Irreversible failure of pancreatic β-cells is the main culprit in the pathophysiology of diabetes, a disease that is now a global epidemic. Recently, elevated plasma levels of deoxysphingolipids, including 1-deoxysphinganine, have been identified as a novel biomarker for the disease. In this study, we analyzed whether deoxysphingolipids directly compromise the functionality of insulin-producing Ins-1 cells and primary islets. Treatment with 1-deoxysphinganine induced dose-dependent cytotoxicity with senescent, necrotic, and apoptotic characteristics and compromised glucose-stimulated insulin secretion. In addition, 1-deoxysphinganine altered cytoskeleton dynamics, resulting in intracellular accumulation of filamentous actin and activation of the Rho family GTPase Rac1. Moreover, 1-deoxysphinganine selectively upregulated ceramide synthase 5 expression and was converted to 1-deoxy-dihydroceramides without altering normal ceramide levels. Inhibition of intracellular 1-deoxysphinganine trafficking and ceramide synthesis improved the viability of the cells, indicating that the intracellular metabolites of 1-deoxysphinganine contribute to its cytotoxicity. Analyses of signaling pathways identified Jun N-terminal kinase and p38 mitogen-activated protein kinase as antagonistic effectors of cellular senescence. The results revealed that 1-deoxysphinganine is a cytotoxic lipid for insulin-producing cells, suggesting that the increased levels of this sphingolipid observed in diabetic patients may contribute to the reduced functionality of pancreatic β-cells. Thus, targeting deoxysphingolipid synthesis may complement the currently available therapies for diabetes.

ALPPS, a novel two-staged hepatectomy, accelerates liver regeneration, thereby helping to treat patients with otherwise unresectable liver tumors. The molecular mechanisms behind this accelerated regeneration are unknown. Here, we elucidate that Indian hedgehog, a secreted ligand important for fetal development, is a crucial mediator of the regenerative acceleration triggered by ALPPS surgery.

BACKGROUND AND PURPOSEPancreatitis is a common inflammation of the pancreas with rising incidence in many countries. Despite improvements in diagnostic techniques, the disease is associated with high risk of severe morbidity and mortality and there is an urgent need for new therapeutic interventions. In this study, we evaluated whether histone deacetylases (HDACs), key epigenetic regulators of gene transcription, are involved in the development of the disease. EXPERIMENTAL APPROACHWe analysed HDAC regulation during cerulein-induced acute, chronic and autoimmune pancreatitis using different transgenic mouse models. The functional relevance of class I HDACs was tested with the selective inhibitor MS-275 in vivo upon pancreatitis induction and in vitro in activated macrophages and primary acinar cell explants. KEY RESULTSHDAC expression and activity were up-regulated in a time-dependent manner following induction of pancreatitis, with the highest abundance observed for class I HDACs. Class I HDAC inhibition did not prevent the initial acinar cell damage. However, it effectively reduced the infiltration of inflammatory cells, including macrophages and T cells, in both acute and chronic phases of the disease, and directly disrupted macrophage activation. In addition, MS-275 treatment reduced DNA damage in acinar cells and limited acinar de-differentiation into acinar-to-ductal metaplasia in a cell-autonomous manner by impeding the EGF receptor signalling axis. CONCLUSIONS AND IMPLICATIONSThese results demonstrate that class I HDACs are critically involved in the development of acute and chronic forms of pancreatitis and suggest that blockade of class I HDAC isoforms is a promising target to improve the outcome of the disease. IntroductionAbnormal activity of histone deacetylases (HDACs), a family of enzymes involved in the epigenetic control of gene transcription, has been implicated in the aetiology and development of several malignancies. However, recent evidence indicates that HDACs are also involved in the development of inflammatory diseases, highlighting the potential of targeting the activity of HDACs as a therapeutic approach to improve the outcome of rheumatoid arthritis (Choo et al., 2010(Choo et al., , 2013, neuritis (Zhang et al., 2010;Zhang and Schluesener, 2013), cholitis (Felice et al., 2015) and autoimmunity (Hancock et al., 2012).HDACs control the acetylation status of histone and non-histone proteins, thus regulating the expression of target genes (reviewed in Delcuve et al., 2012). The complexity of acetylation-based epigenetic regulation is reflected by the size of the mammalian HDAC family, composed of 11 zinc-dependent enzymes divided into three subfamilies (classes I, II and IV) and seven NAD-dependent enzymes in a fourth (sirtuin) subfamily (class III), with non-redundant functions.The function of HDAC subfamilies in the pathophysiology of pancreatitis, a highly debilitating inflammatory disease with a potentially lethal outcome, has not been thoroughly investigated. During pancreatitis, the ...

Determining signalling pathways that regulate pancreatic regeneration following pancreatitis is critical for implementing therapeutic interventions. In this study we elucidated the molecular mechanisms underlying the effects of transforming growth factor-β (TGFβ) in pancreatic epithelial cells during tissue regeneration. To this end, we conditionally inactivated TGFβ receptor II (TGFβ-RII) using a Cre-LoxP system under the control of pancreas transcription factor 1a (PTF1a) promoter, specific for the pancreatic epithelium, and evaluated the molecular and cellular changes in a mouse model of cerulein-induced pancreatitis. We show that TGFβ-RII signalling does not mediate the initial acinar cell damage observed at the onset of pancreatitis. However, TGFβ-RII signalling not only restricts acinar cell replication during the regenerative phase of the disease but also limits ADM formation in vivo and in vitro in a cell-autonomous manner. Analyses of molecular mechanisms underlying the observed phenotype revealed that TGFβ-RII signalling stimulates the expression of cyclin-dependent kinase inhibitors and intersects with the EGFR signalling axis. Finally, TGFβ-RII ablation in epithelial cells resulted in increased infiltration of inflammatory cells in the early phases of pancreatitis and increased activation of pancreatic stellate cells in the later stages of pancreatitis, thus highlighting a TGFβ-based crosstalk between epithelial and stromal cells regulating the development of pancreatic inflammation and fibrosis. Collectively, our data not only contribute to clarifying the cellular processes governing pancreatic tissue regeneration, but also emphasize the conserved role of TGFβ as a tumour suppressor, both in the regenerative process following pancreatitis and in the initial phases of pancreatic cancer.

Molecular signalling mediated by the phosphatidylinositol-3-kinase (PI3K)-Akt axis is a key regulator of cellular functions. Importantly, alteration of the PI3K-Akt signalling underlies the development of different human diseases, thus prompting the investigation of the pathway as a molecular target for pharmacologic intervention. In this regard, recent studies showed that small molecule inhibitors of PI3K, the upstream regulator of the pathway, reduced the development of inflammation during acute pancreatitis, a highly debilitating and potentially lethal disease. Here we investigated whether a specific reduction of Akt activity, by using either pharmacologic Akt inhibition, or genetic inactivation of the Akt1 isoform selectively in pancreatic acinar cells, is effective in ameliorating the onset and progression of the disease. We discovered that systemic reduction of Akt activity did not protect the pancreas from initial damage and only transiently delayed leukocyte recruitment. However, reduction of Akt activity decreased acinar proliferation and exacerbated acinar-to-ductal metaplasia (ADM) formation, two critical events in the progression of pancreatitis. These phenotypes were recapitulated upon conditional inactivation of Akt1 in acinar cells, which resulted in reduced expression of 4E-BP1, a multifunctional protein of key importance in cell proliferation and metaplasia formation. Collectively, our results highlight the critical role played by Akt1 during the development of acute pancreatitis in the control of acinar cell proliferation and ADM formation. In addition, these results harbour important translational implications as they raise the concern that inhibitors of PI3K-Akt signalling pathways may negatively affect the regeneration of the pancreas. Finally, this work provides the basis for further investigating the potential of Akt1 activators to boost pancreatic regeneration following inflammatory insults.

These results identify a 5-HT-mediated regulation of zymogen secretion in pancreatic acinar cells. In addition, they demonstrate that 5-HT is required for the onset but not for the progression of pancreatic inflammation. These findings provide novel insights into the normal physiology of pancreatic acinar cells and into the pathophysiology of pancreatitis, with potential therapeutic implications.

Pancreatic ductal adenocarcinoma (PDAC), which is the primary cause of pancreatic cancer mortality, is poorly responsive to currently available interventions. Identifying new targets that drive PDAC formation and progression is critical for developing alternative therapeutic strategies to treat this lethal malignancy. Using genetic and pharmacological approaches, we investigated in vivo and in vitro whether uptake of the monoamine serotonin [5-hydroxytryptamine (5-HT)] is required for PDAC development. We demonstrated that pancreatic acinar cells have the ability to readily take up 5-HT in a transport-mediated manner. 5-HT uptake promoted activation of the small GTPase Ras-related C3 botulinum toxin substrate 1 (Rac1), which is required for transdifferentiation of acinar cells into acinar-to-ductal metaplasia (ADM), a key determinant in PDAC development. Consistent with the central role played by Rac1 in ADM formation, inhibition of the 5-HT transporter Sert (Slc6a4) with fluoxetine reduced ADM formation both in vitro and in vivo in a cell-autonomous manner. In addition, fluoxetine treatment profoundly compromised the stromal reaction and affected the proliferation and lipid metabolism of malignant PDAC cells. We propose that Sert is a promising therapeutic target to counteract the early event of ADM, with the potential to stall the initiation and progression of pancreatic carcinogenesis. Copyright © 2018 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

The exocrine pancreas exhibits a distinctive capacity for tissue regeneration and renewal following injury. This regenerative ability has important implications for a variety of disorders, including pancreatitis and pancreatic cancer, diseases associated with high morbidity and mortality. Thus, understanding its underlying mechanisms may help develop therapeutic interventions. Serotonin (5-hydroxytryptamine, 5-HT) has been recognized as a potent mitogen for a variety of cells and tissues. Here we investigated whether serotonin exerts a mitogenic effect in pancreatic acinar cells in three regenerative models, namely inflammatory tissue injury following pancreatitis, tissue loss following partial pancreatectomy and thyroid hormone-stimulated acinar proliferation. Genetic and pharmacological techniques were used to modulate serotonin levels in vivo. Acinar de-differentiation and cell cycle progression during the regenerative phase were investigated over the course of two weeks. By comparing acinar proliferation in the different murine models of regeneration, we found that serotonin did not affect clonal regeneration of mature acinar cells. Serotonin was however required for acinar de-differentiation following inflammation-mediated tissue injury. Specifically, lack of serotonin resulted in delayed up-regulation of progenitor genes, delayed formation of acinar-to-ductal metaplasia and defective acinar cell proliferation. We identified serotonin-dependent acinar secretion as a key step in the progenitor-based regeneration, as it promoted acinar cell de-differentiation and the recruitment of type 2 macrophages. Finally, we identified a regulatory Hes1-Ptfa axis in the uninjured adult pancreas activated by zymogen secretion. Our findings indicate that serotonin plays a critical role in the regeneration of the adult pancreas following pancreatitis by promoting de-differentiation of acinar cells. investigated over the course of two weeks. By comparing acinar proliferation in the different murine models of regeneration, we found that serotonin did not affect clonal regeneration of mature acinar cells. However, it was required for acinar de-differentiation following inflammation-mediated tissue injury. Specifically, lack of serotonin resulted in delayed up-regulation of progenitor genes, delayed formation of acinar-to-ductal metaplasia and defective acinar cell proliferation. We identified serotonin-dependent acinar secretion as a key step in the progenitor-based regeneration, as it promoted acinar cell de-differentiation and the recruitment of type 2 macrophages. Finally, we identified a regulatory Hes1-Ptfa axis in the uninjured adult pancreas activated by zymogen secretion. Our findings indicate that serotonin plays a critical role in the regeneration of the adult pancreas following pancreatitis by promoting de-differentiation of acinar cells.3