Sarcostemma viminale activates macrophages to a pro-inflammatory phenotype

Abstract

Sarcostemma viminale (L.) R.Br, also known as caustic or milk bush, is a semi-succulent plant commonly found in the North West of Australia. Local Aboriginal populations have long used the milky white sap from this plant to treat skin cancers. An ethanol extract from S. viminale was tested by exposing the RAW264.7 cell line as an in vitro murine macrophage model, to the extract. Flow cytometric analysis was performed to determine if S. viminale skewed macrophages towards a pro-inflammatory or antiinflammatory phenotype using a number of cell surface markers. Cell culture supernatants were also analysed by cytometric bead array to determine if S. viminale exposed macrophages produced pro-inflammatory or antiinflammatory cytokines. After exposure to S. viminale, a significantly greater number of macrophages expressed proinflammatory major histocompatibility complex (MHC) class II molecules and significantly greater expression levels of the dendritic cell marker CD11c. Cytometric bead array analysis found that S. viminale induced significant amounts of the potent pro-inflammatory cytokine tumour necrosis factor (TNF) from macrophages. The markers CD40 and ICAM-1 were expressed but were not significantly different from the controls. Also, significantly higher expression of CX3CR1 indicated that macrophages were preparing to migrate. No anti-inflammatory cytokines were produced. No significant production of NO 2 − , IL-6, IFN-γ or IL-12 was found. These results demonstrate that S. viminale drives resting macrophages into a pro-inflammatory phenotype, reminiscent of activated immature dendritic cells. If this activation could be achieved in the peri-tumour environment, then S. viminale could be useful as an adjunct therapy for skin cancer.

Indigenous Uses, Phytochemical Analysis, and Anti-Inflammatory Properties of Australian Tropical Medicinal Plants

“…Whole plant extract NS Whole plant extract inhibited the production of pro-inflammatory cytokines in RAW 264.7 cells [337].…”

seco-Pregnane Glycosides from Australian Caustic Vine (Cynanchum viminale subsp. australe)

“…Cynavimigenin A (5), cynaviminoside A (6), cynaviminoside B (7), and cynavimigenin B ( 8) were evaluated for their potential to elicit cholinergic toxicity by studying their inhibition of Electrophorus electricus acetylcholinesterase (Ee-AChE) and equine butyrylcholinesterase (eqBuChE), using previously described methods. 24,25 Although no significant activity was observed, 5−8 were relatively more potent inhibitors of eqBuChE than EeAChE when tested at 100 μM (compound, % inhibition of eqBuChE, % inhibition of EeAChE): 5 (7.72 ± 0.81%, 3.86 ± 0.42%); 6 (13.5 ± 1.19%, 4.39 ± 0.80%); 7 (2.64 ± 0.51%, 0.47 ± 1.73%); 8 (14.0 ± 1.12%, 4.30 ± 0.58%); and positive control cholinesterase inhibitor drug donepezil (91.3 ± 0.20%, 91.5 ± 0.93%).…”

“…Cynaviminoside A ( 6) and cynaviminoside B (7) were screened against scabies mites, eggs, and hatched larvae as previously reported. 27 Cynaviminoside A (6) was the most active toward mites with a 30% mortality rate, whereas cynaviminoside B (7) did not outperform the DMSO control. Neither 6 or 7 inhibited Sarcoptes scabiei egg hatching nor induced hatched larvae mortality at a concentration of 100 μM.…”

“…In addition, crude extracts of C. viminale subsp. australe have been reported to display cancer cell line cytotoxicity activity and are especially active against skin cancer . Interestingly, C. viminale subsp.…”