Mitochondria are key cellular organelles that regulate numerous important cellular processes. Their dysfunction is associated with diseases such as cancer, inflammatory conditions, and neurodegenerative disorders, making them promising therapeutic targets. Mitochondrial voltage-gated potassium channels (mitoKv1.3) are located in the inner mitochondrial membrane, where they regulate the intrinsic apoptotic pathway, and their increased expression is characteristic of several types of tumors. One approach to cancer treatment involves Kv1.3 channel inhibitors, which induce apoptosis in cancer cells and may prevent disease progression. For the targeted delivery of Kv1.3 inhibitors to mitochondria, mitochondria-targeting moieties (MTMs) are required, among which the triphenylphosphonium cation (TPP⁺) has long been considered the gold standard. However, since TPP⁺ is not completely biologically inert and has certain limitations, a series of disubstituted pyridinium cations was synthesized as alternative MTMs using the Suzuki–Miyaura reaction. The compounds differed in the position and type of substituents on the pyridine ring. Some contained two phenyl groups, whereas in others one phenyl group was replaced by a morpholinyl group. In the second part of the experimental work, a known Kv1.3 inhibitor was synthesized in five steps and was conjugated to the prepared pyridinium cations via N-alkylation. A short inert alkyl chain was also attached to the synthesized MTMs. The MTM–Kv1.3 inhibitor conjugates were biologically evaluated in Colo-357 human pancreatic adenocarcinoma cells and normal human lung fibroblasts NHLF. Their selectivity factors were calculated, and their logD values and thermodynamic solubility were determined. The results were compared with the reference compound PAPTP and with a conjugate of the same Kv1.3 inhibitor containing a 3,5-diphenylpyridinium cation as the MTM. Conjugates containing two phenyl substituents exhibited higher lipophilicity, more pronounced cytotoxic activity against Colo-357 cells, and greater selectivity towards these cells. Among the investigated compounds, compounds 13 and 14 exhibited activity comparable to the reference compound PAPTP while showing even greater selectivity. The results indicate that the MTM structure plays an important role in determining the physicochemical properties and biological activity of the conjugates and support further investigation of pyridinium-based MTMs for the targeted delivery to mitochondria.
|
