Unconjugated
Aberrant CD40 expression by dendritic cells (DCs), induced by microbial stimuli, such as CpG, contributes to the pathogenesis of many human/murine diseases, particularly autoimmune and inflammatory diseases. Given the importance of CD40 in these diseases, and the contribution of DCs to the diseases process, it is very important to investigate the mechanisms of CD40 expression induced by CpG on DCs. In this study, we made the observation that CpG-B is a potent inducer on CD40 expression on murine bone marrow-derived DCs. Based on this finding, we undertook an analysis of the molecular basis of CpG-induced CD40 expression on DCs. By using selective inhibitors, it was demonstrated that MAPKs (JNK and p38 MAPK but not ERK) and NF-κB were involved in CpG-induced CD40 expression on DCs. In addition, RNA interference analysis revealed that IRF8 was a key transcription factor in the basal expression of CD40 upon CpG stimulation. Moreover, up-regulating miRNA-146a in DCs effectively decreased CD40 expression by targeting TRAF6 and IRAK1. Thus, our results have elucidated the molecular mechanisms underlying CpG-induced CD40 expression and DC maturation.
Oxidative and nitrative stresses have been established to play a pivotal role in neuroinflammation. During inflammation-mediated neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease, reactive oxygen species (ROS) and nitric oxide (NO) are produced by activated microglia, further inducing increased neuronal injury in the brain. Protosappanin A (PTA) is a bioactive compound isolated from a traditional Chinese medicine, Caesalpinia sappan L. (Lignum Sappan), showing immunosuppressive effects. However, the molecular mechanisms responsible for the anti-oxidative and nitrative activity of PTA have not been elucidated, particularly in central nervous system. In this study, we found that PTA significantly inhibited ROS and NO production by suppression of NADPH oxidase and inducible nitric oxide synthase (iNOS) activity on lipopolysaccharide (LPS)-stimulated BV-2 microglia. Moreover, PTA modulated IKK/IκB/NF-κB inflammation signal pathway to inhibit the activity and expressions of NADPH oxidase and iNOS. A further study indicated that PTA didn't inhibit LPS interaction with transmembrane protein CD14, which is a receptor for LPS binding. However, PTA interfered with the interaction of CD14 with Toll-like receptor (TLR4), an early cell event of IKK/IκB/NF-κB inflammation signal activation, resulting in a block on LPS translocation from CD14 to TLR4. Therefore, CD14/TLR4 interaction may be a potential drug target in neuroinflammation-related oxidative and nitrative stress. Taken together, these results suggest that PTA has anti-oxidative/nitrative activities on brain immune and neuroinflammation through regulation of CD14/TLR4-dependent IKK/IκB/NF-κB inflammation signal pathway.
