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Blood‑Brain Barrier Transport Mechanisms in Neurodegeneration: A Comprehensive Review PMID: 30280653

Pathway Diagram

...

bbb-transport-mechanisms

Blood‑Brain Barrier Transport Mechanisms in Neurodegeneration: A Comprehensive Review PMID: 30280653

Pathway Diagram

Mermaid diagram (expand to render)

Overview

*Blood‑Brain Barrier Transport Mechanisms in Neurodegeneration: A Comprehensive Review* describes a key molecular or cellular mechanism implicated in neurodegenerative disease. This page provides a detailed overview of the pathway components, signaling cascades, and their relevance to conditions such as [Alzheimer's disease](/diseases/alzheimers-disease), [Parkinson's disease](/diseases/parkinsons-disease), and related disorders. @moos2000]

Abstract

The blood‑brain barrier (BBB) is a dynamic interface that safeguards the central nervous system-regions/central-nervous-system) (central nervous system-regions/central-nervous-system)) while simultaneously mediating the flux of nutrients, ions, hormones, and therapeutics. In neurodegenerative such as Alzheimer’s disease (Alzheimer's disease) and Parkinson’s disease (Parkinson's disease), the BBB undergoes structural and functional alterations that contribute to disease progression. Understanding the molecular pathways that govern BBB transport—including receptor‑mediated transcytosis (receptor-mediated transcytosis), carrier‑mediated transport (CMT), active efflux via ATP‑binding cassette (ABC) transporters, and adsorptive‑mediated endocytosis (AME)—is essential for developing strategies that either restore barrier integrity or enhance drug delivery to the brain. This review synthesises recent insights into BBB biology, the role of ABC and solute‑carrier (SLC) transporters, and how these systems are perturbed in Alzheimer's disease and Parkinson's disease. Emphasis is placed on “Trojan‑horse” delivery platforms, emerging nanocarrier technologies, and the challenges that still impede effective central nervous system pharmacotherapy. [@duffy1987]

Keywords: blood‑brain barrier, neurodegeneration, receptor‑mediated transcytosis, ABC transporters, SLC transporters, Alzheimer’s disease, Parkinson’s disease, Trojan‑horse delivery, focused ultrasound [@ohtsuki2002]

--- [@simpson2001]

1. Overview

1.1 Structural Foundations of the BBB

The BBB is not a single cellular layer but a neurovascular unit (NVU) composed of endothelial cells of the brain microvasculature, [pericytes](/entities/pericytes), [astrocytes](/entities/astrocytes) end‑feet, [neurons](/entities/neurons), and microglia (Abbott et al., 2006; Zlokovic, 2008). Tight junctions (TJs) between endothelial cells restrict paracellular diffusion of water‑soluble molecules larger than ~400 Da, while theluminal and abluminal membranes host a rich repertoire of transporters and receptors that regulate trans‑cellular flux (Daneman & Prat, 2015). The endothelial glycocalyx and basal lamina further contribute to the barrier’s selective permeability (Nitta et al., 2003). [@broer2005]

1.2 The Neurovascular Unit in Health

In the healthy brain, the NVU maintains: [@schinkel1999]

Metabolic support – supply of glucose and essential amino acids toneurons.
Ion homeostasis – precise regulation of K⁺, Ca²⁺, and pH.
Protection – exclusion of pathogens, toxins, and peripheral hormones.
Signal integration – coupling of neuronal activity to cerebral blood flow (CBF) via neurovascular coupling (Iadecola, 2004).

1.3 Clinical Significance of BBB Dysfunction

BBB breakdown is a hallmark of many neurodegenerative disorders. Leakage of plasma , loss of TJ integrity, and altered transporter expression have been documented in Alzheimer's disease, Parkinson's disease, multiple sclerosis, and amyotrophic lateral sclerosis (Tajes et al., 2014). The resulting “neurovascular unit failure” compromises neuronal metabolism, promotes neuroinflammation, and limits the efficacy of central nervous system-regions/central-nervous-system)‑acting drugs (Zlokovic, 2008). Consequently, restoring or circumventing BBB transport has become a central research focus. [@loo2000]

--- [@stouch2005]

2. Transport Mechanisms Across the BBB

2.1 Receptor‑Mediated Transcytosis (receptor-mediated transcytosis)

receptor-mediated transcytosis enables large molecules (e.g., peptides, antibodies, viral vectors) to cross the BBB by engaging specific receptors on the luminal membrane, undergoing internalisation into clathrin‑coated vesicles, and then being released at the abluminal side. The most extensively studied receptor-mediated transcytosis systems involve the transferrin receptor (TfR) and the insulin receptor (IR) (Pardridge, 1999; Zhang et al., 2004). [@asakura2005]

TfR‑mediated transcytosis – Transferrin (Tf) binds TfR, triggering endocytosis; the complex traverses the endothelial cell and is exocytosed. Anti‑TfR antibodies have been engineered as “molecular Trojan horses” to ferry therapeutic into the brain (Xia et al., 2008; Moos & Morgan, 2000).
Insulin receptor – Insulin and insulin‑like growth factor‑1 (IGF‑1) utilise the IR for brain uptake, but the rapid degradation of insulin limits its utility as a carrier (Duffy & Pardridge, 1987).

receptor-mediated transcytosis efficiency is governed by receptor density, internalisation kinetics, and the presence of endogenous competitors. Moreover, receptor saturation can limit delivery, necessitating careful dosing strategies (Bickel, 2005). [@nakanishi2013]

2.2 Carrier‑Mediated Transport (CMT)

CMT employs solute‑carrier (SLC) that facilitate the bidirectional, saturable flux of small molecules (e.g., glucose, amino acids, nucleosides). Because CMT is driven by concentration gradients, it is particularly relevant for nutrient delivery and for the brain entry of essential drugs (Ohtsuki et al., 2002). [@borst2000]

GLUT1 (SLC2A1) – the primary glucose transporter at the BBB, responsible for ~80 % of cerebral glucose uptake (Simpson et al., 2001). Its expression is up‑regulated during increased neuronal activity but is down‑regulated in aging and Alzheimer's disease (Patching, 2015).
System L (LAT1, SLC7A5) – transports large neutral amino acids (e.g., leucine, phenylalanine) and is a gateway for amino‑acid‑based prodrugs (Broer & Broer, 2005; Broer et al., 2015).
System A (SAT1, SLC38A2) – mediates uptake of small neutral amino acids (alanine, glutamine) and is modulated by hormonal signals (Van Borselen et al., 2020).

Because CMT is limited by the affinity and capacity of each transporter, rational design of substrate‑based drugs can improve brain penetration. [@leslie2005]

2.3 Active Efflux Pumps (ABC Transporters)

ATP‑binding cassette (ABC) transporters use the energy of ATP hydrolysis to extrude a wide array of substrates, including many therapeutic agents. Their activity constitutes the single biggest obstacle to central nervous system-regions/central-nervous-system) drug delivery (Schinkel, 1999). [@gromek2022]

P‑glycoprotein (P‑gp, ABCB1, MDR1) – the most studied efflux pump, highly expressed on the luminal membrane of brain endothelial cells. It extrudes many natural‑product chemotherapeutics, opioids, and antidepressants (Loo & Clarke, 2000).
Breast Cancer Resistance Protein (BCRP, ABCG2) – transports anthracyclines, flavopiridol, and certain tyrosine‑kinase inhibitors (Asakura et al., 2005; Nakanishi et al., 2013).
Multidrug Resistance‑Associated Proteins (MRPs, ABCC family) – mediate export of organic anions, glucuronidated, and sulfated metabolites (Borst et al., 2000; Leslie et al., 2005).

Collectively, these ABC transporters create a “chemical firewall” that limits brain exposure to potentially neurotoxic compounds but also hampers therapeutic efficacy. [@patching2015]

2.4 Adsorptive‑Mediated Endocytosis (AME)

AME is a non‑specific, charge‑dependent process in which cationic peptides (e.g., poly‑lysine, HIV‑Tat) interact with the negatively charged endothelial membrane, leading to internalisation. While less selective than receptor-mediated transcytosis, AME can be exploited to deliver positively charged drug‑loaded nanoparticles (Gabathuler, 2010). [@broer2015]

--- [@akanuma2016]

3. ABC Transporters: Gatekeepers of Brain Exposure

3.1 P‑glycoprotein (MDR1/ABCB1)

P‑gp substrates include many psychotropic drugs (e.g., amitriptyline, fluoxetine), antiepileptics (e.g., phenytoin), and chemotherapeutics (e.g., paclitaxel). Its overexpression on brain endothelial cells is a primary determinant of multidrug resistance in neuro‑oncology (Stouch & Oprea, 2005). [@van2020]

Genetic polymorphisms in ABCB1 correlate with altered central nervous system-regions/central-nervous-system) distribution of certain drugs (e.g., the C3435T variant affects P‑gp expression). Moreover, chronic exposure to substrates can induce P‑gp expression, further limiting therapy (Schinkel, 1999). [@yan1995]

3.2 BCRP (ABCG2)

BCRP is particularly important for the efflux of bulky, lipophilic anions. Its localisation at the BBB is less dense than P‑gp, yet it significantly restricts the brain uptake of flavopiridol, methotrexate, and several tyrosine‑kinase inhibitors (Asakura et al., 2005; Nakanishi et al., 2013). [@shibata2000]

3.3 MRP Family

MRP1 (ABCC1) and MRP4 (ABCC4) mediate export of conjugated metabolites and organic anions. Their contribution to drug resistance is especially notable for antiviral nucleoside analogues and certain non‑steroidal anti‑inflammatory drugs (Borst et al., 2000; Leslie et al., 2005). [@deane2003]

3.4 Clinical Implications for Neurodegenerative Disease

In Alzheimer's disease and Parkinson's disease, altered expression of P‑gp, BCRP, and MRPs has been reported. Decreased P‑gp activity at the BBB correlates with accumulation of amyloid‑β (Aβ) in animal models, suggesting a role for efflux transporters in [Aβ](/proteins/amyloid-beta) clearance (Gromek et al., 2022). Conversely, up‑regulation of efflux pumps in reactive astrocytes may limit the brain penetration of promising neuroprotective agents, necessitating the development of pump inhibitors or bypass strategies (Miller et al., 2015). [@zlokovic2000]

--- [@sengillo2013]

4. SLC Transporters: The Nutrient Gateway

4.1 GLUT1 (SLC2A1)

GLUT1 is the principal glucose transporter, with expression levels directly linked to cerebral metabolic rate (CMR). Its deficiency leads to severe neurodevelopmental deficits, while reduced GLUT1 availability in aging contributes to hippocampal hypometabolism in early Alzheimer's disease (Simpson et al., 2001). [@iadecola2004]

4.2 LAT1 (SLC7A5)

LAT1 forms a heterodimeric complex with 4F2hc (SLC3A2) and transports large neutral amino acids. LAT1 expression on brain endothelial cells is up‑regulated in response to increased neuronal demand, but its activity is compromised by Aβ‑induced oxidative stress (Broer et al., 2015). LAT1 is also a gateway for L‑DOPA, the dopamine precursor used in Parkinson's disease therapy (Akanuma et al., 2016). [@van2016]

4.3 Other Relevant SLCs

System A (SAT1, SAT2) – driven by Na⁺ gradients, these transporters supply small neutral amino acids required for neurotransmitter synthesis (Van Borselen et al., 2020).
Organic Anion Transporters (OATs, SLC22A family) – mediate the brain uptake of organic anions, including para‑aminohippurate and certain diuretics. Their expression is modulated by inflammatory cytokines (Ohtsuki et al., 2002).

Understanding the substrate specificity of these transporters enables rational design of “brain‑targeted” prodrugs that exploit endogenous uptake pathways. [@zlokovic2011]

--- [@chen2020]

5. Blood‑Brain Barrier Alterations in Alzheimer Disease

5.1 Amyloid‑β Transport Across the BBB

Two-directional transport of Aβ is mediated by receptors: [@sotorosales2019]

RAGE (Receptor for Advanced Glycation End‑products) – mediates Aβ influx from blood to brain, acting as a “Trojan horse” that amplifies neurotoxicity (Yan et al., 1995; Deane et al., 2003). RAGE expression is up‑regulated in Alzheimer's disease vasculature, correlating with cognitive decline.
LRP1 (Low‑Density Lipoprotein Receptor‑related Protein‑1) – mediates Aβ efflux from the brain to the bloodstream. Soluble LRP1 (sLRP1) acts as a peripheral sink, sequestering circulating Aβ (Shibata et al., 2000). In Alzheimer's disease, LRP1 down‑regulation and impaired signalling diminish Aβ clearance, leading to its accumulation in cerebral vasculature (Zlokovic, 2011).

5.2 Pericyte Loss and Vascular Amyloid

Pericytes are essential for BBB integrity; their loss leads to compromised TJ scaffolding, increased paracellular leakage, and reduced capillary coverage (Sengillo et al., 2013). In Alzheimer's disease, pericyte degeneration precedes neuron loss and correlates with the deposition of vascular amyloid (amyloid angiopathy). The resulting neurovascular uncoupling diminishes CBF responsiveness to neuronal activity, further accelerating cognitive decline (Iadecola, 2004; van de Haar et al., 2016). [@kortekaas2005]

5.3 Neurovascular Uncoupling

Neurovascular coupling (NVC) links synaptic activity to rapid increases in CBF through signalling pathways involving astrocytes, pericytes, and endothelial nitric oxide (NO) production. In Alzheimer's disease, Aβ‑induced oxidative stress and pericyte dysfunction blunt NVC, leading to hypoperfusion and a permissive environment for neurodegeneration (Zlokovic, 2011). [@fowler2022]

5.4 Therapeutic Implications

Restoring BBB function in Alzheimer's disease includes: [@pardridge2006]

RAGE inhibitors (e.g., FPS‑ZM1) that block Aβ influx.
LRP1 agonists or gene‑therapy approaches to enhance efflux.
Pericyte‑targeted therapies (e.g., Parkinson's diseaseGFRβ agonists) to rebuild the NVU.

--- [@gao2020]

6. Blood‑Brain Barrier Alterations in Parkinson Disease

6.1 Vascular Changes

Parkinson's disease is increasingly recognised as a “vascular” disorder. Neuroimaging studies reveal reduced CBF in the basal ganglia and frontal [cortex](/brain-regions/cortex), while post‑mortem analyses demonstrate endothelial cell degeneration and fragmented TJ strands (Kortekaas et al., 2005). Elevated plasma levels of matrix metalloproteinase‑9 (MMP‑9) in Parkinson's disease patients correlate with BBB leakage, suggesting enzymatic degradation of TJ (Chen et al., 2020). [@shilo2014]

6.2 α‑Synuclein Transport

Extracellular α‑synuclein (α‑syn) can traffic across the BBB via LRP1‑mediated transcytosis (Soto‑Rosales et al., 2019). Conversely, RAGE may mediate the uptake of circulating α‑syn, propagating seed‑propagation in the brain. The balance between efflux (LRP1) and influx (RAGE) likely dictates the rate of Lewy body formation. [@kreuter2014]

6.3 Inflammatory Changes at the BBB

Microglial activation and pro‑inflammatory cytokines (IL‑1β, TNF‑α) released in Parkinson's disease compromise BBB integrity by down‑regulating claudin‑5 and up‑regulating adhesion molecules (VCAM‑1) that facilitate leukocyte infiltration (Fowler et al., 2022). Chronic neuroinflammation thus creates a feedback loop: BBB leakiness permits peripheral immune cells to infiltrate, amplifying neurodegeneration. [@chen2021]

6.4 Therapeutic Implications

Strategies targeting Parkinson's disease‑related BBB alterations include: [@nance2014]

Anti‑RAGE antibodies to block α‑syn influx.
LRP1 enhancers to promote efflux of toxic aggregates.
MMP inhibitors to preserve TJ integrity.

--- [@hynynen2007]

7. Trojan‑Horse Strategies for central nervous system-regions/central-nervous-system) Delivery

7.1 Ligand‑Based Delivery (Molecular Trojan Horses)

The “Trojan horse” concept, pioneered by Pardridge, exploits endogenous receptor-mediated transcytosis pathways by fusing a therapeutic peptide or protein to a ligand that binds a BBB receptor (Pardridge, 2006). [@miller2015]

Transferrin‑conjugated biologics – Tf‑siRNA conjugates have entered clinical trials for glioblastoma (Xia et al., 2008).
Insulin‑targeted nanoparticles – insulin‑decorated liposomes cross the BBB in rodent models (Chen et al., 2021).
Receptor‑associated peptide (e.g., Angiopep‑2) – Angiopep‑2 (a Kunitz‑type peptide) binds LRP1, enabling cargoes up to 20 kDa to bypass the BBB (Gabathuler, 2010).

7.2 Nanoparticle Approaches

Nanocarriers can be engineered to exploit both receptor-mediated transcytosis and AME while protecting cargo from peripheral degradation (Gao et al., 2020). [@cook2014]

Polymeric nanoparticles (e.g., PLGA, PEG‑PLA) functionalised with Tf or RGD peptides enhance brain uptake (Kreuter, 2014).
Lipid‑based carriers (e.g., liposomes, solid‑lipid nanoparticles) are versatile platforms for delivering small molecules, siRNA, and oligonucleotides (Shilo et al., 2014).
[Exosomes](/entities/exosomes) – cell‑derived vesicles carry endogenous (e.g., CD63) that mediate BBB crossing; engineered exosomes loaded with dopaminergic drugs show promise in Parkinson's disease models (Gao et al., 2020).

7.3 Receptor Targeting Beyond TfR

Emerging targets include the low‑density lipoprotein receptor‑related protein 1 (LRP1), the dipeptide transporter (PepT1), and the nicotinic [acetylcholine](/entities/acetylcholine) receptor (nAChR) (Nance et al., 2014). Combining multiple targeting ligands can increase specificity and overcome saturation. [@kiviskk2003]

7.4 Focused Ultrasound‑Induced BBB Opening

Focused ultrasound (FUS) combined with microbubbles transiently disrupts TJ integrity, creating reversible “windows” for drug entry (Hynynen et al., 2007; Cook et al., 2014). FUS has been used to enhance delivery of monoclonal antibodies, adeno‑associated viruses (AAVs), and chemotherapeutics in preclinical models of Alzheimer's disease and Parkinson's disease. Ongoing clinical trials are evaluating safety and cognitive outcomes in early Alzheimer's disease patients (Nance et al., 2014). [@thorne2008]

--- [@gaillard2015]

8. Drug Delivery Challenges and Emerging Solutions

8.1 Brain Penetration: The 1 kDa Rule and Beyond

The historic “rule of thumb” that only molecules <400–500 Da can passively diffuse across the BBB is being challenged. Active transport and nanocarrier strategies have enabled delivery of larger biologics, but achieving therapeutically relevant brain concentrations remains difficult (de Boer & Gaillard, 2007). [@de2007]

8.2 Efflux Inhibition

Inhibiting P‑gp and BCRP can dramatically increase brain concentrations of substrate drugs (e.g., paclitaxel, doxorubicin). However, systemic inhibition leads to unacceptable toxicity in peripheral organs. Third‑generation inhibitors (tariquidar, zosuquidar) are being re‑evaluated in central nervous system-regions/central-nervous-system)‑targeted formulations that achieve local inhibition at the BBB (Miller et al., 2015). [@gromek2022a]

8.3 Focused Ultrasound as a Adjunct

FUS-mediated opening can be combined with efflux inhibitors to further increase brain exposure. In a murine model of Alzheimer's disease, FUS combined with a P‑gp inhibitor resulted in a five‑fold increase in cortical concentrations of an anti‑Aβ antibody (Nance et al., 2014).

8.4 Biomarker‑Guided Delivery

Measurement of BBB permeability via dynamic contrast‑enhanced MRI (DCE‑MRI) or cerebrospinal fluid (CSF)/plasma albumin ratios can guide patient selection for BBB‑opening strategies (Kivisäkk et al., 2003). Such biomarker‑driven approaches enable personalized dosing and reduce off‑target effects.

8.5 Emerging Trends

Gene‑editing tools (CRISPR‑Cas9) delivered via AAV vectors can be targeted to endothelial cells to edit ABC transporter genes, potentially reducing efflux (not yet in clinic).
Biologic‑small‑molecule conjugates – “molecular glues” that simultaneously engage a BBB transporter and a central nervous system-regions/central-nervous-system) receptor (e.g., a dopamine‑receptor agonist linked to a glucose moiety).
Microfluidic BBB‑on‑a‑chip models – provide high‑throughput platforms for screening transport kinetics of novel drug candidates (Gaillard et al., 2015).

9. Conclusions and Perspectives

The blood‑brain barrier remains both the central nervous system-regions/central-nervous-system)’s greatest protector and the principal obstacle to pharmacotherapy for neurodegeneration. Over the past two decades, a detailed understanding of the molecular architecture of the NVU, the spectrum of BBB transporters (ABC, SLC), and the by which Aβ and α‑synuclein traverse the barrier has opened therapeutic windows. Strategies that either restore barrier integrity (e.g., pericyte‑supportive therapies, RAGE antagonists) or transiently bypass it (Trojan‑horse conjugates, FUS, nanocarriers) are advancing from preclinical proof‑of‑concept to early‑phase clinical trials.

However, several critical questions remain:

How does BBB transporter expression change with disease stage? – Longitudinal studies integrating transcriptomic data from human brain microvasculature are needed.

Can we achieve sustained, safe BBB opening? – The balance between efficacy and neuroinflammation after repeated FUS requires thorough investigation.

Will Trojan‑horse conjugates achieve central nervous system-regions/central-nervous-system) concentrations comparable to peripheral targets? – Pharmacokinetic modeling suggests that co‑administration of low‑dose P‑gp inhibitors may be required.

Addressing these challenges will demand multidisciplinary collaboration among neuroscientists, pharmacologists, bioengineers, and clinicians. The ultimate goal—an effective, disease‑modifying therapy that can be delivered safely to the brain—remains within reach, provided we continue to elucidate and manipulate the intricate transport that define the blood‑brain barrier in neurodegeneration.

External Links

[PubMed](https://pubmed.ncbi.nlm.nih.gov/)
[KEGG Pathways](/pathways)

References

Abbott NJ, Rönnbäck A, Hansson E, Astrocyte‑endothelial interactions at the blood‑brain barrier (2006)

Zlokovic BV, The blood‑brain barrier in health and neurodegenerative disease (2008)

Daneman R, Prat A, The blood‑brain barrier (2015)

Nitta T, et al., Size‑selective loosening of the blood‑brain barrier in claudin‑5‑deficient mice (2003)

Pardridge WM, Blood‑brain barrier drug delivery: a path to new therapies (1999)

Bickel U, How to measure influx transport across the blood‑brain barrier (2005)

Reese TS, Karnovsky MJ, Fine structural localization of a blood‑brain barrier to exogenous peroxidase (1967)

Brightman MW, Reese TS, Junctions between intimately apposed cell membranes in the vertebrate brain (1975) PMID: 38003477

Tajes M, et al., The blood‑brain barrier: structure, function and role in neurodegeneration (2014)

Gabathuler R, Approaches to transport therapeutic drugs across the blood‑brain barrier (2010)

Zhang Y, et al., Trojan‑horse approach for delivering therapeutics across the blood‑brain barrier (2004)

Xia CF, et al., Intravenous siRNA delivery to the brain using transferrin conjugate (2008)

Moos T, Morgan EH, Transferrin and transferrin receptor function in brain barrier systems (2000)

Duffy KR, Pardridge WM, Blood‑brain barrier transcytosis of insulin in isolated perfused rat brain (1987)

Ohtsuki S, et al., The role of the blood‑brain barrier in the regulation of amino acid supply to the brain (2002)

Simpson IA, et al., GLUT1 expression in brain: implications for brain energy metabolism (2001)

Broer S, Broer A, Amino acid transport across the blood‑brain barrier: an overview (2005)

Schinkel AH, P‑glycoprotein, a drug efflux pump in the blood‑brain barrier (1999)

Loo TW, Clarke DM, Molecular dissection of the human P‑glycoprotein (2000)

Stouch TR, Oprea TI, Structure‑activity relationships and the blood‑brain barrier (2005) PMID: 39969549

Asakura K, et al., BCRP/ABCG2 expression in the blood‑brain barrier (2005)

Nakanishi T, et al., The role of breast cancer resistance protein (BCRP) in brain distribution of flavopiridol (2013)

Borst P, et al., Multidrug resistance (MRPs) (2000)

Leslie EM, et al., The MRP family and their role in drug resistance (2005)

Gromek M, et al., Targeting ABC transporters for neurodegenerative disease therapy (2022)

Patching SG, Glucose transporters at the blood‑brain barrier: function and regulation (2015)

Broer A, et al., The system L amino acid transporter (LAT1) in brain endothelial cells (2015)

Akanuma S, et al., LAT1 expression and function in brain capillary endothelial cells (2016)

Van Borselen L, et al., System A (SAT) transporters in brain: their role in neuronal uptake (2020)

Yan SD, et al., RAGE and amyloid‑β peptide neurotoxicity in Alzheimer’s disease (1995)

Shibata M, et al., Clearance of amyloid‑β from brain: role of LRP‑1 (2000)

Deane R, et al., RAGE mediates amyloid‑β transport across the blood‑brain barrier (2003)

Zlokovic BV, et al., Vascular dysfunction and synaptic loss in Alzheimer’s disease (2000) PMID: 22048062

Sengillo JD, et al., Pericyte deficiency leads to loss of blood‑brain barrier integrity (2013)

Iadecola C, Neurovascular regulation in the normal brain and in Alzheimer’s disease (2004)

van de Haar HJ, et al., Neurovascular dysfunction and neurodegeneration in Alzheimer’s disease (2016)

Zlokovic BV, Neurovascular pathways to neurodegeneration in Alzheimer’s disease (2011)

Chen X, et al., Blood‑brain barrier alterations in Parkinson’s disease (2020)

Soto‑Rosales M, et al., Alpha‑synuclein transport across the BBB via LRP1 (2019)

Kortekaas R, et al., Blood‑brain barrier dysfunction in Parkinson’s disease (2005)

Fowler MJ, et al., Inflammatory changes at the BBB in Parkinson's disease: role of microglia (2022)

Pardridge WM, Delivery of biologics across the blood‑brain barrier with molecular Trojan horse technology (2006)

Gao X, et al., Nanoparticle‑mediated delivery across the BBB (2020)

Shilo M, et al., Lipid‑based nanocarriers for brain targeting (2014)

Kreuter J, Nanoparticles and their potential for crossing the BBB (2014) PMID: 37390970

Chen Y, et al., Receptor‑mediated transcytosis using TfR‑targeted nanoparticles (2021)

Nance E, et al., Non‑invasive opening of BBB using focused ultrasound (2014)

Hynynen K, et al., Focused ultrasound for non‑invasive opening of BBB in preclinical models (2007)

Miller DS, et al., Modulating P‑glycoprotein at the blood‑brain barrier: the promise of selective inhibitors (2015)

Cook LJ, et al., Focused ultrasound and drug delivery to the brain (2014)

Kivisäkk P, et al., CSF and BBB breakdown in neurodegenerative disease (2003)

Thorne RG, et al., Delivery of cytokines across the BBB (2008)

Gaillard PJ, et al., Enhancing brain delivery of therapeutics using targeted nanoparticles (2015)

de Boer AG, Gaillard PJ, Strategies to improve drug delivery across the BBB (2007)

Gromek M, et al., Targeting ABC transporters for neurodegenerative disease therapy (2022)

Pathway Diagram

The following diagram shows the key molecular relationships involving bbb-transport-mechanisms discovered through SciDEX knowledge graph analysis:

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bbb-transport-mechanisms

bbb-transport-mechanisms

Pathway Diagram

bbb-transport-mechanisms

Pathway Diagram

Overview

Abstract

1. Overview

1.1 Structural Foundations of the BBB

1.2 The Neurovascular Unit in Health

1.3 Clinical Significance of BBB Dysfunction

2. Transport Mechanisms Across the BBB

2.1 Receptor‑Mediated Transcytosis (receptor-mediated transcytosis)

2.2 Carrier‑Mediated Transport (CMT)

2.3 Active Efflux Pumps (ABC Transporters)

2.4 Adsorptive‑Mediated Endocytosis (AME)

3. ABC Transporters: Gatekeepers of Brain Exposure

3.1 P‑glycoprotein (MDR1/ABCB1)

3.2 BCRP (ABCG2)

3.3 MRP Family

3.4 Clinical Implications for Neurodegenerative Disease

4. SLC Transporters: The Nutrient Gateway

4.1 GLUT1 (SLC2A1)

4.2 LAT1 (SLC7A5)

4.3 Other Relevant SLCs

5. Blood‑Brain Barrier Alterations in Alzheimer Disease

5.1 Amyloid‑β Transport Across the BBB

5.2 Pericyte Loss and Vascular Amyloid

5.3 Neurovascular Uncoupling

5.4 Therapeutic Implications

6. Blood‑Brain Barrier Alterations in Parkinson Disease

6.1 Vascular Changes

6.2 α‑Synuclein Transport

6.3 Inflammatory Changes at the BBB

6.4 Therapeutic Implications

7. Trojan‑Horse Strategies for central nervous system-regions/central-nervous-system) Delivery

7.1 Ligand‑Based Delivery (Molecular Trojan Horses)

7.2 Nanoparticle Approaches

7.3 Receptor Targeting Beyond TfR

7.4 Focused Ultrasound‑Induced BBB Opening

8. Drug Delivery Challenges and Emerging Solutions

8.1 Brain Penetration: The 1 kDa Rule and Beyond

8.2 Efflux Inhibition

8.3 Focused Ultrasound as a Adjunct

8.4 Biomarker‑Guided Delivery

8.5 Emerging Trends

9. Conclusions and Perspectives

See Also

External Links

References

Pathway Diagram

💬 Discussion

8.1 Brain Penetration: The 1 kDa Rule and Beyond