Modulation of M1/M2 Cytokines and Inflammatory Enzymes by Persicaria Species Leaf Extracts in Lipopolysaccharide-stimulated RAW 264.7 Cell Macrophages

Investigating the impacts of plant-based substances on the regulation of pro-inflammatory M1 and anti-inflammatory M2 cytokines could have significant implications for immune-related health conditions. Seven Persicaria plant species from sub-Saharan Africa were specifically selected for analysis, based on their traditional use in treating inflammation.

To investigate the inhibitory effects of methanol leaf extracts from selected plants on enzymes involved in chronic inflammation.

The inhibition of nitric oxide production, acetylcholinesterase activity, and 15-lipoxygenase activity was assessed using the Griess reagent method, Ellman's colorimetric method, and the ferrous oxidation-xylenol orange assay. The quantity of M1/M2 cytokines released was quantified using a flow cytometer.

At a concentration of 50 µg/mL, the methanol extracts of P. limbata exhibited the highest NO inhibition (97.67%), followed by P. nepalensis (93.06%) and P. setosula (92.78%). The NO inhibition caused by the plant extracts was correlated directly with the decrease in NO release by the LPS-stimulated macrophages. Furthermore, the pro-inflammatory enzyme assays indicated that the methanol extracts of P. setosula exhibited the highest enzyme inhibitory activity (LOX 89.59%, AChE 72.12 %). This was followed by P. limbata (with 92.76% for LOX and 56.93% for AChE) and P. nepalensis (with 88.16% for LOX and 47.17% for AChE). Cytokine assays revealed that the extracts of P. limbata had significant dose-dependent suppressive effects on IFN-γ and TNF-α expression while promoting the secretion of IL-2, IL-4, IL-6, and IL-10.

Extracts of P. limbata contain immunomodulatory compounds that could be further explored as potential remedies to target the molecular drivers of chronic inflammation.