Effects of formaldehyde on the frog's mucociliary epithelium as a surrogate to evaluate air pollution effects on the respiratory epithelium

A Comprehensive Literature Review on the Effects of Formaldehyde on the Upper Respiratory Tract

Prolonged exposure to indoor air pollutants at high concentrations can have adverse health effects on the respiratory system of individuals who spend most of their time indoors. Formaldehyde (FA) is a common indoor air pollutant because of its extensive use in household products such as cleaners, floorings, and furnishings. As a chemical, FA is highly water soluble and reactive. When its airborne form is inhaled, it is mainly absorbed in the upper airways. FA has been extensively studied for its carcinogenic effects, but it can also cause inflammation in the upper airways. The objective of the current review was to assess the secondary effects of such inflammation and how it can contribute to an increased risk for upper respiratory infections, which are mostly caused by viruses. A rigorous literature review was conducted through gathering, reading, and analyzing relevant literature, including peer-reviewed articles published after 1990 and seminal literature regardless of publication date. Findings from the review provide a greater understanding of the outcomes of FA exposure, the potential accumulative damage to the upper respiratory tract, and the associated increased risk for acute infections of the upper respiratory tract. This information can help in the development and enforcement of stricter regulations for furniture and building materials for household-related products to limit exposure to indoor pollutants such as FA.

An Adverse Outcome Pathway for Decreased Lung Function Focusing on Mechanisms of Impaired Mucociliary Clearance Following Inhalation Exposure

Adverse outcome pathways (AOPs) help to organize available mechanistic information related to an adverse outcome into key events (KEs) spanning all organizational levels of a biological system(s). AOPs, therefore, aid in the biological understanding of a particular pathogenesis and also help with linking exposures to eventual toxic effects. In the regulatory context, knowledge of disease mechanisms can help design testing strategies using in vitro methods that can measure or predict KEs relevant to the biological effect of interest. The AOP described here evaluates the major processes known to be involved in regulating efficient mucociliary clearance (MCC) following exposures causing oxidative stress. MCC is a key aspect of the innate immune defense against airborne pathogens and inhaled chemicals and is governed by the concerted action of its functional components, the cilia and airway surface liquid (ASL). The AOP network described here consists of sequences of KEs that culminate in the modulation of ciliary beat frequency and ASL height as well as mucus viscosity and hence, impairment of MCC, which in turn leads to decreased lung function.

Evaluating the Sub-Acute Toxicity of Formaldehyde Fumes in an In Vitro Human Airway Epithelial Tissue Model

Formaldehyde (FA) is an irritating, highly reactive aldehyde that is widely regarded as an asthmagen. In addition to its use in industrial applications and being a product of combustion reaction and endogenous metabolism, FDA-regulated products may contain FA or release FA fumes that present toxicity risks for both patients and healthcare workers. Exposure to airborne FA is associated with nasal neoplastic lesions in both animals and humans. It is classified as a Group 1 carcinogen by International Agency for Research on Cancer (IARC) based on the increased incidence of cancer in animals and a known human carcinogen in the Report on Carcinogens by National Toxicology Program (NTP). Herein, we systematically evaluated the tissue responses to FA fumes in an in vitro human air-liquid-interface (ALI) airway tissue model. Cultures were exposed at the air interface to 7.5, 15, and 30 ppm of FA fumes 4 h per day for 5 consecutive days. Exposure to 30 ppm of FA induced sustained oxidative stress, along with functional changes in ciliated and goblet cells as well as possible squamous differentiation. Furthermore, secretion of the proinflammatory cytokines, IL-1β, IL-2, IL-8, GM-CSF, TNF-a and IFN-γ, was induced by repeated exposures to FA fumes. Expression of MMP-1, MMP-3, MMP-7, MMP-10, MMP-12, and MMP-13 was downregulated at the end of the 5-day exposure. Although DNA-damage was not detected by the comet assay, FA exposures downregulated the DNA repair enzymes MGMT and FANCD2, suggesting its possible interference in the DNA repair capacity. Overall, a general concordance was observed between our in vitro responses to FA fume exposures and the reported in vivo toxicity of FA. Our findings provide further evidence supporting the application of the ALI airway system as a potential in vitro alternative for screening and evaluating the respiratory toxicity of inhaled substances.

Beneficial effects of polyherbal formulation (Bronco-T) on formaldehyde-induced lung toxicity in male Wistar rats

Polyherbal compound (Bronco-T) has been extensively used as a traditional medicine for various therapies. However, very few report studies on anti-inflammatory and lung regeneration properties are evidenced. In the present study, we evaluated the beneficial actions and anti-inflammatory properties of polyherbal medicine, Bronco-T, exhibited by treating the lungs of rats exposed to formaldehyde to evaluate the beneficial properties. For this study, we divided into five groups': i.e. Group-I served as a control and the other four groups such as II, III, IV, and V are experimental. All animals maintained by regular feed and water ad libitum during the study. Formaldehyde vapors exposure at a single period of time (1 hour) daily (40%formaldehyde at room temperature) for 21 days period exposed all groups. The Bronco-T extracts about 50 mg/kg BW administered to experimental groups and group IV rats treated with 500μ grams/Kg BW salbutamol. To understand the impact of formaldehyde exposure on the beneficial effects of Bronco-T, we evaluated hematological parameters, bronchoalveolar lavage (BAL), histamine levels, and histological alterations of lung architecture. Formaldehyde-induced adverse effects in lung and increased histamine levels in BAL compared to Bronco-T-treated rats act as a preventive immunological role in blood toxicity and recovery of lung architecture in Bronco-T-treated rats. This study showed the evaluation of antihistamine levels through HPLC analysis. Bronco-T has antioxidant and anti-histamine properties as the widest therapeutic window, and we continue to evaluate the pharmacological evaluations needed in our further studies.

Effect of sub-chronic exposure to cigarette smoke, electronic cigarette and waterpipe on human lung epithelial barrier function

BACKGROUND

Taking into consideration a recent surge of a lung injury condition associated with electronic cigarette use, we devised an in vitro model of sub-chronic exposure of human bronchial epithelial cells (HBECs) in air-liquid interface, to determine deterioration of epithelial cell barrier from sub-chronic exposure to cigarette smoke (CS), e-cigarette aerosol (EC), and tobacco waterpipe exposures (TW).

METHODS

Products analyzed include commercially available e-liquid, with 0% or 1.2% concentration of nicotine, tobacco blend (shisha), and reference-grade cigarette (3R4F). In one set of experiments, HBECs were exposed to EC (0 and 1.2%), CS or control air for 10 days using 1 cigarette/day. In the second set of experiments, exposure of pseudostratified primary epithelial tissue to TW or control air exposure was performed 1-h/day, every other day, until 3 exposures were performed. After 16-18 h of last exposure, we investigated barrier function/structural integrity of the epithelial monolayer with fluorescein isothiocyanate-dextran flux assay (FITC-Dextran), measurements of trans-electrical epithelial resistance (TEER), assessment of the percentage of moving cilia, cilia beat frequency (CBF), cell motion, and quantification of E-cadherin gene expression by reverse-transcription quantitative polymerase chain reaction (RT-qPCR).

RESULTS

When compared to air control, CS increased fluorescence (FITC-Dextran assay) by 5.6 times, whereby CS and EC (1.2%) reduced TEER to 49 and 60% respectively. CS and EC (1.2%) exposure reduced CBF to 62 and 59%, and cilia moving to 47 and 52%, respectively, when compared to control air. CS and EC (1.2%) increased cell velocity compared to air control by 2.5 and 2.6 times, respectively. The expression of E-cadherin reduced to 39% of control air levels by CS exposure shows an insight into a plausible molecular mechanism. Altogether, EC (0%) and TW exposures resulted in more moderate decreases in epithelial integrity, while EC (1.2%) substantially decreased airway epithelial barrier function comparable with CS exposure.

CONCLUSIONS

The results support a toxic effect of sub-chronic exposure to EC (1.2%) as evident by disruption of the bronchial epithelial cell barrier integrity, whereas further research is needed to address the molecular mechanism of this observation as well as TW and EC (0%) toxicity in chronic exposures.

Electronic cigarettes in the indoor environment

The use of electronic cigarettes (e-cigarettes or "vaping") has seen an unprecedented increase worldwide. Vaping has been promoted as a beneficial smoking cessation tool and an alternative nicotine delivery device that contains no combustion by-products. However, nicotine is highly addictive, and the increased use of nicotine-containing e-cigarettes among teens and individuals who are not in need of smoking cessation may lead to overall greater nicotine dependence in the population. Furthermore, available research indicates that vaping solutions and their emissions may contain much more than just nicotine, including aerosolized flavorings, propylene glycol (PG), and other intentional and unintentional contaminants. These materials could present undefined potential health hazards to both e-cigarette users and bystanders, the full extent of which is not well understood at this time. Whereas e-cigarette usage and exposures may lower some or most of the risks associated with conventional cigarette use, the health effects of nicotine and aerosol exposures from e-cigarettes are not well understood. Research indicates that vaping aerosols are not benign, especially for nearby people in areas with limited ventilation and people with compromised health conditions. In addition, e-juice liquids have already been responsible for an increase in accidental poisonings in children. Because the magnitude of health and safety hazards that vaping may present to nonusers remains unclear, it is prudent to manage and control vaping in indoor locations where smoking is currently restricted. Based on a review of current scientific information, the American Industrial Hygiene Association (AIHA) recommends that e-cigarettes should be considered a source of aerosols, volatile organic compounds (VOCs), and particulates in the indoor environment that have not been thoroughly characterized or evaluated for health risk or safety.

How to characterize a nasal product. The state of the art of in vitro and ex vivo specific methods

Nasal delivery offers many benefits over other conventional routes of delivery (e.g. oral or intravenous administration). Benefits include, among others, a fast onset of action, non-invasiveness and direct access to the central nervous system. The nasal cavity is not only limited to local application (e.g. rhinosinusitis) but can also provide direct access to other sites in the body (e.g. the central nervous system or systemic circulation). However, both the anatomy and the physiology of the nose impose their own limitations, such as a small volume for delivery or rapid mucociliary clearance. To meet nasal-specific criteria, the formulator has to complete a plethora of tests, in vitro and ex vivo, to assess the efficacy and tolerance of a new drug-delivery system. Moreover, depending on the desired therapeutic effect, the delivery of the drug should target a specific pathway that could potentially be achieved through a modified release of this drug. Therefore, this review focuses on specific techniques that should be performed when a nasal formulation is developed. The review covers both the tests recommended by regulatory agencies (e.g. the Food and Drug Administration) and other complementary experiments frequently performed in the field.

Short-term exposure to formaldehyde promotes oxidative damage and inflammation in the trachea and diaphragm muscle of adult rats

Formaldehyde (FA) is an environmental pollutant widely used in industry. Exposure to FA causes irritation of the respiratory mucosa and is associated with inflammation and oxidative stress in the airways. This study aimed at investigating the oxidative effects on the inflammatory response in the trachea and the diaphragm muscle (DM) of rats exposed to different concentrations of formaldehyde. Twenty-eight Fischer male rats were divided into four groups: control group (CG) exposed to the ambient air; and three groups exposed to the following formaldehyde concentrations of 1% (FA1), 5% (FA5) and 10% (FA10), respectively. The exposure occurred for twenty minutes, three times a day for five days. Oxidative stress analyses were performed by carbonyl protein, lipid peroxidation and catalase activity. The assessment of inflammatory cell influx in both organs and the mucus production in the trachea was carried out. There was an increase of lipid peroxidation in the trachea and the DM of FA1 and FA5 groups compared to the CG and FA10. The oxidation of DM proteins increased in FA10 group compared to CG, FA1 and FA5. The catalase enzyme activity in the DM was reduced in FA1, FA5 and FA10 compared to the CG. Meanwhile, there was a reduction in the enzymatic activity of FA10 compared to the CG in the trachea. The morphometric analysis in the DM demonstrated an influx of inflammatory cells in FA10 compared to the CG. In FA10 group, the tracheal epithelium showed metaplasia and ulceration. In addition, the tracheal epithelium showed more mucus deposits in FA5 compared to CG, FA1 and FA10. The results demonstrated that the exposure to formaldehyde at different concentrations in a short period of time promotes oxidative damage and inflammation in the DM and the trachea and causes metaplasia, ulceration and increased mucus at the latter.

Therapeutic role of curcumin in oxidative DNA damage caused by formaldehyde

PURPOSE

Formaldehyde is a common environmental contaminant that causes oxidative DNA damage in cells by increasing the production of reactive oxygen species. The aim of this study was to investigate the amount of 8-hydroxy-deoxyguanosine (8-OhdG), tumor protein 53(TP53), beta-amyloid[Aß(1-42), Aß (1-40)], total antioxidant capacity (TAC) and malondialdehyde (MDA) and the therapeutic role of curcumin in rat cells with oxidative DNA damage caused by formaldehyde.

METHOD

The control group was given physiological saline for 15 days (i.p.) and the second group was given 37% formaldehyde (i.p.) at a dose of 9 mg/kg group every other day. The third group was given 9 mg/kg formaldehyde (i.p.) every other day and treated therapeutically with 100 mg/kg curcumin every day by gavage. At the end of the trial period, urine, blood, and brain tissue was collected from the rats.

RESULTS

The levels of MDA in sera were increased and the TAC, TP53, and Aß (1-40) levels were reduced in the formaldehyde-treated group with respect to the control group (p<0.005). After treatment with curcumin, the levels of sera MDA were significantly reduced, the TAC, TP53, and Aß (1-40) levels were significantly increased (P < 0.05). The levels of whole brain Aß (1-42) and 8-OhdG were increased in the formaldehyde-treated group and reduced after treatment with curcumin (P < 0.05). Urinary 8-OhdG excretion increased in the formaldehyde-treated group (P < 0.05) and decreased after treatment with curcumin (P > 0.05).

CONCLUSIONS

In conclusion, the oxidative stress caused by formaldehyde exposure was reduced with the application of curcumin.

BDNF-TrkB pathway mediates neuroprotection of hydrogen sulfide against formaldehyde-induced toxicity to PC12 cells

Formaldehyde (FA) is a common environmental contaminant that has toxic effects on the central nervous system (CNS). Our previous data demonstrated that hydrogen sulfide (H2S), the third endogenous gaseous mediator, has protective effects against FA-induced neurotoxicity. As is known to all, Brain-derived neurotropic factor (BDNF), a member of the neurotrophin gene family, mediates its neuroprotective properties via various intracellular signaling pathways triggered by activating the tyrosine kinase receptor B (TrkB). Intriguingly, our previous data have illustrated the upregulatory role of H2S on BDNF protein expression in the hippocampus of rats. Therefore, in this study, we hypothesized that H2S provides neuroprotection against FA toxicity by regulating BDNF-TrkB pathway. In the present study, we found that NaHS, a donor of H2S, upregulated the level of BDNF protein in PC12 cells, and significantly rescued FA-induced downregulation of BDNF levels. Furthermore, we found that pretreatment of PC12 cells with K252a, an inhibitor of the BDNF receptor TrkB, markedly reversed the inhibition of NaHS on FA-induced cytotoxicity and ablated the protective effects of NaHS on FA-induced oxidative stress, including the accumulation of intracellular reactive oxygen species (ROS), 4-hydroxy-2-trans-nonenal (4-HNE), and malondialdehyde (MDA). We also showed that K252a abolished the inhibition of NaHS on FA-induced apoptosis, as well as the activation of caspase-3 in PC12 cells. In addition, K252a reversed the protection of H2S against FA-induced downregulation of Bcl-2 protein expression and upregulation of Bax protein expression in PC12 cells. These data indicate that the BDNF-TrkB pathway mediates the neuroprotection of H2S against FA-induced cytotoxicity, oxidative stress and apoptosis in PC12 cells. These findings provide a novel mechanism underlying the protection of H2S against FA-induced neurotoxicity.

Exposure to low doses of formaldehyde during pregnancy suppresses the development of allergic lung inflammation in offspring

Formaldehyde (FA) is an environmental and occupational pollutant, and its toxic effects on the immune system have been shown. Nevertheless, no data are available regarding the programming mechanisms after FA exposure and its repercussions for the immune systems of offspring. In this study, our objective was to investigate the effects of low-dose exposure of FA on pregnant rats and its repercussion for the development of allergic lung inflammation in offspring. Pregnant Wistar rats were assigned in 3 groups: P (rats exposed to FA (0.75 ppm, 1 h/day, 5 days/week, for 21 days)), C (rats exposed to vehicle of FA (distillated water)) and B (rats non-manipulated). After 30 days of age, the offspring was sensitised with ovalbumin (OVA)-alum and challenged with aerosolized OVA (1%, 15 min, 3 days). After 24 h the OVA challenge the parameters were evaluated. Our data showed that low-dose exposure to FA during pregnancy induced low birth weight and suppressed the development of allergic lung inflammation and tracheal hyperresponsiveness in offspring by mechanisms mediated by reduced anaphylactic antibodies synthesis, IL-6 and TNF-alpha secretion. Elevated levels of IL-10 were found. Any systemic alteration was detected in the exposed pregnant rats, although oxidative stress in the uterine environment was evident at the moment of the delivery based on elevated COX-1 expression and reduced cNOS and SOD-2 in the uterus. Therefore, we show the putative programming mechanisms induced by FA on the immune system for the first time and the mechanisms involved may be related to oxidative stress in the foetal microenvironment.

The putative role of ovary removal and progesterone when considering the effect of formaldehyde exposure on lung inflammation induced by ovalbumin

OBJECTIVE

Formaldehyde exposure during the menstrual cycle is known to affect the course of allergic lung inflammation. Because our previous data demonstrated that formaldehyde combined with an ovariectomy reduced allergic lung inflammation, we investigated the putative role of ovary removal and progesterone treatment when considering the effect of formaldehyde on allergic lung inflammation.

METHOD

Ovariectomized rats and their matched controls were exposed to formaldehyde (1%, 3 days, 90 min/day) or vehicle, and immediately after exposure, the rats were sensitized to ovalbumin by a subcutaneous route. After 1 week, the rats received a booster by the same route, and after an additional week, the rats were challenged with ovalbumin (1%) by an aerosol route. The leukocyte numbers, interleukin-10 (IL-10) release, myeloperoxidase activity, vascular permeability, ex vivo tracheal reactivity to methacholine and mast cell degranulation were determined 24 h later.

RESULTS

Our results showed that previous exposure to formaldehyde in allergic rats decreased lung cell recruitment, tracheal reactivity, myeloperoxidase activity, vascular permeability and mast cell degranulation while increasing IL-10 levels. Ovariectomy only caused an additional reduction in tracheal reactivity without changing the other parameters studied. Progesterone treatment reversed the effects of formaldehyde exposure on ex vivo tracheal reactivity, cell influx into the lungs and mast cell degranulation.

CONCLUSION

In conclusion, our study revealed that formaldehyde and ovariectomy downregulated allergic lung inflammation by IL-10 release and mast cell degranulation. Progesterone treatment increased eosinophil recruitment and mast cell degranulation, which in turn may be responsible for tracheal hyperreactivity and allergic lung inflammation.

Formaldehyde inhalation reduces respiratory mechanics in a rat model with allergic lung inflammation by altering the nitric oxide/cyclooxygenase-derived products relationship

Bronchial hyperresponsiveness is a hallmark of asthma and many factors modulate bronchoconstriction episodes. A potential correlation of formaldehyde (FA) inhalation and asthma has been observed; however, the exact role of FA remains controversial. We investigated the effects of FA inhalation on Ovalbumin (OVA) sensitisation using a parameter of respiratory mechanics. The involvement of nitric oxide (NO) and cyclooxygenase-derived products were also evaluated. The rats were submitted, or not, to FA inhalation (1%, 90 min/day, 3 days) and were OVA-sensitised and challenged 14 days later. Our data showed that previous FA exposure in allergic rats reduced bronchial responsiveness, respiratory resistance (Rrs) and elastance (Ers) to methacholine. FA exposure in allergic rats also increased the iNOS gene expression and reduced COX-1. L-NAME treatment exacerbated the bronchial hyporesponsiveness and did not modify the Ers and Rrs, while Indomethacin partially reversed all of the parameters studied. The L-NAME and Indomethacin treatments reduced leukotriene B₄ levels while they increased thromboxane B₂ and prostaglandin E₂. In conclusion, FA exposure prior to OVA sensitisation reduces the respiratory mechanics and the interaction of NO and PGE₂ may be representing a compensatory mechanism in order to protect the lung from bronchoconstriction effects.

Effects of nitric oxide in mucociliary transport

The airways are made up of ciliated epithelium which secretes mucous, protecting the respiratory tract from particles inhaled during breathing. Its is paramount to understand the physiology and the mechanisms involved in mucociliary activity. Literature suggests that Nitric oxide (NO), especially the one produced by iNOS expression, maintains the mucociliary function and the immune defense of the nasal cavity.

Aim

to assess NO participation and the enzymatic pathways in the production of NO and mucociliary transport, using constructive and inductive NO synthetase inhibitors, L-NAME and aminoguanidine, respectively.

Materials and methods

frog palates were prepared and immerse in ringer (control), L-NAME or aminoguanidine solutions. The palates were immerse in these solutions for four periods of 15 minutes. Mucociliary transport measures were carried out before and after each exposure.

Results

control palates maintained stable their transportation speed. L-NAME increased, while aminoguanidine reduced mucous transportation velocity.

Conclusion

unspecific cNOS block with L-NAME and relatively specific iNOS block with aminoguanidine results leads us to propose that depending on the pathway, the NO can increase or reduce mucociliary transport in frog palates.

Formaldehyde induces apoptosis through decreased Prx 2 via p38 MAPK in lung epithelial cells

Formaldehyde (FA) is an important substance that induces sick house syndrome and diseases, such as asthma and allergies. Oxidative stress is involved in the development of respiratory disease, and diverse antioxidants may protect respiratory tract cells from apoptosis. Peroxiredoxin is a pivotal endogenous antioxidant. In the present study, FA induced death in A549 cells, a lung epithelial cell line, in a dose-dependent manner. FA also increased lipid peroxide formation (LPO) in A549 cells, suggesting a role for oxidative stress. Additionally, FA decreased peroxiredoxin 2 (Prx 2) protein levels after a 24 or 48h exposure to FA. We also examined whether the FA-induced decrease in Prx 2 was associated with apoptosis. Prx 2 overexpression protected against FA-induced cell apoptosis but not necrosis. Prx 2 overexpression blocked FA-induced increase in Bax, a pro-apoptotic molecule, and a decrease in Bcl-2, an anti-apoptotic molecule. Prx 2 overexpression also protected against FA-induced activation of some special apoptosis-associated proteins [caspase-3, caspase-9, and polypeptide poly (ADP-ribose) polymerase (PARP)]. Furthermore, we examined the signaling molecules involved in the FA-induced decrease in Prx 2 expression. The FA-induced decrease in Prx 2 and increase in cell apoptosis was restored by treatment with SB203580 [a p38 mitogen activated protein kinase (MAPK) inhibitor], but not by SP600125 [a c-jun-N-terminal kinase (JNK) inhibitor]. Also, FA-induced events were blocked by treatment with p38 siRNA, but not by scrambled siRNA. Indeed, FA increased p38 MAPK activation, suggesting a role for p38 MAPK in FA action. In conclusion, FA mediated apoptosis in lung epithelial cells by decreasing Prx 2 via p38 MAPK.

Reduced allergic lung inflammation in rats following formaldehyde exposure: long-term effects on multiple effector systems

Clinical and experimental evidences show that formaldehyde (FA) exposure has an irritant effect on the upper airways. As being an indoor and outdoor pollutant, FA is known to be a causal factor of occupational asthma. This study aimed to investigate the repercussion of FA exposure on the course of a lung allergic process triggered by an antigen unrelated to FA. For this purpose, male Wistar rats were subjected to FA inhalation for 3 consecutive days (1%, 90-min daily), subsequently sensitized with ovalbumin (OVA)-alum via the intraperitoneal route, and 2 weeks later challenged with aerosolized OVA. The OVA challenge in rats after FA inhalation (FA/OVA group) evoked a low-intensity lung inflammation as indicated by the reduced enumerated number of inflammatory cells in bronchoalveolar lavage as compared to FA-untreated allergic rats (OVA/OVA group). Treatment with FA also reduced the number of bone marrow cells and blood leukocytes in sensitized animals challenged with OVA, which suggests that the effects of FA had not been only localized to the airways. As indicated by passive cutaneous anaphylactic reaction, FA treatment did not impair the anti-OVA IgE synthesis, but reduced the magnitude of OVA challenge-induced mast cell degranulation. Moreover, FA treatment was associated to a diminished lung expression of PECAM-1 (platelet-endothelial cell adhesion molecule 1) in lung endothelial cells after OVA challenge and an exacerbated release of nitrites by BAL-cultured cells. Keeping in mind that rats subjected solely to either FA or OVA challenge were able to significantly increase the cell influx into lung, our study shows that FA inhalation triggers long-lasting effects that affect multiple mediator systems associated to OVA-induced allergic lung such as the reduction of mast cells activation, PECAM-1 expression and exacerbation of NO generation, thereby contributing to the decrease of cell recruitment after the OVA challenge. In conclusion, repeated expositions to air-borne FA may impair the lung cell recruitment after an allergic stimulus, thereby leading to a non-responsive condition against inflammatory stimuli likely those where mast cells are involved.

Dendrimers as a Carrier for Pulmonary Delivery of Enoxaparin, a Low-Molecular Weight Heparin

This study was designed to test the hypothesis that positively charged dendrimers form a complex with enoxaparin, a low-molecular weight heparin (LMWH), and that the resulting drug-dendrimer complex is effective in preventing deep vein thrombosis after pulmonary administration. Fourier Transform Infrared (FTIR) spectroscopy and the azure A assay were used to evaluate interactions between dendrimers and enoxaparin. The efficacy of polyamidoamine (PAMAM) dendrimers in enhancing pulmonary absorption of enoxaparin was studied by administering enoxaparin-dendrimer formulations into the lungs of anesthetized rats and monitoring drug absorption by measuring plasma anti-factor Xa activity. The optimized formulations were evaluated for their efficacy in preventing deep vein thrombosis in a rodent model. The safety of the formulations was tested by studying their effects on mucociliary transport rate (MTR) in a frog palate model and by measuring injury markers in rat bronchoalveolar fluid. The FTIR data and azure A assay revealed ionic interactions between the amino groups of cationic dendrimers and the carboxylic and sulfate groups of enoxaparin. Positively charged dendrimers increased the relative bioavailability of enoxaparin by 40%, while a negatively charged dendrimer had no effect. Formulations containing 1% G2 or 0.5% G3 PAMAM dendrimer plus enoxaparin were as efficacious in preventing deep vein thrombosis in a rat model as subcutaneously administered enoxaparin. The formulations did not adversely affect the MTR or produce extensive damage to the lungs. Positively charged dendrimers are a suitable carrier for pulmonary delivery of enoxaparin. They enhance pulmonary absorption of LMWH probably by reducing negative surface charge density of the drug molecule.