Biology subjects

Daniels, B. P.

Publications and source records attributed to Daniels, B. P..

9 recordsLinked to original sources

bioRxiv2026

SIRT1 remodels astrocyte metabolism and promotes viral replication during neurotropic orthoflavivirus infection

Orthoflaviviruses depend on host metabolic resources to replicate, but how distinct cell types in the central nervous system (CNS) alter their metabolism in response to infection remains incompletely understood. Here, we examined whether the NAD+-dependent deacetylase SIRT1 is engaged during Zika virus (ZIKV) and West Nile virus (WNV) infection and whether its activity influences infection outcomes. SIRT1 activity increased in astrocytes isolated from infected mouse brains and in infected primary human astrocytes, but not in neurons or CNS myeloid cells. In astrocytes, infection induced transcriptomic, metabolomic, and functional changes consistent with SIRT1 activation, enhanced NAD+ salvage, and enhanced oxidative metabolism. Pharmacologic inhibition of SIRT1 or NAD+ salvage reduced ZIKV replication in astrocytes, whereas SIRT1 activation or supplementation with an NAD+ precursor increased replication. In mice, SIRT1 inhibition or nicotinamide (NAM) treatment reduced viral burden and mortality following ZIKV and WNV infection, while SIRT1 activation worsened disease. Together, these findings identify NAD+/SIRT1 as key regulators of cellular metabolism in infected astrocytes and support a role for this pathway in promoting orthoflavivirus replication and pathogenesis.

immunology↗

bioRxiv2024

Astrocytic RIPK3 exerts protective anti-inflammatory activity during viral encephalitis via induction of serpin protease inhibitors.

Flaviviruses pose a significant threat to public health due to their ability to infect the central nervous system (CNS) and cause severe neurologic disease. Astrocytes play a crucial role in the pathogenesis of flavivirus encephalitis through their maintenance of blood-brain barrier (BBB) integrity and their modulation of immune cell recruitment and activation within the CNS. We have previously shown that receptor interacting protein kinase-3 (RIPK3) is a central coordinator of neuroinflammation during CNS viral infection, a function that occurs independently of its canonical function in inducing necroptotic cell death. To date, however, roles for necroptosis-independent RIPK3 signaling in astrocytes are poorly understood. Here, we use mouse genetic tools to induce astrocyte-specific deletion, overexpression, and chemogenetic activation of RIPK3 to demonstrate an unexpected anti-inflammatory function for astrocytic RIPK3. RIPK3 activation in astrocytes was required for host survival in multiple models of flavivirus encephalitis, where it restricted neuropathogenesis by limiting immune cell recruitment to the CNS. Transcriptomic analysis revealed that, despite inducing a traditional pro-inflammatory transcriptional program, astrocytic RIPK3 paradoxically promoted neuroprotection through the upregulation of serpins, endogenous protease inhibitors with broad immunomodulatory activity. Notably, intracerebroventricular administration of SerpinA3N in infected mice preserved BBB integrity, reduced leukocyte infiltration, and improved survival outcomes in mice lacking astrocytic RIPK3. These findings highlight a previously unappreciated role for astrocytic RIPK3 in suppressing pathologic neuroinflammation and suggests new therapeutic targets for the treatment of flavivirus encephalitis.

immunology↗

bioRxiv2024

RIPK3 promotes neuronal survival by suppressing excitatory neurotransmission during CNS viral infection

While recent work has identified roles for immune mediators in the regulation of neural activity, the capacity for cell intrinsic innate immune signaling within neurons to influence neurotransmission remains poorly understood. However, the existing evidence linking immune signaling with neuronal function suggests that modulation of neurotransmission may serve previously undefined roles in host protection during infection of the central nervous system. Here, we identify a specialized function for RIPK3, a kinase traditionally associated with necroptotic cell death, in preserving neuronal survival during neurotropic flavivirus infection through the suppression of excitatory neurotransmission. We show that RIPK3 coordinates transcriptomic changes in neurons that suppress neuronal glutamate signaling, thereby desensitizing neurons to excitotoxic cell death. These effects occur independently of the traditional functions of RIPK3 in promoting necroptosis and inflammatory transcription. Instead, RIPK3 promotes phosphorylation of the key neuronal regulatory kinase CaMKII, which in turn activates the transcription factor CREB to drive a neuroprotective transcriptional program and suppress deleterious glutamatergic signaling. These findings identify an unexpected function for a canonical cell death protein in promoting neuronal survival during viral infection through the modulation of neuronal activity, highlighting new mechanisms of neuroimmune crosstalk.

neuroscience↗

bioRxiv2024

RIPK3 coordinates RHIM domain-dependent inflammatory transcription in neurons

Neurons are post-mitotic, non-regenerative cells that have evolved fine-tuned immunological responses to maintain life-long cellular integrity; this includes resistance to common programmed cell death (PCD) pathways, including apoptosis and necroptosis. We have previously demonstrated a necroptosis-independent role for the key necroptotic kinase RIPK3 in host defense against neurotropic flavivirus infection. While this work showed that neuronal RIPK3 expression is essential for chemokine production and recruitment of peripheral immune cells to the infected CNS, the full RIPK3-dependent transcriptional signature, and the molecular mechanism underlying RIPK3-dependent transcription in neurons are incompletely understood. It also remains unclear what factors govern differential RIPK3 effector functions in different cell types. Here, we show that RIPK3 activation has distinct outcomes in primary cortical neurons when compared to mouse embryonic fibroblasts (MEFs) during Zika virus (ZIKV) infection or following sterile activation. We found that RIPK3 activation does not induce death in neurons; in these cells, RIPK3 is the dominant driver of antiviral gene transcription following ZIKV infection. While RIPK3 activation in MEF cells induces cell death, ablation of downstream cell death effectors unveils a RIPK3-dependent transcriptional program which largely overlaps with that observed in ZIKV-infected neurons. Using death resistant MEFs as a model to study RIPK3 signaling revealed that RIPK3 transcription relied on interactions with the RHIM domain-containing proteins RIPK1 and TRIF, effects mirrored in the RIPK3-dependent antiviral transcriptional signature observed in ZIKV-infected neurons. These findings suggest the pleotropic functions of RIPK3 are largely context dependent and that in cells that are resistant to cell death, RIPK3 acts as a mediator of inflammatory transcription. One Sentence SummaryRHIM-domain containing proteins form a conserved signaling network capable of mediating inflammatory transcription and cell death.

immunology↗

bioRxiv2023

Neuronal DAMPs exacerbate neurodegeneration via astrocytic RIPK3 signaling

Astrocyte activation is a common feature of neurodegenerative diseases. However, the ways in which dying neurons influence the activity of astrocytes is poorly understood. RIPK3 signaling has recently been described as a key regulator of neuroinflammation, but whether this kinase mediates astrocytic responsiveness to neuronal death has not yet been studied. Here, we used the MPTP model of Parkinsons disease to show that activation of astrocytic RIPK3 drives dopaminergic cell death and axon damage. Transcriptomic profiling revealed that astrocytic RIPK3 promoted gene expression associated with neuroinflammation and movement disorders, and this coincided with significant engagement of DAMP signaling. Using human cell culture systems, we show that factors released from dying neurons signal through RAGE to induce RIPK3-dependent astrocyte activation. These findings highlight a mechanism of neuron-glia crosstalk in which neuronal death perpetuates further neurodegeneration by engaging inflammatory astrocyte activation via RIPK3.

neuroscience↗

bioRxiv2023

RIPK3 promotes brain region-specific interferon signaling and restriction of tick-borne flavivirus infection

Innate immune signaling in the central nervous system (CNS) exhibits many remarkable specializations that vary across cell types and CNS regions. In the setting of neuroinvasive flavivirus infection, neurons employ the immunologic kinase receptor-interacting kinase 3 (RIPK3) to promote an antiviral transcriptional program, independently of the traditional function of this enzyme in promoting necroptotic cell death. However, while recent work has established roles for neuronal RIPK3 signaling in controlling mosquito-borne flavivirus infections, including West Nile virus and Zika virus, functions for RIPK3 signaling in the CNS during tick-borne flavivirus infection have not yet been explored. Here, we use a model of Langat virus (LGTV) encephalitis to show that RIPK3 signaling is specifically required in neurons of the cerebellum to control LGTV replication and restrict disease pathogenesis. This effect did not require the necroptotic executioner molecule mixed lineage kinase domain like protein (MLKL), a finding similar to previous observations in models of mosquito-borne flavivirus infection. However, control of LGTV infection required a unique, region-specific dependence on RIPK3 to promote expression of key antiviral interferon-stimulated genes (ISG) in the cerebellum. This RIPK3- mediated potentiation of ISG expression was associated with robust cell-intrinsic restriction of LGTV replication in cerebellar granule cell neurons. These findings further illuminate the complex roles of RIPK3 signaling in the coordination of neuroimmune responses to viral infection, as well as provide new insight into the mechanisms of region-specific innate immune signaling in the CNS. ImportanceInteractions between the nervous and immune systems are very carefully orchestrated in order to protect the brain and spinal cord from immune-mediated damage, while still maintaining protective defenses against infection. These specialized neuro-immune interactions have been shown to vary significantly across regions of the brain, with innate antiviral signaling being particularly strong in the cerebellum, although the reasons for this are poorly understood. Here, we show a specialized adaptation of programmed cell death signaling that uniquely protects the cerebellum from tick-borne flavivirus infection. These findings provide important new insight into the molecular mechanisms that promote the uniquely robust antiviral immunity of the cerebellum. They also provide new clues into the pathogenesis of tick-borne encephalitis, a zoonosis of significant global concern.

immunology↗

bioRxiv2021

Zika virus-induced TNF-α signaling dysregulates expression of neurologic genes associated with psychiatric disorders

Zika virus (ZIKV) is an emerging flavivirus of global concern. ZIKV infection of the central nervous system has been linked to a variety of clinical syndromes, including microcephaly in fetuses and rare but serious neurologic disease in adults. However, the potential for ZIKV to influence brain physiology and host behavior following recovery from apparently mild or subclinical infection is less well understood. Furthermore, though deficits in cognitive function are well-documented following recovery from neuroinvasive viral infection, the potential impact of ZIKV on other host behavioral domains has not been thoroughly explored. In our study, we performed transcriptomic profiling of primary neuron cultures following ZIKV infection, which revealed altered expression of key genes associated with major psychiatric disorders, such as bipolar disorder and schizophrenia. Gene ontology enrichment analysis also revealed significant changes in gene expression associated with fundamental neurobiological processes, including neuronal development, neurotransmission, and others. These alterations to neurologic gene expression were also observed in the brain in vivo using an immunocompetent mouse model of ZIKV infection. Mechanistic studies identified TNF- signaling via TNFR1 as a major regulatory mechanism controlling ZIKV-induced changes to neurologic gene expression. Our studies reveal that cell-intrinsic innate immune responses to ZIKV infection profoundly shape neuronal transcriptional profiles, highlighting the need to further explore associations between ZIKV infection and disordered host behavioral states.

neuroscience↗

bioRxiv2020

Fibrillar α-synuclein induces neurotoxic astrocyte activation via RIP kinase signaling and NF-κB

Parkinsons disease (PD) is a neurodegenerative disorder characterized by death of midbrain dopamine neurons. The pathogenesis of PD is poorly understood, though misfolded and/or aggregated forms of the protein -synuclein have been implicated in several neurodegenerative disease processes, including neuroinflammation and astrocyte activation. Astrocytes in the midbrain play complex roles during PD, initiating both harmful and protective processes that vary over the course of disease. However, despite their significant regulatory roles during neurodegeneration, the cellular and molecular mechanisms that promote pathogenic astrocyte activity remain mysterious. Here, we show that -synuclein preformed fibrils (PFFs) induce pathogenic activation of human midbrain astrocytes, marked by inflammatory transcriptional responses, downregulation of phagocytic function, and conferral of neurotoxic activity. These effects required the necroptotic kinases RIPK1 and RIPK3, but were independent of MLKL and necroptosis. Instead, both transcriptional and functional markers of astrocyte activation occurred via RIPK-dependent activation of NF-{kappa}B signaling. Our study identifies a previously unknown function for -synuclein in promoting neurotoxic astrocyte activation, as well as new cell death-independent roles for RIP kinase signaling in the regulation of glial cell biology and neuroinflammation. Together, these findings highlight previously unappreciated molecular mechanisms of pathologic astrocyte activation and neuronal cell death with implications for Parkinsonian neurodegeneration.

neuroscience↗

bioRxiv2020

Developing Human Pluripotent Stem Cell-Based Cerebral Organoids with a Controllable Microglia Ratio for Modeling Brain Development and Pathology

Microglia, as brain-resident macrophages, play critical roles in brain development, homeostasis, and disease. Microglia in animal models cannot accurately model the properties of human microglia due to notable transcriptomic and functional differences between human and other animal microglia. Efficient generation of microglia from human pluripotent stem cells (hPSCs) provides unprecedented opportunities to study the function and behavior of human microglia. Particularly, incorporating hPSCs-derived microglia into brain organoids facilitates their development in a 3-dimensional context, mimicking the brain environment. However, an optimized method that integrates an appropriate amount of microglia into brain organoids at a proper time point, resembling in vivo brain development, is still lacking. Here, we report the development of a new brain region-specific, microglia-containing organoid model by co-culturing hPSCs-derived primitive neural progenitor cells (pNPCs) and primitive macrophage progenitors (PMPs). In these organoids, hPSCs-derived pNPCs and PMPs interact with each other and develop into functional neurons, astroglia, and microglia, respectively. Importantly, the numbers of human microglia in the organoids can be controlled, resulting in a cell type ratio similar to that seen in the human brain. Using super-resolution microscopy, we demonstrate that these human microglia are able to phagocytize neural progenitor cells (NPCs) and apoptotic cells, as well as to prune synapses at different developmental stages of the organoids. Furthermore, these human microglia respond to Zika virus infection of the organoids, as indicated by amoeboid-like morphology, increased expression of gene transcripts encoding inflammatory cytokines, and excessive pruning of synaptic materials. Together, our findings establish a new microglia-containing brain organoid model that will serve to study human microglial function in a variety of neurological disorders.

neuroscience↗