Effects of aging on acute toxicity of nicotine in rats

Protective effect of Enicostemma axillare - Swertiamarin on oxidative stress against nicotine-induced liver damage in SD rats

OBJECTIVE

The current investigation was aimed to determine the hepatoprotective benefits of Swertiamarin (ST) administration against nicotine-induced hepatotoxicity in SD rats.

MATERIAL AND METHODS

A total of 48 adult male SD rats were allocated into six groups using a fully randomised approach. As a control, group I was given oral (PO) normal saline. For 65 days, the animals in groups II, III, IV, V and VI received 2.5mg/kg/day of nicotine intraperitoneally (IP), 100mg/kg/day of ST orally (PO), 200mg/kg/day of ST orally (PO), 2.5mg/kg/day of nicotine (IP)+100mg/kg/day of ST (PO), and 2.5mg/kg/day of nicotine (IP)+200mg/kg/day of ST (PO), respectively. Animals were killed on 66thday, liver tissue was removed and used for histopathological analysis as well as biochemical testing (oxidative stress parameters and liver function enzymes).

RESULTS

When compared to control animals, the animals in group II showed a substantial rise in their aspartate aminotransferase (AST), alanine aminotransferase (ALT), urea, and creatinine levels (P˂0.001). Furthermore, compared to control animals, these animals displayed enhanced hepatic oxidative stress as indicated by significantly higher Malondialdehyde (MDA) levels (P˂0.001) and lower levels of Catalase (CAT), Glutathione (GSH), Glutathione peroxidase (GSH-Px) and Superoxide dismutase (SOD) (P˂0.001). Further, more histological anomalies were seen in the liver of nicotine-treated rats compared to control rats, including significant vacuolization, poor tissue architecture, the growth of pycnotic nuclei, and dilated sinusoids. Contrary to nicotine-treated rats, the co-administration of ST and nicotine was observed to prevent the abnormalities caused by nicotine (groups V and VI).

CONCLUSION

The results of the current study show that nicotine can seriously harm liver tissue and that swertiamarin can prevent the harmful effects of nicotine on rat liver. Future research is necessary to delve deeply into the mechanisms behind swertiamarin protective impact against nicotine-induced hepatotoxicity.

Nanonaringenin and Vitamin E Ameliorate Some Behavioral, Biochemical, and Brain Tissue Alterations Induced by Nicotine in Rats

Nicotine is the major alkaloid present in cigarettes that induces various biochemical and behavioral changes. Nanonaringenin (NNG) and vitamin E are antioxidants that are reported to mitigate serious impairments caused by some toxins and oxidants. Thus, we aimed to investigate the efficacy of NNG, vitamin E, and their combinations to ameliorate behavioral, biochemical, and histological alterations induced by nicotine in rats. Adult male albino rats were randomly grouped into six equal groups (10 rats/group): control, N (nicotine 1 mg/kg b.w./day S/C from 15^th to 45^th day, 5 days a week), NNG (25 mg/kg b.w./day orally for 45 days), N + NNG, N + E (nicotine + vitamin E 200 mg/kg b.w./day orally), and N + NNG + E (nicotine + NNG + vitamin E at the aforementioned doses). Behavioral tests were conducted on day 15 and 30 postnicotine injection, while memory tests, brain neurotransmitters, antioxidants, and histopathological examination were examined at day 30 only. As a result, nicotine impaired rats' activity (hypoactivity and hyperactivity) and memory, induced anxiolytic and anxiogenic effects on rats, and altered neurotransmitters (acetylcholinesterase, serotonin, and dopamine), and redox markers (MDA, H₂O₂, GSH, and catalase) levels in brain homogenates. Thickening and congestion of the meninges and degeneration of the cerebral neurons and glia cells were observed. Cosupplementation with NNG, vitamin E, and their combination with nicotine was beneficial in the alleviation of activity impairments and improved short memory and cognition defects and exploratory behaviors. Our results indicate the antioxidant potential of NNG and vitamin E by modulating redox markers and neurotransmitters in the brain. Thus, data suggest that the prophylactic use of NNG, vitamin E, and/or their combination for (45 days) may have a successful amelioration of the disrupted behavior and cognition and biochemical and histopathological alterations induced by nicotine.

Antineoplastic agents aggravate the damages caused by nicotine on the peri-implant bone: an in vivo histomorphometric and immunohistochemical study in rats

OBJECTIVE

To assess the interaction between chemotherapy and normal tissues is critical to assure quality of life during and after the treatment of cancer. This study evaluated the influence of cisplatin (CIS) and 5-fluorouracil (5-FU) over the peri-implant tissues around osseointegrated titanium implants in animals previously exposed to nicotine. Materials and methods One hundred twenty male rats were divided into two groups, receiving via subcutaneous injection, either physiological saline solution (PSS) (n = 30) or nicotine hemissulfate (NIC) (n = 90) for 30 days prior to implants' placement. One titanium implant (4.0 × 2.2 mm) was installed in each tibia of all animals. PSS and NIC were continued for 30 days after surgery. Five days after cessation, rats were subdivided into three subgroups in accordance with systemic treatments with either PSS, CIS, or 5-FU. Euthanasia was performed at 50, 65, and 95 days post-surgery. Histometric, histopathological, and immunohistochemical analyses were performed.

RESULTS

NIC-CIS and NIC-5FU presented lower BIC (50, 65, and 95 days) and bone area fraction occupancy (BAFO) (65 and 95 days) than group NIC. Intense inflammatory infiltration, severe tissue breakdown, reduced expression of bone formation biomarkers, and upregulation of TRAP were observed in NIC-CIS and NIC-5FU when compared with group NIC. TRAP expression was significantly higher in NIC-5FU as compared with NIC-CIS at 50 and 95 days. Groups NIC, NIC-CIS, and NIC-5FU presented statistically significant negative impact in all outcome parameters than group PSS.

CONCLUSION

CIS and 5-FU severely disrupted the peri-implant tissues around osseointegrated implants in animals previously exposed to nicotine.

CLINICAL RELEVANCE

Assessing the interaction between chemotherapy and normal tissues is critical to assure quality of life during and after the cancer treatment.

Ameliorative effect of fractionated low-dose gamma radiation in combination with ellagic acid on nicotine-induced hormonal changes and testicular toxicity in rats

Nicotine is an active pharmacological ingredient in cigarette smoke, which may negatively influence the male reproductive system and fertility. This study aims to investigate the effect of fractionated low-dose radiation (fractionated-LDR) and/or ellagic acid (EA) on nicotine-induced hormonal changes and testicular toxicity in rats. Nicotine was administrated orally (1 mg/kg) for 30 days, afterward, rats were treated with LDR (2 × 0.25 Gy/1-week interval), EA (10 mg/kg, 14 consecutive days p.o.), or a combination of both fractionated-LDR and EA. Rats were sacrificed 24 h after the last dose of treatment, then testes were dissected for histopathology examination, along with some biochemical parameters in serum and testicular tissue were evaluated. Nicotine-induced oxidative stress was evidenced by an increase in testicular thiobarbituric acid reactive substances (TBARS) and a decrease in reduced glutathione (GSH) content. Additionally, the activities of testicular androgenic enzymes were decreased, and the activity of serum lactate dehydrogenase (LDH) was significantly increased. The hormonal changes were verified by a noticeable reduction in follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone serum levels. Histological evaluation revealed that the testicular seminiferous tubules structure was distorted. On the contrary, fractionated-LDR plus EA attenuated the negative changes caused by nicotine observed through biochemical and histological findings. Accordingly, the exposure to fractionated-LDR combined with EA may be a promising candidate for treating hormonal changes and testicular toxicity caused by nicotine.

Fatal Suicidal Attempt by Deliberate Ingestion of Nicotine-containing Solution in Childhood-onset Depression Mediated through Internet Suicide Guideline: A Case Report

Nicotine is one of the most easily accessible, commonly abused drugs worldwide and if taken in overdose can cause serious clinical presentation, including cardiac arrhythmias and neurotoxicity mediated through oxidative stress. Its toxicity though rare can cause sudden deaths by cardiovascular arrest, respiratory muscle paralysis, and/or central respiratory failure. Here, we describe a case of intentional fatal ingestion of nicotine sulfate decoction used as a mean for fatal suicidal attempt by a 15-year-old adolescent male who was suffering from childhood-onset depression since about 3 months. He developed drooling of saliva, syncopal attacks, paroxysmal episodes of hematemesis, abdominal pain, signs and symptoms of hypoxia, nonfatal atrial tachycardia, and encephalopathy after ingestion of heavy dose of nicotine-containing concoction; however, he recovered successfully within 24-48 hours without any significant cardiac, respiratory, or neurological deficits (except short-term verbal memory). Authors discussed the details of management and reasons behind the reversible encephalopathy and molecular mechanism of nicotine toxicity.

How to cite this article

Kamble A, Khairkar P, Kalantri SP, Babhulkar S. Fatal Suicidal Attempt by Deliberate Ingestion of Nicotine-containing Solution in Childhood-onset Depression Mediated through Internet Suicide Guideline: A Case Report. Indian J Crit Care Med 2020;24(8):719-721.

Resetting the Aging Clock: Implications for Managing Age-Related Diseases

Worldwide, individuals are living longer due to medical and scientific advances, increased availability of medical care and changes in public health policies. Consequently, increasing attention has been focused on managing chronic conditions and age-related diseases to ensure healthy aging. The endogenous circadian system regulates molecular, physiological and behavioral rhythms orchestrating functional coordination and processes across tissues and organs. Circadian disruption or desynchronization of circadian oscillators increases disease risk and appears to accelerate aging. Reciprocally, aging weakens circadian function aggravating age-related diseases and pathologies. In this review, we summarize the molecular composition and structural organization of the circadian system in mammals and humans, and evaluate the technological and societal factors contributing to the increasing incidence of circadian disorders. Furthermore, we discuss the adverse effects of circadian dysfunction on aging and longevity and the bidirectional interactions through which aging affects circadian function using examples from mammalian research models and humans. Additionally, we review promising methods for managing healthy aging through behavioral and pharmacological reinforcement of the circadian system. Understanding age-related changes in the circadian clock and minimizing circadian dysfunction may be crucial components to promote healthy aging.

Aging and the clock: Perspective from flies to humans

Endogenous circadian oscillators regulate molecular, cellular and physiological rhythms, synchronizing tissues and organ function to coordinate activity and metabolism with environmental cycles. The technological nature of modern society with round-the-clock work schedules and heavy reliance on personal electronics has precipitated a striking increase in the incidence of circadian and sleep disorders. Circadian dysfunction contributes to an increased risk for many diseases and appears to have adverse effects on aging and longevity in animal models. From invertebrate organisms to humans, the function and synchronization of the circadian system weakens with age aggravating the age-related disorders and pathologies. In this review, we highlight the impacts of circadian dysfunction on aging and longevity and the reciprocal effects of aging on circadian function with examples from Drosophila to humans underscoring the highly conserved nature of these interactions. Additionally, we review the potential for using reinforcement of the circadian system to promote healthy aging and mitigate age-related pathologies. Advancements in medicine and public health have significantly increased human life span in the past century. With the demographics of countries worldwide shifting to an older population, there is a critical need to understand the factors that shape healthy aging. Drosophila melanogaster, as a model for aging and circadian interactions, has the capacity to facilitate the rapid advancement of research in this area and provide mechanistic insights for targeted investigations in mammals.

Alteration of adolescent aversive nicotine response and anxiety-like behavior in nicotine-exposed rats during late lactation period

Early nicotine exposure is an important cause of further habitual tobacco smoking. Although nicotine has not only rewarding but also aversive properties, the effects of early nicotine exposure on the distinct properties of nicotine are not well known. To reveal the effects of early adolescent nicotine exposure on further persistent tobacco smoking, we demonstrated developmental changes in nicotine-related appetitive and aversive behaviors of rats exposed to nicotine during the late lactation period. Sprague-Dawley rats were injected with saline or nicotine (2, 6 and 12mg/kg). We performed a two bottle free-choice test using escalating doses of nicotine (25, 50 and 100μg/ml), saccharin and quinine and the open field test in both adolescent and adult rats. The rats' aversive response to nicotine was increased according to the increase in nicotine concentration. Adolescent rats showed higher nicotine preference and consumption behaviors than did adult rats at an aversive dose of nicotine. Nicotine-exposed rats increased adolescent nicotine consumption when the nicotine concentration was 12mg/kg. We observed significant increases in anxious behaviors in adolescent nicotine-injected rats compared to saline-injected rats, but there were no alterations in adult rats. In both adolescent and adult rats, saccharin and quinine intake were not significantly different between groups. Taken together, it suggests that repeated nicotine exposure in late lactation period affect changes in aversive nicotine responses and anxious behaviors during adolescence but there is no difference in adults.

Aging and circadian dysfunction increase alcohol sensitivity and exacerbate mortality in Drosophila melanogaster

Alcohol abuse is a rising problem in middle-aged and older individuals resulting in serious health, family and economic consequences. Effective treatment necessitates the identification of factors influencing alcohol toxicity with aging. We investigated the interaction between aging, alcohol toxicity and circadian function using Drosophila as a model system. We found as wild type flies age, sensitivity to alcohol increases and circadian regulation of alcohol-induced behaviors weakens. Decreased circadian modulation is correlated with significantly greater alcohol sensitivity during the subjective day. The circadian clock modulates alcohol-induced mortality in younger flies with increased mortality following alcohol exposure at night. Older flies exhibit significantly longer recovery times following alcohol-induced sedation and increased mortality following binge-like or chronic alcohol exposure. Flies rendered arrhythmic either genetically or environmentally exhibit significantly increased alcohol sensitivity, longer recovery times and increased mortality. We hypothesize that the circadian clock phase specifically buffers behavioral and cellular alcohol sensitivity with this protection diminishing as the circadian clock weakens with age.

Plant products and secondary metabolites with acaricide activity against ticks

The present review documents the results of studies evaluating the acaricidal activity of different plant products and secondary metabolites against ticks that are resistant and susceptible to conventional acaricides. Studies published from 1998 to 2016 were included. The acaricidal activity of plant extracts, essential oils and secondary compounds from plants have been evaluated using bioassays with ticks in the larval and adult stages. There is variable effectiveness according to the species of plant and the concentrations used, with observed mortalities ranging from 5 to 100% against the Rhipicephalus (Boophilus), Amblyomma, Dermacentor, Hyalomma, and Argas genera. A number of plants have been reported to cause high mortalities and/or affect the reproductive capacity of ticks in the adult phase. In the majority of these trials, the main species of plants evaluated correspond to the families Lamiaceae, Fabaceae, Asteraceae, Piperaceae, Verbenaceae, and Poaceae. Different secondary metabolites such as thymol, carvacrol, 1,8-cineol and n-hexanal, have been found to be primarily responsible for the acaricidal activity of different essential oils against different species of ticks, while nicotine, dibenzyldisulfide and dibenzyltrisulfide have been evaluated for plant extracts. Only thymol, carvacrol and 1,8-cineol have been evaluated for acaricidal activity under in vivo conditions. The information in the present review allows the conclusion that the secondary metabolites contained in plant products could be used as an alternative for the control of ticks that are susceptible or resistant to commercial acaricides.

Labelling of electronic cigarettes: regulations and current practice

BACKGROUND

Over the past decade e-cigarettes have established themselves in the global market. E-cigarettes triggered much interest in relation to their content and efficacy as smoking cessation tools, but less attention has been paid to users and environmental safety warnings and guidance. Several regulations have been introduced to promote their safe handling and disposal. From May 2016, liquids and cartridges will be regulated by European Community Directives (ECDs) 2001/83/EC and 93/42/EEC, or 2014/40/EU if marketed as tobacco-related products. Currently, manufacturers and distributors must abide by the Chemical (Hazard Information and Packaging for Supply) Regulations 2009 (CHIP) or Classification, Labelling and Packaging Regulations (CLP), the latter replacing CHIP in June 2015.

OBJECTIVE

In this work, the compliance of marketed e-liquids and e-cigarettes with current European Union and UK legislations is assessed.

RESULTS

E-liquids and e-cigarettes (21 and 9 brands, respectively) were evaluated. Evidence of non-compliance was found in relation to the CHIP/CLP toxic (13%) and environmental (37%) pictograms, tactile warning (23%), nominal amount of solution (30%), supplier contact telephone number and address (40%). None of the evaluated e-cigarettes displayed information on the correct disposal/recycling of batteries in line with the ECD 2006/66/EC.

CONCLUSIONS

More stringent enforcement of regulations is needed to ensure not only the user's safety and awareness, but also the safeguarding of the environment.

Hepatic Transcript Levels for Genes Coding for Enzymes Associated with Xenobiotic Metabolism are Altered with Age

Metabolism studies are crucial for data interpretation from rodent toxicity and carcinogenicity studies. Metabolism studies are usually conducted in 6 to 8 week old rodents. Long-term studies often continue beyond 100 weeks of age. The potential for age-related changes in transcript levels of genes encoding for enzymes associated with metabolism was evaluated in the liver of male F344/N rats at 32, 58, and 84 weeks of age. Differential expression was found between the young and old rats for genes whose products are involved in both phase I and phase II metabolic pathways. Thirteen cytochrome P450 genes from CYP families 1–3 showed alterations in expression in the older rats. A marked age-related decrease in expression was found for 4 members of the Cyp3a family that are critical for drug metabolism in the rat. Immunohistochemical results confirmed a significant decrease in Cyp3a2 and Cyp2c11 protein levels with age. This indicates that the metabolic capacity of male rats changes throughout a long-term study. Conducting multiple hepatic microarray analyses during the conduct of a long-term study can provide a global view of potential metabolic changes that might occur. Alterations that are considered crucial to the interpretation of long-term study results could then be confirmed by subsequent metabolic studies.

Developmental toxicity assay using high content screening of zebrafish embryos

Typically, time-consuming standard toxicological assays using the zebrafish (Danio rerio) embryo model evaluate mortality and teratogenicity after exposure during the first 2 days post-fertilization. Here we describe an automated image-based high content screening (HCS) assay to identify the teratogenic/embryotoxic potential of compounds in zebrafish embryos in vivo. Automated image acquisition was performed using a high content microscope system. Further automated analysis of embryo length, as a statistically quantifiable endpoint of toxicity, was performed on images post-acquisition. The biological effects of ethanol, nicotine, ketamine, caffeine, dimethyl sulfoxide and temperature on zebrafish embryos were assessed. This automated developmental toxicity assay, based on a growth-retardation endpoint should be suitable for evaluating the effects of potential teratogens and developmental toxicants in a high throughput manner. This approach can significantly expedite the screening of potential teratogens and developmental toxicants, thereby improving the current risk assessment process by decreasing analysis time and required resources.

Auditory middle latency responses in chronic smokers compared to nonsmokers: differential effects of stimulus and age

PURPOSE

Effects of clicks and tonebursts on early and late auditory middle latency response (AMLR) components were evaluated in young and older cigarette smokers and nonsmokers.

METHOD

Participants ( n = 49) were categorized by smoking and age into 4 groups: (a) older smokers, (b) older nonsmokers, (c) young smokers, and (d) young nonsmokers. Monaural, 2-channel AMLRs were acquired from Fz and Cz electrodes with 3 stimuli (clicks, 500 Hz, and 3000 Hz).

RESULTS

Group differences included significantly higher V-Na amplitude in young adults and shorter Pb latency in older nonsmokers. Young smokers had a significantly higher Nb-Pb amplitude and shorter Nb latency than other groups. Toneburst stimuli yielded significantly longer V, Na, and Pa latencies compared to clicks. Pb latency was shorter at Fz than at Cz. Relative amplitudes were significantly higher at Fz than at Cz overall; Pa-Nb and Nb-Pb were significantly lower for 3000 Hz than for 500 Hz and clicks.

CONCLUSIONS

Responses from young smokers revealed a higher amplitude and shorter latency for later AMLR waves, reflecting an arousal effect of smoking in cortical and subcortical generators. AMLR differences in older adults may be due to age-related neurochemical changes in the central nervous system. Stimulus and electrode differences plus smoking and aging effects can guide neurodiagnostic AMLR protocols, especially in young adult smokers.

Age-related changes in hepatic activity and expression of detoxification enzymes in male rats

Process of aging is accompanied by changes in the biotransformation of xenobiotics and impairment of normal cellular functions by free radicals. Therefore, this study was designed to determine age-related differences in the activities and/or expressions of selected drug-metabolizing and antioxidant enzymes in young and old rats. Specific activities of 8 drug-metabolizing enzymes and 4 antioxidant enzymes were assessed in hepatic subcellular fractions of 6-week-old and 21-month-old male Wistar rats. Protein expressions of carbonyl reductase 1 (CBR1) and glutathione S-transferase (GST) were determined using immunoblotting. Remarkable age-related decrease in specific activities of CYP2B, CYP3A, and UDP-glucuronosyl transferase was observed, whereas no changes in activities of CYP1A2, flavine monooxygenase, aldo-keto reductase 1C, and antioxidant enzymes with advancing age were found. On the other hand, specific activity of CBR1 and GST was 2.4 folds and 5.6 folds higher in the senescent rats compared with the young ones, respectively. Interindividual variability in CBR1 activity increased significantly with rising age. We suppose that elevated activities of GST and CBR1 may protect senescent rats against xenobiotic as well as eobiotic electrophiles and reactive carbonyls, but they may alter metabolism of drugs, which are CBR1 and especially GSTs substrates.

Caffeine in floral nectar enhances a pollinator's memory of reward

Plant defense compounds occur in floral nectar, but their ecological role is not well understood. We provide evidence that plant compounds pharmacologically alter pollinator behavior by enhancing their memory of reward. Honeybees rewarded with caffeine, which occurs naturally in nectar of Coffea and Citrus species, were three times as likely to remember a learned floral scent as were honeybees rewarded with sucrose alone. Caffeine potentiated responses of mushroom body neurons involved in olfactory learning and memory by acting as an adenosine receptor antagonist. Caffeine concentrations in nectar did not exceed the bees' bitter taste threshold, implying that pollinators impose selection for nectar that is pharmacologically active but not repellent. By using a drug to enhance memories of reward, plants secure pollinator fidelity and improve reproductive success.

The missing link between long-term stimulation of nicotinic receptors and the increases of acetylcholine release and vasodilation in the cerebral cortex of aged rats

In adult rats (4-9 months), chronic nicotine infusion increases the basal level of acetylcholine (ACh) release in the cerebral cortex and enhances responses of cortical ACh release and cortical vasodilation elicited by nucleus basalis of Meynert (NBM) stimulation. In the present study, we examined whether these effects of nicotine are detected in aged rats. Aged rats (27-30 months) received sustained subcutaneous nicotine (100 μg/kg/h) or saline for 14 days. Under urethane anesthesia, ACh release and regional blood flow in the parietal cortex were measured. The basal level of ACh release in the cerebral cortex was not changed by chronic nicotine. In addition, the magnitudes of ACh release and vasodilation by NBM stimulation were similar between the saline-treated and nicotine-treated groups. The lack of an effect of chronic nicotine in aged rats may be due to a decrease in nicotinic receptors in the cerebral cortex during aging (Nordberg et al., J Neurosci Res 31:103-111, 1992).

Toxicity of nicotine by repeated intratracheal instillation to f344 rats

In vivo, nicotine in cigarette smoke induces various effects not only on the respiratory system but also the central and peripheral nerve systems, circulatory organs and digestive organs, and there is a possibility of promotion of lung tumorigenesis. The present experiment was conducted to examine histopathological changes caused by nicotine in the lung with repeated intratracheal instillation (i.t.). Six-week-old male F344 rats were administered nicotine by i.t. at doses of 0.05, 0.1 and 0.2 mg nicotine/rat every 3 weeks beginning at week 4, for up to a total of 9 times and were then sacrificed at week 30. The total number of administrations, total dose of nicotine and effective number of rats were 9 times, 0.45 mg and 5 rats and 4 times, 0.20 mg and 5 rats for the 0.05 mg nicotine/rat group; 3 times, 0.30 mg and 5 rats and 4 times, 0.40 mg and 3 rats for the 0.1 mg group; and 3 times, 0.60 mg and 3 rats for the 0.2 mg group, respectively. As a control group, 5 rats were administered 0.2 ml saline/rat 9 times. Some rats administered 0.1 and 0.2 mg nicotine suffered convulsions just after administration. Histopathologically, though proliferative changes were not observed, neutrophil infiltration, edema and fibrosis in the lung were induced by nicotine. In conclusion, repeated treatment of nicotine promoted neurologic symptoms in the acute phase, and strong inflammation in the lungs in the chronic phase, even at a low dose. Toxicity of nicotine is suggested to depend not on total dose of nicotine in the experiment but rather on repeated injury with consecutive administration.

An interspecific Nicotiana hybrid as a useful and cost-effective platform for production of animal vaccines

The use of transgenic plants to produce novel products has great biotechnological potential as the relatively inexpensive inputs of light, water, and nutrients are utilised in return for potentially valuable bioactive metabolites, diagnostic proteins and vaccines. Extensive research is ongoing in this area internationally with the aim of producing plant-made vaccines of importance for both animals and humans. Vaccine purification is generally regarded as being integral to the preparation of safe and effective vaccines for use in humans. However, the use of crude plant extracts for animal immunisation may enable plant-made vaccines to become a cost-effective and efficacious approach to safely immunise large numbers of farm animals against diseases such as avian influenza. Since the technology associated with genetic transformation and large-scale propagation is very well established in Nicotiana, the genus has attributes well-suited for the production of plant-made vaccines. However the presence of potentially toxic alkaloids in Nicotiana extracts impedes their use as crude vaccine preparations. In the current study we describe a Nicotiana tabacum and N. glauca hybrid that expresses the HA glycoprotein of influenza A in its leaves but does not synthesize alkaloids. We demonstrate that injection with crude leaf extracts from these interspecific hybrid plants is a safe and effective approach for immunising mice. Moreover, this antigen-producing alkaloid-free, transgenic interspecific hybrid is vigorous, with a high capacity for vegetative shoot regeneration after harvesting. These plants are easily propagated by vegetative cuttings and have the added benefit of not producing viable pollen, thus reducing potential problems associated with bio-containment. Hence, these Nicotiana hybrids provide an advantageous production platform for partially purified, plant-made vaccines which may be particularly well suited for use in veterinary immunization programs.

Effects of nicotine on guided bone augmentation in rat calvarium

OBJECTIVE

A limited number of experimental animal studies and in vitro studies have confirmed that nicotine impairs bone healing, diminishes osteoblast function, causes autogenous bone graft morbidity, and decreases graft biomechanical properties. The aim of this study was the histomrphometric assessment of the effect of nicotine on guided bone augmentation in a rat model.

MATERIAL AND METHODS

Twenty-four male Wistar rats were randomly divided into a nicotine group and a control group. All animals received either nicotine (3 mg/kg) or saline 4 weeks before the surgical procedure and continued to receive nicotine or saline from surgery until death at 12 weeks. Two plastic caps were placed in the exposed calvaria of rats. Images of bone augmentation within the plastic caps were then taken using microfocus computed tomography (micro-CT). Histological sections were cut along the same plane as that used for micro-CT images.

RESULTS

Bone augmentation beyond the skeletal envelope occurred in both the nicotine and control groups. However, the nicotine group showed significantly smaller increases in bone volume and bone height than the controls.

CONCLUSION

Nicotine jeopardized, but did not prevent, the process of guided bone augmentation in a rat model.

Nicotine-induced survival signaling in lung cancer cells is dependent on their p53 status while its down-regulation by curcumin is independent

Background

Lung cancer is the most lethal cancer and almost 90% of lung cancer is due to cigarette smoking. Even though nicotine, one of the major ingredients of cigarette smoke and the causative agent for addiction, is not a carcinogen by itself, several investigators have shown that nicotine can induce cell proliferation and angiogenesis. We observed that the proliferative index of nicotine is different in the lung cancer cell lines H1299 (p53-/-) and A549 (p53+/+) which indicates that the mode of up-regulation of survival signals by nicotine might be different in cells with and without p53.

Results

While low concentrations of nicotine induced activation of NF-κB, Akt, Bcl2, MAPKs, AP1 and IAPs in H1299, it failed to induce NF-κB in A549, and compared to H1299, almost 100 times higher concentration of nicotine was required to induce all other survival signals in A549. Transfection of WT-p53 and DN-p53 in H1299 and A549 respectively, reversed the mode of activation of survival signals. Curcumin down-regulated all the survival signals induced by nicotine in both the cells, irrespective of their p53 status. The hypothesis was confirmed when lower concentrations of nicotine induced NF-κB in two more lung cancer cells, Hop-92 and NCI-H522 with mutant p53 status. Silencing of p53 in A549 using siRNA made the cells susceptible to nicotine-induced NF-κB nuclear translocation as in A549 DN-p53 cells.

Conclusions

The present study reveals a detrimental role of nicotine especially in lung cancer patients with impaired p53 status and identifies curcumin as a potential chemopreventive.

Effect of erythromycin on biological activities induced by clostridium perfringens alpha-toxin

Clostridium perfringens alpha-toxin, an important agent of gas gangrene with inflammatory myopathies, possesses lethal, hemolytic, and necrotic activities. Here, we show that alpha-toxin-induced lethality in mice was inhibited by i.v. preadministration of erythromycin (ERM). Administration of ERM resulted in a drastic reduction in the release of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 and systemic hemolysis induced by alpha-toxin, whereas the administration of kitasamycin did not. Furthermore, the lethality and systemic hemolysis caused by alpha-toxin were blocked by the preinjection of anti-TNF-alpha, but not the anti-IL-1beta- or anti-IL-6-antibody. In addition, TNF-alpha-deficient mice were resistant to alpha-toxin, indicating that TNF-alpha plays an important role in the lethality. ERM inhibited the toxin-induced release of TNF-alpha from neutrophils and phosphorylation of toropomyosin-related kinase receptor A (TrkA) and extracellular-regulated kinase (ERK) 1/2. Furthermore, K252a, a TrkA inhibitor, and PD98059 (2'-amino-3'-methoxyflavone), an ERK1/2 inhibitor, inhibited the toxin-induced release of TNF-alpha from neutrophils. The observation shows that the toxin-induced release of TNF-alpha is dependent on the activation of ERK/mitogen-activated protein kinase signal transduction via TrkA in neutrophils and that ERM specifically blocks the toxin-induced events through the activation of neutrophils.

A histologic and histometric assessment of the influence of nicotine on alveolar bone loss in rats

BACKGROUND

Cigarette smoking has long been recognized as a risk factor for periodontal disease. The aim of this study was to perform quantitative and qualitative analyses of bone loss in the furcation region of periodontally healthy rats after daily systemic administration of nicotine or saline solution.

METHODS

Thirty adult male Wistar rats were assigned randomly to twice daily subcutaneous injections of saline solution (control, group C) or nicotine (group N). The animals were sacrificed at 37, 44, or 51 days after the first subcutaneous injection. The specimens were processed for serial histologic sections, and the area of bone loss in the furcation region of the second molar was analyzed histometrically.

RESULTS

Greater bone loss was detected in group N compared to group C on day 37 (16.36 +/- 5.84 mm(2) and 7.24 +/- 2.66 mm(2)), day 44 (15.12 +/- 4.57 mm(2) and 7.76 +/- 1.35 mm(2)), and day 51 (18.80 +/- 3.71 mm(2) and 8.74 +/- 2.61 mm(2)), respectively (P <0.05). Extension of bone loss appeared greater in the furcation region of group N where a thinner trabeculae bone was found. After day 37, bone loss did not increase significantly.

CONCLUSIONS

Daily systemic administration of nicotine resulted in significantly greater bone loss in the furcation region compared to saline solution. This indicated a close association between nicotine and periodontal morbidity in rats.

Chronic nicotine improves working and reference memory performance and reduces hippocampal NGF in aged female rats

The cholinergic system is involved in cognition and several forms of dementia, including Alzheimer's disease, and nicotine administration has been shown to improve cognitive performance in both humans and rodents. While experiments with humans have shown that nicotine improves the ability to handle an increasing working memory load, little work has been done in animal models evaluating nicotine effects on performance as working memory load increases. In this report, we demonstrate that in aged rats nicotine improved the ability to handle an increasing working memory load as well as enhanced performance on the reference memory component of the water radial arm maze task. The dose required to exert these effects (0.3mg/kg/day) was much lower than doses shown to be effective in young rats and appears to be a lower maintenance dose than is seen in light to moderate smokers. In addition, our study reports a nicotine-induced reduction in nerve growth factor (NGF) protein levels in the hippocampus of the aged rat. The effects of nicotine on hippocampal NGF levels are discussed as a potential mechanism of nicotine-induced improvements in working and reference memory.

A search for residual behavioral effects of trichloroethylene (TCE) in rats exposed as young adults

Trichloroethylene (TCE) is an organic solvent with robust acute effects on the nervous system, but poorly documented long-term effects. This study employed a signal detection task (SDT) to assess the persistence of effects of repeated daily inhalation of TCE on sustained attention in rats. Adult male Long-Evans rats inhaled TCE at 0, 1600, or 2400 ppm, 6 h/day for 20 days (n=8/group) and began learning the SDT 3 weeks later. Rats earned food by pressing one retractable response lever in a signal trial and a second lever in a blank (no signal) trial. TCE did not affect acquisition of the response rule or performance of the SDT after the intertrial interval (ITI) was changed from a constant value to a variable one. Increasing the trial presentation rate reduced accuracy equivalently in all groups. Injections of ethanol (0, 0.5, 1.0, 1.5 g/kg ip) and d-amphetamine (0, 0.1, 0.3, 1.0 mg/kg sc) systematically impaired performance as functions of drug dose. d-Amphetamine (1.0 mg/kg) reduced P(hit) more in the 2400-ppm TCE group than in the other groups. All rats required remedial training to learn a reversal of the response contingencies, which TCE did not interfere with. Thus, a history of exposure to TCE did not significantly alter learning or sustained attention in the absence of drugs. Although ethanol did not differentially affect the TCE groups, the effect of d-amphetamine is consistent with solvent-induced changes in dopaminergic functions in the CNS. Calculations indicated power values of 0.5 to 0.8 to detect main effects of TCE for the three primary endpoints.

Nicotinic receptors in aging and dementia

Activation of neuronal nicotinic acetylcholine receptors (nAChRs) has been shown to maintain cognitive function following aging or the development of dementia. Nicotine and nicotinic agonists have been shown to improve cognitive function in aged or impaired subjects. Smoking has also been shown in some epidemiological studies to be protective against the development of neurodegenerative diseases. This is supported by animal studies that have shown nicotine to be neuroprotective both in vivo and in vitro. Treatment with nicotinic agonists may therefore be useful in both slowing the progression of neurodegenerative illnesses, and improving function in patients with the disease. While increased nicotinic function has been shown to be beneficial, loss of cholinergic markers is often seen in patients with dementia, suggesting that decreased cholinergic function could contribute to both the cognitive deficits, and perhaps the neuronal degeneration, associated with dementia. In this article we will review the literature on each of these areas. We will also present hypotheses that might address the mechanisms underlying the ability of nAChR function to protect against neurodegeneration or improve cognition, two potentially distinct actions of nicotine.