Alpha1-antitrypsin counteracts heme-induced endothelial cell inflammatory activation, autophagy dysfunction and death

Alpha1-antitrypsin improves survival in murine abdominal sepsis model by decreasing inflammation and sequestration of free heme

Background

Excessive inflammation, hemolysis, and accumulation of labile heme play an essential role in the pathophysiology of multi-organ dysfunction syndrome (MODS) in sepsis. Alpha1-antitrypsin (AAT), an acute phase protein with heme binding capacity, is one of the essential modulators of host responses to inflammation. In this study, we evaluate the putative protective effect of AAT against MODS and mortality in a mouse model of polymicrobial abdominal sepsis.

Methods

Polymicrobial abdominal sepsis was induced in C57BL/6N mice by cecal ligation and puncture (CLP). Immediately after CLP surgery, mice were treated intraperitoneally with three different forms of human AAT-plasma-derived native (nAAT), oxidized nAAT (oxAAT), or recombinant AAT (recAAT)-or were injected with vehicle. Sham-operated mice served as controls. Mouse survival, bacterial load, kidney and liver function, immune cell profiles, cytokines/chemokines, and free (labile) heme levels were assessed. In parallel, in vitro experiments were carried out with resident peritoneal macrophages (MPMΦ) and mouse peritoneal mesothelial cells (MPMC).

Results

All AAT preparations used reduced mortality in septic mice. Treatment with AAT significantly reduced plasma lactate dehydrogenase and s-creatinine levels, vascular leakage, and systemic inflammation. Specifically, AAT reduced intraperitoneal accumulation of free heme, production of cytokines/chemokines, and neutrophil infiltration into the peritoneal cavity compared to septic mice not treated with AAT. In vitro experiments performed using MPMC and primary MPMΦ confirmed that AAT not only significantly decreases lipopolysaccharide (LPS)-induced pro-inflammatory cell activation but also prevents the enhancement of cellular responses to LPS by free heme. In addition, AAT inhibits cell death caused by free heme in vitro.

Conclusion

Data from the septic CLP mouse model suggest that intraperitoneal AAT treatment alone is sufficient to improve sepsis-associated organ dysfunctions, preserve endothelial barrier function, and reduce mortality, likely by preventing hyper-inflammatory responses and by neutralizing free heme.

Inhibition of ADAM9 promotes the selective degradation of KRAS and sensitizes pancreatic cancers to chemotherapy

Kirsten rat sarcoma virus (KRAS) signaling drives pancreatic ductal adenocarcinoma (PDAC) malignancy, which is an unmet clinical need. Here, we identify a disintegrin and metalloproteinase domain (ADAM)9 as a modulator of PDAC progression via stabilization of wild-type and mutant KRAS proteins. Mechanistically, ADAM9 loss increases the interaction of KRAS with plasminogen activator inhibitor 1 (PAI-1), which functions as a selective autophagy receptor in conjunction with light chain 3 (LC3), triggering lysosomal degradation of KRAS. Suppression of ADAM9 by a small-molecule inhibitor restricts disease progression in spontaneous models, and combination with gemcitabine elicits dramatic regression of patient-derived tumors. Our findings provide a promising strategy to target the KRAS signaling cascade and demonstrate a potential modality to enhance sensitivity to chemotherapy in PDAC.

Heme-Inducing Endothelial Pyroptosis Plays a Key Role in Radiofrequency Ablation of Hepatic Hemangioma Leading to Systemic Inflammatory Response Syndrome

Purpose

Systemic inflammatory response syndrome (SIRS) is a common complication of radiofrequency ablation (RFA) for hepatic hemangiomas. RFA can cause hemolytic reactions during hepatic hemangioma ablation. However, the mechanisms underlying RFA-induced SIRS remain unclear.

Methods

We established an orthotopic liver hemangioma model and performed radiofrequency ablation. The levels of interleukin (IL)-1β and IL-18 and the production of ROS were measured. The wet-to-dry lung ratio, inflammation score, and in vivo endothelial cell permeability were examined. GSDMD-/- mice were used to investigate the effect of heme-inducing SIRS. RNA sequencing (RNA-seq) was performed to identify the main pathways underlying heme-induced SIRS. Western blotting and immunoprecipitation were used to determine the changes and interactions of associated proteins.

Results

The levels of heme, IL-1β, and IL-18 were significantly increased after RFA. The wet-to-dry lung ratio increased in hepatic hemangiomas after RFA, indicating that SIRS occurred. Heme induced increased levels of IL-1β and IL-18, cell death, wet-to-dry lung radio, and inflammation score in vitro and in vivo, indicating that heme induced SIRS and pyroptosis. Furthermore, GSDMD participates in heme-induced SIRS in mice, and GSDMD deletion in mice reverses the effect of heme. Heme regulates NLRP3 activation through the NOX4/ROS/TXNIP-TRX pathway, and an N-acetyl-L-cysteine (NAC) or NOX4 inhibitor (GLX351322) reverses heme-induced SIRS.

Conclusion

Our findings suggest that heme induces endothelial cell pyroptosis and SIRS in mice and decreasing heme levels and ROS scavengers may prevent SIRS in hepatic hemangioma after RFA.

NAFLD and AATD Are Two Diseases with Unbalanced Lipid Metabolism: Similarities and Differences

Non-alcoholic fatty liver disease (NAFLD) is a type of steatosis commonly associated with obesity, dyslipidemia, hypertension, and diabetes. Other diseases such as inherited alpha-1 antitrypsin deficiency (AATD) have also been related to the development of liver steatosis. The primary reasons leading to hepatic lipid deposits can be genetic and epigenetic, and the outcomes range from benign steatosis to liver failure, as well as to extrahepatic diseases. Progressive hepatocellular damage and dysregulated systemic immune responses can affect extrahepatic organs, specifically the heart and lungs. In this review, we discuss the similarities and differences between the molecular pathways of NAFLD and AATD, and the putative value of hepatic organoids as novel models to investigate the physio pathological mechanisms of liver steatosis.

Role and mechanism of alpa1-antitrypsin in polycystic ovary syndrome

OBJECTIVES

To determine the relationships among alpha1-antitrypsin (A1AT), pro-inflammatory cytokines, neutrophil elastase (NE), interleukin (IL)- 1β, and IL-8 in cases with polycystic ovary syndrome (PCOS).

METHODS

Female rats in the control group were fed and watered normally. Female rats in the PCOS group were given high-fat diets and letrozole (1% carboxymethyl cellulose' [CMC] solution) CMC by gavage at a dose of l mg/kg body weight daily for 23 days. The mRNA levels of A1AT and NE in rat ovaries were detected by performing real-time polymerase chain reaction (PCR) in the laboratory of Norman Bethune College of Medicine, Jilin University, China in 2017. All serum samples were collected from the Second Hospital of Jilin University from October 2021 to November 2021 for obesity concurrent with PCOS. Molecular docking of A1AT with NE, IL-8, and IL-1β was investigated using the Insight II software ZDOCK tool. This study was carried out at the Reproductive Center, The Second Hospital of Jilin University, Changchun, China from June 2021 to July 2022.

RESULTS

The expression of the A1AT mRNA decreased in the ovary tissues of PCOS rats relative to that of healthy controls, while the expression of NE mRNA increased compared to that of normal controls. The serum A1AT expression in PCOS cases decreased considerably relative to their expression in normal controls. However, the expression of NE, IL-1β, and IL-8 increased significantly relative to their expression in the control (p<0.05 for all). The Insight II ZDOCK molecular docking simulations showed that A1AT has direct interaction sites for NE, IL-1β, and IL-8.

CONCLUSION

Alpha1-antitrypsin is closely associated with NE, IL-1β, and IL-8. Therefore, we speculate that A1AT might ameliorate PCOS symptoms by inhibiting pro-inflammatory factors: NE, IL-1β, and IL-8.

Indirect effect of alpha-1-antitrypsin on endotoxin-induced IL-1β secretion from human PBMCs

Human alpha-1-antitrypsin (AAT) encoded by the SERPINA1 gene, is an acute phase glycoprotein that regulates inflammatory responses via both protease inhibitory and non-inhibitory activities. We previously reported that AAT controls ATP-induced IL-1β release from human mononuclear cells by stimulating the release of small bioactive molecules. In the current study, we aimed to elucidate the identity of these putative effectors released from human PBMCs in response to AAT, which may inhibit the LPS-induced release of IL-1β. We pre-incubated human PBMCs alone or with different preparations of AAT (4 mg/ml) for 30 min at 37°C, 5% CO₂, and collected cell supernatants filtered through centrifugal filters (cutoff 3 kDa) to eliminate AAT and other high molecular weight substances. Supernatants passed through the filters were used to culture PBMCs isolated from the autologous or a heterologous donors with or without adding LPS (1 μg/ml) for 6 h. Unexpectedly, supernatants from PBMCs pre-incubated with AAT (Zemaira^®), but not with other AAT preparations tested or with oxidized AAT (Zemaira^®), lowered the LPS-induced release of IL-1β by about 25%–60% without affecting IL1B mRNA. The reversed-phase liquid chromatography coupled with mass spectrometry did not confirm the hypothesis that small pro-resolving lipid mediators released from PBMCs after exposure to AAT (Zemaira^®) are responsible for lowering the LPS-induced IL-1β release. Distinctively from other AAT preparations, AAT (Zemaira^®) and supernatants from PBMCs pre-treated with this protein contained high levels of total thiols. In line, mass spectrometry analysis revealed that AAT (Zemaira^®) protein contains freer Cys232 than AAT (Prolastin^®). Our data show that a free Cys232 in AAT is required for controlling LPS-induced IL-1β release from human PBMCs. Further studies characterizing AAT preparations used to treat patients with inherited AAT deficiency remains of clinical importance.