Canagliflozin ameliorates high glucose-induced apoptosis in NRK-52E cells via inhibiting oxidative stress and activating AMPK/mTOR-mediated autophagy.

BACKGROUND: Sodium-glucose cotransporter-2 (SGLT-2) inhibitors, as a new type of hypoglycemic drug, can prevent proximal renal tubule injury related to glucose toxicity and play a renoprotective role. Canagliflozin, a recognized SGLT-2 inhibitor, has been proved to have potential protection in diabetic nephropathy (DN), but its mechanism has not been fully elucidated. In this study, the protective effect of canagliflozin against high glucose (HG)-induced renal tubular epithelial cell (NRK-52E) injury in vitro was assessed. METHODS: The viability and apoptosis of NRK-52E cells were detected using cell counting kit-8 (CCK-8) assay and flow cytometry analysis, respectively. The expression levels of cleaved caspase-3, oxidative stress-related proteins (NOX4 and Nrf2), autophagy marker light chain 3 (LC3) I/II, and adenosine monophosphate-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) signaling pathway-related proteins were evaluated by Western blot. Reactive oxygen species (ROS) level was evaluated by dihydroethidium (DHE) reactive oxygen species assay, the activities of SOD, CAT, GSH-Px and MDA were analyzed using kits. The changes of morphology and red fluorescent protein (RFP)-LC3 fluorescence were observed under microscopy. RESULTS: Canagliflozin significantly ameliorated HG-induced NRK-52E cell apoptosis and caspase-3 cleavage. Furthermore, canagliflozin markedly ameliorated HG-induced NRK-52E cell oxidative stress. Moreover, canagliflozin significantly increased LC3-II levels and induced RFP-LC3-containing punctate structures in NRK-52E cells. Finally, canagliflozin increased the phosphorylation of AMPK and suppressed the phosphorylation of mTOR. The AMPK inhibitor compound C abolished canagliflozin-induced autophagy activation, as well as the anti-apoptotic effect of canagliflozin. CONCLUSION: Canagliflozin effectively ameliorate HG-induced apoptosis of NRK-52E cells in vitro that involved its antioxidant effect and induction of autophagy through the AMPK/mTOR pathway.

Neutrophil-inspired photothermo-responsive drug delivery system for targeted treatment of bacterial infection and endotoxins neutralization.

BACKGROUND: P. aeruginosa, a highly virulent Gram-negative bacterium, can cause severe nosocomial infections, and it has developed resistance against most antibiotics. New therapeutic strategies are urgently needed to treat such bacterial infection and reduce its toxicity caused by endotoxin (lipopolysaccharide, LPS). Neutrophils have been proven to be able to target inflammation site and neutrophil membrane receptors such as Toll-like receptor-4 (TLR4) and CD14, and exhibit specific affinity to LPS. However, antibacterial delivery system based on the unique properties of neutrophils has not been reported. METHODS: A neutrophil-inspired antibacterial delivery system for targeted photothermal treatment, stimuli-responsive antibiotic release and endotoxin neutralization is reported in this study. Specifically, the photothermal reagent indocyanine green (ICG) and antibiotic rifampicin (RIF) are co-loaded into poly(lactic-co-glycolic acid) (PLGA) nanoparticles (NP-ICG/RIF), followed by coating with neutrophil membrane to obtain antibacterial delivery system (NM-NP-ICG/RIF). The inflammation targeting properties, synergistic antibacterial activity of photothermal therapy and antibiotic treatment, and endotoxin neutralization have been studied in vitro. A P. aeruginosa-induced murine skin abscess infection model has been used to evaluate the therapeutic efficacy of the NM-NP-ICG/RIF. RESULTS: Once irradiated by near-infrared lasers, the heat generated by NP-ICG/RIF triggers the release of RIF and ICG, resulting in a synergistic chemo-photothermal antibacterial effect against P. aeruginosa (~ 99.99% killing efficiency in 5 min). After coating with neutrophil-like cell membrane vesicles (NMVs), the nanoparticles (NM-NP-ICG/RIF) specifically bind to inflammatory vascular endothelial cells in infectious site, endowing the nanoparticles with an infection microenvironment targeting function to enhance retention time. Importantly, it is discovered for the first time that NMVs-coated nanoparticles are able to neutralize endotoxins. The P. aeruginosa murine skin abscess infection model further demonstrates the in vivo therapeutic efficacy of NM-NP-ICG/RIF. CONCLUSION: The neutrophil-inspired antibacterial delivery system (NM-NP-ICG/RIF) is capable of targeting infection microenvironment, neutralizing endotoxin, and eradicating bacteria through a synergistic effect of photothermal therapy and antibiotic treatment. This drug delivery system made from FDA-approved compounds provides a promising approach to fighting against hard-to-treat bacterial infections.

Interpenetrating Polymer Network Hydrogels Formed Using Antibiotics as a Dynamic Crosslinker for Treatment of Infected Wounds.

Antibacterial hydrogels, particularly antibiotic-loaded hydrogels, are promising wound dressing materials for treatment of bacteria-infected wound. However, it is challenging to achieve sustained release of antibiotics from hydrogels through physical encapsulation of the antibiotics. Herein, an interpenetrating polymer network P(AA-co-HEMA)Gen hydrogel is reported with double crosslinking formed by free radical polymerization of 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA), while using the antibiotic gentamicin (Gen) as the dynamic physical crosslinker. Gentamicin is incorporated into the hydrogel networks via electrostatic interaction between the carboxyl groups of poly(acrylic acid) and the amino groups of gentamicin, which leads to pH-responsive drug release and a significant increase in mechanical strength (i.e., elastic modulus, viscous modulus, and compressive modulus). More importantly, the hydrogels with optimal compositions demonstrate long-lasting antibacterial activity against both Gram-positive bacteria (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli) over 28 d. The in vivo studies that are conducted in an S. aureus-infected full-thickness skin wound model demonstrate that the double crosslinking hydrogels loaded with gentamicin eliminate bacteria in the wounds more effectively and significantly accelerate wound healing as compared to 3M dressing and the control without any treatment. Taken together, this antibiotic-loaded interpenetrating polymer network hydrogel is potentially a promising wound dressing material for the treatment of bacteria-infected wound.

Synthetic peptide hydrogels as 3D scaffolds for tissue engineering.

The regeneration of tissues and organs poses an immense challenge due to the extreme complexity in the research work involved. Despite the tissue engineering approach being considered as a promising strategy for more than two decades, a key issue impeding its progress is the lack of ideal scaffold materials. Nature-inspired synthetic peptide hydrogels are inherently biocompatible, and its high resemblance to extracellular matrix makes peptide hydrogels suitable 3D scaffold materials. This review covers the important aspects of peptide hydrogels as 3D scaffolds, including mechanical properties, biodegradability and bioactivity, and the current approaches in creating matrices with optimized features. Many of these scaffolds contain peptide sequences that are widely reported for tissue repair and regeneration and these peptide sequences will also be discussed. Furthermore, 3D biofabrication strategies of synthetic peptide hydrogels and the recent advances of peptide hydrogels in tissue engineering will also be described to reflect the current trend in the field. In the final section, we will present the future outlook in the design and development of peptide-based hydrogels for translational tissue engineering applications.