Salmeterol (GR33343X)

In vitro activity: In a previoius study, it was found that salmeterol could reduce retinal Müller cell death through the inhibition of the phosphorylation of IRS-1(Ser307). In addition, the findings also suggest the importance of IRS-1 in beta-adrenergic receptor signaling in the prevention of cell death in retinal Müller cells.

Kinase Assay: The cells are rinsed twice with ice-cold phosphate-buffered saline and mechanically detached in ice-cold buffer containing 10 mM Tris·HCl, pH 7.4, 5 mM EDTA, 10 μg/mL benzamidine, 10 μg/mL soybean trypsin inhibitor (type II-S), and 5 μg/mL leupeptin (lysis buffer). The lysate is centrifuged at 45,000 ×g for 10 min at 4°C. The pellet is rehomogenized in lysis buffer, with a Potter-type homogenizer, and stored at −80°C until use. The competition binding assays are performed in buffer containing 75 mM Tris·HCl, pH 7.4, 12.5 mM MgCl2, and 2 mM EDTA, using 1-5 μg of membrane protein, 50 pM 125I-CYP, and 0-100 μM unlabeled ligand in the presence of 100 μM GTP, for 60 min at 37°C. The binding reaction is terminated by dilution and rapid filtration through Whatman GF/C filters; the filters are washed three times with solution containing 25 mM Tris·HCl, pH 7.4, and 1 mM MgCl2. Nonspecific binding is determined in the presence of 5 μM (±)-propranolol. The radioactivity on the filters is counted with a γ-counter.

Cell Assay: Salmeterol significantly inhibits production of pro-inflammatory mediators by RAW264.7 and THP-1 cells. Salmeterol downregulates PgLPS-mediated phosphorylation of the ERK1/2 and JNK but not p38 MAP kinases (MAP-K). Salmeterol also attenuates the activation of NF-κB via inhibition of nuclear translocation of p65-NFκB, the transcriptional activity of NF-κB and IκBα phosphorylation. Salmeterol shows very high selectivity for the WT β2AR (β1 Ki /β2 Ki ratio of approximately 1500) with Ki of 1.5±0.4 nM. Salmeterol prevents phosphorylation levels of IRS-1Ser307 induced by tumor necrosis factor-α. Salmeterol alone prevents cell death in retinal Müller cells (p<0.05 versus 25 mM glucose). Salmeterol in conbination with IRS-1 shRNA shows a significant increase in cell death compared to salmeterol alone. Moreover, salmeterol alone treatment significantly reduces cytochrome C levels, with the effect lessened when salmeterol is combined with IRS-1 shRNA. Salmeterol (100 μM) causes apoptosis of DCs, and can not affect the differentiation and maturation of DCs at 10 μM. Salmeterol (10 μM) decreases the mRNA and protein levels of pro-inflammatory cytokines in LPS-activated DCs and inhibits MAPK and NF-κB activation.