1. ¹Department of Cell Biology and Anatomy, University of Miami Miller School of Medicine, Miami, Florida, USA
2. ²Department of Neurological Surgery, University of Miami Miller School of Medicine, Miami, Florida, USA
3. ³The Miami Project to Cure Paralysis, University of Miami Miller School of Medicine, Miami, Florida, USA
4. ⁴Department of Physiology and Biophysics, University of Miami Miller School of Medicine, Miami, Florida, USA

Correspondence: Dr WD Dietrich, The Miami Project to Cure Paralysis, Department of Neurological Surgery, University of Miami Miller School of Medicine, 1095 NW 14th Terrace, Suite 2-30, Miami, FL 33136, USA. E-mail: ddietrich@miami.edu

Received 8 April 2008; Revised 16 October 2008; Accepted 12 November 2008; Published online 10 December 2008.

Abstract

Inflammation is a major contributor to the pathogenesis of cerebral ischemia and stroke. In the peripheral immune response, caspase-1 activation involves the formation of a macromolecular complex termed the inflammasome. We determined whether nucleotide-binding, leucine-rich repeat, pyrin domain containing 1 (NLRP1), molecular platform consisting of capase-1, apoptosis-associated speck-like protein containing a caspase-activating recruitment domain (ASC), and NLRP1, is expressed in the normal and postischemic brain. Mice underwent thromboembolic stroke to investigate the formation of the inflammasome and subsequent activation of downstream inflammatory responses. Western blot analysis showed expression and activation of interleukin (IL) IL-1 and IL-18 at 24 h after stroke. Size-exclusion chromatography and coimmunoprecipitation analysis showed protein association between NLRP1, ASC, caspase-1, and the X-linked inhibitor of apoptosis protein (XIAP). After ischemia, immunohistochemical analysis revealed inflammasome proteins in neurons, astrocytes, and microglia/macrophages. The potential of the inflammasome as an antiinflammatory target was showed by interference of inflammasome activation resulting in reduced cytokine levels in mice treated after ischemia with a neutralizing antibody against NLRP1. These findings show that the inflammasome complex forms after focal brain ischemia and may be a novel therapeutic target for reducing the detrimental consequences of postischemic inflammation.