RESUMO
Butyrylcholinesterase (BChE) is widely expressed in multiple tissues and has a vital role in several key human disorders, such as Alzheimer's disease and tumorigenesis. However, the role of BChE in human disorders has not been investigated. Thus, to quantitatively detect and visualize dynamical variations in BChE activity is essential for exploring the biological roles of BChE in the progression of a number of human disorders. Herein, based on the substrate characteristics of BChE, we customized and synthesized three near-infrared (NIR) fluorescent probe substrates with cyanine-skeleton, and finally selected a NIR fluorescence probe substrate named CYBA. The CYBA demonstrated a significant increase in fluorescence when interacting with BChE, but mainly avoided AChE. Upon the addition of BChE, CYBA could be specifically hydrolyzed to TBO, resulting in a significant NIR fluorescence signal enhancement at 710 nm. Systematic evaluation revealed that CYBA exhibited exceptional chemical stability in complex biosamples and possessed remarkable selectivity and sensitivity towards BChE. Moreover, CYBA was successfully applied for real-time imaging of endogenous BChE activity in two types of nerve-related living cells. Additionally, CYBA demonstrated exceptional stability in the detection of complex biological samples in plasma recovery studies (97.51%-104.01%). Furthermore, CYBA was used to construct a high-throughput screening (HTS) method for BChE inhibitors using human plasma as the enzyme source. We evaluated inhibitory effects of a series of natural products and four flavonoids were identified as potent inhibitors of BChE. Collectively, CYBA can serve as a practical tool to track the changes of BChE activity in complicated biological environments due to its excellent capabilities.
RESUMO
OBJECTIVE: Plumbagin, a naphthoquinone constituent of Plumbago zeylanica L. (Plumbaginaceae), has been extensively studied for its pharmacological activities and reported to show a good anti-cancer activity in different human cancer cell lines. It is known to exhibit proapoptotic, antiangiogenic and antimetastatic effects in cancer cells. Plumbagin is also known to inhibit NF-κB, JNK (Hsu), PKCε, and STAT-3. However, the anti-proliferatory activity and their core molecular mechanisms have been poorly determined. METHODS: Human osteosarcoma (MG-63) cells were exposed to plumbagin and the anti-proliferative activity was evaluated by MTT assay. The mechanism of action for the growth inhibitory activity of plumbagin on MG-63 cells was evaluated using flow cytometry for cell cycle distribution, and western blot for assessment of accumulation and phosphorylation of potential target proteins. Furthermore, morphology of MG-63 cells was assessed after treatment with Plumbagin. RESULTS: Plumbagin has significantly induced growth inhibition against osteosarcoma MG-63 cells, primarily by S-phase cell cycle arrest which is confirmed by the down regulation of cyclin A and CDK2 protein levels determined by western blot analysis. It was also found that plumbagin has triggered the DNA damage in MG-63 cells, subsequently initiating the arrest in S-phase, which is evident by the up-regulation of phosphorylated p53 and histone. Furthermore, plumbagin resulted in the down-regulation of c-myc protein expression in the MG-63 cells. CONCLUSION: Plumbagin has triggered DNA damage and had induced S-phase arrest in MG-63 cells, suggesting it to be a potential compound in treatment against malignant human osteosarcoma.