Researchers at Massachusetts General Hospital (MGH) are investigating why people with red hair sometimes demonstrate altered sensitivity to certain kinds of pain. The findings are published in Science Advances.
In people with red hair, and other mammalian species with red hair or fur, contain a pigment-producing variant form of melanocortin 1 receptor. Previous research led by David E. Fisher, Director of the Mass General Cancer Center's Melanoma Program and MGH's Cutaneous Biology Research Center, demonstrated that the inability of red-haired individuals to tan or darken their skin pigment is traced to inactive variants of this receptor.
To study the mechanism behind different pain thresholds in red-haired subjects, Fisher and his colleagues studied a strain of red-haired mice that (as in humans) contains a variant that lacks melanocortin 1 receptor function and also exhibits higher pain thresholds. Their team discovered that the loss of melanocortin 1 receptor function in the red-haired mice caused the animals' melanocytes to secrete lower levels of POMC (proopiomelanocortin). POMC is cut into different hormones including one that sensitizes to pain and one that blocks pain. These hormones maintain a balance between opioid receptors that inhibit pain and melanocortin 4 receptors that enhance the perception of pain.
"These findings describe the mechanistic basis behind earlier evidence suggesting varied pain thresholds in different pigmentation backgrounds," says Fisher. "Understanding this mechanism provides validation of this earlier evidence and a valuable recognition for medical personnel when caring for patients whose pain sensitivities may vary."
Image credit: Mitchell Griest