Heat Shock Prevents Tissue Factor Induction after Rewarming from Lethal Hypothermia in a c-Jun-Dependent Manner.

Decrease in body core temperature is associated with life threatening coagulation disturbances in humans. Although rewarming from hypothermia is a prerequisite for survival, it can lead to mobilization of large amounts of tissue factor (TF) from damaged tissues, which in turn can induce disseminated intravascular coagulation. Using immunoblotting, In-Cell Western assay, fluorescence activated cell sorting (FACS) and TF activity assay, we studied post-rewarming TF levels, activity and surface redistribution, along with the regulation of TF gene transcription in mononuclear cells (MNCs) obtained from an in vivo rat model. Twenty-four male Wistar rats were randomly assigned into four groups: normothermic control group (n=6); hypothermic followed by rewarming group (n=6); heat shock pretreated hypothermic followed by rewarming group (n=6); and heat shock pretreated normothermic group (n=6). Rewarming after a 5-hour episode of 15^oC hypothermia caused a 5-fold rise of TF protein levels and 2-fold increase in surface TF signal intensity and serface redistribution of TF antigen, judged by 2-fold increase in surface-to-total TF ratio. TF activity was enhanced from 5.6±0.7 mU 10⁶/cells in normothermic group to 13.9±3.6 mU 10⁶/cells after hypothermia/rewarming. This was accompanied by a dramatic elevation of c-Jun and c-Jun-N-terminal kinase (JNK) phosphorylation, and the absence of early growth response-1 and NF-kB activation. Reflecting certain limitations of the method when dealing with detection of low levels of antigens, FACS analysis of TF-positive population of MNCs failed to detect any differences between the groups. To search for a stimulus to counteract c-Jun-mediated induction of TF activity in MNCs from rewarmed rats, we applied heat shock pretreatment one day before the hypothermia/rewarming experiment. Heat shock pretreatment restored post-rewarming TF activity, protein levels and surface-to-total TF ratio in rat MNCs to normothermic levels. Furthermore, in heat shock-pretreated animals, rewarming from hypothermia failed to increase phosphorylated c-Jun and JNK levels. We attribute this to the profound overexpression of heat shock protein 70 and inhibition of JNK. Taken together, in our present study, we report an induction of TF activity, protein levels and redistribution of TF antigen to the surface of MNCs, isolated from rats rewarmed from hypothermia. This increase was counteracted by a full body heat shock 24 hours prior to hypothermia via suppression of hypothermia-induced activation of c-Jun.