Search Results (7)

This study investigates the potential use of tire-derived carbon black “N-330” as a sustainable waste binder in asphalt concrete mixtures, combined with resin as an alternative to the usual binding material in asphalt mixtures, “bitumen”. With the increasing demand for environmentally friendly construction materials, this research aims to assess the feasibility of incorporating resin tire carbon black N-330 “RTCB N-330” into asphalt as a full replacement for conventional binders. A comprehensive experimental program has been designed to evaluate the mechanical and performance properties of asphalt mixtures containing varying proportions of RTCB N-330, ranging from 2% to 10% by weight of the binder. The impact of replacing bitumen with resin that contains TCB N-330 on the physical, rheological, and thermal characteristics of RTCB N-330 as a modified asphalt binder is assessed in this study. To assess the binders, a number of tests were carried out, including standard tests for ductility, the softening point, and penetration. DTG (Derivative Thermogravimetric Analysis) and testing the thermal susceptibility index were performed. A higher percentage of TCB N-330 reduced the penetration while increasing both the softening point and ductility. Resin with 8% of TCB N-330 was the optimum percentage, which was compared with bitumen as a new environmentally friendly binder. The testing program involved the preparation of asphalt concrete specimens using a Marshall mix design, followed by a Marshall Stability test to evaluate the deformation resistance of the modified mixtures. The results were anticipated to demonstrate that incorporating N-330 into asphalt mixtures can enhance stability. The Marshall test results indicated that samples with 6% resin tire carbon black as the binder percentage “AC-RTCB6” demonstrated the highest stability among all RTCB samples. Moreover, these samples outperformed asphalt mixtures using bitumen as the binder in terms of stability. Also, the AC-B mixes exhibited lower flow values compared to the AC-RTCB mixes. The higher flow observed in the AC-RTCB specimens suggests that the addition of 1.5% xylene as a solvent to the resin was effective and positively influenced the flow characteristics. Full article

The increasing emergence of multidrug-resistant Acinetobacter baumannii brings great threats to public health. Minocycline is a kind of semisynthetic derivative of the antibacterial drug tetracycline and is often used to treat infections caused by multidrug-resistant A. baumannii with other antibiotics. However, minocycline-resistant A. baumannii appears constantly. To rapidly explore the response of A. baumannii to minocycline stress, RNA-seq was carried out to compare the difference in the transcriptome of A. baumannii ATCC19606 in the presence or absence of minocycline. The results showed that 25 genes were differentially expressed, including 10 downregulated genes and 15 upregulated genes, and 24 sRNA were upregulated and 24 were downregulated based on the filter criteria (Log2FC > 1 or <−1 and FDR < 0.05). RtcB family protein and ABC transporter ATP-binding protein were upregulated by 2.6- and 11.3-fold, and molecular chaperone GroES, chaperonin GroL, class C beta-lactamase ADC-158, amino acid ABC transporter permease, and APC family permease were downregulated by at least two-fold in the presence of half-MIC minocycline. The differentially expressed genes are mainly involved in the stress response, the GroES/GroEL chaperonin system, and transport metabolic pathways. sRNA 1248 was significantly upregulated, and sRNA 1767, 5182, and 6984 were downregulated in a rapid response to minocycline. These results provide insights into the adaptive mechanism of A. baumannii to minocycline. Full article

Under stress conditions, transfer RNAs (tRNAs) are cleaved by stress-responsive RNases such as angiogenin, generating tRNA-derived RNAs called tiRNAs. As tiRNAs contribute to cytoprotection through inhibition of translation and prevention of apoptosis, the regulation of tiRNA production is critical for cellular stress response. Here, we show that RTCB ligase complex (RTCB-LC), an RNA ligase complex involved in endoplasmic reticulum (ER) stress response and precursor tRNA splicing, negatively regulates stress-induced tiRNA production. Knockdown of RTCB significantly increased stress-induced tiRNA production, suggesting that RTCB-LC negatively regulates tiRNA production. Gel-purified tiRNAs were repaired to full-length tRNAs by RtcB in vitro, suggesting that RTCB-LC can generate full length tRNAs from tiRNAs. As RTCB-LC is inhibited under oxidative stress, we further investigated whether tiRNA production is promoted through the inhibition of RTCB-LC under oxidative stress. Although hydrogen peroxide (H₂O₂) itself did not induce tiRNA production, it rapidly boosted tiRNA production under the condition where stress-responsive RNases are activated. We propose a model of stress-induced tiRNA production consisting of two factors, a trigger and booster. This RTCB-LC-mediated boosting mechanism may contribute to the effective stress response in the cell. Full article

In the bid to survive and thrive in an environmental setting, bacterial species constantly interact and compete for resources and space in the microbial ecosystem. Thus, they have adapted to use various antibiotics and toxins to fight their rivals. Simultaneously, they have evolved an ability to withstand weapons that are directed against them. Several bacteria harbor colicinogenic plasmids which encode toxins that impair the translational apparatus. One of them, colicin E3 ribotoxin, mediates cleavage of the 16S rRNA in the decoding center of the ribosome. In order to thrive upon deployment of such ribotoxins, competing bacteria may have evolved counter-conflict mechanisms to prevent their demise. A recent study demonstrated the role of PrfH and the RtcB2 module in rescuing a damaged ribosome and the subsequent re-ligation of the cleaved 16S rRNA by colicin E3 in vitro. The rtcB2-prfH genes coexist as gene neighbors in an operon that is sporadically spread among different bacteria. In the current study, we report that the RtcB2-PrfH module confers resistance to colicin E3 toxicity in E. coli ATCC25922 cells in vivo. We demonstrated that the viability of E. coli ATCC25922 strain that is devoid of rtcB2 and prfH genes is impaired upon action of colicin E3, in contrast to the parental strain which has intact rtcB2 and prfH genes. Complementation of the rtcB2 and prfH gene knockout with a high copy number-plasmid (encoding either rtcB2 alone or both rtcB2-prfH operon) restored resistance to colicin E3. These results highlight a counter-conflict system that may have evolved to thwart colicin E3 activity. Full article

The opportunistic pathogen Pseudomonas aeruginosa is a significant cause of infection in immunocompromised individuals, cystic fibrosis patients, and burn victims. To benefit its survival, the bacterium adapt to either a motile or sessile lifestyle when infecting the host. The motile bacterium has an often activated type III secretion system (T3SS), which is virulent to the host, whereas the sessile bacterium harbors an active T6SS and lives in biofilms. Regulatory pathways involving Gac-Rsm or secondary messengers such as c-di-GMP determine which lifestyle is favorable for P. aeruginosa. Here, we introduce the RNA binding protein RtcB as a modulator of the switch between motile and sessile bacterial lifestyles. Using the wild-type P. aeruginosa PAO1, and a retS mutant PAO1(∆retS) in which T3SS is repressed and T6SS active, we show that deleting rtcB led to simultaneous expression of T3SS and T6SS in both PAO1(∆rtcB) and PAO1(∆rtcB∆retS). The deletion of rtcB also increased biofilm formation in PAO1(∆rtcB) and restored the motility of PAO1(∆rtcB∆retS). RNA-sequencing data suggested RtcB as a global modulator affecting multiple virulence factors, including bacterial secretion systems. Competitive killing and infection assays showed that the three T6SS systems (H1, H2, and H3) in PAO1(∆rtcB) were activated into a functional syringe, and could compete with Escherichia coli and effectively infect lettuce. Western blotting and RT-PCR results showed that RtcB probably exerted its function through RsmA in PAO1(∆rtcB∆retS). Quantification of c-di-GMP showed an elevated intracellular levels in PAO1(∆rtcB), which likely drove the switch between T6SS and T3SS, and contributed to the altered phenotypes and characteristics observed. Our data demonstrate a pivotal role of RtcB in the virulence of P. aeruginosa by controlling multiple virulence determinants, such as biofilm formation, motility, pyocyanin production, T3SS, and T6SS secretion systems towards eukaryotic and prokaryotic cells. These findings suggest RtcB as a potential target for controlling P. aeruginosa colonization, establishment, and pathogenicity. Full article

The protein quality control network, including autophagy, the proteasome and the unfolded protein response (UPR), is triggered by stress and is overactive in acquired antiestrogen therapy resistance. We show for the first time that the aggresome load correlates with apoptosis and is increased in antiestrogen-sensitive cells compared to endocrine-resistant variants. LC-MS/MS analysis of the aggregated proteins obtained after 4OH-tamoxifen and Fulvestrant treatment identified proteins with essential function in protein quality control in antiestrogen-sensitive cells, but not in resistant variants. These include the UPR modulators RTCB and PDIA6, as well as many proteasome proteins such as PSMC2 and PSMD11. RTCB is a tRNA and XBP1 ligase and its aggregation induced by antiestrogens correlated with impaired XBP1s expression in sensitive cells. Knock down of RTCB was sufficient to restore sensitivity to tamoxifen in endocrine-resistant cells and increased the formation of aggresomes, leading to apoptotic cell death. Analysis of primary human breast cancer samples and their metastases appearing after endocrine treatment showed that RTCB is only localized to aggresomes in the primary tumors, while total aggresomes, including aggregated RTCB, were significantly reduced in the metastases. Therefore, different protein aggregation patterns may indicate loss of function of essential proteins resulting in enhanced protein aggregation that can be used to identify antiestrogen-resistant breast cancer cells and improve the response to antiestrogenic therapy. Full article

Genistein, a soy-derived phytoestrogen, has been shown to exhibit anti-neoplastic activities in various cancers. Nevertheless, its effects on the elimination of tumor-initiating cells of head and neck cancer (HNC-TICs) remain unclear. Here, we investigated the inhibitory effect of genistein on HNC-TICs and potential mechanisms. Our results demonstrated that genistein lowered the proliferation of HNC-TICs by examining the percentage of ALDH1+ or CD44+ cells. Aside from the downregulation of epithelial-mesenchymal transition (EMT) in HNC-TICs, genistein restricted their tumor propagating capacities in a dose-dependent fashion. Moreover, genistein potentiated cell death caused by three commonly used chemotherapeutic agents (doxorubicin, cisplatin, and 5-FU). Our findings proved that genistein induced ROS production through upregulation of miR-34a, leading to apoptosis in HNC-TICs. The genistein-elicited miR-34a reduced self-renewal, migration, invasion capacities and ALDH1 activity, which may be partly owing to the repression of EMT. Furthermore, we showed that RTCB was a novel target that was negatively regulated by miR-34a and involved in the tumor repressive effect of genistein. Besides, the in vivo study validated that genistein retarded tumor growth through the elevation of miR-34a and suppression of RTCB. These results suggested that genistein-induced miR-34a contributed to the ROS-associated apoptosis and diminished stemness properties via repression of RTCB in HNC-TICs. Full article