Methysergide attenuates systemic burn edema in rats

Highlights

• We evaluate systemic effects of Met after thermal injury.

• Significant systemic capillary leakage was observed after burnplasma-transfer.

• Edema formation was significantly lower in negative controls.

• Application of methysergide reduced FITC-efflux to baseline levels.

Abstract

Background

Thermal injuries of more than 20% total body surface area result in systemic shock with generalized edema. Burn shock is induced by a variety of mediators, mainly immunomodulative cytokines. Administration of methysergide (Met), a serotoninergic receptor blocking agent, reduces generalized edema in endotoxemia in rats. In this study we evaluated the systemic effects of Met after thermal injury.

Methods

Donor rats (DR [n = 8]) for positive controls and study groups underwent thermal injury (100 °C water, 30% TBSA (Total Burn Surface Area), 12 s). Shamburn plasma was harvested after a shamburn procedure ([n = 4], 37 °C water, 30% TBSA, 12 s). Plasma was harvested 4 h posttrauma and was transferred to healthy individuals. Recipient animals were randomized in 3 groups (1: burnplasma, 2: shamburn, 3: burnplasma plus methysergide (Bolus of 1 mg/kg body weight)). Intravital microscopy was performed in mesenteric venules (0/60/120 min). Edema was assessed by FITC-albumin extravasation. Leukocyte sticking (cells/mm²) and microhemodynamic parameters were assessed.

Results

Significant systemic capillary leakage was observed after burnplasma-transfer. Edema formation was significantly lower in negative controls. Application of methysergide reduced FITC-efflux to baseline levels. Adherent leukocytes increased in all groups, at 120 min the amount of adherent leukocytes in positive controls was significantly higher in comparison to shamburn, differences to MET-groups were not significant.

Conclusion

Burnplasma transfer to healthy individuals induces leukocyte activation and plasma extravasation and this effect is reduced by administration of Met. This may be attributed to leukocyte dependent as well as independent mechanisms. Evaluation of more specific serotoninergic antagonists is required to distinguish between systemic and local effects.

Introduction

Despite marked improvements in burn care, systemic complications still remain the major cause of death in patients who have thermal injuries exceeding 20% of total body surface area (TBSA)(Mann et al., 2012). The systemic response to burns is characterized by systemic capillary leakage and immunologic activation, which occurs as early as 2 to 4 h posttrauma (Cioffi, 2001, Gibran and Heimbach, 2000, Lund et al., 1992). Excessive loss of intravascular fluid and plasma proteins results in hypovolemic shock and generalized malperfusion, potentially leading to multiple organ failure (Arturson, 2000). Edema formation may cause local tissue ischemia and infection, inhibit cell mediated immune response and contribute to respiratory insufficiency and vascular compression (Keck et al., 2009, Lund et al., 1992). The systemic inflammatory response is at least partially induced by leukocyte activation and the consecutive release of several immunomodulative cytokines (Allgöwer et al., 1995, Horton et al., 2004, Sparkes, 1997). Serotonin (5-hydroxytryptamine; 5HT) appears to be a contributing factor in the development of burn edema (Carvajal et al., 1975, Taheri et al., 1994) as well as other diseases (Langer et al., 1995, Ross et al., 1985). 5-HT receptors have been implicated in several vascular diseases, including preeclampsia, coronary spasm, pulmonary and portal hypertension, migraine and Raynauds phenomenon (Kaumann and Levy, 2006). Continuous serotonin receptor activation was shown to be important in the pathophysiology of local burn-induced vasodilatation in dogs (Taheri et al., 1994).

Using intravital microscopy, Walther et al. demonstrated that systemic capillary leakage can be reduced by serotonin receptor antagonists in endotoxemia (Walther et al., 2000, Walther et al., 2002, Walther et al., 2007).

Methysergide (Met), a semisynthetic ergot alkaloid (1-methyl-D-lysergic acid butanolamide) was described as a non-specific serotonin antagonist in the late nineteen-fifties (Sicuteri, 1959). To date, seven different families of serotonin receptors have been identified (Hoyer et al., 1994) and Met was shown to act on 5-HT_1a − and 5-HT_2a/b/c and 5-HT₇ receptors. It was used for migraine therapy until significant side effects such as retroperitoneal fibrosis were observed. However, Met is still used in experimental studies (Koehler and Tfelt-Hansen, 2008). Serotonin uses at least three distinct types of molecular pathways: guanine nucleotide binding G protein-coupled receptors, ligand-gated ion channels and transporters (Silberstein, 1994). Previous studies have shown that Met blunts local blood flow and edema formation in burned skin (Ferrara et al., 1995).

Carlson et al. demonstrated that burnplasma, harvested 4 h posttrauma, already induces myocyte apostosis (Carlson et al., 2002). According to these findings we have been able to show, that plasma harvested as early as 4 h posttrauma and subsequently transferred to healthy individuals leads to systemic burn edema in rats (Kremer et al., 2008). This new experimental model proved to easily allow a standardized evaluation of therapeutic strategies in systemic burn shock (Kremer et al., 2009, Kremer et al., 2010). Using this model of burnplasma transfer the aims of the current study were to evaluate whether Met reduces systemic burn edema and if leukocyte activation can be inhibited or reduced by nonspecific serotonin antagonism.