Sleep deprivation occurs frequently in older adults, which can result in delirium and cognitive impairment. CD44 is a key molecular in blood-brain barrier (BBB) regulation. However, whether CD44 participates in the role of sleep deprivation in cognitive impairment remains unclear. In this study, the effect of sleep deprivation on cognitive ability, tissue inflammation, BBB permeability, and astrocyte activity were evaluated in vivo. The differentially expressed genes (DEGs) were identified by RNA sequencing. A CD44 overexpression in the BBB model was performed in vitro to assess the effect and mechanisms of CD44. Sleep deprivation impaired the learning and memory ability and increased the levels of inflammatory cytokines, along with increased BBB permeability and activated astrocytes in hippocampus tissue. RNA sequencing of the hippocampus tissue revealed that 329 genes were upregulated in sleep deprivation-induced mice compared to control mice, and 147 genes were downregulated. GO and pathways showed that DEGs were mainly involved in BBB permeability and astrocyte activation, including nervous system development, neuron development, and brain development, and neuroactive ligand-receptor interaction. Moreover, the PCR analysis revealed that CD44 was dramatically increased in mice with sleep deprivation induction. The overexpression of CD44 in astrocytes promoted BBB permeability in vitro and induced the expression of the downstream gene NANOG. Our results indicate that sleep deprivation upregulated CD44 expression in hippocampus tissue, and increased BBB permeability, resulting in cognitive impairment.

Ligustilide exerts potential neuroprotective effects against various cerebral ischaemic insults and neurodegenerative disorders. However, the function and mechanisms of LIG‐mediated hippocampal neural stem cells (H‐NSCs) activation as well as cognitive recovery in the context of post‐operative cognitive dysfunction (POCD) remain elusive and need to be explored. Mice were subjected to transient global cerebral ischaemia and reperfusion (tGCI/R) injury and treated with LIG (80 mg/kg) or vehicle for 1 month. Morris water maze test and western blot were employed to assess cognitive function. Nissl staining and immunofluorescence (IF) staining were used to detect H‐NSCs proliferation and neurogenesis in hippocampus. Subsequently, primary H‐NSCs were treated with LIG, and the level of H‐NSCs proliferation and neuronal‐differentiation was examined by IF staining for Edu and β‐Tubulin III. The protein levels of ERK1/2, β‐catenin, NICD, TLR4, Akt and FoxO1 were examined using western blotting. Finally, pretreatment with the ERK agonist SCH772984 was performed to observe the change in ERK expression. LIG treatment promoted H‐NSCs proliferation and neurogenesis, increased the number of neurons in the hippocampal subfields, and ultimately reversed cognitive impairment in tGCI/R injury. Furthermore, LIG also promoted primary H‐NSCs proliferation and neuronal‐differentiation, as well as ERK1/2 phosphorylation. Pretreatment with SCH772984 effectively reversed the ability of LIG to induce ERK1/2 phosphorylation and promote H‐NSCs proliferation and neuronal‐differentiation. LIG can promote cognitive recovery after tGCI/R injury by activating ERK1/2 in H‐NSCs to promote their proliferation and neurogenesis in the hippocampus. Therefore, LIG has potential for use in the prevention and/or treatment of POCD.