From left to right, researchers Carlos Sebastián, Jorge Lloberas, Carlos Batlle and Antonio Celada.
Photo Credit: Courtesy of University of Barcelona
Scientific Frontline: Extended "At a Glance" Summary: The Role of Protein Polμ in the Inflammatory Response
The Core Concept: Polμ (Polymerase mu) is a crucial protein that facilitates DNA repair in macrophages during an immune response, ensuring the survival of these essential cells. By protecting innate immune cells from the genetic damage caused by their own pathogen-destroying mechanisms, Polμ enables effective tissue repair and limits chronic inflammation.
Key Distinction/Mechanism: When macrophages engulf pathogens, they release high volumes of reactive oxygen species (ROS) to neutralize the external threat. While effective against infectious agents, ROS inadvertently induce severe DNA damage within the macrophages themselves. Polμ functions as the primary repair mechanism for this specific genetic damage, allowing the macrophages to survive the hostile environment they create and subsequently trigger the necessary tissue repair processes.
Major Frameworks/Components:
- Macrophages: Innate immune system cells that act as the body's first line of defense, responsible for both eliminating pathogens and initiating post-inflammatory tissue repair.
- Reactive Oxygen Species (ROS): Highly reactive chemical molecules deployed by macrophages to destroy infectious agents, which simultaneously pose a collateral threat to the cell's own DNA integrity.
- DNA Polymerase mu (Polμ): The specific polymerase protein that mitigates ROS-induced DNA damage, sustaining macrophage viability throughout the full cycle of the inflammatory response.
Branch of Science: Immunology, Molecular Biology, and Cellular Physiology.
Future Application: The pharmacological inhibition of Polμ could be developed as a targeted therapy to suppress macrophage hyperactivity in critical, life-threatening conditions such as septic shock. By strategically reducing the excessive activity of these immune cells, medical professionals could lower the systemic damage caused by an overactive immune response and improve patient survival rates.
Why It Matters: This discovery provides a critical molecular missing link in the study of immune regulation and autoinflammatory diseases. A deficiency or mutation in the Polμ protein may be the underlying, previously undetected cause of conditions characterized by chronic, inappropriate immune activation and tissue damage, such as interferonopathies. This opens new diagnostic avenues and potential targeted treatments for chronic inflammatory disorders.
Whenever there is a wound or infection, the body produces an inflammatory response. This is the body’s first line of defense, and macrophages — cells of the innate immune system — play a key role: first, they help eliminate pathogens and other infectious agents, and then they trigger the mechanisms that repair the damage caused during the inflammatory process.
Now, a study by the University of Barcelona, the findings of which have been published in the journal Cell Reports, has discovered that a protein called Polμ is essential to this repair process, as it enables macrophages to survive at the site of inflammation. According to the researchers, a deficiency of this protein could be the cause of certain autoinflammatory diseases, conditions in which the immune system is activated inappropriately, leading to chronic inflammation and tissue damage.
The collateral damage caused by defense mechanisms
When the innate immune system triggers the inflammatory response to an external threat, macrophages engulf the pathogens and produce large quantities of reactive oxygen species (ROS) to destroy them. However, ROS also have a harmful effect on the macrophages themselves, as they can induce DNA damage that may lead to the death of these defense cells and promote chronic inflammation.
Previous studies had demonstrated the importance of Polμ in lymphocyte development and its involvement in the repair of genetic damage, but until now, its role in macrophages and in the inflammatory response was unknown. The researchers have discovered this by analyzing the protein’s role in this process using animal models of skin inflammation and muscle injury. “Using mice lacking Polμ, we have been able to demonstrate, in both in vitro and in vivo experiments, that the two phases of the inflammatory response are defective in the absence of this polymerase,” they explain.
The study shows, in animal models, that a deficiency of this protein compromises the survival of essential immune system cells.
Implications for disease and potential therapeutic strategies
In light of these findings, the researchers suggest that a deficiency in the Polμ protein could underlie certain diseases, such as interferonopathies, which are characterized by autoinflammatory processes that chronically activate type I interferons — key molecules of the immune system that coordinate the response to viral infections — causing damage to tissues and organs. Although no inflammatory conditions associated with Polμ have been described in humans to date, the researchers suggest that this may be because this possibility has not yet been sufficiently studied in certain clinical contexts. “It is possible that, in the case of some inflammatory conditions, the presence of mutations in Polμ has simply not been analyzed,” they note.
Furthermore, the findings could also have implications in other situations, such as cases of macrophage hyperactivity, as occurs during septic shock. “In such cases, Polμ activity could be inhibited to reduce the excessive activity of these cells, which could help lower patient mortality,” the researchers note. Indeed, experiments involving infection with various pathogens and the experimental induction of septic shock carried out in mice show that survival rates are higher in Polμ-deficient mice.
Published in journal: Cell Reports
Title: DNA polymerase μ protects macrophages from DNA damage produced during pro-inflammatory activation
Authors: Carlos Batlle-Recoder, Lorena Valverde-Estrella, Marta Ferri, Maria Serra, Antonio Bernad, Carlos Sebastián, Jorge Lloberas, and Antonio Celada
Source/Credit: University of Barcelona
Reference Number: imgy042726_01
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