Figure 1: Various growth factors and acneigenic stimuli activate PI3K/Akt signal transduction. Phosphorylated (green hexagons) FoxO1 is exported out of the nucleus into the cytoplasm. The resulting derepression and activation of acne target genes as well as the derepression of inhibitory nuclear receptors (NR) induce androgen receptor (AR) transactivation, comedogenesis, lipogenesis and follicular inflammation and T-cell proliferation. PI3K: Phosphoinositol-3 kinase; Akt: Akt kinase; IR: Insulin Receptor; IGF1R: IGF1- Receptor; FGFR2: Fibroblast Growth Factor Receptor-2; CRHR: Corticotropin Releasing Hormone Receptor; MC5R: Melanocortin-5-Receptor; IL1R: Interleukin-1 Receptor; PGs: Peptidoglykanes; TLR2: Toll-like-Receptor-2; 5HTR: Serotonin Receptor; nAChR: Nicotine Receptor; APN: Aminopeptidase N, DP IV: Dipeptidylpeptidase IV; AhR/ARNT: Arylhydrocarbon Receptor/aryl Hydrocarbon Nuclear Translocator.