Proteomic analysis of the soluble and the lysosomal+mitochondrial fractions from rat pancreas: Implications for cerulein-induced acute pancreatitis

Temporal Proteomic and Lipidomic Profiles of Cerulein-Induced Acute Pancreatitis Reveal Novel Insights for Metabolic Alterations in the Disease Pathogenesis

The pathophysiological mechanisms of acute pancreatitis (AP) are complex and have remained a mystery to date, but metabolism is gradually recognized as an important driver of AP onset and development. We used a cerulein-induced AP mouse model to conduct liquid chromatography-mass spectrometry (LC-MS/MS)-based time-course proteomics and lipidomics in order to better understand the underlying metabolic alterations linked with AP. Results showed that a series of significant changes in proteins over time with a boost in expression were enriched in lipase activity, lipoprotein, and lipids absorption and transport regulation. Furthermore, 16 proteins associated with lipid metabolism and signaling pathways together with the whole lipid species changing profile led to the vital identification of changing law in glycerides, phosphoglycerides, and free fatty acids. In addition to lipid metabolism and regulation-associated proteins, several digestive enzymes and adaptive anti-trypsin, stress response, and energy metabolism-related proteins showed an increment in abundance. Notably, central carbon and branched chain amino acid metabolism were enhanced during 0-24 h from the first cerulein stimulation. Taken together, this integrated proteomics and lipidomics revealed a novel metabolic insight into metabolites transforming rules that might be relevant to their function and drug targets investigation. (Created with Biorender.com.).

Multifactorial Scores and Biomarkers of Prognosis of Acute Pancreatitis: Applications to Research and Practice

Acute pancreatitis (AP) is a severe inflammation of the pancreas presented with sudden onset and severe abdominal pain with a high morbidity and mortality rate, if accompanied by severe local and systemic complications. Numerous studies have been published about the pathogenesis of AP; however, the precise mechanism behind this pathology remains unclear. Extensive research conducted over the last decades has demonstrated that the first 24 h after symptom onset are critical for the identification of patients who are at risk of developing complications or death. The identification of these subgroups of patients is crucial in order to start an aggressive approach to prevent mortality. In this sense and to avoid unnecessary overtreatment, thereby reducing the financial implications, the proper identification of mild disease is also important and necessary. A large number of multifactorial scoring systems and biochemical markers are described to predict the severity. Despite recent progress in understanding the pathophysiology of AP, more research is needed to enable a faster and more accurate prediction of severe AP. This review provides an overview of the available multifactorial scoring systems and biochemical markers for predicting severe AP with a special focus on their advantages and limitations.

A tandem mass tag (TMT) proteomic analysis during the early phase of experimental pancreatitis reveals new insights in the disease pathogenesis

Changes in the protein expression occurring within the initiation phase of acute pancreatitis (AP) might be vital in the development of this complex disease. However, the exact mechanisms involved in the onset of AP remains elusive and most of our knowledge about the pathobiology of AP comes from animal models. We performed in a rat pancreatitic model a high-throughput shotgun proteomic profiling of the soluble and whole membrane fractions from the pancreas during the early phase of cerulein (Cer)-induced AP. We identified 997 proteins, of which 353 were significantly different (22, 276 or 55 in both, the soluble or the membrane fractions, respectively). Gene Ontology and KEGG PATHWAY analyses revealed that these proteins were implicated in molecular mechanisms relevant to AP pathogenesis, including vesicle-mediated and protein transport, lysosomal and mitochondrial impairment or proteolysis. Numerous metabolic processes were downregulated apparently to reduce energy consumption, and a remarkable increase in inflammatory and stress responses was also highlighted. The proteomic data were verified by immunoblotting of 11 and 7 different soluble or membrane-associated proteins, either novel (VPS29 and MCTS1) or known factors in AP. Also, our first observation of the imbalance of some COP proteins during AP early phase deserves further characterization.

BIOLOGICAL SIGNIFICANCE

AP is one of the most important pathological inflammatory states of the exocrine pancreas but its pathophysiology remains incompletely understood, especially the early acinar events. Proteomic analysis of pancreatic subcellular fractions simplifies protein maps and helps in the identification of new protein alterations and biomarkers characterizing pancreatic tissue damage. Our shotgun approach has not been previously used to profile the early proteomic alterations of the disease, which are considered crucial for its development and for the founding of clinical procedures. Furthermore, our subcellular fractionation protocol allowed us to detect changes in membrane proteins so far overlooked in the proteomic study of AP. Accordingly, using TMT proteomics and bioinformatic tools, we were able to detect significant changes in protein expression related to many pathobiological pathways of acute pancreatitis as from the early phase of the disease. To our knowledge, some of these changes, such as the imbalance of some COP proteins, have never been described in this disease.

Apoptosis of rat hepatic stellate cells induced by diallyl trisulfide and proteomics profiling in vitro

Diallyl trisulfide (DATS), a major garlic derivative, inhibits cell proliferation and triggers apoptosis in a variety of cancer cell lines. However, the effects of DATS on hepatic stellate cells (HSCs) remain unknown. The aim of this study was to analyze the effects of DATS on cell proliferation and apoptosis, as well as the protein expression profile in rat HSCs. Rat HSCs were treated with or without 12 and 24 μg/mL DATS for various time intervals. Cell proliferation and apoptosis were determined using tetrazolium dye (MTT) colorimetric assay, bromodeoxyuridine (5-bromo-2'-deoxyuridine; BrdU) assay, Hoechst 33342 staining, electroscopy, and flow cytometry. Protein expression patterns in HSCs were systematically studied using 2-dimensional electrophoresis and mass spectrometry. DATS inhibited cell proliferation and induced apoptosis of HSCs in a time-dependent manner. We observed clear morphological changes in apoptotic HSCs and dramatically increased annexin V-positive - propidium iodide negative apoptosis compared with the untreated control group. Twenty-one significant differentially expressed proteins, including 9 downregulated proteins and 12 upregulated proteins, were identified after DATS administration, and most of them were involved in apoptosis. Our results suggest that DATS is an inducer of apoptosis in HSCs, and several key proteins may be involved in the molecular mechanism of apoptosis induced by DATS.

Changes in the expression of LIMP-2 during cerulein-induced pancreatitis in rats: Effect of inhibition of leukocyte infiltration, cAMP and MAPKs early on in its development

Lysosomal integral membrane protein-2 (LIMP-2) is an important protein in lysosomal biogenesis and function and also plays a role in the tissue inflammatory response. It is known that lysosomes play a central role in acute pancreatitis, with inflammatory cell infiltration triggering the disease early on. In this study we report increases in pancreatic LIMP-2 protein and mRNA levels as early events that occur during the development of cerulein (Cer)-induced acute pancreatitis (AP) in rats. GdCl3, a macrophage inhibitor, but not FK506, a T lymphocyte inhibitor, was able to reverse the increase in LIMP-2 expression after Cer treatment, although such reversion was abolished if the animals were depleted of neutrophils due to a vinblastine sulfate pre-treatment. Immunostaining revealed that the cellular source of LIMP-2 was mainly acinar cells. Additionally, pre-treatments with the MAPKs inhibitors SP600125 and PD98059, inhibitors of JNK and ERK½ activation, respectively, but not of rolipram, a type IV phosphodiesterase inhibitor, suppressed the increase in the expression of LIMP-2 after Cer administration. Together, these results indicate that neutrophils are able to drive a macrophage activation that would regulate the increase in LIMP-2 expression during the early phase of Cer-induced AP, with the stress kinases JNK and ERK½ also playing a coordinated role in the increase of LIMP-2 expression due to Cer.

Hepatic steatosis depresses alpha-1-antitrypsin levels in human and rat acute pancreatitis

Hepatic steatosis (HS) can exacerbate acute pancreatitis (AP). This study aimed to investigate the relation between α1-antitrypsin (AAT) and acute pancreatitis when patients have HS. Using proteomic profiling, we identified 18 differently expressed proteins pots in the serum of rats with or without HS after surgical establishment of AP. AAT was found to be one of the significantly down-regulated proteins. AAT levels were significantly lower in hepatic steatosis acute pancreatitis (HSAP) than in non-HSAP (NHSAP) (P < 0.001). To explore the clinical significance of these observations, we measured the levels of AAT in the serum of 240 patients with HSAP, NHSAP, fatty liver disease (FLD), or no disease. Compared with healthy controls, serum AAT levels in patients with NHSAP were significantly higher (P < 0.01), while in patients with HSAP serum AAT levels were significantly lower (P < 0.01). Further studies showed that acute physiology and chronic health evaluation (APACHE-II) scores were negatively correlated with serum AAT levels (r = −0.85, P < 0.01). In conclusion, low serum levels of AAT in patients with HSAP are correlated with disease severity and AAT may represent a potential target for therapies aiming to improve pancreatitis.

Mitochondria in metabolic disease: getting clues from proteomic studies

Mitochondria play a key role as major regulators of cellular energy homeostasis, but in the context of mitochondrial dysfunction, mitochondria may generate reactive oxidative species and induce cellular apoptosis. Indeed, altered mitochondrial status has been linked to the pathogenesis of several metabolic disorders and specially disorders related to insulin resistance, such as obesity, type 2 diabetes, and other comorbidities comprising the metabolic syndrome. In the present review, we summarize information from various mitochondrial proteomic studies of insulin-sensitive tissues under different metabolic states. To that end, we first focus our attention on the pancreas, as mitochondrial malfunction has been shown to contribute to beta cell failure and impaired insulin release. Furthermore, proteomic studies of mitochondria obtained from liver, muscle, and adipose tissue are summarized, as these tissues constitute the primary insulin target metabolic tissues. Since recent advances in proteomic techniques have exposed the importance of PTMs in the development of metabolic disease, we also present information on specific PTMs that may directly affect mitochondria during the pathogenesis of metabolic disease. Specifically, mitochondrial protein acetylation, phosphorylation, and other PTMs related to oxidative damage, such as nitrosylation and carbonylation, are discussed.

Modulation in the expression of SHP-1, SHP-2 and PTP1B due to the inhibition of MAPKs, cAMP and neutrophils early on in the development of cerulein-induced acute pancreatitis in rats

The protein tyrosine phosphatases (PTPs) SHP-1, SHP-2 and PTP1B are overexpressed early on during the development of cerulein -induced acute pancreatitis (AP) in rats, and their levels can be modulated by some species of mitogen-activated protein kinases (MAPKs), the intracellular levels of cAMP and by general leukocyte infiltration, the latter at least for SHP-2 and PTP1B. In this study we show that cerulein treatment activates extracellular signal-regulated kinase (ERK) and c-Jun NH2-terminal kinase (JNK) but not p38 MAPK during the early phase of cerulein-induced AP (2h after the first injection of cerulein). Therefore, by using the MAPK inhibitors SP600125 (a specific JNK inhibitor) and PD98059 (a specific ERK inhibitor), we have unmasked the particular MAPK that underlies the modulation of the expression levels of these PTPs. JNK would act by preventing SHP-1 protein expression from increasing beyond a certain level. ERK 1/2 was the main MAPK involved in the increase in SHP-2 protein expression due to cerulein. JNK negatively modulated the SH2-domain containing PTPs. Both MAPKs played a role in the increase in PTP1B protein expression due to cerulein. Finally, by using the white blood cell inhibitors vinblastine sulfate, gadolinium chloride and FK506 (tacrolimus), we show that the macrophage activity or T-lymphocytes does not modulate the expression of any of the PTPs, although neutrophil infiltration was found to be a regulator of SHP-2 and PTP1B protein expression due to cerulein.