Specialized pro-resolving mediators — resolvins, protectins, maresins and lipoxins — are lipid signalling molecules derived from omega-3 and omega-6 fatty acids. They are not peptides; they appear in this formulary because they are used alongside peptides in inflammatory protocols. The biology behind them represents a genuine shift in understanding.
This guide situates SPMs within the broader field of peptide therapy and is written for clinicians. It is clinical education, not medical advice, and nothing here should be read as a treatment recommendation or protocol.
Resolution is an active process
Inflammation was long assumed to end passively — the stimulus is cleared, mediators dilute away, and the tissue returns to baseline. Work led by Charles Serhan and colleagues established that this is wrong.
Resolution is an actively driven biochemical program with its own dedicated mediators. As an inflammatory response matures, there is a deliberate class switch in lipid mediator production: the cell moves from generating pro-inflammatory prostaglandins and leukotrienes to generating pro-resolving mediators from the same fatty acid substrates.
Those mediators do specific work. They stop further neutrophil recruitment, promote macrophage clearance of apoptotic neutrophils (efferocytosis), stimulate removal of debris, and support tissue repair — without immunosuppression. This distinction matters: anti-inflammatory and pro-resolving are not the same thing. Blocking inflammation suppresses a defensive response; promoting resolution helps complete it.
The clinically interesting hypothesis follows: some chronic inflammatory disease may reflect failed resolution rather than excessive initiation — inflammation that started appropriately and never finished.
The SPM families
Lipoxins derive from arachidonic acid and were the first identified. E-series resolvins derive from EPA. D-series resolvins, protectins and maresins derive from DHA, with maresins produced particularly by macrophages.
This provides a specific molecular link between omega-3 fatty acid status and inflammatory regulation. EPA and DHA are not merely competing with arachidonic acid for enzyme access — they are the required substrate for an entire class of resolution signals. That is a more precise account of omega-3 biology than the usual framing.
Aspirin also intersects here: acetylated COX-2 generates aspirin-triggered epimers of several SPMs, which are more resistant to degradation. This may contribute to aspirin effects that inhibition of prostaglandin synthesis alone does not explain.
Where the human evidence stands
The underlying biology is well established. SPMs are measurable in human tissue and fluids, their synthetic pathways are characterized, and their actions on leukocytes are reproducible in laboratory systems. Altered SPM profiles have been described in conditions including chronic inflammatory disease and obesity.
Supplementation is a separate question. SPM supplements — typically marine oil fractions enriched in mediator precursors or in the mediators themselves — are sold on the strength of that biology. Controlled human trials demonstrating that oral SPM supplementation improves clinical outcomes in defined conditions remain limited.
Several honest uncertainties persist: oral bioavailability and stability of these lipids, whether supplementation meaningfully raises tissue mediator levels, and whether raising them produces clinical benefit in patients who are not deficient in substrate.
The most defensible practical position is that ensuring adequate EPA and DHA intake supplies the substrate this system requires, which is supported by a far larger evidence base than SPM products themselves.
Status
SPM products are sold as dietary supplements in the United States and are not approved drugs for any condition. They are generally well tolerated, with the usual considerations for marine oil products.
The framing for patients: the resolution biology is real and important, adequate omega-3 status is the evidence-supported way to support it, and the specific supplement claims currently run ahead of the trials. Our omega-3 guide covers substrate status in more depth.
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