京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21302号 / 医博第4391号 / 新制||医||1030(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 生田 宏一, 教授 椛島 健治, 教授 杉田 昌彦 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Ferroptosis is a regulated junction between cell death, metabolism, and disease, and it hasbeen implicated in many pathologies. The assorted ferroptosis pharmacology modulators offer valuable means to modulate ferroptosis in multiple diseases, to explore disease etiology, and to develop potential therapeutics. In the first part, the work focuses on inhibiting ferroptosis in a Huntington’s disease model. Ferrostatin-1 (Fer-1) is a potent small-molecule ferroptosis inhibitor that has been adopted to investigate the role of ferroptosis in many disease models. However, its further application is limited by its low potency, poor stability, possible toxicity, and lack of brain penetration. We developed the fourth and fifth generations of ferrostatins and investigated the in vitro and in vivo pharmacokinetics of lead compounds. We identified PHB4082 preferentially accumulating in the kidney as a potential candidate for kidney disease-relevant contexts. Moreover, TH-4-55-2 displayed an excellent brain penetration, preferentially accumulating in the brain at concentrations of magnitude higher than the in vitro IC50 values. In the in vivo toxicity study, it was well-tolerated over 30 days in wild-type and R6/2 mice and exhibited a protective effect against weight loss in a Huntington’s disease model, suggesting it is a strong candidate for application in HD and more neurodegenerative disease models. The second part describes the efforts to explore the therapeutic potential of inducing ferroptosis in a tumor model. Imidazole ketone erastin (IKE) induced ferroptosis by specifically inhibiting system xc– in a subcutaneous xenograft model of Diffuse Large B Cell Lymphoma (DLBCL), suggesting the potential of IKE as a therapeutic strategy for cancer. A biodegradable polyethylene glycol-poly (lactic-co-glycolic acid) nanoparticle formulation was used to aid in delivering IKE to cancer cells in vivo, exhibiting improved tumor accumulation and therapeutic index relative to free IKE, indicating its potential for treating DLBCL. In summary, this work explored the possibility to modulate ferroptosis using small molecule modulators in multiple disease models and identified some potential drug candidates and useful chemical probes.

Equine hyperelastosis cutis (HC or HERDA), a connective tissue disorder in American Quarter Horses, results in hyperelastic skin with poor wound healing. Similar conditions are found in many species and all forms display decreased skin tensile strength. Fibroblasts produce collagen and elastin fibers, forming networks, providing the dermis with strength, and elasticity. This study aims to carry out a 3-part evaluation between horse skin fibroblast (cells from horses affected with HERDA, cells from horses that are carriers of HERDA (recessive HERDA gene), and cells from horses that are normal (neither affected or carriers of HERDA); Studies include: 1. Cell proliferation assay 2. Apoptosis analysis of fibroblasts 3. Mechanobiology of stretched fibroblast. Studies have shown cellular deformation to have an overall effect on mechanical properties of healthy and unhealthy tissues. This investigation provides a micromechanical evaluation of HC/HERDA in an effort to quantify the cellular level differences between each condition.

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京都大学 / 新制・課程博士 / 博士(医学) / 甲第24796号 / 医博第4988号 / 新制||医||1066(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 竹内 理, 教授 上野 英樹, 教授 椛島 健治 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

The regulated cell death apoptosis enables redundant or compromised cells in ontogeny and homeostasis to remove themselves receptor-dependent after extrinsic signaling or after internal stress by BCL-2 proteins on the outer mitochondrial membrane (OMM). Mitochondrial BCL-2 proteins are also often needed for receptor-mediated signaling in apoptosis. Then, the truncated BH3-only protein BID (tBID) blocks retrotranslocation of the pro-apoptotic BCL-2 proteins BAX and BAK from the mitochondria into the cytosol. BAX and BAK in turn permeabilize the OMM. Although the BCL-2 proteins are controlled by a complex regulatory network, a specific mechanism for the inhibition of tBID remained unknown. Curiously, it was suggested that hexokinases, which channel glucose into the metabolism, have an intriguing function in the regulation of apoptosis. Recent analysis of transient hexokinase interactions with BAX revealed its participation in the inhibition of BAX and also BAK by retrotranslocation from mitochondria to the cytosol. In contrast to general apoptosis inhibition by anti-apoptotic BCL-2 proteins, hexokinase I and hexokinase 2 specifically inhibit tBID and thus the mitochondrial apoptosis pathway in response to death receptor signaling. Mitochondrial hexokinase localization and BH3 binding of cytosolic hexokinase domains are prerequisites for protection against receptor-mediated cell death, whereas glucose metabolism is not. This mechanism protects cells from apoptosis induced by cytotoxic T cells.

Background and Purpose - Women have worse stroke outcomes than men, especially after menopause. Few studies have focused on female-specific mechanisms, other than hormones. We investigated the role of the blood protein VTN (vitronectin) after ischemic stroke in mice. Methods - Adult male and female VTN knockout and wild-type littermates and C57BL/6 mice received a middle cerebral artery occlusion and the injured brain tissue analyzed 24 hours to 3 weeks later for cell loss and inflammation, as well as neurological function. Blood VTN levels were measured before and after stroke. Results - Intravenously injected VTN leaked extensively from bloodstream into brain infarct and penumbra by 24 hours after stroke. Strikingly, VTN was detrimental in female, but not male, mice, as shown by reduced brain injury (26.2±2.6% versus 13.4±3.8%; P=0.018; n=6 and 5) and forelimb dysfunction in female VTN knockout mice. Stroke increased plasma VTN 2- to 8-fold at 24 hours in females (36±4 versus 145±24 μg/mL; P<0.0001; n=10 and 7), but not males (62±8 versus 68±6; P>0.99; n=10 and 7), and returned to control levels by 7 days. Individually variable VTN levels at 24 hours correlated with stroke-induced brain injury at 7 days only in females. VTN promoted stroke-induced microglia/macrophage activation and leukocyte infiltration in females. Proinflammatory IL (interleukin)-6 greatly increased in the striatum at 24 hours in wild-type mice but was increased ≈60% less in female (739±159 versus 268±111; P=0.02; n=7 and 6), but not male (889±178 versus 1179±295; P=0.73; n=10 and 11), knockout mice. In individual wild-type females, plasma VTN levels correlated with striatal IL-6 expression at 24 hours. The female-specific effect of VTN-induced IL-6 expression following stroke was not due to gonadal hormones, as shown by ovariectomy and castration. Lastly, intrastriatal injection of IL-6 in female mice immediately before stroke reversed the VTN knockout phenotypes of reduced brain injury and microglia/macrophage activation. Conclusions - VTN plays a novel sexually dimorphic detrimental pathophysiological role in females and might ultimately be a therapeutic target to improve stroke outcomes in women.

LIMD1 (LIM domain-containing protein 1) is considered as a tumor suppressor, being deregulated in many cancers to include hematological malignancies; however, very little is known about the underlying mechanisms of its deregulation and its roles in carcinogenesis. Epstein-Barr Virus (EBV) is associated with a panel of malignancies of lymphocytic and epithelial origin. Using high throughput expression profiling, we have previously identified LIMD1 as a common marker associated with the oncogenic transcription factor IRF4 in EBV-related lymphomas and other hematological malignancies. In this study, we have identified potential conserved IRF4- and NFκB-binding motifs in the LIMD1 gene promoter, and both are demonstrated functional by promoter-reporter assays. We further show that LIMD1 is partially upregulated by EBV latent membrane protein 1 (LMP1) via IRF4 and NFκB in EBV latency. As to its role in the setting of EBV latent infection, we show that LIMD1 interacts with TRAF6, a crucial mediator of LMP1 signal transduction. Importantly, LIMD1 depletion impairs LMP1 signaling and functions, potentiates ionomycin-induced DNA damage and apoptosis, and inhibits p62-mediated selective autophagy. Taken together, these results show that LIMD1 is upregulated in EBV latency and plays an oncogenic role rather than that of a tumor suppressor. Our findings have identified LIMD1 as a novel player in EBV latency and oncogenesis, and open a novel research avenue, in which LIMD1 and p62 play crucial roles in linking DNA damage response (DDR), apoptosis, and autophagy and their potential interplay during viral oncogenesis

BACKGROUND: Stevens-Johnson Syndrome/Toxic Epidermal Necrolysis (SJS/TEN) is the most severe form of cutaneous adverse drug reaction and is characterized by extensive epidermal destruction of the skin and mucosal surfaces. Controversy remains regarding the immunopathogenesis of the disease. It has long been assumed that CD8 cytotoxic T cells mediate cell death by releasing cytotoxic granules and soluble granulysin that trigger keratinocyte apoptosis. However, this does not explain the massive cell death or inflammation that is observed clinically. We have preliminary evidence from transcriptional profiling of patient skin samples suggesting that the cell death pathways necroptosis and pyroptosis may mediate SJS/TEN. Herein we utilize retrospectively and prospectively collected patient samples to investigate these cell death pathways. OBJECTIVE: The goals of this study are two-fold: (i) to investigate cell death pathways in retrospectively-collected (SJS/TEN) patient skin samples and (ii) to directly test the cell death mediators and pathways mediating SJS/TEN using a novel in vitro model. METHODS: Clinically and histopathologically confirmed SJS/TEN skin specimens and control skin specimens from non-blistering T cell mediated drug reactions and healthy skin were obtained following retrospective analysis from a multi-centered patient database. Gene expression profiling is being performed using the NanoString nCounter® System on these samples as a second patient cohort to confirm and expand on preliminary study findings. In parallel, we have optimized the use of a novel human skin platform for an in vitro model of SJS/TEN. We also collected human serum from a prospective study of SJS/TEN and control patients and have optimized and are actively collecting blister fluid from SJS/TEN and control patients in an ongoing prospective study for use in this model. RESULTS: Through an extensive pathology database and medical record search of potential cases at Brigham and Women's Hospital, we identified a second patient cohort of SJS/TEN, non-blistering delayed-type drug hypersensitivity reactions and healthy controls. We identified and are collecting thorough demographic, clinical and laboratory data on 61 potential candidates for SJS/TEN, 4 for Drug Reaction with Eosinophilia Syndrome (DRESS), and 200 for Morbilliform Drug Eruptions (MDE). This second cohort is in the final step of analysis with review by an expert clinician to confirm cases. In parallel, we have designed an expansive gene panel to confirm cell death mediator and marker transcription in our bank of skin samples. This 815 gene panel uses the pre-designed panel from Nanostring®, spiked with an additional 30 genes specific to apoptosis, pyroptosis, and necroptosis. We reviewed multiple potential in vitro skin models and identified GenoSkin® as the most suitable human skin platform for our in vitro model. We collected serum from 6 SJS/TEN patients and 6 non-blistering drug reaction patients and 3 healthy controls, and are actively collecting blister fluid from SJS/TEN and thermal burn control patients for analysis in this model. CONCLUSIONS: Our preliminary data suggest necroptosis and pyroptosis induced by soluble death mediators tumor necrosis factor (TNF) alpha and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) as the main cell death pathways responsible for SJS/TEN. We have successfully identified a large number of potential patient samples of both cases and controls to perform transcriptional profiling using a self-designed gene panel to confirm and expand upon our preliminary data. We have successfully collected prospectively patient serum and are actively collecting patient blister fluid for analysis in an optimized in vitro model using GenoSkin®. SJS/TEN is severely understudied and lacks a standard protocol for care. This stems from uncertainty surrounding disease pathobiology. It is critical that we use innovative approaches to interrogate the mechanism mediating disease to advance the field, and, most importantly, to improve the quality of care for these patients.