How cannabis suppresses immune functions: Cannabis compounds found to trigger unique immune cells which promote cancer growth
November 26, 2010
Science Daily/Wiley-Blackwell
An international team of immunologists studying the effects of cannabis have discovered how smoking marijuana can trigger a suppression of the body's immune functions. The research, published in the European Journal of Immunology, reveals why cannabis users are more susceptible to certain types of cancers and infections.
The team, led by Dr Prakash Nagarkatti from the University of South Carolina, focused their research on cannabinoids, a group of compounds found inside the cannabis plant, including THC (delta-9 tetahydrocannabinol) which is already used for medical purposes such as pain relief.
"Cannabis is one of the most widely used drugs of abuse worldwide and it is already believed to suppress immune functions making the user more susceptible to infections and some types of cancer," said Dr Nagarkatti. "We believe the key to this suppression is a unique type of immune cell, which has only recently been identified by immunologists, called myeloid-derived suppressor cells, MDSCs."
While most immune cells fight against infections and cancers to protect the host, MDSCs actively suppress the immune system. The presence of these cells is known to increase in cancer patients and it is believed that MDSCs may suppress the immune system against cancer therapy, actually promoting cancer growth.
Dr Nagarkatti's team demonstrated that cannabinoids can trigger a massive number of MDSCs through activation of cannabinoid receptors. This research reveals, for the first time, that marijuana cannabinoids may suppress the immune system by activating these unique cells.
"These results raise interesting questions on whether increased susceptibility to certain types of cancers or infections caused from smoking marijuana results from induction of MDSCs," said Nagarkatti. "MDSCs seem to be unique and important cells that may be triggered by inappropriate production of certain growth factors by cancer cells or other chemical agents such as cannabinoids, which lead to a suppression of the immune system's response."
In a related study, also published in the European journal of Immunology, Dr Christian Vosshenrich from the Institut Pasteur in Paris, reveals that when cancer cells grow they produce a molecule called interleukin-1 β (IL-1β), which also triggers MDSCs. This study identifies how MDSCs produced during cancer growth also weaken the ability of immune cells to kill cancer cells.
"Marijuana cannabinoids present us with a double edged sword," concluded Dr Nagarkatti. "On one hand, due to their immunosuppressive nature, they can cause increased susceptibility to cancer and infections. However, further research of these compounds could provide opportunities to treat a large number of clinical disorders where suppressing the immune response is actually beneficial."
https://www.sciencedaily.com/releases/2010/11/101124214728.htm
Smoking Pot Alters More Than Mood — Human Immune System Affected
August 28, 2002
Science Daily/University Of South Florida Health Sciences Center
Marijuana may alter immune function in people -- but the jury is still out on whether it hurts or helps the body's ability to fight infection or other diseases, report researchers at the University of South Florida College of Medicine and the UCLA School of Medicine in Los Angeles. "The bottom line is you cannot routinely smoke marijuana without it affecting your immune system," said Thomas Klein, PhD, professor of medical microbiology and immunology at USF. "However, because of the complexity of the immune system, we can't say yet whether the effect we've observed in humans is good or bad."
A study by USF and UCLA is the first to show that healthy humans who smoke marijuana appear to alter the expression of marijuana receptors, or molecules, on immune cells in their blood. The findings were reported in the June issue of the Journal of Neuroimmunology.
Pot's influence on the immune system continues to be hotly debated. While more human studies are needed, overwhelming evidence from animal studies indicates that marijuana and its psychoactive compounds, known as cannabinoids, suppress immune function and inflammation.
"This suggests marijuana or cannabinoids might benefit someone with chronic inflammatory disease, but not someone who has a chronic infectious disease such as HIV infection," said Dr. Klein, lead investigator of the study.
The USF/UCLA group is one of few in the world conducting studies to define the role of cannabinoid receptors in regulating immunity in both drug abusers and nonusers.
If the results in animals hold true in humans, their work might lead to the development of safe and effective cannabinoid drugs for certain diseases, Dr. Klein said. "If the cannabinoids in marijuana are effective immune suppressors, this property might be harnessed to treat patients with overly aggressive immune responses or inflammatory diseases like multiple sclerosis and rheumatoid arthritis."
Receptors that react to delta-9 tetrahydrocannabinol or THC, the compound in marijuana that produces a high, have been found in tissues throughout the body and in the brain. A naturally circulating THC-like substance called anandamide also binds to and activates these marijuana, or cannabinoid, receptors, indicating that the body's own cannabinoid system plays a physiological role in normal immunity as well as defining moods, Dr. Klein said.
In the USF/UCLA study, researchers analyzed blood samples from 56 healthy volunteers -- including 10 chronic marijuana smokers, ages 22 to 46, participating in lung and immune function studies at UCLA. The marijuana smokers denied use of any other drugs, and the nonsmokers denied all illegal drug use. Because no accurate way yet exists to directly study the expression of cannabinoid receptors on immune cells, the researchers looked at the genetic material (messenger RNA) that is the direct predecessor, or precursor, of the receptor.
They found that the baseline genetic expression of precursor RNA was consistent across all age, gender and ethnic groups. But, the peripheral blood cells from the marijuana users expressed significantly higher levels of cannabinoid receptor messenger RNA than blood cells from non-users. The levels increased regardless of the amount of marijuana use, although all users in the study had a history of smoking pot several times or more a week.
https://www.sciencedaily.com/releases/2002/08/020828062229.htm
Marijuana may help HIV patients keep mental stamina longer
December 12, 2017
Science Daily/Michigan State University
A chemical found in marijuana, known as tetrahydrocannabinol, or THC, has been found to potentially slow the process in which mental decline can occur in up to 50 percent of HIV patients, says a new Michigan State University study.
"It's believed that cognitive function decreases in many of those with HIV partly due to chronic inflammation that occurs in the brain," said Norbert Kaminski, lead author of the study, now published in the journal AIDS. "This happens because the immune system is constantly being stimulated to fight off disease."
Kaminski and his co-author, Mike Rizzo, a graduate student in toxicology, discovered that the compounds in marijuana were able to act as anti-inflammatory agents, reducing the number of inflammatory white blood cells, called monocytes, and decreasing the proteins they release in the body.
"This decrease of cells could slow down, or maybe even stop, the inflammatory process, potentially helping patients maintain their cognitive function longer," Rizzo said.
The two researchers took blood samples from 40 HIV patients who reported whether or not they used marijuana. Then, they isolated the white blood cells from each donor and studied inflammatory cell levels and the effect marijuana had on the cells.
"The patients who didn't smoke marijuana had a very high level of inflammatory cells compared to those who did use," Kaminski said. "In fact, those who used marijuana had levels pretty close to a healthy person not infected with HIV."
Kaminski, director of MSU's Institute for Integrative Toxicology, has studied the effects of marijuana on the immune system since 1990. His lab was the first to identify the proteins that can bind marijuana compounds on the surface of immune cells. Up until then, it was unclear how these compounds, also known as cannabinoids, affected the immune system.
HIV, which stands for human immunodeficiency virus, infects and can destroy or change the functions of immune cells that defend the body. With antiretroviral therapy -- a standard form of treatment that includes a cocktail of drugs to ward off the virus -- these cells have a better chance of staying intact.
Yet, even with this therapy, certain white blood cells can still be overly stimulated and eventually become inflammatory.
"We'll continue investigating these cells and how they interact and cause inflammation specifically in the brain," Rizzo said. "What we learn from this could also have implications to other brain-related diseases like Alzheimer's and Parkinson's since the same inflammatory cells have been found to be involved."
Knowing more about this interaction could ultimately lead to new therapeutic agents that could help HIV patients specifically maintain their mental function.
"It might not be people smoking marijuana," Kaminski said. "It might be people taking a pill that has some of the key compounds found in the marijuana plant that could help."
https://www.sciencedaily.com/releases/2017/12/171212092100.htm