Uptake of all-transretinoic acid–containing aerosol by inhalation to lungs in a guinea pig model system—A pilot study

Abstract

Systemic therapies with retinoic acid (RA) can result in toxic side effects without yielding biologically effective levels in target tissues such as lung. The authors adapted a PARI LC Star nebulizer to create a tubular system for short-term inhalation treatment of guinea pigs using a water-miscible formulation of all-trans RA (ATRA) or vehicle. Based on the initial average weight, animals received an estimated average ATRA doses of either 0.32 mg·kg −1 (low dose, 1.4 mM), or 0.62 mg·kg −1 (medium dose, 2.8 mM), or 1.26 mg·kg −1 (high dose, 5.6 mM) 20 minutes per day for 6 consecutive days. This system led to a rise of ATRA levels in lung, but not liver or plasma. Cellular lung levels of retinol, retinyl palmitate, and retinyl stearate also appeared to be unaffected (245.6 ± 10.7, 47.4 ± 3.4, and 132.8 ± 7.7 ng·g −1 wet weight, respectively). The application of this aerosolized ATRA also induced a dose-dependent protein expression of the cellular retinol-binding protein 1 (CRBP-1) in lung, without apparent harmful side effects. Keywordsaerosol; CRBP-1; guinea pig; inhalation; lung; retinoic acid; therapy Biologically active derivatives of vitamin A, most notably retinoic acid (RA) isomers, exert a wide variety of effects on development and cellular differentiation [1]. The actions of RA are mediated by nuclear retinoid receptors, RARs and RXRs [2], each encoded by three genes (RARα, β, γ and RXRα, β, γ) [3]. Vitamin A and its derivatives also show therapeutic activity toward several cancer and skin disorders [4].The major problem with the use of retinoids is their toxicity. ATRA (tretinoin) causes headache, nausea, vomiting, bleeding, irregular heartbeat, hearing loss, liver failure, plus teratogenic effects in pregnant women [5]. Massaro and Massaro [6] reported in their work that RA treatment reverses anatomical characteristics and increases lung volume of elastase-induced emphysema in SpragueDawley rats. Although demonstrating a beneficial effect, animals received the RA treatment via intraperitoneal administration.Two recent human trials investigated the effects of orally applied 13-cis retinoic acid [7] in patients with stage I non-small-cell lung cancer and 9-cis RA [8] Both studies reported significant toxic side effects. Thus, the ratio of efficacy to toxicity, termed the "therapeutic ratio," became a critical consideration.Inhalation therapy seems a more hopeful approach. Using a PARI-based inhalation device, in this pilot study we exposed guinea pigs to a 100% water-soluble ATRA nebulizing solution. We evaluated the uptake of inhaled ATRA in guinea pig lungs by high-performance liquid chromatography (HPLC) analysis. Furthermore, we also analyzed the effects of inhaled ATRA on a direct RA-inducible biomarker, the cellular retinol-binding protein (CRBP-1), which has been shown to contain a RA-responsive element in its promotor [12,13].CRBP-1 plays a major role in the cellular uptake of retinol from the blood into the cells via a receptor-bound mechanism (STRA6) [14] and in the generation of i...

Qualitative and quantitative analysis of retinol, retinyl esters, tocopherols and selected carotenoids out of various internal organs from different species by HPLC

“…In order to detect such a signal with a signal to noise ratio of at least 3 in extracts with our method under the described parameters, at least 3.7 g mouse liver would need to be extracted, which is approximately the weight of a whole mouse liver. However, this method is suitable for the determination of RA-isomers since we reported very recently the uptake of an all- trans RA aerosol to guinea pig lungs at detectable levels [17]. …”

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

“…The number of CFU was enumerated three weeks later. The dose for ATRA treatments was selected following a dose response study (data not shown), keeping in mind the level of toxicity previously reported for this compound (29,(51)(52)(53)(54)(55)(56)(57). Rifampicin was added to one treatment group to assess the adjunctive effect of ATRA.…”

Retinol and Retinyl Palmitate

“…In a 1987 safety assessment of retinyl palmitate and retinol, the Cosmetic Ingredient Review Expert Panel stated that these ingredients are safe as cosmetic ingredients in the present practices of use and concentration. 1 The Panel reviewed newly available studies since that assessment along with updated information regarding types and concentration of use 2 …”