Resveratrol chemosensitizes HER-2-overexpressing breast cancer cells to docetaxel chemoresistance by inhibiting docetaxel-mediated activation of HER-2-Akt axis.

As breast cancer cells often develop chemoresistance, better therapeutic options are in search to circumvent it. Here we demonstrate that human epidermal growth factor receptor-2 (HER-2)-overexpressing breast cancer cells resist docetaxel-induced cytotoxicity by upregulating HER-2 and its activity downstream, through Akt and mitogen-activated protein kinase (MAPK) pathways. We observed that introducing resveratrol as a chemosensitizer in docetaxel chemotherapy blocks upregulation and activation of HER-2 in addition to blocking downstream signaling pathways such as Akt. Resveratrol and docetaxel combination results in the synergistic induction of cell death in HER-2-overexpressing SK-BR-3 cells, whereas introduction of wild-type HER-2 in MDA-MD-231 cells increased the resistance to docetaxel. Dominant-negative HER-2 sensitizes SK-BR-3 cells to docetaxel. Our study identified a new synergistic therapeutic combination that targets HER-2-induced breast cancer resistance and might help to overcome therapeutic resistance during breast cancer therapy. The synergism of docetaxel and resveratrol was maximum in SK-BR-3, which is unique among the cell lines studied, due to its high expression status of HER-2, a receptor known to dictate the signaling environment of breast cancer cells. Docetaxel could further induce HER-2 activity in these cells, which was downregulated on resveratrol treatment. Transfection of DN-HER-2 in SK-BR-3 cells inhibits the synergism as the transfection itself sensitizes these cells to docetaxel, leaving no role for resveratrol, whereas ectopic expression of HER-2 introduces the synergism in MDA-MB-231, the triple-negative cell line, in which the synergism was minimum, attesting the crucial role of HER-2 in suppressing the sensitivity to docetaxel. Single-agent docetaxel induced HER-2-mediated resistance to cell death, which was blocked by resveratrol. Resveratrol also downregulated docetaxel-induced activation of MAPK and Akt, survival signaling pathways downstream of HER-2. In short, this study, for the first time, establishes the role of HER-2-Akt signaling axis in regulating the synergistic effect of docetaxel and resveratrol in breast cancer cells overexpressing HER-2.

Movement- and behavioral state-dependent activity of pontine reticulospinal neurons.

Forty-five years ago Shik and colleagues were the first to demonstrate that electrical stimulation of the dorsal pontine reticular formation induced fictive locomotion in decerebrate cats. This supraspinal motor site was subsequently termed the "mesencephalic locomotor region (MLR)". Cholinergic neurons of the pedunculopontine tegmental nucleus (PPT) have been suggested to form, or at least comprise in part, the neuroanatomical basis for the MLR, but direct evidence is lacking. In an effort to clarify the location and activity profiles of pontine reticulospinal neurons supporting locomotor behaviors, we employed in the present study a retrograde tracing method in combination with single-unit recordings and antidromic spinal cord stimulation as well as characterized the locomotor- and behavioral state-dependent activities of both reticulospinal and non-reticulospinal neurons. The retrograde labeling and antidromic stimulation responses suggested a candidate group of reticulospinal neurons that were non-cholinergic and located just medial to the PPT cholinergic neurons and ventral to the cuneiform nucleus (CnF). Unit recordings from these reticulospinal neurons in freely behaving animals revealed that the preponderance of neurons fired in relation to motor behaviors and that some of these neurons were also active during rapid eye movement sleep. By contrast, non-reticulospinal neurons, which likely included cholinergic neurons, did not exhibit firing activity in relation to motor behaviors. In summary, the present study provides neuroanatomical and electrophysiological evidence that non-cholinergic, pontine reticulospinal neurons may constitute the major component of the long-sought neuroanatomic MLR in mammals.

The development of hypocretin (orexin) deficiency in hypocretin/ataxin-3 transgenic rats.

Narcolepsy is linked to a widespread loss of neurons containing the neuropeptide hypocretin (HCRT), also named orexin. A transgenic (TG) rat model has been developed to mimic the neuronal loss found in narcoleptic humans. In these rats, HCRT neurons gradually die as a result of the expression of a poly-glutamine repeat under the control of the HCRT promoter. To better characterize the changes in HCRT-1 levels in response to the gradual HCRT neuronal loss cerebrospinal fluid (CSF) HCRT-1 levels were measured in various age groups (2-82 weeks) of wild-type (WT) and TG Sprague-Dawley rats. TG rats showed a sharp decline in CSF HCRT-1 level at week 4 with levels remaining consistently low (26%+/-9%, mean+/-S.D.) thereafter compared with WT rats. In TG rats, HCRT-1 levels were dramatically lower in target regions such as the cortex and brainstem (100-fold), indicating decreased HCRT-1 levels at terminals. In TG rats, CSF HCRT-1 levels significantly increased in response to 6 h of prolonged waking, indicating that the remaining HCRT neurons can be stimulated to release more neuropeptide. Rapid eye movement (REM) sleep in TG rats (n=5) was consistent with a HCRT deficiency. In TG rats HCRT immunoreactive (HCRT-ir) neurons were present in the lateral hypothalamus (LH), even in old rats (24 months) but some HCRT-ir somata were in various stages of disintegration. The low output of these neurons is consistent with a widespread dysfunction of these neurons, and establishes this model as a tool to investigate the consequences of partial hypocretin deficiency.

Role of wake inducing brain stem area on rapid eye movement sleep regulation in freely moving cats.

Some of the characteristic symptoms associated with rapid eye movement (REM) sleep are opposite to, while some apparently resemble, those of wakefulness. Therefore, it was hypothesised that the neurons present in the wakefulness inducing area(s) in the brain are likely to communicate with the REM sleep related neurons. Brain stem neurons were classified based on their firing rates in relation to electrophysiological correlates associated with spontaneous sleep and wakefulness recorded from freely moving, normally behaving cats. Thereafter, the responses of those classified neurons to stimulation of brain stem reticular wakefulness inducing area were studied. Results from 63 neurons showed that the wake inducing area affected 62% of the neurons. Fifty-eight percent of the neurons which increased firing during wakefulness, including the REM-OFF neurons, were excited, while 70% of the neurons which decreased firing during wakefulness, including the REM-ON neurons, were inhibited. These observations support our hypothesis and, along with their physiological significance, are discussed.

Differential responses of brain stem neurons during spontaneous and stimulation-induced desynchronization of the cortical eeg in freely moving cats.

The EEG is desynchronized during wakefulness and REM sleep. There are awake and REM sleep-related neurons in the brain stem. This study was carried out to investigate if the same neuron in the brain stem reticular formation may be responsible for EEG desynchronization during wakefulness and REM sleep. Single neuronal activity was recorded in chronically prepared freely moving normal cats and their activities were correlated with EEG desynchronization during spontaneous wakefulness, REM sleep, and during wakefulness induced by stimulation of the brain stem reticular formation. A majority of the neurons showed an increased firing associated with spontaneous EEG desynchronization during wakefulness and REM sleep, however, about 55% of them showed a similar behavior during stimulation-induced desynchronization. It was found that responses of a majority of the neurons during stimulation-induced desynchronization were similar to that of their firing rate during EEG desynchronization associated with spontaneous wakefulness irrespective of their behavior during REM sleep; the REM-ON neurons were not affected by the stimulation-induced desynchronization. A majority of the neurons which showed an increased firing during spontaneous and stimulation-induced EEG desynchronization received an excitatory input from the brain stem reticular formation. The results of this study suggest that although some neurons may be common, there is a strong possibility that the same neuron in the brain stem reticular formation is not involved in EEG desynchronization during wakefulness and REM sleep.