Brain lateralization and immunomodulation

From cytoskeletal dynamics to organ asymmetry: a nonlinear, regulative pathway underlies left-right patterning

Consistent left-right (LR) asymmetry is a fundamental aspect of the bodyplan across phyla, and errors of laterality form an important class of human birth defects. Its molecular underpinning was first discovered as a sequential pathway of left- and right-sided gene expression that controlled positioning of the heart and visceral organs. Recent data have revised this picture in two important ways. First, the physical origin of chirality has been identified; cytoskeletal dynamics underlie the asymmetry of single-cell behaviour and patterning of the LR axis. Second, the pathway is not linear: early disruptions that alter the normal sidedness of upstream asymmetric genes do not necessarily induce defects in the laterality of the downstream genes or in organ situs Thus, the LR pathway is a unique example of two fascinating aspects of biology: the interplay of physics and genetics in establishing large-scale anatomy, and regulative (shape-homeostatic) pathways that correct molecular and anatomical errors over time. Here, we review aspects of asymmetry from its intracellular, cytoplasmic origins to the recently uncovered ability of the LR control circuitry to achieve correct gene expression and morphology despite reversals of key 'determinant' genes. We provide novel functional data, in Xenopus laevis, on conserved elements of the cytoskeleton that drive asymmetry, and comparatively analyse it together with previously published results in the field. Our new observations and meta-analysis demonstrate that despite aberrant expression of upstream regulatory genes, embryos can progressively normalize transcriptional cascades and anatomical outcomes. LR patterning can thus serve as a paradigm of how subcellular physics and gene expression cooperate to achieve developmental robustness of a body axis.This article is part of the themed issue 'Provocative questions in left-right asymmetry'.

Lateralization of Squamous Cell Carcinomas in the Head-Neck Region

Earlier studies have shown the lateralization of several immune disorders, including herpes zoster infection and breast cancer. We investigated whether there is lateralization of squamous cell carcinomas in the head-neck region and a relation of handedness with this cancer. Analysis showed right-sided lateralization of head-heck cancers in right-handed patients and vice versa in left-handed ones and a higher rate of left-handedness in patients with squamous cell cancer. Associations among left-handedness, squamous cell carcinoma, and its lateralization may result from a genetic togetherness.

Immunological functioning in Alzheimer's disease: differential effects of relative left versus right temporoparietal dysfunction

The cerebral hemispheres are differentially involved in regulating immunological functioning and the neuropathology associated with Alzheimer's disease (AD) is asymmetrical. Thus, subgroups of AD patients may exhibit different patterns of immunological dysfunction. We explored this possibility in a group of AD patients and found that patients with low white blood cell counts and low lymphocyte numbers exhibited better performance on tests of right temporoparietal functioning. Also, a significant positive relationship exists between lymph numbers and performance on a test of left temporoparietal functioning. Thus, some AD patients have greater immunological dysfunction based on relative left versus right temporoparietal functioning.

The differential contribution of dopamine D(1) and D (2) receptors to mu-opioidergic immunomodulation

Activation of mu-opioid receptors (mu-OR) by the highly selective agonist DAGO (100 microg/kg) significantly increased the immune response in CBA mice. This effect of the mu agonist was prevented by prior blockade of dopamine D(2) receptors with haloperidol (2 mg/kg). In contrast, the selective D(1) receptor antagonist SCH 23390 (1 mg/kg) had no effect on the nature of the immune reaction in response to antigen (sheep erythrocytes, 5 x 10(8) cells). However, blockade of both types of dopamine receptor led to the same effect--immunosuppression. These data lead to the suggestion that D(1) and D(2) receptors make different contributions to modulating immunogenesis on activation of mu-OR.

The effect of a naturalistic stressor on frontal EEG asymmetry, stress, and health

The aim of the current study was to investigate the effect of a naturalistic stressor, examination stress, on frontal EEG asymmetry, psychological stress, hormonal stress, and negative health. Forty-nine subjects were tested during periods of low and high examination stress. During the high examination stress period, subjects reported higher levels of stress on the Spielberger State Anxiety Inventory and Cohen's Perceived Stress Scale. However, no change in cortisol was detected across the two sessions. Furthermore, a shift from relatively greater left frontal activity during the low examination session to relatively greater right frontal activity during the high examination session was also found. Moreover, the increasing right frontal activity asymmetry associated with the high exam session compared to the low exam session correlated with increasing reports of negative health. No evidence was found for the prediction that cortisol mediated either the relationship between examination stressor and right frontal asymmetry or between right frontal asymmetry and negative health. In conclusion, while the findings from this study are compelling, the mechanism mediating increases in psychological stress, relatively greater right frontal activity, and increases in negative health from naturally occurring stressors is in need of further investigation.

Nature of the distribution of serotonin and a serotonin metabolite in brain structures and the development of immunosuppression in submissive mice

Studies of C57BL/6J mice with acquired submissive behavior in a sensory contact model demonstrated increases in serotonin (5-HT) levels in the amygdaloid complex, hippocampus, the dopaminergic nuclei A11, A10, and A9, and in the caudate nucleus and hypothalamus, compared with controls, after 10 and 20 days of confrontations. Levels of the 5-HT metabolite 5-hydroxyindoleacetic acid (5-HIAA) in most structures were significantly higher after 20 days of confrontations than after 10 days. Increases in the 5-HIAA/5-HT ratio in the cervical nuclei of the midbrain, nucleus accumbens, A9, and hypothalamus as compared with controls were seen in mice with 10 and 20 days of confrontations. Immunization of mice on days 10 and 20 of confrontations showed suppression of immune responses as compared with controls, while immune measures reached control values by 40 days of experience of defeat. Thus, experience of 10 days of defeat led to immunosuppression on a background of activation of the 5-HT system in a series of brain structures: the cervical nuclei of the midbrain, the nucleus accumbens, and A9. As confrontations continued, there were decreases in the 5-HIAA/5-HT ratio on these structures, along with a tendency for immune responses to increase.

An investigation into asymmetrical cortical regulation of salivary S-IgA in conscious man using transcranial magnetic stimulation

Transcranial magnetic stimulation (TMS) can activate discrete areas of the cerebral cortex through the intact skull of healthy conscious volunteers. A magnetic coil generates a brief and focused magnetic field that penetrates the skull to activate the specific area of cerebral cortex beneath. This non-invasive procedure is painless, well tolerated by participants and now widely used to explore brain function. We used TMS to investigate asymmetrical cortical regulatory influences on one aspect of immune function: secretion of the antibody immunoglobulin A (S-IgA) into saliva. The right and left temporo-parietal-occipital cortex of 16 healthy, conscious subjects was stimulated on two different occasions, at least 1 week apart. There was an immediate increase in S-IgA concentration following both right and left stimulation. Saliva volume was reduced immediately post-right but not left stimulation. When secretion (microg/min) of S-IgA was calculated (controlling for changing saliva volume) an increase was apparent following left but not right hemisphere stimulation. Furthermore, a significant difference between the relationship between S-IgA concentration and volume of saliva post-left and right stimulation was observed. We conclude that TMS can be used as a tool to investigate cortical regulation of autonomic and immune function in healthy, conscious human subjects and that secretion of saliva and S-IgA is differentially affected by stimulation of the left and right cerebral cortex.

Prenatal disturbance alters the size of the corpus callosum in young monkeys

Many factors during fetal life and early infancy have been found to affect the development of the brain. The following study investigated whether maternal stress during pregnancy would influence the size and shape of one sensitive brain region, the corpus callosum, in infant monkeys. For 30% of the gestation period, from Days 90 to 140 postconception, gravid females were disturbed using an acoustical startle protocol for 10 min per day. Magnetic resonance imaging was then employed to obtain sagittal and coronal scans of their infants' brains. Morphometric measures of the corpus callosum were compared in 16 monkeys (5 controls and 11 from disturbed pregnancies). Prenatal conditions altered the corpus callosum, but in a differential manner for male and female monkeys. Based on the midsagittal and parasagittal scans, prenatally disturbed male offspring showed a decrease in overall size of the corpus callosum whereas the prenatal disturbance resulted in an increased area in females. An evaluation of callosal height from the coronal images suggested that the volumetric change was associated with a shift in anterior-to-posterior shape from the genu back toward the splenium. These findings concur with observations in other animals and humans, which have indicated that prenatal and postnatal factors can influence the development of the corpus callosum, possibly affecting communication between the hemispheres.

Environmental stress mediates changes in neuroimmunological interactions

Combinations of environmental stress coordinately increase toxicological assaults on health, dependent on the genetics of the exposed organism. Multiple gene variances between individuals influence the risks associated with environmental exposures, and environmental stress presents in multiple forms including chemical, physical, and psychological stresses. Combined chemical, physical, and psychological stresses are suggested as exacerbating the initiation and/or duration of illnesses, and many of the detrimental outcomes on health are posited to relate to changes in neuroendocrine immune circuitry. However, most human epidemiological or experimental animal studies have not considered the combination of chemical, physical, and psychological stress on health status. Current consideration is being given to "real world" exposures for assessment of health risk, but this mainly relates to evaluation of chemical mixtures. In addition to concomitant chemical exposures having agonistic and/or antagonistic interactions, the physical and psychological status of the individual can influence exposure outcomes. An individual's psychosocial environment is likely to be important in epidemiological investigations. Neuroimmunology is a burgeoning discipline, and neurotoxicology and immunotoxicology studies should consider the bidirectional regulatory mechanisms between these organ systems and the potential long-term influences of psychological stress. This mini-review discusses some intriguing data from animal and human studies, which address the regulatory pathways between the neural, endocrine, and immune systems, with emphasis on psychological stress.

Schizophrenia and viral infection during neurodevelopment: a focus on mechanisms

The task of defining schizophrenia pathogenesis has fascinated and frustrated researchers for nearly a century. In recent years, unprecedented advances from diverse fields of study have given credence to both viral and developmental theories. This review considers possible mechanisms by which viral and developmental processes may interact to engender schizophrenia. Many of the current controversies in schizophrenia pathogenesis are reviewed in light of the viral hypothesis, including: epidemiological findings and the role of a genetic diathesis, phenotype heterogeneity, abnormalities in excitatory and inhibitory neurotransmitter systems, anomalous cerebral latereralization, and static vs progressive disease. The importance of animal models in elucidating the impact of viral infections on developing neurons is illustrated by recent studies in which neonatal rats are infected with lymphocytic choriomeningitis virus in order to examine alterations in hippocampal circuitry. Finally, consideration is given to a new hypothesis that some cases of schizophrenia could be instigated by a viral infection that disrupts developing inhibitory circuits, consequently unleashing glutamatergic neurotransmission leading to selective excitotoxicity, and a degenerative disease course.

Cellular and humoral immunity, mood and exam stress: the influences of self-hypnosis and personality predictors

The effects of self-hypnosis training on immune function and mood were examined in medical students at exam time. Hypnosis involved relaxation and imagery directed at improved immune function and increased energy, alertness and concentration. Hypotheses were made about activated and withdrawn personality differences. Eight high and eight low hypnotically susceptible participants were given 10 sessions of hypnosis, one live and nine tape-recorded, and were compared with control subjects (N=12). CD3, CD4, CD8, CD19 and CD56 NK cells and blood cortisol were assayed. Life-style, activated vs. withdrawn temperament, arousal and anxiety questionnaires were administered. Self-hypnosis buffered the decline found in controls in NK (P<0.002) and CD8 cells (P<0.0.07) and CD8/CD4% (P<0.06) (45-35% order of magnitude differences) while there was an increase in cortisol (P<0.05). The change in NK cell counts correlated positively with changes in both CD8 cells and cortisol. Results were independent of changes in life-style. Energy ratings were higher after hypnosis (P<0.01), and increased calmness with hypnosis correlated with an increase in CD4 counts (P<0.01). The activated temperament, notably the cognitive subscale (speaking and thinking quickly), was predictive of exam levels of T and B lymphocytes (P&z.Lt;0.08-P<0.02), and reaching r=0.72 (P<0.001) in the non-intervention control group. The sizeable influences on cell-mediated immunity achieved by a relatively brief, low cost psychological intervention in the face of a compelling, but routine, stress in young, healthy adults have implications for illness prevention and for patients with compromised immunity.

Lateralized EEG findings in patients with neuropsychiatric manifestations of systemic lupus erythematosus

Routine and quantitative EEG were used to determine whether there is a lateralized pattern of electrophysiologic dysfunction in patients with diverse neuropsychiatric manifestations of SLE. Twenty consecutive patients with neuropsychiatric symptoms of SLE underwent 20-minute EEG recordings with an 18-channel polygraph. Ten 1-second intervals were randomly selected for each patient. Once selected, the intervals were analyzed for the presence of theta and delta slow activity. Mapping was done by four-point interpolation around the 18 acquired data points. On routine EEG, abnormalities were identified in 14/20 patients with SLE. In 12/14 patients, the abnormalities were localized to the left temporal region. Quantitative EEG analyses revealed theta and delta slow activity predominantly affecting the left hemisphere in 16/19 patients with SLE. Taken together, these findings suggest selective involvement of the left hemisphere in patients with diverse neuropsychiatric manifestations of SLE.

Bilateral injections of amyloid-beta 25-35 into the amygdala of young Fischer rats: behavioral, neurochemical, and time dependent histopathological effects

To examine the time course of the histopathological effects of bilateral injections of amyloid-beta 25-35 (A beta) and to determine if these effects are associated with a reduction in choline acetyltransferase activity and behavioral impairments, we injected A beta (5.0 nmol) into the amygdala of young male Fischer rats. Control rats received vehicle infusions. For histological analysis, animals were sacrificed at 8, 32, 64, 96, and 128 days postoperatively (n = 21-33 per timepoint). A beta induced neuronal tau-2 staining in the right, but not the left amygdala and hippocampus. A beta also induced reactive astrocytosis and neuronal shrinkage within the right hippocampus and amygdala, respectively. As with tau-2, these same brain regions within the left hemisphere in the A beta-treated rats were significantly less affected. In addition, A beta appeared to induce microglial and neuronal interleukin-1beta staining. The histopathological effects of A beta peaked at 32 days postoperatively but were not associated with a reduction in amygdaloid choline acetyltransferase activity. In a separate experiment, behavioral effects of bilateral intra-amygdaloid injections of A beta were analyzed at 34-52 days postoperatively. In an open field test, the treatment groups differed only in the numbers of rears emitted (p = 0.016). There was no effect of A beta in the Morris water maze or in the acquisition and retention of a one-way conditioned avoidance response. These data suggest a laterality in the histopathological effects of A beta and that the effects of single injections are in part transient. These findings also suggest a direct association between plaque and tangle formation in Alzheimer's disease, and support the use of this rat model to screen drugs that may alter the initial pathological events associated with Alzheimer's disease, that occur before the manifestations of extensive behavioral impairments become evident.

Prospective associations between lateralised brain function and immune status in HIV infection: analysis of EEG, cognition and mood over 30 months

Prospective relations between individual differences in both lateralised neuro-psychophysiological functions and mood ratings with immune status (CD4 and CD8 counts) were examined in asymptomatic HIV-positive men (n = 27) over thirty months. They participated in a controlled study of zidovudine versus placebo (results published elsewhere). Measures included EEG spectra, neuropsychological tests and mood ratings. A model of reciprocal lateralised influences on the immune system was tested whereby patients with left superior to right hemispheric functions were predicted to show a less deleterious outcome than those with the opposite asymmetry pattern. Prospective relations with immune status were found in the EEG with lateralised theta, alpha and beta activity; among cognitive measures with word fluency, semantic processing, and lateralised motor and recognition memory (word/face) processes; with mood ratings including depression, confusion and the total mood score. The nature of the effects supported the laterality predictions. These unique data, showing that neuro-psychophysiological factors in HIV+ but otherwise healthy subjects predict immune competence and compromise present 2-3 years later, warrant replication in a larger cohort.

Asymmetrical modulation of immune reactivity in left- and right-biased rats after ipsilateral ablation of the prefrontal, parietal and occipital brain neocortex

We report here on the lateralized brain immunomodulation in male Wistar rats, a phenomenon related to the rotational bias of animal and the site of cortical lesion. Rats assigned to left- and right-rotators in a cylindrical Plexiglass rotometer were subjected to the ablation of the ipsilateral prefrontal cortex (PFC), parietal cortex (PC) and occipital cortex (OC) and sensitized with bovine serum albumin (BSA) in complete Freund's adjuvant. Intact and sham-lesioned left-biased animals demonstrated increased Arthus and delayed hypersensitivity skin reactions and antibody production to BSA in comparison with corresponding right-biased animals. PFC ablation decreased humoral and cellular immune responses to BSA in left- but increased in right-biased rats. Lesioning of PC decreased humoral immune reactions in left- but increased in right-rotating animals. OC ablation failed to produce immunological abnormalities. These results suggest that immunopotentiation is associated with the left neocortex, and immunosuppression with the right neocortex. The prefrontal cortex appears to be particularly associated with immune reactions.

Behavioral and immunological events induced by electrical stimulation of the rat midbrain periaqueductal gray region

We report here on the immunological and behavioral alterations induced by stimulation of the mesencephalic periaqueductal gray matter (PAG), a component of the brain aversive system. Male Wistar rats were implanted with stimulating electrodes in the caudal dorsolateral part of the PAG. After recovery, animals were screened for aversive behavior, characterized by running, jumping, vocalization or freezing reaction. Then, rats were subdivided to those which could control aversive stimulation (AS) by switch-off response (cAS group) and those which could not interrupt AS (uAS group). After sensitization with bovine serum albumin (BSA) in complete Freund's adjuvant, rats were stimulated 3 times/week for 40 days, each session lasting 30 min/rat. Immunological assessment included antibody production and hypersensitivity skin reactions to BSA 14 and 21 days after immunization. A behavioral profile of aversively stimulated animals was determined by a poststartle response, open field (OF) activity and two-way shuttle-box avoidance task. The results revealed elevated antibody production to BSA in cAS and lowered in uAS rats, compared to sham-stimulated and intact controls. Arthus and delayed hypersensitivity skin reactions increased in PAG-stimulated animals on day 14 but not on day 21 after immunization. Poststartle response was enhanced both in cAS and uAS rats. Along with immunopotentiation, administration of cAS produced hyperactivity in OF test and facilitation of the active avoidance learning, whereas uAS caused only moderate suppression of rearing in a novel OF environment. Physiological implications and possible mechanisms that may account for PAG-mediated immunobehavioral changes are outlined.