Semax peptide suppresses key proinflammatory gene transcripts induced by ischemic stroke in a rat model

The peptide Semax is already utilized in the treatment of ischemic stroke due to its established nootropic, neuroprotective, and immunomodulatory properties. Following a stroke, a cascade of inflammation contributes significantly to secondary brain injury. Previous broad-spectrum RNA-Seq analysis suggested that Semax could suppress many proinflammatory genes activated by ischemia, but the expression levels of several critically important mediators, including interleukins like Il1a, Il1b, and Il6, and tumor necrosis factor Tnfa, were too low for reliable quantification with that method. This created a knowledge gap, leaving the precise impact of Semax on these potent but less abundant inflammatory signals unconfirmed and unquantified, despite their central role in post-stroke pathology.

This study used a rat model of ischemic stroke, induced by transient (reversible) occlusion of the middle cerebral artery. The researchers analyzed brain tissue to investigate the effects of the peptide drug Semax on gene expression. Rather than using the broader RNA-Seq technique, they employed the more sensitive quantitative real-time polymerase chain reaction (qRT-PCR) method. This allowed them to specifically measure the mRNA levels of weakly expressed genes encoding proinflammatory mediators following ischemia-reperfusion and to determine how Semax administration altered their expression compared to ischemia-only controls.

The highly sensitive qRT-PCR analysis confirmed that ischemia-reperfusion significantly increased the transcription of several key proinflammatory genes. Administration of Semax effectively counteracted this surge. The study demonstrated that Semax treatment led to a statistically significant decrease in the mRNA levels for interleukin-1 alpha (Il1a), interleukin-1 beta (Il1b), interleukin-6 (Il6), C-C motif chemokine ligand 3 (Ccl3), and C-X-C motif chemokine ligand 2 (Cxcl2). This suppression compensated for the initial increase caused by the stroke model.

The results show that exposure to Semax leads to a statistically significant decrease in the Il1a, Il1b, Il6, Ccl3, and Cxcl2 mRNAs, which compensates for the increase in the transcription of these genes induced by ischemia-reperfusion.

This specific anti-inflammatory action at the gene expression level provides a molecular basis for the protective effects of Semax observed in stroke. The findings also highlight the methodological limitations of RNA-Seq for quantifying less abundant transcripts, underscoring the value of qRT-PCR for validating such results.

Written by TitrateLab, separately from the study summarized above.