Effects Of IUGR On Immune Function Development Of The Liver And Spleen In Newborn Piglet

Animals complete immune system is extremely important for body development and health, intrauterine growth retardation (IUGR) leads to newborn animals imperfect development of immune system, so that IUGR newborn animals display a weakened immunity, as well higher morbidity and mortality compared with normal born weight(NBW) animals.However the reporters on the immune function alteration of IUGR newborn piglets were rare. The spleen, which is an important site to immune response and production of immunologic effector substance, is the largest peripheral immune organs in animal body, while the liver is an important effector organ in systemic immune and local innate immune. In this thesis, in order to investigate the effects of IUGR on piglet immune function and probable mechanism, the liver and spleen were adopted as study objects, and learnt the effect of IUGR on newborn piglets’livers and spleens organ weight, biochemical indicators of blood, livers and spleens, hepatic tissue microstructure composition, cytokines production, correlated regulatory proteins (HSP70, Foxo3a, and mTOR) expression and positioning in the livers and spleens.Test one,30litters of piglets were given birth by30same parity sows, and then one normal birth weight (NBW) piglet and one IUGR piglet were randomly selected in each litter, to divide into NBW group and the IUGR group with equal number of male and female. Two groups of piglets were fed with cow’s milk and administered in same optimum condition for7days, then slaughtered and taken blood, livers and spleens to test the changes of liver and spleen weight and the relative weight, the variations of serum, liver, spleen protein metabolism enzymes and metabolites, and the variances of microstructure in piglet livers through histological staining observation. The results showed that:(1) the body weight, livers and spleens weight were extremely notable decreased in IUGR group piglets on7days after birth (P<0.01), and were45.31%、52.05%and54.09%lower than NBW group piglets, respectively; Liver relative weight of IUGR group piglets significantly depressed than that of NBW piglets(P<0.05), while there was no significantly difference in spleen relative weight, prompted that the effect of IUGR on organs development presented an asymmetry, and leaded to more reduction in livers than in spleens; Compared with NBW piglets, the levels of serum protein and albumin cut down for13.77%(P<0.05)and19.74%(P<0.05) in IUGR piglets serum, respectively, the content of BUN and the activities of GPT and GOT were heightened8.97%(P>0.05),23.55%(P<0.05) and7.40%(P>0.05) in IUGR piglets serum, respectively, while in IUGR piglets livers and spleens, total protein levels respectively increased 32.24%(P<0.05) and9.73%(P>0.05), and urea nitrogen contents, GPT and GOT activities decreased31.30%(P<0.05),26.06%(P<0.05),28.13%(P<0.05) and15.79%(P>0.05),20.71%(P<0.05),27.94%(P<0.05), respectively, which prompted that the functions of IUGR piglets livers and spleens were damaged, and the protein metabolism function of the liver and spleen were depressed.(2) results of hepatic tissue microexamination show that, IUGR piglets hepatic tissue structure development were weaker than that of NB W piglets, the numbers of pipages texture such as blood vessel and lymph vessel lessened, tissual lesion can be seen in certain site; there were obvious alterations in the IUGR piglets livers cells mass composition, the total number of cells in the livers, the amount of hepatocyte, Kupffer cells and lymphoid cells were reduced by18.58%(P<0.05),21.42%(P<0.05),14.07%(P<0.05) and17.50%(P<0.05) per unit area than those in NBW piglets livers, while the number of sinusoidal endothelial cells showed no significant difference (P>0.05) in two groups, these prompted that the intense reduction of liver weight was closely related to the diminution of cells amount in IUGR piglets livers; at the same time, the number of accounted as high as0.79±0.00of the total cells number in NBW piglets livers, while it accounted for only0.76±0.01of IUGR piglets liver cells, the proportion of hepatocytes decreased significantly(P<0.05), but the cells educed immune function such as Kupffer cells and endothelial cells display an significant heightened proportion of total liver cells, the proportions of Kupffer cells and endothelial cells increased4.55%(P<0.05)and24.94%(P<0.05),respectively, while the proportion of lymphoid cells was on the rise with no significant levels (P>0.05), these indicated that liver metabolism and immune function may be deflected in IUGR piglets, which manifested an declining metabolism and enhancing immune function.Test two, test animals and their dealing were same as test one, enzyme-linked immunosorbent assay and radioimmunoassay were used to detect the levels of several cytokines in IUGR and NBW piglets liver and spleen, results exhibited that:(1) IUGR piglets spleen pro-inflammatory cytokines IL-1, IL-6and TNF levels were significantly respectively increased36.35%(P<0.05),34.87%(P<0.05) and64.70%(P<0.05) than NBW piglets’, spleen IL-8levels were significantly grown downwards, was9.52%lower than NBW piglets (P<0.05), while spleen INF-γ content was3.29%lower than NBW piglets (P>0.05); compare with NBW piglets, spleen anti-inflammatory cytokines IL-2and IL-10levels respectively reduced71.81%(P <0.05) and6.19%(P>0.05), IL-4levels of0.83%(P>0.05) in IUGR piglets, indicating antigen-induced splenic immune activity increased;(2) liver pro-inflammatory cytokines IL-1β,IL-6, IL-8, TNF, and INF-y concentration in IUGR piglets were significantly descended8.65%(P<0.05),55.40%(P<0.05),22.58%(P <0.05),17.55%(P<0.05) and6.01%(P<0.05) than those in NBW piglets, respectively; compared with NBW piglets, anti-inflammatory cytokines IL-2, IL-4and IL-10levels were respectively increased by48.44%(P<0.05),29.40%(P<0.05) and5.29%(P>0.05), prompts that the livers attempted to repair the immune abnormalities caused by IUGR, and livers immune tolerance enhanced. Both of hepar and spleen cytokine levels reflected IUGR led to the increase of antigen and environment stimulus in the body, and immune function enhanced. Test three, the test animals and their dealing were same as test one, protein immunoblot (Western Blot) technology was detect HSP70, Foxo3a, and mTOR protein expression in the livers and spleens of piglets, and immunohistochemistry method was used to inspect the cells who expressed HSP70and Foxo3a, the results showed that:(1) there were protein expressions and secretion of HSP70and Foxo3a in7-day NBW pigles livers and spleens, and they were expressed mainly by immune cells, although some hepatocytes around the central vein could synthesis HSP70in liver lobule of NBW piglets; however, IUGR caused a large number and range of hepatocytes to express HSP70and Foxo3a;(2) compared with NBW, piglets the expressions of HSP70were significantly increased17.85%(P<0.05) and30.69%(P <0.05) in IUGR piglets livers and spleens, respectively, while Foxo3a expressions decreased by22.61%(P<0.05) and21.38%(P<0.05), respectively, prompted that stress increased in IUGR piglets livers and spleens, HSP70expression was increased in order to promote the activation and proliferation of immune cells and enhanced HSP70-mediated anti-apoptosis, while less Foxo3a mediated the reduction of apoptosis, these results were consistent with the increase of immune cells proportion in IUGR newborn piglets livers found in test one;(3) the mTOR protein levels were37.14%lower in IUGR piglets livers than NBW piglets livers, significantly decreased (P<0.05), while spleens mTOR content was significantly increased23.72%(P<0.05) in IUGR piglets livers, which may be due to livers construct mainly by hepatocytes, IUGR lead to the descent of hepatocytes number and proportion, and caused the reduction of mTOR levels, so that reduced the hepatic function of protein synthesis, in the other hand, spleens were composed by a large number of immune cells, IUGR caused bodies to accept an increase of antigen stimulation, which increased expression of mTOR to promote the proliferation of immune cells.In conclusion, IUGR adversely affected the structure and function of piglets livers, damaged livers function, decreased the metabolism of proteins, and enhanced immune tolerance of hepars, so that livers function appeared immune and metabolism deflection; at the same time, IUGR led to decline of spleen metabolic function and enhancement immune function; Conjecture:in IUGR piglets livers, the changes of cytokine network, the increase of HSP70levels and the decline of Foxo3a concentration were important molecular mechanisms on enhancement of immune tolerance function, while the changes of cytokine network, the increase of HSP70levels, the decline of Foxo3a concentration, as well the higher expression of mTOR, were key molecular mechanisms to mediate the elevation of splenic immune activity in IUGR piglets.