Figure 5: Molecular action mechanism of glucocorticostreoids
The effect of the glucocorticosteroids is conveyed by cytoplasmatic receptors (glucocortocoid receptor: GR). Steroids are lipophile and can thus quickly penetrate the cell membrane. Binding to the receptor releases a protein that inactivates it in a resting state. The glucocorticosteroid receptor complex penetrates the cell nucleus and operates as a transcription factor of special DNA sequences in the promoter region, so-called GRE (GCS responsive elements).
Due to their pharmacological properties (pronounced lipophilicity), new substances such as FP and MOM are extremely well absorbed into the nasal mucosa and are characterised by a high local level of effectivity (BMP (Beclometasone-diproprionate), budesonide (BU), flunisolide (FLU), triamcinolonacetonide (TRIA), fluticasone-17-Propionate (FP) and mometasone (MOM).
The oral bioavailability of the new substances is under 1%, which considerably reduces the systemic absorption of GCS.