The Effects Of TPN On The Expressions Of Rat Intestinal Toll-like Receptors

Objective:Total parenteral nutrition (TPN) may cause the atrophy of intestine mucous, dysfunction of the mucosal barrier, bacterial translocation, increased risk of severe infection, and even septic shock. However, the mechanism underlying these alterations of mucosal immunity is largely unknown. Recently the role of innate immunity against pathogen invasion has drawn increasing attention. Toll-like receptors, among the most important pattern recognition receptors, play a crucial role in the initiation of innate cellular immune responses and subsequent acquired immune response to microbial pathogens. There has been little literature in China and abroad about changes in the expressions of intestinal toll-like receptors after TPN administration. In an effort to provide laboratorial basis for preventing and treating TPN associated complications, this study discusses the function of intestinal toll-like receptors after TPN administration in the breakdown of intestine immunity after examining the changes in their expressions by means of the transcription polymerase chain reaction (PCR) technique, and probes into their role in improving mucosal immunity with the intervention ofω-3 fish oil.Material and methods:18 specific pathogen free male SD rats were randomized into 3 groups:NS, TPN and fish oil. They were fed commercial rat food and tap water and were housed under controlled temperature (around 22 C) and relative humidity (40%-60%) conditions with a 12-12 hour light-dark cycle. A silicone catheter was sterilely inserted into the superior vena cava through the right jugular vein under general anesthesia. All rats were allowed food and water for the first two days after surgery to recover from the stress of surgery. From the third day, they received infusion through a multi-channel pump for a whole week. The NS group received saline and rat food as well as water at the same time; the TPN group received TPN (see Table 1 for formula); the fish oil group received fish oil supplement; no food or water was given to the TPN and fish oil groups. The infusion for each group was 20ml for Day 1,40ml for Day 2, and 60ml daily from Day 3 to Day 7. After the upper treatment, all rats were killed quickly through decollation for small intestinal tissues excised at 1/3 of the proximal, middle and distal sections. PCR array was used to analyze the differential expressions of TLR2,3,4,5,7,9 between the three groups.Results:The result of PCR showed varying expressing levels of TLRs at different sites on small intestine. Almost all TLR subtypes were expressed in the proximal, middle and distal small intestine. TLR4, TLR5, TLR7 and TLR9 showed up-regulated expressions in proximal and middle small intestine in response to TPN administration. TLR2, TLR3, TLR4, TLR5, TLR7 and TLR9 showed up-regulated expressions in distal intestine in response to TPN administration. TLR4, TLR5, TLR7 and TLR9 showed down-regulated expression in proximal and middle small intestine in the fish oil group compared with the TPN group. TLR2, TLR3, TLR4, TLR5, TLR7 and TLR9 showed down-regulated expression in distal small intestine in the fish oil group compared with the TPN group.Conclusion:TPN administration and a lack of enteral nutrition lead to the up-regulation of TLRs in intestine, which may be associated with an increased risk of septic shock due to bacterial translocation. Fish oil supplement emulsion, as a special nutrion element, can prevent the intestine mucosal damage after TPN administration.