Background: Chronically dysregulated neuroinflammation has been implicated in neurodegenerative dementias, with separate studies reporting increased brain levels of inflammatory mediators and gliosis in Alzheimer’s disease (AD) as well as in Lewy body dementias (LBD). However, it is unclear whether the nature and extent of neuroinflammatory responses in LBD are comparable to those in AD. In this study, we performed head-to-head measurements of a panel of cytokines in the post-mortem neocortex of AD versus the two major clinical subtypes of LBD, namely, dementia with Lewy bodies (DLB) and Parkinson’s disease dementia (PDD). Methods: Post-mortem tissues from the mid-temporal cortex (Brodmann area 21) of a cohort of neuropathologically well-defined AD, PDD and DLB patients were processed and measured for a comprehensive range of cytokines (IL-1α, IL-1Ra, IL-8, IL-10, IL-12p70, IL-13, IFN-γ, GM-CSF and FGF-2) using a multiplex immunoassay platform. Associations between inflammation markers and neuropathological measures of neuritic plaques, neurofibrillary tangles as well as Lewy bodies were also performed. Results: We found IL-1α, IFN-γ, GM-CSF and IL-13 to be elevated in the mid-temporal cortex of AD patients. In contrast, none of the measured cytokines were significantly altered in either DLB or PDD. Similar cytokine changes were observed in two other neocortical areas of AD patients. Furthermore, increases of IL-1α, IFN-γ, GM-CSF, IL-10 and IL-13 associated with moderate-to-severe neurofibrillary tangle burden, but not with neuritic plaques or Lewy bodies. Our findings of elevated neocortical pro- and anti-inflammatory cytokines in AD, but not in DLB or PDD, suggest that neuroinflammatory responses are strongly linked to neurofibrillary tangle burden, which is higher in AD compared to LBD. In conclusion, neuroinflammation may not play a prominent role in the pathophysiology of late-stage LBD.

Dysregulation of astroglia-mediated neuroinflammation is known to be involved in neurodegenerative diseases. Amongst multiple inflammatory pathways, pyroptosis is characterized by inflammatory cell death following inflammasome activation. Recently, the omega-3 poly-unsaturated fatty acid, DHA, has been identified as a pyroptosis inducer, although the underlying mechanisms remain unclear. In this study, we investigated the role of the alternatively spliced T-isoform of Fyn kinase (FynT) in DHA-induced astroglial pyroptosis. Immortalized normal human astrocytes (iNHA) expressing wild-type FynT (FynT-WT), kinase-dead mutant FynT (FynT-KD), or empty vector (EV) controls were treated with DHA and assessed for pyroptotic activation. We found that DHA-treated FynT-WT cells exhibited significantly reduced cytosolic lactate dehydrogenase release, pyroptotic morphology and markers (cleaved caspase-1 and its substrates, cleaved caspase-3 and gasdermin-D N fragments) compared to either EV or FynT-KD cells. No significant differences in pyroptotic activation were observed between EV and FynT-KD cells. In addition, no differences in immunoreactivities of pro- or anti-apoptotic markers (Bax or Bcl-2) were observed across the DHA-treated cells. In summary, our study postulates a negative regulatory role of FynT kinase in DHA-induced pyroptosis in astrocytes, with implications for further understanding neuroinflammatory mechanisms in neurodegenerative diseases and identification of potential therapeutic targets.

Dysregulation of astroglia-mediated neuroinflammation is known to be involved in neurodegen-erative diseases. Amongst multiple inflammatory pathways, pyroptosis is characterized by in-flammatory cell death following inflammasome activation. Recently, the omega-3 poly-unsaturated fatty acid, DHA, has been identified as a pyroptosis inducer, although the un-derlying mechanisms remain unclear. In this study, we investigated the role of the alternative-ly-spliced T-isoform of Fyn kinase (FynT) in DHA-induced astroglial pyroptosis. Immortalized normal human astrocytes (iNHA) expressing wild-type FynT (FynT-WT), kinase-dead mutant FynT (FynT-KD), or empty vector (EV) controls were treated with DHA and assessed for pyrop-totic activation. We found that DHA-treated FynT-WT cells exhibited significantly reduced cyto-solic lactate dehydrogenase release, pyroptotic morphology and markers (cleaved caspase-1 and its substrates, cleaved caspase-3 and gasdermin-D N fragments) compared to either EV or FynT-KD cells. No significant differences in pyroptotic activation were observed between EV and FynT-KD cells. In addition, no differences in immunoreactivities of pro- or anti-apoptotic markers (Bax or Bcl-2) were observed across the DHA-treated cells. In summary, our study postulates a negative regulatory role of FynT kinase on DHA-induced pyroptosis in astrocytes, with implica-tions for further understanding neuroinflammatory mechanisms in neurodegenerative diseases and identification of potential therapeutic targets.