Peripheral benzodiazepine receptor expression on leukocytes and neutrophil function during anticonvulsant monotherapy

N-Formyl-Methionyl-Leucyl-Phenylalanine Plays a Neuroprotective and Anticonvulsant Role in Status Epilepticus Model

Status epilepticus (SE) is described as continuous and self-sustaining seizures, which triggers hippocampal neurodegeneration, inflammation, and gliosis. N-formyl peptide receptor (FPR) has been associated with inflammatory process. N-formyl-methionyl-leucyl-phenylalanine (fMLP) peptide plays an anti-inflammatory role, mediated by the activation of G-protein-coupled FPR. Here, we evaluated the influence of fMLP peptides on the behavior of limbic seizures, memory consolidation, and hippocampal neurodegeneration process. Male Wistar rats (Rattus norvegicus) received microinjections of pilocarpine in hippocampus (H-PILO, 1.2 mg/μL, 1 μL) followed by fMLP (1 mg/mL, 1 μL) or vehicle (VEH, saline 0.9%, 1 μL). During the 90 min of SE, epileptic seizures were analyzed according to the Racine's Scale. After 24 h of SE, memory impairment was assessed by the inhibitory avoidance test and the neurodegeneration process was evaluated in hippocampal areas. There was no change in latency and number of wet dog shake (WDS) after administration of fMLP. However, our results showed that the intrahippocampal infusion of fMLP reduced the severity of seizures, as well as the number of limbic seizures. In addition, fMLP infusion protected memory dysfunction followed by SE. Finally, the intrahippocampal administration of fMLP attenuated the process of neurodegeneration in both hippocampi. Taken together, our data suggest a new insight into the functional role of fMLP peptides, with important implications for their potential use as a therapeutic agent for the treatment of brain disorders, such as epilepsy. Schematic drawing on the neuroprotective and anticonvulsant role of fMLP during status epilepticus. Initially, a cannula was implanted in hippocampus and pilocarpine/saline was administered into the hippocampus followed by fMLP/saline (A-C). fMLP reduced seizure severity and neuronal death in the hippocampus, as well as protecting against memory deficit (D).

The impact of histone deacetylase inhibitors on immune cells and implications for cancer therapy

Many cancers possess the ability to suppress the immune response to malignant cells, thus facilitating tumour growth and invasion, and this has fuelled research to reverse these mechanisms and re-activate the immune system with consequent important therapeutic benefit. One such approach is to use histone deacetylase inhibitors (HDACi), a novel class of targeted therapies, which manipulate the immune response to cancer through epigenetic modification. Four HDACi have recently been approved for clinical use in malignancies including multiple myeloma and T-cell lymphoma. Most research in this context has focussed on HDACi and tumour cells, however, little is known about their impact on the cells of the immune system. Additionally, HDACi have been shown to impact the mechanisms by which other anti-cancer therapies exert their effects by, for example, increasing accessibility to exposed DNA through chromatin relaxation, impairing DNA damage repair pathways and increasing immune checkpoint receptor expression. This review details the effects of HDACi on immune cells, highlights the variability in these effects depending on experimental design, and provides an overview of clinical trials investigating the combination of HDACi with chemotherapy, radiotherapy, immunotherapy and multimodal regimens.

Valproic acid inhibits interferon-γ production by NK cells and increases susceptibility to Listeria monocytogenes infection

Valproic acid (VPA) is a drug commonly used for epileptic seizure control. Recently, it has been shown that VPA alters the activation of several immune cells, including Natural Killer (NK) cells, which play an important role in the containment of viruses and intracellular bacteria. Although VPA can increase susceptibility to extracellular pathogens, it is unknown whether the suppressor effect of VPA could affect the course of intracellular bacterial infection. This study aimed to evaluate the role of VPA during Listeria monocytogenes (L.m) infection, and whether NK cell activation was affected. We found that VPA significantly augmented mortality in L.m infected mice. This effect was associated with increased bacterial load in the spleen, liver, and blood. Concurrently, decreased levels of IFN-γ in serum and lower splenic indexes were observed. Moreover, in vitro analysis showed that VPA treatment decreased the frequency of IFN-γ-producing NK cells within L.m infected splenocytes. Similarly, VPA inhibited the production of IFN-γ by NK cells stimulated with IL-12 and IL-18, which is a crucial system for early IFN-γ production in listeriosis. Finally, VPA decreased the phosphorylation of STAT4, p65, and p38, without affecting the expression of IL-12 and IL-18 receptors. Altogether, our results indicate that VPA increases the susceptibility to Listeria monocytogenes infection and suggest that NK cell is one of the main targets of VPA, but further work is needed to ascertain this effect.

Exploring the Drug Repurposing Versatility of Valproic Acid as a Multifunctional Regulator of Innate and Adaptive Immune Cells

Valproic acid (VPA) is widely recognized for its use in the control of epilepsy and other neurological disorders in the past 50 years. Recent evidence has shown the potential of VPA in the control of certain cancers, owed in part to its role in modulating epigenetic changes through the inhibition of histone deacetylases, affecting the expression of genes involved in the cell cycle, differentiation, and apoptosis. The direct impact of VPA in cells of the immune system has only been explored recently. In this review, we discuss the effects of VPA in the suppression of some activation mechanisms in several immune cells that lead to an anti-inflammatory response. As expected, immune cells are not exempt from the effect of VPA, as it also affects the expression of genes of the cell cycle and apoptosis through epigenetic modifications. In addition to inhibiting histone deacetylases, VPA promotes RNA interference, activates histone methyltransferases, or represses the activation of transcription factors. However, during the infectious process, the effectiveness of VPA is subject to the biological nature of the pathogen and the associated immune response; this is because VPA can promote the control or the progression of the infection. Due to its various effects, VPA is a promising alternative for the control of autoimmune diseases and hypersensitivity and needs to be further explored.

Interleukin-8 production induced by the endozepine triakontatetraneuropeptide in human neutrophils: role of calcium and pharmacological investigation of signal transduction pathways

The endozepine triakontatetraneuropeptide (TTN) induces intracellular calcium ([Ca(2+)](i)) changes and is chemotactic for human neutrophils (PMNs). Because interleukin-8 (IL-8) production is Ca(2+) dependent and can be induced by chemotactic stimuli, we have investigated the ability of TTN to induce IL-8 production in PMNs, as well as the signal transduction mechanisms involved. Our results show that TTN increases IL-8 release and IL-8 mRNA expression in a concentration- and time-dependent fashion, and these effects are prevented by the Ca(2+) chelator BAPTA-AM. TTN-induced [Ca(2+)](i) changes and IL-8 mRNA expression are sensitive to pertussis toxin, to the phospholipase C (PLC) inhibitor U73122 (but not to its inactive analogue U73343) and to the protein kinase C (PKC) inhibitor calphostin C. It is therefore suggested that TTN-induced IL-8 production in human PMNs results from a G protein-operated, PLC-activated [Ca(2+)](i) rise, and PKC contributes to this effect. These findings further support the possible role of TTN in the modulation of the inflammatory processes.

Diazepam stimulates migration and phagocytosis of human neutrophils: possible contribution of peripheral-type benzodiazepine receptors and intracellular calcium

In isolated human neutrophils, diazepam (10 nmol/l to 10 micromol/l) concentration-dependently increased migration and phagocytosis. Diazepam-induced migration and phagocytosis were inhibited by the peripheral benzodiazepine receptor (PBR) antagonist PK11195 (10 micromol/l). The PBR agonist Ro5-4864 (10 nmol/l to 10 micromol/l) did not affect migration but slightly enhanced phagocytosis, while clonazepam, which binds to the central-type benzodiazepine receptors but has no affinity for PBRs, was ineffective on both parameters up to 10 micromol/l. Phagocytosis induced by diazepam or Ro5-4864 was inhibited by the Ca2+ channel blocker L-verapamil (10 micromol/l), which however did not affect the action of diazepam on migration. Competition binding experiments performed by fluorescent staining of PBRs showed that diazepam directly interacts with PBRs on human neutrophils. Both diazepam and Ro5-4864 (10 nmol/l to 10 micromol/l) induced a rise of intracellular free Ca2+ concentrations ([Ca2+]i), which was inhibited by PK11195 (10 micromol/l) and L-verapamil (10 micromol/l) and prevented by extracellular Ca2+ chelation with EGTA (5 mmol/l). In conclusion, experimental evidence indicates that in human neutrophils diazepam stimulates both migration and phagocytosis through activation of PBRs. Diazepam-induced [Ca2+]i changes depend on a PBR-operated, L-verapamil-sensitive increase in the plasma membrane permeability and subsequent extracellular Ca2+ entry, and contribute to diazepam-induced phagocytosis. On the contrary, the effect of diazepam on migration seems to occur through Ca2+ -independent mechanisms.

Increased expression of peripheral benzodiazepine receptors on leukocytes in silent myocardial ischemia

OBJECTIVES

The purpose of this study was to evaluate benzodiazepine receptor expression on leukocytes from patients with symptomatic or silent myocardial ischemia.

BACKGROUND

Silent myocardial ischemia is frequently observed in patients with coronary artery disease. Pain can be effectively controlled by various endogenous mechanisms. Benzodiazepines and their receptors play key roles in pain, in interactions with peptide opioids, in inflammation and in the response to stress.

METHODS

The study group consisted of 57 patients with reproducible exercise-induced myocardial ischemia. The presence of a constant behavior in the anginal pain perception during both exercise-induced ischemia and daily life was the most important inclusion criterion. Venous blood samples were taken from all patients to evaluate the expression of peripheral benzodiazepine receptors by flow cytometry. The study cohort was classified into two groups: 24 patients who had anginal pain both at home and during the exercise stress test and 33 patients who were asymptomatic during both daily life and exercise-induced ischemia.

RESULTS

Flow cytometry analysis showed increased expression of peripheral benzodiazepine receptors on all types of leukocytes in the asymptomatic patients. The difference was statistically significant for lymphocytes (p < 0.005), monocytes (p < 0.001) and granulocytes (p < 0.001).

CONCLUSIONS

These data show that expression of peripheral benzodiazepine receptors was higher in patients with silent myocardial ischemia than in symptomatic patients.