Impaired Transport Research Articles

Disrupted Mitochondrial Dynamics Impair Corneal Epithelial Healing in Neurotrophic Keratopathy

Neurotrophic keratopathy (NK) is a degenerative corneal disease characterized by impaired corneal sensitivity and epithelial repair that is often linked to sensory nerve dysfunction. To establish a clinically relevant model and explore the mechanisms underlying NK pathogenesis, we developed a novel mouse model through partial transection of the ciliary nerve. This approach mimics the progressive nature of NK, reproducing key clinical features such as corneal epithelial defects, reduced sensitivity, diminished tear secretion, and delayed wound healing. Using this model, we investigated how disruptions in mitochondrial dynamics contribute to corneal epithelial dysfunction and impaired repair in NK. Our findings revealed substantial disruptions in mitochondrial dynamics, including reduced expression of fusion proteins (OPA1), downregulation of fission regulators (FIS1 and MFF), and impaired mitochondrial transport, as evidenced by decreased expression of Rhot1 and Kif5b. Additionally, the downregulation of mitophagy-related genes (Pink1 and Prkn) contributed to the accumulation of dysfunctional mitochondria, leading to DNA damage and impaired corneal epithelial repair. These mitochondrial abnormalities were accompanied by increased γH2AX staining, indicative of DNA double-strand breaks and cellular stress. This study highlights the pivotal role of mitochondrial dynamics in corneal epithelial health and repair, suggesting that therapeutic strategies aimed at restoring mitochondrial function, enhancing mitophagy, and mitigating oxidative stress may offer promising avenues for treating NK.

Compromised PPARγ Mediated Impaired Placental Glucose Transport via the PI3K/AKT Signaling Pathway is Associated with FGR.

Fetal growth restriction (FGR) is a condition in which a fetus cannot grow to its full potential during pregnancy. It is a leading cause of perinatal mortality and morbidity. However, the underlying etiology remains elusive. Here, we report that peroxisome proliferator-activated receptor γ (PPARγ) is inactivated in the trophoblasts of human placenta of FGR-complicated pregnancies. In the FGR placentas, p-PI3KTyr458 and p-AKTSer473 levels were also lowered. Additionally, there was a reduction in GLUT3 and GLUT4 levels in the cell membrane. Consistently, FGR patients showed decreased glucose concentrations in both the placenta and umbilical cord blood compared to that in normal pregnancy. In mouse models, deletion of PPARγ in trophoblasts and RUPP surgery successfully induced FGR and replicated these changes. Modulating PPARγ activity using rosiglitazone or GW9662 in BeWo cells resulted in the activation or inhibition of the PI3K/AKT signaling pathway, as well as the promotion or reduction of membrane translocation of GLUT3 and GLUT4, ultimately affecting glucose uptake in trophoblast cells. MK-2206 blocked these regulatory effects of rosiglitazone in BeWo cells. Furthermore, the administration of rosiglitazone encapsulated in placenta-targeting nanoparticles improved the growth and development of fetal mice in the RUPP group. In summary, PPARγ in trophoblast cells orchestrates the translocation of GLUT3 and GLUT4 to the cellular membrane via the PI3K/AKT signaling pathway, thereby regulating cellular glucose uptake and transport. Dysfunctions in this mechanism are strongly associated with FGR. Therefore, targeted activation of PPARγ in the placenta may be a potentially efficacious intrauterine intervention for FGR.

Defective Slc7a7 transport reduces erythropoietin compromising erythropoiesis

BackgroundLysinuric protein intolerance is a rare autosomal disorder caused by mutations in the Slc7a7 gene that lead to impaired transport of neutral and basic amino acids. The gold standard treatment for lysinuric protein intolerance involves a low-protein diet and citrulline supplementation. While this approach partially improves cationic amino acid plasma levels and alleviates some symptoms, long-term treatment is suggested to be detrimental and may lead to life-threatening complications characterized by a wide range of hematological and immunological abnormalities. The specific cause of these hematopoietic defects—whether intrinsic to hematopoietic cells or driven by external factors—remains unclear. Given the limitations of current citrulline-based treatments and the unknown role of SLC7A7 in red blood cell production, there is an urgent need to investigate the pathways affected by SLC7A7 deficiency.MethodsWe employed total inducible and cell type-specific Slc7a7 knockout mouse models to determine whether the hematological abnormalities observed in LPI are due to the loss of Slc7a7 function in hematopoietic cells. We analyzed erythropoiesis in these mice and performed bone marrow transplantation experiments to assess the role of Slc7a7 in erythroblasts and myeloid cells. The statistical significance of differences between groups was evaluated via standard statistical tests, including Student’s t test and ANOVA.ResultsWhole-body Slc7a7 knockout mice presented impaired erythropoiesis. However, this defect was not replicated in mice with Slc7a7 deficiency restricted to erythroblasts or myeloid cells, suggesting that the observed hematopoietic abnormalities are not due to intrinsic Slc7a7 loss in these cell types. Additionally, bone marrow transplants from control mice did not rescue the hematopoietic defects in Slc7a7-deficient mice, nor did the transplantation of Slc7a7-deficient cells induce defects in control recipients. Further investigation indicated that defective erythropoiesis is linked to impaired erythropoietin production in the kidney and subsequent iron overload.ConclusionsThe hematopoietic defects in the Lysinuric protein intolerance mouse model are not caused by intrinsic Slc7a7 loss in hematopoietic cells but rather by impaired erythropoietin production in the kidney. This finding opens potential avenues for therapeutic strategies targeting erythropoietin production to address hematological abnormalities in humans with lysinuric protein intolerance.

MAGED2 Enhances Expression and Function of NCC at the Cell Surface via cAMP Signaling Under Hypoxia

Mutations in MAGED2 cause transient antenatal Bartter syndrome (tBS) characterized by excessive amounts of amniotic fluid due to impaired renal salt transport via NKCC2 and NCC, high perinatal mortality, and pre-term birth. Surprisingly, renal salt handling completely normalizes after birth. Previously, we demonstrated that, under hypoxic conditions, MAGED2 depletion enhances endocytosis of GalphaS (Gαs), reducing adenylate cyclase (AC) activation and cAMP production. This impaired cAMP signaling likely contributes to the dysfunction of salt transporters NKCC2 and NCC, explaining salt wasting and the subsequent recovery with renal oxygenation after birth. In this study, we show that MAGED2 depletion significantly decreases both total cellular and plasma membrane NCC expression and activity. We further demonstrate that MAGED2 depletion disrupts NCC trafficking by reducing exocytosis, increasing endocytosis, and promoting lysosomal degradation via enhanced ubiquitination. Additionally, forskolin (FSK), which increases cAMP production by activating AC, rescues NCC expression and localization in MAGED2-depleted cells. Conversely, MAGED2 overexpression increases NCC expression and membrane localization, although this effect is diminished in Gαs-depleted cells, indicating that Gαs acts downstream of MAGED2. In summary, our findings reveal the essential role of MAGED2 in regulating NCC function and trafficking under hypoxic conditions, providing new insights into the mechanisms behind salt loss in tBS and identifying potential therapeutic targets.

Impaired axonal transport contributes to neurodegeneration in a Cre-inducible mouse model of myocilin-associated glaucoma.

Elevation of intraocular pressure (IOP) due to trabecular meshwork (TM) dysfunction, leading to neurodegeneration, is the pathological hallmark of primary open-angle glaucoma (POAG). Impaired axonal transport is an early and critical feature of glaucomatous neurodegeneration. However, a robust mouse model that accurately replicates these human POAG features has been lacking. We report the development and characterization of a novel Cre-inducible mouse model expressing a DsRed-tagged Y437H mutant of human myocilin (Tg.CreMYOCY437H). A single intravitreal injection of HAd5-Cre induced selective MYOC expression in the TM, causing TM dysfunction, reducing the outflow facility, and progressively elevating IOP in Tg.CreMYOCY437H mice. Sustained IOP elevation resulted in significant loss of retinal ganglion cells (RGCs) and progressive axonal degeneration in Cre-induced Tg.CreMYOCY437H mice. Notably, impaired anterograde axonal transport was observed at the optic nerve head before RGC degeneration, independent of age, indicating that impaired axonal transport contributes to RGC degeneration in Tg.CreMYOCY437H mice. In contrast, axonal transport remained intact in ocular hypertensive mice injected with microbeads, despite significant RGC loss. Our findings indicate that Cre-inducible Tg.CreMYOCY437H mice replicate all glaucoma phenotypes, providing an ideal model for studying early events of TM dysfunction and neuronal loss in POAG.

Sciatic nerve analysis in thyroid hormone transporters Mct8 and Oatp1c1 knockout mice.

Mutations in the thyroid hormone (TH) transporter monocarboxylate transporter 8 (MCT8) cause Allan-Herndon-Dudley syndrome (AHDS), a severe form of psychomotor retardation with muscle hypoplasia and spastic paraplegia as key symptoms. These abnormalities have been attributed to impaired TH transport across brain barriers and into neural cells, thereby affecting brain development and function. Likewise, Mct8/Oatp1c1 (organic anion-transporting polypeptide 1c1) double knockout (M/Odko) mice, a well-established murine AHDS model, display a strongly reduced TH passage into the brain as well as locomotor abnormalities. To which extent the peripheral nervous system is affected by combined MCT8/OATP1C1 deficiency has not been addressed. Using the sciatic nerve as a model, we studied the spatiotemporal expression of TH transporters as well as the sciatic thyroidal state, sciatic nerve myelination and function in M/Odko mice by immunofluorescence, qPCR, Western blotting and electrophysiology. We detected MCT8 protein expression in sciatic nerve axons, whereas OATP1C1 expression was observed in a subset of endothelial cells early in postnatal development. The absence of MCT8 and OATP1C1 did not alter the thyroidal state of isolated nerves at P12. Moreover, electrophysiological studies did not disclose any significant alteration in sciatic nerve signal propagation parameters in adult M/Odko mice. Although Schwann cell numbers were similar, Western blot analysis showed a mild form of hypermyelination in adult M/Odko mice. Altogether, our data point to a largely unaffected sciatic nerve structure and function in the absence of MCT8 and OATP1C1.

Impact of Genetic Variants on Vitamin E Levels in an Italian Cohort of Bariatric Surgery Patients: A Focus on SNPs Involved with Transport and Bioavailability.

Obesity is a global epidemic associated with chronic inflammation, oxidative stress, and metabolic disorders. Bariatric surgery is a highly effective intervention for sustained weight loss and the improvement of obesity-related comorbidities. However, post-surgery nutritional deficiencies, including vitamin E, remain a concern. This study investigates the role of single-nucleotide polymorphisms (SNPs) in genes related to vitamin E transport and bioavailability in determining vitamin E levels post bariatric surgery. A cohort of 140 patients with obesity undergoing bariatric surgery was analyzed. Serum vitamin E levels were measured before and one year after surgery, and SNPs in genes associated with vitamin E transport and metabolism were genotyped using PCR, DHPLC, and sequencing methods. Associations between SNPs, haplotypes, and vitamin E levels were statistically evaluated. Significant associations were observed between the APOE rs7412 SNP and serum vitamin E levels. The rare T allele was linked to lower vitamin E levels post surgery, with an increased frequency in patients with severe deficiency (<11.6 μmol/L). Haplotype analysis of APOE revealed that the ε2 haplotype (T-T) was strongly associated with vitamin E deficiency. Other SNPs, including CD36 rs1761667, SCARB1 rs4238001, and ABCA1 rs4149314, were also linked to changes in vitamin E levels, suggesting that an impaired bioavailability and transport can be the reason for low vitamin E levels post surgery. Genetic polymorphisms in APOE, CD36, SCARB1, and ABCA1 significantly influence vitamin E status after bariatric surgery. These findings highlight the importance of personalized supplementation strategies considering patients' genetic profiles to mitigate the risk of vitamin E deficiency and related complications.

Landscape of Cyclic Vomiting Syndrome: From Bedside to Bench, Past to Present.

Investigations into mechanisms of cyclic(al) vomiting syndrome (CVS) began at the bedside more than a century ago. The modern era started with the formation of the Cyclic Vomiting Syndrome Association in 1993 that helped initiate robust efforts in education, advocacy, family physician conferences, scientific symposia, dedicated clinical programs, therapeutic guidelines, and research. Even today, bedside clues continue to emerge with the recent description of cannabinoid hyperemesis syndrome (CHS) and subsequent evidence of a perturbed endocannabinoid system. The clinical picture of CVS has evolved from that of a straightforward emetic disorder related to migraine requiring short-term antiemetics or prophylactic anti-migraine therapy, to a complicated, heterogenous one with multiple comorbid associations (anxiety, dysautonomia) and endophenotypes (migraine, Sato, CHS). This expanded view has important therapeutic implications which necessitate managing the comorbidities which can in turn impact the disease itself and proffered promising evidence that behavioral management (meditation) and vagal neuromodulation appear efficacious with few untoward effects, perhaps by reestablishing autonomic (parasympathetic) balance. The pathophysiologic picture now appears to be inscribed on an autonomic polyvagal design but multiple additional pathways interact, some confirmed (NK1, CB1, HPA axis, PPM1D gene, biological calendar, estrogen), and others, possible (TRPV-1, CGRP, GDF-15, mitochondrial dysfunction, impaired cation transport). CVS and its cousin CHS continue to challenge clinicians and perplex investigators and in the current era require not only a critical mass of specific pathway expertise but also syncretic biopsychosocial thinking to integrate these disparate threads. We may have reached such a tipping point at this Symposium.

The role of neutrophilia in hyperlactatemia, blood acidosis, impaired oxygen transport, and mortality outcome in critically ill COVID-19 patients.

COVID-19 severity and high in-hospital mortality are often associated with severe hypoxemia, hyperlactatemia, and acidosis, yet the key players driving this association remain unclear. It is generally assumed that organ damage causes toxic acidosis, but since neutrophil numbers in severe COVID-19 can exceed 80% of the total circulating leukocytes, we asked if metabolic acidosis mediated by the glycolytic neutrophils is associated with lung damage and impaired oxygen delivery in critically ill patients. Based on prospective mortality outcome, critically ill COVID-19 patients were divided into ICU- survivors and ICU-non-survivors. Samples were analyzed to explore if correlations exist between neutrophil counts, lung damage, glycolysis, blood lactate, blood pH, hemoglobin oxygen saturation, and mortality outcome. We also interrogated isolated neutrophils, platelets, and PBMCs for glycolytic activities. Arterial blood gas analyses showed remarkable hypoxemia in non-survivors with no consistent differences in PCO2 or [HCO3 -]. The hemoglobin oxygen dissociation curve revealed a right-shift, consistent with lower blood-pH and elevated blood lactate in non-survivors. Metabolic analysis of different blood cells revealed increased glycolytic activity only when considering the total number of neutrophils. This indicates the role of neutrophilia in hyperlactatemia and lung damage, subsequently contributing to mortality outcomes in severe SARS-CoV-2 infection.

Axonal distribution of mitochondria maintains neuronal autophagy during aging via eIF2β.

Neuronal aging and neurodegenerative diseases are accompanied by proteostasis collapse, while cellular factors that trigger it are not identified. Impaired mitochondrial transport in the axon is another feature of aging and neurodegenerative diseases. Using Drosophila, we found that genetic depletion of axonal mitochondria causes dysregulation of protein degradation. Axons with mitochondrial depletion showed abnormal protein accumulation and autophagic defects. Lowering neuronal ATP levels by blocking glycolysis did not reduce autophagy, suggesting that autophagic defects are associated with mitochondrial distribution. We found that eIF2β was increased by the depletion of axonal mitochondria via proteome analysis. Phosphorylation of eIF2α, another subunit of eIF2, was lowered, and global translation was suppressed. Neuronal overexpression of eIF2β phenocopied the autophagic defects and neuronal dysfunctions, and lowering eIF2β expression rescued those perturbations caused by depletion of axonal mitochondria. These results indicate the mitochondria-eIF2β axis maintains proteostasis in the axon, of which disruption may underly the onset and progression of age-related neurodegenerative diseases.

Impaired renal transporter gene expression and uremic toxin excretion as aging hallmarks in cats with naturally occurring chronic kidney disease.

Aging leads to nephron senescence and chronic kidney disease (CKD). In cats, indoxyl sulfate (IxS) has been previously quantified and associated with CKD, and little is known about tubular transporters. Two cohorts of cats aged 6 to 21 years were enrolled. Cohort 1 included 41 colony cats with 28 control and 13 CKD cats. Cohort 2 had 30 privately-owned cats with 10 control and 20 CKD cats. In cohort 1, serum concentrations of IxS, trimethylamine N-oxide (TMAO), p-cresol sulfate (PCS), and phenyl sulfate were higher in CKD vs. control cats (all P<0.05). This observation was independently validated in cohort 2. Renal cortical and medullar tissues were collected from a third cohort of cats euthanized for humane reasons unrelated to the study. We provided the evidence that renal tubular transporter genes, OAT1, OAT4, OATP4C1, and ABCC2, but not OAT3, were expressed in the kidneys of cats, and their expressions were downregulated in CKD (all FDR<0.1). Cats and humans share 90.9%, 77.8%, and 82.5% identities in OAT1, OATP4C1, and ABCC2 proteins, respectively. In healthy cats, circulating TMAO and IxS are significantly correlated with age. Our study reveals impaired uremic toxin secretion and tubular transporter expression in cats with CKD.

Temperature induces brain-intake shift of recombinant high-density lipoprotein after traumatic brain injury

Traumatic brain injury (TBI) is one of the leading public health concerns in the world. Therapeutic hypothermia is routinely used in severe TBI, and pathophysiological hyperthermia, frequently observed in TBI patients, has an unclear impact on drug transport in the injured brain due to a lack of study on its effects. We investigated the effect of post-traumatic therapeutic hypothermia at 33°C and pathophysiological hyperthermia at 39°C on brain transport and cell uptake of neuroprotectants after TBI. Recombinant high-density lipoprotein (rHDL), which possesses anti-inflammatory, antioxidant activity, and blood–brain barrier (BBB) permeability, was chosen as the model drug. First, we found that mild hypothermia and hyperthermia impaired rHDL transport to the brain and lesion targeting in controlled cortical impact mice. Second, we investigated the temperature-induced rHDL uptake shift by various brain cell types. Mild hypothermia impeded the uptake of rHDL by endothelial cells, neurons, microglia, and astrocytes. Hyperthermia impeded the uptake of rHDL by endothelial cells and neurons while promoting its uptake by microglia and astrocytes. In an attempt to understand the mechanisms behind the above phenomena, it was found that temperature induced brain-intake shift of rHDL through the regulation of low-density lipoprotein receptor (LDLR) and LDLR-related protein 1 (LRP1) stability in brain cells. We therefore reported the full view of the temperature-induced brain-intake shift of rHDL after TBI for the first time. It would be of help in coordinating pharmacotherapy with temperature management in individualization and precision medicine.Graphical

Polyphenol Mediated Assembly: Tailored Nano-Dredger Unblocks Axonal Autophagosomes Retrograde Transport Traffic Jam for Accelerated Alzheimer's Waste Clearance.

Clear-cut evidence has linked defective autophagy to Alzheimer's disease (AD). Recent studies underscore a unique hurdle in AD neuronal autophagy: impaired retrograde axonal transport of autophagosomes, potent enough to induce autophagic stress and neurodegeneration. Nonetheless, pertinent therapy is unavailable. Here, a novel combinational therapy composed of siROCK2 and lithospermic acid B (LA) is introduced, tailored to dredge blocked axonal autophagy by multi-mitigating microtubule disruption, ATP depletion, oxidative stress, and autophagy initiation impediments in AD. Leveraging the recent discovery of multi-interactions between polyphenol LA and siRNA, ε-Poly-L-lysine, and anionic lipid nanovacuoles, LA and siROCK2 are successfully co-loaded into a fresh nano-drug delivery system, LIP@PL-LA/siRC, via a ratio-flexible and straightforward fabrication process. Further modification with the TPL peptide onto LIP@PL-LA/siRC creates a brain-neuron targeted, biocompatible, and pluripotent nanomedicine, named "Nano-dredger" (T-LIP@PL-LA/siRC). Nano-dredger efficiently accelerates axonal retrograde transport and lysosomal degradation of autophagosomes, thereby facilitating the clearance of neurotoxic proteins, improving neuronal complexity, and alleviating memory defects in 3×Tg-AD transgenic mice. This study provides a fresh and flexible polyphenol/siRNA co-delivery paradigm and furnishes conceptual proof that dredging axonal autophagy represents a promising AD therapeutic avenue.

Exploring the Role of Axons in ALS from Multiple Perspectives.

Amyotrophic lateral sclerosis (ALS), commonly known as motor neuron disease, is a neurodegenerative disorder characterized by the progressive degeneration of both upper and lower motor neurons. This pathological process results in muscle weakness and can culminate in paralysis. To date, the precise etiology of ALS remains unclear. However, a burgeoning body of research indicates that axonal dysfunction is a pivotal element in the pathogenesis of ALS and significantly influences the progression of disease. Dysfunction of axons in ALS can result in impediments to nerve impulse transmission, leading to motor impairment, muscle atrophy, and other associated complications that severely compromise patients' quality of life and survival prognosis. In this review, we concentrate on several key areas: the ultrastructure of axons, the mechanisms of axonal degeneration in ALS, the impact of impaired axonal transport on disease progression in ALS, and the potential for axonal regeneration within the central nervous system (CNS). Our objective is to achieve a more holistic and profound understanding of the multifaceted role that axons play in ALS, thereby offering a more intricate and refined perspective on targeted axonal therapeutic interventions.

Advancing the Battle against Cystic Fibrosis: Stem Cell and Gene Therapy Insights.

Cystic fibrosis (CF) is a hereditary disorder characterized by mutations in the CFTR gene, leading to impaired chloride ion transport and subsequent thickening of mucus in various organs, particularly the lungs. Despite significant progress in CF management, current treatments focus mainly on symptom relief and do not address the underlying genetic defects. Stem cell and gene therapies present promising avenues for tackling CF at its root cause. Stem cells, including embryonic, induced pluripotent, mesenchymal, hematopoietic, and lung progenitor cells, offer regenerative potential by differentiating into specialized cells and modulating immune responses. Similarly, gene therapy aims to correct CFTR gene mutations by delivering functional copies of the gene into affected cells. Various approaches, such as viral and nonviral vectors, gene editing with CRISPR-Cas9, small interfering RNA (siRNA) therapy, and mRNA therapy, are being explored to achieve gene correction. Despite their potential, challenges such as safety concerns, ethical considerations, delivery system optimization, and long-term efficacy remain. This review provides a comprehensive overview of the current understanding of CF pathophysiology, the rationale for exploring stem cell and gene therapies, the types of therapies available, their mechanisms of action, and the challenges and future directions in the field. By addressing these challenges, stem cell and gene therapies hold promise for transforming CF management and improving the quality of life of affected individuals.

Effects of Xhosa specific solute carrier family 22-member 2 haplotypes on the cellular uptake of metformin and cimetidine.

Studies have shown that solute carrier transporters play an important role in the transport and distribution of metformin, and that genetic variation(s) in solute carrier genes have play a role in the variation of metformin efficacy and disposition observed in populations. This study aimed to determine the cellular uptake efficiency of metformin in SLC22A2 coding haplotypes of an indigenous South African population. To determine metformin and cimetidine cellular uptake in transfected HEK-293 cells, ultra high-performance liquid chromatography was used to quantitate substrate concentration(s). Haplotypes 3 and 4 showed decreased metformin uptake, and haplotypes 2 and 5 displayed increased metformin uptake in comparison to haplotype 1 (i.e. wildtype haplotype). Haplotypes 2-5 showed decreased uptake of cimetidine in comparison to haplotype 1, implying a reduced sensitivity to the inhibition of cimetidine. In all haplotypes, no significant transport was observed for metformin and cimetidine. Passive permeability of metformin was favoured in haplotypes 3 and 5, whilst the remaining haplotypes demonstrate higher passive permeability ratios in favour of cimetidine. Haplotype 4, which is characterised by the non-synonymous single nucleotide polymorphisms rs316019 and rs8177517, demonstrates potential impaired metformin transport.

Biallelic SLC13A1 loss-of-function variants result in impaired sulfate transport and skeletal phenotypes including short stature, scoliosis, and skeletal dysplasia

Biallelic SLC13A1 loss-of-function variants result in impaired sulfate transport and skeletal phenotypes including short stature, scoliosis, and skeletal dysplasia

Development of an inhalable contrast agent targeting the respiratory tract mucus layer for pulmonary ultrasonic imaging

Impaired mucociliary transport is a distinguishing sign of cystic fibrosis, but current methods of evaluation are invasive or expose young patients to ionizing radiation. Contrast-enhanced ultrasound imaging may provide a feasible alternative. We formulated a cationic microbubble ultrasound contrast agent, to optimize adhesion to the respiratory mucus layer when inhaled. Potential toxicity was evaluated in human bronchial epithelial cell (hBEC) cultures following a 24-hour exposure, compared to positive and negative control conditions. In vivo tolerability and pulmonary image enhancement feasibility were evaluated in mice, comparing oropharyngeal administration of contrast agent to saline control. When induced to flow across mucus plated on microscope slides, cationic microbubbles demonstrated greater affinity for target samples than standard microbubbles. Cationic microbubbles elicited no proinflammatory or cytotoxic response in hBECs, nor were any cross-links to the cilia observed. Unlike standard microbubbles, cationic microbubbles mixed into the mucus layer, without epithelial absorption, and were observed to move with the mucus layer by the action of mucociliary transport. When administered to mice, cationic microbubbles enhanced sonographic visualization of the trachea, and were well-tolerated with no adverse effects. This developmental work supports the safety and feasibility of a mucus-targeting contrast agent that may be useful for pulmonary ultrasound applications.

Mechanistic links between TMEM106B and TDP‐43 dysfunction in AD‐related dementias

AbstractBackgroundInclusions of TAR DNA binding protein of 43kDa (TDP‐43) constitute the main characteristic pathology in the majority (∼97%) of amyotrophic lateral sclerosis (ALS) cases and approximately 50% of patients with frontotemporal lobar degeneration (FTLD). TDP‐43 is a nuclear RNA binding protein; however, in disease, it becomes hyperphosphorylated and/or insoluble, hindering its nuclear function in maintaining RNA homeostasis. Importantly, the incidence of TDP‐43 proteinopathy extends to aging brains (LATE) and may be concomitant with Alzheimer’s disease (AD) neuropathological changes (LATE/AD) in up to 70% of AD patients. Interestingly, LATE/AD cases are characterized by worse memory and greater hippocampal atrophy than AD alone. Therefore, TDP‐43 dysfunction could have diverse, disease‐specific effects on pathogenesis, making it imperative to elucidate the mechanism of TDP‐43 deposition in the brain and its role in AD‐related dementias (ADRDs).MethodWe used standardized molecular biology techniques and single‐nuclei RNA sequencing to evaluate TDP‐43 dysfunction across brain regions in both LATE/AD and FTLD‐TDP, identify common and distinct molecular mechanisms involved in each ADRD, as well as assess the relevance of TMEM106B rs3173615, a genetic variation linked to risk of FTLD haplotype, in TDP‐43 pathology.ResultWe detected misspliced, TDP‐43‐regulated cryptic RNAs in the amygdala and hippocampus of LATE/AD and FTLD‐TDP. FTLD‐TDP, but not LATE/AD, frontal cortex also showed significant accumulation of these aberrant transcripts. The topographic distribution of cryptic RNAs mimicked that of insoluble, phosphorylated TDP‐43, regardless of TDP‐43 subtype classification. Despite common misregulated transcripts in these ADRDs, we also identified unique transcriptome changes, even within each TDP‐43 subtype. Finally, we observed that TMEM106B core deposition, which is linked to the presence of the risk TMEM106B rs3173615 haplotype, was associated with enhanced TDP‐43 dysfunction and pathology, and interactome data suggested a role for TMEM106B core filaments in impaired RNA transport, local translation, and endolysosomal function in FTLD‐TDP.ConclusionOur results emphasize the use of cryptic RNAs to identify cases with TDP‐43 pathology, and raises the possibility that unique transcriptome signatures may further distinguish FTLD‐TDP from LATE/AD and within different TDP‐43 subtypes. We showed a relationship between increased TMEM106B core deposition and greater susceptibility to TDP‐43 dysfunction, potentially through dysregulation of endolysosomal function.

Longitudinal Analysis of BCAA Levels and Hypometabolism in ApoE4‐Positive Alzheimer’s Patients Over A 48‐Month Period

AbstractBackgroundAlzheimer’s Disease (AD) is a chronic, incurable neurodegenerative condition characterized by extensive systemic, cellular, and molecular abnormalities. One such aspect recent studies have highlighted is the reduction in plasma branched‐chain amino acid (BCAA) concentrations, identifying them as a potential emerging marker for the disease. Although BCAAs have been implicated in the pathogenesis of AD, their utility in clinical prognosis remains unexplored. This study aims to investigate the role of BCAA levels in AD progression, considering the presence or absence of the APOE4 phenotype over a period of forty‐eight months.MethodBiomarker and clinical diagnosis data for 31 subjects with varying cognitive statuses were obtained from the Alzheimer’s Disease Neuroimaging Initiative (CN, n = 10; LMCI, n = 21). Cognitive status was assessed using the Hypometabolic Convergence Index (HCI), a tool designed to quantify the magnitude and severity of cerebral hypometabolism typical in probable Alzheimer’s Disease patients. BCAA levels were measured through a nuclear magnetic resonance‐based blood biomarker analysis and expressed as concentrations in plasma.ResultA significant correlation was observed between the initial HCI and BCAA measurements and HCI values taken forty‐eight months later, indicating cognitive decline (n = 31, r = 0.362, p‐value = 0.0383). Stratification by APOE4 phenotype revealed more nuanced insights: subjects with zero alleles showed no significant correlation (n = 16, r = 0.165, p‐value = 0.0542), while those with one or two alleles demonstrated a stronger, tighter correlation (n = 15, r = 0.564, p‐value = 0.0183).ConclusionThis study corroborates prior research on the association between diminished plasma BCAA levels and reduced neuronal activity in regions pertinent to AD, as reflected by HCI assessments over a forty‐eight month period. Importantly, our findings reveal a significant correlation between BCAA concentrations and cognitive decline predominantly in individuals carrying one or two APOE4 alleles. This observation highlights the potential influence of the APOE4 allele on the impaired transport of BCAAs to the brain, contributing to cognitive deterioration in these groups. Further research is needed to explore the diagnostic value of BCAA levels in broader AD populations and to understand the mechanistic links in non‐carriers of the APOE4 allele.