1,720,985 research outputs found
Effects of host and pathogenicity on mutation rates in avian influenza A viruses
No full textMutation is the primary determinant of genetic diversity in influenza viruses. The rate of mutation, measured in an absolute time-scale, is likely to be dependent on the rate of errors in copying RNA sequences per replication and the number of replications per unit time. Conditions for viral replication are probably different among host taxa, potentially generating the host specificity of the viral mutation rate, and possibly between highly and low pathogenic (HP and LP) viruses. This study investigated whether mutation rates per year in avian influenza A viruses depend on host taxa and pathogenicity. We inferred mutation rates from the rates of synonymous substitutions, which are assumed to be neutral and thus equal to mutation rates, at four segments that code internal viral proteins (PB2, PB1, PA, NP). On the phylogeny of all avian viral sequences for each segment, multiple distinct subtrees (clades) were identified that represent viral subpopulations, which are likely to have evolved within particular host taxa. Using simple regression analysis, we found that mutation rates were significantly higher in viruses infecting chickens than domestic ducks and in those infecting wild shorebirds than wild ducks. Host dependency of the substitution rate was also confirmed by Bayesian phylogenetic analysis. However, we did not find evidence that the mutation rate is higher in HP than in LP viruses. We discuss these results considering viral replication rate as the major determinant of mutation rate per unit time.Y
Pyrimidine nucleotide starvation induces a decrease in the number of effector T cells but not memory T cells
No full textY
Why are children less affected than adults by severe acute respiratory syndrome coronavirus 2 infection?
No full textY
Novel cancer stem cell marker MVP enhances temozolomide-resistance in glioblastoma
No full textThe resistance of highly aggressive glioblastoma multiforme (GBM) to chemotherapy is a major clinical problem resulting in a poor prognosis. GBM contains a rare population of self-renewing cancer stem cells (CSCs) that proliferate, spurring the growth of new tumors, and evade chemotherapy. In cancer, major vault protein (MVP) is thought to contribute to drug resistance. However, the role of MVP as CSCs marker remains unknown and whether MVP could sensitize GBM cells to Temozolomide (TMZ) also is unclear. We found that sensitivity to TMZ was suppressed by significantly increasing the MVP expression in GBM cells with TMZ resistance. Also, MVP was associated with the expression of other multidrug-resistant proteins in tumorsphere of TMZ-resistant GBM cell, and was highly co-expressed with CSC markers in tumorsphere culture. On the other hands, knockdown of MVP resulted in reduced sphere formation and invasive capacity. Moreover, high expression of MVP was associated with tumor malignancy and survival rate in glioblastoma patients. Our study describes that MVP is a potentially novel maker for glioblastoma stem cells and may be useful as a target for preventing TMZ resistance in GBM patients.Y
Hyperglycemia-induced oxidative stress promotes tumor metastasis by upregulating vWF expression in endothelial cells through the transcription factor GATA1
No full textDiabetes mellitus (DM) characterized by hyperglycemia is a chronic metabolic disorder that leads to many symptoms and vascular complications. Despite the close association between DM and cancer progression, the response and role of endothelial cells (ECs) under diabetic conditions in tumor metastasis remain to be elucidated. In this study, we sought to determine whether and how ECs under diabetic conditions contribute to tumor metastasis. We have taken advantage of syngeneic mouse tumor models of Lewis lung carcinoma (LLC) and melanoma (B16F10) cells and a streptozotocin (STZ)-induced hyperglycemia model. We demonstrated that hyperglycemia increased the metastasis of LLC and B16F10 cells in an experimental metastasis model with an intravenous injection of the tumor cells. We also found that hyperglycemia promoted lung metastasis of tumor cells by increasing the adhesiveness of ECs to facilitate the adhesion of tumor cells to ECs rather than affecting the metastatic behavior of tumor cells themselves. From the analysis of gene expression in primary lung ECs from STZ-treated mice, we identified that vWF promoted the adhesion of tumor cells to ECs and the transendothelial migration of tumor cells. Mechanistically, hyperglycemia-induced oxidative stress in ECs, and increased oxidative stress enhanced vWF expression in ECs through an increase in the transcription factor GATA1. These results provide evidence for the role of vWF in ECs in promoting hyperglycemia-induced tumor metastasis and potential therapeutic targets for the regulation of vWF expression in ECs and hyperglycemia-induced tumor metastasis.N
Impaired BCAA catabolism in adipose tissues promotes age-associated metabolic derangement
No full textAdipose tissues are central in controlling metabolic homeostasis and failure in their preservation is associated with age-related metabolic disorders. The exact role of mature adipocytes in this phenomenon remains elusive. Here we describe the role of adipose branched-chain amino acid (BCAA) catabolism in this process. We found that adipocyte-specific Crtc2 knockout protected mice from age-associated metabolic decline. Multiomics analysis revealed that BCAA catabolism was impaired in aged visceral adipose tissues, leading to the activation of mechanistic target of rapamycin complex (mTORC1) signaling and the resultant cellular senescence, which was restored by Crtc2 knockout in adipocytes. Using single-cell RNA sequencing analysis, we found that age-associated decline in adipogenic potential of visceral adipose tissues was reinstated by Crtc2 knockout, via the reduction of BCAA–mTORC1 senescence-associated secretory phenotype axis. Collectively, we propose that perturbation of BCAA catabolism by CRTC2 is critical in instigating age-associated remodeling of adipose tissue and the resultant metabolic decline in vivo. © 2023, The Author(s), under exclusive licence to Springer Nature America, Inc.FALSEsciescopu
IL-7R alpha(low) CD8(+) T Cells from Healthy Individuals Are Anergic with Defective Glycolysis
No full textEffector memory (EM) CD8(+) T cells expressing lower levels of IL-7R alpha (IL-7R alpha(low)) from healthy individuals are partly compromised in vitro, but the identity of these cells has remained unclear. In this study, we demonstrate that human IL-7R alpha(lo)(w) EM CD8(+) T cells are naturally occurring anergic cells in vivo and impaired in proliferation and IL-2 production but competent in IFN-gamma and TNF-alpha production, a state that can be restored by IL-2 stimulation. IL-7R alpha(lo)(w) EM CD8(+) T cells show decreased expression of GATA3 and c-MYC and are defective in metabolic reprogramming toward glycolysis, a process required for the proliferation of T cells. However, IL-7R alpha(lo)(w) EM CD8(+) T cells can proliferate with TCR stimulation in the presence of IL-2 and IL-15, suggesting that these cells can be restored to normality or increased activity by inflammatory conditions and may serve as a reservoir for functional immunity.Y
Different degree of cytokinemia and T-cell activation according to serum IL-6 levels in critical COVID-19
No full textIntroductionTocilizumab, a humanized anti-interleukin-6 receptor (IL-6R) antibody, is recommended for the treatment of severe to critical coronavirus diseases 2019 (COVID-19). However, there were conflicting results on the efficacy of tocilizumab. Therefore, we hypothesized that the differences in tocilizumab efficacy may stem from the different immune responses of critical COVID-19 patients. In this study, we described two groups of immunologically distinct COVID-19 patients, based on their IL-6 response. MethodsWe prospectively enrolled critical COVID-19 patients, requiring oxygen support with a high flow nasal cannula or a mechanical ventilator, and analyzed their serial samples. An enzyme-linked immunosorbent assay and flow cytometry were used to evaluate the cytokine kinetics and cellular immune responses, respectively. ResultsA total of nine patients with critical COVID-19 were included. The high (n = 5) and low IL-6 (n = 4) groups were distinguished by their peak serum IL-6 levels, using 400 pg/mL as the cut-off value. Although the difference of flow cytometric data did not reach the level of statistical significance, the levels of pro-inflammatory cytokines and the frequencies of intermediate monocytes (CD14(+)CD16(+)), IFN-gamma(+) CD4(+) or CD8(+) T cells, and HLA-DR+PD-1(+) CD4(+) T cells were higher in the high IL-6 group than in the low IL-6 group. ConclusionThere were distinctive two groups of critical COVID-19 according to serum IL-6 levels having different degrees of cytokinemia and T-cell responses. Our results indicate that the use of immune modulators should be more tailored in patients with critical COVID-19.Y
Aberrant hyperactivation of cytotoxic T-cell as a potential determinant of COVID-19 severity
Get PDFObjectives: We hypothesized that immune response may contribute to progression of coronavirus disease-19 (COVID-19) at the second week of illness. Therefore, we compared cell-mediated immune (CMI) responses between severe and mild COVID-19 cases. Methods: We examined peripheral blood mononuclear cells of laboratory-confirmed COVID-19 patients from their first and third weeks of illness. Severe pneumonia was defined as an oxygen saturation <= 93% at room air. Expressions of molecules related to T-cell activation and functions were analyzed by flow cytometry. Results: The population dynamics of T cells at the first week were not different between the two groups. However, total numbers of CD4(+) and CD8(+) T cells tended to be lower in the severe group at the third week of illness. Expressions of Ki-67, PD-1, perforin, and granzyme B in CD4(+) or CD8(+) T cells were significantly higher in the severe group than in the mild group at the third week. In contrast to the mild group, the levels of their expression did not decrease in the severe group. Conclusions: Severe COVID-19 had a higher degree of proliferation, activation, and cytotoxicity of T-cells at the late phase of illness without cytotoxic T-cell contraction, which might contribute to the development of severe COVID-19. (c) 2020 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Y
- …
