Department of Anatomy, Dalian Medical University, No, 9, West Segment of South Lvshun Road, Dalian, Liaoning, 116044, China.
J Neuroinflammation. 2012 May 20;9:96. doi: 10.1186/1742-2094-9-96.
Cathepsin C (Cat C) functions as a central coordinator for activation of many serine proteases in inflammatory cells. It has been recognized that Cat C is responsible for neutrophil recruitment and production of chemokines and cytokines in many inflammatory diseases. However, Cat C expression and its functional role in the brain under normal conditions or in neuroinflammatory processes remain unclear. Our previous study showed that Cat C promoted the progress of brain demyelination in cuprizone-treated mice. The present study further investigated the Cat C expression and activity in lipopolysaccharide (LPS)-induced neuroinflammation in vivo and in vitro.
C57BL/6 J mice were intraperitoneally injected with either 0.9% saline or lipopolysaccharide (LPS, 5 mg/kg). Immunohistochemistry (IHC) and in situ hybridization (ISH) were used to analyze microglial activation, TNF-α, IL-1β, IL-6, iNOS mRNAs expressions and cellular localization of Cat C in the brain. Nitrite assay was used to examine microglial activation in vitro; RT-PCR and ELISA were used to determine the expression and release of Cat C. Cat C activity was analyzed by cellular Cat C assay kit. Data were evaluated for statistical significance with paired t test.
Cat C was predominantly expressed in hippocampal CA2 neurons in C57BL/6 J mice under normal conditions. Six hours after LPS injection, Cat C expression was detected in cerebral cortical neurons; whereas, twenty-four hours later, Cat C expression was captured in activated microglial cells throughout the entire brain. The duration of induced Cat C expression in neurons and in microglial cells was ten days and three days, respectively. In vitro, LPS, IL-1β and IL-6 treatments increased microglial Cat C expression in a dose-dependent manner and upregulated Cat C secretion and its activity.
Taken together, these data indicate that LPS and proinflammatory cytokines IL-1β, IL-6 induce the expression, release and upregulate enzymatic activity of Cat C in microglial cells. Further investigation is required to determine the functional role of Cat C in the progression of neuroinflammation, which may have implications for therapeutics for the prevention of neuroinflammation-involved neurological disorders in the future.
组织蛋白酶 C（Cat C）作为炎症细胞中许多丝氨酸蛋白酶激活的中心协调因子发挥作用。已经认识到 Cat C 负责许多炎症性疾病中的中性粒细胞募集以及趋化因子和细胞因子的产生。然而，Cat C 在正常条件下或神经炎症过程中在大脑中的表达及其功能作用尚不清楚。我们之前的研究表明 Cat C 促进了杯状藻毒素处理的小鼠大脑脱髓鞘的进展。本研究进一步研究了脂多糖（LPS）诱导的体内和体外神经炎症中 Cat C 的表达和活性。
C57BL/6 J 小鼠经腹腔注射 0.9%生理盐水或脂多糖（LPS，5mg/kg）。免疫组织化学（IHC）和原位杂交（ISH）用于分析大脑中小胶质细胞激活、TNF-α、IL-1β、IL-6、iNOS mRNAs 表达和 Cat C 的细胞定位。亚硝酸盐测定用于检测体外小胶质细胞激活；RT-PCR 和 ELISA 用于确定 Cat C 的表达和释放。通过细胞 Cat C 测定试剂盒分析 Cat C 活性。使用配对 t 检验评估数据的统计学意义。
Cat C 在正常条件下主要在 C57BL/6 J 小鼠的海马 CA2 神经元中表达。LPS 注射后 6 小时，在大脑皮质神经元中检测到 Cat C 表达；而 24 小时后，Cat C 表达在整个大脑的激活小胶质细胞中被捕获。诱导神经元和小胶质细胞中 Cat C 表达的持续时间分别为 10 天和 3 天。体外，LPS、IL-1β 和 IL-6 处理以剂量依赖性方式增加小胶质细胞 Cat C 的表达，并上调 Cat C 分泌及其活性。
综上所述，这些数据表明 LPS 和促炎细胞因子 IL-1β、IL-6 诱导小胶质细胞中 Cat C 的表达、释放和上调酶活性。需要进一步研究以确定 Cat C 在神经炎症进展中的功能作用，这可能对未来预防神经炎症相关神经疾病的治疗具有重要意义。
