Elimination Pathway Research Articles

RELATIONSHIP OF LEAD WITH FREE RADICALS, REACTIVE OXYGEN SPECIES, OXIDATIVE STRESS AND ANTIOXIDANT ENZYMES

Heavy metals, which are high in the environment, are substances that have a high toxic effect even at low concentrations. Heavy metals taken into the organism through mouth, respiration and skin cannot be eliminated by the body's excretory pathways. In addition, since they have a durable structure, they participate in the food chain and accumulate in various body tissues. With the increase in industrial activities, heavy metal pollution has also emerged and has increased day by day. Lead is an element that is widely used in industry because it has a low melting temperature. However, it is known that lead, like other heavy metals, has an effect on problems such as environmental pollution and health problems. Occupational diseases such as lead poisoning occur as a result of direct exposure to lead. Direct exposure in this way can also cause death. Lead causes undesirable conditions such as increase of reactive oxygen species (ROS), emergence of oxidative stress and weakening of antioxidant system. Lead disrupts the prooxidant/antioxidant ratio. As a result, effects such as an increase in ROS and thus damage to the basic components of the cell such as lipid, protein and nucleic acid are observed.In particular, lead inhibits enzymes and prevents some enzymes from acting as antioxidants. As a result of exposure to lead, there is a decrease in the defense abilities of antioxidant enzymes such as catalase (CAT), superoxide dismutase (SOD), glutathione (GSH) and ascorbic acid in blood and tissues. Lead increases lipid peroxidation and thus causes oxidative damage. Evaluation of the effect of lead at the cellular level is important in terms of developing solutions for the toxic effects of lead. In this study, the effect of lead on the cellular level in the organism and its effects on free radicals, ROS and oxidative stress were evaluated.

Monitoring drug metabolic pathways through extracellular vesicles in mouse plasma.

The ability to monitor the response of metabolic enzymes to drug exposure in individuals is highly appealing and critical to personalized medicine. Although pharmacogenomics assesses genotypic differences, it does not report changes in metabolic enzyme activities due to environmental factors such as drug interactions. Here, we report a quantitative proteomics strategy to monitor drug metabolic pathways by profiling metabolic enzymes in circulating extracellular vesicles (EVs) upon drug exposure. Mass spectrometry (MS)-based measurement revealed that changes in metabolic enzyme abundance in EVs paralleled those in hepatic cells isolated from liver tissue. Coupling with multiplexed isotopic labeling, we temporally quantified 34 proteins involved in drug absorption, distribution, metabolism, and excretion (ADME) pathways. Out of 44 known ADME proteins in plasma EVs, previously annotated mouse cytochrome P450 3A11 (Cyp3a11), homolog to human CYP3A4, and uridine 5'-diphospho (UDP) glucuronosyltransferase 2A3 (Ugt2a3), increased upon daily rifampicin dosage. Dasatinib, a tyrosine kinase inhibitor to treat leukemia, also elevated Cyp3a11 levels in plasma EVs, but to a lesser extent. Altogether, this study demonstrates that measuring drug enzymes in circulating EVs as an effective surrogate is highly feasible and may transform today's drug discovery and development for personalized medicine.

A computational model of endogenous hydrogen peroxide metabolism in hepatocytes, featuring a critical role for GSH

This paper presents an ordinary differential equation (ODE) model of endogenous H2O2metabolism in hepatocytes that is unique, at the time of writing, in its ability to accurately compute intracellular H2O2concentration during incidents of oxidative stress and in its usefulness for constructing PBPK/PD models for ROS-generating xenobiotics. Versions of the model are presented for rat hepatocytes in vitro and mouse liver in vivo. A generic method is given for using the model to create PBPK/PD models which predict intracellular H2O2concentration and oxidative-stress-induced hepatocyte death; these are identifiable from in vitro data sets reporting cell mortality following xenobiotic exposure at various levels. The procedure is demonstrated for the trivalent arsenical dimethylarsinous acid (DMAIII), which is produced in liver as part of the arsenic elimination pathway. This is the first model of H2O2metabolism in hepatocytes to feature values for the endogenous rates of H2O2production by mitochondria and other organelles which are inferred from the physiology literature, and to feature a detailed, realistic treatment of GSH metabolism; the latter is achieved by incorporating a minimal version of Reed and coworkers’ pioneering model of GSH metabolism in liver. Model simulations indicate that critical GSH depletion is the immediate trigger for intracellular H2O2rising to concentrations associated with apoptosis (>1μM), that this may only occur hours after the xenobiotic concentration peaks (“delay effect”), that when critical GSH depletion does occur, H2O2concentration rises rapidly in a sequence of two boundary layers, characterized by the kinetics of glutathione peroxidase (first boundary layer) and catalase (second boundary layer), and that intracellular H2O2concentration >1μM implies critical GSH depletion. There has been speculation that ROS levels in the range associated with apoptosis simply indicate, rather than cause, an apoptotic milieu. Model simulations are consistent with this view. In a result of interest to the wider physiology community, the delay effect is shown to provide a GSH-based mechanism by which cells can distinguish transient elevations in H2O2concentration, of use in intracellular signaling, from persistent ones indicative of either pathology or the presence of toxins, the second state of affairs eventually triggering apoptosis.

Whey Protein Peptide Pro-Glu-Trp Ameliorates Hyperuricemia by Enhancing Intestinal Uric Acid Excretion, Modulating the Gut Microbiota, and Protecting the Intestinal Barrier in Rats.

Hyperuricemia (HUA) is a metabolic disorder characterized by an increase in the concentrations of uric acid (UA) in the bloodstream, intricately linked to the onset and progression of numerous chronic diseases. The tripeptide Pro-Glu-Trp (PEW) was identified as a xanthine oxidase (XOD) inhibitory peptide derived from whey protein, which was previously shown to mitigate HUA by suppressing UA synthesis and enhancing renal UA excretion. However, the effects of PEW on the intestinal UA excretion pathway remain unclear. This study investigated the impact of PEW on alleviating HUA in rats from the perspective of intestinal UA transport, gut microbiota, and intestinal barrier. The results indicated that PEW inhibited the XOD activity in the serum, jejunum, and ileum, ameliorated intestinal morphology changes and oxidative stress, and upregulated the expression of ABCG2 and GLUT9 in the small intestine. PEW reversed gut microbiota dysbiosis by decreasing the abundance of harmful bacteria (e.g., Bacteroides, Alloprevotella, and Desulfovibrio) and increasing the abundance of beneficial microbes (e.g., Muribaculaceae, Lactobacillus, and Ruminococcus) and elevated the concentration of short-chain fatty acids. PEW upregulated the expression of occludin and ZO-1 and decreased serum IL-1β, IL-6, and TNF-α levels. Our findings suggested that PEW supplementation ameliorated HUA by enhancing intestinal UA excretion, modulating the gut microbiota, and restoring the intestinal barrier function.

Pharmacokinetics, Disposition, and Biotransformation of [14C]Lenacapavir, a Novel, First-in-Class, Selective Inhibitor of HIV-1 Capsid Function, in Healthy Participants Following a Single Intravenous Infusion.

Lenacapavir (LEN) is a novel, first-in-class, multistage, selective inhibitor of human immunodeficiency virus type 1 (HIV-1) capsid function recently approved for the treatment of HIV-1 infection in heavily treatment-experienced adults with multidrug-resistant HIV-1 infection. The purpose of this multicohort study was to evaluate the pharmacokinetics, metabolism, excretion, safety, and tolerability of LEN following a single intravenous (IV) infusion of 10 mg LEN or 20 mg [14C]LEN in healthy participants. Twenty-one healthy adult participants were enrolled into the study and received either a single IV dose of 10 mg LEN (n = 8 active, n = 3 placebo; cohort 1) or a single IV dose of 20 mg [14C]LEN containing 200 µCi (n = 10; cohort 2). Blood, urine, and feces samples (when applicable) were collected after dosing, and radioactivity (cohort 2) was assessed using liquid scintillation counting in both plasma and excreta. LEN in plasma was quantified by liquid chromatography (LC) tandem mass spectroscopy (MS/MS) method bioanalysis. Metabolite profiling in plasma and excreta were performed using LC-fraction collect (FC)-high-resolution MS and LC-FC-accelerator mass spectrometry in plasma. Between the 10 mg and 20 mg doses of LEN, the observed plasma exposure of LEN doubled, while the elimination half-life was similar. Following administration of 20 mg [14C]LEN (200 µCi), the mean cumulative recovery of [14C] radioactivity was 75.9% and 0.24% from feces and urine, respectively. The mean whole [14C] blood-to-plasma concentration ratio was 0.5-0.7, which showed a low distribution of LEN to red blood cells. Intact LEN was the predominant circulating species in plasma (representing 68.8% of circulating radioactivity), and no single metabolite contributed to >10% of total radioactivity exposure through 1176 h postdose. Similarly, intact LEN was the most abundant component (32.9% of administered dose; 75.9% of recovered dose) measured in feces, with metabolites accounting for trace amounts. These results suggest metabolism of LEN is not a primary pathway of elimination. Of the metabolites observed in the feces, the three most abundant metabolites were direct phase 2 conjugates (glucuronide, hexose, and pentose conjugates), with additional metabolites formed to a lesser extent via other pathways. The administered LEN IV doses were generally safe and well-tolerated across participants in this study. The results of this mass balance study indicated that LEN was majorly eliminated as intact LEN via the feces. The renal pathway played a minor role in LEN elimination (0.24%). In addition, no major circulating metabolites in plasma or feces were found, indicating minimal metabolism of LEN.

Indole Synthesis by Cobalt-Catalyzed Intramolecular Amidation via the Oxidatively Induced Reductive Elimination Pathway

Indole Synthesis by Cobalt-Catalyzed Intramolecular Amidation via the Oxidatively Induced Reductive Elimination Pathway

Expression and function of the urea cycle in widely-used hepatic cellular models.

The group of rare metabolic defects termed urea cycle disorders (UCDs) occur within the ammonia elimination pathway and lead to significant neurocognitive sequelae for patients surviving decompensation episodes. Besides orthotopic liver transplantation, curative options are lacking for UCDs, with dietary management being the gold clinical standard. Novel therapeutic approaches are essential for UCDs; however, such effort presupposes preclinical testing in cellular models that effectively capture disease manifestation. Several cellular and animal models exist and aim to recapitulate the broad phenotypic spectrum of UCDs; however, the majority of those lack extensive molecular and biochemical characterization. The development of cellular models is emerging since animal models are extremely time and cost consuming, and subject to ethical considerations, including the 3R principle that endorses animal welfare over unchecked preclinical testing. The aim of this study was to compare the extent of expression and functionality of the urea cycle in two commercial hepatoma-derived cell lines, induced pluripotent stem cell hepatocytes (iPSC-Heps), primary human hepatocytes (PHHs) and human liver cell preparations. Using immunoblotting, immunocytochemistry, and stable isotope tracing of the urea cycle metabolites, we identified that the hepatoma-derived, 2-week differentiated HepaRG cells are urea cycle proficient and behave as cellular alternatives to PHHs. Furthermore, HepaRG cells were superior to iPSC-Heps, which are known to exhibit batch-to-batch variabilities in terms of hepatic maturity and enzyme expression. Finally, HepG2 cells lack the urea cycle enzymes ornithine transcarbamylase and arginase 1, the transporter ORNT1, which limits their suitability as model for the study of UCDs.

Micellar solution of [223Ra]RaCl2: Reaching renal excretion, potent efficacy in osteoblastic osteosarcoma in PDX model, biochemistry alterations and pharmacokinetics

Despite the successful use of the radiopharmaceutical radium-223 dichloride ([223Ra]RaCl2) for targeted alpha therapy of castration-resistant prostate cancer patients with bone metastases, some short-term side effects, such as diarrhea and vomiting, have been documented, causing patient discomfort. Hence, we prepared a nanosized micellar solution of [223Ra]RaCl2 and evaluated its biodistribution, pharmacokinetics, and induced biochemical changes in healthy mice up to 96 h after intraperitoneal administration as an alternative to overcome the previous limitations. In addition, we evaluated the bone specificity of micellar [223Ra]RaCl2 in patient-derived xenografts in the osteosarcoma model. The biodistribution studies revealed the high bone-targeting properties of the micellar [223Ra]RaCl2. Interestingly, the liver uptake remained significantly low (%ID/g = 0.1–0.02) from 24 to 96 h after administration. In addition, the micellar [223Ra]RaCl2 exhibited a significantly higher uptake in left (%ID/g = 0.85–0.23) and right (%ID/g = 0.76–0.24) kidneys than in small (%ID/g = 0.43–0.06) and large intestines (%ID/g = 0.24–0.09) over time, suggesting its excretion pathway is primarily through the kidneys into the urine, in contrast to the non-micellar [223Ra]RaCl2. The micellar [223Ra]RaCl2 also had low distribution volume (0.055 ± 0.003 L) and longer elimination half-life (28 ± 12 days). This nanosystem was unable to change the enzymatic activities of alanine aminotransferase, aspartate aminotransferase, gamma GT, glucose, and liquiform lipase in the treated mice. Finally, microscopic examination of the animals' osteosarcoma tumors treated with micellar [223Ra]RaCl2 indicated regression of the tumor, with large areas of necrosis. In contrast, in the control group, we observed tumor cellularity and cell anaplasia, mitotic figures and formation of neoplastic extracellular bone matrix, which are typical features of osteosarcoma. Therefore, our findings demonstrated the efficiency and safety of nanosized micellar formulations to minimize the gastrointestinal excretion pathway of the clinical radiopharmaceutical [223Ra]RaCl2, in addition to promoting regression of the osteosarcoma. Further studies must be performed to assess dose–response outcomes and organ/tissue dosimetry for clinical translation.

Crafting an innovative bimetallic MOF-on-MOF/TiO2 composite for effective removal of Imatinib anticancer agent through adsorption and photodegradation

Imatinib (IMB), a widely employed anticancer agent, poses significant environmental concerns due to its release into aquatic ecosystems via pharmaceutical industries and hospital effluents, contributing to water source contamination and consequential impacts on both human and animal health. In light of this, a novel bimetallic MIL-53(Co-Fe)@MIL-53(Ni)/TiO2 composite material has been synthesized utilizing hydrothermal approaches for the efficient adsorption and photodegradation of IMB. Comparative assessments were conducted between this composite and MIL-53(Ni), bimetallic MIL-53(Co-Fe)@MIL-53(Ni), bare TiO2 for their respective capacities in IMB removal through adsorption and photodegradation. Remarkably enhanced efficacy was observed in the synthetic composite's performance for both adsorption and photodegradation, surpassing that of other compounds. Through systematic exploration, critical parameters influencing the adsorption and photodegradation processes were meticulously examined and subsequently optimized utilizing experimental design strategies. Optimal conditions led to the identification of a pseudo-second-order kinetic model for IMB adsorption with a notable rate constant of 8.39 and an equilibrium time of 75 min. The adsorption process conformed favorably to the Freundlich isotherm, as evidenced by the Freundlich constant of 25.498 mg g−1 and adsorption intensity of 2.09. These values underscored the heightened affinity of the synthetic composite relative to IMB, ascribed to the favorable absorption. A complementary investigation into the kinetics of IMB photodegradation unveiled a substantially elevated rate constant of 0.0407 min−1, coupled with a proper half-life of 17.03 min. These collective findings validate the exceptional capacity of the synthesized composite for dual-mode IMB elimination, encompassing both adsorption and photodegradation pathways. This advancement holds significant promise for addressing the environmental repercussions of IMB contamination and points to the potential for broader applications in wastewater treatment and ecological restoration endeavors.

Metabolite characterisation of the peptide–drug conjugate LN005 in liver S9s by UHPLC-Orbitrap-HRMS

LN005 is a peptide–drug conjugate (PDC) targeting glucose-regulated protein 78 (GRP78) to treat several types of cancer, such as breast, colon, and prostate cancer. As a new drug modality, understanding its metabolism and elimination pathways will help us to have a whole picture of it. Currently, there are no metabolic studies on LN005; therefore, this study aimed to investigate the metabolism of LN005, clarify its metabolic profile in the liver S9s of different species, and identify the major metabolic pathways and differences between species. The incubation samples were measured by ultra-high performance liquid chromatography combined with orbitrap tandem mass spectrometry (UHPLC-Orbitrap-HRMS). The results showed that LN005 was metabolised by liver S9s, and four metabolites were identified. The main metabolic pathway of LN005 in liver S9s was oxidative deamination to ketone or hydrolysis. Similar metabolic profiles were observed in mouse, rat, dog, monkey, and human liver S9s, indicating no differences between these four animal species and humans. This study provides information for the structural modification and optimisation of LN005 and affords a reference for subsequent animal experiments and human metabolism of other PDCs.

Pharmacokinetics and pharmacodynamics of perfluoropropane after intra-venous bolus injection of perflutren lipid microsphere injection (DEFINITY®) in healthy Chinese volunteers

Background and objectiveDefinity is an ultrasound contrast agent consisting of phospholipids-encapsulated perfluoropropane (PFP), also known as perflutren, microspheres, which is initially designed to enhance echocardiographic ultrasound images. With no pharmacologic action, Definity can increase the backscatter of ultrasound resulting enhanced ultrasound signals. The objective of this study was to determine the pharmacokinetics (PKs), Pharmacodynamics (PDs) and safety of Definity in healthy male and female Chinese volunteers.MethodsA simple GC-MS method was developed and applied to simultaneously quantify PFP both in human whole blood and in expired air using Perfluorobutane (PFB) as internal standard. Meanwhile, the blood microbubble Doppler intensities were continuously monitored as companion PDs by a Doppler ultrasonography system using a non-imaging method.ResultsAfter intravenous infusion of 10 µL/kg of PFP within 30 seconds, the mean AUClast of the pharmacokinetic analysis set was 0.000653 (uL/mL)*min, the average AUC∞ was 0.001051 (uL/mL)*min. The main coefficient of variation of parameters were within 30%. In this trial, the blood drug concentration of female subjects was lower than that of males. Female Cmax, AUClast and AUC∞ were lower than males’, Tmax and t1/2 was close to males’, Vss and CL were slightly higher than males’. The concentration of PFP in the expired air of the subject reached the maximum value 1–2 min after administration and the PFP accumulation curve in the expired air began to become flat at 9.5–11 min after administration. The PFP in the expired air at the last sampling point of most subjects was still measurable. The results of the analysis showed that female subjects had slightly more and faster PFP excretion via the lungs than males. The change of blood drug concentration in this trial was related to the change process of Doppler signal intensity. The trend of the two was close, but the peak time of blood drug concentration was slightly delayed compared with the peak time of the Doppler signal intensity. The results showed that female tmax−pd, t10 was earlier than male, and women have lower AUCpd than men.ConclusionThe pharmacokinetics and pharmacodynamics of Definity in blood and expired air were systematically evaluated for the first time in this study. The PK/PD analysis results of this trial showed that the change of blood concentration was related to the change process of Doppler signal intensity, the trend of the two was close and expired air are the main excretion pathways of Definity. Definity was well tolerated by all subjects in the trial.Trial registrationThis study was registered on 08 December 2017 at the Chinese Clinical Trial Registry (CTR20171087).

Mechanistic insights into copper-mediated benzylic C(sp3)-H bond trifluoromethylation.

The mechanisms underlying copper-mediated trifluoromethylation of benzylic C(sp3)-H bonds were investigated using density functional theory (DFT) calculations. Two distinct pathways were identified: radical recombination/reductive elimination and single-electron transfer (SET). In the radical recombination/reductive elimination pathway, the CuII species recombines with benzyl radicals to generate a CuIII intermediate, which subsequently undergoes reductive elimination. Conversely, the SET pathway involves single-electron transfer from benzyl radicals to CuII species, forming a cationic benzylic intermediate and CuI species, followed by coupling with a CF3 group coordinated to Cu. DFT calculations revealed that the radical recombination/reductive elimination pathway is favoured for trifluoromethylation of primary and secondary benzylic C(sp3)-H bonds, with the reductive elimination step being rate-determining. In contrast, the SET pathway exhibits preference for trifluoromethylation of tertiary benzylic C(sp3)-H bonds. These mechanistic insights have significant implications for enhancing the selectivity of copper-mediated trifluoromethylation reactions.

Palladium and copper co-catalyzed chloro-arylation of gem-difluorostyrenes - use of a nitrite additive to suppress β-F elimination.

The installation of fluorine and fluorinated functional groups in organic molecules perturbs the physicochemical properties of those molecules and enables the development of new therapeutics, agrichemicals, biological probes and materials. However, current synthetic methodologies cannot access some fluorinated functional groups and fluorinated scaffolds. One such group, the gem-difluorobenzyl motif, might be convergently synthesized by reacting a nucleophilic aryl precursor and an electrophilic gem-difluoroalkene. Previous attempts have relied on forming unstable anionic or organometallic intermediates that rapidly decompose through a β-F elimination process to deliver monofluorovinyl products. In contrast, we report a fluorine-retentive palladium and copper co-catalyzed chloro-arylation of gem-difluorostyrenes that takes advantage of a nitrite (NO2 -) additive to avoid the favorable β-F elimination pathway that forms monofluorinated products, instead delivering difluorinated products.

Using waste to treat waste: facile synthesis of hollow carbon nanospheres from lignin for water decontamination.

Lignin, the most abundant natural material, is considered as a low-value commercial biomass waste from paper mills and wineries. In an effort to turn biomass waste into a highly valuable material, herein, a new-type of hollow carbon nanospheres (HCNs) is designed and synthesized by pyrolysis of biomass dealkali lignin, as an efficient nanocatalyst for the elimination of antibiotics in complex water matrices. Detailed characterization shows that HCNs possess a hollow nanosphere structure, with abundant graphitic C/N and surface N and O-containing functional groups favorable for peroxydisulfate (PDS) activation. Among them, HCN-500 provides the maximum degradation rate (95.0%) and mineralization efficiency (74.4%) surpassing those of most metal-based advanced oxidation processes (AOPs) in the elimination of oxytetracycline (OTC). Density functional theory (DFT) calculations and high-resolution mass spectroscopy (HR-MS) were employed to reveal the possible degradation pathway of OTC elimination. In addition, the HCN-500/PDS system is also successfully applied to real antibiotics removal in complex water matrices (e.g. river water and tap water), with excellent catalytic performances.

Unveiling the oxygen addition kinetics of 1-Hydroxy-2-Hexyl and 2-Hydroxy-1-Hexyl at low temperature

Hydroxyalkyl radicals formed from addition of OH to alkenes play a crucial role in the oxidation of alkenes. The oxygen addition kinetics of 1‑hydroxy-2-hexyl and 2‑hydroxy-1-hexyl at low temperature has been investigated by using quantum chemical calculations coupled with the RRKM/master equation simulations. The main reaction pathways that occur on the potential energy surfaces of HOC6H12 + O2 were studied at the CCSD(T)/CBS(cc-pV[T,Q]Z)//M06–2X/jun-cc-pVTZ level. Rate coefficients of key reactions have been determined at the high-pressure limit and the falloff region. The isomerizations of hydroxyhexylperoxy to hydroperoxy-hydroxyalkyl are found to be of great importance. The formed hydroperoxy-hydroxyalkyl radicals can either dissociate rapidly into aldehydes and ketones, or be accumulated to participate in the second oxygen addition. The formation of formaldehyde, n-pentanal and OH via the Waddington mechanism is among the most important product channels. H2O elimination pathways are identified for the most stable HOQOOH intermediates, with the radical site at α-carbon to the hydroxy group. The present study recognizes those hydroperoxy-hydroxyalkyl radicals that are able to undergo the second oxygen addition. Kinetic analysis reveals that the facile formation via 1,5 or 1,6 H-transfer and lack of fast decomposition pathways combine to enable the accumulation of particular hydroperoxy-hydroxyalkyl radicals, facilitating their involvement in subsequent chain-branching chemistry. This study further illuminates the intricate understanding of the low temperature chemistry of larger alkenes.

Formation of uranium disulfide from a uranium thioamidate single-source precursor.

A single-source-precursor approach was developed to synthesize uranium-based materials outside of the typically-studied oxides. This approach allows for shorter reaction times, milder reaction conditions, and control over the chemicals present in synthesis. To this end, the first homoleptic uranium thioamidate complex was synthesized as a precursor for US2 materials. Pyrolysis of the thioamidate results in decomposition via an alkene elimination pathway and formation of γ-US2, which has historically been hard to access without the need for a secondary sulfur source. Despite the oxophilicity of uranium, the method successfully forms US2 without the inclusion of oxygen in the bulk final product. These findings are supported by simultaneous thermal analysis, elemental analysis, powder X-ray diffraction, and uranium L3-edge X-ray absorption fine-structure spectroscopy. This work represents the first example of a single-source precursor approach to target and synthesize actinide materials other than the oxides.

Mechanistic insights into facilitating reductive elimination from Ni(II) species.

Reductive elimination is a key step in Ni-catalysed cross-couplings, which is often considered to result in new covalent bonds. Due to the weak oxidizing ability of Ni(II) species, reductive eliminations from Ni(II) centers are challenging. A thorough mechanistic understanding of this process could inspire the rational design of Ni-catalysed coupling reactions. In this article, we give an overview of recent advances in the mechanistic study of reductive elimination from Ni(II) species achieved by our group. Three possible models for reductive elimination from Ni(II) species were investigated and discussed, including direct reductive elimination, electron density-controlled reductive elimination, and oxidation-induced reductive elimination. Notably, the direct reductive elimination from Ni(II) species often requires a high activation energy in some cases. In contrast, the electron density-controlled and oxidation-induced reductive elimination pathways can significantly enhance the driving force for reductive elimination, accelerating the formation of new covalent bonds. The intricate reaction mechanisms for each of these pathways are thoroughly discussed and systematically summarized in this paper. These computational studies showcase the characteristics of three models for reductive elimination from Ni(II) species, and we hope that it will spur the development of mechanistic studies of cross-coupling reactions.

In vivo pharmacokinetics of Glycyrrhiza uralensis polysaccharides.

Glycyrrhiza uralensis polysaccharides (GUPS) are widely applied in biomedicine and functional food due to their multiple pharmacological activities and low toxicity. Despite their widespread use, the in vivo metabolic profile of GUPS remains poorly understood. To address this gap, we developed a quantitative analysis method that involves labeling GUPS with visible fluorescein (5-DTAF) and near-infrared (NIR) fluorescein (Cy7), resulting in stable conjugates with substitution degrees of 0.81% for 5-DTAF and 0.39% for Cy7. The pharmacokinetic studies showed a biphasic elimination pattern in the blood concentration-time curve following both intravenous and oral administration, consistent with a two-compartment model. Using fluorescence quantification and NIR imaging, we observed that GUPS was distributed to various tissues, exhibiting higher concentrations particularly in liver, kidney and lung. Excretion studies indicated that feces were the major excretion pathway of GUPS after oral administration (60.98%), whereas urine was the main pathway after intravenous administration (31.16%). Notably, GUPS could be absorbed rapidly by gut (Tmax 1 ± 0.61h) and showed a biological half-time t1/2 26.4 ± 7.72h after oral administration. Furthermore, the Caco-2 cells uptake studies illustrated that macropinocytosis and clathrin-mediated endocytosis were participated in the transport of GUPS in intestine epithelium. This comprehensive analysis of the in vivo pharmacokinetics of GUPS not only enhances our understanding of its metabolic pathways but also establishes a foundational basis for its clinical application, optimizing its therapeutic potential and safety profile.

Ultrasmall Mn-doped iron oxide nanoparticles with dual hepatobiliary and renal clearances for T1 MR liver imaging.

Although magnetic nanoparticles demonstrate significant potential as magnetic resonance imaging (MRI) contrast agents, their negative contrasts, liver accumulation, and limited excretion hinder their application. Herein, we developed ultrasmall Mn-doped iron oxide nanoparticles (UMIOs) with distinct advantages as T1 MRI contrast agents. Exceptionally small particle sizes (ca. 2 nm) and magnetization values (5 emu gMn+Fe-1) of UMIOs provided optimal T1 contrast effects with an ideally low r2/r1 value of ∼1. Furthermore, the use of Mn as a dopant facilitated hepatocyte uptake of the particles, allowing liver imaging. In animal studies, UMIOs exhibited significantly enhanced contrasts for sequential T1 imaging of blood vessels and the liver, distinguishing them from conventional magnetic nanoparticles. UMIOs were systematically cleared via dual hepatobiliary and renal excretion pathways, highlighting their safety profile. These characteristics imply substantial potential of UMIOs as T1 contrast agents for the accurate diagnosis of liver diseases.

Modeling the Drug delivery Lifecycle of PLG Nanoparticles Using Intravital Microscopy.

Polylactide-co-glycolide (PLG) nanoparticles hold immense promise for cancer therapy due to their enhanced efficacy and biodegradable matrix structure. Understanding their interactions with blood cells and subsequent biodistribution kinetics is crucial for optimizing their therapeutic potential. In this study, three doxorubicin-loaded PLG nanoparticle systems are synthesized and characterized, analyzing their size, zeta potential, morphology, and in vitro release behavior. Employing intravital microscopy in 4T1-tumor-bearing mice, real-time blood and tumor distribution kinetics are investigated. A mechanistic pharmacokinetic model is used to analyze biodistribution kinetics. Additionally, flow cytometry is utilized to identify cells involved in nanoparticle hitchhiking. Following intravenous injection, PLG nanoparticles exhibit an initial burst release (<1min) and rapidly adsorb to blood cells (<5min), hindering extravasation. Agglomeration leads to the clearance of one carrier species within 3min. In stable dispersions, drug release rather than extravasation remains the dominant pathway for drug elimination from circulation. This comprehensive investigation provides valuable insights into the interplay between competing kinetics that influence the lifecycle of PLG nanoparticles post-injection. The findings advance the understanding of nanoparticle behavior and lay the foundation for improved cancer therapy strategies using nanoparticle-based drug delivery systems.