Cu(ATSM) Increases P-Glycoprotein Expression and Function at the Blood-Brain Barrier in C57BL6/J Mice

Effect of Cu(ATSM) on the expression and activity of ABC export proteins in killifish (Fundulus heteroclitus) kidney tubules

ABC transporters are important for excretion of xenobiotics and metabolites into urine. They are sensitive to metallic pollutants like cadmium, mercury, zinc, or arsenic. Here, we show that copper (Cu(ATSM)) stimulates ABC transporter-mediated export in isolated renal proximal tubules from Atlantic killifish (Fundulus heteroclitus) with main focus on Mrp2. Transporter stimulation was reduced by cycloheximide (CHX), an inhibitor of translation, suggesting that it is partially caused by induced expression. Functional activation was reversed by modulators of the endothelin receptor (ETB)/nitric oxide synthase/protein kinase C signaling pathway. Transporter activating effects were reversed by Gö6976 and peptide C2-4, both being PKCα inhibitors. Cu(ATSM)-induced activation was further suppressed by phosphatidylinositol 3-kinase inhibitor LY-294002 and mTOR inhibitor rapamycin. Activation was also inhibited by GSK650394, an inhibitor of serum-and-glucocorticoid-inducible-kinase-1 being a subsequent target. Given the parallelism with other metals, this ABC transporter regulation appears to be a general defense mechanism of teleosts to react on metallic pollutants.

The role of intracellular and extracellular copper compartmentalization in Alzheimer's disease pathology and its implications for diagnosis and therapy

Copper is a trace element indispensable for cellular physiology, integral to cellular redox balance, and a constituent of enzyme active sites, thereby playing a pivotal role in cellular physiological function. Concerning the pathogenesis of Alzheimer's disease (AD), the homeostatic balance of copper is perturbed both intracellularly and extracellularly. The copper-amyloid precursor protein (APP) complex facilitates the efflux of copper from cells, leading to intracellular copper depletion. Concurrently, extracellular copper associates with amyloid-beta (Aβ) plaques, precipitating copper-enriched Aβ deposition and augmenting reactive oxygen species (ROS) in the brain tissue, which finally culminates in oxidative brain damage. The interaction between copper and APP enhances the α-secretase pathway of APP processing while suppressing the β-secretase pathway, resulting in an increased production of soluble APP (sAPP), which contributes to neuroinflammation in the brain tissue. Utilizing the affinity of copper for Aβ plaques, the application of chelating agents to sequester copper within the brain can mitigate neurodegeneration associated with AD pathology. Furthermore, the use of metal imaging techniques to detect copper in the brain offers a potential diagnostic tool for the early identification of AD.

Ferric Ammonium Citrate Reduces Claudin-5 Abundance and Function in Primary Mouse Brain Endothelial Cells

BACKGROUND

Iron overload is implicated in many neurodegenerative diseases, where there is also blood-brain barrier (BBB) dysfunction. As there is a growing interest in the role of iron in modulating key BBB proteins, this study assessed the effect of iron on the expression and function of P-glycoprotein (P-gp), breast cancer resistance protein (BCRP) and claudin-5 in primary mouse brain endothelial cells (MBECs) and their abundance in mouse brain microvessel-enriched membrane fractions (MVEFs).

METHODS

Following a 48 h treatment with ferric ammonium citrate (FAC, 250 µM), MBEC protein abundance (P-gp, BCRP and claudin-5) and mRNA (abcb1a, abcg2, and cldn5) were assessed by western blotting and RT-qPCR, respectively. Protein function was evaluated by assessing transport of substrates 3H-digoxin (P-gp), 3H-prazosin (BCRP) and 14C-sucrose (paracellular permeability). C57BL/6 mice received iron dextran (100 mg/kg, intraperitoneally) over 4 weeks, and MVEF protein abundance and iron levels (in MVEFs and plasma) were quantified via western blotting and inductively coupled plasma-mass spectrometry (ICP-MS), respectively.

RESULTS

FAC treatment reduced P-gp protein by 50% and abcb1a mRNA by 43%, without affecting 3H-digoxin transport. FAC did not alter BCRP protein or function, but decreased abcg2 mRNA by 59%. FAC reduced claudin-5 protein and cldn5 mRNA by 65% and 70%, respectively, resulting in a 200% increase in 14C-sucrose permeability. In vivo, iron dextran treatment significantly elevated plasma iron levels (2.2-fold) but did not affect brain MVEF iron content or alter P-gp, BCRP or claudin-5 protein abundance.

CONCLUSIONS

Iron overload modulates BBB transporters and junction proteins in vitro, highlighting potential implications for CNS drug delivery in neurodegenerative diseases.

Bridging the Gap: Endothelial Dysfunction and the Role of iPSC-Derived Endothelial Cells in Disease Modeling

Endothelial cells (ECs) are crucial for vascular health, regulating blood flow, nutrient exchange, and modulating immune responses and inflammation. The impairment of these processes causes the endothelial dysfunction (ED) characterized by oxidative stress, inflammation, vascular permeability, and extracellular matrix remodeling. While primary ECs have been widely used to study ED in vitro, their limitations-such as short lifespan and donor variability-pose challenges. In this context, induced iECs derived from induced pluripotent stem cells offer an innovative solution, providing an unlimited source of ECs to explore disease-specific features of ED. Recent advancements in 3D models and microfluidic systems have enhanced the physiological relevance of iEC-based models by better mimicking the vascular microenvironment. These innovations bridge the gap between understanding ED mechanisms and drug developing and screening to prevent or treat ED. This review highlights the current state of iEC technology as a model to study ED in vascular and non-vascular disorders, including diabetes, cardiovascular, and neurodegenerative diseases.

Mechanism of Metal Complexes in Alzheimer's Disease

Alzheimer's disease (AD) is a kind of neurodegenerative diseases characterized by beta-amyloid deposition and neurofibrillary tangles and is also the main cause of dementia. According to statistics, the incidence of AD is constantly increasing, bringing a great burden to individuals and society. Nonetheless, there is no cure for AD, and the available drugs are very limited apart from cholinesterase inhibitors and N-Methyl-D-aspartic acid (NMDA) antagonists, which merely alleviate symptoms without delaying the progression of the disease. Therefore, there is an urgent need to develop a medicine that can delay the progression of AD or cure it. In recent years, increasing evidence suggests that metal complexes have the enormous potential to treat AD through inhibiting the aggregation and cytotoxicity of Aβ, interfering with the congregation and hyperphosphorylation of tau, regulating dysfunctional synaptic and unbalanced neurotransmitters, etc. In this review, we summarize the current metal complexes and their mechanisms of action for treating AD, including ruthenium, platinum, zinc, vanadium, copper, magnesium, and other complexes.

The Role of ABCB1, ABCG2, and SLC Transporters in Pharmacokinetic Parameters of Selected Drugs and Their Involvement in Drug-Drug Interactions

Membrane transporters are expressed in a wide range of tissues in the human organism. These proteins regulate the penetration of various substances such as simple ions, xenobiotics, and an extensive number of therapeutics. ABC and SLC drug transporters play a crucial role in drug absorption, distribution, and elimination. Recent decades have shown their contribution to the systemic exposure and tissue penetration of numerous drugs, thereby having an impact on pharmacokinetic and pharmacodynamic parameters. Importantly, the activity and expression of these transporters depend on numerous conditions, including intestinal microbiome profiles or health conditions. Moreover, the combined intake of other drugs or natural agents further affects the functionality of these proteins. In this review, we will discuss the involvement of ABC and SLC transporters in drug disposition. Moreover, we will present current evidence of the potential role of drug transporters as therapeutic targets.

Patient-Derived Blood-Brain Barrier Model for Screening Copper Bis(thiosemicarbazone) Complexes as Potential Therapeutics in Alzheimer's Disease

Alzheimer's disease (AD) is the most prevalent cause of dementia characterized by a progressive cognitive decline. Addressing neuroinflammation represents a promising therapeutic avenue to treat AD; however, the development of effective antineuroinflammatory compounds is often hindered by their limited blood-brain barrier (BBB) permeability. Consequently, there is an urgent need for accurate, preclinical AD patient-specific BBB models to facilitate the early identification of immunomodulatory drugs capable of efficiently crossing the human AD BBB. This study presents a unique approach to BBB drug permeability screening as it utilizes the familial AD patient-derived induced brain endothelial-like cell (iBEC)-based model, which exhibits increased disease relevance and serves as an improved BBB drug permeability assessment tool when compared to traditionally employed in vitro models. To demonstrate its utility as a small molecule drug candidate screening platform, we investigated the effects of diacetylbis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(atsm)) and a library of metal bis(thiosemicarbazone) complexes─a class of compounds exhibiting antineuroinflammatory therapeutic potential in neurodegenerative disorders. By evaluating the toxicity, cellular accumulation, and permeability of those compounds in the AD patient-derived iBEC, we have identified 3,4-hexanedione bis(N(4)-methylthiosemicarbazonato)copper(II) (CuII(dtsm)) as a candidate with good transport across the AD BBB. Furthermore, we have developed a multiplex approach where AD patient-derived iBEC were combined with immune modulators TNFα and IFNγ to establish an in vitro model representing the characteristic neuroinflammatory phenotype at the patient's BBB. Here, we observed that treatment with CuII(dtsm) not only reduced the expression of proinflammatory cytokine genes but also reversed the detrimental effects of TNFα and IFNγ on the integrity and function of the AD iBEC monolayer. This suggests a novel pathway through which copper bis(thiosemicarbazone) complexes may exert neurotherapeutic effects on AD by mitigating BBB neuroinflammation and related BBB integrity impairment. Together, the presented model provides an effective and easily scalable in vitro BBB platform for screening AD drug candidates. Its improved translational potential makes it a valuable tool for advancing the development of metal-based compounds aimed at modulating neuroinflammation in AD.

Approaches for Increasing Cerebral Efflux of Amyloid-β in Experimental Systems

Amyloid protein-β (Aβ) concentrations are increased in the brain in both early onset and late onset Alzheimer's disease (AD). In early onset AD, cerebral Aβ production is increased and its clearance is decreased, while increased Aβ burden in late onset AD is due to impaired clearance. Aβ has been the focus of AD therapeutics since development of the amyloid hypothesis, but efforts to slow AD progression by lowering brain Aβ failed until phase 3 trials with the monoclonal antibodies lecanemab and donanemab. In addition to promoting phagocytic clearance of Aβ, antibodies lower cerebral Aβ by efflux of Aβ-antibody complexes across the capillary endothelia, dissolving Aβ aggregates, and a "peripheral sink" mechanism. Although the blood-brain barrier is the main route by which soluble Aβ leaves the brain (facilitated by low-density lipoprotein receptor-related protein-1 and ATP-binding cassette sub-family B member 1), Aβ can also be removed via the blood-cerebrospinal fluid barrier, glymphatic drainage, and intramural periarterial drainage. This review discusses experimental approaches to increase cerebral Aβ efflux via these mechanisms, clinical applications of these approaches, and findings in clinical trials with these approaches in patients with AD or mild cognitive impairment. Based on negative findings in clinical trials with previous approaches targeting monomeric Aβ, increasing the cerebral efflux of soluble Aβ is unlikely to slow AD progression if used as monotherapy. But if used as an adjunct to treatment with lecanemab or donanemab, this approach might allow greater slowing of AD progression than treatment with either antibody alone.