Marta Bombardo

Ibuprofen and diclofenac treatments reduce proliferation of pancreatic acinar cells upon inflammatory injury and mitogenic stimulation.

Nonsteroidal anti‐inflammatory drugs (NSAIDs) are administered to manage the pain typically found in patients suffering from pancreatitis. NSAIDs also display anti‐proliferative activity against cancer cells; however, their effects on normal, untransformed cells are poorly understood. Here, we evaluated whether NSAIDs inhibit the proliferation of pancreatic acinar cells during the development of acute pancreatitis.

Class I histone deacetylase inhibition improves pancreatitis outcome by limiting leukocyte recruitment and acinar‐to‐ductal metaplasia

Pancreatitis 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.

Inactivation of TGFβ receptor II signalling in pancreatic epithelial cells promotes acinar cell proliferation, acinar-to-ductal metaplasia and fibrosis during pancreatitis

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. Copyright

Serotonin promotes acinar dedifferentiation following pancreatitis-induced regeneration in the adult pancreas

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 in developing therapeutic interventions. Serotonin 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, 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 dedifferentiation and cell cycle progression during the regenerative phase were investigated over the course of 2 weeks. By comparing acinar proliferation in the different murine models of regeneration, we found that serotonin did not affect the clonal regeneration of mature acinar cells. Serotonin was, however, required for acinar dedifferentiation following inflammation‐mediated tissue injury. Specifically, lack of serotonin resulted in delayed up‐regulation of progenitor genes and delayed the formation of acinar‐to‐ductal metaplasia and defective acinar cell proliferation. We identified serotonin‐dependent acinar secretion as a key step in progenitor‐based regeneration, as it promoted acinar cell dedifferentiation 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 indicated that serotonin plays a critical role in the regeneration of the adult pancreas following pancreatitis by promoting the dedifferentiation of acinar cells. Copyright

Class I HDAC inhibition improves pancreatitis outcome by limiting leukocyte recruitment and acinar-to-ductal metaplasia

Pancreatitis 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.

Serotonin uptake is required for Rac1 activation in Kras-induced acinar-to-ductal metaplasia in the pancreas

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

Enhanced proliferation of pancreatic acinar cells in MRL/MpJ mice is driven by severe acinar injury but independent of inflammation

Adult pancreatic acinar cells have the ability to re-enter the cell cycle and proliferate upon injury or tissue loss. Despite this mitotic ability, the extent of acinar proliferation is often limited and unable to completely regenerate the injured tissue or restore the initial volume of the organ, thus leading to pancreatic dysfunction. Identifying molecular determinants of enhanced proliferation is critical to overcome this issue. In this study, we discovered that Murphy Roths Large (MRL/MpJ) mice can be exploited to identify molecular effectors promoting acinar proliferation upon injury, with the ultimate goal to develop therapeutic regimens to boost pancreatic regeneration. Our results show that, upon cerulein-induced acinar injury, cell proliferation was enhanced and cell cycle components up-regulated in the pancreas of MRL/MpJ mice compared to the control strain C57BL/6. Initial damage of acinar cells was exacerbated in these mice, manifested by increased serum levels of pancreatic enzymes, intra-pancreatic trypsinogen activation and acinar cell apoptosis. In addition, MRL/MpJ pancreata presented enhanced inflammation, de-differentiation of acinar cells and acinar-to-ductal metaplasia. Manipulation of inflammatory levels and mitogenic stimulation with the thyroid hormone 5,3-L-tri-iodothyronine revealed that factors derived from initial acinar injury rather than inflammatory injury promote the replicative advantage in MRL/MpJ mice.

Inhibition of Class I Histone Deacetylases Abrogates Tumor Growth Factor β Expression and Development of Fibrosis during Chronic Pancreatitis

Pancreatic fibrosis is the hallmark of chronic pancreatitis, a highly debilitating disease for which there is currently no cure. The key event at the basis of pancreatic fibrosis is the deposition of extracellular matrix proteins by activated pancreatic stellate cells (PSCs). Transforming growth factor β (TGFβ) is a potent profibrotic factor in the pancreas as it promotes the activation of PSC; thus, pharmacologic interventions that effectively reduce TGFβ expression harbor considerable therapeutic potential in the treatment of chronic pancreatitis. In this study, we investigated whether TGFβ expression is reduced by pharmacologic inhibition of the epigenetic modifiers histone deacetylases (HDACs). To address this aim, chronic pancreatitis was induced in C57BL/6 mice with serial injections of cerulein, and the selective class 1 HDAC inhibitor MS-275 was administered in vivo in a preventive and therapeutic manner. Both MS-275 regimens potently reduced deposition of extracellular matrix and development of fibrosis in the pancreas after 4 weeks of chronic pancreatitis. Reduced pancreatic fibrosis was concomitant with lower expression of pancreatic TGFβ and consequent reduced PSC activation. In search of the cell types targeted by the inhibitor, we found that MS-275 treatment abrogated the expression of TGFβ in acinar cells stimulated by cerulein treatment. Our study demonstrates that MS-275 is an effective antifibrotic agent in the context of experimental chronic pancreatitis and thus may constitute a valid therapeutic intervention for this severe disease.