Ketamine reduces inducible superoxide generation in human neutrophils in vitro by modulating the p38 mitogen-activated protein kinase (MAPK)-mediated pathway

The Ketamine Antidepressant Story: New Insights

Ketamine is a versatile agent primarily utilized as a dissociative anesthetic, which acts by blocking the excitatory receptor N-methyl-d-aspartate receptor (NMDA). It functions to inhibit the current of both Na⁺ and K⁺ voltage-gated channels, thus preventing serotonin and dopamine reuptake. Studies have indicated that administering a single subanesthetic dose of ketamine relieves depression rapidly and that the effect is sustained. For decades antidepressant agents were based on the monoamine theory. Although ketamine may not be the golden antidepressant, it has opened new avenues toward mechanisms involved in the pathology of treatment-resistant depression and achieving rapid antidepressant effects. Thus, preclinical studies focusing on deciphering the molecular mechanisms involved in the antidepressant action of ketamine will assist in the development of a new antidepressant. This review was conducted to elucidate the emerging pathways that can explain the complex dose-dependent mechanisms achieved by administering ketamine to treat major depressive disorders. Special attention was paid to reviewing the literature on hydroxynorketamines, which are ketamine metabolites that have recently attracted attention in the context of depression.

NMDA receptor modulation of glutamate release in activated neutrophils

Background

Neutrophil depletion improves neurologic outcomes in experimental sepsis/brain injury. We hypothesized that neutrophils may exacerbate neuronal injury through the release of neurotoxic quantities of the neurotransmitter glutamate.

Methods

Real-time glutamate release by primary human neutrophils was determined using enzymatic biosensors. Bacterial and direct protein-kinase C (Phorbol 12-myristate 13-acetate; PMA) activation of neutrophils in human whole blood, isolated neutrophils or human cell lines were compared in the presence/absence of N-Methyl-d-aspartic acid receptor (NMDAR) antagonists. Bacterial and direct activation of neutrophils from wild-type and transgenic murine neutrophils deficient in NMDAR-scaffolding proteins were compared using flow cytometry (phagocytosis, reactive oxygen species (ROS) generation) and real-time respirometry (oxygen consumption).

Findings

Both glutamate and the NMDAR co-agonist d-serine are rapidly released by neutrophils in response to bacterial and PMA-induced activation. Pharmacological NMDAR blockade reduced both the autocrine release of glutamate, d-serine and the respiratory burst by activated primary human neutrophils. A highly specific small-molecule inhibitor ZL006 that limits NMDAR-mediated neuronal injury also reduced ROS by activated neutrophils in a murine model of peritonitis, via uncoupling of the NMDAR GluN2B subunit from its' scaffolding protein, postsynaptic density protein-95 (PSD-95). Genetic ablation of PSD-95 reduced ROS production by activated murine neutrophils. Pharmacological blockade of the NMDAR GluN2B subunit reduced primary human neutrophil activation induced by Pseudomonas fluorescens, a glutamate-secreting Gram-negative bacillus closely related to pathogens that cause hospital-acquired infections.

Interpretation

These data suggest that release of glutamate by activated neutrophils augments ROS production in an autocrine manner via actions on NMDAR expressed by these cells.

Fund

GLA: Academy Medical Sciences/Health Foundation Clinician Scientist. AVG is a Wellcome Trust Senior Research Fellow.

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Neutrophil depletion improves neurologic outcome after injury and infection.

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Pharmacologic NMDAR blockade reduces rapid autocrine release of glutamate/d-serine from activated neutrophils.

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Genetic ablation/small-molecule inhibition of PSD-95 reduces neutrophil ROS.

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NMDAR blockade reduces human neutrophil activated by glutamate-secreting bacteria.

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Activated neutrophils may exacerbate neuronal injury in various forms of critical illness through the release of glutamate.

p38 mitogen-activated protein kinase gene silencing rescues rat hippocampal neurons from ketamine-induced apoptosis: An in vitro study

Ketamine (KTM) is an anesthetic drug with several advantages, including the elevation of cardiac output and blood pressure. However, KTM may also induce the apoptosis of hippocampal neurons. Notably, p38 mitogen-activated protein kinase (p38MAPK) has previously been studied for its role in neuronal injury. Therefore, the present study evaluated the effect of lentivirus-mediated p38MAPK gene silencing on KTM-induced apoptosis of rat hippocampal neurons. Hippocampal neurons were extracted from neonatal Sprague-Dawley rats, and then treated with KTM, p38MAPK-short hairpin RNA or SB203580 (an inhibitor of p38MAPK). Next, the expression levels of p38MAPK and apoptosis-associated genes, including caspase-3, B-cell lymphoma 2 (Bcl-2) and Bcl-2-associated X protein (Bax), were detected. In addition, cell viability and apoptosis were determined using an MTT assay and flow cytometry, respectively. Finally, telomerase activity of hippocampal neurons was detected by ELISA. The results revealed that silencing of p38MAPK in KTM-treated cells decreased the expression levels of p38MAPK, caspase-3 and Bax, and the extent of p38MAPK phosphorylation, while it increased the expression of Bcl-2. Furthermore, silencing p38MAPK promoted cell viability, cell cycle progression and the telomerase activity of hippocampal neurons, and inhibited the apoptosis of hippocampal neurons. Taken together, the results suggested an inhibitory role of lentivirus-mediated p38MAPK gene silencing on KTM-induced apoptosis of rat hippocampal neurons. Thus, p38MAPK gene silencing may serve as a potential target for preventing the KTM-induced apoptosis of hippocampal neurons.

Ketamine Affects In Vitro Differentiation of Monocyte into Immature Dendritic Cells

Background:

Monocytes (MOs) have the unique ability to differentiate into immature dendritic cells (iDCs) (MO→iDC) under the influence of interleukin-4 and granulocyte–monocyte colony-stimulating factor (IL-4&GM-CSF). In this study, the authors investigated the influence of ketamine on the process of MO→iDC.

Methods:

iDCs were cultured from MO obtained from 36 subjects in the presence of IL-4 and GM-CSF and ketamine at 100, 10, and 1 μg/ml for 5 days. In some of the experiments, the authors used nonspecific N-methyl-d-aspartate (NMDA) receptor antagonist MK-801, NMDA, or a neutralizing antibody for transforming growth factor β (TGFβ). The expression of surface markers and functional assays were used to assess the effect of ketamine on IL-4&GM-CSF-stimulated MO. IL-4&GM-CSF-stimulated MO’s supernatants were assessed for cytokine levels.

Results:

Ketamine at 10 μg/ml, and higher concentrations, diminished the expression of CD1a on IL-4&GM-CSF-stimulated MO and retarded both their ability to process DQ ovalbumin and mixed lymphocyte reaction stimulation. The addition of ketamine to IL-4&GM-CSF-differentiated MO resulted in the persistent expression of CD14 and unchanged expression of CD86 and CD206. The phagocytic abilities of IL-4&GM-CSF-differentiated MO were not changed by ketamine. MK-801, a nonselective NMDA agonist, mimicked ketamine’s effect on MO→iDC differentiation. Adding exogenous NMDA to IL-4&GM-CSF-stimulated MO in the presence of ketamine partially restored the level of CD1a+. TGFβ was elevated in supernatants of IL-4&GM-CSF-stimulated MO in the presence of ketamine. Adding neutralizing TGFβ antibody or TGFβR1 blocker (SB431542) resulted in the full recovery of MO→iDC, despite the presence of ketamine.

Conclusions:

Ketamine diminishes the process of MO→iDC in vitro. This is mediated via NMDA-dependent mechanisms and TGFβ.

The immune response to anesthesia: part 2 sedatives, opioids, and injectable anesthetic agents

OBJECTIVE

To review the immune response to injectable anesthetics and sedatives and to compare the immunomodulatory properties between inhalation and injectable anesthetic protocols.

STUDY DESIGN

Review.

METHODS AND DATABASES

Multiple literature searches were performed using PubMed and Google Scholar from March 2012 through November 2013. Relevant anesthetic and immune terms were used to search databases without year published or species constraints. The online database for Veterinary Anaesthesia and Analgesia and the Journal of Veterinary Emergency and Critical Care were searched by issue starting in 2000 for relevant articles.

CONCLUSION

Sedatives, injectable anesthetics, opioids, and local anesthetics have immunomodulatory effects that may have positive or negative consequences on disease processes such as endotoxemia, generalized sepsis, tumor growth and metastasis, and ischemia-reperfusion injury. Therefore, anesthetists should consider the immunomodulatory effects of anesthetic drugs when designing anesthetic protocols for their patients.

Combining ketamine with astrocytic inhibitor as a potential analgesic strategy for neuropathic pain ketamine, astrocytic inhibitor and pain

BACKGROUND

Neuropathic pain is an intractable clinical problem. Intrathecal ketamine, a noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist, is reported to be useful for treating neuropathic pain in clinic by inhibiting the activity of spinal neurons. Nevertheless, emerging studies have disclosed that spinal astrocytes played a critical role in the initiation and maintenance of neuropathic pain. However, the present clinical therapeutics is still just concerning about neuronal participation. Therefore, the present study is to validate the coadministration effects of a neuronal noncompetitive N-methyl-D-aspartate receptor (NMDAR) antagonist ketamine and astrocytic cytotoxin L-α-aminoadipate (LAA) on spinal nerve ligation (SNL)-induced neuropathic pain.

RESULTS

Intrathecal ketamine (10, 100, 1000 μg/kg) or LAA (10, 50, 100 nmol) alleviated SNL-induced mechanical allodynia in a dose-dependent manner respectively. Phosphorylated NR1 (pNR1) or glial fibrillary acidic protein (GFAP) expression was down-regulated by intrathecal ketamine (100, 1000 μg/kg) or LAA (50, 100 nmol) respectively. The combination of ketamine (100 μg/kg) with LAA (50 nmol) showed superadditive effects on neuropathic pain compared with that of intrathecal administration of either ketamine or LAA alone. Combined administration obviously relieved mechanical allodynia in a quick and stable manner. Moreover, down-regulation of pNR1 and GFAP expression were also enhanced by drugs coadministration.

CONCLUSIONS

These results suggest that combining NMDAR antagonist ketamine with an astrocytic inhibitor or cytotoxin, which is suitable for clinical use once synthesized, might be a potential strategy for clinical management of neuropathic pain.