Small molecules, called microRNA-144, or miR-144, are capable of inhibiting a gene that facilitates the elimination of cholesterol from the body. This makes miR-144 and other microRNAs a potential target for new drugs that could complement the effect of statins, a medicine used to reduce cholesterol and the incidence of heart attacks, and one of the most profitable drugs in the world. The pioneering article that describes the discovery of the role of miR-144 in controlling cholesterol is one of the ten most cited in 2013 in the journal Circulation Research, and two of its co-authors, the Brazilian couple Amarylis Wanschel and Alessandro Salerno, are former students of postgraduate and current postdoctoral students at the Biology Institute (IB) at Unicamp.

Wanschel and Salerno studied microRNA-144 during their time at New York University (NYU). With the losses suffered by the institution during the passage of Hurricane Sandy through the United States, at the end of 2012, the two returned to Brazil and started new post-doctoral projects at Unicamp, bringing their experience with cutting-edge research to the Metabolism Laboratory of Lipids at the Institute of Biology (IB), under the coordination of professor Helena Coutinho Franco de Oliveira.

“I was looking forward to them coming back,” the teacher told the Journal of Unicamp. Both completed their doctorates in the Functional and Molecular Biology Program at Unicamp. “They were doing very well there, I even advised them that they should make the most of that opportunity. With the damage to NYU caused by the hurricane, their return was anticipated.”

The Lipid Metabolism Laboratory researches the possible causes and mechanisms by which environmental and genetic factors predispose to the so-called metabolic syndrome. “When we talk about metabolic syndrome, we are mainly including obesity, diabetes and atherosclerosis, which are problems that reach epidemic proportions,” said Helena.

“We study the basic mechanisms to understand how the genetic background, which already confers a predisposition to the incidence of these diseases, interacts with environmental factors, such as diet, drugs, physical activity, etc. We have experimental models and approaches that range from the whole organism to the molecular level: we are able to study different tissues, different cells, and what happens inside each cell. Therefore, we look for the most relevant and interventionable events, with the potential to prevent or reverse the progression of these disorders.”

Cholesterol

In this context, the study of the role of microRNAs as regulators of gene expression – the intensity with which certain genes are activated or inhibited – is very important. “Our students should not leave Brazil to work on projects or with methodologies already established in the country,” said Helena. “So they went, really, to acquire completely new skills and do cutting-edge research. MicroRNA research has had a tree very recent. They were discovered about two decades ago, but the scientific community only recently realized their importance in regulating the functioning of our cells, something that we didn't even suspect.”

MicroRNAs, explains Salerno, are very short RNA sequences, first discovered in 1993 and which have been increasingly studied in recent years. “Our group at New York University was the first to describe the role of microRNAs in controlling cholesterol metabolism,” added Wanschel.

Salerno explains that the group discovered that a specific microRNA, miR-144, reduces the expression of the transporter protein ABCA1. This protein transports excess cholesterol from cells to HDL, or “good cholesterol”, which takes it to be eliminated from the body by the liver.

“Therefore, this microRNA targets the ABCA1 gene,” said the researcher. “It reduces the synthesis and expression of ABCA1. Knowing this, what would be the next objective? Produce an inhibitor of miR-144. By inhibiting miR-144, it would be possible to increase the expression of ABCA1, increase the formation of HDL, remove cholesterol from tissues, take it to the liver and eliminate it from the body.”

Macrophages

In addition to the article in collaboration with Alessandro Salerno and other researchers from New York University on miR-144, Amarylis Wanschel was also co-author of an article published in March this year in the journal Nature Medicine, on the role of the netrin-1 molecule produced by macrophages, which are the body's defense cells, in controlling chronic inflammation.

“By blocking the action of netrin-1, chronic inflammation and insulin resistance associated with obesity induced by consuming a high-fat diet are prevented,” explained the scientist.

The New York University team, of which Wanschel was part, discovered that the release of netrin-1 by macrophages present in adipose tissue acts to attract even more macrophages. “Instead of resolving the inflammation, the macrophages become trapped and attract more macrophages, amplifying the reaction,” she said.

This process results in chronic inflammation and, if associated with difficulty eliminating cholesterol – such as that caused by the overexpression of miR-144 – leads to the production of so-called “foam cells” (foam cells) initial event of atherosclerosis. The foam cell is “the macrophage saturated with cholesterol”, in the words of Professor Helena.

“In the case of atherosclerosis, the macrophage that is in the wall of the arteries phagocytozes oxidized LDL (“bad” cholesterol). This process of phagocytosis has no control, it continues until the moment when the foam cells they begin to die, forming the atherosclerotic plaque,” ​​said Salerno.

Metabolism

Thus, while control of netrin-1 may prevent macrophages from accumulating and causing chronic inflammation, both in adipose tissue and in the atherosclerosis plaque, control of miR-144 should be able to prevent macrophages from clogging up. transform in foam cells avoiding this unresolved inflammation that occurs in the walls of blood vessels. Furthermore, macrophages also play an important role in certain types of diabetes. “The infiltration of macrophages into the part of the pancreas that produces insulin is very harmful. In the case of type 1 diabetes, there is an attack by immune system cells on the pancreas,” said Helena. “So, there are some basic events that permeate all these cardiometabolic disorders that act together: those who are more obese have more atherosclerosis and a higher risk of diabetes. Those who are diabetic also have more atherosclerosis”, she explains.

Getting the results of these research to pharmacies is a long and expensive process. According to data released in the United States in 2012, it takes at least 13 years between the discovery of an active ingredient and its approval by the drug market regulator, the FDA, in a process that has an estimated cost of US$1 billion. And of every ten drugs that enter the human testing phase, only one ends up obtaining final approval to go to market, according to a study published in the journal Nature Biotechnology earlier this year.

In the case of metabolic processes, the situation gains extra complexity, since many of the molecules and processes that could be targets for control or inhibition have an important function in a healthy organism – therefore, simply deactivating a protein or increasing the level of antioxidants It may not only not bring the expected solution, but also cause unforeseen problems. One example cited by the researchers was that of CETP protein inhibitors.

“The pharmaceutical industry has sought the synthesis of an inhibitor for CETP for more than 20 years. Precisely because, when this protein is inhibited, HDL increases”, said Professor Helena. “I worked with this protein in my doctorate under the guidance of Professor Helena,” added Salerno. In 2006, human trials with the inhibitor Torcetrapib were stopped because of increased mortality in the group of patients treated with the drug.

“Our group has been working with CETP for several years and published several studies showing that there were specific metabolic contexts in which the protein was beneficial, and that, therefore, its inhibition should be viewed with great caution,” said Helena.

“Both the mentioned proteins and microRNAs themselves are important parts of complex processes that maintain the organism's homeostasis under normal conditions. But during a condition of physiological stress or illness, they can become important control points and therefore targets for therapy,” Amarylis added.

The Lipid Metabolism Laboratory carries out cutting-edge experimental research in this area. His team is also part of the Center for Research, Innovation and Diffusion (CEPID) on Obesity and Comorbidities, funded by Fapesp and led by professor Lício Velloso from FCM-Unicamp (https://ocrc.com.br/site). “There are 14 groups that make up the Center, which carry out research, education and technological development in the areas of obesity, diabetes, hypertension, atherosclerosis, drug chemistry, nutrition, physical activity and cancer. Thus, the interaction between basic, clinical and pharmaceutical research increases our chances of making relevant scientific contributions”, said Helena.

Publication

Articles

Control of cholesterol metabolism and plasma high-density lipoprotein levels by microRNA-144. Ramírez CM, Rotllan N, Vlassov AV, Dávalos A, Li M, Goedeke L, Aranda JF, Cirera-Salinas D, Araldi E, Salerno A, Wanschel A, Zavadil J, Castrillo A, Kim J, Suárez Y, Fernández-Hernando C. Circ Res. 2013 Jun 7;112(12):1592-601. doi: 10.1161/CIRCRESAHA.112.300626. Epub 2013 Mar 21.

The 10 Most Read Articles Published in Traffic Research in 2013. Roberto Bolli for the Editors. Circ Res. 2014;114:765-769. doi: 10.1161/CIRCRESAHA.114.303612. 

Netrin-1 promotes adipose tissue macrophage retention and insulin resistance in obesity. Ramkhelawon B, Hennessy EJ, Ménager M, Ray TD, Sheedy FJ, Hutchison S, Wanschel A, Oldebeken S, Geoffrion M, Spiro W, Miller G, McPherson R, Rayner KJ, Moore KJ. Nat Med. 2014 Apr;20(4):377-84. doi: 10.1038/nm.3467. Epub 2014 Mar 2.