Incorporation of alpha-tocopherol in liposomes promotes the retention of liposome-encapsulated glutathione in the rat lung

Modification of α-Tocopherol Succinate with a Tumor-targeting Peptide Conjugate Enhances the Antitumor Efficacy of a Paclitaxel-loaded Lipid Aggregate

Paclitaxel (PTX) is a widely used chemotherapeutic agent in the clinic. However, its clinical benefit is limited due to its low water solubility, off-target toxicity, and for being a multidrug-resistant (MDR) substrate. To overcome these limitations in this study, a tumor-targeting peptide (CRGDK peptide, a ligand for NRP-1 receptor) conjugate of α-tocopheryl succinate (α-TOS) was synthesized and modified on PTX-loaded lipid aggregate (TL-PTX) to leverage the benefits of α-TOS, which include a) anti-cancer activity, b) increased PTX loading, and c) inhibition of MDR activity. Use of peptide conjugate of α-TOS (α-TOS-CRGDK) in lipid aggregate increased PTX entrapment efficiency by 20%, helped in NRP-1 specific cellular uptake and significantly enhanced apoptotic and cell killing activity (p <0.01) of PTX compared to control formulation (CL-PTX) by inhibiting MDR-activity in melanoma resulting in ∼70% increment in overall survival of melanoma tumor-bearing mice. In conclusion, CRGDK- α-TOS conjugate in association with PTX-loaded liposome provided a unique NRP-1 targeted, drug-resistant reversing anticancer regimen for treating aggressive melanoma.

Protein and peptide delivery to lungs by using advanced targeted drug delivery

The challenges and difficulties associated with conventional drug delivery systems have led to the emergence of novel, advanced targeted drug delivery systems. Therapeutic drug delivery of proteins and peptides to the lungs is complicated owing to the large size and polar characteristics of the latter. Nevertheless, the pulmonary route has attracted great interest today among formulation scientists, as it has evolved into one of the important targeted drug delivery platforms for the delivery of peptides, and related compounds effectively to the lungs, primarily for the management and treatment of chronic lung diseases. In this review, we have discussed and summarized the current scenario and recent developments in targeted delivery of proteins and peptide-based drugs to the lungs. Moreover, we have also highlighted the advantages of pulmonary drug delivery over conventional drug delivery approaches for peptide-based drugs, in terms of efficacy, retention time and other important pharmacokinetic parameters. The review also highlights the future perspectives and the impact of targeted drug delivery on peptide-based drugs in the coming decade.

Compiling Evidence for EVALI: A Scoping Review of In Vivo Pulmonary Effects After Inhaling Vitamin E or Vitamin E Acetate

BACKGROUND

Vitamin E acetate (VEA) has come under significant scrutiny due to its association with E-cigarette or vaping product use-associated lung injury (EVALI). Various theoretical mechanisms have been proposed for toxicity, including tocopherol (vitamin E)-mediated surfactant damage, recruitment of inflammation, and pyrolysis of acetate to the pulmonary irritant ketene.

OBJECTIVE

Characterize studies in mammals evaluating inhaled VEA, vitamin E analogues, or pyrolyzed acetate that describe subsequent effects on the lung.

ELIGIBILITY

Research in all languages from time of inception to October 1, 2020, regarding mammals (human or animal) exposed to inhaled vitamin E analogues, or any compound containing acetate administered via inhalation after pyrolysis, and subsequent description of pulmonary effect.

SOURCES OF EVIDENCE

Ovid MEDLINE, Scopus, and Web of Science Core Collection.

RESULTS

In total, 786 unique articles were identified. After duplicate reviewer screening, 16 articles were eligible for inclusion. Tocopherol was evaluated in 68.8% (11/16) of the studies, VEA in 18.8% (3/16), and both VEA and tocopherol were evaluated in 12.5% (2/16). Of the five studies evaluating VEA, it was given by pyrolysis in 60.0% (3/5). No human studies were identified. All included trials were conducted on non-human mammals: 75.0% (12/16) rodent models and 25.0% (4/16) sheep models. Outcomes assessed were heterogeneous and included 57 unique outcomes.

CONCLUSIONS

Several questions still exist regarding the pulmonary toxicity of inhaled tocopherol and VEA. More studies are needed to determine whether tocopherol alone (i.e., without acetate) can cause pulmonary injury. Additionally, further studies of VEA should evaluate the impact that pyrolysis and co-administration with other compounds, such as tetrahydrocannabinol, have on the toxic potential of VEA.

Cationic liposomes containing antioxidants reduces pulmonary injury in experimental model of sepsis: Liposomes antioxidants reduces pulmonary damage

The intracellular redox state of alveolar cells is a determining factor for tolerance to oxidative and pro-inflammatory stresses. This study investigated the effects of intratracheal co-administration of antioxidants encapsulated in liposomes on the lungs of rats subjected to sepsis. For this, male rats subjected to sepsis induced by lipopolysaccharide from Escherichia coli or placebo operation were treated (intratracheally) with antibiotic, 0.9% saline and antioxidants encapsulated or non-encapsulated in liposomes. Experimental model of sepsis by cecal ligation and puncture (CLP) was performed in order to expose the cecum. The cecum was then gently squeezed to extrude a small amount of feces from the perforation site. As an index of oxidative damage, superoxide anions, lipid peroxidation, protein carbonyls, catalase activity, nitrates/nitrites, cell viability and mortality rate were measured. Infected animals treated with antibiotic plus antioxidants encapsulated in liposomes showed reduced levels of superoxide anion (54% or 7.650±1.263 nmol/min/mg protein), lipid peroxidation (33% or 0.117±0.041 nmol/mg protein), protein carbonyl (57% or 0.039 ± 0.022 nmol/mg protein) and mortality rate (3.3%), p value <0.001. This treatment also reduced the level of nitrite/nitrate and increased cell viability (90.7%) of alveolar macrophages. Taken togheter, theses results support that cationic liposomes containing antioxidants should be explored as coadjuvants in the treatment of pulmonary oxidative damage.

Antioxidant strategies in respiratory medicine

Pulmonary oxidant stress plays an important pathogenetic role in disease conditions including acute lung injury/adult respiratory distress syndrome (ALI/ARDS), hyperoxia, ischemia-reperfusion, sepsis, radiation injury, lung transplantation, COPD, and inflammation. Reactive oxygen species (ROS), released from activated macrophages and leukocytes or formed in the pulmonary epithelial and endothelial cells, damage the lungs and initiate cascades of pro-inflammatory reactions propagating pulmonary and systemic stress. Diverse molecules including small organic compounds (e.g. gluthatione, tocopherol (vitamin E), flavonoids) serve as natural antioxidants that reduce oxidized cellular components, decompose ROS and detoxify toxic oxidation products. Antioxidant enzymes can either facilitate these antioxidant reactions (e.g. peroxidases using glutathione as a reducing agent) or directly decompose ROS (e.g. superoxide dismutases [SOD] and catalase). Many antioxidant agents are being tested for treatment of pulmonary oxidant stress. The administration of small antioxidants via the oral, intratracheal and vascular routes for the treatment of short- and long-term oxidant stress showed rather modest protective effects in animal and human studies. Intratracheal and intravascular administration of antioxidant enzymes are being currently tested for the treatment of acute oxidant stress. For example, intratracheal administration of recombinant human SOD is protective in premature infants exposed to hyperoxia. However, animal and human studies show that more effective delivery of drugs to cells experiencing oxidant stress is needed to improve protection. Diverse delivery systems for antioxidants including liposomes, chemical modifications (e.g. attachment of masking pegylated [PEG]-groups) and coupling to affinity carriers (e.g. antibodies against cellular adhesion molecules) are being employed and currently tested, mostly in animal and, to a limited extent, in humans, for the treatment of oxidant stress. Further studies are needed, however, in order to develop and establish effective applications of pulmonary antioxidant interventions useful in clinical practice. Although beyond the scope of this review, antioxidant gene therapies may eventually provide a strategy for the management of subacute and chronic pulmonary oxidant stress.

Lipid-based carriers for pulmonary products: preclinical development and case studies in humans

A number of lipid-based technologies have been applied to pharmaceuticals to modify their drug release characteristics, and additionally, to improve the drug loading for poorly soluble drugs. These technologies, including solid-state lipid microparticles, many of which are porous in nature, liposomes, solid lipid nanoparticles and nanostructured lipid carriers, are increasingly being developed for inhalation applications. This article provides a review of the rationale for the use of these technologies in the pulmonary delivery of drugs, and summarizes the manufacturing processes and their limitations, the in vitro and in vivo performance of these systems, the safety of these lipid-based systems in the lung, and their promise for commercialization.

Liposomal Antioxidants for Protection against Oxidant-Induced Damage

Reactive oxygen species (ROS), including superoxide anion, hydrogen peroxide, and hydroxyl radical, can be formed as normal products of aerobic metabolism and can be produced at elevated rates under pathophysiological conditions. Overproduction and/or insufficient removal of ROS result in significant damage to cell structure and functions. In vitro studies showed that antioxidants, when applied directly and at relatively high concentrations to cellular systems, are effective in conferring protection against the damaging actions of ROS, but results from animal and human studies showed that several antioxidants provide only modest benefit and even possible harm. Antioxidants have yet to be rendered into reliable and safe therapies because of their poor solubility, inability to cross membrane barriers, extensive first-pass metabolism, and rapid clearance from cells. There is considerable interest towards the development of drug-delivery systems that would result in the selective delivery of antioxidants to tissues in sufficient concentrations to ameliorate oxidant-induced tissue injuries. Liposomes are biocompatible, biodegradable, and nontoxic artificial phospholipid vesicles that offer the possibility of carrying hydrophilic, hydrophobic, and amphiphilic molecules. This paper focus on the use of liposomes for the delivery of antioxidants in the prevention or treatment of pathological conditions related to oxidative stress.

Ability of antioxidant liposomes to prevent acute and progressive pulmonary injury

We recently showed that acute oxidant-related lung injury (ALI) in rats after application of 2-chloroethyl ethyl sulfide (CEES) is attenuated by the airway instillation of antioxidants. We investigated whether intratracheal administration of antioxidant-containing liposomes immediately after instillation of CEES would attenuate short-term as well as long-term (fibrotic) effects of CEES-induced lung injury. In the acute injury model (4 h after injury), N-acetylcysteine (NAC)-containing liposomes were protective and reduced to baseline levels both the lung permeability index and the appearance of proinflammatory mediators in bronchoalveolar lavage fluids from CEES-exposed lungs. Similar results were obtained when rat alveolar macrophages were incubated in vitro with either CEES or lipopolysaccharide in the presence of NAC-liposomes. When lung fibrosis 3 weeks after CEES was quantitated by using hydroxyproline content, liposomes containing NAC or NAC + glutathione had no effects, but liposomes containing alpha/gamma-tocopherol alone or with NAC significantly suppressed the increase in lung hydroxyproline. The data demonstrate that delivery of antioxidants via liposomes to CEES-injured lungs is, depending on liposomal content, protective against ALI, prevents the appearance of proinflammatory mediators in bronchoalveolar fluids, and suppresses progressive fibrosis. Accordingly, the liposomal strategy may be therapeutically useful in CEES-induced lung injury in humans.

Role of antioxidants in prophylaxis and therapy: A pharmaceutical perspective

Antioxidants are emerging as prophylactic and therapeutic agents. These are the agents, which scavenge free radicals otherwise reactive oxygen species and prevent the damage caused by them. Free radicals have been associated with pathogenesis of various disorders like cancer, diabetes, cardiovascular diseases, autoimmune diseases, neurodegenerative disorders and are implicated in aging. Several antioxidants like SOD, CAT, epigallocatechin-3-O-gallate, lycopene, ellagic acid, coenzyme Q10, indole-3-carbinol, genistein, quercetin, vitamin C and vitamin E have been found to be pharmacologically active as prophylactic and therapeutic agents for above mentioned diseases. Antioxidants are part of diet but their bioavailability through dietary supplementation depends on several factors. This major drawback of dietary agents may be due to one or many of the several factors like poor solubility, inefficient permeability, instability due to storage of food, first pass effect and GI degradation. Conventional dosage forms may not result in efficient formulation owing to their poor biopharmaceutical properties. Principles of novel drug delivery systems need to be applied to significantly improve the performance of antioxidants. Novel drug delivery systems (NDDS) would also help in delivery of these antioxidants by oral route, as this route is of prime importance when antioxidants are intended for prophylactic purpose. Implication of NDDS for the delivery of antioxidants is largely governed by physicochemical characteristics, biopharmaceutical properties and pharmacokinetic parameters of the antioxidant to be formulated. Recently, chemical modifications, coupling agents, liposomes, microparticles, nanoparticles and gel-based systems have been explored for the delivery of these difficult to deliver molecules. Results from several studies conducted across the globe are positive and provided us with new anticipation for the improvement of human healthcare.

Reduction of Oxidative Stress Marker in Lung Fluid of Preterm Infants after Administration of Intra-Tracheal Liposomal Glutathione

BACKGROUND

Low levels of glutathione are associated with subsequent chronic lung disease in preterm infants. Incorporation of glutathione into liposomes offers a method of increasing levels with a prolonged half-life compared with direct inhalation.

OBJECTIVES

The aim of this study was to examine the clinical feasibility of administering a single dose of liposomal glutathione and its effectiveness at raising glutathione at 12 and 24 h after treatment.

METHODS

Fourteen ventilated preterm infants from the Regional Neonatal Intensive Care Unit at Liverpool Women's Hospital received 1 mg/kg or 10 mg/kg liposomal glutathione intra-tracheally and bronchoalveolar lavage fluid was collected prior to treatment, 12 and 24 h after dosing for glutathione and malondialdehyde estimation.

RESULTS

Mean glutathione was initially 12.2 micromol/l, increasing to 52.8 micromol/l at 12 h (p = 0.006). Mean malondialdehyde was initially 265.6 nmol/l decreasing to 11.2 nmol/l at 12 h (p = 0.018).

CONCLUSIONS

Intra-tracheal liposomal glutathione instillation offers a feasible method of raising pulmonary glutathione in preterm infants and shows biochemical antioxidant effects.

Pharmacokinetics and efficacies of liposomal and conventional formulations of tobramycin after intratracheal administration in rats with pulmonary Burkholderia cepacia infection

The objective of the present study was to determine the pharmacokinetics and efficacies of liposomal and conventional formulations of tobramycin against Burkholderia cepacia in a model of chronic lung infection. Male Sprague-Dawley rats were inoculated intratracheally with 10(6) CFU of a very resistant strain of B. cepacia (strain BC 1368; MIC, 128 micro g/ml) to establish lung infection. A 1,200- micro g dose of tobramycin was administered intratracheally as a liposomal formulation and as a conventional formulation. Rats were anesthetized and exsanguinated by cardiac puncture at different times over 24 h to assess pulmonary tobramycin concentrations and the number of residual CFU. Pharmacokinetic parameters were calculated by using a two-compartment model with NONMEM. The mean half-life at the beta phase (t(1/2beta)) and the pulmonary exposure (the area under the concentration-time curve [AUC]) of liposomal tobramycin were 19.7 h (coefficient of variation [CV], 24.2%) and 6,811 micro g. h/lungs (CV, 19.7%), respectively. The pharmacokinetics of conventional tobramycin were statistically different, with a t(1/2beta) and AUC of 12.9 h (CV, 31.4%) and 821 micro g. h/lungs (CV, 15.0%), respectively. Pearson chi-square analyses were performed on residual CFU data distributed in the following categories: <10(3), 10(3) to 10(5), and >10(5). Differences in CFU data between formulations showed a statistical trend (P < 0.10) when data from all time points were used, and statistically significant differences were found after 12 h (P < 0.05), with greater eradication achieved with the liposomal formulation. In conclusion, intratracheal administration of tobramycin in liposomes was associated with marked changes in the pharmacokinetics of the drug in the lung and an apparent trend for a prolonged efficacy against B. cepacia. These results support the hypothesis that inhalation of liposomal tobramycin may improve the management of chronic pulmonary infections caused by resistant bacteria in patients with cystic fibrosis.

Liposomal antioxidants provide prolonged protection against acute respiratory distress syndrome

BACKGROUND

We have previously shown that N-acetylcysteine (NAC), an antioxidant, in the resuscitation fluid after shock prevents lung injury in response to lipopolysaccharide (LPS) by inhibiting chemokine generation by alveolar macrophages in the lung. However, the protection was short-lived. We hypothesized that liposomal (Lip) NAC delivered intratracheally might be delivered directly to the target cells and exert prolonged effect.

METHODS

Sprague-Dawley rats were bled to a blood pressure of 40 mm Hg for 1 hour and resuscitated with shed blood and equal volume of Ringer's lactate. In some studies 500 mg/kg NAC was included in the resuscitation fluid. Thirty minutes later, 150 microl LipNAC (9.4 mg/kg NAC) was given intratracheally. One hour and 18 hours after resuscitation, LPS (30 microg/kg) or saline was given intratracheally. Lung injury was assessed by permeability to (125)I-albumin, bronchoalveolar lavage neutrophils and lung myeloperoxidase. The cytokine-induced neutrophil chemoattractant (CINC) expression in the lung was assessed by Northern blot.

RESULTS

At the early time point, both NAC and LipNAC protected the lung with the effects in significantly reducing the increases in transpulmonary albumin flux, neutrophil influx and myeloperoxidase in the lungs of shock/LPS rats. However, by the late time point, only LipNAC retained its salutary effect. This correlated well with persistent ability to prevent CINC increase. In addition, Lipalpha-tocopherol (alpha-T) and LipNAC/alpha-T were tested and determined to be effective to protect the lung.

CONCLUSIONS

Liposomal encapsulation of antioxidants at low dose provides long lasting protection against acute respiratory distress syndrome after shock. This may represent a novel treatment approach.

Alleviation of paraquat-induced lung injury by pretreatment with bifunctional liposomes containing alpha-tocopherol and glutathione

Reactive oxygen species are known to play a key role in the development of acute lung injury, and such injury can be alleviated by pretreating the lung with a suitable antioxidant preparation. In this study, we evaluated and compared the antioxidant efficacy of two liposomal preparations: liposomes containing only alpha-tocopherol versus bifunctional liposomes containing both alpha-tocopherol and glutathione (GSH). alpha-Tocopherol liposomes (2 mg alpha-tocopherol/animal) or liposomes containing both alpha-tocopherol and GSH (2 mg alpha-tocopherol and 10 mumol GSH/animal) were intratracheally instilled into the lungs of rats 30 min prior to a challenge with paraquat dichloride (30 mg/kg, i.p.); animals were killed 24 hr post-paraquat challenge. Lungs of paraquat-challenged animals were damaged extensively as evidenced by increases in lung weight, indicative of edema, and decreases in lung activities of angiotensin converting enzyme (ACE) and alkaline phosphatase (AKP), indicative of endothelial and alveolar type II epithelial cell injuries, respectively. While the pretreatment of rats with alpha-tocopherol liposomes or liposomes containing both alpha-tocopherol and GSH significantly attenuated paraquat-induced changes in lung ACE activity to more or less the same extent, the bifunctional liposomal preparation conferred additional protection to alveolar type II epithelial cells, as evidenced by a significantly higher pulmonary AKP activity. Our results also showed that both liposomal preparations failed to ameliorate paraquat-induced lung edema despite a significant protection of pulmonary endothelial cells, suggesting that paraquat-induced edema formation may be independent of endothelial cell damage. In conclusion, liposome-associated antioxidants can protect the lung against an oxidant challenge, and the extent of protection appears to be related to the characteristics of each antioxidant formulation.

Biochemical toxicology of chemical teratogenesis

Although exposure during pregnancy to many drugs and environmental chemicals is known to cause in utero death of the embryo of fetus, or initiate birth defects (teratogenesis) in the surviving offspring, surprisingly, little is known about the underlying biochemical and molecular mechanisms, or the determinants of teratological susceptibility, particularly in humans. In vitro and in vivo studies based primarily on rodent models suggest that many potential embryotoxic xenobiotics are actually proteratogens that must be bioactivated by enzymes such as the cytochromes P450 and peroxidases such as prostaglandin H synthase to teratogenic reactive intermediary metabolites. These reactive intermediates generally are electrophiles or free radicals that bind covalently (irreversibly) to, or directly of indirectly oxidize, embryonic cellular macromolecules such as DNA, protein, and lipid, irreversibly altering cellular function. Target oxidation, known as oxidase stress, often appears to be mediated by reactive oxygen species (ROS) such as hydroxyl radicals. The precise nature of the teratologically relevant molecular targets remains to be established, as do the relative conditions of the various types of macromolecular lesions. Teratological suseptibility appears to be determined in part by a balance among pathways of maternal xenobiotic elimination, embryonic xenobiotic bioactivation and detoxification of the xenobiotic reactive intermediate, direct and indirect pathways for the detoxification of ROS (cytoprotection), and repair of macromolecular lesions. Due largely to immature or otherwise compromised embryonic pathways for detoxification, Cytoprotection, and repair, the embryo is relatively susceptible to reactive intermediates, and teratogenesis via this mechanism can occur from exposure to therapeutic concentrations of drugs, or supposedly safe concentrations of environmental chemicals. Greater insight into the mechanisms involved in human reactive intermediate-mediated teratogenicity, and the determinants of individual teratological susceptibility, will be necessary to reduce the unwarranted embryonic attrition from xenobiotic exposure.

Prevention of phorbol myristate acetate-induced acute lung injury by alpha-tocopherol liposomes

Phorbol-myristate acetate (PMA) is commonly used to produce experimental edema and other tissue injuries in the lung. Lung injuries induced by the administration of PMA has been shown to be mediated mainly by neutrophils. Neutrophils recruited to the lower respiratory tract may damage lung tissues by releasing reactive oxygen species, neutral proteases, and lysosomal enzymes. The present study was conducted to investigate whether alpha-tocopherol, entrapped in dipalmitoylphosphatidylcholine liposomes and delivered directly to the lung, could counteract some of the PMA-induced lung injuries. Plain liposomes or alpha-tocopherol containing liposomes (8 mg alpha-tocopherol/kg body weight) were intratracheally instilled into the lungs of rats 24 hr prior to PMA exposure (25 micrograms/kg) and treated rats were killed 3 hr later. Lungs of control animals exposed to PMA developed an increase in lung weight and lipid peroxidation as well as a decrease in lung angiotensin converting enzyme (ACE) and alkaline phosphatase (AKP) activities. PMA treatment also caused an increase in myeloperoxidase (MPO) activity in the lung, suggestive of neutrophil infiltration. Pretreatment of PMA-treated rats with plain liposomes had no effect on PMA-induced injuries. In contrast, pretreatment of rats with liposomal alpha-tocopherol, 24 hr prior to PMA administration, resulted in a significant elevation of pulmonary alpha-tocopherol concentration, accompanied by a concomitant reduction in MPO activity and reversal of PMA-induced changes in lung edema, lipid peroxidation, ACE and AKP activities. These results appear to demonstrate that the intratracheal administration of a liposome-associated lipophilic antioxidant, such as alpha-tocopherol, can significantly ameliorate the toxic effects of reactive oxygen species, putatively released from PMA-stimulated pulmonary target cells and infiltrating neutrophils.

Liposomes in pulmonary applications: physicochemical considerations, pulmonary distribution and antioxidant delivery

The application of liposomes for improved drug delivery to the lung is promising. Liposome-mediated pulmonary drug delivery promotes an increase in drug retention-time in the lung and more importantly, a reduction in extrapulmonary side-effects, invariably resulting in enhanced therapeutic efficacies. The engineering of an effective liposomal drug formulation for inhalation therapy must take into consideration the leakage problem associated with the nebulization process; vesicle stability and release kinetics within the pulmonary milieu; and, the altered pharmacokinetics of the entrapped drug. The delivery of liposome-entrapped antioxidants via the tracheobronchial route has been found to be very useful in increasing the half-times of the administered agents, thus providing a sustained release effect for prolonged drug action. The entrapment in liposomes of alpha-tocopherol, an extremely insoluble but highly effective antioxidant, has been shown to be very effective in ameliorating oxidant-induced injuries in the lung. The use of bifunctional liposomes containing two antioxidants have been determined to provide excellent resistance to an oxidative challenge and appears to hold promise for improved clinical applications in antioxidant therapy.