Transcription factor Wilms' tumor 1 regulates developmental RNAs through 3' UTR interaction

Bharathavikru et al. show that Wilms’ tumour 1 (WT1) binds preferentially to 3′ UTRs of developmental targets, which are down-regulated upon WT1 depletion in cell culture and developing kidney mesenchyme. Combining experimental and computational analyses, they propose that WT1 influences key developmental and disease processes in part through regulating mRNA turnover.

Wilms’ tumor 1 (WT1) is essential for the development and homeostasis of multiple mesodermal tissues. Despite evidence for post-transcriptional roles, no endogenous WT1 target RNAs exist. Using RNA immunoprecipitation and UV cross-linking, we show that WT1 binds preferentially to 3′ untranslated regions (UTRs) of developmental targets. These target mRNAs are down-regulated upon WT1 depletion in cell culture and developing kidney mesenchyme. Wt1 deletion leads to rapid turnover of specific mRNAs. WT1 regulates reporter gene expression through interaction with 3′ UTR-binding sites. Combining experimental and computational analyses, we propose that WT1 influences key developmental and disease processes in part through regulating mRNA turnover.

Visceral and subcutaneous fat have different origins and evidence supports a mesothelial source

Fuelled by the obesity epidemic, there is considerable interest in the developmental origins of white adipose tissue (WAT) and the stem/progenitor cells from which it arises. While increased visceral fat mass is associated with metabolic dysfunction, increased subcutaneous WAT is protective. There are 6 visceral fat depots: perirenal, gonadal, epicardial, retroperitoneal, omental and mesenteric and it is a subject of much debate whether these have common developmental origins and whether this differs from subcutaneous WAT. Here we show that all 6 visceral WAT depots receive a significant contribution from cells expressing Wt1 late in gestation. Conversely, no subcutaneous WAT or brown adipose tissue (BAT) arises from Wt1 expressing cells. Postnatally, a subset of visceral WAT continues to arise from Wt1 expressing cells, consistent with the finding that Wt1 marks a proportion of cell populations enriched in WAT progenitors. We show all visceral fat depots have a mesothelial layer like the visceral organs with which they are associated and provide several lines of evidence that Wt1 expressing mesothelium can produce adipocytes. These results: reveal a major ontogenetic difference between visceral and subcutaneous WAT; pinpoint the lateral plate mesoderm as a major source of visceral WAT; support the notion that visceral WAT progenitors are heterogeneous; and suggest that mesothelium is a source of adipocytes.

WT1 regulates the expression of inhibitory chemokines during heart development

The embryonic epicardium is an important source of cardiovascular precursor cells and paracrine factors that are required for adequate heart formation. Signaling pathways regulated by WT1 that promote heart development have started to be described; however, there is little information on signaling pathways regulated by WT1 that could act in a negative manner. Transcriptome analysis of Wt1KO epicardial cells reveals an unexpected role for WT1 in repressing the expression of interferon-regulated genes that could be involved in a negative regulation of heart morphogenesis. Here, we showed that WT1 is required to repress the expression of the chemokines Ccl5 and Cxcl10 in epicardial cells. We observed an inverse correlation of Wt1 and the expression of Cxcl10 and Ccl5 during epicardium development. Chemokine receptor analyses of hearts from Wt1(gfp/+) mice demonstrate the differential expression of their chemokine receptors in GFP(+) epicardial enriched cells and GFP(-) cells. Functional assays demonstrate that CXCL10 and CCL5 inhibit epicardial cells migration and the proliferation of cardiomyocytes respectively. WT1 regulates the expression levels of Cxcl10 and Ccl5 in epicardial cells directly and indirectly through increasing the levels of IRF7. As epicardial cell reactivation after a myocardial damage is linked with WT1 expression, the present work has potential implications in adult heart repair.

A universal vector for high-efficiency multi-fragment recombineering of BACs and knock-in constructs

There is an increasing need for more efficient generation of transgenic constructs. Here we present a universal multi-site Gateway vector for use in recombineering reactions. Using transgenic mouse models, we show its use for the generation of BAC transgenics and targeting vectors. The modular nature of the vector allows for rapid modification of constructs to generate different versions of the same construct. As such it will help streamline the generation of series of related transgenic models.

A wt1-controlled chromatin switching mechanism underpins tissue-specific wnt4 activation and repression

Wt1 regulates the epithelial-mesenchymal transition (EMT) in the epicardium and the reverse process (MET) in kidney mesenchyme. The mechanisms underlying these reciprocal functions are unknown. Here, we show in both embryos and cultured cells that Wt1 regulates Wnt4 expression dichotomously. In kidney cells, Wt1 recruits Cbp and p300 as coactivators; in epicardial cells it enlists Basp1 as a corepressor. Surprisingly, in both tissues, Wt1 loss reciprocally switches the chromatin architecture of the entire Ctcf-bounded Wnt4 locus, but not the flanking regions; we term this mode of action "chromatin flip-flop." Ctcf and cohesin are dispensable for Wt1-mediated chromatin flip-flop but essential for maintaining the insulating boundaries. This work demonstrates that a developmental regulator coordinates chromatin boundaries with the transcriptional competence of the flanked region. These findings also have implications for hierarchical transcriptional regulation in development and disease.

Actin: a novel interaction partner of WT1 influencing its cell dynamic properties

The Wilms' tumour suppressor, WT1, is a zinc finger protein with key roles in normal development of the genitourinary system and tumourigenesis. Mutations or deletion of WT1 result in a spectrum of developmental disorders and susceptibility to Wilms' tumour in children. Ectopic expression of Wt1 associated with oncogenic functions has been observed in a large number of malignancies, including haematological and solid cancers. Although Wt1 is predominantly a nuclear protein in normal tissues, it is mostly cytoplasmic in the majority of Wt1-expressing tumours. Actin was identified in this study as a new WT1 interaction partner both in the nucleus and in the cytoplasm. We confirmed this interaction both in vitro and in vivo and started to explore its functional significance. Perturbation of the actin cytoskeleton moved Wt1 off the polysome fraction in the cytoplasm, cancelled its nucleo-cytoplasmic shuttling and altered Wt1 DNA- and RNA-binding abilities. These data have implications for Wt1 functions in relation to RNA metabolism and response to cytoskeletal alterations in cancer cells. Thus, our findings could shed more light on the functions of both these proteins and possibly pave way for the development of new cancer therapies.

High-efficiency Rosa26 knock-in vector construction for Cre-regulated overexpression and RNAi

INTRODUCTION

Rosa26 is a genomic mouse locus commonly used to knock-in cDNA constructs for ubiquitous or conditional gene expression in transgenic mice. However, the vectors generally used to generate Rosa26 knock-in constructs show instability problems, which have a severe impact on the efficiency of the system.

RESULTS

We have optimized the cloning procedure to generate targeting vectors for Cre-regulated expression of constructs within several days with minimal hands-on time, thereby enabling high-throughput approaches. We demonstrate that transient expression of Cre still results in expression of the construct, as shown by the expression level and via functional assays. In addition to its well-established possibilities in expressing cDNA constructs, we show that the Rosa26 locus can be used to drive expression of functional miRNA constructs from its endogenous promoter.

CONCLUSION

We provide a new high-efficiency cloning system for Rosa26 knock-in constructs to express either cDNA or miRNA fragments. Our system will enable high-throughput approaches for controlled expression of cDNA or miRNA constructs, with the latter providing a potential high-speed alternative for conditional knock-out models.

hnRNP-U directly interacts with WT1 and modulates WT1 transcriptional activation

The Wilms' tumour suppressor gene, WT1, encodes a zinc-finger protein that is mutated in Wilms' tumours and highly expressed in a wide variety of other malignancies. WT1 is a transcription factor that is likely to have additional, post-transcriptional, regulatory roles, although the molecular mechanisms by which WT1 acts remain poorly understood. We have combined genetic and biochemical approaches to show, that endogenous WT1 binds to heterogeneous nuclear ribonuclear protein U (hnRNP-U), that this interaction does not require any other proteins or nucleic acids, involves the zinc-fingers of WT1 and the middle domain of hnRNP-U, and that hnRNP-U can modulate WT1 transcriptional activation of a bona fide WT1 target gene. These findings increase our knowledge of how WT1 exerts its transcriptional regulatory role and suggests that hnRNP-U may be a candidate Wilms' tumour gene at 1q44.

The Wilms' tumour protein (WT1) shuttles between nucleus and cytoplasm and is present in functional polysomes

Mutations of the Wilms' tumour-1 (WT1) gene in humans can lead to childhood kidney cancer, life-threatening glomerular nephropathy and gonadal dysgenesis. The WT1 protein is normally expressed in the developing genitourinary tract, heart, spleen and adrenal glands and is crucial for their development, however it's function at the molecular level is yet to be fully understood. The protein is predominantly nuclear and there is evidence that the two different isoforms of WT1 (-KTS and +KTS) are involved in two different steps of gene expression control: transcription and RNA processing. In this study we report a novel property of WT1, namely that it shuttles between the nucleus and cytoplasm. Moreover, western blot analysis showed that between 10 and 50% of total cellular WT1 can be detected in the cytoplasm depending on the cell type. A significant proportion of cytoplasmic WT1 is in association with ribonucleoprotein particles (RNPs), which strengthens the idea of its involvement in RNA metabolism. Furthermore, we report that WT1 is associated with actively translating polysomes, extending even further the potential roles of WT1 and opening the possibility that it is involved in the regulation of translation. Interestingly, despite the functional differences between two of the WT1 isoforms (+/-KTS) within the nucleus, both isoforms share the shuttling property and are found in translating polysomes.

Expression in Xenopus oocytes shows that WT1 binds transcripts in vivo, with a central role for zinc finger one

The Wilms' tumour suppressor gene WT1 encodes a protein involved in urogenital development and disease. The salient feature of WT1 is the presence of four 'Krüppel'-type C(2)-H(2) zinc fingers in the C-terminus. Uniquely to WT1, an evolutionarily conserved alternative splicing event inserts three amino acids (KTS) between the third and fourth zinc fingers, which disrupts DNA binding. The ratio of +KTS:-KTS isoforms is crucial for normal development. Previous work has shown that WT1 (+KTS) interacts with splice factors and that WT1 zinc fingers, particularly zinc finger one, bind to RNA in vitro. In this study we investigate the role of zinc finger one and the +KTS splice in vivo by expressing tagged proteins in mammalian cells and Xenopus oocytes. We find that both full-length +/-KTS isoforms and deletion constructs that include zinc finger one co-sediment with ribonucleoprotein particles (RNP) on density gradients. In Xenopus oocytes both isoforms located to the lateral loops of lampbrush chromosomes. Strikingly, only the +KTS isoform was detected in B-snurposomes, but not when co-expressed with -KTS. However, co-expression of the C-terminus (amino acids 233-449, +KTS) resulted in snurposome staining, which is consistent with an in vivo interaction between isoforms via the N-terminus. Expressed WT1 was also detected in the RNA-rich granular component of nucleoli and co-immunoprecipitated with oocyte transcripts. Full-length WT1 was most stably bound to transcripts, followed by the C-terminus; the least stably bound was CTDeltaF1 (C-terminus minus zinc finger one). Expression of the transcription factor early growth response 1 (EGR1), whose three zinc fingers correspond to WT1 zinc fingers 2-4, caused general chromosomal loop retraction and transcriptional shut-down. However, a construct in which WT1 zinc finger one was added to EGR1 mimicked the properties of WT1 (-KTS). We suggest that in evolution, WT1 has acquired the ability to interact with transcripts and splice factors because of the modification of zinc finger one and the +KTS alternative splice.

Mice lacking the 68-amino-acid, mammal-specific N-terminal extension of WT1 develop normally and are fertile

Mutations in the Wilms' tumor 1 gene, WT1, cause pediatric nephroblastoma and the severe genitourinary disorders of Frasier and Denys-Drash syndromes. High levels of WT1 expression are found in the developing kidney, uterus, and testis--consistent with this finding, the WT1 knockout mouse demonstrates that WT1 is essential for normal genitourinary development. The WT1 gene encodes multiple isoforms of a zinc finger-containing protein by a combination of alternative splicing and alternative translation initiation. The use of an upstream, alternative CUG translation initiation codon specific to mammals results in the production of WT1 protein isoforms with a 68-amino-acid N-terminal extension. To determine the function in vivo of mammal-specific WT1 isoforms containing this extension, gene targeting was employed to introduce a subtle mutation into the WT1 gene. Homozygous mutant mice show a specific absence of the CUG-initiated WT1 isoforms yet develop normally to adulthood and are fertile. Detailed histological analysis revealed normal development of the genitourinary system.

Presence of WT1, the Wilm's tumor suppressor gene product, in nuclear poly(A)(+) ribonucleoprotein

The tumor suppressor gene WT1 encodes a zinc finger protein, which consists of four C-terminal C(2)-H(2) zinc fingers of the Krüppel type, and at the N terminus a Q/P-rich trans-regulatory domain, both characteristic of transcription factors. However, recent findings suggest that WT1 may also be involved in a post-transcriptional process. Specifically, WT1 isoforms containing the alternatively spliced exon 9 (+lysine-threonine-serine (KTS)) preferentially associate with nuclear speckles and co-immunoprecipitate splicing antigens (Larsson, S. H., Charlieu, J.-P., Miyagawa, K., Engelkamp, D., Rassoulzadegan, M., Ross, A., Cuzin, F., van Heyningen, V., and Hastie, N. D. (1995) Cell 81, 391-401); furthermore, WT1 has been shown to interact with the ubiquitous splicing factor U2AF65 (Davies, R. C., Calvo, C., Larsson, S. H., Lamond, A. I., and Hastie, N. D. (1998) Genes Dev. 12, 3217-3225) and binds to RNA in vitro (Caricasole, A., Duarte, A., Larsson, S. H., Hastie, N. D., Little, M., Holmes, G., Todorov, I., and Ward, A. (1996) Proc. Natl. Acad. Sci. U. S. A. 93, 7562-7566; Bardeesy, N., and Pelletier, J. (1998) Nucleic Acids Res. 26, 1784-1792). To extend these findings, we have fractionated nuclear extracts to see if particles containing WT1 have the properties of ribonucleoprotein (RNP). In summary, WT1 is enriched by oligo(dT) chromatography, as are U2AF65, the U5 small nuclear RNP-associated protein p116 and hnRNP A1. Gel filtration and sedimentation profiles suggest that WT1 is present in RNase-sensitive particles, >2 MDa in size, peaking at approximately 60 S, and approximately 1.27 g/cm(3) on Nycodenz. Similar results were obtained from two cell lines expressing WT1, fetal kidneys (day E17), and transiently transfected cells, suggesting that the presence of WT1 protein in nuclear poly(A)(+) RNP is a general aspect of WT1 function.

Diffusible component from the spore surface of the fungus Aspergillus fumigatus which inhibits the macrophage oxidative burst is distinct from gliotoxin and other hyphal toxins

BACKGROUND

The fungus Aspergillus fumigatus, whose spores are present ubiquitously in the air, causes a range of diseases in the human lung. A small molecular weight (< 10 kD) heat stable toxin released from the spores of clinical and environmental isolates of A fumigatus within minutes of deposition in aqueous solution has previously been described. A key effect of the toxin was to inhibit the oxidative burst of macrophages as measured by superoxide anion release. It was hypothesised that the toxin was one of the commonly found A fumigatus hyphal toxins such as gliotoxin. This inhibitor may be an important factor which allows the fungus to colonise the lung.

METHODS

The spore derived inhibitor was shown to inhibit the respiratory burst of rat alveolar macrophages, as measured by the generation of superoxide anion. Samples of the spore diffusate were subject to reversed phase high performance liquid chromatography (HPLC), thin layer chromatography (TLC), high performance thin layer chromatography (HPTLC), or organic extraction followed by TLC or HPLC to identify the presence of gliotoxin, fumagillin, helvolic acid, fumigaclavine-C, and aurasperone-C. Commercially obtained preparations of the toxins gliotoxin, fumagillin and helvolic acid and extracts enriched for fumigaclavine-C and aurasperone-C were used as internal and external standards and in the respiratory burst measurements.

RESULTS

Gliotoxin, fumagillin, helvolic acid, fumigaclavine-C, and aurasperone-C were not detected in spore derived diffusate using PHLC or TLC. Using extraction procedures with solvents known to extract gliotoxin from A fumigatus culture supernatants, no gliotoxin was detected in the spore derived diffusate. Commercial gliotoxin, fumagillin, and helvolic acid or extracts enriched for fumigaclavine-C and aurasperone-C did not inhibit the oxidative burst of macrophages.

CONCLUSIONS

The hypothesis that the spore derived toxin is one of the toxins derived from hyphae such as gliotoxin, helvolic acid, fumagillin, fumigaclavine-C, or aurasperone-C is not proved. The spore toxin may exert its effect through its ability to diffuse rapidly into the lung lining fluid, diminish the macrophage oxidative burst, and play a part in allowing A fumigatus to persist in the lung and manifest its well known pathogenic effects.

Inhibition of the transcription factors NF-kappa B and AP-1 underlies loss of cytokine gene expression in rat alveolar macrophages treated with a diffusible product from the spores of Aspergillus fumigatus

The spores of Aspergillus fumigatus have a survival advantage over other respirable fungal spores in the lung, leading to a number of lung diseases associated with this fungus. We have hypothesized that a component on the spore surface can inhibit the activation of alveolar macrophages, known to play an essential role in immune regulation in the lung. A diffusible product from the spores of A. fumigatus (AfD) inhibited the production of tumor necrosis factor alpha (TNF alpha) protein by alveolar macrophages in an enzyme-linked immunosorbent assay. Using a semiquantitative reverse transcription-polymerase chain reaction, we also demonstrated a potent inhibitory effect of AfD on the production of proinflammatory cytokine transcripts in rat alveolar macrophages. The inhibition occurred at the level of transcription, with AfD inhibiting the synthesis of TNF alpha-and interleukin 6 (IL-6)-specific mRNA transcripts. No effect was seen on the synthesis of interleukin 1 beta (IL-1 beta) cytokine transcripts or on the expression of the housekeeping gene beta-actin. Furthermore, AfD specifically inhibited the activation of nuclear transcription factors NF-kappa B and AP-1, both of which are required for the coordinate upregulation of transcription of the proinflammatory cytokines TNF alpha, IL-1 beta, and IL-6. We conclude that AfD can inhibit normal alveolar macrophage responses by selectively inhibiting the production of key inflammatory cytokines, and that the mechanism of inhibition is primarily at the level of transcriptional activation.

Inhibition of the alveolar macrophage oxidative burst by a diffusible component from the surface of the spores of the fungus Aspergillus fumigatus

BACKGROUND

Aspergillus fumigatus is a fungus that grows on dead and decaying organic matter in the environment and whose spores are present ubiquitously in the air. The fungus causes a range of diseases in the human lung. A study was undertaken to demonstrate and partially characterise an inhibitor of the macrophage respiratory burst from the surface of A fumigatus spores that could be an important factor in allowing the fungus to colonise the lung.

METHODS

The spore-derived inhibitor of the respiratory burst of rat alveolar macrophages, as measured by generation of superoxide anion, was demonstrated in Hank's balanced salt solution extracts of four clinical isolates and an environmental isolate of A fumigatus. The time course of the release of the inhibitor into aqueous solution was assessed and the cytotoxic potential of the spore-derived inhibitor towards macrophages was tested using the propidium iodide method. An oxygen electrode was used to confirm the superoxide anion measurements. Molecular weight cutoff filters were used to determine the size of the inhibitor as assessed in the respiratory burst assay and also by its ability to inhibit macrophage spreading on glass. The crude diffusate from the spore surface was fractionated by reversed phase high pressure liquid chromatography (HPLC) and the fractions analysed for inhibitory activity, protein, and carbohydrate content.

RESULTS

A small molecular weight (< 10 kD) heat stable toxin was released from the spores of clinical and environmental isolates of A fumigatus within minutes of deposition in aqueous solution. The key effect of the toxin demonstrated here was its ability to inhibit the oxidative burst of macrophages as measured by superoxide anion release. The inhibition was not due to cell death or detectable loss of membrane integrity as measured by permeability to propidium iodide. The toxin was not a scavenger of superoxide anion. Oxygen electrode studies suggested indirectly that the inhibitor acted to inhibit the assembly of the macrophage NADPH-oxidase complex. Fractions of < 10 kD also inhibited the spreading of alveolar macrophages, confirming that the toxin had an additional effect on macrophages that leads to loss of adherence or impairment of cytoskeletal function. In reversed phase HPLC fractions the inhibitory activity eluted with an associated carbohydrate, although the exact chemical nature of the toxin remains to be elucidated.

CONCLUSIONS

This spore toxin may, through its ability to diffuse rapidly into lung lining fluid, diminish the macrophage respiratory burst and play a part in allowing A fumigatus to persist in the lung and manifest its well known pathogenic effects. Future research will be focused on further molecular characterisation of the toxin and elaboration of the effect of the toxin on intracellular signalling pathways involved in the activation of alveolar macrophages.

Asbestos fibre length-dependent detachment injury to alveolar epithelial cells in vitro: role of a fibronectin-binding receptor

A short and a long fibre sample of amosite asbestos were tested for their effects on cells of the human Type 2 alveolar epithelial cell-line A549 in vitro. The long amosite sample was found to cause a rapid detachment of the epithelial cells live from their substratum. At the highest dose, on average 28% of the cells present were detached in this way. Studies on the mechanism of the detachment injury showed that it did not involve oxidants since it was not ameliorated by scavengers of active oxygen species. Neither was the effect reduced by treatment of the fibres with the iron chelator Desferal. Treatments reported to increase the interaction between fibres and cells, serum and poly-L-lysine, did not influence the detachment injury, nor did lung lining fluid. Conversely, the fibronectin tripeptide RGD alone could cause detachment which suggested that a fibronectin-binding integrin was involved. This receptor could be reduced in activity by long fibre exposure, leading to detachment. The detaching effect of fibre could be mimicked by the protein kinase C activator PMA, and so the second messenger system of the cell could also be involved. This type of injury could be important in the pathology associated with exposure to long fibres.

Leukocyte-mediated epithelial injury in ozone-exposed rat lung

Both epithelial injury and inflammation are characteristic findings in the centriacinar regions of the lungs of rats exposed to ozone. In humans such effects could lead to long-term lung damage and disease. In animals, neoplastic change in the lungs after exposure to ozone has been described previously. The possible relationships between inflammatory cell recruitment, epithelial injury, and hyperplasia, with special regard to the important role of repair processes in leading to increased incidence of tumors in some species, have been addressed in the present study. We have previously described that leukocytes from lungs inflamed by different agents can injure epithelial cells in vitro. We have suggested that this leukocyte-mediated epithelial injury could enhance epithelial turnover in ozone-exposed lungs and so enhance the likelihood of tumor development. We, therefore, set out to test the hypothesis that bronchoalveolar leukocytes from ozone-exposed lungs can injure epithelial cells in vitro. PVG rats were exposed to 0.2, 0.4, 0.6, and 0.8 parts per million2 (ppm) ozone for seven hours per day for up to four days. On the morning following the last exposure, bronchoalveolar lavage was used to sample the bronchoalveolar leukocytes and the following parameters were assessed: total number, differential leukocyte count, production of oxidants, ability to degrade fibronectin, and ability to injure epithelial cells. In addition to these parameters, which were measured at all concentrations and time points in limited experiments, we also assessed macrophage size in short-term culture and inflammation in histological sections of lungs. Total number of lavageable cells was not affected by ozone inhalation. However, the percentage of macrophages decreased with ozone treatment and the percentage of neutrophils increased on days 1 and 2 at 0.6 and 0.8 ppm ozone. There was no significant effect of ozone exposure on the ability of neutrophils to degrade fibronectin or injure epithelial cells. Production of superoxide anion in response to stimulation with phorbol myristate acetate was significantly decreased by exposure to 0.6 ppm ozone, as described in previous studies. Macrophages from the lungs of rats exposed to ozone were larger than control macrophages.

Persistent biological reactivity of quartz in the lung: raised protease burden compared with a non-pathogenic mineral dust and microbial particles

This study assessed the potential harmfulness of particles in the lung by measuring their ability to elicit and maintain an inflammatory response and to damage lung tissue. It compared the inflammogenicity of two nondurable, biological particulates (Corynebacterium parvum and zymosan) with a pathogenic mineral dust (quartz) and a nonpathogenic dust (titanium dioxide) by dosing rats via the intratracheal route and measuring the consequent alveolitis. The magnitude and duration of the inflammatory response were assessed by measuring the total number of leucocytes and the percentage of neutrophils obtained by bronchoalveolar lavage. Two key functional parameters of the lavaged leucocytes--ability to degrade fibronectin and production of plasminogen activator--were also measured. A marked inflammatory response had occurred by one day after instillation, characterised by increases in total leucocyte numbers and percentage of neutrophils in the bronchoalveolar lavages, with all four test materials. In all but the quartz exposed animals, the inflammation subsided rapidly thereafter, approaching control levels by 15 days after injection; in the quartz exposed animals the alveolitis persisted for up to 30 days. All of the inflammogens generated chemotaxins in rat serum in vitro and so, by analogy, might also be expected to generate chemotactic activity in alveolar lining fluid which could contribute to the generation of an inflammatory response. The cellular inflammatory response was accompanied by a concomitant increase in the proteolytic activity of the bronchoalveolar lavage leucocytes but production of plasminogen activator remained unchanged. In vitro exposure to the inflammogens had no effect on the proteolytic activity against fibronectin or on the plasminogen activator activity of bronchoalveolar leucocytes.

Inflammation in the lungs of rats after deposition of dust collected from the air of wool mills: the role of epithelial injury and complement activation

In a previous study assessing respiratory symptoms in individuals employed in wool textile mills in the north of England relations between symptoms of chronic bronchitis, breathlessness and wheeze, and rhinitis and current exposure to airborne mass concentration of dust were shown. As preliminary steps in defining the potential hazard associated with dust from the air of wool mills the ability of inspirable dust, collected from the air of wool textile mills, to cause inflammation when injected into the lungs of rats was determined. Dusts were collected from the beginning of wool processing (opening) in one factory and from the middle (combing) and late (backwinding) stages of the process in two other factories. Ability of the dusts to cause inflammation was assessed by instillation into the lungs of rats followed by bronchoalveolar lavage. All the dusts caused some inflammation which peaked on day 1 and did not persist beyond one week. A distinctive aggregation response of mononuclear cells in the lavage, however, had a different time course, peaking at day 7. An attempt was made to determine how the wool mill dusts caused inflammation and experiments showed that the dusts themselves had no inherent chemotactic activity but that they did have a pronounced ability to generate chemotaxins in serum and so could activate complement in lung fluid. In addition, dust collected from ledges in the mills had the ability to injure epithelial cells in vitro which could also contribute to inflammation. A role for endotoxin in the inflammatory activity of the dusts was not discounted and a leachate of the dust had the ability to cause inflammation when injected into the lungs of rats. Wool mill dust is likely to be a complex mixture of materials and these experiments represent a preliminary approach to understanding the biological activity of the whole unfractionated dust and further studies are in progress to define more accurately the toxic material(s) in the dust.

Impaired chemotactic responses of bronchoalveolar leukocytes in experimental pneumoconiosis

Rats were exposed to clouds of the following pneumoconiotic dusts: quartz, coal-mine dust, and chrysotile asbestos at 10 or 50 mg/m3 for 8, 32, and 75 days; for comparison, rats were also exposed to the non-pathogenic dust titanium dioxide (TiO2). The bronchoalveolar leukocytes (macrophages and neutrophils) from dust-exposed and control rats were obtained by lavage and tested for their ability to migrate toward zymosan-activated serum. Varying amounts of neutrophils were present depending on the ability of the dust to cause inflammation and the length of exposure. There was a marked loss of chemotactic ability in leukocytes from rats inhaling the pneumoconiotic dusts compared with controls; TiO2-exposed leukocytes had some impairment of chemotaxis, but this was substantially less than that found with the pneumoconiotic dusts. The loss of chemotactic activity did not correlate with the percentage of neutrophils in the lavage cells except when there were very high levels of neutrophils, and there was substantial impairment of chemotaxis with negligible numbers of neutrophils, showing that macrophage chemotaxis was impaired. A phagocytic burden within the leucocytes was not sufficient alone to inhibit chemotaxis, nor was the loss of chemotactic activity due to occupied receptors, since incubation failed to restore chemotaxis. Loss to chemotactic activity by leukocytes from pneumoconiotic dust-exposed lung could be an important factor in the development of pneumoconiosis.

Effects of products from inflammatory pulmonary neutrophils on alveolar macrophage chemotaxis, spreading, and thymidine incorporation

Since macrophages and neutrophils are found together in the alveolar region of the lung during alveolar inflammation, we assessed whether neutrophil products could influence three key functions of alveolar macrophages: chemotaxis, spreading, and thymidine incorporation. Neutrophils were obtained from the lungs of rats treated by intratracheal instillation of heat-killed Corynebacterium parvum and cultured overnight, alone or in the presence of zymosan, PMA, an inert particulate (titanium dioxide), or a toxic dust, (quartz). Supernatants were collected from these cells and a lysate, obtained by freeze-thawing neutrophils, was also used. Neutrophil supernatants caused a slight reduction in chemotaxis and a significant loss of ability to spread on glass which varied depending on the in vitro treatment of the neutrophils. In addition neutrophil supernatants also had a substantial effect in stimulating uptake of thymidine which was, once again, very dependent on the treatment of the neutrophils during preparation of the supernatants, with unstimulated and TiO2-treated neutrophils producing maximum stimulation. The increases in thymidine uptake were not matched by increased proliferation, suggesting that another signal may be necessary for expanison of alveolar macrophage numbers during alveolar inflammation.

The effect of products from bronchoalveolar-derived neutrophils on oxidant production and phagocytic activity of alveolar macrophages

Neutrophils and alveolar macrophages are found together in the alveolar region during pulmonary inflammation where neutrophil products could influence important macrophage defensive functions. We set out therefore to investigate the ability of neutrophil products to modulate alveolar macrophage phagocytosis and oxidant production. Neutrophils derived from acutely inflamed rat lung were incubated along with a range of potential triggers of neutrophil secretion and supernatants collected. Using two quantitative assays of rat alveolar macrophage phagocytosis, the supernatants were found to have no effect except for the quartz supernatant, which slightly enhanced phagocytosis via non-specific receptors and the PMA supernatant, which caused reduction in phagocytosis via non-specific and Fc receptors; this reduction could however be mimicked by PMA alone. None of the supernatants affected macrophage production of superoxide anion or hydrogen peroxide except for the PMA supernatant and once again the inhibitory effect of the PMA supernatant could be mimicked with PMA alone. It is concluded that products of inflammatory neutrophils do not affect phagocytosis or oxidative metabolism of alveolar macrophages, although in quartz-exposed lung neutrophils may exert a small enhancing effect on macrophage phagocytosis.

Kinetics of the bronchoalveolar leucocyte response in rats during exposure to equal airborne mass concentrations of quartz, chrysotile asbestos, or titanium dioxide

The kinetics of the bronchoalveolar response was assessed in rats exposed, at equal airborne mass concentration (10 mg/m3), to titanium dioxide--a non-pathogenic dust--and the two pathogenic mineral dusts quartz and chrysotile asbestos. Rats were killed at intervals over a 75 day exposure period and groups of rats exposed for 32 and 75 days after recovery for two months. Bronchoalveolar lavage was carried out and the lavage fluid characterised for cellular content, macrophage activation, and concentrations of free total protein, lactate dehydrogenase, and N-acetyl-beta-D-glucosaminidase. Inhalation exposure to the two pathogenic dusts resulted in an increased number of leucocytes, macrophage activation, and increased levels of free enzymes and total protein. The pattern and magnitude of the responses to quartz and chrysotile differed. Chrysotile caused less inflammation than quartz, and the main cellular response peaked around the middle of the period of dust exposure whereas the highest levels of enzymes occurred towards the end. The difference in timing suggests that macrophages were not available for lavage towards the end of the exposure, owing to their playing a part possibly in deposition of granulation tissue. Quartz caused a greater cellular and enzyme response than chrysotile, particularly towards the end of the dust exposure phase. There was a noticeable progression of inflammation in the quartz exposed groups left to recover for two months, but not in the chrysotile recovery groups.

Oxidant production by control and inflammatory bronchoalveolar leukocyte populations treated with mineral dusts in vitro

Using a rat model we set out to determine whether exposure of bronchoalveolar-derived leukocytes to pathogenic mineral dusts in vitro caused them to undergo an oxidative burst and release potentially harmful oxidants. Three different populations, obtained by bronchoalveolar lavage, were chosen: control cells, cells obtained following instillation of heat-killed Corynebacterium parvum into the lung, and cells obtained following instillation of quartz. None of the populations showed any evidence of superoxide anion or hydrogen peroxide production when treated in vitro with the pathogenic dusts quartz and chrysotile asbestos, or the inert particulate titanium dioxide. Zymosan caused modest release of superoxide anion with all three populations, indicating that a respiratory burst was being provoked, while PMA, a soluble inducer of leukocyte oxidative burst, caused large-scale production of both oxidants. Preopsonization of mineral dust in rat serum did not render them capable of provoking an oxidative burst from lung-derived leukocytes.

The ability of inflammatory bronchoalveolar leucocyte populations elicited with microbes or mineral dust to injure alveolar epithelial cells and degrade extracellular matrix in vitro

Inflammatory cells are recruited to the parenchyma of the lung in a range of conditions where they are considered to have the ability to exert damaging effects on elements of the alveolus. The injurious effects of rat bronchoalveolar-derived inflammatory cells on an alveolar Type II epithelial cell line were therefore assessed. Inflammatory populations produced by intratracheal injection of Corynebacterium parvum or quartz caused non-lethal detachment injury to the epithelial cells on co-culture whereas control bronchoalveolar cells had no effect on epithelial cells. The pathogenic mineral dusts quartz and chrysotile asbestos caused increased detachment injury when added to co-cultures of epithelial cells and bronchoalveolar leucocyte populations; neither titanium dioxide, a control mineral dust, nor zymosan were active in this respect. Detachment injury was particularly marked when quartz was added to co-cultures of epithelial cells and inflammatory bronchoalveolar cells from quartz treated lung. On the basis of anti-protease and anti-oxidant studies, the detachment injury was found to be mediated by protease alone in the case of quartz cells and protease plus oxidant in the case of C. parvum cells. The two inflammatory bronchoalveolar cell populations were found to have increased proteolytic activity, compared to control bronchoalveolar cells, as shown by increased ability to degrade fibronectin, laminin and denatured collagen. Inflammatory bronchoalveolar cells therefore have the potential to attack elements of the septal extracellular matrix as well as to compromise the integrity of the alveolar epithelium.

In vitro fibrinolytic activity and viability of rat alveolar macrophages treated with inflammation generating mineral dusts

Rat alvolar macrophages demonstrated plasminogen dependent fibrinolysis in vitro which was inhibited to varying degrees by the addition of zymosan, the non-toxic particulate titanium dioxide, and the toxic dusts quartz and chrysotile asbestos. Assessment of viability suggested that the inhibition produced by zymosan and titanium dioxide could be accounted for by cytotoxic effects but in the case of quartz and chrysotile asbestos there was evidence that stimulation of fibrinolysis preceded cell death. Zymosan, which caused no observeable enhancement of alveolar macrophage fibrinolysis was found to markedly stimulate peritoneal macrophage fibrinolysis. The choice of assays of cell function to assess the action of toxic dusts are discussed.

A G-band study of chromosomes in liveborn infants

The results of a chromosome survey of 3993 liveborn infants, the majority of which have been studied using G-banding, are reported. The frequency of all types of chromosome abnormalities detected was similar to that found in previous newborn surveys, which were carried out on different socio-economic structure, but the incidence of aneuploid chromosome abnormalities was comparable in the two localities.