Antirheumatic effect of IDS 23, a stinging nettle leaf extract, on in vitro expression of T helper cytokines

Stinging nettle leaf extracts are registered in Germany for adjuvant therapy of rheumatic diseases. In a whole blood culture system the nettle extract IDS 23 (Rheuma-Hek) inhibited lipopolysaccharide stimulated monocyte cytokine expression, indicating an immunomodulating effect. We investigated the immunomodulating effects of IDS 23 on phytohemagglutinin (PHA) stimulated peripheral blood mononuclear cells (PBMC) in vitro.

Using commercial immunoassays the distinct cytokine patterns of Th1 and Th2 cells were determined. Interleukin 2 (IL-2) and interferon-gamma (IFN-gamma) mRNA expression was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) with PHA stimulated PBMC.

IDS 23 inhibited PHA stimulated production of Th1-specific IL-2 and IFN-gamma in PBMC culture (n = 10) in a dose dependent manner up to 50+/-32% and 77+/-14%, respectively. In contrast, IDS 23 stimulated the secretion of Th2-specific IL-4. The dose dependent inhibiting effect on IL-2 and IFN-gamma expression was also detected with RT-PCR, while the amount of actin-specific mRNA transcript was not modified by IDS 23.

Our results suggest the effective ingredient of IDS 23 acts by mediating a switch in T helper cell derived cytokine patterns. IDS 23 may inhibit the inflammatory cascade in autoimmune diseases like rheumatoid arthritis.