Crashing the computer: apoptosis vs. necroptosis in neuroinflammation

Blood Brain Barrier-Crossing Delivery of Felodipine Nanodrug Ameliorates Anxiety-Like Behavior and Cognitive Impairment in Alzheimer's Disease

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder leading to cognitive decline. Excessive cytosolic calcium (Ca2+) accumulation plays a critical role in the pathogenesis of AD since it activates the NOD-like receptor family, pyrin domain containing 3 (NLRP3), switches the endoplasmic reticulum (ER) unfolded protein response (UPR) toward proapoptotic signaling and promotes Aβ seeding. Herein, a liposomal nanodrug (felodipine@LND) is developed incorporating a calcium channel antagonist felodipine for Alzheimer's disease treatment through a low-intensity pulse ultrasound (LIPUS) irradiation-assisted blood brain barrier (BBB)-crossing drug delivery. The multifunctional felodipine@LND is effectively delivered to diseased brain through applying a LIPUS irradiation to the skull, which resulted in a series of positive effects against AD. Markedly, the nanodrug treatment switched the ER UPR toward antioxidant signaling, prevented the surface translocation of ER calreticulin (CALR) in microglia, and inhibited the NLRP3 activation and Aβ seeding. In addition, it promoted the degradation of damaged mitochondria via mitophagy, thereby inhibiting the neuronal apoptosis. Therefore, the anxiety-like behavior and cognitive impairment of 5xFAD mice with AD is significantly ameliorated, which manifested the potential of LIPUS - assisted BBB-crossing delivery of felodipine@LND to serve as a paradigm for AD therapy based on the well-recognized clinically available felodipine.

Ursolic acid improves necroptosis via STAT3 signaling in intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion injury (IRI) poses a serious threat to human survival and quality of life with high mortality and morbidity rates. The current absence of effective treatments for intestinal IRI highlights the urgent need to identify new therapeutic targets. Ursolic acid (UA), a pentacyclic triterpene natural compound, has been shown to possess various pharmacological properties including intestinal protection. However, its potential protective efficacy on intestinal IRI remains elusive. This study aimed to investigate the effect of UA on intestinal IRI and explore the underlying mechanisms. To achieve this, we utilized network pharmacology to analyze the mechanism of UA in intestinal IRI and assessed UA's effects on intestinal IRI using a mouse model of superior mesenteric artery occlusion/reperfusion and an in vitro model of oxygen-glucose deprivation and reperfusion-induced IEC-6 cells. Our results demonstrated that UA improved necroptosis through the RIP1/RIP3/MLKL pathway, reduced necroinflammation via the HMGB1/TLR4/NF-κB pathway, attenuated morphological damage, and enhanced intestinal barrier function. Furthermore, UA pretreatment downregulated the phosphorylation level of signal transducer and activator of transcription 3 (STAT3). The effects of UA were attenuated by the STAT3 agonist Colivelin. In conclusion, our study suggests that UA can improve intestinal IRI by inhibiting necroptosis in enterocytes via the suppression of STAT3 activation. These results provide a theoretical basis for UA treatment of intestinal IRI and related clinical diseases.

New perspectives on the role of biological factors in anorexia nervosa: Brain volume reduction or oxidative stress, which came first?

Anorexia nervosa (AN) is an eating disorder (ED) that has seen an increase in its incidence in the last thirty years. Compared to other psychosomatic disorders, ED can be responsible for many major medical complications, moreover, in addition to the various systemic impairments, patients with AN undergo morphological and physiological changes affecting the cerebral cortex. Through immunohistochemical studies on portions of postmortem human brain of people affected by AN and healthy individuals, and western blot studies on leucocytes of young patients and healthy controls, this study investigated the role in the afore-mentioned processes of altered redox state. The results showed that the brain volume reduction in AN could be due to an increase in the rate of cell death, mainly by apoptosis, in which mitochondria, main cellular organelles affected by a decreased dietary intake, and a highly compromised intracellular redox balance, may play a pivotal role.

Gancao decoction attenuates hepatic necroptosis via activating caspase 8 in cholestatic liver injury

ETHNOPHARMACOLOGICAL RELEVANCE

Gancao Decoction (GCD) is widely used to treat cholestatic liver injury. However, it is unclear whether is related to prevent hepatocellular necroptosis.

AIM OF THE STUDY

The purpose of this study is to clarify the therapeutic effects of GCD against hepatocellular necroptosis induced by cholestasis and its active components.

MATERIALS AND METHODS

We induced cholestasis model in wild type mice by ligating the bile ducts or in Nlrp3-/- mice by intragastrical administering Alpha-naphthylisothiocyanate (ANIT). Serum biochemical indices, liver pathological changes and hepatic bile acids (BAs) were measured to evaluate GCD's hepatoprotective effects. Necroptosis was assessed by expression of hallmarkers in mice liver. Moreover, the potential anti-necroptotic effect of components from GCD were investigated and confirmed in ANIT-induced cholestasis mice and in primary hepatocytes from WT mouse stimulated with Tumor Necrosis Factor alpha (TNF-α) and cycloheximide (CHX).

RESULTS

GCD dose-dependently alleviated hepatic necrosis, reduced serum aminotranferase activity in both BDL and ANIT-induced cholestasis models. More importantly, the expression of hallmarkers of necroptosis, including MLKL, RIPK1 and RIPK3 phosphorylation (p- MLKL, p-RIPK1, p-RIPK3) were reduced upon GCD treatment. Glycyrrhetinic acid (GA), the main bioactive metabolite of GCD, effectively protected against ANIT-induced cholestasis, with decreased expression of p-MLKL, p-RIPK1 and p-RIPK3. Meanwhile, the expression of Fas-associated death domain protein (FADD), long isoform of cellular FLICE-like inhibitory protein (cFLIPL) and cleaved caspase 8 were upregulated upon GA treatment. Moreover, GA significantly increased the expression of active caspase 8, and reduced that of p-MLKL in TNF-α/CHX induced hepatocytes necroptosis.

CONCLUSIONS

GCD substantially inhibits necroptosis in cholestatic liver injury. GA is the main bioactive component responsible for the anti-necroptotic effects, which correlates with upregulation of c-FLIPL and active caspase 8.

Neuronal DAMPs exacerbate neurodegeneration via astrocytic RIPK3 signaling

Astrocyte activation is a common feature of neurodegenerative diseases. However, the ways in which dying neurons influence the activity of astrocytes is poorly understood. Receptor interacting protein kinase-3 (RIPK3) signaling has recently been described as a key regulator of neuroinflammation, but whether this kinase mediates astrocytic responsiveness to neuronal death has not yet been studied. Here, we used the 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine model of Parkinson's disease to show that activation of astrocytic RIPK3 drives dopaminergic cell death and axon damage. Transcriptomic profiling revealed that astrocytic RIPK3 promoted gene expression associated with neuroinflammation and movement disorders, and this coincided with significant engagement of damage-associated molecular pattern signaling. In mechanistic experiments, we showed that factors released from dying neurons signaled through receptor for advanced glycation endproducts to induce astrocytic RIPK3 signaling, which conferred inflammatory and neurotoxic functional activity. These findings highlight a mechanism of neuron-glia crosstalk in which neuronal death perpetuates further neurodegeneration by engaging inflammatory astrocyte activation via RIPK3.

Oxidative Stress and Chronic Myeloid Leukemia: A Balance between ROS-Mediated Pro- and Anti-Apoptotic Effects of Tyrosine Kinase Inhibitors

The balanced reciprocal translocation t (9; 22) (q34; q11) and the BCR-ABL fusion gene, which produce p210 bcr-abl protein production with high tyrosine kinase activity, are characteristics of chronic myeloid leukemia, a myeloproliferative neoplasm. This aberrant protein affects several signaling pathways connected to both apoptosis and cell proliferation. It has been demonstrated that tyrosine kinase inhibitor treatment in chronic myeloid leukemia acts by inducing oxidative stress and, depending on its level, can activate signaling pathways responsible for either apoptosis or survival in leukemic cells. Additionally, oxidative stress and reactive oxygen species generation also mediate apoptosis through genomic activation. Furthermore, it was shown that oxidative stress has a role in both BCR-ABL-independent and BCR-ABL-dependent resistance pathways to tyrosine kinases, while patients with chronic myeloid leukemia were found to have a significantly reduced antioxidant level. The ideal environment for tyrosine kinase inhibitor therapy is produced by a favorable oxidative status. We discuss the latest studies that aim to manipulate the redox system to alter the apoptosis of cancerous cells.

Impaired autophagy following ex vivo cooling of simulated hypothermic temperatures in peripheral blood mononuclear cells from young and older adults

Hypothermia is a critical consequence of extreme cold exposure that increases the risk of cold-related injury and death in humans. While the initiation of cytoprotective mechanisms including the process of autophagy and the heat shock response (HSR) is crucial to cellular survival during periods of stress, age-related decrements in these systems may underlie cold-induced cellular vulnerability in older adults. Moreover, whether potential sex-related differences in autophagic regulation influence the human cold stress response remain unknown. We evaluated the effect of age and sex on mechanisms of cytoprotection (autophagy and the HSR) and cellular stress (apoptotic signaling and the acute inflammatory response) during ex vivo hypothermic cooling. Venous blood samples from 20 healthy young (10 females; mean [SD]: 22 [2] years) and 20 healthy older (10 females; 66 [5] years) adults were either isolated immediately (baseline) for peripheral blood mononuclear cells (PBMCs) or exposed to water bath temperatures maintained at 37, 35, 33, 31, or 4 °C for 90 min before PBMC isolation. Proteins associated with autophagy, apoptosis, the HSR, and inflammation were analyzed via Western blotting. Indicators of autophagic initiation and signaling (LC3, ULK1, and beclin-2) and the HSR (HSP90 and HSP70) increased when exposed to hypothermic temperatures in young and older adults (all p ≤ 0.007). Sex-related differences were only observed with autophagic initiation (ULK1; p = 0.015). However, despite increases in autophagic initiators ULK1 and beclin-2 (all p < 0.001), this was paralleled by autophagic dysfunction (increased p62) in all groups (all p < 0.001). Further, apoptotic (cleaved-caspase-3) and inflammatory (IL-6 and TNF-α) signaling increased in all groups (all p < 0.001). We demonstrated that exposure to hypothermic conditions is associated with autophagic dysfunction, irrespective of age or sex, although there may exist innate sex-related differences in cytoprotection in response to cold exposure as evidenced through altered autophagic initiation.

Bicyclol alleviates obesity-induced renal injury by inhibiting JNK and NF-κB-mediated inflammation

Obesity is recognized as a major risk factor for chronic kidney disease (CKD), which is accompanied by increased renal lipid build-up, fibrosis, inflammation, apoptosis and pyroptosis. Bicyclol (BIC), a Chinese marketed hepatoprotective drug, has shown excellent anti-inflammatory, anti-fibrosis, anti-apoptotic, and lipid regulation effects in different animal models. In this study, we explored the role and mechanism of BIC in high-fat diet (HFD)-induced obesity-related nephropathy. Mice were fed with HFD for 24 weeks to develop obesity-related nephropathy, while mice in the BIC administration group were treated with BIC (50 mg/kg or 100 mg/kg, once every two days) at the last 12 weeks. We found that BIC treatment relieved the impairment of kidney structure and renal dysfunction caused by HFD. In addition, we found that BIC mitigated HFD-induced renal fibrosis, inflammation, apoptosis and pyroptosis by inhibiting JNK and NF-κB pathways. SV40-MES-13 cells treated with palmitate (PA) were used as the in vitro model. Our data show that BIC pre-administration relieved cellular damage caused by PA through suppressing JNK and NF-κB signaling pathways. In conclusion, we demonstrated that BIC attenuated obesity-induced renal injury by inhibiting chronic inflammation, fibrosis, apoptosis and pyroptosis via targeting JNK and NF-κB pathways. Our data suggested that BIC could be potentially used to prevent obesity-associated nephropathy, which warrants future investigation.

Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Homer1 ameliorates ischemic stroke by inhibiting necroptosis-induced neuronal damage and neuroinflammation

OBJECTIVE

Proinflammatory necroptosis is the main pathological mechanism of ischemic stroke. Homer scaffolding protein 1 (Homer1) is a postsynaptic scaffolding protein that exerts anti-inflammatory effects in most central nervous system diseases. However, the relationship between Homer1 and proinflammatory necroptosis in ischemic stroke remains unclear.

AIM

This study aimed to investigate the role of Homer1 in ischemia-induced necroptosis.

METHODS

C57BL/6 mice were used to establish a model of permanent middle cerebral artery occlusion model (pMCAO). Homer1 knockdown mice were generated using adeno-associated virus (AAV) infection to explore the role of Homer1 and its impact on necroptosis in pMCAO. Finally, Homer1 protein was stereotaxically injected into the ischemic cortex of Homer1flox/flox/Nestin-Cre +/- mice, and the efficacy of Homer1 was investigated using behavioral assays and molecular biological assays to explore potential mechanisms.

RESULTS

Homer1 expression peaked at 8 h in the ischemic penumbral cortex after pMCAO and colocalized with neurons. Homer1 knockdown promoted neuronal death by enhancing necroptotic signaling pathways and aggravating ischemic brain damage in mice. Furthermore, the knockdown of Homer1 enhanced the expression of proinflammatory cytokines. Moreover, injection of Homer1 protein reduced necroptosis-induced brain injury inhibited the expression of proinflammatory factors, and ameliorated the outcomes in the Homer1flox/flox/Nestin-Cre+/- mice after pMCAO.

CONCLUSIONS

Homer1 ameliorates ischemic stroke by inhibiting necroptosis-induced neuronal damage and neuroinflammation. These data suggested that Homer1 is a novel regulator of neuronal death and neuroinflammation.

Targeting Cx43 to Reduce the Severity of Pressure Ulcer Progression

In the skin, repeated incidents of ischemia followed by reperfusion can result in the breakdown of the skin and the formation of a pressure ulcer. Here we gently applied paired magnets to the backs of mice to cause ischemia for 1.5 h and then removed them to allow reperfusion. The sterile inflammatory response generated within 4 h causes a stage 1 pressure ulcer with an elevation of the gap junction protein Cx43 in the epidermis. If this process is repeated the insult will result in a more severe stage 2 pressure ulcer with a breakdown of the epidermis 2-3 days later. After a single pinch, the elevation of Cx43 in the epidermis is associated with the inflammatory response with an increased number of neutrophils, HMGB1 (marker of necrosis) and RIP3 (responsible for necroptosis). Delivering Cx43 specific antisense oligonucleotides sub-dermally after a single insult, was able to significantly reduce the elevation of epidermal Cx43 protein expression and reduce the number of neutrophils and prevent the elevation of HMGB1 and RIP3. In a double pinch model, the Cx43 antisense treatment was able to reduce the level of inflammation, necroptosis, and the extent of tissue damage and progression to an open wound. This approach may be useful in reducing the progression of stage 1 pressure ulcers to stage 2.

Knowledge mapping of programmed cell death in osteonecrosis of femoral head: a bibliometric analysis (2000-2022)

BACKGROUND

Osteonecrosis of the femoral head (ONFH) is a common, refractory and disabling disease of orthopedic department, which is one of the common causes of hip pain and dysfunction. Recent studies have shown that much progress has been made in the research of programmed cell death (PCD) in ONFH. However, there is no bibliometric analysis in this research field. This study aims to provide a comprehensive overview of the knowledge structure and research hot spots of PCD in ONFH through bibliometrics.

METHOD

The literature search related to ONFH and PCD was conducted on the Web of Science Core Collection (WoSCC) database from 2002 to 2021. The VOSviewers, "bibliometrix" R package and CiteSpace were used to conduct this bibliometric analysis.

RESULTS

In total, 346 articles from 27 countries led by China and USA and Japan were included. The number of publications related to PCD in ONFH is increasing year by year. Shanghai Jiao Tong University, Xi An Jiao Tong University, Wuhan University and Huazhong University of Science and Technology are the main research institutions. Molecular Medicine Reports is the most popular journal in the field of PCD in ONFH, and Clinical Orthopaedics and Related Research is the most cocited journal. These publications come from 1882 authors among which Peng Hao, Sun Wei, Zhang Chang-Qing, Zhang Jian and Wang Kun-zheng had published the most papers and Ronald S Weinstein was cocited most often. Apoptosis, osteonecrosis, osteonecrosis of the femoral head, glucocorticoid and femoral head appeared are the main topics the field of PCD in ONFH. Autophagy was most likely to be the current research hot spot for PCD in ONFH.

CONCLUSION

This is the first bibliometric study that comprehensively summarizes the research trends and developments of PCD in ONFH. This information identified recent research frontiers and hot directions, which will provide a reference for scholars studying PCD in ONFH.

Identification of Pyrido[3,4-d]pyrimidine derivatives as RIPK3-Mediated necroptosis inhibitors

Necroptosis executed by RIPK3-mediated phosphorylation of MLKL is a programmed necrotic cell death and implicated with various diseases such as sterile inflammation. We designed and synthesized pyrido[3,4-d]pyrimidine derivatives as novel necroptosis inhibitors capable of suppressing the phosphorylation of MLKL. Our SAR studies reveal that 20 possesses comparable inhibitory activity against RIPK3-mediated pMLKL in HT-29 cells relative to GSK872 (2), a representative selective RIPK3 inhibitor. Based on biochemical kinase assay results, 20 is comparable to GSK872 (2) with regard to activity against RIPK3 and less potent against RIPK1 than GSK872, indicating selectivity of 20 towards RIPK3 over RIPK1 is higher than that of GSK872. In HT-29 cells, 20 inhibits necroptosis via MLKL oligomerization impediment. Moreover, 20 suppresses migration and invasion of AsPC-1 cells by necroptosis induced- CXCL5 secretion downregulation. Significantly, 20 could relieve the TNFα-induced systemic inflammatory response syndrome in vivo. Taken together, this study would provide a useful insight into the design of novel necroptosis inhibitors possessing RIPK3-mediated pMLKL inhibitory activity.

LncRNA MALAT1 Promoted Neuronal Necroptosis in Cerebral Ischemia-reperfusion Mice by Stabilizing HSP90

The objective of this research was to investigate the role of lncRNA MALAT1 and HSP90 in the regulation of neuronal necroptosis in mice with cerebral ischemia-reperfusion (CIR). We used male C57BL/6J mice to establish a middle cerebral artery occlusion (MCAO) model and conducted in vitro experiments using the HT-22 mouse hippocampal neuron cell line. The cellular localization of NeuN and MLKL, as well as the expression levels of neuronal necroptosis factors, MALAT1, and HSP90 were analyzed. Cell viability and necroptosis were assessed, and we also investigated the relationship between MALAT1 and HSP90. The results showed that MALAT1 expression increased after MCAO and oxygen-glucose deprivation/re-oxygenation (OGD/R) treatment in both cerebral tissues and cells compared with the control group. The levels of neuronal necroptosis factors and the co-localization of NeuN and MLKL were also increased in MCAO mice compared with the Sham group. MALAT1 was found to interact with HSP90, and inhibition of HSP90 expression led to decreased phosphorylation levels of neuronal necroptosis factors. Inhibition of MALAT1 expression resulted in decreased co-localization levels of NeuN and MLKL, decreased phosphorylation levels of neuronal necroptosis factors, and reduced necroptosis rate in cerebral tissues. Furthermore, inhibiting MALAT1 expression also led to a shorter half-life of HSP90, increased ubiquitination level, and decreased phosphorylation levels of neuronal necroptosis factors in cells. In conclusion, this study demonstrated that lncRNA MALAT1 promotes neuronal necroptosis in CIR mice by stabilizing HSP90.

Nrf2/HO-1 blocks TXNIP/NLRP3 interaction via elimination of ROS in oxygen-glucose deprivation-induced neuronal necroptosis

Acute ischemic stroke (AIS) is known to trigger a cascade of inflammatory events that induces secondary tissue damages. As a type of regulated inflammatory cell death, necroptosis is associated with AIS, whilst its regulation during neuroinflammation is not well understood. In particular, the actual function of NOD-like-receptor family pyrin domain-containing-3(NLRP3) inflammasome in cortical neuronal necroptosis still not clear. Herein, we explored the function of nuclear factor erythroid-2 related factor-2 (Nrf2)/heme oxygenase-1 (HO-1) in oxygen-glucose deprivation (OGD) induced neuronal necroptosis and its underlying mechanism. To establish an in vitro model of neuronal necrosis, we used OGD/caspase-8 inhibitors (Q-VD-OPh, QVD) to treat rat primary cortical neurons (PCNs) after reoxygenation, wherein we found that the model cause an elevated ROS levels by mediating TXNIP/NLRP3 interactions, which in turn activated the NLRP3 inflammasome. Also, we observed that regulation of nuclear factor erythroid-2 related factor-2 (Nrf2) promoted heme oxygenase-1 (HO-1) expression and decreased TXNIP (a protein that relate oxidative stress to activation of inflammasome) and ROS levels, which negatively regulated the expression of OGD-induced activation of NLRP3 inflammasomes. In addition, HO-1 weakened NLRP3 inflammation body activation, which suggests that Nrf2-regulated HO-1 could block the interaction between TXNIP and NLRP3 in OGD/R-treated cortical neurons by inhibiting ROS production. Our study has discovered the importance of Nrf2/HO-1 signaling cascade for inhibiting inflammasome of NLRP3, which negatively regulated necrosis. Therefore, NLRP3 is considered a potential target for a novel neuroprotective approach, which can expand the therapeutic windows of stroke drugs.

Cell Death Mechanism of Organometallic Ruthenium(II) and Iridium(III) Arene Complexes on HepG2 and Vero Cells

Due to side effects and toxicity associated with platinum-derived metal-based drugs, extensive research has been conducted on ruthenium (Ru) complexes. We aim to synthesize a highly oil soluble Ru(II)-p-cymene complex (Ru1) with an aliphatic chain group, a bimetallic Ru(II)-p-cymene complex (Ru2) with N,S,S triple-coordination and a bimetallic Ir(III)-pentamethylcyclopentadienyl complex (Ir1) with S,S double-coordination. Subsequently, we investigate the effects of these complexes on Vero and HepG2 cell lines, focusing on cell death mechanisms. Characterization of the complexes is performed through nuclear magnetic resonance spectroscopy (1H and 13C NMR) and Fourier-transform infrared spectroscopy. The effective doses are determined using the (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide) (MTT) assay, applying different doses of the complexes to the two cell lines for 24 and 48 h, respectively. Immunoreactivities of Bax, Bcl2, caspase-3, RIP3, and RIPK1 are analyzed using the indirect immunoperoxidase technique. Notably, all the complexes (Ru1, Ru2, and Ir1) exhibit distinct cell death mechanisms, showing greater effectiveness than cisplatin. This study reveals the diverse mechanisms of action of Ru and Ir complexes based on different ligands. To the best of our knowledge, this study represents the first investigation of a novel RAED-type complex (Ru1) and unexpected bimetallic complexes (Ru2 and Ir1).

Alleviation of temporomandibular joint osteoarthritis by targeting RIPK1-mediated inflammatory signalling

Temporomandibular joint osteoarthritis (TMJOA), prevalent in adolescents and the elderly, has serious physical and psychological consequences. TMJOA is a degenerative disease of the cartilage and bone, mostly driven by inflammation, and synoviocytes are the first and most important inflammatory factor releasers. Receptor-interacting serine/threonine-protein kinase (RIPK1) promotes inflammatory response and cell death during an array of illnesses. This research aimed to explore the impacts of RIPK1 inhibitor therapy in TMJOA and the mechanism of RIPK1 in inducing inflammation during TMJOA. Herein, inhibition of RIPK1 suppressed the elevated levels of inflammatory factors, nuclear factor kappa B (NF-κB), along with markers of apoptosis and necroptosis after tumour necrosis factor (TNF)-α/cycloheximide (CHX) treatment in synoviocytes. Moreover, inflammation models were constructed in vivo through complete Freund's adjuvant (CFA) induction and disc perforation, and the findings supported that RIPK1 inhibition protected TMJ articular cartilage against progressive degradation. RIPK1 regulates NF-κB activation via cellular inhibitor of apoptosis proteins (cIAP), apoptosis via caspase-8, and necroptosis via RIPK3/mixed lineage kinase domain-like (MLKL) in synoviocytes, which in turn facilitates TMJOA inflammation progression.

Immunomodulatory and Antioxidant Drugs in Glaucoma Treatment

Glaucoma, a group of diseases characterized by progressive retinal ganglion cell loss, cupping of the optic disc, and a typical pattern of visual field defects, is a leading cause of severe visual impairment and blindness worldwide. Elevated intraocular pressure (IOP) is the leading risk factor for glaucoma development. However, glaucoma can also develop at normal pressure levels. An increased susceptibility of retinal ganglion cells to IOP, systemic vascular dysregulation, endothelial dysfunction, and autoimmune imbalances have been suggested as playing a role in the pathophysiology of normal-tension glaucoma. Since inflammation and oxidative stress play a role in all forms of glaucoma, the goal of this review article is to present an overview of the inflammatory and pro-oxidant mechanisms in the pathophysiology of glaucoma and to discuss immunomodulatory and antioxidant treatment approaches.

Neuronal DAMPs exacerbate neurodegeneration via astrocytic RIPK3 signaling

Astrocyte activation is a common feature of neurodegenerative diseases. However, the ways in which dying neurons influence the activity of astrocytes is poorly understood. RIPK3 signaling has recently been described as a key regulator of neuroinflammation, but whether this kinase mediates astrocytic responsiveness to neuronal death has not yet been studied. Here, we used the MPTP model of Parkinson's disease to show that activation of astrocytic RIPK3 drives dopaminergic cell death and axon damage. Transcriptomic profiling revealed that astrocytic RIPK3 promoted gene expression associated with neuroinflammation and movement disorders, and this coincided with significant engagement of DAMP signaling. Using human cell culture systems, we show that factors released from dying neurons signal through RAGE to induce RIPK3-dependent astrocyte activation. These findings highlight a mechanism of neuron-glia crosstalk in which neuronal death perpetuates further neurodegeneration by engaging inflammatory astrocyte activation via RIPK3.

Protrudin-mediated ER-endosome contact sites promote phagocytosis

During phagocytosis, endosomes both contribute with membrane to forming phagosomes and promote phagosome maturation. However, how these vesicles are delivered to the phagocytic cup and the phagosome has been unknown. Here, we show that Protrudin-mediated endoplasmic reticulum (ER)-endosome contact sites facilitate anterograde translocation of FYCO1 and VAMP7-positive late endosomes and lysosomes (LELys) to forming phagocytic cups in a retinal pigment epithelial-derived cell line (RPE1). Protrudin-dependent phagocytic cup formation required SYT7, which promotes fusion of LELys with the plasma membrane. RPE1 cells perform phagocytosis of dead cells (efferocytosis) that expose phosphatidylserine (PS) on their surface. Exogenous addition of apoptotic bodies increased the formation of phagocytic cups, which further increased when Protrudin was overexpressed. Overexpression of Protrudin also led to elevated uptake of silica beads coated with PS. Conversely, Protrudin depletion or abrogation of ER-endosome contact sites inhibited phagocytic cup formation resulting in reduced uptake of PS-coated beads. Thus, the Protrudin pathway delivers endosomes to facilitate formation of the phagocytic cup important for PS-dependent phagocytosis.

Dual identity of tumor-associated macrophage in regulated cell death and oncotherapy

Tumor-associated macrophage (TAM) affects the intrinsic properties of tumor cells and the tumor microenvironment (TME), which can stimulate tumor cell proliferation, migration, and genetic instability, and macrophage diversity includes the diversity of tumors with different functional characteristics. Macrophages are now a central drug target in various diseases, especially in the TME, which, as "tumor promoters" and "immunosuppressors", have different responsibilities during tumor development and accompany by significant dynamic alterations in various subpopulations. Remodelling immunosuppression of TME and promotion of pre-existing antitumor immune responses is critical by altering TAM polarization, which is relevant to the efficacy of immunotherapy, and uncovering the exact mechanism of action of TAMs and identifying their specific targets is vital to optimizing current immunotherapies. Hence, this review aims to reveal the triadic interactions of macrophages with programmed death and oncotherapy, and to integrate certain relationships in cancer treatment.

Viral-induced neuronal necroptosis: Detrimental to brain function and regulation by necroptosis inhibitors

Neuronal necroptosis (programmed necrosis) in the CNS naturally occurs through a caspase-independent way and, especially in neurodegenerative diseases (NDDs) such as Alzheimer's disease (AD), Parknson's disease (PD), Amyotrophic Lateral Sclerosis (ALS) and viral infections. Understanding necroptosis pathways (death receptor-dependent and independent), and its connections with other cell death pathways could lead to new insights into treatment. Receptor-interacting protein kinase (RIPK) mediates necroptosis via mixed-lineage kinase-like (MLKL) proteins. RIPK/MLKL necrosome contains FADD, procaspase-8-cellular FLICE-inhibitory proteins (cFLIPs), RIPK1/RIPK3, and MLKL. The necrotic stimuli cause phosphorylation of MLKL and translocate to the plasma membrane, causing an influx of Ca2+ and Na+ ions and, the immediate opening of mitochondrial permeability transition pore (mPTP) with the release of inflammatory cell damage-associated molecular patterns (DAMPs) like mitochondrial DNA (mtDNA), high-mobility group box1 (HMGB1), and interleukin1 (IL-1). The MLKL translocates to the nucleus to induce transcription of the NLRP3 inflammasome complex elements. MLKL-induced NLRP3 activity causes caspase-1 cleavage and, IL-1 activation which promotes neuroinflammation. RIPK1-dependent transcription increases illness-associated microglial and lysosomal abnormalities to facilitate amyloid plaque (Aβ) aggregation in AD. Recent research has linked neuroinflammation and mitochondrial fission with necroptosis. MicroRNAs (miRs) such as miR512-3p, miR874, miR499, miR155, and miR128a regulate neuronal necroptosis by targeting key components of necroptotic pathways. Necroptosis inhibitors act by inhibiting the membrane translocation of MLKL and RIPK1 activity. This review insights into the RIPK/MLKL necrosome-NLRP3 inflammasome interactions during death receptor-dependent and independent neuronal necroptosis, and clinical intervention by miRs to protect the brain from NDDs.

Necroptosis in the developing brain: role in neurodevelopmental disorders

Cell death is vital to various organismal developmental processes including brain development. Apoptosis, the most recognized programmed cell death, has been linked to several developmental processes and implicated in pruning cells to provide the ultimate tissue integrity. However, more recently, other forms of non-apoptotic programmed cell death have been identified, of which necroptosis is of predominant interest. Necroptosis is a regulated form of necrosis, activated under apoptotic-deficient conditions. Tumour necrosis factor (TNF) is a major activator of necroptosis, and the process is mediated by several kinases including receptor-interacting protein kinase (RIPK) and mixed lineage kinase domain-like protein (MLKL). Potential roles for necroptosis during brain development have been muted. Necroptosis has been implicated in mediating neurological disorders, and contributing to the severity of these disorders. Here we will review the literature on the role of necroptosis in neurodevelopment, summarizing its molecular mechanisms and highlighting potential implications for disorders of the developing brain.

Alfaxalone Alleviates Neurotoxicity and Cognitive Impairment Induced by Isoflurane Anesthesia in Offspring Rats

BACKGROUND

The anesthetic isoflurane can cause neurotoxicity in fetuses and offspring of rats, affecting their neurodevelopment. However, the underlying mechanisms and therapeutic targets of isoflurane-induced neurotoxicity remain to be identified. Alfaxalone (ALF) is a steroid anesthetic. Steroids have been reported to have neuroprotective effects. This study aimed to investigate whether ALF could alleviate the isoflurane-induced neurotoxicity in fetuses and offspring of rats.

METHODS

On gestation day 15 (G15), the pregnant SD rats were randomly assigned to 4 groups: control 1 (CTL1) + control 2 (CTL2), isoflurane (ISO) + CTL2, CTL1 + ALF, and ISO + ALF. To analyze the changes in the expression levels of inflammatory cytokines, apoptotic factors, and synaptophysin, the brain tissues from the G15 fetuses and offspring at postnatal day 7 (P7), postnatal day 14 (P14), and postnatal day 31 (P31) were collected. The newborn neurons in the rats' offspring at P7, P14, and P31 were counted using immunofluorescence techniques. The Morris water maze (MWM) test was performed to assess the learning and memory abilities of P31 offspring rats.

RESULTS

ALF significantly alleviated the isoflurane-induced increase in the expression levels of inflammatory cytokines and apoptotic factors, such as interleukin (IL)-6 (ISO + CTL2 versus ISO + ALF: 5.133 ± 0.739 versus 1.093 ± 0.213, P < .001) and Caspase-3 (6.457 ± 0.6 versus 1.062 ± 0.1, P < .001) in the G15 fetuses. In P31 offspring rats, the expression levels of synaptophysin (0.719 ± 0.04 versus 1.068 ± 0.072, P < .001) and the number of newborn neurons in the dentate gyrus of the hippocampus were significantly lower in the ISO + CTL2 group as compared to those in the ISO + ALF group (118 ± 6 versus 140 ± 7, P < .001). These changes also occurred in the rat offspring at P7 and P14. In the MWM test, the escape latency of CTL1 + ALF group rats was significantly lower than that of ISO + ALF group rats (41 ± 6 versus 31 ± 7, P < .001) at P31.

CONCLUSIONS

Based on these findings, this study suggested that isoflurane exposure during pregnancy in rats could cause neuroinflammation and death of embryos as well as impairment of cognitive function in the offspring rats. ALF can be used to counteract the negative effects of isoflurane.

Shock lung is not "wet" but characterized as necroptotic inflammation in a mouse model of hypotension

OBJECTIVES

Hypotension episodes before or after donor brain death are assumed to trigger hypoxia-reoxygenation, causing diffuse alveolar-capillary damage via necrosis. However, alveolar-capillary membranes have direct access to oxygen in alveoli. We hypothesized hypotension-induced lung injury is not diffuse alveolar-capillary damage but interstitial inflammation resulting from nonhypoxic lung ischemia and systemic responses to hypoxic extrapulmonary ischemia.

METHODS

The 4-hour hypotension model was established by subjecting C57BL/6J mice to 4-hour hypotension at 15 ± 5 mm Hg of mean artery pressure and resuscitated with whole shed blood and norepinephrine. Nonhypoxic lung ischemia model was established by 4-hour left pulmonary artery ligation. At 24 hours postprocedure, an arterial blood gas analysis and a gastroduodenal occult blood test were conducted. Lung samples were assessed for histology, cytokine transcripts, regulated cell death, and alveolar-capillary permeability.

RESULTS

The 4-hour hypotension model had an intraoperative mortality rate of 17.7% (41/231) and a stress-ulcer bleeding rate of 15.3% (29/190). No signs of alveolar flooding were observed in both models. Four-hour hypotension without stress ulcer showed normal oxygenation and permeability but increased interstitial infiltration, transcription of Tnf and Il1b, phosphorylation of MLKL and RIPK3, and cleaved caspase 3 compared with 4-hour pulmonary artery ligation and naïve control. Animals that developed stress ulcer presented with worse pulmonary infiltration, intracellular edema, and oxygenation but just slightly increased permeability. Immunoblotting showed significant upregulations of protein expression and phosphorylation of MLKL and RIPK3, cleaved Caspase-3, but not its prototype in 4-hour hypotension with stress ulcer.

CONCLUSIONS

Hypotensive lung injury is essentially a nonhypoxic ischemia-reperfusion injury enhanced by systemic responses. It is predominated by necroptosis-induced inflammation rather than necrosis-induced diffuse alveolar-capillary damage.

Low-intensity pulsed ultrasound (LIPUS) switched macrophage into M2 phenotype and mitigated necroptosis and increased HSP 70 in gentamicin-induced nephrotoxicity

BACKGROUND AND AIM

Many attempts to control acute kidney injury (AKI) have failed due to a lack of understanding of its pathophysiological key components. Macrophages are a crucial determinant of AKI, which can be categorized functionally as M1 pro-inflammatory and M2 anti-inflammatory macrophages. Low-intensity pulsed ultrasound (LIPUS) is currently being investigated as an immune modulator. The present study aimed to explore the potential effects of LIPUS on the polarization of renal macrophages, as well as the possible interplay between macrophage polarization and necroptosis in gentamicin-induced acute kidney injury.

METHOD

All rats were randomly allocated into one of four groups: control, LIPUS-treated control, gentamicin acute kidney (GM-AKI), and LIPUS-treated GM-AKI. Renal functions, macrophage polarization, necroptosis, and heat shock protein-70 (HSP70) were analyzed using real-time reverse-transcriptase-polymerase chain reaction (rT-PCR), Western Blot, Enzyme-linked immunosorbent assay (ELISA) as well as immunohistological analysis.

RESULTS

we found that LIPUS markedly inhibited the expressions of M1 macrophage-related genes and promoted significantly the expression of M2 macrophages related genes. This was accompanied by an inhibition of necroptosis and a marked reduction of HSP-70, resulting in a reversal of gentamicin-induced renal alteration.

CONCLUSION

Functional switching of macrophage responses from M1 into M2 seems to be a potential approach to ameliorate necroptosis as well as HSP-70 by low pulsed ultrasound waves in GM-AKI.

Surviving death: emerging concepts of RIPK3 and MLKL ubiquitination in the regulation of necroptosis

Lytic forms of programmed cell death, like necroptosis, are characterised by cell rupture and the release of cellular contents, often provoking inflammatory responses. In the recent years, necroptosis has been shown to play important roles in human diseases like cancer, infections and ischaemia/reperfusion injury. Coordinated interactions between RIPK1, RIPK3 and MLKL lead to the formation of a dedicated death complex called the necrosome that triggers MLKL-mediated membrane rupture and necroptotic cell death. Necroptotic cell death is tightly controlled by post-translational modifications, among which especially phosphorylation has been characterised in great detail. Although selective ubiquitination is relatively well-explored in the early initiation stages of necroptosis, the mechanisms and functional consequences of RIPK3 and MLKL ubiquitination for necrosome function and necroptosis are only starting to emerge. This review provides an overview on how site-specific ubiquitination of RIPK3 and MLKL regulates, fine-tunes and reverses the execution of necroptotic cell death.

Improving therapeutic synergy score predictions with adverse effects using multi-task heterogeneous network learning

Drug combinations could trigger pharmacological therapeutic effects (TEs) and adverse effects (AEs). Many computational methods have been developed to predict TEs, e.g. the therapeutic synergy scores of anti-cancer drug combinations, or AEs from drug-drug interactions. However, most of the methods treated the AEs and TEs predictions as two separate tasks, ignoring the potential mechanistic commonalities shared between them. Based on previous clinical observations, we hypothesized that by learning the shared mechanistic commonalities between AEs and TEs, we could learn the underlying MoAs (mechanisms of actions) and ultimately improve the accuracy of TE predictions. To test our hypothesis, we formulated the TE prediction problem as a multi-task heterogeneous network learning problem that performed TE and AE learning tasks simultaneously. To solve this problem, we proposed Muthene (multi-task heterogeneous network embedding) and evaluated it on our collected drug-drug interaction dataset with both TEs and AEs indications. Our experimental results showed that, by including the AE prediction as an auxiliary task, Muthene generated more accurate TE predictions than standard single-task learning methods, which supports our hypothesis. Using a drug pair Vincristine-Dasatinib as a case study, we demonstrated that our method not only provides a novel way of TE predictions but also helps us gain a deeper understanding of the MoAs of drug combinations.

New insights of necroptosis and immune infiltration in sepsis-induced myocardial dysfunction from bioinformatics analysis through RNA-seq in mice

Sepsis is a life-threatening organ dysfunction caused by dysregulated host immune response to infection. Sepsis-induced myocardial dysfunction (SIMD) is a common complication in patients with severe sepsis and is associated with increased mortality. The molecular mechanisms underlying SIMD are complex and not well characterized. Excessive inflammation due to impaired regulation of immune response is one of the major causes of SIMD. Necroptosis is a novel type of cell death that is closely related to tissue injury and inflammation. However, the role of necroptosis in SIMD is not known. Therefore, in this study, we performed an in-depth bioinformatics analysis to investigate the relationship between necroptosis and SIMD using a mouse model generated by intraperitoneal injection of lipopolysaccharide (LPS) and the underlying mechanisms. Myocardial function was assessed by echocardiography. Histopathological changes in SIMD were analyzed by hematoxylin and eosin (H&E) staining. Gene expression profiles of the heart tissues from the SIMD and control mice were analyzed by bioinformatics analysis. Transcriptome sequencing demonstrated significant differences in the expression levels of 3654 genes in the heart tissues of SIMD mice including 1810 up-regulated and 1844 down-regulated genes. The necroptosis pathway genes were significantly enriched in the heart tissues from the SIMD group mice. We identified 35 necroptosis-related differentially expressed genes (NRDEGs) including MLKL and RIPK3. Cardiomyocyte necroptosis was confirmed by qRT-PCR and western blot analysis. The expression levels of most NRDEGs showed positive correlation with the infiltration levels of mast cells, macrophages, and neutrophils, and negative correlation with the infiltration levels of B cells and plasma cells in the heart tissues of the SIMD group mice. In conclusion, this study demonstrated that necroptosis was associated with changes in the infiltration levels of several immune cell types in the heart tissues of the SIMD model mice. This suggested that necroptosis influenced SIMD development by modulating the immune microenvironment. This suggested that NRDEGs are potential diagnostic biomarkers and therapeutic targets for patients with SIMD.

Paradoxical roles for programmed cell death signaling during viral infection of the central nervous system

Programmed cell death (PCD) is an essential mechanism of antimicrobial defense. Recent work has revealed an unexpected diversity in the types of PCD elicited during infection, as well as defined unique roles for different PCD modalities in shaping the immune response. Here, we review recent work describing unique ways in which PCD signaling operates within the infected central nervous system (CNS). These studies reveal striking complexity in the regulation of PCD signaling by CNS cells, including both protective and pathological outcomes in the control of infection. Studies defining the specialized molecular mechanisms shaping PCD responses in the CNS promise to yield much needed new insights into the pathogenesis of neuroinvasive viral infection, informing future therapeutic development.

Wun2-mediated integrin recycling promotes apoptotic cell clearance in Drosophila melanogaster

Apoptotic cell (AC) clearance is a complex process in which phagocytes recognize, engulf, and digest ACs during organismal development and tissue homeostasis. Impaired efferocytosis results in developmental defects and autoimmune diseases. In the current study, we performed RNA-sequencing to systematically identify regulators involved in the phagocytosis of ACs by Drosophila melanogaster macrophage-like S2 cells, followed by targeted RNA interference screening. Wunen2 (Wun2), a homolog of mammalian lipid phosphate phosphatase (LPP), was deemed as required for efferocytosis both in vitro and in vivo. However, efferocytosis was independent of Wun2 phosphatase activity. Proteomic analysis further revealed that Rab11 and its effector Rip11 are interaction partners of Wun2. Therefore, Wun2 collaborates with Rip11 and Rab11 to mediate efficient recycling of the phagocytic receptor βν integrin subunit to the plasma membrane. The loss of Wun2 results in the routing of βv integrin subunit (Itgbn) into lysosomes, leading to its degradation. The deficiency of βv integrin subunit on the cell surface leads to aberrant and disorganized actin cytoskeleton, thereby influencing the formation of macrophage pseudopodia toward ACs and thus failure to engulf them. The findings of this study provide insights that clarify how phagocytes coordinate AC signals and adopt a precise mechanism for the maintenance of engulfment receptors at their cell membrane surface to regulate efferocytosis.

Iron Brain Menace: The Involvement of Ferroptosis in Parkinson Disease

Parkinson disease (PD) is the second-most common neurodegenerative disease. The characteristic pathology of progressive dopaminergic neuronal loss in people with PD is associated with iron accumulation and is suggested to be driven in part by the novel cell death pathway, ferroptosis. A unique modality of cell death, ferroptosis is mediated by iron-dependent phospholipid peroxidation. The mechanisms of ferroptosis inhibitors enhance antioxidative capacity to counter the oxidative stress from lipid peroxidation, such as through the system x_c^-/glutathione (GSH)/glutathione peroxidase 4 (GPX4) axis and the coenzyme Q10 (CoQ10)/FSP1 pathway. Another means to reduce ferroptosis is with iron chelators. To date, there is no disease-modifying therapy to cure or slow PD progression, and a recent topic of research seeks to intervene with the development of PD via regulation of ferroptosis. In this review, we provide a discussion of different cell death pathways, the molecular mechanisms of ferroptosis, the role of ferroptosis in blood-brain barrier damage, updates on PD studies in ferroptosis, and the latest progress of pharmacological agents targeting ferroptosis for the intervention of PD in clinical trials.

PGAM5: A necroptosis gene associated with poor tumor prognosis that promotes cutaneous melanoma progression

Cutaneous melanoma is the deadliest type of skin cancer, and its highly aggressive and metastatic nature leads to an extremely poor prognosis. Necrotizing apoptosis, a specific form of programmed cell death, has been extensively studied in recent years. In this study, we analyzed the relationship between necroptosis-related functional genes and cutaneous melanoma in order to identify the biomarkers associated with the prognosis and progression of cutaneous melanoma. Cutaneous melanoma samples were classified into three subgroups on the basis of a necroptosis gene set. These subgroups were subjected to a prognostic survival analysis, and the greatest differences were observed between subgroups C1 and C3. Between these subgroups, 28 necrotizing apoptosis-related genes were significantly differently expressed. Among these, 16 necrotizing apoptosis-related genes were associated with cutaneous melanoma prognosis. Downscaling analysis and prognostic modeling using the least absolute shrinkage and selection operator analysis yielded nine pivotal genes and revealed phosphoglycerate translocase 5 (PGAM5) as the key gene. Then, qRT-PCR was used to verify the expression level of PGAM5. The results showed that PGAM5 was highly expressed in cutaneous melanoma tissues. In this study, a bioinformatics approach was used to identify PGAM5, a biomarker whose high expression is associated with the poor prognosis of cutaneous melanoma.

A Pan-Cancer Atlas of Differentially Interacting Hallmarks of Cancer Proteins

Cancer hallmark genes and proteins orchestrate and drive carcinogenesis to a large extent, therefore, it is important to study these features in different cancer types to understand the process of tumorigenesis and discover measurable indicators. We performed a pan-cancer analysis to map differentially interacting hallmarks of cancer proteins (DIHCP). The TCGA transcriptome data associated with 12 common cancers were analyzed and the differential interactome algorithm was applied to determine DIHCPs and DIHCP-centric modules (i.e., DIHCPs and their interacting partners) that exhibit significant changes in their interaction patterns between the tumor and control phenotypes. The diagnostic and prognostic capabilities of the identified modules were assessed to determine the ability of the modules to function as system biomarkers. In addition, the druggability of the prognostic and diagnostic DIHCPs was investigated. As a result, we found a total of 30 DIHCP-centric modules that showed high diagnostic or prognostic performance in any of the 12 cancer types. Furthermore, from the 16 DIHCP-centric modules examined, 29% of these were druggable. Our study presents candidate systems' biomarkers that may be valuable for understanding the process of tumorigenesis and improving personalized treatment strategies for various cancers, with a focus on their ten hallmark characteristics.

Macrophages in Skin Wounds: Functions and Therapeutic Potential

Macrophages regulate cutaneous wound healing by immune surveillance, tissue repair and remodelling. The depletion of dermal macrophages during the early and middle stages of wound healing has a detrimental impact on wound closure, characterised by reduced vessel density, fibroblast and myofibroblast proliferation, delayed re-epithelization and abated post-healing fibrosis and scar formation. However, in some animal species, oral mucosa and foetal life, cutaneous wounds can heal normally and remain scarless without any involvement of macrophages. These paradoxical observations have created much controversy on macrophages' indispensable role in skin wound healing. Advanced knowledge gained by characterising macrophage subsets, their plasticity in switching phenotypes and molecular drivers provides new insights into their functional importance during cutaneous wound healing. In this review, we highlight the recent findings on skin macrophage subsets, their functional role in adult cutaneous wound healing and the potential benefits of targeting them for therapeutic use.

Single-cell RNA sequencing reveals a landscape and targeted treatment of ferroptosis in retinal ischemia/reperfusion injury

BACKGROUND

The aim of this study was to establish a complete retinal cell atlas of ischemia-reperfusion injury by single-cell RNA sequencing, and to explore the underlying mechanism of retinal ischemia-reperfusion injury in mice.

METHODS

Single-cell RNA sequencing was used to evaluate changes in the mouse retinal ischemia reperfusion model. In vivo and in vitro experiments were performed to verify the protective effect of inhibiting ferroptosis in retinal ischemia-reperfusion injury.

RESULTS

After ischemia-reperfusion injury, retinal cells were significantly reduced, accompanied by the activation of myeloid and a large amount of blood-derived immune cell infiltration. The IFNG, MAPK and NFKB signaling pathways in retinal neuronal cells, together with the TNF signaling pathway in myeloid give rise to a strong inflammatory response in the I/R state. Besides, the expression of genes implicating iron metabolism, oxidative stress and multiple programed cell death pathways have changed in cell subtypes described above. Especially the ferroptosis-related genes and blocking this process could apparently alleviate the inflammatory immune responses and enhance retinal ganglion cells survival.

CONCLUSIONS

We established a comprehensive landscape of mouse retinal ischemia-reperfusion injury at the single-cell level, revealing the important role of ferroptosis during this injury, and targeted inhibition of ferroptosis can effectively protect retinal structure and function.

Catching a killer: Mechanisms of programmed cell death and immune activation in Amyotrophic Lateral Sclerosis

In the central nervous system (CNS), execution of programmed cell death (PCD) is crucial for proper neurodevelopment. However, aberrant activation of these pathways in adult CNS leads to neurodegenerative diseases including amyotrophic lateral sclerosis (ALS). How a cell dies is critical, as it can drive local immune activation and tissue damage. Classical apoptosis engages several mechanisms to evoke "immunologically silent" responses, whereas other forms of programmed death such as pyroptosis, necroptosis, and ferroptosis release molecules that can potentiate immune responses and inflammation. In ALS, a fatal neuromuscular disorder marked by progressive death of lower and upper motor neurons, several cell types in the CNS express machinery for multiple PCD pathways. The specific cell types engaging PCD, and ultimate mechanisms by which neuronal death occurs in ALS are not well defined. Here, we provide an overview of different PCD pathways implicated in ALS. We also examine immune activation in ALS and differentiate apoptosis from necrotic mechanisms based on downstream immunological consequences. Lastly, we highlight therapeutic strategies that target cell death pathways in the treatment of neurodegeneration and inflammation in ALS.

Cytokine profiling in pulmonary arterial hypertension: the role of redox homeostasis and sex

Pulmonary arterial hypertension (PAH) is a fatal disease with a well-established sexual dimorphism. Activated inflammatory response and altered redox homeostasis, both known to manifest in a sex-specific manner, are implicated in the pathogenic mechanisms involved in PAH development. This study aimed to evaluate the impact of sex and plasma redox status on circulating cytokine profiles. Plasma oxidation-reduction potential (ORP), as a substitute measure of redox status, was analyzed in male and female Group 1 PAH and healthy subjects. The profiles of 27 circulating cytokines were compared in 2 PAH groups exhibiting the highest and lowest quartile for plasma ORP, correlated with clinical parameters, and used to predict patient survival. The analysis of the PAH groups with the highest and lowest ORP revealed a correlation between elevated cytokine levels and increased oxidative stress in females. In contrast, in males, cytokine expressions were increased in the lower oxidative environment (except for IL-1b). Correlations of the increased cytokine expressions with PAH severity were highly sex-dependent and corresponded to the increase in PAH severity in males and less severe PAH in females. Machine learning algorithms trained on the combined cytokine and redox profiles allowed the prediction of PAH mortality with 80% accuracy. We conclude that the profile of circulating cytokines in PAH patients is redox- and sex-dependent, suggesting the vital need to stratify the patient cohort subjected to anti-inflammatory therapies. Combined cytokine and/or redox profiling showed promising value for predicting the patients' survival.

COX-2 Expression in Hepatocytes Improves Mitochondrial Function after Hepatic Ischemia-Reperfusion Injury

Cyclooxygenase 2 (COX-2) is a key enzyme in prostanoid biosynthesis. The constitutive hepatocyte expression of COX-2 has a protective role in hepatic ischemia-reperfusion (I/R) injury (IRI), decreasing necrosis, reducing reactive oxygen species (ROS) levels, and increasing autophagy and antioxidant and anti-inflammatory response. The physiopathology of IRI directly impacts mitochondrial activity, causing ATP depletion and being the main source of ROS. Using genetically modified mice expressing human COX-2 (h-COX-2 Tg) specifically in hepatocytes, and performing I/R surgery on the liver, we demonstrate that COX-2 expression has a beneficial effect at the mitochondrial level. Mitochondria derived from h-COX-2 Tg mice livers have an increased respiratory rate associated with complex I electron-feeding pathways compared to Wild-type (Wt) littermates, without affecting complex I expression or assembly. Furthermore, Wt-derived mitochondria show a loss of mitochondrial membrane potential (ΔΨm) that correlates to increased proteolysis of fusion-related OPA1 through OMA1 protease activity. All these effects are not observed in h-COX-2 Tg mitochondria, which behave similarly to the Sham condition. These results suggest that COX-2 attenuates IRI at a mitochondrial level, preserving the proteolytic processing of OPA1, in addition to the maintenance of mitochondrial respiration.

Identification of cuprotosis-mediated subtypes, the development of a prognosis model, and influence immune microenvironment in hepatocellular carcinoma

Purpose

Cuprotosis is a newly discovered form of non-apoptotic regulated cell death and is characterized by copper-dependent and associated with mitochondrial respiration. However, the prognostic significance and function of cuprotosis-related genes (CRGs) in hepatocellular carcinoma (HCC) are unknown. This study aims to develop cuprotosis-mediated patterns-related gene (CMPRG) prediction models for the prognosis of patients with HCC, exploring the functional underlying the CRGs on the influence of tumor microenvironment (TME) features.

Experimental design

This study obtained transcriptome profiling and the corresponding clinical information from the TCGA and GEO databases. Besides, the Cox regression model with LASSO was implemented to build a multi-gene signature, which was then validated in an internal validation set and two external validation sets through Kaplan-Meier, DCA, and ROC analyses.

Results

According to the LASSO analysis, we screened out a cuprotosis-mediated pattern 5-gene combination (including PBK; MMP1; GNAZ; GPC1 and AKR1D1). A nomogram was constructed for the presentation of the final model. The ROC curve assessed the model’s predictive ability, which resulted in an area under the curve (AUC) values ranging from 0.604 to 0.787 underwent internal and two external validation sets. Meanwhile, the risk score divided the patients into two groups of high and low risk, and the survival rate of high-risk patients was significantly lower than that of low-risk patients (P<0.01). The risk score could be an independent prognostic factor in the multifactorial Cox regression analysis (P<0.01). Functional analysis revealed that immune status, mutational loads, and drug sensitivity differed between the two risk groups.

Conclusions

In summary, we identified three cuprotosis-mediated patterns in HCC. And CMPRGs are a promising candidate biomarker for HCC early detection, owing to their strong performance in predicting HCC prognosis and therapy. Quantifying cuprotosis-mediated patterns in individual samples may help improve the understanding of multiomic characteristics and guide the development of targeted therapy for HCC.

Moxifloxacin rescues SMA phenotypes in patient-derived cells and animal model

Spinal muscular atrophy (SMA) is a genetic disease resulting in the loss of α-motoneurons followed by muscle atrophy. It is caused by knock-out mutations in the survival of motor neuron 1 (SMN1) gene, which has an unaffected, but due to preferential exon 7 skipping, only partially functional human-specific SMN2 copy. We previously described a Drosophila-based screening of FDA-approved drugs that led us to discover moxifloxacin. We showed its positive effect on the SMN2 exon 7 splicing in SMA patient-derived skin cells and its ability to increase the SMN protein level. Here, we focus on moxifloxacin's therapeutic potential in additional SMA cellular and animal models. We demonstrate that moxifloxacin rescues the SMA-related molecular and phenotypical defects in muscle cells and motoneurons by improving the SMN2 splicing. The consequent increase of SMN levels was higher than in case of risdiplam, a potent exon 7 splicing modifier, and exceeded the threshold necessary for a survival improvement. We also demonstrate that daily subcutaneous injections of moxifloxacin in a severe SMA murine model reduces its characteristic neuroinflammation and increases the SMN levels in various tissues, leading to improved motor skills and extended lifespan. We show that moxifloxacin, originally used as an antibiotic, can be potentially repositioned for the SMA treatment.

Beyond the behavioural phenotype: Uncovering mechanistic foundations in aquatic eco-neurotoxicology

During the last decade, there has been an increase in awareness of how anthropogenic pollution can alter behavioural traits of diverse aquatic organisms. Apart from understanding profound ecological implications, alterations in neuro-behavioural indices have emerged as sensitive and physiologically integrative endpoints in chemical risk assessment. Accordingly, behavioural ecotoxicology and broader eco-neurotoxicology are becoming increasingly popular fields of research that span a plethora of fundamental laboratory experimentations as well as applied field-based studies. Despite mounting interest in aquatic behavioural ecotoxicology studies, there is, however, a considerable paucity in deciphering the mechanistic foundations underlying behavioural alterations upon exposure to pollutants. The behavioural phenotype is indeed the highest-level integrative neurobiological phenomenon, but at its core lie myriads of intertwined biochemical, cellular, and physiological processes. Therefore, the mechanisms that underlie changes in behavioural phenotypes can stem among others from dysregulation of neurotransmitter pathways, electrical signalling, and cell death of discrete cell populations in the central and peripheral nervous systems. They can, however, also be a result of toxicity to sensory organs and even metabolic dysfunctions. In this critical review, we outline why behavioural phenotyping should be the starting point that leads to actual discovery of fundamental mechanisms underlying actions of neurotoxic and neuromodulating contaminants. We highlight potential applications of the currently existing and emerging neurobiology and neurophysiology analytical strategies that should be embraced and more broadly adopted in behavioural ecotoxicology. Such strategies can provide new mechanistic discoveries instead of only observing the end sum phenotypic effects.

Radiosynthesis and characterization of a carbon-11 PET tracer for receptor-interacting protein kinase 1

INTRODUCTION

Receptor-interacting protein kinase 1 (RIPK1) has emerged as a crucial regulator of necroptosis and the inflammatory response by activating a group of downstream immune receptors. It has been recognized as a pivotal contributor to cell death and inflammation in various physiological and pathological processes. RIPK1 deficiency or dysregulation in humans can cause severe immunodeficiency and neurodegenerative diseases such as multiple sclerosis and amyotrophic lateral sclerosis. Recently, diverse structures of RIPK1 inhibitors have been developed as potential therapeutics for neurodegenerative diseases and other pathological inflammatory processes. 7-oxo-2,4,5,7-tetrahydro-6H-pyrazolo[3,4-c]pyridine (Compound 5 or TZ7774) was reported as a novel RIPK1 inhibitor with a Ki of 0.91 nM that can suppress necroptosis in mouse and human cells. To develop a radiotracer for investigating the RIPK1 in vivo, we radiosynthesized [11C]TZ7774 and performed preliminary in vitro and in vivo evaluations in rodents and macaque.

METHODS

Synthesis of the desmethyl precursor TZ7790 was performed and optimized. The radiosynthesis of [11C]TZ7774 was achieved through TZ7790 reacting with [11C]methyl iodide via N-methylation. Ex vivo biodistribution of [11C]TZ7774 was performed in normal Sprague-Dawley rats. Characterization of [11C]TZ7774 in response to inflammation was performed using ex vivo biodistribution study in normal and LPS treated (10 mg/kg) C57BL/6 mice, and in vitro autoradiography and immunohistochemistry of the spleen. MicroPET brain study of [11C]TZ7774 in the macaque was also performed.

RESULTS AND CONCLUSIONS

The radiosynthesis of [11C]TZ7774 was achieved with good radiochemical yield (30-40%, decay corrected to the end of bombardment (EOB)), high chemical purity (>90%), high radiochemical purity (>99%), and high molar activity (>207 GBq/μmol, decay corrected to EOB). Biodistribution studies in Sprague-Dawley rats showed [11C]TZ7774 has a high brain uptake of 0.53 (%ID/g) at 5 min post injection; pancreas, spleen, kidney, and liver also showed a relatively high initial uptake of 0.49, 0.41, 0.62, and 0.95 at 5 min respectively. Uptake of [11C]TZ7774 increased in LPS-treated C57BL/6 mice by 40.9%, 90.4%, and 54.9% in liver, spleen, and kidney respectively. In vitro autoradiography study also revealed increased uptake of [11C]TZ7774 in the spleen of LPS-treated mice. Further characterization with immunohistochemistry confirmed increased expression of RIPK1 in red and white pulp of the spleen for mice pre-treated with LPS. MicroPET demonstrated that [11C]TZ7774 had good initial brain uptake in macaque with an (SUV) of ∼3.7 at 6-10 min, and quickly washed out from brain. These data confirm successful radiosynthesis of a RIPK1 specific radiotracer [11C]TZ7774. Our preliminary studies showed good response to LPS-induced inflammation in rodents and good uptake in macaque brain. [11C]TZ7774 has a potential to image RIPK1 related necroptosis and inflammatory processes.

Targeting Necroptosis as a Promising Therapy for Alzheimer's Disease

Alzheimer's disease (AD) is an irreversible and progressive neurodegenerative disorder featured by memory loss and cognitive default. However, there has been no effective therapeutic approach to prevent the development of AD and the available therapies are only to alleviate some symptoms with limited efficacy and severe side effects. Necroptosis is a new kind of cell death, being regarded as a genetically programmed and regulated pattern of necrosis. Increasing evidence reveals that necroptosis is tightly related to the occurrence and development of AD. This review aims to summarize the potential role of necroptosis in AD progression and the therapeutic capacity of targeting necroptosis for AD patients.

Ars moriendi: Proteases as sculptors of cellular suicide

The Ars moriendi, which translates to "The Art of Dying," encompasses two Latin texts that gave advice on how to die well and without fear according to the Christian precepts of the late Middle Ages. Given that ten to hundred billion cells die in our bodies every day, it is obvious that the concept of a well and orderly ("regulated") death is also paramount at the cellular level. In apoptosis, as the most well-studied form of regulated cell death, proteases of the caspase family are the central mediators. However, caspases are not the only proteases that act as sculptors of cellular suicide, and therefore, we here provide an overview of the impact of proteases in apoptosis and other forms of regulated cell death.

A new cell death program regulated by toll-like receptor 9 through p38 mitogen-activated protein kinase signaling pathway in a neonatal rat model with sepsis associated encephalopathy

Background:

Sepsis, a serious condition with high mortality, usually causes sepsis associated encephalopathy (SAE) that involves neuronal cell death. However, the cell death programs involved and their underlying mechanisms are not clear. This study aimed to explore the regulatory mechanisms of different cell death programs in SAE.

Methods:

A neonatal rat model of SAE was established by cecal ligation and perforation. Survival rate and vital signs (mean arterial pressure and heart rate) were monitored, nerve reflexes were evaluated, and cortical pathological changes were observed by hematoxylin and eosin staining. The expression of pyroptosis, apoptosis, and necroptosis (PANoptosis)-related proteins, mitogen- activated protein kinase (MAPK), and its upstream regulator toll-like receptor 9 (TLR9) were detected. The expression of TLR9 in neurons was observed by immunofluorescence staining. The ultrastructure of neurons was observed by transmission electron microscope.

Results:

First, PANoptosis was found in cortical nerve cells of the SAE rats. Meanwhile, the subunits of MAPKs, p38 MAPK, Jun N- terminal kinase, and extracellular signal-regulated kinase (ERK) were activated. After pharmacologically inhibiting each of the subunits, only p38 MAPK was found to be associated with PANoptosis. Furthermore, blocking the p38 MAPK signaling pathway activated necroptosis but inhibited apoptosis and pyroptosis. When necroptosis was pharmacologically inhibited, apoptosis and pyroptosis were reactivated. Finally, we found that the expression of TLR9, a regulator of MAPKs, was significantly increased in this model. After down-regulation of TLR9, p38 MAPK, and ERK signaling pathways were inhibited, which led to the inhibition of PANoptosis. Further analysis found that down-regulation of TLR9 improved the survival rate and reduced the pathological changes in SAE rats.

Conclusions:

Our study showed that the programs comprising PANoptosis are activated simultaneously in SAE rats. TLR9 activated PANoptosis through the p38 MAPK signaling pathway. TLR9 may work as a potential target for SAE treatment.

Regulated cell death joins in atherosclerotic plaque silent progression

Non-apoptotic regulated cell death (ferroptosis and necroptosis) leads to the release of damage-associated molecular patterns (DAMPs), which initiate and perpetuate a non-infectious inflammatory response. We hypothesize that DAMPs and non-apoptotic regulated cell death are critical players of atherosclerotic plaque progression with inadequate response to lipid-lowering treatment. We aimed to uncover the silent mechanisms that govern the existing residual risk of cardiovascular-related mortality in experimental atherosclerosis. Proteomic and genomic approaches were applied on the ascending aorta of hyperlipidemic rabbits and controls with and without lipid-lowering treatment. The hyperlipidemic animals, which presented numerous heterogeneous atherosclerotic lesions, exhibited high concentrations of serum lipids and increased lipid peroxidation oxidative stress markers. The analyses revealed the significant upregulation of DAMPs and proteins implicated in ferroptosis and necroptosis by hyperlipidemia. Some of them did not respond to lipid-lowering treatment. Dysregulation of five proteins involved in non-apoptotic regulated cell death proteins (VDAC1, VDAC3, FTL, TF and PCBP1) and nine associated DAMPs (HSP90AA1, HSP90AB1, ANXA1, LGALS3, HSP90B1, S100A11, FN, CALR, H3-3A) was not corrected by the treatment. These proteins could play a key role in the atherosclerotic silent evolution and may possess an unexplored therapeutic potential. Mass spectrometry data are available via ProteomeXchange with identifier PXD026379.

m6A: An Emerging Role in Programmed Cell Death

Programmed cell death is an active extinction process, including autophagy, ferroptosis, pyroptosis, apoptosis, and necroptosis. m6A is a reversible RNA modification which undergoes methylation under the action of methylases (writers), and is demethylated under the action of demethylases (erasers). The RNA base site at which m6A is modified is recognized by specialized enzymes (readers) which regulate downstream RNA translation, decay, and stability. m6A affects many aspects of mRNA metabolism, and also plays an important role in promoting the maturation of miRNA, the translation and degradation of circRNA, and the stability of lncRNA. The regulatory factors including writers, erasers and readers promote or inhibit programmed cell death via up-regulating or down-regulating downstream targets in a m6A-dependent manner to participate in the process of disease. In this review, we summarize the functions of m6A with particular reference to its role in programmed cell death.

Axonal spheroids in neurodegeneration

Axonal spheroids are bubble-like biological features that form on most degenerating axons, yet little is known about their influence on degenerative processes. Their formation and growth has been observed in response to various degenerative triggers such as injury, oxidative stress, inflammatory factors, and neurotoxic molecules. They often contain cytoskeletal elements and organelles, and, depending on the pathological insult, can colocalize with disease-related proteins such as amyloid precursor protein (APP), ubiquitin, and motor proteins. Initial formation of axonal spheroids depends on the disruption of axonal and membrane tension governed by cytoskeleton structure and calcium levels. Shortly after spheroid formation, the engulfment signal phosphatidylserine (PS) is exposed on the outer leaflet of spheroid plasma membrane, suggesting an important role for axonal spheroids in phagocytosis and debris clearance during degeneration. Spheroids can grow until they rupture, allowing pro-degenerative factors to exit the axon into extracellular space and accelerating neurodegeneration. Though much remains to be discovered in this area, axonal spheroid research promises to lend insight into the etiologies of neurodegenerative disease, and may be an important target for therapeutic intervention. This review summarizes over 100 years of work, describing what is known about axonal spheroid structure, regulation and function.

Oridonin inhibits DNMT3A R882 mutation-driven clonal hematopoiesis and leukemia by inducing apoptosis and necroptosis

DNA (cytosine-5)-methyltransferase 3A (DNMT3A) mutations occur in ~20% of de novo acute myeloid leukemia (AML) patients, and >50% of these mutations in AML samples are heterozygous missense alterations within the methyltransferase domain at residue R882. DNMT3A R882 mutations in AML patients promote resistance to anthracycline chemotherapy and drive relapse. In this study, we performed high-throughput screening and identified that oridonin, an ent-kaurene diterpenoid extracted from the Chinese herb Rabdosia rubescens, inhibits DNMT3A R882 mutant leukemic cells at a low-micromolar concentration (IC50 = 2.1 µM) by activating both RIPK1-Caspase-8-Caspase-3-mediated apoptosis and RIPK1-RIPK3-MLKL-mediated necroptosis. The inhibitory effect of oridonin against DNMT3A R882 mutant leukemia cells can also be observed in vivo. Furthermore, oridonin inhibits clonal hematopoiesis of hematopoietic stem cells (HSCs) with Dnmt3a R878H mutation comparing to normal HSCs by inducing apoptosis and necroptosis. Overall, oridonin is a potential and promising drug candidate or lead compound targeting DNMT3A R882 mutation-driven clonal hematopoiesis and leukemia.