notes on nettle 

Be Nice to Nettles: Take a look at the stinging nettle, its value to wildlife and its role in society

from Greg Kelly

Today both the root and leaves of stinging nettle are used in the supplement industry; however, many traditional cultures used nettles topically to stimulate paralyzed muscles or to provide temporary relief from rheumatic pains. While the leaf and root overlap a bit in their activities (especially in the area of balancing immune messenger molecules), each of these parts of the plant have some unique actions.

Pharmacology 

Stinging nettle contains formic acid, a high proportion of chlorophyll, flavonoids, plant sterols, plant enzymes, a wide range of minerals, and plant lignans. Stinging nettle also contains a small-molecular-weight lectin (Urtica dioica agglutinin (UDA)) purified from the rhizomes (roots), which exhibits antiviral activity and is capable of favourably inducing a balanced immune response.

Anti-inflammatory 

Stinging nettle demonstrates anti-inflammatory activity in experimental situations. The extract partially inhibits the activity of 5-lipoxygenase and shows a concentration dependent inhibition of the synthesis of cyclooxygenase derived reactions.(2) (Note: these are the same enzymes that aspirin inhibits). A new class of drugs (called Cox2 inhibitors) aimed specifically at modulating cyclooxygenase enzymes is one of the new darling in the pharmaceutical industry.

Stinging nettle (both the leaf and root) also appears to prevent the over stimulation of proinflammatory cytokines like tumor necrosis factor-alpha and interleukin-1 beta. Cytokines can be thought of in simple terms as immune system messengers. And while a discussion of these proinflammatory cytokines and immune system balance is beyond the scope of this column, cytokine balance is a growing area of interest in medicine.

In fact, virtually all immune disorders (from HIV, to cancer, to autoimmune diseases), allergic conditions (like asthma and allergies) and even obesity/insulin resistance have characteristic imbalances in cytokine levels as part of the functional derangement occurring at a metabolic level. Between the lipoxygenase, cyclooxygenase, and cytokine modulating activities of this plant, stinging nettle is literally a treasure chest of unexplored potential.

Anti-viral and Immune Balancing

UDA Superantigen Stinging nettle actually contains a "super lectin" called UDA superantigen (UDA for short). For those interested, UDA appears to be an N-acetylglucosamine specific lectin. Evidence indicates that this super lectin can inhibit a range of viruses including those responsible for HIV, colds, and influenza.(4)

UDA is also T-cell mitogen, distinguishable from classical T-cell lectin mitogens, by its ability to discriminate a particular population of CD4+ and CD8+ T-cells, as well as its capacity to induce an original pattern of T-cell activation and cytokine production.(5) Basically, what this means is that unlike most things that stimulate the immune system only toward greater activity, the super lectin in stinging nettles appears to stimulate the immune system to be in balance.(6)

While studies in humans are lacking (and would be extremely desirable), the UDA super lectin has been shown to prevent the progression of experimentally induced systemic lupus erythematosus-like pathology in mice. In the experiment, UDA-lectin treated animals did not develop overt clinical signs of lupus and nephritis (kidney disease). UDA was also shown to alter the production of autoantibodies in a sex-dependent manner.(14)

Allergic Rhinitis 

The leaf of stinging nettle was investigated for allergies (the root is typically not used for this application). Sixty-nine individuals completed a double-blind randomized study comparing the effects of a freeze-dried preparation of stinging nettle with placebo on allergic rhinitis. Efficacy with stinging nettle was rated higher than placebo in global assessments and slightly higher than placebo when comparing diary data.(7) While the overall improvement in this study was not mind-boggling, I have had many patients who have felt benefits from taking this as a dietary supplement during allergy season.

References

1. Smallman BN, Maneckjee A. The synthesis of acetylcholine by plants. Biochem J 1981;194:361-364.

2. Obertreis B, Giller K, Teucher T, et al. Anti-inflammatory effect of Urtica dioica folia extract in comparison to caffeic malic acid. Arzneimittelforschung 1996;46:52-56. [Article in German]

3. Obertreis B, Ruttkowski T, Teucher T, et al. Ex-vivo in-vitro inhibition of lipopolysaccharide stimulated tumor necrosis factor-alpha and interleukin-1 beta secretion in human whole blood by extractum urticae dioicae foliorum. Arzneimittelforschung 1996;46:389-394.

4. Balzarini J, Neyts J, Schols D, et al. The mannose-specific plant lectins from Cymbidium hybrid and Epipactis helleborine and the (N-acetylglucosamine)n-specific plant lectin from Urtica dioica are potent and selective inhibitors of human immunodeficiency virus and cytomegalovirus replication in vitro. Antiviral Res 1992;18:191-207.

5. Galelli A, Truffa-Bachi P. Urtica dioica agglutinin. A superantigenic lectin from stinging nettle rhizome. J Immunol 1993;151:1821-1831.

6. Galelli A, Delcourt M, Wagner MC, et al. Selective expansion followed by profound deletion of mature V beta 8.3+ T cells in vivo after exposure to the superantigenic lectin Urtica dioica agglutinin. J Immunol 1995;154:2600-2611.

7. Mittman P. Randomized, double-blind study of freeze-dried Urtica dioica in the treatment of allergic rhinitis. Planta Med 1990;56:44-47.

8. Hirano T, Homma M, Oka K. Effects of stinging nettle root extracts and their steroidal components on the Na+,K(+)-ATPase of the benign prostatic hyperplasia. Planta Med 1994;60:30-33.

9. Hryb DJ, Khan MS, Romas NA, Rosner W. The effect of extracts of the roots of the stinging nettle (Urtica dioica) on the interaction of SHBG with its receptor on human prostatic membranes. Planta Med 1995;61:31-32.

10. Schottner M, Gansser D, Spiteller G. Lignans from the roots of Urtica dioica and their metabolites bind to human sex hormone binding globulin. Planta Med 1997;63:529-532.

11. Schneider HJ, Honold E, Masuhr T. Treatment of benign prostatic hyperplasia. Results of a treatment study with the phytogenic combination of Sabal extract WS 1473 and Urtica extract WS 1031 in urologic specialty practices. Fortschr Med 1995;113:37-40. [Article in German]

12. Sokeland J, Albrecht J. Combination of Sabal and Urtica extract vs. finasteride in benign prostatic hyperplasia (Aiken stages I to II). Comparison of therapeutic effectiveness in a one year double-blind study. Urologe A 1997;36:327-333. [Article in German]

13. Krzeski T, Kazon M, Borkowski A, et al. Combined extracts of Urtica dioica and Pygeum africanum in the treatment of benign prostatic hyperplasia: double-blind comparison of two doses. Clin Ther 1993;15:1011-1020.

14. Musette P, Galelli A, Chabre H, Callard P, Peumans W, et al. Urtica dioica agglutinin, a V beta 8.3-specific superantigen, prevents the development of the systemic lupus erythematosus-like pathology of MRL lpr/lpr mice. Eur J Immunol 1996;26:1707-1711