Comparative Analysis of the Effects of the Diterpene Alkaloid Napelline and its Derivative on the MitoK+ATP Channel and mPTP in Rat Liver and Heart Mitochondria

Mitochondria play crucial role in cellular energy metabolism and ion homeostasis, and their dysfunction is associated with various pathological conditions. The mitochondrial ATP-sensitive potassium channel (mitoK+ATP channel) and the mitochondrial permeability transition pore (mPTP) are considered key regulators of mitochondrial function and potential targets for cytoprotective therapies. This study examined the effects of the diterpene alkaloid napelline and its derivative, 1-O-benzoylnapelline hydrochloride, on mitoK⁺ATP channel activity and mPTP opening in liver and heart mitochondria isolated from male Wistar rats. Mitochondrial swelling assays were used to assess mitoK⁺ATP channel activation in the presence of ATP (as an inhibitor), and calcium-induced swelling was used to evaluate mPTP opening. Napelline (50 μM) activated the activity of the liver mitoK+ATP channel by 191.0 ± 2.3% compared to the control, and 1-O-benzoylnapelline (10 μM) - by 208%. In heart mitochondria, these values were 127.6 ± 3.1% and 156.5 ± 2.5%, respectively. Both compounds inhibited mPTP opening, with 1-O-benzoylnapelline showing greater efficacy: At 10 µM, it suppressed swelling by 92.3 ± 2.5% in liver and 78.6 ± 2.4% in heart mitochondria. Liver mitochondria exhibited a more pronounced response, indicating tissue-specific sensitivity. The increased activity of 1-O-benzoylnapelline may be attributed to the acylation of the C-1 hydroxyl group, which likely enhances its interaction with mitochondrial membranes. These results indicate that 1-O-benzoylnapelline is a more effective modulator of mitochondrial ion channels than napelline and may serve as a promising lead compound for the development of novel cytoprotective agents, warranting further investigation. HIGHLIGHTS The higher influence of 1-O-benzoylnapelline on the activity of the mitoK+ATP-channel of the liver and heart of rats compared to the napelline alkaloid can be explained by the fact that the benzoyl group is attached to the C-1 position. According to the results of the study, 1-O-benzoylnapelline at low concentrations reliably activated the mitoK+ATP-channel of the liver and heart of rats, and also exhibited membrane-active properties, more strongly inhibiting the Ca2+-dependent conductive pore compared to the alkaloid napelline. GRAPHICAL ABSTRACT