Akkermansia muciniphila-derived extracellular vesicles influence gut permeability through the regulation of tight junctions

Chaithanya Chelakkot,최영우,김대겸,Hyun T Park,김재왕,권용훈,정진성,김민선,지영구,Yong S Gho,박해심,김윤근,류성호 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-

The gut microbiota has an important role in the gut barrier, inflammation and metabolic functions. Studies have identified a close association between the intestinal barrier and metabolic diseases, including obesity and type 2 diabetes (T2D). Recently, Akkermansia muciniphila has been reported as a beneficial bacterium that reduces gut barrier disruption and insulin resistance. Here we evaluated the role of A. muciniphila-derived extracellular vesicles (AmEVs) in the regulation of gut permeability. We found that there are more AmEVs in the fecal samples of healthy controls compared with those of patients with T2D. In addition, AmEV administration enhanced tight junction function, reduced body weight gain and improved glucose tolerance in high-fat diet (HFD)-induced diabetic mice. To test the direct effect of AmEVs on human epithelial cells, cultured Caco-2 cells were treated with these vesicles. AmEVs decreased the gut permeability of lipopolysaccharide-treated Caco-2 cells, whereas Escherichia coli-derived EVs had no significant effect. Interestingly, the expression of occludin was increased by AmEV treatment. Overall, these results imply that AmEVs may act as a functional moiety for controlling gut permeability and that the regulation of intestinal barrier integrity can improve metabolic functions in HFD-fed mice.

Mechanisms regulating intestinal barrier integrity and its pathological implications

Chaithanya Chelakkot,김재왕,류성호 생화학분자생물학회 2018 Experimental and molecular medicine Vol.50 No.-

The gastrointestinal tract is a specialized organ in which dynamic interactions between host cells and the complex environment occur in addition to food digestion. Together with the chemical barrier of the mucosal layer and the cellular immune system, the epithelial cell layer performs a pivotal role as the first physical barrier against external factors and maintains a symbiotic relationship with commensal bacteria. The tight junction proteins, including occludin, claudins, and zonula occludens, are crucial for the maintenance of epithelial barrier integrity. To allow the transport of essential molecules and restrict harmful substances, the intracellular signaling transduction system and a number of extracellular stimuli such as cytokines, small GTPases, and post-translational modifications dynamically modulate the tight junction protein complexes. An imbalance in these regulations leads to compromised barrier integrity and is linked with pathological conditions. Despite the obscurity of the causal relationship, the loss of barrier integrity is considered to contribute to inflammatory bowel disease, obesity, and metabolic disorders. The elucidation of the role of diseases in barrier integrity and the underlying regulatory mechanisms have improved our understanding of the intestinal barrier to allow the development of novel and potent therapeutic approaches.

Selection Strategies and Practical Application of BRAF V600E-Mutated Non–Small Cell Lung Carcinoma

황인우,최윤라,이현우,황수현,이보람,양호빈,Chaithanya Chelakkot,한정호 대한암학회 2022 Cancer Research and Treatment Vol.54 No.3

PurposeThe incidence of <i>BRAF</i> V600E mutation in non-small cell lung carcinoma (NSCLC) is lower than 2%, which poses difficulties in finding legitimate patients for targeted therapy. We investigated the predictive factors pertaining to <i>BRAF</i> V600E and the effectiveness of the VE1 antibody as a screening method for patient selection.Materials and MethodsThe study was designed into two steps. In a first group, <i>BRAF</i>-mutated NSCLCs were identified from sequencing data to determine the features of <i>BRAF</i> V600E mutation. The results of the first group helped the collection of adenocarcinomas with a papillary or micropapillary pattern but without <i>EGFR</i> or <i>ALK</i> alterations as a second group so that the frequency of <i>BRAF</i> V600E mutation could be calculated. The sensitivity and specificity of the VE1 were compared with <i>BRAF</i> V600E status. ResultsAmong 39 <i>BRAF</i>-mutated NSCLCs in the first group, 20 (51%) were V600E. <i>BRAF</i> V600E mutation was more common in female patients and showed no significant correlation with smoking status. Nineteen cases were adenocarcinomas without <i>EGFR</i> and <i>ALK</i> alterations. The most common patterns of invasion were papillary and micropapillary along with central fibrosis. The sensitivity and specificity of the VE1 were 90.0% and 92.3%, respectively. In the second group, 6.7% of cases were VE1-positive, indicating that the prevalence was significantly higher than that reported in previous studies (0.3-1.8%). Conclusion<i>BRAF</i> V600E-mutated NSCLCs could be enriched with the application of clinicopathologic parameters, which are not perfect. Therefore, additional VE1 immunohistochemistry may be useful as a screening method.

SMAD4 Controls Cancer Cell Metabolism by Regulating Methylmalonic Aciduria Cobalamin Deficiency (cbl) B Type

Kyoung Song,이헌석,Lina Jia,Chaithanya Chelakkot,Nirmal Rajasekaran,Young Kee Shin 한국분자세포생물학회 2022 Molecules and cells Vol.45 No.6

Suppressor of mothers against decapentaplegic homolog (SMAD) 4 is a pluripotent signaling mediator that regulates myriad cellular functions, including cell growth, cell division, angiogenesis, apoptosis, cell invasion, and metastasis, through transforming growth factor β (TGF-β)-dependent and -independent pathways. SMAD4 is a critical modulator in signal transduction and functions primarily as a transcription factor or cofactor. Apart from being a DNA-binding factor, the additional SMAD4 mechanisms in tumor suppression remain elusive. We previously identified methyl malonyl aciduria cobalamin deficiency B type (MMAB) as a critical SMAD4 binding protein using a proto array analysis. This study confirmed the interaction between SMAD4 and MMAB using bimolecular fluorescence complementation (BiFC) assay, proximity ligation assay (PLA), and conventional immunoprecipitation. We found that transient SMAD4 overexpression down-regulates MMAB expression via a proteasome-dependent pathway. SMAD4-MMAB interaction was independent of TGF-β signaling. Finally, we determined the effect of MMAB downregulation on cancer cells. siRNA-mediated knockdown of MMAB affected cancer cell metabolism in HeLa cells by decreasing ATP production and glucose consumption as well as inducing apoptosis. These findings suggest that SMAD4 controls cancer cell metabolism by regulating MMAB.

Amelioration of Atherosclerosis by the New Medicinal Mushroom Grifola gargal Singer

Etsuko Harada,Corina N. D’Alessandro-Gabazza,Masaaki Toda,Toshihiro Morizono,Ayshwarya-Lakshmi Chelakkot-Govindalayathil,Ziaurahman Roeen,Masahito Urawa,Taro Yasuma,Yutaka Yano,Toshimitsu Sumiya,Esteb 한국식품영양과학회 2015 Journal of medicinal food Vol.18 No.8

The beneficial effects of edible mushrooms for improving chronic intractable diseases have been documented. However, the antiatherogenic activity of the new medicinal mushroom Grifola gargal is unknown. Therefore, we evaluated whether Grifola gargal can prevent or delay the progression of atherosclerosis. Atherosclerosis was induced in ApoE lipoprotein-deficient mice by subcutaneous infusion of angiotensin II. Grifola gargal extract (GGE) was prepared and intraperitoneally injected. The weight of heart and vessels, dilatation/atheroma formation of thoracic and abdominal aorta, the percentage of peripheral granulocytes, and the blood concentration of MCP-1/CCL2 were significantly reduced in mice treated with GGE compared to untreated mice. By contrast, the percentage of regulatory T cells and the plasma concentration of SDF-1/CXCL12 were significantly increased in mice treated with the mushroom extract compared to untreated mice. In vitro, GGE significantly increased the secretion of SDF-1/CXCL12, VEGF, and TGF-β1 from fibroblasts compared to control. This study demonstrated for the first time that Grifola gargal therapy can enhance regulatory T cells and ameliorate atherosclerosis in mice.

Endothelial Deletion of Phospholipase D2 Reduces Hypoxic Response and Pathological Angiogenesis

Ghim, Jaewang,Moon, Jin-Sook,Lee, Chang Sup,Lee, Junyeop,Song, Parkyong,Lee, Areum,Jang, Jin-Hyeok,Kim, Dayea,Yoon, Jong Hyuk,Koh, Young Jun,Chelakkot, Chaithanya,Kang, Byung Jun,Kim, Jung-Min,Kim, Ky American Heart Association, Inc. 2014 Arteriosclerosis, thrombosis, and vascular biology Vol.34 No.8

<P><B>Objective—</B></P><P>Aberrant regulation of the proliferation, survival, and migration of endothelial cells (ECs) is closely related to the abnormal angiogenesis that occurs in hypoxia-induced pathological situations, such as cancer and vascular retinopathy. Hypoxic conditions and the subsequent upregulation of hypoxia-inducible factor-1α and target genes are important for the angiogenic functions of ECs. Phospholipase D2 (PLD2) is a crucial signaling mediator that stimulates the production of the second messenger phosphatidic acid. PLD2 is involved in various cellular functions; however, its specific roles in ECs under hypoxia and in vivo angiogenesis remain unclear. In the present study, we investigated the potential roles of PLD2 in ECs under hypoxia and in hypoxia-induced pathological angiogenesis in vivo.</P><P><B>Approach and Results—</B></P><P><I>Pld2</I> knockout ECs exhibited decreased hypoxia-induced cellular responses in survival, migration, and thus vessel sprouting. Analysis of hypoxia-induced gene expression revealed that PLD2 deficiency disrupted the upregulation of hypoxia-inducible factor-1α target genes, including <I>VEGF</I>, <I>PFKFB3</I>, <I>HMOX-1</I>, and <I>NTRK2</I>. Consistent with this, PLD2 contributed to hypoxia-induced hypoxia-inducible factor-1α expression at the translational level. The roles of PLD2 in hypoxia-induced in vivo pathological angiogenesis were assessed using oxygen-induced retinopathy and tumor implantation models in endothelial-specific <I>Pld2</I> knockout mice. <I>Pld2</I> endothelial-specific knockout retinae showed decreased neovascular tuft formation, despite a larger avascular region. Tumor growth and tumor blood vessel formation were also reduced in <I>Pld2</I> endothelial-specific knockout mice.</P><P><B>Conclusions—</B></P><P>Our findings demonstrate a novel role for endothelial PLD2 in the survival and migration of ECs under hypoxia via the expression of hypoxia-inducible factor-1α and in pathological retinal angiogenesis and tumor angiogenesis in vivo.</P>