Effect of peripheral benzodiazepine receptor ligands on lipopolysaccharide-induced tumor necrosis factor activity in thioglycolate-treated mice

Ro5-4864, a translocator protein ligand, regulates T cell-mediated inflammatory responses in skin

Translocator protein (TSPO) is a mitochondrial outer membrane protein expressed on a variety of immune cells, including macrophages, dendritic cells, and T cells, in addition to neurons and steroid-producing cells. Previous studies of TSPO ligands have suggested that TSPO is involved in multiple cellular functions, including steroidogenesis, immunomodulation, and cell proliferation. Currently, there are limited reports on the effects of TSPO or TSPO ligands on T cell-mediated immune responses. Here, we investigated the involvement of TSPO/TSPO ligand in T cell responses using a 2,4-dinitro-1-fluorobenzene (DNFB)-induced contact hypersensitivity (CH) model. Treatment with Ro5-4864, a TSPO ligand, during DNFB sensitization reduced the number and activation status of CD4+ and CD8+ T cells in draining lymph nodes and alleviated skin inflammation after DNFB challenge. Adoptive transfer of Ro5-4864-treated mouse-derived DNFB-sensitized T cells to naive mice inhibited CH responses after DNFB challenge. Ro5-4864-treated sensitized T cells showed lower proliferative responses when stimulated with DNFB-pulsed antigen-presenting cells compared to control-treated sensitized T cells. Ro5-4864 also suppressed cell proliferation, as well as adenosine triphosphate and lactate production, during T cell activation. Moreover, the inhibitory effects of Ro5-4864 on T cell responses were conserved in TSPO-deficient cells. Our results suggest that Ro5-4864 inhibits CH responses by suppressing energy metabolism, at least via glycolysis, to reduce the T cell primary response in a TSPO-independent manner.

A comprehensive review of remimazolam for sedation

Benzodiazepines are one of the most commonly used medications in the field of anesthesia. They offer excellent anxiolytic and amnestic properties ideal for the perioperative period when patient anxiety is understandably heightened. Remimazolam has presented a favorable alternative to some of the common intravenous anesthetic agents used given its fast onset of action, high safety profile, and reasonably short duration of action. The drugs within the four classes of benzodiazepines, 2-keto-benzodiazepines, 3-hydroxy-benzodiazepines, triazolo-benzodiazepines, and 7-nitro-benzodiazepines provide varying degrees of anxiolysis, sedation, and amnesia. This is provided by the benzodiazepine molecule binding and causing a conformational change to the chloride ion channel to cause hyperpolarization and thus inhibition of the central nervous system. Each type of benzodiazepine has a preferred role within the realm of medicine. For instance, diazepam is used for the treatment of seizures and anxiety. Midazolam's anxiolytic and anterograde amnestic properties are taking advantage of during the perioperative period. Lorazepam is beneficial for anxiety and status epilepticus. Remimazolam, currently in phase II and III clinical trials, has demonstrated a very short during of action and low context-sensitive half-time, allowing for its rapid removal even during a prolonged infusion. Much of its properties may be credited to being a soft drug, meaning it is a metabolically active drug that is rapidly inactivated in the body. This provides anesthesiologists and other practitioners administering it with a more predictable sedative. These properties have the potential to push it towards becoming the drug of choice for premedication during the perioperative period and sedation in the ICU. Furthermore, remimazolam does not seem to rely on any specific organ to be metabolized. The drug's ester moiety makes it a substrate for non-specific tissue esterase enzymes, meaning its metabolism and elimination are not impaired in patients with hepatic and/or renal disease. Its addictive potential closely resembles that of its parent compound, midazolam. Reports of its adverse reactions include headache and somnolence after an involuntary movement during infusion. Benzodiazepines are a great adjunct to anesthetic care. Remimazolam's safety profile, pharmacokinetics, pharmacodynamics, and potential practical use make it quite favorable in this regard. It has the potential to equip anesthesiologists and other medical practitioners with a more predictable medication that has a good safety profile. However, further large clinical trials will provide us with a better understanding of the advantages and disadvantages of remimazolam.

The Relationship Between Sedatives, Sedative Strategy, and Healthcare-Associated Infection: A Systematic Review

BACKGROUND Healthcare-associated infections (HAIs) cause significant morbidity in critically ill patients. An underappreciated but potentially modifiable risk factor for infection is sedation strategy. Recent trials suggest that choice of sedative agent, depth of sedation, and sedative management can influence HAI risk in mechanically ventilated patients. OBJECTIVE To better characterize the relationships between sedation strategies and infection. METHODS Systematic literature review. RESULTS We found 500 articles and accepted 70 for review. The 3 most common sedatives for mechanically ventilated patients (benzodiazepines, propofol, and dexmedetomidine) have different pharmacologic and immunomodulatory effects that may impact infection risk. Clinical data are limited but retrospective observational series have found associations between sedative use and pneumonia whereas prospective studies of sedative interruptions have reported possible decreases in bloodstream infections, pneumonia, and ventilator-associated events. CONCLUSION Infection rates appear to be highest with benzodiazepines, intermediate with propofol, and lowest with dexmedetomidine. More data are needed but studies thus far suggest that a better understanding of sedation practices and infection risk may help hospital epidemiologists and critical care practitioners find new ways to mitigate infection risk in critically ill patients. Infect Control Hosp Epidemiol 2016;1-9.

Antiseizure Activity of Midazolam in Mice Lacking δ-Subunit Extrasynaptic GABA(A) Receptors

Midazolam is a benzodiazepine anticonvulsant with rapid onset and short duration of action. Midazolam is the current drug of choice for acute seizures and status epilepticus, including those caused by organophosphate nerve agents. The antiseizure activity of midazolam is thought to result from its allosteric potentiation of synaptic GABA(A) receptors in the brain. However, there are indications that benzodiazepines promote neurosteroid synthesis via the 18-kDa cholesterol transporter protein (TSPO). Therefore, we investigated the role of neurosteroids and their extrasynaptic GABA(A) receptor targets in the antiseizure activity of midazolam. Here, we used δ-subunit knockout (DKO) mice bearing a targeted deletion of the extrasynaptic receptors to investigate the contribution of the extrasynaptic receptors to the antiseizure activity of midazolam using the 6-Hz and hippocampus kindling seizure models. In both models, midazolam produced rapid and dose-dependent protection against seizures (ED50, 0.4 mg/kg). Moreover, the antiseizure potency of midazolam was undiminished in DKO mice compared with control mice. Pretreatment with PK11195 [1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxamide], a TSPO blocker, or finasteride, a 5α-reductase neurosteroid inhibitor, did not affect the antiseizure effect of midazolam. The antiseizure activity of midazolam was significantly reversed by pretreatment with flumazenil, a benzodiazepine antagonist. Plasma and brain levels of the neurosteroid allopregnanolone were not significantly greater in midazolam-treated animals. These studies therefore provide strong evidence that neurosteroids and extrasynaptic GABA(A) receptors are not involved in the antiseizure activity of midazolam, which mainly occurs through synaptic GABA(A) receptors via direct binding to benzodiazepine sites. This study reaffirms midazolam's use for controlling acute seizures and status epilepticus.

Increased plasma levels of endozepines, endogenous ligands of benzodiazepine receptors, during systemic inflammation: a prospective observational study

Introduction

Recent work has shown that benzodiazepines interact with the immune system and exhibit anti-inflammatory effects. By using in vitro models, researchers in several studies have shown that the peptidergic endogenous ligands of benzodiazepine receptors, named endozepines, are involved in the immune response. All endozepines identified so far derive from diazepam-binding inhibitor (DBI), which generates several biologically active fragments. The aim of the present study was to measure plasma levels of DBI-like immunoreactivity (DBI-LI) in a rat model of sepsis and in patients with systemic inflammation from septic or non-septic origin.

Methods

Cecal ligation and puncture (CLP) or sham surgery was performed in rats. Blood samples were taken from animals, patients hospitalized for digestive surgery with inflammatory diseases, and healthy volunteers. Measurements of plasma DBI-related peptides were carried out by radioimmunoassay in animal and human samples.

Results

In the rats, CLP provoked an increase of plasma DBI-LI (+37%) 6 hours postsurgery. In humans, DBI-LI levels were significantly higher in the systemic inflammation group than in the healthy volunteer group (48.6 (32.7 to 77.7) pg/ml versus 11.1 (5.9 to 35.3) pg/ml, P < 0.001). We found a positive correlation between endozepine levels and Acute Physiology and Chronic Health Evaluation II score (r_s = 0.33 (0.026 to 0.58), P < 0.05) and tumor necrosis factor α levels (r_s = 0.43 (0.14 to 0.65), P < 0.01). The area under the receiver operating characteristic curve for endozepines was 0.842 (95% CI (0.717 to 0.966), P < 0.0001) for discriminating patients with inflammation from healthy volunteers.

Conclusions

Endozepines might be involved in the inflammatory response in patients with systemic inflammation.

Immunosuppressive aspects of analgesics and sedatives used in mechanically ventilated patients: an underappreciated risk factor for the development of ventilator-associated pneumonia in critically ill patients

OBJECTIVE

To evaluate the evidence describing the immunosuppressive and pharmacokinetic properties of commonly used analgesic and sedation agents in critically ill patients.

DATA SOURCES

MEDLINE (January 1980-September 2013) was searched.

STUDY SELECTION AND DATA EXTRACTION

All in vitro and in vivo studies that evaluated the immune-modulating properties of analgesic and sedation agents commonly used in the critically ill were included. Full-text and abstract-only articles (noted) were included in this review. Inclusion criteria were met by 46 studies and were evaluated.

DATA SYNTHESIS

Analgesic and sedation agents have been shown to be immunosuppressive in a variety of models. In vitro models use a variety of immune cells to demonstrate the immunosuppressive properties of opioids, benzodiazepines, and to a lesser extent, propofol. In each case, animal studies provide more robust data supporting the concept that opioids, benzodiazepines, and propofol exhibit immunosuppressive activities ranging from innate to adaptive immune alterations. Human studies, though more limited, provide further support that these agents inhibit the immune response. In contrast, data have shown that dexmedetomidine may attenuate the immune system. Clinical trial data evaluating the immunosuppressive properties of these agents is limited.

CONCLUSIONS

Analgesic and sedation agents have clearly been shown to alter cellular function and other mediators of the immune system; yet the clinical impact remains to be fully elucidated. The mechanism by which sedation interruption reduces ventilator-associated pneumonia may in fact be a reduction in immunosuppressive effects. Studies linking the immune-modulating effects of analgesic and sedation agents in critically ill patients are needed.

Effects of peripheral benzodiazepine receptor ligand Ro5-4864 in four animal models of acute lung injury

BACKGROUND

Acute lung injury (ALI) is a syndrome of inflammation and increased permeability of the blood-gas barrier. It is associated with high morbidity and mortality. Despite intensive research, treatments remain limited. The aim of the present study was to investigate the protective efficacy of a specific peripheral benzodiazepine receptor ligand, Ro5-4864, in experimental models of ALI in rats.

METHODS

ALI was generated by four different methods: (1) intravenous (tail vein) injection of Escherichia coli (0111:B4) lipopolysaccaride (LPS), (2) cecal ligation and puncture (CLP), (3) mesenteric ischemia/reperfusion, and (4) intraperitoneal injection of α-naphthylthiourea (ANTU). Ro5-4864 was administered to rats intraperitoneally 30 min before ANTU and LPS administration or intravenously 15 min before reperfusion and CLP. The levels of pulmonary edema (lung weight/body weight ratio) and pleural effusion were measured, and the severity of ALI was scored (0-3).

RESULTS

Ro5-4864 showed a dose-dependent and significant prophylactic effect on the ANTU-induced lung weight/body weight and pleural effusion/body weight ratios and histopathologic scores. Ro5-4864 also showed significant prophylactic effects against the LPS-induced lung weight/body weight ratio and histopathologic scores. Ro5-4864 significantly decreased the intra-alveolar edema and perialveolar hemorrhage scores in the CLP group. However, we found no prophylactic effect of Ro5-4864 on mesenteric ischemia/reperfusion-induced ALI at the dose used (2 mg/kg intraperitoneally).

CONCLUSIONS

These results have demonstrated, for the first time, a protective effect of Ro5-4864 on experimental ALI induced by ANTU, LPS, and CLP. Ro5-4864 might be a useful therapeutic agent for lung diseases, including ALI, in intensive care patients.

Role of neurosteroids in the anticonvulsant activity of midazolam

BACKGROUND AND PURPOSE

Midazolam is a short-acting benzodiazepine that is widely used as an i.v. sedative and anticonvulsant. Besides interacting with the benzodiazepine site associated with GABA(A) receptors, some benzodiazepines act as agonists of translocator protein (18 kDa) (TSPO) to enhance the synthesis of steroids, including neurosteroids with positive modulatory actions on GABA(A) receptors. We sought to determine if neurosteroidogenesis induced by midazolam contributes to its anticonvulsant action.

EXPERIMENTAL APPROACH

Mice were pretreated with neurosteroid synthesis inhibitors and potentiators followed by midazolam or clonazepam, a weak TSPO ligand. Anticonvulsant activity was assessed with the i.v. pentylenetetrazol (PTZ) threshold test.

KEY RESULTS

Midazolam (500-5000 µg·kg(-1) , i.p.) caused a dose-dependent increase in seizure threshold. Pretreatment with the neurosteroid synthesis inhibitors finasteride, a 5α-reductase inhibitor, and a functional TSPO antagonist PK 11195, reduced the anticonvulsant action of midazolam. The anticonvulsant action of midazolam was enhanced by the neurosteroidogenic drug metyrapone, an 11β-hydroxylase inhibitor. In contrast, the anticonvulsant action of clonazepam (100 µg·kg(-1) ) was reduced by finasteride but not by PK 11195, indicating a possible contribution of neurosteroids unrelated to TSPO.

CONCLUSION AND IMPLICATIONS

Enhanced endogenous neurosteroid synthesis, possibly mediated by an interaction with TSPO, contributed to the anticonvulsant action of midazolam. Enhanced neurosteroidogenesis may also be a factor in the actions of other benzodiazepines, even those that only weakly interact with TSPO.

Sedation & immunomodulation

As the armamentarium for sedation in the critically ill expands, opportunities will develop to modulate the immune responses of patients by way of the direct immune and neural-immune interactions of the sedatives. Control of autonomic activity through the use of appropriate sedation may be critical in this matter. Likewise analgesic-based sedation, with increased opioid dosage, may not prove beneficial in the setting of infection; whether avoidance of morphine in preference for a fentanyl derivative will help is unclear. However, as the immune effects seem dependent on the m receptor, it is improbable that a significant difference would be uncovered. Similarly, the present evidence suggests benzodiazepines are deleterious in infection; further studies are required urgently to evaluate this evidence. As an alternative to benzodiazepine-based sedation, dexmedetomidine has shown a remarkable 70% mortality benefit in a small secondary analysis of septic patients from the MENDS trial. Further powered clinical studies should now be undertaken to investigate the potential benefit of the α2-adrenoceptor agonist in this setting, with comparisons with propofol.

Midazolam suppresses interleukin-1β-induced interleukin-6 release from rat glial cells

Background

Peripheral-type benzodiazepine receptor (PBR) expression levels are low in normal human brain, but their levels increase in inflammation, brain injury, neurodegenerative states and gliomas. It has been reported that PBR functions as an immunomodulator. The mechanisms of action of midazolam, a benzodiazepine, in the immune system in the CNS remain to be fully elucidated. We previously reported that interleukin (IL)-1β stimulates IL-6 synthesis from rat C6 glioma cells and that IL-1β induces phosphorylation of inhibitory kappa B (IκB), p38 mitogen-activated protein (MAP) kinase, stress-activated protein kinase (SAPK)/c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase 1/2, and signal transducer and activator of transcription (STAT)3. It has been shown that p38 MAP kinase is involved in IL-1β-induced IL-6 release from these cells. In the present study, we investigated the effect of midazolam on IL-1β-induced IL-6 release from C6 cells, and the mechanisms of this effect.

Methods

Cultured C6 cells were stimulated by IL-1β. IL-6 release from C6 cells was measured using an enzyme-linked immunosorbent assay, and phosphorylation of IκB, the MAP kinase superfamily, and STAT3 was analyzed by Western blotting.

Results

Midazolam, but not propofol, inhibited IL-1β-stimulated IL-6 release from C6 cells. The IL-1β-stimulated levels of IL-6 were suppressed by wedelolactone (an inhibitor of IκB kinase), SP600125 (an inhibitor of SAPK/JNK), and JAK inhibitor I (an inhibitor of JAK 1, 2 and 3). However, IL-6 levels were not affected by PD98059 (an inhibitor of MEK1/2). Midazolam markedly suppressed IL-1β-stimulated STAT3 phosphorylation without affecting the phosphorylation of p38 MAP kinase, SAPK/JNK or IκB.

Conclusion

These results strongly suggest that midazolam inhibits IL-1β-induced IL-6 release in rat C6 glioma cells via suppression of STAT3 activation. Midazolam may affect immune system function in the CNS.

Sedation improves early outcome in severely septic Sprague Dawley rats

INTRODUCTION

Sepsis, a systemic inflammatory response to infective etiologies, has a high mortality rate that is linked both to excess cytokine activity and apoptosis of critical immune cells. Dexmedetomidine has recently been shown to improve outcome in a septic cohort of patients when compared to patients randomized to a benzodiazepine-based sedative regimen. We sought to compare the effects of dexmedetomidine and midazolam, at equi-sedative doses, on inflammation and apoptosis in an animal model of severe sepsis.

METHODS

After central venous access, Sprague Dawley rats underwent cecal ligation and intestinal puncture (CLIP) with an 18 G needle without antibiotic cover and received either saline, or an infusion of comparable volume of saline containing midazolam (0.6 mg.kg-1.h-1) or dexmedetomidine (5 ug.kg-1.h-1) for 8 hours. Following baseline measurements and CLIP, blood was sampled for cytokine measurement (tumour necrosis factor (TNF)-alpha and interleukin (IL)-6; n = 4-6 per group) at 2, 4 and 5 hours, and animal mortality rate (MR) was monitored (n = 10 per group) every 2 hours until 2 hours had elapsed. In addition, spleens were harvested and apoptosis was assessed by immunoblotting (n = 4 per group).

RESULTS

The 24 hour MR in CLIP animals (90%) was significantly reduced by sedative doses of either dexmedetomidine (MR = 20%) or midazolam (MR = 30%). While both sedatives reduced systemic levels of the inflammatory cytokine TNF-alpha (P < 0.05); only dexmedetomidine reduced the IL-6 response to CLIP, though this narrowly missed achieving significance (P = 0.05). Dexmedetomidine reduced splenic caspase-3 expression (P < 0.05), a marker of apoptosis, when compared to either midazolam or saline.

CONCLUSIONS

Sedation with midazolam and dexmedetomidine both improve outcome in polymicrobial severely septic rats. Possible benefits conveyed by one sedative regimen over another may become evident over a more prolonged time-course as both IL-6 and apoptosis were reduced by dexmedetomidine but not midazolam. Further studies are required to evaluate this hypothesis.

Sedation & immunomodulation

The management of critically ill patients necessitates the use of sedatives and analgesics to provide patient comfort and cooperation. These drugs exert profound effects on all organ systems, not only the central nervous system, and this article describes the immunologic effects of the commonly used critical care sedatives: propofol, the benzodiazepines, opioids, and alpha(2)-adrenoceptor agonists. Benzodiazepines, opioids, and possibly even propofol worsen outcome in animal models of infection, whereas preliminary evidence suggests that the alpha(2)-adrenoceptor agonist, dexmedetomidine, may improve outcomes in the setting of infection. Given the burden of sepsis and secondary infections in critical care, choice of sedation may need to be carefully considered to preserve immune responses in critically ill patients.

Ketamine suppresses intestinal TLR4 expression and NF-kappaB activity in lipopolysaccharide-treated rats

AIM

To investigate whether ketamine suppresses lipopolysaccharide (LPS)-induced increase in Toll-like receptor 4 (TLR4) expression and nuclear factor-kappa B (NF-kappaB) activity in the intestines of rats.

METHODS

Six groups of rats received one of the following: normal saline control, LPS (5 mg/kg) plus saline, LPS (5 mg/kg) plus ketamine (0.5 mg/kg), LPS (5 mg/kg) plus ketamine (2.5 mg/kg), LPS (5 mg/kg) plus ketamine (10 mg/kg), or ketamine (10 mg/kg) alone. Intestinal TLR4 mRNA expression was analyzed by reverse transcription polymerase chain reaction (RT-PCR), and NF-kappaB activity was tested by electrophoretic mobility shift assay (EMSA) 1, 3, or 5 hours after the LPS injection.

RESULTS

Lipopolysaccharide increased TLR4 expression and NF-kappaB activity in the intestines of rats. Ketamine at the dosage of 0.5, 2.5, and 10 mg/kg suppressed the LPS-induced increase in TLR4 expression and NF-kappaB activity. Ketamine alone had no effect.

CONCLUSION

The study demonstrated that ketamine inhibits NF-kappaB activation in the intestines of LPS-treated rats, possibly by suppressing TLR4 expression.

Peripheral benzodiazepine receptors on platelets of fibromyalgic patients

OBJECTIVE

The aim of the present study was to analyze if alterations of peripheral-type benzodiazepine receptor (PBR) characteristics occurred in platelet membranes of patients affected by primary fibromyalgia (FM).

DESIGN AND METHODS

Platelets were obtained from 30 patients with FM. Evaluation of kinetic parameters of PBR was performed using [(3)H] PK11195 as specific radioligand compared with 16 healthy volunteers.

RESULTS

The results showed a significant increase of PBR binding sites value in platelet membranes from FM patients (B(max) was 5366+/-188 fmol/mg vs. controls, 4193+/-341 fmol/mg, mean+/-SEM) (**p<0.01) but not for affinity value (K(d) was 4.90+/-0.39 nM vs. controls, 4.74+/-0.39 nM, mean+/-SEM) (p>0.05). Symptom severity scores (pain and tiredness) were positively correlated with B(max).

CONCLUSIONS

Our results showed an up-regulation of PBR in platelets of FM patients, and this seems to be related to the severity of fibromyalgic symptoms.

[3H]PK11195 binding sites in human neutrophils: effect of fMLP stimulation and modulation in rheumatic diseases

OBJECTIVE

The objectives of this study were to evaluate the [3H]PK11195 binding parameters in a model of acute inflammation, the N-formylmethionine-leucine-phenylalanine (fMLP)-stimulated neutrophil cell membranes, and to analyze if alterations of peripheral-type benzodiazepine receptor (PBR) characteristics occurred in neutrophil cell membranes of patients affected by osteoarthritis (OA), rheumatoid arthritis (RA), and psoriasic arthritis (PA).

DESIGN AND METHODS

Neutrophils were obtained from 15 patients with OA, 15 patients with RA, and 15 patients with PA. fMLP stimulation was performed to aliquots of neutrophils from six healthy individuals. Evaluation of kinetic parameters of PBR was performed using [3H]PK11195, as specific radioligand compared with 15 healthy volunteers.

RESULTS

The results showed a significant decrease of Kd and Bmax in fMLP-stimulated neutrophil membranes. Moreover, an increase of PBR binding sites and affinity value was observed in neutrophils membranes from PA patients.

CONCLUSIONS

Our data suggested a fMLP modulation on [3H]PK11195 binding in human neutrophils. Moreover, our results showed an up-regulation of PBR in neutrophils of PA patients.

Peripheral-type benzodiazepine receptors in human mononuclear cells of patients affected by osteoarthritis, rheumatoid arthritis or psoriasic arthritis

OBJECTIVES

The objective of this study was to evaluate the kinetic parameters at equilibrium of peripheral benzodiazepine receptors (PBR) in human mononuclear cells from patients affected by osteoarthritis (OA), rheumatoid arthritis (RA) and psoriasic arthritis (PA).

DESIGN AND METHODS

Mononuclear cells were obtained from 10 patients with OA, 10 patients with RA and 10 patients with PA. Evaluation of kinetic parameters of PBR was performed using [(3)H]PK 11195, a specific radioligand for this receptor, and compared with 10 healthy controls.

RESULTS

The results show a statistically significant decrease (37.5%, as an absolute percentage) in the maximal number of binding sites (B(max)) of patients with OA, compared with healthy controls; however, the values of the dissociation constant (K(d)) at equilibrium do not show any statistically significant variations.

CONCLUSIONS

These data further confirm the presence of peripheral biochemical alterations in OA. As peripheral benzodiazepine receptors appear to be involved in the immune function, and in the protection of hematopoietic cells against oxygen radical damage, the observed decrease in B(max) might be related to cellular protection.

Diazepam inhibits HIV-1 Tat-induced migration of human microglia

During HIV-1 encephalitis, the chemotaxis-inducing activity of Tat may enhance the viral life cycle through recruitment of additional susceptible microglial cells to foci of infection. Benzodiazepines (BDZs) readily penetrate the blood-brain barrier and are known to possess anti-inflammatory properties. Pretreatment of human microglial cells with peripheral (Ro5-4864) and mixed (diazepam), but not central (clonazepam), benzodiazepine receptor ligands was found to potently suppress HIV-1 Tat-induced chemotaxis. Application of Tat to microglial cells evokes an increase in intracellular calcium concentration ([Ca(2+)]i) that rapidly desensitizes the cells. Diazepam's inhibitory effect was associated with its ability to block Tat-induced [Ca(2+)]i mobilization. These data support the notion that through their effects on microglia, peripheral BDZ receptor ligands could alter the neuropathogenesis of HIV-1.

Effect of midazolam on interleukin-6 mRNA expression in human peripheral blood mononuclear cells in the absence of lipopolysaccharide

Midazolam, a benzodiazepine, has an hypnotic effect via benzodiazepine receptors and is widely used as an anaesthetic. Recently, it has been suggested that benzodiazepines modulate cytokine responses. The purpose of the present study was to evaluate the effect of midazolam on interleukin-6 (IL-6) response by observing mRNA expression levels in human peripheral blood mononuclear cells (PBMCs) in the absence of lipopolysaccharide (LPS). PBMCs were isolated from healthy volunteers in endotoxin-free 0.9% sodium chloride solution. The cells were incubated for 2 h at 37 degrees C immediately after isolation. IL-6 mRNA expression levels in the cells were quantified using reverse transcription and competitive polymerase chain reaction. It was found that midazolam time-dependently inhibited the IL-6 mRNA expression in PBMCs in the absence of LPS, and significantly inhibited the IL-6 mRNA expression at 1 microg/ml (P<0.05) or 10 microg/ml (P<0.01) in the absence of LPS. However, neither a specific agonist of peripheral-type benzodiazepine receptors, Ro5-4864, nor a specific agonist of central-type benzodiazepine receptors, clonazepam, inhibited IL-6 mRNA expression. These findings indicated a suppression of the IL-6 response in human PBMCs by midazolam in the absence of LPS, and suggests that midazolam has its effect not via benzodiazepine receptors, but by another mechanism.

Melatonin reduces anxiety induced by lipopolysaccharide in the rat

In male Sprague-Dawley rats intraperitoneal (i.p.) injection of Escherichia coli lipopolysaccharide (0.25, 0.50 and 1 mg/kg) increased anxiety levels. This effect was reversed by a prior, concomitant, and subsequent i.p. treatment with melatonin (4 and 6 mg/kg). As the effects of melatonin upon the actions induced by lipopolysaccharide were reversed by the melatonin receptor antagonist luzindole (30 and 60 mg/kg, i.p.), we argued that they are, but not only, melatonin receptor mediated. These findings, in accordance with our previous works, suggest that melatonin could be useful in the treatment of sickness behaviour associated with systemic infection diseases or as adjuvant in the anti-anxiety therapy.

Melatonin enhances Th2 cell mediated immune responses: lack of sensitivity to reversal by naltrexone or benzodiazepine receptor antagonists

Chronic administration of melatonin for 5 days to antigen-primed mice increased the production of pro-inflammatory cytokine IL-10 but decreased the secretion of anti-inflammatory cytokine TNF-alpha. These results further confirm that melatonin activates Th2-like immune response. Whether melatonin-mediated Th2 response is dependent on opioid or central and peripheral benzodiazepine receptors was also examined. Hence, melatonin was administered to antigen-sensitised mice with either naltrexone (a mu opioid receptor antagonist) or flumazenil (a central benzodiazepine receptor antagonist) or PK11195 (a peripheral benzoidiazepine receptor antagonist). No significant difference in melatonin-induced Th2 cell response was observed by naltrexone, flumazenil or PK11195 treatment. These findings suggest that the Th2 cell response induced by melatonin in antigen sensitised mice neither dependent on endogenous opioid system nor is modulated through the central or peripheral benzodiazepine receptors.

Effect of acute lipopolysaccharide administration on (+/-)-1-(2,5-dimethoxy-4-iodophenyl)-2 aminopropane-induced wet dog shake behavior in rats: comparison with body weight change and locomotor activity

1. Several reports have shown that serotonin (5-HT)2A receptor density and its function are altered after physiological or pharmacological stress. To examine whether an acute administration of lipopolysaccharide (LPS), a bacterial endotoxin, affected 5-HT2A receptor function, wet dog shakes of male Wistar rats were observed after a subcutaneous injection of DOI, a 5-HT2A receptor agonist following LPS treatment. Body weight change and locomotor activity were also observed. 2. DOI (1 mg/kg)-induced WDS significantly decreased after 400 or 1000 microg/kg LPS treatment compared with that of control rats 1 and 3 hr after injection, and WDS completely recovered 8 hr after LPS treatment. Treatment with 10 mg/kg indomethacin (IND) or 1 mg/kg naltrexone (NLTX) canceled the effect of 400 microg/kg LPS on DOI-induced WDS. 3. Body weight decrease was significantly greater in LPS-treated rats compared with control rats 3, 5 and 8 hr after treatment. Treatment with IND (10 mg/kg) significantly recovered the reduction in body weight induced by 400 microg/kg LPS. Treatment with NLTX (1 mg/kg) also prevented the LPS effect on body weight decrease. 4. Eight hr after treatment with LPS (400 microg/kg), the rats showed significant attenuation of locomotor activity. IND (10 mg/kg) treatment abolished the inhibitory effect of LPS on locomotor activity, and NLTX (1 mg/kg) also improved the decrease in locomotion 8 hr after LPS treatment. 5. Plasma tumor necrosis factor (TNF)-alpha concentration dramatically increased 1 hr after the injection of 400 microg/kg LPS, and returned almost to the basal level 3 hr later. Next, rats were injected with 50 microg/kg TNF-alpha intraperitoneally, and body weight change and DOI-induced WDS was determined 3 hr after TNF-alpha injection. Body weight loss was significantly greater in rats treated with TNF-alpha. On the other hand, DOI-induced WDS was not altered when rats were treated with TNF-alpha. 6. These results suggest that acute treatment with LPS inhibited 5-HT2A receptor-mediated behavior via cyclooxygenase and opioid receptor activation, but that the inhibition of the WDS by LPS appears to be independent of TNF-alpha production.

Role of interleukin-10 on hyporesponsiveness of endotoxin during surgery

OBJECTIVE

To examine whether surgical stress causes blood cells to lose their responsiveness to endotoxin during surgery.

DESIGN

Prospective case series.

SETTING

A university hospital.

PATIENTS

Sixteen volunteers classified as American Society of Anesthesiologists physical status I-II who were scheduled for elective distal partial gastrectomy.

INTERVENTIONS

We studied nine patients who underwent elective distal partial gastrectomy. Blood samples for tumor necrosis factor (TNF) and interleukin (IL)-10 assay were obtained before anesthesia, preincision, 2 hrs and 4 hrs postincision, postextubation, and 24 hrs postincision. The rest of each blood sample was diluted with 5 volumes of endotoxin-free saline, incubated for 4 hrs in the presence of lipopolysaccharide (LPS), centrifuged to remove cells, and assayed for TNF. In another seven patients, antihuman IL-10 antibody was added into the diluted whole blood sample before LPS stimulation.

MEASUREMENTS AND MAIN RESULTS

TNF activity was not detected in the blood of any patient throughout the study. In contrast, plasma cortisol and IL-10 levels increased rapidly during surgery (p < .01, p < .05, respectively). LPS-induced TNF activity in whole blood decreased significantly during surgery (p < .01) and recovered to control levels by 24 hrs postincision. The peak suppression of LPS-induced TNF and the peak value of plasma IL-10 levels occurred postextubation. Treatment with anti-IL-10 antibody partially restored the ability of LPS to induce TNF activity postextubation (p < .05).

CONCLUSIONS

Surgical trauma rapidly induces a transient hyporesponsiveness of blood cells to endotoxin. Plasma IL-10, which increases during surgery, participates in this hyporesponsiveness.

Inhibitory action of 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) on some mononuclear phagocyte functions

Peripheral benzodiazepine receptors (PBRs) are widely distributed throughout the body, but their functions are unknown. They are found on mononuclear phagocytes, and they are up-regulated in a number of neurological and other disease states. We explored the functional consequences of PBR ligand binding to mononuclear-derived cells using the high-affinity ligands 1-(2-chlorophenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinolinecarboxam ide (PK 11195) and 4'-chlorodiazepam (7-chloro-5-(4'-chlorophenyl)-1, 3-dihydro-1-methyl-2H-1,4-benzodiazepin-2-one; Ro 5-4864). The functions were the following: respiratory burst; secretion of glutamate, interleukin-1beta (IL-1beta), and tumor necrosis factor-alpha (TNF-alpha); toxicity of culture supernatants towards SH-SY5Y human neuroblastoma cells; and expression of the inflammatory surface markers HLA-DR and Fcgamma RII (CDw32). PK 11195 inhibited the respiratory burst response, reduced release of glutamate and IL-1beta, and suppressed secretion of products cytotoxic to neuronal cells. Selectivity was suggested by the failure of PK 11195 to influence TNF-alpha secretion or expression of HLA-DR and CDw32. Powerful ligands of PBRs, such as PK 11195, may be useful inhibitors of selective macrophage functions, retarding both local and systemic inflammation. Since PK 11195 readily enters the brain, it may be beneficial in treating central as well as peripheral inflammatory diseases.

Benzodiazepines, glia, and HIV-1 neuropathogenesis

Although the precise mechanisms whereby HIV-1 infection induces neurodegeneration have yet to be determined, a great deal of evidence has incriminated glial cells and the production of proinflammatory mediators in this pathologic process. For this reason, ideal therapeutic agents for the treatment of AIDS dementia would attenuate HIV-1 neuropathogenesis through both direct inhibition of viral expression and suppression of brain cell-produced immune mediators. Benzodiazepines (BDZs), such as Valium, are extensively prescribed drugs for anxiety disorders, which readily cross the blood-brain barrier and have demonstrated immunomodulatory properties. BDZs bind to primary human microglial cells, the principal site of HIV-1 replication in the brain, and inhibit lipopolysaccharide (LPS) induced tumour necrosis factor (TNF-alpha) production by these cells in a concentration-dependent manner. Treatment of HIV-1-infected primary human microglial, as well as mixed glial/neuronal, cell cultures with BDZs inhibits the expression of HIV-1 p24 antigen. BDZ-induced inhibition of HIV-1 expression in chronically infected promonocytic (U1) cells has been found to be associated with decreased activation of the nuclear transcription factor kappa B (NF-kappa B). Because HIV-1 expression is critically dependent on the cellular transcription machinery, inhibition of the activation of transcription factors, which participate in both HIV-1 expression and the production of neurotoxic immune mediators, by BDZ analogs may provide new therapeutic options for AIDS dementia.

Diazepam-mediated inhibition of human immunodeficiency virus type 1 expression in human brain cells

Treatment of acutely infected human brain cell and enriched microglial cell cultures with diazepam inhibited human immunodeficiency virus type 1 (HIV-1) p24 antigen expression. Similarly, diazepam suppressed HIV-1 expression in chronically infected promonocytic (U1) cells and acutely infected monocyte-derived macrophages, and this antiviral activity was associated with decreased activation of nuclear factor kappa B.