Identification and structural studies of natural inhibitors against SARS-CoV-2 viral RNA methyltransferase (NSP16).

Pathogenic RNA viruses are emerging as one of the major threats and posing challenges to human community. RNA viruses have an exceptionally shorter generation time and easy to adapt in host cells. The recent emergence of SARS-CoV-2, a long RNA virus, has shown us how difficult it is to overcome this kind of pandemic without understanding the viral infection and replication mechanisms. It is essential to comprehend replications of the viral genome, including RNA polymerization and the final capping process. The mRNAs of SARS-CoV-2 coronaviruses are protected at their 5'-ends by cap structure. The cap-like system plays a significant role in viral translational process, viral RNA stability, and scatting in detecting innate immune recognition in host cells. Two coronavirus enzymes, Nsp14 and Nsp16, critically help in the formation of capping and are considered as potential drug targets for antiviral therapy. Natural and herbal medicines have a past record of treating various acute respiratory diseases. In this work, we have exploited 56000 natural compounds to screen potential inhibitors against NSP16. In silico virtual screening, docking and Molecular Dynamics (MD) simulation studies were performed to understand how these potential inhibitors are bound to NSP16. We observed that the most highly screened compound binds to protein molecules with a high dock score, primarily through hydrophobic interactions and hydrogen bonding, as previously reported for NSP16. Compound-13 (2-hydroxy-N-({1-[2-hydroxy-1-(hydroxymethyl)ethyl]piperidin-3-yl}methyl)-5-methylbenzamide) and compound-51 (N-(2-isobutoxybenzyl)-N,2-dimethyl-2,8-diazaspiro[4.5]decane-3-carboxamide) occupied in active site along with good pharmokinetices properties. In conclusion, the selected compounds could be used as a novel therapeutic against SARS-CoV-2.Communicated by Ramaswamy H. Sarma.

Repurposing sodium diclofenac as a radiation countermeasure agent: A cytogenetic study in human peripheral blood lymphocytes.

We assessed the radioprotective and mitigative actions of sodium diclofenac, a non-steroidal anti-inflammatory drug using cultured human peripheral blood as a model. Both pre- and post-irradiation treatments with the drug reduced gamma radiation-induced formation of dicentric chromosome, cytochalasin-blocked micronuclei and γ-H2AX foci in human peripheral blood lymphocytes. This work supports the concept that sodium diclofenac may be a useful radiation countermeasure agent.

Tetracycline hydrochloride: A potential clinical drug for radioprotection.

Radiation exposure in planned scenario necessarily requires radioprotector for protection against radiation injuries in tissues and organs. A large number of potential radioprotectors have been investigated but no approved radioprotector is available. Hence, in quest for radioprotector, repurposing of clinical drug is an approach which aims at finding the radioprotective potential of known drugs so that in case of untoward accident the knowledge could be translated to drug usage. In this study, we have investigated the radical scavenging properties of tetracycline pertaining to radioprotection. Our study suggests that tetracycline hydrochloride efficiently scavenges free radicals in ABTS (2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl) and FRAP (ferric reducing antioxidant power) assays. Hydroxyl radical scavenging assay has demonstrated its ability to scavenge gamma radiation induced free radicals by lowering the formation of malondialdehyde. Radiation causes damage to macromolecules and hence the protection offered by tetracycline hydrochloride to DNA and protein shows its radioprotective potential. Plasmid DNA relaxation study with pBR322 has shown that tetracycline hydrochloride confers dose modification factor (DMF) of 2 and 4 at 100 µM and 250 µM concentration respectively. Tetracycline hydrochloride has also protected bovine serum albumin (BSA) from radiation induced degradation. The ex vivo studies for lipid peroxidation and mitochondrial membrane potential further substantiate our findings. The whole body animal survival study has shown the drug to offer 20% protection at a lethal radiation dose of 9 Gy. This study demonstrates the radioprotective potential of the drug by providing some insight into ex vivo and in vivo efficacy.

Evaluation of sesamol-induced histopathological, biochemical, haematological and genomic alteration after acute oral toxicity in female C57BL/6 mice.

The objective of this study was to evaluate organ-wise toxicological effects of sesamol and determine the LD50 cut-off value and GHS category following acute oral toxicity method OECD 423. An acute oral toxicity study was carried out in female C57BL/6 mice. Observations for physical behaviour and measurements on haematology, biochemistry, histology of vital organs were performed. In addition, genotoxicity assessment using comet and micronuclei assays was also performed. Acute toxicological effects were observed at 2000 mg/kg, while no adverse effects observed at 300 mg/kg. The effects of 2000 mg/kg were manifested as severe histopathological changes in all organs (femur, spleen, gastrointestine, lungs, heart, kidney, liver, stomach and brain) and excessive DNA strands breaks occurred in femoral bone marrow cells and splenocytes. A single dose of sesamol (2000 mg/kg, body weight) caused the death of two mice (out of three) within 2 h. Hence, sesamol is in GHS category 4 (>300-2000) with LD50 cut-off value of 500 mg/kg body weight. In contrast, this study is correlated with the obtained GHS category 4 and LD50 cut-off value 580 mg/kg body weight by ProTox. In conclusions, the present study has classified sesamol toxicity and assessed organ-wise acute oral toxicity of sesamol in female C57BL/6 mice. Therefore, these findings may be useful for the selection of dosages for further pre-clinical evaluation and potential drug developmental of sesamol.

Mean frequency and relative fluorescence intensity measurement of γ-H2AX foci dose response in PBL exposed to γ-irradiation: An inter- and intra-laboratory comparison and its relevance for radiation triage.

Measurement of γ-H2AX protein changes in the peripheral blood lymphocytes (PBL) of individuals exposed to ionizing radiation is a simple, sensitive, and rapid assay for radiation triage and early marker of dose estimation. The qualitative and quantitative measurements of the protein changes were examined using flow cytometry and microscopy. Whole blood and isolated lymphocytes were exposed in vitro between 0.1 and 5 Gy doses of (60) Co γ-radiation at a dose rate of 1 Gy/min. Radiation induced γ-H2AX foci frequency (n = 3) and relative fluorescence intensity (n = 7) in PBL was measured at 0.5 and 2 hrs postexposure. The observed dose response for γ-H2AX foci frequency at both time points, for whole blood and isolated lymphocytes did not show any significant (P > 0.05) differences. However, when compared with γ-H2AX foci frequency scored manually (microscopy), the semiautomated analysis (captured images) showed a better correlation (r(2) = 0.918) than that obtained with automated (Metafer) scoring (r(2) = 0.690). It is noteworthy to mention that, the γ-H2AX foci frequency quantified using microscopy showed a dose dependent increase up to 2 Gy and the relative fluorescence intensity (RFI) measured with flow cytometry revealed an increase up to 5 Gy in the PBL exposed in vitro. Moreover, a better correlation was observed between the γ-H2AX foci frequency obtained by manual scoring and RFI (r(2) = 0.910). Kinetic studies showed that the γ-H2AX foci remain more or less unchanged up to 4 hrs and reduces gradually over 48 hrs of postexposure at 37°C. Further, inter and intra-laboratory comparisons showed consistency in the scoring of γ-H2AX foci frequency by manual and semiautomated scoring. The overall results suggest that measurement of γ-H2AX (microscopy and flow cytometry) should be employed within 4 to 6 hrs for a reliable dosimetry either by sharing the work load between the laboratories or investing more manpower; however, triage can be possible even up to 48 hrs of postirradiation.

Radioprotective role of clinical drug diclofenac sodium.

The potential of clinical drug diclofenac sodium which is routinely used in clinics as non-steroid anti-inflammatory drugs opens a new insight in development of radioprotector. The drug has shown its potential radioprotective efficacy in clonogenic cell survival in Chinese hamster V79 cells with a DMF of 1.4. The pBR322 plasmid DNA gets damaged by radiation in which the supercoiled form gradually disappears with increasing radiation dose. Diclofenac sodium has shown its radioprotective potential by scavenging radiation induced free radicals which are depicted by its ability in restoring the fraction of supercoiled form of plasmid DNA back to normal. 250µM concentration of the drug provides GSSB yield of 3.65±0.5×10(-9)Da(-1)Gy(-1). This drug has shown to have a free radical scavenging activity because the radical cation with blue color is converted to the colorless neutral form by addition of diclofenac sodium in ABTS assay. Whole body survival study has shown it to protect 45.5% of C57BL/6 mice at a lethal irradiation dose of 9Gy. Therefore, this molecule offers a potential radioprotective ability besides being used routinely as analgesic and anti inflammatory compound.

Evaluating the efficacy of simulators and multimedia for refreshing ACLS skills in India.

OBJECTIVE: Data on the efficacy of the simulation and multimedia teaching modalities is limited, particularly in developing nations. This study evaluates the effectiveness of simulator and multimedia educational tools in India. METHODS: Advanced Cardiac Life Support (ACLS) certified paramedic students in India were randomized to either Simulation, Multimedia, or Reading for a 3-h ACLS refresher course. Simulation students received a lecture and 10 simulator cases. The Multimedia group viewed the American Heart Association (AHA) ACLS video and played a computer game. The Reading group independently read with an instructor present. Students were tested prior to (pre-test), immediately after (post-test), and 3 weeks after (short-term retention test), their intervention. During each testing stage subjects completed a cognitive, multiple-choice test and two cardiac arrest scenarios. Changes in exam performance were analyzed for significance. A survey was conducted asking students' perceptions of their assigned modality. RESULTS: One hundred and seventeen students were randomized to Simulation (n=39), Multimedia (n=38), and Reading (n=40). Simulation demonstrated greater improvement managing cardiac arrest scenarios compared to both Multimedia and Reading on the post-test (9% versus 5% and 2%, respectively, p<0.05) and Reading on the short-term retention test (6% versus -1%, p<0.05). Multimedia showed significant improvement on cognitive, short-term retention testing compared to Simulation and Reading (5% versus 0% and 0%, respectively, p<0.05). On the survey, 95% of Simulation and 84% of Multimedia indicated they enjoyed their modality. CONCLUSION: Simulation and multimedia educational tools were effective and may provide significant additive benefit compared to reading alone. Indian students enjoyed learning via these modalities.