PI3Kγ inhibition alleviates symptoms and increases axon number in experimental autoimmune encephalomyelitis mice

Targeting PI3Kγ in cancer

The phosphoinositide 3-kinases (PI3Ks) have been the focus of a significant body of cancer research since their discovery nearly 40 years ago. These lipid kinases are now known to play central roles in cancer cell proliferation, survival, migration, metabolism, and immunity and serve as the target of numerous investigational and approved therapeutics. One of these kinases, the unique class IB PI3Kγ, which is highly expressed in myeloid lineage cells and myeloid leukemias, plays prominent roles in tumor immune suppression. Inhibition of this kinase has promoted improved antitumor immune responses in recent solid tumor preclinical studies and clinical trials. New studies also identify this kinase as a driver of acute myeloid leukemia self-renewal and as a new target for the treatment of aggressive leukemias.

Patients with multiple sclerosis who develop immunogenicity to interferon-beta have distinct transcriptomic and proteomic signatures prior to treatment which are associated with disease severity

Anti-drug antibodies (ADA) reduce the efficacy of immunotherapies in multiple sclerosis (MS) and are associated with increased disease progression risk. Blood biomarkers predicting immunogenicity to biopharmaceuticals represent an unmet clinical need. Patients with relapsing remitting (RR)MS were recruited before (baseline), three, and 12 (M12) months after commencing interferon-beta treatment. Neutralising ADA-status was determined at M12, and patients were stratified at baseline according to their M12 ADA-status (ADA-positive/ADA-negative). Patients stratified as ADA-positive were characterised by an early dampened response to interferon-beta (prior to serum ADA detection) and distinct proinflammatory transcriptomic/proteomic peripheral blood signatures enriched for 'immune response activation' including phosphoinositide 3-kinase-γ and NFκB-signalling pathways both at baseline and throughout the treatment course, compared to ADA-negative patients. These immunogenicity-associated proinflammatory signatures significantly overlapped with signatures of MS disease severity. Thus, whole blood molecular profiling is a promising tool for prediction of ADA-development in RRMS and could provide insight into mechanisms of immunogenicity.

Designing Small Molecule PI3Kγ Inhibitors: A Review of Structure-Based Methods and Computational Approaches

The PI3K/AKT/mTOR pathway plays critical roles in a wide array of biological processes. Phosphatidylinositol 3-kinase gamma (PI3Kγ), a class IB PI3K family member, represents a potential therapeutic opportunity for the treatment of cancer, inflammation, and autoimmunity. In this Perspective, we provide a comprehensive overview of the structure, biological function, and regulation of PI3Kγ. We also focus on the development of PI3Kγ inhibitors over the past decade and emphasize their binding modes, structure-activity relationships, and pharmacological activities. The application of computational technologies and artificial intelligence in the discovery of novel PI3Kγ inhibitors is also introduced. This review aims to provide a timely and updated overview on the strategies for targeting PI3Kγ.

Development of PI3Kγ selective inhibitors: the strategies and application

The γ isoform of Class I PI3Ks (PI3Kγ) is primarily found in leukocytes and is essential for the function of myeloid cells, as it regulates the migration, differentiation, and activation of myeloid-lineage immune cells. Thus, PI3Kγ has been identified as a promising drug target for the treatment of inflammation, autoimmune disease, and immuno-oncology. Due to the high incidence of serious adverse events (AEs) associated with PI3K inhibitors, in the development of PI3Kγ inhibitors, isoform selectivity was deemed crucial. In this review, an overview of the development of PI3Kγ selective inhibitors in the past years is provided. The isoform selectivity of related drugs was achieved by different strategies, including inducing a specificity pocket by a propeller-shape structure, targeting steric differences in the solvent channel, and modulating the conformation of the Asp-Phe-Gly DFG motif, which have been demonstrated feasible by several successful cases. The insights in this manuscript may provide a potential direction for rational drug design and accelerate the discovery of PI3Kγ selective inhibitors.

Inhibition of phosphoinositide‑3 kinases γ/δ ameliorates pulmonary granuloma by rescuing Treg function in a sarcoidosis model

Sarcoidosis is a multisystem inflammatory disease characterized by the development of Th1/Th17/regulatory T cells (Tregs)-related non-caseating granulomas. Phosphoinositide-3 kinases δ/γ (PI3Kδ/γ) play an important role in the maintenance of effective immunity, especially for Tregs homeostasis and stability. In the present study, superoxide dismutase A (SodA) stimulation was used to establish the sarcoidosis mouse model. The second immune stimulus was accompanied by CAL-101 (PI3Kδ inhibitor) or AS-605240 (PI3Kδ/γ inhibitor) treatment. To detect the effect of the PI3Kδ/γ inhibitor on the morphology of pulmonary granuloma and the activation of the PI3K signaling pathway, hematoxylin and eosin staining and immunofluorescence and western blotting was used, respectively. Fluorescence-activated cell sorting analysis and reverse transcription-quantitative PCR were adopted to detect the effect of the PI3Kδ/γ inhibitor on the SodA-induced sarcoidosis mouse model in respect to immune cell disorder and the function of Treg cells, with CD4⁺CD25^- T cells and CD4⁺CD25⁺ T cells sorted by magnetic cell sorting. The results demonstrated that the inhibition of PI3Kδ/γ by transtracheal CAL-101/AS-605240 administration facilitated pulmonary granuloma formation. These therapeutic effects were associated with certain mechanisms, including suppressing the aberrantly activated PI3K/Akt signaling in both pulmonary granuloma and Tregs, particularly rescuing the suppressive function of Tregs. Notably, CAL-101 was more effective in immune modulation compared with AS-605240 and could overcome the aberrantly activated Akt in the lung and Tregs. These results suggest that PI3K/Akt signaling, especially the PI3Kδ subunit, can play a key role in optimal Tregs-mediated protection against pulmonary sarcoidosis. Therefore, transtracheal usage of PI3Kδ/γ inhibitors is an attractive therapy that may be developed into a new immune-therapeutic principle for sarcoidosis in the future.

The role of PI3Kγ in the immune system: new insights and translational implications

Over the past two decades, new insights have positioned phosphoinositide 3-kinase-γ (PI3Kγ) as a context-dependent modulator of immunity and inflammation. Recent advances in protein structure determination and drug development have allowed for generation of highly specific PI3Kγ inhibitors, with the first now in clinical trials for several oncology indications. Recently, a monogenic immune disorder caused by PI3Kγ deficiency was discovered in humans and modelled in mice. Human inactivated PI3Kγ syndrome confirms the immunomodulatory roles of PI3Kγ and strengthens newly defined roles of this molecule in modulating inflammatory cytokine release in macrophages. Here, we review the functions of PI3Kγ in the immune system and discuss how our understanding of its potential as a therapeutic target has evolved.

The Role of PI3K Isoforms in Autoimmune Disease

Aberrant overactivation of the immune system can give rise to chronic and persistent self-attack, culminating in autoimmune disease. This is currently managed therapeutically using potent immunosuppressive and anti-inflammatory drugs. Class I phosphoinositide-3-kinases (PI3Ks) have been identified as ideal therapeutic targets for autoimmune diseases given their wide-ranging roles in immunological processes. Although progress has been hampered by issues such as poor drug tolerance and drug resistance, several PI3K inhibitors have now received regulatory approval with many others in development, including several intended to suppress the immune response in autoimmune and inflammatory diseases. This chapter reviews the evidence for contribution of aberrant PI3K activity to a range of autoimmune diseases (rheumatoid arthritis, systemic lupus erythematosus, multiple sclerosis and type I diabetes) and possible therapeutic application of isoform-specific PI3K inhibitors as immunosuppressive drugs.

Gene expression signatures of target tissues in type 1 diabetes, lupus erythematosus, multiple sclerosis, and rheumatoid arthritis

Autoimmune diseases are typically studied with a focus on the immune system, and less attention is paid to responses of target tissues exposed to the immune assault. We presently evaluated, based on available RNA sequencing data, whether inflammation induces similar molecular signatures at the target tissues in type 1 diabetes, systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis. We identified confluent signatures, many related to interferon signaling, indicating pathways that may be targeted for therapy, and observed a high (>80%) expression of candidate genes for the different diseases at the target tissue level. These observations suggest that future research on autoimmune diseases should focus on both the immune system and the target tissues, and on their dialog. Discovering similar disease-specific signatures may allow the identification of key pathways that could be targeted for therapy, including the repurposing of drugs already in clinical use for other diseases.

Ellagic acid ameliorates neuroinflammation and demyelination in experimental autoimmune encephalomyelitis: Involvement of NLRP3 and pyroptosis

Multiple sclerosis (MS) is presented as the most common autoimmune and demyelinating neurological disorder with incapacitating complications and with no definite therapy. Most treatments for MS mainly focus on attenuation of its severity and recurrence. To model MS reliably to study pathogenesis and efficacy of possible chemicals, experimental autoimmune encephalomyelitis (EAE) condition is induced in rodents. Ellagic acid is a neuroprotective polyphenol that can protect against demyelination. This study was planned and conducted to assess its possible beneficial effect in MOG-induced EAE model of MS with emphasis on uncovering its modes of action. Ellagic acid was given p.o. (at doses of 10 or 50 mg/kg/day) after development of clinical signs of MS to C57BL/6 mice immunized with MOG_35-55. Results showed that ellagic acid can ameliorate severity of the disease and partially restore tissue level of TNFα, IL-6, IL-17A and IL-10. Besides, ellagic acid lowered tissue levels of NLRP3 and caspase 1 in addition to its mitigation of neuroinflammation, demyelination and axonal damage in spinal cord specimens of EAE group. As well, ellagic acid treatment prevented reduction of MBP and decreased GFAP and Iba1 immunoreactivity. Taken together, ellagic acid can decrease severity of EAE via amelioration of astrogliosis, astrocyte activation, demyelination, neuroinflammation and axonal damage that is partly related to its effects on NLRP3 inflammasome and pyroptotic pathway.

Should mast cells be considered therapeutic targets in multiple sclerosis?

Mast cells are immune cells of the myeloid lineage that are found throughout the body, including the central nervous system. They perform many functions associated with innate and specific immunity, angiogenesis, and vascular homeostasis. Moreover, they have been implicated in a series of pathologies (e.g., hypersensitivity reactions, tumors, and inflammatory disorders). In this review, we propose that this cell could be a relevant therapeutic target in multiple sclerosis, which is a central nervous system degenerative disease. To support this proposition, we describe the general biological properties of mast cells, their contribution to innate and specific immunity, and the participation of mast cells in the various stages of multiple sclerosis and experimental autoimmune encephalomyelitis development. The final part of this review is dedicated to an overview of the available mast cells immunomodulatory drugs and their activity on multiple sclerosis and experimental autoimmune encephalomyelitis, including our own experience related to the effect of ketotifen fumarate on experimental autoimmune encephalomyelitis evolution.

Sinomenine Alleviates Murine Experimental Autoimmune Encephalomyelitis Model of Multiple Sclerosis through Inhibiting NLRP3 Inflammasome

Multiple sclerosis (MS) is known as a chronic neuroinflammatory disorder typified by an immune-mediated demyelination process with ensuing axonal damage and loss. Sinomenine is a natural alkaloid with different therapeutic benefits, including anti-inflammatory and immunosuppressive activities. In this study, possible beneficial effects of sinomenine in an MOG-induced model of MS were determined. Sinomenine was given to MOG_35-55-immunized C57BL/6 mice at doses of 25 or 100 mg/kg/day after onset of MS clinical signs till day 30 post-immunization. Analyzed data showed that sinomenine reduces severity of the clinical signs and to some extent decreases tissue level of pro-inflammatory cytokines IL-1β, IL-6, IL-18, TNFα, IL-17A, and increases level of anti-inflammatory IL-10. In addition, sinomenine successfully attenuated tissue levels of inflammasome NLRP3, ASC, and caspase 1 besides its reduction of intensity of neuroinflammation, demyelination, and axonal damage and loss in lumbar spinal cord specimens. Furthermore, immunoreactivity for MBP decreased and increased for GFAP and Iba1 after MOG-immunization, which was in part reversed upon sinomenine administration. Overall, sinomenine decreases EAE severity, which is attributed to its alleviation of microglial and astrocytic mobilization, demyelination, and axonal damage along with its suppression of neuroinflammation, and its beneficial effect is also associated with its inhibitory effects on inflammasome and pyroptotic pathways; this may be of potential benefit for the primary progressive phenotype of MS.

PI3K activity in dendritic cells exerts paradoxical effects during autoimmune inflammation

The peripheral activation of autoreactive T cells and subsequent central nervous system (CNS) immune cell infiltration are key events relevant for experimental autoimmune encephalomyelitis (EAE), a commonly employed multiple sclerosis (MS) model, influenced by TH1 and TH17 mediated immunity. The phosphoinositide-3-kinase (PI3K)-AKT kinase pathway modulates outcome during EAE, with direct actions of PI3K on adaptive immunity implicated in deleterious and effects on antigen presenting cells involved in beneficial responses during EAE. Here, by genetically deleting the regulatory subunit of Class Ia PI3K, p85α, in selective myeloid cells, we aimed to resolve the impact of PI3K in EAE. While genetically deleting PI3K in LysM expressing cells exerted unremarkable effects, attenuating PI3K function in CD11c+ dendritic cells (DCs), promoted secretion of pathogenic EAE promoting cytokines, particularly skewing TH1 and TH17 immunity, while notably, improving health in EAE. Neutralizing IFN-γ activity using blocking antibodies revealed a prolonged TH1 response was critical for the decreased disease of these animals. Thus, PI3K-AKT signaling in DCs acts in a paradoxical manner. While attenuating EAE associated TH1 and TH17 responses, it impairs health during autoimmune inflammation.

Stem Cell-Derived Exosomes as Nanotherapeutics for Autoimmune and Neurodegenerative Disorders

To dissect therapeutic mechanisms of transplanted stem cells and develop exosome-based nanotherapeutics in treating autoimmune and neurodegenerative diseases, we assessed the effect of exosomes secreted from human mesenchymal stem cells (MSCs) in treating multiple sclerosis using an experimental autoimmune encephalomyelitis (EAE) mouse model. We found that intravenous administration of exosomes produced by MSCs stimulated by IFNγ (IFNγ-Exo) (i) reduced the mean clinical score of EAE mice compared to PBS control, (ii) reduced demyelination, (iii) decreased neuroinflammation, and (iv) upregulated the number of CD4+CD25+FOXP3+ regulatory T cells (Tregs) within the spinal cords of EAE mice. Co-culture of IFNγ-Exo with activated peripheral blood mononuclear cells (PBMCs) cells in vitro reduced PBMC proliferation and levels of pro-inflammatory Th1 and Th17 cytokines including IL-6, IL-12p70, IL-17AF, and IL-22 yet increased levels of immunosuppressive cytokine indoleamine 2,3-dioxygenase. IFNγ-Exo could also induce Tregs in vitro in a murine splenocyte culture, likely mediated by a third-party accessory cell type. Further, IFNγ-Exo characterization by deep RNA sequencing suggested that IFNγ-Exo contains anti-inflammatory RNAs, where their inactivation partially hindered the exosomes potential to induce Tregs. Furthermore, we found that IFNγ-Exo harbors multiple anti-inflammatory and neuroprotective proteins. These results not only shed light on stem cell therapeutic mechanisms but also provide evidence that MSC-derived exosomes can potentially serve as cell-free therapies in creating a tolerogenic immune response to treat autoimmune and central nervous system disorders.

Synthesis of a 6-Aza-Isoindolinone-Based Inhibitor of Phosphoinositide 3-Kinase γ via Ruthenium-Catalyzed [2 + 2 + 2] Cyclotrimerization

Phosphoinositide 3-kinase (PI3Kγ) is a drug target that has been implicated in the treatment of a range of diseases. We have developed a synthesis of a novel PI3Kγ inhibitor containing a 1,2-dihydro-3H-pyrrolo[3,4-c]pyridin-3-one scaffold. The key step in the synthesis involved a ruthenium-catalyzed [2 + 2 + 2] cyclotrimerization reaction between a diyne and an alkoxycarbonyl isocyanate, a previously unreported coupling partner in such a reaction.

Design and Synthesis of a Novel Series of Orally Bioavailable, CNS-Penetrant, Isoform Selective Phosphoinositide 3-Kinase γ (PI3Kγ) Inhibitors with Potential for the Treatment of Multiple Sclerosis (MS)

The lipid kinase phosphoinositide 3-kinase γ (PI3Kγ) has attracted attention as a potential target to treat a variety of autoimmune disorders, including multiple sclerosis, due to its role in immune modulation and microglial activation. By minimizing the number of hydrogen bond donors while targeting a previously uncovered selectivity pocket adjacent to the ATP binding site of PI3Kγ, we discovered a series of azaisoindolinones as selective, brain penetrant inhibitors of PI3Kγ. This ultimately led to the discovery of 16, an orally bioavailable compound that showed efficacy in murine experimental autoimmune encephalomyelitis (EAE), a preclinical model of multiple sclerosis.

MicroRNA-204-3p inhibits lipopolysaccharide-induced cytokines in familial Mediterranean fever via the phosphoinositide 3-kinase γ pathway

Objective

We sought to identify the microRNA (miRNA) profile and potential biomarkers in FMF and to clarify their gene targets to elucidate the pathogenesis of FMF.

Methods

We performed an miRNA microarray using serum from FMF patients in attack and in remission. We then examined the expression of miRNAs in macrophages derived from THP-1 cells stimulated with toll-like receptor (TLR) ligands. Macrophages derived from THP-1 cells transfected with pre-miRNA were stimulated with lipopolysaccharides (LPSs) for the quantification of inflammatory cytokine production. To identify the target genes, we overexpressed their miRNA and performed a complementary DNA microarray. Transfection with reporter construct and the precursor miRNA was performed to confirm the suppression of target mRNA.

Results

We found that miR-204-3p was greatly decreased in the serum from FMF patients in attack. The expression of miR-204-3p was suppressed by LPS stimulation in the macrophages derived from THP-1 cells and the inhibition of miR-204-3p significantly induced the production of TLR4-related cytokines. The bioinformatic analysis showed that miR-204-3p is predicted to target genes implicated in the TLR pathway through the regulation of PI3Kγ signalling. The reporter assay revealed that miR-204-3p directly suppressed the luciferase activity of 3'-UTR of PIK3CG reporter construct. The inhibition of PI3Kγ resulted in decreased amounts of IL-6 and IL-12p40 in monocytes from FMF patients.

Conclusion

These data suggest that serum miR-204-3p has potential as a useful biomarker in FMF patients and that miR-204-3p serves as a suppressor of inflammatory cytokine production in FMF by targeting the PI3Kγ pathway.

Cre-inducible human CD59 mediates rapid cell ablation after intermedilysin administration

Cell ablation is a powerful tool for studying cell lineage and/or function; however, current cell-ablation models have limitations. Intermedilysin (ILY), a cytolytic pore-forming toxin that is secreted by Streptococcus intermedius, lyses human cells exclusively by binding to the human complement regulator CD59 (hCD59), but does not react with CD59 from nonprimates. Here, we took advantage of this feature of ILY and developed a model of conditional and targeted cell ablation by generating floxed STOP-CD59 knockin mice (ihCD59), in which expression of human CD59 only occurs after Cre-mediated recombination. The administration of ILY to ihCD59+ mice crossed with various Cre-driver lines resulted in the rapid and specific ablation of immune, epithelial, or neural cells without off-target effects. ILY had a large pharmacological window, which allowed us to perform dose-dependent studies. Finally, the ILY/ihCD59-mediated cell-ablation method was tested in several disease models to study immune cell functionalities, hepatocyte and/or biliary epithelial damage and regeneration, and neural cell damage. Together, the results of this study demonstrate the utility of the ihCD59 mouse model for studying the effects of cell ablation in specific organ systems in a variety of developmental and disease states.

PI3K inhibitors in inflammation, autoimmunity and cancer

The healthy immune system protects against infection and malignant transformation without causing significant damage to host tissues. Immune dysregulation results in diverse pathologies including autoimmune disease, chronic inflammatory disorders, allergies as well as immune deficiencies and cancer. Phosphoinositide 3-kinase (PI3K) signalling has been shown to be a key pathway in the regulation of the immune response and continues to be the focus of intense research. In recent years we have gained detailed understanding of PI3K signalling, and saw the development of potent and highly selective small molecule inhibitors, of which several are currently in clinical trials for the treatment of immune-related disorders and cancer. The role of PI3K signalling in the immune response has been the subject of detailed reviews; here we focus on relevant recent progress in pre-clinical and clinical development of PI3K inhibitors.

Phosphatidylinositol 3-Kinase γ is required for the development of experimental cerebral malaria

Experimental cerebral malaria (ECM) is characterized by a strong immune response, with leukocyte recruitment, blood-brain barrier breakdown and hemorrhage in the central nervous system. Phosphatidylinositol 3-kinase γ (PI3Kγ) is central in signaling diverse cellular functions. Using PI3Kγ-deficient mice (PI3Kγ-/-) and a specific PI3Kγ inhibitor, we investigated the relevance of PI3Kγ for the outcome and the neuroinflammatory process triggered by Plasmodium berghei ANKA (PbA) infection. Infected PI3Kγ-/- mice had greater survival despite similar parasitemia levels in comparison with infected wild type mice. Histopathological analysis demonstrated reduced hemorrhage, leukocyte accumulation and vascular obstruction in the brain of infected PI3Kγ-/- mice. PI3Kγ deficiency also presented lower microglial activation (Iba-1+ reactive microglia) and T cell cytotoxicity (Granzyme B expression) in the brain. Additionally, on day 6 post-infection, CD3+CD8+ T cells were significantly reduced in the brain of infected PI3Kγ-/- mice when compared to infected wild type mice. Furthermore, expression of CD44 in CD8+ T cell population in the brain tissue and levels of phospho-IkB-α in the whole brain were also markedly lower in infected PI3Kγ-/- mice when compared with infected wild type mice. Finally, AS605240, a specific PI3Kγ inhibitor, significantly delayed lethality in infected wild type mice. In brief, our results indicate a pivotal role for PI3Kγ in the pathogenesis of ECM.

PIPs in neurological diseases

Phosphoinositide (PIP) lipids regulate many aspects of cell function in the nervous system including receptor signalling, secretion, endocytosis, migration and survival. Levels of PIPs such as PI4P, PI(4,5)P2 and PI(3,4,5)P3 are normally tightly regulated by phosphoinositide kinases and phosphatases. Deregulation of these biochemical pathways leads to lipid imbalances, usually on intracellular endosomal membranes, and these changes have been linked to a number of major neurological diseases including Alzheimer's, Parkinson's, epilepsy, stroke, cancer and a range of rarer inherited disorders including brain overgrowth syndromes, Charcot-Marie-Tooth neuropathies and neurodevelopmental conditions such as Lowe's syndrome. This article analyses recent progress in this area and explains how PIP lipids are involved, to varying degrees, in almost every class of neurological disease. This article is part of a Special Issue entitled Brain Lipids.

PI3K signalling in inflammation

PI3Ks regulate several key events in the inflammatory response to damage and infection. There are four Class I PI3K isoforms (PI3Kα,β,γ,δ), three Class II PI3K isoforms (PI3KC2α, C2β, C2γ) and a single Class III PI3K. The four Class I isoforms synthesise the phospholipid 'PIP3'. PIP3 is a 'second messenger' used by many different cell surface receptors to control cell movement, growth, survival and differentiation. These four isoforms have overlapping functions but each is adapted to receive efficient stimulation by particular receptor sub-types. PI3Kγ is highly expressed in leukocytes and plays a particularly important role in chemokine-mediated recruitment and activation of innate immune cells at sites of inflammation. PI3Kδ is also highly expressed in leukocytes and plays a key role in antigen receptor and cytokine-mediated B and T cell development, differentiation and function. Class III PI3K synthesises the phospholipid PI3P, which regulates endosome-lysosome trafficking and the induction of autophagy, pathways involved in pathogen killing, antigen processing and immune cell survival. Much less is known about the function of Class II PI3Ks, but emerging evidence indicates they can synthesise PI3P and PI34P2 and are involved in the regulation of endocytosis. The creation of genetically-modified mice with altered PI3K signalling, together with the development of isoform-selective, small-molecule PI3K inhibitors, has allowed the evaluation of the individual roles of Class I PI3K isoforms in several mouse models of chronic inflammation. Selective inhibition of PI3Kδ, γ or β has each been shown to reduce the severity of inflammation in one or more models of autoimmune disease, respiratory disease or allergic inflammation, with dual γ/δ or β/δ inhibition generally proving more effective. The inhibition of Class I PI3Ks may therefore offer a therapeutic opportunity to treat non-resolving inflammatory pathologies in humans. This article is part of a Special Issue entitled Phosphoinositides.