l‐Theanine inhibits proinflammatory PKC/ERK/ICAM‐1/IL‐33 signaling, apoptosis, and autophagy formation in substance P‐induced hyperactive bladder in rats

Aims: Upregulation of substance P (SP) and neurokinin‐1 receptor (NK1R) activation induces pro‐inflammatory bladder hyperactivity through the PKC/ERK/NF‐κB/ICAM‐1/IL‐33 signaling pathways to increase the leukocyte infiltration and adhesion leading to reactive oxygen species (ROS) production, autophagy, and apoptosis. l‐Theanine is a unique non‐protein‐forming amino acid present in tea (Camellia sinensis [L.] O. Kuntze) with its antioxidant, anti‐inflammatory, and relaxation effects to improve cognition, mood, gastric ulcer injury, and cerebral ischemia/reperfusion injury, and posttraumatic stress disorder. We explored the protective effect of l‐theanine on SP‐induced bladder hyperactivity. Methods: In urethane‐anesthetized female Wistar rats, we explored the transcystometrogram, pelvic nerve activity, proinflammatory PKC/ERK/NF‐κB/ICAM‐1/IL‐33 signaling, apoptosis‐related Caspase 3/poly‐(ADP‐ribose)‐polymerase (PARP), and autophagy‐mediated LC3 II expression by Western blot, electrophoretic‐mobility shift assay and immunohistochemistry, bladder ROS amount by a ultrasensitive chemiluminescence method, and possible ROS sources from the different leukocytes by specific stains in SP‐evoked hyperactive bladder. Results: l‐Theanine dose‐dependently depressed H2O2 and HOCl activity in vitro. In urethane‐anesthetized female Wistar rats, intra‐arterial SP through NK1R activation increased voiding frequency (shortened intercontraction intervals) associated with the increase in bladder nerve activity, proinflammatory PKC/ERK/NF‐κB/ICAM‐1/IL‐33 signaling, Caspase 3/PARP‐mediated apoptosis, LC3 II‐mediated autophagy, ROS amount, neutrophils adhesion, CD68 (monocyte/macrophage) infiltration, and mast cells degranulation in the hyperactive bladder. Intragastrical l‐theanine (15 mg/kg) twice daily for 2 weeks efficiently ameliorated all the enhanced parameters in the SP‐treated hyperactive bladder. Conclusions: In conclusion, l‐theanine through antioxidant and anti‐inflammatory actions ameliorates SP‐induced bladder hyperactivity via the inhibition of proinflammatory PKC/ERK/NF‐κB/ICAM‐1/IL‐33 signaling, oxidative stress, bladder nerve hyperactivity, apoptosis, and autophagy. Neurourol. Urodynam. 36:297–307, 2017. © 2016 Wiley Periodicals, Inc.