Elucidation of the mechanisms underlying tumor aggravation by the activation of stress-related neurons in the paraventricular nucleus of the hypothalamus.

A growing body of evidence suggests that excess stress could aggravate tumor progression. The paraventricular nucleus (PVN) of the hypothalamus plays an important role in the adaptation to stress because the hypothalamic-pituitary-adrenal (HPA) axis can be activated by inducing the release of corticotropin-releasing hormone (CRH) from the PVN. In this study, we used pharmacogenetic techniques to investigate whether concomitant activation of CRHPVN neurons could directly contribute to tumor progression. Tumor growth was significantly promoted by repeated activation of CRHPVN neurons, which was followed by an increase in the plasma levels of corticosterone. Consistent with these results, chronic administration of glucocorticoids induced tumor progression. Under the concomitant activation of CRHPVN neurons, the number of cytotoxic CD8+ T cells in the tumor microenvironment was dramatically decreased, and the mRNA expression levels of hypoxia inducible factor 1 subunit α (HIF1α), glucocorticoid receptor (GR) and Tsc22d3 were upregulated in inhibitory lymphocytes, tumor-associated macrophages (TAMs) and myeloid-derived suppressor cells (MDSCs). Furthermore, the mRNA levels of various kinds of driver molecules related to tumor progression and tumor metastasis were prominently elevated in cancer cells by concomitant activation of CRHPVN neurons. These findings suggest that repeated activation of the PVN-CRHergic system may aggravate tumor growth through a central-peripheral-associated tumor immune system.

Analyses of the possible anti-tumor effect of yokukansan.

The Kampo medicine yokukansan (YKS) has a wide variety of properties such as anxiolytic, anti-inflammatory and analgesic effects, and is also thought to regulate tumor suppression. In this study, we investigated the anti-tumor effect of YKS. We used Lewis lung carcinoma (LLC)-bearing mice that were fed food pellets containing YKS and then performed a fecal microbiota analysis, a microarray analysis for microRNAs (miRNAs) and an in vitro anti-tumor assay. The fecal microbiota analysis revealed that treatment with YKS partly reversed changes in the microbiota composition due to LLC implantation. Furthermore, a miRNA array analysis using blood serum showed that treatment with YKS restored the levels of miR-133a-3p/133b-3p, miR-1a-3p and miR-342-3p following LLC implantation to normal levels. A TargetScan analysis revealed that the epidermal growth factor receptor 1 signaling pathway is one of the major target pathways for these miRNAs. Furthermore, treatment with YKS restored the levels of miR-200b-3p and miR-200c-3p, a recognized mediator of cancer progression and controller of emotion, in the hypothalamus of mice bearing LLC. An in vitro assay revealed that a mixture of pachymic acid, saikosaponins a and d and isoliquiritigenin, which are all contained in YKS, exerted direct and additive anti-tumor effects. The present findings constitute novel evidence that YKS may exert an anti-tumor effect by reversing changes in the fecal microbiota and miRNAs circulating in the blood serum and hypothalamus, and the compounds found in YKS could have direct and additive anti-tumor effects.

Changes in circadian rhythm for mRNA expression of melatonin 1A and 1B receptors in the hypothalamus under a neuropathic pain-like state.

Several clinical reports on neuropathic pain of various etiologies have shown that it significantly interferes with sleep. Inadequate sleep due to neuropathic pain may contribute to the stressful negative consequences of living with pain. It is generally recognized that melatonin (MT) system in the hypothalmus is crusial for circadian rhythm and sleep-wake transition. However, little, if any, is known about whether neuropathic pain could affect the MT system associated with sleep disturbance. In this study, we investigated the possible changes in circadian rhythm for the expression of MT receptors, especially MT1A and MT1B receptors, in the hypothalamus of mice with sciatic nerve ligation. The samples for real-time RT-PCR assay were prepared at 8:00, 14:00, 20:00, and 2:00 on day 7 after sciatic nerve ligation or sham operation. The mRNA expression of MT1A and MT1B receptors at 2:00 in sciatic nerve-ligated mice, which exhibited thermal hyperalgesia along with an increase in wakefulness and a decrease in nonrapid eye movement sleep, was significantly greater than those in sham-operated mice, whereas the levels of both MT1A and MT1B receptors at 8:00 in sciatic nerve-ligated mice were significantly lower than those in sham-operated mice. These findings suggest that neuropathic pain-like stimuli lead to sleep disturbance in parallel with changes in circadian rhythm for mRNA expression of MT 1A and 1B receptors in the hypothalamus of mice.

Post-synaptic action of morphine on glutamatergic neuronal transmission related to the descending antinociceptive pathway in the rat thalamus.

Morphine is a prototypical mu-opioid receptor (MOR) agonist, and can directly inhibit pain transmission at both spinal and supraspinal levels. In the present study, we investigated the properties of thalamic neurons in an opioid-sensitive pain-modulating circuit. Application of morphine to cultured thalamic neurons evoked a potentiation of glutamate-induced peak currents, which was blocked by the MOR antagonist. Application of the protein kinase C inhibitor chelerythrine significantly inhibited the morphine-evoked enhancement of glutamate-induced currents. Immunoreactivity for MOR was observed with high density in the habenular nucleus (Hb) of the thalamus in rats, which was clearly co-localized with NMDA receptor subunit 1 (NRI). In this study, we show that microinjection of morphine into the Hb produced a dose-dependent increase in the tail-flick latency and enhanced the antinociceptive effect induced by the intra-Hb injection of glutamate. When fluoro-gold (FG) was used as a retrograde tracer, we found that FG-labeled neurons in the Hb after the microinjection of FG into the periaqueductal gray expressed both MOR and NR1. The present data suggest that the stimulation of MOR in the Hb may be involved in activation of the descending antinociceptive pathway through glutamatergic neurotransmission via the NMDA receptor.

[The functional change in the 5-HT1A receptor induced by stress and the role of the 5-HT1A receptor in neuroprotection].

Mice exposed to various stresses, especially restrained-stress, revealed the anxiogenic effect detected by the light-dark test. Under this condition, a remarkable decrease in [35S]GTPgammaS binding to membranes from the prefrontal cortex, amygdala and hypothalamus of restrained-stress mice stimulated by the selective 5-HT1A receptor agonist 5-carboxamidotriptamine (5-CT) was clearly observed, whereas a significant increase in [35S]GTPgammaS binding stimulated by the 5-HT1A receptor agonist was clearly observed in the dorsal raphe nuclei (DRN) of restrained-stress mice. The immunohistochemical study showed a drastic reduction in phosphorylated-CREB-like immunoreactivity in the DRN of restrained-stress mice. Furthermore, we found a drastic reduction in myelin-associated glycoprotein (MAG)-like immunoreactivity (MAG-IR) in the DRN, amygdala and hypothalamus, indicating the direct suppression of synaptic transmission in these regions. It has been accepted that GSK3beta in the Wnt signal pathway plays an important role in various neuronal functions including apoptosis, clustering of synapsin I and early growth and axonal remodeling. In the present study, the increase in protein levels of GSK3beta and phosphorylated-GSK3beta to cytosol fractions of the amygdala was noted in restrained-stress mice. Taken together, these results suggest that restrained stress may directly affect the 5-HT1A receptor-regulated synaptic transmission in the brain, leading to the expression of the anxiogenic effect in mice. It is well known that various stresses induce intracellular oxidative stress. The present study was then undertaken to investigate the effect of the stimulation of 5-HT1A receptors on oxidative stress. Treatment with H2O2 caused the activation of caspase-3-positive cells and the reduction in levels of MAG-IR in the limbic neuron/glia cocultures as compared to medium alone. The stimulation of 5-HT1A receptor by 5-CT produced a dramatic protection against H2O2-triggered activation of caspase-3 and reduction in levels of MAG-IR. These results suggest that 5-HT1A receptors were involved in the modulation of anxiety and the understanding of molecular mechanisms of 5-HT1A receptor-related cascades may pave the way for new therapeutic strategies for affective disorders.