Kwang Sik Yu

All-Trans-Retinoic Acid Rescues Neurons After Global Ischemia by Attenuating Neuroinflammatory Reactions

Retinoic acid (RA) plays an important role in the developing mammalian nervous system. Based on this concept, some studies have demonstrated the beneficial effects of RA administration on neurogenesis in neuropathological diseases. Some investigations have revealed the anti-inflammatory effects of RA treatment in multiple systems, in addition to its role in neurogenesis. To date, however, the neuroprotective efficacy of RA after cerebral ischemia, especially in the context of its anti-inflammatory effects, has been poorly demonstrated. Additionally, to the best of our knowledge, experiments of the therapeutic efficacy of RA treatment in a transient global ischemic model in the Mongolian gerbil have been lacking worldwide. Here, we studied the neuroprotective effects and neurobehavioral outcomes of intraperitoneally administered all-trans-RA (ATRA; a synthetic form of RA) on brains with transient global ischemia that was induced with the bilateral common carotid artery occlusion and reperfusion (BCCAO/R) model in the gerbil. In order to identify whether these neuroprotective mechanisms were due to the anti-inflammatory effects of ATRA, in vivo hippocampal expression of proinflammatory cytokines including tissue necrosis factor-alpha (TNF-α), and interleukin-6 (IL-6) after ATRA injection and in vitro levels of release of nitric oxide, TNF-α and IL-6 from lipopolysaccharide (LPS)-stimulated BV2 microglial cells after ATRA treatment were evaluated. The results showed that ATRA can protect pyramidal neurons in the hippocampal CA1 region against BCCAO-induced neuronal apoptosis and significantly reduce the extent of astrocytosis and microglial activation. In addition, the ischemia-induced neurobehavioral changes were normalized by ATRA injection. Consistent with these phenotypic data, we observed the diminishing effects of ATRA treatment on the production of proinflammatory mediators (e.g., TNF-α and IL-6) in hippocampal homogenates and LPS-stimulated BV2 cells, and these effects were dose-dependent. These results suggest a beneficial role of ATRA in the attenuation of global cerebral ischemia due to its anti-inflammatory properties, resulting in, at least partly, the inhibition of microglial secretion of variable proinflammatory cytokines.

Autophagy enhancement contributes to the synergistic effect of vitamin D in temozolomide‑based glioblastoma chemotherapy

Temozolomide (TMZ), an alkylating agent, is recommended as the initial treatment for high-grade glioblastoma. TMZ is widely used, but its short half-life and the frequency of tumor resistance limit its therapeutic efficacy. In the present study, the anticancer effect of vitamin D (VD) combined with TMZ upon glioblastoma was determined, and the underlying mechanism of this effect was identified. Through cell viability, clonogenic and wound healing assays, the current study demonstrated that treatment of a C6 glioblastoma cell line with TMZ and VD resulted in significantly increased in vitro antitumor effects compared with either VD or TMZ alone. Autophagy, hypothesized to be the dominant mechanism underlying TMZ-based tumor cell death, was maximally activated in TMZ and VD co-treated C6 cells. This was demonstrated by ultrastructural observations of autophagosomes, increased size and number of microtubule-associated protein 1 light chain 3 (LC3) puncta and increased conversion of LC3-I to LC3-II. However, the extent of apoptosis was not significantly different between cells treated with TMZ and VD and those treated with TMZ alone. Addition of the autophagy inhibitor 3-methyladenine markedly inhibited the anticancer effect of TMZ and VD treatment, indicating that the chemosensitizing effect of VD in TMZ-based glioblastoma therapy is generated through enhancement of cytotoxic autophagy. TMZ and VD co-treatment also significantly inhibited tumor progression and prolonged survival duration in rat glioblastoma orthotopic xenograft models when compared with TMZ treatment alone. These in vivo results are concordant with the aforementioned in vitro results, together revealing that the combined use of TMZ and VD exerts synergistic antitumor effects on rat models of glioblastoma and may represent an effective therapeutic strategy.

Receptor-Meditated Endocytosis by Hyaluronic Acid@Superparamagnetic Nanovetor for Targeting of CD44-Overexpressing Tumor Cells

The present report proposes a more rational hyaluronic acid (HA) conjugation protocol that can be used to modify the surface of the superparamagnetic iron oxide nanoparticles (SPIONs) by covalently binding the targeting molecules (HA) with glutamic acid as a molecular linker on peripheral surface of SPIONs. The synthesis of HA-Glutamic Acid (GA)@SPIONs was included oxidization of nanoparticle’s surface with H2O2 followed by activation of hydroxyl group and reacting glutamic acid as an intermediate molecule demonstrating transfection of lung cancer cells. Fourier transform infrared (FTIR) and zeta-potential studies confirmed the chemical bonding between amino acid linker and polysaccharides. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay showed that HA-SPIONs-treated cells remained 82.9% ± 2.7% alive at high particle dosage (200 µg/mL iron concentration), whereas GA-SPIONs and bare SPIONs (B-SPIONs) treated cells had only 59.3% ± 13.4% and 26.5% ± 3.1% survival rate at the same conditions, respectively. Confocal microscopy analysis showed increased cellular internalization of HA-SPIONs compared to non-interacting agarose coated SPIONs (AgA-SPIONs).

Rhus verniciflua Stokes attenuates cholestatic liver cirrhosis-induced interstitial fibrosis via Smad3 down-regulation and Smad7 up-regulation

Cholestatic liver cirrhosis (CLC) eventually proceeds to end-stage liver failure by mediating overwhelming deposition of collagen, which is produced by activated interstitial myofibroblasts. Although the beneficial effects of Rhus verniciflua Stokes (RVS) on various diseases are well-known, its therapeutic effect and possible underlying mechanism on interstitial fibrosis associated with CLC are not elucidated. This study was designed to assess the protective effects of RVS and its possible underlying mechanisms in rat models of CLC established by bile duct ligation (BDL). We demonstrated that BDL markedly elevated the serological parameters such as aspartate aminotransferase, alanine transaminase, total bilirubin, and direct bilirubin, all of which were significantly attenuated by the daily uptake of RVS (2 mg/kg/day) for 28 days (14 days before and after operation) via intragastric route. We observed that BDL drastically induced the deterioration of liver histoarchitecture and excessive deposition of extracellular matrix (ECM), both of which were significantly attenuated by RVS. In addition, we revealed that RVS inhibited BDL-induced proliferation and activation of interstitial myofibroblasts, a highly suggestive cell type for ECM production, as shown by immunohistochemical and semi-quantitative detection of α-smooth muscle actin and vimentin. Finally, we demonstrated that the anti-fibrotic effect of RVS was associated with the inactivation of Smad3, the key downstream target of a major fibrogenic cytokine, i.e., transforming growth factor β (TGF-β). Simultaneously, we also found that RVS reciprocally increased the expression of Smad7, a negative regulatory protein of the TGF-β/Smad3 pathway. Taken together, these results suggested that RVS has a therapeutic effect on CLC, and these effects are, at least partly, due to the inhibition of liver fibrosis by the downregulation of Smad3 and upregulation of Smad7.

Extract of Rhus verniciflua stokes protects against renal ischemia-reperfusion injury by enhancing Nrf2-mediated induction of antioxidant enzymes

Ischemia-reperfusion injury (IRI) may cause acute kidney disease (AKD) by mediating the oxidative stress-induced apoptosis of parenchymal cells. The extract of Rhus verniciflua Stokes (RVS) is used as a traditional herbal medicine as it exhibits anti-oxidant, anti-apoptotic and anti-inflammatory properties. Therefore, the current study investigated the therapeutic effect and the underlying mechanism of RVS on IRI-induced AKD in vivo and in vitro. The current study assessed the effects of RVS on a mouse model of renal IRI and in hypoxic human renal tubular epithelial HK-2 cells. The results demonstrated that the IRI-induced elevation of blood urea nitrogen, serum creatinine and lactate dehydrogenase was significantly attenuated by the intraoral administration of RVS (20 mg/kg/day) for 14 days prior to surgery. It was demonstrated that IRI surgery induced histological damage and cellular apoptosis in renal parenchyma, which were attenuated by pretreatment with RVS. Furthermore, in HK-2 cells incubated with 300 µM CoCl2 to induce chemical hypoxia, it was demonstrated that RVS treatment significantly inhibited cell death and the production of reactive oxygen species (ROS). Furthermore, RVS treatment upregulated the levels of endogenous antioxidant enzymes, including heme oxygenase-1 and catalase, as well as their upstream regulator nuclear factor erythroid 2-related factor 2, in HK-2 cells. Taken together, these results suggested that the intraoral administration of RVS induces a therapeutic effect on IRI-induced AKD. These effects are at least partly due to the attenuation of ROS production via upregulation of the antioxidant defense system in renal tubular cells.