In Vitro Effects of Lidocaine on Neutrophils from Patients with Sepsis

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. This involves a failure to restore immune homeostasis because of complex pro- and anti-inflammatory processes. Neutrophils are the most abundant leucocytes, that in sepsis show delayed apoptosis, dysfunctional antimicrobial effector functions and impaired migration.1 This makes them a potential target for immunomodulation. In vitro and animal models have shown septic neutrophils respond to lidocaine, a widely used local anaesthetic. To date, only Berger and colleagues2 have reported effects of lidocaine on recruitment and transmigration of septic neutrophils. Many functions remain unexplored. This study quantified lidocaine's effects on cell surface markers that reflect activation (CD11b), migration (CD192), adhesion (CD62L), and phagocytic properties (CD64) in septic neutrophils, along with cytokine and reactive oxygen species (ROS) production (Fig. 11). Septic patients (n=6) admitted to the intensive care unit at the Royal Infirmary of Edinburgh with SOFA ≥2, initiation of intravenous antibiotics and capacity to consent were recruited from January–March 2019. Arterial whole blood was incubated with 5 μg ml−1 lidocaine or an equal volume of saline for 60 min. Healthy volunteers (n=6) donated venous whole blood which was activated with cytochalasin B and N-formylmethionyl-leucyl-phenylalanine (fMLP) and similarly treated. Fluorescent antibodies were added, blood was lysed for red cells and washed. The median fluorescence intensity (MFI) of PE/Cy7-CD62L, PE/Cy7-CD11b, FITC-CD192,and PE-CD64, and ROS (DHR123) production was quantified in duplicate using flow cytometry (Attune Nx). Difference in MFI was compared using paired t-test. LEGENDPLEX Human inflammation panel was conducted on plasma. Healthy blood incubated with CytochalasinB+fMLP showed a 5.91-fold increase in CD11b (P<0.001), an increase in DHR123, and a decrease in CD62L, demonstrating successful activation of neutrophils. Treatment with lidocaine caused a consistent (mean 7%) decrease in CD11b expression. In both activated healthy and septic neutrophils, lidocaine increased the MFI of DHR123. Contrary to activated healthy neutrophils, lidocaine increased CD11b expression on average 1.28-fold in septic neutrophils. One septic neutrophil sample showed lidocaine-induced decrease in CD11b expression. We found that lidocaine modulates key neutrophil functions: notably activation (CD11b) and ROS production. We observed interpatient variability in the response to lidocaine, indicative of the established heterogeneity in septic host response. Future research is warranted to explore the potential of this novel use of an already existing drug in neutrophil response in sepsis sub-groups. References1.Van der Poll T, Van de Veerdonk FL, Scicluna BP, et al. Nat. Rev. Immunol. 2017; 17: 407–4202.Berger C, Rossaint J, Van Aken H, et al. J. Immunol. 2014; 192: 367–376