Two-photon neuronal and astrocytic stimulation with azobenzene-based photoswitches

This is an open access article published under an ACS AuthorChoice License. See Standard ACS AuthorChoice/Editors' Choice Usage Agreement - https://pubs.acs.org/page/policy/authorchoice_termsofuse.htmlSynthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution

The cellular architecture of memory modules in Drosophila supports stochastic input integration

The ability to associate neutral stimuli with valence information and to store these associations as memories forms the basis for decision making. To determine the underlying computational principles, we build a realistic computational model of a central decision module within the Drosophila mushroom body (MB), the fly’s center for learning and memory. Our model combines the electron microscopy-based architecture of one MB output neuron (MBON-α3), the synaptic connectivity of its 948 presynaptic Kenyon cells (KCs), and its membrane properties obtained from patch-clamp recordings. We show that this neuron is electrotonically compact and that synaptic input corresponding to simulated odor input robustly drives its spiking behavior. Therefore, sparse innervation by KCs can efficiently control and modulate MBON activity in response to learning with minimal requirements on the specificity of synaptic localization. This architecture allows efficient storage of large numbers of memories using the flexible stochastic connectivity of the circuit

Neuronal photoactivation through second-harmonic near-infrared absorption by gold nanoparticles

Zapping neurons to life with infrared light Neuronal impulses can be generated by aiming a near-infrared laser beam at gold nanoparticles precisely tethered to brain cells. Wieteke de Boer and Jan Hirtz of the NeuroTechnology Center at Columbia University, USA, and colleagues developed the technique, which could provide a nontoxic, nongenetic alternative to commonly used optical methods for activating brain cells. They tested it in live mouse brain tissue, and also used it to induce movement in a tiny freshwater animal called Hydra vulgaris. The authors demonstrate the potential for targeted stimulation of neurons through the nonlinear absorption of light by nanoparticles. By using low-power short-pulsed near-infrared excitation, the photodamage of the tissue is minimal. The approach shows promise for application in biological systems and for future treatments of neurological and mental disorders

Two-photon neuronal and astrocytic stimulation with azobenzene-based photoswitches

This is an open access article published under an ACS AuthorChoice License. See Standard ACS AuthorChoice/Editors' Choice Usage Agreement - https://pubs.acs.org/page/policy/authorchoice_termsofuse.htmlSynthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution

Two-Photon Neuronal and Astrocytic Stimulation with Azobenzene-Based Photoswitches

Synthetic photochromic compounds can be designed to control a variety of proteins and their biochemical functions in living cells, but the high spatiotemporal precision and tissue penetration of two-photon stimulation have never been investigated in these molecules. Here we demonstrate two-photon excitation of azobenzene-based protein switches and versatile strategies to enhance their photochemical responses. This enables new applications to control the activation of neurons and astrocytes with cellular and subcellular resolution

α\alpha1-antitrypsin mitigates NLRP3-inflammasome activation in amyloid β\beta-stimulated murine astrocytes

Abstract Background Neuroinflammation has an essential impact on the pathogenesis and progression of Alzheimer’s disease (AD). Mostly mediated by microglia and astrocytes, inflammatory processes lead to degeneration of neuronal cells. The NLRP3-inflammasome (NOD-like receptor family, pyrin domain containing 3) is a key component of the innate immune system and its activation results in secretion of the proinflammatory effectors interleukin-1β (IL-1β) and interleukin-18 (IL-18). Under physiological conditions, cytosolic NLRP3-inflammsome is maintained in an inactive form, not able to oligomerize. Amyloid β1–42 (Aβ1–42) triggers activation of NLRP3-inflammasome in microglia and astrocytes, inducing oligomerization and thus recruitment of proinflammatory proteases. NLRP3-inflammasome was found highly expressed in human brains diagnosed with AD. Moreover, NLRP3-deficient mice carrying mutations associated with familial AD were partially protected from deficits associated with AD. The endogenous protease inhibitor α1-antitrypsin (A1AT) is known for its anti-inflammatory and anti-apoptotic properties and thus could serve as therapeutic agent for NLRP3-inhibition. A1AT protects neurons from glutamate-induced toxicity and reduces Aβ1–42-induced inflammation in microglial cells. In this study, we investigated the effect of Aβ1–42-induced NLRP3-inflammasome upregulation in primary murine astrocytes and its regulation by A1AT. Methods Primary cortical astrocytes from BALB/c mice were stimulated with Aβ1–42 and treated with A1AT. Regulation of NLRP3-inflammasome was examined by immunocytochemistry, PCR, western blot and ELISA. Our studies included an inhibitor of NLRP3 to elucidate direct interactions between A1AT and NLRP3-inflammasome components. Results Our study revealed that A1AT reduces Aβ1–42-dependent upregulation of NLRP3 at the mRNA and protein levels. Furthermore, A1AT time-dependently mitigated the expression of caspase 1 and its cleavage product IL-1β in Aβ1–42-stimulated astrocytes. Conclusion We conclude that Aβ1–42-stimulation results in an upregulation of NLRP3, caspase 1, and its cleavage products in astrocytes. A1AT time-dependently hampers neuroinflammation by downregulation of Aβ1–42-mediated NLRP3-inflammasome expression and thus may serve as a pharmaceutical opportunity for the treatment of Alzheimer’s disease