Jin-Shang Kim

Autophagy induced by resveratrol prevents human prion protein-mediated neurotoxicity.

Our previous study revealed that resveratrol blocks prion protein peptide PrP(106-126)-induced neurotoxicity. However, the mechanism of resveratrol-mediated neuroprotection in prion diseases is not clear. Resveratrol initiates neuroprotective effects via the activation of autophagy, which protects organelles, cells, and organisms against misfolded protein-disorders, including Alzheimers disease and Parkinsons disease via regulation of mitochondrial homeostasis. Thus, we focused on elucidating the mechanisms responsible for resveratrol-mediated neuroprotection related to mitochondrial homeostasis as a result of autophagy activation. Resveratrol prevented PrP(106-126)-induced neuronal cell death by activating autophagy. Moreover, resveratrol-induced autophagy prevented the PrP(106-126)-induced reduction in mitochondrial potential and translocation of Bax to the mitochondria and cytochrome c release. Our results indicate that treatment with resveratrol appears to protect against neurotoxicity caused by prion protein peptides and the neuroprotection is induced by resveratrol-mediated autophagy signals.

Reactive oxygen species mediated ginsenoside Rg3- and Rh2-induced apoptosis in hepatoma cells through mitochondrial signaling pathways

Panax ginseng (P. ginseng) has anti-cancer effects in several cancer models. Ginsenosides are the main bioactive components in P. ginseng. Korean red ginseng (KRG) extract can potently kill various cancer cells and ginsenosides Rg3 (GRg3) and Rh2 (GRh2) are the primary ginsenosides in KRG. This study was carried out to examine whether KRG and its primary ginsenosides (GRg3 and GRh2) affect apoptosis of human hepatocellular carcinoma cells (Hep3B). KRG, GRg3 and GRh2 have obvious cytotoxic and apoptotic effects in Hep3B cells as evidenced by a decrease in cell viability and mitochondria membrane potential, but an increase in LDH release. In the mitochondria-mediated apoptosis pathway, KRG, GRg3 and GRh2 have the ability to stimulate the release of mitochondrial cytochrome c, activation of caspase-3 and Bax protein, inhibition of Bcl-2 protein and production of intracellular reactive oxygen species in Hep3B cells. These results suggest that KRG, GRg3 and GRh2 may induce apoptosis by direct activation of the mitochondrial pathway.

Korean red ginseng and its primary ginsenosides inhibit ethanol-induced oxidative injury by suppression of the MAPK pathway in TIB-73 cells

ETHNOPHARMACOLOGICAL RELEVANCE Panax ginseng (P. ginseng) is one of the most widely used medicinal plants due to its wide spectrum of medicinal effects. Among the currently available Panax ginseng products, Korea red ginseng (KRG) has been shown to exhibit a variety of antioxidative and hepatoprotective action. AIM OF THE STUDY Our aim was to investigate the effects of KRG and its primary ginsenosides (Rg3 and Rh2) on EtOH-induced injury to mouse hepatocytes (TIB-73). MATERIALS AND METHODS We investigated the effects of KRG and its primary ginsenoside on EtOH-induced injury to TIB-73 cells and evaluated MAPKs signals as a possible mechanism of action. Hepatocytic injury was evaluated by biochemical assays as cell viability, lactate dehydrogenase (LDH), aspartate aminotransferase (AST), ROS and mitochondria membrane potential (MMP) level in TIB-73 cells. The levels of MAPK activation were analyzed by Western blots. RESULTS The results showed that exposure of EtOH to TIB-73 cells led to cell death and membrane damage, accompanied by a decrease in cell viability, MMP, and Mg(2+) concentrations, but an increase in LDH, AST, ROS and MAPK activation. KRG and its primary ginsenosides reduced EtOH-induced generation of ROS and the activation of ERK and JNK, and increased Mg(2+) concentrations. CONCLUSION These results suggest that KRG and its primary ginsenosides inhibit EtOH-induced oxidative injury by suppression of the MAPK pathway in TIB-73 cells.

Taurine increases cell proliferation and generates an increase in [Mg2+]i accompanied by ERK 1/2 activation in human osteoblast cells

Taurine has been reported to influence bone metabolism, and its specific transport system, the taurine transporter, is expressed in osteoblasts. The mean [Mg2+]i was 0.51 ± 0.01 mM in normal culture media. Taurine caused an increase in [Mg2+]i by 0.72 ± 0.04 mM in human osteoblast (HOB) cells. This increment in [Mg2+]i was inhibited significantly by PD98059, nifedipine, lidocaine, and imipramine. Taurine was also shown to stimulate the activation of ERK 1/2. This taurine‐stimulated ERK 1/2 activation was inhibited by PD98059. In the present study, taurine was shown to increase cell proliferation and generate an increase in [Mg2+]i accompanied by ERK 1/2 activation in HOB cells.

Taurine Prevents Hypertension and Increases Exercise Capacity in Rats With Fructose-Induced Hypertension

BACKGROUND Fructose-induced hypertension was used to test the hypothesis that taurine supplementation and/or exercise can prevent hypertension and increase exercise capacity. METHODS Five groups of 15 Sprague-Dawley rats were allocated and designated as control, high fructose-fed (fructose), high fructose-fed plus exercise (FE), high fructose-fed plus 2% taurine supplement (FT) and high fructose-fed plus 2% taurine supplement and exercise (FET) groups. Noninvasive systolic blood pressure (SBP) was recorded weekly and invasive arterial blood pressure (ABP) was recorded at the end of the 4-week trial. Three consecutive swimming tests were performed in the selected rats from each group and the plasma biomarkers were measured in the remaining rats. RESULTS Noninvasive SBP differed significantly (P < 0.001) from week 3, both noninvasive and invasive ABP increased significantly (P < 0.001), and exercise capacity significantly decreased (P < 0.001) in the fructose group compared with the control group. The individual effects of swimming and taurine supplementation were incapable of preventing the development of hypertension and SBP significantly (P < 0.001) increased in the FE and FT groups; exercise capacity in those groups remained similar to control. The combined effects of exercise and taurine alleviated hypertension and significantly increased exercise capacity in the FET group. Insulin resistance increased significantly and plasma nitric oxide (NO) decreased significantly in the F, FE, and FT groups. Both parameters remained similar to control values in the FET group with an increasing antioxidant activity. CONCLUSION Taurine supplementation in combination with exercise prevents hypertension and increases exercise capacity by possibly antioxidation and maintaining NO concentrations.

The antioxidant, taurine reduced lipopolysaccharide (LPS)-induced generation of ROS, and activation of MAPKs and Bax in cultured pneumocytes.

Lipopolysaccharide (LPS) can cause damage to the epithelia of the respiratory tract. However, taurine can protect the lung tissue from such oxidant-induced inflammation. This study examined the effects of a LPS treatment on the intracellular calcium levels ([Ca(2+)]i) as well as the specific mechanisms of LPS-induced cell death in pneumocytes. In addition, the effects of taurine on the LPS-induced increase in the accumulation of reactive oxygen species (ROS) in pneumocytes were investigated. The [Ca(2+)]i in cultured pneumocytes was determined using microfluorescence techniques. The level of activation of the mitogen-activated protein kinases (MAPKs) and Bax protein were measured by Western blotting. LPS at 10 and 100 ng/ml induced cell death and decreased the viability of MRC-5 cells. Moreover, the intracellular Ca(2+) and ROS levels were increased by LPS. The LPS treatment led to the phosphorylation of ERK1/2, JNK and the activation of Bax. A pretreatment with 20 mM taurine reduced the LPS-induced production of ROS and MARK activity. These results show that a LPS treatment induces cell death in MRC-5 cells by increasing the intracellular ROS and Ca(2+) levels. The increase in the intracellular level of ROS promotes MAPKs activation and Bax translocation. Overall, LPS induces lung cell death by activating MAPKs. Furthermore, taurine decreased the LPS-induced generation of ROS and activation of MAPK and Bax.

Nitrite‐Induced Methemoglobinaemia Affects Blood Ionized and Total Magnesium Level by Hydrolysis of Plasma Adenosine Triphosphate in Rat

The objective of this study was to evaluate the effects of sodium nitrite (NaNO(2))-induced methemoglobinaemia on plasma ATP (adenosine triphosphate) and corresponding changes of blood-ionized magnesium (iMg(2+)) as well as total magnesium (tMg(2+)) in a time-dependent manner. This study was performed on male Sprague-Dawley rats to which NaNO(2) was injected (10 mg/kg i.p.) to induce methemoglobinaemia. Methemoglobin (MetHb) in blood was measured before (0 min.) and after 10, 30, 60 and 120 min. of NaNO(2) injection. At respective time points, the tMg(2+), blood ions and gases were measured by atomic absorption spectrometry and ion selective electrode, respectively. Haematological parameters were checked by automatic blood cell count, and blood films were observed under light microscope. Plasma ATP was measured by bioluminescence assay using a luminometer, and plasma proteins were measured by an automatic analyser. Blood cell count (RBC, WBC and platelet), haematocrit, and haemoglobin were found to be decreased with the advancement of MetHb concentration. With the gradual increase of MetHb concentration, the plasma ATP decreased and blood iMg(2+) and plasma tMg(2+) increased significantly as time passed by in comparison with the pre-drug values. A significant decrease of the ratio of ionized calcium to iMg(2+), Na(+) and increase of K(+) was observed. In conclusion, NaNO(2)-induced methemoglobinaemia is a cause of hydrolysis of plasma ATP which is responsible for the increase of blood iMg(2+) and plasma tMg(2+) in rats.

Taurine reduces FK506-induced generation of ROS and activation of JNK and Bax in Madin Darby canine kidney cells

The immunosuppressive compound FK506 has been successfully used in kidney and liver transplant recipients. However, the compound can induce significant side effects on kidney function. Taurine is a potent free radical scavenger that attenuates a variety of renal diseases that are the consequence of excessive oxygen free radical damage. The purpose of this study was to investigate FK506-mediated death of Madin Darby canine kidney (MDCK) cells, in relation to reactive oxygen species (ROS) production. We determined the calcium (Ca2+) and magnesium (Mg2+) concentration in cultured MDCK cells by microfluorescence techniques and the level of activation of c-Jun-N-terminal kinase (JNK), extracellular signal regulated kinases (ERK), Bcl-2 and Bax proteins by Western blot. Treatment with 10 μM FK506 induced apoptosis in MDCK cells by increasing the level of intracellular ROS and Ca2+ and by decreaseing the level of intracellular Mg2+. This increase in intracellular ROS promoted JNK and Bax activation, which increased FK506-induced MDCK cell death. Taurine reduced the FK506-induced generation of ROS and activation of JNK and Bax. The results indicate that taurine can prevent FK506-induced kidney toxicity.

Immunosuppressant FK506 decreases the intracellular magnesium in the human osteoblast cell by inhibiting the ERK1/2 pathway

AIMS Previous studies reported that FK506 influences bone mineralizing and hypomagnesemia, and also has immune modifying properties. This study examined whether or not the function of Mg2+ in bone metabolism plays a role in the loss of bone volume caused by immunosuppressants. MAIN METHODS The effects of the FK506 treatment on the intracellular magnesium and lactate dehydrogenase (LDH) activity were examined in cultured human osteoblasts (HOB) cells. The magnesium concentration was determined using microfluorescence techniques and atomic absorption spectrophotometry. Western blotting was used to measure the level of extracellular signal-regulated kinases 1/2 (ERK 1/2) activation. KEY FINDINGS FK506 (0.1 microM) did not affect cell death in HOB cells after a 24 hour treatment but decreased the level of ERK 1/2 activation. In HOB cells, the mean [Mg2+]i after exposure to a 1 mM extracellular Mg2+ ([Mg2+]o) buffer was 0.53+/-0.01 mM (n=25). Exposure to 100 nM FK506 produced a significant decrease in [Mg2+]i (0.41+/-0.01 mM). The ERK inhibitor (PD98059) and FK506 produced similar effects but they were not cumulative. SIGNIFICANCE This study examined the role of ERK1/2 activation on the regulation of magnesium in HOB. These results suggest that the inhibition of ERK phosphorylation is an essential intermediate in the effects of FK506 on magnesium. Overall, FK506 causes bone disorders partly by decreasing [Mg2+]i accompanied by the inhibition of ERK 1/2.

Relationships Between Blood Mg2+ and Energy Metabolites/Enzymes After Acute Exhaustive Swimming Exercise in Rats

Magnesium (Mg) plays a central role in neuronal activity, cardiac excitability, neuromuscular transmission, muscular contraction, vasomotor tone, and blood pressure, all of which are significantly related to physical performance. To date, the available data about detection of blood total Mg (tMg; free-ionized, protein-bound, and anion-complex forms) are inconsistent, and there is limited information on blood free-ionized Mg (Mg2+) in relation to physical exercise. The aim of this study was to determine the biochemical changes related to energy metabolism after acute exhaustive swimming exercise (AESE) in rats in an attempt to correlate the role of blood Mg2+ with metabolites/enzymes related to energy production. After AESE, blood Mg2+, tMg, K+, partial pressure of carbon dioxide, lactate, total protein (T-PRO), high-density lipoprotein (HDL), creatinine (CRE), blood urea nitrogen (BUN), uric acid (UA), alanine aminotransferase (ALT), aspartate aminotransferase (AST), alanine phosphatase (ALP), lactate dehydrogenase (LDH), and creatinine kinase (CK) were significantly increased, whereas pH, partial pressure of oxygen, oxygen saturation, the Mg2+/tMg and Ca2+/Mg2+ ratios, HCO3−, glucose, triglyceride (TG), and low-density lipoprotein (LDL) were significantly decreased. During AESE, lactate, T-PRO, albumin, AST, ALP, LDH, CK, CRE, BUN, and UA showed significant positive correlations with changes in blood Mg2+, while glucose, TG, and LDL correlated to Mg2+ in a negative manner. In conclusion, AESE induced increases in both blood Mg2+ and tMg, accompanied by changes in blood metabolites and enzymes related to energy metabolism due to increased metabolic demands and mechanical damages.