Abstract
Alzheimer’s disease (AD) is a chronic progressive neurodegenerative disease. Its mechanism is still not clear. Majority of research focused on the central nervous system (CNS) changes, while few studies emphasize on peripheral immune system modulation. Our study aimed to investigate the regulation of the peripheral immune system and its relationship to the severity of the disease after treatment in an AD model of APPswe/PSEN1dE9 transgenic (APP/PS1 Tg) mice. APP/PS1 Tg mice (8 months old) were treated with the ROCK-II inhibitor 1-(5-isoquinolinesulfonyl)-homo-piperazine (Fasudil) (intraperitoneal (i.p.) injections, 25 mg/kg/day), bone marrow stromal cells (BMSCs; caudal vein injections, 1 × 106 BMSCs /time/mouse), Fasudil combined with BMSCs, or saline (i.p., control) for 2 months. Morris water maze (MWM) test was used to evaluate learning and memory. The mononuclear cells (MNCs) of spleens of APP/PS1 Tg mice were analyzed using flow cytometry for CD4+ T-cells, macrophages, and the pro-inflammatory and anti-inflammatory molecules of the macrophages. Immunohistochemical staining was used to examine the expression of ROCK-II in the spleens of APP/PS1 Tg mice. The MWM test showed improved spatial learning ability in APP/PS1 Tg mice treated with Fasudil or BMSCs alone or in combination, compared to untreated APP/PS1 Tg mice. Fasudil combined with BMSCs intervention significantly promoted the proliferation of CD4+/CD25+ and CD4+/ IL-10 lymphocytes, induced the release of cytokine factors, and regulated the balance of the immune system to work functionally. It also shifted M1 (MHC-II, CD86) to M2 (IL-10, CD206) phenotype of macrophages of CD11b and significantly enhanced the anti-inflammatory and phagocytic abilities (CD16/32) of macrophages of CD11b. Immunohistochemical staining showed significantly decreased expression of ROCK-II in mice treated with combination of Fasudil with BMSCs as compared to saline control. Fasudil in combination of BMSCs improved cognition of APP/PS1 Tg mice through the regulation of the peripheral immune system, including reduction of ROCK-II expression and increased proportion of anti-inflammatory M2 mononuclear phenotype and phagocytic macrophages in the spleen of the peripheral immune system. The latter was achieved through the communication between brain and spleen to improve the immunoregulation of CNS and AD disease conditions.
Highlights
More than 47 million people worldwide suffer from Alzheimer’s disease (AD) and this number will be increased to 131 million by 2050 (Prince et al, 2016)
Efficacy of Fasudil, bone marrow stromal cells (BMSCs), or Fasudil combined with BMSCs was determined using the Morris water maze (MWM) test in APP/PS1 Tg mice, which were screened for cognitive impairment at the age of 8 months and 2 weeks after the last treatment (Figure 1A)
Our results demonstrated that Fasudil or Fasudil combined with BMSCs improved spatial learning of APP/PS1 Tg mice, the latter of which appeared to be more effective than Fasudil or BMSCs alone
Summary
More than 47 million people worldwide suffer from Alzheimer’s disease (AD) and this number will be increased to 131 million by 2050 (Prince et al, 2016). AD is a progressive neurodegenerative disease, pathologically characterized by amyloid-β (Aβ) peptide plaques and tau protein neurofibrillary tangles. It starts from the hippocampus of the brain, which is an anatomical site for the formation of initial memory. The plaques and tangles from these two proteins destroy neuronal cells of the brain and eventually impair the patient’s memories. Communications between the CNS and peripheral immune system can play an important role in AD. We believe that the mechanism of AD involves immunity dysfunction. There are limited studies on the role of peripheral immune system in AD. It was of interest and importance to investigate how the peripheral immune system contributes to the development of AD (Subramanian et al, 2010)
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