PMC:7296049 / 32795-42663 JSONTXT

{"project":"MyTest","denotations":[{"id":"32581761-28840054-31100172","span":{"begin":872,"end":876},"obj":"28840054"},{"id":"32581761-29210074-31100173","span":{"begin":891,"end":895},"obj":"29210074"},{"id":"32581761-28840054-31100174","span":{"begin":997,"end":1001},"obj":"28840054"},{"id":"32581761-27487766-31100175","span":{"begin":1035,"end":1039},"obj":"27487766"},{"id":"32581761-25819104-31100176","span":{"begin":1120,"end":1124},"obj":"25819104"},{"id":"32581761-28840054-31100177","span":{"begin":1603,"end":1607},"obj":"28840054"},{"id":"32581761-31758330-31100178","span":{"begin":1622,"end":1626},"obj":"31758330"},{"id":"32581761-25805696-31100179","span":{"begin":1871,"end":1875},"obj":"25805696"},{"id":"32581761-29311834-31100180","span":{"begin":1891,"end":1895},"obj":"29311834"},{"id":"32581761-28840054-31100181","span":{"begin":1908,"end":1912},"obj":"28840054"},{"id":"32581761-18931697-31100182","span":{"begin":2054,"end":2058},"obj":"18931697"},{"id":"32581761-9425002-31100183","span":{"begin":2257,"end":2261},"obj":"9425002"},{"id":"32581761-21905080-31100184","span":{"begin":2276,"end":2280},"obj":"21905080"},{"id":"32581761-24606160-31100185","span":{"begin":2358,"end":2362},"obj":"24606160"},{"id":"32581761-25564492-31100186","span":{"begin":2409,"end":2413},"obj":"25564492"},{"id":"32581761-24606160-31100187","span":{"begin":2438,"end":2442},"obj":"24606160"},{"id":"32581761-27664791-31100188","span":{"begin":2460,"end":2464},"obj":"27664791"},{"id":"32581761-21905080-31100189","span":{"begin":2888,"end":2892},"obj":"21905080"},{"id":"32581761-24260524-31100190","span":{"begin":2968,"end":2972},"obj":"24260524"},{"id":"32581761-25819104-31100191","span":{"begin":2986,"end":2990},"obj":"25819104"},{"id":"32581761-23595285-31100192","span":{"begin":3468,"end":3472},"obj":"23595285"},{"id":"32581761-23595285-31100193","span":{"begin":3777,"end":3781},"obj":"23595285"},{"id":"32581761-24267647-31100194","span":{"begin":4011,"end":4015},"obj":"24267647"},{"id":"32581761-27487766-31100195","span":{"begin":4031,"end":4035},"obj":"27487766"},{"id":"32581761-24267647-31100196","span":{"begin":4192,"end":4196},"obj":"24267647"},{"id":"32581761-23254638-31100197","span":{"begin":4430,"end":4434},"obj":"23254638"},{"id":"32581761-15852015-31100198","span":{"begin":4538,"end":4542},"obj":"15852015"},{"id":"32581761-24606160-31100199","span":{"begin":4556,"end":4560},"obj":"24606160"},{"id":"32581761-27664791-31100200","span":{"begin":4578,"end":4582},"obj":"27664791"},{"id":"32581761-20303333-31100201","span":{"begin":4723,"end":4727},"obj":"20303333"},{"id":"32581761-27664791-31100202","span":{"begin":4745,"end":4749},"obj":"27664791"},{"id":"32581761-29864483-31100203","span":{"begin":4765,"end":4769},"obj":"29864483"},{"id":"32581761-20018552-31100204","span":{"begin":4848,"end":4852},"obj":"20018552"},{"id":"32581761-20018552-31100205","span":{"begin":4989,"end":4993},"obj":"20018552"},{"id":"32581761-27487766-31100206","span":{"begin":5214,"end":5218},"obj":"27487766"},{"id":"32581761-10405161-31100207","span":{"begin":5299,"end":5303},"obj":"10405161"},{"id":"32581761-16219674-31100208","span":{"begin":5386,"end":5390},"obj":"16219674"},{"id":"32581761-21474190-31100209","span":{"begin":5409,"end":5413},"obj":"21474190"},{"id":"32581761-14604772-31100210","span":{"begin":5576,"end":5580},"obj":"14604772"},{"id":"32581761-27487766-31100211","span":{"begin":5596,"end":5600},"obj":"27487766"},{"id":"32581761-21738161-31100212","span":{"begin":6226,"end":6230},"obj":"21738161"},{"id":"32581761-24220169-31100213","span":{"begin":6247,"end":6251},"obj":"24220169"},{"id":"32581761-26967380-31100214","span":{"begin":6267,"end":6271},"obj":"26967380"},{"id":"32581761-21738161-31100215","span":{"begin":6527,"end":6531},"obj":"21738161"},{"id":"32581761-30304866-31100216","span":{"begin":6730,"end":6734},"obj":"30304866"},{"id":"32581761-20421294-31100217","span":{"begin":6828,"end":6832},"obj":"20421294"},{"id":"32581761-22238626-31100218","span":{"begin":6952,"end":6956},"obj":"22238626"},{"id":"32581761-11564889-31100219","span":{"begin":7357,"end":7361},"obj":"11564889"},{"id":"32581761-15152190-31100220","span":{"begin":7377,"end":7381},"obj":"15152190"},{"id":"32581761-19008341-31100221","span":{"begin":7395,"end":7399},"obj":"19008341"},{"id":"32581761-21431325-31100222","span":{"begin":7418,"end":7422},"obj":"21431325"},{"id":"32581761-23770291-31100223","span":{"begin":7442,"end":7446},"obj":"23770291"},{"id":"32581761-29864483-31100224","span":{"begin":8020,"end":8024},"obj":"29864483"},{"id":"32581761-30446350-31100225","span":{"begin":8041,"end":8045},"obj":"30446350"},{"id":"32581761-31620963-31100226","span":{"begin":8065,"end":8069},"obj":"31620963"},{"id":"32581761-28798681-31100227","span":{"begin":8669,"end":8673},"obj":"28798681"},{"id":"32581761-25519173-31100229","span":{"begin":9510,"end":9514},"obj":"25519173"}],"namespaces":[{"prefix":"_base","uri":"https://www.uniprot.org/uniprot/testbase"},{"prefix":"UniProtKB","uri":"https://www.uniprot.org/uniprot/"},{"prefix":"uniprot","uri":"https://www.uniprot.org/uniprotkb/"}],"text":"Discussion\nThis is the first study investigating the effects of NBP on remyelination and inflammation in a rat model of VD. We found that NBP alleviated pathologic changes in the hippocampus, promoted oligodendrocyte regeneration, inhibited astrocyte proliferation, and reduced demyelination and the expression of proinflammation cytokines. These effects were accompanied by a dose-dependent upregulation of AMPK/SIRT1 and downregulation of STAT3/NF-κB signaling in rats treated with NBP compared to untreated CCH rats. Our results provide evidence that NBP provides cognitive protection following CCH, likely through a mechanism involving modulation of the AMPK/SIRT1 and STAT3/NF-κB pathways. This is the first demonstration of crosstalk between AMPK/SIRT1 and STAT3/NF-κB signaling axes being implicated in VD.\nDemyelination is often observed in WMLs in VD (Li et al., 2017; Hase et al., 2018). The main pathogenic mechanisms responsible for demyelination are hypoperfusion-hypoxia (Li et al., 2017) and inflammation (Saggu et al., 2016). The adult brain has very limited capacity to repair white matter (Shi et al., 2015), which explains the progressive demyelination and cognitive decline in VD. This is supported by the greater degree of myelin damage and poorer cognitive function at 4 weeks than at 2 weeks post-CCH observed in the present study. However, NBP treatment alleviated spatial learning and memory dysfunction in CCH rats, which was associated with increased hippocampal integrity, myelination, and MBP expression. Myelin loss plays an important role in cognitive decline (Li et al., 2017; Chen et al., 2020). We speculate that NBP improves cognitive function in CCH rats partly by preventing the loss and increasing the integrity of myelin. Indeed, therapeutic strategies that promote myelin repair have been linked to cognitive recovery (Hou et al., 2015; Jiang et al., 2017; Li et al., 2017). A prerequisite of remyelination is OPC proliferation and differentiation into myelinating oligodendrocytes (Franklin and Ffrench-Constant, 2008). The latter was demonstrated by the finding that demyelinating lesions in multiple sclerosis and leukoaraiosis in elderly patients contain an abundance of OPCs but lack oligodendrocytes (Wolswijk, 1998; Back et al., 2011). Adult OPCs differentiate into oligodendrocytes and astrocytes (Sun et al., 2015), which is mediated by Olig2 (Wegener et al., 2015) and STAT3 (Sun et al., 2015; Imamura et al., 2017), respectively. We found here that NBP treatment not only downregulated STAT3 and upregulated Olig2 but also induced the regeneration of Olig2-expressing cells at the expense of astrocytes. Thus, NBP administration restores myelin integrity in CCH rats at least in part by promoting oligodendrocyte regeneration and inhibiting astrocyte proliferation.\nReactive astrocytes inhibit oligodendrocyte regeneration (Back et al., 2011) and exacerbate oligodendrocyte death and demyelination (Johnstone et al., 2013; Shi et al., 2015). In the present study, CCH caused astrocyte proliferation, which was suppressed by NBP treatment. However, in addition to cell proliferation, reactive astrogliosis is characterized by hypertrophy of the cell soma, intertwining processes, and disruption of individual domains. Previous studies have shown that there are different astrocyte subtypes with distinct morphology, degrees of activity, and migratory capacity that have been implicated in brain damage (Wagner et al., 2013). In a rat model of stroke, hyperactivated astrocytes were found to have a larger volume and higher degree of branching than those exhibiting mild or moderate responses, whereas astrocytes expressing glutamine synthetase were more often located in remote areas compared to other subtypes (Wagner et al., 2013). However, we did not examine different astrocyte subtypes, which is a limitation of the present study.\nWe observed that inflammation contributed to pathologic white matter changes, in accordance with previous reports (Iadecola, 2013; Saggu et al., 2016). Reduced cerebral blood flow, oxidative stress, and extravasation of plasma proteins caused by CCH are all thought to induce inflammation in VD (Iadecola, 2013). Although the specific inflammatory mechanism responsible for white matter changes in CCH has not been elucidated, several factors may play a role. STAT3/NF-κB is well known to be involved in pro-inflammatory signaling (Won et al., 2013). STAT3 promotes astrocyte differentiation and inhibits oligodendrocyte fate specification (He et al., 2005; Sun et al., 2015; Imamura et al., 2017). Pharmacologic suppression or conditional deletion of STAT3 was shown to promote oligodendrocyte maturation and remyelination (Cao et al., 2010; Imamura et al., 2017; Elbaz et al., 2018). Crosstalk between STAT3 and NF-κB has been reported (Grivennikov and Karin, 2010), and STAT3-mediated NF-κB activation plays an important role in the pathogenesis of neurodegenerative diseases (Grivennikov and Karin, 2010). NF-κB activation is involved in oligodendrocyte death, demyelination, axonal loss, astrocyte inflammatory cascades, and loss of white matter integrity, which are related to CCH-induced cognitive decline (Saggu et al., 2016). Activated NF-κB positively regulates the expression of TNF-α (Neumann et al., 1999), which can also induce oligodendrocyte death and demyelination (Jurewicz et al., 2005; Caminero et al., 2011). Pharmacologic or transgenic suppression of these proinflammatory cytokines was shown to have a protective effect on oligodendrocytes and myelin (Wakita et al., 2003; Saggu et al., 2016). Consistent with the above findings, the CCH rats in our study showed elevated levels of these cytokines, which was accompanied by oligodendrocytes and myelin loss. However, treatment with NBP reduced the expression of proinflammatory factors while preserving oligodendrocytes and myelin. Thus, the protective effect of NBP on myelination is attributable to the suppression of proinflammatory signaling.\nAnother important hallmark of inflammation in ischemic injury is the migration of circulating immune cells to the brain driven by the activation of brain endothelial cells and chemokine secretion (Iadecola and Anrather, 2011; Möller et al., 2014; Pösel et al., 2016). Immune cell infiltration contributes to either ischemic damage or the resolution of inflammation and subsequent tissue repair in ischemic stroke, depending on different subpopulations of leukocytes and different phases of injury (Iadecola and Anrather, 2011). As such, immune cell invasion warrants more detailed investigation in the context of VD.\nPrevious studies have demonstrated the crosstalk between inflammation and AMPK signaling (Lyons and Roche, 2018). Inflammatory stimuli reduce AMPK phosphorylation in nutrient-rich conditions (Yang et al., 2010). As a downstream target of AMPK, SIRT1 can be suppressed by oxidative stress in addition to inflammation (Ota et al., 2012). These findings may explain the downregulation of AMPK/SIRT1 signaling in 2VO, which is characterized by inflammation and oxidative stress. However, activated AMPK upregulates the level of nicotinamide adenosine dinucleotide to enhance SIRT1 activity and subsequent deacetylation of the RelA/p65 subunit, resulting in inhibition of NF-κB nuclear entry and subsequent inflammation (Ashburner et al., 2001; Yeung et al., 2004; Lee et al., 2009; Salminen et al., 2011; Kauppinen et al., 2013). The regulatory mechanism responsible for the crosstalk between inflammation and AMPK/SIRT1 signaling has not been elucidated. However, in the present study, low levels of nuclear NF-κB and its downstream target TNF-α were associated with the upregulation of the AMPK/SIRT1 pathway in NBP-treated rats. Thus, NBP may function as a regulator between inflammation and AMPK/SIRT1 signaling. Given the crucial impact of inflammation on oligodendrocyte death and demyelination and the finding that AMPK/SIRT1 signaling promotes remyelination and neuroprotection (Elbaz et al., 2018; Dembic et al., 2019; Houshmand et al., 2019), we speculate that the molecular basis for the neuroprotective effect of NBP involves the upregulation of the AMPK/SIRT1 and downregulation of the STAT3/NF-κB pathway. We also observed the opposite trend for these two pathways, suggesting that they cross regulate in VD.\nThis study has several limitations. First, the sample sizes were small, particularly for the histologic analysis. Second, we examined only two post surgery time points because previous studies and our preliminary experiments have shown that significant pathologic changes are observed at 2 and 4 weeks after CCH (Xiong et al., 2017; Li et al., 2019b). In future studies, we will include more time windows that allow assessment of cognitive improvement. Third, we only examined GFAP+/BrdU+ cells in our quantitative analysis of astrocytes. However, given the variety of morphologies and subtypes, astrocytes warrant more detailed investigation in the context of VD. Finally, we used 2VO to mimic inflammation and white matter changes in VD. However, VD comprises many types of vascular disease including large vessel disease with multiple strokes, small vessel disease (SVD) with lacunar infarcts, and white matter disease; there are no established models that recapitulate all of the pathologic changes in VD. Spontaneously hypertensive rats (SHRs) exhibit WMLs, blood brain barrier leakage, and immune activation induced by long-term vascular changes (Kaiser et al., 2014); it would therefore be of interest to evaluate the protective effect of NBP in the SHR model.\nIn conclusion, the findings of this study suggest that NBP may be a promising treatment for alleviating cognitive dysfunction and promoting remyelination in VD, and that the AMPK/SIRT1 and STAT3/NF-κB pathways serve as potential targets for future therapies."}

{"project":"2_test","denotations":[{"id":"32581761-28840054-31100172","span":{"begin":872,"end":876},"obj":"28840054"},{"id":"32581761-29210074-31100173","span":{"begin":891,"end":895},"obj":"29210074"},{"id":"32581761-28840054-31100174","span":{"begin":997,"end":1001},"obj":"28840054"},{"id":"32581761-27487766-31100175","span":{"begin":1035,"end":1039},"obj":"27487766"},{"id":"32581761-25819104-31100176","span":{"begin":1120,"end":1124},"obj":"25819104"},{"id":"32581761-28840054-31100177","span":{"begin":1603,"end":1607},"obj":"28840054"},{"id":"32581761-31758330-31100178","span":{"begin":1622,"end":1626},"obj":"31758330"},{"id":"32581761-25805696-31100179","span":{"begin":1871,"end":1875},"obj":"25805696"},{"id":"32581761-29311834-31100180","span":{"begin":1891,"end":1895},"obj":"29311834"},{"id":"32581761-28840054-31100181","span":{"begin":1908,"end":1912},"obj":"28840054"},{"id":"32581761-18931697-31100182","span":{"begin":2054,"end":2058},"obj":"18931697"},{"id":"32581761-9425002-31100183","span":{"begin":2257,"end":2261},"obj":"9425002"},{"id":"32581761-21905080-31100184","span":{"begin":2276,"end":2280},"obj":"21905080"},{"id":"32581761-24606160-31100185","span":{"begin":2358,"end":2362},"obj":"24606160"},{"id":"32581761-25564492-31100186","span":{"begin":2409,"end":2413},"obj":"25564492"},{"id":"32581761-24606160-31100187","span":{"begin":2438,"end":2442},"obj":"24606160"},{"id":"32581761-27664791-31100188","span":{"begin":2460,"end":2464},"obj":"27664791"},{"id":"32581761-21905080-31100189","span":{"begin":2888,"end":2892},"obj":"21905080"},{"id":"32581761-24260524-31100190","span":{"begin":2968,"end":2972},"obj":"24260524"},{"id":"32581761-25819104-31100191","span":{"begin":2986,"end":2990},"obj":"25819104"},{"id":"32581761-23595285-31100192","span":{"begin":3468,"end":3472},"obj":"23595285"},{"id":"32581761-23595285-31100193","span":{"begin":3777,"end":3781},"obj":"23595285"},{"id":"32581761-24267647-31100194","span":{"begin":4011,"end":4015},"obj":"24267647"},{"id":"32581761-27487766-31100195","span":{"begin":4031,"end":4035},"obj":"27487766"},{"id":"32581761-24267647-31100196","span":{"begin":4192,"end":4196},"obj":"24267647"},{"id":"32581761-23254638-31100197","span":{"begin":4430,"end":4434},"obj":"23254638"},{"id":"32581761-15852015-31100198","span":{"begin":4538,"end":4542},"obj":"15852015"},{"id":"32581761-24606160-31100199","span":{"begin":4556,"end":4560},"obj":"24606160"},{"id":"32581761-27664791-31100200","span":{"begin":4578,"end":4582},"obj":"27664791"},{"id":"32581761-20303333-31100201","span":{"begin":4723,"end":4727},"obj":"20303333"},{"id":"32581761-27664791-31100202","span":{"begin":4745,"end":4749},"obj":"27664791"},{"id":"32581761-29864483-31100203","span":{"begin":4765,"end":4769},"obj":"29864483"},{"id":"32581761-20018552-31100204","span":{"begin":4848,"end":4852},"obj":"20018552"},{"id":"32581761-20018552-31100205","span":{"begin":4989,"end":4993},"obj":"20018552"},{"id":"32581761-27487766-31100206","span":{"begin":5214,"end":5218},"obj":"27487766"},{"id":"32581761-10405161-31100207","span":{"begin":5299,"end":5303},"obj":"10405161"},{"id":"32581761-16219674-31100208","span":{"begin":5386,"end":5390},"obj":"16219674"},{"id":"32581761-21474190-31100209","span":{"begin":5409,"end":5413},"obj":"21474190"},{"id":"32581761-14604772-31100210","span":{"begin":5576,"end":5580},"obj":"14604772"},{"id":"32581761-27487766-31100211","span":{"begin":5596,"end":5600},"obj":"27487766"},{"id":"32581761-21738161-31100212","span":{"begin":6226,"end":6230},"obj":"21738161"},{"id":"32581761-24220169-31100213","span":{"begin":6247,"end":6251},"obj":"24220169"},{"id":"32581761-26967380-31100214","span":{"begin":6267,"end":6271},"obj":"26967380"},{"id":"32581761-21738161-31100215","span":{"begin":6527,"end":6531},"obj":"21738161"},{"id":"32581761-30304866-31100216","span":{"begin":6730,"end":6734},"obj":"30304866"},{"id":"32581761-20421294-31100217","span":{"begin":6828,"end":6832},"obj":"20421294"},{"id":"32581761-22238626-31100218","span":{"begin":6952,"end":6956},"obj":"22238626"},{"id":"32581761-11564889-31100219","span":{"begin":7357,"end":7361},"obj":"11564889"},{"id":"32581761-15152190-31100220","span":{"begin":7377,"end":7381},"obj":"15152190"},{"id":"32581761-19008341-31100221","span":{"begin":7395,"end":7399},"obj":"19008341"},{"id":"32581761-21431325-31100222","span":{"begin":7418,"end":7422},"obj":"21431325"},{"id":"32581761-23770291-31100223","span":{"begin":7442,"end":7446},"obj":"23770291"},{"id":"32581761-29864483-31100224","span":{"begin":8020,"end":8024},"obj":"29864483"},{"id":"32581761-30446350-31100225","span":{"begin":8041,"end":8045},"obj":"30446350"},{"id":"32581761-31620963-31100226","span":{"begin":8065,"end":8069},"obj":"31620963"},{"id":"32581761-28798681-31100227","span":{"begin":8669,"end":8673},"obj":"28798681"},{"id":"32581761-25519173-31100229","span":{"begin":9510,"end":9514},"obj":"25519173"}],"text":"Discussion\nThis is the first study investigating the effects of NBP on remyelination and inflammation in a rat model of VD. We found that NBP alleviated pathologic changes in the hippocampus, promoted oligodendrocyte regeneration, inhibited astrocyte proliferation, and reduced demyelination and the expression of proinflammation cytokines. These effects were accompanied by a dose-dependent upregulation of AMPK/SIRT1 and downregulation of STAT3/NF-κB signaling in rats treated with NBP compared to untreated CCH rats. Our results provide evidence that NBP provides cognitive protection following CCH, likely through a mechanism involving modulation of the AMPK/SIRT1 and STAT3/NF-κB pathways. This is the first demonstration of crosstalk between AMPK/SIRT1 and STAT3/NF-κB signaling axes being implicated in VD.\nDemyelination is often observed in WMLs in VD (Li et al., 2017; Hase et al., 2018). The main pathogenic mechanisms responsible for demyelination are hypoperfusion-hypoxia (Li et al., 2017) and inflammation (Saggu et al., 2016). The adult brain has very limited capacity to repair white matter (Shi et al., 2015), which explains the progressive demyelination and cognitive decline in VD. This is supported by the greater degree of myelin damage and poorer cognitive function at 4 weeks than at 2 weeks post-CCH observed in the present study. However, NBP treatment alleviated spatial learning and memory dysfunction in CCH rats, which was associated with increased hippocampal integrity, myelination, and MBP expression. Myelin loss plays an important role in cognitive decline (Li et al., 2017; Chen et al., 2020). We speculate that NBP improves cognitive function in CCH rats partly by preventing the loss and increasing the integrity of myelin. Indeed, therapeutic strategies that promote myelin repair have been linked to cognitive recovery (Hou et al., 2015; Jiang et al., 2017; Li et al., 2017). A prerequisite of remyelination is OPC proliferation and differentiation into myelinating oligodendrocytes (Franklin and Ffrench-Constant, 2008). The latter was demonstrated by the finding that demyelinating lesions in multiple sclerosis and leukoaraiosis in elderly patients contain an abundance of OPCs but lack oligodendrocytes (Wolswijk, 1998; Back et al., 2011). Adult OPCs differentiate into oligodendrocytes and astrocytes (Sun et al., 2015), which is mediated by Olig2 (Wegener et al., 2015) and STAT3 (Sun et al., 2015; Imamura et al., 2017), respectively. We found here that NBP treatment not only downregulated STAT3 and upregulated Olig2 but also induced the regeneration of Olig2-expressing cells at the expense of astrocytes. Thus, NBP administration restores myelin integrity in CCH rats at least in part by promoting oligodendrocyte regeneration and inhibiting astrocyte proliferation.\nReactive astrocytes inhibit oligodendrocyte regeneration (Back et al., 2011) and exacerbate oligodendrocyte death and demyelination (Johnstone et al., 2013; Shi et al., 2015). In the present study, CCH caused astrocyte proliferation, which was suppressed by NBP treatment. However, in addition to cell proliferation, reactive astrogliosis is characterized by hypertrophy of the cell soma, intertwining processes, and disruption of individual domains. Previous studies have shown that there are different astrocyte subtypes with distinct morphology, degrees of activity, and migratory capacity that have been implicated in brain damage (Wagner et al., 2013). In a rat model of stroke, hyperactivated astrocytes were found to have a larger volume and higher degree of branching than those exhibiting mild or moderate responses, whereas astrocytes expressing glutamine synthetase were more often located in remote areas compared to other subtypes (Wagner et al., 2013). However, we did not examine different astrocyte subtypes, which is a limitation of the present study.\nWe observed that inflammation contributed to pathologic white matter changes, in accordance with previous reports (Iadecola, 2013; Saggu et al., 2016). Reduced cerebral blood flow, oxidative stress, and extravasation of plasma proteins caused by CCH are all thought to induce inflammation in VD (Iadecola, 2013). Although the specific inflammatory mechanism responsible for white matter changes in CCH has not been elucidated, several factors may play a role. STAT3/NF-κB is well known to be involved in pro-inflammatory signaling (Won et al., 2013). STAT3 promotes astrocyte differentiation and inhibits oligodendrocyte fate specification (He et al., 2005; Sun et al., 2015; Imamura et al., 2017). Pharmacologic suppression or conditional deletion of STAT3 was shown to promote oligodendrocyte maturation and remyelination (Cao et al., 2010; Imamura et al., 2017; Elbaz et al., 2018). Crosstalk between STAT3 and NF-κB has been reported (Grivennikov and Karin, 2010), and STAT3-mediated NF-κB activation plays an important role in the pathogenesis of neurodegenerative diseases (Grivennikov and Karin, 2010). NF-κB activation is involved in oligodendrocyte death, demyelination, axonal loss, astrocyte inflammatory cascades, and loss of white matter integrity, which are related to CCH-induced cognitive decline (Saggu et al., 2016). Activated NF-κB positively regulates the expression of TNF-α (Neumann et al., 1999), which can also induce oligodendrocyte death and demyelination (Jurewicz et al., 2005; Caminero et al., 2011). Pharmacologic or transgenic suppression of these proinflammatory cytokines was shown to have a protective effect on oligodendrocytes and myelin (Wakita et al., 2003; Saggu et al., 2016). Consistent with the above findings, the CCH rats in our study showed elevated levels of these cytokines, which was accompanied by oligodendrocytes and myelin loss. However, treatment with NBP reduced the expression of proinflammatory factors while preserving oligodendrocytes and myelin. Thus, the protective effect of NBP on myelination is attributable to the suppression of proinflammatory signaling.\nAnother important hallmark of inflammation in ischemic injury is the migration of circulating immune cells to the brain driven by the activation of brain endothelial cells and chemokine secretion (Iadecola and Anrather, 2011; Möller et al., 2014; Pösel et al., 2016). Immune cell infiltration contributes to either ischemic damage or the resolution of inflammation and subsequent tissue repair in ischemic stroke, depending on different subpopulations of leukocytes and different phases of injury (Iadecola and Anrather, 2011). As such, immune cell invasion warrants more detailed investigation in the context of VD.\nPrevious studies have demonstrated the crosstalk between inflammation and AMPK signaling (Lyons and Roche, 2018). Inflammatory stimuli reduce AMPK phosphorylation in nutrient-rich conditions (Yang et al., 2010). As a downstream target of AMPK, SIRT1 can be suppressed by oxidative stress in addition to inflammation (Ota et al., 2012). These findings may explain the downregulation of AMPK/SIRT1 signaling in 2VO, which is characterized by inflammation and oxidative stress. However, activated AMPK upregulates the level of nicotinamide adenosine dinucleotide to enhance SIRT1 activity and subsequent deacetylation of the RelA/p65 subunit, resulting in inhibition of NF-κB nuclear entry and subsequent inflammation (Ashburner et al., 2001; Yeung et al., 2004; Lee et al., 2009; Salminen et al., 2011; Kauppinen et al., 2013). The regulatory mechanism responsible for the crosstalk between inflammation and AMPK/SIRT1 signaling has not been elucidated. However, in the present study, low levels of nuclear NF-κB and its downstream target TNF-α were associated with the upregulation of the AMPK/SIRT1 pathway in NBP-treated rats. Thus, NBP may function as a regulator between inflammation and AMPK/SIRT1 signaling. Given the crucial impact of inflammation on oligodendrocyte death and demyelination and the finding that AMPK/SIRT1 signaling promotes remyelination and neuroprotection (Elbaz et al., 2018; Dembic et al., 2019; Houshmand et al., 2019), we speculate that the molecular basis for the neuroprotective effect of NBP involves the upregulation of the AMPK/SIRT1 and downregulation of the STAT3/NF-κB pathway. We also observed the opposite trend for these two pathways, suggesting that they cross regulate in VD.\nThis study has several limitations. First, the sample sizes were small, particularly for the histologic analysis. Second, we examined only two post surgery time points because previous studies and our preliminary experiments have shown that significant pathologic changes are observed at 2 and 4 weeks after CCH (Xiong et al., 2017; Li et al., 2019b). In future studies, we will include more time windows that allow assessment of cognitive improvement. Third, we only examined GFAP+/BrdU+ cells in our quantitative analysis of astrocytes. However, given the variety of morphologies and subtypes, astrocytes warrant more detailed investigation in the context of VD. Finally, we used 2VO to mimic inflammation and white matter changes in VD. However, VD comprises many types of vascular disease including large vessel disease with multiple strokes, small vessel disease (SVD) with lacunar infarcts, and white matter disease; there are no established models that recapitulate all of the pathologic changes in VD. Spontaneously hypertensive rats (SHRs) exhibit WMLs, blood brain barrier leakage, and immune activation induced by long-term vascular changes (Kaiser et al., 2014); it would therefore be of interest to evaluate the protective effect of NBP in the SHR model.\nIn conclusion, the findings of this study suggest that NBP may be a promising treatment for alleviating cognitive dysfunction and promoting remyelination in VD, and that the AMPK/SIRT1 and STAT3/NF-κB pathways serve as potential targets for future therapies."}