PURPOSE

The purpose of this study was to investigate the effects of Kava on natural killer (NK) cell activity. Cancer accounts for nearly one-fourth of the deaths in the United States, exceeded only by heart disease. It has been suggested that an increase in the stress response, such as that occurring with surgical excision of tumors, may suppress NK cell activity and that alleviating stress may benefit cancer patients. Natural killer cells are a small fraction of lymphocytes that are specialized to kill certain types of target cells, specifically host cells that have become infected with a virus or that have become cancerous. Kava, an indigenous plant of the Oceania island communities of the Pacific Ocean, has been valued for its anxiolytic and sedative properties for centuries.

BACKGROUND

Since 1950, heart-disease-related deaths have decreased by more than half; however, cancer death rates have remained the same. The American Cancer Society estimates that 1.37 million new cases of cancer will be diagnosed in the United States in the year 2004. The total cost of cancer in 2002 was estimated at $189.5 billion, with $64.2 billion coming directly from medical cost.1 The first line of defense in the treatment of cancer is often surgery. However, surgery is also associated with the risk of metastasis.2 Some possible reasons for metastasis are due to manipulation of the tumor during surgery, possibly causing the release of malignant cells into the bloodstream, enzymatic degradation of the extracellular matrix that surrounds the tumor, local and systemic release of growth factors and cytokines from the surgical sire, and perioperative suppression of cell-mediated immunity. Other clinical contributors that play a role are pain, stress, and anxiety related to surgery and anesthesia. These mechanisms can act synergistically to make the patient vulnerable to metastasis.3 Natural killer cell activity helps in the body's defense against cancer metastasis; however, it is often suppressed during surgery.4 In animals, NK cells have been shown to play an important role in controlling solid tumors and leukemia.5 In human beings, higher levels of NK cell activity have been associated with a good prognosis after excision of various types of cancer.6 Kava has been used for its anxiolytic and sedative effects for centuries. It has been found to have an effect on [gamma]-aminobutyric acid receptors and to be effective at treating mild to moderate anxiety. Currently, there are no anesthetic regimens that have been shown to completely reverse surgical stress-induced suppression of NK cell activity. If, however, Kava is an effective anxiolytic, has minimal interaction with existing anesthetics, and inhibits surgical suppression of NK cell activity, it may increase host resistance against metastasis and thus promote patient survivability.5,6 The major goals of this project are to investigate the effects of Kava on surgical suppression of NK cell activity.

METHODS

The study was a prospective experimental design in which we observed the effects of Kava on NK cell activity and number preoperatively and postoperatively. Male Sprague-Dawley rats are genetically similar and lack extraneous variables that could have confounded the data. Because of the homogeneity of our subjects, we used a Latin square to ensure equal number of rats per groups. Group 1 (n = 11) received the one-time dose of Kava (125 mg/kg) before surgery. Group 2 (n = 11) received just the vehicle before surgery, and group 3 (n = 11) received Kava (125 mg/kg) and did not have surgery. Preoperative and postoperative NK cell activity was compared between and within groups.

RESULTS

A repeated-measures analysis of variance was used to determine if there were any significant differences among the groups. Because of laboratory error, results were determined to be incorrect, and all specimens were rejected from this study.

CONCLUSIONS

These findings may provide invaluable information related to the potential benefits of Kava or similar herbal supplement administration to inhibit the surgical suppression of NK cell activity.

Acknowledgment

Thanks to Norma Garrett, PhD, CRNA, who designed and implemented this project and acted as mentor as well as researcher.

References