Glutathione S-transferase class Kappa: characterization by the cloning of rat mitochondrial GST and identification of a human homologue

We have isolated a cDNA clone that encodes rat glutahione S-transferase (GST) subunit 13, a GST originally isolated from rat liver mitochondrial matrix by Harris, Meyer, Coles and Ketterer [(1991) Biochem. J. 278, 137-141]. The 896 bp cDNA contains an open reading frame of 678 bp encoding a deduced protein sequence of which the first 33 residues (excluding the initiation methionine residue) correspond to the N-terminal sequence reported by Harris et al. Hence like many other nuclear-encoded, mitochondrially located proteins, there is no cleavable mitochondrial presequence at the N-terminus. GST subunit 13 was originally placed into the Theta class of GSTs on the basis of sequence identity at the N-terminus; however, this is the only identity with the Theta class and in fact GST subunit 13 shows little sequence similarity to any of the known GST classes. Most importantly it lacks the SNAIL/TRAIL motif that has so far been a characteristic of soluble GSTs, although it does possess a second motif (FGXXXXVXXVDGXXXXXF) reported for GST-related proteins (Koonin, Mushegian, Tatusov, Altschul, Bryant, Bork and Valencia [(1994) Protein Sci. 3, 2045-2054]. Southern and Northern blot analyses of rat DNA and mRNA are consistent with GST subunit 13's being the product of a single hybridizing gene locus. Searches of EST databases identified numerous similar human DNA sequences and a single pig sequence. We have derived a human cDNA sequence from these EST sequences which shows a high nucleotide similarity (77%) to rat GST subunit 13. The largest open reading frame is identical in length with subunit 13 and yields a deduced protein sequence identity of 70%. Most unusually the 3' non-coding nucleotide sequence identity is also 77%. We conclude that these cDNAs belong to a novel GST class hereby designated Kappa, with the rat GST subunit 13 gene designated rGSTK1 and the human gene being called hGSTK1.

Expression of mRNA encoding decidualization-associated protein, a variant of acute-phase alpha 2 macroglobulin, by rat uterine tissues during pregnancy and pseudopregnancy

The patterns of expression of mRNA encoding decidualization-associated protein (DAP) in the rat uterus from early, mid-, and late stages of pregnancy were examined by in situ hybridization to provide an insight into the function of DAP during pregnancy. Parallel studies were performed on rat uteri during the oestrous cycle and oil-induced deciduomata. DAP transcripts were absent in virgin uteri and during the day of implantation (day 5), low in early gestation tissues (days 8, 9) and high during midgestation (days 10-14). Expression of mRNA encoding DAP was first detected on day 8 of pregnancy in decidual cells of the lateral decidual glycogen wing areas. On day 9, mRNA encoding DAP was found in the same area as on day 8 as well as in the outer layer of cells in the antimesometrial decidua adjacent to the myometrium termed the fibrinoid capsula. On days 11 and 12, expression appeared in the decidual cells of the mesometrial decidua, and was particularly strong around the ectoplacental cone and blood vessels that were invaded by the trophoblast. By day 13 and throughout the remainder of pregnancy, expression occurred in the mesometrial decidua and metrial gland. No signal was observed in granulated metrial gland cells. mRNA encoding DAP was also found in the smooth circular muscle coat adjacent to the mesometrial decidua. A similar pattern and cellular localization of expression of mRNA encoding DAP expression was detected during the development of the deciduomata, artificially induced in the absence of a conceptus. The spatial and temporal patterns of expression correlated with a possible role for DAP in mediating fetal-maternal interactions and the establishment of the placental structure.

In vitro translation of apple chlorotic leaf spot virus (ACLSV) RNA

The genomic RNA of apple chlorotic leaf spot virus was translated in a rabbit reticulocyte lysate system, yielding a large, 190 K product as well as several other polypeptides of smaller size (60, 56, 22 and 15 kDa). The 22 kDa product was immunoprecipitated by an anti-ACLSV serum and comigrated with purified ACLSV coat protein. In vitro translation of RNA transcripts prepared from cloned ACLSV cDNAs demonstrates that the coat protein is synthesised by initiation on the second in frame AUG codon of the 28 kDa open reading frame located at the 3' end of the genome. In the in vitro translation system used, the ability of various ACLSV-derived RNAs to direct the synthesis of the coat protein appears to be the result of initiation on the internal AUG codon.

The regulation mechanism of HLA class II gene expression at the level of mRNA stability

The number of major histocompatibility complex (MHC) class II antigens may be regulated at different levels. Although transcriptional regulation has been studied most intensely, evidence for control mechanisms acting on the stability of MHC class II mRNAs has been reported. We have previously shown, in fact, that the half-life of MHC class II mRNA rapidly decreases in Raji cells upon inhibition of translation by cycloheximide; further data indicated that this effect was not correlated with the inhibition of the synthesis of trans-acting protein(s) required for mRNA stability. In the present work, we developed an in vitro mRNA decay assay system to measure HLA-DRA mRNA stability and used inhibitors of protein synthesis affecting different steps of the process of translation in order to discriminate among possible mechanisms determining controlled MHC class II mRNA hydrolysis. We found that HLA-DRA mRNA associated with polysomes derived from cells treated with either puromycin (which causes dispersion of polysomes and accumulation of monosomes) or cycloheximide (which slows down translation causing ribosome stalling) is more rapidly degraded than in the absence of protein synthesis inhibitors. On the basis of our findings, we suggest that arrest of protein synthesis per se exposes the HLA-DRA mRNA molecules to degradative activities co-sedimenting with the polysomal fraction.

Changes in the regulatory effects of cell-cell interactions on neuronal AChR subunit transcript levels after synapse formation

Nicotinic acetylcholine receptors (AChRs) mediate excitatory synaptic transmission in the chick ciliary ganglion. AChR protein and mRNA levels are increased by both innervation and retrograde signals from target tissues during synapse formation. We now show that AChR alpha3, beta4, and alpha5 subunit transcript levels stop increasing after synaptogenesis. Moreover, maintenance of these mRNA levels requires the continued presence of regulatory signals from both pre- and postganglionic tissues. Unilateral preganglionic denervation or postganglionic axotomy causes declines in alpha3, beta4, and alpha5 transcript levels, ranging from twofold to 3. 5-fold, relative to contralateral control neuron values in newly hatched chicks. The reductions are not merely an injury response; cbeta4-tubulin mRNA levels are not affected by either axotomy or denervation. Further, similar decreases in AChR mRNA levels are observed after local application of colchicine to the postganglionic nerves, which blocks fast transport without disturbing axonal integrity. These results also demonstrate a developmental change in the regulatory effects of target tissues. Reductions in alpha5 mRNA levels caused by axotomy or colchicine treatment after peripheral synapse formation contrast with the lack of an effect on alpha5 when synapse formation with the target tissue is prevented. The ability of the target tissue to regulate alpha5 mRNA levels after synaptogenesis is interesting, because this subunit may be necessary for the formation of high-conductance AChRs. The specific regulatory effects of target tissues and inputs at different developmental stages demonstrate that neurons continually depend on signals from their pre- and postsynaptic tissues to accomplish mature levels of AChR subunit expression and optimal functioning of that neuronal circuit.

Reperfusion causes significant activation of heat shock transcription factor 1 in ischemic rat heart

BACKGROUND

The myocardial protective role of heat shock protein (HSP) has been demonstrated, and there has been increasing interest in stress response in the heart. We examined the DNA-binding activity of heat shock transcription factor (HSF), by which the transcription of heat shock genes is mainly regulated, during heat shock or ischemia/reperfusion in isolated rat heart.

METHODS AND RESULTS

Rat hearts were isolated and perfused with Krebs-Henseleit buffer by the Langendorff method. Whole-cell extracts were prepared for gel mobility shift assay using oligonucleotides containing the heat shock element, which is present upstream of all heat shock genes. Induction of mRNAs for HSP70, HSP90, and GRP78 (glucose-regulated protein) was examined by Northern blot analysis. Although the activation of HSF during global ischemia was weak and rapidly attenuated, postischemic reperfusion induced a significant activation of HSF. In addition, although HSP70 mRNA was hardly induced during ischemia, its burst induction was detected during postischemic reperfusion. Supershift assays using specific antisera for HSF1 and HSF2 revealed that ischemia/reperfusion as well as heat shock induced the activation of HSF1 in hearts. Although the expression of HSP70 mRNA during heat shock was more vigorous than the expression during ischemia/reperfusion, the induction of HSP90 mRNA in postischemic reperfusion was significantly greater than that in heat shock.

CONCLUSIONS

Our findings demonstrated that reperfusion causes a significant activation of HSF1 in ischemia-reperfused heart. The striking contrast between the induction of HSP70 mRNA and that of HSP90 mRNA suggests the presence of regulatory mechanisms other than HSF.

Expression of mRNAs for neurotrophins and their receptors in developing rat heart

Because the neurotrophic system has not been systematically studied in developing heart, we studied the expression of mRNAs for neurotrophins and their high- and low-affinity receptors by radioactive in situ hybridization in the rat heart from embryonic day 9 (E9) to parturition. The neurotrophin-3 (NT-3) transcripts were seen in the group of Leu-7 immunoreactive cells in the ventricular region from E11 to parturition, suggesting that NT-3 is expressed in the part of the developing conduction system, mRNAs for truncated trk receptors, trkC.TK- and trkB.T1, were expressed in the outflow tract at E12 and in the walls of developing aorta and pulmonary trunk from E13 to parturition, whereas the mRNA for catalytic trkC.TK+ was revealed in the walls of aorta and pulmonary trunk from E13 to parturition and in the cardiac ganglion neurons from E14 to adult stage. Transcripts for low-affinity neurotrophin receptor (p75) were transiently seen in the distal outflow tract from E11 to E13, declining by E14. At E18, p75 transcripts were also seen in the cardiac ganglia. Transcripts for nerve growth factor, neurotrophin-4/5, trkA, or trkB.TK+ were not detected. Expression of NT-3 mRNA in the developing conduction system and of trkC.TK + mRNA in the cardiac neurons suggests a role for NT-3 in the innervation of the conduction system. Expression of trkC.TK+ in the wall of aorta and pulmonary trunk suggests that NT-3 also may affect the development of the smooth muscle cells.

Messenger ribonucleic acid for insulin-like growth factors-I and -II, insulin-like growth factor-binding protein-2, gonadotropin receptors, and steroidogenic enzymes in porcine follicles

Several aspects of growth, development, and steroidogenesis in ovarian follicles are controlled by the interaction of insulin-like growth factors (IGF-I and IGF-II) and gonadotropins (LH and FSH). The objective of this study was to determine the developmental stage and location at which mRNA for IGF, IGF-binding protein (IGFBP)-2, gonadotropin receptors, and steroidogenic enzyme genes are expressed within porcine follicles. Ovaries from pigs on Days 10 (n = 3; midluteal phase) and 19 (n = 3; preovulatory phase) of the estrous cycle were collected, frozen, and sectioned. The mRNA for IGF-I, IGF-II, IGFBP-2, LH receptor, FSH receptor, cytochrome P450 side-chain cleavage (P450scc), 3 beta-hydroxysteroid dehydrogenase (3 beta-HSD), 17 alpha-hydroxylase (P45017 alpha), and aromatase (P450arom) were detected by in situ hybridization, and relative amounts were determined by image analysis. Expression of mRNA for IGF-I and IGF-II was cell specific (granulosa and theca interna cells, respectively) and increased with follicular size. The IGFBP-2 mRNA was expressed in greater amounts for theca interna cells than for granulosa cells. The pattern of expression for LH and FSH receptors diverged as follicles grew. For LH receptor, mRNA was detected in the theca interna cells of small antral follicles and in both the theca interna and granulosa cells of large antral follicles. Amount of LH receptor mRNA increased with follicular diameter. For FSH receptor, mRNA increased as follicles grew to a small antral size. However, FSH receptor mRNA disappeared in large antral follicles on Day 19 of the estrous cycle. Steroidogenic enzyme mRNA for 3 beta-HSD (theca interna cells), P450scc (theca interna cells), P45017 alpha (theca interna cells), and P450arom (granulosa cells) increased with follicular diameter. In summary, coordinated expression of IGF, IGFBP-2, gonadotropin receptors, and steroidogenic enzyme mRNA throughout different stages of follicular development was observed. Changes in mRNA suggested increased IGF-I and -II action and a switch from FSH to LH dependence in porcine preovulatory follicles.

Up-regulation of estrogen receptor mRNA and estrogen receptor activity by estradiol in liver of rainbow trout and other teleostean fish

Injection of estradiol (E2) into immature rainbow trout resulted in the induction of the hepatic vitellogenin gene mediated by the nuclear estrogen receptor (ER). Liver ER mRNA rose markedly on E2 treatment in three groups of trout kept at different temperatures. Only in the group kept at 4 degrees C did the total cellular ER, as measured by [3H]estradiol-binding activity in nuclear and cytosol fractions, parallel the ER mRNA level. In fish kept at 9 degrees C and 15 degrees C, the ratio of total ER activity to ER mRNA fell during chronic E2 treatment, probably reflecting translational of post-translational control mechanisms. Upregulation of ER mRNA also occurred in sea raven, sculpin, winter flounder, and Atlantic salmon after E2 treatment. Intrahepatic ER activity rose proportionately in Atlantic salmon kept at 6-9 degrees C but not in sea raven, sculpin, or flounder. We conclude that the regulation of ER expression in teleosts is complex and includes transcriptional, translational, and post-translational elements and is influenced by environmental temperature.

Rapid loss of oestrogen and progesterone receptors in human leiomyoma and myometrial explant cultures

Oestrogen and progesterone are promoters of uterine leiomyoma growth: oestrogen receptors (ER) and progesterone receptors (PR) are over-expressed in these tumours. Paradoxically, there is a heterogeneity in responsiveness of leiomyoma growth to oestrogen and progesterone in culture. In this study, leiomyoma and adjacent myometrium were obtained at hysterectomy. The effect of oestrogen and progesterone on steroid receptor maintenance was examined using minced explants. Quantitative enzyme-linked immunoassay and Northern analysis were performed to assess ER and PR protein and mRNA content respectively. There was an approximately 75% decrease in ER and PR protein content within 8 h of incubation in both leiomyoma and myometrium. The presence or absence of oestrogen and/or progesterone had no effect on receptor protein loss. Northern analysis indicated a parallel loss of ER and PR mRNA transcripts. These findings suggest that the ER and PR expression in leiomyoma may require other extracellular factors. In-vitro studies designed to test the effects of sex steroids and their respective inhibitors on growth and function of leiomyoma and myometrial cells should consider this phenomenon.

Lymphocyte apoptosis and apoptosis-associated gene expression in Sjögren's syndrome

OBJECTIVE

To study the mechanism and regulation of apoptosis in peripheral blood T and B lymphocytes from patients with Sjögren's syndrome (SS).

METHODS

The mode of in vitro lymphocyte death in the peripheral blood of patients with SS was determined by fluorescence microscopic analysis, terminal deoxynucleotidyl transferase assay, and DNA fragmentation analysis. Apoptotic cell death of T and B cells was determined at 48 hours of culture by fluorescence-activated cell sorter analysis of propidium iodidestained cells. Messenger RNA (mRNA) expression of bcl-2, bcl-x, bax, and c-myc in T and B cells was determined by enzyme-linked immunosorbent assay-polymerase chain reaction (ELISA-PCR). Expression of bcl-xL and bcl-xS was determined by Southern blot analysis of PCR products. Gene expression was calculated as the ratio of each gene message to the message of the GAPDH gene. Bcl-2 protein levels in SS T cells were determined by ELISA.

RESULTS

SS T cells showed increased in vitro apoptosis compared with normal T cells (mean +/- SD 12.3 +/- 4.5% versus 7.3 +/- 2.0%; P < 0.01). Freshly isolated SS T cells showed increased expression of bcl-2 mRNA compared with normal controls (mean +/- SD 1.50 +/- 0.65 versus 0.88 +/- 0.23; P < 0.05). There was no significant difference in levels of bax or c-myc mRNA in T cells and B cells between SS patients and normal controls. When SS T lymphocytes were cultured in vitro for 72 hours, Bcl-2 protein levels decreased with time.

CONCLUSION

SS T cells showed accelerated apoptosis in vitro. Freshly isolated SS T cells had increased expression of bcl-2. An increase in death-promoter signals and decrease in death-suppressor signals in vitro may have been responsible, in part, for the apoptosis in SS T lymphocytes.

IL-4 and IL-5 mRNA and protein in bronchial biopsies from patients with atopic and nonatopic asthma: evidence against "intrinsic" asthma being a distinct immunopathologic entity

Intrinsic (nonatopic) asthma is considered to be a distinct pathogenetic variant of asthma since, unlike extrinsic (atopic) asthma, patients with the disease are skin test-negative to common aeroallergens, and have total serum IgE concentrations within the normal range. Nevertheless, the recent demonstration of increased numbers of cells expressing the high-affinity IgE receptor in bronchial biopsies from atopic and nonatopic asthmatic subjects, together with epidemiologic evidence indicating that serum IgE concentrations relate closely to asthma prevalence regardless of atopic status, suggests that IgE-mediated mechanisms may participate in the pathogenesis of both atopic and nonatopic asthma. Furthermore both variants of the disease are associated with bronchial mucosal eosinophilic inflammation. Interleukin-4 (IL-4) is an essential cofactor for IgE synthesis, and there is strong evidence that IL-5 plays a major role in eosinophil accumulation in asthmatic inflammation. For these reasons we compared the expression of IL-4 and IL-5 mRNA and protein product using a semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) amplification, in situ hybridization, and immunohistochemistry in bronchial biopsies from symptomatic atopic and nonatopic asthmatic subjects and atopic and nonatopic controls. The results showed that as compared with controls, biopsies from both groups of asthmatic subjects had increased numbers of IL-4 and IL-5 mRNA copies relative to beta-actin mRNA as detected by RT-PCR. Similarly, in situ hybridization and immunohistochemistry demonstrated increased numbers of cells expressing IL-4 and IL-5 mRNA and protein in asthmatic subjects, irrespective of their atopic status. We conclude that individuals with either atopic or nonatopic asthma show infiltration of the bronchial mucosa with cells expressing Th2-type cytokines, providing further evidence for similarities in the immunopathogenesis of these clinically distinct forms of asthma.

Mechanisms responsible for dominant expression of human growth hormone gene mutations

Point mutations of the donor splice site of intron 3 of the human GH-1 gene cause autosomal dominant inherited isolated growth hormone deficiency (IGHD II). The mechanism by which a defect in one GH-1 allele results in GH deficiency is obscure. Previously reported reverse transcription-nested PCR data suggested an overexpression of the mutant GH-1 allele. We employed alternative methods to determine the relative expression of mutant (C for G at +1 of intron 3) and normal GH-1 allele. The use of a second round PCR primer bridging exons 2 and 3 and specific for normal GH-1 messenger ribonucleic acid (mRNA) indicated equal quantities in mutant and control cells. Large scale messenger RNA extraction from Epstein-Barr virus-transformed lymphoblasts permitted assay by ribonuclease protection. In normal pituitary, there were three GH-1 mRNA species. The variant lacking exon 3 comprised 5% of the total GH-1 mRNA. The proband's lymphoblasts contained equal amounts of mRNA with and without exon 3. Only normal GH-1 mRNA was detected in controls. Secreted GH, measured by enzyme-linked immunosorbent assay was present in equal concentrations in media from normal and mutant cells. Thus, GH-1 mRNA lacking exon 3 was expressed in proportion to the dosage of the mutant gene, and dominant effects on GH secretion were not observed in lymphoblasts. These findings are compatible with a dominant negative mechanism involving interaction between normal and mutant proteins in secretory vesicles of somatotropes.

Inhibition of tissue factor surface expression in human peripheral blood monocytes exposed to cytokines

Interleukin (IL)-4, IL-10, IL-13 and transforming growth factor beta (TGF-beta) are known to regulate several monocyte functions, including inhibition of the synthesis of different cytokines. Using quantitative RT-PCR and flow cytometry analysis we investigated the effects of these cytokines on bacterial lipopolysaccharide (LPS)-induced tissue factor (TF) expression in human monocytes. The effects of IL-4 and IL-10 on monocyte chemoattractant protein-1 (MCP-1)-and C-reactive protein (CRP)-induced TF expression were also studied. A direct comparison revealed that IL-4, IL-10 and IL-13 all down-regulated LPS-induced TF expression in a concentration-dependent manner without the need for priming. In contrast, TGF-beta required 4 h of priming to inhibit TF expression induced by LPS. IL-10 was the most powerful inhibitor, causing almost complete inhibition at 5 ng/ml. IL-4 and IL-13 exhibited a significantly lower inhibitory capacity even at concentrations of 100 ng/ml. IL-4 and IL-10 showed similar concentration-dependent inhibition of MCP-1- and CRP-induced TF expression. We also showed that the regulatory effect of the interleukins occurred at the mRNA level. In vivo, these inhibitory cytokines may play an important regulatory role in preventing thrombosis. IL-10, in particular, may be a possible candidate as a TF-preventing drug.

Peroxisome proliferator-activated receptor-gamma activation by thiazolidinediones induces adipogenesis in bone marrow stromal cells

The thiazolidinediones improve insulin sensitivity in animal models and have promise as potent oral antidiabetic agents. Their clinical use has been limited because of the resulting anemia and cardiac hypertrophy. Some compounds of this class have been reported to induce bone marrow fat accumulation in animals, and this effect could account for the observed anemia. We examined the biological mechanism contributing to this phenomenon. The thiazolidinediones BRL49653 and pioglitazone induced adipocyte differentiation in the BMS2 bone marrow stromal cell line in a dose- and time-dependent manner. These actions were further enhanced by the presence of glucocorticoids and other adipogenic agonists. The thiazolidinediones increased the mRNA levels of adipocyte-specific genes, including that of their receptor, the peroxisome proliferator-activated receptor-gamma (PPAR gamma). In contrast, mRNA levels of genes encoding other PPAR family members (PPAR alpha, PPAR delta, or NUC-1) were unchanged or decreased. Thiazolidinedione treatment of primary bone marrow stromal cells elicited a comparable dose-dependent response. Using a polyclonal antibody, PPAR gamma was detected in protein lysates from adipose-rich bone marrow. Thus, thiazolidinedione directly regulates bone marrow stromal cell differentiation; induced PPAR gamma expression may play a key regulatory role in this process.

Delta subunit inhibits neurosteroid modulation of GABAA receptors

Neurosteroid modulation of GABAA receptors has been observed with all subunit combinations investigated; however, hetero-oligomeric GABAA receptors containing delta subunits were not studied previously. We describe the effect of delta subunit expression on 3alpha,21-dihydroxy-5alpha-pregnan-20-1 (THDOC)-induced potentiation of GABA-gated currents in transfected HEK 293 cells and in cerebellar granule cells in vitro. THDOC (100 nM) significantly potentiated GABA-gated currents in cells transfected with combinations of alpha1, alpha6, beta3, and gamma2 subunit cDNAs, whereas cotransfection of delta subunit cDNA inhibited this potentiation. In contrast, the direct Cl- channel activation by THDOC at higher concentrations (1-10 microM) was not significantly dependent on delta subunit cotransfection. These results suggest that the presence of the delta subunit inhibits GABAA receptor modulation but not the direct activation by neurosteroids. Cotransfection with delta subunit also affected the negative allosteric modulation by pregnenolone sulfate. THDOC potentiation of GABA-gated currents was greater in cerebellar granule cell cultures at 4 d in vitro (DIV) compared with those at 14 DIV. Single-cell reverse transcription-PCR analysis of the mRNAs expressed in cultured cerebellar granule cells shows that an increased number of granule cells at 14 DIV express delta subunit mRNAs as compared with 4 DIV granule cells. The presence of delta subunit mRNAs detected in individual cells correlated well with the lack of sensitivity to THDOC. These results suggest that developmental expression of GABAA receptor delta subunits may play an important role in determining the region-specific neurosteroid-induced modification of fast inhibitory synaptic function.

Cellular expression of GDNF mRNA suggests multiple functions inside and outside the nervous system

Glial-cell-line-derived neurotrophic factor (GDNF) is a distant member of the transforming growth factor-beta family and has potent neurotrophic effects on several classes of neurons including dopamine neurons and motoneurons. Here, we have used in situ hybridization to describe the development of the cellular expression of GDNF mRNA pre- and postnatally. Consistent with dopaminotrophic activity, GDNF mRNA is expressed in the developing basal ganglia and the olfactory tubercle. It is also found in a thalamic nucleus, in neurons of the substantia innominata, in the developing Purkinje neurons and the developing locus coeruleus area, and in trigeminal brainstem nuclei. In the spinal cord, neuronal expression is found in Clarke's column. GDNF mRNA is also expressed in the dorsal horns during development. Additional GDNF mRNA expression in the head region includes the carotid body, the retina, the vibrissae, the inner ear, the ear canal, and epithelium in the nasal cavity. Prominent expression is also found in the developing teeth. The widespread expression of GDNF in developing skeletal muscle is consistent with trophic activity on alpha-motoneurons. The smooth muscle layers of the gastrointestinal tract are also strongly positive. A very strong signal is found in the outer mesenchyme of the developing metanephric kidney. We conclude that GDNF mRNA is expressed in many different cellular systems inside and outside the central nervous system during development, suggesting multiple functions of GDNF in the developing organism.

Differential tissue-specific expression of neurofibromin isoform mRNAs in rat

We have cloned the full-length cDNA encoding the rat homolog of type I neurofibromin isoform, a protein product of a gene linked to neurofibromatosis type 1. Rat type I neurofibromin isoform is composed of 2,820 amino acid residues and shares about 98.5% amino acid identity with the human counterpart. By S1 nuclease mapping analysis of the alternatively spliced neurofibromin mRNAs in adult rat tissues, we showed that type I isoform mRNA was predominantly expressed in the brain, pituitary, and testis, while type II mRNA, carrying a 63-nucleotide insertion in the region coding for the domain related to GTPase-activating protein, was predominantly expressed in most other tissues, such as heart, kidney, and ovary. Furthermore, type II mRNA is predominant in the testis at age 1 week, while type I mRNA becomes predominant at 3 weeks and is subsequently expressed at higher levels, as seen in the adult testis. In contrast, type I mRNA is the predominant form in the brain throughout the postnatal development. Thus, the relative expression levels of type I and type II mRNAs may be specific to the tissues and to the developmental stage of certain tissues.

Differential compartmentalization of mRNAs in squid giant axon

Previously, we reported that the squid giant axon contains a heterogeneous population of mRNAs that includes beta-actin, beta-tubulin, kinesin, neurofilament proteins, and enolase. To define the absolute levels and relative distribution of these mRNAs, we have used competitive reverse transcription-PCR to quantify the levels of five mRNAs present in the giant axon and giant fiber lobe (GFL), the location of the parental cell soma. In the GFL, the number of transcripts for these mRNAs varied over a fourfold range, with beta-tubulin being the most abundant mRNA species (1.25 x 10(9) molecules per GFL). Based on transcript number, the rank order of mRNA levels in the GFL was beta-tubulin > beta-actin > kinesin > enolase > microtubule-associated protein (MAP) H1. In contrast, kinesin mRNA was most abundant in the axon (4.1 x 10(7) molecules per axon) with individual mRNA levels varying 15-fold. The rank order of mRNA levels in the axon was kinesin > beta-tubulin > MAP H1 > beta-actin > enolase. The relative abundance of the mRNA species in the axon did not correlate with the size of the transcript, nor was it directly related to their corresponding levels in the GFL. Taken together, these findings confirm that significant amounts of mRNA are present in the giant axon and suggest that specific mRNAs are differentially transported into the axonal domain.

Localization by in situ hybridization of gamma-glutamylcysteine synthetase mRNA expression in rat kidney following acute methylmercury treatment

In previous studies we reported that prolonged treatment of rats with subtoxic levels of mercury as methylmercury hydroxide (MMH) elicited a two- to threefold increase in renal glutathione (GSH) content and a three- to fourfold increase in the mRNA encoding the catalytically active heavy subunit of gamma-glutamylcysteine synthetase (GCS), the rate-limiting enzyme in GSH synthesis. In the present studies, we demonstrate that enhanced expression of GCS mRNA and GSH synthesis rapidly occur following acute MMH treatment and, moreover, that increased expression of renal GCS mRNA is localized predominantly to regions of the kidney cortex consistent with the principal distribution of mercury in the kidney. Previous studies have demonstrated that resistance to mercury toxicity during prolonged MMH exposure may be associated with the ability to up-regulate GSH synthesis subsequent to intracellular dealkylation of MMH to Hg2+. The present finding that GCS mRNA and GSH levels are rapidly increased in kidney cells which are most susceptible to mercury toxicity supports the view that up-regulation of GSH synthesis occurs as an initial adaptive response to Hg2(+)-mediated cytotoxicity following acute as well as prolonged mercury exposure.

Dietary linoleic acid increases and palmitic acid decreases hepatic LDL receptor protein and mRNA abundance in young pigs

The present study was conducted to determine the effects of dietary fatty acids on hepatic LDL receptor (LDLr) protein abundance and mRNA levels. Sixty pigs were randomized into 10 groups and fed corn-soybean meal diets containing three cholesterol levels (0.25%, 0.5%, and 1.0%, w/w) with no added fat, or fats rich (30% of calories) in palmitic acid or linoleic acid. A control group was fed the base diet with no added fat. After 30 days, plasma LDL-cholesterol (LDL-C) levels increased as the dietary cholesterol increased (P < 0.05); however, there was no significant effect of either fatty acid. Dietary fatty acids, however, had distinctly different effects on hepatic LDLr protein (analyzed by ELISA) and mRNA (analyzed by Northern blot) abundance. When pigs consumed diets containing 0.25% cholesterol, linoleic acid increased hepatic LDLr protein 40% whereas palmitic acid reduced it 40% (P < 0.05). These changes in LDLr protein abundance were accompanied by parallel changes in hepatic LDLr mRNA; linoleic acid increased LDLr mRNA 2-fold (P < 0.01), whereas palmitic acid decreased it 60% (P < 0.01). The differential effects of fatty acids on LDLr expression were only observed at 0.25% cholesterol, suggesting that higher intakes of cholesterol have a dominant and repressive effect on regulation of LDLr expression. Cholesterol intake increased hepatic total cholesterol levels (P < 0.01) while dietary fatty acids had no effect on hepatic sterols. In summary, our results indicate that dietary linoleic acid and palmitic acid have markedly different effects on hepatic LDLr protein abundance that are mediated by differential effects on LDLr mRNA and protein levels. Further studies are needed to fully elucidate the molecular mechanisms by which fatty acids regulate LDLr mRNA and protein levels.

Aberrantly spliced mRNAs of the 3-hydroxy-3-methylglutaryl coenzyme A lyase (HL) gene with a donor splice-site point mutation produce hereditary HL deficiency

A novel point mutation in the 3-hydroxy-3methyl-glutaryl coenzyme A lyase gene was found in a Turkish patient with homozygous 3-hydroxy-3-methylglutaric acidemia. Amplification by RT-PCR of the mRNA using a six different pairs of oligonucleotides produced no differences in four of the fragments amplified with respect to the control, but generated two fragments of different size. One was representative of a deletion of 126 bp and the other of an insertion of 78 bp. These abnormal mRNAs resulted from a G-->C transversion at the nucleotide +1 of an intron, which changed the invariant GT dinucleotide of the 5' donor splice site. This was associated with the occurrence of an alternative splicing, which led to the skipping of the whole exon of 126 bp, and also with the activation of one cryptic donor splice site in the same intron. These aberrant spliced mRNAs are predicted to encode two abnormal HMG-CoA lyase proteins: the first results in a protein with an internal deletion of 42 amino acids, whose enzyme activity is largely abolished, as the catalytic site was completely removed; the second contains 17 missense amino acids that precede a stop codon. Northern blot analysis showed that the overall content of these aberrantly spliced mRNAs in proband fibroblasts was the same as that found in control fibroblasts. However, hardly any transcript was observed corresponding to the inserted mutated mRNA when it was examined by a specific probe. To quantify the relative proportion of the two mRNAs, a quantitative RT-PCR (the DNA-mimic PCR reaction) was carried out. Results show that the proportion of the inserted mRNAs with respect to the deleted mRNA is only 1.2%. The father, mother, and two brothers of the proband were heterozygous in the G-->C mutation in the +1 nucleotide of the intron considered, while the two alleles of another brother were free of the mutation.

Regulation of P-selectin expression by inflammatory mediators in canine jugular endothelial cells

Canine endothelial cells express the adhesion molecule P-selectin to mediate the initial attachment of leukocytes to the vessel wall. Although it is known that agents like histamine and thrombin stimulate the surface expression of P-selectin, the effect of inflammatory mediators and cytokines such as lipopolysaccharides (LPS), tumor necrosis factor-alpha (TNF-alpha), and interleukin-1 beta (IL-1 beta) on canine P-selectin expression has not been investigated. Therefore, the objective of this study was to analyze the regulation of P-selectin messenger RNA (mRNA) and protein by these cytokines in canine endothelial cells isolated from jugular veins. Analyses of cytoplasmic RNA by Northern blotting showed that stimulation of culture endothelial cells with either LPS (100 ng/ml) or recombinant human TNF-alpha (30 U/ml) for 3 or 6 hours significantly increased (P < 0.05) steady-state levels of mRNA for P-selectin (3.8- +/- 1.0- and 3.0- +/- 0.4-fold increase for LPS at 3 and 6 hours, respectively, and 2.5- +/- 0.8- and 2.7- +/- 0.9-fold increase for TNF-alpha at 3 and 6 hours, respectively). P-selectin mRNA had decreased by 48 hours to levels found in unstimulated cells. In contrast, human IL-1 beta had no effect on P-selectin mRNA. Increased levels of mRNA with LPS stimulation were associated with the synthesis of new protein, as demonstrated by the positive staining in LPS-stimulated cells using immunocytochemistry with a monoclonal antibody against canine P-selectin (MD3). These results reveal that important inflammatory mediators and cytokines such as LPS and TNF-alpha induce the synthesis of new P-selectin and suggest that this process could represent a means of sustaining local leukocyte recruitment for several hours during an acute inflammatory reaction.

Thioredoxin and thioredoxin reductase gene expression in human tumors and cell lines, and the effects of serum stimulation and hypoxia

Thioredoxin and thioredoxin reductase are redox proteins that have been implicated in the control of cell proliferation and transformation. We report the levels and activity of these proteins and their mRNAs in human primary tumors and tumor cell lines. Half of human primary colorectal carcinomas (5/10) examined had increased thioredoxin mRNA, of 3- to over 100-fold, compared to adjacent normal colonic mucosa from the same subject. Thioredoxin reductase protein and activity were increased an average of 2-fold in human colorectal tumors compared to normal mucosa. A number of human hematologic and solid tumor cell lines were studied and showed a 10-fold range of thioredoxin mRNA and a 23-fold range of thioredoxin reductase mRNA. Increased proliferation and hypoxia are factors that might contribute to the increased expression in solid tumors. We found that serum stimulation of growth arrested MCF-7 breast cancer cells caused a 59% increase in thioredoxin mRNA and a 62% increase in thioredoxin reductase mRNA by 24 hours. Exposure of HT-20 colon cancer cells to hypoxia resulted in a 14-fold increase in thioredoxin mRNA by 16 hours, and a transient 4-fold increase in thioredoxin reductase mRNA at 1 hour that had returned to control levels by 8 hours. Cancer cells were found to release thioredoxin into the medium at rates between 1 to 2 pmole/10(6) cells/3 hours. The rate of secretion was not, however, related to cellular-levels of thioredoxin. The results of the study show that the expression of thioredoxin and thioredoxin reductase are increased several fold in some human solid tumors compared to normal tissue. Secretion of thioredoxin, which is known to have a direct growth stimulating activity, by human tumor cells might lead to the stimulation of cancer cell growth.

The expression of E.coli threonyl-tRNA synthetase is regulated at the translational level by symmetrical operator-repressor interactions

Threonyl-tRNA synthetase from Escherichia coli represses the translation of its own mRNA by binding to the operator region located upstream from the ribosome binding site. The operator contains two stemloop structures which interact specifically with the homodimeric enzyme. Here, we provide in vitro and in vivo evidence that these two stem-loop structures are recognized by the enzyme in an analogous way and mimic the anticodon arm of E.coli tRNA(Thr). Determination of the stoichiometry of the different RNA-threonyl-tRNA synthetase complexes reveals that two tRNA(Thr) molecules bind to the enzyme whereas only one thrS operator interacts with the homodimeric enzyme. A model is presented in which the two anticodon-like domains of the operator bind symmetrically to the two tRNA(Thr) anticodon recognition sites (one per subunit) of the dimeric threonyl-tRNA synthetase. Although symmetrical operator-repressor interactions in transcriptional control are widespread, this report stresses the importance of such interactions in translational regulation of gene expression.

Stimulatory G-protein alpha-subunit mRNA levels are not increased in autopsied cerebral cortex from patients with bipolar disorder

Increased alpha-subunit (alpha s) levels of both the 45- and 52-kDa isoforms of the stimulatory guanine nucleotide binding protein (G-protein), have been found in postmortem brain and mononuclear leukocytes from patients with bipolar disorder (BD). The pathophysiological mechanism responsible for increased alpha s protein levels is unknown, however, it may involve increased expression of the gene encoding this protein. To assess this possibility, alpha s mRNA levels were determined by RT-PCR in postmortem brain from 10 subjects with an antemortem diagnosis of BD and age- and sex-matched control subjects in whom we had previously reported increased alpha s protein levels. There were no significant differences in alpha s mRNA levels in frontal, temporal, or occipital cortex between BD and control subjects. Cerebral cortex alpha s mRNA levels did not correlate with age or postmortem interval. These findings do not support the notion that higher alpha s levels found in BD postmortem brain are a result of increased gene expression.

Expression of S-adenosylmethionine synthetase isozyme genes in regenerating rat liver after partial hepatectomy

Mammalian S-adenosylmethionine (AdoMet) synthetase exists as two isozymes, liver-type and non-hepatic-type enzymes. To investigate the possible role of AdoMet synthetase in proliferating cells, we have examined the expression of these two isozyme genes in regenerating rat liver after partial hepatectomy using Northern blot analysis. In normal adult rat liver the non-hepatic-type isozyme mRNA was not detectable, however, when partial hepatectomy was performed, there was an obvious appearance of the non-hepatic-type enzyme mRNA after operation. The levels of non-hepatic-type isozyme mRNA was peaked at 4h and maintained the level at least till 8 h after operation, then decreased. In addition, the liver-type AdoMet synthetase gene expression was also induced by partial hepatectomy with similar time course. These results indicate that these two AdoMet synthetase isozymes may play an important role during the prereplicative phase which precedes DNA synthesis.

Production of granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor by carcinomas in a dog and a cat with paraneoplastic leukocytosis

A dog with a pulmonary papillary carcinoma and a cat with a dermal tubular adenocarcinoma had profound paraneoplastic neutrophilic leukocytosis with no clinically detectable inflammatory foci. To investigate the mechanism of the leukocytosis, oligonucleotide primers were designed from the cDNA sequences of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) of dogs. Reverse transcription polymerase chain reaction was performed on tumor tissues, and specific amplification of G-CSF and GM-CSF was obtained with the tumor RNA in the dog. The tumor RNA in the cat demonstrated specific amplification of G-CSF but not GM-CSF. These findings are consistent with the production of G-CSF and/or GM-CSF by neoplasms as a mechanism for paraneoplastic leukocytosis in small animals.

Changes in content of mRNA encoding oxytocin in the pig uterus during the oestrous cycle, pregnancy, at parturition and in lactational anoestrus

The aim of this study was to show that the pig uterus synthesizes oxytocin. Uteri were obtained from 2-7 pigs at regular intervals during the oestrous cycle, throughout pregnancy, at parturition and in lactational anoestrus. Localization of mRNA encoding oxytocin was by in situ hybridization and oxytocin concentrations were measured by radioimmunoassay. As reproductive status changed, mRNA encoding oxytocin varied significantly (P < 0.05). Uterine tissue type was a significant factor in determining synthesis of mRNA encoding oxytocin (P < 0.001). In luminal epithelia, concentrations of mRNA encoding oxytocin were greater at oestrus than during day 14 of the luteal phase (P < 0.01) or at any stage of pregnancy (P < 0.05), with concentrations minimal at parturition. This trend was also exhibited in uterine circular muscle. In longitudinal muscle, concentrations of mRNA encoding oxytocin were lower during late pregnancy than at oestrus (P < 0.05) or during the luteal phase (P < 0.05). Concentrations were minimal at parturition. The oxytocin content in endometrial and myometrial tissue was positively correlated across reproductive status (P < 0.02, r = 0.402, n = 35). These data are the first indication that the uterine endometrium and musculature of the pig express mRNA encoding oxytocin. The luminal epithelium of animals at oestrus was particularly rich in mRNA encoding oxytocin, whilst late pregnant and parturient animals did not show a rise in mRNA encoding oxytocin. Local uterine synthesis of oxytocin may therefore be more important in control of the oestrous cycle than in pregnancy or at parturition in pigs.

Prolactin-induced activation and binding of stat proteins to the IL-6RE of the alpha 2-macroglobulin (alpha 2M) promoter: relation to the expression of alpha 2M in the rat ovary

Cellular signaling events by which prolactin (PRL) might regulate gene expression were analyzed in rat ovarian tissues. Whole cell extracts (WCE) were prepared from ovaries of pregnant rats (Days 4, 7, 9-11, 15, 17, and 21) and of hormonally primed (estradiol and FSH) hypophysectomized (H) immature rats before, or 15 min to 24 h after, acute administration of PRL (10 micrograms, i.v.). The DNA binding activity in the WCE was analyzed by electrophoretic mobility shift assays using the alpha 2-macroglobulin (alpha 2M) promoter interleukin (IL)-6 response element (IL-6RE) known to confer PRL and IL-6 inducibility to transgenes in target cells, including cultures of luteinized granulosa cells. Injections of PRL stimulated the appearance of a specific binding activity in ovarian extracts of H rats and in corpora lutea and interstitial extracts of pregnant rats from Days 4-9 of pregnancy. The presence of this protein/DNA complex was transient. The greater amount of binding was observed in luteinized tissue and interstitial tissue compared to follicles; and the binding activity contained specific tyrosine phosphorylated Stat (signal transduction and activators of transcription) factors identified by specific antibodies as acute phase response factor (APRF or Stat 3) and mammary gland factor (MGF, or Stat 5 [a and b]). In contrast to the transient activation and appearance of these factors in response to acute PRL treatment as administered to H rats or to pulsatile PRL release as occurs in early pregnancy, elevated levels of the same activated Stat factors were observed in WCE of CL and interstitial tissue prepared at mid-gestation (Days 10-17) when endogenous release of rat placental lactogen (rPL) is chronically elevated in serum. During this period, administration of additional exogenous PRL did not stimulate further activation (binding) of the Stat factors. During luteal regression (Day 21 of gestation) no binding was observed in the absence of PRL, and the response to PRL was markedly diminished despite the constitutive presence of Stat proteins and the Janus kinase that phosphorylates and activates these factors. Elevated binding of these factors to the IL-6RE of the alpha 2M promoter was associated with the expression of alpha 2M mRNA in luteinized granulosa cells and corpora lutea, indicating that activation of Stat factors is one mechanism by which PRL/rPL transactivates the alpha 2M gene in the tissue.

Stimulation by retinoids of the natriuretic peptide system of osteoblastic MC3T3-E1 cells

The effects were examined of treatment with retinoids of osteoblastic MC3T3-E1 cells on the natriuretic peptide system that promotes the differentiation of osteoblastic cells. Northern blot analysis revealed high levels of mRNA for the retinoid X receptor beta (RXR beta) and moderate levels of mRNAs for retinoic acid receptors alpha (RAR alpha) and gamma (RAR gamma). Exposure of MC3T3-E1 cells to 1 microM retinoid caused increases in the levels of C-type natriuretic peptide (CNP) and natriuretic peptide receptor-C (NPR-C). The activity of natriuretic peptide receptor-B (NPR-B) was unchanged after the addition of retinoid to the culture system. These results suggest that retinoids might influence the metabolism of osteoblastic cells through regulation of the natriuretic peptide system.

Rat 17 beta-hydroxysteroid dehydrogenase type IV is a novel peroxisome proliferator-inducible gene

To better understand the molecular mechanisms of the pleiotropic responses induced by exposure to peroxisome proliferator chemicals (PPCs), we conducted a systematic search for genes whose mRNA levels are modulated by the PPC WY-14,643 (WY) in rat liver. The sequence of one up-regulated cDNA (2480 bp) was predicted to encode a protein of 735 aa with 82% identity to the porcine 17 beta-hydroxysteroid dehydrogenase type IV (HSD IV). Like the porcine enzyme, the rat HSD IV contains' a region homologous to yeast hydratase-dehydrogenase-epimerases and to sterol carrier proteins, indicating that the rat HSD IV has broad substrate specificity and contributes to cholesterol metabolism. The rat HSD IV was regulated by diverse PPCs via two distinct mechanisms. Induction of HSD IV and acyl-CoA oxidase (ACO) proteins in rat liver at different treatment times and concentrations of gemfibrozil and di-n-butyl phthalate were almost identical, indicating that HSD IV mRNA induction involves the peroxisome proliferator-activated receptor alpha, a regulator of ACO. In contrast, HSD IV protein levels were only weakly induced by WY, a strong inducer of ACO protein, even though the levels of HSD IV and ACO mRNA were strongly stimulated by WY and gemfibrozil. Thus, HSD IV protein levels were uniquely regulated pretranslationally by WY via a novel mechanism. Increased conversion of estradiol to the less-active estrone by HSD IV induction may explain how phthalate exposure leads to decreases in serum estradiol levels and suppression of ovulation.

Expression of CYP2B1 in freshly isolated and proliferating cultures of epithelial rat lung cells

Bronchiolar Clara cells and alveolar type 2 cells of the lung are known to express relatively high levels of P450 enzymes compared to other pulmonary cells. Populations of enriched type 2 cells and Clara cells were isolated from rat lung by a procedure including lung perfusion, protease digestion, centrifugal elutriation, and differential attachment. Alveolar macrophages were removed by lavage. The purity of the type 2 cell-enriched population was approximately 90%, and the purity of the Clara cell-enriched population was 40-50%. Both type 2 cells and the cells of the Clara cell-enriched population proliferated in culture. CYP2B1 mRNA was expressed approximately to the same level in type 2 cells and the Clara cell-enriched population. The mRNA levels remained roughly constant for both cell types throughout the culture period, except for an early transient reduction. The apoenzyme level of CYP2B1 was 2-3 times higher in freshly isolated cells of the Clara cell-enriched population than in the type 2 cells. Both epithelial cell types showed decreased level of CYP2B1 apoenzyme in culture. The differences in the CYP2B1 mRNA and apoenzyme expression levels in freshly isolated cells and cultured cells suggest the existence of a post-transcriptional regulatory mechanism for CYP2B1 expression in lung cells. The characterization of specific functions of lung cells in culture, such as P450 gene expression, provides necessary information for the use of the cells in in vitro pulmonary toxicology.

Tie endothelial cell-specific receptor tyrosine kinase is upregulated in the vasculature of arteriovenous malformations

Arteriovenous malformations (AVMs) are congenital lesions composed of abnormal vasculature, with no capillary component, and are clinically significant due to their tendency to spontaneously hemorrhage. The mechanisms regulating the genesis and progression of these lesions are unknown. In order to study the role of angiogenesis in AVMs, we have analyzed the expression of the endothelial cell mitogen vascular endothelial growth factor (VEGF) and a novel endothelial cell-specific receptor tyrosine kinase, Tie, by in situ hybridization and immunohistochemistry in these malformations and surrounding brain tissue. We have previously shown upregulation of Tie accompanying wound healing and tumor progression. In this study, we demonstrate significantly elevated levels of Tie mRNA and protein in AVM and surrounding brain vasculature. Upregulation of VEGF mRNA was observed in the cells of brain parenchyma adjacent to the AVM, and VEGF protein was detected in this tissue as well as in AVM endothelia. Normal brain, in comparison, expressed little or no Tie or VEGF. The significant upregulation of VEGF and Tie in AVMs may indicate some ongoing angiogenesis, possibly contributing to the slow growth and maintenance of the AVM, and could be of potential use in the therapeutic targeting of these lesions.

Axotomy-induced loss of m2 muscarinic receptor mRNA in the rat facial motor nucleus precedes a decrease in concentration of muscarinic receptors

The abundance of muscarinic receptors and m2 muscarinic receptor mRNA in the facial nuclei of rats was evaluated by autoradiographic procedures at various times up to 14 days after transection of the right facial nerve. Receptors were labelled by in vitro incubation of brain sections with L-[3H]quinuclidinyl benzilate, while in situ hybridization with a 35S-labelled oligonucleotide was used to identify m2 muscarinic receptor mRNA in neighbouring sections. The right and left facial nuclei of non-operated control rats appeared equivalent in abundance of muscarinic receptors (359 +/- 8 versus 376 +/- 9 fmol per mg tissue, n = 5) and the presence of m2 mRNA. Axotomy had no effect on the concentration of receptors in the contralateral facial nucleus but caused a gradual loss of receptors from the ipsilateral side. No change was detected at 1 day after nerve transection, but a 23% decrease relative to the contralateral facial nucleus had occurred by 3 days. A maximum decrease of 51% was achieved by 1 week after nerve transection. By comparison, m2 mRNA was nearly eliminated from the ipsilateral facial nucleus at 1 day post-taxonomy and remained depleted for the duration of study. Previous work has established that no significant loss of motoneurons occurs within this period. Accordingly, it is postulated that axonal injury inhibits transcription of the m2 muscarinic receptor gene, resulting in a later decrease in muscarinic receptor protein expression.

ACTH angiotensin II and TGF beta participate in the regulation of steroidogenesis in bovine adrenal glomerulosa cells

Bovine zona glomerulosa cells, on the first day of culture, produce aldosterone as their major steroid with no detectable cortisol secretion. Continuous incubation with ACTH had no effect on aldosterone production nor on aldosterone synthase activity. This treatment resulted in a dose and time dependent rise in 17 alpha-hydroxylase activity, in parallel with an increase in cytochrome P-450(17 alpha) (CYP17) protein and mRNA. We have previously shown that TGF beta 1 is a potent inhibitor of differentiated functions of bovine fasciculata-reticularis cells and that CYP17 and AII receptors are the major targets explaining this effect. The present study examined whether 17 alpha-hydroxylase activity in glomerulosa cells could be regulated by angiotensin II (AII) and transforming growth factor-beta 1 (TGF beta 1). AII inhibits the induction of CYP17 by ACTH in a dose dependent manner. TGF beta 1 also blocks almost completely the stimulatory effect of ACTH. In order to suppress the endogenous action of TGF beta 1, incubations were performed with an anti-TGF beta antibody. This specific antibody induces the expression of CYP17 resulting in increased activity and mRNA levels. These results show that AII is able to modulate the expression of CYP17 in adrenal glomerulosa cells following ACTH stimulation. Furthermore, TGF beta 1 exerts an autocrine effect on the differentiation of glomerulosa cells through a regulatory loop repressing CYP17 activity.

The resistance of the Wistar/Furth rat strain to steroid hypertension

We have previously reported that the Wistar/Furth (W/Fu) rat strain is resistant to mineralocorticoid hypertension. In the current study, we have examined renal mRNA levels for mineralocorticoid receptor (MR), glucocorticoid receptor (GR), renin and Na+, K(+)-ATPase in response to treatment with mineralocorticoids. Uninephrectomized male Wistar (WI) and W/Fu rats were treated with aldosterone or deoxycorticosterone acetate (DOCA) and were given 1% NaCl to drink. Rats were sacrificed after 1, 3 or 7 days of treatment. Renal MR and ATPase mRNA levels were significantly reduced in aldosterone and DOCA-treated WI rats (e.g. MR was 30% on day 3 and ATPase was 50% of control on day 7 of aldosterone treatment). Unexpectedly, GR mRNA levels paralleled the changes in MR. In W/Fu rats the level of message was either unchanged or only moderately altered by this treatment. In vivo administration of the MR antagonist RU28318 or the GR antagonist RU38486 to WI rats for 4 days reduced renal mRNA levels for both subunits of ATPase. In the W/Fu rat, this treatment resulted in no change in the alpha subunit and an increase in the beta subunit of ATPase. In preliminary studies, we have determined that the W/Fu rat is also resistant to dexamethasone-induced hypertension. These studies suggest that altered MR- and GR-mediated mechanisms may contribute to the resistance of the W/Fu rat strain to steroid-induced hypertension.

Ontogeny of insulin-like growth factor-I and -II gene expression in ovine fetal heart

OBJECTIVE

Insulin-like growth factors (IGF)-I and -II have been implicated in growth and differentiation during embryonic and fetal development. To examine the role of the IGFs in growth of the fetal heart, we determined the gene expression of IGF-I and IGF-II in the four cardiac chambers of the ovine fetus from 58 to 146 days' gestation (term = 147 days).

METHODS

Total RNA was obtained from the cardiac chambers, analyzed by Northern blot, and hybridized to ovine specific cDNA probes for IGF-I and IGF-II. The resulting autoradiograms were subjected to light densitometry, and the intensity of the IGF signals was normalized to the respective 28S ribosomal RNA signals.

RESULTS

In the atria and ventricles, IGF-I mRNA abundance was very low throughout the gestational period studied, whereas IGF-II mRNA levels were higher and readily detectable. In the atria, IGF-I mRNA was very low at 60 days' gestation and appeared to increase gradually toward term. Abundance of IGF-II mRNA was high at 60 days, increased further until 120 days, and decreased slightly toward term. In contrast, in the ventricles, IGF-I mRNA increased from 60 to 100 days and then declined moderately at term. Levels of IGF-II mRNA in the ventricles were high at 60 days and decreased progressively to low levels at term. No difference in IGF-I or IGF-II mRNA levels was noted between the right and left atria or right and left ventricles.

CONCLUSION

These results suggest that developmental patterns for IGF-I and IGF-II gene expression exist in the ovine fetal heart, and the patterns differ between the atria and ventricles. Further, these gestational trends differ from those for atrial natriuretic factor (ANF) found in our previous studies, indicating that expression of the ANF gene in the fetal heart may not be associated with cardiac growth and differentiation.

Differential gene expression of extracellular matrix components in dilated cardiomyopathy

Extracellular matrix metalloproteinases (MMPs) are activated in dilated cardiomyopathic (DCM) hearts [Tyagi et al. (1996): Mol Cell Biochem 155:13-21]. To examine whether the MMP activation is occurring at the gene expression level, we performed differential display mRNA analysis on tissue from six dilated cardiomyopathy (DCM) explanted and five normal human hearts. Specifically, we identified three genes to be induced and several other genes to be repressed following DCM. Southern blot analysis of isolated cDNA using a collagenase cDNA probe indicated that one of the genes induced during DCM was interstitial collagenase (MMP-1). Northern blot analysis using MMP-1 cDNA probe indicated that MMP-1 was induced three- to fourfold in the DCM heart as compared to normal tissue. To analyze posttranslational expression of MMP and tissue inhibitor of matrix metalloproteinase (TIMP) we performed immunoblot, immunoassay, and substrate zymographic assays. TIMP-1 and MMP-1 levels were 37 +/- 8 ng/mg and 9 +/- 2 ng/mg in normal tissue specimens (P < 0.01) and 2 +/- 1 ng/mg and 45 +/- 11 ng/mg in DCM tissue (P < 0.01), respectively. Zymographic analysis demonstrated lytic bands at 66 kDa and 54 kDa in DCM tissue as compared to one band at 66 kDa in normal tissue. Incubation of zymographic gel with metal chelator (phenanthroline) abolished both bands suggesting activation of neutral MMP in DCM heart tissue. TIMP-1 was repressed approximately twentyfold in DCM hearts when compared with normal heart tissue. In situ immunolabeling of MMP-1 indicated phenotypic differences in the fibroblast cells isolated from the DCM heart as compared to normal heart. These results suggest disruption in the balance of myopathic-fibroblast cell ECM-proteinase and antiproteinase in ECM remodeling which is followed by dilated cardiomyopathy.

Interleukin (IL)-6 as a pancreas carcinoma-derived vascular permeability regulator in vitro

The interaction between pancreas adenocarcinoma and vascular endothelial cells in vitro was investigated. Culture media of pancreas carcinoma cells PCI-10, but not PCI-24, induced an augmented albumin permeability across the endothelial monolayer, an event which was blocked by the calmodulin antagonist, W-7. Only marginal inhibitory effects were obtained using protein kinase inhibitors, H-7 and HA-1004. When cytokine production by pancreas carcinoma cells was examined, production of IL-6 in large amounts by PCI-10, but not by PCI-24 cells was evident. As recombinant IL-6 generated a dose-dependent permeability increase, and as this effect was inhibited by W-7, we considered that the enhancement of vascular permeability was mediated by this cytokine. The activity of culture supernatants for enhanced permeability was almost completely absorbed by the addition of an antibody specific for IL-6. Tumor-derived IL-6 as a soluble mediator regulates vascular permeability in vitro, and the production of this factor by pancreas adenocarcinoma cells presumably modulates biologic behavior.

Regulation of insulin-like growth factor I biosynthesis in porcine granulosa cells

In the present studies we examined the regulation of insulin-like growth factor I (IGF-I) expression in porcine granulosa cells in vitro. Using Northern analysis and ribonuclease protection assays with exon-specific probes, we identified the IGF-I messenger RNA (mRNA) transcripts present in these cells under basal and hormone-stimulated conditions. We also assessed changes in secreted IGF-I using Western blots and correlated the change in protein secretion after hormone treatment with changes in mRNA levels. By analogy to the human IGF-I gene and its transcription, two major transcripts of approximately 1 and 7.5 kilobases, seen in freshly isolated granulosa cells and follicle wall and in single passaged granulosa (MDGp1) cells, most likely correspond to IGF-IA. Minor transcripts of 3-4 kilobases, which appeared after FSH or forskolin treatments or in control cells after long exposure of the autoradiographs, were attributed to incompletely processed RNA precursors. Ribonuclease protection assay analysis using probes to detect alternative use of exon 5 or exon 6 indicated that most, if not all, of the transcripts contained only exon 6 sequence (IGF-IA). Both class 1 and class 2 transcripts were identified using exon 1- and exon 2-specific probes, respectively. GH increased steady state levels of IGF-I mRNA 3-fold, FSH increased it approximately 10-fold, and forskolin maximally increased it 12- to 15-fold. Estradiol had no effect alone or in combination with the other treatments. All treatments that increased IGF-I mRNA coordinately increased both class 1 and class 2 transcripts, with the increase in class 1 greater than that in class 2. Multiple forms of IGF-I protein were seen under basal conditions and after hormone treatment. These were identified based on mRNA analysis and biochemical methods as both glycosylated and nonglycosylated IGF-IA prohormone, incompletely processed forms of prohormone, and the mature peptide. Changes in the levels of total protein were similar to the changes in mRNA (GH, 3-fold; FSH and forskolin, 10- to 20-fold). All forms of the protein changed coordinately, suggesting that these hormones had no major effect on the intracellular processing mechanism. IGF-binding protein-3 was able to bind to all IGF-I forms. These data conclusively demonstrate FSH and GH induction of ovarian IGF-I. The porcine granulosa cell culture system used in these studies should be an excellent system for studying the hormonal regulation of IGF-I expression.

Lowering glucose depletes a thapsigargin-sensitive calcium pool and inhibits transcription of the S14 gene

S14 is a nuclear protein that is rapidly and synergistically induced by glucose and thyroid hormone, and the level of it's messenger RNA correlates with hepatocyte and adipocyte lipogenesis. We previously reported that the calcium ionophore A23187 markedly inhibits the carbohydrate response of the S14 gene without inhibiting glucose metabolism. Because the calcium ionophore not only increased intracellular cytosolic free calcium but also depletes intracellular calcium stores, we examined which of these two possibilities accounts for the regulation of S14 gene transcription. We found that increasing cytosolic calcium with arginine vasopressin is insufficient to inhibit S14 gene transcription. Furthermore, reduction of intracellular calcium by addition of EGTA to medium containing A23187 leads to further inhibition of S14 transcription. Measurement of intracellular free calcium in indo-1-loaded hepatocytes showed no significant changes induced by high glucose. These results suggested that depletion of an intracellular pool of calcium by A23187 causes the inhibition of S14 transcription. Addition of thapsigargin, which depletes intracellular calcium pools by inhibition of endoplasmic reticulum Ca2+-ATPase, led to significant inhibition of glucose-regulated S14 transcription. Lastly, continuous incubation in 5.5 mM glucose depletes the thapsigargin-sensitive calcium pool. These studies imply that the ability of glucose to induce S14 transcription is related to a thapsigargin-sensitive calcium pool, and depletion of this pool by lowering glucose inhibits S14 transcription.

Dietary sodium effects on renin and angiotensinogen gene expression in preweanling WKY and SHR

The influence of altered dietary sodium on angiotensinogen and renin gene expression was examined in young normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive rats (SHR). Artificial rearing was used to increase or decrease dietary sodium intake during the preweanling period. In normally reared control animals, renal renin and liver angiotensinogen mRNA decreased between 6 and 30 postnatal days of age. In contrast, in the central nervous system, angiotensinogen mRNA increased between 6 and 30 days of age, and renin mRNA remained stable. Dietary sodium manipulation between postnatal days (PD) 6 and 18 significantly influenced renal renin gene expression, with low-sodium diet increasing renin mRNA on PD12 and PD18 and high-sodium diet decreasing renin mRNA on PD18. Liver angiotensinogen mRNA decreased for animals on either diet on PD12 and PD18. Brain angiotensinogen and renin mRNA were not affected by dietary sodium levels. There were no strain-related differences in the response to high and low dietary sodium. These results demonstrate that 1) the peripheral and central renin-angiotensin systems do not have a common ontogenetic pattern of development, 2) they are independently regulated in response to dietary sodium variations, and 3) young WKY and SHR share very similar ontogenetic patterns of angiotensinogen and renin gene expression.

TNF-mediated cytotoxicity and resistance in human prostate cancer cell lines

BACKGROUND

The contribution of TNF receptor (TNF-R) expression was investigated with respect to TNF sensitivity or insensitivity for androgen-dependent and androgen-independent human prostate cancer (PCA) cell lines, respectively.

METHODS

Flow cytometric analyses using monoclonal antibodies against the 55-kDa receptor (TNF-R1) and the 75-kDa receptor (TNF-R2) indicated that both receptors were expressed on all three cell lines.

RESULTS

Moreover, expression of TNF-R1 was greater than expression of TNF-R2 in these PCA cells. All three PCA cell lines produced IL-6. However, IL-6 production was enhanced when TNF-insensitive JCA-1 and PC-3 cells, but not TNF-sensitive LNCaP cells, were treated with rTNF (10(-9) M).

CONCLUSIONS

These data suggest that the lack of an antiproliferative effect of rTNF on the androgen-independent PCA cell lines PC-3 and JCA-1 is not due to the failure of these cells to express TNF-R, but may be related to the differences in TNF-mediated IL-6 expression by these PCA cell lines.

An androgen-regulated homeobox gene expressed in rat testis and epididymis

Homeobox genes encode DNA-binding proteins that regulate the transcription of subordinate downstream genes. In this study, we show that the Pem homeobox gene is expressed and regulated in a unique manner in neonatal and adult rats. Pem gene expression was primarily confined to reproductive tissue: epididymis, testis, ovary, and placenta. In the epididymis, Pem transcripts were localized by in situ hybridization analysis to the proximal cauda region, a site where spermatozoa gain fertilization competence. Pem mRNA levels dramatically increased between Days 21 and 26 postpartum in the epididymis, coincident with the induction of genes known to be responsive to testosterone (T), but in contrast to that of other genes examined, including the Hoxc-8 homeobox gene. Pem expression was shown to be T-dependent on the basis of an absence of Pem transcripts in the epididymides of hypophysectomized rats and restoration of normal Pem mRNA levels after administration of T. In the testis, Pem mRNA levels were elevated earlier (between Days 12 and 15 postpartum) and less dramatically than in epididymis. Pem gene expression in the testis was depressed after hypophysectomy, but normal levels of Pem expression were not restored by T treatment under the same conditions that permitted normal Pem expression in the epididymis. To our knowledge Pem is the first reported putative transcription factor that has been demonstrated to depend on androgens for expression in the epididymis, and thus Pem is a candidate as a regulator of androgen-dependent events in this tissue.

The primary structures of rat ribosomal proteins S3a (the V-Fos transformation effector) and of S3b

The amino acid sequence of the rat 40S ribosomal subunit protein S3a was deduced from the sequence of nucleotides in two recombinant cDNAs and confirmed by the determination of the NH2-terminal sequence by Edman degradation. Ribosomal protein S3a has 263 amino acids (the NH2-terminal methionine is removed after translation of the mRNA) and the molecular weight is 29,794. The protein designated S3b has the same amino acid sequence as S3a except that it lacks the carboxyl-terminal 12 residues. We are unable to determine whether there are separate genes for S3a and S3b, or whether there is a single gene and alternate splicing of the precursor to yield separate mRNAs for S3a and S3b, or whether there is a single gene and a single mRNA whose translation yields S3a which is converted by proteolysis, either physiological or fortuitous, to S3b. The mRNA for S3a is about 1000 nucleotides in length. Hybridization of cDNA to digests of nuclear DNA suggests that there are 8-13 copies of the S3a gene. Rat ribosomal protein S3a is identical to the product of the rat Fte-1 gene which encodes the V-Fos transformation effector; S3a is also related to the plant protein cyc07, which is encoded by a cell cycle S-phase specific gene.

Uptake of radioactive octanoate in astrocytoma cells: basic studies for application of [11C]octanoate as a PET tracer

Fatty acids are taken up and metabolized in the brain. In vitro uptake experiments on astrocytoma cells were carried out to assess the potential use of [1-11C]octanoate as a positron emission tomography (PET) tracer for astroglial functions. Uptake of [1-14C]octanoate increased in a time-dependent fashion until 60 min after application. The uptake of [1-11C]octanoate showed similar results to that of [1-14C]octanoate until 10 min. As for medium pH, [1-14C]octanoate uptake increased gradually with the decrease in pH. We also examined the effects of glutamate, glucose deprivation and hypoxia on the uptake of octanoate and found that these conditions did not bring about any change in the extent of [1-14C]octanoate uptake. These results show that the octanoate uptake was not influenced by any of several pathological conditions. When the number of astrocytes increases in the area of hypoglycemia or hypoxia near a brain lesion, the amount of octanoate uptake also increases, so this indicates the possibility that 11C-octanoate will detect a brain lesion.