Authors:	Röwe, Julian
Title:	Inorganic polyphosphates – novel modulators of immune response
Online publication date:	21-Jun-2018
Year of first publication:	2018
Language:	english
Abstract:	Inorganic polyphosphates (PolyP) are multiple phosphate units linked linearly by high energy phosphoanhydride bonds. Mammalian platelets contain high concentrations of short-chains of PolyP with approximately 70 units (S-PolyP), while bacteria accumulate PolyP of several hundred phosphate units in length (L-PolyP) during starvation and environmental stress as phosphorus/energy storage and as chaperone-like structures. In this dissertation, the hypothesis was tested that L PolyP of bacterial origin, but not S-PolyP, act as a pathogen-associated molecular pattern (PAMP) during host-pathogen interactions and that L-PolyP possess modulatory effects in the course of bacterial infections. To study the effects of PolyP in bacterial sepsis, we monocolonized the intestine of hitherto germ-free mice with either a PolyP proficient Escherichia coli (E. coli) wild type or a mutant strain with a decreased capacity to accumulate PolyP. Peritoneal sepsis was induced by cecal ligation and puncture. The E. coli wild type monocolonized group showed increased bacterial burden and lethality with concurrent reduction of the amount of and the bactericidal characteristics of macrophages at the local site of infection-induced inflammation. In addition, in situ phagocytosis of E. coli particles in the peritoneum by neutrophils, monocytes, and macrophages was significantly reduced in the presence of ‘bacterial’ L-PolyP. Furthermore, the attraction of monocytes and macrophages to the peritoneum by thioglycollate was attenuated by L PolyP but not S-PolyP. The direct effects of L-PolyP on macrophages were further investigated in vitro. While L-PolyP antagonized an efficient lipopolysaccharide (LPS)-induced polarization of bone marrow-derived macrophages to a pro-inflammatory M1 phenotype, L-PolyP enhanced the expression of distinct markers of the interleukin 4-induced anti-inflammatory M2 subtype. Furthermore, L-PolyP reduced the LPS-induced presence of proteins associated with antigen presentation of pathogenic peptides such as MHC class II. The reduction of type I interferon was deciphered as one key mechanism of L PolyP mediated immune interference. While L-PolyP attenuated LPS-induced phosphorylation of the transcription factor signal transducer and activator of transcription 1 (STAT1), it induced the phosphorylation of the signaling factor protein kinase B (Akt) and the internalization of the integrin α-M (ITGAM or CD11b). These observations identify bacterial L-PolyP as a novel PAMP signal which is distinguished from the S-PolyP released by platelets as hypothesized. However, the sensing of L PolyP in macrophages does not induce a ‘classical’ pro inflammatory phenotype, concluding that L-PolyP represent a novel immune-modulatory bacterial metabolite and a potential pathogen immune-evasion strategy. In future, further investigations on the mechanistic aspect of this pathogen-host interaction are desirable. PolyP neutralization may be evaluated as a novel therapeutic strategy in the context of infection-associated inflammatory diseases to restore interferon responses, antigen presentation, and prevent misguiding macrophage polarization.
DDC:	570 Biowissenschaften 570 Life sciences
Institution:	Johannes Gutenberg-Universität Mainz
Department:	FB 04 Medizin
Place:	Mainz
ROR:	https://ror.org/023b0x485
DOI:	http://doi.org/10.25358/openscience-4451
URN:	urn:nbn:de:hebis:77-diss-1000020570
Version:	Original work
Publication type:	Dissertation
License:	In Copyright
Information on rights of use:	https://rightsstatements.org/vocab/InC/1.0/
Extent:	168 Seiten
Appears in collections:	JGU-Publikationen