Comparative Anti-Inflammatory Effects of Salix Cortex Extracts and Acetylsalicylic Acid in SARS-CoV-2 Peptide and LPS-Activated Human In Vitro Systems

Abstract

The usefulness of anti-inflammatory drugs as an adjunct therapy to improve outcomes in COVID-19 patients is intensely discussed in this paper. Willow bark (Salix cortex) has been used for centuries to relieve pain, inflammation, and fever. Its main active ingredient, salicin, is metabolized in the human body into salicylic acid, the precursor of the commonly used pain drug acetylsalicylic acid (ASA). Here, we report on the in vitro anti-inflammatory efficacy of two methanolic Salix extracts, standardized to phenolic compounds, in comparison to ASA in the context of a SARS-CoV-2 peptide challenge. Using SARS-CoV-2 peptide/IL-1β- or LPS-activated human PBMCs and an inflammatory intestinal Caco-2/HT29-MTX co-culture, Salix extracts, and ASA concentration-dependently suppressed prostaglandin E2 (PGE2), a principal mediator of inflammation. The inhibition of COX-2 enzyme activity, but not protein expression was observed for ASA and one Salix extract. In activated PBMCs, the suppression of relevant cytokines (i.e., IL-6, IL-1β, and IL-10) was seen for both Salix extracts. The anti-inflammatory capacity of Salix extracts was still retained after transepithelial passage and liver cell metabolism in an advanced co-culture model system consisting of intestinal Caco-2/HT29-MTX cells and differentiated hepatocyte-like HepaRG cells. Taken together, our in vitro data suggest that Salix extracts might present an additional anti-inflammatory treatment option in the context of SARS-CoV-2 peptides challenge; however, more confirmatory data are needed.

Identification of Salicylates in Willow Bark (Salix Cortex) for Targeting Peripheral Inflammation

“…However, ASA revealed a higher inhibitory potential against COX-2 in contrast to the Salix extracts. Recently, it has been already shown by our group that a methanolic S. pentandra cortex extract (S6 clone), but no other tested Salix cortex extract, blocked COX-1 and COX-2 enzyme activities [ 28 ]. The inhibitory potential of S6 in this study was greater compared to the present study.…”

“…The inhibitory potential of S6 in this study was greater compared to the present study. This may be explained by extract standardization of the total phenolic glycosides [ 28 ]. SPE fraction F5 showed an inhibitory effect of 47% and 17% of COX-1 and COX-2 enzyme activity, respectively, comparable to the initial methanol extract of S. pentandra .…”

“…However, the adjacent SPE fractions F4 and F6 did not inhibit COX-1/2 activity. It was shown previously by us that 2′- O -acetylsalicortin ( 1 ), one compound present in SPE fraction F5, did not inhibit the enzyme activity of COX-1/2 [ 28 ]. Thus, other compounds eluting in SPE fraction F5 are mainly responsible for the observed enzyme activity, which should be investigated in further studies.…”

“…The inhibitory effect of the extracts and SPE fractions on the COX enzyme activity was determined using Cayman COX (human) Inhibitor Screening Assay kits according to the protocols of the manufacturer (Cayman, Hamburg, Germany) and as described previously [ 28 ]. Briefly, the human recombinant COX-1 or COX-2 enzyme was incubated with extracts or fractions for 8 min at 37 °C.…”

Drug-Drug Interaction Potential, Cytotoxicity, and Reactive Oxygen Species Production of Salix Cortex Extracts Using Human Hepatocyte-Like HepaRG Cells

“…The bark of various willow ( Salix cortex) varieties has long been used in medicine against inflammation, as a painkiller and against fever ( Wood, 2015 ). Recently, our group demonstrated the anti-inflammatory potential of Salix cortex extracts in SARS-CoV-2 peptide and bacterial lipopolysaccharide (LPS)-activated human in vitro systems, providing new evidence of the potential usefulness of Salix products as therapeutics ( Le et al, 2021 ). Salix cortex is also used in dietary supplements, e.g., for weight reduction and to enhance performance in sports ( Matyjaszczyk and Schumann, 2018 ).…”