Priming of microglia with IFN-γ slows neuronal gamma oscillations in situ

Type II IFN (IFN-γ) is a proinflammatory T lymphocyte cytokine that serves in priming of microglia—resident CNS macrophages—during the complex microglial activation process under pathological conditions. Priming generally permits an exaggerated microglial response to a secondary inflammatory stimulus. The impact of primed microglia on physiological neuronal function in intact cortical tissue (in situ) is widely unknown, however. We explored the effects of chronic IFN-γ exposure on microglia in hippocampal slice cultures, i.e., postnatal parenchyma lacking leukocyte infiltration (adaptive immunity). We focused on fast neuronal network waves in the gamma-band (30–70 Hz). Such gamma oscillations are fundamental to higher brain functions, such as perception, attention, and memory, and are exquisitely sensitive to metabolic and oxidative stress. IFN-γ induced substantial morphological changes and cell population expansion in microglia as well as moderate up-regulation of activation markers, MHC-II, CD86, IL-6, and inducible nitric oxide synthase (iNOS), but not TNF-α. Cytoarchitecture and morphology of pyramidal neurons and parvalbumin-positive inhibitory interneurons were well-preserved. Notably, gamma oscillations showed a specific decline in frequency of up to 8 Hz, which was not mimicked by IFN-α or IL-17 exposure. The rhythm disturbance was caused by moderate microglial nitric oxide (NO) release demonstrated by pharmacological microglia depletion and iNOS inhibition. In conclusion, IFN-γ priming induces substantial proliferation and moderate activation of microglia that is capable of slowing neural information processing. This mechanism might contribute to cognitive impairment in chronic brain disease featuring elevated IFN-γ levels, blood–brain barrier leakage, and/or T cell infiltration, well before neurodegeneration occurs.

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TLR4-activated microglia require IFN-γ to induce severe neuronal dysfunction and death in situ

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1513853113 ◽

2015 ◽

Vol 113 (1) ◽

pp. 212-217 ◽

Cited By ~ 65

Author(s):

Ismini E. Papageorgiou ◽

Andrea Lewen ◽

Lukas V. Galow ◽

Tiziana Cesetti ◽

Jörg Scheffel ◽

...

Keyword(s):

Nitric Oxide ◽

Field Potential ◽

Population Expansion ◽

Pyramidal Cells ◽

Gamma Oscillations ◽

Extracellular Potassium ◽

Neuronal Dysfunction ◽

No Release ◽

Ifn Γ

Microglia (tissue-resident macrophages) represent the main cell type of the innate immune system in the CNS; however, the mechanisms that control the activation of microglia are widely unknown. We systematically explored microglial activation and functional microglia–neuron interactions in organotypic hippocampal slice cultures, i.e., postnatal cortical tissue that lacks adaptive immunity. We applied electrophysiological recordings of local field potential and extracellular K+ concentration, immunohistochemistry, design-based stereology, morphometry, Sholl analysis, and biochemical analyses. We show that chronic activation with either bacterial lipopolysaccharide through Toll-like receptor 4 (TLR4) or leukocyte cytokine IFN-γ induces reactive phenotypes in microglia associated with morphological changes, population expansion, CD11b and CD68 up-regulation, and proinflammatory cytokine (IL-1β, TNF-α, IL-6) and nitric oxide (NO) release. Notably, these reactive phenotypes only moderately alter intrinsic neuronal excitability and gamma oscillations (30–100 Hz), which emerge from precise synaptic communication of glutamatergic pyramidal cells and fast-spiking, parvalbumin-positive GABAergic interneurons, in local hippocampal networks. Short-term synaptic plasticity and extracellular potassium homeostasis during neural excitation, also reflecting astrocyte function, are unaffected. In contrast, the coactivation of TLR4 and IFN-γ receptors results in neuronal dysfunction and death, caused mainly by enhanced microglial inducible nitric oxide synthase (iNOS) expression and NO release, because iNOS inhibition is neuroprotective. Thus, activation of TLR4 in microglia in situ requires concomitant IFN-γ receptor signaling from peripheral immune cells, such as T helper type 1 and natural killer cells, to unleash neurotoxicity and inflammation-induced neurodegeneration. Our findings provide crucial mechanistic insight into the complex process of microglia activation, with relevance to several neurologic and psychiatric disorders.

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IP-10 and Mig Production by Glomerular Cells in Human Proliferative Glomerulonephritis and Regulation by Nitric Oxide

Journal of the American Society of Nephrology ◽

10.1681/asn.v13153 ◽

2002 ◽

Vol 13 (1) ◽

pp. 53-64

Author(s):

Paola Romagnani ◽

Elena Lazzeri ◽

Laura Lasagni ◽

Carmelo Mavilia ◽

Chiara Beltrame ◽

...

Keyword(s):

Nitric Oxide ◽

Mesangial Cells ◽

Primary Cultures ◽

Nuclear Antigen ◽

No Donors ◽

Human Mesangial Cells ◽

Tnf Α ◽

Ifn Γ ◽

Immunohistochemical Analyses

ABSTRACT. High levels of expression of mRNA and protein for the chemokines interferon-γ (IFN-γ)-inducible protein of 10 kD (IP-10) (CXCL10) and the monokine induced by IFN-γ (Mig) (CXCL9) were observed, by using in situ hybridization and immunohistochemical analyses, in kidney biopsy specimens from patients with glomerulonephritis (GN), particularly those with membranoproliferative or crescentic GN, but not in normal kidneys. Double-immunostaining or combined in situ hybridization and immunohistochemical analyses for IP-10, Mig, and proliferating cell nuclear antigen (PCNA) or α-smooth muscle actin (α-SMA) revealed that IP-10 and Mig production by resident glomerular cells was a selective property of glomeruli in which mesangial cells demonstrated active proliferation. IP-10 and Mig mRNA and protein were also expressed by primary cultures of human mesangial cells and human visceral epithelial cells after stimulation with IFN- γ or with IFN-γ plus tumor necrosis factor-α (TNF-α) (which produced greater stimulation). The induction of IP-10 and Mig mRNA and protein expression by IFN-γ plus TNF-α was strongly inhibited by nitric oxide (NO) donors, such as sodium nitroprusside or S-nitroso-N-acetylpenicillamine, but not by cGMP analogues. Electrophoretic mobility shift assays demonstrated that NO donors repressed IP-10 gene transcription induced by IFN-γ plus TNF-α through the inhibition of NF-κB activation. These data demonstrate that resident glomerular cells in kidneys of patients with proliferative GN produce large amounts of IP-10 and Mig, which may play important pathogenic roles in this disease. These data also indicate that the production of IP-10 and Mig by human mesangial cells can be downregulated by NO donors through cGMP-independent inhibition of NF-κB activation.

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Mild metabolic stress is sufficient to disturb the formation of pyramidal cell ensembles during gamma oscillations

Journal of Cerebral Blood Flow & Metabolism ◽

10.1177/0271678x19892657 ◽

2019 ◽

Vol 40 (12) ◽

pp. 2401-2415 ◽

Cited By ~ 2

Author(s):

Shehabeldin Elzoheiry ◽

Andrea Lewen ◽

Justus Schneider ◽

Martin Both ◽

Dimitri Hefter ◽

...

Keyword(s):

Pyramidal Cell ◽

Metabolic Stress ◽

Pyramidal Cells ◽

Gamma Oscillations ◽

System Level ◽

Attention And Memory ◽

Neuronal Ensembles ◽

Brain Functions ◽

Fast Spiking ◽

Underlying Mechanisms

Disturbances of cognitive functions occur rapidly during acute metabolic stress. However, the underlying mechanisms are not fully understood. Cortical gamma oscillations (30–100 Hz) emerging from precise synaptic transmission between excitatory principal neurons and inhibitory interneurons, such as fast-spiking GABAergic basket cells, are associated with higher brain functions, like sensory perception, selective attention and memory formation. We investigated the alterations of cholinergic gamma oscillations at the level of neuronal ensembles in the CA3 region of rat hippocampal slice cultures. We combined electrophysiology, calcium imaging (CamKII.GCaMP6f) and mild metabolic stress that was induced by rotenone, a lipophilic and highly selective inhibitor of complex I in the respiratory chain of mitochondria. The detected pyramidal cell ensembles showing repetitive patterns of activity were highly sensitive to mild metabolic stress. Whereas such synchronised multicellular activity diminished, the overall activity of individual pyramidal cells was unaffected. Additionally, mild metabolic stress had no effect on the rate of action potential generation in fast-spiking neural units. However, the partial disinhibition of slow-spiking neural units suggests that disturbances of ensemble formation likely result from alterations in synaptic inhibition. Our study bridges disturbances on the (multi-)cellular and network level to putative cognitive impairment on the system level.

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Airway contribution to alveolar nitric oxide in healthy subjects and stable asthma patients

Journal of Applied Physiology ◽

10.1152/japplphysiol.01032.2007 ◽

2008 ◽

Vol 104 (4) ◽

pp. 918-924 ◽

Cited By ~ 68

Author(s):

Yannick Kerckx ◽

Alain Michils ◽

Alain Van Muylem

Keyword(s):

Nitric Oxide ◽

Asthma Control ◽

Healthy Subjects ◽

Molecular Diffusion ◽

Forced Expiratory Volume ◽

No Production ◽

Asthma Control Questionnaire ◽

Asthma Patients ◽

The Impact

Alveolar nitric oxide (NO) concentration (FaNO), increasingly considered in asthma, is currently interpreted as a reflection of NO production in the alveoli. Recent modeling studies showed that axial molecular diffusion brings NO molecules from the airways back into the alveolar compartment during exhalation (backdiffusion) and contributes to FaNO. Our objectives in this study were 1) to simulate the impact of backdiffusion on FaNO and to estimate the alveolar concentration actually due to in situ production (FaNO,prod); and 2) to determine actual alveolar production in stable asthma patients with a broad range of NO bronchial productions. A model incorporating convection and diffusion transport and NO sources was used to simulate FaNO and exhaled NO concentration at 50 ml/s expired flow (FeNO) for a range of alveolar and bronchial NO productions. FaNO and FeNO were measured in 10 healthy subjects (8 men; age 38 ± 14 yr) and in 21 asthma patients with stable asthma [16 men; age 33 ± 13 yr; forced expiratory volume during 1 s (FEV1) = 98.0 ± 11.9%predicted]. The Asthma Control Questionnaire (Juniper EF, Buist AS, Cox FM, Ferrie PJ, King DR. Chest 115: 1265–1270, 1999) assessed asthma control. Simulations predict that, because of backdiffusion, FaNO and FeNO are linearly related. Experimental results confirm this relationship. FaNO,prod may be derived by FaNO,prod = (FaNO − 0.08·FeNO)/0.92 ( Eq. 1 ). Based on Eq. 1 , FaNO,prod is similar in asthma patients and in healthy subjects. In conclusion, the backdiffusion mechanism is an important determinant of NO alveolar concentration. In stable and unobstructed asthma patients, even with increased bronchial NO production, alveolar production is normal when appropriately corrected for backdiffusion.

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Fatal Dengue Cases Reveal Brain Injury and Viral Replication in Brain-Resident Cells Associated with the Local Production of Pro-Inflammatory Mediators

Viruses ◽

10.3390/v12060603 ◽

2020 ◽

Vol 12 (6) ◽

pp. 603 ◽

Cited By ~ 1

Author(s):

Natália Salomão ◽

Kíssila Rabelo ◽

Carlos Basílio-de-Oliveira ◽

Rodrigo Basílio-de-Oliveira ◽

Luiz Geraldo ◽

...

Keyword(s):

Endothelial Cells ◽

Inflammatory Mediators ◽

Denv Infection ◽

Microglial Cells ◽

Tnf Α ◽

Ifn Γ ◽

Lymphocytic Infiltrates ◽

The Impact ◽

Arboviral Disease

Dengue is an arboviral disease caused by dengue virus (DENV), which is transmitted to humans by Aedes aegypti mosquitoes. Infection by DENV most commonly results in a mild flu-like illness; however, the disease has been increasingly associated with neurological symptomatology. This association draws attention to further investigations on the impact of DENV infection in the host’s central nervous system. Here, we analyzed brain samples of three fatal dengue cases that occurred in 2002 during an outbreak in Rio de Janeiro, Brazil. Brain tissues of these cases were marked by histopathological alterations, such as degenerated neurons, demyelination, hemorrhage, edema, and increased numbers of astrocytes and microglial cells. Samples were also characterized by lymphocytic infiltrates mainly composed of CD8 T cells. DENV replication was evidenced in neurons, microglia and endothelial cells through immunohistochemistry and in situ hybridization techniques. Pro-inflammatory cytokines, such as TNF-α and IFN-γ were detected in microglia, while endothelial cells were marked by the expression of RANTES/CCL5. Cytoplasmic HMGB1 and the production of nitric oxide were also found in neurons and microglial cells. This work highlights the possible participation of several local pro-inflammatory mediators in the establishment of dengue neuropathogenesis.

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Inducible nitric oxide synthase gene deletion exaggerates MAPK-mediated cyclooxygenase-2 induction by inflammatory stimuli

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.00144.2010 ◽

2010 ◽

Vol 299 (3) ◽

pp. H613-H623 ◽

Cited By ~ 18

Author(s):

Brian D. Lamon ◽

Rita K. Upmacis ◽

Ruba S. Deeb ◽

Hilal Koyuncu ◽

David P. Hajjar

Keyword(s):

Nitric Oxide ◽

Atherosclerotic Lesion ◽

No Synthase ◽

No Production ◽

Nitrite Production ◽

Inflammatory Stimuli ◽

Ifn Γ ◽

Cox 2 ◽

The Impact ◽

Inducible Nitric Oxide

Cyclooxygenase (COX)-2 and inducible nitric oxide (NO) synthase (iNOS) are responsive to a wide array of inflammatory stimuli, have been localized to vascular smooth muscle cells (SMCs), and are intimately linked to the progression of vascular disease, including atherosclerotic lesion formation. We and others have shown that the production and subsequent impact of COX products appear to be correlative with the status of NO synthesis. This study examined the impact of inflammation-driven NO production on COX-2 expression in SMCs. Concurrent stimulation of quiescent rat aortic SMCs with lipopolysaccharide (LPS) and interferon (IFN)-γ increased COX-2, iNOS, and nitrite production. Pharmacological inhibition of NO synthase ( NG-monomethyl-l-arginine) concentration- and time-dependently magnified LPS + IFN-γ-mediated COX-2 mRNA and protein induction in a cGMP-independent manner. COX-2 induction was associated with activation of the ERK, p38, and JNK mitogen-activated protein kinase (MAPK) pathways. Interestingly, NO synthase inhibition enhanced ERK, p38, and to a lesser extent JNK phosphorylation but suppressed MAPK phosphatase (MKP)-1 induction in response to LPS + IFN-γ. Similarly, the exposure of SMCs from iNOS−/− mice to LPS + IFN-γ produced an enhancement of COX-2 induction, p38, and JNK phosphorylation and an attenuated upregulation of MKP-1 versus their wild-type counterparts. Taken together, our data indicate that NO, in part derived from iNOS, negatively regulates the immediate early induction of COX-2 in response to inflammatory stimuli.

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