Saturday, January 1, 2011

USC researcher expands understanding of marijuana’s health impact
Thursday, Dec. 02, 2010


Chemical compounds in marijuana can suppress the body’s immune functions — potentially speeding the growth of some cancers but possibly helping in the fight against arthritis, multiple sclerosis or allergies.

The good-news, bad-news findings were published in this month’s European Journal of Immunology, based on a study led by USC researcher Prakash Nagarkatti. An immunologist who has been exploring the potential of cannabis for eight years, Nagarkatti refers to the findings as “a double-edged sword.”

Nagarkatti’s earlier studies dealt mostly with marijuana’s potential to treat leukemia. The latest report, at first glance, seems to contradict his earlier findings. But Nagarkatti says the seeming contradiction just emphasizes the complexities of both marijuana and cancer.

“Cancer is not one illness. It is a very wide range of illnesses,” said Nagarkatti, the Carolina Distinguished Professor in the department of pathology, microbiology and immunology at the USC School of Medicine. “And marijuana has over 400 different chemicals. It’s such a complex plant that we don’t know the impact of all of those chemicals.”

The latest study on lab mice opens avenues for more research on the subject. Nagarkatti hopes it’ll lead to human clinical trials.

He also knows it will stir up the medicinal marijuana debate.

“I’m getting a lot of e-mails from both sides already,” he said.

Many comments tacked onto early online reporting about the study blast Nagarkatti as anti-medicinal marijuana. Those commenting don’t realize his earlier studies showed the promise of marijuana components, or that this study indicated as much positive and negative.

The research focused on cannabinoids, compounds found in the marijuana plant, and their impact on myeloid-derived suppressor cells. Research shows those cells suppress the immune system. Nagarkatti, along with co-authors Venkatesh Hegde and Mitzi Nagarkatti, found cannabinoids trigger creation of huge amounts of myeloid-derived suppressor cells in mice.

If the findings in mice are replicated in humans, doctors might re-think the use of the one FDA-approved, marijuana-derived drug — Marinol — to battle the nausea of chemotherapy and stimulate appetite in HIV-AIDS patients.

While reducing nausea, marijuana’s cannabinoids might also speed death by suppressing the immune system critical to battling many forms of cancer and infections. Of course, since HIV-AIDS also destroys the immune system, the impact of marijuana on the system in those cases might be minimal.

Conversely, cannabinoids might be a new tool for doctors to treat arthritis and multiple sclerosis. In those auto-immune diseases, your immune system goes into overdrive, destroying healthy cells. By suppressing immune response, cannabinoids could lessen the severity of those diseases. It also could help people battle allergies and fight transplant rejection, Nagarkatti said.

While smoking medicinal marijuana has been legalized in some states, the only FDA-approved application of cannabinoids in the U.S. is Marinol. Nagarkatti is fascinated by the medical possibilities of marijuana cannabinoids, but he doesn’t recommend self-prescribing its use.

“It’s a complex mixture of chemicals that’s not something to be played with,” Nagarkatti said.

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