The potent activation of Ca2+-activated K+ current by NVP-AUY922 in the human pancreatic duct cell line (PANC-1) possibly independent of heat shock protein 90 inhibition

Revealing Prdx4 as a potential diagnostic and therapeutic target for acute pancreatitis based on machine learning analysis

Acute pancreatitis (AP) is a common systemic inflammatory disease resulting from the activation of trypsinogen by various incentives in ICU. The annual incidence rate is approximately 30 out of 100,000. Some patients may progress to severe acute pancreatitis, with a mortality rate of up to 40%. Therefore, the goal of this article is to explore the key genes for effective diagnosis and treatment of AP. The analysis data for this study were merged from two GEO datasets. 1357 DEGs were used for functional enrichment and cMAP analysis, aiming to reveal the pathogenic genes and potential mechanisms of AP, as well as potential drugs for treating AP. Importantly, the study used LASSO and SVM-RFE machine learning to screen the most likely AP occurrence biomarker for Prdx4 among numerous candidate genes. A receiver operating characteristic of Prdx4 was used to estimate the incidence of AP. The ssGSEA algorithm was employed to investigate immune cell infiltration in AP. The biomarker Prdx4 gene exhibited significant associations with a majority of immune cells and was identified as being expressed in NKT cells, macrophages, granulocytes, and B cells based on single-cell transcriptome data. Finally, we found an increase in Prdx4 expression in the pancreatic tissue of AP mice through immunohistochemistry. After treatment with recombinant Prdx4, the pathological damage to the pancreatic tissue of AP mice was relieved. In conclusion, our study identified Prdx4 as a potential AP hub gene, providing a new target for treatment.

Involvement of the γ1 subunit of the large-conductance Ca2+-activated K+ channel in the proliferation of human somatostatinoma cells

Pancreatic neuroendocrine tumors (pNETs) occur due to the abnormal growth of pancreatic islet cells and predominantly develop in the duodenal-pancreatic region. Somatostatinoma is one of the pNETs associated with tumors of pancreatic δ cells, which produce and secrete somatostatin. Limited information is currently available on the pathogenic mechanisms of somatostatinoma. The large-conductance Ca²⁺-activated K⁺ (BK_Ca) channel is expressed in several types of cancer cells and regulates cell proliferation, migration, invasion, and metastasis. In the present study, the functional expression of the BK_Ca channel was examined in a human somatostatinoma QGP-1 cell line. In QGP-1 cells, outward currents were elicited by membrane depolarization at pCa 6.5 (300 nM) in the pipette solution and inhibited by the specific BK_Ca channel blocker, paxilline. Paxilline-sensitive currents were detected, even at pCa 8.0 (10 nM) in the pipette solution, in QGP-1 cells. In addition to the α and β2-4 subunits of the BK_Ca channel, the novel regulatory γ1 subunit (BK_Caγ1) was co-localized with the α subunit in QGP-1 cells. Paxilline-sensitive currents at pCa 8.0 in the pipette solution were reduced by the siRNA knockdown of BK_Caγ1. Store-operated Ca²⁺ entry was smaller in BK_Caγ1 siRNA-treated QGP-1 cells. The proliferation of QGP-1 cells was attenuated by paxilline or the siRNA knockdown of BK_Caγ1. These results strongly suggest that BK_Caγ1 facilitates the proliferation of human somatostatinoma cells. Therefore, BK_Caγ1 may be a novel therapeutic target for somatostatinoma.

Stimulatory actions of a novel thiourea derivative on large-conductance, calcium-activated potassium channels

In this study, we examine whether an anti-inflammatory thiourea derivative, compound #326, actions on ion channels. The effects of compound #326 on Ca²⁺ -activated K⁺ channels were evaluated by patch-clamp recordings obtained in cell-attached, inside-out or whole-cell configuration. In pituitary GH₃ cells, compound #326 increased the amplitude of Ca²⁺ -activated K⁺ currents (I_K(Ca) ) with an EC₅₀ value of 11.6 μM, which was reversed by verruculogen, but not tolbutamide or TRAM-34. Under inside-out configuration, a bath application of compound #326 raised the probability of large-conductance Ca²⁺ -activated K⁺ (BK_Ca ) channels. The activation curve of BK_Ca channels was shifted to less depolarised potential with no modification of the gating charge of the curve; consequently, the difference of free energy was reduced in the presence of this compound. Compound #326-stimulated activity of BK_Ca channels is explained by a shortening of mean closed time, despite its inability to alter single-channel conductance. Neither delayed-rectifier nor erg-mediated K⁺ currents was modified. Compound #326 decreased the peak amplitude of voltage-gated Na⁺ current with no clear change in the overall current-voltage relationship of this current. In HEK293T cells expressing α-hSlo, compound #326 enhanced BK_Ca channels effectively. Intriguingly, the inhibitory actions of compound #326 on interleukin 1β in lipopolysaccharide-activated microglia were significantly reversed by verruculogen, whereas BK_Ca channel inhibitors suppressed the expressions of inducible nitric oxide synthase. The BK_Ca channels could be an important target for compound #326 if similar in vivo results occur, and the multi-functionality of BK_Ca channels in modulating microglial immunity merit further investigation.

Caffeic acid phenethyl ester: Inhibition of metastatic cell behaviours via voltage-gated sodium channel in human breast cancer in vitro

Caffeic acid phenethyl ester, derived from natural propolis, has been reported to have anti-cancer properties. Voltage-gated sodium channels are upregulated in many cancers where they promote metastatic cell behaviours, including invasiveness. We found that micromolar concentrations of caffeic acid phenethyl ester blocked voltage-gated sodium channel activity in several invasive cell lines from different cancers, including breast (MDA-MB-231 and MDA-MB-468), colon (SW620) and non-small cell lung cancer (H460). In the MDA-MB-231 cell line, which was adopted as a 'model', long-term (48 h) treatment with 18 μM caffeic acid phenethyl ester reduced the peak current density by 91% and shifted steady-state inactivation to more hyperpolarized potentials and slowed recovery from inactivation. The effects of long-term treatment were also dose-dependent, 1 μM caffeic acid phenethyl ester reducing current density by only 65%. The effects of caffeic acid phenethyl ester on metastatic cell behaviours were tested on the MDA-MB-231 cell line at a working concentration (1 μM) that did not affect proliferative activity. Lateral motility and Matrigel invasion were reduced by up to 14% and 51%, respectively. Co-treatment of caffeic acid phenethyl ester with tetrodotoxin suggested that the voltage-gated sodium channel inhibition played a significant intermediary role in these effects. We conclude, first, that caffeic acid phenethyl ester does possess anti-metastatic properties. Second, the voltage-gated sodium channels, commonly expressed in strongly metastatic cancers, are a novel target for caffeic acid phenethyl ester. Third, more generally, ion channel inhibition can be a significant mode of action of nutraceutical compounds.

Inhibitory actions by ibandronate sodium, a nitrogen-containing bisphosphonate, on calcium-activated potassium channels in Madin-Darby canine kidney cells

The nitrogen-containing bisphosphonates used for management of the patients with osteoporosis were reported to influence the function of renal tubular cells. However, how nitrogen-containing bisphosphates exert any effects on ion currents remains controversial. The effects of ibandronate (Iban), a nitrogen-containing bisphosphonate, on ionic channels, including two types of Ca²⁺-activated K⁺ (K_Ca) channels, namely, large-conductance K_Ca (BK_Ca) and intermediate-conductance K_Ca (IK_Ca) channels, were investigated in Madin–Darby canine kidney (MDCK) cells. In whole-cell current recordings, Iban suppressed the amplitude of voltage-gated K⁺ current elicited by long ramp pulse. Addition of Iban caused a reduction of BK_Ca channels accompanied by a right shift in the activation curve of BK_Ca channels, despite no change in single-channel conductance. Ca²⁺ sensitivity of these channels was modified in the presence of this compound; however, the magnitude of Iban-mediated decrease in BK_Ca-channel activity under membrane stretch with different negative pressure remained unchanged. Iban suppressed the probability of BK_Ca-channel openings linked primarily to a shortening in the slow component of mean open time in these channels. The dissociation constant needed for Iban-mediated suppression of mean open time in MDCK cells was 12.2 μM. Additionally, cell exposure to Iban suppressed the activity of IK_Ca channels, and DC-EBIO or 9-phenanthrol effectively reversed its suppression. Under current-clamp configuration, Iban depolarized the cells and DC-EBIO or PF573228 reversed its depolarizing effect. Taken together, the inhibitory action of Iban on K_Ca-channel activity may contribute to the underlying mechanism of pharmacological or toxicological actions of Iban and its structurally similar bisphosphonates on renal tubular cells occurring in vivo.

Mg(2+)-dependent facilitation and inactivation of L-type Ca(2+) channels in guinea pig ventricular myocytes

This study aimed to investigate the intracellular Mg(2+) regulation of the L-type Ca(2+) channels in guinea pig ventricular myocytes. By adopting the inside-out configuration of the patch clamp technique, single channel currents of the L-type Ca(2+) channels were recorded at different intracellular Mg(2+) concentrations ([Mg(2+)]i). At free [Mg(2+)]i of 0, 10(-9), 10(-7), 10(-5), 10(-3), and 10(-1) M, 1.4 μM CaM + 3 mM ATP induced channel activities of 44%, 117%, 202%, 181%, 147%, and 20% of the control activity in cell-attached mode, respectively, showing a bell-shaped concentration-response relationship. Moreover, the intracellular Mg(2+) modulated the Ca(2+) channel gating properties, accounting for alterations in channel activities. These results imply that Mg(2+) has a dual effect on the L-type Ca(2+) channels: facilitation and inhibition. Lower [Mg(2+)]i maintains and enhances the basal activity of Ca(2+) channels, whereas higher [Mg(2+)]i inhibits channel activity. Taken together, our data from the application of an [Mg(2+)]i series suggest that the dual effect of Mg(2+) upon the L-type Ca(2+) channels exhibits long open-time dependence.