title: Neuroinflammation and white matter pathology in schizophrenia: systematic review.
abstract: BACKGROUND
  Neuroinflammation and white matter pathology have each been independently associated with schizophrenia, and experimental studies have revealed mechanisms by which the two can interact in vitro, but whether these abnormalities simultaneously co-occur in people with schizophrenia remains unclear.
  
  
  METHODS
  We searched MEDLINE, EMBASE, PsycINFO and Web of Science from inception through 12 January 2014 for studies reporting human data on the relationship between microglial or astroglial activation, or cytokines and white matter pathology in schizophrenia.
  
  
  RESULTS
  Fifteen studies totaling 792 subjects (350 with schizophrenia, 346 controls, 49 with bipolar disorder, 37 with major depressive disorder and 10 with Alzheimer's disease) met all eligibility criteria. Five neuropathological and two neuroimaging studies collectively yielded consistent evidence of an association between schizophrenia and microglial activation, particularly in white rather than gray matter regions. Ultrastructural analysis revealed activated microglia near dystrophic and apoptotic oligodendroglia, demyelinating and dysmyelinating axons and swollen and vacuolated astroglia in subjects with schizophrenia but not controls. Two neuroimaging studies found an association between carrier status for a functional single nucleotide polymorphism in the interleukin-1β gene and abnormal white as well as gray matter volumes in schizophrenia but not controls. A neuropathological study found that orbitofrontal white matter neuronal density was increased in schizophrenia cases exhibiting high transcription levels of pro-inflammatory cytokines relative to those exhibiting low transcription levels and to controls. Schizophrenia was associated with decreased astroglial density specifically in subgenual cingulate white matter and anterior corpus callosum, but not other gray or white matter areas. Astrogliosis was consistently absent. Data on astroglial gene expression, mRNA expression and protein concentration were inconsistent.
  
  
  CONCLUSIONS
  Neuroinflammation is associated with white matter pathology in people with schizophrenia, and may contribute to structural and functional disconnectivity, even at the first episode of psychosis.
authors.affiliation: Neuroinflammation Research Group, Epilepsy Center Division, Department of Neurology, NYU School of Medicine, New York, New York, United States. Electronic address: mna1024231@aol.com.
authors.forename: Souhel
authors.initials: S
authors.lastname: Najjar
authors.affiliation: Neuroinflammation Research Group, Epilepsy Center Division, Department of Neurology, NYU School of Medicine, New York, New York, United States; The Dartmouth Institute of Health Policy and Clinical Practice, Audrey and Theodor Geisel School of Medicine at Dartmouth, Hanover, New Hampshire, United States.
authors.forename: Daniel M
authors.initials: DM
authors.lastname: Pearlman
mesh_terms: D016207:Cytokines / Q000378:metabolism*; D016206:Databases, Bibliographic / Q000706:statistics & numerical data; D006801:Humans; D007249:Inflammation / Q000209:etiology*; D009457:Neuroglia / Q000378:metabolism; D012559:Schizophrenia / Q000150:complications* / Q000473:pathology*; D066127:White Matter / Q000473:pathology*
chemical_list: D016207:Cytokines
keywords: Neuroinflammation; Neuropathology; Schizophrenia; Systematic review; White matter