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Silencing Mist1 Gene Expression Is Essential for Recovery from Acute Pancreatitis.

Karki A, Humphrey SE, Steele RE, Hess DA, Taparowsky EJ, Konieczny SF - PLoS ONE (2015)

Bottom Line: Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses.We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells.The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, the Purdue Center for Cancer Research, and the Bindley Bioscience Center, Purdue University, West Lafayette, IN, 47907-2057, United States of America.

ABSTRACT
Acinar cells of the exocrine pancreas are tasked with synthesizing, packaging and secreting vast quantities of pro-digestive enzymes to maintain proper metabolic homeostasis for the organism. Because the synthesis of high levels of hydrolases is potentially dangerous, the pancreas is prone to acute pancreatitis (AP), a disease that targets acinar cells, leading to acinar-ductal metaplasia (ADM), inflammation and fibrosis-events that can transition into the earliest stages of pancreatic ductal adenocarcinoma. Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses. In this study, we examined the importance of the acinar-specific maturation transcription factor MIST1 to AP damage and organ recovery. Analysis of wild-type and Mist1 conditional mice revealed that Mist1 gene transcription and protein accumulation were dramatically reduced as acinar cells underwent ADM alterations during AP episodes. To test if loss of MIST1 function was primarily responsible for the damaged status of the organ, mice harboring a Cre-inducible Mist1 transgene (iMist1) were utilized to determine if sustained MIST1 activity could alleviate AP damage responses. Unexpectedly, constitutive iMist1 expression during AP led to a dramatic increase in organ damage followed by acinar cell death. We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells. The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

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The Mist1 gene is transcriptionally silenced during acute pancreatitis.(A) Analysis of MIST1 (arrows) in Mist1CreERT/+ pancreata. Damaged acinar cells exhibit greatly reduced MIST1 levels that recover by 10d post-AP. (B) MIST1 immunoblot analysis of Mist1CreERT/+ pancreata over the indicated post-AP time points. HSP90 was used as a loading control. Relative expression levels are indicated below the MIST1 panel, normalized to the corresponding HSP90 signal. (C) RT-qPCR analysis of Mist1 gene expression during AP damage and recovery. (D) RT-qPCR of MIST1 gene targets during AP. *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001.
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pone.0145724.g002: The Mist1 gene is transcriptionally silenced during acute pancreatitis.(A) Analysis of MIST1 (arrows) in Mist1CreERT/+ pancreata. Damaged acinar cells exhibit greatly reduced MIST1 levels that recover by 10d post-AP. (B) MIST1 immunoblot analysis of Mist1CreERT/+ pancreata over the indicated post-AP time points. HSP90 was used as a loading control. Relative expression levels are indicated below the MIST1 panel, normalized to the corresponding HSP90 signal. (C) RT-qPCR analysis of Mist1 gene expression during AP damage and recovery. (D) RT-qPCR of MIST1 gene targets during AP. *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001.

Mentions: The major phenotype associated with caerulein-induced AP is loss of acinar cell integrity [22, 69–71]. Because the transcription factor MIST1 is critical for maintaining acinar cell polarity and function, we examined if MIST1 protein accumulation was altered in AP mice. As shown in Fig 2A and 2B, high levels of MIST1 protein were detected in all control acinar cells, whereas duct and islet cells remained MIST1 negative (S2 Fig). However, in AP mice, Mist1 transcripts and protein were rapidly lost in damaged acinar cells (Fig 2A–2C). The absence of MIST1 was observed 6h-2d post-AP during the period corresponding to the major time frame for ADM lesion induction. Nonetheless, as mouse acinar cells recovered (4d-10d post-AP), Mist1 transcript and protein levels greatly increased, achieving levels that were comparable to those observed in control acinar cells. The transient change in Mist1 transcripts and protein during the AP response was also reflected in the expression profiles of known MIST1 target genes [33, 44, 56]. Transcripts from MIST1-induced genes Atp2c2, Copz2 and Rab3d were reduced during the 6h-2d post-AP period while transcripts from MIST1-repressed genes (e.g., Rnd2) were up-regulated (Fig 2D). Thus, transient silencing of Mist1 influences a number of key events associated with acinar cell integrity. These results suggest that the process of silencing and then re-expressing Mist1 may be critical in allowing the exocrine pancreas to properly recover from an acute pancreatitis episode.


Silencing Mist1 Gene Expression Is Essential for Recovery from Acute Pancreatitis.

Karki A, Humphrey SE, Steele RE, Hess DA, Taparowsky EJ, Konieczny SF - PLoS ONE (2015)

The Mist1 gene is transcriptionally silenced during acute pancreatitis.(A) Analysis of MIST1 (arrows) in Mist1CreERT/+ pancreata. Damaged acinar cells exhibit greatly reduced MIST1 levels that recover by 10d post-AP. (B) MIST1 immunoblot analysis of Mist1CreERT/+ pancreata over the indicated post-AP time points. HSP90 was used as a loading control. Relative expression levels are indicated below the MIST1 panel, normalized to the corresponding HSP90 signal. (C) RT-qPCR analysis of Mist1 gene expression during AP damage and recovery. (D) RT-qPCR of MIST1 gene targets during AP. *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001.
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Related In: Results  -  Collection

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pone.0145724.g002: The Mist1 gene is transcriptionally silenced during acute pancreatitis.(A) Analysis of MIST1 (arrows) in Mist1CreERT/+ pancreata. Damaged acinar cells exhibit greatly reduced MIST1 levels that recover by 10d post-AP. (B) MIST1 immunoblot analysis of Mist1CreERT/+ pancreata over the indicated post-AP time points. HSP90 was used as a loading control. Relative expression levels are indicated below the MIST1 panel, normalized to the corresponding HSP90 signal. (C) RT-qPCR analysis of Mist1 gene expression during AP damage and recovery. (D) RT-qPCR of MIST1 gene targets during AP. *p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001.
Mentions: The major phenotype associated with caerulein-induced AP is loss of acinar cell integrity [22, 69–71]. Because the transcription factor MIST1 is critical for maintaining acinar cell polarity and function, we examined if MIST1 protein accumulation was altered in AP mice. As shown in Fig 2A and 2B, high levels of MIST1 protein were detected in all control acinar cells, whereas duct and islet cells remained MIST1 negative (S2 Fig). However, in AP mice, Mist1 transcripts and protein were rapidly lost in damaged acinar cells (Fig 2A–2C). The absence of MIST1 was observed 6h-2d post-AP during the period corresponding to the major time frame for ADM lesion induction. Nonetheless, as mouse acinar cells recovered (4d-10d post-AP), Mist1 transcript and protein levels greatly increased, achieving levels that were comparable to those observed in control acinar cells. The transient change in Mist1 transcripts and protein during the AP response was also reflected in the expression profiles of known MIST1 target genes [33, 44, 56]. Transcripts from MIST1-induced genes Atp2c2, Copz2 and Rab3d were reduced during the 6h-2d post-AP period while transcripts from MIST1-repressed genes (e.g., Rnd2) were up-regulated (Fig 2D). Thus, transient silencing of Mist1 influences a number of key events associated with acinar cell integrity. These results suggest that the process of silencing and then re-expressing Mist1 may be critical in allowing the exocrine pancreas to properly recover from an acute pancreatitis episode.

Bottom Line: Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses.We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells.The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, the Purdue Center for Cancer Research, and the Bindley Bioscience Center, Purdue University, West Lafayette, IN, 47907-2057, United States of America.

ABSTRACT
Acinar cells of the exocrine pancreas are tasked with synthesizing, packaging and secreting vast quantities of pro-digestive enzymes to maintain proper metabolic homeostasis for the organism. Because the synthesis of high levels of hydrolases is potentially dangerous, the pancreas is prone to acute pancreatitis (AP), a disease that targets acinar cells, leading to acinar-ductal metaplasia (ADM), inflammation and fibrosis-events that can transition into the earliest stages of pancreatic ductal adenocarcinoma. Despite a wealth of information concerning the broad phenotype associated with pancreatitis, little is understood regarding specific transcriptional regulatory networks that are susceptible to AP and the role these networks play in acinar cell and exocrine pancreas responses. In this study, we examined the importance of the acinar-specific maturation transcription factor MIST1 to AP damage and organ recovery. Analysis of wild-type and Mist1 conditional mice revealed that Mist1 gene transcription and protein accumulation were dramatically reduced as acinar cells underwent ADM alterations during AP episodes. To test if loss of MIST1 function was primarily responsible for the damaged status of the organ, mice harboring a Cre-inducible Mist1 transgene (iMist1) were utilized to determine if sustained MIST1 activity could alleviate AP damage responses. Unexpectedly, constitutive iMist1 expression during AP led to a dramatic increase in organ damage followed by acinar cell death. We conclude that the transient silencing of Mist1 expression is critical for acinar cells to survive an AP episode, providing cells an opportunity to suppress their secretory function and regenerate damaged cells. The importance of MIST1 to these events suggests that modulating key pancreas transcription networks could ease clinical symptoms in patients diagnosed with pancreatitis and pancreatic cancer.

Show MeSH
Related in: MedlinePlus