Characterization of proteasome inhibition on astrocytes cell cycle.

Increasing evidence indicates that proteasome inhibition occurs in multiple central nervous system (CNS) disorders, including Alzheimer's disease (AD) and Parkinson's disease (PD). Compared with the extensive studies on neurons, little attention is paid on the proteasome inhibition in astrocytes. Here, we demonstrated that lactacystin inhibited proteasome dose-dependently in cultured astrocytes. Simultaneously, lactacystin suppressed the expression of cell cycle proteins in astrocytes and caused the proliferating astrocytes arrested at G1/S checkpoint. Western blots showed that proteasome inhibition led to a decrease in cdk-2, cdk-4, cyclin D1 expression accompanied with an increase in p21waf1/cip1 expression. The effect of chronic low-level proteasome inhibition on astrocytes was consistent with that in acute proteasome inhibition. Furthermore, increased levels of interleukin-6 (IL-6) secretion, STAT-3 and phospho-STAT-3 expression were found, suggesting that proteasome inhibition in astrocytes could stabilize signals of grow arrest through the JAK/STAT signaling cascade.