Role of proteases and antiprotease in the etiology of chronic pancreatitis

Differential Plasma Proteins Identified via iTRAQ-Based Analysis Serve as Diagnostic Markers of Pancreatic Ductal Adenocarcinoma

Objective

We aimed to identify differentially expressed proteins in the plasma of patients with pancreatic cancer and control subjects, which could serve as potential tumor biomarkers.

Methods

Differentially expressed proteins were determined via isostatic labeling and absolute quantification (iTRAQ). Potential protein biomarkers were identified via enzyme-linked immunosorbent assay (ELISA) in 40 patients and 40 control subjects, and those eventually selected were further validated in 40 pancreatic cancer and normal pancreatic tissues.

Results

In total, 30 proteins displayed significant differences in expression among which 21 were downregulated and 9 were upregulated compared with the control group. ELISA revealed downregulation of peroxiredoxin-2 (PRDX2) and upregulation of alpha-1-antitrypsin (AAT), Ras-related protein Rab-2B (RAB2B), insulin-like growth factor-binding protein 2 (IGFBP2), Rho-related GTP-binding protein RhoC (RHOC), and prelamin-A/C (LMNA) proteins in 40 other samples of pancreatic cancer. Notably, only AAT, RAB2B, and IGFBP2 levels were consistent with expression patterns obtained with iTRAQ. Moreover, all three proteins displayed a marked increase in pancreatic cancer tissues. Data from ROC curve analysis indicated that the diagnostic ability of AAT, RAB2B, and IGFBP2 combined with carbohydrate antigen 19-9 (CA19-9) for pancreatic cancer was significantly greater than that of the single indexes (area under the curve (AUC): 90% vs. 75% (CA19-9), 76% (AAT), 71% (RAB2B), and 71% (IGFBP2), all P < 0.01).

Conclusion

AAT, RAB2B, and IGFBP2 could serve as effective biomarkers to facilitate the early diagnosis of pancreatic cancer.

Does pendimethalin develop in pancreatic cancer induced inflammation?

Pendimethalin, one of the dinitroaniline group herbicides, is applied for controlling weeds in cereals, legumes and vegetable crops, and has been classified as possible human carcinogen. It is indicated that pendimethalin should arise risks of developing some cancer types; however, there is no data on the effects of pendimethalin on pancreatic cancer-induced inflammation. Injuries resulting from by acute pancreatitis attacks and inflammation are significant factors in the development of pancreatic cancer. Therefore, we investigated whether pendimethalin triggers inflammation as a mechanism of pancreatic cancer development. Parameters related to pancreatic activation, oxidative stress, and inflammation were measured in the human pancreatic (PANC-1) cell line. In the range of 0-100 μM, the levels of chymotrypsin decreased. It should be indicated that the reason for the decrease in chymotrypsin may be the high rates of cell death (20%) observed in the high concentration levels. We observed that pendimethalin significantly induced oxidative damage, while levels of interleukin-6 (IL-6) and interleukin-8 (IL-8) did not change. The obtained results may draw attention to the usage and possible toxic effect of pendimethalin due to oxidative damage induction; however, detailed inflammation mechanisms and other cancer pathways should be investigated.

Framework for interpretation of trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis

Early intracellular premature trypsinogen activation was interpreted as the key initiator of pancreatitis. When the balance in the homeostasis of trypsin and antitrypsin system is disequilibrated, elevated aggressive enzymes directly attack the pancreatic tissue, which leads to pancreatic destruction and inflammation. However, trypsin alone is not enough to cause complications in pancreatitis, which may play a crucial role in modulating signaling events in the initial phase of the disease. NFκB activation is the major inflammatory pathway involved in the occurrence and development of pancreatitis and it can be induced by intrapancreatic activation of trypsinogen. Synthesis of trypsinogen occurs in endoplasmic reticulum (ER), and ER stress is an important early acinar cell event. Components of ER stress response are known to be able to trigger cell death as well as NFκB signaling cascade. The strongest evidence supporting the trypsin-centered theory is that gene mutations, which lead to the generation of more trypsin, or reduce the activity of trypsin inhibitors or trypsin degradation, are associated with pancreatitis. Thus, trypsin-antitrypsin imbalance may be the first step leading to pancreatic autodigestion and inducing other pathways. Continued experimental studies are necessary to determine the specific relationships between trypsin-antitrypsin imbalance and genetic heterogeneity in pancreatitis. In this article, we review the latest advances that contributed to the understanding of the basic mechanisms behind the occurrence and development of pancreatitis with a focus on the interpretation of trypsin-antitrypsin imbalance and their relationships with other inflammation pathways. We additionally highlight genetic predispositions to pancreatitis and possible mechanisms associated with them.

The reactive centre loop of corticosteroid-binding globulin (CBG) is a protease target for cortisol release

Corticosteroid-binding globulin (CBG) binds more than 90% of circulating cortisol and is a non-inhibitory member of the family of serine protease inhibitors (SERPINS) with an exposed elastase sensitive reactive centre loop (RCL). At sites of inflammation neutrophil activation can release elastase which may cleave the RCL and result in cortisol release from CBG. The RCL sequence also has two theoretical chymotrypsin cleavage sites and we used a monoclonal antibody with specificity for the RCL to investigate chymotrypsin cleavage of CBG. Here we show, for the first time, rapid chymotrypsin cleavage of the RCL of CBG, resulting in undetectable levels of intact CBG, whereas total CBG levels were unchanged. Coincident with both chymotrypsin and elastase cleavage there was an increase in the free cortisol fraction of serum to levels similar to when CBG had been inactivated by heat indicating total cortisol release from CBG. These findings demonstrate a new mechanism for cortisol release from its binding globulin.