[Sleep deprivation aggravates cognitive impairment in septic rats by activating neuronal glycolytic isoenzyme PFKFB3]

To evaluate the effect of sleep deprivation on cognitive function in septic rats and its relationship with neuronal glycolysis isoenzyme phosphofructokinase-2/fructose-2, 6-diphosphatase 3 (PFKFB3).

Fifty-six healthy male Sprague-Dawley (SD) rats were randomly divided into 4 groups (n = 14): control group (Con group), sepsis group (LPS group), sepsis+sleep deprivation group (LPS+SD group), sepsis+sleep deprivation+glycolysis inhibitor 3-PO treatment group (LPS+SD+3-PO group). The sepsis model was established by intraperitoneal injection of lipopolysaccharide (LPS) 10 mg/kg. Rats in LPS+SD group were treated with sleep deprivation using a sleep deprivation instrument 24 hours after LPS injection. The LPS+SD+3-PO group was intraperitoneally injected with LPS for 24 hours, and then injected with 3-PO 50 mg/kg, followed by sleep deprivation. Novel object recognition experiments were performed 72 hours after LPS injection. Subsequently, blood and brain tissue samples were collected. The contents of lactate (Lac), reactive oxygen species (ROS) and serum tumor necrosis factor-α (TNF-α), neuron-specific enolase (NSE), pyruvate in brain tissue were detected by enzyme-linked immunosorbent assay (ELISA). Then, the lactate/pyruvate ratio was calculated. Na⁺-K⁺-ATPase activity in brain tissue was detected by colorimetry. Morphological changes in hippocampus were detected by hematoxylin-eosin (HE) staining. And the protein expression levels of PFKFB3, ZO-1 and cleaved caspase-3 were measured by Western blotting.

Compared with Con group, the novel object recognition index of LPS group was decreased, the levels of NSE, TNF-α, lactate/pyruvate ratio in serum and the levels of Lac, ROS and dry-wet weight ratio in brain tissue were significantly increased, Na⁺-K⁺-ATPase activity in brain tissue was decreased, the protein expressions of PFKFB3, caspase-3 were up-regulated, ZO-1 expression was down-regulated, and the neurons in hippocampus were slightly degenerated. Compared with LPS group, the novel object recognition index of LPS+SD group was further decreased [(39.4±5.3)% vs. (54.5±7.6)%)], serum NSE, TNF-α, lactate/pyruvate ratio and brain tissue Lac, ROS, dry-wet weight ratio were further increased [NSE (μg/L): 3.21±0.42 vs. 2.55±0.36, TNF-α (ng/L): 139.4±19.7 vs. 92.2±13.5, lactate/pyruvate ratio: 29.7±5.5 vs. 19.2±4.2, Lac (μmol/g): 19.51±2.33 vs. 11.34±1.52, ROS (kU/g): 117.4±18.7 vs. 78.2±11.8, dry-wet weight ratio: (81.3±9.2)% vs. (64.3±6.6)%], and Na⁺-K⁺-ATPase activity was further decreased (mmol×L^-1×h^-1: 1.88±0.34 vs. 2.91±0.39), the protein expressions of PFKFB3, caspase-3 were further up-regulated and ZO-1 expression was further down-regulated (PFKFB3/β-actin: 0.80±0.11 vs. 0.45±0.07, caspase-3/β-actin: 0.71±0.09 vs. 0.37±0.05, ZO-1/β-actin: 0.31±0.05 vs. 0.61±0.08). The differences were statistically significant (all P < 0.05). HE staining showed that the degeneration of neurons in hippocampus was significantly aggravated. Compared with LPS+SD group, the novel object recognition index of LPS+SD+3-PO group was increased [(50.8±5.9)% vs. (39.4±5.3)%], NSE, TNF-α, lactate/pyruvate ratio of serum and Lac, ROS, dry-wet weight ratio of brain tissue were significantly decreased [NSE (μg/L): 2.60±0.33 vs. 3.21±0.42, TNF-α (ng/L): 103.7±18.3 vs. 139.4±19.7, lactate/pyruvate ratio: 17.4±5.1 vs. 29.7±5.5, Lac (μmol/g): 13.68±2.02 vs. 19.51±2.33, ROS (kU/g): 86.9±14.5 vs. 117.4±18.7, dry-wet weight ratio: (67.7±6.9)% vs. (81.3±9.2)%], and Na⁺-K⁺-ATPase activity was increased (mmol×L^-1×h^-1: 2.82±0.44 vs. 1.88±0.34). The protein expressions of PFKFB3, caspase-3 were down-regulated and ZO-1 expression was up-regulated (PFKFB3/β-actin: 0.50±0.06 vs. 0.80±0.11, caspase-3/β-actin: 0.43±0.06 vs. 0.71±0.09, ZO-1/β-actin: 0.52±0.06 vs. 0.31±0.05). The differences were statistically significant (all P < 0.05). HE staining showed that the degeneration of neurons in hippocampus was significantly improved.

Sleep deprivation could aggravate neuroinflammation, neuronal degeneration and apoptosis in septic rats, resulting in destruction of blood-brain barrier and cognitive impairment. 3-PO treatment significantly alleviate the injury and degeneration of hippocampal neurons in septic rats, inhibit neuroinflammation and apoptosis, and improve cognitive dysfunction, which may be related to the inhibition of glycolytic isoenzyme PFKFB3.