Stroke Exacerbates Respiratory Disorder and Cognition Impairment in Mice with Cerebral Amyloid Angiopathy.

Stroke is a known risk factor for dementia. Most Alzheimer's patients exhibit mixed neuropathology, with evidence of both ischemic damage and amyloid-beta (Aβ) plaque accumulation. Breathing disorders, such as apnea, are also associated with cognitive dysfunction and dementia progression. We hypothesized that stroke exacerbates respiratory dysfunction and cognitive impairment in Tg-SwDI mice, a model of cerebral amyloid angiopathy (CAA). Female CAA mice (11-13 months old) underwent permanent distal middle cerebral artery occlusion (pd-MCAO) surgery, with age- and sex-matched wild-type and sham-operated controls. Cognitive assessments included the Barnes maze, and novel object recognition test (NORT). Respiratory metrics were quantified using whole-body plethysmography, while immunohistochemistry measured Aβ deposition in the hippocampus and cortex, astrocytic markers (C3⁺GFAP⁺ for A1; S100A10⁺GFAP⁺ for A2) in the retrotrapezoid nucleus (RTN), and lymphatic vessel area (LYVE1) in deep cervical lymph nodes (dCLNs). Aβ in cerebrospinal fluid was also assessed. CAA mice without stroke exhibited higher apnea rates and impaired cognitive performance compared to wild-type controls. Stroke further increased apnea events and worsened Barnes maze escape latencies in CAA mice. Molecular analysis revealed an increase in GFAP as well as in A1 astrocytes and a reduction in A2 astrocytes in the RTN following stroke. Additionally, stroke accelerated Aβ deposition in the hippocampus and cortex while reducing Aβ clearance via cerebrospinal fluid and dCLNs. These findings suggest that stroke exacerbates respiratory dysfunction, impairs glymphatic-lymphatic clearance, and accelerates cognitive decline in CAA mice. Targeting post-stroke respiratory dysfunction may offer therapeutic potential for mitigating ischemic damage in dementia patients.