Crosstalk Between Apoptosis and Autophagy: Environmental Genotoxins, Infection, and Innate Immunity

Autoimmune disorders constitute a major and growing health concern. However, the genetic and environmental factors that contribute to or exacerbate disease symptoms remain unclear. Type I interferons (IFNs) are known to break immune tolerance and be elevated in the serum of patients with autoimmune diseases such as lupus. Extensive work over the past decade has characterized the role of a protein termed stimulator of interferon genes, or STING, in mediating IFN expression and activation in response to cytosolic DNA and cyclic dinucleotides. Interestingly, this STING-dependent innate immune pathway both utilizes and is targeted by the cell’s autophagic machinery. Given that aberrant interplay between the apoptotic and autophagic machineries contributes to deregulation of the STING-dependent pathway, IFN-regulated autoimmune phenotypes may be influenced by the combined exposure to environmental carcinogens and pathogenic microorganisms and viruses. This review therefore summarizes recent data regarding these important issues in the field of autoimmunity.

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Bacterial Cyclic Dinucleotides and the cGAS–cGAMP–STING Pathway: A Role in Periodontitis?

Pathogens ◽

10.3390/pathogens10060675 ◽

2021 ◽

Vol 10 (6) ◽

pp. 675

Author(s):

Samira Elmanfi ◽

Mustafa Yilmaz ◽

Wilson W. S. Ong ◽

Kofi S. Yeboah ◽

Herman O. Sintim ◽

...

Keyword(s):

Immune Response ◽

Periodontal Disease ◽

Innate Immune ◽

Host Cells ◽

Type I Interferons ◽

Type I ◽

Vaccine Adjuvants ◽

Cyclic Dinucleotides ◽

Sting Pathway

Host cells can recognize cytosolic double-stranded DNAs and endogenous second messengers as cyclic dinucleotides—including c-di-GMP, c-di-AMP, and cGAMP—of invading microbes via the critical and essential innate immune signaling adaptor molecule known as STING. This recognition activates the innate immune system and leads to the production of Type I interferons and proinflammatory cytokines. In this review, we (1) focus on the possible role of bacterial cyclic dinucleotides and the STING/TBK1/IRF3 pathway in the pathogenesis of periodontal disease and the regulation of periodontal immune response, and (2) review and discuss activators and inhibitors of the STING pathway as immune response regulators and their potential utility in the treatment of periodontitis. PubMed/Medline, Scopus, and Web of Science were searched with the terms “STING”, “TBK 1”, “IRF3”, and “cGAS”—alone, or together with “periodontitis”. Current studies produced evidence for using STING-pathway-targeting molecules as part of anticancer therapy, and as vaccine adjuvants against microbial infections; however, the role of the STING/TBK1/IRF3 pathway in periodontal disease pathogenesis is still undiscovered. Understanding the stimulation of the innate immune response by cyclic dinucleotides opens a new approach to host modulation therapies in periodontology.

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TheN-Ethyl-N-Nitrosourea-InducedGoldenticketMouse Mutant Reveals an Essential Function ofStingin theIn VivoInterferon Response toListeria monocytogenesand Cyclic Dinucleotides

Infection and Immunity ◽

10.1128/iai.00999-10 ◽

2010 ◽

Vol 79 (2) ◽

pp. 688-694 ◽

Cited By ~ 334

Author(s):

John-Demian Sauer ◽

Katia Sotelo-Troha ◽

Jakob von Moltke ◽

Kathryn M. Monroe ◽

Chris S. Rae ◽

...

Keyword(s):

Bacterial Infections ◽

Bacterial Pathogen ◽

Type I Interferons ◽

Interferon Response ◽

Type I ◽

Single Nucleotide ◽

Type I Ifns ◽

Cyclic Dinucleotides

ABSTRACTType I interferons (IFNs) are central regulators of the innate and adaptive immune responses to viral and bacterial infections. Type I IFNs are induced upon cytosolic detection of microbial nucleic acids, including DNA, RNA, and the bacterial second messenger cyclic-di-GMP (c-di-GMP). In addition, a recent study demonstrated that the intracellular bacterial pathogenListeria monocytogenesstimulates a type I IFN response due to cytosolic detection of bacterially secreted c-di-AMP. The transmembrane signaling adaptor Sting (Tmem173, Mita, Mpys, Eris) has recently been implicated in the induction of type I IFNs in response to cytosolic DNA and/or RNA. However, the role of Sting in response to purified cyclic dinucleotides or duringin vivo L. monocytogenesinfection has not been addressed. In order to identify genes important in the innate immune response, we have been conducting a forward genetic mutagenesis screen in C57BL/6 mice using the mutagenN-ethyl-N-nitrosourea (ENU). Here we describe a novel mutant mouse strain,Goldenticket(Gt), that fails to produce type I IFNs uponL. monocytogenesinfection. By genetic mapping and complementation experiments, we found thatGtmice harbor a single nucleotide variant (T596A) ofStingthat functions as a null allele and fails to produce detectable protein. Analysis of macrophages isolated fromGtmice revealed thatStingis absolutely required for the type I interferon response to both c-di-GMP and c-di-AMP. Additionally,Stingis required for the response to c-di-GMP andL. monocytogenes in vivo. Our results provide new functions forStingin the innate interferon response to pathogens.

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The Role of Toll-Like Receptors and Type I Interferons in Host Responses to Bacteria

Current Immunology Reviews ◽

10.2174/157339509788166994 ◽

2009 ◽

Vol 5 (2) ◽

pp. 143-149

Author(s):

Marja Ojaniemi ◽

Mari Liljeroos ◽

Reetta Vuolteenaho

Keyword(s):

Type I Interferons ◽

Host Responses ◽

Type I ◽

Toll Like Receptors

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Role of the Inflammasome, IL-1β, and IL-18 in Bacterial Infections

The Scientific World JOURNAL ◽

10.1100/2011/212680 ◽

2011 ◽

Vol 11 ◽

pp. 2037-2050 ◽

Cited By ~ 123

Author(s):

Manoranjan Sahoo ◽

Ivonne Ceballos-Olvera ◽

Laura del Barrio ◽

Fabio Re

Keyword(s):

Bacterial Infections ◽

Innate Immune ◽

Host Responses ◽

Inflammasome Activation ◽

Different Types ◽

Molecular Aspects ◽

Immune Pathway ◽

Innate Immune Pathway ◽

Receptor Family

The inflammasome is an important innate immune pathway that regulates at least two host responses protective against infections: (1) secretion of the proinflammatory cytokines IL-1βand IL-18 and (2) induction of pyroptosis, a form of cell death. Inflammasomes, of which different types have been identified, are multiprotein complexes containing pattern recognition receptors belonging to the Nod-like receptor family or the PYHIN family and the protease caspase-1. The molecular aspects involved in the activation of different inflammasomes by various pathogens are being rapidly elucidated, and their role during infections is being characterized. Production of IL-1βand IL-18 and induction of pyroptosis of the infected cell have been shown to be protective against many infectious agents. Here, we review the recent literature concerning inflammasome activation in the context of bacterial infections and identify important questions to be answered in the future.

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