Biology subjects

Ostapchenko, V.

Publications and source records attributed to Ostapchenko, V..

2 recordsLinked to original sources

bioRxiv2020

Chronic hM3Dq signaling in microglia ameliorates neuroinflammation in male mice

Microglia express muscarinic G protein-coupled receptors (GPCRs) that sense cholinergic activity and are activated by acetylcholine to potentially regulate microglial functions. Knowledge about how distinct types of muscarinic GPCR signaling regulate microglia function in vitro and in vivo is still poor, partly due to the fact that some of these receptors are also present in astrocytes and neurons. We generated mice expressing the hM3Dq Designer Receptor Exclusively Activated by Designer Drugs (DREADD) selectively in microglia to investigate the role of muscarinic M3Gq-linked signaling. We show that activation of hM3Dq using clozapine N-oxide (CNO) elevated intracellular calcium levels and increased phagocytosis of FluoSpheres in vitro. Acute treatment with CNO in vivo did not affect male mouse behavior, however chronic CNO treatment decreased sickness behavior triggered by lipopolysaccharide (LPS) treatment. Interestingly, whereas acute treatment with CNO increased synthesis of cytokine mRNA, chronic treatment attenuated LPS-induced cytokine mRNA changes in the brain, likely explaining the improvement in sickness behavior by chronic hM3Dq activation. No effect of CNO was observed in DREADD-negative mice. These results suggest that chronic activation of M3 muscarinic receptors (the hM3Dq progenitor) in microglia, and potentially other Gq-coupled GPCRs, preconditions microglia to decrease their response to further immunological challenges. Our results indicate that hM3Dq can be a useful tool to modulate neuroinflammation and study microglial immunological memory in vivo, which may be applicable for manipulations of neuroinflammation in neurodegenerative and psychiatric diseases. HighlightsO_LIMicroglial function was manipulated by specific activation of hM3Dq signaling. C_LIO_LIChronic hM3Dq activation prevented LPS-induced sickness behavior in mice. C_LIO_LIMicroglial hM3Dq signaling modulated expression of pro-inflammatory cytokines. C_LI

neuroscience↗

bioRxiv2017

Mapping nonapoptotic caspase activity with a transgenic reporter in mice

The protease caspase-3 is a key mediator of apoptotic programmed cell death. But weak or transient caspase activity can contribute to neuronal differentiation, axonal pathfinding, and synaptic long-term depression. Despite the importance of sublethal, or nonapoptotic, caspase activity in neurodevelopment and neural plasticity, there has been no simple method for mapping and quantifying nonapoptotic caspase activity in rodent brains. We therefore generated a transgenic mouse expressing a highly sensitive and specific fluorescent reporter of caspase activity, with peak signal localized to the nucleus. As a proof of concept, we first obtained evidence that nonapoptotic caspase activity influences neurophysiology in an amygdalar circuit. Then focusing on the amygdala, we were able to quantify a sex-specific persistent elevation in caspase activity in females after restraint stress. This simple in vivo caspase activity reporter will facilitate systems-level studies of apoptotic and nonapoptotic phenomena in behavioral and pathological models. Significance StatementCaspase-3 is an enzyme that can cause cell death when highly active but can also perform important cellular functions, such as maturation and structural changes, when only weakly or transiently active. Despite the importance of this nonlethal type of caspase activity, there is no straightforward method to measure it in live rodents. We therefore developed mice that have a fluorescent reporter that is sensitive enough to detect nonlethal caspase activity. Surprisingly, we found that weak caspase activity influences the synchrony of neuronal firing across different brain regions. We also observed increased caspase activity in female mice after severe stress. This simple caspase activity reporter can subserve multiple applications in behavior and pathology research.

neuroscience↗