Effects Of The Main Stress Hormones On Macrophage Functions And Their Molecular Mechanisms

Systemic Infection sepsis is a common complication of sever traumatic injury, there are still no effective therapeutic methods so far. Therefore it might be important to prevent infection at the early stage of injury. Stress, which is also known as neuro-endocrine response, takes place immediately after trauma. There is increasing evidence revealing that neuro-endocrine system has regulating effects on the immune system, but it is still not clear how it acts. Hypothalamic -pituitary-adrenal axis and the sympathic-adreno-medulae axis are the two main neuro-endocrine response axis, and glucocorticoid, epinephrine and norepinephrine are their major effector hormones. Endoplasmic reticulum is the main compartment of protein synthesis and secretion, which is very important for maintaining cell common functions. And the endoplasmic reticulum stress response is a defensive mechanism when the environment is disturbed. Pattern recognition receptors play key roles in recognition of bacteria components and in activating the effector cells during infection. Based on such researches, this study was designed to investigate the effects of the main stress hormones on macrophage functions and their potential molecular mechanisms, which includes three directions of in vitro experiments: (1) The effects of corticosterone , epinephrine and norepinephrine on immune functions of peritoneal macrophages. (2) The role of endoplasmic reticulum stress response in the regulation process of stress hormones on macrophages. (3) The effects of such hormones on the activation of peritoneal macrophages induced by LPS, and the potential role of the pattern recognition receptors. The purpose of this study is to investigate the effects of the neuro-endocrine response on the immune functions of macrophages at the early stages of traumatic injury and reveal their potential molecular mechanisms. And provide new viewpoint for the early prevention and later remedy of traumatic infections.Methods: (1) TNFαlevels were measured by ELISA kit, and the adherence, chemotactic and phagocytic capacities of peritoneal macrophage were also evaluated to observe its immune functions. (2) GRP78 and XBP1 mRNA expression levels were measured by RT-PCR. ER stress response of macrophage was induced by ER stress response inducer Thapsigargin. And the XBP1 mRNA expression level was interfered by infection of the XBP1-RNAi lentivirus. (3) CD14, SR and TLR4 mRNA expression levels were measured by RT-PCR methods. And the CD14 mRNA expression level was interfered by the transfection of CD14 siRNA.Results: (1) The adherence, chemotactic and phagocytic capacities of peritoneal macrophages were all enhanced, and the TNFαlevels were improved by corticosterone, epinephrine and norepinephrine at low concentrations obviously. But they had no effects on such functions of peritoneal macrophages at higher concentrations. (2) The corticosterone, epinephrine and norepinephrine at the concentrations that proved to have the enhancing effects on macrophages immune functions could also improve the GRP78 and XBP1 mRNA expression levels. The chemotactic and phagocytic abilities of macrophages were enhanced, and the TNFαlevels were improved when the cells were induced to ER stress response by the inducer TG. But when the ER stress response was blocked by the XBP1-RNAi lentivirus infection, the phagocytic function of macrophage was inhibited, and the TNFαlevels were reduced. (3) The phagocytic function and the TNFαsecretion levels of macrophages induced by LPS were both enhanced by corticosterone, epinephrine and norepinephrine at low concentrations. CD14 and SR mRNA expression levels were also improved by such hormones at the concentrations that had been proved to have the enhancing effects on macrophage functions. Once shutting down the CD14 mRNA levels by CD14 siRNA transfection, the phagocytic function and the secretion TNFαlevels of macrophages were inhibited obviously.Conclusions:The main stress hormones at low concentrations can enhance the immune functions of peritoneal macrophages, and ER stress response plays important roles. Pretreatment of such hormones at a suitable concentration can enhance the activation of macrophages induced by LPS, which is related to the improved expression levels of the pattern recognition receptors of macrophages. Such results infer that neuro-endocrine response at a suitable extent at the early stage of injury can not only enhance immune functions, but also affect the activation progress of immune cells at the later stage of injury when infection happens. The ER stress response and the pattern recognition receptors play important roles correspondingly. Because all of these results are observed in vitro experiments, so it needs further confirmation by in vivo studies.