N-acetylcysteine reduces glutamate-induced cytotoxicity to fibroblasts of rat supraspinatus tendons

<b>Purpose</b>: Neuronal theory regarding rotator cuff degeneration has developed from the findings that glutamate, an amino acid and an excitatory neurotransmitter, is present in increased concentrations in tendon tissues with tendinopathy and that glutamate induces cell death in fibroblasts of origin in rat supraspinatus tendon. The purpose of the current study was to determine whether N-acetylcysteine (NAC) has cytoprotective effects against glutamate-induced fibroblast death. <b>Materials and Methods</b>: Primary cultured fibroblasts were obtained from rat supraspinatus tendons. Varying concentrations of glutamate (0.5, 1, 5, and 10 mM) and of NAC (0.5, 1, 2, and 5 mM) were used for evaluation of cytotoxicity. Cell viability, cell cycles, types of cell death, intracellular ROS production, expressions of caspase-3/7, and Ca²⁺ influx were evaluated. <b>Results</b>: Glutamate significantly induced cell death, apoptosis, and Ca²⁺ influx and significantly increased caspase-3/7 activity and intracellular ROS production (<i>p </i>2+ influx, caspase-3/7 activity, and intracellular ROS production (<i>p </i> <b>Conclusions</b>: The glutamate-induced cytotoxic effects can be reduced by NAC, an antioxidant, through the reduction of intracellular oxidative stress and/or Ca²⁺ influx.

**目的**：关于肩袖退变的神经相关理论，源于下述研究发现：作为氨基酸类兴奋性神经递质的谷氨酸（glutamate），在肌腱病患者的肌腱组织中浓度升高，且谷氨酸可诱导大鼠冈上肌腱来源的成纤维细胞发生死亡。本研究旨在探讨N-乙酰半胱氨酸（N-acetylcysteine, NAC）是否对谷氨酸诱导的成纤维细胞死亡具有细胞保护作用。
**材料与方法**：本研究从大鼠冈上肌腱中分离获得原代培养成纤维细胞。设置不同浓度梯度的谷氨酸（0.5、1、5、10 mM）与N-乙酰半胱氨酸（0.5、1、2、5 mM），用于细胞毒性评价。检测指标包括细胞活力、细胞周期、细胞死亡类型、细胞内活性氧（Reactive Oxygen Species, ROS）生成、半胱天冬酶-3/7（caspase-3/7）表达以及钙离子（Ca²⁺）内流情况。
**结果**：谷氨酸可显著诱导细胞死亡、凋亡及钙离子内流，并显著升高半胱天冬酶-3/7活性与细胞内活性氧生成（*p* ）；钙离子内流、半胱天冬酶-3/7活性及细胞内活性氧生成（*p* ）。
**结论**：作为抗氧化剂的N-乙酰半胱氨酸，可通过减轻细胞内氧化应激及/或钙离子内流，缓解谷氨酸诱导的细胞毒性效应。