Formulation, Characterization, and the Diuretic Effects of a New Intravenous Metolazone Emulsion.

OBJECTIVE: Acute decompensated heart failure is often treated with a combination of loop and thiazide-like diuretics. Of these thiazide-like diuretics, two common choices are intravenous chlorothiazide or oral metolazone. Metolazone is more potent and has a longer duration of action, but since it is an oral formulation, it has a longer on-set time as compared to chlorothiazide. In addition, metolazone is poorly water-soluble, thereby rendering intravenous formulation more challenging. To address these issues, we proposed the formulation of a solvent-free metolazone emulsion for intravenous administration. METHODS: An oil-in-water emulsion containing 1 mg/mL of metolazone was formulated by homogenizing soybean oil and l-lecithin in water in the presence of optimized concentrations of glycerin with tween 80 or poloxamer 188 as surfactant. The emulsion was characterized on the basis of particle size, zeta potential, morphology and metolazone release kinetics. The diuretic effect of the metolazone emulsion was evaluated in rats. RESULTS: The 1 mg/mL metolazone emulsion prepared with 5% tween 80 displayed the best physical stability. The emulsion exhibited a hydrodynamic diameter of 157.13±1.52 nm. About 93% of metolazone was released from the formulation within 2 h. The 2 mg/kg and 4 mg/kg dose of the metolazone emulsion increased urine output in the rats by 68.9 and 134%, respectively, as compared to control rats. Furthermore, the 4 mg/kg dose exhibited a 168.8%, 25.8%, and 150.9% increase in sodium, potassium, and chloride, respectively. CONCLUSION: This metolazone emulsion was capable of increasing urine volume output and demonstrated both natriuretic and kaliuretic properties.

Age-Dependent Changes in the Plasma and Brain Pharmacokinetics of Amyloid-ß Peptides and Insulin.

BACKGROUND: Age is the most common risk factor for Alzheimer's disease (AD), a neurodegenerative disorder characterized by the hallmarks of toxic amyloid-ß (Aß) plaques and hyperphosphorylated tau tangles. Moreover, sub-physiological brain insulin levels have emerged as a pathological manifestation of AD. OBJECTIVE: Identify age-related changes in the plasma disposition and blood-brain barrier (BBB) trafficking of Aß peptides and insulin in mice. METHODS: Upon systemic injection of 125I-Aß40, 125I-Aß42, or 125I-insulin, the plasma pharmacokinetics and brain influx were assessed in wild-type (WT) or AD transgenic (APP/PS1) mice at various ages. Additionally, publicly available single-cell RNA-Seq data [GSE129788] was employed to investigate pathways regulating BBB transport in WT mice at different ages. RESULTS: The brain influx of 125I-Aß40, estimated as the permeability-surface area product, decreased with age, accompanied by an increase in plasma AUC. In contrast, the brain influx of 125I-Aß42 increased with age, accompanied by a decrease in plasma AUC. The age-dependent changes observed in WT mice were accelerated in APP/PS1 mice. As seen with 125I-Aß40, the brain influx of 125I-insulin decreased with age in WT mice, accompanied by an increase in plasma AUC. This finding was further supported by dynamic single-photon emission computed tomography (SPECT/CT) imaging studies. RAGE and PI3K/AKT signaling pathways at the BBB, which are implicated in Aß and insulin transcytosis, respectively, were upregulated with age in WT mice, indicating BBB insulin resistance. CONCLUSION: Aging differentially affects the plasma pharmacokinetics and brain influx of Aß isoforms and insulin in a manner that could potentially augment AD risk.

Nanotechnology-based therapies for the prevention and treatment of Streptococcus mutans-derived dental caries.

BACKGROUND: Dental caries results from long-term acid production when sugar is metabolized by a bacterial biofilm, resulting in a loss of calcium and phosphate from the enamel. Streptococcus mutans is a type of acid-producing bacteria and a virulent contributor to oral biofilms. Conventional treatment options, such as cefazolin and ampicillin, have significant levels of bacterial resistance. Other topical agents, such as fluoride, tend to be washed away by saliva, resulting in low therapeutic efficacy. HIGHLIGHT: This review aims to highlight the solubility issues that plague poorly water-soluble therapeutic agents, various novel polymeric, and lipid-based nanotechnology systems that aim to improve the retention of therapeutic agents in the oral cavity. CONCLUSION: In this review, different formulation types demonstrated improved therapeutic outcomes by enhancing drug solubility, promoting penetration into the deep layers of the biofilm, facilitating prolonged residence time in the buccal cavity, and reducing the emergence of drug-resistant phenotypes. These formulations have a strong potential to give new life to therapeutic agents that have limited physicochemical characteristics.

Distinct Uptake Kinetics of Alzheimer Disease Amyloid-ß 40 and 42 at the Blood-Brain Barrier Endothelium.

Blood-brain barrier (BBB) endothelial cells lining the cerebral microvasculature maintain dynamic equilibrium between soluble amyloid-ß (Aß) levels in the brain and plasma. The BBB dysfunction prevalent in Alzheimer disease contributes to the dysregulation of plasma and brain Aß and leads to the perturbation of the ratio between Aß42 and Aß40, the two most prevalent Aß isoforms in patients with Alzheimer disease. We hypothesize that BBB endothelium distinguishes between Aß40 and Aß42, distinctly modulates their trafficking kinetics between plasma and brain, and thereby contributes to the maintenance of healthy Aß42/Aß40 ratios. To test this hypothesis, we investigated Aß40 and Aß42 trafficking kinetics in hCMEC/D3 monolayers (human BBB cell culture model) in vitro as well as in mice in vivo. Although the rates of uptake of fluorescein-labeled Aß40 and Aß42 (F-Aß40 and F-Aß42) were not significantly different on the abluminal side, the luminal uptake rate of F-Aß42 was substantially higher than F-Aß40. Since higher plasma Aß levels were shown to aggravate BBB dysfunction and trigger cerebrovascular disease, we systematically investigated the dynamic interactions of luminal [125I]Aß peptides and their trafficking kinetics at BBB using single-photon emission computed tomography/computed tomography imaging in mice. Quantitative modeling of the dynamic imaging data thus obtained showed that the rate of uptake of toxic [125I]Aß42 and its subsequent BBB transcytosis is significantly higher than [125I]Aß40. It is likely that the molecular mechanisms underlying these kinetic differences are differentially affected in Alzheimer and cerebrovascular diseases, impact plasma and brain levels of Aß40 and Aß42, engender shifts in the Aß42/Aß40 ratio, and unleash downstream toxic effects. SIGNIFICANCE STATEMENT: Dissecting the binding and uptake kinetics of Aß40 and Aß42 at the BBB endothelium will facilitate the estimation of Aß40 versus Aß42 exposure to the BBB endothelium and allow assessment of the risk of BBB dysfunction by monitoring Aß42 and Aß40 levels in plasma. This knowledge, in turn, will aid in elucidating the role of these predominant Aß isoforms in aggravating BBB dysfunction and cerebrovascular disease.

High-Density Lipoprotein Mimetic Peptide 4F Efficiently Crosses the Blood-Brain Barrier and Modulates Amyloid-ß Distribution between Brain and Plasma.

Treatments to elevate high-density lipoprotein (HDL) levels in plasma have decreased cerebrovascular amyloid -ß (Aß) deposition and mitigated cognitive decline in Alzheimer disease (AD) transgenic mice. Since the major protein component of HDL particles, apolipoprotein A-I (ApoA-I), has very low permeability at the blood-brain barrier (BBB), we investigated 4F, an 18-amino-acid ApoA-I/HDL mimetic peptide, as a therapeutic alternative. Specifically, we examined the BBB permeability of 4F and its effects on [125I]Aß trafficking from brain to blood and from blood to brain. After systemic injection in mice, the BBB permeability of [125I]4F, estimated as the permeability-surface area (PS) product, ranged between 2 and 5 × 10-6 ml/g per second in various brain regions. The PS products of [125I]4F were ∼1000-fold higher compared with those determined for [125I]ApoA-I. Moreover, systemic infusion with 4F increased the brain efflux of intracerebrally injected [125I]Aß42. Conversely, 4F infusion decreased the brain influx of systemically injected [125I]Aß42. Interestingly, 4F did not significantly alter the brain influx of [125I]Aß40. To corroborate the in vivo findings, we evaluated the effects of 4F on [125I]Aß42 transcytosis across polarized human BBB endothelial cell (hCMEC/D3) monolayers. Treatment with 4F increased the abluminal-to-luminal flux and decreased the luminal-to-abluminal flux of [125I]Aß42 across the hCMEC/D3 monolayers. Additionally, 4F decreased the endothelial accumulation of fluorescein-labeled Aß42 in the hCMEC/D3 monolayers. These findings provide a mechanistic interpretation for the reductions in brain Aß burden reported in AD mice after oral 4F administration, which represents a novel strategy for treating AD and cerebral amyloid angiopathy. SIGNIFICANCE STATEMENT: The brain permeability of the ApoA-I mimetic peptide 4F was estimated to be ∼1000-fold greater than ApoA-I after systemic injection of radiolabeled peptide/protein in mice. Further, 4F treatment increased the brain efflux of amyloid -ß and also decreased its brain influx, as evaluated in mice and in blood-brain barrier cell monolayers. Thus, 4F represents a potential therapeutic strategy to mitigate brain amyloid accumulation in cerebral amyloid angiopathy and Alzheimer disease.

Cationic carrier peptide enhances cerebrovascular targeting of nanoparticles in Alzheimer's disease brain.

Accumulation of amyloid beta (Aß) peptides in the cerebral vasculature, referred to as cerebral amyloid angiopathy (CAA), is widely observed in Alzheimer's disease (AD) brain and was shown to accelerate cognitive decline. There is no effective method for detecting cerebrovascular amyloid (CVA) and treat CAA. The targeted nanoparticles developed in this study effectively migrated from the blood flow to the vascular endothelium as determined by using quartz crystal microbalance with dissipation monitoring (QCM-D) technology. We also improved the stability, and blood-brain barrier (BBB) transcytosis of targeted nanoparticles by coating them with a cationic BBB penetrating peptide (K16ApoE). The K16ApoE-Targeted nanoparticles demonstrated specific targeting of vasculotropic DutchAß40 peptide accumulated in the cerebral vasculature. Moreover, K16ApoE-Targeted nanoparticles demonstrated significantly greater uptake into brain and provided specific MRI contrast to detect brain amyloid plaques.

Insulin differentially affects the distribution kinetics of amyloid beta 40 and 42 in plasma and brain.

Impaired brain clearance of amyloid-beta peptides (Aß) 40 and 42 across the blood-brain barrier (BBB) is believed to be one of the pathways responsible for Alzheimer's disease (AD) pathogenesis. Hyperinsulinemia prevalent in type II diabetes was shown to damage cerebral vasculature and increase Aß accumulation in AD brain. However, there is no clarity on how aberrations in peripheral insulin levels affect Aß accumulation in the brain. This study describes, for the first time, an intricate relation between plasma insulin and Aß transport at the BBB. Upon peripheral insulin administration in wild-type mice: the plasma clearance of Aß40 increased, but Aß42 clearance reduced; the plasma-to-brain influx of Aß40 increased, and that of Aß42 reduced; and the clearance of intracerebrally injected Aß40 decreased, whereas Aß42 clearance increased. In hCMEC/D3 monolayers (in vitro BBB model) exposed to insulin, the luminal uptake and luminal-to-abluminal permeability of Aß40 increased and that of Aß42 reduced; the abluminal-to-luminal permeability of Aß40 decreased, whereas Aß42 permeability increased. Moreover, Aß cellular trafficking machinery was altered. In summary, Aß40 and Aß42 demonstrated distinct distribution kinetics in plasma and brain compartments, and insulin differentially modulated their distribution. Cerebrovascular disease and metabolic disorders may disrupt this intricate homeostasis and aggravate AD pathology.