Plasma exosomal miR-223 expression regulates inflammatory responses during cardiac surgery with cardiopulmonary bypass

Cardiopulmonary bypass (CPB) induces inflammatory responses, and effective endogenous homeostasis is important for preventing systemic inflammation. We assessed whether plasma exosomal microRNAs in patients undergoing cardiac surgery with CPB are involved in the regulation of inflammatory responses. Plasma samples were isolated from CPB patients (n = 21) at 5 specified time points: pre-surgery, pre-CPB and 2 hours (h), 4 h and 24 h after CPB began. Plasma TNF-alpha expression was increased after CPB began compared to that in the pre-surgery samples. Plasma IL-8 and IL-6 expression peaked at 4 h after CPB began but was downregulated at 24 h. The number of plasma exosomes collected at 2 h (55.1 +/- 8.3%), 4 h (63.8 +/- 10.1%) and 24 h (83.5 +/- 3.72%) after CPB began was significantly increased compared to that in the pre-CPB samples (42.8 +/- 0.11%). These exosomes had a predominantly parental cellular origin from RBCs and platelets. Additionally, the plasma exosomal miR-223 levels were significantly increased after CPB began compared to those in the pre-CPB samples. Further, exosomal miR-223 from plasma collected after CPB began downregulated IL-6 and NLRP3 expression in the monocytes. Here, we present the novel findings that increased plasma exosomal miR-223 expression during cardiac surgery with CPB might play homeostatic roles in downregulating inflammatory responses through intercellular communication.