Tetramethylpyrazine protects Schwann cells from ischemia-like injury and increases cell survival in cold ischemic rat nerves

Tetramethylpyrazine (TMP), a major active ingredient of Ligusticum wallichi Franchat extract (a Chinese herb), exhibits neuroprotective properties in ischemia. In this study, we assessed its protective effects on Schwann cells (SCs) by culturing them in the presence of oxygen glucose deprivation (OGD) conditions and measuring cell survival in cold ischemic rat nerves. In the OGD-induced ischemic injury model of SCs, we demonstrated that TMP treatment not only reduced OGD-induced cell viability losses, cell death, and apoptosis of SCs in a dose-dependent manner, and inhibited LDH release, but also suppressed OGD-induced downregulation of Bcl-2 and upregulation of Bax and caspase-3, as well as inhibited the consequent activation of caspase-3. In the cold ischemic nerve model, we found that prolonged cold ischemic exposure for four weeks was markedly associated with the absence of SCs, a decrease in cell viability, and apoptosis in preserved nerve segments incubated in University of Wisconsin solution (UWS) alone. However, TMP attenuated nerve segment damage by preserving SCs and antagonizing the decrease in nerve fiber viability and increase in TUNEL-positive cells in a dose-dependent manner. Collectively, our results indicate that TMP not only provides protective effects in an ischemia-like injury model of cultured rat SCs by regulating Bcl-2, Bax, and caspase-3, but also increases cell survival and suppresses apoptosis in the cold ischemic nerve model after prolonged ischemic exposure for four weeks. Therefore, TMP may be a novel and effective therapeutic strategy for preventing peripheral nervous system ischemic diseases and improving peripheral nerve storage.

川芎嗪（Tetramethylpyrazine, TMP）是中药川芎（Ligusticum wallichi Franchat）提取物的核心活性成分，在缺血性损伤中具有明确的神经保护作用。本研究通过建立氧糖剥夺（oxygen glucose deprivation, OGD）细胞模型培养大鼠雪旺细胞（Schwann cells, SCs），并结合低温缺血大鼠神经样本检测细胞存活情况，评估了TMP对雪旺细胞的保护效应。在氧糖剥夺诱导的雪旺细胞缺血损伤模型中，本研究证实：TMP给药可呈剂量依赖性缓解氧糖剥夺导致的雪旺细胞存活率降低、细胞死亡与凋亡，同时抑制乳酸脱氢酶（Lactate Dehydrogenase, LDH）释放；此外，TMP还可逆转氧糖剥夺诱导的Bcl-2表达下调、Bax与caspase-3表达上调，并抑制caspase-3的后续激活。在低温缺血神经模型中，本研究发现：仅用威斯康星大学溶液（University of Wisconsin solution, UWS）孵育的神经节段，经4周长时间低温缺血暴露后，会出现雪旺细胞缺失、细胞活力下降及细胞凋亡现象。而TMP可通过保留雪旺细胞、拮抗神经纤维活力降低与TUNEL阳性细胞增多，呈剂量依赖性减轻神经节段损伤。综上，本研究结果表明：TMP不仅可通过调控Bcl-2、Bax及caspase-3的表达，对培养的大鼠雪旺细胞缺血样损伤模型发挥保护作用，还可在4周长时间缺血暴露后的低温缺血神经模型中提升细胞存活率、抑制细胞凋亡。因此，TMP或可作为一种新型有效的治疗策略，用于预防外周神经系统缺血性疾病并改善外周神经储存效果。