Jacob-Filho, W. | Search bioRxiv

bioRxiv2024

Spatially conserved pathoprotein profiling in the human suprachiasmatic nucleus in progressive Alzheimer disease stages

Individuals with Alzheimers Disease (AD) experience circadian rhythm disorder. The circadian rhythm is synchronized by a master clock, the suprachiasmatic nucleus (SCN), which is a tiny hypothalamic nucleus. Little is known about the molecular and pathological changes that occur in the SCN during AD progression. We examined postmortem brains of 12 controls without AD neuropathological changes (Braak stage 0) and 36 subjects at progressive Braak stages (I, II, and VI). To investigate potential AD-specific changes, we measured the neuronal counts of arginine vasopressin (AVP) and vasoactive intestinal peptide (VIP) positive neurons, along with the Braak stages in the SCN. We investigated in adjacent hypothalamic nuclei which are also composed of AVP+ neurons but show more resilience to AD: paraventricular nucleus (PVN) and supraoptic nucleus (SON). To understand the dysregulated proteins associated to AD progression, we performed in-situ proteomics, investigating 57 proteins, including commonly dysregulated in AD, using GeoMx Digital Spatial Profiling (DSP) in the three nuclei (total of 703 area of interests). Neurofibrillary tangles (NFTs) and tau fibrils were found selectively in SCN. We failed to detect NFTs in SON, only a mild dysregulation of p-tau at Braak VI in PVN and SON. Amyloid plaque was absent in the SCN and SON. Additionally, the SCN showed increased glial proteins already at Braak stage I, whereas the level of these proteins sustained in the other nuclei. The SCN is exclusively vulnerable to AD-tau pathology and show immune dysregulation even at Braak I but is protected against amyloid plaque. This finding revealed selectively in amnestic AD, showing more resilience in AD variant. This tau-related molecular dysregulation in the SCN contributes to circadian rhythm disturbances in AD, a phenomenon observed before the onset of cognitive disorder.

neuroscience↗

bioRxiv2021

Loss of lamin-B1 and defective nuclear morphology are hallmarks of astrocyte senescence in vitro and in the aging human hippocampus

The increase in senescent cells in tissues, including the brain, is a general feature of normal aging and age-related pathologies. Senescent cells exhibit a specific phenotype, which includes an altered nuclear morphology and transcriptomic changes. Astrocytes undergo senescence in vitro and in age-associated neurodegenerative diseases, but little is known about whether this process also occurs in physiological aging. Here, we investigated astrocyte senescence in vitro, in old mouse brains and in post-mortem human brain tissue of elderly. We identified a significant loss of lamin-B1, a major component of the nuclear lamina, as a hallmark of senescent astrocytes. We showed a severe reduction of lamin-B1 in the dentate gyrus of aged mice, including in hippocampal astrocytes, and in the granular cell layer of the hippocampus of post-mortem human tissue from non-demented elderly. Interestingly, the lamin-B1 reduction was associated with nuclear deformations, represented by an increased incidence of invaginated nuclei and loss of nuclear circularity in senescent astrocytes in vitro and in the aging human hippocampus. In conclusion, our findings show that reduction of lamin-B1 is a conserved hallmark of astrocyte aging, as well as shed light on significant defects in nuclear lamina structure, which may impact astrocyte function during human aging.

neuroscience↗