Liver Ischemia and Reperfusion Induce Periportal Expression of Necroptosis Executor pMLKL Which Is Associated With Early Allograft Dysfunction After Transplantation

Equal performance of HTK-based and UW-based perfusion solutions in sub-normothermic liver machine perfusion

Machine perfusion (MP) is gaining importance in liver transplantation, the only cure for many end-stage liver diseases. Varieties of different MP protocols are available. Currently, various MP protocols are available, differing not only in perfusion temperature but also in the specific perfusion solution required. We aimed to investigate the performance of an HTK-based perfusate during sub-normothermic MP (SNMP) of discarded human liver grafts compared to that of a UW-based solution. Twenty discarded livers (rejected for transplantation by all centers) were subjected to ex-vivo SNMP at 21°C with either HTK- or UW-based solution for 12 h. Perfusate and tissue samples collected before the start, after 6 h, and at the end of SNMP were analyzed for liver enzymes, along with mRNA expression of perfusate and tissue markers associated with organ damage. Hepatocellular viability was assessed by measuring bile production, monitoring pH stability, and analyzing histological changes in HE stained tissue sections. After propensity score matching 16 livers were analyzed. Overall, no differences between HTK- and UW-based solution were detected, except for an increased MLKL mRNA expression and impaired pH stability during SNMP with HTK-based perfusate. No other investigated parameters of cell injury, inflammation or hepatocellular viability supported this finding. Bile production was higher in the 6 HTK-perfused livers compared to the three UW-perfused livers that produced bile. Overall, these findings suggest that HTK performs comparably to a UW-based solution during 12 h of liver SNMP.

The role of ferroptosis in liver injury after cold ischemia-reperfusion in rats with autologous orthotopic liver transplantation

Using autologous orthotopic liver transplantation (AOLT) model in rats, the effect of lipid reactive oxygen species (L-ROS) inhibitor Ferrostain-1 on ferroptosis signal pathway was observed to determine whether ferroptosis occurred in rat liver injury after cold ischemia-reperfusion (I/R). Thirty-two healthy adult SPF male SD rats, 8 ~ 10 weeks old, weight 240 ~ 260 g, were divided into four groups by the method of random number table (n = 8): sham group, I/R group, I/R + Fer-1 group, I/R + DFO group. In the I/R + Fer-1 group, ferristatin-1(5 mg /kg) was intraperitoneally injected 30 min before surgery; in the I/R + DFO group, DFO 100 mg/kg was injected intraperitoneally 1 h before operation and 12 h after operation. Blood samples were taken from the inferior hepatic vena cava 24 h after reperfusion. After anesthesia, the rats were killed and part of their liver tissue was removed. The pathological changes of liver tissue sections were observed under a high-power microscope, and the liver injury was evaluated. Serum malondialdehyde (MDA) and serum levels of ALT, AST and IL-6 were determined by the ELISA method, Reduced glutathione (GSH), glutathione peroxidase 4 (GPX4), MDA, Fe2 + and superoxide dismutase (SOD) were determined in the liver tissue. Compared with the sham group, the serum levels of the IL-6,MDA, AST and ALT in I/R group were obviously higher (P < 0.05); The levels of MDA and Fe2+ in liver tissue were significantly increased (P < 0.05).The levels of SOD, GSH and GPX4 in liver tissue were decreased. The levels of serum MDA, IL-6, AST, and ALT in the I/R + Fer-1 and I/R + DFO groups were significantly lower than those in the I/R group at 24 h after reperfusion. In the I/R + Fer-1 group, the level of MDA in liver tissue decreased significantly, while the level of SOD, GSH and GPX4 in intestinal tissue increased (P < 0.05). In The I/R + DFO group, the levels of MDA and Fe2+ in liver tissue decreased significantly, while the level of SOD in intestinal tissue increased (P < 0.05). Ferroptosis is involved in pathophysiological process of liver injury after cold ischemia-reperfusion in AOLT rats.

Liver Transplantation: A Test of Cellular Physiology, Preservation, and Injury

Liver transplantation has evolved into a mature clinical field, but scarcity of usable organs poses a unique challenge. Expanding the donor pool requires novel approaches for protecting hepatic physiology and cellular homeostasis. Here we define hepatocellular injury during transplantation, with an emphasis on modifiable cell death pathways as future therapeutics.

Effect of Sodium Thiosulfate Pre-Treatment on Renal Ischemia-Reperfusion Injury in Kidney Transplantation

We recently reported in a rat model of kidney transplantation that the addition of sodium thiosulfate (STS) to organ preservation solution improved renal graft quality and prolonged recipient survival. The present study investigates whether STS pre-treatment would produce a similar effect. In vitro, rat kidney epithelial cells were treated with 150 μM STS before and/or during exposure to hypoxia followed by reoxygenation. In vivo, donor rats were treated with PBS or 2.4 mg/kg STS 30 min before donor kidneys were procured and stored in UW or UW+150 μM STS solution at 4 °C for 24 h. Renal grafts were then transplanted into bilaterally nephrectomised recipient rats which were then sacrificed on post-operative day 3. STS pre-treatment significantly reduced cell death compared to untreated and other treated cells in vitro (p < 0.05), which corresponded with our in vivo result (p < 0.05). However, no significant differences were observed in other parameters of tissue injury. Our results suggest that STS pre-treatment may improve renal graft function after transplantation.

Cell Death in Liver Disease and Liver Surgery

Cell death is crucial for maintaining tissue balance and responding to diseases. However, under pathological conditions, the surge in dying cells results in an overwhelming presence of cell debris and the release of danger signals. In the liver, this gives rise to hepatic inflammation and hepatocellular cell death, which are key factors in various liver diseases caused by viruses, toxins, metabolic issues, or autoimmune factors. Both clinical and in vivo studies strongly affirm that hepatocyte death serves as a catalyst in the progression of liver disease. This advancement is characterized by successive stages of inflammation, fibrosis, and cirrhosis, culminating in a higher risk of tumor development. In this review, we explore pivotal forms of cell death, including apoptosis, pyroptosis, and necroptosis, examining their roles in both acute and chronic liver conditions, including liver cancer. Furthermore, we discuss the significance of cell death in liver surgery and ischemia-reperfusion injury. Our objective is to illuminate the molecular mechanisms governing cell death in liver diseases, as this understanding is crucial for identifying therapeutic opportunities aimed at modulating cell death pathways.

Involvement of IL-1β-Mediated Necroptosis in Neurodevelopment Impairment after Neonatal Sepsis in Rats

The mechanism of long-term cognitive impairment after neonatal sepsis remains poorly understood, although long-lasting neuroinflammation has been considered the primary contributor. Necroptosis is actively involved in the inflammatory process, and in this study, we aimed to determine whether neonatal sepsis-induced long-term cognitive impairment was associated with activation of necroptosis. Rat pups on postnatal day 3 (P3) received intraperitoneal injections of lipopolysaccharide (LPS, 1 mg/kg) to induce neonatal sepsis. Intracerebroventricular injection of IL-1β-siRNA and necrostatin-1 (NEC1) were performed to block the production of IL-1β and activation of necroptosis in the brain, respectively. The Morris water maze task and fear conditioning test were performed on P28-P32 and P34-P35, respectively. Enzyme-linked immunosorbent assay (ELISA), quantitative real-time PCR (RT-PCR), and Western blotting were used to examine the expression levels of proinflammatory cytokines and necroptosis-associated proteins, such as receptor-interacting protein 1 (RIP1) and receptor-interacting protein 3 (RIP3). Sustained elevation of IL-1β level was observed in the brain after initial neonatal sepsis, which would last for at least 32 days. Sustained necroptosis activation was also observed in the brain. Knockdown of IL-1β expression in the brain alleviated necroptosis and improved long-term cognitive function. Direct inhibition of necroptosis also improved neurodevelopment and cognitive performance. This research indicated that sustained activation of necroptosis via IL-1β contributed to long-term cognitive dysfunction after neonatal sepsis.

Necroptosis in Organ Transplantation: Mechanisms and Potential Therapeutic Targets

Organ transplantation remains the only treatment option for patients with end-stage organ dysfunction. However, there are numerous limitations that challenge its clinical application, including the shortage of organ donations, the quality of donated organs, injury during organ preservation and reperfusion, primary and chronic graft dysfunction, acute and chronic rejection, infection, and carcinogenesis in post-transplantation patients. Acute and chronic inflammation and cell death are two major underlying mechanisms for graft injury. Necroptosis is a type of programmed cell death involved in many diseases and has been studied in the setting of all major solid organ transplants, including the kidney, heart, liver, and lung. It is determined by the underlying donor organ conditions (e.g., age, alcohol consumption, fatty liver, hemorrhage shock, donation after circulatory death, etc.), preservation conditions and reperfusion, and allograft rejection. The specific molecular mechanisms of necroptosis have been uncovered in the organ transplantation setting, and potential targeting drugs have been identified. We hope this review article will promote more clinical research to determine the role of necroptosis and other types of programmed cell death in solid organ transplantation to alleviate the clinical burden of ischemia-reperfusion injury and graft rejection.

Defective efferocytosis by aged macrophages promotes STING signaling mediated inflammatory liver injury

Aged livers have shown aggravated liver ischemia and reperfusion (IR) injury. Timely efferocytosis of apoptotic cells is a key mechanism for avoiding excessive inflammation and tissue injury. Here, we investigated the alteration of efferocytosis by aged macrophages and its role in regulating macrophage STING (stimulator of interferon genes) signaling and liver IR injury. Aged and young mice were subjected to liver partial IR model. Liver injury and inflammation were measured. Efferocytosis by aged macrophages and the underlying regulatory mechanism were analyzed as well. Aged macrophages exhibited impaired efferocytosis with decreased MerTK (c-mer proto-oncogene tyrosine kinase) activation, which was reversed by treatment of the MerTK CRISPR activation plasmid. Increased MerTK cleavage by ADAM17 (a disintegrin and metalloproteinase 17) due to enhanced ROS (reactive oxygen species) levels contributed to defective efferocytosis by aged macrophages. MerTK activation by suppressing ADAM17 or ROS improved aged macrophage efferocytosis, leading to reduced inflammatory liver injury. Moreover, increased apoptotic hepatocytes, DNA accumulation, and macrophage STING activation were observed in aged ischemic livers. Improvement in efferocytosis by aged macrophages via MerTK activation suppressed STING activation and inflammatory liver injury. Our study demonstrates that aging suppresses MerTK- mediated macrophage efferocytosis to promote macrophage STING activation and inflammatory liver IR injury, suggesting a new mechanism and potential therapy to promote inflammation resolution and efferocytosis in aged livers.

Breaking bad: necroptosis in the pathogenesis of gastrointestinal diseases

A delicate balance between programmed cell death and proliferation of intestinal epithelial cells (IEC) exists in the gut to maintain homeostasis. Homeostatic cell death programs such as anoikis and apoptosis ensure the replacement of dead epithelia without overt immune activation. In infectious and chronic inflammatory diseases of the gut, this balance is invariably disturbed by increased levels of pathologic cell death. Pathological forms of cell death such as necroptosis trigger immune activation barrier dysfunction, and perpetuation of inflammation. A leaky and inflamed gut can thus become a cause of persistent low-grade inflammation and cell death in other organs of the gastrointestinal (GI) tract, such as the liver and the pancreas. In this review, we focus on the advances in the molecular and cellular understanding of programmed necrosis (necroptosis) in tissues of the GI tract. In this review, we will first introduce the reader to the basic molecular aspects of the necroptosis machinery and discuss the pathways leading to necroptosis in the GI system. We then highlight the clinical significance of the preclinical findings and finally evaluate the different therapeutic approaches that attempt to target necroptosis against various GI diseases. Finally, we review the recent advances in understanding the biological functions of the molecules involved in necroptosis and the potential side effects that may occur due to their systemic inhibition. This review is intended to introduce the reader to the core concepts of pathological necroptotic cell death, the signaling pathways involved, its immuno-pathological implications, and its relevance to GI diseases. Further advances in our ability to control the extent of pathological necroptosis will provide better therapeutic opportunities against currently intractable GI and other diseases.