Disruption of the Jak1 gene demonstrates obligatory and nonredundant roles of the Jaks in cytokine-induced biologic responses

Functional CRISPR screens in T cells reveal new opportunities for cancer immunotherapies

T cells are fundamental components in tumour immunity and cancer immunotherapies, which have made immense strides and revolutionized cancer treatment paradigm. However, recent studies delineate the predicament of T cell dysregulation in tumour microenvironment and the compromised efficacy of cancer immunotherapies. CRISPR screens enable unbiased interrogation of gene function in T cells and have revealed functional determinators, genetic regulatory networks, and intercellular interactions in T cell life cycle, thereby providing opportunities to revamp cancer immunotherapies. In this review, we briefly described the central roles of T cells in successful cancer immunotherapies, comprehensively summarised the studies of CRISPR screens in T cells, elaborated resultant master genes that control T cell activation, proliferation, fate determination, effector function, and exhaustion, and highlighted genes (BATF, PRDM1, and TOX) and signalling cascades (JAK-STAT and NF-κB pathways) that extensively engage in multiple branches of T cell responses. In conclusion, this review bridged the gap between discovering element genes to a specific process of T cell activities and apprehending these genes in the global T cell life cycle, deepened the understanding of T cell biology in tumour immunity, and outlined CRISPR screens resources that might facilitate the development and implementation of cancer immunotherapies in the clinic.

Protein Dynamic Landscape during Mouse Mammary Gland Development from Virgin to Pregnant, Lactating, and Involuting Stages

The mammary gland undergoes significant physiological changes as it undergoes a transition from virgin to pregnancy, lactation, and involution. However, the dynamic role of proteins in regulating these processes during mouse mammary gland development has not been thoroughly explored. In this study, we collected mouse mammary gland tissues from mature virgins aged 8-10 weeks (V), day 16 of pregnancy (P16d), day 12 of lactation (L12d), day 1 of forced weaning (FW 1d), and day 3 of forced weaning (FW 3d) stages for analysis using DIA-based quantitative proteomics technology. A total of 3,312 proteins were identified, of which 843 were DAPs that were categorized into nine clusters based on their abundance changes across developmental stages. Notably, DAPs in cluster 2, which peaked at the L12d stage, were primarily associated with mammary gland development and lactation. The protein-protein interaction network revealed that the epidermal growth factor (EGF) was central to this cluster. Our study provides a comprehensive overview of the mouse mammary gland development proteome and identifies some important proteins, such as EGF, Janus kinase 1 (JAK1), and signal transducer and activator of transcription 6 (STAT6) that may serve as potential targets for future research to provide guidelines for a deeper understanding of the developmental biology of mammary glands.

Design, synthesis and evaluation of C-5 substituted pyrrolopyridine derivatives as potent Janus Kinase 1 inhibitors with excellent selectivity

The development of highly selective Janus Kinase 1 (JAK1) inhibitors is crucial for improving efficacy and minimizing adverse effects in the clinical treatment of autoimmune diseases. In a prior study, we designed a series of C-5 4-pyrazol substituted pyrrolopyridine derivatives that demonstrated significant potency against JAK1, with a 10 ∼ 20-fold selectivity over Janus Kinase 2 (JAK2). Building on this foundation, we adopted orthogonal strategy by modifying the C-5 position with 3-pyrazol/4-pyrazol/3-pyrrol groups and tail with substituted benzyl groups on the pyrrolopyridine head to enhance both potency and selectivity. In this endeavor, we have identified several compounds that exhibit excellent potency and selectivity for JAK1. Notably, compounds 12b and 12e, which combined 4-pyrazol group at C-5 site and meta-substituted benzyl tails, displayed IC50 value with 2.4/2.2 nM and high 352-/253-fold selectivity for JAK1 over JAK2 in enzyme assays. Additionally, both compounds showed good JAK1-selective in Ba/F3-TEL-JAK1/2 cell-based assays. These findings mark a substantial improvement, as these compounds are 10-fold more potent and over 10-fold more selective than the best compound identified in our previous study. The noteworthy potency and selectivity properties of compounds 12b and 12e suggest their potential utility in furthering the development of drugs for autoimmune diseases.

Extramedullary hematopoiesis in cancer

Hematopoiesis can occur outside of the bone marrow during inflammatory stress to increase the production of primarily myeloid cells at extramedullary sites; this process is known as extramedullary hematopoiesis (EMH). As observed in a broad range of hematologic and nonhematologic diseases, EMH is now recognized for its important contributions to solid tumor pathology and prognosis. To initiate EMH, hematopoietic stem cells (HSCs) are mobilized from the bone marrow into the circulation and to extramedullary sites such as the spleen and liver. At these sites, HSCs primarily produce a pathological subset of myeloid cells that contributes to tumor pathology. The EMH HSC niche, which is distinct from the bone marrow HSC niche, is beginning to be characterized. The important cytokines that likely contribute to initiating and maintaining the EMH niche are KIT ligands, CXCL12, G-CSF, IL-1 family members, LIF, TNFα, and CXCR2. Further study of the role of EMH may offer valuable insights into emergency hematopoiesis and therapeutic approaches against cancer. Exciting future directions for the study of EMH include identifying common and distinct EMH mechanisms in cancer, infectious diseases, and chronic autoimmune diseases to control these conditions.

Application of JAK inhibitors in paradoxical reaction through immune-related dermatoses

Biologics play a positive and effective role in the treatment of immune-related dermatoses. However, many other immune-related diseases have also manifested along with biologics treatment. Paradoxical reaction through immune-related dermatoses refer to the new onset or exacerbation of other immune-mediated dermatoses (mainly psoriasis and atopic dermatitis) after biologics treatment of inflammatory dermatoses (mainly psoriasis and atopic dermatitis), such as new atopic dermatitis (AD) in psoriasis (PsO) treatment and new PsO in AD treatment. A common genetic background and Inflammatory pathway are possible pathogenesis. Faced with paradoxical reactions, the choice of therapy needs to be directed toward therapies effective for both diseases, such as Janus kinase (JAK) inhibitors. The Janus kinase and signal transducer and activator of transcription (JAK-STAT) pathway plays an important role in the inflammatory pathway, and has been widely used in the treatment of AD and PsO in recent years. This article focuses on JAK inhibitors such as tofacitinib, baricitinib, ruxolitinib, Abrocitinib, upadacitinib, and deucravacitinib, to explore the possible application in treatment of paradoxical reactions. Common side effects, baseline risk factors and safety use of JAK inhibitors were discussed.

Pacritinib inhibits proliferation of primary effusion lymphoma cells and production of viral interleukin-6 induced cytokines

Primary effusion lymphoma (PEL) and a form of multicentric Castleman's disease (MCD) are both caused by Kaposi sarcoma herpesvirus (KSHV). There is a critical need for improved therapies for these disorders. The IL-6/JAK/STAT3 pathway plays an important role in the pathogenesis of both PEL and KSHV-MCD. We explored the potential of JAK inhibitors for use in PEL and KSHV-MCD, and found that pacritinib was superior to others in inhibiting the growth of PEL cell lines. Pacritinib induced apoptosis in PEL cells and inhibited STAT3 and NF-κB activity as evidenced by reduced amount of phosphorylated moieties. Pacritinib also inhibits FLT3, IRAK1, and ROS1; studies utilizing other inhibitors of these targets revealed that only FLT3 inhibitors exhibited similar cell growth inhibitory effects. FLT3's likely contribution to pacritinib's cell growth inhibition was further demonstrated by siRNA knockdown of FLT3. RNA sequencing and RT-PCR showed that many key host genes including cyclins and IL-6 were downregulated by pacritinib, while KSHV genes were variably altered. Finally, pacritinib suppressed KSHV viral IL-6-induced human IL-6 and IL-10 production in peripheral blood mononuclear cells, which may model an important step in KSHV-MCD pathogenesis. These results suggest that pacritinib warrants testing for the treatment of KSHV-MCD and PEL.

Regulation of IL-10 expression and function by JAK-STAT in CD8+ T cells

IL-10 is a pleiotropic cytokine that plays a significant role in antiviral and antitumor immunity. Potent CD8+ T cells express IL-10 after stimulation by strong TCR signaling, which promotes the killing effect of CD8+ T cells. However, the regulation of IL-10 expression in CD8+ T cells and its signaling pathway to enhance CD8+ T cell function are largely unknown. In this study, we investigated the JAK-STAT signaling molecules that regulate IL-10 expression in CD8+ T cells and the JAK-STAT signaling pathway that IL-10 enhances the function of CD8+ T cells through its receptor, using small molecule inhibitors and CRISPR-Cas9 gene editing. Our findings provide new insights and a theoretical basis for the immunotherapy of tumors.

Janus kinase inhibition in the treatment and prevention of graft-versus-host disease

Graft-versus-host disease (GVHD) is a significant cause of morbidity and mortality after allogeneic hematopoietic stem cell transplantation (HSCT). For many years, corticosteroids have been the mainstay treatment for GVHD, but cases of steroid-refractory GVHD and the severe adverse effects of high-dose corticosteroids have increased the need for preventative and therapeutic strategies for GVHD. Due to the nature of alloreactive T cells, GVHD is inherently linked to the graft-versus-leukemia (GVL) effect, the therapeutic driving force behind stem cell transplantation. A considerable clinical challenge is to preserve GVL while suppressing GVHD. The field of GVHD research has greatly expanded over the past decades, including advancements in T cell modulation and depletion, antibody therapies, chemotherapeutics, cellular therapies, and Janus kinase inhibition. In this review, we discuss current approaches and advances in the prophylaxis and treatment of GVHD with a focus on new emerging advancements in Janus kinase inhibitor therapy.

Oncostatin M: Dual Regulator of the Skeletal and Hematopoietic Systems

PURPOSE OF THE REVIEW

The bone and hematopoietic tissues coemerge during development and are functionally intertwined throughout mammalian life. Oncostatin M (OSM) is an inflammatory cytokine of the interleukin-6 family produced by osteoblasts, bone marrow macrophages, and neutrophils. OSM acts via two heterodimeric receptors comprising GP130 with either an OSM receptor (OSMR) or a leukemia inhibitory factor receptor (LIFR). OSMR is expressed on osteoblasts, mesenchymal, and endothelial cells and mice deficient for the Osm or Osmr genes have both bone and blood phenotypes illustrating the importance of OSM and OSMR in regulating these two intertwined tissues.

RECENT FINDINGS

OSM regulates bone mass through signaling via OSMR, adaptor protein SHC1, and transducer STAT3 to both stimulate osteoclast formation and promote osteoblast commitment; the effect on bone formation is also supported by action through LIFR. OSM produced by macrophages is an important inducer of neurogenic heterotopic ossifications in peri-articular muscles following spinal cord injury. OSM produced by neutrophils in the bone marrow induces hematopoietic stem and progenitor cell proliferation in an indirect manner via OSMR expressed by bone marrow stromal and endothelial cells that form hematopoietic stem cell niches. OSM acts as a brake to therapeutic hematopoietic stem cell mobilization in response to G-CSF and CXCR4 antagonist plerixafor. Excessive OSM production by macrophages in the bone marrow is a key contributor to poor hematopoietic stem cell mobilization (mobilopathy) in people with diabetes. OSM and OSMR may also play important roles in the progression of several cancers. It is increasingly clear that OSM plays unique roles in regulating the maintenance and regeneration of bone, hematopoietic stem and progenitor cells, inflammation, and skeletal muscles. Dysregulated OSM production can lead to bone pathologies, defective muscle repair and formation of heterotopic ossifications in injured muscles, suboptimal mobilization of hematopoietic stem cells, exacerbated inflammatory responses, and anti-tumoral immunity. Ongoing research will establish whether neutralizing antibodies or cytokine traps may be useful to correct pathologies associated with excessive OSM production.

Medicinal chemistry perspective of JAK inhibitors: synthesis, biological profile, selectivity, and structure activity relationship

JAK-STAT signalling pathway was discovered more than quarter century ago. The JAK-STAT pathway protein is considered as one of the crucial hubs for cytokine secretion which mediates activation of different inflammatory, cellular responses and hence involved in different etiological factors. The various etiological factors involved are haematopoiesis, immune fitness, tissue repair, inflammation, apoptosis, and adipogenesis. The presence of the active mutation V617K plays a significant role in the progression of the JAK-STAT pathway-related disease. Consequently, targeting the JAK-STAT pathway could be a promising therapeutic approach for addressing a range of causative factors. In this current review, we provided a comprehensive discussion for the in-detail study of anatomy and physiology of the JAK-STAT pathway which contributes structural domain rearrangement, activation, and negative regulation associated with the downstream signaling pathway, relationship between different cytokines and diseases. This review also discussed the recent development of clinical trial entities. Additionally, this review also provides updates on FDA-approved drugs. In the current investigation, we have classified recently developed small molecule inhibitors of JAK-STAT pathway according to different chemical classes and we emphasized their synthetic routes, biological evaluation, selectivity, and structure-activity relationship.

Navigating the Cytokine Seas: Targeting Cytokine Signaling Pathways in Cancer Therapy

Cancer remains one of the leading causes of morbidity and mortality worldwide, necessitating continuous efforts to develop effective therapeutic strategies. Over the years, advancements in our understanding of the complex interplay between the immune system and cancer cells have led to the development of immunotherapies that revolutionize cancer treatment. Cytokines, as key regulators of the immune response, are involved in both the initiation and progression of cancer by affecting inflammation and manipulating multiple intracellular signaling pathways that regulate cell growth, proliferation, and migration. Cytokines, as key regulators of inflammation, have emerged as promising candidates for cancer therapy. This review article aims to provide an overview of the significance of cytokines in cancer development and therapy by highlighting the importance of targeting cytokine signaling pathways as a potential therapeutic approach.

Selectivity, efficacy and safety of JAKinibs: new evidence for a still evolving story

Fundamental insight gained over the last decades led to the discovery of cytokines as pivotal drivers of inflammatory diseases such as rheumatoid arthritis, psoriasis/psoriasis arthritis, inflammatory bowel diseases, atopic dermatitis and spondylarthritis. A deeper understanding of the pro-inflammatory and anti-inflammatory effects of various cytokines has prompted new cytokine-targeting therapies, which revolutionised the treatment options in the last years for patients with inflammatory disorders. Disease-associated immune responses typically involve a complex interplay of multiple cytokines. Therefore, blockade of one single cytokine does not necessarily lead to a persistent remission in all patients with inflammatory disorders and fostered new therapeutic strategies targeting intracellular pathways shared by multiple cytokines. By inhibiting JAK-STAT signalling pathways common to families of cytokines, JAK-inhibitors (JAKinibs) have created a new paradigm for the treatment of inflammatory diseases. Multiple agents have been approved for various disorders and more are being investigated for several new indications. Second-generation selective JAKinibs have been devised with the aim to achieve an increased selectivity and a possible reduced risk of side effects. In the current review, we will summarise the current body of evidence of pan versus selective JAKinibs and the most recent insights on new side effects and indications, including COVID-19.

Inhibiting JAK1, not NF-κB, reverses the effect of pro-inflammatory cytokines on engineered human ligament function

The role of inflammation in chronic tendon/ligament injury is hotly debated. There is less debate about inflammation following acute injury. To better understand the effect of acute inflammation, in this study we developed a multi-cytokine model of inflammatory tendinitis. The combined treatment with TNF-α, IL-1β, and IL-6, at dosages well below what are routinely used in vitro, decreased the mechanical properties and collagen content of engineered human ligaments. Treatment with this cytokine mixture resulted in an increase in phospho-NF-κB and MMP-1, did not affect procollagen production, and decreased STAT3 phosphorylation relative to controls. Using this more physiologically relevant model of acute inflammation, we inhibited NF-κB or JAK1 signaling in an attempt to reverse the negative effects of the cytokine mixture. Surprisingly, NF-κB inhibition led to an even greater decrease in mechanical function and collagen content. By contrast, inhibiting JAK1 led to an increase in mechanical properties, collagen content and thermal stability concomitant with a decrease in MMP-1. Our results suggest that inhibition of JAK1, not NF-κB, reverses the negative effects of pro-inflammatory cytokines on collagen content and mechanics in engineered human ligaments.

JAK-STAT signaling in inflammation and stress-related diseases: implications for therapeutic interventions

The Janus kinase-signal transducer and transcription activator pathway (JAK-STAT) serves as a cornerstone in cellular signaling, regulating physiological and pathological processes such as inflammation and stress. Dysregulation in this pathway can lead to severe immunodeficiencies and malignancies, and its role extends to neurotransduction and pro-inflammatory signaling mechanisms. Although JAK inhibitors (Jakinibs) have successfully treated immunological and inflammatory disorders, their application has generally been limited to diseases with similar pathogenic features. Despite the modest expression of JAK-STAT in the CNS, it is crucial for functions in the cortex, hippocampus, and cerebellum, making it relevant in conditions like Parkinson's disease and other neuroinflammatory disorders. Furthermore, the influence of the pathway on serotonin receptors and phospholipase C has implications for stress and mood disorders. This review expands the understanding of JAK-STAT, moving beyond traditional immunological contexts to explore its role in stress-related disorders and CNS function. Recent findings, such as the effectiveness of Jakinibs in chronic conditions such as rheumatoid arthritis, expand their therapeutic applicability. Advances in isoform-specific inhibitors, including filgotinib and upadacitinib, promise greater specificity with fewer off-target effects. Combination therapies, involving Jakinibs and monoclonal antibodies, aiming to enhance therapeutic specificity and efficacy also give great hope. Overall, this review bridges the gap between basic science and clinical application, elucidating the complex influence of the JAK-STAT pathway on human health and guiding future interventions.

Scope of JAK Inhibitors in Children: Recent Evidence and Way Forward

Over the last decade, there has been an increase in the use of targeted therapy using small molecules such as Janus kinase (JAK) inhibitors. Since the introduction of ruxolitinib, the first non-selective JAK inhibitor approved for use in myelofibrosis, many other JAK inhibitors have been tried in a wide spectrum of immune-mediated disorders. Although various trials have shown the promising efficacy of JAK inhibitors in immune-mediated inflammatory disorders (IMIDs), there is a growing concern over the major cardiovascular events and malignancies associated with the use of these molecules in older adults, particularly those over 65 years of age. In this review, we aim to discuss the immunology of the JAK-STAT pathway, the scope of use of JAK inhibitors, and their safety in paediatric practice. Here, we discuss high-quality evidence favouring the use of JAK inhibitors in children with juvenile idiopathic arthritis (JIA) who are refractory to one or more conventional/biological disease-modifying drugs, demonstrated in two randomised controlled trials (RCTs). In addition to JIA, there are reports favouring the role of JAK inhibitors in other IMIDs such as systemic-onset JIA and interferonopathies. Thus far, the existing literature suggests an acceptable safety profile for JAK inhibitors in children. With the expanding scope of JAK inhibitors in a wide range of IMIDs in children, there is a significant need for long-term close vigilance for any potential harm.

Modulation of JAK-STAT Signaling by LNK: A Forgotten Oncogenic Pathway in Hormone Receptor-Positive Breast Cancer

Breast cancer remains the most frequently diagnosed cancer in women worldwide. Tumors that express hormone receptors account for 75% of all cases. Understanding alternative signaling cascades is important for finding new therapeutic targets for hormone receptor-positive breast cancer patients. JAK-STAT signaling is commonly activated in hormone receptor-positive breast tumors, inducing inflammation, proliferation, migration, and treatment resistance in cancer cells. In hormone receptor-positive breast cancer, the JAK-STAT cascade is stimulated by hormones and cytokines, such as prolactin and IL-6. In normal cells, JAK-STAT is inhibited by the action of the adaptor protein, LNK. However, the role of LNK in breast tumors is not fully understood. This review compiles published reports on the expression and activation of the JAK-STAT pathway by IL-6 and prolactin and potential inhibition of the cascade by LNK in hormone receptor-positive breast cancer. Additionally, it includes analyses of available datasets to determine the level of expression of LNK and various members of the JAK-STAT family for the purpose of establishing associations between expression and clinical outcomes. Together, experimental evidence and in silico studies provide a better understanding of the potential implications of the JAK-STAT-LNK loop in hormone receptor-positive breast cancer progression.

Pathological mechanism and targeted drugs of ulcerative colitis: A review

Ulcerative colitis (UC) is a chronic inflammatory disease of the colon with abdominal pain, diarrhea, and mucopurulent stools as the main symptoms. Its incidence is increasing worldwide, and traditional treatments have problems such as immunosuppression and metabolic disorders. In this article, the etiology and pathogenesis of ulcerative colitis are reviewed to clarify the targeted drugs of UC in the latest research. Our aim is to provide more ideas for the clinical treatment and new drug development of UC, mainly by analyzing and sorting out the relevant literature on PubMed, summarizing and finding that it is related to the main genetic, environmental, immune and other factors, and explaining its pathogenesis from the NF-κB pathway, PI3K/Akt signaling pathway, and JAK/STAT signaling pathway, and obtaining anti-TNF-α monoclonal antibodies, integrin antagonists, IL-12/IL-23 antagonists, novel UC-targeted drugs such as JAK inhibitors and SIP receptor agonists. We believe that rational selection of targeted drugs and formulation of the best dosing strategy under the comprehensive consideration of clinical evaluation is the best way to treat UC.

Matrix mechanics regulate the polarization state of bone marrow-derived neutrophils through the JAK1/STAT3 signaling pathway

Matrix mechanics regulate essential cell behaviors through mechanotransduction, and as one of its most important elements, substrate stiffness was reported to regulate cell functions such as viability, communication, migration, and differentiation. Neutrophils (Neus) predominate the early inflammatory response and initiate regeneration. The activation of Neus can be regulated by physical cues; however, the functional alterations of Neus by substrate stiffness remain unknown, which is critical in determining the outcomes of engineered tissue mimics. Herein, a three-dimensional (3D) culture system made of hydrogels was developed to explore the effects of varying stiffnesses (1.5, 2.6, and 5.7 kPa) on the states of Neus. Neus showed better cell integrity and viability in the 3D system. Moreover, it was shown that the stiffer matrix tended to induce Neus toward an anti-inflammatory phenotype (N2) with less adhesion molecule expression, less reactive oxygen species (ROS) production, and more anti-inflammatory cytokine secretion. Additionally, the aortic ring assay indicated that Neus cultured in a stiffer matrix significantly increased vascular sprouting. RNA sequencing showed that a stiffer matrix could significantly activate JAK1/STAT3 signaling in Neus and the inhibition of JAK1 ablated the stiffness-dependent increase in the expression of CD182 (an N2 marker). Taken together, these results demonstrate that a stiffer matrix promotes Neus to shift to the N2 phenotype, which was regulated by JAK1/STAT3 pathway. This study lays the groundwork for further research on fabricating engineered tissue mimics, which may provide more treatment options for ischemic diseases and bone defects. STATEMENT OF SIGNIFICANCE.

Understanding the efficacy of individual Janus kinase inhibitors in the treatment of ulcerative colitis for future positioning in inflammatory bowel disease treatment

Recent studies have gradually elucidated the pathogenesis of inflammatory bowel disease; thus, the Janus kinase (JAK)-signal transducers and activators of transcription pathway are strongly involved in the pathophysiology of inflammatory bowel disease. Generally, Janus kinase inhibitors are being used for the treatment of rheumatoid arthritis and other immunological diseases, with the therapeutic promising effects. Currently, in Japan, three Janus kinase inhibitors, namely tofacitinib, filgotinib, and upadacitinib, are available for the treatment of patients with active ulcerative colitis. Therefore, evaluating the efficacy and safety of each JAK inhibitor is essential for determining the role of JAK inhibitors in future therapeutic strategies for inflammatory bowel disease (IBD).

Progress on the Pharmacological Targeting of Janus Pseudokinases

The Janus kinases (JAKs) are key components of the JAK-STAT signaling pathway and are involved in myriad physiological processes. Though they are the molecular targets of many FDA-approved drugs, these drugs manifest adverse effects due in part to their inhibition of the requisite JAK kinase activity. However, the JAKs uniquely possess an integrated pseudokinase domain (JH2) that regulates the adjacent kinase domain (JH1). The therapeutic targeting of JH2 domains has been less thoroughly explored and may present an avenue to modulate the JAKs without the adverse effects associated with targeting the adjacent JH1 domain. The potential of this strategy was recently demonstrated with the FDA approval of the TYK2 JH2 ligand deucravacitinib for treating plaque psoriasis. In this light, the structure and targetability of the JAK pseudokinases are discussed, in conjunction with the state of development of ligands that bind to these domains.

Palmitoylation-dependent control of JAK1 kinase signaling governs responses to neuropoietic cytokines and survival in DRG neurons

Janus Kinase-1 (JAK1) plays key roles during neurodevelopment and following neuronal injury, while activatory JAK1 mutations are linked to leukemia. In mice, Jak1 genetic deletion results in perinatal lethality, suggesting non-redundant roles and/or regulation of JAK1 for which other JAKs cannot compensate. Proteomic studies reveal that JAK1 is more likely palmitoylated compared to other JAKs, implicating palmitoylation as a possible JAK1-specific regulatory mechanism. However, the importance of palmitoylation for JAK1 signaling has not been addressed. Here, we report that JAK1 is palmitoylated in transfected HEK293T cells and endogenously in cultured Dorsal Root Ganglion (DRG) neurons. We further use comprehensive screening in transfected non-neuronal cells and shRNA-mediated knockdown in DRG neurons to identify the related enzymes ZDHHC3 and ZDHHC7 as dominant protein acyltransferases (PATs) for JAK1. Surprisingly, we found palmitoylation minimally affects JAK1 localization in neurons, but is critical for JAK1's kinase activity in cells and even in vitro. We propose this requirement is likely because palmitoylation facilitates transphosphorylation of key sites in JAK1's activation loop, a possibility consistent with structural models of JAK1. Importantly, we demonstrate a leukemia-associated JAK1 mutation overrides the palmitoylation-dependence of JAK1 activity, potentially explaining why this mutation is oncogenic. Finally, we show that JAK1 palmitoylation is important for neuropoietic cytokine-dependent signaling and neuronal survival and that combined Zdhhc3/7 loss phenocopies loss of palmitoyl-JAK1. These findings provide new insights into the control of JAK signaling in both physiological and pathological contexts.

New Possible Ways to Use Exosomes in Diagnostics and Therapy via JAK/STAT Pathways

Exosomes have the potential to be the future of personalized diagnostics and therapy. They are nano-sized particles between 30 and 100 nm flowing in the extracellular milieu, where they mediate cell-cell communication and participate in immune system regulation. Tumor-derived exosomes (TDEs) secreted from different types of cancer cells are the key regulators of the tumor microenvironment. With their immune suppressive cargo, TDEs prevent the antitumor immune response, leading to reduced effectiveness of cancer treatment by promoting a pro-tumorigenic microenvironment. Involved signaling pathways take part in the regulation of tumor proliferation, differentiation, apoptosis, and angiogenesis. Signal transducers and activators of transcription factors (STATs) and Janus kinase (JAK) signaling pathways are crucial in malignancies and autoimmune diseases alike, and their potential to be manipulated is currently the focus of interest. In this review, we aim to discuss exosomes, TDEs, and the JAK/STAT pathways, along with mediators like interleukins, tripartite motif proteins, and interferons.

Cell death checkpoints in the TNF pathway

Tumor necrosis factor (TNF) plays a central role in orchestrating mammalian inflammatory responses. It promotes inflammation either directly by inducing inflammatory gene expression or indirectly by triggering cell death. TNF-mediated cell death-driven inflammation can be beneficial during infection by providing cell-extrinsic signals that help to mount proper immune responses. Uncontrolled cell death caused by TNF is instead highly detrimental and is believed to cause several human autoimmune diseases. Death is not the default response to TNF sensing. Molecular brakes, or cell death checkpoints, actively repress TNF cytotoxicity to protect the organism from its detrimental consequences. These checkpoints therefore constitute essential safeguards against inflammatory diseases. Recent advances in the field have revealed the existence of several new and unexpected brakes against TNF cytotoxicity and pathogenicity.

JAK/STAT as a Potential Therapeutic Target for Osteolytic Diseases

Several cytokines with major biological functions in inflammatory diseases exert their functions through the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signal transduction pathway. JAKs phosphorylate the cytoplasmic domain of the receptor, inducing the activation of its substrates, mainly the proteins known as STATs. STATs bind to these phosphorylated tyrosine residues and translocate from the cytoplasm to the nucleus, further regulating the transcription of several genes that regulate the inflammatory response. The JAK/STAT signaling pathway plays a critical role in the pathogenesis of inflammatory diseases. There is also increasing evidence indicating that the persistent activation of the JAK/STAT signaling pathway is related to several inflammatory bone (osteolytic) diseases. However, the specific mechanism remains to be clarified. JAK/STAT signaling pathway inhibitors have gained major scientific interest to explore their potential in the prevention of the destruction of mineralized tissues in osteolytic diseases. Here, our review highlights the importance of the JAK/STAT signaling pathway in inflammation-induced bone resorption and presents the results of clinical studies and experimental models of JAK inhibitors in osteolytic diseases.

JAK/STAT Signaling and Cervical Cancer: From the Cell Surface to the Nucleus

The Janus kinase (JAK)/signal transducer and activator of transcription (STAT) signaling pathway constitutes a rapid signaling module from the cell surface to the nucleus, and activates different cellular responses, such as proliferation, survival, migration, invasion, and inflammation. When the JAK/STAT pathway is altered, it contributes to cancer progression and metastasis. STAT proteins play a central role in developing cervical cancer, and inhibiting the JAK/STAT signaling may be necessary to induce tumor cell death. Several cancers show continuous activation of different STATs, including cervical cancer. The constitutive activation of STAT proteins is associated with a poor prognosis and overall survival. The human papillomavirus (HPV) oncoproteins E6 and E7 play an essential role in cervical cancer progression, and they activate the JAK/STAT pathway and other signals that induce proliferation, survival, and migration of cancer cells. Moreover, there is a crosstalk between the JAK/STAT signaling cascade with other signaling pathways, where a plethora of different proteins activate to induce gene transcription and cell responses that contribute to tumor growth. Therefore, inhibition of the JAK/STAT pathway shows promise as a new target in cancer treatment. In this review, we discuss the role of the JAK/STAT pathway components and the role of the HPV oncoproteins associated with cellular malignancy through the JAK/STAT proteins and other signaling pathways to induce tumor growth.

Deficiencies and Dysregulation of STAT Pathways That Drive Inborn Errors of Immunity: Lessons from Patients and Mouse Models of Disease

The STAT family proteins provide critical signals for immune cell development, differentiation, and proinflammatory and anti-inflammatory responses. Inborn errors of immunity (IEIs) are caused by single gene defects leading to immune deficiency and/or dysregulation, and they have provided opportunities to identify genes important for regulating the human immune response. Studies of patients with IEIs due to altered STAT signaling, and mouse models of these diseases, have helped to shape current understanding of the mechanisms whereby STAT signaling and protein interactions regulate immunity. Although many STAT signaling pathways are shared, clinical and immune phenotypes in patients with monogenic defects of STAT signaling highlight both redundant and nonredundant pathways. In this review, we provide an overview of the shared and unique signaling pathways used by STATs, phenotypes of IEIs with altered STAT signaling, and recent discoveries that have provided insight into the human immune response and treatment of disease.

Discovery of C-5 Pyrazole-Substituted Pyrrolopyridine Derivatives as Potent and Selective Inhibitors for Janus Kinase 1

Developing selective inhibitors for Janus kinase 1 (JAK1) is a significant focus for improving the efficacy and alleviating the adverse effects in treating immune-inflammatory diseases. Herein, we report the discovery of a series of C-5 pyrazole-modified pyrrolopyrimidine derivatives as JAK1-selective inhibitors. The potential hydrogen bond between the pyrazole group and E966 in JAK1 is the key point that enhances JAK1 selectivity. These compounds exhibit 10- to 20-fold JAK1 selectivity over JAK2 in enzyme assays. Compound 12b also exhibits excellent JAK1 selectivity in Ba/F3-TEL-JAK cellular assays. Metabolism studies and the results of the hair growth model in mice indicate that compound 12b may be a viable lead compound for the development of highly JAK1-selective inhibitors for immune and inflammatory diseases.

JAKs and STATs from a Clinical Perspective: Loss-of-Function Mutations, Gain-of-Function Mutations, and Their Multidimensional Consequences

The JAK/STAT signaling pathway plays a key role in cytokine signaling and is involved in development, immunity, and tumorigenesis for nearly any cell. At first glance, the JAK/STAT signaling pathway appears to be straightforward. However, on closer examination, the factors influencing the JAK/STAT signaling activity, such as cytokine diversity, receptor profile, overlapping JAK and STAT specificity among non-redundant functions of the JAK/STAT complexes, positive regulators (e.g., cooperating transcription factors), and negative regulators (e.g., SOCS, PIAS, PTP), demonstrate the complexity of the pathway's architecture, which can be quickly disturbed by mutations. The JAK/STAT signaling pathway has been, and still is, subject of basic research and offers an enormous potential for the development of new methods of personalized medicine and thus the translation of basic molecular research into clinical practice beyond the use of JAK inhibitors. Gain-of-function and loss-of-function mutations in the three immunologically particularly relevant signal transducers STAT1, STAT3, and STAT6 as well as JAK1 and JAK3 present themselves through individual phenotypic clinical pictures. The established, traditional paradigm of loss-of-function mutations leading to immunodeficiency and gain-of-function mutation leading to autoimmunity breaks down and a more differentiated picture of disease patterns evolve. This review is intended to provide an overview of these specific syndromes from a clinical perspective and to summarize current findings on pathomechanism, symptoms, immunological features, and therapeutic options of STAT1, STAT3, STAT6, JAK1, and JAK3 loss-of-function and gain-of-function diseases.

The role of upadacitinib in the treatment of ulcerative colitis

The JAK signaling pathway plays a major role in the immunopathology of autoimmune diseases, including inflammatory bowel disease. JAK enzymes provide novel targets for rapidly effective inflammatory bowel disease therapy, particularly in ulcerative colitis. Upadacitinib is a targeted JAK1 inhibitor. In multiple phase III clinical trials, upadacitinib has demonstrated significant improvement in clinical and endoscopic outcomes and quality of life for patients with moderate-to-severe ulcerative colitis. In this drug evaluation we describe the role of the JAK signaling pathway in ulcerative colitis, the mechanism of action of upadacitinib and the current clinical evidence for its use in ulcerative colitis; we also review its safety and tolerability, including for special populations.

Targeting Leukemia Inhibitory Factor in Pancreatic Adenocarcinoma

INTRODUCTION

Leukemia Inhibitory Factor (LIF) is a member of the interleukin-6 (IL-6) cytokine family. Known to induce differentiation of myeloid leukemia cells, evidence has accumulated supporting its role in cancer evolution though regulating cell differentiation, renewal, and survival. LIF has recently emerged as a biomarker and therapeutic target for pancreatic ductal adenocarcinoma (PDAC). The first-in-human clinical trial has shown promising safety profile and has suggested a potential role for LIF inhibitor in combination regimen.

AREAS COVERED

Herein, we summarize, discuss, and give an expert opinion on the role of LIF in PDAC promotion, and its potential role as a biomarker and target of anti-cancer therapy. We conducted an exhaustive PubMed search for English-language articles published from January 1, 1970, to August 1, 2022.

EXPERT OPINION

PDAC carries a devastating prognosis for patients, highlighting the need for advancing drug development. The results of the phase 1 trial with MSC-1 demonstrated tolerability and safety but modest efficacy. Future research should focus on investigating LIF targets in combination with current standard-of-care chemotherapy and immunotherapy can be a promising approach. Further, larger multicenter clinical trials are needed to define the use of LIF as a new biomarker in PDAC patients.

The Use of JAK/STAT Inhibitors in Chronic Inflammatory Disorders

The Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway plays a critical role in orchestrating immune and inflammatory responses, and it is essential for a wide range of cellular processes, including differentiation, cell growth, and apoptosis. Over the years, this pathway has been heavily investigated due to its key role in the pathogeneses of several chronic inflammatory conditions, e.g., psoriasis, atopic dermatitis (AD), and inflammatory bowel diseases (IBDs). Nevertheless, the impact of this pathway on the pathogenesis of inflammatory conditions remains unclear. This review describes the role of the JAK/STAT signaling pathway in the pathogenesis of inflammatory diseases such as psoriasis (Pso), psoriatic arthritis (PsA), AD, and IBD with a focus on ulcerative colitis (UC) and briefly resumes the use of JAK inhibitors in their clinical management.

Phosphorylation of Tyrosine 841 Plays a Significant Role in JAK3 Activation

Janus Kinase 3 (JAK3) plays a key role in the development, proliferation, and differentiation of various immune cells. It regulates gene expression by phosphorylation of Signal Transducers and Activators of Transcriptions (STATs) via the JAK/STAT pathway. Recently, we found a new JAK3 phosphorylation site, tyrosine 841 (Y841). The results showed that pY841 helps the kinase domain flip around the pseudo kinase domain, which may cause JAK3 conformational changes. It also reduces the size of the cleft between the N-lobe and the C-lobe of the JAK3 kinase domain. However, pY841 was found to enlarge the cleft when ATP/ADP was bound to the kinase. The increase in the cleft size suggested that pY841 enhanced the elasticity of the kinase domain. For unphosphorylated JAK3 (JAK3-Y841), the binding forces between the kinase domain and ATP or ADP were similar. After phosphorylation of Y841, JAK3-pY841 exhibited more salt bridges and hydrogen bonds between ATP and the kinase than between ADP and the kinase. Consequently, the electrostatic binding force between ATP and the kinase was higher than that between ADP and the kinase. The result was that compared to ADP, ATP was more attractive to JAK3 when Y841 was phosphorylated. Therefore, JAK3-pY841 tended to bind ATP rather than ADP. This work provides new insights into the role of phosphorylation in kinase activation and ATP hydrolysis and sheds light on the importance of understanding the molecular mechanisms that regulate the kinase function.

Janus kinase 1 in Megalobrama amblycephala: Identification, phylogenetic analysis and expression profiling after Aeromonas hydrophila infection

Janus kinase 1 (JAK1), a member of the JAK family, plays an essential and non-redundant role in the mammalian immune system. However, the potential role of JAK1 in fish immune response remains largely unclear. In the present study, the JAK1 gene of Megalobrama amblycephala (MamJAK1) was identified and characterized. The open reading frame (ORF) of MamJAK1 was 3462 bp, encoding 1153 amino acids. MamJAK1 consists of four common domains of the JAK family, including B41, SH2, STyrKc (a pseudo kinase domain), and TyrKc (a kinase domain). Phylogenetic analysis showed that JAK1s are divided into two evolutionary clades, one containing fish JAK1s, and the other containing JAK1s from other vertebrates. The results of quantitative real-time PCR (qPCR) showed that in healthy M. amblycephala, MamJAK1 mRNA was highest expressed in blood, followed by spleen, intestine and mid-kidney, and lowly expressed in other tissues including gill, liver, head kidney, muscle, brain and heart. After Aeromonas hydrophila infection, the expression of MamJAK1 mRNA was significantly induced in four selected tissues including spleen, mid-kidney, liver and intestine, reaching a peak at 24 hpi (hour post infection) in spleen and mid-kidney, at 12 hpi in liver and at 4 hpi in intestine, and then the expression level was restricted to control levels at 72 or 120 hpi. In addition, the results of Western blot showed that the phosphorylation level of MamJAK1 protein in spleen and mid-kidney increased significantly after A. hydrophila infection, although MamJAK1 protein did not change obviously. Further, the JAK1 phosphorylation in Ctenopharyngodon idellus kidney (CIK) cells was found to be significantly induced by LPS stimulation and IL-6R over-expression. The results above suggest that MamJAK1 may play an essential role in the immune response against bacterial infection through the IL-6R mediated JAK1/STAT signaling pathway, which further deepen our understanding of JAK1 and provides a potential target for the treatment and prevention of bacterial diseases in teleost.

Network Approaches to Uncover Pathogenesis and Therapeutic Targets of Inflammatory Bowel Diseases

Inflammatory bowel diseases (IBD) are currently recognized to involve chronic intestinal inflammation in genetically susceptible individuals. Patients with IBD mainly develop gastrointestinal inflammation, but it is sometimes accompanied by extraintestinal manifestations such as arthritis, erythema nodosum, episcleritis, pyoderma gangrenosum, uveitis, and primary sclerosing cholangitis. These clinical aspects imply the importance of interorgan networks in IBD. In the gastrointestinal tract, immune cells are influenced by multiple local environmental factors including microbiota, dietary environment, and intercellular networks, which further alter molecular networks in immune cells. Therefore, deciphering networks at interorgan, intercellular, and intracellular levels should help to obtain a comprehensive understanding of IBD. This review focuses on the intestinal immune system, which governs the physiological and pathological functions of the digestive system in harmony with the other organs.

Exploring the Pipeline of Novel Therapies for Inflammatory Bowel Disease; State of the Art Review

Crohn’s disease (CD) and ulcerative colitis (UC), known as inflammatory bowel diseases (IBD), are characterized by chronic inflammation of the gastrointestinal tract. Over the last two decades, numerous medications have been developed and repurposed to induce and maintain remission in IBD patients. Despite the approval of multiple drugs, the major recurring issues continue to be primary non-response and secondary loss of response, as well as short- and long-term adverse events. Most clinical trials show percentages of response under 60%, possibly as a consequence of strict inclusion criteria and definitions of response. That is why these percentages appear to be more optimistic in real-life studies. A therapeutic ceiling has been used as a term to define this invisible bar that has not been crossed by any drug yet. This review highlights novel therapeutic target agents in phases II and III of development, such as sphingosine-1-phosphate receptor modulators, selective Janus kinase inhibitors, anti-interleukins, and other small molecules that are currently under research until 1 January 2023. Emerging treatments for CD and UC that have just received approval or are undergoing phase III clinical trials are also discussed in this review.

Distinct Mechanisms of Mismatch-Repair Deficiency Delineate Two Modes of Response to Anti-PD-1 Immunotherapy in Endometrial Carcinoma

Mismatch repair-deficient (MMRd) cancers have varied responses to immune-checkpoint blockade (ICB). We conducted a phase II clinical trial of the PD-1 inhibitor pembrolizumab in 24 patients with MMRd endometrial cancer (NCT02899793). Patients with mutational MMRd tumors (6 patients) had higher response rates and longer survival than those with epigenetic MMRd tumors (18 patients). Mutation burden was higher in tumors with mutational MMRd compared with epigenetic MMRd; however, within each category of MMRd, mutation burden was not correlated with ICB response. Pretreatment JAK1 mutations were not associated with primary resistance to pembrolizumab. Longitudinal single-cell RNA-seq of circulating immune cells revealed contrasting modes of antitumor immunity for mutational versus epigenetic MMRd cancers. Whereas effector CD8+ T cells correlated with regression of mutational MMRd tumors, activated CD16+ NK cells were associated with ICB-responsive epigenetic MMRd tumors. These data highlight the interplay between tumor-intrinsic and tumor-extrinsic factors that influence ICB response.

SIGNIFICANCE

The molecular mechanism of MMRd is associated with response to anti-PD-1 immunotherapy in endometrial carcinoma. Tumors with epigenetic MMRd or mutational MMRd are correlated with NK cell or CD8+ T cell-driven immunity, respectively. Classifying tumors by the mechanism of MMRd may inform clinical decision-making regarding cancer immunotherapy. This article is highlighted in the In This Issue feature, p. 247.

Early administration of tofacitinib in COVID-19 pneumonitis: An open randomised controlled trial

BACKGROUND

Controversies on sub-populations most sensitive to therapy and the best timing of starting the treatment still surround the use of immunomodulatory drugs in COVID-19.

OBJECTIVES

We designed a multicentre open-label randomised controlled trial to test the effect of prompt adding of tofacitinib to standard therapy for hospitalised patients affected by mild/moderate COVID-19 pneumonitis.

METHODS

Patients admitted to three Italian hospitals affected by COVID-19 pneumonitis not requiring mechanical ventilation were randomised to receive standard treatment alone or tofacitinib (10 mg/bid) for 2 weeks, starting within the first 24 h from admission.

RESULTS

A total of 116 patients were randomised; 49 in the experimental arm completed the 14-day treatment period, 9 discontinued tofacitinib as the disease worsened and were included in the analysis, and 1 died of respiratory failure. All 58 control patients completed the study. Clinical and demographic characteristics were similar between the study groups. In the tofacitinib group, 9/58 (15.5%) patients progressed to noninvasive ventilation (CPAP) to maintain SO₂  > 93%, invasive mechanical ventilation or death by day 14 was 15.5%, significantly less than in the control group (20/58, 34.4%, RR 0,45, RRR -55%, NNT 5; p = .018). No differences in severe adverse effect incidence had been observed across the groups.

CONCLUSION

High-dose tofacitinib therapy in patients with COVID pneumonitis is safe and may prevent deterioration to respiratory failure.

Regulation of effector and memory CD8 + T cell differentiation: a focus on orphan nuclear receptor NR4A family, transcription factor, and metabolism

CD8 + T cells undergo rapid expansion followed by contraction and the development of memory cells after their receptors are activated. The development of immunological memory following acute infection is a complex phenomenon that involves several molecular, transcriptional, and metabolic mechanisms. As memory cells confer long-term protection and respond to secondary stimulation with strong effector function, understanding the mechanisms that influence their development is of great importance. Orphan nuclear receptors, NR4As, are immediate early genes that function as transcription factors and bind with the NBRE region of chromatin. Interestingly, the NBRE region of activated CD8 + T cells is highly accessible at the same time the expression of NR4As is induced. This suggests a potential role of NR4As in the early events post T cell activation that determines cell fate decisions. In this review, we will discuss the influence of NR4As on the differentiation of CD8 + T cells during the immune response to acute infection and the development of immunological memory. We will also discuss the signals, transcription factors, and metabolic mechanisms that control cell fate decisions. HIGHLIGHTS: Memory CD8 + T cells are an essential subset that mediates long-term protection after pathogen encounters. Some specific environmental cues, transcriptional factors, and metabolic pathways regulate the differentiation of CD8 + T cells and the development of memory cells. Orphan nuclear receptor NR4As are early genes that act as transcription factors and are highly expressed post-T cell receptor activation. NR4As influence the effector function and differentiation of CD8 + T cells and also control the development of immunological memory following acute infection.

Identification of TUL01101: A Novel Potent and Selective JAK1 Inhibitor for the Treatment of Rheumatoid Arthritis

Janus kinase 1 (JAK1) is a potential target for the treatment of rheumatoid arthritis (RA). In this study, the introduction of a spiro ring with a difluoro-substituted cyclopropionamide resulted in the identification of TUL01101 (compound 36) based on a triazolo[1,5-a]pyridine core of filgotinib. It showed excellent potency on JAK1 with an IC₅₀ value of 3 nM and exhibited more than 12-fold selectivity for JAK2 and TYK2. Whole blood assay also demonstrated the high activity and selectivity (37-fold for JAK2). At the same time, TUL01101 also demonstrated excellent metabolic stability and pharmacokinetics (PK) profiles were assayed in three species (mouse, rat, and dog). Moreover, it has been validated for effective activity in the treatment of RA both in collagen-induced arthritis (CIA) and adjuvant-induced arthritis (AIA) models, with low dose and low toxicity. Now, TUL01101 has progressed into phase I clinical trials.

New insights into Chlamydia pathogenesis: Role of leukemia inhibitory factor

Chlamydia trachomatis (Ct) is the leading cause of bacterial sexually transmitted infections worldwide. Since the symptoms of Ct infection are often subtle or absent, most people are unaware of their infection until they are tested or develop severe complications such as infertility. It is believed that the primary culprit of Ct-associated tissue damage is unresolved chronic inflammation, resulting in aberrant production of cytokines, chemokines, and growth factors, as well as dysregulated tissue influx of innate and adaptive immune cells. A member of the IL-6 cytokine family, leukemia inhibitory factor (LIF), is one of the cytokines induced by Ct infection but its role in Ct pathogenesis is unclear. In this article, we review the biology of LIF and LIF receptor (LIFR)-mediated signaling pathways, summarize the physiological role of LIF in the reproductive system, and discuss the impact of LIF in chronic inflammatory conditions and its implication in Ct pathogenesis. Under normal circumstances, LIF is produced to maintain epithelial homeostasis and tissue repair, including the aftermath of Ct infection. However, LIF/LIFR-mediated signaling – particularly prolonged strong signaling – can gradually transform the microenvironment of the fallopian tube by altering the fate of epithelial cells and the cellular composition of epithelium. This harmful transformation of epithelium may be a key process that leads to an enhanced risk of infertility, ectopic pregnancy and cancer following Ct infection.

The JAK-STAT pathway at 30: Much learned, much more to do

The discovery of the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway arose from investigations of how cells respond to interferons (IFNs), revealing a paradigm in cell signaling conserved from slime molds to mammals. These discoveries revealed mechanisms underlying rapid gene expression mediated by a wide variety of extracellular polypeptides including cytokines, interleukins, and related factors. This knowledge has provided numerous insights into human disease, from immune deficiencies to cancer, and was rapidly translated to new drugs for autoimmune, allergic, and infectious diseases, including COVID-19. Despite these advances, major challenges and opportunities remain.

Interferon gamma mediates the reduction of adipose tissue regulatory T cells in human obesity

Decreased adipose tissue regulatory T cells contribute to insulin resistance in obese mice, however, little is known about the mechanisms regulating adipose tissue regulatory T cells numbers in humans. Here we obtain adipose tissue from obese and lean volunteers. Regulatory T cell abundance is lower in obese vs. lean visceral and subcutaneous adipose tissue and associates with reduced insulin sensitivity and altered adipocyte metabolic gene expression. Regulatory T cells numbers decline following high-fat diet induction in lean volunteers. We see alteration in major histocompatibility complex II pathway in adipocytes from obese patients and after high fat ingestion, which increases T helper 1 cell numbers and decreases regulatory T cell differentiation. We also observe increased expression of inhibitory co-receptors including programmed cell death protein 1 and OX40 in visceral adipose tissue regulatory T cells from patients with obesity. In human obesity, these global effects of interferon gamma to reduce regulatory T cells and diminish their function appear to instigate adipose inflammation and suppress adipocyte metabolism, leading to insulin resistance.

Induction of T cell exhaustion by JAK1/3 inhibition in the treatment of alopecia areata

Alopecia areata (AA) is an autoimmune disease caused by T cell-mediated destruction of the hair follicle (HF). Therefore, approaches that effectively disrupt pathogenic T cell responses are predicted to have therapeutic benefit for AA treatment. T cells rely on the duality of T cell receptor (TCR) and gamma chain (γc) cytokine signaling for their development, activation, and peripheral homeostasis. Ifidancitinib is a potent and selective next-generation JAK1/3 inhibitor predicted to disrupt γc cytokine signaling. We found that Ifidancitinib robustly induced hair regrowth in AA-affected C3H/HeJ mice when fed with Ifidancitinib in chow diets. Skin taken from Ifidancitinib-treated mice showed significantly decreased AA-associated inflammation. CD44⁺CD62L^- CD8⁺ T effector/memory cells, which are associated with the pathogenesis of AA, were significantly decreased in the peripheral lymphoid organs in Ifidancitinib-treated mice. We observed high expression of co-inhibitory receptors PD-1 on effector/memory CD8⁺ T cells, together with decreased IFN-γ production in Ifidancitinib-treated mice. Furthermore, we found that γc cytokines regulated T cell exhaustion. Taken together, our data indicate that selective induction of T cell exhaustion using a JAK inhibitor may offer a mechanistic explanation for the success of this treatment strategy in the reversal of autoimmune diseases such as AA.

Selective inhibitors of JAK1 targeting an isoform-restricted allosteric cysteine

The Janus tyrosine kinase (JAK) family of non-receptor tyrosine kinases includes four isoforms (JAK1, JAK2, JAK3, and TYK2) and is responsible for signal transduction downstream of diverse cytokine receptors. JAK inhibitors have emerged as important therapies for immun(onc)ological disorders, but their use is limited by undesirable side effects presumed to arise from poor isoform selectivity, a common challenge for inhibitors targeting the ATP-binding pocket of kinases. Here we describe the chemical proteomic discovery of a druggable allosteric cysteine present in the non-catalytic pseudokinase domain of JAK1 (C817) and TYK2 (C838), but absent from JAK2 or JAK3. Electrophilic compounds selectively engaging this site block JAK1-dependent trans-phosphorylation and cytokine signaling, while appearing to act largely as 'silent' ligands for TYK2. Importantly, the allosteric JAK1 inhibitors do not impair JAK2-dependent cytokine signaling and are inactive in cells expressing a C817A JAK1 mutant. Our findings thus reveal an allosteric approach for inhibiting JAK1 with unprecedented isoform selectivity.

Deucravacitinib for the Treatment of Psoriatic Disease

Psoriasis is an immune-mediated disease, with the interleukin (IL)-23/IL-17 axis currently considered its main pathogenic pathway. Tyrosine kinase 2 (TYK2) is responsible for mediating immune signalling of IL-12, IL-23 and type I interferons, without interfering with other critical systemic functions as other JAK proteins do. This article aims to review the current knowledge on deucravacitinib, a new oral drug that selectively inhibits TYK2, granting it a low risk of off-target effects. After good efficacy and safety results in a phase II, placebo-controlled trial, two phase III, 52-week trials evaluated deucravacitinib 6 mg against placebo and apremilast—an active comparator. POETYK PSO-1 and PSO-2 involved 1688 patients with moderate-to-severe psoriasis. After 16 weeks, in both studies, over 50% of patients treated with deucravacitinib reached PASI75, which was significantly superior to placebo and apremilast. In POETYK PSO-1, these results improved until week 24 and were maintained through week 52, with over 65% of patients achieving PASI75 at this point. A reduction in signs and symptoms was also reported by patients, with greater impact on itch. Deucravacitinib was well tolerated and safe. There were no reports of serious infections, thromboembolic events, or laboratory abnormalities, which are a concern among other JAK inhibitors. Persistent efficacy and consistent safety profiles were reported for up to 2 years. Despite advances in the treatment of psoriasis, namely among biologic agents, an oral, effective and safe new drug can bring several advantages to prescribers and patients. Further investigation is required to understand where to place deucravacitinib among current psoriasis treatment options.

Digesting the Role of JAK-STAT and Cytokine Signaling in Oral and Gastric Cancers

When small proteins such as cytokines bind to their associated receptors on the plasma membrane, they can activate multiple internal signaling cascades allowing information from one cell to affect another. Frequently the signaling cascade leads to a change in gene expression that can affect cell functions such as proliferation, differentiation and homeostasis. The Janus kinase-signal transducer and activator of transcription (JAK-STAT) and the tumor necrosis factor receptor (TNFR) are the pivotal mechanisms employed for such communication. When deregulated, the JAK-STAT and the TNF receptor signaling pathways can induce chronic inflammatory phenotypes by promoting more cytokine production. Furthermore, these signaling pathways can promote replication, survival and metastasis of cancer cells. This review will summarize the essentials of the JAK/STAT and TNF signaling pathways and their regulation and the molecular mechanisms that lead to the dysregulation of the JAK-STAT pathway. The consequences of dysregulation, as ascertained from founding work in haematopoietic malignancies to more recent research in solid oral-gastrointestinal cancers, will also be discussed. Finally, this review will highlight the development and future of therapeutic applications which modulate the JAK-STAT or the TNF signaling pathways in cancers.

JAK Inhibition as a New Treatment Strategy for Patients with COVID-19

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) epidemic continues to spread globally. The rapid dispersion of coronavirus disease 2019 (COVID-19) caused by SARS-CoV-2 drives an urgent need for effective treatments, especially for patients who develop severe pneumonia. The excessive and uncontrolled release of pro-inflammatory cytokines has proved to be an essential factor in the rapidity of disease progression, and some cytokines are significantly associated with adverse outcomes. Most of the upregulated cytokines signal through the Janus kinase-signal transducer and activator of transcription (JAK/STAT) pathway. Therefore, blocking the exaggerated release of cytokines, including IL-2, IL-6, TNF-α, and IFNα/β/γ, by inhibiting JAK/STAT signaling will, presumably, offer favorable pharmacodynamics and present an attractive prospect. JAK inhibitors (JAKi) can also inhibit members of the numb-associated kinase (NAK) family, including AP2-associated kinase 1 (AAK1) and cyclin G-associated kinase (GAK), which regulate the angiotensin-converting enzyme 2 (ACE-2) transmembrane protein and are involved in host viral endocytosis. According to the data released from current clinical trials, JAKi treatment can effectively control the dysregulated cytokine storm and improve clinical outcomes regarding mortality, ICU admission, and discharge. There are still some concerns surrounding thromboembolic events, opportunistic infection such as herpes zoster virus reactivation, and repression of the host's type-I IFN-dependent immune repair for both viral and bacterial infection. However, the current JAKi clinical trials of COVID-19 raised no new safety concerns except a slightly increased risk of herpes virus infection. In the updated WHO guideline, Baricitinb is strongly recommended as an alternative to IL-6 receptor blockers, particularly in combination with corticosteroids, in patients with severe or critical COVID-19. Future studies will explore the application of JAKi to COVID-19 treatment in greater detail, such as the optimal timing and course of JAKi treatment, individualized medication strategies based on pharmacogenomics, and the effect of combined medications.

Tyrosine phosphorylation tunes chemical and thermal sensitivity of TRPV2 ion channel

Transient receptor potential vanilloid 2 (TRPV2) is a multimodal ion channel implicated in diverse physiopathological processes. Its important involvement in immune responses has been suggested such as in the macrophages’ phagocytosis process. However, the endogenous signaling cascades controlling the gating of TRPV2 remain to be understood. Here, we report that enhancing tyrosine phosphorylation remarkably alters the chemical and thermal sensitivities of TRPV2 endogenously expressed in rat bone marrow-derived macrophages and dorsal root ganglia (DRG) neurons. We identify that the protein tyrosine kinase JAK1 mediates TRPV2 phosphorylation at the molecular sites Tyr(335), Tyr(471), and Tyr(525). JAK1 phosphorylation is required for maintaining TRPV2 activity and the phagocytic ability of macrophages. We further show that TRPV2 phosphorylation is dynamically balanced by protein tyrosine phosphatase non-receptor type 1 (PTPN1). PTPN1 inhibition increases TRPV2 phosphorylation, further reducing the activation temperature threshold. Our data thus unveil an intrinsic mechanism where the phosphorylation/dephosphorylation dynamic balance sets the basal chemical and thermal sensitivity of TRPV2. Targeting this pathway will aid therapeutic interventions in physiopathological contexts.

All the cells in our body have a membrane that separates their interior from the outside environment. However, studded across this barrier are numerous ion channels which allow the cell to sense and react to changes in its surroundings. This includes the ion channel TRPV2, which opens in response to mechanical pressure, certain chemical signals, or rising temperature levels.

Many types of cell express TRPV2, including cells in the nervous system, muscle, and the immune system. However, despite being extensively studied, it is still not clear how TRPV2 opens and closes upon encountering high temperatures. In particular, previous work suggested that TRPV2 only responds when a cell’s surroundings reach around 52°C, which is a much higher temperature than cells inside our body normally encounter, even during a fever.

To help resolve this mystery, Mo, Pang et al. studied TRPV2 in neurons responsible for sending sensory information and in immune cells called macrophages which had been extracted from rodents and grown in the laboratory. They found that when the cells were bathed in solutions containing magnesium ions, their TRPV2 channels were more sensitive to a number of different cues, including temperature.

Further biochemical experiments showed that magnesium ions do not directly affect TRPV2, but increase the activity of another protein called JAK1. The magnesium ions caused JAK1 to attach specialized structures called phosphorylation tags to TRPV2. This modification (known as phosphorylation) made the channel more sensitive, allowing it to open in response to temperatures as low as 40°C.

Mo, Pang et al. found that inhibiting JAK1 reduced the activity of TRPV2. Conversely, inhibiting the enzyme that removes the phosphorylation tags, called PTPN1, increased the channel’s activity. They also discovered that when JAK1 was blocked, macrophages were less able to ‘eat up’ bacteria, which is one of their main roles in the immune system.

Taken together these experiments advance our understanding of how TRPV2 becomes active. The balance between the phosphorylation by JAK1 and the dephosphorylation by PTPN1 controls the temperature at which TRPV2 opens. Since TRPV2 contributes to several biological functions, including the development of the nervous system, the maintenance of heart muscles, and inflammation, these findings will be important to scientists in a broad range of fields.

The Interaction Between Autophagy and JAK/STAT3 Signaling Pathway in Tumors

Tumor is one of the important factors affecting human life and health in today’s world, and scientists have studied it extensively and deeply, among which autophagy and JAK/STAT3 signaling pathway are two important research directions. The JAK/STAT3 axis is a classical intracellular signaling pathway that assumes a key role in the regulation of cell proliferation, apoptosis, and vascular neogenesis, and its abnormal cell signaling and regulation are closely related to the occurrence and development of tumors. Therefore, the JAK/STAT3 pathway in tumor cells and various stromal cells in their microenvironment is often considered as an effective target for tumor therapy. Autophagy is a process that degrades cytoplasmic proteins and organelles through the lysosomal pathway. It is a fundamental metabolic mechanism for intracellular degradation. The mechanism of action of autophagy is complex and may play different roles at various stages of tumor development. Altered STAT3 expression has been found to be accompanied by the abnormal autophagy activity in many oncological studies, and the two may play a synergistic or antagonistic role in promoting or inhibiting the occurrence and development of tumors. This article reviews the recent advances in autophagy and its interaction with JAK/STAT3 signaling pathway in the pathogenesis, prevention, diagnosis, and treatment of tumors.

Design, Synthesis and Activity Study of Pyridine Derivatives as Highly Effective and Selective TYK2 Inhibitors

Due to the high homology of the ATP sites of the JAK family, the development of selective inhibitors for a certain JAK isoform is extremely challenging. Our strategy to achieve high selectivity for TYK2 relies on targeting the TYK2 pseudokinase (JH2) domain. Based on the clinical compound BMS-986165, through structure-activity relationship studies, a class of acyl compounds with excellent TYK2 inhibitory activity and selectivity to other subtypes of the JAK family was discovered.