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Dexamethasone induces NPY expression in insulin-producing RINm5F cells: Evidence for constitutive release of NPY and impaired insulin secretion
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Abstracts from the 11 th International Symposium on Regulatory Peptides
Dexamethasone induces NPY expression in insulin-producing RINm5F cells: Evidence for constitutive release of NPY and impaired insulin secretion. Ulrika Myrs6n, IBo Ahr6n and Frank Sundler Departments of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, Lund and 1Medicine, Malm6, University of Lund, Sweden We have previously shown that treatment of rats with dexamethasone (DEX) induces NPY expression in pancreatic [3 cells. In this study we examined the effect of the steroid on NPY expression in the insulin producing cell line RINm5F. Cells were cultured for 5 days in 24-well plates and on slides with and without DEX (10TM). Aliquots of the culture media were taken dally and assayed for insulin and NPY. In situ hybridization for NPY mRNA was performed each day of the period studied. NPY mRNA could not be detected in cells cultured without DEX. When cultured with DEX the frequency of cells expressing NPY mRNA increased gradually and after 5 days, NPY mRNA was abundantly expressed in the vast majority of cells. RIA analysis of the culture media revealed a time dependent increase of NPY levels and a simultaneous decrease of insulin levels when cells were cultured with DEX. In the absence of DEX, NPY was not detected and insulin levels were steady. Acute stimulation of cells cultured for 5 days in the presence of DEX revealed an augmented insulin secretion in response to glyceraldehyde (GA; 10mM) and KCI (20mM), though at lower levels when compared to cells cultured without DEX. This augmentation was abolished upon removal of extracellular Ca . In contrast, neither stimulation with GA or KCI nor removal of Ca 2÷ affected the release of NPY from RIN m5F cells cultured with DEX. In conclusion; 1) DEX induces expression of the NPY gene in insulin producing RINm5F cells by a direct effect concomitant with a reduction of insulin secretion and 2) secretion of the formed NPY is not subject to regulation in parallel with that of insulin. Thus, RINm5F cells display steroid-sensitive plasticity The data suggest that the upregulated NPY could have an inhibitory effect on insulin secretion by autocrine or paracrine mechanisms. Finally, the results suggest that a constitutive rather than a regulated pathway accounts for secretion of NPY.
Expression of NPY, PYY, PP and their coexistence with other islet hormones during development of the rat pancreas. Ulrika Myrs6n, Eva Ekblad and Frank Sundler. Dept of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, University of Lund, Sweden. Members of the neuropeptide Y (NPY) family of regulatory peptides [NPY, peptide YY (PYY) and pancreatic polypeptide (PP)] have been suggested to play an important role in the development of the endocrine pancreas. The rat endocrine pancreas from embryonic (E) day 12 until 30 days postpartum (P) was studied with emphasis on NPY, PYY and PP using single and double immunocytochemistry and in situ hybridization. Already at E 12, PYY was detected together with both insulin and glueagon, distributed in small clusters of cells. At this stage PYY, insulin and glucagon were found to be colocalised within the same cells. At E 15 insulin and glucagon started to separate into distinct cell populations and at E 16 most of the insulin-immunoreactive (IR) cells were separated from the PYWglucagon-IR cells. Interestingly, at E 16 NPY mRNA appeared in a few, scattered endocrine cells. NPY-IR endocrine cells were however, fn-st detected at E 17. Virtually all NPY-IR endocrine cells were insulin containing [3 cells. At E 18 the endocrine cells started to form typical islets with centrally located insulin/NPY-IR cells surrounded by glucagon/PYY-IR cells. At E 20-21, the number of NPY-IR endocrine cells increased and the vast majority of these cells contained insulin. However, immediately after birth (day 0) NPY mRNA disappeared from the islet cells. The number and immunostaining intensity of NPY-IR islet cells rapidly declined postnatally, being non-detectable at P5. Cells containing PP immunoreactivity and PP mRNA were first detected perinatally. The adult pattern of NPY, PYY and PP distribution within the islets (NPY confined to neuronal elements, PYY and PP exclusively in endocrine cells) was established at PI4. In the adult rat, treatment with the glucocorticoid dexamethasone induces NPY expression preferentially in the islet [3 cells. The 13 cell expression of NPY during the latter part of gestation coincides with high serum levels of free glucocorticoid and rapid cell replication and could indicate a role for NPY in the transition to a mature regulation of insulin secretion, which occurs in the neonatal period.
Abstracts from the 11 th International Symposium on Regulatory Peptides
Dexamethasone induces NPY expression in insulin-producing RINm5F cells: Evidence for constitutive release of NPY and impaired insulin secretion. Ulrika Myrs6n, IBo Ahr6n and Frank Sundler Departments of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, Lund and 1Medicine, Malm6, University of Lund, Sweden We have previously shown that treatment of rats with dexamethasone (DEX) induces NPY expression in pancreatic [3 cells. In this study we examined the effect of the steroid on NPY expression in the insulin producing cell line RINm5F. Cells were cultured for 5 days in 24-well plates and on slides with and without DEX (10TM). Aliquots of the culture media were taken dally and assayed for insulin and NPY. In situ hybridization for NPY mRNA was performed each day of the period studied. NPY mRNA could not be detected in cells cultured without DEX. When cultured with DEX the frequency of cells expressing NPY mRNA increased gradually and after 5 days, NPY mRNA was abundantly expressed in the vast majority of cells. RIA analysis of the culture media revealed a time dependent increase of NPY levels and a simultaneous decrease of insulin levels when cells were cultured with DEX. In the absence of DEX, NPY was not detected and insulin levels were steady. Acute stimulation of cells cultured for 5 days in the presence of DEX revealed an augmented insulin secretion in response to glyceraldehyde (GA; 10mM) and KCI (20mM), though at lower levels when compared to cells cultured without DEX. This augmentation was abolished upon removal of extracellular Ca . In contrast, neither stimulation with GA or KCI nor removal of Ca 2÷ affected the release of NPY from RIN m5F cells cultured with DEX. In conclusion; 1) DEX induces expression of the NPY gene in insulin producing RINm5F cells by a direct effect concomitant with a reduction of insulin secretion and 2) secretion of the formed NPY is not subject to regulation in parallel with that of insulin. Thus, RINm5F cells display steroid-sensitive plasticity The data suggest that the upregulated NPY could have an inhibitory effect on insulin secretion by autocrine or paracrine mechanisms. Finally, the results suggest that a constitutive rather than a regulated pathway accounts for secretion of NPY.
Expression of NPY, PYY, PP and their coexistence with other islet hormones during development of the rat pancreas. Ulrika Myrs6n, Eva Ekblad and Frank Sundler. Dept of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, University of Lund, Sweden. Members of the neuropeptide Y (NPY) family of regulatory peptides [NPY, peptide YY (PYY) and pancreatic polypeptide (PP)] have been suggested to play an important role in the development of the endocrine pancreas. The rat endocrine pancreas from embryonic (E) day 12 until 30 days postpartum (P) was studied with emphasis on NPY, PYY and PP using single and double immunocytochemistry and in situ hybridization. Already at E 12, PYY was detected together with both insulin and glueagon, distributed in small clusters of cells. At this stage PYY, insulin and glucagon were found to be colocalised within the same cells. At E 15 insulin and glucagon started to separate into distinct cell populations and at E 16 most of the insulin-immunoreactive (IR) cells were separated from the PYWglucagon-IR cells. Interestingly, at E 16 NPY mRNA appeared in a few, scattered endocrine cells. NPY-IR endocrine cells were however, fn-st detected at E 17. Virtually all NPY-IR endocrine cells were insulin containing [3 cells. At E 18 the endocrine cells started to form typical islets with centrally located insulin/NPY-IR cells surrounded by glucagon/PYY-IR cells. At E 20-21, the number of NPY-IR endocrine cells increased and the vast majority of these cells contained insulin. However, immediately after birth (day 0) NPY mRNA disappeared from the islet cells. The number and immunostaining intensity of NPY-IR islet cells rapidly declined postnatally, being non-detectable at P5. Cells containing PP immunoreactivity and PP mRNA were first detected perinatally. The adult pattern of NPY, PYY and PP distribution within the islets (NPY confined to neuronal elements, PYY and PP exclusively in endocrine cells) was established at PI4. In the adult rat, treatment with the glucocorticoid dexamethasone induces NPY expression preferentially in the islet [3 cells. The 13 cell expression of NPY during the latter part of gestation coincides with high serum levels of free glucocorticoid and rapid cell replication and could indicate a role for NPY in the transition to a mature regulation of insulin secretion, which occurs in the neonatal period.