Coexistence and gene expression of phenylethanolamine N-methyltransferase, tyrosine hydroxylase, and neuropeptide tyrosine in the rat and bovine adrenal gland: effects of reserpine

Adaptive remodeling of the stimulus-secretion coupling: Lessons from the 'stressed' adrenal medulla

Stress is part of our daily lives and good health in the modern world is offset by unhealthy lifestyle factors, including the deleterious consequences of stress and associated pathologies. Repeated and/or prolonged stress may disrupt the body homeostasis and thus threatens our lives. Adaptive processes that allow the organism to adapt to new environmental conditions and maintain its homeostasis are therefore crucial. The adrenal glands are major endocrine/neuroendocrine organs involved in the adaptive response of the body facing stressful situations. Upon stress episodes and in response to activation of the sympathetic nervous system, the first adrenal cells to be activated are the neuroendocrine chromaffin cells located in the medullary tissue of the adrenal gland. By releasing catecholamines (mainly epinephrine and to a lesser extent norepinephrine), adrenal chromaffin cells actively contribute to the development of adaptive mechanisms, in particular targeting the cardiovascular system and leading to appropriate adjustments of blood pressure and heart rate, as well as energy metabolism. Specifically, this chapter covers the current knowledge as to how the adrenal medullary tissue remodels in response to stress episodes, with special attention paid to chromaffin cell stimulus-secretion coupling. Adrenal stimulus-secretion coupling encompasses various elements taking place at both the molecular/cellular and tissular levels. Here, I focus on stress-driven changes in catecholamine biosynthesis, chromaffin cell excitability, synaptic neurotransmission and gap junctional communication. These signaling pathways undergo a collective and finely-tuned remodeling, contributing to appropriate catecholamine secretion and maintenance of body homeostasis in response to stress.

Single-cell transcriptomics of human embryos identifies multiple sympathoblast lineages with potential implications for neuroblastoma origin

Characterization of the progression of cellular states during human embryogenesis can provide insights into the origin of pediatric diseases. We examined the transcriptional states of neural crest- and mesoderm-derived lineages differentiating into adrenal glands, kidneys, endothelium and hematopoietic tissue between post-conception weeks 6 and 14 of human development. Our results reveal transitions connecting the intermediate mesoderm and progenitors of organ primordia, the hematopoietic system and endothelial subtypes. Unexpectedly, by using a combination of single-cell transcriptomics and lineage tracing, we found that intra-adrenal sympathoblasts at that stage are directly derived from nerve-associated Schwann cell precursors, similarly to local chromaffin cells, whereas the majority of extra-adrenal sympathoblasts arise from the migratory neural crest. In humans, this process persists during several weeks of development within the large intra-adrenal ganglia-like structures, which may also serve as reservoirs of originating cells in neuroblastoma.

Enhanced neuropeptide Y synthesis during intermittent hypoxia in the rat adrenal medulla: role of reactive oxygen species-dependent alterations in precursor peptide processing

Intermittent hypoxia (IH) associated with recurrent apneas often leads to cardiovascular abnormalities. Previously, we showed that IH treatment elevates blood pressure and increases plasma catecholamines (CAs) in rats via reactive oxygen species (ROS)-dependent enhanced synthesis and secretion from the adrenal medulla (AM). Neuropeptide Y (NPY), a sympathetic neurotransmitter that colocalizes with CA in the AM, has been implicated in blood pressure regulation during persistent stress. Here, we investigated whether IH facilitates NPY synthesis in the rat AM and assessed the role of ROS signaling. IH increased NPY-like immunoreactivity in many dopamine-β-hydroxylase-expressing chromaffin cells with a parallel increase in preproNPY mRNA and protein. IH increased the activities of proNPY-processing enzymes, which were due, in part, to elevated protein expression and increased proteolytic processing. IH increased ROS generation, and antioxidants reversed IH-induced increases in ROS, preproNPY, and its processing to bioactive NPY in the AM. IH treatment increased blood pressure and antioxidants and inhibition of NPY amidation prevented this response. These findings suggest that IH-induced elevation in NPY expression in the rat AM is mediated by ROS-dependent augmentation of preproNPY mRNA expression and proNPY-processing enzyme activities and contributes to IH-induced elevation of blood pressure.

Environmental light conditions alter gene expression of rat catecholamine biosynthetic enzymes and Neuropeptide Y: differential effect in superior cervical ganglia and adrenal gland

The hypothalamic suprachiasmatic nuclei (SCN) comprise the main site in the brain involved in the control of the homeostatic mechanism which respond to environmental daily light changes. The sympathetic nervous system and hypothalamic releasing or inhibiting factors mediate the SCN control of a number of peripheral organs and tissues. In this work we analyzed the involvement of two environmental light conditions, constant light (LL) and constant dark (DD) for 20 days, on the expression of mRNAs for catecholamines biosynthetic enzymes and neuropeptide Y (NPY) genes in rat superior cervical ganglia (SCG) and adrenal gland. The results of Northern blot analysis show that LL exposure reduces mRNA levels for tyrosine hydroxylase (TH) the rate limiting catecholamine biosynthetic enzyme and also of dopamine beta-hydroxylase (DBH) as well as for NPY in SCG to about half the levels in control animals. In contrast, exposure of the rats to DD did not elicit any change in the SCG. In the adrenal gland, both, LL and DD conditions increased the TH, DBH as well as phenylethanolamine N-methyltransferase (PNMT) mRNA levels. Under the same conditions, adrenal NPY mRNA levels were decreased by either LL or DD. The results show, for the first time, that prolonged changes in environmental light can alter the gene expression of catecholamine biosynthetic enzymes and of NPY. There was differential response in SCG and adrenal gland.

Protein kinase A and protein kinase C signaling pathway interaction in phenylethanolamine N-methyltransferase gene regulation

The protein kinase A (PKA) and protein kinase C (PKC) signaling pathways appear to interact in regulating phenylethanolamine N-methyltransferase (PNMT) promoter-driven gene transcription in PC12 cells. Forskolin treatment of cells transfected with the rat PNMT promoter-luciferase reporter gene construct pGL3RP893 increased promoter activity approximately two-fold whereas phorbol-12-myristate-13 acetate (PMA) treatment had no effect. However, simultaneous forskolin and PMA treatment synergistically activated the PNMT promoter approximately four-fold, suggesting that PKC stimulation requires prior induction of the PKA pathway. Consistent with this possibility the adenylate cyclase inhibitor MDL12,330A, and the PKA inhibitor H-89 prevented PNMT promoter stimulation by the combination of forskolin and PMA. PKA and PKC regulation seems to be mediated in part by Egr-1 and Sp1 through their consensus elements in the PNMT promoter. Forskolin and PMA treatment of PC12 cells increased Egr-1 protein and phosphorylated Egr-1/DNA-binding complex formation to the same extent but only increased phosphorylated Sp1/DNA binding complex formation without altering Sp1 protein levels. Mutation of the - 165 bp Egr-1 and - 48 bp Sp1 sites, respectively, attenuated and abolished combined forskolin and PMA-mediated promoter activation. PNMT promoter analysis further showed that synergistic stimulation by PKA and PKC involves DNA sequences between - 442 and - 392 bp, and potentially a GCM binding element lying within this region.

Cyclooxygenase-2 mRNA expression is associated with c-fos mRNA expression and transient water ADC reduction detected with diffusion MRI during acute focal ischemia in rats

Cyclooxygenase-2 (COX-2) plays an important role in the development of injury during cerebral ischemia and inhibition of its activity can reduce infarct size. COX-2 expression during acute ischemia is caused by activation of post-synaptic glutamate receptors, which occurs during spreading depression and ischemic depolarization. Both of these phenomena cause a reduction in the apparent diffusion coefficient of water (ADC), which can be detected with diffusion-weighted magnetic resonance imaging. The reduction is believed to be caused by cellular swelling that occurs as cells depolarize. The goal of this work was to determine the spatial relationship between cyclooxygenase-2 mRNA (cox-2) expression, c-fos mRNA expression and ADC reduction during acute focal cerebral ischemia. Adult rats were subjected to either 30- or 60-min permanent occlusion of the middle cerebral artery. A 2-Tesla scanner was used to acquire diffusion-weighted echo-planar images throughout the ischemic period, which were used to calculate ADC maps. Cox-2 and c-fos mRNA were detected with (35)S in situ hybridization. The results indicate that, for rats subjected to 60-min ischemia, cox-2 was observed in superficial layers of cortex, where transient ADC reduction and c-fos expression were observed. The same was true for most rats subjected to 30-min ischemia. However, in a small number of rats of the 30-min group, cox-2 mRNA expression was observed in regions exhibiting transient and persistent ADC reduction with no c-fos expression. The results suggest that cox-2 mRNA expression during acute MCA occlusion is caused by either or both spreading depression and transient ischemic depolarization.

Induction of heat shock protein 40 and GrpE mRNAs following transient focal cerebral ischemia in the rat

Cerebral ischemia is associated with the induction of several heat shock proteins (HSPs), but the effects on HSP40 and GrpE are less clear. The present study investigated the induction of Hsp40 and GrpE mRNAs following 30 min of middle cerebral artery occlusion in the rat model. Reverse transcription-polymerase chain reaction (PCR) and in situ hybridization analyses showed significant induction of both mRNAs in the ischemic cortex. These results demonstrate the synergic induction of HSP70 molecular chaperone machinery in cerebral ischemia.

Transgenic mice expressing human copper-zinc superoxide dismutase exhibit attenuated apparent diffusion coefficient reduction during reperfusion following focal cerebral ischemia

Since ADC reduction reflects intracellular edema which is an early indicator of ischemic cellular metabolic stress, we hypothesized that a decrease in ADC as determined by diffusion weighted MR imaging could be attenuated by SOD expression in transgenic mice during reperfusion following focal cerebral ischemia. Diffusion weighted imaging (DWI) was performed to evaluate apparent diffusion coefficient (ADC) reduction by constructing ADC maps with a color scale to localize ADC change in transgenic (Tg) mice expressing human CuZn superoxide dismutase (SOD) and wild type (Wt) mice during 1 h middle cerebral artery occlusion (MCAO) and 1 h reperfusion. Heat shock protein (hsp) 70-kDa mRNA analysis was evaluated as a marker of sublethal cell stress by in situ hybridization after 4 h reperfusion for comparison with Nissl staining of adjacent sections to assess infarction. Sequential ADC maps were prepared in Tg mice with sufficient temporal and spatial resolution to permit comparison with Wt mice. Tg mice showed substantial recovery of the ADC lesion after reperfusion, while Wt mice showed no recovery. There was no difference between Tg and Wt mice in the size or distribution of the ADC lesion during ischemia. The area with strong expression of hsp70 mRNA in the ischemic hemisphere was substantially larger in the Tg mice. Nissl staining showed less damage of brain tissue in Tg mice than Wt mice especially in the cortex after 4 h reperfusion following 1 h MCAO. Results demonstrate that antioxidant effects of human CuZn-SOD reduce cellular edema due to oxidative stress during reperfusion but not during ischemia after 1 h MCAO. Hsp70 could be one of the proteins that mediates protection by SOD against oxidative stress.

Induction of mitochondrial heat shock protein 60 and 10 mRNAs following transient focal cerebral ischemia in the rat

Heat shock proteins (HSPs) 60 and 10 are stress-inducible mitochondrial matrix proteins that form a chaperonin complex that is important for mitochondrial protein folding and function. The effect of cerebral ischemia on mitochondrial HSPs is unclear. The topographical and chronological patterns of HSP60 and HSP10 messenger ribonucleic acid (mRNA) expression and induction were investigated in the rat focal cerebral ischemia model. Focal cerebral ischemia was produced by transient middle cerebral artery occlusion for 30 or 90 min. Expression of mRNAs was analyzed using reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. RT-PCR analysis showed that both HSP60 and HSP10 mRNA levels increased significantly in the ischemic cortex from 4 to 24 h of reperfusion after 30 min of occlusion. In situ hybridization analysis demonstrated significant induction of both mRNAs in the whole ischemic cortex after 30 min of occlusion and in the dorsomedial border (penumbra) of the ischemic cortex and ipsilateral hippocampus after 90 min of occlusion. Expression patterns and the timing of the induction of both HSP60 and HSP10 mRNAs were identical throughout the experiments. Simultaneous induction of the mRNAs for the mitochondrial chaperonins, HSP60 and HSP10, in various regions in focal cerebral ischemia demonstrates that mitochondrial stress conditions persist concomitantly with cytosolic stress conditions in focal cerebral ischemia.

Neuropeptide Y and the adrenal gland: a review

This paper sets out to review several aspects of NPY and adrenal function, starting with the localisation of NPY in the adrenal, then describing the regulation of NPY release and considering whether the adrenal is a significant source of circulating NPY. The review then describes the regulation of adrenal content of peptide, and finally covers the actions of NPY on the adrenal gland, and the receptor subtypes thought to mediate these effects. The regulation and actions of NPY are discussed with reference to both the adrenal cortex and the medulla.

Mild hypothermia decreases the incidence of transient ADC reduction detected with diffusion MRI and expression of c-fos and hsp70 mRNA during acute focal ischemia in rats

The effects of mild hypothermia on the apparent diffusion coefficient of water (ADC) and expression of c-fos and hsp70 mRNA were examined during acute focal cerebral ischemia. Young adult rats were subjected to 60-min middle cerebral artery occlusion under either normothermia (37.5 degrees C) or hypothermia (33 degrees C). Diffusion-weighted echo-planar magnetic resonance imaging was used to monitor changes in ADC throughout the ischemic period. Perfusion MRI with dysprosium contrast was used at the end of the ischemic period to verify that the occlusion was successful. C-fos and hsp70 mRNA expression were examined with in situ hybridization at the end of the ischemic period. The results indicate that the size of the region that exhibited reduced ADC was smaller during hypothermia than during normothermia. Hypothermia also decreased the frequency of occurrence of transient ADC reductions, especially in dorsal aspects of cortex. Expression of both c-fos and hsp70 mRNA were markedly reduced by hypothermia. Transient ADC reduction and c-fos expression are associated with spreading depression, which is believed to contribute to lesion expansion during acute focal ischemia. The results suggest that part of the neuroprotective effect of hypothermia may be due to a reduced incidence of spreading depression.

Deletion of tyrosine hydroxylase gene reveals functional interdependence of adrenocortical and chromaffin cell system in vivo

Catecholamines are produced in the medulla of the adrenal gland and may participate in the intraglandular regulation of its cortex. We analyzed the adrenal structure and function of albino tyrosine hydroxylase-null (TH-null) mice that are deficient in adrenal catecholamine production. Adrenal catecholamines were markedly reduced, and catecholamine histofluorescence was abrogated in 15-day-old TH-null mice. Chromaffin cell structure was strikingly altered at the ultrastructural level with a depletion of chromaffin vesicles and an increase in rough endoplasmic reticulum compared with wild-type mice. Remaining chromaffin vesicles lined up proximally to the cell membrane in preparation for exocytosis providing a "string-of-pearls" appearance. There was a 5-fold increase in the expression of proenkephalin mRNA (502.8 +/- 142% vs. 100 +/- 17.5%, P = 0.016) and a 2-fold increase in the expression of neuropeptide Y (213.4 +/- 41.2% vs. 100 +/- 59.9%, P = 0.014) in the TH-null animals as determined by quantitative TaqMan (Perkin-Elmer) PCR. Accordingly, immunofluorescence for met-enkephalin and neuropeptide tyrosine in these animals was strongly enhanced. The expression of phenylethanolamine N-methyl transferase and chromogranin B mRNA was similar in TH-null and wild-type mice. In TH-null mice, adrenocortical cells were characterized by an increase in liposomes and by tubular mitochondria with reduced internal membranes, suggesting a hypofunctional state of these steroid-producing cells. In accordance with these findings, plasma corticosterone levels were decreased. Plasma ACTH levels were not significantly different in TH-null mice. In conclusion, both the adrenomedullary and adrenocortical systems demonstrate structural and functional changes in catecholamine-deficient TH-null mice, underscoring the great importance of the functional interdependence of these systems in vivo.

Simultaneous induction of mitochondrial heat shock protein mRNAs in rat forebrain ischemia

Several investigations have postulated evidence of the involvement of apoptosis in delayed neuronal death following brief periods of global cerebral ischemia. Apoptosis may be closely linked to mitochondrial dysfunction. Heat shock protein (HSP) 60 and HSP10 are mitochondrial matrix proteins induced by stress and form the chaperonin complex that is implicated in protein folding and assembly within the mitochondria. This study investigated the induction of these mitochondrial stress protein genes in the hippocampal CA1 region and less vulnerable regions following transient forebrain ischemia. In situ hybridization analysis revealed that the induction pattern of HSP60 mRNA was identical to that of HSP10 mRNA throughout the entire ischemic course. No changes occurred in the expression of both mRNAs after 2 min ischemia. Strong induction of both mRNAs occurred in the CA1 region after 10 min ischemia and persisted until 1 d after reperfusion. In contrast, induction of both mRNAs in the less vulnerable regions was terminated by 1 d after reperfusion. These results demonstrate that mitochondrial stress conditions persist concomitantly with cytosolic stress conditions in regions vulnerable to transient forebrain ischemia.

Induction of cyclooxygenase-2 messenger RNA after transient and permanent middle cerebral artery occlusion in rats: comparison with c-fos messenger RNA by using in situ hybridization

OBJECT

Recently, two different cyclooxygenase (COX) genes, COX-1 and -2, were identified. In this study, topographic and chronological profiles of COX-2 messenger (m)RNA and c-fos mRNA expression were investigated using in situ hybridization after focal cerebral ischemia.

METHODS

Rats undergoing permanent ischemia were decapitated at 30 and 90 minutes and at 2, 4, 8, and 24 hours after middle cerebral artery (MCA) occlusion, and rats undergoing transient ischemia were decapitated at 4, 8, and 24 hours after MCA occlusion that lasted for either 30 or 90 minutes. After brief transient MCA occlusion, c-fos mRNA was induced in the whole MCA territory, adjacent cortex (cingulate cortex), and distant brain regions such as the hippocampus and substantia nigra. In contrast, COX-2 mRNA was not induced in the ischemic core (lateral striatum) but only in the penumbral area (MCA cortex). Long transient and permanent MCA occlusion did not induce c-fos and COX-2 mRNAs in the ischemic core but strongly induced both mRNAs in the penumbral area (medial striatum and periphery of MCA cortex) and adjacent cortex (cingulate cortex). In brain regions distant from the ischemic territory, although c-fos mRNA was induced in the thalamus, substantia nigra, and hippocampus after extended transient and permanent occlusion, COX-2 mRNA was only induced in the bilateral hippocampi. The induction of COX-2 mRNA persisted in all locations even at 24 hours after MCA occlusion.

CONCLUSIONS

The distribution of COX-2 mRNA induction was apparently different from that of c-fos mRNA after MCA occlusion. These results pertaining to COX-2 mRNA agree well with the previous observations of changes in prostaglandin metabolism induced by focal cerebral ischemia. However, whether this induction of the COX-2 gene contributes to the histopathological outcome of cerebral ischemia remains to be elucidated.

Multiple signalling pathways exist in the stress-triggered regulation of gene expression for catecholamine biosynthetic enzymes and several neuropeptides in the rat adrenal medulla

A critical component of the response to stress is the coincident activation of the hypothalamic-pituitary-adrenal axis and the sympathoadrenal system - comprised of sympathetic ganglia and the adrenal medullae. The sympathoadrenal system produces the catecholamines - noradrenaline and adrenaline, and several neuropeptides, involved in the homeostatic mechanisms that govern the adaptation to stress. This brief survey aims to provide a general overview of the present knowledge about the impact of stress on neurotransmitter gene expression in the adrenal medulla, with particular attention paid to the apparent heterogeneity in stress-evoked signals and regulatory pathways.

Transient MRI-detected water apparent diffusion coefficient reduction correlates with c-fos mRNA but not hsp70 mRNA induction during focal cerebral ischemia in rats

Cerebral ischemia induces immediate early genes such as c-fos and stress genes such as hsp70. In this study, the spatial relationships between c-fos and hsp70 mRNA expression and changes detectable with diffusion and perfusion magnetic resonance (MR) imaging were examined. The middle cerebral artery (MCA) of young adult rats was occluded for 30 or 60 min. Diffusion MR (D-MR) images were acquired continuously during the ischemic period and dysprosium-contrast perfusion (P-MR) images were acquired at the end of the ischemic period. C-fos and hsp70 mRNA expression were examined with in situ hybridization. The most significant finding of this work was that for both durations of ischemia, c-fos induction was observed in cortical and sub-cortical regions exhibiting a transient reduction in the apparent diffusion coefficient of water (ADC). Transients which occurred on a time scale of 3 min may have been caused by spreading depression. Those occurring on a 10-min time scale may have been caused by an initial reduction in blood flow with occlusion that was followed by an ischemia-induced increase in collateral blood flow. P-MR imaging showed that perfusion in c-fos positive regions was higher than in regions with persistently reduced ADC. Hsp70 induction did not correlate with transient ADC reduction. It was induced in the MCA territory in regions showing persistent ADC changes, with induction being greatest at the periphery of these regions. It was also induced in regions that exhibited both spontaneous reversal of the diffusion changes and decreased perfusion.

Endogenous interleukin-6 contributes to hypersensitivity to cutaneous stimuli and changes in neuropeptides associated with chronic nerve constriction in mice

Partial nerve injury is a potential cause of distressing chronic pain for which conventional analgesic treatment with opiates or anti-inflammatory agents is not very effective. Constriction nerve injury, widely used to study neuropathic pain, was shown here to induce interleukin-6 (IL-6) mRNA in a subset of rat primary sensory neurons. When we inflicted chronic nerve constriction on mice with null mutation of the IL-6 gene, the hypersensitivity to cutaneous heat and pressure that is induced in wild-type mice was not evident, the loss of substance P in sensory neurons was excessive and the induction of galanin in central sensory projections was reduced. In additional experiments, intrathecal infusion of IL-6 in rats was shown to stimulate synthesis of galanin in approximately one-third of lumbar dorsal root ganglion neurons. The results of these experiments indicate that endogenous IL-6 mediates some of the hypersensitive responses that characterize peripheral neuropathic pain, and influences two neuropeptides that have been implicated in pain transmission.

Effects of acute stress on the contents of catecholamines and neuropeptides in chromaffin tissues of the newborn rabbit

The neuropeptides enkephalin (ENK), galanin (GAL) and neuropeptide Y (NPY) are abundantly expressed in the paraaortic body (PAB) and adrenal glands of the newborn rabbit. To examine whether these neuropeptides are affected by acute stress, we exposed neonatal rabbits to asphyxia, insulin-induced hypoglycemia, and reserpine. Asphyxia, caused by rebreathing for 60 min in an airtight box, reduced the content of catecholamines (CAs) in the adrenal glands and increased ENK-like immunoreactivity (-LI) in the PAB. Insulin-induced hypoglycemia reduced the content of CAs as well as ENK-LI in the adrenal glands. Reserpine caused a marked depletion of the CAs both in the PAB and in the adrenal glands. In contrast, reserpine did not cause any change in the contents of the neuropeptides in either organ. These data indicate that tissue levels of the neuropeptides GAL-LI and NPY-LI, coexisting with CA in the PAB and the adrenal glands, are not biochemically affected by asphyxia, hypoglycemia or reserpine, whereas tissue levels of ENK-LI are reduced by hypoglycemia and, to some extent, are increased by asphyxia. Furthermore, even the CAs in the PAB were unaffected by asphyxia and hypoglycemia. Also, while reserpine reduces CA content, peptide levels are unaffected.

Decreased expression of bcl-2 and bcl-x mRNA coincides with apoptosis following intracerebral administration of 3-nitropropionic acid

The mitochondrial toxin, 3-nitropropionic acid (3-NP), is an irreversible inhibitor of succinate dehydrogenase that induces apoptosis in vitro and in vivo. We injected 3-NP into the striatum of rats to examine the potential role of Bcl-2 or Bcl-x, proteins that can inhibit apoptosis, in brain injury due to 3-NP. Electrophoretic examination of striatal tissue indicated that 3-NP induced internucleosomal fragmentation typical of apoptosis. There was also histologic evidence of apoptosis based on staining by the terminal deoxynucleotidyl transferase mediated dUTP-biotin nick end labeling (TUNEL) method. Apoptosis was first observed 6 h after injection, was maximal at 1 day, and was still observed on day 7. Expression of bcl-2, bcl-x, and c-jun mRNA expression was evaluated 1, 3, 6, and 12 h and 1, 3, 5, and 7 days after injection using in situ hybridization. Both bcl-2 and bcl-x mRNA expression in the striatum decreased starting at 6 h and continued to 5 days after injection. This was in contrast to an apparent increase in c-jun expression. The similarity in the time course of apoptosis to that of suppression of bcl-2 and bcl-x mRNA suggests that changes in expression of these genes may contribute to apoptosis following 3-NP injection.

Expression of c-fos and hsp70 mRNA in neonatal rat cerebrocortical slices during NMDA-induced necrosis and apoptosis

Respiring neonatal rat cerebrocortical slices were exposed for 30 min to toxic concentrations of N-methyl-D-aspartate (NMDA; 100 microM, 500 microM and 1000 microM). In situ hybridization was used to study c-fos and hsp70 mRNA before, during, and for 8 h after NMDA exposure. Cell swelling and nuclear morphology were assessed using Cresyl violet (Nissl) staining. Possible evidence for apoptosis was examined using in situ terminal transferase d-UTP nick-end labeling (TUNEL) staining and agarose-gel electrophoresis of extracted slice DNA. After NMDA administration c-fos and hsp70 mRNA expression increased, with maxima occurring, respectively, at 1 h and 4 h after NMDA exposure. When treatment with dizocilpine (MK-801; 10 microM), a non-competitive NMDA antagonist, was started before NMDA exposures, expression of both c-fos and hsp70 mRNA was decreased to values near control, indicating that activation of NMDA receptors induces both genes. Only a minority of induced cells expressed FOS protein and no HSP70 protein expression was seen. These apparent failures of translation might be related to the stress response. Histologically, 1000 microM NMDA produced substantial necrosis, with no evidence of apoptosis. Evidence for apoptosis was found at the two lower NMDA concentrations, which produced TUNEL-positive fragmented nuclei and faint ladder patterns in DNA electrophoresis. Dizocilpine pre-treatment blocked NMDA-induced necrosis and attenuated TUNEL-positive staining in slice parenchyma. TUNEL-positive staining with a different morphology was found in the injury layer, a region 50-micron thick where mechanical trauma was inflicted when slices were cut from brain. When slices received dizocilpine immediately after decapitation, TUNEL-positive staining no longer occurred in the injury layer, in agreement with previous cell culture studies that implicated NMDA receptor activation after mechanical trauma to neurons. We conclude that at the toxic doses studied, NMDA receptor activation results primarily in necrosis. However, data at low NMDA concentrations are consistent with a small amount of apoptosis.

Immediate-early gene expression in the brain of the thiamine-deficient rat

Pyrithiamine-induced thiamine deficiency (PTD) in the rat is associated with neuronal loss in the thalamus and inferior colliculus. Recently, we were able to demonstrate the occurrence of apoptosis in the thalamus of these animals. Given that immediate-early genes (IEGs) participate in signal transduction pathways that mediate programmed cell death, the present study utilized in situ hybridization and immunohistochemistry to examine the expression of four IEGs (c-fos, c-jun, fos-B, and NGFI-A) during the progression of PTD. Elevated c-fos mRNA levels were initially observed in the posterior medial thalamus on d 12 of the deficiency. At the acute symptomatic stage (characterized by a loss of righting reflex on d 16-17), the posterior-medial thalamus exhibited increased mRNA for all genes examined, whereas the inferior colliculus demonstrated mRNA induction for c-fos, c-jun, and NGFI-A. Immunohistochemical analysis revealed that elevations of IEG mRNA associated with the acute symptomatic stage were consistently translated into protein in the thalamus. In contrast, whereas elevated Fos- and Jun-like immunoreactivity were detected in the inferior colliculus at this stage, NGFI-A-like immunoreactivity declined significantly below basal levels, suggesting a translational block. These results are consistent with our recent findings of apoptotic cell death, and indicate that differential patterns of IEG expression occur in the thalamus and inferior colliculus during PTD, which may contribute to the pathogenesis of this disorder.

Effects of thioacetamide-induced hepatic failure on the N-methyl-D-aspartate receptor complex in the rat cerebral cortex, striatum, and hippocampus. Binding of different ligands and expression of receptor subunit mRNAs

Hepatic encephalopathy (HE) is characterized by symptoms pointing at disturbances in glutamatergic neurotransmission in the brain, particularly in the striatum. The binding parameters of ligands specific for different recognition sites in the N-methyl-D-aspartate (NMDA) receptor complex and the distribution of the receptor subunit mRNAs (NR1, NR2A-D) were assessed in rats with acute HE induced with a hepatotoxin, thioacetamide (TAA). The binding of: 1. L-[3H]glutamate (NMDA-displaceable); 2. [3H]dizocilpine and N-(1-[2-thienyl]-cyclohexyl) [3H]piperidine ([3H]TCP); and 3. The coactivator site agonist [3H]glycine was assayed in purified membranes of the cerebral cortex, hippocampus, and striatum. In HE rats, Bmax of NMDA-displaceable glutamate binding was increased in the cerebral cortex and hippocampus, but slightly decreased in the striatum. In this region, the binding affinity was also slightly increased. In HE, Bmax of [3H]dizocilpine binding was unchanged in the striatum and cerebral cortex, but substantially decreased in the hippocampus. Pretreatment with phorbol ester enhanced the binding of dizocilpine more in HE than in control rats. Bmax of [3H]TCP binding was decreased in the cerebral cortex and striatum, but increased in the hippocampus. The different responses of these two phencyclidine site antagonists to HE may be indicative of a conformational change within the ion channel and/or the presence of microdomains reacting differently to extrinsic factors. HE did not affect glycine binding, but potentiated the maximal stimulation of [3H]dizocilpine binding by glycine in the cerebral cortex. The results emphasize the brain region and domain specificity of the responses of the NMDA receptor complex to HE.

Local transcriptional control of utrophin expression at the neuromuscular synapse

Recently, the use of a transgenic mouse model system for Duchenne muscular dystrophy has demonstrated the ability of utrophin to functionally replace dystrophin and alleviate the muscle pathology (see Tinsley, J. M., Potter, A. C., Phelps, S. R., Fisher, R., Trickett, J. I., and Davies, K. E. (1996) Nature 384, 349-353). However, there is currently a clear lack of information concerning the regulatory mechanisms presiding over utrophin expression during normal myogenesis and synaptogenesis. Using in situ hybridization, we show that utrophin mRNAs selectively accumulate within the postsynaptic sarcoplasm of adult muscle fibers. In addition, we demonstrate that a 1.3-kilobase fragment of the human utrophin promoter is sufficient to confer synapse-specific expression to a reporter gene. Deletion of 800 base pairs from this promoter fragment reduces the overall expression of the reporter gene and abolishes its synapse-specific expression. Finally, we also show that utrophin is present at the postsynaptic membrane of ectopic synapses induced to form at sites distant from the original neuromuscular junctions. Taken together, these results indicate that nerve-derived factors regulate locally the transcriptional activation of the utrophin gene in skeletal muscle fibers and that myonuclei located in extrasynaptic regions are capable of expressing utrophin upon receiving appropriate neuronal cues.

Effects of neuroprotective dose of fructose-1,6-bisphosphate on hypoxia-induced expression of c-fos and hsp70 mRNA in neonatal rat cerebrocortical slices

In situ hybridization (ISH) measurements of c-fos and hsp70 expression were made in brain slice studies of hypoxia, with or without fructose-1,6-bisphosphate (FBP) pretreatment. Each experiment used eighty 350 microns thick cerebrocortical slices, obtained from twenty 7-day old rats. Thirty minute periods of hypoxia were followed by 8 h of hyperoxic perfusion. Slices were removed at eight predetermined times, and processed for ISH and immunohistochemistry. In three of six hypoxia experiments, slices were pretreated for 60 min with 2 mM FBP, a condition known to maintain ATP level in brain slices during hypoxia. In three other hypoxia experiments slices received no pretreatment. In two control experiments slices were perfused for 11.5 h without hypoxia. In control experiments, hsp70 mRNA was barely detectable in slices at all times, although moderate c-fos mRNA expression occurred at 1 h after decapitation. Hypoxia produced a modest but statistically significant increase in c-fos mRNA and hsp70 mRNA induction 4 h following reoxygenation. At all times after hypoxia, FBP pretreatment reduced expression of c-fos and hsp70 mRNA. The absence of hsp70 mRNA in control slices suggests that intracellular protein denaturation was minimal in this preparation. In slices made hypoxic, the decrease in c-fos and hsp70 mRNA caused by FBP pretreatment suggests ameliorated progression towards injury. Immunohistochemistry showed no HSP70 protein at any time following hypoxia, with or without FBP pretreatment, presumably due to delayed HSP70 protein synthesis, or to a block in translation, as observed in vivo in other studies.

Delayed cytokine expression in rat brain following experimental contusion

Proinflammatory cytokines mediate brain injury in experimental studies. This study was undertaken to analyze the production of proinflammatory cytokines in experimental contusion. A brain contusion causing delayed edema was mimicked experimentally in rats using a weight-drop model. Intracerebral expression of the cytokines interleukin (IL)-1 beta, tumor necrosis factor-alpha (TNF alpha), IL-6, and interferon-gamma (IFN gamma) was studied by in situ hybridization and immunohistochemistry. The animals were killed at 6 hours or 1, 2, 4, 6, 8, or 16 days postinjury. In the injured area, no messenger (m)RNA expression was seen during the first 2 days after the trauma. On Days 4 to 6 posttrauma, however, strong IL-1 beta, TNF alpha, and IL-6 mRNA expression was detected in mononuclear cells surrounding the contusion. Expression of IFN gamma was not detected. Immunohistochemical double labeling confirmed the in situ hybridization results and demonstrated that mononuclear phagocytes and astrocytes produced IL-1 beta and that mainly astrocytes produced TNF alpha. The findings showed, somewhat unexpectedly, a late peak of intracerebral cytokine production in the injured area and in the contralateral corpus callosum, allowing for both local and global effects on the brain. An unexpected difference in the cellular sources of TNF alpha and IL-1 beta was detected. The cytokine pattern differs from that seen in other central nervous system inflammatory diseases and trauma models, suggesting that the intracerebral immune response is not a uniform event. The dominance of late cytokine production indicates that many cytokine effects are late events in an experimental contusion: Different pathogenic mechanisms may thus be operative at different times after brain injury.

DNA fragmentation and Prolonged expression of c-fos, c-jun, and hsp70 in kainic acid-induced neuronal cell death in transgenic mice overexpressing human CuZn-superoxide dismutase

Kainic acid (KA) neurotoxicity was examined in transgenic (Tg) mice overexpressing human CuZn-superoxide dismutase (SOD-1). The doses of KA required to produce seizures, the severity of the seizures, and the regions damaged were similar in SOD-1 Tg and non-transgenic wild-type mice. Intraperitoneal KA injection induced seizure-related neuronal damage in the CA3 and CA1 regions of the hippocampus and in other regions of the brain in both SOD-1 Tg and wild-type mice. These damaged neurons were labeled with the terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling (TUNEL) technique up to 72 h, although no significant difference in the number of TUNEL-positive neurons was observed between SOD-1 Tg and wild-type mice. In situ hybridization showed that c-fos, c-jun, and hsp70 genes were expressed in the hippocampus, cortex, and other regions of the brain after KA treatment. The expression of these genes was maximal 1 to 4 h following KA treatment but persisted longer in the hippocampus and other regions in SOD-1 Tg compared with wild-type mice; however, cell death in the hippocampus, assessed using cresyl violet staining, was similar in SOD-1 Tg and wild-type mice. The data show that superoxide radicals modulate both immediate early gene and heat shock gene expression after KA-induced seizures. The prolonged expression of c-fos, c-jun, and hsp70 in SOD-1 Tg compared with wild-type mice may indicate that hippocampal neurons survive longer in SOD-1 Tg than in wild-type animals; however, cell death as well as the seizure threshold, seizure severity and the pattern of regional vulnerability were not affected substantially by increased levels of SOD in the brain.

Hypermethylation of the WT1 and calcitonin gene promoter regions at chromosome 11p in human colorectal cancer

The short arm of the chromosome 11, known to harbour a number of putative and established tumour-suppressor genes, is frequently hypermethylated in various human neoplasms. We subjected the promoter regions of two genes residing at 11p, namely the tumour-suppressor gene WT1 (Wilms' tumour gene) (11p13) and the calcitonin gene (11p15.5), to methylation analysis in human sporadic colorectal cancer using genomic sequencing. Both genes showed significant hypermethylation of CpG sites within their promoter regions in adenomas and carcinomas compared with normal colonic mucosa. Although the WT1 promoter region was significantly hypermethylated, two CpG sites located in Sp1 motifs were unmethylated in the majority of cases (68-74% of carcinomas). The expression of WT1 gene, as revealed by in situ hybridization, showed no differences between normal colonic mucosa and malignant carcinoma. Together with earlier observations, our present results support the view that the short arm of human chromosome 11 is subjected to widespread regional hypermethylation in various human malignancies.

NGF prevents further atrophy of cholinergic cells of the nucleus basalis due to cortical infarction in adult post-hypothyroid rats but does not restore cell size compared to euthyroid [correction of euthroid] rats

We have tested the hypotheses that nerve growth factor treatment in adult post-hypothyroid rats can: (1) restore cross-sectional area of cholinergic cells of the nucleus basalis and (2) prevent further atrophy of these neurons following cortical infarction. In addition, we assessed the expression of p75NGFR and p140trkA mRNAs in the nucleus basalis cells of post-hypothyroid rats. Rats were rendered hypothyroid by the addition of propylthiouracil to their diet beginning on embryonic day 19 until the age of 1 month. At this time both the pups and their dams continued to receive 0.05% propylthiouracil in their diet and the pups were thyroidectomized. At 60 days, propylthiouracil treatment was interrupted and thyroxine levels were restored to normal by daily subcutaneous administration of physiological levels of thyroxine. Morphometric analysis identified atrophied nucleus basalis magnocellularis cholinergic cells at two ages, days 75 and 105, identified by in situ hybridization for p75NGFR and p140trkA mRNAs in methylene blue stained cells (day 75) and choline acetyltransferase immunostaining (day 105). The mean number of silver grains (pixels) per microns2 (mean +/- S.E.M.) of cell body cross-sectional area for p75NGFR mRNA in the nucleus basalis magnocellularis of euthyroid rats was 3.43 +/- 0.89, which was not statistically different from post-hypothyroid animals (4.02 +/- 1.07). A similar finding was noted for p140trkA mRNA: mean number of grains in the euthyroid group was 5.54 +/- 0.96 and was not statistically different from the post-hypothyroid group (6.32 +/- 1.45). Nerve growth factor treatment in adulthood (between days 75 and 82) did not restore cross-sectional area from early thyroid deprivation. However, it prevented further atrophy of nucleus basalis magnocellularis neurons following cortical devascularization inflicted in adulthood (day 75).

Expression of hsp70 mRNA is induced in the brain of transgenic mice overexpressing human CuZn-superoxide dismutase following transient global cerebral ischemia

We examined hsp70 mRNA expression in the brains of transgenic (Tg) mice overexpressing CuZn-superoxide dismutase and in wild-type (Wt) littermates after 3 min of bilateral common carotid artery occlusion. Significant induction of hsp70 mRNA occurred in the hippocampus, the cortex, and other brain regions of the Tg mice 4 h after ischemia compared to the Wt mice. However, there was no histological damage in the brains of Tg and Wt mice as assessed by both Cresyl violet staining and by TUNEL staining for DNA fragmentation. These data suggest that high levels of CuZn-superoxide dismutase activity increase hsp70 mRNA expression and that intense hsp70 mRNA expression does not predict neuronal damage, even in vulnerable hippocampal CA1 neurons.

Histochemical detection of age- and injury-related changes in signal transduction in the superior cervical ganglion

The superior cervical ganglion (SCG) is thought to be a good model for correlation studies of morphology, function and metabolism of neurons. The SCG has a relatively simple organization, it can be easily manipulated in situ, and it maintains synaptic transmission and a high metabolic rate during in vitro incubations. The histology and structure of SCG neurons have been characterized in detail, and physiologic stimuli, injury and aging have all been found to induce changes in the SCG morphology. During the last decade, research in the field of signal transduction has greatly expanded. Several signal transduction pathways have been identified that participate in the regulation of neurotransmitter synthesis, gene expression, neuronal excitability and growth factor responses of sympathetic neurons. We have been interested in using the SCG to study some of the second and third messengers involved in converting external stimuli received by sympathetic neurons into cellular short- and long-term events. Using immunohistochemistry, we have investigated protein kinase C-subtypes and the immediate early gene product Fos in the SCG, and characterized some of the changes induced by injury and aging in these messenger molecules. We will review the results and discuss the advantages and disadvantages of using histological methods in the study of signal transduction in sympathetic neurons.

Subarachnoid injections of lysed blood induce the hsp70 stress gene and produce DNA fragmentation in focal areas of the rat brain

BACKGROUND AND PURPOSE

Most experimental studies of subarachnoid hemorrhage have demonstrated little histological evidence of injury. In the present study we examined both the expression of the hsp70 heat-shock gene, a molecular marker of reversible neuronal injury, and DNA fragmentation, a marker of irreversible cell injury and death.

METHODS

Lysed blood, whole blood, oxyhemoglobin, bovine serum albumin, and saline were injected into the cisterna magna of adult rats. The induction of hsp70 mRNA and HSP70 heat-shock protein was assessed with the use of in situ hybridization and immunocytochemistry, respectively. Fragmentation of genomic DNA was studied by DNA nick end- labeling with the use of terminal deoxynucleotidyl transferase and biotinylated dATP.

RESULTS

Expression of the hsp70 gene was not induced in the brains of rats injected with whole blood, oxyhemoglobin, bovine serum albumin, or saline. Lysed blood injections, however, induced hsp70 mRNA at 6 and 24 hours in the cerebellar hemispheres and in focal regions of the basal forebrain. HSP70 protein was induced by 24 hours and persisted for at least 4 days in the same regions. HSP70 protein was localized to patches of glial cells and occasional neurons in the forebrain. In the cerebellum HSP70 was localized to Bergmann glial cells, granule cells, molecular layer stellate cells, and occasional Purkinje cells. DNA nick end-labeling showed patches of labeled cells in the basal forebrain that occurred in the same regions that hsp70 mRNA was induced.

CONCLUSIONS

The results demonstrate focal stress gene induction and DNA fragmentation after subarachnoid hemorrhage. It is hypothesized that the focal areas of hsp70 induction may reflect ischemic injury due to vasospasm produced by lysed blood and/or injury mediated by direct toxic effects of the lysed blood. The hsp70 induction and DNA nick end-labeling in the same regions suggests that lysed blood produces a spectrum of injury from HSP70 protein-labeled, reversibly injured cells to dead cells with fragmented DNA. Induction of the hsp70 stress gene and DNA nick end-labeling may be useful for evaluating the causes of injury, the spectrum of injury, and potential pharmacological therapies in experimental models of subarachnoid hemorrhage.

Cerebral energy metabolism and immediate early gene induction following severe incomplete ischaemia in transgenic mice overexpressing the human ornithine decarboxylase gene: evidence that putrescine is not neurotoxic in vivo

Cerebral ischaemia causes activation of ornithine decarboxylase followed by accumulation of putrescine, and these biochemical phenomena have been thought to contribute to the development of neuronal damage. We have used a transgenic mouse line overexpressing the human ornithine decarboxylase gene in their neurons with constitutively high putrescine to study the possible role of putrescine in development of neuronal damage in forebrain ischaemia. An incomplete forebrain ischaemia model was developed in which common carotid arteries were bilaterally occluded and reduction of blood pressure caused by orthostatic reaction was used as a way of decreasing cerebral circulation. Cerebral high-energy metabolites, intracellular pH and lactate were monitored by means of 31P and 1H nuclear magnetic resonance spectroscopy respectively. Incomplete ischaemia for 15 min resulted in severe energy failure, as indicated by an increase in the inorganic phosphate/phosphocreatine ratio, intracellular acidification from a pH of approximately 7.1 to approximately 6.5 and an increase in lactate concentration from < 1 to approximately 10 mmol/kg in both syngenic and transgenic mice. Following deocclusion, recovery of energy metabolites intracellular pH and lactate were identical in both animal groups. Ornithine decarboxylase activity rose 9- and 3-fold in syngenic and transgenic mice respectively 6 h after ischaemia, which was approximately 50-fold greater than the basal level in syngenic mice. In situ hybridization experiments revealed induction of transcription factors c-Fos and zif-268 in the hippocampus, throughout the cerebral cortex and striatum 1-3 h after ischaemia. Messenger RNA of heat shock protein 70 was induced in dentate gyrus and CA3 and CA4 subfields of the hippocampus 1 h after ischaemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of transcription factor Egr-1 in phorbol ester-induced phenylethanolamine N-methyltransferase gene expression

Transfection of PC12-variant RS1 cells with an Egr-1 expression construct has previously been shown to stimulate phenylethanolamine N-methyltransferase (PNMT) promoter activity, thus suggesting a putative role of Egr-1 as a factor regulating PNMT gene expression. To elucidate the physiological implication of this finding, the effects of phorbol 12-myristate 13-acetate (PMA) on PNMT promoter activity and Egr-1 expression were examined. PMA stimulated luciferase expression in RS1 cells transfected with a rat PNMT promoter-luciferase reporter gene construct, and also elevated both Egr-1 mRNA and Egr-1 protein levels in the untransfected cells. Further study on the concentration dependence of PMA action showed that the stimulation of luciferase expression correlated with the elevation of Egr-1 mRNA level. Finally, the stimulatory action of PMA on luciferase expression was dramatically diminished in the cells transfected with a mutant construct in which the Egr-1 binding site in PNMT promoter was mutated. These findings suggest that PMA-stimulated PNMT gene expression requires the enhancement of Egr-1 expression, thus providing further evidence for the physiological role of Egr-1 in the regulation of PNMT gene expression in the adrenergic cell.

Cloning of rat grp75, an hsp70-family member, and its expression in normal and ischemic brain

Following metabolic stress a variety of gene products are induced in cells in the brain, some of which may protect the tissue from subsequent stresses. The heat shock proteins (hsps), in particular hsp70, have been widely studied in this context, but evidence for the involvement of known hsps in protection of the CNS is inconclusive. We have therefore undertaken the search for other stress-induced proteins which may mitigate ischemic injury. Beginning with degenerate RT-PCR, we have isolated a rat-brain cDNA encoding a protein highly similar to human grp75, a mitochondrial member of the hsp70-family of stress proteins. It is also highly similar to two non-mitochondrial proteins; mortalin, a senescence-related gene product, and pbp74, a protein implicated in B-cell peptide processing. Sequence structure and phylogenetic analyses predict mitochondrial localization and induction by a calcium ionophore and glucose deprivation in PC12 cells support its identification as rat grp75. In situ analysis of normal brain reveals an unusual distribution, with very high expression in neurons of the basal forebrain, reticular and subthalamic nuclei, globus pallidus, amygdala and elsewhere. grp75-mRNA is upregulated following focal brain ischemia in a distinctive fashion. When the degree of injury is small, induction occurs in the area of injury, similar to the pattern observed for hsp70. However, when the injury is extensive, hsr is upregulated in neurons outside the ischemic area. The induction of grp75 may represent a sensitive marker of metabolically compromised tissue.

Neural regulation of acetylcholinesterase mRNAs at mammalian neuromuscular synapses

We examined the role of innervation on acetylcholinesterase (AChE) gene expression within mammalian skeletal muscle fibers. First, we showed the selective accumulation of AChE mRNAs within the junctional vs extrajunctional sarcoplasm of adult muscle fibers using a quantitative reverse transcription PCR assay and demonstrated by in situ hybridization experiments that AChE transcripts are concentrated immediately beneath the postsynaptic membrane of the neuromuscular junction. Next, we determined the influence of nerve-evoked activity vs putative trophic factors on the synaptic accumulation of AChE mRNA levels in muscle fibers paralyzed by either surgical denervation or selective blockage of nerve action potentials with chronic superfusion of tetrodotoxin. Our results indicated that muscle paralysis leads to a marked decrease in AChE transcripts from the postsynaptic sarcoplasm, yet the extent of this decrease is less pronounced after tetrodotoxin inactivation than after denervation. These results suggest that although nerve-evoked activity per se appears a key regulator of AChE mRNA levels, the integrity of the synaptic structure or the release of putative trophic factors contribute to maintaining the synaptic accumulation of AChE transcripts at adult neuromuscular synapses. Furthermore, the pronounced downregulation of AChE transcripts in paralyzed muscles stands in sharp contrast to the well-documented increase in nicotinic acetylcholine receptor mRNAs under these conditions, and indicates that expression of the genes encoding these two synaptic proteins are subjected to different regulatory mechanisms in adult muscle fibers in vivo.

Prolonged expression of hsp70 mRNA following transient focal cerebral ischemia in transgenic mice overexpressing CuZn-superoxide dismutase

The distribution of heat shock protein hsp70 mRNA after 10 min of middle cerebral artery (MCA) occlusion was investigated through in situ hybridization in transgenic (Tg) mice overexpressing CuZn-superoxide dismutase (CuZn-SOD) and in control nontransgenic (nTg) littermates. In the ischemic cortex of nTg mice, hsp70 mRNA was detected 1 h after reperfusion and was observed for up to 6 h. In Tg mice, however, it was still detectable within the cortex even at 24 h. In the caudate putamen, hsp70 mRNA appeared at 1 h and was present for up to 6 h in both nTg and Tg mice. Although hsp70 mRNA was detected in the thalamus only at 1 h in nTg mice, it was observed for up to 6 h in Tg mice. Similarly, hsp70 mRNA was detected in the hippocampus of nTg mice only at 1 h, whereas it was detected in Tg mice at 1 h and continued up to 24 h, with high intensity in the CA1 subfield. Despite the significant amounts of hsp70 mRNA in both Tg and nTg mice following ischemia, there was no observable neuronal necrosis (as assessed using hematoxylin and eosin staining) for up to 7 days. Cortical cerebral blood flow (CBF), measured by laser-Doppler flowmetry, did not differ between nTg and Tg mice during ischemia and reperfusion, despite exhibiting hyperemia following hypoperfusion. These results suggest that oxidative stress affects the expression of hsp70 following temporary focal ischemia. An alteration in oxidation stress, which resulted from reduced levels of superoxide radicals in the presence of the CuZn-SOD transgenes, may permit the prolonged expression of hsp70.(ABSTRACT TRUNCATED AT 250 WORDS)

Pentylenetetrazol seizures increase pro-nerve growth factor-like immunoreactivity in the reticular thalamic nucleus and nerve growth factor mRNA in the dentate gyrus

Neurotrophins may have a neuroprotective role and are probably involved in the control of axonal sprouting and synaptic plasticity. An antibody raised against a pro-sequence of nerve growth factor (NGF) was tested. In control undisturbed rats, a strong immunoreactivity was detected in scattered cells in and around the pyramidal and granule cell layer of the hippocampus and a moderate labeling was found in the reticular thalamic nucleus. In situ hybridization showed specific expression of NGF mRNA in a similar population of scattered cells in the hippocampal formation but not in the reticular thalamic nucleus. Acute epileptic seizures, induced by a convulsive dose of 50 mg/kg pentylenetetrazol (PTZ), strongly increased NGF mRNA in neurons of the granular layer of the dentate gyrus 3 hr but not 6 hr after the injection. No change in pro-NGF-like immunoreactivity was observed in the hippocampus or reticular thalamic nucleus after acute seizures. Chemical kindling was induced by daily injections of subconvulsive doses (30 mg/kg) of PTZ for 4 weeks. This treatment significantly increased pro-NGF-like immunoreactivity in the reticular thalamic nucleus but did not affect NGF mRNA. These data strengthen a role for the reticular thalamic nucleus and NGF in PTZ kindling.

The biology and behaviour of intracerebral adrenal transplants in animals and man

The catecholamine containing chromaffin cells of the adrenal medulla have recently been employed as intracerebral grafts in man and animals with lesions of the nigrostriatal dopaminergic system. This review outlines the basic biology of the chromaffin cell with reference to its efficacy as a source of dopamine in the grafted state. This is followed by an evaluation of the use of these grafts in experimentally lesioned animals and in patients with Parkinson's disease.

Cholecystokinin in mammalian primary sensory neurons and spinal cord: in situ hybridization studies in rat and monkey

The peptide cholecystokinin (CCK) has been suggested to be involved in nociception, but its exact localization at the level of the spinal cord and in spinal ganglia has been a controversial issue. Therefore the distribution of messenger RNA (mRNA) for CCK was studied by in situ hybridization using oligonucleotide probes on sections of adult rat lumbar dorsal root ganglia following unilateral section of the sciatic nerve and on sections of untreated monkey trigeminal ganglia, spinal cord and spinal ganglia from all levels. For comparison, calcitonin gene-related peptide (CGRP) mRNA was also studied in the monkey tissue using the same techniques. Peripheral sectioning of the sciatic nerve in the rat resulted in the appearance of detectable CCK mRNA in up to 30% of remaining ipsilateral L4 and L5 dorsal root ganglion neurons 3 weeks after surgery, with a distinct but more limited appearance also in the contralateral ganglia. No cells, or only single cells, could be seen in normal control rat ganglia. In contrast, in the normal monkey, approximately 20% of dorsal root ganglion neurons, regardless of spinal level, and 10% of trigeminal ganglia neurons expressed mRNA for CCK. CGRP mRNA was expressed at detectable levels in approximately 80% of these monkey dorsal root ganglion neurons. In the monkey spinal cord, CCK mRNA was detected in the dorsal horn and in motoneurons, whereas CGRP mRNA was only seen in motoneurons. The present results suggest that CCK peptides can be involved in sensory processing in the dorsal horn of the spinal cord in normal monkeys and in rats after peripheral nerve injury, adding one more possible excitatory peptide to the group of mediators in the dorsal horn.

Distributions of mRNAs for alpha-2 adrenergic receptor subtypes in rat brain: an in situ hybridization study

Selective 35S-labeled oligonucleotide probes were designed to sequences of the rat alpha-2A (RG20), alpha-2B (RNG), and alpha-2C (RG10) adrenoreceptor mRNAs for use in in situ hybridization experiments on sections of unfixed rat brain, spinal cord and kidney. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each probe and region of the central nervous system were observed. Alpha-2A mRNA labeling was most pronounced in neurons in layer six of the cerebral cortex, hypothalamic paraventricular nucleus, reticular thalamic nucleus, pontine nuclei, locus coeruleus, vestibular nuclei, trapezoid nuclei, deep cerebellar nuclei, nucleus tractus solitarii, ventrolateral medullary reticular formation, and the intermediolateral cell column of the thoracic spinal cord. In some of these locations, the receptor mRNA, in all probability, is present in noradrenaline and perhaps adrenaline neurons. The alpha-2B probe, which primarily labels the kidney, gave only a very light signal in the thalamus in the central nervous system after extended exposure times. Alpha-2C mRNA labeling was primarily observed in the olfactory bulb, cerebral cortex, islands of Calleja, striatum, hippocampal formation, cerebellar cortex, and dorsal root ganglia. Labeling patterns disappeared when excess unlabeled probes were added to their respective radiolabeled probes, or when sense probes were employed. When a hybrid antisense probe homologous to all three alpha-2 probes was used, labeling patterns also disappeared. The present study therefore justifies the pharmacological subclassification of alpha-2 receptors by providing anatomical evidence for specific and selective cell groups in the rat central nervous system containing mRNA for three alpha-2 receptor subtypes.

Modulation of a neuronal calmodulin mRNA species in the rat brain stem by reserpine

Reserpine evokes transsynaptic impulse activity by depleting catecholaminergic neurotransmitters in the rat brain. Previous studies suggest a relationship between catecholaminergic activity and calmodulin concentration. In this report we employ Northern blot analysis to examine the effect of a single subcutaneous injection of reserpine on levels of calmodulin mRNA species which are preferentially expressed in neurons of the rat brain. Regional differences in mRNA levels were also investigated by in situ hybridization and drug-induced changes were noted particularly in specific regions of the rat brain stem. The riboprobe used in the in situ hybridization study recognized a 4.0 kilobase neuronal calmodulin mRNA species (NGB1), which was derived from the rat CaM1 gene. A calmodulin radio-immunoassay was utilized to demonstrate a drug-induced increased in calmodulin protein levels in a region which included the brain stem.

p-chlorophenylalanine increases tryptophan-5-hydroxylase mRNA levels in the rat dorsal raphe: a time course study using in situ hybridization

The effects of a single dose of p-chlorophenylalanine on the mRNA encoding tryptophan-5-hydroxylase (EC 1.14.16.4) in the rat dorsal raphe nucleus were analyzed using in situ hybridization. The levels of tryptophan-5-hydroxylase mRNA were markedly increased in cell bodies located in the ventromedial part of the dorsal raphe 1-2 days after p-chlorophenylalanine (300 mg/kg, i.p.) administration. This was followed by a decrease in the amount of tryptophan-5-hydroxylase mRNA, which returned to basal values by 5 days after treatment. An almost symmetric time course was observed for the midbrain serotonin concentration. Our results on the temporal pattern of changes in tryptophan-5-hydroxylase mRNA levels in the ventromedial part of the dorsal raphe are opposite to those reported for the enzyme activity and serotonin concentration after p-chlorophenylalanine treatment. These changes may result from modifications in enzyme mRNA expression, suggesting that tryptophan-5-hydroxylase gene transcription is involved in feedback mechanisms regulating serotonin synthesis.

Expression of neuropeptides and neuropeptide mRNAs in spinal cord after axotomy in the rat, with special reference to motoneurons and galanin

The extent to which the plasticity in peptide expression observed in developing spinal motoneurons occurs following proximal peripheral axotomy in the adult rat was examined using in situ hybridization and immunohistochemical techniques to visualize the changes. Transient upregulation of galanin, vasoactive intestinal polypeptide (VIP) and substance P messenger ribonucleic acids (mRNAs) was observed within subpopulations of motoneurons ipsilateral to lesion for periods lasting 2-3 weeks after injury. In contrast, the axotomy-induced heterogenous increases in somatostatin and neuropeptide tyrosine mRNA expression in ipsilateral motoneurons remained elevated, or, in the case of somatostatin, continued to increase for the time period studied (1 month). Immunohistochemical analysis agreed with the in situ hybridization results, showing some motoneurons within the injured ventral horn to contain galanin-, VIP- or somatostatin-like immunoreactivity. In some instances, galanin-immunoreactive motoneurons colocalized with calcitonin gene-related peptide immunoreactivity. Most of the neurons expressing the injury-induced peptides appeared large, presumably alpha-motoneurons but there were also many small neurons expressing galanin in the ventral horn ipsilateral to lesion. This may represent evidence for peptide synthesis in gamma-motoneurons. The only peptide mRNA studied to be down-regulated in response to axotomy was enkephalin. The results show that peptide expression in injured motoneurons is dramatically altered, the significance of which remains to be determined.

Induction of 70-kDa heat shock protein and hsp70 mRNA following transient focal cerebral ischemia in the rat

Induction of the 70-kDa heat shock protein (HSP70) was demonstrated immunocytochemically in adult rats 4 h to 7 days following temporary middle cerebral artery (MCA) occlusions lasting 30, 60, or 90 min. Maximal HSP70 induction occurred approximately 24 h following ischemia. Thirty minutes of ischemia induced HSP70 in neurons throughout the cortex in the MCA distribution, whereas 90 min of ischemia induced HSP70 in neurons in the penumbra. HSP70 protein was induced in endothelial cells in infarcted neocortex following 60-90 min of MCA occlusion, and HSP70 was induced in endothelial cells in infarcted regions of lateral striatum following 30-90 min of MCA occlusion. hsp70 mRNA was induced in the MCA distribution in cortex and to a lesser extent in striatum at 2 h to 3 days following 60 min of ischemia. It is proposed that brief ischemia induces hsp70 mRNA and HSP70 protein in the cells most vulnerable to ischemia--the neurons. HSP70 protein is not induced in most neurons and glia following 60-90 min of ischemia in areas destined to infarct, whereas it is induced in vascular endothelial cells.

Sensitive mRNA detection using unfixed tissue: combined radioactive and non-radioactive in situ hybridization histochemistry

In the present study some experimental parameters for in situ hybridization histochemistry (ISHH) have been analysed using 35S-labelled and alkaline phosphatase-conjugated probes, in order to develop a reproducible double-labelling procedure. We have compared the total exclusion of tissue fixation with tissue sections fixed by immersion in formalin. In addition, the effect of dithiothreitol was assessed both when combining radiolabelled and non-radioactive probes on a single tissue section and when the probes were used separately. Hybridization of unfixed tissue resulted in stronger specific labelling and lower background both for radiolabelled and alkaline phosphatase-conjugated probes. No loss in tissue preservation was seen at the light microscopic level after hybridization of unfixed tissue. High concentrations (200 mM) of dithiothreitol strongly suppressed background when using 35S-labelled probes, whereas in the non-radioactive procedure, alkaline phosphatase labelling could only be achieved with very low dithiothreitol concentrations (less than 1 mM). This incompatibility led to a protocol using unfixed tissue sections and a sequential hybridization procedure, with the radiolabelled probe and high concentrations of dithiothreitol in the first step and the alkaline phosphatase-conjugated probe without dithiothreitol in the second step.

Reserpine-induced processing of chromogranin A in cultured bovine adrenal chromaffin cells

The effect of reserpine on the processing of the secretory granule protein chromogranin A (CgA) in isolated bovine adrenal chromaffin cells was investigated using two radioimmunoassays employing site-specific antisera. The two antisera were directed against closely associated regions of the CgA molecule which would be exposed by specific processing: antiserum L331 was raised against the C-terminus of the regulatory peptide pancreastatin, and the second antiserum, L300, was raised against the synthetic peptide [Tyr0]CgA306-313 (YLSKEWEDA), a sequence that lies immediately C-terminal to pancreastatin and adjacent to a dibasic amino acid cleavage site. Chronic reserpine treatment of chromaffin cells produced a time- and dose-dependent increase in processing, as demonstrated by an increase in pancreastatin- and YLSKEWEDA-immunoreactivity (ir). The reserpine-induced rise in pancreastatin-ir was due predominantly to an increase in pancreastatin 1-47, whereas the rise in YLSKEWEDA-ir was due to increases in three polypeptides: a 51-kDa YLSKEWEDA-ir polypeptide, CgA297-313, and CgA248-313. The latter predominated. The action of reserpine on both pancreastatin- and YLSKEWEDA-ir was found to be largely inhibited by the protein synthesis inhibitor cycloheximide. The results show that treatment of isolated chromaffin cells with reserpine induces both the selective proteolytic processing and peptidyl-glycine amidation of CgA and its derived fragments. As reserpine has a similar effect on proenkephalin in chromaffin cells, the results suggest that reserpine induces a general increase in the activity of the processing enzymes, partially by an increase in protein synthesis.