Cyclic AMP-independent stimulation of steroidogenesis in Y-1 adrenal tumor cells by antimitotic agents

The stimulation of steroidogenesis by antimitotic drugs has been studied in wild-type (Y-1) and cAMP-dependent protein kinase-deficient (kin-8) mouse adrenal tumor cell lines. Unlike some other cells, Y-1 cells do not increase their cAMP output upon exposure to antimitotic drugs such as colchicine, vinblastine or podophyllotoxin, which readily increase steroidogenesis. Moreover, no increase in cAMP can be detected over an extended time span. Stabilization of tubulin polymers by taxol or high concentrations of vinblastine blocks ACTH-, cholera toxin- or colchicine-stimulated steroidogenesis without major effects on cAMP levels. Colchicine and podophyllotoxin stimulate steroidogenesis in the cAMP-dependent protein kinase-deficient mutant to the same degree as in the wild-type Y-1 cells, although absolute steroid yields are lower in the mutant cells. We suggest that the antimitotic agents stimulate adrenal steroidogenesis by a cAMP-independent pathway that may involve facilitation of cholesterol access to the mitochondrion.     

Marked Cortisol Production by Intracrine ACTH in GIP-Treated Cultured Adrenal Cells in Which the GIP Receptor Was Exogenously Introduced

The ectopic expression of the glucose-dependent insulinotropic polypeptide receptor (GIPR) in the human adrenal gland causes significant hypercortisolemia after ingestion of each meal and leads to Cushing’s syndrome, implying that human GIPR activation is capable of robustly activating adrenal glucocorticoid secretion. In this study, we transiently transfected the human GIPR expression vector into cultured human adrenocortical carcinoma cells (H295R) and treated them with GIP to examine the direct link between GIPR activation and steroidogenesis. Using quantitative RT-PCR assay, we examined gene expression of steroidogenic related proteins, and carried out immunofluorescence analysis to prove that forced GIPR overexpression directly promotes production of steroidogenic enzymes CYP17A1 and CYP21A2 at the single cell level. Immunofluorescence showed that the transfection efficiency of the GIPR gene in H295R cells was approximately 5%, and GIP stimulation enhanced CYP21A2 and CYP17A1 expression in GIPR-introduced H295R cells (H295R-GIPR). Interestingly, these steroidogenic enzymes were also expressed in the GIPR (–) cells adjacent to the GIPR (+) cells. The mRNA levels of a cholesterol transport protein required for all steroidogenesis, StAR, and steroidogenic enzymes, HSD3β2, CYP11A1, CYP21A2, and CYP17A1 increased 1.2-2.1-fold in GIP-stimulated H295R-GIPR cells. These changes were reflected in the culture medium in which 1.5-fold increase in the cortisol concentration was confirmed. Furthermore, the levels of adenocorticotropic hormone (ACTH) receptor and ACTH precursor proopiomelanocortin (POMC) mRNA were upregulated 2- and 1.5-fold, respectively. Immunofluorescence showed that ACTH expression was detected in GIP-stimulated H295R-GIPR cells. An ACTH-receptor antagonist significantly inhibited steroidogenic gene expression and cortisol production. Immunostaining for both CYP17A1 and CYP21A2 was attenuated in cells treated with ACTH receptor antagonists as well as with POMC siRNA. These results demonstrated that GIPR activation promoted production and release of ACTH, and that steroidogenesis is activated by endogenously secreted ACTH following GIP administration, at least in part, in H295R cells.     

NCI-H295R,a Human Adrenal Cortex-Derived Cell Line,Expresses Purinergic Receptors Linked to Ca2+-Mobilization/Influx and Cortisol Secretion

Purinergic receptor expression and involvement in steroidogenesis were examined in NCI-H295R (H295R), a human adrenal cortex cell line which expresses all the key enzymes necessary for steroidogenesis. mRNA/protein for multiple P1 (A_2A and A_2B), P2X (P2X₅ and P2X₇), and P2Y (P2Y₁, P2Y₂, P2Y₆, P2Y₁₂, P2Y₁₃, and P2Y₁₄) purinergic receptors were detected in H295R. 2MeS-ATP (10–1000 µM), a P2Y₁ agonist, induced glucocorticoid (GC) secretion in a dose-dependent manner, while other extracellular purine/pyrimidine agonists (1–1000 µM) had no distinct effect on GC secretion. Extracellular purines, even non-steroidogenic ones, induced Ca²⁺-mobilization in the cells, independently of the extracellular Ca²⁺ concentration. Increases in intracellular Ca²⁺ concentration induced by extracellular purine agonists were transient, except when induced by ATP or 2MeS-ATP. Angiotensin II (AngII: 100 nM) and dibutyryl-cyclic AMP (db-cAMP: 500 µM) induced both GC secretion and Ca²⁺-mobilization in the presence of extracellular Ca²⁺ (1.2 mM). GC secretion by AngII was reduced by nifedipine (10–100 µM); whereas the Ca²⁺ channel blocker did not inhibit GC secretion by 2MeS-ATP. Thapsigargin followed by extracellular Ca²⁺ exposure induced Ca²⁺-influx in H295R, and the cells expressed mRNA/protein of the component molecules for store-operated calcium entry (SOCE): transient receptor C (TRPC) channels, calcium release-activated calcium channel protein 1 (Orai-1), and the stromal interaction molecule 1 (STIM1). In P2Y₁-knockdown, 2MeS-ATP-induced GC secretion was significantly inhibited. These results suggest that H295R expresses a functional P2Y₁ purinergic receptor for intracellular Ca²⁺-mobilization, and that P2Y₁ is linked to SOCE-activation, leading to Ca²⁺-influx which might be necessary for glucocorticoid secretion.     

The role of Rho-associated kinase inhibitor,Y-27632 on primary culture of ovine spermatogonial stem cells

The access to sufficient numbers of spermatogonial stem cells (SSCs) is a prerequisite for the study of their regulation and further biomanipulation. Rho kinase (ROCK) belongs to a family of serine/threonine kinases and involves in a wide range of fundamental cellular functions. The aim of the present study was to study the effect of ROCK inhibitor, Y-27632 (0.1-40 µM), during the primary culture of ovine SSCs. SSCs were collected from 3-5-month-old’s lamb testes. The viability of SSCs, the apoptosis assay of SSCs, the intracellular reactive oxygen species (ROS) analysis, and the SSCs markers and apoptosis-related gene expressions were detected by MTT reduction assay, Annexin V–FITC/ Propidium Iodide (PI) dual staining, flow cytometry and real-time-PCR studies, respectively. Morphological analyses indicated that the 5-10 µM Y-27632 had an optimal effect on the number of presumptive SSCs colonies and the area covered by them after a 10 days culture. The cell viability, apoptosis and necrosis of SSCs after 10 days’ culture were not affected in comparison with the control group, and the 20 µM of Y-27632 resulted in significantly decreased cell viability (P<0.05) and an increased necrosis of cells. On day 10 after culture, the expression of P53 was decreased with an increase from 0 to 10 µM in the Y-27632 dose. In the 20 µM Y-27632 group, the expressions of P53 and Bax were higher and the Bcl-2 was lower than other groups and these values were significantly different from 5 and 10 µM Y-27632 groups (P<0.05). The level of intracellular ROS was decreased with an increase in the Y-27632 dose from 5 to 20 µM in comparison with the control group. In conclusion, the present study demonstrated that Y-27632 at a concentration of 5-10 µM provided optimal culture conditions for the primary culture of ovine SSCs.     

Molecular basis underlying the biological effects elicited by extremely low-frequency magnetic field (ELF-MF) on neuroblastoma cells

Extremely low-frequency magnetic fields (ELF-MFs) may affect human health because of the possible associations with leukemia but also with cancer, cardiovascular, and neurological disorders. In the present work, human SH-SY5Y neuroblastoma cells were exposed to a 50 Hz, 1 mT sinusoidal ELF-MF at three different times, that is, 5 days (T5), 10 days (T10), and 15 days (T15) and then the effects of ELF-MF on proteome expression and biological behavior were investigated. Through comparative analysis between treated and control samples, we analyzed the proteome changes induced by ELF-MF exposure. Nine new proteins resolved in sample after a 15-day treatment were involved in a cellular defense mechanism and/or in cellular organization and proliferation such as peroxiredoxin isoenzymes (2, 3, and 6), 3-mercaptopyruvate sulfurtransferase, actin cytoplasmatic 2, t-complex protein subunit beta, ropporin-1A, and profilin-2 and spindlin-1. Our results indicated that ELF-MFs exposure altered the proliferative status and other important cell biology-related parameters, such as cell growth pattern, and cytoskeletal organization. These findings support our hypothesis that ELF radiation could trigger a shift toward a more invasive phenotype.     

The effect of theophylline on adenosine 3′, 5′-monophosphate-dependent protein kinase and ACTH1–24 stimulated steroidogenesis in bovine adrenal cortical cells

Theophylline (theo), a known phosphodiesterase (PDE) inhibitor, was tested for its effects on ACTH_1–24 regulated steroidogenesis in isolated bovine adrenal cortical cells. Theo produced a dose related inhibition of ACTH_1–24 stimulated cortisol synthesis with half maximal inhibition occuring at 7 mM. Theo enhanced ACTH_1–24 stimulated cellular adenosine 3′, 5′-monophosphate (cAMP) levels above that produced by ACTH_1–24 alone confirming its inhibition of cAMP PDE. When tested on cAMP binding protein and cAMP-dependent protein kinase activities in cytosol prepared from bovine adrenal cortex, theo displaced ³H-cAMP binding to cAMP binding protein and inhibited cAMP-stimulated protein kinase activity. The half maximal inhibition of cAMP binding and protein kinase activity was observed at 10 and 5 mM, respectively. Inhibition of cAMP-dependent protein kinase by theo provides a possible explanation of its inhibitory effects on adrenal steroidogenesis and further implicates cAMP-dependent protein kinase in mediating ACTH stimulated steroidogenesis. Furthermore these studies suggest a novel mechanism of action for theo in addition to its known action on cAMP PDE.     

Recovery of Adrenal Function after Long-Term Glucocorticoid Therapy for Giant Cell Arteritis: A Cohort Study

Objectives

Giant cell arteritis (GCA) is a chronic systemic vasculitis of large and medium-sized arteries, for which long-term glucocorticoid (GC) treatment is needed. During GC withdrawal patients can suffer adrenal insufficiency. We sought to determine the time until recovery of adrenal function after long-term GC therapy, and to assess the prevalence and predictors for secondary adrenal insufficiency.

Subjects and Design

150 patients meeting the ACR criteria for GCA between 1984 and 2012 were analyzed. All received the same GC treatment protocol. The low-dose ACTH stimulation test was repeated annually until adrenal recovery. Biographical, clinical and laboratory data were collected prospectively and compared.

Results

At the first ACTH test, 74 (49%) patients were non-responders: of these, the mean time until recovery of adrenal function was 14 months (max: 51 months). A normal test response occurred within 36 months in 85% of patients. However, adrenal function never recovered in 5% of patients. GC of >15 mg/day at 6 months, GC of >9.5 mg/day at 12 months, treatment duration of >19 months, a cumulative GC dose of >8.5 g, and a basal cortisol concentration of <386 nmol/L were all statistically associated with a negative response in the first ACTH test (p <0.05).

Conclusion

Adrenal insufficiency in patients with GCA, treated long-term with GC, was frequent but transitory. Thus, physicians’ vigilance should be increased and an ACTH test should be performed when GC causes the above associated statistical factors.     

Relevance of c-fos proto-oncogene induction for the steroidogenic response to ACTH,dcAMP and phorbol ester in adrenocortical cells

We previously reported that ACTH, but not dibutyryl cAMP, rapidly induces the c-fos proto-oncogene in Y-1 adrenocortical cells.Here we show that PMA induces c-fos with similar kinetics when compared with ACTH (0.5–1 h peak) but reaches only 60% of the maximal ACTH induction and dcAMP is a weak c-fos inducer (15% of ACTH). However, combination of PMA and dcAMP has a synergistic effect leading to maximal c-fos induction. c-fos expression may play a role in the RNA synthesis-dependent corticosteroidogenesis response and/or growth regulation by ACTH.We also show that, in contrast to dcAMP, PMA is a poor steroidogenesis stimulator (15 to 17% of maximum ACTH-stimulated level), its activity being completely dependent on RNA synthesis. Combination of dcAMP and PMA yields an additive steroidogenesis stimulation, an effect that is also dependent on RNA synthesis. Although no strict correlation was found between c-fos induction and early steroidogenesis stimulation, particularly with respect to cAMP derivatives, the results suggest that a PKC pathway is likely to cooperate with the classical cAMP-PKA pathway in adrenal cells' RNA-dependent steroidogenesis.Abbreviations ACTH Adrenocorticotropic Hormone - PMA Phorbol-12-Myrystate-13-Acetate - dcAMP dibutyryl cyclic AMP - DME Dulbecco's Modified Eagle's minimal medium - FCS Fetal Calf Serum     

The role of chloride ions in the regulation of steroidogenesis in rat Leydig cells and adrenal cells

The role of chloride ions in the regulation of steroidogenesis in rat Leydig cells and adrenal cells has been investigated. It was found that the chloride channel blocker 4,4′-diisothiocyanatostilbene-2,2′-disulphonic acid (DIDS) inhibited LH but not dibutyryl cAMP (dbcAMP)-stimulated steroidogenesis in the Leydig cells. This was found to be via an inhibition of cAMP production, because both LH- and forskolin-stimulated cAMP productions were inhibited by DIDS. The exclusion of chloride ions enhanced steroidogenesis during incubation of Leydig cells and adrenal cells with dbcAMP. The adrenal cells were found to be more sensitive to dbcAMP than Leydig cells and the enhancing effects of chloride removal were higher. In the presence of chloride ions, near maximum steroidogenesis was achieved with approximately 60 μM and 1 mM dbcAMP in the adrenal and Leydig cells, respectively. In the absence of chloride ions the concentrations required decreased approximately 50-fold and 10-fold, respectively. It is concluded that although LH may regulate DIDS sensitive chloride channels, the enhanced stimulation of cAMP-mediated steroidogenesis by chloride exclusion is not mediated via these channels. We propose a model based on the present and previous studies [1] with Leydig tumour (MA10) cells i.e. that intracellular chloride ion depletion enhances the action of cAMP on protein synthesis which results in increased synthesis of the Steroidogenic Acute Regulator (StAR) protein and consequently increased steroidogenesis.     

LCAT deficiency in mice is associated with a diminished adrenal glucocorticoid function

In vitro studies have suggested that HDL and apoB-containing lipoproteins can provide cholesterol for synthesis of glucocorticoids. Here we assessed adrenal glucocorticoid function in LCAT knockout (KO) mice to determine the specific contribution of HDL-cholesteryl esters to adrenal glucocorticoid output in vivo. LCAT KO mice exhibit an 8-fold higher plasma free cholesterol-to-cholesteryl ester ratio (P < 0.001) and complete HDL-cholesteryl ester deficiency. ApoB-containing lipoprotein and associated triglyceride levels are increased in LCAT KO mice as compared with C57BL/6 control mice (44%; P < 0.05). Glucocorticoid-producing adrenocortical cells within the zona fasciculata in LCAT KO mice are devoid of neutral lipids. However, adrenal weights and basal corticosterone levels are not significantly changed in LCAT KO mice. In contrast, adrenals of LCAT KO mice show compensatory up-regulation of genes involved in cholesterol synthesis (HMG-CoA reductase; 516%; P < 0.001) and acquisition (LDL receptor; 385%; P < 0.001) and a marked 40–50% lower glucocorticoid response to adrenocorticotropic hormone exposure, endotoxemia, or fasting (P < 0.001 for all). In conclusion, our studies show that HDL-cholesteryl ester deficiency in LCAT KO mice is associated with a 40–50% lower adrenal glucocorticoid output. These findings further highlight the important novel role for HDL as cholesterol donor for the synthesis of glucocorticoids by the adrenals.     

Cytochalasin-stimulated steroidogenesis from high density lipoproteins

The cytochalasins stimulate steroid secretion of Y-1 adrenal tumor cells two-to threefold. The order of potencies is cytochalasin E is greater than D is greater than B, but the maximum response is the the same and always less than with ACTH. Like that with ACTH, the stimulation has a rapid onset, is easily reversible, is inhibited by cucloheximide and aminoglutethimide, and occurs at a stage before pregnenolone. Although the cytochalasin, like ACTH, produce cell rounding, it is shown that this morphological change is not necessarily coupled to steridogenesis. Unlike ACTH, cytochalasin B does not measurably increase cellular levels of cAMP at concentrations that lead to maximal steroidogenesis. The cytochalasin B-induced stimulation of steroidogenesis, unlike the short-term ACTH effect, fails to occur in the absence of serum. This lack of response can be corrected by even low concentrations of human high density lipoproteins (HDL) but not by low density lipoproteins (LDL). We, therefore, propose that cytochalasin B enhances the availability of cholesterol bound to HDL for steroidogenesis by Y-1 adrenal cells.     

Exogenous steroids alter steroidogenesis in cultured Y-1 adrenal tumor cells by actions preceding cyclic AMP

Using cultured Y-1 mouse adrenal tumor cells which produce 20 alpha-hydroxy-4-pregnen-3-one (20-DHP), it was found that 0.01 mM corticosterone and deoxycorticosterone increased basal and inhibited ACTH-induced 20-DHP production during consecutive 30 and 120 min incubations. Steroid effects were concentration-dependent and reversible. Six other steroids tested did not stimulate 20-DHP production and varied in ability to inhibit ACTH-stimulated steroidogenesis. Experiments demonstrated that 20-DHP production following treatment with cholera toxin, N,0'-dibutyryl cyclic AMP (dbcAMP), or pregnenolone was not inhibited by exogenous steroids. Corticosterone (0.01 mM) increased basal and inhibited ACTH-induced intracellular cyclic AMP (cAMP) production. Cytochalasin D, a microfilament perturbing agent, inhibited steroid-stimulated 20-DHP production, suggesting that ACTH and steroid stimulation mechanisms were similar. These findings taken together suggest that exogenous steroids can alter steroidogenesis by modifying plasma membrane adenylate cyclase activity.     

A Cell-Autonomous Molecular Cascade Initiated by AMP-Activated Protein Kinase Represses Steroidogenesis

Steroid hormones regulate essential physiological processes, and inadequate levels are associated with various pathological conditions. In testosterone-producing Leydig cells, steroidogenesis is strongly stimulated by luteinizing hormone (LH) via its receptor leading to increased cyclic AMP (cAMP) production and expression of the steroidogenic acute regulatory (STAR) protein, which is essential for the initiation of steroidogenesis. Steroidogenesis then passively decreases with the degradation of cAMP into AMP by phosphodiesterases. In this study, we show that AMP-activated protein kinase (AMPK) is activated following cAMP-to-AMP breakdown in MA-10 and MLTC-1 Leydig cells. Activated AMPK then actively inhibits cAMP-induced steroidogenesis by repressing the expression of key regulators of steroidogenesis, including Star and Nr4a1. Similar results were obtained in Y-1 adrenal cells and in the constitutively steroidogenic R2C cells. We have also determined that maximum AMPK activation following stimulation of steroidogenesis in MA-10 Leydig cells occurs when steroid hormone production has reached a plateau. Our data identify AMPK as a molecular rheostat that actively represses steroid hormone biosynthesis to preserve cellular energy homeostasis and prevent excess steroid production.     

Isolation and characterization of cyclic AMP-resistant variants from a functional adrenal cortical cell line.

We have isolated a number of cyclic AMP-resistant cell lines and characterized two of them, 3B4 and 10F2s, from a functional adrenal cortical cell line, Y-1. At seeding densities above $\text{100}\text{cells}\text{10}\text{cm}$ diameter plates, the variant cells are resistant in their morphological change, plating efficiency and growth to the normal effects of dibutyryl cyclic AMP (db-cAMP). At lower seeding densities, 3B4 and 10F2 have retained a slight sensitivity to db-cAMP in their plating efficiency and in their morphology. Studies with various nucleotides and cAMP analogues show that the inhibitory effects of db-cAMP on the growth and morphology of Y-1 cells are not due to degradation products of db-cAMP. There is loss of response to ACTH in the variant cell lines such that there are no effects of ACTH on plating efficiency, growth, morphology, steroidogenesis and cAMP excretion. In addition, the variant cell lines show lowered activities of the cAMP binding receptor and cAMP-dependent protein kinase. Preliminary studies indicate that in Y-1, cAMP markedly reduces protein phosphorylation, and it inhibits phosphate uptake. In the variants, the protein phosphorylation and phosphate uptake are maintained even in the presence of db-cAMP. The maintenance of phosphorylation in the presence of db-cAMP may play an important role in the ability of the cells to survive in high concentrations of db-cAMP. The variant cell lines can be stimulated by db-cAMP to increase steroidogenesis, although the stimulated levels of steroidogenesis in 3B4 and 10F2 are less than those in Y-1. The variant phenotype is stable in vitro and in vivo.     

Extremely Low-Frequency Magnetic Fields and the Risk of Childhood B-Lineage Acute Lymphoblastic Leukemia in a City With High Incidence of Leukemia and Elevated Exposure to ELF Magnetic Fields

It is important to study the relationship between extremely low-frequency magnetic fields (ELF-MFs) and childhood leukemia, particularly in locations with a high incidence of this neoplasm in children and an elevated exposure to ELF-MF, such as Mexico City. The aim was to investigate the association between ELF-MF exposure and the risk of B-lineage acute lymphoblastic leukemia (B-ALL). A case–control study was conducted in Mexico City during the period from 2010 to 2011. Residential 24-h ELF-MF measurements were obtained for 290 incident B-ALL patients and 407 controls, aged less than 16 years. Controls were frequency-matched by sex, age (±18 months), and health institution. The adjusted odds ratios (aOR) and 95% confidence intervals (CIs) were calculated. ELF-MF exposure at <0.2 μT was used to define the reference group. ELF-MF exposure at ≥0.3 μT was observed in 11.3% of the controls. Different ELF-MF intensity cutoff values were used to define the highest exposure category; the highest exposure category for each cutoff value was associated with an increased risk of B-ALL compared with the corresponding lower exposure categories. The aORs were as follows: ≥0.2 μT = 1.26 (95% CI: 0.84–1.89); ≥0.3 μT = 1.53 (95% CI: 0.95–2.48); ≥0.4 μT = 1.87 (95% CI: 1.04–3.35); ≥0.5 μT = 1.80 (95% CI 0.95–3.44); ≥0.6 μT = 2.32 (95% CI: 1.10–4.93). ELF-MF exposure as a continuous variable (per 0.2 μT intervals) was associated with B-ALL risk (aOR = 1.06; 95% CI: 1.01–1.12). In the present study, the proportion of children exposed to ≥0.3 μT is among the highest reported worldwide. Additionally, an ELF-MF exposure ≥0.4 μT may be associated with the risk of B-ALL. Bioelectromagnetics. © 2020 Bioelectromagnetics Society     

Regulation of rat and bovine adrenal metabolism of polycyclic aromatic hydrocarbons by adrenocorticotropin and 2,3,7,8-tetrachlorodibenzo-p-dioxin

The effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) on polycyclic aromatic hydrocarbon (PAH) metabolism and steroidogenesis in primary cultures of bovine adrenal cortical (BAC) and rat adrenal cortical (RAC) cells have been examined. Remarkably TCDD is an ineffective inducer (15-50%) of PAH metabolism in confluent BAC cells and completely antagonizes a 5-fold induction by benz[alpha]anthracene (BA). In the same concentration range (EC50 5 X 10(-11) M) TCDD suppresses steroidogenesis through an effect on cholesterol metabolism. Adrenocorticotropin (ACTH) and cAMP also suppress PAH metabolism at concentrations which stimulate steroidogenesis (10(-7) M). In RAC cells ACTH potently induces PAH metabolism (7-fold) at a comparable concentration to the stimulation of steroidogenesis. Parallel stimulation of PAH metabolism and steroidogenesis by cAMP suggest that ACTH induction of PAH metabolism is mediated by cAMP. TCDD induces PAH metabolism (2.8-fold, EC50 8 X 10(-11) M) at similar concentrations to the inhibitory effect in BAC cells and this action is additive with ACTH induction. In male rats in vivo TCDD induces adrenal microsomal PAH metabolism (72%) and is more effective in this respect than 3-methylcholanthrene (3MC). Rabbit antibodies against rat liver cytochrome P-450c (the major TCDD-inducible liver form) inhibited the TCDD-induced adrenal metabolism of 7,12-dimethylbenz[alpha]anthracene (DMBA), which also exhibited regioselectivity typical of metabolism by P-450c. Constitutive adrenal microsomal metabolism, which exhibited regioselectivity of DMBA metabolism comparable to the ACTH-sensitive cellular metabolism, was not affected by anti-P-450c. It is concluded that ACTH and TCDD induce distinct forms of cytochrome P-450 in RAC cells and that the latter represents a typical Ah-receptor mediated response. The anomalous effect on PAH metabolism in BAC cells that parallels inhibition of steroidogenesis may derive from repression of a distinct adrenal form of P-450 by the TCDD-Ah-receptor complex.     

Effects of 50 Hz sinusoidal magnetic fields on Hsp27, Hsp70, Hsp90 expression in porcine aortic endothelial cells (PAEC)

The aim of the present study was to investigate the influence of 50 Hz sinusoidal magnetic field on Hsp27, Hsp70, and Hsp90 expression in a model of primary culture of porcine aortic endothelial cells (PAEC). We took into consideration the Hsp profile in terms of mRNA expression, protein expression and protein localization inside the cells. The choice of the cell system was motivated by the involvement of the endothelial cells in the onset of many diseases; moreover, only few reports describe the effects of extremely low frequency magnetic fields (ELF-MFs) on such cells. ELF-MF exposure induced an increase in the mRNA levels of the three proteins, which was statistically significant for Hsp70. On the contrary, we did not observe any influence on Hsp27, Hsp70, and Hsp90 protein levels. Analysis in situ by immunofluorescence revealed that ELF-MF exposure affected the cellular distribution of Hsp27; in particular a partial relocalization in the nucleus was observed.