Effect of dialkyl phthalates on the degranulation and Ca2+ response of RBL-2H3 mast cells

Mono-2-ethylhexylphthalate (MEHP) is a potent agonist of human TRPA1 channel

Phthalates are extensively used as plasticizers in diverse consumer care products but have been reported to cause adverse health effects in humans. A commonly used phthalate, di-2-ethylhexylphthalate (DEHP) causes developmental and reproductive toxicities in humans, but the associated molecular mechanisms are not fully understood. Mono-2-ethylhexylphthalate (MEHP), a hydrolytic product of DEHP generated by cellular esterases, is proposed to be the active toxicant. We conducted a screen for sensory irritants among compounds used in consumer care using an assay for human Transient Receptor Potential A1 (hTRPA1). We have identified MEHP as a potent agonist of hTRPA1. MEHP-induced hTRPA1 activation was blocked by the TRPA1 inhibitor A-967079. Patch clamp assays revealed that MEHP induced inward currents in cells expressing hTRPA1. In addition, the N855S mutation in hTRPA1 associated with familial episodic pain syndrome decreased MEHP-induced hTRPA1 activation. In summary, we report that MEHP is a potent agonist of hTRPA1 which generates new possible mechanisms for toxic effects of phthalates in humans.

Adverse cardiovascular effects of long-term exposure to diethyl phthalate in the rat aorta

Phthalates are classified as priority environmental pollutants, since they are ubiquitous in the environment, have endocrine disrupting properties and can contribute to impaired health. Used primarily in personal care products and excipients for pharmaceuticals, diethyl phthalate (DEP) is a short-chain alkyl phthalate that has been linked to decreased blood pressure, glucose tolerance, and increased gestational weight gain in humans, while in animals it has been associated with atherosclerosis and metabolic syndrome. Although all these findings are related to risk factors or cardiovascular diseases, DEP's vascular impacts still need to be clarified. Thus, performing ex vivo and in vitro experiments, we aimed to understand the vascular DEP effects in rat. To evaluate the vascular contractility of rat aorta exposed to different doses of DEP (0.001-1000 μM), an organs bath was used; and resorting to a cell line of the rat aorta vascular smooth muscle, electrophysiology experiments were performed to analyse the effects of a rapid (within minutes with no genomic effects) and a long-term (24 h with genomic effects) exposure of DEP on the L-type Ca2+ current (ICa,L), and the expression of several genes related with the vascular function. For the first time, vascular electrophysiological properties of an EDC were analysed after a long-term genomic exposure. The results show a hormetic response of DEP, inducing a Ca2+ current inhibition of the rat aorta, which may be responsible for impaired cardiovascular electrical health. Thus, these findings contribute to a greater scientific knowledge about DEP's effects in the cardiovascular system, specifically its implications in the development of electrical disturbances like arrhythmias and its possible mechanisms.

The Relationship between Phthalates and Diabetes: A Review

Since the beginning of their production, in the 1930s, phthalates have been widely used in the plastics industry to provide durability and elasticity to polymers that would otherwise be rigid, or as solvents in hygiene and cosmetic products. Taking into account their wide range of applications, it is easy to understand why their use has been increasing over the years, making them ubiquitous in the environment. This way, all living organisms are easily exposed to these compounds, which have already been classified as endocrine disruptor compounds (EDC), affecting hormone homeostasis. Along with this increase in phthalate-containing products, the incidence of several metabolic diseases has also been rising, namely diabetes. That said, and considering that factors such as obesity and genetics are not enough to explain this substantial increase, it has been proposed that the exposure to environmental contaminants may also be a risk factor for diabetes. Thus, the aim of this work is to review whether there is an association between the exposure to phthalates and the development of the several forms of diabetes mellitus, during pregnancy, childhood, and adulthood.

Dibutyl phthalate rapidly alters calcium homeostasis in the gills of Danio rerio

This study investigates the impacts of exposure to an environment Ca²⁺ challenge and the mechanism of action of dibutyl phthalate (DBP) on Ca²⁺ influx in the gills of Danio rerio. In vitro profile of ⁴⁵Ca²⁺ influx in gills was verified through the basal time-course. Fish were exposed to low, normal and high Ca²⁺ concentrations (0.02, 0.7 and 2 mM) for 12 h. So, gills were morphologically analysed and ex vivo⁴⁵Ca²⁺ influx at 30 and 60 min was determined. For the in vitro studies, gills were treated for 60 min with DBP (1 pM, 1 nM and 1 μM) with/without blockers/activators of ionic channels, Ca²⁺ chelator, inhibitors of ATPases, ionic exchangers and protein kinase C to study the mechanism of DBP-induced ⁴⁵Ca²⁺ influx. Exposure to high environmental Ca²⁺ augmented ⁴⁵Ca²⁺ influx when compared to fish exposed to normal and low Ca²⁺ concentrations. Additionally, histopathological changes were observed in the gills of fish maintained for 12 h in low and high Ca²⁺. In vitro exposure of gills to DBP (1 pM) disturbed Ca²⁺ homeostasis. DBP stimulated ⁴⁵Ca²⁺ influx in gills through the transitory receptor potential vanilloid 1 (TRPV1), and reverse-mode Na⁺/Ca²⁺ exchanger (NCX) activation, protein kinase C and K⁺ channels and sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA). These data suggest that in vivo short-term exposure of gills to low and high Ca²⁺ leads to ⁴⁵Ca²⁺ influx and histopathological changes. Additionally, the DBP-induced rapid ⁴⁵Ca²⁺ influx is mediated by TRPV1, NCX activation with the involvement of PKC, K⁺-channels and SERCA, thereby altering Ca²⁺ homeostasis.

Perinatal androgens organize sex differences in mast cells and attenuate anaphylaxis severity into adulthood

Mast cell (MC)-associated diseases, including allergy/anaphylaxis and neuroinflammatory pain disorders, exhibit a sex bias, with females at increase risk. While much attention has been directed toward adult sex hormones as drivers of sex differences, that female sex bias in MC-associated diseases is evident in prepubertal children, suggesting early-life origins of sex differences which have yet to be explored. Utilizing rodent models of MC-mediated anaphylaxis, our data here reveal that, 1) compared with females, males exhibit significantly reduced severity of MC-mediated anaphylactic responses that emerge prior to puberty and persist into adulthood, 2) reduced severity of MC-mediated anaphylaxis in males is linked with the naturally high level of perinatal androgens and can be recapitulated in females by perinatal exposure to testosterone proprionate, 3) perinatal androgen exposure guides bone marrow MC progenitors toward a masculinized tissue MC phenotype characterized by decreased concentration of prestored MC granule mediators (e.g., histamine, serotonin, and proteases) and reduced mediator release upon degranulation, and 4) engraftment of MC-deficient Kit W-sh/W-sh mice with adult male, female, or perinatally androgenized female MCs results in MC-mediated anaphylaxis response that reflects the MC sex and not host sex. Together, these data present evidence that sex differences in MC phenotype and resulting disease severity are established in early life by perinatal androgens. Thus, factors affecting levels of perinatal androgens could have a significant impact on MC development and MC-associated disease risk across the life span.

Acute exposure to bis(2-ethylhexyl)phthalate disrupts calcium homeostasis, energy metabolism and induces oxidative stress in the testis of Danio rerio

Bis(2-ethylhexyl)phthalate (BEHP) negatively affects testicular functions in different animal species, disturbing reproductive physiology and male fertility. The present study investigated the in vitro acute effect of BEHP on the mechanism of action of ionic calcium (Ca²⁺) homeostasis and energy metabolism. In addition, the effect of BEHP on oxidative stress was studied in vitro and in vivo in the testis of Danio rerio (D. rerio). Testes were treated in vitro for 30 min with 1 μM BEHP for ⁴⁵Ca²⁺ influx measurements. Testes were also incubated with 1 μM BEHP for 1 h (in vitro) or 12 h (in vivo) for the measurements of lactate content, ¹⁴C-deoxy-d-glucose uptake, lactate dehydrogenase (LDH) and gamma-glutamyl transpeptidase (GGT) activity, total reactive oxygen species (ROS) production and lipid peroxidation. In addition, the effect of BEHP (1 μM) on GGT, glutamic oxaloacetic transferase (GOT) and glutamic pyruvic transferase (GPT) activity in the liver was evaluated after in vivo treatment for 12 h. BEHP disturbs the Ca²⁺ balance in the testis when given acutely in vitro. BEHP stimulated Ca²⁺ influx occurs through L-type voltage-dependent Ca²⁺ channels (L-VDCC), transitory receptor potential vaniloid (TRPV1) channels, reverse-mode Na⁺/Ca²⁺ exchanger (NCX) activation and inhibition of sarco/endoplasmic reticulum Ca²⁺-ATPase (SERCA). BEHP affected energy metabolism in the testis by decreasing the lactate content and LDH activity. In vitro and in vivo acute effects of BEHP promoted oxidative stress by increasing ROS production, lipid peroxidation and GGT activity in the testis. Additionally, BEHP caused liver damage by increasing GPT activity.

The chemical disruption of human metabolism

BACKGROUND

Recent evidence highlights the reality of unprecedented human exposure to toxic chemical agents found throughout our environment - in our food and water supply, in the air we breathe, in the products we apply to our skin, in the medical and dental materials placed into our bodies, and even within the confines of the womb. With biomonitoring confirming the widespread bioaccumulation of myriad toxicants among population groups, expanding research continues to explore the pathobiological impact of these agents on human metabolism.

METHODS

This review was prepared by assessing available medical and scientific literature from Medline as well as by reviewing several books, toxicology journals, government publications, and conference proceedings. The format of a traditional integrated review was chosen.

RESULTS

Toxicant exposure and accrual has been linked to numerous biochemical and pathophysiological mechanisms of harm. Some toxicants effect metabolic disruption via multiple mechanisms.

CONCLUSIONS

As a primary causative determinant of chronic disease, toxicant exposures induce metabolic disruption in myriad ways, which consequently result in varied clinical manifestations, which are then categorized by health providers into innumerable diagnoses. Chemical disruption of human metabolism has become an etiological determinant of much illness throughout the lifecycle, from neurodevelopmental abnormalities in-utero to dementia in the elderly.

DBP-induced endoplasmic reticulum stress in male germ cells causes autophagy, which has a cytoprotective role against apoptosis in vitro and in vivo

Recently, spermatogenic cell apoptosis was shown to play a key role in the induction of testicular atrophy by dibutyl phthalate (DBP), thus causing reproductive toxicology. However, the molecular events induced by DBP in apoptotic germ cells remain unclear. In the present study, the mouse spermatocyte-derived GC-2 cell line was exposed to different doses of DBP. We found that DBP induced marked apoptosis in GC-2 cells. The levels of the major endoplasmic reticulum (ER) stress markers GRP-78, ATF-6, and p-EIF2α were elevated when GC-2 cells were exposed to 25 μM DBP and increased in a dose-dependent manner at higher concentrations. Furthermore, at a concentration that resulted in significant apoptosis (100 μM), CHOP, which plays a convergent role in ER stress-mediated apoptosis and is regulated by various upstream ER stress signals, was activated and partially contributed to the DBP-induced apoptosis. However, inhibition of ER stress by 4-PBA, a chemical with chaperone-like activities, augmented the GC-2 cell apoptosis induced by DBP. Further experiments demonstrated that DBP-induced ER stress additionally had a protective role, mediated through the activation of autophagy. These results were confirmed in prepubertal rat testis germ cells; DBP treatment significantly induced testicular atrophy, accompanied by apoptosis, ER stress, and autophagy. Inhibition of ER stress and autophagy significantly aggravated the DBP-induced damage to the germ cells and testes. Taken together, our data suggest that DBP-induced ER stress in germ cells has a cytoprotective effect that is mediated through autophagy activation. These findings provide novel clues regarding the molecular events involved in DBP-induced germ cell apoptosis.

The association between phthalate exposure and asthma

Asthma is a chronic inflammatory disorder of the airway, characterized by airway hyperresponsiveness. It is a disabling disease with an increasing prevalence, resulting in heavy social and economic burdens worldwide. Humans are extensively exposed to phthalates, and many epidemiological studies have shown a relationship between phthalate exposure and asthma in recent decades. Earlier experimental studies focused on inflammatory cells, demonstrating the adjuvant effects, immunomodulatory effects, or immunosuppressive effects related to phthalate exposure. Recent studies have shown that phthalates may have a direct effect on airway epithelial cells and contribute to airway remodeling, which is the cardinal pathologic characteristic of chronic asthma, with a high correlation with disease severity. Through these efforts, phthalates have been recognized as important environmental factors in the pathogenesis of asthma, but further studies are still required to elucidate the detailed mechanism. This review discusses the current status of human exposure to phthalates in Taiwan and summarizes the epidemiological and experimental evidence related to the roles of phthalate exposure in the development of asthma and associated diseases.

Mechanistic considerations for human relevance of cancer hazard of di(2-ethylhexyl) phthalate

Di(2-ethylhexyl) phthalate (DEHP) is a peroxisome proliferator agent that is widely used as a plasticizer to soften polyvinylchloride plastics and non-polymers. Both occupational (e.g., by inhalation during its manufacture and use as a plasticizer of polyvinylchloride) and environmental (medical devices, contamination of food, or intake from air, water and soil) routes of exposure to DEHP are of concern for human health. There is sufficient evidence for carcinogenicity of DEHP in the liver in both rats and mice; however, there is little epidemiological evidence on possible associations between exposure to DEHP and liver cancer in humans. Data are available to suggest that liver is not the only target tissue for DEHP-associated toxicity and carcinogenicity in both humans and rodents. The debate regarding human relevance of the findings in rats or mice has been informed by studies on the mechanisms of carcinogenesis of the peroxisome proliferator class of chemicals, including DEHP. Important additional mechanistic information became available in the past decade, including, but not limited to, sub-acute, sub-chronic and chronic studies with DEHP in peroxisome proliferator-activated receptor (PPAR) α-null mice, as well as experiments utilizing several transgenic mouse lines. Activation of PPARα and the subsequent downstream events mediated by this transcription factor represent an important mechanism of action for DEHP in rats and mice. However, additional data from animal models and studies in humans exposed to DEHP from the environment suggest that multiple molecular signals and pathways in several cell types in the liver, rather than a single molecular event, contribute to the cancer in rats and mice. In addition, the toxic and carcinogenic effects of DEHP are not limited to liver. The International Agency for Research on Cancer working group concluded that the human relevance of the molecular events leading to cancer elicited by DEHP in several target tissues (e.g., liver and testis) in rats and mice can not be ruled out and DEHP was classified as possibly carcinogenic to humans (Group 2B).

Allergy-related cytokines (IL-4 and TNF-α) are induced by Di(2-ethylhexyl) phthalate and attenuated by plant-originated glycoprotein (75 kDa) in HMC-1 cells

Phthalate esters as plasticizers have been widespread in the environment and may be associated with development of allergic diseases such as asthma and atopic dermatitis. In this study, we demonstrated that the CTB glycoprotein attenuates allergic reactions caused by di(2-ethylhexyl) phthalate (DEHP) in human mast cells (HMC-1). This experiment evaluated degranulation of histamine and β-hexosaminidase as well as activities of protein kinase C (PKC), stress-activated protein kinase/c-Jun N-terminal kinase (SAPK/JNK), activator protein (AP)-1 and interleukin (IL)-4 and tumor necrosis factor (TNF)-α using immunoblotting and reverse transcription-polymerase chain reaction (RT-PCR). Our results revealed that the CTB glycoprotein in the presence of DEHP inhibits degranulation of mast cell, translocation of PKC from cytosol to membrane, and phosphorylation of SAPK/JNK in HMC -1 cells. We also found that the CTB glycoprotein (100 μg mL(-1) ) has suppressive effects on transcriptional activation of AP-1, and on the expression of IL-4 and TNF-α in DEHP-treated HMC-1 cells. We suggest that the CTB glycoprotein inhibits degranulation of mast cells and expressions of cytokines in HMC-1 cells.

Inhibitory effect of phytoglycoprotein (24kDa) on allergy-related factors in compound 48/80-induced mast cells in vivo and in vitro

Mast cells are involved in immediate allergic reactions such as asthma, allergic rhinitis, and atopic dermatitis. Allergic reactions caused by extracellular allergens such as xenobiotics may become a critical problem in living circumstances. Recently, we isolated and purified glycoprotein from Zanthoxylum piperitum DC fruit (ZPDC), and demonstrated that ZPDC glycoprotein (5-20mg/kg, 25-100mug/ml) has an inhibitory effect on allergy-related mediators in the compound 48/80-treated BALB/c and human mast cells (HMC-1 cells). Our results obtained from this study showed that ZPDC glycoprotein (10mg/kg) inhibited interleukin-4 (IL-4), immunoglobulin E (IgE), and histamine are released in mouse serum. Also, ZPDC glycoprotein (50mug/ml) attenuated the degranulation of mast cells, intracellular Ca(2+) levels, and the activities of phosphorylation of p38 mitogen-activated protein kinase (MAPK), nuclear factor (NF)-kappaB (p50 and p65), and cyclooxygenase-2 (COX-2) in the HMC-1 cells. Taken together, we speculate that the ZPDC glycoprotein might be one component found in natural products that has the ability to prevent dysfunction in the immune system caused by several different allergens.

Phthalate exposure and asthma in children

During the last decades more than 100 000 new chemicals have been introduced to the environment. Many of these new chemicals and many common consumer products that include these have been shown to be toxic in animal studies and an increasing body of evidence suggests that they are also impacting human health. Among the suspect chemicals, the endocrine disrupting chemicals (EDCs) are of particular concern. One such chemical group is the phthalates, used in soft poly vinyl chloride (PVC) material and in a huge number of consumer products. During the same period of time that the prevalence of these modern chemicals has increased, there has been a remarkable increase in several chronic illnesses, including asthma and allergy in children. In this article we outline the scientific knowledge on phthalate exposure for asthma and airway diseases in children by examining epidemiological and experimental peer review data for potential explanatory mechanisms. Epidemiological data point to a possible correlation between phthalate exposure and asthma and airway diseases in children. Experimental studies present support for an adjuvant effect on basic mechanisms in allergic sensitization by several phthalates. Despite variations in the experimental design and reported result in the individual studies, a majority of published reports have identified adjuvant effects on Th2 differentiation, production of Th2 cytokines and enhanced levels of Th2 promoted immunoglobulins (mainly IgG1 but also IgE) in mice. A limited amount of data do also suggest phthalate-induced enhancement of mast cell degranulation and eosinophilic infiltration which are important parts in the early inflammation phase. Thus, some of the early key mechanisms in the pathology of allergic asthma could possibly be targeted by phthalate exposure. But the important questions of clinical relevance of real life exposure and identification of molecular targets that can explain interactions largely remain to be answered.

Phthalates, Pesticides, and Bisphenol-A Exposure and the Development of Nonoccupational Asthma and Allergies: How Valid Are the Links?

Phthalates, pesticides, and bisphenol-A (BPA) are three groups of chemicals, implicated in endocrine disruption and commonly found in the local environment, that have been implicated in the pathogenesis of asthma and allergies [1-3]. Multiple observational studies have demonstrated an association between exposure to phthalates and the development of asthma and allergies in humans. Associations with exposure to pesticides and BPA and the development of respiratory disease are less clear. However, recent evidence suggests that prenatal or early postnatal exposure to BPA may be deleterious to the developing immune system. Future cohort-driven epidemiological or translational research should focus on determining whether these ubiquitous chemicals contribute to the development of asthma and allergies in humans, and attempt to establish the routes and mechanisms by which they operate. Determining dose-response relationships will be important to establishing safe levels of these chemicals in the environment and in consumer products. Attempts to reduce exposures to chemicals such as phthalates, pesticides, and BPA may have environmental repercussions as well as public health impact for the developing child.

The role of exposure to phthalates from polyvinyl chloride products in the development of asthma and allergies: a systematic review and meta-analysis

BACKGROUND

Phthalates from polyvinyl chloride (PVC) plastics may have adverse effects on airways and immunologic systems, but the evidence has not been reviewed systematically.

OBJECTIVE

We reviewed the evidence for the role of exposure to phthalates from PVC products in the development of asthma and allergies.

METHODS

We conducted a Medline database search (1950 through May 2007) for relevant studies on the respiratory and allergic effects of exposure to phthalates from PVC products.

RESULTS

We based this review on 27 human and 14 laboratory toxicology studies. Two mouse inhalation experiments indicated that mono-2-ethylhexyl phthalate (MEHP) has the ability to modulate the immune response to exposure to a coallergen. The data suggested a no observed effect level of 30 microg MEHP/m3, calculated to be below the estimated level of human exposure in common environments. Case reports and series (n = 9) identified and verified cases of asthma that were very likely caused by fumes emitted from PVC film. Epidemiologic studies in adults (n = 10), mostly small studies in occupational settings, showed associations between heated PVC fumes and asthma and respiratory symptoms; studies in children (n = 5) showed an association between PVC surface materials in the home and the risk of asthma [fixed-effects model: summary odds ratio (OR), 1.55; 95% confidence interval (CI), 1.18-2.05; four studies] and allergies (OR, 1.32; 95% CI, 1.09-1.60; three studies).

CONCLUSIONS

High levels of phthalates from PVC products can modulate the murine immune response to a coallergen. Heated PVC fumes possibly contribute to development of asthma in adults. Epidemiologic studies in children show associations between indicators of phthalate exposure in the home and risk of asthma and allergies. The lack of objective exposure information limits the epidemiologic data.

Mast cell-associated TNF promotes dendritic cell migration

Mast cells represent a potential source of TNF, a mediator which can enhance dendritic cell (DC) migration. Although the importance of mast cell-associated TNF in regulating DC migration in vivo is not clear, mast cells and mast cell-derived TNF can contribute to the expression of certain models of contact hypersensitivity (CHS). We found that CHS to FITC was significantly impaired in mast cell-deficient Kit(W-sh/W-sh) or TNF(-/)(-) mice. The reduced expression of CHS in Kit(W-sh/W-sh) mice was fully repaired by local transfer of wild-type bone marrow-derived cultured mast cells (BMCMCs), but was only partially repaired by transfer of TNF(-/)(-) BMCMCs. Thus, mast cells, and mast cell-derived TNF, were required for optimal expression of CHS to FITC. We found that the migration of FITC-bearing skin DCs into draining lymph nodes (LNs) 24 h after epicutaneous administration of FITC in naive mice was significantly reduced in mast cell-deficient or TNF(-/)(-) mice, but levels of DC migration in these mutant mice increased to greater than wild-type levels by 48 h after FITC sensitization. Mast cell-deficient or TNF(-/)(-) mice also exhibited significantly reduced migration of airway DCs to local LNs at 24 h after intranasal challenge with FITC-OVA. Migration of FITC-bearing DCs to LNs draining the skin or airways 24 h after sensitization was repaired in Kit(W-sh/W-sh) mice which had been engrafted with wild-type but not TNF(-/)(-) BMCMCs. Our findings indicate that mast cell-associated TNF can contribute significantly to the initial stages of FITC-induced migration of cutaneous or airway DCs.

Gene expression profiling of dexamethasone-treated RBL-2H3 cells: induction of anti-inflammatory molecules

Glucocorticoids are well known for their anti-inflammatory effect through the regulation of gene expression in many types of immune cells, including mast cells. However, the genes that are involved in suppression of mast cell-mediated inflammation by glucocorticoids have not been fully identified. Therefore, we examined the dexamethasone (Dex)-responsive genes in RBL-2H3 mast cells using a high-density oligonucleotide microarray technique. Gene expression profiling revealed that the antigen-induced up-regulation of pro-inflammatory factors, including monocyte chemoattractant protein-1, was markedly inhibited by 100 nM Dex. On the other hand, Dex treatment itself caused the substantial up-regulation of many genes, including phenylethanolamine-N-methyl transferase (PNMT) and cytokine-inducible SH2-containing protein (CISH), in the mast cells. The expression of these two genes significantly increased 6 h after Dex exposure and lasted for more than 24 h. Considering that PNMT is the rate-determining enzyme in epinephrine synthesis and that CISH is a suppressor of cytokine signaling, these Dex-responsive genes may be potential anti-inflammatory factors. Thus, gene expression profiling suggested that Dex might exert its anti-inflammatory effect through two pathways in mast cells: the suppression and induction of potentially pro- and anti-inflammatory factors, respectively.

Effect of two nitrogenous diphenyl ether pesticides on mast cell activation

We examined the effect of two nitrogenous diphenyl ether pesticides, nitrofen (NIP) and chlornitrofen (CNP), on mast cell activation. RBL-2H3 (rat basophilic leukemia) cells were exposed to NIP or CNP for 30 min to investigate their effect on degranulation, and for 3 h to investigate their effect on cytokine production and gene expression. NIP and CNP increased IgE receptor-mediated beta-hexosaminidase release, MCP-1 release, and TNF-alpha release in a dose-dependent manner. The increasing effect of CNP on their release was greater than that of NIP. In the gene expression experiment, 30 microg/ml CNP significantly upregulated Egr-1, MCP-1 and GADD45a gene expression. These results suggest that at higher concentrations (more than 30 microg/ml) the nitrogenous diphenyl ether pesticides had both a degranulation-enhancing effect and proinflammatory cytokine-production enhancing effect through the expression of some transcription factors in RBL-2H3 cells.

Crucial role of type 2 inositol 1,4,5-trisphosphate receptors for acetylcholine-induced Ca2+ oscillations in vascular myocytes

OBJECTIVE

The aim of this study was to correlate the expression of InsP3R subtypes in native vascular and visceral myocytes with specific Ca2+-signaling patterns.

METHODS AND RESULTS

By Western blot and immunostaining, we showed that rat portal vein expressed InsP3R1 and InsP3R2 but not InsP3R3, whereas rat ureter expressed InsP3R1 and InsP3R3 but not InsP3R2. Acetylcholine induced single Ca2+ responses in all ureteric myocytes but only in 50% of vascular myocytes. In the remaining vascular myocytes, the first transient peak was followed by Ca2+ oscillations. By correlating Ca2+ signals and immunostaining, we revealed that oscillating vascular cells expressed both InsP3R1 and InsP3R2 whereas nonoscillating vascular cells expressed only InsP3R1. Acetylcholine-induced oscillations were not affected by inhibitors of ryanodine receptors, Ca2+-ATPases, Ca2+ influx, and mitochondrial Ca2+ uniporter but were inhibited by intracellular infusion of heparin. Using specific antibodies against InsP3R subtypes, we showed that acetylcholine-induced Ca2+ oscillations were specifically blocked by the anti-InsP3R antibody. These data were supported by antisense oligonucleotides targeting InsP3R2, which selectively inhibited Ca2+ oscillations.

CONCLUSIONS

Our results suggest that in native smooth muscle cells, a differential expression of InsP3R subtypes encodes specific InsP3-mediated Ca2+ responses and that the presence of the InsP3R2 subtype is required for acetylcholine-induced Ca2+ oscillations in vascular myocytes.

No immunotoxic effect on T cells with di (2-ethylhexyl) phthalate in male C57BL/6 mice

OBJECTIVES

To clarify whether di (2-ethylhexyl) phthalate (DEHP) has immunotoxic effects on both the expression of surface molecules (CD3, CD4, CD8 and CD28) on T cells of the thymus and spleen in male C57BL/6 mice.

METHODS

Animals were orally administered a 0.1% or 0.2% DEHP-containing diet for 10 or 20 days. Dietary corn oil was used as the vehicle for DEHP in preparing the diet.

RESULTS

Significant hepatic hypertrophy was clearly observed in the DEHP-exposed groups, while no atrophy was seen in the thymus or spleen in any treatment groups. In the thymus and spleen, no variation in the proportions of both T cells expressing CD3, CD4 and CD8 was shown with cytometry analysis. The surface expression of CD3, CD4, CD8 and CD28 on both T cells was also invariable in all analyzed stages of thymic differentiation and in the spleen. No effect of DEHP on mitogenesis was shown in the splenic T cells with anin vitro [(3)H]-thymidine-incorporation technique.

CONCLUSIONS

DEHP is probably not an immunosuppressor, particularly for T cells.