Plasma kallikrein‐kinin system contributes to peripheral inflammation in temporal lobe epilepsy

Temporal lobe epilepsy (TLE) is a chronic disease, characterized by severe and refractory seizures, triggered in the hippocampus and/or amygdala, disrupting the blood-brain barrier. This disruption can sustain, or aggravate, the epileptic condition. The aim of this study was to evaluate the activation of the kallikrein-kinin system in patients with TLE, as it relates to the maintenance of blood-brain barrier. Human hippocampal sclerotic tissues removed after surgery for seizure control, plasma, and serum were used in the following assays: immunostaining for white blood cells in the TLE hippocampus, C-reactive protein in serum, quantification of plasma kallikrein (PKal) and cathepsin B (CatB) activity in serum and plasma, quantification of C1-inhibitor, analysis of high-molecular-weight kininogen (H-kininogen) fragments, and activation of plasma prekallikrein for comparison with healthy controls. Infiltration of white blood cells in the sclerotic hippocampus and a significant increase in the neutrophil/lymphocyte ratio in the blood of TLE patients were observed. High levels of C-reactive protein (TLE = 1.4 ± 0.3 µg/mL), PKal (TLE = 5.4 ± 0.4 U/mL), and CatB (TLE = 4.9 ± 0.4 U/mL) were also evident in the serum of TLE patients comparing to controls. A strong linear correlation was observed between active CatB and PKal in the serum of TLE patients (r = 0.88). High levels of cleaved H-kininogen and free PKal, and low levels of C1-inhibitor (TLE = 188 ± 12 µg/mL) were observed in the serum of TLE patients. Our data demonstrated that the plasma kallikrein-kinin system is activated in patients with TLE. OPEN SCIENCE BADGES: This article has received a badge for *Open Materials* because it provided all relevant information to reproduce the study in the manuscript. The complete Open Science Disclosure form for this article can be found at the end of the article. More information about the Open Practices badges can be found at https://cos.io/our-services/open-science-badges/.