Balaji Krishnamachary

Volatile anesthetics and surgery can trigger neuroinflammation and neurological dysfunction, but their long-term effects remain poorly understood. Young adult male and female C57BL/6 mice underwent 4 h of 2% isoflurane anesthesia combined with laparotomy (Iso/OP) or sham treatment. At 12 weeks, olfactory and cognitive functions were assessed, followed by RNA sequencing of olfactory bulbs and hippocampi and plasma extracellular vesicle (EV) profiling. EV-associated inflammatory bioactivity was evaluated by hippocampal injection into naïve male mice. Iso/OP induced olfactory deficits at 12 weeks, with greater impairment in females. Female mice also exhibited deficits in spatial working memory and associative learning, whereas males showed relatively preserved cognitive function. Transcriptomic analyses revealed sex-dependent alterations in pathways related to synaptic function, neurodevelopment, extracellular matrix remodeling, stress responses, and chemotaxis. Iso/OP reduced circulating EV abundance, particularly among 40–100 nm particles, and altered EV proteomic profiles. Exploratory analyses of pooled hippocampal tissues revealed distinct cytokine and chemokine profiles following injection of plasma EVs from the four donor groups. Collectively, these findings demonstrate sex-dependent neurological and molecular alterations persisting 12 weeks after Iso/OP, accompanied by changes in circulating EVs. The exploratory EV transfer findings warrant further investigation into the potential contribution of circulating EVs to brain inflammatory responses.

Approximately 20% of all spinal cord injuries (SCI) occur in persons aged 65 years or older. Longitudinal, population-based studies showed that SCI is a risk factor for dementia. However, little research has addressed the potential mechanisms of SCI-mediated neurological impairment in the elderly. We compared young adult and aged C57BL/6 male mice subjected to contusion SCI, using a battery of neurobehavioral tests. Locomotor function showed greater impairment in aged mice, which was correlated with reduced, spared spinal cord white matter and increased lesion volume. At 2 months post-injury, aged mice displayed worse performance in cognitive and depressive-like behavioral tests. Transcriptomic analysis identified activated microglia and dysregulated autophagy as the most significantly altered pathways by both age and injury. Flow cytometry demonstrated increased myeloid and lymphocyte infiltration at both the injury site and brain of aged mice. SCI in aged mice was associated with altered microglial function and dysregulated autophagy involving both microglia and brain neurons. Altered plasma extracellular vesicles (EVs) responses were found in aged mice after acute SCI. EV-microRNA cargos were also significantly altered by aging and injury, which were associated with neuroinflammation and autophagy dysfunction. In cultured microglia, astrocytes, and neurons, plasma EVs from aged SCI mice, at a lower concentration comparable to those of young adult SCI mice, induced the secretion of pro-inflammatory cytokines CXCL2 and IL-6, and increased caspase3 expression. Together, these findings suggest that age alters the EVs pro-inflammatory response to SCI, potentially contributing to worse neuropathological and functional outcomes.