A novel insight on SARS-CoV-2 S-derived fragments in the control of the host immunity.

Despite all efforts to combat the pandemic of COVID-19, we are still living with high numbers of infected persons, an overburdened health care system, and the lack of an effective and definitive treatment. Understanding the pathophysiology of the disease is crucial for the development of new technologies and therapies for the best clinical management of patients. Since the manipulation of the whole virus requires a structure with an adequate level of biosafety, the development of alternative technologies, such as the synthesis of peptides from viral proteins, is a possible solution to circumvent this problem. In addition, the use and validation of animal models is of extreme importance to screen new drugs and to compress the organism's response to the disease. Peptides derived from recombinant S protein from SARS-CoV-2 were synthesized and validated by in silico, in vitro and in vivo methodologies. Macrophages and neutrophils were challenged with the peptides and the production of inflammatory mediators and activation profile were evaluated. These peptides were also inoculated into the swim bladder of transgenic zebrafish larvae at 6 days post fertilization (dpf) to mimic the inflammatory process triggered by the virus, which was evaluated by confocal microscopy. In addition, toxicity and oxidative stress assays were also developed. In silico and molecular dynamics assays revealed that the peptides bind to the ACE2 receptor stably and interact with receptors and adhesion molecules, such as MHC and TCR, from humans and zebrafish. Macrophages stimulated with one of the peptides showed increased production of NO, TNF-α and CXCL2. Inoculation of the peptides in zebrafish larvae triggered an inflammatory process marked by macrophage recruitment and increased mortality, as well as histopathological changes, similarly to what is observed in individuals with COVID-19. The use of peptides is a valuable alternative for the study of host immune response in the context of COVID-19. The use of zebrafish as an animal model also proved to be appropriate and effective in evaluating the inflammatory process, comparable to humans.

Photobiomodulation Reduces the Cytokine Storm Syndrome Associated with COVID-19 in the Zebrafish Model.

Although the exact mechanism of the pathogenesis of coronavirus SARS-CoV-2 (COVID-19) is not fully understood, oxidative stress and the release of pro-inflammatory cytokines have been highlighted as playing a vital role in the pathogenesis of the disease. In this sense, alternative treatments are needed to reduce the level of inflammation caused by COVID-19. Therefore, this study aimed to investigate the potential effect of red photobiomodulation (PBM) as an attractive therapy to downregulate the cytokine storm caused by COVID-19 in a zebrafish model. RT-qPCR analyses and protein-protein interaction prediction among SARS-CoV-2 and Danio rerio proteins showed that recombinant Spike protein (rSpike) was responsible for generating systemic inflammatory processes with significantly increased levels of pro-inflammatory (il1b, il6, tnfa, and nfkbiab), oxidative stress (romo1) and energy metabolism (slc2a1a and coa1) mRNA markers, with a pattern similar to those observed in COVID-19 cases in humans. On the other hand, PBM treatment was able to decrease the mRNA levels of these pro-inflammatory and oxidative stress markers compared with rSpike in various tissues, promoting an anti-inflammatory response. Conversely, PBM promotes cellular and tissue repair of injured tissues and significantly increases the survival rate of rSpike-inoculated individuals. Additionally, metabolomics analysis showed that the most-impacted metabolic pathways between PBM and the rSpike treated groups were related to steroid metabolism, immune system, and lipid metabolism. Together, our findings suggest that the inflammatory process is an incisive feature of COVID-19 and red PBM can be used as a novel therapeutic agent for COVID-19 by regulating the inflammatory response. Nevertheless, the need for more clinical trials remains, and there is a significant gap to overcome before clinical trials can commence.

Toxicity of spike fragments SARS-CoV-2 S protein for zebrafish: A tool to study its hazardous for human health?

Despite the significant increase in the generation of SARS-CoV-2 contaminated domestic and hospital wastewater, little is known about the ecotoxicological effects of the virus or its structural components in freshwater vertebrates. In this context, this study evaluated the deleterious effects caused by SARS-CoV-2 Spike protein on the health of Danio rerio, zebrafish. We demonstrated, for the first time, that zebrafish injected with fragment 16 to 165 (rSpike), which corresponds to the N-terminal portion of the protein, presented mortalities and adverse effects on liver, kidney, ovary and brain tissues. The conserved genetic homology between zebrafish and humans might be one of the reasons for the intense toxic effects followed inflammatory reaction from the immune system of zebrafish to rSpike which provoked damage to organs in a similar pattern as happen in severe cases of COVID-19 in humans, and, resulted in 78,6% of survival rate in female adults during the first seven days. The application of spike protein in zebrafish was highly toxic that is suitable for future studies to gather valuable information about ecotoxicological impacts, as well as vaccine responses and therapeutic approaches in human medicine. Therefore, besides representing an important tool to assess the harmful effects of SARS-CoV-2 in the aquatic environment, we present the zebrafish as an animal model for translational COVID-19 research.

Biological effects of an oxyphytosterol generated by ß-Sitosterol ozonization.

ß-Sitosterol (ßSito) is the most abundant phytosterol found in vegetable oils, grains such as wheat, beans, and corn, and in many phytosterol-enriched foods. It is prone to oxidation by reactive oxygen species, such as ozone, leading to the formation of oxyphytosterols. A better understanding regarding the biological effects and mechanism of action of oxyphytosterols is required since the beneficial and adverse side effects of these compounds on human health remain highly controversial. In this work, we investigated the biological effects of ß-Secosterol (ßSec), a new oxyphytosterol generated by the reaction of ßSito with ozone. Treatment of HepG2 cells with ßSito or ßSec (0.1-100 µM) for 24, 48, and 72 h induced a dose-dependent reduction of cell viability in the MTT assay, with ßSec showing higher efficacy than ßSito. However, ßSec presented a lower potency than ßSito, showing IC50 = 37.32 µM, higher than ßSito (IC50 = 0.23 µM) at 48 h. Cell cycle analyses by flow cytometry showed a slight decrease of G0/G1 phase with ßSito 0.5 µM, but a significant cell cycle arrest at the G0/G1 phase in the treatment for 48 h with ßSec 20 µM (62.69 ± 2.15%, p < 0.05) and ßSec 40 µM (66.96 ± 5.39%, p < 0.0001) when compared to control (56.97 ± 2.60%). No suggestion of apoptosis was indicated by flow cytometry data. Also, ßSec (20 and 40 µM) reduced the mitotic index. In the laser scanning confocal microscopy analysis no alterations in cell morphology were observed with ßSito (0.5 µM). Nevertheless, round-shaped cells, abnormal nuclear morphology with shrinkage, and formation of microtubules clusters were observed in the treatment with ßSec, indicating a disruption in the microtubules network organization. N-acetyl-l-cysteine was not able to inhibit any of these cellular effects, indicating a lack of involvement of oxidative stress in the mechanism of action of ßSec. Although not further investigated in this study, it was discussed the hypothesis that covalent adduct formation with lysine residues of proteins, could play an important role in the biological effects elicited by ßSec. Elucidation of the primary cellular processes induced by ßSec provides the essential knowledge to be aware of its potential adverse side effects or therapeutic use of this oxyphytosterol.

Biological effects of an oxyphytosterol generated by β-Sitosterol ozonization

β-Sitosterol (βSito) is the most abundant phytosterol found in vegetable oils, grains such as wheat, beans, and corn, and in many phytosterol-enriched foods. It is prone to oxidation by reactive oxygen species, such as ozone, leading to the formation of oxyphytosterols. A better understanding regarding the biological effects and mechanism of action of oxyphytosterols is required since the beneficial and adverse side effects of these compounds on human health remain highly controversial. In this work, we investigated the biological effects of β-Secosterol (βSec), a new oxyphytosterol generated by the reaction of βSito with ozone. Treatment of HepG2 cells with βSito or βSec (0.1–100 μM) for 24, 48, and 72 h induced a dose-dependent reduction of cell viability in the MTT assay, with βSec showing higher efficacy than βSito. However, βSec presented a lower potency than βSito, showing IC50 = 37.32 μM, higher than βSito (IC50 = 0.23 μM) at 48 h. Cell cycle analyses by flow cytometry showed a slight decrease of G1 phase with βSito 0.5 μM, but a significant cell cycle arrest at the G0/G1 phase in the treatment for 48 h with βSec 20 μM (62.69 ± 2.15%, p < 0.05) and βSec 40 μM (66.96 ± 5.39%, p < 0.0001) when compared to control (56.97 ± 2.60%). No suggestion of apoptosis was indicated by flow cytometry data. Also, βSec (20 and 40 μM) reduced the mitotic index. In the analysis with a confocal laser-scanning microscope, no alterations in cell morphology were observed with βSito (0.5 μM). Nevertheless, round-shaped cells, abnormal nuclear morphology with shrinkage, and formation of microtubules clusters were observed in the treatment with βSec, indicating a disruption in the microtubules network organization. N-acetyl-l-cysteine was not able to inhibit any of these cellular effects, indicating a lack of involvement of oxidative stress in the mechanism of action of βSec. Although not further investigated in this study, it was discussed the hypothesis that covalent adduct formation with lysine residues of proteins, could play an important role in the biological effects elicited by βSec. Elucidation of the primary cellular processes induced by βSec provides the essential knowledge to be aware of its potential adverse side effects or therapeutic use of this oxyphytosterol.