ABSTRACT
The current COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is an enormous threat to public health. The SARS-CoV-2 3C-like protease (3CLpro), which is critical for viral replication and transcription, has been recognized as an ideal drug target. Herein, it is identified that three herbal compounds, Salvianolic acid A (SAA), (-)-Epigallocatechin gallate (EGCG), and Oridonin, directly inhibit the activity of SARS-CoV-2 3CLpro. Further, blocking SARS-CoV-2 infectivity by Oridonin is confirmed in cell-based experiments. By solving the crystal structure of 3CLpro in complex with Oridonin and comparing it to that of other ligands with 3CLpro, it is identified that Oridonin binds at the 3CLpro catalytic site by forming a C-S covalent bond, which is confirmed by mass spectrometry and kinetic study, blocking substrate binding through a nonpeptidomimetic covalent binding mode. Thus, Oridonin is a novel candidate to develop a new antiviral treatment for COVID-19.
ABSTRACT
OBJECTIVE: Platelet-rich plasma (PRP) can stimulate intervertebral disc cell proliferation, promote extracellular matrix synthesis, and inhibit annulus fibrosus cell apoptosis. To investigate the effects of autologous PRP on the treatment of the early intervertebral disc degeneration (IDD) so as to provide the experimental basis for its clinical application. METHODS: Forty-five healthy New Zealand white rabbits (male or female, weighing 2.5-3.0 kg) were randomly divided into the experimental group (n = 15), the control group (n = 15), and the sham group (n = 15). PRP was prepared from the arterial blood of rabbit's ears of the experimental group with Landesberg's method. The platelet concentrations in both whole blood and PRP were detected. The rabbit model of early IDD was established by annulus fibrosus puncture (L4, 5, L5, 6) in both the experimental group and the control group; 100 microL autologous PRP and 100 microL PBS were injected into the degenerative intervertebral discs respectively after 2 weeks of models creation. In sham group, intervertebral discs were separated and exposed without treatment. The general conditions of the rabbits were observed after building models; at 2 weeks after degeneration, 1 and 2 weeks after intervention, 5 rabbits were selected randomly from each group respectively for MRI observation, histological observation by using HE staining and collagen type II immunohistochemical staining. The signal of lumbar MRI was assessed and the contents of collagen type II were detected. RESULTS: The platelet concentration of PRP was about 4.92 times as much as that of the whole blood. All the animals survived to the end of the experiment. At 2 weeks after degeneration, a lower T2 signal was observed in both the experimental group and the control group; the nucleus pulposus cells decreased and extracellular matrix degenerated; and the expression of collagen type II decreased in both the experimental group and control group. The degenerative grade of lumbar MRI in the experimental group and control group were significantly higher than that in the sham group (P < 0.05), and the content of collagen type II were significantly lower than that in the sham group (P < 0.05). At 1, 2 weeks after intervention, disc degeneration in the experimental group was significantly lower than that in control group (P < 0.05), and significant difference was found between experimental group and sham group (P < 0.05). The nucleus pulposus cells and chondroid matrix in the experimental group were more than those in the control group, showing slight stromal fibrosis; but the expression of collage type II was significantly higher than that in the control group (P < 0.05). CONCLUSION: The disc injection of autologous PRP may terminate or even reverse the progress of rabbit early IDD, which may be associated with the role of multiple growth factors of PRP in regulating cell function, improving the tissue microenvironment, and promoting tissue regeneration.