Search Results (41)

This study evaluated the effects of mechanical agitation of Aloe vera Barbadensis Miller solution at different concentrations using passive ultrasonic irrigation (PUI), XP Endo Finisher (XPF), XP Clean (XPC), and Easy Clean (ECL), compared to conventional endodontic irrigation (CIE), on bond strength and adhesive failure patterns in the cervical, middle, and apical thirds of the root canal. Aloe vera solutions at 1%, 3%, and 5% were tested to reverse collagen fiber collapse induced by hypochlorous acid, a free radical released by 2.5% sodium hypochlorite, which impairs dentin hybridization and the light curing of resin cement. Fiberglass posts were cemented using an etch-and-rinse adhesive system (Ambar; FGM) and conventional dual resin cement (Allcem Core) in root dentin across all thirds. Human teeth underwent chemical–mechanical preparation, and the Aloe vera solution was agitated using the CIE, PUI, XPF, XPC, or ECL protocols. Slices from each root third were evaluated under a stereomicroscope at 10× magnification and subjected to the push-out test. Cytotoxicity was assessed by applying various Aloe vera concentrations to stem cells from the apical papilla (SCAPs) for 24 h, followed by analysis of cell metabolism (Alamar Blue), viability (Live/Dead), and proliferation (F-actin). Aloe vera demonstrated significant biological activity and enhanced bond strength, particularly at 3% and 5%, irrespective of the agitation method or root third. Thus, it can be concluded that using Aloe vera solution is an alternative for pre-treatment before the cementation of fiberglass posts with conventional dual-cure resin cement in endodontically treated dentin. Full article

Biogas plants for sewage and organic waste treatment are rapidly expanding. While these facilities provide valuable benefits, such as renewable energy production and the promotion of circular economy practices, they also emit airborne particles of biological origin, which may pose potential health risks. This study aims to evaluate, by in vitro assay, the cytotoxic and genotoxic potential of PM₁₀ sub-fractions (0.49–10 µm and <0.49 µm) generated in eight different plants, also assessing the endotoxin component using the Limulus Amebocyte Lysate (LAL) assay. Human embryonic lung fibroblasts (HELF) were exposed to organic extracts of particulate matter (PM). Cytotoxic effects (XTT assay) were analyzed, along with the modulation of gene expression involved in DNA repair (ERCC1, XRCC1, XPA, and XPF) and IL-8 production as a marker of inflammatory response. PM₁₀ and endotoxin concentrations varied significantly among the plants (ANOVA, p < 0.01), with PM₁₀ levels ranging from 14 to 18,000 µg/m³ and endotoxin content from 1 to 138 EU/m³. Exposure significantly increased ERCC1 and IL-8 expression by 25% and 53%, respectively (paired t-test, p < 0.01). IL-8 expression correlated with endotoxin exposure (Spearman’s rho = 0.35; p < 0.01). A deeper understanding of the biological component of airborne PM₁₀ can enhance risk assessments for occupational and nearby resident communities’ safety. Full article

Background/Objectives: Since biomineralization by calcium silicate-based sealers (CSBSs) was reported, retrieving canal filling materials may be challenging during endodontic retreatment due to their adhesion to dentin. This study aimed to evaluate the possibility of removing residual mineral deposits from two kinds of CSBSs compared to the AH Plus Jet (AHJ). Methods: Root canals of mandibular premolars were prepared, obturated with the sealer-based obturation method using a WOG medium gutta-percha cone and one of the following sealers: AHJ, AH Plus Bioceramic (AHB), and Ceraseal (CER) (n = 12/group). After 3 weeks, endodontic retreatment was conducted with the WOG files, followed by instrumentation with XP-endo Finisher (XPF). Micro-computed tomography scanning was obtained after canal filling, after retreatment with WOG, and after the use of XPF. The percentage of the removed filling volume was calculated. One-way ANOVA with Tukey’s test and a non-parametric test with Bonferroni’s correction were performed. Root canal dentin after retreatment was examined using a scanning electron microscope (SEM). Results: After supplementary instrumentation with XPF, the mean residual filling volumes for the AHJ, AHB, and CER groups were 1.35 mm³, 0.55 mm³, and 0.82 mm³, respectively. The AHJ group showed greater residual volume compared to the AHB group (p < 0.05). The AHB and CER groups demonstrated higher mean percentages of removed filling volume at 94.8%, and 92.5%, respectively, compared to 87.1% for the AHJ group (p < 0.05). More mineral deposits were observed in the CER group with SEM. Conclusions: AHB and CER are retrievable during endodontic retreatment, with CER preferable due to greater mineral deposits in dentinal tubules. Full article

DNA repair involves various intricate pathways that work together to maintain genome integrity. XPF (ERCC4) is a structural endonuclease that forms a heterodimer with ERCC1 that is critical in both single-strand break repair (SSBR) and double-strand break repair (DSBR). Although the mechanistic function of ERCC1/XPF has been established in nucleotide excision repair (NER), its role in long-patch base excision repair (BER) has recently been discovered through the 5′-Gap pathway. This study briefly explores the roles of XPF in different pathways to emphasize the importance of XPF in DNA repair. XPF deficiency manifests in various diseases, including cancer, neurodegeneration, and aging-related disorders; it is also associated with conditions such as Xeroderma pigmentosum and fertility issues. By examining the molecular mechanisms and pathological consequences linked to XPF dysfunction, this study aims to elucidate the crucial role of XPF in genomic stability as a repair protein in BER and provide perspectives regarding its potential as a therapeutic target in related diseases. Full article

Eradication of microorganisms present in the root canal system during endodontic therapy is one of the critical factors affecting the final outcome of endodontic treatment. However, even adequate technique of the root canal treatment and use of irrigants according to the established protocol does not lead to the complete elimination of microorganisms during endodontic treatment. The presence of Enterococcus (E.) faecalis inside the root canal system may be an important factor contributing to the failure of the treatment. Introducing agitation techniques in irrigation, such as passive ultrasonic irrigation (PUI) and the use of the activating instrument XP-endo Finisher (XPF), contribute to a better debridement and disinfection of the root canal. This study was conducted on 42 root canals experimentally inoculated with E. faecalis and exposed to three irrigation protocols. These have included a standard irrigation protocol using a syringe and needle, passive ultrasonic irrigation, and activation of the irrigant using an XPF instrument. The reduction in microorganisms was evaluated using the quantitative polymerase chain reaction in real-time (RT-PCR) as well as via the method of determining the number of colony forming units on nutrient medium (CFUs). The results of this study showed that the use of supplementary irrigation protocols, PUI, and XPF led to a significant decrease in the number of microorganisms inside the root canal of experimental teeth. These findings indicate a significant positive impact of these procedures on the disinfection of the root canal system. Full article

Standard first-line chemotherapy in small cell lung cancer (SCLC) is based on the platinum plus etoposide combination. Despite a high objective response rate, responses are not durable and chemotherapy-induced toxicity may compromise treatment. Genetic variants in genes involved in the DNA-repair pathways and in etoposide metabolization could predict treatment efficacy and safety and help personalize platinum-based chemotherapy. Germline polymorphisms in XRCC1, ERCC1, ERCC2, ABCB1, ABCC3, UGT1A1 and GSTP1 genes were investigated in 145 patients with SCLC. The tumor expression of ERCC1 was determined using immunohistochemistry, and the tumor expression of ERCC1-XPF was determined via a proximity ligation assay. Survival analyses showed a statistically significant association between the ERCC1 rs11615 variant and median progression-free survival (PFS) in patients with limited-stage (LS) SCLC (multivariate: hazard ratio 3.25, [95% CI 1.38–7.70]; p = 0.007). Furthermore, we observed differences between the ERCC1-XPF complex and median PFS in LS-SCLC, although statistical significance was not reached (univariate: positive expression 10.8 [95% CI 4.09–17.55] months versus negative expression 13.3 [95% CI 7.32–19.31] months; p = 0.06). Safety analyses showed that the ERCC2 rs1799793 variant was significantly associated with the risk of grade ≥ 3 thrombocytopenia in the total cohort (multivariate: odds ratio 3.15, [95% CI 1.08–9.17]; p = 0.04). Our results provide evidence that ERCC1 and ERCC2 variants may predict the efficacy and safety of platinum-based chemotherapy in SCLC patients. LS-SCLC patients may benefit most from ERCC1 determination, but prospective studies are needed. Full article

Nucleotide excision repair (NER) is the most universal repair pathway, which removes a wide range of DNA helix-distorting lesions caused by chemical or physical agents. The final steps of this repair process are gap-filling repair synthesis and subsequent ligation. XPA is the central NER scaffolding protein factor and can be involved in post-incision NER stages. Replication machinery is loaded after the first incision of the damaged strand that is performed by the XPF–ERCC1 nuclease forming a damaged 5′-flap processed by the XPG endonuclease. Flap endonuclease I (FEN1) is a critical component of replication machinery and is absolutely indispensable for the maturation of newly synthesized strands. FEN1 also contributes to the long-patch pathway of base excision repair. Here, we use a set of DNA substrates containing a fluorescently labeled 5′-flap and different size gap to analyze possible repair factor–replication factor interactions. Ternary XPA–FEN1–DNA complexes with each tested DNA are detected. Furthermore, we demonstrate XPA–FEN1 complex formation in the absence of DNA due to protein–protein interaction. Functional assays reveal that XPA moderately inhibits FEN1 catalytic activity. Using fluorescently labeled XPA, formation of ternary RPA–XPA–FEN1 complex, where XPA accommodates FEN1 and RPA contacts simultaneously, can be proposed. We discuss possible functional roles of the XPA–FEN1 interaction in NER related DNA resynthesis and/or other DNA metabolic processes where XPA can be involved in the complex with FEN1. Full article

Repetitive DNA sequences are abundant in the human genome and can adopt alternative (i.e., non-B) DNA structures. These sequences contribute to diverse biological functions, including genomic instability. Previously, we found that Z-DNA-, H-DNA- and cruciform DNA-forming sequences are mutagenic, implicating them in cancer etiology. These sequences can stimulate the formation of DNA double-strand breaks (DSBs), causing deletions via cleavage by the endonuclease ERCC1-XPF. Interestingly, the activity of ERCC1-XPF in H-DNA-induced mutagenesis is nucleotide excision repair (NER)-dependent, but its role in Z-DNA-induced mutagenesis is NER-independent. Instead, Z-DNA is processed by ERCC1-XPF in a mechanism dependent on the mismatch repair (MMR) complex, MSH2-MSH3. These observations indicate distinct mechanisms of non-B-induced genomic instability. However, the roles of NER and MMR proteins, as well as additional nucleases (CtIP and MRE11), in the processing of cruciform DNA remain unknown. Here, we present data on the processing of cruciform-forming short inverted repeats (IRs) by DNA repair proteins using mammalian cell-based systems. From this pilot study, we show that, in contrast to H-DNA and Z-DNA, short IRs are processed in a NER- and MMR-independent manner, and the nucleases CtIP and MRE11 suppress short IR-induced genomic instability in mammalian cells. Full article

Background and Objectives: Several polymorphisms have been described in various DNA repair genes. Nucleotide excision DNA repair (NER) detects defects of DNA molecules and corrects them to restore genome integrity. We hypothesized that the XPC, XPD, XPF, and XPG gene polymorphisms influence the appearance of myeloproliferative neoplasms (MPNs). Materials and Methods: We investigated the XPC 1496C>T (rs2228000, XPC Ala499Val), XPC 2920A>C (rs228001, XPC Lys939Gln), XPD 2251A>C (rs13181, XPD Lys751Gln), XPF-673C>T (rs3136038), XPF 11985A>G (rs254942), and XPG 3507G>C (rs17655, XPG Asp1104His) polymorphisms by polymerase chain reaction–restriction fragment length polymorphism analysis in 393 MPN patients [153 with polycythemia vera (PV), 201 with essential thrombocythemia (ET), and 39 with primary myelofibrosis (PMF)] and 323 healthy controls. Results: Overall, we found that variant genotypes of XPD 2251A>C were associated with an increased risk of MPN (OR = 1.54, 95% CI = 1.15–2.08, p = 0.004), while XPF-673C>T and XPF 11985A>G were associated with a decreased risk of developing MPN (OR = 0.56, 95% CI = 0.42–0.76, p < 0.001; and OR = 0.26, 95% CI = 0.19–0.37, p < 0.001, respectively). Conclusions: In light of our findings, XPD 2251A>C polymorphism was associated with the risk of developing MPN and XPF-673C>T and XPF 11985A>G single nucleotide polymorphisms (SNPs) may have a protective role for MPN, while XPC 1496C>T, XPC 2920A>C, and XPG 3507G>C polymorphisms do not represent risk factors in MPN development. Full article

Background and Objectives: Nucleotide Excision Repair (NER), the most extensively researched DNA repair mechanism, is responsible for repairing a variety of DNA damages, and Xeroderma Pigmentosum (XP) genes participate in NER. Herein, we aimed to update the previous results with a meta-analysis evaluating the association of XPA, XPB/ERCC3, XPF/ERCC4, and XPG/ERCC5 polymorphisms with the susceptibility to HNC. Materials and Methods: PubMed/Medline, Web of Science, Scopus, and Cochrane Library databases were searched without any restrictions until 18 November 2023 to find relevant studies. The Review Manager 5.3 (RevMan 5.3) software was utilized to compute the effect sizes, which were expressed as the odds ratio (OR) with a 95% confidence interval (CI). Results: Nineteen articles were involved in the systematic review and meta-analysis that included thirty-nine studies involving ten polymorphisms. The results reported that the CC genotype of rs17655 polymorphism showed a significantly decreased risk of HNC in the recessive model (OR: 0.89; 95%CI: 0.81, 0.99; p-value is 0.03). In addition, the CT genotype (OR: 0.65; 95%CI: 0.48, 0.89; p-value is 0.008) of the rs751402 polymorphism was associated with a decreased risk, and the T allele (OR: 1.28; 95%CI: 1.05, 1.57; p-value is 0.02), the TT (OR: 1.74; 95%CI: 1.10, 2.74; p-value is 0.02), and the TT + CT (OR: 2.22; 95%CI: 1.04, 4.74; p-value is 0.04) genotypes were associated with an increased risk of HNC. Conclusions: The analysis identified two polymorphisms, rs17655 and rs751402, as being significantly associated with the risk of HNC. The study underscored the influence of various factors, such as the type of cancer, ethnicity, source of control, and sample size on these associations. Full article

The use of the orthogonal array L₄ allows a determination of the effect between the welding parameters peak current (I_p), background current (I_b) and frequency (f) on the porosities in a dissimilar welded lap joint of CP800 and XPF1000 steel weldment by the gas metal arc welding process with the transfer pulsed mode. According to the results, modifications in the welding parameters affect the heat input during welding. A heat input higher than 0.30 KJ/mm generates up to 0.32% porosity in the weld metal, while a heat input lower than 0.25 KJ/mm generates up to 28% porosity in the weld metal. The variation in heat input generated by the process allowed the observation of the final microstructure of the welded joints and the effect of mechanical properties such as hardness because the results show values of hardness from 300 Hv to 400 Hv in the heat affected zone (HAZ). Full article

Nucleotide excision repair (NER) is a multistep biochemical process that maintains the integrity of the genome. Unlike other mechanisms that maintain genomic integrity, NER is distinguished by two irreversible nucleolytic events that are executed by the xeroderma pigmentosum group G (XPG) and xeroderma pigmentosum group F (XPF) structure-specific endonucleases. Beyond nucleolysis, XPG and XPF regulate the overall efficiency of NER through various protein–protein interactions. The current experiments evaluated whether an environmental stressor could negatively affect the expression of Xpg (Ercc5: excision repair cross-complementing 5) or Xpf (Ercc4: excision repair cross-complementing 4) in the mammalian cochlea. Ubiquitous background noise was used as an environmental stressor. Gene expression levels for Xpg and Xpf were quantified from the cochlear neurosensory epithelium after noise exposure. Further, nonlinear cochlear signal processing was investigated as a functional consequence of changes in endonuclease expression levels. Exposure to stressful background noise abrogated the expression of both Xpg and Xpf, and these effects were associated with pathological nonlinear signal processing from receptor cells within the mammalian inner ear. Given that exposure to environmental sounds (noise, music, etc.) is ubiquitous in daily life, sound-induced limitations to structure-specific endonucleases might represent an overlooked genomic threat. Full article

Modifications in DNA repair pathways are recognized as prognostic markers and potential therapeutic targets in various cancers, including non-small cell lung cancer (NSCLC). Overexpression of ERCC1 correlates with poorer prognosis and response to platinum-based chemotherapy. As a result, there is a pressing need to discover new inhibitors of the ERCC1–XPF complex that can potentiate the efficacy of cisplatin in NSCLC. In this study, we developed a structure-based virtual screening strategy targeting the inhibition of ERCC1 and XPF interaction. Analysis of crystal structures and a library of small molecules known to act against the complex highlighted the pivotal role of Phe293 (ERCC1) in maintaining complex stability. This residue was chosen as the primary binding site for virtual screening. Using an optimized docking protocol, we screened compounds from various databases, ultimately identifying more than one hundred potential inhibitors. Their capability to amplify cisplatin-induced cytotoxicity was assessed in NSCLC H1299 cells, which exhibited the highest ERCC1 expression of all the cell lines tested. Of these, 22 compounds emerged as promising enhancers of cisplatin efficacy. Our results underscore the value of pinpointing crucial molecular characteristics in the pursuit of novel modulators of the ERCC1–XPF interaction, which could be combined with cisplatin to treat NSCLC more effectively. Full article

Replicative DNA polymerases are blocked by nearly all types of DNA damage. The resulting DNA replication stress threatens genome stability. DNA replication stress is also caused by depletion of nucleotide pools, DNA polymerase inhibitors, and DNA sequences or structures that are difficult to replicate. Replication stress triggers complex cellular responses that include cell cycle arrest, replication fork collapse to one-ended DNA double-strand breaks, induction of DNA repair, and programmed cell death after excessive damage. Replication stress caused by specific structures (e.g., G-rich sequences that form G-quadruplexes) is localized but occurs during the S phase of every cell division. This review focuses on cellular responses to widespread stress such as that caused by random DNA damage, DNA polymerase inhibition/nucleotide pool depletion, and R-loops. Another form of global replication stress is seen in cancer cells and is termed oncogenic stress, reflecting dysregulated replication origin firing and/or replication fork progression. Replication stress responses are often dysregulated in cancer cells, and this too contributes to ongoing genome instability that can drive cancer progression. Nucleases play critical roles in replication stress responses, including MUS81, EEPD1, Metnase, CtIP, MRE11, EXO1, DNA2-BLM, SLX1-SLX4, XPF-ERCC1-SLX4, Artemis, XPG, FEN1, and TATDN2. Several of these nucleases cleave branched DNA structures at stressed replication forks to promote repair and restart of these forks. We recently defined roles for EEPD1 in restarting stressed replication forks after oxidative DNA damage, and for TATDN2 in mitigating replication stress caused by R-loop accumulation in BRCA1-defective cells. We also discuss how insights into biological responses to genome-wide replication stress can inform novel cancer treatment strategies that exploit synthetic lethal relationships among replication stress response factors. Full article

The purpose of this study was to analyze the influence of Chitosan 0.2% in various final cleaning methods on the bond strength of fiberglass post (FP) to intrarradicular dentin. Ninety bovine incisors were sectioned to obtain root remnants measuring 18 mm in length. The roots were divided: G1: EDTA 17%; G2: EDTA 17% + PUI; G3: EDTA 17% + EA; G4: EDTA 17% + XPF; G5: Chitosan 2%; G6: Chitosan 2% + PUI; G7: Chitosan 2% + EA; G8: Chitosan 2% +XPF. After carrying out the cleaning methods, the posts were installed, and the root was cleaved to generate two disks from each root third. Bond strength values (MPa) obtained from the micro push-out test data were assessed by using Kruskal–Wallis and Dwass–Steel–Critchlow–Fligner tests for multiple comparisons (α = 5%). Differences were observed in the cervical third between G1 and G8 (p = 0.038), G4 and G8 (p = 0.003), G6 and G8 (p = 0.049), and Control and G8 (p = 0.019). The final cleaning method influenced the adhesion strength of cemented FP to intrarradicular dentin. Chitosan 0.2% + XPF positively influenced adhesion strength, with the highest values in the cervical third. Full article