The Ca²⁺ sensor STIM1 and the Ca²⁺ channel Orai1 that form the store-operated Ca²⁺ (SOC) channel complex are key targets for drug development. Selective SOC inhibitors are currently undergoing clinical evaluation for the treatment of auto-immune and inflammatory responses and are also deemed promising anti-neoplastic agents since SOC channels are linked with enhanced cancer cell progression. Here, we describe an investigation of the site of binding of the selective inhibitor Synta66 to the SOC channel Orai1 using docking and molecular dynamics simulations, and live cell recordings. Synta66 binding was localized to the extracellular site close to the transmembrane (TM)1 and TM3 helices and the extracellular loop segments, which, importantly, are adjacent to the Orai1-selectivity filter. Synta66-sensitivity of the Orai1 pore was, in fact, diminished by both Orai1 mutations affecting Ca²⁺ selectivity and permeation of Na⁺ in the absence of Ca²⁺. Synta66 also efficiently blocked SOC in three glioblastoma cell lines but failed to interfere with cell viability, division and migration. These experiments provide new structural and functional insights into selective drug inhibition of the Orai1 Ca²⁺ channel by a high-affinity pore blocker.

Nongenetic optical control of neurons is a powerful technique to study and manipulate the function of the nervous system. This research has benchmarked the performance of organic electrolytic photocapacitor (OEPC) optoelectronic stimulators at the level of single mammalian cells: human embryonic kidney (HEK) cells with heterologously expressed voltage‐gated K⁺ channels and hippocampal primary neurons. OEPCs act as extracellular stimulation electrodes driven by deep red light. The electrophysiological recordings show that millisecond light stimulation of OEPC shifts conductance‐voltage plots of voltage‐gated K⁺ channels by ≈30 mV. Models are described both for understanding the experimental findings at the level of K⁺ channel kinetics in HEK cells, as well as elucidating interpretation of membrane electrophysiology obtained during stimulation with an electrically floating extracellular photoelectrode. A time‐dependent increase in voltage‐gated channel conductivity in response to OEPC stimulation is demonstrated. These findings are then carried on to cultured primary hippocampal neurons. It is found that millisecond time‐scale optical stimuli trigger repetitive action potentials in these neurons. The findings demonstrate that OEPC devices enable the manipulation of neuronal signaling activities with millisecond precision. OEPCs can therefore be integrated into novel in vitro electrophysiology protocols, and the findings can inspire in vivo applications.

Vitamin D (VD) is the most discussed antioxidant supplement for multiple sclerosis (MS) patients and many studies suggest correlations between a low VD serum level and onset and progression of the disease. While many studies in animals as well as clinical studies focused on the role of VD in the relapsing-remitting MS, knowledge is rather sparse for the progressive phase of the disease and the development of cortical pathology. In this study, we used our established rat model of cortical inflammatory demyelination, resembling features seen in late progressive MS, to address the question about whether VD could have positive effects on reducing cortical pathology, oxidative stress, and neurofilament light chain (NfL) serum levels. For this purpose, we used male Dark Agouti (DA) rats, with one group being supplemented with VD (400 IE per week; VD⁺) from the weaning on at age three weeks; the other group received standard rodent food. The rat brains were assessed using immunohistochemical markers against demyelination, microglial activation, apoptosis, neurons, neurofilament, and reactive astrocytes. To evaluate the effect of VD on oxidative stress and the antioxidant capacity, we used two different oxidized lipid markers (anti- Cu⁺⁺ and HOCl oxidized LDL antibodies) along with colorimetric methods for protective polyphenols (PP) and total antioxidative capacity (TAC). NfL serum levels of VD⁺ and VD⁻ animals were analyzed by fourth generation single-molecule array (SIMOA) analysis. We found significant differences between the VD⁺ and VD⁻ animals both in histopathology as well as in all serum markers. Myelin loss and microglial activation is lower in VD⁺ animals and the number of apoptotic cells is significantly reduced with a higher neuronal survival. VD⁺ animals show significantly lower NfL serum levels, a higher TAC, and more PP. Additionally, there is a significant reduction of oxidized lipid markers in animals under VD supplementation. Our data thus show a positive effect of VD on cellular features of cortical pathology in our animal model, presumably due to protection against reactive oxygen species. In this study, VD enhanced remyelination and prevented neuroaxonal and oxidative damage, such as demyelination and neurodegeneration. However, more studies on VD dose relations are required to establish an optimal response while avoiding overdosing.

Neurostimulation employing photoactive organic semiconductors offers an appealing alternative to conventional techniques, enabling targeted action and wireless control through light. In this study, organic electrolytic photocapacitors (OEPC) are employed to investigate the effects of light‐controlled electric stimulation on neuronal networks in vitro and in vivo. The interactions between the devices and biological systems are characterized. Stimulation of primary rat cortical neurons results in an elevated expression of c‐Fos within a mature neuronal network. OEPC implantation for three weeks and subsequent stimulation of the somatosensory cortex leads to an increase of c‐Fos in neurons at the stimulation site and in connected brain regions (entorhinal cortex, hippocampus), both in the ipsi‐ and contralateral hemispheres. Reactivity of glial and immune cells after semi‐chronic implantation of OEPC in the rat brain is comparable to that of surgical controls, indicating minimal foreign body response. Device functionality is further substantiated through retained charging dynamics following explantation. OEPC‐based, light‐controlled electric stimulation has a significant impact on neural responsiveness. The absence of detrimental effects on both the brain and device encourages further use of OEPC as cortical implants. These findings highlight its potential as a novel mode of neurostimulation and instigate further exploration into applications in fundamental neuroscience.

Objective: This study aims to explore the potential of organic electrolytic photocapacitors (OEPCs), an innovative photovoltaic device, in mediating the activation of native voltage-gated Cav1.2 channels ( I _Ca,L ) in Guinea pig ventricular cardiomyocytes. Methods: Whole-cell patch-clamp recordings were employed to examine light-triggered OEPC mediated I _Ca,L activation, integrating the channel's kinetic properties into a multicompartment cell model to take intracellular ion concentrations into account. A multidomain model was additionally incorporated to evaluate effects of OEPC-mediated stimulation. The final model combines external stimulation, multicompartmental cell simulation, and a patch-clamp amplifier equivalent circuit to assess the impact on achievable intracellular voltage changes. Results: Light pulses activated I _Ca,L , with amplitudes similar to voltage-clamp activation and high sensitivity to the L-type Ca ²⁺ channel blocker, nifedipine. Light-triggered I _Ca,L inactivation exhibited kinetic parameters comparable to voltage-induced inactivation. Conclusion: OEPC-mediated activation of I _Ca,L demonstrates their potential for nongenetic optical modulation of cellular physiology potentially paving the way for the development of innovative therapies in cardiovascular health. The integrated model proves the light-mediated activation of I _Ca,L and advances the understanding of the interplay between the patch-clamp amplifier and external stimulation devices. Significance: Treating cardiac conduction disorders by minimal-invasive means without genetic modifications could advance therapeutic approaches increasing patients’ quality of life compared with conventional methods employing electronic devices.

Hypericin, a tumour-selective photosensitizer, has shown potential in cancer therapy, but its poor water solubility has limited clinical use. To address this, we developed a water-soluble variant called high hypericin-loaded polyvinylpyrrolidone (HHL-PVP) to enhance hypericin's applicability, particularly for treating glioblastoma, a typically terminal disease. We tested HHL-PVP in both in vitro and in vivo models, first confirming its fluorescent properties in the lab and then assessing its efficacy in more complex animal models. Using subcutaneous and orthotopic tumour mouse models, we combined HHL-PVP administration with fluorescence-guided surgery and photodynamic therapy (PDT) to target residual tumour cells. Histological analysis of both healthy and tumour tissue showed HHL-PVP's over 97 % sensitivity and 100 % specificity in distinguishing tumour tissue. In subcutaneous glioblastoma models, significant tumour necrosis and remission occurred after HHL-PVP administration and a 20-minute white light application through the skin. These results highlight HHL-PVP's effectiveness in targeting and eradicating glioblastoma cells. Our findings provide strong evidence that HHL-PVP is a promising therapeutic option for glioblastoma, with its high sensitivity, specificity, and potential for tumour remission through PDT. This approach warrants further investigation in clinical trials and could improve outcomes for a disease that has been difficult to treat.