Dexamethasone Induces $Fc{\gamma}RIIb$ Expression in RBL-2H3 Cells

Silwal, Prashanta,Lee, Mi-Nam,Lee, Choong-Jae,Hong, Jang-Hee,NamGung, Uk,Lee, Zee-Won,Kim, Jinhyun,Lim, Kyu,Kweon, Gi Ryang,Park, Jong Il,Park, Seung Kiel The Korean Society of Pharmacology 2012 The Korean Journal of Physiology & Pharmacology Vol.16 No.6

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress $Fc{\varepsilon}RI$-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE ($Fc{\varepsilon}R$) I and increased the mRNA levels of the inhibitory Fc receptor for IgG $Fc{\gamma}RIIb$. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG ($Fc{\gamma}R$) I and $Fc{\gamma}RIII$. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced $Fc{\gamma}RI$ and $Fc{\gamma}RIII$ mRNA levels potently, while $Fc{\varepsilon}RI$ and $Fc{\gamma}RIIb$ were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only $Fc{\gamma}RIIb$ protein expression was significantly enhanced by Dex treatment, while $Fc{\gamma}RI$, $Fc{\gamma}RIII$ and $Fc{\varepsilon}RI$ expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor $Fc{\gamma}RIIb$.

AMP-Activated Protein Kinase and Host Defense against Infection

Silwal, Prashanta,Kim, Jin Kyung,Yuk, Jae-Min,Jo, Eun-Kyeong MDPI 2018 INTERNATIONAL JOURNAL OF MOLECULAR SCIENCES Vol.19 No.11

<P>5′-AMP-activated protein kinase (AMPK) plays diverse roles in various physiological and pathological conditions. AMPK is involved in energy metabolism, which is perturbed by infectious stimuli. Indeed, various pathogens modulate AMPK activity, which affects host defenses against infection. In some viral infections, including hepatitis B and C viral infections, AMPK activation is beneficial, but in others such as dengue virus, Ebola virus, and human cytomegaloviral infections, AMPK plays a detrimental role. AMPK-targeting agents or small molecules enhance the antiviral response and contribute to the control of microbial and parasitic infections. In addition, this review focuses on the double-edged role of AMPK in innate and adaptive immune responses to infection. Understanding how AMPK regulates host defenses will enable development of more effective host-directed therapeutic strategies against infectious diseases.</P>

Chemical mimetics of the N-degron pathway alleviate systemic inflammation by activating mitophagy and immunometabolic remodeling

Silwal Prashanta,Kim Young Jae,Lee Yoon Jee,Kim In Soo,Jeon Sang Min,Roh Taylor,Kim Jin Kyung,Lee Min Joung,Heo Jun Young,Jo Doo Sin,Lee Sang-Hee,Cho Dong-Hyung,Kim Jin Man,Kwon Yong Tae,Jo Eun-Kyeong 생화학분자생물학회 2023 Experimental and molecular medicine Vol.55 No.-

The Arg/N-degron pathway, which is involved in the degradation of proteins bearing an N-terminal signal peptide, is connected to p62/SQSTM1-mediated autophagy. However, the impact of the molecular link between the N-degron and autophagy pathways is largely unknown in the context of systemic inflammation. Here, we show that chemical mimetics of the N-degron Nt-Arg pathway (p62 ligands) decreased mortality in sepsis and inhibited pathological inflammation by activating mitophagy and immunometabolic remodeling. The p62 ligands alleviated systemic inflammation in a mouse model of lipopolysaccharide (LPS)-induced septic shock and in the cecal ligation and puncture model of sepsis. In macrophages, the p62 ligand attenuated the production of proinflammatory cytokines and chemokines in response to various innate immune stimuli. Mechanistically, the p62 ligand augmented LPS-induced mitophagy and inhibited the production of mitochondrial reactive oxygen species in macrophages. The p62 ligand-mediated anti-inflammatory, antioxidative, and mitophagy-activating effects depended on p62. In parallel, the p62 ligand significantly downregulated the LPS-induced upregulation of aerobic glycolysis and lactate production. Together, our findings demonstrate that p62 ligands play a critical role in the regulation of inflammatory responses by orchestrating mitophagy and immunometabolic remodeling.

Adenine attenuates lipopolysaccharide-induced inflammatory reactions

Silwal, Prashanta,Lim, Kyu,Heo, Jun-Young,Park, Jong IL,Namgung, Uk,Park, Seung-Kiel The Korean Society of Pharmacology 2018 The Korean Journal of Physiology & Pharmacology Vol.22 No.4

A nucleobase adenine is a fundamental component of nucleic acids and adenine nucleotides. Various biological roles of adenine have been discovered. It is not produced from degradation of adenine nucleotides in mammals but produced mainly during polyamine synthesis by dividing cells. Anti-inflammatory roles of adenine have been supported in IgE-mediated allergic reactions, immunological functions of lymphocytes and dextran sodium sulfate-induced colitis. However adenine effects on Toll-like receptor 4 (TLR4)-mediated inflammation by lipopolysaccharide (LPS), a cell wall component of Gram negative bacteria, is not examined. Here we investigated anti-inflammatory roles of adenine in LPS-stimulated immune cells, including a macrophage cell line RAW264.7 and bone marrow derived mast cells (BMMCs) and peritoneal cells in mice. In RAW264.7 cells stimulated with LPS, adenine inhibited production of pro-inflammatory cytokines $TNF-{\alpha}$ and IL-6 and inflammatory lipid mediators, prostaglandin $E_2$ and leukotriene $B_4$. Adenine impeded signaling pathways eliciting production of these inflammatory mediators. It suppressed $I{\kappa}B$ phosphorylation, nuclear translocation of nuclear factor ${\kappa}B$ ($NF-{\kappa}B$), phosphorylation of Akt and mitogen activated protein kinases (MAPKs) JNK and ERK. Although adenine raised cellular AMP which could activate AMP-dependent protein kinase (AMPK), the enzyme activity was not enhanced. In BMMCs, adenine inhibited the LPS-induced production of $TNF-{\alpha}$, IL-6 and IL-13 and also hindered phosphorylation of $NF-{\kappa}B$ and Akt. In peritoneal cavity, adenine suppressed the LPS-induced production of $TNF-{\alpha}$ and IL-6 by peritoneal cells in mice. These results show that adenine attenuates the LPS-induced inflammatory reactions.

Tryptophan Negatively Regulates IgE-mediated Mast Cell Activation

Prashanta Silwal(실왈 프라산타),Keuna Shin(신근아),Seulgi Choi(최슬기),Uk Namgung(남궁욱),Chan Yong Lee(이찬용),Jun-Young Heo(허준영),Kyu Lim(임규),Jong IL Park(박종일),Ki-Hwan Kim(김기환),Seung-Kiel Park(박승길) 대한체질인류학회 2017 해부·생물인류학 (Anat Biol Anthropol) Vol.30 No.2

비만세포는 알레르기 반응을 일으키는 주된 세포로서 항원 자극에 반응하여 알레르기 유발 물질인 히스타민, 단백질 분해효소, 염증성 지질 물질 및 사이토카인 등을 분비한다. 아미노산인 트립토판은 염증반응을 조절한다. 트립토판 투여는 비만세포가 관여하는 염증성 장염 증상을 완화시킨다. 그러나 트립토판이 비만세포의 알레르기 반응에 미치는 영향에 대한 연구는 없다. 본 저자들은 트립토판이 IgE 매개 알레르기 반응에 미치는 영향을 비만세포 수준에서 그리고 실험동물 생쥐에서 연구하였다. IgE-매개 수동 피부 아나필락시스를 생쥐에서 연구하였다. 또한 IgE-매개 비만세포 활성화 반응 즉, 탈과립 반응, 염증성 지질인 LTB4와 사토카인 (TNF-α와 IL-4) 등의 분비를 측정하였다. 트립토판을 생쥐에 복강 주사하면 IgE 매개 수동 피부 아나필락시스를 억제하였다. 또한 비만세포 수준에서도 트립토판은 IgE 매개 알레르기 반응들, 즉 탈과립 반응과 염증성 지질인 LTB4 및 사이토카인인 TNF-α와 IL4의 분비를 억제하였다. 이러한 결과로부터 트립토판은 IgE 매개 알레르기 반응을 세포 수준 및 실험동물 수준에서 억제함을 알 수 있었다. Mast cells are major immune cells in allergy to secrete allergic mediators by a degranulation process and make and secrete inflammatory lipids and cytokines in response to antigen stimulation. An amino acid tryptophan regulates immune functions. Tryptophan ameliorates inflammatory colitis in which mast cells are engaged. However, its effects on mast cells remain to be solved. We investigated the effect of tryptophan on IgE-mediated allergic responses in the mast cells and mice. IgEmediated passive cutaneous anaphylaxis (PCA) in mice were examined. Also IgE-mediated mast cell activation responses such as degranulation of stored granules and secretion of inflammatory lipid LTB4 and cytokines (TNF-α and IL-4) were measured. Intraperitoneal administration of tryptophan suppressed PCA in mice. Also, in the cellular level tryptophan inhibited IgE-mediated mast cell activation such as IgE-mediated degranulation and the production of LTB4. Also, it inhibited production of inflammatory cytokines TNF-α and IL-4. In summary, tryptophan suppressed IgE-mediated allergic activation in vivo and in vitro. Tryptophan supplementation is beneficial for IgE-mediated allergy.

Dexamethasone Induces FcgRIIb Expression in RBL-2H3 Cells

Prashanta Silwal,Mi-Nam Lee,Choong-Jae Lee,Jang-Hee Hong,Uk Namgung,Zee-Won Lee,Jinhyun Kim,Kyu Lim,Gi Ryang Kweon,Jong IL Park,Seung Kiel Park 대한생리학회-대한약리학회 2012 The Korean Journal of Physiology & Pharmacology Vol.16 No.6

Mast cells are involved in allergic responses, protection against pathogens and autoimmune diseases. Dexamethasone (Dex) and other glucocorticoids suppress FcՅRI-mediated release of inflammatory mediators from mast cells. The inhibition mechanisms were mainly investigated on the downstream signaling of Fc receptor activations. Here, we addressed the effects of Dex on Fc receptor expressions in rat mast cell line RBL-2H3. We measured mRNA levels of Fc receptors by real-time PCR. As expected, Dex decreased the mRNA levels of activating Fc receptor for IgE (FcՅR) I and increased the mRNA levels of the inhibitory Fc receptor for IgG FcՃRIIb. Interestingly, Dex stimulated transcriptions of other activating receptors such as Fc receptors for IgG (FcՃR) I and FcՃRIII. To investigate the mechanisms underlying transcriptional regulation, we employed a transcription inhibitor actinomycin D and a translation inhibitor cycloheximide. The inhibition of protein synthesis without Dex treatment enhanced FcՃRI and FcՃRIII mRNA levels potently, while FcՅRI and FcՃRIIb were minimally affected. Next, we examined expressions of the Fc receptors on cell surfaces by the flow cytometric method. Only FcՃRIIb protein expression was significantly enhanced by Dex treatment, while FcՃRI, FcՃRIII and FcՅRI expression levels were marginally changed. Our data showed, for the first time, that Dex regulates Fc receptor expressions resulting in augmentation of the inhibitory receptor FcՃRIIb.

Adenine attenuates lipopolysaccharide

Prashanta Silwal,Kyu Lim,Jun-Young Heo,Jong IL Park,Uk Namgung,Seung-Kiel Park 대한생리학회-대한약리학회 2018 The Korean Journal of Physiology & Pharmacology Vol.22 No.4

A nucleobase adenine is a fundamental component of nucleic acids and adenine nucleotides. Various biological roles of adenine have been discovered. It is not produced from degradation of adenine nucleotides in mammals but produced mainly during polyamine synthesis by dividing cells. Anti-inflammatory roles of adenine have been supported in IgE-mediated allergic reactions, immunological functions of lymphocytes and dextran sodium sulfate-induced colitis. However adenine effects on Toll-like receptor 4(TLR4)-mediated inflammation by lipopolysaccharide(LPS), a cell wall component of Gram negative bacteria, is not examined. Here we investigated anti-inflammatory roles of adenine in LPS-stimulated immune cells, including a macrophage cell line RAW264.7 and bone marrow derived mast cells(BMMCs) and peritoneal cells in mice. In RAW264.7 cells stimulated with LPS, adenine inhibited production of pro-inflammatory cytokines TNF-α and IL-6 and inflammatory lipid mediators, prostaglandin E2 and leukotriene B4. Adenine impeded signaling pathways eliciting production of these inflammatory mediators. It suppressed IκB phosphorylation, nuclear translocation of nuclear factor κB (NF-κB), phosphorylation of Akt and mitogen activated protein kinases (MAPKs) JNK and ERK. Although adenine raised cellular AMP which could activate AMP-dependent protein kinase(AMPK), the enzyme activity was not enhanced. In BMMCs, adenine inhibited the LPS-induced production of TNF-α, IL-6 and IL-13 and also hindered phosphorylation of NF-κB and Akt. In peritoneal cavity, adenine suppressed the LPS-induced production of TNF-α and IL-6 by peritoneal cells in mice. These results show that adenine attenuates the LPS-induced inflammatory reactions.

Adenine Inhibits B16-F10 Melanoma Cell Proliferation

Prashanta Silwal,Seung-Kiel Park 대한의생명과학회 2020 Biomedical Science Letters Vol.26 No.3

Adenine, a purine base, is a structural component of essential biomolecules such as nucleic acids and adenine nucleotides. Its physiological roles have been uncovered. Adenine suppresses IgE-mediated allergy and LPS-induced inflammation. Although adenine is known to inhibit lymphocyte proliferation, the effect of adenine to melamoma cells is not reported. Here, we investigated the growth inhibitory effects of adenine on B16-F10 mouse melanoma cells. Adenine suppressed the proliferation of B16-F10 cells in dose-dependent manner with the maximal inhibitory dose of 2 mM. Adenine treatment induced cell death molecular markers such as PARP and caspase 3 cleavages. Pan-caspase inhibitor z-VAD dramatically rescued the cell death molecular markers, cell proliferation recovered marginally. These results provide the possibility of adenine to be used as an anti-tumor agent.

히스티딘의 IgE 매개 알레르기 반응 억제 효과

실왈 프라산타(Prashanta Silwal),최슬기(Seulgi Choi),신근아(Keuna Shin),이찬용(Chan Yong Lee),박종일(Jong Il Park),허준영(Jun-Young Heo),임규(Kyu Lim),박승길(Seung-Kiel Park) 한국식품영양과학회 2018 한국식품영양과학회지 Vol.47 No.7

비만세포는 알레르기를 유발하는 중요한 세포로서 항원의 자극을 받으면 알레르기 유발 물질을 분비한다. 히스티딘은 비만세포가 관여하는 만성 장염 증세를 완화하는 기능이 있다. 그러나 히스티딘이 비만세포의 활성화에 미치는 영향에 대한 연구는 없다. 우리는 알레르기 반응 연구의 동물모델인 IgE 매개 수동 피부 아나필락시스 방법 그리고 비만세포가 알레르기 유발 물질을 분비하는 반응(탈과립 반응, 염증성 지질 및 사이토카인 분비)을 통해 히스티딘이 알레르기에 미치는 영향을 연구하였다. 생쥐의 복강으로 히스티딘을 100 mg/kg으로 투여하면 수동 피부 아나필락시스를 통계적으로 의미 있는 수준으로 억제하였고, 비만세포에서도 탈과립 반응과 알레르기 유발 불질의 분비를 억제하였다. 이러한 결과는 히스티딘 섭취는 IgE 매개 알레르기를 억제하는 데 유익할 것으로 생각할 수 있다. Mast cells are major immune cells in allergies that secrete allergic mediators in response to antigen stimulation. The amino acid, histidine, ameliorates the inflammation that mast cells are involved. On the other hand, there are no reports of the effects of histidine on the activation of mast cells. This study examined the anti-allergic effects of histidine with well-established experimental methods in allergy studies, including IgE-mediated passive cutaneous anaphylaxis (PCA) in mice and mast cell activation responses, such as degranulation, secretion of inflammatory lipid LTB4 and cytokines (TNF-α and IL-4). The intraperitoneal administration of 100 mg/kg histidine suppressed PCA significantly (P<0.05) in mice. In addition, histidine inhibited IgE-mediated mast cell activation, including degranulation and the production of LTB4 and the inflammatory cytokines, TNF-α and IL-4. Overall, histidine suppressed the IgE-mediated allergic responses in vivo and in vitro. Histidine supplementation is expected to beneficial for IgE-mediated allergies.

Host-Pathogen Dialogues in Autophagy, Apoptosis, and Necrosis during Mycobacterial Infection

김진경,Prashanta Silwal,조은경 대한면역학회 2020 Immune Network Vol.20 No.5

Mycobacterium tuberculosis (Mtb) is an etiologic pathogen of human tuberculosis (TB), a serious infectious disease with high morbidity and mortality. In addition, the threat of drug resistance in anti-TB therapy is of global concern. Despite this, it remains urgent to research for understanding the molecular nature of dynamic interactions between host and pathogens during TB infection. While Mtb evasion from phagolysosomal acidification is a well-known virulence mechanism, the molecular events to promote intracellular parasitism remains elusive. To combat intracellular Mtb infection, several defensive processes, including autophagy and apoptosis, are activated. In addition, Mtb-ingested phagocytes trigger inflammation, and undergo necrotic cell death, potentially harmful responses in case of uncontrolled pathological condition. In this review, we focus on Mtb evasion from phagosomal acidification, and Mtb interaction with host autophagy, apoptosis, and necrosis. Elucidation of the molecular dialogue will shed light on Mtb pathogenesis, host defense, and development of new paradigms of therapeutics.