Injection Of All-trans Retinoic Acid Research Articles

Short communication: In ovo injection of all-trans retinoic acid causes adipocyte hypertrophy in embryos but lost its effect in posthatch chickens.

The regulation of adipose deposition in broiler chickens is an important factor for production efficiency to poultry producers and health concerns to customers. Although vitamin A and its metabolite [all-trans retinoic acid (atRA)] have been used for studies on adipogenesis in mammals and avian, effects of embryonic atRA on adipose development in embryonic (E) and posthatch (D) ages in broiler chickens have not been studied yet. Different concentrations of atRA (0M-2μM) were injected in broiler eggs at E10, and adipose tissues were sampled at E16. Percentages of adipose tissues in chicken embryos were significantly increased in the group injected with 500nM of atRA compared to the 0M group (P<0.05). In addition, the adipocyte cross-sectional area (CSA) was significantly greater by in ovo injection of 500nM atRA compared to the injection of 0M (P<0.01). Moreover, in ovo atRA-injected embryos were hatched and BWs were measured at D0, D7, and D14. BWs were not different from those of the 0M group. Percentages of adipose tissues and CSA of the in ovo atRA-injected group (500nM) were not different from those of the 0M group at D14. Taken together, the current study clearly showed that in ovo injection of atRA promoted adipose deposition with hypertrophy during embryonic development, but its effects were not maintained in early posthatch age in broiler chickens, implying that embryonic atRA has an important role in the regulation of adipose development in chicken embryos.

Downregulation of Astrocyte Elevated Gene-1 Expression Combined with All-Trans Retinoic Acid Inhibits Development of Vasculogenic Mimicry and Angiogenesis in Glioma.

This study aimed to investigate the effects of downregulating astrocyte elevated gene-1 (AEG-1) expression combined with all-trans retinoic acid (ATRA) on vasculogenic mimicry (VM) formation and angiogenesis in glioma. U87 glioma cells were transfected with AEG-1 shRNA lentiviral vectors (U87-siAEG-1) and incubated in a medium containing 20 µmol/L ATRA. Matrigel-based tube formation assay was performed to evaluate VM formation, and the cell counting kit-8 (CCK-8) assay was used to analyze the proliferation of glioma cells in vitro. Reverse transcription-quantitative polymerase chain reaction and Western blot analysis were used to investigate the mRNA and protein expression of related genes, respectively. Glioma xenograft models were generated via subcutaneous implantation of glioma cells in nude mice. Tumor-bearing mice received an intraperitoneal injection of ATRA (10 mg/kg per day). Immunohistochemistry was used to evaluate the expression of related genes and the microvessel density (MVD) in glioma xenograft models. CD34/periodic acid-Schiff double staining was performed to detect VM channels in vivo. The volume and weight of tumors were measured, and a tumor growth curve was drawn to evaluate tumor growth. A combination of ATRA intervention and downregulation of AEG-1 expression significantly inhibited the proliferation of glioma cells in vitro and glioma VM formation in vitro and in vivo. It also significantly decreased MVD and inhibited tumor growth. Further, the expression levels of matrix metalloproteinase (MMP)-2, MMP-9, vascular endothelial-cadherin (VE-cadherin), and vascular endothelial growth factor (VEGF) in glioma significantly decreased in vivo and in vivo. Hence, a combinatorial approach might be effective in treating glioma through regulating MMP-2, MMP-9, VEGF, and VE-cadherin expression.

Hypertrophy of Adipose Tissues in Quail Embryos by in ovo Injection of All-Trans Retinoic Acid.

Excessive adipose accretion causes health issues in humans and decreases feed efficiency in poultry. Although vitamin A has been known to be involved in adipogenesis, effects of all-trans retinoic acid (atRA), as a metabolite of vitamin A, on embryonic adipose development have not been studied yet. Avian embryos are developing in confined egg environments, which can be directly modified to study effects of nutrients on embryonic adipogenesis. With the use of quail embryos, different concentrations of atRA (0 M to 10 μM) were injected in ovo at embryonic day (E) 9, and adipose tissues were sampled at E14. Percentages of fat pad weights in embryo weights were significantly increased in the group injected with 300 nM of atRA. Also, among three injection time points, E5, E7, or E9, E7 showed the most significant increase in weight and percentage of inguinal fat at E14. Injection of atRA at E7 increased fat cell size in E14 embryos with up-regulation of pro-adipogenic marker genes (Pparγ and Fabp4) and down-regulation of a preadipocyte marker gene (Dlk1) in adipose tissues. These data demonstrate that atRA promotes hypertrophic fat accretion in quail embryos, implying important roles of atRA in embryonic development of adipose tissues.

All-trans retinoic acid suppresses bone morphogenetic protein 4 in mouse diabetic nephropathy through a unique retinoic acid response element.

Diabetic nephropathy (DN) causes mesangial matrix expansion, which results in glomerulosclerosis and renal failure. Collagen IV (COL4) is a major component of the mesangial matrix that is positively regulated by bone morphogenetic protein 4 (BMP4)/suppressor of mothers against decapentaplegic (Smad1) signaling. Because previous studies showed that retinoids treatment had a beneficial effect on kidney disease, we investigated the therapeutic potential of retinoids in DN, focusing especially on the regulatory mechanism of BMP4. Diabetes was induced with streptozotocin in 12-wk-old male Crl:CD1(ICR) mice, and, 1 mo later, we initiated intraperitoneal injection of all-trans retinoic acid (ATRA) three times weekly. Glomerular matrix expansion, which was associated with increased BMP4, phosphorylated Smad1, and COL4 expression, worsened in diabetic mice at 24 wk of age. ATRA administration alleviated DN and downregulated BMP4, phosopho-Smad1, and COL4. In cultured mouse mesangial cells, treatment with ATRA or a retinoic acid receptor-α (RARα) agonist significantly decreased BMP4 and COL4 expression. Genomic analysis suggested two putative retinoic acid response elements (RAREs) for the mouse Bmp4 gene. Chromatin immunoprecipitation analysis and reporter assays indicated a putative RARE of the Bmp4 gene, located 11,488-11,501 bp upstream of exon 1A and bound to RARα and retinoid X receptor (RXR), which suppressed BMP4 expression after ATRA addition. ATRA suppressed BMP4 via binding of a RARα/RXR heterodimer to a unique RARE, alleviating glomerular matrix expansion in diabetic mice. These findings provide a novel regulatory mechanism for treatment of DN.

Testosterone-retinoic acid signaling directs spermatogonial differentiation and seasonal spermatogenesis in the Plateau pika (Ochotona curzoniae)

During evolution, animals optimize their reproductive strategies to increase offspring survival. Seasonal breeders reproduce only during certain times of the year. In mammals, reproduction is tightly controlled by hypothalamus-pituitary-gonad axis. Although pathways regulating gametogenesis in non-seasonal model species have been well established, molecular insights into seasonal reproduction are severely limited. Using the Plateau pika (Ochotona curzoniae), a small rodent animal species native to the Qinghai-Tibetan plateau, as a model, here we report that seasonal spermatogenesis is governed at the level of spermatogonial differentiation. In testis of the reproductively dormant animals, undifferentiated spermatogonia failed to differentiate and accumulated in the seminiferous tubules. RNA-seq analyses of the active and dormant testes revealed that genes modulating retinoic acid biogenesis and steriodogenesis were differentially regulated. A single injection of all-trans retinoic acid (ATRA) reinitiated spermatogenesis and inhibition the function of RA-degrading enzyme CYP26B1 for 10 days induced spermatogonial differentiation. Strikingly, testosterone injection reinitiated spermatogenesis in short day adapted animals. Testosterone provides a permissive environment of RA biogenesis and actions in testis, therefore, indirectly controls spermatogonial differentiation. Collectively, these findings provide a key mechanistic insight regarding the molecular regulation of seasonal reproduction in mammals.

All-trans retinoic acid attenuates bleomycin-induced pulmonary fibrosis via downregulating EphA2-EphrinA1 signaling

The role of all-trans retinoic acid (ATRA) in pulmonary fibrosis is relatively unknown, although this metabolite modulates cell differentiation, proliferation, and development. We aimed to evaluate the role of ATRA in bleomycin-induced pulmonary fibrosis, and whether the mechanism involves EphA2-EphrinA1 and PI3K-Akt signaling. We evaluated three groups of mice: a control group (intraperitoneal DMSO injection 3 times weekly after PBS instillation), bleomycin group (intraperitoneal DMSO injection 3 times weekly after bleomycin instillation), and bleomycin + ATRA group (intraperitoneal ATRA injection 3 times weekly after bleomycin instillation). The cell counts and protein concentration in the bronchoalveolar lavage fluid (BALF), changes in histopathology, Ashcroft score, hydroxyproline assay, expression of several signal pathway proteins including EphA2-EphrinA1, and PI3K-Akt, and cytokine levels were compared among the groups. We found that bleomycin significantly increased the protein concentration in the BALF, Ashcroft score in lung tissue, and hydroxyproline contents in lung lysates. Furthermore, bleomycin upregulated EphA2, EphrinA1, PI3K 110γ, Akt, IL-6 and TNF-α. However, administration of ATRA attenuated the upregulation of EphA2-EphrinA1 and PI3K-Akt after bleomycin instillation, and decreased pulmonary fibrosis. In addition, ATRA suppressed IL-6 and TNF-α production induced by bleomycin-induced injury. Collectively, these data suggest that ATRA attenuates bleomycin-induced pulmonary fibrosis by regulating EphA2-EphrinA1 and PI3K-Akt signaling.

Chromatin reader ZMYND8 is a key target of all trans retinoic acid-mediated inhibition of cancer cell proliferation

All trans retinoic acid (ATRA), an active vitamin-A derivative, has been shown to regulate gene expression program and thus imparts anti-proliferative activity to cancer cells. Previously, we identified a dual histone reader ZMYND8 (zinc finger MYND (Myeloid, Nervy and DEAF-1)-type containing 8), to be a novel target of ATRA. In the present study, we attempted to decipher the detail mechanism of its transcription regulation. ATRA can reprogram the epigenetic landscape in the upstream regulatory region of ZMYND8 thereby promoting its expression. Interestingly, there is a unique H3K27Me3 to H3K27Ac switch upon ATRA-treatment. We show here that ATRA causes dynamic changes in recruitment of transcription factor YY1 in concert with HDAC1 at ZMYND8 promoter. Further, we show that ATRA treatment triggers an anti-proliferative activity in cancer cells through regulation of ZMYND8 expression. Subsequently, in 4T1-induced syngenic tumor mouse model, ATRA injection caused significant upregulation of ZMYND8. Overall our findings highlight a novel mechanism underlying ATRA-mediated changes in ZMYND8 expression which, in turn, activates the anti-proliferative program in a cancer cell. Thus, histone reader mediated modulation of epigenetic language could play a significant role in retinoid based therapeutic strategy which is well exploited to combat tumor growth.

Exogenous Modulation of Retinoic Acid Signaling Affects Adult RGC Survival in the Frog Visual System after Optic Nerve Injury.

After lesions to the mammalian optic nerve, the great majority of retinal ganglion cells (RGCs) die before their axons have even had a chance to regenerate. Frog RGCs, on the other hand, suffer only an approximately 50% cell loss, and we have previously investigated the mechanisms by which the application of growth factors can increase their survival rate. Retinoic acid (RA) is a vitamin A-derived lipophilic molecule that plays major roles during development of the nervous system. The RA signaling pathway is also present in parts of the adult nervous system, and components of it are upregulated after injury in peripheral nerves but not in the CNS. Here we investigate whether RA signaling affects long-term RGC survival at 6 weeks after axotomy. Intraocular injection of all-trans retinoic acid (ATRA), the retinoic acid receptor (RAR) type-α agonist AM80, the RARβ agonist CD2314, or the RARγ agonist CD1530, returned axotomized RGC numbers to almost normal levels. On the other hand, inhibition of RA synthesis with disulfiram, or of RAR receptors with the pan-RAR antagonist Ro-41-5253, or the RARβ antagonist LE135E, greatly reduced the survival of the axotomized neurons. Axotomy elicited a strong activation of the MAPK, STAT3 and AKT pathways; this activation was prevented by disulfiram or by RAR antagonists. Finally, addition of exogenous ATRA stimulated the activation of the first two of these pathways. Future experiments will investigate whether these strong survival-promoting effects of RA are mediated via the upregulation of neurotrophins.

All-trans retinoic acid potentiates cisplatin-induced kidney injury in rats: impact of retinoic acid signaling pathway.

Cisplatin (cis-diammine dichloroplatinum (II), CDDP) is a widely used drug for treatment of various types of cancers. However, CDDP-induced nephrotoxicity remains the main dose-limiting side effect. Retinoids are a group of vitamin A-related compounds that exert their effects through retinoid receptors activation. In this study, we investigated the effect of CDDP treatment on retinoic acid receptor-α (RAR-α) and retinoid X receptor-α (RXR-α) expression. In addition, we investigated the possible modulatory effects of RAR agonist, all-trans retinoic acid (ATRA), on CDDP-induced nephrotoxicity. Rats were treated with saline, DMSO, CDDP, ATRA, or CDDP/ATRA. Twenty-four hours after the last ATRA injection, rats were killed; blood samples were collected; kidneys were dissected; and biochemical, immunohistochemical, and histological examinations were performed. Our results revealed that CDDP treatment significantly increased serum levels of creatinine and urea, with concomitant decrease in serum albumin. Moreover, reduced glutathione (GSH) content as well as superoxide dismutase (SOD) and catalase (CAT) activities were significantly reduced with concurrent increase in kidney malondialdehyde (MDA) content following CDDP treatment. Furthermore, CDDP markedly upregulated tubular RAR-α, RXR-α, fibrin, and inducible nitric oxide synthase (iNOS) protein expression. Although administration of ATRA to control rats did not produce marked alterations in kidney function parameters, administration of ATRA to CDDP-treated rats significantly exacerbated CDDP-induced nephrotoxicity. In addition, CDDP/ATRA co-treatment significantly increased RAR-α, RXR-α, fibrin, and iNOS protein expression compared to CDDP alone. In conclusion, we report, for the first time, the crucial role of retinoid receptors in CDDP-induced nephrotoxicity. Moreover, our findings indicate that co-administration of ATRA with CDDP, although beneficial on the therapeutic effects, their deleterious effects on the kidney may limit their clinical use.

All-trans retinoic acid mitigates methotrexate-induced liver injury in rats; relevance of retinoic acid signaling pathway

Methotrexate (MTX) is a widely used drug for treatment of rheumatic and autoimmune diseases as well as different types of cancer. One of the major side effects of MTX is hepatotoxicity. Retinoid receptors, including retinoid X receptor (RXR), and retinoic acid receptor (RAR) are vitamin A receptors that are highly expressed in the liver and regulate important physiological processes through regulation of different genes. In this study, we investigated the effect of MTX on RXR-α and RAR-α expression in the liver and the potential protective effects of all-trans retinoic acid (ATRA) in MTX-induced hepatotoxicity. Rats were randomly divided into five groups: The rates were treated with saline, DMSO, MTX (20mg/kg/IP; single dose), ATRA (7.5mg/kg/day, I.P), or MTX and ATRA. Rats were killed 24h after the last ATRA injection. The liver tissues were dissected out, weighed, and subjected to histological, immunohistochemical, and biochemical examinations. Our results demonstrated that treatment with MTX resulted in significant decrease in reduced glutathione (GSH) content and superoxide dismutase (SOD) activity, with concomitant increase in ALT, AST, and MDA levels. In addition, MTX markedly downregulated the expression of both RXR-α and RAR-α, and changed the appearance of RXR-α to be very small speckled droplets. Treatment with ATRA significantly ameliorated MTX-induced effects on GSH, ALT, and MDA. Moreover, ATRA administration increased the expression and nuclear translocation of RXR-α in rat hepatocytes. In conclusion, our study revealed, for the first time, that retinoid receptors may play an important role in the MTX-induced hepatotoxicity.

Prenatal retinoic acid increases lipofibroblast expression in hypoplastic rat lungs with experimental congenital diaphragmatic hernia

Background/purposePrenatal administration of all-trans retinoic acid (ATRA) has been shown to stimulate alveolarization in nitrofen-induced pulmonary hypoplasia (PH) associated with congenital diaphragmatic hernia (CDH). Lipid-containing interstitial lipofibroblasts (LIFs), characterized by adipocyte differentiation-related protein (ADRP), play a critical role in alveolar development by coordinating lipid homeostasis. Previous studies have demonstrated that ATRA positively affects LIF expression in developing lungs. We hypothesized that pulmonary LIF expression is increased after prenatal ATRA treatment in the nitrofen model of CDH-associated PH. MethodsTimed-pregnant rats were treated with nitrofen or vehicle on E9.5, followed by injection of ATRA or placebo on E18.5, E19.5, and E20.5. Fetal lungs were dissected on E21.5 and divided into Control+Placebo, Control+ATRA, Nitrofen+Placebo, and Nitrofen+ATRA. Pulmonary gene expression levels of ADRP were analyzed by quantitative real-time polymerase chain reaction, and LIF expression was investigated by ADRP immunohistochemistry, oil-red-O-, and immunofluorescence-double-staining. ResultsRelative mRNA expression of pulmonary ADRP was significantly increased in Nitrofen+ATRA compared to Nitrofen+Placebo (0.31±0.02 vs. 0.08±0.01; P<0.0001). ADRP immunoreactivity and oil-red-O-staining were markedly increased in alveolar interstitium of Nitrofen+ATRA compared to Nitrofen+Placebo. Immunofluorescence-double-staining confirmed markedly increased LIF expression in alveolar walls of Nitrofen+ATRA compared to Nitrofen+Placebo. ConclusionsIncreased LIF expression after prenatal treatment with ATRA in nitrofen-induced PH suggests that ATRA may have a therapeutic potential in attenuating CDH-associated PH by stimulating alveolar development.

ATRA alters humoral responses associated with amelioration of EAMG symptoms by balancing Tfh/Tfr helper cell profiles

All-trans retinoic acid (ATRA) is a vitamin A metabolite with diverse immunomodulatory actions used therapeutically in the treatment of some autoimmune diseases. However, the effects that ATRA may have on diminishing myasthenia gravis (MG) symptoms remain undefined. This study investigated the effect of ATRA on experimental autoimmune myasthenia gravis (EAMG) in vivo and in vitro. Data presented in this study demonstrated that intraperitoneal injection of ATRA ameliorated EAMG pathology in rats associated with reduced total anti-acetylcholine receptor (AChR) serum IgG levels. We observed that EAMG development was accompanied by an increase in follicular helper T cells (Tfh, defined as CD4(+)CXCR5(+)ICOS(high)) and a decrease of follicular regulatory T cells (Tfr, defined as CD4(+)Foxp3(+)CXCR5(+)ICOS(median)) and that the Tfh:Tfr ratio was altered following ATRA administration. In addition, ATRA treatment restored the Th1/Th2/Th17/Treg balance. In vitro, ATRA inhibited AChR-specific cell proliferation and eliciting apoptosis in these cells without affecting the cell cycle. ATRA also altered the Th distribution in animals presenting with EAMG resulting in a reduction in Th1/Th17/Tfh cells and increasing the number of Th2/Treg/Tfr cell types. These results suggested that ATRA reduced EAMG severity by regulating Th cell profiles thereby providing new insights into the development of novel MG (or related) therapies.

972 RELAXATION EFFECT OF ALL-TRANS RETINOIC ACID VIA NO-SGC-CGMP PATHWAY AND CALCIUM ACTIVATED POTASSIUM CHANNELS IN RAT MESENTERIC ARTERY

Background: Intraperitoneal injection of all-trans retinoic acid (ATRA) results in a reduction of blood pressure in spontaneously hypertensive rats. However, the mechanisms are not clear. We hypothesized that ATRA may relax resistance arteries. Results: In this study, we found that ATRA relaxes preconstricted mesenteric arterial rings induced by phenylephrine (PhE) which is abrogated by removal of the endothelium. Pretreatment of endothelium-intact arterial rings with an inhibitor of endothelial nitric oxide synthase (eNOS), L-NAME, or an inhibitor of soluble guanylyl cyclase (sGC), ODQ, reduced the vasorelaxant effect of ATRA. Incubation of mesenteric arterial rings with ATRA increased the production of NO and cyclic guanosine monophosphate (cGMP) which was blocked by L-NAME. The vasorelaxant effect of ATRA was markedly attenuated in the presence of a small- (apamin) and large-conductance calcium-activated potassium channel blocker (charybdotoxin), but not by an inhibitor of voltage dependent potassium channel (4-aminopynidine), or an inhibitor of ATP sensitive potassium channel (glibenclamide). Activation of retinoic acid receptors (RAR) with CH55 or retinoic X receptors (RXR) with LGD1069 induced the vasorelaxation of mesenteric arterial rings preconstricted by PhE. The RAR (BMS493) and RXR (UVI3003) antagonists blocked the ATRA-induced vasorelaxation. Conclusions: We conclude that ATRA relaxes resistance vessels, via both RAR and RXR receptors that is mediated by the endothelium-dependent NO-cGMP pathway.

Effect of retinoic acid on hemolymph glucose regulation in the fresh water edible crab Oziotelphusa senex senex

9- cis-Retinoic acid (9CRA) and all- trans-retinoic acid (ATRA) are known to be involved in the regulation of glucose homeostasis in vertebrates by inducing insulin release and expression of glucose reporter proteins. In view of the fact that 9CRA and ATRA are endogenous in crustaceans and a retinoic acid X-receptor exists in crabs, we investigated whether 9CRA and ATRA also plays a role in glucose homeostasis in freshwater crab, Oziotelphusa senex senex. Injection of 9CRA into intact crabs significantly increased the hemolymph glucose level in a dose-dependent manner. Such 9CRA-induced hyperglycemia was apparently mediated by the CHH since injection of 9CRA into eyestalk-ablated crabs did not result in hyperglycemia. In support of this, administration of 9CRA in to crabs resulted in reduced hyperglycemic activity of eyestalks and elevated titers of CHH in hemolymph. ATRA injection did not cause any changes in hemolymph glucose and CHH levels. The results provide the first evidence that 9- cis-retinoic acid, but not all- trans-retinoic acid, is involved in the regulation of glucose homeostasis and apparently mediated by the eyestalk hormone CHH.

Inhibition of liver metastasis by all- trans retinoic acid incorporated into O/W emulsions in mice

All- trans retinoic acid (ATRA) was incorporated into lipid emulsions in an attempt to alter its distribution characteristics and improve its inhibition of liver cancer metastasis. Lipid emulsions composed of egg phosphatidylcholine, cholesterol, and soybean oil were the optimized carriers for ATRA delivery, as shown by the submicron particle size and high incorporation efficiency. The particle size and zeta potential of ATRA incorporated into emulsions were about 133 nm and −11 mV, respectively. In vitro drug release study demonstrated that the release of ATRA from emulsions was sustained in the absence and present of bovine serum albumin, suggesting that ATRA was stable when incorporated in emulsions. After intravenous administration in mice, [ 3H]cholesteryl hexadecyl ether incorporated into emulsion, which is the inherent distribution of emulsions, accumulated gradually mainly in the liver. The blood concentration and hepatic accumulation of [ 3H]ATRA incorporated into emulsion was significantly higher than that of serum dissolving [ 3H]ATRA, which represent the original distribution characteristic of free ATRA. In a murine liver metastasis model by colon adenocarcinoma, the liver metastasis number and liver weight were significantly reduced and the survival time of mice was prolonged following intravenous injection of ATRA incorporated into emulsions.

Inhibitory effect of all-trans retinoic acid on androgen-induced growth of mouse seminal vesicles in vivo and its mechanism

We examined the effect of all-trans retinoic acid (ATRA) on the androgen-induced growth of mouse seminal vesicles (SVs) in vivo and its mechanisms. Testosterone propionate (TP) alone or with ATRA was injected daily into adult castrated BALB/c mice. Injections of ATRA significantly inhibited the TP-induced growth of SVs in terms of wet weight and DNA synthesis by a pair of SVs evaluated by [3H]thymidine uptake. The bromodeoxyuridine labelling index showed that ATRA inhibited the proliferation of both epithelial and stromal cells. Immunoreactivity for retinoic acid receptor-alpha was found in the basal epithelial cells. Injections of ATRA affected neither 5alpha-reductase activity nor the expression of mRNAs for TGF-beta1, 2 and 3 and TGF-beta receptor 1 and 2 in the SVs. However, androgen receptor (AR) binding assays and Western blotting revealed a decrease in AR without a change in ligand-binding affinity. The present study showed that retinoid inhibited the androgen-induced growth of mouse SVs in vivo, and suggests that a decrease in AR is one of its mechanisms.

Effects of Strain and Treatment with Inhaled All-Trans-Retinoic Acid on Cigarette Smoke-Induced Pulmonary Emphysema in Mice

Models of emphysema produced by exposing animals to cigarette smoke (CS) have potential for use in testing treatments of this disease. To better characterize development of emphysema in an animal model, male and female mice of the B6C3F1 and A/J strains were exposed to CS at 250 mg total particulate material (TPM)/m3 for 15 weeks. Emphysema was evident in both strains of mice to differing degrees of severity. The CS-induced increase in the mean linear intercept (normalized to BW) of A/J mice was 51% greater than the control value, while CS-exposed B6C3F1 had an increase of 38% in this morphometric measurement of alveolar air space enlargement. In separate experiments, female B6C3F1 mice and male A/J mice were exposed to CS for 32 weeks and 15 weeks, respectively, and were then used to test the efficacy of all trans-retinoic acid (ATRA) treatments to ameliorate emphysema lesions. Following CS exposure, the B6C3F1 mice were treated once daily for 14 days in a 3-week period by nose-only inhalation exposure to aerosols of 180 or 1,800 mg-minutes ATRA/m3. The A/J mice were treated once daily, 4 days/week, for three weeks by either intraperitoneal injection of ATRA (0.5 or 2.5 mg/kg) or inhalation exposure to ATRA (3,600 or 18,000 mg-minutes/m3). Neither the injections nor inhalation exposures of ATRA in either strain of mouse caused reversal of the emphysema. In summary, CS-induced emphysema was more severe in A/J mice than in B6C3F1 mice. Treatment with ATRA did not reverse emphysema in either strain of CS-exposed mice.

Effects of Strain and Treatment with Inhaled All-Trans-Retinoic Acid on Cigarette Smoke-Induced Pulmonary Emphysema in Mice

Models of emphysema produced by exposing animals to cigarette smoke (CS) have potential for use in testing treatments of this disease. To better characterize development of emphysema in an animal model, male and female mice of the B6C3F1 and A/J strains were exposed to CS at 250 mg total particulate material (TPM)/m3 for 15 weeks. Emphysema was evident in both strains of mice to differing degrees of severity. The CS-induced increase in the mean linear intercept (normalized to BW) of A/J mice was 51% greater than the control value, while CS-exposed B6C3F1 had an increase of 38% in this morphometric measurement of alveolar air space enlargement. In separate experiments, female B6C3F1 mice and male A/J mice were exposed to CS for 32 weeks and 15 weeks, respectively, and were then used to test the efficacy of all trans-retinoic acid (ATRA) treatments to ameliorate emphysema lesions. Following CS exposure, the B6C3F1 mice were treated once daily for 14 days in a 3-week period by nose-only inhalation exposure to aerosols of 180 or 1,800 mg-minutes ATRA/m3. The A/J mice were treated once daily, 4 days/week, for three weeks by either intraperitoneal injection of ATRA (0.5 or 2.5 mg/kg) or inhalation exposure to ATRA (3,600 or 18,000 mg-minutes/m3). Neither the injections nor inhalation exposures of ATRA in either strain of mouse caused reversal of the emphysema. In summary, CS-induced emphysema was more severe in A/J mice than in B6C3F1 mice. Treatment with ATRA did not reverse emphysema in either strain of CS-exposed mice.

Antenatal retinoic acid does not alter alveolization or postnatal lung function in preterm sheep.

Retinoic acid exposure has been shown to promote surfactant production in foetal rats and to promote alveolization in neonatal rats. It was hypothesized that antenatal retinoic acid treatment would promote alveolization and accelerate functional maturation in the lungs of late gestation preterm sheep. Foetuses received a single i.m. injection of all-trans retinoic acid (RA, 20 mg x kg(-1)) or vehicle control at 115 days gestation (term=150 days) and were delivered at 125 days gestation. To examine the longer term effects of RA on alveolization a second group of animals received RA or vehicle at 121 days gestation and were delivered at 146 days gestation. Liver retinol levels at time of delivery were 2-3-fold higher in both preterm and near-term RA treated animals, indicating a significant impact of RA treatment on retinol metabolism. Dynamic compliance, gas exchange, lung gas volume and saturated phosphatidylcholine pool size at 125 days were unaffected by antenatal RA treatment. Alveolar volume, wall thickness and number at 125 or 146 days were also unaffected by RA treatment. Retinoic acid, as administered in this study, does not appear to accelerate structural or functional maturation of the foetal sheep lung. Response to retinoic acid may be species dependent, highlighting a need for caution when interpreting results from animal based studies.

Retinoic acid increases BDNF-dependent regeneration of chick retinal ganglion cells in vitro.

Brain-derived neurotrophic factor (BDNF) supports survival and regeneration of retinal ganglion cells (RGC). Since the expression of its receptor TrkB can be induced by the transcriptional activator retinoic acid (RA), we have investigated the possibility that RA promotes axonal regeneration of differentiated chick RGC synergistically with BDNF. After injection of all-trans RA onto the chorio-allantoic membrane of stage E16 chick embryos, axonal regeneration was monitored in organ cultures supplemented with BDNF. RA enhanced neurite outgrowth of retinal ganglion cells 2- to 3-fold. The dose-dependent effect was observed only after application of RA in ovo and subsequent use of the neurotrophin, not with RA alone.