Delivery Of All-trans Retinoic Acid Research Articles

Microfluidics produced ATRA-loaded PLGA NPs reduced tuberculosis burden in alveolar epithelial cells and enabled high delivered dose under simulated human breathing pattern in 3D printed head models

Tuberculosis, caused by Mycobacterium tuberculosis (Mtb), is second only to COVID-19 as the top infectious disease killer worldwide. Multi-drug resistant TB (MDR-TB) may arise because of poor patient adherence to medications due to lengthy treatment duration and side effects. Delivering novel host directed therapies (HDT), like all trans retinoic acid (ATRA) may help to improve drug regimens and reduce the incidence of MDR-TB. Local delivery of ATRA to the site of infection leads to higher bioavailability and reduced systemic side effects. ATRA is poorly soluble in water and has a short half-life in plasma. Therefore, it requires a formulation step before it can be administered in vivo. ATRA loaded PLGA nanoparticles suitable for nebulization were manufactured and optimized using a scalable nanomanufacturing microfluidics (MF) mixing approach (MF-ATRA-PLGA NPs). MF-ATRA-PLGA NPs demonstrated a dose dependent inhibition of Mtb growth in TB-infected A549 alveolar epithelial cell model while preserving cell viability. The MF-ATRA-PLGA NPs were nebulized with the Aerogen Solo vibrating mesh nebulizer, with aerosol droplet size characterized using laser diffraction and the estimated delivered dose was determined. The volume median diameter (VMD) of the MF-ATRA-PLGA NPs was 3.00 ± 0.18 μm. The inhaled dose delivered in adult and paediatric 3D printed head models under a simulated normal adult and paediatric breathing pattern was found to be 47.05 ± 3 % and 20.15 ± 3.46 % respectively. These aerosol characteristics of MF-ATRA-PLGA NPs supports its suitability for delivery to the lungs via inhalation. The data generated on the efficacy of an inhalable, scalable and regulatory friendly ATRA-PLGA NPs formulation provides a foundation on which further pre-clinical testing can be built. Overall, the results of this project are promising for future research into ATRA loaded NPs formulations as inhaled host directed therapies for TB.

PH-sensitive niosomes for ATRA delivery: A promising approach to inhibit Pin1 in high-grade serous ovarian cancer

The peptidyl-prolyl cis/trans isomerase Pin1 positively regulates numerous cancer-driving pathways, and it is overexpressed in several malignancies, including high-grade serous ovarian cancer (HGSOC). The findings that all-trans retinoic acid (ATRA) induces Pin1 degradation strongly support that ATRA treatment might be a promising approach for HGSOC targeted therapy. Nevertheless, repurposing ATRA into the clinics for the treatment of solid tumors remains an unmet need mainly due to the insurgence of resistance and its ineffective delivery. In the present study, niosomes have been employed for improving ATRA delivery in HGSOC cell lines. Characterization of niosomes including hydrodynamic diameter, ζ-potential, morphology, entrapment efficiency and stability over time and in culture media was performed. Furthermore, pH-sensitiveness and ATRA release profile were investigated to demonstrate the capability of these vesicles to release ATRA in a stimuli-responsive manner. Obtained results documented a nanometric and monodispersed samples with negative ζ-potential. ATRA was efficiently entrapped, and a substantial release was observed in the presence of acidic pH (pH 5.5). Finally, unloaded niosomes showed good biocompatibility while ATRA-loaded niosomes significantly increased ATRA Pin1 inhibitory activity, which was consistent with cell growth inhibition. Taken together, ATRA-loaded niosomes might represent an appealing therapeutic strategy for HGSOC therapy.

Advancement of All-Trans Retinoic Acid Delivery Systems in Dermatological Application

Dermatological conditions, such as acne, photoaging, psoriasis, and wounds, have been treated topically with all-trans retinoic acid (ATRA) for many years owing to its anti-inflammatory activity, comedolytic effect, and ability to increase collagen production. However, common side effects of ATRA known as the retinoid reaction can occur. These side effects are countered by ATRA encapsulation in solid lipid nanoparticles (SLN), nanostructured lipid carriers (NLCs), and liposomes. Liposomes used to encapsulate ATRA include niosomes, ethosomes, and transfersomes. Side effects involving inflammatory reactions, such as irritation, redness, and erythema, were diminished using these approaches. The use of such carriers enhanced the efficacy of ATRA by enhancing its permeation into skin. These formulations have been compared in terms of improving the activity of ATRA and the ability to relieve the side effects. Further research into different delivery systems for ATRA using various formulations will improve the future of topical ATRA delivery.

Novel pH-sensitive nanoparticles based on prodrug strategy to delivery All-Trans Retinoic Acid for breast cancer

Developing chemotherapy with nanoparticle-based prodrugs provides promising strategies for improving the safety and delivery of anti-cancer drugs therapeutics and effective cancer treatment. Herein, we developed a pH-sensitive prodrug delivery system (All-Trans-Retinoic Acid (ATRA) grafted poly (β-amino esters) (PBAE) copolymers, ATRA-g-PBAE) for delivery of ATRA with some physicochemical and biological properties. The in vitro release of ATRA-g-PBAE prodrug nanoparticles (PNPs) was sustained-release and pH-sensitive. The cytotoxicity and uptake of different preparations in vitro were evaluated on MCF-7 cells at pH 7.4 and 5.5. The carrier PBAE had no cytotoxicity, and ATRA-g-PBAE PNPs could significantly inhibit cell growth at pH 5.5. MCF-7 cells treated with Cy5.5 grafted PBAE (Cy5.5-PBAE) showed stronger fluorescence signals at pH 5.5. Meanwhile, ATRA-g-PBAE PNPs entered the cell via a clathrin-mediated endocytic pathway. Subsequently, PBAE protonation facilitated the escape of PNPs from the lysosome and released the drug. ATRA-g-PBAE seems promising as a novel pH-sensitive prodrug to overcome the limitations of ATRA for breast cancer therapy.

Oral Delivery of Encapsulated All-Trans Retinoic Acid Ameliorates Disease in Rodent Models of Colitis.

All-trans retinoic acid (ATRA) is a biologically active isomer of retinoic acid (RA). Topical ATRA (retin-a, retin-a micro, atralin, renova, and avita) is the active pharmaceutical ingredient for FDA-approved treatments for acne and skin wrinkles. Oral formulations (Vesanoid) treat acute promyelocytic leukemia, but oral dosing can induce severe side effects. Despite benefits in various rodent models of inflammatory bowel disease (IBD), toxicity and controversial clinical observations have diminished enthusiasm for ATRA IBD clinical trials. To circumvent these issues and to use ATRA's key role in maintaining gut tolerance, we developed a poly(lactic-co-glycolic acid) (PLGA) microsphere (MS) encapsulated ATRA formulation aimed at directing ATRA delivery to immune structures of the gut, limiting systemic exposure. Initially, ATRA MS was developed as a component of a combinatorial product (TreXTAM) that also contained encapsulated transforming growth factor (TGF)-β and ATRA in a 1:2 w/w ratio. Although the combination was optimal, benefit was also observed when ATRA MS was given alone in the CD4+ CD25-T-cell adoptive transfer (ACT) colitis model. We used the ACT and DSS-induced murine models of colitis to expand on the dose-dependent effects of oral ATRA MS when given alone. The DSS model was also used to compare the efficacy of ATRA MS and soluble ATRA, while healthy animals were used to compare the pharmacokinetics of the two drugs. In both the ACT and DSS-induced murine models of colitis, ATRA MS was observed to be effective in ameliorating disease. ATRA MS was also observed to be more effective than soluble ATRA in these models and displayed more favorable pharmacokinetics. We suggest ATRA MS, as a standalone product, may attenuate IBD and perhaps limit fibrosis, while limiting systemic side effects.

Phospholipid/zein hybrid nanoparticles as promising carriers for the protection and delivery of all-trans retinoic acid

A totally biodegradable mixed system made up of phospholipids and zein was developed in order to effectively improve the photostability of all-trans retinoic acid (ATRA) preserving its pharmacological properties. Photon correlation spectroscopy showed that the formulation obtained using phospholipon 85G and zein at a ratio of 7:3 w/w was characterized by an average diameter of less than 200 nm, a narrow size distribution and a significant time- and temperature-dependent stability. The use of specific cryoprotectants such as mannose and glucose favoured the long-term storage of the nanocarriers after the freeze-drying procedure. The nanoparticles increased the stability of the ATRA against photochemical degradation with respect to the free drug and its antitumor effect was preserved as a consequence of the cell uptake of the colloidal systems. The results demonstrate the potential of the proposed hybrid nanosystems to provide a high level of stabilization for sensitive and labile antitumor compounds.

Oral delivery of all-trans retinoic acid mediated by liposome carriers

All-trans retinoic acid (ATRA) is a molecule that finds wide applications in medicine. Connection between cancer cell proliferation and ATRA is a well-established item. Driven by the potential applications of liposomes in stabilizing and protecting therapeutic compounds thus enabling effective delivery of encapsulated compounds, recent research efforts have been directed to understanding mechanisms of oral delivery through the gastrointestinal tract. The surface charge of the liposome bilayers can modify the interactions between the aggregates and the gastrointestinal fluids.Here, we investigated the ability of cationic and anionic liposomes to encapsulate, protect and deliver ATRA in an in-vitro digestion process as a different oral administration route.Stability and encapsulation efficiency of ATRA in negatively and positively charged liposomes enriched with α-tocopherol were investigated by means of UV–vis spectroscopy, dynamic light scattering and ζ-potential. The applicability of the carriers was tested by means of an in-vitro digestion procedure allowing for the measurement of the bioavailability of ATRA.From this study evidence was provided that the water insoluble molecules, ATRA and α-tocopherol are intercalated in liposome membranes regardless of the surface charge of the vesicle bilayers. Comparisons between cationic and anionic liposomes incorporating retinoic acid show differences in bioavailability. The cationic vesicles are preferable for a larger amount of ATRA bioavailability, which can be understood from electrostatic interactions. Thus ATRA is ionized in a wide range of pHs but protonated in anionic vesicles.

Retinoic acid receptor γ is a therapeutically targetable driver of growth and survival in prostate cancer.

BackgroundProstate cancer (PC) tissue contains all‐trans retinoic acid (ATRA) at a very low level (10−9 M), at least an order of magnitude lower than in adjacent normal healthy prostate cells or benign prostate hyperplasia. When this is coupled with deregulated expression of the intracellular lipid‐binding proteins FABP5 and CRABP2 that is frequently found in PC, this is likely to result in the preferential delivery of ATRA to oncogenic PPARβ/δ rather than retinoic acid receptors (RARs). There are three isotypes of RARs (RARα, RARβ, and RARγ) and recent studies have revealed discrete physiological roles. For example, RARα and RARγ promote differentiation and self‐renewal, respectively, which are critical for proper hematopoiesis.AimsWe have previously shown that ATRA stimulates transactivation of RARγ at sub‐nanomolar concentrations (EC50 0.24 nM), whereas an 80‐fold higher concentration was required for RARα‐mediated transactivation (EC50 19.3 nM). Additionally, we have shown that RAR pan‐antagonists inhibit the growth of PC cells (at 16‐34 nM). These findings, together with the low level of ATRA in PC, led us to hypothesize that RARγ plays a role in PC pathogenesis and that RARγ‐selective antagonism may be an effective treatment.Methods and resultsWe found that concentrations of 10−9 M and below of ATRA promoted survival/proliferation and opposed adipogenic differentiation of human PC cell lines by a mechanism that involves RARγ. We also found that a RARγ‐selective antagonist (AGN205728) potently induced mitochondria‐dependent, but caspase‐independent, cell death in PC cell lines. Furthermore, AGN205728 demonstrated synergism in killing PC cells in combination with cytotoxic chemotherapeutic agents.ConclusionWe suggest that the use of RARγ‐selective antagonists may be effective in PC (and potentially other cancers), either as a single agent or in combination with cytotoxic chemotherapy.

Current Trends in ATRA Delivery for Cancer Therapy.

All-Trans Retinoic Acid (ATRA) is the most active metabolite of vitamin A. It is critically involved in the regulation of multiple processes, such as cell differentiation and apoptosis, by activating specific genomic pathways or by influencing key signaling proteins. Furthermore, mounting evidence highlights the anti-tumor activity of this compound. Notably, oral administration of ATRA is the first choice treatment in Acute Promyelocytic Leukemia (APL) in adults and NeuroBlastoma (NB) in children. Regrettably, the promising results obtained for these diseases have not been translated yet into the clinics for solid tumors. This is mainly due to ATRA-resistance developed by cancer cells and to ineffective delivery and targeting. This up-to-date review deals with recent studies on different ATRA-loaded Drug Delivery Systems (DDSs) development and application on several tumor models. Moreover, patents, pre-clinical, and clinical studies are also reviewed. To sum up, the main aim of this in-depth review is to provide a detailed overview of the several attempts which have been made in the recent years to ameliorate ATRA delivery and targeting in cancer.

Retinoid metabolism and functions mediated by retinoid binding-proteins.

Cellular retinoid-binding proteins (BP) chaperone retinol through esterification, conversion of retinol into retinal, reduction of retinal, conversion of retinal into all-trans-retinoic acid (ATRA), and ATRA to catabolism. They also deliver ATRA to nuclear receptors and mediate non-genomic ATRA actions. These retinoid-specific binding-proteins include: cellular retinol binding-protein, type 1 (Crbp1), cellular retinol binding-protein type 2 (Crbp2), cellular retinol binding-protein type 3 (Crbp3), cellular retinoic acid binding-protein type 1 (Crabp1); cellular retinoic acid binding-protein type 2 (Crabp2). Retinoid BP bind their ligands specifically and with high-affinity. These BP seemingly evolved to solubilize the lipophilic retinoids in the aqueous cellular medium, and allow retinoid access only to enzymes that recognize both the BP and the retinoid. By chaperoning retinoids through cells, retinoid BP provide specificity to retinoids' metabolism and protect the scarce resource from dispersing into cell membranes and/or undergoing catabolism as xenobiotics. Other functions include non-genomic actions of Crabp1, delivery of ATRA to RAR by holo-Crabp2, and stabilization of HuR by apo-Crabp2. In addition to the retinoid-specific BP, Fabp5 also binds ATRA and delivers it to Pparδ. This article describes these BP and their functions, with a focus on experimental protocols to distinguish protein-protein interactions from diffusion-mediated transfer of ligand from BP to enzymes or receptors, and methods for quantifying retinoids.

A 3D bioprinted hydrogel mesh loaded with all-trans retinoic acid for treatment of glioblastoma

Treatment of glioblastoma (GBM), as the most lethal type of brain tumor, still remains a major challenge despite the various therapeutic approaches developed over the recent decades. GBM is considered as one of the most therapy-resistant human tumors. Treatment with temozolomide (TMZ) chemotherapy and radiotherapy in GBM patients has led to 30% of two-year survival rate (American Brain Tumor Association), representing a demanding field to develop more effective therapeutic strategies. This study presents a novel method for local delivery of all-trans retinoic acid (ATRA) for targeting GBM cells as a possible adjuvant therapeutic strategy for this disease. We have used 3D bioprinting to fabricate hydrogel meshes laden with ATRA-loaded polymeric particles. The ATRA-loaded meshes have been shown to facilitate a sustained release of ATRA with tunable release rate. Cell viability assay was used to demonstrate the ability of fabricated meshes in reducing cell growth in U-87 MG cell line. We later showed that the developed meshes induced apoptotic cell death in U-87 MG. Furthermore, the use of hydrogel for embedding the ATRA-loaded particles can facilitate the immobilization of the drug next to the tumor site. Our current innovative approach has shown the potential to open up new avenues for treatment of GBM, benefiting patients who suffer from this debilitating disease.

Lipid-polymer nanoparticles with CD133 aptamers for targeted delivery of all-trans retinoic acid to osteosarcoma initiating cells

Osteosarcoma, a common type of bone cancer in children, and represents an aggressive and fetal cancer worldwide. Osteosarcoma initiating cells are considered to be a subpopulation of cancer cells which contribute to the progression, recurrence, metastasis and multi-drug resistance of osteosarcoma. CD133 is considered to be one marker for osteosarcoma initiating cells. All-trans retinoic acid (ATRA), an active metabolite of vitamin A under the family retinoid, is an up-and-coming drug which was able to effectively treat various cancer initiating cells. Nevertheless, there have been no research that reported the activity of ATRA against osteosarcoma initiating cells. In this research, we hereby examined the potential activity of ATRA in osteosarcoma initiating cells, and developed lipid-polymer nanoparticles with CD133 aptamers for targeted ATRA delivery to osteosarcoma initiating cells. Using the cytotoxicity assay, colony formation assay, tumorsphere formation assay and flow cytometry, the therapeutic effect of ATRA and ATRA-loaded lipid-polymer nanoparticles conjugated with CD133 aptamers (ATRA-PLNP-CD133) against osteosarcoma initiating cells were investigated. The results showed that ATRA exerted potent activity towards osteosarcoma initiating cells. ATRA-PLNP-CD133, which showed a size of 129.9 nm and a sustained release of ATRA during 144 h, was demonstrated to efficiently and specifically promote the ATRA delivery to osteosarcoma initiating cells, and achieve superior therapeutic efficacy in osteosarcoma compared with ATRA and non-targeted nanoparticles. This is the first report of the therapeutic efficacy of ATRA towards osteosarcoma initiating cells, and the increased ATRA delivery by nanoparticles to osteosarcoma initiating cells using CD133 aptamers. ATRA-PLNP-CD133 represent an up-and coming approach for the therapy of osteosarcoma initiating cells.

Inhalable poly(lactic-co-glycolic acid) (PLGA) microparticles encapsulating all-trans-Retinoic acid (ATRA) as a host-directed, adjunctive treatment for Mycobacterium tuberculosis infection

Ending the tuberculosis (TB) epidemic by 2030 was recently listed in the United Nations (UN) Sustainable Development Goals alongside HIV/AIDS and malaria as it continues to be a major cause of death worldwide. With a significant proportion of TB cases caused by resistant strains of Mycobacterium tuberculosis (Mtb), there is an urgent need to develop new and innovative approaches to treatment. Since 1989, researchers have been assessing the anti-bacterial effects of the active metabolite of vitamin A, all trans-Retinoic acid (ATRA) solution, in Mtb models. More recently the antibacterial effect of ATRA has been shown to regulate the immune response to infection via critical gene expression, monocyte activation and the induction of autophagy leading to its application as a host-directed therapy (HDT). Inhalation is an attractive route for targeted treatment of TB, and therefore we have developed ATRA-loaded microparticles (ATRA-MP) within the inhalable size range (2.07 ± 0.5 µm) offering targeted delivery of the encapsulated cargo (70.5 ± 2.3%) to the site of action within the alveolar macrophage, which was confirmed by confocal microscopy. Efficient cellular delivery of ATRA was followed by a reduction in Mtb growth (H37Ra) in THP-1 derived macrophages evaluated by both the BACT/ALERT® system and enumeration of colony forming units (CFU). The antibacterial effect of ATRA-MP treatment was further assessed in BALB/c mice infected with the virulent strain of Mtb (H37Rv). ATRA-MP treatments significantly decreased the bacterial burden in the lungs alongside a reduction in pulmonary pathology following just three doses administered intratracheally. The immunomodulatory effects of targeted ATRA treatment in the lungs indicate a distinct yet effective mechanism of action amongst the formulations. This is the first study to-date of a controlled release ATRA treatment for TB suitable for inhalation that offers improved targeting of a HDT, retains antibacterial efficacy and improves pulmonary pathology compared to ATRA solution.

All-trans retinoic acid-encapsulated, CD20 antibody-conjugated poly(lactic-co-glycolic acid) nanoparticles effectively target and eliminate melanoma-initiating cells in vitro.

PurposeMelanoma, which is initiated from melanocytes, is the most fatal type of skin cancer. Melanoma-initiating cells significantly contribute to the initiation, metastasis, and recurrence of melanoma, and CD20 is a marker of melanoma-initiating cells. All-trans retinoic acid (ATRA) has been demonstrated to induce differentiation, inhibit proliferation, and promote the apoptosis of cancer cells and cancer-initiating cells (CICs). However, there has been no report on ATRA activity against melanoma-initiating cells. In this study, we examined the activity of ATRA against melanoma-initiating cells and developed ATRA-encapsulated poly(lactic-co-glycolic acid) (PLGA) nanoparticles, which were conjugated with a CD20 antibody (ATRA-PNP-CD20) for targeted delivery of ATRA to CD20+ melanoma-initiating cells.Materials and methodsThe effects of ATRA and ATRA-PNP-CD20 against melanoma-initiating cells were investigated using a cytotoxicity assay, tumorsphere formation assay, and flow cytometry.ResultsATRA-PNP-CD20 had a size of 126.9 nm and a negative zeta potential. The drug-loading capacity of ATRA-PNP-CD20 was 8.7%, and ATRA-PNP-CD20 displayed a sustained release of ATRA for 144 hours. The results showed that ATRA-PNP-CD20 could effectively and specifically deliver ATRA to CD20+ melanoma-initiating cells, achieving superior inhibitory effects against CD20+ melanoma-initiating cells compared with those of free ATRA and nontargeted nanoparticles. To the best of our knowledge, we report for the first time a potent activity of ATRA against CD20+ melanoma-initiating cells, targeted drug delivery of ATRA via nanoparticles to melanoma-initiating cells, and the achievement of a superior inhibitory effect against melanoma-initiating cells by using a CD20 antibody.ConclusionATRA-PNP-CD20 represents a promising tool for eliminating melanoma-initiating cells and shows a potential for the therapy of melanoma.

Anti-Fibrotic Potential of All Trans Retinoic Acid in Inflammatory Bowel Disease.

Inflammatory bowel disease (IBD) embraces Crohn’s disease (CD), ulcerative colitis (UC) and the less common indeterminate colitis, all chronic inflammatory processes of the gastrointestinal (GI) tract. Together, they cause significant morbidity for a million and a half Americans [1]. Symptoms include diarrhea, nausea, abdominal pain, weight loss, which can occasionally prove fatal (i.e., toxic megacolon, perforated bowel) [2]. Patients are also at increased risk for colorectal cancer [3]. First line treatments, including various anti-inflammatory agents and antibiotics, are variably effective against active disease [4]. Remissions can be short-lived and uncontrolled activity is associated with significant side-effects [3]. Gut fibrosis will require most patients (80% and 45% of CD and UC patients, respectively) to undergo surgery [4]. Over the last decade, the so-called biological response modifiers or ‘biologics’, macromolecules that target inflammatory lymphocytes or the cytokines they produce, have emerged as effective therapeutic agents [5]. For example, infliximab, a chimeric anti-human tumor necrosis factor (TNF)-α antibody earned FDA approval almost 20 years ago, based on a high response rate, significant mucosal and fistula healing and long-term remissions in both CD and UC. Additional targets of biologics, either marketed or in various stages of development, include anti-p40, anti-p19, anti-interleukin (IL)-12/23, and anti-alpha 4/beta 7 integrin antibodies [5, 6]. However, an estimated 30% of patients will not respond to such treatments, and of those who initially respond, 50% will relapse within a year risking significant, often serious side effects including infections and increased risk of cancer. So far, biologics have had only a modest impact on surgery rates [7]. The need for novel therapies remains acute. Literature reports indicate that All trans retinoic acid (ATRA) provides benefit in various rodent models of IBD, including potential anti-fibrotic activity [8, 9]. Retinoic acid can exist in the body as any of five different chemical isomers (all-trans-RA, 9-cisRA, 13-cisRA, 11-cisRA and 9, 13-dicisRA). ATRA is the biologically active isomer and the primary enzymatic product of retinaldehyde oxidation. The retinoic acid family regulates a wide range of biological processes, including embryonic development, reproduction, vision, cell growth and differentiation, as well as, apoptosis and inflammation [10]. Topical ATRA is known as tretinoin, and is currently marketed under several trade names such as Retin-A®, Retin-A Micro®, Atralin®, Renova®, and Avita® as FDA approved topical treatment for acne and skin wrinkles. Oral formulations, called isotretinoin (Accutane®, Claravis®, Sotret® and Amnesteem® and Vesanoid®) can cure severe acne and treat acute promyelocytic leukemia (APL), but oral dosing induces more severe side effects. Isotretinoin has not been tested in IBD clinical trials, perhaps due to the serious side effects associated with oral administration, including teratogenicity, suicidality, headache, dizziness, fever, weakness, tiredness, dry mouth, dry skin, other skin changes, thinning hair, nausea, vomiting, itching, bone pain, mouth sores, increased sweating, earaches, and perhaps even colitis. Black-box warnings for oral formulations have been issued by the FDA because of these serious side effects, including retinoic acid syndrome in APL patients. Retinoic acid syndrome may manifest as life threatening upper respiratory tract disturbances (dyspnea, respiratory insufficiency, pleural effusion, expiratory wheezing and increased susceptibility to pneumonia). Its frequency, mechanism and treatment have recently been reviewed [11]. Efforts to circumvent toxicities by tissue targeted administration have included encapsulation in liposomes and aerosolization, although none of these have progressed further in development or resulted in marketed products [12,13]. This review begins with an analysis of published studies bearing on the efficacy of ATRA as an anti-inflammatory treatment for IBD, including in vitro and in vivo work in rodents, as well as ex vivo studies using human tissues. Clinical reports about ATRA attenuation or induction of IBD will also be reviewed. Efforts to deliver ATRA directly to gut tissue to improve activity and reduce side effects will then be discussed. Finally, the potential of ATRA to treat fibrosis will be considered. If successful, oral delivery of ATRA directly to the immune structures of the gut could represent a novel IBD therapy with a potential to reduce fibrosis and the subsequent need for surgery.

Reduced RAR-β gene expression in Benzo(a)Pyrene induced lung cancer mice is upregulated by DOTAP lipo-ATRA treatment

Molecular targeted therapy for specific genes is an emerging research. Retinoic Acid Receptor (RAR-β) is a key tumor suppressor which is found to be lost drastically during much cancer progression. We hence, analyzed the expression level of RAR-β gene during B(a)P induced lung cancer development in mice and studied the lung cancer targeted action of All Trans Retinoic Acid (ATRA) in DOTAP liposomal formulation. The effect of its treatment on lung cancer was determined by histopathological analysis. RAR-β gene expression was assessed by RT-PCR and qPCR. A distinct band for RAR-β gene (density - 0.5123 for lung and 0.5160 for liver) was observed in normal mice, whereas no visible band was observed in cancer induced group, indicating loss of RAR-β gene expression. Both ATRA and lipo-ATRA treated groups showed detectable RAR-β expression with relatively lesser density than the normal group. The expression was more intense in lipo-ATRA treatment (density-0.2973) compared with free ATRA treatment (density-0.1549) in lung tissues. The qPCR results also have highlighted a highly significant (p ≤ 0.01) variation RQ values between lipo-ATRA group (15.46 ± 1.54) and free ATRA group (7.58 ± 1.30) in lung tissue sample on 30th day. The mean RQ value for normal lung on 30th day was 20.86 ± 2.58 against the cancer control. The 120th day mice also showed the similar RAR-β expression pattern with further declined expression levels as there was no treatment given after 30 days. Interestingly, the lipo-ATRA treatment could show a highly significant (p ≤ 0.001) expression (12.00 ± 2.31) when compared with free ATRA treatment (3.31 ± 0.58) which implies that the lipo-ATRA formulation could result in sustained delivery of ATRA in target site. Histopathology of lung and liver on 120th day also revealed an effective therapeutic indication in lipo-ATRA treatment compared to free ATRA treatment due to lipo-ATRA's stealth property and it efficiently inhibited the metastasis to liver. These results revealed that the lipo-ATRA treatment has efficiently delivered ATRA into target site than free ATRA and in-turn it might have induced the expression of RAR-β gene or prevented loss of RAR-β gene in cancer animals.

Inhibiting intimal hyperplasia in prosthetic vascular grafts via immobilized all-trans retinoic acid

Peripheral arterial disease is a leading cause of morbidity and mortality. The most commonly utilized prosthetic material for peripheral bypass grafting is expanded polytetrafluoroethylene (ePTFE) yet it continues to exhibit poor performance from restenosis due to neointimal hyperplasia, especially in femoral distal bypass procedures. Recently, we demonstrated that periadventitial delivery of all-trans retinoic acid (atRA) immobilized throughout porous poly(1,8 octamethylene citrate) (POC) membranes inhibited neointimal formation in a rat arterial injury model. Thus, the objective of this study was to investigate whether atRA immobilized throughout the lumen of ePTFE vascular grafts would inhibit intimal formation following arterial bypass grafting. Utilizing standard ePTFE, two types of atRA-containing ePTFE vascular grafts were fabricated and evaluated: grafts whereby all-trans retinoic acid was directly immobilized on ePTFE (atRA-ePTFE) and grafts where all-trans retinoic acid was immobilized onto ePTFE grafts coated with POC (atRA-POC-ePTFE). All grafts were characterized by SEM, HPLC, and FTIR and physical characteristics were evaluated in vitro. Modification of these grafts, did not significantly alter their physical characteristics or biocompatibility, and resulted in inhibition of intimal formation in a rat aortic bypass model, with atRA-POC-ePTFE inhibiting intimal formation at both the proximal and distal graft sections. In addition, treatment with atRA-POC-ePTFE resulted in increased graft endothelialization and decreased inflammation when compared to the other treatment groups. This work further confirms the biocompatibility and efficacy of locally delivered atRA to inhibit intimal formation in a bypass setting. Thus, atRA-POC-ePTFE grafts have the potential to improve patency rates in small diameter bypass grafts and warrant further investigation.

Iontophoretic delivery of lipophilic and hydrophilic drugs from lipid nanoparticles across human skin

The combined effects of iontophoresis and lipid nanoparticles on drug delivery across human epidermal membrane (HEM) were investigated. The delivery of lipophilic and hydrophilic drugs, all trans-retinoic acid (ATRA), salicylate (SA), and acyclovir (ACV), across HEM from lipid nanoparticles, solid lipid nanoparticles (SLN) and nanostructured lipid carriers (NLC), was compared in passive and iontophoresis experiments in vitro. Iontophoresis experiments were also performed with synthetic Nuclepore membrane for comparison. Drug distribution in the skin after iontophoretic delivery with the lipid nanoparticles was examined using a model probe rhodamine B base (RhoB). The drug-loaded lipid nanoparticles had average sizes of ∼118–169nm and a negative zeta potential. Iontophoresis did not enhance the delivery of ATRA across HEM from SLN and NLC. However, HEM distribution study of RhoB suggested that lipophilic drugs could be delivered into the deeper layer of the skin following iontophoretic delivery of the drugs from the lipid nanoparticles. Iontophoresis enhanced the delivery of hydrophilic drug SA with the lipid nanoparticles. Similarly, iontophoresis enhanced the delivery of ACV when it was loaded in SLN. These results suggest that lipid nanoparticles are a promising drug delivery method that can be combined with iontophoresis to improve skin delivery of hydrophilic drugs.

A new nanostructured carrier design including oil to enhance the pharmaceutical properties of retinoid therapy and its therapeutic effects on chemo-resistant ovarian cancer

All-trans retinoic acid (ATRA) is an appealing alternative drug for the cancers that have failed the conventional chemotherapy and become chemo-resistant and more tumorigenic. In this study, we specifically addressed two issues commonly associated with ATRA nanotherapeutics: (1) insufficient, unstable entrapment and uncontrolled release of the highly lipophilic ATRA and (2) lack of studies in therapeutically relevant chemo-resistant cancer cell models. A polymer-oil nanostructured carrier (PONC) composed of oil and PLGA was designed and studied in an ovarian cancer cell subline SKOV-3PR that could withstand up to 300nM paclitaxel and expressed high levels of multidrug resistance transporter ABCB1 and tumorigenic marker CD133. Differential scanning calorimetry of PONC revealed superior polymer amorphosity and dispersion of the entrapped ATRA in a manner comparable to nanostructured lipid carriers. With this design, the ATRA encapsulation efficiency was increased up to 8.5-fold and a 5-day controlled release profile was obtained. ATRA-PONC was able to induce extensive apoptotic cell death and exert substantially higher long-term anti-tumorigenic effects (IC50 of ATRA-PONC: 2μg/ml versus free ATRA: 17.5μg/ml; p<0.05) in SKOV-3PR cells. Mechanistic studies indicated that these enhanced anticancer effects were likely attributable to higher cell permeation by the well-dispersed drug/oil steadily released from PONC. To conclude, a nanostructured, oil-in-polymer hybrid carrier design has been developed for efficient ATRA delivery and treatment of the chemo-exposed, chemo-resistant sub-population of ovarian cancer, exemplifying a convenient strategy to vastly improve the pharmaceutical and therapeutic properties of tough-to-deliver lipophilic, poorly water-soluble anticancer compounds.

Development of a novel therapeutic approach using a retinoic acid-loaded microneedle patch for seborrheic keratosis treatment and safety study in humans

Seborrheic keratosis is one of the most common skin benign tumors in humans with a high occurrence rate of 80%–100% in people >50years of age; however, its pathogenesis is still unclear. The standard treatment includes cryotherapy and laser surgery for physically removing lesions. Drug therapy for this condition has not been well established. We aimed to evaluate the use of all-trans retinoic acid (ATRA)-loaded microneedle (MN) patches as a simple, alternative therapeutic option to traditional surgical treatments. This therapeutic strategy was designed to induce the proliferation of basal keratinocytes and accelerate stratum corneum turnover, leading to the lesion falling off the surface of the skin. The MN patch induced epidermal hyperplasia and marked expression of heparin-binding epidermal growth factor-like growth factor mRNA and protein corresponding to ATRA activity in the skin of HR-1 hairless mice. The acceleration of stratum corneum turnover was also observed by the dansyl chloride method. The skin irritation study in mice and safety study in humans support the safety findings of our study. Overall, MN patches can offer an effective and safe means of ATRA delivery into the skin, and the ATRA-loaded MN patch appears to be an effective pharmaceutical product providing a novel therapeutic option for seborrheic keratosis.