Wild-type amyloid beta 1-40 peptide induces vascular smooth muscle cell death independently from matrix metalloprotease activity

ADAR1 Is Essential for Smooth Muscle Homeostasis and Vascular Integrity

Vascular smooth muscle cells (VSMCs) play a critical role in maintaining vascular integrity. VSMC dysfunction leads to numerous vascular diseases. Adenosine deaminases acting on RNA 1 (ADAR1), an RNA editing enzyme, has shown both RNA editing and non-editing functions. Global deletion of ADAR1 causes embryonic lethality, but the phenotype of homozygous ADAR1 deletion specifically in SMCs (ADAR1sm-/-) remains to be determined. By crossing ADAR1fl/fl mice with Myh11-CreERT2 mice followed by Tamoxifen induction, we found that ADAR1sm-/- leads to lethality in adult mice 14 days after the induction. Gross examination revealed extensive hemorrhage and detrimental vascular damage in different organs. Histological analyses revealed destruction of artery structural integrity with detachment of elastin laminae from VSMCs in ADAR1sm-/- aortas. Furthermore, ADAR1sm-/- resulted in severe VSMC apoptosis and mitochondrial dysfunction. RNA sequencing analyses of ADAR1sm-/- aorta segments demonstrated profound transcriptional alteration of genes impacting vascular health including a decrease in fibrillin-1 expression. More importantly, ADAR1sm-/- disrupts the elastin and fibrillin-1 interaction, a molecular event essential for artery structure. Our results indicate that ADAR1 plays a critical role in maintaining SMC survival and vascular stability and resilience.

Cerebral microbleeds in patients with COVID-19: is there an inevitable connection?

The COVID-19 pandemic has underscored the critical interplay between systemic infections and neurological complications, notably cerebral microbleeds. This comprehensive review meticulously aggregates and analyses current evidence on cerebral microbleeds' prevalence, pathophysiological underpinnings and clinical implications within COVID-19 cohorts. Our findings reveal a pronounced correlation between cerebral microbleeds and increased severity of COVID-19, emphasizing the role of direct viral effects, inflammatory responses and coagulation disturbances. The documented association between cerebral microbleeds and elevated risks of morbidity and mortality necessitates enhanced neurological surveillance in managing COVID-19 patients. Although variability in study methodologies presents challenges, the cumulative evidence substantiates cerebral microbleeds as a critical illness manifestation rather than mere coincidence. This review calls for harmonization in research methodologies to refine our understanding and guide targeted interventions. Prioritizing the detection and study of neurological outcomes, such as cerebral microbleeds, is imperative for bolstering pandemic response strategies and mitigating the long-term neurological impact on survivors.

Moxifloxacin Disrupts and Attenuates Aβ42 Fibril and Oligomer Formation: Plausibly Repositioning an Antibiotic as Therapeutic against Alzheimer's Disease

The aggregation of Aβ42 is established as a key factor in the development of Alzheimer's disease (AD). Consequently, molecules that inhibit aggregation of peptide may lead to therapies to prevent or control AD. Several studies suggest that oligomeric intermediates present during aggregation may be more cytotoxic than fibrils themselves. In this work, we examine the inhibitory activity of an antibiotic MXF on aggregation (fibrils and oligomers) and disaggregation of Aβ42 using various biophysical and microscopic studies. Computational analysis was done to offer mechanistic insight. The amyloid formation of Aβ42 is suppressed by MXF, as demonstrated by the decrease in both the corresponding ThT fluorescence intensity and other biophysical techniques. The lag phase of amyloid formation doubled from 4.53 to 9.66 h in the presence of MXF. The addition of MXF at the completion of the fibrillation reaction, as monitored by ThT, led to a rapid, concentration dependent, exponential decrease in fluorescence signal that was consistent with loss of fibrils. We used TEM to directly demonstrate that MXF caused fibrils to disassemble. Our docking results show that MXF binds to both monomeric and fibrillar forms of Aβ42 with significant affinities. We also observed breaking of fibrils in the presence of MXF through molecular dynamics simulation. These findings suggest that antibiotic MXF could be a promising lead compound with dual role as fibril/oligomer inhibitor and disaggregase for further development as potential repurposed therapeutic against AD.

Beta-secretase-1 antisense RNA is associated with vascular ageing and atherosclerotic cardiovascular disease

Background  The noncoding antisense transcript for β-secretase-1 ( BACE1-AS ) is a long noncoding RNA with a pivotal role in the regulation of amyloid-β (Aβ). We aimed to explore the clinical value of BACE1-AS expression in atherosclerotic cardiovascular disease (ASCVD).

Methods  Expression of BACE1-AS and its target, β-secretase 1 ( BACE1 ) mRNA, was measured in peripheral blood mononuclear cells derived from 434 individuals (259 without established ASCVD [non-CVD], 90 with stable coronary artery disease [CAD], and 85 with acute coronary syndrome). Intima-media thickness and atheromatous plaques evaluated by ultrasonography, as well as arterial wave reflections and pulse wave velocity, were measured as markers of subclinical ASCVD. Patients were followed for a median of 52 months for major adverse cardiovascular events (MACE).

Results  In the cross-sectional arm, BACE1-AS expression correlated with BACE1 expression ( r  = 0.396, p  < 0.001) and marginally with Aβ1–40 levels in plasma ( r  = 0.141, p  = 0.008). Higher BACE1-AS was associated with higher estimated CVD risk assessed by HeartScore for non-CVD subjects and by European Society of Cardiology clinical criteria for the total population ( p  < 0.05 for both). BACE1-AS was associated with higher prevalence of CAD (odds ratio [OR] = 1.85, 95% confidence interval [CI]: 1.37–2.5), multivessel CAD (OR = 1.36, 95% CI: 1.06–1.75), and with higher number of diseased vascular beds (OR = 1.31, 95% CI: 1.07–1.61, for multiple diseased vascular beds) after multivariable adjustment for traditional cardiovascular risk factors. In the prospective arm, BACE1-AS was an independent predictor of MACE in high cardiovascular risk patients (adjusted hazard ratio = 1.86 per ascending tertile, 95% CI: 1.011–3.43, p  = 0.046).

Conclusion   BACE1-AS is associated with the incidence and severity of ASCVD.

Retinal Microvascular Alterations as the Biomarkers for Alzheimer Disease: Are We There Yet?

BACKGROUND

Alzheimer disease (AD) is a heterogeneous and multifactorial disorder with an insidious onset and slowly progressive disease course. To date, there are no effective treatments, but biomarkers for early diagnosis and monitoring of disease progression offer a promising first step in developing and testing potential interventions. Cerebral vascular imaging biomarkers to assess the contributions of vascular dysfunction to AD are strongly recommended to be integrated into the current amyloid-β (Aβ) [A], tau [T], and neurodegeneration [(N)]-the "AT(N)" biomarker system for clinical research. However, the methodology is expensive and often requires invasive procedures to document cerebral vascular dysfunction. The retina has been used as a surrogate to study cerebral vascular changes. There is growing interest in the identification of retinal microvascular changes as a safe, easily accessible, low cost, and time-efficient approach to enhancing our understanding of the vascular pathogenesis associated with AD.

EVIDENCE ACQUISITION

A systemic review of the literature was performed regarding retinal vascular changes in AD and its prodromal stages, focusing on functional and structural changes of large retinal vessels (vessels visible on fundus photographs) and microvasculature (precapillary arterioles, capillary, and postcapillary venules) that are invisible on fundus photographs.

RESULTS

Static and dynamic retinal microvascular alterations such as retinal arterial wall motion, blood flow rate, and microvascular network density were reported in AD, mild cognitive impairment, and even in the preclinical stages of the disease. The data are somewhat controversial and inconsistent among the articles reviewed and were obtained based on cross-sectional studies that used different patient cohorts, equipment, techniques, and analysis methods.

CONCLUSIONS

Retinal microvascular alterations exist across the AD spectrum. Further large scale, within-subject longitudinal studies using standardized imaging and analytical methods may advance our knowledge concerning vascular contributions to the pathogenesis of AD.

Amyloid Aggregates of Smooth-Muscle Titin Impair Cell Adhesion

Various amyloid aggregates, in particular, aggregates of amyloid β-proteins, demonstrate in vitro and in vivo cytotoxic effects associated with impairment of cell adhesion. We investigated the effect of amyloid aggregates of smooth-muscle titin on smooth-muscle-cell cultures. The aggregates were shown to impair cell adhesion, which was accompanied by disorganization of the actin cytoskeleton, formation of filopodia, lamellipodia, and stress fibers. Cells died after a 72-h contact with the amyloid aggregates. To understand the causes of impairment, we studied the effect of the microtopology of a titin-amyloid-aggregate-coated surface on fibroblast adhesion by atomic force microscopy. The calculated surface roughness values varied from 2.7 to 4.9 nm, which can be a cause of highly antiadhesive properties of this surface. As all amyloids have the similar structure and properties, it is quite likely that the antiadhesive effect is also intrinsic to amyloid aggregates of other proteins. These results are important for understanding the mechanisms of the negative effect of amyloids on cell adhesion.

Amyloid Beta Peptides and Th1 Cytokines Modulate Human Brain Vascular Smooth Muscle Tonic Contractile Capacity In Vitro: Relevance to Alzheimer's Disease?

Alzheimer's Disease (AD) is a neurodegenerative condition characterized both by the presence of tau protein neurofibrillary tangles and amyloid beta (Aβ) containing extracellular "plaques". The cleavage of amyloid precursor protein (APP) yields several Aβ peptides. Although Aβ toxicity to neurons has been described extensively, its effects on other components of the neurovasculature such as vascular smooth muscle cells have been less well characterized. AD is now also recognized as a neurovascular disease characterized by cerebral microbleeds and disturbances in autoregulation. AD is also a neuroinflammatory condition in which several proinflammatory cytokines are elevated and may contribute to the intensification of AD severity. Cerebral autoregulation (the mechanism by which brain blood flow is maintained despite changes in perfusion pressure) is extremely tightly controlled in the brain and shows disturbances in AD. The failure of autoregulation in AD may make the brain susceptible to cerebral microbleeds through a reduced capacity to limit blood flow when pressure is increased. Conversely, reduced vasodilation during low flow might could also exacerbate tissue hypoxia. Currently, whether and how Aβ peptides and inflammatory cytokines depress brain smooth muscle cell tonic contraction is not known, but could reveal important targets in the preservation of autoregulation which is disturbed in AD. We used a collagen gel contractility assay to evaluate the influence of Aβ25-35, Aβ1-40 and Aβ1-42 peptides and inflammatory cytokines on the tonic contractility of human brain vascular smooth muscle cells (HBVSMC) as an in vitro model of cerebral autoregulation. We found that 5 and 10 μM Aβ1-42 significantly depressed HBVSM contractility, while Aβ1-40 5-20 μM had no effect on contractility. Conversely, Aβ25-35 (1-50 μM) increased contractility. Interestingly, the inflammatory cytokines TNF-α (20 ng/mL), IL-1β (20 ng/mL) and IFN-γ (1000 U/mL) also depressed HBVSM tonic contractility alone and in combination. These data suggest that both the inflammatory milieu in AD as well as the abundance of Aβ peptides may promote autoregulatory failure and increase brain susceptibility to dysregulated perfusion and microbleeds which are an important and devastating characteristic of AD.

In vivo characterization of spontaneous microhemorrhage formation in mice with cerebral amyloid angiopathy

The pathophysiology of microhemorrhages in the context of cerebral amyloid angiopathy (CAA) remains poorly understood. Here we used in vivo two-photon microscopy in aged APP/PS1 mice with mild-to-moderate CAA to assess the formation of microhemorrhages and their spatial relationship with vascular Aβ depositions in the surrounding microvascular network. Mice with chronic cranial windows were intravenously injected with fluorescent dextran to visualize the vessels and a fluorescently labeled anti-fibrin antibody to visualize microhemorrhages. Focal vessel irradiations resulted in extravascular fibrin-positive clots at individual rupture sites that remained visible for weeks. Spontaneous extravascular fibrin-positive clots were more often observed in 19-month-old transgenic APP/PS1 mice compared to their wild-type littermate controls (p = 0.039), after heparin administration. In the transgenic mice, these spontaneous leakage sites frequently occurred at arteriolar segments without CAA at bifurcations or vessel bends. These findings suggest that the presence of vascular Aβ per se does not directly predispose vessels to leak, but that complex flow dynamics within CAA-affected vascular networks likely play a role. Our in vivo approach for the detection of individual spontaneous leakage sites may be used in longitudinal studies aimed to assess structural and functional alterations at the single-vessel level leading up to microhemorrhage formation.

Reduced Influence of apoE on Aβ43 Aggregation and Reduced Vascular Aβ43 Toxicity as Compared with Aβ40 and Aβ42

The amyloid-β 43 (Aβ43) peptide has been shown to be abundantly expressed in Alzheimer's disease plaques, whereas only relatively low levels have been demonstrated in cerebral amyloid angiopathy (CAA). To better understand this discrepant distribution, we studied various biochemical properties of Aβ43, in comparison with Aβ40 and Aβ42. We assessed the interaction of Aβ43 with the three apoE isoforms (apoE2, apoE3, and apoE4) using SDS-PAGE/Western blotting and ELISA, aggregation propensity using thioflavin T assays, and cytotoxicity towards cerebrovascular cells using MTT assays. We found that Aβ43 did not differ from Aβ42 in its interaction with apoE, whereas Aβ40 had a significantly lower degree of interaction with apoE. At a molar ratio of 1:100 (apoE:Aβ), all apoE isoforms were comparably capable of inhibiting aggregation of Aβ40 and Aβ42, but not Aβ43. All Aβ variants had a concentration-dependent negative effect on metabolic activity of cerebrovascular cells. However, the degree of this effect differed for the three Aβ isoforms (Aβ40 > Aβ42 > Aβ43), with Aβ43 being the least cytotoxic peptide towards cerebrovascular cells. We conclude that Aβ43 has different biochemical characteristics compared with Aβ40 and Aβ42. Aggregation of Aβ43 is not inhibited by apoE, in contrast to the aggregation of Aβ40 and Aβ42. Furthermore, cerebrovascular cells are less sensitive towards Aβ43, compared with Aβ40 and Aβ42. In contrast, Aβ43 neither differed from Aβ42 in its aggregation propensity (in the absence of apoE) nor in its apoE-binding capacity. Altogether, our findings may provide an explanation for the lower levels of Aβ43 accumulation in cerebral vessel walls.

Vasomotion as a Driving Force for Paravascular Clearance in the Awake Mouse Brain

Paravascular drainage of solutes, including β-amyloid (Aβ), appears to be an important process in brain health and diseases such as Alzheimer's disease (AD) and cerebral amyloid angiopathy (CAA). However, the major driving force for clearance remains largely unknown. Here we used in vivo two-photon microscopy in awake head-fixed mice to assess the role of spontaneous vasomotion in paravascular clearance. Vasomotion correlated with paravascular clearance of fluorescent dextran from the interstitial fluid. Increasing the amplitude of vasomotion by means of visually evoked vascular responses resulted in increased clearance rates in the visual cortex of awake mice. Evoked vascular reactivity was impaired in mice with CAA, which corresponded to slower clearance rates. Our findings suggest that low-frequency arteriolar oscillations drive drainage of solutes. Targeting naturally occurring vasomotion in patients with CAA or AD may be a promising early therapeutic option for prevention of Aβ accumulation in the brain.

GC content shapes mRNA storage and decay in human cells

mRNA translation and decay appear often intimately linked although the rules of this interplay are poorly understood. In this study, we combined our recent P-body transcriptome with transcriptomes obtained following silencing of broadly acting mRNA decay and repression factors, and with available CLIP and related data. This revealed the central role of GC content in mRNA fate, in terms of P-body localization, mRNA translation and mRNA stability: P-bodies contain mostly AU-rich mRNAs, which have a particular codon usage associated with a low protein yield; AU-rich and GC-rich transcripts tend to follow distinct decay pathways; and the targets of sequence-specific RBPs and miRNAs are also biased in terms of GC content. Altogether, these results suggest an integrated view of post-transcriptional control in human cells where most translation regulation is dedicated to inefficiently translated AU-rich mRNAs, whereas control at the level of 5’ decay applies to optimally translated GC-rich mRNAs.

Cerebrovascular β-amyloid deposition and associated microhemorrhages in a Tg2576 Alzheimer mouse model are reduced with a DHA-enriched diet

Cerebral amyloid angiopathy (CAA) is a major contributor to Alzheimer's disease (AD) pathogenesis. Like AD, CAA is often accompanied by marked inflammation, aggravating associated vasculopathies. No evidence-based prevention or treatment strategies are available. Here, we evaluate the possible beneficial effect of a diet enriched with docosahexaenoic acid (DHA), which is known to attenuate inflammation in CAA. Tg2576 mice, a transgenic model of AD/CAA, were fed a DHA-enriched diet starting at 2 mo of age and ending at 10, 14, or 18 mo of age. β-Amyloid (Aβ)-peptide deposition and bleeding were visualized by immunohistochemistry or histochemistry on coronal sections of the brain. DHA, arachidonic acid, and eicosanoid levels were measured by liquid chromatography/mass spectrometry or GC-MS. DHA-enriched diet throughout aging limits the accumulation of vascular Aβ peptide deposits as well as the likelihood of microhemorrhages. There is a strong correlation between systemic 12-hydroxyeicosatetraenoic acid (HETE) levels and the size of the area affected by both vascular amyloid deposits and hemorrhages. The lowest levels of 12-HETE, a lipid-derived proinflammatory product of 12-lipoxygenase (LOX), were found in DHA-fed mice. In vitro experiments performed on amyloid vascular smooth muscle cells showed that a 12-LOX inhibitor almost completely blocked the Aβ_1-40 peptide-induced apoptosis of these cells. This study yet again highlights the important role of inflammation in CAA pathogenesis and identifies potential new targets for preventive care.-Hur, J., Mateo, V., Amalric, N., Babiak, M., Béréziat, G., Kanony-Truc, C., Clerc, T., Blaise, R., Limon, I. Cerebrovascular β-amyloid deposition and associated microhemorrhages in a Tg2576 Alzheimer mouse model are reduced with a DHA-enriched diet.

Impaired retinal microcirculation in patients with Alzheimer's disease

The goal of this study was to determine the retinal blood flow rate (BFR) and blood flow velocity (BFV) of pre-capillary arterioles and post-capillary venules in patients with mild cognitive impairment (MCI) and Alzheimer’s disease (AD). Forty patients (20 AD and 20 MCI) and 21 cognitively normal (CN) controls with a similar age range (± 5 yrs) were recruited. A retinal function imager (RFI) was used to measure BFRs and BFVs of arterioles and venules in the macular region. The thickness of the ganglion cell-inner plexiform layer (GCIPL) was measured using Zeiss Cirrus optical coherence tomography. Macular BFRs in AD group were 2.64 ± 0.20 nl/s (mean ± standard deviation) in arterioles and 2.23 ± 0.19 nl/s in venules, which were significantly lower than in MCI and CN groups (P < 0.05). In addition, BFRs in MCI were lower than in CN in both arterioles and venules (P < 0.05). The BFV of the arterioles was 3.20 ± 1.07 mm/s in AD patients, which was significantly lower than in CN controls (3.91 ± 0.77 mm/s, P = 0.01). The thicknesses of GCIPL in patients with AD and MCI were significantly lower than in CN controls (P < 0.05). Neither BFV nor BFR in arterioles and venules was related to age, GCIPL thickness, mini mental state examination (MMSE) score and disease duration in patients with AD and MCI (P > 0.05). The lower BFR in both arterioles and venules in AD and MCI patients together with the loss of GCIPL were evident, indicating the impairment of the two components in the neurovascular-hemodynamic system, which may play a role in disease progression.

Is Vasomotion in Cerebral Arteries Impaired in Alzheimer's Disease?

A substantial body of evidence supports the hypothesis of a vascular component in the pathogenesis of Alzheimer’s disease (AD). Cerebral hypoperfusion and blood-brain barrier dysfunction have been indicated as key elements of this pathway. Cerebral amyloid angiopathy (CAA) is a cerebrovascular disorder, frequent in AD, characterized by the accumulation of amyloid-β (Aβ) peptide in cerebral blood vessel walls. CAA is associated with loss of vascular integrity, resulting in impaired regulation of cerebral circulation, and increased susceptibility to cerebral ischemia, microhemorrhages, and white matter damage. Vasomotion— the spontaneous rhythmic modulation of arterial diameter, typically observed in arteries/arterioles in various vascular beds including the brain— is thought to participate in tissue perfusion and oxygen delivery regulation. Vasomotion is impaired in adverse conditions such as hypoperfusion and hypoxia. The perivascular and glymphatic pathways of Aβ clearance are thought to be driven by the systolic pulse. Vasomotion produces diameter changes of comparable amplitude, however at lower rates, and could contribute to these mechanisms of Aβ clearance. In spite of potential clinical interest, studies addressing cerebral vasomotion in the context of AD/CAA are limited. This study reviews the current literature on vasomotion, and hypothesizes potential paths implicating impaired cerebral vasomotion in AD/CAA. Aβ and oxidative stress cause vascular tone dysregulation through direct effects on vascular cells, and indirect effects mediated by impaired neurovascular coupling. Vascular tone dysregulation is further aggravated by cholinergic deficit and results in depressed cerebrovascular reactivity and (possibly) impaired vasomotion, aggravating regional hypoperfusion and promoting further Aβ and oxidative stress accumulation.

Smooth muscle titin forms in vitro amyloid aggregates

Amyloids are insoluble fibrous protein aggregates, and their accumulation is associated with amyloidosis and many neurodegenerative diseases, including Alzheimer's disease. In the present study, we report that smooth muscle titin (SMT; 500 kDa) from chicken gizzard forms amyloid aggregates in vitro. This conclusion is supported by EM data, fluorescence analysis using thioflavin T (ThT), Congo red (CR) spectroscopy and X-ray diffraction. Our dynamic light scattering (DLS) data show that titin forms in vitro amyloid aggregates with a hydrodynamic radius (Rh) of approximately 700–4500 nm. The initial titin aggregates with Rh approximately 700 nm were observed beyond first 20 min its aggregation that shows a high rate of amyloid formation by this protein. We also showed using confocal microscopy the cytotoxic effect of SMT amyloid aggregates on smooth muscle cells from bovine aorta. This effect involves the disorganization of the actin cytoskeleton and result is cell damage. Cumulatively, our results indicate that titin may be involved in generation of amyloidosis in smooth muscles.

Non-neuronal and neuronal BACE1 elevation in association with angiopathic and leptomeningeal β-amyloid deposition in the human brain

Background

Cerebral amyloid angiopathy (CAA) refers to the deposition of β-amyloid (Aβ) peptides in the wall of brain vasculature, commonly involving capillaries and arterioles. Also being considered a part of CAA is the Aβ deposition in leptomeninge. The cellular origin of angiopathic Aβ and the pathogenic course of CAA remain incompletely understood.

Methods

The present study was aimed to explore the pathogenic course of CAA in the human cerebrum via examination of changes in β-secretase-1 (BACE1), the obligatory Aβ producing enzyme, relative to Aβ and other cellular markers, by neuroanatomical and biochemical characterizations with postmortem brain samples and primary cell cultures.

Results

Immunoreactivity (IR) for BACE1 was essentially not visible at vasculature in cases without cerebral amyloidosis (control group, n = 15, age = 86.1 ± 10.3 year). In cases with brain amyloid pathology (n = 15, age = 78.7 ± 12.7 year), increased BACE1 IR was identified locally at capillaries, arterioles and along the pia, localizing to endothelia, perivascular dystrophic neurites and meningeal cells, and often coexisting with vascular iron deposition. Double immunofluorescence with densitometric analysis confirmed a site-specific BACE1 elevation at cerebral arterioles in the development of vascular Aβ deposition. Levels of BACE1 protein, activity and its immediate product (C99) were elevated in leptomeningeal lysates from cases with CAA relative to controls. The expression of BACE1 and other amyloidogenic proteins in the endothelial and meningeal cells was confirmed in primary cultures prepared from human leptomeningeal and arteriolar biopsies.

Conclusion

These results suggest that BACE1 elevation in the endothelia and perivascular neurites may be involved in angiopathic Aβ deposition, while BACE1 elevation in meningeal cells might contribute Aβ to leptomeningeal amyloidosis.

Modeling cerebrovascular pathophysiology in amyloid-β metabolism using neural-crest-derived smooth muscle cells

There is growing recognition of cerebrovascular contributions to neurodegenerative diseases. In the walls of cerebral arteries, amyloid-beta (Aβ) accumulation is evident in a majority of aged people and patients with cerebral amyloid angiopathy. Here, we leverage human pluripotent stem cells to generate vascular smooth muscle cells (SMCs) from neural crest progenitors, recapitulating brain-vasculature-specific attributes of Aβ metabolism. We confirm that the lipoprotein receptor, LRP1, functions in our neural-crest-derived SMCs to mediate Aβ uptake and intracellular lysosomal degradation. Hypoxia significantly compromises the contribution of SMCs to Aβ clearance by suppressing LRP1 expression. This enabled us to develop an assay of Aβ uptake by using the neural crest-derived SMCs with hypoxia as a stress paradigm. We then tested several vascular protective compounds in a high-throughput format, demonstrating the value of stem-cell-based phenotypic screening for novel therapeutics and drug repurposing, aimed at alleviating amyloid burden.

Tanshinones inhibit amyloid aggregation by amyloid-β peptide, disaggregate amyloid fibrils, and protect cultured cells

The misfolding and aggregation of amyloid-β (Aβ) peptides into amyloid fibrils is regarded as one of the causative events in the pathogenesis of Alzheimer's disease (AD). Tanshinones extracted from Chinese herb Danshen (Salvia Miltiorrhiza Bunge) were traditionally used as anti-inflammation and cerebrovascular drugs due to their antioxidation and antiacetylcholinesterase effects. A number of studies have suggested that tanshinones could protect neuronal cells. In this work, we examine the inhibitory activity of tanshinone I (TS1) and tanshinone IIA (TS2), the two major components in the Danshen herb, on the aggregation and toxicity of Aβ1-42 using atomic force microscopy (AFM), thioflavin-T (ThT) fluorescence assay, cell viability assay, and molecular dynamics (MD) simulations. AFM and ThT results show that both TS1 and TS2 exhibit different inhibitory abilities to prevent unseeded amyloid fibril formation and to disaggregate preformed amyloid fibrils, in which TS1 shows better inhibitory potency than TS2. Live/dead assay further confirms that introduction of a very small amount of tanshinones enables protection of cultured SH-SY5Y cells against Aβ-induced cell toxicity. Comparative MD simulation results reveal a general tanshinone binding mode to prevent Aβ peptide association, showing that both TS1 and TS2 preferentially bind to a hydrophobic β-sheet groove formed by the C-terminal residues of I31-M35 and M35-V39 and several aromatic residues. Meanwhile, the differences in binding distribution, residues, sites, population, and affinity between TS1-Aβ and TS2-Aβ systems also interpret different inhibitory effects on Aβ aggregation as observed by in vitro experiments. More importantly, due to nonspecific binding mode of tanshinones, it is expected that tanshinones would have a general inhibitory efficacy of a wide range of amyloid peptides. These findings suggest that tanshinones, particularly TS1 compound, offer promising lead compounds with dual protective role in anti-inflammation and antiaggregation for further development of Aβ inhibitors to prevent and disaggregate amyloid formation.

β-Amyloid context intensifies vascular smooth muscle cells induced inflammatory response and de-differentiation

Several studies have shown that the accumulation of β-amyloid peptides in the brain parenchyma or vessel wall generates an inflammatory environment. Some even suggest that there is a cause-and-effect relationship between inflammation and the development of Alzheimer's disease and/or cerebral amyloid angiopathy (CAA). Here, we studied the ability of wild-type Aβ1-40 -peptide (the main amyloid peptide that accumulates in the vessel wall in sporadic forms of CAA) to modulate the phenotypic transition of vascular smooth muscle cells (VSMCs) toward an inflammatory/de-differentiated state. We found that Aβ1-40 -peptide alone neither induces an inflammatory response, nor decreases the expression of contractile markers; however, the inflammatory response of VSMCs exposed to Aβ1-40 -peptide prior to the addition of the pro-inflammatory cytokine IL-1β is greatly intensified compared with IL-1β-treated VSMCs previously un-exposed to Aβ1-40 -peptide. Similar conclusions could be drawn when tracking the decline of contractile markers. Furthermore, we found that the mechanism of this potentiation highly depends on an Aβ1-40 preactivation of the PI3 Kinase and possibly NFκB pathway; indeed, blocking the activation of these pathways during Aβ1-40 -peptide treatment completely suppressed the observed potentiation. Finally, strengthening the possible in vivo relevance of our findings, we evidenced that endothelial cells exposed to Aβ1-40 -peptide generate an inflammatory context and have similar effects than the ones described with IL-1β. These results reinforce the idea that intraparietal amyloid deposits triggering adhesion molecules in endothelial cells, contribute to the transition of VSMCs to an inflammatory/de-differentiated phenotype. Therefore, we suggest that acute inflammatory episodes may increase vascular alterations and contribute to the ontogenesis of CAA.

Bradykinin-induced asthmatic fibroblast/myofibroblast activities via bradykinin B2 receptor and different MAPK pathways

Bradykinin drives normal lung fibroblasts into myofibroblasts, induces fibroblast proliferation and activates mitogen activated protein kinase pathways (MAPK) but its effects on bronchial fibroblasts from asthmatics (HBAFb) have not been yet studied. We studied bradykinin-induced fibroblast proliferation and differentiation and the related intracellular mechanisms in HBAFb compared to normal bronchial fibroblasts (HNBFb). Bradykinin-stimulated HBAFb and HNBFb were used to assess: bradykinin B2 receptor expression by Western blot analysis; cell proliferation by [(3)H] thymidine incorporation; α-smooth muscle actin (SMA) expression/polymerization by Western blot and immunofluorescence; epidermal growth factor (EGF) receptor, extracellular-regulated kinase (ERK) 1/2 and p38 MAPK activation by immunoprecipitation and Western blot, respectively. Constitutive bradykinin B2 receptor and α-SMA expression was higher in HBAFb as compared to HNBFb. Bradykinin increased bradykinin B2 receptor expression in HBAFb. Bradykinin, via bradykinin B2 receptor, significantly increased fibroblast proliferation at lower concentration (10(-11)M) and α-SMA expression/polymerization at higher concentration (10(-6)M) in both cells. Bradykinin increased ERK1/2 and p38 phosphorylation via bradykinin B2 receptor; EGF receptor inhibitor AG1478 and panmetalloproteinase inhibitor GM6001 blocked bradykinin-induced ERK1/2 activation but not p38 phosphorylation. Bradykinin, via bradykinin B2 receptor, induced EGF receptor phosphorylation that was suppressed by AG1478. In HBAFb AG1478, GM6001, the ERK1/2-inhibitor U0126 and the p38 inhibitor SB203580 suppressed bradykinin-induced cell proliferation, but only SB203580 reduced myofibroblast differentiation. These data indicate that bradykinin is actively involved in asthmatic bronchial fibroblast proliferation and differentiation, through MAPK pathways and EGF receptor transactivation, by which bradykinin may contribute to airway remodeling in asthma, opening new horizons for potential therapeutic implications in asthmatic patients.