In vitro immunomodulation of RAW 264.7 macrophages by medicinal plants used traditionally to treat pulmonary tuberculosis in South Africa.

Abstract Background Pulmonary tuberculosis is one of the leading causes of death in developing countries. The global health burden, which is worsened by the emergence of multi-drug resistance against the standard World Health Organization treatment regimen, calls for new interventions and alternative methods to address the pandemic, and medicinal plants remain a source of hope for the development of new interventions. This study aimed to investigate the in vitro immunomodulatory effects of three plants used traditionally for the treatment of PTB in the Eastern Cape Province of South Africa. For M. tuberculosis to be destroyed when it enters the lung tissue, immune macrophages must maintain the pro-inflammatory M1 phenotype. Thus, a plant extract with a high potential for anti-tuberculosis effects is expected to produce a high concentration of nitric oxide (NO) as the indicator for the pro-inflammatory M1 phenotype. Methods To test this effect, lipopolysaccharide-activated RAW 264.7 macrophages were cultured and treated with the ethanolic crude extracts of three plants: Anthrixia philycoides , Lippia javaniva , and Sanicula elata at concentrations of 50µg/ml, 100µg/ml, and 200 µg/ml. After 24h, 50µl Griess reagent was added to the plates and absorbance was measured using a Bio Tek R Power Wave XS spectrophotometer (Winooski, VT, USA) at 540nm. A standard curve of sodium nitrite dissolved in culture media was used to determine the concentration of NO in each sample. Results The results showed that two plants; Anthrixia philycoides, and Lippia javanica , displayed anti-inflammatory activity compared with the positive control (+ AG) control, while Sanicula elata exhibited pro-inflammatory activity, producing a high amount of NO at the lowest concentration, compared with the positive control (LPS). Conclusion Our results have revealed the polarizing activity of Sanicula elata on macrophages towards M1 phenotype which is evident of the nitric oxide production seen in this study, thus warranting further investigations of medicinal plant for anti-TB activity in the animal model.