Cytokine variations within brain structures in rats selected for differences in aggression.

The present study examined the content of cytokines (IL-1ß, IL-2, IL-6, IL-10) in the brain structures (the hypothalamus, striatum, frontal cortex, and hippocampus) in two rat lines selected for differences in fear-induced aggression at 2, 4, and 24 h after a peripheral injection of saline or lipopolysaccharide (LPS, 250 µg/kg). LPS stimulation elevated cytokine activity above baseline levels in both aggressive and nonaggressive rats, but the pattern, time course of cytokine changes, and their regional characteristics varied according to the animal aggressiveness. After LPS administration, aggressive rats showed increased levels of IL-1ß in the hypothalamus at 2 and 4 h and in the frontal cortex at 4 and 24 h compared to LPS-treated nonaggressive line. IL-2 was increased in the frontal cortex and striatum of aggressive rats within 24 h, while IL-6 elevation in the hypothalamus was found at 4 h and in the frontal cortex at 2 and 4 h. In the hippocampus, the levels of IL-1ß, IL-2, and IL-6 were lower in LPS-treated aggressive rats than in nonaggressive animals. The levels of anti-inflammatory cytokine IL-10 were also decreased in all brain structures of aggressive rats receiving LPS. The results indicate that genetic predisposition to increased aggression is associated with a time and region-dependent changes in the levels of pro- and anti-inflammatory cytokines.

Changes in plasma steroids and cytokines levels in betel chewing patients in Taiwan.

Betel nut is the second largest economic food product in Taiwan. In Southeast Asia, the habit of chewing betel nut seems to be highly correlated with oral submucous fibrosis and oral squamous cell carcinoma. Oral submucous fibrosis is characterized by abnormal accumulation of oral submucous collagen fibers and limitation of mouth opening. Although the mechanism responsible for tissue damage is still unknown, prolonged irritation caused by betel nut and tobacco is considered to be a major factor contributing to the pathogenesis of oral submucous fibrosis. The effect of betel nut chewing on immune system remains unknown. Present study aims to investigate the change of plasma hormones including cortisol, testosterone, and inflammatory cytokine concentrations in male chewing betel nut compared with normal subjects. Heparinized blood was obtained from control group (normal young+mid-aged individuals), betel nut-chewing, and oral cancer male subjects. The study was approved by the Ethics Committee of the Chang-Gung Memorial Hospital. Written informed consent was granted by the patients. Plasma cortisol and testosterone concentrations were detected by commercial enzyme-linked immunosorbent assay (ELISA). The inflammatory cytokines, including interleukin-1ß (IL-1ß), IL-15, tumor necrosis factor-α (TNF-α), were analyzed by ELISA with commercial monoclonal capture antibodies and polyclonal detection antibodies. The median concentrations of plasma IL-1ß, IL-15, and TNF-α were 3.14pg/ml, 3.14pg/ml, and 6.85pg/ml, respectively, in patients with oral cancer, compared with median plasma IL-1ß, IL-15, and TNF-α concentration of 2.64pg/ml, 5.86pg/ml, and 5.38pg/ml, respectively, in patients with betel nut-chewing habit. In contrast, the median concentrations of plasma IL-1ß, IL-15, and TNF-α in mid-aged males (aged 30-50) were 7.00pg/ml, 10.64pg/ml, and 31.73pg/ml, respectively, compared with median plasma concentration of IL-1ß, IL-15, and TNF-α of 4.48pg/ml, 33.36pg/ml, and 97.77pg/ml in young males (aged 20-22), respectively. Also, significantly elevated plasma cortisol concentration was noted in betel nut-chewing (median 727.2ng/ml) and oral cancer patients (561.9ng/ml) compared to the mid-aged (176.8ng/ml) and young males (173.4ng/ml), respectively. In addition, lower plasma testosterone concentrations were found in betel nut-chewing subjects compared with young males (2.6±3.3ng/ml vs 6.2±2.9ng/ml). To summarize, the inflammatory cytokines and steroid hormones may reflect the degree of inflammation in betel nut-chewing males and the oral cancer subjects. The above findings suggest that betel nut-chewing or oral cancer inhibits plasma cytokines and regulates steroid hormones concentrations compared to mid-aged or young normal subjects. It is also indicated that betel nut-chewing causes decreased inflammatory cytokines as the same levels as in oral cancer subjects.

Role of testosterone in regulating induction of TNF-α in rat spleen via ERK signaling pathway.

Spleen is a pivotal organ for regulating immune homeostasis. It has been shown that testosterone diminishes secretion of various inflammatory molecules under multiple conditions. However, the mechanisms of action of endogenous testosterone affecting immune responses in the spleen remain unknown. The aim of the present study was to evaluate the immune functions of the spleen in response to testosterone withdrawal after orchidectomy, and the impact of splenocytes on the bacterial endotoxin lipopolysaccharide (LPS)-induced secretion of inflammatory molecules. Male rats were divided into 3 groups, i.e. intact, orchidectomized (Orch) and orchidectomized plus replacement of testosterone propionate (TP) (Orch+TP). The Orch and Orch+TP rats underwent bilateral orchidectomy one week before TP replacement (2mg/kg body weight) or sesame oil in intact rats as controls for seven days. Orch resulted in a significant increase of spleen weight and basal secretion of nitric oxide (NO) from splenocytes. Additionally, LPS up-regulated cell proliferation and the secretion of tumor necrosis factor-alpha (TNF-α) in splenocytes of Orch rats. Orch further up-regulated phosphorylation of extracellular signal-regulated kinases. Interestingly, the plasma corticosterone concentration in the Orch group was higher than that in the intact and Orch+TP groups. Deficiency of testosterone-elevated TNF-α and NO secretion in response to LPS were confirmed in the rat splenocytes. Testosterone also significantly attenuated LPS-elicited release of TNF-α and NO in a dose-dependent manner. However, testosterone did not suppress splenic blastogenesis at doses in the 10(-10)-10(-7)M concentration range. In this context, testosterone might have a protective role against inflammatory responses in the spleen. The present study provides evidence to indicate that testosterone might modulate the immune system.

Effects of acrolein on the production of corticosterone in male rats.

Acrolein, an α, ß-unsaturated aldehyde, exists in a wide range of sources. Acrolein can be not only generated from all types of smoke but also produced endogenously from the metabolism by lipid peroxidation. The cellular influence of acrolein is due to its electrophilic character via binding to and depleting cellular nucleophiles. Although the toxicity of acrolein has been extensively studied, there is relatively little information about its impact on hormone release. This study aimed at the effect of acrolein on hypothalamic-pituitary-adrenal (H-P-A) axis. In an in vivo study, male rats were administrated with acrolein for 1 or 3days. The plasma corticosterone in response to a single injection of adrenocorticotropic hormone (ACTH) increased slowly in acrolein-pretreated rats than in control rats. Further investigating the steroidogenic pathway, the protein expressions of steroidogenic acute regulatory protein (StAR) and the upper receptor-melanocortin 2 receptor (MC2R) were attenuated in acrolein-treated groups. Another experiment using trilostane showed less activity of P450scc in zona fasciculata-reticularis (ZFR) cells in acrolein-treated groups. In addition to the suppressed ability of corticosterone production in ZFR cells, acrolein even had extended influence at higher concentrations. The lower ACTH was observed in the plasma from acrolein-pretreated rats. In an in vitro study, ZFR cells were incubated with acrolein and the results showed that corticosterone concentrations in media were decreased in a dose-dependent manner. Acrolein also desensitized the response of the ZFR cells to ACTH. These results suggested that acrolein decreased the releasing ability of corticosterone via an inhibition on the response of ZFR cells to ACTH and the reduction of protein expressions of StAR and MC2R as well as the activity of P450scc in rat ZFR cells. The present evidences showed that the H-P-A axis was affected by the administration of acrolein.

Effects of acrolein on aldosterone release from zona glomerulosa cells in male rats.

A positive correlation between smoking and hypertension has been well established. Acrolein is a major toxic volatile compound found in cigarette smoke. Human exposure to low levels of acrolein is unavoidable due to its production in daily activities, such as smoke from industrial, hot oil cooking vapors, and exhaust fumes from vehicles. The toxicity and the action mechanism of acrolein to induce apoptosis have been extensively studied, but the effects of acrolein on hypertension are still unknown. The present study aimed to examine the effects of acrolein on aldosterone release both in vivo and in vitro. Male rats were divided into three groups, and intraperitoneally injected with normal saline, or acrolein (2mg/kg) for 1 (group A-1) or 3 (group A-3) days, respectively. After sacrificing, rat blood samples were obtained to measure plasma aldosterone and angiotensin II (Ang II) levels. Zona glomerulosa (ZG) cells were prepared from rat adrenal cortex, and were incubated with or without stimulants. We found that the serum aldosterone was increased by 1.2-fold (p<0.05) in A-3 group as compared to control group. Basal aldosterone release from ZG cells in A-3 group was also increased significantly. Moreover, acrolein enhanced the stimulatory effects of Ang II and 8-bromo-cyclic AMP on aldosterone secretion from ZG cells prepared in both A-1 and A-3 groups. Furthermore, the enzyme activity of P450scc, the rate-limiting step of aldosterone synthesis, was elevated after acrolein injection. Plasma level of Ang II was increased in both A-1 and A-3 groups. These results suggested that acrolein exposure increased aldosterone production, at least in part, through elevating the level of plasma Ang II and stimulating steroidogenesis pathways.

Immune reactivity in rats selected for the enhancement or elimination of aggressiveness towards humans.

This study analyzes immune reactivity in two lines of rats selected for the enhancement or elimination of aggressiveness toward humans. Compared to nonaggressive line, aggressive rats showed increased blood ratio of CD4(+) and CD8(+)T lymphocytes, monocyte chemoattractant protein (MCP)-1 level both before and after immunization with sheep red blood cells (SRBC), enhanced IgM-immune response, as well as decreased level of interleukin (IL)-1α before immunization. However, antigen administration produced IL-1α increase in aggressive rats and its decrease in nonaggressive rats compared to non-immunized rats of the same lines. In addition, line-dependent alterations of T lymphocyte distribution in response to immune activation have been found only in the spleen. It is suggested that genetic differences in aggressive behavior may contribute to differences in immune function.

Contribution of brain dopamine, serotonin and opioid receptors in the mechanisms of neuroimmunomodulation: evidence from pharmacological analysis.

Neuromediators such as dopamine (DA), serotonin (5-HT) and neuroopioids are known to be involved in the immune response control. This review has summarized the evidence supporting roles for brain DA (D(1), D(2)), 5-HT (5-HT(1A), 5-HT(2A)) and opioid (mu, delta, kappa) receptor subtypes in regulating immune function. Activation of postsynaptic D(1)- and D(2)-receptors produced immunostimulation while their blockade or activation of presynaptic D(2)-receptors mediated an immunoinhibitory effect. Activation of mu- and delta(1)-opioid receptors also increased the immune reaction intensity. Activation of postsynaptic 5-HT(1A)-, 5-HT(2A)-receptors, delta(2)- and kappa-opioid receptors resulted in immunosuppression while the blockade of postsynaptic 5-HT(1A)-, 5-HT(2A)-receptors or activation of somatodendritic 5-HT(1A)-autoreceptors resulted in the immune response stimulation. Immunomodulating effects of drugs acting at various mediator and opioid receptor subtypes depend on the initial psychoemotional state of animals (aggression, submission, depression). The presented data may have implications for the treatment of emotional stress and mental disorders associated with changes in activity of brain DA, 5-HT, opioid systems and their receptor function as well as immune reactivity.

Serotoninergic mechanisms of immunomodulation under different psychoemotional states: I. A role of 5-HT 1A receptor subtype.

The present study demonstrates the involvement of serotonin (5-HT) receptors of the 5-HT 1A type in immunoinhibitory effect of 5-HTergic system of the brain. A selective agonist of 5-HT 1A receptors 8-OH-DPAT (1 mg/kg) induces the immunosuppression, whereas 5-HT 1A blockade with WAY-100635 (1 mg/kg) resulted in immunostimulation. It is also shown that immunomodulating effects of the drugs were dependent on psychoemotional status of animals acquired aggressive or submissive behavior under social conflict conditions. Activation of 5-HT 1A receptors produced a decrease of the immunity in aggressive mice, whereas 5-HT 1A receptor blockade caused immunostimulation in submissive animals.

Regional changes of brain serotonin and its metabolite 5-hydroxyindolacetic Acid and development of immunosuppression in submissive mice.

The production of submissive behavior in C57BL/6J mice during 10 or 20 days of social confrontations resulted in increases in serotonin (5-HT) content in the amygdala, hippocampus, nucleus caudatus, Al1, A10, A9, and hypothalamus. The level of 5-hydroxyindolacetic acid (5-HIAA) was higher in most structures after 20 daily encounters compared to animals tested for 10 days. The ratio 5-HIAA/5-HT was increased in the nucleus raphe, accumbens, A9, and hypothalamus in mice displaying submission during 10 and 20 confrontations. The experience of defeats during 10 days accompanied with 5-HT system activation in a number of brain structures (nucleus raphe, accumbens, and A9) produced immunosuppression. With increasing number of confrontations the ratio 5-HIAA/5-HT was decreased in the same structures and a tendency to the immune response elevation appeared.

Evidence for a role of dopaminergic mechanisms in the immunostimulating effect of mu-opioid receptor agonist DAGO.

The present study demonstrates that: (1) activation of micro -opioid receptors by systemic administration of a highly selective agonist DAGO (100 microg/kg) results in a significant increase in the number of plaque- and rosette-forming cells in the spleen of CBA mice as well as Wistar rats on the 5th day following sheep red blood cells (5 x 10(8)) immunization, (2) the immunostimulatory effect of DAGO is mediated by central mechanisms including the hypothalamus-hypophysis complex; (3) the postsynaptic dopamine (DA) receptors of D2 type are involved in the DAGO-induced immunostimulation since the combined treatment of animals with haloperidol (2 mg/kg), a blocker of DA D2 receptors, and DAGO abolished this effect; (4) the nuclei caudatus and accumbens of the nigrostriatal and mesolimbic DAergic systems, respectively, are implicated in the immune response stimulation caused by DAGO.