| It is well known that trauma and infection are the two most common reasons for MODS. Bacterial lipopolysaccharide (LPS), the major structural component of the outer wall of Gram-negative bacteria, is a potent activator of effector cells. CD 14 and Toll-like receptor 4 (TLR4), two components of LPS receptor complex, play key roles in LPS signaling transduction and in modulating the activity of intracellular transcription factors, nuclear factor-kappa B (NF-kB), which is essential for the synthesis of inflammatory cytokines, such as tumor necrosis factor alpha(TNF-α)and interleukin-6 (IL-6), and for the genesis and development of multiple organ dysfunction syndrome (MODS).MODS is a particularly serious problem in the geriatric population, as the elderly show a significantly elevated mortality rate during MODS. In particular, multiple organ dysfunction syndrome in the elderly (MODSE) is often secondary to lung infection and the lung is the first and serious injured organ. It suggests that the lung play a key role in genesis and developing of MODS and the susceptibility to infection of the lung enhance in the elderly, though the precise mechanisms for this age-dependent and tissue-dependent vulnerability to damage remain unknown. In this study, MODSE and multiple organ dysfunction syndrome in the young (MODSY) models were established by injection of oleic acid (OA) and LPS. The contents of TNF- α . IL-6 in plasma and tissues and expression of CD 14 and TLR4 were determined. The changes of activity of NF-kB in lung were also detected.Methods1. Models of MODSE and MODSY were established by injection of OA at the dose of 0.25 ml/kg and LPS at dose of 3.5mg/kg into SD rats (4 h interval).2. TNF-α and IL-6 contents in plasma and in the lung, heart, liver, and kidney tissues were determined with enzyme linked immunoadsorbent assay (ELISA). Levels of TNF-α and IL-6 mRNA in above tissues were determined with RT-PCR.3. Tissue endotoxin levels in lung, heart, liver, and kidney were quantified by tachypleus amebocyte lysate (TAL) technique.4. Levels of CD 14 and TLR4 mRNA in lung, heart, liver, and kidney tissues were determined with RT-PCR. The changes of CD 14 and TLR4 expression in above tissues were detected with immunohistochemistry.5. By using immunohistochemistry with in situ quantitative analysis, the distribution and relative contents of NF- κ B in lung were determined.Results1. Injection of OA and LPS into the young and the elder rats led to multiple organs dysfunctions. PaO2 of Young Group and Elderly Group decreased to minimum at 2 h [(67.5 ± 8.66) and (59.3 ± 7.41) mmHg, respectively, P<0.01].While the biochemical indexes of the heart, liver, and kidney organ injuries increased to maximum at 6 h ( P< 0.05- 0.01). Furthermore, the organs in Elderly Group were damaged more seriously than those in Young Group at the same time points (P< 0.05- 0.01).2. The stress-mediated induction of TNF-α and IL-6 in serum and tissues and the mRNA for them expressions in tissues increased significantly (especially in the lungs) after LPS injection and peaked at 2 h time point (P< 0.05- 0.01). The induction of mRNA for TNF-α and IL-6 at 2 h and 6 h time points was significantly enhanced with aging. (P<0.05-0.01).3. Endotoxin was determined in tissues in Control Group with the highest level in lung. It was found that endotoxin levels in lung, heart, liver, and kidneys increased markedly 2 h after injection of OA and LPS (P<0.01), which increased especially in the lungs by 12 folds and 9.8 folds in Elderly Group and Young Group. Endotoxin levels in tissues tended to decrease 6 ~ 24 h after damage, but still to remain higher than Control Group respectively (P<0.01). Which increased more markedly in Elderly Group than in Young Group at 2 ~ 24 h time point (P<0.01).4. Levels of CD 14 and TLR4 mRNA in tissues increased significantly (especially in the lungs) ( p<0.05, p<0.01), which increased to minimum at 2 h in lung tissue, and at 6 h in heart, liver, and kidney tissues. Furthermore, which mRNA levels increased more markedly in Elderly Group than those in Young Group at the same time points ( p<0.05-0.01). The changes of CD 14 and TLR4 expression on surface mostly of monocyte/ macrophage, endothelial cell and cells of various tissues were paralleled with its mRNA.5. NF- κ B weakly expressed mostly on cytoplasm of alveolar macrophage, alveolar epithelial cell and endothelial cell of blood vessel in lung of control group. The expression of NF-κ B in lung up-regulated after damage, which expressed not only on cytoplasm butalso on nucleus. The relative contents of NF- κ B in lung increased significantly especially at 2 h and which tended to attenuate at 24 h. Furthermore, the expression of NF- κ B increased more markedly in Elderly Group than those in Young Group at the same time points, especially at 2 h (P<0.05~ 0.01). Conclusion1. OA and LPS injection can lead to more serious multiple organs injures in elder rats than those in young rats. The lung is injured firstly and most seriously.2. Early and quickly increase of TNF-α and IL-6 concentration in tissues participate in multiple organ injures after injection of OA and LPS. Higher concentration of TNF-α and IL-6 in elder rats than in young rats especially in lung relates to lung injures firstly and seriously during MODSE progress.3. Endotoxin contents increase markedly in various tissues, especially in lung after injection of OA and LPS. The lung tissue with higher affinity to endotoxin may play an important role in mediating lung injures firstly and seriously during MODSE progress.4. Expression of CD 14 and TLR4 in lung increase markedly among various tissues, higher in elder rats than in young rats after injection of OA and LPS. Enhanced susceptibility of CD 14 and TLR4 in lung in elderly rats might be the background of lung injures firstly. NF-kB might participate in modulating expression of TNF-α and IL-6 genes and then inducing lung injures firstly.
|
PDF Full Text Request