scholarly journals A motogenic GABAergic system of mononuclear phagocytes facilitates dissemination of coccidian parasites

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Amol K Bhandage ◽  
Gabriela C Olivera ◽  
Sachie Kanatani ◽  
Elizabeth Thompson ◽  
Karin Loré ◽  
...  
Keyword(s):  
Neospora Caninum ◽  
Mononuclear Phagocytes ◽  
Gamma Aminobutyric Acid ◽  
Gaba A ◽  
Voltage Dependent ◽  
Coccidian Parasites ◽  
Voltage Dependent Calcium Channels

Gamma-aminobutyric acid (GABA) serves diverse biological functions in prokaryotes and eukaryotes, including neurotransmission in vertebrates. Yet, the role of GABA in the immune system has remained elusive. Here, a comprehensive characterization of human and murine myeloid mononuclear phagocytes revealed the presence of a conserved and tightly regulated GABAergic machinery with expression of GABA metabolic enzymes and transporters, GABA-A receptors and regulators, and voltage-dependent calcium channels. Infection challenge with the common coccidian parasites Toxoplasma gondii and Neospora caninum activated GABAergic signaling in phagocytes. Using gene silencing and pharmacological modulators in vitro and in vivo in mice, we identify the functional determinants of GABAergic signaling in parasitized phagocytes and demonstrate a link to calcium responses and migratory activation. The findings reveal a regulatory role for a GABAergic signaling machinery in the host-pathogen interplay between phagocytes and invasive coccidian parasites. The co-option of GABA underlies colonization of the host by a Trojan horse mechanism.

Multinucleated rat alveolar macrophages express functional receptors for calcitonin

1991 ◽  
Vol 261 (6) ◽  
pp. F1026-F1032 ◽  
Author(s):  
A. Vignery ◽  
M. J. Raymond ◽  
H. Y. Qian ◽  
F. Wang ◽  
S. A. Rosenzweig
Keyword(s):  
Plasma Membrane ◽  
Alveolar Macrophages ◽  
Giant Cells ◽  
Mononuclear Phagocytes ◽  
Inflammatory Reactions ◽  
Calcitonin Gene ◽  
Novel Model

The fusion of mononuclear phagocytes occurs spontaneously in vivo and leads to the differentiation of either multinucleated giant cells or osteoclasts in chronic inflammatory sites or in bone, respectively. Although osteoclasts are responsible for resorbing bone, the functional role of giant cells in chronic inflammatory reactions and tumors remains poorly understood. We recently reported that the plasma membrane of multinucleated macrophages is, like that of osteoclasts, enriched in Na-K-adenosinetriphosphatases (ATPases). We also observed that the localization of their Na-K-ATPases is restricted to the nonadherent domain of the plasma membrane of cells both in vivo and in vitro, thus imposing a functional polarity on their organization. By following this observation, we wished to investigate whether these cells also expressed, like osteoclasts, functional receptors for calcitonin (CT). To this end, alveolar macrophages were fused in vitro, and both their structural and functional association with CT was analyzed and compared with those of mononucleated peritoneal and alveolar macrophages. Evidence is presented that multinucleated alveolar macrophages express a high copy number of functional receptors for CT. Our results also indicate that alveolar macrophages, much like peritoneal, express functional receptors for calcitonin gene-related peptide. It is suggested that multinucleated rat alveolar macrophages offer a novel model system to study CT receptors and that calcitonin may control local immune reactions where giant cells differentiate.

Role of calcium and calmodulin in release of kallikrein and tonin from rat submandibular gland

1986 ◽  
Vol 250 (3) ◽  
pp. C480-C485 ◽  
Author(s):  
S. R. Maitra ◽  
O. A. Carretero ◽  
S. W. Smith ◽  
S. F. Rabito
Keyword(s):  
Submandibular Gland ◽  
Incubation Medium ◽  
High Concentration ◽  
Calcium Blockers ◽  
Control Value ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels ◽  
Intracellular Mediators

We investigated the role of calcium and calmodulin as intracellular mediators of kallikrein and tonin release induced by norepinephrine (NE). We studied the secretion rate of kallikrein and tonin from submandibular gland of rat in response to NE in the presence or absence of calcium, two calcium blockers, and four different calmodulin antagonists. Submandibular gland slices were incubated in vitro, and glandular kallikrein and tonin secreted into the incubation medium were determined by direct radioimmunoassays and expressed as nanograms per minute per milligram tissue. NE (10(-5) and 10(-4) M) increased the kallikrein secretion from the control value of 8.2 +/- 2.6 to 134.9 +/- 41.4 (P less than 0.05) and to 191.2 +/- 62.7 (P less than 0.05), and the release of tonin from a basal rate of 3.5 +/- 0.6 to 51.5 +/- 9.1 (P less than 0.05) and to 64.4 +/- 13.7 (P less than 0.05). The deletion of calcium and addition of EGTA into the incubation medium significantly attenuated the secretion of kallikrein and tonin induced by NE. Nifedipine, at concentrations which inhibit voltage-dependent calcium channels, did not affect the release of kallikrein and tonin, and only a high concentration (10(-4) M) reduced the release. TMB-8, a blocker of intracellular calcium, had no effect either. Phenothiazines, triflupromazine (10(-6) M) and trifluoperazine (10(-4) M), decreased significantly the kallikrein release elicited by 10(-5) M NE.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Autonomous TNF is critical for in vivo monocyte survival in steady state and inflammation

2017 ◽  
Vol 214 (4) ◽  
pp. 905-917 ◽  
Author(s):  
Yochai Wolf ◽  
Anat Shemer ◽  
Michal Polonsky ◽  
Mor Gross ◽  
Alexander Mildner ◽  
...  
Keyword(s):  
Spinal Cord ◽  
Mononuclear Phagocytes ◽  
Autoimmune Encephalomyelitis ◽  
Wild Type Counterpart ◽  
And Function ◽  
Necrosis Factor ◽  
Experimental Autoimmune

Monocytes are circulating mononuclear phagocytes, poised to extravasate to sites of inflammation and differentiate into monocyte-derived macrophages and dendritic cells. Tumor necrosis factor (TNF) and its receptors are up-regulated during monopoiesis and expressed by circulating monocytes, as well as effector monocytes infiltrating certain sites of inflammation, such as the spinal cord, during experimental autoimmune encephalomyelitis (EAE). In this study, using competitive in vitro and in vivo assays, we show that monocytes deficient for TNF or TNF receptors are outcompeted by their wild-type counterpart. Moreover, monocyte-autonomous TNF is critical for the function of these cells, as TNF ablation in monocytes/macrophages, but not in microglia, delayed the onset of EAE in challenged animals and was associated with reduced acute spinal cord infiltration of Ly6Chi effector monocytes. Collectively, our data reveal a previously unappreciated critical cell-autonomous role of TNF on monocytes for their survival, maintenance, and function.

scholarly journals Amnestic Concentrations of Etomidate Modulate GABAA,slowSynaptic Inhibition in Hippocampus

2009 ◽  
Vol 111 (4) ◽  
pp. 766-773 ◽  
Author(s):  
Shuiping Dai ◽  
Misha Perouansky ◽  
Robert A. Pearce
Keyword(s):  
Time Constant ◽  
Hippocampal Slices ◽  
Effective Concentration ◽  
Detectable Effect ◽  
Gamma Aminobutyric Acid ◽  
Gaba A ◽  
Phasic Inhibition ◽  
Half Maximal Effective Concentration

Background Gamma-aminobutyric acid type A (GABA(A)) receptor-mediated inhibition in the central nervous system exists in two forms: phasic (inhibitory postsynaptic currents, IPSCs) and tonic (nonsynaptic). Phasic inhibition is further subdivided into fast (GABA(A,fast)) and slow (GABA(A,slow)) IPSCs. By virtue of its dendritic location and kinetics, GABA(A,slow) has been proposed to control synaptic plasticity and memory. Etomidate is a nonbarbiturate, intravenous anesthetic that selectively modulates GABA(A) receptors and produces amnesia at low doses in vivo. This study tested whether correspondingly low concentrations of etomidate in vitro alter GABA(A,fast) and GABA(A,slow) phasic inhibition. Methods Electrophysiological recordings were obtained from hippocampal slices prepared from postnatal day 3-8 mice and maintained in organotypic culture for 10-14 days. Etomidate was applied at concentrations corresponding to one-half to four times the half maximal effective concentration that impairs hippocampus-dependent learning and memory--i.e., 0.125-1.0 microm. Results Etomidate 0.25 microm (the half maximal effective concentration) doubled the time constant of decay of GABA(A,slow) IPSCs, but it had no detectable effect on GABA(A,fast) IPSCs. Higher concentrations of etomidate had stronger effects on both types of phasic inhibition: 0.5 and 1 microm etomidate prolonged the time constant of decay by 310% and 410% for GABA(A,slow) and by 25% and 78% for GABA(A,fast). Concentrations of etomidate up to 1 microm had no significant effects on the amplitudes of either GABA(A,fast) or GABA(A,slow) IPSCs. Conclusions At concentrations that impair hippocampus-dependent memory, etomidate modulates GABA(A,slow) more strongly than GABA(A,fast) IPSCs. Effects of etomidate on GABA(A,slow) IPSCs may contribute to etomidate-induced amnesia.

Voltage-dependent K+ channels regulate the duration of reactive hyperemia in the canine coronary circulation

2008 ◽  
Vol 294 (5) ◽  
pp. H2371-H2381 ◽  
Author(s):  
Gregory M. Dick ◽  
Ian N. Bratz ◽  
Léna Borbouse ◽  
Gregory A. Payne ◽  
Ü. Deniz Dincer ◽  
...  
Keyword(s):  
Blood Flow ◽  
Channel Blocker ◽  
Myocardial Metabolism ◽  
Reactive Hyperemia ◽  
No Donor ◽  
Voltage Dependent ◽  
Hyperemic Flow

We previously demonstrated a role for voltage-dependent K+ (KV) channels in coronary vasodilation elicited by myocardial metabolism and exogenous H2O2, as responses were attenuated by the KV channel blocker 4-aminopyridine (4-AP). Here we tested the hypothesis that KV channels participate in coronary reactive hyperemia and examined the role of KV channels in responses to nitric oxide (NO) and adenosine, two putative mediators. Reactive hyperemia (30-s occlusion) was measured in open-chest dogs before and during 4-AP treatment [intracoronary (ic), plasma concentration 0.3 mM]. 4-AP reduced baseline flow 34 ± 5% and inhibited hyperemic volume 32 ± 5%. Administration of 8-phenyltheophylline (8-PT; 0.3 mM ic or 5 mg/kg iv) or NG-nitro-l-arginine methyl ester (l-NAME; 1 mg/min ic) inhibited early and late portions of hyperemic flow, supporting roles for adenosine and NO. 4-AP further inhibited hyperemia in the presence of 8-PT or l-NAME. Adenosine-induced blood flow responses were attenuated by 4-AP (52 ± 6% block at 9 μg/min). Dilation of arterioles to adenosine was attenuated by 0.3 mM 4-AP and 1 μM correolide, a selective KV1 antagonist (76 ± 7% and 47 ± 2% block, respectively, at 1 μM). Dilation in response to sodium nitroprusside, an NO donor, was attenuated by 4-AP in vivo (41 ± 6% block at 10 μg/min) and by correolide in vitro (29 ± 4% block at 1 μM). KV current in smooth muscle cells was inhibited by 4-AP (IC50 1.1 ± 0.1 mM) and virtually eliminated by correolide. Expression of mRNA for KV1 family members was detected in coronary arteries. Our data indicate that KV channels play an important role in regulating resting coronary blood flow, determining duration of reactive hyperemia, and mediating adenosine- and NO-induced vasodilation.

scholarly journals GABAergic signaling in human and murine NK cells upon challenge with Toxoplasma gondii

2021 ◽  
Author(s):  
Amol K Bhandage ◽  
Laura M Friedrich ◽  
Sachie Kanatani ◽  
Simon Jakobsson-Bjoerken ◽  
J. Ignacio Escrig-Larena ◽  
...  
Keyword(s):  
Toxoplasma Gondii ◽  
Nk Cells ◽  
Cell Function ◽  
Nk Cell ◽  
Mononuclear Phagocytes ◽  
Gamma Aminobutyric Acid ◽  
Gaba A ◽  
Gaba Signaling ◽  
Infection And Inflammation

Protective cytotoxic and proinflammatory cytokine responses by natural killer (NK) cells impact the outcome of infections by Toxoplasma gondii, a common parasite in humans and other vertebrates. However, T. gondii can also sequester within NK cells and downmodulate their effector functions. Recently, the implication of gamma-aminobutyric acid (GABA) signaling in infection and inflammation-related responses of mononuclear phagocytes and T cells has become evident. Yet, the role of GABAergic signaling in NK cells has remained unknown. Here, we report that human and murine NK cells synthesize and secrete GABA in response to infection challenge. Parasitized NK cells secreted GABA while activation stimuli, such as IL-12/IL-18 or parasite lysates, failed to induce GABA secretion. GABA secretion by NK cells was associated to a transcriptional upregulation of GABA synthesis enzymes (GAD65/67) and was abrogated by GAD-inhibition. Further, NK cells expressed GABA-A receptor subunits and GABA signaling regulators, with transcriptional modulations taking place upon challenge with T. gondii. Exogenous GABA and GABA-containing supernatants from parasitized dendritic cells (DCs) impacted NK cell function by reducing the degranulation and cytotoxicity of NK cells. Conversely, GABA-containing supernatants from NK cells enhanced the migratory responses of parasitized DCs. This enhanced DC migration was abolished by GABA-A receptor antagonism or GAD-inhibition and was reconstituted by exogenous GABA. Jointly, the data show that NK cells are GABAergic cells and that GABA hampers NK cell cytotoxicity in vitro. We hypothesize that GABA secreted by parasitized immune cells modulates the immune responses to T. gondii infection.

scholarly journals The Protective Role of TLR2 Mediates Impaired Autophagic Flux by Activating the mTOR Pathway During Neospora caninum Infection in Mice

2021 ◽  
Vol 11 ◽  
Author(s):  
Jielin Wang ◽  
Xiaocen Wang ◽  
Pengtao Gong ◽  
Fu Ren ◽  
Xin Li ◽  
...  
Keyword(s):  
Kinase Inhibitor ◽  
Neospora Caninum ◽  
Early Stage ◽  
Infection Process ◽  
Autophagic Flux ◽  
Caninum Infection ◽  
Early Stages

Autophagy has been shown to play an essential role in defending against intracellular bacteria, viruses, and parasites. Mounting evidence suggests that autophagy plays different roles in the infection process of different pathogens. Until now, there has been no conclusive evidence regarding whether host autophagy is involved in Neospora caninum infection. In the current study, we first monitored the activation of autophagy by N. caninum, which occurred mainly in the early stages of infection, and examined the role of host autophagy in N. caninum infection. Here, we presented evidence that N. caninum induced an increase in autophagic vesicles with double-membrane structures in macrophages at the early stage of infection. LC3-II expression peaked and decreased as infection continued. However, the expression of P62/SQSTM1 showed significant accumulation within 12 h of infection, indicating that autophagic flux was blocked. A tandem fluorescence protein mCherry-GFP-LC3 construct was used to corroborate the impaired autophagic flux. Subsequently, we found that N. caninum infection induced the activation of the TLR2–AKT–mTOR pathways. Further investigation revealed that TLR2–mTOR, accompanied by the blockade of autophagic flux, was responsible for impaired autophagy but was not associated with AKT. In vitro and in vivo, N. caninum replication was strongly blocked by the kinase inhibitor 3-methyladenine (3-MA, autophagy inhibitor). In contrast, rapamycin (Rapa, an autophagy inducer) was able to promote intracellular proliferation and reduce the survival rate of N. caninum-infected mice. On the other hand, the accumulation of autophagosomes facilitated the proliferation of N. caninum. Collectively, our findings suggest that activation of host autophagy facilitates N. caninum replication and may counteract the innate immune response of the host. In short, inhibition of the early stages of autophagy could potentially be a strategy for neosporosis control.

Myogenic constriction of human coronary arterioles

1997 ◽  
Vol 273 (1) ◽  
pp. H257-H264 ◽  
Author(s):  
F. J. Miller ◽  
K. C. Dellsperger ◽  
D. D. Gutterman
Keyword(s):  
Vessel Diameter ◽  
Intraluminal Pressure ◽  
Calphostin C ◽  
Graded Response ◽  
Resistance Vessels ◽  
Basal Tone ◽  
Voltage Dependent ◽  
Voltage Dependent Calcium Channels

Myogenic constriction is an important mechanism of blood flow regulation; however, it has never been demonstrated in the human coronary circulation. We examined responses of human coronary resistance vessels in vitro to changes in intraluminal pressure and evaluated the role of protein kinase C (PKC). Microvessels (passive diameter 44-227 microns) were dissected from atrial appendages obtained during cardiac surgery and studied under conditions of zero flow. In response to stepped increases in pressure, there was a graded response such that at 100 mmHg, vessels constricted to 55 +/- 4% of their passive diameter. There was an inverse relationship between vessel diameter and myogenic responsiveness. Basal tone was attenuated by inhibition of voltage-dependent calcium channels (VDCC) with diltiazem and by inhibition of PKC with calphostin C. Activation of PKC with phorbol 12-myristate 13-acetate (PMA) enhanced basal tone. Active myogenic constriction was also impaired by calphostin C and augmented by PMA. Arterioles from patients with hypertension demonstrated enhanced myogenic constriction compared with vessels from normotensive patients (0.55 +/- 0.04 vs. 0.74 +/- 0.03; P < 0.01). These results demonstrate myogenic constriction in the human coronary microcirculation. Regulation of extracellular calcium by VDCC and intracellular calcium by PKC are important in mediating the magnitude of basal tone and myogenic responsiveness of these vessels.

scholarly journals Synaptically Recruited Apical Currents Are Required to Initiate Axonal and Apical Spikes in Hippocampal Pyramidal Cells: Modulation by Inhibition

2005 ◽  
Vol 93 (2) ◽  
pp. 909-918 ◽  
Author(s):  
S. Canals ◽  
L. López-Aguado ◽  
O. Herreras
Keyword(s):  
Action Potentials ◽  
Pyramidal Cells ◽  
Excitatory Input ◽  
Synaptic Potentials ◽  
Local Inhibition ◽  
Voltage Dependent ◽  
Cell Firing

Dendritic voltage-dependent currents and inhibition modulate the information flow between synaptic and decision areas. Subthreshold and spike currents are sequentially recruited by synaptic potentials in the apical shaft of pyramidal cells, which may also decide cell output. We studied the global role of proximal apical recruited currents on cell output in vitro and in the anesthetized rat after local blockade of Na+ currents in the axon initial segment (AIS) or the proximal apical shaft and their modulation by inhibition. Microejection of TTX, field potentials, and intrasomatic and intradendritic recordings were employed. Dendritic population spikes (PSs) were much smaller in vitro, but the gross relations between synaptic and active currents are similar to in vivo. Activation of Schaffer collaterals triggered PSs and action potentials (APs) in the apical shaft that fully propagated to the axon. However, the specific blockade of proximal Na+ currents avoided cell firing, although antidromic PSs and APs readily invaded somata. The somatic depolarization of subthreshold excitatory postsynaptic potentials (EPSPs) also decreased to about 50%. These results were not due to decreased excitatory input by TTX. However, when GABAA inhibition was locally removed, Schaffer synaptic currents skipped the proximal dendrite and fired somatic PSs, although initiated at the AIS. It is concluded that apical currents recruited en passant by Schaffer synaptic potentials in the apical shaft constitute a necessary amplifier for this input to cause output decision. Local inhibition decides when and where an AP will initiate, constituting an efficient mechanism to discriminate and weight different inputs.

An Fc-Optimized Monoclonal Antibody Against CD32B, the Human Inhibitory Fc-γ Receptor IIB, in the Immunotherapy of B-Cell Malignanacy.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 2529-2529
Author(s):  
Jeffrey B. Stavenhagen ◽  
Sergey Gorlatov ◽  
Nadine Tuaillon ◽  
Christopher T. Rankin ◽  
Maria-Concetta Veri ◽  
...  
Keyword(s):  
B Cell ◽  
Mononuclear Phagocytes ◽  
Effector Cells ◽  
Binding Ratio ◽  
Functional Homolog ◽  
Animal Tumor ◽  
Activating Receptor

Abstract Monoclonal antibodies (mAbs) are widely used in the treatment of lymphoma and autoimmune diseases. The activity of several mAbs depends on the binding of the Fcγ regions to low-affinity Fcγ receptors (FcγR) expressed on effector cells, chiefly mononuclear phagocytes, cells that express both activating and inhibitory FcγRs. FcγRIIB (CD32B), the inhibitory FcγR, is expressed by normal and malignant B lymphocytes and is itself an immunotherapeutic target. A recently characterized anti-human CD32B-specific mAb (2B6) was Fc engineered to customize the FcγR binding profile for increased binding to the activating receptor FcγRIIIA (CD16A), resulting in an improved activating-to-inhibitory binding ratio. Fc-optimized versions of 2B6 showed enhanced cytotoxicity in vitro and increased potency in animal tumor models, including transgenic mice harboring the human low-affinity allele of the activating receptor, CD16A-158phe. The enhancement in tumor depletion correlated with an increased binding to FcγRIV, a mouse functional homolog to human CD16A. The expression of FcγRIV is limited to monocyte and macrophages, consistent with the role of these cells in tumor cell killing in vivo. These data support CD32B as a target for immunotherapy of B cell lymphoproliferative disorders and Fc optimization to increase the activating-to-inhibitory FcγR-binding ratio as a means to designing improved antibodies.

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