Suppression of monocyte chemoattractant protein 1, but not IL-8, by alprazolam: Effect of alprazolam on c-Rel/p65 and c-Rel/p50 binding to the monocyte chemoattractant protein 1 promoter region

Alprazolam is a hypnotic/tranquilizer that has been shown to specifically inhibit the platelet-activating factor (PAF)-induced aggregation of human platelets. The goal of this study was to elucidate whether alprazolam modulates IL-1α-initiated responses. For this purpose we investigated the effects of alprazolam on the IL-1α-induced production of inflammatory cytokines (IL-8 and monocyte chemoattractant protein 1 (MCP-1)) in a human glioblastoma cell line, T98G, and explored the signaling pathways involved. We found that alprazolam inhibited IL-1α-elicited MCP-1 production within a range of 0.1-3 μM. In contrast, it did not inhibit IL-1α-induced IL-8 production. Although NF-κB is involved in regulating the IL-1α-induced expression of MCP-1 and IL-8, the degradation of IκB-α stimulated by IL-1α was not inhibited by alprazolam. Alprazolam prevented NF-κB from binding to the MCP-1 promoter region (the A2 and A1 oligonucleotide probes), but binding of NF-κB to IL-8/NF-κB was not inhibited. Moreover, alprazolam inhibited c-Rel/p50 binding to the A2 oligonucleotide probe, but not p50/p65 from binding to the IL-8/NF-κB site. While AP-1 is involved in regulating the IL-1α-induced expression of IL-8, but not MCP-1, alprazolam potentiated the binding of c-Jun/c-Fos to the AP-1 oligonucleotide probe. These results show that the inhibition of IL-1α-mediated MCP-1 production by alprazolam is mainly due to inhibition of c-Rel/p65 and c-Rel/p50 binding to the MCP-1 promoter region, since alprazolam did not affect the IL-1α-mediated activation of NF-κB (p50/p65) or AP-1 (c-Jun/c-Fos) binding to the IL-8 promoter region. In conclusion, a new action of alprazolam was elucidated, as shown in the inhibition of c-Rel/p65- and c-Rel/p50-regulated transcription.