Sodium diethyldithiocarbamate protects against the MPTP-induced inhibition of immune responses in mice

Vaccination strategies for Parkinson disease: induction of a swift attack or raising tolerance?

Parkinson disease is the second most common neurodegenerative disease in the world, but there is currently no available cure for it. Current treatments only alleviate some of the symptoms for a few years, but they become ineffective in the long run and do not stop the disease. Therefore it is of outmost importance to develop therapeutic strategies that can prevent, stop, or cure Parkinson disease. A very promising target for these therapies is the peripheral immune system due to its probable involvement in the disease and its potential as a tool to modulate neuroinflammation. But for such strategies to be successful, we need to understand the particular state of the peripheral immune system during Parkinson disease in order to avoid its weaknesses. In this review we examine the available data regarding how dopamine regulates the peripheral immune system and how this regulation is affected in Parkinson disease; the specific cytokine profiles observed during disease progression and the alterations documented to date in patients' peripheral blood mononuclear cells. We also review the different strategies used in Parkinson disease animal models to modulate the adaptive immune response to salvage dopaminergic neurons from cell death. After analyzing the evidence, we hypothesize the need to prime the immune system to restore natural tolerance against α-synuclein in Parkinson disease, including at the same time B and T cells, so that T cells can reprogram microglia activation to a beneficial pattern and B cell/IgG can help neurons cope with the pathological forms of α-synuclein.

Time-course evaluation of whole blood phagocytosis in mice treated with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Immunological abnormalities have been described in idiopathic Parkinson's disease and in the mouse model of this disorder induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). This investigation was aimed to study the effect of MPTP on inflammatory response of whole blood phagocytes at different time intervals. C57BL male mice were injected intraperitoneally with either MPTP (30 mg/kg) or saline (control group) and the blood samples were collected at 4, 24 and 48 h. 50 microl of a 500-fold diluted blood sample was mixed with 150 microl of reaction mixture (0.4 mM luminol + 50 microg opsonized zymosan + 0.1% gelatin, in Hanks' balanced salt solution) and the chemiluminescence (CL) signal was measured in a luminometer at 37 degrees C. Although the CL response of the whole blood from control and MPTP groups was similar at 4 h, a significant increase in the CL signal was observed in MPTP-treated mice at 24 h post-treatment, which got subsided at 48 h. The findings of this study suggest that in an early stage a pro-inflammatory response following MPTP might trigger a chain of potentially toxic pathways mediated by reactive oxygen species, leading to progressive neuronal damage.

Central catecholamine depletion inhibits peripheral lymphocyte responsiveness in spleen and blood

Experimental and clinical evidence has demonstrated extensive communication between the CNS and the immune system. To analyse the role of central catecholamines in modulating peripheral immune functions, we injected the neurotoxin 6-hydroxydopamine (6-OHDA) i.c.v. in rats. This treatment significantly reduced brain catecholamine content 2, 4 and 7 days after injection, and in the periphery splenic catecholamine levels were reduced 4 days after treatment. Central catecholamine depletion induced an inhibition of splenic and blood lymphocyte proliferation and splenic cytokine production and expression (interleukin-2 and interferon-gamma) 7 days after injection. In addition, central treatment with 6-OHDA reduced the percentage of spleen and peripheral blood natural killer (CD161 +) cells, and T-cytotoxic (CD8 +) cells in peripheral blood. The reduction in splenocyte proliferation was not associated with a glucocorticoid alteration but was completely abolished by prior peripheral sympathectomy. These data demonstrate a crucial role of central and peripheral catecholamines in modulating immune function.

Restoration of splenic noradrenergic nerve fibers and immune reactivity in old F344 rats: a comparison between L-deprenyl and L-desmethyldeprenyl

L-deprenyl, a monoamine oxidase-B inhibitor, partially reversed the age-associated decline in splenic sympathetic noradrenergic (NA) innervation and immune reactivity in old male rats. The purpose of the present study was to examine whether the effects of deprenyl on splenic sympathetic NA nerve fibers and immune functions are mediated through a metabolite of deprenyl, L-desmethyldeprenyl. Old male F344 rats were treated with 0, 0.25, or 1.0 mg L-(-)-deprenyl/kg BW; 0.025, 0.25, or 1.0 mg L-(-)-desmethyldeprenyl/kg BW; and 1.0 mg D-(+)-desmethyldeprenyl/kg BW i.p. daily for 8 weeks. The animals were sacrificed after a 10-day drug wash-out period and the spleens were removed for histofluorescence, immunocytochemistry, neurochemical, and immunological analysis. The volume density of NA nerve fibers was increased in the spleens of deprenyl- and L-desmethyldeprenyl-treated old rats. Con A-induced IFN-gamma production by spleen cells was elevated in 1.0 mg/kg deprenyl- and L-desmethyldeprenyl-treated rats in comparison to saline- and D-desmethyldeprenyl-treated old rats. Deprenyl and desmethyldeprenyl treatment did not alter the percentage of CD5+ T cells, but treatment with 1.0 mg/kg deprenyl and 0.025 mg/kg L-desmethyldeprenyl prevented the decline in the percentage of sIgM(+)B cells in the spleens of old rats. These results suggest that L-desmethyldeprenyl may be as equipotent as deprenyl in preventing age-associated diminution in splenic sympathetic NA innervation and immunocompetence.

Dopamine, a neurotransmitter, influences the immune system

Dopamine (DA) is a monoamine neurotransmitter of both central and peripheral nervous system. Its role in the neural-immune communication has been discussed in the present review. Results reveal that in vivo damage or stimulation of specific central dopaminergic system suppresses or enhances functional activities of the immune effector cells. The possible influences of other immunomodulators of the brain by altering brain DA may be the underlying mechanism. Direct effects of DA on the immune effector cells are also contradictory, it is suppressive in vitro, while in pharmacological doses, it is mostly stimulatory in vivo. The possible mechanisms have been discussed. Lastly, future areas of relevance on DA and immunity have been highlighted to advance our knowledge regarding DA as an immune regulator.

Cocaine induced T cell proliferation in the rat: role of amygdala dopamine D1 receptors

The immunomodulatory effects of local administration of cocaine into the amygdala were studied in the rat. Intra-amygdala infusion of cocaine significantly and dose-dependently increased the proliferative response of splenocytes to concanavalin A (Con A). A similar effect on the immune response was also observed in rats, microinfused into the central amygdala with the selective D1 receptor agonist SKF 38393. The increase of the proliferative response of splenocytes to Con A was inhibited by coinfusion within the central amygdala of the dopamine D1 receptor antagonist SCH 23390, together with cocaine, but not by coinfusion of the dopamine D2 receptor antagonist eticlopride. These results suggest that cocaine may produce at least some of its effects on the immune system through the activation of brain dopamine neurotransmission and that the central amygdala may represent a critical structure mediating cocaine-induced T cell proliferation.

Effect of dopamine on immune cell proliferation in mice

Dopamine is known as a precursor of catecholamine and one of the neurotransmitters in brain and peripheral tissues. Recent studies suggest an important role of dopamine in immune responses. In the present study, intraperitoneal administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) which lowered endogenous dopamine suppressed splenocyte proliferation in response to mitogens such as lipopolysaccharide (LPS) and concanavalin A (Con A). Moreover, intravenous injection of the specific agonists of dopamine DA-1 receptor (SKF38393) or DA-2 receptor (LY171555) into mice enhanced the splenocyte proliferation stimulated by LPS or Con A. In the in vitro cultures, dopamine, SKF38393 and LY171555 directly promoted cell proliferation to LPS or Con A. These results indicate that dopamine has an ability to regulate B- and T-cell proliferation both in vivo and in vitro.

Enhanced tumor growth in brain dopamine-depleted mice following 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treatment

Brain dopamine influences immune functions and the role of immune functions in tumor growth is well established. Therefore, a study has been carried out to evaluate the correlation, if any, between brain dopamine and tumor growth. MPTP selectively destroys dopaminergic neurons in the brain. In the present study, Ehrlich carcinoma growth was evaluated in MPTP-treated mice. Results showed a correlation between depletion of striatal dopamine and enhanced tumor growth. Since in the present study striatal dopamine depletion in mice was associated with significantly decreased immune responses, the suggested correlation between brain dopamine and tumor growth was possibly mediated by the immune system.

Dopamine D1 receptors in the amygdala enhance the immune response in the rat

Indirect evidence suggests that dopamine within the brain may participate in the regulation of immune responses in both man and rodents. The aim of the present study was to investigate the possible role played by the specific dopamine D1 receptor subtype within the central amygdala in the modulation of immunity. Mitogen responsiveness of splenocytes and NK cell activity were measured in rats following local microinfusion of SKF 38393, a specific dopamine D1 receptor agonist. Microinfusion of SKF 38393 (100 nmol) within the central amygdala increased the proliferative response of splenocytes to Con A, whereas it did not modify the proliferative response of splenocytes to LPS or NK cell activity. The effects of SKF 38393 were prevented by prior systemic administration of SCH 23390 (0.3 mg/kg ip), a specific D1 receptor antagonist. These results indicate that activation of dopamine D1 receptors within the central amygdala induced selective stimulation of mitogen responsiveness of splenocytes and suggest that specific activation of dopamine neurotransmission within selected areas of the limbic system may produce immunoenhancing effects. These findings further confirm the immunomodulatory role played by dopaminergic mechanisms in the brain.

Modulation of immune reactivity by unilateral striatal and mesolimbic dopaminergic lesions

Asymmetrical modulation of immune reactivity by central dopaminergic pathways was suggested by previous reports which described an association between alterations of immune response and peculiar patterns of dopamine asymmetries in pathological and physiological situations. In the present experiments, we studied the respective roles of the nigrostriatal and mesolimbic dopaminergic networks in the asymmetrical modulation of immune responses. Lymphocyte proliferation as well as natural killer (NK) cell activity were analysed in mice, 2 weeks after unilateral lesions of dopaminergic projections by in situ injection of 6-hydroxydopamine in the striatum or the nucleus accumbens. After lesions of the striatum, proliferation of splenic lymphocytes was impaired only in the right-lesioned group. Left-lesions appeared to not modify T lymphocyte reactivity. After lesions of the nucleus accumbens, no modification of T lymphocyte mitogenesis was observed but splenic NK cell activity was depressed in left-lesioned mice as compared with controls or right-lesioned animals. Proliferation of B lymphocytes was not affected by striatal or mesolimbic dopaminergic lesions. It was concluded that both striatal and mesolimbic dopaminergic pathways are asymmetrically involved in neuro-immunomodulation. These dopaminergic regions appear to function independently as the effective side as well as the immune parameters that were altered differ according to the structure lesioned.

Brain lateralization and immunomodulation

The two sides of the brain may be differently involved in the modulation of immune responses as demonstrated by lesional and behavioral approaches in rodents. Lesions of right or left neocortex induced opposite effects on various immune parameters including mitogen-induced lymphoproliferation, interleukin-2 production, macrophage activation or natural killer cell activity. This animal model, useful to elucidate whereby the brain and the immune system can communicate, appears to be suitable for studying the immune perturbations observed during stroke in humans. Brain asymmetry in modulation of immune reactivity may also be demonstrated in intact animal using a behavioral paradigm. The direction of a lateralized motor behavior ie paw preference in a food reaching task, correlated with an asymmetrical brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. The association between paw preference and immune reactivity in mice varies according to the immune parameters tested and is a sex-dependent phenomenon in which genetic background may be involved. The experimental models for investigating asymmetrical brain modulation of the immune system should be useful for studying several physiological, pathological and genetic aspects of neuroimmunomodulation.

Immunological changes in the MPTP-induced Parkinson's disease mouse model

The role of the central dopaminergic system in modulating immune response is not completely established. We examined the influence of central dopamine depletion on selected parameters of immune functions in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) treated and untreated mice. IgM antibody production of splenocytes to sheep red blood cells was reduced in MPTP-treated mice (P < 0.001). Proliferation of splenocytes in response to a wide range of mitogen concentrations (Concanavalin A, phytohaemagglutinin, lipopolysaccharide) was also significantly diminished in MPTP-treated mice. Production of migration inhibition factor (MIF) was diminished only in low mitogen concentration. Our results obtained in the experimental model of Parkinson's disease provide evidence that the damage of the central dopaminergic pathways induces alterations of some immune functions in mice.

Effects of MPTP and vitamin E treatments on immune function in mice

The effects of treatment with the neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) and vitamin E, an antioxidant, on immune functions were examined. Male C57/B1 mice were fed daily with natural vitamin E for 12 weeks, subsequently injected i.p. with MPTP or its vehicle, and sacrificed 1 week later. Control mice received the stripped corn oil vehicle daily, in place of vitamin E. Oral vitamin E feeding increased cerebral vitamin E content by 60% (P = 0.05). However, MPTP attenuated this rise in cerebral vitamin E content when measured 1 week after treatment with the neurotoxin (P = 0.05). MPTP also produced an 80-90% reduction in striatal dopamine content in both the stripped corn oil control group and the vitamin E-treated group (P = 0.0000). One week after MPTP injection, the numbers of peripheral blood lymphocytes and the percent of spleen T-cells, but not B-cells, were decreased in those groups receiving MPTP alone or MPTP plus vitamin E (P less than 0.05 and 0.02, respectively). The Con A-induced IL-2 production of spleen cells was decreased in all treated groups (P less than 0.005). There was no difference in the mitogenic stimulative response to PHA, Con A or LPS. However, the response to PWM was increased in both MPTP and MPTP plus vitamin E-treated groups (P less than 0.05 and 0.001, respectively). On the other hand, the one-way mixed lymphocyte response of the splenocytes from the MPTP-treated group was increased (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemispheric asymmetry in the effects of substantia nigra lesioning on lymphocyte reactivity in mice

Asymmetry in brain modulation of the immune system has previously been demonstrated at the neocortex level. In these experiments, the possibility of subcortical immunomodulation was investigated. In mice the substantia nigra was lesioned using the neurotoxin 6-hydroxydopamine. Four and six weeks after left or right lesions of the substantia nigra, spleen lymphocyte mitogenesis was slightly depressed or enhanced respectively as compared to sham operated controls. Differences appeared when comparing left and right lesioned groups. However, natural killer cell activity was unaffected by unilateral lesions of the substantia nigra. These results show that asymmetrical brain modulation may occur at the sub-cortical level and suggest that central dopamine is involved in neuroimmunomodulation.

Asymmetrical brain modulation of the immune response

It is now well known that the central nervous system can regulate the immune system. Interestingly the two sides of the brain have been demonstrated to be differently involved in the modulation of immune responses. In rodents, lesions of right or left neocortex induced opposite effects on various immune parameters including mitogen-induced lymphoproliferation, interleukin-2 production, macrophage activation or natural killer cell activity. Furthermore in humans, left-handedness has been reported to be associated with a high incidence of immune disorders. Likewise in mice, the direction of a lateralized motor behavior, i.e., paw preference in a food reaching task, correlated with an asymmetrical pattern of brain organization, was shown to be associated with lymphocyte reactivity, natural killer cell activity and auto-antibody production. Conversely the immune system could send to the brain information that may be asymmetrically expressed. The experimental models for investigating asymmetrical brain modulation of the immune system may be useful for studying physiological, pathological and genetic aspects of neuroimmunomodulation.

Early effects of unilateral lesions of substantia nigra on immune reactivity

It has recently been demonstrated that central dopaminergic pathways are asymmetrically involved in the modulation of the immune response. Mitogen-induced proliferation of T lymphocytes was shown to be enhanced 4-6 weeks after right lesion of the substantia nigra (SN) in mice, when compared to left lesioned and control animals. In order to study the involvement of post lesion neuronal reorganization in these results, the same immunological parameters were determined as early as 2 weeks after right or left lesion of the SN. We showed that the lymphoproliferation induced by alpha CD3 and concanavalin A was decreased in both lesioned groups, but phytohemagglutinin-induced mitogenesis was more impaired in the right than in the left lesioned animals. Hence, the time course effects of the right lesions of SN shifted from depression to enhancement of the T lymphocyte responsiveness. This shift appeared to occur around the two weeks period following the lesion. These immunomodulatory effects of unilateral SN lesioning, which depended on time and side of lesion, were similar to those observed after hemidecortication. Based on these findings, it is reasonable to suggest that asymmetry in brain immunomodulation involves functionally related dopaminergic and cortical networks.

Asymmetrical effects of cortical ablation on brain monoamines in mice

Neurochemical changes induced by right or left cortical ablation which have previously been described to have immunological effects were investigated in mice. Catecholamine and indolamine levels were determined in the contralateral cortex and in subcortical structures involved in immunoregulation 14 and 60 days after unilateral cortical ablation. Unilateral cortical ablation induced profound and widespread changes in the contralateral cortex but also in subcortical regions of both sides at 14 days after surgery. Lesions of the left neocortex appeared mainly to affect the activity of serotoninergic inputs to the right neocortex, whereas ablations of the right cortex influenced the activity of the catecholaminergic inputs to the left. Sixty days after surgery, modifications in monoamine levels were observed only in the ipsilateral, but not contralateral, subcortical regions, the only exception being that DA turnover in the tuberoinfundibular system remained lowered in both hemispheres after either right or left cortical ablations. Furthermore, some asymmetrical effects of cortical lesions depended on functional brain lateralization as assessed by paw preference. It may be hypothesized that some neurochemical modifications induced by unilateral cortical lesions are, at least partially, responsible for the immunological perturbations observed after cortical ablation.

Relative effectiveness of some compounds for the control of cisplatin-induced nephrotoxicity

Several procedures which have been reported as effective for the control of cisplatin induced nephrotoxicity were compared in the Sprague-Dawley rat using the same dose of cisplatin. The treatments examined were based on the use of sodium thiosulfate, sodium diethyldithiocarbamate (DDTC), glutathione (GSH), sodium N-methyl-D-glucamine dithiocarbamate (NaG) and S-2-(3-aminopropylamino)ethylphosphorothioic acid (WR-2721). The differences in the effectiveness of the procedures were assessed using BUN and serum creatinine values, histopathological examination, body weight changes, and renal platinum levels as indices. The effect of such treatments on the antineoplastic activity of cisplatin were examined with both the Walker 256 carcinosarcoma in the rat and the L1210 murine leukemia in mice. Under the conditions used, GSH was found to be more effective than the other nucleophiles in protecting against the nephrotoxicity of cisplatin while providing the least amount of interference with the antitumor activity as measured against the Walker 256 carcinosarcoma and the L1210 murine leukemia. Simultaneous i.v. administration of cisplatin and any of the sulfur-containing nucleophiles leads to a significant protection against the nephrotoxicity but reduced the anti-neoplastic activity of cisplatin when measured against the Walker 256 carcinosarcoma.

Behavioural effects of angiotensin II in the mouse following MPTP administration

1. The effects of the octapeptide angiotensin II (AT II) on some types of behaviour [threshold of seizures induced by timed intravenous infusion of pentylenetetrazol (PTZ), exploratory behaviour: ambulation, rearing and head-dips on a hole-board, and passive avoidance performance--step-through paradigm] were studied following repeated systemic administration of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) to mice (30 mg/kg, i.p., twice daily for 5 days). AT II was administered s.c. (200 micrograms/kg), single and repeated (for 7 days) 7 days after withdrawal of MPTP. 2. PTZ seizure threshold was significantly increased by AT II both in groups with single and repeated administration (stronger than in the group treated only with MPTP and in the group untreated with MPTP). 3. AT II significantly increased the ambulation and rearing as well as the head-dips both on single and repeated administration as compared to groups treated and untreated with MPTP. 4. Administered immediately after the passive training trial AT II, on single and repeated administration, significantly increased latencies, i.e. it facilitated retention, in MPTP-treated mice. 5. These results were discussed in the light of DA and perhaps, GABA receptor supersensitivity developed in susceptible brain structures after withdrawal of repeated MPTP administration. 6. The adaptive changes in the effects of AT II on seizure threshold, exploratory behaviour and retention of passive avoidance performance might be associated with the altered receptor-receptor (AT II-DA-GABA) interactions in the brain.