PE-22-28

What it is

PE-22-28 takes its name from its position, amino acids 22 through 28, within the sequence of Spadin, a peptide that itself comes from a larger protein released when a cell-surface receptor called sortilin matures. The shortened version binds far more tightly to its target than the full-length peptide does.

Its target, TREK-1, is a channel in the cell membrane that lets potassium ions flow out of nerve cells, which normally calms the cell down. Blocking that channel makes certain nerve cells, particularly in a brain region tied to mood called the dorsal raphe nucleus, more active, and researchers report that this raises the firing rate of serotonin-releasing nerve cells and the activity of CREB, a protein involved in nerve-cell growth and memory.

How it is studied

The evidence for PE-22-28 comes from laboratory receptor-binding work and from behavioral testing in rodents, using standard tests researchers use to model depression-like and anxiety-like behavior, such as how long an animal keeps trying to escape a difficult situation. No human trial of PE-22-28 has been published in the sources reviewed for this entry.

What studies report

• A laboratory binding study found that Spadin, the longer peptide PE-22-28 is shortened from, specifically blocks TREK-1 at the point where a fatty molecule called arachidonic acid normally turns the channel on, rather than acting as a general blocker; researchers suggested this selectivity may explain why it does not trigger the same side effects as less selective potassium-channel blockers. [1]
• A widely cited review of TREK-1 biology describes the channel as playing a key role in neuroprotection, pain, general anesthesia, and mood, based on animal research, supporting the idea that blocking it is a plausible route to new mood-related research compounds. [2]
• In the study that first described PE-22-28 by name, mice treated with it for 4 days showed less time spent immobile in a standard mood-research swim test and ate a food pellet sooner in a test that measures anxiety-like hesitation, and PE-22-28 blocked the TREK-1 channel more strongly and for longer in the body than the full-length Spadin peptide it was shortened from. [3]
• In that same study, PE-22-28 triggered signs of new nerve-cell growth in the hippocampus after only 4 days and raised the level of a protein called PSD-95, a marker of the connection points between nerve cells, in cortical nerve cells grown in a dish. [3]
• A review of Spadin-family development reports that its mood-related effects in animal models appear within about 4 days, compared with 3 to 4 weeks for standard antidepressant research compounds such as fluoxetine, and that this rapid effect is linked to new nerve-cell growth and new connections between nerve cells in the brain. [4]

What is not known

All of the evidence reviewed here is preclinical, meaning it comes from molecular and animal research rather than human trials, so there is no human safety or effectiveness data for PE-22-28. How the rapid effects seen in rodents would translate to timing or degree of effect in people remains unstudied, and it is not known whether PE-22-28's stronger, longer-lasting TREK-1 blocking compared with Spadin translates into a meaningfully different behavioral effect rather than just a longer window of action.

Reported adverse findings

• The sources reviewed here are mechanism, behavioral, and review papers rather than dedicated safety studies, and none report a formal toxicity or adverse-event profile for PE-22-28 or Spadin in any species. [1][2][3][4]

Regulatory status

No regulatory body identified in the sources reviewed, including the FDA, has cleared PE-22-28 for use, and it has not entered human clinical trials.