Transcriptional and epigenetic regulation of memory NK cell responses

Maternal high-fat diet exacerbates atherosclerosis development in offspring through epigenetic memory

Maternal exposure to a Western-type diet (WD) increases the susceptibility of adult offspring to atherosclerosis, partly because fetal endothelial cells (ECs) become dysfunctional and inflamed due to risk factors transmitted via maternal-fetal blood exchange. However, the underlying mechanisms remain unclear. Here we show that maternal WD accelerates atherogenesis in adult offspring mice by regulating chromatin dynamics through activator protein-1 (AP-1) in aortic ECs, inducing inflammatory memory at the chromatin level. We found that 27-hydroxycholesterol is involved in memory establishment and also acts as a secondary stimulator, amplifying the expression of inflammatory factors and enhancing the enrichment of AP-1/p300 and H3K27ac in ECs. Inhibiting AP-1 binding to chromatin reduced the inflammatory response in human umbilical vein ECs from mothers with hypercholesterolemia and decreased atherogenesis in offspring mice exposed to maternal WD. Our findings demonstrate that maternal WD exacerbates EC dysfunction and atherosclerosis in adult offspring by inducing AP-1-associated epigenetic memory, which increases chromatin accessibility to inflammatory genes.

Natural killer cell memory: challenges and opportunities for cancer immunotherapy

Substantial advancements have been made in recent years in comprehending immune memory, which enhances the secondary response through prior infections. The ability of vertebrate T and B lymphocytes to exhibit classic recall responses has long been regarded as a distinguishing characteristic. However, natural killer (NK) cells have been found to acquire immunological memory in a manner akin to T and B cells. The fundamental principles derived from the investigation of NK cell memory offer novel insights into innate immunity and have the potential to pave the way for innovative strategies to enhance therapeutic interventions against multiple diseases including cancer. Here, we reviewed the fundamental characteristics, memory development and regulatory mechanism of NK cell memory. Moreover, we will conduct a comprehensive evaluation of the accomplishments, obstacles, and future direction pertaining to the utilization of NK cell memory in the field of cancer immunotherapy.

Nutrient transporter pattern in CD56dim NK cells: CD16 (FcγRIIIA)-dependent modulation and association with memory NK cell functional profile

Background

Human memory NK cells represent a heterogeneous CD56dim population that expands and persists in human cytomegalovirus (HCMV)-seropositive healthy individuals. They are characterized by the preferential, not fully overlapping, expression of NKG2C (activating receptor for HLA-E) and CD57 maturation marker, and by the lack of FcεRIγ adaptor chain. Hyperresponsiveness to Fcγ receptor IIIA (CD16) engagement represents the distinctive functional signature of memory NK cells. Although CD16 engagement was shown to acutely enhance glycolytic and oxidative pathways, its capability to induce a persisting metabolic reprogramming of human NK cells is poorly understood yet.

Results

Here, we describe the peculiar nutrient transporter expression pattern of FcεRIγ- memory NK cells, characterized by higher levels of CD98 neutral amino acid antiporter and CD71 transferrin receptor, and lower expression of GLUT1 glucose transporter, with respect to FcεRIγ+ conventional NK cells. Although CD16 engagement acutely enhances glycolytic and oxidative pathways, its capability to induce a persisting metabolic reprogramming of human NK cells is poorly understood yet. Our results firstly show that sustained CD16 engagement by contact with IgG-opsonized target cells induces the mTORC1-dependent upregulation of CD98 and CD71 nutrient receptors on CD56dim NK cells, in a transporter-specific fashion, that is finely tuned by cell-dependent (grade of functional maturation, and memory or conventional lineage) and stimulus-dependent (time length and cooperation with cytokines) factors. We also demonstrate that CD98 antiporter function is required for CD16-dependent IFN-γ production, and that enhanced CD98-mediated neutral amino acid uptake associates with heightened memory NK cell functional response.

Conclusion

Collectively, our work documents that CD16 engagement leads to a metabolic rewiring of human NK cells and suggests that a distinct nutrient transporter expression pattern may contribute to memory NK cell peculiar functional features.

Epigenetic regulation of innate lymphoid cells

Innate lymphoid cells (ILCs) lack antigen-specific receptors and are considered the innate arm of the immune system, phenotypically and functionally mirroring CD4+ helper T cells. ILCs are categorized into groups 1, 2, and 3 based on transcription factors and cytokine expression. ILCs predominantly reside in mucosal tissues and play important roles in regional immune responses. The development and function of ILC subsets are controlled by both transcriptional and epigenetic mechanisms, which have been extensively studied in recent years. Epigenetic regulation refers to inheritable changes in gene expression that occur without affecting DNA sequences. This mainly includes chromatin status, histone modifications, and DNA methylation. In this review, we summarize recent discoveries on epigenetic mechanisms regulating ILC development and function, and how these regulations affect disease progression under pathological conditions. Although the ablation of specific epigenetic regulators can cause global changes in corresponding epigenetic modifications to the chromatin, only partial genes with altered epigenetic modifications change their mRNA expression, resulting in specific outcomes in cell differentiation and function. Therefore, elucidating epigenetic mechanisms underlying the regulation of ILCs will provide potential targets for the diagnosis and treatment of inflammatory diseases.

The novel mechanism facilitating chronic hepatitis B infection: immunometabolism and epigenetic modification reprogramming

Hepatitis B Virus (HBV) infections pose a global public health challenge. Despite extensive research on this disease, the intricate mechanisms underlying persistent HBV infection require further in-depth elucidation. Recent studies have revealed the pivotal roles of immunometabolism and epigenetic reprogramming in chronic HBV infection. Immunometabolism have identified as the process, which link cell metabolic status with innate immunity functions in response to HBV infection, ultimately contributing to the immune system's inability to resolve Chronic Hepatitis B (CHB). Within hepatocytes, HBV replication leads to a stable viral covalently closed circular DNA (cccDNA) minichromosome located in the nucleus, and epigenetic modifications in cccDNA enable persistence of infection. Additionally, the accumulation or depletion of metabolites not only directly affects the function and homeostasis of immune cells but also serves as a substrate for regulating epigenetic modifications, subsequently influencing the expression of antiviral immune genes and facilitating the occurrence of sustained HBV infection. The interaction between immunometabolism and epigenetic modifications has led to a new research field, known as metabolic epigenomics, which may form a mutually reinforcing relationship with CHB. Herein, we review the recent studies on immunometabolism and epigenetic reprogramming in CHB infection and discuss the potential mechanisms of persistent HBV infection. A deeper understanding of these mechanisms will offer novel insights and targets for intervention strategies against chronic HBV infection, thereby providing new hope for the treatment of related diseases.

NFκB1 inhibits memory formation and supports effector function of ILC2s in memory-driven asthma

Background

ILC2s are capable of generating memory. The mechanism of memory induction and memory-driven effector function (trained immunity) in ILC2s is unknown.

Objective

NFκB1 is preferentially expressed at a high level in ILC2s. We examined the role of NFkB1 in memory induction and memory-driven effector function in a mouse model of asthma.

Methods

Intranasal administration of Alternaria, flexivent, ELISA, histology, real-time PCR, western blot, flow cytometry and immunofluorescence staining.

Results

NFκB1 was essential for the effector phase of memory-driven asthma. NFκB1 was critical for IL33 production, ILC2 generation, and production of type-2 cytokines, which resulted in eosinophilic inflammation and other features of asthma. NFκB1 induction of type-2 cytokines in ILC2s was independent of GATA3. NFκB1 was important for allergen induction of ILC3s and FoxP3+ Tregs. NFκB1 did not affect Th2 cells or their cytokine production. In contrast to its protagonistic role in the effector phase, NFκB1 had an antagonistic role in the memory phase. NFκB1 inhibited allergen-induced upregulation of memory-associated repressor and preparedness genes in ILC2s. NFκB1 upregulated RUNX1. NFκB1 formed a heterodimer with RUNX1 in ILC2s.

Conclusions

NFκB1 positively regulated the effector phase but inhibited the induction phase of memory. The foregoing pointed to an interdependent antagonism between the memory induction and the memory effector processes. The NFκB1-RUNX1 heterodimer represented a non-canonical transcriptional activator of type-2 cytokines in ILC2s.

Harnessing the power of memory-like NK cells to fight cancer

Natural killer (NK) cells possess the innate ability to eliminate cancerous cells effectively. Their crucial role in immunosurveillance has been widely recognized and exploited for therapeutic intervention. Despite the fast-acting nature of NK cells, NK adoptive cell transfer lacks favorable response in some patients. Patient NK cells often display diminished phenotype in preventing cancer progression resulting in poor prognosis. Tumor microenvironment plays a significant role in causing the downfall of NK cells in patients. The release of inhibitory factors by tumor microenvironment hinders normal function of NK cells against tumor. To overcome this challenge, therapeutic strategies such as cytokine stimulation and genetic manipulation are being investigated to improve NK tumor-killing capacity. One of the promising approaches includes generation of more competent NK cells via ex vivo cytokines activation and proliferation. Cytokine-induced ML-NK demonstrated phenotypic alterations such as enhanced expression of activating receptors which help elevate their antitumor response. Previous preclinical studies showed enhanced cytotoxicity and IFNγ production in ML-NK cells compared to normal NK cells against malignant cells. Similar effects are shown in clinical studies in which MK-NK demonstrated encouraging results in treating hematological cancer. However, there is still a lack of in-depth studies using ML-NK in treating different types of tumors and cancers. With convincing preliminary response, this cell-based approach could be used to complement other therapeutic modalities to achieve better clinical outcomes.

The application of autologous cancer immunotherapies in the age of memory-NK cells

Cellular immunotherapy has revolutionized the oncology field, yielding improved results against hematological and solid malignancies. NK cells have become an attractive alternative due to their capacity to activate upon recognition of "stress" or "danger" signals independently of Major Histocompatibility Complex (MHC) engagement, thus making tumor cells a perfect target for NK cell-mediated cancer immunotherapy even as an allogeneic solution. While this allogeneic use is currently favored, the existence of a characterized memory function for NK cells ("memory-like" NK cells) advocates for an autologous approach, that would benefit from the allogeneic setting discoveries, but with added persistence and specificity. Still, both approaches struggle to exert a sustained and high anticancer effect in-vivo due to the immunosuppressive tumor micro-environment and the logistical challenges of cGMP production or clinical deployment. Novel approaches focused on the quality enhancement and the consistent large-scale production of highly activated therapeutic memory-like NK cells have yielded encouraging but still unconclusive results. This review provides an overview of NK biology as it relates to cancer immunotherapy and the challenge presented by solid tumors for therapeutic NKs. After contrasting the autologous and allogeneic NK approaches for solid cancer immunotherapy, this work will present the current scientific focus for the production of highly persistent and cytotoxic memory-like NK cells as well as the current issues with production methods as they apply to stress-sensitive immune cells. In conclusion, autologous NK cells for cancer immunotherapy appears to be a prime alternative for front line therapeutics but to be successful, it will be critical to establish comprehensives infrastructures allowing the production of extremely potent NK cells while constraining costs of production.

Transcriptional reprogramming of natural killer cells by vaccinia virus shows both distinct and conserved features with mCMV

Natural killer (NK) cells have an established role in controlling poxvirus infection and there is a growing interest to exploit their capabilities in the context of poxvirus-based oncolytic therapy and vaccination. How NK cells respond to poxvirus-infected cells to become activated is not well established. To address this knowledge gap, we studied the NK cell response to vaccinia virus (VACV) in vivo, using a systemic infection murine model. We found broad alterations in NK cells transcriptional activity in VACV-infected mice, consistent with both direct target cell recognition and cytokine exposure. There were also alterations in the expression levels of specific NK surface receptors (NKRs), including the Ly49 family and SLAM receptors, as well as upregulation of memory-associated NK markers. Despite the latter observation, adoptive transfer of VACV-expercienced NK populations did not confer protection from infection. Comparison with the NK cell response to murine cytomegalovirus (MCMV) infection highlighted common features, but also distinct NK transcriptional programmes initiated by VACV. Finally, there was a clear overlap between the NK transcriptional response in humans vaccinated with an attenuated VACV, modified vaccinia Ankara (MVA), demonstrating conservation between the NK response in these different host species. Overall, this study provides new data about NK cell activation, function, and homeostasis during VACV infection, and may have implication for the design of VACV-based therapeutics.

Late Effects of Heavy-Ion Space Radiation on Splenocyte Subpopulations and NK Cytotoxic Function

With current goals of increased space exploration and travel to Mars, there has been great interest in understanding the long-term effects of high atomic number, high energy (HZE) ion exposure on various organ systems and the immune system. Little is known about late effects on the immune system after high-LET exposure. Therefore, our objective was to determine how natural killer (NK) cell populations were affected in geriatric mice that were exposed to HZE particles during middle-age, thereby representing elderly retired astronauts that undertook deep space missions.

Methods

10 month old male CBA/CaJ mice were whole-body irradiated: sham (control); 150-cGy gamma-rays (delivered in 1 fraction); 40-cGy 1-GeV/nu 28Si14+ ions (delivered in 3 fractions); 40-cGy 1-GeV/nu 16O8+ ions (1 fraction); and 40-cGy 1-GeV/nu 16O8+ ions (3 fractions). The mice were sacrificed 1-1.5 yr post-exposure, and the spleens harvested. Splenocyte effector (E) cells were harvested and added to 51Cr-labeled Yac-1 target (T) cells in E:T ratios of 12:1, 25:1, 50:1, and 100:1. NK cytotoxicity was measured with 51Cr release. In addition, 2 million splenocytes were aliquoted and stained with a seven-antibody cocktail, and flow cytometry was used to determine the percentage of NK, B lymphocytes, and T lymphocytes in the splenocyte population.

Results

Mice exposed to either a single fraction of 150-cGy gamma rays or 40-cGy 16O8+ ions in 3 fractions were found to have significant decreases in NK cytotoxicity of approximately 30% and 25%, respectively. No significant differences were observed in NK cytotoxicity for 40-cGy 16O8+ ions delivered in 1 fraction, or 40-cGy 28Si14+ ions delivered in 3 fractions. No significant differences were observed in the percentage of spleen cells that were NK (%NK) amongst the groups.

Conclusion

Fractionated HZE ion exposure has the potential to affect the innate arm of the immune system long after exposure, leading to decreases in NK cell function. Therefore, protective countermeasures may need to be considered to decrease the risk of reduced long-term immune function in elderly retired astronauts that undertook deep space missions.

Natural killer cells and immune-checkpoint inhibitor therapy: Current knowledge and new challenges

The discovery of immune checkpoints (ICs) and the development of specific blockers to relieve immune effector cells from this inhibiting mechanism has changed the view of anti-cancer therapy. In addition to cytotoxic T lymphocyte antigen 4 (CTLA4) and programmed death 1 (PD1), classical ICs of T lymphocytes and recently described also on a fraction of natural killer (NK) cells, several NK cell receptors, including killer immunoglobulin-like inhibitory receptors (KIRs) and NGK2A, have been recognized as checkpoint members typical of the NK cell population. This offers the opportunity of a dual-checkpoint inhibition approach, targeting classical and non-classical ICs and leading to a synergistic therapeutic effect. In this review, we will overview and discuss this new perspective, focusing on the most relevant candidates for this role among the variety of potential NK ICs. Beside listing and defining classical ICs expressed also by NK cells, or non-classical ICs either on T or on NK cells, we will address their role in NK cell survival, chronic stimulation or functional exhaustion, and the potential relevance of this phenomenon on anti-tumor immune response. Furthermore, NK ICs will be proposed as possible new targets for the development of efficient combined immunotherapy, not forgetting the relevant concerns that may be raised on NK IC blockade. Finally, the impact of epigenetic drugs in such a complex therapeutic picture will be briefly addressed.

Weaning differentially affects the maturation of piglet peripheral blood and jejunal Peyer's patches

The study aimed to assess how the post-weaning condition changes piglet peripheral blood (PB) and jejunal Peyer's patches (JPPs) as compared to the suckling period, and how these changes are associated with intestinal microbiota evolution. Sixteen pigs were slaughtered and sampled for PB, JPPs and jejunal content (JC) at weaning (26 days) or at 12 days fed on a pre-starter diet. The PB and JPP transcriptomes were analysed using mRNA-seq. The Gene Set Enrichment Analysis was used to demonstrate enriched gene clusters, depending on sampling time. Jejunal microbiota was profiled using 16S rRNA gene sequencing. Post-weaning JPPs were enriched for processes related to the activation of IFN-γ and major histocompatibility complex (MHC) class I antigen processing which clustered with the reduced abundance of the Weisella genus and Faecalibacterium prausnitzii in JC. The post-weaning microbiome differed from that seen in just-weaned pigs. For just-weaned PB, the enrichment of genes related to hemoglobin and the iron metabolism indicated the greater presence of reticulocytes and immature erythrocytes. The JPP genes involved in the I MHC and IFN-γ activations were markers of the post-weaning phase. Several genes attributable to reticulocyte and erythrocyte maturation could be interesting for testing the iron nutrition of piglets.

Key Activating and Inhibitory Ligands Involved in the Mobilization of Natural Killer Cells for Cancer Immunotherapies

Natural killer (NK) cells are the most potent arm of the innate immune system and play an important role in immunity, alloimmunity, autoimmunity, and cancer. NK cells recognize “altered-self” cells due to oncogenic transformation or stress due to viral infection and target to kill them. The effector functions of NK cells depend on the interaction of the activating and inhibitory receptors on their surface with their cognate ligand expressed on the target cells. These activating and inhibitory receptors interact with major histocompatibility complex I (MHC I) expressed on the target cells and make decisions to mount an immune response. NK cell immune response includes cytolytic activity and secretion of cytokines to help with the ongoing immune response. The advancement of our knowledge on the expression of inhibitory and activating molecules led us to exploit these molecules in the treatment of cancer. This review discusses the importance of activating and inhibitory receptors on NK cells and their clinical importance in cancer immunotherapy.

Natural killer (NK) cell-based immunotherapies and the many faces of NK cell memory: A look into how nanoparticles enhance NK cell activity

Natural killer (NK) cells are lymphocytes able to exert potent antitumor and antiviral functions by different means. Besides their classification as innate lymphoid cells (ILCs), NK cells exhibit memory-like and memory responses after cytokine preactivation, viral infections and hapten exposure. Multiple NK cell-based immunotherapies have been developed and are currently being tested, including the possibility to translate the NK cell memory responses into the clinic. Nevertheless, still there is a need to improve these therapies, especially for the treatment of solid tumors, and nanotechnology represents an attractive option to increase NK cell effector functions against transformed cells. In this article, we review the basis of NK cell activity, the diversity of the NK cell memory responses and the current NK cell-based immunotherapies that are being used in the clinic. Furthermore, we take a look into nanotechnology-based strategies targeting NK cells to modulate their responses for effective immunotherapy.

Radium-223 dichloride causes transient changes in natural killer cell population and cytotoxic function

RATIONALE

Natural killer (NK) cells play an important role in both the innate and adaptive arms of the immune system. While previous studies have demonstrated the effects of ionizing radiation on cytotoxic function of NK cells, little is known about how a chronic exposure to high LET alpha particles emitted by radionuclides will affect both NK population size and function. This study was conducted to determine the effects of ²²³RaCl₂ on splenic NK cell population size and function in Swiss Webster mice.

METHODS

Swiss Webster mice were administered intravenously with 0, 50, or 600 kBq/kg ²²³RaCl₂. Spleens were harvested at 5, 12, and 19 days post-administration. The numbers of splenocytes per spleen were enumerated and flow cytometry was used to assess changes in the distribution of splenocyte subpopulations of B, CD4 and CD8 T lymphocytes, and NK cells. NK functional activity was quantified using YAC-1 target cells and the ⁵¹Cr-release assay.

RESULTS

The total number of splenocytes was unaffected by ²²³RaCl₂. However, significant changes in the distribution of splenocyte subpopulations were observed for NK cells and CD8 T lymphocytes. NK functional activity was enhanced substantially relative to controls at 12 days post-administration, but decreased markedly by day 19.

CONCLUSION

NK functional activity is both diminished and enhanced by ²²³RaCl₂ depending on both administered activity and time post-administration. These results suggest that there may be an optimum window of time to combine the ²²³RaCl₂-induced antitumor NK cell response with other cancer therapies that elicit immune activation.

A Brief Analysis of Tissue-Resident NK Cells in Pregnancy and Endometrial Diseases: The Importance of Pharmacologic Modulation

NK cells are lymphocytes involved in the innate and adaptative immune response. These cells are located in peripheral blood and tissues with ample functions, from immune vigilant to tolerogenic reactions. In the endometrium, NK cell populations vary depending on age, hormones, and inflammation. When pregnancy occurs, tissue-resident NK cells and conventional NK cells are recruited to protect the fetus, a tolerogenic response. On the contrary, in the inflamed endometrium, various inflammatory cells down-regulate NK tolerance and impair embryo implantation. Therefore, NK cells’ pharmacological modulation is difficult to achieve. Several strategies have been used, from progesterone, lipid emulsions to steroids; the success has not been as expected. However, new therapeutic approaches have been proposed to decrease the endometrial inflammatory burden and increase pregnancy success based on understanding NK cell physiology.