A study in rats showed that the tiny peptide Pro‑Gly‑Pro (a part of the drug Semax) changes the activity of many genes in the brain after a stroke, especially lowering immune‑related genes after 24 hours. This was done in a lab model of brain injury, not in healthy people.

Biologically active regulatory peptide, tripeptide Pro-Gly-Pro (PGP) was used as C-terminal fragment for peptide drugs Semax and Selank. In recent years the independent effects of PGP were observed. The question was raised, whether PGP contributes to the effects ofpeptide drugs containing PGP as a fragment. The genome-wide analysis was performed to investigate the influence of PGP on the transcriptome of ischemic rat brain cortex tissues. The gene expression alterations caused by the action of the tripeptide PGP were compared with the gene expression of the control group "ischemia" at 3 and 24 h after permanent occlusion of left middle cerebral artery. The altered expression was detected for 29 genes at 3 h and 57--at 24 h. The proteins encoded by these genes have variety of functions: cytokines, transport proteins, transcription factors, transmembrane receptors, etc. Biological processes, which are related to the genes with altered expression, were distinguished. The influence of PGP on the diversity of biological processes in different systems of the organism is demonstrated for the first time. The process "Immune response" was the most statistically notable at 24 h after occlusion. The expression of the immune system genes was predominately down regulated.