Study on the effect of polyethylene glycol emodin in the treatment of severe acute pancreatitis in rats

Severe acute pancreatitis (SAP) is a common gastrointestinal disorder requiring hospitalization. Pancreatic edema, hemorrhage, and pancreatic necrosis are potentially fatal complications. Therefore, the development of new drugs for the treatment of SAP is essential. We developed a nanocomposite drug (polyethylene glycol [PEG]-loaded emodin [EMD] liposomes [PEG-EMD Lip]) for the treatment of SAP that was constructed based on the excellent biocompatibility, non-toxicity, moisture retention, and favorable dispersive properties of PEG. In vitro experiments revealed that the effect of PEG-EMD Lip (15 μg/mL) modified by PEG on the activity of mononuclear macrophages (RAW264.7) remained above 93.3%, which was 1.12 times higher than that of EMD Lip alone. This suggests that PEG-modified EMD can effectively reduce the side effects observed with the parental drug. In addition, PEG–EMD Lip significantly decreased the levels of serum inflammatory factors, oxidative stress induced by SAP, and the degree of damage to the pancreas and lung organized system.

Hypothyroidism Affects Vascularization and Promotes Immune Cells Infiltration into Pancreatic Islets of Female Rabbits

Thyroidectomy induces pancreatic edema and immune cells infiltration similarly to that observed in pancreatitis. In spite of the controverted effects of hypothyroidism on serum glucose and insulin concentrations, the number and proliferation of Langerhans islet cells as well as the presence of extracellular matrix are affected depending on the islet size. In this study, we evaluated the effect of methimazole-induced hypothyroidism on the vascularization and immune cells infiltration into islets. A general observation of pancreas was also done. TwelveChinchilla-breed female adult rabbits were divided into controln=6and hypothyroid groups (n=6, methimazole, 0.02% in drinking water for 30 days). After the treatment, rabbits were sacrificed and their pancreas was excised, histologically processed, and stained with Periodic Acid-Schiff (PAS) or Masson’s Trichrome techniques. Islets were arbitrarily classified into large, medium, and small ones. The external and internal portions of each islet were also identified. Student-t-test and Mann-Whitney-Utest or two-way ANOVAs were used to compare variables between groups. In comparison with control rabbits, hypothyroidism induced a strong infiltration of immune cells and a major presence of collagen and proteoglycans in the interlobular septa. Large islets showed a high vascularization and immune cells infiltration. The present results show that hypothyroidism induces pancreatitis and insulitis.

Local disruption of the celiac ganglion inhibits substance P release and ameliorates caerulein-induced pancreatitis in rats

Primary sensory neurons of the C and Aδ subtypes express the vanilloid capsaicin receptor TRPV1 and contain proinflammatory peptides such as substance P (SP) that mediate neurogenic inflammation. Pancreatic injury stimulates these neurons causing the release of SP in the pancreas resulting in pancreatic edema and neutrophil infiltration that contributes to pancreatitis. Axons of primary sensory neurons innervating the pancreas course through the celiac ganglion. We hypothesized that disruption of the celiac ganglion by surgical excision or inhibition of C and Aδ fibers through blockade of TRPV1 would reduce the severity of experimental pancreatitis by inhibiting neurogenic inflammation. Resiniferatoxin (RTX) is a specific TRPV1 agonist that, in high doses, selectively destroys C and Aδ fibers. Sprague-Dawley rats underwent surgical ganglionectomy or application of 10 μg RTX (vs. vehicle alone) to the celiac ganglion. One week later, pancreatitis was induced by six hourly intraperitoneal injections of caerulein (50 μg/kg). The severity of pancreatitis was assessed by serum amylase, pancreatic edema, and pancreatic myeloperoxidase (MPO) activity. SP receptor (neurokinin-1 receptor, NK-1R) internalization in acinar cells, used as an index of endogenous SP release, was assessed by immunocytochemical quantification of NK-1R endocytosis. Caerulein administration caused significant increases in pancreatic edema, serum amylase, MPO activity, and NK-1R internalization. RTX treatment and ganglionectomy significantly reduced pancreatic edema by 46% ( P < 0.001) and NK-1R internalization by 80% and 51% ( P < 0.001 and P < 0.05, respectively). RTX administration also significantly reduced MPO activity by 47% ( P < 0.05). Neither treatment affected serum amylase, consistent with a direct effect of caerulein. These results demonstrate that disruption of or local application of RTX to the celiac ganglion inhibits SP release in the pancreas and reduces the severity of acute secretagogue-induced pancreatitis. It is possible that selectively disrupting TRPV1-bearing neurons could be used to reduce pancreatitis severity.

Subcellular kinetics of early trypsinogen activation in acute rodent pancreatitis

To investigate the debated role of intracellular trypsinogen activation and its relation to lysosomal enzyme redistribution in the pathogenesis of acute pancreatitis, rats were infused with the cholecystokinin analog caerulein at 5 μg ⋅ kg−1⋅ h−1for intervals up to 3 h, and the changes were contrasted with those in animals receiving saline or 0.25 μg ⋅ kg−1⋅ h−1caerulein. Saline or 0.25 μg ⋅ kg−1⋅ h−1caerulein did not induce significant changes. In contrast, 5 μg ⋅ kg−1⋅ h−1caerulein caused significant hyperamylasemia and pancreatic edema within 30 min. Pancreatic content of trypsinogen activation peptide (TAP) increased continuously (significant within 15 min). TAP generation was predominantly located in the zymogen fraction during the first hour but expanded to other intracellular compartments thereafter. Cathepsin B activity in the zymogen compartment increased continuously throughout the experiments and correlated significantly with TAP generation in the same compartment. Total trypsinogen content increased to 143% with marked interstitial trypsinogen accumulation after 3 h. Supramaximal caerulein stimulation causes trypsinogen activation by 15 min that originates in the zymogen compartment and is associated with increasing cathepsin B activity in this subcellular compartment. However, a much larger pool of trypsinogen survives and accumulates in the extracellular space and may become critical in the evolution of necrotizing pancreatitis.

Edema and intrapancreatic trypsinogen activation precede glutathione depletion during caerulein pancreatitis

Acute pancreatitis is characterized by hyperamylasemia, pancreatic edema, and the presence of activated digestive enzymes within the pancreas. The secretagogue-induced model of acute pancreatitis is also characterized by pancreatic acinar cell vacuolation, subcellular redistribution of lysosomal hydrolases, and a fall in pancreatic glutathione levels. We have performed time-dependence studies to determine the sequence with which these phenomena appear and to establish their cause-and-effect relationship. Evidence of lysosomal enzyme redistribution and trypsinogen activation within the pancreas could be detected within 10-15 min of the onset of supramaximal secretagogue stimulation, while hyperamylasemia (30 min), pancreatic edema (60 min), and acinar cell vacuolation (60 min) occurred at later times. Pancreatic glutathione levels were either unchanged (15 and 30 min) or elevated (60 min) during the early times of supramaximal stimulation and were only noted to be decreased at a later time. These results support the conclusion that intrapancreatic digestive enzyme activation, possibly occurring by a mechanism involving lysosomal hydrolase redistribution, is an early and likely a critical event in the evolution of secretagogue-induced pancreatitis but that glutathione depletion is neither early nor critical to the evolution of this model of pancreatitis.