Crossgrove Janelle S, Yokel Robert A
Graduate Center for Toxicology, University of Kentucky Medical Center, Lexington, KY 40536-0305, USA.
Neurotoxicology. 2005 Jun;26(3):297-307. doi: 10.1016/j.neuro.2004.09.004. Epub 2004 Nov 11.
Manganese (Mn) is a required co-factor for many ubiquitous enzymes; however, chronic Mn overexposure can cause manganism, a parkinsonian-like syndrome. Previous studies showed Mn influx into brain is carrier-mediated, though the putative carrier(s) were not established. Studies conducted with cultured bovine brain microvascular endothelial cells (bBMECs), which comprise the blood-brain barrier, revealed (54)Mn (II) uptake positively correlated with pH, was temperature-dependent, and was sodium- and energy-independent. Brain (54)Mn uptake correlated inversely with calcium (Ca) concentration, but (45)Ca uptake was unaltered by high Mn concentration. Lanthanum (La), a non-selective inhibitor of several Ca channel types, as well as verapamil and amiloride, inhibitors of voltage-operated Ca channels, failed to inhibit Mn uptake into cells. Nickel (Ni), another non-selective inhibitor of several Ca channel types, inhibited Mn and Ca uptake into cells by 88 and 85%, respectively. Cyclopiazonic acid (CPA) and thapsigargin, which activate store-operated calcium channels (SOCCs), increased (54)Mn and (45)Ca uptake into cultured bBMECs. In situ brain perfusion studies were conducted in adult, male Sprague-Dawley rats to verify the cell culture results. Both nickel and verapamil produced a non-significant decrease in Mn and Ca influx. Lanthanum significantly increased Mn influx to 675 and 450% of control in parietal cortex and caudate, respectively, while producing no significant effect on Ca influx. Vanadate, which inhibits Ca-ATPase, inhibited Mn uptake into cultured blood-brain barrier cells, but not into perfused rat brain. Overall these results suggest that both Ca-dependent and Ca-independent mechanisms play a role in brain Mn influx. This work provides evidence that store-operated Ca channels, as well as another mechanism at the blood-brain barrier, likely play a role in carrier-mediated Mn influx into the brain.
锰（Mn）是许多普遍存在的酶所必需的辅助因子；然而，长期过度接触锰会导致锰中毒，一种类似帕金森氏症的综合征。先前的研究表明，锰流入大脑是由载体介导的，尽管尚未确定假定的载体。对构成血脑屏障的培养牛脑微血管内皮细胞（bBMECs）进行的研究表明，（54）Mn（II）摄取与pH呈正相关，具有温度依赖性，且与钠和能量无关。脑（54）Mn摄取与钙（Ca）浓度呈负相关，但高锰浓度对（45）Ca摄取无影响。镧（La）是几种钙通道类型的非选择性抑制剂，以及维拉帕米和氨氯吡脒，电压门控钙通道的抑制剂，均未能抑制锰摄取进入细胞。镍（Ni）是几种钙通道类型的另一种非选择性抑制剂，分别抑制锰和钙摄取进入细胞88%和85%。环匹阿尼酸（CPA）和毒胡萝卜素可激活储存操纵性钙通道（SOCCs），增加培养的bBMECs对（54）Mn和（45）Ca的摄取。在成年雄性Sprague-Dawley大鼠中进行原位脑灌注研究以验证细胞培养结果。镍和维拉帕米均使锰和钙流入量出现不显著的下降。镧分别使顶叶皮质和尾状核中的锰流入量显著增加至对照的675%和450%，而对钙流入量无显著影响。抑制钙-ATP酶的钒酸盐抑制锰摄取进入培养的血脑屏障细胞，但不抑制锰摄取进入灌注的大鼠脑。总体而言，这些结果表明，依赖钙和不依赖钙的机制在脑锰流入中均起作用。这项工作提供了证据，表明储存操纵性钙通道以及血脑屏障处的另一种机制可能在载体介导的锰流入大脑中起作用。
