Blood interleukin-6, interleukin-8 and metal matrix protease-9 in neonatal rat lung injury caused by intrauterine infection / 中国新生儿科杂志

ABSTRACT

Objective To investigate the significance of interleukin-6 IL-6),interleukin-8 (IL-8) and metal matrix protease-9 (MMP-9) in lung injury caused by intrauterine infection in ueonatal rats.Method Eighteen 18-day-old SD pregnant rats were selected and randomly assigned into 0.6,0.7,0.8,0.9,1.0 mg/kg lipopolysaccharide (LPS) groups and control group.Rats of LPS group were injected intraperitoneally with LPS 0.6.0.7,0.8,0.9,1.0 mg/kg,those of control group was injected with equal volume of sterile saline.After 24 hours of injection,one pregnant rat from each group underwent cesarean seetion and placentae were collected for pathological evaluation.The other pregnant rats delivered spontaneously.When the neonatal rats came to 1,3,and 7 days of age,8 rats were randomly selected from each group.The respiratory frequency,body weight,lung weight,and blood samples for detecting inflammatory factors using enzyme-linked immunosorbent assay were measured among 3-day-old neonatal rats.Lung tissue for hematoxylin-eosin staining and lung pathology score were taken in the 1,3 and 7-day-old neonatal rats.Result (1) The mortality rate of neonatal rats increased gradually with the increasing dose of LPS injection.The mortality rate of neonatal rats in the LPS 1.0 mg/kg group was 20％.The placental pathology score and the frequency of 3-day-old neonatal rats in LPS 0.8,0.9,and 1.0 mg/kg groups were higher than control group and other LPS groups (P ＜ 0.05).(2) The histopathological scores of the neonatal rats in the control group and LPS 0.6,0.7,0.8,0.9,1.0 mg/kg groups on the first day after birth were (0.08±0.08),(0.17±0.11),(1.33±0.19),(1.75±0.33),(1.92±0.36),(2.67±0.14),respectively,and that of the third day after birth were (0.00 ± 0.00),(0.50 ± 0.15),(0.67 ±0.19),(1.33 ±0.36),(2.17 ±0.21),(2.92 ±0.08),respectively.LPS 1.0 mg/kg group on the 1st and 3rd day after birth were significantly different from the other groups (P ＜0.05),LPS 0.8 mg/kg group on the 1st and 3rd day after birth were significantly different from the control group and LPS 0.6 mg/kg group (P ＜ 0.05),and there was significant difference among the LPS 0.9 mg/kg group and the other groups on the 3rd day after birth (P ＜ 0.05).When the concentration of LPS was less than 0.8 mg/kg,there was no significant difference in the pathological scores of the lung tissues between each group (P ＞0.05).(3) The concentrations of IL-6,IL-8,and MMP-9 in the neonatal rats of LPS 0.7,0.8,0.9,and 1.0 mg/kg groups were significantly higher than those in the control group at 3 days of age,and the difference among LPS groups were statistically significant (P ＜ 0.05).Conclusion The intraperitoneal injection of LPS in rats 18 days after gestation can lead to lung injury,pulmonary edema,and increasing level of blood IL-6,IL-8,and MMP-9 in the neonatal rats,and this damage lasts until 7 days after birth which suggests the important meaning for lung diseases caused by intrauterine infection.