JEV Infection Induces M-MDSC Differentiation Into CD3+ Macrophages in the Brain

PANoptosis as a Two-Edged Sword in Colorectal Cancer: A Pathogenic Mechanism and Therapeutic Opportunity

The examination of PANoptosis in colorectal cancer is particularly important, as many tumor cells can evade apoptotic cell death while continuing to proliferate through inflammatory mediators and creating an immunosuppressive environment. The PANoptosome functions as a regulatory complex that unites proteins governing pyroptotic, apoptotic, and necroptotic pathways, rather than allowing distinct death pathways to compete. The expression and functional status of key molecules within the PANoptosome, such as ZBP1, RIPK1, RIPK3, CASP8, and ASC, may influence tumor viability and immune detection. The tumorigenic impact of PANoptosis is complex and predominantly manifests through chronic inflammation, immune response modulation, and changes in the tumor microenvironment. PANoptosis also aids in the defense against colon cancer by directly eradicating tumor cells and modifying the cellular environment. The expression profile of PANoptosis components may possess prognostic and predictive significance. The therapeutic ramifications of PANoptosis in colorectal cancer are now being investigated through many avenues. It provides an opportunity to develop targeted therapeutic techniques. In contrast, it may also be pertinent in conjunction with immunotherapy, as PANoptosis signifies an immunogenic type of cell death and may consequently enhance the anti-tumor immune response. A thorough comprehension of how these parameters influence PANoptosis is crucial for practical implementation.

Myeloid-Derived Suppressor Cells Induce Exhaustion-Like CD8+ T Cells during JEV Infection

Japanese encephalitis (JE), caused by Japanese encephalitis virus (JEV), is a mosquito-borne zoonotic disease and a leading cause of viral encephalitis worldwide. While JEV has the ability to traverse the blood-brain barrier (BBB), the precise mechanisms by which it inhibits the immune response prior to penetrating the BBB remain unclear, presenting obstacles in the development of efficacious therapeutic interventions. This study investigated the impact of JEV on CD8+ T cell responses, with a particular focus on the dysfunction of CD8+ T cells during JEV infection. Our results demonstrated that JEV infection significantly elevated the expression of PD-1 and TIM-3 on CD8+ T cells, which are markers of T cell exhaustion, leading to inhibited function and impaired differentiation, resulting in a poorer prognosis in mice. Compared with nondiseased mice, symptomatic mice presented a greater proportion of exhaustion-like CD8+ T cells. In vitro experiments further demonstrated that MDSCs induced an exhaustion-like state in CD8+ T cells, characterized by significant upregulation of PD-1 and TIM-3 expression. Notably, blocking TIM-3 or depleting MDSCs restored CD8+ T cell functionality by rescuing the expression of IFN-γ and TNF-α. Furthermore, the depletion of MDSCs not only alleviated T cell exhaustion-like phenotypes but also improved survival rates in JEV-infected mice. These findings suggest that JEV promotes immune evasion through MDSC-induced CD8+ T cell exhaustion-like states and identify TIM-3 as a promising therapeutic target for JE treatment.

Neuroprotective Role of AQP4 Knockdown in Astrocytes After Oxygen-Glucose Deprivation

BACKGROUND

Aquaporin-4 (AQP4), predominantly expressed in astrocytes, has been implicated in the development of brain edema following ischemic events. However, its role in post-stroke neuroinflammation is not fully understood.

METHODS

Using a middle cerebral artery occlusion (MCAO) mouse model, we assessed AQP4's role in post-stroke inflammation. Brain tissue slices from male C57BL/6 mice were subjected to immunohistochemistry and western blot post-MCAO. Additionally, primary astrocytes were isolated for quantitative real-time PCR and immunofluorescence assays to evaluate the expression of inflammatory markers glial fibrillary acidic protein (GFAP) and AQP4. AQP4 modulation was achieved using viral knockdown and overexpression methods. Neuronal damage was assessed using flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) tests in co-culture studies.

RESULTS

MCAO mice exhibited a significant upregulation in GFAP. This reactive astrogliosis corresponded with an elevation in inflammatory markers. AQP4 expression responded to this inflammatory trend, peaking at 6 h after OGD and returning to baseline levels at 24 and 48 h. Co-culture experiments revealed that AQP4(+) astrocytes exacerbated injury in OGD-treated neurons, as evidenced by increased TUNEL positivity and apoptotic events. Conversely, AQP4(-) astrocytes appeared to have a protective effect. Knockdown of AQP4 resulted in reduced post-OGD inflammatory response, whereas AQP4 overexpression intensified the injury to neurons post-OGD. In vivo experiments also confirmed that AQP4 inhibitor TGN-020 reduced and overexpression of AQP4 increased behavioral abnormalities and brain infarcts.

CONCLUSION

Our findings underscore AQP4's pivotal role in modulating post-stroke neuroinflammation. Targeting AQP4 may present a novel therapeutic avenue for mitigating ischemia-induced neuronal damage.

TLR9 promotes monocytic myeloid-derived suppressor cell induction during JEV infection

Myeloid-derived suppressor cells (MDSCs) are a group of heterologous populations of immature bone marrow cells consisting of progenitor cells of macrophages, dendritic cells and granulocytes. Recent studies have revealed that the accumulation of MDSCs in the mouse spleen plays a pivotal role in suppressing the immune response following JEV infection. However, the mechanisms by which JEV induces MDSCs are poorly understood. Here, it was found that JEV infection induces mitochondrial damage and the release of mitochondrial DNA (mtDNA), which further leads to the activation of TLR9. TLR9 deficiency decreases the M-MDSCs population and their suppressive function both in vitro and in vivo. Moreover, the increase of MHCⅡ expression on antigen-presenting cells and CD28 expression on T cells in TLR9-/- mice was positively correlated with M-MDSCs reduction. Accordingly, the survival rate of TLR9-/- mice dramatically increased after JEV infection. These findings reveal the connections of mitochondrial damage and TLR9 activation to the induction of M-MDSCs during JEV infection.

A single amino acid substitution in the capsid protein of Zika virus contributes to a neurovirulent phenotype

Increasing evidence shows the African lineage Zika virus (ZIKV) displays a more severe neurovirulence compared to the Asian ZIKV. However, viral determinants and the underlying mechanisms of enhanced virulence phenotype remain largely unknown. Herein, we identify a panel of amino acid substitutions that are unique to the African lineage of ZIKVs compared to the Asian lineage by phylogenetic analysis and sequence alignment. We then utilize reverse genetic technology to generate recombinant ZIKVs incorporating these lineage-specific substitutions based on an infectious cDNA clone of Asian ZIKV. Through in vitro characterization, we discover a mutant virus with a lysine to arginine substitution at position 101 of capsid (C) protein (termed K101R) displays a larger plaque phenotype, and replicates more efficiently in various cell lines. Moreover, K101R replicates more efficiently in mouse brains and induces stronger inflammatory responses than the wild type (WT) virus in neonatal mice. Finally, a combined analysis reveals the K101R substitution promotes the production of mature C protein without affecting its binding to viral RNA. Our study identifies the role of K101R substitution in the C protein in contributing to the enhanced virulent phenotype of the African lineage ZIKV, which expands our understanding of the complexity of ZIKV proteins.

TRAF3/STAT6 axis regulates macrophage polarization and tumor progression

Converting tumor-associated macrophages (TAMs) from the M2 to the M1 phenotype is considered an effective strategy for cancer therapy. TRAF3 is known to regulate NF-κB signaling. However, the role of TRAF3 in TAM polarization has not yet been completely elucidated. Here, we found that ablation of TRAF3 increased M1 markers, iNOS, FGR and SLC4A7, while down-regulated M2 markers, CD206, CD36 and ABCC3, expression levels in macrophages. Moreover, TRAF3 deficiency enhanced LPS-induced M1 and abolished IL-4-induced macrophage polarization. Next, quantitative ubiquitomics assays demonstrated that among the quantitative 7618 ubiquitination modification sites on 2598 proteins, ubiquitination modification of IL-4 responding proteins was the most prominently reduced according to enrichment analysis. STAT6, a key factor of IL-4 responding protein, K450 and K129 residue ubiquitination levels were dramatically decreased in TRAF3-deficient macrophages. Ubiquitination assay and luciferase assay demonstrated that TRAF3 promotes STAT6 ubiquitination and transcriptional activity. Site mutation analysis revealed STAT6 K450 site ubiquitination played a vital role in TRAF3-mediated STAT6 activation. Finally, B16 melanoma mouse model demonstrated that myeloid TRAF3 deficiency suppressed tumor growth and lung metastasis in vivo. Taken together, TRAF3 plays a vital role in M2 polarization via regulating STAT6 K450 ubiquitination in macrophages.

The role of immunometabolism in macrophage polarization and its impact on acute lung injury/acute respiratory distress syndrome

Lung macrophages constitute the first line of defense against airborne particles and microbes and are key to maintaining pulmonary immune homeostasis. There is increasing evidence suggesting that macrophages also participate in the pathogenesis of acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), including the modulation of inflammatory responses and the repair of damaged lung tissues. The diversity of their functions may be attributed to their polarized states. Classically activated or inflammatory (M1) macrophages and alternatively activated or anti-inflammatory (M2) macrophages are the two main polarized macrophage phenotypes. The precise regulatory mechanism of macrophage polarization is a complex process that is not completely understood. A growing body of literature on immunometabolism has demonstrated the essential role of immunometabolism and its metabolic intermediates in macrophage polarization. In this review, we summarize macrophage polarization phenotypes, the role of immunometabolism, and its metabolic intermediates in macrophage polarization and ALI/ARDS, which may represent a new target and therapeutic direction.

ZBP1 and heatstroke

Heatstroke, which is associated with circulatory failure and multiple organ dysfunction, is a heat stress-induced life-threatening condition characterized by a raised core body temperature and central nervous system dysfunction. As global warming continues to worsen, heatstroke is expected to become the leading cause of death globally. Despite the severity of this condition, the detailed mechanisms that underlie the pathogenesis of heatstroke still remain largely unknown. Z-DNA-binding protein 1 (ZBP1), also referred to as DNA-dependent activator of IFN-regulatory factors (DAI) and DLM-1, was initially identified as a tumor-associated and interferon (IFN)-inducible protein, but has recently been reported to be a Z-nucleic acid sensor that regulates cell death and inflammation; however, its biological function is not yet fully understood. In the present study, a brief review of the main regulators is presented, in which the Z-nucleic acid sensor ZBP1 was identified to be a significant factor in regulating the pathological characteristics of heatstroke through ZBP1-dependent signaling. Thus, the lethal mechanism of heatstroke is revealed, in addition to a second function of ZBP1 other than as a nucleic acid sensor.

The immune-metabolic crosstalk between CD3+C1q+TAM and CD8+T cells associated with relapse-free survival in HCC

Introduction

Although multiple targeted treatments have appeared, hepatocellular carcinoma (HCC) is still one of the most common causes of cancer-related deaths. The immunosuppressive tumor microenvironment (TME) is a critical factor in the oncogenesis and progression of HCC. The emerging scRNA-seq makes it possible to explore the TME at a high resolution. This study was designed to reveal the immune-metabolic crosstalk between immune cells in HCC and provide novel strategies to regulate immunosuppressive TME.

Method

In this study, we performed scRNA-seq on paired tumor and peri-tumor tissues of HCC. The composition and differentiation trajectory of the immune populations in TME were portrayed. Cellphone DB was utilized to calculate interactions between the identified clusters. Besides, flow cytometry, RT-PCR and seahorse experiments were implemented to explore potential metabolic and epigenetic mechanisms of the inter-cellular interaction.

Result

A total of 19 immune cell clusters were identified and 7 were found closely related to HCC prognosis. Besides, differentiation trajectories of T cells were also presented. Moreover, a new population, CD3+C1q+ tumor-associated macrophages (TAM) were identified and found significantly interacted with CD8+ CCL4+T cells. Compared to the peri-tumor tissue, their interaction was attenuated in tumor. Additionally, the dynamic presence of this newly found cluster was also verified in the peripheral blood of patients with sepsis. Furthermore, we found that CD3+C1q+TAM affected T cell immunity through C1q signaling-induced metabolic and epigenetic reprogramming, thereby potentially affecting tumor prognosis.

Conclusion

Our study revealed the interaction between CD3+C1q+TAM and CD8+ CCL4+T cells and may provide implications for tackling the immunosuppressive TME in HCC.

Single-cell RNA sequencing reveals TCR+ macrophages in HPV-related head and neck squamous cell carcinoma

The prognosis of human papillomavirus (HPV)-infected head and neck squamous cell carcinoma (HNSCC) is often better than that of HPV^- cancer, which is possibly caused by the differences in their immune microenvironments. The contribution of macrophage, as a principal innate immune cell, to this phenomenon is still unclear. In this study, a single-cell atlas of 4,388 high-quality macrophages from 18 HPV^- and 8 HPV⁺ HNSCC patients was constructed with single-cell RNA sequencing data. Eight macrophage subsets were identified from HNSCC, whereas their functional properties and developmental trajectory were delineated based on HPV status. Our results demonstrated that macrophages in HPV⁺ HNSCC exhibit stronger phagocytic ability, although the infiltration rate of macrophages decreased. From the results, a unique macrophage subset with TCR and CD3-specific signatures was identified from HPV-related HNSCC. These TCR⁺ macrophages potentially participate in the regulation of the TCR signaling pathway and phagocytosis. In conclusion, our results suggested that HPV could affect the infiltration rate, function, and differentiation of macrophages in HNSCC, whereas TCR⁺ macrophages play a critical role in the HNSCC microenvironment. These results provide new insights into the immune microenvironment of HNSCC and offer a valuable resource for the understanding of the immune landscape of HPV-related HNSCC, which will in turn help the development of immunotherapy strategies for the disease.