Curcumin inhibits reactive oxygen species formation and vascular hyperpermeability following haemorrhagic shock

1. Oxidative stress induced by reactive oxygen species (ROS) is a key mediator of haemorrhagic shock (HS)‐induced vascular hyperpermeability. In the present study, curcumin, a natural anti‐oxidant obtained from turmeric (Curcuma longa), was tested against HS‐induced hyperpermeability and associated ROS formation in rat mesenteric post‐capillary venules in vivo and in rat lung microvascular endothelial cells (RLMEC) in vitro. 2. In rats, HS was induced by withdrawing blood to reduce mean arterial pressure to 40 mmHg for 60 min, followed by resuscitation for 60 min. To investigate vascular permeability, rats were given fluorescein isothiocyanate (FITC)–albumin (50 mg/kg, i.v.). The FITC–albumin flux was measured in mesenteric post‐capillary venules by determining optical intensity intra‐ and extravascularly under intravital microscopy. Mitochondrial ROS formation was determined using dihydrorhodamine 123 in vivo. Parallel studies were conducted in vitro using serum collected after HS. The serum was tested on rat lung microvascular endothelial cell RLMEC monolayers. 3. In rats, HS induced a significant increase in vascular hyperpermeability and ROS formation in vivo (P < 0.05). Treatment with curcumin (20 μmol/L) attenuated both these effects (P < 0.05). In RLMEC in vitro, HS serum induced monolayer permeability and ROS formation. Curcumin (10 μmol/L) attenuated HS serum‐induced monolayer hyperpermeability and ROS formation. Curcumin (2–100 μmol/L) scavenged 2,2′‐azino‐bis(3‐ethylbenzthiazoline‐6‐sulphonic acid) and 1,1‐diphenyl‐2‐picrylhydrazyl radicals in vitro, indicating its potential as a free radical scavenger. 4. The present study demonstrates that curcumin is an inhibitor of vascular hyperpermeability following HS, with its protective effects mediated through its anti‐oxidant properties.