Whole body Hyperthermia (wbh) Attenuates
Experimental Autoimmune Myocarditis in the Rat

Itzhak Herz, M.D.
Department of Cardiology Tel Aviv Medical Center, Tel Aviv

Myocarditis is a potentially lethal condition with various etiologies, for which no treatment is currently optimal. Experimental autoimmune myocarditis (EAM) is a T cell mediated model induced in susceptible Lewis rats by immunization against porcine or human myosin. Brief periods of heat stress prior to induction of various forms of tissue injury (myocardial infarction, vascular injury) has been shown to result in preconditioning and attenuation of subsequent damage. We reasoned that application of WBH prior to induction of EAM would result in amelioration of immune mediated tissue injury.

Lewis rats (properly sedated) were pretreated with a brief 30 min period of hyperthermia (400C) immediately prior to EAM induction (A). Control groups were either heated 10 days following EAM induction (group B), or non-heated and induced to develop EAM (group C). All rats were sacrificed 21 days following EAM induction for evaluation of myocarditis histologic score.

Rats from groups A (n=10) exhibited significant protection from myocarditis evident by a reduced histologic score (mean±SD 1.45±0.98) as compared to rats from group B (2.60±0.52; p<0.05) or from group C (2.8±0.26; p<0.005). IgG anti-myosin antibodies levels in the serum were significantly reduced in the preheated rats with EAM compared to control, a finding that may partially explain the improved histologic score.

Thus, WBH may represent an approach towards treatment of myocarditis. The favorable effect was maintained, although reduced, when WBH was applied after histologic evidence of myocarditis was already evident. WBH beneficial effect may be related to immunomodulatory effect and stress proteins expression.