Meningeal lymphatics affect microglia responses and anti-Aß immunotherapy.

Alzheimer's disease (AD) is the most prevalent cause of dementia1. Although there is no effective treatment for AD, passive immunotherapy with monoclonal antibodies against amyloid beta (Aß) is a promising therapeutic strategy2,3. Meningeal lymphatic drainage has an important role in the accumulation of Aß in the brain4, but it is not known whether modulation of meningeal lymphatic function can influence the outcome of immunotherapy in AD. Here we show that ablation of meningeal lymphatic vessels in 5xFAD mice (a mouse model of amyloid deposition that expresses five mutations found in familial AD) worsened the outcome of mice treated with anti-Aß passive immunotherapy by exacerbating the deposition of Aß, microgliosis, neurovascular dysfunction, and behavioural deficits. By contrast, therapeutic delivery of vascular endothelial growth factor C improved clearance of Aß by monoclonal antibodies. Notably, there was a substantial overlap between the gene signature of microglia from 5xFAD mice with impaired meningeal lymphatic function and the transcriptional profile of activated microglia from the brains of individuals with AD. Overall, our data demonstrate that impaired meningeal lymphatic drainage exacerbates the microglial inflammatory response in AD and that enhancement of meningeal lymphatic function combined with immunotherapies could lead to better clinical outcomes.

The binding of kaempferol-3-O-rutinoside to vascular endothelial growth factor potentiates anti-inflammatory efficiencies in lipopolysaccharide-treated mouse macrophage RAW264.7 cells.

BACKGROUND: Vascular Endothelial Growth Factors (VEGFs) are a group of growth factor in regulating development and maintenance of blood capillary. The VEGF family members include VEGF-A, placenta growth factor (PGF), VEGF-B, VEGF-C and VEGF-D. VEGF receptor activation leads to multiple complex signaling pathways, particularly in inducing angiogenesis. Besides, VEGF is produced by macrophages and T cells, which is playing roles in inflammation. In macrophages, VEGF receptor-3 (VEGFR-3) and its ligand VEGF-C are known to attenuate the release of pro-inflammatory cytokines. METHODS: Immunoprecipitation and molecular docking assays showed the binding interaction of kaempferol-3-O-rutinoside and VEGF-C. Western blotting and qRT-PCR methods were applied to explore the potentiating effect of kaempferol-3-O-rutinoside in VEGF-C-mediated expressions of proteins and genes in endothelial cells and LPS-induced macrophages. Enzyme-linked immunosorbent assay (ELISA) was employed to reveal the release of proinflammatory cytokines in LPS-induced macrophages. Immunofluorescence assay was performed to determine the effect of kaempferol-3-O-rutinoside in regulating nuclear translocation of NF-κB p65 subunit in the VEGF-C-treated cultures. In addition, Transwell® motility assay was applied to detect the ability of cell migration after drug treatment in LPS-induced macrophages. RESULTS: We identified kaempferol-3-O-rutinoside, a flavonoid commonly found in vegetable and fruit, was able to act on cultured macrophages in inhibiting inflammatory response, and the inhibition was mediated by its specific binding to VEGF-C. The kaempferol-3-O-rutinoside-bound VEGF-C showed high potency to trigger the receptor activation. In LPS-treated cultured macrophages, applied kaempferol-3-O-rutinoside potentiated inhibitory effects of exogenous applied VEGF-C on the secretions of pro-inflammatory cytokines, i.e. IL-6 and TNF-α, as well as expressions of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). This inhibition was in parallel to transcription and translocation of NF-κB. Moreover, the binding of kaempferol-3-O-rutinoside with VEGF-C suppressed the LPS-induced migration of macrophage. CONCLUSION: Taken together, our results suggested the pharmacological roles of kaempferol-3-O-rutinoside in VEGF-C-mediated anti-inflammation.

Selective Stimulation of Cardiac Lymphangiogenesis Reduces Myocardial Edema and Fibrosis Leading to Improved Cardiac Function Following Myocardial Infarction.

BACKGROUND: The lymphatic system regulates interstitial tissue fluid balance, and lymphatic malfunction causes edema. The heart has an extensive lymphatic network displaying a dynamic range of lymph flow in physiology. Myocardial edema occurs in many cardiovascular diseases, eg, myocardial infarction (MI) and chronic heart failure, suggesting that cardiac lymphatic transport may be insufficient in pathology. Here, we investigate in rats the impact of MI and subsequent chronic heart failure on the cardiac lymphatic network. Further, we evaluate for the first time the functional effects of selective therapeutic stimulation of cardiac lymphangiogenesis post-MI. METHODS AND RESULTS: We investigated cardiac lymphatic structure and function in rats with MI induced by either temporary occlusion (n=160) or permanent ligation (n=100) of the left coronary artery. Although MI induced robust, intramyocardial capillary lymphangiogenesis, adverse remodeling of epicardial precollector and collector lymphatics occurred, leading to reduced cardiac lymphatic transport capacity. Consequently, myocardial edema persisted for several months post-MI, extending from the infarct to noninfarcted myocardium. Intramyocardial-targeted delivery of the vascular endothelial growth factor receptor 3-selective designer protein VEGF-CC152S, using albumin-alginate microparticles, accelerated cardiac lymphangiogenesis in a dose-dependent manner and limited precollector remodeling post-MI. As a result, myocardial fluid balance was improved, and cardiac inflammation, fibrosis, and dysfunction were attenuated. CONCLUSIONS: We show that, despite the endogenous cardiac lymphangiogenic response post-MI, the remodeling and dysfunction of collecting ducts contribute to the development of chronic myocardial edema and inflammation-aggravating cardiac fibrosis and dysfunction. Moreover, our data reveal that therapeutic lymphangiogenesis may be a promising new approach for the treatment of cardiovascular diseases.