Stress and chemotherapy. Combined effects on tumor progression and immunity in animal models

Adrenaline induces chemoresistance in HT-29 colon adenocarcinoma cells

Psychological distress and its ensuing chronic elevation of plasma catecholamines (adrenaline and noradrenaline) lead to poor response of tumors to chemotherapy, and constitute a poor prognostic factor for survival. Colorectal cancer patients suffer from various forms of psychological stress reflected in elevated plasma catecholamines, and their cancer cells express adrenergic receptors. Our objective was to investigate whether adrenergic activation contributes to the chemoresistance of colon cancers, and to explore the signal transduction pathway involved in the activation. The mRNA expression of the ABCB1 gene (previously MDR1) in human colon carcinoma HT-29 cell line was measured after treatment with an adrenergic receptor agonist (adrenaline) and various antagonists (propranolol, prazosin, and yohimbine). The function of P-glycoprotein, the protein product of the ABCB1 gene, was assessed by rhodamine 123 (Rh123)-retention assay, and chemosensitivity was determined by evaluating the cytotoxicity of 5-fluorouracil (5-FU) on the tumor cells. Increased ABCB1 mRNA expression and P-glycoprotein function levels in HT-29 cells by adrenaline was dose-dependent. This was accompanied by promotion of Rh123 efflux, and resistance to the growth-inhibiting effect of 5-FU in the tumor cells. The alpha2-adrenergic receptor antagonist yohimbine completely abolished the induction of ABCB1 mRNA, the stimulatory effect of adrenaline on Rh123 efflux, and the growth-inhibiting effect of 5-FU. The alpha1-adrenergic receptor and beta-adrenergic receptor antagonists did not inhibit the induction of ABCB1. The stimulating effects were coupled with extracellular receptor kinase 1/2 (Erk1/2) phosphorylation, but were not associated with protein kinase A activity. We conclude that adrenaline induces multidrug resistance in colon cancer cells by upregulating ABCB1 gene expression via alpha2-adrenergic receptors, and such effects were associated with the mitogen activated protein kinase (MAPK) pathway.

Psychological stress induces chemoresistance in breast cancer by upregulating mdr1

Psychological distress reduces the efficacy of chemotherapy in breast cancer patients. The mechanism may be related to the altered neuronal or hormonal secretions during stress. Here, we reported that adrenaline, a hormone mediating the biological activities of stress, upregulates mdr1 gene expression in MCF-7 breast cancer cells via alpha(2)-adrenergic receptors in a dose-dependent manner. Mdr1 upregulation can be specifically inhibited by pretreatment with mdr1-siRNA. Consequently, adrenergic stimulation enhances the pump function of P-glycoprotein and confers resistance of MCF-7 cells to paclitaxel. In vivo, restraint stress increases mdr1 gene expression in the MCF-7 cancers that are inoculated subcutaneously into the SCID mice and provokes resistance to doxorubicin in the implanted tumors. The effect can be blocked by injection of yohimbine, an alpha(2)-adrenergic inhibitor, but not by metyrapone, a corticosterone synthesis blocker. Therefore, we conclude that breast cancers may develop resistance against chemotherapeutic drugs under psychological distress by over-expressing mdr1 via adrenergic stimulation.

Tonic pain response in mice: effects of sex, season and time of day

Seasonal and diurnal variations in tonic pain reactions were examined in female and male CBA/J mice maintained in a 12/12 dark/light cycle, at controlled temperature and humidity conditions. Animals were injected into the dorsum of one hindpaw with a dilute (20 microl, 1%) formalin solution. Pain-related behaviors were quantified as the time spent licking the injected paw and the number of flinching episodes. The experiments were performed during the first part of the light phase (Light: from 7 to 10 a.m.) or during the first part of the dark phase of the diurnal cycle (Dark: from 7 to 10 p.m.), in two different periods of the year: Spring (March-June) and Winter (November-January). Considering all data, females showed a slightly enhanced licking response, as well as an increase in the time spent in self-grooming, in comparison with males. In Spring, the licking and flinching responses were higher during the Dark phase than during the Light phase. This held for both sexes and for both phases of the behavioral response to formalin injection. By contrast, no significant diurnal variation in pain reactions was found in Winter. These seasonal and diurnal differences were not due to nonspecific changes in motor behavior, inasmuch as locomotor activity and self-grooming showed a different pattern: during the second phase after formalin, self-grooming was higher in the Light period in the experiments performed in Spring, whereas locomotor activity showed no significant seasonal changes. These results show that the behavioral reactions to prolonged noxious input, integrated both at spinal and supraspinal sites, undergo similar seasonal and diurnal variations in both sexes, strengthening the importance of chronobiological factors in the modulation of nociception.