minocycline and Hypoxia

Severe hypoxia induces seizures, which reduces ventilation and worsens the ictal state. It is a health threat to patients, particularly those with underlying hypoxic respiratory pathologies, which may be conducive to a sudden unexpected death in epilepsy (SUDEP). Recent studies provide evidence that brain microglia are involved with both respiratory and ictal processes. Here, we investigated the hypothesis that microglia could interact with hypoxia-induced seizures. To this end, we recorded electroencephalogram (EEG) and acute ventilatory responses to hypoxia (5% O

Topics: Animals; Brain; Hypoxia; Mice; Microglia; Minocycline; Seizures

Perinatal inflammation triggers breathing disturbances early in life and affects the respiratory adaptations to challenging conditions, including the generation of amplitude long-term facilitation (LTF) by acute intermittent hypoxia (AIH). Some of these effects can be avoided by anti-inflammatory treatments like minocycline. Since little is known about the effects of perinatal inflammation on the inspiratory rhythm generator, located in the preBötzinger complex (preBötC), we tested the impact of acute lipopolysaccharide (LPS) systemic administration (sLPS), as well as gestational LPS (gLPS) and gestational chronic IH (gCIH), on respiratory rhythm generation and its long-term response to AIH in a brainstem slice preparation from neonatal mice. We also evaluated whether acute minocycline administration could influence these effects. We found that perinatal inflammation induced by sLPS or gLPS, as well as gCIH, modulate the frequency, signal-to-noise ratio and/or amplitude (and their regularity) of the respiratory rhythm recorded from the preBötC in the brainstem slice. Moreover, all these perinatal conditions inhibited frequency LTF and amplitude long-term depression (LTD); gCIH even induced frequency LTD of the respiratory rhythm after AIH. Some of these alterations were not observed in slices pre-treated in vitro with minocycline, when compared with slices obtained from naïve pups, suggesting that ongoing inflammatory conditions affect respiratory rhythm generation and its plasticity. Thus, it is likely that alterations in the inspiratory rhythm generator and its adaptive responses could contribute to the respiratory disturbances observed in neonates that suffered from perinatal inflammatory challenges.

Topics: Animals; Animals, Newborn; Anti-Inflammatory Agents; Central Pattern Generators; Disease Models, Animal; Humans; Hypoxia; Infant, Newborn; Infant, Newborn, Diseases; Inflammation; Minocycline; Neuronal Plasticity; Respiratory Center; Respiratory Rate

Clinical trials of therapeutics for traumatic brain injury (TBI) demonstrating preclinical efficacy for TBI have failed to replicate these results in humans, in part due to the absence of clinically feasible therapeutic windows for administration. Minocycline, an inhibitor of microglial activation, has been shown to be neuroprotective when administered early after experimental TBI but detrimental when administered chronically to human TBI survivors. Rather than focusing on the rescue of primary injury with early administration of therapeutics which may not be clinically feasible, we hypothesized that minocycline administered at a clinically feasible time point (24 h after injury) would be neuroprotective in a model of TBI plus delayed hypoxemia. We first explored several different regimens of minocycline dosing with the initial dose 24 h after injury and 2 h prior to hypoxemia, utilizing short-term neuropathology to select the most promising candidate. We found that a short course of minocycline reduced acute microglial activation, monocyte infiltration and hippocampal neuronal loss at 1 week post injury. We then conducted a preclinical trial to assess the long-term efficacy of a short course of minocycline finding reductions in hippocampal neurodegeneration and synapse loss, preservation of white matter myelination, and improvements in fear memory performance at 6 months after injury. Timing in relation to injury and duration of minocycline treatment and its impact on neuroinflammatory response may be responsible for extensive neuroprotection observed in our studies.

Topics: Animals; Brain Injuries, Traumatic; Female; Hypoxia; Male; Memory; Mice; Minocycline; Neuroprotective Agents; Recovery of Function

In a recent study of young mice, we showed that chronic mild hypoxia (CMH, 8% O

Topics: Aged; Animals; Blood-Brain Barrier; Brain; Humans; Hypoxia; Mice; Microglia; Minocycline

Microglia modulate cardiorespiratory activities during chronic hypoxia. It has not been clarified whether microglia are involved in the cardiorespiratory responses to acute hypoxia. Here we investigated this issue by comparing cardiorespiratory responses to two levels of acute hypoxia (13% O

Topics: Animals; Blood Pressure; Hypoxia; Lung; Microglia; Minocycline; Rats

Rats subjected to sustained hypoxia (SH) present increases in arterial pressure (AP) and in glutamatergic transmission in the nucleus tractus solitarius (NTS) neurons sending projections to ventrolateral medulla (VLM). Treatment with minocycline, a microglial inhibitor, attenuated the increase in AP in response to SH. The increase in the amplitude of glutamatergic postsynaptic currents in the NTS-VLM neurons, induced by postsynaptic mechanisms, was blunted by minocycline treatment. The number of microglial cells was increased in the NTS of vehicle-treated SH rats but not in the NTS of minocycline-treated rats. The data show that microglial recruitment/proliferation induced by SH is associated with the enhancement of excitatory neurotransmission in NTS-VLM neurons, which may contribute to the observed increase in AP.

Topics: Animals; Arterial Pressure; Excitatory Postsynaptic Potentials; Hypoxia; Male; Microglia; Minocycline; Neurons; Rats, Wistar; Solitary Nucleus

Topics: Autonomic Nervous System; Biomarkers; Brain; Humans; Hypoxia; Minocycline

Ventilatory acclimatization to hypoxia (VAH) is the time-dependent increase in ventilation, which persists upon return to normoxia and involves plasticity in both central nervous system respiratory centers and peripheral chemoreceptors. We investigated the role of glial cells in VAH in male Sprague-Dawley rats using minocycline, an antibiotic that inhibits microglia activation and has anti-inflammatory properties, and barometric pressure plethysmography to measure ventilation. Rats received either minocycline (45mg/kg ip daily) or saline beginning 1 day before and during 7 days of chronic hypoxia (CH, Pi

Topics: Acclimatization; Analysis of Variance; Animals; Anti-Bacterial Agents; Glial Fibrillary Acidic Protein; Hypoxia; Male; Minocycline; Neuroglia; Plethysmography; Rats; Rats, Sprague-Dawley; Respiration; Respiratory Center; Solitary Nucleus

Neonatal sustained hypoxia exposure modifies brainstem microglia and serotonin expression. The altered brainstem neurochemistry is associated with impaired ventilatory responses to acute hypoxia and mortality. The deleterious effects of sustained hypoxia exposure can be prevented by an inhibitor of activated microglia. These observations demonstrate a potential cause of the brainstem serotonin abnormalities thought to be involved in sudden infant death syndrome.. We showed previously that the end of the second postnatal week (days P11-15) represents a period of development during which the respiratory neural control system exhibits a heightened vulnerability to sustained hypoxia (SH, 11% O2 , 5 days) exposure. In the current study, we investigated whether the vulnerability to SH during the same developmental time period is associated with changes in brainstem serotonin (5-HT) expression and whether it can be prevented by the microglia inhibitor minocycline. Using whole-body plethysmography, SH attenuated the acute (5 min) hypoxic ventilatory response (HVR) and caused a high incidence of mortality compared to normoxia rats. SH also increased microglia cell numbers and decreased 5-HT immunoreactivity in the nucleus of the solitary tract (nTS) and dorsal motor nucleus of the vagus (DMNV). The attenuated HVR, mortality, and changes in nTS and DMNV immunoreactivity was prevented by minocycline (25 mg kg(-1) /2 days during SH). These data demonstrate that the 5-HT abnormalities in distinct respiratory neural control regions can be initiated by prolonged hypoxia exposure and may be modulated by microglia activity. These observations share several commonalities with the risk factors thought to underlie the aetiology of sudden infant death syndrome, including: (1) a vulnerable neonate; (2) a critical period of development; (3) evidence of hypoxia; (4) brainstem gliosis (particularly the nTS and DMNV); and (5) 5-HT abnormalities.

Topics: Age Factors; Animals; Animals, Newborn; Brain Stem; Female; Gene Expression; Hypoxia; Microglia; Minocycline; Pregnancy; Rats; Rats, Inbred Lew; Serotonin

Inflammation has been linked to the induction of apneas and Sudden Infant Death Syndrome, whereas proinflammatory mediators inhibit breathing when applied peripherally or directly into the CNS. Considering that peripheral inflammation can activate microglia in the CNS and that this cell type can directly release all proinflammatory mediators that modulate breathing, it is likely that microglia can modulate breathing generation. It might do so also in hypoxia, since microglia are sensitive to hypoxia, and peripheral proinflammatory conditions affect gasping generation and autoresuscitation. Here, we tested whether microglial activation or inhibition affected respiratory rhythm generation. By measuring breathing as well as the activity of the respiratory rhythm generator (the preBötzinger complex), we found that several microglial activators or inhibitors, applied intracisternally in vivo or in the recording bath in vitro, affect the generation of the respiratory rhythms both in normoxia and hypoxia. Furthermore, microglial activation with lipopolysaccharide affected the ability of the animals to autoresuscitate after hypoxic conditions, an effect that is blocked when lipopolysaccharide is co-applied with the microglial inhibitor minocycline. Moreover, we found that the modulation of respiratory rhythm generation induced in vitro by microglial inhibitors was reproduced by microglial depletion. In conclusion, our data show that microglia can modulate respiratory rhythm generation and autoresuscitation.

Topics: Animals; Animals, Newborn; Anti-Bacterial Agents; Brain Stem; Central Pattern Generators; Disease Models, Animal; Hypoxia; Immunohistochemistry; Lipopolysaccharides; Mice; Microelectrodes; Microglia; Minocycline; Periodicity; Plethysmography, Whole Body; Respiration; Tissue Culture Techniques

The aim of the present study was to investigate the effects of minocycline on cognitive functions in neonatal rat after hypoxia exposure and the underlying mechanism. A model of hypoxic brain damage (HBD) was developed by exposing postnatal 1 day (P1) rats to systemic hypoxia. The rats were intraperitoneally injected with normal saline (Hy group) or minocycline (Hy + M group) 2 h after hypoxia exposure. Some other P1 rats that were not subjected to systemic hypoxia were used as normal control (NG group). The Y-maze test was used to evaluate learning and memory ability on postnatal day 30. Inflammatory mediators (Iba-1, IL-1β, TNF-α and TGF-β1), glutamate transporters (EAAT1 and EAAT2), total Tau and phosphorylated Tau (phosphorylation sites: Tyr18, Thr205, Thr231, Ser396 and Ser404) protein expressions in the hippocampus were detected by Western blot 7 d after hypoxic exposure. The results showed that hypoxia induced learning and memory impairments of the neonatal rats, and minocycline administration could reverse the effects of hypoxia. The protein expression levels of Iba-1, IL-1β, TNF-α, EAAT2 and Tau phosphorylated at T231 were increased, but the total Tau expression was decreased in the hippocampus of the rats from Hy group 7 d after hypoxia exposure. In the hypoxia-treated rats, minocycline down-regulated Iba-1, IL-1β, TNF-α and EAAT2 protein expressions significantly, but did not affect total Tau and phosphorylated Tau protein expressions. Our results suggest that minocycline can prevent cognitive deficits of rats with hypoxia exposure, and the underlying mechanism may involve the inhibition of neuroinflammation and dysfunctional glutamate transporters but not the regulation of the Tau hyperphosphorylation.

Topics: Amino Acid Transport System X-AG; Animals; Animals, Newborn; Cognition; Cognition Disorders; Disease Models, Animal; Glutamates; Hippocampus; Hypoxia; Inflammation; Learning; Memory; Memory Disorders; Minocycline; Phosphorylation; Rats; tau Proteins; Transforming Growth Factor beta1; Tumor Necrosis Factor-alpha

Hypertensive small vessel disease is a major cause of vascular cognitive impairment (VCI). Spontaneously hypertensive/stroke prone rats (SHR/SP) with unilateral carotid artery occlusion (UCAO) and a Japanese permissive diet (JPD) have white-matter (WM) damage similar to that seen in VCI. We hypothesized that WM injury was due to hypoxia-mediated, blood-brain barrier (BBB) disruption. Twelve-week-old SHR/SP had UCAO/JPD and were studied with immunohistochemistry, biochemistry, multimodal magnetic resonance imaging (MRI), and Morris water maze (MWM) testing. One week after UCAO/JPD, WM showed a significant increase in hypoxia inducible factor-1α (HIF-1α), which increased further by 3 weeks. Prolyl hydroxylase-2 (PHD2) expression decreased at 1 and 3 weeks. Infiltrating T cells and neutrophils appeared around endothelial cells from 1 to 3 weeks after UCAO/JPD, and matrix metalloproteinase-9 (MMP-9) colocalized with inflammatory cells. At 3 weeks, WM immunostained for IgG, indicating BBB leakage. Minocycline (50 mg/kg intraperitoneally) was given every other day from weeks 12 to 20. Multimodal MRI showed that treatment with minocycline significantly reduced lesion size and improved cerebral blood flow. Minocycline improved performance in the MWM and prolonged survival. We propose that BBB disruption occurred secondary to hypoxia, which induced an MMP-9-mediated infiltration of leukocytes. Minocycline significantly reduced WM damage, improved behavior, and prolonged life.

Topics: Animals; Anti-Bacterial Agents; Anti-Inflammatory Agents; Blood-Brain Barrier; Cerebrovascular Circulation; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Inflammation; Male; Matrix Metalloproteinase 2; Matrix Metalloproteinase 9; Minocycline; Rats; Rats, Inbred SHR; White Matter

Minocycline, a broad-spectrum tetracycline antibiotic, has shown anti-inflammatory and neuroprotective effects in ischemic brain injury. The present study seeks to determine whether monocyte chemotactic protein-induced protein 1 (MCPIP1), a recently identified modulator of inflammatory reactions, is involved in the cerebral neuroprotection conferred by minocycline treatment in the animal model of focal cerebral ischemia and to elucidate the mechanisms of minocycline-induced ischemic brain tolerance.. Focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h in male C57BL/6 mice and MCPIP1 knockout mice followed by 24- or 48-h reperfusion. Twelve hours before ischemia or 2 h after MCAO, mice were injected intraperitoneally with 90 mg/kg of minocycline hydrochloride. Thereafter, the animals were injected twice a day, at a dose of 90 mg/kg after ischemia until sacrificed. Transcription and expression of MCPIP1 gene was monitored by quantitative real-time PCR (qRT-PCR), Western blot, and immunohistochemistry. The neurobehavioral scores, infarction volumes, and proinflammatory cytokines in brain and NF-κB signaling were evaluated after ischemia/reperfusion.. MCPIP1 protein and mRNA levels significantly increased in mouse brain undergoing minocycline pretreatment. Minocycline treatment significantly attenuated the infarct volume, neurological deficits, and upregulation of proinflammatory cytokines in the brain of wild type mice after MCAO. MCPIP1-deficient mice failed to evoke minocycline-treatment-induced tolerance compared with that of the control MCPIP1-deficient group without minocycline treatment. Similarly, in vitro data showed that minocycline significantly induced the expression of MCPIP1 in primary neuron-glial cells, cortical neurons, and reduced oxygen glucose deprivation (OGD)-induced cell death. The absence of MCPIP1 blocked minocycline-induced protection on neuron-glial cells and cortical neurons treated with OGD.. Our in vitro and in vivo studies demonstrate that MCPIP1 is an important mediator of minocycline-induced protection from brain ischemia.

Topics: Animals; Brain Edema; Brain Infarction; Cells, Cultured; Cytokines; Disease Models, Animal; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Glucose; Hypoxia; Infarction, Middle Cerebral Artery; Mice; Mice, Inbred C57BL; Mice, Knockout; Minocycline; Neurologic Examination; Neurons; Neuroprotective Agents; Phosphopyruvate Hydratase; Reperfusion Injury; Ribonucleases; Time Factors

Premature infants are at an increased risk of developing cognitive and motor handicaps due to chronic hypoxia. Although the current therapies have reduced the incidence of these handicaps, untoward side effects abound. Using a murine model of sublethal hypoxia, we demonstrated reduction in several transcription factors that modulate expression of genes known to be involved in several neural functions. We demonstrate the induction of these genes by minocycline, a tetracycline antibiotic with noncanonical functions, in both in vitro and in vivo studies. Specifically, there was induction of genes, including Sox10, Hif1a, Hif2a, Birc5, Yap1, Epo, Bdnf, Notch1 (cleaved), Pcna, Mag, Mobp, Plp1, synapsin, Adgra2, Pecam1, and reduction in activation of caspase 3, all known to affect proliferation, apoptosis, synaptic transmission, and nerve transmission. Minocycline treatment of mouse pups reared under sublethal hypoxic conditions resulted in improvement in open field testing parameters. These studies demonstrate beneficial effects of minocycline treatment following hypoxic insult, document up-regulation of several genes associated with improved cognitive function, and support the possibility of minocycline as a potential therapeutic target in the treatment of neurodevelopmental handicaps observed in the very premature newborn population. Additionally, these studies may aid in further interpretation of the effects of minocycline in the treatment trials and animal model studies of fragile X syndrome and multiple sclerosis.

Topics: Adaptor Proteins, Signal Transducing; Animals; Apoptosis; Cell Cycle Proteins; Disease Models, Animal; Hypoxia; Hypoxia-Inducible Factor 1, alpha Subunit; Inhibitor of Apoptosis Proteins; Mice, Inbred C57BL; Minocycline; Multiple Sclerosis; Phosphoproteins; Repressor Proteins; SOXE Transcription Factors; Survivin; Up-Regulation; YAP-Signaling Proteins

Nucleus tractus solitarius (NTS) is the integrative sensory relay of autonomic functions in the brainstem. To explore the nonneuronal cellular basis of central chemosensitivity during the first 24 hr of ventilatory acclimatization to hypoxia (VHA), we have investigated glial activation markers in the NTS. Conscious mice (C57/BL6) were placed in a hermetic hypoxia chamber containing a plethysmograph to record ventilation. After 4 days of habituation to the normoxic environment, mice were subjected to physiological hypoxia (10% O2 ) for 1, 6, or 24 hr. To dissociate interactions between microglia and astrocytes, another group received daily minocycline, a microglia activation blocker. By immunochemical localization of astrocytes (GFAP), activated microglia (Cd11b), and total microglia (Iba-1), we identified an oxygen-sensing glial layer in the NTS, in which astrocytes are first activated after 1-6 hr of hypoxia, followed by microglia after 6-24 hr of hypoxia. Minocycline administration suppressed microglial activation and decreased astrocyte activation at 6 hr and VHA at 24 hr of hypoxia. These results suggest that astrocytes contribute to the neuronal response during the first hour of hypoxia, whereas microglial cells, via cross-talk with astrocytes, are involved in the VHA during the first 24 hr of acclimatization.

Topics: Acclimatization; Animals; Astrocytes; Calcium-Binding Proteins; CD11b Antigen; Disease Models, Animal; Gene Expression Regulation; Glial Fibrillary Acidic Protein; Hypoxia; Male; Mice; Mice, Inbred C57BL; Microfilament Proteins; Microglia; Minocycline; Plethysmography; Respiration; Solitary Nucleus; Time Factors; Wakefulness

Minocycline, a tetracycline-derived compound, mitigates damage caused by ischemia/reperfusion (I/R) injury. Here, 19 tetracycline-derived compounds were screened in comparison to minocycline for their ability to protect hepatocytes against damage from chemical hypoxia and I/R injury. Cultured rat hepatocytes were incubated with 50μM of each tetracycline-derived compound 20 min prior to exposure to 500μM iodoacetic acid plus 1mM KCN (chemical hypoxia). In other experiments, hepatocytes were incubated in anoxic Krebs-Ringer-HEPES buffer at pH6.2 for 4h prior to reoxygenation at pH7.4 (simulated I/R). Tetracycline-derived compounds were added 20 min prior to reperfusion. Ca(2+) uptake was measured in isolated rat liver mitochondria incubated with Fluo-5N. Cell killing after 120 min of chemical hypoxia measured by propidium iodide (PI) fluorometry was 87%, which decreased to 28% and 42% with minocycline and doxycycline, respectively. After I/R, cell killing at 120 min decreased from 79% with vehicle to 43% and 49% with minocycline and doxycycline. No other tested compound decreased killing. Minocycline and doxycycline also inhibited mitochondrial Ca(2+) uptake and suppressed the Ca(2+)-induced mitochondrial permeability transition (MPT), the penultimate cause of cell death in reperfusion injury. Ru360, a specific inhibitor of the mitochondrial calcium uniporter (MCU), also decreased cell killing after hypoxia and I/R and blocked mitochondrial Ca(2+) uptake and the MPT. Other proposed mechanisms, including mitochondrial depolarization and matrix metalloprotease inhibition, could not account for cytoprotection. Taken together, these results indicate that minocycline and doxycycline are cytoprotective by way of inhibition of MCU.

Topics: Animals; Anti-Bacterial Agents; Calcium; Calcium Channels; Doxycycline; Hepatocytes; Hypoxia; Iron; Male; Minocycline; Mitochondria, Liver; Mitochondrial Membrane Transport Proteins; Mitochondrial Permeability Transition Pore; Rats; Rats, Sprague-Dawley; Reperfusion Injury; Tetracycline

Ischemic brain injury is widely modeled in vitro with paradigms of oxygen-glucose deprivation (OGD), which leads to cell death. The prevention and attenuation of brain injury by the tetracycline antibiotic minocycline has been attributed largely to suppression of microglial activation, but its benefits in oligodendrocyte cells have not been well characterized. Using primary cultures of rat oligodendroglial precursor cells (OPC) exposed to OGD, we investigated the direct effects of minocycline on the survival, proliferation, and maturation of oligodendroglial lineage cells. OGD for 2 hr caused a decrease in the total number of OPC and the amount of proliferating progenitors by 50%, which was attenuated by inclusion of minocycline. The reduced numbers of immature oligodendroglial cells at 72 hr and of mature oligodendrocytes at 120 hr after OGD were partially restored by minocycline. In OPC, OGD caused an increase of reactive oxygen species (ROS) and production of TUNEL-positive cell numbers, which was abolished by minocycline. Minocycline preferentially increased the expression of superoxide dismutase under OGD but not in control OPC. Minocycline also prevented the OGD-induced downregulation of the transcription factors Sox10 and Olig2 and of myelin-specific genes 2'3' cyclic nucleotide phosphodiesterase (CNP) and myelin basic protein (MBP) in response to OGD. These studies demonstrate direct protective actions of minocycline on oligodendroglial-lineage cells, suggesting potential benefit in white matter injury involving OGD.

Topics: Analysis of Variance; Animals; Apoptosis; Cell Differentiation; Cell Proliferation; Cells, Cultured; Embryo, Mammalian; Embryonic Stem Cells; Female; Gangliosides; Gene Expression Regulation; Glucose; Hypoxia; Ki-67 Antigen; Minocycline; Myelin Basic Protein; O Antigens; Oligodendroglia; Oxidative Stress; Pregnancy; Rats; Rats, Sprague-Dawley; Tetrazolium Salts; Thiazoles; Time Factors; Transcription Factors

Minocycline, a second-generation tetracycline with anti-inflammatory and anti-apoptotic properties, has been shown to promote therapeutic benefits in experimental stroke. However, equally compelling evidence demonstrates that the drug exerts variable and even detrimental effects in many neurological disease models. Assessment of the mechanism underlying minocycline neuroprotection should clarify the drug's clinical value in acute stroke setting.. Here, we demonstrate that minocycline attenuates both in vitro (oxygen glucose deprivation) and in vivo (middle cerebral artery occlusion) experimentally induced ischemic deficits by direct inhibition of apoptotic-like neuronal cell death involving the anti-apoptotic Bcl-2/cytochrome c pathway. Such anti-apoptotic effect of minocycline is seen in neurons, but not apparent in astrocytes. Our data further indicate that the neuroprotection is dose-dependent, in that only low dose minocycline inhibits neuronal cell death cascades at the acute stroke phase, whereas the high dose exacerbates the ischemic injury.. The present study advises our community to proceed with caution to use the minimally invasive intravenous delivery of low dose minocycline in order to afford neuroprotection that is safe for stroke.

Topics: Adenosine Triphosphate; Animals; Apoptosis; Astrocytes; Blotting, Western; Cell Count; Cells, Cultured; Corpus Striatum; Cytochromes c; Cytoprotection; Dose-Response Relationship, Drug; Glucose; Hypoxia; Immunohistochemistry; In Situ Nick-End Labeling; Infarction, Middle Cerebral Artery; Male; Minocycline; Motor Skills; Neurons; Neuroprotective Agents; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley

In brain, monomeric immunoglobin G (IgG) is regarded as quiescent and only poised to initiate potentially injurious inflammatory reactions via immune complex formation associated with phagocytosis and tumor necrosis factor alpha (TNF-alpha) production in response to disease. Using rat hippocampal slice and microglial cultures, here we show instead that physiological levels (i.e., 0.2-20 microg/ml) of monomeric IgG unassociated with disease triggered benign low-level proinflammatory signaling that was neuroprotective against CA1 area excitotoxicity and followed a U-shaped or hormetic dose-response. The data indicate that physiological IgG levels activated microglia by enhancing recycling endocytosis plus TNF-alpha release from these cells to produce the neuroprotection. Minocycline, known for its anti-inflammatory and neuroprotective effects when given after disease onset, abrogated IgG-mediated neuroprotection and related microglial effects when given before injury. In contrast, E-prostanoid receptor subtype 2 (EP2) activation, which served as an exemplary paracrine stimulus like the one expected from neuronal activity, amplified IgG-mediated increased microglial recycling endocytosis and TNF-alpha production. Furthermore, like monomeric IgG these EP2 related effects took days to be effective, suggesting both were adaptive anabolic effects consistent with those seen from other long-term preconditioning stimuli requiring de novo protein synthesis. The data provide the first evidence that brain monomeric IgG at physiological levels can have signaling function via enhanced recycling endocytosis/TNF-alpha production from microglia unassociated with disease and that these IgG-mediated changes may be a means by which paracrine signaling from neuronal activity influences microglia to evoke neuroprotection. The data provide further support that low-level proinflammatory neural immune signaling unassociated with disease enhances brain function.

Topics: Animals; Cells, Cultured; Dinoprostone; Dose-Response Relationship, Drug; Ectodysplasins; Endocytosis; Glucose; Hippocampus; Hypoxia; Immunoglobulin G; Interleukin-1beta; Lysosomal-Associated Membrane Protein 1; Microglia; Minocycline; N-Methylaspartate; Neuroprotective Agents; Neurotoxins; Organ Culture Techniques; Phosphopyruvate Hydratase; rab GTP-Binding Proteins; Rats; Tumor Necrosis Factor-alpha

We report an instructive case of minocycline-induced eosinophilic pneumonia confirmed by re-challenge test, in which a preceding lymphocyte-stimulation test indicated acetaminophen as the etiologic agent. A 55-year-old woman developed high fever and lung infiltrates with pulmonary eosinophilia after exposure to minocycline, acetaminophen, theophylline and procaterol. All of the medicines were discontinued, resulting in prompt improvement. The lymphocyte stimulation tests provided a positive result for acetaminophen, but not for the other medicines; however, a negative result was given by a re-challenge test with acetaminophen. In contrast, symptoms and hypoxemia reappeared when minocycline was re-administered. We would like to emphasize that lymphocyte stimulation test results need to be carefully interpreted for individual drugs.

Topics: Acetaminophen; Acute Disease; Analgesics, Non-Narcotic; Anti-Bacterial Agents; False Negative Reactions; False Positive Reactions; Female; Humans; Hypoxia; Immunologic Techniques; Lymphocyte Activation; Middle Aged; Minocycline; Pulmonary Eosinophilia; Radiography, Thoracic; Tomography, X-Ray Computed

Lung involvement is rarely observed in the DRESS syndrome (Drug rash with eosinophilia and systemic symptoms). We report here a severe minocycline induced hypersensitivity syndrome with initial respiratory distress.. A 19 year old man was admitted to the intensive care unit for acute respiratory distress with fever (400C), lymph node enlargement, hepatomegaly, splenomegaly and eosinophilia (1640/mm3). Bilateral alveolar opacities were observed on the chest x-ray. Sedation and mechanical ventilation rapidly became necessary because of severe hypoxaemia (47 mm Hg) and the sudden onset of severe aggressive behaviour. The diagnosis of DRESS was immediately suspected as the patient had been treated for acne with minocycline for 28 days, and IV corticosteroids (2 mmg/kg/day) were initiated. Skin lesions were delayed and appeared 3 days later. The outcome was uncertain for the following 6 weeks with serious disturbance of hepatic and renal function. Serology for human herpes virus (HHV6) was initially negative but became positive. One year later, after progressive withdrawal of corticosteroid therapy, the patient had made a complete recovery with no sequelae.. The DRESS syndrome can cause considerable morbidity with multiple, severe visceral functional disturbances. Respiratory physicians should be aware of this syndrome as lung involvement can be serious and may precede cutaneous symptoms.

Topics: Adult; Anti-Bacterial Agents; Drug Eruptions; Eosinophilia; Hepatomegaly; Humans; Hypoxia; Lymphatic Diseases; Male; Minocycline; Respiratory Distress Syndrome; Splenomegaly; Syndrome

Many neurological insults are accompanied by a marked acute inflammatory reaction, involving the activation of microglia. Using a model of exogenous application of fluorescence-labeled BV2 microglia in pathophysiologically relevant concentrations onto organotypic hippocampal slice cultures, we investigated the specific effects of microglia on neuronal damage after ischemic injury. Neuronal cell death after oxygen-glucose deprivation (OGD) was determined by propidium iodide incorporation and Nissl staining. Migration and interaction with neurons were analyzed by time resolved 3-D two-photon microscopy. We show that microglia protect against OGD-induced neuronal damage and engage in close physical cell-cell contact with neurons in the damaged brain area. Neuroprotection and migration of microglia were not seen with integrin regulator CD11a-deficient microglia or HL-60 granulocytes. The induction of migration and neuron-microglia interaction deep inside the slice was markedly increased under OGD conditions. Lipopolysaccharide-prestimulated microglia failed to provide neuroprotection after OGD. Pharmacological interference with microglia function resulted in a reduced neuroprotection. Microglia proved to be neuroprotective even when applied up to 4 h after OGD, thus defining a "protective time window." In acute injury such as trauma or stroke, appropriately activated microglia may primarily have a neuroprotective role. Anti-inflammatory treatment within the protective time window of microglia would therefore be counterintuitive.

Topics: Animals; Anisomycin; Anti-Bacterial Agents; Brain Ischemia; CD11a Antigen; Cell Death; Cell Line; Glucose; Granulocytes; Hippocampus; HL-60 Cells; Humans; Hypoxia; Mice; Mice, Transgenic; Microglia; Minocycline; Neurons; Rats; Rats, Wistar

Blood-brain barrier (BBB) disruption after stroke can worsen ischemic injury by increasing edema and causing hemorrhage. We determined the effect of microglia on the BBB and its primary constituents, endothelial cells (ECs) and astrocytes, after ischemia using in vivo and in vitro models.. Primary astrocytes, ECs, or cocultures were prepared with or without added microglia. Primary ECs were more resistant to oxygen-glucose deprivation/reperfusion than astrocytes. ECs plus astrocytes showed intermediate vulnerability. Microglia added to cocultures nearly doubled cell death. This increase was prevented by minocycline and apocynin. In vivo, minocycline reduced infarct volume and neurological deficits and markedly reduced BBB disruption and hemorrhage in mice after experimental stroke.. Inhibition of microglial activation may protect the brain after ischemic stroke by improving BBB viability and integrity. Microglial inhibitors may prove to be an important treatment adjunct to fibrinolysis.

Topics: Acetophenones; Animals; Antioxidants; Astrocytes; Blood-Brain Barrier; Brain; Brain Ischemia; Cell Death; Cells, Cultured; Cerebral Hemorrhage; Cerebral Infarction; Coculture Techniques; Endothelial Cells; Glucose; Hydrogen Peroxide; Hypoxia; Male; Mice; Mice, Inbred C57BL; Microglia; Minocycline; Nervous System Diseases; Superoxides; Tumor Necrosis Factor-alpha

Robust neuroprotective effects have been shown for minocycline. Whether it also protects nonneuronal cells or tissues is unknown. More importantly, the mechanisms of minocycline protection appear multifaceted and remain to be clarified. Here we show that minocycline can protect kidney epithelial cells in vitro and protect the kidneys from ischemic injury in vivo. We further show that Bcl-2 is a key molecular determinant of minocycline protection. Minocycline protected kidney epithelial cells against apoptosis induced by hypoxia, azide, cisplatin, and staurosporine. The protection occurred at mitochondria, involving the suppression of Bax accumulation, outer membrane damage, and cytochrome c release. Minocycline induced Bcl-2, which accumulated in mitochondria and interacted with death-promoting molecules including Bax, Bak, and Bid. Down-regulation of Bcl-2 by specific antisense oligonucleotides abolished the cytoprotective effects of minocycline. Thus, minocycline can protect neuronal as well as nonneuronal cells and tissues. One mechanism for minocycline protection involves the induction of Bcl-2, an antiapoptotic protein.

Topics: Animals; Anti-Bacterial Agents; Apoptosis; bcl-2 Homologous Antagonist-Killer Protein; bcl-2-Associated X Protein; Caspases; Cell Death; Cells, Cultured; Cisplatin; Cytosol; Dose-Response Relationship, Drug; Down-Regulation; Enzyme Activation; Epithelial Cells; Hypoxia; In Situ Nick-End Labeling; Ischemia; Kidney; Male; Membrane Proteins; Microscopy, Fluorescence; Minocycline; Mitochondria; Oligonucleotides, Antisense; Precipitin Tests; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Rats; Rats, Sprague-Dawley; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sodium Azide; Staurosporine; Subcellular Fractions; Time Factors; Up-Regulation