A peptide derived from erythropoietin (EPO) demonstrated potent clinical benefits in animal models of multiple sclerosis (MS) without inducing hematologic side effects, according to research published online ahead of print August 14 in Neurotherapeutics. The peptide, JM-4, reduced disability and protected against demyelination in mice with experimental autoimmune encephalomyelitis (EAE). Unlike full-length EPO, JM-4 did not elevate hematocrit in mice with EAE, said RuiRong Yuan, MD, of the VA Medical Center of East Orange and the Department of Neurology and Neurosciences at Rutgers New Jersey Medical School in Newark.
JM-4 “may hold considerable potential for direct clinical application in the treatment of neuroinflammatory diseases, demyelinating illnesses, CNS trauma, and stroke, as well as in the treatment of inflammatory/immune diseases of non-neural origins,” said Dr. Yuan and her research colleagues.
Dissecting EPO
Prior studies have found that full-length EPO may be tissue-protective in several animal models of neurologic injuries, including traumatic brain injury and stroke, but EPO may induce hazardous increases in red cell mass, which can lead to cardiovascular complications. Dr. Yuan and colleagues hypothesized that the erythropoietic and tissue-protective elements of EPO reside in different domains of the molecule and the tissue-protective domains could be separated from the regions responsible for erythropoiesis.
To test their hypothesis, the researchers generated a set of EPO-derived small peptides that contain one or two cysteines within a 7- to 25-mer peptide. They screened these peptides for biologic activity and stability in vitro. They then studied whether the peptides retained their tissue-protective properties in two mouse models of EAE: C57BL/6 mice with EAE induced by immunization with proteolipid protein (PLP) and SJL/J mice with EAE induced by immunization with myelin oligodendrocyte glycoprotein (MOG).
Peptides Did Not Elevate Hematocrit
The investigators previously reported that full-length EPO demonstrated beneficial effects in EAE C57BL/6 mice without significantly altering hematocrit. In EAE SJL/J mice, however, half of the animals rapidly developed clinical symptoms related to erythrocytosis and died after less than seven days of EPO therapy.
In studying the EPO-derived peptides, researchers compared SJL/J mice that were treated with full-length EPO or EPO-derived peptides, and a control group that received phosphate-buffered saline (PBS) as a sham treatment. Hematocrit increased dramatically after whole EPO treatment for seven days, rising to approximately 75% by day 14, said Dr. Yuan. In contrast, hematocrit levels in groups treated with PBS or the peptides, including JM-4, remained unchanged at approximately 51% over the five-week follow-up period.
JM-4 Reduced Disability
The investigators found that the 19-mer JM-4 peptide possessed more consistent beneficial effects than all of the other EPO-derived peptides in their set. To determine if JM-4 could prevent disease exacerbation, SJL/J mice were first immunized with a suboptimal dose of PLP, which induced significant neurologic disability by day 10. Symptomatic mice were then treated with IV JM-4 at 250 μg/kg/day in 200 μL of PBS, or sham-treated with PBS for seven days. Early sustained clinical improvement occurred in the JM-4 treated group compared with the group receiving sham treatment.
Similar results were observed in experiments using the monophasic C57BL/6 EAE disease model. Significant clinical improvement was observed in both the EPO- and JM-4-treated groups, compared with the control group.
Modifying Flare-Ups
To see if JM-4 could modify recurrent disease flare-ups and if symptom improvement could be sustained after termination of therapy, the researchers employed a relapsing-remitting model of EAE. The investigators immunized SJL/J mice with a suboptimal dose of PLP and allowed the animals to recover without intervention. The recovered mice were then separated into two groups that received treatment with JM-4 or PBS for seven days before being challenged with a second immunization containing the same amount of PLP antigen. Previous JM-4 therapy delayed the onset of disease and significantly reduced EAE-induced motor dysfunction compared with the sham-treated mice. Over the following five weeks, the sham-treated group continued to exhibit protracted relapses and more pronounced neurologic deficit, while the JM-4-treated mice had mild disease with little or no hindlimb impairment.
Further examination revealed that JM-4 treatment protected against demyelination and axonal damage in the acute EAE spinal cord, compared with sham treatment. JM-4 treatment also modulated inflammatory and immune reaction within the peripheral lymphatic tissue. In addition, the peptide suppressed proinflammatory cytokine production in MOG peptide enriched T cells and provided neuroprotection against cytotoxic insult, said the researchers.
Potential in a Range of Diseases?
It was important that JM-4 demonstrated therapeutic effect during early neurologic presentation in the EAE animal models because that time point more accurately reflects the human clinical situation.