Molecular basis for the dosing time-dependency of anti-allodynic effects of gabapentin in a mouse model of neuropathic pain

<p>Abstract</p> <p>Background</p> <p>Neuropathic pain is characterized by hypersensitivity to innocuous stimuli (tactile allodynia) that is nearly always resistant to NSAIDs or even opioids. Gabapentin, a GABA analogue, was originally developed to treat epilepsy. Accumulating clinical evidence supports the effectiveness of this drug for diverse neuropathic pain. In this study, we showed that the anti-allodynic effect of gabapentin was changed by the circadian oscillation in the expression of its target molecule, the calcium channel α2δ-1 subunit.</p> <p>Results</p> <p>Mice were underwent partial sciatic nerve ligation (PSL) to create a model of neuropathic pain. The paw withdrawal threshold (PWT) in PSL mice significantly decreased and fluctuated with a period length about 24 h. The PWT in PSL mice was dose-dependently increased by intraperitoneal injection of gabapentin, but the anti-allodynic effects varied according to its dosing time. The protein levels of α2δ-1 subunit were up-regulated in the DRG of PSL mice, but the protein levels oscillated in a circadian time-dependent manner. The time-dependent oscillation of α2δ-1 subunit protein correlated with fluctuations in the maximal binding capacity of gabapentin. The anti-allodynic effect of gabapentin was attenuated at the times of the day when α2δ-1 subunit protein was abundant.</p> <p>Conclusions</p> <p>These findings suggest that the dosing time-dependent difference in the anti-allodynic effects of gabapentin is attributable to the circadian oscillation of α2δ-1 subunit expression in the DRG and indicate that the optimizing its dosing schedule helps to achieve rational pharmacotherapy for neuropathic pain.</p

Time-Dependent Interaction between Differentiated Embryo Chondrocyte-2 and CCAAT/Enhancer-Binding Protein ␣ Underlies the Circadian Expression of CYP2D6 in Serum- Shocked HepG2 Cells

ABSTRACT Differentiated embryo chondrocyte-2 (DEC2), also known as bHLHE41 or Sharp1, is a pleiotropic transcription repressor that controls the expression of genes involved in cellular differentiation, hypoxia responses, apoptosis, and circadian rhythm regulation. Although a previous study demonstrated that DEC2 participates in the circadian control of hepatic metabolism by regulating the expression of cytochrome P450, the molecular mechanism is not fully understood. We reported previously that brief exposure of HepG2 cells to 50% serum resulted in 24-h oscillation in the expression of CYP3A4 as well as circadian clock genes. In this study, we found that the expression of CYP2D6, a major drug-metabolizing enzyme in humans, also exhibited a significant oscillation in serum-shocked HepG2 cells. DEC2 interacted with CCAAT/enhancer-binding protein (C/EBP␣), accompanied by formation of a complex with histone deacetylase-1, which suppressed the transcriptional activity of C/EBP␣ to induce the expression of CYP2D6. The oscillation in the protein levels of DEC2 in serum-shocked HepG2 cells was nearly antiphase to that in the mRNA levels of CYP2D6. Transfection of cells with small interfering RNA against DEC2 decreased the amplitude of CYP2D6 mRNA oscillation in serumshocked cells. These results suggest that DEC2 periodically represses the promoter activity of CYP2D6, resulting in its circadian expression in serum-shocked cells. DEC2 seems to constitute a molecular link through which output components from the circadian clock are associated with the time-dependent expression of hepatic drug-metabolizing enzyme

Brain natriuretic peptide and cancer

Background Natriuretic peptides have been proposed as biomarkers of cardiovascular disease, especially heart failure. Brain natriuretic peptide (BNP) has also been shown to be upregulated at the transcriptional and translational levels by pro-inflammatory cytokines in cardiac myocytes. Although we often measure plasma BNP levels in cancer patients, it remains unknown whether cancer-related inflammation affects the plasma BNP levels. We investigated the relationship between the BNP and human cancers. Methods We retrospectively studied 2,923 patients in whom the plasma BNP levels and serum C-reactive protein (CRP) were measured and echocardiography was performed. Patients with clinically evident heart failure (NYHA II or higher), heart disease requiring medical treatment or surgery, renal dysfunction, and inflammatory disease were excluded. There were 234 patients in the final analysis. Blood sampling was performed before surgery and chemotherapy. In addition, we evaluated the relationship between the inflammation and plasma BNP levels in mouse models of colon cancer. Results Of the 234 patients, 80 were diagnosed with cancer. Both the plasma BNP and serum CRP levels were significantly higher in cancer patients than those without. There were no significant differences in the echocardiographic parameters. There was a significant positive correlation between the plasma BNP and serum CRP levels in cancer patients (r = 0.360, P<0.01) but not in those without. In cancer patients, only the CRP correlated with the BNP independent of the age, creatinine level, hypertension, and body mass index. In addition, in nude mice with subcutaneous colon cancer, the plasma BNP level was elevated compared with that in non-cancer mice, and there was a significant relationship between the plasma BNP and serum levels of the inflammatory markers. Conclusions In cancer patients, as well as colon cancer model mice, the plasma BNP levels were elevated, possibly due to cancer-related inflammation. The effect of cancer on the BNP levels should be considered when using BNP as an indicator of heart failure in cancer patients

Dietary supplementation with essence of chicken enhances daily oscillations in plasma glucocorticoid levels and behavioral adaptation to the phase-shifted environmental light–dark cycle in mice

Maintenance of circadian rhythms is essential to many aspects of human health, including metabolism and neurological and psychiatric well-being. Chronic disruption of circadian clock function is implicated in increasing the risk of metabolic syndrome, cardiovascular events and development of cancers. However, there are little approaches to reinforce the function of circadian clock for prevention of these diseases. Essence of Chicken (EC) is a nutritional supplement that is traditionally made by extracting water soluble substances derived from cooking the whole chicken. In this study, we found that dietary supplementation with EC enhanced circadian oscillation of glucocorticoid secretion in mice, and this was accompanied by enhancement of circadian oscillation in the adrenal expression of steroidogenic acute regulatory (StAR) protein that mediates the rate-limiting step of glucocorticoid synthesis. Furthermore, EC facilitated re-entrainment of behavioral rhythm in mice when phase of the light–dark cycle was suddenly advanced. These results suggest that intake of EC has enhancement effect on circadian clock function in mice, which may contribute to sustain health and also offer new preventive strategies against circadian-related diseases

Optimizing the dosing schedule of l-asparaginase improves its anti-tumor activity in breast tumor-bearing mice

Proliferation of acute lymphoblastic leukemic cells is nutritionally dependent on the external supply of asparagine. l-asparaginase, an enzyme hydrolyzing l-asparagine in blood, is used for treatment of acute lymphoblastic leukemic and other related blood cancers. Although previous studies demonstrated that l-asparaginase suppresses the proliferation of cultured solid tumor cells, it remains unclear whether this enzyme prevents the growth of solid tumors in vivo. In this study, we demonstrated the importance of optimizing dosing schedules for the anti-tumor activity of l-asparaginase in 4T1 breast tumor-bearing mice. Cultures of several types of murine solid tumor cells were dependent on the external supply of asparagine. Among them, we selected murine 4T1 breast cancer cells and implanted them into BALB/c female mice kept under standardized light/dark cycle conditions. The growth of 4T1 tumor cells implanted in mice was significantly suppressed by intravenous administration of l-asparaginase during the light phase, whereas its administration during the dark phase failed to show significant anti-tumor activity. Decreases in plasma asparagine levels due to the administration of l-asparaginase were closely related to the dosing time-dependency of its anti-tumor effects. These results suggest that the anti-tumor efficacy of l-asparaginase in breast tumor-bearing mice is improved by optimizing the dosing schedule. Keywords: l-asparaginase, Asparagine, Solid tumor, Chrono-pharmacotherap