The protective function of neutrophil elastase inhibitor in liver ischemia/reperfusion injury

Calorie restriction mimetic, resveratrol, attenuates hepatic ischemia and reperfusion injury through enhancing efferocytosis of macrophages via AMPK/STAT3/S1PR1 pathway

Calorie restriction (CR) mimetic, resveratrol (RSV), has the capacity of promoting phagocytosis. However, its role in hepatic ischemia and reperfusion injury (HIRI) remains poorly understood. This study aimed to investigate the effect of RSV on alleviating HIRI and explore the underlying mechanisms. RSV was intraperitoneally injected in mice HIRI model, while RSV was co-incubated with culture medium for 24 h in RAW 264.7 cells and kupffer cells. Macrophage efferocytosis was assessed by immunostaining of PI and F4/80. The clearance of apoptotic neutrophils in the liver was determined by immunostaining of Ly6-G and cleaved-caspase-3. HE staining, Suzuki's score, serum levels of ALT, AST, TNF-α and IL-1β were analyzed to evaluate HIRI. The efferocytosis inhibitor, Cytochalasin D, was utilized to investigate the effect of RSV on HIRI. Western blot was employed to measure the levels of AMPKα, phospho-AMPKα, STAT3, phospho-STAT3 and S1PR1. SiSTAT3 and inhibitors targeting AMPK, STAT3 and S1PR1, respectively, were used to confirm the involvement of AMPK/STAT3/S1PR1 pathway in RSV-mediated efferocytosis and HIRI. RSV facilitated the clearance of apoptotic neutrophils and attenuated HIRI, which was impeded by Cytochalasin D. RSV boosted macrophage efferocytosis by up-regulating the levels of phospho-AMPKα, phospho-STAT3 and S1PR1, which was reversed by AMPK, STAT3 and S1PR1 inhibitors, respectively. Inhibition of STAT3 suppressed RSV-induced clearance of apoptotic neutrophils and exacerbated HIRI. CR mimetic, RSV, alleviates HIRI by promoting macrophages efferocytosis through AMPK/STAT3/S1PR1 pathway, providing valuable insights into the mechanisms underlying the protective effects of CR on attenuating HIRI.

The transplant rejection response involves neutrophil and macrophage adhesion-mediated trogocytosis and is regulated by NFATc3

The anti-foreign tissue (transplant rejection) response, mediated by the immune system, has been the biggest obstacle to successful organ transplantation. There are still many enigmas regarding this process and some aspects of the underlying mechanisms driving the immune response against foreign tissues remain poorly understood. Here, we found that a large number of neutrophils and macrophages were attached to the graft during skin transplantation. Furthermore, both types of cells could autonomously adhere to and damage neonatal rat cardiomyocyte mass (NRCM) in vitro. We have demonstrated that Complement C3 and the receptor CR3 participated in neutrophils/macrophages-mediated adhesion and damage this foreign tissue (NRCM or skin grafts). We have provided direct evidence that the damage to these tissues occurs by a process referred to as trogocytosis, a damage mode that has never previously been reported to directly destroy grafts. We further demonstrated that this process can be regulated by NFAT, in particular, NFATc3. This study not only enriches an understanding of host-donor interaction in transplant rejection, but also provides new avenues for exploring the development of novel immunosuppressive drugs which prevent rejection during transplant therapy.

Modulatory immune responses in fungal infection associated with organ transplant - advancements, management, and challenges

Organ transplantation stands as a pivotal achievement in modern medicine, offering hope to individuals with end-stage organ diseases. Advancements in immunology led to improved organ transplant survival through the development of immunosuppressants, but this heightened susceptibility to fungal infections with nonspecific symptoms in recipients. This review aims to establish an intricate balance between immune responses and fungal infections in organ transplant recipients. It explores the fundamental immune mechanisms, recent advances in immune response dynamics, and strategies for immune modulation, encompassing responses to fungal infections, immunomodulatory approaches, diagnostics, treatment challenges, and management. Early diagnosis of fungal infections in transplant patients is emphasized with the understanding that innate immune responses could potentially reduce immunosuppression and promise efficient and safe immuno-modulating treatments. Advances in fungal research and genetic influences on immune-fungal interactions are underscored, as well as the potential of single-cell technologies integrated with machine learning for biomarker discovery. This review provides a snapshot of the complex interplay between immune responses and fungal infections in organ transplantation and underscores key research directions.

Interplay Between Inflammatory-immune and Interleukin-17 Signalings Plays a Cardinal Role on Liver Ischemia-reperfusion Injury-Synergic Effect of IL-17Ab, Tacrolimus and ADMSCs on Rescuing the Liver Damage

BACKGROUND

This study tested the hypothesis that inflammatory and interleukin (IL)-17 signalings were essential for acute liver ischemia (1 h)-reperfusion (72 h) injury (IRI) that was effectively ameliorated by adipose-derived mesenchymal stem cells (ADMSCs) and tacrolimus.

METHODS

Adult-male SD rats (n = 50) were equally categorized into groups 1 (sham-operated-control), 2 (IRI), 3 [IRI + IL-17-monoclonic antibody (Ab)], 4 (IRI + tacrolimus), 5 (IRI + ADMSCs) and 6 (IRI + tacrolimus-ADMSCs) and liver was harvested at 72 h.

RESULTS

The main findings included: (1) circulatory levels: inflammatory cells, immune cells, and proinflammatory cytokines as well as liver-damage enzyme at the time point of 72 h were highest in group 2, lowest in group 1 and significantly lower in group 6 than in groups 3 to 5 (all p < 0.0001), but they did not differ among these three latter groups; (2) histopathology: the liver injury score, fibrosis, inflammatory and immune cell infiltration in liver immunity displayed an identical pattern of inflammatory cells among the groups (all p < 0.0001); and (3) protein levels: upstream and downstream inflammatory signalings, oxidative-stress, apoptotic and mitochondrial-damaged biomarkers exhibited an identical pattern of inflammatory cells among the groups (all p < 0.0001).

CONCLUSION

Our results obtained from circulatory, pathology and molecular-cellular levels delineated that acute IRI was an intricate syndrome that elicited complex upstream and downstream inflammatory and immune signalings to damage liver parenchyma that greatly suppressed by combined tacrolimus and ADMSCs therapy.

Application of microphysiologic system to assess neutrophil extracellular trap in xenotransplantation

Transplantation of organs, cells, or tissues from one species to another, known as xenotransplantation, has the potential to alleviate organ donor shortages and enhance the success of organ transplantation. However, the possibility of immunological rejection by the recipient is one of the biggest difficulties associated with xenotransplantation. The creation of neutrophil extracellular traps (NETs), also known as NETosis, is hypothesized as a mechanism of rejection. Innovations in microfluidics and co-culturing techniques have provided access to several classes of microengineered model systems in experimental models, connecting animal research and traditional in vitro methods such as organoids, microphysiological systems, and organs-on-chip. To achieve this goal, we established a perfusable 3D Xeno vessel chip using a porcine aortic endothelial cell line and examined how NETs grow when isolated human and primate neutrophils were used. Neutrophils from both humans and monkeys displayed the usual NETosis phases, including nuclear decondensation, enlargement, and rounding of DNA, occupying the entire cytoplasm, and discharge of fragmented DNA after cell membrane rupture. Using confocal fluorescence imaging of DNA and citrullinated histone colocalization and DNA histone complex formation in supernatants from xeno vessel chips, we confirmed NETs generation by human and monkey neutrophils when cocultured in a xeno-vessel chip.

Neutrophil subsets in noncancer liver diseases: Cellular crosstalk and therapeutic targets

Neutrophils are the most abundant circulating granulocytes, linking innate and adaptive immunity. Neutrophils can regulate inflammatory and immune responses through degranulation, reactive oxygen species generation, the production of cytokines and chemokines, and NETosis. Emerging evidence has indicated that neutrophils contribute to the pathogenesis of various noncancer liver diseases, including nonalcoholic fatty liver disease, alcohol-associated liver disease, hepatic ischemia-reperfusion injury, and liver fibrosis. Cellular interactions among neutrophils, other immune cells, and nonimmune cells constitute a complex network that regulates the immune microenvironment of the liver. This review summarizes novel neutrophil subtypes, including CD177+ neutrophils and low-density neutrophils. Moreover, we provide an overview of the cellular cros stalk of neutrophils in noncancer liver diseases, aiming to shed new light on mechanistic studies of novel neutrophil subtypes. In addition, we discuss the potential of neutrophils as therapeutic targets in noncancer liver diseases, including inhibitors targeting NETosis, granule proteins, and chemokines.

Essential Involvement of Neutrophil Elastase in Acute Acetaminophen Hepatotoxicity Using BALB/c Mice

Intense neutrophil infiltration into the liver is a characteristic of acetaminophen-induced acute liver injury. Neutrophil elastase is released by neutrophils during inflammation. To elucidate the involvement of neutrophil elastase in acetaminophen-induced liver injury, we investigated the efficacy of a potent and specific neutrophil elastase inhibitor, sivelestat, in mice with acetaminophen-induced acute liver injury. Intraperitoneal administration of 750 mg/kg of acetaminophen caused severe liver damage, such as elevated serum transaminase levels, centrilobular hepatic necrosis, and neutrophil infiltration, with approximately 50% mortality in BALB/c mice within 48 h of administration. However, in mice treated with sivelestat 30 min after the acetaminophen challenge, all mice survived, with reduced serum transaminase elevation and diminished hepatic necrosis. In addition, mice treated with sivelestat had reduced NOS-II expression and hepatic neutrophil infiltration after the acetaminophen challenge. Furthermore, treatment with sivelestat at 3 h after the acetaminophen challenge significantly improved survival. These findings indicate a new clinical application for sivelestat in the treatment of acetaminophen-induced liver failure through mechanisms involving the regulation of neutrophil migration and NO production.

DNase I and Sivelestat Ameliorate Experimental Hindlimb Ischemia-Reperfusion Injury by Eliminating Neutrophil Extracellular Traps

Purpose

Neutrophil extracellular traps (NETs) play an important role in ischemia-reperfusion injury (IRI) of the hindlimb. The aim of this study was to investigate the effect of recombinant DNase I and sivelestat in eliminating NETs and their effects on IRI limbs.

Patients and Methods

An air pump was used to apply a pressure of 300 mmHg to the root of the right hindlimb of the rat for 2 h and then deflated to replicate the IRI model. The formation of NETs was determined by the detection of myeloperoxidase (MPO), neutrophil elastase (NE), and histone H3 in the skeletal muscles of the hindlimbs. Animals were administered 2.5 mg/kg bw/d DNase I, 15 or 60 mg/kg bw/d sivelestat by injection into the tail vein or intramuscularly into the ischemic area for 7d. Elimination of NETs, hindlimb perfusion, muscle fibrosis, angiogenesis and motor function were assessed.

Results

DNase I reduced NETs, attenuated muscle fibrosis, promoted angiogenesis in IRI area and improved limb motor function. Local administration of DNase I improved hindlimb perfusion more than intravenous administration. Sivelestat at a dose of 15 mg/kg bw/d increased perfusion, counteracted skeletal muscle fibrosis, promoted angiogenesis and enhanced motor function. However, sivelestat at a dosage of 60 mg/kg bw/d had an adverse effect on tissue repair, especially when injected locally.

Conclusion

Both DNase I and moderate doses of sivelestat can eliminate IRI-derived NETs. They improve hindlimb function by improving perfusion and angiogenesis, preventing muscle fibrosis. Appropriate administration mode and dosage is the key to prevent IRI by elimination of NETs. DNase I is more valid when administered topically and sivelestat is more effective when administered intravenously. These results will provide a better strategy for the treatment of IRI in clinical.

The Ninj1/Dusp1 Axis Contributes to Liver Ischemia Reperfusion Injury by Regulating Macrophage Activation and Neutrophil Infiltration

BACKGROUND & AIMS

Liver ischemia-reperfusion (IR) injury represents a major risk factor in both partial hepatectomy and liver transplantation. Nerve injury-induced protein 1 (Ninj1) is widely recognized as an adhesion molecule in leukocyte trafficking under inflammatory conditions, but its role in regulating sterile inflammation during liver IR injury remains unclear.

METHODS

Myeloid Ninj1-deficient mice were generated by bone marrow chimeric models using Ninj1 knockout mice and wild-type mice. In vivo, a liver partial warm ischemia model was applied. Liver injury and hepatic inflammation were investigated. In vitro, primary Kupffer cells (KCs) isolated from Ninj1 knockout and wild-type mice were used to explore the function and mechanism of Ninj1 in modulating KC inflammation upon lipopolysaccharide stimulation.

RESULTS

Ninj1 deficiency in KCs protected mice against liver IR injury during the later phase of reperfusion, especially in neutrophil infiltration, intrahepatic inflammation, and hepatocyte apoptosis. This prompted ischemia-primed KCs to decrease proinflammatory cytokine production. In vitro and in vivo, using small-interfering RNA against dual-specificity phosphatase 1 (DUSP1), we found that Ninj1 deficiency diminished the inflammatory response in KCs and neutrophil infiltration through DUSP1-dependent deactivation of the c-Jun-N-terminal kinase and p38 pathways. Sivelestat, a neutrophil elastase inhibitor, functioned similarly to Ninj1 deficiency, resulting in both mitigated hepatic IR injury in mice and a more rapid recovery of liver function in patients undergoing liver resection.

CONCLUSIONS

The Ninj1/Dusp1 axis contributes to liver IR injury by regulating the proinflammatory response of KCs, and influences neutrophil infiltration, partly by subsequent regulation of C-X-C motif chemokine ligand 1 (CXCL1) production after IR.

Xenotransplantation: Current Challenges and Emerging Solutions

To address the ongoing shortage of organs available for replacement, xenotransplantation of hearts, corneas, skin, and kidneys has been attempted. However, a major obstacle facing xenotransplants is rejection due to a cycle of immune reactions to the graft. Both adaptive and innate immune systems contribute to this cycle, in which natural killer cells, macrophages, and T-cells play a significant role. While advancements in the field of genetic editing can circumvent some of these obstacles, biomarkers to identify and predict xenograft rejection remain to be standardized. Several T-cell markers, such as CD3, CD4, and CD8, are useful in both the diagnosis and prediction of xenograft rejection. Furthermore, an increase in the levels of various circulating DNA markers and microRNAs is also predictive of xenograft rejection. In this review, we summarize recent findings on the advancements in xenotransplantation, with a focus on pig-to-human, the role of immunity in xenograft rejection, and its biomarkers.

Updated Views on Neutrophil Responses in Ischemia-Reperfusion Injury

Ischemia-reperfusion injury is an inevitable event during organ transplantation and represents a primary risk factor for the development of early graft dysfunction in lung, heart, liver, and kidney transplant recipients. Recent studies have implicated recipient neutrophils as key mediators of this process and also have found that early innate immune responses after transplantation can ultimately augment adaptive alloimmunity and affect late graft outcomes. Here, we discuss signaling pathways involved in neutrophil recruitment and activation after ischemia-mediated graft injury in solid organ transplantation with an emphasis on lung allografts, which have been the focus of recent studies. These findings suggest novel therapeutic interventions that target ischemia-reperfusion injury-mediated graft dysfunction in transplant recipients.

Current status of xenotransplantation research and the strategies for preventing xenograft rejection

Transplantation is often the last resort for end-stage organ failures, e.g., kidney, liver, heart, lung, and pancreas. The shortage of donor organs is the main limiting factor for successful transplantation in humans. Except living donations, other alternatives are needed, e.g., xenotransplantation of pig organs. However, immune rejection remains the major challenge to overcome in xenotransplantation. There are three different xenogeneic types of rejections, based on the responses and mechanisms involved. It includes hyperacute rejection (HAR), delayed xenograft rejection (DXR) and chronic rejection. DXR, sometimes involves acute humoral xenograft rejection (AHR) and cellular xenograft rejection (CXR), which cannot be strictly distinguished from each other in pathological process. In this review, we comprehensively discussed the mechanism of these immunological rejections and summarized the strategies for preventing them, such as generation of gene knock out donors by different genome editing tools and the use of immunosuppressive regimens. We also addressed organ-specific barriers and challenges needed to pave the way for clinical xenotransplantation. Taken together, this information will benefit the current immunological research in the field of xenotransplantation.

Pancreas Preservation with a Neutrophil Elastase Inhibitor, Alvelestat, Contributes to Improvement of Porcine Islet Isolation and Transplantation

For pancreatic islet transplantation, pancreas procurement, preservation, and islet isolation destroy cellular and non-cellular components and activate components such as resident neutrophils, which play an important role in the impairment of islet survival. It has been reported that inhibitors of neutrophil elastase (NE), such as sivelestat and α1-antitrypsin, could contribute to improvement of islet isolation and transplantation. In this study, we investigated whether pancreatic preservation with alvelestat, a novel NE inhibitor, improves porcine islet yield and function. Porcine pancreata were preserved with or without 5 μM alvelestat for 18 h, and islet isolation was performed. The islet yields before and after purification were significantly higher in the alvelestat (+) group than in the alvelestat (−) group. After islet transplantation into streptozotocin-induced diabetic mice, blood glucose levels reached the normoglycemic range in 55% and 5% of diabetic mice in the alvelestat (+) and alvelestat (−) groups, respectively. These results suggest that pancreas preservation with alvelestat improves islet yield and graft function and could thus serve as a novel clinical strategy for improving the outcome of islet transplantation.

The Innate Cellular Immune Response in Xenotransplantation

Xenotransplantation is very attractive strategy for addressing the shortage of donors. While hyper acute rejection (HAR) caused by natural antibodies and complement has been well defined, this is not the case for innate cellular xenogeneic rejection. An increasing body of evidence suggests that innate cellular immune responses contribute to xenogeneic rejection. Various molecular incompatibilities between receptors and their ligands across different species typically have an impact on graft outcome. NK cells are activated by direct interaction as well as by antigen dependent cellular cytotoxicity (ADCC) mechanisms. Macrophages are activated through various mechanisms in xenogeneic conditions. Macrophages recognize CD47 as a "marker of self" through binding to SIRPα. A number of studies have shown that incompatibility of porcine CD47 against human SIRPα contributes to the rejection of xenogeneic target cells by macrophages. Neutrophils are an early responder cell that infiltrates xenogeneic grafts. It has also been reported that neutrophil extracellular traps (NETs) activate macrophages as damage-associated pattern molecules (DAMPs). In this review, we summarize recent insights into innate cellular xenogeneic rejection.

Liver ischaemia-reperfusion injury: a new understanding of the role of innate immunity

Liver ischaemia-reperfusion injury (LIRI), a local sterile inflammatory response driven by innate immunity, is one of the primary causes of early organ dysfunction and failure after liver transplantation. Cellular damage resulting from LIRI is an important risk factor not only for graft dysfunction but also for acute and even chronic rejection and exacerbates the shortage of donor organs for life-saving liver transplantation. Hepatocytes, liver sinusoidal endothelial cells and Kupffer cells, along with extrahepatic monocyte-derived macrophages, neutrophils and platelets, are all involved in LIRI. However, the mechanisms underlying the responses of these cells in the acute phase of LIRI and how these responses are orchestrated to control and resolve inflammation and achieve homeostatic tissue repair are not well understood. Technological advances allow the tracking of cells to better appreciate the role of hepatic macrophages and platelets (such as their origin and immunomodulatory and tissue-remodelling functions) and hepatic neutrophils (such as their selective recruitment, anti-inflammatory and tissue-repairing functions, and formation of extracellular traps and reverse migration) in LIRI. In this Review, we summarize the role of macrophages, platelets and neutrophils in LIRI, highlight unanswered questions, and discuss prospects for innovative therapeutic regimens against LIRI in transplant recipients.

FAM49B, restrained by miR-22, relieved hepatic ischemia/reperfusion injury by inhibiting TRAF6/IKK signaling pathway in a Rac1-dependent manner

Hepatic ischemia/reperfusion (I/R) injury plays a pivotal pathogenic role in trauma, hepatectomy, and liver transplantation. However, the whole mechanism remains undescribed. The objective of this study is to investigate the internal mechanism by which microRNA-22 (miR-22) targets family with sequence similarity 49 member B (FAM49B), thus aggravating hepatic I/R injury. Here, we found that miR-22 was upregulated while FAM49B was reduced in hepatic I/R injury. Inhibition of miR-22 in vitro was able to intensify expression of FAM49B, thus reducing phosphorylation of inhibitors of nuclear factor kappa-B kinase (IKK) and downstream pro-inflammatory proteins. A dual luciferase reporter assay indicated that miR-22 directly targeted FAM49B. Remission of hepatic pathologic alterations, apoptosis, and release of cytokines derived from constraints of miR-22 were abolished in vivo by repressing FAM49B. Further interference of Ras-related C3 botulinum toxin substrate 1 (Rac1) reversed the function of FAM49B inhibition, thus achieving anti-inflammatory consequences.

Contribution of Liver and Pancreatic Islet Crosstalk to β-Cell Function/Dysfunction in the Presence of Fatty Liver

Tissue-to-tissue crosstalk regulates organ function, according to growing data. This phenomenon is relevant for pancreatic β-cells and the liver, as both tissues are involved in glucose homeostasis and lipid metabolism. The ability to fine-tune regulation and adaptive responses is enabled through communication between pancreatic β-cells and the liver. However, the crosstalk between both tissues changes when metabolic dysregulation is present. Factors and cargo from extracellular vesicles (EVs) released by liver and pancreatic β-cells that reach the circulation form the words of this interaction. The molecules released by the liver are called hepatokines and are usually secreted in response to the metabolic state. When hepatokines reach the pancreatic islets several mechanisms are initiated for their protection or damage. In the case of the crosstalk between pancreatic β-cells and the liver, only one factor has been found to date. This protein, pancreatic derived factor (PANDER) has been proposed as a novel linker between insulin resistance (IR) and type 2 diabetes mellitus (T2D) and could be considered a biomarker for non-alcoholic fatty liver disease (NAFLD) and T2D. Furthermore, the cargo released by EVs, mainly miRNAs, plays a significant role in this crosstalk. A better knowledge of the crosstalk between liver and pancreatic β-cells is essential to understand both diseases and it could lead to better prevention and new therapeutic options.

NETosis in ischemic/reperfusion injuries: An organ-based review

Neutrophil extracellular trap (NETosis), the web-like structures induced by neutrophil death, is an important inflammatory mechanism of the immune system leading to reactive oxygen species production/coagulopathy, endothelial dysfunction, atherosclerosis, and ischemia. NETosis exerts its role through different mechanisms such as triggering Toll-like receptors, inflammatory cytokines, platelet aggregation, neutrophil activation/infiltration, and vascular impairment. NETosis plays a key role in the prognosis of coronary artery disease, ischemic injury of kidney, lung, gastrointestinal tract and skeletal muscles. In this review, we explored the molecular mechanisms involved in NETosis, and ischemic/reperfusion injuries in body organs.

The Regulation of Neutrophil Extracellular Trap-induced Tissue Damage by Human CD177

Background

Neutrophil-induced tissue damage contributes to the rejection in xenotransplantation. Therefore, suppressing neutrophil function could be effective in suppressing xenogeneic rejection. In a previous study, we demonstrated that the ectopic expression of human cluster of differentiation 31 (CD31) on porcine endothelial cells (PEC) significantly suppressed neutrophil-mediated cytotoxicity through the homophilic binding of CD31. Cluster of differentiation 177 (CD177) was recently reported to be a high-affinity heterophilic binding partner for CD31 on endothelial cells. Thus, we hypothesized that human CD177 on PEC might induce a stronger suppression in neutrophil-mediated cytotoxicity compared with CD31. In this study, the inhibitory function of human CD177 on PEC in neutrophil-mediated cytotoxicity was investigated.

Methods

PEC were transfected with a cloning plasmid containing cDNA inserts that encoded for hCD177 and hCD31 genes. Neutrophil-induced cytotoxicity was evaluated by flow cytometry after coculturing with PEC or PEC/CD177 in the presence of phorbol 12-myristate 13-acetate. To elucidate the mechanisms responsible for hCD177-induced suppression, the phosphorylation of src homology region 2 domain containing phosphatase 1 was measured by immunoblot analysis.

Results

Human CD177 on PEC induced a significant reduction in neutrophil-induced cytotoxicity. In addition, CD177 on PEC induced a significant increase in the phosphorylation of src homology region 2 domain-containing phosphatase 1 in neutrophils and suppressed NETosis.

Conclusions

These findings suggest that human CD177 suppresses neutrophil-mediated cytotoxicity through the inhibition of NETosis.

The Influence of Macrophage-Activating Lipopeptide-2 in Regard to Liver-Specific Changes Within a Murine Two-Hit Model

Trauma hemorrhage (TH) and subsequent sepsis are well known to frequently result in severe organ damage. Although macrophage-activating lipopeptide-2 (MALP-2) has been described to exert beneficial effects on organ damage, and further clinical course after both isolated trauma and sepsis, little is known about the impact of MALP-2 in a clinically realistic two-hit scenario of TH and subsequent sepsis. As the liver represents a key organ for the posttraumatic immune response and development of complications, the effects of MALP-2 on the posttraumatic hepatic immunologic response and tissue damage were investigated in a murine "two-hit" model. In C57BL/6 mice, blood pressure-controlled (35 ± 5 mm Hg) TH was induced. Cecal ligation and puncture (CLP) was performed 48 h after TH. Mice were divided into two control groups (control 1, TH and laparotomy without CLP; control 2, TH and CLP) and three experimental groups (TH + CLP) treated with MALP-2 at different timepoints (ETH, end of TH; ECLP, end of CLP; 6CLP, 6 h after CLP). The observation time lasted for 168 h after induction of TH. Kupffer cells (KC) were isolated and cultured, and MPO activity was analyzed. Cell culture supernatants were taken for cytokine analysis (TNF-α, IL-6, MCP-1, GM-CSF, IL-10). Histological analysis was performed using the Hepatic Injury Severity Scoring (HISS). Statistical evaluation was carried out using SPSS (version 24.0.0; IBM, Armonk, NY, USA). MPO activity of control 1 group was lowest compared with all the other groups (p < 0.01). MPO activity of control 2 group was significantly higher than that in all experimental groups (ETH (p < 0.01), ECLP (p < 0.01), and 6CLP (p = 0.03)). Within the experimental groups, MPO activity was significantly reduced in the ETH (p = 0.04) and the ECLP (p < 0.01) groups compared with the 6CLP group. Moreover, ETH was also associated with the most pronounced reduction of cytokine expression by KC (p < 0.05). HISS revealed the largest damage in the group control 2. TH and subsequent sepsis lead to a distinct immunologic reaction in the liver with an increase of cytokine expression of KC and pronounced infiltration of granulocytes with associated severe tissue damage. MALP application decreases the hepatic immune response and liver damage, with the most pronounced effects if applied at the end of TH.

MMP-9-mediated regulation of hypoxia-reperfusion injury-related neutrophil inflammation in an in vitro proximal tubular cell model

Background

Hypoxia-reperfusion (HR) and inflammation are causes of renal allograft injury. Pathological evidence has indicated that ischemia followed by reperfusion leads to the proteolysis and destruction of the extracellular matrix (ECM) in renal tubular epithelial cells. Matrix metalloproteinases (MMPs), such as MMP-2 and MMP-9, play roles in cleaving and reshaping the ECM. Acute accumulation of MMP-9 secreted from neutrophils promotes the incidence of inflammation and exacerbates graft trauma. Our goal was to investigate the activities of MMP-9/MMP-2 and their correlation with HR injury and neutrophil-related inflammation in renal proximal tubular cells.

Methods

This model was established by placing HK-2 cells under hypoxic conditions (5% CO₂, 1% O₂) for 6 h and then exposing them to reperfusion (5% CO₂, 21% O₂) for 12 h in a tri-gas incubator. The cell culture medium was collected for culturing polymorphonuclear leukocytes (PMNs). BB-94 (MMP-9 inhibitor) was added to the culture medium in the inhibitor group.

Results

Flow cytometry showed a significant increase in reactive oxygen species (ROS) levels in HK-2 cells from the HR injury group. MMP-9 expression was significantly increased and MMP-2 expression was significantly decreased in HK-2 cells from the HR group. MMP-9 and MPO expression were significantly increased in the HR group, while MPO expression was significantly decreased in the PMN inhibitor group.

Conclusions

The outcomes indicated that MMP-9 and MMP-2 are important components of an underlying pathophysiological mechanism of injury following HR. MMP-9 inhibition may be a potential approach to mitigateHR injury.

Topical Application of Conditioned Medium from Hypoxically Cultured Amnion-Derived Mesenchymal Stem Cells Promotes Wound Healing in Diabetic Mice

BACKGROUND

Mesenchymal stem cells or their conditioned medium improve chronic wound healing, and their effect is enhanced by hypoxia. Diabetic foot ulcers are chronic wounds characterized by abnormal and delayed healing, which frequently require amputation. The authors evaluated the effect of topical application of conditioned medium from hypoxically cultured amnion-derived mesenchymal stem cells on wound healing in diabetic mice.

METHODS

Amnion-derived mesenchymal stem cells were cultured under 21% oxygen to prepare normoxic conditioned medium and under 1% oxygen to prepare hypoxic conditioned medium. Hydrogels containing standard medium, normoxic conditioned medium, or hypoxic conditioned medium were topically applied to excisional wounds of mice with streptozotocin-induced diabetes. Ulcer tissues were harvested on day 9; immunohistochemical and quantitative polymerase chain reaction analyses were performed to analyze angiogenesis, inflammatory cell infiltration, and expression levels of inflammation-related genes.

RESULTS

Hypoxic conditioned medium significantly enhanced wound closure, increased capillary density and epithelization, and reduced macrophage infiltration. It also tended to reduce the infiltration of neutrophils and enhance the infiltration of regulatory T cells; it showed a tendency to downregulate the expression of the inflammation-related genes interleukin-1β, interleukin-6, chemokine ligand 1, and chemokine ligand 2. Normoxic conditioned medium exhibited similar effects, although they were of lesser magnitude than those of hypoxic conditioned medium.

CONCLUSIONS

Hydrogels containing hypoxically cultured, amnion-derived mesenchymal stem cell conditioned medium accelerated wound healing in diabetic mice by enhancing angiogenesis, accelerating epithelization, and suppressing inflammation. Therefore, topical application of amnion mesenchymal stem cell-derived hypoxic conditioned medium could be a novel treatment for diabetic foot ulcers.

Possible involvement of progranulin in the protective effect of elastase inhibitor on cerebral ischemic injuries of neuronal and glial cells

In a previous study, we demonstrated that neutrophil elastase is activated in the brain parenchyma after cerebral ischemia, which enzyme cleaves progranulin (PGRN), an anti-inflammatory factor. In that study, we also found that sivelestat, a selective neutrophil elastase inhibitor, attenuates ischemia-induced inflammatory responses. However, it was not clear whether this anti-inflammatory effect was due to the direct effect of sivelestat. In this study, we evaluated the effects of sivelestat or recombinant PGRN (rPGRN) on cell injuries in cultured neurons, astrocytes, and microglia under oxygen/glucose deprivation (OGD) conditions. We demonstrated that OGD-induced neuronal cell injury, astrocyte activation, and increased proinflammatory cytokines caused by microglial activation, were suppressed by rPGRN treatment, whereas sivelestat had no effect on any of these events. These results indicate that the anti-inflammatory responses after in vivo cerebral ischemia were not due to the direct action of sivelestat but due to the suppression of PGRN cleavage by inhibition of elastase activity. It was also suggested that the pleiotropic effect of rPGRN could be attributed to the differentiation of M1 microglia into anti-inflammatory type M2 microglia. Therefore, the inhibition of PGRN cleavage by sivelestat could contribute to the establishment of a new therapeutic approach for cerebral ischemia.

The Roles of Neutrophils in the Pathogenesis of Liver Diseases

Neutrophils are the largest population of circulating leukocytes and the first responder against invading pathogens or other danger signals. Sophisticated machineries help them play critical roles in immunity and inflammation, including phagocytosis, superoxide production, cytokine and chemokine production, degranulation, and formation of neutrophil extracellular traps (NETs). After maturation and release from the bone marrow, neutrophils migrate to inflamed tissues in response to many stimuli. Increasing evidences indicate that neutrophils are critically involved in the pathogenesis of liver diseases, including liver cancer, thus making them promising target for the treatment of liver diseases. Here, we would like to provide the latest finding about the role of neutrophils in liver diseases and discuss the potentiality of neutrophils as target for liver diseases.

The lectin-like domain of thrombomodulin is a drug candidate for both prophylaxis and treatment of liver ischemia and reperfusion injury in mice

Ischemia and reperfusion injury (IRI) can occur in any tissue or organ. With respect to liver transplantation, the liver grafts from donors by definition experience transient ischemia and subsequent blood reflow. IRI is a problem not only in organ transplantation but also in cases of thrombosis or circulatory disorders such as mesenteric ischemia, myocardial, or cerebral infarction. We have reported that recombinant human soluble thrombomodulin (rTM), which is currently used in Japan to treat disseminated intravascular coagulation (DIC), has a protective effect and suppresses liver IRI in mice. However, rTM may not be fully safe to use in humans because of its inherent anticoagulant activity. In the present study, we used a mouse liver IRI model to explore the possibility that the isolated lectin-like domain of rTM (rTMD1), which has no anticoagulant activity, could be effective as a therapeutic modality for IRI. Our results indicated that rTMD1 could suppress ischemia and reperfusion-induced liver damage in a dose-dependent manner without concern of associated hemorrhage. Surprisingly, rTMD1 suppressed the liver damage even after IR insult had occurred. Taken together, we conclude that rTMD1 may be a candidate drug for prevention of and therapy for human liver IRI without the possible risk of hemorrhage.

Therapeutic targeting of neutrophil exocytosis

Dysregulation of neutrophil activation causes disease in humans. Neither global inhibition of neutrophil functions nor neutrophil depletion provides safe and/or effective therapeutic approaches. The role of neutrophil granule exocytosis in multiple steps leading to recruitment and cell injury led each of our laboratories to develop molecular inhibitors that interfere with specific molecular regulators of secretion. This review summarizes neutrophil granule formation and contents, the role granule cargo plays in neutrophil functional responses and neutrophil-mediated diseases, and the mechanisms of granule release that provide the rationale for development of our exocytosis inhibitors. We present evidence for the inhibition of granule exocytosis in vitro and in vivo by those inhibitors and summarize animal data indicating that inhibition of neutrophil exocytosis is a viable therapeutic strategy.

Combination of sivelestat and N-acetylcysteine alleviates the inflammatory response and exceeds standard treatment for acetaminophen-induced liver injury

Hepatocyte death during acetaminophen (APAP) intoxication elicits a reactive inflammatory response, with hepatic recruitment of neutrophils and monocytes, which further aggravates liver injury. Neutrophil elastase (NE), secreted by activated neutrophils, carries degradative and cytotoxic functions and maintains a proinflammatory state. We investigated NE as a therapeutic target in acetaminophen-induced liver injury (AILI). C57BL/6 mice were administered a toxic dose of APAP, 2 h prior to receiving the NE inhibitor sivelestat, N-acetylcysteine (NAC), or a combination therapy, and were euthanized after 24 and 48 h. Upon APAP overdose, neutrophils and monocytes infiltrate the injured liver, accompanied by increased levels of NE. Combination therapy of NAC and sivelestat significantly limits liver damage, as evidenced by lower serum transaminase levels and less hepatic necrosis compared to mice that received APAP only, and this to a greater extent than NAC monotherapy. Lower hepatic expression of proinflammatory markers was observed in the combination treatment group, and flow cytometry revealed significantly less monocyte influx in livers from mice treated with the combination therapy, compared to untreated mice and mice treated with NAC only. The potential of NE to induce leukocyte migration was confirmed in vitro. Importantly, sivelestat did not impair hepatic repair. In conclusion, combination of NE inhibition with sivelestat and NAC dampens the inflammatory response and reduces liver damage following APAP overdose. This strategy exceeds the standard of care and might represent a novel therapeutic option for AILI.

Neutrophil Elastase Inhibitors Suppress Oxidative Stress in Lung during Liver Transplantation

Background

Neutrophil infiltration plays a critical role in the pathogenesis of acute lung injury following liver transplantation (LT). Neutrophil elastase is released from neutrophils during pulmonary polymorphonuclear neutrophil activation and sequestration. The aim of the study was to investigate whether the inhibition of neutrophil elastase could lead to the restoration of pulmonary function following LT.

Methods

In in vivo experiments, lung tissue and bronchoalveolar lavage fluid (BALF) were collected at 2, 4, 8, and 24 h after rats were subjected to orthotopic autologous LT (OALT), and neutrophil infiltration was detected. Next, neutrophil elastase inhibitors, sivelestat sodium hydrate (exogenous) and serpin family B member 1 (SERPINB1) (endogenous), were administered to rats before OALT, and neutrophil infiltration, pulmonary oxidative stress, and barrier function were measured at 8 h after OALT.

Results

Obvious neutrophil infiltration occurred from 2 h and peaked at 8 h in the lungs of rats after they were subjected to OALT, as evidenced by an increase in naphthol-positive cells, BALF neutrophil elastase activity, and lung myeloperoxidase activity. Treatment with neutrophil elastase inhibitors, either sivelestat sodium hydrate or SERPINB1, effectively reduced lung naphthol-positive cells and BALF inflammatory cell content, increased expression of lung HO-1 and tight junction proteins ZO-1 and occludin, and increased the activity of superoxide dismutase.

Conclusion

Neutrophil elastase inhibitors, sivelestat sodium hydrate and SERPINB1, both reduced lung neutrophil infiltration and pulmonary oxidative stress and finally restored pulmonary barrier function.

Involvement of Progranulin and Granulin Expression in Inflammatory Responses after Cerebral Ischemia

Progranulin (PGRN) plays a crucial role in diverse biological processes, including cell proliferation and embryonic development. PGRN can be cleaved by neutrophil elastase to release granulin (GRN). PGRN has been found to inhibit inflammation. Whereas, GRN plays a role as a pro-inflammatory factor. However, the pathophysiological roles of PGRN and GRN, at early stages after cerebral ischemia, have not yet been fully understood. The aim of this study was to obtain further insight into the pathologic roles of PGRN and GRN. We demonstrated that the amount of PGRN was significantly increased in microglial cells after cerebral ischemia in rats and that neutrophil elastase activity was also increased at an early stage after cerebral ischemia, resulting in the production of GRN. The inhibition of neutrophil elastase activity suppressed PGRN cleavage and GRN production, as well as the increase in pro-inflammatory cytokines, after cerebral ischemia. The administration of an elastase inhibitor decreased the number of injured cells and improved the neurological deficits test scores. Our findings suggest that an increase in the activity of elastase to cleave PGRN, and to produce GRN, was involved in an inflammatory response at the early stages after cerebral ischemia, and that inhibition of elastase activity could suppress the progression of cerebral ischemic injury.

Premedication with a cathepsin C inhibitor alleviates early primary graft dysfunction in mouse recipients after lung transplantation

Neutrophil serine proteases (NSPs), like proteinase 3 (PR3) and neutrophil elastase (NE) are implicated in ischemia-reperfusion responses after lung transplantation (LTx). Cathepsin C (CatC) acts as the key regulator of NSP maturation during biosynthesis. We hypothesized that CatC inhibitors would reduce vascular breakdown and inflammation during reperfusion in pretreated lung transplant recipients by blocking NSP maturation in the bone marrow. An orthotopic LTx model in mice was used to mimic the induction of an ischemia-reperfusion response after 18 h cold storage of the graft and LTx. Recipient mice were treated subcutaneously with a chemical CatC inhibitor (ICatC) for 10 days prior to LTx. We examined the effect of the ICatC treatment by measuring the gas exchange function of the left lung graft, protein content, neutrophil numbers and NSP activities in the bone marrow 4 h after reperfusion. Pre-operative ICatC treatment of the recipient mice improved early graft function and lead to the disappearance of active NSP protein in the transplanted lung. NSP activities were also substantially reduced in bone marrow neutrophils. Preemptive NSP reduction by CatC inhibition may prove to be a viable and effective approach to reduce immediate ischemia reperfusion responses after LTx.

Up-regulation of FOXO1 and reduced inflammation by β-hydroxybutyric acid are essential diet restriction benefits against liver injury

Liver ischemia and reperfusion injury (IRI) is a major challenge in liver surgery. Diet restriction reduces liver damage by increasing stress resistance; however, the underlying molecular mechanisms remain unclear. We investigated the preventive effect of 12-h fasting on mouse liver IRI. Partial warm hepatic IRI model in wild-type male C57BL/6 mice was used. The control ischemia and reperfusion (IR) group of mice was given food and water ad libitum, while the fasting IR group was given water but not food for 12 h before ischemic insult. In 12-h fasting mice, serum liver-derived enzyme level and tissue damages due to IR were strongly suppressed. Serum β-hydroxybutyric acid (BHB) was significantly raised before ischemia and during reperfusion. Up-regulated BHB induced an increment in the expression of FOXO1 transcription factor by raising the level of acetylated histone. Antioxidative enzyme heme oxigenase 1 (HO-1), a target gene of FOXO1, then increased. Autophagy activity was also enhanced. Serum high-mobility group box 1 was remarkably lowered by the 12-h fasting, and activation of NF-κB and NLRP3 inflammasome was suppressed. Consequently, inflammatory cytokine production and liver injury were reduced. Exogenous BHB administration or histone deacetylase inhibitor administration into the control fed mice ameliorated liver IRI, while FOXO1 inhibitor administration to the 12-h fasting group exacerbated liver IRI. The 12-h fasting exerted beneficial effects on the prevention of liver IRI by increasing BHB, thus up-regulating FOXO1 and HO-1, and by reducing the inflammatory responses and apoptotic cell death via the down-regulation of NF-κB and NLRP3 inflammasome.

Protective role of heme oxygenase-1 in fatty liver ischemia-reperfusion injury

Ischemia-reperfusion (IR) injury is a kind of injury resulting from the restoration of the blood supply after blood vessel closure during liver transplantation and is the main cause of graft failure. The pathophysiological mechanisms of hepatic IR include a variety of oxidative stress responses. Hepatic IR is characterized by ischemia and hypoxia inducing oxidative stress, immune response and apoptosis. Fat-denatured livers are also used as donors due to the lack of liver donors. Fatty liver is less tolerant to IR than normal liver. Heme oxygenase (HO) is an enzyme that breaks down hemoglobin to bilirubin, ferrous iron and carbon monoxide (CO). Inducible HO subtype HO-1 is an important protective molecule in mammalian cells used to improve acute and chronic liver injury owing to its characteristic anti-inflammatory and anti-apoptotic qualities. HO-1 degrades heme, and its reaction product CO has been shown to reduce hepatic IR injury and increase the survival rate of grafts. As an induced form of HO, HO-1 also exerts a protective effect against liver IR injury and may be useful as a new strategy of ameliorating this kind of damage. This review summarizes the protective effects of HO-1 in liver IR injury, especially in fatty liver.

Neutrophil elastase plays a non-redundant role in remodeling the venular basement membrane and neutrophil diapedesis post-ischemia/reperfusion injury

Ischemia/reperfusion (I/R) injury is a severe inflammatory insult associated with numerous pathologies, such as myocardial infarction, stroke and acute kidney injury. I/R injury is characterized by a rapid influx of activated neutrophils secreting toxic free radical species and degrading enzymes that can irreversibly damage the tissue, thus impairing organ functions. Significant efforts have been invested in identifying therapeutic targets to suppress neutrophil recruitment and activation post‐I/R injury. In this context, pharmacological targeting of neutrophil elastase (NE) has shown promising anti‐inflammatory efficacy in a number of experimental and clinical settings of I/R injury and is considered a plausible clinical strategy for organ care. However, the mechanisms of action of NE, and hence its inhibitors, in this process are not fully understood. Here we conducted a comprehensive analysis of the impact of NE genetic deletion on neutrophil infiltration in four murine models of I/R injury as induced in the heart, kidneys, intestine and cremaster muscle. In all models, neutrophil migration into ischemic regions was significantly suppressed in NE^−/− mice as compared with wild‐type controls. Analysis of inflamed cremaster muscle and mesenteric microvessels by intravital and confocal microscopy revealed a selective entrapment of neutrophils within venular walls, most notably at the level of the venular basement membrane (BM) following NE deletion/pharmacological blockade. This effect was associated with the suppression of NE‐mediated remodeling of the low matrix protein expressing regions within the venular BM used by transmigrating neutrophils as exit portals. Furthermore, whilst NE deficiency led to reduced neutrophil activation and vascular leakage, levels of monocytes and prohealing M2 macrophages were reduced in tissues of NE^−/− mice subjected to I/R. Collectively our results identify a vital and non‐redundant role for NE in supporting neutrophil breaching of the venular BM post‐I/R injury but also suggest a protective role for NE in promoting tissue repair. © 2019 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Effects of SB202190 on expression levels of IL-6 and NF-κB in flap ischemia-reperfusion injury

The aim of the current study was to investigate the effect of SB202190, a specific inhibitor of p38 MAPK signaling pathway, on the expression levels of IL-6 and NF-κB in flap ischemia-reperfusion injury. Healthy Sprague-Dawley rats were randomly divided into four groups of 12 each. For the ischemia-reperfusion group, the flap was constructed and then sutured after 8 h of ischemia. For the saline group, rats were intraperitoneally infused with saline at regular intervals after flap ischemia-reperfusion. For the inhibitor group, rats were intraperitoneally infused with SB202190 at regular intervals after flap ischemia-reperfusion. For the control group, the flap was constructed and then sutured immediately. The flap survival rate of each group was measured after 7 days. The concentration of IL-6 in serum was measured by ELISA kit. The mRNA and protein expression levels of IL-6 and NF-κB in the flap were measured using RT-PCR and western blot analysis, respectively. In the ischemia-reperfusion group and the saline group, the flap survival rates were much lower than that in the control group (P<0.05). By contrast, the mRNA and protein expression levels of IL-6 and NF-κB in the flap and the concentration of IL-6 in serum were much higher (P<0.05). In the inhibitor group, the flap survival rate was significantly higher than those in the ischemia-reperfusion and saline groups (P<0.05). By contrast, the concentration of IL-6 in serum and the mRNA and protein expression levels of NF-κB and IL-6 in the flap were significantly decreased (P<0.05). The results show that, SB202190 played a role in the protection of the flap by reducing the inflammatory response in flap ischemia-reperfusion injury.

Human CD31 on porcine cells suppress xenogeneic neutrophil-mediated cytotoxicity via the inhibition of NETosis

BACKGROUND

Xenotransplantation is one of the promising strategies for overcoming the shortage of organs available for transplant. However, many immunological obstructions need to be overcome for practical use. Increasing evidence suggests that neutrophils contribute to xenogeneic cellular rejection. Neutrophils are regulated by activation and inhibitory signals to induce appropriate immune reactions and to avoid unnecessary immune reactivity. Therefore, we hypothesized that the development of neutrophil-targeted therapies may have the potential for increased graft survival in xenotransplantation.

METHODS

A plasmid containing a cDNA insert encoding the human CD31 gene was transfected into swine endothelial cells (SEC). HL-60 cells were differentiated into neutrophil-like cells by culturing them in the presence of 1.3% dimethyl sulfoxide for 48 hours. The cytotoxicity of the differentiated HL-60 cells (dHL-60) and peripheral blood-derived neutrophils was evaluated by WST-8 assays. To investigate the mechanism responsible for hCD31-induced immunosuppression, citrullinated histone 3 (cit-H3) and phosphorylation of SHP-1 were detected by a cit-H3 enzyme-linked immunosorbent assay (ELISA) and Western blotting, respectively.

RESULTS

A significant decrease in dHL-60 and neutrophil-mediated cytotoxicity in SEC/hCD31 compared with SEC was seen, as evidenced by a cytotoxicity assay. Furthermore, the suppression of NETosis and the induction of SHP-1 phosphorylation in neutrophils that had been co-cultured with SEC/CD31 were confirmed by cit-H3 ELISA and Western blotting with an anti-phosphorylated SHP-1.

CONCLUSION

These data suggest that human CD31 suppresses neutrophil-mediated xenogenic cytotoxicity via the inhibition of NETosis. As CD31 is widely expressed in a variety of inflammatory cells, human CD31-induced suppression may cover the entire xenogeneic cellular rejection, thus making the generation of human CD31 transgenic pigs very attractive for use in xenografts.

SIRT6 protects against hepatic ischemia/reperfusion injury by inhibiting apoptosis and autophagy related cell death

Silent information regulator 6 (SIRT6), a class III histone deacetylase, has been revealed to participate in multiple metabolic processes in the liver, and it plays important roles in protecting against ischemia/reperfusion (I/R) injury in multiple organs. In this study, we explored whether SIRT6 is protective against hepatic I/R injury and elucidated the underlying mechanisms. The expression of SIRT6 was significantly decreased during reperfusion compared with the control group. SIRT6-LKO mice exhibited significantly aggravated oxidative stress, mitochondrial dysfunction, inflammatory responses, mitogen-activated protein kinase (MAPK) signaling activation, and apoptosis and autophagy related hepatocyte death compared with control mice. In vitro studies in SIRT6-KO hepatocytes exhibited similar results. In contrast, SIRT6 upregulation alleviated liver damage during hepatic I/R injury. Our study demonstrated for the first time that SIRT6 upregulation effectively protects against hepatic I/R injury. The underlying mechanisms involve the maintenance of oxidative homeostasis and mitochondrial function, which subsequently inhibit the inflammatory responses and MAPK signaling, and finally attenuate apoptosis and autophagy related hepatocyte death. These results suggest that the activation of SIRT6 exerts multifaceted protective effects during hepatic I/R injury, which can provide a novel therapeutic target for hepatic I/R injury.

Neutrophils: a cornerstone of liver ischemia and reperfusion injury

Ischemia-reperfusion injury (IRI) is the main cause of morbidity and mortality due to graft rejection after liver transplantation. During IRI, an intense inflammatory process occurs in the liver. This hepatic inflammation is initiated by the ischemic period but occurs mainly during the reperfusion phase, and is characterized by a large neutrophil recruitment to the liver. Production of cytokines, chemokines, and danger signals results in activation of resident hepatocytes, leukocytes, and Kupffer cells. The role of neutrophils as the main amplifiers of liver injury in IRI has been recognized in many publications. Several studies have shown that elimination of excessive neutrophils or inhibition of their function leads to reduction of liver injury and inflammation. However, the mechanisms involved in neutrophil recruitment during liver IRI are not well known. In addition, the molecules necessary for this type of migration are poorly defined, as the liver presents an atypical sinusoidal vasculature in which the classical leukocyte migration paradigm only partially applies. This review summarizes recent advances in neutrophil-mediated liver damage, and its application to liver IRI. Basic mechanisms of activation of neutrophils and their unique mechanisms of recruitment into the liver vasculature are discussed. In particular, the role of danger signals, adhesion molecules, chemokines, glycosaminoglycans (GAGs), and metalloproteinases is explored. The precise definition of the molecular events that govern the recruitment of neutrophils and their movement into inflamed tissue may offer new therapeutic alternatives for hepatic injury by IRI and other inflammatory diseases of the liver.

Berberine ameliorates non-alcoholic steatohepatitis in ApoE-/- mice

The aim of the present study was to explore the protective effects of Berberine (BBR) against non-alcoholic steatohepatitis (NASH). Male 4-week-old C57BL/6J Apolipoprotein E-deficient (ApoE^-/-) mice were divided into the following three groups, which were given different diets: Normal chow diet (SC group); high-fat high-cholesterol diet (HFHC group); and HFHC diet supplemented with BBR (BBR group). Serum biochemical indicators of hepatic function and histological liver tissue changes were evaluated. The expression of neutrophil elastase (NE) and genes involved in the inflammatory response was measured. ApoE^-/- mice fed a HFHC diet for 12 weeks developed NASH, characterized by steatosis and liver inflammation. Body weight, and serum triglyceride and cholesterol levels were markedly reduced by BBR. BBR supplementation significantly lowered serum alanine aminotransferase and aspartate aminotransferase levels in mice with HFHC diet-induced NASH, and significantly downregulated hepatic expression and activity of NE, whereas α1-antitrypsin (α1-AT) expression was significantly recovered by BBR (all P<0.05 vs. the HFHC group). Furthermore, treatment with BBR induced a significant reduction in the expression of key genes, including phospoinositide 3-kinase, nuclear factor-κB and interleukin-8, in the C-X-C chemokine receptor type 4 (CXCR4) signaling pathway (all P<0.05 vs. the HFHC group). These results suggest that BBR alleviates NASH in ApoE^-/- mice fed a HFHC diet. Restoration of the balance of NE and α1-AT levels, which in turn facilitate the inhibition of the CXCR4 signaling pathways, may be involved in the hepatoprotective effect of BBR. These results indicate that BBR may be a candidate therapeutic agent for the treatment of NASH.

Bruton Tyrosine Kinase Inhibition Attenuates Liver Damage in a Mouse Warm Ischemia and Reperfusion Model

BACKGROUND

Bruton tyrosine kinase (Btk) is a central player in multiple signaling pathways of lymphoid and myeloid cells. Myeloid cells are crucial early effectors in organ ischemia-reperfusion (IR) injury. BTKB66 is a selective, irreversible inhibitor of Btk. In this study, we hypothesized that Btk inhibition would reduce hepatocellular injury in a murine model of liver warm hepatic IR.

METHODS

First, BTKB66 was tested in in vitro models of lipopolysaccharide-mediated neutrophil and macrophage activation. Then, to assess its efficacy in vivo, BTKB66 was administered orally to mice for 7 days before subjecting them to 90 minutes of warm hepatic ischemia followed by reperfusion for 6 or 24 hours. Clinical and pathologic features in the livers, including AST, ALT, and a panel of cytokines and chemokines, were examined.

RESULTS

BTKB66 potently inhibited lipopolysaccharide-mediated activation of bone marrow-derived neutrophils and macrophages in vitro. It also reduced the severity of IR injury as determined by AST and ALT levels, as well as immune cell infiltrates. BTKB66 significantly decreased hepatic markers of sterile inflammation, such as C-X-C motif chemokine 1, C-X-C motif chemokine 2, and C-X-C motif chemokine 10, in parallel with depression of serum markers of the myeloid cell activation, such as CCL5, CCL11, and C-X-C motif chemokine 5.

CONCLUSIONS

BTKB66 treatment ameliorated hepatocellular injury in a well-established model of liver partial warm ischemia and in situ reperfusion. These findings confirm that neutrophil recruitment and activation play an essential role in IR stress, and that targeting Btk activity may provide a useful approach for preventing hepatocellular damage and improving outcomes in liver transplantation.

Melatonin treatment enhances therapeutic effects of exosomes against acute liver ischemia-reperfusion injury

This study tests the hypothesis that combined melatonin and exogenic adipose mesenchymal stem cell (ADMSC)-derived exosome treatment offers superior protection against liver ischemia-reperfusion (LIR) injury compared to either alone. In vitro studies utilized a macrophage cell line (RAW) pretreated with lipopolysaccharide and hepatocytes pretreated with melatonin or exosomes before hypoxia treatment, while in vitro experiments involved analyses of liver specimens from male adult Sprague-Dawley rats (n = 50) equally categorized into sham controls (SC), LIR only, LIR-exosome (100 µg, 30 minute post-LIR), LIR-melatonin (20 mg/kg, 30 minute post-LIR and 50 mg/kg at 6 and 18 hours post-LIR), and LIR-exosome-melatonin groups. In vitro studies showed suppression of inflammation (MIF, MMP-9, IL-1β, TNF-α, COX-2) and oxidative stress (NOX-1, NOX-2, oxidized protein)/apoptosis (cleaved caspase 3 and PARP) by exosome and exosome/melatonin treatment, respectively (all P<0.001). In vivo data demonstrated lowest liver injury score and plasma AST concentrations in LIR-exosome-melatonin group compared with other groups (P<0.001). Besides, expressions of inflammatory markers at protein (ICAM-1, IL-1β, MMP-9, TNF-α, NF-κB, RANTES) and cellular (CD3+, CD4+, CD8+, CD161+, CD11+, CD14+, F4/80) levels, and protein expressions of apoptosis (cleaved caspase-3, PARP), oxidative stress (NOX-1, NOX-2), DNA damage (γ-H2AX) and mitochondrial damage (cytosolic cytochrome-C) markers displayed a pattern similar to that of liver injury score, whereas protein expression of anti-oxidants (HO-1, NQO-1) showed progressive increase from SC to the combined treatment group (all P<0.001). In conclusion, combined exosome-melatonin regimen was superior to either alone in protecting the liver against ischemia-reperfusion injury.

The Role of Neutrophils in Transplanted Organs

Neutrophils are often viewed as nonspecialized effector cells whose presence is a simple indicator of tissue inflammation. There is new evidence that neutrophils exist in subsets and have specialized effector functions that include extracellular trap generation and the stimulation of angiogenesis. The application of intravital imaging to transplanted organs has revealed novel requirements for neutrophil trafficking into graft tissue and has illuminated direct interactions between neutrophils and other leukocytes that promote alloimmunity. Paradoxically, retaining some neutrophilia may be important to induce or maintain tolerance. Neutrophils can stimulate anti-inflammatory signals in other phagocytes and release molecules that inhibit T cell activation. In this article, we will review the available evidence of how neutrophils regulate acute and chronic inflammation in transplanted organs and discuss the possibility of targeting these cells to promote tolerance.

Sirtuin 2 aggravates postischemic liver injury by deacetylating mitogen-activated protein kinase phosphatase-1

Sirtuin 2 (Sirt2) is known to negatively regulate anoxia-reoxygenation injury in myoblasts. Because protein levels of Sirt2 are increased in ischemia-reperfusion (I/R)-injured liver tissues, we examined whether Sirt2 is protective or detrimental against hepatic I/R injury. We overexpressed Sirt2 in the liver of C57BL/6 mice using a Sirt2 adenovirus. Wild-type and Sirt2 knockout mice were subjected to a partial (70%) hepatic ischemia for 45 minutes, followed by various periods of reperfusion. In another set of experiments, wild-type mice were pretreated intraperitoneally with AGK2, a Sirt2 inhibitor. Isolated hepatocytes and Kupffer cells from wild-type and Sirt2 knockout mice were subjected to hypoxia-reoxygenation injury to determine the in vitro effects of Sirt2. Mice subjected to I/R injury showed typical patterns of hepatocellular damage. Prior injection with Sirt2 adenovirus aggravated liver injury, as demonstrated by increases in serum aminotransferases, prothrombin time, proinflammatory cytokines, hepatocellular necrosis and apoptosis, and neutrophil infiltration relative to control virus-injected mice. Pretreatment with AGK2 resulted in significant improvements in serum aminotransferase levels and histopathologic findings. Similarly, experiments with Sirt2 knockout mice also revealed reduced hepatocellular injury. The molecular mechanism of Sirt2's involvement in this aggravation of hepatic I/R injury includes the deacetylation and inhibition of mitogen-activated protein kinase phosphatase-1 and consequent activation of mitogen-activated protein kinases.

CONCLUSION

Sirt2 is an aggravating factor during hepatic I/R injury. (Hepatology 2017;65:225-236).

Paeoniflorin attenuates hepatic ischemia/reperfusion injury via anti-oxidative, anti-inflammatory and anti-apoptotic pathways

During liver surgery, hepatic blood flow needs to be blocked in order to reduce bleeding, which inevitably results in hepatic ischemia/reperfusion injury (HI/R). Paeoniflorin (PF) is the main active ingredient of the traditional Chinese herbal medicine peony, which has been shown to exert anti-oxidative and anti-apoptotic properties. In the present study, a mouse model of HI/R was generated by clamping the hepatoportal vein, hepatic artery, and hepatic duct of BALB/c mice with a vascular clamp for 30 min, followed by reperfusion for 6 h under anesthesia. Six mice in the three PF treatment groups (5, 10 and 20 mg/kg) were then injected with PF, via the tail vein. A sham group, consisting of six mice that did not undergo the procedure, and a vehicle group, consisting of 6 mice that underwent the procedure but subsequently received injections of physiological saline only, were used as controls. Liver injury was indicated by serum levels of the enzymes alanine transaminase (ALT) and aspartate transaminase (AST). The activities of oxidative stress biomarkers, including superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-PX) and malondialdehyde (MDA), were also measured. Furthermore, the activity of caspase-3 was analyzed in hepatic tissue using a commercial kit. Treatment with PF significantly attenuated HI/R injury histologically, as compared with the vehicle group. In addition, significant reductions in the serum levels of ALT and AST were observed in the PF-treated ischemic mice. Furthermore, treatment with PF enhanced the activities of hepatic tissue SOD, GSH and GSH-PX, but decreased the MDA content. Treatment of ischemic mice with PF markedly reduced the expression levels of inflammatory mediators, including nuclear factor-κB, tumor necrosis factor-α, interleukin (IL)-6, and IL-1β, and decreased the HI/R injury-induced expression of caspase-3. The results of the present study suggest that PF attenuates the HI/R injury of mice via anti-oxidative, anti-inflammatory and anti-apoptotic activities.

Neutrophil Elastase Inhibitor Following Liver Resection: A Matched Cohort Study

BACKGROUND

Sivelestat is a neutrophil elastase inhibitor (NEI) with positive impact on the respiratory complications in thoracic surgery. Based on the findings of a recent study, NEI may have a good response for avoiding ischemia reperfusion injury in liver resection.

OBJECTIVES

The current study aimed to examine the impact of NEI on the postoperative outcomes after liver resection.

PATIENTS AND METHODS

The data were collected from 374 consecutive patients scheduled to undergo liver resection. Seven perioperative variables were matched on the basis of the patients' background. Then, the NEI (n = 61) and control (n = 61) groups were compared. NEI was administered at a dose of 0.2 mg/kg/h for three days from the postoperative day 0 (POD0). The liver function, coagulation activity, inflammatory response, respiratory complications, and overall complications were compared.

RESULTS

The levels of serum interleukin-6 (NEI group: 113 pg/mL [26.9 - 522.0] vs. control group: 174 [28.6 - 1040.6], P < 0.01) and C-reactive protein (CRP) (2.9 IU/L [range: 0.1 - 8.6] vs. 4.11 [0.3 - 13.8], P = 0.01) on the first postoperative day (POD1) and the alveolar-arterial oxygen tension difference (32.3 Torr [-28.6 - 132.3] vs. 46.6 [-11.2 - 251.6], P = 0.04) on the third postoperative day (POD3) were significantly lower in the NEI group than the control group. The rate of pleural effusion was significantly lower in the NEI group compared to that of the control group [13 patients (21.3%) vs. 23 (37.7%), P = 0.04]. However, the coagulation activities (P = 0.68), liver function (P = 0.69), non-respiratory complications (P = 0.84), and overall complications (P = 0.71) did not differ significantly between the groups.

CONCLUSIONS

Intravenous NEI administration had positive impact on the postoperative inflammatory response and oxygenation while it did not affect either coagulation or the liver function, as well as severe grade complications following resection.

The protective function of galectin-9 in liver ischemia and reperfusion injury in mice

Galectin-9 (Gal-9) has gained attention as a multifaceted player in adaptive and innate immunity. To elucidate the role of Gal-9, we used a mouse model of partial liver ischemia/reperfusion injury (IRI) with wild type (WT) and Gal-9 knockout (KO) mice as well as a recombinant galectin-9 (reGal-9) protein. We found that the expression of Gal-9 was enhanced endogenously in the liver especially by hepatocytes and Kupffer cells during warm IRI for a mouse liver, which causes massive destruction of liver tissue. Gal-9 was released into the extracellular space in the liver and the highest levels in the plasma at 1 hour after reperfusion. The present study elucidates a novel role of Gal-9 signaling in mouse liver IRI, by using Gal-9-deficient mice and a stable form of reGal-9 protein. In the circumstance of Gal-9 absence, liver damage due to ischemia/reperfusion (IR) exacerbated the severity as compared with WT. On the other hand, exogenously administered reGal-9 significantly ameliorated hepatocellular damage. It decreased the local infiltration of the inflammatory cells such as T cells, neutrophils, and macrophages, and it reduced the expression of proinflammatory cytokines/chemokines; then, it strongly suppressed the apoptosis of the liver cells. Interestingly, severe liver damage due to IR in Gal-9 KO mice was improved by the administration of reGal-9. In conclusion, Gal-9 engagement ameliorated local inflammation and liver damage induced by IR, and the present study suggests a significant role of Gal-9 in the maintenance of hepatic homeostasis. In conclusion, targeting Gal-9 represents a novel approach to protect from inflammation such as liver IRI. Exogenous Gal-9 treatment will be a new therapeutic strategy against innate immunity-dominated liver tissue damage.

Paeoniflorin ameliorates acute myocardial infarction of rats by inhibiting inflammation and inducible nitric oxide synthase signaling pathways

Paeoniflorin (PF) is the main active component of the commonly used Traditional Chinese Medicine peony, Paeonia Suffruticosa. PF has diverse biological functions and exhibits anti‑oxidative, anti‑inflammatory and anti‑apoptotic activity. Inducible nitric oxide synthase (iNOS) is a catalyzing enzyme that is involved in the synthesis of nitric oxide (NO). NO has an important regulatory role in the cardiovascular, immune and nervous systems. PF has previously been demonstrated to inhibit the gene expression of iNOS. The present study aimed to identify a potentially novel cytoprotective function of PF, and to elucidate its effects against myocardial ischemic damage in a rat model of acute myocardial infarction (AMI). PF was able to significantly decrease the myocardial infarct size as well as the activities of creatine kinase (CK), the MB isoenzyme of CK, lactate dehydrogenase and cardiac troponin T. In addition, in the PF‑treated groups, the expression levels of tumor necrosis factor‑α, interleukin (IL)‑1β, IL‑6 and nuclear factor‑κB were markedly inhibited. Furthermore, treatment with PF inhibited the activities and protein expression levels of iNOS. Decreased caspase‑3 and caspase‑9 activities were also observed in the AMI rat model treated with various doses of PF. The results of the present study indicated that the cardioprotective effects of PF may be associated with the inhibition of inflammation and iNOS signaling pathways.

Neutrophil serine proteases: mediators of innate immune responses

PURPOSE OF REVIEW

Neutrophil cells have been considered mainly as innate immune cells directed against microbial threats. Their serine proteases neutrophil elastase, proteinase 3 and cathepsin G are main constituents and are released at sites of inflammation. During recent years it became clear that neutrophil serine proteases act as regulators of cell signaling and immune regulation.

RECENT FINDINGS

Neutrophils are able to form so-called neutrophil extracellular traps. Recent studies showed that these extracellular traps might be involved in small vessel vasculitis and lupus nephritis. Neutrophil serine proteases in concert with externalized nucleosomes promote thrombus formation inside blood vessels. This event helps retain bacteria inside liver microvessels and thereby prevents the extravasation of pathogens. Moreover, neutrophil serine proteases act as alternative processing enzymes of pro-inflammatory cytokines IL-1β and IL-18 in vivo and modulate other inflammation-related control mechanisms such as progranulin inactivation, matrix metalloproteinase-9 activation and IL-6 inactivation. Recent studies point to an involvement of neutrophil elastase in lung cancer by inducing mitogenesis after entering the cells.

SUMMARY

The knowledge of the different functions of neutrophils is still expanding. Recent findings underline the importance of neutrophil serine proteases as key mediators of inflammatory processes and point to novel strategies against inflammatory disorders.

SPA0355 attenuates ischemia/reperfusion-induced liver injury in mice

Hepatic ischemia/reperfusion (I/R) injury leads to oxidative stress and acute inflammatory responses that cause liver damage and have a considerable impact on the postoperative outcome. Much research has been performed to develop possible protective techniques. We aimed to investigate the efficacy of SPA0355, a synthetic thiourea analog, in an animal model of hepatic I/R injury. Male C57BL/6 mice underwent normothermic partial liver ischemia for 45 min followed by varying periods of reperfusion. The animals were divided into three groups: sham operated, I/R and SPA0355 pretreated. Pretreatment with SPA0355 protected against hepatic I/R injury, as indicated by the decreased levels of serum aminotransferase and reduced parenchymal necrosis and apoptosis. Liver synthetic function was also restored by SPA0355 as reflected by the prolonged prothrombin time. To gain insight into the mechanism involved in this protection, we measured the activity of nuclear factor-κB (NF-κB), which revealed that SPA0355 suppressed the nuclear translocation and DNA binding of NF-κB subunits. Concomitantly, the expression of NF-κB target genes such as IL-1β, IL-6, TNF-α and iNOS was significantly downregulated. Lastly, the liver antioxidant enzymes superoxide dismutase, catalase and glutathione were upregulated by SPA0355 treatment, which correlated with the reduction in serum malondialdehyde. Our results suggest that SPA0355 pretreatment prior to I/R injury could be an effective method to reduce liver damage.

Interleukin-17 mediates triptolide-induced liver injury in mice

Triptolide (TP)-induced liver injury can be attributed to the Th17/Treg imbalance with the enhancement of the expansion of Th17 cells and suppression of the production of Tregs, especially the significant increase of interleukin (IL)-17 secreted by helper T (Th) 17 cells. To further investigate the involvement of IL-17-mediated immune response in the TP-induced hepatotoxicity, we examined the plasma transaminase, histopathological changes, hepatic frequencies of Th17 cells, hepatic expression of transcriptional factors and cytokines genes and plasma IL-17 levels after administration of TP (600 μg/kg) by oral gavage to female C57BL/6 mice. Mice treated with TP displayed acute liver injury with significantly increased hepatic frequencies of Th17 cells, mRNA expression of retinoid-related orphan receptor (ROR)-γt and plasma IL-17 level as well as the plasma ALT and AST. Neutralization study using anti-IL-17 antibody ameliorated TP-induced liver injury. In contrast, when challenged by coadministration of recombinant IL-17, hepatotoxicity was exacerbated in the triptolide-administered mice. In summary, this report was demonstrated for the first time that IL-17-mediated immune response is involved in the pathogenesis of TP-induced liver injury in mice, which may shed light on the mechanisms of TP-induced liver injury.

The role of neutrophils in the development of liver diseases

Liver disease encompasses a wide variety of liver conditions, including liver failure, liver cirrhosis and a spectrum of acute and chronic hepatitis, such as alcoholic, fatty, drug, viral and chronic hepatitis. Liver injury is a primary causative factor in liver disease; generally, these factors include direct liver damage and immune-mediated liver injury. Neutrophils (also known as neutrophilic granulocytes or polymorphonuclear leukocytes (PMNs)) are the most abundant circulating white blood cell type in humans, and PMNs are a major innate immune cell subset. Inappropriate activation and homing of neutrophils to the microvasculature contributes to the pathological manifestations of many types of liver disease. This review summarizes novel concepts of neutrophil-mediated liver injury that are based on current clinical and animal model studies.