Caspase-8 inactivation drives autophagy-dependent inflammasome activation in myeloid cells

Glutamine maintains the stability of alveolar structure and function after lung transplantation by inhibiting autophagy

Excessive autophagy may lead to degradation and damage of alveolar epithelial cells after lung transplantation, eventually leading to alveolar epithelial cell loss, affecting the structural integrity and function of alveoli. Glutamine (Gln), a nutritional supplement, regulates autophagy through multiple signaling pathways. In this study, we explored the protective role of Gln on alveolar epithelial cells by inhibiting autophagy. In vivo, a rat orthotopic lung transplant model was carried out to evaluate the therapeutic effect of glutamine. Ischemia/reperfusion (I/R) induced alveolar collapse, edema, epithelial cell apoptosis, and inflammation, which led to a reduction of alveolar physiological function, such as an increase in peak airway pressure, and a decrease in lung compliance and oxygenation index. In comparison, Gln preserved alveolar structure and function by reducing alveolar apoptosis, inflammation, and edema. In vitro, a hypoxia/reoxygenation (H/R) cell model was performed to simulate IR injury on mouse lung epithelial (MLE) cells and human lung bronchus epithelial (Beas-2B) cells. H/R impaired the proliferation of epithelial cells and triggered cell apoptosis. In contrast, Gln normalized cell proliferation and suppressed I/R-induced cell apoptosis. The activation of mTOR and the downregulation of autophagy-related proteins (LC3, Atg5, Beclin1) were observed in Gln-treated lung tissues and alveolar epithelial cells. Both in vivo and in vitro, rapamycin, a classical mTOR inhibitor, reversed the beneficial effects of Gln on alveolar structure and function. Taken together, Glnpreserved alveolar structure and function after lung transplantation by inhibiting autophagy.

Therapeutic strategies of targeting non-apoptotic regulated cell death (RCD) with small-molecule compounds in cancer

Regulated cell death (RCD) is a controlled form of cell death orchestrated by one or more cascading signaling pathways, making it amenable to pharmacological intervention. RCD subroutines can be categorized as apoptotic or non-apoptotic and play essential roles in maintaining homeostasis, facilitating development, and modulating immunity. Accumulating evidence has recently revealed that RCD evasion is frequently the primary cause of tumor survival. Several non-apoptotic RCD subroutines have garnered attention as promising cancer therapies due to their ability to induce tumor regression and prevent relapse, comparable to apoptosis. Moreover, they offer potential solutions for overcoming the acquired resistance of tumors toward apoptotic drugs. With an increasing understanding of the underlying mechanisms governing these non-apoptotic RCD subroutines, a growing number of small-molecule compounds targeting single or multiple pathways have been discovered, providing novel strategies for current cancer therapy. In this review, we comprehensively summarized the current regulatory mechanisms of the emerging non-apoptotic RCD subroutines, mainly including autophagy-dependent cell death, ferroptosis, cuproptosis, disulfidptosis, necroptosis, pyroptosis, alkaliptosis, oxeiptosis, parthanatos, mitochondrial permeability transition (MPT)-driven necrosis, entotic cell death, NETotic cell death, lysosome-dependent cell death, and immunogenic cell death (ICD). Furthermore, we focused on discussing the pharmacological regulatory mechanisms of related small-molecule compounds. In brief, these insightful findings may provide valuable guidance for investigating individual or collaborative targeting approaches towards different RCD subroutines, ultimately driving the discovery of novel small-molecule compounds that target RCD and significantly enhance future cancer therapeutics.

Caspase-8 promotes NLRP3 inflammasome activation mediates eye development defects in zebrafish larvae exposed to perfulorooctane sulfonate (PFOS)

Epidemiological evidence showed that serum high perfluorooctane sulfonate (PFOS) levels are associated with multiple eye related diseases, but the potential underlying molecular mechanisms remain poorly understood. Zebrafish and photoreceptor cell (661w) models were used to investigate the molecular mechanism of PFOS induced eye development defects. Our results showed a novel molecular mechanism of PFOS-induced inflammation response-mediated photoreceptor cell death associated with eye development defects. Inhibition of Caspase-8 activation significantly decreased photoreceptor cell death in PFOS exposure. Mechanistically, Toll-like receptor 4 (TLR4) mediates activation of Caspase-8 promote activation of NLR family pyrin domain-containing 3 (NLRP3) inflammasome to elicit maturation of interleukin-1 beta (IL-1β) via Caspase-1 activation, facilitating photoreceptor cell inflammation damage in PFOS exposure. In addition, we also made a novel finding that Caspase-3 activation was increased via Caspase-8 activation and directly intensified cell death. Our results show the important role of Caspase-8 activation in PFOS induced eye development defects and highlight Caspase-8 mediated activation of the NLRP3 inflammation triggers activation of Caspase-1 and promote the maturation of IL-1β in retinal inflammatory injury.

Role for Caspase-8 in the Release of IL-1β and Active Caspase-1 from Viable Human Monocytes during Toxoplasma gondii Infection

Monocytes are actively recruited to sites of infection and produce the potent proinflammatory cytokine IL-1β. We previously showed that IL-1β release during Toxoplasma gondii infection of primary human monocytes requires the NLRP3 inflammasome and caspase-1 but is independent of gasdermin D and pyroptosis. To investigate mechanisms of IL-1β release, we generated caspase-1, -4, -5, or -8 knockout (KO) THP-1 monocytic cells. Genetic ablation of caspase-1 or -8, but not caspase-4 or -5, decreased IL-1β release during T. gondii infection without affecting cell death. In contrast, TNF-α and IL-6 secretion were unperturbed in caspase-8 KO cells during T. gondii infection. Dual pharmacological inhibition of caspase-8 and RIPK1 in primary monocytes also decreased IL-1β release without affecting cell viability or parasite infection. Caspase-8 was also required for the release of active caspase-1 from T. gondii-infected cells and for IL-1β release during infection with the related apicomplexan parasite Neospora caninum. Surprisingly, caspase-8 deficiency did not impair synthesis or cleavage of pro-IL-1β, but resulted in the retention of mature IL-1β within cells. Generation of gasdermin E KO and ATG7 KO THP-1 cells revealed that the release of IL-1β was not dependent on gasdermin E or ATG7. Collectively, our data indicate that during T. gondii Infection of human monocytes, caspase-8 functions in a novel gasdermin-independent mechanism controlling IL-1β release from viable cells. This study expands on the molecular pathways that promote IL-1β in human immune cells and provides evidence of a role for caspase-8 in the mechanism of IL-1β release during infection.

Effect of lipopolysaccharide on TAK1-mediated hepatocyte PANoptosis through Toll-like receptor 4 during acute liver failure

BACKGROUND

Intestinal endotoxemia (IETM) is an important pathogenic mechanism of acute liver failure (ALF), and TAK1-mediated PANoptosis is a novel cell death mode. This study investigated whether IETM can induce hepatocyte PANoptosis during ALF.

METHOD

PANoptosis cell and mouse models were generated, and lentiviruses (LVs), adeno-associated viral vectors (AVVs), and small interfering RNAs (siRNAs) were subsequently used to overexpress or knock down TLR and TAK1. Then, the levels of hepatocyte injury, TLR4, TAK1 and PANoptosis were detected via an enzyme-labeling instrument, tissue staining, RT-PCR, western blotting, immunofluorescence, and flow cytometry.

RESULTS

The BioGRID database search revealed that TAK1 might interact with TLR4. According to the in vivo experiments, compared with those in ALF mice, liver tissue damage, hepatocyte mortality and PANoptosis in mice in the AAV-TAK1 group were significantly lower, and liver function was significantly improved. According to the in vitro experiments, after promoting the expression of TLR4 in the model group, the degree of cell damage, TLR4 expression and PANoptosis further increased, while the level of TAK1 further decreased. The opposite result was obtained when TLR4 expression was inhibited. The increase in TAK1 expression in the model group reduced the degree of cell damage and PANoptosis, but the level of TLR4 was not significantly changed. In the model group of cells that exhibited TAK1 expression, further promotion of TLR4 expression inhibited the protective effect of TAK1 on cells. In the model group of cells after TAK1 expression was promoted, if the expression of TLR4 was further promoted, the protective effect of TAK1 on cells was inhibited.

CONCLUSION

IETM inhibited the expression of TAK1 by binding to TLR4 molecules and promoting hepatocyte PANoptosis during ALF. Promoting TAK1 expression effectively relieved lipopolysaccharide-induced hepatocyte PANoptosis.

Reduced interleukin-18 secretion by human monocytic cells in response to infections with hyper-virulent Streptococcus pyogenes

BACKGROUND

Streptococcus pyogenes (group A streptococcus, GAS) causes a variety of diseases ranging from mild superficial infections of the throat and skin to severe invasive infections, such as necrotizing soft tissue infections (NSTIs). Tissue passage of GAS often results in mutations within the genes encoding for control of virulence (Cov)R/S two component system leading to a hyper-virulent phenotype. Dendritic cells (DCs) are innate immune sentinels specialized in antigen uptake and subsequent T cell priming. This study aimed to analyze cytokine release by DCs and other cells of monocytic origin in response to wild-type and natural covR/S mutant infections.

METHODS

Human primary monocyte-derived (mo)DCs were used. DC maturation and release of pro-inflammatory cytokines in response to infections with wild-type and covR/S mutants were assessed via flow cytometry. Global proteome changes were assessed via mass spectrometry. As a proof-of-principle, cytokine release by human primary monocytes and macrophages was determined.

RESULTS

In vitro infections of moDCs and other monocytic cells with natural GAS covR/S mutants resulted in reduced secretion of IL-8 and IL-18 as compared to wild-type infections. In contrast, moDC maturation remained unaffected. Inhibition of caspase-8 restored secretion of both molecules. Knock-out of streptolysin O in GAS strain with unaffected CovR/S even further elevated the IL-18 secretion by moDCs. Of 67 fully sequenced NSTI GAS isolates, 28 harbored mutations resulting in dysfunctional CovR/S. However, analyses of plasma IL-8 and IL-18 levels did not correlate with presence or absence of such mutations.

CONCLUSIONS

Our data demonstrate that strains, which harbor covR/S mutations, interfere with IL-18 and IL-8 responses in monocytic cells by utilizing the caspase-8 axis. Future experiments aim to identify the underlying mechanism and consequences for NSTI patients.

Bisdemethoxycurcumin, a curcumin, protects chondrocytes, and reduces cartilage inflammation via the NRF2/HO-1/NLRP3 pathway

BACKGROUND

The objective of this thesis is to evaluate the effect of bisdemethoxycurcumin (BDMC) on osteoarthritis (OA) and comprehensively evaluate the role of the Nuclear Factor erythroid 2-Related Factor 2 (Nrf2) signalling pathway in chondrocytes.

METHOD

In our study, we treated chondrocytes with BDMC in an in vitro chondrocyte assay and measured its influence on extracellular matrix (ECM) expression, downstream heme oxygenase-1 (HO-1) and NOD-like receptor thermal protein domain associated protein 3 (NLRP3) levels.

RESULTS

Our study indicates that BDMC significantly activates the Nrf2 signaling pathway in chondrocytes in vitro. Furthermore, the expression of matrix metalloproteinase 3, interleukin 1β, recombinant a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)4 and (ADAMTS)5 was significantly suppressed by BDMC.

CONCLUSION

This study confirms the potential for BDMC to activate the Nrf2/HO-1/NLRP3 signalling pathway and alleviate OA symptoms. Therefore, BDMC is a promising therapeutic agent for OA that offers new insights and treatment methods.

RIPK1 and RIPK3 inhibitors: potential weapons against inflammation to treat diabetic complications

Diabetes mellitus is a metabolic disease that is characterized by chronic hyperglycemia due to a variety of etiological factors. Long-term metabolic stress induces harmful inflammation leading to chronic complications, mainly diabetic ophthalmopathy, diabetic cardiovascular complications and diabetic nephropathy. With diabetes complications being one of the leading causes of disability and death, the use of anti-inflammatories in combination therapy for diabetes is increasing. There has been increasing interest in targeting significant regulators of the inflammatory pathway, notably receptor-interacting serine/threonine-kinase-1 (RIPK1) and receptor-interacting serine/threonine-kinase-3 (RIPK3), as drug targets for managing inflammation in treating diabetes complications. In this review, we aim to provide an up-to-date summary of current research on the mechanism of action and drug development of RIPK1 and RIPK3, which are pivotal in chronic inflammation and immunity, in relation to diabetic complications which may be benefit for explicating the potential of selective RIPK1 and RIPK3 inhibitors as anti-inflammatory therapeutic agents for diabetic complications.

Identification of potential necroinflammation-associated necroptosis-related biomarkers for delayed graft function and renal allograft failure: a machine learning-based exploration in the framework of predictive, preventive, and personalized medicine

Delayed graft function (DGF) is one of the key post-operative challenges for a subset of kidney transplantation (KTx) patients. Graft survival is significantly lower in recipients who have experienced DGF than in those who have not. Assessing the risk of chronic graft injury, predicting graft rejection, providing personalized treatment, and improving graft survival are major strategies for predictive, preventive, and personalized medicine (PPPM/3PM) to promote the development of transplant medicine. However, since PPPM aims to accurately identify disease by integrating multiple omics, current methods to predict DGF and graft survival can still be improved. Renal ischemia/reperfusion injury (IRI) is a pathological process experienced by all KTx recipients that can result in varying occurrences of DGF, chronic rejection, and allograft failure depending on its severity. During this process, a necroinflammation-mediated necroptosis-dependent secondary wave of cell death significantly contributes to post-IRI tubular cell loss. In this article, we obtained the expression matrices and corresponding clinical data from the GEO database. Subsequently, nine differentially expressed necroinflammation-associated necroptosis-related genes (NiNRGs) were identified by correlation and differential expression analysis. The subtyping of post-KTx IRI samples relied on consensus clustering; the grouping of prognostic risks and the construction of predictive models for DGF (the area under the receiver operating characteristic curve (AUC) of the internal validation set and the external validation set were 0.730 and 0.773, respectively) and expected graft survival after a biopsy (the internal validation set's 1-year AUC: 0.770; 2-year AUC: 0.702; and 3-year AUC: 0.735) were based on the least absolute shrinkage and selection operator regression algorithms. The results of the immune infiltration analysis showed a higher infiltration abundance of myeloid immune cells, especially neutrophils, macrophages, and dendritic cells, in the cluster A subtype and prognostic high-risk groups. Therefore, in the framework of PPPM, this work provides a comprehensive exploration of the early expression landscape, related pathways, immune features, and prognostic impact of NiNRGs in post-KTx patients and assesses their capabilities as.predictors of post-KTx DGF and graft loss,targets of the vicious loop between regulated tubular cell necrosis and necroinflammation for targeted secondary and tertiary prevention, andreferences for personalized immunotherapy.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13167-023-00320-w.