Johns D G, Webb R C, Charpie J R
Department of Medicine, Boston University, Massachusetts, USA.
J Hypertens. 2001 Jan;19(1):63-70. doi: 10.1097/00004872-200101000-00009.
In hypertension, the vascular wall undergoes morphological changes that alter mechanical responses to vasoactive substances. Ceramide is a recently identified second messenger synthesized in response to cytokines such as tumour necrosis factor alpha (TNF-alpha). It has been previously demonstrated that vascular smooth muscle cells (VSMC) from genetically hypertensive rats proliferate at a higher rate than those of normotensive origin. We tested the hypothesis that the ceramide pathway is impaired in VSMC from spontaneously hypertensive rats (SHR).
VSMC were isolated from aortae of SHR and from Wistar-Kyoto (WKY) rats. Ceramide levels were measured under baseline and agonist-stimulated conditions and cell proliferation was monitored.
Cell proliferation was determined by cell counting. Ceramide levels were determined via radioactive labelling, high-performance thin-layer chromatography and phosphorimaging. Relative mRNA levels of neutral sphingomyelinase were determined using semi-quantitative polymerase chain reaction (PCR).
Basal ceramide levels in untreated cells were lower in cells from SHR compared to WKY rats. During chronic treatment with TNF-alpha, ceramide levels increased in WKY rat cells but remained unchanged in cells from SHR. TNF-alpha treatment had an inhibitory effect on WKY rat VSMC proliferation, but stimulated proliferation in cells from SHR. Short-term incubation with TNF-alpha resulted in a greater increase in ceramide in cells from WKY rats than those from SHR. Semiquantitative PCR analysis indicated that neutral sphingomyelinase mRNA may be reduced in SHR VSMC.
We conclude that ceramide synthesis is impaired in vascular smooth muscle from SHR and may contribute to increased VSMC proliferation in hypertension.
在高血压中，血管壁会发生形态学变化，从而改变对血管活性物质的机械反应。神经酰胺是最近发现的一种第二信使，可响应肿瘤坏死因子α（TNF-α）等细胞因子而合成。先前已经证明，遗传性高血压大鼠的血管平滑肌细胞（VSMC）比正常血压来源的细胞增殖速度更快。我们检验了以下假设：自发性高血压大鼠（SHR）的VSMC中神经酰胺途径受损。
从SHR和Wistar-Kyoto（WKY）大鼠的主动脉中分离VSMC。在基线和激动剂刺激条件下测量神经酰胺水平，并监测细胞增殖。
通过细胞计数确定细胞增殖。通过放射性标记、高效薄层色谱和荧光成像确定神经酰胺水平。使用半定量聚合酶链反应（PCR）测定中性鞘磷脂酶的相对mRNA水平。
与WKY大鼠相比，SHR细胞中未处理细胞的基础神经酰胺水平较低。在用TNF-α进行慢性治疗期间，WKY大鼠细胞中的神经酰胺水平升高，但SHR细胞中的神经酰胺水平保持不变。TNF-α治疗对WKY大鼠VSMC增殖有抑制作用，但刺激了SHR细胞的增殖。与SHR细胞相比，用TNF-α短期孵育导致WKY大鼠细胞中的神经酰胺增加更多。半定量PCR分析表明，SHR VSMC中的中性鞘磷脂酶mRNA可能减少。
我们得出结论，SHR的血管平滑肌中神经酰胺合成受损，可能导致高血压中VSMC增殖增加。
