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Several lines of evidence suggest that proteasomes are involved in multiple aspects of myocardial physiology and pathology, including myocardial ischemia-reperfusion injury. It is well established that the 26S proteasome is an ATP-dependent enzyme and that ischemic heart disease is associated with changes in the ATP content of the cardiomyocyte. A functional link between the 26S proteasome, myocardial ATP concentrations, and ischemic cardiac injury, however, has been suggested only recently. This review discusses the currently available data on the pathophysiological role of the cardiac proteasome during ischemia and reperfusion in the context of the cellular ATP content. Depletion of the myocardial ATP content during ischemia appears to activate the 26S proteasome via direct regulatory effects of ATP on 26S proteasome stability and activity. This implies pathological degradation of target proteins by the proteasome and could provide a pathophysiological basis for beneficial effects of proteasome inhibitors in various models of myocardial ischemia. In contrast to that in the ischemic heart, reduced and impaired proteasome activity is detectable in the postischemic heart. The paradoxical findings that proteasome inhibitors showed beneficial effects when administered during reperfusion in some studies could be explained by their anti-inflammatory and immune suppressive actions, leading to reduction of leukocyte-mediated myocardial reperfusion injury. The direct regulatory effects of ATP on the 26S proteasome have implications for the understanding of the contribution of the 26S proteasome to the pathophysiology of the ischemic heart and its possible role as a therapeutic target.

Endotoxin-stimulated blood cytokine responses have been widely used to describe compromised host defense mechanisms after trauma. We investigated whether blood cytokine production after endotoxin stimulation is able to define distinct trauma-induced alteration patterns and whether alteration patterns are associated with tumor necrosis factor (TNF) gene polymorphisms. In 48 patients undergoing joint replacement, the levels of TNF alpha (TNF-alpha), interleukin 6 (IL-6), and IL-8 production in blood after endotoxin stimulation were measured preoperatively on the day of surgery and 24 h thereafter. Patients were genotyped for the TNF-alpha position -308 G/A polymorphism and the TNF-beta NcoI polymorphism. Postoperative alterations, i.e., increases or decreases of cytokine levels (TNF-alpha versus IL-6, P = 0.013; TNF-alpha versus IL-8, P = 0.001; IL-6 versus IL-8, P = 0.007), and relative postoperative changes, i.e., percentages of preoperative cytokine levels (TNF-alpha versus IL-6, r(s) = 0.491, P < 0.001; TNF-alpha versus IL-8, r(s) = 0.591, P < 0.001; IL-6 versus IL-8, r(s) = 0.474, P < 0.001 [where r(s) is the Spearman rank correlation coefficient]), had significant positive correlations among the cytokines. Overall enhanced postoperative alteration patterns were found in 10 patients, attenuated patterns were found in 18 patients, and mixed patterns were found in 20 patients. Preoperative cytokine production levels differed significantly between these groups (those of the overall enhanced pattern group were less than those of the mixed pattern group, which were less than those of the overall attenuated pattern group). TNF polymorphisms were not associated with overall alteration patterns, but the A*TNFB1 haplotype was associated with a postoperative increase in TNF-alpha production (P = 0.042). Whole-blood cytokine responses to endotoxin define the following preexisting patterns in leukocyte function: low baseline production and overall enhanced alteration patterns after trauma (type 1), intermediate baseline production and mixed alteration patterns (type 2), and high baseline production and overall attenuated alteration patterns (type 3). TNF gene polymorphisms were associated with changes in TNF-alpha production but do not explain the overall reaction patterns of cytokine production after trauma. The clinical correlate of these newly defined reaction types remains to be determined.

The tumor necrosis factor alpha (TNF-alpha) -308 G/A and TNF-beta NcO1 polymorphisms have been described to be associated with an increased risk for sepsis in critically ill patients. Functional consequences associated with these polymorphisms remain unclear. We compared the genotype distribution of these TNF polymorphisms with susceptibility to severe sepsis and leukocyte function in blunt trauma patients (n = 70; mean injury severity score, 24 points [range, 4 to 57). Severe sepsis was defined according to the American College of Chest Physicians-Society of Critical Care Medicine consensus conference criteria. Genotyping for the NcO1 polymorphism (alleles TNFB1 and TNFB2) was performed by PCR and digestion of the products with NcO1, and that for the TNF-alpha -308 G/A polymorphism (alleles TNF1 and TNF2) was performed by real-time PCR. Leukocyte function was assessed by measurement of the production of endotoxin-induced cytokines (TNF-alpha, interleukin-6 [IL-6], and IL-8) in whole blood. TNF-alpha, IL-6, and IL-8 were determined by enzyme-linked immunosorbent assay. For the genotypes of the TNF-alpha -308 G/A polymorphism, differences in the frequency of development of severe sepsis were not detectable. Patients developing severe sepsis after trauma were significantly more likely to possess a homozygous genotype of the TNF-beta NcO1 polymorphism. Compared with heterozygotes, the odds ratio for the TNFB2/B2 genotype for the development of severe posttraumatic sepsis was 11 (P = 0.01), and that for the TNFB1/B1 genotype was 13 (P = 0.014). TNF-alpha -308:TNF-beta NcO1 haplotype analysis showed that the TNFB2:TNF2 haplotype is significantly negatively associated with development of severe sepsis. Patients homozygous for the TNFB1 or TNFB2 allele showed a persistently higher cytokine-producing capacity during at least 4 to 8 days after trauma than the heterozygotes. In patients homozygous for the TNF1 allele, a higher TNF-alpha- and IL-8-producing capacity was found only at day 1 after trauma. Although the TNF-beta NcO1 polymorphism appears to be less likely to be causative for development of severe sepsis after trauma, it is thus far the only genetic marker identified which can be used as a relevant risk estimate for severe sepsis in trauma patients immediately after the injury.

The aim of this study was to evaluate whether the -174 G/C promoter polymorphism of the interleukin-6 (IL-6) gene is associated with the ex vivo, whole blood IL-6 response to endotoxin with the development of severe sepsis in severely injured, blunt trauma patients. Patients with a severe trauma and an injury severity score of 16 were included in the study. The IL-6 -174 G/C promoter polymorphism was determined by real-time polymerase chain reaction (PCR) assay using specific fluorescence-labelled hybridisation probes. Whole blood of the patients was stimulated with endotoxin and the IL-6 concentrations were measured by ELISA. There was no association between the IL-6 -174 genotypes and the ex vivo, stimulated IL-6 response: 25% of the patients developed severe sepsis later in the clinical course. These patients had higher IL-6 concentrations following whole blood stimulation on day 1 (p = 0.046) after the trauma than patients with uncomplicated post-traumatic recovery. The difference was even more significant on day 2 after the trauma (p = 0.02). High IL-6 responses in a whole blood stimulation assay with endotoxin on days 1 and 2 after a trauma are associated with severe post-traumatic sepsis. Genotyping for the IL-6 -174 G/C polymorphism does not allow early identification of trauma patients with a high, ex vivo IL-6 synthesis capacity.