Expressions Of TLR4 And MD-2 Of Peripheral Blood Monocyte In Injured Patients And Their Clinical Significance

Objective: Gram-negative bacteria (GNB) are common initiators of septic shock following severe trauma. As one of the typical conserved pathogen-associated microbial products, the lipopolysaccharide (LPS) of GNB is a potent activator of the innate inflammatory response that has an important antimicrobial role. Recent work has shown that at least two proteins on inflammatory cells, TLR4 and MD-2, recognize LPS, meanwhile the CD14 and LPS binding protein (LBP) are involved in the process. As the critical coreceptor of LPS, TLR4/MD-2 can transmit a transmembrane signal into cytoplasm and stimulate the NF-κB, AP-1. Subsequently, amount of inflammatory mediates are released and induce SIRS, sepsis and even MODS.So many papers about TLR4/MD-2 in vitro have been published, however the expression of the coreceptor in traumatic patients has not yet reported up to now. For this reason, 35 trauma patients with injury severity score (ISS) more than 9 were studied in this article. In addition, the values of the coreceptor in prognosis prediction following severe trauma were discussed.Methods: Ten milliliters heparinized vein blood were obtained from 35 traumatic patients (ISS more than 9) at the 1st, 3rd, 5th days after injury respectively. The same treated blood from 8 healthvolunteers were collected as control. The monocyte was separated by the density centrifugation and adhesion-washing way. After the total mRNA of monocyte was isolated, the mRNA levels of TLR4 and MD-2 were tested with RT-PCR. The levels of TLR4 and CD14 on the monocyte and serum were determined with ELISA. The LPS concentration in serum was detected with limulus lysate test and the serum levels of IL-6, IL-10 and TNF-αwere estimated with ELISA.Results: According to the prognosis, the patients were divided into three groups. Group A (n=17) recovered. Group B (n=10) suffered from bad outcome (paralysis) and Group C (n=8) died from respiratory failure and circulatory failure. Increased LPS content were found in all patients, and reach to peak at the 3 days postinjury. The higher levels were found in group B and C. However the decreased expressions of mRNA of TLR4 and MD-2 of monocytes were shown. The severer of the patients, the lower of the mRNA. When the expression restore to normal level in group A at the 5th day postinjury, the group B and C kept lower markedly compared with the group A. The expression of TLR4 and CD14 protein showed the same characters. After analyzing the levels of the CD14, TLR4, IL-6, IL-10 and TNF-α in serum, the data showed that the worse of the prognosis of the patients, the higher of the proteins or cytokines in serum. When the parameters restored to normal at the 5 days postinjury in group A, group B and C were still in higher levels.Conclution: Endotoxemia is a common complications after severe trauma. In early phase after injury, over-inflammation may take a major part but at the later anti-inflammatory response became the primary problem. The low expression of TLR4, MD-2 and CD14 in monocyte may be the feedback action to the over inflammatoryresponse. An interesting phenomenon was noticed that the high level of TLR4 in serum was found in our research. Does it mean there is a soluble form of TLR4? These results suggested that the level of TLR4, MD-2 might be potential parameters to predict the prognosis of severe injury.