Mitochondria-Targeted Peptide SS-31 Protected Against Lung Damage After Spinal Cord Injury in Mice | Research

The takeaway

The mitochondria-targeted peptide SS-31 reduced lung edema, inflammation, cell death, and mitochondrial dysfunction in mice with spinal cord injury-induced lung damage.

Multiple protective effects in 3 days
SS-31 reduced lung edema, cell death, macrophage infiltration, ROS, and NLRP3 inflammasome activation after spinal cord injury

What the researchers found

SS-31 treatment administered immediately after spinal cord injury and for the following two days produced multiple protective effects in the lungs:

- Attenuated lung edema and tissue damage

- Reduced apoptosis (cell death) in alveolar type II cells, which are critical for lung function

- Decreased total macrophages, pro-inflammatory M1 macrophages, and neutrophil infiltration

- Lowered reactive oxygen species (ROS) levels

- Reversed mitochondrial dysfunction

- Inhibited NLRP3 inflammasome activation, a key driver of inflammatory lung damage

These results demonstrate that targeting mitochondrial dysfunction with SS-31 can control the inflammatory cascade that leads to secondary lung injury after spinal cord trauma.

Why it matters

Secondary organ damage — particularly to the lungs — is a major cause of complications and death after spinal cord injury, yet there are currently no targeted treatments for this problem. By showing that a mitochondria-targeted peptide can protect the lungs from SCI-induced damage through multiple mechanisms, this study opens a potential new therapeutic avenue for one of the most devastating consequences of spinal cord trauma.

How the study worked

C57BL/6 mice underwent spinal cord injury and were divided into treatment and control groups. Treatment groups received daily intraperitoneal injections of SS-31 for three days starting immediately after injury. Sham and SCI-only groups received vehicle (DMSO and 0.9% NaCl, 1:3 ratio). Lung tissue was examined for edema, tissue damage, apoptosis of alveolar type II cells, macrophage and neutrophil infiltration, reactive oxygen species levels, mitochondrial function, and NLRP3 inflammasome activation.

What this study cannot tell us

This is a mouse study, and SCI-induced lung injury in rodents may differ from the human condition in important ways. The abstract does not report specific quantitative data (e.g., exact measurements of edema reduction or percentage of apoptotic cells). The three-day treatment window is very short, and longer-term outcomes are unknown. The SS-31 dose is not specified in the abstract. Only female C57BL/6 mice were used, limiting generalizability across sexes and strains.

How to read the evidence

This is a preclinical animal study using a mouse model of spinal cord injury. While it demonstrates clear protective effects through multiple mechanistic endpoints, the findings have not been validated in larger animals or human clinical trials. The evidence is preliminary but mechanistically informative.

When this study was published

Published in 2017, this study contributed to the growing body of evidence for SS-31/elamipretide as a mitochondrial protectant. SS-31 has since been studied in clinical trials for other conditions, though not specifically for SCI-induced lung injury.

The bigger picture

SS-31 (also known as elamipretide or Bendavia) is one of the most extensively studied mitochondria-targeted peptides, with research spanning heart failure, kidney disease, neurodegenerative disorders, and aging. This study extends its protective effects to a new context — secondary lung injury after spinal cord trauma — reinforcing the idea that mitochondrial dysfunction is a common driver of organ damage across many conditions. The NLRP3 inflammasome pathway identified here is also a major therapeutic target in inflammatory diseases, adding mechanistic depth to SS-31's profile.

Questions still open

Would SS-31 still be protective if treatment is delayed hours or days after spinal cord injury, as would be realistic in clinical settings?
Does SS-31's lung protection extend to other causes of systemic inflammatory lung injury, such as sepsis or major trauma?
Could SS-31 be combined with anti-inflammatory therapies for even greater protection against secondary organ damage after SCI?

Common questions

What is SS-31 and how does it target mitochondria?

SS-31 (also called elamipretide) is a small synthetic peptide that concentrates in mitochondria — the energy-producing structures inside cells. It binds to cardiolipin, a lipid found exclusively in the inner mitochondrial membrane, and helps stabilize the electron transport chain that generates cellular energy. By protecting mitochondrial function, SS-31 reduces the production of damaging reactive oxygen species and helps cells survive stress.

Why does spinal cord injury damage the lungs?

Spinal cord injury triggers a massive body-wide inflammatory response called systemic inflammatory response syndrome (SIRS). Immune cells flood the bloodstream and infiltrate distant organs, particularly the lungs, causing tissue swelling, cell death, and impaired function. This secondary lung damage is a major cause of complications after SCI and can be life-threatening, yet there are currently no specific treatments for it.

Read the original research

Mitochondria Targeted Peptide Attenuates Mitochondrial Dysfunction, Controls Inflammation and Protects Against Spinal Cord Injury-Induced Lung Injury.

Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology, 44(1), 388-400

View on PubMed ↗Publisher’s paper ↗

Citation

Zhu, Liu-Long; Li, Mao-Qiang; He, Fan; Zhou, Shao-Bo; Jiang, Wu. (2017). Mitochondria Targeted Peptide Attenuates Mitochondrial Dysfunction, Controls Inflammation and Protects Against Spinal Cord Injury-Induced Lung Injury.. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology, 44(1), 388-400. https://doi.org/10.1159/000484919