Administration Of Retinoic Acid Research Articles

Influence of initiation time and white blood cell count on the efficacy of cytotoxic agents in acute promyelocytic leukemia during induction treatment.

The present study retrospectively analyzed 96 newly diagnosed acute promyelocytic leukemia (APL) patients with low-intermediate mortality risk to identify the optimum timing to initiate cytotoxic chemotherapy following all-trans retinoic acid (ATRA) administration. Based on white blood cell (WBC) at chemotherapy initiation, the patients were divided into three groups: low WBC (WBC count ≤4×109/l), intermediate WBC (WBC count >4×109/l and <15×109/l) and high WBC group (WBC count ≥15×109/l). According to the period from ATRA commencement to chemotherapy, 96 patients were further divided into two groups: ≤3 days group (chemotherapy within 3 days of ATRA) and >3 days group (chemotherapy >3 days after ATRA). Clinical effects were compared by univariate analysis and multivariate analyses. The incidence rate of differentiation syndrome (DS; also termed retinoic acid syndrome) was 0.0, 11.1 and 40.0% in the low, intermediate and high WBC groups, respectively (P<0.001); complete remission (CR) rate was 90.5, 100.0 and 73.3%, respectively (P<0.001); and the rate of early mortality (defined as fatality during induction treatment) was 4.8, 0.0 and 26.7%, respectively (P<0.001). No differences were identified in clinicolaboratory parameters between the ≤3 days and >3 days groups, except in time to achieve CR (P=0.004) and rate of bleeding related to chemotherapy (P=0.009), both being higher in the >3 days group. Multivariate analyses indicated WBC count at chemotherapy was the only independent risk factor for the occurrence of DS [P=0.002; odds ratio (OR) =1.058, 95% confidence interval (CI) =1.021-1.095] and early mortality (P=0.036; OR =1.036, 95% CI =1.002-1.070). For newly diagnosed APL patients with low-intermediate risk, chemotherapy initiation should be recommended until WBC count rises to between 4×109/l and 15×109/l during induction treatment.

Nanostructured Ti surfaces and retinoic acid/dexamethasone present a spatial framework for the maturation and amelogenesis of LS-8 cells.

PurposeTo investigate the amelogenesis-inductive effects of surface structures at the nanoscale. For this purpose, variable nanostructured titanium dioxide (TiO2) surfaces were used as a framework to regulate the amelogenic behaviors of ameloblasts with the administration of retinoic acid (RA)/dexamethasone (DEX).Materials and methodsTiO2 nanotubular (NT) surfaces were fabricated via anodization. Mouse ameloblast-like LS-8 cells were seeded and cultured on NT surfaces in the presence or absence of RA/DEX for 48 h. The amelogenic behaviors and extracellular matrix (ECM) mineralization of LS-8 cells on nanostructured Ti surfaces were characterized using field emission scanning electron microscope, laser scanning confocal microscope, quantitative polymerase chain reaction, MTT assay, and flow cytometry.ResultsTiO2 NT surfaces (tube size ~30 and ~80 nm) were constructed via anodization at 5 or 20 V and denoted as NT5 and NT20, respectively. LS-8 cells exhibited significantly increased spread and proliferation, and lower rates of apoptosis and necrosis on NT surfaces. The amelogenic gene expression and ECM mineralization differed significantly on the NT20 and the NT5 and polished Ti sample surfaces in standard medium. The amelogenic behaviors of LS-8 cells were further changed by RA/DEX pretreatment, which directly drove maturation of LS-8 cells.ConclusionControlling the amelogenic behaviors of ameloblast-like LS-8 cells by manipulating the nanostructure of biomaterials surfaces represents an effective tool for the establishment of a systemic framework for supporting enamel regeneration. The administration of RA/DEX is an effective approach for driving the amelogenesis and maturation of ameloblasts.

Vitamin A deficiency provokes aberrant T cell responses and exacerbates liver injury in LCMV-infected mice

Abstract Vitamin A deficiency (VAD) is a public health problem worldwide; however, its role and underlying mechanisms in viral infection are not entirely understood. In this study, we detected elevated LCMV-specific T cell responses in VAD mice at the acute stage (7 dpi). These VAD mice exhibited higher serum ALT levels and increased liver permeability. Consistently, enhanced antiviral T cell responses were observed in VAD mice in persistent infection (30 dpi), as evidenced by decreased PD-1 expression and increased cytokine production. To investigate whether VAD causes an intrinsic abnormality of T cells during animal development and growth, we transferred spleen cells from control and VAD mice into CD45.1 recipient mice, followed by LCMV infection, and found that antiviral T cell responses were comparable between control and VAD donor cells. However, when CD45.1 cells were transferred into control and VAD recipient mice, they showed a highly activated phenotype in VAD mice. These results suggest that vitamin A or its metabolites restrict T cell activation through an extrinsic way. Retinoic acid (RA) is considered one of the important metabolites of vitamin A. We found that RA administration inhibited excessive T cell responses in VAD mice. To dissect the mechanism of RA, we treated splenocytes and purified CD8+ T cells with RA, followed by PMA stimulation. RA treatment reduced the phosphorylation of AKT, p38, ERK, and S6, as well as the abundance of transcriptional factor NFATc1. Together, our study demonstrated that VAD caused an aberrant T cell response to viral infection, and RA may have the potential to serve as a therapeutic agent for excessive immune responses and tissue injury in VAD patients.

Generation of motor neurons requires spatiotemporal coordination between retinoic acid and Mib-mediated Notch signaling

ABSTRACTMind bomb (Mib) is an E3 ubiquitin ligase that activates the Notch signaling pathway. A previous study demonstrated that the generation of late-born GABAergic neurons may be regulated by the interplay between Mib and retinoic acid (RA). However, the relationship between Mib function and the retinoid pathway during the generation of late-born motor neurons remains unclear. We investigated the differentiation of neural progenitors into motor neurons by inhibition of Notch signaling and administration of RA to Tg[hsp70-Mib:EGFP] embryos. The number of motor neurons in the ventral spinal cord increased or decreased depending on the temporal inhibition of Mib-mediated Notch signaling. Inhibition of the retinoid pathway by citral treatment had a synergistic effect with overexpression of Mib:EGFP on the generation of ectopic motor neurons. Additionally, the proteolytic fragment of Mib was detected in differentiated P19 cells following treatment with RA. Our observations imply that the function of Mib may be attenuated by the retinoid pathway, and that Mib-mediated Notch signaling and the retinoid pathway play critical roles in the spatiotemporal differentiation of motor neurons.

Effects of Fifty-Hertz Electromagnetic Fields on Granulocytic Differentiation of ATRA-Treated Acute Promyelocytic Leukemia NB4 Cells

Background/Aims: Life on Earth is constantly exposed to electromagnetic fields (EMFs) and the effects induced by EMFs on biological systems have been extensively studied producing different and sometimes contradictory results. Extremely low-frequency electromagnetic fields (ELF-EMFs) have shown to play a role in regulating cell proliferation and differentiation, although how EMFs influence these processes remains unclear. Human acute promyelocytic leukemia (APL) cells are characterized by the arrest of differentiation at the promyelocytic stage due to epigenetic perturbations induced by PML/RARα fusion protein (Promyelocytic Leukemia protein - PML/Retinoic Acid Receptor alpha - RARα). Therapeutic administration of all-trans retinoic acid (ATRA) re-establishes the leukemogenic mechanism re-inducing the normal differentiation processes. Methods: We studied the effects of ELF-EMFs (50 Hz, 2 mT) on the ATRA-mediated granulocytic differentiation process of APL NB4 cells (a cell line established from the bone marrow of a patient affected by the acute promyelocytic leukemia) by monitoring cellular proliferation and morphology, nitrob lue tetrazolium (NBT) reduction and the expression of differentiation surface markers. Finally, we investigated mechanisms focusing on reactive oxygen species (ROS) generation and related molecular pathways. Results: ELF-EMF exposure decreases cellular proliferation potential and helps ATRA-treated NB4 cells to mature. Furthermore, the analysis of ROS production and the consequent extracellular signal regulated kinases (ERK1/2) phosphorylation suggest that a changed intracellular oxidative balance may influence the biological effects of ELF-EMFs. Conclusions: These results indicate that the exposure to ELF-EMF promotes ATRA-induced granulocytic differentiation of APL cells.

Retinoic acid signaling maintains epithelial and mesenchymal progenitors in the developing mouse ureter

The differentiated cell types of the mature ureter arise from the distal ureteric bud epithelium and its surrounding mesenchyme. Uncommitted epithelial cells first become intermediate cells from which both basal and superficial cells develop. Mesenchymal progenitors give rise to separated layers of adventitial fibrocytes, smooth muscle cells and lamina propria fibrocytes. How progenitor expansion and differentiation are balanced is poorly understood. Here, we addressed the role of retinoic acid (RA) signaling in these programs. Using expression analysis of components and target genes, we show that pathway activity is restricted to the mesenchymal and epithelial progenitor pools. Inhibition of RA signaling in ureter explant cultures resulted in tissue hypoplasia with a relative expansion of smooth muscle cells at the expense of lamina propria fibroblasts in the mesenchyme, and of superficial cells at the expense of intermediate cells in the ureteric epithelium. Administration of RA led to a slight reduction of smooth muscle cells, and almost completely prevented differentiation of intermediate cells into basal and superficial cells. We identified cellular programs and transcriptional targets of RA signaling that may account for this activity. We conclude that RA signaling is required and sufficient to maintain mesenchymal and epithelial progenitors in early ureter development.

Combined treatment with alendronate and Drynaria rhizome extracts : Effect on fracture healing in osteoporotic rats.

The effects of both alendronate (ALN) and Drynaria rhizome extracts (DRE) alone could promote bone healing in osteoporotic fractures but there are no reports about the combined use of ALN and DRE for promotion of bone healing of fractures in osteoporotic settings. This study investigated the effects of ALN plus DRE on fractures in osteopenic rats. Osteopenic rats underwent unilateral transverse osteotomy on the femur fixed by asterilized Kirschner wire 2weeks after intragastric administration of retinoic acid (80 mg/kg body weight/day). Subsequently, the animals were randomly divided into four groups: control, ALN, DRE and ALN+ DRE. All rats from groups ALN, DRE and ALN+ DRE received ALN (40 mg/kg, weekly), DRE (90 mg/kg/day), or both for 2, 4 and 6weeks. The results of our study indicated that all treatment promoted fracture healing and callus formation compared to controls but ALN+ DRE treatment showed significantly stronger effects than ALN or DRE alone in histological, X‑ray and biomechanical tests. These results seem to indicate that combined treatment with ALN and DRE has an additive effect on fracture healing and callus formation in osteoporotic rats.

All-trans retinoic acid and arsenic trioxide fail to derepress the monocytic differentiation driver Irf8 in acute promyelocytic leukemia cells

All-trans retinoic acid (ATRA) and/or arsenic trioxide (ATO) administration leads to granulocytic maturation and/or apoptosis of acute promyelocytic leukemia (APL) cells mainly by targeting promyelocytic leukemia/retinoic acid receptor alpha (PML/RARα). Yet, ~10–15% of APL patients are not cured by ATRA- and ATO-based therapies, and a potential failure of ATRA and ATO in completely reversing PML/RARα-driven oncogenic alterations has not been comprehensively examined. Here we characterized the in vivo primary responses of dysregulated genes in APL cells treated with ATRA and ATO using a GFP-labeled APL model. Although induced granulocytic differentiation of APL cells was evident after ATRA or ATO administration, the expression of the majority of dysregulated genes in the c-Kit+ APL progenitors was not consistently corrected. Irf8, whose expression increased along with spontaneous differentiation of the APL progenitors in vivo, represented such a PML/RARα-dysregulated gene that was refractory to ATRA/ATO signaling. Interestingly, Irf8 induction, but not its knockdown, decreased APL leukemogenic potential through driving monocytic maturation. Thus, we reveal that certain PML/RARα-dysregulated genes that are refractory to ATRA/ATO signaling are potentially crucial regulators of the immature status and leukemogenic potential of APL cells, which can be exploited for the development of new therapeutic strategies for ATRA/ATO-resistant APL cases.

Effects of tracheal occlusion with retinoic acid administration on normal lung development.

Tracheal occlusion (TO) is an investigational therapy for severe congenital diaphragmatic hernia that decreases pulmonary hypoplasia, but sustained TO also induces deficient surfactant synthesis. Intramuscular maternal administration of retinoic acid (RA) in a surgical rabbit model of congenital diaphragmatic hernia showed a beneficial effect on lung maturation. We evaluated the potential of RA delivery into the trachea and studied the combined effects of TO and RA on normal lung development. Experiments were performed on normal rabbit fetuses. Liposomes and capric triglyceride (Miglyol® ), alone and with RA, were administered in the trachea just before TO (d26). Lung morphology and surfactant production were studied at term (d30). Tracheal occlusion increased lung weight and enhanced alveolar development but increased apoptotic activity and decreased surfactant expression. Tracheal injection of RA improved surfactant production to levels of normal controls. We established the potential of liposome and Miglyol as RA vehicle for delivering this bioactive molecule in the fetal airways. Tracheal RA injection seems to oppose the effects of TO in fetuses with normal lungs. © 2017 John Wiley & Sons, Ltd.

Maternal Retinoids Increase PDGFRα+ Progenitor Population and Beige Adipogenesis in Progeny by Stimulating Vascular Development

Maternal vitamin A intake varies but its impact on offspring metabolic health is unknown. Here we found that maternal vitamin A or retinoic acid (RA) administration expanded PDGFRα+ adipose progenitor population in progeny, accompanied by increased blood vessel density and enhanced brown-like (beige) phenotype in adipose tissue, protecting offspring from obesity. Blockage of retinoic acid signaling by either BMS493 or negative RA receptor (RARαDN) over-expression abolished the increase in blood vessel density, adipose progenitor population, and beige adipogenesis stimulated by RA. Furthermore, RA-induced beige adipogenesis was blocked following vascular endothelial growth factor receptor (VEGFR) 2 knock out in PDGFRα+ cells, suggesting its mediatory role. Our data reveal an intrinsic link between maternal retinoid level and offspring health via promoting beige adipogenesis. Thus, enhancing maternal retinoids is an amiable therapeutic strategy to prevent obesity in offspring, especially for those born to obese mothers which account for one third of all pregnancies.

Evaluation of motor neuron differentiation potential of human umbilical cord blood- derived mesenchymal stem cells, in vitro

Many people suffer from spinal cord injuries annually. These deficits usually threaten the quality of life of patients. As a postpartum medically waste product, human Umbilical Cord Blood (UCB) is a rich source of stem cells with self- renewal properties and neural differentiation capacity which made it useful in regenerative medicine.Since there is no report on potential of human umbilical cord blood-derived mesenchymal stem cells into motor neurons, we set out to evaluate the differentiation properties of these cells into motor neuron-like cells through administration of Retinoic Acid(RA), Sonic Hedgehog(Shh) and BDNF using a three- step in vitro procedure. The results were evaluated using Real-time PCR, Flowcytometry and Immunocytochemistry for two weeks. Our data showed that the cells changed into bipolar morphology and could express markers related to motor neuron; including Hb-9, Pax-6, Islet-1, NF-H, ChAT at the level of mRNA and protein. We could also quantitatively evaluate the expression of Islet-1, ChAT and NF-H at 7 and 14days post- induction using flowcytometry. It is concluded that human UCB-MSCs is potent to express motor neuron- related markers in the presence of RA, Shh and BDNF through a three- step protocol; thus it could be a suitable cell candidate for regeneration of motor neurons in spinal cord injuries.

Low oxygen availability and malignant evolution of non-invasive breast tumors: potential protective role of all-trans retinoic acid (ATRA)

Reduced oxygen availability plays a crucial role in malignancy of solid tumors, including breast cancer. Even if the presence of hypoxic areas is common in all breast lesions, no data clearly correlate low oxygenation with the acquisition of malignant features by non-invasive cells, particularly by cells from ductal carcinoma in situ (DCIS), the most frequently diagnosed tumor in women in industrialized countries [1]. We demonstrated that 96 hours of culture under moderate hypoxia is sufficient to induce in DCIS-derived cells motility and epithelial-to-mesenchymal transition (EMT) and to enlarge the number of cells expressing the stem cell marker CD133, indicative of their increased malignant potential. Administration of all-trans retinoic acid (ATRA), a well-known anti-leukemic drug with an anti-tumor role in invasive breast tumor cells [2], supports the epithelial phenotype of DCIS-derived cells cultured under hypoxia and reduces the number of CD133 positive cells, abrogating almost completely the effects of poor oxygenation. In DCIS-derived cells, as in leukemic cells, ATRA up-regulates the β2 isoform of PI-PLC (PLC-β2), ectopically expressed in invasive breast tumors in which counteracts the effects of hypoxia on both EMT and CD133 levels [3]. This suggests that the mechanisms triggered by ATRA in non-invasive breast tumor cells cultured under hypoxia may, at least in part, depend on PLC-β2 activity. Overall, we assigned to hypoxia a role in increasing the malignant potential of DCIS-derived cells and identified in ATRA, currently used in treating acute promyelocytic leukemia (APL), an agonist potentially useful in preventing malignant progression of non-invasive breast lesions with hypoxic areas.

Retinoid acid-induced microRNA-27b-3p impairs C2C12 myoblast proliferation and differentiation by suppressing α-dystrobrevin

We previously reported that excess retinoic acid (RA) resulted in hypoplastic and derangement of myofilaments in embryonic tongue by inhibiting myogenic proliferation and differentiation through CamKIID pathway. Our further studies revealed that the expression of a series of miRNAs was altered by RA administration in embryonic tongue as well as in C2C12 cells. Thus, if excess RA impairs myogenic proliferation and differentiation through miRNAs is taken into account. In present study, miR-27b-3p was found up-regulated in RA-treated C2C12 cells as in embryonic tongue, and predicted to target the 3′UTR of α-dystrobrevin (DTNA). Luciferase reporter assays confirmed the direct interaction between miR-27b-3p and the 3′UTR of DTNA. MiR-27b-3p mimics recapitulated the RA repression on DTNA expression, C2C12 proliferation and differentiation, while the miR-27b-3p inhibitor circumvented these defects resulting from excess RA. As expected, the effects of siDTNA on C2C12 were coincided with those by RA treatment or miR-27b-3p mimics. Therefore, these findings indicated that excess RA inhibited the myoblast proliferation and differentiation by up-regulating miR-27b-3p to target DTNA, which implied a new mechanism in myogenic hypoplasia.

Endogenous retinoic acid signaling is required for maintenance and regeneration of cornea

Retinoic acid (RA) is a biologically active metabolite of vitamin A (retinol) that serves as an important signaling molecule in orchestrating diverse developmental processes including multiple roles during ocular development. Loss-of-function studies using gene knockouts of RA-synthesizing enzymes encoded by Aldh1a1, Aldh1a2, and Aldh1a3 (also known as Raldh1, Raldh2, and Raldh3) have provided valuable insight into how RA controls eye morphogenesis including corneal development. However, it is unclear whether endogenous RA is required for maintenance and regeneration of adult cornea. Here, we investigated the role of Aldh1a genes in the adult cornea using a novel conditional Aldh1a1,2,3-flox/flox;Rosa26-CreERT2 loss-of-function mouse model to determine the biological function of RA. Our findings indicate that loss of RA synthesis results in corneal thinning characterized by reduced thickness of the stromal layer, impaired corneal epithelial cell proliferation, and increased apoptosis. Corneal thinning in Aldh1a-deficient mice was significantly rescued by RA administration, indicating an important role of endogenous RA signaling in adult corneal homeostasis and regeneration. Thus, Aldh1a1,2,3-flox/flox;Rosa26-CreERT2 mice provide a useful model for investigating the mechanistic role of RA signaling in adult corneal maintenance and could provide new insights into therapeutic approaches for controlling corneal repair to prevent vision loss.

Retinoic Acid Improves Incidence and Severity of Necrotizing Enterocolitis by Lymphocyte Balance Restitution and Repopulation of LGR5+ Intestinal Stem Cells.

Necrotizing enterocolitis (NEC) is the most devastating gastrointestinal disease of the premature infant. We have recently shown that NEC development occurs after an increase in proinflammatory CD4Th17 (Th17) cells and reduced anti-inflammatory forkhead box P3 regulatory T cells (Tregs) to the premature small intestine of mice and humans, which can be experimentally reversed in mice by administration of all-trans retinoic acid (ATRA). We have also shown that NEC is characterized by apoptosis of Lgr5-positive intestinal stem cells (ISCs-Lgr5 cells) within the crypts of Lieberkühn, which are subsequently essential for intestinal homeostasis. We now hypothesize that the normal lymphocyte balance within the lamina propria of the intestine can be achieved via administration of ATRA which restores mucosal integrity by preventing the loss of ISCs. Using both in vivo and in vitro strategies, we now demonstrate that Th17 recruitment and Treg depletion lead to increased apoptosis within ISC niches, significantly impairing proliferative capacity and mucosal healing. ATRA exerted its protective effects by preventing T cell imbalance, ultimately leading to the protection of the ISC pool preventing the development of NEC in mice. These findings raise the exciting possibility that dietary manipulations could prevent and treat NEC by modulating lymphocyte balance and the ISC pool within the newborn small intestine.

Activation of Notch1 inhibits medial edge epithelium apoptosis in all-trans retinoic acid-induced cleft palate in mice

Administration of all-trans retinoic acid (atRA) on E12.0 (embryonic day 12.0) leads to failure of medial edge epithelium (MEE) disappearance and cleft palate. However, the molecular mechanism underlying the relationship between atRA and MEE remains to be identified. In this study, atRA (200 mg/kg) administered by gavage induced a 75% incidence of cleft palate in C57BL/6 mice. Notch1 was up-regulated in MEE cells in the atRA-treated group compared with the controls at E15.0, together with reduced apoptosis and elevated proliferation. Next, we investigated the mechanisms underlying atRA, Notch1 and MEE degradation in palate organ culture. Our results revealed that down-regulation of Notch1 partially rescued the inhibition of atRA-induced palate fusion. Molecular analysis indicated that atRA increased the expression of Notch1 and Rbpj and decreased the expression of P21. In addition, depletion of Notch1 expression decreased the expression of Rbpj and increased the expression of P21. Moreover, inhibition of Rbpj expression partially reversed atRA-induced MEE persistence and increased P21 expression. These findings demonstrate that atRA inhibits MEE degradation, which in turn induces a cleft palate, possibly through the Notch1/RBPjk/P21 signaling pathway.

Antiviral effect of vitamin A on norovirus infection via modulation of the gut microbiome

The effect and underlying mechanism of vitamin A on norovirus infection are largely unknown. This study aimed to investigate how vitamin A administration affects the gut microbiome after norovirus infection. Here, we demonstrate that treatment with either retinol or retinoic acid (RA) inhibits murine norovirus (MNV) replication using both in vitro and in vivo models. Compositional changes in the gut microbiome associated with RA administration and/or norovirus infection were also investigated. Oral administration of RA and/or MNV significantly altered intestinal microbiome profiles. Particularly, bacterial species belonging to the Lactobacillaceae families were remarkably increased by MNV inoculation and RA administration, suggesting that the antiviral effects of RA occur via the modulation of specific microbiota. The antiviral causal effect of Lactobacillus was identified and demonstrated using in vitro models in RAW264.7 cells. The antiviral immune response to MNV was mediated by IFN-β upregulation. This study represents the first comprehensive profiling of gut microbiota in response to RA treatment against norovirus infection. Moreover, we conclude that the abundance of Lactobacillus through gut microbiota modulation by RA is at least partially responsible for norovirus inhibition.

Mo1919 Repopulation of Lgr5+ Intestinal Stem Cells after Retinoic Acid Administration Reflects Lymphocyte Balance Restitution in Necrotizing Enterocolitis

Mo1919 Repopulation of Lgr5+ Intestinal Stem Cells after Retinoic Acid Administration Reflects Lymphocyte Balance Restitution in Necrotizing Enterocolitis

Role of monocyte chemoattractant protein-1, stromal derived factor-1 and retinoic acid in pathophysiology of neuropathic pain in rats.

Chemokines have been recently recognized to play a role in chronic pain syndromes' pathophysiology. This study investigated the role of monocyte chemoattractant protein-1 (MCP-1), stromal cell derived factor-1 (SDF-1), and retinoic acid (RA) as targets for the therapeutic approach of neuropathic pain. A chronic constriction injury (CCI) model of neuropathic pain by unilateral ligation of left sciatic nerve was performed in adult female Wistar rats. The effects of doxycycline (Dox, 50 mg/kg/day i.p. for 7 days), single dose of bicyclam (5 mg/kg i.p.), RA (15 mg/kg/day i.p. for 7 days), and their combination(s) on behavioral tests of nociception (Von Frey filaments; paw pressure test) on days 0, 1, 3, 5, and 7 of operation were studied. Serum concentrations of MCP-1 and SDF-1 were measured by ELISA. Histological examination of the sciatic nerve was investigated. CCI of sciatic nerve significantly induced mechanical allodynia and hyperalgesia and an increase of MCP-1 and SDF-1 serum levels. Dox-treated groups (Dox, Dox+bicyclam, Dox+RA, Dox+bicyclam+RA) and bicyclam-treated groups (bicyclam, Dox+bicyclam, bicyclam+RA, Dox+bicyclam+RA) attenuated CCI-induced behavioral and biochemical changes. RA inhibited CCI-induced mechanical hyperalgesia but produced a time-dependent reversal of allodynia. Histological findings showed degenerative changes of sciatic nerve after CCI that were partially recovered in Dox-treated groups. These findings demonstrate an association between serum MCP-1 and SDF-1 concentrations and behavioral manifestations of neuropathic pain. RA administration decreased neuropathic pain (antihyperalgesic effect) but did not cause any improvement in sciatic nerve tissues, either alone or in combination with chemokine antagonists. Thus, chemokines may serve as potential targets for drug development in neuropathic pain treatment.

Retinoic acid triggers meiosis initiation via stra8-dependent pathway in Southern catfish, Silurus meridionalis

Existing studies demonstrated that retinoic acid (RA) regulates meiotic initiation via stra8-independent pathway in teleosts which lack stra8 in their genomes. However, stra8 was recently identified from several fish species including Southern catfish (Silurus meridionalis). To explore the existence of stra8-dependent pathway in RA mediated meiotic initiation in fishes, in the present study, the genes encoding RA synthase aldh1a2 and catabolic enzyme cyp26a1 and cyp26b1 were cloned from the Southern catfish. By immunohistochemistry, Aldh1a2 signal was observed in gonads of both sexes during the meiotic initiation period. By real-time PCR, differentially expressed gene was observed for cyp26a1, but not for cyp26b1, in gonads during the meiotic initiation. Administration of exogenous RA or inhibition of endogenous RA degradation by either KET (RA catabolic enzyme inhibitor) or cyp26a1 knockdown using CRISPR/Cas9 induced advanced meiotic initiation in the ovaries as demonstrated by increased Stra8/stra8 expression and appearance of oocytes. In contrast, treatment with RA synthase inhibitor DEAB resulted in delayed meiotic initiation and Stra8/stra8 expression in the ovaries, which was rescued by exogenous RA administration. These results indicated that (1) RA triggers the onset of meiosis via stra8-dependent pathway in stra8 existing teleosts, as it does in tetrapods; (2) exogenous RA can rescue the endogenous RA deficiency; (3) Cyp26a1, instead of Cyp26b1, is the key catabolic enzyme involved in meiosis initiation in teleosts. Taken together, RA might trigger meiotic initiation via stra8-dependent and -independent pathway in different teleosts.