Rafal Pawel Kampa

Luteolin (LUT) is a well-known flavonoid that exhibits a number of beneficial properties. Among these, it shows cardioprotective effects, as confirmed by numerous studies. However, its effect on mitochondrial potassium channels, the activation of which is related to cytoprotection, as well as on heart ischemia/reperfusion (I/R) damage prevention, has not yet been investigated. The large conductance calcium-regulated potassium channel (mitoBK_Ca) has been identified in both the mitochondria of the vascular endothelial cells, which plays a significant role in the functioning of the cardiovascular system under oxidative stress-related conditions, and in the mitochondria of cardiomyocytes, where it is deeply involved in cardiac protection against I/R injury. Therefore, the aim of this study was to explore the role of the mitoBK_Ca channel in luteolin-induced cytoprotection. A number of in vitro, in vivo, ex vivo and in silico studies have confirmed that luteolin activates this channel in the mitochondria of cardiomyocytes and endothelial cells, which in turn leads to the protection of the endothelium and a significant reduction in the extent of damage resulting from myocardial infarction, where this effect was partially abolished by the mitoBK_Ca channel blocker paxilline. In conclusion, these results suggest that luteolin has cardioprotective effects, at least in part, through the activation of the mitoBK_Ca channel, shedding light on a new putative mechanism of action.

The mitochondrial K⁺ concentration changes resulting from stimulation with nigericin can be observed via emission modulation of a novel diketopyrrolopyrrole-based probe.

Mitochondria play a key role in energy metabolism within the cell. Potassium channels such as ATP-sensitive, voltage-gated or large-conductance Ca²⁺-regulated channels have been described in the inner mitochondrial membrane. Several hypotheses have been proposed to describe the important roles of mitochondrial potassium channels in cell survival and death pathways. In the current study, we identified two populations of mitochondrial large-conductance Ca²⁺-regulated potassium (mitoBK_Ca) channels in human bronchial epithelial (HBE) cells. The biophysical properties of the channels were characterized using the patch-clamp technique. We observed the activity of the channel with a mean conductance close to 285 pS in symmetric 150/150 mM KCl solution. Channel activity was increased upon application of the potassium channel opener NS11021 in the micromolar concentration range. The channel activity was completely inhibited by 1 µM paxilline and 300 nM iberiotoxin, selective inhibitors of the BK_Ca channels. Based on calcium and iberiotoxin modulation, we suggest that the C-terminus of the protein is localized to the mitochondrial matrix. Additionally, using RT-PCR, we confirmed the presence of α pore-forming (Slo1) and auxiliary β3-β4 subunits of BK_Ca channel in HBE cells. Western blot analysis of cellular fractions confirmed the mitochondrial localization of α pore-forming and predominately β3 subunits. Additionally, the regulation of oxygen consumption and membrane potential of human bronchial epithelial mitochondria in the presence of the potassium channel opener NS11021 and inhibitor paxilline were also studied. In summary, for the first time, the electrophysiological and functional properties of the mitoBK_Ca channel in a bronchial epithelial cell line were described.

Naringenin, a flavanone obtained from citrus fruits and present in many traditional Chinese herbal medicines, has been shown to have various beneficial effects on cells both in vitro and in vivo. Although the antioxidant activity of naringenin has long been believed to be crucial for its effects on cells, mitochondrial pathways (including mitochondrial ion channels) are emerging as potential targets for the specific pharmacological action of naringenin in cardioprotective strategies. In the present study, we describe interactions between the mitochondrial large-conductance calcium-regulated potassium channel (mitoBK_Ca channel) and naringenin. Using the patch-clamp method, we showed that 10 µM naringenin activated the mitoBK_Ca channel present in endothelial cells. In the presence of 30 µM Ca²⁺, the increase in the mitoBK_Ca channel probability of opening from approximately 0.25 to 0.50 at −40 mV was observed. In addition, regulation of the mitoBK_Ca channel by naringenin was dependent on the concentration of calcium ions. To confirm our data, physiological studies on the mitochondria were performed. An increase in oxygen consumption and a decrease in membrane potential was observed after naringenin treatment. In addition, contributions of the mitoBK_Ca channel to apoptosis and necrosis were investigated. Naringenin protected cells against damage induced by tumor necrosis factor α (TNF-α) in combination with cycloheximide. In this study, we demonstrated that the flavonoid naringenin can activate the mitoBK_Ca channel present in the inner mitochondrial membrane of endothelial cells. Our studies describing the regulation of the mitoBK_Ca channel by this natural, plant-derived substance may help to elucidate flavonoid-induced cytoprotective mechanisms.

Flavonoids belong to a large group of polyphenolic compounds that are widely present in plants. Certain flavonoids, including naringenin, have cytoprotective properties. Although the antioxidant effect has long been thought to be a crucial factor accounting for the cellular effects of flavonoids, mitochondrial channels have emerged recently as targets for cytoprotective strategies. In the present study, we characterized interactions between naringenin and the mitochondrial potassium (mitoBK_Ca and mitoK_ATP) channels recently described in dermal fibroblasts. With the use of the patch‐clamp technique and mitoplasts isolated from primary human dermal fibroblast cells, our study shows that naringenin in micromolar concentrations leads to an increase in mitoBK_Ca channel activity. The opening probability of the channel decreased from 0.97 in the control conditions (200 μmol/L Ca²⁺) to 0.06 at a low Ca²⁺ level (1 μmol/L) and increased to 0.85 after the application of 10 μmol/L naringenin. Additionally, the activity of the mitoK_ATP channel increased following the application of 10 μmol/L naringenin. To investigate the effects of naringenin on mitochondrial function, the oxygen consumption of dermal fibroblast cells was measured in potassium‐containing media. The addition of naringenin significantly and dose‐dependently increased the respiratory rate from 5.8 ± 0.2 to 14.0 ± 0.6 nmol O₂ × min⁻¹ × mg protein⁻¹. Additionally, a Raman spectroscopy analysis of skin penetration indicated that the naringenin was distributed in all skin layers, including the epidermis and dermis. In this study, we demonstrated that a flavonoid, naringenin, can activate two potassium channels present in the inner mitochondrial membrane of dermal fibroblasts.

Receptor naskórkowego czynnika wzrostu EGFR (Epidermal Growth Factor Receptor), ze względu na jego ważny udział w patogenezie nowotworów złośliwych, jest obiektem intensywnych badań naukowych ostatnich lat. W wielu typach nowotworów wewnątrzkomórkowe szlaki sygnalizacyjne pobudzane przez EGFR mają wręcz kluczowe znaczenie w ich rozwoju. Z drugiej strony wykazano, iż EGFR może stanowić bardzo obiecujący punkt uchwytu dla czynników terapeutycznych. Podjęto próby modyfikacji transdukcji sygnału przekazywanego przez aktywny EGFR wewnątrz komórek poprzez blokowanie aktywności elementów tego szlaku bądź samego receptora. Wykazano też, że blokowanie receptora EGFR przez przeciwciała monoklonalne podwyższa efektywność stosowanych w terapii konwencjonalnych czynników przeciwnowotworowych, np. cisplatyny. Dodatkowo opracowano wiele terapii przeciwnowotworowych opierając się na zastosowaniu inhibitorów wybranych, kluczowych składowych szlaku sygnalizacyjnego EGFR, z których wiele bazuje na zastosowaniu przeciwciał monoklonalnych.