全反式维甲酸对兔动脉粥样硬化病灶中MCP-1 和TLR-4

目的:观察全反式维甲酸(ATRA)对兔颈动脉粥样硬化性病灶中内膜增生、MCP-1及TLR-4表达的影响,探讨其可能的抗炎机制。方法:新西兰雄性大白兔随机分为9组(n=6):对照组(A、B、C)、治疗组(A、B、C)、假手术组(A、B、C)。除假手术组外,其余两组给予高脂饮食2周后,对照组及治疗组给予颈动脉内膜空气干燥术损伤颈动脉内膜,假手术组分离暴露颈动脉但不损伤内膜,治疗组术前3天给予ATRA灌胃,直至处死。术后分别于7d、14d、28d处死。采取颈动脉标本,对血管粥样硬化病变进行形态学观察及测定,采用免疫组化法检测MCP-1及TLR-4表达水平。结果:从形态学观察及免疫组化检测看,对照组较假手术组内膜明显增生,MCP-1及TLR-4表达增多,治疗组内膜较对照组增生减轻,两种因子表达减少。结论:全反式维甲酸(ATRA)对兔颈动脉粥样硬化性病灶中的抗炎作用可能是通过抑制MCP-1及TLR-4等炎症因子的表达来发挥作用的。     

Induction of apoptosis and immune response by all-<Emphasis Type="Italic">trans</Emphasis> retinoic acid plus interferon-gamma in human malignant glioblastoma T98G and U87MG cells

Glioblastoma is the most common and highly malignant brain tumor. It is also one among the most therapy-resistant human neoplasias. Patients die within a year of diagnosis despite the use of available treatment strategies such as surgery, radiotherapy, and chemotherapy. Thus, there is a critical need to find a novel therapeutic strategy for treating this disease. Here, we have investigated the molecular mechanisms for induction of apoptosis as well as for activation of immune components in human malignant glioblastoma T98G and U87MG cells following treatment with all-trans retinoic acid (ATRA) plus interferon-gamma (IFN-gamma). Treatment of glioblastoma cells with ATRA alone prevented cell proliferation and induced astrocytic differentiation, while IFN-gamma alone induced apoptosis and modulated expression of human leukocyte antigen (HLA) class II molecules such as HLA-DRalpha, HLA-DR complex, invariant chain (Ii), HLA-DM (an important catalyst of the class II-peptide loading), and gamma interferon-inducible lysosomal thiol-reductase (GILT). Interestingly, both T98G and U87MG cells showed more increase in apoptosis with expression of the HLA class II components for an effective immune response following treatment with ATRA plus IFN-gamma than with IFN-gamma alone. Apoptotic mode of cell death was confirmed morphologically by Wright staining and biochemically by measuring an increase in caspase-3 activity. While conversion of tumor cells into HLA class II+/Ii- cells by stimulation with the helper CD4+ T cells is thought to be challenging, this study reports for the first time that treatment of glioblastoma cells with ATRA plus IFN-gamma can simultaneously enhance apoptosis and expression of the HLA class II immune components with a marked suppression of Ii expression. Taken together, this study suggests that induction of apoptosis and immune components of the HLA class II pathway by ATRA plus IFN-gamma may be a promising chemoimmunotherapeutic strategy for treatment of human malignant glioblastoma.     

Role of Vitamin D3 Receptor in the Synergistic Differentiation of WEHI-3B Leukemia Cells by Vitamin D3 and Retinoic Acid

WEHI-3B D⁻ cells differentiate in response to 1,25-dihydroxyvitamin D₃ (1,25-(OH)₂D₃) but not to all-trans-retinoic acid (RA) or other inducing agents. Combinations of RA with 1,25-(OH)₂D₃ interact to produce synergistic differentiation of WEHI-3B D⁻ cells. To determine factors involved in the synergistic interaction, expression of the 1,25-(OH)₂D₃ receptor (VDR) and retinoid receptors, RARα and RXRα, was measured. No VDR was detected in untreated WEHI-3B D⁻ cells; however, RA and 1,25-(OH)₂D₃ when used as single agents caused a slight induction of the VDR and in combination produced a marked increase in the VDR. In contrast, no changes in RARα and RXRα were initiated by these compounds. An RAR-selective agonist combined with 1,25-(OH)₂D₃ produced synergistic differentiation of WEHI-3B D⁻ cells, whereas an RXR-selective agonist did not. To gain information on the role of the VDR in the synergistic interaction, the VDR gene was transferred into WEHI-3B D⁺ cells, in which no VDR was detected and no synergism was produced. Expression of the VDR conferred differentiation responsiveness to 1,25-(OH)₂D₃ in WEHI-3B D⁺ cells. These findings suggest that (a) induction of VDR expression is a key component in the synergistic differentiation induced by 1,25-(OH)₂D₃ and RA and (b) RAR and not RXR must be activated for enhanced induction of the VDR and for the synergistic differentiation produced by RA and 1,25-(OH)₂D₃.