Autophagy regulation in pancreatic acinar cells is independent of epidermal growth factor receptor signaling

Double deficiency of cathepsin B and L in the mouse pancreas alters trypsin activity without affecting acute pancreatitis severity

BACKGROUND

Premature intracellular trypsinogen activation has long been considered a key initiator of acute pancreatitis (AP). Cathepsin B (CTSB) activates trypsinogen, while cathepsin L (CTSL) inactivates trypsin(ogen), and both proteins play a role in the onset of AP.

METHODS

AP was induced by 7 hourly intraperitoneal injections of cerulein (50 μg/kg) in wild-type and pancreas-specific conditional Ctsb knockout (Ctsb^Δpan), Ctsl knockout (Ctsl^Δpan), and Ctsb;Ctsl double-knockout (Ctsb^Δpan;Ctsl^Δpan) mice. Pancreatic samples were collected and analyzed by histology, immunohistochemistry, real-time PCR, and immunoblots. Trypsin activity was measured in pancreatic homogenates. Peripheral blood was collected, and serum amylase activity was measured.

RESULTS

Double deletion of Ctsb and Cstl did not affect pancreatic development or mouse growth. After 7 times cerulein injections, double Ctsb and Ctsl deficiency in mouse pancreases increased trypsin activity to the same extent as that in Ctsl-deficient mice, while Ctsb deficiency decreased trypsin activity but did not affect the severity of AP. Ctsb^Δpan;Ctsl^Δpan mice had comparable serum amylase activity and histopathological changes and displayed similar levels of proinflammatory cytokines, apoptosis, and autophagy activity compared with wild-type, Ctsb^Δpan, and Ctsl^Δpan mice.

CONCLUSION

Double deletion of Ctsb and Ctsl in the mouse pancreas altered intrapancreatic trypsin activity but did not affect disease severity and inflammatory response after cerulein-induced AP.

Identification of Acute Pancreatitis-Related Genes and Pathways by Integrated Bioinformatics Analysis

BACKGROUND AND AIMS

The present study aimed to identify the differential expressed genes that are related to acute pancreatitis.

METHODS

Microarray datasets GSE109227 and GSE3644 were downloaded from the public database and analyzed to screen the genes. Afterward, integrated analysis of these genes were performed, including gene ontology and pathway enrichment analysis, protein-protein interaction network construction, expression level evaluation in human organs, relevant miRNAs and TFs prediction, and prognosis values of hub genes in pancreatic carcinoma.

RESULTS

A total number of 93 differential expressed genes were screened from the datasets, and EGFR, CDH1, ACTB, CD44, and VCL were identified as hub DEGs. Functional enrichment analysis demonstrated that these genes were mostly enriched in biological processes such as cell adhesion, platelet aggregation, glycoprotein binding, and also involved in multiple pathways included adherent junction, proteoglycans in cancer, bacterial invasion of epithelial cells, focal adhesion, Rap1 signaling pathway, regulation of actin cytoskeleton, and pathways in cancers. The five hub genes were all expressed in human pancreas organs with various levels. Hub gene-related network investigation predicted core miRNAs including hsa-mir-16-5p and main TFs like SOX9 with close interactions with these hub genes. Survival analysis also indicated that the high expression of EGFR, CDH1, ACTB, CD44, and VCL were significantly associated with poor prognosis in pancreatic carcinoma.

CONCLUSIONS

The study suggested that hub genes EGFR, CDH1, ACTB, CD44, and VCL may play vital role in the pathogenesis of acute pancreatitis and may serve as potential biomarkers to facilitate future acute pancreatitis diagnosis and treatment.

Autophagy in the pancreatic islets after the administration of cladribine in accordance to two different modes of therapy

The treatment of neoplastic and neurodegenerative diseases is still difficult. This because the cytostatic drugs have adverse effects on healthy organs. Among the drugs that have been investigated in the therapy of cancers and multiple sclerosis are the purine analogues. The aim of our study was the evaluation of the effect of cladribine on the process of autophagy in the healthy pancreas via two dosage models. The experiment was conducted on female Wistar rats which were placed within the experimental and control groups of two dosage models: model (A) - cladribine being administered in a daily dose of 0.1 mg/kg by weight for 7 days, and model (B) - cladribine being administered in a daily dose of 0.07 mg/kg by weight in 3 cycles of 6 days with 5 weeks break. A-bis and B-bis groups were included within, respectively, groups A and B. Here, decapitation occurred after 4 weeks break in drug administration. In our work, autophagy was investigated via the expression of the LC3B protein (Light Chain 3B protein). The comparison of the results of many independent trials was built upon the use of the Kruskal-Wallis non-parametric test. Significance was set at p < 0.005. In our results, average LC3B expression was observed in 100% of all cells in the group A, 70% in group B and 60% in group B-bis. We not observed average LC3B expression in the other groups. Moreover, a poor reaction was observed in 55% of all cells in group A-bis. We noted significant relationships between control group and group A, between the control group and group B, and between group A-bis and groups B and B-bis. These results demonstrate that cladribine has led to the induction of autophagy in the pancreatic islet cells.

Cathepsin D in pancreatic acinar cells is implicated in cathepsin B and L degradation, but not in autophagic activity

Cathepsin D (CD) is the major lysosomal aspartic protease and is widely distributed in the cells of various mammalian tissues. CD participates in various physiological events such as regulation of programmed cell death, activation of enzymatic precursors, and metabolic degradation of intracellular proteins through macroautophagy. To investigate the role of CD in pancreatic acinar cells, which constitute the exocrine pancreas, we generated and examined mice specifically deficient for CD in pancreatic acinar cells. CD deficient mice showed normal pancreatic development and autophagic activity, although LC3-II, which is a marker of the autophagosome, accumulates in both physiological and pancreatitis conditions. Moreover, CD deficiency leads to accumulation of matured cathepsin B (CB) and cathepsin L (CL) which are members of the cysteine protease family. We therefore conclude that CD in pancreatic acinar cells is implicated in CB and CL degradation but not in autophagic activity.