Health consequences of exposure to aircraft contaminated air and fume events: a narrative review and medical protocol for the investigation of exposed aircrew and passengers

Thermally degraded engine oil and hydraulic fluid fumes contaminating aircraft cabin air conditioning systems have been well documented since the 1950s. Whilst organophosphates have been the main subject of interest, oil and hydraulic fumes in the air supply also contain ultrafine particles, numerous volatile organic hydrocarbons and thermally degraded products. We review the literature on the effects of fume events on aircrew health. Inhalation of these potentially toxic fumes is increasingly recognised to cause acute and long-term neurological, respiratory, cardiological and other symptoms. Cumulative exposure to regular small doses of toxic fumes is potentially damaging to health and may be exacerbated by a single higher-level exposure. Assessment is complex because of the limitations of considering the toxicity of individual substances in complex heated mixtures.There is a need for a systematic and consistent approach to diagnosis and treatment of persons who have been exposed to toxic fumes in aircraft cabins. The medical protocol presented in this paper has been written by internationally recognised experts and presents a consensus approach to the recognition, investigation and management of persons suffering from the toxic effects of inhaling thermally degraded engine oil and other fluids contaminating the air conditioning systems in aircraft, and includes actions and investigations for in-flight, immediately post-flight and late subsequent follow up.

Outdoor air pollution from industrial chemicals causing new onset of asthma or COPD: a systematic review protocol

Background

Until today, industrial sources contribute to the multifaceted contamination of environmental air. Exposure to air pollutants has the potential to initiate and promote asthma and chronic obstructive pulmonary disease (COPD). At global scale, both entities cause the majority of about 4 million annual deaths by respiratory disease. However, we identified industrial contamination as a subgroup of air pollution that may be associated with this burden and is underinvestigated in research. Therefore, the aim of this study is to investigate associations between substances industrially released into environmental air and the occurrence of asthma and COPD in the human population. Here we present the protocol for our systematic review of the current evidence.

Methods

The following determinations will be applied during the systematic review process and are specified in the protocol that complies with the PRISMA-P statement. Populations of children and adults, as well as outdoor workers, exposed to industrially released air pollutants are of interest. Eligible studies may include subjects as controls who are non- or less exposed to the investigated air pollutants. The outcomes new-onset asthma and/or COPD investigated with risk ratio, odds ratio, hazard ratio, incidence rate ratio, cumulative incidence, and incidence rate are eligible. We will search the electronic literature databases EMBASE, MEDLINE, and Web of Science for peer-reviewed reports of incidence studies and incidence case-control studies. After systematic sorting of initial records, included studies will be subjected to quality assessment. Data will be synthesized qualitatively and, if appropriate, quantitatively for risk ratio and odds ratio. We will maintain and provide a PRISMA report.

Discussion

Results of this systematic review may indicate alterations of incidence and risk of asthma and/or COPD in populations within industrial exposure radiuses including outdoor workplaces. Specific causal substances and compositions will be identified, but results will depend on the exposure assessment of the eligible studies. Our approach covers effects of industrial contributions to overall air pollution if studies reportedly attribute investigated emissions to industry. Results of this study may raise the question wether the available higher-level evidence sufficiently covers the current scale of industrial exposure scenarios and their potential harm to respiratory health.

Trial registration

This protocol was registered in PROSPERO, registration number CRD42020151573.

Comparative cyto- and genotoxicity assessment of glyphosate and glyphosate-based herbicides in human peripheral white blood cells

Glyphosate is the most heavily applied active compound of agricultural pesticides. It is solely used in more than 750 different glyphosate-based herbicide formulations (GBHs) that also contain other substances, mostly presumed as inert by regulatory agencies. The toxicity of formulations is currently assessed substance by substance, neglecting possible combined effects in mixtures and many of the findings regarding the toxic effects of glyphosate and GBHs to human cells are inconsistent. This is the first study to investigate and compare the cyto- and genotoxic potential of the active ingredient glyphosate and GBHs in human mononuclear white blood (HMWB) cells. HMWB cells were treated for 4 h at 37 °C with increasing concentrations (1-1000 μM) of glyphosate alone and in three GBHs (Roundup Mega, Fozat 480 and Glyfos) to test cytotoxic effect with fluorescent colabelling and genotoxic effect with comet assay. In addition, each concentration was tested with and without metabolic activation using human liver S9 fraction. We found that glyphosate alone does not induce significant cytotoxicity and genotoxicity over the tested concentration range. Contrarily, GBHs induced statistically significant cell death from 250 μM (Roundup Mega and Glyfos) and 500 μM (Fozat 480), as well as statistically significant increase of DNA damage from 500 μM (Roundup Mega and Glyfos) and 750 μM (Fozat 480); however, the latter observation may not be explained by direct DNA injuries, rather due to the high level of cell death (>70%) exerted by the formulations. Metabolic activation significantly increased the DNA damage levels induced by Glyfos, but not of the other GBHs and of glyphosate. The differences observed in the toxic pattern of formulations and the active principle may be attributed to the higher cytotoxic activity of other ingredients in the formulations or to the interaction of them with the active ingredient glyphosate. Hence, further investigation of formulations is crucial for assessing the true health risks of occupational and environmental exposures.

Immunological methods for diagnosis and monitoring of IgE-mediated allergy caused by industrial sensitizing agents (IMExAllergy)

Industrial sensitizing agents (allergens) in living and working environments play an important role in eliciting type 1 allergic disorders including asthma and allergic rhinitis. Successful management of allergic diseases necessitates identifying their specific causes (ie, identify the causative agent(s) and the route of contact to allergen: airborne, or skin contact) to avoid further exposure. Identification of sensitization by a sensitive and validated measurement of specific IgE is an important step in the diagnosis. However, only a limited number of environmental and occupational allergens are available on the market for use in sIgE testing. Accordingly, specific in‐house testing by individual diagnostic and laboratory centers is often required. Currently, different immunological tests are in use at various diagnostic centers that often produce considerably divergent results, mostly due to lack of standardized allergen preparation and standardized procedures as well as inadequate quality control. Our review and meta‐analysis exhibited satisfactory performance of sIgE detection test for most high molecular weight (HMW) allergens with a pooled sensitivity of 0.74 and specificity of 0.71. However, for low molecular weight (LMW) allergens, pooled sensitivity is generally lower (0.28) and specificity higher (0.89) than for HMW tests. Major recommendations based on the presented data include diagnostic use of sIgE to HMW allergens. A negative sIgE result for LMW agents does not exclude sensitization. In addition, the requirements for full transparency of the content of allergen preparations with details on standardization and quality control are underlined. Development of standard operating procedures for in‐house sIgE assays, and clinical validation, centralized quality control and audits are emphasized. There is also a need for specialized laboratories to provide a custom service for the development of tests for the measurement of putative novel occupational allergens that are not commercially available.

Mercury pollution in modern times and its socio-medical consequences

Mercury plays a critical role in serious health problems due to environmental or occupational exposures. Aquatic ecosystems are an essential component of the global biogeochemical cycle of mercury, as inorganic mercury can be converted to toxic methyl mercury in these environments and reemissions of elemental mercury rival anthropogenic mercury releases on a global scale. The history of the Minamata disease, a typical example of industrial pollution, has shown how corporate secrecy and ignorance on part of the health authorities may influence the devastating spread of environmental contamination and the progress of disease. While the Minamata Convention, in place since 2017, is aiming to lower mercury exposure and to prevent adverse effects, there are still knowledge gaps in the areas of global environmental mercury exposure. Areas of uncertainty in the global biogeochemical cycle of mercury include oxidation processes in the atmosphere, land-atmosphere and ocean-atmosphere cycling, and methylation processes in the ocean. Pollution related to climate change (especially in boreal and arctic regions), bioaccumulation and biomagnification of methyl mercury in the food chain, especially in fish and marine mammals, needs to be addressed in more detail. Information is lacking on numerous hidden contaminant exposures i.e. from globally applied traditional medicine, mercury containing skin creams and soaps, dental amalgam, ethyl mercury containing vaccines and latex paint additives, as well as on mercury releases from power plants, e-waste/fluorescent lamps, wildfire emissions, and global artisanal small-scale gold mining activities. Mercury occurs in various forms with different levels of toxicity. While much is already known and documented on the health effects of mercury, present knowledge and translation into preventive actions is still incomplete. Risks for long term health effects trough prolonged low dose exposure and trough cumulative exposures of various mercury forms should be further addressed. Preventive actions should include adequate human biomonitoring programs. Research data should be translated swiftly into management tools for local policy makers and health professionals, also paying attention at the major differences in mercury contamination across the globe.

Performance of specific immunoglobulin E tests for diagnosing occupational asthma: a systematic review and meta-analysis

OBJECTIVES

To determine the test performance parameters for the retrievable range of high-molecular-weight (HMW) and low-molecular-weight (LMW) occupational allergens and to evaluate the impact of allergenic components and the implementation of measures for test validation.

METHODS

A protocol with predefined objectives and inclusion criteria was the basis of an electronic literature search of MEDLINE and EMBASE (time period 1967-2016). The specific inhalation challenge and serial peak flow measurements were the reference standards for the specific IgE (sIgE) test parameters. All of the review procedures were reported according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses.

RESULTS

Seventy-one studies were selected, and 62 entered meta-analysis. Pooled pairs analysis indicated a sensitivity of 0.74(95% CI 0.66 to 0.80) and specificity of 0.71(95% CI 0.63 to 0.77) for HMW allergens and a sensitivity of 0.28(95% CI 0.18 to 0.40) and specificity of 0.89(95% CI 0.77 to 0.95) for LMW allergens. Component-specific analysis improved the test parameters for some allergens. Test validation was handled heterogeneously among studies.

CONCLUSION

sIgE test performance is rather satisfactory for a wide range of HMW allergens with the potential for component-specific approaches, whereas sensitivity for LMW allergens is considerably lower, indicating methodological complications and/or divergent pathomechanisms. A common standard for test validation is needed.

Diagnosis, monitoring and prevention of exposure-related non-communicable diseases in the living and working environment: DiMoPEx-project is designed to determine the impacts of environmental exposure on human health

The WHO has ranked environmental hazardous exposures in the living and working environment among the top risk factors for chronic disease mortality. Worldwide, about 40 million people die each year from noncommunicable diseases (NCDs) including cancer, diabetes, and chronic cardiovascular, neurological and lung diseases. The exposure to ambient pollution in the living and working environment is exacerbated by individual susceptibilities and lifestyle-driven factors to produce complex and complicated NCD etiologies. Research addressing the links between environmental exposure and disease prevalence is key for prevention of the pandemic increase in NCD morbidity and mortality. However, the long latency, the chronic course of some diseases and the necessity to address cumulative exposures over very long periods does mean that it is often difficult to identify causal environmental exposures. EU-funded COST Action DiMoPEx is developing new concepts for a better understanding of health-environment (including gene-environment) interactions in the etiology of NCDs. The overarching idea is to teach and train scientists and physicians to learn how to include efficient and valid exposure assessments in their research and in their clinical practice in current and future cooperative projects. DiMoPEx partners have identified some of the emerging research needs, which include the lack of evidence-based exposure data and the need for human-equivalent animal models mirroring human lifespan and low-dose cumulative exposures. Utilizing an interdisciplinary approach incorporating seven working groups, DiMoPEx will focus on aspects of air pollution with particulate matter including dust and fibers and on exposure to low doses of solvents and sensitizing agents. Biomarkers of early exposure and their associated effects as indicators of disease-derived information will be tested and standardized within individual projects. Risks arising from some NCDs, like pneumoconioses, cancers and allergies, are predictable and preventable. Consequently, preventative action could lead to decreasing disease morbidity and mortality for many of the NCDs that are of major public concern. DiMoPEx plans to catalyze and stimulate interaction of scientists with policy-makers in attacking these exposure-related diseases.

Alternative drugs go global: possible lead and/ or mercury intoxication from imported natural health products and a need for scientifically evaluated poisoning monitoring from environmental exposures

Background

With increases in globalization, cultural remedies from Chinese, Ayurvedic, Arab and other traditions have become more available to international consumers, offering unfamiliar “Natural Health Products” (NHP), used as alternative medicine or supplementary medicine.

Contamination with toxic ingredients including lead, mercury, arsenic, and other toxic elements has been documented in several of these products from various parts of the globe, particularly from some parts of Asia and the Orient.

Findings

We have been following this development in the last 6 years and have analyzed n = 20 such products (60 analyses) from patients with intoxication symptoms in a pilot study, showing alarming high concentrations of mercury and/or lead (the first one in “therapeutic” doses). 82 % of the studied NHP contained lead concentrations above the EU limit for dietary supplements. 62 % of the samples exceeded the limit values for mercury. Elevated blood lead and mercury levels in patients along with clinical intoxication symptoms corroborate the causal assumption of intoxication (s). We present one detailed clinical case report of severe lead and mercury intoxications and give an overview about blood concentration related symptoms and signs of n = 41 case reports of mercury intoxications of the German monitoring BfR-DocCenter.

Conclusions

For NHP there is evidence on a distinct toxicological risk with alarming low awareness for a possible intoxication which prevents potentially life-saving diagnostic steps in affected cases. In many cases patients do not communicate the events to their physicians or the local health authority so that case reports (e.g. the BfR-DocCentre) are missing. Thus, there is an urgent need to raise awareness and to initiate more suitable monitory systems (e.g. National Monitoring of Poisonings) and control practice protecting the public.

How conflicted authors undermine the World Health Organization (WHO) campaign to stop all use of asbestos: spotlight on studies showing that chrysotile is carcinogenic and facilitates other non-cancer asbestos-related diseases

The silicate mineral asbestos is categorized into two main groups based on fiber structure: serpentine asbestos (chrysotile) and amphibole asbestos (crocidolite, amosite, anthophyllite, tremolite, and actinolite). Chrysotile is used in more than 2 000 applications and is especially prevalent in the construction industry. Although its use is banned or restricted in more than 52 countries, an estimated 107 000 workers die from asbestos exposure each year, and approximately 125 million workers continue to be exposed. Furthermore, ambient exposures persist to which the public is exposed, globally. Today, the primary controversies regarding the use of asbestos are the potencies of different types of asbestos, as opposed whether or not asbestos causes morbidity and mortality. The asbestos industry has promoted and funded research based on selected literature, ignoring both clinical and scientific knowledge. In this piece, we highlight a prominent example of a conflicted publication that sought to undermine the World Health Organization (WHO) campaign to stop the use of all forms of asbestos, including chrysotile asbestos. Independent and rigorous scientific data provide sufficient evidence that chrysotile asbestos, like other forms of asbestos, is a cause of asbestos-related morbidity and premature mortality.

Ethics, morality, and conflicting interests: how questionable professional integrity in some scientists supports global corporate influence in public health

Clinical and public health research, education, and medical practice are vulnerable to influence by corporate interests driven by the for-profit motive. Developments over the last 10 years have shown that transparency and self-reporting of corporate ties do not always mitigate bias. In this article, we provide examples of how sound scientific reasoning and evidence-gathering are undermined through compromised scientific enquiry resulting in misleading science, decision-making, and policy intervention. Various medical disciplines provide reference literature essential for informing public, environmental, and occupational health policy. Published literature impacts clinical and laboratory methods, the validity of respective clinical guidelines, and the development and implementation of public health regulations. Said literature is also used in expert testimony related to resolving tort actions on work-related illnesses and environmental risks. We call for increased sensitivity, full transparency, and the implementation of effective ethical and professional praxis rules at all relevant regulatory levels to rout out inappropriate corporate influence in science. This is needed because influencing the integrity of scientists who engage in such activities cannot be depended upon.

Accidental exposure to gas emissions from transit goods treated for pest control

BACKGROUND

International phytosanitary standards ISPM 15 require (since 2007) fumigation or heat treatment for shipping and storage. Those dealing with fumigated freight might be accidentally exposed. In this paper we report a series of three accidents of six storage room workers in a medium sized company regularly importing electronic production parts from abroad.

METHODS

Patients (n=6, aged from 32-54 yrs.) and control group (n=30, mean 40 yrs.) donated blood and urine samples. The fumigants: ethylene oxide, methyl bromide, chloropicrin, ethylene dichloride, other halo-alkanes and solvents were analyzed by headspace gas chromatography/mass spectrometry (GCMS). For the quantitation of long term exposure/s, macromolecular reaction products (hemoglobin adducts) were used (with GCMS) as molecular dosimeter; additionally 8-OHdG and circulating mtDNA (cmtDNA) were analyzed as nonspecific biological effect markers.

RESULTS

The hemoglobin adducts N-methyl valine (MEV) and N-(2-hydroxy ethyl) valine (HEV) were elevated after exposure to the alkylating chemicals methyl bromide and ethylene oxide. Under the consideration of known elimination kinetics and the individual smoking status (biomonitored with nicotine metabolite cotinine and tobacco specific hemoglobin adduct: N-(2 cyan ethyl) valines, CEV), the data allow theoretical extrapolation to the initial protein adduct concentrations at the time of the accident (the MEV/CEV levels were from 1,616 pmol/g globin to 1,880 pmol/g globin and HEV/CEV levels from 1,407 pmol/g globin to 5,049 pmol/g globin, and correlated with inhaled 0.4-1.5 ppm ethylene oxide. These integrated, extrapolated internal doses, calculated on the basis of biological exposure equivalents, confirmed the clinical diagnosis for three patients, showing severe intoxication symptoms. Both, cmtDNA and 8-OHdG, as non-specific biomarkers of toxic effects, were elevated in four patients.

CONCLUSION

The cases reported here, stress the importance of a suitable risk assessment and control measures. We put emphasis on the necessity of human biomonitoring guidelines and the urgency for the relevant limit values.

Allergic asthma caused by exposure to bacterial alpha-amylase Termamyl®

BACKGROUND

Airborne enzymes behave as potent respiratory allergens. Till date, allergic disorders caused by genetically engineered enzymes widely used in the industry, have not been reported.

RESULTS AND CONCLUSIONS

We describe a worker employed in the detergent industry who developed asthma and rhinitis from IgE-mediated sensitization to the thermostable endo-alpha-amylase Termamyl® and to the protease Savinase®. This is the first report showing that Termamyl® elicits allergic respiratory disorders in humans.

Determination of phosphine and other fumigants in air samples by thermal desorption and 2D heart-cutting gas chromatography with synchronous SIM/Scan mass spectrometry and flame photometric detection

Fumigants and volatile industrial chemicals are particularly hazardous to health when a freight container is fumigated or the contaminated material is introduced into its enclosed environment. Phosphine is now increasingly used as a fumigant, after bromomethane--the former fumigant of choice--has been banned by the Montreal Protocol. We have enhanced our previously established thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) method by integrating a second gas chromatographic dimension and a flame photometric detector to allow the simultaneous detection of phosphine and volatile organic compounds (VOCs), providing a novel application. A thermal desorption system is coupled to a two dimensional gas chromatograph using both mass spectrometric and flame photometric detection (TD-2D-GC-MS/FPD). Additionally, the collection of mass spectrometric SIM and Scan data has been synchronised, so only a single analysis is now sufficient for qualitative scanning of the whole sample and for sensitive quantification. Though detection limits for the herewith described method are slightly higher than in the previous method, they are in the low μL m(-3) range, which is not only below the respective occupational exposure and intervention limits but also allows the detection of residual contamination after ventilation. The method was developed for the separation and identification of 44 volatile substances. For 12 of these compounds (bromomethane, iodomethane, dichloromethane, 1,2-dichlorethane, benzene, tetrachloromethane, 1,2-dichloropropane, toluene, trichloronitromethane, ethyl benzene, phosphine, carbon disulfide) the method was validated as we chose the target compounds due to their relevance in freight container handling.

Heavy metal exposure in patients suffering from electromagnetic hypersensitivity

BACKGROUND

Risks from electromagnetic devices are of considerable concern. Electrohypersensitive (EHS) persons attribute a variety of rather unspecific symptoms to the exposure to electromagnetic fields. The pathophysiology of EHS is unknown and therapy remains a challenge.

OBJECTIVES

Heavy metal load has been discussed as a potential factor in the symptomatology of EHS patients. The main objective of the study was to test the hypothesis of a link between EHS and heavy metal exposure.

METHODS

We measured lead, mercury and cadmium concentrations in the blood of 132 patients (n=42 males and n=90 females) and 101 controls (n=34 males and n=67 females).

RESULTS

Our results show that heavy metal load is of no concern in most cases of EHS but might play a role in exceptional cases.

CONCLUSIONS

The data do not support the general advice to heavy metal detoxification in EHS.

High frequency of fumigants and other toxic gases in imported freight containers--an underestimated occupational and community health risk

Residues of pesticide fumigants and toxic industrial chemicals in freight containers represent a health hazard to employees and consumers, especially since freight containers are sealed for transport and distributed widely throughout the importing countries before being opened for unloading. We investigated 2113 freight containers arriving at the second largest container terminal in Europe, Hamburg, Germany, over a 10-week period in 2006. The countries of origin, type of contents and the pesticide fumigation history declared on labels attached to the container were recorded. We determined that 1478 (70%) containers were contaminated with toxic chemicals above chronic reference exposure levels; 761 (36%) even exceeded the higher acute reference exposure level thresholds. Benzene and/or formaldehyde contamination was 4-times greater than for fumigants. Our findings indicate a health risk for dockworkers, container unloaders and even end-consumers, especially as many of the cancerogenic or toxic gases elude subjective detection.

Lysophosphatidic acid antagonizes the morphoregulatory effects of the luteinizing hormone on luteal cells: possible role of small Rho-G-proteins

Lysophosphatidic acid (LPA) is a biologically active phospholipid recently introduced as a new marker for ovarian cancer. Because high concentrations of LPA have also been found in the follicular fluid from healthy subjects, one can presume that this biological mediator may have relevance for normal ovarian physiology as well. We have reported earlier that luteal cells possess specific binding sites for LPA. Using these cells as a model, we show now that LPA is able to modulate the morphological cell shape changes induced by LH in that it inhibits the formation of stellate processes induced by LH. This morphoregulatory effect of LPA is mimicked by cytotoxic necrotizing factor 1, a bacterial toxin known to activate small G-proteins from the Rho family. On the other hand, C3-exotransferase that acts mainly through the inhibition of Rho A mimics the effects of LH. Furthermore, we report here that the morphoregulatory effects of LPA are accompanied by the translocation of Rho proteins from the cytosol to cell membrane, an effect generally considered to be an indicator for the activation of Rho-GTPases. During the development and rescue of the corpus luteum, major morphoregulatory effects are exerted by LH that appear to be modulated by LPA via an activation of Rho proteins.

Inhibitory effects of TNF alpha on mouse tumor Leydig cells: possible role of ceramide in the mechanism of action

TNF alpha is reported to inhibit steroidogenesis in mouse Leydig cells. In primary cells this inhibition resulted mainly from a reduced expression of Cyp-17 gene. Mouse tumor Leydig cells, MA-10, being free of macrophages and lacking Cyp-17, appear to be an excellent model to investigate those effects of TNF alpha which are independent of either macrophages or Cyp-17. We report here that TNF alpha receptors are expressed in this cell line. Treatment of the cells with TNF alpha had no effect on basal progesterone production. In contrast, LH-, 8Br-cAMP and forskolin-stimulated progesterone production was inhibited by TNF alpha. Neither enzymes involved in the conversion of cholesterol to pregnenolone nor hormone-induced hydrolysis of [14C] cholesterol-ester were affected by TNF alpha. The hormone-induced expression of StAR protein was diminished in mitochondrial fractions from TNF alpha-treated cells. Also cell permeable ceramides markedly inhibited StAR protein levels. We show further that TNF alpha was able to induce [14C]-ceramide accumulation in MA-10 cells and suggest that this sphingolipid may be considered as a transmitter of TNF alpha signals to the StAR protein.

Functional lysophosphatidic acid receptor in bovine luteal cells

The aim of this study was to determine whether luteal cells possess functional receptors for lysophosphatidic acid (LPA). We present evidence that [3H]LPA binds to a 38-40 kDa protein in a membrane fraction prepared from luteal cells and that this phospholipid is able to induce tyrosine phosphorylation of several proteins (65-125 kDa). Furthermore, LPA upregulates forskolin- and LH/GTP-stimulated adenylyl cyclase activity by changing its Vmax. Although a pertussis toxin-sensitive G-protein has been reported to transmit the inhibitory signals between the LPA receptor and adenylyl cyclase, the observed upregulation of the enzyme activity in luteal cells is not abolished after pre-treating the cells with the toxin, suggesting that a different mechanism is operative in these cells. According to the pharmacological regulatory pattern it is suggested that the modulated adenylyl cyclase isoform is the enzyme subtype V expressed in luteal cells.

Modulatory action of epidermal growth factor on differentiated human granulosa lutein cells: cross-talk between ligand activated receptors for EGF and gonadotropin

A number of local regulatory factors including polypeptide growth factors like epidermal growth factor (EGF) have been suggested to play an active role within the human ovary. In order to understand the physiology of EGFs action, it is essential to demonstrate and characterize the receptors for this growth factor on ovarian cells which was the aim of this study. We demonstrate using [125I]EGF that specific high affinity sites with Ka for this ligand reaching 2.2 x 10(-9) M for growing cultures of human granulosa-lutein cells and 0.13 x 10(-9) M for the membrane fraction prepared from these cells. Additionally we have identified a 170 kD protein as the EGF receptor with the help of affinity cross linking and immunoblotting procedures. Furthermore, we observed that a pretreatment of granulosa lutein cells with EGF for a short duration (0-30 min) leads to a dose- and time dependent upregulation of the LH-receptor-coupled adenylate cyclase activity. A maximal effect (159 +/- 12% increase compared with untreated cells, P < 0.001, n = 4) was reached at 10-15 min with 10-20 ng/ml EGF. Specific inhibition of the receptor tyrosine kinase activity abolished the observed EGF-induced sensitization of the cyclase activity. Differentiation of granulosa cells in vivo is a prerequisite for ovulation and later transformation into highly differentiated lutein cells, a process depending on the presence of ligands that elevate cAMP production. The observed modulation of the adenylate cyclase by EGF could be a regulatory component for the differentiated status of the granulosa cells during different phases of the cycle.

Phospholipase D treatment enhances gonadotrophin receptor-coupled adenylate cyclase activity in isolated bovine luteal cells

LH-stimulated adenylate cyclase activity in membrane preparations of bovine luteal cells could be enhanced by treating the cells with either phospholipase D or its hydrolysis product, phosphatidic acid. Similar augmentary effects were also produced following treatment of the cells with EGF. Moreover, EGF could stimulate the formation of [3H]phosphatidic acid in [3H]myristic acid preloaded cells, suggesting that EGF is able to activate cellular phospholipase D. Also, PMA was able to increase the phosphatidic acid formation with a parallel increase in the adenylate cyclase activity. We propose, therefore, that phosphatidic acid may act as an intracellular second messenger linking EGF-mediated activation of phospholipase D with the sensitization of LH receptor-coupled adenylate cyclase signalling system.

Pertussis toxin can distinguish the augmentary effect elicited by epidermal growth factor from that of phorbol ester on luteal adenylate cyclase activity

The preincubation of luteal cells with epidermal growth factor (EGF) increases LH/GTP-stimulated adenylate cyclase activity measured subsequently in luteal cell membrane preparations. This reflects an EGF-stimulated increase in the maximum velocity, with no distinct change in the Km value of the enzyme. The augmentary effect of EGF was rapid (maximum after 5-15 min of preincubation and declining thereafter) and was inhibited by preincubation of luteal cells with pertussis toxin. The treatment with this toxin had no effect on [125I] EGF binding to luteal cells. Radiolabeling experiments carried out under ADP-ribosylating conditions revealed diminished radiolabeling of a 40/41-kilodalton pertussis toxin substrate in membranes from pertussis toxin-pretreated cells. In contrast, although the preincubation of luteal cells with the phorbol ester 4 beta-phorbol 12-myristate 13-acetate (PMA) led to a similar increase in LH/GTP-stimulated adenylate cyclase, pretreatment with pertussis toxin did not inhibit the augmentary effects of PMA. In fact, prior exposure of PMA-treated cells to the toxin resulted in a further increase in the enzyme activity. We report here that pertussis toxin can be used to discriminate between the potentiating effects of EGF and PMA on luteal adenylate cyclase. The data reinforce the concept that "cross-talk" with other signal-transducing pathways may modulate hormone-stimulated cAMP production in luteal cells and reveal that although EGF and PMA both amplify this response, they appear to do so by distinct mechanisms that can be distinguished by their sensitivity to pertussis toxin.

Epidermal growth factor, a modulator of luteal adenylate cyclase. Characterization of epidermal growth factor receptors and its interaction with adenylate cyclase system in bovine luteal cell membrane

The epidermal growth factor (EGF) binding sites on bovine luteal cell membrane have been characterized in detail, and evidence has been obtained for a direct stimulatory effect of EGF on membrane-associated adenylate cyclase activity. The membrane fraction prepared showed the presence of high affinity (Ka = 1.2 +/- 0.7 x 10(-11) M-1), specific, and saturable EGF receptors of Mr = 170,000. The EGF receptors underwent rapid autophosphorylation and down-regulation following treatment of the cells with EGF. Treatment of the cells with 4 beta-phorbol 12-myristate 13-acetate resulted in a diminished binding of 125I-EGF to the receptors. When luteal cells were preincubated with EGF, both basal and forskolin-stimulated adenylate cyclase activity was increased severalfold. This enhancement of the adenylate cyclase activity was dependent upon the duration of the exposure to EGF and on the concentration of the growth factor. An optimal enhancement was observed when the cells were preincubated with 10 ng/ml EGF for 10-15 min. Furthermore, when the membrane fraction prepared from luteal cells was preincubated in vitro with EGF, a similar dose-related and time-dependent increase in basal, as well as forskolin-stimulated, adenylate cyclase activity was observed. These results demonstrate that luteal cell adenylate cyclase activity is finely regulated by EGF. Such a direct interaction between EGF and membrane-associated adenylate cyclase has not been previously recognized.

Phorbol ester- and luteinizing hormone-induced phosphorylation of membrane proteins in bovine luteal cells

In this study we have investigated the protein phosphorylation pattern in the membrane fraction prepared from bovine luteal cells. The phosphorylation reaction was carried out in vitro, under defined conditions, using either [gamma-32P]ATP or [gamma-35S]ATP as the phosphate donor. The results obtained show that [gamma-35S]ATP was a suitable phosphate donor for performing in vitro phosphorylation studies, and that thiophosphorylation of at least eight protein bands (120 kDa to 18 kDa) was observed. The extent of phosphorylation was dependent upon the duration of incubation and the amount of membrane protein used. The presence of Ca2+ was obligatory for phosphorylation and an enhanced phosphorylation was observed in the presence of Ca2+, phosphatidyl serine and phorbol 12-myristate 13-acetate (PMA), agents known to activate protein kinase C. Interestingly, when phosphorylation was carried out in the presence of luteinizing hormone (LH), a phosphorylation pattern was obtained which was similar to that obtained in the presence of calcium and phospholipid. Furthermore, in the case of two protein bands corresponding to 80-82 and 44-46 kDa, an additive phosphorylation was observed when the phosphorylation reaction was carried out for 5 min in the presence of both LH and Ca2+, phosphatidyl serine and PMA. To conclude, we have demonstrated a calcium- and phospholipid-dependent endogenous protein phosphorylation in the membrane fraction prepared from bovine luteal cells and the data obtained suggest that LH is able to stimulate this endogenous protein phosphorylation via a protein kinase C-mediated mechanism.

Atrial natriuretic peptide-induced stimulation of cyclic GMP formation by isolated bovine luteal cells

Incubation of bovine luteal cells with an atrial natriuretic peptide (rat atriopeptin II, rAP-II) did not affect hCG-stimulated or basal cyclic AMP accumulation and progesterone production, but cyclic GMP formation was stimulated by rAP-II in a dose-dependent manner, being maximally stimulatory in the nanomolar range. This stimulatory influence of rAP-II on cyclic GMP formation results from a specific stimulation of particulate guanylate cyclase. We suggest that, although rAP-II mediated cyclic GMP formation can be demonstrated in bovine luteal cells, there appear to be no acute effects of the atrial peptide on the regulation of progesterone production by these cells.

Desensitisation of LH-stimulated cyclic AMP accumulation in isolated bovine luteal cells--effect of phorbol ester

In this study, we have characterized the LH-mediated desensitisation of receptor-linked cAMP generation in bovine luteal cells. Furthermore, the possibility that protein kinase C could play a role in this process has been investigated. The results obtained, show that the preincubation of Percoll-purified bovine luteal cells with LH diminished the cAMP response during reincubation with LH, depending upon the duration of prior exposure to LH and the concentration of LH used in the first incubation. This desensitisation was specifically dependent upon the prior exposure of the cells to the hormone only, as preincubation with either forskolin or cholera toxin did not result in a desensitised cAMP response to subsequent LH stimulation. On the other hand, LH-desensitised cells retained undiminished responsiveness to restimulation with cholera toxin. Neither the maximum binding capacity nor the affinity of the LH-receptor was affected by exposure of the cells to a desensitising dose of LH. The results demonstrate that in bovine luteal cells, LH produces a homologous desensitisation of the cAMP response which is not mediated by cAMP and that a hormone-receptor interaction appears to be a prerequisite for this process. Preincubation of the cells with varying concentrations of the protein kinase C activator phorbol 12-myristate 13-acetate (PMA) did not result in any reduction of LH-induced cAMP response during reincubation. The affinity of LH-receptor was also not affected by PMA pretreatment. In contrast, PMA-pretreated cells consistently produced increased amounts of cAMP when challenged with any of the agonists, LH, cholera toxin or forskolin. The preincubation of the cells with LH in the presence of PMA appears to prevent, at least partially, the desensitising effect of LH. It is concluded that in bovine luteal cells there is no evidence for a role of protein kinase C in LH-induced desensitisation. On the contrary, PMA pretreatment increased the response of adenylate cyclase to a subsequent hormonal stimulation without changing the affinity of the receptors for the hormone. Either an attenuation of the inhibitory N protein or a direct activation of the catalytic unit of adenylate cyclase could be the explanation for the observed effects of PMA. However, available data at present do not offer a choice between the two possibilities.

Atrial natriuretic factor stimulates luteal guanylate cyclase

Effect of a synthetic atrial natriuretic peptide, rat atriopeptin II (rAP-II) on the formation of cyclic nucleotides and progesterone production in Percoll-purified rat luteal cells was investigated. Incubation of luteal cells with varying concentrations of rAP-II resulted in a dose-related stimulation of intracellular cyclic GMP content; maximum stimulation being achieved with 10 nM rAP-II. The increase in cyclic GMP formation was extremely rapid and a 12-fold increase in the cyclic GMP content over basal level was attained within 5 min of incubation of the cells with 10 nM rAP-II. In the presence of phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthine, both basal and rAP-II-stimulated levels of cyclic GMP were increased approximately 10 times, but the magnitude of stimulation remained similar in the presence or absence of the inhibitor. The atrial peptide at the concentration of 1-100 nM, however, had no effect on either basal or gonadotropin-stimulated progesterone production and cyclic AMP formation by the luteal cells. Furthermore, the increase in the level of cellular cyclic GMP content of rAP-II was demonstrated to result from a selective activation of particulate guanylate cyclase.

Phorbol ester stimulates progesterone production by isolated bovine luteal cells

The tumor promoter, phorbol 12-myristate-13-acetate (PMA), is known to modulate the response of several steroidogenic tissues presumably by activating a Ca++- and phospholipid-dependent protein kinase (protein kinase C). The presence of this kinase has been demonstrated in bovine corpus luteum, although its role in steroidogenesis by these cells is unknown. We report here the effects of PMA on progesterone production by the enzymically dispersed bovine luteal cells in vitro. PMA (1-50 nM) produced a dose- and time-related increase in progesterone production by the luteal cells. The maximum stimulation was achieved with 10 nM PMA. Higher concentrations of PMA led to a decline of steroidogenesis close to the basal level. A nonpromoting derivative, 4 alpha-phorbol 12,13-didecanoate had no effect. The PMA-induced stimulation of progesterone production was not associated with a change in the cAMP level. PMA added together with suboptimal doses of human CG, 8Br-cAMP, cholera toxin, or forskolin significantly increased the amount of progesterone produced. PMA as well as human CG-induced steroidogenesis was sensitive to cycloheximide inhibition. The conversion of exogenous pregnenolone or 25-hydroxycholesterol to progesterone was not altered by PMA. We conclude that PMA at nanomolar concentrations is able to stimulate progesterone production by bovine luteal cells and that the site of action of PMA is distal to the formation of cAMP but before the formation of pregnenolone. The observed effects of PMA in luteal cells are probably linked to its ability to activate protein kinase C, since a diacylglycerol could mimic the steroidogenic action of PMA.