Activation of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in human lung microsomes by cytochromes P450, lipoxygenase, and hydroperoxides

4-(Methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), a potent tobacco-specific carcinogen, has been demonstrated to induce lung tumors in animals and is suspected to be a human carcinogen. Cytochromes P450 are the major enzymes responsible for the activation of NNK in microsomes from the lung and liver of rat and mouse, as well as human liver. The present study investigated the enzymes responsible for the metabolic activation of NNK in human lung microsomes. In the presence of a NADPH-generating system, the formation of keto aldehyde and keto alcohol (alpha-hydroxylation products, measured together), keto acid, hydroxy acid, and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol was observed in human lung microsomes. Carbon monoxide (90%) decreased the rate of NNK oxidation by 5-49%, depending on the human lung microsomal samples analyzed. Coumarin decreased the oxidation of NNK by 9-34%, and an antibody against human P450 2A6 decreased the metabolism of NNK by 8-37%, suggesting the involvement of P450 2A6 in NNK oxidation. alpha-Napthoflavone inhibited NNK oxidation by 6-26%, possibly due to the inhibition of P450 1A1. P450 1A1-expressed microsomes catalyzed the formation of keto aldehyde and keto alcohol, exhibiting Km values of 1400 microM and 371 microM, respectively. In the absence of NADPH, NNK metabolism resulted in the formation of keto acid, keto aldehyde, and keto alcohol, and the activities in different lung samples were decreased by indomethacin (100 microM; cyclooxygenase inhibitor) or nordihydroguaiaretic acid (100 microM; lipoxygenase inhibitor) by 0-27% or 30-66%, respectively. The addition of arachidonic acid (10-100 microM) increased the rate of the formation of keto aldehyde and keto alcohol approximately 2-fold but inhibited the formation of keto acid. Soybean lipoxygenase increased the rate of formation of keto aldehyde and keto alcohol in a concentration-dependent manner. The increased rate in NNK oxidation by arachidonic acid or lipoxygenase was inhibited completely by nordihydroguaiaretic acid. Catalase, thiourea, and conjugated linoleic acid decreased the rate of NNK oxidation by 47, 20, and 45%, respectively. tert-Butyl-hydroperoxide, cumene hydroperoxide, and hydrogen peroxide increased the rate of formation of keto aldehyde and keto alcohol by 210, 40, and 50%, respectively. The results suggest that P450 enzymes are only partially responsible for the activation of NNK in human lung microsomes, and P450 2A6 or a P450 2A6-related enzyme seems to be involved in the activation. Furthermore, lipoxygenase and lipid hydroxperoxides may play important roles in the oxidation of NNK in human lung microsomes.

Healthy worker effect in a longitudinal study of one-second forced expiratory volume (FEV1) and chronic exposure to granite dust

BACKGROUND

Low level effects of granite dust on one-second forced expiratory volume (FEV1) are estimated in 618 Vermont granite workers followed for 5 years with annual pulmonary function tests. Reduced pulmonary function has already been reported for the subset of subjects lost to follow-up (dropouts) suggesting possible bias in analyses based only on survivors.

METHOD

Healthy worker selection bias is directly assessed by comparing the dose-response associations between survivors who remained in the study for the full 5-year observation period and the dropouts.

RESULTS

The 353 survivors had an FEV1 of 96% of predicted at baseline and were losing FEV1 at an average rate of 44 ml/yr. No association was found in this group between the rate of FEV1 decline and lifetime dust exposure. However, the 265 workers with incomplete follow-up, 'dropouts', had a lower FEV1 at baseline (94%) and were losing FEV1 at an average rate of 69 ml/yr. The dose-response parameter in this group was estimated to be 4 ml/yr loss per mg/m3-year and was statistically significant.

CONCLUSIONS

These results provide an illustration of bias due to the healthy worker effect and an example of the failure to detect a true work-related health effect in a study based only on a 'survivor' population.

Differences in initial treatment patterns and outcomes of lung cancer in the elderly

BACKGROUND

Non-small cell lung cancer (NSCLC) accounts for substantial deaths and costs in the elderly greater than 65 years old. The current practice of NSCLC treatment in a Medicare population was examined to ascertain important areas of practice variation, and differences in clinical outcome and costs.

METHODS

Data from incident cases of NSCLC from the Virginia Cancer Registry (VCR), 1985-89, were matched with claims from Medicare Part A and B, census tract data and the Area Resource File. Multivariate models were created to include clinical data, demographics, and access information.

RESULTS

For patients with locoregional disease, increasing age was associated with lower likelihood of therapy (odds ratio (OR) 0.35; confidence intervals (CI) 0.29, 0.43), thoracotomy (OR 0.27; CI 0.21, 0.34), and more use of radiation therapy compared to surgery (OR 1.69; CI 1.39, 2.03). Low education levels were associated with less likelihood of treatment (OR 0.78; CI 0.66, 0.94), or radiation instead of surgery (OR 1.22; CI 1.05, 1.47). Patients in urban areas were less likely to receive therapy (OR 0.67; CI 0.49, 0.92). For distant disease, increasing age was also associated with lower likelihood of treatment (OR 0.48; CI 0.41, 0.56), as was increasing co-morbidity (OR 0.84; CI 0.75, 0.93). Distance to radiation oncologists made no difference in radiotherapy utilization. Two year survival according to therapy was surgery 66%, radiation 15%, no therapy 17%.

CONCLUSIONS

Patterns of care, and survival according to therapy, vary widely for elderly NSCLC patients. Age, low education, higher co-morbidity and urban residence all decrease the likelihood of surgical therapy for locoregional NSCLC. Despite the availability of coverage through the Medicare program, use of therapies and survival is not uniform for all beneficiaries. Possible discrimination by age, co-morbid illnesses not recorded in the Medicare files, or patient and provider choice could all be involved; administrative billing files cannot resolve these important differences.

Prostaglandin E2 alters human orbital fibroblast shape through a mechanism involving the generation of cyclic adenosine monophosphate

Orbital fibroblasts from patients with Graves' ophthalmopathy, when treated with prostaglandin E2 (PGE2), become stellate and develop prominent cellular processes. In this paper, we describe results of studies designed to characterize the action of PGE2 on orbital fibroblast shape changes in vitro. Orbital and dermal fibroblasts were incubated with PGE2, one of several prostanoid analogues, 8-br-cAMP or forskolin and were then visualized by phase-contrast microscopy. Other studies involved seeding cells in special chambers equipped with electrodes for cell sensing using electric cell-substrate impedance sensing (ECIS) to detect changes in shape. PGE2 (10(-7) mol/L) elicited a rapid and dramatic alteration in the shape of orbital fibroblasts but not those derived from the skin. Cells became stellate and developed prominent cytoplasmic processes that extended out from the central area containing the cell nucleus. The effects were stereoselective in that a number of structurally related compounds, including Sulprostone, PGI2, PGF2 alpha, thromboxane A2, thromboxane B2, and 11 deoxy,16,16 dimethyl PGE2 failed to elicit a similar shape change. Butaprost (10(-5) mol/L), a specific EP2 agonist, elicited a similar shape-change as that observed with PGE2. 16,16-dimethyl PGE2, a nonselective agonist, could mimic the action of PGE2. The effect of PGE2 was apparent at 10(-8) mol/L, maximal at a concentration of 10(-7) mol/L and took 4-8 hr to evolve completely. Cycloheximide (10 micrograms/mL) and actinomycin D (1 micrograms/mL) failed to block the shape change. The morphologic change could be reproduced by addition of 8-br-cAMP (3 mmol/L) and by forskolin (5 mumol/L). Moreover, PGE2 and Butaprost treatment elicited in orbital cultures a massive increase in endogenous cAMP production while analogues not affecting cell shape failed to influence cyclic nucleotide generation. Three strains of orbital fibroblasts from patients with Graves' ophthalmopathy and three from normal orbits were tested and all responded to PGE2 (10(-7) mol/L). Four strains of dermal fibroblasts failed to respond to PGE2. The changes in orbital fibroblast morphology were accompanied by a marked decrease in monolayer impedance as assessed by electric cell-substrate impedance sensing. The earliest effects were apparent within 30 min using this sensitive technique. The widely recognized roles of PGE2 and related compounds in the mediation of the inflammatory response make our current findings in orbital fibroblasts of potential importance to the pathogenesis of Graves' ophthalmopathy.

Putative receptor binding sites on alphaviruses as visualized by cryoelectron microscopy

The structures of Sindbis virus and Ross River virus complexed with Fab fragments from monoclonal antibodies have been determined from cryoelectron micrographs. Both antibodies chosen for this study bind to regions of the virions that have been implicated in cell-receptor recognition and recognize epitopes on the E2 glycoprotein. The two structures show that the Fab fragments bind to the outermost tip of the trimeric envelope spike protein. Hence, the same region of both the Sindbis virus and Ross River virus envelope spike is composed of E2 and is involved in recognition of the cellular receptor.

Cost effectiveness and other assessments of adjuvant therapies for early breast cancer

The 1992 metaanalysis of adjuvant therapies after surgery in early breast cancer summarizes the most extensively studied of all cancer treatments via randomized controlled trials. This study found overall benefits with use of adjuvant therapies, and their expanded use outside the clinical trial setting was assumed to be effective and implied to be cost effective. Thus, the primary remaining questions are which form of adjuvant therapy to use and how to identify which patients are unlikely to benefit. In British Columbia, the effectiveness of adjuvant therapy outside the clinical trial setting was reassuringly similar to the metaanalysis efficacy. Our decision analysis model of hypothetical cohorts of women with early breast cancer confirmed that the efficacy of adjuvant treatment is the primary determinate of its incremental cost effectiveness. Future cost-effectiveness and quality of life assessments should move from hypothetical cohorts assessed via models to prospective data collected within clinical trials or integrated health delivery system.

Decision analysis: a practical example

Cancer treatment is often perceived as too toxic, ineffective, and costly, compared with other medical treatments. Decision analysis attempts to define the effectiveness of alternative strategies, then incorporates patient preferences and the cost of care to allow comparisons of cost effectiveness. The provider benefits by being forced to "quantify the qualifiers" and explicitly determine which treatment is better and by how much. The health economist can use decision analysis to allocate resources based on the maximum years of life gained for the least amount of dollars spent. Clinical trialists can use decision analysis to ask "what if" questions about different alternative strategies or assumptions of effectiveness, or to perform computer simulations of interesting but untried clinical trials. Providers and payers can use dollars per life-year gained as one index to help rationally allocate resources. The authors present a practical example of the uses of decision analysis in determining the value to society of high-dose chemotherapy for high-risk stage II breast cancer patients.

Fiber exposure assessment in the Swedish rock wool and slag wool production industry in 1938-1990

OBJECTIVE

A multiplicative model was developed to assess past exposure to respirable fibers among rock wool and slag wool production workers in Sweden in 1938-1990.

METHODS

Information on the job titles, work tasks and employment times of 1487 workers exposed to man-made vitreous fibers was obtained from company records and interviews with older employees. A mathematical model developed earlier for assessing historical fiber exposure, based on factory averages, was further developed. Matrices of multipliers for each plant that were specific for job title were modified to assess fiber exposure with respect to job title and calendar period. The model was based on measurements made in 1977. Two methods of exposure assessment were compared, cumulative exposure based on factory average (model I) and cumulative exposure based on job title (model II).

RESULTS

The exposure changed considerably in the two factories during the period 1938-1990, and it varied also between job titles. The estimated average fiber (f) exposure level at the two plants in the middle of the 1940s was 1.32 and 0.78 f.ml-1. These values are 26 and 16 times higher, respectively, than the exposure in 1980. Process changes, as well as the addition of binders and oil, reduced the exposure drastically around 1950. The mean cumulative respirable fiber exposure for the 1487 subjects was 1.44 (range 0.05-18.40) f.ml-1.year. The cleaners had 14 times higher annual fiber exposure than the preproduction workers.

CONCLUSIONS

Model II was judged to be more valid than model I in assessing exposure to man-made vitreous fibers.

Depletion of cytochrome P-450 by thyroid hormone and cobalt-protoporphyrin IX in rat liver: evidence that susceptibility varies among forms of the heme protein

The ability of 3,5,3'-triiodothyronine (T3) and cobalt-protoporphyrin LX (CoPP) to alter the levels of the cytochrome P-450 isoforms, CYP3A2, CYP2E1, CYP2B1 and CYP2B2, was examined in vitro in thyroidectomized adult male rats. With the exception of CYP2B2, CoPP administration resulted in a decline in each of the cytochrome P450 isoforms examined. The effects of T3 administration on immunoreactive levels of cytochrome P-450 were also examined in the liver of thyroidectomized rats. T3 treatment produced a marked depletion in all four cytochrome P-450 isoforms examined. Moreover, this T3-mediated depletion of hepatic cytochrome P-450 occurred in the absence of elevated heme oxygenase levels but in the presence of increased delta-aminolevulinate synthase activity. Thus, CoPP and T3 appear capable of producing isoform-specific downregulation of cytochrome P-450 in the liver of thyroidectomized rats. Based on relative levels of immunoreactive protein, the phenobarbital-inducible isoforms, CYP2B1 and CYP2B2, are most susceptible to T3-mediated suppression. Evidence is presented to suggest that these agents elicit these effects by entirely different mechanisms.

Tumor biology of infiltrating lobular carcinoma. Implications for management

OBJECTIVE

The purpose of this study was to characterize the biologic determinants that affect the behavior and management of infiltrating lobular cancer.

METHODS

A prospectively accrued data base containing 1548 breast cancer cases was queried for specific pathologic and mammographic features. From this data base, 777 patients treated and followed-up at the H. Lee Moffitt Cancer Center were reviewed, and comparisons were made between the following three histologic subgroups: 661 infiltrating ductal (ID), 42 infiltrating ductal plus infiltrating lobular (ID + IL), and 74 infiltrating lobular (IL).

RESULTS

Comparisons of the three histologic forms of breast cancer demonstrated the following: 1. At diagnosis tumors with IL components were larger than those with ID components (p < 0.001); in addition, a greater percentage of IL cancers were T3 lesions (14.8%), compared with ID cancers (4.5%). 2. Sizes of IL tumors were underestimated frequently by mammographic examinations when compared with pathologic measurements (p < 0.001). 3. By comparison to ID tumors, increasing IL tumor size is less likely to be associated with an increased number of metastatic lymph nodes per patient (p = 0.09). 4. Infiltrating lobular cancers treated by lumpectomy with cytologic surgical margin analysis more often gave false-negative results than did ID cancers (p < 0.001). 5. Infiltrating lobular cancers treated by lumpectomy required conversion to mastectomy over 2 times more frequently than ID cancers treated by lumpectomy. 6. Mastectomy was performed more frequently than lumpectomy for the treatment of IL versus ID tumors (p = 0.039).

CONCLUSIONS

Infiltrating lobular cancers are biologically distinct from ID cancers. Although lumpectomy may be performed safely in selected patients, multiple difficulties exist in the management of IL cancer, particularly when breast conservation is chosen.

Angiotensin-converting enzyme (ACE) gene polymorphism in type II diabetic patients with increased albumin excretion rate

Approximately one in three patients with diabetes is at risk of developing kidney disease, despite current methods of treatment. It has long been suspected that diabetic kidney disease has a genetic basis, but this has been difficult to prove. Polymorphisms of the angiotensin-converting enzyme (ACE) gene have been shown to be related to the occurrence of nephropathy in type I diabetic patients. This study showed that there was no association in the ACE genotype frequency and increased albumin excretion rate in type II diabetic patients.

Ethical considerations in oncology: balancing the interests of patients, oncologists, and society

BACKGROUND

Oncologists face ethical dilemmas every day in deciding about choice of treatment, continuation of treatments, events near the end of life, conflicts of interest, and risk management. Yet, many oncologists have limited training in ethics.

METHODS

Review of existing studies and definitions of useful terms. Case studies analyzed according to ethical principles.

RESULTS

Individual oncology cases can be analyzed according to ethical principles with benefit to the patient, physician, and possibly society. Ethics cannot resolve many of the thorny questions about allocation of resources, justice, or possible conflict of interest.

CONCLUSION

Oncology decision-making fits into formal ethical frameworks, and understanding both can help doctors and patients make difficult choices. Understanding of ethical principles can help daily practice, but does not solve current dilemmas of allocation of resources, unrealistic demands, etc. More formal collaboration between hospital ethics committees or personnel and clinical oncologists is recommended for the day-to-day decision-making process.

Evidence for cellular heterogeneity in primary cultures of human orbital fibroblasts

Orbital fibroblasts in culture display phenotypic attributes that distinguish them from fibroblasts derived from other anatomical regions. The current studies were conducted to define potential cellular heterogeneity among orbital fibroblasts with regard to 1) differential expression of Thy-1, a 25-kilodalton glycoprotein associated with cell signaling; 2) cells undergoing a change in shape in response to prostaglandin E2 (PGE2); and 3) differences in morphology and Thy-1 expression between single cell-derived clonal fibroblast strains. On the basis of flow cytometric analysis using an anti-Thy-1 monoclonal antibody, 65% of intact orbital fibroblasts expressed surface Thy-1 (n = 5; range, 54-71%). In contrast, greater than 95% of the fibroblasts present in the five dermal strains tested were Thy-1 positive. A total of six strains of orbital fibroblasts were assessed for their shape change response to a 4-h treatment with PGE2 (100 nmol/L). A mean of 37% of the fibroblasts present in each culture responded to PGE2 (range, 22-50%). In contrast, only 1% of dermal fibroblasts exhibited any change in morphology. Three separate clones were generated from a single parent strain of Graves' orbital fibroblasts. These clones consisted of homogeneous appearing cells; however, substantial clone to clone differences in morphology were stably expressed for several population doublings. Thy-1 was expressed uniformly in cells of two clones, whereas the third was Thy-1 negative. Factor VIII and smooth muscle-specific alpha-actin were undetectable in any of the orbital or dermal cultures examined. Thus, Thy-1 expression is uniform in fibroblasts from certain anatomical regions such as the skin and heterogeneous in cells derived from human lung and orbit. These findings suggest that human orbital connective tissue may have a complexity not previously appreciated.

Free-riding and the prisoner's dilemma: problems in funding economic analyses of phase III cancer clinical trials

PURPOSE

Both economic and clinical data on new agents are important to policy-makers who approve pharmaceuticals for widespread use. Randomized clinical trials have been used to evaluate both clinical results and total medical costs associated with new agents. With new expensive pharmaceutical agents, early assessments of economic benefit have taken on greater importance to physicians and patients. Who should provide financial support to these integrated economic and clinical analyses in clinical trials? Here we describe issues that hinder funding of economic analyses and propose potential support mechanisms.

RESULTS

The Cancer and Leukemia Group B (CALGB), a large, national cooperative group of academic and community hospitals in the United States, designed a non-small-cell lung cancer (NSCLC) treatment trial to compare two widely used supportive care regimens that varied 20-fold in cost. One important objective of this trial was to compare the cost-effectiveness of the two regimens. While funding for the clinical trial was supported by grants from the National Cancer Institute and the pharmaceutical companies involved in the trial, no specific funding agency was willing and/or able to provide financial support for the economic analyses. After 2 years of planning, the clinical trial was retracted when the funding for the economic analyses could not be secured. The prisoner's dilemma, individual reluctance to support a common social good, explains the lack of funding.

CONCLUSION

Economic theory predicts difficulties in evaluating cost-effectiveness of new pharmaceuticals and reluctance to support economic analyses of clinical trials. Economic analyses will require new sources of funds that will not take scarce resources from clinical trials groups. Options for funding include a new federal agency, coordinated work by existing agencies, or academic centers for economic analysis.

Human orbital fibroblasts in culture express ganglioside profiles distinct from those in dermal fibroblasts

Orbital fibroblasts appear phenotypically distinct from those derived from dermis and other extraorbital anatomical sites. In this study, we examined the profile of gangliosides expressed by orbital and dermal fibroblasts. Gangliosides have a wide range of functions including modulation of transmembrane signal transduction. The aim of this study was to examine the hypothesis that a differential expression of gangliosides by orbital and nonorbital fibroblasts could constitute an important determinant of the immunological properties peculiar to the orbit. Moreover, these differences could provide a molecular basis for the site-specific involvement of the orbit in Graves' ophthalmopathy. Total lipids were extracted from confluent cultures of six different orbital and six dermal fibroblast strains, and purified gangliosides were subjected to two-dimensional thin layer chromatographic analysis. Orbital and dermal fibroblasts contained qualitatively similar ganglioside contents, with two major peaks, one migrating in the mono- and the other in the disialoganglioside regions of the chromatogram. In orbital fibroblasts, the densities of these two peaks were nearly equal, whereas in dermal fibroblasts, the monosialoganglioside peak was 5- to 6-fold greater. Minor ganglioside peaks were resolved and were equally abundant in orbital and dermal fibroblasts. Ganglioside profiles were invariant with respect to treatment of fibroblasts with interferon-gamma. These differences in expression of the two major ganglioside species may be relevant to the peculiarities associated with normal and pathological events in orbital connective tissue.

Economic evaluation of a randomized clinical trial comparing vinorelbine, vinorelbine plus cisplatin, and vindesine plus cisplatin for non-small-cell lung cancer

PURPOSE

To estimate the comparative cost-effectiveness of three regimens for metastatic non-small-cell lung cancer (NSCLC).

METHODS

Results from a randomized clinical trial of 612 European patients with NSCLC, and cost data from an academic cancer center, the Medical College of Virginia, were analyzed. In this post-hoc economic analysis, we compared vinorelbine alone, vinorelbine plus cisplatin, and a common regimen of vindesine plus cisplatin.

RESULTS

Vinorelbine plus cisplatin resulted in the longest mean survival time of the three regimens, 49.6 weeks, followed by vindesine plus cisplatin, 44.3 weeks, and vinorelbine, 41.6 weeks. Compared with vinorelbine alone, vinorelbine plus cisplatin added 56 days at a cost of $2,700, resulting in a cost-effectiveness ratio of $17,700 per year of life gained. Similarly, vindesine plus cisplatin added 19 days at a cost of $1,150, or $22,100 per year of life gained. Compared with vindesine plus cisplatin, vinorelbine plus cisplatin added 37 days at a cost of $1,570, or $15,500 per year of life gained.

CONCLUSION

The most effective regimen of vinorelbine plus cisplatin added substantial benefit compared with vinorelbine alone or another common treatment, vindesine plus cisplatin, at a cost-effectiveness within accepted limits for medical interventions. Vindesine plus cisplatin also added benefit at an acceptable cost per year of life gained. If vinorelbine is preferred because of its toxicity profile, the additional effectiveness of cisplatin added substantial benefit at an acceptable cost. Compared with other common medical interventions, chemotherapy for NSCLC has acceptable efficacy and cost-effectiveness and should not be arbitrarily denied based on clinical or economic grounds.

Structure and function of a virally encoded fungal toxin from Ustilago maydis: a fungal and mammalian Ca2+ channel inhibitor

BACKGROUND

The P4 strain of the corn smut fungus, Ustilago maydis, secretes a fungal toxin, KP4, encoded by a fungal virus (UMV4) that persistently infects its cells. UMV4, unlike most other (non-fungal) viruses, does not spread to uninfected cells by release into the extracellular milieu during its normal life cycle and is thus dependent upon host survival for replication. In symbiosis with the host fungus, UMV4 encodes KP4 to kill other competitive strains of U. maydis, thereby promoting both host and virus survival. KP4 belongs to a family of fungal toxins and determining its structure should lead to a better understanding of the function and evolutionary origins of these toxins. Elucidation of the mechanism of toxin action could lead to new anti-fungal agents against human pathogens.

RESULTS

We have determined the atomic structure of KP4 to 1.9 A resolution. KP4 belongs to the alpha/beta-sandwich family, and has a unique topology comprising a five-stranded antiparallel beta-sheet with two antiparallel alpha-helices lying at approximately 45 degrees to these strands. The structure has two left-handed beta alpha beta cross-overs and a basic protuberance extending from the beta-sheet. In vivo experiments demonstrated abrogation of toxin killing by Ca2+ and, to a lesser extent, Mg2+. These results led to experiments demonstrating that the toxin specifically inhibits voltage-gated Ca2+ channels in mammalian cells.

CONCLUSIONS

Similarities, although somewhat limited, between KP4 and scorpion toxins led us to investigate the possibility that the toxic effects of KP4 may be mediated by inhibition of cation channels. Our results suggest that certain properties of fungal Ca2+ channels are homologous to those in mammalian cells. KP4 may, therefore, be a new tool for studying mammalian Ca2+ channels and current mammalian Ca2+ channel inhibitors may be useful lead compounds for new anti-fungal agents.

Leukoregulin induces plasminogen activator inhibitor type 1 in human orbital fibroblasts

Leukoregulin, a 50-kDa T lymphocyte-derived cytokine, influences the synthesis of collagenase, stromelysin-1, collagen, and hyaluronan in human fibroblasts and is thus a determinant of extracellular matrix economy. We studied the effect of leukoregulin on the expression of plasminogen activator inhibitor type 1 (PAI-1) in human orbital and dermal fibroblasts. The lymphokine upregulated 35S-labeled PAI-1 protein expression in orbital fibroblasts in dose-dependent manner. The effect on extracellular matrix-associated PAI-1 evolved over several hours and was maximal at 10 h, when levels were 75-fold higher than controls, and then fell by 24 h. Leukoregulin treatment increased prostaglandin E2 production in orbital cultures after 24 h. When this increase was blocked with indomethacin, peak PAI-1 levels were maintained. Northern analysis demonstrated a substantial induction of steady-state PAI-1 mRNA levels within 6 h of treatment in orbital cultures. In contrast, leukoregulin lowered PAI-1 protein levels dramatically in skin fibroblasts from the abdominal wall. With regard to PAI-1 expression, it would appear that the anatomic site of origin of fibroblasts is a crucial determinant of the cellular response to leukoregulin.