The role of Adrenomedullin and its active peptide Adrenomedullin 22-52 in an in vitro model of metabolic stress in Acute Myeloid Leukemia

Acute Myeloid Leukemia (AML) is a hematologic malignancy characterized by the uncontrolled proliferation of immature myeloid blasts in the bone marrow. Leukemic cells are located in two specialized niches: the perivascular niche and the endosteal niche. The latter represents a hypoxic and nutrient-deprived microenvironment that supports the survival of the most immature and chemo-resistant leukemic stem cells, which are responsible for minimal residual disease. Adrenomedullin (ADM) is a 52-amino-acid peptide belonging to the calcitonin gene-related peptide family. It is known for its vasodilatory, pro-angiogenic, anti-apoptotic, and immunomodulatory activities. ADM is produced and released in response to various stress conditions, including oxidative stress, growth factors, and hypoxia. ADM exerts its effects through the Calcitonin Receptor-Like Receptor (CRLR), which becomes functionally active when associated with the accessory proteins RAMP2 (Receptor Activity-Modifying Protein 2) or RAMP3 (Receptor Activity-Modifying Protein 3). Both CRLR and ADM have been found to be upregulated in AML patients. However, only high CRLR expression has been associated with poor prognosis, suggesting a potential pathogenic role. Nevertheless, the role of ADM in the context of metabolic stress within the endosteal niche remains poorly characterized. This study evaluated the effect of ADM and its biologically active fragment ADM₂₂₋₅₂ on the cellular response to metabolic stress in an in vitro AML model. KG-1 cells were exposed to metabolic stress conditions by serum deprivation and subsequently treated with ADM or ADM₂₂₋₅₂. Flow cytometry was used to analyze the trafficking of ADM receptors (CRLR and accessory proteins RAMP2 and RAMP3) and the mitochondrial metabolic switch. The results showed a consistent upregulation of CRLR after treatment with both peptides. Notably, a drastic reduction in RAMP2 expression was observed under metabolic stress conditions in all analyzed samples, suggesting a possible differential receptor modulation depending on the bone marrow niche involved. ADM₂₂₋₅₂ induced a greater upregulation of RAMP3 compared to ADM. Metabolic stress promoted a shift from aerobic glycolysis to oxidative phosphorylation in the presence of ADM, consistent with the metabolic profile of the endosteal niche. These data suggest that the ADM/CRLR system undergoes significant modifications in response to metabolic stress, with differential modulation of the RAMP co-receptors potentially influencing signaling specificity. Characterizing these adaptive mechanisms in conditions that mimic the endosteal niche could open new avenues for the development of targeted therapeutic strategies.