Lung As A Site Of Synthesis And Storage Of Cytokines In Experimental Congestive Heart Failure

1. BackgroundChronic heart failure (CHF) is a common complication of patients with heart dysfunction and of those suffering from various chronic illnesses. Although recently developed therapies revolutionized treatment of CHF, its morbidity and mortality is still very high and survival rate in 5 years is even lower than cancer. Recently the interest of investigators has been focused on immune mechanisms in the pathogenesis of CHF. There is increasing evidence that inflammatory cytokines play an important role in the development of heart failure. But the source and site of proinflammatory cytokines in CHF are not yet known. Endotoxin, a component of the outer coat of Gram negative bacteria, is a potent stimulus for cytokines production in Congestive heart failure patients when the oedematous bowel is more permeable to bacteria, which maybe one of the mechanisms. But as many reports have shown that at the early stage of CHF, cytokines can be detectable, and the exactly mechanisms need further research. Left ventricular failure has hemodynamic consequences both to pulmonary circulation upstream and aortic circulation downstream. Nevertheless, for the same cardiac output, hemodynamic changes differ between pulmonary artery and thoracic aorta, the pulmonary arterial bed is a capacitive vascular system in which small changes in pressure induce large changes in dimensions, Pulmonary endothelium is an early upstream hemodynamic target of left ventricular dysfunction in congestive heart failure, especially in those due to hypertension and myocardium infarction which affecting ventricular diastolic earlier than systolic activity. Decreased shear stress as a consequence of the left ventricular diastolic dysfunction leads to a modification of endothelial cell biology in thepulmonary circulation, including decreased endothelial nitric oxide (eNO) synthase activity as well as increased endothelin synthesis and secretion of cytokines. The activation of cytokines (primarily TNF-alpha, IL-6) plays an important role in the pathogenesis of CHF, it can depressed left ventricular contractility as well as diastolic, inducing cardiac remodeling, leading or worsen congestive heart failure. 2.AimFirst establish rat congestive heart failure model using ligation of the left descending anterior coronary, then detect the concentration of cytokines and activity of NF-kB in different tissue samples at different CHF groups. Through which we can know the possible cytokines production sites in CHF, the relationship between cytokine production and activity of NF-kB as well as cytokines expression levels and cardiac function. 3.MateriaI and methodsNormotensive male Wistar rats weighing (250+20) g were used. Infarction of the left ventricle (LV) was obtained by ligature of the left descending coronary artery under artificial ventilation. Sham operated rats underwent the same surgical procedure with the exception of coronary ligature. Before, 4 and 16 weeks following coronary ligature animals were assessed by echocardiography and cardiac catheterization. Serum levels of TNF-alpha and IL-6 were determined by ELISA. In the heart, lung, liver and spleen of different stage of CHF, the expression of IL-6 and TNF-alpha were assessed by RT-PCR> semi-quantitative Western-blot , and immunohistochemistry. MI size was measured in 15 rats using the techniques previously described by Pfeffer MA et al [2] .At 4 weeks after operation, those with Less than 20% MI size were excluded. According to hemodynamic change, rats were enrolled into different groups such as SH(sham group), compensated and decompensated groups, then compare the results of cardiac ultrasound and cardiac catheterization, from which we can know the value of ultrasound in diagnosing rat heart failure as an invasive examination measure.Blood was collected in 10 ml prechilled tubes on citrate (11 mM) and the plasma separated by centrifugation at 2500 rpm for 10 min at 4 ℃, and stored at -70℃ for ELISA determinations. Nuclear proteins from the lung, heart, liver, spleen were extracted separately, using EMSA to assay the activity of NF-kB in tissue at different CHF groups. 4.Results4.1 Serum cytokines can't be detectable in sham group using ELISA methods, while in operated group, the concentration of TNF- a and IL-6 are significantly higher, especially to IL-6;4.2 There was good association between elevated IL-6 serum levels and cardiac ultrasound as well as catheterization results. The higher content of cytokine, the worse cardiac function and higher left ventricular end-diastolic pressure. Especially to the level of IL-6;4.3 The diagnosis coincidence between echocardiography and hemodynamics is as high as 85%, echocardiography can be used as an invasive measures to assess cardiac function in rat heart failure models establish;4.4Compared with other organs, the expression of TNF- α and IL-6 mRNA was significantly earlier increased in the lung of rats with compensated HF, and the concentration shows no difference in heart , liver and spleen, while in decompensated HF, there are no significantly difference in TNF- α expression in the former three organs, but still higher than the SH group; while the expression of IL-6 was increased significantly in lung, heart and liver, especially to the liver. The cytokines expression in the local tissue was positively correlated with the activity of NF-kB. 5.conclusion5.1 Cytokines peptide content as determined by ELISA is higher in compensated compared with the other two groups, and the concentration of cytokines in serum were correlated positively with that of local tissue;5.2 Sustained activation of nuclear factor kappa B and elevation of cytokines in...