Autophagy plays a crucial role in the metabolic process. So far, conventional methods are incapable of rapid, precise, and real-time monitoring of autophagy in living objects. Herein, we describe an in situ intracellular self-assembly strategy for quantitative and temporal determination of autophagy in living objectives. The intelligent building blocks (DPBP) are composed by a bulky dendrimer as a carrier, a bis(pyrene) derivative (BP) as a signal molecule, and a peptide linker as a responsive unit that can be cleaved by an autophagy-specific enzyme, i.e., ATG4B. DPBP maintains the quenched fluorescence with monomeric BP. However, the responsive peptide is specifically tailored upon activation of autophagy, resulting in self-aggregation of BP residues which emit a 30-fold enhanced fluorescence. By measuring the intensity of fluorescent signal, we are able to quantitatively evaluate the autophagic level. In comparison with traditional techniques, such as TEM, Western blot, and GFP-LC3, the reliability and accuracy of this method are finally validated. We believe this in situ intracellular self-assembly strategy provides a rapid, effective, real-time, and quantitative method for monitoring autophagy in living objects, and it will be a useful tool for autophagy-related fundamental and clinical research.

In drug delivery systems, pH-sensitive polymers are commonly used as drug carriers, and significant efforts have been devoted to the aspects of controlled delivery and release of drugs. However, few studies address the possible autophagic effects on cells. Here, for the first time, using a fluorescent autophagy-reporting cell line, this study evaluates the autophagy-induced capabilities of four types of pH-sensitive polymeric nanoparticles (NPs) with different physical properties, including size, surface modification, and pH-sensitivity. Based on experimental results, this study concludes that pH-sensitivity is one of the most important factors in autophagy induction. In addition, this study finds that variation of concentration of NPs could cause different autophagic effect, i.e., low concentration of NPs induces autophagy in an mTOR-dependent manner, but high dose of NPs leads to autophagic cell death. Identification of this tunable autophagic effect offers a novel strategy for enhancing therapeutic effect in cancer therapy through modulation of autophagy.

Various nanomaterials have been demonstrated as autophagy inducers owing to their endocytosis cell uptake pathway and impairment of lysosomes. pH-dependent nanomaterials as drug delivery systems that are capable of dissociating in weakly acidic lysosomal environment (pH 4-5) and consequently releasing the payloads into the cytoplasm have been paid extensive attention, but their autophagy-modulating effects are less reported so far. In this study, we report pH-sensitive micelle-like nanoparticles (NPs) that self-assembled from poly(β-amino ester)s to induce cell autophagy. By encapsulation of gold(I) compounds (Au(I)) into hydrophobic domains of NPs, the resultant Au(I)-loaded NPs (Au(I)⊂NPs) shows synergistic cancer cell killing performance. The Au(I)⊂NPs enter cells through endocytosis pathway and accumulate into acidic lysosomes. Subsequently, the protonation of tertiary amines of poly(β-amino ester)s triggers the dissociation of micelles, damages the lysosomes, and blocks formation of autolysosomes from fusion of lysosomes with autophagosomes. In addition, Au(I) preferentially inhibits thioredoxin reductase (TrxR) in MCF-7 human breast cancer cells that directly links to up-regulate reactive oxygen species (ROS) and consequently induce autophagy and apoptosis. The blockade of autophagy leads to excessive depletion of cellular organelles and essential proteins and ultimately results in cell death. Therefore, pH-sensitive polymeric nanoparticles with gold(I) compound payloads can synergistically induce cancer cell death through regulation of autophagy. Identification of the pH-sensitive nanomaterials for synergistically inducing cell death through regulation autophagy may open a new avenue for cancer therapy.

Objective. To investigate the association between intestinal permeability and severity of nonalcoholic fatty liver disease (NAFLD) and the value of intestinal permeability in predicting the efficacy of metabolic therapy for NAFLD. Methods. Disease severity was compared between patients with normal and elevated intestinal permeability; correlations between D-lactate and different NAFLD parameters were analyzed; and the effects of metabolic therapy on NAFLD patients with normal and elevated intestinal permeability were evaluated. Results. A total of 190 patients with NAFLD were enrolled. NAFLD patients with elevated intestinal permeability had significantly higher levels of liver test parameters, liver ultrasonographic fat attenuation parameter, triglyceride, homeostasis model assessment of insulin resistance value, and diamine oxidase (all P˂0.05) than NAFLD patients with normal intestinal permeability. Furthermore, serum D-lactate levels were positively correlated with alanine transaminase, aspartate transaminase, gamma-glutamyl transpeptidase, total bilirubin, indirect bilirubin, fat attenuation parameter, triglyceride, and diamine oxidase (all P  ˂ 0.05). Moreover, NAFLD patients with elevated intestinal permeability showed less improvement in TG levels ( P  = 0.014) after metabolic therapy. Conclusion. Intestinal permeability correlates with the disease severity in patients with NAFLD. Moreover, intestinal permeability may have value for predicting the efficacy of metabolic therapy for NAFLD patients.