Effect of Ibuprofen on Interleukin-1??-Induced Abnormalities in Hemodynamics and Oxygen Metabolism in Rabbits

Effects of Norepinephrine on the Intestinal Vascular System in Rabbits With Endotoxic Shock

ABSTRACT

We hypothesized that jejunal mucosal tissue blood flow would decrease following norepinephrine (NE) administration in endotoxic shock. We aimed of this study to evaluate changes in superior mesenteric venous (SMV) blood flow and jejunal mucosal tissue blood flow of the intestinal vascular system over time by administration of NE in rabbits with endotoxic shock. We created four groups (n = 8 each): control group, lipopolysaccharide (LPS; 1 mg/kg) group, NE (2 μg/kg/min) group, and LPS+NE group. As indicators of circulation, we measured mean arterial blood pressure (MAP), cardiac output, SMV blood flow, and jejunal mucosal tissue blood flow every 30 min from 0 to 240 min. The drop in MAP observed in the LPS group was suppressed by NE administration. SMV blood flow dropped temporarily with LPS administration, but then rose thereafter. Administration of NE to the LPS group suppressed the transient decline in SMV blood flow, which did not drop below that of the control group. In the LPS group, jejunal mucosal tissue blood flow transiently dropped and then rose, reflecting the pattern in SMV blood flow. In the LPS+NE group, however, although there was no drop in SMV blood flow, jejunal mucosal tissue blood flow remained low. An interaction between NE and LPS was observed regarding jejunal mucosal tissue blood flow from 90 to 180 min (P = 0.033). We showed that NE maintained MAP and SMV blood flow but decreased jejunal mucosal tissue blood flow. In a rabbit model of endotoxic shock, NE had a negative effect on jejunal mucosal tissue blood flow.

Vasodilating prostaglandin E1 does not reproduce interleukin-1β-induced oxygen metabolism abnormalities in rabbits

Background

We have reported that administration of recombinant human interleukin (IL)-1β induced circulatory shock in rabbits by causing overproduction of vasodilating prostaglandin(s) and simultaneously impaired oxygen metabolism by causing an abnormal dependence of oxygen consumption (VO₂) on oxygen delivery (DO₂). The present study was carried out to compare the effect of administration of exogenous PGE₁ with that of IL-1β on oxygen metabolism.

Methods

Sixteen rabbits were assigned to one of three groups and given a single injection of 10 μg/kg IL-1β (IL-1β group, n = 5), continuous infusion of 1 μg/kg/min PGE₁ (PGE₁ group, n = 6), or saline (control group, n = 5). All rabbits were subjected to stepwise cardiac tamponade to decrease DO₂ by inflating a balloon placed into the pericardial sac. The VO₂/DO₂ relation was analyzed by the dual-line method.

Results

Both IL-1β and PGE₁ decreased the baseline value of mean arterial pressure by approximately 25% without inducing significant alteration of the cardiac index. With respect to the VO₂/DO₂ relation, the slope of the supply-independent line was significantly increased in the IL-1β group (y = 0.13x + 6.4), but not in the PGE₁ group (y = 0.01x + 10.0) compared to that in the control group (y = 0.05x + 8.7).

Conclusion

These results indicate that simple vasodilation and hypotension induced by administration of PGE₁ are insufficient to account for the abnormal oxygen metabolism induced by IL-1β.

Heat stroke and cytokines

Heat stroke is a life-threatening illness that affects all segments of society, including the young, aged, sick, and healthy. The recent high death toll in France (Dorozynski, 2003) and the death of high-profile athletes has increased public awareness of the adverse effects of heat injury. However, the etiology of the long-term consequences of this syndrome remains poorly understood such that preventive/treatment strategies are needed to mitigate its debilitating effects. Cytokines are important modulators of the acute phase response (APR) to stress, infection, and inflammation. Current data implicating cytokines in heat stroke responses are mainly from correlation studies showing elevated plasma levels in heat stroke patients and experimental animal models. Correlation data fall far short of revealing the mechanisms of cytokine actions such that additional research to determine the role of these endogenous substances in the heat stroke syndrome is required. Furthermore, cytokine determinations have occurred mainly at end-stage heat stroke, such that the role of these substances in progression and long-term recovery is poorly understood. Despite several studies implicating cytokines in heat stroke pathophysiology, few studies have examined the protective effect(s) of cytokine antagonism on the morbidity and mortality of heat stroke. This is particularly surprising since heat stroke responses resemble those observed in the endotoxemic syndrome, for which a role for endogenous cytokines has been strongly implicated. The implication of cytokines as mediators of endotoxemia and the presence of circulating endotoxin in heat stroke patients suggests that much knowledge can be gained from applying our current understanding of endotoxemic pathophysiology to the study of heat stroke. Heat shock proteins (HSPs) are highly conserved proteins that function as molecular chaperones for denatured proteins and reciprocally modulate cytokine production in response to stressful stimuli. HSPs have been shown repeatedly to confer protection in heat stroke and injury models. Interactions between HSPs and cytokines have received considerable attention in the literature within the last decade such that a complex pathway of interactions between cytokines, HSPs, and endotoxin is thought to be occurring in vivo in the orchestration of the APR to heat injury. These data suggest that much of the pathophysiologic changes observed with heat stroke are not a consequence of heat exposure, per se, but are representative of interactions among these three (and presumably additional) components of the innate immune response. This chapter will provide an overview of current knowledge regarding cytokine, HSP, and endotoxin interactions in heat stroke pathophysiology. Insight is provided into the potential therapeutic benefit of cytokine neutralization for mitigation of heat stroke morbidity and mortality based on our current understanding of their role in this syndrome.