Piperine alleviates inflammation, blood-brain-barrier and myelin destruction
MS has numerous pathologic hallmarks as an inflammatory and autoimmune CNS disease, such as leukocyte cells infiltration, blood-brain-barrier (BBB) and myelin destruction. Spinal cords tissues were subjected to histological analysis on day 22 after MOG’s immunization. As illustrated in Figure 6A, piperine treated-group showed reduced leukocyte cell infiltrations by hematoxylin and eosin (H&E) staining and less demyelination in white matter by Luxol fast blue (LFB) staining as compared to the vehicle-treated mice.
Blood-brain-barrier (BBB) destruction is a pathologic hallmark of EAE. We then aim to investigate the effect of piperine on BBB permeability using a fluorescent BSA conjugate probe BSA-Cy5.5. As shown in Figure 6B, piperine significantly reduce the accumulation of BSA-Cy5.5 in the brain as indicated by in vivo optical imaging when compared to the vehicle treated mice, suggesting improved BBB integrity in EAE challenge. During the pathological process of MS, destructive BBB allows lymphocytes activated in the periphery to infiltrate the CNS, which evoke a local immune reaction resulting in axons and myelin damages. We next examined whether piperine treatment alleviates myelin destruction in EAE model using a myelin-binding near-infrared dye 3,3-diethylthiatricarbocyanine iodide (DBT). DBT dye (0.3 mg/kg) were intravenous injection to mice and the fluorescence signals were imaged. Figure 6C shows a higher fluorescent intensity as compared to the vehicle group, indicating reduced myelin destruction following piperine treatment.
We also investigate the effect of piperine on EAE-related T cell activation. As presented in Figure 6D-E, EAE challenge induce a significantly increase of population of CD4+ and CD8+T cell in spleen (increased from 9.35±0.17% to 13.6±0.32% for CD4+ T cell and from 16.17±0.18% to 24.32±0.39% for CD8+ T cell). Remarkably, piperine treatment group (30 mg/kg) shows a significantly reduction of CD4+population, when compared with the vehicle-treated mice. In addition, reduced CD8+ proportion was also observed following piperine administration. Taken together, these data indicate that piperine can effectively ameliorate inflammation and protect blood-brain-barrier and myelin in EAE mice.