OBJECTIVERecent studies have shown that cytokines TNF-alpha and IL-6 play important roles in myocardial injury or dysfunction. Transcription nuclear factor (NF-kappa B) have been implicated in the regulation of a variety of cytokines in response to cellular defense. The authors observed the activity of NF-kappa B and cytokines TNF-alpha, IL-6 mRNA expression in myocardium to further investigate the mechanism of myocardial injury caused by infectious pneumonia. The therapeutic effect of exogenous adenosine was also studied by observing the influence on NF-kappa B and cytokines.

METHODSThirty rats were divided into three experimental groups at random, each group had 10 rats. The model of pneumonia was induced by the injection of Staphylococcus aureus into the trachea of rats. Adenosine-treated rats were given daily slow intravenous injection of adenosine at a dose of 150 microg/kg.min for 3 days from the second day. All rats were killed on the fifth day. Myocardial tissues were preserved in liquid nitrogen for examination. Pathological examination of myocardium was done and TNF-alpha and IL-6 mRNA expression was detected by reverse transcription polymerase chain reaction (RT-PCR). NF-kappa B activity was measured by electrophoretic mobility shift assay (EMSA).

RESULTS(1) The myocardium in pneumonia group showed significant pathological lesion when compared with control group (P < 0.01). The pathological lesion of myocardium in adenosine-treated group significantly decreased when compared to pneumonia group (P < 0.05). (2) Significant increase of TNF-alpha and IL-6 mRNA expression was observed in myocardium of pneumonic rats when compared with control group (2.27 +/- 0.27 vs. 1.05 +/- 0.16; 1.89 +/- 0.31 vs. 1.12 +/- 0.25: P < 0.01, respectively). NF-kappa B activity of myocardium in pneumonia group was significantly higher than that in control group (13,033 +/- 1286 vs. 383 +/- 15: P < 0.01). (3) TNF-alpha and IL-6 mRNA expression was significantly decreased in adenosine-treated group when compared with pneumonia group (1.25 +/- 0.18 vs. 2.27; 1.31 +/- 0.25 vs. 1.89 +/- 0.31, P < 0.01, respectively). Comparing to that in pneumonia group, NF-kappa B activity of myocardium in adenosine-treated group was significantly decreased (4 487 +/- 562 vs. 13033 +/- 1286, P < 0.01), but it was still significantly higher than that in control group (4487 +/- 562 vs.383 +/- 15, P < 0.01).

CONCLUSIONSIncreased activity of NF-kappa B and subsequent upregulation of TNF-alpha and IL-6 mRNA expression probably play a pivotal role in the mechanism of myocardial injury in rats with pneumonia. Exogenous adenosine can inhibit inflammatory change by lowering NF-kappa B activity and subsequent down-regulation of TNF-alpha and IL-6 expression. Our findings provide novel therapeutic evidence of adenosine in myocardial injury induced by pneumonia in clinic.