5-Lipoxygenase in the Prefrontal Cortex of Suicide Victims

Investigation of the relationship between chronic montelukast treatment, asthma and depression-like behavior in mice

In 2008, the Food and Drug Administration of the US issued a warning about the neuropsychiatric side effects of montelukast. Previous clinical studies on montelukast have reported conflicting results and, to the best of our knowledge, no experimental studies concerning these side effects had been conducted. In the current study, the effect of montelukast on depression-like behavior in an ovalbumin (OVA)-induced mouse model was investigated. A total of 3 OVA challenges were applied at 2 week intervals for the persistence of asthma. Depression-like behavior was assessed using forced swim tests following each challenge and locomotor activities were evaluated using open field tests. At the end of the current study, plasma montelukast concentrations were measured and the development of asthma and effect of montelukast treatment were histopathologically examined. Inflammation scores that were increased in the OVA mice following all challenges were indicated to be reduced by montelukast treatment. The immobility time of mice increased beginning with the first challenge and this was also reduced by montelukast treatment. Montelukast administration to the control mice did not alter immobility times. Moreover, motor activity of the OVA and montelukast-treated mice were not altered. The results indicated there was no association between chronic montelukast treatment and depression. Furthermore, the chronic administration of montelukast to non-asthmatic mice did not increase immobility. However, depressive behavior increased at all time points in the OVA mice. These results indicated that chronic montelukast treatment is not associated with depression-like behavior and confirmed the association between asthma and depression. Further studies are required to provide an improved understanding of the neuropsychiatric side effects of montelukast.

The mechanism of 5-lipoxygenase in the impairment of learning and memory in rats subjected to chronic unpredictable mild stress

OBJECTIVES

To examine the mechanism of 5-lipoxygenase (5-LO) in the learning and memory dysfunction in rats subjected to chronic unpredictable mild stress (CUMS).

METHODS

Eighty rats were divided into eight groups: the 0.5% sodium carboxymethyl cellulose solution (NaCMC)-treated group, empty vector (LV-Mock)-treated group, CUMS+NaCMC-treated group, CUMS+sertraline-treated group, CUMS+caffeic acid (10mg/kg)-treated group, CUMS+caffeic acid (30mg/kg)-treated group, CUMS+LV-Mock-treated group, and CUMS+5-LO-silencers lentiviral vectors (LV-si-5-LO)-treated group, n=10. Sucrose preference tests were performed to assess depression-like behavior. The Morris water maze and step-down tests were used to evaluate learning and memory performance. The levels of inflammatory cytokines, malondialdehyde, and the activity of superoxide dismutase (SOD) were detected to estimate inflammation and oxidative stress. Changes in 5-LO mRNA and protein were detected using reverse transcription polymerase chain reaction and Western blotting. The expression of synaptophysin, postsynaptic density-95 (PSD-95), and brain-derived neurotrophic factor (BDNF) in the hippocampus were measured using immunohistochemical staining.

RESULTS

Treatment with caffeic acid or LV-si-5-LO increased sucrose consumption, decreased escape latency and increased the number of platform crosses in the Morris water maze test, and decreased the number of errors and prolonged the latency in the step-down test. We observed a decreased expression of 5-LO, and levels of malondialdehyde, leukotriene-B4, tumor necrosis factor-α, and interleukin-6, while the protein levels of synaptophysin, PSD-95, BDNF, and the activity of SOD were increased in the hippocampus of the CUMS-treated rats.

CONCLUSIONS

CUMS-induced impairment in learning and memory could be triggered by an inflammatory response in the rat hippocampus, which results in oxidative stress injury and impacts the synaptic plasticity of hippocampal neurons. Inhibition of the activity or expression of 5-LO could suppress hippocampal inflammation, enhance synaptic plasticity, and improve learning and memory function in depressed rats.

Immunopathogenesis of HIV infection in cocaine users: role of arachidonic acid

Arachidonic acid (AA) is known to be increased in HIV infected patients and illicit drug users are linked with severity of viral replication, disease progression, and impaired immune functions. Studies have shown that cocaine accelerates HIV infection and disease progression mediated by immune cells. Dendritic cells (DC) are the first line of antigen presentation and defense against immune dysfunction. However, the role of cocaine use in HIV associated acceleration of AA secretion and its metabolites on immature dendritic cells (IDC) has not been elucidated yet. The aim of this study is to elucidate the mechanism of AA metabolites cyclooxygenase-2 (COX-2), prostaglandin E2 synthetase (PGE₂), thromboxane A2 receptor (TBXA₂R), cyclopentenone prostaglandins (CyPG), such as 15-deoxy-Δ12,14-PGJ2 (15d-PGJ2), 14-3-3 ζ/δ and 5-lipoxygenase (5-LOX) mediated induction of IDC immune dysfunctions in cocaine using HIV positive patients. The plasma levels of AA, PGE_2, 15d-PGJ2, 14-3-3 ζ/δ and IDC intracellular COX-2 and 5-LOX expression were assessed in cocaine users, HIV positive patients, HIV positive cocaine users and normal subjects. Results showed that plasma concentration levels of AA, PGE₂ and COX-2, TBXA₂R and 5-LOX in IDCs of HIV positive cocaine users were significantly higher whereas 15d-PGJ2 and 14-3-3 ζ/δ were significantly reduced compared to either HIV positive subjects or cocaine users alone. This report demonstrates that AA metabolites are capable of mediating the accelerative effects of cocaine on HIV infection and disease progression.

The involvement of 5-lipoxygenase activating protein in anxiety-like behavior

The 5-lipoxygenase is an enzyme widely expressed in the central nervous system, where its activity is dependent on the presence the 5-lipoxygenase activating protein (FLAP) for the formation of leukotrienes, potent bioactive lipid mediators. Emerging evidence has shown that the FLAP/leukotriene pathway may play a role in neuropsychiatric disease contexts. In this study we investigated whether genetic deficiency of FLAP (FLAPKO) modulated some behavioral aspects in mice, and if this effect was age-dependent. While we observed that FLAPKO mice at 3 and 6 months of age did not different from wild type animals in the elevated plus maze, at 12 months of age they manifested a significant increase in anxiety-like behavior. By contrast, we observed no differences between FLAPKO mice and their controls at any of the three ages considered when they were tested for working memory in the Y maze paradigm. Additionally, while we found that cFOS protein and message levels were reduced in the brains of animals lacking FLAP, no changes for other transcription factors were detected. Taken together our findings suggest a novel role for FLAP in the pathogenesis of anxiety-like behavior. Future studies of FLAP neurobiology may be attractive for development of anxiolytic therapeutics.

Knockout of 5-lipoxygenase results in age-dependent anxiety-like behavior in female mice

Background

The enzyme 5-lipoxygenase (5LO) has been implicated in a variety of neurological and psychiatric disorders including anxiety. Knockout of 5LO has previously been shown to alter anxiety-like behavior in mice at a young age but the effect of 5LO knockout on older animals has not been characterized.

Methodology/Principal Findings

Here we used the elevated plus maze behavioral paradigm to measure anxiety-like behavior in female mice lacking 5LO (5LO-KO) at three different ages. Adolescent 5LO-KO animals did not significantly differ from wild-type (WT) animals in anxiety-like behavior. However, adult and older mice exhibited increased anxiety-like behavior compared to WT controls.

Conclusions

These results indicate that 5LO plays a role in the development of the anxiety-like phenotype in an age-dependent manner in female mice. Future work should further investigate this interaction as 5LO may prove to be an important molecular target for the development of novel anxiolytic therapies.

Cyclooxygenases and 5-lipoxygenase in Alzheimer's disease

Typically, cyclooxygenases (COXs) and 5-lipoxygenase (5-LOX), enzymes that generate biologically active lipid molecules termed eicosanoids, are considered inflammatory. Hence, their putative role in Alzheimer's disease (AD) has been explored in the framework of possible inflammatory mechanisms of AD pathobiology. More recent data indicate that these enzymes and the biologically active lipid molecules they generate could influence the functioning of the central nervous system and the pathobiology of neurodegenerative disorders such as AD via mechanisms different from classical inflammation. These mechanisms include the cell-specific localization of COXs and 5-LOX in the brain, the type of lipid molecules generated by the activity of these enzymes, the type and the localization of receptors selective for a type of lipid molecule, and the putative interactions of the COXs and 5-LOX pathways with intracellular components relevant for AD such as the gamma-secretase complex. Considering the importance of these multiple and not necessarily inflammatory mechanisms may help us delineate the exact nature of the involvement of the brain COXs and 5-LOX in AD and would reinvigorate the search for novel targets for AD therapy.

Reports of suicidality in clinical trials of montelukast

BACKGROUND

In recent years, a number of drugs and drug classes have come under scrutiny by the US Food and Drug Administration regarding suicidality (including suicidal behavior and ideation).

OBJECTIVE

We sought to perform 2 reviews (requested by the US Food and Drug Administration) of the number of events possibly related to suicidality reported in Merck clinical trials of montelukast.

METHODS

Method 1 was a descriptive review of clinical adverse experiences (AEs) from 116 studies (double-blind and open-label, adult and pediatric, and single- and multiple-dose studies) completed as of March 2008. Summaries were constructed from investigator-reported AE terms possibly related to suicidality (completed suicide, suicide attempt, and suicidal ideation) or self-injurious behavior. Method 2 used a retrospective adjudication of investigator-reported AEs and other events listed in the study database described as possibly suicidality-related adverse events (PSRAEs) in a prespecified set of 41 double-blind, placebo-controlled trials completed as of April 2008.

RESULTS

No completed suicides were reported in any study. For the descriptive review, 20,131 adults and children received montelukast, 9,287 received placebo, and 8,346 received active control; AEs possibly related to suicidality were rare and were similar between the montelukast and placebo or active-control groups. For the adjudicated review across 22,433 patients, there were 730 adjudicated events. In 9,929 patients taking montelukast, 1 PSRAE was identified (classified as suicidal ideation); none were identified in 7,780 and 4,724 patients taking placebo and active control, respectively.

CONCLUSIONS

Assessed by using 2 complementary methods, there were no reports of completed suicide, and reports of PSRAEs were rare in patients receiving montelukast and similar to those seen in control subjects.

Analysis of behavior-related adverse experiences in clinical trials of montelukast

BACKGROUND

Frequencies of behavior-related adverse experiences (BRAEs) in controlled clinical studies of leukotriene modifier drugs have not been summarized.

OBJECTIVE

We sought to compare the frequency of BRAEs in patients receiving montelukast or placebo in a retrospective analysis of Merck clinical trial data.

METHODS

An adverse experience database was constructed to include all double-blind, placebo-controlled trials of montelukast meeting prespecified criteria. BRAEs (described using the Medical Dictionary for Regulatory Activities controlled vocabulary dictionary) were prespecified to include any term in the Psychiatric Disorders System Organ Class, selected terms related to general disorders, and terms related to akathisia. Frequencies of BRAEs (overall, leading to study discontinuation, and/or serious) were summarized. Analyses estimated the odds ratios (ORs) for montelukast versus placebo based on the frequency of patients with BRAEs in each study.

RESULTS

In total 35 adult and 11 pediatric placebo-controlled trials were included; 11,673 patients received montelukast, 8,827 received placebo, and 4,724 received active control. The frequency of patients with 1 or more BRAEs was 2.73% and 2.27% in the montelukast and placebo groups, respectively; the OR for montelukast versus placebo was 1.12 (95% CI, 0.93-1.36). The frequency of patients with a BRAE leading to study discontinuation was 0.07% and 0.11% in the montelukast and placebo groups, respectively (OR, 0.52; 95% CI, 0.17-1.51). The frequency of patients with a BRAE considered serious was 0.03% in both treatment groups.

CONCLUSION

Reports of BRAEs were infrequent in clinical trials of montelukast. Those leading to study discontinuation or considered serious were rare. Frequencies were similar regardless of treatment group.