Retinoic acid and the differentiation of lymphohaemopoietic stem cells

Impact of Cancer Stem Cells on Therapy Resistance in Gastric Cancer

Gastric cancer (GC) is the fourth leading cause of cancer death worldwide, with an average 5-year survival rate of 32%, being of 6% for patients presenting distant metastasis. Despite the advances made in the treatment of GC, chemoresistance phenomena arise and promote recurrence, dissemination and dismal prognosis. In this context, gastric cancer stem cells (gCSCs), a small subset of cancer cells that exhibit unique characteristics, are decisive in therapy failure. gCSCs develop different protective mechanisms, such as the maintenance in a quiescent state as well as enhanced detoxification procedures and drug efflux activity, that make them insusceptible to current treatments. This, together with their self-renewal capacity and differentiation ability, represents major obstacles for the eradication of this disease. Different gCSC regulators have been described and used to isolate and characterize these cell populations. However, at the moment, no therapeutic strategy has achieved the effective targeting of gCSCs. This review will focus on the properties of cancer stem cells in the context of therapy resistance and will summarize current knowledge regarding the impact of the gCSC regulators that have been associated with GC chemoradioresistance.

Retinoids as an Immunity-modulator in Dermatology Disorders

The skin is the largest epithelial surface protecting the body from invading microbes. Vitamin A plays vital roles in the host defence of the skin, including promoting epithelial cell integrity, proliferation, and differentiation and even mediating immune responses. Furthermore, vitamin A derivatives, retinoid drugs, are widely used to treat skin diseases, such as acne and psoriasis. However, the immunoregulatory mechanisms of retinoids in dermatology have not been systematically described. In this paper, we discuss the immunological functions of retinoids during disease treatment, especially in skin disorders caused by exogenous infections.

Chicken amyloid arthropathy: serum amyloid A, interleukin-1beta, interleukin-6, tumour necrosis factor-alpha and nitric oxide profile in acute phase (12th hour)

Acute phase response (APR) is part of the early defense system, which is triggered by different stimuli including, infection, trauma, stres, inflammation and neoplasia. The APR complex is a reaction which induces homeostasis and recovery. In this research, serum amyloid A (SAA), interlaukin (IL)-1beta, IL-6, tumour necrosis factor alpha (TNF-alpha) and nitric oxide (NO) levels were measured 12 hours following injection. For this purpose, Thirty-two 5 weeks old laying chicken were allocated into four groups and intra-articular injections of Freund's adjuvant were used to induce amylod arthropathy in Groups II, III and IV. Vitamin A in group II, and methylprednisolone in group IV were added to enhance and to reduce the severity of amyloidosis, respectively. At the end of the research, it was observed that TNF-alpha and NO increased significantly (P < 0.05) in vitamin A and methylprednisolone groups whereas SAA decreased significantly (P < 0.05) in all groups. It was also observed that IL-6 increased (P < 0.05) in vitamin A group and decreased in all other gorups however, IL-1beta decreased in vitamin A and methylprednisolone groups, while it was increased in the control group. The results of this study suggest that there is a positive correlation between serum TNF-alpha levels in acute and chronic phase in chickens with amyloid arthropathy.

The Expression of Retinoic Acid Receptors in Lymph Nodes of Young Children and the Effect of All-trans-Retinoic Acid on the B Cells from Lymph Nodes

To elucidate the mechanism of vitamin A enhancing the production of antibody, we examined the expression and distribution of retinoic acid receptors mRNA in lymph nodes of young children ( < or = 5 years of age), and investigated the affection of all-trans-retinoic acid on the maturation and activation of the B cells isolated from the lymph nodes and cultured in vitro. Twenty-four normal lymph nodes were collected. By in situ hybridization, we found that all six retinoic acid receptor genes expressed and distributed widely in the lymph nodes, and the levels of mRNA for retinoic acid receptor genes (detected by RT-fluorescent quantitative PCR) were increased with the development of children. In vitro culture, all-trans retinoic acid promoted the maturation and activation of the B cells from the lymph nodes. Thus, promotion on B cells in lymph node may be the important mechanism of vitamin A reinforcing the humoral immunity in young children.

The effects of vitamin A, pentoxyfylline and methylprednisolone on experimentally induced amyloid arthropathy in brown layer chicks

The effects of vitamin A, pentoxyfylline and methylprednisolone on experimentally induced amyloid arthropathy were investigated. In this study, 175 1-day-old brown layer chicks were used. Throughout the study Group II (vitamin A) received high doses of vitamin A (75,000 IU/kg), whereas Group I (negative control), Group III (positive control), Group IV (pentoxyfylline) and Group V (methylprednisolone) received normal levels of vitamin A in the diet. At the fifth week, the experimental Groups II, III, IV and V were injected with Freund's adjuvant intra-articularly to induce amyloid arthropathy. Group IV received pentoxyfylline and Group V received methylprednisolone (10 mg/kg, intramuscularly) once. Joint and blood samples were examined 13 weeks after the injections. The values in Groups I, II, III, IV and V, respectively, were as follows: amyloid arthropathy formation (%), 0, 100, 87, 76, 66; serum amyloid A (ng/ml), 166+/-17, 607+/-40, 423+/-39, 342+/-27, 293+/-22; serum retinol (microg/dl): 59.75+/-3.8, 42.72+/-3, 59.24+/-3.6, 102+/-9.1, 101.3+/-12.3; heterophil/lymphocyte ratio: 0.504, 0.75, 0.75, 0.087, 0.44. In conclusion, it was observed that vitamin A enhanced the development of amyloid arthropathy and there were positive associations between amyloidosis, increased levels of serum amyloid A and increased numbers of tissue infiltrating macrophages. Methylprednisolone had a more successful inhibitory effect on amyloid arthropathy than pentoxyfylline.

Vitamin A and immunity to viral, bacterial and protozoan infections

Studies in animal models and cell lines show that vitamin A and related retinoids play a major role in immunity, including expression of mucins and keratins, lymphopoiesis, apoptosis, cytokine expression, production of antibody, and the function of neutrophils, natural killer cells, monocytes or macrophages, T lymphocytes and B lymphocytes. Recent clinical trials suggest that vitamin A supplementation reduces morbidity and mortality in different infectious diseases, such as measles, diarrhoeal disease, measles-related pneumonia, human immunodeficiency virus infection and malaria. Immune responses vary considerably during different infections, and the available data suggest that the modulation of immune function by vitamin A may also vary widely, depending on the type of infection and immune responses involved.