Carbamazepine at environmentally relevant concentrations caused DNA damage and apoptosis in the liver of Chinese rare minnows (Gobiocypris rarus) by the Ras/Raf/ERK/p53 signaling pathway

The combined effects of polystyrene nanoplastics and dissolved organic matter on the environmental bioavailability of carbamazepine

The bioavailability of active pharmaceutical ingredients (APIs) plays a crucial role in determining the toxicity and risk of contaminants in the environment. However, the bioavailability of APIs in complex environmental matrices is still unclear. In this study, the combined effects of polystyrene nanoplastics (PS NPs) with various particle sizes (50, 100, and 1000 nm) and fulvic acid (FA) on the bioavailability of carbamazepine (CBZ) were investigated via negligible depletion solid-phase microextraction (nd-SPME) and Daphnia magna (D. magna) accumulation. The uptake kinetic study revealed that both PS NPs and FA reduced the elimination rate (k2) in most cases. The availability of CBZ to nd-SPME was determined by the hydrodynamic particle size of PS NPs, whereas the bioavailability to D. magna depended on the intrinsic particle size. The CBZ bioavailability was greater in co-exposed matrices due to the attenuated sorption of PS NPs to CBZ by FA modification. Notably, co-exposure of PS NPs and FA resulted in a higher bioaccumulation factor (BAF) of CBZ, probably due to the desorption and reabsorption of particle-associated CBZ. This study demonstrated that both PS NP particle size and FA binding affect the bioavailability of CBZ, and nd-SPME can mimic only the bioaccumulation of CBZ via diffusion.

Molecular Events in Response to Triclosan-Induced Oxidative Stress in CRISPR/Cas9-Mediated p53-Targeted Mutants in Daphnia magna

Triclosan (TCS), a widely used antimicrobial agent, has been implicated in the oxidative stress induction and disruption of cellular processes in aquatic organisms. As TCS is ubiquitous in the aquatic environment, many previous studies have documented the effects of exposure to TCS on aquatic organisms. Nevertheless, most of the research has concentrated on the molecular and physiological responses of TCS, but there are still limited studies on the function of specific genes and the consequences of their absence. In this study, we focused on p53, a gene that is crucial for molecular responses such as autophagy and apoptosis as a result of TCS exposure. In order to ascertain the role and impact of the p53 gene in TCS-induced molecular responses, we examined the molecular responses to TCS-induced oxidative stress in wild-type (WT) and CRISPR/Cas9-mediated p53 mutant (MT) water fleas. The result has been accomplished by examining changes in molecular mechanisms, including in vivo end points, enzyme activities, adenosine triphosphate release rate, and apoptosis, to determine the role and impact of the p53 gene on TCS-induced molecular responses. The results indicated that the sensitivity of MT water fleas to TCS was greater than that of WT water fleas; however, the difference in sensitivity was significant at short exposures within 48 h and decreased toward 48 h. Accordingly, when we confirmed the oxidative stress after 24 h of exposure, the oxidative stress to TCS exposure was stronger in the MT group, with an imbalance of redox. To identify the mechanisms of tolerance to TCS in WT and MT Daphnia magna, we checked mitochondrial and ER-stress-related biomarkers and found an increase in apoptosis and greater sensitivity to TCS exposure in the MT group than in the WT. Our results suggest that the absence of p53 caused alterations in molecular processes in response to TCS exposure, resulting in increased sensitivity to TCS, and that p53 plays a critical role in response to TCS exposure.

Environmentally Relevant Levels of Antiepileptic Carbamazepine Altered Intestinal Microbial Composition and Metabolites in Amphibian Larvae

There is growing concern about the potential ecological risks posed by pharmaceutical residues in the aquatic environment. However, our understanding of the toxic effects of antiepileptic pharmaceuticals, such as carbamazepine (CBZ), on aquatic animal larvae is still limited. In this study, the tadpoles of the black-spotted pond frog (Pelophylax nigromaculatus) were exposed to environmentally relevant concentrations of CBZ (0.3 and 3.0 μg/L) for 30 days, and their growth, intestinal microbial composition, and metabolites were investigated to assess the potential toxic effects of CBZ in non-targeted aquatic organisms. Some tadpoles died during exposure, but there was no significant among-group difference in the survival and growth rates. CBZ exposure significantly altered the composition of tadpole intestinal microbiota. Relative abundances of some bacterial genera (e.g., Blautia, Prevotella, Bacillus, Microbacterium, etc.) decreased, while others (e.g., Paucibacter, etc.) increased in CBZ-exposed tadpoles. Interestingly, CBZ-induced alterations in some bacteria might not necessarily lead to adverse outcomes for animals. Meanwhile, small molecular intestinal metabolites related to energy metabolism, and antioxidant and anti-inflammatory activities were also altered after exposure. Taken together, environmentally relevant levels of CBZ might alter the metabolic and immune performances of amphibian larvae by modifying the abundance of some specific bacteria and the level of metabolites in their intestines, thereby potentially causing a long-term effect on their fitness.

Emerging Contaminants in the Effluent of Wastewater Should Be Regulated: Which and to What Extent?

Effluent discharged from urban wastewater treatment plants (WWTPs) is a major source of emerging contaminants (ECs) requiring effective regulation. To this end, we collected discharge datasets of pharmaceuticals (PHACs) and endocrine-disrupting chemicals (EDCs), representing two primary categories of ECs, from Chinese WWTP effluent from 2012 to 2022 to establish an exposure database. Moreover, high-risk ECs' long-term water quality criteria (LWQC) were derived using the species sensitivity distribution (SSD) method. A total of 140 ECs (124 PHACs and 16 EDCs) were identified, with concentrations ranging from N.D. (not detected) to 706 μg/L. Most data were concentrated in coastal regions and Gansu, with high ecological risk observed in Gansu, Hebei, Shandong, Guangdong, and Hong Kong. Using the assessment factor (AF) method, 18 high-risk ECs requiring regulation were identified. However, only three of them, namely carbamazepine, ibuprofen, and bisphenol-A, met the derivation requirements of the SSD method. The LWQC for these three ECs were determined as 96.4, 1010, and 288 ng/L, respectively. Exposure data for carbamazepine and bisphenol-A surpassed their derived LWQC, indicating a need for heightened attention to these contaminants. This study elucidates the occurrence and risks of ECs in Chinese WWTPs and provides theoretical and data foundations for EC management in urban sewage facilities.

Cooperative adaptation strategies of different tissues in blunt snout bream (Megalobrama amblycephala) juvenile to acute ammonia nitrogen stress

Ammonia-nitrogen is a common stress factor for aquatic organisms in their habitation environment, which is enriched in water due to high-density farming and environmental pollution. Ammonia nitrogen can enter fish body through gill, epidermis, digestive tract, and other tissues, causing fish ammonia poisoning. In the present study, juvenile blunt snout bream (average weight, 45 ± 5 g) were exposed to high concentrations of ammonia-nitrogen stress (25.0 ± 0.5 mg/L) for six different treatment times (0, 3, 6, 12, 24, 48, and 72 h); the tissue ultrastructure, mRNA levels of antioxidation system, and apoptosis patterns were studied. The antioxidant systems of malondialdehyde (MDA), catalase (CAT), acid phosphatase (ACP), and reduced glutathione (GSH) in various tissues were highly transcripted at 6 or 12 h (hpt) after treatment under high ammonia-nitrogen, which may play a role in preventing cells from being attacked by highly toxic reactive oxygen species (ROS). After 24 hpt, the antioxidant capacity threshold is breached, followed by the decline of antioxidant enzyme activity. Thus, with the prolonging of high ammonia-nitrogen processing time, ammonia-nitrogen stress caused irreversible damage of organs (gill, liver, and kidney). Furthermore, the expression of caspase-3 apoptotic pathway was highly induced in different tissues, implying the apoptotic system is activated, which causes extensive cell apoptosis in different tissues as shown using TUNEL analysis. In conclusion, we observed that, in response to acute ammonia-nitrogen stress, blunt snout bream enhances antioxidant capacity and cell apoptosis.

The occurrence of emerging compounds in real urban wastewater before and after the COVID-19 pandemic in Cali, Colombia

The COVID-19 pandemic is considered one of the most significant global disasters in the last years. The rapid increase in infections, deaths, treatment, and the vaccination process has resulted in the excessive use of pharmaceuticals that have entered the environment as micropollutants. Considering the prior information about the presence of pharmaceuticals found in the wastewater of Cali, Colombia, which was collected from 2015 to 2022. The data monitored after the COVID-19 pandemic showed an increase in the concentration of analgesics and anti-inflammatory drugs of up to 91%. This increase was associated with the consumption of pharmaceuticals for mild symptoms, such as fever and pain. Moreover, the increase in concentration of pharmaceuticals poses a highly ecological threat, which was up to 14 times higher than that reported before of COVID-19 pandemic. These results showed that the COVID-19 had not only impacted human health but also had an effect on environmental health.

Carbamazepine, venlafaxine, tramadol, and their main metabolites: Toxicological effects on zebrafish embryos and larvae

Pharmaceutical compounds and their metabolites are found in natural and wastewater. However, investigation of their toxic effects on aquatic animals has been neglected, especially for metabolites. This work investigated the effects of the main metabolites of carbamazepine, venlafaxine and tramadol. Zebrafish embryos were exposed (0.1-100 µg/L) for 168hpf exposures to each metabolite (carbamazepine-10,11-epoxide, 10,11-dihydrocarbamazepine, O-desmethylvenlafaxine, N-desmethylvenlafaxine, O-desmethyltramadol, N-desmethyltramadol) or the parental compound. A concentration-response relationship was found for the effects of some embryonic malformations. Carbamazepine-10,11-epoxide, O-desmethylvenlafaxine and tramadol elicited the highest malformation rates. All compounds significantly decreased larvae responses on a sensorimotor assay compared to controls. Altered expression was found for most of the 32 tested genes. In particular, abcc1, abcc2, abcg2a, nrf2, pparg and raraa were found to be affected by all three drug groups. For each group, the modelled expression patterns showed differences in expression between parental compounds and metabolites. Potential biomarkers of exposure were identified for the venlafaxine and carbamazepine groups. These results are worrying, indicating that such contamination in aquatic systems may put natural populations at significant risk. Furthermore, metabolites represent a real risk that needs more scrutinising by the scientific community.

Chronic exposure to environmentally relevant concentrations of carbamazepine interferes with anxiety response of adult female zebrafish through GABA /5-HT pathway and HPI axis

Carbamazepine (CBZ) is one of the widely distributed pharmaceutical residues in aquatic environments, yet few researches have addressed its chronic effect on the anxiety of fish, and the mechanisms possibly involved remained elusive. In this study, adult female zebrafish (Danio rerio) were exposed to environmental relevant concentrations of CBZ (CBZ-low, 10 μg/L; CBZ-high, 100 μg/L) for 28 days. After exposure, CBZ-high didn't affect the anxiety of fish. However, the onset time to the higher half of the tank was delayed and the total duration in the lower half of the tank was increased in CBZ-low fish, suggesting an increased anxiety. Further investigation indicated that CBZ-low significantly decreased the gamma-aminobutyric acid (GABA) level in the brain, while increased the serotonin (5-HT) level in the brain and cortisol level in plasma. Accordingly, the mRNA levels of genes in GABA (gad2, abat, gabrb2, gabrg2, gria1a and slc12a2) pathway and HPI (crha, actha, pc1 and pc2) axis were also altered. Despite the upregulation of tph2 was consistent with increased 5-HT level in the brain, significantly downregulated htr1aa and htr1b may indicate attenuated 5-HT potency. Although CBZ-high significantly reduced GABA level in the brain and increased cortisol level in plasma, the effects were dramatically alleviated than that of CBZ-low. Consistently, the expression of genes in HPI (crha, actha, pc1 and pc2) axis and GABA (gad2 and abat) pathway were also altered by CBZ-high, probably due to inconspicuous anxiety response of CBZ-high. Briefly, our data suggested that low concentration of CBZ disrupted zebrafish anxiety by interfering with neurotransmission and endocrine system, thereby bringing about adverse ecological consequences.

Integrated genotoxicity of secondary and tertiary treatment effluents in North China

Genotoxic effects on aquatic organisms caused by wastewater discharging have raised extensive concerns. However, the efficiency of various wastewater treatment processes to reduce effluent genotoxicity was not well known. Genotoxic effects of effluents from four secondary wastewater treatment plants (SWTPs) and a tertiary wastewater treatment plant (TTP) in north China on Chinese rare minnows (Gobiocypris rarus) were evaluated and the toxicity reduction efficiency of various treatment techniques was compared. SWTPs and TTP final effluents disturbed the antioxidant system and lipid peroxidation, with malondialdehyde (MDA) contents in the fish livers and gills increasing to 1.4-2.4 folds and 1.6-3.1 folds of control, respectively. Significant increases in erythrocytes micronucleus (MN) frequency were induced by effluent, and liver DNA damage caused by final SWTPs effluent was 29-54 % lower than TTP effluent. Further, DNA repair gene atm and growth arrest gene gadd45a were remarkably upregulated by SWTP and TTP final effluents to 1.8-12 folds and 4.1-15 folds, respectively, being consistent with the chromosomal aberration and DNA damage in liver tissue. Integrated biomarker response (IBR) of the tertiary effluent was 49 %-69 % lower than the secondary effluents. However, the final ozone disinfection at TTP caused an increase in the DNA damage, suggesting the generation of genotoxic by-products. UV disinfection at secondary treatment removed part of genotoxicity, with a reduction in IBR of 0 %-47 %. The total semi-volatile organic compounds (SVOCs) detected in the final effluent contained 5 %-56 % potential genotoxic substances, removal of which was 9 %-51 % lower than non-genotoxic compounds. Microfiltration and reverse osmosis process exhibited good performance in removing both the integrated genotoxicity and the potential genotoxic SVOCs. Our finding shows that TTP is superior than SWTP for wastewater treatment due to higher genotoxicity removal, but ozone disinfection needs improvement by optimizing performance parameters or adding post-treatment processes, to achieve better protection for aquatic organisms against genotoxic contaminants.

Reduction of Genotoxicity of Carbamazepine to Human Lymphocytes by Pre-treatment with Vitamin B12

BACKGROUND

Carbamazepine (CBZ) is widely used as an anti-epileptic drug. Vitamin B12 has been shown to protect against DNA damage caused by several mutagenic agents.

OBJECTIVE

This study aimed to investigate the effect of vitamin B12 on CBZ-induced genotoxicity in cultured human lymphocytes.

METHODS

Sister chromatid exchanges (SCEs) and chromosomal aberrations (CAs) genotoxic assays were utilized to achieve the study objective.

RESULTS

The results showed significantly higher frequencies of CAs and SCEs in the CBZ-treated cultures (12 μg/mL) compared to the control group (P<0.01). The genotoxic effects of CBZ were reduced by pre-treatment of cultures with vitamin B12 (13.5μg/ml, P<0.05). Neither CBZ nor vitamin B-12 showed any effects on mitotic and proliferative indices.

CONCLUSION

CBZ is genotoxic to lymphocyte cells, and this genotoxicity can be reduced by vitamin B12.

Carbamazepine-induced renal toxicity may be associated with oxidative stress and apoptosis in male rat

Carbamazepine (CBZ) is the antiepileptic drug used in epilepsy and some psychiatric disorders. Besides its widely used, many adverse effects have been reported including hematotoxicity, hepatotoxicity, endocrine disorders, and testicular damages due to oxidative stress. However, the role of CBZ on renal toxicity is not fully known. In this study, we attempted to explain the connected mechanisms by focusing on the metabolism of CBZ-induced renal toxicity in rats. Twenty male Wistar-Albino rats were randomized into 2 groups (n = 10); control (1 mL/day distilled water, orally) and CBZ (25 mg/kg/day CBZ, orally) groups. After 60 days, TAS (total oxidant status) and TOS (total oxidant status) levels, histopathological features, some genes involved in apoptosis, 8-hydroxy-2-deoxyguanosine (8-OHdG) activity, and apoptotic cells were assessed of kidney tissue. The oxidative stress index (OSI) was measured from TAS and TOS levels. TOS levels and OSI significantly increased, while TAS levels decreased in the CBZ group relative to the control group. Histopathological observations, Caspase-3 (Casp3), Poly [ADP-ribose] polymerase-1 (PARP-1), 8-OHdG immunoreactivities, and apoptotic cells markedly raised in the CBZ group compared with the control group. Also, mRNA expression of Cytochrome c (Cytc) and CASP3 significantly increased in the CBZ group compared to the control group. In conclusion, long-term use of CBZ may promote renal damage in rats by inducing oxidative stress and apoptosis.

Chronic Effects of Carbamazepine, Progesterone and Their Mixtures at Environmentally Relevant Concentrations on Biochemical Markers of Zebrafish (Danio rerio)

The impact of pharmaceuticals on non-target organisms in the environment is of increasing concern and study. Pharmaceuticals and other pollutants are often present as mixtures in an environmental compartment. Studies on the toxicological implications of these drugs on fish, particularly as mixtures at environmentally relevant concentrations, are very limited. Thus, this study aimed to evaluate the chronic effects of the anticonvulsant drug carbamazepine (CBZ) and progesterone (P4) at environmentally relevant concentrations, individually and in binary mixtures, applying a suite of biomarkers at the molecular level in zebrafish (Danio rerio). The effects on biotransformation enzymes 7-ethoxyresorufin O-deethylase (EROD) and glutathione-S-transferase (GST), antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidases (GPxSe and GPxTOT), and glutathione reductase (GR), and markers of damage, such as DNA strand breaks (DNAsb), lactate dehydrogenase (LDH), lipid peroxidation (LPO), and vitellogenin-like proteins (VTG), were evaluated. Analyses of the biochemical markers indicated that a synergistic dose-ratio-dependent effect of CBZ and P4 in zebrafish occurs after chronic exposure regarding VTG, biotransformation enzymes (EROD, GST), and oxidative stress marker (DNAsb). The results suggest a synergistic effect regarding VTG, thus indicating a high risk to the reproductive success of fish if these pharmaceuticals co-occur.

Derivation of Water Quality Criteria for Carbamazepine and Ecological Risk Assessment in the Nansi Lake Basin

Carbamazepine, as one of several pharmaceutical and personal care products, has gained much attention in recent years because of its continuous discharge in natural waters and toxicity to aquatic ecosystems. However, it is difficult to evaluate and manage carbamazepine pollution because of the lack of a rational and scientific Water Quality Criteria (WQC) of carbamazepine. In this study, the carbamazepine toxicity data of thirty-five aquatic species from eight taxonomic groups were selected, and the species sensitivity distribution (SSD) method was applied to derive the WQC for carbamazepine based on the Log-logistic model, which was 18.4 ng/L. Meanwhile, the occurrence and distribution of carbamazepine in the Nansi Lake basin was studied. Results showed that concentrations of carbamazepine in 29 sampling sites were in the range of 3.3 to 128.2 ng/L, with the mean of 17.3 ng/L. In general, the levels of carbamazepine in tributaries were higher than those in the lakes. In addition, qualitative and quantitative ecological risk assessment methods were applied to assess the adverse effect of carbamazepine on aquatic systems. The hazard quotient (HQ) method showed that there were 24 and 5 sampling sites, in which risk levels were low and moderate, respectively. The joint probability curve (JPC) method indicated that ecological risks might exist in 1.4% and 1.0% of surface water, while a 5% threshold and 1% threshold were set up to protect aquatic species, respectively. Generally, carbamazepine posed a low risk to the aquatic organisms in the Nansi Lake basin.

Biochemical Marker Assessment of Chronic Carbamazepine Exposure at Environmentally Relevant Concentrations in Juvenile Common Carp (Cyprinus carpio)

Worldwide, the anticonvulsant drug carbamazepine (CBZ) is the most frequently identified pharmaceutical residue detected in rivers. Reported chronic effects of CBZ in non-target freshwater organisms, particularly fish, include oxidative stress and damage to liver tissues. Studies on CBZ effects in fish are mostly limited to zebrafish and rainbow trout studies. Furthermore, there are only a few chronic CBZ studies using near environmental concentrations. In this study, we provide data on subacute effects of CBZ exposure (28 days) to common carp (Cyprinus carpio), employing a set of biochemical markers of damage and exposure. CBZ was found to induce a significant change in the hepatic antioxidant status of fish subjected to 5 µg/L. Moreover, with increasing concentrations, enzymatic and non-enzymatic biomarkers of oxidative defence (catalase (CAT), superoxide dismutase (SOD), glutathione reductase (GR), DNA strand breaks)), toxicant biotransformation (ethoxyresorufin-o-demethylase (EROD), glutathione-S-transferase (GST)), and organ and tissue damage (lactate dehydrogenase (LDH), cetylcholinesterase (AChE)) were altered. The AChE, LDH, and lipid peroxidation (LPO) results indicate the occurrence of apoptotic process activation and tissue damage after 28 days of exposure to CBZ. These findings suggest significant adverse effects of CBZ exposure to common carp at concentrations often found in surface waters.

Environmentally relevant concentrations of benzophenones triggered DNA damage and apoptosis in male Chinese rare minnows (Gobiocypris rarus)

Benzophenone-type ultraviolet (UV) filters (BPs) are commonly used as sunscreen agents, fragrance enhancers and plastic additives, and are great threats to aquatic organisms due to their high detected concentrations in the aquatic environment. However, few studies on their toxicity and mechanism in fish have been clearly reported. In this study, Chinese rare minnows (Gobiocypris rarus) were exposed to benzophenone (BP), 2,4-dihydroxybenzophenone (BP-1), and 5-benzoyl-4-hydroxy-2-methoxybenzenesulfonic acid (BP-4) at 5, 50, 500 µg/L for 28 d to assess their toxicity. Transcriptomics screening showed that cell cycle, DNA replication and repair were significantly altered pathways (p < 0.05). The altered transcripts were similar to those identified by RNA-seq. DNA damage and 8-OHdG levels were significantly increased at 50 and 500 μg/L groups (p < 0.05). The DNA methylcytosine level was not significantly changed exposure to BP, BP-1 and BP-4. TUNEL assays indicated that hepatic apoptosis was significantly improved at 500 μg/L BP and BP-4 and 50 and 500 μg/L BP-1 (p < 0.05), with the significantly increasing the activity of caspase-3, -8 and -9 (p < 0.05). Molecular docking analysis revealed that BP, BP-1 and BP-4 could bind differently to caspase-3 through different binding interactions. Therefore, BP-1 induced more serious oxidative DNA damage and apoptosis by activating caspase-3 than BP and BP-4, which will provide theoretical basis and data support for ecological evaluation of aquatic organisms induced by BPs.

Effects of carbamazepine in aquatic biota

Carbamazepine (CBZ) is one of the most common pharmaceuticals found in the aquatic environment. Here, we reviewed studies in aquatic animals highlighting that CBZ affected ROS homeostasis but also the neuroendocrine system, cell viability, immunity, reproduction, feeding behavior and growth. Notably, the acetylcholinesterase activity was modified by concentrations of the order of ng L^-1 CBZ. At ≥10 μg L^-1, data pointed that CBZ triggered the production of ROS, modifying the activity of antioxidant enzymes and produced a significant cellular stress at concentrations ≥100 μg L^-1. However, the response appeared species-, organ- and time-dependent, and was impacted by different experimental conditions and the origin of animals. In this context, this review discusses the available data and proposes future research priorities.

An integrated metabolomics and proteogenomics approach reveals molecular alterations following carbamazepine exposure in the male mussel Mytilus galloprovincialis

Carbamazepine is one of the most abundant pharmaceutical active compounds detected in aquatic systems. Based on laboratory exposures, carbamazepine has been proven to adversely affect aquatic organisms. However, the underlying molecular events remain poorly understood. This study aims to investigate the molecular mechanisms potentially associated with toxicological effects of carbamazepine on the mussel Mytilus galloprovincialis exposed for 3 days at realistic concentrations encountered in coastal environments (80 ng/L and 8 μg/L). An integrated metabolomics and proteogenomics approach, including data fusion strategy, was applied to gain more insight in molecular events and cellular processes triggered by carbamazepine exposure. Consistent metabolic and protein signatures revealed a metabolic rewiring and cellular stress at both concentrations (e.g. intensification of protein synthesis, transport and catabolism processes, disruption of lipid and amino acid metabolisms). These highlighted molecular signatures point to the induction of autophagy, closely related with carbamazepine mechanism of action, as well as a destabilization of the lysosomal membranes and an enzymatic overactivity of the peroxisomes. Induction of programmed cell death was highlighted by the modulation of apoptotic cognate proteins. The proposed integrative omics data analysis was shown to be highly relevant to identify the modulations of the two molecular levels, i.e. metabolites and proteins. Multi-omics approach is able to explain the resulting complex biological system, and document stronger toxicological pieces of evidence on pharmaceutical active compounds at environmental concentrations in sentinel organisms.

Epigenetic Mechanisms in DNA Double Strand Break Repair: A Clinical Review

Upon the induction of DNA damage, the chromatin structure unwinds to allow access to enzymes to catalyse the repair. The regulation of the winding and unwinding of chromatin occurs via epigenetic modifications, which can alter gene expression without changing the DNA sequence. Epigenetic mechanisms such as histone acetylation and DNA methylation are known to be reversible and have been indicated to play different roles in the repair of DNA. More importantly, the inhibition of such mechanisms has been reported to play a role in the repair of double strand breaks, the most detrimental type of DNA damage. This occurs by manipulating the chromatin structure and the expression of essential proteins that are critical for homologous recombination and non-homologous end joining repair pathways. Inhibitors of histone deacetylases and DNA methyltransferases have demonstrated efficacy in the clinic and represent a promising approach for cancer therapy. The aims of this review are to summarise the role of histone deacetylase and DNA methyltransferase inhibitors involved in DNA double strand break repair and explore their current and future independent use in combination with other DNA repair inhibitors or pre-existing therapies in the clinic.

Colour Changes during the Carbamazepine Oxidation by Photo-Fenton

The oxidation of aqueous solutions of carbamazepine is conducted using the Fenton reagent, combined with the photolytic action of a 150 W medium pressure UV lamp, operating at T = 40 °C. The effect of acidity is analysed at an interval pH = 2.0–5.0, verifying that operating at pH = 5.0 promotes colour formation (Colour = 0.15 AU). The effect of iron is studied, finding that the colour of the water increases in a linear way, Colour = 0.05 + 0.0075 [Fe]0. The oxidising action of hydrogen peroxide is tested, confirming that when operating with [H2O2]0 = 2.0 mM, the maximum colour is generated (Colourmax = 0.381 AU). The tint would be generated by the degradation of by-products of carbamazepine, which have chromophoric groups in their internal structure, such as oxo and dioxocarbazepines, which would produce tint along the first minutes of oxidation, while the formation of acridones would slowly induce colour in the water.