Intracellular histamine binding site (HIC)

The Intracellular histamine binding site (HIC) is a pharmacologically distinct, non-G protein-coupled receptor primarily located in the microsomal membranes and nuclei of mammalian cells [1, 4]. Unlike the classical surface-expressed histamine receptors (H1-H4), HIC possesses a lower affinity for its ligand and is involved in the regulation of fundamental cellular processes, including DNA synthesis, cell proliferation, and platelet aggregation [1, 2]. The site is highly relevant in oncology as the primary target for the small molecule drug tesmilifene (DPPE), which acts as a specific antagonist to inhibit histamine-mediated mitogenic responses [1, 3, 4]. By blocking histamine binding at HIC, these agents can effectively sensitize multi-drug resistant (MDR) tumor cells to the cytotoxic effects of various chemotherapy treatments [4]. Research further indicates that HIC is functionally and physically associated with anti-estrogen binding sites (AEBS) and may involve components of the cytochrome P450 enzyme system, particularly the CYP3A4 complex [1, 3].

Other names

HICMicrosomal histamine binding siteIntracellular histamine receptorIntracellular histamine-binding siteMicrosomal anti-estrogen binding site

The mechanism involves the specific antagonism of histamine binding to the HIC site within the microsomes and nucleus [1]. This blockade disrupts the role of intracellular histamine as a second messenger in cell growth and proliferation signaling pathways, thereby inhibiting mitogenesis and increasing the sensitivity of malignant cells to cytotoxic chemotherapeutic agents [4].