Neuroprotective effects of tanshinone IIA and/or tetramethylpyrazine in cerebral ischemic injury in vivo and in vitro

Abstract

The present study compared the potential neuroprotective effects of tanshinone (Tan) IIA monotherapy, tetramethylpyrazine (TMP) monotherapy, and Tan IIA+TMP combination therapy in adult rat subjected to cerebral ischemic injury using the permanent middle cerebral artery occlusion (MCAO) model and in primary cortical neuron culture exposed to oxygen-glucose deprivation (OGD) model. Male Sprague Dawley rats (n=84) were randomly divided into sham-operated, MCAO, cmc-Na (sodium carboxymethyl cellulose), TMP, Tan IIA+TMP, and Tan IIA groups. In agreement with the in vivo experiment, primary cortical neuron culture was prepared from one-day-old SD rats and grouped according to exposure: normoxia control (NC), OGD, dimethyl sulfoxide, TMP, Tan IIA+TMP, and Tan IIA groups. The neurological deficits and infarct volume were evaluated at 24h after the MCAO models. Oxidative stress (malondialdehyde, glutathione, and superoxide dismutase) and intracellular [Ca(2+)](i) concentration were measured through spectrophotometric analysis. Neurocyte apoptosis and viability were respectively evaluated through terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, respectively. Apoptosis factors (Bax, Bcl-2, caspase-3, and trmp-7) were analyzed using western blot and immunohistochemistry. The results suggest that Tan IIA+TMP combination therapy was more effective than TMP monotherapy but not Tan IIA monotherapy. Tan IIA monotherapy is more effective than TMP monotherapy in protecting the neuron against hypoxia/ischemia both in vitro and in vivo. Interestingly, Tan IIA significantly increased the phosphorylation of AKT in primary cortical neuronal culture exposed to OGD, which was abolished by PI3K inhibitor LY294002. The PI3K/AKT signaling pathway may be involved in the neuroprotective mechanism of Tan IIA on primary cortical neurons.