Neuropathic pain is caused by nerve damage that can be associated with chronic inflammation or direct nerve injury. This type of pain differs from ordinary pain in that it is usually perceived as ongoing burning or as ‘pins and needles’ electric-shock type of sensation. It is the type of pain that often associated with shingles, cancer, repetitive motion disorders, HIV/AIDS, and trauma and does not respond well to conventional pain-relieving drugs.
One cause of neuropathic pain is thought to be inflammatory cytokines, proteins which are involved in developing and sustaining chronic pain states. Cytokines act as messengers to either stimulate or inhibit the immune response and are produced by many cell types including white blood cells present during infection and inflammation.
UC San Diego researchers observed that injured peripheral nerves in both mice and rats release protein LRP1 into the surrounding tissue. Administrating LRP1 into the rodents’ sciatic nerves prior to injury provided a protective effect, decreasing the level and activity of injury-induced proinflammatory cytokines and inhibiting spontaneous pain.
In addition to decreasing inflammatory cytokines locally, treatment with LRP1 also decreased inflammatory cytokines in a region called the spinal dorsal horn, where central pain processing occurs. LRP1 does have limits and does not completely block the increase in proinflammatory cytokines after nerve injury. The researchers feel that their study opens up a number of new research directions for understanding and treating chronic neuropathic pain.