Alterations in splenic HSP70 and IL‐6 associated protein expression following heat stroke in mice

Abstract

Plasma protein expression of HSP70 and IL‐6 are elevated following heat stroke (HS) in mice. The spleen is the largest secondary lymphoid organ in the body and we have shown this organ to be damaged following HS. Despite this, splenic expression of HSP70, IL‐6, and the IL‐6 receptor (IL‐6R) are not well understood. This study tested the hypothesis that HS would be accompanied by increased protein expression of IL‐6, IL‐6R, and HSP70 at HS collapse (Tc,Max=42.7°C), hypothermia depth (HD), and fever (24h) in splenic tissue. Spleens were harvested from control (n=4 per group) and HS mice at HS collapse (n=4), HD (n=4), and fever (n=4), protein isolated, and immunoblotting performed. Splenic HSP70 protein expression was only modestly increased at HS collapse but significantly elevated at HD through 24h of recovery. Splenic IL‐6 protein was not detected at any time point whereas IL‐6R was expressed, but not altered, at any point during or after HS. These data demonstrate that IL‐6 and IL‐6R protein expression are not significantly affected by HS or contribute to the development of splenic tissue damage. In contrast, splenic HSP70 protein expression is dynamic. Although HSP70 expression is significantly enhanced by HD and 24h the molecular chaperone is unable to protect the spleen against HS‐related tissue damage. Research supported by USAMRMC.Author views not official US Army or DoD policy