Calcium Signaling Consequences of RyR2-S4938F Mutation Expressed in Human iPSC-Derived Cardiomyocytes.

Type-2 ryanodine receptor (RyR2) is the major Ca2+ release channel of the cardiac sarcoplasmic reticulum (SR) that controls the rhythm and strength of the heartbeat, but its malfunction may generate severe arrhythmia leading to sudden cardiac death or heart failure. S4938F-RyR2 mutation in the carboxyl-terminal was expressed in human induced pluripotent stem cells derived cardiomyocytes (hiPSC-CMs) using CRISPR/Cas9 gene-editing technique. Ca2+ signaling and electrophysiological properties of beating cardiomyocytes carrying the mutation were studied using total internal reflection fluorescence microscopy (TIRF) and patch clamp technique. In mutant cells, L-type Ca2+ currents (ICa), measured either by depolarizations to zero mV or repolarizations from +100 mV to -50 mV, and their activated Ca2+ transients were significantly smaller, despite their larger caffeine-triggered Ca2+ release signals compared to wild type (WT) cells, suggesting ICa-induced Ca2+ release (CICR) was compromised. The larger SR Ca2+ content of S4938F-RyR2 cells may underlie the higher frequency of spontaneously occurring Ca2+ sparks and Ca2+ transients and their arrhythmogenic phenotype.

Effect of the isotiazole adjuvants in combination with cisplatin in chemotherapy of neuroepithelial tumors: experimental results and modeling.

Chemotherapy is one of the main treatment options for cancer, but it is usually accompanied with negative side effects. The classical drugs combination with synergistic adjuvants can be the solution to this problem, allowing reducing therapeutic dose. Elucidating the mechanism of adjuvant action is of key importance for the selection of the optimal agent. Here we examine the system drug-adjuvant to explain the observed effect in practice. We used the first line drug cisplatin. Morpholinium and 4-methylpiperazinium 4,5-dichloro isothiazol-3-carboxylates were selected as adjuvants. The study of the cisplatin-adjuvant system was carried out by quantum chemical modeling using DFT. It turned out that adjuvants form conjugates with cisplatin that lead to the relocation of frontier molecular orbitals as well as increase of conjugate's dipole moment. It resulted in change of the interaction character with DNA and increase of the bioactivity of the system. The data obtained are the basis for expanding the studies to include other drugs and adjuvants. Oncologists will have opportunity to use "classical" chemotherapy drugs in combination with synergists for those patients who have not been previously recommended to such a treatment because of pronounced toxic side effects.