Yong Pil Hwang

The coffee diterpene kahweol induces heme oxygenase-1 via the PI3K and p38/Nrf2 pathway to protect human dopaminergic neurons from 6-hydroxydopamine-derived oxidative stress.

In this study, we investigated the mechanisms of kahweol protection of neuronal cells from cell death induced by the Parkinsons disease‐related neurotoxin 6‐hydroxydopamine (6‐OHDA). Pretreatment of SH‐SY5Y cells with kahweol significantly reduced 6‐OHDA‐induced generation of ROS, caspase‐3 activation, and subsequent cell death. Kahweol also up‐regulated heme oxygenase‐1 (HO‐1) expression, which conferred neuroprotection against 6‐OHDA‐induced oxidative injury. Moreover, kahweol induced PI3K and p38 activation, which are involved in the induction of Nrf2, HO‐1 expression, and neuroprotection. These results suggest that regulation of the anti‐oxidant enzyme HO‐1 via the PI3K and p38/Nrf2 signaling pathways controls the intracellular levels of ROS.

Mechanism of phytoestrogen puerarin-mediated cytoprotection following oxidative injury: Estrogen receptor-dependent up-regulation of PI3K/Akt and HO-1

Phytoestrogens are polyphenolic non-steroidal plant compounds with estrogen-like biological activity. The phytoestrogen puerarin, the main isoflavone glycoside found in the root of Pueraria lobata, has been used for various medicinal purposes in traditional Chinese medicines for thousands of years. Recent studies have indicated that the estrogen receptor (ER), through interaction with p85, regulates phosphoinositide 3-kinase (PI3K) activity, revealing a physiologic, non-nuclear function of ER that may be relevant in cytoprotection. In this study, we demonstrate that the phytoestrogen puerarin inhibits tert-butyl hydroperoxide (t-BHP)-induced oxidative injury via an ER-dependent Gbeta1/PI3K/Akt and heme oxygenase-1 (HO-1) pathway. Pretreatment of Hepa1c1c7 and HepG2 cells with puerarin significantly reduced t-BHP-induced caspase-3 activation and subsequent cell death. Also, puerarin up-regulated HO-1 expression and this expression conferred cytoprotection against oxidative injury induced by t-BHP. Moreover, puerarin induced Nrf2 nuclear translocation, which is upstream of puerarin-induced HO-1 expression, and PI3K activation, a pathway that is involved in induced Nrf2 nuclear translocation, HO-1 expression and cytoprotection. Puerarin-induced up-regulation of HO-1 and cytoprotection against t-BHP were abolished by silencing Nrf2 expression with specific siRNA. Also, puerarin-mediated increases in PI3K activation and HO-1 induction were reversed by co-treatment with ICI 182,780 and pertussis toxin. Taken together, these results suggest that puerarin augments cellular antioxidant defense capacity through ER-dependent HO-1 induction via the Gbeta1/PI3K/Akt-Nrf2 signaling pathway, thereby protecting cells from oxidative stress.

Immunostimulatory activity of aqueous extract isolated from Prunella vulgaris

Prunella vulgaris (P. vulgaris) has been used as a traditional medicine in the clinical treatment of herpetic keratitis and for its antioxidative and antimicrobial activities. In this study, we examined the immunostimulatory and antitumor activity of P. vulgaris in murine macrophage RAW 264.7 cells. Thus, we investigated the effects of an aqueous extract of P. vulgaris (PVAE) on macrophage function. We found that PVAE stimulated macrophage phagocytic activity, nitric oxide (NO) production and cytostatic activity. In addition, PVAE induced gene expression and production of macrophage-related cytokines such as TNF-alpha, IL-1beta and IL-6. Transient transfection revealed that NF-kappaB mediated the PVAE-induced increases in macrophage-related cytokine expression levels. Mitogen-activated protein kinases (MAP Kinase) were also significantly activated by the PVAE-induced NF-kappaB activation. Pretreatment with NF-kappaB inhibitor and MAP Kinase inhibitors inhibited the NO production and the phagocytic activity induced by PVAE. This demonstrates that PVAE stimulates macrophage activation via NF-kappaB transactivation and MAP kinase activation.

Protective effect of saponins derived from the roots of Platycodon grandiflorum against carbon tetrachloride induced hepatotoxicity in mice

The purpose of this study was to investigate the protective effects of the saponins isolated from the root of Platycodi Radix (Changkil saponins: CKS) on carbon tetrachloride (CCl(4))-induced hepatotoxicities in mice. Pretreatment with CKS prior to the administration of CCl(4) significantly prevented the increase in serum alanine aminotransferase and aspartate aminotransferase activities and hepatic lipid peroxidation formation. In addition, CKS prevented CCl(4)-induced apoptosis and necrosis, as indicated by a liver histopathologic study and DNA laddering. To determine whether Fas/Fas ligand (FasL) pathway involved in CCl(4)-induced acute liver injury, Fas and FasL proteins and caspase-3, -8 activities were tested by western blotting and ELISA. CKS markedly decreased CCl(4)-induced Fas/FasL protein expression levels and in turn attenuated CCl(4)-induced caspase-3, -8 activities in mouse livers. Additionally, CKS protected the CCl(4)-induced depletion of hepatic glutathione levels. The effect of CKS on CYP2E1, the major isozyme involved in CCl(4) bioactivation, was investigated. Treatment with CKS resulted in a significant decrease in the CYP2E1-dependent hydroxylation of aniline. In addition, CKS exhibited antioxidant effects on FeCl(2)-ascorbate induced lipid peroxidation in liver homogenates, and on superoxide radical scavenging activity. These findings suggest that the protective effects of CKS against CCl(4)-induced acute liver injury possibly involve mechanisms related to its ability to block CYP2El-mediated CCl(4) bioactivation and its free radical scavenging effects, and that is also protects against Fas/FasL pathway mediated apoptosis.

Protective effect of the Aralia continentalis root extract against carbon tetrachloride-induced hepatotoxicity in mice.

The root of Aralia continentalis Kitagawa has been used in traditional Korean medicine to relieve pain and to treat inflammation. The purpose of this study was to investigate the protective effects of the extract of A. continentalis roots (AC) against hepatotoxicity induced by carbon tetrachloride (CCl4) and the mechanism of its hepatoprotective effect. In mice, pretreatment with AC prior to the administration of CCl4 significantly prevented the increased serum enzymatic activity of ALT and AST as well as the formation of hepatic malondialdehyde. Histopathological evaluation of the livers also revealed that AC reduced the incidence of liver lesions induced by CCl4. In addition, pretreatment with AC significantly prevented both the depletion of reduced glutathione (GSH) content and the decrease in glutathione-S-transferase (GST) activity in the liver of CCl4-intoxicated mice. Hepatic GSH levels and GST activity were increased by treatment with AC alone. Heme oxygenase-1 (HO-1) is known to be induced by oxidative stress and to confer protection against oxidative tissue injuries. Interestingly, AC markedly upregulated hepatic HO-1 expression in CCl4-treated mice, which might provide anti-oxidative activity in the liver. These results indicate that AC plays a critical protective role in CCl4-induced acute liver injury by promoting anti-oxidative protein expression.

Saponins isolated from the root of Platycodon grandiflorum protect against acute ethanol-induced hepatotoxicity in mice

The protective effects of saponins isolated from the root of Platycodon grandiflorum (Changkil saponins: CKS) against alcoholic steatosis in liver injury induced by acute ethanol administration were investigated. Pretreatment with CKS prior to ethanol administration significantly prevented the increases in serum alanine aminotransferase activity, hepatic TNF-alpha level, hepatic lipid peroxidation and hepatic triglyceride level. CKS prevented ethanol-induced steatosis and necrosis, as indicated by liver histopathological studies. Additionally, CKS protected against ethanol-induced depletion of hepatic glutathione levels. CYP2E1 has been suggested as a major contributor to ethanol-induced oxidative stress and liver injury. The concurrent administration of CKS efficaciously abrogated the CYP2E1 induction and CYP2E1-dependents hydroxylation of aniline as compared to the individual treatment at higher doses. These findings suggest that CKS may prevent ethanol-induced acute liver injury, possibly through its ability to block CYP2El-mediated ethanol bioactivation and its free radical scavenging effects.

Inhibitory Effect of the Saponins Derived from Roots of Platycodon grandiflorum on Carrageenan-Induced Inflammation

Previous studies have reported that the saponins isolated from the roots of Platycodon grandiflorum A. DC (Campanulaceae), Changkil saponins (CKS), inhibited cyclooxygenase-2 (COX-2) expression in cultured lipopolysaccharide-activated macrophages. The aim of this presented study was to confirm the anti-inflammatory effects of CKS by examining their effect on the inflammatory response induced by carrageenan in a rat by using an acute air pouch inflammation model. CKS significantly reduced the levels of the inflammatory process markers in the air pouch, such as the volume of exudates, the amount of protein and the number of leukocytes and neutrophils. The levels of TNF-α and prostaglandin E2 (PGE2) were also markedly lower in the air pouch of the CKS-treated animals than in the controls. An immunoblot analysis showed that CKS reduced the COX-2 expression level in the exudate cells. In addition, CKS significantly reduced the paw edema induced by carrageenan and also markedly reduced the level of PGE2 production in the inflamed paw. These results suggest that CKS had significant anti-inflammatory effects in vivo.

Protective effects of puerarin on carbon tetrachloride-induced hepatotoxicity

Puerarin, the main isoflavone glycoside found in the root ofPueraria lobata, has been used for various medicinal purposes in traditional Chinese medicine for thousands of years. The purpose of this study was to investigate the protective effects of puerarin against hepatotoxicity induced by carbon tetrachloride (CCI4) and the mechanism of its hepatoprotective effect. In mice, pretreatment with puerarin prior to the administration of CCI4 significantly prevented the increased serum enzymatic activity of alanine aspartate aminotransferase and hepatic malondialdehyde formation in a dose-dependent manner. In addition, pretreatment with puerarin significantly prevented both the depletion of reduced glutathione (GSH) content and the decrease in glutathione S-transferase (GST) activity in the liver of CCI4-intoxicated mice. Hepatic GSH levels and GST activity were increased by treatment with puerarin alone. CCI4-induced hepatotoxicity was also prevented, as indicated by liver histopathology. The effects of puerarin on cytochrome P450 (CYP) 2E1, the major isozyme involved in CCI4 bioactivation, were also investigated. Treatment of the mice with puerarin resulted in a significant decrease in the CYP2E1-dependent aniline hydroxylation in a dose-dependent manner. Consistent with these observations, the CYP2EI protein levels were also lowered. Puerarin exhibited anti-oxidant effects on FeCI2-ascorbate induced lipid peroxidation in mouse liver homogenates, and on Superoxide radical scavenging activity. These results suggest that the protective effects of puerarin against the CCI4-induced hepatotoxicity possibly involve mechanisms related to its ability to block CYP-mediated CCI4 bioactivation, induction of GST activity and free radical scavenging effects.

Inhibitory effect of Platycodi Radix on ovalbumin-induced airway inflammation in a murine model of asthma

Asthma is a chronic inflammatory disease of the airways characterized by an associated increase in airway responsiveness. In this study, we investigated the inhibitory effect of an aqueous extract from the root of Platycodi Radix (Changkil: CK) on airway inflammation in a murine model of asthma. Mice were sensitized and challenged by ovalbumin (OVA) inhalation to induce chronic airway inflammation and airway remodeling. CK markedly decreased the number of infiltrated inflammatory cells and the levels of Th1 and Th2 cytokines and chemokines compared with those in the OVA-induced group. In addition, CK reduced OVA-specific IgE levels in bronchoalveolar lavage (BAL) fluid. Based on lung histopathological studies, inflammatory cell infiltration and mucus hypersecretion were inhibited by CK administration compared to that in the OVA-induced group. Lung weight was reduced after CK administration. Also, increased generation of ROS in BAL fluid, as well as NF-kappaB nuclear translocation, by inhalation of OVA was diminished by CK. Moreover, CK reduced the OVA-induced upregulation of matrix metalloproteases activity. These findings indicate that oxidative stress may play a crucial role in the pathogenesis of bronchial asthma induced by OVA and that CK may be useful as an adjuvant therapy for the treatment of bronchial asthma.

Metallothionein-III protects against 6-hydroxydopamine-induced oxidative stress by increasing expression of heme oxygenase-1 in a PI3K and ERK/Nrf2-dependent manner.

The zinc-binding protein metallothionein-III (MT-III) is associated with resistance to neuronal injury. However, the underlying mechanism for its effects is unclear. In this study, we demonstrate that MT-III prevents the accumulation of reactive oxygen species (ROS) in dopaminergic SH-SY5Y cells challenged with the Parkinsons disease-related neurotoxin 6-hydroxydopamine (6-OHDA) by a mechanism that involves phosphatidylinositol 3-kinase (PI3K) and ERK kinase/NF-E2-related factor 2 (Nrf2) dependent induction of the stress response protein heme oxygenase-1 (HO-1). Pretreatment of SH-SY5Y cells with MT-III significantly reduced 6-OHDA-induced generation of ROS, caspase-3 activation, and subsequent cell death. Also, MT-III up-regulates HO-1 expression and this expression confers neuroprotection against oxidative injury induced by 6-OHDA. Moreover, MT-III induces Nrf2 nuclear translocation, which is upstream of MT-III-induced HO-1 expression, and PI3K and ERK1/2 activation, a pathway that is involved in induced Nrf2 nuclear translocation, HO-1 expression and neuroprotection. Taken together, these results suggest that the PI3K and ERK/Nrf2 signaling pathway controls the intracellular levels of ROS by regulating the expression of the antioxidant enzyme HO-1.