The enzyme HPGD is critical for regulatory T cell function in adipose tissue

Regulatory T cells (Treg cells) are essential for maintaining immune homeostasis. However, how Treg cells exert their function in tissue specific environments is often unknown. We have found hydroxyprostaglandin dehydrogenase (Hpgd), the major Prostaglandin E2 (PGE2) metabolizing enzyme, to be significantly upregulated in Treg cells compared to conventional T cells (Tconv). In the murine system, this upregulation is especially pronounced in the visceral adipose tissue (VAT), a prostaglandin-rich environment. Furthermore, we could show that through the metabolism of PGE2 into 15-keto-PGE2 Hpgd enhances the suppressive capabilities of Treg cells in an, at least partially, Pparγ-dependent manner. In vivo, we found that Hpgd-deficient Treg cells were less efficient in preventing the onset of both DSS-induced and adoptive transfer colitis, further indicating that Hpgd plays a role in the suppressive capacity of Treg cells. However, analysis of the transcriptome of these Hpgd-deficient Treg cells did not differ significantly from Hpgd-competent Treg cells, indicating that the observed changes are due to the extrinsic effect caused by the loss of the enzymatic function of Hpgd. When analyzing the VAT of aged animals with Hpgd-deficient Treg cells, we could detect an influx of non-functional Treg cells as well as an accumulation of pro-inflammatory macrophages and an increase in adipocyte size. Furthermore, while we could neither detect a change in body or organ weight of these animals, nor a change in motility, food and water intake, or respiration, we could observe impaired metabolic signaling. Aged animals with Hpgd-deficient Treg cells respond less to insulin and glucose challenge and show a reduction in insulin signaling. When subjecting animals with Hpgd-deficient Treg cells to a high fat diet (HFD), we could not detect a difference in weight gain when compared to wildtype littermate control animals. Even though we could detect a slight decrease in insulin responsiveness in animals on a HFD with Hpgd-deficient Treg cells, no difference in the VAT-resident immune cell population or in any other metabolic parameters could be observed. Additionally, in peripheral blood from human type II diabetes (T2D) patients we observed a dysregulation of the Treg cell population as well as a decrease in HPGD expression in these cells compared to healthy, age-matched controls. Taken together, these data indicate that both in humans and in the murine system, HPGD expression in Treg cells might be involved in metabolic regulation. Finally, we analyzed the role of the Treg cell specific transcription factor mesenchyme homeobox 1 (MEOX1) for HPGD expression. We found that MEOX1 is highly upregulated in human Treg cells, especially after stimulation with interleukin (IL) 2. Furthermore, we could show that while MEOX1 expression, like HPGD, is regulated by FOXP3, a loss of MEOX1 does not affect HPGD expression, thus disproving our hypothesis that HPGD may be regulated by the transcription factor MEOX1. Taken together, we could describe that HPGD is an important mediator of Treg cell suppression, independently of MEOX1. We found that a Treg cell specific deletion of Hpgd in the mouse leads to a dysregulation of the metabolism, and that HPGD levels are significantly decreased in Treg cells isolated from the peripheral blood of T2D patients compared to Treg cells isolated from healthy subjects

Cellular Differentiation of Human Monocytes Is Regulated by Time-Dependent Interleukin-4 Signaling and the Transcriptional Regulator NCOR2.

Human in vitro generated monocyte-derived dendritic cells (moDCs) and macrophages are used clinically, e.g., to induce immunity against cancer. However, their physiological counterparts, ontogeny, transcriptional regulation, and heterogeneity remains largely unknown, hampering their clinical use. High-dimensional techniques were used to elucidate transcriptional, phenotypic, and functional differences between human in vivo and in vitro generated mononuclear phagocytes to facilitate their full potential in the clinic. We demonstrate that monocytes differentiated by macrophage colony-stimulating factor (M-CSF) or granulocyte macrophage colony-stimulating factor (GM-CSF) resembled in vivo inflammatory macrophages, while moDCs resembled in vivo inflammatory DCs. Moreover, differentiated monocytes presented with profound transcriptomic, phenotypic, and functional differences. Monocytes integrated GM-CSF and IL-4 stimulation combinatorically and temporally, resulting in a mode- and time-dependent differentiation relying on NCOR2. Finally, moDCs are phenotypically heterogeneous and therefore necessitate the use of high-dimensional phenotyping to open new possibilities for better clinical tailoring of these cellular therapies

MCT4 blockade increases the efficacy of immune checkpoint blockade

Background & Aims Intratumoral lactate accumulation and acidosis impair T-cell function and antitumor immunity. Interestingly, expression of the lactate transporter monocarboxylate transporter (MCT) 4, but not MCT1, turned out to be prognostic for the survival of patients with rectal cancer, indicating that single MCT4 blockade might be a promising strategy to overcome glycolysis-related therapy resistance. Methods To determine whether blockade of MCT4 alone is sufficient to improve the efficacy of immune checkpoint blockade (ICB) therapy, we examined the effects of the selective MCT1 inhibitor AZD3965 and a novel MCT4 inhibitor in a colorectal carcinoma (CRC) tumor spheroid model co-cultured with blood leukocytes in vitro and the MC38 murine CRC model in vivo in combination with an antibody against programmed cell death ligand-1(PD-L1). Results Inhibition of MCT4 was sufficient to reduce lactate efflux in three-dimensional (3D) CRC spheroids but not in two-dimensional cell-cultures. Co-administration of the MCT4 inhibitor and ICB augmented immune cell infiltration, T-cell function and decreased CRC spheroid viability in a 3D co-culture model of human CRC spheroids with blood leukocytes. Accordingly, combination of MCT4 and ICB increased intratumoral pH, improved leukocyte infiltration and T-cell activation, delayed tumor growth, and prolonged survival in vivo. MCT1 inhibition exerted no further beneficial impact. Conclusions These findings demonstrate that single MCT4 inhibition represents a novel therapeutic approach to reverse lactic-acid driven immunosuppression and might be suitable to improve ICB efficacy

Transcriptome-Based Network Analysis Reveals a Spectrum Model of Human Macrophage Activation

SummaryMacrophage activation is associated with profound transcriptional reprogramming. Although much progress has been made in the understanding of macrophage activation, polarization, and function, the transcriptional programs regulating these processes remain poorly characterized. We stimulated human macrophages with diverse activation signals, acquiring a data set of 299 macrophage transcriptomes. Analysis of this data set revealed a spectrum of macrophage activation states extending the current M1 versus M2-polarization model. Network analyses identified central transcriptional regulators associated with all macrophage activation complemented by regulators related to stimulus-specific programs. Applying these transcriptional programs to human alveolar macrophages from smokers and patients with chronic obstructive pulmonary disease (COPD) revealed an unexpected loss of inflammatory signatures in COPD patients. Finally, by integrating murine data from the ImmGen project we propose a refined, activation-independent core signature for human and murine macrophages. This resource serves as a framework for future research into regulation of macrophage activation in health and disease

Precursors for Nonlymphoid-Tissue Treg Cells Reside in Secondary Lymphoid Organs and Are Programmed by the Transcription Factor BATF

Specialized regulatory T (Treg) cells accumulate and perform homeostatic and regenerative functions in nonlymphoid tissues. Whether common precursors for nonlymphoid-tissue Treg cells exist and how they differentiate remain elusive. Using transcription factor nuclear factor, interleukin 3 regulated (Nfil3) reporter mice and single-cell RNA-sequencing (scRNA-seq), we identified two precursor stages of interleukin 33 (IL-33) receptor ST2-expressing non lymphoid tissue Treg cells, which resided in the spleen and lymph nodes. Global chromatin profiling of nonlymphoid tissue Treg cells and the two precursor stages revealed a stepwise acquisition of chromatin accessibility and reprogramming toward the nonlymphoid-tissue Treg cell phenotype. Mechanistically, we identified and validated the transcription factor Batf as the driver of the molecular tissue program in the precursors. Understanding this tissue development program will help to harness regenerative properties of tissue Treg cells for therapy

MCT4 blockade increases the efficacy of immune checkpoint blockade

Background & Aims Intratumoral lactate accumulation and acidosis impair T-cell function and antitumor immunity. Interestingly, expression of the lactate transporter monocarboxylate transporter (MCT) 4, but not MCT1, turned out to be prognostic for the survival of patients with rectal cancer, indicating that single MCT4 blockade might be a promising strategy to overcome glycolysis-related therapy resistance.Methods To determine whether blockade of MCT4 alone is sufficient to improve the efficacy of immune checkpoint blockade (ICB) therapy, we examined the effects of the selective MCT1 inhibitor AZD3965 and a novel MCT4 inhibitor in a colorectal carcinoma (CRC) tumor spheroid model co-cultured with blood leukocytes in vitro and the MC38 murine CRC model in vivo in combination with an antibody against programmed cell death ligand-1(PD-L1).Results Inhibition of MCT4 was sufficient to reduce lactate efflux in three-dimensional (3D) CRC spheroids but not in two-dimensional cell-cultures. Co-administration of the MCT4 inhibitor and ICB augmented immune cell infiltration, T-cell function and decreased CRC spheroid viability in a 3D co-culture model of human CRC spheroids with blood leukocytes. Accordingly, combination of MCT4 and ICB increased intratumoral pH, improved leukocyte infiltration and T-cell activation, delayed tumor growth, and prolonged survival in vivo. MCT1 inhibition exerted no further beneficial impact.Conclusions These findings demonstrate that single MCT4 inhibition represents a novel therapeutic approach to reverse lactic-acid driven immunosuppression and might be suitable to improve ICB efficacy

Single-cell chromatin accessibility landscape identifies tissue repair program in human regulatory T cells.

Murine regulatory T (Treg) cells in tissues promote tissue homeostasis and regeneration. We sought to identify features that characterize human Treg cells with these functions in healthy tissues. Single-cell chromatin accessibility profiles of murine and human tissue Treg cells defined a conserved, microbiota-independent tissue-repair Treg signature with a prevailing footprint of the transcription factor BATF. This signature, combined with gene expression profiling and TCR fate mapping, identified a population of tissue-like Treg cells in human peripheral blood that expressed BATF, chemokine receptor CCR8 and HLA-DR. Human BATF+CCR8+ Treg cells from normal skin and adipose tissue shared features with nonlymphoid T follicular helper-like (Tfh-like) cells, and induction of a Tfh-like differentiation program in naive human Treg cells partially recapitulated tissue Treg regenerative characteristics, including wound healing potential. Human BATF+CCR8+ Treg cells from healthy tissue share features with tumor-resident Treg cells, highlighting the importance of understanding the context-specific functions of these cells

Enzymatic Activity of HPGD in Treg Cells Suppresses Tconv Cells to Maintain Adipose Tissue Homeostasis and Prevent Metabolic Dysfunction

Regulatory T cells (Treg cells) are important for preventing autoimmunity and maintaining tissue homeostasis, but whether Treg cells can adopt tissue- or immune-context-specific suppressive mechanisms is unclear. Here, we found that the enzyme hydroxyprostaglandin dehydrogenase (HPGD), which catabolizes prostaglandin E-2 (PGE(2)) into the metabolite 15-keto PGE(2), was highly expressed in Treg cells, particularly those in visceral adipose tissue (VAT). Nuclear receptor peroxisome proliferator-activated receptor-gamma (PPAR gamma)-induced HPGD expression in VAT Treg cells, and consequential Treg-cell-mediated generation of 15-keto PG E2 suppressed conventional T cell activation and proliferation. Conditional deletion of Hpgd in mouse Treg cells resulted in the accumulation of functionally impaired Treg cells specifically in VAT, causing local inflammation and systemic insulin resistance. Consistent with this mechanism, humans with type 2 diabetes showed decreased HPGD expression in Treg cells. These data indicate that HPGD-mediated suppression is a tissue- and context-dependent suppressive mechanism used by Treg cells to maintain adipose tissue homeostasis

Tumor-necrosis factor impairs CD4(+) T cell-mediated immunological control in chronic viral infection

Persistent viral infections are characterized by the simultaneous presence of chronic inflammation and T cell dysfunction. In prototypic models of chronicity-infection with human immunodeficiency virus (HIV) or lymphocytic choriomeningitis virus (LCMV)-we used transcriptome-based modeling to reveal that CD4(+) T cells were co-exposed not only to multiple inhibitory signals but also to tumor-necrosis factor (TNF). Blockade of TNF during chronic infection with LCMV abrogated the inhibitory gene-expression signature in CD4(+) T cells, including reduced expression of the inhibitory receptor PD-1, and reconstituted virus-specific immunity, which led to control of infection. Preventing signaling via the TNF receptor selectively in T cells sufficed to induce these effects. Targeted immunological interventions to disrupt the TNF-mediated link between chronic inflammation and T cell dysfunction might therefore lead to therapies to overcome persistent viral infection