6formylindolo32bcarbazole

6-formylindolo[3,2-b]carbazole, commonly abbreviated FICZ, is an indolocarbazole compound featuring a formyl group at the 6-position. It is an endogenous, UV-activated metabolite derived from tryptophan and acts as a high-affinity ligand for the aryl hydrocarbon receptor (AHR). FICZ is formed in skin and other tissues after ultraviolet exposure and can also be prepared synthetically for research use.

In biology, FICZ binds AHR with high affinity, triggering receptor translocation to the nucleus, dimerization with ARNT, and binding to xenobiotic response elements. This sequence upregulates transcription of AHR target genes, including the cytochrome P450 enzymes CYP1A1 and related xenobiotic-metabolizing genes, thereby influencing cellular detoxification pathways and metabolic processes.

FICZ is notable for its rapid metabolism, being promptly degraded by CYP1A1, which creates a short-lived but potent signal. This property supports the view of FICZ as a dynamic endogenous regulator of AHR activity, linking environmental cues such as light exposure to transcriptional responses.

Physiologically, FICZ has been investigated for roles in immune regulation, skin barrier maintenance, and mucosal homeostasis, though ongoing research aims to clarify its in vivo significance. In laboratory settings, FICZ serves as a potent tool to study AHR signaling pathways, gene regulation, and downstream effects on metabolism and immunity.