Yang-Gyu Park

Sulforaphane induced adipolysis via hormone sensitive lipase activation, regulated by AMPK signaling pathway

Sulforaphane, an aliphatic isothiocyanate derived from cruciferous vegetables, is known for its antidiabetic properties. The effects of sulforaphane on lipid metabolism in adipocytes are not clearly understood. Here, we investigated whether sulforaphane stimulates lipolysis. Mature adipocytes were incubated with sulforaphane for 24h and analyzed using a lipolysis assay which quantified glycerol released into the medium. We investigated gene expression of hormone-sensitive lipase (HSL), and levels of HSL phosphorylation and AMP-activated protein kinase on sulforaphane-mediated lipolysis in adipocytes. Sulforaphane promoted lipolysis and increased both HSL gene expression and HSL activation. Sulforaphane suppressed AMPK phosphorylation at Thr-172 in a dose-dependent manner, which was associated with a decrease in HSL phosphorylation at Ser-565, enhancing the phosphorylation of HSL Ser-563. Taken together, these results suggest that sulforaphane promotes lipolysis via hormone sensitive lipase activation mediated by decreasing AMPK signal activation in adipocytes.

Lactoferrin protects against prion protein-induced cell death in neuronal cells by preventing mitochondrial dysfunction

Prion disorder-related neurodegenerative diseases are characterized by the accumulation of prion protein (PrP) scrapie isoform (PrPsc) within the central nervous system. PrPsc induces neuronal cell death by increasing intracellular generation of reactive oxygen species (ROS). Lactoferrin (LF) is an 80 kDa protein, which has antioxidant abilities due to the scavenging of ROS. The effects of LF treatment on PrP (106-126)-mediated neurotoxicity and ROS generation were the focus of this study. LF treatment protected against PrP (106-126)-induced neuronal cell death and decreased ROS generation. The reduced ROS generation prevented PrP (106-126)-induced mitochondrial dysfunction. Moreover, PrP (106-126)-induced protein activation including c-Jun N-terminal kinase and caspase-3 were blocked by LF treatment. These results demonstrated that LF protects neuronal cells against PrP (106-126)-mediated neurotoxicity through the scavenging of ROS and provide evidence that LF treatment prevents neuronal cell death caused by PrP (106-126).

Neuroprotective Effects of Sigesbeckia pubescens Extract on Glutamate-Induced Oxidative Stress in HT22 Cells via Downregulation of MAPK/caspase-3 Pathways

Sigesbeckia pubescens (SP) is a traditional Chinese medicine, possessing antioxidant and anti-inflammatory activities. In this study, we evaluate the neuroprotective activities of SP extract on glutamate-induced oxidative stress in HT22 cells and the molecular mechanism underlying neuroprotection. We applied 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), crystal violet, reactive oxygen species (ROS), lactate dehydrogenase (LDH), quantitative real-time polymerase chain reaction (qPCR), and western blot analyses for assessing the neuroprotective effects of SP extract. The experimental study revealed that SP considerably increased the cell viability, and reduced the oxidative stress promoted ROS and LDH generation in HT22 cells in a dose-dependent manner. Additionally, the morphology of HT22 cells was effectively improved by SP. Upregulated gene expressions of mitogen-activated protein kinase (MAPK) were markedly attenuated by SP. Similarly, SP notably suppressed the ROS-mediated phosphorylation of MAPK (pERK1/2, pJNK, and pp38) cascades and activation of apoptotic factor caspase-3 signaling pathway that overall contributed to the neuroprotection. Taken together, SP may exert neuroprotective effects via alteration of MAPK and caspase-3 pathways under oxidative stress condition. Therefore, SP is a potential agent for preventing oxidative stress-mediated neuronal cell death.

Gingerol-Induced Hypoxia-Inducible Factor 1 Alpha Inhibits Human Prion Peptide-Mediated Neurotoxicity

Prion diseases are a family member of neurodegenerative disorders caused by the accumulation of misfolded‐prion proteins (scrapie form of PrP, PrPSc). The accumulation of PrPSc in the brain leads to neurotoxicity by the induction of mitochondrial‐apoptotic pathways. Recent studies implicated gingerol in protection against neurodegeneration. However, the basis of the neuroprotection in prion disease remains unclear. Thus, we investigated the influence of gingerol on prion peptide‐induced neuronal damage. Gingerol blocked PrP(106‐126)‐mediated neurotoxicity by protecting mitochondrial function. Moreover, the protective effect of gingerol against PrP(106‐126)‐induced mitochondrial damage was associated with hypoxia‐inducible factor 1 alpha (HIF‐1α) expression. Gingerol‐induced HIF‐1α expression inhibited the PrP(106‐126)‐induced mitochondrial dysfunction. On the other hand, inhibition of gingerol‐induced HIF‐1 α expression attenuated the gingerol‐mediated neuroprotective effect. Here, we demonstrate for the first time that treatment with gingerol prevents prion peptide‐mediated neuronal cell death and that the neuroprotection is induced by HIF‐1α‐mediated signals. This study suggests that treatment with gingerol may provide a novel therapeutic strategy for prion‐mediated neurotoxicity. Copyright

Lactoferrin from bovine colostrum regulates prolyl hydroxylase 2 activity and prevents prion protein-mediated neuronal cell damage via cellular prion protein

Prion disorders are associated with the conversion of normal cellular prion protein (PrPc) to the abnormal scrapie isoform of prion protein (PrPsc). Recent studies have shown that expression of normal PrPc is regulated by hypoxia-inducible factor-1 alpha (HIF-1α), and that lactoferrin increases full-length PrPc on the cell surface. Lactoferrin is an 80-kDa iron-binding glycoprotein with various biological activities, including iron-chelating ability. HIF-1α and the associated ubiquitin-proteasome pathway are regulated by HIF prolyl-hydroxylases 2 (PHD2). We hypothesized that lactoferrin regulates PHD2 expression and enzymatic activity, and the PHD2 regulation promotes HIF-1α stability and prevention of neuronal cell death mediated by prion protein (PrP) residues (106-126). Lactoferrin prevented PrP (106-126)-induced neurotoxicity by the induction of PrPc expression via promoting HIF-1α stability in neuronal cells. Our results demonstrated that lactoferrin prevented PrP (106-126)-induced neurotoxicity via the up-regulation of HIF-1α stability determined by PHD2 expression and enzymatic activity. These findings suggest that possible therapies such as PHD2 inhibition, or promotion of lactoferrin secretion, may have clinical benefits in neurodegenerative diseases, including prion disease.

Sphingosine-1-phosphate protects against bisphosphonate‑induced HUVEC cell death via regulation of c-Jun‑N‑terminal kinase signaling

Bisphosphonates (BPs) remain the most widely used and effective antiresorptive agents in the treatment of postmenopausal osteoporosis. In particular, nitrogen-containing BPs (N-BPs) are more potent at inhibiting bone resorption in vivo than simple BPs, but they are associated with a number of side-effects including increased endothelial cell apoptosis in patients with multiple myeloma. Sphingosine-1-phosphate (S1P), a sphingolipid metabolite, plays important roles in the regulation of cell growth, differentiation and programmed cell death as a multifunctional bioactive lipid mediator. The aim of this study was to elucidate the protective effect and the possible mechanism of S1P against BP-induced cell damage using human umbilical vein endothelial cells (HUVECs). HUVECs were treated with S1P for 1 h and then with BP including alendronate, zoledronate and risedronate. S1P protects HUVECs against BP-induced cell death and the protective effect was increased by S1P in a dose-dependent manner. S1P blocked BP-induced caspase-3 activation, nuclear factor-κB activation, c-Jun-N-terminal kinase (JNK) phosphorylation and DNA fragmentation. The blocking of JNK phosphorylation inhibited BP-induced caspase activation and HUVEC cell death. The present study demonstrates that S1P inhibits BP-induced endothelial cell death via regulation of JNK phosphorylation, and also suggests that S1P has the potential to be a therapeutic drug in various vascular diseases induced by BP.

Gingerol prevents prion protein-mediated neuronal toxicity by regulating HIF prolyl hydroxylase 2 and prion protein

Prion diseases are a family of progressive neurodegenerative disorders, which are fatal in the majority of cases and affect both humans and domestic animals. Prion protein (PrP) (106–126) retains the neurotoxic properties of the entire pathological PrPsc and it is generally used as a reasonable model to study the mechanisms responsible for prion diseases. In our previous studies, we demonstrated that hypoxia-inducible factor (HIF)-1α is involved in the gingerol-mediated protection of neuronal cells. HIF mediates cellular adaptations to low oxygen. Prolyl hydroxylase domain-containing protein 2 (PHD2) is an oxygen sensor that hydroxylates the HIF-α-subunit, promoting its proteasomal degradation under normoxic conditions. Thus, in the present study we wished to determine whether gingerol inhibits the catalytic activity of PHD2 and prevents HIF-1α protein proteasomal degradation, thereby preventing the occurrence of PrP (106–126)-induced neuronal apoptosis. We used the pharmacological inhibition of PHD2 by dimethyloxalylglycine (DMOG) or deferoxamine (DFO) and the genetic inhibition of HIF-1α by HIF-1α small interfering RNA (siRNA) to block the effects of gingerol against PrP (106–126)-induced neurotoxicity. Our results demonstrated that gingerol prevented PrP (106–126)-induced neuronal apoptosis by upregulating HIF-1α and inhibiting the catalytic activity of PHD2 under normoxic conditions. Moreover, the protective effects of gingerol against PrP (106–126)-induced neuronal apoptosis were associated with the upregulation of the expression of cellular prion protein (PrPc). In conclusion, our results indicate that gingerol has therapeutic potential for use in the treatment or prevention of prion diseases, and its inhibitory effects on the catalytic activity of PHD2 may be of clinical benefit.

Effect of herbal mixture composed of Alchemilla vulgaris and Mimosa on wound healing process

Alchemilla vulgaris and Mimosa tenuiflora (Mimosa) have been used to treat cutaneous wounds as a traditional remedy due to their various biological activities. But, there are only a few studies about the effects of these herbs on wound healing. The purpose of this study is to investigate the wound healing effect of the herbal mixture, consisting of A. vulgaris and Mimosa, in mice and to determine the activity of the extract in vitro. In present study, application of an ointment containing the herbal mixture on the dorsal skin wounds of mice showed that the wound healing process was faster than treatment of Fusidic acid. Histological analysis demonstrated the herbal mixture promoted re-epithelialization, collagen synthesis, and especially the regeneration of skin appendages such as hair follicles. Immunohistochemical analysis revealed the herbal mixture improved angiogenesis and the stabilization of blood vessels, as well as accelerated the formation of granulation tissue. In addition, we demonstrated that herbal mixture enhanced the migration of HaCaT, fibroblasts, and HUVECs on a two-dimensional wound, and promoted the proliferation of macrophages and lymphatic vessels. Our results demonstrated that herbal mixture can promote the migration of keratinocytes, fibroblasts, and endothelial cells, and the proliferation of macrophages and lymphatic vessels. Furthermore, it showed that herbal mixture accelerates wound healing. Therefore, we suggest that herbal mixture may have a potential for therapeutic use for treatment and management of cutaneous wound.

Fluid shear stress regulates vascular remodeling via VEGFR-3 activation, although independently of its ligand, VEGF-C, in the uterus during pregnancy

Early pregnancy is characterized by an increase in the blood volume of the uterus for embryonic development, thereby exerting fluid shear stress (FSS) on the vascular walls. The uterus experiences vascular remodeling to accommodate the increased blood flow. The blood flow-induced FSS elevates the expression of vascular endothelial growth factors (VEGFs) and their receptors, and regulates vascular remodeling through the activation of VEGF receptor-3 (VEGFR-3). However, the mechanisms responsible for FSS-induced VEGFR-3 expression in the uterus during pregnancy are unclear. In this study, we demonstrate that vascular remodeling in the uterus during pregnancy is regulated by FSS-induced VEGFR-3 expression. We examined the association between VEGFR-3 and FSS through in vivo and in vitro experiments. In vivo experiments revealed VEGFR-3 expression in the CD31-positive region of the uterus of pregnant mice; VEGF-C (ligand for VEGFR-3) was undetected in the uterus. These results confirmed that VEGFR-3 expression in the endometrium is independent of its ligand. In vitro studies experiments revealed that FSS induced morphological changes and increased VEGFR-3 expression in human uterine microvascular endothelial cells. Thus, VEGFR-3 activation by FSS is associated with vascular remodeling to allow increased blood flow in the uterus during pregnancy.