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ABSTRACT: Melatonin is a circulating hormone that is primarily released from the pineal gland. It is best known as a regulator of seasonal and circadian rhythms; its levels are high during the night and low during the day. Interestingly, insulin levels also exhibit a nocturnal drop, which has previously been suggested to be controlled, at least in part, by melatonin. This regulation can be explained by the proposed inhibitory action of melatonin on insulin release. Indeed, both melatonin receptor 1A (MTNR1A) and MTNR1B are expressed in pancreatic islets. The role of melatonin in the regulation of glucose homeostasis has been highlighted by three independent publications based on genome-wide association studies of traits connected with type 2 diabetes, such as elevated fasting glucose, and, subsequently, of the disease itself. The studies demonstrate a link between variations in the MTNR1B gene, hyperglycaemia, impaired early phase insulin secretion and beta cell function. The risk genotype predicts the future development of type 2 diabetes. Carriers of the risk genotype exhibit increased expression of MTNR1B in islets. This suggests that these individuals may be more sensitive to the actions of melatonin, leading to impaired insulin secretion. Blocking the inhibition of insulin secretion by melatonin may be a novel therapeutic avenue for type 2 diabetes.
Diabetologia 05/2009; 52(7):1240-9. · 6.81 Impact Factor
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M Fex,
G Haemmerle,
N Wierup,
M Dekker-Nitert,
M Rehn,
M Ristow,
R Zechner,
F Sundler,
C Holm,
L Eliasson, H Mulder
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ABSTRACT: The enzyme hormone-sensitive lipase (HSL) is produced and is active in pancreatic beta cells. Because lipids are known to play a crucial role in normal control of insulin release and in the deterioration of beta cell function, as observed in type 2 diabetes, actions of HSL in beta cells may be critical. This notion has been addressed in different lines of HSL knockout mice with contradictory results.
To resolve this, we created a transgenic mouse lacking HSL specifically in beta cells, and characterised this model with regard to glucose metabolism and insulin secretion, using both in vivo and in vitro methods.
We found that fasting basal plasma glucose levels were significantly elevated in mice lacking HSL in beta cells. An IVGTT at 12 weeks revealed a blunting of the initial insulin response to glucose with delayed elimination of the sugar. Additionally, arginine-stimulated insulin secretion was markedly diminished in vivo. Investigation of the exocytotic response in single HSL-deficient beta cells showed an impaired response to depolarisation of the plasma membrane. Beta cell mass and islet insulin content were increased, suggesting a compensatory mechanism, by which beta cells lacking HSL strive to maintain normoglycaemia.
Based on these results, we suggest that HSL, which is located in close proximity of the secretory granules, may serve as provider of a lipid-derived signal essential for normal insulin secretion.
Diabetologia 12/2008; 52(2):271-80. · 6.81 Impact Factor
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ABSTRACT: Hyperinsulinaemia maintains euglycaemia in insulin-resistant states. The precise cellular mechanisms by which the beta cells adapt are still unresolved. A peripherally derived cue, such as increased circulating fatty acids, may instruct the beta cell to initiate an adaptive programme to maintain glucose homeostasis. When this fails, type 2 diabetes ensues. Because mitochondria play a key role in beta cell pathophysiology, we tested the hypothesis that mitochondrial metabolism is critical for beta cell adaptation to insulin resistance.
C57BL/6J mice were given high-fat (HF) diet for 12 weeks. We then analysed islet hormone secretion, metabolism in vivo and in vitro, and beta cell morphology.
HF diet resulted in insulin resistance and glucose intolerance but not frank diabetes. Basal insulin secretion was elevated in isolated islets from HF mice with almost no additional response provoked by high glucose. In contrast, a strong secretory response was seen when islets from HF mice were stimulated with fuels that require mitochondrial metabolism, such as glutamate, glutamine, alpha-ketoisocaproic acid and succinate. Moreover, while glucose oxidation was impaired in islets from HF mice, oxidation of glutamine and palmitate was enhanced. Ultrastructural analysis of islets in HF mice revealed an accumulation of lipid droplets in beta cells and a twofold increase in mitochondrial area.
We propose that beta cells exposed to increased lipid flux in insulin resistance respond by increasing mitochondrial volume. This expansion is associated with enhanced mitochondrial metabolism as a means of beta cell compensation.
Diabetologia 02/2007; 50(1):74-83. · 6.81 Impact Factor
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ABSTRACT: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion.
Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K(+) channel (K(ATP)-channel) conductance.
We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca(2+)-induced exocytosis and K(ATP)-channel conductance in single cells, were unaffected. Insulin secretion induced by alpha-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K(ATP)-independent actions of fuel secretagogues are operational, as well as the first and K(ATP)-dependent phase.
Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion.
Diabetologia 08/2006; 49(7):1578-86. · 6.81 Impact Factor
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ABSTRACT: AIMS/HYPOTHESIS: The molecular mechanisms of insulin release are only partially known. Among putative factors for coupling glucose metabolism to insulin secretion, anaplerosis has lately received strong support. The anaplerotic enzyme pyruvate carboxylase is highly expressed in beta cells, and anaplerosis influences insulin secretion in beta cells. By inhibiting pyruvate carboxylase in rat islets, we aimed to clarify the hitherto unknown metabolic events underlying anaplerotic regulation of insulin secretion. METHODS: Phenylacetic acid (5 mmol/l) was used to inhibit pyruvate carboxylase in isolated rat islets, which were then assessed for insulin secretion, fuel oxidation, ATP:ADP ratio, respiration, mitochondrial membrane potential, exocytosis and ATP-sensitive K(+) channel (K(ATP)-channel) conductance. RESULTS: We found that the glucose-provoked rise in ATP:ADP ratio was suppressed by inhibition of pyruvate carboxylase. In contrast, fuel oxidation, respiration and mitochondrial membrane potential, as well as Ca(2+)-induced exocytosis and K(ATP)-channel conductance in single cells, were unaffected. Insulin secretion induced by alpha-ketoisocaproic acid was suppressed, whereas methyl-succinate-stimulated secretion remained unchanged. Perifusion of rat islets revealed that inhibition of anaplerosis decreased both the second phase of insulin secretion, during which K(ATP)-independent actions of fuel secretagogues are operational, as well as the first and K(ATP)-dependent phase. CONCLUSIONS/INTERPRETATION: Our results are consistent with the concept that anaplerosis via pyruvate carboxylase determines pyruvate cycling, which has previously been shown to correlate with glucose responsiveness in clonal beta cells. These processes, controlled by pyruvate carboxylase, seem crucial for generation of an appropriate ATP:ADP ratio, which may regulate both phases of fuel-induced insulin secretion.
Diabetologia 05/2006; · 6.81 Impact Factor
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ABSTRACT: Ghrelin is produced mainly by endocrine cells in the stomach and is an endogenous ligand for the growth hormone secretagogue receptor (GHS-R). It also influences feeding behavior, metabolic regulation, and energy balance. It affects islet hormone secretion, and expression of ghrelin and GHS-R in the pancreas has been reported. In human islets, ghrelin expression is highest pre- and neonatally. We examined ghrelin and GHS-R in rat islets during development with immunocytochemistry and in situ hybridization. We also studied the effect of ghrelin on insulin secretion from INS-1 (832/13) cells and the expression of GHS-R in these cells. We found ghrelin expression in rat islet endocrine cells from mid-gestation to 1 month postnatally. Islet expression of GHS-R mRNA was detected from late fetal stages to adult. The onset of islet ghrelin expression preceded that of gastric ghrelin. Islet ghrelin cells constitute a separate and novel islet cell population throughout development. However, during a short perinatal period a minor subpopulation of the ghrelin cells co-expressed glucagon or pancreatic polypeptide. Markers for cell lineage, proliferation, and duct cells revealed that the ghrelin cells proliferate, originate from duct cells, and share lineage with glucagon cells. Ghrelin dose-dependently inhibited glucose-stimulated insulin secretion from INS-1 (832/13) cells, and GHS-R was detected in the cells. We conclude that ghrelin is expressed in a novel developmentally regulated endocrine islet cell type in the rat pancreas and that ghrelin inhibits glucose-stimulated insulin secretion via a direct effect on the beta-cell.
Journal of Histochemistry and Cytochemistry 04/2004; 52(3):301-10. · 2.72 Impact Factor
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ABSTRACT: Cocaine- and amphetamine-regulated transcript (CART) is an anorexigenic peptide widely expressed in the central and peripheral, including the enteric, nervous systems. CART is also expressed in pituitary endocrine cells, adrenomedullary cells, islet somatostatin cells, and in rat antral gastrin cells. We used immunocytochemistry (IHC) and in situ hybridization (ISH) to study CART expression in developing rat pancreas. We also examined co-expression of CART and islet hormones and developmental markers and the effect of CART on proliferation using clonal insulin cells (INS-1 832/13). A major portion of each of the islet cell types, except the ghrelin cells, expressed CART during a period before and around birth. Two weeks postnatally, CART expression was restricted to somatostatin cells. Pre- and early postnatally, many of the CART-expressing cells co-expressed cytokeratin 20 (CK20), a marker of duct cells and islet precursor cells, the trophic hormone gastrin, and a smaller subpopulation also harbored the proliferation marker Ki67. CART was also expressed in pancreatic nerve fibers, both sensory and autonomic, and in ganglion nerve cell bodies. Although highly expressed in the developing islets, CART did not affect proliferation of INS-1 cells. We have demonstrated that CART is expressed in several islet cell types during rat development but is restricted to somatostatin cells and neurons in the adult rat.
Journal of Histochemistry and Cytochemistry 03/2004; 52(2):169-77. · 2.72 Impact Factor
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ABSTRACT: Ghrelin, an endogenous ligand of the growth hormone secretagogue receptor (GHS-R), was recently identified in the stomach. Ghrelin is produced in a population of endocrine cells in the gastric mucosa, but expression in intestine, hypothalamus and testis has also been reported. Recent data indicate that ghrelin affects insulin secretion and plays a direct role in metabolic regulation and energy balance. On the basis of these findings, we decided to examine whether ghrelin is expressed in human pancreas. Specimens from fetal to adult human pancreas and stomach were studied by immunocytochemistry, for ghrelin and islet hormones, and in situ hybridisation, for ghrelin mRNA.
We identified ghrelin expression in a separate population of islet cells in human fetal, neonatal, and adult pancreas. Pancreatic ghrelin cells were numerous from midgestation to early postnatally (10% of all endocrine cells). The cells were few, but regularly seen in adults as single cells at the islet periphery, in exocrine tissue, in ducts, and in pancreatic ganglia. Ghrelin cells did not express any of the known islet hormones. In fetuses, at midgestation, ghrelin cells in the pancreas clearly outnumbered those in the stomach.
Ghrelin is expressed in a quite prominent endocrine cell population in human fetal pancreas, and ghrelin expression in the pancreas precedes by far that in the stomach. Pancreatic ghrelin cells remain in adult islets at lower numbers. Ghrelin is not co-expressed with any known islet hormone, and the ghrelin cells may therefore constitute a new islet cell type.
Regulatory Peptides 08/2002; 107(1-3):63-9. · 2.11 Impact Factor
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ABSTRACT: Islet amyloid, derived from islet amyloid polypeptide (IAPP or amylin), frequently occurs in type 2 diabetes. Availability of this peptide for amyloid formation may be enhanced by increased islet expression of IAPP. In the insulin resistant state, euglycemia is maintained by hypersecretion of insulin. Whether
Metabolism 01/2001; 49(12):1518-22. · 2.66 Impact Factor
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ABSTRACT: Islet amyloid polypeptide (IAPP), or amylin, was originally discovered as the constituent peptide in amyloid occurring in human insulinomas and in pancreatic islets in human subjects with Type II (non-insulin-dependent) diabetes mellitus. Its normal expression in beta cells and its co-secretion with insulin in response to nutrient stimuli, suggest a metabolic function for the peptide. Specifically, IAPP has most frequently been shown to inhibit insulin secretion, implying that IAPP has a role in the regulation of islet hormone homeostasis. The physiological significance of IAPP in islets has been difficult to assess; very high IAPP concentrations are required to alter insulin secretion. Moreover, until recently, IAPP receptors have not been characterised at the molecular level, thus leaving the actual target cells for IAPP unidentified. Furthermore, in experimental diabetes in rodents, the ratio of IAPP expression to that of insulin invariably is increased. In view of the pleiotropic effects attributed to IAPP, such regulation could be both adverse and beneficial in diabetes. Metabolic characterisation of mice carrying a null mutation in the IAPP gene or which overexpress IAPP in beta cells have recently confirmed that IAPP is a physiological inhibitor of insulin secretion. Based on experiments in which IAPP-deficient mice develop a more severe form of alloxan-induced diabetes, we argue that the action of IAPP in the islets normally is beneficial for beta-cell function and survival; thus, the established up regulation of IAPP expression compared with that of insulin in experimental rodent diabetes could serve to protect islets under metabolically challenging circumstances.
Diabetologia 07/2000; 43(6):687-95. · 6.81 Impact Factor
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ABSTRACT: To examine whether islet amyloid polypeptide (IAPP), other than through amyloid formation, may be of importance in diabetes pathogenesis, IAPP-deficient mice (IAPP(-/-)) were challenged with alloxan (day 0). Diabetes in IAPP(-/-) mice was more severe at day 35, indicated by greater weight loss; glucose levels were higher in alloxan-treated IAPP(-/-) mice, whereas insulin levels were lower, indicating a greater impairment of islet function. Accordingly, glucose levels upon intravenous glucose challenges at days 7 and 35 were consistently higher in alloxan-treated IAPP(-/-) mice. At day 35, insulin mRNA expression, but not beta-cell mass, was lower in untreated IAPP(-/-) mice. Yet, upon alloxan administration, beta-cell mass and numbers of beta-cell-containing islets were significantly more reduced in IAPP(-/-) mice. Furthermore, they displayed exaggerated beta-cell dysfunction, because in their remaining beta-cells, insulin mRNA expression was significantly more impaired and the localization of glucose transporter-2 was perturbed. Thus the lack of IAPP has allowed exaggerated beta-cell cytotoxic actions of alloxan, suggesting that there may be beneficial features of IAPP actions in situations of beta-cell damage.
AJP Endocrinology and Metabolism 05/2000; 278(4):E684-91. · 4.75 Impact Factor
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ABSTRACT: Primary sensory neurons serve a dual role as afferent neurons, conveying sensory information from the periphery to the central nervous system, and as efferent effectors mediating, e.g., neurogenic inflammation. Neuropeptides are crucial for both these mechanisms in primary sensory neurons. In afferent functions, they act as messengers and modulators in addition to a principal transmitter; by release from peripheral terminals, they induce an efferent response, "neurogenic inflammation," which comprises vasodilatation, plasma extravasation, and recruitment of immune cells. In this article, we introduce two novel members of the sensory neuropeptide family: pituitary adenylate cyclase-activating polypeptide (PACAP) and islet amyloid polypeptide (IAPP). Whereas PACAP, a vasoactive intestinal polypeptide-resembling peptide, predominantly occurs in neuronal elements, IAPP, which is structurally related to calcitonin gene-related peptide, is most widely known as a pancreatic beta-cell peptide; as such, it has been recognized as a constituent of amyloid deposits in type 2 diabetes. In primary sensory neurons, under normal conditions, both peptides are predominantly expressed in small-sized nerve cell bodies, suggesting a role in nociception. On axotomy, the expression of PACAP is rapidly induced, whereas that of IAPP is reduced. Such a regulation of PACAP suggests that it serves a protective role during nerve injury, but that of IAPP may indicate that it is an excitatory messenger under normal conditions. In contrast, in localized adjuvant-induced inflammation, expression of both peptides is rapidly induced. For IAPP, studies in IAPP-deficient mice support the notion that IAPP is a pronociceptive peptide, because these mutant mice display a reduced nociceptive response when challenged with formalin.
Molecular Neurobiology 07/1999; 19(3):229-53. · 5.74 Impact Factor
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ABSTRACT: Triglycerides in the beta-cell may be important for stimulus-secretion coupling, through provision of a lipid-derived signal, and for pathogenetic events in NIDDM, where lipids may adversely affect beta-cell function. In adipose tissues, hormone-sensitive lipase (HSL) is rate-limiting in triglyceride hydrolysis. Here, we investigated whether this enzyme is also expressed and active in beta-cells. Northern blot analysis and reverse transcription-polymerase chain reaction demonstrated that HSL is expressed in rat islets and in the clonal beta-cell lines INS-1, RINm5F, and HIT-T15. Western blot analysis identified HSL in mouse and rat islets and the clonal beta-cells. In mouse and rat, immunocytochemistry showed a predominant occurrence of HSL in beta-cells, with a presumed cytoplasmic localization. Lipase activity in homogenates of the rodent islets and clonal beta-cells constituted 2.1 +/- 0.6% of that in adipocytes; this activity was immunoinhibited by use of antibodies to HSL. The established HSL expression and activity in beta-cells offer a mechanism whereby lipids are mobilized from intracellular stores. Because HSL in adipocytes is activated by cAMP-dependent protein kinase (PKA), PKA-regulated triglyceride hydrolysis in beta-cells may participate in the regulation of insulin secretion, possibly by providing a lipid-derived signal, e.g., long-chain acyl-CoA and diacylglycerol.
Diabetes 02/1999; 48(1):228-32. · 8.29 Impact Factor
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ABSTRACT: The islet response to a high-fat diet, which induces insulin resistance, was investigated in Sprague-Dawley rats. It was found that the insulin response to glucose (15 or 25 mg/min, i.v.) was not different between rats given a high-fat diet and control rats after 2 weeks but was significantly reduced in rats fed high-fat diets after 4 (by 46+/-9%; p<0.001) and 8 weeks (by 68+/-12%; p<0.001). However, after 2 weeks of a high-fat diet, stimulated insulin secretion from isolated islets incubated for 60 min in 5.6, 8.3, and 11.1 mM glucose was impaired. When islets isolated from rats given a high-fat diet for 2 weeks were perifused, it was evident that the first-phase insulin secretion was impaired (seen during the first 6 min after increase of glucose from 3.3 to 8.3 mM). Insulin gene expression, examined by quantitative in situ hybridization, was impaired after 2 weeks of high-fat diet (52% decrease in mRNA-labeling; p<0.001). Islet hypertrophy was not evident in rats given high-fat diet, as determined by areas of either islet profiles in dark-field images or isolated islets. Islet innervation, as revealed by immunostaining for vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY), was increased after 2, 4, and 8 weeks of high-fat diet. Thus induction of insulin resistance by high-fat diet in Sprague-Dawley rats results after 2 weeks in impaired glucose-stimulated insulin secretion in vitro, impaired insulin gene expression, and hyperinnervation of the islets without any sign of islet hypertrophy, whereas the in vivo insulin response to glucose, although normal after 2 weeks, is impaired after 4 weeks.
Pancreas 01/1999; 18(1):75-83. · 2.39 Impact Factor
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ABSTRACT: Understanding of islet embryogenesis may prove to be key in the design of future therapies for diabetes directed at re-initiating islet growth, with the goal to replace and/or replenish the impaired beta-cell mass in the disease. In this context, studies of islet neurohormonal peptides, known to play a role in the local regulation of islet function, and their expression during islet embryogenesis are important. Here we review our studies on the embryonic islet expression of islet amyloid polypeptide (IAPP) and the PP-fold peptides pancreatic polypeptide (PP), peptide YY (PYY) and neuropeptide Y (NPY). IAPP, which is constitutively expressed in beta- and delta-cells in the adult rat, was found to occur in the assumed pluripotent islet progenitor cell, together with PYY, glucagon, and to a lesser extent with insulin. As development proceeds, the insulin/IAPP phenotype is segregated from that of PYY/glucagon; with the formation of islet-like structures, insulin/IAPP-expressing cells primarily occupy their central portions, while PYY/glucagon-expressing cells are found in their periphery. At the time of formation of islet-like structures, expression of NPY is induced in the insulin/IAPP-containing cells. Whereas NPY-expression ceases at birth, PYY is constitutively expressed in non-beta-cells in the mature rat. Expression of PP is induced just prior to birth in a separate population of islet cells, occasionally co-expressed with PYY. Although a clear role for these peptides during embryogenesis has not been identified, they conceivably could play a role in the control of insulin secretion, islet growth and islet blood flow.
Microscopy Research and Technique 12/1998; 43(4):313-21. · 1.79 Impact Factor
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ABSTRACT: Protein kinase B (PKB) is involved in signaling to a multitude of important cellular events and is activated by insulin and growth factors, including insulin-like growth factor I (IGF-I). We show here expression of PKB in pancreatic islets and in the beta cell lines HIT-T15, INS-1, and RINm5F. Expression of PKB mRNA and the presence of PKB isoforms (alpha, beta, and gamma) were assessed by Northern blot analysis and RT-PCR, respectively. Antibodies recognizing different parts of PKB isoforms were employed to demonstrate PKB protein expression by immunoblot analysis. By use of immunohistochemistry in rat and mouse pancreatic tissue sections, PKB was localized to predominantly beta cells. Regulation of PKB was examined in INS-1 and RINm5F cells; upon stimulation with IGF-I (5-10 min), PKB was phosphorylated and activated (approximately 3-fold) by a wortmannin-sensitive mechanism, indicating involvement of phosphatidylinositol-3 kinase. The possible participation of PKB in signal transduction pathways modulating cAMP-dependent insulin secretion and in proliferation of beta cells is discussed.
Biochemical and Biophysical Research Communications 10/1998; 250(1):181-6. · 2.48 Impact Factor
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ABSTRACT: The neuropeptide pituitary adenylate cyclase-activating peptide (PACAP) is expressed in sensory neurons. Expression of several neuropeptides is up-regulated in sensory neurons following inflammation. To examine whether also PACAP expression is regulated by inflammation, PACAP expression in L5 dorsal root ganglion (DRG) was determined, using in situ hybridization, after unilateral adjuvant-induced inflammation in the rat paw. At 12 h and day 3, but not day 21, the percentage of neurons expressing PACAP mRNA was greater in the innervating L5 DRG. Similarly, PACAP mRNA expression in individual neurons was higher in the innervating L5 DRG at 12 h and day 3, but not day 21. Up-regulated PACAP expression following adjuvant injection suggests a role for PACAP in inflammation.
Neuroreport 09/1998; 9(12):2833-6. · 1.66 Impact Factor
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ABSTRACT: Nitric oxide (NO) is a novel neurotransmitter candidate to which a large number of physiological roles has been ascribed. In the present study, immunocytochemistry was used to demonstrate NO synthase (NOS) and to investigate possible co-localization with other neurotransmitters. In the trigeminal ganglion of the cat, a moderate number of NOS immunoreactive nerve cell bodies was seen, of which the major part also expressed calcitonin gene-related peptide (CGRP). The nerve cell bodies expressing NOS in the trigeminal ganglion were predominantly of small to medium size; while numerous cell bodies of varying size contained CGRP. With in situ hybridization using oligonucleotide probes, CGRP mRNA was demonstrated in almost all trigeminal neurons of the cat. Stimulation of the nasociliary nerve resulted in a frequency-dependent increase in ipsilateral local cortical blood flow by 30 +/- 6%. Administration of the NOS inhibitor NG-nitro-L-arginine-methylester (L-NAME) did not significantly alter this response when applied intravenously or on the cortical surface. Local cortical administration of the CGRP blocker h-CGRP (8-37) did not alter the cerebral vasodilator response to hypercapnia or resting flow. However, the nasociliary nerve response was reduced by 50% after h-CGRP (8-37), with a general shift to the right of the frequency-response curve. These data suggest that although NOS is seen in several trigeminal ganglion cells and coexists with CGRP in a subpopulation of the sensory neurons, its role in trigeminally mediated vasodilatation was not significant.
Journal of the Autonomic Nervous System 06/1998; 70(1-2):15-22.
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ABSTRACT: The expression of pituitary adenylate cyclase activating polypeptide (PACAP) was studied in the gastrointestinal tract (GI-tract) of normal rats using radioimmunoassay, chromatography, immunocytochemistry, and in situ hybridization. PACAP-38, PACAP-27, and PACAP-related peptide were demonstrated in all parts of the GI-tract, PACAP-38 being the predominant form confirmed by chromatography. PACAP-immunoreactive nerve fibers and nerve cell bodies were found in the myenteric ganglia throughout the GI-tract. PACAP-containing nerve cell bodies were also demonstrated in the submucous ganglia of the small and large intestine. The synthesis of PACAP in intrinsic neurons was confirmed by in situ hybridization. Double immunostaining showed that PACAP is present in calcitonin gene-related peptide-containing sensory nerve fibers as well as in vasoactive intestinal polypeptide (VIP)- or VIP/gastrin-releasing peptide (GRP)-containing (intramural) nerve fibers in the upper GI-tract and in anally projecting, intrinsic VIP-and VIP/nitric oxide syntase-containing nerve cell bodies and nerve fibers in the small and large intestine. Neonatal treatment with capsaicin significantly reduced the concentration of PACAP-38 in the esophagus, stomach, and colon. Extrinsic denervation decreased the PACAP-38 concentration in the stomach, while no change was observed in the small intestine. These results indicate that PACAP- immunoreactive nerve fibers in the GI-tract originate from both intrinsic (enteric) and extrinsic (presumably sensory) sources suggesting that PACAP may have diverse gastrointestinal functions.
Cell and Tissue Research 02/1998; 291(1):65-79. · 3.11 Impact Factor
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ABSTRACT: After unilateral adjuvant-induced inflammation, expression of neuropeptides believed to be involved in the inflammatory response, e.g. substance P and calcitonin gene-related peptide (CGRP), is upregulated in innervating sensory neurons. Islet amyloid polypeptide (IAPP) is structurally related to CGRP and constitutively expressed in sensory CGRP-containing neurons; the role of IAPP in sensory neurons is unknown. To examine whether IAPP could play a role in inflammation, IAPP expression in L5 dorsal root ganglion (DRG) and its distribution in the dorsal horn were investigated after unilateral adjuvant-induced inflammation in the rat paw and compared with CGRP, using in situ hybridization and immunocytochemistry. At 12 h and day 3, but not day 21, the percentage of nerve cell profiles expressing IAPP and CGRP mRNA was greater in the ipsilateral L5 DRG; these changes paralleled the occurrence of edema around the tarsotibial joint and a slight limp. IAPP expression in individual nerve cell profiles was higher in the ipsilateral L5 DRG at 12 h, but not at days 3 and 21; the corresponding CGRP mRNA level was higher at days 3 and 21. At day 3, the higher expression of IAPP and CGRP on the ipsilateral side was accompanied by increased numbers of immunoreactive DRG neurons and fibers in the spinal cord dorsal horn. Largely, expression of IAPP and CGRP seems to be co-ordinately regulated by localized inflammation, although the rapid, but transient, upregulation in DRG neurons of IAPP mRNA expression and the slower, but sustained, upregulation of CGRP mRNA expression may indicate dissociated regulation of the peptides. Thus, IAPP could play a role in the initial phase of localized inflammation.
Molecular Brain Research 11/1997; 50(1-2):127-35. · 2.00 Impact Factor
