| Background and purpose Cerebral ischemic stroke(CIS)is one of the leading causes of human death and disability worldwide.At present,except the early use of tissue plasminogen activator(t PA)and intravascular thrombectomy,there is no obvious effective treatment for it.However,the therapeutic time window of such treatment is too short for clinical use.We need to find a new treatment to improve the prognosis of patients after ischemic stroke.Immune and inflammatory responses are involved in the entire process of ischemic stroke.Studies have shown that infectious complications such as pneumonia and urinary tract infection account for about 20% of deaths in stroke victims.Cerebral ischemia not only leads to the destruction of the blood-brain barrier,accelerates the formation of brain edema,aggravates the neurological damage after cerebral infarction,but also induces systemic immunosuppression and increases the sensitivity of infection.Accumulating evidence has revealed that stroke-induced brain injury activates neurogenic pathways including sympathetic innervation and hypothalamic-pituitary-adrenal(HPA)axis,resulting in suppression of systemic immunity.However,the molecular mechanisms through which stroke suppress systemic immune response in peripheral blood remain poorly understood.MicroRNAs(miRNAs)are molecular switches in immune cells,but the alterations of miRNAs in human immune cells in response to brain ischemia and their impact on immune defense remain elusive.Natural killer(NK)cells are cytotoxic innate lymphocytes that are critical for early host defenses against pathogens.Animal experiments have found that spleen atrophy and the number of NK cells were reduced after induction of the middle cerebral artery occlusion(MCAO).In this study,we characterized the immune competence of human peripheral blood NK cells after acute ischemic stroke,and performed unbiased miRNA sequencing analysis of NK cells after brain ischemia.Methods A total of 28 stroke patients were recruited from Tianjin Medical University General Hospital,male20,female7,average age 61.46 ± 1.64 years old.18 age-matched healthy subjects were recruited into this study as controls,male13,female5,average age 55.39 ± 2.91 years old.After blood samples obtained from stroke patients and healthy controls,flow cytometry was used to measure NK cell activation and function in peripheral blood mononuclear cells(PBMC).Total RNA was extracted from purified NK cells and then subjected to multiplexed small RNA c DNA library preparation for miRNA sequencing.Finally,microRNA inhibitors were cultured with purified NK cells after isolated by microbeads to observed the difference of activity and function on NK cells after ischemic stroke.Results We found that brain ischemia significantly but transiently suppresses peripheral NK cell number and activity,and the severity of ischemic brain injury determine the extent of NK cell suppression in the periphery.Mi RNA sequencing analysis revealed that miR451 a and miR122 are dramatically upregulated in NK cells when they are suppressed after acute ischemic stroke.Notably,our in vitro results demonstrate the contribution of miR451 a and miR122 to NK cell suppression after brain ischemia,suggesting a profound role of miRNA in stroke-induced impairment of NK cell-mediated immune defense.Conclusions Brain ischemia significantly altered miRNA expression profiles in circulating NK cells,and the inhibition of miR451 a or miR122 augmented the expression of activation-associated receptors in NK cells. |
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