title: Recombinant Slit2 attenuates neuroinflammation after surgical brain injury by inhibiting peripheral immune cell infiltration via Robo1-srGAP1 pathway in a rat model.
abstract: OBJECTIVE
  Peripheral immune cell infiltration to the brain tissue at the perisurgical site can promote neuroinflammation after surgical brain injury (SBI). Slit2, an extracellular matrix protein, has been reported to reduce leukocyte migration. This study evaluated the effect of recombinant Slit2 and the role of its receptor roundabout1 (Robo1) and its downstream mediator Slit-Robo GTPase activating protein 1 (srGAP1)-Cdc42 on peripheral immune cell infiltration after SBI in a rat model.
  
  
  METHODS
  One hundred and fifty-three adult male Sprague-Dawley rats (280-350 g) were used. Partial resection of right frontal lobe was performed to induce SBI. Slit2 siRNA was administered by intracerebroventricular injection 24h before SBI. Recombinant Slit2 was injected intraperitoneally 1h before SBI. Recombinant Robo1 used as a decoy receptor was co-administered with recombinant Slit2. srGAP1 siRNA was administered by intracerebroventricular injection 24h before SBI. Post-assessments included brain water content measurement, neurological tests, ELISA, Western blot, immunohistochemistry, and Cdc42 activity assay.
  
  
  RESULTS
  Endogenous Slit2 was increased after SBI. Robo1 was expressed by peripheral immune cells. Endogenous Slit2 knockdown worsened brain edema after SBI. Recombinant Slit2 administration reduced brain edema, neurological deficits, and pro-inflammatory cytokines after SBI. Recombinant Slit2 reduced peripheral immune cell markers cluster of differentiation 45 (CD45) and myeloperoxidase (MPO), as well as Cdc42 activity in the perisurgical brain tissue which was reversed by recombinant Robo1 co-administration and srGAP1 siRNA.
  
  
  CONCLUSIONS
  Recombinant Slit2 improved outcomes by reducing neuroinflammation after SBI, possibly by decreasing peripheral immune cell infiltration to the perisurgical site through Robo1-srGAP1 mediated inhibition of Cdc42 activity. These results suggest that Slit2 may be beneficial to reduce SBI-induced neuroinflammation.
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.
authors.forename: Prativa
authors.initials: P
authors.lastname: Sherchan
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.; Department of Anesthesiology, Loma Linda University, CA 92354, U.S.A.
authors.forename: Lei
authors.initials: L
authors.lastname: Huang
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.
authors.forename: Yuechun
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.
authors.forename: Onat
authors.initials: O
authors.lastname: Akyol
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.
authors.forename: Jiping
authors.initials: J
authors.lastname: Tang
authors.affiliation: Department of Physiology and Pharmacology, Loma Linda University, Loma Linda, CA 92354, U.S.A.; Department of Anesthesiology, Loma Linda University, CA 92354, U.S.A.; Department of Neurosurgery, Loma Linda University, CA 92354, U.S.A.. Electronic address: johnzhang3910@yahoo.com.
authors.forename: John H
authors.initials: JH
authors.lastname: Zhang
mesh_terms: D000818:Animals; D001929:Brain Edema / Q000209:etiology / Q000276:immunology / Q000628:therapy; D001930:Brain Injuries / Q000209:etiology / Q000276:immunology* / Q000628:therapy; D004195:Disease Models, Animal; D005625:Frontal Lobe / Q000276:immunology* / Q000293:injuries* / Q000601:surgery; D020690:GTPase-Activating Proteins / Q000235:genetics / Q000378:metabolism; D055785:Gene Knockdown Techniques; D015316:Genetic Therapy / Q000379:methods; D057967:Infusions, Intraventricular; D036341:Intercellular Signaling Peptides and Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D007431:Intraoperative Complications / Q000276:immunology* / Q000628:therapy; D008297:Male; D009419:Nerve Tissue Proteins / Q000008:administration & dosage* / Q000235:genetics / Q000378:metabolism; D017207:Rats, Sprague-Dawley; D011971:Receptors, Immunologic / Q000008:administration & dosage / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000008:administration & dosage* / Q000235:genetics; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein
chemical_list: D020690:GTPase-Activating Proteins; D036341:Intercellular Signaling Peptides and Proteins; D009419:Nerve Tissue Proteins; D011971:Receptors, Immunologic; D011994:Recombinant Proteins; D000097905:Roundabout Proteins; D000098552:Slit Homolog 2 Protein; C499133:tGAP1 protein, rat
keywords: Brain edema; Cdc42; Neuroinflammation; Peripheral immune cell infiltration; Robo1; Slit2; Surgical brain injury; srGAP1