A recent study shows evidence that cannabidiol, an important active ingredient in the Cannabis sativa plant, can augment the antiviral innate immune response and prophylactically prime the innate antiviral response of cells – enabling in turn improved response against viruses such as the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). The research paper is currently available on the bioRxiv* preprint server while it undergoes peer review.
Study: Effect of cannabidiol on apoptosis and cellular interferon and interferon-stimulated gene responses to the SARS-CoV-2 genes ORF8, ORF10 and M protein. Image Credit: Dmytro Tyshchenko / Shutterstock
A current situation with the emerging variants of SARS-CoV-2, a causative agent of the ongoing coronavirus disease (COVID-19) pandemic, shows how a multifaceted approach will be ultimately needed in order to mitigate medical, social, and economic ramifications of this disease.
This means not only finding effective drugs alongside vaccine options that we have at our disposal but also harnessing our innate immune system to fight of the infection more easily. This is important, as unlike adaptive immunity (mediated by specialized cells of the immune system), basically all human cells can mount an innate immune response.
Nonetheless, viruses frequently evolve functions to disrupt this protective facet of our immunity, which is also a function of several non-structural proteins in the SARS-CoV-2 genetic make-up. Therefore, scientists are quite interested in finding ways to protect our innate immune response.
Recent evidence from the medical literature supports the notion that some constituents of the Cannabis sativa plant (such as cannabidiol) have anti-inflammatory traits, with a possible role as a protective agent or therapeutic in cells confronting metabolic distress (such as that associated with viral infection).
Based on this, a research group from the Faculty of Health of the University of Waterloo in Canada hypothesized that SARS-CoV-2 genes are proapoptotic (which means they can cause disassembly of innate immune cells) and that cannabidiol may actually reverse these effects.
Appraising markers of apoptosis
In the current study, the researchers aimed to examine the effects of expression of ORF8 and ORF10 genes, as well as the SARS-CoV-2 structural membrane protein, reported to inhibit Type I and III interferon responses, on apoptosis (i.e., programmed cell death) and expression of interferons and downstream effectors.
In addition to appraising the effects of expression of these genes alone, they have also investigated the impact of combining their expression with cannabidiol, a major non-psychotropic phytocannabinoid constituent of Cannabis sativa.
Immortalized human embryonic kidney cells (HEK293) cells were transfected with a control plasmid (or plasmids expressing ORF8, ORF10, M protein) and assayed for markers of apoptosis at 24 hours. Furthermore, the expression of interferon and interferon-stimulated genes at 14 hours has been assessed as well.
Effect of ORF8, ORF10, or M protein expression, with and without CBD treatment, on HEK293 cell number and apoptosis indexes. (A) Dose-dependent effects of CBD on the relative number of cells per well 24 h after transfection with control plasmid (pCMV), or plasmids expressing ORF8, ORF10, or M protein (n=3-12). IC50 values for CBD concentration in combination with each group are shown. (B-D) Dose-response effect to CBD on the early apoptosis index in HEK293 cells expressing pCMV or viral genes at 24 h. (E-G) Dose-response effect to CBD on the late apoptosis index in HEK293 cells transfected with control or viral plasmids. Apoptotic indexes were calculated by dividing the relative absorption of the respective marker by the number of cells per well. Apoptosis data were analyzed by 2-way ANOVA with Tukey’s post-hoc test, n=3-9. Differences among groups are as indicated, *P<0.05, **P<0.01, ***P<0.001, ****P<0.0001, where (****) denotes a significant difference (P<0.0001) between cells treated with 2 μM CBD and transfected with a viral gene-encoding plasmid, and all other groups.
Mediating apoptosis in SARS-CoV-2-infected cells
Overall, the results demonstrate a poor ability of HEK293 cells to respond to SARS-CoV-2 genes alone but highlight an improved innate antiviral response to these genes in the presence of cannabidiol. In other words, this compound may prime components of the innate immune system and increase the readiness to respond to viral infection without activating the apoptosis process.
A substantial reduction in cell number, as well as an increase in apoptosis, has been found after 24 hours in cells where the expression of viral genes has been combined with cannabidiol treatment, but not in control-transfected cells treated with cannabidiol or in cells expressing viral genes but treated only with vehicle.
Moreover, the finding that cannabidiol regulates OAS family gene expression is especially interesting, considering the role of these enzymes as potent mediators of the virus-associated apoptosis process.
From clinical use to public health benefits
“Our results demonstrating increased apoptosis in cells treated with cannabidiol and transfected with SARS-CoV-2 viral genes suggests a potential protective effect of cannabidiol at initial infection”, say study authors in this bioRxiv paper. “However, it also raises the question of whether this could be harmful in an individual who already had a high viral load”, they add.
Even though we still eagerly await the results from many other registered clinical trials, thus far, none of them have been interrupted prematurely by the medical oversight committees, which points toward the conclusion that no significant harm has not been detected.
Hence, it is possible that cannabidiol may offer prophylaxis against initial viral infection through a proapoptotic mechanism that does not lead to widespread cell death in highly infected patients. Still, further research will be needed to fully grasp the nature of cannabidiol effects for SARS-CoV-2 and other viral pathogens.
bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.