Cuong Thach Nguyen

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.

Anti-oxidative stress effect of red ginseng in the brain is mediated by peptidyl arginine deiminase type IV (PADI4) repression via estrogen receptor (ER) β up-regulation

AIM OF THE STUDY Ginseng has been used as an anti-stress agent, and its active ingredient, ginsenoside, is similar in structure to estrogen. However, the effect of ginseng on the stressed brain is not completely understood. The aim of this study is to understand systematically how red ginseng (RG) affects gene expressions in the brain of immobilization (IMO) stressed mice to elucidate its underlying mechanism. MATERIALS AND METHODS For in vivo experiments, mice were stressed by immobilization for 30, 45, or 60 min, and gene expression in the mice brain was analyzed by microarray and system biology. Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick-end labeling (TUNEL) staining, and gene expression by Western blot or qPCR. For in vitro study, the SK-N-SH neuroblastoma cells were stressed by H2O2 exposure. The resultant cytotoxicity was measured by MTT assay, and gene expression by Western blot, ELISA, or qPCR. RESULTS Microarray analysis of genes in IMO stressed mice brains showed that RG administration prior to IMO stress downregulated >40 genes including peptidyl arginine deiminase type 4 (PADI4). Interestingly, PADI4 was up-regulated by various stresses such as H2O2, acrylamide, and tunicamycin in neuroblastoma SK-N-SH cells but inhibited by RG. IMO stress and in vitro H2O2 stress depressed the estrogen receptor (ER)-β expression but not ERα. However, RG treatment increased ERβ expression both in vivo and in vitro. Comparative analysis regarding the networks by systems biology revealed that TNF-α plays a critical role in IMO stress, and the cell death associated network was much higher than other categories. Consistently, the IMO stress induced TNF-α and Cox-2 expressions, malondialdehyde (MDA), and cell death in the brain, whereas RG administration inhibited these inductions in vivo. siRNA and transient expression studies revealed that ERβ inhibited the PADI4 expression. CONCLUSION PADI4 could be used as an oxidative stress marker. RG seems to inhibit oxidative stress-inducible PADI4 by up-regulating ERβ expression in the brain thus protecting brain cells from apoptosis.

ATF3 Confers Resistance to Pneumococcal Infection Through Positive Regulation of Cytokine Production

BACKGROUND Activating transcription factor-3 (ATF3) is known as a suppressor of cytokine production after exposure to lipopolysaccharide or during gram-negative bacterial infection. However, the mechanism by which ATF3 regulates innate immunity against gram-positive bacterial infection, particularly Streptococcus pneumoniae, remains unknown. METHODS The wild-type and ATF3 knock-out (KO) mice were infected intranasally (i.n) or intraperitoneally with S. pneumoniae, and bacterial colonization or survival rate was determined. Pneumococcal pneumonia was induced by i.n infection, and ATF3 level was determined by Western blot. ATF3 KO cells or ATF3 siRNA transfection were used to determine expression of ATF3 downstream genes. Enzyme-linked immunosorbent assay was used to examine cytokines levels. RESULTS ATF3 was highly expressed in various cell lines in vitro and in many organs in vivo. Pneumolysin was a novel inducer of ATF3. Pneumococcal infection induced ATF3, which subsequently stimulated production of cytokines (tumor necrosis factor [TNF]-α, interleukin [IL]-1β, and interferon [IFN]-γ). ATF3-mediated cytokine induction protected the host from pneumococcal infection. In the pneumonia infection model, the bacterial clearance of wild-type mice was more efficient than those of ATF3 KO mice. CONCLUSIONS Taken together, we can conclude that ATF3 regulates innate immunity positively upon pneumococcus infection by enhancing TNF-α, IL-1β, and IFN-γ expression and modulating bacterial clearance.

Ethanol-Induced Alcohol Dehydrogenase E (AdhE) Potentiates Pneumolysin in Streptococcus pneumoniae

ABSTRACT Alcohol impairs the host immune system, rendering the host more vulnerable to infection. Therefore, alcoholics are at increased risk of acquiring serious bacterial infections caused by Streptococcus pneumoniae, including pneumonia. Nevertheless, how alcohol affects pneumococcal virulence remains unclear. Here, we showed that the S. pneumoniae type 2 D39 strain is ethanol tolerant and that alcohol upregulates alcohol dehydrogenase E (AdhE) and potentiates pneumolysin (Ply). Hemolytic activity, colonization, and virulence of S. pneumoniae, as well as host cell myeloperoxidase activity, proinflammatory cytokine secretion, and inflammation, were significantly attenuated in adhE mutant bacteria (ΔadhE strain) compared to D39 wild-type bacteria. Therefore, AdhE might act as a pneumococcal virulence factor. Moreover, in the presence of ethanol, S. pneumoniae AdhE produced acetaldehyde and NADH, which subsequently led Rex (redox-sensing transcriptional repressor) to dissociate from the adhE promoter. An increase in AdhE level under the ethanol condition conferred an increase in Ply and H2O2 levels. Consistently, S. pneumoniae D39 caused higher cytotoxicity to RAW 264.7 cells than the ΔadhE strain under the ethanol stress condition, and ethanol-fed mice (alcoholic mice) were more susceptible to infection with the D39 wild-type bacteria than with the ΔadhE strain. Taken together, these data indicate that AdhE increases Ply under the ethanol stress condition, thus potentiating pneumococcal virulence.

Streptococcus pneumoniae ClpL Modulates Adherence to A549 Human Lung Cells through Rap1/Rac1 Activation

ABSTRACT Caseinolytic protease L (ClpL) is a member of the HSP100/Clp chaperone family, which is found mainly in Gram-positive bacteria. ClpL is highly expressed during infection for refolding of stress-induced denatured proteins, some of which are important for adherence. However, the role of ClpL in modulating pneumococcal virulence is poorly understood. Here, we show that ClpL impairs pneumococcal adherence to A549 lung cells by inducing and activating Rap1 and Rac1, thus increasing phosphorylation of cofilin (inactive form). Moreover, infection with a clpL mutant (ΔclpL) causes a greater degree of filopodium formation than D39 wild-type (WT) infection. Inhibition of Rap1 and Rac1 impairs filopodium formation and pneumococcal adherence. Therefore, ClpL can reduce pneumococcal adherence to A549 cells, likely via modulation of Rap1- and Rac1-mediated filopodium formation. These results demonstrate a potential role for ClpL in pneumococcal resistance to host cell adherence during infection. This study provides insight into further understanding the interactions between hosts and pathogens.

TLR4 Mediates Pneumolysin-Induced ATF3 Expression through the JNK/p38 Pathway in Streptococcus pneumoniae-Infected RAW 264.7 Cells

Activating transcription factor-3 (ATF3) acts as a negative regulator of cytokine production during Gram-negative bacterial infection. A recent study reported that ATF3 provides protection from Streptococcus pneumoniae infection by activating cytokines. However, the mechanism by which S. pneumoniae induces ATF3 after infection is still unknown. In this study, we show that ATF3 was upregulated via Toll-like receptor (TLR) pathways in response to S. pneumoniae infection in vitro. Induction was mediated by TLR4 and TLR2, which are in the TLR family. The expression of ATF3 was induced by pneumolysin (PLY), a potent pneumococcal virulence factor, via the TLR4 pathway. Furthermore, ATF3 induction is mediated by p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK). Thus, this study reveals a potential role of PLY in modulating ATF3 expression, which is required for the regulation of immune responses against pneumococcal infection in macrophages.

Panax ginseng aqueous extract prevents pneumococcal sepsis in vivo by potentiating cell survival and diminishing inflammation.

BACKGROUND More than 50% of sepsis cases are caused by Streptococcus pneumoniae, and hospital mortality related to sepsis comprises 52% of all hospital deaths. Therefore, sepsis is a medical emergency, and any treatment against the agent that produces it, is welcome. PURPOSE The role of Panax ginseng C.A. Meyer (Araliaceae) aqueous extract in bacterial infection in vivo is not well understood. Here, the protective effect of Korean red ginseng (KRG) extract against pneumococcal infection and sepsis was elucidated. STUDY DESIGN In this study, mice were administrated KRG (25, 50, 100 mg/kg) for 15 days, and then infected with a lethal S. pneumoniae strain. Survival rate, body weight, and colonization were determined. METHODS The RAW 264.7 macrophage cells were infected with S. pneumoniae and cell viability was assessed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Inflammation was examined using an enzyme-linked immunosorbent assay (ELISA) and hematoxylin and eosin (HE) staining while gene expression was determined using western blotting. RESULTS KRG-pre-treated mice (100 mg/kg of KRG) had significantly higher survival rates and body weights than those of the non-treated controls; KRG-pre-treated mice had lower bacterial number and morbidity than those of the non-treated controls. 100 mg/kg of KRG administration decreased cytokine levels including tumor necrosis factor (TNF)-α (897 and 623 pg/ml, control and KRG groups, respectively, P < 0.05) and interleukin (IL)-1β (175 and 127 pg/ml, control and KRG groups, respectively, P = 0.051), nitric oxide level (149 and 81 nM, control and KRG groups, respectively, P < 0.05), and neutrophil infiltration 48 h post-infection, in vivo. In pneumococcal infection, KRG pre-treatment downregulated toll-like receptor (TLR) 4 and TNF-ɑ expressions in RAW 264.7 macrophage cells and increased cell survival by activating phosphoinositide 3-kinase (PI3K)/AKT signaling. CONCLUSION Taken together, 100 mg/kg of KRG appeared to protect host cells from lethal pneumococcal sepsis by inhibiting inflammation as well as by enhancing bacterial clearance thereby reinforcing cell survival against pneumococcal infection.

Stress responses in Streptococcus species and their effects on the host

Streptococci cause a variety of diseases, such as dental caries, pharyngitis, meningitis, pneumonia, bacteremia, endocarditis, erysipelas, and necrotizing fasciitis. The natural niche of this genus of bacteria ranges from the mouth and nasopharynx to the skin, indicating that the bacteria will inevitably be subjected to environmental changes during invasion into the host, where it is exposed to the host immune system. Thus, the Streptococcus-host interaction determines whether bacteria are cleared by the host’s defenses or whether they survive after invasion to cause serious diseases. If this interaction was to be deciphered, it could aid in the development of novel preventive and therapeutic agents. Streptococcus species possess many virulent factors, such as peroxidases and heat-shock proteins (HSPs), which play key roles in protecting the bacteria from hostile host environments. This review will discuss insights into the mechanism(s) by which streptococci adapt to host environments. Additionally, we will address how streptococcal infections trigger host stress responses; however, the mechanism by which bacterial components modulate host stress responses remains largely unknown.

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.

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.