Gyu-Lee Kim

Korean Red Ginseng inhibits apoptosis in neuroblastoma cells via estrogen receptor β-mediated phosphatidylinositol-3 kinase/Akt signaling

Background Ginseng has been shown to exert antistress effects both in vitro and in vivo. However, the effects of ginseng on stress in brain cells are not well understood. This study investigated how Korean Red Ginseng (KRG) controls hydrogen peroxide-induced apoptosis via regulation of phosphatidylinositol-3 kinase (PI3K)/Akt and estrogen receptor (ER)-β signaling. Methods Human neuroblastoma SK-N-SH cells were pretreated with KRG and subsequently exposed to H2O2. The ability of KRG to inhibit oxidative stress-induced apoptosis was assessed in MTT cytotoxicity assays. Apoptotic protein expression was examined by Western blot analysis. The roles of ER-β, PI3K, and p-Akt signaling in KRG regulation of apoptosis were studied using small interfering RNAs and/or target antagonists. Results Pretreating SK-N-SH cells with KRG decreased expression of the proapoptotic proteins p-p53 and caspase-3, but increased expression of the antiapoptotic protein BCL2. KRG pretreatment was also associated with increased ER-β, PI3K, and p-Akt expression. Conversely, ER-β inhibition with small interfering RNA or inhibitor treatment increased p-p53 and caspase-3 levels, but decreased BCL2, PI3K, and p-Akt expression. Moreover, inhibition of PI3K/Akt signaling diminished p-p53 and caspase-3 levels, but increased BCL2 expression. Conclusion Collectively, the data indicate that KRG represses oxidative stress-induced apoptosis by enhancing PI3K/Akt signaling via upregulation of ER-β expression.

Effect of decreased BCAA synthesis through disruption of ilvC gene on the virulence of Streptococcus pneumoniae

Streptococcus pneumoniae (pneumococcus) is responsible for significant morbidity and mortality worldwide. It causes a variety of life-threatening infections such as pneumonia, bacteremia, and meningitis. In bacterial physiology, the metabolic pathway of branched-chain amino acids (BCAAs) plays an important role in virulence. Nonetheless, the function of IlvC, one of the enzymes involved in the biosynthesis of BCAAs, in S. pneumoniae remains unclear. Here, we demonstrated that downregulation of BCAA biosynthesis by ilvC ablation can diminish BCAA concentration and expression of pneumolysin (Ply) and LytA, and subsequently attenuate virulence. Infection with an ilvC mutant showed significantly reduced mortality and colonization in comparison with strain D39 (serotype 2, wild type), suggesting that ilvC can potentiate S. pneumoniae virulence due to adequate BCAA synthesis. Taken together, these results suggest that the function of ilvC in BCAA synthesis is essential for virulence factor and could play an important role in the pathogenesis of respiratory infections.

Pneumonia and Streptococcus pneumoniae vaccine

Pneumonia is an inflammatory disease of the lung, responsible for high morbidity and mortality worldwide. It is caused by bacteria, viruses, fungi, or other microorganisms. Streptococcus pneumoniae, a gram-positive bacterium with over 90 serotypes, is the most common causative agent. Moreover, comorbid factors including heart failure, renal disease, and pulmonary disease could increase the risk of pneumococcal pneumonia. Since the advent of the pneumococcal vaccine in the 1980s, the incidence of pneumonia has decreased significantly. However, current vaccines confer only limited protection against serotypes included in the vaccine. Thus, to overcome this limitation, new types of pneumococcal vaccines have been sought and under clinical trials. In this review, we discuss pneumonia and summarize the various types of pneumococcal vaccines in progress.

Pulmonary Colonization Resistance to Pathogens via Noncanonical Wnt and Interleukin-17A by Intranasal pep27 Mutant Immunization

Background Previous studies have focused on colonization resistance of the gut microbiota against antibiotic resistant strains. However, less research has been performed on respiratory colonization resistance. Methods Because respiratory colonization is the first step of respiratory infections, intervention to prevent colonization would represent a new approach for preventive and therapeutic measures. The Th17 response plays an important role in clearance of respiratory pathogens. Thus, harnessing the Th17 immune response in the mucosal site would be an effective method to design a respiratory mucosal vaccine. Results In this study, we show that intranasal Δpep27 immunization induces noncanonical Wnt and subsequent interleukin (IL)-17 secretion, and it inhibits Streptococcus pneumoniae, Staphylococcus aureus, and Klebsiella pneumoniae colonization. Moreover, IL-17A neutralization or nuclear factor of activated T-cell inhibition augmented bacterial colonization, indicating that noncanonical Wnt signaling is involved in pulmonary colonization resistance. Conclusions Therefore, Δpep27 immunization can provide nonspecific respiratory colonization resistance via noncanonical Wnt signaling and IL-17A-related pathways.

Induction of the pneumococcal vncRS operon by lactoferrin is essential for pneumonia

ABSTRACT Streptococcus pneumoniae (pneumococcus), the major pathogen for pneumonia, commonly colonizes the lung, but the mechanism underlying the coordination of virulence factors during invasion via the host protein remains poorly understood. Bacterial lysis releases the components of the cell wall, and triggers innate immunity and the subsequent secretion of pro-inflammatory cytokines. Previously, the virulence of the pep27 mutant was shown to be attenuated as a feasible candidate for vaccine development. However, the role of pep27 gene, belonging to the vancomycin-resistance locus (vncRS operon), in virulence, is largely unknown. This study demonstrates that transferrin in the host serum reduces the survival of the host during S. pneumoniae infections in mice. The exposure of the pneumococcal D39 strain to lactoferrin induced the vncRS operon, lysis, and subsequent in vivo cytokine production, resulting in lung inflammation. However, these responses were significantly attenuated in pneumococci harboring a mutation in pep27. Mechanistically, the VncS ligand, identified as lactoferrin, induced the vncRS operon and increased the in vivo mortality rates. Thus, serum-induced activation of vncRS plays an essential role in inducing pneumonia.

ATF3 Stimulates IL-17A by Regulating Intracellular Ca2+/ROS-Dependent IL-1β Activation During Streptococcus pneumoniae Infection

Activating transcription factor-3 (ATF3) in the ER stress pathway induces cytokine production and promotes survival during gram-positive bacterial infection. IL-17A is a critical cytokine that is essential for clearance of Streptococcus pneumoniae. However, the mechanism by which ATF3 induces IL-17A production remains unknown. Here, we show that ATF3 induces IL-17A production via NLRP3 inflammasome-dependent IL-1β secretion. Survival rates were comparable in IL-17A-depleted and ATF3 KO mice but were lower than in WT mice treated with isotype control, indicating that ATF3 positively regulated IL-17A production. Indeed, ATF3 KO mice showed a marked reduction in IL-17A protein and mRNA expression compared to levels in WT mice. Moreover, mitochondrial IL-1β production by bone marrow-derived macrophages was significantly reduced in ATF3 KO mice as a result of the disruption of cellular ROS and Ca2+ homeostasis. Accordingly, ATF3 KO mice displayed diminished survival and bacterial clearance following S. pneumoniae infection. Taken together, these data suggest a mechanism in which macrophage ATF3 promotes IL-17A production in γδ T cells to rapidly induce host defenses during early S. pneumoniae infection.

Estrogen receptor-β of microglia underlies sexual differentiation of neuronal protection via ginsenosides in mice brain

Streptococcus pneumoniae infection in acute bacterial meningitis can lead to widespread brain damage and mortality. Inflammatory responses by immune cells in the brain are thought to determine the degree of brain injury. Yet, the mechanisms underlying host responses to pneumococcal meningitis are largely unknown. To explore host responses as a potential therapeutic target for preventing brain injury after pneumococcal meningitis.

Inhibition of Autolysis by Lipase LipA in Streptococcus pneumoniae Sepsis

More than 50% of sepsis cases are associated with pneumonia. Sepsis is caused by infiltration of bacteria into the blood via inflammation, which is triggered by the release of cell wall components following lysis. However, the regulatory mechanism of lysis during infection is not well defined. Mice were infected with Streptococcus pneumoniae D39 wild-type (WT) and lipase mutant (ΔlipA) intranasally (pneumonia model) or intraperitoneally (sepsis model), and survival rate and pneumococcal colonization were determined. LipA and autolysin (LytA) levels were determined by qPCR and western blotting. S. pneumoniae Spd_1447 in the D39 (type 2) strain was identified as a lipase (LipA). In the sepsis model, but not in the pneumonia model, mice infected with the ΔlipA displayed higher mortality rates than did the D39 WT-infected mice. Treatment of pneumococci with serum induced LipA expression at both the mRNA and protein levels. In the presence of serum, the ΔlipA displayed faster lysis rates and higher LytA expression than the WT, both in vitro and in vivo. These results indicate that a pneumococcal lipase (LipA) represses autolysis via inhibition of LytA in a sepsis model.

Effect of Korean Red Ginseng extracts on drug-drug interactions

Background Ginseng has been the subject of many experimental and clinical studies to uncover the diverse biological activities of its constituent compounds. It is a traditional medicine that has been used for its immunostimulatory, antithrombotic, antioxidative, anti-inflammatory, and anticancer effects. Ginseng may interact with concomitant medications and alter metabolism and/or drug transport, which may alter the known efficacy and safety of a drug; thus, the role of ginseng may be controversial when taken with other medications. Methods We extensively assessed the effects of Korean Red Ginseng (KRG) in rats on the expression of enzymes responsible for drug metabolism [cytochrome p450 (CYP)] and transporters [multiple drug resistance (MDR) and organic anion transporter (OAT)] in vitro and on the pharmacokinetics of two probe drugs, midazolam and fexofenadine, after a 2-wk repeated administration of KRG at different doses. Results The results showed that 30 mg/kg KRG significantly increased the expression level of CYP3A11 protein in the liver and 100 mg/kg KRG increased both the mRNA and protein expression of OAT1 in the kidney. Additionally, KRG significantly increased the mRNA and protein expression of OAT1, OAT3, and MDR1 in the liver. Although there were no significant changes in the metabolism of midazolam to its major metabolite, 1′-hydroxymidazolam, KRG significantly decreased the systemic exposure of fexofenadine in a dose-dependent manner. Conclusion Because KRG is used as a health supplement, there is a risk of KRG overdose; thus, a clinical trial of high doses would be useful. The use of KRG in combination with P-glycoprotein substrate drugs should also be carefully monitored.

Corrigendum: ATF3 provides protection from Staphylococcus aureus and Listeria monocytogenes infections

School of Pharmacy, Sungkyunkwan University, Su-Won 440–746, South Korea ∗Corresponding Author: School of Pharmacy, Sungkyunkwan University, 300 Chunchundong, Su-won 440–746, South Korea. Tel: +82-31-2907707; Fax: +82-31-2907727; E-mail: dkrhee@skku.ac.kr †Present Address: Department of Microbiology & Molecular Genetics, University of Texas Health Science Center, Houston, TX 77030, USA. One sentence summary: Gram-positive Staphylococcus aureus and Listeria monocytogenes infections induce ATF3 (eukaryotic transcriptional regulator), which subsequently functions as a positive regulator for cytokine production and provides protection from these lethal infections. Editor: Jan-Ingmar Flock