Transfer RNA fragments replace microRNA regulators of the cholinergic poststroke immune blockade

Area of Science:

• Neuroscience
• Immunology
• Molecular Biology

Background:

• Stroke recovery hinges on balancing immune responses, but molecular regulators are unknown.
• Peripheral cholinergic pathways modulate immune reactions, yet their specific controllers remain elusive.
• Understanding post-stroke immune dynamics is crucial for developing effective treatments.

Purpose of the Study:

• To identify molecular regulators of immune response shifts after ischemic stroke.
• To investigate changes in small RNA profiles in stroke patients.
• To explore the role of specific small RNAs and immune cells in post-stroke homeostasis.

Main Methods:

• Small RNA sequencing of patient blood 2 days post-ischemic stroke.
• Validation of differentially expressed microRNAs and transfer RNA fragments (tRFs) using qRT-PCR.
• Analysis of independent RNA sequencing datasets to identify key immune cell subsets.
• In vitro stimulation of immune cells and functional assays with specific tRFs.

Main Results:

• A significant shift in small RNA profiles was observed, with decreased microRNA and increased tRF levels.
• Top upregulated tRFs were validated in stroke patients and implicated CD14+ monocytes.
• tRFs were shown to target cholinergic transcripts and modulate immune regulator Z-DNA binding protein 1.
• Lipopolysaccharide stimulation confirmed tRF upregulation in immune cells.

Conclusions:

• A regulatory shift between microRNA and tRF types occurs post-stroke, affecting immune homeostasis.
• CD14+ monocytes play a key role in the cholinergic inflammatory reflex following stroke.
• Identified pathways and small RNAs present novel therapeutic and biomarker opportunities for stroke.