A molecule reverses the process that leads to heart failure

A molecule developed by researchers at Stanford University in the United States and the Universidade de São Paulo proved able to stabilize and even reverse the degenerative process observed in congestive heart failure.

By Karina Toledo

Agência FAPESP – A molecule developed by researchers at Stanford University in the United States and the Universidade de São Paulo (USP) proved able to stabilize and even reverse the degenerative process observed in congestive heart failure. The illness, which is characterized by the heart’s inability to adequately pump blood, leads to the death of 70% of all patients within the first five years.

The results of the pre-clinical testing on the molecule, called βIIV5-3, were published in PLoS One. The study is part of the post-doctoral studies of FAPESP fellow Julio Cesar Batista Ferreira.

“Heart failure is the common end result of different cardiovascular diseases like myocardial infarction and arterial hypertension. Once the condition has set in, patients don’t tend to live for very long, even with the help of all the medications on the market,” said Ferreira, professor at the USP Institute of Biomedical Sciences.

While he was still working toward his doctorate at the USP School of Physical Education and Sports as an advisee of Professor Patricia Chakur Brum, Ferreira found evidence that a protein called PKCβII (protein kinase C isoform βII) could be the villain behind the process that leads to heart failure.

To test his hypothesis, he sought to create a molecule capable of inhibiting the action of this protein in heart cells. The work was performed in collaboration with researcher Daria Mochly-Rosen at the Stanford Medical School.

“βIIV5-3 is a combination of six amino acids bonded to a carrier molecule able to cross cell membranes. This characteristic inhibits interaction of the protein with its receptor,” said Ferreira.

To arrive at this combination, the scientists used computer programs to align two proteins and identify structural similarities and differences. He explained, “This allows you to choose specific regions for interaction between the proteins.”

The team then tested the molecule in two animal models. In the first, a group of rats underwent surgery to obstruct one coronary artery, inducing a heart attack. Approximately one month later, the animals showed signs of heart failure. Half were treated with βIIV5-3 for six weeks and the other half received a placebo.

“At the end of six weeks,” Ferreira said, “heart function had improved by about double in the animals treated with βIIV5-3 when compared with the control group. Plus, mortality dropped from 35% to 3%,”

The second experiment was performed on rats that showed high sodium sensibility. At six weeks of age, the animals were given a high-sodium diet and they developed hypertension soon thereafter. When they were 11 weeks old, they showed signs of heart failure and began receiving either the treatment or the placebo.

The improvement in cardiac function of the animals that received βIIV5-3 was twice that of the control group; the function was the same as that in rats without heart failure. The mortality rate fell from 50% to 0%.

“Even after the treatment was over, the rats that received the βIIV5-3 showed a lower mortality rate when compared with the placebo group,” observed Ferreira.

Validation

To prove that PKCβII plays a significant role in worsening cardiac failure in humans as well, the researchers evaluated cardiac biopsy specimens from patients with previously diagnosed cardiovascular disease.

“There was a clear relationship: the higher the levels of PKCβII, the worse the heart function in the patients,” said Ferreira. Berta Napchan Boer and Max Grinberg, both from the USP Heart Institute (Incor), took part in the research.

The next step was to determine why the PKCβII protein is deleterious to cardiac muscle. To do this, the researchers performed a series of in vitro experiments with the isolated protein and cultures of rat heart cells.

“We discovered that PKCβII deregulates the quality control of the proteins inside the cardiac cells. It connects itself to the proteasome, an intracellular complex that eliminates oxidized proteins, and keeps it from functioning well,” explained Ferreira.

To make things worse, a failing heart becomes a pro-oxidizing environment. In other words, the heart becomes an environment favorable for the production of free radicals and other toxic substances that damage proteins and other cellular macromolecules.

“As there is an increase in the production of oxidized proteins and the quality control is deregulated, they begin to accumulate and keep the cardiac cells from reacting appropriately. With time, the heart stops beating well and the cells begin to die,” said Ferreira.

In the experiments carried out on rats, the developed molecule showed that it was able to reactivate the quality control system in the heart cells. The oxidized proteins again began to be eliminated by the proteasome, and the degenerative process was interrupted.

Before testing the potential new drug on humans, the scientists intend to carry out another round of pre-clinical testing on larger animals, possibly pigs.

“The molecule was already successful in the toxicity tests carried out on animals. If everything goes well, we will know with certainty within about seven years if it could become a medication,” affirmed Ferreira.

The article, “Protein Quality Control Disruption by PKCβII in Heart Failure; Rescue by the Selective PKCβII Inhibitor βIIV5-3” (doi:10.1371/journal.pone.0033175), by Julio Ferreira and others, can be read at www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0033175.