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Rationale Accumulating evidence suggests that the primary symptoms of schizophrenia may be associated with altered central glutamate transmission. LY2140023 monohydrate is the methionine prodrug of the selective mGlu 2/3 receptor agonist LY404039 and is currently being assessed for the treatment of schizophrenia. Objective The objective of this study was to evaluate the central pharmacological activity of LY2140023 monohydrate in preclinical and clinical studies. Methods Effects on neurotransmitter/metabolite concentrations were assessed in male rats following single oral doses of LY2140023 monohydrate (microdiasylates from the prefrontal cortex), single intraperitoneal injection of LY404039 [cerebrospinal fluid (CSF)], or LY2140023 monohydrate dosed once daily for 7 days (CSF). A clinical study in 16 healthy subjects assessed the effects of LY2140023 monohydrate 40 mg orally twice daily for 14 days in lumbar CSF. Results Rat studies : Acute dosing with LY2140023 monohydrate resulted in significant dose-dependent increases in extracellular concentrations of dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), but not 5-hydroxyindoleacetic acid (5-HIAA), in the prefrontal cortex. LY2140023 monohydrate dosing for 7 days elevated the concentrations of HVA in CSF, while acutely dosed LY404039 increased the concentrations of DOPAC, HVA, and methoxy-hydroxyphenylglycol (MHPG), but not 5-HIAA. Clinical study : Significant increases were seen for DOPAC, HVA, 5-HIAA, and MHPG in the CSF of subjects receiving LY2140023 monohydrate, but not placebo. Conclusions LY2140023 monohydrate and/or LY404039 dosing potently affected dopamine turnover and also significantly affected serotonin turnover in the human and rat central nervous systems. The measurement of biogenic amine metabolites such as DOPAC and HVA may serve as useful biomarkers of LY2140023 monohydrate and/or LY404039 central pharmacodynamic activity.

ObjectiveTo investigate the impact of systemic inhibition of interleukin 6 (IL-6) or signal transducer and activator of transcription (Stat3) in an experimental model of osteoarthritis (OA).MethodsExpression of major catabolic and anabolic factors of cartilage was determined in IL-6-treated mouse chondrocytes and cartilage explants. The anti-IL-6-receptor neutralising antibody MR16-1 was used in the destabilisation of the medial meniscus (DMM) mouse model of OA. Stat3 blockade was investigated by the small molecule Stattic ex vivo and in the DMM model.ResultsIn chondrocytes and cartilage explants, IL-6 treatment reduced proteoglycan content with increased production of matrix metalloproteinase (MMP-3 and MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS-4 and ADAMTS-5). IL-6 induced Stat3 and extracellular signal-regulated kinase (ERK) 1/2 signalling but not p38, c-Jun N-terminal kinase or Akt. In the DMM model, Stat3 was activated in cartilage, but neither in the synovium nor in the subchondral bone. Systemic blockade of IL-6 by MR16-1 alleviated DMM-induced OA cartilage lesions, impaired the osteophyte formation and the extent of synovitis. In the same model, Stattic had similar beneficial effects on cartilage and osteophyte formation. Stattic, but not an ERK1/2 inhibitor, significantly counteracted the catabolic effects of IL-6 on cartilage explants and suppressed the IL-6-induced chondrocytes apoptosis.ConclusionIL-6 induces chondrocyte catabolism mainly via Stat3 signalling, a pathway activated in cartilage from joint subjected to DMM. Systemic blockade of IL-6 or STAT-3 can alleviate DMM-induced OA in mice.

Immunosuppressive myeloid-derived suppressor cells (MDSC) subvert antitumor immunity and limit the efficacy of chimeric antigen receptor T cells (CAR-T). Previously, we reported that the GM-CSF/JAK2/STAT3 axis drives liver-associated MDSC (L-MDSC) proliferation and blockade of this axis rescued antitumor immunity. We extended these findings in our murine liver metastasis (LM) model, by treating tumor-bearing mice with STAT3 inhibitors (STATTIC or BBI608) to further our understanding of how STAT3 drives L-MDSC suppressive function. STAT3 inhibition caused significant reduction of tumor burden as well as L-MDSC frequencies due to decrease in pSTAT3 levels. L-MDSC isolated from STATTIC or BBI608-treated mice had significantly reduced suppressive function. STAT3 inhibition of L-MDSC was associated with enhanced antitumor activity of CAR-T. Further investigation demonstrated activation of apoptotic signaling pathways in L-MDSC following STAT3 inhibition as evidenced by an upregulation of the pro-apoptotic proteins Bax, cleaved caspase-3, and downregulation of the anti-apoptotic protein Bcl-2. Accordingly, there was also a decrease of pro-survival markers, pErk and pAkt, and an increase in pro-death marker, Fas, with activation of downstream JNK and p38 MAPK. These findings represent a previously unrecognized link between STAT3 inhibition and Fas-induced apoptosis of MDSCs. Our findings suggest that inhibiting STAT3 has potential clinical application for enhancing the efficacy of CAR-T cells in LM through modulation of L-MDSC.

Background Signal transducer and activator of transcription 3 (STAT3), a multifaceted transcription factor, modulates host immune responses by activating cellular response to signaling ligands. STAT3 has a pivotal role in the pathophysiology of kidney injury by counterbalancing resident macrophage phenotypes under inflammation conditions. However, STAT3’s role in acute kidney injury (AKI), particularly in macrophage migration, and in chronic kidney disease (CKD) through fibrosis development, remains unclear. Methods Stattic (a JAK2/STAT3 inhibitor, 5 mg/kg or 10 mg/kg) was administered to evaluate the therapeutic effect on LPS-induced AKI (L-AKI) and LPS-induced CKD (L-CKD), with animals sacrificed 6–24 h and 14 days post-LPS induction, respectively. The immune mechanisms of STAT3 blockade were determined by comparing the macrophage phenotypes and correlated with renal function parameters. Also, the transcriptomic analysis was used to confirm the anti-inflammatory effect of L-AKI, and the anti-fibrotic role was further evaluated in the L-CKD model. Results In the L-AKI model, sequential increases in BUN and blood creatinine levels were time-dependent, with a marked elevation of 0–6 h after LPS injection. Notably, two newly identified macrophage subpopulations (CD11b high F4/80 low and CD11b low F4/80 high ), exhibited population changes, with an increase in the CD11b high F4/80 low population and a decrease in the CD11b low F4/80 high macrophages. Corresponding to the FACS results, the tubular injury score, NGAL, F4/80, and p-STAT3 expression in the tubular regions were elevated. STAT3 inhibitor injection in L-AKI and L-CKD mice reduced renal injury and fibrosis. M2-type subpopulation with CD206 in CD11b low F4/80 high population increased in the Stattic-treated group compared with that in the LPS-alone group in the L-AKI model. Additionally, STAT3 inhibitor reduced inflammation driven by LPS-stimulated macrophages and epithelial cells injury in the co-culture system. Transcriptomic profiling identified 3 common genes in the JAK-STAT, TLR, and TNF signaling pathways and 11 common genes in the LPS with macrophage response. The PI3K-AKT ( IL-6 , Akt3 , and Pik3r1 ) and JAK-STAT pathways were determined as potential Stattic targets. Further confirmation through mRNA and protein expressions analyses showed that Stattic treatment reduced inflammation in the L-AKI and fibrosis in the L-CKD mice. Conclusions STAT3 blockade effectively mitigated inflammation by retrieving the CD11b low F4/80 high population, further emphasizing the role of STAT3-associated macrophage-driven inflammation in kidney injury. Plain English summary This study investigated the role of STAT3 in LPS-induced acute kidney injury (AKI) and its prolonged pathophysiological effect. In a mouse model, blocking STAT3 with Stattic reduced inflammation and fibrosis, decreased the levels of inflammatory and extracellular matrix (ECM) substances, reduced the number of certain immune cells (macrophages), and influenced specific genes related to inflammation. The findings suggest that targeting STAT3 is a promising approach to treat AKI and CKD by controlling the inflammation and the immune response as well as ECM accumulation. This study provides novel insights into AKI and CKD progression and will facilitate the development of new treatments for kidney injuries at various stages.

Kainate receptors, a subclass of ionotropic glutamate receptors, are tetrameric ligand-gated ion channels that mediate excitatory neurotransmission 1 – 4 . Kainate receptors modulate neuronal circuits and synaptic plasticity during the development and function of the central nervous system and are implicated in various neurological and psychiatric diseases, including epilepsy, depression, schizophrenia, anxiety and autism 5 – 11 . Although structures of kainate receptor domains and subunit assemblies are available 12 – 18 , the mechanism of kainate receptor gating remains poorly understood. Here we present cryo-electron microscopy structures of the kainate receptor GluK2 in the presence of the agonist glutamate and the positive allosteric modulators lectin concanavalin A and BPAM344. Concanavalin A and BPAM344 inhibit kainate receptor desensitization and prolong activation by acting as a spacer between the amino-terminal and ligand-binding domains and a stabilizer of the ligand-binding domain dimer interface, respectively. Channel opening involves the kinking of all four pore-forming M3 helices. Our structures reveal the molecular basis of kainate receptor gating, which could guide the development of drugs for treatment of neurological disorders. Structures of the kainate receptor GluK2 with and without concanavilin A and BPAM344 show how these ligands modulate channel activity and reveal the molecular basis of kainate receptor gating.

Background: Hepatocellular carcinoma (HCC) growth relies on angiogenesis via vascular endothelial growth factor (VEGF) release. Hypoxia within tumour environment leads to intracellular stabilisation of hypoxia inducible factor 1 alpha (Hif1 α ) and signal transducer and activator of transcription (STAT3). Melatonin induces apoptosis in HCC, and shows anti-angiogenic features in several tumours. In this study, we used human HepG2 liver cancer cells as an in vitro model to investigate the anti-angiogenic effects of melatonin. Methods: HepG2 cells were treated with melatonin under normoxic or CoCl 2 -induced hypoxia. Gene expression was analysed by RT–qPCR and western blot. Melatonin-induced anti-angiogenic activity was confirmed by in vivo human umbilical vein endothelial cells (HUVECs) tube formation assay. Secreted VEGF was measured by ELISA. Immunofluorescence was performed to analyse Hif1 α cellular localisation. Physical interaction between Hif1 α and its co-activators was analysed by immunoprecipitation and chromatin immunoprecipitation (ChIP). Results: Melatonin at a pharmacological concentration (1 m M ) decreases cellular and secreted VEGF levels, and prevents HUVECs tube formation under hypoxia, associated with a reduction in Hif1 α protein expression, nuclear localisation, and transcriptional activity. While hypoxia increases phospho-STAT3, Hif1 α , and CBP/p300 recruitment as a transcriptional complex within the VEGF promoter, melatonin 1 m M decreases their physical interaction. Melatonin and the selective STAT3 inhibitor Stattic show a synergic effect on Hif1 α , STAT3, and VEGF expression. Conclusion: Melatonin exerts an anti-angiogenic activity in HepG2 cells by interfering with the transcriptional activation of VEGF, via Hif1 α and STAT3. Our results provide evidence to consider this indole as a powerful anti-angiogenic agent for HCC treatment.

Cancer cells frequently have amplified centrosomes that must be clustered together to form a bipolar mitotic spindle, and targeting centrosome clustering is considered a promising therapeutic strategy. A high-content chemical screen for inhibitors of centrosome clustering identified Stattic, a Stat3 inhibitor. Stat3 depletion and inhibition in cancer cell lines and in tumours in vivo caused significant inhibition of centrosome clustering and viability. Here we describe a transcription-independent mechanism for Stat3-mediated centrosome clustering that involves Stathmin, a Stat3 interactor involved in microtubule depolymerization, and the mitotic kinase PLK1. Furthermore, PLK4-driven centrosome amplified breast tumour cells are highly sensitive to Stat3 inhibitors. We have identified an unexpected role of Stat3 in the regulation of centrosome clustering, and this role of Stat3 may be critical in identifying tumours that are sensitive to Stat3 inhibitors. Cancer cells have amplified centrosomes and deal with this abnormality by clustering them together so that they can be segregated in daughter cells. Here the authors perform a screening looking for inhibitors of this clustering process and find that STAT3 regulates this process independently of its transcriptional function.

Fibroblast growth factor receptor (FGFR) gene alterations are relatively frequent in lung squamous cell carcinoma (LUSC) and represent potential targets for therapy with FGFR inhibitors. However, FGFR inhibitor monotherapy is often undermined by compensatory survival pathways. In this study, a combinatorial therapeutic approach using the STAT3 inhibitor Stattic together with the pan-FGFR inhibitor AZD4547 for FGFR1-positive LUSC were assessed. The results showed that AZD4547 suppresses FGFR1 phosphorylation, triggers IL-6/STAT3 activation and induces RRM2-dependent DNA repair, limiting single-agent efficacy. Combining AZD4547 with the STAT3 inhibitor Stattic synergistically impaired cell proliferation, colony formation, and survival, and markedly enhanced apoptosis in vitro and in vivo. Mechanistically, dual inhibition disrupted the STAT3/RRM2 axis, promoting DNA damage and simultaneously provoking ROS-induced mitochondrial dysfunction. These findings nominate concurrent FGFR1 and STAT3 blockade as a promising therapeutic approach for FGFR1-positive lung squamous cell carcinomas.

Background CD8 + T cell trafficking to the tumor site is essential for effective colorectal cancer (CRC) immunotherapy. However, the mechanism underlying CD8 + T cell infiltration in colorectal tumor tissues is not fully understood. In the present study, we investigated CD8 + T cell infiltration in CRC tissues and the role of chemokine–chemokine receptor signaling in regulation of T cell recruitment. Methods We screened chemokines and cytokines in healthy donor and CRC tissues from early- and advanced-stage patients using multiplex assays and PCR screening. We also utilized transcription factor activation profiling arrays and established a xenograft mouse model. Results Compared with tumor tissues of early-stage CRC patients, CD8 + T cell density was lower in advanced-stage tumor tissues. PCR screening showed that CXCL10 levels were significantly increased in advanced-stage tumor tissues. CXCR3 (the receptor of CXCL10) expression on CD8 + T cells was lower in the peripheral blood of advanced-stage patients. The migratory ability of CD8 + T cells to CXCL10 depended on CXCR3 expression. Multiplex arrays showed that IL-17A was increased in advanced-stage patient sera, which markedly downregulated CXCR3 expression via activating STAT3 signaling and reduced CD8 + T cell migration. Similar results were found after CD8 + T cells were treated with Th17 cell supernatant. Adding anti-IL-17A or the STAT3 inhibitor, Stattic, rescued these effects in vitro and in vivo. Moreover, survival analysis showed that patients with low CD8 and CXCR3 expression and high IL-17A levels had significantly worse prognosis. Conclusions CD8 + T cell infiltration in advanced-stage tumor was systematically inhibited by Th17 cells via IL-17A/STAT3/CXCR3 axis. Our findings indicate that the T cell infiltration in the tumor microenvironment may be improved by inhibiting STAT3 signaling.