title: Implications of the release of high-mobility group box 1 protein from dying cells during human immunodeficiency virus type 1 infection in vitro.
abstract: Plasma levels of high-mobility group box 1 protein (HMGB1) are elevated during the course of human immunodeficiency virus type 1 (HIV-1) infection and the molecule has an impact on virus replication. This study investigated the mode of cell death and release of HMGB1 during HIV-1 infection in vitro. MT4 cells and primary CD4(+) T cells were infected with HIV-1 isolates, and HMGB1 release was monitored in relation to cytopathic effects (CPE) and apoptosis. HMGB1 release from cells was analysed by Western blotting. For MT4 cells, an enzyme-linked immunosorbent spot (ELISPOT) assay was adapted to measure the release during necrosis. Lactate dehydrogenase (LDH) activity was quantified using a commercial assay. Flow cytometry was used to determine the level of infection and apoptosis. MT4 cells were > or =90 % infected at 48 h post-infection (p.i.). CPE was first observed at 60 h and correlated with release of HMGB1, LDH activity and caspase-3 (C3) activation. HMGB1 spots were clearly detected by ELISPOT assay at 72 h p.i. Annexin V and C3 staining showed that apoptosis was substantially involved in HIV-1-related cell death. Addition of Z-VAD (a caspase inhibitor) in a single dose at 24 or 40 h p.i. decreased both the number of caspase-positive cells and the release of HMGB1. Infection of primary CD4(+) T cells showed a 22 % (median) infection rate at 96 h. Related CPE corresponded to LDH and HMGB1 release. Both necrosis and apoptosis contributed to HMGB1 liberation during HIV-1-induced cell death and the protein could induce tumour necrosis factor-alpha release from peripheral mononuclear blood cells. These data imply that passive HMGB1 release contributes to the excessive immune activation characteristic of HIV-1 pathogenesis.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Babilonia
authors.initials: B
authors.lastname: Barqasho
authors.forename: Piotr
authors.initials: P
authors.lastname: Nowak
authors.forename: Samir
authors.initials: S
authors.lastname: Abdurahman
authors.forename: Lillian
authors.initials: L
authors.lastname: Walther-Jallow
authors.forename: Anders
authors.initials: A
authors.lastname: Sönnerborg
mesh_terms: D017209:Apoptosis; D015496:CD4-Positive T-Lymphocytes / Q000502:physiology* / Q000821:virology*; D002478:Cells, Cultured; D005786:Gene Expression Regulation; D015497:HIV-1 / Q000502:physiology*; D024243:HMGB1 Protein / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology; D006801:Humans; D007770:L-Lactate Dehydrogenase; D007963:Leukocytes, Mononuclear / Q000187:drug effects / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D024243:HMGB1 Protein; D014409:Tumor Necrosis Factor-alpha; D007770:L-Lactate Dehydrogenase