Melatonin prevents oxidative stress in ovariectomized rats treated with aluminium

The Effect of Aluminum Exposure on Reproductive Ability in the Bank Vole (Myodes glareolus)

Human impact on the environment is steadily increasing the amounts of aluminum in the ecosystems. This element accumulates in plants and water, potentially exposing herbivores to its harmful effect. In heavily polluted sites, a decrease in the density of small rodent populations has been observed. This decline may be caused by many factors, including decreased fertility. The aim of the presented research was to determine how aluminum, administered at concentrations similar to those recorded in industrial districts (Al I = 3 mg/l, Al II = 200 mg/l), affects the reproductive abilities of small rodents. As the indicators of reproductive abilities, body weight, weight of the testes and accessory sex glands of males, and uterus weight of females were estimated. In females, the number of matured follicles (types 6, 7, and 8) was analyzed, while in males, the quantity and quality (matured, viable, swollen, motile, head abnormalities) of epididymal sperm cells were assessed. Moreover, the development of testes, measured by spermatogenic index, was determined. The model species was the bank vole. Our results have proven that aluminum impairs adult individuals' reproductive abilities by decreasing the quality and quantity of sperm cells and by causing morphologically abnormal development of the gonads. However, no difference in male organometric parameters was found, and only in females treated with 3 mg/l Al, the uterus weight was higher than control. No differences were found in the total number of matured follicles. These results suggest that the decline in rodent numbers in industrial districts is due, at least in part, to poorer males' reproductive abilities, resulting from exposure to aluminum contamination.

Daily NO rhythms in peripheral clocks in aging male Wistar rats: protective effects of exogenous melatonin

In mammals suprachiasmatic nucleus (SCN), acts as a light entrainable master clock and by generation of temporal oscillations regulates the peripheral organs acting as autonomous clocks resulting in overt behavioral and physiological rhythms. SCN also controls synthesis and release of melatonin (hormonal message for darkness) from pineal. Nitric Oxide (NO) acts as an important neurotransmitter in generating the phase shifts of circadian rhythms and participates in sleep-wake processes, maintenance of vascular tone as well as signalling and regulating inflammatory processes. Aging is associated with disruption of circadian timing system and decline in endogenous melatonin leading to several physiological disorders. Here we report the effect of aging on NO daily rhythms in various peripheral clocks such as kidney, intestine, liver, heart, lungs and testis. NO levels were measured at zeitgeber time (ZT) 0, 6, 12 and 18 in these tissues using Griess assay in male Wistar rats. Aging resulted in alteration of NO levels as well as phase of NO in both 12 and 24 months groups. Correlation analysis demonstrated loss of stoichiometric interaction between the various peripheral clocks with aging. Age induced alterations in NO daily rhythms were found to be most significant in liver and, interestingly least in lungs. Neurohormone melatonin, an endogenous synchroniser and an antiaging agent decreases with aging. We report further differential restoration with exogenous melatonin administration of age induced alterations in NO daily rhythms and mean levels in kidney, intestine and liver and the stoichiometric interactions between the various peripheral clocks.

Orchiectomy attenuates oxidative stress induced by aluminum in rats

The aim of this work was to study whether the increase in antioxidant defenses associated with orchiectomy may account for the reduced susceptibility to aluminum (Al) in male kidney and also to examine whether the reduced antioxidant defenses are associated with androgen levels in orchiectomized (ORX) rats treated with testosterone propionate (TP). Rats were divided into nine groups, namely, intact males (without treatment, treated with sodium lactate, and treated with Al), sham males, ORX males (without treatment, treated with sodium lactate, treated with TP, treated with Al, and treated with TP and Al). Al groups were chronically treated with aluminum lactate for 12 weeks (0.575 mg Al/100 g of body weight, intraperitoneally, three times per week). We reported that ORX rats treated with Al had significantly less lipid peroxidation and an increased level of reduced glutathione (GSH) and GSH/oxidized glutathione ratio in the kidney when compared with intact and TP-treated ORX rats. The activity of superoxide dismutase, catalase, and glutathione peroxidase in ORX rats was much greater than in intact or TP-administered ORX rats. Castration reduced the glomerular alterations caused by Al as well as the number of necrotic tubular cells and nuclear abnormalities. However, we observed a slight alteration in brush border, dilation of proximal tubules, mononuclear infiltrates, and interstitial fibrosis. Castrated males treated with TP showed that this intervention cancels the protective effect of the ORX. This finding suggests that androgens contribute to the development of renal alterations and proteinuria in rats treated with Al. Our results showed that ORX rats are protected against the induction of oxidative stress by Al, but the morphological damage to the kidney tissue induced by the cation was only reduced. Male intact rats treated with Al had more severe glomerulosclerosis, tubular damage, and proteinuria than ORX rats.

Systematic review of potential health risks posed by pharmaceutical, occupational and consumer exposures to metallic and nanoscale aluminum, aluminum oxides, aluminum hydroxide and its soluble salts

Abstract Aluminum (Al) is a ubiquitous substance encountered both naturally (as the third most abundant element) and intentionally (used in water, foods, pharmaceuticals, and vaccines); it is also present in ambient and occupational airborne particulates. Existing data underscore the importance of Al physical and chemical forms in relation to its uptake, accumulation, and systemic bioavailability. The present review represents a systematic examination of the peer-reviewed literature on the adverse health effects of Al materials published since a previous critical evaluation compiled by Krewski et al. (2007) . Challenges encountered in carrying out the present review reflected the experimental use of different physical and chemical Al forms, different routes of administration, and different target organs in relation to the magnitude, frequency, and duration of exposure. Wide variations in diet can result in Al intakes that are often higher than the World Health Organization provisional tolerable weekly intake (PTWI), which is based on studies with Al citrate. Comparing daily dietary Al exposures on the basis of "total Al"assumes that gastrointestinal bioavailability for all dietary Al forms is equivalent to that for Al citrate, an approach that requires validation. Current occupational exposure limits (OELs) for identical Al substances vary as much as 15-fold. The toxicity of different Al forms depends in large measure on their physical behavior and relative solubility in water. The toxicity of soluble Al forms depends upon the delivered dose of Al(+3) to target tissues. Trivalent Al reacts with water to produce bidentate superoxide coordination spheres [Al(O2)(H2O4)(+2) and Al(H2O)6 (+3)] that after complexation with O2(•-), generate Al superoxides [Al(O2(•))](H2O5)](+2). Semireduced AlO2(•) radicals deplete mitochondrial Fe and promote generation of H2O2, O2 (•-) and OH(•). Thus, it is the Al(+3)-induced formation of oxygen radicals that accounts for the oxidative damage that leads to intrinsic apoptosis. In contrast, the toxicity of the insoluble Al oxides depends primarily on their behavior as particulates. Aluminum has been held responsible for human morbidity and mortality, but there is no consistent and convincing evidence to associate the Al found in food and drinking water at the doses and chemical forms presently consumed by people living in North America and Western Europe with increased risk for Alzheimer's disease (AD). Neither is there clear evidence to show use of Al-containing underarm antiperspirants or cosmetics increases the risk of AD or breast cancer. Metallic Al, its oxides, and common Al salts have not been shown to be either genotoxic or carcinogenic. Aluminum exposures during neonatal and pediatric parenteral nutrition (PN) can impair bone mineralization and delay neurological development. Adverse effects to vaccines with Al adjuvants have occurred; however, recent controlled trials found that the immunologic response to certain vaccines with Al adjuvants was no greater, and in some cases less than, that after identical vaccination without Al adjuvants. The scientific literature on the adverse health effects of Al is extensive. Health risk assessments for Al must take into account individual co-factors (e.g., age, renal function, diet, gastric pH). Conclusions from the current review point to the need for refinement of the PTWI, reduction of Al contamination in PN solutions, justification for routine addition of Al to vaccines, and harmonization of OELs for Al substances.

The effect of zinc deficiency and zinc supplementation on element levels in the bone tissue of ovariectomized rats: histopathologic changes

OBJECTIVE

Study aimed to determine the effects of zinc supplementation/deficiency on the histological structure and elements levels in bone tissue in ovariectomized rats.

METHODS

The study included 40 Sprague-Dawley type adult female rats, divided as follows: Control, ovariectomized, ovariectomized + zinc supplemented, ovariectomized + zinc deficient groups. At the end of the study bone tissues (femur) were collected to determine the levels of calcium, phosphorus, magnesium, zinc, iron, aluminium, chrome, lithium, lead, nickel, and manganese. The bone tissue was examined for histopathology.

RESULTS

Ovariectomy leaded to significant decrease in magnesium. Zinc supplementation to ovariectomized rats restored the reduced calcium, phosphorus, zinc. However, zinc deficiency in ovariectomized rats further reduced calcium, phosphorus, zinc, and manganese levels. Zinc deficiency in ovariectomized significantly increased Al, Cr, Li, Pb, and Ni levels. Tissue integrity was impaired due to ovariectomy and zinc deficiency.

CONCLUSION

Ovariectomy and zinc deficiency leads significant decreases elements of the bone.

A review of metal-catalyzed molecular damage: protection by melatonin

Metal exposure is associated with several toxic effects; herein, we review the toxicity mechanisms of cadmium, mercury, arsenic, lead, aluminum, chromium, iron, copper, nickel, cobalt, vanadium, and molybdenum as these processes relate to free radical generation. Free radicals can be generated in cells due to a wide variety of exogenous and endogenous processes, causing modifications in DNA bases, enhancing lipid peroxidation, and altering calcium and sulfhydryl homeostasis. Melatonin, an ubiquitous and pleiotropic molecule, exerts efficient protection against oxidative stress and ameliorates oxidative/nitrosative damage by a variety of mechanisms. Also, melatonin has a chelating property which may contribute in reducing metal-induced toxicity as we postulate here. The aim of this review was to highlight the protective role of melatonin in counteracting metal-induced free radical generation. Understanding the physicochemical insights of melatonin related to the free radical scavenging activity and the stimulation of antioxidative enzymes is of critical importance for the development of novel therapeutic strategies against the toxic action of these metals.

Determination of aluminium induced metabolic changes in mice liver: a Fourier transform infrared spectroscopy study

In this study, we made a new approach to evaluate aluminium induced metabolic changes in liver tissue of mice using Fourier transform infrared spectroscopy analysis taking one step further in correlation with strong biochemical evidence. This finding reveals the alterations on the major biochemical constituents, such as lipids, proteins, nucleic acids and glycogen of the liver tissues of mice. The peak area value of amide A significantly decrease from 288.278±3.121 to 189.872±2.012 between control and aluminium treated liver tissue respectively. Amide I and amide II peak area value also decrease from 40.749±2.052 to 21.170±1.311 and 13.167±1.441 to 8.953±0.548 in aluminium treated liver tissue respectively. This result suggests an alteration in the protein profile. The absence of olefinicCH stretching band and CO stretching of triglycerides in aluminium treated liver suggests an altered lipid levels due to aluminium exposure. Significant shift in the peak position of glycogen may be the interruption of aluminium in the calcium metabolism and the reduced level of calcium. The overall findings exhibit that the liver metabolic program is altered through increasing the structural modification in proteins, triglycerides and quantitative alteration in proteins, lipids, and glycogen. All the above mentioned modifications were protected in desferrioxamine treated mice. Histopathological results also revealed impairment of aluminium induced alterations in liver tissue. The results of the FTIR study were found to be in agreement with biochemical studies and which demonstrate FTIR can be used successfully to indicate the molecular level changes.

Melatonin administration differentially affects age-induced alterations in daily rhythms of lipid peroxidation and antioxidant enzymes in male rat liver

A central clock/pacemaker, suprachiasmatic nuclei of the hypothalamus coordinates and entrains circadian oscillations in the peripheral tissues such as the liver, kidney, heart, lungs etc. called peripheral clocks. These also have endogenous circadian oscillations. The circadian rhythms of antioxidants present in cytosol signify redox state of the cell during day/night cycle. The liver has a major impact on homeostasis through its control on serum protein composition and plays a pivotal role in the metabolism of nutrients, drugs, hormones, and metabolic waste products and undergoes substantial changes in structure and function upon aging. In present study, the temporal patterns of oxidative stress indicators in liver were studied. Daily rhythms of lipid peroxidation end products, reduced glutathione (GSH), oxidized glutathione (GSSG) and antioxidant enzymes such as glutathione peroxidase (GPx), superoxide dismutase (SOD) and catalase (CAT) were studied in liver at variable time points (Zeitgeber Time (ZT) 0, 6, 12 and 18) in three age groups: 3 (adult), 12 and 24 months old male Wistar rats. There was increase in oxidative stress in 12 and 24 months old rats indicated through a significant increase in lipid peroxidation, decrease in GSH/GSSG ratio and antioxidant enzyme activities. In 3 months old rats, lipid peroxidation was maximum at ZT-12 whereas GSH, SOD and CAT activities were minimum at ZT-12. The maximum level in 24 h i.e., acrophases of lipid peroxidation, GPx, SOD and CAT activities in liver cell free extracts altered upon aging. As melatonin, messenger of darkness, an endogenous synchronizer of rhythm, an antioxidant and an antiaging drug, declines with aging we studied the effects of melatonin on activities of these antioxidant enzymes in aging rats. Melatonin administration resulted in differential restoration of acrophases, amplitude, mean as well as daily rhythms of lipid peroxidation and antioxidants in liver of 12 and 24 months old rats.