DNA hypomethylation promotes the expression of CASPASE-4 which exacerbates inflammation and amyloid-β deposition in Alzheimer's disease

Alzheimer's disease (AD) is the sixth leading cause of death in the USA. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release pro-inflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed reduced representation bisulfite sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed promotes the generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4 and CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4-/-). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA-sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (GSDMD). Therefore, here we unravel the role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential DNA methylation in AD microglia contributes to the progression of AD pathobiology. Thus, we identify CASP4 as a potential target for immunotherapies for the treatment and prevention of AD.

DNA hypomethylation promotes the expression of CASPASE-4 which exacerbates neuroinflammation and amyloid-β deposition in Alzheimer's disease The Ohio State University College of Medicine

Alzheimer's Disease (AD) is the 6th leading cause of death in the US. It is established that neuroinflammation contributes to the synaptic loss, neuronal death, and symptomatic decline of AD patients. Accumulating evidence suggests a critical role for microglia, innate immune phagocytes of the brain. For instance, microglia release proinflammatory products such as IL-1β which is highly implicated in AD pathobiology. The mechanisms underlying the transition of microglia to proinflammatory promoters of AD remain largely unknown. To address this gap, we performed Reduced Representation Bisulfite Sequencing (RRBS) to profile global DNA methylation changes in human AD brains compared to no disease controls. We identified differential DNA methylation of CASPASE-4 (CASP4), which when expressed, can be involved in generation of IL-1β and is predominantly expressed in immune cells. DNA upstream of the CASP4 transcription start site was hypomethylated in human AD brains, which was correlated with increased expression of CASP4. Furthermore, microglia from a mouse model of AD (5xFAD) express increased levels of CASP4 compared to wild-type (WT) mice. To study the role of CASP4 in AD, we developed a novel mouse model of AD lacking the mouse ortholog of CASP4, CASP11, which is encoded by mouse Caspase-4 (5xFAD/Casp4-/-). The expression of CASP11 was associated with increased accumulation of pathologic protein aggregate amyloid-β (Aβ) and increased microglial production of IL-1β in 5xFAD mice. Utilizing RNA sequencing, we determined that CASP11 promotes unique transcriptomic phenotypes in 5xFAD mouse brains, including alterations of neuroinflammatory and chemokine signaling pathways. Notably, in vitro, CASP11 promoted generation of IL-1β from macrophages in response to cytosolic Aβ through cleavage of downstream effector Gasdermin D (G SDMD). We describe a role for CASP11 and GSDMD in the generation of IL-1β in response to Aβ and the progression of pathologic inflammation in AD. Overall, our results demonstrate that overexpression of CASP4 due to differential methylation in AD microglia contributes to the progression of AD pathobiology, thus identifying CASP4 as a potential target for immunotherapies for the treatment of AD.

Rebalancing TGFβ1/BMP signals in exhausted T cells unlocks responsiveness to immune checkpoint blockade therapy

T cell dysfunctionality prevents the clearance of chronic infections and cancer. Furthermore, epigenetic programming in dysfunctional CD8+ T cells limits their response to immunotherapies, including immune checkpoint blockade (ICB). However, it is unclear which upstream signals drive acquisition of dysfunctional epigenetic programs, and whether therapeutically targeting these signals can remodel terminally dysfunctional T cells to an ICB-responsive state. Here we innovate an in vitro model system of stable human T cell dysfunction and show that chronic TGFβ1 signaling in posteffector CD8+ T cells accelerates their terminal dysfunction through stable epigenetic changes. Conversely, boosting bone morphogenetic protein (BMP) signaling while blocking TGFβ1 preserved effector and memory programs in chronically stimulated human CD8+ T cells, inducing superior responses to tumors and synergizing the ICB responses during chronic viral infection. Thus, rebalancing TGFβ1/BMP signals provides an exciting new approach to unleash dysfunctional CD8+ T cells and enhance T cell immunotherapies.

Rebalancing TGFβ1/BMP Signaling Epigenetically Reprograms Fully Exhausted Human CD8 T Cells into a Functional State

Epigenetic scarring of exhausted T cells (Tex) remains a major obstacle to achieving durable responses by T cell immunotherapies. While we established that de novo DNA methylation programs are causally linked to T cell’s full exhaustion and poor response to immune checkpoint blockade (ICB), major gaps remain in our current understanding of T cell exhaustion—(1) What are the upstream signals that regulate acquisition of exhaustion-specific epigenetic programs? (2) Can we remodel the epigenetic state of Tex to an ICB-responsive state? To address these questions, we developed a novel in vitro model of human T cell dysfunction. First, we demonstrated that chronic TCR stimulation of CD8 T cells is insufficient to develop T cell exhaustion. Instead, our integrative analyses of epigenetic and transcriptional changes in CD8 T cell subsets during chronic virus infections and cancer revealed TGFβ1 as the most significant upstream regulator linked to full exhaustion in mice and humans. Indeed, we found that post-effector TGFβ1 signaling accelerates full exhaustion in chronically stimulated CD8 T cells through stable epigenetic changes linked to impaired effector function and memory potential. Therapeutic rebalancing of TGFβ1/BMP signals by blocking TGFβ1 while boosting BMP signals not only restored effector function, but also unlocked memory programs in human Tex cells. This new therapeutic approach induced a superior anti-tumor activity of human T cells and synergized the ICB response in a murine model of chronic LCMV infection. Our findings highlight the role of TGFβ1/BMP signals in T cell exhaustion and propose a novel therapeutic strategy to epigenetically reprogram fully exhausted T cells, ultimately enhancing T cell immunotherapies.

New detection configuration for low activity levels of PET tracers during the analysis of plasma samples

A new radio-HPLC detection system for measuring radioactivity in plasma samples during Positron Emission Tomography [PET] studies was developed. It is based on detecting both the positron and one of the annihilation photons. The system focused on improving the measurement of radioactivity concentrations on an unmetabolized positron emitting a radiopharmaceutical [PER] in the presence of its radioactive metabolites, all containing the same positron emitter. This paper presents a new detection configuration that improves the minimal detectible activity (MDA), simplify the measuring systems and reduces the error caused by the metabolites. The detector is based on a plastic scintillator and a BGO scintillation crystal, that produces different light output spectra for signal and noise events. By summing the positron and the annihilated photon light outputs, different spectra are obtained for the metabolite and for the parent compound tracer and for tracer marked by different positron emitting isotopes. This new detection system can improve quantitative analysis of plasma samples. The spectrum change provides up to a three-fold improvement in sensitivity compared to the currently used detection systems that measure only the annihilation coincidence events. Results showed that for ¹¹C the MDA was improved by approximately 520%. Furthermore, it provides the additional advantage of reliability by providing a method for separating the signal and noise readings from the gross detector readout. Accurate reconstruction algorithm of the signal was achieved over a wide measuring range even when the signal was only 5% of the gross measurement.

Recent developments in neutron capture therapy

The conditions for the possible initiation of clinical trials with neutron capture therapy at a number of locations in the U.S. is reviewed. There are several new technical developments or plans at the Brookhaven Medical Research Reactor (BMRR), the Power Burst Facility (PBF) at INEL, the Massachusetts Institute of Technology Reactor (MITR) and the Georgia Institute of Technology Research Reactor (GTRR). Emphasis is on the development of epithermal beams for the treatment of deepseated tumors with neutron fluxes in between 10(9) to 10(10) n/cm2s. Therapeutic dose gains, defined as the ratio of tumour dose to maximum normal tissue dose in the treatment volume are expected to be between 2 and 4, depending on the degree of suppression of fast neutron dose. Boron concentrations considered in this case in the tumour are around 35 micrograms 10B/g and tumour/normal tissue concentrations are around 10. The compound development throughout three generations is discussed. The compound proposed nowadays, Na2B12H11SH (or BSH), employed in the treatments in Japan, will likely be replaced in the future by analogous of biomolecules being enriched in the tumour by physiological pathways. Examples are p-boronophenylalanine or boronated porphyrius. The most promising solution envisaged would be the employment of tumour cell specific brononated monoclonal antibodies. Finally the mode of therapy is discussed which will likely be based on a fractioned scheme, to achieve optimized results.

Iodothiouracil as a melanoma localizing agent

Thiouracil and various derivatives are selectively incorporated into the melanin pigment of melanomas during biosynthesis by serving as false melanin precursors. Using the transplantable Harding-Passey melanoma carried in BALB/c mice, we have extended our previous studies with sulfur-35 (35S) thiouracil. The persistence of high levels of [35S]thiouracil in tumor for periods of up to 2 wk has been demonstrated; during this time the drug content in normal tissues returned to near background levels. The variety of iodine isotopes available makes iodothiouracil a particularly promising melanoma-localizing agent. Tumor uptake and biodistribution of [35S]thiouracil and iodothiouracil (both iodine-127 (127I) and iodine-125 (125I) labeled) have been compared and were found to be essentially the same. The selectivity of [125I]thiouracil for melanoma has been qualitatively demonstrated by autoradiography of whole-body sections and quantitated by analysis of tumor and selected tissues. Iodothiouracil was also shown to localize in remote secondary metastases using a metastatic variant of the Harding-Passey melanoma currently being developed in our laboratory. These studies confirm the melanoma localizing capabilities of an iodinated thiouracil, and therefore the potential of using iodinated thiouracil derivatives for diagnosis and therapy of melanotic melanomas.