Role of ascorbic acid in scavenging free radicals and lead toxicity from biosystems

Ascorbic acid as antioxidant

Ascorbic acid, as one of the basic exogenous vitamins, is known for its tremendous antioxidant properties. This review has been prepared to show not only the importance of ascorbic acid as a free radical scavenger, but also to summarize its antioxidant action based on other mechanisms, including activation of intracellular antioxidant systems. Ascorbic acid interacts with small molecule antioxidants, including tocopherol, glutathione and thioredoxin, but also can stimulate the biosynthesis and activation of antioxidant enzymes, such as superoxide dismutase, catalase or glutathione peroxidase. Moreover, ascorbic acid promotes the activity of several transcription factors (Nrf2, Ref-1, AP-1), which enables the expression of genes encoding antioxidant proteins. Additionally, it supports the action of other exogenous antioxidants, mainly polyphenols. In this connection, both DNA, protein and lipids are protected against oxidation. Although ascorbic acid has strong antioxidant properties, it can also have pro-oxidant effects in the presence of free transition metals. However, its role in prevention of DNA mutation and cellular apoptosis, especially in relation to cancer cells is controversial.

Antioxidative and Anti-Inflammatory Activity of Ascorbic Acid

Ascorbic acid, as a one of the basic exogenous vitamins, occurs in the body in the form of ascorbate, known for its strong antioxidant and anti-inflammatory properties. The presented review shows not only the importance of ascorbate as a free radical scavenger but also summarizes its antioxidant action based on other mechanisms, including the activation of intracellular antioxidant systems and its effect on the NFκB/TNFα pathway and apoptosis. Ascorbate interacts with small-molecule antioxidants, including tocopherol, glutathione, and thioredoxin; it can also stimulate biosynthesis and the activation of antioxidant enzymes, such as superoxide dismutase, catalase, or glutathione peroxidase. Moreover, ascorbate promotes the activity of transcription factors (Nrf2, Ref-1, AP-1), which enables the expression of genes encoding antioxidant proteins. Additionally, it supports the action of other exogenous antioxidants, mainly polyphenols. In this regard, both DNA, proteins, and lipids are protected against oxidation, leading to an inflammatory reaction and even cell death. Although ascorbate has strong antioxidant properties, it can also have pro-oxidant effects in the presence of free transition metals. However, its role in the prevention of DNA mutation, inflammation, and cell apoptosis, especially in relation to cancer cells, is controversial.

Degradation kinetics and isomerization of 5-O-caffeoylquinic acid under ultrasound: Influence of epigallocatechin gallate and vitamin C

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The increase of pH accelerated the degradation of 5-CQA.

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The isomerization of 5-CQA was found at neutral and alkaline conditions.

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Ultrasound boosted the degradation and isomerization of 5-CQA.

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EGCG and VC slowed down the degradation of 5-CQA induced by ultrasound.

5-O-Caffeoylquinic acid (5-CQA), also known as chlorogenic acid, exhibits various biological activities. Hence the interest in its property change during processing and extraction has increased. The present work studied the influence of ultrasound on the stability of 5-CQA at different pH (pH 4.69, 7.09, 7.69 and 9.22) in water and 50% methanol-water system. Different parameters including solvent, ultrasonic power, time, temperature, duty cycle, and liquid height were investigated during the treatment. Results indicate that ultrasound accelerated the degradation of 5-CQA. Based on Weibull model, the degradation kinetics were described. The rate constant (k) of the degradation increased with the increasing pH, demonstrating the alkali sensitivity of 5-CQA. The isomerization of 5-CQA to 3- and 4-O-caffeoylquinic acid was found at neutral and alkaline conditions, which was further boosted by ultrasound. The stability of 5-CQA was improved by adding epigallocatechin gallate (EGCG) and vitamin C (VC) respectively.

(Ascorb)ing Pb Neurotoxicity in the Developing Brain

Lead (Pb) neurotoxicity is a major concern, particularly in children. Developmental exposure to Pb can alter neurodevelopmental trajectory and has permanent neuropathological consequences, including an increased vulnerability to further stressors. Ascorbic acid is among most researched antioxidant nutrients and has a special role in maintaining redox homeostasis in physiological and physio-pathological brain states. Furthermore, because of its capacity to chelate metal ions, ascorbic acid may particularly serve as a potent therapeutic agent in Pb poisoning. The present review first discusses the major consequences of Pb exposure in children and then proceeds to present evidence from human and animal studies for ascorbic acid as an efficient ameliorative supplemental nutrient in Pb poisoning, with a particular focus on developmental Pb neurotoxicity. In doing so, it is hoped that there is a revitalization for further research on understanding the brain functions of this essential, safe, and readily available vitamin in physiological states, as well to justify and establish it as an effective neuroprotective and modulatory factor in the pathologies of the nervous system, including developmental neuropathologies.

Sub-chronic treatment with high doses of ascorbic acid reduces lead levels in hen eggs intentionally exposed to a concentrated source of lead: a pilot study

Background

Hen eggs contaminated with lead can be harmful to the health of children and adults. The objective of this pilot study was to investigate if sub-chronic treatment with ascorbic acid can reduce lead levels in the different parts of hen eggs after intentionally exposing the laying hens to a concentrated source of lead.

Methods

Clinically normal mixed-breed egg laying hens (n = 18) were used in this pilot study. Hens were exposed to a concentrated source of lead (200 mg/kg_{body weight}/day lead acetate) for 1 week. Subsequently, egg laying hens were either treated with sub-chronic doses of ascorbic acid (500 mg/kg_{body weight}/day) or left untreated for 4 weeks. Lead levels were assessed in egg-shell, egg-albumen, and egg-yolk samples using a graphite furnace atomic absorption spectrophotometer.

Results

Lead levels increased significantly (p-value < 0.01) from baseline in egg-yolk, egg-albumen, and egg-shell samples following 1 week exposure to lead acetate. Sub-chronic treatment of egg laying hens with high doses of ascorbic acid could bring statistically significant reduction (p-value < 0.01) in lead levels in egg-yolk, egg-albumen, and egg-shell samples after intentional exposure to a concentrated source of lead.

Conclusions

Findings of this pilot study showed that sub-chronic treatment of egg laying hens with ascorbic acid can reduce lead levels in different egg parts after intentional exposure to a concentrated source of lead. Supplementing feedstuffs and water with sources of ascorbic acid could be beneficial in reducing lead levels in hen egg tissues following environmental exposure. Further studies are still required to investigate if ascorbic acid can reduce lead levels in other chicken tissues.

Investigating the Effect of Melissa Officinalis on After-Pains: A Randomized Single-Blind Clinical Trial

Introduction: Regarding high prevalence of postpartum pain and side-effects of pharmaceutical analgesics on maternal and neonatal health, the present study aimed to explore the effect of Melissa officinalis on after-pain among mothers hospitalized in Asgariyeh Hospital, Isfahan, 2016.

Methods: In this single-blind clinical trial, 110 women with moderate to severe after-pain were divided into two M.officinalis and mefenamic acid groups by random allocation. Samples in the first group received 250mg of mefenamic acid and the second group received 395mg of M.officinalis oral capsules every 6hours for 24hours following childbirth. The primary outcome (After-pain) was assessed using a numeric 10-point scale before intervention, 1,2 and 3hours after the first intervention and every 6hours to 24hours after delivery for each of second, third and fourth interventions. Data were analyzed, using SPSS by independent t-test, Mann-Whitney and chi-square test.

Results: The demographic and obstetric variables and after-pain severity before the intervention in both groups were homogenous. Pain intensity wasn’t significantly different between the two groups during first and second hours after the first intervention, but there was a significant difference in the third hour, The severity of pain was significantly different between the two groups in different assessments including: an hour after the second, third and fourth intervention (P<0.05). A significant difference was found between mefenamic acid and M.officinalis in pain relief.

Conclusion: M.officinalis can reduce the severity of after-pain, because it eliminates the need for pharmaceutical analgesics and works much better than mefenamic acid.

Protective effect of curcumin on lead acetate-induced testicular toxicity in Wistar rats

In recent years, the use of the antioxidant in reducing heavy metal toxicities has increased worldwide. Curcumin has been reported to have a strong antioxidant activity. In this study, we investigated the protective effects of curcumin on lead acetate-induced testicular damage in rats. The sample used 40 male rats divided into 5 groups: negative control (rats were given daily with corn oil); positive control (rats were given daily with lead acetate 50 mg/kg BW orally once in a day for 35 days); and the treatment group (rats were given the curcumin 100 mg, 200 mg, and 400 mg/kg BW orally once in a day for 40 days, and on the 5^th day, were given lead acetate 50 mg/kg BW one h after the curcumin administration). After 40 days, levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) in testicular tissue, and sperm count, motility and viability in the epididymis were measured in rats. Testis samples were also collected for histopathological studies. Results showed that lead acetate administration significantly decreased the SOD, GPx, and increased MDA levels. Lead acetate also decreased the sperm count, motility, viability, and altered histopathological testis (testicular damage, necrosis of seminiferous tubules and loss of spermatid) compared to the negative control. However, administration of curcumin significantly improved the histopathological in testis, increased the sperm count, motility, viability, and also significantly increased the SOD, GPx, and decreased MDA in testis of lead acetate-treated rats. From the results of this study we concluded that the curcumin could be a potent natural product provide a promising protective effect against lead acetate induced testicular toxicity in rats.

Lead Toxicity, Antioxidant Defense and Environment

Environmental and occupational exposure to a large number of chemicals occurs at various stages throughout human life. Many of these are devoid of toxicity, but some could pose a significant health risk, i.e. the exposure to environmental xenobiotic metals as lead, mercury (Sinicropi et al. 2010a; Carocci et al. 2014), cadmium, etc. In particular, lead has long been a widespread public concern (Basha and Reddy 2010). Lead is one of the earliest heavy metals discovered by men. Due to its unique properties, as low melting point, softness, malleability, ductility, and resistance to corrosion, men have used lead for the last 5000 years in a wide range of applications.

Evaluation and management of lead exposure

Lead, which is widely used in industry, is a common element found in low concentrations in the Earth's crust. Implementations to reduce environmental lead concentrations have resulted in a considerable reduction of lead levels in the environment (air) and a sustained reduction in the blood lead levels of the average citizen. However, people are still being exposed to lead through a variety of routes in everyday commodities. Lead causes health problems such as toxicity of the liver, kidneys, hematopoietic system, and nervous system. Having a carcinogenic risk as well, the IARC classifies inorganic lead compounds as probably carcinogenic to humans (Group 2A). Occupational lead poisonings have decreased due to the efforts to reduce the lead concentrations in the working environment. In contrast, health hazards associated with long-term environmental exposure to low concentrations of lead have been reported steadily. In particular, chronic exposure to low concentrations of lead has been reported to induce cognitive behavioral disturbances in children. It is almost impossible to remove lead completely from the human body, and it is not easy to treat health hazards due to lead exposure. Therefore, reduction and prevention of lead exposure are very important. We reviewed the toxicity and health hazards, monitoring and evaluation, and management of lead exposure.

Effect of ascorbic acid (vitamin C) on the ESR spectra of the red and black hair: pheomelanin free radicals are not always present in red hair

Increased incidence of melanoma in the population with red hair is conditioned by synthesis of pheomelanin pigments in the skin and their phototoxic properties. The recent research has shown that free radicals of pheomelanin are produced not only by the influence of UV irradiation, but also in UV-independent pathways of oxidative stress. It has been ascertained, that the color of the hair is not always determinant of the amount of pheolemanin radicals in red hair. Therefore, in order to evaluate the risk of melanoma in different individuals, it is necessary to define the amount of free radicals of pheomelanin in red hair using ESR spectroscopy method. Besides, it is very important to find effective antioxidant, capable of neutralizing free radicals of pheomelanin. It was proved that ascorbic acid neutralizes free radicals of pheomelanin very effectively. The main goal of our research was to define the presumably optimal concentration of ascorbic acid as an antioxidant and study the kinetics of the influence of this concentration on red and black hair. It has been found out, that ascorbic acid influences the free radicals of red and black hair, and its appropriate optimal concentration is 10 mM. The obtained results can be considered in dermatology and cosmetology.

Survey of the detoxification effect of green tea extract on the reproductive system in rats exposed to lead acetate

Background:

Lead poisoning has been an old but perpetual public health problem in developing countries. Lead has an adverse effect on fertility, and this study aimed to examine the effect of consuming green tea extract (GTE) on fertility parameters in rats exposed to lead.

Materials and Methods:

In this experimental study, 70 rats have been classified, as it is described later, into 4 groups of 10 and were studied over 2 months. Group 1: Normal diet and tap water; Group 2: 10 mg/kg intraperitoneal lead acetate weekly over 8 weeks; Group 3: Lead acetate + 100 mg/kg green tea, Group 4: Extract green tea. Distal epididymal sperm samples were collected to assess the sperm counts, motility, and morphology. Testicular tissue and blood level of testosterone were also studies. Data were analyzed by SPSS-17 software using ANOVA and independent t-test with a significant level of 0.05.

Results:

The rats exposed to lead acetate had the lowest weight, and green tea had the highest weight. Green tea consumption in rats exposed to lead, reduced the effect of lead and the difference in mean body weight in these rats, compared to other groups, was minimized (P < 0.05). The group exposed to lead acetate had the highest sperm abnormalities, and the lowest sperm abnormalities were observed in groups taking green tea.

Conclusion:

Consumption of green tea can reduce the adverse effects of lead, and also can effectively prevent fertility reduction.

Ocular Fluid As a Replacement for Serum in Cell Cryopreservation Media

Cryostorage is of immense interest in biomedical research, especially for stem cell-based therapies and fertility preservation. Several protocols have been developed for efficient cryopreservation of cells and tissues, and a combination of dimethyl sulfoxide (DMSO) and fetal bovine serum (FBS) is commonly used. However, there is a need for an alternative to FBS because of ethical reasons, high cost, and risk of contamination with blood-borne diseases. The objective of the present study was to examine the possibility of using buffalo (Bubalus bubalis) ocular fluid (BuOF) to replace FBS in cryomedia. Frozen-thawed cells, which were cryopreserved in a cryomedia with BuOF, were assessed for viability, early and late apoptosis, and proliferation. Three cell lines (CHO, HEK, and C18-4), mouse embryonic stem (mES) cells, and primary cells, such as mouse embryonic fibroblast (MEF) cells, human peripheral blood mononuclear cells (hPBMCs), and mouse bone marrow cells (mBMCs), were cryopreserved in cryomedia containing 10% DMSO (D10) with 20% FBS (D10S20) or D10 with 20% BuOF (D10O20). For all three cell lines and mES cells cryopreserved in either D10S20 or D10O20, thawed cells showed no difference in cell viability or cell recovery. Western blot analysis of frozen-thawed-cultured cells revealed that the expression of Annexin V and proliferating cell nuclear antigen (PCNA) proteins, and the ratio of BAX/BCL2 proteins were similar in all three cell lines, mES cells, and hPBMCs cryopreserved in D10S20 and D10O20. However, initial cell viability, cell recovery after culture, and PCNA expression were significantly lower in MEF cells, and the BAX/BCL2 protein ratio was elevated in mBMCs cryopreserved in D10O20. Biochemical and proteomic analysis of BuOF showed the presence of several components that may have roles in imparting the cryoprotective property of BuOF. These results encourage further research to develop an efficient serum-free cryomedia for several cell types using BuOF.

Toxicity of lead: A review with recent updates

Lead poisoning has been recognized as a major public health risk, particularly in developing countries. Though various occupational and public health measures have been undertaken in order to control lead exposure, cases of lead poisoning are still reported. Exposure to lead produces various deleterious effects on the hematopoietic, renal, reproductive and central nervous system, mainly through increased oxidative stress. These alterations play a prominent role in disease manifestations. Modulation of cellular thiols for protection against reactive oxygen species (ROS) has been used as a therapeutic strategy against lead poisoning. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin and a few herbal extracts show prophylaxis against the majority of lead mediated injury in both in vitro and in vivo studies. This review provides a comprehensive account of recent updates describing health effects of lead exposure, relevant biomarkers and mechanisms involved in lead toxicity. It also updates the readers about recent advances in chelation therapy and newer therapeutic strategies, like nanoencapsulation, to treat lead induced toxic manifestations.

The protective effect of Rubia cordifolia against lead nitrate-induced immune response impairment and kidney oxidative damage

OBJECTIVES

To evaluate the in vivo antioxidant activity of the ethanolic extract of the roots of Rubia cordifolia (RC) and to study its influence on lead nitrate-induced impairment of immune responses.

MATERIALS AND METHODS

Seventy-two adult male Swiss albino mice were used for biochemical and immunological studies and were divided into six groups of six mice each. Mice were treated with lead nitrate (40 mg/kg, orally) either alone and or in combination with RC (50 and 100 mg/kg body weight) daily for 40 days. For immunological studies, all mice were challenged twice with sheep RBC with on days 14 and 20 of the experiment. The immune function was assessed using macrophage yield, viability of macrophage, phagocytic index, serum immunoglobulin level, and plaque forming cell count (PFC), whereas the oxidative stress was assessed by estimating lipid peroxidation (LPO), reduced glutathione (GSH) content, and the activities of superoxide dismutase (SOD) and catalase (CAT).

RESULTS

Lead nitrate administration induced a significant (P<0.001) increase in LPO, whereas a significant (P<0.001) depletion of CAT and GSH in renal tissues. In addition, it also showed a significant (P<0.001) reduction in macrophage yield, viability of macrophage, phagocyte index, serum immunoglobulin level, and PFC in kidney. However, combination treatment with RC observed a significant (P<0.001) reversal of lead nitrate-induced toxicity on oxidative stress and immunological parameters.

CONCLUSION

The lead nitrate-induced immunosuppression is due to oxidative stress and RC can prevent the same by virtue of its in vivo antioxidant property.

Association of blood lead (Pb) and plasma homocysteine: a cross sectional survey in Karachi, Pakistan

BACKGROUND

High blood lead (Pb) and hyperhomocysteinemia have been found to be associated with cardiovascular disease (CVD). Mean blood Pb and mean plasma homocysteine levels have been reported to be high in Pakistani population. The objective of the present study was to assess the relationship of blood Pb to the risk of hyperhomocysteinemia in a low income urban population of Karachi, Pakistan.

METHODOLOGY/PRINCIPAL FINDINGS

In a cross sectional survey, 872 healthy adults (355 males, 517 females; age 18-60 years) were recruited from a low income urban population of Karachi. Fasting venous blood was obtained and assessed for blood Pb and plasma/serum homocysteine, folate, pyridoxal phosphate (PLP, a coenzymic form of vitamin B6) and vitamin B12. The study population had median (IQR) blood Pb of 10.82 microg/dL (8.29-13.60). Prevalence of high blood Pb (levels>10 microg/dL) was higher in males compared to females (62.5% males vs 56% females; p value=0.05). Mean+/-SD/median (IQR) value of plasma homocysteine was significantly higher in the highest quartile of blood Pb compared to the lowest quartile 16.13+/-11.2 micromol/L vs 13.28+/-9.7micromol/L/13.15 (10.33-17.81) micromol/L vs 11.09 (8.65 14.31) micromol/L (p value<0.001). Daily consumption of fruit juice had a positive influence on both levels of plasma homocysteine and blood Pb. Compared with the lowest quartile of blood Pb, the OR for hyperhomocysteinemia was 1.69 (95% CI, 1.00 to 2.85) for the fourth quartile when the model was adjusted for age, gender, folate and vitamin B12.

CONCLUSIONS/SIGNIFICANCE

This study showed a relationship between blood Pb and hyperhomocysteinemia in a general population of Karachi, Pakistan. The harmful effect of Pb on cardiovascular system could be due to its association with hyperhomocysteinemia.

Prospective role of ascorbic acid (vitamin C) in attenuating hexavalent chromium-induced functional and cellular damage in rat thyroid

Occupational exposure to toxic heavy metals may render industrial workers with thyroid-related problems. Here, we examined the role of ascorbic acid (vitamin C) against hexavalent chromium Cr (VI)-induced damage in rat thyroid gland. Potassium dichromate (K2Cr2O7) and ascorbic acid doses were 60 µg and 120 mg kg—1 body wt (intraperitoneally [i.p.]) respectively. Treatment regimens were group I rats, saline treated control; group II, only K2Cr2O7; group III, ascorbic acid 1 hour prior K2Cr2O7; group IV, simultaneous doses of ascorbic acid and K2Cr2O 7, and group V, a combined premix dose of ascorbic acid and K2 Cr2O7 (2:1 ratio). Blood samples were taken before dosing the animals and 48 hours post exposure to determine the serum thyroid-stimulating hormone (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) concentrations. Toward end of experiment, rats were sacrificed and thyroid glands were processed to evaluate the extent of cellular insult. Results showed significantly increased TSH and decreased FT3 and FT4 concentrations in groups II, III and IV rats as compared to control levels (p < 0.05). In contrast, in group V rats, serum TSH, FT3 and FT4 concentrations neared control concentrations. Histopathologically, protective effect of ascorbic acid was found in group V rats only, where thyroid gland structure neared control thyroid except the follicular size that was decreased (p < 0.05). Follicular density was no different from control. Basal laminae were intact, interfollicular spaces were normal. Colloid retraction and/or reabsorption were reduced maximally. Epithelial cell height was no different from control; epithelial follicular index increased only 1.3 fold, whereas nuclear-cytoplasmic (N/C) ratio was decreased by 14% only. The study indicates that the ascorbic acid may have the potential to protect thyroid gland from chromium toxicity; however, the study warrants further in-depth experimentation to precisely elucidate this role.

PPARalpha-mediated effects of dietary lipids on intestinal barrier gene expression

Background

The selective absorption of nutrients and other food constituents in the small intestine is mediated by a group of transport proteins and metabolic enzymes, often collectively called 'intestinal barrier proteins'. An important receptor that mediates the effects of dietary lipids on gene expression is the peroxisome proliferator-activated receptor alpha (PPARα), which is abundantly expressed in enterocytes. In this study we examined the effects of acute nutritional activation of PPARα on expression of genes encoding intestinal barrier proteins. To this end we used triacylglycerols composed of identical fatty acids in combination with gene expression profiling in wild-type and PPARα-null mice. Treatment with the synthetic PPARα agonist WY14643 served as reference.

Results

We identified 74 barrier genes that were PPARα-dependently regulated 6 hours after activation with WY14643. For eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) and oleic acid (OA) these numbers were 46, 41, and 19, respectively. The overlap between EPA-, DHA-, and WY14643-regulated genes was considerable, whereas OA treatment showed limited overlap. Functional implications inferred form our data suggested that nutrient-activated PPARα regulated transporters and phase I/II metabolic enzymes were involved in a) fatty acid oxidation, b) cholesterol, glucose, and amino acid transport and metabolism, c) intestinal motility, and d) oxidative stress defense.

Conclusion

We identified intestinal barrier genes that were PPARα-dependently regulated after acute activation by fatty acids. This knowledge provides a better understanding of the impact dietary fat has on the barrier function of the gut, identifies PPARα as an important factor controlling this key function, and underscores the importance of PPARα for nutrient-mediated gene regulation in intestine.