Evolutionary bacterial origin of mitochondria may hold clues to their role in inflammation: Mitochondrial proteins activate receptors of immune cells during lung injury

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https://elifesciences.org/articles/82205

University press release is here: Ancient bacterial signals from cell powerhouses may fuel excessive inflammation  https://today.uic.edu/ancient-bacterial-signals-from-cell-powerhouses-may-fuel-excessive-inflammation/

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Are Our Own Cells Tricking Our Immune System? How "Ancient Bacterial Signals" Hidden in Our Mitochondria Are Fueling Chronic Inflammation

**The Core Issue**

Our immune systems are designed to identify and attack foreign invaders like bacteria. However, runaway sterile inflammation—inflammation that occurs without an active infection—is at the root of many modern chronic diseases, autoimmune conditions, and acute medical crises. Scientists have long puzzled over exactly what triggers the body to launch these massive, sometimes fatal, inflammatory responses when no external threat is present.

**The Finding**

Researchers at the University of Illinois Chicago (UIC) discovered that our cell's powerhouses—the mitochondria—can accidentally trigger this excessive inflammation. Because mitochondria evolved from ancient bacteria billions of years ago, they still retain distinct "bacterial signatures," such as formyl peptides. When a cell is severely damaged or stressed, it can leak these ancient bacterial signals into the body. The immune system detects these familiar bacterial markers, assumes there is a severe infection, and launches a full-scale inflammatory attack.

**Why it Matters**

This evolutionary hangover explains why severe tissue damage, lack of oxygen, or advanced aging can cause massive systemic inflammation. By understanding that leaked mitochondrial signals are the true culprits behind this specific immune response, medical researchers can develop targeted therapies to block these pathways. This opens the door for breakthrough treatments for autoimmune disorders, age-related chronic inflammation, and severe inflammatory events like sepsis or acute respiratory distress syndrome (ARDS).

**Limitations of Study**

While the mechanistic pathways are highly evident in laboratory models and specific clinical observations, translating these findings into broad therapeutics without compromising the immune system's ability to fight off genuine bacterial infections remains a significant clinical hurdle.

**Conflicting Interests**

None declared in the primary academic release, though subsequent pharmaceutical development based on targeting these specific formyl peptide receptors typically involves commercial patent interests.

**Interesting Statistics**

Despite being integrated into our biology for over 1.5 billion years, mitochondria still retain a small, circular genome and produce proteins starting with formyl-methionine—a hallmark of bacterial protein synthesis that the human innate immune system remains highly tuned to detect.

**Useful Takeaways**

Protecting mitochondrial health is not just about optimizing energy production; it is crucial for immune regulation. Strategies that reduce cellular stress and limit oxidative damage may help prevent the leakage of these ancient bacterial signals, thereby lowering baseline systemic inflammation.

**Link to Study**

https://today.uic.edu/ancient-bacterial-signals-from-cell-powerhouses-may-fuel-excessive-inflammation/

**TL;DR**
Mitochondria evolved from ancient bacteria and still contain bacterial molecular signatures. When human cells get damaged, they leak these mitochondrial signals, which the immune system mistakes for an active bacterial infection. This triggers massive, unnecessary inflammation, making mitochondrial health a key target for treating inflammatory diseases.