Lead exposure disturbs ATP7B-mediated copper export from brain barrier cells by inhibiting XIAP-regulated COMMD1 protein degradation.

The brain barrier is an important structure for metal ion homeostasis. According to studies, lead (Pb) exposure disrupts the transportation of copper (Cu) through the brain barrier, which may cause impairment of the nervous system; however, the specific mechanism is unknown. The previous studies suggested the X-linked inhibitor of apoptosis (XIAP) is a sensor for cellular Cu level which mediate the degradation of the MURR1 domain-containing 1 (COMMD1) protein. XIAP/COMMD1 axis was thought to be an important regulator in Cu metabolism maintenance. In this study, the role of XIAP-regulated COMMD1 protein degradation in Pb-induced Cu disorders in brain barrier cells was investigated. Pb exposure significantly increased Cu levels in both cell types, according to atomic absorption technology testing. Western blotting and reverse transcription PCR (RT-PCR) showed that COMMD1 protein levels were significantly increased, whereas XIAP, ATP7A, and ATP7B protein levels were significantly decreased. However, there were no significant effects at the messenger RNA (mRNA) level (XIAP, ATP7A, and ATP7B). Pb-induced Cu accumulation and ATP7B expression were reduced when COMMD1 was knocked down by transient small interfering RNA (siRNA) transfection. In addition, transient plasmid transfection of XIAP before Pb exposure reduced Pb-induced Cu accumulation, increased COMMD1 protein levels, and decreased ATP7B levels. In conclusion, Pb exposure can reduce XIAP protein expression, increase COMMD1 protein levels, and specifically decrease ATP7B protein levels, resulting in Cu accumulation in brain barrier cells.

[Simultaneous determination of trace amounts of iron(II), copper(I) and cobalt(II) in aloe by second derivative peak area spectrophotometry].

A new method for simultaneous determination of iron(II), copper(I) and cobalt(II) was established by second derivative peak area spectrophotometry in chromogenic system of 1,10-phenanthroline. The method could avoid disturbing by some ions. The accuracy and sensitivity were improved. There is a linear relationship in the range of 0.0-8.5 microg x mL(-1) for Fe(II); of 0.0-7.3 microg x mL(-1) for Cu(I); and of 0.0-5.9 microg x mL(-1) for Co(II). The method has been applied to simultaneous determination of iron(II), copper(I) and cobalt(II) in aloe with satisfactory results. The average recovery is 98.6%-102% and the RSD is 0.1%-0.2%. There is no remarkable difference between these results and those of ICP-AES method.