Glioma-induced inhibition of caspase-3 in microglia promotes a tumor-supportive phenotype.

Glioma cells recruit and exploit microglia (the resident immune cells of the brain) for their proliferation and invasion ability. The underlying molecular mechanism used by glioma cells to transform microglia into a tumor-supporting phenotype has remained elusive. We found that glioma-induced microglia conversion was coupled to a reduction in the basal activity of microglial caspase-3 and increased S-nitrosylation of mitochondria-associated caspase-3 through inhibition of thioredoxin-2 activity, and that inhibition of caspase-3 regulated microglial tumor-supporting function. Furthermore, we identified the activity of nitric oxide synthase 2 (NOS2, also known as iNOS) originating from the glioma cells as a driving stimulus in the control of microglial caspase-3 activity. Repression of glioma NOS2 expression in vivo led to a reduction in both microglia recruitment and tumor expansion, whereas depletion of microglial caspase-3 gene promoted tumor growth. Our results provide evidence that inhibition of the denitrosylation of S-nitrosylated procaspase-3 mediated by the redox protein Trx2 is a part of the microglial pro-tumoral activation pathway initiated by glioma cancer cells.

Definition of the contribution of an Osteopontin-producing CD11c+ microglial subset to Alzheimer's disease.

Alzheimer's disease (AD) is the most common form of incurable dementia and represents a critical public health issue as the world's population ages. Although microglial dysregulation is a cardinal feature of AD, the extensive heterogeneity of these immunological cells in the brain has impeded our understanding of their contribution to this disease. Here, we identify a pathogenic microglial subset which expresses the CD11c surface marker as the sole producer of Osteopontin (OPN) in the 5XFAD mouse model of AD. OPN production divides Disease-Associated Microglia (DAM) into two functionally distinct subsets, i.e., a protective CD11c+OPN- subset that robustly ingests amyloid ß (Aß) in a noninflammatory fashion and a pathogenic CD11c+OPN+ subset that produces proinflammatory cytokines and fails to ingest significant amounts of Aß. Genetic ablation of OPN or administration of monoclonal anti-OPN antibody to 5XFAD mice reduces proinflammatory microglia, plaque formation, and numbers of dystrophic neurites and results in improved cognitive function. Analysis of brain tissue from AD patients indicates that levels of OPN-producing CD11c+ microglia correlate strongly with the degree of cognitive deficit and AD neuropathology. These findings define an OPN-dependent pathway to disease driven by a distinct microglial subset, and identify OPN as a novel therapeutic target for potentially effective immunotherapy to treat AD.

Definition of a mouse microglial subset that regulates neuronal development and proinflammatory responses in the brain.

Expression of Itgax (encoding the CD11c surface protein) and Spp1 (encoding osteopontin; OPN) has been associated with activated microglia that can develop in healthy brains and some neuroinflammatory disorders. However, whether CD11c and OPN expression is a consequence of microglial activation or represents a portion of the genetic program expressed by a stable microglial subset is unknown. Here, we show that OPN production in the brain is confined to a small CD11c+ microglial subset that differentiates from CD11c- precursors in perinatal life after uptake of apoptotic neurons. Our analysis suggests that coexpression of OPN and CD11c marks a microglial subset that is expressed at birth and persists into late adult life, independent of environmental activation stimuli. Analysis of the contribution of OPN to the intrinsic functions of this CD11c+ microglial subset indicates that OPN is required for subset stability and the execution of phagocytic and proinflammatory responses, in part through OPN-dependent engagement of the αVß3-integrin receptor. Definition of OPN-producing CD11c+ microglia as a functional microglial subset provides insight into microglial differentiation in health and disease.

Antibody-mediated blockade of the IL23 receptor destabilizes intratumoral regulatory T cells and enhances immunotherapy.

Regulatory T cells (Treg) can impede antitumor immunity and currently represent a major obstacle to effective cancer immunotherapy. Targeting tumor-infiltrating regulatory Treg while sparing systemic Treg represents an optimal approach to this problem. Here, we provide evidence that the interleukin 23 receptor (IL23R) expressed by tumor-infiltrating Treg promotes suppressive activity. Disruption of the IL23R results in increased responsiveness of destabilized Treg to the IL12 cytokine, the production of γ-interferon, and the recruitment of CD8 T cells that inhibit tumor growth. Since the Treg destabilization pathway that is initiated by IL23R blockade is distinct and independent from the destabilization pathway coupled to glucocorticoid-induced TNFR-related protein (GITR) activation, we examined the impact of the coordinate induction of the two destabilization pathways on antitumor immune responses. Combined GITR and IL23R antibody treatment of mice inoculated with MC38 tumors resulted in robust and synergistic antitumor responses. These findings indicate that the delineation of independent Treg destabilization pathways may allow improved approaches to the development of combination immunotherapy for cancers.

Associations of cortical SPP1 and ITGAX with cognition and common neuropathologies in older adults.

INTRODUCTION: The secreted phosphoprotein 1 (SPP1) gene expressed by CD11c+ cells is known to be associated with microglia activation and neuroinflammatory diseases. As most studies rely on mouse models, we investigated these genes and proteins in the cortical brain tissue of older adults and their role in Alzheimer's disease (AD) and related disorders. METHODS: We leveraged protein measurements, single-nuclei, and RNASeq data from the Religious Orders Study and Rush Memory and Aging Project (ROSMAP) of over 1200 samples for association analysis. RESULTS: Expression of SPP1 and its encoded protein osteopontin were associated with faster cognitive decline and greater odds of common neuropathologies. At single-cell resolution,  integrin subunit alpha X (ITGAX) was highly expressed in microglia, where specific subpopulations were associated with AD and cerebral amyloid angiopathy. DISCUSSION: The study provides evidence of SPP1 and ITGAX association with cognitive decline and common neuropathologies identifying a microglial subset associated with disease.

Solving the planning and scheduling problem simultaneously in a hospital with a bi-layer discrete particle swarm optimization.

The operating room is one of the most capital-intensive resources for a hospital. To achieve further improvements and to restrict cost increases, hospitals may need to operate more efficiently with the resources they already possess. The paper considers the joint problem of planning and scheduling patients in operating rooms on an operational level (weekly basis) with two objectives: maximizing the overall patients' satisfaction and minimizing the cost of overtime in operating rooms as well as the daily cost of operating rooms and recovery beds, which is NP-hard. The decision problem is solved using a bi-layer discrete particle swarm optimization, introducing a repair mechanism for infeasible solutions, specific operators like crossover, insertion and exchange. Moreover, a gap finding scheduling heuristic is designed to solve the surgical case sequencing problem. We first compare the performance of the proposed solution method to that of Fei et al. for three instances separately, using data of a Chinese hospital. Next, the efficient Pareto solutions for the joint problem are presented. The results show that the bi-layer discrete particle swarm optimization can solve the operating room scheduling efficiently and effectively.

The Secretome of Microglia Regulate Neural Stem Cell Function.

Brain injury is associated with neuroinflammation, and microglia are key players in this process. Microglia can acquire pro-inflammatory or anti-inflammatory properties, but how this affects neural stem cells (NSCs) remains controversial. Here, NSCs were grown in conditioned media collected from either non-stimulated microglia, or microglia stimulated with pro- or anti-inflammatory agents. NSC survival, proliferation, migration, and differentiation were investigated thereafter. We found that NSCs kept in conditioned medium from the anti-inflammatory microglial subtype had better survival, increased migration, and lower astrocytic differentiation compared to NSCs grown in conditioned medium collected from the pro-inflammatory subtype. Finally, we found that NSCs differentiated in microglial conditioned media generated cells expressing the pro-inflammatory chemokine CCL2, most pronounced when differentiated in medium from the pro-inflammatory microglia subtype. Our results show that microglial subtypes regulate NSCs differently and induce generation of cells with inflammatory properties.

TET2 Regulates the Neuroinflammatory Response in Microglia.

Epigenomic mechanisms regulate distinct aspects of the inflammatory response in immune cells. Despite the central role for microglia in neuroinflammation and neurodegeneration, little is known about their epigenomic regulation of the inflammatory response. Here, we show that Ten-eleven translocation 2 (TET2) methylcytosine dioxygenase expression is increased in microglia upon stimulation with various inflammogens through a NF-κB-dependent pathway. We found that TET2 regulates early gene transcriptional changes, leading to early metabolic alterations, as well as a later inflammatory response independently of its enzymatic activity. We further show that TET2 regulates the proinflammatory response in microglia of mice intraperitoneally injected with LPS. We observed that microglia associated with amyloid ß plaques expressed TET2 in brain tissue from individuals with Alzheimer's disease (AD) and in 5xFAD mice. Collectively, our findings show that TET2 plays an important role in the microglial inflammatory response and suggest TET2 as a potential target to combat neurodegenerative brain disorders.

Caspases orchestrate microglia instrumental functions.

Microglia, the resident immune cells of the brain, can acquire various cell phenotypes based on their location and current role. This level of plasticity is required to fulfil the vast variety of functions that microglia perform. Adequate microglial functions are crucial for a healthy brain. However, microglial activation can also contribute to both degenerative/traumatic and proliferative diseases. We review current evidence supporting roles for caspases, a family of proteases, in the overall control of microglia, from the regulation of their activation, their biological functions, to their death. Further, we discuss possible roles for these microglial caspase-dependent signaling pathways in brain diseases.

Glioma-induced SIRT1-dependent activation of hMOF histone H4 lysine 16 acetyltransferase in microglia promotes a tumor supporting phenotype.

High-grade gliomas are malignant aggressive primary brain tumors with limited therapeutic options, and dismal prognosis for patients. Microglia, the resident immune cells of the brain, are recruited and reprogrammed into tumor-supporting cells by glioma cells, which in turn positively influence tumor expansion and infiltration into surrounding brain tissues. Here, we report that glioma-induced microglia conversion is coupled to an increase of histone H4 lysine 16 (H4K16) acetylation level in microglia, through increased nuclear localization of the deacetylase SIRT1, which in turn results in deacetylation of the H4K16 acetyltransferase hMOF and its recruitment to the chromatin at promoter regions of microglial target genes. Furthermore, we demonstrate that manipulation of the microglial H4K16 acetylation level, taking advantage of the intrinsic H4K16 deacetylase or acetyltransferase activities of SIRT1 and hMOF, respectively, modulated the tumor-supporting function of microglia. This study provides evidence that post-translational modifications of histones and the histone-modifying enzymes controlling them, such as H4K16 acetylation regulated by hMOF and SIRT1, are part of the microglial pro-tumoral activation pathway initiated by glioma cancer cells and represent potentially novel therapeutic targets.