BackgroundThe prolonged time course of Huntington's disease (HD) neurodegeneration increases both the time and cost of testing potential therapeutic compounds in mammalian models. An alternative is to initially assess the efficacy of compounds in invertebrate models, reducing time of testing from months to days.Methodology/Principal FindingsWe screened candidate therapeutic compounds that were identified previously in cell culture/animal studies in a C. elegans HD model and found that two FDA approved drugs, lithium chloride and mithramycin, independently and in combination suppressed HD neurotoxicity. Aging is a critical contributor to late onset neurodegenerative diseases. Using a genetic strategy and a novel assay, we demonstrate that lithium chloride and mithramycin remain neuroprotective independent of activity of the forkhead transcription factor DAF-16, which mediates the effects of the insulin-like signaling pathway on aging.Conclusions/SignificanceThese results suggest that pathways involved in polyglutamine-induced degeneration are distinct from specific aging pathways. The assays presented here will be useful for rapid and inexpensive testing of other potential HD drugs and elucidating pathways of drug action. Additionally, the neuroprotection conferred by lithium chloride and mithramycin suggests that these drugs may be useful for polyglutamine disease therapy.

Glioblastoma (GBM) is an incurable primary malignant brain cancer hallmarked with a substantial protumorigenic immune component. Knowledge of the GBM immune microenvironment during tumor evolution and standard of care treatments is limited. Using single-cell transcriptomics and flow cytometry, we unveiled large-scale comprehensive longitudinal changes in immune cell composition throughout tumor progression in an epidermal growth factor receptor-driven genetic mouse GBM model. We identified subsets of proinflammatory microglia in developing GBMs and anti-inflammatory macrophages and protumorigenic myeloid-derived suppressors cells in end-stage tumors, an evolution that parallels breakdown of the blood–brain barrier and extensive growth of epidermal growth factor receptor+ GBM cells. A similar relationship was found between microglia and macrophages in patient biopsies of low-grade glioma and GBM. Temozolomide decreased the accumulation of myeloid-derived suppressor cells, whereas concomitant temozolomide irradiation increased intratumoral GranzymeB+ CD8+T cells but also increased CD4+ regulatory T cells. These results provide a comprehensive and unbiased immune cellular landscape and its evolutionary changes during GBM progression.

Huntington's disease (HD) is a fatal inherited neurodegenerative disorder. HD is caused by polyglutamine expansions in the huntingtin (htt) protein that result in neuronal loss and contribute to HD pathology. The mechanisms of neuronal loss in HD are elusive, and there is no therapy to alleviate HD. To find small molecules that slow neuronal loss in HD, we screened 1,040 biologically active molecules to identify suppressors of cell death in a neuronal cell culture model of HD. We found that inhibitors of mitochondrial function or glycolysis rescued cell death in this cell culture and in in vivo HD models. These inhibitors prevented cell death by activating prosurvival ERK and AKT signaling but without altering cellular ATP levels. ERK and AKT inhibition through the use of specific chemical inhibitors abrogated the rescue, whereas their activation through the use of growth factors rescued cell death, suggesting that this activation could explain the protective effect of metabolic inhibitors. Both ERK and AKT signaling are disrupted in HD, and activating these pathways is protective in several HD models. Our results reveal a mechanism for activating prosurvival signaling that could be exploited for treating HD and possibly other neurodegenerative disorders.caspase ͉ ERK ͉ survival signaling ͉ drugs ͉ neurodegeneration H untington's disease (HD) is an inherited, adult onset, progressive neurodegenerative disorder (1). HD is caused by a polyglutamine expansion (Ͼ36 glutamine repeats) in the huntingtin protein (htt) that leads to neuronal dysfunction and death (1, 2). The mechanism(s) by which the polyglutamine expansion in htt leads to HD pathology remain elusive. Numerous mechanisms including transcriptional dysregulation, altered intracellular trafficking, sequestration of critical cellular proteins in aggregates, aberrant caspase activation, and altered energy metabolism have been implicated in HD (2).HD is a fatal disease with no therapy. To identify potential compounds for development as drugs and to use these compounds to gain mechanistic understanding of HD, we used a screening approach to identify small molecule suppressors of cell death in a cell culture model of HD. In this model, rat striatal neurons that were immortalized by expression of a temperaturesensitive large T antigen were engineered to express a mutant N-terminal, 548-aa fragment of human htt with 120 glutamine repeats to generate the N548 mutant cell line (3). Serum deprivation and a change to the nonpermissive temperature (39°C) causes T antigen degradation and N548 mutant cell death (3). Cell death can be used as an indicator of mutant htt toxicity because the cells expressing mutant htt die faster than parental cells (3). By using a previously described high-throughput assay (4), we discovered that metabolic inhibitors rescued cell death in this cell culture model and in two in vivo HD models. These compounds activated ERK and AKT prosurvival signaling. Furthermore, growth-factor-induced activation of ERK and AKT rescued cell death, thus el...