Does high mobility group 1 protein function as a late mediator for LPS- or TNF-induced shock in galactosamine-sensitized mice?

The role of high mobility group-1 protein (HMG-1) in LPS- and TNF-alpha-induced lethal shock in galactosamine (GalN)-sensitized mice was investigated. No detectable HMG-1 levels were observed by immunoblotting analysis in plasma from untreated or GalN-sensitized BALB/c mice 5 h after LPS injection, although significant levels of HMG-1 were detected in plasma 6 h after the challenge. All GalN-sensitized BALB/c but not BALB/lps(d) mice succumbed by 6 h after LPS injection. When GalN-sensitized mice were injected with TNF-alpha, the presence of HMG-1 was seen at 5.5 h in plasma of BALB/c mice and at 6 h in BALB/lps(d) mice, although almost all GalN-sensitized BALB/c mice died by 6 h after challenge. The time-dependent phenomenon correlated with elevated serum aspartate aminotransferase (AST) levels and the appearance of apoptotic cells in livers. Administration of pooled plasma, equivalent to approximately 200 microg recombinant murine HMG-1, taken from mice on the verge of near death, did not result in induction of lethal shock in GalN-sensitized mice. Taken together with the late appearance of HMG-1 in moribund mice, these data suggest that HMG-1 does not decisively contribute to lethality in the GalN sensitization model.