Influence of maternal nicotine exposure on neonatal rat oxidant-antioxidant system and effect of ascorbic acid supplementation

Histopathologic and Immunohistochemical Investigation of the Effects of Vitamin C on Bone Healing in Rats Exposed to Nicotine

PURPOSE

The aim of the present study was to perform a histopathologic and immunohistochemical investigation of the effects of vitamin C on bone healing in rats exposed to nicotine.

MATERIALS AND METHODS

A total of 52 male Sprague-Dawley rats were assigned to 4 main groups: control, vitamin C, nicotine, and nicotine plus vitamin C. The rats in the nicotine groups were injected with nicotine at 12-hour intervals for 4 weeks. At the end of 4 weeks, a tibial defect was created in all the rats. Subcutaneous injections were administered at the same intervals postoperatively, and the vitamin C groups received intraperitoneal vitamin C injections every day for the first 3 days and then every other day postoperatively. The rats were sacrificed on postoperative days 7 and 21. The blood samples collected during sacrifice were tested to determine the blood cotinine levels, and histopathological and immunohistochemical analyses were performed on tibia samples.

RESULTS

The histopathologic evaluation revealed that nicotine significantly increased the amount of necrosis and significantly decreased new bone formation and the bone healing score. The presence of necrosis in the nicotine plus vitamin C group was significantly lower on day 21 (P = .005). A statistically significant difference was observed among the new bone formation of the control, nicotine, vitamin C, and nicotine plus vitamin C groups on day 21 (P = .001). The new bone healing score of the nicotine group was significantly lower than that of the control, vitamin C, and nicotine plus vitamin C groups (P = .003, P = .001, and P = .001). The immunohistochemical evaluation showed that nicotine increased the hypoxia-inducible factor-1α and vascular endothelial growth factor levels and decreased the bone morphogenetic protein-2 levels, especially in the groups sacrificed on day 21.

CONCLUSIONS

Vitamin C did not have a significant effect on bone healing. However, vitamin C administered with nicotine decreased the metabolism of nicotine and, thus, increased nicotine excretion.

The protective effect of melatonin in lungs of newborn rats exposed to maternal nicotine

We investigated possible healing effects of melatonin (MEL) on biochemical and histological changes in the lungs of rat offspring caused by exposure to nicotine (NT) in utero. Pregnant rats were divided randomly into five groups. The SP group was treated with physiological saline. The EA group was treated with ethyl alcohol. The MEL group was treated with MEL. The NT group was treated with NT. The NT + MEL group was treated with NT and MEL. At the end of the study, the biochemistry and histopathology of lung tissue of the offspring were examined. Reduced alveolar development and increased numbers of alveolar macrophages and mast cells were observed in the NT group compared to the SP, EA and MEL groups. We also found increased malondialdehyde (MDA) levels and decreased total glutathione (GSH) levels in the NT group. Application of MEL ameliorated the histological and biochemical damage caused by NT. The number of alveoli was greater in the NT + MEL group than in the NT group. Also, the increased numbers of alveolar macrophages and mast cells resulting from exposure to NT were decreased following MEL treatment. We found that MEL caused a significant decrease in the level of MDA. Maternal exposure to NT caused significant structural and biochemical changes in the lungs of the offspring and administration of MEL ameliorated the changes.

Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP): Rationale, design, and methods of a randomized, controlled trial of vitamin C supplementation in pregnancy for the primary prevention of effects of in utero tobacco smoke exposure on infant lung function and respiratory health

Despite strong anti-smoking efforts, at least 12% of American women cannot quit smoking when pregnant resulting in >450,000 smoke-exposed infants born yearly. Smoking during pregnancy is the largest preventable cause of childhood respiratory illness including wheezing and asthma. Recent studies have shown a protective effect of vitamin C supplementation on the lung function of offspring exposed to in utero smoke in a non-human primate model and an initial human trial. Vitamin C to Decrease the Effects of Smoking in Pregnancy on Infant Lung Function (VCSIP) is a randomized, double-blind, placebo-controlled trial to evaluate pulmonary function at 3months of age in infants delivered to pregnant smokers randomized to 500mg/day of vitamin C versus placebo during pregnancy. Secondary aims evaluate the incidence of wheezing through 12months and pulmonary function testing at 12months of age. Women are randomized between 13 and 23weeks gestation from clinical sites in Portland, Oregon at Oregon Health & Science University and PeaceHealth Southwest Medical Center and in Indianapolis, Indiana at Indiana University and Wishard Hospital. Vitamin C supplementation occurs from randomization to delivery. Monthly contact with participants and monitoring of medical records is performed to document medication adherence, changes in smoking and medical history, and adverse events. Pulmonary function testing of offspring occurs at 3 and 12months of age and incidence of wheezing and respiratory illness through 12months is captured via at least quarterly questionnaires. Ancillary studies are investigating the impact of vitamin C on placental blood flow and DNA methylation.

Increased Fetal Thymocytes Apoptosis Contributes to Prenatal Nicotine Exposure-induced Th1/Th2 Imbalance in Male Offspring Mice

Nicotine, a definite risk factor during pregnancy, is an immunomodulator. This study was designed to investigate the effects of prenatal nicotine exposure (PNE) on the balance of Th1/Th2 in offspring, and further explore the developmental origin mechanisms from the perspective of fetal thymocytes apoptosis. Pregnant Balb/c mice were administered 1.5 mg/kg nicotine subcutaneously twice per day from gestational day (GD) 9 to GD18. Results showed that PNE could cause a Th2 shift in male offspring, manifested as increased ratio of IgG1/IgG2a, IL-4 production in serum, and IL-4/IFN-γ expression ratio in spleen. Increased apoptosis of total thymocytes and CD4SP and reduced cell proportion of CD4SP were found in PNE male offspring on postnatal day (PND) 14 and PND 49. In the fetuses, decreased body weight and organ index of fetal thymus, histological changes in fetal thymus, reduced CD4SP proportion and increased fetal thymocyte apoptosis were observed in nicotine group. The increased mRNA expression of genes involved in Fas-mediated apoptotic pathway and protein expression of Fas were also detected. In conclusion, PNE could cause a Th2 shift in male offspring mediated by reduced CD4⁺ T cells output, which may result from the increasing apoptosis of total thymocytes and CD4SP.

DNA hypermethylation of acetoacetyl-CoA synthetase contributes to inhibited cholesterol supply and steroidogenesis in fetal rat adrenals under prenatal nicotine exposure

Prenatal nicotine exposure is a risk factor for intrauterine growth retardation (IUGR). Steroid hormones synthesized from cholesterol in the fetal adrenal play an important role in the fetal development. The aim of this study is to investigate the effects of prenatal nicotine exposure on steroidogenesis in fetal rat adrenals from the perspective of cholesterol supply and explore the underlying epigenetic mechanisms. Pregnant Wistar rats were administered 1.0mg/kg nicotine subcutaneously twice a day from gestational day (GD) 7 to GD17. The results showed that prenatal nicotine exposure increased IUGR rates. Histological changes, decreased steroid hormone concentrations and decreased cholesterol supply were observed in nicotine-treated fetal adrenals. In the gene expression array, the expression of genes regulating ketone metabolic process decreased in nicotine-treated fetal adrenals. The following conjoint analysis of DNA methylation array with these differentially expressed genes suggested that acetoacetyl-CoA synthetase (AACS), the enzyme utilizing ketones for cholesterol supply, may play an important role in nicotine-induced cholesterol supply deficiency. Moreover, the decreased expression of AACS and increased DNA methylation in the proximal promoter of AACS in the fetal adrenal was verified by real-time reverse-transcription PCR (RT-PCR) and bisulfite sequencing PCR (BSP), respectively. In conclusion, prenatal nicotine exposure can cause DNA hypermethylation of the AACS promoter in the rat fetal adrenal. These changes may result in decreased AACS expression and cholesterol supply, which inhibits steroidogenesis in the fetal adrenal.

Role of vitamin C and selenium in attenuation of nicotine induced oxidative stress, P53 and Bcl2 expression in adult rat spleen

Forty adult female rats were randomly divided into four groups: control, nicotine, nicotine+vitamin C and nicotine+selenium group. Splenic tissues concentrations of thiobarbituric acid reactive substances (TBARS), nitric oxide, superoxide dismutase (SOD) and catalase (CAT) activities were measured. The P53 and Bcl2 proteins were detected by Western blot and their expression in splenic tissues were measured by quantitative real time PCR in all groups. Compared to control group, nicotine increased the concentrations of TBARS and nitric oxide significantly. However, Vit. C or Se supplementation with nicotine caused a significant decrease in these concentrations. SOD and CAT activities of nicotine group decreased significantly compared to control group. Treatment with Vit. C or Se plays a significant role in elevation of SOD and CAT activities. In splenic tissues, nicotine significantly decreases the protein levels and the mRNA expression of P53 and increases the protein levels of Bcl2 and its expression. Administration of Vit. C. to nicotine-treated rats completely reversed the decrease in P53 levels and its mRNA expression and the increase in Bcl2 levels and its mRNA expression to the control values. In contrast, Se administration did not induce any significant changes in these genes levels or expressions compared to nicotine group.

CONCLUSION

Vit. C supplementation to nicotine treated rats was more effective than selenium in attenuation of nicotine-induced oxidative stress, p53 and Bcl2 expression in rat spleen tissues.

Prenatal exposure to cigarette smoke causes persistent changes in the oxidative balance and in DNA structural integrity in rats submitted to the animal model of schizophrenia

Epidemiological studies have indicated that prenatal exposure to environmental insults can bring an increased risk of schizophrenia. The objective of our study was to determine biochemical parameters in rats exposed to cigarette smoke (CS) in the prenatal period, evaluated in adult offspring submitted to animal model of schizophrenia induced by acute subanaesthetic doses of ketamine (5 mg/kg, 15 mg/kg and 25 mg/kg). Pregnant female Wistar rats were exposed to 12 commercially filtered cigarettes per day, daily for a period of 28 days. We evaluated the oxidative damage in lipid and protein in the rat brain, and DNA damage in the peripheral blood of male adult offspring rats. To determine oxidative damage in the lipids, we measured the formation of thiobarbituric acid reactive species (TBARS) and the oxidative damage to the proteins was assessed by the determination of carbonyl groups content. We also evaluated DNA damage using single-cell gel electrophoresis (comet assay). Our results showed that rats exposed to CS in the prenatal period presented a significant increase of the lipid peroxidation, protein oxidation and DNA damage in adult age. We can observe that the animals submitted at acute doses of ketamine also presented an increase of the lipid peroxidation and protein oxidation at different doses and structures. Finally, we suggest that exposure to CS during the prenatal period affects two essential cerebral processes during development: redox regulation and DNA integrity, evaluated in adult offspring. These effects can leads to several neurochemical changes similar to the pathophysiology of schizophrenia.

Prenatal nicotine exposure in rhesus monkeys compromises development of brainstem and cardiac monoamine pathways involved in perinatal adaptation and sudden infant death syndrome: amelioration by vitamin C

Maternal smoking during pregnancy greatly enhances perinatal morbidity/mortality and is the major risk factor for Sudden Infant Death Syndrome (SIDS). Studies in developing rodents indicate that nicotine is a neuroteratogen that targets monoamine pathways involved in the responses to hypoxia that are in turn, hypothesized to contribute to these adverse events. We administered nicotine to pregnant Rhesus monkeys from gestational day 30 through 160 by continuous infusion, achieving maternal plasma levels comparable to those in smokers; we examined neurochemical parameters immediately after Cesarean delivery at the end of the exposure period. Nicotine evoked elevations in brainstem serotonin levels and serotonin turnover, indicating hyperactivity of these pathways. The same treatment evoked a deficit in cardiac norepinephrine levels. Both effects were offset by coadministration of the antioxidant, Vitamin C. Brainstem serotonin hyperinnervation is a hallmark of SIDS, and the hyperactivity seen here can also account for the downregulation of serotonin receptors noted in this disorder. Deficient cardiac sympathetic innervation is also consistent with increased vulnerability to hypoxia during delivery or in the agonal event in SIDS. Our results thus indicate that nicotine exposure in a primate model produces brainstem and autonomic abnormalities of the key monoamine systems that govern the response to hypoxia, indicate an important role of oxidative stress in the adverse effects, and point to potential amelioration strategies that could offset these particular effects of nicotine.