Inhibition of GFAP synthesis by antisense RNA in astrocytes

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Abstract
Glial fibrillary acidic protein (GFAP) accumulation is a prominent feature of astrocytic gliosis. The inhibition or delay in GFAP synthesis might delay scar formation resulting from an insult such as spinal cord injury or central nervous system (CNS) demyelination. The delay in the formation of a physical barrier might allow the neurons and oligodendrocytes to reestablish a functional environment. We delivered antisense GFAP RNA complexed with LipofectinTM (LF), a cationic liposome, into cerebral astrocytes in culture and tested the feasibility of inhibiting GFAP synthesis. Our results demonstrate that LF facilitated antisense RNA uptake into astrocytes. Astrocytes took up 3H‐antisense GFAP RNA alone and reached an equilibrium of 7–8.8 ηg per mg protein after 2.5 hr. When complexed with LF, astrocytes could increase the uptake to 14 ηg per mg protein and the time for reaching this quantity was shortened to 10 min. This uptake level was further enhanced if experiments were carried out in HEPES buffered saline (HBS). All uptake studies were dose‐ and time‐dependent. Dibutyryl cyclic AMP (dBcAMP) is known to induce an increase of GFAP content in cultured astrocytes. We studied the effect of LF/antisense GFAP RNA on the GFAP content in dBcAMP (0.25 mM)‐treated astrocytes. Cultures of astrocytes treated with dBcAMP contained almost twice as much GFAP as untreated cultures after 2 days. Similar cultures treated with LF/antisense RNA in HBS did not show an increase but a 30–40% decrease in GFAP content 2 days after treatment. A similar decrease in GFAP content was obtained in cultures grown in a chemically defined medium, another condition known to induce an increase in GFAP content in cultures. This study has demonstrated that antisense GFAP RNA can inhibit GFAP synthesis in astrocytes and may be useful for regulating astrogliosis immediately following CNS injury.