It is now commonly accepted that many severe or fatal reactions to influenza are caused by intense inflammatory overreactions of the immune system. A group from the Research School of Biology, Australian National University released an article on September 24, 2009 compiling evidence on this topic.
Cytokines are chemicals which are produced in immunological inflammatory reactions in the body. Studies indicate that certain plant extracts can be protective against lethal reactions for mice which are infected with a virulent influenza strain. This occurs through inhibition of novel inflammatory cytokine High Mobility Group Box 1 protein (HMGB1) by these plant extracts. Angelica sinensis (also known as Dang Gui) and Salvia Miltiorrhzia (also known as Dan Shen) were two of the herbal medicines studied which had this effect on HMGB1.
A drug known as gemfibrozil (a drug normally used to lower blood lipids) prevented a significant proportion of mice infected with H1N2 influenza from developing a fatal disease in a 2007 study. Gemfibrozil has a known ability to reduce expression of inflammatory cytokines, and this is thought to be the mechanism through which it protects against severe or fatal reactions in the mice. The action of this drug adds to the evidence that it is the body’s overproduction of cytokines which is involved in these severe cases of influenza.
Other studies have investigated Red Clover, Ginseng, Isatis, and Andrographis indicating that they modulate and reduce various aspects of cytokine response. Forsythia, Honeysuckle, Balloon Flower root, Licorice, Camilla sinensis (green tea) and Ginger have also been researched, results of which indicate that they reduce both production of pro-inflammatory cytokines and pro- inflammatory mediators (such as reactive oxygen species and nitric oxide). This is likely caused by suppressing a gene known as NF-kB which is often elevated in severe viral disease states, and which is related to disease conditions leading to multiple organ failure such as those in fatal influenza sepsis.
Combinations of these herbs are often used in Traditional Chinese Medicine to treat influenza from the earliest stages onward. For this reason it is particularly interesting to determine the immunological mechanisms through which they work.
In summary, this information indicates that it is the host response of the human body which may be involved in many of the fatal reactions in viral influenza infections. Treatments which can modulate this response in a patient who has contracted a viral influenza are therefore of great interest. More research needs to be done on these herbs since due to their mechanisms, they may be promising therapies to integrate with conventional influenza treatments.
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