A preliminary study of the innate immune memory of Kupffer cells induced by PEGylated nanoemulsions.

The accelerated blood clearance (ABC) phenomenon describes a dilemma of polyethylene glycol (PEG) applied in drug delivery system (DDS) caused by its immunogenicity, that results in the enhanced blood clearance rate and increased hepatic and splenic accumulation after secondary injection of PEGylated nanocarriers. However, the ABC index, as the judgement of ABC phenomenon, only describes the accelerated blood clearance rate, but ignores the enhanced hepatic and splenic accumulation. Therefore, we proposed the hepatic accumulation (HA) index and the splenic accumulation (SA) index as supplements for assessing the ABC phenomenon, to emphasize the contribution of liver and spleen, especially the liver, possessing the most population of tissue resident macrophages. By altering the first injection site from the tail vein to the liver portal vein, there was no impact on anti-PEG IgM production, and the secondary hepatic accumulation of PEGylated nanoemulsions (PE) was observed to be proportionate to the first PE stimulation strength on the liver. We also determined that Kupffer cells (KCs) were the main contributor to this enhancement. On this basis, we revealed a definite phenomenon that PE could induce innate immune memory in KCs, by enhancing the phagocytosis of KCs toward PE during the secondary stimulation. The PE-stimulated KCs could carry this memory to the naïve rats through adoptive transfer, resulting in increased hepatic accumulation in the recipient rats without antibody production. Studies examining the phagocytosis of KCs in vivo, ex vivo and in vitro revealed that the memory of KCs against PE triggered by first-stimulated PE could be maintained independently of other cells or components until 21 days after the first stimulation, and possessing specificity to PEG, which was invalid to long-circulating GE (GM1 modified nanoemulsions). The discovery of immune memory in KCs induced by PE highlights the importance of focusing on the relationship between the innate immune system and PEGylated nanocarriers during the development of DDS to improve medication safety in the clinic.

The detoxification mechanisms of low-accumulating and non-low-accumulating medicinal plants under Cd and Pb stress.

Recently, the levels of heavy metals in medicinal plants have aroused widespread concern because these elements usually enter the food chain through plants and are gradually passed to the final consumers, greatly threatening human health. To reduce heavy metal pollution, it is necessary to solve the problem from the source to ensure environmental quality during medicinal material production. We use low-accumulating and non-low-accumulating medicinal plants to remediate soil contaminated by Cd and Pb. This experiment aims to study the amino acid levels in root exudates, to study antioxidant enzymes and malondialdehyde (MDA) in leaves, and to discuss the detoxification mechanisms of low-accumulating and non-low-accumulating medicinal plants under Cd and Pb stress. In soil contaminated with Cd or Pb, catnip, thyme and Fineleaf Schizonepeta Herb were cultivated. Enrichment factor (EF) and translocation factor (TF) levels were calculated to determine which are low-accumulating medicinal plants with respect to Cd or Pb. The relationships between the amino acid levels in root exudates, the levels of antioxidant enzymes, the present heavy metal species, heavy metal concentrations, and plant species were discussed. Under Pb and Cd stress, the total amounts of amino acids secreted by plant roots and the level of each amino acid were associated with the heavy metal concentrations and plant species. Plants alleviate Pb and Cd stress via adding malondialdehyde (MDA) and antioxidant enzymes. Thyme can be used as a low-accumulating medicinal plant with any concentration of the heavy metal Pb. These results are of great significance for understanding the chemical behaviors of heavy metals at the root/soil interface under Cd and Pb stress and the detoxification mechanisms of medicinal plants.

Accelerated Blood Clearance of Nanoemulsions Modified with PEG-Cholesterol and PEG-Phospholipid Derivatives in Rats: The Effect of PEG-Lipid Linkages and PEG Molecular Weights.

Various types of nanocarriers modified with poly(ethylene glycol) (PEG) exhibit the accelerated blood clearance (ABC) phenomenon, resulting in reduced circulation time and abnormal increase in hepatic and splenic accumulations. Based on the abundance of esterases in the serum of rats, we developed cleavable methoxy PEG-cholesteryl methyl carbonate (mPEG-CHMC) with a carbonate linkage and noncleavable N-(carbonyl-methoxy PEG-n)-1,2-distearoyl-sn-glycero-3-phos-phoethanolamine (mPEG-DSPE) with a carbamate linkage on the surface of the nanoemulsions (CHMCE and PE, respectively). Both PEG derivatives possessed PEG with six different molecular weights (n = 350, 550, 750, 1000, 2000, and 5000). The pharmacokinetic behaviors and biodistributions of single and repeated injection of the two types of PEGylated nanoemulsions were determined to investigate the influence of cleavable linkages and PEG molecular weights on the ABC phenomenon in an attempt to find a potential strategy to eliminate the ABC phenomenon. CHMCEns (n = 1000, 2000, and 5000) exhibited the same pharmacokinetic behaviors as PE550 and PE750 and only alleviated the ABC phenomenon to a certain extent at the expense of shortened cycle time, indicating that the cleavable carbonate linkage was not an ideal strategy to eliminate the ABC phenomenon. As the molecular weights of PEG increased, the ABC phenomenon became more severe. Surprisingly, PE5000 induced a lower anti-PEG IgM level and a weaker ABC phenomenon compared with PE2000 while possessing a similar long circulation time. The results suggested that increasing the molecular weight of PEG in the PEG derivatives could be a potential strategy for eliminating the ABC phenomenon while simultaneously guaranteeing longer circulation time.