Autophagy in Acute Pancreatitis: Organelle Interaction and microRNA Regulation

Transfection of 12/15-lipoxygenase effectively alleviates inflammatory responses during experimental acute pancreatitis

BACKGROUND

Acute pancreatitis (AP), the initially triggered inflammatory process in the pancreas, can be life-threatening. It has been reported that 15-lipoxygenase may promote the removal of damaged intracellular components, maintain intracellular homeostasis, and promote apoptosis by upregulating the activity of caspases. Despite an increased understanding of the lipoxygenase pathway in inflammation and immune diseases, the role of the Alox15 gene product in modulating the inflammatory changes during AP is not well defined.

AIM

To investigate the effect of Alox15 expression in cerulein-induced AP in rats.

METHODS

Model rats were transfected with Alox15 by injecting a recombinant lentivirus vector encoding Alox15 into the left gastric artery before inducing AP. The expression of Alox15 was then assessed at the mRNA and protein levels.

RESULTS

Our in vivo results showed that serum amylase activity and pancreatic tissue water content were significantly reduced in Alox15-transfected rats. Further, the mRNA expression levels of tumor necrosis factor alpha, interleukin (IL)-1β, IL-6, and monocyte chemoattractant protein-1, as well as the protein expression of nuclear factor kappa B in pancreatic tissue were reduced. Additionally, we observed an upregulation of cleaved caspase-3 that implies an induction of apoptosis in pancreatic cells. The transfection of Alox15 resulted in a lower number of autophagic vacuoles in AP.

CONCLUSION

Our findings demonstrate a regulatory role of Alox15 in apoptosis and autophagy, making it a potential therapeutic target for AP.

ALKBH5 suppresses autophagic flux via N6-methyladenosine demethylation of ZKSCAN3 mRNA in acute pancreatitis

BACKGROUND

Increasing evidence has demonstrated that N6-methyladenosine (m6A) RNA modification plays an essential role in a wide range of pathological conditions. Impaired autophagy is a critical hallmark of acute pancreatitis (AP).

AIM

To explore the role of the m6A modification of ZKSCAN3 in the regulation of autophagy in AP.

METHODS

The AP mouse cell model was established by cerulein-treated mouse pancreatic acinar cells (MPC-83), and the results were confirmed by the levels of amylase and inflammatory factors. Autophagy activity was evaluated by specific identification of the autophagy-related microstructure and the expression of autophagy-related genes. ZKSCAN3 and ALKBH5 were knocked down to study the function in AP. A m6A RNA binding protein immunoprecipitation assay was used to study how the m6A modification of ZKSCAN3 mRNA is regulated by ALKBH.

RESULTS

The increased expression of amylase and inflammatory factors in the supernatant and the accumulation of autophagic vacuoles verified that the AP mouse cell model was established. The downregulation of LAMP2 and upregulation of LC3-II/I and SQSTM1 demonstrated that autophagy was impaired in AP. The expression of ZKSCAN3 was upregulated in AP. Inhibition of ZKSCAN3 increased the expression of LAMP2 and decreased the expression of the inflammatory factors, LC3-II/I and SQSTM1. Furthermore, ALKBH5 was upregulated in AP. Knockdown of ALKBH5 downregulated ZKSCAN3 expression and restored decreased autophagic flux in AP. Notably, the bioinformatic analysis revealed 23 potential m6A modification sites on ZKSCAN3 mRNA. The m6A modification of ZKSCAN3 mRNA was significantly decreased in AP. Knockdown of ALKBH5 increased the modification of ZKSCAN3 mRNA, which confirmed that ALKBH5 upregulated ZKSCAN3 expression in a m6A-dependent manner.

CONCLUSION

ALKBH5 inhibits autophagic flux through m6A demethylation of ZKSCAN3 mRNA in AP, thereby aggravating the severity of the disease.

miR-148a and miR-551b-5p regulate inflammatory responses via regulating autophagy in acute pancreatitis

Acute pancreatitis (AP) is a common inflammatory response that occurs in the pancreas with mortality rates as high as 30 %. However, there is still no consistent and effective treatment for AP now. MicroRNA-148 was reported to be involved in AP through IL-6 signaling pathway. Therefore, we aimed to further explore the detailed mechanisms of AP, to develop more therapeutic approach for AP. Exosomes were isolated from peripheral blood mononuclear cells of 20 AP patients and 20 healthy volunteers to evaluate the abnormally expressed miRNA. Then pancreatic acinar cells (PACs) were transfected with retrovirus to overexpress miR-148a/miR-551b-5p to evaluate their function. Both miR-148a and miR-551b-5p were highly expressed in AP patients than these in healthy cases. Then overexpressing miR-551b-5p in PACs could regulate autophagy through directly binding to Baculoviral IAP Repeat Containing 6, leading to the increased secretions of interleukin-1β (IL-1β) and interleukin-18 (IL-18) through interleukin-1 (IL-1) signaling pathway. Moreover, overexpressing miR-148a in PACs could decrease the secretions of IL-1β and IL-18 to modulate autophagy. The exosomal miRNA-148a and miRNA-551b-5p derived from peripheral blood mononuclear cells of AP patients may two-way mediate autophagy damage through IL-6/STAT3 signaling pathway, which participated in the AP pathogenesis. Our findings may provide new targets for the diagnosis and treatment of AP.

Association between autophagy and acute pancreatitis

Autophagy pathway involves maintaining intracellular homeostasis by regulating the degradation of cytoplasmic components. Disfunction of autophagic process has been confirmed to be critical mechanism in many diseases, including cancer, inflammation, infection, degeneration and metabolic disorders. Recent studies have shown that autophagy is one of the early events in acute pancreatitis. Impaired autophagy promotes the abnormal activation of zymogen granules and results in apoptosis and necrosis of exocrine pancreas. Furthermore, multiple signal paths involve progression of acute pancreatitis by regulating autophagy pathway. This article provides a comprehensive review of the recent advances in epigenetic regulation of autophagy and the role of autophagy in acute pancreatitis.

The Role of MicroRNAs in Pancreatitis Development and Progression

Pancreatitis (acute and chronic) is an inflammatory disease associated with significant morbidity, including a high rate of hospitalization and mortality. MicroRNAs (miRs) are essential post-transcriptional modulators of gene expression. They are crucial in many diseases' development and progression. Recent studies have demonstrated aberrant miRs expression patterns in pancreatic tissues obtained from patients experiencing acute and chronic pancreatitis compared to tissues from unaffected individuals. Increasing evidence showed that miRs regulate multiple aspects of pancreatic acinar biology, such as autophagy, mitophagy, and migration, impact local and systemic inflammation and, thus, are involved in the disease development and progression. Notably, multiple miRs act on pancreatic acinar cells and regulate the transduction of signals between pancreatic acinar cells, pancreatic stellate cells, and immune cells, and provide a complex interaction network between these cells. Importantly, recent studies from various animal models and patients' data combined with advanced detection techniques support their importance in diagnosing and treating pancreatitis. In this review, we plan to provide an up-to-date summary of the role of miRs in the development and progression of pancreatitis.

Long-term copper exposure caused hepatocytes autophagy in broiler via miR-455-3p-OXSR1 axis

Copper (Cu) is a common environmental pollutant which has been identified to cause toxic effects on animal bodies. MicroRNAs (miRNAs) are a type of non-coding RNAs involved in the regulation of various cellular activities including autophagy, but the potential regulatory mechanisms after excess Cu intake are still uncertain. Our previous study has prompted that Cu exposure reduced liver miR-455-3p levels. Herein, miR-455-3p was found to be an important molecule in the regulation of Cu-induced autophagy in vivo and in vitro. Histopathology observation of liver tissue indicated that Cu-induced severe hepatic damage including cellular swelling and vacuolization. Meanwhile, excessive Cu exposure not only heighten the mRNA and protein expression levels of Beclin1, Atg5, LC3Ⅰ and LC3Ⅱ, but also decreased miR-455-3p levels. In vitro experiment, Cu-induced autophagy can be attenuated by miR-455-3p overexpression. Additionally, oxidative stress-responsive 1 (OXSR1) was identified as a direct downstream target of miR-455-3p by dual luciferase reporter assays. Moreover, knockdown of OXSR1 can attenuate the autophagy induced by Cu treatment and the miR-455-3p inhibitor. Overall, the miR-455-3p-OXSR1 axis works as a regulator of autophagy under Cu stress, which provides a basis for further revealing the mechanism of chronic Cu poisoning.

[Abdominal puncture drainage alleviates severe acute pancreatitis in rats by activating Nrf-2/HO-1 pathway and promoting autophagy]

OBJECTIVE

To assess the effect of early abdominal puncture drainage (APD) on autophagy and Nrf-2/HO-1 pathway in rats with severe acute pancreatitis (SAP) and explore the possibile mechanism.

METHODS

Thirty-two male SD rats were randomly divided into sham-operated (SO) group, SAP group with retrograde injection of 4% sodium taurocholate, APD group with insertion of a drainage tube into the lower right abdomen after SAP induction, and APD + ZnPP group with intraperitoneal injection of 30 mg/kg ZnPP 12 h before APD modeling. Blood samples were collected from the rats 12 h after modeling for analysis of amylase and lipase levels and serum inflammatory factors. The pathological changes of the pancreatic tissue were observed with HE staining. Oxidative stress in the pancreatic tissue was detected with colorimetry, and sub-organelle structure and autophagy in pancreatic acinar cells were observed by transmission electron microscopy. The expressions of autophagy-related proteins and Nrf-2/HO-1 pathway were detected using RT-PCR and Western blotting.

RESULTS

Compared with those in SAP group, the rats with APD treatment showed significantly alleviated pathologies in the pancreas, reduced serum levels of lipase, amylase and inflammatory factors, lowered levels of oxidative stress, and activated expressions of Nrf-2/HO-1 pathway in the pancreas. The ameliorating effect of ADP was significantly inhibited by ZnPP treatment before modeling. APD obviously reversed mitochondrial and endoplasmic reticulum damages and p62 accumulation induced by SAP.

CONCLUSION

APD treatment can suppress oxidative stress and repair impaired autophagy in rats with SAP by activating the Nrf-2/HO-1 pathway, thereby reducing the severity of SAP.

Tetrahedral Framework Nucleic Acids Can Alleviate Taurocholate-Induced Severe Acute Pancreatitis and Its Subsequent Multiorgan Injury in Mice

Severe acute pancreatitis (SAP) is an inflammatory disease of the pancreas accompanied by tissue injury and necrosis. It not only affects the pancreas but also triggers a systemic inflammatory response that leads to multiorgan failure or even death. Moreover, there is no effective treatment currently that can reverse the disease progression. In this study, tetrahedral framework nucleic acids (tFNAs) were utilized to treat SAP in mice for the first time and proved to be effective in suppressing inflammation and preventing pathological cell death. Serum levels of pancreatitis-related biomarkers witnessed significant changes after tFNAs treatment. Reduction in the expression of certain cytokines involved in local and systemic inflammatory response were observed, together with alteration in proteins related to cell death and apoptosis. Collectively, our results demonstrate that tFNAs could both alleviate SAP and its subsequent multiorgan injury in mice, thus offering a novel and effective option to deal with SAP in the future.