Discover how red and near-infrared light therapy may help relieve neuropathic pain by reducing inflammation and promoting nerve repair.
Imagine that the movement of a single hair on your arm triggers severe pain. For people with neuropathic pain — a chronic condition affecting roughly 7–8 % of Europeans and lacking reliable treatments — this can be everyday life.
Scientists at EMBL Rome have now pinpointed a distinct population of skin nerve cells that detect gentle touch and, in neuropathic pain, relay it as intense pain. The team, led by group leader Paul Heppenstall, created a light-sensitive compound that binds only to these cells. After injecting the chemical into affected skin and illuminating the area with near-infrared light, the targeted nerve endings retract, reducing pain. Nature Communications published the findings on 24 April 2018.
The "spicy" effect
By clipping the nerve endings with light, the gentle touch that once hurt no longer registers. "It's like eating a hot chili: the nerve endings in your mouth burn and then go numb for a while," Heppenstall explains. "The advantage of our approach is that we hit the precise subgroup of neurons driving neuropathic pain."
Skin contains many types of sensory neurons that signal vibration, cold, heat, or ordinary pain; these remain untouched. Only the lightest sensations — a breeze, tickle, or an insect crawling — are temporarily blocked.
Light versus drugs
Most earlier drug strategies aimed at single molecules. "We believe many molecules are involved," Heppenstall notes. "Blocking one or two usually lets others take over. Our illumination method bypasses that problem."
The researchers assessed touch and pain by measuring paw-withdrawal reflexes in mice with limb neuropathy. After treatment, the animals reacted normally to gentle touch. Relief lasted several weeks; once the nerve endings regenerated, hypersensitivity returned.
Preliminary work on human skin samples showed similar neuron characteristics, suggesting the technique might translate to patients. "Ultimately, we want to tackle pain in both humans and animals," Heppenstall says. "Much more work is needed before clinical studies, so we are seeking partners to advance the method."
