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The innate inflammatory response must be tightly regulated to ensure effective immune protection. NF-κB is a key mediator of the inflammatory response, and its dysregulation has been associated with immune-related malignancies. Here, we describe a miRNA-based regulatory network that enables precise NF-κB activity in mouse macrophages. Elevated miR-155 expression potentiates NF-κB activity in miR-146a-deficient mice, leading to both an overactive acute inflammatory response and chronic inflammation. Enforced miR-155 expression overrides miR-146a-mediated repression of NF-κB activation, thus emphasizing the dominant function of miR-155 in promoting inflammation. Moreover, miR-155-deficient macrophages exhibit a suboptimal inflammatory response when exposed to low levels of inflammatory stimuli. Importantly, we demonstrate a temporal asymmetry between miR-155 and miR-146a expression during macrophage activation, which creates a combined positive and negative feedback network controlling NF-κB activity. This miRNA-based regulatory network enables a robust yet time-limited inflammatory response essential for functional immunity. MicroRNAs (miR) are important regulators of gene transcription, with miR-155 and miR-146a both implicated in macrophage activation. Here the authors show that NF-κB signalling, miR-155 and miR-146a form a complex network of cross-regulations to control gene transcription in macrophages for modulating inflammatory responses.

Reciprocal interactions between B and follicular T helper (Tfh) cells orchestrate the germinal center (GC) reaction, a hallmark of humoral immunity. Abnormal GC responses could lead to the production of pathogenic autoantibodies and the development of autoimmunity. Here we show that miR-146a controls GC responses by targeting multiple CD40 signaling pathway components in B cells; by contrast, loss of miR-146a in T cells does not alter humoral responses. However, specific deletion of both miR-146a and its paralog, miR-146b, in T cells increases Tfh cell numbers and enhanced GC reactions. Thus, our data reveal differential cell-intrinsic regulations of GC B and Tfh cells by miR-146a and miR-146b. Together, members of the miR-146 family serve as crucial molecular brakes to coordinately control GC reactions to generate protective humoral responses without eliciting unwanted autoimmunity. In the germinal center (GC), B and T cells interact to induce the production of protective antibodies against threats. Here the authors show that microRNA miR-146a modulates CD40 signaling in GC B cells, while both miR-146a and miR-146b synergize to control GC T cell responses, thereby implicating intricate controls of GC response by miR-146.

Contrary to the proinflammatory role of mast cells in allergic disorders, the results obtained in this study establish that mast cells are essential in CD4 + CD25 + Foxp3 + regulatory T (T Reg )-cell-dependent peripheral tolerance. Here we confirm that tolerant allografts, which are sustained owing to the immunosuppressive effects of T Reg cells, acquire a unique genetic signature dominated by the expression of mast-cell-gene products. We also show that mast cells are crucial for allograft tolerance, through the inability to induce tolerance in mast-cell-deficient mice. High levels of interleukin (IL)-9—a mast cell growth and activation factor—are produced by activated T Reg cells, and IL-9 production seems important in mast cell recruitment to, and activation in, tolerant tissue. Our data indicate that IL-9 represents the functional link through which activated T Reg cells recruit and activate mast cells to mediate regional immune suppression, because neutralization of IL-9 greatly accelerates allograft rejection in tolerant mice. Finally, immunohistochemical analysis clearly demonstrates the existence of this novel T Reg –IL-9–mast cell relationship within tolerant allografts. Mast Cells and Graft Rejection Mast cells are important immune system components, best known as responders in allergic reactions such as anaphylaxis and asthma. Recent work suggests that they also act as immunoregulatory cells in both innate and adaptive immunity and surprisingly, gene expression profiles point to an association with tolerance to tissue transplants. Studies in mice now confirm that mast cells are major cellular players in immune suppression, needed for peripheral suppression dependent on regulatory T cells. This also implies a role for interleukin 9 (IL-9) as a link between activated T cells and mast cell recruitment and makes IL-9, mast cells and their gene products of interest as targets for drugs to prevent graft rejection.

Microgravity can induce alterations in liver morphology, structure, and function, with mitochondria playing an important role in these changes. Tail suspension (TS) is a well-established model for simulating the effects of microgravity on muscles and bones, but its impact on liver function remains unclear. In the current study, we explored the regulatory mechanisms of apoptosis, autophagy, fission, and fusion in maintaining liver mitochondrial homeostasis in mice subjected to TS for 2 or 4 weeks (TS2 and TS4). The results showed the following: (1) No significant differences were observed in nuclear ultrastructure or DNA fragmentation between the control and TS-treated groups. (2) No significant differences were detected in the mitochondrial area ratio among the three groups. (3) Cysteine aspartic acid-specific protease 3 (Caspase3) activity and the Bcl-2-associated X protein (bax)/B-cell lymphoma-2 (bcl2) ratio were not higher in the TS2 and TS4 groups compared to the control group. (4) dynamin-related protein 1 (DRP1) protein expression was increased, while mitochondrial fission factor (MFF) protein levels were decreased in the TS2 and TS4 groups compared to the control, suggesting stable mitochondrial fission. (5) No significant differences were observed in the optic atrophy 1 (OPA1), mitofusin 1 and 2 (MFN1 and MFN2) protein expression levels across the three groups. (6) Mitochondrial autophagy vesicles were present in the TS2 and TS4 groups, with a significant increase in Parkin phosphorylation corresponding to the duration of the TS treatment. (7) ATP synthase and citrate synthase activities were significantly elevated in the TS2 group compared to the control group but were significantly reduced in the TS4 group compared to the TS2 group. In summary, the coordinated regulation of apoptosis, mitochondrial fission and fusion, and particularly mitochondrial autophagy preserved mitochondrial morphology and contributed to the restoration of the activities of these two key mitochondrial enzymes, thereby maintaining liver mitochondrial homeostasis in mice under TS conditions.

The development of cancer is a complex and dynamically regulated multiple-step process that involves many changes in gene expression. Over the last decade, microRNAs (miRNAs), a class of short regulatory non-coding RNAs, have emerged as key molecular effectors and regulators of tumorigenesis. While aberrant expression of miRNAs or dysregulated miRNA-mediated gene regulation in tumor cells have been shown to be capable of directly promoting or inhibiting tumorigenesis, considering the well-reported role of the immune system in cancer, tumor-derived miRNAs could also impact tumor growth through regulating anti-tumor immune responses. Here, we discuss howmiRNAs can function as central mediators that influence the crosstalk between cancer and the immune system. Moreover, we also review the current progress in the development of novel experimental approaches for miRNA target identification that will facilitate our understanding of miRNA-mediated gene regulation in not only human malignancies, but also in other genetic disorders.

Macrophages play a crucial role in coordinating the skeletal muscle repair response, but their phenotypic diversity and the transition of specialized subsets to resolution-phase macrophages remain poorly understood. Here, to address this issue, we induced injury and performed single-cell RNA sequencing on individual cells in skeletal muscle at different time points. Our analysis revealed a distinct macrophage subset that expressed high levels of Gpnmb and that coexpressed critical factors involved in macrophage-mediated muscle regeneration, including Igf1, Mertk and Nr1h3 . Gpnmb gene knockout inhibited macrophage-mediated efferocytosis and impaired skeletal muscle regeneration. Functional studies demonstrated that GPNMB acts directly on muscle cells in vitro and improves muscle regeneration in vivo. These findings provide a comprehensive transcriptomic atlas of macrophages during muscle injury, highlighting the key role of the GPNMB macrophage subset in regenerative processes. Our findings suggest that modulating GPNMB signaling in macrophages may represent a promising avenue for future research into therapeutic strategies for enhancing skeletal muscle regeneration. GPNMB macrophages drive muscle regeneration after injury Skeletal muscle, a major tissue in our bodies, needs to heal well after injury. Researchers have found that a protein called GPNMB plays a key role in this process. Researchers used a mouse model to explore how GPNMB affects muscle repair. They injured the muscles of mice and observed changes in macrophages over time. They found that GPNMB levels increased in certain macrophages, which helped the muscle heal. They used techniques such as single-cell RNA sequencing to identify five types of macrophage involved in healing. One type, with high GPNMB levels, was crucial for muscle repair. When they removed GPNMB from mice, muscle healing was impaired. Adding GPNMB back improved healing by promoting the growth of new muscle cells. This study suggests that targeting GPNMB could facilitate the development of treatments for muscle injuries. This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.

T cells expressing chimeric antigen receptors (CAR T cells) have shown impressive therapeutic efficacy against leukemias and lymphomas. However, they have not been as effective against solid tumors because they become hyporesponsive (“exhausted” or “dysfunctional”) within the tumor microenvironment, with decreased cytokine production and increased expression of several inhibitory surface receptors. Here we define a transcriptional network that mediates CD8⁺ T cell exhaustion. We show that the high-mobility group (HMG)-box transcription factors TOX and TOX2, as well as members of the NR4A family of nuclear receptors, are targets of the calcium/calcineurin-regulated transcription factor NFAT, even in the absence of its partner AP-1 (FOS-JUN). Using a previously established CAR T cell model, we show that TOX and TOX2 are highly induced in CD8⁺ CAR⁺ PD-1high TIM3high (“exhausted”) tumor-infiltrating lymphocytes (CAR TILs), and CAR TILs deficient in both TOX and TOX2 (Tox DKO) are more effective than wild-type (WT), TOX-deficient, or TOX2-deficient CAR TILs in suppressing tumor growth and prolonging survival of tumor-bearing mice. Like NR4A-deficient CAR TILs, Tox DKO CAR TILs show increased cytokine expression, decreased expression of inhibitory receptors, and increased accessibility of regions enriched for motifs that bind activation- associated nuclear factor κB (NFκB) and basic region-leucine zipper (bZIP) transcription factors. These data indicate that Tox and Nr4a transcription factors are critical for the transcriptional program of CD8⁺ T cell exhaustion downstream of NFAT. We provide evidence for positive regulation of NR4A by TOX and of TOX by NR4A, and suggest that disruption of TOX and NR4A expression or activity could be promising strategies for cancer immunotherapy.

ABSTRACT Low/cold ambient temperatures can induce hepatic damage in mammals, prompting the evolution of huddling as an adaptive strategy among small mammals to survive cold conditions in the wild. However, the specific mechanisms by which low/cold ambient temperatures and huddling influence the liver remain poorly characterized. This study examined the impact of huddling on liver glycogen and lipid metabolism in wild Brandt’s vole, Lasiopodomys brandtii (Radde, 1861) under low/cold ambient conditions. Results indicated that: (1) Compared to the Control group (CON), the Resting Metabolic Rate of the Cool separated group (CS) increased, whereas the Cool huddling group (CH) exhibited no change; (2) Liver glycogen content decreased, and glycogen phosphorylase activity increased in both the CH and CS groups compared to the CON group. However, CH showed a less pronounced reduction in glycogen content and attenuated glycogen phosphorylase hyperactivity compared to CS. Glycogen synthase activity remained consistent across all groups; (3) Compared with the CON group, the CS group exhibited decreased triglyceride content, fatty acid synthase activity, and acetyl-coenzyme A carboxylase activity. Conversely, triglyceride content and fatty acid synthase activity in CH were unchanged, while acetyl-coenzyme A carboxylase activity was higher compared to CS. Hepatic lipase activity was stable across all experimental groups. These results indicate that low/cold ambient temperatures decrease hepatic glycogen and lipid reserves in the livers of Brandt’s voles. However, huddling mitigates these effects by inhibiting glycogen breakdown and promoting lipid synthesis, thereby enhancing physiological resilience to cold stress.

Background Interleukin(IL)-30/IL-27p28 production by Prostate Cancer (PC) Stem-Like Cells (SLCs) has proven, in murine models, to be critical to tumor onset and progression. In PC patients, IL-30 expression by leukocytes infiltrating PC and draining lymph nodes correlates with advanced disease grade and stage. Here, we set out to dissect the role of host immune cell-derived IL-30 in PC growth and patient outcome. Methods PC-SLCs were implanted in wild type (WT) and IL-30 conditional knockout (IL-30KO) mice. Histopathological and cytofluorimetric analyses of murine tumors and lymphoid tissues prompted analyses of patients’ PC samples and follow-ups. Results Implantation of PC-SLCs in IL-30KO mice, gave rise to slow growing tumors characterized by apoptotic events associated with CD4 + T lymphocyte infiltrates and lack of CD4 + Foxp3 + T regulatory cells (Tregs). IL-30 knockdown in PC-SLCs reduced cancer cell proliferation, vascularization and intra-tumoral Indoleamine 2,3-Dioxygenase (IDO) + CD11b + Gr-1 + myeloid-derived cells (MDCs) and led to a significant delay in tumor growth and increase in survival. IL-30-silenced tumors developed in IL-30KO mice, IL-30 −/− tumors, lacked vascular supply and displayed frequent apoptotic cancer cells entrapped by perforin + TRAIL + CD3 + Tlymphocytes, most of which had a CD4 + T phenotype, whereas IL-10 + TGFβ + Foxp3 + Tregs were lacking. IL-30 silencing in PC-SLCs prevented lung metastasis in 73% of tumor-bearing WT mice and up to 80% in tumor-bearing IL-30KO mice. In patients with high-grade and locally advanced PC, those with IL-30 −/− tumors, showed distinct intra-tumoral cytotoxic granule-associated RNA binding protein (TIA-1) + CD4 + Tlymphocyte infiltrate, rare Foxp3 + Tregs and a lower biochemical recurrence rate compared to patients with IL-30 +/+ tumors in which IL-30 is expressed in both tumor cells and infiltrating leukocytes. Conclusion The lack of host leukocyte-derived IL-30 inhibits Tregs expansion, promotes intra-tumoral infiltration of CD4 + T lymphocytes and cancer cell apoptosis. Concomitant lack of MDC influx, obtained by IL-30 silencing in PC-SLCs, boosts cytotoxic T lymphocyte activation and cancer cell apoptosis resulting in a synergistic tumor suppression with the prospective benefit of better survival for patients with advanced disease.