J Physiol Pharmacol. 2014 Dec;65(6):791-800.

The dynamics of heat shock system activation in Monomac-6 cells upon Helicobacter pylori infection.

Pierzchalski P, Jastrzebska M, Link-Lenczowski P, Leja-Szpak A, Bonior J, Jaworek J, Okon K, Wojcik P.

Faculty of Health Sciences, Department of Medical Physiology, Jagiellonian University Medical College, Cracow, Poland. piotr.pierzchalski@uj.edu.pl.

 

Abstract

Immune system cells, particularly phagocytes, are exposed to direct contact with pathogens. Because of its nature – elimination of pathogenes – their cytoprotective systems supposed to be quick and forceful. Physiological consequence of phagocytosis for the phagocyte is the apoptotic death to prevent the eventual survival of bacteria as intracellular parasites. However, in some cases, defense systems used by the bacteria force the immune cells to prolong the contact with the pathogen for its effective elimination. Experiments were performed on Monomac-6 cells exposed to live CagA, VacA expressing Helicobacter pylori (H. pylori) over different period of time. Total cellular RNA, cytoplasmic and nuclear proteins were isolated for polymerase chain reaction, Western-blot and electrophoretic mobility shift assay, respectively. We found that Monomac-6 cells infection with H. pylori resulted in the translocation of the entire cellular content of the heat shock protein 70 (HSP70) into the cytoplasm, where its presence could protect cell against toxic products of engulfed bacteria and premature apoptosis. At the same time the nuclear translocation of heat shock factor 1 (HSF-1) and activation of HSP70 gene transcription was noticed. Action of HSP70 might to postpone monocyte apoptosis through protecting cytoplasmic and nuclear proteins from damaging effect of bacterial products, what could be the defending mechanism against the toxic stress caused by engulfed bacteria and provide the immune cell with the sufficient amount of time required for neutralization of the bacteria from phagosomes, even at the expense of temporary lack of the protection of nuclear proteins.

PMID: 25554983

 

Supplements:

Immune system cells, particularly phagocytes, are exposed to direct contact with pathogens. Because of its nature – elimination of pathogenes – their cytoprotective systems supposed to be quick and forceful. Physiological consequence of phagocytosis for the phagocyte is the apoptotic death to prevent the eventual survival of bacteria as intracellular parasites. However, in some cases, defense systems used by the bacteria force the immune cells to prolong the contact with the pathogen for its effective elimination. The heat shock system is one of the most important in regard to maintenance of cellular homeostasis. In certain situations, this system favors reactions leading to cell death, in others to the contrary, promotes cell survival. Such a “Janus attitude” is nothing new in biology and is represented by several molecular “switches”.

Heat shock system, in response to various stimuli, triggers a series of processes which may lead to the contradictory effects. Studied extensively since the 70′ of the last century, HSPs became well known, especially as the molecular chaperons. Most often that term refers to the ongoing, energy dependent binding reaction and stabilization of unstable conformers of other proteins to prevent them from aggregationand maintenance of the correct structure to ensure proper cellular localization. Based on the results presented in this paper, we propose the mechanism of heat shock system action in monocytic cells which had contact with the live H. pylori bacteria and this reaction contributes to the maintaining of proper conformation of the cellular proteins and the delay of apoptotic cell death. Such reaction might be beneficial as a defense mechanism against the toxic stress caused by engulfed bacteria and provide the immune cell with the sufficient amount of time required for neutralization of the pathogen from phagosomes.

Experiments were performed on Monomac-6 cells exposed to live CagA, VacA expressing Helicobacter pylori (H. pylori) over different period of time. Total cellular RNA, cytoplasmic and nuclear proteins were isolated for polymerase chain reaction, Western-blot and electrophoretic mobility shift assay, respectively. We found that Monomac-6 cells infection with H. pylori resulted in the translocation of the entire cellular content of the heat shock protein 70 (HSP70) into the cytoplasm, where its presence could protect cell against toxic products of engulfed bacteria and premature apoptosis. At the same time the nuclear translocation of heat shock factor 1 (HSF-1) and activation of HSP70 gene transcription was noticed. Action of HSP70 might to postpone monocyte apoptosis through protecting cytoplasmic and nuclear proteins from damaging effect of bacterial products, what could be the defending mechanism against the toxic stress caused by engulfed bacteria and provide the immune cell with the sufficient amount of time required for neutralization of the bacteria from phagosomes, even at the expense of temporary lack of the protection of nuclear proteins

 

 pp fig1

Diagram presenting postulated mechanism of heat shock system activation in monocytes in response to the contact with live Hp bacteria. Solid lines represent the steps of early phase response, dashed lines represent the steps of late phase response.

 

Analysis of the results presented above entitle us to propose a model of the heat shock response in monocytic cells after infection with Hp bacteria. According to our data the heat shock reaction in Monomac-6 cells to Hp infection occurs in two stages: I – early and II – late. The early phase includes reactions occurring within a few hours after infection and is characterized by nuclear translocation of HSF-1 and HSP70 movement from the nucleus into the cytoplasm. Late phase addresses the phenomena occurring during tens of hours after infection and consist of HSF-1 binding to DNA, activation of heat shock protein genes as well as de novo synthesis of HSP70 and supplementation the nuclear pool of the protein

 

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