SHIP1-expressing mesenchymal stem cells regulate hematopoietic stem cell homeostasis and lineage commitment during aging

Loss of Inpp5d has disease-relevant and sex-specific effects on glial transcriptomes

INTRODUCTION

Inpp5d is genetically associated with Alzheimer's disease risk. Loss of Inpp5d alters amyloid pathology in models of amyloidosis. Inpp5d is expressed predominantly in microglia but its function in brain is poorly understood.

METHODS

We performed single-cell RNA sequencing to study the effect of Inpp5d loss on wild-type mouse brain transcriptomes.

RESULTS

Loss of Inpp5d has sex-specific effects on the brain transcriptome. Affected genes are enriched for multiple neurodegeneration terms. Network analyses reveal a gene co-expression module centered around Inpp5d in female mice. Inpp5d loss alters Pleotrophin (PTN), Prosaposin (PSAP), and Vascular Endothelial Growth Factor A (VEGFA) signaling probability between cell types.

DISCUSSION

Our data suggest that the normal function of Inpp5d is entangled with mechanisms involved in neurodegeneration. We report the effect of Inpp5d loss without pathology and show that this has dramatic effects on gene expression. Our study provides a critical reference for researchers of neurodegeneration, allowing separation of disease-specific changes mediated by Inpp5d in disease from baseline effects of Inpp5d loss.

HIGHLIGHTS

Loss of Inpp5d has different effects in male and female mice. Genes dysregulated by Inpp5d loss relate to neurodegeneration. Total loss of Inpp5d in female mice collapses a conserved gene co-expression module. Loss of microglial Inpp5d affects the transcriptome of other cell types.

SHIP1 and its role for innate immune regulation-Novel targets for immunotherapy

Phosphoinositide-3-kinase/AKT (PI3K/AKT) signaling plays key roles in the regulation of cellular activity in both health and disease. In immune cells, this PI3K/AKT pathway is critically regulated by the phosphoinositide phosphatase SHIP1, which has been reported to modulate the function of most immune subsets. In this review, we summarize our current knowledge of SHIP1 with a focus on innate immune cells, where we reflect on the most pertinent aspects described in the current literature. We also present several small-molecule agonists and antagonists of SHIP1 developed over the last two decades, which have led to improved outcomes in several preclinical models of disease. We outline these promising findings and put them in relation to human diseases with unmet medical needs, where we discuss the most attractive targets for immune therapies based on SHIP1 modulation.

Targeting SHIP1 and SHIP2 in Cancer

Simple Summary

Phosphoinositol signaling pathways and their dysregulation have been shown to have a fundamental role in health and disease, respectively. The SH2-containing 5′ inositol phosphatases, SHIP1 and SHIP2, are regulators of the PI3K/AKT pathway that have crucial roles in cancer progression. This review aims to summarize the role of SHIP1 and SHIP2 in cancer signaling and the immune response to cancer, the discovery and use of SHIP inhibitors and agonists as possible cancer therapeutics.

Abstract

Membrane-anchored and soluble inositol phospholipid species are critical mediators of intracellular cell signaling cascades. Alterations in their normal production or degradation are implicated in the pathology of a number of disorders including cancer and pro-inflammatory conditions. The SH2-containing 5′ inositol phosphatases, SHIP1 and SHIP2, play a fundamental role in these processes by depleting PI(3,4,5)P₃, but also by producing PI(3,4)P₂ at the inner leaflet of the plasma membrane. With the intent of targeting SHIP1 or SHIP2 selectively, or both paralogs simultaneously, small molecule inhibitors and agonists have been developed and tested in vitro and in vivo over the last decade in various disease models. These studies have shown promising results in various pre-clinical models of disease including cancer and tumor immunotherapy. In this review the potential use of SHIP inhibitors in cancer is discussed with particular attention to the molecular structure, binding site and efficacy of these SHIP inhibitors.

Small molecule targeting of SHIP1 and SHIP2

Modulating the activity of the Src Homology 2 (SH2) — containing Inositol 5′-Phosphatase (SHIP) enzyme family with small molecule inhibitors provides a useful and unconventional method of influencing cell signaling in the PI3K pathway. The development of small molecules that selectively target one of the SHIP paralogs (SHIP1 or SHIP2) as well as inhibitors that simultaneously target both enzymes have provided promising data linking the phosphatase activity of the SHIP enzymes to disorders and disease states that are in dire need of new therapeutic targets. These include cancer, immunotherapy, diabetes, obesity, and Alzheimer's disease. In this mini-review, we will provide a brief overview of research in these areas that support targeting SHIP1, SHIP2 or both enzymes for therapeutic purposes.

Pan-SHIP1/2 inhibitors promote microglia effector functions essential for CNS homeostasis

We show here that both SHIP1 (Inpp5d) and its paralog SHIP2 (Inppl1) are expressed at protein level in microglia. To examine whether targeting of SHIP paralogs might influence microglial physiology and function, we tested the capacity of SHIP1-selective, SHIP2-selective and pan-SHIP1/2 inhibitors for their ability to impact on microglia proliferation, lysosomal compartment size and phagocytic function. We find that highly potent pan-SHIP1/2 inhibitors can significantly increase lysosomal compartment size, and phagocytosis of dead neurons and amyloid beta (Aβ)1-42 by microglia in vitro We show that one of the more-potent and water-soluble pan-SHIP1/2 inhibitors, K161, can penetrate the blood-brain barrier. Consistent with this, K161 increases the capacity of CNS-resident microglia to phagocytose Aβ and apoptotic neurons following systemic administration. These findings provide the first demonstration that small molecule modulation of microglia function in vivo is feasible, and suggest that dual inhibition of the SHIP1 and 2 paralogs can provide a novel means to enhance basal microglial homeostatic functions for therapeutic purposes in Alzheimer's disease and, possibly, other types of dementia where increased microglial function could be beneficial.

Integrated Transcriptome Analysis of microRNA and mRNA in Mouse Skin Derived Precursors (SKPs) and SKP Derived Fibroblast (SFBs) by RNA-Seq

Background:

Skin-derived precursors (SKPs) display the characteristics of self-renewal and multilineage differentiation.

Objective:

The study aimed to explore the molecular mechanisms of mouse SKPs differentiation into SKP-derived fibroblasts (SFBs).

Methods:

We compared the microRNA (miRNA) profile in mouse SKPs and SFBs by RNA sequenc-ing. Real-time quantitative reverse transcription PCR (qRT-PCR) was performed to validate the miRNA expression. The integrated analysis of miRNA and mRNA expression data was performed to explore the potential crosstalk of miRNA-mRNA in SKP differentiation.

Results:

207 differentially expressed miRNAs and 835 miRNA target genes in the gene list of integrated mRNA expression profiling were identified. Gene Ontology (GO) enrichment analysis revealed that cell differentiation and cell proliferation process were significantly enriched. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed the target genes were significantly most enriched in the cytokine-cytokine receptor interaction, cancer pathways and axon guidance signaling pathway. The most upregulated and downregulated target genes were involved in the Wnt, Notch, cytokine-cytokine receptor interaction, TGF-β, p53 and apoptotic signaling pathway. The miRNA-mRNA regulatory net-works and 507 miRNA-mRNA pairs were constructed. Seven miRNAs (miR-486-3p, miR-504-5p, miR-149-3p, miR-31-5p, miR-484, miR-328-5p and miR-22-5p) and their target genes Wnt4, Dlx2, Se-ma4f, Kit, Kitl, Inpp5d, Igfbp3, Prdm16, Sfn, Irf6 and Clu were identified as miRNA-mRNA crosstalk pairs.

Conclusion:

These genes and signaling pathways might control SKPs proliferation and SKPs differen-tiation into SFBs during the process of SKPs differentiation, which might promote the application of SKPs in the clinical treatment of skin-related diseases by regulating SKPs proliferation and SKPs differ-entiation.

Regulation of hematopoietic cell signaling by SHIP-1 inositol phosphatase: growth factors and beyond

SHIP-1 is a hematopoietic-specific inositol phosphatase activated downstream of a multitude of receptors including those for growth factors, cytokines, antigen, immunoglobulin and toll-like receptor agonists where it exerts inhibitory control. While it is constitutively expressed in all immune cells, SHIP-1 expression is negatively regulated by the inflammatory and oncogenic micro-RNA miR-155. Knockout mouse studies have shown the importance of SHIP-1 in various immune cell subsets and have revealed a range of immune-mediated pathologies that are engendered due to loss of SHIP-1's regulatory activity, impelling investigations into the role of SHIP-1 in human disease. In this review, we provide an overview of the literature relating to the role of SHIP-1 in hematopoietic cell signaling and function, we summarize recent reports that highlight the dysregulation of the SHIP-1 pathway in cancers, autoimmune disorders and inflammatory diseases, and lastly we discuss the importance of SHIP-1 in restraining myeloid growth factor signaling.

Conditional deletion of Ahr alters gene expression profiles in hematopoietic stem cells

The aryl hydrocarbon receptor (AHR) is a ligand activated bHLH transcription factor that belongs to the Per-Arnt-Sim (PAS) superfamily of proteins involved in mediating responses to cellular environment regulating normal physiological and developmental pathways. The AHR binds a broad range of naturally derived and synthetic compounds, and plays a major role in mediating effects of certain environmental chemicals. Although our understanding of the physiological roles of the AHR in the immune system is evolving, there is little known about its role in hematopoiesis and hematopoietic diseases. Prior studies demonstrated that AHR null (AHR-KO) mice have impaired hematopoietic stem cell (HSC) function; they develop myeloproliferative changes in peripheral blood cells, and alterations in hematopoietic stem and progenitor cell populations in the bone marrow. We hypothesized mice lacking AHR expression only within hematopoietic cells (AHRVav1 mice) would develop similar changes. However, we did not observe a complete phenocopy of AHR-KO and AHRVav1 animals at 2 or 18 months of age. To illuminate the signaling mechanisms underlying the alterations in hematopoiesis observed in these mice, we sorted a population of cells highly enriched for HSC function (LSK cells: CD34-CD48-CD150+) and performed microarray analyses. Ingenuity Pathway and Gene Set Enrichment Analyses revealed that that loss of AHR within HSCs alters several gene and signaling networks important for HSC function. Differences in gene expression networks among HSCs from AHR-KO and AHRVav1 mice suggest that AHR in bone marrow stromal cells also contributes to HSC function. In addition, numerous studies have suggested a role for AHR in both regulation of hematopoietic cells, and in the development of blood diseases. More work is needed to define what these signals are, and how they act upon HSCs.

Local delivery of tetramethylpyrazine eliminates the senescent phenotype of bone marrow mesenchymal stromal cells and creates an anti-inflammatory and angiogenic environment in aging mice

Aging drives the accumulation of senescent cells (SnCs) including stem/progenitor cells in bone marrow, which contributes to aging‐related bone degenerative pathologies. Local elimination of SnCs has been shown as potential treatment for degenerative diseases. As LepR⁺ mesenchymal stem/progenitor cells (MSPCs) in bone marrow are the major population for forming bone/cartilage and maintaining HSCs niche, whether local elimination of senescent LepR⁺MSPCs delays aging‐related pathologies and improves local microenvironment need to be well defined. In this study, we performed local delivery of tetramethylpyrazine (TMP) in bone marrow of aging mice, which previously showed to be used for the prevention and treatment of glucocorticoid‐induced osteoporosis (GIOP). We found the increased accumulation of senescent LepR⁺MSPCs in bone marrow of aging mice, and TMP significantly inhibited the cell senescent phenotype via modulating Ezh2‐H3k27me3. Most importantly, local delivery of TMP improved bone marrow microenvironment and maintained bone homeostasis in aging mice by increasing metabolic and anti‐inflammatory responses, inducing H‐type vessel formation, and maintaining HSCs niche. These findings provide evidence on the mechanisms, characteristics and functions of local elimination of SnCs in bone marrow, as well as the use of TMP as a potential treatment to ameliorate human age‐related skeletal diseases and to promote healthy lifespan.

Mechanisms of Hematopoietic Stem Cell Ageing and Targets for Hematopoietic Tumour Prevention

Hematopoietic stem cells represent a rare population in the bone marrow, with the capacity of generating all blood lineage and themselves at the same time. With aging, the reconstitution capacity of hematopoietic stem cells decreases accompanying with differentiation skewing wherein the myeloid branch dominates in both mouse and human. In recent years, various molecular mechanisms that induce functional decline of HSC during aging were disclosed including DNA damage accumulation, metabolic alteration, defects in protein homeostasis, and aging-induced changes in the blood circulatory environment. Deciphering the nature of HSC aging could improve our knowledge of HSC aging-related diseases and furthermore promote the developing of therapeutic interventions for human HSC aging and diseases.

A small-molecule inhibitor of SHIP1 reverses age- and diet-associated obesity and metabolic syndrome

Low-grade chronic inflammation is a key etiological phenomenon responsible for the initiation and perpetuation of obesity and diabetes. Novel therapeutic approaches that can specifically target inflammatory pathways are needed to avert this looming epidemic of metabolic disorders. Genetic and chemical inhibition of SH2-containing inositol 5' phosphatase 1 (SHIP1) has been associated with systemic expansion of immunoregulatory cells that promote a lean-body state; however, SHIP1 function in immunometabolism has never been assessed. This led us to investigate the role of SHIP1 in metabolic disorders during excess caloric intake in mice. Using a small-molecule inhibitor of SHIP1 (SHIPi), here we show that SHIPi treatment in mice significantly reduces body weight and fat content, improves control of blood glucose and insulin sensitivity, and increases energy expenditure, despite continued consumption of a high-fat diet. Additionally, SHIPi reduces age-associated fat in mice. We found that SHIPi treatment reverses diet-associated obesity by attenuating inflammation in the visceral adipose tissue (VAT). SHIPi treatment increases IL-4-producing eosinophils in VAT and consequently increases both alternatively activated macrophages and myeloid-derived suppressor cells. In addition, SHIPi decreases the number of IFN-γ-producing T cells and NK cells in VAT. Thus, SHIPi represents an approach that permits control of obesity and diet-induced metabolic syndrome without apparent toxicity.

Regulation of PtdIns(3,4,5)P3/Akt signalling by inositol polyphosphate 5-phosphatases

The phosphoinositide 3-kinase (PI3K) generated lipid signals, PtdIns(3,4,5)P3 and PtdIns(3,4)P2, are both required for the maximal activation of the serine/threonine kinase proto-oncogene Akt. The inositol polyphosphate 5-phosphatases (5-phosphatases) hydrolyse the 5-position phosphate from the inositol head group of PtdIns(3,4,5)P3 to yield PtdIns(3,4)P2. Extensive work has revealed several 5-phosphatases inhibit PI3K-driven Akt signalling, by decreasing PtdIns(3,4,5)P3 despite increasing cellular levels of PtdIns(3,4)P2. The roles that 5-phosphatases play in suppressing cell proliferation and transformation are slow to emerge; however, the 5-phosphatase PIPP [proline-rich inositol polyphosphate 5-phosphatase; inositol polyphosphate 5-phosphatase (INPP5J)] has recently been identified as a putative tumour suppressor in melanoma and breast cancer and SHIP1 [SH2 (Src homology 2)-containing inositol phosphatase 1] inhibits haematopoietic cell proliferation. INPP5E regulates cilia stability and INPP5E mutations have been implicated ciliopathy syndromes. This review will examine 5-phosphatase regulation of PI3K/Akt signalling, focussing on the role PtdIns(3,4,5)P3 5-phosphatases play in developmental diseases and cancer.

Synthesis and initial evaluation of quinoline-based inhibitors of the SH2-containing inositol 5'-phosphatase (SHIP)

Recently, inhibition of the SH2-containing inositol 5'-phosphatase 1 (SHIP1) has become an attractive strategy for facilitating engraftment of MHC-I mismatched bone marrow grafts, increasing the number of adult stem cells in vivo, and inducing mobilization of hematopoietic stem cells. Utilizing high-throughput screening, two quinoline small molecules (NSC13480 and NSC305787) that inhibit SHIP1 enzymatic activity were discovered. New syntheses of these inhibitors have been developed which verified the relative stereochemistry of these structures. Utilizing this synthetic route, some analogs of these quinolines have been prepared and tested for their ability to inhibit SHIP. These structure activity studies determined that an amine tethered to the quinoline core is required for SHIP inhibition. SHIP inhibition may explain the antitumor effects of similar quinoline amino alcohols and provides an impetus for further synthetic studies in this class of compounds.

Role of SHIP1 in Invariant NKT Cell Development and Functions

SHIP1 is a 5'-inositol phosphatase known to negatively regulate the signaling product of the PI3K pathway, phosphatidylinositol (3-5)-trisphosphate. SHIP1 is recruited to a large number of inhibitory receptors expressed on invariant NK (iNKT) cells. We hypothesized that SHIP1 deletion would have major effects on iNKT cell development by altering the thresholds for positive and negative selection. Germline SHIP1 deletion has been shown to affect T cells as well as other immune cell populations. However, the role of SHIP1 on T cell function has been controversial, and its participation on iNKT cell development and function has not been examined. We evaluated the consequences of SHIP1 deletion on iNKT cells using germline-deficient mice, chimeric mice, and conditionally deficient mice. We found that T cell and iNKT cell development are impaired in germline-deficient animals. However, this phenotype can be rescued by extrinsic expression of SHIP1. In contrast, SHIP1 is required cell autonomously for optimal iNKT cell cytokine secretion. This suggests that SHIP1 calibrates the threshold of iNKT cell reactivity. These data further our understanding of how iNKT cell activation is regulated and provide insights into the biology of this unique cell lineage.

Mesenchymal stem cell aging: Mechanisms and influences on skeletal and non-skeletal tissues

The aging population and the incidence of aging-related diseases such as osteoporosis are on the rise. Aging at the tissue and organ levels usually involves tissue stem cells. Human and animal model studies indicate that aging affects two aspects of mesenchymal stem cell (MSC): a decrease in the bone marrow MSC pool and biased differentiation into adipocyte at the cost of osteoblast, which underlie the etiology of osteoporosis. Aging of MSC cells is also detrimental to some non-skeletal tissues, in particular the hematopoietic system, where MSCs serve as a niche component. In addition, aging compromises the therapeutic potentials of MSC cells, including cells isolated from aged individuals or cells cultured for many passages. Here we discuss the recent progress on our understanding of MSC aging, with a focus on the effects of MSC aging on bone remodeling and hematopoiesis and the mechanisms of MSC aging.

SHIPi Enhances Autologous and Allogeneic Hematolymphoid Stem Cell Transplantation

Hematopoietic stem cell transplantation (HSCT) is a highly effective procedure enabling long-term survival for patients with hematologic malignancy or heritable defects. Although there has been a dramatic increase in the success rate of HSCT over the last two decades, HSCT can result in serious, sometimes untreatable disease due to toxic conditioning regimens and Graft-versus-Host-Disease. Studies utilizing germline knockout mice have discovered several candidate genes that could be targeted pharmacologically to create a more favorable environment for transplant success. SHIP1 deficiency permits improved engraftment of hematopoietic stem-progenitor cells (HS-PCs) and produces an immunosuppressive microenvironment ideal for incoming allogeneic grafts. The recent development of small molecule SHIP1 inhibitors has opened a different therapeutic approach by creating transient SHIP1-deficiency. Here we show that SHIP1 inhibition (SHIPi) mobilizes functional HS-PC, accelerates hematologic recovery, and enhances donor HS-PC engraftment in both allogeneic and autologous transplant settings. We also observed the expansion of key cell populations known to suppress host-reactive cells formed during engraftment. Therefore, SHIPi represents a non-toxic, new therapeutic that has significant potential to improve the success and safety of therapies that utilize autologous and allogeneic HSCT.

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SHIPi facilitates HS-PC mobilization.

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SHIPi facilitates engraftment of autologous BM without myeloablation.

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SHIPi enhances engraftment of allogeneic BM without cytotoxic effects on the host.