engleski

Peptidoglycan-monomer linked with zinc upregulates the expression of the heat protein gp96 and metallothioneins in the liver and spleen in old and young mice

Introduction: Owing to the presence of immunosenescence in elderly and our previous findings that peptidoglycan monomer linked with zinc (PGM-Zn) has marked immunocorrective and hepatoprotective properties in this study we compared the effects of in vivo application of PGM-Zn in very old and in young mice, estimating the phenotypic and functional characteristic of their intrahepatic and splenic mononuclear lymphatic cells (MNLC). Furthermore, since Zn++ might have metallothionein-inducing capacities, while Toll-like receptors and CD14 have been posited to transduce chaperone-mediated signaling, we analyzed also the tissue expression of metallothioneins (MT) and heat shock protein gp96 in their livers and spleens. Material & Method: C57BL6 mice aged 2 years or 2 months were treated during the 6 days (every second day) with PGM-Zn (3x10 mg/kg i.p.) or with the same amount of the solvent. Two days after the last injection, the phenotype of lymphatic cells was determined by FACS staining, and the spontaneous cytotoxic activity of freshly isolated intrahepatic and splenic MNLC was measured against NK-sensitive (YAC-1) and against NKT-sensitive targets (syngeneic thymocytes). Hepatic and splenic metallothioneins I+II (MT), and gp96 proteins were determined by immunohistology. Results: In the liver of control, very old mice the greater proportions of CD3+, CD8+, CD122+ (IL-2Rb+) and CD3+/CD122+, and a lower proportion of NK1.1+ cells were found. PGM-Zn in both groups significantly increased the proportion of NK1.1+, CD69+ and CD3+/NK1.1+ cells, but in old mice decreased the percentage of hepatic CD8+ T cells, and the percentage of splenic CD19+ cells. Simultaneously, we noticed that control "very old" hepatic and splenic MNLCs were more cytotoxic against the syngeneic thymocytes (p<0.0001) and less reactive against the YAC-1 targets than analogous "young" cells, suggesting the presence of auto-reactive clones of cells. PGM-Zn stimulated both types of cytotoxicity, but in young mice it was more directed against YAC-1 target. Simultaneously, we noticed that the liver and spleen of control old mice had the greater quantities of MT and gp96 than did those in young mice. PGM-Zn in both age groups provoked an additional overexpression of MT and gp96, which in old mice became very impressive in the liver, and in the young mice in the spleen. Conclusions: The data point to the possibility that immunostimulatory effects of PGM-Zn on autoreactive NKT cells and NK cells are mediated by hepatic and splenic MT and gp96, which delivers antigenic peptides and maturation signal to APC. (Supported by grants from Croatian Ministry of Science, project No 0062018).

Peptidoglycan-monomer; zinc; aging; metallothioneins; heat shock proteins

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