Scientists describe protein that regulates iron metabolism in horses

Hepcidin is secreted during inflammatory processes to reduce the iron level in the blood and hinder the multiplication of microorganisms, according to a Unesp study.

By Karina Toledo

Agência FAPESP – Hepcidin is a peptide that performs a fundamental role in iron metabolism and the organism’s immune response against bacteria and fungi. Its mechanism of action, which was demonstrated in humans in 2000, has now also been described in equines, ovines and asinines by scientists at Universidade Estadual Paulista (Unesp).

“Iron is an essential element for multiplication of some microorganisms,” says Alexandre Secorun Borges, professor at the Botucatu Veterinary Medicine and Zootechny School (FMVZ). “At the first sign of infection, however, hepcidin kicks into action to reduce the levels of the mineral in the blood system and make the environment less propitious to invaders.”

“Expressed principally by liver cells, hepcidin connects itself to another protein called ferroportin. This helps in the retention of iron within some specific cells instead of being exported to the blood stream. This is why chronic inflammation often causes anemia,” explains the veterinarian.

It is estimated that this defense mechanism is present in all mammals and some fish. However, according to Borges, in the majority of species, the peptide has not been characterized, and its function has not been proven.

The team coordinated by Borges sequenced the hepcidin gene in equines. Expression of the peptide gene was analyzed in liver cells and other healthy horse tissues.

The study, conducted in partnership with scientists from Cornell University, resulted in the doctoral thesis of José Paes de Oliveira Filho, funded by FAPESP and concluded in December 2010.

The results were published in an article in Veterinary Immunology and Immunopathology.

Using resources from a FAPESP Doctoral Fellowship and a Regular Research Award, the team formed the Molecular Biology Laboratory at FMVZ’s Veterinary Clinic.

Induced inflammation

The second stage of the study consisted of proving the role of hepcidin in the organism’s defense against infection. Two experimental models were used to induce light inflammation in healthy horses.

In the first experiment, the researchers intravenously injected a toxin extracted from the membrane of bacteria, lipopolysaccharide (LPS). “This causes a discrete, short-term systemic inflammation that does not cause long-term damage to the animals,” explains Borges.

Every two hours after the LPS was administered, the researchers collected and analyzed the horse blood. “The plasmatic iron level dropped rapidly. Through a liver biopsy, we proved that hepcidin gene expression had increased in this organ,” comments Borges. The results of this study were published in Innate Immunity.

The second experiment consisted of intramuscular injection of a substance called Freund’s complete adjuvant, which is composed of inactive microbacteria. This adjuvant causes inflammation in animals.

The results, which were similar to the first study, were presented at American College Veterinary Internal Medicine in the United States in 2010 and should soon be published. The group conducted similar experiments in ovines with financing from the National Council of Scientific and Technological Development (CNPq). The study was the topic of Peres Ramos Badial’s master’s thesis.

The sequencing and the expression of hepcidin in asinines were also the objectives of a scientific initiation project funded through a FAPESP scholarship.

This line of research began during Borges’ post-doctoral studies at Cornell University. “We analyzed the medical records of horses with chronic, systemic and localized inflammation and compared them to those of healthy horses. We observed iron drop considerably and quickly, therefore making it a reliable marker of inflammation in horses,” he said.

In the future, the team intends to evaluate the characteristics of iron metabolism in different illnesses. “We want to discover if the intensity in the decline of iron levels is related to the aggressiveness of the inflammation,” explains Borges.
 
Another future project is to evaluate whether the artificial reduction of iron in the blood stream could facilitate fighting infections. “We will test whether administering hepcidin as a medication helps in the initial phases of the disease,” he says.