Research in horses may eventually lead to a treatment for people who develop blindness as a result of the autoimmune disease recurrent uveitis, according to a study recently published in the Frontiers in Immunology journal.
According to the study authors, recurrent uveitis (RU) is “a leading cause of ocular detriment” in both humans and horses. In Equine Ophthalmology by Ann E. Dwyer, she notes that data suggests at least 1% of horses lose sight in one or both eyes during their lifetime. A 2012 study published in the Ophthalmology journal said uveitis was estimated to cause 30,000 new cases of legal blindness in humans annually in the U.S.
“Equine and human RU share many similarities including spontaneous disease and aberrant cytokine signaling,” said authors of the recent study. Cytokines are a type of protein made by certain immune and non-immune cells and they effect on the immune system.
SOCS1 is “a critical regulator of cytokine signaling,” per the study authors, and reduced levels of it are associated with multiple autoimmune diseases. In the past, topical administration of SOCS1-KIR, a substance that mimics SOCS1, was linked with reduced ocular issues in horses with RU.
To dive further into the impact of SOCS1-KIR, the research team assessed its impact on equine peripheral blood mononuclear cells (PBMC) and its impact via topical administration of SOCS1-KIR into the eyes of experimental (non-uveitic) horses. They said the research included applying SOCS1-KIR or carrier eye-drops to “experimental horse eyes” twice daily for 21 days.
“Topical administration of a SOCS1 peptide mimic is safe to the equine,” the researchers said. Additionally, the team determined that the application reduced two ERU associated cytokines: IL-10 and TNFα.
They explained that “IL-10 is produced by monocytes and lymphocytes following proinflammatory response,” while “TNFα can be produced by numerous cell types of myeloid and lymphoid origins.”
In patients with RU, “TNFα is thought to disrupt the blood–retina barrier, promote proinflammatory immune cell influx into the eye, and play a critical role in disease progression,” the researchers said. Substances that block TNFα are already used in some patients with uveitis, but they are not always effective and they have been implicated in susceptibility to some cancers.
“Notably, SOCS1 is a critical regulator of not only TNFα production but also cellular responsiveness to the cytokine,” said the study. Its authors also said that the impact of SOCS1-KIR on the cytokines could serve as “potential biomarkers of drug efficacy in a future clinical trial.”
Going forward, the researchers said the success of SOCS1-KIR in horses could be relevant to treatments for RU in humans.
“There is evidence for translation between horses and humans in recurrent uveitis,” said the study.
According to the National Federation of the Blind, “there are several ways to define blindness,” and there are also different reasons why 7 million people in the U.S. deal with either blindness or vision loss, as estimated by the U.S. Centers for Disease Control and Prevention. In 2022, Audacy reported on how another animal – pigs – helped researchers develop a treatment that helped restore some vision in patients who had visual impairment related to corneal stroma diseases such as keratoconus (thinning and bulging of the cornea).