Effect of lanthanum exposure during early postnatal period on matrix metalloproteinase-9 expression in hippocampus of rats

  Objective  To observe the effect of postnatal lanthanum exposure on protein and mRNA expression of matrix metalloproteinase-9 (MMP-9) in hippocampus of rats.

  Methods  Forty pregnant Wistar rats were randomly divided into a control group and low-, moderate-, and high-dose lanthanum groups and then their offspring were exposed to lanthanum of different concentration (0.25 %, 0.50 %, and 1.00 %) through drinking water during lactation until one month after delactation. MMP-2 and MMP-9 protein expression in hippocampus were detected with Western blot, while MMP-2/9 and tissue inhibitors of metalloproteinase (Timp 2/1) mRNA levels were measured with real-time PCR.

  Results  In comparison with those of the control group, significantly increased MMP-9 protein expression (0.172 ± 0.017 and 0.236 ± 0.022) and mRNA expression (1.267 ± 0.102 and 1.456 ± 0.081) were detected in offspring rats' hippocampuses of the moderate- and high-dose lanthanum groups (both P < 0.05); moreover, a significant decrease in Timp1 mRNA expression (0.784 ± 0.034) was observed in hippocampuses of the offspring rats with high-dose lanthanum exposure.

  Conclusion  Early postnatal period lanthanum exposure up-regulates protein and mRNA expression of MMP-9, but down-regulates Timp1 mRNA expression in hippocampus of offspring rats, resulting in blood-brain barrier damage due to the activation of MMP-9 and subcequent degradation of tight junction proteins.