Browsing by Subject "Caspase"

Now showing 1 - 4 of 4
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    Caspase-1 causes truncation and aggregation of the Parkinson's disease-associated protein α-synuclein
    (National Academy of Sciences, 2016-08-23) Wang, Wei; Nguyen, Linh T. T.; Burlak, Christopher; Chegini, Fariba; Guo, Feng; Chataway, Tim; Ju, Shulin; Fisher, Oriana S.; Miller, David W.; Datta, Debajyoti; Wu, Fang; Wu, Chun-Xiang; Landeru, Anuradha; Wells, James A.; Cookson, Mark R.; Boxer, Matthew B.; Thomas, Craig J.; Gai, Wei Ping; Ringe, Dagmar; Petsko, Gregory A.; Hoang, Quyen Q.; Department of Biochemistry & Molecular Biology, IU School of Medicine
    The aggregation of α-synuclein (aSyn) leading to the formation of Lewy bodies is the defining pathological hallmark of Parkinson's disease (PD). Rare familial PD-associated mutations in aSyn render it aggregation-prone; however, PD patients carrying wild type (WT) aSyn also have aggregated aSyn in Lewy bodies. The mechanisms by which WT aSyn aggregates are unclear. Here, we report that inflammation can play a role in causing the aggregation of WT aSyn. We show that activation of the inflammasome with known stimuli results in the aggregation of aSyn in a neuronal cell model of PD. The insoluble aggregates are enriched with truncated aSyn as found in Lewy bodies of the PD brain. Inhibition of the inflammasome enzyme caspase-1 by chemical inhibition or genetic knockdown with shRNA abated aSyn truncation. In vitro characterization confirmed that caspase-1 directly cleaves aSyn, generating a highly aggregation-prone species. The truncation-induced aggregation of aSyn is toxic to neuronal culture, and inhibition of caspase-1 by shRNA or a specific chemical inhibitor improved the survival of a neuronal PD cell model. This study provides a molecular link for the role of inflammation in aSyn aggregation, and perhaps in the pathogenesis of sporadic PD as well.
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    Human adipose derived stromal/stem cells (hASCs) protect against STZ-induced hyperglycemia; analysis of hASC-derived paracrine effectors
    (Wiley, 2014-07) Kono, Tatsuyoshi M.; Sims, Emily K.; Moss, Dan R.; Yamamoto, Wataru; Ahn, Geonyoung; Diamond, Julie; Tong, Xin; Day, Kathleen H.; Territo, Paul R.; Hanenberg, Helmut; Traktuev, Dmitry O.; March, Keith L.; Evans-Molina, Carmella; Department of Medicine, IU School of Medicine
    Adipose-derived stromal/stem cells (ASCs) ameliorate hyperglycemia in rodent models of islet transplantation and autoimmune diabetes, yet the precise human ASC (hASC)-derived factors responsible for these effects remain largely unexplored. Here, we show that systemic administration of hASCs improved glucose tolerance, preserved β cell mass, and increased β cell proliferation in streptozotocin-treated nonobese diabetic/severe combined immunodeficient mice. Coculture experiments combining mouse or human islets with hASCs demonstrated that islet viability and function were improved by hASCs following prolonged culture or treatment with proinflammatory cytokines. Analysis of hASC-derived factors revealed vascular endothelial growth factor and tissue inhibitor of metalloproteinase 1 (TIMP-1) to be highly abundant factors secreted by hASCs. Notably, TIMP-1 secretion increased in the presence of islet stress from cytokine treatment, while TIMP-1 blockade was able to abrogate in vitro prosurvival effects of hASCs. Following systemic administration by tail vein injection, hASCs were detected in the pancreas and human TIMP-1 was increased in the serum of injected mice, while recombinant TIMP-1 increased viability in INS-1 cells treated with interleukin-1beta, interferon-gamma, and tumor necrosis factor alpha. In aggregate, our data support a model whereby factors secreted by hASCs, such as TIMP-1, are able to mitigate against β cell death in rodent and in vitro models of type 1 diabetes through a combination of local paracrine as well as systemic effects.
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    RIPK1 and RIPK3 regulate TNFα-induced β-cell death in concert with caspase activity
    (Elsevier, 2022) Contreras, Christopher J.; Mukherjee, Noyonika; Branco, Renato C.S.; Lin, Li; Hogan, Meghan F.; Cai, Erica P.; Oberst, Andrew A.; Kahn, Steven E.; Templin, Andrew T.; Medicine, School of Medicine
    Objective: Type 1 diabetes (T1D) is characterized by autoimmune-associated β-cell loss, insulin insufficiency, and hyperglycemia. Although TNFα signaling is associated with β-cell loss and hyperglycemia in non-obese diabetic mice and human T1D, the molecular mechanisms of β-cell TNF receptor signaling have not been fully characterized. Based on work in other cell types, we hypothesized that receptor interacting protein kinase 1 (RIPK1) and receptor interacting protein kinase 3 (RIPK3) regulate TNFα-induced β-cell death in concert with caspase activity. Methods: We evaluated TNFα-induced cell death, caspase activity, and TNF receptor pathway molecule expression in immortalized NIT-1 and INS-1 β-cell lines and primary mouse islet cells in vitro. Our studies utilized genetic and small molecule approaches to alter RIPK1 and RIPK3 expression and caspase activity to interrogate mechanisms of TNFα-induced β-cell death. We used the β-cell toxin streptozotocin (STZ) to determine the susceptibility of Ripk3+/+ and Ripk3-/- mice to hyperglycemia in vivo. Results: Expression of TNF receptor signaling molecules including RIPK1 and RIPK3 was identified in NIT-1 and INS-1 β cells and isolated mouse islets at the mRNA and protein levels. TNFα treatment increased NIT-1 and INS-1 cell death and caspase activity after 24-48 h, and BV6, a small molecule inhibitor of inhibitor of apoptosis proteins (IAPs) amplified this TNFα-induced cell death. RIPK1 deficient NIT-1 cells were protected from TNFα- and BV6-induced cell death and caspase activation. Interestingly, small molecule inhibition of caspases with zVAD-fmk (zVAD) did not prevent TNFα-induced cell death in either NIT-1 or INS-1 cells. This caspase-independent cell death was increased by BV6 treatment and decreased in RIPK1 deficient NIT-1 cells. RIPK3 deficient NIT-1 cells and RIPK3 kinase inhibitor treated INS-1 cells were protected from TNFα+zVAD-induced cell death, whereas RIPK3 overexpression increased INS-1 cell death and promoted RIPK3 and MLKL interaction under TNFα+zVAD treatment. In mouse islet cells, BV6 or zVAD treatment promoted TNFα-induced cell death, and TNFα+zVAD-induced cell death was blocked by RIPK3 inhibition and in Ripk3-/- islet cells in vitro. Ripk3-/- mice were also protected from STZ-induced hyperglycemia and glucose intolerance in vivo. Conclusions: RIPK1 and RIPK3 regulate TNFα-induced β-cell death in concert with caspase activity in immortalized and primary islet β cells. TNF receptor signaling molecules such as RIPK1 and RIPK3 may represent novel therapeutic targets to promote β-cell survival and glucose homeostasis in T1D.
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    The Nrf2/SKN-1-dependent Glutathione S-transferase π Homologue GST-1 Inhibits Dopamine Neuron Degeneration in a Caenorhabditis elegans Model of Manganism
    (Elsevier, 2013) Settivari, Raja; VanDuyn, Natalia; LeVora, Jennifer; Nass, Richard; Pharmacology and Toxicology, School of Medicine
    Exposure to high levels of manganese (Mn) results in a neurological condition termed manganism, which is characterized by oxidative stress, abnormal dopamine (DA) signaling, and cell death. Epidemiological evidence suggests correlations with occupational exposure to Mn and the development of the movement disorder Parkinson's disease (PD), yet the molecular determinants common between the diseases are ill-defined. Glutathione S-transferases (GSTs) of the class pi (GSTπ) are phase II detoxification enzymes that conjugate both endogenous and exogenous compounds to glutathione to reduce cellular oxidative stress, and their decreased expression has recently been implicated in PD progression. In this study we demonstrate that a Caenorhabditis elegans GSTπ homologue, GST-1, inhibits Mn-induced DA neuron degeneration. We show that GST-1 is expressed in DA neurons, Mn induces GST-1 gene and protein expression, and GST-1-mediated neuroprotection is dependent on the PD-associated transcription factor Nrf2/SKN-1, as a reduction in SKN-1 gene expression results in a decrease in GST-1 protein expression and an increase in DA neuronal death. Furthermore, decreases in gene expression of the SKN-1 inhibitor WDR-23 or the GSTπ-binding cell death activator JNK/JNK-1 result in an increase in resistance to the metal. Finally, we show that the Mn-induced DA neuron degeneration is independent of the dopamine transporter DAT, but is largely dependent on the caspases CED-3 and the novel caspase CSP-1. This study identifies a C. elegans Nrf2/SKN-1-dependent GSTπ homologue, cell death effectors of GSTπ-associated xenobiotic-induced pathology, and provides the first in vivo evidence that a phase II detoxification enzyme may modulate DA neuron vulnerability in manganism.