Acute pre-operative ibuprofen improves cognition in a rat model for postoperative cognitive dysfunction

Abstract

Background: Inflammation is considered a key factor in the development of postoperative cognitive dysfunction (POCD). Therefore, we hypothesized that pre-operative anti-inflammatory treatment with ibuprofen would inhibit POCD in our rat-model.

Methods: Male Wistar rats of 3 or 23 months old received a single injection of ibuprofen (15 mg/kg i.p.) or were control handled before abdominal surgery. Timed blood and fecal samples were collected for analyses of inflammation markers and gut microbiome changes. Behavioral testing was performed from 9 to 14 days after surgery, in the open field, novel object- and novel location-recognition tests and Morris water maze. Neuroinflammation and neurogenesis were assessed by immune histochemistry after sacrifice on postoperative day 14.

Results: Ibuprofen improved short-term spatial memory in the novel location recognition test, and increased hippocampal neurogenesis. However, these effects were associated with increased hippocampal microglia activity. Whereas plasma cytokine levels (IL1-β, IL6, IL10, and TNFα) were not significantly affected, VEGF levels increased and IFABP levels decreased after ibuprofen. Long-term memory in the Morris water maze was not significantly improved by ibuprofen. The gut microbiome was neither significantly affected by surgery nor by ibuprofen treatment. In general, effects in aged rats appeared similar to those in young rats, though less pronounced.

Conclusion: A single injection of ibuprofen before surgery improved hippocampus-associated short-term memory after surgery and increased neurogenesis. However, this favorable outcome seemed not attributable to inhibition of (neuro)inflammation. Potential contributions of intestinal and blood-brain barrier integrity need further investigation. Although less pronounced compared to young rats, effects in aged rats indicate that even elderly individuals could benefit from ibuprofen treatment.

Keywords: Cognition; Ibuprofen; Inflammation; Neuroinflammation; Postoperative cognitive dysfunction.

Fig. 1

Time line of the experimental protocol. Ibuprofen (IBU)-treated rats (young n = 12; aged n = 11) received a single i.p. injection of ibuprofen 30 min before surgery; control (C) rats (young n = 14; aged n = 11) were handled. Rats were sacrificed (+) at day 14. Blood samples were collected at 30 min, and 1, 6, and 24 h after surgery and at sacrifice. Fecal samples were collected before and 7 days after surgery. MWM, Morris water maze

Fig. 2

Preference for the objects in the setting with 2 identical objects (side preference; A), for the novel object in the novel object recognition test (B) and for the relocated object in novel location recognition test (C) (mean ± SEM). Dotted line, reference line (50%) for random exploration. C, control (young n = 13; old n = 11); IBU, ibuprofen treatment (young n = 10-11; old n = 8-9). F, F statistics for A, main effect of age; I, main effect of intervention; A*I, interaction effect of age and intervention. *p < 0.05

Fig. 3

Learning curve as latency to find the platform in the Morris water maze (MWM) for the different experimental groups. C, control (young n = 13; old n = 12); IBU, ibuprofen treatment (young n = 11; old n = 9). F, F statistics for A, main effect of age; I, main effect of intervention; A*I, interaction effect of age and intervention

Fig. 4

Microglial activity in hippocampal areas (mean ± SEM). Top, representative images of microglia staining of the dentate gyrus. Bottom, ratio between the cell body size and total cell size in the hippocampal regions dentate gyrus inner blade (DG), cornu ammonis 1 (CA1), cornu ammonis 3 (CA3), and Hilus. C, control (young n = 12; old n = 9-10); IBU, ibuprofen (young n = 8; old n = 6). F statistics (F) are displayed for age A, main effect of age; I, main effect of intervention; A*I, interaction effect of age and intervention

Fig. 5

Neurogenesis measured as DCX positive cells (mean ± SEM). Left, the number of DCX positive cells in the dentate gyrus (DG) corrected for the length of the DG in mm (cells/mm). Right, representative images of DCX stained sections of the dentate gyrus. C, control (young n = 13; old n = 11), IBU, ibuprofen (young n = 11; old n = 9). F statistics are displayed for: A, main effect of age; I, main effect of intervention; A*I, interaction effect of age and intervention. *p < 0.05, ***p < 0.001

Fig. 6

Time course for plasma markers (A, C, E, G) and area under the curve (AUC; B, D, F, H) during the first 24 h after surgery in the different experimental groups. C, control; IBU, ibuprofen; IFABP, intestinal fatty acid binding protein (n = 7-12); IL6, interleukine-6 (n = 3-4); IL10, interleukin-10 (n = 3-6); IL1-β, interleukin-1-β (n = 5-8). F statistics are displayed for A, main effect of age; I, main effect of intervention; A*I, interaction effect of age and intervention

Fig. 7

Plasma and hippocampal levels of IL1-β, at the time of sacrifice, 14 days after surgery. C, control (young n = 13; old n = 10), IBU, ibuprofen (young n = 10-11; old n = 8-9). F statistics are displayed for age (A), intervention (I), and age*intervention (A*I) effects

Fig. 8

Ordination of the gut microbiome (bacterial communities) based on all samples. The principal coordinate analysis (PCO) plot is based on the weighted UniFrac distance matrix calculated on rarefied OTU abundances (1000 sequences per sample) for all samples. Variance explained by each PCO axis is given in parentheses

Fig. 9

Relative abundance of bacterial phyla, at baseline (before surgery) and 7 days after surgery in young and aged rats. C, control (young n = 10; old n = 12); IBU, ibuprofen (young n = 6; old n = 6)