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BackgroundCognitive dysfunction in schizophrenia is the key predictor of functional disability and drives economic burden. Inflammation has been increasingly implicated in the pathogenesis of schizophrenia, yet its role in cognitive decline has not been evaluated. This study explores the association between inflammation and cognitive functioning in persons with schizophrenia.MethodsParticipants included 143 persons with schizophrenia (PwS) and 139 non-psychiatric comparison subjects (NCs) from an ongoing study of aging. Cognitive assessments included validated measures for executive functioning, processing speed, and visuospatial skills. Plasma levels of nine biomarkers associated with inflammation (high sensitivity C-reactive protein, intercellular adhesion molecule 1, serum amyloid A, interleukin-6, interleukin-8, interferon gamma-induced protein-10, monocyte chemotactic protein-1, fractalkine, and brain-derived neurotrophic factor) were quantified using commercially available, enzyme-linked immunosorbent assays. Partial least squares regression was used to develop a composite "inflammatory profile" to maximize correlations with the cognitive outcomes. We then constructed a best-fit model using these composites and their interactions with diagnosis and sex as the predictors, controlling for covariates.ResultsThe biomarker composite, which best correlated with scores on cognitive testing, included high sensitivity C-reactive protein, intercellular adhesion molecule 1, serum amyloid A, interleukin-6, and brain-derived neurotrophic factor, for a 5-biomarker "inflammatory profile." The best-fit model showed a significant biomarker composite by diagnosis by sex three-way interaction, for executive function and processing speed, but not visuospatial skill.ConclusionsThis approach to building an "inflammatory profile" may provide insight into inflammatory pathways affecting brain function and potential targets for anti-inflammatory interventions to improve cognition in schizophrenia.

Despite considerable research to uncover them, the anatomic and neuropathologic correlates of memory impairment in dementia with Lewy bodies (DLB) remain unclear. While some studies have implicated Lewy bodies in the neocortex, others have pointed to α-synuclein pathology in the hippocampus. We systematically examined hippocampal Lewy pathology and its distribution in hippocampal subfields in 95 clinically and neuropathologically characterized human cases of DLB, finding that α-synuclein pathology was highest in two hippocampal-related subregions: the CA2 subfield and the entorhinal cortex (EC). While the EC had numerous classic somatic Lewy bodies, CA2 contained mainly Lewy neurites in presumed axon terminals, suggesting the involvement of the EC → CA2 circuitry in the pathogenesis of DLB symptoms. Clinicopathological correlations with measures of verbal and visual memory supported a role for EC Lewy pathology, but not CA2, in causing these memory deficits. Lewy pathology in CA1-the main output region for CA2-correlated best with results from memory testing despite a milder pathology. This result indicates that CA1 may be more functionally relevant than CA2 in the context of memory impairment in DLB. These correlations remained significant after controlling for several factors, including concurrent Alzheimer's pathology (neuritic plaques and neurofibrillary tangles) and the interval between time of testing and time of death. Our data suggest that although hippocampal Lewy pathology in DLB is predominant in CA2 and EC, memory performance correlates most strongly with CA1 burden.SIGNIFICANCE STATEMENT This study provides a detailed neuropathologic analysis of hippocampal Lewy pathology in human patients with autopsy-confirmed dementia with Lewy bodies. The approach-informed by regional molecular markers, concurrent Alzheimer's pathology analysis, and relevant clinical data-helps tease out the relative contribution of Lewy pathology to memory dysfunction in the disease. Levels of Lewy pathology were found to be highest in the hippocampal CA2 subregion and entorhinal cortex, implicating a potentially overlooked circuit in disease pathogenesis. However, correlation with memory performance was strongest with CA1. This unexpected finding suggests that Lewy pathology must reach a critical burden across hippocampal circuitry to contribute to memory dysfunction beyond that related to other factors, notably coexisting Alzheimer's disease tau pathology.