Curcumin prevents As3+-induced carcinogenesis through regulation of GSK3ß/Nrf2.

BACKGROUND: Arsenic (As3+) is a carcinogen with considerable environmental and occupational relevancy. Its mechanism of action and methods of prevention remain to be investigated. Previous studies have demonstrated that ROS is responsible for As3+-induced cell transformation, which is considered as the first stage of As3+ carcinogenesis. The NF-E2 p45-related factor-2 (Nrf2) signaling pathway regulates the cellular antioxidant response, and activation of Nrf2 has recently been shown to limit oxidative damage following exposure to As3+ METHODS AND RESULTS: In this study, molecular docking was used to virtually screen natural antioxidant chemical databases and identify molecules that interact with the ligand-binding site of Keap1 (PDB code 4L7B). The cell-based assays and molecular docking findings revealed that curcumin has the best inhibitory activity against Keap1-4L7B. Co-immunoprecipitation (Co-IP) results indicated that curcumin is a potent Keap1 Kelch domain-dependent Nrf2 activator that stabilizes Nrf2 by hindering its ubiquitination. The increased activation of Nrf2 and its target antioxidant genes by curcumin could significantly decrease As3+-generated ROS. Moreover, curcumin induced autophagy in As3+-treated BEAS-2B via inducing autophagy by the formation of a p62/LC-3 complex and increasing autophagic flux by promoting transcription factor EB (TFEB) and lysosome-associated membrane protein 1 (LAMP1) expression. Knockdown of Nrf2 abolished curcumin-induced autophagy and downregulated ROS. Further studies showed that inhibition of autophagosome and lysosome fusion with bafilomycin a1 (BafA1) could block curcumin and prevented As3+-induced cell transformation. These results demonstrated that curcumin prevents As3+-induced cell transformation by inducing autophagy via the activation of the Nrf2 signaling pathway in BEAS-2B cells. However, overexpression of Keap-1 showed a constitutively high level of Nrf2 in As3+-transformed BEAS-2B cells (AsT) is Keap1-independent regulation. Overexpression of Nrf2 in AsT demonstrated that curcumin increased ROS levels and induced cell apoptosis via the downregulation of Nrf2. Further studies showed that curcumin decreased the Nrf2 level in AsT by activating GSK-3ß to inhibit the activation of PI3K/AKT. Co-IP assay results showed that curcumin promoted the interaction of Nrf2 with the GSK-3ß/ß-TrCP axis and ubiquitin. Moreover, the inhibition of GSK-3ß reversed Nrf2 expression in curcumin-treated AsT, indicating that the decrease in Nrf2 is due to activation of the GSK-3ß/ß-TrCP ubiquitination pathway. Furthermore, in vitro and in vivo results showed that curcumin induced cell apoptosis, and had anti-angiogenesis and anti-tumorigenesis effects as a result of activating the GSK-3ß/ß-TrCP ubiquitination pathway and subsequent decrease in Nrf2. CONCLUSIONS: Taken together, in the first stage, curcumin activated Nrf2, decreased ROS, and induced autophagy in normal cells to prevent As3+-induced cell transformation. In the second stage, curcumin promoted ROS and apoptosis and inhibited angiogenesis via inhibition of constitutive expression of Nrf2 in AsT to prevent tumorigenesis. Our results suggest that antioxidant natural compounds such as curcumin can be evaluated as potential candidates for complementary therapies in the treatment of As3+-induced carcinogenesis.

Bio-inspired crosslinking and matrix-drug interactions for advanced wound dressings with long-term antimicrobial activity.

There is a growing demand for durable advanced wound dressings for the management of persistent infections after deep burn injuries. Herein, we demonstrated the preparation of durable antimicrobial nanofiber mats, by taking advantage of strong interfacial interactions between polyhydroxy antibiotics (with varying number of OH groups) and gelatin and their in-situ crosslinking with polydopamine (pDA) using ammonium carbonate diffusion method. Polydopamine crosslinking did not interfere with the antimicrobial efficacy of the loaded antibiotics. Interestingly, incorporation of antibiotics containing more number of alcoholic OH groups (NOH ≥ 5) delayed the release kinetics with complete retention of antimicrobial activity for an extended period of time (20 days). The antimicrobials-loaded mats displayed superior mechanical and thermal properties than gelatin or pDA-crosslinked gelatin mats. Mats containing polyhydroxy antifungals showed enhanced aqueous stability and retained nanofibrous morphology under aqueous environment for more than 4 weeks. This approach can be expanded to produce mats with broad spectrum antimicrobial properties by incorporating the combination of antibacterial and antifungal drugs. Direct electrospinning of vancomycin-loaded electrospun nanofibers onto a bandage gauze and subsequent crosslinking produced non-adherent durable advanced wound dressings that could be easily applied to the injured sites and readily detached after treatment. In a partial thickness burn injury model in piglets, the drug-loaded mats displayed comparable wound closure to commercially available silver-based dressings. This prototype wound dressing designed for easy handling and with long-lasting antimicrobial properties represents an effective option for treating life-threatening microbial infections due to thermal injuries.

Interaction of gelatin with polyenes modulates antifungal activity and biocompatibility of electrospun fiber mats.

Topical application of antifungals does not have predictable or well-controlled release characteristics and requires reapplication to achieve therapeutic local concentration in a reasonable time period. In this article, the efficacy of five different US Food and Drug Administration-approved antifungal-loaded (amphotericin B, natamycin, terbinafine, fluconazole, and itraconazole) electrospun gelatin fiber mats were compared. Morphological studies show that incorporation of polyenes resulted in a two-fold increase in fiber diameter and the mats inhibit the growth of yeasts and filamentous fungal pathogens. Terbinafine-loaded mats were effective against three filamentous fungal species. Among the two azole antifungals compared, the itraconazole-loaded mat was potent against Aspergillus strains. However, activity loss was observed for fluconazole-loaded mats against all of the test organisms. The polyene-loaded mats displayed rapid candidacidal activities as well. Biophysical and rheological measurements indicate strong interactions between polyene antifungals and gelatin matrix. As a result, the polyenes stabilized the triple helical conformation of gelatin and the presence of gelatin decreased the hemolytic activity of polyenes. The polyene-loaded fiber mats were noncytotoxic to primary human corneal and sclera fibroblasts. The reduction of toxicity with complete retention of activity of the polyene antifungal-loaded gelatin fiber mats can provide new opportunities in the management of superficial skin infections.

Dual functionalization of titanium with vascular endothelial growth factor and ß-defensin analog for potential application in keratoprosthesis.

Functionalization of material surfaces can improve their biointegration and bactericidal effect. To expand the biomedical applications of titanium in artificial cornea implantation surgery, titanium alloy substrates were coated with polydopamine and dual bound with recombinant vascular endothelial growth factor (VEGF) and anti-microbial peptide (AMP), SESB2V. Successful chemical binding was assessed with attenuated total reflectance-Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Coating thickness was assessed by atomic force microscopy. Cellular studies revealed that the functionalized substrates displayed the abilities to enhance primary human corneal fibroblast adhesion, proliferation, and viability. Angiogenesis assay with human mesenchymal stem cells was used to verify the biological functions of immobilized VEGF while bactericidal assay was evaluated for the anti-microbial activities of immobilized SESB2V peptide. We found that the titanium surface that was sequentially functionalized with VEGF and SESB2V had enhanced fibroblast proliferation and anti-microbial properties. The incorporation of such peptides into an artificial cornea implant is important for implant-tissue integration and wound healing. This may improve implant integration and reduce the risk of device infection following artificial cornea implantation.

Defensins: antimicrobial peptides for therapeutic development.

A novel class of endogenous antimicrobial peptides called defensins has shown great versatility in their activity against a diverse range of microorganisms including bacteria, viruses and fungi. Their mode of action of bacterial cell lysis seems largely nonspecific and so promises to avert the development of resistance. These two features have made them an area of intense research activity and growing commercial interest. A successful multidisciplinary effort to investigate and develop novel defensins analogues has been established in Singapore that involves computer modeling, biochemistry, proteomics, chemical synthesis, molecular biology and clinical sciences.