Byung-Il Min

Resveratrol stimulates glucose transport in C2C12 myotubes by activating AMP-activated protein kinase

trans-Resveratrol (t-RVT), a naturally occurring polyphenol found in Polygonum cuspidatum, grape, and red wine, has been reported to have anti- inflammatory, cardioprotective, and cancer chemopreventive properties. However antidiabetic effect of t-RVT has not yet been reported. In this study, we show that t-RVT increases glucose uptake in C2C12 myotubes by activating AMP-activated protein kinase (AMPK), uncovering an antidiabetic potential of t-RVT for the first time. AMPK plays a central role in the regulation of glucose and lipid metabolism, and hence it is considered a novel therapeutic target for metabolic syndrome such as type 2 diabetes. t-RVT significantly induced glucose uptake in C2C12 cells, via AMPK activation, but not a phosphatidylinositol-3 kinase (PI-3 kinase) signal pathway. The induced glucose uptake was attenuated by pretreatment with a pharmacological inhibitor for AMPK, indicating that the effect of t-RVT primarily depends on AMPK activation. However, in the presence of insulin, t-RVT also potentiated the effect of insulin on glucose uptake via AMPK activation, which led to further activation of PI-3 kinase/Akt signal pathway.

Effects of electroacupuncture on cold allodynia in a rat model of neuropathic pain: Mediation by spinal adrenergic and serotonergic receptors

The present study was performed to examine the effects of electroacupuncture (EA) on cold allodynia and its mechanisms related to the spinal adrenergic and serotonergic systems in a rat model of neuropathic pain. For the neuropathic surgery, the right superior caudal trunk was resected at the level between S1 and S2 spinal nerves innervating the tail. Two weeks after the nerve injury, EA stimulation (2 or 100 Hz) was delivered to Zusanli (ST36) for 30 min. The behavioral signs of cold allodynia were evaluated by the tail immersion test [i.e., immersing the tail in cold water (4 degrees C) and measuring the latency to an abrupt tail movement] before and after the stimulation. And then, we examined the effects of intrathecal injection of prazosin (alpha1-adrenoceptor antagonist, 30 microg), yohimbine (alpha2-adrenoceptor antagonist, 30 microg), NAN-190 (5-HT1A antagonist, 15 microg), ketanserin (5-HT2A antagonist, 30 microg), and MDL-72222 (5-HT3 antagonist, 12 microg) on the action of EA stimulation. Although both 2 Hz and 100 Hz EA significantly relieved the cold allodynia signs, 2 Hz EA induced more robust effects than 100 Hz EA. In addition, intrathecal injection of yohimbine, NAN-190, and MDL-72222, but not prazosin and ketanserin, significantly blocked the relieving effects of 2 Hz EA on cold allodynia. These results suggest that low-frequency (2 Hz) EA is more suitable for the treatment of cold allodynia than high-frequency (100 Hz) EA, and spinal alpha2-adrenergic, 5-HT1A and 5-HT3, but not alpha1-adrenergic and 5-HT2A, receptors play important roles in mediating the relieving effects of 2 Hz EA on cold allodynia in neuropathic rats.

Relieving effects of electroacupuncture on mechanical allodynia in neuropathic pain model of inferior caudal trunk injury in rat: mediation by spinal opioid receptors.

The relieving effects of electroacupuncture (EA) on mechanical allodynia and its mechanism related to the spinal opioid system were investigated in a rat model of neuropathic pain. To produce neuropathic pain in the tail, the right superior caudal trunk was resected between the S1 and S2 spinal nerves. Two weeks after the surgery, EA stimulation (2 or 100 Hz, 0.3 ms, 0.2-0.3 mA) was delivered to Zusanli (ST36) for 30 min. The degree of mechanical allodynia was evaluated quantitatively by touching the tail with von Frey hair (2.0 g) at 10 min intervals. These rats were then subjected to an i.t. injection with one of the three specific opioid agonists in successive ways: the mu agonist (DAMGO 25, 50 and 100 pmol), the delta agonist (DADELT II 0.5, 1 and 2 nmol), and the kappa agonist (U50488H 5, 10 and 20 nmol) separated by 10 min in cumulative doses. During 30 min of EA stimulation, specific opioid antagonists were subjected to i.t. injection: the mu antagonist (beta-FNA 5, 10 and 20 nmol), the delta antagonist (naltrindole 5, 10 and 20 nmol), and the kappa antagonist (nor-BNI 3, 6 and 12 nmol) separated by 10 min in cumulative doses. As a result, EA reduced the behavioral signs of mechanical allodynia. Two Hz EA induced a robust and longer lasting effect than 100 Hz. All three opioid agonists also showed relieving effects on mechanical allodynia. However, nor-BNI could not block the EA effects on mechanical allodynia, whereas beta-FNA or naltrindole significantly blocked EA effects. These results suggest that the mu and delta, but not kappa, opioid receptors in the spinal cord of the rat, play important roles in mediating relieving effects on mechanical allodynia induced by 2 Hz EA.

The difference between electroacupuncture only and electroacupuncture with manipulation on analgesia in rats

Plain acupuncture uses manipulation (rotation or varying the depth of insertion of the needle) to increase its effect. However, in commonly used electroacupunture (EA), variable manipulations have not been used. This study was performed to investigate the possibility of an increase in analgesic effect by adding manipulation to EA. The pain index used was the Tail-Flick latency (TFL) of the rat, which was lightly anesthetized with thiopental sodium (intraperitoneally). Four types of manipulation were used. Rotation and varying the depth of the needle (RN and VN) was employed using two different types of manipulation during each 20 min stimulation of EA. Each manipulation persisted for 1 min out of every 5 min (long - duration and long - interval: LDLI) or 12 s every 1 min (short - duration and short interval: SDSI). EA produced an increase in TFL; peak value was 49.7+/-12.2% of the pre - EA and occurred immediately after cessation of 20 min of EA stimulation. Performing RN or VN combined with EA also increased TFL more than just EA and a greater peak increase in TFL was observed with a SDSI - RN and SDSI - VN as compared to a LDLI - RN and LDLI - VN (77.5+/-13.8, 79.2+/-19.8 and 67.3+/-14.0%, 65.6+/-23.7% of the pre - EA, respectively). These results indicate that manipulation combined with EA produces a more potent antinociception than when only EA is applied.

The antioxidant effects of genistein are associated with AMP-activated protein kinase activation and PTEN induction in prostate cancer cells.

Epidemiological evidence suggests a lower incidence of prostate cancer in Asian countries, where soy products are more frequently consumed than in Western countries, indicating that isoflavones from soy have chemopreventive activities in prostate cells. Here, we tested the effects of the soy isoflavone genistein on antioxidant enzymes in DU145 prostate cancer cells. Genistein significantly decreased reactive oxygen species levels and induced the expression of the antioxidant enzymes manganese (Mn) superoxide dismutase (SOD) and catalase, which were associated with AMP-activated protein kinase (AMPK) and phosphatase and tensin homolog deleted from chromosome 10 (PTEN) pathways. The induced expression of catalase, MnSOD, and PTEN were attenuated by pretreatment with a pharmacological inhibitor for AMPK, indicating the effects of genistein primarily depend on AMPK. Furthermore, PTEN is essential for genistein activity, as shown by PTEN transfection in PTEN-deficient PC3 cells. Thus, genistein induces antioxidant enzymes through AMPK activation and increased PTEN expression.

Effects of electroacupuncture on the mechanical allodynia in the rat model of neuropathic pain.

The analgesic effects of acupuncture on the mechanical allodynia in the rat model of neuropathic pain have not yet been studied. The aim of the present study is: first, to determine if electroacupuncture (EA) or morphine attenuates the mechanical allodynia; and secondly, to examine if the EA effect may be mediated by endogenous opioids. To produce neuropathic pain, the right superior caudal trunk was resected between the S3 and S4 spinal nerves. Twenty-one days after the neuropathic surgery, low frequency EA stimulation (2 Hz, 0.3 ms, 0.07 mA) delivered to Houxi (S13) for 30 min relieved significantly the signs of mechanical allodynia. Intraperitoneal (i.p.) morphine (0.5 or 1.5 mg/kg) also relieved the signs of mechanical allodynia in a dose-dependent manner. In addition, the antiallodynic effect of Houxi EA was blocked by pretreatment with naloxone (2 mg/kg, i.p.). However, combined application of EA and morphine did not show an obvious synergistic effect. These results suggest that low frequency EA or morphine can relieve the mechanical allodynia signs and the EA effect can be mediated by endogenous opioid systems.

Inhibitory effects of electroacupuncture on stress responses evoked by tooth-pulp stimulation in rats.

The mechanism of electroacupuncture (EA) on the stress responses induced by tooth-pulp stimulation was investigated in anesthetized adult female Sprague-Dawley rats. The Hoku point in the Chinese meridian was used for acupuncture stimulation. Constant rectangular current (1 mA) pulses of 5-ms duration were delivered at 3 Hz through a pair of needles for 15 min. As for stress response indexes, we have monitored changes in arterial blood pressure and the levels of blood catecholamines, corticosterone, and ACTH. Arterial blood pressure was increased by high frequency stimulation (0.1 mA, 0.5 ms, 100 Hz for 15 s) of tooth-pulp in the control condition. After EA, we did not observe the same responses of the arterial blood pressure changes with the same stimuli. The tooth-pulp stimulation increased the concentrations of plasma norepinephrine (NE), epinephrine (E), dopamine (DA), corticosterone, and ACTH significantly from the levels of those before stress. After treatment with EA, the stress-induced increase in NE, DA, corticosterone, and ACTH but not the rise in E, were inhibited. When naloxone, an opioid antagonist, was administered intraperitoneally before EA, the effects of EA on stress responses were reduced. In this study, it can be suggested that EA has not only an analgesic effect but also suppressive effects on the stress responses primarily through the mediation of an endogenous opioid.

Modulation of glycine-induced chloride current in acutely dissociated rat periaqueductal gray neurons by μ-opioid agonist, DAGO

Effect of a mu-opioid agonist (D-Ala2,N-MePhe4,Gly5-ol-enkephalin, DAGO), on glycine (Gly)-induced chloride current (IGly) was investigated in the periaqueductal gray (PAG) neurons acutely dissociated 1-2-week-old Wistar rats by the use of nystatin-perforated patch recording configuration under voltage-clamp condition. At a holding potential (VH) of -40 mV, DAGO caused a sustained potentiation of IGly at the low concentrations (10(-6)-10(-5) M) but reduced slightly the Gly response at the high concentration (10(-4) M). The reversal potential of IGly was equal to the Cl- equilibrium potential (ECl) and was not changed in the presence of 10(-6) M DAGO. The 10(-5) M Gly response was inhibited by the simultaneous treatment of forskolin and 3-isobutyl-1-methylxanthine (IBMX). H-89, a protein kinase A (PKA) inhibitor, increased the 10(-5) M Gly response but had little effect on the 10(-4) M Gly response. DAGO increased 10(-5) M Gly response in the presence of forskolin and IBMX but, not more than in the absence of forskolin and IBMX. The 10(-5) M Gly response augumented by DAGO was not affected by adding H-89. The present results suggest that the glycine-induced chloride current is cAMP dependent and is inhibited by PKA, and that the potentiation of the glycine response by DAGO is also cAMP dependent and is due to the inhibition of PKA as that of H-89. We conclude that the potentiation of glycine response by DAGO is mediated by an inhibition of cAMP-dependent PKA in the PAG neurons.

Electroacupuncture attenuates mechanical and warm allodynia through suppression of spinal glial activation in a rat model of neuropathic pain

Neuropathic pain remains one of the most difficult clinical pain syndromes to treat. It is traditionally viewed as being mediated solely by neurons; however, glial cells have recently been implicated as powerful modulators of pain. It is known that the analgesic effects of electroacupuncture (EA) are mediated by descending pain inhibitory systems, which mainly involve spinal opioid, adrenergic, dopaminergic, serotonergic, and cholinergic receptors. However, studies investigating the suppressive effects of EA on spinal glial activation are rare. In the present study, we assessed the cumulative analgesic effects of EA on mechanical and warm allodynia in a rat model of neuropathic pain. We investigated the clinical efficacy of EA as long-term therapy and examined its effects on spinal glia, matrix metalloproteinase (MMP)-9/MMP-2, proinflammatory cytokines and serum immunoglobulin G (IgG) concentration. Rats were randomly divided into four groups as follows: the operation group (OP), operation with EA-non acupoint (EA-NA), operation with EA-ST36 acupoint (EA-ST36), and sham operation (shamOP). Following neuropathic or sham surgery, repeated EA was performed every other day after the behavioral test. On day 53 after the behavioral test, rats were perfused for immunohistochemistry and Western blot analysis to observe quantitative changes in spinal glial markers such as OX-42, astrocytic glial fibrillary acidic protein (GFAP), MMP-9/MMP-2, and proinflammatory cytokines. Allodynia and OX-42/GFAP/MMP-9/MMP-2/tumor necrosis factor (TNF)-α/interleukin (IL)-1β activity in the EA-ST36 group was significantly reduced, compared to the OP and EA-NA groups, and IgG in EA-ST36 rats significantly increased. Our results suggest that the analgesic effect of EA may be partly mediated via inhibition of inflammation and glial activation and repeated EA stimulation may be useful for treating chronic pain clinically.

Acupuncture suppresses ischemia-induced increase in c-Fos expression and apoptosis in the hippocampal CA1 region in gerbils.

Acupuncture has been used for the enhancement of functional recovery from various disorders including stroke. In the present study, the effects of acupuncture on the c-Fos expression and apoptosis in the hippocampal CA1 region of gerbils following transient global ischemia were investigated via immunohistochemistry for c-Fos and caspase-3 and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay. Enhanced Fos, TUNEL, and caspase-3 positivities were detected in the hippocampal CA1 region in the ischemic gerbils. Acupunctural treatment suppressed the ischemia-induced increment in the number of Fos-, TUNEL-, and caspase-3-positive cells: the most potent suppressive effect was observed at the Zusanli acupoint. These results suggest that acupunctural treatment alleviates ischemia-induced apoptosis and may aid in the recovery following ischemic cerebral injury.