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- Jia, Juan, 1979-, et al.
(författare)
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Heparanase cleavage of heparin modulates protease storage in mast cells
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Overexpression of heparanase caused extensive degradation of heparan sulfate (HS), and elimination of heparanase resulted in non-degraded HS chains in mice. In this study, we have investigated the impact of heparanase in the processing of heparin and storage of proteases in mast cells. We used fetal skin mast cells (FSMCs) isolated from wild type (WT) embryos and embryos either overexpressing human heparanase (hpa-tg), or lacking heparanase (Hpse-KO). FSMCs from hpa-tg embryos produced substantially shorter heparin chains than did WT counterparts, whereas FSMCs from Hpse-KO embryos expressed longer chains than WT cells. Extensive fragmentation of heparin in hpa-tg FSMC caused losing of proteases in the cells; in contrast, increased storage of proteases was observed in Hpse-KO cells. These results provide the first in vivo evidence demonstrating that heparanase is responsible for processing of mast cell heparin. Control of heparin degradation by heparanase in mast cell may contribute to modulating protease storage in the cells.
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| 2. |
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| 3. |
- O'Callaghan, Paul, et al.
(författare)
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Apolipoprotein-E increases cell-associated amyloid-β through a heparan sulfate-dependent pathway
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The increased risk of Alzheimer’s disease (AD) associated with specific apolipoprotein E (ApoE) isoforms appears to relate to altered amyloid-β (Aβ) homeostasis. The efficiency of Aβ clearance from the brain is reduced in the presence of the AD-associated ApoE4 isoform, which may explain the accumulation of Aβ deposits in the parenchyma and vasculature. The low density lipoprotein receptor-related protein 1 (LRP1) and heparan sulfate proteoglycans (HSPGs) are involved in Aβ uptake, with LRP1 further implicated in Aβ transcytosis across the blood brain barrier. However, both are also established ApoE receptors and function co-operatively to mediate cell interactions with lipoproteins and Aβ. Here we determined that HS, ApoE and LRP1 co-occur in Aβ40-positive microvessels of AD brain, establishing the relevance of studying interactions between these molecules. Using Chinese hamster ovary (CHO) cells deficient in HS or LRP1 we found that ApoE increases the levels of cell-associated Aβ in primarily a HSPG-dependent manner. Furthermore, in this model we found that ApoE is alternatively processed in the absence of cell surface HS, supporting a role for HSPGs in ApoE metabolism. The findings presented here raise the possibility that ApoE can increase Aβ associations with HSPGs and LRP1 in the vasculature. This may facilitate clearance, but if unbalanced could contribute to Aβ accumulation and the pathogenesis of AD.
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| 4. |
- O'Callaghan, Paul, et al.
(författare)
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Microglial heparan sulfate proteoglycans mediate pro-inflammatory signaling
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Microglia are the central nervous system’s (CNS) first line of defense against pathogenic insults and acute inflammatory responses are necessary for the resolution of infection. However, unregulated and/or chronic activation of microglia is associated with neurodegeneration. Heparan sulfate proteoglycans (HSPGs) have been attributed various roles in inflammation, but the possibility that HSPGs are integral to pro-inflammatory signaling mechanisms has not been fully explored. To analyze the relevance of microglial HSPGs in the pro-inflammatory response we isolated primary microglia from mice overexpressing human heparanase (Hpa-tg), the HS-degrading endoglucuronidase, and challenged them with the pro-inflammatory endotoxin lipopolysaccharide (LPS). The LPS-induced upregulation of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) was inhibited in Hpa-tg microglia, as was upregulation of the LPS-receptor CD14. Analysis of HSPG structures revealed that Hpa-tg microglia produced truncated HS chains. Importantly, co-treatment of microglia with heparin attenuated LPS-induced cytokine upregulation. Together these findings implicate microglial HSPGs as key facilitators of the pro-inflammatory response. Astrocytes constitute a critical support network in the CNS, but are also implicated in inflammation. LPS induced comparable levels of TNF-α in Hpa-tg and Ctrl astrocytes, indicating that the mechanism of HSPG-dependent inflammation is specific to microglia. We conclude that microglial HSPGs are required for pro-inflammatory signaling events and that heparanase, through its HS-degrading activity, can regulate this mechanism.
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