DNA damage and arterial hypertension. A systematic review and meta-analysis

Oxidative DNA damage markers (8OHdG, comet assay, gammaH2AX) are becoming widely used in clinical cardiology research. To conduct this review of DNA damage in relation to hypertension in humans, we used databases (e.g. PubMed, Web of Science) to search for English-language publications up to June 30, 2022 and the terms: DNA damage, comet assay, gammaH2AX, 8OHdG, strand breaks, and arterial hypertension. Exclusion criteria were: children, absence of relevant controls, extra-arterial hypertensive issues, animal, cell lines. From a total of 79526, 15 human studies were selected. A total of 902 hypertensive patients (pts): (comet: N=418 pts; 8OHdG: N=484 pts) and 587 controls (comet: N=203; 8OHdG: N=384) were included. DNA damage was significantly higher in hypertensive pts than healthy controls (comet 26.6±11.0 vs 11.7±4.07 arbitrary units /A.U./; P<0.05 and="" 8ohdg="" 13="" 1="" 4="" 12="" vs="" 6="" 97="" 2="" 67="" ng="" mg="" creatinine="" i=""> P<0.05) confirmed with meta-analysis for both. Greater DNA damage was observed in more adverse cases (concentric cardiac hypertrophy 43.4±15.4 vs 15.6±5.5; sustained/untreated hypertension 31.4±12.1 vs 14.2±5/35.0±5.0 vs 25.0 ±5.0; non-dippers 39.2±15.5 vs 29.4±11.1 A.U.; elderly 14.9±4.5 vs 9.3±4.1 ng/mg creatinine; without carvedilol 9.1±4.2 vs 5.7±3.9; with coronary heart disease 0.5±0.1 vs 0.2±0.1 ng/mL) (P<0.05) confirmed with meta-analysis. DNA damage correlated strongly positively with serum glycosylated haemoglobin (r=0.670; P<0.05) and negatively with total antioxidant status (r=-0.670 to -0.933; P<0.05). This is the first systematic review with meta-analysis showing that oxidative DNA damage was increased in humans with arterial hypertension compared to controls.

Antiproliferative activity and apoptosis-inducing mechanism of Amaryllidaceae alkaloid montanine on A549 and MOLT-4 human cancer cells

The isoquinoline alkaloids found in Amaryllidaceae are attracting attention due to attributes that can be harnessed for the development of new drugs. The possible molecular mechanisms by which montanine exerts its inhibitory effects against cancer cells have not been documented. In the present study, montanine, manthine and a series of 15 semisynthetic montanine analogues originating from the parent alkaloid montanine were screened at a single test dose of 10 μM to explore their cytotoxic activities against a panel of eight cancer cell lines and one non-cancer cell line. Among montanine and its analogues, montanine and its derivatives 12 and 14 showed the highest cytostatic activity in the initial single-dose screening. However, the native montanine exhibited the greatest antiproliferative activity against cancer cells, with a lower mean IC50 value of 1.39 µM, compared to the displayed mean IC50 values of 2.08 µM for 12 and 3.57 µM for 14. Montanine exhibited the most potent antiproliferative activity with IC50 values of 1.04 µM and 1.09 µM against Jurkat and A549 cell lines, respectively. We also evaluated montanine's cytotoxicity and cell death mechanisms. Our results revealed that montanine triggered apoptosis of MOLT-4 cells via caspase activation, mitochondrial depolarisation and Annexin V/PI double staining. The Western blot results of MOLT-4 cells showed that the protein levels of phosphorylated Chk1 Ser345 were upregulated with increased montanine concentrations. Our findings provide new insights into the mechanisms underlying the cytostatic, cytotoxic and pro-apoptotic activities of montanine alkaloids in lung adenocarcinoma A549 and leukemic MOLT-4 cancer cell types.

Abstract 1411: Utilizing 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures for novel cancer chemosensitizers

A quickly developing chemoresistance is the hallmark of the standard treatment failure and the poor patient prognosis. Resistance is often connected to the overexpression of the specific kinases that are involved in DNA damage response. Contrary, their inhibition could lead to augmented cancer cell sensitization to conventional approach. Among them, ataxia-telangiectasia and Rad3-related kinase (ATR), the major replication stress responder, is one of the most attractive target. Within this study our aim was to find novel chemosensitizing agents for the cancer treatment employment. Inspired by clinical candidates targeting ATR, we designed and prepared large library of 40 novel compounds utilizing 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures. Initially, our presumption to have ATR inhibitors were confirmed by molecular dynamic study. All the compounds alone or in combination with cisplatin were screened against panel of nine cancer cell lines and one healthy cell line. The results were compared with well-known ATR inhibitor VE-821. Several compounds significantly inhibit the cell viability and some were able to potentiate cisplatin effect. From structure-activity relationship point of view, 7-azaindoles were the most cytotoxic compounds when substituted in position 3 and 5. Contrary, 2,7-diazaindoles expressed the most potent chemosensitizing capabilities. 1H-Pyrazoles were the least potent compounds within this screen. Interestingly, the status of tumor suppressor protein p53 (defect in G1) did not significantly influence chemosensitization or cytotoxic effect. Three highlighted compounds 3, 22, and 29 were selected for Broad oncology panel screening containing 104 kinases which could be potentially targeted. Only compound 29, the 2,7-diazaindole representative, showed ATR inhibitory efficacy with the IC50 around 10 µM. In contrast, the compound 22, 7-azaindole and the most cytotoxic one, expressed the multi-kinase activity with the substantial inhibitory capability against vascular endothelial growth factor receptor 3 protein (VEGFR-3). VEGFR-3 is also very attractive anticancer target with several inhibitors already approved. Finally, several compounds showed chemosensitizing potencies for temozolomide against secondary astrocytoma cell line. In overall, we showed that both, 7-azaindoles, and 2,7-diazaindoles, could be effectively utilized as novel anticancer agents. Whereas 2,7-diazaindoles could become efficient ATR inhibitors, 7-azaindoles have potential as antiangiogenics, VEGFR-3 inhibitors. Besides, both structures could be used for a glioblastoma treatment as temozolomide sensitizers. More research is currently ongoing to fully exploit potential of these compounds.

Citation Format: Lukas Gorecki, Darina Muthna, Sara Merdita, Martin Andrs, Tomas Kucera, Tereza Kobrlova, Martina Rezacova, Jan Korabecny. Utilizing 7-azaindoles, 2,7-diazaindoles, and 1H-pyrazoles as core structures for novel cancer chemosensitizers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1411.

141 Evaluation of Use of NABCOP Frailty Score and Interprofessional Variety of WHO Performance Score in Breast Cancer Patients Over 70 Years of Age

Aim

There is requirement to assess frailty of older patients with breast cancer as it can influence practice of treatment. In our department the fitness assessment was inconsistent. Therefore, we have decided to conduct qualitative study to evaluate ease of use of NABCOP frailty score (in comparison with other scales) as well as interprofessional variety of WHO performance score.

Method

We have conducted prospective data over 2 weeks period in our busy fast track breast clinic. All new patients over 70 years of age have been identified and asked to perform self-rating assessment. The patient has been later evaluated by NABCOP frailty score and WHO performance score by consultant, nurse, and HCA. This was compared to GP assessment which is part of 2WW referral.

Results

There have been matching results between patient’s self-assessment, clinician, and HCA in majority of patients. HCA perform assessment well with no discrepancy to other physician.

Conclusions

Self-rating and HCA assessment of performance status is accurate and can speed up clinic time. WHO performance scale is found easier and less time consuming by users (and felt provides similar information). We have now provided new assessment system which is undergoing trial in practice at present.

Discovery of ATR kinase inhibitor berzosertib (VX-970, M6620): Clinical candidate for cancer therapy

Chemoresistance, radioresistance, and the challenge of achieving complete resection are major driving forces in the search for more robust and targeted anticancer therapies. Targeting the DNA damage response has recently attracted research interest, as these processes are enhanced in tumour cells. The major replication stress responder is ATM and Rad3-related (ATR) kinase, which is attracting attention worldwide with four drug candidates currently in phase I/II clinical trials. This review addresses a potent and selective small-molecule ATR inhibitor, which is known as VX-970 (also known as berzosertib or M6620), and summarizes the existing preclinical data to provide deep insight regarding its real potential. We also outline the transition from preclinical to clinical studies, as well as its relationships with other clinical candidates (AZD6738, VX-803 [M4344], and BAY1895344). The results suggest that VX-970 is indeed a promising anticancer drug that can be used both as monotherapy and in combination with either chemotherapy or radiotherapy strategies. Based on patient anamnesis and biomarker identification, VX-970 could become a valuable tool for oncologists in the fight against cancer.

New Light on An Old Friend: Targeting PUMA in Radioprotection and Therapy of Cardiovascular and Neurodegenerative Diseases

This review summarizes recent progress in understanding the role of p53-upregulated mediator of apoptosis (PUMA) in molecular pathways with respect to its potential therapeutic applications. Particular emphasis is given to the PUMA´s role in ionizing radiation-induced signalling as radiotoxicity of normal tissue is mediated mostly via apoptosis. PUMA and its p53-dependent and p53- independent induction are described and potential use as a new target for the development of radioprotective agents is suggested. Further implications, including targeting PUMA to prevent and treat cardiovascular and neurodegenerative diseases, are also discussed together with an overview of other therapeutic applications. Finally, basic chemical structures for the development of novel PUMA modulators such as pifithrine derivatives, kinase inhibitors or modulators of Bcl-2 protein family are described.

The effect of sodium butyrate and cisplatin on expression of EMT markers

Histone modifications play a key role in the epigenetic regulation of gene transcription in cancer cells. Histone acetylations are regulated by two classes of enzymes, histone acetyltransferases (HATs) and histone deacetylases (HDACs). HDACs are increased in ovarian carcinomas and they are involved in carcinogenesis and resistance to chemotherapeutic agents. In our study we investigated anticancer effect of HDAC inhibitor sodium butyrate (NaBu) on cisplatin-sensitive and cisplatin-resistant ovarian cell lines A2780 and A2780cis. A2780 and A2780cis were treated with NaBu alone or in combination with cisplatin (CP). NaBu inhibited the growth of both cell lines and enhanced cytotoxic effect of CP. Exposure to NaBu for 24 h induced cell cycle arrest. The expressions of EMT-related genes and proteins were further investigated by qPCR and western blot analysis. Loss of E-cadherin has been shown to be crucial in ovarian cancer development. We found that NaBu dramatically induce expression of E-cadherin gene (CDH1) and protein levels in A2780 and A2780cis. We investigated correlation between transcription and methylation of CDH1gene. Methylation level analysis in 32 CpG sites in CDH1 gene (promoter/exon1 regions) was performed using bisulfite NGS (Next Generation Sequencing). We found that cisplatin-resistant cell line A2780cis cells differ from their cisplatin-sensitive counterparts in the CDH1 methylation. Methylation in A2780cis cells is elevated compared to A2780. However, NaBu-induced expression of CDH1 was not accompanied by CDH1 demethylation. NaBu treatment induced changes in expression of EMT-related genes and proteins. Interestingly E-cadherin zinc finger transcriptional repressor SNAIL1 was upregulated in both cell lines. Mesenchymal marker vimentin was downregulated. Matrix metalloproteases (MMPs) are necessary for pericellular proteolysis and facilitate migration and invasion of tumour cells. NaBu induced mRNA expression of MMPs, mild changes in activities of gelatinases MMP2 and MMP9 were detected. Our data demonstrate that NaBu sensitizes cisplatin-resistant ovarian cancer cells, re-established E-cadherin expression, but it was not able to reverse the EMT phenotype completely.

Chelidonine and Homochelidonine Induce Cell Death through Cell Cycle Checkpoints and MAP Kinase Pathways

This study focuses on the comparative in vitro cytotoxicity of chelidonine and homochelidonine on human cancer and non-cancer cells. Both alkaloids produced a decrease in cellular growth in a dose-dependent manner exhibiting greater potency in cancer cells. The growth inhibitory effect was evidenced in both ovarian carcinoma A2780 and lung fibroblast MRC-5 cells by inducing G2 and mitotic phase cell cycle arrest. Results indicated that the extent of apoptosis induced by chelidonine and homochelidonine was correlated to sensitivity to the antiproliferative activity of the evaluated compounds. Western blotting suggested that the cellular toxicological mechanism of chelidonine is related to the differential upregulation of phospho-Chk2, p21Cip1/Waf1, phospho-ERK1/2 and phospho-p38 in various cell types, leading to alternations in the suppression of proliferation and either induction or prevention of apoptosis. Chelidonine showed the more potent effects and also affected the cell cycle checkpoints and MAPK signaling pathways within cells.

Anticancer potential of Amaryllidaceae alkaloids evaluated by screening with a panel of human cells, real-time cellular analysis and Ehrlich tumor-bearing mice

In this study, twenty-two Amaryllidaceae alkaloids were screened for their anticancer potential. All isolates were evaluated for antiproliferative activities on a panel of 17 human cell types of different tissue origin using WST-1 assay. In addition, we determined the antiproliferative effect with a real-time cell analysis xCELLigence system. Thereafter, to evaluate the barely known in vivo anticancer potential of the most potent molecule haemanthamine, a preliminary study was performed using an Ehrlich tumor-bearing mice model. The results showed that haemanthamine, lycorine and haemanthidine exerted the highest antiproliferative activity. The mean growth percent (GP) value after a single-dose 10 μM treatment was for haemanthamine 21%, for lycorine 21% and for haemanthidine 27% that of untreated control cells (100%). Furthermore, haemanthamine, lycorine and haemanthidine exhibited significant cytotoxicities against all the tested cell lines with individual IC₅₀ values in the micromolar range. Dynamic real-time measures of impedance by xCELLigence indicated that these three compounds suppress cell proliferation after 10 h of treatment at a concentration of 10 μM or higher. Regrettably, in a follow-up in vivo antitumor activity study, haemanthamine showed no statistically significant reduction in the tumor size with no prolongation of survival time of Ehrlich tumor-bearing mice. Taken together, these results provide a new clue and guidance for exploiting Amaryllidaceae alkaloids as anticancer agents.

Small molecule inhibitors of DNA-PK for tumor sensitization to anticancer therapy

The most sensitive cell structure - a DNA molecule, is the common target of cancer therapy. DNA damage response (controlled by enzymes from the phosphatidylinositol 3-kinase-related kinases family - PIKK) presents many encouraging targets for improving both conventional cytotoxic anticancer therapy and individualized monotherapy. DNA-dependent protein kinase (DNA-PK) is a member of the PIKK superfamily and plays an important role in the detection and repair of DNA double-strand breaks via the non-homologous end-joining pathway. The ability of cancer cells to repair DNA damage is an important element determining their sensitivity to radio- or chemo-therapy. The overactivation of DNA-PK in cancers can result in resistance to anticancer therapy. The inhibition of DNA-PK is a very promising target in anticancer research. However, the specific DNA-PK inhibitors currently known are limited by poor solubility and high metabolic lability in vivo, leading to a short serum half-life. Construction of new compounds based on existing drugs is the most important strategy to improve drug efficacy, pharmacokinetic parameters and to reduce toxicity. This review will describe small molecule inhibitors and summarize their efficacy in synergizing radio- and chemotherapy in vitro.

The 9aaTAD Transactivation Domains: From Gal4 to p53

The family of the Nine amino acid Transactivation Domain, 9aaTAD family, comprises currently over 40 members. The 9aaTAD domains are universally recognized by the transcriptional machinery from yeast to man. We had identified the 9aaTAD domains in the p53, Msn2, Pdr1 and B42 activators by our prediction algorithm. In this study, their competence to activate transcription as small peptides was proven. Not surprisingly, we elicited immense 9aaTAD divergence in hundreds of identified orthologs and numerous examples of the 9aaTAD species' convergence. We found unforeseen similarity of the mammalian p53 with yeast Gal4 9aaTAD domains. Furthermore, we identified artificial 9aaTAD domains generated accidentally by others. From an evolutionary perspective, the observed easiness to generate 9aaTAD transactivation domains indicates the natural advantage for spontaneous generation of transcription factors from DNA binding precursors.

Comparative cytotoxicity of chelidonine and homochelidonine, the dimethoxy analogues isolated from Chelidonium majus L. (Papaveraceae), against human leukemic and lung carcinoma cells

BACKGROUND

The search for new anticancer compounds is a crucial element of natural products research.

PURPOSE

In this study the effects of naturally occurring homochelidonine in comparison to chelidonine on cell cycle progression and cell death in leukemic T-cells with different p53 status are described.

METHODS

The mechanism of cytotoxic, antiproliferative, apoptosis-inducing effects and the effect on expressions of cell cycle regulatory proteins was investigated using XTT assay, Trypan blue exclusion assay, flow cytometry, Western blot analysis, xCELLigence, epi-fluorescence and 3D super resolution microscopy. A549 cells were used for xCELLigence, clonogenic assay and for monitoring microtubule stability.

RESULTS

We found that homochelidonine and chelidonine displayed significant cytotoxicity in examined blood cancer cells with the exception of HEL 92.1.7 and U-937 exposed to homochelidonine. Unexpectedly, homochelidonine and chelidonine-induced cytotoxicity was more pronounced in Jurkat cells contrary to MOLT-4 cells. Homochelidonine showed an antiproliferative effect on A549 cells but it was less effective compared to chelidonine. Biphasic dose-depended G1 and G2/M cell cycle arrest along with the population of sub-G1 was found after treatment with homochelidonine in MOLT-4 cells. In variance thereto, an increase in G2/M cells was detected after treatment with homochelidonine in Jurkat cells. Treatment with chelidonine induced cell cycle arrest in the G2/M cell cycle in both MOLT-4 and Jurkat cells. MOLT-4 and Jurkat cells treated with homochelidonine and chelidonine showed features of apoptosis such as phosphatidylserine exposure, a loss of mitochondrial membrane potential and an increase in the caspases -3/7, -8 and -9. Western blots indicate that homochelidonine and chelidonine exposure activates Chk1 and Chk2. Studies conducted with fluorescence microscopy demonstrated that chelidonine and homochelidonine inhibit tubulin polymerization in A549 cells.

CONCLUSION

Collectively, the data indicate that chelidonine and homochelidonine are potent inducers of cell death in cancer cell lines, highlighting their potential relevance in leukemic cells.

Novel caffeine derivatives with antiproliferative activity

Beyond the psychoactive and cardiovascular effects of caffeine, this substance is also known for altering the cell's DNA damage response.

Breast cancer and cancer stem cells: a mini-review

Breast cancer is the most common type of malignant disease in women worldwide. In developing countries the past few years have sustained an increasing incidence of this type of cancer. Currently, breast cancer is the second leading cause of death due to cancer in women. In 2008 alone it was diagnosed in more than 1 million patients and each year the number of breast cancer-related deaths is estimated to be ~450,000. The mortality rate in breast cancer patients has been decreasing over the years thanks to the development of early diagnostic methods and more effective treatments. But despite the new advances in cancer diagnosis and treatment, the risk of recurrence and metastasis is ever present. It has been theorized that cancer stem cells are involved in the process of tumor growth and metastases. Due to their self-renewing and differentiation capabilities, they are now considered the underlying factor in tumor recurrence and the main reason for therapy resistance. Therefore, the characterization of cancer stem cells may contribute to the development of more effective treatment strategies that should make it possible to eliminate cancer stem cells in order to prevent tumor relapse and metastasis in diagnosed patients.

The effect of Amaryllidaceae alkaloids haemanthamine and haemanthidine on cell cycle progression and apoptosis in p53-negative human leukemic Jurkat cells

Plants from the Amaryllidaceae family have been shown to be a promising source of biologically active natural compounds of which some selected are currently in pre-clinical development. Regardless of interesting pioneer works, little is known about Amaryllidaceae alkaloids that have shown promising anti-cancer activities. The crinane group of the Amaryllidaceae, including haemanthamine and haemanthidine, was amongst the first of these compounds to exhibit an interesting cytotoxic potential against cancer cell lines. However, the mechanism of cytotoxic and anti-proliferative activity is not yet entirely clear. The primary objectives of the current study were to investigate the effects of haemanthamine and haemanthidine on the induction of apoptosis and the cell cycle regulatory pathway in p53-null Jurkat cells. Results indicate that haemanthamine and haemanthidine treatment decreases cell viability and mitochondrial membrane potential, leads to a decline in the percentage of cells in the S phase of the cell cycle, induces apoptosis detected by Annexin V staining and increases caspase activity. Dose dependent apoptosis was cross verified by fluorescence and bright field microscopy through Annexin V/propidium iodine staining and morphological changes which characteristically attend programmed cell death. The apoptotic effect of haemanthamine and haemanthidine on leukemia cells is more pronounced than that of gamma radiation. Contrary to gamma radiation, Jurkat cells do not completely halt the cell cycle 24h upon haemanthamine and haemanthidine exposure. Both Amaryllidaceae alkaloids accumulate cells preferentially at G1 and G2 stages of the cell cycle with increased p16 expression and Chk1 Ser345 phosphorylation. Concerning the pro-apoptotic effect, haemanthidine was more active than haemanthamine in the Jurkat leukemia cell line.

Boldine and Related Aporphines: From Antioxidant to Antiproliferative Properties

Plant and folk medicine represent nowadays a source of either new therapeutic substances or substrates for drug synthesis. One such promising group for possible further exploitation is the family of aporphine alkaloids containing boldine and related compounds. In this mini-review we focus on boldine and its newly described effects, which predominantly arise from its antioxidant properties. Moreover, we try to compare its antiproliferative properties with other better known members of the aporphine group.

Boldine and related aporphines: from antioxidant to antiproliferative properties

Plant and folk medicine represent nowadays a source of either new therapeutic substances or substrates for drug synthesis. One such promising group for possible further exploitation is the family of aporphine alkaloids containing boldine and related compounds. In this mini-review we focus on boldine and its newly described effects, which predominantly arise from its antioxidant properties. Moreover, we try to compare its antiproliferative properties with other better known members of the aporphine group.

The cytotoxic effect of α-tomatine in MCF-7 human adenocarcinoma breast cancer cells depends on its interaction with cholesterol in incubation media and does not involve apoptosis induction

In recent years, α-tomatine has been studied for its anticancer activity. In the present study, we focused on the cytotoxic effect of α-tomatine in the MCF-7 human breast adenocarcinoma cell line, its mechanism of action, biotransformation and stability in the culture medium. We observed an inhibition of cell proliferation and viability at concentrations of 6 and 9 μM but then a recovery of cells occurred. The recovery was not caused by the biotransformation of α-tomatine in MCF-7 cells, but by a substantial decrease in the concentration of α-tomatine in the culture medium due to its binding with cholesterol. Regarding the mechanism of action of α-tomatine, we observed no DNA damage, no changes in the levels of the proteins p53 and p21^WAF1/Cip1, and no apoptosis (neither activated caspase-8 and -9, nor sub-G1 peak, or morphological signs). We found a loss of ATP in α-tomatine-treated cells. These results support the conclusion that α-tomatine does not induce apoptosis in the MCF-7 cell line.

Mitoxantrone ability to induce premature senescence in human dental pulp stem cells and human dermal fibroblasts

In this study we assessed the effects of the frequently used chemotherapeutic agent mitoxantrone (MTX) on dental pulp stem cells (DPSCs) and compared it with the response of human dermal fibroblasts (HDFs). DPSCs are valuable source of mesenchymal stem cells which may be extremely useful in a number of clinical applications. It is evident that both normal and tumor cells are being affected during therapy and characterization of these cells under genotoxic stress contributes to the evaluation of their safety usage. In the experiment cells were exposed to doses 5-150 nmol/l MTX. Proliferation of cells was detected by Z2 counter and viability by Vi-Cell XR using Trypan blue exclusion staining. Cell cycle analysis was determinated by flow cytometry, induction of apoptosis by monitoring the activities of caspases. The expression of key proteins was detected by Western blotting. Senescence was analyzed by activity of β-galactosidase and by detection of persisting DSBs-associated γH2AX foci. Exposure of both cell types to lower concentrations of MTX resulted in premature senescence (SIPS), which was accompanied with typical morphological changes, increased activity of senescence-associated β-galactosidase, persisting DSBs-associated γH2AX foci and cell cycle arrest in G2 phase. MTX provokes the activation of p53-p21(WAF1/Cip1) pathway in both cell types and activates cell-cycle inhibitor p16(INK4a) in HDFs, but not in DPSCs. Higher concentrations of MTX induced caspase-mediated apoptosis.

CONCLUSIONS

MTX induces apoptosis or SIPS in both cell types in dependency on MTX doses. Both pathways prevent the proliferation of cells with damaged DNA.

The effect of ATM kinase inhibition on the initial response of human dental pulp and periodontal ligament mesenchymal stem cells to ionizing radiation

PURPOSE

This study evaluates early changes in human mesenchymal stem cells (MSC) isolated from dental pulp and periodontal ligament after γ-irradiation and the effect of ataxia-telangiectasia mutated (ATM) inhibition.

METHODS

MSC were irradiated with 2 and 20 Gy by (60)Co. For ATM inhibition, specific inhibitor KU55933 was used. DNA damage was measured by Comet assay and γH2AX detection. Cell cycle distribution and proteins responding to DNA damage were analyzed 2-72 h after the irradiation.

RESULTS

The irradiation of MSC causes an increase in γH2AX; the phosphorylation was ATM-dependent. Irradiation activates ATM kinase, and the level of p53 protein is increased due to its phosphorylation on serine15. While this phosphorylation of p53 is ATM-dependent in MSC, the increase in p53 was not prevented by ATM inhibition. A similar trend was observed for Chk1 and Chk2. The increase in p21 is greater without ATM inhibition. ATM inhibition also does not fully abrogate the accumulation of irradiated MSC in the G2-phase of the cell-cycle.

CONCLUSIONS

In irradiated MSC, double-strand breaks are tagged quickly by γH2AX in an ATM-dependent manner. Although phosphorylations of p53(ser15), Chk1(ser345) and Chk2(thr68) are ATM-dependent, the overall amount of these proteins increases when ATM is inhibited. In both types of MSC, ATM-independent mechanisms for cell-cycle arrest in the G2-phase are triggered.

Differences in vanadocene dichloride and cisplatin effect on MOLT-4 leukemia and human peripheral blood mononuclear cells

Modern chemotherapy is interested in developing new agents with high efficiency of treatment in low-dose medication strategies, lower side toxicity and stronger specificity to the tumor cells. Vanadocene dichloride (VDC) belongs to the group of the most promising metallocene antitumor agents; however, its mechanism of action and cytotoxicity profile are not fully understood. In this paper we assess cytotoxic effects of VDC in comparison to cisplatin using opposite prototype of cells; human peripheral blood mononuclear (PBMCs) cells and human acute lymphoblastic leukemia cell line (MOLT-4). Our findings showed cytotoxic effect of VDC on leukemia cells, but unfortunately on human peripheral blood mononuclear cells as well. VDC induces apoptosis in leukemia cells; the induction is, however, lower than that of cisplatin, and in contrary to cisplatin, VDC does not induce p53 up-regulation. Cytotoxic effect of VDC on leukemia cells is less pronounced than that of cisplatin and more pronounced in PBMCs than in MOLT-4 cells.

Gamma radiation induces senescence in human adult mesenchymal stem cells from bone marrow and periodontal ligaments

PURPOSE

Mesenchymal stem cells isolated from bone marrow (BM-MSC) and periodontal ligament (PLSC) are cells with high proliferative potential and ability to self-renewal. Characterization of these cells under genotoxic stress conditions contributes to the assessment of their prospective usage. The aim of our study was to evaluate changes in BM-MSC and PLSC caused by ionizing radiation.

METHODS

Human BM-MSC and PLSC were irradiated with the doses up to 20 Gy by Co(60) and observed 13 days; viability, proliferation, apoptosis and senescence induction, and changes in expression and phosphorylation status of related proteins were studied.

RESULTS

Irradiation with the doses up to 20 Gy significantly reduces proliferation, but has no significant effect on cell viability. The activation of tumor suppressor protein 53 (p53) and its phosphorylations on serines 15 and 392 were detected from the first day after irradiation by 20 Gy and remained elevated to day 13. Expression of cyclin-dependent kinases inhibitor 1A (p21(Cip1/Waf1)) increased. The cell cycle was arrested in G2 phase. Instead of apoptosis we have detected hallmarks of stress-induced premature senescence: increase in cyclin-dependent kinases inhibitor 2A (p16(INK4a)) and increased activity of senescence-associated β-galactosidase.

CONCLUSION

Mesenchymal stem cells isolated from bone marrow and periodontal ligament respond to ionizing radiation by induction of stress-induced premature senescence without apparent differences in their radiation response.

Valproic acid decreases the reparation capacity of irradiated MOLT-4 cells

The aim of our work was to evaluate mechanisms leading to radiosensitization of MOLT-4 leukemia cells following valproic acid (VA) treatment. Cells were pretreated with 2 mM VA for 24 h followed by irradiation with a dose of 0.5 or 1 Gy. The effect of both noxae, alone and combined, was detected 1 and 24 hours after the irradiation. Induction of apoptosis was evaluated by a flow cytometry. The extent of DNA damage was further determined by phosphorylation of histone H2AX using confocal microscopy. Changes in protein expression were identified by SDS-PAGE/immunoblotting. Two-millimolar VA increased apoptosis induction after irradiation as well as phosphorylation of H2AX and provokes an increase in the level of p53 and its phosphorylation at Ser392 in 4 h post-irradiation. Likewise, p21 protein reached its maximal expression in 4 h after the irradiation of VA-treated cells. Twenty four hours later, only the p53 phosphorylated at Ser15 was detected. At the same time, the protein mdm2 (negative regulator of p53) was maximally activated. The 24-hour treatment of MOLT-4 leukemia cells with 2 mM VA results in radiosensitizing, increases apoptosis induction, H2AX phosphorylation, and also p53 and p21 activation.

Early changes in L-arginine-nitric oxide metabolic pathways in response to the whole-body gamma irradiation of rats

PURPOSE

Nitric oxide (NO), a reactive radical, is formed in higher amounts from L-arginine by inducible NO synthase (iNOS) during early response to ionizing radiation presumably as a part of signal transduction pathways. This study investigated the changes in L-arginine-NO metabolic pathways within a 24-hour period after whole-body gamma irradiation of rats with the range of low to supra-lethal doses.

MATERIALS AND METHODS

Young adult female Wistar rats received either 0-50 Gy whole-body irradiation or an intraperitoneal injection of bacterial lipopolysaccharide (LPS, 10 mg/kg). Exhaled NO was monitored using chemiluminiscence, nitrite + nitrate (NO(x)) and L-arginine were assayed by high-performance liquid chromatography, and expression of iNOS was determined using Western blot.

RESULTS

Irradiation resulted in a dose-dependent increase of plasma NO(x) to maximum levels which were 4-fold higher compared to controls (p < 0.001). The NO(x) levels increased less in the bronchoalveolar lavage fluid (BAL) (1.7-fold, p < 0.001) and liver homogenate (2.5-fold, p < 0.05), respectively, and were dose-independent. Exhaled NO, lung NO(x), plasma and BAL L-arginine, and the expression of iNOS in lung and liver tissues of irradiated rats and controls were similar. LPS caused a considerable increase (p < 0.001) in exhaled NO (61-fold), NO(x) levels (plasma 34-fold, BAL 6-fold, lung 5-fold, liver 4-fold), and in iNOS expression, respectively.

CONCLUSION

In contrast to the LPS treatment of rats, the radiation-induced changes in L-arginine-NO metabolic pathways are modest, particularly in the airways and lungs. Noninvasive measurement of exhaled NO within a 24-h period following the exposure of rats to ionizing radiation has no value for biodosimetry.

Irradiation of adult human dental pulp stem cells provokes activation of p53, cell cycle arrest, and senescence but not apoptosis

Adult human dental pulp contains stem cells (DPSCs) that are capable of differentiation into osteoblasts, odontoblasts, adipocytes, and neuronal-like cells. Because these cells have potential use in tissue regeneration, herein we characterized the response of DPSC lines to ionizing radiation (IR). These DPSC lines have been developed from the extracted molars of healthy donors. DPSCs were cultivated in a unique media supplemented with epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). Since tissue homeostasis depends on a precise balance among cell proliferation, senescence, and cell death, we explored the effects of IR (2-20 Gy) on the proliferative activity of DPSCs and the molecular pathways involved. Even the highest dose used (20 Gy) did not induce DPSC apoptosis. After irradiation with doses of 6 and 20 Gy, DPSCs accumulated in the G2 phase of the cell cycle. DPSCs responded to IR (20 Gy) with senescence detected as SA-β-galactosidase positivity, beginning on the third day after irradiation. Twenty-four hours after irradiation, p53 and its serine 15 and 392 phosphorylated forms were detected. At this time, p21 (WAF1) was induced. Increases in protein p16 were observed from the third day following irradiation and continued till the end of the examination (Day 13). We conclude that DPSCs respond to IR-induced damage by permanent cell cycle arrest in the G2 phase and by stress-induced premature senescence.

Increased melibiose/rhamnose ratio in bile of rats with acute cholestasis

BACKGROUND AND AIM

Melibiose/rhamnose permeability test is used for noninvasive intestinal mucosa barrier testing. However, the possible escape route of the absorbed saccharides through either intact or impaired blood-biliary barriers has not so far been explored. The objective of the present study was therefore two-fold: First, to describe in detail the biliary pharmacokinetics of melibiose and rhamnose in rats; second, to evaluate the changes of both sugars' pharmacokinetics upon impairment of the blood-biliary barrier by acute extrahepatic cholestasis in rats.

METHODS

Bile duct obstructed (BDO), sham-operated and intact (unoperated) male Wistar rats were administered, 24 h after the appropriate intervention, with a single intravenous dose of melibiose and rhamnose, and a 4-h pharmacokinetic study was performed.

RESULTS

In intact animals, the biliary excretion of melibiose and rhamnose was only 0.06% and 0.4% of the administered dose, respectively, while the urinary excretion accounted for 70.6% and 61.7%, respectively. In BDO animals, the biliary excretion rate of both saccharides, especially that of melibiose, was increased with a consequent 4.4-fold rise of the biliary melibiose/rhamnose ratio, the accepted paracellular permeability indicator. Both, the renal clearance of melibiose and the urinary melibiose/rhamnose ratio remained uninfluenced by cholestasis.

CONCLUSION

The present study is the first to describe in detail pharmacokinetic parameters and the biliary excretion of melibiose and rhamnose in healthy and cholestatic rats. The altered melibiose/rhamnose biliary excretion ratio in BDO rats indicates that the test is able to detect the impairment of the blood-biliary barrier in acute extrahepatic cholestasis.

Antileukemic activity of the combination of ionizing radiation with valproic acid in promyelocytic leukemia cells HL-60

Valproic acid (VA) possesses anticonvulsant as well as anticancer properties of histondeacetylases inhibitor. Incubation of human promyelocytic leukemia cells HL-60 with VA leads to acetylation of nuclear histones H3 and H4. Using 2 mmol/l concentration we proved the expression of protein p21, which relates to the arrest of cell proliferation and decrease in number of cells in S phase of cell cycle. Treatment of HL-60 cells with VA causes their differentiation, proved as increase in CD11b expression. The most widely used method in cancer treatment is radiotherapy. 24 hours after irradiation by the therapeutical dose of 2 Gy, 56% of HL-60 cells are accumulated in G2 phase of cell cycle. VA had no influence on this accumulation, but 24 h-long pretreatment of cells with 1 mmol/l VA provoked higher decrease in cell number in S phase (18%) comparing with only irradiated cells (25%). The results of our work show that VA posseses radiosensitizing properties when applied 24 hours prior to irradiation and that during parallel long-term action of VA and IR the cells undergo differentiation and faster apoptosis induction. Radiosensitizing effect of VA is not caused by abrogation of G2/M cell cycle arrest, but VA induces p21 and leads to differentiation of HL-60 cells.