Effect of iodine excess on morphology of mouse thyroid follicle and pancreatic acinar cells / 中华地方病学杂志

Objective To explore the effect of different levels of iodine excess on morphological changes of mouse thyroid follicle and pancreatic acinar cells.Methods Sixty female mice (BALB/c) were selected and their body weight were 18-22 g.The mice were divided into 6 groups according to body weight via the random number table method,10 mice in each group.Potassium iodate was added to drinking water in exposure groups with iodine contents of 300,600,1 200,2 400,and 4 800 μg/L,while normal group (control) was given normal levels of iodine (5 μg/L) tap water.After feeding for one month,the thyroid and pancreas of the mice were harvested,and the morphology of thyroid follicle and pancreatic acinar cells were observed through light microscope and ultrastructural changes of pancreas were observed through electron microscope.Results After one month of feeding,mice in the high iodine drinking water groups,starting from the 1 200 μg/L group,thyroid follicular cavity gradually enlarged and cells became flat;swollen and vacuolar-like deformation were observed in the mouse pancreas acinar cells under light microscope.Under the electron microscope,the ultrastructure of pancreatic acinar cells changed significantly starting from the 600 μg/L group,the number of zymogens decreased,organelle degeneration and necrosis,and endoplasmic reticulum expanded.Conclusion Iodine excess can cause damage to pancreatic acinar cells in mice.

Hydrogen peroxide attenuates refilling of intracellular calcium store in mouse pancreatic acinar cells

Intracellular calcium (Ca²⁺) oscillation is an initial event in digestive enzyme secretion of pancreatic acinar cells. Reactive oxygen species are known to be associated with a variety of oxidative stress-induced cellular disorders including pancreatitis. In this study, we investigated the effect of hydrogen peroxide (H₂O₂) on intracellular Ca²⁺ accumulation in mouse pancreatic acinar cells. Perfusion of H₂O₂ at 300 µM resulted in additional elevation of intracellular Ca²⁺ levels and termination of oscillatory Ca²⁺ signals induced by carbamylcholine (CCh) in the presence of normal extracellular Ca²⁺. Antioxidants, catalase or DTT, completely prevented H₂O₂-induced additional Ca²⁺ increase and termination of Ca²⁺ oscillation. In Ca²⁺-free medium, H₂O₂ still enhanced CCh-induced intracellular Ca²⁺ levels and thapsigargin (TG) mimicked H₂O₂-induced cytosolic Ca²⁺ increase. Furthermore, H₂O₂-induced elevation of intracellular Ca²⁺ levels was abolished under sarco/endoplasmic reticulum Ca²⁺ ATPase-inactivated condition by TG pretreatment with CCh. H₂O₂ at 300 µM failed to affect store-operated Ca²⁺ entry or Ca²⁺ extrusion through plasma membrane. Additionally, ruthenium red, a mitochondrial Ca²⁺ uniporter blocker, failed to attenuate H₂O₂-induced intracellular Ca²⁺ elevation. These results provide evidence that excessive generation of H₂O₂ in pathological conditions could accumulate intracellular Ca²⁺ by attenuating refilling of internal Ca²⁺ stores rather than by inhibiting Ca²⁺ extrusion to extracellular fluid or enhancing Ca²⁺ mobilization from extracellular medium in mouse pancreatic acinar cells.

Modelling the transition from simple to complex Ca2+oscillations in pancreatic acinar cells.

The worldwide increase in the use of antibiotics as an integral part of poultry and livestock production industry has recently received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria in human beings. To gauge the presence of the aforementioned scenario in the Indian context, a preliminary survey was conducted to assess the use of chlortetracycline (CTC) in 12 commercial layer farms and to quantify and confirm its residue in the egg. Samples of feed and eggs were collected at day 0 (prior to CTC addition), 3rd, 5th and 7th day during treatment and on the 9th and 14th day (2nd and 7th day after withdrawal of CTC) from each of the 12 commercial poultry farms studied. Concentration of CTC in feed was significantly (P<0.01) high on the 3rd, 5th and 7th day. On the 9th day and 14th day CTC concentration in feed was significantly (P<0.01) lower compared to the earlier 3 days studied. A highly significant difference (P<0.01) of the antibiotic residue in egg was observed in all the 5 days with high residual levels of CTC in egg. CTC in feed and its residue in egg were detected even on the 9th and 14th day respectively.

The Transcription Factor Mist1 Regulates the Cellular Polarity in Mouse Pancreatic Acinar Cells

Pancreatic acinar cells exhibit a polarity that is characterized by the localization of secretory granules at the apical membrane. However, the factors that regulate cellular polarity in these cells are not well understood. In this study, we investigated the effect of Mist1, a basic helix-loop-helix transcription factor, on the cellular architecture of pancreatic acinar cells. Mist1-null mice displayed secretory granules that were diffuse throughout the pancreatic acinar cells, from the apical to basolateral membranes, whereas Mist1 heterozygote mice showed apical localization of secretory granules. Deletion of the Mist1 gene decreased the expression of type 3 inositol 1,4,5-triphosphate receptors (IP3R) but did not affect apical localization and expression of IP3R2. Mist1-null mice also displayed an increase in luminal areas and an increase in the expression of zymogen granules in pancreatic acinar cells. These results suggest that Mist1 plays a critical role in polar localization of cellular organelles and in maintaining cellular architecture in mouse pancreatic acinar cells.

Role of Regulators of G-Protein Signaling 4 in Ca2+ Signaling in Mouse Pancreatic Acinar Cells

Regulators of G-protein signaling (RGS) proteins are regulators of Ca2+ signaling that accelerate the GTPase activity of the G-protein alpha-subunit. RGS1, RGS2, RGS4, and RGS16 are expressed in the pancreas, and RGS2 regulates G-protein coupled receptor (GPCR)-induced Ca2+ oscillations. However, the role of RGS4 in Ca2+ signaling in pancreatic acinar cells is unknown. In this study, we investigated the mechanism of GPCR-induced Ca2+ signaling in pancreatic acinar cells derived from RGS4-/- mice. RGS4-/- acinar cells showed an enhanced stimulus intensity response to a muscarinic receptor agonist in pancreatic acinar cells. Moreover, deletion of RGS4 increased the frequency of Ca2+ oscillations. RGS4-/- cells also showed increased expression of sarco/endoplasmic reticulum Ca2+ ATPase type 2. However, there were no significant alterations, such as Ca2+ signaling in treated high dose of agonist and its related amylase secretion activity, in acinar cells from RGS4-/- mice. These results indicate that RGS4 protein regulates Ca2+ signaling in mouse pancreatic acinar cells.

Membrane Proteome Analysis of Cerulein-Stimulated Pancreatic Acinar Cells: Implication for Early Event of Acute Pancreatitis

BACKGROUND/AIMS: Cerulein pancreatitis is similar to human edematous pancreatitis with dysregulation of the production and secretion of digestive enzymes, edema formation, cytoplasmic vacuolization and the death of acinar cells. We hypothesized that membrane proteins may be altered as the early event during the induction of acute pancreatitis. Present study aims to determine the differentially expressed proteins in the membranes of cerulein-treated pancreatic acinar cells. METHODS: Pancreatic acinar AR42J cells were treated with 10(-8) M cerulein for 1 hour. Membrane proteins were isolated from the cells and separated by two-dimensional electrophoresis using pH gradients of 5-8. Membrane proteins were identified by matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) analysis of the peptide digests. The differentially expressed proteins, whose expression levels were more or less than three-fold in cerulein-treated cells, were analyzed. RESULTS: Two differentially expressed proteins (mannan-binding lectin-associated serine protease-2, heat shock protein 60) were up-regulated while four proteins (protein disulfide isomerase, gamma-actin, isocitrate dehydrogenase 3, seven in absentia homolog 1A) were down-regulated by cerulein treatment in pancreatic acinar cells. These proteins are related to cell signaling, oxidative stress, and cytoskeleton arrangement. CONCLUSIONS: Oxidative stress may induce cerulein-induced cell injury and disturbances in defense mechanism in pancreatic acinar cells.

Ca2+ signaling in pancreatic acinar cells: physiology and pathophysiology

The pancreatic acinar cell is a classical model for studies of secretion and signal transduction mechanisms. Because of the extensive endoplasmic reticulum and the large granular compartment, it has been possible - by direct measurements - to obtain considerable insights into intracellular Ca2+ handling under both normal and pathological conditions. Recent studies have also revealed important characteristics of stimulus-secretion coupling mechanisms in isolated human pancreatic acinar cells. The acinar cells are potentially dangerous because of the high intra-granular concentration of proteases, which become inappropriately activated in the human disease acute pancreatitis. This disease is due to toxic Ca2+ signals generated by excessive liberation of Ca2+ from both the endoplasmic reticulum and the secretory granules.

NF-kB and cytokines in pancreatic acinar cells

Reactive oxygen species (ROS), generated by infiltrating neutrophils, are considered as an important regulator in the pathogenesis and deveolpment of pancreatitis. A hallmark of the inflammatory response is the induction of cytokine gene expression, which may be regulated by oxidant-sensitive transcription factor, nuclear factor-kappaB (NF-KB). Present study aims to investigate whether neutrophils primed by 4beta-phorbol 12beta-myristate 13alpha-acetate (PMA) affect the productions of H2O2 and lipid peroxide (LPO), NF-kappaB activation and cytokine production in pancreatic acinar cells, and whether these alterations were inhibited by N-acetylcysteine (NAC) and superoxide dismutase (SOD). ROS generation in neutrophils increased by PMA, which was inhibited by NAC and SOD. The productions of H2O2, LPO and TNF-alpha were increased with the amounts of PMA-primed neutrophils added to acinar cells while the productions of H2O2, LPO and cytokines increased with time. PMA-primed neutrophils resulted in the activation of two species of NF-kappaB dimers (a p50/p65 heterodimer and a p50 homodimer). Both NAC and SOD inhibited neutrophil-induced alterations in acinar cells. In conclusion, ROS, generated by neutrophils, activates NF-kappaB, resulting in upregulation of inflammatory cytokines in acinar cells. Antioxidants such as NAC might be clinically useful antiinflammatory agents by inhibiting oxidant-mediated activation of NF-KB and decreasing cytokine production.

Modulation of InsP3 receptor properties by phosphorylation: targeting of PKA to InsP3 receptors shapes oscillatory calcium signals in pancreatic acinar cells

No abstract available.