Effects of nefazodone on the immune system of mice

Effects of nefazodone on the development of experimentally induced tumors in stressed rodents

RATIONALE

Anxiety and depression are commonly encountered in patients with cancer and constitute risk and prognostic factors for the disease. Although previous findings do not support an overall association between the use of antidepressants and higher prevalence of cancer, results for serotonin uptake inhibitors are not entirely reassuring.

OBJECTIVES

We evaluated the effects of nefazodone, a serotonin and norepinephrine (NE) reuptake inhibitor and 5-HT(2A) receptor antagonist antidepressant, on the appearance of breast cancer induced by mammary tumor virus (MTV) in mice, and on the development of lung metastases in rats injected intravenously with Walker 256 (W-256) carcinosarcoma cells.

METHODS

Female C3H/He mice carrying the MTV were monitored for mammary tumor incidence and latent periods while being treated with a daily intraperitoneal injection with placebo or nefazodone. Rats were administered 10(4) W-256 cells, exposed to a chronic auditory stressor for 8 days, and then killed to evaluate metastatic nodules in the lungs.

RESULTS

Although all of the mice were potential candidates for MTV-induced breast cancer, those treated with nefazodone were partially protected against adverse effects of stress induced by the daily administration of placebo on both parameters. Relative to placebo, nefazodone reduced the stress-induced increase in the number and percentage area of metastases in the frontal section through pulmonary hilus and increased the survival periods of rats given W-256 cells and exposed to a chronic auditory stressor.

CONCLUSIONS

Our results provide evidence of the beneficial effects of nefazodone against the adverse effects of stress on tumor development and metastaticity in rodents, but did not show significant effects in unstressed rodents.

Serotonin upregulates the activity of phagocytosis through 5-HT1A receptors

1 In this study, we investigated whether serotonin could regulate the in vitro activity of phagocytosis through 5-hydroxytryptamine or serotonin (5-HT(1A)) receptors. 2 Mouse peritoneal macrophages were cultured with serotonin and the activity of phagocytosis was assessed by the uptake of zymosan and latex particles added to the culture media. Specific binding of [(3)H]8-OH-DPAT and immunohistochemistry using an affinity-purified anti-5-HT(1A)-receptor antibody were assayed in the macrophages. In addition, we took advantage of the availability of pharmacological inhibitors of nuclear factor-kappaB (NF-kappaB) to explore its role in the regulation of the 5-HT(1A) receptor. 3 Serotonin increased the in vitro activity of phagocytosis in a dose-dependent manner. The 5-HT(1A) receptor agonist (+/-)-8-hydroxy-2-(di-n-propyl-amino)-tetralin (R(+)-8-OH-DPAT) reproduced these effects. Serotonin- or R(+)-8-OH-DPAT-induced increases in phagocytosis were blocked by the 5-HT(1A) receptor antagonist WAY100635 and the NF-kappaB inhibitor pyrrolidinedithiocarbamate. Moreover, mouse peritoneal macrophages expressed specific binding sites for [(3)H]8-OH-DPAT when cultivated in the presence of zymosan or latex beads. Immunohistochemistry confirmed the expression of the 5-HT(1A) receptor protein in the macrophages. 4 These results show that serotonin can upregulate the activity of peritoneal macrophages through 5-HT(1A) receptors.

Effects of fluoxetine on the activity of phagocytosis in stressed mice

We studied the effects of 1, 2, 5, 10 and 20 mg/kg of fluoxetine on the activity of phagocytosis in mice subjected to a chronic auditory stressor. Both the in vitro and in vivo activity of phagocytosis, measured using the zymosan-particle uptake method and the carbon clearance test, respectively, were reduced after 2, 4, 8 and 16 days of stress exposure. A partial recovery on the in vivo activity of phagocytosis was found on day 16th. Daily treatment with fluoxetine partially reversed the adverse effects of stress in a dose-dependent manner on both parameters but did not significantly affect the activity of phagocytosis in unstressed mice. Significant differences appeared when fluoxetine was administered at 2 mg/kg. Maximum effect was reached at 5 mg/kg.

Effects of psychological stress and alprazolam on development of oral candidiasis in rats

Psychological stress has been found to suppress cell-mediated immune responses that are important in limiting the proliferation of Candida albicans. Since anxiolytic drugs can restore cellular immunity in rodents exposed to stress conditions, we designed experiments conducted to evaluate the effects of alprazolam (1 mg/kg of body weight/day), a central benzodiazepine anxiolytic agonist, on the development of oral candidiasis in Sprague-Dawley rats exposed to a chronic auditory stressor. Animals were submitted to surgical hyposalivation in order to facilitate the establishment and persistence of C. albicans infection. Application of stress and treatment with drugs (placebo or alprazolam) were initiated 7 days before C. albicans inoculation and lasted until the end of the experiments (day 15 postinoculation). Establishment of C. albicans infection was evaluated by swabbing the inoculated oral cavity with a sterile cotton applicator on days 2 and 15 after inoculation, followed by plating on YEPD (yeast extract-peptone-dextrose) agar. Tissue injury was determined by the quantification of the number and type (normal or abnormal) of papillae on the dorsal tongue per microscopic field. A semiquantitative scale was devised to assess the degree of colonization of the epithelium by fungal hyphae. Our results show that stress exacerbates C. albicans infection of the tongues of rats. Significant increases in Candida counts, the percentage of the tongue's surface covered with clinical lesions, the percentage of abnormal papillae, and the colonization of the epithelium by fungal hyphae were found in stressed rats compared to those found in the unstressed rats. Treatment with alprazolam significantly reversed these adverse effects of stress, showing that, besides the psychopharmacological properties of this anxiolytic drug against stress, it has consequences for Candida infection.