Submitted on April 1, 2005
Accepted on June 10, 2005
Hypothermia enhances phosphorylation of I kappa B kinase andprolongs nuclear localization of NF-kappa B in LPS-activated macrophages
Karen D Fairchild1*, Ishwar S Singh2, Heather C Carter3, Lisa Hester4, and Jeffrey D Hasday5
1 Pediatrics, University of Virginia Children's Hospital, Charlottesville, VA, USA
2 Medicine, University of Maryland School of Medicine, Baltimore, MD, USA; Medicine and Research Services, Baltimore VA Medical Center, Baltimore, MD, USA
3 Pediatrics, University of Maryland School of Medicine, Baltimore, MD, USA
4 Medicine, University of Maryland School of Medicine, Baltimore, MD, USA; UMB Cytokine Core Laboratory, Baltimore, MD, USA
5 Medicine, University of Maryland School of Medicine, Baltimore, MD, USA; UMB Cytokine Core Laboratory, Baltimore, MD, USA; Medicine and Research Services, Baltimore VA Medical Center, Baltimore, MD, USA
* To whom correspondence should be addressed. E-mail: kdf2n{at}virginia.edu.
Hypothermia (HT) has been associated with both beneficial and detrimental consequences in various pathophysiologic states. While HT is generally thought to have anti-inflammatory and cytoprotective effects, we have previously shown that moderate in vitro HT prolongs TNF
production by LPS-stimulated mononuclear phagocytes, in part by prolonging TNF gene transcription and activation of the pleiotropic transcription factor, nuclear factor-kappa B (NF-
B). In this study we further characterize the effect of moderate (32°C) and marked (28°C) HT in human monocytic THP-1 cells by showing that even short (2h) exposure to HT followed by return to normothermic conditions for 22h results in augmented and prolonged production of TNF. Production of heat shock protein-72 and activation of heat shock factor-1 are not affected by HT in these studies, suggesting the effect is not part of a generalized stress response. Using immunoblotting we show that HT augments phosphorylation of IKK beta and IKK alpha (up to 8-fold increase at 28°C and 3.6-fold increase at 32°C vs. 37°C). Furthermore, nuclear accumulation of NF-B p65 is significantly prolonged in hypothermic cells (1.4 and 2.5-fold more nuclear p65 at 2h and 4h at 28°C vs. 37°C). Reexpression of I kappa B alpha, which contributes to termination of NF-B-dependent transcription, is delayed several hours in HT-exposed cells. Thus, we have shown that clinically relevant HT alters both cytosolic and nuclear events responsible for NF-B activation and deactivation. Enhanced NF-B activation may contribute to the immunomodulatory effects of HT in various clinical settings.
