β-Arrestin1 alleviates acute pancreatitis via repression of NF-κBp65 activation

ARRB1 downregulates acetaminophen-induced hepatoxicity through binding to p-eIF2α to inhibit ER stress signaling

Acetaminophen (APAP) stands as the predominant contributor to drug-induced liver injury (DILI), and limited options are available. β-Arrestin1 (ARRB1) is involved in numerous liver diseases. However, the role of ARRB1 in APAP-induced liver injury remained uncertain. Wild-type (WT) and ARRB1 knockout (KO) mice were injected with APAP and sacrificed at the indicated times. The histological changes, inflammation, endoplasmic reticulum (ER) stress, and apoptosis were then evaluated. Hepatic cell lines AML-12 and primary hepatocytes were used for in vitro analyses. Systemic ARRB1-KO mice were susceptible to APAP-induced hepatotoxicity, as indicated by larger areas of centrilobular necrosis area and higher levels of ALT, AST, and inflammation level. Moreover, ARRB1-KO mice exhibited increased ER stress (indicated by phosphorylated α subunit of eukaryotic initiation factor 2 (p-eIF2α)-activating transcription factor 4 (ATF4)-CCAAT-enhancer-binding protein homologous protein (CHOP)) and apoptosis (indicated by cleaved caspase 3). Further rescue experiments demonstrated that the induction of apoptosis was partially mediated by ER stress. Overexpression of ARRB1 alleviated APAP-induced ER stress and apoptosis. Moreover, co-IP analysis revealed that ARRB1 directly bound to p-eIF2α and eIF2α. ARRB1 protected against APAP-induced hepatoxicity through targeting ER stress and apoptosis. ARRB1 is a prospective target for treating APAP-induced DILI.

β-arrestin1 regulates astrocytic reactivity via Drp1-dependent mitochondrial fission: implications in postoperative delirium

Postoperative delirium (POD) is a frequent and debilitating complication, especially amongst high risk procedures, such as orthopedic surgery. This kind of neurocognitive disorder negatively affects cognitive domains, such as memory, awareness, attention, and concentration after surgery; however, its pathophysiology remains unknown. Multiple lines of evidence supporting the occurrence of inflammatory events have come forward from studies in human patients' brain and bio-fluids (CSF and serum), as well as in animal models for POD. β-arrestins are downstream molecules of guanine nucleotide-binding protein (G protein)-coupled receptors (GPCRs). As versatile proteins, they regulate numerous pathophysiological processes of inflammatory diseases by scaffolding with inflammation-linked partners. Here we report that β-arrestin1, one type of β-arrestins, decreases significantly in the reactive astrocytes of a mouse model for POD. Using β-arrestin1 knockout (KO) mice, we find aggravating effect of β-arrestin1 deficiency on the cognitive dysfunctions and inflammatory phenotype of astrocytes in POD model mice. We conduct the in vitro experiments to investigate the regulatory roles of β-arrestin1 and demonstrate that β-arrestin1 in astrocytes interacts with the dynamin-related protein 1 (Drp1) to regulate mitochondrial fusion/fission process. β-arrestin1 deletion cancels the combination of β-arrestin1 and cellular Drp1, thus promoting the translocation of Drp1 to mitochondrial membrane to provoke the mitochondrial fragments and the subsequent mitochondrial malfunctions. Using β-arrestin1-biased agonist, cognitive dysfunctions of POD mice and pathogenic activation of astrocytes in the POD-linked brain region are reduced. We, therefore, conclude that β-arrestin1 is a promising target for the understanding of POD pathology and development of POD therapeutics.

The Role of Endoplasmic Reticulum Stress in Cell Injury Induced by Methimazole on Pancreatic Cells

Purpose: Methimazole is an anti-thyroid agent, especially as main therapy option for Graves' disease in children and adults. Drug induced pancreatitis is one of the known adverse effect of methimazole mentioned in case reports. However, the detailed molecular mechanisms of methimazole-induced pancreatitis are still unclear. In this study, the aim is to investigate the adverse effect of methimazole on pancreas cell stress mechanism and apoptosis. Methods: Cytotoxicity was evaluated in human pancreas/duct (PANC-1) cell line. Total oxidant (TOS) and antioxidant status (TAS) for oxidative stress index, glutathione (GSH) level and endoplasmic reticulum (ER) stress biomarkers were evaluated by ELISA. Reactive oxygen species (ROS) levels and apoptosis were evaluated by flow-cytometer. Results: The 30% inhibition rate concentration (IC₃₀) value was determined as 53 mM in PANC1 cells. The exposure concentrations were in the range of 0-40 mM for 48 hours. Methimazole might induce cellular stress conditions. ROS production increases depending on concentration, and this increase shows parallelism with the increase in ER stress biomarkers such as TOS, ERN1 and CASPASE12. Conversely, there was no significant difference between control and exposure groups in terms of apoptosis. Conclusion: In conclusion, methimazole might have triggered the mechanisms of inflammation or autophagy in the pancreatic cells. However, there is still a need for in vitro and in vivo studies including other cellular parameters related to apoptosis.

ARRB1 suppresses the activation of hepatic macrophages via modulating endoplasmic reticulum stress in lipopolysaccharide-induced acute liver injury

Acute liver injury (ALI) caused by multiple inflammatory responses is a monocyte-/macrophage-mediated liver injury that is associated with high morbidity and mortality. Liver macrophage activation is a vital event that triggers ALI. However, the mechanism of liver macrophage activation has not been fully elucidated. This study examined the role of β-arrestin1 (ARRB1) in wild-type (WT) and ARRB1-knockout (ARRB1-KO) mouse models of ALI induced by lipopolysaccharide (LPS), and ARRB1-KO mice exhibited more severe inflammatory injury and liver macrophage activation compared to WT mice. We found that LPS treatment reduced the expression level of ARRB1 in Raw264.7 and THP-1 cell lines, and mouse primary hepatic macrophages. Overexpression of ARRB1 in Raw264.7 and THP-1 cell lines significantly attenuated LPS-induced liver macrophage activation, such as transformation in cell morphology and enhanced expression of proinflammatory cytokines (tumor necrosis factor-α, interleukin-1β, and interleukin-6), while downregulation of ARRB1 by small interfering RNA and ARRB1 deficiency in primary hepatic macrophages both aggravated macrophage activation. Moreover, overexpression of ARRB1 suppressed LPS-induced endoplasmic reticulum (ER) stress in liver macrophages, and inhibition of ER stress impeded excessive hepatic macrophage activation induced by downregulation of ARRB1. Our data demonstrate that ARRB1 relieves LPS-induced ALI through the ER stress pathway to regulate hepatic macrophage activation and that ARRB1 may be a potential therapeutic target for ALI.

Drug discovery and formulation development for acute pancreatitis

Acute pancreatitis is a sudden inflammation and only last for a short time, but might lead to a life-threatening emergency. Traditional drug therapy is an essential supportive method for acute pancreatitis treatment, yet, failed to achieve satisfactory therapeutic outcomes. To date, it is still challenging to develop therapeutic medicine to redress the intricate microenvironment promptly in the inflamed pancreas, and more importantly, avoid multi-organ failure. The understanding of the acute pancreatitis, including the causes, mechanism, and severity judgment, could help the scientists bring up more effective intervention and treatment strategies. New formulation approaches have been investigated to precisely deliver therapeutics to inflammatory lesions in the pancreas, and some even could directly attenuate the pancreatic damages. In this review, we will briefly introduce the involved pathogenesis and underlying mechanisms of acute pancreatitis, as well as the traditional Chinese medicine and the new drug option. Most of all, we will summarize the drug delivery strategies to reduce inflammation and potentially prevent the further development of pancreatitis, with an emphasis on the bifunctional nanoparticles that act as both drug delivery carriers and therapeutics.

ARRB1 ameliorates liver ischaemia/reperfusion injury via antagonizing TRAF6-mediated Lysine 6-linked polyubiquitination of ASK1 in hepatocytes

Hepatic ischaemia/reperfusion (I/R) injury is a major clinical problem during liver surgical procedures, which usually lead to early transplantation failure and higher organ rejection rate, and current effective therapeutic strategies are still limited. Therefore, in‐depth exploring of the molecular mechanisms underlying liver I/R injury is key to the development of new therapeutic methods. β‐arrestins are multifunctional proteins serving as important signalling scaffolds in numerous physiopathological processes, including liver‐specific diseases. However, the role and underlying mechanism of β‐arrestins in hepatic I/R injury remain largely unknown. Here, we showed that only ARRB1, but not ARRB2, was down‐regulated during liver I/R injury. Hepatocyte‐specific overexpression of ARRB1 significantly ameliorated liver damage, as demonstrated by decreases in serum aminotransferases, hepatocellular necrosis and apoptosis, infiltrating inflammatory cells and secretion of pro‐inflammatory cytokines relative to control mice, whereas experiments with ARRB1 knockout mice gotten opposite effects. Mechanistically, ARRB1 directly interacts with ASK1 in hepatocytes and inhibits its TRAF6‐mediated Lysine 6‐linked polyubiquitination, which then prevents the activation of ASK1 and its downstream signalling pathway during hepatic I/R injury. In addition, inhibition of ASK1 remarkably abolished the disruptive effect result from ARRB1 deficiency in liver I/R injury in vivo, indicating that ASK1 was required for ARRB1 function in hepatic I/R injury. In conclusion, we proposed that ARRB1 is a novel protective regulator during liver I/R injury, and modulation of the regulatory axis between ARRB1 and ASK1 could be a novel therapeutic strategy to prevent this pathological process.

ARRB1 inhibits non-alcoholic steatohepatitis progression by promoting GDF15 maturation

BACKGROUND & AIMS

Non-alcoholic steatohepatitis (NASH) is associated with the dysregulation of lipid metabolism and hepatic inflammation. The causal mechanism underlying NASH is not fully elucidated. This study investigated the role of β-Arrestin1 (ARRB1) in the progression of NASH.

METHODS

Liver tissue from patients with NASH and controls were obtained to evaluate ARRB1 expression. NASH models were established in Arrb1-knockout and wild-type mice fed either a high-fat diet (HFD) for 26 weeks or a methionine/choline-deficient (MCD) diet for 6 weeks.

RESULTS

ARRB1 expression was reduced in liver samples from patients with NASH. Reduced Arrb1 levels were also detected in murine NASH models. Arrb1 deficiency accelerated steatohepatitis development in HFD-/MCD-fed mice (accompanied by the upregulation of lipogenic genes and downregulation of β-oxidative genes). Intriguingly, ARRB1 was found to interact with growth differentiation factor 15 (GDF15) and facilitated the transportation of GDF15 precursor (pro-GDF15) to the Golgi apparatus for cleavage and maturation. Treatment with recombinant GDF15 ablated the lipid accumulation in the presence of Arrb1 deletion both in vitro and in vivo. Re-expression of Arrb1 in the NASH models ameliorated the liver disease, and this effect was greater in the presence of pro-GDF15 overexpression. By contrast, the effect of pro-GDF15 overexpression alone was impaired in Arrb1-deficient mice. In addition, the severity of liver disease in patients with NASH was negatively correlated with ARRB1 expression.

CONCLUSION

ARRB1 acts as a vital regulator in the development of NASH by facilitating the translocation of GDF15 to the Golgi apparatus and its subsequent maturation. Thus, ARRB1 is a potential therapeutic target for the treatment of NASH.

LAY SUMMARY

Non-alcoholic steatohepatitis (NASH) is associated with the progressive dysfunction of lipid metabolism and a consequent inflammatory response. Decreased ARRB1 is observed in patients with NASH and murine NASH models. Re-expression of Arrb1 in the murine NASH model ameliorated liver disease, an effect which was more pronounced in the presence of pro-GDF15 overexpression, highlighting a promising strategy for NASH therapy.

Combinatory antibiotic treatment protects against experimental acute pancreatitis by suppressing gut bacterial translocation to pancreas and inhibiting NLRP3 inflammasome pathway

Gut bacterial translocation following impaired gut barrier is a critical determinant of initiating and aggravating acute pancreatitis (AP). Antibiotic combination (ABX; vancomycin, neomycin and polymyxin b) is capable of reducing gut bacteria, but its efficacy in AP prevention and the underlying mechanism have not been investigated yet. AP was induced in BALB/c mice by caerulein (CAE) hyperstimulation. We found that ABX supplementation attenuated the severity of AP as evidenced by reduced pancreatic oedema and myeloperoxidase activity. The protective effect was also confirmed by improved histological morphology of the pancreas and decreased pro-inflammatory markers (IL-1β, TNF-α, MCP-1) in pancreas. ABX administration inhibits the activation of colonic TLR4/NLRP3 inflammasome pathway. Subsequently, down-regulated NLRP3 resulted in decreased colonic pro-inflammation (IL-1β, IL-6, MCP-1) and enhanced gut physical barrier as evidenced by up-regulation of tight junction proteins including occludin, claudin-1 and ZO-1, as well as improved histological morphology of the colon. Together, combinatory ABX therapy inhibited the translocation of gut bacteria to pancreas and its amplification effects on pancreatic inflammation by inhibiting the pancreatic NLRP3 pathway, and inhibiting intestinal-pancreatic inflammatory responses. The current study provides the basis for potential clinical application of ABX in AP.

Murine Models of Acute Pancreatitis: A Critical Appraisal of Clinical Relevance

Acute pancreatitis (AP) is a severe disease associated with high morbidity and mortality. Clinical studies can provide some data concerning the etiology, pathophysiology, and outcomes of this disease. However, the study of early events and new targeted therapies cannot be performed on humans due to ethical reasons. Experimental murine models can be used in the understanding of the pancreatic inflammation, because they are able to closely mimic the main features of human AP, namely their histologic glandular changes and distant organ failure. These models continue to be important research tools for the reproduction of the etiological, environmental, and genetic factors associated with the pathogenesis of this inflammatory pathology and the exploration of novel therapeutic options. This review provides an overview of several murine models of AP. Furthermore, special focus is made on the most frequently carried out models, the protocols used, and their advantages and limitations. Finally, examples are provided of the use of these models to improve knowledge of the mechanisms involved in the pathogenesis, identify new biomarkers of severity, and develop new targeted therapies.