGF is shown to induce the expression of c-met in two human glioblastoma cell lines, U-373 MG and T98G, and the signaling pathways involved in this induction are dissected. SF/HGF activated mitogen-activated protein kinase (MAPK) and inhibition of either Ras or MAPK-kinase completely inhibited SF/HGF-mediated c-met induction. Inhibition of phospholipase-C (PLC) did not affect c-met induction in either cell line. Inhibition of phosphoinositide 3-kinase (PI3-kinase) substantially reduced c-met induction by SF/HGF in T98G cells but had no effect in U-373 MG cells. Protein kinase C (PKC) inhibition reduced c-met induction in T98G cells but not in U-373 MG cells. SF/HGF induced the expression of c-fos and c-jun mRNA and increased the levels of AP-1 transcription factor in both cells lines as determined by AP-1-luciferase reporter expression. Transfection of either cell line with TAM-67, a dominant negative for the jun transactivation domain, completely inhibited AP-1 and c-met induction by SF/HGF. These results support a model of c-met induction by SF/HGF in human glioma cells that uniformly involves Ras, MAPK, and AP-1 and additionally involves PI3-kinase and PKC in some cell lines.

Multiple ligand binding sites on domain seven of human complement factor H

Foreign particles and damaged host cells can activate the complement system leading to their destruction by the host defense system. Factor H (fH) plays a vital role in restricting complement activation on host cells through interactions with polyanions such as heparin, while allowing activation to proceed on foreign surfaces. Complement activation by damaged host cells is also down regulated by fH, which is localized to injured areas through interactions with C-reactive protein (CRP). A number of pathogens have developed mechanisms by which they can also bind fH and thus exploit its protective properties. One such organism is Group A Streptococcus (GAS) which mediates fH binding via its surface expressed M-protein. fH consists of 20 conserved short consensus repeat (SCR) units and mutagenesis studies indicate that the seventh repeat is responsible for interactions with heparin, CRP and M-protein. We recently performed molecular modelling of fH SCR 7 and identified a cluster of positively charged residues on one face of the domain. By alanine replacement mutagenesis, we demonstrated that these residues are involved in heparin, CRP and M protein binding, which indicates that there is a common site within fH SCR 7 responsible for multiple ligand recognition.

Microsporum gypseum complex in Madras, India

In Madras, India, 312 soil samples were collected from different habitats and screened for the presence of keratinophilic fungi especially those belonging to the Microsporum gypseum complex.

Pinpointing the putative heparin/sialic acid-binding residues in the 'sushi' domain 7 of factor H: a molecular modeling study

Factor H, a secretory glycoprotein comprising 20 short consensus repeat (SCR) or 'sushi' domains of about 60 amino acids each, is a regulator of the complement system. The complement-regulatory functions of factor H are targeted by its binding to polyanions such as heparin/sialic acid, involving SCRs 7 and 20. Recently, the SCR 7 heparin-binding site was shown to be co-localized with the Streptococcus Group A M protein binding site on factor H (T.K. Blackmore et al., Infect. Immun. 66, 1427 (1998)). Using sequence analysis of all heparin-binding domains of factor H and its closest homologues, molecular modeling of SCRs 6 and 7, and surface electrostatic potential studies, the residues implicated in heparin/sialic acid binding to SCR 7 have been localized to four regions of sequence space containing stretches of basic as well as histidine residues. The heparin-binding site is spatially compact and lies near the interface between SCRs 6 and 7, with residues in the interdomain linker playing a significant role.

Anti-Cryptococcus activity of combination of extracts of Cassia alata and Ocimum sanctum

The paper reports the anti-Cryptococcus activity of combination of ethanolic extracts of leaves of Cassia alata and Ocimum sanctum. The activity of combination of the extracts was heat-stable and worked at acidic pH.

Phase I pharmacokinetic trial of perillyl alcohol (NSC 641066) in patients with refractory solid malignancies

Perillyl alcohol (POH) is a monoterpene with anticarcinogenic and antitumor activity in murine tumor models. Putative mechanisms of action include activation of the transforming growth factor beta pathway and/or inhibition of p21ras signaling, leading to differentiation or apoptosis. In this Phase I trial, 17 patients took POH p.o. three times daily for 14 days of each 28-day cycle. The starting dose of POH was 1600 mg/m2/dose, with escalations to 2100 and 2800 mg/m2/dose in subsequent cohorts. Chronic nausea and fatigue were dose-limiting toxic effects at 2800 mg/m2. Grade 1-2 hypokalemia was common at 2100 and 2800 mg/m2. Although POH could not be detected in plasma, two of its metabolites, dihydroperillic acid (DHPA) and perillic acid (PA), were measured in plasma and urine on days 1 and 15 after the first and last doses of POH, respectively. Both area under the concentration versus time curve and peak plasma concentration (Cmax) values increased with dose and exhibited high intersubject variability. Day 15 DHPA Cmax values ranged from a mean +/- SD of 22.6+/-12 microM at 1600 mg/m2/dose to 42.4+/-15.24 microM at 2800 mg/m2/dose. Corresponding mean +/- SD Cmax values for PA were 433.2+/-245.8 and 774.1+/-439.6 microM. One patient treated at the 2800 mg/m2/dose had markedly prolonged plasma levels of both PA and DHPA and developed grade 3 mucositis. POH treatment did not consistently alter the expression of p21ras, rap1, or rhoA in peripheral blood mononuclear cells obtained from patients treated at the highest dose level. The metabolites PA and DHPA did not change expression or isoprenylation of p21ras in MCF-7 breast or DU145 prostate carcinoma cells at concentrations that exceeded those achieved in patient plasma after POH treatment. We conclude that POH at 1600-2100 mg/m2 p.o. three times daily is well tolerated on a 14-day on/14-day off dosing schedule. Inhibition of p21ras function in humans is not likely to occur after POH administration at safe doses of the present oral formulation.

The gene for a novel member of the whey acidic protein family encodes three four-disulfide core domains and is asynchronously expressed during lactation

Secretion of whey acidic protein (WAP) in milk throughout lactation has previously been reported for a limited number of species, including the mouse, rat, rabbit, camel, and pig. We report here the isolation of WAP from the milk of a marsupial, the tammar wallaby (Macropus eugenii). Tammar WAP (tWAP) was isolated by reverse-phase HPLC and migrates in SDS-polyacrylamide gel electrophoresis at 29.9 kDa. tWAP is the major whey protein, but in contrast to eutherians, secretion is asynchronous and occurs only from approximately days 130 through 240 of lactation. The full-length cDNA codes for a mature protein of 191 amino acids, which is comprised of three four-disulfide core domains, contrasting with the two four-disulfide core domain arrangement in all other known WAPs. A three-dimensional model for tWAP has been constructed and suggests that the three domains have little interaction and could function independently. Analysis of the amino acid sequence suggests the protein belongs to a family of protease inhibitors; however, the predicted active site of these domains is dissimilar to the confirmed active site for known protease inhibitors. This suggests that any putative protease ligand may be unique to either the mammary gland, milk, or gut of the pouch young. Examination of the endocrine regulation of the tWAP gene showed consistently that the gene is prolactin-responsive but that the endocrine requirements for induction and maintenance of tWAP gene expression are different during lactation.

Effects of a high-fat-sucrose diet on enzymes in homocysteine metabolism in the rat

Hyperhomocysteinemia (HH) and hyperinsulinemia are both risk factors for cardiovascular disease. To examine the effects of hyperinsulinemia on homocysteine metabolism, we fed rats a high-fat-sucrose (HFS) diet and then measured the hepatic mRNA and activity of 2 key enzymes involved in this metabolic pathway: 5,10-methylenetetrahydrofolate reductase (MTHFR) and cystathionine-beta-synthase (CbetaS). Fischer rats made insulin-resistant by a HFS diet were examined at 6 months and 2 years of age and compared with control rats fed a low-fat, complex-carbohydrate (LFCC) diet. At the end of 6 months, the HFS rats were heavier than the LFCC rats (214 +/- 3.4 v 188 +/- 1.4 g, P < .01). There were no differences in blood glucose between HFS and LFCC rats; however, plasma insulin and homocysteine concentrations were elevated in HFS rats (insulin, 56 +/- 12 v 14.5 +/- 2.9 microU/mL; homocysteine, 10.77 +/- 0.9 v 6.89 +/- 0.34 micromol/L, P < .01). Hepatic CbetaS enzyme activity was significantly lower in HFS compared with LFCC rats (0.45 v 0.64 U/mg, P = .0001), and this decrease was reflected in a decrease of the CbetaS mRNA concentration. In contrast, hepatic MTHFR enzyme activity and mRNA concentration were significantly elevated in the HFS group compared with controls (HFS and LFCC, 8.62 and 4.8 nmol/h/mg protein, respectively, P = .0001). These changes in plasma homocysteine, CbetaS, and MTHFR were significantly correlated with the degree of obesity and hyperinsulinemia. Fasting plasma insulin correlated significantly and positively with plasma homocysteine (r = .51, P < .01) and MTHFR activity (r = .48, P < .01) and negatively with CbetaS activity (r = -.54, P < .001). CbetaS and MTHFR activities were inversely correlated with each other (r = -.58, P < .001). In conclusion, rats fed a HFS diet are hyperinsulinemic, and the hyperinsulinemia is associated with an elevated homocysteine concentration and changes in 2 key enzymes in homocysteine metabolism.

Thrombospondin-1 binds to polyhistidine with high affinity and specificity

Thrombospondin-1 (TSP1) is a secreted trimeric glycoprotein of 450 kDa with demonstrated effects on cell growth, adhesion and migration. Its complex biological activity is attributed to its ability to bind to cell-surface receptors, growth factors and extracellular-matrix proteins. In this study, we used a (125)I solid-phase binding assay to demonstrate that TSP1 binds specifically to proteins containing polyhistidine stretches. Based on studies with three different six-histidine-containing recombinant proteins, we derived an average dissociation constant of 5 nM. The binding of (125)I-labelled TSP1 to these proteins was inhibited by peptides containing histidine residues, with the degree of competition being a function of the number of histidines within the peptide. Binding was not inhibited by excess histidine or imidazole, indicating that the imidazole ring is not sufficient for recognition by TSP1. Heparin was a potent inhibitor of binding with a K(i) of 50 nM, suggesting that the heparin-binding domain of TSP1 may be involved in this interaction. This was confirmed by the ability of a recombinant heparin-binding domain of TSP1 to directly compete for TSP1 binding to polyhistidine-containing proteins. Affinity chromatography with a polyhistidine-containing peptide immobilized on agarose revealed that TSP1 in platelet releasates is the major polypeptide retained on the six-histidine-peptide column. We conclude that TSP1 contains a high-affinity binding site for polyhistidine and this is likely to be the molecular basis for the observed binding of TSP1 to histidine-rich glycoprotein. The possibility that other polyhistidine-containing proteins also interact with TSP1 warrants further study.

Complement factor H: sequence analysis of 221 kb of human genomic DNA containing the entire fH, fHR-1 and fHR-3 genes

Complement factor H (fH) is a member of a family of proteins involved in the regulation of complement activation (RCA). These proteins share a common structural motif, the Short Consensus Repeat (SCR), which is structurally conserved among related genes and between phylogenetically divergent species. fH is composed of 20 such SCRs and a variety of biological functions have been localised to specific SCR domains. The majority of individual SCRs identified are encoded by single exons, and processes such as gene conversion, duplication and exon shuffling have been implicated in the evolution and genomic radiation of SCR-encoding genes. We have analysed two GenBank sequence entries relating to two overlapping PAC clones sequenced at the Sanger Centre which contain the entire human fH gene and two adjacent fH-related (fHR) genes, fHR-1 and fHR-3. Here, we report the detailed analysis of the assembled 221 kb of contiguous, ungapped genomic sequence from human chromosome 1q32, in part employing the RUMMAGE-DP automated annotation tool. Genomic duplications involving fH and fHR exons were identified and Alu/L1 repeat dating established that the duplications occurred after the separation of rodent and primate lineages. The analysis indicates that retrotransposition as well as single and multiple exon duplication events are likely to have been involved in SCR radiation and RCA gene evolution, facilitated by conservation of splice-phasing and the single-exon, single-SCR nature of the encoded domains.

Genomic sequence of human glyoxalase-I: analysis of promoter activity and its regulation

Glyoxalase-I is a glutathione-binding protein involved in the detoxification of methylglyoxal, a by-product of glycolysis. Aberrations in the expression of human glyoxalase in cancer and diabetes have been reported. To gain a better understanding of the glyoxalase-I regulation under normal physiological conditions and in disease processes, we have cloned 12kb of genomic sequence, comprising five exons, separated by four introns. A fragment comprising 982bp of 5' flanking region was used in the pSEAP reporter system to identify the minimal promoter and to locate any cis-acting functional elements. This region contained a minimal promoter between -20 and -160bp. Cells transfected with a construct containing the 5' flanking sequence exhibited a 45-fold higher activity over vector transfected cells. A twofold reproducible increase in reporter activity was seen with insulin and ZnCl(2) treatments, indicating a functionally operative insulin response element (IRE) and metal response element (MRE). Knowledge regarding the regulation of glyoxalase-I may provide insights into the importance of this enzyme in human diseases.

Reversion of human glioblastoma malignancy by U1 small nuclear RNA/ribozyme targeting of scatter factor/hepatocyte growth factor and c-met expression

BACKGROUND

Expression of scatter factor (SF), also known as hepatocyte growth factor (HGF), and its receptor, c-met, is often associated with malignant progression of human tumors, including gliomas. Overexpression of SF/HGF in experimental gliomas enhances tumorigenicity and tumor-associated angiogenesis (i.e., growth of new blood vessels). However, the role of endogenous SF/HGF or c-met expression in the malignant progression of gliomas has not been examined directly. In this study, we tested the hypothesis that human glioblastomas can be SF/HGF-c-met dependent and that a reduction in endogenous SF/HGF or c-met expression can lead to inhibition of tumor growth and tumorigenicity.

METHODS

Expression of the SF/HGF and c-met genes was inhibited by transfecting glioblastoma cells with chimeric transgenes consisting of U1 small nuclear RNA, a hammerhead ribozyme, and antisense sequences. The effects of reduced SF/HGF and c-met expression on 1) SF/HGF-dependent induction of immediate early genes (c-fos and c-jun), indicative of signal transduction; 2) anchorage-independent colony formation (clonogenicity), an in vitro correlate of solid tumor malignancy; and 3) intracranial tumor formation in immunodeficient mice were quantified. Statistical tests were two-sided.

RESULTS

Introduction of the transgenes into glioblastoma cells reduced expression of the SF/HGF and c-met genes to as little as 2% of control cell levels. Reduction in c-met expression specifically inhibited SF/HGF-dependent signal transduction (P<.01). Inhibition of SF/HGF or c-met expression in glioblastoma cells possessing an SF/HGF-c-met autocrine loop reduced tumor cell clonogenicity (P =.005 for SF/HGF and P=.009 for c-met) and substantially inhibited tumorigenicity (P<.0001) and tumor growth in vivo (P<.0001).

CONCLUSIONS

To our knowledge, this is the first successful inhibition of SF/HGF and c-met expression in a tumor model directly demonstrating a role for endogenous SF/HGF and c-met in human glioblastoma. Our results suggest that targeting the SF/HGF-c-met signaling pathway may be an important approach in controlling tumor progression.

Functional and structural studies of wild type SOX9 and mutations causing campomelic dysplasia

In humans, mutations in SOX9 result in a skeletal malformation syndrome, campomelic dysplasia (CD). The present study investigated two major classes of CD mutations: 1) point mutations in the high mobility group (HMG) domain and 2) truncations and frameshifts that alter the C terminus of the protein. We analyzed the effect of one novel mutation and three other point mutations in the HMG domain of SOX9 on the DNA binding and DNA bending properties of the protein. The F12L mutant HMG domain shows negligible DNA binding, the H65Y mutant shows minimal DNA binding, whereas the A19V mutant shows near wild type DNA binding and bends DNA normally. Interestingly, the P70R mutant has altered DNA binding specificity, but also bends DNA normally. The effects of the point mutations were interpreted using a molecular model of the SOX9 HMG domain. We analyzed the effects upon transcription of mutations resembling the truncation and frameshift mutations in CD patients, and found that progressive deletion of the C terminus causes progressive loss of transactivation. Maximal transactivation by SOX9 requires both the C-terminal domain rich in proline, glutamine, and serine and the adjacent domain composed entirely of proline, glutamine, and alanine. Thus, CD arises by mutations that interfere with DNA binding by SOX9 or truncate the C-terminal transactivation domain and thereby impede the ability of SOX9 to activate target genes during organ development.

Scatter factor/hepatocyte growth factor gene transfer increases rat blood-glioma barrier permeability

Malignant gliomas are associated with a dysfunctional blood-tumor barrier (BTB) that causes substantial morbidity. Scatter factor/hepatocyte growth factor (SF/HGF) is a multifunctional growth factor that correlates with glioma malignancy and has several biological properties that suggest a role in enhancing blood-glioma barrier permeability. In this study, we examined the effects of glioma cell SF/HGF expression on BTB permeability to horseradish peroxidase (HRP). Fischer 344 rats bearing intrastriatal 9L tumors engineered to secrete SF/HGF (9L-SF) and SF/HGF-negative control tumors (9L-neo) received intracardiac injections of HRP and were rapidly decapitated. Densitometric analysis of brain sections reacted with diaminobenzidine showed significantly greater extravascular HRP surrounding SF/HGF-secreting tumors than 9L-neo tumors of comparable size (p<0.05). HRP enzymatic activity associated with striata containing SF/HGF-expressing tumors was 1. 6-fold greater than that of striata containing control tumors (p<0. 05). Northern analysis showed that expression of vascular endothelial growth factor/vascular permeability factor (VEGF/VPF) did not differ between 9L-neo and 9L-SF tumors. These data demonstrate that SF/HGF expression by intracerebral glial tumors can enhance BTB permeability independent of changes in VEGF/VPF expression.

Effect of vitamin C and E in modulating peripheral vascular response to local cold stimulus in man at high altitude

At high altitude (HA), cold stress is aggravated by hypoxia, perhaps due to the increased formation of free radicals which trigger oxidative stress. This may be one of the contributing factors for adverse effects including disturbances in microcirculation and capillary permeability resulting in decreased peripheral blood flow. This leads to altered cold-induced-vasodilatation (CIVD) response on exposure to HA. The present study was conducted on 40 male volunteers (4 groups of 10 each) to evaluate the utility of supplementation of vitamin C (500 mg/d)and vitamin E (400 mg/d) singly, as well as in combination, in modulating peripheral vascular response by assessing CIVD response under local cold stimulus both at Delhi (200 m) and at HA (3,700 m). On exposure to 3,700 m, decreased CIVD response was observed in all the groups. The responses were better in vitamin supplemented groups, in general, as compared to the placebo group. The best CIVD response was seen in the vitamin C (singly)-treated group. Administration of vitamin C and E together did not result in any additional benefit. Facilitation of CIVD response due to supplementation of vitamin C may be attributed to its (a) antioxidant effect, and (b) major physiological functions of increased metabolism and thermogenic properties, facilitation of collagen synthesis, restoration of intercellular substances and better maintenance of the rheological status of the blood. Hence, vitamin C is effective for improving peripheral blood flow and thereby reduces the incidence of cold injuries during acclimatization or outdoor duties at HA.

The whey acidic protein family: a new signature motif and three-dimensional structure by comparative modeling

Whey acidic proteins (WAP) from the mouse, rat, rabbit, camel, and pig comprise two "four-disulfide core" domains. From a detailed analysis of all sequences containing this domain, we propose a new PROSITE motif ([KRHGVLN]-X-¿PF¿-X-[CF]-[PQSVLI]-X(9,19)-C-¿P¿-X-[DN]-X-¿N¿ -[CE]-X(5)-C-C) to accurately identify new four-disulfide core proteins. A consensus model for the WAP proteins is proposed, based on the human mucous proteinase inhibitor crystal structure. This article presents a detailed atomic model for the two-domain porcine WAP sequence by comparative modeling. Surface electrostatic potential calculations indicate that the second domain of the pig WAP model is similar to the functional human mucous proteinase inhibitor domains, whereas the first domain may be nonfunctional.

Measurement of airway resistance using the interrupter technique in preschool children in the ambulatory setting

This study describes the feasibility, repeatability, and interrater reliability of the measurement of airway resistance by the interrupter technique (Rint) in children 2-5 yrs of age, and examines whether reversibility to bronchodilator can be demonstrated in wheezy children. The mean of six Rint values was taken as a measurement. If subjects could complete one measurement and then a second 15 min after bronchodilator, baseline testing and reversibility testing were considered feasible. To measure repeatability, two measurements 30 s apart and measurements before and 15 min after placebo bronchodilator were compared. Measurements by two testers were compared for interrater reliability. Change in Rint in wheezy children was measured after bronchodilator. Fifty-six per cent of 2-3-yr-olds (n=79), 81% of 3-4-yr-olds (n=104) and 95% of 4-5-yr-olds (n=88) completed baseline testing, and 53%, 71% and 91% completed reversibility testing. Baseline measurements were 0.47-2.56 kPa x L(-1) x s. Repeatabilities (2 SD of the mean differences between measurements) at 30 s in the three age bands were 0.21, 0.17 and 0.15 kPa x L(-1) x s and 0.19 kPa x L(-1) x s after placebo. Using 0.21 kPa x L(-1) x s as the threshold for reversibility, reversibility was demonstrated in most wheezy children. Interrater reliability was 0.15 kPa x L(-1) x s. Preschool children can undertake measurements of airway resistance by the interrupter technique in ambulatory settings and reversibility to bronchodilator in wheezy children can be demonstrated. This technique promises to be a useful clinical and research tool.

Pertussis is increasing in unimmunized infants: is a change in policy needed?

The proportion and trend in absolute number of pertussis notifications in young infants has increased each year in England and Wales since the accelerated immunization schedule was introduced. We report five infants all less than 3 months of age admitted with life threatening pertussis infection to two paediatric intensive care units. Despite aggressive cardiorespiratory support measures, three of the infants died. Pertussis remains a significant cause of morbidity and mortality in unimmunized infants. In this age group presentation is likely to be atypical and infection more severe. Public health measures to prevent the disease could be strengthened. Chemoprophylaxis should be offered to susceptible contacts and booster vaccinations against pertussis considered.