GPR15LG, a chemokine-like ligand for the G-protein coupled receptor 15 (GPR15), is abundantly expressed in the gastrointestinal mucosa and inflamed skin. Emerging evidence suggests its involvement in inflammatory disorders and cancers. C-X-C chemokine receptor type 4 (CXCR4) plays a critical role in immune cell trafficking and cancer metastasis. Recent evidence suggests a connection between GPR15LG and CXCR4 signaling, which has not been investigated so far. We investigated the effects of GPR15LG on CXCR4 signaling and downstream functions. Binding assays and computational modeling were performed to assess the interaction between GPR15LG and CXCR4. Functional assays, including wound healing and cell migration assays, were conducted across various cell types, including CD4⁺ T cells and cancer cells, to evaluate the impact of GPR15LG on CXCL12-mediated CXCR4 signaling. The results demonstrate that GPR15LG binds to the orthosteric site of CXCR4, modulating downstream signaling in a context-dependent manner. Specifically, GPR15LG enhances CXCL12-mediated CXCR4 signaling synergistically, promoting wound healing and cell migration across various cell types, including CD4 + T cells and cancer cells. These findings underscore the role of GPR15LG in inflammation and metastasis, offering potential therapeutic avenues for CXCR4-mediated diseases.

The semen-derived enhancer of viral infection (SEVI) is an amyloid fibril formed by the self-assembly of the PAP248-286 peptide, a cleavage product of prostatic acid phosphatase, which is naturally present in human seminal plasma. SEVI is known to enhance HIV-1 infection by promoting virion attachment to cells, potentially facilitating sexual spread. Beyond its role in HIV transmission, findings highlight a physiological function for SEVI in innate immunity. As many amyloids display antimicrobial effects, we tested SEVI fibrils for antibacterial activity against microbial ESKAPE pathogens and urogenital bacteria, including Pseudomonas aeruginosa, Klebsiella quasipneumoniae, Escherichia coli, Acinetobacter baumannii, Staphylococcus aureus, Streptococcus agalactiae and Listeria monocytogenes. SEVI exhibited direct dose-dependent antibacterial effects in radial diffusion and survival assays, with activity observed at physiologically relevant concentrations. Bacterial surface molecules such as lipopolysaccharides and lipoteichoic acid induced the formation of SEVI fibrils, as confirmed by kinetic assays. Preincubation with epigallocatechin gallate, a fibril disruptor, abolished SEVI's antibacterial activity, pointing to the importance of its fibrillar structure. Mechanistic studies and electron microscopy revealed limited bacterial membrane disruption and the intracellular accumulation of polyphosphate granules in P. aeruginosa, indicating a stress response. In conclusion, SEVI exerts a potent antibacterial activity against pathogens found in the urogenital tract indicating a potential physiological role in vaginal mucosal immunity. ### Competing Interest Statement The authors have declared no competing interest.

Despite advances in the treatment and care of severe physical injuries, trauma remains one of the main reasons for disability-adjusted life years worldwide. Trauma patients often suffer from disturbances in energy utilization and metabolic dysfunction, including hyperglycemia and increased insulin resistance. White adipose tissue plays an essential role in the regulation of energy homeostasis and is frequently implicated in traumatic injury due to its ubiquitous body distribution but remains poorly studied. Initial triggers of the trauma response are mainly damage-associated molecular patterns (DAMPs) such as histones. We hypothesized that DAMP-induced adipose tissue inflammation contributes to metabolic dysfunction in trauma patients. Therefore, we investigated whether histone release during traumatic injury affects adipose tissue. Making use of a murine polytrauma model with hemorrhagic shock, we found increased serum levels of histones accompanied by an inflammatory response in white adipose tissue. In vitro, extracellular histones induced an inflammatory response in human adipocytes. On the molecular level, this inflammatory response was mediated via a MYD88-IRAK1-ERK signaling axis as demonstrated by pharmacological and genetic inhibition. Histones also induced lytic cell death executed independently of caspases and RIPK1 activity. Importantly, we detected increased histone levels in the bloodstream of patients after polytrauma. Such patients might benefit from a therapy consisting of activated protein C and the FDA-approved ERK inhibitor trametinib, as this combination effectively prevented histone-mediated effects on both, inflammatory gene activation and cell death in adipocytes. Preventing adipose tissue inflammation and adipocyte death in patients with polytrauma could help minimize posttraumatic metabolic dysfunction.

Glucocorticoids represent the mainstay of therapy for a broad spectrum of immune-mediated inflammatory diseases. However, the molecular mechanisms underlying their anti-inflammatory mode of action have remained incompletely understood1. Here we show that the anti-inflammatory properties of glucocorticoids involve reprogramming of the mitochondrial metabolism of macrophages, resulting in increased and sustained production of the anti-inflammatory metabolite itaconate and consequent inhibition of the inflammatory response. The glucocorticoid receptor interacts with parts of the pyruvate dehydrogenase complex whereby glucocorticoids provoke an increase in activity and enable an accelerated and paradoxical flux of the tricarboxylic acid (TCA) cycle in otherwise pro-inflammatory macrophages. This glucocorticoid-mediated rewiring of mitochondrial metabolism potentiates TCA-cycle-dependent production of itaconate throughout the inflammatory response, thereby interfering with the production of pro-inflammatory cytokines. By contrast, artificial blocking of the TCA cycle or genetic deficiency in aconitate decarboxylase 1, the rate-limiting enzyme of itaconate synthesis, interferes with the anti-inflammatory effects of glucocorticoids and, accordingly, abrogates their beneficial effects during a diverse range of preclinical models of immune-mediated inflammatory diseases. Our findings provide important insights into the anti-inflammatory properties of glucocorticoids and have substantial implications for the design of new classes of anti-inflammatory drugs. Glucocorticoids reprogram the mitochondrial metabolism of macrophages, resulting in increased and sustained production of the anti-inflammatory metabolite itaconate and, as a consequence, inhibition of the inflammatory response.

BACKGROUND:Cushing syndrome (CS) is a rare disease caused by excess cortisol levels with high cardiovascular morbidity and mortality. Hypertension in CS promotes hypercortisolism-associated cardiovascular events. Adipose tissue is a highly plastic tissue with most cell types strongly affected by the excess cortisol exposure. We hypothesized that the molecular and cellular changes of periadrenal adipose tissue in response to cortisol excess impact systemic blood pressure levels in patients with CS. METHODS:We investigated gene expression signatures in periadrenal adipose tissue from patients with adrenal CS collected during adrenal surgery. RESULTS:During active CS we observed a downregulation of gene programs associated with inflammation in periadrenal adipose tissue. In addition, we observed a clustering of the patients based on tissue gene expression profiles into 2 groups that differed in blood pressure levels (CS low blood pressure and CS high blood pressure). The 2 clusters showed significant differences in gene expression pattens of the renin-angiotensin-aldosterone-system. Renin was the strongest regulated gene compared with control patients and its expression correlated with increased blood pressure observed in our patients with CS. In the CS high blood pressure group, systemic renin plasma levels were suppressed indicative of an abnormal blood pressure associated with periadrenal adipose tissue renin-angiotensin-aldosterone-system activation. CONCLUSIONS:Here, we show for the first time a relevant association of the local renin-angiotensin-aldosterone-system and systemic blood pressure levels in patients with CS. Patients from the CS high blood pressure group still had increased blood pressure levels after 6 months in remission, highlighting the importance of local tissue effects on long-term systemic effects observed in CS.

Mutations of the postsynaptic scaffold protein Shank2 lead to autism spectrum disorders (ASD). These patients frequently suffer from higher fracture risk. Here, we investigated whether Shank2 directly regulates bone mass. We show that Shank2 is expressed in bone and that Shank2 levels are increased during osteoblastogenesis. Knockdown of Shank2 by siRNA targeting the encoding regions for PDZ and SAM domain inhibits osteoblastogenesis of primary murine calvarial osteoblasts. Shank2 knockout mice (Shank2 -/-) have a decreased bone mass due to reduced osteoblastogenesis and bone formation, whereas bone resorption remains unaffected. Induced pluripotent stem cells (iPSCs)-derived osteoblasts from a loss-of-function Shank2 mutation in a patient showed a significantly reduced osteoblast differentiation potential. Moreover, silencing of known Shank2 interacting proteins revealed that a majority of them promote osteoblast differentiation. From this we conclude that Shank2 and interacting proteins known from the central nervous system are decisive regulators in osteoblast differentiation. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Insulin resistance (IR) during obesity is linked to adipose tissue macrophage (ATM)-driven inflammation of adipose tissue. Whether anti-inflammatory glucocorticoids (GCs) at physiological levels modulate IR is unclear. Here, we report that deletion of the GC receptor (GR) in myeloid cells, including macrophages in mice, aggravates obesity-related IR by enhancing adipose tissue inflammation due to decreased anti-inflammatory ATM leading to exaggerated adipose tissue lipolysis and severe hepatic steatosis. In contrast, GR deletion in Kupffer cells alone does not alter IR. Co-culture experiments show that the absence of GR in macrophages directly causes reduced phospho-AKT and glucose uptake in adipocytes, suggesting an important function of GR in ATM. GR-deficient macrophages are refractory to alternative ATM-inducing IL-4 signaling, due to reduced STAT6 chromatin loading and diminished anti-inflammatory enhancer activation. We demonstrate that GR has an important function in macrophages during obesity by limiting adipose tissue inflammation and lipolysis to promote insulin sensitivity.

Fasting metabolism and immunity are tightly linked; however, it is largely unknown how immune cells contribute to metabolic homeostasis during fasting in healthy subjects. Here, we combined cell-type-resolved genomics and computational approaches to map crosstalk between hepatocytes and liver macrophages during fasting. We identified the glucocorticoid receptor (GR) as a key driver of fasting-induced reprogramming of the macrophage secretome including fasting-suppressed cytokines and showed that lack of macrophage GR impaired induction of ketogenesis during fasting as well as endotoxemia. Mechanistically, macrophage GR suppressed the expression of tumor necrosis factor (TNF) and promoted nuclear translocation of hepatocyte GR to activate a fat oxidation/ketogenesis-related gene program, cooperatively induced by GR and peroxisome proliferator-activated receptor alpha (PPARα) in hepatocytes. Together, our results demonstrate how resident liver macrophages directly influence ketogenesis in hepatocytes, thereby also outlining a strategy by which the immune system can set the metabolic tone during inflammatory disease and infection.

Macrophages are key cells after tissue damage since they mediate both acute inflammatory phase and regenerative inflammation by shifting from pro‐inflammatory to restorative cells. Glucocorticoids (GCs) are the most potent anti‐inflammatory hormone in clinical use, still their actions on macrophages are not fully understood. We show that the metabolic sensor AMP‐activated protein kinase (AMPK) is required for GCs to induce restorative macrophages. GC Dexamethasone activates AMPK in macrophages and GC receptor (GR) phosphorylation is decreased in AMPK‐deficient macrophages. Loss of AMPK in macrophages abrogates the GC‐induced acquisition of their repair phenotype and impairs GC‐induced resolution of inflammation in vivo during post‐injury muscle regeneration and acute lung injury. Mechanistically, two categories of genes are impacted by GC treatment in macrophages. Firstly, canonical cytokine regulation by GCs is not affected by AMPK loss. Secondly, AMPK‐dependent GC‐induced genes required for the phenotypic transition of macrophages are co‐regulated by the transcription factor FOXO3, an AMPK substrate. Thus, beyond cytokine regulation, GR requires AMPK‐FOXO3 for immunomodulatory actions in macrophages, linking their metabolic status to transcriptional control in regenerative inflammation.

OBJECTIVES:Glucocorticoids (GCs) are one of the most widely prescribed anti-inflammatory drugs. By acting through their cognate receptor, the glucocorticoid receptor (GR), GCs downregulate the expression of pro-inflammatory genes and upregulate the expression of anti-inflammatory genes. Metabolic pathways have recently been identified as key parts of both the inflammatory activation and anti-inflammatory polarization of macrophages, immune cells responsible for acute inflammation and tissue repair. It is currently unknown whether GCs control macrophage metabolism, and if so, to what extent metabolic regulation by GCs confers anti-inflammatory activity.METHODS:Using transcriptomic and metabolomic profiling of macrophages, we identified GC-controlled pathways involved in metabolism, especially in mitochondrial function.RESULTS:Metabolic analyses revealed that GCs repress glycolysis in inflammatory myeloid cells and promote tricarboxylic acid (TCA) cycle flux, promoting succinate metabolism and preventing intracellular accumulation of succinate. Inhibition of ATP synthase attenuated GC-induced transcriptional changes, likely through stalling of TCA cycle anaplerosis. We further identified a glycolytic regulatory transcription factor, HIF1α, as regulated by GCs, and as a key regulator of GC responsiveness during inflammatory challenge.CONCLUSIONS:Our findings link metabolism to gene regulation by GCs in macrophages.

Regulation of cellular catabolic metabolism in immune cells has recently become a major concept for resolution of inflammation. Nuclear receptors (NRs), including peroxisome proliferator activator receptors, 1,25‐dihydroxyvitamin D (3) receptor, liver X receptors, glucocorticoid receptors, oestrogen‐related receptor α and nuclear receptor 4A1, have been identified as major modulators of inflammation, affecting innate immune cells, such as macrophages. Evidence emerges on how NRs regulate cellular metabolism in macrophages during inflammatory processes and contribute to the resolution of inflammation. This could have new implications for our understanding of how NRs shape immune responses and inform anti‐inflammatory drug design. This review will highlight the recent developments about NRs and their role in cellular metabolism in macrophages.

Obesity and insulin resistance are a global health problem and directly linked to macrophage-driven inflammation of the adipose tissue. Glucocorticoid (GC) therapy, widely used to treat inflammatory conditions, is associated with metabolic side effects, including adiposity and insulin resistance. It is unknown however, whether anti-inflammatory actions of glucocorticoids at physiological levels can have beneficial effects on adipose tissue inflammation. We hypothesized that GCs may limit insulin resistance by acting on immune cells. By deletion of the GC receptor (GR) in macrophages in mice, we show that GC signaling in macrophages protects against obesity-related insulin resistance, by limiting adipose tissue inflammation. Consequently, the reduction of anti-inflammatory macrophages leads to diminished maintenance of body temperature during cold exposure and endotoxin shock, linking GC action in macrophages to homeothermy. Mechanistically, Macrophages deficient for GR are unable to fully develop into an anti-inflammatory phenotype and are refractory to IL-4 signaling, due to reduced STAT6 DNA loading. Our results demonstrate that GCs play an important homeostatic role in macrophages during obesity by limiting adipose tissue inflammation and promoting insulin sensitivity. We also identify a cooperation of GC signaling with STAT6 in macrophages to promote alternative activation, in turn assisting in homeothermy.

Searchable abstracts of presentations at key conferences in endocrinology ISSN 1470-3947 (print) | ISSN 1479-6848 (online)