The patch clamp technique

Magnetoelectric Extracellular Vesicle Latency-Targeting (MELT) Nanotherapeutic for the Block-Lock-and-Kill HIV Eradication Strategy

BACKGROUND

Human immunodeficiency virus (HIV) establishes latent infections in cellular reservoirs, including microglia. HC69 cells, a microglial model of HIV latency, contain an HIV promoter long terminal repeat (LTR)-GFP reporter and were used for testing the efficacy of a two-step magnetoelectric nanoparticle (MENP) and extracellular vesicle (xEV) latency-targeting (MELT) nanotherapeutic. GFP expression in HC69 at rest is low (GFPLo), and upon exposure to LTR, transcription-activating agents (i.e., TNF-α) are induced to be high expressing (GFPHi).

METHODS

The first step of MELT utilized ZL0580, an HIV Tat inhibitor loaded into EVs (80%) via incubation. ZL0580-EVs were taken up by GFPLo and blocked LTR transcriptional reactivation by 50% and were 90% less toxic than ZL0580 alone. The second step in MELT involved conjugation of monomethyl auristatin E (MMAE) to MENPs. HPLC measurements showed 80% MMAE attachment to MENPs. Flow cytometry-based measurements of the membrane potential indicated that the membranes of GFPHi HC69 were 60% more polarized than GFPLo HC69 cells. More MMAE-MENPs were internalized by GFPLo HC69.

RESULTS

Using a mixed-cell blood-brain barrier (BBB) Transwell model, we demonstrated that 20% of MELT crossed the BBB, was taken up by HC69 cells, and reduced LTR reactivation by 10%.

CONCLUSIONS

Overall, this study demonstrated that MELT can potentially be utilized as a nanotherapeutic to target HIV latency in microglia.

Single-particle fluorescence tracking combined with TrackMate assay reveals highly heterogeneous and discontinuous lysosomal transport in freely orientated axons

Axonal transport plays a significant role in the establishment of neuronal polarity, axon growth, and synapse formation during neuronal development. The axon of a naturally growing neuron is a highly complex and multifurcated structure with a large number of bends and branches. Nowadays, the study of dynamic axonal transport in morphologically complex neurons is greatly limited by the technological barrier. Here, a sparse gene transfection strategy was developed to locate fluorescent mCherry in the lysosome of primary neurons, thus enabling us to track the lysosome-based axonal transport with a single-particle resolution. Thereby, several axonal transport models were observed, including the forward or backward transport model, stop-and-go model, repeated back-and-forth transport model, and cross-branch transport model. Then, the accurate single-particle velocity quantification by TrackMate revealed a highly heterogeneous and discontinuous transportation process of lysosome-based axonal transport in freely orientated axons. And, multiple physical factors, such as the axonal structure and the size of particles, were disclosed to affect the velocity of particle transporting in freely orientated axons. The combined single-particle fluorescence tracking and TrackMate assay can be served as a facile tool for evaluating axonal transport in neuronal development and axonal transport-related diseases.

Chemical Biology Tools To Investigate Malaria Parasites

Parasitic diseases like malaria tropica have been shaping human evolution and history since the beginning of mankind. After infection, the response of the human host ranges from asymptomatic to severe and may culminate in death. Therefore, proper examination of the parasite's biology is pivotal to deciphering unique molecular, biochemical and cell biological processes, which in turn ensure the identification of treatment strategies, such as potent drug targets and vaccine candidates. However, implementing molecular biology methods for genetic manipulation proves to be difficult for many parasite model organisms. The development of fast and straightforward applicable alternatives, for instance small-molecule probes from the field of chemical biology, is essential. In this review, we will recapitulate the highlights of previous molecular and chemical biology approaches that have already created insight and understanding of the malaria parasite Plasmodium falciparum. We discuss current developments from the field of chemical biology and explore how their application could advance research into this parasite in the future. We anticipate that the described approaches will help to close knowledge gaps in the biology of P. falciparum and we hope that researchers will be inspired to use these methods to gain knowledge - with the aim of ending this devastating disease.

Adhesion Stabilized en Masse Intracellular Electrical Recordings from Multicellular Assemblies

Coordinated collective electrochemical signals in multicellular assemblies, such as ion fluxes, membrane potentials, electrical gradients, and steady electric fields, play an important role in cell and tissue spatial organization during many physiological processes like wound healing, inflammatory responses, and hormone release. This mass of electric actions cumulates in an en masse activity within cell collectives which cannot be deduced from considerations at the individual cell level. However, continuously sampling en masse collective electrochemical actions of the global electrochemical activity of large-scale electrically coupled cellular assemblies with intracellular resolution over long time periods has been impeded by a lack of appropriate recording techniques. Here we present a bioelectrical interface consisting of low impedance vertical gold nanoelectrode interfaces able to penetrate the cellular membrane in the course of cellular adhesion, thereby allowing en masse recordings of intracellular electrochemical potentials that transverse electrically coupled NRK fibroblast, C2C12 myotube assemblies, and SH-SY5Y neuronal networks of more than 200,000 cells. We found that the intracellular electrical access of the nanoelectrodes correlates with substrate adhesion dynamics and that penetration, stabilization, and sealing of the electrode-cell interface involves recruitment of surrounding focal adhesion complexes and the anchoring of actin bundles, which form a caulking at the electrode base. Intracellular recordings were stable for several days, and monitoring of both basal activity as well as pharmacologically altered electric signals with high signal-to-noise ratios and excellent electrode coupling was performed.

Current advances in cell electrophysiology: applications for the analysis of intercellular communications within the neurovascular unit

Patch clamp is a golden standard for studying (patho)physiological processes affecting membranes of excitable cells. This method is rather labor-intensive and requires well-trained professionals and long-lasting experimental procedures; therefore, accurate designing of the experiments with patch clamp methodology as well as collecting and analyzing the data obtained are essential for the widely spread implementation of this method into the routine research practice. Recently, the method became very prospective not only for the characterization of single excitable cells but also for the detailed assessment of intercellular communication, i.e. within the neurovascular unit. Here, we analyze the main advantages and disadvantages of patch clamp method, with special focus on the tendencies in clamping technique improvement with the help of patch electrodes for the assessment of intercellular communication in the brain.

The avian embryo to study development of the cardiac conduction system

The avian embryo has long been a popular model system in developmental biology. The easy accessibility of the embryo makes it particularly suitable for in ovo microsurgery and manipulation. Re-incubation of the embryo allows long-term follow-up of these procedures. The current review focuses on the variety of techniques available to study development of the cardiac conduction system in avian embryos. Based on the large amount of relevant data arising from experiments in avian embryos, we conclude that the avian embryo has and will continue to be a powerful model system to study development in general and the developing cardiac conduction system in particular.

Microfluidic impedance flow cytometry enabling high-throughput single-cell electrical property characterization

This article reviews recent developments in microfluidic impedance flow cytometry for high-throughput electrical property characterization of single cells. Four major perspectives of microfluidic impedance flow cytometry for single-cell characterization are included in this review: (1) early developments of microfluidic impedance flow cytometry for single-cell electrical property characterization; (2) microfluidic impedance flow cytometry with enhanced sensitivity; (3) microfluidic impedance and optical flow cytometry for single-cell analysis and (4) integrated point of care system based on microfluidic impedance flow cytometry. We examine the advantages and limitations of each technique and discuss future research opportunities from the perspectives of both technical innovation and clinical applications.

Computational modeling of anoctamin 1 calcium-activated chloride channels as pacemaker channels in interstitial cells of Cajal

Interstitial cells of Cajal (ICC) act as pacemaker cells in the gastrointestinal tract by generating electrical slow waves to regulate rhythmic smooth muscle contractions. Intrinsic Ca(2+) oscillations in ICC appear to produce the slow waves by activating pacemaker currents, currently thought to be carried by the Ca(2+)-activated Cl(-) channel anoctamin 1 (Ano1). In this article we present a novel model of small intestinal ICC pacemaker activity that incorporates store-operated Ca(2+) entry and a new model of Ano1 current. A series of simulations were carried out with the ICC model to investigate current controversies about the reversal potential of the Ano1 Cl(-) current in ICC and to predict the characteristics of the other ion channels that are necessary to generate slow waves. The model results show that Ano1 is a plausible pacemaker channel when coupled to a store-operated Ca(2+) channel but suggest that small cyclical depolarizations may still occur in ICC in Ano1 knockout mice. The results predict that voltage-dependent Ca(2+) current is likely to be negligible during the slow wave plateau phase. The model shows that the Cl(-) equilibrium potential is an important modulator of slow wave morphology, highlighting the need for a better understanding of Cl(-) dynamics in ICC.

Model systems for cardiovascular regenerative biology

There is an urgent clinical need to develop new therapeutic approaches to treat heart failure, but the biology of cardiovascular regeneration is complex. Model systems are required to advance our understanding of biological mechanisms of cardiac regeneration as well as to test therapeutic approaches to regenerate tissue and restore cardiac function following injury. An ideal model system should be inexpensive, easily manipulated, easily reproducible, physiologically representative of human disease, and ethically sound. In this review, we discuss computational, cell-based, tissue, and animal models that have been used to elucidate mechanisms of cardiovascular regenerative biology or to test proposed therapeutic methods to restore cardiac function following disease or injury.

Patch clamp: a powerful technique for studying the mechanism of acupuncture

Cellular and molecular events can be investigated using electrophysiological techniques. In particular, the patch-clamp method provides detailed information. In addition, the patch-clamp technique has become a powerful method for investigating the mechanisms underlying the effects of acupuncture. In this paper, recent researches on how acupuncture might modulate electrophysiological responses in the central nervous system (CNS) and affect peripheral structures are reviewed.

Studying plant salt tolerance with the voltage clamp technique

Voltage clamp is one of the key techniques for the dissection, identification, and monitoring of ion transporters in plant cells. Voltage clamp-based research work on salinity stress in plants enables the characterization of many plant ATP-dependent pumps, ion channels, and ion-coupled carriers through heterologous expression in Xenopus laevis oocytes and in vivo measurements in salt-tolerant and salt-sensitive giant green algae such as Chara and many plant species. We have modified and developed a reliable set of procedures for voltage clamp analysis in intact guard cells and root epidermal cells from Arabidopsis thaliana with potentially broad applications in the salinity response of plants. These procedures greatly extend the duration of measurements and scope for analysis of the predominant K(+) and anion channels.

High-Throughput Screening for N-Type Calcium Channel Blockers Using a Scintillation Proximity Assay

N-type calcium channels located on presynaptic nerve terminals regulate neurotransmitter release, including that from the spinal terminations of primary afferent nociceptors. Accordingly, N-type calcium channel blockers may have clinical utility as analgesic drugs. A selective N-type calcium channel inhibitor, ziconotide (Prialt), is a neuroactive peptide recently marketed as a novel nonopioid treatment for severe chronic pain. To develop a small-molecule N-type calcium channel blocker, the authors developed a 96-well plate high-throughput screening scintillation proximity assay (SPA) for N-type calcium channel blockers using [125I]-labeled ω-conotoxin GVIA as a channel-specific ligand. Assay reagents were handled using Caliper’s Allegro automation system, and bound ligands were detected using a PerkinElmer TopCount. Using this assay, more than 150,000 compounds were screened at 10 μM and approximately 340 compounds were identified as hits, exhibiting at least 40% inhibition of [125I]GVIA binding. This is the 1st demonstration of the use of [125I]-labeled peptides with SPA beads to provide a binding assay for the evaluation of ligand binding to calcium channels. This assay could be a useful tool for drug discovery.

Single-molecule enzymology of chymotrypsin using water-in-oil emulsion

Single-molecule studies allow the study of subtle activity differences due to local folding in proteins, but are time consuming and difficult because only a few molecules are observed in one experiment. We developed an assay where we can simultaneously measure the activity of hundreds of individual molecules. The assay utilizes a synthetic chymotrypsin substrate that is nonfluorescent before cleavage by chymotrypsin, but is intensely fluorescent afterward. We encapsulated the enzyme and substrate in micron-sized droplets of water surrounded by silicone oil where each microdroplet contains <1 enzyme on average. A microscope and charge-coupled device camera are used to measure the fluorescence intensity of the same individual droplet over time. Based on these measurements, we conclude that enzymatic reactions could occur within this emulsion system, the statistical average activity of individual chymotrypsin molecules is similar to that measured in bulk, and the activity of individual chymotrypsin is heterogeneous.