A chemical storm 

During a heart attack, a portion of the heart muscle is cut off from its oxygen supply. The cells then switch to emergency mode. Their metabolism slows down, energy production drops, and the mitochondria—the tiny cellular “power plants”—begin to function erratically. 

When blood flow is restored, for example, during angioplasty, oxygen returns to the cells. This might seem like good news. In reality, however, a large amount of reactive oxygen species—very aggressive chemical molecules—is produced in cells. This phenomenon is called oxidative stress. This process can be compared to a situation in the power grid—after a long power outage, the sudden restoration of voltage causes power surges that damage part of the system. In heart cells, reactive oxygen species play a similar role. 

As explained by Prof. Iwona Bil-Lula, the study’s author 

- In our study using an ex vivo model of a rat heart subjected to ischemia and reperfusion, we demonstrated that activation of the mitochondrial isoform NTT-MMP-2 under these conditions leads to increased oxidative stress, mitochondrial dysfunction, and the activation of apoptotic pathways in cardiomyocytes, resulting in damage and impaired mechanical function of the heart. 

The interleukin paradox 

However, the experiment also yielded a surprising observation. After inhibiting MMP-2, levels of interleukin-6 increased—a signaling molecule belonging to the cytokine family, which plays a key role in communication between immune system cells. At first glance, this might seem like an undesirable effect. Interleukin-6 is often associated with inflammatory processes, and in many diseases—from infections to autoimmune disorders—elevated levels of it are a sign of an activated inflammatory response. 

But in biology, things are rarely that simple. A growing body of research shows that IL-6 is a molecule with a dual nature. Depending on the biological context, the timing of its action, and the type of cells involved, it can both exacerbate inflammation and trigger protective mechanisms. In the case of myocardial ischemia, its role is particularly complex. 

As Prof. Bil-Lula explains: 

- Interleukin-6 is a cytokine with complex effects—in addition to its pro-inflammatory functions, it can also activate protective signaling pathways, including those related to cell survival and adaptation to oxidative stress. 

 
In the experiment under analysis, the increase in IL-6 levels occurred precisely when MMP-2 inhibition began to limit damage to heart cells. Furthermore, increased expression of this cytokine was associated with less myocardial damage and improved cardiac mechanical function after reperfusion. This suggests that heart cells, which were partially protected from NTT-MMP-2, may have simultaneously activated additional adaptive mechanisms. 

- Thus, the increase in IL-6 expression following siRNA administration may reflect a compensatory mechanism aimed at cardioprotection, the researcher concludes. 

From a biological standpoint, such a mechanism is not surprising. Interleukin-6 can activate multiple signaling pathways that support cell survival under severe stress. In the short term following an ischemic episode, it can, among other things, stabilize mitochondrial function, limit apoptotic processes, and enhance cellular adaptation to oxidative stress. As a result, cells have a better chance of surviving the sudden return of oxygen, which normally triggers a cascade of damage. 

In the study, the increase in IL-6 was thus associated with less heart damage and better myocardial mechanical function. It is therefore possible that the observed effect is part of a natural, compensatory cellular response—a kind of biological “rescue system” that activates when cells attempt to survive extreme stress.