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Objective: To perform testing for cytokines involved in dermal inflammatory reactions and to document and compare the effects of an oleander extract (OE), oleandrin, and oclacitinib on biomarkers relevant to allergic reactions. The effects of these compounds under inflamed culture conditions are of direct importance to the treatment of canine atopic dermatitis., Methods: Testing involved primary canine dermal fibroblasts and the canine DH82 macrophage cell line; both cell types are important for initiating, regulating, and resolving dermal allergic reactions via cytokine communication., Results: Under inflamed conditions, OE and oleandrin downregulated key cytokines secreted by canine dermal fibroblasts and the DH82 macrophage cell line; all of which are treatment targets in dermatitis. In the DH82 macrophage cultures, the most noteworthy reductions involved IL-6, IL-12/IL-23p40, interferon-γ, tumor necrosis factor-α, VEGF, and nerve growth factor-β. Oclacitinib triggered reductions of some cytokines involved in allergic reactions, including TGF-β1, IL-12/IL-23p40, and tumor necrosis factor-α; however, these reductions were less robust than the reductions triggered by OE and oleandrin and accompanied by increases in other cytokines involved in dermal inflammation, including IL-6, interferon-γ, and nerve growth factor-β. In cultures of primary dermal fibroblasts, OE and oleandrin reduced the levels of IL-8 and monocyte chemoattractant protein-1, whereas oclacitinib had little or no effect., Conclusions: Oleander extract and oleandrin directly modulate immune responses under inflamed conditions. Moreover, OE and oleandrin appear to provide a more beneficial overall cytokine regulation than oclacitinib under inflamed culture conditions., Clinical Relevance: These results suggest that OE and oleandrin are efficacious agents to treat canine atopic dermatitis. Future studies should evaluate the efficacy of these compounds in dogs affected by atopic dermatitis.

Background: Bovine viral diarrhea virus (BVDV), bovine respiratory syncytial virus (BRSV). and bovine coronavirus (BCV) threaten the productivity of cattle worldwide. Development of therapeutics that can control the spread of these viruses is an unmet need. The present research was designed to explore the in vitro antiviral activity of the Nerium oleander derived cardiac glycoside oleandrin and a defined N. oleander plant extract (PBI-05204) containing oleandrin., Methods: Madin Darby Bovine Kidney (MDBK) cells, Bovine Turbinate (BT) cells, and Human Rectal Tumor-18 (HRT-18) cells were used as in vitro culture systems for BVDV, BRSV and BCV, respectively. Cytotoxicity was established using serial dilutions of oleandrin or PBI-05204. Noncytotoxic concentrations of each drug were used either prior to or at 12 h and 24 h following virus exposure to corresponding viruses. Infectious virus titers were determined following each treatment., Results: Both oleandrin as well as PBI-05204 demonstrated strong antiviral activity against BVDV, BRSV, and BCV, in a dose-dependent manner, when added prior to or following infection of host cells. Determination of viral loads by PCR demonstrated a concentration dependent decline in virus replication. Importantly, the relative ability of virus produced from treated cultures to infect new host cells was reduced by as much as 10,000-fold at noncytotoxic concentrations of oleandrin or PBI-05204., Conclusions: The research demonstrates the potency of oleandrin and PBI-05204 to inhibit infectivity of three important enveloped bovine viruses in vitro . These data showing non-toxic concentrations of oleandrin inhibiting infectivity of three bovine viruses support further investigation of in vivo antiviral efficacy.

With continued expansion of the coronavirus disease (COVID-19) pandemic, caused by severe acute respiratory syndrome 2 (SARS-CoV-2), both antiviral drugs as well as effective vaccines are desperately needed to treat patients at high risk of life-threatening disease. Here, we present in vitro evidence for significant inhibition of SARS-CoV-2 by oleandrin and a defined extract of N. oleander (designated as PBI-06150). Using Vero cells, we found that prophylactic (pre-infection) oleandrin (as either the pure compound or as the active principal ingredient in PBI-06150) administration at concentrations as low as 0.05 µg/ml exhibited potent antiviral activity against SARS-CoV-2, with an 800-fold reduction in virus production, and a 0.1 µg/ml concentration resulted in a greater than 3000-fold reduction in infectious virus production. The half maximal effective concentration (EC 50 ) values were 11.98 ng/ml when virus output was measured at 24 h post-infection, and 7.07 ng/ml measured at 48 h post-infection. Therapeutic (post-infection) treatment up to 24 h after SARS-CoV-2 infection of Vero cells also reduced viral titers, with 0.1 µg/ml and 0.05 µg/ml concentrations causing greater than 100-fold reduction as measured at 48 h, and the 0.05 µg/ml concentration resulting in a 78-fold reduction. Concentrations of oleandrin up to 10 µg/ml were well tolerated in Vero cells. We also present in vivo evidence of the safety and efficacy of defined N. oleander extract (PBI-06150), which was administered to golden Syrian hamsters in a preparation containing as high as 130 µg/ml of oleandrin. In comparison to administration of control vehicle, PBI-06150 provided a statistically significant reduction of the viral titer in the nasal turbinates (nasal conchae). The potent prophylactic and therapeutic antiviral activities demonstrated here, together with initial evidence of its safety and efficacy in a relevant hamster model of COVID-19, support the further development of oleandrin and/or defined extracts containing this molecule for the treatment of SARS-CoV-2 and associated COVID-19 disease and potentially also for reduction of virus spread by persons diagnosed early after infection., (Copyright © 2021 The Authors. Published by Elsevier Masson SAS.. All rights reserved.)

Over the past 15 years, investigators have reported on the utility and safety of cardiac glycosides for numerous health benefits including those as treatments for malignant disease, stroke-mediated ischemic injury and certain neurodegenerative diseases. In addition to those, there is a growing body of evidence for novel antiviral effects of selected cardiac glycoside molecules. One unique cardiac glycoside, oleandrin derived from Nerium oleander , has been reported to have antiviral activity specifically against 'enveloped' viruses including HIV and HTLV-1. Importantly, a recent publication has presented in vitro evidence for oleandrin's ability to inhibit production of infectious virus particles when used for treatment prior to, as well as after infection by SARS-CoV-2/COVID-19. This review will highlight the known in vitro antiviral effects of oleandrin as well as present previously unpublished effects of this novel cardiac glycoside against Ebola virus, Cytomegalovirus , and Herpes simplex viruses., Competing Interests: Robert A. Newman is the Chief Science Officer and a Director of Phoenix Biotechnology, Inc., reports personal fees from Phoenix Biotechnology, Inc., during the conduct of the study, and has a patent issued: 10,729,735. K Jagannadha Sastry reports personal fees from Phoenix Biotechnology Inc., during the conduct of the study and outside the submitted work. Ravit Arav-Boger reports grants from Nerium Biotechnology, during the conduct of the study and has a patent, Inhibition of Human Cytomegalovirus Replication by Novel Digitoxin Analogs Depends on Specific Alpha Isoforms of the Na-K-ATPase Pump, issued to US patent application US20160143934. Rick Matos is a Director and consultant for Phoenix Biotechnology. Robert Harrod reports personal fees from Phoenix Biotechnology, Inc., outside the submitted work. The other authors report no other potential conflicts of interest for this work., (© 2020 Newman et al.)