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Exocrine pancreas ER stress differentially induced by different fatty acids.
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Abstracts / Pancreatology 14 (2014) S1eS129
O-32. Exocrine pancreas ER stress differentially induced by different fatty acids. Ruth Birk a, Hila Danino a, Karin Ben-Dor a a
Department of Nutrition, Faculty of Health Science, Ariel University, Israel
Background: High dietary fat consumption, typical to obesity, is a risk factor and has a role in the etiology of pancreatitis and pancreatic cancer. Overload of dietary fatty acids (FAs) in non-adipose tissues is associated with cellular dysfunction, ER stress and cell death. Aims: We studies chronic and acute exposure of different FAs on exocrine acinar cells stress. Materials & methods: AR42J cells were challenged with different FAs for chronic and acute periods and cellular stress markers were studied. Results: We demonstrate that saturated FAs chronic overload induce an acinar cell lipotoxic effect expressed in triglycerides accumulation and prompted apoptotic process. As the effect of different dietary FAs on the exocrine pancreas ER stress response is unknown, we further studied the effect of acute challenge of different types of FAs (saturated, mono and poly-unsaturated) at normal and overload concentrations (typical to obesity) on fat accumulation and ER stress indicators (XBP splicing, UPR transcripts, immunohistochemistry) in exocrine pancreas acinar (AR42J) cells. We show that pancreatic acinar cells acutely challenged with different FAs exhibit significantly increased triglycerides accumulation. Acute challenge with saturated FA in high concentration significantly increased stress levels, reflected by increased expression levels of inflammatory (TNF-a and TGFb), apoptotic and ER stress markers (Xbp1, CHOP, Bip and Xbp splicing). Treatment with mono and poly-unsaturated FAs did not significantly alter these markers. Conclusion: We demonstrate that different FAs affect acinar cell stress and might exacerbate pancreatic pathologies in dietary fat overload, typical to obesity. The differential effect of the various FAs could have potential nutritional implications.
O-33. Acinar cell secretion is necessary for acinar cell de-differentiation during pancreatic regeneration Enrica Saponara, Sabrina Sonda, Kamile Grabliauskaite, Theresia Reding, Yingua Tian, Rolf Graf Swiss HPB Centre, Visceral & Transplantation Surgery, University Hospital Zurich, Switzerland Background: Pancreatic regeneration following pancreatitis is characterized by a transient acinar cell de-differentiation with loss of zymogens, up-regulation of progenitor cell markers and proliferation. Aims: We previously demonstrated that serotonin (5-hydroxytryptamine, 5-HT) is essential for zymogen secretion. We now investigated whether 5-HT-dependent secretion is necessary to allow loss of zymogens, acinar cell de-differentiation and proliferation during organ regeneration. Materials & methods: The potential of pancreatic acinar cells to dedifferentiate and replicate following cerulein-induced pancreatitis was compared in wild type (WT) mice, mice deficient in peripheral 5-HT (tryptophan hydroxylase 1 knocked-out, TPH-1-/-) and WT mice treated with the 5-HT precursor 5-hydroxythryptophan (5-HTP). In addition, the role of secretion in acinar replication was evaluated during pancreatic regeneration following 60% pancreatectomy, which is not dependent on substantial acinar de-differentiation. Results: During experimental pancreatitis, the observed down-regulation of amylase transcripts was not followed by loss of amylase in TPH-1-/mice. Up-regulation of progenitor cell markers and acinar proliferation were impaired in these animals compared with WT mice. On the contrary, progenitor cell marker expression increased following stimulation of zymogen secretion with 5-HTP, both in healthy and cerulein-treated WT mice. One week after 60% pancreatectomy, the level of zymogen loss and
acinar de-differentiation was minimal and acinar replication was comparable in WT and TPH-1-/- mice. Conclusion: Our results indicate that zymogen secretion is the underlying mechanism regulating acinar cell de-differentiation and replication during regeneration. We also demonstrate that 5-HT and its precursor 5-HTP are not direct mitogens for acinar cells, but are required for acinar de-differentiation by stimulating zymogen secretion.
O-34. Lymphotoxin promotes acinar cell reprogramming and accelerates pre-neoplastic conversion in Kras induced pancreatic tumorigenesis Gitta Maria Seleznik a, Theresia Reding a, Sabrina Sonda a, Mathias Heikenwalder b, Rolf Graf a a
Swiss HPB Center, Visceral & Transplantation Surgery, University Hospital Zurich, Switzerland b €t München Helmholtz Institute of Virology, Technische Universita Zentrum München, Munich, Germany Background: Pancreatic inflammation is a well-known risk factor for pancreatic ductal adenocarcinoma (PDAC) development in humans. PDAC initiation is linked to activating mutations in KRAS oncogene. Pancreatic acinar cell transdifferentiation results in acinar-to-ductal metaplasia (ADM), which can give rise to pancreatic intraepithelial neoplasia (PanIN), the most common PDAC precursor. Aims: To explore the inflammatory mechanisms promoting ADM and PanIN development. Materials & methods: We established a new genetic model (LTKP) by intercrossing the p48+/Cre;Kras+/G12D (KP) model for pancreatic tumorigenesis, to a transgenic mouse developing spontaneous pancreatitis, due to Lymphotoxin (LT) overexpression. Immunohistochemistry and RT-PCR were used to obtain an inflammatory signature. In-vitro transdifferentiation experiments were performed to investigate the role of LT in ADM development. Results: Lymphotoxin overexpression in mice harbouring a constitutively active form of Kras mutation in the pancreas (LTKP) dramatically accelerates the development of premalignant PanIN lesions compared to KP animals. Already after 6 weeks of age highly proliferating cells, extensive ADM and PanIN development are observed in LTKP mice. This coincides with a significant upregulation of inflammatory genes and increased activated (GTP-bound) Kras. These molecular and phenotypic changes are only observed around 16 weeks of age in Kras animals. In vitro experiments show that LT overexpression in wt acinar cells is sufficient to initiate spontaneous transdifferentiation. Furthermore, acinar cells derived from LTKP-animals form ADMs significantly faster than acini from KP animals. Conclusion: We conclude that Lymphotoxin may contribute to the initiation of spontaneous and pancreatitis-accelerated PDAC precursor formation: By (1) inducing inflammatory environment and by (2) regulating acinar cell transdifferentiation, leading to accelerated pre-malignant PanIN lesion development.
Abstracts / Pancreatology 14 (2014) S1eS129
O-32. Exocrine pancreas ER stress differentially induced by different fatty acids. Ruth Birk a, Hila Danino a, Karin Ben-Dor a a
Department of Nutrition, Faculty of Health Science, Ariel University, Israel
Background: High dietary fat consumption, typical to obesity, is a risk factor and has a role in the etiology of pancreatitis and pancreatic cancer. Overload of dietary fatty acids (FAs) in non-adipose tissues is associated with cellular dysfunction, ER stress and cell death. Aims: We studies chronic and acute exposure of different FAs on exocrine acinar cells stress. Materials & methods: AR42J cells were challenged with different FAs for chronic and acute periods and cellular stress markers were studied. Results: We demonstrate that saturated FAs chronic overload induce an acinar cell lipotoxic effect expressed in triglycerides accumulation and prompted apoptotic process. As the effect of different dietary FAs on the exocrine pancreas ER stress response is unknown, we further studied the effect of acute challenge of different types of FAs (saturated, mono and poly-unsaturated) at normal and overload concentrations (typical to obesity) on fat accumulation and ER stress indicators (XBP splicing, UPR transcripts, immunohistochemistry) in exocrine pancreas acinar (AR42J) cells. We show that pancreatic acinar cells acutely challenged with different FAs exhibit significantly increased triglycerides accumulation. Acute challenge with saturated FA in high concentration significantly increased stress levels, reflected by increased expression levels of inflammatory (TNF-a and TGFb), apoptotic and ER stress markers (Xbp1, CHOP, Bip and Xbp splicing). Treatment with mono and poly-unsaturated FAs did not significantly alter these markers. Conclusion: We demonstrate that different FAs affect acinar cell stress and might exacerbate pancreatic pathologies in dietary fat overload, typical to obesity. The differential effect of the various FAs could have potential nutritional implications.
O-33. Acinar cell secretion is necessary for acinar cell de-differentiation during pancreatic regeneration Enrica Saponara, Sabrina Sonda, Kamile Grabliauskaite, Theresia Reding, Yingua Tian, Rolf Graf Swiss HPB Centre, Visceral & Transplantation Surgery, University Hospital Zurich, Switzerland Background: Pancreatic regeneration following pancreatitis is characterized by a transient acinar cell de-differentiation with loss of zymogens, up-regulation of progenitor cell markers and proliferation. Aims: We previously demonstrated that serotonin (5-hydroxytryptamine, 5-HT) is essential for zymogen secretion. We now investigated whether 5-HT-dependent secretion is necessary to allow loss of zymogens, acinar cell de-differentiation and proliferation during organ regeneration. Materials & methods: The potential of pancreatic acinar cells to dedifferentiate and replicate following cerulein-induced pancreatitis was compared in wild type (WT) mice, mice deficient in peripheral 5-HT (tryptophan hydroxylase 1 knocked-out, TPH-1-/-) and WT mice treated with the 5-HT precursor 5-hydroxythryptophan (5-HTP). In addition, the role of secretion in acinar replication was evaluated during pancreatic regeneration following 60% pancreatectomy, which is not dependent on substantial acinar de-differentiation. Results: During experimental pancreatitis, the observed down-regulation of amylase transcripts was not followed by loss of amylase in TPH-1-/mice. Up-regulation of progenitor cell markers and acinar proliferation were impaired in these animals compared with WT mice. On the contrary, progenitor cell marker expression increased following stimulation of zymogen secretion with 5-HTP, both in healthy and cerulein-treated WT mice. One week after 60% pancreatectomy, the level of zymogen loss and
acinar de-differentiation was minimal and acinar replication was comparable in WT and TPH-1-/- mice. Conclusion: Our results indicate that zymogen secretion is the underlying mechanism regulating acinar cell de-differentiation and replication during regeneration. We also demonstrate that 5-HT and its precursor 5-HTP are not direct mitogens for acinar cells, but are required for acinar de-differentiation by stimulating zymogen secretion.
O-34. Lymphotoxin promotes acinar cell reprogramming and accelerates pre-neoplastic conversion in Kras induced pancreatic tumorigenesis Gitta Maria Seleznik a, Theresia Reding a, Sabrina Sonda a, Mathias Heikenwalder b, Rolf Graf a a
Swiss HPB Center, Visceral & Transplantation Surgery, University Hospital Zurich, Switzerland b €t München Helmholtz Institute of Virology, Technische Universita Zentrum München, Munich, Germany Background: Pancreatic inflammation is a well-known risk factor for pancreatic ductal adenocarcinoma (PDAC) development in humans. PDAC initiation is linked to activating mutations in KRAS oncogene. Pancreatic acinar cell transdifferentiation results in acinar-to-ductal metaplasia (ADM), which can give rise to pancreatic intraepithelial neoplasia (PanIN), the most common PDAC precursor. Aims: To explore the inflammatory mechanisms promoting ADM and PanIN development. Materials & methods: We established a new genetic model (LTKP) by intercrossing the p48+/Cre;Kras+/G12D (KP) model for pancreatic tumorigenesis, to a transgenic mouse developing spontaneous pancreatitis, due to Lymphotoxin (LT) overexpression. Immunohistochemistry and RT-PCR were used to obtain an inflammatory signature. In-vitro transdifferentiation experiments were performed to investigate the role of LT in ADM development. Results: Lymphotoxin overexpression in mice harbouring a constitutively active form of Kras mutation in the pancreas (LTKP) dramatically accelerates the development of premalignant PanIN lesions compared to KP animals. Already after 6 weeks of age highly proliferating cells, extensive ADM and PanIN development are observed in LTKP mice. This coincides with a significant upregulation of inflammatory genes and increased activated (GTP-bound) Kras. These molecular and phenotypic changes are only observed around 16 weeks of age in Kras animals. In vitro experiments show that LT overexpression in wt acinar cells is sufficient to initiate spontaneous transdifferentiation. Furthermore, acinar cells derived from LTKP-animals form ADMs significantly faster than acini from KP animals. Conclusion: We conclude that Lymphotoxin may contribute to the initiation of spontaneous and pancreatitis-accelerated PDAC precursor formation: By (1) inducing inflammatory environment and by (2) regulating acinar cell transdifferentiation, leading to accelerated pre-malignant PanIN lesion development.