Abed Zubidat - Academia.edu (original) (raw)

Papers by Abed Zubidat

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2007

To examine the effect of adrenergic blockade on daily rhythms of rectal body temperature (T b), u... more To examine the effect of adrenergic blockade on daily rhythms of rectal body temperature (T b), urine production rate, and melatonin (MEL; measured as urinary 6-sulfatoxymelatonin; 6-SMT), social voles Microtus socialis received a single intra-peritoneal injection of either prazosin (PRAZ, 1 mg/kg) or propranolol (PROP, 4.5 mg/kg); αand β-adrenergic blocking agents respectively, 1 h prior to scotophase onset (light/dark, 12L:12D; lights on 07:00 h). Both blockers caused significant decrease in T b values mainly during scotophase. Nocturnal urine production rates were higher for M. socialis treated with the drugs compared with controls. Overall, urine production rates were systematically higher in PROP-voles over the 24 h period when compared with PRAZ-voles; however these differences were not statistically significant. Interestingly, PROP caused significant elevation in urinary 6-SMT at the second half of the dark phase, whereas PRAZ had no effects. These data suggest that the mechanisms regulating MEL synthesis and thermoregulatory responses in M. socialis are different from those described in other rodents' species. Importantly, the data also suggest that the β-blockade-induced elevation in MEL levels may be directly associated with increased urination in M. socialis.

Sustainability

Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transi... more Artificial light at night (ALAN) is increasing exponentially worldwide, accelerated by the transition to new efficient lighting technologies. However, ALAN and resulting light pollution can cause unintended physiological consequences. In vertebrates, production of melatonin—the “hormone of darkness” and a key player in circadian regulation—can be suppressed by ALAN. In this paper, we provide an overview of research on melatonin and ALAN in vertebrates. We discuss how ALAN disrupts natural photic environments, its effect on melatonin and circadian rhythms, and different photoreceptor systems across vertebrate taxa. We then present the results of a systematic review in which we identified studies on melatonin under typical light-polluted conditions in fishes, amphibians, reptiles, birds, and mammals, including humans. Melatonin is suppressed by extremely low light intensities in many vertebrates, ranging from 0.01–0.03 lx for fishes and rodents to 6 lx for sensitive humans. Even lower...

Epigenetics [Working Title]

Epigenetics is an important tool for understanding the relation between environmental exposures a... more Epigenetics is an important tool for understanding the relation between environmental exposures and cellular functions, including metabolic and proliferative responses. At our research center, we have devolved a mouse model for characterizing the relation between exposure to artificial light at night (ALAN) and both global DNA methylation (GDM) and breast cancer. Generally, the model describes a close association between ALAN and cancer responses. Cancer responses are eminent at all light spectra, with the prevalent manifestation at the shorter end of the visible spectrum. ALAN-induced pineal melatonin suppression is the principal candidate mechanism mediating the environmental exposure at the molecular level by eliciting aberrant GDM modifications. The carcinogenic potential of ALAN can be ameliorated in mice by exogenous melatonin treatment. In contrast to BALB/c mice, humans are diurnal species, and thus, it is of great interest to evaluate the ALAN-melatonin-GDM nexus also in a diurnal mouse model. The fat sand rat (Psammomys obesus) provides an appropriate model as its responses to photoperiod are comparable to humans. Interestingly, melatonin and thyroxin have opposite effects on GDM levels in P. obesus. Melatonin, GDM levels, and even thyroxin may be utilized as novel biomarkers for detection, staging, therapy, and prevention of breast cancer progression.

Chronobiology International

Journal of Cancer Biology and Therapeutics

In an attempt to reduce Carbon Dioxide production, lighting technologies are aiming toward the de... more In an attempt to reduce Carbon Dioxide production, lighting technologies are aiming toward the developing of energetically efficient illumination sources as light-emitting diodes (LEDs). LED lamps emit light at short-wavelengths close to the sensitivity peak of melatonin suppression and expected to further exacerbate circadian disruption and cancer risk from increasing exposure to artificial light-at-night (ALAN). We report the effect of ALAN (1x30 min per night) emitted from yellow incandescent or blue-white LED bulbs and melatonin on urinary 6-sulfatoxymelatonin (6-SMT), tumor growth, and global DNA methylation in 4T1 inoculated Balb/c female mice. Blue ALAN significantly decreased 6-SMT, increased tumor growths, and promoted metastasis formation verses yellow exposure. In blue-treated mice, DNA methylation levels were decreased in tumor and liver cells but not in lung and spleen cells compared with yellow-treated mice. Melatonin treatment inhibited tumor growth, reduced metastasi...

Cancer Control

Lighting technology is rapidly advancing toward shorter wavelength illuminations that offer energ... more Lighting technology is rapidly advancing toward shorter wavelength illuminations that offer energy-efficient properties. Along with this advantage, the increased use of such illuminations also poses some health challenges, particularly breast cancer progression. Here, we evaluated the effects of artificial light at night (ALAN) of 4 different spectral compositions (500-595 nm) at 350 Lux on melatonin suppression by measuring its urine metabolite 6-sulfatoxymelatonin, global DNA methylation, tumor growth, metastases formation, and urinary corticosterone levels in 4T1 breast cancer cell-inoculated female BALB/c mice. The results revealed an inverse dose-dependent relationship between wavelength and melatonin suppression. Short wavelength increased tumor growth, promoted lung metastases formation, and advanced DNA hypomethylation, while long wavelength lessened these effects. Melatonin treatment counteracted these effects and resulted in reduced cancer burden. The wavelength suppressio...

Journal of Basic and Clinical Physiology and Pharmacology

Both obesity and breast cancer are already recognized worldwide as the most common syndromes in o... more Both obesity and breast cancer are already recognized worldwide as the most common syndromes in our modern society. Currently, there is accumulating evidence from epidemiological and experimental studies suggesting that these syndromes are closely associated with circadian disruption. It has been suggested that melatonin (MLT) and the circadian clock genes both play an important role in the development of these syndromes. However, we still poorly understand the molecular mechanism underlying the association between circadian disruption and the modern health syndromes. One promising candidate is epigenetic modifications of various genes, including clock genes, circadian-related genes, oncogenes, and metabolic genes. DNA methylation is the most prominent epigenetic signaling tool for gene expression regulation induced by environmental exposures, such as artificial light-at-night (ALAN). In this review, we first provide an overview on the molecular feedback loops that generate the circ...

Chronobiology International, 2015

Philosophical transactions of the Royal Society of London. Series B, Biological sciences, Jan 5, 2015

The adverse effects of excessive use of artificial light at night (ALAN) are becoming increasingl... more The adverse effects of excessive use of artificial light at night (ALAN) are becoming increasingly evident and associated with several health problems including cancer. Results of epidemiological studies revealed that the increase in breast cancer incidents co-distribute with ALAN worldwide. There is compiling evidence that suggests that melatonin suppression is linked to ALAN-induced cancer risks, but the specific genetic mechanism linking environmental exposure and the development of disease is not well known. Here we propose a possible genetic link between environmental exposure and tumorigenesis processes. We discuss evidence related to the relationship between epigenetic remodelling and oncogene expression. In breast cancer, enhanced global hypomethylation is expected in oncogenes, whereas in tumour suppressor genes local hypermethylation is recognized in the promoter CpG chains. A putative mechanism of action involving epigenetic modifications mediated by pineal melatonin is d...

Artificial light at night is becoming a worldwide problem in both developed as well as the develo... more Artificial light at night is becoming a worldwide problem in both developed as well as the developing countries. Massive new building programs in urban areas and increased illumination in public spaces create light pollution. There is no doubt that artificial lighting increases the time we have for work and leisure. However, there are environmental and health issues associated with exposure to light at night. The use of incandescent bulbs is in the process of being phased out in favor of so-called "environmentally friendly " illumination. This is light produced by devices such as light emitting diodes (LEDs) which emit a shorter wavelength of light than regular incandescent bulbs. Indeed, LED illumination is considered the illumination of the future for domestic and public spaces. However, chronobiologists and other scientists are becoming increasingly aware of the health issued associated with the use of such illumination. In this paper, the authors want to share their fi...

Journal of Experimental Biology, 2013

We tested the effects of photoperiod, water and food availability on body mass, reproductive stat... more We tested the effects of photoperiod, water and food availability on body mass, reproductive status and arginine vasopressin receptor 1A (Avpr1a) mRNA expression in males of desert-adapted golden spiny mice, Acomys russatus. In Experiment 1, males were acclimated to short-day (SD; 8h:16h light:dark) or long-day (LD; 16h:8h light:dark) photoperiods with either saline (control) or vasopressin treatment for 3weeks. The results of this experiment revealed that under control conditions, SD mice increased body mass by ~5% while LD mice decreased it by ~4%. SD photoperiod had no effect on reproductive status and leptin levels, whereas LD males increased testes mass and serum testosterone, but the photoperiod had no effect on leptin levels. Vasopressin administration decreased LD-induced reproductive enhancement. Because no consistent effect of SD treatment was found on reproductive status, Experiment 2 was carried out only on LD-acclimated males kept under 75% food restriction (decrease from ad libitum) with saline or leptin treatment. Body mass, testes mass, serum testosterone, leptin concentrations and Avpr1a mRNA expression were measured. Food restriction remarkably decreased body mass, with a more potent effect in leptin-treated males, showing enhanced reproductive status and a significant increase in serum leptin compared with controls. Avpr1a expression was significantly upregulated in LD, vasopressin-treated and food-restricted males, with higher levels in the hypothalamus compared with the testes. We conclude that in A. russatus, LD photoperiod interacts with water and food availability to advance reproductive responses. Avpr1a is suggested to integrate nutritional and osmotic signals to optimize reproduction by modulating reproductive and energetic neuroendocrine axes at the central level. The interaction between photoperiod and other environmental cues is of an adaptive value to desert-adapted small rodents for timing reproduction in unpredictable ecosystems such as extreme deserts.

Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2008

We compared body temperature (T b) and metabolic rates, measured as oxygen consumption (VO 2), da... more We compared body temperature (T b) and metabolic rates, measured as oxygen consumption (VO 2), daily rhythms of two sibling species of the genus Mastomys. We also studied their responses to long day (16L: 8D, LD) and short day (8L: 16D, SD) photoperiod manipulations at a constant ambient temperature of 26 + 1°C. We noted significant differences in T b and VO 2 daily rhythm patterns, under SD and LD-acclimation between the sibling species. These differences explain adaptation to the climatic conditions that prevail in the different ecosystems where these species live. To the best of our knowledge, this is the first time that physiological differences between the two siblings are measured by using chronobiological methods.

Chronobiology International, 2007

In mammals, nocturnal light pulses (NLP) have been demonstrated to affect physiology and behavior... more In mammals, nocturnal light pulses (NLP) have been demonstrated to affect physiology and behavior. However, the impact of NLP as a stressor has been less broadly examined. The purpose of this study was to examine the effect of NLP (three 15 min 450 lux light pulses) during each scotophase on both thermoregulation and endocrine stress responses under short-day (SD; 8L:16D) acclimation. Voles were acclimated to either SD (SD voles) or SD+NLP (NLP voles). Resistance to cold was estimated by measurements of body temperature (T(b)) during cold exposure (5 degrees C). Daily rhythms of energy expenditure (calculated from oxygen consumption), urine production, and urinary adrenaline and serum cortisol levels were measured. T(b) values of SD voles were generally unaffected by the cold stimulus, whereas in NLP voles, resistance to cold was markedly lowered. While SD- and NLP voles showed similar ultradian characteristics in energy expenditure with a period of 3.5 h, mean energy expenditure levels were lowest for voles exposed to NLP-treatment. In SD voles, but not in NLP voles, urine production rates showed clear time variations and were consistently highest for SD voles, with significant differences during the scotophase. Both mean total urinary adrenaline and serum cortisol levels were significantly elevated in NLP-treated voles compared with the control group. Taken together, the results suggest that NLP negatively affects winter acclimatization of thermoregulatory mechanisms of M. socialis, probably by mimicking summer acclimatization, and consequently the thermoregulatory mechanisms respond inappropriately to ambient conditions. One important finding of this study is that NLP may act as a stressor and correspondingly impose a major threat to the physiological homeostasis of M. socialis, such that over-winter survival might be compromised.