title: Neuron-microglia interaction induced bi-directional cytotoxicity associated with calpain activation.
abstract: Activated microglia release pro-inflammatory factors and calpain into the extracellular milieu, damaging surrounding neurons. However, mechanistic links to progressive neurodegeneration in disease such as multiple sclerosis (MS) remain obscure. We hypothesize that persistent damaged/dying neurons may also release cytotoxic factors and calpain into the media, which then activate microglia again. Thus, inflammation, neuronal damage, and microglia activation, i.e., bi-directional interaction between neurons and microglia, may be involved in the progressive neurodegeneration. We tested this hypothesis using two in vitro models: (i) the effects of soluble factors from damaged primary cortical neurons upon primary rat neurons and microglia and (ii) soluble factors released from CD3/CD28 activated peripheral blood mononuclear cells of MS patients on primary human neurons and microglia. The first model indicated that neurons due to injury with pro-inflammatory agents (IFN-γ) release soluble neurotoxic factors, including COX-2, reactive oxygen species, and calpain, thus activating microglia, which in turn released neurotoxic factors as well. This repeated microglial activation leads to persistent inflammation and neurodegeneration. The released calpain from neurons and microglia was confirmed by the use of calpain inhibitor calpeptin or SNJ-1945 as well as μ- and m-calpain knock down using the small interfering RNA (siRNA) technology. Our second model using activated peripheral blood mononuclear cells, a source of pro-inflammatory Th1/Th17 cytokines and calpain released from auto-reactive T cells, corroborated similar results in human primary cell cultures and confirmed calpain to be involved in progressive MS. These insights into reciprocal paracrine regulation of cell injury and calpain activation in the progressive phase of MS, Parkinson's disease, and other neurodegenerative diseases suggest potentially beneficial preventive and therapeutic strategies, including calpain inhibition.
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, Charleston, South Carolina, USA.|Ralph H. Johnson VA Medical Center, Charleston, South Carolina, USA.|Laboratory of Signaling Proteins, Ludwik Hirszfeld Institute of Immunology & Experimental Therapy, Polish Academy of Sciences, Wroclaw, Poland.
authors.forename: Maria
authors.initials: M
authors.lastname: Podbielska
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Arabinda
authors.initials: A
authors.lastname: Das
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Amena W
authors.initials: AW
authors.lastname: Smith
authors.affiliation: Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina, USA.
authors.forename: Ashok
authors.initials: A
authors.lastname: Chauhan
authors.affiliation: Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina, USA.
authors.forename: Swapan K
authors.initials: SK
authors.lastname: Ray
authors.affiliation: Senju Pharmaceutical, Co LTD, Kobe, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Inoue
authors.affiliation: Senju Pharmaceutical, Co LTD, Kobe, Japan.
authors.forename: Mitsuyoshi
authors.initials: M
authors.lastname: Azuma
authors.affiliation: Department of Neurology, University of Alabama School of Medicine, Birmingham, Alabama, USA.
authors.forename: Kenkichi
authors.initials: K
authors.lastname: Nozaki
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, Charleston, South Carolina, USA.
authors.forename: Edward L
authors.initials: EL
authors.lastname: Hogan
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, Charleston, South Carolina, USA. baniknl@musc.edu.|Ralph H. Johnson VA Medical Center, Charleston, South Carolina, USA. baniknl@musc.edu.
authors.forename: Naren L
authors.initials: NL
authors.lastname: Banik
mesh_terms: D000818:Animals; D002154:Calpain / Q000037:antagonists & inhibitors / Q000187:drug effects* / Q000235:genetics; D002219:Carbamates / Q000494:pharmacology; D002470:Cell Survival / Q000187:drug effects*; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D004151:Dipeptides / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D055785:Gene Knockdown Techniques; D006801:Humans; D007249:Inflammation / Q000139:chemically induced / Q000473:pathology; D017628:Microglia / Q000187:drug effects*; D009046:Motor Neurons / Q000187:drug effects / Q000473:pathology; D009103:Multiple Sclerosis / Q000378:metabolism / Q000473:pathology; D019636:Neurodegenerative Diseases / Q000139:chemically induced / Q000473:pathology; D009474:Neurons / Q000187:drug effects*; D018696:Neuroprotective Agents / Q000494:pharmacology; D061251:Primary Cell Culture; D051381:Rats; D017207:Rats, Sprague-Dawley; D018417:Th1 Cells / Q000378:metabolism; D058504:Th17 Cells / Q000378:metabolism
chemical_list: C515164:((1S)-1-((((1S)-1-benzyl-3-cyclopropylamino-2,3-di-oxopropyl)amino)carbonyl)-3-methylbutyl)carbamic acid 5-methoxy-3-oxapentyl ester; D002219:Carbamates; D015853:Cysteine Proteinase Inhibitors; D004151:Dipeptides; D018696:Neuroprotective Agents; C071482:calpeptin; D002154:Calpain
keywords: calpain; microglia; microgliosis; multiple sclerosis; neurodegeneration; neurons