Altered expression of surface protein WI-1 in genetically related strains of Blastomyces dermatitidis that differ in virulence regulates recognition of yeasts by human macrophages

The molecular basis for pathogenicity and virulence of the dimorphic fungus Blastomyces dermatitidis remains unknown. WI-1 is a major cell wall protein of B. dermatitidis yeasts and is a recognition target of both humoral and cell-mediated immunity. As an initial study to determine if WI-1 might be linked to virulence of B. dermatitidis, we quantified WI-1 expression on three genetically related strains that differ in their virulence for mice: wild-type virulent ATCC strain 26199, mutant ATCC strain 60915 (which is 10,000-fold reduced in virulence), and mutant ATCC strain 60916 (which is avirulent). Two principal alterations in WI-1 expression were observed in the mutants. First, the mutants express more WI-1 on their surface, as quantified by flow cytometry with monoclonal antibody to WI-1 and by radioimmunoassay, but the WI-1 on their cell wall is less extractable than that on the wild-type strain. Second, the mutants shed less WI-1 during culture and demonstrate impaired processing of shed WI-1. Surface alterations in WI-1 were accompanied by significant differences in the binding of the virulent and mutant strains to human monocyte-derived macrophages. Attachment of yeasts to macrophages paralleled and was proportional to the expression of WI-1. Compared with wild-type yeasts, both mutants bound to macrophages more rapidly and in two- to threefold-greater magnitude. Furthermore, about 75% of yeast binding to macrophages was inhibited by a Fab anti-WI-1 monoclonal antibody. These results suggest that altered WI-1 expression on attenuated and avirulent mutant B. dermatitidis yeasts greatly facilitates macrophage recognition and binding of yeasts and, in turn, may contribute to more rapid ingestion and killing in the host.

Utility of anti-WI-1 serological testing in the diagnosis of blastomycosis in Wisconsin residents

WI-1, a 120-kD protein found in the outer cell wall of Blastomyces dermatitidis, has been purified, labeled with 125I, and used as a target in a radioimmunoassay (RIA). In an assessment of the usefulness of anti-WI-1 serology in the diagnosis of blastomycosis, the RIA was used to test four panels of sera from residents of Wisconsin, a state in which blastomycosis is endemic. Twenty-four (75%) of 32 patients whose blastomycosis had been reported to the Wisconsin Division of Health had at least one serum sample positive for antibody to WI-1; 25 (93%) of 27 serum samples obtained from these patients within 60 days of diagnosis were positive. In an effort to simulate clinical practice, 132 serum samples were assayed from another 107 patients in whom blastomycosis was being considered as a cause of illness. The result was positive for at least one sample from 83% of the 23 patients with confirmed blastomycosis and from 5% of the 84 patients from whom the fungus was not documented. Serum samples from another five patients with blastomycosis identified during investigation of a 1990 outbreak in Oconto Falls, Wisconsin, also gave a positive result, whereas none of the serum specimens from 57 healthy family members or neighbors did so. Only three (0.56%) of 535 serum samples from random blood donors residing in two counties with a high annual incidence of blastomycosis were positive for antibody to WI-1. Modification of the RIA so that IgM rather than IgG antibody was detected did not enhance diagnostic sensitivity.(ABSTRACT TRUNCATED AT 250 WORDS)

Radiation and taxol effects on synchronized human cervical carcinoma cells

PURPOSE

To evaluate the effectiveness of the plant derived chemotherapeutic agent taxol alone and in combination with ionizing radiation on synchronous and asynchronous human cervical carcinoma cells and to define the mechanistic basis for this cytotoxic response.

METHODS AND MATERIALS

Asynchronous and synchronous cells (obtained by modified mitotic shake-off) derived from carcinomas of the human uterine cervix were treated with a range of concentrations of taxol (0, 1.0, 2.5, 5.0, 10.0 and 20.0 nM) for either 8, 24 or 48 h. Synchronized cell cycling was evaluated by counting mitotic indices and by uptake of bromodeoxyuridine (BrdUrd). Cells were irradiated (137Cs gamma rays at 1.12 Gy/min) alone and after taxol treatment and plating efficiencies and radiosensitivity determined.

RESULTS

Taxol treatment resulted in a dose time dependent loss of colony forming ability with 10 nM for 24 h producing about 10% cell survival. Irradiating taxol treated cells resulted in a strictly additive response in contrast to previous supra-additive results with astrocytoma and melanoma cells. Mitotically synchronized cells rapidly moved into G1 phase with a second mitotic peak at 28 h (total cycle time). Taxol treatment resulted in a continued accumulation of mitoses, and a failure and/or delay of entry of a fraction of cells into S phase after a G1 phase of at least 10 h. That is, taxol effects cell cycling at a stage other than G2/M. Irradiating (3 Gy) synchronized cells showed a 10-fold variation in sensitivity, with mitosis as the most sensitive phase with taxol alone resulting in some cytotoxicity and combined effects additive or less than additive.

CONCLUSION

Taxol effects these cervical carcinoma cells at other stages of the cell cycle than G2/M. This may explain the failure to obtain taxol radiosensitization with these cells and it may indicate that taxol has a multiplicity of actions with differences in effectiveness likely between cells of different origins.

The significance of patient appearance in predicting severity of injury

The observations of pallor, sweating, agitation and restlessness, at the time of an injured patient's admission to the resuscitation room, were compared with other more complex indices of injury severity and the ability of each observation to predict mortality was observed. The number of positive observations was significantly related to the Revised Trauma Score and the Injury Severity Score, and pallor was significantly related to mortality. The observation that an injured patient is pale is an important index of severity.

Comparison of percutaneous anaesthesia for venous cannulation after topical application of either amethocaine or EMLA cream

We have compared, in a double-blind study, the efficacy of topical amethocaine cream 1 g (5% w/w) in alleviating the pain of venous cannulation with that of 5% EMLA cream 2.5 g. One hundred and twenty unpremedicated female patients undergoing minor gynaecological surgery, were allocated randomly to one of four groups: 5% EMLA cream 2.5 g for 30 min: 5% EMLA cream 2.5 g for 60 min; amethocaine cream 1 g (5% w/w) for 30 min; amethocaine cream 1 g (5% w/w) for 60 min. After removal of the cream, venous cannulation was performed with an 18-gauge cannula. Patients assessed the pain experienced using a 100-mm visual analogue score and four-point rank score. In addition, a blinded observer assessed the patient's response to venous cannulation using a four-point rank score. Good analgesia was obtained in all groups and there was no statistically significant difference in pain scores between the groups.

Conserved linkage of early growth response 4, annexin 4, and transforming growth factor alpha on mouse chromosome 6

The mouse genes encoding early growth response 4 (Egr4), annexin IV (Anx4), and transforming growth factor alpha (Tgfa) have been mapped to a linkage group on mouse chromosome 6 that is conserved on human chromosome 2p11-p13. The genes are closely linked, with 0/215 recombinants between Anx4 and Tgfa and 1/215 recombinants between these genes and Egr4. The genes are located approximately 2 cM distal to mnd2, a mouse mutation causing neuromuscular disease. The results demonstrate that mnd2 is located at an internal position within this conserved linkage group.

Candida albicans exocellular antigens released into a synthetic culture medium: characterization and serological response in rabbits

Different exocellular extracts were isolated by concentrating the supernatants of yeast- and mycelial-phase Candida albicans cultures incubated in a synthetic medium. The only difference between the extracts obtained from the two phases was the presence in those obtained from mycelial cultures of a polysaccharide-rich, high-molecular-mass component, migrating in SDS-polyacrylamide gels at a position that would correspond to proteins with molecular masses of 245-265 kDa. The electrophoretic band patterns obtained before and after concanavalin A-Sepharose 4B affinity column treatments confirmed that the 245-265 kDa band was the only one of mannoprotein nature. The extract obtained from 24 h mycelial-phase culture (EA) was selected as the exocellular antigen for this work. The dry weight of EA obtained from 1 litre of culture medium was 30 mg; it contained 53% carbohydrate (18.3% glucose and 21.7% mannose measured by gas-liquid chromatography) and 10% protein. Rabbit antisera against EA were absorbed with yeast-phase organisms and used to stain Western blots of gels loaded with EAs. These antisera clearly recognized bands in the 21, 33 and 44 kDa areas. The antiserum obtained was employed to develop a double-antibody enzyme-linked immunosorbent assay for measuring EA concentrations in a culture medium. Most of the EA was released during the exponential phase of growth.

Insertional mutation of the hairless locus on mouse chromosome 14

Crosses between heterozygous transgenic mice from line 5053 produced offspring with progressive irreversible hair loss beginning at day 19. With increasing age, the skin of these animals became thicker and plicated in appearance. Histological analysis revealed the complete absence of normal hair follicles and numerous intradermic cystic structures, which enlarged with time and became filled with keratinaceous material. Test crosses demonstrated that the affected animals are homozygous for the transgene insertion. The clinical and histological phenotype of the new mutant closely resembles that of the rhino allele at the hairless locus on Chromosome (Chr) 14. Complementation tests and linkage analysis indicate that the transgene has interrupted the hairless locus. It has been demonstrated previously that mutation at the hr locus is accompanied by a variety of immune deficiencies. Many of the older affected transgenic mice developed an impetigo-like skin eruption which responded to antibiotic ointment and which may reflect impaired immune function. The transgenic allele, hrTgN5053Mm, will be useful for identification of the transcription unit of the hairless locus.

The spectrum of disease associated with a positive ANCA

This is a retrospective analysis of all patients with a raised titre of ANCA in a single centre over a two-year period. Sixty-five patients were identified and clinical data is presented for 58 of these-34 male and 24 female. The median age is 56 years (13-83). Fourteen patients had Wegener's granulomatosis, 14 microscopic polyarteritis nodosa and 30 had other diagnoses. The patients with unexpectedly positive results are discussed in detail. This study confirms the sensitivity of ANCA in Wegener's granulomatosis and microscopic polyarteritis nodosa but suggests that the test is not as specific as initially claimed.

Ombrotrophic peat as a medium for historical monitoring of heavy metal pollution

Knowledge of historical trends in heavy metal deposition can aid the study and impact prediction of contemporary pollution. For this purpose, analysis of ombrotrophic peat cores has proved a valuable complement to other sedimentary analyses. However, doubts still remain concerning the mobility of heavy metals in peat. The debate cannot be resolved until the behaviour of these elements in peat is better understood.Peat cores were collected from hollows and hummocks on Ringinglow Bog in the southern Pennines. The cores were sliced into contiguous 1-cm slices. Samples were analysed for total concentrations of major elements (Al, Ca, K, Mg, Na) and trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn) using atomic absorption spectrophotometry. Multivariate statistical analysis was conducted on the data.Preliminary results indicate relatively high concentrations of Cd, Cu, Fe, Pb and Zn reflecting the influence of industrial activities in Sheffield and Manchester. As aluminium, cadmium, copper, lead and zinc exhibit similar profiles they may be suitable surrogates for monitoring historical pollution. However, other elements (e.g. Fe, K, Mn, Na) are clearly influenced by bog hydrology or plant translocation and would be inappropriate monitors.

Immunologic recognition of a 25-amino acid repeat arrayed in tandem on a major antigen of Blastomyces dermatitidis

A 120-kD glycoprotein antigen abundantly expressed on Blastomyces dermatitidis yeasts is a target of cellular and humoral immune responses in human infection. To investigate the antigen and immune response more carefully at the molecular level, we screened an expression library from B. dermatitidis to identify clones that encode this antigen, designated WI-1. A 942-bp cDNA was isolated by immunologic screening with polyclonal, rabbit anti-WI-1 antiserum. Northern hybridization analysis showed that the cDNA hybridized to yeast message approximately equal to 3.9 kb. DNA and deduced protein sequence analysis of the clone demonstrated a 25-amino acid repeat arrayed in tandem, present in 4.5 copies near the 5' end, and rich in predicted antigenic epitopes. Further analysis showed strong homology in these tandem repeats with invasin, an adhesin of Yersiniae. Cloned cDNA was used to express a 30-kD fusion protein strongly recognized in western blots by rabbit anti-WI-1 antiserum, and by sera from all 35 blastomycosis patients studied. The fusion protein product of subcloned cDNA encoding only the tandem repeat also was strongly recognized in western blots by sera from the 35 blastomycosis patients, but not by sera from 10 histoplasmosis and 5 coccidioidomycosis patients. An antigen-inhibition radioimmunoassay showed that the tandem repeat alone completely eliminated rabbit and human anti-WI-1 antibody binding to radiolabeled native WI-1. From these results, we conclude that the 25-amino acid repeat of WI-1 displays an immunodominant B cell epitope, and that the carboxyl-terminus of the molecule exhibits an architecture that may promote adhesion of Blastomyces yeasts to host cells or extracellular matrix proteins and ultimately provide a clearer picture of the molecular pathogenesis of blastomycosis.

mnd2: a new mouse model of inherited motor neuron disease

The autosomal recessive mutation mnd2 results in early onset motor neuron disease with rapidly progressive paralysis, severe muscle wasting, regression of thymus and spleen, and death before 40 days of age. mnd2 has been mapped to mouse chromosome 6 with the gene order: centromere-Tcrb-Ly-2-Sftp-3-D6Mit4-mnd2-D6Mit 6, D6Mit9-D6Rck132-Raf-1, D6Mit11-D6Mit12-D6Mit14, mnd2 is located within a conserved linkage group with homologs on human chromosome 2p12-p13. Spinal motor neurons of homozygous affected animals are swollen and stain weakly, and electromyography revealed spontaneous activity characteristic of muscle denervation. Myelin staining was normal throughout the neuraxis. The clinical observations are consistent with a primary abnormality of lower motor neuron function. This new animal model will be of value for identification of a genetic defect responsible for motor neuron disease and for evaluation of new therapies.

An audit of outcome of treatment in acromegaly

In order to determine whether acromegaly is still associated with increased mortality, a hospital case note review of all patients with acromegaly followed up in Stoke-on-Trent since 1967 was carried out. Of 79 subjects identified, 51 are alive and being monitored and 28 have died. Mortality was compared to the general population by life table analysis. Secretion of growth hormone was assessed and compared in dead and alive patients. The effect of diabetes, hypertension, and growth hormone secretion on long-term outcome was assessed. Acromegaly is still associated with increased mortality, with an overall ratio of observed to expected deaths equal to 2.68 (95% C.I. 1.8-3.9; p < 0.001), but the survival of 31 (39%) patients whose growth hormone level had been reduced to below 5 mU/l was equal to that of the general population (O/E = 1.42; 95% C.I. 0.46-3.31: p > 0.05). The dead patients had had significantly higher growth hormone levels than those still alive, but mortality did not appear to be influenced by diabetes or hypertension. The cause of death was vascular in 57% of cases. Growth hormone hypersecretion is still associated with excess mortality in acromegaly. The present study suggests that the therapeutic objective should be to lower average daytime growth hormone levels to less than 5 mU/l. There is need for a large study to compare different modes of treatment in terms of their effect on growth hormone secretion and on long-term outcome.

Role Modeling: A Method for Teaching Caring in Nursing Education

This study focused on the belief of some nurse educators that caring cannot be taught directly and is learned by students from faculty role-modeling and faculty student interactions in clinical, classroom, and other situations. The purpose was to further explore these beliefs to determine if nursing students perceived that they learn caring behaviors through observing role-modeling by faculty, as well as to explore students' perceptions of other means by which they learn about caring. Since opportunities for faculty to model nurse caring behaviors in the clinical setting are varied and serendipitous, a videotaped scenario simulating a patient care situation, using professional actors, was created and shown to nursing students. The videotape was seen by 137 BSN and ADN students who then recorded their perceptions on a two-page open-ended questionnaire developed by the researchers. Results from this study indicated that students do learn about caring from faculty role-modeling, as well as from health care staff they encounter, often in a very paradoxical way. Many interesting and unintended results also occurred through the use of this research approach.

Indomethacin in severe twin-to-twin transfusion syndrome

Despite advances in maternal fetal medicine, the management of severe twin-to-twin transfusion syndrome in the second trimester presents a significant challenge. Presently, there is no uniformly accepted management protocol that is available for the treatment of this syndrome. We report the use of indomethacin in three cases of severe twin-to-twin transfusion syndrome in the second trimester. In the three cases of severe twin-to-twin transfusion syndrome no reduction of amniotic fluid in either sac was demonstrated. Two cases were complicated by single intrauterine fetal death within 72 hours of initiating indomethacin therapy. Because of our experience with these three cases, we conclude that indomethacin does not prevent perinatal mortality in patients with severe twin-to-twin transfusion syndrome.

Integrate osteopathic principles and practices in postgraduate medical education--now

We issue a call for an "osteopathic medical renaissance" in teaching osteopathic principles and osteopathic manipulative techniques. This article describes a seminar series in the postdoctoral training program at the College of Osteopathic Medicine of the Pacific. We ask osteopathic physicians to enhance their manual dexterity skills to better serve as role models for physicians-in-training. We challenge osteopathic physicians to stimulate a renewed emphasis in teaching distinctive osteopathic medical care.

The evolution of chronic pain among patients with musculoskeletal problems: a pilot study in primary care

Little is known about the evolution of chronic pain in primary care. Forty five patients with a four week history of musculoskeletal pain were assessed and followed up over 26 weeks by a research nurse using a structured interview and formal assessment instruments. Patients aged 18 to 65 years were recruited on presentation at two semirural Cheshire general practices and subsequently interviewed on a domiciliary visit. Twenty patients (44%) continued to have pain at 26 weeks and these patients were considered to have chronic pain. Nineteen patients had no pain after 12 weeks and a further six had no pain after 26 weeks; these patients together formed the group with acute pain. Comparing the two groups at entry into the study (pain of four weeks' duration) demonstrated significantly higher visual analogue scale scores for intensity of pain (P < 0.01) and a higher incidence of depression (P < 0.01) in the group which subsequently developed chronic pain. In this group, the presence of depression at 12 weeks was associated with higher visual analogue scale scores (P < 0.05) but at 26 weeks scores were similar in depressed and non-depressed patients. The correlation between visual analogue scale score for intensity of pain and the use of passive coping strategies to cope with pain appeared more strongly positive with duration of pain (P < 0.05 at 26 weeks). It is suggested that high pain intensity scores, the presence of depression, and the increasing use of passive coping strategies may be identifiable associations with the development of chronic pain. Areas for further research are identified.

Long term follow up of women after hysterectomy with a history of pre-invasive cancer of the cervix

OBJECTIVE

A long term review of women after hysterectomy with a history of pre-invasive carcinoma of the cervix.

DESIGN

193 women had cervical intra-epithelial neoplasia and two had adenocarcinoma in situ either at hysterectomy or at previous cone biopsy. These were followed up by annual cytology.

SETTING

South Glamorgan Health Authority.

SUBJECTS

Of 195 women who had a hysterectomy, 143 have been followed up cytologically for more than 10 years and 43 for more than 20 years: a total of 2800 women years of experience.

MAIN OUTCOME MEASURES

Timing of abnormal smears.

RESULTS

A detailed review of the five women with abnormal smears. The estimated percentage of women who remain negative is 98% at five years, 98.4%, at 10 years and 96.5% at 20 years.

CONCLUSION

Cytological screening of all women who had a hysterectomy with a history of CIN is indicated for the first two years after hysterectomy. Thereafter the estimated incidence of 0.7 per 1000 women years is higher than the general population but it is not a sufficient reason to screen more frequently. We recommend screening for the carcinoma of the vagina to be every three years which is the same screening frequency as for cervical carcinoma in the general population.

WI-1, a novel 120-kilodalton surface protein on Blastomyces dermatitidis yeast cells, is a target antigen of cell-mediated immunity in human blastomycosis

A large body of experimental data has demonstrated the central role of T cells in acquired resistance to the dimorphic fungus Blastomyces dermatitidis. We examined the human T-cell response to WI-1, a 120-kDa B. dermatitidis yeast cell surface protein recently shown to be an immunodominant antigen of the B-cell response in infected humans. Peripheral blood lymphocytes from 10 blastomycosis patients studied proliferated in response to WI-1 (mean, 19,431 cpm) and to the standard, crude cell wall antigen, Blastomyces alkali- and water-soluble antigen (B-ASWS) (mean, 19,131 cpm); lymphocytes from 10 histoplasmosis patients and 10 normal control subjects did not respond to WI-1. WI-1 stimulation of patient lymphocytes and rechallenge with WI-1 or B-ASWS showed that the antigens share immunodominant epitopes. Of 100 WI-1-responsive T-cell clones derived from peripheral blood, 10 were studied in detail to assess the phenotype, function, and ligands recognized. The clones exhibit the CD3+ CD4+ phenotype of helper T cells; 2 of 10 clones (and 21% of antigen-stimulated peripheral blood lymphocytes) use the V beta 8 T-cell receptor gene element to respond to WI-1. All the clones proliferate in response to both WI-1 and B-ASWS but not other fungal antigens, and some mediate potent cytolytic effects on WI-1- and B-ASWS-labeled targets. WI-1 recognition requires antigen processing and presentation of epitopes in association with HLA-DR (to noncytolytic clones) and HLA-DP (to cytolytic clones). From these findings, we conclude that CD4+ T cells with regulatory and cytolytic properties are involved in the development of acquired resistance of B. dermatitidis, that the cells are directed against WI-1, and that the manner of display of WI-1 peptide epitopes in conjunction with major histocompatibility complex class II may influence the profile of the immune response.

Localization of insulin-2 (Ins-2) and the obesity mutant tubby (tub) to distinct regions of mouse chromosome 7

A DNA mapping panel derived from an interspecific backcross was used to position the mouse insulin-2 locus (Ins-2) on Chromosome 7, near H19 (0/114 recombinants) and Th (1/114 recombinants). Ins-2 is part of a human-mouse conserved linkage group that includes Th, H19, and Igf-2. Analysis of segregation in the F2 generation from the cross C57BL/6J-tub/tub x CAST/Ei demonstrated that Ins-2 and the obesity mutant tubby (tub) are distinct loci, thus eliminating Ins-2 as a candidate gene for tub. These results also refine the estimated genetic distance between tub and Hbb to 2.4 +/- 1.4 cM. The predicted location for a human homolog of tubby is HSA 11p15.

Posterior lymph heart pressure and rate and lymph flow in the toad Bufo marinus in response to hydrated and dehydrated conditions

Posterior lymph heart pressure, rate and flow were measured in chronically cannulated Bufo marinus during normal hydrated and dehydrated conditions. A new surgical technique was developed which allowed direct and constant measurement of the functioning of the posterior lymph hearts with minimal disruption to normal lymph drainage. The mean intra-lymph-heart systolic pressure was 2.29 +/− 0.12 kPa for hydrated animals at rest, decreasing to 1.01 +/− 0.10 kPa after 24 h of dehydration. Similarly, lymph heart rate, which was 48.2 +/− 1.7 beats min-1 under hydrated conditions, decreased to 31.8 +/− 4.6 beats min-1 after 18 h of dehydration. Lymph flow decreased almost to zero during dehydration from a hydrated rate of 1.11 +/− 0.04 ml h-1 100 g-1. This is the first study to measure directly and to correlate these variables in an amphibian and to show specifically that pressure, rate and lymph flow are significantly reduced during periods of dehydration.

Identification of a novel annexin in Hydra vulgaris. Characterization, cDNA cloning, and protein kinase C phosphorylation of annexin XII

As a first step toward the elucidation of a simple animal model in which to investigate annexin function, we identified, isolated, and characterized a novel annexin from Hydra vulgaris, annexin XII. A hydra cDNA library was screened using a probe generated by polymerase chain reaction from primers based on the partial amino acid sequence of annexin XII. Annexin XII cDNA was cloned and the functional protein was expressed in high yields in Escherichia coli. The annexin XII cDNA sequence predicted a 316-amino acid protein that had between 44 and 54% sequence identity with the Ca2+-binding core domains of previously characterized vertebrate and Drosophila annexins. The amino-terminal domain of annexin XII did not have sequence similarity with other known annexins except at and around a site that resembled known protein kinase C (PKC) phosphorylation sites in other annexins. As anticipated from its sequence, annexin XII was a high affinity substrate for purified rat brain PKC; half-maximal phosphorylation occurred below 0.1 microM annexin XII, and incorporation of up to 0.8 mol of phosphate/mol of annexin XII was observed. A PKC-like activity in hydra extracts also phosphorylated annexin XII. In summary, hydra promises to be a valuable model system for investigating the biological function of annexins and for determining how this function is modulated by PKC phosphorylation.

Differential regulation of fos and jun gene expression and AP-1 cis-element activity by endothelin isopeptides. Possible implications for mitogenic signaling by endothelin

Endothelins (ET) are potent vasoconstrictor peptides that also function as mitogens for numerous cell types. Although regulation of second messenger pathways by ET peptides has been extensively investigated, little is known about the pathways of nuclear signaling by which ET controls gene expression. The present experiments investigated whether fos and jun contribute to nuclear signaling and gene regulation by ET isopeptides. ET isopeptides induced a subset of fos and jun mRNAs in mesangial cells, including c-fos, fra-1, c-jun, and JunB. fos and jun mRNAs were induced as members of the immediate-early gene response. Activation of the high affinity ET receptor moderately increased c-fos and fra-1 mRNA, whereas activation of the low affinity receptor markedly induced both fos and jun mRNAs. Thus, different ET receptor subtypes evoke distinct patterns of fos and jun induction. Prominent isopeptide- and cell-specific differences in the magnitude and kinetics of fos and jun expression were observed. Most striking was the marked elevation of c-fos steady-state mRNA and protein by ET-1, as compared with ET-3. In addition, ET-1, but not ET-3, increased transcriptional activity conferred by an AP-1 cis-element and directed collagenase gene expression. These results suggest that differential regulation of fos and jun expression and of AP-1 cis-element activity by ET isopeptides contributes to regulation of gene expression by ET. Furthermore, a role for AP-1 in mitogenic signaling by ET is suggested by the close correlation between AP-1 cis-element activity and cell growth.

Protein kinase C regulates activation of mitogen-activated protein kinase and induction of proto-oncogene c-fos by endothelin-1

Endothelins (ETs) are potent regulatory peptides that cause numerous phenotypic changes in glomerular mesangial cells including differential regulation of gene expression and mitogenesis. Although the second messengers produced by activated ET receptors are well characterized, little is known about pathways of nuclear signaling. In this report, we evaluate the role of a well-characterized effector linked to ET receptor activation, protein kinase C, in the stimulation of mitogen-activated protein kinase (p42-44mapk) and the induction of protooncogene c-fos. Stimulation of protein kinase C by phorbol ester was sufficient to increase p42-44mapk activity and induce c-fos. When ET-1 was added to mesangial cells depleted of protein kinase C, the increase in p42-44mapk was attenuated and the induction of c-fos was abolished. Taken together with previous data, these experiments suggest that protein kinase C, p42-44mapk, and c-fos constitute a pathway by which ET-1 regulates expression of mesangial cell genes. These effectors might have relevance to the role of ET-1 in cell growth and vascular remodeling.