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For amyotrophic lateral sclerosis (ALS), achieving and maintaining effective drug levels in the brain is challenging due to the activity of ATP-binding cassette (ABC) transporters which efflux drugs that affect drug exposure and response in the brain. We investigated the expression and cellular distribution of the ABC transporters P-glycoprotein (P...
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... functional decline or ALSFRS-R score) but also only in a subset of patients with early stage ALS (52). Several other agents that demonstrated benefit in preclinical models failed to show efficacy in clinical trials (53) ( Table 2). Although lack of efficacy may have various roots, this may include suboptimal drug exposure due to insufficient BBB penetration. ...Similar publications
Multidrug resistance (MDR), which is a significant impediment to the success of cancer chemotherapy, is attributable to various defensive mechanisms in cancer. Initially, overexpression of ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp) was considered the most important mechanism for drug resistance; hence, many investigators...
Citations
... The expression of P-gp in human brain capillary endothelial cells is well documented 43 . However, its expression in astrocyte, pericytes, and neurons is still under investigation [44][45][46][47] . No significant differences were noted in astrocytes and pericytes when NMR was administered alone or with RTV (Fig. 1a). ...
Three years after SARS-CoV-2 emerged as a global infectious threat, the virus has become endemic. The neurological complications such as depression, anxiety, and other CNS complications after COVID-19 disease are increasing. The brain, and CSF have been shown as viral reservoirs for SARS-CoV-2, yielding a potential hypothesis for CNS effects. Thus, we investigated the CNS pharmacology of orally dosed nirmatrelvir/ritonavir (NMR/RTV). Using both an in vitro and an in vivo rodent model, we investigated CNS penetration and potential pharmacodynamic activity of NMR. Through pharmacokinetic modeling, we estimated the median CSF penetration of NMR to be low at 18.11% of plasma with very low accumulation in rodent brain tissue. Based on the multiples of the 90% maximal effective concentration (EC90) for SARS-CoV-2, NMR concentrations in the CSF and brain do not achieve an exposure level similar to that of plasma. A median of only 16% of all the predicted CSF concentrations in rats were > 3xEC90 (unadjusted for protein binding). This may have implications for viral persistence and neurologic post-acute sequelae of COVID-19 if increased NMR penetration in the CNS leads to decreased CNS viral loads and decreased CNS inflammation.
... C9-ALS BMEC-like cells displayed a significant increase in the expression and function of the P-glycoprotein transporter (ABCB1), which is crucial for drug delivery. P-glycoprotein upregulation is a very common feature in many diseases, including ALS, epilepsy and cancer in in vivo models [37,38]. It is of great relevance for the development of disease-specific drug-permeability in vitro assays that the BBB model described here recapitulates increased P-gp functionality, thus providing a unique tool for the advancement of such pharmacodynamic assays. ...
The blood-brain barrier (BBB) serves as a highly intricate and dynamic interface connecting the brain and the bloodstream, playing a vital role in maintaining brain homeostasis. BBB dysfunction has been associated with multiple neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS); however, the role of the BBB in neurodegeneration is understudied. We developed an ALS patient-derived model of the BBB by using cells derived from 5 patient donors carrying C9ORF72 mutations. Brain microvascular endothelial-like cells (BMEC-like cells) derived from C9ORF72-ALS patients showed altered gene expression, compromised barrier integrity, and increased P-glycoprotein transporter activity. In addition, mitochondrial metabolic tests demonstrated that C9ORF72-ALS BMECs display a significant decrease in basal glycolysis accompanied by increased basal and ATP-linked respiration. Moreover, our study reveals that C9-ALS derived astrocytes can further affect BMECs function and affect the expression of the glucose transporter Glut-1. Finally, C9ORF72 patient-derived BMECs form leaky barriers through a cell-autonomous mechanism and have neurotoxic properties towards motor neurons.
Graphical Abstract
... The BBB efflux transporters MDR1 and BCRP constitute some of the major hurdles in drug delivery to the brain [38]. One possible explanation for MDR1 and BCRP is that astrocytes and brain pericytes, present in microvessels, also express these transporters, as previously demonstrated [39,40]. This conclusion is strengthened by the fact that the functionality of these transporters has been largely demonstrated in our recent studies using this BBB model [14,16,18,41]. ...
We previously developed an in vitro model of the human blood–brain barrier (BBB) based on the use of endothelial cells derived from CD34+-hematopoietic stem cells and cultured with brain pericytes. The purpose of the present study was to provide information on the protein expression levels of the transporters, receptors, tight junction/adherence junction molecules, and transporter-associated molecules of human brain-like endothelial cells (hBLECs). The absolute protein expression levels were determined by liquid chromatography–mass spectrometry-based quantitative targeted absolute proteomics and compared with those from human brain microvessels (hBMVs). The protein levels of CD144, CD147, MRP4, Annexin A6 and caveolin-1 showed more than 3-fold abundance in hBLECs, those of MCT1, Connexin 43, TfR1, and claudin-5 showed less than 3-fold differences, and the protein levels of other drug efflux transporters and nutrient transporters were less represented in hBLECs than in hBMVs. It is noteworthy that BCRP was more expressed than MDR1 in hBLECs, as this was the case for hBMVs. These results suggest that transports mediated by MCT1, TfR1, and claudin-5-related tight junction function reflect the in vivo BBB situation. The present study provided a better characterization of hBLECs and clarified the equivalence of the transport characteristics between in vitro BBB models and in vivo BBB models using LC-MS/MS-based protein quantification.
... Multidrug resistance is still one the main problems for cancer treatment, since many chemotherapeutic agents are P-gp substrates and P-gp is overexpressed in cancer cells, hampering the internalization and leading to resistance to chemotherapeutic drugs; hence, recent research has focused on developing P-gp inhibitors [37]. P-gp is also upregulated in several neurological disorders, such as Parkinson's disease [38], Alzheimer's disease [39], amyotrophic lateral sclerosis (ALS) [40], and epilepsy. Many antiepileptic drugs (AEDs) are P-gp substrates, and their repeated administration leads to P-gp upregulation, thus resulting in drug resistance [41]. ...
Opioids are widely used in cancer and non-cancer pain management. However, many transporters at the blood–brain barrier (BBB), such as P-glycoprotein (P-gp, ABCB1/MDR1), may impair their delivery to the brain, thus leading to opioid tolerance. Nonetheless, opioids may regulate P-gp expression, thus altering the transport of other compounds, namely chemotherapeutic agents, resulting in pharmacoresistance. Other kinds of painkillers (e.g., acetaminophen, dexamethasone) and adjuvant drugs used for neuropathic pain may act as P-gp substrates and modulate its expression, thus making pain management challenging. Inflammatory conditions are also believed to upregulate P-gp. The role of P-gp in drug–drug interactions is currently under investigation, since many P-gp substrates may also act as substrates for the cytochrome P450 enzymes, which metabolize a wide range of xenobiotics and endobiotics. Genetic variability of the ABCB1/MDR1 gene may be accountable for inter-individual variation in opioid-induced analgesia. P-gp also plays a role in the management of opioid-induced adverse effects, such as constipation. Peripherally acting mu-opioid receptors antagonists (PAMORAs), such as naloxegol and naldemedine, are substrates of P-gp, which prevent their penetration in the central nervous system. In our review, we explore the interactions between P-gp and opioidergic drugs, with their implications in clinical practice.
... 94,95 While vital to reducing excitotoxicity, the effectiveness of Riluzole is limited by the upregulation of the P-gp seen in ALS. 80,94,96 Appropriate P-gp levels are necessary to achieve therapeutic benefits of most pharmaceuticals, 97 thus, the BCNSB integrity should be a primary target for all future therapies for ALS. Without reimplementing this barrier and normalizing P-gp expression, other pharmaceutical interventions would be futile. ...
Amyotrophic lateral sclerosis (ALS) is a debilitating disease with poor prognosis. The pathophysiology of ALS is commonly debated, with theories involving inflammation, glutamate excitotoxity, oxidative stress, mitochondria malfunction, neurofilament accumulation, inadequate nutrients or growth factors, and changes in glial support predominating. These underlying pathological mechanisms, however, act together to weaken the blood brain barrier and blood spinal cord barrier, collectively considered as the blood central nervous system barrier (BCNSB). Altering the impermeability of the BCNSB impairs the neurovascular unit, or interdependent relationship between the brain and advances the concept that ALS is has a significant neurovascular component contributing to its degenerative presentation. This unique categorization of ALS opens a variety of treatment options targeting the reestablishment of BCNSB integrity. This review will critically assess the evidence implicating the significant neurovascular components of ALS pathophysiology, while also offering an in-depth discussion regarding the use of stem cells to repair these pathological changes within the neurovascular unit.
... ABC transporters that are known to be expressed in astrocytes include P-gp [20,164,165], Bcrp [166], and MRP/Mrp isoforms [62,167,168]. Various MRP and OATP isoforms (i.e., OATP1A2, OATP1C1, OATP2B1, and OATP4A1) have been detected at the gene (i.e., mRNA) level in human glioma tissue [75]. ...
Ischemic stroke is a primary origin of morbidity and mortality in the United States and around the world. Indeed, several research projects have attempted to discover new drugs or repurpose existing therapeutics to advance stroke pharmacotherapy. Many of these preclinical stroke studies have reported positive results for neuroprotective agents; however, only one compound (3K3A-activated protein C (3K3A-APC)) has advanced to Phase III clinical trial evaluation. One reason for these many failures is the lack of consideration of transport mechanisms at the blood–brain barrier (BBB) and neurovascular unit (NVU). These endogenous transport processes function as a “gateway” that is a primary determinant of efficacious brain concentrations for centrally acting drugs. Despite the knowledge that some neuroprotective agents (i.e., statins and memantine) are substrates for these endogenous BBB transporters, preclinical stroke studies have largely ignored the role of transporters in CNS drug disposition. Here, we review the current knowledge on specific BBB transporters that either limit drug uptake into the brain (i.e., ATP-binding cassette (ABC) transporters) or can be targeted for optimized drug delivery (i.e., solute carrier (SLC) transporters). Additionally, we highlight the current knowledge on transporter expression in astrocytes, microglia, pericytes, and neurons with an emphasis on transport mechanisms in these cell types that can influence drug distribution within the brain.
... However, although these results have been successfully replicated for P-gp in other SOD1 ALS models, this was not the case for BRCP [15]. An immunohistochemical evaluation of P-gp and BCRP in 25 ALS patients and 14 controls revealed a strong increase in these proteins in glial cells but not in blood vessels [45]. In 2019, Mohammed et al. found elevated protein expression of P-gp in human-iPS-derived ECs after co-culture with ALS human iPS-derived astrocytes [46]. ...
Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder that still lacks an efficient therapy. The barriers between the central nervous system (CNS) and the blood represent a major limiting factor to the development of drugs for CNS diseases, including ALS. Alterations of the blood-brain barrier (BBB) or blood-spinal cord barrier (BSCB) have been reported in this disease but still require further investigations. Interestingly, these alterations might be involved in the complex etiology and pathogenesis of ALS. Moreover, they can have potential consequences on the diffusion of candidate drugs across the brain. The development of techniques to bypass these barriers is continuously evolving and might open the door for personalized medical approaches. Therefore, identifying robust and non-invasive markers of BBB and BSCB alterations can help distinguish different subgroups of patients, such as those in whom barrier disruption can negatively affect the delivery of drugs to their CNS targets. The restoration of CNS barriers using innovative therapies could consequently present the advantage of both alleviating the disease progression and optimizing the safety and efficiency of ALS-specific therapies.
... One of the most difficult obstacles faced by the pharmaceutical industry in recent years has been the development of drug resistance. This resistance, which can occur in several diseases, including human immunodeficiency virus (HIV) [5]; cancer [6]; nervous system disorders, such as schizophrenia, epilepsy and amyotrophic lateral sclerosis (ALS) [7,8,9]; systemic autoimmune disorders, such as lupus erythematosus (LE) and rheumatoid arthritis (RA) [10,11]; and inflammatory pain [12,13] has been largely attributed to the multidrug transporter protein, P-glycoprotein (PGP). ...
... Elevated PGP levels have also been identified in neurodegenerative disorders, such as ALS [9,261,262]. In some forms of ALS, sporadic astrocytes that modulate PGP expression through NMDA receptors have been shown to be present [262]. ...
The multidrug resistance phenomenon presents a major threat to the pharmaceutical industry. This resistance is a common occurrence in several diseases and is mediated by multidrug transporters that actively pump substances out of the cell and away from their target regions. The most well-known multidrug transporter is the P-glycoprotein transporter. The binding sites within P-glycoprotein can accommodate a variety of compounds with diverse structures. Hence, numerous drugs are P-glycoprotein substrates, with new ones being identified every day. For many years, the mechanisms of action of P-glycoprotein have been shrouded in mystery, and scientists have only recently been able to elucidate certain structural and functional aspects of this protein. Although P-glycoprotein is highly implicated in multidrug resistant diseases, this transporter also performs various physiological roles in the human body and is expressed in several tissues, including the brain, kidneys, liver, gastrointestinal tract, testis, and placenta. The expression levels of P-glycoprotein are regulated by different enzymes, inflammatory mediators and transcription factors; alterations in which can result in the generation of a disease phenotype. This review details the discovery, the recently proposed structure and the regulatory functions of P-glycoprotein, as well as the crucial role it plays in health and disease.
... These pharmacoresistance proteins include specialized ATP binding cassette (ABC) efflux transporters that actively pump a number of endogenous and exogenous substrates out of the BCNSB (Mohamed et al., 2017). Relevant to ALS, the upregulation of key pharmacoresistance efflux proteins, Pglycoprotein (P-gp) and breast cancer resistance protein (BCRP), has been shown in multiple animal models (Milane et al., 2010;Jablonski et al., 2012;Chan et al., 2017), a finding also supported by postmortem human tissue studies (Jablonski et al., 2012;Qosa et al., 2016;Van Vliet et al., 2020). ...
... In vitro, the P-gp upregulation in the endothelial cells was mediated by nuclear factor κB (NF-κB) activation and was induced when these cells were co-cultured with ALS-derived astrocytes (Qosa et al., 2016;Mohamed et al., 2019). In postmortem tissue, P-gp and BCRP upregulation was observed in the spinal cord and motor cortex of both sporadic and familial ALS cases (Van Vliet et al., 2020). It has been suggested that P-gp evolved for the purpose of responding to harmful substances (Broeks et al., 1995). ...
Introduction
Recent studies have implicated changes in the blood-central nervous system barriers (BCNSB) in amyotrophic lateral sclerosis (ALS). The objective of this scoping review is to synthesize the current evidence for BCNSB structure and functional abnormalities in ALS studies and propose how BCNSB pathology may impact therapeutic development.
Methods
A literature search was conducted using Ovid Medline, EMBASE, and Web of Science, from inception to November 2021 and limited to entries in English language. Simplified search strategy included the terms ALS/motor neuron disease and [BCNSB or blood-brain barrier (BBB) or blood-spinal cord barrier (BSCB)]. Henceforth, BCNSB is used as a term that is inclusive of the BBB and BSCB. Four independent reviewers conducted a title and abstract screening, hand-searched the reference lists of review papers, and performed a full text review of eligible studies. Included studies were original peer-reviewed full text publications, evaluating the structure and function of the BCNSB in preclinical models of ALS, clinical ALS, or postmortem human ALS tissue. There was no restriction on study design. The four reviewers independently extracted the data.
Results
The search retrieved 2,221 non-duplicated articles and 48 original studies were included in the synthesis. There was evidence that the integrity of the BCNSB is disrupted throughout the course of the disease in rodent models, beginning prior to symptom onset and detectable neurodegeneration. Increased permeability, pharmacoresistance with upregulated efflux transporters, and morphological changes in the supporting cells of the BCNSB, including pericytes, astrocytes, and endothelial cells were observed in animal models. BCNSB abnormalities were also demonstrated in postmortem studies of ALS patients. Therapeutic interventions targeting BCNSB dysfunction were associated with improved motor neuron survival in animal models of ALS.
Conclusion
BCNSB structural and functional abnormalities are likely implicated in ALS pathophysiology and may occur upstream to neurodegeneration. Promising therapeutic strategies targeting BCNSB dysfunction have been tested in animals and can be translated into ALS clinical trials.
... | Increased expression of P-gp and BCRPThe cellular distribution and expression of P-gp and BCRP has been assessed in the cervical spinal cord and motor cortex obtained from individuals with ALS. Using immunohistochemistry, van Vliet et al.have demonstrated a dramatic (30-fold) increase in P-gp abundance in cervical spinal cord and motor cortex astrocytes in ALS tissues relative to control specimens, while P-gp abundance at the endothelial cell lining of microvessels was comparable between control and ALS spinal cord and motor cortex specimens(van Vliet et al., 2020). A similar study was conducted by Jablonski et al., who reported an elevated P-gp abundance in microvessels from ALS lumbar spinal cord(Jablonski et al., 2012). ...
... The discrepancies between these studies could be due to different CNS regions assessed (cervical spinal cord, lumbar spinal cord, and motor cortex). In terms of BCRP, microvasculature expression was observed in both control and ALS specimens, and its abundance did not differ between control and ALS in the cervical spinal cord but was marginally increased in the ALS motor cortex(van Vliet et al., 2020).Further studies are required to confirm these findings and possibly improve our understanding of CNS barriers protein expression in ALS, that is beyond P-gp and BCRP. Specialised microvascular isolation techniques can be implemented to obtain high purity of microvessels or isolated endothelial cells, which can be analysed via proteomic approaches. ...
The access of drugs into the central nervous system (CNS) is regulated by the blood–brain barrier (BBB) and blood–spinal cord barrier (BSCB). A large body of evidence supports perturbation of these barriers in neurodegenerative diseases, including Alzheimer's disease and Parkinson's disease. Modifications to the BBB and BSCB are also reported in amyotrophic lateral sclerosis (ALS), albeit these modifications have received less attention relative to those in other neurodegenerative diseases. Such alterations to the BBB and BSCB have the potential to impact on CNS exposure of drugs in ALS, modulating the effectiveness of drugs intended to reach the brain and the toxicity of drugs that are not intended to reach the brain. Given the clinical importance of these phenomena, this review will summarise reported modifications to the BBB and BSCB in ALS, discuss their impact on CNS drug exposure, and suggest further research directions so as to optimise medicine use in people with ALS.
