Sun-Jae Lee

Mechanisms of fibrogenesis in liver cirrhosis: The molecular aspects of epithelial-mesenchymal transition

Liver injuries are repaired by fibrosis and regeneration. The cause of fibrosis and diminished regeneration, especially in liver cirrhosis, is still unknown. Epithelial-mesenchymal transition (EMT) has been found to be associated with liver fibrosis. The possibility that EMT could contribute to hepatic fibrogenesis reinforced the concept that activated hepatic stellate cells are not the only key players in the hepatic fibrogenic process and that other cell types, either hepatic or bone marrow-derived cells could contribute to this process. Following an initial enthusiasm for the discovery of this novel pathway in fibrogenesis, more recent research has started to cast serious doubts upon the real relevance of this phenomenon in human fibrogenetic disorders. The debate on the authenticity of EMT or on its contribution to the fibrogenic process has become very animated. The overall result is a general confusion on the meaning and on the definition of several key aspects. The aim of this article is to describe how EMT participates to hepatic fibrosis and discuss the evidence of supporting this possibility in order to reach reasonable and useful conclusions.

Apamin inhibits hepatic fibrosis through suppression of transforming growth factor β1-induced hepatocyte epithelial–mesenchymal transition

Apamin is an integral part of bee venom, as a peptide component. It has long been known as a highly selective block Ca(2+)-activated K(+) (SK) channels. However, the cellular mechanism and anti-fibrotic effect of apamin in TGF-β1-induced hepatocytes have not been explored. In the present study, we investigated the anti-fibrosis or anti-EMT mechanism by examining the effect of apamin on TGF-β1-induced hepatocytes. AML12 cells were seeded at ∼60% confluence in complete growth medium. Twenty-four hours later, the cells were changed to serum free medium containing the indicated concentrations of apamin. After 30 min, the cells were treated with 2 ng/ml of TGF-β1 and co-cultured for 48 h. Also, we investigated the effects of apamin on the CCl4-induced liver fibrosis animal model. Treatment of AML12 cells with 2 ng/ml of TGF-β1 resulted in loss of E-cadherin protein at the cell-cell junctions and concomitant increased expression of vimentin. In addition, phosphorylation levels of ERK1/2, Akt, Smad2/3 and Smad4 were increased by TGF-β1 stimulation. However, cells treated concurrently with TGF-β1 and apamin retained high levels of localized expression of E-cadherin and showed no increase in vimentin. Specifically, treatment with 2 μg/ml of apamin almost completely blocked the phosphorylation of ERK1/2, Akt, Smad2/3 and Smad4 in AML12 cells. In addition, apamin exhibited prevention of pathological changes in the CCl4-injected animal models. These results demonstrate the potential of apamin for the prevention of EMT progression induced by TGF-β1 in vitro and CCl4-injected in vivo.

Apamin inhibits PDGF-BB-induced vascular smooth muscle cell proliferation and migration through suppressions of activated Akt and Erk signaling pathway

The increased proliferation and migration of vascular smooth muscle cells (VSMC) are key process in the development of atherosclerosis lesions. Platelet-derived growth factor (PDGF) initiates a multitude of biological effects that contribute to VSMC proliferation and migration. Apamin, a component of bee venom, has been known to block the Ca(2+)-activated K(+) channels. However, the effects of apamin in the regulation PDGF-BB-induced VSMC proliferation and migration has not been identified. In this study, we investigate the inhibitory effect of apamin on PDGF-BB-induced VSMC proliferation and migration. Apamin suppressed the PDGF-BB-induced VSMC proliferation and migration with no apparent cytotoxic effect. In accordance with these findings, apamin induced the arrest of cell cycle progression at G0/G1 phase. Apamin also decreased the expressions of G0/G1 specific regulatory proteins including proliferating cell nuclear antigen (PCNA), cyclin D1, cyclin-dependent kinases (CDK) 4, cyclin E and CDK2, as well as increased the expression of p21(Cip1) in PDGF-BB-induced VSMC. Moreover, apamin inhibited PDGF-BB-induced phosphorylation of Akt and Erk1/2. These results suggest that apamin plays an important role in prevention of vascular proliferation and migration through the G0/G1 cell cycle arrest by PDGF signaling pathway. Thus, apamin may be a promising candidate for the therapy of atherosclerosis.

Inhibitory effects of bee venom on Propionibacterium acnes-induced inflammatory skin disease in an animal model

Propionibacterium acnes (P. acnes) is a major contributing factor to the inflammatory component of acne. The many prescription medications for acne allow for a large number of potential combination treatments. However, several antibiotics, apart from their antibacterial effects, exert side‑effects, such as the suppression of host inflammatory responses. Purified bee venom (BV) is a natural toxin produced by honeybees (Apis mellifera L.). BV has been widely used as a traditional medicine for various diseases. In the present study, to investigate the therapeutic effects of BV against P. acnes-induced inflammatory skin disease, P. acnes was intradermally injected into the ears of mice. After the injection, BV was applied to the skin surface of the right ear. Histological observation revealed that P. acnes induced a considerable increase in the number of infiltrated inflammatory cells. However, treatment with BV markedly reduced these reactions compared with the P. acnes-injected mice not treated with BV. Moreover, the expression levels of tumor necrosis factor (TNF)-α, and interleukin (IL)-1β were significantly reduced in the BV-treated mice compared with the untreated P. acnes-injected mice. In addition, treatment with BV significantly inhibited Toll-like receptor (TLR)2 and CD14 expression in P. acnes-injected tissue. The binding activity of nuclear factor-κB (NF-κB) and activator protein (AP)-1 was markedly suppressed following treatment with BV. The results from our study, using an animal model, indicate that BV exerts an inhibitory effect on inflammatory skin diseases. In conclusion, our data indicate that BV has potential for use as an anti-acne agent and may be useful in the pharmaceutical and cosmetics industries.

The pathogenesis of drug-induced liver injury

ABSTRACT Introduction: Drugs can induce liver injury when taken as an over-dose, or even at therapeutic doses in susceptible individuals. Although severe drug-induced liver injury (DILI) is a relatively uncommon clinical event, it is a potentially life threatening adverse drug reaction and is the most common indication for the drug withdrawal. Areas covered: However, the diagnosis of DILI remains a significant challenge, because the establishment of causality is very difficult, and the histopathologic findings of DILI may be indistinguishable from those of other hepatic disorders, such as viral and alcoholic hepatitis. In this review, we provide an overview of recent advances in identification of serologic markers of diagnosis and prognosis, etiologic factors for susceptibility and diagnostic evaluation of DILI, with a focus on its pathogenic mechanisms and the role of liver biopsy. Expert commentary: Further studies of divergent research platforms, using a systems biology approach such as genomics and transcriptomics, may provide a deeper understanding of human drug metabolism and the causes, risk factors, and pathogenesis of DILI.

Apamin inhibits TNF-α- and IFN-γ-induced inflammatory cytokines and chemokines via suppressions of NF-κB signaling pathway and STAT in human keratinocytes

BACKGROUND Atopic dermatitis (AD) is identified by an increase in infiltrations of several inflammatory cells including type 2 helper (Th2) lymphocytes. Th2-related chemokines such as thymus and activation-regulated chemokine (TARC/CCL17) and macrophage-derived chemokine (MDC/CCL22), and pro-inflammatory cytokines including interleukin (IL)-1β and IL-6 are considered to play a crucial role in AD. Tumor necrosis factor (TNF)-α- and interferon (IFN)-γ induce the inflammatory condition through production of TARC, MDC, IL-1β and IL-6, and activations of related transcription factors, such as nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and signal transducer and activator of transcription (STAT) in keratinocytes. Apamin, a peptide component of bee venom, has been reported its beneficial activities in various diseases. However, anti-inflammatory effects of apamin on inflammatory condition in keratinocytes have not been explored. Therefore, the present study aimed to demonstrate the anti-inflammatory effect of apamin on TNF-α- and IFN-γ-induced inflammatory condition in keratinocytes. METHODS HaCaT was used as human keratinocytes cell line. Cell Counting Kit-8 was performed to measure a cytotoxicity of apamin. The effects of apamin on TNF-α-/IFN-γ-induced inflammatory condition were determined by real-time PCR and Western blot analysis. Further, NF-κB signaling pathways, STAT1, and STAT3 were analyzed by Western blot and immunofluorescence. RESULTS Apamin ameliorated the inflammatory condition through suppression of Th2-related chemokines and pro-inflammatory cytokines. Further, apamin down-regulated the activations of NF-κB signaling pathways and STATs in HaCaT cells. CONCLUSIONS These results suggest that apamin has therapeutic effect on AD through improvement of inflammatory condition.