Antenatal taurine supplementation improves neural axon development in fetal rats with intrauterine growth restriction by inhibiting the activity of Rho-ROCK signaling pathway

Objective To investigate the effects of prenatal taurine supplementation on the Rho-ROCK signaling pathway activity and synaptophysin (Syp) expression in brain tissues of rats with intrauterine growth restriction. Methods Eighteen pregnant Sprague-Dawley rats were randomly divided into control group, fetal growth restriction (FGR) group and taurine group, with six rats in each group. Low-protein diet was given in FGR and taurine groups to establish an FGR model. Taurine 300 mg/(kg·d) was supplemented from gestational day 12 until delivery in taurine group. The mRNA expression levels of neurite growth inhibitor-A(Nogo-A), neurite growth inhibitor receptor (NgR), Rho-A and ROCKⅡin fetal rat brain were detected using reverse transcriptase polymerase chain reaction (n=24), which are the key signaling molecules of the Rho-ROCK signal pathway. The protein expression levels of Nogo-A and NgR were detected by Western blot (n=12). The mean optical density in Nogo-A, NgR and Syp was determined by immunohistochemistry (n=18). One-way analysis of variance and LSD-t test were used for statistical analysis. Results (1) Expression of mRNA: the expression levels of Nogo-A, NgR, Rho-A and ROCKⅡ mRNA in fetal rat brain were 4.09±1.34, 3.01±0.77, 39.89±7.71 and 7.82±1.83, respectively in FGR group, and were significantly higher than in control group (1.00±0.13, 1.00±0.10, 1.02±0.30 and 1.00±0.10) (t=4.735, 5.204, 7.682 and 10.675, all P 0.05). (2) Expression of protein by Western blot: the expressions of Nogo-A and NgR protein in fetal rat brain were 1.51±0.09 and 0.31±0.05 in FGR group, 0.82±0.06 and 0.06±0.01 in taurine group, and 1.04±0.10 and 0.09±0.12 in control group. The expression was significantly higher in FGR group than in control group (t=9.644 and 5.285, both P 0.05). (3) Positive expression of protein: the positive expressions of Nogo-A and NgR protein in fetal rat brain were 0.28±0.06 and 0.11±0.02 in FGR group, 0.10±0.02 and 0.04±0.01 in taurine group, and 0.07±0.01 and 0.04±0.01 in control group. The expression was significantly higher in FGR group than in control group (t=9.778 and 7.645, both P 0.05). The positive expression of Syp protein in fetal rat brain was 0.08±0.01 in FGR group, and was significantly lower than in control group (0.16±0.04, t=4.600, P 0.05). Conclusions Prenatal taurine supplementation can improve neural axon development via down-regulating the expressions of the key molecules of Rho-ROCK signal pathway in fetal rat brain tissue. Key words: Fetal growth retardation; Taurine; Rho-associated kinases; Synaptophysin; Signal transduction; Axons; Rats, Sprague-Dawley