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.

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BACKGROUND:: CRS/HIPEC gained acceptance as a treatment for selected patients with peritoneal metastasis. However, the pathophysiology behind HIPEC is poorly understood, and a variety of regimens are currently in use. In this study, we describe for the first-time changes in the postoperative systemic inflammatory reaction, highly different among HIPEC treatment protocols. METHODS:: HIPEC was performed with three protocols, different with regard to perfusion times and drugs: (mito-mycinC/doxorubicin, 90min), (cisplatin, 90min) (oxaliplatin, 30min). Serial blood samples were assessed for C-reactive protein (CRP), white blood cells (WBC), pancreatic stone protein (PSP) and bacterial component (16s rDNA). The study was approved by the local ethics committee and registered at clinicaltirals.gov (NCT02741167). RESULTS:Overall, 140 patients from two European centers were included. In patients without postoperative complications, a secondary peak of inflammatory parameters, CRP (p = 0.015) and PSP (p = 0.004) was observed after HIPEC for 90 min with mitomycinC/doxorubicin or cisplatin but not after 30 min oxaliplatin. In patients after 90 min HIPEC, postoperative serum bacterial 16srDNA level were 2.1 times higher (95% CI 0.646-3.032, p = 0.015) compared to 30 min oxaliplatin. DISCUSSION: In conclusion, we identified a secondary inflammatory reaction after 90 min HIPEC, either with mitomycinC/doxorubicin or cisplatin, not observed after short course HIPEC with oxaliplatin. This protocol dependent physiology of acute phase proteins should be known in the clinical management of patients after HIPEC.

Pancreatitis is known to be painful in humans and companion animals. However, the extent of pain in experimental mouse models of acute pancreatitis is unknown. Consequently, the severity classification of acute pancreatitis in mice is controversially discussed and standardized pain management is missing. In this study, we investigated acute Cerulein-induced pancreatitis with pain-specific and well-being orientated parameters to detect its impact on mice. Male C57BL/6J male mice were injected with Cerulein; animals that received saline injections served as control group. The animals were observed for weight change and water intake. To assess pain, behaviors like stretch-and-press and reduced rearing, the Mouse Grimace Scale, and von Frey hypersensitivity were assessed. Fecal corticosterone metabolites and burrowing behavior were assessed to detect changes in the animal’s well-being. Pancreatitis severity was evaluated with amylase and lipase in the blood and pancreas histology. To investigate whether different analgesics can alleviate signs of pain, and if they influence pancreas inflammation, animals received Buprenorphine, Paracetamol in combination with Tramadol, or Metamizole in the drinking water. The calculated intake of these analgesics via drinking reached values stated to be efficient for pain alleviation. While pancreatitis did not seem to be painful, we detected acute pain from Cerulein injections that could not be alleviated by analgesics. The number of inflammatory cells in the pancreas did not differ with the analgesic administered. In conclusion: (1) Cerulein injections appear to be acutely painful but pain could not be alleviated by the tested analgesics, (2) acute pancreatitis induced by our protocol did not induce obvious signs of pain, (3) analgesic substances had no detectable influence on inflammation. Nevertheless, protocols inducing more severe or even chronic pancreatitis might evoke more pain and analgesic treatment might become imperative. Considering our results, we recommend the use of Buprenorphine via drinking water in these protocols. Further studies to search for efficient analgesics that can alleviate the acute pain induced by Cerulein injections are needed.

BACKGROUND The expression of amino acid transporters is known to vary during acute pancreatitis (AP) except for LAT1 ( slc7a5 ), the expression of which remains stable. LAT1 supports cell growth by importing leucine and thereby stimulates mammalian target of rapamycin (mTOR) activity, a phenomenon often observed in cancer cells. The mechanisms by which LAT1 influences physiological and pathophysiological processes and affects disease progression in the pancreas are not yet known. AIM To evaluate the role of LAT1 in the development of and recovery from AP. METHODS AP was induced with caerulein (cae) injections in female and male mice expressing LAT1 or after its knockout (LAT1 Cre/LoxP). The development of the initial AP injury and its recovery were followed for seven days after cae injections by daily measuring body weight, assessing microscopical tissue architecture, mRNA and protein expression, protein synthesis, and enzyme activity levels, as well as by testing the recruitment of immune cells by FACS and ELISA. RESULTS The initial injury, evaluated by measurements of plasma amylase, lipase, and trypsin activity, as well as the gene expression of dedifferentiation markers, did not differ between the groups. However, early metabolic adaptations that support regeneration at later stages were blunted in LAT1 knockout mice. Especially in females, we observed less mTOR reactivation and dysfunctional autophagy. The later regeneration phase was clearly delayed in female LAT1 knockout mice, which did not regain normal expression of the pancreas-specific differentiation markers recombining binding protein suppressor of hairless-like protein (rbpjl) and basic helix-loop-helix family member A15 (mist1). Amylase mRNA and protein levels remained lower, and, strikingly, female LAT1 knockout mice presented signs of fibrosis lasting until day seven. In contrast, pancreas morphology had returned to normal in wild-type littermates. CONCLUSION LAT1 supports the regeneration of acinar cells after AP. Female mice lacking LAT1 exhibited more pronounced alterations than male mice, indicating a sexual dimorphism of amino acid metabolism.