Amygdaloid kindled seizures can induce functional and pathological changes in thymus of rat: role of the sympathetic nervous system

A "Drug-Dependent" Immune System Can Compromise Protection against Infection: The Relationships between Psychostimulants and HIV

Psychostimulant use is a major comorbidity in people living with HIV, which was initially explained by them adopting risky behaviors that facilitate HIV transmission. However, the effects of drug use on the immune system might also influence this phenomenon. Psychostimulants act on peripheral immune cells even before they reach the central nervous system (CNS) and their effects on immunity are likely to influence HIV infection. Beyond their canonical activities, classic neurotransmitters and neuromodulators are expressed by peripheral immune cells (e.g., dopamine and enkephalins), which display immunomodulatory properties and could be influenced by psychostimulants. Immune receptors, like Toll-like receptors (TLRs) on microglia, are modulated by cocaine and amphetamine exposure. Since peripheral immunocytes also express TLRs, they may be similarly affected by psychostimulants. In this review, we will summarize how psychostimulants are currently thought to influence peripheral immunity, mainly focusing on catecholamines, enkephalins and TLR4, and shed light on how these drugs might affect HIV infection. We will try to shift from the classic CNS perspective and adopt a more holistic view, addressing the potential impact of psychostimulants on the peripheral immune system and how their systemic effects could influence HIV infection.

Consequences of pilocarpine-induced status epilepticus in immunodeficient mice

Systemic injection of pilocarpine in rodents induces status epilepticus (SE) and reproduces the main characteristics of temporal lobe epilepsy (TLE). Different mechanisms are activated by SE contributing to cell death and immune system activation. We used BALB/c nude mice, a mutant that is severely immunocompromised, to characterize seizure pattern, neurochemical changes, cell death and c-Fos activation secondarily to pilocarpine-induced SE. The behavioral seizures were less severe in BALB/c nude than in BALB/c wild type mice. However, nude mice presented more tonic-clonic episodes and higher mortality rate during SE. The c-Fos expression was most prominent in the caudate-putamen, CA3 (p<0.05), dentate gyrus, entorhinal cortex (p<0.001), basolateral nucleus of amygdala (p<0.01) and piriform cortex (p<0.05) of BALB/c nude mice than of BALB/c. Besides, nude mice subjected to SE presented high number of Fluorojade-B (FJB) stained cells in the piriform cortex, amygdala (p<0.05) and hilus (p<0.001) in comparison with BALB/c mice. A significant increase in the level of glutamate and GABA was found in the hippocampus and cortex of BALB/c mice presenting SE in comparison to controls. However, the level of glutamate was higher in the brains of BALB nude mice than in the brains of BALB/c wild type mice, while the levels of GABA were unchanged. These results indicate that the brains of immunodeficient nude mice are more vulnerable to the deleterious effects of pilocarpine-induced SE as they present intense activation, increased glutamate levels and more cell death.

Treatment of epilepsy to optimize bone health

OPINION STATEMENT

When treating a person with epilepsy, one must consider many factors in addition to the obvious need to treat the seizures. Both epilepsy itself and treatment with antiepileptic drugs (AEDs) subject one to numerous potential secondary long-term health concerns. Poor bone health is one of these concerns. Studies suggest that persons with epilepsy treated with AEDs have an increased risk of fracture, low bone mineral density (BMD), and abnormalities in bone metabolism. Multiple factors likely contribute to the increased risk. Falls during generalized tonic-clonic seizures, secondary effects of AEDs on balance, inactivity, low BMD, reduced calcium intake, reduced active vitamin D metabolites, and a genetic predisposition to low BMD may all contribute. Studies suggest a differential influence of AEDs. Phenytoin, phenobarbital, and primidone are most consistently associated with a negative impact on bone. Carbamazepine and valproate may also result in bone abnormalities, but data are mixed. Current studies suggest that lamotrigine has limited (if any) effect, but again, data are inconsistent. Other AEDs have received limited study. Screening for poor bone health includes serologic testing of vitamin D metabolites (notably 25-hydroxyvitamin D) as well as BMD testing using dual energy x-ray absorptiometry. Optimizing intake of calcium and vitamin D is important for all persons with epilepsy treated with AEDs. Although many treatments for low BMD are available, these agents have not been studied in persons with epilepsy treated with AEDs. Overall, physicians treating persons with epilepsy must consider the potential effect of having epilepsy and its main treatment, AED therapy, on bone health. For patients in whom bone health is a particular concern (eg, those with diagnosed bone disease or with significant risk factors for bone disease, including glucocorticosteroid use), it is best to avoid AEDs known to negatively affect bone. In addition, practitioners should work with other treating physicians to optimize bone health in these patients.

Decrease of lymphoproliferative response by amphetamine is mediated by dopamine from the nucleus accumbens: influence on splenic met-enkephalin levels

Despite the mesocorticolimbic dopaminergic pathway being one of the main substrates underlying stimulating and reinforcing effects induced by psychostimulant drugs, there is little information regarding its role in their effects at the immune level. We have previously demonstrated that acute exposure to amphetamine (5 mg/kg, i.p.) induced an inhibitory effect on the splenic T-cell proliferative response, along with an increase in the methionine(met)-enkephalin content at limbic and immune levels, 4 days after drug administration. In this study, we investigated if a possible dopamine mechanism underlies these amphetamine-induced effects by administering D1 and D2 dopaminergic antagonists or a dopaminergic terminal neurotoxin before the drug. Pre-treatment with either SCH-23390 (0.1 mg/kg, i.p.) or raclopride (0.1 mg/kg, i.p.), a D1 or D2 dopaminergic receptor antagonist, respectively, abrogated the effects of amphetamine on the lymphoproliferative response and on met-enkephalin levels of the spleen. The amphetamine-induced increase in limbic met-enkephalin content was suppressed by SCH-23390 but not by raclopride pre-treatment. Finally, an intra-accumbens 6-hydroxy-dopamine injection administered 2 weeks previously prevented amphetamine-induced effects on the lymphoproliferative response and on met-enkephalin levels in the prefrontal cortex and spleen. These findings strongly suggest that D1 and D2 dopaminergic receptors are involved in amphetamine-induced effects at immune level as regards the lymphoproliferative response and the changes in spleen met-enkephalin content, whereas limbic met-enkephalin levels were modulated only by the D1 dopaminergic receptors. In addition, this study showed that a mesolimbic component modulated amphetamine-induced effects on the immune response, as previously shown at a behavioral level.

The role of the sympathetic nervous system in the thymus in health and disease

The existence of a network of immunoneuroendocrine interactions that results in the reciprocal modulation of the classical functions of each system is well established at present. Most of the evidence derives from studies on secondary lymphoid organs, such as the spleen and lymph nodes. In this article, several aspects relevant to understand the role of the sympathetic nervous system in the establishment of these interactions in the thymus are discussed. At present, the sympathetic innervation of the thymus, the expression of adrenergic receptors in thymic cells, particularly of β-adrenergic receptors, and the effect of sympathetic neurotransmitters, although mainly derived from in vitro or pharmacological studies, seem to be relatively well studied. However, other aspects, such as the relevance that immune-sympathetic interactions at the thymic level may have for certain diseases, specially autoimmune or other diseases that primarily involve the activation of the immune system, as well as how the integration of sympathetic and hormonal signals at local levels may affect thymic functions, certainly deserve further investigation.

Tac1 regulation by RNA-binding protein and miRNA in bone marrow stroma: Implication for hematopoietic activity

Hematopoiesis is the process by which immune and blood cells are produced from a finite number of relatively few hematopoietic stem cells (HSCs). In adults, hematopoiesis occurs in the adult bone marrow (BM), with the support of stromal cells. This support partly occurs through the production of hematopoietic regulators belonging to the families of cytokines and neuropeptides/neurotransmitters, which mediate their actions through specific receptors. Thus, stromal cells could be central to the neural-hematopoietic-immune axis. This study focuses on Tac1, which encodes hematopoietic regulators belonging to the tachykinin family of neuropeptides. We examined post-transcriptional regulation of Tac1 in BM stroma. Since this gene is inducible in stroma, we selected cytokines with varying hematopoietic effects: stimulator Stem Cell Factor (SCF), broad-acting IL-11 and suppressive TGF-beta1. RNA shift with Tac1 mRNA and cytoplasmic extracts from IL-11 and SCF-stimulated stroma showed RNA shift after 15min at 37 degrees C, whereas a shift was detected with extracts from TGF-beta1-stimulated stroma after 5min at room temperature. Another level of post-transcriptional regulation was observed by the detection of miRNAs that interact with the 3' untranslated region of Tac1 mRNA. In summary, this study showed that cytokine induced miRNA downregulation and RNA-binding protein(s) are involved in post-transcriptional regulation of Tac1 in BM stroma. The broad categories of cytokines as hematopoietic stimulators or inhibitors might depend on the avidity of RNA-binding protein(s) for Tac1 mRNA, as well as the ability to degrade or stabilize the specific miRNAs.

NK and CD4+ T cell changes in blood after seizures in temporal lobe epilepsy

Immunological phenomena may affect the course of focal epilepsy. We analyzed prospectively the pre- and postictal distribution of leukocyte subsets in epileptic patients.

METHODS

Twenty-two patients (age 36.6+/-10.8 years, 50% men) with temporal lobe epilepsy were included. Distribution of leukocyte subsets and serum levels of epinephrine were measured in peripheral blood immediately and 24 h after seizures and compared to baseline values.

RESULTS

In the immediate postictal state (10+/-6 min), we observed a significant relative increase of total leukocytes (42%, p=0.0004), neutrophil leukocytes (55%, p=0.0007), total lymphocytes (45%, p=0.0019), natural killer (NK) cells (104%, p=0.0017), and epinephrine (454%, p=0.0014). CD4(+) T cells decreased by 13% (p=0.0113). These postictal changes remained significant considering only complex partial seizures (n=17). The alterations were more pronounced in patients with hippocampal sclerosis. Treatment with valproic acid (VPA) was accompanied by a greater postictal decrease of CD4(+) T cells (25% compared to 5% in patients without VPA, p=0.041) while treatment with levetiracetam (LEV) correlated with a low postictal increase of NK-like T cells (4% versus 41%, p=0.016). Twenty-four hours after the seizures the alterations had resolved.

CONCLUSION

Profound postictal changes in the immune cell composition of the peripheral blood may have been mediated by epinephrine release. The greater immune response in patients with mesial temporal lobe epilepsy due to hippocampal sclerosis may reflect a close relationship between mesial temporal structures and the sympathetic nerve system. VPA and LEV may have an impact on seizure induced immunological changes.

Perspective is everything: an irreverent discussion of CNS-immune system interactions as viewed from different scientific traditions

The immune system is a host defense system comprised of both innate mechanisms able to rapidly recognize and respond to conserved pathogen associated molecular patterns (PAMPs) as well as adaptive mechanisms able to respond to a wide variety of non-conserved and conserved pathogen associated molecules. In vitro and in vivo studies have demonstrated that the kinetics and type of immune response triggered by pathogenic insults is a function of both the nature of the insult and the subsequent cross-regulatory interactions between the responding immune cells. In this context, the potential immunomodulatory influences of the nervous system have been often viewed as exerting minimal modulatory effects and thus of being largely irrelevant in the development of immune responses. Here, using a Saturday Night Live (SNL)-styled point:counterpoint format, we discuss whether and to what extent the nervous system can shape the responses of the immune system. Finally, we examine whether primary degenerative disorders of the CNS are likely to lead to alterations in immune function.