85 research outputs found
Oxidative Stress Induces Telomere Dysfunction and Senescence by Replication Fork Arrest
No full textOxidative DNA damage, particularly 8-oxoguanine, represents the most frequent DNA damage in human cells, especially at the telomeric level. The presence of oxidative lesions in the DNA can hinder the replication fork and is able to activate the DNA damage response. In this study, we wanted to understand the mechanisms by which oxidative damage causes telomere dysfunction and senescence in human primary fibroblasts. After acute oxidative stress at telomeres, our data demonstrated a reduction in TRF1 and TRF2, which are involved in proper telomere replication and T-loop formation, respectively. Furthermore, we observed a higher level of γH2AX with respect to 53BP1 at telomeres, suggesting a telomeric replication fork stall rather than double-strand breaks. To confirm this finding, we studied the replication of telomeres by Chromosome Orientation-FISH (CO-FISH). The data obtained show an increase in unreplicated telomeres after hydrogen peroxide treatment, corroborating the idea that the presence of 8-oxoG can induce replication fork arrest at telomeres. Lastly, we analyzed the H3K9me3 histone mark after oxidative stress at telomeres, and our results showed an increase of this marker, most likely inducing the heterochromatinization of telomeres. These results suggest that 8-oxoG is fundamental in oxidative stress-induced telomeric damage, principally causing replication fork arrest
Targeting telomerase and telomeres to enhance ionizing radiation effects in in vitro and in vivo cancer models
No full textOne of the hallmarks of cancer consists in the ability of tumor cells to divide indefinitely, and to maintain stable telomere lengths throughout the activation of specific telomere maintenance mechanisms (TMM). Therefore in the last fifteen years, researchers proposed to target telomerase or telomeric structure in order to block limitless replicative potential of cancer cells providing a fascinating strategy for a broad-spectrum cancer therapy.In the present review, we report in vitro and in vivo evidence regarding the use of chemical agents targeting both telomerase or telomere structure and showing promising antitumor effects when used in combination with ionizing radiation (IR). RNA interference, antisense oligonucleotides (e.g., GRN163L), non-nucleoside inhibitors (e.g., BIBR1532) and nucleoside analogs (e.g., AZT) represent some of the most potent strategies to inhibit telomerase activity used in combination with IR. Furthermore, radiosensitizing effects were demonstrated also for agents acting directly on the telomeric structure such as G4-ligands (e.g., RHPS4 and Telomestatin) or telomeric-oligos (T-oligos). To date, some of these compounds are under clinical evaluation (e.g., GRN163L and KML001).Advantages of Telomere/Telomerase Targeting Compounds (T/TTCs) coupled with radiotherapy may be relevant in the treatment of radioresistant tumors and in the development of new optimized treatment plans with reduced dose adsorbed by patients and consequent attenuation of short- end long-term side effects. Pros and cons of possible future applications in cancer therapy based on the combination of T/TCCs and radiation treatment are discussed
In vitro effects of 1-MHz ultrasound on the mitotic spindle
No full textThe effects of ultrasound on the cytoskeleton, comprising microtubules, had been studied decades ago. Nonetheless, very little attention has been paid to the effects of ultrasound on the mitotic spindle, which is also formed by microtubules. In this study, we treated human fibroblasts and human cancer cells (HeLa and MCF-7) with 1-MHz ultrasound at low intensities (70, 140, and 300 mW/cm 2 ). In all cell lines, 5 min after the end of sonication, we found an intensity-dependent increase of mitotic abnormalities (including multipolar spindles). Two hours after sonication, these abnormalities were present, but at much lower frequencies. Twenty-four hours after sonication, mitotic abnormalities were at the same level of untreated samples, suggesting a transient effect due to ultrasound. Beside abnormalities of the mitotic spindle, we also observed an increase of metaphases with nonaligned chromosomes. The mitotic index of fibroblasts and HeLa cells, two hours after sonication, showed an intensity-dependent decrease; this was not observed in MCF-7 cells. In agreement with this last result, ultrasound-induced growth inhibition (which was also intensity-dependent) was more marked in fibroblasts and HeLa cells compared to MCF-7 cells. This work indicates that therapeutic ultrasound, even at intensities below the cavitation threshold, can affect genome integrity, showing the need to increase the knowledge of the potential risks of ultrasound to human health. Environ. Mol. Mutagen. 2019. © 2019 Wiley Periodicals, Inc
X-rays Activate Telomeric Homologous Recombination Mediated Repair in Primary Cells
No full textCancer cells need to acquire telomere maintenance mechanisms in order to counteract progressive telomere shortening due to multiple rounds of replication. Most human tumors maintain their telomeres expressing telomerase whereas the remaining 15%-20% utilize the alternative lengthening of telomeres (ALT) pathway. Previous studies have demonstrated that ionizing radiations (IR) are able to modulate telomere lengths and to transiently induce some of the ALT-pathway hallmarks in normal primary fibroblasts. In the present study, we investigated the telomere length modulation kinetics, telomeric DNA damage induction, and the principal hallmarks of ALT over a period of 13 days in X-ray-exposed primary cells. Our results show that X-ray-treated cells primarily display telomere shortening and telomeric damage caused by persistent IR-induced oxidative stress. After initial telomere erosion, we observed a telomere elongation that was associated to the transient activation of a homologous recombination (HR) based mechanism, sharing several features with the ALT pathway observed in cancer cells. Data indicate that telomeric damage activates telomeric HR-mediated repair in primary cells. The characterization of HR-mediated telomere repair in normal cells may contribute to the understanding of the ALT pathway and to the identification of novel strategies in the treatment of ALT-positive cancers
Relation between telomere lenght and genomic instability induced by acute and prolonged oxidative stress
No full textRole of telomere on chromosome instability induced by oxidative stress in human primary fibroblast
No full textTelomere alterations and chromosome segregation defects induced by prolonged oxidative stress treatment
No full textContinuous glucose monitoring (CGM) in a non-Icu hospital setting: The patient's journey
No full textAims: Although consistent data support the outpatient use of continuous glucose monitoring (CGM) to improve glycemic control and reduce hypoglycemic burden, and clinical outcomes, there are limited data regarding its use in the hospital setting, particularly in the non-intensive care unit (non-ICU) setting. The emerging use of CGM in the non-critical care setting may be useful in increasing the efficiency of hospital care and reducing the length of stay for patients with diabetes while improving glycemic control. Data synthesis: The purpose of this Expert Opinion paper was to evaluate the state of the art and provide a practical model of how CGM can be implemented in the hospital. Setting: A patient's CGM journey from admission to the ward to the application of the sensor, from patient education on the device during hospitalization until discharge of the patient to maintain remote control. Conclusions: This practical approach for the implementation and management of CGM in patients with diabetes admitted to non-ICUs could guide hospitals in their diabetes management initiatives using CGM, helping to identify patients most likely to benefit and suggesting how this technology can be implemented to maximize clinical benefits
The effect of dexmedetomidine on status epilepticus in a patient with anti-NMDA receptor encephalitis
No full textThe effect of dexmedetomidine on status epilepticus in a patient
with anti-NMDA receptor encephalitis
A 35-yr-old Caucasian woman was hospitalized in psychiatry, after childbirth, for psychomotor agitation, visual hallucinations, and incoherent speech. On admission, electroencephalography, brain imaging and cerebrospinal fluid examination showed no abnormalities. On day 7, she was found unconscious, and admitted to the intensive care unit (ICU). She developed status epilepticus alternating with periods of agitation. SE persisted despite combined treatment with phenytoin sodium, levetiracetam, and delorazepam. Intravenous dexmedetomidine (0.4 lgkg-1hr-1) was administrated for conscious sedation, and improvement from the SE was observed in 30min,as documented with EEG tracings. Electroencephalography spectral analysis showed a significant increase in beta activity, which is typical of dexmedetomidine.
SE relapsed after dexmedetomidine interruption and resolved when the infusion was restarted.
Anti-N-methyl-D-aspartate receptor (NMDA-R) antibodies were detected in the CSF.
N-methyl-D-aspartate receptor antibodies are a rare cause of autoimmune encephalitis, often misdiagnosed with psychosis, which typically leads to seizures and drugresistant SE.
Contradictory results have been reported on the effects of the alpha-2 agonist dexmedetomidine in epilepsy.
In animals, dexmedetomidine has been shown both to reduce and increase the seizure threshold in local anestheticinduced epilepsy.
Another question is the exact relationship between dexmedetomidine and NMDA-R. N-methyl-Daspartate receptors are ionotropic glutamate receptors that play a key role in excitatory synaptic transmission. Dexmedetomidine can depress NMDA-R-mediated transmission.
Dexmedetomidine exerts its activity on G-protein coupled alpha-2 adrenoreceptors through inhibition of cyclic adenosine monophosphate and
Our observations suggest a possible role for dexmedetomidine in the management of drug-resistant SE in the ICU. In patients with NMDA-R encephalitis and seizures, dexmedetomidine could be a useful bridge between typical pharmacological approaches and plasmapheresis
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