Role of melatonin mediated G-CSF induction in hematopoietic system of gamma-irradiated mice.

AIMS: Hematopoietic acute radiation syndrome (H-ARS) can cause lethality, and therefore, the necessity of a safe radioprotector. The present study was focused on investigating the role of melatonin in granulocytes colony-stimulating factor (G-CSF) and related mechanisms underlying the reduction of DNA damage in hematopoietic system of irradiated mice. MAIN METHODS: C57BL/6 male mice were exposed to 2, 5, and 7.5Gy of whole-body irradiation (WBI), 30 min after intra-peritoneal administration of melatonin with different doses. Mice were sacrificed at different time intervals after WBI, and bone marrow, splenocytes, and peripheral blood lymphocytes were isolated for studying various parameters including micronuclei (MN), cell cycle, comet, γ-H2AX, gene expression, amino acid profiling, and hematology. KEY FINDINGS: Melatonin100mg/kg ameliorated radiation (7.5Gy and 5Gy) induced MN frequency and cell death in bone marrow without mortality. At 24 h of post-WBI (2Gy), the frequency of micronucleated polychromatic erythrocytes (mnPCE) with different melatonin doses revealed 20 mg/kg as optimal i.p. dose for protecting the hematopoietic system against radiation injury. In comet assay, a significant reduction in radiation-induced % DNA tail (p ≤ 0.05) was observed at this dose. Melatonin reduced γ-H2AX foci/cell and eventually reached to the control level. Melatonin also decreased blood arginine levels in mice after 24 h of WBI. The gene expression of G-CSF, Bcl-2-associated X protein (BAX), and Bcl2 indicated the role of melatonin in G-CSF regulation and downstream pro-survival pathways along with anti-apoptotic activity. SIGNIFICANCE: The results revealed that melatonin recovers the hematopoietic system of irradiated mice by inducing G-CSF mediated radioprotection.

Sesamol ameliorates radiation induced DNA damage in hematopoietic system of whole body γ-irradiated mice.

Ionizing radiation exposure is harmful and at high doses can lead to acute hematopoietic radiation syndrome. Therefore, agents that can protect hematopoietic system are important for development of radioprotector. Sesamol is a potential molecule for development of radioprotector due to its strong free radical scavenging and antioxidant properties. In the present study, sesamol was evaluated for its role in DNA damage and repair in hematopoietic system of γ-irradiated CB57BL/6 mice and compared with amifostine. C57BL/6 male mice were administered with sesamol 20 mg/kg (i.p.) followed by 2 Gy whole body irradiation (WBI) at 30 min. Mice were sacrificed at 0.5, 3, 24 h postirradiation; bone marrow, splenocytes, and peripheral blood lymphocytes were isolated to measure DNA damages and repair using alkaline comet,γ-H2AXand micronucleus assays. An increase in % of tail DNA was observed in all organs of WBI mice. Whereas in pre-administered sesamol reduced %DNA in tail (P ≤ 0.05). Sesamol has also reduced formation of radiation induced γ-H2AX foci after 0.5 h in these organs and further lowered to respective control values at 24 h of WBI. Similar reduction of % DNA in tail and γ-H2AX foci were observed with amifostine (P ≤ 0.05). Analysis of mnPCE frequency at 24 h has revealed similar extent of protection by sesamol and amifostine. Interestingly, both sesamol and amifostine, alone and with radiation, also increased the granulocytes count significantly compared to the control (P ≤ 0.05). These findings suggest that sesamol has strong potential to protect hematopoietic system by lowering radiation induced DNA damages and can prevent acute hematopoietic syndrome in mice. Environ. Mol. Mutagen. 59:79-90, 2018. © 2017 Wiley Periodicals, Inc.

Sesamol attenuates genotoxicity in bone marrow cells of whole-body γ-irradiated mice.

Ionising radiation causes free radical-mediated damage in cellular DNA. This damage is manifested as chromosomal aberrations and micronuclei (MN) in proliferating cells. Sesamol, present in sesame seeds, has the potential to scavenge free radicals; therefore, it can reduce radiation-induced cytogenetic damage in cells. The aim of this study was to investigate the radioprotective potential of sesamol in bone marrow cells of mice and related haematopoietic system against radiation-induced genotoxicity. A comparative study with melatonin was designed for assessing the radioprotective potential of sesamol. C57BL/6 mice were administered intraperitoneally with either sesamol or melatonin (10 and 20mg/kg body weight) 30 min prior to 2-Gy whole-body irradiation (WBI) and sacrificed after 24h. Total chromosomal aberrations (TCA), MN and cell cycle analyses were performed using bone marrow cells. The comet assay was performed on bone marrow cells, splenocytes and lymphocytes. Blood was drawn to study haematological parameters. Prophylactic doses of sesamol (10 and 20mg/kg) in irradiated mice reduced TCA and micronucleated polychromatic erythrocyte frequency in bone marrow cells by 57% and 50%, respectively, in comparison with radiation-only groups. Sesamol-reduced radiation-induced apoptosis and facilitated cell proliferation. In the comet assay, sesamol (20mg/kg) treatment reduced radiation-induced comets (% DNA in tail) compared with radiation only (P < 0.05). Sesamol also increased granulocyte populations in peripheral blood similar to melatonin. Overall, the radioprotective efficacy of sesamol was found to be similar to that of melatonin. Sesamol treatment also showed recovery of relative spleen weight at 24h of WBI. The results strongly suggest the radioprotective efficacy of sesamol in the haematopoietic system of mice.

Nordihydroguiaretic acid attenuates skin tumorigenesis in Swiss albino mice with the condition of topical co-administration of an immunosuppressant.

Drug and chemically-induced immunosuppression has been implicated as a confounding factor for cancer development. Management of cancer in such situation is often a challenging task. We tested the efficacy of nordihydroguiaretic acid (NDGA) against immunosuppressant tacrolimus-induced augmentation of mouse skin tumorigenesis. It was observed that topical administration of tacrolimus significantly accelerated the tumor promotion events in dimethylbenz(a)anthracene (DMBA)-initiated and 12-O-tetradecanoylphorbol-13-acetate (TPA) promoted two-stage mouse skin carcinogenesis, which were accompanied by reduced CD4(+)/CD8(+) ratio of lymph nodes and serum IL-2 level. NDGA pre-treatment before each TPA application reduced the tumor incidence, its multiplicity and volume together with improvement in histopathological alterations and decrease in proliferating cell nuclear antigen (PCNA) labeling index (LI). However, NDGA had no significant influence on the immunosuppressive effect of tacrolimus. The present study demonstrates chemopreventive effect of NDGA in normal as well as in the condition of immunosuppression. Thus, NDGA has the potential to inhibit or delay the onset of tumor development during immunosuppressive regimen.

Sulforaphane mitigates genotoxicity induced by radiation and anticancer drugs in human lymphocytes.

Sulforaphane, present in cruciferous vegetables such as broccoli, is a dietary anticancer agent. Sulforaphane, added 2 or 20 h following phytohemaglutinin stimulation to cultured peripheral blood lymphocytes of individuals accidentally exposed to mixed γ and ß-radiation, reduced the micronucleus frequency by up to 70%. Studies with whole blood cultures obtained from healthy volunteers confirmed the ability of sulforaphane to ameliorate γ-radiation-induced genotoxicity and to reduce micronucleus induction by other DNA-damaging anticancer agents, such as bleomycin and doxorubicin. This reduction in genotoxicity in lymphocytes treated at the G(0) or G(1) stage suggests a role for sulforaphane in modulating DNA repair. Sulforaphane also countered the radiation-induced increase in lymphocyte HDAC activity, to control levels, when cells were treated 2 h after exposure, and enhanced histone H4 acetylation status. Sulforaphane post-irradiation treatment enhanced the CD 34(+)Lin(-) cell population in culture. Sulforaphane has therapeutic potential for management of the late effects of radiation.

Calcium channel antagonist (nifedipine) attenuates Plasmodium berghei-specific T cell immune responses in Balb/C mice.

Nifedipine and verapamil (Martin et al. Science 1987;235:899-901) are a class of calcium channel blockers involved in the reversal of chloroquine (CQ) drug resistance in CQ-sensitive Plasmodium spp. Nifedipine alters calcium-dependent functions of macrophages and neutrophils during Plasmodium berghei malaria. However, knowledge of nifedipine-induced immunomodulation of T cell functions during P. berghei malaria is still limited. We investigated the effect of nifedipine on the immune status of splenic T cells during P. berghei malaria. The intracellular calcium levels were determined in the FURA-2A/M loaded T cells by spectrofluorometry. Splenic T cell proliferation, phosphatidylserine (PS) externalization, Fas expression and Bcl2/Bax expression were determined by flow cytometry. We report a significant increase in mean percent parasitemia in nifedipine-treated and P. berghei-infected mice. Although nifedipine treatment alone did not affect the resting state free calcium levels in splenic T cells, the rise in intracellular calcium levels of T cells following P. berghei infection was significantly less in nifedipine-treated mice compared to untreated groups at various parasitemia levels. Antigen-specific splenic T cell proliferation and apoptosis was ablated in nifedipine-treated and untreated groups at various parasitemia levels. The study unequivocally reflects the suppression of P. berghei-specific T cell immune responses by nifedipine.

Flow-cytometric analysis of reactive oxygen species in peripheral blood mononuclear cells of patients with thyroid dysfunction.

BACKGROUND: Thyroid hormones are major regulators of energy metabolism and increased levels of the hormones (hyperthyroidism) results in an increase in the metabolic rate. Thyroid dysfunction causing alteration in hormone secretion leads to perturbations in the metabolic status. The hypermetabolic state may cause increased generation of reactive oxygen species (ROS), leading to oxidative stress in these patients. This study was carried out to verify our proposition by measuring the ROS in the terminally differentiated cells like the peripheral blood mononuclear cells of the patients. METHODS: Flow-cytometric analysis of the ROS was carried out using 2',7' dichlorofluorescein diacetate in the isolated peripheral blood mononuclear cells of the subjects. RESULTS: ROS generation was found to be 3-folds higher in hyperthyroids as compared with euthyroids and hypothyroids and this was not found to be gender specific. CONCLUSIONS: Hyperthyroidism results in ROS generation in patients, which can be detected flow cytometrically in the peripheral blood mononuclear cells. Hence, this could complement the other thyroid function tests facilitating the diagnosis and design of appropriate therapy.

Acetoxy drug: protein transacetylase catalyzed activation of human platelet nitric oxide synthase by polyphenolic peracetates.

An enhanced intracellular level of Nitric oxide (NO) is essential to ameliorate several pathological conditions of heart and vasculature necessitating the activation of NOS. We have projected in this report the acetylation of eNOS by polyphenolic peracetates (PA) catalyzed by the novel enzyme acetoxy drug: protein transacetylase (TAase) discovered in our laboratory as an unambiguous way of activating NOS which results in the manifestation of physiological action. The human platelet was chosen as the experimental system in order to validate the aforementioned proposition. PA caused profound irreversible activation of platelet NADPH cytochrome c reductase mediated by TAase. The convincing biochemical evidences are presented to show that PA could cause acetylation of the reductase domain of NOS leading to the activation of eNOS in tune with their specificities to platelet TAase. As a result, the enhanced level of NO due to activation of platelet eNOS by PA was found to inhibit the ADP-induced platelet aggregation. The present studies highlight for the first time the role of PA as the novel potent agent for enhancing the intracellular NO levels.