Steiner J, Bernstein H-G, Bogerts B, Gos T, Richter-Landsberg C, Wunderlich M T, Keilhoff G
Department of Psychiatry, University of Magdeburg, Leipziger Strasse 44, Magdeburg, Germany.
Neuroscience. 2008 Jun 23;154(2):496-503. doi: 10.1016/j.neuroscience.2008.03.060. Epub 2008 Apr 8.
S100B (member of a family of proteins that are 100% soluble in ammonium sulfate at neutral pH) has been widely used as astrocyte marker in animal models and in human brain diseases. Recent studies revealed S100B-immunopositivity in oligodendrocytes and O2A oligodendroglial progenitor cells. It is unknown, however, if oligodendrocytes produce S100B themselves, or if the S100B-immunolabeling is caused by binding or absorption of the protein. To address this question, S100B expression and protein release were analyzed in a highly pure oligodendrocytic OLN-93 cell line (from rat), in the astrocytic C6 cell line (from rat) and primary astrocytes. S100B was gene expressed in all cultures, as revealed by reverse transcriptase polymerase chain reaction (RT-PCR) analysis. OLN-93 cells and glial fibrillary acidic protein (GFAP)-negative astrocytes expressed the multiligand receptor for advanced glycation end products (RAGE). S100B protein levels were determined in supernatants and cell homogenates by immunoluminometry under normal conditions and after serum and glucose deprivation (SGD). SGD led to a several-fold increased release of S100B (after 6 and 24 h), which was particularly pronounced in primary astrocytes. Increased S100B in cell homogenates was most notable in OLN-93 cells under SGD, indicating activated S100B synthesis. These cells also showed the highest percentage of dead cells, as determined by propidium iodide-positivity, after SGD. Incubation with 0.5, 2 and 5 microg/l exogenous S100B was not toxic to OLN-93 cells. In conclusion, OLN-93 cells produce more S100B under SGD than astrocytes and are more susceptible to cell death upon SGD, which provokes leakage of S100B. Our data indicate active S100B secretion from astrocytes under SGD since highly elevated levels of S100B were detected in the supernatant despite a low percentage of dead cells. The experimental results provide further evidence for a production/release of S100B in/from oligodendrocytes, e.g. in metabolic stress conditions like cerebral ischemia. Studies on S100B in bodily fluids should be carefully interpreted in order to avoid misleading hypotheses concerning the specific involvement of astrocytes, due to the various cellular sources of S100B.
S100B（一类在中性pH值下能100%溶于硫酸铵的蛋白质家族成员）已在动物模型和人类脑部疾病中被广泛用作星形胶质细胞标志物。最近的研究揭示了少突胶质细胞和少突胶质前体细胞O2A中存在S100B免疫阳性。然而，尚不清楚少突胶质细胞自身是否产生S100B，或者S100B免疫标记是由该蛋白质的结合或吸附引起的。为了解决这个问题，对一种高度纯化的少突胶质细胞系OLN - 93（来自大鼠）、星形胶质细胞系C6（来自大鼠）和原代星形胶质细胞进行了S100B表达和蛋白质释放分析。逆转录聚合酶链反应（RT - PCR）分析显示，S100B在所有培养物中均有基因表达。OLN - 93细胞和胶质纤维酸性蛋白（GFAP）阴性的星形胶质细胞表达晚期糖基化终产物多配体受体（RAGE）。通过免疫发光法在正常条件下以及血清和葡萄糖剥夺（SGD）后测定上清液和细胞匀浆中的S100B蛋白水平。SGD导致S100B释放增加数倍（6小时和24小时后），这在原代星形胶质细胞中尤为明显。在SGD条件下，OLN - 93细胞匀浆中S100B增加最为显著，表明S100B合成被激活。用碘化丙啶阳性测定法确定，这些细胞在SGD后死亡细胞百分比也最高。用0.5、2和5微克/升的外源性S100B孵育对OLN - 93细胞无毒。总之，OLN - 93细胞在SGD条件下比星形胶质细胞产生更多的S100B，并且在SGD时更易发生细胞死亡，从而导致S100B泄漏。我们的数据表明，在SGD条件下星形胶质细胞会主动分泌S100B，因为尽管死亡细胞百分比很低，但在上清液中检测到S100B水平大幅升高。实验结果为少突胶质细胞中S100B的产生/释放提供了进一步证据，例如在脑缺血等代谢应激条件下。由于S100B有多种细胞来源，因此对体液中S100B的研究应谨慎解读，以避免关于星形胶质细胞具体作用的误导性假设。
