Laser light used in targeted treatment of arthritis

While there are drugs that help reduce the symptoms of rheumatoid arthritis in the joints, those medications can have unpleasant side effects in other parts of the body. An experimental new light-based system, however, is being designed to change that.

One of the problems with existing rheumatoid arthritis drugs lies in the fact that after they’ve been ingested or injected, they’re distributed throughout (and are active within) the entire body. This means that if they’re taken in the quantities needed to reduce inflammation of the joints, they may produce side effects such as stomach aches or insomnia.

If they could only become active when they were at the joints, then much smaller doses would be required, resulting in fewer side effects. That’s where the new system comes in.

Developed by scientists at the University of North Carolina in Chapel Hill, it involves attaching an existing drug to specially-engineered vitamin B12 molecules. Those molecules are then loaded into red blood cells, which get injected into the bloodstream.

As long as those cells aren’t subsequently exposed to long-wavelength tissue-penetrating laser light, the drug remains trapped and inactive within them for up to two hours. If a laser is held to the skin at an arthritic joint, however, even low levels of its light within that joint trigger the nearby B12 molecules to release their drug payload from within the red blood cells. As a result, the medication only kicks in once it’s at the target joint.

In lab tests, the technology was successfully used to deliver the arthritis drug dexamethasone to the arthritic paws of mice. When compared to simply injecting pure dexamethasone straight into the bloodstream, the laser-activated system required a three-fold lower dose to achieve the same therapeutic effect.

“We hope that our drug delivery platform will better control drug delivery and decrease the amount of systemic exposure and off-target effects,” says team member and doctoral candidate Emilia Zywot. “We envision that it will be useful for any drug that can be synthetically attached to our light-responsive system, making it amenable to applications beyond arthritis.”

The abstract for a paper on the research was recently published in The FASEB Journal.

Source: Experimental Biology via EurekAlert

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