Neuroinflammation plays a critical role in the progression of many neurodegenerative diseases and neuropsychiatric illnesses. It is evident that microglia in particular are central to mediating the effects of neuroinflammation. Activated microglia release a number of cytokines and chemokines, which in turn activate many signal transduction pathways. For instance, interleukin-1 beta and tumor necrosis factor alpha regulate transcription of a number of genes within the brain including proinflammatory products of the arachidonic acid (AA) cascade. Co-activation of pro-inflammatory markers and associated cytotoxic products during neuroinflammation process are detrimental to neurons by altering the synaptic proteins. In this review, we discuss both neuroinflammation as well as excitotoxicity insults reduce synaptic markers such as synaptophysin and drebrin in rat brain. Further we discuss here, neurodegenerative and neuropsychiatric illness are associated with increased neuroinflammatory and excitotoxicity markers as well as upregulated brain arachidonic acid markers and the loss of synaptic markers. The decrease in synaptic markers might contribute to reported cognitive defects in neurodegenerative and neuropsychiatric illnesses.

Schizophrenia (SZ) is a progressive, neuropsychiatric disorder associated with cognitive impairment. A number of brain alterations have been linked to cognitive impairment, including neuroinflammation, excitotoxicity, increased arachidonic acid (AA) signaling and reduced synaptic protein. On this basis, we tested the hypothesis that SZ pathology is associated with these pathological brain changes. To do this, we examined postmortem frontal cortex from 10 SZ patients and 10 controls and measured protein and mRNA levels of cytokines, and astroglial, microglial, neuroinflammatory excitotoxic, AA cascade, apoptotic and synaptic markers. Mean protein and mRNA levels of interleukin-1β, tumor necrosis factor-α, glial acidic fibrillary protein (GFAP), a microglial marker CD11b, and nuclear factor kappa B subunits were significantly increased in SZ compared with control brain. Protein and mRNA levels of cytosolic and secretory phospholipase A2 and cyclooxygenase were significantly elevated in postmortem brains from SZ patients. N-methyl-D-aspartate receptor subunits 1 and 2B, inducible nitric oxide synthase and c-FOS were not significantly different. In addition, reduced protein and mRNA levels of brain-derived neurotrophic factor, synaptophysin and drebrin were found in SZ compared with control frontal cortex. Increased neuroinflammation and AA cascade enzyme markers with synaptic protein loss could promote disease progression and cognitive defects in SZ patients. Drugs that downregulate these changes might be considered for new therapies in SZ.