Yan-Hua Lin

Antidepressant effects of curcumin in the forced swim test and olfactory bulbectomy models of depression in rats

Curcuma longa is a major constituent of Xiaoyao-san, the traditional Chinese medicinal formula, which has been used to effectively manage stress and depression-related disorders in China. Curcumin is the active component of curcuma longa, and we hypothesized that curcumin would have an influence on depressive-like behaviors. The purpose of the present study was to confirm the putative antidepressant effect of chronic administrations of curcumin (1.25, 2.5, 5 and 10 mg/kg, p.o.) in the forced swimming test and bilateral olfactory bulbectomy (OB) models of depression in rats. In the first study, chronic treatment with curcumin (14 days) reduced the immobility time in the forced swimming test. In the second experiment, curcumin reversed the OB-induced behavioral abnormalities such as hyperactivity in the open field, as well as deficits in step-down passive avoidance. In addition, OB-induced low levels of serotonin (5-HT), noradrenaline (NA), high 5-hydroxyindoleacetic acid (5-HIAA) and 4-dihydroxyphenylacetic acid (DOPAC) in the hippocampus were observed, and were completely reversed by curcumin administration. A slight decrease in 5-HT, NA and dopamine (DA) levels was found in the frontal cortex of OB rats which was also reversed by curcumin treatment. These results confirm the antidepressant effects of curcumin in the forced swim and the OB models of depression in rats, and suggest that these antidepressant effects may be mediated by actions in the central monoaminergic neurotransmitter systems.

Sex differences in stress responses: Focus on ovarian hormones

Women in the reproductive age are more vulnerable to develop affective disorders than men. This difference may attribute to anatomical differences, hormonal influences and environmental factors such as stress. However, the higher prevalence in women normalizes once menopause is established, suggesting that ovarian hormones may play an important role in the development of depression in women. Ovarian hormones such as estrogen can pass the brain-blood barrier and bind to cytoplasmatic estrogen receptor (ER)-alpha and ER-beta in different areas of the limbic system. During stress, estrogen can modulate the behavioral and neurobiological response depending on the concentrations of estrogen. In this review we present evidence for disparate effects of chronic stress on neuroplasticity and brain activity in male and female rats. Furthermore, we will demonstrate that effects of social support on coping with stress can be mimicked by social housing of rats and that this model can be used for identification of underlying neurobiological mechanisms, including behavior, phosphorylation of CREB and ERK1/2, and brain activity changes as measured with fos expression. Using cyclic administration of estrogen in ovariectomized female rats we could specifically address effects of different plasma estrogen levels and antidepressants on stress-induced neuroplasticity and activity changes. In this model we also studied effects of estrogen on recovery after chronic stress. We conclude that the female brain has a different innate strategy to handle stress than the male brain and that female animal models are necessary for studying the underlying mechanisms and options for treatment.

Effect of chronic unpredictable mild stress on brain–pancreas relative protein in rat brain and pancreas

Brain-pancreas relative protein (BPRP) is a novel protein whose biological function remains unknown. Here, we report a possible role of BPRP in male rats exposed to chronic unpredictable mild stress (CUMS) to induce depression for 3 weeks. Compared to unstressed rats, those exposed to CUMS showed significantly less weight gain with age, decreased consumption of (and preference for) sucrose without a change in total fluid consumption. Exposure to CUMS significantly reduced open-field exploration, rearing and grooming indicative of lethargy, apathy and bodily neglect, respectively. Brain MAO-A and MAO-B activity were both significantly increased in the stressed rats. These results verified induction of depressive symptoms by CUMS. The stressed animals showed a significant reduction in pancreatic BPRP, which was accompanied by an increase in levels of blood sugar and a decrease of insulin. But they showed no apparent alteration in levels or distribution of BPRP in the hippocampal formation, which nevertheless displayed a thinner dentate granule cell layer perhaps related to elevated MAO-B activity. These findings suggest that stress-induced reduction of pancreatic BPRP may cause diabetic symptoms. Whether those symptoms in turn contribute to the onset of depression requires further study.

Sex Differences in the Effects of Acute and Chronic Stress and Recovery after Long-Term Stress on Stress-Related Brain Regions of Rats

Studies show that sex plays a role in stress-related depression, with women experiencing a higher vulnerability to its effect. Two major targets of antidepressants are brain-derived neurotrophic factor (BDNF) and cyclic adenosine monophosphate response element–binding protein (CREB). The aim of this study was to investigate the levels of CREB, phosphorylation of CREB (pCREB), and BDNF in stress-related brain regions of male and female rats after stress and recovery. CREB and pCREB levels were examined in CA1, CA2, CA3, paraventricular nucleus of the thalamus (PVT), amygdala, anterior cingulate area, dorsal part (ACAd), and infralimbic area of prefrontal cortex (PFC), whereas dentate gyrus (DG) and prelimbic area (PL) of PFC were examined for BDNF levels. Our results demonstrate that levels of CREB and pCREB in male CA1, CA2 and CA3, PVT, amygdala, and ACAd were reduced by stress, whereas the same brain regions of female rats exhibited no change. BDNF levels were decreased by chronic stress in female PL but were increased by acute stress in female DG. BDNF levels in male DG and PL were found not to undergo change in response to stress. Abnormalities in morphology occurred after chronic stress in males but not in females. In all cases, the levels of CREB, pCREB, and BDNF in recovery animals were comparable to the levels of these proteins in control animals. These findings demonstrate a sexual dimorphism in the molecular response to stress and suggest that these differences may have important implications for potential therapeutic treatment of depression.

Salvianolic acid B protects human endothelial cells from oxidative stress damage: a possible protective role of glucose-regulated protein 78 induction

AIMS The purposes of the present study were to both evaluate the protective effects of Salvianolic acid B (Sal B) and to determine the possible molecular mechanisms by which Sal B protects endothelial cells from damage caused by oxidative stress. METHODS AND RESULTS Pretreatment with Sal B markedly attenuated H(2)O(2)-induced viability loss, lactate dehydrogenase leakage and apoptosis in human umbilical vein endothelial cells (HUVECs). The mechanism of Sal B protection was studied using two-dimensional gel electrophoresis coupled with hybrid quadrupole time-of-flight mass spectrometry. Database searching implicated that glucose-regulated protein 78 (GRP78), a central regulator for endoplasmic reticulum (ER) stress, was up-regulated in Sal B-exposed HUVECs. GRP78 expression regulation was confirmed by western blot and RT-PCR (reverse transcription-polymerase chain reaction) analyses. Additionally, GRP94, which shares significant sequence homology with GRP78, was also up-regulated in Sal B-treated cells. Sal B caused pancreatic ER kinase (PKR)-like ER kinase (PERK) activation followed by the phosphorylation of eukaryotic translation initiation factor 2 alpha (eIF2 alpha) and the expression of activating transcription factor 4 (ATF4). Knockdown of endogenous ATF4 expression partially repressed Sal B-induced GRP78 induction. Further investigation showed that ATF6 was also activated by Sal B. Knockdown of GRP78 by siRNA significantly reduced the protective effects of Sal B. CONCLUSION The results suggest that Sal B induces the expression of GRP78 by activating ATF6 and the PERK-eIF2 alpha-ATF4 pathway. Furthermore, up-regulation of GRP78 by Sal B may play an important role in protecting human endothelial cells from oxidative stress-induced cellular damage.

Effects of Long-Term Stress and Recovery on the Prefrontal Cortex and Dentate Gyrus in Male and Female Rats

Women show a higher prevalence for depression than men. However, the biological basis of gender differences in stress response and recovery still remain poorly understood. Therefore, the aim of the study was to assess the gender differences in response to acute stress, chronic stress and recovery in rats. Our results showed that stress decreased male body weight but had no effect on female rats. Open field test demonstrated behavioral changes in grooming and velocity after chronic stress and recovery. Increased activity of hypothalamic-pituitary-adrenocortical axis was reflected by adrenal hypertrophy and increase of plasma corticosterone levels except in the socially housed female rats after stress. Gender and brain region differences in response to stress and recovery were found in the expression of cAMP response element-binding protein (CREB) and phosphorylated CREB (pCREB). On the whole, expression of CREB and pCREB in male dentate gyrus (DG) and prefrontal cortex (PFC) was sensitive but in female DG and PFC it was resistant to acute and chronic stress. Interestingly, recovery restored the measured parameters to the normal level in male rats but not in female rats. In conclusion, these results suggest that male and female rats responded to stress and recovery in a different way.

Hypoxia-induced Up-regulation of Aquaporin-1 Protein in Prostate Cancer Cells in a p38-dependent Manner

Background/Aims: Aquaporin-1 (AQP1) is a glycoprotein that mediates osmotic water transport, its expression has been found to correlate with tumour stage in some tumours. However, the mechanism by which AQP1 protein expression is regulated in tumor cells remains to be fully elucidated. We hypothesized that hypoxia might play an important role in AQP1 induction during tumorigenesis and at the late stages of tumor development. Methods: Isotonic and serum-free hypoxic models were used to investigate AQP1 expression in PC-3M human prostate cancer cells. Results: AQP1 expression was up-regulated by density-induced pericellular hypoxia and cobalt(II) chloride (CoCl2)-induced hypoxia at the transcriptional level. Moreover, phosphorylation of p38 mitogen-activated protein kinase (MAPK) was induced by density-induced pericellular hypoxia and CoCl2-induced hypoxia, specific inhibitors of p38 MAPK could concentration-dependently block those effects of hypoxia on AQP1 expression. Intracellular calcium ion (Ca2+) and protein kinase C (PKC) were shown to be responsible for the activation of p38 MAPK pathway. In addition, AQP1 induction in dense cultures was dependent on lowered oxygen (O2) tension. In high cell density culture, certain secretory proteins might induce AQP1 expression indirectly. Conclusion: These findings suggest that AQP1 could be induced by hypoxia at transcription level, and the regulation of AQP1 in PC-3M cells is dependent on calcium, PKC and p38 MAPK, as well as low oxygen tension.

GLB prevents tumor metastasis of Lewis lung carcinoma by inhibiting tumor adhesion actions

AbstractAim:To investigate the inhibitory effect of a new compound of GLB on tumor metastasis in vivo and analyze its actions on tumor cell adhesion to clarify its mechanism.Methods:The effect of GLB on tumor metastasis was analyzed by Lewis lung carcinoma model. The pathological morphology of lung alveolar was evaluated by hematoxylin-eosin staining. The effect of GLB on the proliferation of human prostate cancer cell (PC-3M, with a high metastatic characteristic) was studied using the MTT method, and its actions on PC-3M cell adhesion to human umbilical vein endothelial cells (HUVEC) and laminin were analyzed in vitro.Results:GLB (100 mg·kg−1·d−1 for 28 d, ig) reduced the number of lung colonies of Lewis lung carcinoma metastasis significantly (P < 0.05). Simultaneously, GLB could mitigate the damage of lung alveolar caused by metastasic tumor deposits. In vitro, GLB inhibited dramatically the adhesion of PC-3M cells to HUVEC (P < 0.01) and laminin (P < 0.05), without cytotoxic or anti-proliferative action on PC-3M cells.Conclusion:GLB has anti-tumor metastatic activity, which partly depends on its inhibition of tumor adhesion.

Inhibitive effects of low oxygen and glucose deprivation on brain-pancreas relative protein expression via hypoxia- inducible factor-1 pathways.

Background: Brain-Pancreas Relative Protein (BPRP), a novel protein discovered in our lab, was decreased in ischemic rat brain. However, the mechanisms regulating BPRP expression during ischemia need further investigation. Methods: In the present study we cultured PC12 cells with low oxygen and glucose deprivation (LOGD, a model of ischemia in vitro) media, then examined the signal transduction pathways of BPRP expression under LOGD. Results: It was found that LOGD significantly decreased BPRP expression, but increased the intracellular Ca2+ concentration ([Ca2+]i), p38 mitogen-activated protein kinases (MAPK) phosphorylation and hypoxia inducible factor 1 α subunit (HIF-1α) expression. However, BAPTA-AM (an intracellular calcium chelator), SB 203580 (an inhibitor of p38) and HIF-1α antisense significantly inhibited the [Ca2+]i, p38 MAPK phosphorylation and HIF-1α expression respectively. Our results also showed that p38 MAPK phosphorylation was reduced by BAPTA-AM, and HIF-1α expression was inhibited by SB203580 and BAPTA-AM, suggesting that calcium, p38 MAPK and HIF-1α are in the same signal transduction pathways during LOGD. Noticeably, reduced BPRP expression by LOGD can be recovered by SB203580, BAPTA-AM and HIF-1α antisense. Conclusion: All together, our observations suggest that calcium, p38 MAPK activation and HIF-1α are necessary for LOGD-reduced BPRP expression in PC12 cells.

Epinephrine increases phosphorylation of MAP-2c in rat pheochromocytoma cells (PC12 Cells) via a protein kinase C- and mitogen activated protein kinase-dependent mechanism.

Adrenoceptors mediate effects of endogenous catecholamines and have been shown to affect the neuronal development. Microtubule-associated protein-2 (MAP-2) is an important cytoskeleton protein whose phosphorylation in response to extracellular signal is involved in the regulation of neurite outgrowth and neuronal plasticity. The present study was designed to determine the effect of activation of adrenoceptor by epinephrine on MAP-2 phosphorylation in differentiation PC12 cells and, if so, to explore the mediating mechanism. We found that epinephrine could significantly increase the phosphorylation of MAP-2c at ser136 in a dose- and time-dependent manner in differentiated PC12 cells as well as microtubule arrays. Differentiated PC12 cells express alpha 2A-adrenoceptor, whose antagonists could block these mentioned effects of epinephrine, and clonidine which is the agonist of alpha 2-adrenoceptor could mimic the effect of epinephrine. Moreover phosphorylation of ERK and PKC was induced by epinephrine, and ERK and PKC specific inhibitors concentration-dependently prevented epinephrine-induced phosphorylation of MAP-2c at ser136. In addition, pretreatment of PC12 cells with epinephrine partly inhibited 30 microM nocodazole induced neurites retraction. These findings suggest that epinephrine induces phosphorylation of MAP-2c at ser136 through a alpha 2-adrenoceptor mediated, ERK/PKC-dependent signaling pathway, which may contribute to the stabilization of neurites.