Role of selenium in regulation of spermatogenesis: involvement of activator protein 1

Selenium (Se) is involved in the process of male reproduction. Several studies have been carried out to find the mechanism of Se action through identified selenoproteins. Especially selenoenzyme phospholipid glutathione peroxidase (PHGPx, GPx-4) plays a pivotal role in regulating spermatogenesis. However, the action of selenium is best known as an antioxidant which acts through various selenoproteins viz. glutathione peroxidase, thioredoxin reductase and selenoprotein P. Oxidative stress is currently being considered a leading cause of male infertility. Presently, the involvement of redox active transcription factor, AP1 (Activator protein1) in testicular function was studied. AP1 is redox sensitive and also controls cell proliferation. The effects of Se might be mediated through it. Different Se status - deficient, adequate and excess Se - were generated in male Balb/c mice by feeding yeast based selenium deficient diet and deficient diet supplemented with Se as sodium selenite (0.2 and 1 ppm Se), respectively, for a period of 4 and 8 weeks. Se status was checked by measuring the Se levels and glutathione peroxidase (GSH-Px) activity in testis and liver. The reproductive potential of mice was affected at these changed Se levels. Changes in the activity of superoxide dismutase (SOD), levels of reduced glutathione (GSH) and oxidized glutathione (GSSG) were observed indicating increased oxidative stress at both the levels. Further, changes in the mRNA expression of GSH-Px, gamma-glutamylcysteine synthetase gammaGCS) and Mn superoxide dismutase (MnSOD) were observed. Decrease in cjun and cfos mRNA levels were observed at both the Se status (deficient and excess) which might be responsible for decreased germ cell number, differentiation and reduced fertility observed at the altered Se levels.

[Induction of meiotic disturbances in spermatocytes I by pheromones as an inhibiting mechanism of male reproductive function in house mice]

The influence of pheromons on reproduction and other important physiological characteristics has been reported for many mammalian species. However, mechanisms of this action at the level of target cells still remain unclear. A study was made of the influence of non-identified pheromones from adult males and a female pheromone 2,5-dimethylpyrazine on germ cells of CBA inbred strain mice. Cytogenetic analysis shows a significant increase in such meiotic disturbances as multivalent associations and autsomal univalents 24 h after exposure to pheromonal cues. Results of in situ hybridization show that the level of c-fos and c-jun expression is significantly higher 3.5 h after exposure to pheromones of adult males. It is likely that destabilization of chromosomal apparatus in dividing meiotic cells forms the basis of some reproductive effects of murine pheromones. Possible mechanisms of pheromone influence on reproduction are discussed.

Fibroblast growth factor-2 stimulates interleukin-6 secretion in human pancreatic periacinar myofibroblasts

OBJECTIVES

Fibroblast growth factor-2 (FGF-2) plays an important role in the pathophysiology of acute and chronic pancreatitis. In the present study, to evaluate the proinflammatory nature of FGF-2, we investigated the effects of FGF-2 on IL-6 secretion in human pancreatic periacinar myofibroblasts.

METHODS

IL-6 supernatant levels were determined by enzyme-linked immunosorbent assays (ELISA). IL-6 mRNA expression were determined by Northern blots and quantitative PCRs. Activated protein (AP)-1 DNA-binding activities were evaluated by electrophoretic gel mobility shift assays (EMSA).

RESULTS

FGF-2 induced IL-6 release in a dose- and time-dependent manner. FGF-2 activity for IL-6 induction was the same as that of IL-17. The combination of FGF-2 and IL-17 exerted additive effects at mRNA and protein levels. FGF-2 induced AP-1 DNA-binding activity, but blockage of AP-1 signaling by adenovirus-mediated transfer of a dominant negative c-Jun gene did not affect FGF-2-induced IL-6 mRNA expression. FGF-2 rapidly induced activation of ERK1/2 and p38 MAP kinases, and specific inhibitors for these enzymes significantly reduced FGF-2-induced IL-6 release.

CONCLUSION

In the pancreas, FGF-2 may not only play a role as a growth factor in tissue injury repair processes but also as an inducer of acute-phase response via stimulation of IL-6 release.

Activation of stress-responsive promoters by ionizing radiation for deployment in targeted gene therapy

Radiotherapy is one of the principal modalities of cancer treatment, but the delivery of a curative dose of ionizing radiation (IR) to the tumour is frequently limited by the need to protect the normal tissues within the irradiated area from radiation damage. This problem could be circumvented if tumour cells could be selectively sensitized to killing by IR. One way to achieve this goal would be to transduce the tumour cells with expression vectors carrying toxin genes under the control of promoters that are inactive unless induced by IR. For this approach to be successful, two parameters must be met: (i) the expression vector has to be delivered to the tumour or its immediate vicinity (e.g. its vasculature) and (ii) the promoter driving the expression of the toxin gene has to have negligible basal activity, yet has to be activated by clinically-achievable doses of IR. Several vectors that fulfil these criteria are currently reaching clinical trials. In this review, we examine the response of mammalian cells to IR, and the current status of radiation-induced suicide gene therapy that is dependent on this response.

Differential expression of AP-1 transcription factor genes c-fos and c-jun in the helminth parasites Taenia crassiceps and Taenia solium

Homologues of c-fos and c-jun from total DNA of Taenia crassiceps and Taenia solium were cloned and sequenced. The amino acid alignment analysis revealed that c-fos DNAs from T. crassiceps and T. solium were highly homologous (96%), and both have high homology compared to several mammalian c-fos proteins (93% to mouse, 96% to rat and 86% to human). The c-jun protein alignment showed higher homology (T. crassiceps and T. solium have 98%), when compared with mouse, rat and human, being 92%, 98% and 93% respectively. RT-PCR amplification of the parasite's total RNA, showed that T. crassiceps expressed both AP-1 complex genes, while T. solium only expressed c-fos. Southern blot hybridization analysis confirmed the true origin of each amplified gene. AP-1 transcription gene expression is regulated by oestradiol in the same fashion as their mammalian counterparts only in T. crassiceps. To study if AP-1 genes are involved in a physiological function of the cyst, reproduction was studied in vitro. Oestradiol treatment stimulated reproduction in T. crassiceps but not in T. solium cysticerci. This is the first report of the detection and functionality of AP-1 transcription factor genes in any species of helminth parasite.

Molecular Mechanism of c-jun Antisense Gene Transfection in Alleviating Injury of Cardiomyocytes Treated with Burn Serum and Hypoxia

To explore the molecular mechanism of c-jun antisense gene transfection in alleviating injury of cardiomyocytes treated with burn serum and hypoxia, burn serum was collected from Wistar rats inflicted with 30% third-degree burn of the total body surface area. The cardiomyocytes of neonatal Wistar rats were cultured and then treated with burn serum and hypoxia (a gas mixture containing 1% O2). The constructed c-jun antisense gene recombinant was transfected into the cardiomyocytes of neonatal Wistar rats. TdT-mediated d-utp nick end labeling (TUNEL) was adopted to examine cardiomyocyte apoptosis. Morphological changes of cardiomyocytes were observed under an optic-microscope and an electron-microscope. Expression of troponin T and beta-tubulin protein, c-jun protein, protein kinase Ca (PKCa), and c-jun N-terminal kinase (JNK) were assayed with Western blot in the transfected and non-transfected groups. The morphology of cardiomyocytes in the non-transfected group changed explicitly, but the change was not so obvious in the transfected cardiomyocytes. The expression of beta-tubulin and troponin increased significantly in the transfected group as compared with the non-transfected group. In the non-transfected group, numbers of apoptotic cardiomyocytes were significantly higher than in the transfected group. The c-jun protein, PKCa, and JNK were significantly expressed in the non-transfected group, and they reached a maximum at the 24th hour after cardiomyocytes were treated with burn serum and hypoxia. In the transfected group, however, expressions of c-jun protein, PKCa, and JNK decreased significantly compared with the non-transfected group. The c-jun antisense gene recombinant transfection alleviates injury to cardiomyocytes treated with burn serum and hypoxia, probably through low expression of PKCa and JNK.

Myocardial hypertrophy is not a prerequisite for changes in early gene expression in left ventricular volume overload

Currently it is not certain whether hypertrophy or the underlying disease is the primary trigger of the alterations in early gene expression in the progression of cardiac disease to end-stage heart failure. In this study, we tested the notion that in left ventricular overload disorders, the changes in early gene expression in the progression to heart failure is independent of the manifestation of cardiac hypertrophy. We compared the expression of the early genes c-fos, c-myc, and c-jun in six dilated cardiomyopathic hearts (DCM) and 15 patients with left ventricular volume overload (VOL) resulting from mitral/aortic regurgitation and no significant stenosis or hypertrophic manifestations, using eight healthy donor hearts as controls. In VOL, c-myc was elevated by 88% (P < 0.01) in the left ventricle, 46% in the right ventricle, onefold (P < 0.01) in the left atrium, and 54% (P < 0.05) in the right atrium, while in DCM, it was increased by 71% (P < 0.02), 55%, 48% (P < 0.05) and 91% (P < 0.05), respectively. Similarly, c-jun was elevated by 41% (P < 0.01) in the left ventricle, 39% (P < 0.05) in the right ventricle, 83% (P < 0.02) in the left atrium and 21% in the right atrium in VOL, while in DCM it was elevated by 13% in the left ventricle, 29% in the left atrium, and 41% in the right atrium, but decreased by 13% in the right ventricle. In contrast, c-fos was slightly decreased in the left ventricle and atrium of both DCM and VOL, and in left atrium of the VOL group, but remained unchanged in the other myocardial chambers. These results show that, in the human myocardium, the three early genes are regulated differently, possibly in disease- and chamber-specific fashions, and manifestation of left ventricular hypertrophy is not a prerequisite for the elevation in their expression in left ventricular overload disorders.

A mechanism underlying STAT4-mediated up-regulation of IFN-gamma induction inTCR-triggered T cells

IL-12 promotes T(h)1 development/IFN-gamma expression by activating STAT4. However, it is still unclear how STAT4 elicits IFN-gamma promoter activation. Here, we investigated the mechanism by which IL-12-activated STAT4 functions for IFN-gamma induction in TCR-triggered T cells. TCR stimulation induced high levels of IFN-gamma production depending on co-stimulation with IL-12. IL-12 stimulation greatly enhanced the promoter-binding activity of c-Jun/AP-1, a critical transcription factor for IFN-gamma gene expression in wild-type T cells, but not in STAT4-deficient (STAT4(-/-)) T cells. Comparable amounts of c-Jun were induced by TCR stimulation in both wild-type and STAT4(-/-) T cells irrespective of IL-12 co-stimulation. However, c-Jun bound to STAT4 in IL-12-co-stimulated wild-type T cells. c-Jun forming a complex with STAT4 efficiently interacted with the AP-1-related sequence of the IFN-gamma promoter. Such an enhanced c-Jun binding did not occur in STAT4(-/-) T cells. These results show that STAT4 contributes to enhancing IFN-gamma expression by up-regulating the binding of TCR signal-induced AP-1 to the relevant promoter sequence.

Expression of JunB induced by X-rays in mice

OBJECTIVE

To explore JunB gene expression in spleen cells of mice after the whole body irradiation as well as in normal hematopoietic and leukemia cells in the primary culture after different dosages of X-ray irradiation.

METHODS

Spleen cells were isolated from the mice irradiated with 3 Gy X-rays. Primary cultured cells from mice were incubated in different intervals after X-irradiation at different dosages. Total RNA was extracted from the cells and the fluctuation of JunB mRNA level was assessed by the RNA ratio of JunB/beta-actin measured by quantitative Northern blot hybridization.

RESULTS

After the mice were exposed to 3 Gy X-rays irradiation, JunB expression in spleen cells was remarkably and rapidly increased, and reached its peak 0.5 h later in C3H/He mice and 1 h later in Balb/c mice. In the primary culture of normal spleen and leukemia cells, JunB mRNA levels increased 30 min after irradiation. The enhanced levels of JunB mRNA were returned to a normal level within 240 min after irradiation.

CONCLUSIONS

JunB gene is responsive to ionizing irradiation and is induced at immediate-early phase after the stimulation. This suggests that the JunB gene plays an important role in the early process of the cells against radiation.

Human Bcl-2 activates ERK signaling pathway to regulate activating protein-1, lens epithelium-derived growth factor and downstream genes

The proto-oncogene, bcl-2, has various functions besides its role in protecting cells from apoptosis. One of the functions is to regulate expression of other genes. Previous studies have demonstrated that Bcl-2 regulates activities of several important transcription factors including NF-kappaB and p53, and also their downstream genes. In our recent studies, we reported that Bcl-2 substantially downregulates expression of the endogenous alphaB-crystallin gene through modulating the transcriptional activity of lens epithelium-derived growth factor (LEDGF). In the present communication, we report that human Bcl-2 can positively regulate expression of the proto-oncogenes c-jun and c-fos. Moreover, it enhances the DNA binding activity and transactivity of the activating protein-1 (AP-1). Furthermore, we present evidence to show that Bcl-2 can also activate both ERK1 and ERK2 MAP kinases. Inhibition of the activities of these kinases or the upstream activating kinases by pharmacological inhibitors or dominant-negative mutants abolishes the Bcl-2-mediated regulation of AP-1, LEDGF and their downstream genes. Together, our results demonstrate that through activation of the ERK kinase signaling pathway, Bcl-2 regulates the transcriptional activities of multiple transcription factors, and hence modulates the expression of their downstream genes. Thus, our results provide a mechanism to explain how Bcl-2 may regulate expression of other genes.

Dominant-negative c-Jun (TAM67) target genes: HMGA1 is required for tumor promoter-induced transformation

Activation of the transcription factor AP-1 (activator protein-1) is required for tumor promotion and maintenance of malignant phenotype. A number of AP-1-regulated genes that play a role in tumor progression have been identified. However, AP-1-regulated genes driving tumor induction are yet to be defined. Previous studies have established that expression of a dominant-negative c-Jun (TAM67) inhibits phorbol 12-tetradecanoyl-13-acetate (TPA)-induced AP-1 transactivation as well as transformation in mouse epidermal JB6/P+ cells and tumor promotion in mouse skin carcinogenesis. In this study, we utilized the tumor promotion-sensitive JB6/P+ cells to identify AP-1-regulated TAM67 target genes and to establish causal significance in transformation for one target gene. A 2700 cDNA microarray was queried with RNA from TPA-treated P+ cells with or without TAM67 expression. Under conditions in which TAM expression inhibited TPA-induced transformation, microarray analysis identified a subset of six genes induced by TPA and suppressed by TAM67. One of the identified genes, the high-mobility group protein A1 (Hmga1) is induced by TPA in P+, but not in transformation-resistant P cells. We show that TPA induction of the architectural transcription factor HMGA1 is inhibited by TAM67, is extracellular-signal-regulated kinase (ERK)-activation dependent, and is mediated by AP-1. HMGA1 antisense construct transfected into P+ cells blocked HMGA1 protein expression and inhibited TPA-induced transformation indicating that HMGA1 is required for transformation. HMGA1 is not however sufficient as HMGA1a or HMGA1b overexpression did not confer transformation sensitivity on P- cells. Although HMGA1 expression is ERK dependent, it is not the only ERK-dependent event required for transformation because it does not suffice to rescue ERK-deficient P- cells. Our study shows (a) TAM 67 when it inhibits AP-1 and transformation, targets a relatively small number of genes; (b) HMGA1, a TAM67 target gene, is causally related to transformation and therefore a potentially important target for cancer prevention.

The gut-brain peptide neuromedin U is involved in the mammalian circadian oscillator system

Immunohistochemical analysis revealed the presence of a gut-brain peptide, neuromedin U (NMU), in the suprachiasmatic nucleus (SCN), which is the site of the master circadian oscillator. The expression of NMU mRNA exhibited a circadian rhythm, with the peak expression in the SCN occurring at CT4-8h. The two NMU-binding receptors (NMU-R1 and NMU-R2) were also expressed in the SCN, but their phase angles were different. Intracerebroventricular injection (ICV) of NMU induced the expression of Fos protein in the SCN cells and caused a phase-dependent phase shift of the circadian locomotor activity rhythm. The magnitude of the phase shift was dose dependent. This NMU-induced phase shift was of the nonphotic type. Quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis revealed increases in the expression in the SCN of immediate early genes, such as c-fos, NGFI-A, NGFI-B, and JunB. Furthermore, ICV injection of NMU increased the expression of Per1, but not Per2, in the SCN. These results indicate that NMU may play some important role in the circadian oscillator by exerting an autocrine or paracrine action in the SCN.

7, 8-Dihydroxyflavanone as an inhibitor for Jun-Fos-DNA complex formation and its cytotoxic effect on cultured human cancer cells

7,8-Dihydroxyflavanone, isolated from the seeds of Alpinia Katsumadai Hayata, showed an inhibitory effect on Jun-Fos dimer action. 7,8-Dihydroxyflavanone blocked the action of the dimer on a DNA consensus sequence, the AP-1 binding site. We have concluded that the Jun-Fos heterodimer, bound with 7,8-dihydroxyflavanone, cannot bind to the AP-1 site and therefore results in signal interruption. The 7,8-dihydroxyflavanone was also found to have an in vitro cytotoxic effect against A549 (a human lung cancer cell line) and K562 (a human leukemia cell line).

Effects of progesterone and 18-methyl levonorgestrel on osteoblastic cells

OBJECTIVE

To study the effects of progesterone (P) and 18-methyl levonorgestrel (LNG) on the expression of P receptors (PRA and PRB), c-fos, c-jun, and osteocalcin in the human osteosarcoma cell line MG-63 and human normal osteoblasts in order to understand the mechanism of progestin action on the proliferation and differentiation of osteoblasts.

METHODS

Cell proliferation was tested by MTT assay. The expression of PR, c-fos, c-jun, and osteocalcin was measured by semi-quantitative RT-PCR, Western immunoblot or immunocytochemistry.

RESULTS

Progesterone and LNG (10(-10)-10(-6)M) stimulated cell proliferation in a dose-dependent manner. Progesterone and LNG did not affect the expression of PRA and PRB mRNA and protein, but c-fos and c-jun mRNA and protein were upregulated in a dose-dependent manner. The expression of osteocalcin mRNA was also increased in human osteoblasts in a dose and time-dependent manner with greater effects of LNG than P, while the expression of osteocalcin mRNA in MG-63 cells was not changed by P or LNG.

CONCLUSION

Progesterone and LNG promote osteocalcin gene transcription by stimulating the expression of c-fos and c-jun, and result in osteoblast proliferation and differentiation.

c-jun mRNA expression and profilin mRNA amplification in rat alveolar macrophages exposed to volcanic ash and sulfur dioxide

Local residents exposed to heavy falls of ash discharged by Mt. Sakurajima, an active volcano, have been reported to develop acute and chronic inflammation of the respiratory tract. The present study aimed to determine the primary cause of this inflammation using an experimental model. Wistar rats were exposed for 5 days (4 h/d) to air containing 100 mg/m3 volcanic ash (mass median aerodynamic diameter, 4.3 microm; geometric standard deviation, 1.7) with or without 1.5 ppm sulfur dioxide (SO2). The lungs were then lavaged, and mRNA was extracted from alveolar macrophages and assessed by reverse transcription-polymerase chain reaction (RT-PCR). In the lavage fluid, no change in cellularity or increase in the content of tumor necrosis factor (TNF)-alpha was detected. However, at 1 h following exposure, 80% of macrophages were seen to have phagocytosed the volcanic ash. This percentage was unchanged at 24 h after exposure. Profilin mRNA content of the macrophages was elevated, and c-jun mRNA was expressed. Alveolar macrophages exposed to volcanic ash and SO2, therefore, are likely to have some inflammatory and fibrogenic potential.

Retrograde reactions of Clarke's nucleus neurons after human spinal cord injury

Successful axon regeneration depends on the expression of regeneration-associated genes by axotomized neurons. Here, we demonstrate, for the first time to our knowledge, the expression of regeneration-associated genes by axotomized human CNS neurons. In situ hybridization and immunohistochemistry showed a transient induction of GAP-43 and c-jun in Clarke's nucleus neurons caudal to traumatic human spinal cord injury. These results support experimental data that nonregenerating central nervous system neurons can temporarily upregulate regeneration-associated genes, reflecting a transient regenerative capacity that fails over time.

Molecular mechanism and role of endothelial monocyte chemoattractant protein-1 induction by vascular endothelial growth factor

OBJECTIVE

We investigated the role of monocyte chemoattractant protein-1 (MCP-1) in vascular endothelial growth factor (VEGF)-induced angiogenesis and vascular permeability and the underlying molecular mechanism of VEGF-induced endothelial MCP-1 expression in vitro and in vivo.

METHODS AND RESULTS

We used an anti-MCP-1 neutralizing antibody for specific inhibition of MCP-1. VEGF increased tubule formation in the angiogenesis assay and vascular permeability in the Miles assay, and these effects were markedly inhibited by anti-MCP-1 antibody. Using a luciferase MCP-1 promoter-gene assay, we found that the activator protein-1 (AP-1) binding site of the MCP-1 promoter region contributes to the increase in MCP-1 promoter activity by VEGF. To specifically inhibit AP-1, we used recombinant adenovirus containing a dominant-negative c-Jun (Ad-DN-c-Jun). Ad-DN-c-Jun inhibited VEGF-induced endothelial MCP-1 mRNA expression and promoter activity in vitro. In vivo gene transfer of DN-c-Jun into rat carotid artery, with the hemagglutinating virus of the Japan liposome method, significantly blocked VEGF-induced MCP-1 and macrophage/monocyte (ED1) expression in endothelium.

CONCLUSIONS

These results reveal that endothelial MCP-1 induced by VEGF seems to participate in angiogenesis, vascular leakage, or arteriosclerosis. AP-1 plays a critical role in the molecular mechanism underlying induction of MCP-1 by VEGF.

Epithelial migration: open your eyes to c-Jun

Tissue-specific removal of c-jun from epidermal cells in mice leads to a failure of eyelid fusion during embryogenesis and reveals roles for c-Jun in wound repair and tumorigenesis in adult skin. This has provided a definitive test of the in vivo function of AP-1 signalling and shown that EGF signalling is key to all of c-Jun's roles in the epidermis.

Expression of dominant negative c-jun inhibits ultraviolet B-induced squamous cell carcinoma number and size in an SKH-1 hairless mouse model

UVB radiation is a complete carcinogen able to initiate, promote, and progress keratinocyte cells toward carcinogenesis. Exposure to UVB leads to the propagation of a number of signal transduction pathways resulting in increased DNA binding of transcription factors, including activator protein-1 (AP-1), and subsequent gene expression. To test the hypothesis that AP-1 activation plays a role in the promotion of UVB-induced skin tumors, a dominant negative c-jun (TAM67) mutant transgene was expressed in the epidermis of SKH-1 hairless mice and bred with mice expressing an AP-1 luciferase reporter gene. Single UVB exposure experiments showed a significant decrease in AP-1 activity, as measured by luciferase levels, in mice expressing TAM67 72 h postexposure. Transgenic and nontransgenic littermates were placed into a chronic UVB exposure experiment, three exposures per week for 25 weeks. Expression of TAM67 reduced the number of tumors per mouse by 58% and tumor sizes were 79% smaller than the tumors present in the nontransgenic study group. These tumors were histologically identified as squamous cell carcinomas. TAM67 had no effect on UVB-induced hyperplasia because comparable epidermal thickening was observed in both study groups over a 5-day period post-UVB exposure. Immunohistochemical analysis showed a reduction in the number of cyclin D(1)-expressing cells in squamous cell carcinoma samples removed from the TAM67 study group. These data show that TAM67 can inhibit UVB-induced squamous cell carcinoma formation, suggesting that AP-1 is a good candidate target for the development of new chemoprevention strategies to prevent sunlight-induced skin cancers.

Acute stress increases calcium current amplitude in rat hippocampus: temporal changes in physiology and gene expression

Activation of hippocampal glucocorticoid receptors in vitro increases calcium current amplitude through a process requiring DNA binding of receptor homodimers. We here investigated (i). whether similar increased calcium currents also occur following in vivo glucocorticoid receptor activation due to stress and (ii). if so, whether this can be explained by increased expression of calcium channel subunits. Rats were exposed to a novelty stress; some of the animals were pretreated with a glucocorticoid receptor antagonist. In subsequently prepared hippocampal slices, calcium currents were recorded from identified CA1 pyramidal neurons, after which RNA was collected, linearly amplified and hybridized with cDNA clones. Glucocorticoid receptor activation due to novelty exposure was associated with large total peak calcium currents and high-threshold noninactivating currents. Low-threshold calcium currents were not affected. Large total peak and noninactivating current amplitudes were also seen when animals received a more severe stressor, i.e. additional ether exposure. In the stressed groups, the total peak and high-threshold calcium current gradually increased with time resulting in a significant enhancement at >or=3 h after stress exposure. In the same cells, the summated (relative) RNA expression of various alpha1 calcium channel subunits was only transiently enhanced, prior to the functional changes. These data indicate that in vivo activation of glucocorticoid receptors due to stress gradually increases specific calcium current components. Prior to the functional change, increased expression of calcium channel subunits was observed, suggesting that the enhanced function could be explained by transcriptional regulation of the channels.

AP1 genes in Fugu indicate a divergent transcriptional control to that of mammals

The draft genomic sequence of the Japanese puffer fish, Fugu rubripes, has now been announced. This is the first complete sequence of a teleost fish and the second available vertebrate sequence, the first being that of human. For the first time, whole-genome comparisons between two vertebrates can be undertaken. Early analysis has suggested that there may be surprising differences in gene regulation between human and fish. In mammals, a gene commonly has several functions, and this may not always be the case in fish. Many gene families comprise more members in fish than they do in mammals, possibly because each fish gene has evolved an individual function. Complexities of gene regulation in mammals has hampered studies of all biological processes from cell proliferation to cell death. Determining the activities of the AP1 transcription factor proteins has been non-trivial. The AP1 complex typically comprises two proteins, a Jun (c-Jun, JunB, and JunD) and a Fos (c-Fos, FosB, Fra1, and Fra2). These proteins can form both homodimers and heterodimers among-themselves and can interact with additional proteins; thus, dissecting their individual roles has been difficult. We have determined that Fugu has more Jun and Fos genes than mammals, and if each proves to have a separate function, then addressing the roles of the individual AP1 proteins in Fugu may be simpler than in human.

[Comparison of conventional and real-time RT-PCR for the quantitation of jun protooncogene mRNA and analysis of junB mRNA expression in synovial membranes and isolated synovial fibroblasts from rheumatoid arthritis patients]

AP-1 dependent genes, e.g., matrix-metallo-proteinases, are involved in the pathogenesis of rheumatoid arthritis (RA). Therefore, the transcription factor AP-1 and its subunits, proteins of the Jun and Fos proto-oncogene families, are interesting targets for analysis in RA. In this study, we analyzed the mRNA expression of junB in synovial membrane (SM) samples and isolated synovial fibroblasts of patients with RA, osteoarthritis (OA), and normal, non-inflammatory controls. To address the suitability of real-time RT-PCR for the quantitation of Jun proto-oncogene family members, conventional RTPCR and real-time PCR were comparatively applied for junD, a gene representing a major challenge because of its high GC-content (70%, increasing the probability of secondary structures interfering with the PCR) and its sequence homology to other Jun proto-oncogenes. In addition, a comparison was performed concerning the precision, reproducibility, costs, as well as labor and time consumption of the two PCR methods. Real-time RT-PCR proved superior to conventional PCR in terms of precision (mean deviation of measured from employed concentration 58% for real-time PCR vs 225% for conventional PCR), reproducibility, as well as labor and time consumption (4 times less for real-time RT-PCR). Experimental cDNA normalization for equivalent cDNA concentrations by sample dilution was more reliable than mathematical cDNA normalization. However, real-time PCR was 3.6-fold more expensive. Applying the more reliable real-time RT-PCR for the ex vivo analysis of junB mRNA-expression, no significantly different expression of junB was observed in SM or isolated synovial fibroblasts from RA as compared to OA. Interestingly, however, junBmRNA expression was significantly lower in RA SM and borderline significantly lower in OA SM than in normal/non-inflammatory SM, with potential effects on the functional properties of the resulting AP-1 complexes. Immunohistochemical staining of the SM with JunB-specific antibodies showed comparable JunB protein expression in SFB (collagen III mRNA-positive) of RA and OA samples. Thus, real-time RT-PCR appears suitable and time-saving for the quantitation of jun proto-oncogene mRNA-expression in tissue and cell samples with high precision and reproducibility.

Transgenic TGR(mREN2)27 rats as a model for disturbed circadian organization at the level of the brain, the heart, and the kidneys

In transgenic hypertensive TGR(mREN2)27 rats (TGR) harboring the murine Ren-2 gene an inverse 24h blood pressure (BP) profile was described in relation to a normal pattern in heart rate (HR) and motility (MA), normotensive Sprague-Dawley rats (SDR) were used as controls. Transgenic rats as an animal model of human secondary hypertension (non-dipper) was studied in detail at different levels: (1) Radiotelemetry was applied to document gross circadian rhythms/rhythm disturbances in cardiovascular functions, MA and body temperature under normal LD conditions, under DD and after a light pulse. (2) Signal transduction of the overexpressed renin-angiotensin in TGR was studied by determation of AT1-receptors in kidney glomeruli together with kidney functions. (3) Expression of key processes involved in increased sympathetic regulation in TGR, mRNAs, the tyrosine-hydroxylase (TH) and norepinephrine (NE) reuptake1-carrier were determined. (4) In the SCN mRNA of c-fos and c-jun were determined under LD and after light pulse. (5) In primary cultures of pinealocytes the effects of adrenergic agonists and antagonists were evaluated on second messenger (cAMP, cGMP) accumulation and melatonin release. The results of these studies clearly demonstrate that the additional mouse renin genin in TGR greatly affected not only the renin-angiotensin-system and led--as expected--to an increased BP in this rat but also disturbed circadian rhythms from the BP pattern down to the level of hormones, processes of signal transduction, and expression of transcription factors and clock genes. In conclusion, the expression of a single additional gene is able to disturb the circadian system of an animal in a highly complex way. These findings are importance for chronobiologic as well as pharmacologic research.

Reversal of Bcl-2-mediated resistance of the EW36 human B-cell lymphoma cell line to arsenite- and pesticide-induced apoptosis by PK11195, a ligand of the mitochondrial benzodiazepine receptor

Opening of the permeability transition (PT) pore is a central feature of apoptosis induction by chemical stress. One component of the PT pore, the mitochondrial benzodiazepine receptor (mBzR), has recently received attention for its potential role in modulating PT pore function. Specifically, antagonistic ligands of the mBzR, such as 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carboxamide (PK11195), have been shown to sensitize Bcl-2 overexpressing cells to apoptosis induction by facilitating the opening of the PT pore and the subsequent loss of mitochondrial membrane potential (Deltapsim). We examined whether PK11195 can sensitize EW36, a human B-cell lymphoma cell line that over-expresses Bcl-2, to apoptosis induction and mitochondrial depolarization by environmental chemicals including mitochondrial toxicants. We found that, although EW36 cells are refractory to apoptosis induction by antimycin A, rotenone, pyridaben, alachlor, and carbonyl cyanide m-chlorophenylhydrazone (mClCCP), they are dramatically sensitized to induction of apoptosis by low concentrations of these same agents following pre-treatment with PK11195. The sensitization of EW36 cells is accompanied by a rapid and extensive loss of Deltapsim within a few hours following chemical exposure. Furthermore, using sodium arsenite, we examined the role of the c-Jun N-terminal kinase (JNK) pathway and protein synthesis in apoptosis induction in EW36. We found that, unlike untreated cells, EW36 cells treated with PK11195 no longer show an association of JNK pathway activation with apoptosis induction. Importantly, PK11195 eliminates a requirement for protein synthesis in chemically induced apoptosis in EW36 cells. These results show significant drug-mediated alteration of cell sensitivity and JNK pathway activation to environmental chemicals and mitochondrial toxicants, following ligation of the mBzR.

Jun N-terminal kinase activation and upregulation of p53 and p21(WAF1/CIP1) in selenite-induced apoptosis of regenerating liver

To investigate apoptosis induced by selenite in hepatocytes in vivo, rats received a single injection of sodium selenite immediately after partial hepatectomy. Characteristic DNA fragmentation in gel electrophoresis and in situ end-labeling and the increase in caspase-3 activity were observed at 4 h after partial hepatectomy with selenite injection. The activation of Jun N-terminal kinase (JNK) was observed as early as 15 min and increased to about 10-fold the maximal level of the control at 1 and 2 h after partial hepatectomy in selenite-injected rats, while a transient increase was observed at 1 h in the control. Western blot analysis revealed that the c-Jun and the phosphorylated c-Jun protein markedly increased after 30 min and reached a maximal level at 1 and 2 h after partial hepatectomy with selenite injection, although c-Jun and a faint band of the phosphorylated c-Jun were observed after 1 h in the control. The levels of c-jun mRNA and c-Fos protein and mRNA in selenite-injected rats also increased more than in the control. The rise in the p53 protein level after partial hepatectomy with selenite injection was followed by the upregulation of p21(WAF1/CIP1) mRNA and protein expression. These results suggested that selenite induced apoptosis accompanied by the activation of caspase-3 and JNK and the upregulation of c-jun, c-fos, p53 and p21(WAF1/CIP1) at the early stage of liver regeneration.