Interleukin-1 alpha and tumor necrosis factor-alpha differentially regulate enkephalin, vasoactive intestinal polypeptide, neurotensin, and substance P biosynthesis in chromaffin cells

The pattern of expression of at least four neuropeptides contained in adrenomedullary chromaffin cells is altered by exposure to the cytokines interleukin-1 alpha (IL-1 alpha) and tumor necrosis factor-alpha (TNF alpha), alone or in combination with stimulation of other second messenger pathways. Vasoactive intestinal polypeptide (VIP) was elevated 2- to 3-fold by 1 nM IL-1 alpha within 48 h of exposure, while neurotensin and substance P synthesis were unaffected, and met-enkephalin levels were decreased 25-35%. Stimulation of VIP and substance P biosynthesis by forskolin was markedly enhanced by IL-1 alpha, while forskolin stimulation of enkephalin and neurotensin biosynthesis was unaffected. IL-1 alpha amplified the effect of phorbol myristate acetate to increase the VIP content of chromaffin cells, but antagonized phorbol ester-induced elevation of neurotensin levels. TNF alpha also demonstrated a neuropeptide-specific pattern of modulation of second-messenger effects on chromaffin cell neuropeptide levels similar to those seen with IL-1 alpha. The neuroendocrine actions of IL-1 alpha described above, unlike IL-1 action in the immune system, do not appear to be mediated through IL-2 as this cytokine did not affect VIP or enkephalin expression in the presence or absence of protein kinase stimulation. Neither IL-1 alpha nor TNF alpha affected the calcium-coupled stimulation of neuropeptide secretion and biosynthesis that occurs in response to cell depolarization in these and other neuroendocrine cells in vitro and in vivo. These data provide a functional demonstration of IL-1 and TNF receptors in chromaffin cell cultures and suggest a physiological role for cytokine production in the adrenal medulla. Since both the magnitude and direction of neuropeptide synthesis modulation by IL-1 alpha and TNF alpha are highly peptide-specific, it appears that these cytokines do not merely augment second messenger pathways that affect neuropeptide synthesis, but potentially regulate the activity of factors controlling the pattern of neuropeptide gene expression in chromaffin cells.

Cognitive and motor impairments associated with SIV infection in rhesus monkeys

Cognitive and motor deficits are now recognized as significant clinical features of infection with the human immunodeficiency virus (HIV). Juvenile rhesus macaques infected with simian immunodeficiency virus (SIV) were found to exhibit cognitive and motor deficits characteristic of HIV infection. Impairment on a motor skill task was the most reliable indicator of infection. Various cognitive impairments were also evident. These deficits were related to SIV infection of the brain but not to inflammatory lesions at a particular locus. The results suggest that the SIV-infected rhesus macaque is a valuable model for understanding the cause of HIV-associated central nervous system dysfunction and for developing a treatment.

The bovine chromogranin A gene: structural basis for hormone regulation and generation of biologically active peptides

The structure of the gene encoding bovine chromogranin-A has been determined by characterization of two isolated genomic clones. Chromogranin-A is encoded by eight exons, which organize the coding region into several distinct structural and functional domains. Exons 1-5 represent the highly conserved signal peptide and N-terminal domain, which are separated into regions corresponding to the signal peptide, N-terminal sequence, disulfide-bonded loop, and remainder of the conserved N-terminal domain. Exon 6 represents the variable domain and encodes a region that is identical to the novel chromogranin-A-derived peptide chromostatin. Exon 7 encodes the biologically active peptide pancreastatin as well as most of the conserved C-terminal domain, with the remainder found on exon 8. The mRNA sequence obtained from the gene contains five nucleotide differences from the consensus sequence of four reported bovine chromogranin-A cDNA clones. Two of the differences in the gene result in two amino acid changes in the region encoded by exon 6. The structural organization of the chromogranin-A gene resembles that of the chromogranin-B gene in the exons corresponding to the signal peptide, N-terminal sequence, disulfide loop, and C-terminal sequence.(ABSTRACT TRUNCATED AT 250 WORDS)

Dual presence of chromogranin A-like immunoreactivity in a population of endocrine-like cells and in nerve fibers in the human anal canal

Light microscopic immunohistochemistry was used to investigate the presence and distribution of chromogranin A-like immunoreactivity in the human anal canal. In the anal transitional zone (ATZ), anal duct and anal gland epithelium, a varied number of mostly elongated cells strongly stained for CGA, using an antibody directed to a highly species-conserved region of the CGA molecule or the monoclonal antibody LK2H10. The density of CGA-immunoreactive (ir) cells strikingly increased from the ATZ epithelium towards the anal gland epithelium. CGA-ir cells possessed single processes running perpendicularly to reach the epithelial surface and exhibited basal ramifications that extended parallel to the basal lamina. The number of CGA-ir cells in anal glands exceeded CGA-ir cells in the crypt-bearing colorectal-type mucosa. The abundant population of CGA-ir cells in the anal canal most likely represents a population of specialized endocrine or paracrine cells. CGA-like immunoreactivity was also present in anocutaneous Merkel cells. A sparse number of vascular and non-vascular CGA-ir varicose nerve fibers was present throughout the layers and rostrocaudal divisions of the anal canal and in the perianal skin. Proposed functions of CGA in neuroendocrine cells and nerves of the anal canal include calcium binding and regulation, secretory granule matrix formation, and generation of bioactive peptides.

Stimulation of glycoprotein gp120 dissociation from the envelope glycoprotein complex of human immunodeficiency virus type 1 by soluble CD4 and CD4 peptide derivatives: implications for the role of the complementarity-determining region 3-like region in membrane fusion

We have used a recombinant vaccinia virus vector encoding the envelope glycoprotein of human immunodeficiency virus type 1 to study receptor-induced structural changes related to membrane fusion. A truncated soluble form of human CD4 (sCD4) was found to stimulate dissociation of the external subunit (gp120) from the envelope glycoprotein complex of human immunodeficiency virus type 1 expressed at the cell surface. sCD4 stimulation of gp120 release was time- and concentration-dependent and was associated with specific binding of sCD4 to gp120. Synthetic peptide derivatives corresponding to residues 81-92 of human CD4 (overlapping the complementarity-determining region 3-like region) inhibited cell-cell fusion mediated by the interaction between recombinant vaccinia-encoded CD4 and human immunodeficiency virus envelope glycoprotein. These peptide derivatives also stimulated gp120 release from the envelope glycoprotein complex. An analogous peptide derivative from chimpanzee CD4 (containing a single Glu----Gly substitution at the position corresponding to CD4 residue 87) was considerably less active at inhibition of cell-cell fusion and stimulation of gp120 release, consistent with the known inhibitory effect of this substitution on the ability of membrane-associated CD4 to mediate cell fusion. These results suggest that the sCD4-induced release of gp120 reflects postbinding structural changes in the envelope glycoprotein complex involved in membrane fusion, with the complementarity-determining region 3-like region playing a critical role.

Synthetic peptides allow discrimination of structural features of CD4(81-92) important for HIV-1 infection versus HIV-1-induced syncytium formation

Benzylated peptides with a primary amino acid sequence corresponding to either human CD4(81-92) (#18), or chimpanzee CD4(81-92) (#18C), were equipotent inhibitors of human immunodeficiency virus type 1 (HIV-1) infection of CD4+ cells and high-affinity binding of 125I-gp120 to CD4+ cells. The chimpanzee-based CD4(81-92) peptide, however, which differs from the human peptide by a single amino acid substitution (E for G) at position 87, was considerably less potent than the human CD4(81-92)-based peptide congener to inhibit HIV-1-induced cell-cell fusion. These data suggest that a portion of the CD4 molecule contained within the sequence CD4(81-92) is involved in binding gp120 during both HIV-1 infection and HIV-1-induced syncytium formation in human cells, but that the presence of a glutamic acid at position 87 in this sequence is more critical for the CD4/gp120 interaction leading to syncytium formation than for the CD4/gp120 interaction leading to primary infection of CD4-positive cells. The region CD4(81-92) may critically contribute to CD4-mediated HIV-1 pathogenesis in humans, and its alteration might explain the lack of pathogenic sequelae of HIV-1 infection in chimpanzees.

Spontaneous electrical activity regulates vasoactive intestinal peptide expression in dissociated spinal cord cell cultures

Activity-dependent expression of vasoactive intestinal peptide (VIP) was investigated in spinal cord/dorsal root ganglia cultures derived from embryonic mice. Since all spinal cord neurons appear to exhibit spontaneous action potentials after one week in vitro, activity-dependent regulation of VIP-transcripts (mRNAVIP) could be studied with or without electrical blockade induced by tetrodotoxin (TTX). In 10-day-old cultures, a 50% decrease in mRNAVIP was observed after 3 days of treatment with TTX. The decrease in mRNAVIP was reversed upon removal of the TTX and was dependent on the age of the cultures: no decreases from control were observed in 5-day-old cultures and much smaller decrements were produced in one month old cultures treated with TTX. A variety of neuroactive substances were tested for effects on mRNAVIP in electrically active and electrically blocked cultures. Application of 8-bromo-cAMP (cAMP), N-methyl-D-aspartate (NMDA), substance P, muscimol, A23187 and VIP to electrically active cultures resulted in a 2- to 3-fold increase in mRNAVIP, while phorbol myristate 13-acetate (PMA) and 8-bromo-cGMP (cGMP) had no effect. In contrast, electrically inactive cultures exhibited a 3 to 4-fold increase in mRNAVIP after treatment with PMA, cAMP and VIP, while NMDA, substance P, muscimol, A23187 and cGMP produced no increases. In summary, the regulation of VIP gene expression in embryonic spinal cord neurons shows a temporal sensitivity to TTX-induced electrical blockade and may be mediated by multiple neurotransmitter inputs which converge on cAMP- and calcium-related processes in an activity-dependent manner.

Regional distribution and partial molecular characterization of CD4-related mRNA in human brain and peripheral tissues

We purified human poly(A)+ RNA from 11 individuals to assess the regional distribution of CD4 and CD4-related mRNA transcripts in human brain and in peripheral tissues by Northern blot hybridization. A 3.0 kb CD4 mRNA transcript was expressed in all brain areas and several peripheral tissues examined. A second CD4-related 1.8 kb mRNA species showed an uneven distribution in the brain with cortical regions possessing highest levels and basal ganglia, thalamus, cerebellum and spinal cord containing relatively lower amounts. Messenger RNA transcripts for CD8, a T cell specific marker, were not detectable in human brain by Northern analysis, yet were as abundant as CD4 in spleen. The expression of the 1.8 kb mRNA was tissue specific as it was not observed in peripheral tissues such as spleen, adrenal, colon, or lung, nor was it found in the choroid plexus, dorsal root ganglion and human neuronal (SY5Y) or astroglial (N132N1) cell lines. Blot hybridization and S1 nuclease protection analysis of poly(A)+ RNA with selective probes derived from CD4 indicated that the 1.8 kb mRNA transcript is truncated, lacking the extracellular protein coding region of CD4, and may in fact be a unique transcript from the CD4 gene locus rather than an alternatively spliced or processed CD4 mRNA.

Calcium-dependent regulation of the enkephalin phenotype by neuronal activity during early ontogeny

Genetic components of the neuronal phenotype are regulated by epigenetic factors--trophic molecules and neuronal activity--during neurodifferentiation. Developing neurons in dissociated cultures of embryonic mouse spinal cord show spontaneous electrical activity after one week in culture. We now report that the blockade of this spontaneous electrical activity for two days with tetrodotoxin (TTX) causes virtually complete down-regulation of preproenkephalin A gene transcripts in embryonic spinal cord cultures. This TTX-induced down-regulation is fully reversed upon reinitiation of neuronal activity (removal of TTX from cultures). This reversible, tetrodotoxin-induced down-regulation of enkephalin mRNA is confined to a restricted period of early neurodevelopment (days 7 to 21 in culture). Since depolarization triggers calcium entry through voltage-activated calcium channels, we have investigated the involvement of calcium in the mechanism of this activity- and age-dependent regulation of preproenkephalin A expression. The selective activation of the L-type of voltage-sensitive calcium channels by a dihydropyridine derivative [(+) 202-791] prevented this TTX-induced down-regulation without reducing methionine enkephalin secretion. This effect was observed only when the drug was applied to electrically active cultures, prior to the addition of TTX. Simultaneous application of (+) 202-791 and TTX, or pretreatment with TTX, failed to prevent TTX-induced down-regulation. Thus, activity-dependent phenotypic plasticity of met-enkephalinergic neurons in spinal cord is: 1) maximum at an early age of neuronal development (less than 10 days in culture) and becomes less apparent in old cultures (greater than 30 days); 2) reversible throughout; and 3) mediated by calcium entry through L-type channels.

Evidence by peptide mapping that the region CD4(81-92) is involved in gp120/CD4 interaction leading to HIV infection and HIV-induced syncytium formation

Peptide fragments of the CD4 molecule were compared in their ability to 1) inhibit CD4-dependent HIV-induced cell fusion; 2) inhibit CD4-dependent HIV infection in vitro; and 3) block gp120 envelope glycoprotein binding to CD4. Peptides from the region CD4(81-92), although inactive when underivatized, were equipotent inhibitors of CD4-dependent virus infection, cell fusion, and CD4/gp120 binding when derivatized via benzylation and acetylation. Peptides of identical chemical composition, but altered sequence and derivatization pattern that blocked gp120 binding to either CD4-positive cells or solubilized CD4, also blocked infection and fusion with similar potencies. Those that did not block gp120/CD4 interaction were also inactive in HIV-1 infection and cell fusion assays. No other peptide fragments of the CD4 molecule inhibited fusion, infection, or CD4/gp120 interaction. The peptide CD4(23-56), derived from a region of CD4 implicated in binding of CD4 antibodies that neutralize HIV infection and cell fusion, had no effect on CD4-dependent cell fusion, HIV-1 infection, or CD4/gp120 binding, but did reverse OKT4A and anti-Leu 3a blockade of gp120 binding to CD4. These data provide evidence that the 81-92 region of CD4 is directly involved in gp120 binding leading to CD4-dependent HIV infection and syncytium formation. Previous observations with structural mutants of CD4 suggest that the CDR2-homologous region of CD4 is also involved, either directly or indirectly, in binding of gp120 to CD4. The CDR2- and CDR3-like domains of CD4 may both contribute to the binding of the HIV envelope necessary for HIV-1 infection and HIV-1-induced cell fusion.

Evidence by peptide mapping that the region CD4(81-92) is involved in gp120/CD4 interaction leading to HIV infection and HIV-induced syncytium formation

Peptide fragments of the CD4 molecule were compared in their ability to 1) inhibit CD4-dependent HIV-induced cell fusion; 2) inhibit CD4-dependent HIV infection in vitro; and 3) block gp120 envelope glycoprotein binding to CD4. Peptides from the region CD4(81-92), although inactive when underivatized, were equipotent inhibitors of CD4-dependent virus infection, cell fusion, and CD4/gp120 binding when derivatized via benzylation and acetylation. Peptides of identical chemical composition, but altered sequence and derivatization pattern that blocked gp120 binding to either CD4-positive cells or solubilized CD4, also blocked infection and fusion with similar potencies. Those that did not block gp120/CD4 interaction were also inactive in HIV-1 infection and cell fusion assays. No other peptide fragments of the CD4 molecule inhibited fusion, infection, or CD4/gp120 interaction. The peptide CD4(23-56), derived from a region of CD4 implicated in binding of CD4 antibodies that neutralize HIV infection and cell fusion, had no effect on CD4-dependent cell fusion, HIV-1 infection, or CD4/gp120 binding, but did reverse OKT4A and anti-Leu 3a blockade of gp120 binding to CD4. These data provide evidence that the 81-92 region of CD4 is directly involved in gp120 binding leading to CD4-dependent HIV infection and syncytium formation. Previous observations with structural mutants of CD4 suggest that the CDR2-homologous region of CD4 is also involved, either directly or indirectly, in binding of gp120 to CD4. The CDR2- and CDR3-like domains of CD4 may both contribute to the binding of the HIV envelope necessary for HIV-1 infection and HIV-1-induced cell fusion.

Galanin gene expression in chromaffin cells is controlled by calcium and protein kinase signaling pathways

The neuropeptide galanin (GAL) is widely distributed throughout the diffuse neuroendocrine system, and is coexpressed with acetylcholine, norepinephrine, prolactin, and a variety of other messenger substances in different cell types. Bovine chromaffin cells in primary culture synthesize and store GAL along with catecholamines, chromogranin A, and enkephalin peptides, as well as other neurosecretory products, and secrete all these molecules in response to nicotinic stimulation. The regulation of GAL biosynthesis and secretion were studied by measuring changes in messenger RNA (mRNA(GAL], and peptide immunoreactivity, 24-72 h after stimulation of secretion (40 mM potassium or 10 microM veratridine), or exposure to stimulators of protein kinase C (100 nM phorbol myristate acetate) and protein kinase A (25 microM forskolin). Depolarization-induced stimulation of GAL biosynthesis, like that of enkephalin and other neuropeptides, was calcium dependent, suggesting that calcium generally mediates both exocytotic release and new peptide synthesis thus coordinating maintenance of neuropeptide levels in chromaffin cells. GAL and mRNA(GAL) were also upregulated by stimulation of protein kinase A with forskolin. Treatment with PMA increased GAL and mRNA(GAL) to an even greater extent than depolarization. Thus GAL expression can be regulated by three distinct signal transduction systems in chromaffin cells: depolarization-stimulated calcium influx, activation of protein kinase C and activation of protein kinase A, which in addition differentially up- and down-regulate the expression of several other neurosecretory proteins and peptides resulting in different patterns of GAL/neuropeptide coexistence in bovine chromaffin cells. GAL coexistence with diverse neuroendocrine substances may reflect the relative activity of these three signalling systems in other neuroendocrine cell types as well.

Neuropeptide content and connectivity of the rat claustrum

The rat claustrum has a homogeneous distribution of the neuropeptides somatostatin (SOM), cholecystokinin (CCK) and vasoactive intestinal polypeptide (VIP) along its rostrocaudal axis. In general, neuropeptide levels are comparable to those of overlying pyriform cortex. Visualization of mRNA encoding SOM, CCK and VIP in cell bodies of the claustrum by in situ hybridization histochemistry demonstrates that all 3 neuropeptides are contained in intrinsic claustral neurons. Mid-coronal section of the claustrum itself, or interruption of potential rostral, caudal or medial connections between the claustrum and the rest of the brain did not significantly alter levels of VIP, SOM or CCK in claustrum, cerebral cortex, or basal ganglia. Isolation of the claustrum from the cerebral cortex immediately dorsal to it along its rostrocaudal aspect caused no change in peptide levels in claustrum indicating that VIP, SOM and CCK projections to claustrum do not arrive from dorsal cortical areas. Transection of the external capsule above the claustrum caused a 50-100% elevation of all 3 peptides on the contralateral side of the lesion, suggesting that VIP, SOM and CCK synthesis and/or release within the claustrum may be regulated by projections from the contralateral side. VIP, SOM and CCK are candidates for neurotransmitters contained in neurons whose cell bodies are within the claustrum and possibly also immediately overlying lateral neocortex, and have their terminals mainly within the claustrum itself.

Sequence analysis, tissue distribution and regulation by cell depolarization, and second messengers of bovine secretogranin II (chromogranin C) mRNA

Secretogranin II is a very acidic, tyrosine-sulfated protein found in secretory granules of cells belonging to the diffuse neuroendocrine system. It gained more general importance recently as a universal immunohistochemical marker for endocrine neoplasms. Sequence information was obtained from secretogranin II isolated from bovine anterior pituitaries, allowing the isolation of cDNA clones and deduction of its primary structure. Bovine secretogranin II is a 586-amino acid protein of 67,455 Da which is preceded by a signal peptide of 27 residues and contains 9 pairs of basic amino acids in its sequence which are used as potential cleavage sites for generation of physiologically active peptides. Moderately abundant mRNA levels were found in adrenal medulla, pituitary, hippocampus, and caudate. Secretogranin II message was absent from parathyroid gland, adrenal cortex, kidney, liver, and spleen. Depolarization of isolated chromaffin cells by various secretagogues significantly up-regulated secretogranin II mRNA levels by mechanisms distinct from those established for chromogranins and neuropeptides, components maintained along with secretogranin II in neuroendocrine storage vesicles.

Functional expression of dihydropyridine-insensitive calcium channels during PC12 cell differentiation by nerve growth factor (NGF), oncogenic ras, or src tyrosine kinase

1. Recombinant retroviruses were used to introduce a temperature-sensitive v-src gene and oncogenic c-Ha-ras into PC12 cells, and stable cell lines expressing these genes were established. 2. As previously reported, expression of v-src (Alema et al., 1985) or c-Ha-ras (Noda et al., 1985) in PC12 cells results in neurite outgrowth resembling that induced by NGF. We report here that v-src but not oncogenic c-Ha-ras induces a stable morphologic neuronal differentiation similar to treatment with NGF. Oncogenic c-Ha-ras-induced neurite outgrowth is not stable with long-term culture, rather the cells revert to an undifferentiated morphology with altered cell cycle kinetics. 3. The stable neuronal phenotype induced by v-src and NGF is characterized by the functional expression of dihydropyridine-insensitive calcium currents.

CD4 antigen-based antireceptor peptides inhibit infectivity of human immunodeficiency virus in vitro at multiple stages of the viral life cycle

Benzylated derivatives of peptides corresponding to residues 81 through 92 of the CD4 molecule [CD4-(81-92)] inhibit human immunodeficiency virus 1 (HIV-1)-induced cell fusion and infection in vitro. If such peptides are to be considered as candidates in the therapy of HIV infection, it is crucial to know if the anti-HIV efficacy of CD4-based peptides is limited to blockade of infection and virus-induced cell fusion or if other stages of the viral life cycle are affected by these compounds. Accordingly, an in vitro quantitative microassay for acute HIV infection was divided into two kinetic phases corresponding to the two general stages of the viral life cycle: (i) viral infection and (ii) transmission of virus and viral protein products through cell contact or release of free virions. CEM-SS cell cultures were treated with peptide during either the infection or the transmission phase of the assay. When peptides were present during the infection phase, inhibition of syncytium formation correlated with decreased expression of viral core protein p24 and lack of infectious cell centers when cells exposed to virus were washed and replated onto fresh uninfected indicator cells. These data are consistent with complete inhibition of viral infection when peptide is present only during initial exposure to virus. Unexpectedly, parallel inhibition of syncytium formation, decreased p24 levels, and inhibition of infectious cell center formation were also seen even when peptides were added as late as 48 hr after inoculation, during the transmission period of the assay. Since viral binding and penetration are completed well before 48 hr in this assay system, CD4-(81-92) peptide derivatives appear to exert a virostatic effect on cultures already infected with HIV-1, decreasing p24 production, cytopathicity, and cell-mediated infectivity.

Differentiation of PC12 cells with v-src: comparison with nerve growth factor

The PC12 rat pheochromocytoma cell line is used extensively as a model to study neuronal differentiation. These cells resemble adrenal chromaffin cells, differentiating both morphologically and biochemically when cultured in the presence of dexamethasone, but develop a sympathetic neuron-like phenotype when cultured in the presence of nerve growth factor. Expression of the protein product of the v-src oncogene in PC12 cells also induces neurite outgrowth similar to that resulting from nerve growth factor treatment (Alema et al: Nature 316:557-559, 1985). It is thus possible that c-src or a src-like tyrosine kinase participates in the signal transduction pathway by which nerve growth factor acts on PC12 cells. In this study a temperature-sensitive v-src gene has been introduced into PC12 cells. When cultures of these src-transformed cells are switched from the nonpermissive (40 degrees C) to the permissive (37 degrees C) temperature they elaborate neurites. The differentiation induced by src has been compared with that induced by nerve growth factor by determining whether src-transformed PC12 cells at 37 degrees C exhibit the same biochemical alterations as those induced in PC12 cells treated with nerve growth factor. Neurite extension at 37 degrees C in v-src-transformed cells, like NGF-induced differentiation, is accompanied by an increase in the nerve growth factor-inducible large external (NILE) protein. However, neurite extension in v-src-transformed cells is not blocked by the protein kinase inhibitor K-252a, which completely blocks NGF-induced neurite extension. Likewise, EGF receptor down-regulation and the development of saxitoxin and tetanus toxin binding sites are either much reduced or completely absent in src-differentiated compared with NGF-differentiated PC12 cells.

Regulation of discrete sub-populations of transmitter-identified neurones after inhibition of electrical activity in cultures of mouse spinal cord

The effects of blockade of electrical activity by tetrodotoxin in cultures of mouse spinal cord and dorsal root ganglion on immunohistochemically-identified neuronal sub-populations have been investigated. Some spinal cord neuronal types, such as those storing methionine-enkephalin, substance P or calcitonin gene-related peptide were almost totally depleted after inhibition of electrical activity for 4 days. By contrast, putative substance P- and calcitonin gene-related peptide-immunoreactive dorsal root ganglion neurones were not significantly affected by such treatment. Several other neuronal types were reduced by about 30-40% after exposure to tetrodotoxin. The decrement in methionine-enkephalin-, substance P- and calcitonin gene-related peptide-immunoreactive neurones caused by tetrodotoxin was reversible, and, in the case of methionine-enkephalin, could not be elicited after day 30 in culture. Radioimmunoassay of levels of methionine-enkephalin in cultures confirmed the immunohistochemical data. It is concluded, therefore, that exposure to tetrodotoxin selectively reduces peptide immunoreactivity in specific neuronal sub-populations, but that the selectivity is not based on a single known neuronal characteristic such as transmitter phenotype, or a particular structural protein. The action of tetrodotoxin on those cells most severely attenuated is an alteration in transmitter expression rather than a lethal effect. The diminution with time of the ability of tetrodotoxin to attenuate methionine-enkephalin levels may reflect a reduction in the activity-dependent regulation of peptide expression relative to other competing trophic influences.

Onset of glucocorticoid responsiveness of anterior pituitary corticotrophs during development is scheduled by corticotropin-releasing factor

Expression of the CRF gene in the hypothalamus and that of the POMC gene in the anterior pituitary are reduced during the first week of life in the rat. During this so-called stress nonresponsive period (SNRP), stimuli such as ether vapors, electroshocks, and hypoxia do not elicit ACTH secretion from the pituitary, as occurs later in development. The current hypothesis to explain the SNRP is an increased negative glucocorticoid feedback on POMC and CRF synthesis and/or release during this time. To test this hypothesis we studied the effects of adrenalectomy (ADX) on anterior pituitary POMC mRNA expression. In 7-day-old rats POMC mRNA levels were increased only 3-fold 48 h post-ADX, compared to a 7-fold increase in 14-day-old animals. This blunted effect of endogenous glucocorticoid removal on pituitary POMC mRNA could be due to decreased up-regulation of CRF after removal of glucocorticoids or normal up-regulation of CRF but decreased pituitary responsiveness to CRF relative to those in 14-day-old animals. Therefore, we studied in vitro beta-endorphin release from pituitaries obtained from 7- and 14-day-old rats. CRF stimulated basal beta-endorphin release to the same extent in pituitaries from both groups. The inhibition by corticosterone of CRF-stimulated beta-endorphin secretion was also indistinguishable in pituitaries obtained from 7- or 14-day-old rats. Since the responsiveness of the 7-day-old pituitary was normal, the blunted enhancement of POMC biosynthesis after ADX must be mediated at the level of the hypothalamus. Indeed, in situ hybridization showed that while in 14-day-old rats ADX induced a significant increase [190 +/- 10% (+/- SE) of control; n = 5; P less than 0.0005] in hypothalamic mRNA levels, ADX did not change the expression of the CRF gene in the paraventricular nucleus of 7-day-old rats, indicating a lack of glucocorticoid modulation of hypothalamic CRF synthesis. Finally, we studied the effects of 48 h CRF treatment on the post-ADX increase in POMC mRNA levels in 7-day-old rats. Daily injections of 200 ng CRF/rat induced an increase in anterior pituitary POMC mRNA concentrations [669 +/- 139% (+/- SE) of control; n = 6; P less than 0.02 vs. adrenalectomized vehicle-treated rats] comparable to that in adrenalectomized untreated 14-day-old rats. In conclusion, our data indicate that the glucocorticoid regulation of hypothalamic CRF gene expression is not mature during the first week of life, i.e. within the so-called SNRP.(ABSTRACT TRUNCATED AT 400 WORDS)

Chromogranin A and B messenger ribonucleic acids in pituitary and other normal and neoplastic human endocrine tissues

The distribution of the messenger ribonucleic acids (mRNAs) for chromogranin A and B was analyzed by in situ hybridization in normal and neoplastic endocrine tissues using frozen and paraffin tissue sections. Combined in situ hybridization and immunochemical staining was also done on tissue sections from the same cases using a monoclonal antibody against chromogranin A (LK2H10). Most endocrine tumors expressed chromogranin A and B mRNAs as well as chromogranin A protein. Normal pituitary expressed chromogranin A and B mRNAs and chromogranin A protein in the anterior pituitary gland. Most of these cells were gonadotropic hormone-producing cells. Prolactinomas (5/5) did not express chromogranin A mRNA or protein, but contained chromogranin B mRNA. Null cell or nonfunctional adenomas (8/8) expressed chromogranin A and B mRNAs and reacted with antibody LK2H10. In some tumors such as Merkel cell carcinomas, insulinomas, and parathyroid adenomas, a stronger signal for chromogranin A mRNA was detected than for the immunoreactive proteins. These results indicate that in situ hybridization complements immunochemical techniques in the analysis of endocrine cells and neoplasms. The gene products for chromogranin A and B are widely distributed in many endocrine cells and tumors, but some neoplasms such as prolactinomas have a differential distribution of chromogranin A and B mRNA and proteins.

Chromogranin A messenger RNA expression in the rat anterior pituitary is permissively regulated by the adrenal gland

The influence of the adrenal gland on the expression of chromogranin A in the anterior pituitary was studied in the rat. Adrenalectomy caused a progressive and pronounced (20% of control levels at day 10 after adrenalectomy) decrease of Chromogranin A mRNA levels in anterior pituitary. Daily injection of dexamethasone (15 micrograms/animal, s.c.) fully reversed the postadrenalectomy decrement in chromogranin A mRNA levels. Chromogranin A protein content, however, was unchanged 10 days after adrenalectomy. In contrast, pro-opiomelanocortin mRNA levels were significantly elevated after adrenalectomy and restored to normal by dexamethasone, with a time course similar to the changes in chromogranin A mRNA levels. These data demonstrate that the adrenal gland permissively regulates chromogranin A expression in the anterior pituitary, at a pretranslational locus, and that this regulation is probably mediated by glucocorticoids.

Lineage-specific regulation of the vasoactive intestinal peptide gene in neuroblastoma cells is conferred by 5.2 kilobases of 5'-flanking sequence

The expression of a transfected plasmid containing 5.2 kilobases (kb) of 5' regulatory DNA sequence of the human vasoactive intestinal peptide (VIP) gene attached to coding sequences of the reporter gene chloramphenicol acetyltransferase (CAT) was compared with endogenous VIP expression in subclones of the human neuroblastoma cell line SK-N-SH. These subclones vary widely in basal and inducible quantities of VIP and its precursor mRNA and can be interconverted under specified culture conditions. Endogenous VIP immunoreactivity, detectable in all subclones, was lowest in the neuronal subclone SH-SY-5Y, whereas 15- to 25-fold higher levels were observed in the epithelial-appearing SH-EP and intermediate SH-IN subclones. Treatment with 10 nM phorbol 12-myristate 13-acetate (PMA) stimulated VIP peptide levels approximately 5-fold in SH-SY-5Y cells but did not increase appreciably VIP levels in the other subclones. Treatment with 2.5 microM forskolin resulted in less than 50% stimulation of VIP expression in all subclones. Levels of mRNA encoding the VIP precursor generally paralleled these differences in VIP immunoreactivity. In cells transfected with the VIP/CAT fusion gene, CAT activity reflected closely these differences in basal VIP expression and the changes in response to PMA and forskolin. Deletion of 2.7 kb of the most upstream sequences resulted in an 80-90% reduction in basal CAT activity in SH-IN, but not SH-SY-5Y cells, and resulted in an 80% reduction in PMA stimulation in SH-SY-5Y cells. Deletion to within 74 nucleotides of the transcription start site resulted in CAT expression in SH-IN cells that was only 3% of that seen with the full 5.2-kb flanking sequences and further diminished the remaining PMA responsiveness in SH-SY-5Y cells. The data indicate that important cell-type-specific transcription regulatory sequences reside greater than 2.5 kb upstream from the VIP transcription start site.

Ontogeny of enkephalin- and VIP-containing neurons in dissociated cultures of embryonic mouse spinal cord and dorsal root ganglia

The ontogeny of vasoactive intestinal polypeptide (VIP), and Met-enkephalin in primary cultures of spinal cord/dorsal root ganglia from 12-day mouse embryos was examined by radioimmunoassay and immunohistochemistry. Met-enkephalin levels rose from less than 5 to 700 pg/culture over 26 days and were half maximal by day 16-18 in culture. VIP levels rose from less than 1 to 30 pg/culture over the same period, but were already half maximal by day 9. Met-enkephalin immunoreactivity was localized in multipolar medium sized neurons while VIP immunoreactivity was visualized both in neurons with extensively branched processes and in bipolar cells some of which appeared to be dorsal root ganglion cells. Tetrodotoxin (TTX)-sensitive spontaneous release of both peptides developed in parallel with the ability to stimulate peptide release with elevated potassium. Factors affecting the ontogeny of neuropeptide expression in, and release from, spinal cord neurons can now be examined in vitro in a strictly defined neurochemical environment.