We discuss the translocation of inhaled asbestos fibers based on pulmonary and pleuro-pulmonary interstitial fluid dynamics. Fibers can pass the alveolar barrier and reach the lung interstitium via the paracellular route down a mass water flow due to combined osmotic (active Na + absorption) and hydraulic (interstitial pressure is subatmospheric) pressure gradient. Fibers can be dragged from the lung interstitium by pulmonary lymph flow (primary translocation) wherefrom they can reach the blood stream and subsequently distribute to the whole body (secondary translocation). Primary translocation across the visceral pleura and towards pulmonary capillaries may also occur if the asbestos-induced lung inflammation increases pulmonary interstitial pressure so as to reverse the trans-mesothelial and trans-endothelial pressure gradients. Secondary translocation to the pleural space may occur via the physiological route of pleural fluid formation across the parietal pleura; fibers accumulation in parietal pleura stomata (black spots) reflects the role of parietal lymphatics in draining pleural fluid. Asbestos fibers are found in all organs of subjects either occupationally exposed or not exposed to asbestos. Fibers concentration correlates with specific conditions of interstitial fluid dynamics, in line with the notion that in all organs microvascular filtration occurs from capillaries to the extravascular spaces. Concentration is high in the kidney (reflecting high perfusion pressure and flow) and in the liver (reflecting high microvascular permeability) while it is relatively low in the brain (due to low permeability of blood-brain barrier). Ultrafine fibers (length < 5 µm, diameter < 0.25 µm) can travel larger distances due to low steric hindrance (in mesothelioma about 90% of fibers are ultrafine). Fibers translocation is a slow process developing over decades of life: it is aided by high biopersistence, by inflammation-induced increase in permeability, by low steric hindrance and by fibers motion pattern at low Reynolds numbers; it is hindered by fibrosis that increases interstitial flow resistances.
Alzheimer's disease is characterized by the accumulation and deposition of plaques of -amyloid (A) peptide in the brain. Given its pivotal role, new therapies targeting A are in demand. We rationally designed liposomes targeting the brain and promoting the disaggregation of A assemblies and evaluated their efficiency in reducing the A burden in Alzheimer's disease mouse models. Liposomes were bifunctionalized with a peptide derived from the apolipoprotein-E receptor-binding domain for blood-brain barrier targeting and with phosphatidic acid for A binding. Bifunctionalized liposomes display the unique ability to hinder the formation of, and disaggregate, A assemblies in vitro (EM experiments). Administration of bifunctionalized liposomes to APP/presenilin 1 transgenic mice (aged 10 months) for 3 weeks (three injections per week) decreased total brain-insoluble A 1-42 (Ϫ33%), assessed by ELISA, and the number and total area of plaques (Ϫ34%) detected histologically. Also, brain A oligomers were reduced (Ϫ70.5%), as assessed by SDS-PAGE. Plaque reduction was confirmed in APP23 transgenic mice (aged 15 months) either histologically or by PET imaging with [ 11 C]Pittsburgh compound B (PIB). The reduction of brain A was associated with its increase in liver (ϩ18%) and spleen (ϩ20%). Notably, the novel-object recognition test showed that the treatment ameliorated mouse impaired memory. Finally, liposomes reached the brain in an intact form, as determined by confocal microscopy experiments with fluorescently labeled liposomes. These data suggest that bifunctionalized liposomes destabilize brain A aggregates and promote peptide removal across the blood-brain barrier and its peripheral clearance. This all-in-one multitask therapeutic device can be considered as a candidate for the treatment of Alzheimer's disease.
Spike protein (S protein) is the virus “key” to infect cells and is able
to strongly bind to the human angiotensin-converting enzyme2 (ACE2), as has been
reported. In fact, Spike structure and function is known to be highly important for cell
infection as well as for entering the brain. Growing evidence indicates that different
types of coronaviruses not only affect the respiratory system, but they might also
invade the central nervous system (CNS). However, very little evidence has been so far
reported on the presence of COVID-19 in the brain, and the potential exploitation, by
this virus, of the lung to brain axis to reach neurons has not been completely
understood. In this Article, we assessed the SARS-CoV and SARS-CoV-2 Spike protein
sequence, structure, and electrostatic potential using computational approaches. Our
results showed that the S proteins of SARS-CoV-2 and SARS-CoV are highly similar,
sharing a sequence identity of 77%. In addition, we found that the SARS-CoV-2 S protein
is slightly more positively charged than that of SARS-CoV since it contains four more
positively charged residues and five less negatively charged residues which may lead to
an increased affinity to bind to negatively charged regions of other molecules through
nonspecific and specific interactions. Analysis the S protein binding to the host ACE2
receptor showed a 30% higher binding energy for SARS-CoV-2 than for the SARS-CoV S
protein. These results might be useful for understanding the mechanism of cell entry,
blood-brain barrier crossing, and clinical features related to the CNS infection by
SARS-CoV-2.
of glutamate-glutamine cycle between astrocytes and neurons inhibits epileptiform activity in hippocampus. 88: 2302-2310, 2002; 10.1152/jn.00665.2001. Recurrent epileptiform activity occurs spontaneously in cultured CNS neurons and in brain slices in which GABA inhibition has been blocked. We demonstrate here that pharmacological treatments resulting in either the block of glutamine production by astrocytes or the inhibition of glutamine uptake by neurons suppress or markedly decrease the frequency of spontaneous epileptiform discharges both in primary hippocampal cultures and in disinhibited hippocampal slices. These data point to an important role for the neuron-astrocyte metabolic interaction in sustaining episodes of intense rhythmic activity in the CNS, and thereby reveal a new potential target for antiepileptic treatments.
J Neurophysiol
Basal forebrain neurons control cerebral blood flow (CBF) by releasing acetylcholine (Ach), which binds to endothelial muscarinic receptors to induce nitric (NO) release and vasodilation in intraparenchymal arterioles. Nevertheless, the mechanism whereby Ach stimulates human brain microvascular endothelial cells to produce NO is still unknown. Herein, we sought to assess whether Ach stimulates NO production in a Ca -dependent manner in hCMEC/D3 cells, a widespread model of human brain microvascular endothelial cells. Ach induced a dose-dependent increase in intracellular Ca concentration ([Ca ] ) that was prevented by the genetic blockade of M5 muscarinic receptors (M5-mAchRs), which was the only mAchR isoform coupled to phospholipase Cβ (PLCβ) present in hCMEC/D3 cells. A comprehensive real-time polymerase chain reaction analysis revealed the expression of the transcripts encoding for type 3 inositol-1,4,5-trisphosphate receptors (InsP R3), two-pore channels 1 and 2 (TPC1-2), Stim2, Orai1-3. Pharmacological manipulation showed that the Ca response to Ach was mediated by InsP R3, TPC1-2, and store-operated Ca entry (SOCE). Ach-induced NO release, in turn, was inhibited in cells deficient of M5-mAchRs. Likewise, Ach failed to increase NO levels in the presence of l-NAME, a selective NOS inhibitor, or BAPTA, a membrane-permeant intracellular Ca buffer. Moreover, the pharmacological blockade of the Ca response to Ach also inhibited the accompanying NO production. These data demonstrate for the first time that synaptically released Ach may trigger NO release in human brain microvascular endothelial cells by stimulating a Ca signal via M5-mAchRs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.