Hyung-Mun Yun

Potential therapeutic effects of functionally active compounds isolated from garlic

The medicinal properties of functionally active organosulfur compounds such as allin, diallyl disulfide, S-allylmercaptocysteine, and S-trityl-L-cysteine isolated from garlic have received great attention from a large number of investigators who have studied their pharmacological effects for the treatment of various diseases. These organosulfur compounds are able to prevent for development of cancer, cardiovascular, neurological, and liver diseases as well as allergy and arthritis. There have been also many reports on toxicities and pharmacokinetics of these compounds. The aim of this study is to review a variety of experimental and clinical reports, and describe the effectiveness, toxicities and pharmacokinetics, and possible mechanisms of pharmaceutical actions of functionally active compounds isolated from garlic.

PRDX6 Exacerbates Dopaminergic Neurodegeneration in a MPTP Mouse Model of Parkinson’s Disease

Peroxiredoxin 6 (PRDX6) is a bifunctional protein with both glutathione peroxidase (GPx) and calcium-independent phospholipase A2 (iPLA2) activities. Expression of PRDX6 has been detected in human Parkinson’s disease (PD) and dementia patients. However, no study has described PRDX6 function in the dopaminergic neurodegeneration in PD. Herein, we investigated the effects of PRDX6 on 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced dopaminergic neurodegeneration using PRDX6 transgenic (Tg) mice. Immunohistochemistry (IHC) and Western blot data for tyrosine hydroxylase (TH) showed that PRDX6 Tg mice had much higher loss of dopaminergic neurons by MPTP administration compared to non-Tg mice, as well as there was much higher behavioral impairment and astrocyte activation in PRDX6 Tg mice. MPTP-induced GPx activity was not different between PRDX6 Tg mice and non-Tg mice, which is accompanied by hyperoxidation of PRDX6. While iPLA2 activity was increased in PRDX6 Tg mice followed by an increase in the level of ROS and 4-hydroxynonenal (4-HNE). Intriguingly, the expression pattern of PRDX6 showed similar distribution and co-localization with astrocytes, but not neuron in the mouse and human brain. Furthermore, we demonstrated that iPLA2 activity of PRDX6 induced astrocytic activation followed by increased proinflammatory cytokines (TNF-α and IL1-β), 4-HNE, and PRDX6 hyperoxidation in primary cultured astrocytes. Our findings provide novel insights for PRDX6 function on nigrostriatal dopaminergic neuronal system, and we suggest that PRDX6 has an important role in dopaminergic neurodegeneration of PD.

Anti-cancer effect of tectochrysin in NSCLC cells through overexpression of death receptor and inactivation of STAT3

Phenolic compounds (flavonoids and phenolic acid derivatives) are the most important pharmacologically active ingredients, and these compounds could inhibit proliferation of human cancer cells by inducing of apoptotic cell death. Here we focused on the anticancer effects of tectochrysin on human non-small-cell lung cancer (NSCLC) cells and its mechanism of action. We analysed the activity of tectochrysin on NSCLC cells (A549 and NCI-H460) by use of Western blot analysis for major apoptotic proteins and death receptor expression. We also used EMSA for effects on STAT3 DNA binding activity. Tectochrysin (0-80 μM) suppressed the growth of A549 and NCI-H460 lung cancer cells by inducing of apoptotic cell death in a concentration dependent manner. Expression of DR3 and Fas as well as DR downstream pro-apoptotic proteins including cleaved caspase-3, cleaved caspase-8, cleaved caspase-9 and Bax were concomitantly increased, but the expression of anti-apoptotic proteins; Bcl-2 was decreased in both cancer cells. In addition, tectochrysin treatment also inhibited phosphorylation of STAT3 in A549 and NCI-H460 cells. However, deletion of DR3 and Fas by small interfering RNA significantly reversed tectochrysin-induced cell growth inhibitory effect as well as down regulation of STAT3 in A549 and NCI-H460 lung cancer cells. Pull down assay and docking model showed interaction of tectochrysin with STAT3. We propose that tectochrysin leads to apoptotic cell death in NSCLC cells through activation of DR3 and Fas expression via inhibition of STAT3 phosphorylation.

Acceleration of the Development of Alzheimer's Disease in Amyloid Beta-Infused Peroxiredoxin 6 Overexpression Transgenic Mice

The amyloid beta (Aβ) peptide in the brains of patients with Alzheimer’s disease (AD) is cytotoxic to neurons and has a central role in the pathogenesis of the disease. Peroxiredoxin 6 (Prdx6) is an antioxidant protein and could act as a cytoprotective protein. However, the role of Prdx6 in neurodegenerative disease has not been studied. Thus, the roles and action mechanisms in the development of AD were examined. Aβ1–42-induced memory impairment in Prdx6 transgenic mice was worse than C57BL/6 mice, and the expression of amyloid precursor protein cleavage, C99, β-site APP-cleaving enzyme 1, inducible nitric oxide synthase, and cyclooxygenase-2 was greatly increased. In addition, the astrocytes and microglia cells of Aβ-infused Prdx6 transgenic mice were more activated, and Aβ also significantly increased lipid peroxidation and protein carbonyl levels, but decreased glutathione levels. Furthermore, we found that translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) to the nucleus was increased in Aβ-infused Prdx6 transgenic mice. These results suggest that the overexpression of Prdx6 could accelerate the development of AD through increased amyloidogenesis through independent PLA2 activation and Nrf2 transcription.

PRDX6 promotes lung tumor progression via its GPx and iPLA2 activities

PRDX6 is a bifunctional protein with both glutathione peroxidase (GPx) and calcium-independent phospholipase A2 (iPLA2) activities, which are concomitantly increased with the expression of PRDX6. PRDX6 promoted lung tumor growth in an in vivo allograft model. Herein, we further studied the vital roles in tumor progression of PRDX6 in lung cancer using nude mice bearing PRDX6-overexpressing lung cancer cells. Nude mice xenografted with PRDX6 showed increases in tumor size and weight compared to control mice. Histopathological and Western blotting examination demonstrated that expression of proliferating cell nuclear antigen, vascular endothelial growth factor, metalloproteinases 2 and 9, and cyclin-dependent kinases accompanied by increased iPLA2 and GPx activities were increased in the tumor tissues of PRDX6-overexpressing nude mice. In tumor tissues of PRDX6-overexpressing mice, the activation of mitogen-activated protein kinases and AP-1 DNA binding were also increased. The growth of lung cancer cell lines (A549 and NCI-H460) was enhanced by the increase in iPLA2 and GPx activities of PRDX6. In addition, mutant PRDX6 (C47S) attenuated PRDX6-mediated p38, ERK1/2, and AP-1 activities as well as its enzyme activities in the A549 and NCI-H460 lines. Furthermore, tumor growth and p38, ERK1/2, and AP-1 activities were also inhibited in nude mice bearing mutant PRDX6 (C47S) compared to PRDX6. Therefore, our findings indicate that PRDX6 promotes lung tumor growth via increased glutathione peroxidase and iPLA2 activities.

Anti-Cancer Effect of Thiacremonone through Down Regulation of Peroxiredoxin 6

Thiacremonone (2, 4-dihydroxy-2, 5-dimethyl-thiophene-3-one) is an antioxidant substance as a novel sulfur compound generated from High-Temperature-High-Pressure-treated garlic. Peroxiredoxin 6 (PRDX6) is a member of peroxidases, and has glutathione peroxidase and calcium-independent phospholipase A2 (iPLA2) activities. Several studies have demonstrated that PRDX6 stimulates lung cancer cell growth via an increase of glutathione peroxidase activity. A docking model study and pull down assay showed that thiacremonone completely fits on the active site (cys-47) of glutathione peroxidase of PRDX6 and interacts with PRDX6. Thus, we investigated whether thiacremonone inhibits cell growth by blocking glutathione peroxidase of PRDX6 in the human lung cancer cells, A549 and NCI-H460. Thiacremonone (0–50 μg/ml) inhibited lung cancer cell growth in a concentration dependent manner through induction of apoptotic cell death accompanied by induction of cleaved caspase-3, -8, -9, Bax, p21 and p53, but decrease of xIAP, cIAP and Bcl2 expression. Thiacremonone further inhibited glutathione peroxidase activity in lung cancer cells. However, the cell growth inhibitory effect of thiacremonone was not observed in the lung cancer cells transfected with mutant PRDX6 (C47S) and in the presence of dithiothreitol and glutathione. In an allograft in vivo model, thiacremonone (30 mg/kg) also inhibited tumor growth accompanied with the reduction of PRDX6 expression and glutathione peroxidase activity, but increased expression of cleaved caspase-3, -8, -9, Bax, p21 and p53. These data indicate that thiacremonone inhibits tumor growth via inhibition of glutathione peroxidase activity of PRDX6 through interaction. These data suggest that thiacremonone may have potentially beneficial effects in lung cancer.

Interleukin-32β ameliorates metabolic disorder and liver damage in mice fed high-fat diet

Chronic excessive food intake leads to energy imbalance, resulting in hepatic steatosis and inflammation. Interleukin‐32 (IL‐32) is known to be a pro‐inflammatory cytokine associated with chronic inflammation and cancer. Therefore, the relationship between IL‐32 and chronic excessive food intake‐induced liver disease was investigated.

Reducing Effect of IL-32α in the Development of Stroke Through Blocking of NF-κB, but Enhancement of STAT3 Pathways

Neuroinflammation is important for the development of several neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease, and stroke. Since changes of cytokine level are critical for neuroinflammation in the brain, we investigated whether IL-32α overexpression could change neuroinflammation and, thus, affect stroke development. Middle cerebral artery occlusion (MCAO) induced development of ischemia, and ischemic neuronal cell death were reduced in IL-32α-overexpressing transgenic mice (IL-32α mice) brain through the decreased release of neuroinflammatory cytokines (IL-6, IL-1β, TNF-α) and activation of astrocytes, but enhancement of anti-neuroinflammatory cytokines (IL-10). Reactive oxygen species generation and lipid peroxidation as well as expression of inducible nitric oxide and cyclooxygenase-2 were also reduced in the IL-32α mice brain. Nuclear factor-kappa B (NF-κB), a critical transcriptional factor regulating neuroinflammation, was much lower, but activation of signal transducer and activator of transcription 3 (STAT3), which plays a crucial role in cell survival and proliferation, was much higher in IL-32α-overexpressing mice brain compared to those of wild-type mice brain. These results suggest that IL-32α can prevent cerebral ischemia damage via upregulation of anti-neuroinflammatory cytokine expression and STAT3 activation, but downregulation of neuroinflammatory cytokines and NF-κB activation.