Molecular Visual Sensing, Boolean Logic Computing, and Data Security Using a Droplet-Based Superwetting Paradigm

Inspired by information processing and logic operations of life, many artificial biochemical systems have been designed for applications in molecular information processing. However, encoding the binary synergism between matter, energy, and information in a superwetting system remains challenging. Herein, a superwetting paradigm was proposed for multifunctional applications including molecular visual sensing and data security on a superhydrophobic surface. A Triton X-100-encapsulated gelatin (TeG) hydrogel was prepared and selectively decomposed by trypsin, releasing the surfactant to decrease the surface tension of a droplet. Integrating the droplet with the superhydrophobic surface, the superwetting behavior was utilized for visual detection and information encoding. Interestingly, the proposed TeG hydrogel can function as an artificial gelneuron for molecular-level logic computing, where the combination of matters (superhydrophobic surface, trypsin, and leupeptin) acts as inputs to interact with energy (liquid surface tension and solid surface energy) and information (binary character), resulting in superwettability transitions (droplet surface tension, contact angle, rolling angle, and bounce) as outputs. Impressively, the TeG gelneuron can be further developed as molecular-level double cryptographic steganography to encode, encrypt, and hide specific information (including the maze escape route and content of the classical literature) due to its programmability, stimuli responsive ability, and droplet concealment. This study will encourage the development of advanced molecular paradigms and their applications, such as superwetting visual sensing, molecular computing, interaction, and data security.

Acute exercise rapidly activates hepatic mitophagic flux

Exercise is critical for improving metabolic health and putatively maintains or enhances mitochondrial quality control in metabolic tissues. Although previous work has shown that exercise elicits hepatic mitochondrial biogenesis, it is unknown if acute exercise activates hepatic mitophagy, the selective degradation of damaged or low-functioning mitochondria. We tested if an acute bout of treadmill running increased hepatic mitophagic flux both right after and 2-h postexercise in 15- to 24-wk-old C57BL/6J female mice. Acute exercise did not significantly increase markers of autophagic flux, however, mitophagic flux was activated 2-h post-treadmill running as measured by accumulation of both LC3-II and p62 in isolated mitochondria in the presence of leupeptin, an inhibitor of autophagosome degradation. Furthermore, mitochondrial-associated ubiquitin, which recruits the autophagy receptor protein p62, was also significantly increased at 2 h. Further examination via Western blot and proteomics analysis revealed that acute exercise elicits a time-dependent, dynamic activation of mitophagy pathways. Moreover, the results suggest that exercise-induced hepatic mitophagy is likely mediated by both polyubiquitination and receptor-mediated signaling pathways. Overall, we provide evidence that acute exercise activates hepatic mitophagic flux while also revealing specific receptor-mediated proteins by which exercise maintains mitochondrial quality control in the liver.NEW & NOTEWORTHY This study provides evidence that acute exercise activates hepatic mitophagic flux and mitochondrial polyubiquitination while additionally revealing specific receptor-mediated proteins by which exercise maintains mitochondrial quality control in the liver.

Mechanism of Microbial Metabolite Leupeptin in the Treatment of COVID-19 by Traditional Chinese Medicine Herbs

Coronavirus disease 2019 (COVID-19) has caused huge deaths and economic losses worldwide in the current pandemic. The main protease (M^pro) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is thought to be an ideal drug target for treating COVID-19. Leupeptin, a broad-spectrum covalent inhibitor of serine, cysteine, and threonine proteases, showed inhibitory activity against M^pro, with a 50% inhibitory concentration (IC₅₀) value of 127.2 μM in vitro in our study here. In addition, leupeptin can also inhibit SARS-CoV-2 in Vero cells, with 50% effective concentration (EC₅₀) values of 42.34 μM. More importantly, various strains of streptomyces that have a broad symbiotic relationship with medicinal plants can produce leupeptin and leupeptin analogs to regulate autogenous proteases. Fingerprinting and structure elucidation using high-performance liquid chromatography (HPLC) and high-resolution mass spectrometry (HRMS), respectively, further proved that the Qing-Fei-Pai-Du (QFPD) decoction, a traditional Chinese medicine (TCM) formula for the effective treatment of COVID-19 during the period of the Wuhan outbreak, contains leupeptin. All these results indicate that leupeptin at least contributes to the antiviral activity of the QFPD decoction against SARS-CoV-2. This also reminds us to pay attention to the microbiomes in TCM herbs as streptomyces in the soil might produce leupeptin that will later infiltrate the medicinal plant. We propose that plants, microbiome, and microbial metabolites form an ecosystem for the effective components of TCM herbs.

Making and Breaking Leupeptin Protease Inhibitors in Pathogenic Gammaproteobacteria

Leupeptin is a bacterial small molecule that is used worldwide as a protease inhibitor. However, its biosynthesis and genetic distribution remain unknown. We identified a family of leupeptins in gammaproteobacterial pathogens, including Photorhabdus, Xenorhabdus, and Klebsiella species, amongst others. Through genetic, metabolomic, and heterologous expression analyses, we established their construction by discretely expressed ligases and accessory enzymes. In Photorhabdus species, a hypothetical protein required for colonizing nematode hosts was established as a new class of proteases. This enzyme cleaved the tripeptide aldehyde protease inhibitors, leading to the formation of "pro-pyrazinones" featuring a hetero-tricyclic architecture. In Klebsiella oxytoca, the pathway was enriched in clinical isolates associated with respiratory tract infections. Thus, the bacterial production and proteolytic degradation of leupeptins can be associated with animal colonization phenotypes.

Age-related disruption of autophagy in dermal fibroblasts modulates extracellular matrix components

Autophagy is an intracellular degradative system that is believed to be involved in the aging process. The contribution of autophagy to age-related changes in the human skin is unclear. In this study, we examined the relationship between autophagy and skin aging. Transmission electron microscopy and immunofluorescence microscopy analyses of skin tissue and cultured dermal fibroblasts derived from women of different ages revealed an increase in the number of nascent double-membrane autophagosomes with age. Western blot analysis showed that the amount of LC3-II, a form associated with autophagic vacuolar membranes, was significantly increased in aged dermal fibroblasts compared with that in young dermal fibroblasts. Aged dermal fibroblasts were minimally affected by inhibition of autophagic activity. Although lipofuscin autofluorescence was elevated in aged dermal fibroblasts, the expression of Beclin-1 and Atg5-genes essential for autophagosome formation-was similar between young and aged dermal fibroblasts, suggesting that the increase of autophagosomes in aged dermal fibroblasts was due to impaired autophagic flux rather than an increase in autophagosome formation. Treatment of young dermal fibroblasts with lysosomal protease inhibitors, which mimic the condition of aged dermal fibroblasts with reduced autophagic activity, altered the fibroblast content of type I procollagen, hyaluronan and elastin, and caused a breakdown of collagen fibrils. Collectively, these findings suggest that the autophagy pathway is impaired in aged dermal fibroblasts, which leads to deterioration of dermal integrity and skin fragility.

Prion formation correlates with activation of translation-regulating protein 4E-BP and neuronal transcription factor Elk1

Cellular mechanisms play a role in conversion of the normal prion protein PrP(C) to the disease-associated protein PrP(Sc). The cells provide not only PrP(C), but also still largely undefined factors required for efficient prion replication. Previously, we have observed that interference with ERK and p38-JNK MAP kinase pathways has opposing effects on the formation of prions indicating that the process is regulated by a balance in intracellualar signaling pathways. In order to obtain a "flow-chart" of such pathways, we here studied the activation of MEK/ERK and mTORC1 downstream targets in relation to PrP(Sc) accumulation in GT1-1 cells infected with the RML or 22L prion strains. We show that inhibition of mTORC1 with rapamycin causes a reduction of PrP(Sc) accumulation at similar low levels as seen when the interaction between the translation initiation factors eIF4E and eIF4G downstream mTORC1 is inhibited using 4EGI-1. No effect is seen following the inhibition of molecules (S6K1 and Mnk1) that links MEK/ERK signaling to mTORC1-mediated control of translation. Instead, stimulation (high [KCl] or [serum]) or inhibition (MEK-inhibitor) of prion formation is associated with increased or decreased phosphorylation of the neuronal transcription factor Elk1, respectively. This study shows that prion formation can be modulated by translational initiating factors, and suggests that MEK/ERK signaling plays a role in the conversion of PrP(C) to PrP(Sc) via an Elk1-mediated transcriptional control. Altogether, our studies indicate that prion protein conversion is under the control of intracellular signals, which hypothetically, under certain conditions may elicit irreversible responses leading to progressive neurodegenerative diseases.

Protease inhibitor coinfusion with amyloid beta-protein results in enhanced deposition and toxicity in rat brain

Amyloid beta-protein, Abeta, is normally produced in brain and is cleared by unknown mechanisms. In Alzheimer's disease (AD), Abeta accumulates in plaque-like deposits and is implicated genetically in neurodegeneration. Here we investigate mechanisms for Abeta degradation and Abeta toxicity in vivo, focusing on the effects of Abeta40, which is the peptide that accumulates in apolipoprotein E4-associated AD. Chronic intraventricular infusion of Abeta40 into rat brain resulted in limited deposition and toxicity. Coinfusion of Abeta40 with the cysteine protease inhibitor leupeptin resulted in increased extracellular and intracellular Abeta immunoreactivity. Analysis of gliosis and TUNEL in neuron layers of the frontal and entorhinal cortex suggested that leupeptin exacerbated Abeta40 toxicity. This was supported further by the neuronal staining of cathepsin B in endosomes or lysosomes, colocalizing with intracellular Abeta immunoreactivity in pyknotic cells. Leupeptin plus Abeta40 caused limited but significant neuronal phospho-tau immunostaining in the entorhinal cortex. Intriguingly, Abeta40 plus leupeptin induced intracellular accumulation of the more toxic Abeta, Abeta42, in a small group of septal neurons. Leupeptin infusion previously has been reported to interfere with lysosomal proteolysis and to result in the accumulation of lipofuscin, dystrophic neurites, tau- and ubiquitin-positive inclusions, and structures resembling paired helical filaments. Coinfusion of Abeta40 with the serine protease inhibitor aprotinin also increased diffuse extracellular deposition but reduced astrocytosis and TUNEL and was not associated with intracellular Abeta staining. Collectively, these data suggest that an age or Alzheimer's-related defect in lysosomal/endosomal function could promote Abeta deposition and DNA fragmentation in neurons and glia similar to that found in Alzheimer's disease.

Role of the degradation process in the mitogenic effect of epidermal growth factor

The protease inhibitor leupeptin inhibits the degradation process of (125)I-labeled epidermal growth factor ((125)I-EGF) by cultured bovine granulosa cells. At 80 mug/ml, leupeptin inhibited the appearance of degradation products of (125)I-EGF in the medium by 95% during 1 hr of incubation and by 90% during 24 hr of incubation when the cells were exposed to 5 ng of (125)I-EGF per ml. In contrast, cultures exposed to either saturating (10 ng/ml) or nonsaturating (0.1 ng/ml) concentrations of EGF in the presence of leupeptin (80 mug/ml) exhibited an increase in DNA synthesis that was 70-80% that of cultures exposed to EGF alone. Cultures responded to either EGF or fibroblast growth factor with a logarithmic increase in cell number and, over a period of 8 days, the number of cells increased 10- to 18-fold. Addition of leupeptin did not diminish the growth rate of the cultures. In the presence of leupeptin, (125)I-EGF accumulated within the granulosa cells and was in a form that was precipitable with antiserum against EGF and that comigrated on isoelectric focusing with native (125)I-EGF. That a full mitogenic response can be obtained despite a 90-95% inhibition of EGF degradation at either saturating or nonsaturating concentrations of the mitogen suggests that a proteolytic degradation of a given mitogen may not be involved in the induction of a proliferative response.