Researchers from the University of South Carolina say that tetrahydrocannabinol, the principal constituent of marijuana, may have another medical use – treating those with autoimmune disorders.

Tetrahydrocannabinol (THC) is known to have analgesic effects so can be used to treat pain. It also aids relaxation and can reduce feelings of nausea and stimulate appetite, making it useful for those undergoing chemotherapy.

Now, a new study, published in the Journal of Biological Chemistry, explores how microRNAs are influenced by THC.

MicroRNAs (miRNAs) are small, single-stranded, non-coding RNAs that play a vital role in regulating gene expression. And the authors claim that the ability to alter miRNA expression may be the key to successful treatment for many autoimmune diseases, including multiple sclerosis, arthritis and type 1 diabetes.

The researchers, from the university’s School of Medicine, injected mice with THC and analyzed their RNA. Of the 609 miRNAs tested, the researchers identified 13 that were highly altered by the THC.

MiRNAs greatly influence the immune system, acting as “brakes” that target more than 60% of all gene expression. Since miRNAs usually suppress the expression of genes, when a miRNA is over-expressed, the affected gene gets silenced.

But when a miRNA is turned off, the affected gene is expressed at a higher level.

The report states that the regulation of gene expression by miRNAs is thought to be vital in a wide range of biological processes. The authors point to emerging evidence that suggests miRNAs “regulate the development, differentiation and function of a variety of immune cells including myeloid cells.”

For this study, the researchers also explored one specific miRNA – miRNA-690 – that was greatly over-expressed by the presence of THC and targets an important protein called C/EBPα. This protein, in turn, triggers myeloid-derived suppressor cells (MDSC), which suppress inflammation.

When the researchers successfully knocked out the miRNA-690, the effect of THC was reversed.

The current study, led by Dr. Venkatesh Hegde, suggests the effects of marijuana may be “a double-edged sword.” Its ability to suppresses inflammation provides effective treatment against inflammatory and autoimmune diseases, but that very action may leave the body open and vulnerable to other diseases.

Lead authors Drs. Prakash and Mitzi Nagarkatti have studied how marijuana can alter immune functions and inflammation for over a decade. They were the first to show that marijuana components trigger MDSC to suppress inflammation.

Dr. Mitzi Nagarkatti, chair of the Department of Pathology, Microbiology and Immunology at USC’s School of Medicine, says the latest study demonstrates that understanding how to control microRNA expression holds tremendous potential for new medical breakthroughs.

She explains:

MicroRNA therapeutics is an important, rapidly growing area with major pharmaceutical companies getting into this discovery and development. While our study identifies the molecular mechanism of immune-altering effects of marijuana, select microRNA identified here could serve as important molecular targets to manipulate MDSC activity in cancer and inflammatory diseases.”

This is not the first study to herald the medicinal qualities of marijuana. Medical News Today reported last month that chemicals within the plant may protect the body against multiple sclerosis.