Preclinical development of 1B7/CD3, a novel anti-TSLPR bispecific antibody that targets CRLF2-rearranged Ph-like B-ALL

Patients harboring CRLF2-rearranged B-lineage acute lymphocytic leukemia (B-ALL) face a 5-year survival rate as low as 20%. While significant gains have been made to position targeted therapies for B-ALL treatment, continued efforts are needed to develop therapeutic options with improved duration of response. Here, first we have demonstrated that patients with CRLF2-rearranged Ph-like ALL harbor elevated thymic stromal lymphopoietin receptor (TSLPR) expression, which is comparable with CD19. Then we present and evaluate the anti-tumor characteristics of 1B7/CD3, a novel CD3-redirecting bispecific antibody (BsAb) that co-targets TSLPR. In vitro, 1B7/CD3 exhibits optimal binding to both human and cynomolgus CD3 and TSLPR. Further, 1B7/CD3 was shown to induce potent T cell activation and tumor lytic activity in both cell lines and primary B-ALL patient samples. Using humanized cell- or patient-derived xenograft models, 1B7/CD3 treatment was shown to trigger dose-dependent tumor remission or growth inhibition across donors as well as induce T cell activation and expansion. Pharmacokinetic studies in murine models revealed 1B7/CD3 to exhibit a prolonged half-life. Finally, toxicology studies using cynomolgus monkeys found that the maximum tolerated dose of 1B7/CD3 was ≤1 mg/kg. Overall, our preclinical data provide the framework for the clinical evaluation of 1B7/CD3 in patients with CRLF2-rearranged B-ALL.

Superoxide dismutase-deficient mutants of Helicobacter pylori are hypersensitive to oxidative stress and defective in host colonization

Superoxide dismutase (SOD) is a nearly ubiquitous enzyme among organisms that are exposed to oxic environments. The single SOD of Helicobacter pylori, encoded by the sodB gene, has been suspected to be a virulence factor for this pathogenic microaerophile, but mutations in this gene have not been reported previously. We have isolated mutants with interruptions in the sodB gene and have characterized them with respect to their response to oxidative stress and ability to colonize the mouse stomach. The sodB mutants are devoid of SOD activity, based on activity staining in nondenaturing gels and quantitative assays of cell extracts. Though wild-type H. pylori is microaerophilic, the mutants are even more sensitive to O(2) for both growth and viability. While the wild-type strain is routinely grown at 12% O(2), growth of the mutant strains is severely inhibited at above 5 to 6% O(2). The effect of O(2) on viability was determined by subjecting nongrowing cells to atmospheric levels of O(2) and plating for survivors at 2-h time intervals. Wild-type cell viability dropped by about 1 order of magnitude after 6 h, while viability of the sodB mutant decreased by more than 6 orders of magnitude at the same time point. The mutants are also more sensitive to H(2)O(2), and this sensitivity is exacerbated by increased O(2) concentrations. Since oxidative stress has been correlated with DNA damage, the frequency of spontaneous mutation to rifampin resistance was studied. The frequency of mutagenesis of an sodB mutant strain is about 15-fold greater than that of the wild-type strain. In the mouse colonization model, only 1 out of 23 mice inoculated with an SOD-deficient mutant of a mouse-adapted strain became H. pylori positive, while 15 out of 17 mice inoculated with the wild-type strain were shown to harbor the organism. Therefore, SOD is a virulence factor which affects the ability of this organism to colonize the mouse stomach and is important for the growth and survival of H. pylori under conditions of oxidative stress.

The chaperone/usher pathways of Pseudomonas aeruginosa: identification of fimbrial gene clusters (cup) and their involvement in biofilm formation

Pseudomonas aeruginosa, an important opportunistic human pathogen, persists in certain tissues in the form of specialized bacterial communities, referred to as biofilm. The biofilm is formed through series of interactions between cells and adherence to surfaces, resulting in an organized structure. By screening a library of Tn5 insertions in a nonpiliated P. aeruginosa strain, we identified genes involved in early stages of biofilm formation. One class of mutations identified in this study mapped in a cluster of genes specifying the components of a chaperone/usher pathway that is involved in assembly of fimbrial subunits in other microorganisms. These genes, not previously described in P. aeruginosa, were named cupA1-A5. Additional chaperone/usher systems (CupB and CupC) have been also identified in the genome of P. aeruginosa PAO1; however, they do not appear to play a role in adhesion under the conditions where the CupA system is expressed and functions in surface adherence. The identification of these putative adhesins on the cell surface of P. aeruginosa suggests that this organism possess a wide range of factors that function in biofilm formation. These structures appear to be differentially regulated and may function at distinct stages of biofilm formation, or in specific environments colonized by this organism.

Regulation of ornithine decarboxylase activity and polyamine transport by agmatine in rat pulmonary artery endothelial cells

Agmatine, a product of arginine decarboxylation in mammalian cells, is believed to govern cell polyamines by inducing antizyme, which in turn suppresses ornithine decarboxylase (ODC) activity and polyamine uptake. However, since agmatine is structurally similar to the polyamines, it is possible that it exerts antizyme-independent actions on polyamine regulatory pathways. The present study determined whether agmatine inhibited ODC activity and polyamine transport in rat pulmonary artery endothelial cells (PAECs) by an antizyme-dependent mechanism. Agmatine caused time-dependent reductions in ODC activity, which occurred before increases in antizyme. Interventions that suppressed proteasome function caused large increases in ODC activity but failed to attenuate inhibitory effects of agmatine. When agmatine was present in the culture medium, 14C-polyamine uptake was competitively inhibited as evidenced by substantial elevations in K(m) values. If PAECs were incubated with agmatine for periods sufficient to increase antizyme, there were modest decreases in V(max) for putrescine and spermidine but not for spermine. These effects of agmatine on polyamine transport were insensitive to protein synthesis inhibition. Collectively, our findings show that agmatine decreases ODC activity and polyamine transport in PAECs, but a causal role for antizyme in these actions of agmatine is difficult to establish. Nevertheless, these observations are consistent with a model in which PAECs express both antizyme-1 and -2, but only the latter contributes to agmatine-mediated suppression of ODC activity.

Requirement of nickel metabolism proteins HypA and HypB for full activity of both hydrogenase and urease in Helicobacter pylori

The nickel-containing enzymes hydrogenase and urease require accessory proteins in order to incorporate properly the nickel atom(s) into the active sites. The Helicobacter pylori genome contains the full complement of both urease and hydrogenase accessory proteins. Two of these, the hydrogenase accessory proteins HypA (encoded by hypA) and HypB (encoded by hypB), are required for the full activity of both the hydrogenase and the urease enzymes in H. pylori. Under normal growth conditions, hydrogenase activity is abolished in strains in which either hypA (HypA:kan) or hypB (HypB:kan) have been interrupted by a kanamycin resistance cassette. Urease activity in these strains is 40 (HypA:kan)- and 200 (HypB:kan)-fold lower than for the wild-type (wt) strain 43504. Nickel supplementation in the growth media restored urease activity to almost wt levels. Hydrogenase activity was restored to a lesser extent, as has been observed for hyp mutants in other (H(2)-oxidizing) bacteria. Expression levels of UreB (the urease large subunit) were not affected by inactivation of either hypA or hypB, as determined by immunoblotting. Urease activity was not affected by lesions in the genes for either the hydrogenase accessory proteins HypD or HypF or the hydrogenase large subunit structural gene, indicating that the urease deficiency was not caused by lack of hydrogenase activity. When crude extracts of wt, HypA:kan and HypB:kan were separated by anion exchange chromatography, the urease-containing fractions of the mutant strains contained about four (HypA:kan)- and five (HypB:kan)-fold less nickel than did the urease from wt, indicating that the lack of urease activity in these strains results from a nickel deficiency in the urease enzyme.

Characterization of the NifU and NifS Fe-S cluster formation proteins essential for viability in Helicobacter pylori

The Fe-S cluster formation proteins NifU and NifS are essential for viability in the ulcer causing human pathogen Helicobacter pylori. Obtaining viable H. pylori mutants upon mutagenesis of the genes encoding NifU and NifS was unsuccessful even by growing the potential transformants under many different conditions including low O(2) atmosphere and supplementation with both ferric and ferrous iron. When a second copy of nifU was introduced into the chromosome at a unrelated site, creating a mero-diploid strain for nifU, this second copy of the gene could be disrupted at high frequency. This indicates that the procedures used for transformation were capable of nifU mutagenesis, so that the failure to recover mutants is solely due to the requirement of nifU for H. pylori viability. H. pylori NifU and NifS were expressed in Escherichia coli and purified to near homogeneity, and the proteins were characterized. Purified NifU is a red protein that contains approximately 1.5 atoms of iron per monomer. This iron was determined to be in the form of a redox-active [2Fe-2S](2+,+) cluster by characteristic UV-visible, EPR, and MCD spectra. The primary structure of NifU also contains the three conserved cysteine residues which are involved in providing the scaffold for the assembly of a transient Fe-S cluster for insertion into apoprotein. Purified NifS has a yellow color and UV-visible spectra characteristic of a pyridoxal phosphate containing enzyme. NifS is a cysteine desulfurase, releasing sulfur or sulfide (depending on the reducing environment) from L-cysteine, in agreement with its proposed role as a sulfur donor to Fe-S clusters. The results here indicate that the NifU type of Fe-S cluster formation proteins is not specific for maturation of the nitrogenase proteins and, as H. pylori lacks other Fe-S cluster assembly proteins, that the H. pylori NifS and NifU are responsible for the assembly of many (non-nitrogenase) Fe-S clusters.

Long-term assessment (5 to 71 months) of endosseous dental implants placed in the augmented maxillary sinus

BACKGROUND

It is not uncommon for the placement of endosseous dental implants in the maxillary posterior jaw region to be complicated by the pneumatization of the maxillary sinus. When this occurs, the residual bone between the floor of the sinus and the crestal ridge is inadequate for the placement of implants. The sinus lift procedure provides a way to increase the amount of available bone and the placement of longer implants.

METHODS

One hundred twenty (120) implants were placed in 45 augmented maxillary sinuses. Patients ranged in age from 34 to 78 years. The implant design included a limited number of non-hydroxyapatite (HA)-coated titanium screws, with the majority of the implants being HA-coated cylinders, grooved cylinders, and screws. The augmentation materials were autogenous bone, allogenic bone (demineralized freeze-dried bone allograft, DFDBA), alloplastic bone (HA), combination grafts of HA and DFDBA, and combination grafts of autogenous bone and DFDBA. All the cases were successfully restored with implant-supported, bar-retained overdentures or fixed partial dentures. The follow-up began at Stage 2 uncovering and ranged from 5 to 71 months, with a mean of 38.2 and standard deviation of 14.6 months.

RESULTS

Three (2.5%) of the 120 implants failed between the period of implant placement and 36 months. Failures appeared to be associated with a history of smoking. Other complications encountered during the study are presented. Implant survival was higher in those placed in grafted sinuses (97.5%) than in those placed in the posterior maxilla without sinus grafting (90.3%).

CONCLUSION

These findings support the use of implants placed in augmented sinuses to support dental prostheses.

Periodontal-type measurements associated with hydroxyapatite-coated and non-HA-coated implants: uncovering to 36 months

BACKGROUND

While the use of hydroxyapatite (HA)-coated endosseous dental implants has gained in popularity over the past 10 years, the short-term and long-term predictability and indications for their use remain highly controversial. Some reports suggest that the HA coating may separate from the substructure, undergo dissolution in tissue fluids, and/or contribute to rapid osseous breakdown around the implant. Other reports, however, relate favorable responses to HA-coated implants, which include rapid bone adaptation to the HA, greater stability at uncovering, and increased coronal bone growth. These contradictions may be related to differences in chemical composition of the HA on the implant surface. Most clinicians and researchers may agree that long-term, independent, scientific clinical studies are needed to compare HA-coated and non-HA-coated (titanium-alloy and CP-titanium) implants under the same conditions. Concerns appear in the literature that HA-coated implants experience greater breakdown because they are more susceptible to bacterial colonization due to their roughness and hydrophilicity. Some studies suggest that specific putative periodontal pathogens may adhere to the HA, thereby predisposing the implant to greater peri-implantitis than that experienced by non-HA implants.

METHODS

A total of 32 clinical research centers, located in various geographic regions of the United States, were selected to participate in a comprehensive clinical study. More than 2,900 HA-coated and non-HA implants were randomized as to location within one of three jaw regions--maxillary anterior, mandibular anterior, and mandibular posterior--and followed for 36 months. It can be assumed that in each of these jaw regions, the conditions associated with both implant surface types would be similar enough to permit meaningful comparisons of periodontal-type measurements that have not previously been reported. Periodontal-type measurements (gingiva, plaque, suppuration, and calculus indices; probing depth; attachment levels; recession; and keratinized tissue width) for each aspect of each implant (mesial, facial, distal, and lingual) were recorded at 3, 6, 9, 12, 18, 24, and 36 months following implant uncovering. The implant was considered the experimental unit for analysis using generalized estimating equation and repeated measure methods. Data for the four aspects of each implant, as well as measurements over time, were all clustered in the unit of analysis.

RESULTS

The percentages of implants with zeros recorded for the indices was remarkably similar for both HA-coated and non-HA implants. While statistically significant differences were found for some of the measurements associated with HA-coated and non-HA implants under certain conditions, these differences were too small to be considered clinically significant.

CONCLUSIONS

Overall, there was no clinically significant difference between the periodontal-type measurements for HA-coated and non-HA-coated implants followed for a period from 3 through 36 months. The concerns about HA-coated implants being associated with adverse periodontal responses for the HA chemical composition included in this study appear to be unfounded for a period of clinical performance up to 36 months.

The influence of preoperative antibiotics on success of endosseous implants at 36 months

The benefits of prophylactic antibiotics are well recognized in dentistry. However, their routine use in the placement of endosseous dental implants remains controversial. As part of the comprehensive Dental Implant Clinical Research Group (DICRG) clinical implant study, the preoperative or postoperative use of antibiotics, the type used, and the duration of coverage were left to the discretion of the surgeon. These data for 2,973 implants were recorded and correlated with failure of osseointegration during healing (Stage 1), at surgical uncovering (Stage 2), before loading the prosthesis (Stage 3), and from prosthesis loading to 36 months (Stage 4). The results showed a significantly higher survival rate at each stage of treatment in patients who had received preoperative antibiotics.

Dental endosseous implant assessments in a type 2 diabetic population: a prospective study

Diabetes mellitus, a prevalent disorder worldwide, is associated with systemic adverse sequelae, such as wound healing alterations, which may affect osseointegration of dental implants. This prospective multicenter study assessed the success of 2-stage endosseous root-form implants (3 different implant systems) placed in the mandibular symphysis of 89 male type 2 diabetic subjects. The implants were uncovered approximately 4 months after placement, restored with an implant-supported, Hader bar clip-retained overdenture, and maintained at scheduled follow-up data collection examinations for 60 months after loading. Sixteen (9.0%) of the 178 implants failed. Life table methods calculated implant survival at approximately 88%, from prosthesis placement through the 60-month follow-up, and at approximately 90% from implant placement through the observation period. No implants failed between surgical placement and uncovering, 5 failed at uncovering, 7 failed after uncovering before prosthesis placement, and 4 failed after prosthesis placement. Fasting plasma glucose (FPG) and glycosylated hemoglobin (HbA1c) values were determined before implant placement (baseline) and approximately 4 months later at surgical uncovering (follow-up). The 5-year implant outcomes (successes versus failures) were analyzed against the following predictor variables: (1) baseline and follow-up FPG values, (2) baseline and follow-up HbA1c values, (3) subject age, (4) duration of diabetes (years), (5) baseline diabetic therapy, (6) smoking history, and (7) implant length. Regression analysis found only duration of diabetes (P < .025) and implant length (P < .001) to be statistically significant predictors of implant failure. There was no statistically significant difference in failure rates between the 3 different implant systems used. This study supports the use of dental implants in type 2 diabetic patients.

Odontogenic carcinoma occurring in a dentigerous cyst: case report and clinical management

This case report describes an unusual odontogenic carcinoma, which was detected during routine periodontal examination. The lesion occurred in a dentigerous cyst associated with an impacted third molar in an otherwise asymptomatic 66-year-old male patient. The impacted tooth and lesion were excised based on evidence of radiographic change and clinical findings. An unusual histopathologic presentation is reported. The treatment provided for this tumor and the management of impacted teeth is reviewed.

Regulation of gadd153 mRNA expression by hypoxia in pulmonary artery smooth muscle cells

Hypoxia causes pulmonary hypertension and induces oxygen radicals in pulmonary artery smooth muscle cells (PASMCs). Since oxidative stress regulates gaddl53 expression, we examined gaddl53 mRNA in PASMCs cultured in a hypoxic environment. Gadd153 mRNA content was increased in PASMCs cultured for 24 hours in 1% oxygen. This increase was not abrogated by inhibition of protein synthesis. To explore the signaling pathways mediating hypoxic regulation of gaddl53 mRNA, the impact of calcium channel blockade by verapamil, G protein inhibition by pertussis toxin, and protein kinase C (PKC) down-regulation, was examined. Although none of these interventions reduced basal expression of gaddl53 mRNA in PASMCs, all of them suppressed the induction by hypoxia. In contrast, antioxidants had no effect. These observations indicate hypoxia induces gaddl53 expression in PASMCs through common signaling pathways.

Interactions between agmatine and polyamine uptake pathways in rat pulmonary artery endothelial cells

Agmatine, a product of arginine metabolism in vascular endothelial cells, is structurally similar to the natural polyamines, putrescine, spermidine and spermine. To test the hypothesis that agmatine and polyamines interacted at the level of the polyamine transporter, we determined if polyamines competed with agmatine for import and whether interventions modulating polyamine import exerted coordinate effects on agmatine uptake. Multiple lines of evidence were obtained to suggest that agmatine enters pulmonary artery endothelial cells (PAECs) via the polyamine transporter, though its intracellular disposition after uptake appears different from the natural polyamines.

Dual roles of Bradyrhizobium japonicum nickelin protein in nickel storage and GTP-dependent Ni mobilization

The hydrogenase accessory protein HypB, or nickelin, has two functions in the N(2)-fixing, H(2)-oxidizing bacterium Bradyrhizobium japonicum. One function of HypB involves the mobilization of nickel into hydrogenase. HypB also carries out a nickel storage/sequestering function in B. japonicum, binding nine nickel ions per monomer. Here we report that the two roles (nickel mobilization and storage) of HypB can be separated in vitro and in vivo using molecular and biochemical approaches. The role of HypB in hydrogenase maturation is completely dependent on its intrinsic GTPase activity; strains which produce a HypB protein that is severely deficient in GTPase activity but that fully retains nickel-sequestering ability cannot produce active hydrogenase even upon prolonged nickel supplementation. A HypB protein that lacks the nickel-binding polyhistidine region near the N terminus lacks only the nickel storage capacity function; it is still able to bind a single nickel ion and also retains complete GTPase activity.

Cellular disposition of transported polyamines in hypoxic rat lung and pulmonary arteries

The polyamines putrescine, spermidine (SPD), and spermine are a family of low-molecular-weight organic cations essential for cell growth and differentiation and other aspects of signal transduction. Hypoxic pulmonary vascular remodeling is accompanied by depressed lung polyamine synthesis and markedly augmented polyamine uptake. Cell types in which hypoxia induces polyamine transport in intact lung have not been delineated. Accordingly, rat lung and rat main pulmonary arterial explants were incubated with [(14)C]SPD in either normoxic (21% O(2)) or hypoxic (2% O(2)) environments for 24 h. Autoradiographic evaluation confirmed previous studies showing that, in normoxia, alveolar epithelial cells are dominant sites of polyamine uptake. In contrast, hypoxia was accompanied by prominent localization of [(14)C]SPD in conduit, muscularized, and partially muscularized pulmonary arteries, which was not evident in normoxic lung tissue. Hypoxic main pulmonary arterial explants also exhibited substantial increases in [(14)C]SPD uptake relative to control explants, and autoradiography revealed that enhanced uptake was most evident in the medial layer. Main pulmonary arterial explants denuded of endothelium failed to increase polyamine transport in hypoxia. Conversely, medium conditioned by endothelial cells cultured in hypoxic, but not in normoxic, environments enabled hypoxic transport induction in denuded arterial explants. These findings in arterial explants were recapitulated in rat cultured main pulmonary artery cells, including the enhancing effect of a soluble endothelium-derived factor(s) on hypoxic induction of [(14)C]SPD uptake in smooth muscle cells. Viewed collectively, these results show in intact lung tissue that hypoxia enhances polyamine transport in pulmonary artery smooth muscle by a mechanism requiring elaboration of an unknown factor(s) from endothelial cells.

Postmortem histologic evaluation of hydroxyapatite-coated cylinder and titanium alloy basket implants in situ for 37 months in the posterior mandible. Dental Implant Clinical Research Group

Histologic examination of the tissues surrounding a titanium alloy basket implant and a hydroxyapatite-coated titanium cylinder implant from the mandible of a cadaver were examined. The 67-year-old man died 37 months after first-stage surgery from cardiovascular failure. Clinical and radiographic examinations indicated that the implants were functional, immobile, and integrated. Light microscopy revealed that the gingival tissues adjacent to the implants were healthy and, in general, free of inflammatory cells. The transmucosal area demonstrated a tight connective tissue apposition to the implants. The sulcular epithelial appearance was similar to that of a natural tooth. Histomorphometric analysis revealed that 72.2 percent of the basket implant and 75.3 percent of the hydroxyapatite-coated implant were in direct contact with bone. Generally, the bone along the surface of the basket implant was thicker than the bone along the surface of the hydroxyapatite-coated cylinder. Bone grew through the vent hole areas of both implants.

The influence of maxillary sinus augmentation on the success of dental implants through second-stage surgery

An interim evaluation of the status of 102 implants placed in 42 augmented sinuses in 27 patients involved in an alternate category of the Dental Implant Clinical Research Group's long-term, randomized, prospective clinical investigation is presented. Autogeneic, allogeneic, and alloplastic sinus grafts were used, individually or mixed. Through second-stage surgery, 101 implants were found to be integrated. The mean Periotest value at uncovering was -3.36, with a standard deviation of 4.19. The results suggest that root form implants placed in augmented sinuses are successful through second-stage surgery, regardless of the augmentation material or implant design used.

The XcpR protein of Pseudomonas aeruginosa dimerizes via its N-terminus

Extracellular protein secretion by the main terminal branch of the general secretory pathway in Pseudomonas aeruginosa requires a secretion machinery comprising the products of at least 12 genes. One of the components of this machinery, the XcpR protein, belongs to a large family of related proteins distinguished by the presence of a highly conserved nucleotide binding domain (Walker box A). The XcpR protein is essential for the process of extracellular secretion and amino acid substitutions within the Walker A sequence result in inactive XcpR. The same mutations exert a dominant negative effect on protein secretion when expressed in wild-type bacteria. Transdominance of XcpR mutants suggests that this protein is involved in interactions with other components of the secretion machinery or that it functions as a multimer. In this study, the amino-terminal portion of the cl repressor protein of phage lambda was used as a reporter of dimerization in Escherichia coli following fusion to full-length as well as a truncated form of XcpR. The cl-XcpR hybrid proteins were able to dimerize, as demonstrated by the immunity of bacteria expressing them to killing by lambda phage. The full-length XcpR as well as several deletion mutants of XcpR were able to disrupt the dimerization of the chimeric cl-XcpR protein. The disruption of cl-XcpR dimers using the deletion mutants of XcpR, combined with the analysis of their dominant negative effects on protein secretion, was used to map the minimal dimerization domain of XcpR, which is located within an 85 amino acid region in its N-terminal domain. Taken together, the data presented in this paper suggest that the XcpR protein dimerizes via its N-terminus and that this dimerization is essential for extracellular protein secretion.

The influence of preoperative antibiotics on success of endosseous implants up to and including stage II surgery: a study of 2,641 implants

According to the American College of Surgeons, complex oral surgical procedures, including the transoral placement of endosseous implants, are of the type that may require prophylactic antibiotics. However, the routine use of prophylactic antibiotics in the field of dental implantology continues to be controversial, and their utilization varies widely. No data from a randomized prospective clinical study of the prophylactic use of antibiotics in implant surgery have been previously published. As part of the comprehensive Dental Implant Clinical Research Group clinical implant study, the preoperative or postoperative use of antibiotics, the type used, and the duration of coverage was left to the discretion of the surgeon. These data were recorded and correlated with failure of osseointegration during healing (stage I) and at stage II surgery (uncovering). The results showed that significantly fewer failures occurred when preoperative antibiotics were used.

Translation of ODC mRNA and polyamine transport are suppressed in ras-transformed CREF cells by depleting translation initiation factor 4E

Rapid tumor growth and metastasis require increased polyamine metabolism, which is coordinately regulated by ornithine decarboxylase (ODC) and the polyamine transporter. Both activities are stimulated by ras signalling and are dependent upon protein biosynthesis. T24ras oncogene expression in rat embryo fibroblasts (CREFT24) induces cellular transformation and malignancy, in part, by stimulating the rate-limiting translation initiation factor, eIF-4E. CREFT24 expressing antisense RNA to eIF-4E (AS4E) have markedly decreased tumor growth rates and metastatic capacity, without altered monolayer growth rates. Herein, we demonstrate that in AS4E, ODC is translationally suppressed resulting in decreased ODC activity. Additionally, exogenous polyamine uptake is suppressed in AS4E cells indicating that AS4E can neither generate nor import the polyamines necessary to support rapid tumor growth. These data provide evidence that eIF-4E is the link between ras-induced malignancy and increased polyamine metabolism and support the hypothesis that eIF-4E plays a pivotal role in mediating ras-induced malignancy.

The sequences of hypF, hypC and hypD complete the hyp gene cluster required for hydrogenase activity in Bradyrhizobium japonicum

A region of DNA 6 kb downstream of the hydrogenase (H2ase) structural genes and directly downstream of the hypB gene of Bradyrhizobium japonicum was shown by mutational analysis to be necessary for H2ase synthesis. Sequencing of this region revealed two complete open reading frames, and the 5' fragment of a third ORF. They encode proteins with homologies to the HypF, HypC and the N-terminus of HypD from other H2ase-containing organisms. The hypF of B. japonicum encodes a 753-aa protein with a predicted molecular mass of 80.3 kDa that contains the two zinc-finger motifs characteristic of other HypF proteins. The hypC encodes a 85-aa protein with a predicted molecular mass of 8.4 kDa. The 5' portion of hypD, which encodes the first 35 aa, upon combining with the previously reported C-terminus of HypD, designated HypD' (Van Soom et al. (1993) Mol. Gen. Genet. 239, 235-240) encodes a protein with a predicted molecular mass of 42.4 kDa. Complementation studies on a H2 uptake defective strain of B. japonicum containing a polar mutation in the hyp operon revealed that the products of the hyp F, C, D, E genes are required for H2ase production. Evidence is also presented that the hyp genes are co-transcribed from a large operon together with the downstream genes hupGHIJK, making a polycistronic message of 11 genes.

Multiple polyamine regulatory pathways control compensatory cardiovascular hypertrophy in coarctation hypertension

While a number of factors may initiate structural alterations within the cardiovascular system in response to hypertension, there are obligate cellular signaling mechanisms, such as the polyamines, through which they must operate. This study examined the effects of polyamine synthesis inhibition using eflornithine, a suicide inhibitor of ornithine decarboxylase on blood pressure, compensatory remodeling of the cardiovascular system, and cardiac and aortic polyamine contents using an aortic coarctation model in rats. Eflornithine treatment failed to reduce carotid arterial blood pressure and actually significantly elevated vascular pressure above and below the coarctation site by 14 days of hypertension. Eflornithine only transiently reduced aortic polyamine content of hypertensive rats while this agent reduced coarctation-induced aortic medial wall thickening and the synthesis/deposition of fibronectin and laminin in the hypertensive aorta. Increases in left ventricular mass and polyamine content were concomitantly reduced in hypertensive rats administered eflornithine. These results suggest that multiple polyamine regulatory pathways may maintain vascular polyamine content in response to aortic coarctation; however de novo polyamine synthesis is essential for select aspects of vascular remodeling, including matrix synthesis. Cardiac tissue, in contrast, may rely principally on de novo polyamine synthesis.

The HypB protein from Bradyrhizobium japonicum can store nickel and is required for the nickel-dependent transcriptional regulation of hydrogenase

The HypB protein from Bradyrhizobium japonicum is a metal-binding GTPase required for hydrogenase expression. In-frame mutagenesis of hypB resulted in strains that were partially or completely deficient in hydrogenase expression, depending on the degree of disruption of the gene. Complete deletion of the gene yielded a strain (JH delta Eg) which lacked hydrogenase activity under all conditions tested, including the situation as bacteroids from soybean nodules. Mutant strain JH delta 23H lacking only the N-terminal histidine-rich region (38 amino acids deleted, 23 of which are His residues) expressed partial hydrogenase activity. The activity of strain JH delta 23H was low in comparison to the wild type in 10-50 nM nickel levels, but could be cured to nearly wild-type levels by including 50 microM nickel during the derepression incubation. Studies on strains harbouring the hup promoter-lacZ fusion plasmid showed that the complete deletion of hypB nearly abolished hup promoter activity, whereas the histidine deletion mutant had 60% of the wild-type promoter activity in 50 microM NiCl2. Further evidence that HypB is required for hup promoter-binding activity was obtained from gel-shift assays. HypB could not be detected by immunoblotting when the cells were cultured heterotrophically, but when there was a switch to microaerobic conditions (1% partial pressure O2, 10% partial pressure H2) HypB was detected, and its expression preceded hydrogenase synthesis by 3-6 h. 63Ni accumulation by whole cells showed that both of the mutant strains accumulate less nickel than the wild-type strain at all time points tested during the derepression incubation. Wild-type cultures that received nickel during the HypB expression-specific period and were then washed and derepressed for hydrogenase without nickel had activities comparable to those cells that were derepressed for hydrogenase with nickel for the entire time period. In contrast to the wild type, strain JH delta 23H cultures supplied with nickel only during the HypB expression period achieved hydrogenase activities that were 30% of those cultures supplied with nickel for the entire hydrogenase derepression period. These results indicate that the loss of the metal-binding area of HypB causes a decrease in the ability of the cells to sequester and store nickel for later use in one or more hydrogenase expression steps.

Temporal alterations in basement membrane components in the pulmonary vasculature of the chronically hypoxic rat: impact of hypoxia and recovery

The hypoxic model of pulmonary hypertension was used to examine temporal alterations in the deposition of the basement membrane (BM) and components of fibronectin, laminin, and Type IV collagen within vascular, airway, and gas exchange compartments of the lung. Because hypoxic pulmonary hypertension is a reversible model of hypertension, changes in fibronectin and laminin synthesis/deposition in the recovering lung were also examined. Long-term hypoxic exposure produced decreases in body weight, increased right ventricular and lung dry weights and elevations in pulmonary arterial pressure. Immunohistochemical analysis revealed consistent and progressive increases in the deposition of fibronectin and laminin, but not type IV collagen, in the subendothelial and medial BMs of large and small pulmonary arteries, but not in airways or lung parenchyma. These changes were observed by day 4 of hypoxia and were most prominent in the conducting vasculature. Northern analysis showed a biphasic pattern of alterations in steady-state levels of BM component mRNA in hypoxic rats with early reductions at days 4 and 7 followed by increases at day 12. Recovery from 12 days of hypoxia resulted in regression of pulmonary hypertension and right ventricular hypertrophy but not increased lung weight. Immunohistochemical analysis of fibronectin, laminin, and type IV collagen levels in the vasculature showed a temporal regression to levels that were not remarkably different from time-matched controls at day 30 of recovery. Northern analysis of lungs from hypoxic-recovery rats revealed increased steady-state levels of mRNA for fibronectin, laminin, and type IV collagen at all time points. These data indicate that long-term hypoxic exposure elicits marked alterations in the synthetic capacity and deposition of the important cell attachment BM glycoproteins fibronectin and laminin. In addition, recovery from hypoxia appears to be characterized by a lack of increased fibronectin and laminin levels in the conducting vasculature, suggesting a marked and rapid reorganization of the vascular BMs on both hypoxic exposure and recovery from hypoxia.

Regulation of ornithine decarboxylase by hypoxia in pulmonary artery smooth muscle cells

The polyamines are a family of low-molecular-weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Elevations in cellular polyamine contents necessary for most physiological and pathological events in the lung appear to be driven by increase de novo synthesis. In contrast, increases in lung cell polyamines required for hypoxic pulmonary vascular disease can be attributed to augmented transmembrane polyamine transport which may, in turn, be the result of hypoxia-related decreases in the activity of the initial and generally rate-limiting enzyme in de novo polyamine synthesis, ornithine decarboxylase (ODC). To begin to define the unusual mechanism whereby hypoxia governs polyamine regulatory pathways, the present study examined the impact of varying severity and durations of hypoxic exposure on ODC activity and mRNA content in cultured bovine main pulmonary artery smooth muscle cells (PASMC). The effect of hypoxia on the activity of another rate-limiting enzyme in polyamine synthesis, S-adenosylmethionine decarboxylase (AdoMet-DC), also was examined. Hypoxia caused time-dependent decreases in ODC and AdoMet-DC activities that were related to the severity of hypoxic exposure. Similarly, ODC mRNA content also was depressed by hypoxic exposure. The relationship between the decline in ODC activity and mRNA content was roughly linear. To determine whether hypoxia impairs ODC mRNA stability, two different inhibitors of transcription and Northern analyses were used to follow the decay in ODC mRNA abundance in hypoxic and normoxic PASMC. Densitometric scanning of Northern analysis indicated that ODC mRNA stability did not differ between hypoxic and normoxic PASMC. These results suggest that the reduction in ODC activity provoked by hypoxia in cultured bovine PASMC can be ascribed in part to a diminished transcriptional rate rather than to alterations in mRNA stability.

The potential of a novel polyamine transport inhibitor in cancer chemotherapy

The polyamines, putrescine (PUT), spermidine (SPD) and spermine (SPM), are a family of low molecular weight organic cations that are essential for cell growth, differentiation and neoplastic transformation. The marked compensatory increase in extracellular polyamine influx may be a reason for the unsatisfactory clinical chemotherapeutic effect of polyamine synthesis blockers like difluoromethylornithine (DFMO). In this study, a polymeric conjugate of SPM (poly-SPM) that blocks the import of polyamines into mammalian cells was used to test the potential therapeutic exploitation of the polyamine transport system in anticancer therapy. Our results indicate that a temperature-dependent polyamine transport system is expressed in two human cancer cell lines, MES-SA uterine sarcoma cells, K562 leukemic cells and their respective multiple drug resistance (MDR) positive counterparts, Dx5 and K562/R7 cells. The V(max) values for 14C-PUT and 14C-SPD uptake were significantly higher in MES-SA than in Dx5 cells, whereas the respective Km values were significantly lower. Addition of 20 microM poly-SPM reduced both the uptake of 14C-polyamines and the cellular polyamine contents in both cancer cell lines. In addition, the poly-SPM conjugate evoked a concentration-dependent cytotoxicity in MES-SA and K562 cells and their MDR-positive variants. Presence of aminoguanidine, an amine oxidase blocker, failed to alter the IC50 values generated with poly-SPM, which indicates that this polymer is not a substrate for amine oxidase. Moreover, coadministration of 25 microM SPD reversed the cytotoxic effect exerted by poly-SPM on both the MES-SA and Dx5 cells as reflected by an increase in their IC50 values. Relative to parental cells, the MDR-positive variants exhibited a lower 14C-polyamine uptake rate and were more resistant to the cytotoxic effect of poly-SPM. Pretreatment with 1 mM DFMO for 24 hr significantly increased polyamine transport, but failed to reduce intracellular SPM contents or exert a cytotoxic effect in both cancer cell lines. On other hand, the combination of DFMO and poly-SPM produced a greater depletion of polyamine content accompanied by a higher cytotoxicity than either agent alone. These results provide the first direct evidence that pharmacologic interruption of polyamine uptake may be an effective approach to cancer therapy. In addition, it appears that expression of MDR influences polyamine transport and renders cells more resistant to the cytotoxic effects of SPM polymer.

Reversal of doxorubicin, etoposide, vinblastine, and taxol resistance in multidrug resistant human sarcoma cells by a polymer of spermine

We have previously described the synthesis of a cytotoxic polymeric conjugate of spermine (Poly-SPM) which is able to inhibit the transport of polyamines (spermine, spermidine, and putrescine) into normal and malignant cells. Recent studies examining the toxicity of Poly-SPM in parental and multidrug resistant (MDR) cancer cells have revealed a cross-resistance in the MDR variant Dx5 to the toxic effects of the conjugate in the MDR-positive cells. There were also differences in spermine and putrescine uptake rates between parental and MDR-positive with the MDR-positive cells having a lower Vmax and a higher Km. The ability of this Poly-SPM to reverse MDR was examined in MDR variants (Dx5 cells) of the human sarcoma cell line MES-SA. The cells express high levels of the mdr1 gene product, P-glycoprotein, and are 25-to 60-fold resistant to doxorubicin (DOX), etoposide (VP-16), vinblastine (VBL), and taxol (TAX). Cytotoxicity was measured by the MTT [3-(4,5-dimethyldiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay. Poly-SPM (50 microM) lowered the drug concentration IC50 values in the Dx5 cells by 37-fold with VBL, 42-fold with DOX, 29-fold with VP-16, and 25-fold with TAX when compared to the control IC50 values without Poly-SPM. This reversal of resistance was concentration dependent, decreasing 17-fold with DOX, 6.1-fold with VBL, 19-fold with VP-16, and 5-fold with TAX when 25 microM Poly-SPM was used. No modulation was observed in the parental cell line MES-SA, which does not express the mdr1 gene. Poly-SPM had no influence on the IC50 of non-MDR chemotherapeutic agents such as cisplatin. The modulation studies correlated with the ability of Poly-SPM to reverse the cellular accumulation defect of [3H]-VBL and [3H]-TAX in the Dx5 but not MES-SA cells. Pretreatment of the Dx5 cell with alpha-difluoromethylornithine (DFMO at 2 and 5 microM) for 24 h increased the function of the MDR transporter to further decrease the cellular accumulation of VBL and TAX when compared to untreated cells. DFMO pretreatment is known to upregulate the polyamine transporter(s). These findings show that, in addition to inhibiting polyamine transport, Poly-SPM reverses MDR in Dx5 cells, suggesting a potential relationship between the polyamine influx transporter and the MDR efflux pump. This potential functional link between the polyamine influx transporter(s) and the MDR efflux transporter (P-glycoprotein) offers a novel approach to inhibiting this form of drug resistance.

Temperature-dependent regulation of Yersinia enterocolitica Class III flagellar genes

Temperature is a key environmental cue for Yersinia enterocolitica as well as for the two other closely related pathogens, Yersinia pestis and Yersinia pseudotuberculosis. Between the range of 30 degrees C and 37 degrees C, Y. enterocolitica phase-varies between motility and plasmid-encoded virulence gene expression. To determine how temperature regulates Y. enterocolitica motility, we have been dissecting the flagellar regulatory hierarchy to determine at which level motility is blocked by elevated temperature (37 degrees C). Here we report the cloning, DNA sequences, and regulation of the two main regulators of Class III flagellar genes, fliA (sigma F) and flgM (anti-sigma F), and a third gene, flgN, which we show is required for filament assembly. Identification of the Y. enterocolitica fliA and flgM genes was accomplished by functional complementation of both S. typhimurium and Y. enterocolitica mutations and by DNA sequence analysis. The Y. enterocolitica fliA gene, encoding the flagellar-specific sigma-factor, sigma F, maps immediately downstream of the three flagellin structural genes. The flgM and flgN genes, encoding anti-sigma F and a gene product required for filament assembly, respectively, map downstream of the invasin (inv) gene but are transcribed in the opposite (convergent) direction. By using Northern blot analyses we show that transcription of both fliA and flgM is immediately arrested when cells are exposed to 37 degrees C, coincident with the timing of virulence gene induction. Unlike S. typhimurium flgM mutants, Y. enterocolitica flgM mutants are fully virulent.

A novel polymeric spermine conjugate inhibits polyamine transport in pulmonary artery smooth muscle cells

The polyamines putrescine, spermidine and spermine (SPM) are low molecular weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Whereas both de novo polyamine synthesis and transmembrane transport regulate cell polyamine contents, exploitation of pathways as pharmacologic targets has been limited by the lack of agents which specifically block polyamine transport. We now report the synthesis and biologic activity of novel polymeric glutaraldehyde conjugates of putrescine, spermidine and SPM which act at the cell membrane to inhibit polyamine uptake in cultured bovine pulmonary artery smooth muscle cells. Each conjugate caused dose-related inhibition of [14C]polyamine transport in pulmonary artery smooth muscle cells with the polymeric SPM conjugate being most effective in inhibiting the uptake of all three polyamines. Polymeric SPM failed to impair uptake of neutral or charged amino acids or to associate with pulmonary artery smooth muscle cells in a temperature-dependent manner. The polymeric SPM conjugate caused substantial decreases in cell polyamine contents which were associated with concentration-dependent cytotoxicity. Spectroscopic analyses of the polymeric SPM conjugate indicated that its molecular weight was 25 +/- 0.5 kDa, which is equivalent to approximately 90 monomeric--HN(CH2)3NH(CH2)4NH(CH2)3NH(CH2)5--units. These findings indicate that reduced polymeric glutaraldehyde conjugates of the polyamines may function as specific inhibitors of polyamine transport and thus provide a basis for examination of polyamine transport as a pharmacologic target in disorders characterized by dysregulated cell growth and differentiation.

HypB protein of Bradyrhizobium japonicum is a metal-binding GTPase capable of binding 18 divalent nickel ions per dimer

Bradyrhizobium japonicum hypB encodes a protein containing an extremely histidine-rich region (24 histidine residues within a 39-amino-acid stretch) and guanine nucleotide-binding domains. The product of the hypB gene was overexpressed in Escherichia coli and purified by Ni(2+)-charged metal chelate affinity chromatography (MCAC) in a single step. In SDS/PAGE, HypB migrated at 38 kDa--slightly larger than the calculated molecular mass (32.8 kDa). Purified HypB has GTPase activity with a kcat of 0.18 min-1 and a Km for GTP of 7 microM, and it has dGTPase activity as well. HypB exists as a dimer of molecular mass 78 kDa in native solution as determined by fast protein liquid chromatography on Superose 12. It binds 9.0 +/- 0.14 divalent nickel ions per monomer (18 Ni2+ per dimer) with a Kd of 2.3 microM; it also binds Zn2+, Cu2+, Co2+, Cd2+, and Mn2+. In-frame deletion of the histidine-rich region (deletion of 38 amino acids including 23 histidine residues) resulted in a truncated HypB that did not bind to the MCAC column, whereas in-frame deletion of 14 amino acids including 8 histidine residues within HypB resulted in a truncated HypB that still bound to the column. The results indicate that the histidine residues within the histidine-rich region of HypB are involved in metal binding.

Basic fibroblast growth factor alterations during development of monocrotaline-induced pulmonary hypertension in rats

The chemical signaling pathways which orchestrate lung cell responses in hypertensive pulmonary vascular disease are poorly understood. The present study examined temporal alterations in lung basic Fibroblast Growth Factor (bFGF) in a well characterized rat model of monocrotaline (MCT)-induced pulmonary hypertension. By immunohistochemical analysis, there were progressive increases in bFGF in airway, vascular and gas exchange regions of MCT-treated rat lungs. Increases in bFGF preceded the onset of right ventricular hypertrophy at day 21 after MCT administration. Enhanced bFGF immunostaining was observed as early as day 4 in focal areas of the parenchyma, and by day 14 there was enhanced bFGF staining in alveolar macrophages, neutrophils and alveolar septa, which persisted through day 21. In conducting airways, there was elevated bFGF immunostaining in the smooth muscle cell (SMC) layer by days 4 and 7 and in the ciliated epithelium and its basement membrane at days 14 and 21. Cells morphologically similar to Clara cells in the luminal surfaces of bronchioles stained intensely on days 14 and 21. In the nucleus and cytoplasm of medial SMCs within pulmonary arteries, there was a progressive increase in bFGF staining starting at day 4. Lung bFGF mRNA was increased slightly at days 1, 4 and 7, while lung bFGF protein, as judged by western blot analysis, was increased at days 14 and 21 compared to controls. The present results, considered in teh light of teh documented roles of bFGF in vascular cell migration, growth and synthesis of extracellular matrix components, suggest that bFGF may contribute to the structural remodeling processes underlying the development of chronic pulmonary hypertension in MCT-treated rats.

Monocrotaline alters type II pneumocyte morphology and polyamine regulation

Lungs from monocrotaline (MCT)-treated rats exhibit altered polyamine metabolism and content. One of the prominent morphological abnormalities in MCT-treated lungs is a decrease in population density of type II pneumocytes. Against this background, the present study tested the hypothesis that failure to maintain normal population density of type II pneumocytes is associated with MCT-induced derangements in polyamine biosynthesis and/or transmembrane polyamine transport. After a 24-hr treatment, cultured type II pneumocytes exhibited numerous vacuoles at the highest dose of 3.2 mM MCT but not at the lower dose of 1.6 mM MCT. Intracellular spermidine content was significantly reduced at the highest dose of MCT. Relative to controls, the abundance of mRNA for both ornithine decarboxylase, and S-adenosylmethionine decarboxylase, key regulatory enzymes in polyamine synthesis, was not altered. However, the activities of both of these enzymes were dramatically reduced. Increased mRNA for the catabolic polyamine enzyme, spermine/spermidine-N1-acetyltransferase (SAT), paralleled significant increases in SAT activity. MCT also caused a concentration-related inhibition of spermidine uptake in type II cells, characterized by a fourfold decrease in Vmax with little change in Km. These results show that MCT alters type II pneumocyte polyamine regulatory mechanisms and may help explain the decreased population density of type II pneumocytes in MCT-treated rats.

Role of ATP and sodium in polyamine transport in bovine pulmonary artery smooth cells

Increased polyamine transport may be a key mechanism driving elevations in lung cell polyamine content necessary for the development of chronic hypoxic pulmonary hypertension. Bovine pulmonary artery smooth muscle cells (PASMCs) in culture exhibit two carriers for polyamines, a non-selective one shared by the three polyamines, putrescine (PUT), spermidine (SPD), and spermine (SPM), and another that is selective for SPD and SPM. Hypoxia appears to up-regulate both carriers. In this study, we examined the role of ATP and the Na+ gradient in regulating polyamine transport in control PASMCs and in PASMCs with polyamine transport augmented by culture under hypoxic conditions (Po2: 15-30 torr). Inhibition of ATP synthesis with dinitrophenol+iodoacetate profoundly reduced polyamine uptake in both control and hypoxic PASMCs. Putrescine uptake was somewhat more sensitive to iso-osmotic replacement of extracellular Na+ with choline chloride or sucrose than were SPD or SPM in both hypoxic and standard cells, but under no conditions did Na+ replacement substantially alter polyamine uptake. Treatment of PASMCs with ouabain, a Na(+)-K+ ATPase inhibitor, or with gramicidin, a Na+ ionophore, minimally attenuated polyamine transport, whereas the Na+/K+ ionophore monensin increased polyamine uptake in standard, but not in hypoxic, cells. In general, the reduction in the extracellular Na+ content or ionophore-induced increases in Na+ permeability had a greater suppressive effect on polyamine transport in hypoxic cells than in standard cells, suggestive of the induction of Na(+)-dependent polyamine carriers by hypoxia. These observations indicate that the activities of the two putative polyamine transport pathways in standard PASMCs, as well as their up-regulation by hypoxia, require ATP synthesis. In addition, it appears that polyamine transport in PASMCs is composed of two components: one a prominent sodium-independent transporter and the other a relatively minor component that is sodium dependent. The latter may be activated by hypoxic exposure in combination with the induction of new polyamine carriers.

Eflornithine treatment in SHR: potential role of vascular polyamines and ornithine decarboxylase in hypertension

This study was performed to assess the potential role of polyamines in the alterations in vascular structure and function in spontaneously hypertensive rats (SHR). The effects of chronic administration of eflornithine (alpha-difluoromethylornithine; DFMO), a highly specific inhibitor of ornithine decarboxylase (the rate limiting enzyme in polyamine biosynthesis), on vascular polyamine contents, vascular structure and function, and blood pressure was studied. Male SHR (16-17 weeks of age) with an average systolic blood pressure (SBP) of 161 +/- 3 mmHg were used. The rats were divided into two groups and received either tap water or a 1% DFMO solution to drink for 6 weeks. SBP and body weight were recorded prior to and once-a-week during the experiment. Standard in vitro vascular reactivity studies on ring segments of aorta and tail artery were performed. Ring segment weight, arterial medial thickness, and vascular polyamine contents were also determined. Body weights were not significantly affected by the DFMO treatment. SBP in control SHR rose progressively to an average value of 185 +/- 5 mmHg by the sixth experimental week. Although DFMO treatment did not cause a significant decrease in SBP compared to pretreatment values, it did prevent a further increase in SBP. Aortic and tail artery responsiveness to norepinephrine and electrical stimulation, respectively, ring segment weight, arterial medial thickness, and vascular polyamine contents were all significantly less in SHR receiving the DFMO treatment. These data are the first to demonstrate the effectiveness of DFMO to lower polyamine contents in the vasculature of hypertensive SHR.(ABSTRACT TRUNCATED AT 250 WORDS)

Surfactant disposition in rats with monocrotaline-induced pneumotoxicity

Monocrotaline (MCT)-treated rats exhibit airways and gas exchange abnormalities which precede development of sustained pulmonary hypertension (Lai et al., 1991). Because the density of type II pneumocytes is reduced in MCT-treated rat lungs (Wilson and Segall, 1990), decreased abundance or activity of type II pneumocyte-derived surfactant may contribute to pulmonary dysfunction. On the other hand, since the remaining type II pneumocytes undergo an apparent hypertrophic response, it is possible that they compensate for the reduction in population density by elaborating more surfactant or surfactant with enhanced surface activity. As an initial means of discriminating between these possibilities, the amount, surface activity, and synthesis rate of surfactant was examined in rats at 1, 2, and 3 weeks after MCT administration. The amounts of surfactant phospholipid and protein recovered in bronchoalveolar lavage fluid did not differ substantially between control and MCT-treated rats at any time post MCT administration. Similarly, neither the initial rate of surface tension reduction nor the maximum reduction in surface tension differed between surfactant preparations recovered from control and MCT-treated rats. The rate of surfactant synthesis in lung explants, as determined by incorporation of [3H]glycerol into phospholipid, also was not different between MCT-treated and control rats at any time after MCT administration. MCT treatment failed to alter the distribution of [3H]glycerol into surfactant phospholipid. Collectively, these data indicate that airways abnormalities in MCT-treated rats cannot be ascribed to a reduction in the abundance or the activity of surfactant. Furthermore, in light of previous studies indicating that the density of type II pneumocytes is reduced in MCT pneumotoxicity, the present findings suggest that surfactant regulatory pathways must undergo a compensatory response that preserves normal functional status.

Multiple polyamine transport pathways in cultured pulmonary artery smooth muscle cells: regulation by hypoxia

The polyamines putrescine (PUT), spermidine (SPD), and spermine (SPM) are a family of low molecular weight organic cations that play essential intracellular regulatory roles in cell growth and differentiation. Consistent with this important function, increases in cellular polyamine contents are necessary for a variety of physiologic and pathologic events in the lung, including development of hypertensive pulmonary vascular disease secondary to chronic alveolar hypoxia. In intact rat lungs, hypoxia depresses ornithine decarboxylase activity, the initial rate-limiting enzyme in de novo polyamine synthesis, and enhances uptake of PUT from the vascular compartment, thus suggesting that increased polyamine transport is the driving mechanism behind hypoxia-induced increases in lung polyamine contents. Cultured bovine pulmonary artery smooth muscle cells (PASMCs) also express a transport system for SPD that is augmented by culture under hypoxic conditions. Because there may be multiple uptake pathways that are relatively selective for specific polyamines, the present study determined whether cultured bovine PASMCs expressed discrete transporters for [14C]PUT, [14C]SPD, and [14C]SPM, and whether they were differentially regulated by hypoxia. [14C]PUT, [14C]SPD, and [14C]SPM transport was examined in PASMCs cultured under "standard" (culture medium PO2: > 100 torr), "normoxic" (culture medium PO2: 50 to 70 torr), or "hypoxic" (culture medium PO2: 18 to 30 torr) conditions. Uptake of all three [14C]polyamines in cells cultured under standard conditions was temperature- and concentration-dependent, exhibited saturation kinetics, and could be modeled by Michaelis-Menten kinetics. In hypoxic PASMCs, values of Vmax for PUT, SPD, and SPM uptake increased by 3-, 2-, and 2-fold, respectively, relative to cells cultured under normoxic or standard incubator conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Temporal alterations in specific basement membrane components in lungs from monocrotaline-treated rats

The present study utilized the monocrotaline (MCT) model of pulmonary hypertension in rats to examine temporal alterations in steady-state levels of basement membrane (BM) component mRNA and deposition of protein using Northern analysis and immunohistochemistry, respectively. MCT (60 mg/kg, subcutaneous) produced sustained increases in lung dry tissue mass by 7 days, right ventricular mass by 14 days, and pulmonary arterial pressure by 21 days after administration. mRNA levels specific for laminin (LM) were elevated as early as 1 day after MCT treatment, while mRNA for all BM components examined except type IV collagen were increased in lungs from MCT-treated rats by day 4. Differences in LM, perlecan (PN), and type IV collagen-specific mRNAs from lung tissue between MCT-treated and control rats disappeared by day 14. In contrast, fibronectin (FN) mRNA remained elevated in lung tissue from MCT-treated rats from day 4 onward. Increases in immunolocalizable FN and LM in the vasculature, and PN and type IV collagen in gas exchange areas, were observed 4 days after MCT treatment compared with controls. These changes generally became more pronounced by 21 days after MCT administration, at which time the parenchyma of MCT-treated rats also demonstrated increases in immunolocalizable FN, LM, and BM-chondroitin sulfate proteoglycan (BM-CSPG). The pulmonary vasculature additionally showed increases in type IV collagen, PN, and BM-CSPG in MCT-treated rats compared with controls by 21 days. These observations suggest that the accumulation of specific BM components in the pulmonary vasculature and parenchyma may contribute to the pathogenesis and maintenance of MCT-induced hypertensive pulmonary vascular disease.

Alterations of growth factor transcripts in rat lungs during development of monocrotaline-induced pulmonary hypertension

Although pathologic and hemodynamic changes in monocrotaline (MCT)-induced pulmonary hypertension have been studied extensively, relatively little is known about the inter- and intracellular signaling mechanisms underlying such alterations. As a first step to delineating signaling mechanisms governing adverse structural alterations in the hypertensive lungs, we examined changes in the steady-state levels of mRNAs encoding several growth factors including transforming growth factors (TGF), platelet-derived growth factors (PDGF), vascular endothelial cell growth factor (VEGF) and endothelin (ET) as a function of time in MCT-induced pulmonary hypertension in rats. These studies demonstrated a very diverse pattern of growth factor gene expression in response to MCT administration. In general, alterations in the steady-state levels of mRNAs encoding the growth factors preceded the onset of MCT-induced pulmonary hypertension. TGF-beta 1, -beta 2 and -beta 3 transcripts were seen to be elevated, whereas that of TGF-alpha and PDGF-A remained unchanged. Transcripts for PDGF-B and ET were increased in the early stages but declined to less than controls in the latter stages of MCT-induced hypertension. In contrast, levels of VEGF mRNA decreased to less than controls as the disease progressed. Viewed collectively, the diverse pattern of expression suggests that alterations in the levels of the growth factor transcripts may have a significant role in the development of pulmonary hypertensive disease and may be relevant to the pathological and structural changes in MCT-induced pulmonary hypertension.

Expression of polyamine transporter activity during B lymphocyte cell cycle progression

The movement of resting B cells into the early stages of the cell cycle is accompanied by elevations in cellular polyamine levels. Our previous results indicate that part of this increase is a consequence of enhanced levels of ornithine decarboxylase activity in activated B cells. However, the levels of ornithine decarboxylase wane within 30 h post-stimulation, suggesting that B cells may acquire polyamines from an alternative source. Results in the present communication indicate that B cells initiate the transport of extracellular polyamines as they enter the G1 stage of the cell cycle. This induction of polyamine transport activity is seen after the stimulation of B cell cycle progression by both PMA and ionomycin, as well as cognate help from activated Th cells. The transport activities are energy and temperature sensitive, and can be competitively inhibited by unlabeled ligands. The results of the competition studies are compatible with the presence of at least two types of transporters, a low affinity transporter for both putrescine and spermidine, and a higher affinity transporter selective for spermidine. The results are discussed in terms of biochemical events associated with Th cell-mediated, B cell activation.

Expression of polyamine transporter activity during B lymphocyte cell cycle progression

The movement of resting B cells into the early stages of the cell cycle is accompanied by elevations in cellular polyamine levels. Our previous results indicate that part of this increase is a consequence of enhanced levels of ornithine decarboxylase activity in activated B cells. However, the levels of ornithine decarboxylase wane within 30 h post-stimulation, suggesting that B cells may acquire polyamines from an alternative source. Results in the present communication indicate that B cells initiate the transport of extracellular polyamines as they enter the G1 stage of the cell cycle. This induction of polyamine transport activity is seen after the stimulation of B cell cycle progression by both PMA and ionomycin, as well as cognate help from activated Th cells. The transport activities are energy and temperature sensitive, and can be competitively inhibited by unlabeled ligands. The results of the competition studies are compatible with the presence of at least two types of transporters, a low affinity transporter for both putrescine and spermidine, and a higher affinity transporter selective for spermidine. The results are discussed in terms of biochemical events associated with Th cell-mediated, B cell activation.

Transcription-independent activation of ornithine decarboxylase activity by heparin in cloned cerebral endothelial cells

Heparin, a highly sulfated glycosaminoglycan, is known to be obligatory for long-term endothelial cell cultures; it potentiates the mitogenic activities of endothelial cell growth factors and prolongs the replicative life span of the cells. Here we have shown that besides its growth factor-supportive role, heparin exerts a specific action on cerebral capillary endothelial cells (cECs), unrelated to serum or growth factors, by increasing activity of ornithine decarboxylase (ODC; EC 4.1.1.17) in these cells. For our experiments we have used two different types of cloned cECs: type I cECs, grown in the presence of endothelial cell growth factor and heparin, and type II cECs, usually cultivated without growth factors. Heparin action on ODC activity was shown to be dose dependent within the range of 1-100 micrograms/ml. Increasing concentrations of or depletion of endothelial cell growth factor from type I cultures had no effect on ODC activity. The increase in enzyme activity was highest after 30 min to 1 h of heparin treatment. As evidenced by northern analysis, the heparin-mediated enhancement of ODC activity was not accompanied by changes of ODC mRNA levels. Studies of DNA replication revealed that in the absence of heparin-binding growth factors, heparin did not affect the proliferative activity of cloned cECs.

Surface lysine and tyrosine residues are required for interaction of the major herpes simplex virus type 1 DNA-binding protein with single-stranded DNA

Modification of the herpes simplex virus type 1 major DNA-binding protein (ICP8) with reagents and conditions specific for arginine, lysine, and tyrosine residues indicates that surface lysine and tyrosine residues are required for the interaction of this protein with single-stranded DNA. Modification of either of these two amino acids resulted in a loss and/or modification of binding activity as judged by nitrocellulose filter assays and gel shift. Modification specific for arginine residues did not affect binding within the limits of the assays used. Finally, quenching of the intrinsic tryptophan fluorescence of ICP8 in the presence of single-stranded DNA either suggests involvement of this amino acid in the binding reaction or reflects a conformational change in the protein upon binding.

Polyamine transport and ornithine decarboxylase activity in hypoxic pulmonary artery smooth muscle cells

Hypoxia causes remodeling of the pulmonary circulation that is dependent on increases in lungs polyamine contents. Mechanisms by which polyamines are regulated in hypoxic lung cells are unknown, but ornithine decarboxylase (ODC) activity, the initial enzyme in de novo biosynthesis, is depressed and polyamine transport is augmented in lungs from hypoxic rats (R.-T. Shiao et al. 1990. Am. J. Physiol. 259:L351-L358). To determine if hypoxia directly influences polyamine regulatory mechanisms in pulmonary vascular cells, we examined [14C]spermidine (SPD) transport and ODC activity in bovine main pulmonary artery smooth muscle cells (PASMCs) cultured under standard (culture medium Po2: greater than 100 mm Hg), "normoxic" (culture medium Po2: 50 to 70 mm Hg), or "hypoxic" (culture medium Po2: 18 to 30 mm Hg) conditions. Uptake of [14C]SPD in cells cultured under standard conditions was temperature- and concentration-dependent, exhibited saturation kinetics, and was abolished by metabolic inhibition. Modeling of transport according to Michaelis-Menten kinetics revealed that [14C]SPD uptake in cells cultured under standard conditions was characterized by Km and Vmax values of 0.78 microM and 4.5 pmol/min/10(6) cells, respectively. In comparison to cells cultured under standard conditions, Km was unaffected by culture under normoxic or hypoxic conditions while Vmax was increased to 18 pmol/min/10(6) cells in normoxic cells and to 33 pmol/min/10(6) cells in preparations cultured under hypoxic conditions. Inhibition of ODC with alpha-difluoromethylornithine (DFMO) also induced SPD transport, as evidenced by an increase in the Vmax to 65 pmol/min/10(6) cells. Both hypoxia- and DFMO-induced increases in [14C]SPD transport were suppressed by cycloheximide and actinomycin D, thus highlighting the importance of protein and RNA synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)

Polyamines, vascular smooth muscle, and deoxycorticosterone acetate-salt hypertension

This study was performed to determine if an alteration in vascular polyamine contents is associated with the development of deoxycorticosterone acetate-salt hypertension. The effects of chronic administration of alpha-difluoromethylornithine, a specific irreversible inhibitor of ornithine decarboxylase and thus polyamine biosynthesis, on vascular polyamine contents, structure, and function as well as the development of hypertension was studied. Control and deoxycorticosterone acetate-salt rats received either tap water or a drinking solution containing alpha-difluoromethylornithine for 6 weeks, during which period systolic blood pressures were recorded. Vascular reactivity studies were performed on rings of aorta and tail artery. Medial thickness, vessel weight, and vascular polyamine contents were also assessed in these arteries. alpha-difluoromethylornithine treatment had no significant effect on either systolic blood pressure or vascular structure, function, and polyamine contents of control animals. The elevation in blood pressure and the increase in medial thickness, ring weight, and vascular polyamine contents as well as altered vascular reactivity observed in deoxycorticosterone acetate-salt rats was significantly attenuated by alpha-difluoromethylornithine treatment. These results are the first to demonstrate that vascular polyamine contents are elevated in the deoxycorticosterone acetate-salt rat and that chronic alpha-difluoromethylornithine treatment prevents the rise in vascular polyamines as well as the elevation in blood pressure and attendant changes in the vasculature. Thus, the increase in vascular polyamines may comprise a critical link between the initiating stimuli and the alterations in vascular structure and function implicated in the pathogenesis of deoxycorticosterone acetate-salt hypertension.

The major herpes simplex virus type-1 DNA-binding protein is a zinc metalloprotein

The primary amino acid sequence of the major herpes simplex virus type 1 (HSV-1)-infected cell polypeptide 8 (ICP8) deduced from the DNA sequence of the unique long open reading frame 29 (UL29 ORF) contains a potential metal-binding domain of the form Cys-X2-5-Cys-X2-15-A-X2-4-A where A may be either histidine or cysteine and X is any amino acid. The putative metal-binding sequence in ICP8 encompasses residues 499-512 as follows: C-N-L-C-T-F-D-T-R-H-A-C-V-H-. Atomic absorption analysis of several preparations of ICP8 indicates the presence of 1 mol of zinc/mol of protein. The zinc is resistant to removal by dialysis against concentrations of EDTA which deplete zinc from alcohol dehydrogenase. The bound zinc can be removed by reaction with the reversible sulfhydryl reagent p-hydroxymercurimethylsulfonate and the zinc-depleted protein transiently retains DNA binding activity. Digestion of both native and zinc-depleted ICP8 with V8 protease indicates that the bound zinc is required for the structural integrity of the protein.

Lifetime toxicity/carcinogenicity studies of FD & C red no. 40 (allura red) in mice

FD & C Red No. 40 (allura red) was fed to Charles River HaM/ICR (CD-1) (study A) and CD-1 outbred (study B) mice as a dietary admixture in two separate lifetime toxicity/carcinogenicity studies. Each study included an in utero exposure phase during which the colouring was fed at dietary concentrations of 0.0, 0.37, 1.39 or 5.19% throughout the mating, gestation and lactation periods. After random selection, the lifetime exposure phase was initiated using the same dietary concentrations with 50 mice/sex/group in study A and 100 mice/sex/group in study B. Exposure was for 104 wk in study A and 109 wk in study B. No compound-related adverse effects were observed. The no-observable-adverse-effect level in these studies was 5.19%; approximately 7300 and 8300 mg/kg body weight/day for male and female mice, respectively.

The development of competence in resting B cells. The induction of cyclic AMP and ornithine decarboxylase activity after direct contact between B and T helper cells

In the present communication, an experimental approach is utilized that facilitates the study of biochemical processes induced in B cells after their interaction with Th cells. In this approach, Th cell clones are stimulated for 18 h upon anti-CD3-coated plates, fixed with paraformaldehyde, and added at a 2 to 3:1 ratio to small, resting B cells (isolated from Percoll gradients). Th cells not stimulated on anti-CD3-coated plates, but fixed with paraformaldehyde, serve as controls for these experiments. The activated, fixed Th cells induce a transient, sixfold increase in B cell levels of cAMP, as well as an increase in B cell expression of ornithine decarboxylase (ODC) activity. This enzyme initiates the synthesis of polyamines and has been shown to be increased as cells enter the growth phase. In addition, previous studies have shown that the cellular levels of ODC activity are controlled by a multi-tiered regulatory cascade. To examine this aspect, polyclonally stimulated B cells were studied. Such cells demonstrated a gradual increase in ODC mRNA levels that peaked between 6 and 15 h and can be partially explained by a three- to fourfold increase in mRNA stability but not by changes in the enzyme affinity for substrate. The increase in ODC mRNA occurs in the absence of protein synthesis, suggesting that the ODC gene is a member of the immediate/early gene family. Finally, the early increase in ODC mRNA was enhanced in cells in which cAMP levels were artificially elevated, suggesting the possibility that the cAMP-dependent signaling pathway participates during the regulation of this gene expression. The significance of these experimental results concerning the process of B cell activation is discussed.

The development of competence in resting B cells. The induction of cyclic AMP and ornithine decarboxylase activity after direct contact between B and T helper cells

In the present communication, an experimental approach is utilized that facilitates the study of biochemical processes induced in B cells after their interaction with Th cells. In this approach, Th cell clones are stimulated for 18 h upon anti-CD3-coated plates, fixed with paraformaldehyde, and added at a 2 to 3:1 ratio to small, resting B cells (isolated from Percoll gradients). Th cells not stimulated on anti-CD3-coated plates, but fixed with paraformaldehyde, serve as controls for these experiments. The activated, fixed Th cells induce a transient, sixfold increase in B cell levels of cAMP, as well as an increase in B cell expression of ornithine decarboxylase (ODC) activity. This enzyme initiates the synthesis of polyamines and has been shown to be increased as cells enter the growth phase. In addition, previous studies have shown that the cellular levels of ODC activity are controlled by a multi-tiered regulatory cascade. To examine this aspect, polyclonally stimulated B cells were studied. Such cells demonstrated a gradual increase in ODC mRNA levels that peaked between 6 and 15 h and can be partially explained by a three- to fourfold increase in mRNA stability but not by changes in the enzyme affinity for substrate. The increase in ODC mRNA occurs in the absence of protein synthesis, suggesting that the ODC gene is a member of the immediate/early gene family. Finally, the early increase in ODC mRNA was enhanced in cells in which cAMP levels were artificially elevated, suggesting the possibility that the cAMP-dependent signaling pathway participates during the regulation of this gene expression. The significance of these experimental results concerning the process of B cell activation is discussed.

Ventilatory dysfunction precedes pulmonary vascular changes in monocrotaline-treated rats

Rats with established monocrotaline (MCT)-induced pulmonary hypertension also exhibit a profound increase in lung resistance (RL) and a decrease in lung compliance. Because airway/lung dysfunction could precede and influence the evolution of MCT-induced pulmonary vascular disease, it is important to establish the temporal relationship between development of pulmonary hypertension and altered ventilatory function in MCT-treated rats. To resolve this issue, we segregated 47 young Sprague-Dawley rats into four groups: control (n = 13), MCT1 (n = 9), MCT2 (n = 11), and MCT3 (n = 14). Each MCT rat received a single subcutaneous injection of MCT (60 mg/kg) 1 MCT1), 2 (MCT2), or 3 (MCT3) wk before the functional study. At 1 wk after MCT, significant increases in RL and alveolar wall thickness were observed, as was a significant decrease in carbon monoxide diffusing capacity (DLCO). Medial thickness of pulmonary arteries (50-100 microns OD) and right ventricular hypertrophy were not observed until 2 and 3 wk post-MCT, respectively. Coincident with the right ventricular hypertrophy at 3 wk post-MCT were decreased DLCO and increased alveolar wall thickness and lung dry weight. Pressure-volume curves of air-filled and saline-filled lungs showed marked rightward shifts during the 1st and 2nd wk after MCT administration and then decreased at the 3rd wk. These data suggest that MCT-induced alterations in airway/lung function preceded those of pulmonary vasculature and, therefore, implicate airway/lung dysfunctions as potentially contributing to the later development of pulmonary vascular abnormalities.