Stress responses in Streptococcus species and their effects on the host

Cuong Thach Nguyen,박상상,이동권 한국미생물학회 2015 The journal of microbiology Vol.53 No.11

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.

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

Cuong Thach Nguyen,이동권,김은혜,Truc Thanh Luong,표석능 한국분자세포생물학회 2015 Molecules and cells Vol.38 No.1

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.

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

Cuong Thach Nguyen,Truc Thanh Luong,Gyu-Lee Kim,Suhkneung Pyo,Dong-Kwon Rhee 고려인삼학회 2015 Journal of Ginseng Research Vol.39 No.3

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 byWestern 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.

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

Nguyen, Cuong Thach,Kim, Eun-Hye,Luong, Truc Thanh,Pyo, Suhkneung,Rhee, Dong-Kwon Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.1

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.

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

Nguyen, Cuong Thach,Le, Nhat-Tu,Tran, Thao Dang-Hien,Kim, Eun-Hye,Park, Sang-Sang,Luong, Truc Thanh,Chung, Kyung-Tae,Pyo, Suhkneung,Rhee, Dong-Kwon American Society for Microbiology 2014 Infection and immunity Vol.82 No.9

<P>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 <I>clpL</I> mutant (Δ<I>clpL</I>) 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.</P>

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

Nguyen, Cuong Thach,Kim, Eun-Hye,Luong, Truc Thanh,Pyo, Suhkneung,Rhee, Dong-Kwon Oxford University Press 2014 The Journal of Infectious Diseases Vol.210 No.11

<P><B><I>Background.</I></B> 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 <I>Streptococcus pneumoniae</I>, remains unknown.</P><P><B><I>Methods.</I></B> The wild-type and ATF3 knock-out (KO) mice were infected intranasally (<I>i.n</I>) or intraperitoneally with <I>S. pneumoniae</I>, and bacterial colonization or survival rate was determined. Pneumococcal pneumonia was induced by <I>i.n</I> 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.</P><P><B><I>Results.</I></B> 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.</P><P><B><I>Conclusions.</I></B> 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.</P>

Korean Red Ginseng inhibits apoptosis in neuroblastoma cells via estrogen receptor ${\beta}$-mediated phosphatidylinositol-3 kinase/Akt signaling

Nguyen, Cuong Thach,Luong, Truc Thanh,Kim, Gyu-Lee,Pyo, Suhkneung,Rhee, Dong-Kwon The Korean Society of Ginseng 2015 Journal of Ginseng Research Vol.39 No.1

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)-${\beta}$ signaling. Methods: Human neuroblastoma SK-N-SH cells were pretreated with KRG and subsequently exposed to $H_2O_2$. The ability of KRG to inhibit oxidative stress-induced apoptosis was assessed in MTT cytotoxicity assays. Apoptotic protein expression was examined byWestern blot analysis. The roles of ER-${\beta}$, 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-${\beta}$, PI3K, and p-Akt expression. Conversely, ER-${\beta}$ 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-${\beta}$ expression.

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

Cuong Thach Nguyen,Truc Thanh Luong,Gyu-Lee Kim,Suhkneung Pyo,Dong-Kwon Rhee 고려인삼학회 2015 Journal of Ginseng Research Vol.39 No.1

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)-b 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 byWestern 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-b 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-b expression.

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

Cuong Thach Nguyen,Truc Thanh Luong,김규리,표석능,이동권 고려인삼학회 2015 Journal of Ginseng Research Vol.39 No.1

Background: Ginseng has been shown to exert antistress effects both in vitro and in vivo. However, theeffects of ginseng on stress in brain cells are not well understood. This study investigated how KoreanRed Ginseng (KRG) controls hydrogen peroxide-induced apoptosis via regulation of phosphatidylinositol-3 kinase (PI3K)/Akt and estrogen receptor (ER)-b signaling. Methods: Human neuroblastoma SK-N-SH cells were pretreated with KRG and subsequently exposed toH2O2. The ability of KRG to inhibit oxidative stress-induced apoptosis was assessed in MTT cytotoxicityassays. Apoptotic protein expression was examined byWestern blot analysis. The roles of ER-b, PI3K, andp-Akt signaling in KRG regulation of apoptosis were studied using small interfering RNAs and/or targetantagonists. Results: Pretreating SK-N-SH cells with KRG decreased expression of the proapoptotic proteins p-p53and caspase-3, but increased expression of the antiapoptotic protein BCL2. KRG pretreatment was alsoassociated with increased ER-b, PI3K, and p-Akt expression. Conversely, ER-b inhibition with smallinterfering 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 byenhancing PI3K/Akt signaling via upregulation of ER-b expression.

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

김규리,이승엽,Truc Thanh Luong,Cuong Thach Nguyen,박상상,Suhk neung Pyo,이동권 대한약학회 2017 Archives of Pharmacal Research Vol.40 No.8

Streptococcus pneumoniae (pneumococcus) isresponsible for significant morbidity and mortality worldwide. It causes a variety of life-threatening infections suchas pneumonia, bacteremia, and meningitis. In bacterialphysiology, the metabolic pathway of branched-chainamino acids (BCAAs) plays an important role in virulence. Nonetheless, the function of IlvC, one of the enzymesinvolved in the biosynthesis of BCAAs, in S. pneumoniaeremains unclear. Here, we demonstrated that downregulationof BCAA biosynthesis by ilvC ablation can diminishBCAA concentration and expression of pneumolysin (Ply)and LytA, and subsequently attenuate virulence. Infectionwith an ilvC mutant showed significantly reduced mortalityand colonization in comparison with strain D39 (serotype2, wild type), suggesting that ilvC can potentiate S. pneumoniaevirulence due to adequate BCAA synthesis. Takentogether, these results suggest that the function of ilvC inBCAA synthesis is essential for virulence factor and couldplay an important role in the pathogenesis of respiratoryinfections.