HISTOLOGY AND HISTOPATHOLOGY

Cellular and Molecular Biology

 

Heat shock protein-GP96 as an innate sensor of damage and activator of autoreactive NKT and regulatory T cells during liver regeneration

Ines Mrakovčić-Šutić*, Hrvoje Jakovac*, Marija Šimin, Damir Grebić, Mira Čuk, Zlatko Trobonjača and Biserka Radošević-Stašić

Department of Physiology and Immunology, Medical Faculty, University of Rijeka, Rijeka, Croatia
*These authors equally contributed to this work.

Offprint requests to: Biserka Radoˇsevi´c-Staˇsi´c, Medical School, University of Rijeka, B. Brancheta 22, 51000 Rijeka, Croatia. e-mail: biserr@medri.hr


Summary. Tissue disintegration after injury leads, in the endoplasmic reticulum (ER), to activation of adaptive pathways known as the ER stress response. It is directed to the correction of unfolded proteins and to the activation of proteasome-dependent ER-associated degradation of the misfolded proteins, but induces also a rapid activation of natural and adaptive immunity, since a ER resident heat shock protein-gp96 acts not only as a molecular chaperone, but also as a strong adjuvant, able to cross-present the antigenic peptides onto MHC class I or MHC class II pathways.
Analyzing its potential role in processes of normal growth, in mice subjected to 1/3 partial hepatectomy (pHx) we determined the tissue expression of gp96 protein and mRNA in regenerating liver, thymus and spleen, determining simultaneously the phenotypic profile and spontaneous cytotoxic activity of intrahepatic and splenic mononuclear lymphatic cells (MNLC) against NKT- and NK-cells sensitive targets (syngeneic thymocytes and YAC-1) in wild, perforin and FasL deficient mice.
The data have shown that pHx induces fast overexpression of gp96 protein and mRNA in hepatocytes, spleen and thymus, with accumulation of CD3intermediate/NK1.1+/CD69+ cells (liver) and Foxp3+CD4+CD25+ cells (liver and thymus). Simultaneously, intrahepatic MNLC acquired the FasL-dependent cytotoxic potential against NKT-sensitive targets and both, intrahepatic and splenic MNLC, acquired the perforin-dependent cytotoxic potential against NK-sensitive targets, implying that during the disturbance of morphostasis gp96 serves as a natural adjuvant for chaperoning antigenic self peptides into the immune surveillance pathways, resulting in activation of autoreactive NKT and regulatory cells, as well as NK cells. Moreover, cell cycle analysis revealed that G2+M phase of regenerating hepatocytes in PKO mice was translocated from the 1st to the 7th p. o. day, as well as that hepatocytes from FasL deficient mice were arrested in G0/G1 phase. Histol Histopathol 23, 1111-1126 (2008)

Key words: Endoplasmic reticulum resident heat shock protein-gp96, Partial hepatectomy, liver regeneration, NKT cells, regulatory T cells

DOI: 10.14670/HH-23.1111