BACKGROUND: Microglia and infiltrated macrophages (M/M) are integral components of the innate immune system that play a critical role in facilitating brain repair after ischemic stroke (IS) by clearing cell debris. Novel therapeutic strategies for IS therapy involve modulating M/M phenotype shifting. This study aims to elucidate the pivotal role of S100A9 in M/M and its downstream STAT6/PPARγ signaling pathway in neuroinflammation and phagocytosis after IS.
METHODS: In the clinical study, we initially detected the expression pattern of S100A9 in monocytes from patients with acute IS and investigated its association with the long-term prognosis. In the in vivo study, we generated the S100A9 conditional knockout (CKO) mice and compared the stroke outcomes with the control group. We further tested the S100A9-specific inhibitor paqunimod (PQD), for its pharmaceutical effects on stroke outcomes. Transcriptomics and in vitro studies were adopted to explore the mechanism of S100A9 in modulating the M/M phenotype, which involves the regulation of the STAT6/PPARγ signaling pathway.
RESULTS: S100A9 was predominantly expressed in classical monocytes and was correlated with unfavorable outcomes in patients of IS. S100A9 CKO mitigated infarction volume and white matter injury, enhanced cerebral blood flow and functional recovery, and prompted anti-inflammation phenotype and efferocytosis after tMCAO. The STAT6/PPARγ pathway, an essential signaling cascade involved in immune response and inflammation, might be the downstream target mediated by S100A9 deletion, as evidenced by the STAT6 phosphorylation inhibitor AS1517499 abolishing the beneficial effect of S100A9 inhibition in tMCAO mice and cell lines. Moreover, S100A9 inhibition by PQD treatment protected against neuronal death in vitro and brain injuries in vivo.
CONCLUSIONS: This study provides evidence for the first time that S100A9 in classical monocytes could potentially be a biomarker for predicting IS prognosis and reveals a novel therapeutic strategy for IS. By demonstrating that S100A9-mediated M/M polarization and phagocytosis can be reversed by S100A9 inhibition in a STAT6/PPARγ pathway-dependent manner, this study opens up new avenues for drug development in the field.

孤立性纤维性肿瘤（SFT）伴有广泛的上皮性包含物罕见，在组织学上容易误诊为双相型的上皮和间叶性肿瘤。本文报道1例原发于膀胱的SFT伴有广泛的上皮性包含物，组织学上表现为富于细胞的梭形细胞增生伴有鹿角形血管，其内可见广泛的内陷的巢状或筛状尿路上皮增生，梭形肿瘤细胞免疫组织化学染色表达CD34和STAT6，经二代测序发现NAB2：：STAT6基因融合最终确诊。本例肿瘤在组织学上需要与膀胱的叶状肿瘤、富于细胞的纤维间质上皮性息肉以及内翻性乳头状瘤鉴别诊断。.

Co-evolutionary adaptation of hookworms with their mammalian hosts has been selected for immunoregulatory excretory/secretory (E/S) products. However, it is not known whether, or if so, how host immunological status impacts the secreted profile of hematophagous adult worms. This study interrogated the impact of host Signal transducer and activator of transcription 6 (STAT6) expression during the experimental evolution of hookworms through the sequential passage of the life cycle in either STAT6 deficient or WT C57BL/6 mice. Proteomic analysis of E/S products by LC-MS showed increased abundance of 15 proteins, including myosin-3, related to muscle function, and aconitate hydratase, related to iron homeostasis. However, most E/S proteins (174 of 337 unique identities) were decreased, including those in the Ancylostoma-secreted protein (ASP) category, and metallopeptidases. Several identified proteins are established immune-modulators such as fatty acid-binding protein homologue, cystatin, and acetylcholinesterase. Enrichment analysis of InterPro functional categories showed down-regulation of Cysteine-rich secretory proteins, Antigen 5, and Pathogenesis-related 1 proteins (CAP), Astacin-like metallopeptidase, Glycoside hydrolase, and Transthyretin-like protein groups in STAT6 KO-adapted worms. Taken together, these data indicate that in an environment lacking Type 2 immunity, hookworms alter their secretome by reducing immune evasion proteins- and increasing locomotor- and feeding-associated proteins.

Macrophages polarize into alternatively activated M2 macrophages through interleukin (IL)-4, and they express high levels of arginase-1, which promotes anti-inflammatory responses. Several studies have confirmed the anti-inflammatory effects of cyclin-dependent kinase (CDK) 8/19 inhibition, and hence, numerous CDK8/19 inhibitors, such as BRD6989, have been developed. However, the effects of CDK8/19 inhibitors on arginase-1 expression in macrophages have not yet been elucidated. This study investigated the effects of CDK8/19 inhibitor on arginase-1 expression in IL-4-activated macrophages. The results showed that BRD6989 increased arginase-1 expression transcriptionally in murine peritoneal macrophages and the murine macrophage cell line RAW264.7 in an IL-4-dependent manner. In addition, the results indicated that BRD6989 enhances signal transducer and activator of transcription (STAT) 6 phosphorylation. Meanwhile, BRD6989 exhibited the capability to activate p38 mitogen-activated protein kinase (MAPK） even in the absence of IL-4 stimulation. Moreover, we observed that a p38 MAPK inhibitor suppressed the BRD6989-induced increase in arginase-1 expression. Besides, BRD6989 increased the surface expression of CD206, an M2 macrophage marker. Thus, this study demonstrated for the first time that CDK8/19 inhibition increases arginase-1 expression, suggesting that this mechanism involves the activation of STAT6 and p38 MAPK. This finding implies that CDK8/19 inhibition may facilitate the production of anti-inflammatory M2 macrophages.

Fibrosis is a pathological change mainly characterized by an increase of fibrous connective tissue and decrease of parenchymal cells. Its continuous progress may lead to the destruction of organ structure and function decline. An excess of alternatively activated M2 macrophages have been considered crucial candidates in the progression of fibrosis. Bone morphogenetic proteins (BMPs), a group of multifunctional growth factors, are essential for organ development and pathophysiological process, however, the roles that BMPs play in innate immune homeostasis in the development of fibrosis and the downstream signals have not been fully explored. In the current study, we firstly found that the expression of BMP4 was significantly down-regulated in human and mouse fibrosis samples. Then we investigated the effects of BMP4 on macrophage polarization in IL-4 environment and related molecular mechanisms, and found that BMP4 caused a decrease in polarized response towards M2, reflected in the expression of the markers Fizz1, Ym1 and Arg1, together with an inhibition in Stat6 phosphorylation. This relied on the Smad1/5/8 signaling, which had a crosstalk with Stat6. Moreover, the in vivo study showed that BMP4 treatment can reduce collagen deposition and delay the development of experimental pulmonary fibrosis in mice by inhibiting M2 macrophages through adoptive transfer experiment. These findings revealed a novel role of BMP4 in regulating macrophages, offering potential strategies for treating pulmonary fibrosis.

Allergic asthma is a major health burden on society as a chronic respiratory disease characterized by inflammation and muscle tightening around the airways in response to inhaled allergens. Daphne kiusiana Miquel is a medicinal plant that can suppress allergic airway inflammation; however, its specific molecular mechanisms of action are unclear. In this study, we aimed to elucidate the mechanisms by which D. kiusiana inhibits allergic airway inflammation. We evaluated the anti-inflammatory effects of the ethyl acetate (EA) fraction of D. kiusiana and its major compound, daphnetin, on murine T lymphocyte EL4 cells stimulated with phorbol 12-myristate 13-acetate and ionomycin in vitro and on asthmatic mice stimulated with ovalbumin in vivo. The EA fraction and daphnetin inhibited T-helper type 2 (Th2) cytokine secretion, serum immunoglobulin E production, mucus secretion, and inflammatory cell recruitment in vivo. In vitro, daphnetin suppressed intracellular Ca2+ mobilization (a critical regulator of nuclear factor of activated T cells) and functions of the activator protein 1 transcription factor to reduce interleukin (IL)-4 and IL-13 expression. Daphnetin effectively suppressed the IL-4/-13-induced activation of Janus kinase (JAK)/signal transducer and activator of transcription 6 (STAT6) signaling in vitro and in vivo, thereby inhibiting the expression of GATA3 and PDEF, two STAT6-target genes responsible for producing Th2 cytokines and mucins. These findings indicate that daphnetin suppresses allergic airway inflammation by stabilizing intracellular Ca2+ levels and subsequently inactivating the JAK/STAT6/GATA3/PDEF pathway, suggesting that daphnetin is a promising alternative to existing asthma treatments.

BACKGROUND: Intracranial solitary fibrous tumors (SFTs) are rare mesenchymal neoplasms, often challenging to diagnose due to their resemblance to meningiomas and other central nervous system tumors. While advancements in molecular genetics have aided in classification, diagnostic nuances and optimal management strategies remain areas of interest.
METHODS: This retrospective study analyzed 11 cases of intracranial SFTs treated at a neurosurgical centre in India between February 2020 and January 2024. Clinical data, radiological findings, histopathological features, and follow-up details were reviewed. Immunohistochemistry, particularly STAT6, facilitated diagnosis confirmation.
RESULTS: The median age of presentation was 32 years, with a male predominance. Headache was the most common presenting symptom, often leading to misdiagnosis as meningiomas on radiological imaging. Histologically, SFTs exhibited spindle to ovoid cells with staghorn vessels and collagenized stroma, posing challenges in differential diagnosis. WHO grading predominantly revealed grade 1 tumors, though recurrence occurred, emphasizing the importance of long-term follow-up. Immunohistochemistry, particularly STAT6, played a pivotal role in distinguishing SFTs from other entities.
CONCLUSIONS: Intracranial SFTs present diagnostic challenges due to overlapping features with other tumors, warranting a comprehensive approach integrating clinical, radiological, and histopathological findings. Immunohistochemistry, particularly STAT6, emerges as a valuable diagnostic tool. Long-term follow-up is essential for monitoring recurrence and potential malignant transformation. Further research is needed to delineate optimal treatment strategies, including the role of radiotherapy in SFT management.

Peripheral blood mononuclear cells (PBMC), sourced autologously, offer numerous advantages when procured: easier acquisition process, no in vitro amplification needed, decreased intervention and overall increased acceptability make PBMC an attractive candidate for cell therapy treatment. However, the exact mechanism by which PBMC treat diseases remains poorly understood. Immune imbalance is the pathological basis of many diseases, with macrophages playing a crucial role in this process. However, research on the role and mechanisms of PBMC in regulating macrophages remains scarce. This study employed an in vitro co-culture model of PBMC and RAW264.7 macrophages to explore the role and mechanisms of PBMC in regulating macrophages. The results showed that the co-culturing led to decreased expression of inflammatory cytokines and increased expression of anti-inflammatory cytokines in RAW264.7 or in the culture supernatant. Additionally, the pro-inflammatory, tissue matrix-degrading M1 macrophages decreased, while the anti-inflammatory, matrix-synthesizing, regenerative M2 macrophages increased in both RAW264.7 and monocytes within PBMC. Moreover, co-cultured macrophages exhibited a significantly decreased p-STAT1/STAT1 ratio, while the p-STAT6/STAT6 ratio significantly increased. This suggests that PBMC may inhibit M1 macrophage polarization by blocking STAT1 signaling cascades and may promote M2 macrophage polarization through the activation of STAT6 signaling cascades. Overall, this study sheds light on the role and mechanism of PBMC in regulating macrophages. Moreover, it was found that monocytes within co-cultured PBMC differentiated into M2 macrophages in the presence of macrophages. This finding provides experimental evidence for the use of PBMC in treating inflammatory diseases, especially macrophage-depleting inflammatory diseases such as osteoarthritis.

Ewing sarcoma is a pediatric bone and soft tissue tumor treated with chemotherapy, radiation, and surgery. Despite intensive multimodality therapy, ~50% patients eventually relapse and die of the disease due to chemoresistance. Here, using phospho-profiling, we find Ewing sarcoma cells treated with chemotherapeutic agents activate TAM (TYRO3, AXL, MERTK) kinases to augment Akt and ERK signaling facilitating chemoresistance. Mechanistically, chemotherapy-induced JAK1-SQ phosphorylation releases JAK1 pseudokinase domain inhibition allowing for JAK1 activation. This alternative JAK1 activation mechanism leads to STAT6 nuclear translocation triggering transcription and secretion of the TAM kinase ligand GAS6 with autocrine/paracrine consequences. Importantly, pharmacological inhibition of either JAK1 by filgotinib or TAM kinases by UNC2025 sensitizes Ewing sarcoma to chemotherapy in vitro and in vivo. Excitingly, the TAM kinase inhibitor MRX-2843 currently in human clinical trials to treat AML and advanced solid tumors, enhances chemotherapy efficacy to further suppress Ewing sarcoma tumor growth in vivo. Our findings reveal an Ewing sarcoma chemoresistance mechanism with an immediate translational value.

Immunoregulatory mechanisms established in the lymphoid organs are vital for preventing autoimmunity. However, the presence of similar mechanisms in non-lymphoid tissues remains unclear. Through transcriptomic and lipidomic analyses, we find a negative association between psoriasis and fatty acid metabolism, as well as Th2 signature. Homeostatic expression of liver X receptor (LXR) and peroxisome proliferator-activated receptor gamma (PPARγ) is essential for maintaining fatty acid metabolism and for conferring resistance to psoriasis in mice. Perturbation of signal transducer and activator of transcription 6 (STAT6) diminishes the homeostatic levels of LXR and PPARγ. Furthermore, mice lacking STAT6, interleukin 4 receptor alpha (IL-4Rα), or IL-13, but not IL-4, exhibit increased susceptibility to psoriasis. Under steady state, innate lymphoid cells (ILCs) are the primary producers of IL-13. In human skin, inhibiting tonic type 2 immunity exacerbates psoriasis-like inflammation and IL-17A, while activating LXR or PPARγ inhibits them. Hence, we propose that tonic type 2 immunity, driven by IL-13-producing ILCs, represents a crucial tissue checkpoint that represses autoimmunity and maintains lipid homeostasis in the skin.