Depletion of catecholamines with alpha-methyl-p-tyrosine suppresses splenic NK cell activity

Premature aging in behavior and immune functions in tyrosine hydroxylase haploinsufficient female mice. A longitudinal study

Aging is accompanied by impairment in the nervous, immune, and endocrine systems as well as in neuroimmunoendocrine communication. In this context, there is an age-related alteration of the physiological response to acute stress, which is modulated by catecholamine (CA), final products of the sympathetic-adreno-medullary axis. The involvement of CA in essential functions of the nervous system is consistent with the neuropsychological deficits found in mice with haploinsufficiency (hemizygous; HZ) of tyrosine hydroxylase (TH) enzyme (TH-HZ). However, other possible alterations in regulatory systems have not been studied in these animals. The aim of the present work was to analyze whether adult TH-HZ female mice presented the impairment of behavioral traits and immunological responses that occurs with aging and whether they had affected their mean lifespan. ICR-CD1 female TH-HZ and wild type (WT) mice were used in a longitudinal study. Behavioral tests were performed on adult and old mice in order to evaluate their sensorimotor abilities and exploratory capacity, as well as anxiety-like behaviors. At the ages of 2 ± 1, 4 ± 1, 9 ± 1, 13 ± 1 and 20 ± 1 months, peritoneal leukocytes were extracted and several immune functions were assessed (phagocytic capacity, Natural Killer (NK) cytotoxicity, and lymphoproliferative response to lipopolysaccharide (LPS) and concanavalin A (ConA)). In addition, several oxidative stress parameters (catalase, glutathione reductase and glutathione peroxidase activities, and reduced glutathione (GSH) concentrations as antioxidant compounds as well as xanthine oxidase activity, oxidized glutathione (GSSG) concentrations, and GSSG/GSH ratio as oxidants) were analyzed. As inflammatory stress parameters TNF-alpha and IL-10 concentrations, and TNF-alpha/IL-10 ratios as inflammatory/anti-inflammatory markers, were measured. Animals were maintained in standard conditions until their natural death. The results indicate that adult TH-HZ mice presented worse sensorimotor abilities and exploratory capacity than their WT littermates as well as greater anxiety-like behaviors. With regards to the immune system, adult TH-HZ animals exhibited lower values of phagocytic capacity, NK cytotoxicity, and lymphoproliferative response to LPS and ConA than WT mice. Moreover, immune cells of TH-HZ mice showed higher oxidative and inflammatory stress than those of WT animals. Although these differences between TH-HZ and WT, in general, decreased with aging, this premature immunosenescence and impairment of behavior of TH-HZ mice was accompanied by a shorter mean lifespan in comparison to WT counterparts. In conclusion, haploinsufficiency of th gene in female mice appears to provoke premature aging of the regulatory systems affecting mean lifespan.

Suppression of NK cell activity and of resistance to metastasis by stress: a role for adrenal catecholamines and beta-adrenoceptors

Although acute stress has been reported to suppress natural killer cell activity (NKA) and host resistance to metastasis, it is unclear whether the sympathetic nervous system (SNS) has a role in these effects. The current study in Fischer 344 rats assessed the involvement of adrenal catecholamines and beta(1)- and beta(2)-adrenoceptors in mediating these deleterious effects of swim stress. In addition to assessing the number and activity of NK cells following swim stress, we used a tumor model based on the MADB106 mammary adenocarcinoma line: this syngeneic tumor metastasizes only to the lungs, and its lung tumor retention (LTR) and metastatic colonization are highly sensitive to NKA. The findings indicate that stress increased both LTR, assessed 24 h after inoculation, and the number of lung metastases, counted 3 weeks later. These effects were attenuated or completely abolished by the ganglionic blocker chlorisondamine (3 mg/kg i.p.), by adrenal demedullation, by a selective beta-adrenergic antagonist (nadolol, 0.4 mg/kg), and additively by a selective beta(1)- (atenolol, 1-6 mg/kg) and a selective beta(2)-antagonist (either butoxamine 4-32 mg/kg or ICI-118,551 0.3-8 mg/kg). Stress also suppressed NKA, and adrenal demedullation prevented this suppression. Administration of adrenaline (0.1-1 mg/kg) or of a beta-adrenergic agonist (metaproterenol, 0.8 mg/kg), in physiologically relevant doses, suppressed NKA in a dose-dependent manner, and increased LTR to levels characteristic of swim stress. Taken together, these findings suggest that acute stress, by releasing catecholamines from the adrenal glands and activating beta(1)- and beta(2)-adrenoceptors, suppresses NKA and consequently compromises resistance to NK-sensitive metastasis.

Suppression of natural killer cell activity in mouse spleen lymphocytes by several dopamine receptor antagonists

The effects of dopaminergic receptor inhibitors such as thiothixine (D1/D2), fluphenazine (D1/D2), trifluoperazine (D1/D2), pimozide (D2), flupenthixol (D1/D2), (+/-)-SKF 83566 (D1), and spiperone (D2) on splenic natural killer (NK) cell cytotoxic activities were assessed in vitro using mouse spleen lymphocytes or enriched NK cells. Both the activities of the splenic NK cell cytotoxicity and the effector-target cell conjugation were suppressed by thiothixine, fluphenazine, and trifluoperazine at concentrations from 2.64 to 14.78 microM. In addition, the augmentation of the cytolytic activity of NK cells induced by interferon-alpha or interleukin-2 was antagonized by pretreatment with these neuroleptic compounds. However, neither the splenic NK cell cytotoxicity nor the effector-target cell conjugation were affected by treatment with other neuroleptic compounds such as pimozide, flupenthixol, (+/-)-SKF 83566, and spiperone. Thus, it appears that neuroleptic compounds such as thiothixine, fluphenazine, and trifluoperazine may act through the mechanisms other than a dopaminergic pathway to affect the NK cell-target cell interaction.