Transfer RNA fragments replace microRNA regulators of the cholinergic post-stroke immune blockade III
Ontology highlight
ABSTRACT: After ischemic stroke, the brain initiates intensive communication with the immune system, and acetylcholine contributes to this process. Stroke triggers peripheral immunosuppression leading to increased susceptibility to infections; and post-stroke pneumonia is linked with poor stroke outcome, but the responsible processes are yet unknown. We discovered a “change of guards” where microRNA levels decreased but small transfer RNA fragments (tRFs) accumulated in post-stroke blood cells. This molecular switch may re-balance acetylcholine signaling in CD14+ monocytes by regulating their gene expression and modulating post-stroke immunity. Our observations point to tRFs as new molecular regulators of post-stroke immune responses that may become potential therapeutic targets.
Project description:After ischemic stroke, the brain initiates intensive communication with the immune system, and acetylcholine contributes to this process. Stroke triggers peripheral immunosuppression leading to increased susceptibility to infections; and post-stroke pneumonia is linked with poor stroke outcome, but the responsible processes are yet unknown. We discovered a “change of guards” where microRNA levels decreased but small transfer RNA fragments (tRFs) accumulated in post-stroke blood cells. This molecular switch may re-balance acetylcholine signaling in CD14+ monocytes by regulating their gene expression and modulating post-stroke immunity. Our observations point to tRFs as new molecular regulators of post-stroke immune responses that may become potential therapeutic targets.
Project description:After ischemic stroke, the brain initiates intensive communication with the immune system, and acetylcholine contributes to this process. Stroke triggers peripheral immunosuppression leading to increased susceptibility to infections; and post-stroke pneumonia is linked with poor stroke outcome, but the responsible processes are yet unknown. We discovered a “change of guards” where microRNA levels decreased but small transfer RNA fragments (tRFs) accumulated in post-stroke blood cells. This molecular switch may re-balance acetylcholine signaling in CD14+ monocytes by regulating their gene expression and modulating post-stroke immunity. Our observations point to tRFs as new molecular regulators of post-stroke immune responses that may become potential therapeutic targets.
Project description:Stroke is a leading cause of death and disability. Recovery depends on a delicate balance between inflammatory responses and immune suppression, tipping the scale between brain protection and susceptibility to infection. Peripheral cholinergic blockade of immune reactions fine-tunes this immune response, but its molecular regulators are unknown. Here, we report a regulatory shift in small RNA types in patient blood sequenced 2 d after ischemic stroke, comprising massive decreases of microRNA levels and concomitant increases of transfer RNA fragments (tRFs) targeting cholinergic transcripts. Electrophoresis-based size-selection followed by qRT-PCR validated the top six up-regulated tRFs in a separate cohort of stroke patients, and independent datasets of small and long RNA sequencing pinpointed immune cell subsets pivotal to these responses, implicating CD14+ monocytes in the cholinergic inflammatory reflex. In-depth small RNA targeting analyses revealed the most-perturbed pathways following stroke and implied a structural dichotomy between microRNA and tRF target sets. Furthermore, lipopolysaccharide stimulation of murine RAW 264.7 cells and human CD14+ monocytes up-regulated the top six stroke-perturbed tRFs, and overexpression of stroke-inducible tRF-22-WE8SPOX52 using a single-stranded RNA mimic induced down-regulation of immune regulator Z-DNA binding protein 1. In summary, we identified a "changing of the guards" between small RNA types that may systemically affect homeostasis in poststroke immune responses, and pinpointed multiple affected pathways, which opens new venues for establishing therapeutics and biomarkers at the protein and RNA level.
Project description:Bulk RNA expression profiles were captured from hearts of alpha7 nicotinic acetylcholine receptor (Chrna7) knockout (KO) and wild type (WT) mice that underwent myocardial infarction (MI) or sham (SH) surgery at postnatal day 1 and full ventricle collection at 7 days post-surgery
Project description:Blood monocytes/macrophages infiltrate the brain after ischemic stroke and critically influence brain injury and regeneration. We investigated stroke-induced transcriptomic changes of monocytes/macrophages by RNA sequencing profiling, using a mouse model of permanent focal cerebral ischemia. Compared to non-ischemic conditions, brain ischemia induced only moderate genomic changes in blood monocytes, but triggered robust genomic reprogramming in monocytes/macrophages invading the brain. Surprisingly, functional enrichment analysis of the transcriptome of brain macrophages revealed significant overrepresentation of biological processes linked to neurovascular remodeling, such as angiogenesis and axonal regeneration, as early as 5 days after stroke, suggesting a previously underappreciated role for macrophages in initiating post-stroke brain repair. Upstream Regulator analysis predicted peroxisome proliferator-activated receptor gamma (PPARγ) as a master regulator driving the transcriptional reprogramming in post-stroke brain macrophages. Importantly, myeloid cell-specific PPARγ knockout (mKO) mice demonstrated lower post-stroke angiogenesis and neurogenesis than wild-type mice, which correlated significantly with the exacerbation of post-stroke neurological deficits in mKO mice. Collectively, our findings reveal a novel repair-enhancing transcriptome in brain macrophages during post-stroke neurovascular remodeling. As a master switch controlling genomic reprogramming, PPARγ is a rational therapeutic target for promoting and maintaining beneficial macrophage functions, facilitating neurorestoration, and improving long-term functional recovery after ischemic stroke.