Adenosine deficiency facilitates CA1 synaptic hyperexcitability in the presymptomatic phase of a knock in mouse model of Alzheimer's disease.

The disease's trajectory of Alzheimer's disease (AD) is associated with and worsened by hippocampal hyperexcitability. Here we show that during the asymptomatic stage in a knock in mouse model of Alzheimer's disease (APPNL-G-F/NL-G-F; APPKI), hippocampal hyperactivity occurs at the synaptic compartment, propagates to the soma and is manifesting at low frequencies of stimulation. We show that this aberrant excitability is associated with a deficient adenosine tone, an inhibitory neuromodulator, driven by reduced levels of CD39/73 enzymes, responsible for the extracellular ATP-to-adenosine conversion. Both pharmacologic (adenosine kinase inhibitor) and non-pharmacologic (ketogenic diet) restorations of the adenosine tone successfully normalize hippocampal neuronal activity. Our results demonstrated that neuronal hyperexcitability during the asymptomatic stage of a KI model of Alzheimer's disease originated at the synaptic compartment and is associated with adenosine deficient tone. These results extend our comprehension of the hippocampal vulnerability associated with the asymptomatic stage of Alzheimer's disease.

Impact of Membrane Voltage on Formation and Stability of Human Renal Proximal Tubules in Vitro.

More than 15% of adults in the United States suffer from some form of chronic kidney disease (CKD). Current strategies for CKD consist of dialysis or kidney transplant, which, however, can take several years. In this light, tissue engineering and regenerative medicine approaches are the key to improving people's living conditions by advancing previous tissue engineering approaches and seeking new targets as intervention methods for kidney repair or replacement. The membrane voltage (Vm) dynamics of a cell have been associated with cell migration, cell cycle progression, differentiation, and pattern formation. Furthermore, bioelectrical stimuli have been used as a means in the treatment of diseases and wound healing. Here, we investigated the role of Vm as a novel target to guide and manipulate in vitro renal tissue models. Human-immortalized renal proximal tubule epithelial cells (RPTECs-TERT1) were cultured on Matrigel to support the formation of 3D proximal tubular-like structures with the incorporation of a voltage-sensitive dye indicator─bis-(1,3-dibutylbarbituric acid)timethine oxonol (DiBAC). The results demonstrated a correlation between the depolarization and the reorganization of human renal proximal tubule cells, indicating Vm as a candidate variable to control these events. Accordingly, Vm was pharmacologically manipulated using glibenclamide and pinacidil, KATP channel modulators, and proximal tubule formation and tubule stability over 21 days were assessed. Chronic manipulation of KATP channels induced changes in the tubular network topology without affecting lumen formation. Thus, a relationship was found between the preluminal tubulogenesis phase and KATP channels. This relationship may provide future options as a control point during kidney tissue development, treatment, and regeneration goals.

Optogenetically induced cellular habituation in non-neuronal cells.

Habituation, defined as the reversible decrement of a response during repetitive stimulation, is widely established as a form of non-associative learning. Though more commonly ascribed to neural cells and systems, habituation has also been observed in single aneural cells, although evidence is limited. Considering the generalizability of the habituation process, we tested the degree to which organism-level behavioral and single cell manifestations were similar. Human embryonic kidney (HEK) cells that overexpressed an optogenetic actuator were photostimulated to test the effect of different stimulation protocols on cell responses. Depolarization induced by the photocurrent decreased successively over the stimulation protocol and the effect was reversible upon withdrawal of the stimulus. In addition to frequency- and intensity-dependent effects, the history of stimulations on the cells impacted subsequent depolarization in response to further stimulation. We identified tetraethylammonium (TEA)-sensitive native K+ channels as one of the mediators of this habituation phenotype. Finally, we used a theoretical model of habituation to elucidate some mechanistic aspects of the habituation response. In conclusion, we affirm that habituation is a time- and state-dependent biological strategy that can be adopted also by individual non-neuronal cells in response to repetitive stimuli.

Defined extracellular ionic solutions to study and manipulate the cellular resting membrane potential.

All cells possess an electric potential across their plasma membranes and can generate and receive bioelectric signals. The cellular resting membrane potential (RMP) can regulate cell proliferation, differentiation and apoptosis. Current approaches to measure the RMP rely on patch clamping, which is technically challenging, low-throughput and not widely available. It is therefore critical to develop simple strategies to measure, manipulate and characterize the RMP. Here, we present a simple methodology to study the RMP of non-excitable cells and characterize the contribution of individual ions to the RMP using a voltage-sensitive dye. We define protocols using extracellular solutions in which permeable ions (Na+, Cl- and K+) are substituted with non-permeable ions [N-Methyl-D-glucamine (NMDG), gluconate, choline, SO42-]. The resulting RMP modifications were assessed with both patch clamp and a voltage sensitive dye. Using an epithelial and cancer cell line, we demonstrate that the proposed ionic solutions can selectively modify the RMP and help determine the relative contribution of ionic species in setting the RMP. The proposed method is simple and reproducible and will make the study of bioelectricity more readily available to the cell biology community.This article has an associated First Person interview with the first author of the paper.