Identifying Stress-Exacerbated Thermal-Injury Induced MicroRNAs

Area of Science:

• Neuroscience
• Molecular Biology
• Stress Physiology

Background:

• Combat and operational stress reaction (COSR) and thermal injury can increase pain sensitivity.
• Extracellular vesicle-microRNAs (EV-miRNAs) normally suppress inflammation but are downregulated in neuropathic pain models.
• Previous studies showed unpredictable combat stress (UPCS) prior to thermal injury increases pain in male rats.

Purpose of the Study:

• To investigate the effects of UPCS and thermal injury on circulating EV-miRNAs in both male and female rats.
• To determine if EV-miRNAs can serve as biomarkers for COSR and associated mechanical sensitivity.
• To explore potential therapeutic targets for COSR and thermal injury-induced pain.

Main Methods:

• Adult male and female Sprague Dawley rats were exposed to UPCS for 2 or 4 weeks.
• Experimental groups included non-stress (NS), stress (S), NS + thermal injury (TI), and S + TI.
• Mechanical sensitivity was measured, plasma was collected, and EV-miRNAs were isolated for small RNA sequencing and analysis.

Main Results:

• UPCS exposure alone induced mechanical allodynia in both sexes.
• Thermal injury during peak UPCS exacerbated mechanical allodynia compared to thermal injury alone.
• Differential expression of EV-miRNAs was observed between stress and non-stress groups, with and without thermal injury.

Conclusions:

• Consistent differences in EV-miRNAs are detectable during COSR and the development of mechanical sensitivity.
• EV-miRNAs show potential as key regulators, biomarkers, and therapeutic targets for COSR and thermal injury-induced pain.
• These findings in an animal model suggest potential clinical relevance for prognostic and diagnostic biomarkers.